In culture, cell fragments are often able to migrate across a substratum despite their lack of nuclei and other organelles. This phenomenon can be observed among some of the small sections of debris formed when a cell in the lower left-hand corner of the field of view attempts to retract its surface extensions before dividing. The sites of attachment between the myoblast and the surface of the imaging chamber are not properly released, causing the cell to take the draconian measure of severing parts of its own cytoplasm. The resulting debris seems to have a life of its own as it enjoys a frenzied dance across the screen. Later in the video, other cell fragments can be seen mimicking the Dionysian movements of the previously-formed debris.

The large nuclei and small, round nucleoli of several A-10 myoblasts can be clearly distinguished during the high speed playback of this time-lapse sequence. A large number of granular-appearing mitochondria can also be observed. As demonstrated, these organelles are predominantly found in the central portion of the cell. The cytoplasm in this region of the cell, known as plasmasol, is more liquid than the cytoplasm located around the cell’s periphery. The latter form of cytoplasm, which is called plasmagel, can be found along the margins of lamellipodia and filopodia, but when the surface extensions are retracted, the gel-like material liquefies into plasmasol, which flows back toward the center of the cell.

Stress fibers are established when cells form focal adhesions with the substratum. Bundles of actin comprise each fiber, which also contain the protein myosin. The myosin renders the structures somewhat contractile and facilitates their production of tension. Cells whose functions necessitate the generation of significant amounts of tension, such as the cells that line blood vessels, tend to form the most stress fibers. A number of stress fibers can be seen forming among the embryonic rat thoracic aorta cells presented in this video. They appear as striations extending through the broad rim of lamellipodia spread around each cell.