PRINCIPLES OF TOXICOLOGY - Biology East Borneo

566 GLOSSARYmitochondria Small spherical or rod-shaped components (organelles) found in the cytoplasm ofcells, enclosed in a double membrane. They are the principal sites of energy generation (ATP) andthey contain the enzymes of the Krebs and fatty acid cycles and the respiratory pathways.Mitochondria contain an extranuclear source of DNA and have genetic continuity.mitosis The process in cell division by which the nucleus divides, typically consisting of fourstages—prophase, metaphase, anaphase, and telophase—followed by cytokinesis and normallyresulting in two new cells, each of which contains a complete copy of the parental chromosomes.mixed-function oxidase system (MFO) A nonspecific, multienzyme complex on the smoothendoplasmic reticulum of cells in the liver and various other tissues. These enzymes constitute theimportant enzyme system involved in phase I reactions (i.e., oxidation/reduction reactions). Alsocalled cytochrome P450 enzymes.monclonal antibody A homogeneous antibody that is produced by a clone of antibody-forming cellsand that binds with a single antigenic determinant.monocyte A mononuclear phagocytic leukocyte with an ovoid or kidney-shaped nucleus, containinglacy, linear chromatin, and abundant gray-blue cytoplasm fitted with fine, reddish and azuregranules.morbidity The rate of sickness or ratio of sick persons to well persons in community.multiple myeloma A malignant proliferation of plasma cells in bone marrow causing numeroustumors and characterized by the presence of abnormal proteins in the blood.muscarine A highly toxic alkaloid C 9H 20NO 2, related to the cholines, derived from the red form ofthe mushroom Amanita muscaria.mutagen Any substance causing genetic mutation.mutagenesis The induction of those alterations in the information content (DNA) of an organism orcell that are not due to the normal process of recombination. Mutagenesis is irreversible and iscumulative, in the event of increased mutation rates or decreased selection pressures.mutagenic tests Test of an agent to determine effects on the faithful replication of genetic material.The genetic damage can occur in both somatic and germinal cell lines.mutation A permanent offspring-transmissible change in genetic material or structure. Such changesmay manifest themselves as altered morphology or altered ability to direct the synthesis of proteins.myalgia Muscular pain or tenderness, especially when diffuse and nonspecific.myasthenia gravis A disease characterized by progressive fatigue and generalized weakness of theskeletal muscles, especially those of the face, neck, arms, and legs, caused by impaired transmissionof nerve impulses following an autoimmune attack on acetylcholine receptors.myelin sheath The insulating envelope of myelin that surrounds the core of a nerve fiber or axonand facilitates the transmission of nerve impulses. In the peripheral nervous system, the sheath isformed from the cell membrane of the Schwann cell and, in the central nervous system, fromoligodendrocytes. Also called medullary sheath.myeloid leukemia Leukemia arising from myeloid tissue (bone marrow) characterized by unrestrainedgrowth of the granular, polymorphonuclear leukocytes and their precursors.myelotoxin A cytotoxin that causes destruction of bone marrow cells.myoclonus A sudden twitching of muscles or parts of muscles, without any rhythm or pattern,occurring in various brain disorders.myotonia Tonic spasm or temporary rigidity of one or more muscles, often characteristic of variousmuscular disorders.narcosis A condition of deep stupor or unconsciousness produced by a drug or other chemicalsubstance.nasopharyngeal region The part of the pharynx lying above the level of the soft palate (also knownas the postnasal space).