Regulation of myelin genes implicated in psychiatric disorders by functional activity in axons

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Philip R Lee

2009-06-01

Full Text Available Myelination is a highly dynamic process that continues well into adulthood in humans. Several recent gene expression studies have found abnormal expression of genes involved in myelination in the prefrontal cortex of brains from patients with schizophrenia and other psychiatric illnesses. Defects in myelination could contribute to the pathophysiology of psychiatric illness by impairing information processing as a consequence of altered impulse conduction velocity and synchrony between cortical regions carrying out higher level cognitive functions. Myelination can be altered by impulse activity in axons and by environmental experience. Psychiatric illness is treated by psychotherapy, behavioral modification, and drugs affecting neurotransmission, raising the possibility that myelinating glia may not only contribute to such disorders, but that activity-dependent effects on myelinating glia could provide one of the cellular mechanisms contributing to the therapeutic effects of these treatments. This review examines evidence showing that genes and gene networks important for myelination can be regulated by functional activity in axons.

An αII Spectrin-Based Cytoskeleton Protects Large-Diameter Myelinated Axons from Degeneration.

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Huang, Claire Yu-Mei; Zhang, Chuansheng; Zollinger, Daniel R; Leterrier, Christophe; Rasband, Matthew N

2017-11-22

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, because spectrins also participate in assembly of axon initial segments (AISs) 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. The axons of these neurons are very long and exposed to the mechanical forces associated with limb movement; most lack an AIS, and some are unmyelinated and have no nodes. We analyzed αII spectrin-deficient mice of both sexes and found that, in myelinated axons, αII spectrin forms a periodic cytoskeleton with βIV and βII spectrin at nodes of Ranvier and paranodes, respectively, but that loss of αII spectrin disrupts this organization. Avil-cre;Sptan1 f/f mice have reduced numbers of nodes, disrupted paranodal junctions, and mislocalized Kv1 K + channels. We show that the density of nodal βIV spectrin is constant among axons, but the density of nodal αII spectrin increases with axon diameter. Remarkably, Avil-cre;Sptan1 f/f mice have intact nociception and small-diameter axons, but severe ataxia due to preferential degeneration of large-diameter myelinated axons. Our results suggest that nodal αII spectrin helps resist the mechanical forces experienced by large-diameter axons, and that αII spectrin-dependent cytoskeletons are also required for assembly of nodes of Ranvier. SIGNIFICANCE STATEMENT A periodic axonal cytoskeleton consisting of actin and spectrin has been proposed to help axons resist the mechanical forces to which they are exposed (e.g., compression, torsion, and stretch). However, until now, no vertebrate animal model has tested the requirement of the spectrin cytoskeleton in

A role for myelin-associated peroxisomes in maintaining paranodal loops and axonal integrity.

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Kassmann, Celia M; Quintes, Susanne; Rietdorf, Jens; Möbius, Wiebke; Sereda, Michael Werner; Nientiedt, Tobias; Saher, Gesine; Baes, Myriam; Nave, Klaus-Armin

2011-07-21

Demyelinating diseases of the nervous system cause axon loss but the underlying mechanisms are not well understood. Here we show by confocal and electron microscopy that in myelin-forming glia peroxisomes are associated with myelin membranes. When peroxisome biogenesis is experimentally perturbed in Pex5 conditional mouse mutants, myelination by Schwann cells appears initially normal. However, in nerves of older mice paranodal loops become physically unstable and develop swellings filled with vesicles and electron-dense material. This novel model of a demyelinating neuropathy demonstrates that peroxisomes serve an important function in the peripheral myelin compartment, required for long-term axonal integrity. Copyright © 2011 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Kif13b Regulates PNS and CNS Myelination through the Dlg1 Scaffold.

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Roberta Noseda

2016-04-01

Full Text Available Microtubule-based kinesin motors have many cellular functions, including the transport of a variety of cargos. However, unconventional roles have recently emerged, and kinesins have also been reported to act as scaffolding proteins and signaling molecules. In this work, we further extend the notion of unconventional functions for kinesin motor proteins, and we propose that Kif13b kinesin acts as a signaling molecule regulating peripheral nervous system (PNS and central nervous system (CNS myelination. In this process, positive and negative signals must be tightly coordinated in time and space to orchestrate myelin biogenesis. Here, we report that in Schwann cells Kif13b positively regulates myelination by promoting p38γ mitogen-activated protein kinase (MAPK-mediated phosphorylation and ubiquitination of Discs large 1 (Dlg1, a known brake on myelination, which downregulates the phosphatidylinositol 3-kinase (PI3K/v-AKT murine thymoma viral oncogene homolog (AKT pathway. Interestingly, Kif13b also negatively regulates Dlg1 stability in oligodendrocytes, in which Dlg1, in contrast to Schwann cells, enhances AKT activation and promotes myelination. Thus, our data indicate that Kif13b is a negative regulator of CNS myelination. In summary, we propose a novel function for the Kif13b kinesin in glial cells as a key component of the PI3K/AKT signaling pathway, which controls myelination in both PNS and CNS.

Na(v)1.8 channelopathy in mutant mice deficient for myelin protein zero is detrimental to motor axons

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Moldovan, Mihai; Alvarez Herrero, Susana; Pinchenko, Volodymyr

2011-01-01

Myelin protein zero mutations were found to produce Charcot-Marie-Tooth disease phenotypes with various degrees of myelin impairment and axonal loss, ranging from the mild 'demyelinating' adult form to severe and early onset forms. Protein zero deficient homozygous mice ( ) show a severe and prog......Myelin protein zero mutations were found to produce Charcot-Marie-Tooth disease phenotypes with various degrees of myelin impairment and axonal loss, ranging from the mild 'demyelinating' adult form to severe and early onset forms. Protein zero deficient homozygous mice ( ) show a severe...... and progressive dysmyelinating neuropathy from birth with compromised myelin compaction, hypomyelination and distal axonal degeneration. A previous study using immunofluorescence showed that motor nerves deficient of myelin protein zero upregulate the Na(V)1.8 voltage gated sodium channel isoform, which...... is normally present only in restricted populations of sensory axons. The aim of this study was to investigate the function of motor axons in protein zero-deficient mice with particular emphasis on ectopic Na(V)1.8 voltage gated sodium channel. We combined 'threshold tracking' excitability studies...

Neutron scattering from myelin revisited: bilayer asymmetry and water-exchange kinetics

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Denninger, Andrew R. [Boston College, Chestnut Hill, MA 02467 (United States); Demé, Bruno; Cristiglio, Viviana [Institut Laue–Langevin (ILL), CS 20156, F-38042 Grenoble CEDEX 9 (France); LeDuc, Géraldine [European Synchrotron Radiation Facility (ESRF), CS 40220, F-38043 Grenoble CEDEX 9 (France); Feller, W. Bruce [NOVA Scientific Inc., Sturbridge, MA 01566 (United States); Kirschner, Daniel A., E-mail: kirschnd@bc.edu [Boston College, Chestnut Hill, MA 02467 (United States)

2014-12-01

The structure of internodal myelin in the rodent central and peripheral nervous systems has been determined using neutron diffraction. The kinetics of water exchange in these tissues is also described. Rapid nerve conduction in the central and peripheral nervous systems (CNS and PNS, respectively) of higher vertebrates is brought about by the ensheathment of axons with myelin, a lipid-rich, multilamellar assembly of membranes. The ability of myelin to electrically insulate depends on the regular stacking of these plasma membranes and on the presence of a number of specialized membrane-protein assemblies in the sheath, including the radial component, Schmidt–Lanterman incisures and the axo–glial junctions of the paranodal loops. The disruption of this fine-structure is the basis for many demyelinating neuropathies in the CNS and PNS. Understanding the processes that govern myelin biogenesis, maintenance and destabilization requires knowledge of myelin structure; however, the tight packing of internodal myelin and the complexity of its junctional specializations make myelin a challenging target for comprehensive structural analysis. This paper describes an examination of myelin from the CNS and PNS using neutron diffraction. This investigation revealed the dimensions of the bilayers and aqueous spaces of myelin, asymmetry between the cytoplasmic and extracellular leaflets of the membrane, and the distribution of water and exchangeable hydrogen in internodal multilamellar myelin. It also uncovered differences between CNS and PNS myelin in their water-exchange kinetics.

Histological methods for assessing myelin sheaths and axons in human nerve trunks.

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Miko, T L; Gschmeissner, S E

1994-03-01

Although there are many histological techniques for assessing myelin sheaths and axons in paraffin embedded or frozen sections of the peripheral nervous system, modern approaches usually use plastic embedded material. Although plastic embedding is superior for small cutaneous branches, this method has limited value for histological assessment of nerve trunks. We report three methods which together yield a comprehensive approach for thorough and detailed investigation of human nerve trunks. The rapid osmication method permitted assessment of myelinated nerve fibers from frozen sections at operation, thus providing the surgeon with guidance on the extent of nerve resection. The modification presented here resulted in permanent slides, allowing comparison of results with those of the other two procedures. The new osmium-hematoxylin technique could be performed on paraffin embedded nerves. Paraffin, unlike plastic, permitted the study of the whole cross sectional area of the nerve in single sections. Moreover, the sharp image of the myelin permitted computerized morphometry. The significantly modified axonal silver impregnation technique was performed on frozen sections mounted on glass slides, as opposed to the time-consuming impregnation of free-floating sections. The latter technique had a high success rate and permitted semiquantitative assessment of axons in nerve trunks. These methods can be performed in any routine histology laboratory and resulted in greater accuracy compared to conventional methods.

Salvianolic acid B protects the myelin sheath around injured spinal cord axons

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Zhe Zhu

2016-01-01

Full Text Available Salvianolic acid B, an active pharmaceutical compound present in Salvia miltiorrhiza, exerts a neuroprotective effect in animal models of brain and spinal cord injury. Salvianolic acid B can promote recovery of neurological function; however, its protective effect on the myelin sheath after spinal cord injury remains poorly understood. Thus, in this study, in vitro tests showed that salvianolic acid B contributed to oligodendrocyte precursor cell differentiation, and the most effective dose was 20 μg/mL. For in vivo investigation, rats with spinal cord injury were intraperitoneally injected with 20 mg/kg salvianolic acid B for 8 weeks. The amount of myelin sheath and the number of regenerating axons increased, neurological function recovered, and caspase-3 expression was decreased in the spinal cord of salvianolic acid B-treated animals compared with untreated control rats. These results indicate that salvianolic acid B can protect axons and the myelin sheath, and can promote the recovery of neurological function. Its mechanism of action is likely to be associated with inhibiting apoptosis and promoting the differentiation and maturation of oligodendrocyte precursor cells.

Promoting peripheral myelin repair

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Zhou, Ye; Notterpek, Lucia

2016-01-01

Compared to the central nervous system (CNS), peripheral nerves have a remarkable ability to regenerate and remyelinate. This regenerative capacity to a large extent is dependent on and supported by Schwann cells, the myelin-forming glial cells of the peripheral nervous system (PNS). In a variety of paradigms, Schwann cells are critical in the removal of the degenerated tissue, which is followed by remyelination of newly-regenerated axons. This unique plasticity of Schwann cells has been the ...

Observations at the CNS-PNS border of ventral roots connected to a neuroma

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Sten Remahl

2010-10-01

Full Text Available Previous studies have shown that numerous sprouts originating from a neuroma, after nerve injury in neonatal animals, can invade spinal nerve roots. In this study the border between the central and peripheral nervous system (CNS-PNS border of ventral roots in kittens was examined with both light and electron microscopy after early postnatal sciatic nerve resection. A transient ingrowth of substance P positive axons was observed into the CNS, but no spouts remained 6 weeks after the injury. Using serial sections and electron microscopy it was possible to identify small bundles of unmyelinated axons that penetrated from the root fascicles for a short distance into the CNS. These axons ended blindly, sometimes with a growth cone-like terminal swelling filled with vesicles. The axon bundles were accompanied by p75 positive cells in both the root fascicles and the pia mater, but not in the CNS. It may thus be suggested that neurotrophin presenting p75 positive cells could facilitate axonal growth into the pia mater and that the lack of such cells in the CNS compartment might contribute to the failure of growth into the CNS. A maldevelopment of myelin sheaths at the CNS-PNS border of motor axons was observed and it seems possible that this could have consequences for the propagation of action potential across this region after neonatal nerve injury.

Subtle paranodal injury slows impulse conduction in a mathematical model of myelinated axons.

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Charles F Babbs

Full Text Available This study explores in detail the functional consequences of subtle retraction and detachment of myelin around the nodes of Ranvier following mild-to-moderate crush or stretch mediated injury. An equivalent electrical circuit model for a series of equally spaced nodes of Ranvier was created incorporating extracellular and axonal resistances, paranodal resistances, nodal capacitances, time varying sodium and potassium currents, and realistic resting and threshold membrane potentials in a myelinated axon segment of 21 successive nodes. Differential equations describing membrane potentials at each nodal region were solved numerically. Subtle injury was simulated by increasing the width of exposed nodal membrane in nodes 8 through 20 of the model. Such injury diminishes action potential amplitude and slows conduction velocity from 19.1 m/sec in the normal region to 7.8 m/sec in the crushed region. Detachment of paranodal myelin, exposing juxtaparanodal potassium channels, decreases conduction velocity further to 6.6 m/sec, an effect that is partially reversible with potassium ion channel blockade. Conduction velocity decreases as node width increases or as paranodal resistance falls. The calculated changes in conduction velocity with subtle paranodal injury agree with experimental observations. Nodes of Ranvier are highly effective but somewhat fragile devices for increasing nerve conduction velocity and decreasing reaction time in vertebrate animals. Their fundamental design limitation is that even small mechanical retractions of myelin from very narrow nodes or slight loosening of paranodal myelin, which are difficult to notice at the light microscopic level of observation, can cause large changes in myelinated nerve conduction velocity.

Molecular mechanisms of acrolein-mediated myelin destruction in CNS trauma and disease

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Shi, Riyi; Page, Jessica; Tully, Melissa

2016-01-01

Myelin is a critical component of the nervous system facilitating efficient propagation of electrical signals and thus communication between the central and peripheral nervous systems and organ systems they innervate throughout the body. In instances of neurotrauma and neurodegenerative disease, injury to myelin is a prominent pathological feature responsible for conduction deficits and leaves axons vulnerable to damage from noxious compounds. Although the pathological mechanisms underlying myelin loss have yet to be fully characterized, oxidative stress appears to play a prominent role. Specifically, acrolein, a neurotoxic aldehyde that is both a product and instigator of oxidative stress, has been observed in studies to elicit demyelination through calcium-independent and -dependent mechanisms and also by affecting glutamate uptake and promoting excitotoxicity. Furthermore, pharmacological scavenging of acrolein has demonstrated a neuroprotective effect in animal disease models by conserving myelin structural integrity and alleviating functional deficits. This evidence is indicative that acrolein may be a key culprit of myelin damage while acrolein scavenging could potentially be a promising therapeutic approach for patients suffering from nervous system trauma and disease. PMID:25879847

Boric acid reduces axonal and myelin damage in experimental sciatic nerve injury

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Zahir Kizilay

2016-01-01

Full Text Available The aim of this study was to investigate the effects of boric acid in experimental acute sciatic nerve injury. Twenty-eight adult male rats were randomly divided into four equal groups (n = 7: control (C, boric acid (BA, sciatic nerve injury (I , and sciatic nerve injury + boric acid treatment (BAI. Sciatic nerve injury was generated using a Yasargil aneurysm clip in the groups I and BAI. Boric acid was given four times at 100 mg/kg to rats in the groups BA and BAI after injury (by gavage at 0, 24, 48 and 72 hours but no injury was made in the group BA. In vivo electrophysiological tests were performed at the end of the day 4 and sciatic nerve tissue samples were taken for histopathological examination. The amplitude of compound action potential, the nerve conduction velocity and the number of axons were significantly lower and the myelin structure was found to be broken in group I compared with those in groups C and BA. However, the amplitude of the compound action potential, the nerve conduction velocity and the number of axons were significantly greater in group BAI than in group I. Moreover, myelin injury was significantly milder and the intensity of nuclear factor kappa B immunostaining was significantly weaker in group BAI than in group I. The results of this study show that administration of boric acid at 100 mg/kg after sciatic nerve injury in rats markedly reduces myelin and axonal injury and improves the electrophysiological function of injured sciatic nerve possibly through alleviating oxidative stress reactions.

Bony fish myelin: evidence for common major structural glycoproteins in central and peripheral myelin of trout.

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Jeserich, G; Waehneldt, T V

1986-02-01

Peripheral nervous system (PNS) myelin from the rainbow trout (Salmo gairdneri) banded at a density of 0.38 M sucrose. The main myelin proteins consisted of (1) two basic proteins, BPa and BPb (11,500 and 13,000 MW, similar to those of trout central nervous system (CNS) myelin proteins BP1 and BP2), and (2) two glycosylated components, IPb (24,400 MW) and IPc (26,200 MW). IPc comigrated with trout CNS myelin protein IP2 in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, whereas trout CNS myelin protein IP1 had a lower molecular weight (23,000). Following two-dimensional separation, however, both IPb and IPc from PNS showed two components; the more acidic component of IPc comigrated with IP2 from CNS. PNS tissue autolysis led to the formation of IPa (20,000 MW), consisting of two components in isoelectric focusing of which again the more acidic one comigrated with the CNS autolysis product IP0. Limited enzymatic digestion of isolated IP proteins from PNS and CNS led to closely similar degradation patterns, being most pronounced in the case of IP2 and IPc. Immunoblotting revealed that all IP components from trout PNS and CNS myelins reacted with antibodies to trout IP1 (CNS) and bovine P0 protein (PNS) whereas antibodies to rat PLP (CNS) were entirely unreactive. All BP components from trout PNS and CNS myelins bound to antibodies against human myelin basic protein. On the basis of these studies trout PNS and CNS myelins contain at least one common IP glycoprotein, whereas other members of the IP myelin protein family appear closely related. In the CNS myelin of trout the IP components appear to replace PLP.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of Adult CNS Axonal Regeneration by the Post-transcriptional Regulator Cpeb1

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Wilson Pak-Kin Lou

2018-01-01

Full Text Available Adult mammalian central nervous system (CNS neurons are unable to regenerate following axonal injury, leading to permanent functional impairments. Yet, the reasons underlying this regeneration failure are not fully understood. Here, we studied the transcriptome and translatome shortly after spinal cord injury. Profiling of the total and ribosome-bound RNA in injured and naïve spinal cords identified a substantial post-transcriptional regulation of gene expression. In particular, transcripts associated with nervous system development were down-regulated in the total RNA fraction while remaining stably loaded onto ribosomes. Interestingly, motif association analysis of post-transcriptionally regulated transcripts identified the cytoplasmic polyadenylation element (CPE as enriched in a subset of these transcripts that was more resistant to injury-induced reduction at the transcriptome level. Modulation of these transcripts by overexpression of the CPE binding protein, Cpeb1, in mouse and Drosophila CNS neurons promoted axonal regeneration following injury. Our study uncovered a global evolutionarily conserved post-transcriptional mechanism enhancing regeneration of injured CNS axons.

Heteromeric Kv7.2/7.3 channels differentially regulate action potential initiation and conduction in neocortical myelinated axons

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Battefeld, A.; Tran, B.T.; Gavrilis, J.; Cooper, E.C.; Kole, Maarten|info:eu-repo/dai/nl/256257574

2014-01-01

Rapid energy-efficient signaling along vertebrate axons is achieved through intricate subcellular arrangements of voltage-gated ion channels and myelination. One recently appreciated example is the tight colocalization of Kv7 potassium channels and voltage-gated sodium (Nav ) channels in the axonal

Live-imaging in the CNS: New insights on oligodendrocytes, myelination, and their responses to inflammation.

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Rassul, Sayed Muhammed; Neely, Robert K; Fulton, Daniel

2016-11-01

The formation and repair of myelin involves alterations in the molecular and physical properties of oligodendrocytes, and highly coordinated interactions with their target axons. Characterising the nature and timing of these events at the molecular and cellular levels illuminates the fundamental events underlying myelin formation, and provides opportunities for the development of therapies to replace myelin lost through traumatic injury and inflammation. The dynamic nature of these events requires that live-imaging methods be used to capture this information accurately and completely. Developments in imaging technologies, and model systems suitable for their application to myelination, have advanced the study of myelin formation, injury and repair. Similarly, new techniques for single molecule imaging, and novel imaging probes, are providing opportunities to resolve the dynamics of myelin proteins during myelination. Here, we explore these developments in the context of myelin formation and injury, identify unmet needs within the field where progress can be advanced through live-imaging approaches, identify technical challenges that are limiting this progress, and highlight practical applications for these approaches that could lead to therapies for the protection of oligodendrocytes and myelin from injury, and restore myelin lost through injury and disease. This article is part of the Special Issue entitled 'Oligodendrocytes in Health and Disease'. Copyright © 2015 Elsevier Ltd. All rights reserved.

Schwann cell myelination requires Dynein function

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Langworthy Melissa M

2012-11-01

Full Text Available Abstract Background Interaction of Schwann cells with axons triggers signal transduction that drives expression of Pou3f1 and Egr2 transcription factors, which in turn promote myelination. Signal transduction appears to be mediated, at least in part, by cyclic adenosine monophosphate (cAMP because elevation of cAMP levels can stimulate myelination in the absence of axon contact. The mechanisms by which the myelinating signal is conveyed remain unclear. Results By analyzing mutations that disrupt myelination in zebrafish, we learned that Dynein cytoplasmic 1 heavy chain 1 (Dync1h1, which functions as a motor for intracellular molecular trafficking, is required for peripheral myelination. In dync1h1 mutants, Schwann cell progenitors migrated to peripheral nerves but then failed to express Pou3f1 and Egr2 or make myelin membrane. Genetic mosaic experiments revealed that robust Myelin Basic Protein expression required Dync1h1 function within both Schwann cells and axons. Finally, treatment of dync1h1 mutants with a drug to elevate cAMP levels stimulated myelin gene expression. Conclusion Dync1h1 is required for retrograde transport in axons and mutations of Dync1h1 have been implicated in axon disease. Our data now provide evidence that Dync1h1 is also required for efficient myelination of peripheral axons by Schwann cells, perhaps by facilitating signal transduction necessary for myelination.

Cholesterol and myelin biogenesis.

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Saher, Gesine; Simons, Mikael

2010-01-01

Myelin consists of several layers of tightly compacted membranes wrapped around axons in the nervous system. The main function of myelin is to provide electrical insulation around the axon to ensure the rapid propagation of nerve conduction. As the myelinating glia terminally differentiates, they begin to produce myelin membranes on a remarkable scale. This membrane is unique in its composition being highly enriched in lipids, in particular galactosylceramide and cholesterol. In this review we will summarize the role of cholesterol in myelin biogenesis in the central and peripheral nervous system.

Quantifying visual pathway axonal and myelin loss in multiple sclerosis and neuromyelitis optica.

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Manogaran, Praveena; Vavasour, Irene M; Lange, Alex P; Zhao, Yinshan; McMullen, Katrina; Rauscher, Alexander; Carruthers, Robert; Li, David K B; Traboulsee, Anthony L; Kolind, Shannon H

2016-01-01

The optic nerve is frequently injured in multiple sclerosis and neuromyelitis optica, resulting in visual dysfunction, which may be reflected by measures distant from the site of injury. To determine how retinal nerve fiber layer as a measure of axonal health, and macular volume as a measure of neuronal health are related to changes in myelin water fraction in the optic radiations of multiple sclerosis and neuromyelitis optica participants with and without optic neuritis and compared to healthy controls. 12 healthy controls, 42 multiple sclerosis (16 with optic neuritis), and 10 neuromyelitis optica participants (8 with optic neuritis) were included in this study. Optical coherence tomography assessment involved measurements of the segmented macular layers (total macular, ganglion cell layer, inner plexiform layer, and inner nuclear layer volume) and paripapillary retinal nerve fiber layer thickness. The MRI protocol included a 32-echo T2-relaxation GRASE sequence. Average myelin water fraction values were calculated within the optic radiations as a measure of myelin density. Multiple sclerosis and neuromyelitis optica eyes with optic neuritis history had lower retinal nerve fiber layer thickness, total macular, ganglion cell and inner plexiform layer volumes compared to eyes without optic neuritis history and controls. Inner nuclear layer volume increased in multiple sclerosis with optic neuritis history (mean = 0.99 mm(3), SD = 0.06) compared to those without (mean = 0.97 mm(3), SD = 0.06; p = 0.003). Mean myelin water fraction in the optic radiations was significantly lower in demyelinating diseases (neuromyelitis optica: mean = 0.098, SD = 0.01, multiple sclerosis with optic neuritis history: mean = 0.096, SD = 0.01, multiple sclerosis without optic neuritis history: mean = 0.098, SD = 0.02; F3,55 = 3.35, p = 0.03) compared to controls. Positive correlations between MRI and optical coherence tomography measures were also apparent

Adenosine: an activity-dependent axonal signal regulating MAP kinase and proliferation in developing Schwann cells

OpenAIRE

Stevens, Beth; Ishibashi, Tomoko; Chen, Jiang-Fan; Fields, R. Douglas

2004-01-01

Nonsynaptic release of ATP from electrically stimulated dorsal root gangion (DRG) axons inhibits Schwann cell (SC) proliferation and arrests SC development at the premyelinating stage, but the specific types of purinergic receptor(s) and intracellular signaling pathways involved in this form of neuron–glia communication are not known. Recent research shows that adenosine is a neuron–glial transmitter between axons and myelinating glia of the CNS. The present study investigates the possibility...

