Hematology News

4º cuatrimestre licenciatura: criminología

Docente: Dr. Guillermo Arce Hernández

Article 1º

Current knowledge about the mechanism of blood clotting is the result of many decades of clinical observations and laboratory experiments, which in recent years has increased rapidly thanks to advances in protein purification technologies, tissue culture and application in this field advances in molecular biology. Classically interpreted the mechanism of coagulation by the enzymatic cascade hypothesis, distinguishing two ways: the intrinsic pathway activated when blood comes into contact with certain surfaces, and the path taken when extrínseca At present, it is categorically accepted that the exposure of the tissue factor (TF) is the main initiator event of blood coagulation, which brings about the formation of the factor VIIa/TF complex that activates the factors IX and X on the surfaces of the cells expressing the TF and, thus, the first amounts of thrombin are formed. This thrombin has multiple functions in the haemostatic mechanism, but it is insufficient to attain an efficient haemostasis, which is only possible with the assembly of the prothrombinase complex on the platelet surface. The discovery in the 1990’s of the activation of factor XI by thrombin allows to explain the clinical observations made in those patients with deficiency of the coagulation contact phase factors: these patients do not present hemorrhagic complications (excepting the deficit of factor XI). The recent discovery of the activation of precallicrein and factor XI by a cysteine protease located mainly on the surface of the endothelial cells make us think about a new role of these proteins in vivo. Blood coagulation is a closely regulated process and due to its physiological significance it is important the regulation of the tissue factor pathway that limits the initial amounts of thrombin, as well as the regulation of the proteases formed during the mechanism of coagulation by antithrombin III and of the cofactors activated by the protein C system.

Article 2º

Since the 70's, it is accepted that the mechanism of coagulation is the result of the interaction of several compartments macromolecular involving a zymogen and vitamin K dependent serine protease associated with cofactors assembled on a membrana1 (fig.1) . Are essential