CLINICAL
CHEMISTRY DIVISION
COMMISSION ON TOXICOLOGY
Glossary for chemists of terms used in toxicology
(IUPAC Recommmendations 1993)
Alphabetical entries
A | B
| C | D | E
| F | G | H
| I | J | K
| L | M
N | O
| P | Q | R
| S | T | U
| V | W | X
| Y | Z
C
calcification: Process in which organic tissue
becomes hardened by deposition of calcium salts within its substance.
calibration material
See SN reference material.
cancer: Disease resulting
from the development of a malignancy.
RT carcinogen, carcinogenesis,
carcinogenic, carcinogenicity,
carcinoma, malignant,
malignancy.
carboxyhaemoglobin: Compound which is formed between
carbon monoxide and haemoglobin in the blood of animals and which is
incapable of transporting oxygen.
carcinogen n., -ic
adj.: Agent (chemical, physical or biological) which is capable of increasing
the incidence of malignant neoplasms; the induction of benign neoplasms
may in some circumstances contribute to the judgement
hat an agent is carcinogenic.
IARC, 1987
carcinogen/esis
n., -etic adj.: Induction, by chemical, physical, or biological
agents, of malignant neoplasms.
WHO, 1989a
carcinogenicity:
Process of induction of malignant neoplasms by chemical, physical or
biological agents.
carcinogenicity,
classification according to IARC: Classification based on the weight
of the evidence and not on potency as follows.
1. Sufficient evidence. Causal relationship has been established between
exposure to the agent and human cancer: a positive
relationship has been observed between exposure to the
agent and cancer in studies in which chance, bias and confounding
could be ruled out with reasonable confidence.
2. Limited evidence. Positive association has been observed between
exposure to the agent and cancer for which a causal
interpretation is considered to be credible, but chance,
bias or confounding could not be ruled out with reasonable
confidence.
3. Inadequate evidence. Available studies are of insufficient quality,
consistency or statistical power to permit a
conclusion regarding the presence or absence of a causal
association.
4. Evidence suggesting lack of carcinogenicity. There are several adequate
studies covering the full range of doses to
which human beings are known to be exposed, which are mutually
consistent in not showing a positive association between
exposure to the agent and any studied cancer at any observed
level of exposure. A conclusion of "evidence suggesting
lack of carcinogenicity" is inevitably limited to the cancer
sites, circumstances and doses of exposure and length of
observation covered by the available studies. In addition,
the possibility of a very small risk at the levels
of exposure studied can never be excluded.
5. Overall evaluation. Total body of evidence is taken into account;
the agent is described according to the wording of
one of the following categories, and the designated group
is given. The categorization of an agent is a matter of
scientific judgement, reflecting the strength of the evidence
derived from studies in humans and in experimental animals
and from other relevant data.
Group 1 - The agent is carcinogenic to humans.
This category is used only when there is sufficient evidence
of carcinogenicity in humans.
Group 2 - This category includes agents for which,
at one extreme, the degree of evidence of carcinogenicity in humans
is almost sufficient, as well as agents for which, at the
other extreme, there are no human data but for which there is
experimental evidence of carcinogenicity. Agents are assigned
to either 2A (probably carcinogenic) or 2B (possibly
carcinogenic) on the basis of epidemiological, experimental
and other relevant data.
Group 2A - The agent is probably carcinogenic to
humans.
This category is used when there is limited evidence of
carcinogenicity in humans and sufficient evidence of
carcinogenicity in experimental animals. Exceptionally,
an agent may be classified into this category solely on the
basis of limited evidence of carcinogenicity in humans
or of sufficient evidence of carcinogenicity in experimental
animals strengthened by supporting evidence from other
relevant data.
Group 2B - The agent is possibly carcinogenic to
humans.
This category is generally used for agents for which there
is limited evidence in humans in the absence of sufficient
evidence in experimental animals. It may also be used when
there is inadequate evidence of carcinogenicity in humans or
when human data are nonexistent but there is sufficient
evidence of carcinogenicity in experimental animals. In
some instances, an agent for which there
is inadequate evidence or no data in humans but limited evidence of
carcinogenicity in experimental animals together with supporting
evidence from other relevant data may be placed in this
group.
