Transmission electron micrographs of BM megakaryocytes from a mouse injected with 1% NMS (a) and a mouse injected with 250 μg/kg rmMGDF (b). Although considerably larger in size than cells from control animals, the megakaryocytes from MGDF-treated animals contain normally distributed organelles within their cytoplasm, including the demarcation membrane system. Nu, nucleus; dms, demarcation membrane system. Original magnification × 4,000.