| plasma renin activity | The estimation of renin in plasma by measuring the rate of formation of angiotensin I or II. (05 Mar 2000) |
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| solar activity | Any type of variation in the appearance of energy output of the sun. (12 Dec 1998) |
| specific activity | 1. <chemistry> The number of activity units (whatever is appropriate) per unit of mass, volume or molarity. 2. <radiobiology> Total activity of a given nuclide per gram of a compound, element or radioactive nuclide. Perhaps most often usage, in the context of radiochemicals, the number of microcuries per micromole. (16 Dec 1997) |
| structure activity analysis | Study in which systematic variation in the structure of a compound is correlated with its activity, in an attempt to determine the characteristics of the (receptor) site at which it acts. (18 Nov 1997) |
| structure-activity relationship | The relationship between the chemical structure of a compound and its biological or pharmacological activity. Compounds are often classed together because they have structural characteristics in common including shape, size, stereochemical arrangement, and distribution of functional groups. Other factors contributing to structure-activity relationship include chemical reactivity, electronic effects, resonance, and inductive effects. (12 Dec 1998) |
| nonsuppressible insulin-like activity | A blood protein (nsila) which mimics the biological activity of insulin in serum, but is not suppressed by insulin antibodies. During acid-ethanol extraction of cohn fraction III, 10% of the activity is found in the supernatant (nsila-s) and the remaining activity in the precipitate (nsila-p). The latter is a large molecular compound, much less stable than the soluble fraction. Nsila-s is a more potent growth factor than insulin and exhibits sulfation activity. (12 Dec 1998) |
| drug activity | A measure of the physiological response a drug produces. A less active drug produces less response (and visa versa). (12 Dec 1998) |
| insulin-like activity | A measure of substances, usually in plasma, that exert biologic effects similar to those of insulin in various bioassays; sometimes used as a measure of plasma insulin concentrations; always gives higher values than immunochemical techniques for the measurement of insulin. (05 Mar 2000) |
| intrinsic sympathomimetic activity | The property of a drug that causes activation of adrenergic receptors so as to produce effects similar to stimulation of the sympathetic nervous system. (05 Mar 2000) |
| optical activity | The ability of a material to rotate the plane of polarized light. (09 Oct 1997) |
| triggered activity | One or a series of spontaneously generated heart beats originating from an action potential that produces an after-depolarisation which reaches activation threshold. (05 Mar 2000) |
| unit of thyrotrophic activity | The activity of an amount of an extract of the anterior lobe of the hypophysis which, given daily for 5 days, will cause the thyroid of a guinea pig (weighing 200 g) to reach a weight of 600 mg. (05 Mar 2000) |
| zone of polarizing activity | <cell biology> The small group of mesenchyme cells in avian limb buds that is located at the posterior margin of the developing bud and that produces a substance, possibly retinoic acid, that provides positional information to the developing limb bud. (18 Nov 1997) |