Microtubule and Neurofilament Densities in Amphibian Spinal Root Nerve Fibers: Relationship to Axoplasmic Transport

1973 ◽  
Vol 51 (11) ◽  
pp. 798-806 ◽  
Author(s):  
Richard S. Smith
Keyword(s):  
Dorsal Root ◽  
Dark Field ◽  
Nerve Fibers ◽  
Axoplasmic Transport ◽  
Spinal Root ◽  
Myelinated Nerve ◽  
Dorsal Roots ◽  
Dark Field Microscopy ◽  
Spinal Roots ◽  
Ventral Roots

Dark-field microscopy of living myelinated nerve fibers from the spinal roots of Xenopus laevis revealed many spherical organelles moving in the axoplasm of fibers from the ventral roots and in fibers just distal to the dorsal root ganglion. Similar organelles were present but few were seen to move along fibers from the dorsal roots central to the ganglion. This observation prompted an ultrastructural study of microtubule and neurofilament densities in the myelinated fibers of the spinal roots. The density of microtubules was significantly less in fibers from the central part of the dorsal roots than in the rest of the spinal root system. Neurofilament densities were equivalent in all parts of the roots. Microtubules showed a significant association with mitochondria in the ventral roots and in the dorsal roots distal to the ganglion, but no significant association was obtained for the dorsal roots central to the ganglion. The meaning of these results in the axoplasmic transport of large organelles is discussed.

Detection of Organelles in Myelinated Nerve Fibers by Dark-Field Microscopy

1972 ◽  
Vol 50 (5) ◽  
pp. 467-469 ◽  
Author(s):  
R. S. Smith
Keyword(s):  
Optical Detection ◽  
Dark Field ◽  
Nerve Fibers ◽  
Spherical Particles ◽  
Axial Motion ◽  
Myelinated Nerve ◽  
Myelinated Nerve Fibers ◽  
Adult Rat ◽  
Dark Field Microscopy

Dark-field microscopy improves the optical detection of intraaxonal organelles. In living myelinated nerve fibers of the adult rat and the adult toad, fast (approximately 1 μm/s) somatopetal and somatofugal movement of near-spherical particles was seen. Rod-shaped organelles were also detected in nerve fibers from both the rat and the toad, but these organelles showed no axial motion.

scholarly journals A LIGHT AND ELECTRON MICROSCOPE STUDY OF LONG-TERM ORGANIZED CULTURES OF RAT DORSAL ROOT GANGLIA

1967 ◽  
Vol 32 (2) ◽  
pp. 439-466 ◽  
Author(s):  
Mary Bartlett Bunge ◽  
Richard P. Bunge ◽  
Edith R. Peterson ◽  
Margaret R. Murray
Keyword(s):  
Dorsal Root Ganglia ◽  
Dorsal Root ◽  
Lamellar Spacing ◽  
Nerve Fibers ◽  
Myelinated Fiber ◽  
Myelinated Nerve ◽  
Neuronal Soma ◽  
Fetal Rat

Dorsal root ganglia from fetal rats were explanted on collagen-coated coverslips and carried in Maximow double-coverslip assemblies for periods up to 3 months. These cultured ganglia were studied in the living state, in stained whole mounts, and in sections after OsO4 fixation and Epon embedment. From the central cluster of nerve cell bodies, neurites emerge to form a rich network of fascicles which often reach the edge of the carrying coverslip. The neurons resemble their in vivo counterparts in nuclear and cytoplasmic content and organization; e.g., they appear as "light" or "dark" cells, depending on the amount of cytoplasmic neurofilaments. Satellite cells form a complete investment around the neuronal soma and are themselves everywhere covered by basement membrane. The neuron-satellite cell boundary is complicated by spinelike processes arising from the neuronal soma. Neuron size, myelinated fiber diameter, and internode length in the cultures do not reach the larger of the values known for ganglion and peripheral nerve in situ (30). Unmyelinated and myelinated nerve fibers and associated Schwann cells and endoneurial and perineurial components are organized into typical fascicles. The relationship of the Schwann cell and its single myelinated fiber or numerous unmyelinated fibers and the properties of myelin, such as lamellar spacing, mesaxons, Schmidt-Lanterman clefts, nodes of Ranvier, and protuberances, mimic the in vivo pattern. It is concluded that cultivation of fetal rat dorsal root ganglia by this technique fosters maturation and long-term maintenance of all the elements that comprise this cellular community in vivo (except vascular components) and, furthermore, allows these various components to relate faithfully to one another to produce an organotypic model of sensory ganglion tissue.