Analysis of White Matter Damage in Patients with Multiple Sclerosis via a Novel In Vivo MR Method for Measuring Myelin, Axons, and G-Ratio.

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Hagiwara, A; Hori, M; Yokoyama, K; Nakazawa, M; Ueda, R; Horita, M; Andica, C; Abe, O; Aoki, S

2017-10-01

Myelin and axon volume fractions can now be estimated via MR imaging in vivo, as can the g-ratio, which equals the ratio of the inner to the outer diameter of a nerve fiber. The purpose of this study was to evaluate WM damage in patients with MS via this novel MR imaging technique. Twenty patients with relapsing-remitting MS with a combined total of 149 chronic plaques were analyzed. Myelin volume fraction was calculated based on simultaneous tissue relaxometry. Intracellular and CSF compartment volume fractions were quantified via neurite orientation dispersion and density imaging. Axon volume fraction and g-ratio were calculated by combining these measurements. Myelin and axon volume fractions and g-ratio were measured in plaques, periplaque WM, and normal-appearing WM. All metrics differed significantly across the 3 groups ( P ratio between periplaque WM and normal-appearing WM). Those in plaques differed most from those in normal-appearing WM. The percentage changes in plaque and periplaque WM metrics relative to normal-appearing WM were significantly larger in absolute value for myelin volume fraction than for axon volume fraction and g-ratio ( P ratio may potentially be useful for evaluating WM damage in patients with MS. © 2017 by American Journal of Neuroradiology.

Adenosine: an activity-dependent axonal signal regulating MAP kinase and proliferation in developing Schwann cells.

Science.gov (United States)

Stevens, Beth; Ishibashi, Tomoko; Chen, Jiang-Fan; Fields, R Douglas

2004-02-01

Nonsynaptic release of ATP from electrically stimulated dorsal root gangion (DRG) axons inhibits Schwann cell (SC) proliferation and arrests SC development at the premyelinating stage, but the specific types of purinergic receptor(s) and intracellular signaling pathways involved in this form of neuron-glia communication are not known. Recent research shows that adenosine is a neuron-glial transmitter between axons and myelinating glia of the CNS. The present study investigates the possibility that adenosine might have a similar function in communicating between axons and premyelinating SCs. Using a combination of pharmacological and molecular approaches, we found that mouse SCs in culture express functional adenosine receptors and ATP receptors, a far more complex array of purinergic receptors than thought previously. Adenosine, but not ATP, activates ERK/MAPK through stimulation of cAMP-linked A2(A) adenosine receptors. Both ATP and adenosine inhibit proliferation of SCs induced by platelet-derived growth factor (PDGF), via mechanisms that are partly independent. In contrast to ATP, adenosine failed to inhibit the differentiation of SCs to the O4+ stage. This indicates that, in addition to ATP, adenosine is an activity-dependent signaling molecule between axons and premyelinating Schwann cells, but that electrical activity, acting through adenosine, has opposite effects on the differentiation of myelinating glia in the PNS and CNS.

T-cell- and macrophage-mediated axon damage in the absence of a CNS-specific immune response: involvement of metalloproteinases.

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Newman, T A; Woolley, S T; Hughes, P M; Sibson, N R; Anthony, D C; Perry, V H

2001-11-01

Recent evidence has highlighted the fact that axon injury is an important component of multiple sclerosis pathology. The issue of whether a CNS antigen-specific immune response is required to produce axon injury remains unresolved. We investigated the extent and time course of axon injury in a rodent model of a delayed-type hypersensitivity (DTH) reaction directed against the mycobacterium bacille Calmette-Guérin (BCG). Using MRI, we determined whether the ongoing axon injury is restricted to the period during which the blood-brain barrier is compromised. DTH lesions were initiated in adult rats by intracerebral injection of heat-killed BCG followed by a peripheral challenge with BCG. Our findings demonstrate that a DTH reaction to a non-CNS antigen within a CNS white matter tract leads to axon injury. Ongoing axon injury persisted throughout the 3-month period studied and was not restricted to the period of blood-brain barrier breakdown, as detected by MRI enhancing lesions. We have previously demonstrated that matrix metalloproteinases (MMPs) are upregulated in multiple sclerosis plaques and DTH lesions. In this study we demonstrated that microinjection of activated MMPs into the cortical white matter results in axon injury. Our results show that axon injury, possibly mediated by MMPs, is immunologically non-specific and may continue behind an intact blood-brain barrier.

Promoting peripheral myelin repair.

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Zhou, Ye; Notterpek, Lucia

2016-09-01

Compared to the central nervous system (CNS), peripheral nerves have a remarkable ability to regenerate and remyelinate. This regenerative capacity to a large extent is dependent on and supported by Schwann cells, the myelin-forming glial cells of the peripheral nervous system (PNS). In a variety of paradigms, Schwann cells are critical in the removal of the degenerated tissue, which is followed by remyelination of newly-regenerated axons. This unique plasticity of Schwann cells has been the target of myelin repair strategies in acute injuries and chronic diseases, such as hereditary demyelinating neuropathies. In one approach, the endogenous regenerative capacity of Schwann cells is enhanced through interventions such as exercise, electrical stimulation or pharmacological means. Alternatively, Schwann cells derived from healthy nerves, or engineered from different tissue sources have been transplanted into the PNS to support remyelination. These transplant approaches can then be further enhanced by exercise and/or electrical stimulation, as well as by the inclusion of biomaterial engineered to support glial cell viability and neurite extension. Advances in our basic understanding of peripheral nerve biology, as well as biomaterial engineering, will further improve the functional repair of myelinated peripheral nerves. Copyright © 2016 Elsevier Inc. All rights reserved.

Astrocytes promote myelination in response to electrical impulses.

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Ishibashi, Tomoko; Dakin, Kelly A; Stevens, Beth; Lee, Philip R; Kozlov, Serguei V; Stewart, Colin L; Fields, R Douglas

2006-03-16

Myelin, the insulating layers of membrane wrapped around axons by oligodendrocytes, is essential for normal impulse conduction. It forms during late stages of fetal development but continues into early adult life. Myelination correlates with cognitive development and can be regulated by impulse activity through unknown molecular mechanisms. Astrocytes do not form myelin, but these nonneuronal cells can promote myelination in ways that are not understood. Here, we identify a link between myelination, astrocytes, and electrical impulse activity in axons that is mediated by the cytokine leukemia inhibitory factor (LIF). These findings show that LIF is released by astrocytes in response to ATP liberated from axons firing action potentials, and LIF promotes myelination by mature oligodendrocytes. This activity-dependent mechanism promoting myelination could regulate myelination according to functional activity or environmental experience and may offer new approaches to treating demyelinating diseases.

Structure and function of the contactin-associated protein family in myelinated axons and their relationship with nerve diseases

Institute of Scientific and Technical Information of China (English)

Yan Zou; De-en Xu; Wei-feng Zhang; Hai-ying Liu; Xia Li; Xing Zhang; Xiao-fang Ma; Yang Sun; Shi-yi Jiang; Quan-hong Ma

2017-01-01

The contactin-associated protein (Caspr) family participates in nerve excitation and conduction, and neurotransmitter release in myelinated axons. We analyzed the structures and functions of the Caspr family–CNTNAP1 (Caspr1), CNTNAP2 (Caspr2), CNTNAP3 (Caspr3), CNTNAP4 (Caspr4) and CNTNAP5 (Caspr5), Caspr1–5 is not only involved in the formation of myelinated axons, but also participates in maintaining the stability of adjacent connections. Caspr1 participates in the formation, differentiation, and proliferation of neurons and astrocytes, and in motor control and cognitive function. We also analyzed the relationship between the Caspr family and neurodegenerative diseases, multiple sclerosis, and autoimmune encephalitis. However, the effects of Caspr on disease course and prognosis remain poorly understood. The effects of Caspr on disease diagnosis and treatment need further investigation.

Pannexin 1 Modulates Axonal Growth in Mouse Peripheral Nerves

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Steven M. Horton

2017-11-01

Full Text Available The pannexin family of channels consists of three members—pannexin-1 (Panx1, pannexin-2 (Panx2, and pannexin-3 (Panx3 that enable the exchange of metabolites and signaling molecules between intracellular and extracellular compartments. Pannexin-mediated release of intracellular ATP into the extracellular space has been tied to a number of cellular activities, primarily through the activity of type P2 purinergic receptors. Previous work indicates that the opening of Panx1 channels and activation of purinergic receptors by extracellular ATP may cause inflammation and apoptosis. In the CNS (central nervous system and PNS (peripheral nervous system, coupled pannexin, and P2 functions have been linked to peripheral sensitization (pain pathways. Purinergic pathways are also essential for other critical processes in the PNS, including myelination and neurite outgrowth. However, whether such pathways are pannexin-dependent remains to be determined. In this study, we use a Panx1 knockout mouse model and pharmacological inhibitors of the Panx1 and the ATP-mediated signaling pathway to fill gaps in our understanding of Panx1 localization in peripheral nerves, roles for Panx1 in axonal outgrowth and myelination, and neurite extension. Our data show that Panx1 is localized to axonal, myelin, and vascular compartments of the peripheral nerves. Knockout of Panx1 gene significantly increased axonal caliber in vivo and axonal growth rate in cultured dorsal root ganglia (DRG neurons. Furthermore, genetic knockout of Panx1 or inhibition of components of purinergic signaling, by treatment with probenecid and apyrase, resulted in denser axonal outgrowth from cultured DRG explants compared to untreated wild-types. Our findings suggest that Panx1 regulates axonal growth in the peripheral nervous system.

Mast Cells and Innate Lymphoid Cells: Underappreciated Players in CNS Autoimmune Demyelinating Disease.

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Brown, Melissa A; Weinberg, Rebecca B

2018-01-01

Multiple sclerosis (MS) and its mouse model, experimental autoimmune encephalomyelitis, are autoimmune CNS inflammatory diseases. As a result of a breakdown in the relatively impermeable blood-brain barrier (BBB) in affected individuals, myelin-specific CD4 + and CD8 + T cells gain entry into the immune privileged CNS and initiate myelin, oligodendrocyte, and nerve axon destruction. However, despite the absolute requirement for T cells, there is increasing evidence that innate immune cells also play critical amplifying roles in disease pathogenesis. By modulating the character and magnitude of the myelin-reactive T cell response and regulating BBB integrity, innate cells affect both disease initiation and progression. Two classes of innate cells, mast cells and innate lymphoid cells (ILCs), have been best studied in models of allergic and gastrointestinal inflammatory diseases. Yet, there is emerging evidence that these cell types also exert a profound influence in CNS inflammatory disease. Both cell types are residents within the meninges and can be activated early in disease to express a wide variety of disease-modifying cytokines and chemokines. In this review, we discuss how mast cells and ILCs can have either disease-promoting or -protecting effects on MS and other CNS inflammatory diseases and how sex hormones may influence this outcome. These observations suggest that targeting these cells and their unique mediators can be exploited therapeutically.

Structure and function of the contactin-associated protein family in myelinated axons and their relationship with nerve diseases

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Yan Zou

2017-01-01

Full Text Available The contactin-associated protein (Caspr family participates in nerve excitation and conduction, and neurotransmitter release in myelinated axons. We analyzed the structures and functions of the Caspr family–CNTNAP1 (Caspr1, CNTNAP2 (Caspr2, CNTNAP3 (Caspr3, CNTNAP4 (Caspr4 and CNTNAP5 (Caspr5, Caspr1–5 is not only involved in the formation of myelinated axons, but also participates in maintaining the stability of adjacent connections. Caspr1 participates in the formation, differentiation, and proliferation of neurons and astrocytes, and in motor control and cognitive function. We also analyzed the relationship between the Caspr family and neurodegenerative diseases, multiple sclerosis, and autoimmune encephalitis. However, the effects of Caspr on disease course and prognosis remain poorly understood. The effects of Caspr on disease diagnosis and treatment need further investigation.

Expression analysis of the N-Myc downstream-regulated gene 1 indicates that myelinating Schwann cells are the primary disease target in hereditary motor and sensory neuropathy-Lom.

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Berger, Philipp; Sirkowski, Erich E; Scherer, Steven S; Suter, Ueli

2004-11-01

Mutations in the gene encoding N-myc downstream-regulated gene-1 (NDRG1) lead to truncations of the encoded protein and are associated with an autosomal recessive demyelinating neuropathy--hereditary motor and sensory neuropathy-Lom. NDRG1 protein is highly expressed in peripheral nerve and is localized in the cytoplasm of myelinating Schwann cells, including the paranodes and Schmidt-Lanterman incisures. In contrast, sensory and motor neurons as well as their axons lack NDRG1. NDRG1 mRNA levels in developing and injured adult sciatic nerves parallel those of myelin-related genes, indicating that the expression of NDRG1 in myelinating Schwann cells is regulated by axonal interactions. Oligodendrocytes also express NDRG1, and the subtle CNS deficits of affected patients may result from a lack of NDRG1 in these cells. Our data predict that the loss of NDRG1 leads to a Schwann cell autonomous phenotype resulting in demyelination, with secondary axonal loss.

Increase in chemokine CXCL1 by ERβ ligand treatment is a key mediator in promoting axon myelination.

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Karim, Hawra; Kim, Sung Hoon; Lapato, Andrew S; Yasui, Norio; Katzenellenbogen, John A; Tiwari-Woodruff, Seema K

2018-06-12

Estrogen receptor β (ERβ) ligands promote remyelination in mouse models of multiple sclerosis. Recent work using experimental autoimmune encephalomyelitis (EAE) has shown that ERβ ligands induce axon remyelination, but impact peripheral inflammation to varying degrees. To identify if ERβ ligands initiate a common immune mechanism in remyelination, central and peripheral immunity and pathology in mice given ERβ ligands at peak EAE were assessed. All ERβ ligands induced differential expression of cytokines and chemokines, but increased levels of CXCL1 in the periphery and in astrocytes. Oligodendrocyte CXCR2 binds CXCL1 and has been implicated in normal myelination. In addition, despite extensive immune cell accumulation in the CNS, all ERβ ligands promoted extensive remyelination in mice at peak EAE. This finding highlights a component of the mechanism by which ERβ ligands mediate remyelination. Hence, interplay between the immune system and central nervous system may be responsible for the remyelinating effects of ERβ ligands. Our findings of potential neuroprotective benefits arising from the presence of CXCL1 could have implications for improved therapies for multiple sclerosis. Copyright © 2018 the Author(s). Published by PNAS.

Heteromeric Kv7.2/7.3 channels differentially regulate action potential initiation and conduction in neocortical myelinated axons.

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Battefeld, Arne; Tran, Baouyen T; Gavrilis, Jason; Cooper, Edward C; Kole, Maarten H P

2014-03-05

Rapid energy-efficient signaling along vertebrate axons is achieved through intricate subcellular arrangements of voltage-gated ion channels and myelination. One recently appreciated example is the tight colocalization of K(v)7 potassium channels and voltage-gated sodium (Na(v)) channels in the axonal initial segment and nodes of Ranvier. The local biophysical properties of these K(v)7 channels and the functional impact of colocalization with Na(v) channels remain poorly understood. Here, we quantitatively examined K(v)7 channels in myelinated axons of rat neocortical pyramidal neurons using high-resolution confocal imaging and patch-clamp recording. K(v)7.2 and 7.3 immunoreactivity steeply increased within the distal two-thirds of the axon initial segment and was mirrored by the conductance density estimates, which increased from ~12 (proximal) to 150 pS μm(-2) (distal). The axonal initial segment and nodal M-currents were similar in voltage dependence and kinetics, carried by K(v)7.2/7.3 heterotetramers, 4% activated at the resting membrane potential and rapidly activated with single-exponential time constants (~15 ms at 28 mV). Experiments and computational modeling showed that while somatodendritic K(v)7 channels are strongly activated by the backpropagating action potential to attenuate the afterdepolarization and repetitive firing, axonal K(v)7 channels are minimally recruited by the forward-propagating action potential. Instead, in nodal domains K(v)7.2/7.3 channels were found to increase Na(v) channel availability and action potential amplitude by stabilizing the resting membrane potential. Thus, K(v)7 clustering near axonal Na(v) channels serves specific and context-dependent roles, both restraining initiation and enhancing conduction of the action potential.

Heteromeric Kv7.2/7.3 channels differentially regulate action potential initiation and conduction in neocortical myelinated axons

NARCIS (Netherlands)

Battefeld, A.; Tran, Baouyen T; Gavrilis, Jason; Cooper, Edward C; Kole, Maarten H P

2014-01-01

Rapid energy-efficient signaling along vertebrate axons is achieved through intricate subcellular arrangements of voltage-gated ion channels and myelination. One recently appreciated example is the tight colocalization of K(v)7 potassium channels and voltage-gated sodium (Na(v)) channels in the

Cytoskeletal Linker Protein Dystonin Is Not Critical to Terminal Oligodendrocyte Differentiation or CNS Myelination.

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Samantha F Kornfeld

Full Text Available Oligodendrocyte differentiation and central nervous system myelination require massive reorganization of the oligodendrocyte cytoskeleton. Loss of specific actin- and tubulin-organizing factors can lead to impaired morphological and/or molecular differentiation of oligodendrocytes, resulting in a subsequent loss of myelination. Dystonin is a cytoskeletal linker protein with both actin- and tubulin-binding domains. Loss of function of this protein results in a sensory neuropathy called Hereditary Sensory Autonomic Neuropathy VI in humans and dystonia musculorum in mice. This disease presents with severe ataxia, dystonic muscle and is ultimately fatal early in life. While loss of the neuronal isoforms of dystonin primarily leads to sensory neuron degeneration, it has also been shown that peripheral myelination is compromised due to intrinsic Schwann cell differentiation abnormalities. The role of this cytoskeletal linker in oligodendrocytes, however, remains unclear. We sought to determine the effects of the loss of neuronal dystonin on oligodendrocyte differentiation and central myelination. To address this, primary oligodendrocytes were isolated from a severe model of dystonia musculorum, Dstdt-27J, and assessed for morphological and molecular differentiation capacity. No defects could be discerned in the differentiation of Dstdt-27J oligodendrocytes relative to oligodendrocytes from wild-type littermates. Survival was also compared between Dstdt-27J and wild-type oligodendrocytes, revealing no significant difference. Using a recently developed migration assay, we further analysed the ability of primary oligodendrocyte progenitor cell motility, and found that Dstdt-27J oligodendrocyte progenitor cells were able to migrate normally. Finally, in vivo analysis of oligodendrocyte myelination was done in phenotype-stage optic nerve, cerebral cortex and spinal cord. The density of myelinated axons and g-ratios of Dstdt-27J optic nerves was normal, as

Functional recovery of regenerating motor axons is delayed in mice heterozygously deficient for the myelin protein P(0) gene

DEFF Research Database (Denmark)

Rosberg, Mette Romer; Alvarez, Susana; Krarup, Christian

2013-01-01

Mice with a heterozygous knock-out of the myelin protein P0 gene (P0+/-) develop a neuropathy similar to human Charcot-Marie-Tooth disease. They are indistinguishable from wild-types (WT) at birth and develop a slowly progressing demyelinating neuropathy. The aim of this study was to investigate...... whether the regeneration capacity of early symptomatic P0+/- is impaired as compared to age matched WT. Right sciatic nerves were lesioned at the thigh in 7-8 months old mice. Tibial motor axons at ankle were investigated by conventional motor conduction studies and axon excitability studies using...... threshold tracking. To evaluate regeneration we monitored the recovery of motor function after crush, and then compared the fiber distribution by histology. The overall motor performance was investigated using Rotor-Rod. P0+/- had reduced compound motor action potential amplitudes and thinner myelinated...

Myelin injury in the central nervous system and Alzheimer's diseases.

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Wang, Sha-Sha; Zhang, Zhao; Zhu, Tian-Bi; Chu, Shi-Feng; He, Wen-Bin; Chen, Nai-Hong

2018-05-03

Myelin is a membrane wrapped around the axon of the nerve cell, which is composed of the mature oligodendrocytes. The role of myelin is to insulate and prevent the nerve electrical impulses from the axon of the neurons to the axons of the other neurons, which is essential for the proper functioning of the nervous system. Minor changes in myelin thickness could lead to substantial changes in conduction speed and may thus alter neural circuit function. Demyelination is the myelin damage, which characterized by the loss of nerve sheath and the relative fatigue of the neuronal sheath and axon. Studies have shown that myelin injury may be closely related to neurodegenerative diseases and may be an early diagnostic criteria and therapeutic target. Thus this review summarizes the recent result of pathologic effect and signal pathways of myelin injury in neurodegenerative diseases, especially the Alzheimer's disease to provide new and effective therapeutic targets. Copyright © 2018. Published by Elsevier Inc.

Heteromeric K(v)7.2/7.3 Channels Differentially Regulate Action Potential Initiation and Conduction in Neocortical Myelinated Axons

NARCIS (Netherlands)

Battefeld, Arne; Tran, Baouyen T.; Gavrilis, Jason; Cooper, Edward C.; Kole, Maarten H. P.

2014-01-01

Rapid energy-efficient signaling along vertebrate axons is achieved through intricate subcellular arrangements of voltage-gated ion channels and myelination. One recently appreciated example is the tight colocalization of K(v)7 potassium channels and voltage-gated sodium (Na-v) channels in the

Combinatorial actions of Tgfβ and Activin ligands promote oligodendrocyte development and CNS myelination.

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Dutta, Dipankar J; Zameer, Andleeb; Mariani, John N; Zhang, Jingya; Asp, Linnea; Huynh, Jimmy; Mahase, Sean; Laitman, Benjamin M; Argaw, Azeb Tadesse; Mitiku, Nesanet; Urbanski, Mateusz; Melendez-Vasquez, Carmen V; Casaccia, Patrizia; Hayot, Fernand; Bottinger, Erwin P; Brown, Chester W; John, Gareth R

2014-06-01

In the embryonic CNS, development of myelin-forming oligodendrocytes is limited by bone morphogenetic proteins, which constitute one arm of the transforming growth factor-β (Tgfβ) family and signal canonically via Smads 1/5/8. Tgfβ ligands and Activins comprise the other arm and signal via Smads 2/3, but their roles in oligodendrocyte development are incompletely characterized. Here, we report that Tgfβ ligands and activin B (ActB) act in concert in the mammalian spinal cord to promote oligodendrocyte generation and myelination. In mouse neural tube, newly specified oligodendrocyte progenitors (OLPs) are first exposed to Tgfβ ligands in isolation, then later in combination with ActB during maturation. In primary OLP cultures, Tgfβ1 and ActB differentially activate canonical Smad3 and non-canonical MAP kinase signaling. Both ligands enhance viability, and Tgfβ1 promotes proliferation while ActB supports maturation. Importantly, co-treatment strongly activates both signaling pathways, producing an additive effect on viability and enhancing both proliferation and differentiation such that mature oligodendrocyte numbers are substantially increased. Co-treatment promotes myelination in OLP-neuron co-cultures, and maturing oligodendrocytes in spinal cord white matter display strong Smad3 and MAP kinase activation. In spinal cords of ActB-deficient Inhbb(-/-) embryos, apoptosis in the oligodendrocyte lineage is increased and OLP numbers transiently reduced, but numbers, maturation and myelination recover during the first postnatal week. Smad3(-/-) mice display a more severe phenotype, including diminished viability and proliferation, persistently reduced mature and immature cell numbers, and delayed myelination. Collectively, these findings suggest that, in mammalian spinal cord, Tgfβ ligands and ActB together support oligodendrocyte development and myelin formation. © 2014. Published by The Company of Biologists Ltd.

Combinatorial actions of Tgfβ and Activin ligands promote oligodendrocyte development and CNS myelination

Science.gov (United States)

Dutta, Dipankar J.; Zameer, Andleeb; Mariani, John N.; Zhang, Jingya; Asp, Linnea; Huynh, Jimmy; Mahase, Sean; Laitman, Benjamin M.; Argaw, Azeb Tadesse; Mitiku, Nesanet; Urbanski, Mateusz; Melendez-Vasquez, Carmen V.; Casaccia, Patrizia; Hayot, Fernand; Bottinger, Erwin P.; Brown, Chester W.; John, Gareth R.

