THROMBOCYTES

From Big Medical Encyclopedia

THROMBOCYTES (Greek thrombos a piece, a clot - j-kytos a receptacle, here — a cell; synonym:

platelets, G. Bizzozero's plaques) — one of the main kinds of the uniform elements of blood representing cytoplasmatic fragments of megacaryocytes of marrow.

Under different names T. 19 century are known from 40th. Their participation in a blood coagulation is established in the 80th by Gayem's works (G. Nauyesh, 1878) and M. D. Lavdovsky (1883). In 1882 the ital. scientist G. Bizzozero in detail described morphology of thrombocytes, Wright (J. N of Wright, 1906) for the first time observed formation of T. by an otshnurovka of pseudopodiums from megacaryocytes (see the Hemopoiesis). Fonio (A. Fo-nio, 1951, 1953) showed that a granu-lomer (the central area T.) the hyalomere participates in a blood coagulation, and (a peripheral zone T.) causes retraction of a blood clot (see Retraction).

T. form in cytoplasm of megacaryocytes, predecessors to-rykh are megakaryoblasts and pro-megacaryocytes. At a stage about-megakarpotsita a cell loses a basophilia of cytoplasm, gets reddish-lilacky coloring and in it plentiful azurophilic granularity (granularity of Shrid) appears. T. otshnurovyvatsya in sinusoids of marrow and come to blood (in a lymph and serous liquid T. are not found). Formation of T. proceeds until there is a narrow rim of neogenic T. around a kernel mega-karnotsita; after that the kernel breaks up to separate fragments. Period of maturing of T. averages 8 days, duration of their stay in a blood-groove — from 8 to 11 days. Normal T. have diameter of 3 — 4 microns, mikroform have smaller diameter, macroforms — from 4 to 5,5 microns and megathrombocytes — more than 5,5 microns.

In blood T. have the oval or rounded form with a smooth surface (see fig. 3 to the station Krovjg of t. 12, Art. 97). The activated T. (e.g., at contact with an alien surface) are presented by star-shaped forms with threadlike shoots — pseudopodiums. V T. allocate four zones: glycocalyx (nadmembranny

layer), membrane, gel zone (matrix) and zone of organellas. The glycocalyx performs function of receptor proteins, i.e. carries out T. Membran's activation provides interaction of T. with blood-coagulation factors, it is] a source of arachidonic acid. (see) and thromboplastin (see Thrombin). The inner layer of a membrane has a canalicular system * the connecting surface of a membrane of thrombocytes with cytoplasm. Gel zone contains mitochondrions, and also active microfilaments, to-rye perform function kontraktil-ache systems (emergence of pseudopodiums, secretion of granules, etc.). In a zone of organellas distinguish and - R-, 6-and

and - granules.

a-Granuly (granules of accumulation) make the most part of granules of T., they are considered lysosomes (see), they contain factors of thrombocytes, fibrinogen (see), fibrin (see), acid hydrolases (see), lipids (see), mucopolysaccharides (see), etc.; R-granules are characterized by existence of cristas elements of mitochondrions (see); 6 granules are heterogeneous, consist of bubbles, vacuoles, tubules; au granules contain contrast grains — components of ferritin (see the Hemosiderosis).

V T. are found: the factor accelerating transformation of a prothrombin into thrombin; the factor accelerating transformation of fibrinogen into fibrin; t r about mbo and l of nuclear heating plant in; ant yoke of a pas r Eno vy

factor; platelet fibrinogen; Eno's anti-fibers of l itichesky factor; activator of a fibrinolysis; trom-bosterin; serotonin; fibrinostabiliziruyushchy factor; A2 thromboxane (see. Coagulant system of blood).

According to Gaurovitts (F. Naigo-witz), T. contain 71% of proteins, 12% of lipoid and 5,5% of ashes; in them amino acids — glutaminic, asparaginic, a histidine, arginine, serine, glycine, alanine, valine, a leucine, etc. are found, and also the high content of taurine is noted. V T. lipoida in the form of lipo-proteidny complexes, a glycogen preferential in the form of granules of different size contain, is more rare in a diffusion form. The peroxidase, lipids in low concentration revealed during the coloring by Sudan in black B, and also ATP and ADF, ts-AMF is found.

