Process which reverses the effect of a mutation which had inactivated a gene; thus it restores the wild phenotype.
bacterial artificial chromosome (BAC)
DNA vector into which large DNA fragments can be inserted and cloned in a bacterial host.
Substance intended to kill bacteria.
Lung disease caused by the inhalation of dust from sugar-cane residues.
basal lamina, pl -ae
Triple-layered structure on which epithelium sits: it consists of an electron dense layer (lamina densa) between two electron transparent layers (lamina lucida). The lamina densa is composed of type IV collagen and the lamina lucida contains the glycoprotein laminin.
Linking of the complementary pair of polynucleotide chains of nucleic acids by means of hydrogen bonds between complementary purine and pyrimidine bases, adenine with thymine or uracil, cytosine with guanine.
Specialized layers of extra-cellular matrix (basal laminae) that separate epithelial tissue from underlying connective tissue: cancer cells must break through the basement membrane in order to migrate to other parts of the body and form metastases.
Equation expressing the build up and decay in concentration of a substance (usually in plasma) based on first order uptake and elimination in a one compartment model, having the form
C = [ƒDκa/V(κa - κe)][exp(-κet) - exp(-κat)]
where C is the concentration and D the dose of the substance, ƒ the fraction absorbed, and V the volume of distribution. κa and κe) are the first order rate constants of uptake and elimination, respectively, and t is time.
See B lymphocyte
benchmark concentration (BMC)
Statistically calculated lower 95% confidence limit on the concentration that produces a defined response (called the benchmark response or BMR, usually 5 % or 10 %) for an adverse effect compared to background, often defined as 0 % or 5%.
benchmark dose (BMD)
Statistically calculated lower 95 % confidence limit on the dose that produces a defined response (called the benchmark response or BMR, usually 5 % or 10 %) of an adverse effect compared to background, often defined as 0 % or 5 %.
benchmark guidance value
Biological monitoring guidance value set at the 90th percentile of available biological monitoring results collected from a representative sample of workplaces with good occupational hygiene practices.
Advantage to or improvement in condition of an individual or a population.
See beryllium disease
Orange-yellow pigment, a breakdown product of heme-containing proteins (hemoglobin, myoglobin, cytochromes), which circulates in the blood plasma bound to albumin or as water soluble glucuronide conjugates, and is excreted in the bile by the liver.
Potential for a substance to come in contact with a living organism and then interact with it. This may lead to absorption.
Note: A substance trapped inside an insoluble particle is not bio-accessible although substances on the surface of the same particle are accessible and may also be bio-available. Bio-accessibility, like bio-availability, is a function of both chemical speciation and biological properties. Even surface-bound substances may not be accessible to organisms which require the substances to be in solution.
Able to come in contact with a living organism and interact with it.
Progressive increase in the amount of a substance in an organism or part of an organism which occurs because the rate of intake exceeds the organism's ability to remove the substance from the body.
Note: Bio-accumulation often correlates with lipophilicity.
See also bioconcentration, biomagnification
Ability of living organisms to concentrate a substance obtained either directly from the environment or indirectly through its food.
Procedure for estimating the concentration or biological activity of a substance by measuring its effect on a living system compared to a standard system.
bio-availability (in toxico- or
Ratio of the systemic exposure from extravascular (ev) exposure to that following intravenous (iv) exposure as described by the equation:
F = AevDiv / Biv Dev
where F (fraction of dose absorbed) is a measure of the bioavailability, A and B are the areas under the (plasma) concentration time curve following extravascular and intravenous administration respectively, and Dev and Div are the administered extravascular and intravenous doses.
Able to be absorbed by living organisms.
Reaction or series of reactions, usually enzyme-catalysed, associated with a specific physiological event in a living organism.
biochemical (biological) oxygen demand (BOD)
Amount concentration of oxygen taken up through the respiratory activity of micro-organisms growing on organic compounds present when incubated at a specified temperature (usually 20° C) for a fixed period (usually 5 days). It is regarded as a measure of that organic pollution of water which can be degraded biologically but includes the oxidation of inorganic material such as sulfide and iron(II). The empirical test used in the laboratory to determine BOD also measures the oxygen used to oxidize reduced forms of nitrogen unless their oxidation is prevented by an inhibitor such as allyl thiourea.
bioconcentration factor (BCF)
Measure of the tendency for a substance in water to accumulate in organisms, especially fish.
Note 1. The equilibrium concentration of a substance in fish can be estimated by multiplying its concentration in the surrounding water by its bioconcentration factor in fish.
Note 2. This parameter is an important determinant for human intake of aquatic food by the ingestion route.
Removal, usually from the aqueous phase, of a test substance in the presence of living organisms by biological processes supplemented by physico-chemical reactions.
bio-equivalen/ce n., -t
Relationship between two preparations of the same drug in the same dosage form that have a similar bioavailability.
Discipline encompassing the development and utilization of computational facilities to store, analyse and interpret biological data.
