| conversion reaction | A conversion of emotional stress or mental disturbance into a physical symptom. Examples include paralysis, blindness, inability to speak or another sudden debilitating problem for no reason evident through testing. (27 Sep 1997) |
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| coombs' reaction | An immunological lab test to detect antibodies which attack the red blood cells of its own body (called autoantibodies). The test is important to the diagnosis of certain blood disorders. The test first reacts red blood cells with serum from the test individual, then with antibodies to the autoantibodies. If the autoantibodies exist, they will bind to the red blood cells. When the antibodies to the autoantibodies are added, they will bind the autoantibodies (still attached to the red blood cells) and cause the red blood cells to clump together. Large clumps of red blood cells indicate that the autoantibodies exist, absence of the clumps indicates that they don't. (09 Oct 1997) |
| myasthenic reaction | Rapid loss of response to faradic stimulation of a muscle with the galvanic response and the power of voluntary contraction retained. Synonym: myasthenic reaction. (05 Mar 2000) |
| cortical reaction | The reaction of an egg cell to fertilization which changes its surface cell membrane and prevents additional sperm cells from entering (among other things). (09 Oct 1997) |
| polymerase chain reaction | <molecular biology, technique> The first practical system for in vitro amplification of DNA and as such one of the most important recent developments in molecular biology. Two synthetic oligonucleotide primers, which are complementary to two regions of the target DNA (one for each strand) to be amplified, are added to the target DNA (that need not be pure), in the presence of excess deoxynucleotides and Taq polymerase, a heat stable DNA polymerase. In a series (typically 30) of temperature cycles, the target DNA is repeatedly denatured (around 90_C), annealed to the primers (typically at 50-60_C) and a daughter strand extended from the primers (72_C). As the daughter strands themselves act as templates for subsequent cycles, DNA fragments matching both primers are amplified exponentially, rather than linearly. The original DNA need thus be neither pure nor abundant and the polymerase chain reaction has accordingly become widely used not only in research, but in clinical diagnostics and forensic science. Acronym: PCR (14 Oct 1997) |
| myelocytic leukemoid reaction | Leukocytosis of at least moderate degree, e.g., 50,000 or more per cu mm, with a few immature forms, e.g., 1 or 2% myelocytes, but chiefly mature polymorphonuclear leukocytes in the circulating blood; may be observed in association with tuberculosis, chronic osteomyelitis, various types of empyema, malaria, pneumococcal pneumonia, meningococcal meningitis, Hodgkin's disease, and metastases of carcinoma in the bone marrow. (05 Mar 2000) |
| coupled reaction | Two chemical reactions that share a common intermediate (for example, the productof the first reaction is a reactant in the second) and therefore havesome kind of energy exchange between them. (09 Oct 1997) |
| Porter-Silber reaction | The basis of the 17-hydroxycorticosteroid test; C-21 adrenocorticosteroids, which contain a dihydroxyacetone group at carbons 19, 20, and 21, react with phenylhydrazine. (05 Mar 2000) |
| Haber-Weiss reaction | The reaction of superoxide (O2-- with hydrogen peroxide to produce molecular oxygen (O2), hydroxide radical (OH-), and OH-; often, iron catalyzed; a source of oxidative stress in blood cells and various tissues. (05 Mar 2000) |
| cross reaction | <haematology, immunology> Serological reactions in which an antiserum against one antigen reacts with a non-identical but closely related antigen. (12 Dec 1998) |
| haemoclastic reaction | Haemolysis as observed in the laking of the blood. (05 Mar 2000) |
| cutaneous graft versus host reaction | An acute erythematous maculopapular reaction with bulla formation in the most severe cases; chronic changes may resemble lichen planus or scleroderma. (05 Mar 2000) |
| cutaneous reaction | The inflammatory reaction in the case of a skin test in a sensitive (allergic) subject. Synonym: cutaneous reaction. Origin: L. Cutis, skin, + reaction (05 Mar 2000) |
| Prausnitz-Kustner reaction | A test for the presence of immediate hypersensitivity in humans; test serum from an atopic individual is injected intradermally into a normal subject; the normal subject is challenged 24-48 hours later with the antigen suspected of causing the immediate hypersensitivity reaction in the atopic individual. Synonym: P-K test. (05 Mar 2000) |
| precipitin reaction | See: precipitin, precipitin test. (05 Mar 2000) |