Dedifferentiation of the Axolemma Associated with Demyelination

1981 ◽  
Vol 39 ◽  
pp. 496-497 ◽  
Author(s):  
J. Rosenbluth ◽  
A. Sumner ◽  
T. Saida
Keyword(s):  
Sodium Channels ◽  
Peripheral Nerves ◽  
Freeze Fracture ◽  
Fracture Analysis ◽  
Nerve Fibers ◽  
High Concentration ◽  
Myelinated Nerve ◽  
Spinal Roots ◽  
Myelin Deficient

Freeze-fracture analysis of myelinated nerve fibers has shown that the axolemma has a highly differentiated structure. The node is characterized by a high concentration of intramembranous particles, primarily in the E fracture face, which may represent the sodium channels known to be concentrated there, and the paranodal axolemma is characterized by a distinctive paracrystalline pattern that corresponds to the intercellular junction formed with the terminal “loops” of myelin lamellae. Studies of myelin formation in normal animals and of myelin-deficient mutant animals indicate that the development of these axolemmal specializations is profoundly influenced by the associated myelinforming cells. The present study considers whether or not nodal or paranodal specializations that have already formed persist after demyelination.In order to investigate this question, specimens of peripheral nerves were examined following exposure to an antiserum to galactocerebroside (GC), which is known to cause a predictable series of changes leading to demyelination. Freeze-fracture replicas of rat spinal roots exposed to anti-GC serum in situ for six hours showed marked changes in the paranodal axolemma.

scholarly journals ON THE EXISTENCE OF A GRADIENT OF SENSITIVITY TO THE LACK OF SODIUM IN THE SPINAL ROOTS OF THE BULLFROG

1951 ◽  
Vol 35 (2) ◽  
pp. 183-201 ◽  
Author(s):  
R. Lorente de Nó
Keyword(s):  
Spinal Cord ◽  
Dorsal Root ◽  
Nerve Fibers ◽  
Nerve Trunk ◽  
Ventral Root ◽  
Gradual Change ◽  
Anatomical Distribution ◽  
Working Hypothesis ◽  
Temporal Course ◽  
Spinal Roots

The Et class of fibers includes fibers of Gasser's d.r. C group. The fibers of the dorsal root are more sensitive to the effect of lack of sodium than are the fibers of the ventral root. In the two roots there is a gradient of sensitivity to the lack of sodium, which is such that in all the root fibers the sensitivity decreases with increasing distance from the spinal cord. The gradient continues in the trunk up to about 10 to 12 mm. peripheral to the trunk-roots margin. No comparable gradient of sensitivity to the lack of sodium has been observed in the rest of the nerve trunk. The gradient of sensitivity to the lack of sodium has no relationship to the anatomical distribution of the epineurium. As a working hypothesis it is suggested that the gradient of sensitivity to the lack of sodium is one aspect of a transitional gradient that serves to establish a gradual change between the properties that the axons have inside the spinal cord and the properties that they have inside the nerve trunks. Details are given of the temporal course of the loss of excitability by root fibers deprived of sodium. It is suggested that sodium is present in the nerve fibers, in 2 forms, loosely and tightly bound sodium and that loss of loosely bound sodium is sufficient to render the nerve fibers unable to conduct impulses. If the rate of loss of loosely bound sodium is decreased, conversion of tightly bound into loosely bound sodium may temporarily restore the excitability of the nerve fibers.

