Morphological Studies on the Myelin Sheath of Nerve Fibers

2013 ◽  
pp. 19-29
Author(s):  
Ke Xu ◽  
Susumu Terakawa
Keyword(s):  
Myelin Sheath ◽  
Nerve Fibers ◽  
Morphological Studies

scholarly journals Morphological manifestations of experimental paclitaxel-induced sciatic neuropathy under correction of 2-ethyl-6-methyl-3-hydroxypyridine succinate

2021 ◽  
pp. 20-26
Author(s):  
Mykola Ostrovskyi
Keyword(s):  
Peripheral Neuropathy ◽  
Myelin Sheath ◽  
Isotonic Saline ◽  
Nerve Fibers ◽  
Morphological Studies ◽  
White Rats ◽  
Maximum Value ◽  
Prevention And Treatment ◽  
Profile Area ◽  
Axial Cylinder

Paclitaxel is an effective chemotherapeutic agent for many cancers, but it has a number of limiting side effects that not only significantly reduce the quality of life of patients, but also limit their further treatment. Peripheral neuropathy is one of these, but there are currently no proven effective druHS for the prevention or treatment of paclitaxel-induced neuropathic pain (PINP) in particular, or chemotherapy-induced peripheral neuropathy (CIPN) in general. 2-ethyl-6-methyl-3-hydroxypyridine succinate (HS) is a derivative of succinic acid with neuroprotective, antihypoxic, membrane-protective, nootropic, sedative effects. The aim of the study was to study the effect of the neuroprotective agent HS on the pathomorphogenesis of the sciatic nerves under conditions of paclitaxel-induced peripheral neuropathy in the experiment. Materials and methods. The experiment was carried out on 80 white rats, which were injected intraperitoneally with paclitaxel (Actavis, Romania), previously dissolved in isotonic saline at a dose of 2 mg / kg of body weight four times every other day until a total dose of 8 mg / kg was reached. Then forty of these animals were injected intraperitoneally with 2-ethyl-6-methyl-3-hydroxypyridine succinate at a dose of 10 mg / kg (the remaining 40 rats received intraperitoneal water for injection). Morphological studies were carried out on the first, seventh, fifteenth, twenty-eighth, sixtieth, ninetieth and one hundred and twentieth days after the last injection of the drug. We investigated the pharmacological potential of HS in the prevention and treatment of CIPN at the level of sciatic nerve (SN) morphology. Results. The maximum value of the average profile area of myelinated nerve fibers with the use of HS is significantly lower than with uncorrected flow, and is (78.12±2.24) μm2 compared to (94.04±1.03) μm2 (p <0.001). The introduction of HS provides a stable content of the value of the ratio of the areas of the axial cylinder and the fiber within 0.39±0.01 (first day) - 0.44±0.01 (ninetieth day), and a rapid recovery of the indicator value to normal values during the final 30 days of the experiment. the maximum value of the index of the profile area of the myelin sheath with the introduction of HS is 1.4 times less than with an uncorrected flow, and is, respectively, (49.01±1.59) μm2 and (69.77±1.87) μm2 (p <0.001). HS provides a more intensive restoration of the indicator of the area of the myelin sheath during the 90th - 120th day of the experiment. Conclusions. Our results allow us to conclude that the introduction of HS creates a protective effect against paclitaxel-induced peripheral neuropathy (PIPN) by acting on both the axial cylinder and the myelin sheath of the heart failure. Due to the known pathophysiological mechanisms of the development of neuropathy, this method can be a promising therapeutic agent for the prevention and treatment of PIPN

Biofabrication of nerve fibers with mimetic myelin sheath-like structure and aligned fibrous niche

2020 ◽  
Vol 12 (3) ◽  
pp. 035013 ◽  
Author(s):  
Suping Chen ◽  
Chengheng Wu ◽  
Amin Liu ◽  
Dan Wei ◽  
Yun Xiao ◽  
...  
Keyword(s):  
Myelin Sheath ◽  
Nerve Fibers

Computer Model for Action Potential Propagation Through Branch Point in Myelinated Nerves

2001 ◽  
Vol 85 (1) ◽  
pp. 197-210 ◽  
Author(s):  
Lei Zhou ◽  
Shing Yan Chiu
Keyword(s):  
Action Potential ◽  
Branch Point ◽  
Myelin Sheath ◽  
Nerve Fibers ◽  
Myelinated Nerve ◽  
Axonal Membrane ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Action Potential Propagation ◽  
Periaxonal Space

