Thrombocytes membrane

Both pathways depend on the presence of activated thrombocytes, on the surface of which several reactions take place. For example, the prothrombinase complex (left) forms when factors Xa and 11, with the help of Va, bind via Ca "" ions to anionic phospholipids in the thrombocyte membrane. For this to happen, factors 11 and X have to contain the non-proteinogenic amino acid y-carboxygluta-mate (Gla see p. 62), which is formed in the liver by post-translational carboxylation of the factors. The Gla residues are found in groups in special domains that create contacts to the Ca "" ions. Factors Vll and IX are also linked to membrane phospholipids via Gla residues. 

Hematological Effects. Routine blood parameters (hemoglobin, erythrocyte, leukocyte and thrombocyte levels) measured in 11 hexachloroethane workers did not differ from those of the controls (Selden et al. 1994). Plasma hexachloroethane levels in these workers, who wore protective equipment, were 7.3 + 6.04 pg/L at the time of the hematological analysis and 0.08 0.14 gg/L before production resinned (Selden et al. 1993). Mild skin and mucous membrane irritation were reported in the exposed group, suggesting that exposure may have been through either the inhalation or dermal routes of exposure. 

The fats also have a plastic function as they are included in cell membranes and other cell structures. The central and peripheral nervous systems are rich in lipids. PNFA are included in cell membranes, with their most significant function being the synthesis of cell hormones — prostaglandins. The properties of cell membranes as well as their interaction with external factors depend on the relation of PNFA concentration in cell components. In humans, prostaglandins are created not only in tissues but also in thrombocytes (thromboxanes) and in leucocytes (leukotrienes). The biological action of thrombocytes is extremely variant and depends on PNFA type which are the basis for fatty acid creation. 

Medicinal thrombocytopenia can emerge under the use of different medicines, including interferon. The main mechanism of medicinal thrombocytopenia pathogenesis is assisted by the destruction of thrombocytes by the complement which is activated during antibody preparation. On withdrawal, the content of thrombocytes in blood is normalized. The formation of antibodies to thrombocytes in patients with viral hepatitis C occurs due to the destruction of membrane glycoproteins by the viruses. 

Cromolyn stabilizes the membranes of mast cells, stopping the release of allergy mediators and suppressing activation of eosinophiles, neutrophilis, thrombocytes, and macrophages, which take part in the formation of bronchospasms. 

Sulfinpyrazone is used in medicine as a nonsteroid anti-inflammatory, fever-reducing analgesic however, it is believed, that it inhibits cyclooxygenase of thrombocytes. In addition, it is also possible that its action is also linked with the action on membrane of thrombocytes and reduced quantities of secreted adenosine diphosphate and serotonin, which facilitate thrombocyte aggregation. Unlike aspirin, it has no effect on those who do not have irregular aggregation systems. 

Irradiation for 60 min caused more damage. Partial detachment and desquamation of endotheUocytes from the basal membrane took place (Fig. 30.1c). Thrombocytes, fibrin threads and erythrocytes were found on the surfaces of denudated zones. 

Irradiation for 60 min resulted in the desquamation of some cells from the basal membrane and the formation of denudated areas of the intima. The affected areas were covered with thrombocytes, erythrocytes and fibrin threads. But 1-2 days after irradiation the intima microrelief of the vein returned to normal. There were no thrombi formations either in the aorta or the vein. 

Cox-1 is constitutively expressed and responsible for most of the housekeeping functions of eicosanoids, including processes such as calcium metabolism in the bone, and stomach mucous membrane maintenance. It is also responsible for synthesis of thromboxanes in thrombocytes and of prostacyclin (PGI) in endothelial cells, which have antagonistic function in thrombocyte aggregation and activation (see later). 

Figure 17.7 (a) Bacterial cellulose dry membrane mesh and (b) a thrombocyte (blood component). (Reprinted from... 

Human blood consists of red blood cells erythrocytes), white blood cells leukocytes), and platelets thrombocytes) suspended in plasma, an aqueous solution containing a variety of solutes including salts and proteins. Each red blood cell is surrounded by a protective semipermeable membrane. Inside this membrane, the concentration of dissolved substances is about 0.3 M. Likewise, the concentration of dissolved substances in pla.sma is also about 0.3 M. Having the same... 

Blood consists of protein-rich plasma in which the cells or corpuscles are suspended. They are the red and white blood cells (erythroc34 es and leucocytes, respectively) and the platelets (thrombocytes). The red blood cells do not have nuclei and are flexible round or elliptical discs with indented centers. The diameters of red blood cells vary (in pm 4 in goat 6 in pig 10 in whale and up to 50 or more in birds, amphibians, reptiles and fish). Red blood cells contain hemoglobin, the red blood pigment. White blood cells contain nuclei but no pigments, are surrounded by membranes, are 4—14 pm in diameter and are fewer in number than red blood cells. In addition to salts (potassium phosphate, sodium chloride and lesser amounts of Ca-, Mg- and Fe-salts), various proteins, such as albumins, globulins and fibrinogen, are present in blood. 

The measurement of ATP-synthesis rate is also very helpful to investigate phosphorylation processes in chromatophores, energy synthesis by mitochondria in plant and animal cells and metabolic changes in microorganisms. This method can give detailed information about cell membrane damage in cytolysis of erythrocytes and thrombocytes, which is an important factor in blood preservation and extraction of active blood products. BL estimation of ATP is well established in cell culture for tissue and organ transplants. 

Comparable with red blood cells, desialylation of platelets leads to a rapid removal from the circulation (Choi et al. 1972, Greenberg et al. 1979). Despite contradictory results (Nurden and Caen 1976, Gartner et al. 1977, Patschke et al. 1977), there are valid indications that membrane-bound sialic acid does play an important role in the adhesion and aggregation of thrombocytes. (For further details see section IV, Blood Clotting.)... 

Blood coagulation and fibrinolysis are controlled by various plasma glycoproteins and cellular elements. The carbohydrate moiety of the soluble coagulation factors, fibrinolytic enzymes and glycoproteins of the thrombocyte plasma membrane protects the protein from degradation, serves to stabilize its structure and plays a part in signal mediation. The terminal sialic acid of the carbohydrate often makes an important contribution to these various functions. 

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