| density gradient centrifugation | <technique> High-speed centrifugation inwhich molecules float at a point wheretheir density equals that in a gradient of cesium chloride or sucrose. (12 Jan 1998) |
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| systolic gradient | The difference in pressure during systole between two communicating cardiovascular chambers, e.g., between the left ventricle and aorta in aortic stenosis. (05 Mar 2000) |
| electrochemical gradient | A measure of the tendency of an ion to move passively from one point to another, taking into consideration the differences in its concentration and in the electrical potentials between the two points; commonly expressed as the additional voltage needed to achieve equilibrium. (05 Mar 2000) |
| ficoll gradient | A density gradient of ficoll (synthetic sucrose polymer) in solution, where concentration of the ficoll varies continuously through the solution. It is often used to separate different types of cells from each other during the process of sedimentation. (09 Oct 1997) |
| field gradient | In magnetic resonance imaging, a magnetic field that varies with location, superimposed on the uniform field of the magnet, to alter the resonant frequency of nuclei and allow recovery of their spatial position. Synonym: field gradient. (05 Mar 2000) |
| acid-fast | <microbiology> A term used to denote bacteria that are not decolorised by acid-alcohol after having been stained with dyes such as basic fuchsin. The presence of acid fast organisms can be found in cultures that contain mycobacteria or some of the nocardiae. (12 Jul 2000) |
| acid-fast stain | <technique> A staining technique used to determine the cell wall property of a microorganism. After stained with dye such as hot carbolfuschin, an acid-fast organism, (for example Mycobacterium species) will retain the colour in its cell wall after being washed with acid-alcohol. (13 Nov 1997) |
| arsenic-fast | Resistant to the poisonous action of arsenic; denoting especially spirochetes and other protozoan parasites, which acquire resistance after repeated administration of the drug. (05 Mar 2000) |
| centrifugal fast analyzer | An automatic spectrophotometer that uses centrifugal force to mix samples and reagents, and propels the reactants at high speed about a detector that makes multiple absorbance readings. (05 Mar 2000) |
| Wassermann-fast | A term used to designate a case in which the Wassermann reaction remains positive despite all treatment. (05 Mar 2000) |
| histamine-fast | Indicating the absence of the normal response to histamine, especially in speaking of true gastric anacidity. (05 Mar 2000) |
| serum-fast | 1. Pertaining to a serum in which there is little or no change in the titre of antibody, even under conditions of treatment or immunologic stimulation. 2. Resistant to the destructive effect of sera. Synonym: serofast. (05 Mar 2000) |
| spectrometry, mass, fast atom bombardment | A mass spectrometric technique that is used for the analysis of a wide range of biomolecules, such as glycoalkaloids, glycoproteins, polysaccharides, and peptides. Positive and negative fast atom bombardment spectra are recorded on a mass spectrometer fitted with an atom gun with xenon as the customary beam. The mass spectra obtained contain molecular weight recognition as well as sequence information. (12 Dec 1998) |
| sputum for acid-fast organisms | A special microscopic slide that is prepared to detect the presence of acid-fast bacilli. The diagnosis of tuberculosis can be made using this test. If the sputum specimen shows the acid fast organism a sputum culture (for Mycobacterium) is then performed. (27 Sep 1997) |
| drug-fast | Pertaining to microorganisms that resist or become tolerant to an antibacterial agent. (05 Mar 2000) |