| 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) |
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| 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) |
| Bordet and Gengou reaction | <immunology> Binding of complement as a result of its interaction with immune complexes (the classical pathway) or particular surfaces (alternative pathway). (18 Nov 1997) |
| Brunn reaction | The increased absorption of water through the skin of the frog when the animal is injected with pituitrin and immersed in water; one of the physiological reactions used to study and classify posterior pituitary polypeptides and their analogues. (05 Mar 2000) |
| Burchard-Liebermann reaction | A blue-green colour produced by acetic anhydride with cholesterol (and other sterols) dissolved in chloroform, when a few drops of concentrated sulfuric acid are added. See: Liebermann-Burchard test. (05 Mar 2000) |
| Cannizzaro's reaction | Formation of an acid and an alcohol by the simultaneous oxidation of one aldehyde molecule and reduction of another; a dismutation: 2RCHO → RCOOH + RCH2OH; when the aldehydes are not identical, this is referred to as a crossed Cannizzaro reaction. (05 Mar 2000) |
| capsular precipitation reaction | Swelling of the capsule surrounding a bacterium as a result of interaction with anticapsular antibody, consequently the capsule becomes more refractile and conspicuous. (18 Nov 1997) |
| vaccinoid 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) |
| pain reaction | Dilation of the pupil or any other involuntary act occurring in response to a stimulus causing sharp pain anywhere. (05 Mar 2000) |
| galvanic skin reaction | A change in electrical resistance of the skin, occurring in emotion and in certain other conditions. (12 Dec 1998) |
| magnet reaction | A reaction seen in an animal deprived of its cerebellum; when the animal is placed upon its back and the head strongly flexed, the four limbs become flexed in all their joints. Due to stimulation of receptors in the deep layers of the skin, light pressure made upon a toe-pad with the finger causes reflex contraction of the limb extensors; the limb is thus pressed gently against the finger, and when the finger is withdrawn slightly, the experimenter has the sensation that his finger is raising the limb or drawing it out as by a magnet. (05 Mar 2000) |