Studies on Human Platelets

Summary

Human platelets have been separated into 4 more homogeneous populations (A, B, C, and D; D population of highest density) by isopycnic density gradient centrifugation. Newly formed platelets have been identified in band C. These newly formed platelets age in vivo and shift into band D containing mature and old platelets. Newly formed platelets are more active in their ability to incorporate labeled amino acids into protein than mature and/or older platelets. The maturation of newly formed platelets (shift from band C to band D) is concurrent with a gradual loss in their ability to synthesize protein, a increase in density and decrease in size. In addition, newly formed platelets have a lower content of thrombosthenin than do mature (old) platelets.

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