| karyotyping, flow | Use of flow cytometry to analyze and/or separate chromosomes on the basis of their DNA content. Flow cytometry detects the light- absorbing or fluorescing properties of chromosomes passing in a narrow stream through a laser beam and with automated sorting devices can sort successive droplets of the stream into different fractions depending on the fluorescence emitted by each droplet. (12 Dec 1998) |
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| flow | 1. To move with a continual change of place among the particles or parts, as a fluid; to change place or circulate, as a liquid; as, rivers flow from springs and lakes; tears flow from the eyes. 2. To become liquid; to melt. "The mountains flowed down at thy presence." (Is. Lxiv. 3) 3. To pproceed; to issue forth; as, wealth flows from industry and economy. "Those thousand decencies that daily flow From all her words and actions." (Milton) 4. To glide along smoothly, without harshness or asperties; as, a flowing period; flowing numbers; to sound smoothly to the ear; to be uttered easily. "Virgil is sweet and flowingin his hexameters." (Dryden) 5. To have or be in abundance; to abound; to full, so as to run or flow over; to be copious. "In that day . . . The hills shall flow with milk." (Joel III. 18) "The exhilaration of a night that needed not the influence of the flowing bowl." (Prof. Wilson) 6. To hang loose and waving; as, a flowing mantle; flowing locks. "The imperial purple flowing in his train." (A. Hamilton) 7. To rise, as the tide; opposed to ebb; as, the tide flows twice in twenty-four hours. "The river hath thrice flowed, no ebb between." (Shak) 8. To discharge blood in excess from the uterus. Origin: AS. Flowan; akin to D. Vloeijen, OHG. Flawen to wash, Icel. Floa to deluge, Gr. To float, sail, and prob. Ultimately to E. Float, fleet. 80. Cf. Flood. 1. A stream of water or other fluid; a current; as, a flow of water; a flow of blood. 2. A continuous movement of something abundant; as, a flow of words. 3. Any gentle, gradual movement or procedure of thought, diction, music, or the like, resembling the quiet, steady movement of a river; a stream. "The feast of reason and the flow of soul." (Pope) 4. The tidal setting in of the water from the ocean to the shore. See Ebb and flow, under Ebb. 5. A low-lying piece of watery land; called also flow moss and flow bog. Source: Websters Dictionary (01 Mar 1998) |
| flow cytoenzymology | A technique for for separating and sorting cells based on the presence ofspecific enzymes that create acoloured material when they bind to a substrate. (09 Oct 1997) |
| flow cytometry | <technique> Flow cytometry is an emerging technique which holds great promise for the separation, classification and quantitation of blood cells and antibodies which affect blood cells. Complex computerised instruments are used to pass a monocellular stream of cells, platelets or other microscopic particulate elements through a beam of laser light. The cells are categorised first by size and then computer analysed to sort the mixture of cellular elements into cell type by size. Cells are labelled with fluorescent dye and then passed, in suspending medium, through a narrow dropping nozzle so that each cell is in a small droplet. A laser based detector system is used to excite fluorescence and droplets with positively fluorescent cells are given an electric charge. Charged and uncharged droplets are separated as they fall between charged plates and so collect in different tubes. The machine can be used either as an analytical tool, counting the number of labelled cells in a population or to separate the cells for subsequent growth of the selected population. Further sophistication can be built into the system by using a second laser system at right angles to the first to look at a second fluorescent label or to gauge cell size on the basis of light scatter. The great strength of the system is that it looks at large numbers of individual cells and makes possible the separation of populations with, for example: particular surface properties. Tabulation of counted data in conjunction with size analysis enables determination of relative percentages of each specific cellular subset for which monoclonal antibody conjugates are utilised, even when the size of the cell is identical to other subset species. Flow cytometry is a slightly imprecise but common term for the use of the Fluorescence-activated Cell Sorter (FACS). (01 Dec 1998) |
| flow cytophotometry | <technique> Flow cytometry is an emerging technique which holds great promise for the separation, classification and quantitation of blood cells and antibodies which affect blood cells. Complex computerised instruments are used to pass a monocellular stream of cells, platelets or other microscopic particulate elements through a beam of laser light. The cells are categorised first by size and then computer analysed to sort the mixture of cellular elements into cell type by size. Cells are labelled with fluorescent dye and then passed, in suspending medium, through a narrow dropping nozzle so that each cell is in a small droplet. A laser based detector system is used to excite fluorescence and droplets with positively fluorescent cells are given an electric charge. Charged and uncharged droplets are separated as they fall between charged plates and so collect in different tubes. The machine can be used either as an analytical tool, counting the number of labelled cells in a population or to separate the cells for subsequent growth of the selected population. Further sophistication can be built into the system by using a second laser system at right angles to the first to look at a second fluorescent label or to gauge cell size on the basis of light scatter. The great strength of the system is that it looks at large numbers of individual cells and makes possible the separation of populations with, for example: particular surface properties. Tabulation of counted data in conjunction with size analysis enables determination of relative percentages of each specific cellular subset for which monoclonal antibody conjugates are utilised, even when the size of the cell is identical to other subset species. Flow cytometry is a slightly imprecise but common term for the use of the Fluorescence-activated Cell Sorter (FACS). (01 Dec 1998) |
| flow injection analysis | The analysis of a chemical substance by inserting a sample into a carrier stream of reagent using a sample injection valve that propels the sample downstream where mixing occurs in a coiled tube, then passes into a flow-through detector and a recorder or other data handling device. (12 Dec 1998) |
| flow karyotyping | Use of flow cytometry toanalyse and/orseparate chromosomes on the basis of their DNA content. (09 Oct 1997) |
| flow-over vaporiser | A device for vaporization of a liquid anaesthetic by causing gases to pass over the anaesthetic or over material saturated with the anaesthetic. (05 Mar 2000) |
| flow rate | The amount of water that moves through an area (usually pipe) in a given period of time. (05 Dec 1998) |
| flow void | In magnetic resonance imaging, the absence of signal from blood whose activated protons leave a region before their magnetization is measured. See: signal void. (05 Mar 2000) |
| flow-volume curve | The graph produced by plotting the instantaneous flow of respiratory gas against the simultaneous lung volume, usually during maximal forced expiration. (05 Mar 2000) |
| laminar air flow unit | An air-filtering system used at some transplant facilities to remove particulate matter and fungi from the air. (16 Dec 1997) |
| laminar flow | The relative motion of elements of a fluid along smooth parallel paths, which occurs at lower values of Reynolds number. (05 Mar 2000) |
| forced expiratory flow | Expiratory flow during measurement of forced vital capacity; subscripts specify the exact parameter measured, e.g., peak instantaneous flow, the instantaneous flow at some specified point on the curve of volume expired versus time, or on the flow-volume curve, the mean flow between two expired volumes. (05 Mar 2000) |
| forced expiratory flow rates | Measurements of rates of airflow during a forced vital capacity determination. (12 Dec 1998) |