From Big Medical Encyclopedia

PIGMENTS (Latin pigmentum paint) — the painted substances of various chemical structure, eurysynusic in wildlife and the performing most various biological functions — transfer and deposition of oxygen and carbon dioxide gas, participation in tissue respiration, in redoxreactions and photosynthesis, in mechanisms of sight. Pigments are a part of biological membranes, perform functions of light filters, heat insulators etc., define the coloring of live organisms playing an important role in their adaptation to conditions of the environment. Nek-rye P. are provitamins. Maintenance of a row bilious pigments (see) serves as important diagnostic test at diseases of gepatobiliarny system, diseases of blood in blood serum and urine, etc. Genetically caused disturbances of exchange of many P. are the reason of serious hereditary diseases — hemoglobinopathies (see), diseases of the muscular and nervous systems connected with deficit of tsitokhrom of b, etc.

Color P. is caused by existence in their molecules of the chromophoric groups absorbing light of a certain wavelength in a visible part of a range. The most important of such P. are chromoproteids (see) — complex proteins which molecule consists of simple protein and the painted prosthetic group of nonprotein character. As prosthetic group many chromoproteids contain metalderivatives porphyrines (see). Gemoglobin (see) — the pigment of blood of vertebrate animals and the person containing a zhelezoporfirinovy complex (gems) and localized in erythrocytes — carries out transfer of oxygen from a respiratory organs to fabrics and participates in transfer of carbonic acid from fabrics to a respiratory organs. Mioglobin (see) — the respiratory pigment of muscles providing deposition in them of oxygen — also contains ferroporphyrin. The most important oxidizing enzymes of animals and plants also belong to gemsoderzhashchy chromoproteids — catalase (see) and Peroxidase (see), and also Tsitokhroma (see), carrying out electron transfer to oxygen in process biol, oxidations (see. biological oxidation ). In a blood plasma of backboneless animals are found containing ferroporphyrin respiratory pigments (see) eritrokruorin, hlorokruorin and gelikorubin, and also a pigment hemerythrin which part of a molecule iron is, but is absent porphyrias. In blood and a lymph of many invertebrates the blue or greenish-blue respiratory P. containing copper (hemocyanins) are found. Copper is also a part and other pigment of the animal organism which is carrying out deposition and transport of copper — ceruloplasmin — and enzyme of a superoxide scavenger. As a part of the painted protein of a tsitokuprein copper and zinc are found.

As a result of disintegration gem of hemoglobin, a myoglobin and tsitokhrom in an organism of animals and the person is formed special group P. — bilious pigments which treat bilirubin (see), biliverdin, stercobilin (see) and urobilin (see).

Eurysynusic proteins of group in live organisms treat P. yellow enzymes (see) — flavin dehydrogenases (see), the derivatives of Riboflavinum (B2 vitamin) containing in quality of prosthetic group: flavinmononukleotid (FMN) or flavinadenindinukleotid (FAD). In the oxidized form these P. are painted in rich yellow color, in got into condition — are colourless. Melanina (see) — dark brown and black P. of animal origin — are found in hair, skin, feathers, a retina of eyes and a nervous system of vertebrata, and also in organisms of some invertebrates. Melanina cause coloring of a body of animals and the person, protect an organism from harmful action of ultraviolet radiation, from an overheat in the countries with hot climate etc. Lipofustsin (see) — the yellowy-brown pigment of the lipidic nature — collects in various tissues of animals and the person during the aging, at increase in metabolic activity of an organism, a hypoxia, some patol. states. Pigments of the lipidic nature are formed in tissues of animals under the influence of ionizing radiation and at a malignancy of fabrics.

The main function of vegetable P. — implementation photosynthesis (see). A chlorophyll of green plants (see. Chlorophyll ) and the backteriochlorophylls of photosynthesizing bacteria painted in green color, which are contained in chlorolayers P. play the central role in the course of photosynthesis. The complex of heterocyclic tetrapyrrole system of a forbin, related to porphyrine, with magnesium is the cornerstone of chemical structure of a chlorophyll. The important group P. of a plant origin is formed carotinoids (see) — the fat-soluble P. red, orange and yellow color representing polyunsaturated hydrocarbons of a terpenic series, and their oxidized derivative xanthophylls. Carotinoids — multipurpose Items. They take part in photosynthesis and in chlorolayers accompany a chlorophyll. Carotinoids, including. carotene (see), are biologically active compounds, nek-ry of them have properties of provitamin A and turn into vitamin A in an organism of animals and the person. Carotinoids — a source rhodopsin (see) — a light-sensitive pigment of photoreceptors of animals and the person consisting from - protein of opsin and aldehyde of vitamin A — a retinal (see. Rhodopsins ). Obviously, carotinoids participate in deposition of oxygen in living cells, and also perform protective function, protecting a plant from harmful action of ultraviolet radiation, and a chlorophyll — from oxidation by molecular oxygen. For auxiliary photosynthetic P. — the fikobilin found in blue-green seaweed (phycocyanin) and lavers (phycoerythrin). the structure tetrapirro-fishing with an open chain reminding structure of bilious pigments is characteristic. In live organisms of a fikobilina are in a complex with proteins. Treat vegetable pigments flavones (see) — the organic heterocyclic compounds which are the cornerstone of numerous yellow and orange P. of plants (a luteolin, meletin, cythrene, Rutinum, hesperidin). Nek-ry flavones have biological, including and R-vitamin, activity. Treat vegetable P. also related on chemical structure to flavones anthocyans (see) — the glycosides containing mono - or disaccharides and as an aglikon of an antotsianidina. The anthocyans of cellular juice painting parts of plants in red, violet or blue color do not participate in photosynthesis.

