| 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) |
| isometric | 1. Of equal dimensions. 2. In physiology, denoting the condition when the ends of a contracting muscle are held fixed so that contraction produces increased tension at a constant overall length. Compare: auxotonic, isotonic, isovolumic. Origin: iso-+ G. Metron, measure (05 Mar 2000) |
| isometric chart | A chart or graph that displays three dimensions on a plane surface. (05 Mar 2000) |
| isometric contraction | Muscular contractions characterised by increase in tension without change in length. (12 Dec 1998) |
| isometric contraction period | The time between closure of the atrioventricular valves and opening of the semilunar valves. (05 Mar 2000) |
| isometric exercise | Exercise consisting of muscular contractions without movement of the involved parts of the body. (05 Mar 2000) |
| isometric period of cardiac cycle | That period in which the muscle fibres do not shorten although the cardiac muscle is excited and the pressure in the ventricles rises, extending from the closure of the atrioventricular valves to the opening of the semilunar valves (isovolumic constriction) or the reverse (isovolumic relaxation). (05 Mar 2000) |
| isometric relaxation | Decrease in tension of a muscle while the length remains constant due to fixation of the ends. (05 Mar 2000) |
| isometric relaxation period | Early ventricular diastole beginning with closure of the aortic and pulmonic valves and preceding opening of the atrioventricular valves. (05 Mar 2000) |