A binucleated MDOK cell closely flattened against the surface of the imaging chamber prepares to divide by retracting the skirt of lamellipodia that surrounds it and assuming a spherical form. Compared to many other types of cells, the ovine kidney epithelial cell remains in this form for a considerable amount of time. Upon close examination, material can be observed aligned at the cell’s equator, an indication that the cell’s chromosomes have been organized by spindle microtubules to form the metaphase plate. Suddenly there appears to be a rift midway through the material as, presumably, replicated pairs of chromosomes are pulled apart with the abrupt commencement of anaphase.

The daughter cells produced by the process undergo only minor blebbing of their surfaces before they settle on the substratum. Broad lamellipodia roll out around their peripheries like waves. The surface structures are periodically drawn up from the substratum and reenter the main processes of the cells as part of a complex phenomenon known as ruffling. Vacuoles can be observed forming along the margins of the lamellipodia and streaming in an inward fashion. The small vesicles likely contain small amounts of culture medium, which the cells digest in order to obtain nutrients.

Over time, the Madin-Darby ovine kidney cells become extremely flat, as they stretch their lamellipodia out to fill in gaps between them and other cells in the imaging chamber. Other types of epithelial cells often behave in a similar fashion because the cells, which naturally join together to form contiguous epithelial sheets in the body, act similarly in culture as they do in vivo. It is very important for epithelial sheets to maintain continuity because they generally serve as diffusion barriers.