A single cell analysis of apoptosis. Ordering the apoptotic phenotype.

Microcinematography was applied to the analysis of the kinetics of apoptotic cell death. Apoptosis was found to be a process that proceeds in different cells at different times after an initial stress, and therefore kinetic studies of apoptotic events in bulk cultures can be problematic. Using single cell analysis we found that stronger apoptotic stimuli induce an earlier onset of apoptosis, but that there is no relationship between time of onset and duration of the apoptotic process. That is, cells that initiate apoptosis shortly after induction do not proceed more rapidly through the process. This suggests an all-or-non-mechanism that is supported by some models of the biochemical pathways of apoptosis.