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https://www.readbyqxmd.com/read/29467340/saltatory-conduction-as-an-electrostatic-compressional-wave-in-the-axoplasm
#1
Tetsuya Akaishi
Saltatory conduction is an essential phenomenon to facilitate the fast conduction in myelinated nerves. The conventional conductive models assumed electric circuits with local current along the axonal membrane to explain the nerve conduction in unmyelinated nerves. However, whether such models with local current can be also applied to the saltatory conduction in myelinated nerves is unknown. In this report, I propose a new model of saltatory conduction by focusing on the behavior of electric charges in the axoplasm, not limited to the membrane...
2018: Tohoku Journal of Experimental Medicine
https://www.readbyqxmd.com/read/29444299/early-nodal-and-paranodal-disruption-in-autoimmune-optic-neuritis
#2
Aleksandar Stojic, Jovana Bojcevski, Sarah K Williams, Ricarda Diem, Richard Fairless
Disturbances in the nodes of Ranvier are an early phenomenon in many CNS disorders, including the autoimmune demyelinating disease multiple sclerosis (MS). Using an animal model of optic neuritis, a common early symptom of MS, we have investigated nodal and paranodal compartments in the optic nerve during disease progression. Both nodes and paranodes, as identified by immunohistochemistry against sodium channels (Nav) and Caspr, respectively, were observed to increase in length during the late induction phase of the disease, prior to onset of the demyelination and immune cell infiltration characteristic of optic neuritis...
February 10, 2018: Journal of Neuropathology and Experimental Neurology
https://www.readbyqxmd.com/read/29421432/dc-evoked-modulation-of-excitability-of-myelinated-nerve-fibres-and-their-terminal-branches-differences-in-sustained-effects-of-dc
#3
Dominik Kaczmarek, Elzbieta Jankowska
Direct current (DC) evokes long-lasting changes in neuronal networks both presynaptically and postsynaptically and different mechanisms were proposed to be involved in them. Different mechanisms were also suggested to account for the different dynamics of presynaptic DC actions on myelinated nerve fibres stimulated before they entered the spinal grey matter and on their terminal branches. The aim of the present study was to examine whether these different dynamics might be related to differences in the involvement of K+ channels...
February 5, 2018: Neuroscience
https://www.readbyqxmd.com/read/29329312/a-computational-study-of-the-impact-of-inhomogeneous-internodal-lengths-on-conduction-velocity-in-myelinated-neurons
#4
Abby Scurfield, David C Latimer
Age-related decreases in the conduction velocity (CV) of action potentials along myelinated axons have been linked to morphological changes in the myelin sheath. In particular, evidence suggests the presence of segmental demyelination and remyelination of axons. In remyelinated segments, the distance between adjacent nodes of Ranvier is typically shorter, and myelin sheaths are thinner. Both experimental and computational evidence indicates that shortened internodes slows CV. In this computational study, we determine the impact of progressive segmental demyelination and remyelination, modeled by shorter internodes with thinner myelin sheaths interspersed with normal ones, upon the CV...
2018: PloS One
https://www.readbyqxmd.com/read/29323217/node-of-ranvier-as-an-array-of-bio-nanoantennas-for-infrared-communication-in-nerve-tissue
#5
Andrea Zangari, Davide Micheli, Roberta Galeazzi, Antonio Tozzi
Electromagnetic radiation, in the visible and infrared spectrum, is increasingly being investigated for its possible role in the most evolved brain capabilities. Beside experimental evidence of electromagnetic cellular interactions, the possibility of light propagation in the axon has been recently demonstrated using computational modelling, although an explanation of its source is still not completely understood. We studied electromagnetic radiation onset and propagation at optical frequencies in myelinated axons, under the assumption that ion channel currents in the node of Ranvier behave like an array of nanoantennas emitting in the wavelength range from 300 to 2500 nm...
