| animalised cell | <zoology> The 8-16 cell early blastula of sea urchins has animal and vegetal poles, by manipulating the environmental conditions it is possible to shift more cells from vegetal to animal in their characteristics. (12 Nov 1997) |
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| Anitschkow cell | A large mononuclear cell found in connective tissue of the heart wall in inflammatory conditions, especially in the Aschoff body. The ovoid nucleus contains a central chromatin mass appearing as a wavy bar in longitudinal section. Synonym: Anitschkow cell, Anitschkow myocyte, caterpillar cell. (05 Mar 2000) |
| anterior horn cell | Synonym for motoneuron. (18 Nov 1997) |
| antibody-dependent cell cytotoxicity | The phenomenon of antibody-mediated target cell destruction by non-sensitised effector cells. The identity of the target cell varies, but it must possess surface IgG whose fc portion is intact. The effector cell is a "killer" cell possessing fc receptors. It may be a lymphocyte lacking conventional b- or T-cell markers, or a monocyte, macrophage, or polynuclear leukocyte, depending on the identity of the target cell. The reaction is complement-independent. (12 Dec 1998) |
| antibody-forming cell | <immunology> B-cells (plasma cells) that are dedicated to producing secreted antibodies. (09 Feb 1998) |
| antibody producing cell | <immunology> A lymphocyte of the B series synthesising and releasing immunoglobulin. Equivalent to plasmacyte and plasma cell. (18 Nov 1997) |
| antigen presenting cell | A cell that carries on its surface antigen bound to MCH Class I or Class II molecules and presents the antigen in this context to T-cells. Includes macrophages, endothelium, dendritic cells and Langerhans cells of the skin. See: MHC restriction, histocompatibility antigens. (18 Nov 1997) |
| antigen-responsive cell | A small lymphocyte that, although not itself an immunologically activated cell, responds to antigenic (immunogenic) stimulus by a process of division and differentiation that results in the production of immunologically activated cells. Synonym: antigen-responsive cell. (05 Mar 2000) |
| antigen-sensitive cell | A small lymphocyte that, although not itself an immunologically activated cell, responds to antigenic (immunogenic) stimulus by a process of division and differentiation that results in the production of immunologically activated cells. Synonym: antigen-responsive cell. (05 Mar 2000) |
| antiparietal cell antibody | <immunology> A serologic blood test which measures the presence of antibodies to gastric parietal cells. Less than 2% of the general population will be antibody positive although this can be higher in the elderly. Approximately 90% of individuals with pernicious anaemia will be antibody positive. A positive result may also be seen in atrophic gastritis, gastric ulcer, thyroid disease, iron deficiency anaemia and diabetes. (13 Jan 1998) |
| antipodal cell | <plant biology> Three cells of the embryo sac in angiosperms, found at the end of the embryo away from the point of entry of the pollen tube. (13 Jan 1998) |
| apolar cell | A neuron without processes. (05 Mar 2000) |
| APUD cell | <pathology> A group of apparently unrelated endocrine cells found throughout the body which have a number of similar characteristics and which make a number of hormones with similar structures (including serotonin, epinephrine, dopamine, neurotensin, and norepinephrine. See: Amine Precursor Uptake and Decarboxylation. (10 Jan 1998) |
| argentaffin cell | So called because they will form cytoplasmic deposits of metallic silver from silver salts. Their characteristic histochemical behaviour arises from 5 HT, which they secrete. Found chiefly in the epithelium of the gastrointestinal tract (though possibly of neural crest origin) their function is rather obscure, although there is a widely distributed family of such paracrine (local endocrine) cells (APUD cells). (18 Nov 1997) |
| argyrophilic cell | <pathology> Cell's that bind silver salts but that precipitate silver only in the presence of a reducing agent. See: enteroendocrine cells. (05 Mar 2000) |