Megakaryocytopoiesis in the liver of the developing opossum (Didelphis virginiana).

The development of hepatic megakaryocytes has been examined in the livers of 35 young opossums at four different stages of postnatal development. Megakaryocytopoiesis is carried out within the sinusoidals and there appears to be a close relationship between the young megakaryocytes and the sinusoid lining cells. Megakaryocytes in the opossum are relatively small and lack the degree of nuclear complexity seen in other species. Both the nucleus and the cytoplasm undergo sequential maturational changes but, in the newborn especially, these sequences are not necessarily interrelated and there is a rapid cytoplasmic differentiation to provide for early platelet release. A scheme for the maturation of the hepatic megakaryocytes is presented.