Ultracytochemical Studies on Aberrant Structures in Avian Virus Tumor Cells

Summary

Occurrence of aberrant cytoplasmic masses in avian virus tumor cells and their possible relation to virus synthesis by the cells were described in a previous report. As seen earlier, such masses consist of spheres somewhat resembling the nucleoids of the avian tumor viruses with interspersed dense bodies of the size and appearance of ribosomes. The composition of these structures was further investigated in the present work by ultracytochemical study of neoplastic cells of tumors induced by strain MC29 avian leukosis virus. Treatment with ribonuclease of thin sections of cells from growths arising in the kidney completely removed the dense, ribosome-like bodies, leaving a moderately densely stained amorphous mass. Structures exposed to pepsin showed essentially no staining except that of the dense granules removed by ribonuclease. This was in contrast to the relatively deeply stained residual material in the cytoplasm which indicated either a high proportion of protein in the structures or major differences between the constitution of protein in the structures and that of the cytoplasm. The possible origin of the collections of spheres and associated ribosomes and their significance were discussed.