| Arthus reaction | <dermatology, immunology> A localised inflammation due to injection of antigen into an animal that has a high level of circulating antibody against that antigen. A haemorrhagic reaction with oedema occurs due to the destruction of small blood vessels by thrombi. It may occur, as in Farmer's Lung, as a reaction to natural exposure to antigen. (18 Nov 1997) |
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| arthus-type reaction's | Reaction's in man and other species that result from the same basic immunologic (allergic) mechanism which evokes, in the rabbit, the typical Arthus phenomenon. See: immune complex disease. (05 Mar 2000) |
| Ascoli reaction | A method for confirming the diagnosis of anthrax by means of a precipitin reaction which indicates the presence of heat-stable Bacillus anthracis antigen in the extracted tissue. (05 Mar 2000) |
| associative reaction | A secondary or side reaction. (05 Mar 2000) |
| basic reaction | Any test by which an alkaline reaction is recognised, such as the change of red litmus paper to blue, an excess of hydroxide ions over hydrogen ions in aqueous solution as indicated by a pH value greater than 7 (at 22캜). Compare: dissociation constant of water. Synonym: basic reaction. (05 Mar 2000) |
| beam-beam reaction | <radiobiology> Fusion reaction which occurs from the collision of two fast ions originating in injected neutral beams. (09 Oct 1997) |
| beam-plasma reaction | <radiobiology> Fusion reaction which occurs from the collision of a fast beam ion with a thermal plasma ion. (09 Oct 1997) |
| beam-wall reaction | <radiobiology> Fusion reaction which occurs from the collision of a fast beam ion with an ion embedded in or adsorbed onto the reactor wall. (09 Oct 1997) |
| Bence Jones reaction | <investigation> The classic method of identifying Bence Jones protein. This protein precipitates from urine in the range of 45 to 70 degrees Centigrade. It goes into solution at temperatures above or below this range. Used in the diagnosis of multiple myeloma. Less commonly, this test is positive in Waldenstrom's macroglobulinaemia, chronic lymphocytic leukaemia and amyloidosis. (27 Sep 1997) |
| Berthelot reaction | The reaction of ammonia with phenol-hypochlorite to give indophenol; the principle is used to analyze ammonia concentration in body fluids. (05 Mar 2000) |
| bi-bi reaction | A reaction catalyzed by a single enzyme in which two substrates and two products are involved; the ping-pong mechanism may be involved in such a reaction. Compare: mechanism. (05 Mar 2000) |
| Bittorf's reaction | In cases of renal colic, pain radiating to the kidney upon squeezing the testicle or pressing the ovary. (05 Mar 2000) |
| biuret reaction | A reaction characterised by a violet colour upon the addition of copper sulfate to all compounds with two amide or peptide bonds linked directly or through an intermediate carbon atom. Used in the detection and estimation of proteins and peptides having more than two amino acids. (12 Dec 1998) |
| Bloch's reaction | A dark staining observed in fresh tissue sections to which a solution of dopa has been applied, presumably due to the presence of dopa oxidase in the protoplasm of certain cells. Synonym: Bloch's reaction. (05 Mar 2000) |
| blood transfusion reaction | This refers to an immune response against transfused blood cells. Antigens, on the surface of red blood cells, are recognised as foreign proteins and can stimulate sensitised lymphocytes to produce antibodies to the red blood cell antigens. This triggers a complex immunological reaction that results in the destruction of the transfused red blood cell. The blood groups (A, B, AB, O) are classified on the basis of the presence of surface antigens on the red blood cell. Type A blood has A antigens. The plasma component of the blood contains the antibodies against all other blood group antigens other that its own. Another type of surface antigen is known as Rh factor. Rh factor is either present (Rh positive) or absent (Rh negative). Rh compatibility is another requirement for blood transfusion. Symptoms and findings of a transfusion reaction include flank pain, fever, chills, bloody urine, rash, low blood pressure, dizziness and fainting. (27 Sep 1997) |