Group 3 - The agent is not classifiable as to its
carcinogenicity to humans.
Agents are placed in this category when they do not fall
into any other group.
Group 4 - The agent is probably not carcinogenic
to humans.
This category is used for agents which there is evidence
suggesting lack of carcinogenicity in humans together with
evidence suggesting lack of carcinogenicity in experimental
animals. In some circumstances, agents for which there is
inadequate evidence of or no data on carcinogenicity in
humans but evidence suggesting lack of carcinogenicity in
experimental animals, consistently and strongly supported
by a broad range of other relevant data, may be classified in
this group.
IARC, 1987
carcinogenicity
test: Long term (chronic) test designed to detect any possible carcinogenic
effect of a test substance.
carcinoma: Malignant tumour
of an epithelial cell.
SN epithelioma.
cardiotoxic: Chemically harmful to the cells of
the heart.
carry-over:
1. Transfer in farming and agricultural processing of a component from
one system such as soil or feed to another system
such as a plant, animal or human being: carry-over is expressed
as the concentration of a component in the second system
divided by the concentration in the first.
2. Process in analytical studies by which materials are carried into
a reaction mixture in which they do not belong.
case control study:
A study which starts with the identification of persons with the disease
(or other outcome variable) of interest, and a suitable control (comparison,
reference) group of persons without the disease. The relationship of
an attribute to the disease is examined by comparing the diseased and
non-diseased with regard to how frequently the
attribute is present or, if quantitative, the levels of the attribute,
in the two groups.
SN case comparison study, case history study, case referent study,
retrospective study.
Last, 1988
catabolism:
1. Reactions involving the oxidation of organic substrates to provide
chemically available energy (for example ATP) and to
generate metabolic intermediates.
Nagel et al. (eds),
1990
2. Generally, process of breakdown of complex molecules into simpler
ones, often providing biologically available energy.
AN anabolism.
catatonia: Schizophrenia marked by excessive,
and sometimes violent, motor activity and excitement, or by generalised
inhibition.
cathartic: See SN laxative.
SN purgative.
ceiling value (CV):
U.S. term in occupational exposure indicating the airborne concentration
of a potentially toxic substance which should never be exceeded in a
worker's breathing zone.
cell line: Defined unique population of cells
obtained by culture from a primary implant through numerous generations.
cell-mediated
hypersensitivity: State in which an individual reacts with allergic
effects caused by the reaction of antigen-specific T-lymphocytes following
exposure to a certain substance (allergen) after having been exposed
previously to
the same substance or chemical group.
RT allergy, antigen,
immunoglobulin
E-mediated hypersensitivity.
cell-mediated immunity: Immune response mediated
by antigen-specific T-lymphocytes.
cell strain: Cells having specific properties
or markers derived from a primary culture or cell line.
censored data: Sample observations for which the
complete distribution is not known: for example, a cohort study in which
some persons cannot be followed to the predetermined end of the study
("right-censored data") or environmental assay data in which some results
are less than the sample detection limit ("left-censored data").
After Last, 1988
certified reference material: Reference material
provided by a certifying body such as a National Standards Organization
or Metrological Laboratory or by an international body which confirms
its purity and analytical values by technically valid procedures and
provides a certificate detailing the relevant information.
BT reference material.
chain of custody: Sequence of responsibility for
a substance from the manufacturer to the distributor, to the user, or
to the person(s) ultimately responsible for waste disposal. This term
is also used in controlled transmission of samples from collection to
analysis, especially of samples of materials used for medico-legal or
forensic purposes.
chelation therapy: Treatment with a chelating
agent to enhance the elimination or reduce the toxicity of a metal ion.
chemical aetiologic
agent: See SN toxic substance.
chemical conversion:
Change from one state or chemical structure to another.
PS conversion.
chemical etiologic agent: See SN toxic
substance.
chemical oxygen
demand (COD): Substance concentration of available oxygen (derived
from a chemical oxidizing agent) required to oxidize the organic (and
inorganic) matter in waste water.
