Electron Microscope Observations of the Platelet-Fibrin Relationship in Blood Clotting

By E. DE ROBERTIs T HE STUDY OF THE SUBMICROSCOPIC ORGANIZATION of blood platelets iii different. physiologic conditions is of importance in the ebucidation of the function that they have in hemostasis. Although the exact mechanism of action of platelets is miot entirely known, there are evidences that they play a role imi the first stages of hemostasis by agglutinatimig at the woumid and later have varioums functions imi the process of blood clotting amid retraction of the coagumlum. Several imivestigators have studied, with the electron microscope, miormal platelets iii the differemit forms they assume when, leaving the blood stream, they come in contact with a surface.’ ‘ ‘ . . . ‘ These morphologic changes6 are of importamice in explainimig the agglutination of the platelets imi hemostasis. Moreover the dcctron microscope has also been applied4 to study the disintegrating effect of thrombin umpoli the platelets which probably plays a role in the mechanism of physiological 1)bOOd clotting. However, little is knowmi of the actual interaction of the platelets with the fibrin clot, a process which leads to the retract.iomi of the coagubum amid expumisiomi of the serum. rfh process of syneresis is apparently dependent on the presemice of a sufficient number of normal platelets. Already in 1878, Hayem demonstrated that iii thrombocytopenic purpura, blood undergoes coagulation, but there is mno retraction of the coagulum. Since then, there have been miumerous observations amid experimemital data which support the role of the platelets in syneresis amid have established that clot retractiomi is dependent on the concentration of platelets in the blood.” 8, 9