Cellular senescence and the analysis of generation time distributions.

Generation time analysis by time lapse cinematography is an important method for investigating cellular senescence in culture, but its interpretation is complicated by several types of bias and artifact, including small sample size, cut-off bias, changes in global growth rate, and phase of the population growth cycle. When these factors are considered, interpretation of the data base used by previous investigators changes considerably, and does not reveal any differences in growth behavior between middle and late passage WI-38 cells. Nor does it support the transition probability theory either of cell cycle transit or of culture senescence.