The determination of the instantaneous velocity of axonally transported organelles from filmed records of their motion

1982 ◽  
Vol 60 (5) ◽  
pp. 670-679 ◽  
Author(s):  
K. J. Koles ◽  
K. D. McLeod ◽  
R. S. Smith
Keyword(s):  
Power Spectra ◽  
Computational Procedure ◽  
Dark Field ◽  
Nerve Fibers ◽  
Low Noise ◽  
Instantaneous Velocity ◽  
Mean Velocity ◽  
Myelinated Nerve ◽  
Motion Picture Film ◽  
Band Limited

A computational procedure is described for obtaining reproducible, low noise estimates of the instantaneous velocity of axonally transported organelles. Axonally transported organelles were detected in myelinated nerve fibers from Xenopus laevis by dark-field microscopy. The motion of the organelles was recorded on motion picture film at 3 frames/s, and the position of organelles travelling in the retrograde direction was obtained as a pair of x (axial) and y (transverse) coordinates at each 0.33-s interval. The trend in organelle movement with time was calculated for each of the series of x and y coordinates by linear regression. This trend was removed from the measurements of x and y to yield sets of trend-free displacements. The trend yielded a measure of the mean velocity of the organelle in each of the two orthogonal directions. Power spectra of the deviations in x and y about the trend were calculated. For 133 particles studied, 99% of the power in the trend-free deviations occurred at frequencies below 0.3 Hz. The peak power in the x and y deviations occurred at a frequency of 0.1 Hz or less. Positional deviations about the trend were treated with a discrete 21-term differentiating filter that attenuated frequencies above 0.3 Hz. Instantaneous velocities for the organelles were obtained by adding the result of the band-limited differentiation to the appropriate estimates of mean velocity. The 21-term method was compared with a commonly used 2-term approximation to a differentiator and was shown to produce velocity estimates with about one order of magnitude less error. Estimates of organelle velocity obtained with the 21-term method indicate that saltatory particle motion may be viewed either as a smooth variation of particle velocity with respect to time or as an irregular, or discontinuous, variation of velocity with respect to particle position.

scholarly journals The Adverse Effect of Mobile Phone Radiations on Dorsal Root Ganglion of Albino Rats

2021 ◽  
pp. 54-60
Author(s):  
Faisal Taufiq ◽  
Mohammed Bhilal Babu ◽  
Aqeel Ahmad ◽  
Mohammed Eajaz Ahmed Shariff ◽  
Noureldaim Elnoman Elbadawi ◽  
...  
Keyword(s):  
Dorsal Root Ganglion ◽  
Mobile Phone ◽  
Dorsal Root Ganglia ◽  
Dorsal Root ◽  
Nerve Fibers ◽  
Albino Rats ◽  
Histological Structure ◽  
Myelinated Nerve ◽  
Transmission Electron ◽  
Histomorphological Changes

Objectives: To assess the effect of Mobile Phone Radio Frequency Electromagnetic Radiation (RF-EMR) on the histological structure of dorsal root ganglia in albino rats. Methods: Twenty-four albino rats divided into one control and three experimental groups were studied for four weeks. The experimental groups were exposed to three different levels of RF-EMR through complete missed calls of 80,120 and160 calls per day respectively, using a GSM mobile phone of 0.9GHz to1.8 GHz in silent mode. The dorsal root ganglia of the sacrificed Rats were examined under light and transmission electron microscope (TEM). Results: Dorsal root ganglions of exposed rats showed considerable histological changes like reduction in cell size, condensation of cytoplasm, peripherally located heterochromatin nucleus, loss of nucleolus and densely packed myelinated nerve fibers. No such changes were observed in control rats. Conclusion: Dorsal root ganglionic cells showed enduring and continuous changes when exposed to RF-EMR. The severity of histomorphological changes was dose-dependent, which increased constantly with radiation dosage increment. It might be fair to conclude that degenerative changes in the Dorsal Root Ganglion of the spinal cord, could be attributed to the long-term exposure to RF-EMR.