January 11, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29300891/loss-of-cntnap2-causes-axonal-excitability-deficits-developmental-delay-in-cortical-myelination-and-abnormal-stereotyped-motor-behavior
#6
Ricardo Scott, Alberto Sánchez-Aguilera, Kim van Elst, Lynette Lim, Nathalie Dehorter, Sung Eun Bae, Giorgia Bartolini, Elior Peles, Martien J H Kas, Hilgo Bruining, Oscar Marín
Contactin-associated protein-like 2 (Caspr2) is found at the nodes of Ranvier and has been associated with physiological properties of white matter conductivity. Genetic variation in CNTNAP2, the gene encoding Caspr2, has been linked to several neurodevelopmental conditions, yet pathophysiological effects of CNTNAP2 mutations on axonal physiology and brain myelination are unknown. Here, we have investigated mouse mutants for Cntnap2 and found profound deficiencies in the clustering of Kv1-family potassium channels in the juxtaparanodes of brain myelinated axons...
December 28, 2017: Cerebral Cortex
https://www.readbyqxmd.com/read/29282769/glial-m6b-stabilizes-the-axonal-membrane-at-peripheral-nodes-of-ranvier
#7
Marie L Bang, Anya Vainshtein, Hyun-Jeong Yang, Yael Eshed-Eisenbach, Jerome Devaux, Hauke B Werner, Elior Peles
Glycoprotein M6B and the closely related proteolipid protein regulate oligodendrocyte myelination in the central nervous system, but their role in the peripheral nervous system is less clear. Here we report that M6B is located at nodes of Ranvier in peripheral nerves where it stabilizes the nodal axolemma. We show that M6B is co-localized and associates with gliomedin at Schwann cell microvilli that are attached to the nodes. Developmental analysis of sciatic nerves, as well as of myelinating Schwann cells/dorsal root ganglion neurons cultures, revealed that M6B is already present at heminodes, which are considered the precursors of mature nodes of Ranvier...
December 28, 2017: Glia
https://www.readbyqxmd.com/read/29138759/identification-of-persistent-and-resurgent-sodium-currents-in-spiral-ganglion-neurons-cultured-from-the-mouse-cochlea
#8
Lorcan Browne, Katie E Smith, Daniel J Jagger
In spiral ganglion neurons (SGNs), the afferent single units of the auditory nerve, high spontaneous and evoked firing rates ensure preservation of the temporal code describing the key features of incoming sound. During postnatal development, the spatiotemporal distribution of ion channel subtypes contributes to the maturation of action potential generation in SGNs, and to their ability to generate spike patterns that follow rapidly changing inputs. Here we describe tetrodotoxin (TTX)-sensitive Na+ currents in SGNs cultured from mice, whose properties may support this fast spiking behavior...
November 2017: ENeuro
https://www.readbyqxmd.com/read/29125128/action-potential-propagation-ion-current-or-intramembrane-electric-field
#9
Albert Martí, Juan J Pérez, Jordi Madrenas
The established action potential propagation mechanisms do not satisfactorily explain propagation on myelinated axons given the current knowledge of biological channels and membranes. The flow across ion channels presents two possible effects: the electric potential variations across the lipid bilayers (action potential) and the propagation of an electric field through the membrane inner part. The proposed mechanism is based on intra-membrane electric field propagation, this propagation can explain the action potential saltatory propagation and its constant delay independent of distance between Ranvier nodes in myelinated axons...
November 10, 2017: General Physiology and Biophysics
https://www.readbyqxmd.com/read/29114096/fingolimod-protects-against-ischemic-white-matter-damage-by-modulating-microglia-toward-m2-polarization-via-stat3-pathway
#10
Chuan Qin, Wen-Hui Fan, Qian Liu, Ke Shang, Madhuvika Murugan, Long-Jun Wu, Wei Wang, Dai-Shi Tian
BACKGROUND AND PURPOSE: White matter (WM) ischemic injury, a major neuropathological feature of cerebral small vessel diseases, is an important cause of vascular cognitive impairment in later life. The pathogenesis of demyelination after WM ischemic damage are often accompanied by microglial activation. Fingolimod (FTY720) was approved for the treatment of multiple sclerosis for its immunosuppression property. In this study, we evaluated the neuroprotective potential of FTY720 in a WM ischemia model...
