| 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) |
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| 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reflex contraction of the limb extensors; the limb is thus pressed gently against the finger, and when the finger is withdrawn slightly, the experimenter has the sensation that his finger is raising the limb or drawing it out as by a magnet.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) |
| maillard reaction | One of a group of nonenzymatic reactions in which aldehydes, ketones, or reducing sugars react with amino acids, peptides, or proteins. Food browning reactions, such as those that occur with cooking of meats, and also food deterioration reactions, resulting in decreased nutritional value and colour changes, are attributed to this reaction type. The maillard reaction is studied by scientists in the agriculture, food, nutrition, and carbohydrate chemistry fields. (12 Dec 1998) |
| Pandy's reaction | A test to determine the presence of proteins (chiefly globulins) in the spinal fluid, by adding one drop of spinal fluid to 1 ml of solution (e.g., carbolic acid crystals in distilled water, cresol, or pyrogallic acid); the reaction varies from a faint turbidity to a dense "milky" precipitate according to the degree of protein content. Synonym: Pandy's test. (05 Mar 2000) |
| gemistocytic reaction | <cell biology> A reaction to injury resulting in the proliferation of reactive, protoplastic, or gemistocytic astrocytes. (05 Mar 2000) |
| reaction | Standard method for identifying Clostridium perfringens. When grown on agar containg egg yolk, an opalescent halo is formed around colonies that produce _ toxin (lecithinase). (18 Nov 1997) |
| reaction, allergic | A reaction that occurs when the immune system attacks a usually harmless substance (an allergen) that gains access to the body. The immune system calls upon a protective substance called immunoglobulin e (IgE) to fight these invading allergic substances ( allergens). Even though everyone has some IgE, an allergic person has an unusually large army of these IgE defenders -in fact, too many for their own good. This army of IgE antibodies attacks and engages the invading army of allergic substances of allergens. As is often the case in war, innocent bystanders are affected by this battle. These innocent bystanders are special cells called mast cells. These cells are frequently injured during the warring of the IgE antibodies and the allergic substances. When a mast cell is injured, it releases a variety of strong chemicals including histamine into the tissues and blood that frequently cause allergic reactions. These chemicals are very irritating and cause itching, swelling, and fluid leaking from cells. These allergic chemicals can cause muscle spasm and can lead to lung and throat tightening as is found in asthma and loss of voice. (12 Dec 1998) |
| reaction centre | <plant biology> The site in the chloroplast that receives the energy trapped by chlorophyll and accessory pigments and initiates the electron transfer process. A photosynthetic complex containing chlorophyll (or bacteriochlorophyll) and other components, within which occurs the initial electron transfer reactions of photophosphorylation. (09 Oct 1997) |
| reaction formation | In psychoanalysis, a postulated defense mechanism in which attitudes and behaviours that are adopted are the opposites of that which the individual would ordinarily be expected to express and actually feel at an unconscious level. (05 Mar 2000) |
| reaction intermediate | <biochemistry> Any biomolecule which iscreated and destroyed during the course of of a particular reaction pathway. (09 Oct 1997) |