Changes in the A-band width during contraction in horseshoe crab striated muscle

Summary Cinematographic recordings of Ca-activated contraction in glycerinated bundles of myofibrils of the horseshoe crab striated muscle indicated that the A-band width did not change during rapid sarcomere shortening from 11 to 4 m, while it increased by about 10% in nearly isometric conditions.We wish to thank T. Taniguchi, M. Kusama and M. Goto for their excellent technical assistance in taking cinematographic recordings.