These services provide support (pain management, counseling, in-home care, etc.) for dying patients.

4002. host
Definition:

An organism that is infected with/is fed upon by a parasitic or pathogenic organism (e.g., a virus, nematode, fungus, etc.)

4003. host
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

An organism on which a parasite lives and by which it is nourished (also applied, loosely, to a plant supporting an epiphyte).

4004. host cell
Definition:

1. A cell which has been infected by a virus is known as the "host cell" of that virus.
2. A cell which is used in lab techniques such as DNA cloning to receive, maintain, and allow the reproduction of cloning vectors. The DNA introduced with the vector is replicated whenever the cell divides.

4005. host range
Definition:

The range of host species or cell types which a particular virus, bacteria, or parasite is able to infect or parasitize.

4006. host restriction-modification
Definition:

A bacterial system where the bacterium is able to destroy invading DNA from a bacteriophage (virus which infects bacteria) while at the same time preventing the destruction of their own DNA. The phage DNA is cleaved by a restriction enzyme made by the bacterium; the bacterial DNA is modified (usually with methylation) so that the enzyme won't destroy it.

4007. host-vector system
Definition:

A combination of a bacterial host cell (i.e. a specific strain) and a virus vector (i.e. a particular bacteriophage strain) which work well together for DNA cloning.

4008. hot spot (hotspot)
Definition:

A particular area of DNA which is especially prone to spontaneous mutations or recombinations.

4009. housekeeping genes
Definition:

The genes which are expressed in all cells and which code for molecules that are necessary for basic maintenance and essential cellular functions.

4010. human bone growth
Author: Guo Li
Definition:

Bone mass changes in three phases:

1. growth: deposition of bone mass during skeletal growth
2. consolidation: after growth lasting for about 15 years
3. involution: starts between about 40 years, when there is bone loss

4011. human chorionic gonadotropin (HCG)
Author: Fertilitext and Guo Li
Definition:

Human chorionic gonadotropin is the hormone produced early in pregnancy that keeps the corpus luteum producing progesterone; it may be injected to stimulate ovulation and progesterone production.

This hormone is also elevated in trophoblastic disease and germ cell cancers and thus serves as a useful tumor marker for these cancers. Patients with non-cancerous conditons such as inflammatory bowel disease, duodenal ulcers, or cirrhosis or cancers of the breast, lung, pancreas, ovary, or gastrointestinal system may have elevated HCG levels.

4012. human cytomegalovirus group
Definition:

A group of viruses within the subfamily Cytomegalovirus (Betaherpesvirinae) (of the family Herpesviridae) which infects human beings.

4013. human embryo lung cells
Definition:

Diploid, untransformed cells from the lungs of human embryos which are used to make vaccines against certain viruses (such as rabies).

4014. human gene therapy
Definition:

Insertion of normal DNA directly into cells to correct a genetic defect.

4015. Human Genome Initiative (Human Genome Project)
Definition:

Collective name for several projects begun in 1986 by the Department of Energy (DOE) to
1. create an ordered set of DNA segments from known chromosomal locations,
2. develop new computational methods for analyzing genetic map and DNA sequence data, and
3. develop new techniques and instruments for detecting and analyzing DNA.
This DOE initiative is now known as the Human Genome Program. The national effort, led by DOE and National Institute of Health (NIH), is known as the Human Genome Project.

4016. human growth hormone (HGH human somatotrophin)
Author: Susan A.Hagedorn
Definition:

A protein produced in the pituitary gland that stimulates the liver to produce somatomedins, which stimulate growth of bone and muscle.

4017. human leukocyte-associated antigens (HLA antigens)
Author: PharmInfoNet
Definition:

Proteins on the outer part of body cells that help fight illness. These proteins vary from person to person. Scientists think that people with certain types of HLA antigens are more likely to develop insulin-dependent diabetes. The HLA antigens are also responsible for histocompatibility reactions.

4018. human lymphocyte histocompatibility antigens (HLA, HL-A)
Author: Guo Li
Definition:

Human lymphocyte histocompatibility antigens were first detected as surface antigens (glycoproteins) on peripheral blood lymphocytes. Later, the HLA regions which codes for the antigens were localized to chromosome 6. Because the HLA complex is inherited intact as two haplotypes (one from each parent), siblings have 1 in 4 chance of being HLA-identical.

HLA antigens are of clincially significance because these antigens elicite the strongest immunologic response, therefore, it is responsible for rejection of transplanted tissue and graft versu host reactions. It is also the cause of hemolytic diseases of newborn, erythroblastosis fetalis, kernicterus, and tranfustion reactions with poorly matched or mismatched blood. Furthermore, a host of clincial disorders are associated with HLA is various degrees, e.g. ankylosing spondylitis is associated with HLA B27.

4019. human papillomavirus (HPV, genital warts)
Definition:

This virus is a sexually-transmitted infection that causes genital warts and cervical lesions, and is thought to be responsible for most cases of cervical cancer; women whose HPV infections persist over time are thought to be at the greatest risk of cancer.

Genital warts can develop on the cervix, penis, or in the urethra, vagina, anus or rectum. They look like other sorts of warts; they are dry and painless, firm and rough in texture, and can be grayish or skin colored. If left untreated, warts can grow together in clumps that resemble tiny pieces of cauliflower. They may itch slightly; flat warts may not be very noticeable. Many people may have this infection and not realize it.

HPV is mainly transmitted via sexual intercourse (vaginal, oral or anal intercourse) and it may also be transmitted by sharing damp unwashed articles like washcloths, towels or underwear. The disease is highly contagious, but the risk of transmission can be reduced by using a condom during sex.

Treatment involves burning off the warts with liquid nitrogen or lasers or by applying prescription creams (most containing podophyllotoxin)that kill the virus. There are no over-the-counter drugs that can treat this sort of infection.

4020. human T-cell leukemia virus
Definition:

One of a group of retroviruses which causes the disease T-cell leukemia in humans. T-cell leukemia is a type of the cancer leukemia where the body uncontrollably produces large amounts of abnormal (nonworking) T lymphocytes.

4021. human T-lymphotropic virus type I (HTLV-I)
Definition:

A human, single-stranded RNA retrovirus from the subfamily Oncovirinae which causes adult T-cell leukemia and T-cell lymphoma and may also be involved in certain demyelinating diseases (diseases where the protective myelin sheath around nerve fibers are destroyed). HTLV-I is closely related to HTLV-II (60% of their genomes are identical).

4022. human T-lymphotropic virus type II (HTLV-II)
Definition:

A human, single-stranded RNA retrovirus from the subfamily Oncovirinae which may cause diseases such as T-cell leukemia and T-cell lymphoma (but this has not been proven). HTLV-II is closely related to HTLV I (60% of their genomes are identical).

4023. human T-lymphotropic virus type III (HTLV-III)
Definition:

An obsolete term for human immunodeficiency virus (HIV), which causes Acquired Immunity Deficiency Syndrome (AIDS).

4024. humane
Definition:

Marked by sympathy, compassion or concern for other humans or for animals.

4025. Humboldt bridge
Author:
Definition:

A "temporary" stream crossing built by placing logs in a stream along the stream axis and capped with dirt or gravel to the desired road elevation. (Humboldt bridges can be very damaging to streams as they block fish migration and cause erosion.)

4026. humoral antibodies (humoral antibody)
Definition:

Antibodies which are secreted by B lymphocytes circulating in the blood, in response to antigens found in body fluids.

4027. humus
Definition:

The part of dirt or soil which comes from organic matter, such as from dead and decaying plants and animal remains.

4028. Hunter's syndrome (mucopolysaccharidosis type II, MPS disorder II, MPS II)
Definition:

An X-linked disease caused by a deficiency of the enzyme iduronate sulphate sulfatase, which breaks down dermatan sulphate and heparen sulphate, two types of mucopolysaccharides (complex carbohydrates). Consequently, the mucopolysaccharides accumulate in the cells of the body and cause damage. Patients have the two types of sulfates in their urine and suffer from skeletal defects, retinitis pigmentosa (progressive blindness), skin lesions, progressive deafness, and heart problems. There are mild and severe forms of the syndrome and presently no cure. Symptoms are treated as they appear. Hunter’s syndrome is the most common of a number of related rare genetic mucopolysaccharide disorders.

For more information, visit MPS II - Hunter Syndrome and The National Organization for Rare Disorders -- Hunter's Syndrome.

4029. Hunter's syndrome (mucopolysaccharidosis type II, MPS II, MPS2)
Author: Guo Li
Definition:

Hunter's syndrome is characterized by coarse face, enlargement of liver and spleen, and mental retardation. Affected patients has sulfoiduronate sulfatase defeciency. It is inherited as an x-linked recessive condition.

4030. Huntington's disease (Huntington's chorea)
Definition:

An inherited degenerative neuropsychiatric disorder which is caused by a dominant gene on an autosome. Symptoms include chorea (involuntary dancelike movements), clumsiness, slurred speech, depression, irritability, apathy, and losses of attention span, short-term memory and intellectual speed. Symptoms typically begin between the ages of 30 and 50 (though they can start at any other time), and not all individuals will have the same symptoms. Symptoms are treated as they appear. There is currently no cure.

For more information, visit Caring for People with Huntington's Disease and Facing Huntington's Disease: A Handbook for Families and Friends.

4031. Huntington's disease (Huntington's chorea)
Author: Guo Li
Definition:

Huntington's disease is a genetic disease with onset between 30 to 50 years of age and characterized by chorea (involuntary movements), behavior changes and dementia. The defect in on the short arm of chromosome 4 and is an autosomal dominant inherited condition.

4032. Hurler's syndrome (mucopolysaccharidosis type 1 H, MPS disorder I H, MPS IH, gargoylism, Hurler disease)
Definition:

A hereditary metabolic disorder caused by a recessive gene which results in a deficiency of the enzyme alpha-L-iduronidase, which breaks down dermatan sulphate and heparan sulphate, two types of mucopolysaccharides (complex carbohydrates). Consequently, the mucopolysaccharides accumulate in the cells of the body and cause damage. Symptoms include skeletal deformities, mental retardation, severe coronary artery disease, deafness, and stiff joints, among other things. There are mild and severe forms of the syndrome; the mild form is called Scheie Syndrome, the severe form is called Hurler Syndrome, and children with an intermediate form have Hurler-Scheie Syndrome. Patients with the severe form usually die from respiratory and cardiac failure before the age of ten. There is presently no cure. Hurler’s Syndrome is one of a number of related rare genetic mucopolysaccharide disorders, the most common being Hunter’s Syndrome.

For more information, visit MPS II - Hurler's Syndrome and The National Organization for Rare Disorders -- Hurler's Syndrome.

4033. Hurler's syndrome (mucopolysaccharidosis type I, MPS I, MPS1)
Author: Guo Li
Definition:

Hurler's syndrome is characterized by deafness, stiff joints, dwarfing, severe coronary artery disease at an early age, and mental retardation.

4034. hyaline membrane disease
Author: Guo Li
Definition:

Hyaline membrane disease is the most common cause of respiratory distress of the premature infant with incidence up to 65% at about 30 weeks of gestation. The pathology involves inadequate production of lung surfactant which decreases the surface tension of the aveoli during expiration, thus resulting in collapse of the aveoli (atelectasis).

4035. hyaluronic acid
Definition:

A glycosaminoglycan (macromolecule composed of repeating units of disaccharides) where the disaccharide repeating unit consists of the sugars glucuronic acid and N-acetylglucosamine.

4036. hybrid
Definition:

An offspring of parents from different species or sub-species.

4037. hybrid cell
Definition:

A cell which arose from a product of cell fusion and which contains a single nucleus that has genetic material from both of the original parents of the cell fusion product.

4038. hybrid DNA
Definition:

A double-stranded DNA molecule which was made by hybridizing two single-stranded DNA molecules from two different sources. If the two single-stranded DNA molecules have enough nucleotide sequences in common, they are able to form hydrogen bonds to each other’s common sequences.

4039. hybrid dysgenesis
Definition:

The inability of certain strains of the fruit fly Drosophila melanogaster to interbreed with each other because they produce offspring that are all sterile or offspring which have a high number of harmful mutations.

4040. hybrid enzyme
Definition:

An enzyme in a heterozygous individual which has subunits with slightly different sequences of amino acids than other copies of the same enzyme. This occurs because the two alleles of the genes which code for each subunit are slightly different (due to the heterozygosity), so that either of the two versions of the subunit could be produced for any copy of the enzyme.

4041. hybrid inviability
Definition:

The observation that certain hybrid organisms have lower fitness than the parent organisms; for example they grow more poorly or have lower survival rates. Hybrid inviability is the opposite of hybrid vigor.

4042. hybrid molecule
Definition:

A double-stranded nucleic acid molecule which was artificially created from two different single-stranded nucleic acid molecules from different sources, for the purpose of comparing their nucleotide sequences.

4043. hybrid plasmid
Definition:

A plasmid (circular DNA molecule) which is composed partly of the DNA of an organism’s (or virus’s) genome and partly of foreign DNA that has been inserted artificially.

4044. hybrid sterility
Definition:

The inability of a hybrid to produce viable offspring. Whether an animal hybrid is sterile or fertile depends mainly on how closely its two parent species are related. For example, mules (which are hybrids between male donkeys and female horses) are usually sterile, while hybrids between domestic dogs and wolves are fertile (hybrids between wolves and foxes are also fertile, but hybrids between dogs and foxes are sterile).

4045. hybrid swarm
Definition:

A group of morphologically distinctive individuals which results from the creation of hybrids between two parent species, then the backcrossing of the offspring to members of the parent species and the interbreeding among the hybrid individuals.

4046. hybrid-arrested translation
Definition:

The prevention of an mRNA molecule from being translated into a protein by hybridizing it to its corresponding cDNA or to a complementary mRNA. This is used to identify cDNA molecules - the scientist puts the cDNA molecule in question in a test tube with a number of mRNA molecules and observes which protein is no longer able to be made.

4047. hybridization
Definition:

1. The process of joining two complementary strands of DNA or one each of DNA and RNA to form a double- stranded molecule.
   
2. The mating of individuals from different species or sub-species.

4048. hybridization stringency
Definition:

The percentage of nucleotides which must match on two unrelated single-stranded nucleic acid molecules before they will base pair with each other to form a duplex, given a certain set of physical and chemical conditions. The hybridization stringency is used to determine when a hybridization probe and a target nucleic acid will come together, and can be set by the researcher by varying the conditions. In general, if the percentage of matching nucleotides is lower than 70 percent, the two single-stranded nucleic acid molecules are considered nonhomologous and any hybridization is considered nonstringent.

4049. hybridoma
Definition:

An immortalized, antibody-secreting cell line that is used to produce certain desirable antibodies; a hybridoma is created by fusing a lymphocyte with a special myeloma.

4050. hydathodes
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

An epidermal structure specialized for secretion, or for exudation, of water.

4051. hydraulic
Author:
Definition:

Pertaining to liquids (especially water) in motion and the mechanics of that motion.

4052. hydraulic control point
Author:
Definition:

1. The top of an obstruction to which stream flow must rise before passing over.
2. A point in the stream where the flow is constricted.

4053. hydraulic gradient
Author:
Definition:

1. The slope of the water surface.
2. The drop in pressure head per length in the direction of stream flow.

4054. hydraulic radius
Author:
Definition:

The cross-sectional area of a stream divided by the wetted perimeter.

4055. hydric
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Characterized by an abundant supply of water.

4056. hydric soil
Author:
Definition:

A soil that is saturated, flooded or ponded long enough during the growing season to develop anaerobic conditions in the upper part.

4057. hydro-mulching (hydromulching)
Author:
Definition:

Seeding of grasses, mixed with fertilizer, a wood pulp mulch, and a “tackifier” to stick the mix to the ground, applied by a machine blower in a wet condition to exposed, denuded slopes or embankments. (If no mulch is used, it is called hydro-seeding.)

4058. hydrocephalus (hydrocephaly)
Author: Guo Li
Definition:

Hydrocephalus is a disorder in which the volume of the cerebrospinal fluid (CSF) increases in association with dilatation of the ventricles of the brain. There is a condition called normal-pressure hydrocephalus which is associated with dementia.

4059. hydrogen (H, deuterium, tritium)
Definition:

Hydrogen is a gas element which has an atomic number of 1 and an atomic weight of 1.0079. It combines with oxygen to form water (H₂0) and is present in all organic compounds. A few types of bacteria can metabolize atmospheric hydrogen (H₂). Hydrogen gas itself is not poisonous, but when it mixes with air it can easily ignite or explode.

Hydrogen was discovered by Henry Cavendish in 1766 and was named by Lavoisier. There are two main isotopes of hydrogen: deuterium (²H) and tritium (³H, which is radioactive and is used in some glow-in-the-dark paints and as a tracer in biological studies).

4060. hydrogen bond
Definition:

A weak electrostatic link between an electronegative atom (such as oxygen) and a hydrogen atom which is linked covalently to another electronegative atom; hydrogen bonding is what makes water stick to itself.

4061. hydrogen peroxide
Definition:

This alkaline chemical has the formula H₂O₂ and the structure H-O-O-H, which is able to break apart into free radicals. It is a clear, dense liquid at room temperature which freezes at -41°C and boils at 150.2°C. It can be dissolved in water and alcohols. It is also toxic when concentrated and can be a fire and explosion hazard. Hydrogen peroxide is used in bleaches, dyes, cleansers, antiseptics, and disinfectants. It is generated by the body as a potentially harmful byproduct of aerobic cellular respiration which, if left alone, will cause extensive damage to DNA.

4062. hydrogenase
Definition:

An enzyme which oxidizes hydrogen (removes its electrons) and attaches it to another molecule.

4063. hydrogenation
Definition:

1. The adding of hydrogen to another molecule.
2. The adding of hydrogen to unsaturated hydrocarbons or fatty acids (hydrocarbons or fatty acids which contain carbon-carbon double bonds). Oils and fats used in making prepared foods are often hydrogenated to improve their shelf life.

4064. hydrograph
Author:
Definition:

A graph showing the stage, flow, velocity, or other property of water with respect to time.

4065. hydrography (adj.: hydrographic)
Author:
Definition:

The measurement or study of bodies of water and associated terrain.

4066. hydrolase
Definition:

An enzyme such as a lipase that catalyzes a hydrolysis reaction.

4067. hydrologic
Author:
Definition:

Pertaining to the cyclic phenomena of waters of the earth -— successively as precipitation, runoff, storage and evaporation, and quantitatively as to distribution and concentration.

4068. hydrology
Author:
Definition:

1. The branch of physical geography concerned with the behavior of water in the atmosphere, on the surface of the earth and underground.
2. The science dealing with the properties, distribution and circulation of water.

4069. hydrolysate
Definition:

The product of a hydrolysis reaction. Hydrolysates are generally named according to what reactant was hydrolyzed to come up with the product, for example "protein hydrolysate" if the reactant was a protein.

4070. hydrolysis
Definition:

A chemical reaction in which water is used to break down a compound; this is achieved by breaking a covalent bond in the compound by inserting a water molecule across the bond. The opposite of this is a dehydration-condensation reaction.

4071. hydrolytic enzyme
Definition:

An enzyme which uses hydrolysis to break down its substrate.

4072. hydronium ion
Definition:

A positively charged ion that is water with an additional hydrogen atom (H₃O).

4073. hydropathy plot
Definition:

A graph which shows how hydrophobic each amino acid in a polypeptide is versus where it is located on the polypeptide. The hydropathy plot is used to find clusters of hydrophobic amino acids, which could indicate that the polypeptide in question is a transmembrane protein. A transmembrane protein has hydrophilic parts which protrude out on either side of the cellular membrane, and a hydrophobic center which lies within the membrane.

4074. hydrophilic
Definition:

Describes a substance that attracts, dissolves in, or absorbs water.

4075. hydrophilic signaling molecule
Definition:

A type of molecule which, because it is easily dissolved in water (it is hydrophilic), can easily move through cell membranes and thus can be secreted from one cell and move into a target cell where it triggers a particular event. Many hormones and growth factors are hydrophilic signaling molecules.

4076. hydrophily
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Water pollination.

4077. hydrophobic (hydrophobia)
Definition:

Exhibiting hydrophobia; refers to:

1. A substance that repels or will not absorb water.
2. An organism that is harmed by water or a wet environment.
3. A person that has an irrational fear of water.
4. An animal suffering from rabies.

4078. hydrophobic bonding
Definition:

1. The attraction of hydrophobic and nonpolar molecules to each other in the presence of water (or another polar fluid).
2. The attraction of the hydrophobic (or nonpolar) parts of molecules to each other in the presence of water (or another polar fluid).
Because hydrophobic molecules are repelled by water, they will form clumps with one another so that the clumped interiors are hidden away from water.

