Conduction blockade in myelinated fibers by gaseous and volatile substances

1991 ◽  
Vol 260 (3) ◽  
pp. R540-R545
Author(s):  
F. G. Carpenter
Keyword(s):  
Partial Pressure ◽  
Large Diameter ◽  
Small Diameter ◽  
Aqueous Solubility ◽  
Nerve Fibers ◽  
Myelinated Nerve ◽  
Molal Volume ◽  
Axon Membrane ◽  
Anesthetic Action ◽  
Solubility Ratio

The minimum ambient partial pressure required to reversibly disrupt conducted responses in myelinated nerve fibers (Pblock) was determined for 11 gases and chloroform. For all but one substance, Pblock was inversely proportional to their nonaqueous solubility; large-diameter fibers were less vulnerable than fibers of small diameter. No "anesthetic" effect was displayed by SF6. At the Pblock for three of the agents, the time for completion of their anesthetic action (tb) was proportional to their lipid-to-aqueous solubility ratio. When the ratio was large, tb was longer than when the ratio was small; blockade became complete after the partial pressure of the agent in the lipid or nonaqueous phase of the axon membrane became equal to Pblock. The access of these substances to an nonaqueous site was neither pH nor frequency dependent, but in the case of SF6 access did appear to be limited by its molal volume.

scholarly journals Hysto-ultrastructure of the facial nerve and mimic muscles in the norm and in the conditions of eхperimental neuropathy

2017 ◽  
Vol 8 (4) ◽  
pp. 569-576
Author(s):  
V. Myhailiuk ◽  
I. Mykhailiuk ◽  
M. Hembarovskyi ◽  
O. Lebid ◽  
K. Duda ◽  
...  
Keyword(s):  
Facial Nerve ◽  
Morphological Changes ◽  
Motor Nerve ◽  
Muscle Fibers ◽  
Small Diameter ◽  
Nerve Fibers ◽  
Residual Effects ◽  
Myelinated Nerve ◽  
Fine Grained ◽  
Argyrophilic Grains

We studied the structural components of the facial nerve in the norm and with cold neuropathy, indicating morphological changes in neuromuscular endings and muscle fibers at 10, 15, 30 and 60 days from the beginning of the simulation of experimental neuropathy, which was caused by local supercooling of the projection portions of the extracranial parts of the facial nerve on the background of the preliminary introduction of Freud’s complete adjuvant. We established that the pathomorphological changes in the endonevral microcirculatory bed have a phase character: the initial spasm (up to 10 days) changes in paralytic vasodilation, and its residual effects remain until the end of the experiment (60 days). Changes in hemomicrocirculation conditions lead to marked disturbances in the structure of myelinic nerve fibers, which have the character of segmental demyelination with signs of delay in axonal transport and reactive restructuring of neuromuscular endings. The change in the metric composition of myelinated nerve fibers is due to an increase in the number of nerve fibers of medium and large diameters (up to 30 days) and small diameter (after 30 days). In different periods of the experiment, a decrease in the branching area of the terminal branches of the motor axon is observed in the nerve cells, local edema of the endonevria, degenerative changes in a part of the nerve fibers develop. Due to the fine-grained decay of the final nerve branches, degeneration of the motor endings took place two weeks after the start of the experiment. Neuropathy for 30 days caused a pronounced inhibition of spotting in the peripheral parts of the motor nerve fibers. After 60 days of experiment, a large number of muscle fibers underwent destructive changes. The size of a significant part of the neuromuscular endings was reduced. In all terms of cold neuropathy, neurolematocytes reacted in the same way: cytoplasm was swollen, argyrophilic grains appeared in the nuclei, fine-grained decay of individual nuclei occurred. 

scholarly journals Myelination of peripheral nerves is controlled by PI4KB through regulation of Schwann cell Golgi function

