| active site | <chemistry> A specific region of an enzyme where a substrate binds and catalysis takes place (binding site). (06 May 1997) |
|---|---|
| active splint | A splint utilizing springs or elastic bands that aids in movements initiated by the patient by controlling the plane and range of motion. Synonym: active splint, functional splint. (05 Mar 2000) |
| active succinate | The condensation product of succinic acid and CoA; one of the intermediates of the tricarboxylic acid cycle and a precursor in the synthesis of haem. Synonym: active succinate, succinyl-CoA. (05 Mar 2000) |
| active sulfate | 3'-phosphoadenosine 5'-phosphosulfate;an intermediate in the formation of urinary ethereal sulfates, notable for containing a "high energy" sulfate bond; the 3'-OH of adenosine is replaced by -OPO3H2, the 5'-OH by -OP(O2H)-OSO3H. Synonym: active sulfate. Acronym: PAPS (05 Mar 2000) |
| active transport | <biochemistry, chemistry> Transport of ions, nutrients or other molecules into a cell against a concentration gradient, this requires the expenditure of energy through ATP hydrolysis. (06 May 1997) |
| active treatment | A therapeutic substance or course intended to ameliorate the basic disease problem, as opposed to supportive or palliative treatment. Compare: causal treatment. (05 Mar 2000) |
| active vasoconstriction | Reduced caliber of a vessel caused by increased tonus in the smooth muscle in its walls. (05 Mar 2000) |
| active vasodilation | Vasodilation caused by decrease in tonus of smooth muscle in the wall of a vessel. (05 Mar 2000) |
| activities of daily living | The things we normally do in daily living including any daily activity we perform for self-care (such as feeding ourselves, bathing, dressing, grooming), work, homemaking, and leisure. The ability or inability to perform ADLs can be used as a very practical measure of ability/disability in many disorders. (12 Dec 1998) |
| activities of daily living scale | A scale to score physical activity and its limitations, based on answers to simple questions about mobility, self-care, grooming, etc; widely used in geriatrics, rheumatology, etc. (05 Mar 2000) |
| activity | 1. The state of being active, the ability to produce some effect, the extent of some function or action. 2. <chemistry> A thermodynamic quantity that represents the effective concentration of a solute in a nonideal solution, if concentrations are replaced by activities, the equations for equilibrium constants, electrode potentials, osmotic pressure, boiling point elevation, freezing point depression and vapour pressures of volatile solutes are converted from approximations that hold only for dilute solutions to exact equations that hold for all concentrations. The activity is equal to the product of the concentration and the activity coefficient, a dimensionless number measuring deviation from nonideality. Symbol a. The potential or true thermodynamic activity of a substance, as opposed to its molar concentration. 3. <radiobiology> The number of nuclear transitions or disintegrations occurring in a given quantity of radioactive material per unit time. The SI unit of activity is s-1. The special name for the unit of activity is becquerel (Bq). The previously used special unit of activity, curie (Ci), is being replaced by the becquerel. 1 Bq = 2.7 x E-11 Ci. 1 Ci = 3.7 x E10 Bq. 4. Optical activity. (16 Dec 1997) |
| activity coefficient | <chemistry> The factor by which the value of a concentration of a solute must be multiplied to determine its true thermodynamic activity. (06 May 1997) |
| activity cycles | Bouts of physical irritability or movement alternating with periods of quiescence. It includes biochemical activity and hormonal activity which may be cellular. These cycles are shorter than 24 hours and include sleep-wakefulness cycles and the periodic activation of the digestive system. (12 Dec 1998) |
| activity, drug | A measure of the physiological response a drug produces in the body. A less active drug produces less response (and visa versa). (12 Dec 1998) |
| actomyosin | <chemical> A protein complex of actin and myosin occurring in muscle. It is the essential contractile substance of muscle. Chemical name: Actomyosins (12 Dec 1998) |