4079. hydrophobic effect
Definition:

The tendency for the nonpolar portions of a group of lipid molecules to clump together with one another and exclude water and other polar molecules. The polar portions of the lipid molecules end up facing out. The hydrophobic effect is primarily responsible for the construction of lipid bilayers.

4080. hydrophobic interaction
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

The attractive force between molecules due to the close positioning of non-hydrophilic portions of the two molecules.

4081. hydrophobicity
Definition:

A measure of how insoluble (undissolvable) a given molecule is when in water or other polar liquids.

4082. hydrophyte
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

An aquatic plant living on or in water.

4083. hydrophyte (hygrophyte)
Definition:

A plant which can grow only in very wet soil, or which grows with its leaves partly or completely underwater.

4084. hydrophytic vegetation
Author:
Definition:

Plant life growing in water or on a substrate that is at least periodically deficient in oxygen as a result of excessive water content.

4085. hydroplasma
Definition:

The liquid portions of protoplasm. All of the liquid contained within a live cell.

4086. hydroponics
Definition:

The scientific study of the growth of plants in an artificial liquid nutrient medium instead of in soil.

4087. hydropote
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

A cell or cell group found on the lower epidermis of some species such as Nymphaea. These cells are thought to function in the uptake of ions from the water.

4088. hydrops fetalis
Definition:

A severe form of the genetic disorder thalassemia in which all four alpha chain polypeptides making up the hemoglobin molecule (the protein which transports oxygen in the body) are missing due to a defect in the gene which codes for them. As a result, affected individuals die at or before birth.

4089. hydrosalpinx
Definition:

This condition is characterized by the fallopian tubes being chronically distended with fluid; this occurs after an infection of the tubes (salpingitis) has subsided.

4090. hydroseed (hydro-seeding)
Author:
Definition:

To spray land with a mixture of water and seeds, thereby dispersing and watering the seeds simultaneously.

4091. hydrosere
Definition:

An ecological community which results when plants migrate to open water and decompose, creating deposits of moss or peat.

4092. hydroskeleton (hydrostatic skeleton)
Definition:

A type of skeleton found in many soft-bodied invertebrates which consists of water-filled body cavities controlled by muscles. Hydroskeletons are found in echinoderms (starfish, sea urchins), annelids (earthworms), nematodes, and a number of other wormlike invertebrate phyla.

4093. hydrosphere
Definition:

This is the broad name for the water above, on or in the earth's crust, including oceans, seas, lakes, ground water, and atmospheric moisture.

4094. hydrostatic
Author:
Definition:

Pertaining to pressure by and within water due to gravitation acting through depth.

4095. hydrothermal vent
Definition:

A natural spring which vents warm or hot water on the sea floor; associated with spreading of the Earth's crust.

4096. hydrotrope (hydrotropic)
Definition:

A chemical substance which causes other organic substances that are only slightly soluble to become more easily dissolved.

4097. hydrotropism
Definition:

The growth or movement of an organism in the direction of water. The influence of an organism's growth or movements by the presence of water.

4098. hydroxy acid
Definition:

Any molecule which is an acid and which has a hydroxyl group (an -OH or alcohol group) attached to it.

4099. hydroxyapatite (hydroxylapatite)
Definition:

The primary mineral component of bone. It has the chemical formula of 3Ca₃(PO₄)₂·Ca(OH)₂ and in crystal form is a needle-shaped crystal which is arranged with other needles in a rosette. It melts above 1100°C and cannot be dissolved in water. A form of the mineral is used by molecular biologists in certain column chromatography lab techniques to separate single-stranded nucleic acids from double-stranded ones (the mineral tends to hang on to the double-stranded molecules while letting the single-stranded ones through the column unimpeded), or to separate different proteins. "Hydroxyapatite" also applies to similar minerals which have Ba (barium) or Sr (strontium) in the place of the Ca (calcium) atoms. These minerals are found in deposits of phosphorite and in biological tissue.

4100. hydroxychloroquine
Definition:

A drug used to treat and prevent malaria and to treat the symptoms of lupus erythematosus. It is also used to treat rheumatoid arthritis when used in combination with other drugs. It has the chemical formula of C₁₈H₂₆ClN₃O.

4101. hydroxyl group
Definition:

An -OH or alcohol group on a larger molecule. The oxygen is single-bonded to the hydrogen and has one free bond to the rest of the molecule. Molecules with one or more hydroxyl groups are called alcohols.

4102. hydroxylase
Definition:

A type of enzyme which adds -OH groups to its substrate during hydroxylation reactions by attaching oxygen atoms to it.

4103. hydroxylation
Definition:

A reaction which adds one or more hydroxyl groups (-OH groups) to a molecule while oxidizing it.

4104. hydroxyproline
Definition:

An amino acid derived from proline (one of the twenty amino acids used to make proteins) which is found in gelatin and collagen. It has the chemical formula C₅H₉NO₃. Hydroxyproline helps stabilize the collagen molecule. The making of hydroxyproline by the body is dependent on the presence of vitamin C; if there is not enough vitamin C in the body and not enough hydroxyproline is made, the collagen fibers weaken. This results in the skin lesions which are a part of scurvy (a disease caused by a deficiency of vitamin C).

4105. hygiene
Definition:

The science of health and how to maintain it. A condition or practice which promotes good health.

4106. hygromycin (hygromycin A)
Definition:

An antibiotic from the bacterial species Streptomyces hygroscopicus and Streptomyces noboritoensis. It is useful against a wide range of different pathogenic microbes.

4107. hygroscopic
Definition:

1. Pertaining to tissue or substance that is sensitive to water or water vapor.
2. Pertaining to a substance that accelerates the condensation of water vapor.
3. Pertaining to water that is electrostatically bound to the surface of dirt particles and is therefore unavailable to plants.

4108. hymenal caruncle
Author: Guo Li
Definition:

A hymenal caruncle is a small red fleshy swelling at the mucosal opening of the vagina.

4109. hyoscyamine
Definition:

A chemical with the formula C₁₇H₂₃O₃N which is a white powder at room temperature and which melts at 108.5°C. It comes from plants such as henbane and belladona. Hyoscyamine is used medically as the levorotatory isomer of racemic atropine and as an anticholinergic alkaloid.

4110. hypanthium
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A cup or tube bearing floral parts above the base, and often above the top, of the ovary of a flower. Compare calyx tube.

4111. hyper-
Definition:

A prefix which indicates that the word has to do with above, beyond, more, extra, excess, high, etc. Hyper- is the opposite of the prefix hypo-.

4112. hyperaldosteronism
Author: Guo Li
Definition:

Hyperaldosteronism is characterized by hypertension, polyuria, polydipsia, and hypokalemia.

4113. hyperandrogenism
Author: Fertilitext
Definition:

Hyperandrogenism is a term describing excessive production of androgens in women; it is frequently a cause of hirsutism and also associated with polycystic ovarian disease (PCOD).

4114. hyperbaric chamber
Definition:

A high (atmospheric) pressure chamber. Hyperbaric chambers are used to treat certain medical conditions, such as gangrene or anaerobic infections, where high concentrations of oxygen are helpful.

4115. hyperbilirubinemia
Definition:

A medical condition where abnormally high concentrations of the bile pigment bilirubin are found in the bloodstream. This can result in jaundice. Hyperbilirubinemia sometimes occurs in premature babies.

4116. hypercalcemia
Definition:

A medical condition in which abnormally high concentrations of calcium compounds are found in the bloodstream.

Hypercalcemia is the opposite of hypocalcemia.

4117. hypercalcuria (hypercalciuria)
Definition:

A medical term which means that abnormally high concentrations of calcium are present in the urine.

4118. hypercholesteremia (hypercholesterolemia)
Definition:

A medical term which means that abnormally high concentrations of cholesterol are present in the bloodstream. This can lead to heart disease, hardening of the arteries, heart attacks, and strokes.

4119. hyperchromic anemia
Definition:

1. A type of anemia which results when the body lacks sufficient vitamin B.
2. A type of anemia where the red blood cells are thicker than normal, resulting in more deeply colored blood.

4120. hyperchromicity (hyperchromic shift, hyperchromic effect)
Definition:

An increase in the optical density of a solution with nucleic acids in it such that it is able to absorb more ultraviolet (UV) radiation, which occurs when the double-stranded nucleic acid molecules denature into single-stranded molecules.

4121. hyperergia
Definition:

A condition where the body has a much larger immune response to a given antigen than normal, including hypersensitive allergic reactions.

4122. hyperesthesia (oxypathia, oxypathy)
Definition:

A condition where the body is much more sensitive than normal to stimulation from such things as light, touch, or pain.

The opposite of hyperesthesia is hypoesthesia.

4123. hyperglycemia
Author: PharmInfoNet
Definition:

Too high a level of glucose (sugar) in the blood; a sign that diabetes is out of control. Many things can cause hyperglycemia. It occurs when the body does not have enough insulin or cannot use the insulin it does have to turn glucose into energy. Signs of hyperglycemia are a great thirst, a dry mouth, and a need to urinate often. For people with insulin-dependent diabetes, hyperglycemia may lead to diabetic ketoacidosis.

4124. hypergonadotropic
Author: PharmInfoNet
Definition:

Increased production of gonad-stimulating hormone from the anterior pituitary gland.

4125. hyperimmune (hyperimmunity)
Definition:

A state where the body's immune system is extremely reactive against a particular antigen when it normally would not be. This occurs when the antigen is introduced into the body in large amounts (for example, by repeated injections) such that lots of hyperimmune antibodies build up against it.

4126. hyperimmune antibody
Definition:

An antibody which occurs in a hyperimmune individual and which targets the antigen that has brought on the hyperimmunity.

4127. hyperimmune serum
Definition:

A type of antiserum which is made from the blood of a hyperimmune individual. The hyperimmune serum contains lots of hyperimmune antibodies against a particular antigen and can be used to immunize others against the same antigen.

4128. hyperinsulinism
Definition:

A state in which too much insulin is present in the blood (which may result from too much insulin being made and secreted by the pancreas), thus causing blood glucose (a type of sugar) levels to become too low, which may then result in insulin shock.

4129. hyperkeratosis
Author: PharmInfoNet
Definition:

A disease resulting in the abnormal growth of the corneous (hornlike) layer of the skin.

4130. hyperlipidemia
Author: PharmInfoNet
Definition:

Too high a level of fats (lipids) in the blood.

4131. hypermorph
Definition:

A mutant gene which causes the activity that it influences to increase.

4132. hypermutable phenotype
Definition:

A bacterial strain with the hypermutable phenotype is one which is unable to replace uracil (a nucleotide normally found only in RNA) with cytosine in its DNA when the uracil appears in the DNA by mistake. As a result, the strain undergoes much higher rates of mutation than other bacterial strains.

4133. hyperosmotic
Definition:

Describes a cell or other membrane-bound object which has a higher concentration of solutes than its surroundings. For example, a cell which has a higher salt concentration than the salt concentration of the surrounding medium is hyperosmotic. Water is more likely to move into the cell through osmosis as a result. This is the opposite of hypoosmotic.

4134. hyperpigmentation
Author: PharmInfoNet
Definition:

Abnormally increased pigmentation.

4135. hyperpituitarism
Definition:

A medical condition where the pituitary gland produces abnormally high levels of growth hormones. This can result in gigantism in children and acromegaly in adults.

4136. hyperplasia
Author: PharmInfoNet
Definition:

1. A medical condition where an organ or tissue becomes larger because there are more cells making up the organ or tissue.
2. A plant disease or injury where water flow through its vascular tissues has been blocked.

4137. hyperploidy (hyperploid)
Definition:

Describes a cell or organism which has more than the normal total number of chromosomes. For example, humans normally have 46 chromosomes per cell - but if a human individual has 47 or more chromosomes per cell, then that person is hyperploid. Hyperploidy is the opposite of hypoploidy.

4138. hyperpolarization
Definition:

A shift in the electrical charge, or polarity, within a cell toward the negative.

4139. hyperprolactinemia
Author: Fertilitext
Definition:

Hyperprolactinemia means a person has excessive prolactin in his or her blood.

4140. hyperproliferation
Definition:

An abnormally high rate of cell division (which results in a rapid proliferation of the cells). This occurs, for example, in tumors and cancers.

4141. hypersensitive site (hypersensitivity site)
Definition:

A short segment of DNA which is especially prone to being cleaved by endonuclease enzymes like DNase. These sites tend to be within gene promoter regions.

4142. hypersensitivity
Definition:

An increase in the immune reaction by the body to a foreign substance such as an antigen or allergen, often caused by previous exposure to the same substance. Many food allergies, such as to nuts, work in this manner.

4143. hypertely
Definition:

An evolutionary term describing a state in which an organism's body size or body structure becomes overspecialized such that it becomes a disadvantage. For example, overly large body size, or color/marking imitations of another species such that camouflage is no longer possible. Also, many traits which arise from sex selection tend to be disadvantageous overall to the organism (in terms of survival) but advantageous when the organism wants to attract a mate.

4144. hyperthermia (adj.: hyperthermic)
Definition:

1. An abnormally high body temperature.
2. The treatment of diseases (infections, cancer, etc.) with heat.

4145. hyperthermophile
Definition:

A prokaryote which grows best in temperatures of 80 degrees C or higher.

4146. hyperthermophilic (hyperthermophile)
Definition:

Describes an organism that lives in a very high-temperature environment (well over 50 degrees C).

4147. hypertonia (hypertonicity)
Definition:

More than usual tension in a body part, particularly the skeletal muscles or arteries. Hypertonia is the opposite of hypotonia.

4148. hypertonic solution
Definition:

Any solution which has a higher osmotic pressure than another solution (that is, has a higher concentration of solutes than another solution). A solution which contains a higher concentration of solutes than the cells that it is bathing, so that water is drawn out of the cells and into the solution by osmosis. A hypertonic solution is the opposite of a hypotonic solution.

4149. hypertrophied lenticels
Author:
Definition:

An exaggerated (oversized) pore on the stem of woody plants through which gases are exchanged between the plant and the atmosphere; serves to increase oxygen to plant roots during periods of inundation or soil saturation.

4150. hypertrophy
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Excessive growth due to an increase in cell size.

4151. hypertropia
Definition:

This is a misalignment of the eye in which the eye is turned upward.

4152. hypervariable region (hypervariable site)
Definition:

The tips of the Y-shaped antibody protein, consisting of amino acid chains whose sequences vary greatly from antibody to antibody so that many different types of antigens can be combined with them. These occur within the variable regions of the light and heavy chains. Compare constant region.

4153. hyperventilation
Author: Guo Li
Definition:

Hyperventilation is the condition of breathing excessively and often with effort; a clinical sign. The normal rate of respiratory rate can be up to 35 per minute for the an adult and 50 per minute for a newborn. However, biochemically, hyperventilation means ventilation to keep the partial pressure of oxygen in the arterial blood lower than its normal value of 40 mmHg

4154. hypervitaminosis (supervitaminosis)
Definition:

Poisoning due to a person absorbing too much of a particular vitamin into his or her body. This typically occurs because a person overdoses on vitamin supplements. Different symptoms result from different vitamins. Examples include hypervitaminosis A and hypervitaminosis D.

4155. hypervitaminosis A
Definition:

Poisoning due to too much vitamin A within the body. Symptoms include irritability, fatigue, changes in the skin, hair loss, headache, and abdominal discomfort.

4156. hypervitaminosis D
Definition:

Poisoning due to too much vitamin D within the body. Symptoms include headache, weakness, disturbed digestion, increased blood pressure, and tissue calcification (of certain tissues).

4157. hyphae
Definition:

The fine, branching tubes which make up the body (or mycelium) of a multicellular fungus.

4158. hypmenorrhea
Definition:

Hypmenorrhea is unusually light menstrual bleeding.

4159. hypo-
Definition:

A prefix which indicates that the word has to do with below, under, less, deficient, too little, low, etc. Hypo- is the opposite of the prefix hyper-.

4160. hypoallergenic
Definition:

Describes substances (like medicine, cosmetics, toiletries) which are very unlikely to cause an allergic reaction.

4161. hypocalcemia
Definition:

A medical condition in which the blood has abnormally low concentrations of calcium; this can result in muscle cramps, abdominal cramps, spasms, and hyperactive deep tendon reflexes. Hypocalcemia is the opposite of hypercalcemia.

4162. hypochromicity (hypochromic shift, hypochromic effect)
Definition:

A decrease in the optical density of a solution with nucleic acids in it such that it is less able to absorb ultraviolet (UV) radiation, which occurs when single-stranded nucleic acid molecules renature into double-stranded molecules.

4163. hypocotyl
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The part of the stem of an embryo or young seedling below the cotyledonary node.

4164. hypodermis
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A layer of cells below the epidermis.

4165. hypoesthesia (hypesthesia)
Definition:

A condition where the body is much less sensitive than normal to stimulation from such things as light, touch, or pain. The opposite of hypoesthesia is hyperesthesia.

4166. hypogeal
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of germination, having the cotyledon(s) remaining within the seed coat. Compare epigeal.

4167. hypoglossal nerve (cranial nerve XII)
Author: Guo Li
Definition:

This is the motor nerve for the muscles of the tongue

4168. hypoglycemia (adj. hypoglycemic)
Author: PharmInfoNet
Definition:

Too low a level of glucose (sugar) in the blood. This occurs when a person with diabetes has injected too much insulin, eaten too little food, or has exercised without extra food. A person with hypoglycemia may feel nervous, shaky, weak, or sweaty, and have a headache, blurred vision, and hunger. Taking small amounts of sugar, sweet juice, or food with sugar will usually help the person feel better within 10-15 minutes. See also: insulin shock.

4169. hypogonadism
Author: PharmInfoNet
Definition:

Below normal gonad (sex gland) function.

4170. hypogynous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Arising below the level of insertion of the ovary (often applied, loosely, to a flower in which the sepalS, petals and stamens are inserted below the ovary). Compare perigynous, epigynous.

4171. hypolimnion
Author:
Definition:

Lowermost, noncirculating layer of cold water in a thermally stratified lake, usually deficient in oxygen.

4172. hypomenorrhea
Definition:

A medical condition where the monthly menstruation period is abnormally short or where blood flow during menstruation is abnormally low.

4173. hypoosmotic
Definition:

Describes a cell or other membrane-bound object which has a lower concentration of solutes than its surroundings. For example, a cell in a high-salt-concentration medium is hypoosmotic. Water is more likely to move out of the cell by osmosis as a result. This is the opposite of hyperosmotic.

4174. hypopituitarism
Definition:

A medical condition where the pituitary gland produces lower than normal levels of its hormones.

4175. hypoplasia
Definition:

1. A medical condition where an organ or tissue has less than the normal amount of cells that it needs to fully develop. Such an organ or tissue is smaller in size than normal.
2. Destruction of part of an organ or tissue which results in its becoming atrophied.
3. Any plant disease which results in lower than normal numbers of cells being produced, so that the plant is unable to fully develop its organs and/or tissues.

4176. hypoploidy (hypoploid)
Definition:

Describes a cell or organism which has less than the normal total number of chromosomes. For example, humans normally have 46 chromosomes per cell - but if a human individual has 45 or fewer chromosomes per cell, then that person is hypoploid. Hypoploidy is the opposite of hyperploidy.

4177. hypoproliferative anemia
Definition:

Anemia which results from abnormally low levels of red blood cells and hemoglobin in the blood. It is caused because the person has too few of the stem cells which make the red blood cells.

4178. hypostatic
Definition:

Describes a type of interaction between two genes which are not alleles of one another. One gene suppresses the expression of the other gene.

4179. hypotension (low blood pressure)
Author: PharmInfoNet and Guo Li
Definition:

Low blood pressure or a sudden drop in blood pressure. A person rising quickly from a sitting or reclining position may have a sudden fall in blood pressure, causing dizziness or fainting.

While most people have normal systolic pressure above 100 mmHg and diastolic pressure above 50 mmHg, blood pressures lower than these numbers are still regarded as normal for some individuals whose normal blood pressures are low.

4180. hypothalamus
Definition:

A structure in the lower part of the brain that is connected to and controls the pituitary gland.

4181. hypothesis
Definition:

In science, an idea or proposition that is based on certain observations about the natural world. Hypotheses are subject to scientific evaluation. Compare with law and theory.

4182. hypothyroidism
Author: Fertilitext
Definition:

Hypothyroidism means underactivity of the thyroid gland.

4183. hypotonia
Definition:

Less than usual tension in any body part, especially the arteries or the skeletal muscles. In the case of muscles, this can result in the ability to stretch the relaxed muscle much farther than normal. Hypotonia is the opposite of hypertonia.

4184. hypotonic solution
Definition:

Any solution which has a lower osmotic pressure than another solution (that is, has a lower concentration of solutes than another solution). A solution which contains a lower concentration of solutes than the cells that it is bathing, so that water flows into the cells from the solution by osmosis. A hypotonic solution is the opposite of a hypertonic solution.