2020 ◽  
Vol 117 (45) ◽  
pp. 28102-28113 ◽  
Author(s):  
Takashi Baba ◽  
Alejandro Alvarez-Prats ◽  
Yeun Ju Kim ◽  
Daniel Abebe ◽  
Steve Wilson ◽  
...  
Keyword(s):  
Schwann Cell ◽  
Peripheral Nerves ◽  
Large Diameter ◽  
Small Diameter ◽  
Nerve Fibers ◽  
Protein Glycosylation ◽  
Mutant Mice ◽  
Nodes Of Ranvier ◽  
Golgi Compartment ◽  
Sciatic Nerves

Better understanding myelination of peripheral nerves would benefit patients affected by peripheral neuropathies, including Charcot–Marie–Tooth disease. Little is known about the role the Golgi compartment plays in Schwann cell (SC) functions. Here, we studied the role of Golgi in myelination of peripheral nerves in mice through SC-specific genetic inactivation of phosphatidylinositol 4-kinase beta (PI4KB), a Golgi-associated lipid kinase. Sciatic nerves of such mice showed thinner myelin of large diameter axons and gross aberrations in myelin organization affecting the nodes of Ranvier, the Schmidt–Lanterman incisures, and Cajal bands. Nonmyelinating SCs showed a striking inability to engulf small diameter nerve fibers. SCs of mutant mice showed a distorted Golgi morphology and disappearance of OSBP at the cis-Golgi compartment, together with a complete loss of GOLPH3 from the entire Golgi. Accordingly, the cholesterol and sphingomyelin contents of sciatic nerves were greatly reduced and so was the number of caveolae observed in SCs. Although the conduction velocity of sciatic nerves of mutant mice showed an 80% decrease, the mice displayed only subtle impairment in their motor functions. Our analysis revealed that Golgi functions supported by PI4KB are critically important for proper myelination through control of lipid metabolism, protein glycosylation, and organization of microvilli in the nodes of Ranvier of peripheral nerves.

scholarly journals A LIGHT AND ELECTRON HISTOCHEMICAL APPROACH TO THE NODE OF RANVIER AND MYELIN OF PERIPHERAL NERVE FIBERS

1967 ◽  
Vol 15 (12) ◽  
pp. 722-731 ◽  
Author(s):  
O. K. LANGLEY ◽  
D. N. LANDON
Keyword(s):  
Osmium Tetroxide ◽  
Node Of Ranvier ◽  
Nerve Fibers ◽  
Blue Pigment ◽  
Staining Reaction ◽  
Myelinated Nerve ◽  
Structural Localization ◽  
Axon Membrane ◽  
Specific Localization ◽  
Exchange Properties

The Hale staining reaction has been used to study the nature and distribution of acid mucopolysaccharides associated with mammalian peripheral myelinated nerve fibers. Histochemical blocking reactions were employed to determine the specificity of the method. Electron micrographs of parallel preparations were examined to discover the fine structural localization of the optically visible Prussian blue pigment. The observations reported suggest that there is a specific localization of a sulfated mucopolysaccharide in the region immediately surrounding the axolemma at the node of Ranvier. Other parts of the fiber, in particular the myelin sheath, show a preponderance of carboxyl groups. Attention is drawn to the variation in the form and distribution of the Hale stain product after differing fixation procedures. The effect of osmium tetroxide on ferrocyanide-treated material is examined and discussed. Attention is directed to possible physiologic implications of the presence of material with the known ion exchange properties of a sulfated mucopolysaccharide in the immediate environment of the ionically active nodal axon membrane.

scholarly journals Methods Optimization for Routine Sciatic Nerve Processing in General Toxicity Studies

2019 ◽  
Vol 48 (1) ◽  
pp. 19-29
Author(s):  
Jessica S. Fortin ◽  
Elizabeth A. Chlipala ◽  
Daniel P. Shaw ◽  
Brad Bolon
Keyword(s):  
Best Practice ◽  
Structural Integrity ◽  
Ethanol Concentration ◽  
Large Diameter ◽  
Small Diameter ◽  
Nerve Fibers ◽  
Water Bath ◽  
Nerve Preservation ◽  
Toxicity Studies ◽  
The Impact

