Cell versus nuclear morphometry of serum-stimulated fibroblasts: nuclear changes precede cell changes.

Changes in the cell and nuclear morphology of sparsely plated WI38 fibroblasts were followed as a function of time after increasing the serum concentration from 0.3% to 10%. Quantitative measurements were carried out in parallel on Feulgen-stained nuclei and Wright-stained cells using the Quantimet 720-D image analysis system. We report a rapid, significant change in nuclear morphology indicative of nuclear rounding taking place within 30 min after increasing the serum concentration. In contrast, cell morphology showed only a slight change within the first 30 min but showed a significant change, also indicative of cell rounding, between 30 min and 3 h after increasing the concentration. Thus our results indicate a coupling between cell and nuclear morphology, but one in which nuclear changes precede cellular changes. As variations in both cell and nuclear morphology have been linked to the control of cell growth and transformation we also discuss briefly the implications of our results in relation to the regulation of cell growth and transformation.