4185. hypotriglyceridemia (hypotriglyceridaemia)
Definition:

In medicine, this defines the situation characterized by a decreased blood triglyceride content.

4186. hypotropia
Definition:

This is a misalignment of the eye in which the eye is turned downward.

4187. hypovirulence
Definition:

Where a disease-causing organism is less able to cause the disease, or where the disease which results is milder. Decreased virulence in a pathogen.

4188. hypovolemic shock
Definition:

A medical condition where there are abnormally low levels of blood plasma in the body, such that the body is unable to properly maintain blood pressure, cardiac output of blood, and normal amounts of fluid in the tissues. This results in a state of deep physical depression.

4189. hypoxanthine
Definition:

A type of purine. A metabolic reaction intermediate in the breakdown of adenosine and in the formation of nucleic acids (by a salvage pathway).

4190. hypoxanthine-aminopterin-thymine (HAT) medium
Definition:

A type of agar growth medium (a selective medium) which is used to select for cells that are able to make their nucleic acids out of hypoxanthine and/or thymine. All cells are prevented from making nucleotides by any other means (due to the presence of aminopterin or other drugs in the medium), so cells which are unable to use hypoxanthine and/or thymine to do this will not grow, multiply, and become visible colonies. This leaves the cells which are being selected for.

4191. hypoxanthine-guanine phosphoribosyl tranferase marker (HGPRT marker)
Definition:

The gene which codes for the enzyme hypoxanthine-guanine phosphoribosyl transferase. It is a selectable marker because cells which have a defective version of this gene are resistant to poisoning by toxic purine derivatives which result from the metabolic pathway that the HGPRT enzyme catalyzes. (The purine derivatives are toxic because they incorporate into DNA as a result of the HGPRT enzyme's actions). Because the defective gene cannot produce the enzyme, no toxic purine derivatives are produced; the gene can therefore be selected for.

4192. hypoxanthine-guanine phosphoribosyl transferase (HGPRT)
Definition:

An enzyme which plays an important role in the making of ATP and GTP from guanine -- the only way guanine, adenine, or other purine molecules are able to become part of nucleic acids. Biologists study gene action via the incorporation of modified nitrogenous bases into DNA by manipulating the metabolic role which this enzyme plays. Similarly, the enzyme thymidine kinase is used for the same purpose by biologists because it fills the same important and unique role for the pyrimidines (thymine, cytosine, uracil, etc.).

4193. hypoxemia
Author: PharmInfoNet
Definition:

Below-normal oxygen content in arterial blood.

4194. hypoxia
Definition:

1. A medical condition in which the blood is carrying abnormally low levels of oxygen.
2. A condition in which an organism is living in an environment that doesn't contain enough oxygen to keep it alive.

4195. hysterectomy
Author: Fertilitext
Definition:

A hysterectomy is the surgical removal of the uterus.

4196. hysterosalpingogram (HSG)
Author: Fertilitext
Definition:

An x-ray examination of the uterus and fallopian tubes.

4197. hysteroscopy (hysteroscope)
Author: Fertilitext
Definition:

Hysteroscopy is the examination of the inner cavity of the uterus through a fiberoptic telescope inserted through the vagina and cervical canal.

4198. I band
Definition:

A band of area within muscle tissue which consists of the Z line, the sarcomeres (muscle units) on either side of it, and the actin filaments which attach the sarcomeres together across the Z line.

4199. I blood group
Definition:

A blood type classification based on a group of antigens which react with the antibodies anti-I and anti-i. The blood type occurs as a rare phenotype (called i) and in individuals with acquired (as opposed to inherited) hemolytic anemia.

4200. i gene (lac I operon)
Definition:

A gene which is a part of the lac operon. It codes for a repressor protein, which prevents the transcription of genes that code for the enzymes that bring lactose into the bacterial cell and use it as a carbon source. The repressor protein prevents the unnecessary production of these enzymes when no lactose is present.

4201. Ia antigen (class II histocompatibility antigen)
Definition:

A type of antigen which is responsible for any immune reaction, or rejection, of tissue grafts attached to the body which come from a genetically dissimilar donor.

4202. iatrogenic
Definition:

Describes a negative reaction to medical treatment or therapy, usually as a result of an infection caused by the treatment. Also may refer to a disorder which arose due to the doctor's manner of exam or discussion of the patient.

4203. ibuprofen
Definition:

A chemical which is used as an alternative to aspirin to treat headaches and other body pain. It has the chemical formula of C₁₃H₁₈O₂ and at room temperature is a white powder. It is also used to treat inflammation symptoms of rheumatoid arthritis and osteoarthritis.

4204. ice nucleation bacteria
Definition:

A type of bacteria which is able to act as a nucleation site around which ice crystals can form.

4205. ichthy- (ichthyo-)
Definition:

A prefix which indicates that the word has something do with fish or fishlike. For example, ichthyology is the study of fish.

4206. ichthyosis
Author: Guo Li
Definition:

Ichthyosis is any of a group of genetic skin diseases characterized by the presence of excessive scales. Some of the better known are: x-linked ichthyosis, empidermolytic hyperkeratosis, and ichthyosis vulgaris.

4207. icosahedron
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A geometrical shape occurring in many virus particles, with 20 triangular faces and 12 corners.

4208. icteric
Author: Guo Li
Definition:

Pertaining to jaundice.

4209. icterus gravis (massive hepatic necrosis, malignant jaundice)
Definition:

A condition which includes jaundice (icterus), high fever, and delirium. Icterus gravis is either a rare complication of viral hepatitis and other liver diseases, a result of exposure to hepatotoxic substances, or a result of being insensitive to drugs.

4210. icterus gravis neonatorum (extreme newborn jaundice)
Definition:

A condition of extreme jaundice (icterus) in a newborn which may result from a blockage in the bile duct in the liver, an immune reaction of the mother to the baby because of Rh factor (if the mother is negative and the baby is positive), erythroblastosis fetalis (a type of anemia which occurs in Rh⁺ babies of Rh^- mothers), inflamed blood vessels, or complications due to the venereal disease syphilis involving liver cirrhosis.

4211. ictus epilepticus
Author: Guo Li
Definition:

An epileptic attack.

4212. ICU (intensive care unit)
Author: Guo Li
Definition:

An intensive care unit is a hospital ward specially equipped with trained personnel and facility to care for patients who have unstable vital signs, arrythmias, fluid and electrolyte inbalance, and respiratory failure.

4213. ideal solution (Raoult's law)
Definition:

An ideal solution is any solution which obeys Raoult's law. Raoult's law gives the relationship between a solution's vapor pressure and a solvent's vapor pressure when the solute has no measurable vapor pressure (is nonvolatile). The law is stated as follows: "The partial pressure of a solvent over a solution, P₁, is given by the vapor pressure of the pure solvent, P°₁, times the mole fraction of the solvent in the solution, X₁," or

P₁ = X₁·P°₁

4214. ideotype (idiotype)
Definition:

Any specimen which is not the holotype and which was not collected from the same location as the holotype, but which has been determined to be a member of the same taxon as the holotype by the original author of the holotype name.

4215. idioblasts
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Plant cells containing oil, gum, calcium, or other products, and appearing to help provide mechanical support.

4216. idiogram
Definition:

A diagram of a karyotype, which shows the number, sizes, and shapes of each chromosome in the cell.

4217. idiopathic
Author: PharmInfoNet
Definition:

Describing a disease or condition of unknown cause.

4218. idiopathic thrombocytopenic purpura (ITP)
Author: Guo Li
Definition:

Idiopathic thrombocytopenic purpura is an autoimmune disorder involving the creation of IgG autoantibodies against blood platelets.

4219. idiopathy
Definition:

A disease or medical condition which arises without a known cause.

4220. idiophase
Definition:

A period during the growth of a culture when the anabolic pathways of the cultured organisms are altered to make different biomolecular products than normal.

4221. idiosome
Definition:

A general term for almost any specialized organelle or a particular region of a cell.

4222. idiotope
Definition:

The antigenic peptide sequence located on an antibody's variable region near the antigen binding site. Every antigen is associated with a specific idiotope. See also idiotype.

4223. idiotroph
Definition:

A commercially-grown fungi or bacterium that has suffered a mutation that renders it unable to synthesize the substances for which it has been cultured.

4224. idiotype (adj. idiotypic)
Definition:

The characteristics of an antibody that make it unique; the idiotype is determined by the antibody's idiotope.

4225. idiotypic variation
Definition:

The variation of antigens on the surfaces of proteins which results from differences in the genes which code for them.

4226. IgA
Definition:

A class of immunoglobulin proteins found in such bodily fluids as saliva. One of five classes of immunoglobulin.

4227. IgD
Definition:

A class of immunoglobulin proteins which are found attached to the surfaces of B lymphocytes. It is also weakly present in blood serum. One of five classes of immunoglobulin.

4228. IgE
Definition:

A class of immunoglobulin proteins which are produced in response to the presence of allergens and which bind to mast cells (causing the mast cells to produce histamines). One of five classes of immunoglobulin.

4229. IgG
Definition:

A class of immunoglobulin proteins which are the primary type found in the blood serum of humans. One of five classes of immunoglobulin.

4230. IgM
Definition:

A class of immunoglobulin proteins which have complement fixation antibodies and which are excellent at attacking a certain type of antigen (ones with repeated antigenic determinants), including ones found on bacterial cells. One of five classes of immunoglobulin.

4231. IHSS (idiopathic hypertrophic subaortic stenosis)
Author: Guo Li
Definition:

Idiopathic hypertrophic subaortic stenosis is a form of cardiomyopathy in which the apex or septum of the heart is hypertrophied such that together with the anterior mitral valve leaflet, an obstruction to blood flow during systole is formed. In some cases it is an autosomal dominant trait with variable expression.

4232. ilarvirus
Definition:

A virus which causes the plant disease "prunus necrotic ringspot virus" and is spread through sap and seeds.

4233. Ilarvirus group (isometric labile ringspot viruses, tobacco streak virus group)
Definition:

A group of three-part plant viruses which uses single-stranded RNA to code its genome and which are spread through seeds and pollen to infect a wide range of host plants.

4234. ileitis
Definition:

Ileitis is inflammation of the ileum, the part of the small intestine that is near the large intestine.

4235. ileostomy
Author: Guo Li
Definition:

An ileostomy is performed by having the ileum brought through the rectus abdominis muscle, everted upon itself, and its mucosa sutured to the skin. It diverts the fecal material so the functioning of the distal bowel segment is not required.

4236. ileum
Definition:

The part of the small intestine that is near the large intestine.

4237. illegitimate recombination
Definition:

Genetic recombination between two segments of DNA which are not homologous, and which occurs at random locations within their nucleotide sequences. Such a recombination is a rare event.

4238. imaginal disc
Definition:

One of a series of disc-shaped structures in a fruit fly embryo which are located symmetrically along either side of the body. The imaginal discs are present within the larva and eventually develop into the body parts of the adult fruit fly during the pupal stage.

4239. imbricate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of perianth parts, having the edges overlapping in the bud. Compare valvate.

4240. imbricate
Definition:

Overlapping; describes something with many units in an overlapping arrangement, such as shingles on a roof or flat pebbles, or where all units in a structure have their long axes parallel to one another and pointing diagonally in the same direction (but not in the same plane as the bedding surface). This includes both sedimentary structures as in a siliciclastic deposit, and certain arrangements of rock masses between a series of parallel thrust faults.

4241. imipramine (Janimine, Tofranil)
Definition:

This tricyclic drug is used to treat depression.

4242. immediately dangerous to life or health concentration (IDLH)
Definition:

This is a regulatory value defined as the maximum exposure concentration in the workplace from which one could escape within 30 minutes without suffering symptoms which would interfere with escaping ans without suffering any irreversible health effects.

4243. immobilization
Definition:

1. The prevention of movement.
2. The permanent attachment of enzymes, bacteria or other cells (such as plant or animal) to a hard substrate or within a stable matrix via any of a number of physical and/or chemical means.

4244. immobilized enzyme
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

An enzyme attached to a solid support over which substrate is passed and is converted into product.

4245. immortalization
Definition:

1. Causing something (or someone) to exist (or live) forever.
2. The transformation of a line of lab-cultured cells into a line which is able to grow unrestrictedly (given ample nutrients).

4246. immortalized cells
Definition:

Cells which have been transformed so that they are able to grow and reproduce without restriction (given ample nutrients).

4247. immortalizing oncogene
Author: Susan A.Hagedorn
Definition:

A gene that upon transfection enables a primary cell to grow indefinitely in culture.

4248. immune
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

1. An adjective, when a human or animal body which is able to resist infectious disease because of either previous infection, immunization/vacination, or contact with the immunogen/ antigen, then the human or animal is immune to this disease.
2. As a noun, the state of immunity.

4249. immune adherence
Definition:

The tendency of antigen-antibody complexes to stick to nearby red blood cells, certain white blood cells (the macrophages and PMN's), and blood platelets of non-primate animals (animals other than humans, other apes, and monkeys) when a complement is present.

4250. immune gamma globulin (gamma globulin)
Definition:

A concentration of gamma globulin proteins from the donated blood serum of many human donors, which is used as a drug to boost the immune system. It is used to treat such diseases as hepatitis A, measles, rubella, immunoglobulin deficiencies, and immunodeficiency diseases such as AIDS.

4251. immune hemolysis
Definition:

The rupturing, or lysis, of red blood cells after antibodies have attached to their surface proteins (antigens) and complement is present.

4252. immune lysin
Definition:

A substance (such as an antibody or a toxin) which causes cells to lyse (rupture) when complement is present.

4253. immune oposonin
Definition:

A component of blood which is produced during bacterial infections and which helps the process of phagocytosis (engulfment) of the bacterial cells by white blood cells.

4254. immune precipitation
Definition:

A lab technique used to separate a specific protein molecule from a mixture, which involves attaching a particular antibody to it and then precipitating them out of solution.

4255. immune protein
Definition:

An immunoglobulin or antibody protein which is produced in reaction to the presence of a specific antigen, and which then reacts with that antigen.

4256. immune reaction
Definition:

The reaction of the immune system to the presence of an antigen, which includes making antibodies and developing immunity to the antigen on a cellular level. Compare with immune response.

4257. immune response
Definition:

The reaction of the body as a whole (not just the immune system, as in an immune reaction) to the presence of an antigen, which includes making antibodies, developing immunity, developing hypersensitivity to the antigen, and developing tolerance.

4258. immune surveillance
Definition:

The prevention of the growth of tumor cells by the immune system.

4259. immune system
Definition:

The cells and tissues which are responsible for recognizing and attacking foreign microbes and substances in the body.

4260. immune-response gene
Definition:

Any of several genes of the major histocompatibility complex that control the immune response of lymphocytes to specific antigens.

4261. immunization
Definition:

A process that increases an organism's reaction to antigen and therefore improves its ability to resist or overcome infection.

4262. immunization therapy
Definition:

Medical treatment with antiserum and antigenic substances such as vaccines.

4263. immunoadsorbent
Definition:

A substance used to separate antigens from a mixture, usually as a part of immunoaffinity chromatography. The immunoadsorbent is a solid matrix to which antibodies are bound; as the mixture flows through the column and past the stationary immunoadsorbent within, the antigens become attached to the antibodies and stay within the column while the rest of the mixture continues through to the end.

4264. immunoaffinity chromatography
Definition:

A type of column chromatography which is used to separate antigens from a mixture. The lab technique makes use of an immunoadsorbent -- a solid, stationary matrix within the column to which antibodies are attached. As the mixture flows through the column, the antibodies bind to the antigens; the antigens thus stay within the column while the rest of the mixture continues through to the end. The antigens are then flushed out of the column and collected separately.

4265. immunoassay
Definition:

A process that measures and identifies a specific biological substance such as an antigen.

4266. immunoblotting
Definition:

A technique that uses antibodies and protein blotting to detect a specific protein on a nitrocellulose sheet.

4267. immunochemistry
Definition:

A subfield of chemistry that is concerned with the study of the chemical activity involved with immunological processes.

4268. immunochemotherapy
Definition:

The use of a combination of immune system therapy and chemotherapeutic drugs to treat cancer.

4269. immunocompetence
Definition:

The ability of the immune system to react to teh presence of an antigen and stage a defense against it.

4270. immunocompetent
Definition:

Able to recognize and act against invading antigens.

4271. immunocompromised
Definition:

Having an immune system which is weakened by disease, drugs, malnutrition, etc.

4272. immunoconglutinins
Definition:

Antibodies which attach to complements and are formed in response to infection or injection of antigens.

4273. immunocyte
Definition:

A leukocyte that is able to stage an immune response.

4274. immunocyto-adherence
Definition:

A process through which specific antibody-forming cells bind to antigenic particles, forming clusters.

4275. immunodeficient (noun: immunodeficiency)
Definition:

Unable to stage an effective immune response to an invading antigen.

4276. immunodiffusion (diffusion test, gel diffusion)
Definition:

A technique for analyzing antigen and antibody mixtures by watching them as they diffuse toward each other within a support medium (usually a gel).

4277. immunodominant (immunodominance)
Definition:

Refers to the part of an antigenic determinant (a molecule on the surface of a microbe that triggers an immune response) which is most likely to bind with an antibody.

4278. immunoelectron microscopy
Definition:

A technique for using an electron microscope to locate specific antigens in cells or tissue.

4279. immunoelectrophoresis
Definition:

A method for separating and detecting soluble antigenic proteins by first separating them out with electrophoresis and then subjecting them to immunodiffusion.

4280. immunofluorescence
Definition:

A lab technique used to easily locate and examine cells by labelling them with antibodies which have had a fluorescent tag attached (fluorescent antibodies), and then viewing them under ultraviolet light.

4281. immunogen
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A substance which is capable of eliciting (inducing) an immune response. An immunogen usually has a fairly high molecular weight (usually greater than 10,000), thus, a variety of macromolecules such as proteins, lipoproteins, polysaccharides, some nucleic acids, and certain of the teichoic acids, can act as immunogens. Compare with antigen.

4282. immunogenetics
Definition:

A sub-field of genetics that uses both genetic and immunological analyses to study the genetics behind antibody formation and the immune response.

4283. immunogenic
Definition:

Describes a substance which is able to provoke an immune response against it.

4284. immunogenicity
Definition:

Describes the quality of a substance which is able to provoke an immune response against the substance. A measure of how able the substance is at provoking an immune response against it.

4285. immunoglobulin (immune globulin, pl. immunoglobulin)
Definition:

An antibody protein that is generated in response to and will bind to a specific antigen.

4286. immunoglobulin gene
Definition:

Any gene which codes for a part of an immunoglobulin protein (the light chains or heavy chains) or is otherwise involved in production of the immunoglobulin protein.

4287. immunoglobulin gene switching
Definition:

Switching between two (out of five) different classes of immunoglobulin proteins, for example from IgA to IgM. This is accomplished during the development of an immunoglobulin within a lymphocyte, when the expression of genes coding for different parts of the protein can be switched around.

4288. immunogold technique
Definition:

A lab technique used to mark a mixture of antibodies before they are viewed under an electron microscope as a part of immunoelectron microscopy. The antibodies are mixed with gold, which provides areas of high electron densities.

4289. immunolabeling
Definition:

A labeling technique which makes use of antibody-antigen complexes to mark biological molecules or structures.

4290. immunologic memory
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

The ability to rapidly produce large quantities of specific immune cells after subsequent exposure to a previously encountered antigen.

4291. immunologic tolerance
Definition:

Tolerance of a particular antigen by an organism such that antibodies are not produced against it and/or cell-mediated immunity does not occur.

4292. immunological disease
Definition:

Any illness, such as an allergy, that is caused by the action of antibodies.

4293. immunologist
Definition:

A doctor or biomedical researcher who studies immunology.

4294. immunology
Definition:

A subfield of biology that deals with the study of antigens and the immune process and how humans and higher animals fight off disease.

4295. immunopathology
Definition:

A branch of medicine that deals with the study of how the body fights off disease and the study of immunodeficiency diseases.

4296. immunopotentiation
Definition:

The bolstering of the normal response of the immune system to an antigen. Compare immunosuppression.

4297. immunopotentiator
Definition:

Any drug or chemical which increases the body's immune response to an antigen. Compare immunosuppressant.

4298. immunoradiometric assay
Definition:

A test that measures the concentration of antigens in a specimen through serological analysis that involves mixing radioactive antibodies with the antigen in question.

4299. immunosuppressant
Definition:

Any drug or chemical that suppresses the body's ability to react to an antigen; immunosuppressants are frequently used to keep transplant patients' bodies from rejecting the new organs.

4300. immunosuppression
Definition:

This refers to the suppression of the normal response of the immune system to an antigen.

4301. immunosuppressive drugs
Author: PharmInfoNet
Definition:

Drugs that block the body's ability to fight infection or foreign substances that enter the body. A person receiving an organ transplant is given these drugs to stop the body from rejecting the new organ or tissue. Cyclosporin is a commonly used immunosuppressive drug.