Organization of peripheral nerves and spinal roots of the Atlantic stingray, Dasyatis sabina

1978 ◽  
Vol 41 (1) ◽  
pp. 97-107 ◽  
Author(s):  
R. E. Coggeshall ◽  
R. B. Leonard ◽  
M. L. Applebaum ◽  
W. D. Willis
Keyword(s):  
Dorsal Root Ganglion ◽  
Peripheral Nerves ◽  
Dorsal Root ◽  
Ganglion Cells ◽  
Ventral Root ◽  
Dasyatis Sabina ◽  
Unmyelinated Axons ◽  
Spinal Roots ◽  
Ventral Roots ◽  
Dorsal Root Ganglion Cells

1. The sizes and numbers of axons in peripheral nerves and spinal roots were investigated in the stingray, Dasyatis sabina. 2. The axons of the dorsal and ventral roots do not mingle in peripheral nerves of this animal as they do in higher vertebrates. Thus, it was usually possible to split the peripheral nerve into two portions, one containing only dorsal root axons, the other containing only ventral root axons. This feature was useful for the analysis of certain aspects of spinal cord organization. 3. The fact that dorsal and ventral root axons were segregated in peripheral nerves enabled us to demonstrate, without experimental surgery, that the central processes of the dorsal root ganglion cells and the proximal ventral root axons were 10-20% narrower, on the average, than the distal processes of the same dorsal root ganglion cells or the distal parts of the same ventral root axons. 4. The stingray is remarkable in having very few unmyelinated axons in the dorsal roots, ventral roots, or peripheral nerves. This paucity of unmyelinated axons distinguishes the Atlantic stingrays from all other vertebrates whose roots and nerves have been examined for unmyelinated fibers. 5. Similar findings were obtained for one spotted eagle ray (Aetobatus narinari) and two cow-nose rays (Rhinoptera bonasus).

scholarly journals Transplantation of Cultured Olfactory Bulb Cells Prevents Abnormal Sensory Responses during Recovery from Dorsal Root Avulsion in the Rat

2017 ◽  
Vol 26 (5) ◽  
pp. 913-924 ◽  
Author(s):  
Andrew Collins ◽  
Daqing Li ◽  
Stephen B. Mcmahon ◽  
Geoffrey Raisman ◽  
Ying Li
Keyword(s):  
Spinal Cord ◽  
Dorsal Root ◽  
Olfactory Nerve ◽  
Olfactory Ensheathing Cells ◽  
Control Group ◽  
Spinal Root ◽  
Adult Rats ◽  
Dorsal Roots ◽  
Ensheathing Cells ◽  
Previous Demonstration

The central branches of the C7 and C8 dorsal roots were avulsed close to their entry point into the spinal cord in adult rats. The forepaw responses to heat and cold stimuli were tested at 1, 2, and 3 weeks after injury. Over this period, the paws were sensitive to both stimuli at 1-2 weeks and returned toward normal at 3 weeks. Immunohistology showed no evidence of axonal regeneration into the spinal cord in a control group of rats with avulsion only, implying that adjacent dorsal roots and their corresponding dermatomes were involved in the recovery. In a further group of rats, a mixture of bulbar olfactory ensheathing cells and olfactory nerve fibroblasts were transplanted into the gap between the avulsed roots and the spinal cord at the time of avulsion. These rats showed no evidence of either loss of sensation or exaggerated responses to stimuli at any of the time points from 1 to 3 weeks. Immunohistology showed that the transplanted cells formed a complete bridge, and the central branches of the dorsal root fibers had regenerated into the dorsal horn of the spinal cord. These regenerating axons, including Tuj1 and CGRP immunoreactive fibers, were ensheathed by the olfactory ensheathing cells. This confirms our previous demonstration of central regeneration by these transplants and suggests that such transplants may provide a useful means to prevent the development of abnormal sensations such as allodynia after spinal root lesions.

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