Cinemicroscopic Visualization of Shape Change and Motility in Normal and Abnormal Living Human Platelets

Living human blood platelets (P) have been examined with a high extinction differential interference contrast (DIC) microscope capable of detecting structures as small as 20 nm in diameter. During the quarter hour required for complete transformation, the entire shape change sequence is clearly visible, including disk to sphere transformation, extension and retraction of pseudopodia, and spreading and ruffling of the hyalomere. The exocytosis of intact 5-hydroxy tryptamine (serotonin)-containing dense bodies has been observed both by DIC microscopy and by epifluorescence microscopy in P stained with mepacrine. The release of dense bodies is associated with the formation of one or more “craters” in the upper surface of the granulomere. With optical sectioning, it is evident that certain “craters” represent internal chambers of the open canalicular system. Using these techniques, abnormalities in P motility have been observed in hereditary P disorders. In summary, the ability to observe and record permanently on cine film the motility of living P provides a rapid test of P function which allows quantitation of normal vs. abnormal motile behavior.