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CHAPTER 1

ABC transporter See transporter, ABC.

ABL oncogene See oncogene, ABL.

ABO blood group system See blood group system, ABO.

Ad4BP See adrenal 4 binding protein.

A/D ratio Ratio of the adult toxic dose to the developmentally toxic dose. [ref. 5]

AMPA receptor See receptor, 2-amino-3-(3-hydroxy-5-methyl-1,2-oxazol-4-yl)propanoic acid (AMPA).

ANCA-associated vasculitis See vasculitis, antineutrophil cytoplasmic autoantibody-associated vasculitis.

APECED syndrome See polyendocrinopathy, autoimmune.

ATP See adenosine triphosphate.

abdomen (n)/abdominal (adj)

1. Part of the body between the thorax and the pelvis in vertebrates.

2. Most posterior segment of the insect body.

[*]

abdominal cavity See cavity, abdominal.

abiological See abiotic.

abiotic abiological Opposite term: biotic.

Not associated with living organisms. [ref. 1]

abiotic degradation See degradation, abiotic.

abiotic transformation See transformation, abiotic.

ablepharia (n)/ablepharous (adj) Congenital absence of the eyelids. [ref. 5]

abortifacient Substance that causes pregnancy to end prematurely and causes an abortion. [ref. 1]

abortion, induced Intentional termination of a pregnancy with death of the embryo or fetus. [ref. 5]

abortion, spontaneous miscarriage

Unintentional termination of pregnancy before the embryo or fetus has developed to the stage of independent viability, or in humans before the 20th week of gestation. [ref. 5]

absolute bioavailability See bioavailability, absolute.

absolute fitness See fitness.

absolute lethal concentration (LC100) See lethal concentration, absolute

absolute lethal dose (LD100) See lethal dose, absolute.

absolute risk See risk, absolute.

absorbance (A)

Logarithm of the ratio of incident to transmitted radiant power through a sample (excluding the effects of sample cell walls).

Note 1: Depending on the base of the logarithm, decadic and Napierian absorbances are used. Symbols: A, A10, Ae.

Note 2: Absorbance is sometimes called extinction, although the term ''extinction'', better called attenuance, is reserved for the quantity that takes into account the effects of luminescence and scattering as well.

Note 3: When natural logarithms are used, the Napierian absorbance is the logarithm to the base e of the incident spectral radiant power, essentially monochromatic, divided by the transmitted spectral radiant power, Pλ. [ref. 1]

absorbate Substance that enters and is retained inside a solid or semisolid matrix (absorbent). [ref. 2]

absorbed dose (of a substance) See dose, absorbed.

absorbed dose (of ionizing radiation)

Energy imparted by ionizing radiation to a specified volume of matter divided by the mass of that volume. [ref. 1]

absorbent Solid or semisolid matrix that is able to accommodate and retain an absorbate. [ref. 2]

See also sorbate; sorbent.

absorptance (in chemistry), α

Absorbed radiant power divided by the incident radiant power. Also called absorption factor. When α ≤ 1, α ≈ Ae, where Ae is the Napierian absorbance. [ref. 1]

See also absorbance.

absorption (general)

1. Process of one material (absorbate) being retained by another (absorbent). Note: Absorption may be the physical solution of a gas, liquid, or solid in a liquid, attachment of molecules of a gas, vapor, liquid, or dissolved substance to a solid surface by physical forces, etc.

2. Transfer of some or all of the energy of radiation to matter that it traverses. Note: Absorption of light at bands of characteristic wavelengths is used as an analytical method in spectrophotometry to identify the chemical nature of molecules, atoms, or ions and to measure the concentrations of these chemical species.

[ref. 2]

See also adsorption; sorption.

absorption (in biology) uptake

Penetration of a substance into an organism and its cells by various processes, some specialized, some involving expenditure of energy (active transport), some involving a carrier system, and others involving passive movement down an electrochemical gradient (passive transport).

Note: In mammals, absorption is usually through the respiratory tract, gastrointestinal tract, or skin into the circulatory system and from the circulation into organs, tissues, and cells. [ref. 2]

absorption (of radiation)

Phenomenon in which radiation transfers some or all of its energy to matter that it traverses.

[ref. 1]

absorption, systemic

Uptake to the blood and transport via the blood of a substance to one or more organs or compartments in the body distant from the site of absorption.

[ref. 2]

absorption coefficient (in biology) absorption factor

Absorbed quantity (uptake) of a substance divided by the administered quantity (intake).

Note: For exposure by way of the respiratory tract, the absorption coefficient is the ratio of the absorbed amount to the amount of the substance (usually particles) deposited (adsorbed) in the lungs. [ref. 1]

absorption factor See absorptance (in chemistry); absorption coefficient (in biology).

abundance

1. Total number of individual organisms in a population, seen over a defined period of time in a certain place.

Note: For abundance of fish, an estimate of total weight may replace number.

2. Total number of organisms per unit of habitat space seen over a defined period.

3. Amount of an element that exists in nature, usually expressed in relative terms as a percentage of the total amount of all elements in a given medium (e.g., the Earth's crust).

4. Amount of an isotope of an element that exists in nature, usually expressed in relative terms as a percentage of the total amount of all isotopes of the element.

