Ultrastructural observations on the transectioned end of frog skeletal muscle cells

A progressive "clot" formation has been reported to occur at the transected end of frog skeletal muscle fibers. It has been claimed that the transected fiber end does not form a membrane over the cut surface but ultrastructural evidence for this has not previously been offered. Transmission electron microscopic examination of longitudinal sections through the cut surface confirms the lack of formation of a membrane over the cut fiber ends when followed up to 2 hrs post-transection. The data also show a rapid localized contracture of sarcomeres at the cut surface which spreads several sarcomeres away from the cut surface. A temporal loss of sarcomere organization occurs adjacent to the cut muscle surface.