Mgks in bone marrow, proplatelet formation, and platelet life span. (A) Mgks in the bone marrow from the femur and spleen were assessed under an optical microscope (left). Mgks were detected by staining with anti-VWF antibodies. The counts of Mgks in 10 visual fields (200× original magnification) were determined (right). (B) Murine fetal liver cells were harvested from embryonic day 13.5 embryos and cultured with murine TPO. Proplatelet formation was monitored 4 days after the addition of TPO. Images were obtained using the BX51 microscope (Olympus) with 20× objective (left). The scale bars represent 50 μm. The percentages of proplatelet-forming Mgks are demonstrated in the right panel. The results are presented as the mean and SD. Representative results of 2 independent experiments are shown (n = 6). (C) Mice were injected with 600 μg of NHS-biotin via the murine tail vein on day 0, and the percentages of biotinylated platelets at various time points were assessed via flow cytometry. The results are presented as the mean and SD (n = 3 each). ∗∗∗P < .001 (unpaired t test). ns, not significant.