The wave-like motions created by the repeated extension and pulling back of lamellipodia from the culture medium are called ruffling. Though it appears to be erratic, the overall movement of membrane ruffles is toward the back of the cell. In actively migrating cells, lamellipodial activity occurs most heavily along the leading margin. The Madin-Darby ovine kidney filling the center of the field of view in this digital video, however, exhibits ruffling around its entire periphery. Consequently, the cell fails to locomote very far in any particular direction.

In addition to lamellipodia, the flattened MDOK cell sporadically extends and retracts narrow, finger-like filopodia. In addition to being utilized for locomotion, filopodia can act as feelers for the cell, stretching out in various directions to obtain information about the environment. Occasionally the cell surface protrusions come into contact with small cytoplasmic fragments left behind by other cells or produced by the breakdown of dead cells, and the cell absorbs them into its own contents.

Each time a protrusion is formed on the surface of an MDOK cell, cytoplasmic streaming occurs. The cytoplasm in the central region of the cell (termed plasmasol) is much more fluid than the cytoplasm (plasmagel) at the periphery of a lamellipodium or other membranous extension. As a surface structure grows, plasmasol flows into the forming protrusion and assumes a more gel-like consistency around its margins. When the structure is retracted, the plasmagel liquefies and streams back into the center of the cell, where it again assumes a liquefied state. Such cytoplasmic transformations result from modifications in the cross-linking actin filaments present in the cell.