Smooth-surfaced control and transformed C3H/10T-1/2 cells differ in cytology: a study by secondary electron,...

7,12 dimethylbenz-a-anthracene (DMBA)-treated C3H/10T-1/2 mouse embryo fibroblasts have been characterized by the occurrence of pleomorphic microvilli (PMV) in contrast to the non-treated smooth-surfaced C3H/10T-1/2 cells. Recent studies by semiquantitative secondary electron image (SEI) have demonstrated a significant correlation between the number of cells with numerous PMV and the development of oncogenic potential. In these studies, so-called type III transformants scored highest in oncogenic potential and occurrence of cells with pleomorphic microvilli, but always contained a small fraction of cells displaying rather smooth surfaces. Quantitation of the size of nuclei and nucleoli and the number of intranucleolar silver granules after nucleolar organizer region (AgNOR) staining and back scattered electron image (BEI) with an automatic image analysis system (IBAS) revealed that these smooth-surfaced type III cells were significantly different (p less than 0.001) from the non-DMBA transformed smooth-surfaced control C3H/10T-1/2 cells. Compared to PMV transformants, the smooth transformants exhibited smaller nucleoli, a lesser nucleoli/nuclei fraction and fewer AgNOR sites, indicating reduced cellular activity. The biological significance of the smooth-surfaced fraction in PMV-covered type III transformants remains unclear.