Depending on degree of a maturity distinguish mature forms T. (at healthy people they make 80 — 95%), young, old, so-called forms of irritation and degenerative T. (the last occur at healthy people extremely seldom). Mature T. to dia. 3 — 4 microns, a round or oval form, have accurate contours, the plentiful azurophilic granularity which is located usually in the center. Young T. have unsharp contours, to dia. 2,5 — 5 microns, rounded or oval shape, blue or basphilic cytoplasm, small not plentiful granularity. The smaller sizes have the old forms (to dia. 0,5 — 2,5 microns), the rough granularity underestimating the central part. Zone of a hyalomere narrow, light. Forms of irritation differ in big polymorphism and considerable size (meet huge, kolbasovidny, having a tail, etc.). They arise owing to change otshnurovkn. Degenerative forms are characterized by an anisocytosis and a poikilocytosis, existence of microforms. Azurophilic granularity (hyaline blue plates) is absent or it rough, in the form of lumps of dark-violet color, or powdered. Cytoplasm of light tones. Emergence abnormal in a form T. confirms disturbance of a hemopoiesis.

The main fiziol. properties T. are their ability to adhesion (see t. 20, additional materials) and aggregations (see) — adhesive agregatsion-naya function, and also to adsorption on a surface of plasma blood-coagulation factors and to their transport — sorption and transport function. Regional arrangement of T. in vessels (on the periphery of a blood flow) reduces permeability of capillaries, promotes contact with an endothelium of a vascular wall (angiotrofi-chesky function). Interrelation of T. with an endothelium of capillaries it is carried out with the participation of a factor to Willa-branda, to-ry it is synthesized in an endothelium of vessels and stimulates haemo static function T.

Structurally functional changes of T. arise at damage of a wall of a blood vessel when its subendothelial components (collagenic fibers, basal membranes) enter with T. in contact. Stimulators of aggregation (collagen, ADF, serotonin, adrenaline, noradrenaline, thrombin) cause aggregation of thrombocytes, and also so-called reaction of release — secretion of granules and formation of A2 thromboxane. Reaction of release can happen under the influence of complexes antigen — an antibody, and also viruses, bacteria, endotoxins, etc. At the same time T. emit such substances as ATP, serotonin, a histamine, adrenaline, enzymes and nek-ry blood-coagulation factors. Adhesion of thrombocytes with collagen is followed by release of substances, including ADF, to-ry is formed of ATP of thrombocytes and fabrics under the influence of enzyme of ATP-ase. ATP and AMF inhibit reaction of release. From granules of T. calcium is released, to-ry changes a form T. (since activates ATF-aznuyu activity of a trom-bastenin — sokratitelny protein), stimulates reaction of release, reaction of generation of endoperoxides of prostaglandins (see) and A2 thromboxane, the thrombocytes which are activators of irreversible aggregation. T. provide retraction of a blood clot, owing to availability of thrombosthenin in them. T. inhibit a fibrinolysis (see).

T. possess the enzymes necessary for the glycolysis which is intensively proceeding in them (see), an iyentoz-ny cycle (see. At glevodny it is trained) and a cycle tricarboxylic to - t (see Tricarboxylic acids a cycle), for oxidizing phosphorylation (see) and transaminations (see). They synthesize a glycogen, proteins and lipids, using from blood basic elements — amino acids and fat to - you; in them there is a resynthesis of protein and the RNA updating.

T. have group specificity of the AVO system and a Rhesus factor (see Blood groups). Besides, on a surface of T. antigens with ~, } - subjects of histocompatability — HLA and specific to T are located. antigens Znaf Zns, K *, etc. (see Immunity transplant). T. can fix on the surface and transfer antibodies (see). The antibodies induced by platelet antigens possess complement-linked (see the Complement), the cytotoxic and agglutinating action (see Agglutination). Forming cell-bound immune complexes, they cause agglutination of T. at nek-ry autoimmune processes, napr, at a Werlhof's disease (see the Purpura thrombocytopenic). This phenomenon is irreversible and leads to loss of coagulative activity and other functions. T. have ability to phagocytosis (see).

Percentage ratio of different types of T. reflect in a trombotsi-togramma (a thrombocyte to a rny formula), edges depends on age, a functional condition of a hemopoiesis, on existence patol. processes in an organism. At different researchers of a trombotsitogramma so vary that it is impossible to remove a uniform trombotsi-togramma. Increase in blood of number of young T. it is observed at the increased regeneration of marrow (see) in connection with blood loss (see), hemolysis (see), after a splenectomy (see), etc. Emergence in blood of a large number of old forms T. it is noted at various malignant tumors. At nek-ry diseases appear patol. forms T. So, forms of irritation are found at thrombocytopenic states (see Thrombocytopenia), and also can be at a lymphogranulomatosis (see), myeloproliferative diseases (see), hemolitic anemia (see) etc. Myeloproliferative diseases are followed by emergence of the degenerative forms and so-called thromboblasts representing the fragments of a kernel of a megacaryocyte surrounded with cytoplasm with otshnurovyvayushchimisya thrombocytes.

