Abstract
The development and structure of myelin sheaths have been studied in the optic nerves of rats and of Xenopus laevis tadpoles. Both potassium permanganate- and osmium-fixed material was examined with the electron microscope. In the first stage of myelinogenesis the nerve fibre is surrounded by a cell process which envelops it and forms a mesaxon. The mesaxon then elongates into a loose spiral from which the cytoplasm is later excluded, so that compact myelin is formed. This process is similar to myelinogenesis in the peripheral nervous system, although in central fibres the cytoplasm on the outside of the myelin is confined in a tongue-like process to a fraction of the circumference, leaving the remainder of the sheath uncovered, so that contacts are possible between adjacent myelin sheaths. The structure of nodes in the central nervous system has been described and it is suggested that the oligodendrocytes may be the myelin-forming cells.
Full Text
The Full Text of this article is available as a PDF (1.6 MB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- ALLISON A. C., FEINDEL W. H. Nodes in the central nervous system. Nature. 1949 Mar 19;163(4142):449–449. doi: 10.1038/163449b0. [DOI] [PubMed] [Google Scholar]
- DE ROBERTIS E., GERSCHENFELD H. M., WALD F. Cellular mechanism of myelination in the central nervous system. J Biophys Biochem Cytol. 1958 Sep 25;4(5):651–656. doi: 10.1083/jcb.4.5.651. [DOI] [PMC free article] [PubMed] [Google Scholar]
- GRAY E. G. Axo-somatic and axo-dendritic synapses of the cerebral cortex: an electron microscope study. J Anat. 1959 Oct;93:420–433. [PMC free article] [PubMed] [Google Scholar]
- HESS A., YOUNG J. Z. The nodes of Ranvier. Proc R Soc Lond B Biol Sci. 1952 Nov 20;140(900):301–320. doi: 10.1098/rspb.1952.0063. [DOI] [PubMed] [Google Scholar]
- LUFT J. H. Permanganate; a new fixative for electron microscopy. J Biophys Biochem Cytol. 1956 Nov 25;2(6):799–802. doi: 10.1083/jcb.2.6.799. [DOI] [PMC free article] [PubMed] [Google Scholar]
- LUSE S. A. Formation of myelin in the central nervous system of mice and rats, as studied with the electron microscope. J Biophys Biochem Cytol. 1956 Nov 25;2(6):777–784. doi: 10.1083/jcb.2.6.777. [DOI] [PMC free article] [PubMed] [Google Scholar]
- PALADE G. E. A study of fixation for electron microscopy. J Exp Med. 1952 Mar;95(3):285–298. doi: 10.1084/jem.95.3.285. [DOI] [PMC free article] [PubMed] [Google Scholar]
- PETERS A., MUIR A. R. The relationship between axons and Schwann cells during development of peripheral nerves in the rat. Q J Exp Physiol Cogn Med Sci. 1959 Jan;44(1):117–130. doi: 10.1113/expphysiol.1959.sp001366. [DOI] [PubMed] [Google Scholar]
- PETERS A. The structure of myelin sheaths in the central nervous system of Xenopus laevis (Daudin). J Biophys Biochem Cytol. 1960 Feb;7:121–126. doi: 10.1083/jcb.7.1.121. [DOI] [PMC free article] [PubMed] [Google Scholar]
- ROBERTSON J. D. Structural alterations in nerve fibers produced by hypotonic and hypertonic solutions. J Biophys Biochem Cytol. 1958 Jul 25;4(4):349–364. doi: 10.1083/jcb.4.4.349. [DOI] [PMC free article] [PubMed] [Google Scholar]
- ROBERTSON J. D. The ultrastructure of adult vertebrate peripheral myelinated nerve fibers in relation to myelinogenesis. J Biophys Biochem Cytol. 1955 Jul 25;1(4):271–278. doi: 10.1083/jcb.1.4.271. [DOI] [PMC free article] [PubMed] [Google Scholar]
- ROBERTSON J. D. The ultrastructure of frog muscle spindles, motor endings and nerve fibres. J Physiol. 1957 Jun 18;137(1):6–8P. [PubMed] [Google Scholar]
- SCHULTZ R. L., MAYNARD E. A., PEASE D. C. Electron microscopy of neurons and neuroglia of cerebral cortex and corpus callosum. Am J Anat. 1957 May;100(3):369–407. doi: 10.1002/aja.1001000305. [DOI] [PubMed] [Google Scholar]
- UZMAN B. G., NOGUEIRA-GRAF G. Electron microscope studies of the formation of nodes of Ranvier in mouse sciatic nerves. J Biophys Biochem Cytol. 1957 Jul 25;3(4):589–598. doi: 10.1083/jcb.3.4.589. [DOI] [PMC free article] [PubMed] [Google Scholar]