Multiparameter nuclear morphology of the G0-G1 transition

Image analysis was performed using Feulgen-stained smears of L cells that were either confluent or had received a nutritional stimulus to proliferate. The cells were grown directly on slides in order to minimize damage to them during manipulation and to avoid trypsin treatment. A series of experiments was performed by varying the dose and the time of the stimulus. The nuclei were interactively sampled and automatically segmented. Most of the information about the fine chromatin structure was gained after subtracting the original image from a median-filtered image. The results indicate that there were changes in the Feulgen-stained nuclear morphology and densitometry shortly after transition of quiescent G0 cells to the proliferating G1 compartment. Multidimensional cluster analysis provided model-independent discrimination between the resting and the stimulated cells; the latter presented increased nuclear dispersion, indicating increased template activity of the cells. The results obtained are applicable both to obtaining a better understanding of the mechanisms of regulation during the G0-G1 transition and to deriving morphologic criteria applicable in diagnostic routines.