After Nagel et al. (eds), 1991
RT biochemical
oxygen demand.
chemical safety: Practical certainty that there
will be no exposure of organisms to toxic amounts of any substance or
group of substances: this implies attaining an acceptably low risk of
exposure to potentially toxic substances.
Duffus, 1986
RT practical certainty.
chemical species:
Set of chemically identical atomic or molecular structural units in
a solid array or of chemically identical molecular entities that can
explore the same set of molecular energy levels on the time scale of
the experiment. For example, two conformational isomers may interconvert
sufficiently slowly to be detectable by separate nuclear
magnetic resonance spectra and hence be considered to be separate chemical
species on a time scale governed by the radiofrequency of the spectrometer
used. On the other hand, in a slow chemical reaction the same mixture
of conformers may behave as a single chemical species, i.e., there is
a virtually complete equilibrium population of the total set of molecular
energy levels belonging to the two conformers. Except where the context
requires otherwise, the term is taken to refer to a set of molecular
entities containing isotopes in their natural abundance. The wording
of the definition given is intended to embrace both cases such as graphite,
sodium chloride, or a surface oxide where the basic structural units
are not capable of a separate existence as well as those cases where
they are.
Gold, Loening, McNaught and Sehmi, 1987
chemical toxicology:
See BT toxicology.
chemobiokinetics:
See NT toxicokinetics.
chemophobia: Irrational
fear of chemicals.
chemosis: Chemically induced swelling around the
eye caused by oedema of the conjunctiva.
chemosterilizer: Substance used to sterilize mites,
insects, rodents or other animals.
chloracne: Acne-like eruption caused by exposure
to certain chlorinated organic substances such as polychlorinated biphenyls
or 2,3,7,8-tetrachlorodibenzo-p-dioxin.
cholinomimetic: See SN parasympathomimetic.
cholinesterase
inhibitor: Substance which inhibits the action of acetylcholinesterase
(EC 3.1.1.7) and related enzymes which catalyse the hydrolysis of choline
esters: such a substance causes hyperactivity in parasympathetic nerves.
chromatid: Either of two
filaments joined at the centromere which make up a chromosome.
chromatin: Stainable complex of DNA and proteins
present in the nucleus of a eukaryotic cell.
RT eukaryote.
chromosomal aberration: Abnormality of chromosome
number or structure.
chromosome: Self-replicating
structure consisting of DNA complexed with various proteins and involved
in the storage and transmission of genetic information; the physical
structure that contains the genes.
Nagel et al. (eds), 1991
RT chromatid.
chronic effect: Consequence
which develops slowly and has a long-lasting course (often but not always
irreversible).
After WHO, 1979
AN acute effect.
chronic exposure:
Continued exposures occurring over an extended period of time, or a
significant fraction of the test species' or of the group of individuals',
or of the population's life-time.
AN acute exposure.
chronic toxicity
1. Adverse effects following chronic exposure.
2. Effects which persist over a long period of time whether or not they
occur immediately upon exposure or are delayed.
IRIS, 1986
AN acute toxicity.
chronic toxicity
test: Study in which organisms are observed during the greater part
of the life span and in which exposure to the test agent takes place
over the whole observation time or a substantial part thereof.
WHO, 1978a
AN acute toxicity test.
SN long term test.
chronotoxicology: Study of the influence of biological
rhythms on the toxicity of substances.
circulation of substances in the environment:
Movement of xenobiotic substances in the environment with air flow,
river current, soil, water, etc.
RT biological cycle.
IRPTC, 1982
cirrhosis
1. Liver disease defined by histological examination and characterized
by increased fibrous tissue, abnormal physiological
changes such as loss of functional liver cells, and increased
resistance to blood flow through the liver portal
hypertension).
2. Interstitial fibrosis of an organ.
clastogen: Agent causing chromosome breakage and/or
consequent gain, loss or rearrangement of pieces of chromosomes.
clastogenesis: Occurrence
of chromosomal breaks and/or consequent gain, loss or rearrangement
of pieces of chromosomes.
clearance:
1. Volume of blood or plasma or mass of an organ effectively cleared
of a substance by elimination (metabolism and
excretion) in a given time interval: clearance is expressed
in units of volume or mass per unit of time. Total clearance
for a component is the sum of the clearances of each eliminating
organ or tissue for that component.
