Methylcholanthrene-induced Sarcoma and Normal Muscle Fibroblasts of the Mouse — a Comparison of their Ultrastructure

Electron microscope observations of cells from methylcholanthrene induced tumours of the mouse and mouse muscle fibroblasts, grown in vitro , show five main differences in ultrastructure. The surface of the normal fibroblast is smooth when compared with that of the tumour cell; the leading lamella of the normal fibroblast has fewer ruffles (lamellipodia) and fewer cell-substrate plaques than the tumour cell; the tumour cell does not have a layer of cortical filaments like the normal cell but has well marked filamentous tracts in the main body of the cytoplasm and the endoplasmic reticulum of the normal cell is far less abundant and wellorganized than that of the malignant cell. The fact that all these differences are possibly related to the cell surface may be of significance when considering the changes brought about during carcinogenesis.