On-line recording of diffraction pattern changes from single muscle fibers subjected to quick stretch and release

Transient diffraction pattern parameter and tension responses were recorded from isolated frog semitendinosus muscle fibers subjected to quick stretches and release with an on-line digital acquisition system. The sarcomere length was determined from the zero to first order diffraction line spacing detected with a charge-coupled device photosensing array. Diffraction data was digitized and sequentially stored every 18 ms by a PDP-8 machine language program for later analysis. Sarcomere length, diffraction line intensity, and sarcomere length dispersion were determined with an 8080A microcomputer program incorporating extended math and floating point software packages. Tension records were simultaneously photographed from a storage oscilloscope. Quick stretches and release on tetanically stimulated single skeletal muscle fibers indicated that the transient sarcomere length change occurred in less than 18 ms. Transient tension responses demonstrated a long (150-200 ms) tension recovery phase with no corresponding sarcomere length change. There were no significant alterations in the diffraction line intensity or dispersion following the length perturbations.