2. In pulmonary toxicology, clearance refers specifically to removal
of any inhaled substance which deposits on the lining
surface of the lung: lung clearance is expressed in volume
or mass of lung cleared per unit time.
3. In renal toxicology, clearance refers to the quantification of the
removal of a substance by the kidneys by the
processes of filtration and secretion: clearance is calculated
by relating the rate of renal excretion to the plasma
concentration.
RT elimination.
clon/e n., -al adj.
1. Population of genetically identical cells or organisms having a common
ancestor.
2. To produce such a population.
3. Recombinant DNA molecules all carrying the same inserted sequence.
Nagel et al. (eds), 1991
clonic: Pertaining to alternate muscular contraction
and relaxation in rapid succession.
RT tonic.
IRIS, 1986
cluster sampling:
1. A method of sampling in which the population is divided into aggregates
(or clusters) of items bound together in a
certain manner. A sample of these clusters is taken at
random and all the items which constitute them are included in the
sample.
2. A sampling method in which each unit selected is a group of persons
(all persons in a city block, a family, etc.) rather
than an individual.
WHO, 1989a
cocarcinogen: Chemical, physical or biological
factor which intensifies the effect of a carcinogen.
Codex Alimentarius: Collection of internationally
adopted food standards drawn up by the Codex Alimentarius Commission,
the principal body implementing the joint FAO/WHO Food Standards Programme.
IPCS, 1987
cohort: Component of the population born during
a particular period and identified by period of birth so that its characteristics
(such as causes of death and numbers still living) can be ascertained
as it enters successive time and age periods. The term "cohort" has
broadened to describe any designated group of persons followed or traced
over a period
of time, as in the term cohort study (prospective study).
Last, 1988
cohort analysis: Tabulation and analysis of morbidity
or mortality rates in relationship to the ages of a specific group of
people (cohort), identified by their birth period, and followed as they
pass through different ages during part or all of their life span. In
certain circumstances such as studies of migrant populations, cohort
analysis may be performed according to duration of residence in a country
rather than year of birth, in order to relate health or mortality experience
to
duration of exposure.
Last, 1988
cohort study: Method
of epidemiological study in which subsets of a defined population can
be identified who are, have been, or in the future may be exposed or
not exposed, or exposed in different degrees, to a factor or factors
hypothesized to influence the probability of occurrence of a given disease
or other outcome. Alternative terms for such a study - follow-up, longitudinal,
and prospective study - describe an essential feature of the method,
observation of the population for a sufficient number of person-years
to generate reliable incidence or mortality rates in the population
subsets. This generally means studying a large population, study for
a prolonged period (years), or both.
SN concurrent study, follow-up
study, incidence study, longitudinal study, prospective study.
Last, 1988
combined
effect of poisons: Simultaneous or successive effect of two or more
poisons on the organism by the same route of exposure.
RT additive effect, antagonism,
independent effects of poisons, potentiation,
summation, synergism.
IRPTC, 1982
cometabolism: Process by which a normally non-biodegradable
substance is biodegraded only in the presence of an additional carbon
source.
RT analogue metabolism.
comparison group:
See SN control group.
compartment: Part of the body considered as an
independent system for purposes of assessment of distribution and clearance
of a substance. The body is composed of a large number of organs, tissues,
cells, cell organelles and fluids, any one of which could be referred
to as a compartment. In kinetic considerations, a compartment often
refers collectively to the
organs, tissues, cells, and fluids for which the rates of uptake and
subsequent distribution and elimination are sufficiently similar to
preclude kinetic resolution.
After WHO, 1979
compensation: Adaptation
of an organism to changing conditions of the environment (especially
chemical) is accompanied by the emergence of stresses in biochemical
systems which exceed the limits of normal (homeostatic) mechanisms.
Compensation is a temporary concealed pathology which later on can be
manifested in the form of explicit pathological changes (decompensation).
SN pseudoadaptation.
