Growth rate regulation and random transition. A study performed on embryonal carcinoma cell lines. I

Analyses of cell-cycle characteristics of the three embryonal carcinoma (EC) cell lines F9, PCC3 N/1 and PCC4 Azal, have been performed. The three lines reflect successive stages in early mouse embryogenesis as regards cell surface antigens and cell-cycle characteristics. In an attempt to understand changes in cell-cycle characteristics occurring during early embryogenesis, the two-random transition probability (TP) model was applied to the EC-cell system--and particularly to the F9 line. By utilizing an intraclonal heterogeneity in intermitotic times found in these EC lines, a growth-regulating point was introduced as a modification of the two-random TP model. The modified model was found to be very useful when demonstrating the cell-cycle growth kinetics of the F9 line. The model is used in an accompanying paper to extend the analysis of cell-cycle characteristics in undifferentiated EC cells.