Effects of a single injection of PEG-rHuMGDF on megakaryocyte recovery after irradiation in mice. Mice were irradiated at a dose of 3.5 Gy and intravenously given 80 μg/kg PEG-rHuMGDF (•) or vehicle (○) 1 hour after irradiation. The number of megakaryocytes in the femur of the mice before total-body irradiation and at indicated times after irradiation was examined.