A procedure for computing cellular proliferation kinetics during “log phase” of growth

A procedure is described for deriving values for the G 1, S and G 2 phases of the generation cycle from autoradiographic data by exploiting the fact that there is an abrupt doubling of the rate at which the labelled fraction of a cell population increases when the duration of exposure to radioactive thymidine exceeds the G 2 period. When tested in HeLa S3 cells the results by this method were in good agreement with those obtained by the method of scoring labelled metaphases. The new procedure has the advantage that it requires smaller cell populations and shorter periods of observation.