| reversal | 1. The act of reversing; the causing to move or face in an opposite direction, or to stand or lie in an inverted position; as, the reversal of a rotating wheel; the reversal of objects by a convex lens. 2. A change or overthrowing; as, the reversal of a judgment, which amounts to an official declaration that it is false; the reversal of an attainder, or of an outlawry, by which the sentence is rendered void. Origin: From Reverse. Source: Websters Dictionary (01 Mar 1998) |
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| reversal learning | Any situation where an animal or human is trained to respond differentially to two stimuli (e.g., approach and avoidance) under reward and punishment conditions and subsequently trained under reversed reward values (i.e., the approach which was previously rewarded is punished and vice versa). (12 Dec 1998) |
| reversal of organs, total | This condition (medically called situs inversus totalis) involves complete transposition (right to left reversal) of the thoracic and abdominal organs. The heart is not in its usual position in the left chest but is on the right. Specifically related to the heart, this is referred to as dextrocardia (literally, right-hearted). And the stomach, which is normally in the left upper abdomen, is on the right. In patients with situs inversus totalis, all of the chest and abdominal organs are reversed and appear in mirror image when examined or visualised by tests such as X-ray filming. Situs inversus totalis has been estimated to occur once in about 6-8,000 births. Situs inversus occurs in a rare abnormal condition that is present at birth (congenital) called kartagener's syndrome. (12 Dec 1998) |
| adrenaline reversal | The fall in blood pressure produced by epinephrine when given following blockage of alpha-adrenergic receptors by an appropriate drug such as phenoxybenzamine; the vasodilation reflects the ability of epinephrine to activate beta-adrenergic receptors which, in vascular smooth muscle, are inhibitory; in the absence of alpha-receptor blockade, the beta-receptor activation by epinephrine is masked by its predominant action on vascular alpha-receptors, which causes vasoconstriction. Synonym: adrenaline reversal. (05 Mar 2000) |
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| relaxant reversal | Use of acetylcholinesterase inhibitors to terminate the action of nondepolarising neuromuscular relaxants. (05 Mar 2000) |
| pressure reversal | Cessation of anaesthesia by hyperbaric pressure; of major importance in understanding the mode of action of anaesthetics. (05 Mar 2000) |
| sex reversal | A process whereby the sexual identity of an individual is changed from one sex to the other (e.g., by a combination of surgical, pharmacologic, and psychiatric procedures); it may also occur in the life history of pseudohermaphroditic individuals whose sex at birth was uncertain; initially reared as members of one gender or sex role, such individuals may, upon subsequent medical examination and advice, be reared thereafter as members of the opposite gender or sex role. (05 Mar 2000) |
| sex reversal, gonadal | Change from one sex to another with regard to gonadal development; may be induced or occurs naturally in some invertebrates. (12 Dec 1998) |
| narcotic reversal | The use of narcotic antagonists, such as naloxone, to terminate the action of narcotics. (05 Mar 2000) |
| sterilisation reversal | A surgical procedure used to undo a previous sterilisation operation and restore fertility. (09 Oct 1997) |
| sterilization reversal | Reversal of sexual sterilization. (12 Dec 1998) |
| Ornish reversal diet | A diet designed by Dean Ornish, who has evidence that it will reverse coronary artery disease. It consists of 10% of calories from fat (mostly polyunsaturated or monounsaturated, with 5 mg cholesterol per day), 70 to 75% from carbohydrate, and 15 to 20% from protein. (05 Mar 2000) |
| epinephrine reversal | The fall in blood pressure produced by epinephrine when given following blockage of alpha-adrenergic receptors by an appropriate drug such as phenoxybenzamine; the vasodilation reflects the ability of epinephrine to activate beta-adrenergic receptors which, in vascular smooth muscle, are inhibitory; in the absence of alpha-receptor blockade, the beta-receptor activation by epinephrine is masked by its predominant action on vascular alpha-receptors, which causes vasoconstriction. Synonym: adrenaline reversal. (05 Mar 2000) |