Tissue Culture and Circulating Myeloblasts of Avian Leukemia Studied in Electron Micrographs of Ultrathin Sections. ∗

Abstract

Summary

Studies have been made by electron microscopic examination of ultrathin sections of circulating myeloblasts of avian myeloblastosis and of these cells in tissue culture. Examinations were made, also, of tissues of spleen, bone marrow and liver of the diseased birds. The results showed that intracellular virus of typical appearance was very rarely seen in myeloblasts of the circulation and only very infrequently in the cells after culture in vitro. This was the remarkable feature of the findings, since the cells liberate virus at a high rate for long periods in tissue culture, and large amounts of extracellular virus were associated with the cultured cells. In contrast, affected cells not myeloblasts in spleen, bone marrow and liver contained intracytoplasmic virus in high concentrations, most of it in inclusion-like bodies. The significance of the results was discussed in relation to similar findings with the Rous sarcoma and Murray-Begg endothelioma and to exploratory studies for the demonstration of virus in tumors of presently unknown etiology.