RT acclimatization, adaptation.
competent authority: In the context of European
Communities Directive 79/831/EEC, the Sixth Amendment to the European
Community's Directive 67/548/EEC relating to the Classification, Packaging
and Labelling of Dangerous Substances, official government organization
or group receiving and evaluating notifications of new substances.
competent bacteria: Culture of bacteria (or yeast)
treated in such a way that their ability to take up DNA molecules without
transduction or conjugation has been enhanced.
complete mineralization: Complete breakdown of
a complex organic compound to carbon dioxide, water, oxides and oxidative
inorganic products such as nitrate or sulfate.
comprehensive effect of poisons: Simultaneous
or successive effect made on an organism by poisons entering from different
media, from air, from water, from food or through the skin.
concentration (amount-of-substance concentration)
c = n/v: Derived kind-of-quantity defined as the amount of
substance (n) of a component specified by an elementary entity
divided by the volume (V) of the system containing the component.
The fundamental unit is mol m-3 but practical units are mol
dm-3 or mol L-1 (not molarity).
After Gold, Loening, McNaught and Sehmi,
1987
RT absolute lethal
concentration, lethal concentration,
maximum tolerable
concentration, median
effective concentration, median
lethal concentration, median
narcotic concentration, minimum
lethal concentration, threshold concentration.
concentration-effect
curve: Graph of the relation between exposure concentration and
the magnitude of the resultant biological change.
RT dose-effect curve.
SN exposure effect curve.
concentration-effect
relationship: Association between exposure concentration and the
magnitude of the resultant continuously graded change, either in an
individual or in a population.
RT dose-effect relationship.
concentration-response
curve: Graph of the relation between exposure concentration and
the proportion of individuals in a population responding with a quantal
effect.
RT dose-response curve,
response.
concentration-response
relationship: Association between exposure concentration and the
incidence of a defined biological effect in an exposed population.
RT dose-response relationship,
response.
concord/ance n., -ant
adj. Pairs or groups of individuals of identical phenotype: in twin
studies, a condition in which both twins exhibit or fail to exhibit
a trait under investigation.
Last, 1988
RT phenotype.
concurrent study:
See SN cohort study.
concurrent validity:
Measurement and its criterion refer to the same point in time: an example
would be a visual inspection of a wound for evidence of infection validated
against bacteriological examination of a specimen taken at the same
time.
Last, 1988
confounding
1. Situation in which the effects of two processes are
not distinguishable from one another: the distortion of the apparent
effect of an exposure on risk brought about by the association
of other factors which can influence the outcome.
2. Relationship between the effects of two or more causal factors as
observed in a set of data, such that it is not
logically possible to separate the contribution which any
single causal factor has made to an effect.
3. Situation in which a measure of the effect of an exposure on risk
is distorted because of the association of exposure
with other factor(s) which influence the outcome under
study.
Last, 1988
confounding variable: Changing factor that can
cause or prevent the outcome of interest, is not an intermediate variable,
and is not associated with the factor under investigation: such a variable
must be controlled in order to obtain an undistorted estimate of the
effect of the study factor on risk.
SN confounder.
Last, 1988
congener: Substance which by structure, function
or origin is similar to another.
conjugate
1. Derivative of a substance formed by its combination with compounds
such as acetic acid, glucuronic acid, glutathione,
glycine, sulfuric acid etc.
RT phase 2 reaction.
2. Material produced by attaching two or more substances together, for
example - conjugates of antibody with fluorochromes,
radio-isotopes or enzymes.
conjunctiva: Mucous membrane which covers the
eyeball and lines the under-surface of the eyelid.
conjunctivitis: Inflammation of the conjunctiva.
conservative assessment of risk: Assessment of
risk which assumes the worst possible case scenario and therefore gives
the highest possible value for risk: risk management decisions based
on this value will maximize safety.
construct validity:
Extent to which the measurement corresponds to theoretical concepts
(constructs) concerning the phenomenon under study; for example, if
on theoretical grounds, the phenomenon should change with age, a measurement
with construct validity would reflect such a change.