2014-01-01

In the embryonic CNS, development of myelin-forming oligodendrocytes is limited by bone morphogenetic proteins, which constitute one arm of the transforming growth factor-β (Tgfβ) family and signal canonically via Smads 1/5/8. Tgfβ ligands and Activins comprise the other arm and signal via Smads 2/3, but their roles in oligodendrocyte development are incompletely characterized. Here, we report that Tgfβ ligands and activin B (ActB) act in concert in the mammalian spinal cord to promote oligodendrocyte generation and myelination. In mouse neural tube, newly specified oligodendrocyte progenitors (OLPs) are first exposed to Tgfβ ligands in isolation, then later in combination with ActB during maturation. In primary OLP cultures, Tgfβ1 and ActB differentially activate canonical Smad3 and non-canonical MAP kinase signaling. Both ligands enhance viability, and Tgfβ1 promotes proliferation while ActB supports maturation. Importantly, co-treatment strongly activates both signaling pathways, producing an additive effect on viability and enhancing both proliferation and differentiation such that mature oligodendrocyte numbers are substantially increased. Co-treatment promotes myelination in OLP-neuron co-cultures, and maturing oligodendrocytes in spinal cord white matter display strong Smad3 and MAP kinase activation. In spinal cords of ActB-deficient Inhbb−/− embryos, apoptosis in the oligodendrocyte lineage is increased and OLP numbers transiently reduced, but numbers, maturation and myelination recover during the first postnatal week. Smad3−/− mice display a more severe phenotype, including diminished viability and proliferation, persistently reduced mature and immature cell numbers, and delayed myelination. Collectively, these findings suggest that, in mammalian spinal cord, Tgfβ ligands and ActB together support oligodendrocyte development and myelin formation. PMID:24917498

Differential effects of myostatin deficiency on motor and sensory axons.

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Jones, Maria R; Villalón, Eric; Northcutt, Adam J; Calcutt, Nigel A; Garcia, Michael L

2017-12-01

Deletion of myostatin in mice (MSTN -/- ) alters structural properties of peripheral axons. However, properties like axon diameter and myelin thickness were analyzed in mixed nerves, so it is unclear whether loss of myostatin affects motor, sensory, or both types of axons. Using the MSTN -/- mouse model, we analyzed the effects of increasing the number of muscle fibers on axon diameter, myelin thickness, and internode length in motor and sensory axons. Axon diameter and myelin thickness were increased in motor axons of MSTN -/- mice without affecting internode length or axon number. The number of sensory axons was increased without affecting their structural properties. These results suggest that motor and sensory axons establish structural properties by independent mechanisms. Moreover, in motor axons, instructive cues from the neuromuscular junction may play a role in co-regulating axon diameter and myelin thickness, whereas internode length is established independently. Muscle Nerve 56: E100-E107, 2017. © 2017 Wiley Periodicals, Inc.

Association of Myosin Va and Schwann cells-derived RNA in mammal myelinated axons, analyzed by immunocytochemistry and confocal FRET microscopy.

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Canclini, Lucía; Wallrabe, Horst; Di Paolo, Andrés; Kun, Alejandra; Calliari, Aldo; Sotelo-Silveira, José Roberto; Sotelo, José Roberto

2014-03-15

Evidence from multiple sources supports the hypothesis that Schwann cells in the peripheral nervous system transfer messenger RNA and ribosomes to the axons they ensheath. Several technical and methodological difficulties exist for investigators to unravel this process in myelinated axons - a complex two-cell unit. We present an experimental design to demonstrate that newly synthesized RNA is transferred from Schwann cells to axons in association with Myosin Va. The use of quantitative confocal FRET microscopy to track newly-synthesized RNA and determine the molecular association with Myosin Va, is described in detail. Copyright © 2013 Elsevier Inc. All rights reserved.

Myelin down-regulates myelin phagocytosis by microglia and macrophages through interactions between CD47 on myelin and SIRPα (signal regulatory protein-α on phagocytes

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Reichert Fanny

2011-03-01

Full Text Available Abstract Background Traumatic injury to axons produces breakdown of axons and myelin at the site of the lesion and then further distal to this where Wallerian degeneration develops. The rapid removal of degenerated myelin by phagocytosis is advantageous for repair since molecules in myelin impede regeneration of severed axons. Thus, revealing mechanisms that regulate myelin phagocytosis by macrophages and microglia is important. We hypothesize that myelin regulates its own phagocytosis by simultaneous activation and down-regulation of microglial and macrophage responses. Activation follows myelin binding to receptors that mediate its phagocytosis (e.g. complement receptor-3, which has been previously studied. Down-regulation, which we test here, follows binding of myelin CD47 to the immune inhibitory receptor SIRPα (signal regulatory protein-α on macrophages and microglia. Methods CD47 and SIRPα expression was studied by confocal immunofluorescence microscopy, and myelin phagocytosis by ELISA. Results We first document that myelin, oligodendrocytes and Schwann cells express CD47 without SIRPα and further confirm that microglia and macrophages express both CD47 and SIRPα. Thus, CD47 on myelin can bind to and subsequently activate SIRPα on phagocytes, a prerequisite for CD47/SIRPα-dependent down-regulation of CD47+/+ myelin phagocytosis by itself. We then demonstrate that phagocytosis of CD47+/+ myelin is augmented when binding between myelin CD47 and SIRPα on phagocytes is blocked by mAbs against CD47 and SIRPα, indicating that down-regulation of phagocytosis indeed depends on CD47-SIRPα binding. Further, phagocytosis in serum-free medium of CD47+/+ myelin is augmented after knocking down SIRPα levels (SIRPα-KD in phagocytes by lentiviral infection with SIRPα-shRNA, whereas phagocytosis of myelin that lacks CD47 (CD47-/- is not. Thus, myelin CD47 produces SIRPα-dependent down-regulation of CD47+/+ myelin phagocytosis in phagocytes

Increased mitochondrial content in remyelinated axons: implications for multiple sclerosis

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Zambonin, Jessica L.; Zhao, Chao; Ohno, Nobuhiko; Campbell, Graham R.; Engeham, Sarah; Ziabreva, Iryna; Schwarz, Nadine; Lee, Sok Ee; Frischer, Josa M.; Turnbull, Doug M.; Trapp, Bruce D.; Lassmann, Hans; Franklin, Robin J. M.

2011-01-01

Mitochondrial content within axons increases following demyelination in the central nervous system, presumably as a response to the changes in energy needs of axons imposed by redistribution of sodium channels. Myelin sheaths can be restored in demyelinated axons and remyelination in some multiple sclerosis lesions is extensive, while in others it is incomplete or absent. The effects of remyelination on axonal mitochondrial content in multiple sclerosis, particularly whether remyelination completely reverses the mitochondrial changes that follow demyelination, are currently unknown. In this study, we analysed axonal mitochondria within demyelinated, remyelinated and myelinated axons in post-mortem tissue from patients with multiple sclerosis and controls, as well as in experimental models of demyelination and remyelination, in vivo and in vitro. Immunofluorescent labelling of mitochondria (porin, a voltage-dependent anion channel expressed on all mitochondria) and axons (neurofilament), and ultrastructural imaging showed that in both multiple sclerosis and experimental demyelination, mitochondrial content within remyelinated axons was significantly less than in acutely and chronically demyelinated axons but more numerous than in myelinated axons. The greater mitochondrial content within remyelinated, compared with myelinated, axons was due to an increase in density of porin elements whereas increase in size accounted for the change observed in demyelinated axons. The increase in mitochondrial content in remyelinated axons was associated with an increase in mitochondrial respiratory chain complex IV activity. In vitro studies showed a significant increase in the number of stationary mitochondria in remyelinated compared with myelinated and demyelinated axons. The number of mobile mitochondria in remyelinated axons did not significantly differ from myelinated axons, although significantly greater than in demyelinated axons. Our neuropathological data and findings in

Developmental impairment of compound action potential in the optic nerve of myelin mutant taiep rats.

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Roncagliolo, Manuel; Schlageter, Carol; León, Claudia; Couve, Eduardo; Bonansco, Christian; Eguibar, José R

2006-01-05

The taiep rat is a myelin mutant with an initial hypomyelination, followed by a progressive demyelination of the CNS. The neurological correlates start with tremor, followed by ataxia, immobility episodes, epilepsy and paralysis. The optic nerve, an easily-isolable central tract fully myelinated by oligodendrocytes, is a suitable preparation to evaluate the developmental impairment of central myelin. We examined the ontogenic development of optic nerve compound action potentials (CAP) throughout the first 6 months of life of control and taiep rats. Control optic nerves (ON) develop CAPs characterized by three waves. Along the first month, the CAPs of taiep rats showed a delayed maturation, with lower amplitudes and longer latencies than controls; at P30, the conduction velocity has only a third of the normal value. Later, as demyelination proceeds, the conduction velocity of taiep ONs begins to decrease and CAPs undergo a gradual temporal dispersion. CAPs of control and taiep showed differences in their pharmacological sensitivity to TEA and 4-AP, two voltage dependent K+ channel-blockers. As compared with TEA, 4-AP induced a significant increase of the amplitudes and a remarkable broadening of CAPs. After P20, unlike controls, the greater sensitivity to 4-AP exhibited by taiep ONs correlates with the detachment and retraction of paranodal loops suggesting that potassium conductances could regulate the excitability as demyelination of CNS axons progresses. It is concluded that the taiep rat, a long-lived mutant, provides a useful model to study the consequences of partial demyelination and the mechanisms by which glial cells regulate the molecular organization and excitability of axonal membranes during development and disease.

Chemokine expression by glial cells directs leukocytes to sites of axonal injury in the CNS

DEFF Research Database (Denmark)

Babcock, Alicia A; Kuziel, William A; Rivest, Serge

2003-01-01

Innate responses in the CNS are critical to first line defense against infection and injury. Leukocytes migrate to inflammatory sites in response to chemokines. We studied leukocyte migration and glial chemokine expression within the denervated hippocampus in response to axonal injury caused by e...

Neuronal Regulation of Schwann Cell Mitochondrial Ca2+ Signaling during Myelination

OpenAIRE

Daisuke Ino; Hiroshi Sagara; Junji Suzuki; Kazunori Kanemaru; Yohei Okubo; Masamitsu Iino

2015-01-01

Schwann cells (SCs) myelinate peripheral neurons to promote the rapid conduction of action potentials, and the process of myelination is known to be regulated by signals from axons to SCs. Given that SC mitochondria are one of the potential regulators of myelination, we investigated whether SC mitochondria are regulated by axonal signaling. Here, we show a purinergic mechanism that sends information from neurons to SC mitochondria during myelination. Our results show that electrical stimulati...

Oligodendrocyte Development in the Absence of Their Target Axons In Vivo.

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Rafael Almeida

Full Text Available Oligodendrocytes form myelin around axons of the central nervous system, enabling saltatory conduction. Recent work has established that axons can regulate certain aspects of oligodendrocyte development and myelination, yet remarkably oligodendrocytes in culture retain the ability to differentiate in the absence of axons and elaborate myelin sheaths around synthetic axon-like substrates. It remains unclear the extent to which the life-course of oligodendrocytes requires the presence of, or signals derived from axons in vivo. In particular, it is unclear whether the specific axons fated for myelination regulate the oligodendrocyte population in a living organism, and if so, which precise steps of oligodendrocyte-cell lineage progression are regulated by target axons. Here, we use live-imaging of zebrafish larvae carrying transgenic reporters that label oligodendrocyte-lineage cells to investigate which aspects of oligodendrocyte development, from specification to differentiation, are affected when we manipulate the target axonal environment. To drastically reduce the number of axons targeted for myelination, we use a previously identified kinesin-binding protein (kbp mutant, in which the first myelinated axons in the spinal cord, reticulospinal axons, do not fully grow in length, creating a region in the posterior spinal cord where most initial targets for myelination are absent. We find that a 73% reduction of reticulospinal axon surface in the posterior spinal cord of kbp mutants results in a 27% reduction in the number of oligodendrocytes. By time-lapse analysis of transgenic OPC reporters, we find that the reduction in oligodendrocyte number is explained by a reduction in OPC proliferation and survival. Interestingly, OPC specification and migration are unaltered in the near absence of normal axonal targets. Finally, we find that timely differentiation of OPCs into oligodendrocytes does not depend at all on the presence of target axons

High cholesterol level is essential for myelin membrane growth.

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Saher, Gesine; Brügger, Britta; Lappe-Siefke, Corinna; Möbius, Wiebke; Tozawa, Ryu-ichi; Wehr, Michael C; Wieland, Felix; Ishibashi, Shun; Nave, Klaus-Armin

2005-04-01

Cholesterol in the mammalian brain is a risk factor for certain neurodegenerative diseases, raising the question of its normal function. In the mature brain, the highest cholesterol content is found in myelin. We therefore created mice that lack the ability to synthesize cholesterol in myelin-forming oligodendrocytes. Mutant oligodendrocytes survived, but CNS myelination was severely perturbed, and mutant mice showed ataxia and tremor. CNS myelination continued at a reduced rate for many months, and during this period, the cholesterol-deficient oligodendrocytes actively enriched cholesterol and assembled myelin with >70% of the cholesterol content of wild-type myelin. This shows that cholesterol is an indispensable component of myelin membranes and that cholesterol availability in oligodendrocytes is a rate-limiting factor for brain maturation.

Introducing axonal myelination in connectomics: A preliminary analysis of g-ratio distribution in healthy subjects.

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Mancini, Matteo; Giulietti, Giovanni; Dowell, Nicholas; Spanò, Barbara; Harrison, Neil; Bozzali, Marco; Cercignani, Mara

2017-09-14

Microstructural imaging and connectomics are two research areas that hold great potential for investigating brain structure and function. Combining these two approaches can lead to a better and more complete characterization of the brain as a network. The aim of this work is characterizing the connectome from a novel perspective using the myelination measure given by the g-ratio. The g-ratio is the ratio of the inner to the outer diameters of a myelinated axon, whose aggregated value can now be estimated in vivo using MRI. In two different datasets of healthy subjects, we reconstructed the structural connectome and then used the g-ratio estimated from diffusion and magnetization transfer data to characterize the network structure. Significant characteristics of g-ratio weighted graphs emerged. First, the g-ratio distribution across the edges of the graph did not show the power-law distribution observed using the number of streamlines as a weight. Second, connections involving regions related to motor and sensory functions were the highest in myelin content. We also observed significant differences in terms of the hub structure and the rich-club organization suggesting that connections involving hub regions present higher myelination than peripheral connections. Taken together, these findings offer a characterization of g-ratio distribution across the connectome in healthy subjects and lay the foundations for further investigating plasticity and pathology using a similar approach. Copyright © 2017. Published by Elsevier Inc.

Extrinsic and intrinsic regulation of axon regeneration at a crossroads.

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Kaplan, Andrew; Ong Tone, Stephan; Fournier, Alyson E

2015-01-01

Repair of the injured spinal cord is a major challenge in medicine. The limited intrinsic regenerative response mounted by adult central nervous system (CNS) neurons is further hampered by astrogliosis, myelin debris and scar tissue that characterize the damaged CNS. Improved axon regeneration and recovery can be elicited by targeting extrinsic factors as well as by boosting neuron-intrinsic growth regulators. Our knowledge of the molecular basis of intrinsic and extrinsic regulators of regeneration has expanded rapidly, resulting in promising new targets to promote repair. Intriguingly certain neuron-intrinsic growth regulators are emerging as promising targets to both stimulate growth and relieve extrinsic inhibition of regeneration. This crossroads between the intrinsic and extrinsic aspects of spinal cord injury is a promising target for effective therapies for this unmet need.

Mild myelin disruption elicits early alteration in behavior and proliferation in the subventricular zone.

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Gould, Elizabeth A; Busquet, Nicolas; Shepherd, Douglas; Dietz, Robert M; Herson, Paco S; Simoes de Souza, Fabio M; Li, Anan; George, Nicholas M; Restrepo, Diego; Macklin, Wendy B

2018-02-13

Myelin, the insulating sheath around axons, supports axon function. An important question is the impact of mild myelin disruption. In the absence of the myelin protein proteolipid protein (PLP1), myelin is generated but with age, axonal function/maintenance is disrupted. Axon disruption occurs in Plp1 -null mice as early as 2 months in cortical projection neurons. High-volume cellular quantification techniques revealed a region-specific increase in oligodendrocyte density in the olfactory bulb and rostral corpus callosum that increased during adulthood. A distinct proliferative response of progenitor cells was observed in the subventricular zone (SVZ), while the number and proliferation of parenchymal oligodendrocyte progenitor cells was unchanged. This SVZ proliferative response occurred prior to evidence of axonal disruption. Thus, a novel SVZ response contributes to the region-specific increase in oligodendrocytes in Plp1 -null mice. Young adult Plp1- null mice exhibited subtle but substantial behavioral alterations, indicative of an early impact of mild myelin disruption. © 2018, Gould et al.

Axon degeneration: make the Schwann cell great again

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Keit Men Wong

2017-01-01

Full Text Available Axonal degeneration is a pivotal feature of many neurodegenerative conditions and substantially accounts for neurological morbidity. A widely used experimental model to study the mechanisms of axonal degeneration is Wallerian degeneration (WD, which occurs after acute axonal injury. In the peripheral nervous system (PNS, WD is characterized by swift dismantling and clearance of injured axons with their myelin sheaths. This is a prerequisite for successful axonal regeneration. In the central nervous system (CNS, WD is much slower, which significantly contributes to failed axonal regeneration. Although it is well-documented that Schwann cells (SCs have a critical role in the regenerative potential of the PNS, to date we have only scarce knowledge as to how SCs 'sense' axonal injury and immediately respond to it. In this regard, it remains unknown as to whether SCs play the role of a passive bystander or an active director during the execution of the highly orchestrated disintegration program of axons. Older reports, together with more recent studies, suggest that SCs mount dynamic injury responses minutes after axonal injury, long before axonal breakdown occurs. The swift SC response to axonal injury could play either a pro-degenerative role, or alternatively a supportive role, to the integrity of distressed axons that have not yet committed to degenerate. Indeed, supporting the latter concept, recent findings in a chronic PNS neurodegeneration model indicate that deactivation of a key molecule promoting SC injury responses exacerbates axonal loss. If this holds true in a broader spectrum of conditions, it may provide the grounds for the development of new glia-centric therapeutic approaches to counteract axonal loss.

A novel approach to 32-channel peripheral nervous system myelin imaging in vivo, with single axon resolution.

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Grochmal, Joey; Teo, Wulin; Gambhir, Hardeep; Kumar, Ranjan; Stratton, Jo Anne; Dhaliwal, Raveena; Brideau, Craig; Biernaskie, Jeff; Stys, Peter K; Midha, Rajiv

2018-01-19

OBJECTIVE Intravital spectral imaging of the large, deeply situated nerves in the rat peripheral nervous system (PNS) has not been well described. Here, the authors have developed a highly stable platform for performing imaging of the tibial nerve in live rodents, thus allowing the capture of high-resolution, high-magnification spectral images requiring long acquisition times. By further exploiting the qualities of the topically applied myelin dye Nile red, this technique is capable of visualizing the detailed microenvironment of peripheral nerve demyelination injury and recovery, while allowing us to obtain images of exogenous Schwann cell myelination in a living animal. METHODS The authors caused doxorubicin-induced focal demyelination in the tibial nerves of 25 Thy-1 GFP rats, of which 2 subsets (n = 10 each) received either BFP-labeled SKP-SCs or SCs to the zone of injury. Prior to acquiring images of myelin recovery in these nerves, a tibial nerve window was constructed using a silicone hemitube, a fast drying silicone polymer, and a small coverslip. This construct was then affixed to a 3D-printed nerve stage, which in turn was affixed to an external fixation/microscope stage device. Myelin visualization was facilitated by the topical application of Nile red. RESULTS The authors reliably demonstrated intravital peripheral nerve myelin imaging with micron-level resolution and magnification, and minimal movement artifact. The detailed microenvironment of nerve remyelination can be vividly observed, while exogenously applied Schwann cells and skin-derived precursor Schwann cells can be seen myelinating axons. CONCLUSIONS Topically applied Nile red enables intravital study of myelin in the living rat PNS. Furthermore, the use of a tibial nerve window facilitates stable intravital peripheral nerve imaging, making possible high-definition spectral imaging with long acquisition times.

Neuron-glia signaling and the protection of axon function by Schwann cells.

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Quintes, Susanne; Goebbels, Sandra; Saher, Gesine; Schwab, Markus H; Nave, Klaus-Armin

2010-03-01

The interaction between neurons and glial cells is a feature of all higher nervous systems. In the vertebrate peripheral nervous system, Schwann cells ensheath and myelinate axons thereby allowing rapid saltatory conduction and ensuring axonal integrity. Recently, some of the key molecules in neuron-Schwann cell signaling have been identified. Neuregulin-1 (NRG1) type III presented on the axonal surface determines the myelination fate of axons and controls myelin sheath thickness. Recent observations suggest that NRG1 regulates myelination via the control of Schwann cell cholesterol biosynthesis. This concept is supported by the finding that high cholesterol levels in Schwann cells are a rate-limiting factor for myelin protein production and transport of the major myelin protein P0 from the endoplasmic reticulum into the growing myelin sheath. NRG1 type III activates ErbB receptors on the Schwann cell, which leads to an increase in intracellular PIP3 levels via the PI3-kinase pathway. Surprisingly, enforced elevation of PIP3 levels by inactivation of the phosphatase PTEN in developing and mature Schwann cells does not entirely mimic NRG1 type III stimulated myelin growth, but predominantly causes focal hypermyelination starting at Schmidt-Lanterman incisures and nodes of Ranvier. This indicates that the glial transduction of pro-myelinating signals has to be under tight and life-long control to preserve integrity of the myelinated axon. Understanding the cross talk between neurons and Schwann cells will help to further define the role of glia in preserving axonal integrity and to develop therapeutic strategies for peripheral neuropathies such as CMT1A.

Ephaptic coupling of myelinated nerve fibers

DEFF Research Database (Denmark)

Binczak, S.; Eilbeck, J. C.; Scott, Alwyn C.

2001-01-01

Numerical predictions of a simple myelinated nerve fiber model are compared with theoretical results in the continuum and discrete limits, clarifying the nature of the conduction process on an isolated nerve axon. Since myelinated nerve fibers are often arranged in bundles, this model is used...

Excitation block in a nerve fibre model owing to potassium-dependent changes in myelin resistance.

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Brazhe, A R; Maksimov, G V; Mosekilde, E; Sosnovtseva, O V

2011-02-06

The myelinated nerve fibre is formed by an axon and Schwann cells or oligodendrocytes that sheath the axon by winding around it in tight myelin layers. Repetitive stimulation of a fibre is known to result in accumulation of extracellular potassium ions, especially between the axon and the myelin. Uptake of potassium leads to Schwann cell swelling and myelin restructuring that impacts the electrical properties of the myelin. In order to further understand the dynamic interaction that takes place between the myelin and the axon, we have modelled submyelin potassium accumulation and related changes in myelin resistance during prolonged high-frequency stimulation. We predict that potassium-mediated decrease in myelin resistance leads to a functional excitation block with various patterns of altered spike trains. The patterns are found to depend on stimulation frequency and amplitude and to range from no block (less than 100 Hz) to a complete block (greater than 500 Hz). The transitional patterns include intermittent periodic block with interleaved spiking and non-spiking intervals of different relative duration as well as an unstable regime with chaotic switching between the spiking and non-spiking states. Intermittent conduction blocks are accompanied by oscillations of extracellular potassium. The mechanism of conductance block based on myelin restructuring complements the already known and modelled block via hyperpolarization mediated by the axonal sodium pump and potassium depolarization.

Adaptive myelination from fish to man.

