Membrane systems of freeze-etched striated muscle.

The organization of flight muscle of a dragonfly, with special reference to the fibre membrane systems, has been investigated by means of platinum-carbon replicas of freeze-etched material. The fractured surface plasma membrane and origin of transverse tubules are described together with the radial course of the tubules into the cell, along grooves in the mitochondrial surface. The form of the sarcoplasmic reticulum cisternae is also described. Replicas are interpreted as revealing up to three unfractured membrane surfaces and several fractured profiles. The illustrations include stereo-micrographs of replicas.