4302. immunotherapy
Definition:

A medical technique for stimulating a patient's immune system to attack and destroy disease-causing cells (viruses, bacteria, cancer cells, etc.)

4303. immunotherapy
Definition:

A type of medical treatment which includes a combination of immunopotentiator and immunosuppressant agents, desensitization to any allergens, bone marrow transplants, and thymus implantations.

4304. immunotoxic
Definition:

This refers to any substance which damages the immune system.

4305. impaired glucose tolerance (IGT, boderline diabetes)
Author: PharmInfoNet
Definition:

Blood glucose (sugar) levels higher than normal but not high enough to be called diabetes. People with IGT may or may not develop diabetes. Other names (no longer used) for IGT are "borderline," "subclinical," "chemical," or "latent" diabetes.

4306. imparipinnate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Having an uneven number of pinnae, by virtue of having one terminal pinna. Compare paripinnate.

4307. imperfect flower
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

A flower containing stamen and pistil organs required for pollination but lacking sepals or petals or both of these organs.

4308. imperforate anus
Author: Guo Li
Definition:

An imperforate anus is a developmental anomaly of the anus in which there is no anal opening.

4309. impermeable junction
Definition:

An area of contact between two cells which connects them to each other, and where nothing (not even the smallest molecules) can diffuse through from one cell to the other. Similar to "tight junction."

4310. impetigo
Definition:

An infectious skin disease usually found in children where blisters appear (mostly on the face), burst, and form yellowish crusts. Impetigo is caused by infection from streptococcal and staphylococcal bacteria, which enter through cold sores, cuts, scratches, or other breaks in the skin. The disease is most often spread by direct contact with infected skin.

For more information, visit The Impetigo Fact Sheet, Communicable Diseases: Impetigo, and The Group Health Cooperative's Impetigo Page.

4311. impinge
Author:
Definition:

To strike and attack directly, as in curvilinear flow where the current does not follow the curve but continues on tangent into the bank on the outside of a bend in the channel.

4312. implantation
Author: Fertilitext
Definition:

Attachment of the fertilized egg to the uterine lining, usually occurring five to seven days after ovulation.

4313. impotence
Author: Guo Li
Definition:

Impotence is the habitual inability to obtain/maintain an erection of the penis sufficient for sexual intercourse.

4314. improvement flow
Author:
Definition:

That discharge which will improve upon existing aquatic organisms and/or related recreational activity by correcting for water quality deterioration and/or utilization pressures.

4315. IMVIC tests
Definition:

A group of four biochemical tests used to look for the presence of bacteria of the family Enterobacteriaceae in a sample. The tests used are indole, methyl red, Voges-Proskauer, and citrate.

4316. in situ
Definition:

Refers to performing experiments or tests with intact tissues.

4317. in situ hybridization
Definition:

Use of a DNA or RNA probe to detect the presence of the complementary DNA sequence in cloned bacterial or cultured eukaryotic cells.

Also used for locating genes on chromosomes. The process is:


1. Prepare microscope slide with cells in metaphase of mitosis.
2. Treat slide with a weak base. Thus denaturing the DNA.
3. Pour radioactively labeled probe onto the slide.
4. Expose slide to photographic emulsion for a few days or weeks.
5. Develop emulsion.

4318. in utero
Definition:

A term meaning "within the uterus."

4319. in vitro
Definition:

In vitro means, literally, "in glass"; a biologic or biochemical process occuring outside a living organism.

4320. in vitro assay
Definition:

An experimental trial (involving biological matter) which is done in test tubes or on petri plates (in vitro) rather than within a living organism.

4321. in vitro mutagenesis
Definition:

Causing mutations to develop in cells from a tissue culture by exposing the cells to mutagens.

4322. in vitro packaging
Definition:

The packaging of the DNA of a virus into a capsid (outer protein coat of a virus) which forms from components in a laboratory mixture (as opposed to within a host organism, where viral packaging normally occurs).

4323. in vitro protein synthesis
Definition:

Translation of an mRNA molecule into polypeptides within a laboratory mixture which contains ribosomes and all of the necessary components (as opposed to translation within a living cell, where protein synthesis normally occurs).

4324. in vitro replication
Definition:

Replication (the making of copies) of a DNA molecule within a laboratory mixture which contains all of the necessary enzymes and components (as opposed to replication within a living cell, where it normally occurs).

4325. in vitro transcription / in vitro translation
Definition:

The transcription of a DNA molecule into mRNA molecules, and the subsequent translation of the mRNA molecules into polypeptides, within a laboratory mixture which contains ribosomes, enzymes, and all of the necessary components (as opposed to transcription and translation within a living cell, where they normally occur).

4326. in vivo
Definition:

In vivo means, literally, "in life"; a biologic or biochemical process occuring within a living organism.

4327. inactivated vaccine
Definition:

A vaccine where any live microbes within have been killed or otherwise rendered unable to cause disease due to heating or chemical treatment.

4328. inactivation
Definition:

In reference to a virus, the removal or loss of the virus's ability to successfully infect its host.

4329. inborn error
Definition:

A metabolic disorder caused by a genetic, heritable defect.

4330. inborn errors of metabolism
Author: Guo Li
Definition:

Inborn errors of metabolism are genetic disorders due to single gene defects. Many inborn errors of metabolism are abnormalities of enzymes in metabolic pathways. Because this, intermediate metabolites accumulate. Some of the most well known inborn errors of metabolism are: phenylketonurea, Lesch-Nyhan Syndrome, Gaucher's disease and the glycogen storage diseases.

4331. inbreeding
Definition:

Reproduction between two individual organisms which are closely related to each other (e.g., reproduction between siblings or between a parent and offspring).

4332. incidence
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

In reference to disease transmission, the number of cases of the disease in a specific subset of the population.

4333. incidence
Author: PharmInfoNet
Definition:

How often a disease occurs; the number of new cases of a disease among a certain group of people for a certain period of time.

4334. incised
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Cut deeply, sharply and often irregularly (an intermediate condition between toothed and lobed).

4335. included
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Enclosed, not protruding.

4336. inclusion body (inclusion bodies)
Definition:

A cluster of viral particles and/or proteins within an infected cell which can easily be seen with a microscope.

4337. inclusion conjunctivitis
Author: Guo Li
Definition:

Inclusion conjunctivitis is the infection of the conjunctiva by the bacterium Chlamydia trachomatis.

4338. inclusion encephalitis (panencephalitis, subacute sclerosing leukoencephalitis)
Definition:

A disease where the main symptom is inflammation of the brain (both gray and white matter). The disease is apparently caused by an infection from the measles virus and is often fatal.

4339. incompetent cervix
Author: Fertilitext
Definition:

A cervix with the inability to remain closed throughout an entire pregnancy; a frequent cause of premature birth.

4340. incomplete dominance
Definition:

Two alleles of a gene which result in distinctly different phenotypes, but when they are both inherited together in an individual (one from the mother and one from the father -- called heterozygosity), the individual ends up with a blend of the two phenotypes. For example, if one allele is for red hair and the other allele is for blue hair, then the individual will have purple hair. (This is in contrast to codominance, where the individual would inherit patches of blue and patches of red hair).

4341. incomplete penetrance
Definition:

A state in which a group of individuals all have a particular genotype, but not all of them have the corresponding phenotype. Incomplete penetrance is most likely the result of environmental effects. For example, if all of the individuals have the genes to be tall, but not all individuals are actually tall, then the shorter ones may have had bad nutrition.

4342. incomplete protein
Definition:

In nutrition, a protein which does not contain all of the amino acids necessary for growth and good health.

4343. incomplete sex linkage
Definition:

A rare condition where a particular gene can be found on both the X and Y chromosomes, in a homologous segment.

4344. incompletely linked genes
Definition:

Genes which will recombine during crossing over but which are not located close together on the chromosome.

4345. incrassate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Thickened; of a pollen grain, with thickened margins around the apertures.

4346. incross
Definition:

To interbreed two individuals which have identical genotypes for a particular trait. In most cases the two individuals are also closely related to one another.

4347. incubation
Definition:

1. The process of maintaining constant temperature, humidity, and other environmental factors for the purpose of allowing an embryo to develop properly within an egg, a prematurely-born infant to continue its development outside of its mother's womb, or microbe or tissue cultures to grow until they are a scientifically or medically useful size. When done artificially, incubation is done within an "incubator."
2. The period between the initial infection of a host by a microbe and the time that symptoms begin.

4348. incumbent
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of the orientation of an embryo, with the cotyledons lying face to face and folded downwards beside the radicle; of anthers, lying against the inner face of the filament.

4349. incurved
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Bent or curved inwards or upwards; of leaf margins, curved towards the adaxial surface.

4350. indefinite
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Variable in number; numerous; of stamens, more than twice as many as the petals or sepals; of an inflorescence, not terminating in a flower (i.e. having a continuing, terminal growing point).

4351. indehiscent
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Not opening at maturity.

4352. indeterminate (monopodial)
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of growth: the condition in which the terminal bud persists and produces successive lateral branches.

4353. index fossils
Definition:

Fossils (or groups of fossils) which are used by geologists and paleontologists to help correlate different events or processes in different parts of the world which happened at the same time. Species which make good index fossils are able to tolerate a wide range of ecological conditions, are geographically widespread, common, easy to find, and evolutionarily short-lived (that is, they speciated and then quickly became extinct). In general, they are also planktonic and very small.

4354. indicator
Author:
Definition:

An event, entity or condition that typically characterizes a prescribed environment or situation; indicators determine or aid in determining whether or not certain stated circumstances exist or criteria are satisfied.

4355. indicator cell
Definition:

A cell which indicates that it has been infected by a virus by responding to its presence in a certain way.

4356. indicator organisms
Author:
Definition:

Organisms that respond predictably to various environmental changes, and whose presence, or abundance, are used as indicators of environmental conditions.

4357. indicator plant
Author:
Definition:

Plant species indicating some specific characteristic of a certain locality.

4358. indigenous
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Native; originating or occurring naturally in the place specified.

4359. indirect fluorescent antibody technique
Definition:

A lab technique used to detect the presence of antibodies, especially ones which have a fluorescent antibody attached to them as a label.

4360. indirect immunofluorescence
Definition:

A lab technique used to detect the presence of antigens. A detector antibody first reacts with the antigen. Then an indicator antibody which has been labelled with a fluorescent marker attaches to the detector antibody. Finally, the researcher conducting the lab technique looks for fluorescence from the indicator antibody that is attached to the detector antibody that has reacted with the antigen.

4361. indirect-end labeling
Definition:

A lab technique used to show that a particular sequence of DNA is unique in the genome. A hybridization probe is constructed from the end of the unique DNA sequence; any DNA sequences which are able to hybridize to the probe should thus be the same, unique DNA sequence, and only the unique DNA sequence should hybridize to the probe.

4362. individual selection
Definition:

A type of natural selection which acts upon individual organisms within a population. An individual organism which has a particular beneficial characteristic is better able to survive and reproduce than other individuals (which don't have this beneficial characteristic). Individual selection is the most common type of natural selection.

4363. induced enzyme (inducible enzyme, adaptive enzyme)
Definition:

An enzyme which is only produced when another substance (such as the enzyme's substrate) -- called an "inducer" -- is present.

4364. induced fit
Definition:

1. A change in the conformation of an enzyme due to it binding to a substrate that makes it catalytically active.
2. A situation where any molecule changes shape as it binds to a ligand so that its binding site more closely conforms to the shape of the ligand.

4365. induced mutation
Definition:

A mutation, or change in a nucleotide sequence or gene, which was caused by a mutagen.

4366. inducer
Definition:

An extracellular molecule that enters a cell and initiates transcription of a gene or operon.

4367. induction
Definition:

An increase in the expression of a gene due to the activity of a regulatory protein.

4368. induction of a lysogenic phage
Definition:

Causing a bacteriophage (a virus which attacks bacteria) which has been lying dormant within the genome of a hosting bacterium (a lysogenic virus) to reactivate and finish its lytic cycle - destroying the bacterium in the process. The most common cause of this is damage to the bacterium's DNA.

4369. indumentum
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The epidermal appendages (e.g. hairs or scales), collectively.

4370. induplicate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Folded inwards so that the outer faces of the margins are in contact.

4371. indusium
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Tissue covering the sorus of a fern.

4372. industrial melanism
Definition:

An increase in the amount of the pigment melanin in a population which lives in an area that has been darkened with pollution by human industrial activities. The extra melanin helps the individuals of the population to better camouflage themselves against predators in the darker surroundings. Industrial melanism occurs because lighter-colored individuals (ones without extra melanin) are found and eaten at a higher rate than darker-colored individuals.

4373. industrial yeast
Definition:

Any species of yeast which is used in industry, such as for fermentation to make alcoholic beverages or for baking. Saccharomyces is the most common genus used.

4374. infantile eczema (atopic dermatitis)
Definition:

Infantile eczema is any of a group of red, itchy, rashlike or scaly skin lesions often found in infants. Most cases clear up without treatment as the child reaches 3 to 4 years of age.

4375. infection thread
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

In the formation of root nodules, a cellulosic tube through which Rhizobium cells can travel to reach and infect root cells.

4376. infectious disease
Definition:

Any of many diseases or illnesses (caused by bacteria or viruses) that can be transmitted from person to person or from organism to organism. For instance, the common cold and AIDS are infectious diseases, whereas illnesses such as diabetes and gout are not.

4377. infectious mononucleosis screen
Author: Guo Li
Definition:

This is the measurement of the so-called heterophil antibody. Heterophil antibodies are completely adsorbed by bovine red blood cells but not by guinea pig kidney cells. This feature distinguishes the heterophil antibodies due to IM from other causes. Monospot is the name given to a particular arrangement to test for the presence of heterophil antibody. Monospot is usually positive within four weeks after onset of the clinical symptoms. Titers of antibodies against Epstein Barr viral capsid antigen (VCA) and nuclear antigen (EBNA) are elevated.

4378. infectious pancreatic necrosis virus
Definition:

A virus from the genus Birnavirus in the family Birnaviridae which attacks fish. It is highly contagious and causes severe, often fatal infections of the pancreas. It is especially prone to attack young fish in the family Salmonidae (the salmon and trout family) which have been raised in hatcheries.

4379. infectious particle
Definition:

A virus particle or fragment which contains the entire genome of the virus, making it able to successfully infect host cells and reproduce whole viruses.

4380. inferior
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of an ovary, at least partly below the level of attachment of the other floral parts. Compare superior.

4381. infertility
Author: Fertilitext
Definition:

The inability of a couple to achieve a pregnancy or to carry a pregnancy to term after one year of unprotected intercourse.

4382. inflammation
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Characteristic reaction to foreign particles and noxious stimuli, resulting in redness, swelling, heat, and pain.

4383. inflorescence
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The group or arrangement in which flowers are borne on a plant.

4384. influenza (flu, grippe)
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

The disease caused by influenza viruses; influenza is an acute, potentially fatal and highly infectious disease which occurs usually via the respiratory tract.

4385. influenza vaccine
Definition:

A vaccine given to provide immunity to the disease influenza (also known as the flu), which is caused by the influenza virus. The vaccine consists of a mixture of different strains of the virus that have been inactivated by formaldehyde.

4386. influenza virus
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

The causative agent of influenza.

4387. Influenzavirus
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A genus of viruses causing influenza in human; The member of Influenzavirus includes influenza virus type A and B, but not influenza virus type C.

4388. informatics
Definition:

The study of the application of computer and statistical techniques to the management of information. In genome projects, informatics includes the development of methods to search databases quickly, to analyze DNA sequence information, and to predict protein sequence and structure from DNA sequence data.

4389. informative meiosis
Definition:

A lab technique used to determine whether two genetic markers are linked to each other and how closely linked they are. It uses sexual reproduction which produces offspring in which the two markers may have crossed over during DNA recombination. (DNA recombination and crossing over occurs during meiosis to produce gametes in each parent). Information on the proportion of progeny which have crossed over markers is used to determine whether the markers are linked, and if so how closely.

4390. informed consent
Author: The Alzheimer's Association
Definition:

The agreement of a person (or his or her legally authorized representative) to serve as a research subject, in full knowledge of all anticipated risks and benefits of the experiment.

4391. informed consent
Definition:

Permission from a patient or responsible party for a medical procedure or test to be done on the patient, after the patient or responsible party has been given information on all the facts about the procedure or test and any risks involved.

4392. informosome
Definition:

A molecule consisting partly of RNA and partly of protein which is found in the cytoplasm of eggs from certain species of echinoderms and fish. It is thought to be transmitted from the nucleus to the cytoplasm.

4393. infrared radiation (IR radiation)
Definition:

Electromagnetic radiation with wavelengths between 750 nanometers and 1,000,000 nanometers (or 1 millimeter). This is more commonly known as heat energy.

4394. infrared spectroscopy (IR spectroscopy)
Definition:

A type of absorption spectroscopy which is used to measure the ability of an unknown sample to absorb different wavelengths of infrared radiation. How much infrared radiation is absorbed at each wavelength indicates the types of chemical bonds present in the molecules of the unknown sample.

4395. infraspecific
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of lower taxonomic rank than species.

4396. infructescence
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The grouping or arrangement in which fruits are borne on a plant.

4397. inheritance
Definition:

The acquiring of a set of physical or behavioral characteristics from a parent.

4398. inheritance of acquired characteristics (Lamarckism, Lamarckian inheritance)
Definition:

The obsolete theory that offspring can inherit physical or behavioral characteristics from a parent that the parent acquired during its life. For example, a giraffe which stretches its neck to reach leaves at the top of a tall tree and thus ends up with a slightly longer neck can pass on the long neck trait so that its offspring also have long necks and can stretch it even longer. The theory, now known to be incorrect, was popularized by Jean-Baptiste Lamarck (1744-1829) and played an important role in the history of the study of evolutionary biology.

4399. inhibin
Definition:

A hormone secreted by the ovary or testicle which suppresses the secretion of follicle stimulating hormones from the pituitary gland.

4400. inhibitor
Definition:

A molecule which represses or prevents another molecule from engaging in a reaction. See also inhibition.

4401. inhibitor
Definition:

Any substance or state which suppresses, prevents, or slows down a chemical reaction. The opposite of a catalyst.

4402. inhibitory postsynaptic potential
Definition:

An electrochemical potential across the postsynaptic membrane of a neuron which inhibits the formation of an action potential in the neuron.

4403. initiation codon
Definition:

A nucleotide sequence that codes for the first amino acid in a polypeptide sequence; the codon is typically AUG in eukaryotes and sometimes GUG in prokaryotes.

4404. initiation factor (IF)
Definition:

A type of protein which plays an important role in initiating the translation of an mRNA molecule into a polypeptide. Initiation factors help form the complex between the mRNA and a ribosome.

4405. initiator
Definition:

Any substance or state which starts or causes a chemical reaction without being one of the reactants in the reaction.

4406. inner ear
Author: Guo Li
Definition:

The inner ear is made up of the bony labyrinth and the membranous labyrinth.

4407. inoculation
Definition:

1. In medicine, the introduction of a weakened or dead version of a disease-causing microbe (a pathogen) into a healthy body for the purpose of getting the body to become immune to that microbe.
2. In microbiology, the process where a microbe of interest is introduced into a previously-sterilized growth medium for the purpose of starting a culture of that microbe.

4408. inorganic
Definition:

Describes a substance which is not organic, did not come from the materials or processes of living organisms, and/or is not a hydrocarbon or a hydrocarbon derivative compound.

4409. inorganic chemistry
Definition:

A branch of chemistry which studies the structures, synthesis and reactions of compounds other than hydrocarbons and their derivatives.

4410. inosine
Definition:

The purine ribonucleoside in the nucleotide inosine monophosphate (IMP), from which the purine nucleotides adenosine monophosphate and guanosine monophosphate are derived. Its chemical formula is C₁₀H₁₂N₄O₅.

4411. inositol lipid
Author: Susan A.Hagedorn
Definition:

A membrane-anchored phospholipid that transduces hormonal signals by stimulating the release of any of several chemical messengers.

4412. inotropic effect
Author: Guo Li
Definition:

Inotropic effect is the effect of increasing the force of contraction of the heart without a corresponding change in the initial length of the heart muscle (or end-diastolic volume in the clinical setting).

4413. Inoue-Melnick virus
Definition:

A virus found in people who have chronic central nervous system diseases, such as multiple sclerosis.

4414. Inoviridae
Definition:

A family of bacteriophages which are rod-shaped. Members of the family use single-stranded DNA to encode their genomes and do not cause their host cells to lyse. Instead, progeny viruses poke their way out through their host's cell membrane, leaving the host cell intact.

4415. Inovirus
Definition:

A genus of bacteriophages in the family Inoviridae which infect enterobacteria. The members of the Inovirus genus use single-stranded DNA to encode their genomes and do not cause the host cell to lyse to release new viruses.