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Baraban, Marion; Mensch, Sigrid; Lyons, David A

2016-06-15

Myelinated axons with nodes of Ranvier are an evolutionary elaboration common to essentially all jawed vertebrates. Myelin made by Schwann cells in our peripheral nervous system and oligodendrocytes in our central nervous system has been long known to facilitate rapid energy efficient nerve impulse propagation. However, it is now also clear, particularly in the central nervous system, that myelin is not a simple static insulator but that it is dynamically regulated throughout development and life. New myelin sheaths can be made by newly differentiating oligodendrocytes, and mature myelin sheaths can be stimulated to grow again in the adult. Furthermore, numerous studies in models from fish to man indicate that neuronal activity can affect distinct stages of oligodendrocyte development and the process of myelination itself. This begs questions as to how these effects of activity are mediated at a cellular and molecular level and whether activity-driven adaptive myelination is a feature common to all myelinated axons, or indeed all oligodendrocytes, or is specific to cells or circuits with particular functions. Here we review the recent literature on this topic, elaborate on the key outstanding questions in the field, and look forward to future studies that incorporate investigations in systems from fish to man that will provide further insight into this fundamental aspect of nervous system plasticity. This article is part of a Special Issue entitled SI: Myelin Evolution. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

The Effect of the Uncariae Ramulus et Uncus on the Regeneration Following CNS Injury

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Lee Jin-Goo

2009-03-01

Full Text Available Objective : Following central nervous system(CNS injury, inhibitory influences at the site of axonal damage occur. Glial cells become reactive and form a glial scar, gliosis. Also myelin debris such as MAG inhibits axonal regeneration. Astrocyte-rich gliosis relates with up-regulation of GFAP and CD81, and eventually becomes physical and mechanical barrier to axonal regeneration. MAG is one of several endogenous axon regeneration inhibitors that limit recovery from CNS injury and disease. It was reported that molecules that block such inhibitors enhanced axon regeneration and functional recovery. Recently it was reported that treatment with anti-CD81 antibodies enhanced functional recovery in the rat with spinal cord injury. So in this current study, the author investigated the effect of the water extract of Uncariae Ramulus et Uncus on the regulation of CD81, GFAP and MAG that increase when gliosis occurs. Methods : MTT assay was performed to examine cell viability, and cell-based ELISA, western blot and PCR were used to detect the expression of CD81, GFAP and MAG. Then also immunohistochemistry was performed to confirm in vivo. Results : Water extract of Uncariae Ramulus et Uncus showed relatively high cell viability at the concentration of 0.05%, 0.1% and 0.5%. The expression of CD81, GFAP and MAG in astrocytes was decreased after the administration of Uncariae Ramulus et Uncus water extract. These results was confirmed in the brain sections following cortical stab injury by immunohistochemistry. Conclusion : The authors observed that Uncariae Ramulus et Uncus significantly down-regulates the expression of CD81, GFAP and MAG. These results suggest that Uncariae Ramulus et Uncus can be a candidate to regenerate CNS injury.

The lactate receptor HCAR1 promotes neuronal development and protects axons and myelin during hypoglycemia

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Kennedy, L. H.; Andersson, K. A.; Haugen, O. P.

2017-01-01

Lactate plays a significant role as an energy supply for neurons and has a neuroprotective effect in hypoglycemia and ischemia (1±5). Further, oligodendrocytes can use lactate for myelination when glucose levels are low. New studies suggest that lactate is not only a metabolic fuel but also...... in the development and survival of neurons and oligodendrocytes in normal conditions and hypoglycemia. We show that young HCAR1 KO mice have a reduced number of neural progenitor cells in the hippocampus and the cerebral cortex, and the average size of cortical axons is smaller in KO compared with WT mice...

Regeneration of unmyelinated and myelinated sensory nerve fibres studied by a retrograde tracer method

DEFF Research Database (Denmark)

Lozeron, Pierre; Krarup, Christian; Schmalbruch, Henning

2004-01-01

cells that had been labelled, i.e., that had regenerated axons towards or beyond the injection site, were counted in serial sections. Large and small neurons with presumably myelinated and unmyelinated axons, respectively, were classified by immunostaining for neurofilaments. The axonal growth rate......Regeneration of myelinated and unmyelinated sensory nerve fibres after a crush lesion of the rat sciatic nerve was investigated by means of retrograde labelling. The advantage of this method is that the degree of regeneration is estimated on the basis of sensory somata rather than the number...... of axons. Axonal counts do not reflect the number of regenerated neurons because of axonal branching and because myelinated axons form unmyelinated sprouts. Two days to 10 weeks after crushing, the distal sural or peroneal nerves were cut and exposed to fluoro-dextran. Large and small dorsal root ganglion...

Myelin activates FAK/Akt/NF-kappaB pathways and provokes CR3-dependent inflammatory response in murine system.

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Xin Sun

2010-02-01

Full Text Available Inflammatory response following central nervous system (CNS injury contributes to progressive neuropathology and reduction in functional recovery. Axons are sensitive to mechanical injury and toxic inflammatory mediators, which may lead to demyelination. Although it is well documented that degenerated myelin triggers undesirable inflammatory responses in autoimmune diseases such as multiple sclerosis (MS and its animal model, experimental autoimmune encephalomyelitis (EAE, there has been very little study of the direct inflammatory consequences of damaged myelin in spinal cord injury (SCI, i.e., there is no direct evidence to show that myelin debris from injured spinal cord can trigger undesirable inflammation in vitro and in vivo. Our data showed that myelin can initiate inflammatory responses in vivo, which is complement receptor 3 (CR3-dependent via stimulating macrophages to express pro-inflammatory molecules and down-regulates expression of anti-inflammatory cytokines. Mechanism study revealed that myelin-increased cytokine expression is through activation of FAK/PI3K/Akt/NF-kappaB signaling pathways and CR3 contributes to myelin-induced PI3K/Akt/NF-kappaB activation and cytokine production. The myelin induced inflammatory response is myelin specific as sphingomyelin (the major lipid of myelin and myelin basic protein (MBP, one of the major proteins of myelin are not able to activate NF-kappaB signaling pathway. In conclusion, our results demonstrate a crucial role of myelin as an endogenous inflammatory stimulus that induces pro-inflammatory responses and suggest that blocking myelin-CR3 interaction and enhancing myelin debris clearance may be effective interventions for treating SCI.

Localisation of N-acetylaspartate in oligodendrocytes/myelin.

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Nordengen, Kaja; Heuser, Christoph; Rinholm, Johanne Egge; Matalon, Reuben; Gundersen, Vidar

2015-03-01

The role of N-acetylaspartate in the brain is unclear. Here we used specific antibodies against N-acetylaspartate and immunocytochemistry of carbodiimide-fixed adult rodent brain to show that, besides staining of neuronal cell bodies in the grey matter, N-acetylaspartate labelling was present in oligodendrocytes/myelin in white matter tracts. Immunoelectron microscopy of the rat hippocampus showed that N-acetylaspartate was concentrated in the myelin. Also neuronal cell bodies and axons contained significant amounts of N-acetylaspartate, while synaptic elements and astrocytes were low in N-acetylaspartate. Mitochondria in axons and neuronal cell bodies contained higher levels of N-acetylaspartate compared to the cytosol, compatible with synthesis of N-acetylaspartate in mitochondria. In aspartoacylase knockout mice, in which catabolism of N-acetylaspartate is blocked, the levels of N-acetylaspartate were largely increased in oligodendrocytes/myelin. In these mice, the highest myelin concentration of N-acetylaspartate was found in the cerebellum, a region showing overt dysmyelination. In organotypic cortical slice cultures there was no evidence for N-acetylaspartate-induced myelin toxicity, supporting the notion that myelin damage is induced by the lack of N-acetylaspartate for lipid production. Our findings also implicate that N-acetylaspartate signals on magnetic resonance spectroscopy reflect not only vital neurons but also vital oligodendrocytes/myelin.

Myelination and isochronicity in neural networks

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Fumitaka Kimura

2009-07-01

Full Text Available Our brain contains a multiplicity of neuronal networks. In many of these, information sent from presynaptic neurons travels through a variety of pathways of different distances, yet arrives at the postsynaptic cells at the same time. Such isochronicity is achieved either by changes in the conduction velocity of axons or by lengthening the axonal path to compensate for fast conduction. To regulate the conduction velocity, a change in the extent of myelination has recently been proposed in thalamocortical and other pathways. This is in addition to a change in the axonal diameter, a previously identified, more accepted mechanism. Thus, myelination is not a simple means of insulation or acceleration of impulse conduction, but it is rather an exquisite way of actively regulating the timing of communication among various neuronal connections with different length.

Regulation of Central Nervous System Myelination in Higher Brain Functions

OpenAIRE

Nickel, Mara; Gu, Chen

2018-01-01

The hippocampus and the prefrontal cortex are interconnected brain regions, playing central roles in higher brain functions, including learning and memory, planning complex cognitive behavior, and moderating social behavior. The axons in these regions continue to be myelinated into adulthood in humans, which coincides with maturation of personality and decision-making. Myelin consists of dense layers of lipid membranes wrapping around the axons to provide electrical insulation and trophic sup...

Neuronal Regulation of Schwann Cell Mitochondrial Ca(2+) Signaling during Myelination.

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Ino, Daisuke; Sagara, Hiroshi; Suzuki, Junji; Kanemaru, Kazunori; Okubo, Yohei; Iino, Masamitsu

2015-09-29

Schwann cells (SCs) myelinate peripheral neurons to promote the rapid conduction of action potentials, and the process of myelination is known to be regulated by signals from axons to SCs. Given that SC mitochondria are one of the potential regulators of myelination, we investigated whether SC mitochondria are regulated by axonal signaling. Here, we show a purinergic mechanism that sends information from neurons to SC mitochondria during myelination. Our results show that electrical stimulation of rat sciatic nerve increases extracellular ATP levels enough to activate purinergic receptors. Indeed, electrical stimulation of sciatic nerves induces Ca(2+) increases in the cytosol and the mitochondrial matrix of surrounding SCs via purinergic receptor activation. Chronic suppression of this pathway during active myelination suppressed the longitudinal and radial development of myelinating SCs and caused hypomyelination. These results demonstrate a neuron-to-SC mitochondria signaling, which is likely to have an important role in proper myelination. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Neuronal Regulation of Schwann Cell Mitochondrial Ca2+ Signaling during Myelination

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Daisuke Ino

2015-09-01

Full Text Available Schwann cells (SCs myelinate peripheral neurons to promote the rapid conduction of action potentials, and the process of myelination is known to be regulated by signals from axons to SCs. Given that SC mitochondria are one of the potential regulators of myelination, we investigated whether SC mitochondria are regulated by axonal signaling. Here, we show a purinergic mechanism that sends information from neurons to SC mitochondria during myelination. Our results show that electrical stimulation of rat sciatic nerve increases extracellular ATP levels enough to activate purinergic receptors. Indeed, electrical stimulation of sciatic nerves induces Ca2+ increases in the cytosol and the mitochondrial matrix of surrounding SCs via purinergic receptor activation. Chronic suppression of this pathway during active myelination suppressed the longitudinal and radial development of myelinating SCs and caused hypomyelination. These results demonstrate a neuron-to-SC mitochondria signaling, which is likely to have an important role in proper myelination.

Molecular architecture of myelinated nerve fibers: leaky paranodal junctions and paranodal dysmyelination.

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Rosenbluth, Jack; Mierzwa, Amanda; Shroff, Seema

2013-12-01

Myelinated nerve fibers have evolved to optimize signal propagation. Each myelin segment is attached to the axon by the unique paranodal axoglial junction (PNJ), a highly complex structure that serves to define axonal ion channel domains and to direct nodal action currents through adjacent nodes. Surprisingly, this junction does not entirely seal the paranodal myelin sheath to the axon and thus does not entirely isolate the perinodal space from the internodal periaxonal space. Rather the paranode is penetrated by extracellular pathways between the myelin sheath and the axolemma for movement of molecules and the flow of current to and from the internodal axon. This review summarizes past and current studies demonstrating these pathways and considers what functional roles they subserve. In addition, modern genetic engineering methods permit modification of individual PNJ constituents, which provides an opportunity to define their specific functions. One component in particular, the transverse bands, plays a key role in maintaining the structure and function of the PNJ. Loss of transverse bands results not in frank demyelination but rather in subtle dysmyelination, which causes significant functional impairment. The consequences of such subtle defects in the PNJ are considered along with the relevance of these studies to human diseases of myelin.

Myelination in the absence of UDP-galactose:ceramide galactosyl-transferase and fatty acid 2 -hydroxylase

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Gieselmann Volkmar

2011-03-01

Full Text Available Abstract Background The sphingolipids galactosylceramide (GalCer and sulfatide are major myelin components and are thought to play important roles in myelin function. The importance of GalCer and sulfatide has been validated using UDP-galactose:ceramide galactosyltransferase-deficient (Cgt-/- mice, which are impaired in myelin maintenance. These mice, however, are still able to form compact myelin. Loss of GalCer and sulfatide in these mice is accompanied by up-regulation of 2-hydroxylated fatty acid containing (HFA-glucosylceramide in myelin. This was interpreted as a partial compensation of the loss of HFA-GalCer, which may prevent a more severe myelin phenotype. In order to test this hypothesis, we have generated Cgt-/- mice with an additional deletion of the fatty acid 2-hydroxylase (Fa2h gene. Results Fa2h-/-/Cgt-/- double-deficient mice lack sulfatide, GalCer, and in addition HFA-GlcCer and sphingomyelin. Interestingly, compared to Cgt-/- mice the amount of GlcCer in CNS myelin was strongly reduced in Fa2h-/-/Cgt-/- mice by more than 80%. This was accompanied by a significant increase in sphingomyelin, which was the predominant sphingolipid in Fa2h-/-/Cgt-/- mice. Despite these significant changes in myelin sphingolipids, compact myelin was formed in Fa2h-/-/Cgt-/- mice, and g-ratios of myelinated axons in the spinal cord of 4-week-old Fa2h-/-/Cgt-/- mice did not differ significantly from that of Cgt-/- mice, and there was no obvious phenotypic difference between Fa2h-/-/Cgt-/- and Cgt-/- mice Conclusions These data show that compact myelin can be formed with non-hydroxylated sphingomyelin as the predominant sphingolipid and suggest that the presence of HFA-GlcCer and HFA-sphingomyelin in Cgt-/- mice does not functionally compensate the loss of HFA-GalCer.

Axonal GABAA receptors.

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Trigo, Federico F; Marty, Alain; Stell, Brandon M

2008-09-01

Type A GABA receptors (GABA(A)Rs) are well established as the main inhibitory receptors in the mature mammalian forebrain. In recent years, evidence has accumulated showing that GABA(A)Rs are prevalent not only in the somatodendritic compartment of CNS neurons, but also in their axonal compartment. Evidence for axonal GABA(A)Rs includes new immunohistochemical and immunogold data: direct recording from single axonal terminals; and effects of local applications of GABA(A)R modulators on action potential generation, on axonal calcium signalling, and on neurotransmitter release. Strikingly, whereas presynaptic GABA(A)Rs have long been considered inhibitory, the new studies in the mammalian brain mostly indicate an excitatory action. Depending on the neuron that is under study, axonal GABA(A)Rs can be activated by ambient GABA, by GABA spillover, or by an autocrine action, to increase either action potential firing and/or transmitter release. In certain neurons, the excitatory effects of axonal GABA(A)Rs persist into adulthood. Altogether, axonal GABA(A)Rs appear as potent neuronal modulators of the mammalian CNS.

Study of the Peripheral Nerve Fibers Myelin Structure Changes during Activation of Schwann Cell Acetylcholine Receptors.

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Ekaterina E Verdiyan

Full Text Available In the present paper we consider a new type of mechanism by which neurotransmitter acetylcholine (ACh regulates the properties of peripheral nerve fibers myelin. Our data show the importance of the relationship between the changes in the number of Schwann cell (SC acetylcholine receptors (AChRs and the axon excitation (different intervals between action potentials (APs. Using Raman spectroscopy, an effect of activation of SC AChRs on the myelin membrane fluidity was investigated. It was found, that ACh stimulates an increase in lipid ordering degree of the myelin lipids, thus providing evidence for specific role of the "axon-SC" interactions at the axon excitation. It was proposed, that during the axon excitation, the SC membrane K+- depolarization and the Ca2+-influx led to phospholipase activation or exocytosis of intracellular membrane vesicles and myelin structure reorganization.

Nonenzymatic glycosylation of bovine myelin basic protein

International Nuclear Information System (INIS)

Hitz, J.B.

1987-01-01

In the CNS myelin sheath the nonenzymatic glycosylation reaction (at the early stage of the Amadori product) occurs only with the myelin basic protein and not with the other myelin proteins. This was observed in isolated bovine myelin by in vitro incubation with [ 14 C]-galactose and [ 14 C]-glucose. The respective in-vitro incorporation rates for purified bovine myelin basic protein with D-galactose, D-glucose and D-mannose were 7.2, 2.4 and 2.4 mmoles/mole myelin basic protein per day at 37 0 C. A more rapid, HPLC method was devised and characterized to specifically analyze for the Amadori product. The HPLC method was correlated to the [ 14 C]-sugar incorporation method for myelin basic protein under a set of standard reaction conditions using [ 14 C]-glucose and [ 14 C]-mannose with HPLC values at 1/6 and 1/5 of the [ 14 C]-sugar incorporation method. A novel myelin basic protein purification step has been developed that yields a relativity proteolytic free preparation that is easy to work with, being totally soluble at a neutral pH. Nine new spots appear for a trypsinized glycosylated MBP in the paper peptide map of which eight correspond to positions of the [ 3 H]-labeled Amadori product in affinity isolated peptides. These studies provide a general characterization of and a structural basis for investigations on nonenzymatically glycosylated MBP as well as identifying MBP as the only nonenzymatically glycosylated protein in the CNS myelin sheath which may accumulate during aging, diabetes, and demyelinating diseases in general

Noninvasive Detection and Differentiation of Axonal Injury/Loss, Demyelination, and Inflammation

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2014-10-01

phosphorylated neurofilament primary antibody (SMI-31; 1:1000, Covance , US) to stain non-injured axons, and in rabbit anti-myelin basic protein (MBP) primary...neurofilament antibody (SMI- 31; 1:1000, Covance , US) to stain non-injured axons or with rabbit anti-myelin basic protein (MBP) antibody (1:1000, Sigma Inc

Paranodal reorganization results in the depletion of transverse bands in the aged central nervous system

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Shepherd, Mark N.; Pomicter, Anthony D.; Velazco, Cristine S.; Henderson, Scott C.; Dupree, Jeffrey L.

2012-01-01

Paranodal axo-glial junctional complexes anchor the myelin sheath to the axon and breakdown of these complexes presumably facilitates demyelination. Myelin deterioration is also prominent in the aging central nervous system (CNS); however, the stability of the paranodal complexes in the aged CNS has not been examined. Here, we show that transverse bands, prominent components of paranodal junctions, are significantly reduced in the aged CNS; however, the number of paired clusters of both myelin and axonal paranodal proteins is not altered. Ultrastructural analyses also reveal that thicker myelin sheaths display a “piling” of paranodal loops, the cytoplasm-containing sacs that demarcate the paranode. Loops involved in piling are observed throughout the paranode and are not limited to loops positioned in either the nodal- or juxtanodal-most regions. Here, we propose that as myelination continues, previously anchored loops lose their transverse bands and recede away from the axolemma. Newly juxtaposed loops then lose their transverse bands, move laterally to fill in the gap left by the receded loops and finally reform their transverse bands. This paranodal reorganization results in conservation of paranodal length, which may be important in maintaining ion channel spacing and axonal function. Furthermore, we propose that transverse band reformation is less efficient in the aged CNS, resulting in the significant reduction of these junctional components. Although demyelination was not observed, we propose that loss of transverse bands facilitates myelin degeneration and may predispose the aged CNS to a poorer prognosis following a secondary insult. PMID:20888080

Early myelin breakdown following sural nerve crush: a freeze-fracture study

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Martinez A.M.B.

2000-01-01

Full Text Available In this study we describe the early changes of the myelin sheath following surgical nerve crush. We used the freeze-fracture technique to better evaluate myelin alterations during an early stage of Wallerian degeneration. Rat sural nerves were experimentally crushed and animals were sacrificed by transcardiac perfusion 30 h after surgery. Segments of the nerves were processed for routine transmission electron microscopy and freeze-fracture techniques. Our results show that 30 h after the lesion there was asynchrony in the pattern of Wallerian degeneration, with different nerve fibers exhibiting variable degrees of axon disruption. This was observed by both techniques. Careful examination of several replicas revealed early changes in myelin membranes represented by vacuolization and splitting of consecutive lamellae, rearrangement of intramembranous particles and disappearance of paranodal transverse bands associated or not with retraction of paranodal myelin terminal loops from the axolemma. These alterations are compatible with a direct injury to the myelin sheath following nerve crush. The results are discussed in terms of a similar mechanism underlying both axon and myelin breakdown.

Regulation of Central Nervous System Myelination in Higher Brain Functions

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Mara Nickel

2018-01-01

Full Text Available The hippocampus and the prefrontal cortex are interconnected brain regions, playing central roles in higher brain functions, including learning and memory, planning complex cognitive behavior, and moderating social behavior. The axons in these regions continue to be myelinated into adulthood in humans, which coincides with maturation of personality and decision-making. Myelin consists of dense layers of lipid membranes wrapping around the axons to provide electrical insulation and trophic support and can profoundly affect neural circuit computation. Recent studies have revealed that long-lasting changes of myelination can be induced in these brain regions by experience, such as social isolation, stress, and alcohol abuse, as well as by neurological and psychiatric abnormalities. However, the mechanism and function of these changes remain poorly understood. Myelin regulation represents a new form of neural plasticity. Some progress has been made to provide new mechanistic insights into activity-independent and activity-dependent regulations of myelination in different experimental systems. More extensive investigations are needed in this important but underexplored research field, in order to shed light on how higher brain functions and myelination interplay in the hippocampus and prefrontal cortex.

Analysis of Caribbean ciguatoxin-1 effects on frog myelinated axons and the neuromuscular junction.

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Mattei, César; Marquais, Michel; Schlumberger, Sébastien; Molgó, Jordi; Vernoux, Jean-Paul; Lewis, Richard J; Benoit, Evelyne

2010-10-01

Caribbean ciguatoxin-1 (C-CTX-1) induced, after about 1h exposure, muscle membrane depolarisation and repetitive post-synaptic action potentials (APs) in frog neuromuscular preparations. This depolarising effect was also observed in a Ca(2+)-free medium with a strong enhancement of spontaneous quantal transmitter release, compared with control conditions. The ciguatoxin-induced increase in release could be accelerated when Ca(2+) was present in the extracellular medium. C-CTX-1 also enhanced nerve-evoked quantal acetylcholine (ACh) release. At normal neuromuscular junctions loaded with the fluorescent dye FM1-43, C-CTX-1 induced swelling of nerve terminals, an effect that was reversed by hyperosmotic d-mannitol. In myelinated axons, C-CTX-1 increased nodal membrane excitability, inducing spontaneous and repetitive APs. Also, the toxin enlarged the repolarising phase of APs in control and tetraethylammonium-treated axons. Overall, our data suggest that C-CTX-1 affects nerve excitability and neurotransmitter release at nerve terminals. We conclude that C-CTX-1-induced up-regulation of Na(+) channels and the inhibition of K(+) channels, at low nanomolar concentrations, produce a variety of functional dysfunctions that are in part responsible for the human muscle skeletal symptoms observed in ciguatera. All these dysfunctions seem to result from the subtle balance between ionic currents, intracellular Na(+) and Ca(2+) concentrations, and engaged second messengers. Copyright 2009 Elsevier Ltd. All rights reserved.

Requirement of cAMP signaling for Schwann cell differentiation restricts the onset of myelination.

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Ketty Bacallao

Full Text Available Isolated Schwann cells (SCs respond to cAMP elevation by adopting a differentiated post-mitotic state that exhibits high levels of Krox-20, a transcriptional enhancer of myelination, and mature SC markers such as the myelin lipid galactocerebroside (O1. To address how cAMP controls myelination, we performed a series of cell culture experiments which compared the differentiating responses of isolated and axon-related SCs to cAMP analogs and ascorbate, a known inducer of axon ensheathment, basal lamina formation and myelination. In axon-related SCs, cAMP induced the expression of Krox-20 and O1 without a concomitant increase in the expression of myelin basic protein (MBP and without promoting axon ensheathment, collagen synthesis or basal lamina assembly. When cAMP was provided together with ascorbate, a dramatic enhancement of MBP expression occurred, indicating that cAMP primes SCs to form myelin only under conditions supportive of basal lamina formation. Experiments using a combination of cell permeable cAMP analogs and type-selective adenylyl cyclase (AC agonists and antagonists revealed that selective transmembrane AC (tmAC activation with forskolin was not sufficient for full SC differentiation and that the attainment of an O1 positive state also relied on the activity of the soluble AC (sAC, a bicarbonate sensor that is insensitive to forskolin and GPCR activation. Pharmacological and immunological evidence indicated that SCs expressed sAC and that sAC activity was required for morphological differentiation and the expression of myelin markers such as O1 and protein zero. To conclude, our data indicates that cAMP did not directly drive myelination but rather the transition into an O1 positive state, which is perhaps the most critical cAMP-dependent rate limiting step for the onset of myelination. The temporally restricted role of cAMP in inducing differentiation independently of basal lamina formation provides a clear example of the

Subtle changes in myelination due to childhood experiences: label-free microscopy to infer nerve fibers morphology and myelination in brain (Conference Presentation)

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Gasecka, Alicja; Tanti, Arnaud; Lutz, Pierre-Eric; Mechawar, Naguib; Cote, Daniel C.