Last, 1988
contact dermatitis: Inflammatory condition of
the skin resulting from dermal exposure to an allergen (sensitizer)
or an irritating (corrosive, defatting) substance.
containment: Process by which possible release,
discharge or spill of a toxic substance during normal use or after an
accident is prevented by appropriate action.
contaminant:
1. Minor impurity present in a substance.
2. Extraneous material inadvertently added to a sample prior to or during
chemical or biological analysis.
3. In some contexts, as in relation to gas cleaning equipment, used
as a synonym for "pollutant", especially on a small
scale.
4. Unintended component in food that may pose a hazard to the consumer.
PS pollutant.
content validity:
Extent to which the measurement incorporates the domain of the phenomenon
under study; for example, a measurement of functional health status
should embrace activities of daily living, occupational, family, and
social functioning, etc.
Last, 1988
contraindication: Any condition which renders
some particular line of treatment improper or undesirable.
control group: Selected
group, identified as a rule before a study is done, which comprises
humans, animals, or other species who do not have the disease, intervention,
procedure or whatever is being studied, but in all other respects is
as nearly identical to the test group as possible.
After Last, 1988
SN comparison group.
control, matched: Control (individual or group
or case) selected to be similar to a study individual or group, or case,
in specific characteristics: some commonly used matching variables are
age, sex, race and socio-economic status.
After WHO, 1989a
conversion: See NT chemical
conversion, biotransformation.
core grade: Quality rating, based on standard
evaluation criteria established by the US Office of Pesticide Programs
regulatory agencies, given to toxicological studies after submission
by registrants.
IRIS, 1986
corrosive: Causing a surface-destructive effect
on contact; in toxicology, this normally means causing visible destruction
of the skin, eyes, or the lining of the respiratory tract or the gastrointestinal
tract.
count mean diameter: Mean of the diameters of
all particles in a population.
WHO, 1989a
count median diameter: Calculated diameter in
a population of particles in a gas or liquid phase above which there
are as many particles with larger diameters as there are particles below
it with smaller diameters.
WHO, 1989a
crackles: See SN crepitations.
crepitations: Abnormal
respiratory sounds heard on auscultation of the chest, produced by passage
of air through passages which contain secretion or exudate or which
are constricted by spasm or a thickening of their walls; more usually
referred to as crepitations or rhonchi (auscultation is the process
of listening for sounds within the body by ear unassisted or
using a stethoscope).
SN crackles, râles.
criterion: Validated set of data used as a basis
for judgement.
WHO, 1989a
criterion validity:
Extent to which the measurement correlates with an external criterion
of the phenomenon under study.
Last, 1988
critical concentration
(for a cell or organ): Concentration of a potentially toxic substance
at which undesirable (or adverse) functional changes, reversible or
irreversible, occur in the cell or organ.
critical effect: For deterministic effects, the
first adverse effect which appears when the threshold (critical) concentration
or dose is reached in the critical organ. Adverse effects, such as cancer,
with no defined threshold concentration are often regarded as critical.
Decision on whether an effect is critical is a matter of expert judgment.
After WHO, 1989a
critical end-point: Toxic effect used by the USEPA
as the basis for a reference dose.
RT reference dose.
Barnes and Dourson, 1988
critical group: Part of a target population most
in need of protection because it is most susceptible to a given toxicant.
WHO, 1979
critical organ:
1. In toxicology. Organ which first attains the critical concentration
(of a potentially toxic substance) under specified
circumstances of exposure and for a given population.
2. In radiation biology. Organ the damage of which (by radiation) results
in the greatest injury to the individual (or
his/her descendants). The injury may result from inherent
radiosensitivity or indispensability of the organ, or from
high dose, or from a combination of all three.
ICRP, 1965
critical organ concentration (of a substance):
Mean concentration in the critical organ at the time the most sensitive
type of cell reaches the critical concentration.
RT critical concentration,
critical organ.
critical period (of development): Stage of development
of an organism that is of particular importance in the life cycle if
the normal full development of some anatomical, physiological, metabolic,
or psychological structure or function is to be attained: such a period
may be associated with very high susceptibility to specific potentially
toxic substances.
critical study: Investigation yielding the no-observed
adverse effect level that is used by the USEPA as the basis of the reference
dose.