4416. insect
Definition:

An animal of class Insecta (or Hexapoda) of subphylum Uniramia of phylum Arthropoda. Generally, they have three segments to the body (head, thorax, and abdomen) with one pair of antennae attached to the first segment (the head) and three pairs of legs and two pairs of wings attached to the middle segment (the thorax). They are mostly terrestrial (though there are species which live in freshwater environments and in saltwater marshes). Note: centipedes, millipedes, spiders, and mites are not insects (though they are arthropods).

4417. insect picornaviruses
Definition:

Small viruses of the family Picornaviridae which infect insects. They use RNA to encode their genomes instead of DNA.

4418. insecticide
Definition:

A chemical used to kill insects. Insecticides are a type of pesticide.

4419. insectivorous (insectivore)
Definition:

Describes an animal or plant that eats insects.

4420. insert
Definition:

A fragment of DNA which has been inserted into a cloning vector. The insert is the piece of DNA which molecular biologists are interested in studying and/or duplicating in vast quantities.

4421. insertion mutation
Definition:

A mutation caused by the insertion of at least one extra nucleotide base in a DNA sequence.

4422. insertion sequence (insertion element, IS element)
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

The simplest type of transposable element. Has only genes involved in transposition.

4423. insertion sequence selection
Definition:

The selection of cells within a population which have had a foreign piece of DNA -- an insertion sequence -- incorporated into their genomes.

4424. insertion vector
Definition:

A cloning vector derived from bacteriophage lambda which has had most of its normal genes removed to make room for new DNA of interest to science, which are inserted by recombination.

4425. insertional inactivation
Definition:

The inactivation of a gene by inserting a fragment of DNA into the middle of its coding sequence. Any future products from the inactivated gene will not work because of the extra codes added to it.

4426. insertional mutagenesis
Definition:

The generation of an insertion mutation by inserting one or more extra nucleotide bases into the DNA sequence.

4427. insomnia
Author: Guo Li
Definition:

Insomnia is a sleep disorder characterized by difficulty initiating or maintaining sleep, or nonrestorative sleep, for at least 1 month.

4428. inspissation
Definition:

The increase in the viscosity of a complex liquid, such as a deposit of petroleum, by the evaporation of water (and the lighter fractions of oil deposits) and the escape of gases from it.

4429. instantaneous flow
Author:
Definition:

That discharge measured by any instant in time, applied to any recommended flow term when modified by the appropriate adjective.

4430. instar
Author:
Definition:

An insect or other arthropod that is between molts (molting is shedding its outer shell, or exoskeleton).

4431. instream cover
Author:
Definition:

Areas of shelter in a stream channel that provide aquatic organisms protection from predators or competitors and/or a place in which to rest and conserve energy due to a reduction in the force of the current.

4432. instream flow
Author:
Definition:

Streamflow regime required to satisfy a mixture of conjunctive demands being placed on water while it is in the stream.

4433. instream flow incremental methodology (IFIM)
Author:
Definition:

Technique to predict the biomass of a fish species or life stage that a stream reach can support at a given flow, given knowledge of the fishes' physical habitat preferences.

4434. instream flow requirements
Author:
Definition:

That amount of water flowing through a stream course needed to sustain instream values at an acceptable level.

4435. insulated stream
Author:
Definition:

A stream or reach of a stream that neither contributes to nor receives water from the zone of saturation. It is separated from the zones of saturation by an impermeable bed.

4436. insulin
Image: View the chemical structure
Definition:

A polypeptide hormone produced by cells in the islets of Langerhans in the pancreas. Insulin decreases the levels of glucose in the blood and to regulates the metabolism of glucose, fats and proteins. In order to meet the demand for insulin needed by diabetics, the hormone is mass-produced with the aid of genetically engineered bacteria, but can also be taken from pigs and cattle.

4437. insulin allergy
Author: PharmInfoNet
Definition:

When a person's body has an allergic or bad reaction to taking insulin made from pork or beef or from bacteria, or because the insulin is not exactly the same as human insulin or because it has impurities.

The allergy can be of two forms. Sometimes an area of skin becomes red and itchy around the place where the insulin is injected. This is called a local allergy.

In another form, a person's whole body can have a bad reaction. This is called a systemic allergy. The person can have hives or red patches all over the body or may feel changes in the heart rate and in the rate of breathing. A doctor may treat this allergy by prescribing purified insulins or by desensitization. See also: desensitization.

4438. insulin antagonist
Author: PharmInfoNet
Definition:

Something that opposes or fights the action of insulin. Insulin lowers the level of glucose (sugar) in the blood, whereas glucagon raises it; therefore, glucagon is an antagonist of insulin.

4439. insulin binding
Author: PharmInfoNet
Definition:

When insulin attaches itself to something else. This can occur in two ways. First, when a cell needs energy, insulin can bind with the outer part of the cell. The cell then can bring glucose (sugar) inside and use it for energy. With the help of insulin, the cell can do its work very well and very quickly. But sometimes the body acts against itself. In this second case, the insulin binds with antibodies. If the insulin is an injected form of insulin and not made by the body, the body sees the insulin as an outside or "foreign" substance. When the injected insulin binds with the antibodies, it does not work as well as when it binds directly to the cell.

4440. insulin pump
Author: PharmInfoNet
Definition:

A device that delivers a continuous supply of insulin into the body. The insulin flows from the pump through a plastic tube that is connected to a needle inserted into the body and taped in place. Insulin is delivered at two rates: a low, steady rate (called the basal rate) for continuous day-long coverage, and extra boosts of insulin (called bolus doses) to cover meals or when extra insulin is needed. The pump runs on batteries and can be worn clipped to a belt or carried in a pocket. It is used by people with insulin-dependent diabetes.

4441. insulin receptor
Author: PharmInfoNet
Definition:

Areas on the outer part of a cell that allow the cell to join or bind with insulin that is in the blood. When the cell and insulin bind together, the cell can take glucose (sugar) from the blood and use it for energy.

4442. insulin resistance (insulin insensitivity)
Author: PharmInfoNet
Definition:

Many people with noninsulin-dependent diabetes produce enough insulin, but their bodies do not respond to the action of insulin. This may happen because the person is overweight and has too many fat cells, which do not respond well to insulin. Also, as people age, their body cells lose some of the ability to respond to insulin. Insulin resistance is also linked to high blood pressure and high levels of fat in the blood. Another kind of insulin resistance may happen in some people who take insulin injections. They may have to take very high doses of insulin every day (200 units or more) to bring their blood glucose (sugar) down to the normal range.

4443. insulin shock
Author: PharmInfoNet
Definition:

A severe condition that occurs when the level of blood glucose (sugar) drops quickly. The signs are shaking, sweating, dizziness, double vision, convulsions, and collapse. Insulin shock may occur when an insulin reaction is not treated quickly enough. See also: hypoglycemia.

4444. insulin-dependent diabetes mellitus (IDDM, type I diabetes, juvenile diabetes, juvenile-onset diabetes)
Author: PharmInfoNet
Definition:

A chronic condition in which the pancreas makes little or no insulin because the beta cells have been destroyed. The body is then not able to use the glucose (blood sugar) for energy. IDDM usually comes on abruptly, although the damage to the beta cells may begin much earlier. The signs of IDDM are a great thirst, hunger, a need to urinate often, and loss of weight. To treat the disease, the person must inject insulin, follow a diet plan, exercise daily, and test blood glucose several times a day. IDDM usually occurs in children and adults who are under age 30. This type of diabetes used to be known as "juvenile diabetes," "juvenile-onset diabetes," and "ketosis-prone diabetes."

4445. insulinase
Definition:

An enzyme which breaks down the hormone insulin. It is produced in the liver.

4446. insulinlike growth factor (nonsuppressible insulinlike activity)
Definition:

A type of growth factor found in blood serum which resembles insulin but which is not recognized by antibodies that will react with insulin. These growth factors are produced in response to growth hormone and behave like somatomedins (type of growth factor) in promoting growth.

4447. int 1 gene
Definition:

An oncogene (gene associated with cancer) which causes tumors to form in the breast tissue of mice when a copy of the mouse mammary tumor virus (MMTV) is integrated into the mouse genome close to it. It is homologous to a gene found in the fruit fly Drosophila melanogaster which plays an important role in wing development; this suggests that the int 1 gene also plays a role during development in mammals.

4448. intasome
Definition:

A complex which forms in order to allow the DNA of a bacteriophage to incorporate itself into the DNA of its host bacterium during lysogeny. The complex is composed of the bacteriophage DNA and two proteins called IHF and Int.

4449. integral membrane protein
Definition:

A protein that is strongly bound to a membrane by hydrophobic interactions; compare with peripheral proteins.

4450. integrant
Definition:

A cell in which transfection has successfully occurred, and a foreign gene has been incorporated into the cell's genome where it can be passed on to daughter cells.

4451. integrase
Definition:

An enzyme which helps integrate DNA from bacteriophage lambda into the genome of its bacterial host cell. It does this by catalyzing site-specific recombination.

4452. integrated control (integrated approach)
Definition:

A method of controlling or eliminating unwanted plants (weeds) or insects with a combination of natural means and pesticides.

4453. integration
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

The process by which a DNA molecule becomes incorporated into another genome.

4454. integrative suppression
Definition:

Within a bacterium, the suppression of a chromosomal mutation which prevents the chromosome from being replicated, by a plasmid which has become integrated into the chromosome. Because the plasmid's presence in the chromosome suppresses the mutation, the chromosome is able to freely replicate again.

4455. integrator gene
Definition:

A gene which controls a group of other genes.

4456. integument
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A covering; one of the outer layers of tissue of a plant ovule.

4457. interaction
Definition:

1. Any encounter between organisms in which the presence or behavior of one affects the other.
2. The action of one drug on the effectiveness or toxicity of another.

4458. intercalating agent
Definition:

A chemical substance which has a structure like a flat plane so that it can insert itself in between adjacent nucleotides of a DNA molecule. Intercalating agents are used to unwind the double helix, make the helix longer, or to induce mutations.

4459. intercalating mutagen
Definition:

A mutagen that causes frame-shift mutations by inserting itself between two adjacent bases in a genetic sequence.

4460. intercalation
Definition:

The process by which a molecule (such as a mutagen) is inserted between two planar or stacked aromatic rings (such as adjacent bases in a genetic sequence).

4461. interdemic selection
Definition:

A type of natural selection which acts upon populations within a species. Interdemic selection occurs when populations die out or give rise to new populations at different rates, depending on whether they have traits that are beneficial or harmful to the population as a whole. It is also possible for a trait to be harmful to the individuals within the population which have it, but be beneficial to the population as a whole; such a trait would thus be selected for until every individual within the population has the trait (that is, the trait becomes fixed).

4462. interference
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

The overall influence of one plant or groups of plants on another, and encompasses allelopathy or competition, or both of these processes.

4463. interferon
Definition:

Any of several glycoproteins that help the body fight off viral infections. During a viral invasion, infected cells produce three kinds of interferon (alpha, beta, and gamma) which circulate in the blood stream and help make uninfected cells immune to the attack. Interferon was discovered in 1957 by Alick Isaacs.

4464. interferon alpha
Definition:

The main type of interferon (a glycoprotein) produced by the white blood cells. It is also manufactured pharmacologically to treat hairy-cell leukemia.

4465. intergenic regions
Author: Susan A.Hagedorn
Definition:

DNA sequences located between genes that comprise a large percentage of the human genome with no known function.

4466. intergenic suppression
Definition:

The suppression of a mutation that has rendered a gene nonfunctional because the coding has changed to call for a wrong amino acid in the final polypeptide product, or even to call for a wrong stopping point. The mutation is suppressed when another mutation (a suppressor mutation) occurs which creates a mutant tRNA molecule that reads the mutated code as the normal code, and thus puts the correct amino acid into the final polypeptide product, thereby making the gene functional again. The original mutation is "fixed" as a result of another, independent mutation in a different gene. For an example of an intergenic suppression, see amber suppressor.

4467. intergravel flow
Author:
Definition:

That portion of the surface water that infiltrates the stream bed and moves through the substrate pores.

4468. interkinesis
Definition:

A period of time between two nuclear divisions of a cell where no DNA replication occurs. Interkinesis happens between the first meiotic division and second meiotic division of meiosis.

4469. interleukin
Definition:

Any of a group of protein factors which are produced by T lymphocytes and macrophages (a type of white blood cell) in the presence of antigens or mitogens. They cause the T lymphocytes to activate and proliferate.

4470. interleukin 1 (leukocyte activating factor, IL1)
Definition:

A protein factor produced by macrophages (a type of white blood cell) which plays an important role in activating T lymphocytes and B lymphocytes when antigens or mitogens are present. Interleukin 1 and interleukin 2 are both known to be involved in achieving T-cell-mediated immunity.

4471. interleukin 2 (IL2)
Definition:

A protein factor which is produced by T lymphocytes that have been activated by an antigen. Interleukin 2 stimulates other T lymphocytes to activate and differentiate regardless of what specific antigen is involved. Interleukin 1 and interleukin 2 are both known to be involved in achieving T-cell-mediated immunity.

4472. interleukin 3
Definition:

A protein factor which is produced by T lymphocytes that have been activated by a mitogen. Interleukin 3 stimulates bone marrow stem cells and mast cells.

4473. interleukin-4 (IL-4)
Author: Rick Peluso
Definition:

This is a shortened mRNA with no open reading frames. It is a mast cell enhancer and might be important for production of normal mRNA or competing with functional IL-1 blocking expression.

4474. intermediary metabolism
Definition:

Enzyme-catalyzed processes within cells that extract energy from nutrient molecules and use that energy to construct cellular components.

4475. intermediate filament
Definition:

A type of structural protein found within the cytoplasm of eukaryotic cells which forms one type of cell cytoskeleton. In mammalian cells, the intermediate filaments are intermediate in width between actin (a muscle protein) and microtubules. There are six types of intermediate filaments: keratins, desmins, vimentins, glial filaments, neurofilaments, and nuclear lamins.

4476. intermediate host
Definition:

The species (or group of species) that a parasite infects during its immature, juvenile stages. Many parasites live in different host species during different parts of their life cycles. Compare primary host.

4477. intermedin
Definition:

A hormone secreted by the pituitary gland which stimulates the melanocytes in the skin to make more of the pigment melanin.

4478. intermittent stream (seasonal stream)
Author:
Definition:

1. One in contact with the groundwater table that flows only at certain times of the year as when the groundwater table is high and/or when it receives water from springs or from some surface source(e.g., melting snow in mountainous areas). It ceases to flow above the stream bed when losses from evaporation or seepage exceed the available streamflow.
2. A stream that normally flows for at least thirty (30) days after the last major rain of the season and is dry a large part of the year.
3. A stream which flows only during the wet season, may also be called an intermittent stream.

4479. intern
Definition:

An individual person who has graduated from medical school and is engaged in a rigorous year of additional training at a hospital before practicing medicine.

4480. internal membrane
Definition:

Any plasma membrane which is found within a eukaryotic cell, such as those surrounding organelles and vesicles.

4481. international normalized ratio (INR)
Author: Guo Li
Definition:

This is the prothrombin time that is normalized, which removes the variability of PT due to differences in reagents and methods. Normal range: 0.8 to 1.2

4482. internode
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The portion of a stem between the level of insertion of two successive leaves or leaf pairs (or branches of an inflorescence).

4483. interpetiolar
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of stipules, between the petioles of two opposite leaves. Compare intrapetiolar.

4484. interphase
Definition:

The period in the cell cycle when the cell is not reproducing (undergoing mitosis). During this time, the cell is growing rapidly, increasing its size, making new molecules, and doing all of the things that cells do that are not associated with cell division. The period is subdivided into the G1 phase, the S phase, and the G2 phase.

4485. interrupted
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of an inflorescence, having the flowers unevenly distributed along the main stem, with conspicuous gaps.

4486. interrupted stream
Author:
Definition:

A stream that contains alternating reaches that are either perennial, intermittent, or ephemeral.

4487. interspecies hydrogen transfer
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

The process in which organic matter is degraded anaerobically by the interaction of several groups of microorganisms in which hydrogen production and hydrogen consumption are closely coupled among species.

4488. interspecific competition
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Competition between different species for nutrients, space, light, etc.

4489. interstitial
Definition:

Between the grains (or cells or other solid objects). Having to do with the small, narrow spaces (called interstices) found in between grains of sand, large cells or atoms or molecules, different tissues in the body, or within soil. The pores between different minerals in a rock, or (in crystallography) the areas in a crystal which are not lattice sites.

4490. intolerance
Definition:

Lack of tolerance. An inability of the body to digest or break down certain substances (drugs or nutrients) which are normally digestible by others. For example, lactose intolerance is an inability to digest the sugar lactose.

4491. intra-
Definition:

A prefix which indicates that the word has to do with inside, within, internal.

4492. intracellular
Definition:

Describes a substance which is inside a cell, or a process which takes place entirely within a cell.

4493. intracervical insemination (ICI)
Author: Fertilitext
Definition:

Artificial insemination of sperm into the cervical canal.

4494. intracytoplasmic
Definition:

Describes a substance which is located in a cell's cytoplasm, or a process which takes place within the cell's cytoplasm.

4495. intracytoplasmic sperm injection (ICSI)
Author: Fertilitext
Definition:

The direct injection of a single sperm into an egg.

4496. intrafusal fiber
Definition:

A type of striated muscle fiber. It is found within muscle spindles.

4497. intragravel flow
Author:
Definition:

Water moving through the substrate pores of a streambed.

4498. intramolecular
Definition:

Describes situations where the atoms of a molecule interact with one another rather than with other molecules or atoms from other molecules.

4499. intramolecular lyase
Definition:

An enzyme which helps form double bonds by removing a chemical group from a molecule.

4500. intramolecular oxidoreductase
Definition:

An enzyme which simultaneously oxidizes and reduces different parts of the same molecule in an intramolecular redox reaction.

4501. intramolecular transferase
Definition:

An enzyme which moves a functional group from one part of a molecule to another.

4502. intramuscular
Definition:

Describes a substance which is within a muscle, a process which takes place entirely inside a muscle, or an injection of medicine into muscle tissue.

4503. intraoperative radiation therapy (IORT)
Definition:

Treating a tumor site with radiation immediately following surgery to destroy the tumor.

4504. intraperitoneal
Definition:

Describes something which is located within the spaces between the organs in the peritoneal cavity of the abdomen, or the placement or injection of medicine or other substances into the peritoneal cavity.

4505. intrapetiolar
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Between a petiole and the subtending stem. Compare interpetiolar.

4506. intraspecific competition
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

A type of competition whereby an individual plant competes with one or more members of the same species for nutrients, space, light, etc.

4507. intratubal insemination (ITI)
Author: Fertilitext
Definition:

The artificial insemination of sperm cells, which have been washed free of seminal fluid, into the fallopian tubes.

4508. intrauterine devices (IUD)
Author: Guo Li
Definition:

Intrauterine devices are small T-shaped birth control devices made of copper and plastic; some may contain progesterone. They are placed in the uterus to prevent pregnancy and work mainly by preventing the fertilized egg from implanting in the wall of the uterus.

4509. intrauterine insemination (IUI)
Author: Fertilitext
Definition:

The artificial insemination of sperm, which have been washed free of seminal fluid, into the uterine cavity.

4510. intravascular fluid
Author: Guo Li
Definition:

Intravascular fluid is the part of the body fluid that is inside the blood vessels. This includes the blood cells and the plasma. (clinically, plasma is obtained by removing the blood cells from blood). The total blood volume in human is approximately:
• 75 ml / kg. of body weight for males
• 65 ml / kg. of body weight for females
• 85 ml / kg. of body weight for infants

4511. intravenous
Definition:

Describes a substance which is inside a vein, a process which takes place entirely within a vein, or the injection of medicine or nutrients into a vein.

4512. intravenous pyelogram (IVP)
Author: Guo Li
Definition:

IVP is an x-ray study of the kidneys, ureters, bladder and urethra after a radiopaque (iodinated) dye is injected intravenously. The IVP dye is excreted by the kidney, thus enables one to identify the presence of malformations, infections, tumors, obstructions, and stones.

4513. intraventricular hemorrhage (IVH)
Author: Guo Li
Definition:

Intraventricular hemorrhage is bleeding in the ventricles of the brain, most often seen in infants born after less than 31 weeks of gestation. The most common site (over 60% of the time) is the subependymal germinal matrix, which is a primitive cellular region located ventrolateral to the lateral ventricle at the level of the foramen of Monro. Diagnosis is confirmed by real-time ultrasound.

4514. intrinsic factor
Author: Guo Li
Definition:

An intrinsic factor is a substance secreted by the parietal cells of the stomach lining for the absorption of vitamin B12 (cyanocobalamin). Pernicious anemia results in the case of an autoantibody against the parietal cells and the intrinsic factor.

