Ultrastructural differences between the myelin sheaths of peripheral nerve fibres and CNS white matter

Summary Electron microscopic studies of peripheral nerves and spinal cord white matter of adult mice, as prepared by the freeze-etching method, show distinct differences in the periodicity of the myelin lamellae as well as of the ultrastructural lamellar pattern. A periodicity of 185 Å is to be determined for peripheral myelin whereas it is 160 Å in the myelin of central origin.In contrast to the appearance in the peripheral myelin the lamellar structure in the central myelin sheath is less pronounced and tends towards a fundamental repeating unit of 80 Å.This work was supported by the Swiss National Foundation (Nr. 4065).