A mathematical model is developed for simulation of action potential propagation through a single branch point of a myelinated nerve fiber with a parent branch bifurcating into two identical daughter branches. This model is based on a previously published multi-layer compartmental model for single unbranched myelinated nerve fibers. Essential modifications were made to couple both daughter branches to the parent branch. There are two major features in this model. First, the model could incorporate detailed geometrical parameters for the myelin sheath and the axon, accomplished by dividing both structures into many segments. Second, each segment has two layers, the myelin sheath and the axonal membrane, allowing voltages of intra-axonal space and periaxonal space to be calculated separately. In this model, K ion concentration in the periaxonal space is dynamically linked to the activity of axonal fast K channels underneath the myelin in the paranodal region. Our model demonstrates that the branch point acts like a low-pass filter, blocking high-frequency transmission from the parent to the daughter branches. Theoretical analysis showed that the cutoff frequency for transmission through the branch point is determined by temperature, local K ion accumulation, width of the periaxonal space, and internodal lengths at the vicinity of the branch point. Our result is consistent with empirical findings of irregular spacing of nodes of Ranvier at axon abors, suggesting that branch points of myelinated axons play important roles in signal integration in an axonal tree.

scholarly journals A TIME-SEQUENCE AUTORADIOGRAPHIC STUDY OF THE IN VIVO INCORPORATION OF [1, 2-3H]CHOLESTEROL INTO PERIPHERAL NERVE MYELIN

1973 ◽  
Vol 58 (1) ◽  
pp. 42-53 ◽  
Author(s):  
Frank A. Rawlins
Keyword(s):  
Schwann Cell ◽  
Peripheral Nerve ◽  
Myelin Sheath ◽  
Central Zone ◽  
Autoradiographic Study ◽  
Nerve Fibers ◽  
Time Sequence ◽  
Time Interval ◽  
Electron Microscope Autoradiography

A time-sequence study of the incorporation and distribution of cholesterol in peripheral nerve myelin was carried out by electron microscope autoradiography. [1,2-3H]Cholesterol was injected into 10-day old mice and the sciatic nerves were dissected out at 10, 20, 40, 60, 90, 120, and 180 min after the injection. 20 min after injection the higher densities of grains due to the presence of [3H]cholesterol were confined to the outer and inner edges of the myelin sheath. Practically no cholesterol was detected in the midzone of the myelin sheath. 1 ½ h after injection, cholesterol showed a wider distribution within the myelin sheath, the higher densities of grains occurring over the two peripheral myelin bands, each approximately 3,100 Å wide. Cholesterol was also present in the center of the myelin sheath but to a considerably lesser extent. 3 h after injection cholesterol appeared homogeneously distributed within the myelin sheath. Schwann cell and axon compartments were also labeled at each time interval studied beginning 20 min postinjection. These observations indicate that preformed cholesterol enters myelin first and almost simultaneously through the inner and outer edges of the sheath; only after 90 min does the density of labeled cholesterol in the central zone of myelin reach the same density as that in the outer and inner zones. These findings suggest that cholesterol used by the nerve fibers in the formation and maintenance of the myelin sheath enters the lamellae from the Schwann cell cytoplasm and from the axon. The possibility of a bidirectional movement of molecules, i.e. from the Schwann cell to the axon and from the axon to the Schwann cell through the myelin sheath, is noted. The results are discussed in the light of recent observations on the exchange, reutilization, and transaxonal movement of cholesterol.

scholarly journals Cluster Analysis of Myelin Nerve Fibers of the Periferal Nerve

2020 ◽  
Vol 26 (1) ◽  
Author(s):  
Omelian Yurakh ◽  
Oksana Popadynets ◽  
Halyna Yurakh ◽  
Mykhailo Osypchuk ◽  
Nadiya Tokaruk ◽  
...  
Keyword(s):  
Cluster Analysis ◽  
Sciatic Nerve ◽  
Myelin Sheath ◽  
Statistical Processing ◽  
Nerve Fibers ◽  
Software Environment ◽  
Thin Sections ◽  
Male Wistar Rats ◽  
Axial Cylinder

