Alterations of Platelet Aggregation in the Chandler Tube: II. Electron Microscopic Observations

Platelet aggregation in the Chandler tube was evaluated by electron microscopy. Some samples of rabbit platelet-rich plasma (PRP) had small (<5%) changes in optical density during aggregation. In those samples fibrin formation was conspicuous shortly after the onset of aggregation and was found between individual platelets in platelet thrombi at later stages of aggregation. Samples of PRP in which the optical density change exceeded 30% had larger platelet aggregates. Fibrin strands were present at the periphery of such aggregates, but generally were absent within aggregates, both in the initial stages of aggregation and in well-developed platelet thrombi. Platelets in both large and smaller aggregates showed loss of granules and hyaloplasm. Samples of PRP which had increased fibrin formation corresponded to experimental samples in which the blood coagulation system was activated experimentally and those of a small number of samples from normal humans.