November 7, 2017: Stroke; a Journal of Cerebral Circulation
https://www.readbyqxmd.com/read/29114067/regulation-and-dysregulation-of-axon-infrastructure-by-myelinating-glia
#11
REVIEW
Simon Pan, Jonah R Chan
Axon loss and neurodegeneration constitute clinically debilitating sequelae in demyelinating diseases such as multiple sclerosis, but the underlying mechanisms of secondary degeneration are not well understood. Myelinating glia play a fundamental role in promoting the maturation of the axon cytoskeleton, regulating axon trafficking parameters, and imposing architectural rearrangements such as the nodes of Ranvier and their associated molecular domains. In the setting of demyelination, these changes may be reversed or persist as maladaptive features, leading to axon degeneration...
November 7, 2017: Journal of Cell Biology
https://www.readbyqxmd.com/read/29038243/an-%C3%AE-ii-spectrin-based-cytoskeleton-protects-large-diameter-myelinated-axons-from-degeneration
#12
Claire Yu-Mei Huang, Chuansheng Zhang, Daniel R Zollinger, Christophe Leterrier, Matthew N Rasband
Axons must withstand mechanical forces including tension, torsion, and compression. Spectrins and actin form a periodic cytoskeleton proposed to protect axons against these forces. However, since spectrins also participate in assembly of axon initial segments (AIS) and nodes of Ranvier, it is difficult to uncouple their roles in maintaining axon integrity from their functions at AIS and nodes. To overcome this problem and to determine the importance of spectrin cytoskeletons for axon integrity, we generated mice with αII spectrin-deficient peripheral sensory neurons...
October 16, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/29038240/%C3%AE-ii-spectrin-forms-a-periodic-cytoskeleton-at-the-axon-initial-segment-and-is-required-for-nervous-system-function
#13
Claire Yu-Mei Huang, Chuansheng Zhang, Tammy Szu-Yu Ho, Juan Oses-Prieto, Alma L Burlingame, Joshua Lalonde, Jeffrey L Noebels, Christophe Leterrier, Matthew N Rasband
Spectrins form a submembranous cytoskeleton proposed to confer strength and flexibility to neurons and to participate in ion channel clustering at axon initial segments (AIS) and nodes of Ranvier. Neuronal spectrin cytoskeletons consist of diverse β subunits and αII spectrin. Although αII spectrin is found in neurons in both axonal and somatodendritic domains, using proteomics, biochemistry, and super-resolution microscopy we show that αII and βIV spectrin interact and form a periodic AIS cytoskeleton...
October 16, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/29030712/calculating-the-consequences-of-left-shifted-nav-channel-activity-in-sick-excitable-cells
#14
Bela Joos, Benjamin M Barlow, Catherine E Morris
Two features common to diverse sick excitable cells are "leaky" Nav channels and bleb damage-damaged membranes. The bleb damage, we have argued, causes a channel kinetics based "leakiness." Recombinant (node of Ranvier type) Nav1.6 channels voltage-clamped in mechanically-blebbed cell-attached patches undergo a damage intensity dependent kinetic change. Specifically, they experience a coupled hyperpolarizing (left) shift of the activation and inactivation processes. The biophysical observations on Nav1.6 currents formed the basis of Nav-Coupled Left Shift (Nav-CLS) theory...
October 14, 2017: Handbook of Experimental Pharmacology
https://www.readbyqxmd.com/read/28968364/chronic-demyelinating-polyneuropathies
#15
Jeffrey A Allen
PURPOSE OF REVIEW: This article reviews the chronic demyelinating neuropathies, with a focus on the diagnosis and treatment of immune-mediated neuropathies and the features that can help differentiate immune-mediated neuropathies from other chronic demyelinating peripheral nerve conditions. RECENT FINDINGS: Advances in clinical phenotyping and outcomes assessment have enabled neurologists to improve disease recognition, treatment, and disease monitoring. Our understanding of the immunopathogenesis of demyelinating neuropathies is evolving...
October 2017: Continuum: Lifelong Learning in Neurology
https://www.readbyqxmd.com/read/28966641/reassembly-of-the-axon-initial-segment-and-nodes-of-ranvier-in-regenerated-axons-of-the-central-nervous-system
#16
Miguel A Marin, Matthew N Rasband
No abstract text is available yet for this article.
