Figure 3.

Southern blot for SV40 DNA in HM3 and WI38. (A) SV40 DNA extracted from the cells. (B) SV40 DNA recovered in the tissue culture medium. Lanes: 1 and 2, HM 48 h after infection; 3 and 4, HF 48 h after infection; 5 and 6, HM 72 h after infection; 7 and 8, HF 72 h after infection. Each lane represents an independent infection experiment. Almost identical results were obtained with HM2 and MRC-5 HF. HM1 and CCD1069Sk were not tested. The different amounts of DNA (see text) were determined by Cherenkov counting of the individual lanes. DNAs were normalized for number of Tag-positive cells.