One of the unsolved issues in neuromorphology is the classification of myelin nerve fibers (MNF). Objective: to use cluster analysis to classify the sciatic nerve MNF. Material and methods. The work was performed using 5 one-year-old male Wistar rats. Semi-thin sections were stained with methylene blue. MNF morphometry was performed using ImageJ, and statistical processing – using the software environment R. Results of the study. Ward’s and k-means methods were used to cluster the MNF. Three clusters of MNFs are defined and their parameters are determined. The presented algorithm for adapting the literature data to the format of the obtained results includes determining the total average for the combined set of each indicator and the total variance, which is the sum of intragroup and intergroup variances. Conclusions: 1) for the classification of MNF it is advisable to use cluster analysis; 2) clustering should be performed according to the transsection areas of the axial cylinder and myelin sheath; 3) the number of clusters is determined by the agglomerative method of Ward, and their metrics – by the iterative method of k-means; 4) three clusters of MNF of the rat sciatic nerve differ in the transsection areas of the fibers, the axial cylinder and the myelin sheath and the percentage of nerve fibers; 5) when comparing identical indicators according to the obtained and literature data, the results were equivalent in the areas of the axial cylinder and myelin sheath and their shape coefficients, despite the fact that the classification of myelin fibers and their morphometry was performed using different methods.

Frequency extent of two-tone facilitation in onset units in the ventral cochlear nucleus

1996 ◽  
Vol 75 (1) ◽  
pp. 380-395 ◽  
Author(s):  
D. Jiang ◽  
A. R. Palmer ◽  
I. M. Winter
Keyword(s):  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Low Frequency ◽  
Nerve Fibers ◽  
Inhibitory Input ◽  
Ventral Cochlear Nucleus ◽  
Narrow Region ◽  
Morphological Studies ◽  
Wide Range ◽  
Auditory Nerve Fibers

1. The frequency threshold curves (FTCs) of 91 single units in the cochlear nucleus of the anesthetized guinea pig were measured using a conventional single-tone paradigm and a two-tone paradigm designed to elucidate the frequency extent of two-tone facilitation in onset units (On). Units were classified according to existing classification schemes into primary-like (n = 3), chopper (n = 23), and three onset groups: OnI (n = 12), OnC (n = 29), and OnL (n = 24). Histological reconstructions show onset units to be widely distributed within the ventral cochlear nucleus in a manner generally consistent with its tonotopic organization. 2. The FTCs of onset units differed in their minimum thresholds, the steepness of their high- and low-frequency cutoffs, and their sharpness of tuning as quantified by the quality factor at 10 dB (Q10dB) above best frequency (BF) threshold values. There was considerable overlap in the sharpness of tuning between onset units and auditory nerve fibers, as indicated by the distribution of Q10dB values in the octave around 10 kHz: onset units had Q10dB values of 3.56 +/- 1.38 (SD), compared with 6.3 +/- 2.48 for auditory nerve fibers. The tuning of chopper units was similar to that of auditory nerve fibers (5.52 +/- 1.46). 3. Seventy-five percent of onset units showed some degree of facilitation (a threshold reduction) when their FTCs were measured in the presence of BF tones 4 dB below BF threshold. The frequency extent of such facilitation was variable, with a maximum of 6 octaves around the BF. In extreme cases facilitation could be measured when the BF tone was as low as 30 dB below BF threshold. 4. In 17% of onset units, suppressive effects were evident, as shown by noncontiguous frequency regions of facilitation. These suppressive effects might be a reflection either of suppression in the auditory nerve input or of a direct inhibitory input to the onset units. The strength of this effect suggests that inhibition is a likely explanation, consistent with the finding in previous morphological studies of profuse synapses with pleomorphic vesicles on multipolar cells. 5. FTCs of chopper and primary-like units measured in the presence of BF tones showed little facilitation. The facilitation that was observed in chopper units was confined to a narrow region around BF and disappeared when the facilitatory tone was lowered to 4 dB below BF threshold. 6. These data support the hypothesis that onset units, but not chopper or primary-like units, receive excitatory inputs from auditory nerve fibers with a wide range of BFs. However, the frequency range of facilitation and the magnitude of the threshold facilitation varied from unit to unit, suggesting that the off-BF inputs from auditory nerve fibers are not evenly distributed or equally effective in all units.

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