Ultrastructure of Tumors Induced in Mice by Moloney and Harvey Strains of Murine Sarcoma Virus

Summary

The ultrastructure of neoplasms induced in neonatal Prince Henry mice by the Harvey (MSV-H) and Moloney (MSV-M) strains of murine sarcoma virus was examined. Although inflammatory cells and multinucleated giant cells were found in neoplasms induced by both strains, they were more frequent in those produced by MSV-M. A preponderance of abnormal vascular channels, large irregular periendothelial cells, and mesenchymal cells resembling the perivascular cells of developing blood vessels characterized neoplasms induced by MSV-H. Both periendothelial and mesenchymal cells were detected in MSV-M-induced neoplasms, but they lacked the structural irregularities found in similar cells in tumors produced by MSV-H. Differentiation toward striated skeletal muscle was not found in these cells. C-type virus particles budded from mesenchymal cells in all neoplasms, but intracisternal A-type particles were much more frequent in striated muscle cells of animals inoculated with MSV-M. It is suggested that in this experimental system, a malignant transformation of both endothelial and periendothelial cells occurred in neoplasms induced by MSV-H, whereas MSV-M inoculation resulted in transformation of only periendothelial mesenchymal cells.