An ultrastructural study of clots formed in recalcified platelet-rich, human plasma has revealed an intimate platelet-fibrin association. A number of the dense platelet granules, the alpha granules, formed an osmophilic mass in the center of platelets undergoing viscous metamorphosis. Fibrin strands appeared to be connected to the altered alpha granulomere of these platelets.

The observed association between fibrin strands and platelets in the clot was supported by experiments with an electron dense stain for fibrinogen. Clots formed from platelet-rich plasma preincubated with fer-A.F. antibody contained altered platelets with an intracellular distribution of the ferritin conjugated antibody. Connections between intracellular fer-A.F. antibody and fibrin strands periodically banded by the ferritin stain were observed.

These observations indicate that the altered platelet granulomere attached to fibrin strands may play a role in clot retraction.

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© 1965 by American Society of Hematology, Inc.
1965
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