Analysis of the ultrastructure of the platelets during the process of aggregation, with emphasis in the cytoskeleton and membranous changes

ABSTRACT

In this paper we presetn our findings in relation to the ultrastructural changes that are produced in the platelets during the hemostatic activation process. When the platelets are in the resting stage they have a discoid form with are a peripheral microtubular structure that encloses numerous granules, showing an open canalicular system spreading throughout the cytoplasm. Once they are activated, sequential morphological changes take place. First of all, the microtubular structure desintegrates and is replaced by a membranous pseudotubular membranous complex which fuses itself to the granules enhancing the open canalicular system which grows until it takes a sacular-canalicular appearance. Degranulation takes place at the same time. The from of the platelets becomes spherical and irregular. Later on, a microfilament organization appears, specially in the peripheral zozne projecting into the pseudopodical prolongations which are formed in the surface, giving the platelets a very irregular filopoidal form. Finally they loose all their structure becoming hyaline and vacuolated. We believe that the pseudopodical stage is the last step of the activation, prvious to the final vacuolization and destruction (AU)