Freeze-etch studies on fish skeletal muscle

The results of a freeze-etch study of skeletal muscle cells of a fish, the Black Molhe (Mol lienesta sp), correlated well with published descriptions of sectioned material. The arrays of apertures of the T-tubules at the cell surface were clearly demonstrated. Numerous vesicles, communicating with the extracellular space, were also seen at the cell surface. The relation ship of the T-tubules with the adjoining sarcotubular cisternae was studied; in transverse fractures at Z-levels there was a tendency for pieces of T-tubule to adhere to the cisternae No scalloping of the sarcotubular membrane was noted where it apposed the T-tubule, but some ridges on its luminal surface were demonstrated at these regions; elsewhere the luminal surface of the sarcotubular membrane was densely covered with particles. In the myofibrils, a reversal of polarity of the structure of the thick filaments was suggested at the M-line.