Megakaryocyte ultrastructure showing early signs of apoptosis in actin polymerization inhibitor treated megakaryocytes, such as enlarged peripheral margin with concentration of granules towards the center of the cell and more frequently displayed cytoplasmic blebbing.

<p>A) Untreated control B) Actin polymerization inhibitor treated.</p

Actin polymerization inhibitor (Latrunculin) treatment does not affect proplatelet formation and platelet structure.

<p>A) Preplatelet-like cell protrusions stained with β- tubulin and showing characteristic circumferential loops of microtubules. B) Caspase inhibition with ZVAD-FMK or Q-VD-OPH inhibits proplatelet formation from actin polymerization inhibitor treated megakaryocytes. Y-axis represents the sum of all proplatelet (PP) segments counted inside of grids in 10 random field images (40x magnification). C,D) Light microscopy images showing decreased proplatelet formation after caspase inhibitor treatment: C) Actin polymerization inhibitor treated D) ZVAD-FMK E) Q-VD-OPH. * p<0.05</p