Recent “best practice” recommendations for peripheral nervous system sampling and processing provide guidance regarding nerve preparation for animal toxicity studies. This study explored the impact of delayed fixation, type of fixative, processing cycle times, starting ethanol concentration, and water bath temperature to improve nerve preservation in routinely prepared (paraffin-embedded, hematoxylin and eosin [H&E]-stained) sections. Sciatic nerves from adult Wistar rats (diameter, 1.04 ± 0.1 mm) and young domestic pigs (diameter 5.9 ± 1.2 mm) fixed at necropsy (“0” hours) or 3, 6, 12, or 24 hours after death were immersed in neutral-buffered 10% formalin containing 1.2% methanol (NBF) or methanol-free 4% formaldehyde (MFF) at room temperature. After fixation for 24 hours (rat) or 48 hours (pig), specimens were processed into paraffin, and ∼5-μm-thick sections were flattened on water baths set at 35°C, 40°C, or 45°C before H&E staining. Large-diameter nerves (pig) required longer processing cycles to ensure sufficient paraffin infiltration. For both small-diameter (rat) and large-diameter nerves, structural integrity was optimal if fixation by NBF or MFF occurred within 3 hours and the initial ethanol concentration for tissue processing was lowered to 50%. At all time points, structural preservation of nerve fibers was acceptable using NBF but was better with MFF. Use of a water bath at 35°C reduced processing-related nerve fiber separation within sections.

Histology of Nerves and Muscles in Adductor Spasmodic Dysphonia

2003 ◽  
Vol 112 (4) ◽  
pp. 334-341 ◽  
Author(s):  
Dinesh K. Chhetri ◽  
Harry V. Vinters ◽  
Joel H. Blumin ◽  
Gerald S. Berke
Keyword(s):  
Botulinum Toxin ◽  
Muscle Fiber ◽  
Fiber Type ◽  
Large Diameter ◽  
Nerve Fibers ◽  
Spasmodic Dysphonia ◽  
Myelinated Nerve ◽  
Myelinated Nerve Fibers ◽  
Adductor Spasmodic Dysphonia ◽  
The Central Nervous System

To elucidate the etiology and pathophysiology of spasmodic dysphonia, we examined the adductor branch of the recurrent laryngeal nerve and the lateral cricoarytenoid muscle from 9 consecutive patients with this disorder who were previously treated with botulinum toxin. Histologic examination revealed average muscle fiber diameters ranging from 21 to 57 μm. Botulinum toxin treatment-related muscle atrophy was observed up to 5 months after injection. Endomysial fibrosis was present in all samples. Histochemical analysis in 8 patients revealed type 2 fiber predominance in 7 patients and fiber type grouping in 2. Type-specific muscle fiber size changes were not present. Nerve samples were examined in plastic sections. In 8 patients the nerves contained homogeneous, large-diameter myelinated nerve fibers and sparse small fibers. One patient had a relatively increased proportion of small myelinated nerve fibers. Overall, the nerve fiber diameter was slightly larger in patients than in controls. These findings may implicate the central nervous system in the pathophysiology of adductor spasmodic dysphonia.

HISTOMETRIC AND ULTRASTRUCTURAL ORGANIZATION OF THE NERVIMUSCULAR TERMINALS OF SKELETAL MUSCLES AT A HYPOKINESIA

2019 ◽  
pp. 55-63
Author(s):  
Z. M. Yaschyshyn ◽  
S. L. Popel
Keyword(s):  
Skeletal Muscles ◽  
Structural Adjustment ◽  
Muscle Fibers ◽  
Electron Microscopic Examination ◽  
Nerve Fibers ◽  
Ultrastructural Changes ◽  
Ultrastructural Organization ◽  
Electron Microscopic ◽  
Myelinated Nerve ◽  
Male Wistar Rats

