Effect of rmMGDF on megakaryocyte size within individual ploidy classes in mice treated with 25-μg/kg (A) or 250-μg/kg (B) dose. MGDF causes a significant increase in mean megakaryocyte size (see inset) on day 2, with injection of 25 μg/kg (P = .001, Mann-Whitney) or 250 μg/kg (P = .0004, Mann-Whitney) MGDF, with little change in the size of megakaryocytes within individual ploidy classes. The increase in mean megakaryocyte size results from an increase in the relative frequency of large polyploid cells. On day 2, 32N is the modal DNA class, while by day 7 16N is once again the normal modal class. Each data point represents the mean ± SEM of megakaryocyte size. For the 25-μg/kg dose, n = 13 for the control and n = 5 on days 2 and 7. For the 250-μg/kg dose, n = 20 for the control, and n = 5 on day 2 and n = 8 on day 7.