| histadine | <biochemistry> Is intricately involved in a large number of critical metabolic processes, ranging from the production of red and white blood cells to regulating antibody activity. Histadine also helps to maintain the myelin sheaths which surround and insulate nerves. In particular, Histidine has been found beneficial for the auditory nerves and a deficiency of this vital amino acid has been noted in cases of nerve deafness. Histadine is required for the production of histamine and is often used in the treatment of anaemia, allergies, rheumatoid arthritis and other inflammatory reactions. Histadine also possesses vasodilating and hypotensive actions and has an vital role in sexual responses. Research shows that the release of histamine from the mast cells is necessary for the physical action of orgasm. Women who are unable to achieve orgasm may be low in histamine and can possibly benefit from histidine supplementation. Premature ejaculation is also attributed to excess histamine and may be regulated by using methionine and calcium. Studies show that histidine boosts the activity of suppressor T-cells. One researcher reporting the finding of abnormally low levels of Histidine in the blood of patients with rheumatoid arthritis. Histidine is also used as a chelating agent in some cases of arthritis and to treat tissue overload from copper, iron or other heavy metals, to remove them from the body. Histadine also acts as an inhibitory neurotransmitter, boosting the activity of soothing alpha waves in the brain and suporting resistant to the effects of anxiety and stress. In cases of histidine deficiency, there is an unbalancing effect on alpha rhythms, leading to greater beta wave production. Beta waves are responsible for brain activity leading to anger and tension. Histidine is naturally found in most animal and vegetable proteins and is especially high in pork, poultry, cheese and wheat germ. Supplements of histidine should not be larger than 1.5 grams per day, except under a doctors supervision. (22 May 1997) |
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| Histalog test | A test for measurement of maximal production of gastric acidity or anacidity; it is similar to the histamine test, but uses Histalog (betazole hydrochloride), an analogue of histamine. Synonym: maximal Histalog test. (05 Mar 2000) |
| histaminaemia | The presence of histamine in the circulating blood. Origin: histamine + G. Haima, blood (05 Mar 2000) |
| histaminase | amine oxidase (copper-containing) |
| histamine | <biochemistry> Formed by decarboxylation of histidine. Potent pharmacological agent acting through receptors in smooth muscle and in secretory systems. Stored in mast cells and released by antigen. (See hypersensitivity). Responsible for the early symptoms of anaphylaxis. Also present in some venoms. (18 Nov 1997) |
| histamine agents | Drugs used for their actions on histaminergic systems. Included are drugs that act at histamine receptors, affect the life cycle of histamine, or affect the state of histaminergic cells. (12 Dec 1998) |
| histamine agonist | Drugs that bind to and activate histamine receptors. Although they have been suggested for a variety of clinical applications histamine agonists have so far been more widely used in research than therapeutically. (12 Dec 1998) |
| histamine antagonists | Drugs that bind to but do not activate histamine receptors, thereby blocking the actions of histamine or histamine agonist. Classical antihistaminics block the histamine h1 receptors only. (12 Dec 1998) |
| 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) |
| 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) |