retraction of a blood clot

From Big Medical Encyclopedia

RETRACTION of a blood clot (Latin retractio procrastination, reduction) — the active reduction of a clot or plasma which is followed by release of serum.

Retraction is the final stage of formation of a clot or blood clot (see). As R. occurs at presence thrombocytes (see), their concentration determines the size P. Retraction of plasma rich with thrombocytes is expressed in much bigger degree, than R. to whole blood. The major factors determining size P. are the quantity and functional activity of thrombocytes (direct dependence) therefore R.'s disturbance is most often connected with pathology of thrombocytes. R. is influenced also by concentration of thrombin (direct dependence), fibrinogen and erythrocytes (inverse relation), temperature and reaction of the environment, intensity of glycolysis and availability of ATP. The mechanism P. is similar to the mechanism muscular contraction (see). Divalent cations (Sa 2+ , Mn 2+ , Mg 2+ ) and methylxanthines (theophylline, caffeine) have the same impact on R. what they exert on muscle fiber. The river depends on metabolitichesky activity of thrombocytes — ratios in thrombocytes of ATP and sokratitelny protein of thrombosthenin, or the snow groomer-tozima, to-ry, as well as actomyosin of muscles, has high ATF-aznoy activity. Thrombosthenin, according to B. I. Kuznik and V. P. Skipetrov (1974), contains directly in cytoplasm, microtubules and on a surface of thrombocytes. From thrombosthenin are allocated the component A reminding actin, and the component M reminding a myosin on the properties. From thrombosthenin, as well as from actomyosin of muscles, it is possible to receive the threads which are reduced in the presence of ATP and Mg 2+ . Retraction in a blood plasma of the person is followed by reduction half of the content of ATP in thrombocytes and the corresponding increase in content in plasma of inorganic phosphate, to-rye, activating Sa 2+ - dependent ATP-ase of platelet thrombosthenin, leads to change of a form of thrombocytes and emergence of pseudopodiums, to-rye, joining threads of fibrin, pull together them, promoting stabilization of a blood clot.

Fiziol. R.'s role is completely not opened. The serum rich with thrombin which separated at R. causes a further local blood coagulation and strengthening of blood clot. Reduction of platelet units, R. of blood clots in expanded vessels promote a hemostasis. The ruble also warns full occlusion of vessels and promotes recovery of a blood-groove. According to A. A. Markosyan, value P. consists that at this process substance (a so-called factor of the return information) comes to blood, a cut causes increase in anticoagulating and fibrinolitic activity of blood, prevents increase of blood clot and leads to its lysis.

R.'s definition has diagnostic value. Several tens of methods, including micromethods, definitions of River are offered. The greatest distribution was gained by the methods establishing R.'s full value on the relation of volume of the emitted serum to the volume of initial amount of blood or plasma. R.'s definition is carried out as in vitro, and by means of special devices — a tromboelastograf, a koagulograf (see. Tromboelastografiya ), EAM-1 (the device registering change of electrical resistivity of a blood clot, increasing in direct ratio R.'s degrees), etc.

Age changes R. Tak are observed, at advanced and senile age of R. begins later, than in youthful and mature; R.'s degree decreases with age. At women at the age of 25 — 45 years note nek-ry functional weakness of River. R.'s decrease can be observed at trombotsitopeniye (see), Verlgof's diseases (see. Werlhof's disease ), thrombasthenias (see. Trombotsitopatiya ), hemoblastoses (see), at various forms coronary heart disease (see), at radial illness (see), polycythemic states (see. Hyperglobulias ). The river can be raised at anemias (see), small blood losses (see), malaria (see), oncological diseases, at atherosclerosis (see), idiopathic hypertensia (see), inflammatory processes. R.'s definition, coagulations and fibrinolysis (see), and also properties of a blood clot can serve as additional information on a functional condition of system of a hemostasis.

See also Coagulant system of blood .

Bibliography: Baluda V. P., etc. Laboratory methods of a research of system of a hemostasis, page 95, Tomsk, 1980; B and N-d and r and V. A. N and d river Mikrometod of simultaneous definition of retraction, spontaneous fibrinolysis and haemo static properties of a blood clot, Laborat. business, No. 12, page 716, 1971, bibliogr.; B and r to and and N 3. C. Hemorrhagic diseases and syndromes, M., 1980; To at z-N both to B. I. and To about t about in shch and to about in and M. A. K to objective assessment of true retraction of a blood clot, Laborat. business, No. 9, page 524, 1964, bibliogr.; Forgs to B. I. and Skipetrov V. P. Uniform elements of blood, vascular wall, hemostasis and thrombosis, M., 1974, bibliogr.; Markosyan A. A. Physiology of thrombocytes, L., 1970; The circulating platelet, ed. by Sh. A. Johnson, p. 225, N. Y., 1971, bibliogr.; George J. N., N u r d e n A. T. P h i 1 1 i p s D. E. Recommendation of the international committee on thrombosis and hemostasis concerning platelet membrane glycoprotein nomenclature, Thrombos. Haemostas. (Stuttg.), v. 46, p. 764, 1981; Human blood coagulation, haemostasis and thrombosis, ed. by R. Biggs, Oxford, 1976; P h i 1 1 i p s D. R. Surface labeling as a tool to determine structure-function relationships of platelet plasma membrane glycoproteins, Thrombos. Haemostas. (Stuttg.), v. 42, p. 1638, 1980, bibliogr.; Platelets, multidisciplinary approach, ed. by G. de Gaetano a. S. Garattini, N. Y., 1978.

V. P. Baluda, T. I. Lukoyanov.