4515. intro-
Definition:

A prefix which means "within" or "inward."

4516. introduced
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Not indigenous; not native to the area in which it now occurs. Compare adventive.

4517. introgression
Author: Susan A.Hagedorn
Definition:

Backcrossing of hybrids of two plant populations to introduce new genes into a wild population.

4518. introgressive hybridization
Definition:

The incorporation into a population's gene pool of genes from a different species.

4519. introns
Definition:

The DNA base sequences interrupting the protein- coding sequences of a gene; these sequences are transcribed into RNA but are cut out of the message before it is translated into protein. Compare exons.

4520. introrse
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of anthers, dehiscing towards the centre of the flower. Compare extrorse.

4521. intubation
Author: Guo Li
Definition:

Intubation is the process of placing a tube in the trachea, usually for ventilation, suctioning and/or partial protection of the airway from aspirating stomach contents.

4522. intussusception
Author: Guo Li
Definition:

Intussusception is the telescoping of one segment of bowel into an adjacent segment. It is the most common cause of intestinal obstruction in children under 2 years of age. Complications include pain, dehydration, and infarction of the bowel. In about half of the cases, a barium enema is successful in reducing the intussusception; if not, surgery is required.

4523. inulase
Definition:

An enzyme produced by higher plants and some fungi which catalyzes the conversion of inulin into fructose.

4524. inulin
Image: View the chemical structure
Definition:

A starchy carbohydrate found in the roots of some plants which converts to the sugar levulose when it's mixed with oygen and water. Inulin is used in tests which measure kidney function, and it is used as a substitute starch in foods (esp. breads) for diabetics.

4525. inundation
Author:
Definition:

A condition in which water temporarily or permanently covers a land surface.

4526. invasive
Definition:

1. Describes a medical or surgical procedure which requires the skin to be cut open and/or objects to be inserted into the body.
2. Describes a species which takes over a new habitat where it was not previously found, often to the detriment of species which were there before.
3. Describes a microbe which is able to enter the body of a host organism and move about inside at will. The microbe may or may not cause any diseases.
4. Describes a cancerous tumor which is able to destroy surrounding healthy tissue and expand into the area where the healthy tissue was.

4527. invasive species
Author:
Definition:

Non-native species disrupting and replacing native species.

4528. invasiveness
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Degree to which an organism is able to spread through the body from a focus of infection.

4529. inverse density dependence
Definition:

A situation where an environmental factor which affects population density inversely changes when the population density changes, such that an increase in population density will cause the population to grow better, while a decrease in population density will cause the population to not grow as well. Generally the environmental factor affects birth and death rates to cause this to occur.

4530. inversion
Definition:

A type of chromosomal mutation where the nucleotide sequences within a segment of DNA are in reverse order than normal, as if that piece of DNA had been removed, turned over, and put back.

4531. invert (thalweg)
Author:
Definition:

The bottom (at its deepest point) of any streambed or channel, natural or manmade (i.e., the bottom of any culvert, etc.). In a natural stream the term "thalweg" is generally used.

4532. invertebrate
Definition:

Generally, any animal that does not have a spine (vertebrae). Specifically, any animal which is not taxonomically classified within phylum Chordata and subphylum Vertebrata.

4533. invertebrate zoology
Definition:

The field of biology which deals with the study of invertebrate animals.

4534. inverted repeat
Definition:

Either of two copies of a DNA sequence (such as those found at opposite ends of a transposon) which occur in identical but inverted form.

4535. involucel
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

A secondary involucre, as the bracts subtending the secondary umbels in the family Umbelliferae.

4536. involucre
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A group of bracts enveloping a condensed inflorescence; a layer of tissue enveloping some plant parts.

4537. involute
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Rolled inwards; of a leaf, with the margins rolled towards the adaxial surface.

4538. iododeoxyuridine (IUdR)
Definition:

A manmade nucleoside molecule (consists of a nitrogenous base linked to a sugar) which causes cells that have been infected with Epstein-Barr virus to express the viral genes and make viral proteins, when the infected cells normally would not.

4539. iojap
Definition:

A gene found in the corn plant which plays an important role in the development of chloroplasts. Corn plants which are an overall pale green in color (and/or have narrow, white- or green-striped leaves) have a mutated iojap gene.

4540. ion
Definition:

An atom or molecule that has gained or lost electrons and thus has a net positive or negative charge.

4541. ion channel
Definition:

A protein imbedded in a cell membrane that serves as a crossing point for the regulated tranfer of a specific ion or group of ions across the membrane.

4542. ion exchange resin
Definition:

A resin of polymers that have fixed charged groups which is used in chromatographic columns to separate ions.

4543. ionizing radiation
Definition:

Radiation (such as x-rays) that can make organic molecules into ions, and therefore make them more reactive, by knocking off some of their electrons.

4544. ionophore
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A compound which can cause the leakage of ions across membranes.

4545. irritable bowel syndrome
Author: Guo Li
Definition:

Irritable bowel syndrome is a chronic functional disorder of abdominal pain, altered bowel habits and stool consistency which is not due to a discernable physical or biochemical reason. There is often a psychological component to its cause.

4546. irritant
Definition:

This refers to any substance that causes inflammation following immediate, prolonged, or repeated contact with skin or mucous membranes.

4547. ischemia (ischaemia)
Definition:

This medical term refers to an insufficient blood supply to any part of the body.

4548. ischemic heart disease
Definition:

Ischemic heart disease is characterized by atherosclerosis (hardening) of the coronary vessels, which makes the patient likely to suffer from angina (chest pain) and myocardial infarction (heart attack).

4549. islets of Langerhans
Author: PharmInfoNet
Definition:

Special groups of cells in the pancreas. They make and secrete hormones that help the body break down and use food. Named after Paul Langerhans, the German scientist who discovered them in 1869, these cells sit in clusters in the pancreas. There are five types of cells in an islet: beta cells, which make insulin; alpha cells, which make glucagon; delta cells, which make somatostatin; and PP cells and D1 cells, about which little is known.

4550. isoantigen (alloantigen)
Definition:

An antigen which can cause an immune response in genetically distinct individuals from the same species.

4551. isoelectric focusing
Definition:

A technique used in electrophoresis that separates molecules on the basis of their different isoelectric points.

4552. isoelectric point (isoelectric pH)
Definition:

The pH at which molecule in a solution will no longer move in an electric field because it no longer has a net electric charge.

4553. isoenzyme (isozyme)
Definition:

Any of a group of related enzymes that catalyze the same reaction but have different structural, chemical, or immunological characteristics.

4554. isogamy
Definition:

A condition where the gametes of a species are equal in size. Generally this means that there is only one type of gamete with no sexual difference.

4555. isograft
Author: Guo Li
Definition:

An isograft is tissue transplanted between a genetically identical donor and recipient (e.g. between identical twins). It results in the best matched transplantation with the lowest chance of rejection.

4556. isohyet
Author:
Definition:

Line on a map connecting points of equal precipitation.

4557. isoimmunization
Author: Guo Li
Definition:

Isoimmunization is the development of antibodies which are elicited by antigens of another individual of the same species. One clinical example is the Rh isoimmunization of the mother. During the course of pregnancy, fetal red cell fragments are often found in the maternal blood. (about 1/3 of mothers in the third trimester has fetal red cell fragments in their blood). If the mother is Rh negative, and the fetus is Rh positive, the fetal red cells would cause isoimmunization of the mother.

4558. isolated waters
Author:
Definition:

Those non-tidal waters of the U.S. that are:
1. not part of a surface tributary system to interstate or navigable waters of the U.S.; and
2. not adjacent to such tributary waterbodies.

Source: 33 CFR § 330.2(e).

4559. isolateral (isobilateral)
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Having structurally similar upper and lower surfaces.

4560. isolation
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Any procedure in which a given species of organism, present in a particular sample or environment, is obtained in pure culture.

4561. isoleucine
Image: View the chemical structure
Author: Courtesy of MacMolecule
Definition:

One of the twenty naturally occurring amino acids. Has the following chemical characteristics:


pKa1   pKa2     pI      Water Solubility (30deg C)
2.36   9.68    6.02            4.0

4562. isomerase
Definition:

An enzyme that converts molecules into their positional isomers.

4563. isomerism
Definition:

A condition in which several chemical compounds have the same molecular formula (have the same number and type of atoms) but, because those atoms are arranged differently in each, they all have different chemical properties.

4564. isoschisomer (isoschizomer, isoschisomere, isoschizomere)
Definition:

One of several restriction endonucleases which are isolated from different sources but which break a DNA molecule at the same recognition site.

4565. isothermal
Definition:

Refers to a reaction or process that occurs at a constant temperature.

4566. isotope
Definition:

An alternate form of an element that has the usual number of protons but a nonstandard number of neutrons; the fewer or additional neutrons give the isotope a different atomic weight than the regular element and may make the isotope radioactive, but otherwise an isotope has the same chemical action as the regular element. Because of this, isotopes (such as radioactive carbon) are used as tracers in biological systems or processes.

4567. isotype (isotypic)
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A specimen which is, or is believed to be, a duplicate of the holotype, i.e. part of the same collection.

4568. isovel
Author:
Definition:

Line on a diagram of a channel or channel section connecting points of equal velocity.

4569. iteroparous
Author:
Definition:

Able to spawn more than one time; reproducing annually, or having more than one brood.

4570. IVP (intravenous pyelogram)
Author: Guo Li
Definition:

An intravenous pyelogram is an imaging technique by displaying the contour of the urinary tract which is highlighted with radiopaque dyes (contrast) injected intravenously and secreted by the renal tubules of the kidneys. It provides information of the differential filtration rates of the kidneys, the kidney sizes, position, abnormal anatomies or growths, presence of stones in the kidney, and ureter.

4571. J genes
Definition:

Groups of nucleotide sequences in the genes coding for the chains of the T cell receptor and in the immunoglobulin heavy- and light-chain genes which are recombined during lymphocyte development and which contribute to the genes coding for variable domains.

4572. J wave of Osborn
Author: Guo Li
Definition:

The J wave of Osborn is an electrographic abnormality that is indicative of hypothermia. It is an upward wave immediately following the S wave in a QRS complex.

4573. Jaccard coefficient (SJ)
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

An association coefficient used in numerical taxonomy; it is the proportion of characters that match, excluding those that both organisms lack.

4574. jack
Author:
Definition:

Young salmon, usually a male, that matures precociously.

4575. jack (jackstraw)
Author:
Definition:

Bank protection element consisting of wire or cable strung on three mutually perpendicular struts.

4576. jacklines
Author:
Definition:

A series of large steel or iron "jacks," usually up to 10 feet in height and cabled together at intervals and "deadmanned" to the bank or tied to trees along the margin of a stream to prevent cutting and eroding by slowing down high velocity flows. Can help reclaim eroded soils by trapping silt, sand, etc.

4577. jam
Author:
Definition:

Wedged collection of drift in a constriction of a channel, such as a gorge or bridge opening.

4578. Japanese B encephalitis
Definition:

An epidemic viral encephalitis that strikes populations in Japan and other East Asian countries, typically in summer months. Symptoms can resemble poliomyelitis, but the disease can also be virtually symptomless.

4579. jaundice (icterus)
Definition:

Yellowing of the skin and eyes due to excessive bilirubins (bile pigments) in the blood; it is often a major symptom of hepatitis. Jaundice becomes recognizable when the total amount of blood bilirubins is greater than 50 umols per liter.

4580. jaw thrust maneuver
Author: Guo Li
Definition:

The jaw thrust maneuver is a method of maintaining an open airway of an unconscious individual. Jaw thrust is used to open the mouth and lift the tongue which obstructs the patency of the airway. It is usually performed by placing on each side of the face, the index and middle fingers at the angle of the mandible. The thumbs are placed on the chin just below the lower lip. As the mouth is opened by exerting downward force on the chin, the index and middle fingers would lift the entire mandible anterior thus moving the base of the tongue out of obstruction.

4581. jejunostomy
Author: Guo Li
Definition:

Jejunostomy is surgery in which the jejunum is brought outside of the abdominal wall and opened.

4582. jejunum
Definition:

The jejunum is the portion of the small intestine which joins the pylorus of the stomach to the cecum. It is the middle part of the small intestine, between the duodenum and the ileum.

4583. jelly fungus (trembling fungus, tremmellales)
Definition:

Any of several fungi in the order Tremellales, which are characterized by gelatinous fruiting bodies.

4584. jet
Author:
Definition:

An effluent stream from a restricted channel, including a fast current through a slower stream.

4585. jetty
Author:
Definition:

An elongate artificial obstruction projecting into a stream or the sea from bank or shore to control shoaling and scour by deflection of strength of currents and waves.

4586. jimson weed (jimsonweed, jimpson, datura)
Definition:

A poisonous annual plant (Datura stramonium) in Solanaceae, the nightshade family. It has stinky leaves and white trumpet-shaped blooms and is the source of many useful alkaloids, including atropine, hyoscine and hyoscamine. It's name is a corruption of "Jamestown weed"; reputedly, the early settlers in Jamestown, Virginia discovered the toxic effects of the plant when a cook collected several of them as a side dish to a meal.

4587. Johansen, Wilhelm
Definition:

A Dutch geneticist who lived from 1857 to 1927; he coined the word "gene" and demonstrated that environmental adaptations are not inherited.

4588. joining segment
Author: Susan A.Hagedorn
Definition:

A small DNA segment that links genes to yield a functional gene encoding an immunoglobulin.

4589. joints
Definition:

A joint is the place where two or more bones connect. Joints are made of connective tissue and cartillage and can be classified as:
• fibrous joints (such as those in the skull) connect bones with fibrous connective tissue; they allow little or no movement.
• cartilaginous joints (vertebrae, for example) connect bones with cartilage and fibrous connective tissue; they also allow little or no movement.
• synovial joints contain synovial fluid, which lubricate the joint and absorbs frictional heat created by the joint's movement. There are several sub-types of synovial joints:
  • ball and socket joint: the rounded head of one bone fits into a socket-like cavity of another, such as the hip and shoulder joints. These joints allow free rotation
  • hinge joint: elbow and ankles. These joints allow for flexion and extension.
  • saddle joint: the thumb. Bone surfaces are concave, allowing movement in all direction but only limited rotation.
  • ellipsoid joint: structurally similar to a ball and socket joint but without rotation.
  • pivot joint: the skull on its spinal axis; movement is limited to rotation.
  • gliding joint: the wrist. Bone surfaces slide across each other, allowing a wide range of movements.

4590. Jones reducer
Definition:

An apparatus made up of a column filled with amalgamated zinc which is used to reduce solutions.

4591. Jordan's rule
Definition:

An evolutionary rule that states that the closest genetic relatives of a given species are found very near it, but the two groups are isolated by some kind of natural barrier (such as a river) that neither species can cross easily.

4592. jump
Author:
Definition:

Sudden transition from supercritical flow to the complementary subcritical flow, conserving momentum and dissipating energy; the hydraulic jump.

4593. jun oncogene
Definition:

An oncogene (a gene associated with cancer) that a retrovirus found in chickens carries, which causes fibrosarcoma tumors. The normal product of the proto-oncogene is transcription regulation factor AP-1. The product of the oncogene causes abnormal gene transcription rates.

4594. jute netting
Author:
Definition:

A natural fiber mesh used to hold soil and plants in place on eroding slopes.

4595. juvenile
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

1. A young or sexually immature animal; relating to such a young animal.
2. Of leaves, formed on a young plant and different in form from the adult leaves.

4596. juvenile hormone (neotenin)
Image: View the chemical structure
Definition:

A hormone produced by insects in all larval stages. The hormone is produced by a small gland behind the brain, and the insect metamorphs into its adult stage when production ceases.

4597. juvenile rheumatoid arthritis (Still's disease)
Definition:

A disease affecting children which is characterized by joint inflammation, enlarged lymph nodes and fever.

4598. juvenile rheumatoid arthritis (Still's disease)
Author: Guo Li
Definition:

Juvenile rheumatoid arthritis is rheumatoid arthritis with onset before 17 years old with immunogenetic traits that are different from the adult form of rheumatoid arthritis. However, treatment is similar. Four forms of juvenile rheumatoid arthritis are recognized:
• polyarticular form: symmetric arthritis, low-grade fever, rheumatoid nodules
• oligoarticular form: asymmetric arthritis of large weight-bearing joints, iridocyclitis
• systemic-onset disease (Still's disease): acute fever, rash, enlarged spleen and liver
• juvenile form of ankylosing spondylitis: late childhood, mainly in boys, HLA-B27 present

4599. juxtaglomerular apparatus
Author: Guo Li
Definition:

The juxtaglomerular apparatus is form by cells near the glomerulus of the kidney, consisting of:
• juxtaglomerular cells (JG cells), epithelioid cells in the media of the afferent arterioles as they enter the glomerulus
• macula densa: tubular epithelium at the region of afferent arteriole and efferent arteriole to the glomerulus
The JG cells secrete renin, a process mediated by angiotensin II and vasopressin.

4600. k antigen
Definition:

Any of many antigens that are part of a bacterial capsule or form on the outer portion of a cell wall.

4601. k selection
Definition:

In evolution, the selection of traits that aid an organism's competitive capability when the population is at or near its carrying capacity.

4602. K-RAS
Definition:

A proto-oncogene that has point mutations and is associated with melanoma, thyroid carcinoma, and acute myelogenous and lymphoblastic leukemia.

4603. kaemferol
Image: View the chemical structure
Definition:

A flavone-ring-containing plant pigment found in many angiosperms (flowering plants).

4604. kames
Definition:

Mounds of poorly sorted glacial drift, mostly sand and gravel, deposited near the front of a glacier.

4605. kanamycin
Image: View the chemical structure
Author: Susan A.Hagedorn
Definition:

An antibiotic of the aminoglycoside family that poisons translation by binding to the ribosomes.

4606. Kaposi's sarcoma (multiple idiopathic hemorrhagic sarcoma)
Definition:

A type of vascular cancer characterized by soft purple nodules that usually develop first on the feet and then slowly spread across the skin. This cancer is most often found in people with compromised immune systems, such as AIDS patients.

4607. kappa chain
Definition:

Either of two types of light chains (small polypeptide chains) that are found in immunoglobulins.

4608. karnal blunt
Definition:

A fungal wheat disease caused by Tilletia indica.

4609. karyocyte
Definition:

General scientific term for any cell with a nucleus.

4610. karyoevolution
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Evolutionary change in the chromosome set, expressed as changes in number and gross structure of the chromosomes; (more broadly), evolutionary relationships between taxa as indicated by karyotype differences.

4611. karyogamy
Definition:

The fusion of two nuclei.

4612. karyology
Definition:

The scientific study of chromosomes; this usually involves the study of their general shape and banding patterns.

4613. karyolysis
Definition:

The destruction of a cell's nucleus.

4614. karyomegaly
Definition:

The condition of a cell's nucleus being abnormally enlarged (i.e., for reasons other than it being polyploid).

4615. karyoplasm (nuclear sap)
Definition:

Areas within a nucleus that seem to contain only clear fluid.

4616. karyoplast
Definition:

1. The nucleus of any cell.
2. A nucleus that has been excised from a cell.

4617. karyorrhexis
Definition:

Degeneration or fragmentation of a cell's nucleus.

4618. karyosome
Definition:

The central portion of a cell's nucleus that typically contains a glob of heterochromatin.

4619. karyotype (adj. karyotypic)
Definition:

A karyotype is a photomicrograph of an individual's chromosomes arranged in a standard format showing the number, size, and shape of each chromosome type. Each chromosome is characterized by the length of its arms and the location of its centromere, which appears as an indentation or a lightly stained region. Staining methods may result in banding on the chromosomal arms (chromatids); chromosomes can then be identified according to their banding pattern. Karyotypes are used in low-resolution physical mapping to correlate chromosomal abnormalities with the characteristics of specific diseases.

4620. kasugamycin (kasumin)
Definition:

An aminoglycoside antibiotic used against bacteria and some fungi; it is unusual because it is bacteriostatic (inhibits bacterial growth and reproduction) rather than bacteriocidal.

4621. Kawasaki's disease (mucocutaneous lymph node syndrome)
Author: Guo Li
Definition:

This disease occurs mainly in children, and is characterized by fever that lasts longer than 5 days and which is not responsive to antibiotic treatment, plus the following mucocutaneous manifestations:
• conjunctivitis
• mucous membrane changes: cracked lips, strawberry tongue
• extremity changes: edema, desquamation of tips of the toes and fingers, erythema, rash
• lymphadenopathy of the neck greater than 1.5 cm
A major complication is arteritis and aneurysm formation of the coronary vessels, myocarditis, pericarditis and acute myocardial infarction.

4622. keel
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A ridge like the keel of a boat; in particular, a boat-shaped structure formed by fusion of the two anterior petals of a flower.

