SummaryA comparative study of mammalian (human, rat, rabbit, guinea-pig, horse, dog) platelet aggregation was done using phase contrast microscopy and photometric method and gave us the following results :1. The animal platelets do not spread spontaneously onto glass in contrast to human ones (in their own plasma).2. They do not aggregate in presence of adrenalin, noradrenalin, 5-HT but these amines increase the sensitivity of the platelets towards ADP.3. Although all the platelets aggregate in presence of ADP, bovine thrombin, collagen or thimerosal, there exists some quantitative differences from one species to another.4. Adenosine and AMP are inhibitors of ADP-induced aggregation for human, rabbit and dog platelets and not for guinea-pig and horse. As for the rat, if adenosine is not inhibitor, AMP can be inhibitor if used at strong doses.5. There exist great differences in the ability of the various platelet-poor plasmas studied to inactivate the aggregating property of ADP, as for instance the weakest being the human one and the strongest the rat one.6. The authors insist on the importance of ADP-inhibition by AMP and adenosine, and the ADP-inactivation by the plasmas for the mammalian platelet aggregation and almost disaggregation.

SummaryGlycoproteins present at the external surface of cells probably play specific roles in cellular function. Increasing evidence suggests that the glycoproteins span the plasma membrane with the bulk of the bound carbohydrate asymmetrically distributed on the outer surface. Micellar association of glycoproteins in membranes leads to pore formation and functional roles in transport through the membrane, while surface glycoproteins have been shown to be enzymes, to determine cell specificity and contribute to the cell surface charge. The platelet plasma membrane contains 3 major glycoproteins, glycoproteins I, II and III as characterized in order of their decreasing molecular weight. Glycoprotein I appears to have the highest sialic acid content and to give rise to a platelet specific acidic macroglycopeptide on trypsin digestion. Specific glycoprotein abnormalities in the platelets of patients with Glanzmann’s thrombasthenia suggest that the glycoproteins play a role in the mechanism of platelet aggregation. A much reduced content of glycoprotein I in the platelets of 2 patients with the Bernard Soulier syndrome may be associated with their defective adhesion to subendothelium and indicates a possible relationship on the platelet surface with the von Willebrand factor protein. Preliminary evidence suggests that in common with other plasma membranes the platelet membrane has a fluid structure and that the organization of the glycoproteins on the platelet surface is extremely sensitive to stimuli and susceptible to change.

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SummaryTwo patients with a severe von Willebrand’s disease characterized by no detectable factor VIII related antigen in their plasma received transfusions of cryoprecipitate. The bleeding time was corrected for a short period of time and returned to its pretransfusional value although the other parameters of the disease were still corrected. Electrophoretic and immunologic properties of factor VIII related antigen infused were determined serially after transfusion. Modifications of these properties occurred progressively after transfusion. The half disappearance time of F. VIIIR. A. was determined and found to be considerably shorter than in hemophilic recipients. This study suggests an alteration in vivo of F. VIIIR. A. infused into von Willebrand recipients.

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