Studies on Spontaneous Mammary Carcinoma of Low Cancer Strain AKR Mice Ⅲ Electronmicroscopic Studies on Virus Particles in Tissue Culture Cells

This report is concerned with electronmicroscopic studies on tissue culture cells obtained from a spontaneous mammary carcinoma and it's serially transplanted tumors of AKR mice. Numerous type C virus particles were observed in A-419 line, A-319 line, and A-162 line of tissue culture cells. These particles showed a gradual decrease during the serial passages in vitro. This finding is interesting in view of the fact that numerous type A and B particles but no type C particles were observed in the tumors from which those tissue culture cells were derived. In contrast, mature type B particles were observed in A-600 line tissue culture cells, whereas only a few immature type B particles were observed in the 26th transplant generation of the tumor from which A-600 line cells were derived. The results obtained suggest a possible interference between type A and B particles and type C particles. Bioassays of tissue culture fluids from A-419, A-162, and A-600 lines induced neither leukemia nor mammary carcinoma in test mice.