For determination of number of T. several methods are offered (see Gemogramm). One of them are based on calculation of T. in the painted .mazk of blood on 1000 erythrocytes; knowing absolute number of erythrocytes, find T. K number to this group Fonio's method belongs (after a puncture of a finger apply a drop of 14% of solution of magnesium sulfate on skin to avoid pasting of T.; smears paint across Romanovsky — to Gimza in, a current of 2 — 3 hours). At other crumpled

da of T. count in Goryaev's camera (see cytometers). In these cases for cultivation of blood use various solutions preserving and the tinting T. Krov mix with the preserving solution in the mixer for leukocytes, then in Goryaev's camera count number of thrombocytes in 25 big squares and the result increased on 2000 gives quantity of thrombocytes in 1 mkl to blood. For calculation of number of T. use also methods of phase and contrast and luminescent microscopy; use automatic electronic counters (see Avtoanalizatora).

For determination of term of life of T. apply a tracer technique of a research. Marking of T. it is made by various radionuclide connections — sodium chromate (51 Sg), indium (1i1p), phosphorus (32P), etc. Speed of disappearance of radioactivity in blood samples characterizes the term of life of thrombocytes.

Normal the quantity of thrombocytes at adults makes 180 Ltd companies — 320 000 in 1 mkl blood. It is subject to big fluctuations, to-rye depend on various factors — conditions of a vascular tone, century of N of page, physical tension, etc. Physiological changes of quantity of thrombocytes are possible during meal, a menstrual cycle.

Change of number of T., their structures and function it is observed at trombotsitopeniye (see), trombotsi-topatiya (see) and trombotsitemiya (see) also is followed by disturbance of a blood coagulation, retraction of a blood clot and permeability of a wall of vessels. Increase in quantity of thrombocytes (thrombocytosis) can develop after administration of adrenaline (a post-adrenalinic thrombocytosis), physical tension, napr, at athletes, at an injury with crush of muscles (a myogenetic thrombocytosis). The reactive thrombocytosis arises owing to activation of a thrombocytopoiesis such factors as blood loss, hemolysis, asphyxia, a burn, an infection (a thrombocytosis in the postinfectious period), etc. A specific place is held by a splenectomy {see}, edges is followed by the thrombocytosis (asplenicheskpy a thrombocytosis) reaching a maximum usually on 7 — the 14th day; at the same time the thrombocytosis is, as a rule, observed within several weeks or months. The thrombocytosis can be one of the reasons of thromboses (see T romboz).

Reduction of number of T. (thrombocytopenia) can be at shock, parenteral administration of a histamine, etc. Thrombocytopenia is a frequent symptom immune, autoy


munny and intoksikatsionny processes medicinal or inf. genesis.

Bibliography: Guseynov Ch. S. Physiology and pathology of thrombocytes, page 7, M., 1971; Mazurin A. V. A Werlhof's disease (Verlgof's disease) at children, page 77, M., 1971; Mogosh G. Fibrinferments and embolisms at cardiovascular diseases, the lane from Romanians., Bucharest, 1979; Aster R. N and. J a n d. 1 J. N of Platelet sequestration in man, I. Methods, J. clin. Invest., v. 43, p. 843, 1964; Branehog I., Kut-t i J. W e i n f e 1 d A. Platelet survival and platelet production in idiopathic thrombocytopenic purpura (IIP), Brit. J. Haemat., v. 27, p. 127, 1974;

D e-sai R. G., Small W. M e d n i-c o f f I. Studies on the survival and the metabolic activity of platelets in humans, utilizing radioactive phosphorus, J. clin. Invest., v. 34, p. 930, 1955;

Hea ton W. A. a. o. Indium-III, new radionuclide label for studying human platelet kinetics, Brit. J. Haemat., v. 42, p. 613, 1979; Morgenstern E. Ultracytochemistry of human blood platelets, Stuttgart — N. Y., 1980;

N a 1 b a n-dian R. M, Henry R. L. a. In i with k R. L. Thrombotic thrombocytopenic purpura, Semin. Thrombosis Hemostasis, v. 5, p. 216, 1979.

V. T. Morozova; G. V. Sukyasyan (radio isotope research).

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