4623. keeled
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of leaves or bracts, folded and ridged along the midrib.

4624. Kell blood group system
Definition:

Blood type classification based on a group of erythrocyte antigens that is characterized by an antibody called anti-K.

4625. keloid
Author: Guo Li
Definition:

A keloid is a hypertrophic scar due to fibrous nodular growth in a healing process.

4626. keratin
Definition:

A fibrous, insoluble, sulfur-containing protein that serves as the main structural molecule in hair and nails and is also present in the skin.

4627. keratinocyte
Definition:

A skin cell that makes keratin.

4628. keratotomy
Author: Guo Li
Definition:

Keratotomy is surgical incision on the cornea for the correction of myopia (nearsigtedness) and/or astigmatism (an irregular cornea that results in blurred vision).

4629. kernel blight
Definition:

Any of a group of fungal diseases of barley which cause withering and discoloration of the grain; Gibberella zeae, Helminthosporium sativum and Alternaria are typically the culprits.

4630. kernel spot
Definition:

A fungal disease of pecans that causes irregular brown spots on the nuts; it is caused by Coniothyrum caryogenum.

4631. kernicterus
Author: Guo Li
Definition:

Kernicterus is a clinical syndrome afflicting newborns which is caused by high levels of unconjugated bilirubin which passes the immature blood-brain barrier of the newborn and causes degeneration of cells of the basal ganglia and hippocampus. An affected child displays a range of neurologic disorders: hypertonia, seizure, and cerebral palsy. In severe cases, death is likely.

4632. Kernig's sign
Author: Guo Li
Definition:

Kernig's sign is a clinical sign which is present in meningitis. The subject lies down on his or her back and a thigh is flexed to form a right angle with the trunk (i.e. perpendicular to the plane the subject is lying). The examiner then attempts to extend the leg. A positive Kernig's sign is present if complete extension of the leg is not possible because of limitation by pain.

4633. kerosine fungus (creosote fungus)
Definition:

An asexual fungus (Hormoconis resinae in the family Amorphothecaceae) that is found in the air and soil which can grow in and block the fuel filters of jet engines.

4634. ketoacidosis
Author: Guo Li
Definition:

Ketoacidosis is the condition of acid in the blood due to the accumulation of ketone bodies.

4635. ketone
Definition:

A carbon atom double-bonded to an oxygen and single-bonded to two chemical groups (such as methane, benzene, anything besides hydrogen). The carbon-oxygen double bond part is known as a carbonyl group (-C=O). An example is acetone, which is a carbonyl group attached to two methanes (methyl groups: -CH₃).

4636. ketone body (acetone body, ketone bodies)
Definition:

Any of the three compounds created by acetyl coenzyme A (acetoacetate, hydroxybutyrate, and acetone) which are water-soluble cellular fuels normally exported by the liver. They can build up in the blood and body tissues because of starvation, untreated diabetes mellitus, or other disorders that interfere with carbohydrate metabolism.

The body rids itself of ketones mainly through urine, but it rids itself of acetone through the lungs, which gives the breath a characteristic fruity odor. If ketones build up in the body long enough, they cause serious illness and coma (see ketoacidosis.)

4637. ketonemia (acetonemia)
Definition:

Medical term describing the condition of having excess ketone bodies in the bloodstream.

4638. ketonuria
Definition:

The presence of ketone bodies in the urine; this is a symptom of diabetes mellitus.

4639. ketose
Definition:

A simple sugar that has a ketone as its carbonyl group.

4640. ketosis
Definition:

A metabolic disorder in which ketone bodies are at high levels in the blood, body tissues and urine.

4641. ketosteroid
Definition:

A steroid-like chemical which is a by-product of the breakdown of certain steroids; they are found in urine and measuring them can give a good indication of the level of androgen production in the body. The major ketosteroids are:
• androsterone
• etiocholanone
• estrone

4642. kidney disease (nephropathy)
Author: PharmInfoNet
Definition:

Any one of several chronic conditions that are caused by damage to the cells of the kidney. People who have had diabetes for a long time may have kidney damage.

4643. kidney failure (renal failure)
Author: Guo Li
Definition:

Kidney failure is the decrease in the glomerular filtration rate. The most often used laboratory test is serum creatinine (normal 50 to 100 umol/L). If a subject is totally without kidney function, serum creatinine rises by about 80 to 120 umol/L per day.

4644. kidneys
Author: PharmInfoNet
Definition:

Two organs in the lower back that clean waste and poisons from the blood. The kidneys are shaped like two large beans, and they act as the body's filter. They also control the level of some chemicals in the blood such as hydrogen, sodium, potassium, and phosphate.

4645. killer cell (K cell)
Definition:

An effector cell, such as a cytotoxic T cell, leukocyte or macrophage, that regulates antibody-dependent cell toxicity.

4646. killer yeast
Definition:

A yeast that secretes a toxin that can kill other yeasts.

4647. kilobase (kb)
Definition:

Unit of length for DNA fragments equal to 1000 nucleotides.

4648. kinase
Definition:

Any of several enzymes that catalyze the transfer of a phosphate group from one molecule to another.

4649. kinetics
Definition:

1. The study of reaction rates.
2. The study of the relationship between force and mass.

4650. kinetin (cytokinin 6-furfurylaminopurine)
Image: View the chemical structure
Definition:

A powerful plant growth factor found in the callus tissue of tobacco plants.

4651. kinetochore
Definition:

A platelike structure necessary for chromosomal movement during mitosis; it develops on the centromere and links the chromosomes to the mitotic spindle.

4652. kinetoplasm
Definition:

The highly contractile part of a cell's cytoplasm.

4653. kinetoplast
Definition:

A network of interlocked DNA circles found in mitochondria.

4654. kingdom
Definition:

The topmost taxonomic rank, immediately above phylum or division.

This dictionary recognizes five biological kindoms:

Monera
Protista
Fungi
Plantae
Animalia

4655. Kingdom Animalia
Definition:

The members of this kingom are complex, multicellular, eukaryotic organisms that digest food outside their cells and then absorb the digested nutrients. Animals must consume other organisms to obtain most of their nutrients.

4656. Kingdom Fungi (sing. fungus)
Definition:

Kingdom Fungi includes organisms such as slime molds, mushrooms, smuts, rusts, mildews, molds, stinkhorns, puffballs, truffles and yeasts. All are classified in this kingdom because they absorb food in solution directly through their cell walls and reproduce through spores. None conduct photosynthesis.

4657. Kingdom Monera (prokaryotes, monerans)
Definition:

This biological kingdom is composed of bacteria and cyanobacteria, one-celled (sometimes colonial) organisms whose cells lack a nuclear envelope, mitochondria, or plastids. They reproduce asexually through fission (splitting in two) and mainly gain their nutrition by absorbing it from their environment (though some species are chemoautotrophs or photosynthetic).

4658. Kingdom Monera
Definition:

This is the most primitive of the five kingdoms; it encompasses all the bacteria. Monerans are single-celled prokaryotic organisms.

4659. Kingdom Plantae
Definition:

The members of this kingdom are multicellular, eukaryotic organisms that (usually) conduct photosynthesis.

Compare Kingdom Fungi and Kingdom Animalia.

4660. Kingdom Protista (protists)
Definition:

This biologic kingdom is composed of eukaryotic organisms: unicellular and multicellular algae, slime molds, and unicellular or simple colonial protozoans. Protists obtain their nutrition via several methods, including photosynthesis, devouring other organisms, and absorption. Protists can reproduce sexually or asexually, and they can be sedentary or move with pseudopods, flagella, or cilia. There are over 55,000 known living species and over 35,000 known extinct species in this kingdom.

4661. Kingdom Protista
Definition:

This kingdom is composed of single-celled (sometimes multicellular), eukaryotic organisms. Protists are more complex than bacteria and include protozooans and some types of algae.

4662. Klebsiella
Definition:

Klebsiella is a genus of Gram-negative, rod-shaped bacteria in the family Enterobacteriaceae. Facultative anaerobes, they are found in the intestinal and repiratory tracts of many vertebrates (including humans) and are commonly responsible for bladder, kidney, lung, and wound infections. K. pneumoniae can cause pneumonia in people with compromised immune systems.

4663. Kleinschmidt monolayer technique
Definition:

A techniqe for preparing DNA for study under an electron microscope; the DNA molecules are spread as a thin, positively charged protein film on water. The film is then transferred to a copper viewing grid and placed under the 'scope.

4664. Klenow fragment
Definition:

The larger of the two pieces of DNA polymerase I left after proteolytic cleaving; the fragment lacks the 5'-3' exonuclease activity of the whole enzyme but retains its DNA polymerase and 3'-5' exonuclease properties.

4665. kleptoparasite
Definition:

An organism that gets its food by scavenging or stealing it from another organism that it lives in close association with.

4666. Klinefelter syndrome (XXY trisomy)
Definition:

A genetic syndrome in many mammals caused by the presence of an extra X chromosome in the male (normally XY) karyotype. In humans, this syndrome is characterized by small testes, feminine appearance, sterility (except in the case of genetic mosaics) and possibly mental retardation. In domestic cats, male calicos always have this genetic condition.

4667. Klinefelter's syndrome
Author: Guo Li
Definition:

Klinefelter's syndrome is a genetic disorder that afflicts some males and is characterized by tall stature, infertility, abnormal breast tissue development and abnormally small reproductive organs. The affected individuals are genetically XXY.

4668. Klippel-Feil syndrome
Author: Guo Li
Definition:

Klippel-Feil syndrome is characterized by the congenital fusion of two or more cervical vertebrae, resulting in a short and rigid neck.

4669. Koplik's spots
Author: Guo Li
Definition:

Koplik's spots are tiny red vesicular lesions with blue-white centers on the mucous membranes of the cheek, inner conjunctival folds and vagina. Koplik's spots indicate that the patient has a measles infection; the spots appear about 2 days before the characteristic rash and last 1 to 4 days.

4670. Kornberg, Arthur
Definition:

A U.S. biochemist who was co-awared the Nobel Prize for discovering some of the enzymes responsible for DNA synthesis.

4671. Korsakoff's syndrome
Author: Guo Li
Definition:

Korsakoff's syndrome is characterized by confusion, impairment of memory, and unconscious falsification of experience to fill in memory gaps. This syndrome is frequently found in alcoholics.

4672. Krebs cycle (citric acid cycle, tricarboxylic acid cycle)
Definition:

A complex series of reactions following glycolysis in aerobic respiration that convert pyruvic acid into hydrogen, carbon dioxide and electrons.

4673. Krebs, Hans Adolph
Definition:

A German-born British chemist (1900-1981) who was awarded the Nobel for his research in intermediate metabolism.

4674. kreotoxin
Definition:

Term for any basic (pH over 7) toxin produced by bacteria or fungi in meat.

4675. Kussmaul's breathing
Author: Guo Li
Definition:

This is the increased depth and rate of breathing; a clinical sign associated with metabolic acidic condition, especially diabetic acidosis.

4676. kwashiorkor
Definition:

A nutritional deficiency illness in children who aren't getting enough protein; this results in anemia, poor growth, weakness, and edema (which is particularly characterized by a pronounced pot belly). In famine-stricken regions, children typically develop kwashiorkor right after they are weaned.

4677. kyphosis
Author: Guo Li
Definition:

Kyphosis is an exaggerated backward curving of the thoracic part of the vertebral column.

4678. L form (L-phase, L-phase variant)
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

L-forms are bacterial spheroplasts or protoplasts originating from normal bacteria following partial (spheroplasts) or complete (protoplasts) removal of the cell wall. The formation of L-forms can be either spontaneous (occuring during certain phase of growth) or artificial (suppression of the rigid cell wall by stimuli such as enzymes, heat-shock, or specieal L form induction medium, etc.) Bacterial genera from which L-forms have been derived include: Agrobacterium, Bacillus, Bacterodes, Bartonella, Bordetella, Brucella, Clostridium, Corynebacterium, Erysipelothrix, Escherichia, Flavobacterium, Haemophilus, Listeria, Neisseria, Proteus, Pseudomonas, Salmonella, Sarcina, Serratia, Shigella, Staphylococcus, Streptobacillus, Streptococcus, and Vibrio.

4679. labellum
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A lip; in orchids, the distinctive median petal that serves as an alighting platform for pollinating insects.

4680. labiate
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Lipped, as in a calyx or corolla.

4681. labor (childbirth)
Author: Guo Li
Definition:

Labor is the sequence of events including uterine contractions, dilatation and effacement of the cervix (the mouth of the uterus), and the attempt to push the fetus down and out of the vagina. It is common in text books to describe the 3 stages of labor:
• first stage: from the onset of labor (characterized by regular uterine contractions that in time becomes more frequent, more intense and is of longer duration) to full dilatation of the cervix (10 cm).
• second stage: from the time when the cervix is fully dilated to the birth of the infant.
• third stage: from the birth of the infant to the time when the placenta is delivered.

4682. lacerate
Definition:

1. To tear or cut in a ripping fashion.
2. Describes a margin that is irregularly torn, as if lacerated.

4683. laciniate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Slashed into narrow, pointed lobes.

4684. lacrymiform
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Tear-shaped.

4685. lactase (invertase)
Definition:

An enzyme which cuts the disaccharide lactose into its component monosaccharides glucose and galactose. The components, immediately upon being cut apart from each other by the enzyme, invert into their opposite isomers. Lactose intolerance is the result of not enough lactase (invertase) in the body.

4686. lactate dehydrogenase (LDH)
Author: Guo Li
Definition:

This enzyme cannot be used to screen for cancer but can be used as a tumor marker to monitor the course of certain types of cancer.

4687. lactation (verb: lactate)
Definition:

The secretion of milk for the purpose of nursing offspring. All female mammals are able to feed their newborn young in this manner.

4688. lactic acid
Author: Guo Li
Definition:

Lactic acid is formed by the reduction of pyruvate, a process occurring in hypoxic state (this is because further breakdown of pyruvate requires oxygen).

4689. lactic acid bacteria
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A group of Gram-positive, non-sporing bacteria which carry out a lactic acid fermentation of sugars. It includes species of Lactobacillus, Leuconostoc, Pediococcus and Streptococcus.

4690. lactic acid fermentation
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A type of fermentation carried out by lactic acid bacteria in which sugar (e.g. lactose, glucose, pentose) are converted either entirely (or almost entirely) to lactic acid (homolactic fermentation) or to a mixture of lactic acid and other products (heterolactic fermentation).

4691. lactose (lactin, milk sugar)
Definition:

A type of disaccharide which is composed of the monosaccharides galactose and glucose linked together. It has the chemical formula of C₁₂H₂₂O₁₁. It is found in dairy products.

4692. lactose intolerance
Author: NIDDK
Definition:

Lactose intolerance is the inability to digest significant amounts of lactose, the predominant sugar of milk. This inability results from a shortage of the enzyme lactase, which is normally produced by the cells that line the small intestine. Lactase breaks down milk sugar into simpler forms that can then be absorbed into the bloodstream. When there is not enough lactase to digest the amount of lactose consumed, the results, although not usually dangerous, may be very distressing. While not all persons deficient in lactase have symptoms, those who do are considered to be lactose intolerant. Common symptoms include nausea, cramps, bloating, gas, and diarrhea, which begin about 30 minutes to 2 hours after eating or drinking foods containing lactose. The severity of symptoms varies depending on the amount of lactose each individual can tolerate.

For more information, visit the NIDDK's Lactose Intolerance Page.

4693. lactose intolerance
Author: Guo Li
Definition:

Lactose intolerance is the inability to digest lactose (a disaccharide of glucose and galactose). The digestion of lactose requires the enzyme lactase. Undigested lactose causes two major problems:
• fermentation of lactose by intestinal bacteria produces gas and organic acid
• lactose causes an osmotic diarrhea in the large bowel

4694. lacuna
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A gap or cavity.

4695. lacunate
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

With air spaces or chambers in the midst of tissue.

4696. lacustrine
Author:
Definition:

Of or having to do with a lake; of, relating to, or formed in lakes; growing or living in lakes; of or relating to dwellings built on piles in lakes (e.g., prehistoric central Europe, Scotland, and Ireland).

4697. lag phase
Author: Susan A.Hagedorn
Definition:

The initial growth phase of a culture, during which cell number remains relatively constant prior to rapid growth.

4698. lagging strand
Definition:

The DNA strand that is replicated discontinuously from the 5' to the 3' direction; see Okazaki fragments. Also compare leading strand.

4699. lagoon
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

A shallow lake or pond, especially one connected with a larger body of water; an area of shallow salt water separated from the sea by sand dunes; the area of water surrounded by an atoll, or circular coral reef.

4700. lagoon
Author:
Definition:

A small pond-like body of water connected to a larger body of water. A lagoon would be formed in a small stream during the summer when a sand bar closed off the mouth of the stream from the ocean.

4701. lake
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

An inland body of water, usually fresh water, formed by glaciers, river drainage, etc., larger than a pool or pond.

4702. lake
Author:
Definition:

A water-filled basin with restricted or no outlet. Includes reservoirs, tidal ponds, and playas.

4703. lamella
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A thin, plate-like layer; middle lamella, the layer between the walls of two adjacent plant cells.

4704. lamellate
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Made up of thin plates or lamina.

4705. lamina
Author: Guo Li
Definition:

The lamina is part of a vertebral arch.

4706. laminar flow
Author:
Definition:

The type of flow in a stream of water in which each particle moves in a direction parallel to every particle.

4707. laminectomy
Author: Guo Li
Definition:

A laminectomy is surgery to remove part of the lamina of the vertebral body.

4708. lanceolate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Lancelike; of a leaf, about four times as long as it is broad, broadest in the lower half and tapering towards the tip.

4709. lanugo
Author: Guo Li
Definition:

Lanugo is the downy hair covering a fetus.

4710. laparoscope
Author: Guo Li
Definition:

A laparoscope is an instrument for the external viewing of the abdominal contents via a small incision on the abdominal wall.

4711. laparoscopy (diagnostic laparoscopy)
Author: Guo Li
Definition:

This is a visual examination of abdominal contents to rule out ectopic pregnancy, ruptured ovarian cysts, endometriosis, and fibroids. Some surgical procedures can be carried out with laparoscopes.
• The procedure: A periumbilical incision is made. After the abdominal cavity is inflated with carbon dioxide through a small needle inserted into the incision, the laparoscope is introduced. One to two other incisions each about 0.5 to 1 cm diameter is made around the suprapubic area.
• Alternative courses of action: depend on the medical condition for which laparoscopy is indicated.
• Material effects, risks and side effects: residual carbon dioxide may irritate the diaphragm causing shoulder pain for up to 12 hours; potential for trauma to the bladder, bowel and blood vessels, in which case, open laparotomy will be done.
• Consequences of not having the treatment: depend on the medical condition for which laparoscopy is indicated.

4712. laparoscopy
Author: Fertilitext
Definition:

The examination of the pelvic organs through a small scope called a laparoscope.

4713. laparotomy
Author: Fertilitext
Definition:

Surgically opening the abdomen.

4714. large woody debris (LWD, large organic debris, LOD)
Author:
Definition:

1. Any large piece of woody material that intrudes into a stream channel, whose smallest diameter is greater than 10 cm, and whose length is greater than 1 m.
2. A large piece of relatively stable woody material having a diameter greater than 30 cm (12 inches) and a length greater than 2 m (6 feet) that intrudes into the stream channel. Specific types of large woody debris include floating logs, boles, deadheads, root wads, etc.

4715. laryngectomy
Author: Guo Li
Definition:

Laryngectomy is surgery to remove the larynx.

4716. laryngitis
Author: Guo Li
Definition:

Laryngitis is inflammation of the mucosa of the larynx.

4717. laryngoscope (laryngoscopy)
Author: Guo Li
Definition:

A laryngoscope is an instrument inserted through the opening of the mouth for viewing the larynx.

4718. larynx (voicebox, voice box)
Author: Guo Li
Definition:

The larynx is the structure in the throat that enables a person to speak. Its parts include:
• epiglottis (cartilage)
• arytenoid, corniculate, and cuneiform paired cartilages
• hyoid
• thyroid (cartilage)
• cricoid cartilage
• trachea

4719. latent virus
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A virus present in a cell which has not yet caused any detectable effect.

4720. lateral
Author:
Definition:

A man-made channel used to convey water from a canal to its delivery point.

4721. lateral malleolus
Author: Guo Li
Definition:

The lateral malleolus is a bony projection on the side of the ankle formed by the tip of the fibula.

4722. latex
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

1. A viscous fluid exuded from the cut surfaces of the leaves and stems of certain plants, such as the dandelion or the rubber tree.
2. A rubber made from such plant sap.

4723. latiseptate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

With broad partitions.

