The Ultrastructure of Myosin-Extracted Striated Muscle Fibers

Electron microscope examination of myosin-extracted psoas muscleof the rabbit reveals a number of thin filaments, about 25 Äin diameter, bridging the gap between the ends of the actinsand the remaining myosin of the M band. Extraction of actinfrom the region of the Z disc shows similar thin filaments nearthe Z disc. Myosin-extraction of several invertebrate musclesreveals a remaining network of thin filaments in the regionof the A band. These thin filaments are probably elastic, andcould contribute to the functioning of these muscles.