The shape assumed by fibroblasts when they travel is often roughly triangular, broad lamellipodia extending across the leading edge and a tapering uropod or retraction fiber trailing along the rear. The retraction fibers of the CRE BAG 2 cells become very long and narrow before they are eventually retracted into the central region of the cell to which they belong. As the field of view becomes increasingly populated, the adherent retraction fibers of many of the fibroblasts seem to intertwine like the threads of a spider’s web.

During video, flurries of activity along the edges of some of the CRE BAG 2 cells create the impression of a flickering light. Known as ruffling, the phenomenon is caused by the rapid formation and retraction of lamellipodia and other surface extensions. Ruffling tends to be most pronounced at the leading margin of a migrating cell and often ceases in areas that overlap with other cells, as demonstrated by many of the CRE BAG 2 fibroblasts.

An abundance of cell fragments are present in the chamber imaged to produce this time-lapse sequence. Significant amounts of the debris can be seen flowing across the field of view periodically as it is carried by currents in the culture medium. The currents are able to lift the material from the substratum because it lacks contacts sufficiently strong enough to keep the fragments adhered to the surface. Fibroblasts, such as CRE BAG 2 cells, are not carried by currents if they are complete because they form strong junctions called focal adhesions with molecules present in the culture medium.