An electron microscopic study of viral particles was conducted on pancreas, thymus, and bone marrow of normal and leukemic (C57BL x C3Hf) F1 (BC3) and SWR mice. The leukemic mice had developed thymic lymphosarcoma after neonatal injection of N-nitrosomethylurea or urethan. An intense proliferation of type C particles morphologically identical to the murine leukemia virus was found in the acinar cells of the exocrine pancreas of BC3 mice. The particles were predominantly located in intracytoplasmic vacuoles but they were also numerous in dilated cisternae of the rough endoplasmic reticulum and in extracellular spaces. A substantial quantitative difference of type C particles between the pancreases of leukemic and healthy mice was not observed. No viral particles were found in the pancreas of SWR mice. In the thymus and bone marrow of BC3 and SWR mice a small number of type C particles and intracisternal type A particles was found in all the experimental and control groups. The observation of a high number of type C particles in the exocrine pancreas of BC3 mice is discussed in relation to a viral etiology of chemically-induced lymphomas.
Effects of pregnancy and lactation on lymphocytes in the bone marrow of the mouse: A quantitative electron microscopic study.
