| accelerated reaction | A response occurring in a shorter time than expected; the cutaneous manifestations occurring during the period between the second and tenth day following smallpox vaccination; because it is intermediate between a primary reaction and an immediate reaction, it is regarded as evidence of some degree of resistance. Synonym: vaccinoid reaction. (05 Mar 2000) |
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| accelerated conduction | Any pathologically increased speed of conduction; usually occurs between the atrium and ventricles as in the Wolff-Parkinson-White and Lown-Ganong-Levine syndromes; such accelerated pathways provide the bases for particular forms of reentry tachycardia. (05 Mar 2000) |
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| accelerated hypertension | <cardiology> A severe form of acute hypertension that results in the abrupt rise in the blood pressure (diastolic pressure often over 120 mmHg). If left untreated, malignant hypertension can cause damage to the blood vessels in the eye, kidneys, brain and heart. Complications include stroke, heart attack, blindness and renal failure. Symptoms include headache, blurred vision, nausea, vomiting and lethargy. Neurologic symptoms are also a common finding. Malignant hypertension occurs more commonly in males, African Americans and those with a history for hypertension. (27 Sep 1997) |
| accelerated idioventricular rhythm | A transient and intermittent type of arrhythmia with episodes lasting from a few seconds to a minute which usually occurs in patients with acute myocardial infarction or with digitalis toxicity. Suppressive therapy is rarely necessary because the ventricular rate is generally less than 100 beats per minute. (12 Dec 1998) |
| accelerated phase of leukaemia | Refers to chronic myelogenous leukaemia that is progressing. The number of immature, abnormal white blood cells in the bone marrow and blood is higher than in the chronic phase, but not as high as in the blast phase. (12 Dec 1998) |
| accelerated rejection | A transplant rejection manifested in less than three days. (05 Mar 2000) |
| leukaemia, accelerated phase of | Refers to chronic myelogenous leukaemia that is progressing. The number of immature, abnormal white blood cells in the bone marrow and blood is higher than in the chronic phase, but not as high as in the blast phase. (12 Dec 1998) |
| acid reaction | Any test by which an acid reaction is recognised such as the change of blue litmus paper to red, an excess of hydrogen ions over hydroxide ions in aqueous solution indicated by a pH value less than 7 (at 22캜). Compare: dissociation constant of water. (05 Mar 2000) |
| acute-phase reaction | <immunology, rheumatology> Refers to the changes in synthesis of certain proteins within the serum during an inflammatory response, which provides rapid protection for the host against microorganisms via non-specific defense mechanisms. It consists of fever, an increase in inflammatory humoral factors, and an increased synthesis by hepatocytes of a number of proteins or glycoproteins usually found in the plasma; the reaction is mediated by endogenous pyrogens, the hypothalamus, adrenal hormones, and other factors. (12 Jul 2000) |
| acute situational reaction | An acute emotional reaction related to extreme environmental stress. Synonym: acute situational reaction. (05 Mar 2000) |
| acute stress reaction | A sudden bout of anxiety that is often accompanied by the features of hyperventilation (tingling around mouth and in fingertips, rapid breathing, faintness or fainting). (27 Sep 1997) |
| addition reaction | <chemistry> Any reaction in which two chemicals combine to form a single chemical. (15 Jan 1998) |
| adverse drug reaction reporting systems | Systems developed for collecting reports from government agencies, manufacturers, hospitals, physicians, and other sources on adverse drug reactions. (12 Dec 1998) |
| adverse reaction | Any undesirable or unwanted consequence of a preventive, diagnostic, or therapeutic procedure or regimen. (05 Mar 2000) |
| agar-gel reaction | <immunology> The reaction between an antibody and an antigen during an immunology lab procedure where the two are allowed to diffuse toward each other through an agar-gel medium. Lines of precipitation form in the places on the gel where the two react with each other and shows where the reaction has occurred. (09 Oct 1997) |
| alarm reaction | The various phenomena, e.g., stimulated endocrine activity, which the body exhibits as an adaptive response to injury or stress; first phase of the general adaptation syndrome. (05 Mar 2000) |