Barnes and Dourson, 1988
RT reference dose.
cross-product ratio:
See SN odds ratio.
cross-sectional study (of disease prevalence and associations):
Study which examines the relationship between diseases (or other
health-related characteristics) and other variables of interest as they
exist in a defined population at one particular time. Disease prevalence
rather than incidence is normally recorded in a cross-sectional study
and the temporal sequence of cause and effect cannot necessarily be
determined.
SN disease frequency survey, prevalence study.
RT morbidity survey.
After Last, 1988.
cumulative effect: Overall adverse change which
occurs when repeated doses of a harmful substance or radiation have
biological consequences which are mutually enhancing.
SN functional accumulation.
cumulative incidence, cumulative incidence rate:
Number and proportion of a group of people who experience the onset
of a health-related event during a specified time interval; this interval
is generally for all members of the group, but, as in lifetime incidence,
it may vary from person to person without reference to age.
Last, 1988
cumulative incidence ratio: Value obtained by
dividing the cumulative incidence rate in the exposed population by
the cumulative incidence rate in the unexposed population.
Last, 1988
cumulative
median lethal dose: Estimate of the total administered amount of
a substance which is associated with the death of half a population
of animals when the substance is administered repeatedly in doses which
are generally fractions of the median lethal dose. The estimate may
vary with the chosen size of the fraction (0.1, 0.2 etc.) and with the
period of time
over which effects are observed. It is a calculated quantity generally
obtained by interpolation of available dose-response data relating the
total administered amount to the response in the corresponding group
of experimental animals.
BT median lethal dose
cutaneous: Pertaining
to the skin.
SN dermal.
cyanogenic: Compounds able to produce cyanide;
examples are the cyanogenic glycosides such as amygdalin in peach and
apricot stones.
cyanosis: Bluish coloration, especially of the
skin and mucous membranes and fingernail beds, caused by abnormally
large amounts of reduced haemoglobin in the blood vessels as a result
of deficient oxygenation.
cytochrome: Haemoprotein whose characteristic
mode of action involves transfer of reducing equivalents associated
with a reversible change in oxidation state of the haem prosthetic group:
strictly, the cytochrome P450 family are not cytochromes but haem-thiolate
proteins.
Palmer and Reedijk, 1991
cytochrome P-420:
Inactive derivative of cytochrome P-450 found in microsomal preparations.
RT cytochrome P-448, cytochrome
P-450, endoplasmic reticulum,
microsome, mono-oxygenase,
phase 1 reactions.
cytochrome P-448:
Obsolete term for cytochrome P-450 I, A1, and A2, one of the major families
of the cytochromes P-450 haemoproteins. During the mono-oxygenation
of certain substances, often a detoxification process, these iso-enzymes
may produce intermediates which initiate mutations, chemical carcinogenesis,
immunotoxic reactions and other forms of chemical
toxicity.
RT cytochrome P-420, cytochrome
P-450, endoplasmic reticulum,
microsome, mono-oxygenase,
phase 1 reactions.
cytochrome P-450:
Haemoproteins which form the major part of the enzymes concerned with
the mono-oxygenation of many endogenous and exogenous substrates. The
term includes a large number of iso-enzymes which are coded for by a
superfamily of genes. Endogenous substrates of these enzymes include
cholesterol, steroid hormones and the eicosenoids; the exogenous
substrates are xenobiotics. Strictly, the cytochrome P450 family are
not cytochromes but are haem-thiolate proteins.
SN mixed-function oxidase.
RT cytochrome P-420, cytochrome
P-448, endoplasmic reticulum,
microsome, mono-oxygenase,
phase 1 reactions, xenobiotics.
Guengerich, 1988
cytogenetics: Branch of genetics which correlates
the structure and number of chromosomes as seen in isolated cells with
variation in genotype and phenotype.
RT phenotype.
cytoplasm: Fundamental
substance or matrix of the cell (within the plasma membrane) which surrounds
the nucleus, endoplasmic reticulum, mitochondria and other organelles.
cytotoxic: Causing damage to cell structure or
function.
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