DEVELOPMENT AND CHARACTERIZATION OF MYELIN IN TISSUE CULTURE OF CANINE CEREBELLUM

A modified method, in which explants were grown directly on glass coverslips in Leighton tubes, was employed for growing myelinated neuronal processes in tissue cultures of canine cerebellum. Myelination occurred in 60 to 75 per cent of the prepared cultures. Myelin sheaths, which were composed of distinct segments of variable length, regularly appeared after 17 to 28 days of growth. The myelin sheaths first developed along the central or proximal part of the neuronal process and became thicker with age. Nodes similar to nodes of Ranvier of the peripheral nervous system were detected in all myelinated cultures. The mean length of these unmyelinated intervals along different neuronal processes varied between 2 and 6 microns. The internodal length was variable (4 to 270 microns) and was independent of the diameter or length of the process. Activity of myelinated processes, as observed by time-lapse cinematography, was generally low but under certain circumstances it did increase in two distinct ways. A peristaltic-like action, due to the longitudinal movement of axoplasmal accumulations or varicosities, was frequently detected in cultures subjected to noxious influences or held to an advanced culture age. A second, less common type of activity was characterized by a rhythmic segmental pulsation of myelinated processes. © 1969 Springer-Verlag.