Some methods of staining allow you to identify in the cells of certain chemicals. Differential staining of fats, glycogen, nucleic acids, nucleoproteins, certain enzymes and other chemical components of the cell is possible. The contribution of histochemistry to the study of the chemical composition of tissues is constantly increasing. Dyes, fluorochromes and enzymes that can be attached to specific immunoglobulins (antibodies) are selected and, observing the binding of this complex in the cell, identify cellular structures. This field of study constitutes the subject immunohistochemistry. The use of immunological markers in light and electron microscopy contributes to the expansion of knowledge about cell biology, as well as improving the accuracy of medical diagnoses.
Optical coloring. Traditional histological staining methods are associated with fixation, which kills tissue. Optical staining methods are based on the fact that cells and tissues, differing in thickness and chemical composition, have different optical properties. As a result, using polarized light, dispersion, interference or phase contrast, it is possible to obtain images in which the details of the structure are clearly visible due to differences in brightness and / or color, whereas in a conventional light microscope such details are hardly distinguishable. These methods allow studying both living and fixed tissues. Using histochemical techniques, it was possible for the first time to show the association of changes in the amount of RNA with protein synthesis and the constancy of the DNA content in the chromosome set.
Developed at the Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, lab. functional histochemistry (Pushchino); Institute of emergency care to them. N.V. Sklifosovsky, lab. pathomorphology with histochemistry (Moscow). You can read: Luppa H. Fundamentals of histochemistry. M .: Mir, 1980.
Term cytochemistry used in the literature in two ways - either as ultrahistochemistry cells, or as a sum of microscopic methods that allow chemical and enzymatic analysis of cells or groups of cells while maintaining their morphology.
Cytochemistry studies by chemical methods the structure and functions of cells, intracellular structures and their metabolic products. The term "cell" was proposed by the English physicist R. Hooke in 1665, which was its discoverer.
In humans, about 1014 cells of various types. Substances dissolved in the plant sap (sugars, polysaccharides, alkaloids, tannins, pigments, some salts, etc.) cause by osmosis the entry of nutrients and water into the cells creates mechanical stress on the cells and tissues - turgor.
Through osmosis in the cells of all plant and animal organisms water enters. In plant tissues, the osmotic pressure of 0.5-2 MPa (in plants in deserts more than 10 MPa) - this is the main reason for the rise of water from the roots to the tops. In human blood at 37 ° C, the osmotic pressure is 0.78 MPa (7.7 atm.). Thirst is caused by the body's need for water to restore normal osmotic pressure in the cells after it has been raised, for example, by eating salty foods.
Questions of cytochemistry are dealt with at the Institute of Cytology RAS (St. Petersburg), Institute of Cytology and Genetics SB RAS (Novosibirsk). There is a magazine "Cytology". You can read: Brodsky V. Ya., Polyakov N. I. Introduction to quantitative cytochemistry. M .: 1969.