2017-02-01

Adverse childhood experiences have lasting detrimental effects on mental health and are strongly associated with impaired cognition and increased risk of developing psychopathologies. Preclinical and neuroimaging studies have suggested that traumatic events during brain development can affect cerebral myelination particularly in areas and tracts implicated in mood and emotion. Although current neuroimaging techniques are quite powerful, they lack the resolution to infer myelin integrity at the cellular level. Recently demonstrated coherent Raman microscopy has accomplished cellular level imaging of myelin sheaths in the nervous system. However, a quantitative morphometric analysis of nerve fibers still remains a challenge. In particular, in brain, where fibres exhibit small diameters and varying local orientation. In this work, we developed an automated myelin identification and analysis method that is capable of providing a complete picture of axonal myelination and morphology in brain samples. This method performs three main procedures 1) detects molecular anisotropy of membrane phospholipids based on polarization resolved coherent Raman microscopy, 2) identifies regions of different molecular organization, 3) calculates morphometric features of myelinated axons (e.g. myelin thickness, g-ratio). We applied this method to monitor white matter areas from suicides adults that suffered from early live adversity and depression compared to depressed suicides adults and psychiatrically healthy controls. We demonstrate that our method allows for the rapid acquisition and automated analysis of neuronal networks morphology and myelination. This is especially useful for clinical and comparative studies, and may greatly enhance the understanding of processes underlying the neurobiological and psychopathological consequences of child abuse.

Neuroimaging evidence of deficient axon myelination in Wolfram syndrome.

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Lugar, Heather M; Koller, Jonathan M; Rutlin, Jerrel; Marshall, Bess A; Kanekura, Kohsuke; Urano, Fumihiko; Bischoff, Allison N; Shimony, Joshua S; Hershey, Tamara

2016-02-18

Wolfram syndrome is a rare autosomal recessive genetic disease characterized by insulin dependent diabetes and vision, hearing and brain abnormalities which generally emerge in childhood. Mutations in the WFS1 gene predispose cells to endoplasmic reticulum stress-mediated apoptosis and may induce myelin degradation in neuronal cell models. However, in vivo evidence of this phenomenon in humans is lacking. White matter microstructure and regional volumes were measured using magnetic resonance imaging in children and young adults with Wolfram syndrome (n = 21) and healthy and diabetic controls (n = 50). Wolfram patients had lower fractional anisotropy and higher radial diffusivity in major white matter tracts and lower volume in the basilar (ventral) pons, cerebellar white matter and visual cortex. Correlations were found between key brain findings and overall neurological symptoms. This pattern of findings suggests that reduction in myelin is a primary neuropathological feature of Wolfram syndrome. Endoplasmic reticulum stress-related dysfunction in Wolfram syndrome may interact with the development of myelin or promote degeneration of myelin during the progression of the disease. These measures may provide objective indices of Wolfram syndrome pathophysiology that will be useful in unraveling the underlying mechanisms and in testing the impact of treatments on the brain.

Fast-spiking Parvalbumin Interneurons are Frequently Myelinated in the Cerebral Cortex of Mice and Humans

NARCIS (Netherlands)

Stedehouder, J. (J.); J.J. Couey (Jonathan J); Brizee, D. (D.); B. Hosseini; J.A. Slotman (Johan A.); C.M.F. Dirven (Clemens); G. Shpak (Guy); A.B. Houtsmuller (Adriaan); S.A. Kushner (Steven)

2017-01-01

textabstractMyelination, the insulating ensheathment of axons by oligodendrocytes, is thought to both optimize signal propagation and provide metabolic support. Despite the well-established physiological importance of myelination to neuronal function, relatively little is known about the myelination

Regeneration of unmyelinated and myelinated sensory nerve fibres studied by a retrograde tracer method

DEFF Research Database (Denmark)

Lozeron, Pierre; Krarup, Christian; Schmalbruch, Henning

2004-01-01

of axons. Axonal counts do not reflect the number of regenerated neurons because of axonal branching and because myelinated axons form unmyelinated sprouts. Two days to 10 weeks after crushing, the distal sural or peroneal nerves were cut and exposed to fluoro-dextran. Large and small dorsal root ganglion...

Meninges-derived cues control axon guidance.

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Suter, Tracey A C S; DeLoughery, Zachary J; Jaworski, Alexander

2017-10-01

The axons of developing neurons travel long distances along stereotyped pathways under the direction of extracellular cues sensed by the axonal growth cone. Guidance cues are either secreted proteins that diffuse freely or bind the extracellular matrix, or membrane-anchored proteins. Different populations of axons express distinct sets of receptors for guidance cues, which results in differential responses to specific ligands. The full repertoire of axon guidance cues and receptors and the identity of the tissues producing these cues remain to be elucidated. The meninges are connective tissue layers enveloping the vertebrate brain and spinal cord that serve to protect the central nervous system (CNS). The meninges also instruct nervous system development by regulating the generation and migration of neural progenitors, but it has not been determined whether they help guide axons to their targets. Here, we investigate a possible role for the meninges in neuronal wiring. Using mouse neural tissue explants, we show that developing spinal cord meninges produce secreted attractive and repulsive cues that can guide multiple types of axons in vitro. We find that motor and sensory neurons, which project axons across the CNS-peripheral nervous system (PNS) boundary, are attracted by meninges. Conversely, axons of both ipsi- and contralaterally projecting dorsal spinal cord interneurons are repelled by meninges. The responses of these axonal populations to the meninges are consistent with their trajectories relative to meninges in vivo, suggesting that meningeal guidance factors contribute to nervous system wiring and control which axons are able to traverse the CNS-PNS boundary. Copyright © 2017 Elsevier Inc. All rights reserved.

Creatine pretreatment protects cortical axons from energy depletion in vitro

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Shen, Hua; Goldberg, Mark P.

2012-01-01

Creatine is a natural nitrogenous guanidino compound involved in bioenergy metabolism. Although creatine has been shown to protect neurons of the central nervous system (CNS) from experimental hypoxia/ischemia, it remains unclear if creatine may also protect CNS axons, and if the potential axonal protection depends on glial cells. To evaluate the direct impact of creatine on CNS axons, cortical axons were cultured in a separate compartment from their somas and proximal neurites using a modified two-compartment culture device. Axons in the axon compartment were subjected to acute energy depletion, an in vitro model of white matter ischemia, by exposure to 6 mM sodium azide for 30 min in the absence of glucose and pyruvate. Energy depletion reduced axonal ATP by 65%, depolarized axonal resting potential, and damaged 75% of axons. Application of creatine (10 mM) to both compartments of the culture at 24 h prior to energy depletion significantly reduced axonal damage by 50%. In line with the role of creatine in the bioenergy metabolism, this application also alleviated the axonal ATP loss and depolarization. Inhibition of axonal depolarization by blocking sodium influx with tetrodotoxin also effectively reduced the axonal damage caused by energy depletion. Further study revealed that the creatine effect was independent of glial cells, as axonal protection was sustained even when creatine was applied only to the axon compartment (free from somas and glial cells) for as little as 2 h. In contrast, application of creatine after energy depletion did not protect axons. The data provide the first evidence that creatine pretreatment may directly protect CNS axons from energy deficiency. PMID:22521466

Orexin A and Orexin Receptor 1 axonal traffic in dorsal roots at the CNS/PNS interface

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Damien eColas

2014-02-01

Full Text Available Hypothalamic orexin/hypocretin neurons send long axonal projections through the dorsal spinal cord in lamina I-II of the dorsal horn at the interface with the peripheral nervous system (PNS. We show that in the dorsal horn OXA fibers colocalize with substance P (SP positive afferents of dorsal root ganglia (DRG neurons known to mediate sensory processing. Further, OR1 is expressed in p75NTR and SP positive DRG neurons, suggesting a potential signaling pathway between orexin and DRG neurons. Interestingly, DRG sensory neurons have a distinctive bifurcating axon where one branch innervates the periphery and the other one the spinal cord (pseudo-unipolar neurons, allowing for potential functional coupling of distinct targets. We observe that OR1 is transported selectively from DRG toward the spinal cord, while OXA is accumulated retrogradely toward the DRG. We hence report a rare situation of asymmetrical neuropeptide receptor distribution between axons projected by a single neuron. This molecular and cellular data are consistent with the role of OXA/OR1 in sensory processing, including DRG neuronal modulation, and support the potential existence of an OX/HCRT circuit between CNS and PNS.

Paired Immunoglobulin-like Receptor B Knockout Does Not Enhance Axonal Regeneration or Locomotor Recovery after Spinal Cord Injury*

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Nakamura, Yuka; Fujita, Yuki; Ueno, Masaki; Takai, Toshiyuki; Yamashita, Toshihide

2010-01-01

Myelin components that inhibit axonal regeneration are believed to contribute significantly to the lack of axonal regeneration noted in the adult central nervous system. Three proteins found in myelin, Nogo, myelin-associated glycoprotein, and oligodendrocyte-myelin glycoprotein, inhibit neurite outgrowth in vitro. All of these proteins interact with the same receptors, namely, the Nogo receptor (NgR) and paired immunoglobulin-like receptor B (PIR-B). As per previous reports, corticospinal tr...

Epigenetic regulation of axon and dendrite growth

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Ephraim F Trakhtenberg

2012-03-01

Full Text Available Neuroregenerative therapies for central nervous system (CNS injury, neurodegenerative disease, or stroke require axons of damaged neurons to grow and reinnervate their targets. However, mature mammalian CNS neurons do not regenerate their axons, limiting recovery in these diseases (Yiu and He, 2006. CNS’ regenerative failure may be attributable to the development of an inhibitory CNS environment by glial-associated inhibitory molecules (Yiu and He, 2006, and by various cell-autonomous factors (Sun and He, 2010. Intrinsic axon growth ability also declines developmentally (Li et al., 1995; Goldberg et al., 2002; Bouslama-Oueghlani et al., 2003; Blackmore and Letourneau, 2006 and is dependent on transcription (Moore et al., 2009. Although neurons’ intrinsic capacity for axon growth may depend in part on the panoply of expressed transcription factors (Moore and Goldberg, 2011, epigenetic factors such as the accessibility of DNA and organization of chromatin are required for downstream genes to be transcribed. Thus a potential approach to overcoming regenerative failure focuses on the epigenetic mechanisms regulating regenerative gene expression in the CNS. Here we review molecular mechanisms regulating the epigenetic state of DNA through chromatin modifications, their implications for regulating axon and dendrite growth, and important new directions for this field of study.

Impairment of heme synthesis in myelin as potential trigger of multiple sclerosis.

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Morelli, Alessandro; Ravera, Silvia; Calzia, Daniela; Panfoli, Isabella

2012-06-01

The pathogenesis of multiple sclerosis (MS), a disease characterized by demyelination and subsequent axonal degeneration, is as yet unknown. Also, the nature of the disease is as yet not established, since doubts have been cast on its autoimmune origin. Genetic and environmental factors have been implied in MS, leading to the idea of an overall multifactorial origin. An unexpected role in energizing the axon has been reported for myelin, supposed to be the site of consumption of most of oxygen in brain. Myelin would be able to perform oxidative phosphorylation to supply the axons with ATP, thanks to the expression therein of mitochondrial F(o)F(1)-ATP synthase, and respiratory chains. Interestingly, myelin expresses the pathway of heme synthesis, hence of cytochromes, that rely on heme group, in turn depending on Fe availability. Poisoning by these pollutants shares the common characteristic to bring about demyelination both in animal models and in man. Carbon monoxide (CO) and lead poisoning which cause functional imbalance of the heme group, as well as of heme synthesis, cause myelin damage. On the other hand, a lack of essential metals such as iron and copper, produces dramatic myelin decrease. Myelin is a primary target, of iron shortage, indicating that in myelin Fe-dependent processes are more active than in other tissues. The predominant spread of MS in industrialized countries where pollution by heavy metals, and CO poisoning is widespread, suggests a relationship among toxic action of metal pollutants and MS. According to the present hypothesis, MS can be primarily triggered by environmental factors acting on a genetic susceptibility, while the immune response may be a consequence of a primary oxidative damage due to reactive oxygen species produced consequently to an imbalance of cytochromes and respiratory chains in the sheath. Copyright © 2012 Elsevier Ltd. All rights reserved.

Glial membranes at the node of Ranvier prevent neurite outgrowth

DEFF Research Database (Denmark)

Huang, Jeffrey K; Phillips, Greg R; Roth, Alejandro D

2005-01-01

of neurite outgrowth, including the oligodendrocyte myelin glycoprotein (OMgp). In rat spinal cord, OMgp was not localized to compact myelin, as previously thought, but to oligodendroglia-like cells, whose processes converge to form a ring that completely encircles the nodes. In OMgp-null mice, CNS nodes......Nodes of Ranvier are regularly placed, nonmyelinated axon segments along myelinated nerves. Here we show that nodal membranes isolated from the central nervous system (CNS) of mammals restricted neurite outgrowth of cultured neurons. Proteomic analysis of these membranes revealed several inhibitors...

Mouse Intermittent Hypoxia Mimicking Apnea of Prematurity: Effects on Myelinogenesis and Axonal Maturation

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CAI, JUN; TUONG, CHI MINH; ZHANG, YIPING; SHIELDS, CHRISTOPHER B.; GUO, GANG; FU, HUI; GOZAL, DAVID

2014-01-01

Premature babies are at high risk for both infantile apnea and long-term neurobehavioral deficits. Recent studies suggest that diffuse structural changes in brain white matter are a positive predictor of poor cognitive outcomes. Since oligodendrocyte maturation, myelination, axon development and synapse formation mainly occur in the 3rd trimester of gestation and 1st postnatal year, infantile apnea could lead to and/or exaggerate white matter impairments in preterm neonates. Therefore, we investigated oligodendroglia and axon development in a neonatal mouse model of intermittent hypoxia between postnatal days 2 to 10. During critical phases of central nervous system development, intermittent hypoxia induced hypomyelination in the corpus callosum, striatum, fornix and cerebellum, but not the pons or spinal cord. Intermittent hypoxia-elicited alterations in myelin-forming processes were reflected by decreased expression of myelin proteins, including MBP, PLP, MAG and CNPase, possibly due to arrested maturation of oligodendrocytes. Ultra-structural abnormalities were apparent in the myelin sheath and axon. Immature oligodendrocytes were more vulnerable to neonatal intermittent hypoxia exposures than developing axons, suggesting that hypomyelination may contribute, at least partially, to axonal deficits. Insufficient neurofilament synthesis with anomalous components of neurofilament subunits, β-tubulin and MAP2 isoforms indicated immaturity of axons in intermittent hypoxia-exposed mouse brains. In addition, down-regulation of Synapsin I, Synaptophysin and Gap-43 phosphorylation suggested a potential stunt in axonogenesis and synaptogenesis. The region-selective and complex impairment in brain white matter induced by intermittent hypoxia was further associated with electrophysiological changes that may underlie long-term neurobehavioral sequelae. PMID:21953180

Enhanced microglial clearance of myelin debris in T cell-infiltrated central nervous system

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Nielsen, Helle Hvilsted; Ladeby, Rune; Fenger, Christina

2009-01-01

Acute multiple sclerosis lesions are characterized by accumulation of T cells and macrophages, destruction of myelin and oligodendrocytes, and axonal damage. There is, however, limited information on neuroimmune interactions distal to sites of axonal damage in the T cell-infiltrated central nervo...

Quantitative analysis of the myelin g-ratio from electron microscopy images of the macaque corpus callosum

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Nikola Stikov

2015-09-01

Full Text Available We provide a detailed morphometric analysis of eight transmission electron micrographs (TEMs obtained from the corpus callosum of one cynomolgus macaque. The raw TEM images are included in the article, along with the distributions of the axon caliber and the myelin g-ratio in each image. The distributions are analyzed to determine the relationship between axon caliber and g-ratio, and compared against the aggregate metrics (myelin volume fraction, fiber volume fraction, and the aggregate g-ratio, as defined in the accompanying research article entitled ‘In vivo histology of the myelin g-ratio with magnetic resonance imaging’ (Stikov et al., NeuroImage, 2015.

Is There Evidence for Myelin Modeling by Astrocytes in the Normal Adult Brain?

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Alfredo Varela-Echevarría

2017-09-01

Full Text Available A set of astrocytic process associated with altered myelinated axons is described in the forebrain of normal adult rodents with confocal, electron microscopy, and 3D reconstructions. Each process consists of a protuberance that contains secretory organelles including numerous lysosomes which polarize and open next to disrupted myelinated axons. Because of the distinctive asymmetric organelle distribution and ubiquity throughout the forebrain neuropil, this enlargement is named paraxial process (PAP. The myelin envelope contiguous to the PAP displays focal disruption or disintegration. In routine electron microscopy clusters of large, confluent, lysosomes proved to be an effective landmark for PAP identification. In 3D assemblies lysosomes organize a series of interconnected saccules that open up to the plasmalemma next to the disrupted myelin envelope(s. Activity for acid hydrolases was visualized in lysosomes, and extracellularly at the PAP-myelin interface and/or between the glial and neuronal outer aspects. Organelles in astrocytic processes involved in digesting pyknotic cells and debris resemble those encountered in PAPs supporting a likewise lytic function of the later. Conversely, processes entangling tripartite synapses and glomeruli were devoid of lysosomes. Both oligodendrocytic and microglial processes were not associated with altered myelin envelopes. The possible roles of the PAP in myelin remodeling in the context of the oligodendrocyte-astrocyte interactions and in the astrocyte's secretory pathways are discussed.

Perilesional edema in radiation necrosis reflects axonal degeneration

International Nuclear Information System (INIS)

Perez-Torres, Carlos J; Yuan, Liya; Schmidt, Robert E; Rich, Keith M; Ackerman, Joseph JH; Garbow, Joel R

2015-01-01

Recently, we characterized a Gamma Knife® radiation necrosis mouse model with various magnetic resonance imaging (MRI) protocols to identify biomarkers useful in differentiation from tumors. Though the irradiation was focal to one hemisphere, a contralateral injury was observed that appeared to be localized in the white matter only. Interestingly, this injury was identifiable in T2-weighted images, apparent diffusion coefficient (ADC), and magnetization transfer ratio (MTR) maps, but not on post-contrast T1-weighted images. This observation of edema independent of vascular changes is akin to the perilesional edema seen in clinical radiation necrosis. The pathology underlying the observed white-matter MRI changes was explored by performing immunohistochemistry for healthy axons and myelin. The presence of both healthy axons and myelin was reduced in the contralateral white-matter lesion. Based on our immunohistochemical findings, the contralateral white-matter injury is most likely due to axonal degeneration

Role of resident CNS cell populations in HTLV-1-associated neuroinflammatory disease.

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Lepoutre, Veronique; Jain, Pooja; Quann, Kevin; Wigdahl, Brian; Khan, Zafar K

2009-01-01

Human T cell leukemia virus type 1 (HTLV-1), the first human retrovirus discovered, is the etiologic agent for a number of disorders; the two most common pathologies include adult T cell leukemia (ATL) and a progressive demyelinating neuroinflammatory disease, HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The neurologic dysfunction associated with HAM/TSP is a result of viral intrusion into the central nervous system (CNS) and the generation of a hyperstimulated host response within the peripheral and central nervous system that includes expanded populations of CD4+ and CD8+ T cells and proinflammatory cytokines/chemokines in the cerebrospinal fluid (CSF). This robust, yet detrimental immune response likely contributes to the death of myelin producing oligodendrocytes and degeneration of neuronal axons. The mechanisms of neurological degeneration in HAM/TSP have yet to be fully delineated in vivo and may involve the immunogenic properties of the HTLV-1 transactivator protein Tax. This comprehensive review characterizes the available knowledge to date concerning the effects of HTLV-1 on CNS resident cell populations with emphasis on both viral and host factors contributing to the genesis of HAM/TSP.

Death Receptor 6 Promotes Wallerian Degeneration in Peripheral Axons.

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Gamage, Kanchana K; Cheng, Irene; Park, Rachel E; Karim, Mardeen S; Edamura, Kazusa; Hughes, Christopher; Spano, Anthony J; Erisir, Alev; Deppmann, Christopher D

2017-03-20

Axon degeneration during development is required to sculpt a functional nervous system and is also a hallmark of pathological insult, such as injury [1, 2]. Despite similar morphological characteristics, very little overlap in molecular mechanisms has been reported between pathological and developmental degeneration [3-5]. In the peripheral nervous system (PNS), developmental axon pruning relies on receptor-mediated extrinsic degeneration mechanisms to determine which axons are maintained or degenerated [5-7]. Receptors have not been implicated in Wallerian axon degeneration; instead, axon autonomous, intrinsic mechanisms are thought to be the primary driver for this type of axon disintegration [8-10]. Here we survey the role of neuronally expressed, paralogous tumor necrosis factor receptor super family (TNFRSF) members in Wallerian degeneration. We find that an orphan receptor, death receptor 6 (DR6), is required to drive axon degeneration after axotomy in sympathetic and sensory neurons cultured in microfluidic devices. We sought to validate these in vitro findings in vivo using a transected sciatic nerve model. Consistent with the in vitro findings, DR6 -/- animals displayed preserved axons up to 4 weeks after injury. In contrast to phenotypes observed in Wld s and Sarm1 -/- mice, preserved axons in DR6 -/- animals display profound myelin remodeling. This indicates that deterioration of axons and myelin after axotomy are mechanistically distinct processes. Finally, we find that JNK signaling after injury requires DR6, suggesting a link between this novel extrinsic pathway and the axon autonomous, intrinsic pathways that have become established for Wallerian degeneration. Copyright © 2017 Elsevier Ltd. All rights reserved.

Classic and Golli Myelin Basic Protein have distinct developmental trajectories in human visual cortex.

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Siu, Caitlin R; Balsor, Justin L; Jones, David G; Murphy, Kathryn M

2015-01-01

Traditionally, myelin is viewed as insulation around axons, however, more recent studies have shown it also plays an important role in plasticity, axonal metabolism, and neuroimmune signaling. Myelin is a complex multi-protein structure composed of hundreds of proteins, with Myelin Basic Protein (MBP) being the most studied. MBP has two families: Classic-MBP that is necessary for activity driven compaction of myelin around axons, and Golli-MBP that is found in neurons, oligodendrocytes, and T-cells. Furthermore, Golli-MBP has been called a "molecular link" between the nervous and immune systems. In visual cortex specifically, myelin proteins interact with immune processes to affect experience-dependent plasticity. We studied myelin in human visual cortex using Western blotting to quantify Classic- and Golli-MBP expression in post-mortem tissue samples ranging in age from 20 days to 80 years. We found that Classic- and Golli-MBP have different patterns of change across the lifespan. Classic-MBP gradually increases to 42 years and then declines into aging. Golli-MBP has early developmental changes that are coincident with milestones in visual system sensitive period, and gradually increases into aging. There are three stages in the balance between Classic- and Golli-MBP expression, with Golli-MBP dominating early, then shifting to Classic-MBP, and back to Golli-MBP in aging. Also Golli-MBP has a wave of high inter-individual variability during childhood. These results about cortical MBP expression are timely because they compliment recent advances in MRI techniques that produce high resolution maps of cortical myelin in normal and diseased brain. In addition, the unique pattern of Golli-MBP expression across the lifespan suggests that it supports high levels of neuroimmune interaction in cortical development and in aging.

Excitation block in a nerve fibre model owing to potassium-dependent changes in myelin resistance

DEFF Research Database (Denmark)

Brazhe, Alexey; Maksimov, G. V.; Mosekilde, Erik

2011-01-01

. Uptake of potassium leads to Schwann cell swelling and myelin restructuring that impacts the electrical properties of the myelin. In order to further understand the dynamic interaction that takes place between the myelin and the axon, we have modelled submyelin potassium accumulation and related changes...... in myelin resistance during prolonged high-frequency stimulation. We predict that potassium-mediated decrease in myelin resistance leads to a functional excitation block with various patterns of altered spike trains. The patterns are found to depend on stimulation frequency and amplitude and to range from...

