PRINCIPLES OF TOXICOLOGY - Biology East Borneo

GLOSSARY 567necrosis Death of one or more cells, or of part of a tissue or organ, generally owing to irreversibledamage.nematocyst A capsule within specialized cells of certain coelenterates, such as jellyfish, containinga barbed, threadlike tube that delivers a paralyzing sting when propelled into attackers and prey.neoplasm Literally, new growth, usually characterized by a random abnormal “immature,” meiosis-typecell division and proliferation.nephritis Inflammation of the kidney; a focal or diffuse proliferative or destructive process, whichmay involve the glomerulus, tubule, or interstitial renal tissue.neurodermatitis A nonspecific pruritic skin disorder presumed to result from prolonged vigorousscratching, rubbing, or pinching, sometimes forming polymorphic lesions.neuroendocrine Or, relating to, or involving the interaction between the nervous system and thehormones of the endocrine glands.neurofibril One of the delicate threads running in every direction through the cytoplasm of the bodyof a nerve cell and extending into the axon and dendrites of the cell.neuromuscular endplate A flattened discoid expansion at the neuromuscular junction, where amyelinated motor nerve fiber joins a skeletal muscle fiber.neuropathy General term denoting functional disturbances and/or pathologic changes in the nervoussystem.neutropenia A decrease in the number of neutrophilic leukocytes in the blood.neutrophil A granular leukocyte having a nucleus with three to five lobes connected by slenderthreads of chromatin and cytoplasm, containing fine, inconspicuous granules.nicotinic effect Poisoning by nicotine or a compound related in structure or action, characterized bystimulation (low doses) and depression (high doses) of the central and autonomic nervous systems.In extreme cases, death results from respiratory paralysis. Also referred to as nicotinism.nitrosamine Any of a group of n-nitroso derivatives of secondary amines. Some show carcinogenicactivity.NOEL See no-observable-effect level.noncompetitive inhibition Inhibition of enzyme activity by inhibitors that combine with the enzymeon a site other than that utilized by the substrate; such inhibition may be irreversible or reversible.nonspecific chemical action The action of a chemical, such as a strong acid or base or concentratedsolution of organic solvent, which occurs in all cells in direct proportion to the concentration incontact with the tissue. This is a nonselective effect and its intensity is directly related to theconcentration of the chemical.nonspecific receptor Secondary receptor within the body, which combine with or react with achemical; however, the function of the cell is not influenced by the product that is formed. Suchreceptors are usually combining sites on proteins.no-observable-effect level (NOEL) A measure of the toxicity of a substance, established by theU.S. Environmental Protection Agency (USEPA); the level of a substance that, when administeredto a group of experimental animals, does not produce those effects observed at higher levels, andat which no significant differences between the exposed animals and the unexposed or controlanimals are observed.olefin A class of unsaturated aliphatic hydrocarbons having one or more double bonds. Also calledalkene.oncogenic Giving rise to tumors or causing tumor formation.opsoclonus A condition characterized by rapid, irregular, nonrhythmic horizontal and verticaloscillations of the eyes, observed in various disorders of the brainstem or cerebellum.optic neuritis Inflammation of the optic nerve; it may affect the part of the nerve within the eyeball,or the portion behind the eyeball.