Contact behaviour and pattern formation of BHK and polyoma virus-transformed BHK fibroblasts in culture.

Certain behavioural and morphological aspects of cellular transformation have been studied, using baby hamster kidney cells (BHK21/13) and polyoma virus-transformed BHK cells. BHK cellsgrow to monolayer arranged in parallel arrays, whereas the transformed cells show a much greater incidence of crisscrossing and multilayering. Time-lapse cinemicrography and scanning electron microscopy were used to examine the behaviour producing these striking differences in cellular pattern. It was found, contrary to previous thought, that in both cell lines, when contact is made ruffle to ruffle, ruffling is inhibited. When BHK cell contact each other ruffle to side, strong adhesions always occur, as evidence by a large deformation of the contacted cell margin, with accompanying paralysis of ruffling. Then, the contacting cell either changes direction, usually spreading along the side of the contacted cell, or occasionally continues to protrude and underlap the other cell, although the original adhesions are seen to remain. Transformed cells never form strong ruffle-to-side adhesions, and usually underlap each other totally. When the cells were filmed, fixed and the same cells relocated in the scanning electron microscope, neither cell type was seen to move over the surface of another (overlap). Rather, all cells crisscross by underlapping (moving under the other cell). SEM also reveals PyBHK cells to have many fewer side-to-substratum adhesions than BHK cells. The smaller number of these attachments could explain the ease with which PyBHK cells underlap.