See absorption, biological
See acclimatization, biological
biological assessment of exposure
See biological monitoring
Complete circulatory process through which a substance passes in the biosphere. It may involve transport through the various media (air, water, soil), followed by environmental transformation, and carriage through various ecosystems.
biological effect monitoring (BEM)
Continuous or repeated measurement of early biological effects of exposure to a substance to evaluate ambient exposure and health risk by comparison with appropriate reference values based on knowledge of the probable relationship between ambient exposure and biological effects.
biological half life
For a substance the time required for the amount of that substance in a biological system to be reduced to one half of its value by biological processes, when the rate of removal is approximately exponential.
biological half time,
See biological half life
Species or group of species which is representative and typical for a specific status of an ecosystem, which appears frequently enough to serve for monitoring and whose population shows a sensitive response to changes, e.g., the appearance of a toxicant in an ecosystem.
biological assessment of exposure
Continuous or repeated measurement of any naturally occurring or synthetic chemical, including potentially toxic substances or their metabolites or biochemical effects in tissues, secreta, excreta, expired air or any combination of these in order to evaluate occupational or environmental exposure and health risk by comparison with appropriate reference values based on knowledge of the probable relationship between ambient exposure and resultant adverse health effects.
biological oxygen demand
See biochemical oxygen demand
Compound derived from living organisms and their products for use in medicine or as a pesticide etc.
Military operations using any organism (bacteria, virus or other disease-causing organism) or toxin found in nature, to kill, injure or incapacitate human beings, animals, or plants.
Sequence of processes in an ecosystem by which higher concentrations are attained in organisms at higher trophic levels (at higher levels in the food web); at its simplest, a process leading to a higher concentration of a substance in an organism than in its food.
Indicator signaling an event or condition in a biological system or sample and giving a measure of exposure, effect, or susceptibility.
Note: Such an indicator may be a measurable chemical, biochemical, physiological, behavioral or other alteration within an organism.
biomarker of exposure
Biomarker that relates exposure to a xenobiotic to the levels of the substance or its metabolite, or of the product of an interaction between the substance and some target molecule or cell that can be measured in a compartment within an organism.
Complete conversion of organic substances to inorganic derivatives by living organisms, especially micro-organisms.
Substance that is synthesized by and occurs naturally in living organisms.
See biological monitoring
Biological agent with pesticidal activity, e.g., the bacterium Bacillus thuringiensis when used to kill insects.
Excision of a small piece of living tissue for microscopic or biochemical examination; usually performed to establish a diagnosis.
Portion of the planet earth which supports and includes life.
All living organisms as a totality.
Chemical conversion of a substance that is mediated by living organisms or enzyme preparations derived there from.
Mammalian embryo at the stage at which it is implanted into the wall of the uterus.
Physiological interface between brain tissues and circulating blood created by a mechanism that alters the permeability of brain capillaries, so that some substances are prevented from entering brain tissue, while other substances are allowed to enter freely.
Physiological interface between maternal and fetal blood circulations that filters out some substances which could harm the fetus while favoring the passage of others such as nutrients: many fat soluble substances such as alcohol are not filtered out and several types of virus can also cross this barrier.
Note: The effectiveness of the interface as a barrier varies with species and different forms of placentation.
See plasma (in biology)
See exchange transfusion
Physiological interface between the blood supply and the spermatozoa of the seminiferous tubules.
Note: This interface consists of specific junctional complexes between Sertoli cells.
Type of lymphocyte which synthesizes and secretes antibodies in response to the presence of a foreign substance or one identified by it as foreign. The protective effect can be mediated to a certain extent by the antibody alone (contrast T lymphocyte).
Total amount of a substance present in an organism at a given time.
Substance with activity against pests, that is produced naturally within a plant and may act as a defense against predators.
Acute food poisoning caused by botulinum toxin produced in food by the bacterium Clostridium botulinum and characterized by muscle weakness and paralysis, disturbances of vision, swallowing, and speech, and a high mortality rate.
Prefix meaning slow as in bradycardia or bradypnoea.
Abnormal slowness of the heartbeat.
Abnormally slow breathing.
Space within a radius of 0.5 m from a person’s face.
British anti-Lewisite (BAL)
Narrowing of the air passages through the bronchi of the lungs.
Expansion of the air passages through the bronchi of the lungs.
Intermittent violent contraction of the air passages of the lungs.
builder (in chemistry)
Material which enhances or maintains the cleaning efficiency of a surfactant, in a detergent, principally by inactivating water hardness; complex phosphates (especially sodium tripolyphosphate, i.e. pentasodium triphosphate), sodium carbonate, and sodium silicate are the builders most commonly used.
Pneumoconiosis caused by inhalation of dust and associated microbial contaminants and observed in cotton, flax, and hemp workers.
Liability of members of the general public to come in contact with substances arising from operations or processes carried out by other individuals in their vicinity.