CHARACTERIZATION OF A CV-1 CELL-CYCLE .4. NO CRITICAL SIZE FOR S-PHASE ENTRY

Synchronous CV-1 cell cultures were pulse-labeled with [3H]TdR during their entry into S phase, fixed in glutaraldehyde and fractionated according to size by velocity sedimentation on bovine serum albumin gradients. The percent labeled nuclei and the cell size distributions for gradient fractions were determined by autoradiography and Coulter volume analysis, respectively. The distribution of cells with regard to size at several hours during S phase demonstrated that cells in every size category were present within each population. Large cells and small cells within each hourly culture appeared to be labeled to the same extent and no correlation was found between cell size and incorporation of tritiated thymidine. It is concluded that no critical cell size requirement exists for S phase entry. © 1979.