Electron microscopic studies on the stretch-induced disordering of the myofilament lattice in tetanized frog skeletal muscle fibers.

To study the effect of stretch on the hexagonal myofilament lattice in frog skeletal muscle fibers, the fibers were fixed at rest and during the isometric tetanus with or without stretch, and their cross sections were examined electron microscopically. The degree of disorder of the myofilament lattice as estimated by the Fourier transform and rotation methods in the digital image analysis was found to be largest during the isometeric tetanus with stretch and smallest during the isometeric tetanus without stretch, supporting the view that the stretch-induced force enhancement results from the disordering of the myofilament lattice.