ELECTRONIC HISTOCHEMISTRY

From Big Medical Encyclopedia

ELECTRONIC HISTOCHEMISTRY (Greek histos column, fabric + chemistry: synonym; an ultrahistochemistry, ultracytochemistry, an electronic and microscopic histochemistry, electronic and microscopic cytochemistry) — the section of a histochemistry studying at the subcellular level the space organization of a metabolism in cells and fabrics. By means of methods E. investigate localization of various proteins, carbohydrates, fats, nucleinic to - t, biogenic amines, hormones, enzymes, inorganic compounds and other substrates of metabolism in intracellular structures and in extracellular components of bodies and fabrics in normal and patol. conditions.

AA. arose at the end of 50 — the beginning of the 60th of 20 century on the basis of achievements of a light histochemistry (see) and a submicroscopy (see).

The majority of electronic and histochemical methods is modification of already known ways used in a light histochemistry. However methods E. demand observance of the following conditions: good safety of fabric is necessary what the accuracy of definition of localization of the revealed component, the high electron density of reaction product substantially depends on; amorphous character of this product, its ability to maintain fixing, histochemical processing, the conclusion in pitches, radiation by electrons; reaction product shall not be dissolved in environments of a cell.

The preparation of material for an electronic and histochemical research includes a number of the main stages: capture of material, its fixing, cytochemical coloring, additional fixing, the conclusion in pitches, production of ultrathin sections.

Capture of material shall be the most bystry. Pieces of fabric cut the acute razor in several drops of the cold fixer on a plate from tooth wax. Fixing shall ensure safety morfol. and chemical structures and also not to suppress its reactivity. As fixers use various highest aldehydes: acrolein, metacrolein, glyoxal, krotonaldegid, glutaric dialdehyde. The greatest distribution was gained by 1,5 — 2,5% solution of glutaric dialdehyde and solution of formaldehyde, but surely freshly cooked of paraformaldehyde since ofitsinalny formaldehyde contains the additives (methanol and ant to - that) which are negatively influencing structure and inhibiting many reactions. Quite often apply mix of solutions of glutaric dialdehyde and formaldehyde. Fixing is carried out by immersion of pieces to liquid or by perfusion of the fixer through body or fabric, pieces to-rykh then subjected to a research. The fixing solutions shall be hypertensive that is reached by addition of sucrose (7,5%). Though isotonic solutions cause swelling of fabric, in some cases also use them, e.g., during the work with cultures of fabrics. The way of fixing, the fixer, concentration of the fixing solution, its temperature, duration of fixing should be defined in each case depending on the revealed substance and research objectives.

Pieces of the fixed fabric or frozen sections (cryostately cuts can be used) immerse up to 50 microns thick in the incubating medium containing the ingredients necessary for identification of the studied substance. Time and temperature of an incubation vary depending on research objectives. After cytochemical coloring carry out additional fixing by solution of osmium tetroxide. Concentration of solution and time of fixing can change.

The conclusion in pitches, preparation semi-thin and ultrathin sections is carried out in the ways accepted in a submicroscopy. In need of visualization of reaction product carry out after-treatment of semi-thin sections, e.g. by ammonium sulfide at identification of phosphatases by a lead method. If formation of reaction product is expressed poorly, one ultrathin section contrast and dokrashivat, and another is left without changes not to veil results of reaction, in the course the cut is formed a deposit of various electron density.

Bibliography: Gayer G. An electronic histochemistry, the lane with it., M., 1974.

N. T. Raykhlin.

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