Axon-somatic back-propagation in detailed models of spinal alpha motoneurons

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Pietro eBalbi

2015-02-01

Full Text Available Antidromic action potentials following distal stimulation of motor axons occasionally fail to invade the soma of alpha motoneurons in spinal cord, due to their passing through regions of high non-uniformity.Morphologically detailed conductance-based models of cat spinal alpha motoneurons have been developed, with the aim to reproduce and clarify some aspects of the electrophysiological behavior of the antidromic axon-somatic spike propagation. Fourteen 3D morphologically detailed somata and dendrites of cat spinal alpha motoneurons have been imported from an open-access web-based database of neuronal morphologies, NeuroMorpho.org, and instantiated in neurocomputational models. An axon hillock, an axonal initial segment and a myelinated axon are added to each model.By sweeping the diameter of the axonal initial segment (AIS and the axon hillock, as well as the maximal conductances of sodium channels at the AIS and at the soma, the developed models are able to show the relationships between different geometric and electrophysiological configurations and the voltage attenuation of the antidromically travelling wave.In particular, a greater than usually admitted sodium conductance at AIS is necessary and sufficient to overcome the dramatic voltage attenuation occurring during antidromic spike propagation both at the myelinated axon-AIS and at the AIS-soma transitions.

Cholecalciferol (vitamin D₃ improves myelination and recovery after nerve injury.

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Jean-Francois Chabas

Full Text Available Previously, we demonstrated i that ergocalciferol (vitamin D2 increases axon diameter and potentiates nerve regeneration in a rat model of transected peripheral nerve and ii that cholecalciferol (vitamin D3 improves breathing and hyper-reflexia in a rat model of paraplegia. However, before bringing this molecule to the clinic, it was of prime importance i to assess which form - ergocalciferol versus cholecalciferol - and which dose were the most efficient and ii to identify the molecular pathways activated by this pleiotropic molecule. The rat left peroneal nerve was cut out on a length of 10 mm and autografted in an inverted position. Animals were treated with either cholecalciferol or ergocalciferol, at the dose of 100 or 500 IU/kg/day, or excipient (Vehicle, and compared to unlesioned rats (Control. Functional recovery of hindlimb was measured weekly, during 12 weeks, using the peroneal functional index. Ventilatory, motor and sensitive responses of the regenerated axons were recorded and histological analysis was performed. In parallel, to identify the genes regulated by vitamin D in dorsal root ganglia and/or Schwann cells, we performed an in vitro transcriptome study. We observed that cholecalciferol is more efficient than ergocalciferol and, when delivered at a high dose (500 IU/kg/day, cholecalciferol induces a significant locomotor and electrophysiological recovery. We also demonstrated that cholecalciferol increases i the number of preserved or newly formed axons in the proximal end, ii the mean axon diameter in the distal end, and iii neurite myelination in both distal and proximal ends. Finally, we found a modified expression of several genes involved in axogenesis and myelination, after 24 hours of vitamin supplementation. Our study is the first to demonstrate that vitamin D acts on myelination via the activation of several myelin-associated genes. It paves the way for future randomised controlled clinical trials for peripheral

Enlarging the nosological spectrum of hereditary diffuse leukoencephalopathy with axonal spheroids (HDLS).

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Hoffmann, Sarah; Murrell, Jill; Harms, Lutz; Miller, Kelly; Meisel, Andreas; Brosch, Thomas; Scheel, Michael; Ghetti, Bernardino; Goebel, Hans-Hilmar; Stenzel, Werner

2014-09-01

Hereditary diffuse leukoencephalopathy with axonal spheroids (HDLS) is an autosomal dominant disease clinically characterized by cognitive decline, personality changes, motor impairment, parkinsonism and seizures. Recently, mutations in the colony-stimulating factor-1 receptor (CSF1R) gene have been shown to be associated with HDLS. We report clinical, neuropathological and molecular genetic findings of patients from a new family with a mutation in the CSF1R gene. Disease onset was earlier and disease progression was more rapid compared with previously reported patients. Psychiatric symptoms including personality changes, alcohol abuse and severe depression were the first symptoms in male patients. In the index, female patient, the initial symptom was cognitive decline. Magnetic resonance imaging (MRI) showed bilateral, confluent white matter lesions in the cerebrum. Stereotactic biopsy revealed loss of myelin and microglial activation as well as macrophage infiltration of the parenchyma. Numerous axonal swellings and spheroids were present. Ultrastructural analysis revealed pigment-containing macrophages. Axonal swellings were detected by electron microscopy not only in the central nervous system (CNS) but also in skin nerves. We identified a heterozygous mutation (c.2330G>A, p.R777Q) in the CSF1R gene. Through this report, we aim to enlarge the nosological spectrum of HDLS, providing new clinical descriptions as well as novel neuropathological findings from the peripheral nervous system. © 2014 International Society of Neuropathology.

Transcriptional Regulation of Brain-Derived Neurotrophic Factor (BDNF) by Methyl CpG Binding Protein 2 (MeCP2): a Novel Mechanism for Re-Myelination and/or Myelin Repair Involved in the Treatment of Multiple Sclerosis (MS).

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KhorshidAhmad, Tina; Acosta, Crystal; Cortes, Claudia; Lakowski, Ted M; Gangadaran, Surendiran; Namaka, Michael

2016-03-01

Multiple sclerosis (MS) is a chronic progressive, neurological disease characterized by the targeted immune system-mediated destruction of central nervous system (CNS) myelin. Autoreactive CD4+ T helper cells have a key role in orchestrating MS-induced myelin damage. Once activated, circulating Th1-cells secrete a variety of inflammatory cytokines that foster the breakdown of blood-brain barrier (BBB) eventually infiltrating into the CNS. Inside the CNS, they become reactivated upon exposure to the myelin structural proteins and continue to produce inflammatory cytokines such as tumor necrosis factor α (TNFα) that leads to direct activation of antibodies and macrophages that are involved in the phagocytosis of myelin. Proliferating oligodendrocyte precursors (OPs) migrating to the lesion sites are capable of acute remyelination but unable to completely repair or restore the immune system-mediated myelin damage. This results in various permanent clinical neurological disabilities such as cognitive dysfunction, fatigue, bowel/bladder abnormalities, and neuropathic pain. At present, there is no cure for MS. Recent remyelination and/or myelin repair strategies have focused on the role of the neurotrophin brain-derived neurotrophic factor (BDNF) and its upstream transcriptional repressor methyl CpG binding protein (MeCP2). Research in the field of epigenetic therapeutics involving histone deacetylase (HDAC) inhibitors and lysine acetyl transferase (KAT) inhibitors is being explored to repress the detrimental effects of MeCP2. This review will address the role of MeCP2 and BDNF in remyelination and/or myelin repair and the potential of HDAC and KAT inhibitors as novel therapeutic interventions for MS.

A Mechanism of Virus-Induced Demyelination

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Jayasri Das Sarma

2010-01-01

Full Text Available Myelin forms an insulating sheath surrounding axons in the central and peripheral nervous systems and is essential for rapid propagation of neuronal action potentials. Demyelination is an acquired disorder in which normally formed myelin degenerates, exposing axons to the extracellular environment. The result is dysfunction of normal neuron-to-neuron communication and in many cases, varying degrees of axonal degeneration. Numerous central nervous system demyelinating disorders exist, including multiple sclerosis. Although demyelination is the major manifestation of most of the demyelinating diseases, recent studies have clearly documented concomitant axonal loss to varying degrees resulting in long-term disability. Axonal injury may occur secondary to myelin damage (outside-in model or myelin damage may occur secondary to axonal injury (inside-out model. Viral induced demyelination models, has provided unique imminent into the cellular mechanisms of myelin destruction. They illustrate mechanisms of viral persistence, including latent infections, virus reactivation and viral-induced tissue damage. These studies have also provided excellent paradigms to study the interactions between the immune system and the central nervous system (CNS. In this review we will discuss potential cellular and molecular mechanism of central nervous system axonal loss and demyelination in a viral induced mouse model of multiple sclerosis.

Evaluation of dermal myelinated nerve fibers in diabetes mellitus

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Peltier, Amanda C.; Myers, M. Iliza; Artibee, Kay J.; Hamilton, Audra D.; Yan, Qing; Guo, Jiasong; Shi, Yaping; Wang, Lily; Li, Jun

2013-01-01

Skin biopsies have primarily been used to study the non-myelinated nerve fibers of the epidermis in a variety of neuropathies. In the present study, we have expanded the skin biopsy technique to glabrous, non-hairy skin to evaluate myelinated nerve fibers in the most highly prevalent peripheral nerve disease, diabetic polyneuropathy (DPN). Twenty patients with DPN (Type I, n=9; Type II, n=11) and sixteen age-matched healthy controls (ages 29–73) underwent skin biopsy of the index finger, nerve conduction studies, and composite neuropathy scoring. In patients with DPN, we found a statistically significant reduction of both mechanoreceptive Meissner corpuscles (MC) and their afferent myelinated nerve fibers (p=0.01). This myelinated nerve fiber loss was correlated with the decreased amplitudes of sensory/motor responses in nerve conduction studies. This study supports the utilization of skin biopsy to quantitatively evaluate axonal loss of myelinated nerve fibers in patients with DPN. PMID:23781963

Mice with GFAP-targeted loss of neurofibromin demonstrate increased axonal MET expression with aging.

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Su, Weiping; Xing, Rubing; Guha, Abhijit; Gutmann, David H; Sherman, Larry S

2007-05-01

Neurofibromatosis 1 (NF1) is a common genetic disease that predisposes patients to peripheral nerve tumors and central nervous system (CNS) abnormalities including low-grade astrocytomas and cognitive disabilities. Using mice with glial fibrillary acidic protein (GFAP)-targeted Nf1 loss (Nf1(GFAP)CKO mice), we found that Nf1(-/-) astrocytes proliferate faster and are more invasive than wild-type astrocytes. In light of our previous finding that aberrant expression of the MET receptor tyrosine kinase contributes to the invasiveness of human NF1-associated malignant peripheral nerve sheath tumors, we sought to determine whether MET expression is aberrant in the brains of Nf1 mutant mice. We found that Nf1(-/-) astrocytes express slightly more MET than wild-type cells in vitro, but do not express elevated MET in situ. However, fiber tracts containing myelinated axons in the hippocampus, midbrain, cerebral cortex, and cerebellum express higher than normal levels of MET in older (> or =6 months) Nf1(GFAP)CKO mice. Both Nf1(GFAP)CKO and wild-type astrocytes induced MET expression in neurites of wild-type hippocampal neurons in vitro, suggesting that astrocyte-derived signals may induce MET in Nf1 mutant mice. Because the Nf1 gene product functions as a RAS GTPase, we examined MET expression in the brains of mice with GFAP-targeted constitutively active forms of RAS. MET was elevated in axonal fiber tracts in mice with active K-RAS but not H-RAS. Collectively, these data suggest that loss of Nf1 in either astrocytes or GFAP(+) neural progenitor cells results in increased axonal MET expression, which may contribute to the CNS abnormalities in children and adults with NF1. (c) 2007 Wiley-Liss, Inc.

Nerve Regeneration in the Peripheral Nervous System versus the Central Nervous System and the Relevance to Speech and Hearing after Nerve Injuries

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Gordon, Tessa; Gordon, Karen

2010-01-01

Schwann cells normally form myelin sheaths around axons in the peripheral nervous system (PNS) and support nerve regeneration after nerve injury. In contrast, nerve regeneration in the central nervous system (CNS) is not supported by the myelinating cells known as oligodendrocytes. We have found that: 1) low frequency electrical stimulation can be…

SnoN facilitates axonal regeneration after spinal cord injury.

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Jiun L Do

Full Text Available Adult CNS neurons exhibit a reduced capacity for growth compared to developing neurons, due in part to downregulation of growth-associated genes as development is completed. We tested the hypothesis that SnoN, an embryonically regulated transcription factor that specifies growth of the axonal compartment, can enhance growth in injured adult neurons. In vitro, SnoN overexpression in dissociated adult DRG neuronal cultures significantly enhanced neurite outgrowth. Moreover, TGF-β1, a negative regulator of SnoN, inhibited neurite outgrowth, and SnoN over-expression overcame this inhibition. We then examined whether SnoN influenced axonal regeneration in vivo: indeed, expression of a mutant form of SnoN resistant to degradation significantly enhanced axonal regeneration following cervical spinal cord injury, despite peri-lesional upregulation of TGF-β1. Thus, a developmental mechanism that specifies extension of the axonal compartment also promotes axonal regeneration after adult CNS injury.

Microglial reactivity correlates to the density and the myelination of the anterogradely degenerating axons and terminals following perforant path denervation of the mouse fascia dentata

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Jensen, M B; Hegelund, I V; Rom Poulsen, Frantz

1999-01-01

Transection of the entorhino-dentate perforant path is a well known model for lesion-induced axonal sprouting and glial reactions in the rat. In this study, we have characterized the microglial reaction in the dentate molecular layer of the SJL/J and C57Bl/6 mouse. The morphological transformatio...... in the individual cases. The finding of a potentiated or accelerated microglial activation in the medial as compared to the lateral perforant path zone suggests different kinetics of microglial activation in areas with degenerating myelinated and unmyelinated fibers....

Internodal function in normal and regenerated mammalian axons

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Moldovan, M; Krarup, C

2007-01-01

AIM: Following Wallerian degeneration, peripheral myelinated axons have the ability to regenerate and, given a proper pathway, establish functional connections with targets. In spite of this capacity, the clinical outcome of nerve regeneration remains unsatisfactory. Early studies have found...... that regenerated internodes remain persistently short though this abnormality did not seem to influence recovery in conduction. It remains unclear to which extent abnormalities in axonal function itself may contribute to the poor outcome of nerve regeneration. METHODS: We review experimental evidence indicating...... that internodes play an active role in axonal function. RESULTS: By investigating internodal contribution to axonal excitability we have found evidence that axonal function may be permanently compromised in regenerated nerves. Furthermore, we illustrate that internodal function is also abnormal in regenerated...

Biology of Schwann cells.

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Kidd, Grahame J; Ohno, Nobuhiko; Trapp, Bruce D

2013-01-01

The fundamental roles of Schwann cells during peripheral nerve formation and regeneration have been recognized for more than 100 years, but the cellular and molecular mechanisms that integrate Schwann cell and axonal functions continue to be elucidated. Derived from the embryonic neural crest, Schwann cells differentiate into myelinating cells or bundle multiple unmyelinated axons into Remak fibers. Axons dictate which differentiation path Schwann cells follow, and recent studies have established that axonal neuregulin1 signaling via ErbB2/B3 receptors on Schwann cells is essential for Schwann cell myelination. Extracellular matrix production and interactions mediated by specific integrin and dystroglycan complexes are also critical requisites for Schwann cell-axon interactions. Myelination entails expansion and specialization of the Schwann cell plasma membrane over millimeter distances. Many of the myelin-specific proteins have been identified, and transgenic manipulation of myelin genes have provided novel insights into myelin protein function, including maintenance of axonal integrity and survival. Cellular events that facilitate myelination, including microtubule-based protein and mRNA targeting, and actin based locomotion, have also begun to be understood. Arguably, the most remarkable facet of Schwann cell biology, however, is their vigorous response to axonal damage. Degradation of myelin, dedifferentiation, division, production of axonotrophic factors, and remyelination all underpin the substantial regenerative capacity of the Schwann cells and peripheral nerves. Many of these properties are not shared by CNS fibers, which are myelinated by oligodendrocytes. Dissecting the molecular mechanisms responsible for the complex biology of Schwann cells continues to have practical benefits in identifying novel therapeutic targets not only for Schwann cell-specific diseases but other disorders in which axons degenerate. Copyright © 2013 Elsevier B.V. All rights

Cross-population myelination covariance of human cerebral cortex.

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Ma, Zhiwei; Zhang, Nanyin

2017-09-01

Cross-population covariance of brain morphometric quantities provides a measure of interareal connectivity, as it is believed to be determined by the coordinated neurodevelopment of connected brain regions. Although useful, structural covariance analysis predominantly employed bulky morphological measures with mixed compartments, whereas studies of the structural covariance of any specific subdivisions such as myelin are rare. Characterizing myelination covariance is of interest, as it will reveal connectivity patterns determined by coordinated development of myeloarchitecture between brain regions. Using myelin content MRI maps from the Human Connectome Project, here we showed that the cortical myelination covariance was highly reproducible, and exhibited a brain organization similar to that previously revealed by other connectivity measures. Additionally, the myelination covariance network shared common topological features of human brain networks such as small-worldness. Furthermore, we found that the correlation between myelination covariance and resting-state functional connectivity (RSFC) was uniform within each resting-state network (RSN), but could considerably vary across RSNs. Interestingly, this myelination covariance-RSFC correlation was appreciably stronger in sensory and motor networks than cognitive and polymodal association networks, possibly due to their different circuitry structures. This study has established a new brain connectivity measure specifically related to axons, and this measure can be valuable to investigating coordinated myeloarchitecture development. Hum Brain Mapp 38:4730-4743, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Prolonged Sox4 expression in oligodendrocytes interferes with normal myelination in the central nervous system.

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Potzner, Michaela R; Griffel, Carola; Lütjen-Drecoll, Elke; Bösl, Michael R; Wegner, Michael; Sock, Elisabeth

2007-08-01

The highly related transcription factors Sox4 and Sox11 are both expressed in oligodendrocyte precursors. Yet whether they have a function in oligodendrocyte development is unknown. By overexpressing Sox4 under the control of 3.1 kb of 5' flanking sequences of the myelin basic protein gene in transgenic mice, we extended Sox4 expression in the oligodendrocyte lineage from oligodendrocyte precursors to cells undergoing terminal differentiation. As a consequence of transgene expression, mice develop the full spectrum of phenotypic traits associated with a severe hypomyelination during the first postnatal weeks. Myelin gene expression was severely reduced, and myelin dramatically thinned in several central nervous system (CNS) regions. Despite these disturbances in CNS myelination, the number of oligodendrocytic cells remained unaltered. Considering that apoptosis rates were normal and proliferation only slightly increased, oligodendrocytes likely persist in a premyelinating to early myelinating state. This shows that prolonged Sox4 expression in cells of the oligodendrocyte lineage is incompatible with the acquisition of a fully mature phenotype and argues that the presence of Sox4, and possibly Sox11, in oligodendrocyte precursors may normally prevent premature differentiation.

Paired immunoglobulin-like receptor B knockout does not enhance axonal regeneration or locomotor recovery after spinal cord injury.

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Nakamura, Yuka; Fujita, Yuki; Ueno, Masaki; Takai, Toshiyuki; Yamashita, Toshihide

2011-01-21

Myelin components that inhibit axonal regeneration are believed to contribute significantly to the lack of axonal regeneration noted in the adult central nervous system. Three proteins found in myelin, Nogo, myelin-associated glycoprotein, and oligodendrocyte-myelin glycoprotein, inhibit neurite outgrowth in vitro. All of these proteins interact with the same receptors, namely, the Nogo receptor (NgR) and paired immunoglobulin-like receptor B (PIR-B). As per previous reports, corticospinal tract (CST) regeneration is not enhanced in NgR-knock-out mice after spinal cord injury. Therefore, we assessed CST regeneration in PIR-B-knock-out mice. We found that hindlimb motor function, as assessed using the Basso mouse scale, footprint test, inclined plane test, and beam walking test, did not differ between the PIR-B-knock-out and wild-type mice after dorsal hemisection of the spinal cord. Further, tracing of the CST fibers after injury did not reveal enhanced axonal regeneration or sprouting in the CST of the PIR-B-knock-out mice. Systemic administration of NEP1-40, a NgR antagonist, to PIR-B knock-out mice did not enhance the regenerative response. These results indicate that PIR-B knock-out is not sufficient to induce extensive axonal regeneration after spinal cord injury.

Dynamics of myelin content decrease in the rat stroke model

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Kisel, A.; Khodanovich, M.; Atochin, D.; Mustafina, L.; Yarnykh, V.

2017-08-01

The majority of studies were usually focused on neuronal death after brain ischemia; however, stroke affects all cell types including oligodendrocytes that form myelin sheath in the CNS. Our study is focused on the changes of myelin content in the ischemic core and neighbor structures in early terms (1, 3 and 10 days) after stroke. Stroke was modeled with middle cerebral artery occlusion (MCAo) in 15 male rats that were divided into three groups by time points after operation. Brain sections were histologically stained with Luxol Fast Blue (LFB) for myelin quantification. The significant demyelination was found in the ischemic core, corpus callosum, anterior commissure, whereas myelin content was increased in caudoputamen, internal capsule and piriform cortex compared with the contralateral hemisphere. The motor cortex showed a significant increase of myelin content on the 1st day and a significant decrease on the 3rd and 10th days after MCAo. These results suggest that stroke influences myelination not only in the ischemic core but also in distant structures.

Multiple sclerosis and anterograde axonal degeneration study by magnetic resonance

International Nuclear Information System (INIS)

Martinez Pardo, P.; Capdevila Cirera, A.; Sanz Marin, P.M.; Gili Planas, J.

1993-01-01

Multiple sclerosis (MS) is a disease of the central nervous system that affects specifically the myelin. Its diagnosis by imaging techniques is, since the development of magnetic resonance (MR), relatively simple, and its occasional association with anterograde axonal degeneration (WD) has been reported. In both disorders, there is a lengthening of the T1 and T2 relaxation times. In the present report, 76 patients with MS with less than 4 plaques in the typical periventricular position were studied retrospectively, resulting in a rate of association with anterograde axonal degeneration of 8%. We consider that in spite of their same behavior in MR,MS and WD, with moreover represent completely different pathologies, are perfectly differential by MR. The S-E images with longer repetition and echo times in the axial and coronal planes have proved to be those most sensitive for this differentiation. Given that MS is specific pathology of then myelin, the axonal damages in delayed until several plaques adjacent to an axon affect it. We consider that this, added to the restriction of our study group (less than 4 plaques), is the cause of the pow percentage of the MS-WD association in our study. (Author)

Cthrc1 is a negative regulator of myelination in Schwann cells.

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Apra, Caroline; Richard, Laurence; Coulpier, Fanny; Blugeon, Corinne; Gilardi-Hebenstreit, Pascale; Vallat, Jean-michel; Lindner, Volkhard; Charnay, Patrick; Decker, Laurence

2012-03-01

The analysis of the molecular mechanisms involved in the initial interaction between neurons and Schwann cells is a key issue in understanding the myelination process. We recently identified Cthrc1 (Collagen triple helix repeat containing 1) as a gene upregulated in Schwann cells upon interaction with the axon. Cthrc1 encodes a secreted protein previously shown to be involved in migration and proliferation in different cell types. We performed a functional analysis of Cthrc1 in Schwann cells by loss-of- and gain-of-function approaches using RNA interference knockdown in cell culture and a transgenic mouse line that overexpresses the gene. This work establishes that Cthrc1 enhances Schwann cell proliferation but prevents myelination. In particular, time-course analysis of myelin formation intransgenic animals reveals that overexpression of Cthrc1 in Schwann cells leads to a delay in myelin formation with cells maintaining a proliferative state. Our data, therefore, demonstrate that Cthrc1 plays a negative regulatory role, fine-tuning the onset of peripheral myelination.

Prolonged Sox4 Expression in Oligodendrocytes Interferes with Normal Myelination in the Central Nervous System▿ †

Science.gov (United States)

Potzner, Michaela R.; Griffel, Carola; Lütjen-Drecoll, Elke; Bösl, Michael R.; Wegner, Michael; Sock, Elisabeth

2007-01-01

The highly related transcription factors Sox4 and Sox11 are both expressed in oligodendrocyte precursors. Yet whether they have a function in oligodendrocyte development is unknown. By overexpressing Sox4 under the control of 3.1 kb of 5′ flanking sequences of the myelin basic protein gene in transgenic mice, we extended Sox4 expression in the oligodendrocyte lineage from oligodendrocyte precursors to cells undergoing terminal differentiation. As a consequence of transgene expression, mice develop the full spectrum of phenotypic traits associated with a severe hypomyelination during the first postnatal weeks. Myelin gene expression was severely reduced, and myelin dramatically thinned in several central nervous system (CNS) regions. Despite these disturbances in CNS myelination, the number of oligodendrocytic cells remained unaltered. Considering that apoptosis rates were normal and proliferation only slightly increased, oligodendrocytes likely persist in a premyelinating to early myelinating state. This shows that prolonged Sox4 expression in cells of the oligodendrocyte lineage is incompatible with the acquisition of a fully mature phenotype and argues that the presence of Sox4, and possibly Sox11, in oligodendrocyte precursors may normally prevent premature differentiation. PMID:17515609

IFNgamma enhances microglial reactions to hippocampal axonal degeneration

DEFF Research Database (Denmark)

Jensen, M B; Hegelund, I V; Lomholt, N D

2000-01-01

periods. Message for the immune cytokine interferon-gamma (IFNgamma) was undetectable, and glial reactivity to axonal lesions occurred as normal in IFNgamma-deficient mice. Microglial responses to lesion-induced neuronal injury were markedly enhanced in myelin basic protein promoter-driven transgenic mice...

