| defense mechanism | A psychological means of coping with conflict or anxiety, e.g., conversion, denial, dissociation, rationalization, repression, sublimation, the psychic structure underlying a coping strategy, immunological mechanism vs. Non-specific defense mechanism. (05 Mar 2000) |
|---|---|
| double displacement mechanism | A special multisubstrate reaction in which, for a two-substrate, two-product (i.e., bi-bi) system, an enzyme reacts with one substrate to form a product and a modified enzyme, the latter then reacting with a second substrate to form a second, final product, and regenerating the original enzyme. An example of such a mechanism is found in the aminotransferases. More complex ping-pong mechanisms exist for enzymes having more than two substrates. Synonym: double displacement mechanism. (05 Mar 2000) |
| Douglas mechanism | Mechanism of spontaneous evolution in transverse lie; extreme lateral flexion of the vertebral column with birth of the lateral aspect of thorax before the buttocks. (05 Mar 2000) |
| Duncan's mechanism | Passage of the placenta from the uterus with the rough side foremost. (05 Mar 2000) |
| immunological mechanism | The groups of cells (chiefly lymphocytes and cells of the reticuloendothelial system) that function in establishing active acquired immunity (induced sensitivity, allergy). (05 Mar 2000) |
| ordered mechanism | A scheme for substrate binding and product release for multisubstrate enzymes; for a two-substrate two-product enzyme with an ordered mechanism, one particular substrate has to bind to the enzyme first followed by the other substrate; chemistry then occurs, products are formed and are released from the enzyme in a distinct order. More complex ordered schemes exist for enzymes having more than two substrates. Some of the dehydrogenases have such a mechanism. Synonym: ordered. (05 Mar 2000) |
| ordered on-random off mechanism | A scheme for substrate binding and product release for multisubstrate enzymes; for a two-substrate two-product enzyme with this mechanism, the individuals have to bind to the enzyme in a distinct order; however, once the products are formed they may dissociate from the enzyme in either order. It has been suggested that pyruvate kinase has such a mechanism. The random on-ordered off mechanism is simply the reverse of this mechanism. (05 Mar 2000) |
| acceptor control | <biochemistry> The regulation of the respiration rate, governed by ADP's ability to be a phosphate group acceptor. (06 May 1997) |
| anticipatory control | <physiology> The regulation of a system or process based on anticipated events, this isa feed-forward rather than a feedback system. (09 Oct 1997) |
| assist-control ventilation | Artificial respiration in which inspiration is produced automatically after a set interval if the person has not already begun to inspire. Compare: assisted ventilation, controlled ventilation. (05 Mar 2000) |
| autogenous control | <molecular biology> Regulation of how much a gene gets transcribed by the gene's own products. (02 Jan 1998) |
| aversive control | <psychology> Control of the behaviour of another individual by use of psychologically noxious means; e.g., attempting to force better study habits by withholding a child's allowance, or withholding sexual contact unless the partner complies with a request. (05 Mar 2000) |
| biological control | <agriculture> The agricultural use of living things, such as parasites, diseases, and predators, to control or eliminate others, such as weeds and pests, rather than by using chemicals (herbicides and pesticides). (21 Mar 1998) |
| birth control | Restriction of the number of offspring by means of contraceptive measures, projects, programs, or methods to control reproduction, by either improving or diminishing fertility. (05 Mar 2000) |
| gate-control hypothesis | A theory to explain the mechanism of pain; small fibre afferent stimuli, particularly pain, entering the substantia gelatinosa can be modulated by large fibre afferent stimuli and descending spinal pathways so that their transmission to ascending spinal pathways is blocked (gated). Synonym: gate-control hypothesis. (05 Mar 2000) |