The adhesive dendritic pseudopodium of the platelet and the release reaction

Abstract

Adhesive dendritic pseudopia of platelets have been studied in a number of situations and in several species. Adhesion of dendritic pseudopodia appeared to trigger the formation of a multivesicular membranous sac which formed at or near the terminal bulb of the pseudopodium. This sac was at first closely packed with secondary vesicles, but later became swollen, eventually ruptured and released the secondary vesicles into the surrounding medium. Electron micrographs which could be interpreted in this way were taken of specimens derived from experiments in which adhesion between platelets and platelets, basement membrane, bacteria, and tumour cells occurred. The species examined were mouse, rat, rabbit, and man. The morphology of this reaction remained fundamentally similar in each of the species though there were minor differences involving the timing of the process, and the number of secondary vesicles. It is suggested that this process may be the morphological basis of the release reaction.