| HA | H antigen; Hakim-Adams [syndrome]; halothane anesthesia; Hartley [guinea pig]; headache; health alli... |
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| HAP | Handicapped Aid Program; Hazardous Air Pollutants [List]; hazardous air pollution; health alliance p... |
| HC | hair cell; hairy cell; handicapped; head circumference; head compression; health care; healthy contr... |
| HFC | hard filled capsule; high-frequency current; histamine-forming capacity |
| Hi | histamine; histidine |
| histamine flush | Vasodilatation and erythema occurring as a result of release of histamine; thought to be a factor in genesis of flush of carcinoid syndrome. (05 Mar 2000) |
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| histamine h1 antagonists | Drugs that selectively bind to but do not activate histamine h1 receptors, thereby blocking the actions of endogenous histamine. Included here are the classical antihistaminics that antagonise or prevent the action of histamine mainly in immediate hypersensitivity. They act in the bronchi, capillaries, and some other smooth muscles, and are used to prevent or allay motion sickness, seasonal rhinitis, and allergic dermatitis and to induce somnolence. The effects of blocking central nervous system h1 receptors are not as well understood. (12 Dec 1998) |
| histamine h2 antagonists | Drugs that selectively bind to but do not activate histamine h2 receptors, thereby blocking the actions of histamine. Their clinically most important action is the inhibition of acid secretion in the treatment of gastrointestinal ulcers. Smooth muscle may also be affected. Some drugs in this class have strong effects in the central nervous system, but these actions are not well understood. (12 Dec 1998) |
| histamine headache | A term used to describe a headache that is typified by constant, unilateral pain around the eye, with onset usually within 2-3 hours of falling asleep. Can be accompanied by a blocked nasal passage, runny nose, and-or tearing. One may also notice facial flushing, ptosis (dropping eyelid), facial swelling and constriction of the pupils. (27 Sep 1997) |
| histamine liberators | Substances that cause the release of histamine from mast cells or basophils. (05 Mar 2000) |
| histamine n-methyltransferase | <enzyme> An enzyme that catalyses the transfer of a methyl group from s-adenosylmethionine to histamine, forming n-methylhistamine, the major metabolite of histamine in man. Chemical name: S-Adenosyl-L-methionine:histamine N-tele-methyltransferase Registry number: EC 2.1.1.8 (12 Dec 1998) |
| histamine release | The secretion of histamine from mast cell and basophil granules by exocytosis. This can be initiated by a number of factors, all of which involve binding of IgE, cross-linked by antigen, to the mast cell or basophil's fc receptors. Once released, histamine binds to a number of different target cell receptors and exerts a wide variety of effects. (12 Dec 1998) |
| histamine shock | The shock state produced in animals by the injection of histamine; characterised by bronchiolar spasm in the guinea pig and constriction of hepatic veins in the dog. (05 Mar 2000) |
| histamine test | A test for maximal production of gastric acidity or anacidity; after preliminary administration of an antihistamine, histamine acid phosphate is injected subcutaneously in a dose of 0.04 mg/kg of body weight, followed by analysis of gastric contents. Synonym: augmented histamine test. (05 Mar 2000) |