Intranuclear inclusions in the bone marrow cells of miniature pigs.

Intranuclear inclusions were found in bone marrow cells of miniature pigs, whose ultrastructure and nature were examined by electron microscope and by cytochemical techniques. The inclusions were found predominantly in the granulocyte series and in a megakaryocyte and plasma cell. The inclusions consisted of closely packed, wavy filaments, 20-40 in number. They varied in size from 0.5-1.0 mum in length and 0.2-0.5 mum in width. The largest inclusion extended across the entire length of the nucleus. Occasionally, an inclusion extending toward the nuclear pore was observed. the intranuclear inclusions showed a tendency to appear frequently in immature granulocytes. The experiment on enzyme digestion for the epoxy sections showed that the inclusions were insoluble in RNase, DNase, pepsin, trypsin and protease solutions. These results seem to suggest that the intranuclear inclusions of blood cells differ from filamentous inclusions which have been noted previously in some neurons.