Rac1 controls Schwann cell myelination through cAMP and NF2/merlin

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Guo, Li; Moon, Chandra; Niehaus, Karen; Zheng, Yi; Ratner, Nancy

2013-01-01

During peripheral nervous system development, Schwann cells (SCs) surrounding single large axons differentiate into myelinating SCs. Previous studies implicate RhoGTPases in SC myelination, but the mechanisms involved in RhoGTPase regulation of SC myelination are unknown. Here, we show that SC myelination is arrested in Rac1 conditional knockout (Rac1-CKO) mice. Rac1 knockout abrogated phosphorylation of the effector p21-activated kinase (PAK) and decreased NF2/merlin phosphorylation. Mutation of NF2/merlin rescued the myelin deficit in Rac1-CKO mice in vivo, and the shortened processes in cultured Rac1-CKO SCs in vitro. Mechanistically, cyclic adenosine monophosphate (cAMP) levels and E-cadherin expression were decreased in the absence of Rac1, and both were restored by mutation of NF2/merlin. Reduced cAMP is a cause of the myelin deficiency in Rac1-CKO mice, as elevation of cAMP by rolipram in Rac1-CKO mice in vivo allowed myelin formation. Thus NF2/merlin and cAMP function downstream of Rac1 signaling in SC myelination, and cAMP levels control Rac1-regulated SC myelination. PMID:23197717

Aspartoacylase Deficiency in the White Matter of Human Immunodeficiency Virus Encephalitis: Novel Mechanism in Axonal Damage

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Sankar Surendran

2011-01-01

Full Text Available Aspartoacylase/aminoacylase II (ASPA/ACY II is mainly synthesized in oligodendrocytes to contribute in myelin synthesis. Although axonal damage is seen in the brain with human immunodeficiency virus encephalitis (HIVE, ASPA contribution in the pathology is not known. Immunostaining study showed that ASPA protein is reduced in the white matter of patients with HIVE compared to the control. Western blot study further confirmed ASPA deficiency in the HIVE brain compared to the control. This paper suggests that HIVE condition affects ASPA to contribute in myelin loss/axonal damage seen in the disease.

Electrophysiology of Axonal Constrictions

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Johnson, Christopher; Jung, Peter; Brown, Anthony

2013-03-01

Axons of myelinated neurons are constricted at the nodes of Ranvier, where they are directly exposed to the extracellular space and where the vast majority of the ion channels are located. These constrictions are generated by local regulation of the kinetics of neurofilaments the most important cytoskeletal elements of the axon. In this paper we discuss how this shape affects the electrophysiological function of the neuron. Specifically, although the nodes are short (about 1 μm) in comparison to the distance between nodes (hundreds of μm) they have a substantial influence on the conduction velocity of neurons. We show through computational modeling that nodal constrictions (all other features such as numbers of ion channels left constant) reduce the required fiber diameter for a given target conduction velocity by up to 50% in comparison to an unconstricted axon. We further show that the predicted optimal fiber morphologies closely match reported fiber morphologies. Supported by The National Science Foundation (IOS 1146789)

New Insights in the Pathogenesis of Multiple Sclerosis—Role of Acrolein in Neuronal and Myelin Damage

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Riyi Shi

2013-10-01

Full Text Available Multiple sclerosis (MS is an autoimmune disease of the central nervous system (CNS characterized by an inappropriate inflammatory reaction resulting in widespread myelin injury along white matter tracts. Neurological impairment as a result of the disease can be attributed to immune-mediated injury to myelin, axons and mitochondria, but the molecular mechanisms underlying the neuropathy remain incompletely understood. Incomplete mechanistic knowledge hinders the development of therapies capable of alleviating symptoms and slowing disease progression in the long-term. Recently, oxidative stress has been implicated as a key component of neural tissue damage prompting investigation of reactive oxygen species (ROS scavengers as a potential therapeutic option. Despite the establishment of oxidative stress as a crucial process in MS development and progression, ROS scavengers have had limited success in animal studies which has prompted pursuit of an alternative target capable of curtailing oxidative stress. Acrolein, a toxic β-unsaturated aldehyde capable of initiating and perpetuating oxidative stress, has been suggested as a viable point of intervention to guide the development of new treatments. Sequestering acrolein using an FDA-approved compound, hydralazine, offers neuroprotection resulting in dampened symptom severity and slowed disease progression in experimental autoimmune encephalomyelitis (EAE mice. These results provide promise for therapeutic development, indicating the possible utility of neutralizing acrolein to preserve and improve neurological function in MS patients.

A high mitochondrial transport rate characterizes CNS neurons with high axonal regeneration capacity.

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Romain Cartoni

Full Text Available Improving axonal transport in the injured and diseased central nervous system has been proposed as a promising strategy to improve neuronal repair. However, the contribution of each cargo to the repair mechanism is unknown. DRG neurons globally increase axonal transport during regeneration. Because the transport of specific cargos after axonal insult has not been examined systematically in a model of enhanced regenerative capacity, it is unknown whether the transport of all cargos would be modulated equally in injured central nervous system neurons. Here, using a microfluidic culture system we compared neurons co-deleted for PTEN and SOCS3, an established model of high axonal regeneration capacity, to control neurons. We measured the axonal transport of three cargos (mitochondria, synaptic vesicles and late endosomes in regenerating axons and found that the transport of mitochondria, but not the other cargos, was increased in PTEN/SOCS3 co-deleted axons relative to controls. The results reported here suggest a pivotal role for this organelle during axonal regeneration.

Axonal regeneration in zebrafish spinal cord

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Hui, Subhra Prakash

2018-01-01

Abstract In the present review we discuss two interrelated events—axonal damage and repair—known to occur after spinal cord injury (SCI) in the zebrafish. Adult zebrafish are capable of regenerating axonal tracts and can restore full functionality after SCI. Unlike fish, axon regeneration in the adult mammalian central nervous system is extremely limited. As a consequence of an injury there is very little repair of disengaged axons and therefore functional deficit persists after SCI in adult mammals. In contrast, peripheral nervous system axons readily regenerate following injury and hence allow functional recovery both in mammals and fish. A better mechanistic understanding of these three scenarios could provide a more comprehensive insight into the success or failure of axonal regeneration after SCI. This review summarizes the present understanding of the cellular and molecular basis of axonal regeneration, in both the peripheral nervous system and the central nervous system, and large scale gene expression analysis is used to focus on different events during regeneration. The discovery and identification of genes involved in zebrafish spinal cord regeneration and subsequent functional experimentation will provide more insight into the endogenous mechanism of myelination and remyelination. Furthermore, precise knowledge of the mechanism underlying the extraordinary axonal regeneration process in zebrafish will also allow us to unravel the potential therapeutic strategies to be implemented for enhancing regrowth and remyelination of axons in mammals. PMID:29721326

Innate Interferons Regulate CNS Inflammation

DEFF Research Database (Denmark)

Dieu, Ruthe; Khorooshi, Reza M. H.; Mariboe, Anne

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) whose pathology is characterised by demyelination and axonal damage. This results from interplay between CNS-resident glia, infiltrating leukocytes and a plethora of cytokines and chemokines. Currently...... potential IFN-inducing receptor that signals through NF-kB. Receptor activator of NF-kB (RANK) belongs to the TNF-receptor superfamily and has been shown to induce IFN-beta in medullary thymic epithelial cells affecting autoimmune regulatory processes and osteoclast precursor cells in association to bone...

Delayed nerve stimulation promotes axon-protective neurofilament phosphorylation, accelerates immune cell clearance and enhances remyelination in vivo in focally demyelinated nerves.

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Nikki A McLean

Full Text Available Rapid and efficient axon remyelination aids in restoring strong electrochemical communication with end organs and in preventing axonal degeneration often observed in demyelinating neuropathies. The signals from axons that can trigger more effective remyelination in vivo are still being elucidated. Here we report the remarkable effect of delayed brief electrical nerve stimulation (ES; 1 hour @ 20 Hz 5 days post-demyelination on ensuing reparative events in a focally demyelinated adult rat peripheral nerve. ES impacted many parameters underlying successful remyelination. It effected increased neurofilament expression and phosphorylation, both implicated in axon protection. ES increased expression of myelin basic protein (MBP and promoted node of Ranvier re-organization, both of which coincided with the early reappearance of remyelinated axons, effects not observed at the same time points in non-stimulated demyelinated nerves. The improved ES-associated remyelination was accompanied by enhanced clearance of ED-1 positive macrophages and attenuation of glial fibrillary acidic protein expression in accompanying Schwann cells, suggesting a more rapid clearance of myelin debris and return of Schwann cells to a nonreactive myelinating state. These benefits of ES correlated with increased levels of brain derived neurotrophic factor (BDNF in the acute demyelination zone, a key molecule in the initiation of the myelination program. In conclusion, the tremendous impact of delayed brief nerve stimulation on enhancement of the innate capacity of a focally demyelinated nerve to successfully remyelinate identifies manipulation of this axis as a novel therapeutic target for demyelinating pathologies.

Delayed nerve stimulation promotes axon-protective neurofilament phosphorylation, accelerates immune cell clearance and enhances remyelination in vivo in focally demyelinated nerves.

Science.gov (United States)

McLean, Nikki A; Popescu, Bogdan F; Gordon, Tessa; Zochodne, Douglas W; Verge, Valerie M K

2014-01-01

Rapid and efficient axon remyelination aids in restoring strong electrochemical communication with end organs and in preventing axonal degeneration often observed in demyelinating neuropathies. The signals from axons that can trigger more effective remyelination in vivo are still being elucidated. Here we report the remarkable effect of delayed brief electrical nerve stimulation (ES; 1 hour @ 20 Hz 5 days post-demyelination) on ensuing reparative events in a focally demyelinated adult rat peripheral nerve. ES impacted many parameters underlying successful remyelination. It effected increased neurofilament expression and phosphorylation, both implicated in axon protection. ES increased expression of myelin basic protein (MBP) and promoted node of Ranvier re-organization, both of which coincided with the early reappearance of remyelinated axons, effects not observed at the same time points in non-stimulated demyelinated nerves. The improved ES-associated remyelination was accompanied by enhanced clearance of ED-1 positive macrophages and attenuation of glial fibrillary acidic protein expression in accompanying Schwann cells, suggesting a more rapid clearance of myelin debris and return of Schwann cells to a nonreactive myelinating state. These benefits of ES correlated with increased levels of brain derived neurotrophic factor (BDNF) in the acute demyelination zone, a key molecule in the initiation of the myelination program. In conclusion, the tremendous impact of delayed brief nerve stimulation on enhancement of the innate capacity of a focally demyelinated nerve to successfully remyelinate identifies manipulation of this axis as a novel therapeutic target for demyelinating pathologies.

Complement receptor-3 negatively regulates the phagocytosis of degenerated myelin through tyrosine kinase Syk and cofilin

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Hadas Smadar

2012-07-01

Full Text Available Abstract Background Intact myelin, which normally surrounds axons, breaks down in Wallerian degeneration following axonal injury and during neurodegenerative diseases such as multiple sclerosis. Clearance of degenerated myelin by phagocytosis is essential since myelin impedes repair and exacerbates damage. CR3 (complement receptor-3 is a principal phagocytic receptor in myelin phagocytosis. We studied how tyrosine kinase Syk (spleen tyrosine kinase and cofilin control phagocytosis of degenerated myelin by CR3 in microglia and macrophages. Syk is a non-receptor tyrosine kinase that CR3 recruits to convey cellular functions. Cofilin is an actin-depolymerizing protein that controls F-actin (filamentous actin remodeling (i.e., disassembly and reassembly by shifting between active unphosphorylated and inactive phosphorylated states. Results Syk was continuously activated during prolonged phagocytosis. Phagocytosis increased when Syk activity and expression were reduced, suggesting that normally Syk down regulates CR3-mediated myelin phagocytosis. Levels of inactive p-cofilin (phosphorylated cofilin decreased transiently during prolonged phagocytosis. In contrast, p-cofilin levels decreased continuously when Syk activity and expression were continuously reduced, suggesting that normally Syk advances the inactive state of cofilin. Observations also revealed inverse relationships between levels of phagocytosis and levels of inactive p-cofilin, suggesting that active unphosphorylated cofilin advances phagocytosis. Active cofilin could advance phagocytosis by promoting F-actin remodeling, which supports the production of membrane protrusions (e.g., filopodia, which, as we also revealed, are instrumental in myelin phagocytosis. Conclusions CR3 both activates and downregulates myelin phagocytosis at the same time. Activation was previously documented. We presently demonstrate that downregulation is mediated through Syk, which advances the inactive

Axonal and glial currents activated during the post-tetanic hyperpolarization in non-myelinated nerve.

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Robert, A; Jirounek, P

1998-07-01

Changes in membrane potential and potassium concentration in the extracellular space ([K+]e) of rabbit vagus nerve were measured simultaneously during electrical activity and during the period of recovery using a modified sucrose-gap method and potassium-sensitive microelectrodes. After stimulation for 15 s at 15 Hz the main activity-induced increase in [K+]e reached 16.9 mM. This increase in [K+]e was paralleled by a depolarization of the preparation. The period of activity was followed by a post-tetanic hyperpolarization (PTH) lasting tens of seconds, generated by the axonal electrogenic Na+-K+ pump and to a lesser extent by the pump of the surrounding Schwann cells. The amplitude of the PTH dramatically increased in experiments in which inward currents were blocked by removal of Cl– or after application of Cs+ or Ba2+, indicating that under normal conditions the current generated by the Na+-K+ pump is strongly short-circuited. A pharmacological and kinetic study showed that these currents are: (1) the hyperpolarization-activated current I h, and (2) the inwardly rectifying I KIR current. The results show that the latter originates from Schwann cells. Our data indicate that in non-myelinated nerves there is a subtle association of inward ionic channels which (1) helps the cell to maintain an optimal membrane potential after a period of activity, and (2) contributes to the removal of excess K+ from the extracellular space.

Contribution of Schwann Cells to Remyelination in a Naturally Occurring Canine Model of CNS Neuroinflammation.

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Kristel Kegler

Full Text Available Gliogenesis under pathophysiological conditions is of particular clinical relevance since it may provide evidence for regeneration promoting cells recruitable for therapeutic purposes. There is evidence that neurotrophin receptor p75 (p75NTR-expressing cells emerge in the lesioned CNS. However, the phenotype and identity of these cells, and signals triggering their in situ generation under normal conditions and certain pathological situations has remained enigmatic. In the present study, we used a spontaneous, idiopathic and inflammatory CNS condition in dogs with prominent lympho-histiocytic infiltration as a model to study the phenotype of Schwann cells and their relation to Schwann cell remyelination within the CNS. Furthermore, the phenotype of p75NTR-expressing cells within the injured CNS was compared to their counter-part in control sciatic nerve and after peripheral nerve injury. In addition, organotypic slice cultures were used to further elucidate the origin of p75NTR-positive cells. In cerebral and cerebellar white and grey matter lesions as well as in the brain stem, p75NTR-positive cells co-expressed the transcription factor Sox2, but not GAP-43, GFAP, Egr2/Krox20, periaxin and PDGFR-α. Interestingly, and contrary to the findings in control sciatic nerves, p75NTR-expressing cells only co-localized with Sox2 in degenerative neuropathy, thus suggesting that such cells might represent dedifferentiated Schwann cells both in the injured CNS and PNS. Moreover, effective Schwann cell remyelination represented by periaxin- and P0-positive mature myelinating Schwann cells, was strikingly associated with the presence of p75NTR/Sox2-expressing Schwann cells. Intriguingly, the emergence of dedifferentiated Schwann cells was not affected by astrocytes, and a macrophage-dominated inflammatory response provided an adequate environment for Schwann cells plasticity within the injured CNS. Furthermore, axonal damage was reduced in brain stem areas

Local delivery of thyroid hormone enhances oligodendrogenesis and myelination after spinal cord injury

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Shultz, Robert B.; Wang, Zhicheng; Nong, Jia; Zhang, Zhiling; Zhong, Yinghui

2017-06-01

Objective. Traumatic spinal cord injury (SCI) causes apoptosis of myelin-forming oligodendrocytes (OLs) and demyelination of surviving axons, resulting in conduction failure. Remyelination of surviving denuded axons provides a promising therapeutic target for spinal cord repair. While cell transplantation has demonstrated efficacy in promoting remyelination and functional recovery, the lack of ideal cell sources presents a major obstacle to clinical application. The adult spinal cord contains oligodendrocyte precursor cells and multipotent neural stem/progenitor cells that have the capacity to differentiate into mature, myelinating OLs. However, endogenous oligodendrogenesis and remyelination processes are limited by the upregulation of remyelination-inhibitory molecules in the post-injury microenvironment. Multiple growth factors/molecules have been shown to promote OL differentiation and myelination. Approach. In this study we screened these therapeutics and found that 3, 3‧, 5-triiodothyronine (T3) is the most effective in promoting oligodendrogenesis and OL maturation in vitro. However, systemic administration of T3 to achieve therapeutic doses in the injured spinal cord is likely to induce hyperthyroidism, resulting in serious side effects. Main results. In this study we developed a novel hydrogel-based drug delivery system for local delivery of T3 to the injury site without eliciting systemic toxicity. Significance. Using a clinically relevant cervical contusion injury model, we demonstrate that local delivery of T3 at doses comparable to safe human doses promoted new mature OL formation and myelination after SCI.

Gemfibrozil, a lipid-lowering drug, increases myelin genes in human oligodendrocytes via peroxisome proliferator-activated receptor-β.

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Jana, Malabendu; Mondal, Susanta; Gonzalez, Frank J; Pahan, Kalipada

2012-10-05

An increase in CNS remyelination and a decrease in CNS inflammation are important steps to halt the progression of multiple sclerosis. Earlier studies have shown that gemfibrozil, a lipid-lowering drug, has anti-inflammatory properties. The current study identified another novel property of gemfibrozil in stimulating the expression of myelin-specific genes (myelin basic protein, myelin oligodendrocyte glycoprotein, 2',3'-cyclic-nucleotide 3'-phosphodiesterase, and proteolipid protein (PLP)) in primary human oligodendrocytes, mixed glial cells, and spinal cord organotypic cultures. Although gemfibrozil is a known activator of peroxisome proliferator-activated receptor-α (PPAR-α), we were unable to detect PPAR-α in either gemfibrozil-treated or untreated human oligodendrocytes, and gemfibrozil increased the expression of myelin genes in oligodendrocytes isolated from both wild type and PPAR-α(-/-) mice. On the other hand, gemfibrozil markedly increased the expression of PPAR-β but not PPAR-γ. Consistently, antisense knockdown of PPAR-β, but not PPAR-γ, abrogated the stimulatory effect of gemfibrozil on myelin genes in human oligodendrocytes. Gemfibrozil also did not up-regulate myelin genes in oligodendroglia isolated from PPAR-β(-/-) mice. Chromatin immunoprecipitation analysis showed that gemfibrozil induced the recruitment of PPAR-β to the promoter of PLP and myelin oligodendrocyte glycoprotein genes in human oligodendrocytes. Furthermore, gemfibrozil treatment also led to the recruitment of PPAR-β to the PLP promoter in vivo in the spinal cord of experimental autoimmune encephalomyelitis mice and suppression of experimental autoimmune encephalomyelitis symptoms in PLP-T cell receptor transgenic mice. These results suggest that gemfibrozil stimulates the expression of myelin genes via PPAR-β and that gemfibrozil, a prescribed drug for humans, may find further therapeutic use in demyelinating diseases.

Electron microscopic study of the myelinated nerve fibres and the perineurial cell basement membrane in the diabetic human peripheral nerves

International Nuclear Information System (INIS)

ElBarrany, Wagih G.; Hamdy, Raid M.; AlHayani, Abdulmonem A.; Jalalah, Sawsan M.

2009-01-01

To study the quantitative and ultrastructural changes in myelinated nerve fibers and the basement membranes of the perineurial cells in diabetic nerves. The study was performed at the Department of Anatomy, Faculty of Medicine, King Abdul-Aziz University, Jeddah, Saudi Arabia from 2003 to 2005. Human sural nerves were obtained from 15 lower limbs and 5 diabetic nerve biopsies. The total mean and density of myelinated nerve fibers per fascicle were calculated, with density of microtubules and mitochondria in the axoplasm. The number of the perineurial cell basement membrane layers was counted, and thickness of the basement membrane was measured. Among the 15 diabetic and 5 normal human sural nerves, the average diameters, number and surface area of myelinated nerve fibers and axonal microtubules density were found to be less in diabetic nerves. Mitochondrial density was higher in diabetic axons. Thickness of the perineurial cell basement membrane had a greater mean, but the number of perineurial cell layers was less than that of the diabetic group. The inner cellular layer of the perineurium of the diabetic nerves contained large vacuoles containing electron-dense degenerated myelin. A few specimens showed degenerated myelinated nerve fibers, while others showed recovering ones. Retracted axoplasms were encountered with albumin extravasation. Diabetes caused an increase in perineurial permeability. The diabetic sural nerve showed marked decrease in the myelinated nerve fibres, increase degenerated mitochondria, and decreased microtubules. (author)

Tri-partite complex for axonal transport drug delivery achieves pharmacological effect

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Frederickson Martyn

2010-01-01

Full Text Available Abstract Background Targeted delivery of pharmaceutical agents into selected populations of CNS (Central Nervous System neurons is an extremely compelling goal. Currently, systemic methods are generally used for delivery of pain medications, anti-virals for treatment of dermatomal infections, anti-spasmodics, and neuroprotectants. Systemic side effects or undesirable effects on parts of the CNS that are not involved in the pathology limit efficacy and limit clinical utility for many classes of pharmaceuticals. Axonal transport from the periphery offers a possible selective route, but there has been little progress towards design of agents that can accomplish targeted delivery via this intraneural route. To achieve this goal, we developed a tripartite molecular construction concept involving an axonal transport facilitator molecule, a polymer linker, and a large number of drug molecules conjugated to the linker, then sought to evaluate its neurobiology and pharmacological behavior. Results We developed chemical synthesis methodologies for assembling these tripartite complexes using a variety of axonal transport facilitators including nerve growth factor, wheat germ agglutinin, and synthetic facilitators derived from phage display work. Loading of up to 100 drug molecules per complex was achieved. Conjugation methods were used that allowed the drugs to be released in active form inside the cell body after transport. Intramuscular and intradermal injection proved effective for introducing pharmacologically effective doses into selected populations of CNS neurons. Pharmacological efficacy with gabapentin in a paw withdrawal latency model revealed a ten fold increase in half life and a 300 fold decrease in necessary dose relative to systemic administration for gabapentin when the drug was delivered by axonal transport using the tripartite vehicle. Conclusion Specific targeting of selected subpopulations of CNS neurons for drug delivery by axonal

Hydrogels as scaffolds and delivery systems to enhance axonal regeneration after injuries

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Oscar A. Carballo-Molina

2015-02-01

Full Text Available Damage caused to neural tissue by disease or injury frequently produces a discontinuity in the nervous system. Such damage generates diverse alterations that are commonly permanent, due to the limited regeneration capacity of the adult nervous system, particularly the Central Nervous System (CNS. The cellular reaction to noxious stimulus leads to several events such as the formation of glial and fibrous scars, which inhibit axonal regeneration in both the CNS and the Peripheral Nervous System (PNS. Although in the PNS there is some degree of nerve regeneration, it is common that the growing axons reinnervate incorrect areas, causing mismatches. Providing a permissive substrate for axonal regeneration in combination with delivery systems for the release of molecules, which enhances axonal growth, could increase regeneration and the recovery of functions in the CNS or the PNS. Currently, there are no effective vehicles to supply growth factors or cells to the damaged/diseased nervous system. Hydrogels are polymers that are biodegradable, biocompatible and have the capacity to deliver a large range of molecules in situ. The inclusion of cultured neural cells into hydrogels forming three-dimensional structures allows the formation of synapses and neuronal survival. There is also evidence showing that hydrogels constitute an amenable substrate for axonal growth of endogenous or grafted cells, overcoming the presence of axonal regeneration inhibitory molecules, in both the central and peripheral nervous systems. Recent experiments suggest that hydrogels can carry and deliver several proteins relevant for improving neuronal survival and axonal growth. Although the use of hydrogels is appealing, its effectiveness is still a matter of discussion, and more results are needed to achieve consistent recovery using different parameters. This review also discusses areas of opportunity where hydrogels can be applied, in order to promote axonal regeneration of

Investigating the Slow Axonal Transport of Neurofilaments: A Precursor for Optimal Neuronal Signaling

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Johnson, Christopher M.

