THE MECHANISM OF PLATELET-RELEASE

  • 1 January 1980
    • journal article
    • research article
    • Vol. 56  (6) , 996-999
Abstract
The mechanism of platelet release was studied in mouse bone marrow, using scanning and transmission electron microscopy. Cytoplasmic processes extended into sinusoids by megakaryocytes were found to undergo attenuation, and at the distal end develop constrictions between segments of platelet size. Rupture at sites of constriction is thought to release platelets. Microtubules were present in the processes, oriented longitudinally and became concentrated in the constrictions. The narrowest constrictions observed were about 0.2 .mu.m in diameter and several microns in length. The structural similarity of the narrowest constrictions with those found in bridges separating midbody and cell in the terminal phase of cytokinesis suggests that platelets and cells share a common mechanism for release. The presence of a centriole in each cytoplasmic process was revealed by serial sectioning. The microtubules in each cytoplasmic process apparently originate from an organizing center associated with the centriole, and the number of cytoplasmic processes that emerge from a megakaryocyte is governed by its ploidy.