Transmission electron micrographs of megakaryocytes derived from control or BclxL transgenic mice.

Micrographs show megakaryocytes from WT control (A,B), Tg19 (C,D), and Tg16 (E,F) mice. At least 50 megakaryocytes from 3 different mice (control and transgenic) were analyzed. The nucleus (Nu) and demarcation membrane system (dms) are labeled. Note the poor dilation of demarcation membranes in panels C through F. Arrows point to peripheral sheet of cytoplasm which appearance is consistent with platelet shedding in control cells (A,B). Note the extensive outer ring of cytoplasm in panels C and D, and especially in panels E and F. Granule numbers are comparable in control and transgenic megakaryocytes. Original magnifications, × 4500 in panels A, C, and E; × 12 500 in panels B, D, and F.