Stretch-Induced Force Enhancement and Stability of Skeletal Muscle Myofibrils

摘要: The main purpose of the experiments presented in this chapter was to test hypothesis that stretch-induced force enhancement commonly observed skeletal muscle is associated with sarcomere length instability. Single myofibrils isolated from rabbit psoas were attached a nanolever pair for measurement at one end, and glass needle controlled displacements other end. image striation pattern projected onto linear 1024-element photodiode array, which scanned (20 Hz) produce dark-light corresponding A- I-bands, respectively. Starting mean SL approximately 2.55 microm, stretches nominal amplitude 4 10% SL, speed 100 nm x sec(-1) applied activated (pCa2+ = 4.75). Following stretch, isometric, steady-state greater by 10.9% 45.9% than produced before predicted final length. Passive could not account enhancement. Sarcomere lengths along non-uniform, but remained constant stretch or during extended isometric period after stretch. Further, sarcomeres never stretched beyond thick thin filament overlap. It concluded are stable, therefore increased must be sarcomeric property, continuous changes unstable sarcomeres, as had been assumed past.