Abstract

The principal structural characteristics of platelets are first described: thesuperficial membrane, the canalicular systems, granules and microtubules. Subsequent phases of platelet activation are then examined: change of form, adhesion to extraneous surfaces, platelet aggregation induced by various concentrations of ADP, and the release reaction. The behaviour of clotting factors and platelets during muscular work is then examined. During strenuous, shortlived work, an increase in the activity of clotting factors VIII and XII has been noted together with a numerical increase in platelets. The possible causeis discussed. Platelet adhesion and aggregation qualities do not seem to be modified in healthy, young people although the elderly and vasculopathics showincreased aggregation. It is suggested that this hyperaggregability is a moment in the triggering off of vasal occlusion. As regards muscular work of moderate intensity and long duration, platelet number would not appear to vary. Theiradhesion is reduced, however, and the cause of this is unclear. Experimental data regarding aggregability during moderate, long duration work are lacking. Verf.-Referat