Confirmation of the hypothetical diffusion barrier in the region of the Ranvier node of myelinated nerve fibers

A technique has been developed for the extrusion of axon material from myelinated nerve fibers. This material is then compressed and prepared for observation with the electron microscope. All the stages of preparation and purification of the axon material can be checked microscopically and in the present paper they are illustrated with phase contrast photomicrographs. Observation with the electron microscope of the compressed axons showed the presence of the following components: granules, fibrils, and a membranous material. Only the larger granules could be seen with the ordinary microscope. A considerable number of dense granules were observed. Of these the largest resemble typical mitochondria of 250 mµ by 900 mµ. In addition rows or small clusters of dense granules ranging in diameter from 250 to 90 mµ were present. In several specimens fragments of a membrane 120 to 140 A thick and intimately connected with the axon were found. The entire axon appeared to be constituted of a large bundle of parallel tightly packed fibrils among which the granules are interspersed. The fibrils are of indefinite length and generally smooth. They are rather labile structures, less resistant in the rat than in the toad nerve. They varied between 100 and 400 A in diameter and in some cases disintegrated into very fine filaments (less than 100 A thick). The significance is discussed of the submicroscopic structures revealed by electron microscopy of the material prepared in the way described.

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Refractoriness and frequency following behavior in a model of electrical stimulation of mammalian myelinated nerve fibers

Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society ◽

10.1109/iembs.1992.5761835 ◽

1992 ◽

Cited By ~ 1

Author(s):

Johan H. M. Frijns ◽

Ruurd Schoonoven

Keyword(s):

Electrical Stimulation ◽

Nerve Fibers ◽

Myelinated Nerve ◽

Myelinated Nerve Fibers ◽

Stimulation Of

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A simplified empirical modeling of electrophysiological activity in a bundle of myelinated nerve fibers

IEEE Latin America Transactions ◽

10.1109/tla.2016.7587640 ◽

2016 ◽

Vol 14 (7) ◽

pp. 3345-3350 ◽

Cited By ~ 1

Author(s):

Alvaro Gabriel Piza ◽

Fernando Daniel Farfan ◽

Ana Lia Albarracin ◽

Facundo Adrian Lucianna ◽

Jorge Humberto Soletta ◽

...

Keyword(s):

Nerve Fibers ◽

Empirical Modeling ◽

Myelinated Nerve ◽

Myelinated Nerve Fibers ◽

Electrophysiological Activity

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Myelin Basic Protein and Cardiac Sympathetic Neurodegeneration in Nonhuman Primates

Neurology Research International ◽

10.1155/2021/4776610 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

Jeanette M. Metzger ◽

Helen N. Matsoff ◽

Don Vu ◽

Alexandra D. Zinnen ◽

Kathryn M. Jones ◽

...

Keyword(s):

Left Ventricle ◽

Myelin Basic Protein ◽

Basic Protein ◽

Rhesus Macaques ◽

Sympathetic Neurons ◽

Nerve Fibers ◽

Myelinated Nerve ◽

Myelinated Nerve Fibers ◽

Pparγ Agonist ◽

Nerve Bundles

Minimal myelination is proposed to be a contributing factor to the preferential nigral neuronal loss in Parkinson’s disease (PD). Similar to nigral dopaminergic neurons, sympathetic neurons innervating the heart have long, thin axons which are unmyelinated or minimally myelinated. Interestingly, cardiac sympathetic loss in PD is heterogeneous across the heart, yet the spatial relationship between myelination and neurodegeneration is unknown. Here, we report the mapping of myelin basic protein (MBP) expression across the left ventricle of normal rhesus macaques (n = 5) and animals intoxicated with systemic 6-OHDA (50 mg/kg iv) to model parkinsonian cardiac neurodegeneration (n = 10). A subset of 6-OHDA-treated rhesus received daily dosing of pioglitazone (5 mg/kg po; n = 5), a PPARγ agonist with neuroprotective properties. In normal animals, MBP-immunoreactivity (-ir) was identified surrounding approximately 14% of axonal fibers within nerve bundles of the left ventricle, with more myelinated nerve fibers at the base level of the left ventricle than the apex p < 0.014 . Greater MBP-ir at the base was related to a greater number of nerve bundles at that level relative to the apex p < 0.05 , as the percent of myelinated nerve fibers in bundles was not significantly different between levels of the heart. Cardiac sympathetic loss following 6-OHDA was associated with decreased MBP-ir in cardiac nerve bundles, with the percent decrease of MBP-ir greater in the apex (84.5%) than the base (52.0%). Interestingly, cardiac regions and levels with more MBP-ir in normal animals showed attenuated sympathetic loss relative to areas with less MBP-ir in 6-OHDA + placebo (r = −0.7, p < 0.014 ), but not in 6-OHDA + pioglitazone (r = −0.1) subjects. Our results demonstrate that myelination is present around a minority of left ventricle nerve bundle fibers, is heterogeneously distributed in the heart of rhesus macaques, and has a complex relationship with cardiac sympathetic neurodegeneration and neuroprotection.

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