4724. lauric acid hydroxylase (hydroxylation)
Author: Biological Sciences at Heriot-Watt University
Definition:

Lauric acid 11- (=omega-1) or 12 (=omega) hydroxylating enzyme which is used as a marker for the measurement of an isoenzyme of cytochrome P-450. This microsomal enzyme is induced in rodent liver by several peroxisomal proliferators. See microsome, peroxisome.

4725. law
Definition:

A scientific principle that invariably holds true under specific conditions; for instance, the law of magnetism states that like magnetic poles repel one another, while opposite poles attract. See also hypothesis and theory.

4726. law of mass action
Definition:

This law states that the rate of a given chemical reaction is proportional to concentration of the reactants.

4727. lawn
Author: Susan A.Hagedorn
Definition:

A uniform and uninterrupted laver of bacterial growth, in which individual colonies cannot be observed.

4728. layering
Author:
Definition:

A propagation method by which adventitious roots are caused to form on a stem while it is still attached to the parent plant.

4729. LCn (LC50)
Author: Biological Sciences at Heriot-Watt University
Definition:

LC_n and LC₅₀ are abbreviations used for the exposure concentration of a toxicant lethal to n% of a test population. For instance, 50% of a given population would die from toxic effects at LC₅₀. Compare median lethal concentration.

4730. LDn (LD50)
Author: Biological Sciences at Heriot-Watt University
Definition:

LD_n abbreviation is used for the dose of a toxicant lethal to n% of a test population. For instance, at LD₅₀, 50% of the recipients of that particular toxic dose would die. See median lethal dose.

4731. LE cell prep
Author: Guo Li
Definition:

This is a test to diagnose systemic lupus erythematosis (SLE). Nuclear material from lysed WBC is incubated with the patient's serum and neutrophils. If antibodies against nuclear material is present, neutrophils would phagocytize the antibody bound complex. A positive result is one in which neutrophils with a homogenous red-purple inclusion that distends the cell's cytoplasm is found. Of patients with active SLE, 70 to 80% will have positive LE prep.

4732. leach tube
Author:
Definition:

A reusable cone-shaped plastic container used for growing seedlings for revegetation work; the containers can be mounted in a rack for easy transport and were named after Ray Leach, who invented them in Oregon.

4733. lead poisoning
Author: Guo Li
Definition:

Lead poisoning is the condition due to toxic levels of lead (a heavy metal that is used to make bullets, fishing sinkers, some white paints, and some gasoline additives) in the body. The clinical symptoms and signs are non-specific (headache, abdominal pain, learning disorders, and some forms of neuropathy). Diagnosis is made by finding high levels of lead in blood.

4734. leader
Definition:

A sequence near the 5' end of an RNA strand or the amino terminus of a protein that functions in targeting or regulation.

4735. leading strand
Definition:

The DNA strand that is synthesized continuously during replication Compare lagging strand.

4736. leaf blight
Author:
Definition:

Any of various diseases which lead to the browning and dropping of a plant’s leaves.

4737. leaflet
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

One of the ultimate segments of a compound leaf.

4738. least flow
Author:
Definition:

Negotiated lowest flow in a regulated stream that will sustain an aquatic population at agreed upon levels. The flow may vary seasonally.

4739. lectotype (adj. lectotypic)
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A specimen selected from among those cited with the original description to serve in place of a holotype where the holotype is missing or destroyed, or where no holotype was designated.

4740. left ventricular failure
Author: Guo Li
Definition:

Left ventricular failure is the condition characterized by the failure of the pumping function of the left heart as a result, left atrial pressure increases, the atrium and pulmonary vessels are distended. In serious cases, there is left pulmonary edema.

4741. left ventricular hypertrophy
Author: Guo Li
Definition:

Left ventricular hypertrophy is characterized by thickening of the wall of the left ventricle of the heart, often as a result of high blood pressure. Because hypertrophied ventricle demands more blood supply, and such supply have to perfuse a larger area, left ventricular hypertrophy predisposes one to myocardial ischemia and infarction.

4742. Legg Perthes disease
Author: Guo Li
Definition:

Legg Perthes disease is the avascular necrosis of the capital femoral epiphysis. The cause is unknown. This condition affects mainly children of age 4 to 10, boys 5 times more often than girls.

4743. Legionellaceae
Definition:

Legionellaceae is a family of disease-causing gram-negative aquatic aerobic flagellated rod-shaped bacteria. Diseases caused by members of this family includes Legionnaire's disease.

4744. Legionnaire's disease
Author: Guo Li
Definition:

Legionnaire's disease is a community-acquired pneumonia caused by the bacterium Legionella pneumophila. The elderly, immune-compromised, and smokers are particularly at risk of getting sick if they are exposed to this bacterium.

4745. Legionnaire's disease (legionellosis, Legionella pneumonia)
Definition:

Legionnaire's disease is caused by the bacterial species Legionella pneumonophila, a member of the family Legionellaceae, which begins with flu-like symptoms, then moves on to high fever, shaking chills, headaches, diarrhea, pneumonia, and pleurisy, and can result in death. The disease is highly contagious. The bacteria which causes this disease is only harmful when tiny droplets of water floating in the air containing the bacteria are inhaled, and does not cause harm when it is present in drinking water.

4746. legume
Author: Susan A.Hagedorn
Definition:

A member of the pea family (Fabaceae) that possesses root nodules containing nitrogen-fixing bacteria.

4747. leiomyoma (fibroid tumor)
Author: Guo Li
Definition:

A fibroid is a benign tumor of the smooth muscle of the myometrium of the uterus.

4748. Leishman-Donovan bodies
Definition:

Small spheres found in the spleen and liver of patients with visceral leishmaniasis. The spheres are an alternate, non flagellated form of the parasitic protozoan Leishmania donovani which occurs once the parasite has invaded the cells of the reticuloendothelial system in the patient's organs. The spheres are named after Sir William Leishman and Charles Donovan.

4749. Leishmania
Definition:

A genus of parasitic flagellated protozoans which causes diseases in animals including humans, most notably leishmaniasis. A type of trypanosome.

4750. leishmaniasis (kala azar, black fever, dumdum fever, Chiclero ulcer, forest yaws, uta, espundia, aleppo boil)
Definition:

A group of diseases caused by parasitic protozoans of the genus Leishmania. It is transmitted by sandflies and are, in general, infections of the skin, mucous membranes, and certain internal organs by the parasites. Three major types of leishmaniasis occur in humans - cutaneous, mucocutaneous, and visceral:
1. In cutaneous leishmaniasis, also known as aleppo boil, aleppo button, Bagdad boil, Baure ulcer, Delhi boil, oriental sore, and tropical sore, the parasite causes lesions on the face, arms, and legs which begin as inflamed bumps and can turn into skin ulcers that take up to two years to heal.
2. In mucocutaneous leishmaniasis, also known as American leishmaniasis, Chiclero ulcer, espundia, forest yaws, and uta, the parasite invades the mucous membranes and causes ulcers in the nose, mouth, and parts of the sinuses. This can result in lesions and deformity of the face.
3. In visceral leishmaniasis, also known as kala azar (a Hindi term meaning "black fever") or dumdum fever, the parasite invades the spleen, liver, bone marrow, lymph nodes, and skin. Symptoms include fever, fatigue, enlargement of the lymph nodes, the spleen, and the liver, dizziness, weight loss, and secondary infections such as pneumonia, and it can be fatal if left untreated.

4751. lemma
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The lower of two bracts enclosing a grass flower.

4752. lenticel
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A loosely-packed mass of cells in the bark of a woody plant, visible on the surface of a stem as a raised powdery spot, through which gaseous exchange occurs.

4753. lenticular
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Shaped like a biconvex lens: ().

4754. lepidote
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Covered with small, membranous scales.

4755. leprosy (Hansen's disease)
Definition:

A chronic disease that causes lesions on the bones, skin, mucous membranes, and peripheral nervous system. People suffering from leprosy often lose sensation in their limbs and extremities because of nervous system lesions, and can unknowingly injure themselves and/or not care for wounds, thus causing further disfigurement. This disease, which was widely feared in ancient times and is still a problem in undeveloped countries, is caused by the Gram-positive, rod-shaped bacterium Mycobacterium leprae. Armadillos can also catch this disease (there have been a few isolated incidents of people catching leprosy from them) and so are used in medical research on the illness.

4756. leptin
Definition:

A protein which has been linked to obesity. It is produced in adipocyte (fat cell) tissue by the obese (ob) gene and probably acts as a signal to the brain on the amount of fat currently in the body. In obese people, the leptin receptor is thought to be faulty so that much higher levels of leptin need to be secreted before the brain turns off the hunger signal.

For more information, visit More News on Leptin.

4757. Leptospira
Definition:

Leptospira is a genus of bacteria in the family Leptospiraceae which are aerobic (uses oxygen), able to move by themselves (are motile), and shaped like coils. There are free-living members which live in soil, freshwater, and saltwater, as well as parasitic pathogens of humans and other animals which most notably cause leptospirosis (a disease which chiefly afflicts a number of livestock and other domestic animals but can also affect humans).

4758. leptospirosis (spirochetal jaundice, Weil's disease, canicola fever)
Definition:

Any disease caused by a member of the bacterial genus Leptospira, which chiefly afflicts a number of livestock and other domestic animals but can also affect humans. The disease is spread by the urine of infected people and animals. When found in humans, the disease is also called canicola fever, mud fever, swamp fever, hemorrhagic jaundice, infectious jaundice, spirochetal jaundice, swineherd's disease, and Weil's disease, and tends to infect people who handle animals or who come into contact with animal urine (either directly or through contaminated soil and water) or infected animal tissue. Symptoms often include fever, headache, chills, and muscle pain, but can also include jaundice, bleeding and/or hemorrhaging in or below the skin, rash, meningitis, and renal insufficiency (kidney failure).

4759. leptosporangiate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of ferns, having sporangia with walls only one cell thick. Compare eusporangiate.

4760. LeRiche syndrome
Author: Guo Li
Definition:

LeRiche syndrome is characterized by claudication of the hip, thigh, and buttock muscles, atrophy of the leg muscles, impotence, and diminished or absent femoral pulses. It is casued by insufficiency of the aortoiliac circulation.

4761. Lesch-Nyhan syndrome
Author: Guo Li
Definition:

Lesch-Nyhan syndrome is caused by hyperuricemia (high serum levels of uric acid) due to a defective gene called the hypoxanthine guanine phosphoribosyltransferase. Patients with this syndrome are prone to have uric acid kidney stones and mental retardation. It is inherited as an X-linked recessive condition.

4762. lesion
Definition:

A part of a tissue which has been structurally changed due to disease, usually including a fissure or small wound.

4763. lethal dose
Definition:

The amount, or dosage, of a toxin necessary to cause death.

4764. lethal dose 50 (LD50, median lethal dose)
Definition:

The amount, or dosage, of a toxin necessary to kill 50% of the experimental subjects.

4765. lethal mutation
Definition:

A mutation that disrupts a critical gene, thus killing the developing organism.

4766. leucine
Image: View the chemical structure
Author: Courtesy of MacMolecule
Definition:

One of the twenty naturally occurring amino acids. Has the following chemical characteristics:


pKa1   pKa2     pI      Water Solubility (30deg C)
2.36   9.60    5.98            2.4

4767. leucopoiesis
Author: Guo Li
Definition:

The production of white blood cells.

4768. leukemia
Definition:

Any of several cancers of blood-forming organs (usually bone marrow cells) which result in the uncontrolled production of abnormal white blood cells (leukocytes); advanced stages of the disease can turn the blood virtually white (thus the name, since "leuk-" means "white").

4769. leukocyte (white blood cell)
Definition:

A pale, nucleated cell that acts as a part of the immune system by destroying invading cells and removing debris. See also granulocyte, lymphocyte, macrophage and monocyte.

4770. leukodystrophy
Author: Guo Li
Definition:

Leukodystrophy is a group of diseases in which there is a defect in the formation of myelin.

4771. leukopenia (leucopenia)
Definition:

Leukopenia is an abnormal decrease in the number of leukocytes (white blood cells).

4772. leukotriene
Image: View the chemical structure
Definition:

Any of a group of hormones derived from arachidonate (arachidonic acid). They are thought to mediate the allergic response that causes lung constriction and muscle contraction in asthma.

4773. levee
Author:
Definition:

A natural or manmade feature of the landscape that restricts movement of water into or through an area.

4774. levee
Author:
Definition:

1. An embankment built along a river for flood protection.
2. An embankment on or along the bank of a stream or lake to protect outer lowlands from inundation.

4775. levorotatory isomer
Definition:

A stereoisomer that rotates the plane of polarized light counterclockwise.

4776. Leydig cells
Author: Fertilitext
Definition:

The cells in the testicles that make testosterone.

4777. LH surge
Author: Fertilitext
Definition:

The sudden release of luteinizing hormone (LH) that causes the follicle to release a mature egg.

4778. liane
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A climbing or twining plant (usually refers to woody climbers).

4779. library
Definition:

An unordered collection of clones (i.e., cloned DNA from a particular organism), whose relationship to each other can be established by physical mapping. Compare genomic library, arrayed library.

4780. lichen
Image: lichens on bark
Definition:

A mutualistic association of a fungus and photosynthetic organism, either a unicellular alga or a cyanobacterium. Some lichens are used to make natural fabric dyes.

4781. ligand
Definition:

A small molecule that binds to a particular large molecule (e.g. a hormone is a ligand for its receptor).

4782. ligase
Definition:

An enzyme responsible uniting the Okazaki fragments of the lagging strand during DNA replication.

4783. light chain (L chain)
Definition:

The lighter of the two types of polypeptide chains that are found in immunoglobulin and antibody molecules.

4784. light microscope (optical microscope, photon microscope)
Definition:

The most common type of microscope (a device used to magnify small objects or substances) used in laboratories. The device works by passing visible light through a condenser and an objective lens.

4785. light reactions
Definition:

In photosynthesis, a series of reactions in which light energy is converted to chemical energy with the help of chlorophyll. ATP is created along with hydrogen ions and electrons as water molecules are split apart.

4786. lignins
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Organic substances which act as binders for the cellulose fibers in wood and certain plants, and adds strength and stiffness to the cell walls. The chemical structure of lignin is composed of a polymer of high carbon content but distinct from the carbohydrates.

4787. lignotuber
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A woody swelling below or just above the ground, containing adventitious buds from which new shoots develop if the top of the plant is cut or burnt (common in the shrubby eucalypts and in many other fire-tolerant Australian shrubs).

4788. ligulate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Bearing a ligule; strap-shaped.

4789. ligule
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A strap-shaped structure; a membranous or hairy appendage on the adaxial surface of a leaf, especially in grasses, at the junction between sheath and blade.

4790. limb
Author: Def. 3 mirrored from Jim Croft's Flora of Australia
Definition:

1. A leg or arm.
2. A branch of a tree.
3. The upper, free, spreading portion of a corolla or perianth that is connate at the base.

4791. limited habitat
Author:
Definition:

A habitat type that is rare or has been significantly reduced from its historical distribution, either locally or statewide, and is of special importance meeting the general life requirements of many wildlife species.

4792. limiting factor
Author:
Definition:

Environmental factor that limits the growth or activities of an organism or that restricts the size of a population or its geographical range.

4793. limiting reagent
Definition:

The reactant which is proportionally present in the lowest amount and will run out first in a chemical reaction, causing the reaction to stop. (Note that it is not necessarily the reactant with the absolute lowest amount).

4794. limnology
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

The scientific study of physical, chemical, meteorological, and biological conditions in fresh waters.

4795. lindane
Definition:

An insecticide used to treat lice (both head lice and pubic lice) and scabies. It comes in a cream, a lotion, or a shampoo form.

4796. linear
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Very narrow in relation to the length, and with the sides parallel.

4797. liner
Author:
Definition:

A plant seedling grown in a long narrow tube (typically 10 inches tall and 1.5 inches in diameter) for convenient transplanting onto a revegetation site.

4798. lining
Author:
Definition:

Protective cover of the perimeter of a channel.

4799. linitis plastica
Author: Guo Li
Definition:

Linitis plastica is one presentation of stomach carcinoma when malignant cells infiltrate the entire stomach wall so diffusely that no definite mass exists. The entire stomach wall is thickened by the tumor cells.

4800. linkage
Definition:

The proximity of two or more markers (e.g., genes, RFLP markers) on a chromosome; the closer together the markers are, the lower the probability that they will be separated during DNA repair or replication processes (binary fission in prokaryotes, mitosis or meiosis in eukaryotes), and hence the greater the probability that they will be inherited together.

4801. linkage map
Definition:

A map of the relative positions of genetic loci on a chromosome, determined on the basis of how often the loci are inherited together. Distance is measured in centimorgans (cM).

4802. linked genes (linked markers)
Author: Susan A.Hagedorn
Definition:

Genes and/or markers that are so closely associated on the chromosome that they are inherited together in 80% or more of cases.

4803. linker
Author: Susan A.Hagedorn
Definition:

A short, double-stranded oligonucleotide containing a restriction endonuclease recognition site, which is ligated to the ends of a DNA fragment.

4804. lipase
Definition:

Any of many enzymes that help break down lipids by catalyzing the fracture of an ester linkage.

4805. lipid (plural: lipids)
Definition:

A fatty, waxy or oily compound that is characteristically insoluble in water but readily soluble in organic solvents. Lipids contain carbon, hydrogen and oxygen, but have far less oxygen proportionally than carbohydrates.

4806. lipid bilayer
Definition:

A double-layer of amphipathic lipid molecules arranged with their nonpolar hydrocarbon tails facing inward. These bilayers can spontaneously form under certain conditions; the plasma membranes of animal cells are formed mainly from phospholipid (phosphate-containing lipids) bilayers.

4807. lipoate (lipoic acid)
Definition:

A vitamin needed by some bacteria which is an intermediate carrier for acyl groups and hydrogens in alpha-keto acid dehydrogenases.

4808. lipopolysaccharide
Definition:

A lipid bound to a polysaccharide; these biomolecules are frequently found on the outside of cell membranes, especially those of bacteria.

4809. lipoprotein
Definition:

A complex of one or more lipids bound to one or more proteins. In humans, lipoproteins transport water-insoluble fats in the blood and are classified by their density: very-low-density lipoproteins (VLDLs), low-density lipoproteins (LDLs) and high-density lipoproteins (HDLs).

Cholesterol is carried through the bloodstream by lipoproteins. Healthwise, LDLs are known as "bad" cholesterol and HDLs are known as "good" cholesterol. When your doctor measures your cholesterol, he takes readings of the different types of cholesterol in your blood:

LDL Cholesterol

• Desirable: less than 130 mg/dl
• Borderline High: 130-159 mg/dl
• High: more than 160 mg/dl
HDL Cholesterol
• Desirable: more than 35 mg/dl
• Risk Level: less than 35 mg/dl

4810. liposarcoma
Definition:

A liposarcoma is a malignant tumor derived from fat cells.

4811. liposome
Definition:

Small, artificially-created spheres whose walls are phospholipid bilayers. They are made by mixing dry phospholipids, such as egg yolk, in water. The lipid bilayer can fuse with the lipids in cell membranes, so liposomes hold much promise as agents for delivering drugs or other chemicals directly into cells.

4812. liquefaction necrosis
Author: Guo Li
Definition:

This form of necrosis is characterized by tissue softening, sometimes as a result of lytic lysosomal enzymes released by leukocytes.

4813. lithium (Li)
Definition:

Lithium is a metallic element which has an atomic number of 3 and an atomic weight of 6.941. It is classed as an "alkali metal" and in its pure form is silvery white. Its ores were first discovered in 1817 by Johan August Arvedson in Sweden and later isolated by W.T Brande and Humphrey Davy.

It is somewhat toxic, and some lithium compounds can cause cancer or birth defects, but lithium carbonate (Li₂CO₃) is useful as a drug to treat depression and manic-depressive disorders. Lithium is found naturally in the body at about 1.3 parts per million in bone and 0.023 parts per million in muscle tissue.

4814. lithium carbonate (Carbolith, Cibalith, Duralith, Lithane, Lithobid, Eskalith)
Definition:

This compound is used to treat manic depression.

4815. lithophyte
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A plant that grows on the surface of unweathered rock.

4816. lithotripsy
Author: Guo Li
Definition:

Lithotripsy is the technique of using sound waves to fragment stones formed in some organs of the body. The use of extracorporeal shock wave lithotripsy (ESWL) has met with some success in the treatment of gallstones and kidney stones in selected patients.

4817. lithotroph
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

In reference to energy source (electron donor): An organism which uses an inorganic substrate (such as ammonia, hydrogen) as an electron donor in energy metabolism. There are two types of lithotrophs: chemolithotroph and photolithotroph. Compare with autotroph, heterotroph, organotroph, and phototroph.

4818. litter
Author:
Definition:

The undecomposed plant and animal material found on the forest floor.

4819. littoral
Author:
Definition:

Pertaining to or along the shore, particularly to describe currents, deposits, and drift.