The aim: to study the dynamics of histological and ultrastructural changes in muscle fibers and their neuromuscular endings under conditions of prolonged hypokinesia at different stages of ontogenesis. Methods. Studied skeletal muscles and their peripheral nervous apparatus of laboratory male Wistar rats aged 30 to 270 days. The restriction of motor activity was carried out in special canister cells for 30, 60, 90, and 240 days (5 animals for each term). To determine the type of muscle fiber, the Nahlas histochemical method was used, the Kulchitsky method was used to detect myelinated nerve fibers, the Bilshovsky-Gros method and the electron microscopic method to identify neuromuscular endings. Results. The data of histological and electron microscopic examination of skeletal muscle fibers and their neuromuscular endings under conditions of prolonged hypokinesia indicate their regular restructuring during the development of muscles, the formation of their synapses and structures that are associated with them at different stages of ontogenesis. Conclusion. The study provides an in-depth understanding of the relative frequency and nature of the disturbance of the neuromuscular endings during prolonged hypokinesia and its effect on the dynamics of structural adjustment of individual types of muscle fibers in ontogenesis.

HISTOMETRIC AND ULTRASTRUCTURAL ORGANIZATION OF THE NERVIMUSCULAR TERMINALS OF SKELETAL MUSCLES AT A HYPOKINESIA

2019 ◽  
pp. 55-63
Author(s):  
Z. M. Yaschyshyn ◽  
S. L. Popel
Keyword(s):  
Skeletal Muscles ◽  
Structural Adjustment ◽  
Muscle Fibers ◽  
Electron Microscopic Examination ◽  
Nerve Fibers ◽  
Ultrastructural Changes ◽  
Ultrastructural Organization ◽  
Electron Microscopic ◽  
Myelinated Nerve ◽  
Male Wistar Rats

The aim: to study the dynamics of histological and ultrastructural changes in muscle fibers and their neuromuscular endings under conditions of prolonged hypokinesia at different stages of ontogenesis. Methods. Studied skeletal muscles and their peripheral nervous apparatus of laboratory male Wistar rats aged 30 to 270 days. The restriction of motor activity was carried out in special canister cells for 30, 60, 90, and 240 days (5 animals for each term). To determine the type of muscle fiber, the Nahlas histochemical method was used, the Kulchitsky method was used to detect myelinated nerve fibers, the Bilshovsky-Gros method and the electron microscopic method to identify neuromuscular endings. Results. The data of histological and electron microscopic examination of skeletal muscle fibers and their neuromuscular endings under conditions of prolonged hypokinesia indicate their regular restructuring during the development of muscles, the formation of their synapses and structures that are associated with them at different stages of ontogenesis. Conclusion. The study provides an in-depth understanding of the relative frequency and nature of the disturbance of the neuromuscular endings during prolonged hypokinesia and its effect on the dynamics of structural adjustment of individual types of muscle fibers in ontogenesis.

Differences in the brain stem terminations of large- and small-diameter vestibular primary afferents

1995 ◽  
Vol 74 (3) ◽  
pp. 1362-1366 ◽  
Author(s):  
J. A. Huwe ◽  
E. H. Peterson
Keyword(s):  
Brain Stem ◽  
Large Diameter ◽  
Small Diameter ◽  
Movement Control ◽  
Three Dimensions ◽  
Significant Shift ◽  
Axon Diameter ◽  
Vestibular Complex ◽  
The Brain ◽  
Adjacent Brain

1. We visualized the central axons of 32 vestibular afferents from the posterior canal by extracellular application of horseradish peroxidase, reconstructed them in three dimensions, and quantified their morphology. Here we compare the descending limbs of central axons that differ in parent axon diameter. 2. The brain stem distribution of descending limb terminals (collaterals and associated varicosities) varies systematically with parent axon diameter. Large-diameter afferents concentrate their terminals in rostral regions of the medial/descending nuclei. As axon diameter decreases, there is a significant shift of terminal concentration toward the caudal vestibular complex and adjacent brain stem. 3. Rostral and caudal regions of the medial/descending nuclei have different labyrinthine, cerebellar, intrinsic, commissural, and spinal connections; they are believed to play different roles in head movement control. Our data help clarify the functions of large- and small-diameter afferents by showing that they contribute differentially to rostral and caudal vestibular complex.

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