An intense flurry of vacuole formation can be observed in one of the rhesus monkey kidney epithelial cells (located on the left-hand side of the field of view in the first part of the video). Along the leading margin of the locomoting LLC-MK2 cell, the small, membrane enclosed sac-like structures appear at an astonishing rate. The vacuoles are formed via endocytosis, which entails an invagination and pinching off of the cell’s plasma membrane to encapsulate extracellular material into a vesicle. In animal cells, vacuoles are primarily utilized for the temporary storage and transport of water, food, or wastes. The vacuoles formed by the featured epithelial cells presumably contain small segments of culture medium, which they can digest to obtain nutrients.

Several LLC-MK2 cells locomote across the field of view utilizing their broad lamellipodia to produce crawling-like motions. As the surface extensions are stretched out over the substratum, they form contacts with the surface that are used by the cells as anchorage points for contraction. The adhesions remain stationary as the cells pass over them, but as they become increasingly distal due to cell progression, they are usually released.

The wave-like motions created by the repeated extension and pulling back of lamellipodia from the culture medium are known as ruffling. Though it appears to be erratic, the overall movement of membrane ruffles is toward the back of the cell. Most ruffles, collapse near the central region of the cell. During the high speed playback of time-lapse sequences, ruffling membranes often produce the sensation of a flickering light.