The growth of aphidicolin-arrested Schwann cells is linear over time, indicating that it is independent of cell size. (a) Quiescent cells were cultured in complete medium with aphidicolin to arrest the cells in S phase. Cell volume was measured in a Coulter Counter at the time points indicated. Each point represents the mean ± standard deviation of the results derived from three independent experiments, where, for each experiment, the mode cell volumes of three plates were measured and averaged. (b) Cells were cultured as in (a), but protein per cell, rather than cell volume, was measured at the time points shown. The results are shown as the mean ± standard deviation of three cultures in one experiment, in which about 106 cells were assayed for each point. The experiments in (a) and (b) were performed three times with similar results.