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The Fine Anatomy of the Optic Nerve of Anurans—An Electron Microscope Study

In the optic nerve of Anurans numerous myelinated and unmyelinated axons appear under the electron microscope as compact bundles that are closely bounded by one or several glial cells. In these bundles the unmyelinated fibers (0.15 to 0.6 µ in diameter) are many times more numerous than the myelinat...

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Autor principal: Maturana, Humberto R.
Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 1960
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2224865/
https://www.ncbi.nlm.nih.gov/pubmed/13853859
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author Maturana, Humberto R.
author_facet Maturana, Humberto R.
author_sort Maturana, Humberto R.
collection PubMed
description In the optic nerve of Anurans numerous myelinated and unmyelinated axons appear under the electron microscope as compact bundles that are closely bounded by one or several glial cells. In these bundles the unmyelinated fibers (0.15 to 0.6 µ in diameter) are many times more numerous than the myelinated fibers, and are separated from each other, from the bounding glial cells, or from adjacent myelin sheaths, by an extracellular gap that is 90 to 250 A wide. This intercellular space is continuous with the extracellular space in the periphery of the nerve through the numerous mesaxons and cell boundaries which reach the surface. Numerous desmosomes reinforce the attachments of adjacent glial membranes. The myelinated axons do not follow any preferential course and, like the unmyelinated ones, have a sinuous path, continuously shifting their relative position and passing from one bundle to another. At the nodes of Ranvier they behave entirely like unmyelinated axons in their relations to the surrounding cells. At the internodes they lie between the unmyelinated axons without showing an obvious myelogenic connection with the surrounding glial cells. In the absence of connective tissue separating individual myelinated fibers and with each glial cell simultaneously related to many axons, this myelogenic connection is highly distorted by other passing fibers and is very difficult to demonstrate. However, the mode of ending of the myelin layers at the nodes of Ranvier and the spiral disposition of the myelin layers indicate that myelination of these fibers occurs by a process similar to that of peripheral nerves. There are no incisures of Schmidt-Lantermann in the optic myelinated fibers.
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spelling pubmed-22248652008-05-01 The Fine Anatomy of the Optic Nerve of Anurans—An Electron Microscope Study Maturana, Humberto R. J Biophys Biochem Cytol Article In the optic nerve of Anurans numerous myelinated and unmyelinated axons appear under the electron microscope as compact bundles that are closely bounded by one or several glial cells. In these bundles the unmyelinated fibers (0.15 to 0.6 µ in diameter) are many times more numerous than the myelinated fibers, and are separated from each other, from the bounding glial cells, or from adjacent myelin sheaths, by an extracellular gap that is 90 to 250 A wide. This intercellular space is continuous with the extracellular space in the periphery of the nerve through the numerous mesaxons and cell boundaries which reach the surface. Numerous desmosomes reinforce the attachments of adjacent glial membranes. The myelinated axons do not follow any preferential course and, like the unmyelinated ones, have a sinuous path, continuously shifting their relative position and passing from one bundle to another. At the nodes of Ranvier they behave entirely like unmyelinated axons in their relations to the surrounding cells. At the internodes they lie between the unmyelinated axons without showing an obvious myelogenic connection with the surrounding glial cells. In the absence of connective tissue separating individual myelinated fibers and with each glial cell simultaneously related to many axons, this myelogenic connection is highly distorted by other passing fibers and is very difficult to demonstrate. However, the mode of ending of the myelin layers at the nodes of Ranvier and the spiral disposition of the myelin layers indicate that myelination of these fibers occurs by a process similar to that of peripheral nerves. There are no incisures of Schmidt-Lantermann in the optic myelinated fibers. The Rockefeller University Press 1960-02-01 /pmc/articles/PMC2224865/ /pubmed/13853859 Text en Copyright © Copyright, 1960, by The Rockefeller Institute Press
spellingShingle Article
Maturana, Humberto R.
The Fine Anatomy of the Optic Nerve of Anurans—An Electron Microscope Study
title The Fine Anatomy of the Optic Nerve of Anurans—An Electron Microscope Study
title_full The Fine Anatomy of the Optic Nerve of Anurans—An Electron Microscope Study
title_fullStr The Fine Anatomy of the Optic Nerve of Anurans—An Electron Microscope Study
title_full_unstemmed The Fine Anatomy of the Optic Nerve of Anurans—An Electron Microscope Study
title_short The Fine Anatomy of the Optic Nerve of Anurans—An Electron Microscope Study
title_sort fine anatomy of the optic nerve of anurans—an electron microscope study
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2224865/
https://www.ncbi.nlm.nih.gov/pubmed/13853859
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