DITOFOTOMETRYYa (Greek kytos a receptacle, here — a cell + phos, photos light + metreo to measure, measure; synonym: a tsitospektrofotometriya, microphotometry) — the cytochemical method of a research allowing to determine chemical composition of cells by absorption of light by them. C. apply to chemical and morphological studying heterogeneous (on properties, an origin) cell populations, the differential chemical analysis of structures of one cell (e.g., chromosomes of one set, a kernel, etc.), to a research of dynamics of movement of substances in a cell and their time histories. Besides, C. use for diagnosis, and also for clarification of the forecast of a disease. E.g., on number defined by C. polyploid cells estimate intensity of growth of a malignant tumor.
Principles C. are developed in 1936 by the Swedish scientist Kaspersson (T. Caspersson).
At C. through drug pass a bunch of monochromatic light I determine its absorption by a cell. The device for C. — the cytophotometer — includes a microscope, the monochromator allowing to receive the radiation of one wavelength, the device for measurement of light (usually the photo multiplier), the registrar of measurements. Modern cytophotometers are supplied with the computer, a video unit, the graph plotter. Concentration of the studied substance is calculated under Buger's law — Lambert — to the B of an er (see Colorimetry) establishing connection between light absorption by substance, its concentration and thickness of a layer. Test-sensitivity — apprx. 10“ 12 g of substance in structure about 1 mkm2. Accuracy of C. decreases owing to uneven distribution of substance in a cell. For prevention of a mistake use scanning C. — measurement of optical density of a cell small (diameter about 0,5 microns) the moving probe.
The cytophotometry in
the UF-spectral range allows to determine in instained preparations quantity of nucleotides, nucleinic to - t, proteins by natural absorption of UV rays by them. More wide spread occurance received C. in the visible range of a range; at the same time use natural color of separate substances (e.g., hemoglobin, pigments) or, more often, artificial coloring of drugs the histochemical dyes contacting chemical components of a cell in certain quantities. By means of dyes reveal in a cell nucleinic to - you, proteins and their separate reactive groups, and also define activity of a number of enzymes, the maintenance of lipids and polysaccharides.
As a result of use of C. data on a role nucleinic to - t in transfer of ancestral features were obtained, communication between change of content of RNA and proteins in a cell and a functional condition of a cell is revealed (excitement, braking, etc.), it is established biol. value of a cellular polyploidy. Besides, the materials received by means of C., promoted formation of modern ideas of growth and an angenesis, cellular mechanisms of a hypertrophy.
Bibliography: And r about with to and L. S.'s N and Pa -
p and I am G. V's N. Cytophotometry, L., 1977; Brodsky V. Ya. Trophicity of a cell, M., 1966; T. O.'s Caspersson Cell growth and cell function, N. Y., 1950.
V. Ya. Brodsky.