| negative regulation | Negative feedback in biological systems mediated by allosteric regulatory enzymes. (18 Nov 1997) |
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| down-regulation | <physiology> Development of a refractory or tolerant state consequent upon repeated administration of a pharmacologically or physiologically active substance. It is the process that decreases ligand and receptor interactions or reduces the responsiveness of a cell to a stimulus following first exposure. This is often accompanied by an initial decrease in affinity of receptors for the agent and a subsequent reduction in the number of available receptors expressed on the surface which can result from internalisation of the ligand:receptor complex or from decreased expression of the receptor. Classically the concept referred to hormone receptors but contemporary usage includes other cell surface receptors. (03 Jul 1999) |
| target regulation | <physiology> General term for an interaction between neurons and their targets by which target derived signals influence the differentiation of the innervating neurons. (18 Nov 1997) |
| enzyme regulation | <biochemistry> Control of the rate of a reaction catalyzed by an enzyme by some effector (e.g., inhibitors or activators) or by alteration of some condition (e.g., pH or ionic strength). (05 Mar 2000) |
| facility regulation and control | Formal voluntary or governmental procedures and standards required of hospitals and health or other facilities to improve operating efficiency, and for the protection of the consumer. (12 Dec 1998) |
| feedback regulation | <physiology> Control mechanism that uses the consequences of a process to regulate the rate at which the process occurs: if, for example: the products of a reaction inhibit the reaction from proceeding (or slow down the rate of the reaction), then there is negative feedback, something that is very common in metabolic pathways. Positive feedback is liable to lead to exponential increase and may be explosively dangerous in some cases. Other examples are the action of voltage dependent sodium channels in generating action potentials and the activation of blood clotting factors V and VIII by thrombin. Without damping, feedback can lead to resonance (hunting) and oscillation in the system. (18 Nov 1997) |
| up-regulation | Opposite of down-regulation. (05 Mar 2000) |
| up-regulation (physiology) | Process that increases ligand/receptor interactions due to an increase in the number of available receptors. (12 Dec 1998) |