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Pure Appl. Chem., Vol. 65, No. 9, pp. 2003-2122, 1993.



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 


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
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 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.

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

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 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

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
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.

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
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
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


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.

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.

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
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
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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