Ultrastructural Modifications of the Cell Surface and Intercellular Contacts of Some Transformed Cell Strains¹ Free

Normal contact-inhibited and transformed cell cultures have been fixed and embedded in situ for an electron microscopic study of the cell surface and intercellular connections. In a number of experiments, ruthenium red was added to the fixatives following Luft's technic for visualizing the mucopolysaccharide layer on the cell surface. Cultures of normal rat, Chinese and Syrian hamster embryo cells were compared with 5 different strains of transformed cell lines: Chinese hamster cells transformed in vitro by adenovirus 12, Syrian hamster cells transformed in vitro by adenovirus 12, Syrian hamster cells transformed in vivo by SV40 virus, spontaneously transformed BHK21 cell line, and finally a spontaneously transformed rat fibroblast strain. Two main observations are reported: (a) The character of intercellular contacts was changed in the transformed cells. Whereas close junctions and desmosome-like structures are as frequent as in controls, the so-called tight junctions practically disappeared in the transformed cultures. (b) The ruthenium red layer was considerably increased in all the five transformed strains compared to the normal controls, suggesting an increase of the mucopolysaccharide deposit at the cell surface.