Some of the myelin sheaths in the cerebellum of normal adult toads exhibit extensive evaginations of their full thickness. These redundant flaps of myelin are collapsed; i.e., they contain no axon and have no lumen. They extend away from the parent axonal myelin sheaths and tend to enfold other myelinated fibers or granule cell perikarya, producing bizarre configurations of myelin and what appear to be partially or completely myelinated cell bodies. In some instances, only the redundant flap of myelin appears in the plane of section, and its attachment to an axonal myelin sheath in another plane is only inferred. Single lamellae of myelin also tend to invest cerebellar granule cells and other processes, and these too appear to fold on themselves producing two- or four-layered segments. It is suggested that there are two phases of myelinogenesis: an initial "wrapping" phase, followed by a prolonged second phase during which internodes of myelin increase in both length and girth by a process other than wrapping, and that the occurrence of redundant myelin sheaths may reflect overgrowth of myelin during the second phase. Observations on the general organization of the toad cerebellum and on the ultrastructural cytology of its layers are also presented.
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1 January 1966
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January 01 1966
REDUNDANT MYELIN SHEATHS AND OTHER ULTRASTRUCTURAL FEATURES OF THE TOAD CEREBELLUM
Jack Rosenbluth
Jack Rosenbluth
From the Department of Anatomy, Albert Einstein College of Medicine, New York
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Jack Rosenbluth
From the Department of Anatomy, Albert Einstein College of Medicine, New York
Received:
July 14 1965
Online ISSN: 1540-8140
Print ISSN: 0021-9525
1966
J Cell Biol (1966) 28 (1): 73–93.
Article history
Received:
July 14 1965
Citation
Jack Rosenbluth; REDUNDANT MYELIN SHEATHS AND OTHER ULTRASTRUCTURAL FEATURES OF THE TOAD CEREBELLUM . J Cell Biol 1 January 1966; 28 (1): 73–93. doi: https://doi.org/10.1083/jcb.28.1.73
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