[ref. 2]

abundant element See element, abundant.

abundant metal See element, abundant.

abuse (of substances) Improper use of drugs, solvents or other substances. [ref. 1]

abzymeAntibody or antibody construct with catalytic activity. [ref. 3]

acaricide Substance intended to kill mites, ticks, or other Acaridae. [ref. 1]

acceptable daily intake See daily intake, acceptable.

acceptable daily intake (ADI) not allocated See no-acceptable-daily-intake-allocated.

acceptable daily intake, temporary

Value for the acceptable daily intake (ADI) proposed for guidance when data are sufficient to conclude that use of the substance is safe over the relatively short period of time required to generate and evaluate further safety data, but are insufficient to conclude that use of the substance is safe over a lifetime.

Note: A higher-than-normal safety factor (see uncertainty factor) is used when establishing a temporary ADI, and an expiration date is established by which time appropriate data to resolve the safety issue should be available. [ref. 1]

acceptable residue level of an antibiotic See residue level of an antibiotic, acceptable.

acceptable risk See risk, acceptable.

accepted risk See risk, accepted.

accessible

Capable of being entered or reached; easy of access; such as one can go to, come into the presence of, reach, or lay hold of. [ref. 2]

accessibility See bioaccessibility.

accessory cell

Cell that assists in the adaptive immune response but does not directly mediate specific antigen recognition.

Note 1: Accessory cells include phagocytes, mast cells, dendritic cells, and natural killer cells.

Note 2: The term accessory cell is often used to describe antigen-presenting cells. [ref. 3]

accessory molecule

Molecule other than immunoglobulin, T-cell receptor, or major histocompatibility complex molecule that participates in T-lymphocyte recognition and response to antigen. [ref. 3]

accessory rib

Rib arising from a cervical vertebra (cervical rib), or supernumerary rib arising from a thoracic or lumbar vertebra. [ref. 5]

accessory sex gland

Any gland, other than a gonad, associated with the genital tract, such as the bulbourethral gland and prostate. [ref. 5]

accessory sex organ secondary sex organ

Organ or structure other than the gonads that matures at puberty and assists indirectly in sexual reproduction by nurturing and transporting gametes.

Note 1: In the human female the accessory sex organs include the Fallopian tubes, uterus, vagina, and the external genitalia.

Note 2: In the human male, the accessory sex organs include the epididymis, vas deferens, ejaculatory duct, urethra, seminal vesicles, bulbourethral glands, prostate, and penis. [ref. 5]

accidental cell death

Death of a cell by a catastrophic process such as acute physical, mechanical, chemical or osmotic injury, in contrast to programmed cell death. [*]

accidental exposure See exposure, accidental.

acclimation (n)/acclimate (v)

acclimatization (n)/acclimatize (v)

biological acclimatization

1. Modification or adjustment of a biological process or structure that helps to maintain homeostasis in response to a change in environment.

Note: The modification occurring in acclimation may be physiological, in response to changes in the physical environment (e.g., thermoregulation), including changes in the concentration of a toxicant. It may also refer to behavioral changes reflecting psychological adjustment.

2. Processes, including selection and adaptation, by which a population of microorganisms develops a tolerance to a substance that may follow acquisition of the ability to degrade the substance.

3. Experimental manoeuvre of allowing an organism to adjust to its environment prior to undertaking a study. [*]

acclimatization, biological See acclimation.

accumulation (in biology) See bioaccumulation.

accumulation factor (AF) See biota-sediment accumulation factor. See also bioaccumulation factor.

accuracy

Quantity referring to the differences between the mean of a set of results or an individual result and the value that is accepted as the true or correct value for the quantity measured. [ref. 1]

acetylcholine (ACh)

2-acetoxy-N,N,N-trimethylethanaminium

2-(acetyloxy)-N,N,N-trimethylethan-1-aminium (PIN)

Substance that functions as a neurotransmitter between nerve cells and between nerves and muscles. [ref. 4]

acetylcholine receptor See receptor, acetylcholine.

acetylcholinesterase (AChE) acetylcholine hydrolase

Enzyme (EC 3.1.1.7) that hydrolyzes acetylcholine. [ref. 4]

acetylcholinesterase inhibitor

Substance that inhibits the action of acetylcholinesterase (EC 3.1.1.7) and related enzymes that catalyze the hydrolysis of choline esters, causing hyperactivity in parasympathetic nerves.

Note: Examples include organophosphate and carbamate pesticides. [*]

β-N-acetylhexosaminidase

Hydrolytic enzyme (EC 3.2.1.52) that acts on ganglioside GM2, producing N-acetyl-D-galactosamine and ganglioside GM3.

Note: Deficiency of β-N-acetylhexosaminidase is associated with Tay-Sachs disease. [ref. 5]

acetyltransferase acyltransferase

Any of a group of enzymes (EC 2.3.x.y) that transfers an acyl group from a donor (e.g., acetyl-coenzyme A) usually to a hydroxyl or amino (aminoacyltransferase) group of a substrate.

Note: Acetylation of xenobiotics is classified as a phase II biotransformation reaction. [*]

achondroplasia (n)/achondroplastic (adj)

Inherited disorder where ossification of cartilage is retarded, especially affecting growth of long bones, resulting in very short limbs and a comparatively large head. Type of dwarfism.

Note: Achondroplasia results from a mutation in the fibroblast growth factor receptor FGFR3 gene, increasing its activity in suppressing endochondral ossification. [ref. 5]

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Excerpted from "Comprehensive Glossary of Terms Used in Toxicology"
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Copyright © 2017 International Union of Pure and Applied Chemistry.
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