Platelets, and blood coagulation

The haemostatic process is a complex interaction involving the blood vessel wall, platelets and blood coagulation. In the important vascular component can be distinguished passive and active elements. The relative... 

The relatively high incidence of thromboembolic phenomena in women on the pill prompted an examination on the effects of the estrogenic and/or progesteronic components in the pill on the surface charge characteristics of the vascular system. Electrophoretic mobilities of erythrocytes and platelets and blood coagulation times were determined with samples of blood drawn from 33 women on the pill and 30 control subjects. The electrophoretic mobilities were reduced thrombin recalcification times were not affected but thrombin times and partial thromboplastin times were shortened. 

Formation of blood clot of platelets and blood coagulation proteins within a blood vessel that restricts the flow of blood Prostaglandin intermediate causing platelet aggregation and contraction of muscles (Figure 13.11)... 

Platelets and blood coagulation are also influenced by lipids and fatty acids. Saturated fatty acids are activators of the "contact factor" in the intrinsic clotting system and exert an influence on the activation of platelets, as do prostaglandins (E.F. Lxischer). Phospholipids of red blood cells and phospholipids and fatty acids of platelets may differ in nutritionally different areas (Cincinnati, Ohio Milan and Palermo, Italy) and the lipid composition of platelets may have an effect on their function the nutritional state may predispose to thrombogenic phenomena (J.M. lacono et al.). 

The calcium ion, necessary for blood-clot formation, stimulates release of bloodclotting factors from platelets (see Blood, coagulants and anticoagulants) (25). Neuromuscular excitabihty also depends on the relative concentrations of Na", Ca ", Mg ", and (26). Upon a decrease in... 

We shall first describe the coagulation pathway leading to the formation of fibrin. Then we shall briefly describe some aspects of the involvement of platelets and blood vessel walls in the overall process. This separation of clotting factors and platelets is artificial, since both play intimate and often mutually interdependent roles in hemostasis and thrombosis, but it facifitates description of the overall processes involved. 

Hemostasis and thrombosis are complex processes involving coagulation factors, platelets, and blood vessels. 

Platelets play a role in each of the mechanisms of normal hemostasis vasoconstriction, formation of the platelet plug, and blood coagulation. However, they are also involved in pathological processes that lead to atherosclerosis and thrombosis (formation of a blood clot within the vascular system). Antiplatelet drugs interfere with platelet function and are used to prevent the development of atherosclerosis and formation of arterial thrombi. 

The first reason is theoretical. The demonstrated effects of the new substances and combinations on lipids and carbohydrates do not have any major relevance to the thromboembolic process. The latter is linked primarily to changes in the hemostatic system and blood coagulation, involving platelet aggregation, coagulation factors, fibrinogen concentrations, and blood viscosity. 

Harbauer (1984) first described a venous model of thrombosis induced by mechanical injury and stenosis of the jugular vein. In a modification, both arterial and venous thrombosis is produced in rabbits by stenosis of the carotid artery and the jugular vein with simultaneous mechanical damage of the endothelium. This activates platelets and the coagulation system and leads to changes in the bloodstream pattern. As a consequence, occluding thrombi are formed as detected by blood flow measurement. The dominant role of platelets in this model is shown by the inhibitory effect of an antiplatelet serum in both types of vessels (Just 1986). The test is used to evaluate the antithrombotic capacity of compounds in an in vivo model of arterial and venous thrombosis where thrombus formation is highly dependent on platelet activation. 

The damage of a blood vessel results in the formation of a hemostatic plug, which is achieved by several differ-entmechanisms including vascular spasm, formation of a platelet plug, blood coagulation, and growth of fibrous tissue into the blood clot. 

Kelson GJ, Schmidt PS, Bartolini GL, Kelley DS, and Kyle D. (1997). The effect of dietary docosahexaenoic acid on platelet fiinction, platelet fittty acid composition, and blood coagulation in humans. Lipids. 32,1129-1136. 

Hemostasis is a complex sequence of interrelated events involving toe vessel wall, platelets, and the coagulation system. Following injury to the blood vessel, platelets adhere to exposed subendothelium by a process (adhesion) which involves the interaction of a plasma protein, von Willebiand factor (vWF), and a specific protein on the platelet sur ce, glycoprotein Ib (GPIb) (Fig 1). Adhesion is followed by recruitment of additional platelets which form clumps. 

Favero A. Effects of the new glycopeptide antibiotic teicoplanin on platelet function and blood coagulation. Antimicrob Agents Chemother 1987 31(10) 1609-12. 

Venous thromboembolism occurs when red bloods cells, fibrin, and to a lesser extent, platelets and leukocytes coagulate to form a thrombus within an intact cardiovascular system (9). A patient undergoing orthopaedic surgery incurs the greatest risk for VTE (10). Pulmonary embolism occurs when a segment of a thrombus within the deep venous system detaches itself from the blood vessel, travels to the lungs, and lodges within the pulmonary arteries. Both of these conditions, if not... 

Useful for inhibiting platelet aggregation, blood coagulation in extracorporeal circulation, occulusion of arteries and reoclusion of coronary... 

One of the initial events occuring as blood comes in contact with a polymer is the adsorption of a protein layer at the blood-material interface 1 . This layer modifies the original surface and has an important influence on subsequent phenomena such as platelet adhesion and blood coagulation... 

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