Histochemical methods of definition of pigments in fabrics

From the point of view of gistokhy, P.'s definitions in fabrics histologists divide all P. into three groups: proteinogenous, or tyrosine-triptofanovye pigments (melanin, etc.), gemsoderzhashchy pigments (hemoglobin, porphyrines, hemosiderin, Gematoidin, bilirubin, etc.) and lipidogenny pigments (lipofuscin, tseroid, lipochrome).

In a basis gistokhy, identifications of hemoglobin detection of its hematin lies (a complex of protoporphyrin with Fe 3+ ). The most specific results in this relation are yielded by peroxidase reaction which is negative with porphyrines, gematoidiny and hemosiderin. Most often apply methods in which benzidine and the material fixed in formalin (are used see. Lepene way ).

The most reliable gistokhy, the method of identification of porphyrines is based on ability of solutions of these P. to fluoresce after radiation by an ultraviolet light in red or orange color. Hemosiderin in the form of yellow or brown granules is always located only in a cell; it contains trivalent iron, a cut it is easily possible to find histochemical by means of Perls's reaction with acid ferricyanide of potassium (see. Perlsa way ). Fabrics fix neutral formalin, dewaxed cuts of 20 — 30 min. process the freshly cooked mix consisting of equal parts of 2% of solution of ferricyanide of potassium or sodium and 2% salt to - you, wash out in a distilled water, dokrashivat kernels, once again wash out, dehydrate, clarify and conclude in Canada balsam. Places of localization of hemosiderin are painted by Prussian blue in blue color.

Gematoidin and bilirubin histochemical have the general properties, however morphologically they are not identical. Gematoidin unlike hemosiderin is always located ekstratsellyulyarno in the form of yellowish-brown crystals and amorphous grains. Bilirubin in a gall bladder and in bilious channels of a liver is found in the form of bright orange-yellow amorphous accumulations, or bilious «blood clots». The most specific gistokhy, method for identification of bilirubin and a gematoidin is Gmelin's reaction (see. Gmelina test ), at which several drops of the mix consisting of equal parts concentrated nitric to - you and absolute alcohol are applied on the dewaxed cuts received from pieces of the fabric fixed in formalin or alcohol. The cut is covered with cover glass and at once investigated under a microscope; in the sites containing bilirubin and (or) Gematoidin observe at first diffusion green, and then blue or purple coloring. For gistokhy, identifications of bilious pigments the reaction of Matte based on these P.' oxidation in green biliverdin by solution of iodine can be also recommended. Derivatives of hematin are so-called formalin and malarial pigments, gistokhy which properties are identical to properties of hematin. They give double refraction, 3% hydrogen peroxide, 90% ant to - that or saturated spirit solution picric to - you easily become colourless.

For simultaneous identification of lipofuscin, hemosiderin and bilirubin — the main representatives of lipidogenny pigments — G. G. Glenner offered a method of three-colored coloring. Unstable cryostately cuts process 5 min. 2% solution of ferricyanide of potassium, then 20 min. mix of equal parts of 2% of solution of ferricyanide of potassium and 5% acetic to - you, after washing keep 15 min. in 3% in water solution of potassium bichromate, wash out, paint 20 min. fatty red Oh, once again wash out and conclude in Canada balsam. Lipofuscin is painted in orange-red color, hemosiderin — in blue, bilirubin — in dark emerald-green color. Tseroid, also being lipidogenny P., comes to light in the form of yellow grains usually in phagocytes around big fatty drops in cells of various bodies; for the first time it was found in a liver at cirrhosis. Tseroid is well painted by fat colors.

For gistokhy, identifications of carotinoids most often use reaction with a chamois to - that or reaction with solution of antimony trichloride in chloroform.

Philosophy gistokhy, identifications of melanin are connected with its insolubility in organic solvents (e.g., in etilenkhlor-hydrin), and also with its ability to become colourless strong oxidizers (hydrogen peroxide, potassium permanganate, iron trichloride) or to recover ammoniac solution of silver nitrate to metal silver. Masson's method — Fontana whose main stage is serial processing of dewaxed cuts solutions of iodine, ammoniac silver, sodium thiosulphate is based on the last property of melanin; at the same time melaninovy granules are painted in black color. For identification of melanin by decolouration 0,1% use solution of potassium permanganate more often (processing of the dewaxed, frozen or cryostately cuts during 12 — 24 hours) or 10% solution of hydrogen peroxide (cuts are processed during 24 — 48 hours). Lilly (R. D. Lillie) was offered by the method based that in dewaxed cuts melanin is painted in dark green color during the processing of cuts by solution of salt of bivalent iron [cuts within 1 hour process 2,5% solution of ferrous sulfate (FeSO 4 - 7H 2 O), then after washing within 30 min. keep in water in 1% solution of potassium ferrocyanide, wash out in 1% acetic to - those, dehydrate and conclude in Canada balsam].

See also Histochemical methods of a research .

Bibliography: Phytochemistry, the lane with English, under the editorship of V. JI. Kretovich, M., 1968; In e r t at sh to about in V. T., Ivanov I. I. and T and r at with about in B. N. About formation of pigments of the lipidic nature in tissues of animals with a malignant growth and radiation, Biophysics, t. 19, century 2, page 295, 1974; And y e r. An electronic histochemistry, the lane with it., page 192, 338, M., 1974; Davydovsky I. V. General pathology of the person, M., 1969; Karnaukhov V. N. Functions of carotinoids in zooblasts, M., 1973; Karrer P. A course of organic chemistry, the lane with it., D., 1960; Molecules and cells, the lane with English, under the editorship of G. M. Frank, century 4, page 136, M., 1969; Pearce E. A histochemistry, the lane with English, page 558, M., 1962; Rapoport S. M of Medizinische Biochemie, V., 1977.

H. V. Gulyaeva; H. T. Raykhlin (gist.).