Morphology of megakaryocytes in primitive- and adult-type Mk colonies.

In situ appearance of megakaryocyte colonies cultured from 7.5-dpc YS cells for 3 days (A) (original magnification × 300) and cultured from adult BM cells for 5 days (B) (original magnification × 200) in the presence of SCF, IL-3, IL-6, G-CSF, EPO, and TPO. Appearance of megakaryocytes stained with May-Grunwald Giemsa (C, D; the arrowheads show the proplatelets) and AchE (E,F) in megakaryocyte colonies at day 3 of culture of 7.5 dpc YS cells (C,E) and at day 5 of culture of adult BM cells (D,F) (original magnification × 1000). Ultrastructure of megakaryocytes in megakaryocyte colonies at day 3 of culture of 7.5-dpc YS cells (G) (original magnification × 3200) and at day 5 of culture of adult BM cells (H) (original magnification × 7000).