A quantitative cytochemical investigation of the relationship between cell mass and initiation of DNA synthesis in mouse fibroblasts in vitro

The mass of cells entering interphase after cell division, initial mass (mo), and the cell mass at the stage of initiation of DNA synthesis (mG1) were determined in 21 populations of mouse fibroblasts in vitro (L-cells) which exhibited different mo values.

Abstract

The mass of cells entering interphase after cell division, initial mass (mo), and the cell mass at the stage of initiation of DNA synthesis (mG1) were determined in 21 populations of mouse fibroblasts in vitro (L-cells) which exhibited different mo values. Cells in populations with low initial masses had to synthesize more mass before the onset of DNA synthesis than cells in populations with high initial masses. In addition, these smaller cells required more time for this mass synthesis than the bigger cells. The generation times were found to be almost identical for the different L-cell populations. Cells in populations with low initial masses therefore spent a relatively long time in the G1 and a relatively short time in the S + G2 phases of the cell cycle. The opposite applied when the cell populations had high initial masses. These findings support the hypothesis that initiation of DNA synthesis is dependent on the cell mass.