THREE-DIMENSIONAL DISTRIBUTIONOF SMOOTH ENDOPLASMIC RETICULUM IN MYELINATED AXONS

Abstract

An electron microscopic cytochemistry was successfully applied to selectively stain the smooth-surfaced endoplasmic reticulum (SER) in the myelinated axons of mouse peripheral nerves. Using this staining, the three-dimensional distribution of the axonal SER was visualized as combined with the high-voltage electron microscopy of thick sections. The SER was seen as a continuous network of longitudinally running, narrow tubules that were anastomosed with each other. There were few isolated SER fragments and vesicles in the internodal part of the axon, while free vesicles were more frequently observed at the node of Ranvier. The formation of continuous networks of the SER is discussed with special reference to the possible mechanism of axonal transport.