AUTORADIOGRAPHY

From Big Medical Encyclopedia

AUTORADIOGRAPHY (autoradiografiya) — a way of registration alpha and beta radiations, based on photochemical action of ionizing radiation. For detection of radioisotopes photographic emulsion is given to contact with the studied material therefore alpha and beta particles cause blackening of a photoemulsion in the form of lines (tracks) on the course of a range of particle. Alpha particles give direct wide tracks, beta particles — narrow uneven zigzag strips.

An autoradiography in biology E. S. for the first time applied London (1904) to detection of radium in tissues of animals. Further the method was used for studying of accumulation, distribution and removal of trace amounts of radioisotopes in different bodies and body tissues.

In practice it is accepted to distinguish a macroautoradiography and a microautoradiography. By means of a macroautoradiography study distribution of radioisotopes in all organism or in its separate bodies and fabrics (e.g., P 32 — in malignant new growths).

A kind of a macroautoradiography is the balloon Autoradiography which basis the principle of photochemical registration of beta radiation of parenterally entered disubstituted sodium phosphate, marked P is 32 .

Autoradiogramms receive from a mucous membrane of a stomach, a gullet of a pla of a rectum by introduction to these bodies of the thin-walled rubber bulbs covered with the emulsion sensitive to action of beta particles (see. Beta diagnosis ). Existence or absence on autoradiogramms of signs of local adsorption of isotope P 32 supplies with the chain additional information for differentiation of inflammatory changes and malignant tumors of a gullet, a stomach and a rectum.

More the microautoradiography allowing at usual was widely used or submicroscopy (see) to reveal localization of radioisotopes in tissue or cytologic specimens. The analysis of distribution of radioisotopes in microscopic section of fabric is made on the basis of measurement of optical density of blackening of a photographic layer (a contrast Autoradiography) or by calculation under a microscope of number of traces (tracks) alpha and beta particles (a trace Autoradiography).

Gistoavtoradiografiya, being one of types of a microautoradiography, allows to estimate visually various degree of intensity of biochemical processes in cells. It gives the chance to observe dynamics of the processes happening in a kernel and cytoplasm differentially to analyze each of these processes, their relationship, staging, various degree of manifestation in different departments of a cell.

At a gistoavtoradiografiya enter natural components of biochemical processes into an organism, previously having marked them with radioisotopes that gives the chance to watch the course of these processes in a kernel, membranes and various cytoplasmatic structures of a cell by photographic registration of radiation of radioisotopes. Feature of this technique consists in combination of opportunities of qualitative analysis, the quantitative account and studying of spacing in fabric of radioactive materials.

Improvement of a technique of a gistoavtoradiografiya was promoted by creation of the special nuclear emulsions which gave the chance to observe distribution of radioisotopes in cells.

The principle of chemical reaction at a gistoavtoradiografiya comes down to recovery of bromic silver of a photosensitive emulsion in grains of metal silver as a result of ionizing radiation. These grains are formed in the direction of elementary particles in an emulsion and become noticeable after manifestation of the emulsion covering a cut of a pla a smear. Then the cut or a smear are painted in the usual way (applying any histologic coloring or histochemical reaction) together with the developed film or an emulsion. Soft beta radiation at contact of a cut with a fine-grained nuclear emulsion gives the chance of production of the radio autograph.

By means of a gistoavtoradiografiya it is possible to study various exchange processes in cells and their structures in physiological and pathological conditions, to investigate exchange of nucleoproteids, synthesis of protein, hormones and enzymes, to observe formation of cellular and intracellular structures, to study patterns of intracellular biological rhythms, regeneration, an inflammation, tumoral growth. The gistoavtoradiografiya is of great importance for studying of dynamics of a mitotic cycle, its features in cells of different bodies under various conditions.

A necessary condition of successful use of this technique is a fair idea of features of the studied phenomena and the correct selection of the corresponding radioisotopes. So, e.g., N 3 - thymidine, participating in synthesis of DNA, being her predecessor, allows to track DNA-synthetic processes autoradiographic.

After introduction of N 3 - thymidine the tag is perceived only by the cells synthesizing DNA. The percent of marked cells in each type of cells right after administration of radioisotope corresponds to the relation of time of synthesis of DNA (S) to generative time (to length of all cellular cycle — tg) this cellular type. The some of tag in population, the most part of generative time is made by the synthetic period. A number of opportunities opens the analysis of number of granules of radioactive material in a cell as the quantity of granules corresponds to amount of the synthesized DNA.

Gistoavtoradiografiya and the electronic Autoradiography giving the chance to correlate metabolic activity with morphology of separate cells and to study subcellular localization of the incorporated radioisotope, in combination with modern ways of the mathematical analysis represent perspective methods of a research.

Microautoradiography in virology found broad application for studying of the initial stages of interaction of viruses and cells (adsorption, penetration of viruses Into cells etc.) and processes of synthesis of virus components. In the first case the marked virus which is got by hl is used. obr. as a result of infection with a virus of culture of fabric in the presence of marked predecessors — nucleotides or amino acids. In these conditions again formed affiliated virions contain radioisotope in the structure. Using a microautoradiography, it is possible to track destiny of this isotope, and from here and a virus in the course of its interaction with a cell. Use of this technique for definition of synthesis of virus components — nucleic acids and proteins — is that marked predecessors of the specified components bring in various terms after infection of culture of fabric with viruses in culture medium (most often use: N 3 - thymidine for studying of synthesis of DNA, N 3 - uridine — for RNA and N 3 - leucine or N 3 - valine — for protein).

After a certain period of an incubation of a cell of culture carefully wash from the molecules of the predecessor which were not implemented into them, fix, put a fenny layer of a nuclear emulsion (type P, M or P), maintain in the dark (exposure time fluctuates Depending on a dose and type of the applied isotope) and then show.

During the use of a microautoradiography for definition of synthesis of virus components it is possible to receive data not only on localization of the studied process (at a combination to histologic coloring of cells), but also about its intensity (a quantitative Autoradiography), counting the total area of cells and their components and number of the shown grains of silver in a certain quantity of cells. There is a direct dependence between amount of grains and intensity of process of synthesis.

At the Autoradiography in virology use the organic compounds containing the following radioisotopes: With 14 , P 32 , S 35 and H 3 . The broadest application is found by the connections containing hyzone. Using predecessors whose part the isotopes having various disintegration energies are it is possible to mark nucleic acids at the same time (e.g., C 14 ) and proteins (e.g., N 3 ) virions. In this case the called components can be distinguished in the different size of grains (larger are characteristic for With 14 , small for H 3 ). Simultaneous use of a method of fluorescent antibodies allows to define emergence of specific virus proteins in the same drugs.

See also Radio isotope diagnosis .



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And, I. Ishmukhametov; L. D. Krymsky (gist.), I. G. Balangding (vir.).

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