| lactic acid | A byproduct of carbohydrate metabolism (anaerobic metabolism). A lactic acid level may be measured in the bloodstream in conditions of metabolic acidosis. Lactic acid is an intermediate product of carbohydrate metabolism and is derived mainly from muscle cells and red blood cells. Exercise will normally raise lactic acid levels. Conditions of oxygen deprivation (for example shock, heart failure, lung disease) will trigger anaerobic metabolism within muscle tissue resulting in lactic acid build up in the tissues. Normal lactic acid levels are 4.5 to 19.8 mg/dl. (25 Jun 1999) |
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| lactic acid bacillus | A member of the genus Lactobacillus. (05 Mar 2000) |
| lactic acid bacteria | <microbiology> A group of Gram-positive, non-sporing bacteria which carry out a lactic acid fermentation of sugars. It includes species of Lactobacillus, Leuconostoc, Pediococcus and Streptococcus. See: lactic acid fermentation. (25 Jun 1999) |
| lactic acid dehydrogenase | <enzyme> An enzyme with 5 forms: LDH-1 is in the heart, its blood level can rise when heart muscle is damaged. Other forms can be found in the liver, brain, kidney, skeletal muscle and bone. A useful blood test in the evaluation of many disease processes, including heart attack, liver disease, muscular dystrophy and bone disease. (27 Sep 1997) |
| lactic acid fermentation | <biochemistry> A type of fermentation carried out by lactic acid bacteria in which sugar (for example lactose, glucose, pentose) are converted either entirely (or almost entirely) to lactic acid (homolactic fermentation) or to a mixture of lactic acid and other products (heterolactic fermentation). (09 Oct 1997) |
| lactic acid level | <investigation> A test that measures the amount of lactic acid in the blood. (25 Jun 1999) |
| lactic acid oxidative decarboxylase | A flavoprotein oxidoreductase catalyzing oxidation (with O2) of l-lactate to acetate plus CO2 and water. Synonym: lactic acid oxidative decarboxylase. (05 Mar 2000) |
| lactic | <physiology> Of or pertaining to milk; procured from sour milk or whey; as, lactic acid; lactic fermentation, etc. <biochemistry, physiology> Lactic acid, a sirupy, colourless fluid, soluble in water, with an intensely sour taste and strong acid reaction. There are at least three isomeric modifications all having the formula C3H6O3. Sarcolactic or paralactic acid occurs chiefly in dead muscle tissue, while ordinary lactic acid results from fermentation. The two acids are alike in having the same constitution (expressed by the name ethylidene lactic acid), but the latter is optically inactive, while sarcolactic acid rotates the plane of polarization to the right. The third acid, ethylene lactic acid, accompanies sarcolactic acid in the juice of flesh, and is optically inactive. Lactic ferment, an organised ferment (Bacterium lacticum or lactis), which produces lactic fermentation, decomposing the sugar of milk into carbonic and lactic acids, the latter, of which renders the milk sour, and precipitates the casein, thus giving rise to the so-called spontaneous coagulation of milk. Lactic fermentation. See Fermentation. Origin: L. Lac, lactis, milk: cf. F. Lactique. See Lacteal, and cf. Galactic. Source: Websters Dictionary (01 Mar 1998) |
| lactic acidemia | The presence of dextrorotatory lactic acid in the circulating blood. Synonym: lactacidemia. Origin: Lactic acid + G. Haima, blood (05 Mar 2000) |
| lactic acidosis | <biochemistry, physiology> Acidosis caused by accumulation of lactic acid more rapidly than it can be metabolised. It may occur spontaneously or in association with diseases such as diabetes mellitus, leukaemia, or liver failure. (25 Jun 1999) |
| lactic dehydrogenase | <enzyme> The enzyme that catalyses the formation and removal of lactate according to the equation: pyruvate + NADH = lactate NAD. <cell culture> The appearance of lactic dehydrogenase in the medium is often usedas an indication of cell death and the release of cytoplasmic constituents. Acronym: LDH (25 Jun 1999) |
| Abbe theory of image formation | <optics, physics> Abbe's theory is based on the fact that a non-self-luminous particle, which is illuminated by an extraneous source, gives rise to diffracted light rays, in addition to the dioptric pencil. He stated that to form a good microscopical image as many of the diffracted rays as possible should be intercepted by the objective. With closely ruled lines, his theory is easily demonstrated by observing the back lens of the objective, for here the diffracted rays can be observed directly if the aperture diaphragm is closed. It can be shown that, when the illumination is arranged to exclude the diffracted images, resolution is lost. (11 Mar 1998) |
| 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) |
| pattern formation | <cell biology> One of the classic problems in developmental biology is the way in which complex patterns are formed from an apparently uniform field of cells. Various hypotheses have been put forward and there is now evidence for the existence of gradients of diffusible substances (morphogens) specifying the differentiative pathway that should be followed according to the concentration of the morphogen around the cell. (18 Nov 1997) |
| reticular formation | <anatomy, neurology> A region extending from the pons & medulla oblongata through the mesencephalon, characterised by a diversity of neurons of various sizes and shapes, arranged in different aggregations and enmeshed in a complicated fibre network. (12 Dec 1998) |