August 2017: Neural Regeneration Research
https://www.readbyqxmd.com/read/28947766/neurons-define-non-myelinated-axon-segments-by-the-regulation-of-galectin-4-containing-axon-membrane-domains
#17
Natalia Díez-Revuelta, Alonso M Higuero, Silvia Velasco, María Peñas-de-la-Iglesia, Hans-Joachim Gabius, José Abad-Rodríguez
The mechanism underlying selective myelination of axons versus dendrites or neuronal somata relies on the expression of somatodendritic membrane myelination inhibitors (i.e. JAM2). However, axons still present long unmyelinated segments proposed to contribute to axonal plasticity and higher order brain functions. Why these segments remain unmyelinated is still an unresolved issue. The bifunctional lectin galectin-4 (Gal-4) organizes the transport of axon glycoproteins by binding to N-acetyllactosamine (LacNac) termini of N-glycans...
September 25, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28923597/targeting-demyelination-via-%C3%AE-secretases-promoting-sapp%C3%AE-release-to-enhance-remyelination-in-central-nervous-system
#18
Gemma Llufriu-Dabén, Alex Carrete, Elena Chierto, Jo Mailleux, Emeline Camand, Anne Simon, Tim Vanmierlo, Christiane Rose, Bernadette Allinquant, Jerome J A Hendriks, Charbel Massaad, Delphine Meffre, Mehrnaz Jafarian-Tehrani
Remyelination is an endogenous regenerative process of myelin repair in the central nervous system (CNS) with limited efficacy in demyelinating disorders. As strategies enhancing endogenous remyelination become a therapeutic challenge, we have focused our study on α-secretase-induced sAPPα release, a soluble endogenous protein with neuroprotective and neurotrophic properties. However, the role of sAPPα in remyelination is not known. Therefore, we investigated the remyelination potential of α-secretase-induced sAPPα release following CNS demyelination in mice...
September 18, 2017: Neurobiology of Disease
https://www.readbyqxmd.com/read/28880874/discovery-and-mode-of-action-of-a-novel-analgesic-%C3%AE-toxin-from-the-african-spider-ceratogyrus-darlingi
#19
Silmara R Sousa, Joshua S Wingerd, Andreas Brust, Christopher Bladen, Lotten Ragnarsson, Volker Herzig, Jennifer R Deuis, Sebastien Dutertre, Irina Vetter, Gerald W Zamponi, Glenn F King, Paul F Alewood, Richard J Lewis
Spider venoms are rich sources of peptidic ion channel modulators with important therapeutical potential. We screened a panel of 60 spider venoms to find modulators of ion channels involved in pain transmission. We isolated, synthesized and pharmacologically characterized Cd1a, a novel peptide from the venom of the spider Ceratogyrus darlingi. Cd1a reversibly paralysed sheep blowflies (PD50 of 1318 pmol/g) and inhibited human Cav2.2 (IC50 2.6 μM) but not Cav1.3 or Cav3.1 (IC50 > 30 μM) in fluorimetric assays...
2017: PloS One
https://www.readbyqxmd.com/read/28827698/nogo-receptor-1-regulates-caspr-distribution-at-axo-glial-units-in-the-central-nervous-system
#20
Jae Young Lee, Min Joung Kim, Lijun Li, Alexander A Velumian, Pei Mun Aui, Michael G Fehlings, Steven Petratos
Axo-glial units are highly organised microstructures propagating saltatory conduction and are disrupted during multiple sclerosis (MS). Nogo receptor 1 (NgR1) has been suggested to govern axonal damage during the progression of disease in the MS-like mouse model, experimental autoimmune encephalomyelitis (EAE). Here we have identified that adult ngr1 (-/-) mice, previously used in EAE and spinal cord injury experiments, display elongated paranodes, and nodes of Ranvier. Unstructured paranodal regions in ngr1 (-/-) mice are matched with more distributed expression pattern of Caspr...
August 21, 2017: Scientific Reports
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