Neurofilaments are the intermediate filaments of neurons and are the most abundant structure of the neuronal cytoskeleton. Once synthesized within the cell body they are then transported throughout the axon along microtubule tracks, driven by the molecular motors kinesin and dynein. This movement is characterized by long pauses with no movement interrupted by infrequent bouts of rapid movement, resulting in an aggregate dense cytoskeletal structure, which serves to regulate an axon's shape and size. Curiously, the modulated kinetics of these polymers produces a very regular, yet non-uniform, morphology in myelinated axons which are composed of discretely spaced myelin-ensheathed segments that are separated by short constricted regions called "nodes of Ranvier". This unique design optimizes the conduction velocity of myelinated axons at minimal fiber size. Hence, neurofilaments regulate the axon caliber to optimize neuron function. The goal of this dissertation is to investigate the motile mechanism of neurofilament transport as well as the resulting electrophysiological effects that follow. We start by examining highly time-resolved kymograph images generated from recorded neurofilament movement via epifluorescence microscopy. Using kymograph analysis, edge detection algorithms, and pixel smoothing tactics, neurofilament trajectories are extracted and used to obtain statistical distributions for the characteristics of how these filaments move within cells. The results suggest that the observed intermittent and bidirectional motions of these filaments might be explained by a model in which dynein and kinesin motors attach to a single neurofilament cargo and interact through mechanical forces only (i.e. a "tug-of-war" model). We test this hypothesis by developing two discrete-state stochastic models for the kinetic cycles of kinesin and dynein, which are then incorporated into a separate stochastic model that represents the posed tug-of-war scenario. We then

Sensory axon-derived neuregulin-1 is required for axoglial signaling and normal sensory function but not for long-term axon maintenance

DEFF Research Database (Denmark)

Fricker, F.R.; Zhu, N.; Tsantoulas, C.

2009-01-01

" pockets. The total number of axons in the sural nerve was unchanged, but a greater proportion was unmyelinated. In addition, we observed large-diameter axons that were in a 1:1 relationship with Schwann cells, surrounded by a basal lamina but not myelinated. There was no evidence of DRG or Schwann cell...... death; the markers of different DRG cell populations and cutaneous innervation were unchanged. These anatomical changes were reflected in a slowing of conduction velocity at the lower end of the A-fiber conduction velocity range and a new population of more rapidly conducting C-fibers that are likely...

A growing field: The regulation of axonal regeneration by Wnt signaling.

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Garcia, Armando L; Udeh, Adanna; Kalahasty, Karthik; Hackam, Abigail S

2018-01-01

The canonical Wnt/β-catenin pathway is a highly conserved signaling cascade that plays critical roles during embryogenesis. Wnt ligands regulate axonal extension, growth cone guidance and synaptogenesis throughout the developing central nervous system (CNS). Recently, studies in mammalian and fish model systems have demonstrated that Wnt/β-catenin signaling also promotes axonal regeneration in the adult optic nerve and spinal cord after injury, raising the possibility that Wnt could be developed as a therapeutic strategy. In this review, we summarize experimental evidence that reveals novel roles for Wnt signaling in the injured CNS, and discuss possible mechanisms by which Wnt ligands could overcome molecular barriers inhibiting axonal growth to promote regeneration. A central challenge in the neuroscience field is developing therapeutic strategies that induce robust axonal regeneration. Although adult axons have the capacity to respond to axonal guidance molecules after injury, there are several major obstacles for axonal growth, including extensive neuronal death, glial scars at the injury site, and lack of axonal guidance signals. Research in rodents demonstrated that activation of Wnt/β-catenin signaling in retinal neurons and radial glia induced neuronal survival and axonal growth, but that activation within reactive glia at the injury site promoted proliferation and glial scar formation. Studies in zebrafish spinal cord injury models confirm an axonal regenerative role for Wnt/β-catenin signaling and identified the cell types responsible. Additionally, in vitro and in vivo studies demonstrated that Wnt induces axonal and neurite growth through transcription-dependent effects of its central mediator β-catenin, potentially by inducing regeneration-promoting genes. Canonical Wnt signaling may also function through transcription-independent interactions of β-catenin with cytoskeletal elements, which could stabilize growing axons and control growth cone

The retina as a window to the brain-from eye research to CNS disorders.

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London, Anat; Benhar, Inbal; Schwartz, Michal

2013-01-01

Philosophers defined the eye as a window to the soul long before scientists addressed this cliché to determine its scientific basis and clinical relevance. Anatomically and developmentally, the retina is known as an extension of the CNS; it consists of retinal ganglion cells, the axons of which form the optic nerve, whose fibres are, in effect, CNS axons. The eye has unique physical structures and a local array of surface molecules and cytokines, and is host to specialized immune responses similar to those in the brain and spinal cord. Several well-defined neurodegenerative conditions that affect the brain and spinal cord have manifestations in the eye, and ocular symptoms often precede conventional diagnosis of such CNS disorders. Furthermore, various eye-specific pathologies share characteristics of other CNS pathologies. In this Review, we summarize data that support examination of the eye as a noninvasive approach to the diagnosis of select CNS diseases, and the use of the eye as a valuable model to study the CNS. Translation of eye research to CNS disease, and deciphering the role of immune cells in these two systems, could improve our understanding and, potentially, the treatment of neurodegenerative disorders.

Cholesterol regulates the endoplasmic reticulum exit of the major membrane protein P0 required for peripheral myelin compaction.

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Saher, Gesine; Quintes, Susanne; Möbius, Wiebke; Wehr, Michael C; Krämer-Albers, Eva-Maria; Brügger, Britta; Nave, Klaus-Armin

2009-05-13

Rapid impulse conduction requires electrical insulation of axons by myelin, a cholesterol-rich extension of the glial cell membrane with a characteristic composition of proteins and lipids. Mutations in several myelin protein genes cause endoplasmic reticulum (ER) retention and disease, presumably attributable to failure of misfolded proteins to pass the ER quality control. Because many myelin proteins partition into cholesterol-rich membrane rafts, their interaction with cholesterol could potentially be part of the ER quality control system. Here, we provide in vitro and in vivo evidence that the major peripheral myelin protein P0 requires cholesterol for exiting the ER and reaching the myelin compartment. Cholesterol dependency of P0 trafficking in heterologous cells is mediated by a cholesterol recognition/interaction amino acid consensus (CRAC) motif. Mutant mice lacking cholesterol biosynthesis in Schwann cells suffer from severe hypomyelination with numerous uncompacted myelin stretches. This demonstrates that high-level cholesterol coordinates P0 export with myelin membrane synthesis, which is required for the correct stoichiometry of myelin components and for myelin compaction.

Systemic 5-fluorouracil treatment causes a syndrome of delayed myelin destruction in the central nervous system

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Han Ruolan

2008-04-01

Full Text Available Abstract Background Cancer treatment with a variety of chemotherapeutic agents often is associated with delayed adverse neurological consequences. Despite their clinical importance, almost nothing is known about the basis for such effects. It is not even known whether the occurrence of delayed adverse effects requires exposure to multiple chemotherapeutic agents, the presence of both chemotherapeutic agents and the body's own response to cancer, prolonged damage to the blood-brain barrier, inflammation or other such changes. Nor are there any animal models that could enable the study of this important problem. Results We found that clinically relevant concentrations of 5-fluorouracil (5-FU; a widely used chemotherapeutic agent were toxic for both central nervous system (CNS progenitor cells and non-dividing oligodendrocytes in vitro and in vivo. Short-term systemic administration of 5-FU caused both acute CNS damage and a syndrome of progressively worsening delayed damage to myelinated tracts of the CNS associated with altered transcriptional regulation in oligodendrocytes and extensive myelin pathology. Functional analysis also provided the first demonstration of delayed effects of chemotherapy on the latency of impulse conduction in the auditory system, offering the possibility of non-invasive analysis of myelin damage associated with cancer treatment. Conclusions Our studies demonstrate that systemic treatment with a single chemotherapeutic agent, 5-FU, is sufficient to cause a syndrome of delayed CNS damage and provide the first animal model of delayed damage to white-matter tracts of individuals treated with systemic chemotherapy. Unlike that caused by local irradiation, the degeneration caused by 5-FU treatment did not correlate with either chronic inflammation or extensive vascular damage and appears to represent a new class of delayed degenerative damage in the CNS.

Nogo-66 receptor antagonist peptide (NEP1-40) administration promotes functional recovery and axonal growth after lateral funiculus injury in the adult rat

NARCIS (Netherlands)

Cao, Y.; Shumsky, J. S.; Sabol, M. A.; Kushner, R. A.; Strittmatter, S.; Hamers, F. P. T.; Lee, D. H. S.; Rabacchi, S. A.; Murray, M.

2008-01-01

Objective. The myelin protein Nogo inhibits axon regeneration by binding to its receptor (NgR) on axons. Intrathecal delivery of an NgR antagonist (NEP1-40) promotes growth of injured corticospinal axons and recovery of motor function following a dorsal hemisection. The authors used a similar design

Myelination and nodal formation of regenerated peripheral nerve fibers following transplantation of acutely prepared olfactory ensheathing cells

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Dombrowski, Mary A.; Sasaki, Masanori; Lankford, Karen L.; Kocsis, Jeffery D.; Radtke, Christine

2009-01-01

Transplantation of olfactory ensheathing cells (OECs) into injured spinal cord results in improved functional outcome. Mechanisms suggested to account for this functional improvement include axonal regeneration, remyelination and neuroprotection. OECs transplanted into transected peripheral nerve have been shown to modify peripheral axonal regeneration and functional outcome. However, little is known of the detailed integration of OECs at the transplantation site in peripheral nerve. To address this issue cells populations enriched in OECs were isolated from the olfactory bulbs of adult green fluorescent protein (GFP)-expressing transgenic rats and transplanted into a sciatic nerve crush lesion which transects all axons. Five weeks to six months after transplantation the nerves were studied histologically. GFP-expressing OECs survived in the lesion and distributed longitudinally across the lesion zone. The internodal regions of individual teased fibers distal to the transection site were characterized by GFP expression in the cytoplasmic and nuclear compartments of cells surrounding the axons. Immuno-electron microscopy for GFP indicated that the transplanted OECs formed peripheral type myelin. Immunostaining for sodium channel and Caspr revealed a high density of Nav1.6 at the newly formed nodes of Ranvier which were flanked by paranodal Caspr staining. These results indicate that transplanted OECs extensively integrate into transected peripheral nerve and form myelin on regenerated peripheral nerve fibers, and that nodes of Ranvier of these axons display proper sodium channel organization. PMID:17112480

Gemfibrozil, a Lipid-lowering Drug, Increases Myelin Genes in Human Oligodendrocytes via Peroxisome Proliferator-activated Receptor-β*

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Jana, Malabendu; Mondal, Susanta; Gonzalez, Frank J.; Pahan, Kalipada

2012-01-01

An increase in CNS remyelination and a decrease in CNS inflammation are important steps to halt the progression of multiple sclerosis. Earlier studies have shown that gemfibrozil, a lipid-lowering drug, has anti-inflammatory properties. The current study identified another novel property of gemfibrozil in stimulating the expression of myelin-specific genes (myelin basic protein, myelin oligodendrocyte glycoprotein, 2′,3′-cyclic-nucleotide 3′-phosphodiesterase, and proteolipid protein (PLP)) in primary human oligodendrocytes, mixed glial cells, and spinal cord organotypic cultures. Although gemfibrozil is a known activator of peroxisome proliferator-activated receptor-α (PPAR-α), we were unable to detect PPAR-α in either gemfibrozil-treated or untreated human oligodendrocytes, and gemfibrozil increased the expression of myelin genes in oligodendrocytes isolated from both wild type and PPAR-α(−/−) mice. On the other hand, gemfibrozil markedly increased the expression of PPAR-β but not PPAR-γ. Consistently, antisense knockdown of PPAR-β, but not PPAR-γ, abrogated the stimulatory effect of gemfibrozil on myelin genes in human oligodendrocytes. Gemfibrozil also did not up-regulate myelin genes in oligodendroglia isolated from PPAR-β(−/−) mice. Chromatin immunoprecipitation analysis showed that gemfibrozil induced the recruitment of PPAR-β to the promoter of PLP and myelin oligodendrocyte glycoprotein genes in human oligodendrocytes. Furthermore, gemfibrozil treatment also led to the recruitment of PPAR-β to the PLP promoter in vivo in the spinal cord of experimental autoimmune encephalomyelitis mice and suppression of experimental autoimmune encephalomyelitis symptoms in PLP-T cell receptor transgenic mice. These results suggest that gemfibrozil stimulates the expression of myelin genes via PPAR-β and that gemfibrozil, a prescribed drug for humans, may find further therapeutic use in demyelinating diseases. PMID:22879602

Long-lasting increase in axonal excitability after epidurally applied DC.

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Jankowska, Elzbieta; Kaczmarek, Dominik; Bolzoni, Francesco; Hammar, Ingela

2017-08-01

Effects of direct current (DC) on nerve fibers have primarily been investigated during or just after DC application. However, locally applied cathodal DC was recently demonstrated to increase the excitability of intraspinal preterminal axonal branches for >1 h. The aim of this study was therefore to investigate whether DC evokes a similarly long-lasting increase in the excitability of myelinated axons within the dorsal columns. The excitability of dorsal column fibers stimulated epidurally was monitored by recording compound action potentials in peripheral nerves in acute experiments in deeply anesthetized rats. The results show that 1 ) cathodal polarization (0.8-1.0 µA) results in a severalfold increase in the number of epidurally activated fibers and 2 ) the increase in the excitability appears within seconds, 3 ) lasts for >1 h, and 4 ) is activity independent, as it does not require fiber stimulation during the polarization. These features demonstrate an unexplored form of plasticity of myelinated fibers and indicate the conditions under which it develops. They also suggest that therapeutic effects of epidural stimulation may be significantly enhanced if it is combined with DC polarization. In particular, by using DC to increase the number of fibers activated by low-intensity epidural stimuli, the low clinical tolerance to higher stimulus intensities might be overcome. The activity independence of long-lasting DC effects would also allow the use of only brief periods of DC polarization preceding epidural stimulation to increase the effect. NEW & NOTEWORTHY The study indicates a new form of plasticity of myelinated fibers. The differences in time course of DC-evoked increases in the excitability of myelinated nerve fibers in the dorsal columns and in preterminal axonal branches suggest that distinct mechanisms are involved in them. The results show that combining epidural stimulation and transspinal DC polarization may dramatically improve their outcome and

Splanchnic preganglionic neurons in man. III. Morphometry of myelinated fibers of rami communicantes.

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Low, P A; Dyck, P J

1978-01-01

The myelinated fiber (MF) composition of T6-T8 Rami Communicantes were obtained in 9 healthy persons of various ages. The textbook picture that distal rami (DR) contain all of the myelinated fibers and therefore are white, while proximal rami (PR) contain none of them and therefore are grey must be modified. We found that DR usually contained abundant MFs and that PR concordance was found between segmental numbers of intermediolateral nuclei cytons, ventral root small myelinated fibers (SMFs), and rami total small MFs to suggest that both rami probably contain the distal myelinated axons of preganglionic autonomic fibers. Finally, there was an attrition of total MFs of rami with age, similar to what we had previously found for ILC cytons and for root SMFs. The decrease in number of pre-ganglionic autonomic neurons with age is thought to be of sufficient magnitude to account for the dysautonomia of the elderly.

Macrophages Promote Axon Regeneration with Concurrent Neurotoxicity

NARCIS (Netherlands)

Gensel, J.C.; Nakamura, S.; Guan, Z.; Rooijen, van N.; Ankeny, D.P.; Popovich, P.G.

2009-01-01

Activated macrophages can promote regeneration of CNS axons. However, macrophages also release factors that kill neurons. These opposing functions are likely induced simultaneously but are rarely considered together in the same experimental preparation. A goal of this study was to unequivocally

Neutron scattering studies on protein dynamics using the human myelin peripheral membrane protein P2

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Laulumaa Saara

2015-01-01

Full Text Available Myelin is a multilayered proteolipid membrane structure surrounding selected axons in the vertebrate nervous system, which allows the rapid saltatory conduction of nerve impulses. Deficits in myelin formation and maintenance may lead to chronic neurological disease. P2 is an abundant myelin protein from peripheral nerves, binding between two apposing lipid bilayers. We studied the dynamics of the human myelin protein P2 and its mutated P38G variant in hydrated powders using elastic incoherent neutron scattering. The local harmonic vibrations at low temperatures were very similar for both samples, but the mutant protein had increased flexibility and softness close to physiological temperatures. The results indicate that a drastic mutation of proline to glycine at a functional site can affect protein dynamics, and in the case of P2, they may explain functional differences between the two proteins.

Neutron scattering studies on protein dynamics using the human myelin peripheral membrane protein P2

Science.gov (United States)

Laulumaa, Saara; Kursula, Petri; Natali, Francesca

2015-01-01

Myelin is a multilayered proteolipid membrane structure surrounding selected axons in the vertebrate nervous system, which allows the rapid saltatory conduction of nerve impulses. Deficits in myelin formation and maintenance may lead to chronic neurological disease. P2 is an abundant myelin protein from peripheral nerves, binding between two apposing lipid bilayers. We studied the dynamics of the human myelin protein P2 and its mutated P38G variant in hydrated powders using elastic incoherent neutron scattering. The local harmonic vibrations at low temperatures were very similar for both samples, but the mutant protein had increased flexibility and softness close to physiological temperatures. The results indicate that a drastic mutation of proline to glycine at a functional site can affect protein dynamics, and in the case of P2, they may explain functional differences between the two proteins.

Axonal degeneration stimulates the formation of NG2+ cells and oligodendrocytes in the mouse

DEFF Research Database (Denmark)

Nielsen, Helle Hvilsted; Ladeby, Rune; Drøjdahl, Nina

2006-01-01

the response of the NG2+ cells to the different components of demyelinating pathology, we investigated the response of adult NG2+ cells to axonal degeneration in the absence of primary myelin or oligodendrocyte pathology. Axonal degeneration was induced in the hippocampal dentate gyrus of adult mice...... by transection of the entorhino-dentate perforant path projection. The acutely induced degeneration of axons and terminals resulted in a prompt response of NG2+ cells, consisting of morphological transformation, cellular proliferation, and upregulation of NG2 expression days 2-3 after surgery. This was followed...

Diffuse axonal injury: detection of changes in anisotropy of water diffusion by diffusion-weighted imaging

International Nuclear Information System (INIS)

Chan, J.H.M.; Tsui, E.Y.K.; Yuen, M.K.; Peh, W.C.G.; Fong, D.; Fok, K.F.; Leung, K.M.; Fung, K.K.L.

2003-01-01

Myelinated axons of white matter demonstrate prominent directional differences in water diffusion. We performed diffusion-weighted imaging on ten patients with head injury to explore the feasibility of using water diffusion anisotropy for quantitating diffuse axonal injury. We showed significant decrease in diffusion anisotropy indices in areas with or without signal abnormality on T2 and T2*-weighted images. We conclude that the water diffusion anisotropy index a potentially useful, sensitive and quantitative way of diagnosing and assessing patients with diffuse axonal injury. (orig.)

Neurotransmitter signaling in white matter.

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Butt, Arthur M; Fern, Robert F; Matute, Carlos

2014-11-01

White matter (WM) tracts are bundles of myelinated axons that provide for rapid communication throughout the CNS and integration in grey matter (GM). The main cells in myelinated tracts are oligodendrocytes and astrocytes, with small populations of microglia and oligodendrocyte precursor cells. The prominence of neurotransmitter signaling in WM, which largely exclude neuronal cell bodies, indicates it must have physiological functions other than neuron-to-neuron communication. A surprising aspect is the diversity of neurotransmitter signaling in WM, with evidence for glutamatergic, purinergic (ATP and adenosine), GABAergic, glycinergic, adrenergic, cholinergic, dopaminergic and serotonergic signaling, acting via a wide range of ionotropic and metabotropic receptors. Both axons and glia are potential sources of neurotransmitters and may express the respective receptors. The physiological functions of neurotransmitter signaling in WM are subject to debate, but glutamate and ATP-mediated signaling have been shown to evoke Ca(2+) signals in glia and modulate axonal conduction. Experimental findings support a model of neurotransmitters being released from axons during action potential propagation acting on glial receptors to regulate the homeostatic functions of astrocytes and myelination by oligodendrocytes. Astrocytes also release neurotransmitters, which act on axonal receptors to strengthen action potential propagation, maintaining signaling along potentially long axon tracts. The co-existence of multiple neurotransmitters in WM tracts suggests they may have diverse functions that are important for information processing. Furthermore, the neurotransmitter signaling phenomena described in WM most likely apply to myelinated axons of the cerebral cortex and GM areas, where they are doubtless important for higher cognitive function. © 2014 Wiley Periodicals, Inc.

Cross-talk between KLF4 and STAT3 regulates axon regeneration

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Qin, Song; Zou, Yuhua; Zhang, Chun-Li

2013-10-01

Cytokine-induced activation of signal transducer and activator of transcription 3 (STAT3) promotes the regrowth of damaged axons in the adult central nervous system (CNS). Here we show that KLF4 physically interacts with STAT3 upon cytokine-induced phosphorylation of tyrosine 705 (Y705) on STAT3. This interaction suppresses STAT3-dependent gene expression by blocking its DNA-binding activity. The deletion of KLF4 in vivo induces axon regeneration of adult retinal ganglion cells (RGCs) via Janus kinase (JAK)-STAT3 signalling. This regeneration can be greatly enhanced by exogenous cytokine treatment, or removal of an endogenous JAK-STAT3 pathway inhibitor called suppressor of cytokine signalling 3 (SOCS3). These findings reveal an unexpected cross-talk between KLF4 and activated STAT3 in the regulation of axon regeneration that might have therapeutic implications in promoting repair of injured adult CNS.

Ultrastructural study of myelinating cells and sub-pial astrocytes in developing rat spinal cord.

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Nagashima, K

1979-12-01

The anterior funiculus of the spinal cervical cord of post-natal rats was examined ultrastructurally. The myelinating cells found one day after brith contained a large amount of evenly distributed ribosomes up to the outer tongue of mesaxons, representing the cytoplasmic density. These cells were separated by astrocytic processes from the pial basement membrane, even when they were located on the pial surface. Astrocytes contained glial fibrils from one day onwards and often attached their processes to the pial basement membrane. Although the cytoplasmic processes of astrocytes occasionally wrapped axons, they were never shown to form the initial layer of myelin sheaths. However, the tenuous processes of the sub-pial astrocytes were occasionally rolled in myelin lamellae, as if a part of the myelin sheaths was constructed by astrocytic processes. The interpretation for this finding is discussed in relation to function and potency of the astrocytes, and variations and anomalies of nervous ontogeny.

Sox10 Expression in Goldfish Retina and Optic Nerve Head in Controls and after the Application of Two Different Lesion Paradigms.

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Marta Parrilla

Full Text Available The mammalian central nervous system (CNS is unable to regenerate. In contrast, the CNS of fish, including the visual system, is able to regenerate after damage. Moreover, the fish visual system grows continuously throughout the life of the animal, and it is therefore an excellent model to analyze processes of myelination and re-myelination after an injury. Here we analyze Sox10+ oligodendrocytes in the goldfish retina and optic nerve in controls and after two kinds of injuries: cryolesion of the peripheral growing zone and crushing of the optic nerve. We also analyze changes in a major component of myelin, myelin basic protein (MBP, as a marker for myelinated axons. Our results show that Sox10+ oligodendrocytes are located in the retinal nerve fiber layer and along the whole length of the optic nerve. MBP was found to occupy a similar location, although its loose appearance in the retina differed from the highly organized MBP+ axon bundles in the optic nerve. After optic nerve crushing, the number of Sox10+ cells decreased in the crushed area and in the optic nerve head. Consistent with this, myelination was highly reduced in both areas. In contrast, after cryolesion we did not find changes in the Sox10+ population, although we did detect some MBP- degenerating areas. We show that these modifications in Sox10+ oligodendrocytes are consistent with their role in oligodendrocyte identity, maintenance and survival, and we propose the optic nerve head as an excellent area for research aimed at better understanding of de- and remyelination processes.

Activation of Sterol Regulatory Element Binding Factors by Fenofibrate and Gemfibrozil Stimulate Myelination in Zebrafish

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Yuhei Nishimura

2016-07-01

Full Text Available Oligodendrocytes are major myelin-producing cells and play essential roles in the function of a healthy nervous system. However, they are also one of the most vulnerable neural cell types in the central nervous system (CNS, and myelin abnormalities in the CNS are found in a wide variety of neurological disorders, including multiple sclerosis, adrenoleukodystrophy, and schizophrenia. There is an urgent need to identify small molecular weight compounds that can stimulate myelination. In this study, we performed comparative transcriptome analysis to identify pharmacodynamic effects common to miconazole and clobetasol, which have been shown to stimulate myelination by mouse oligodendrocyte progenitor cells (OPCs. Of the genes differentially expressed in both miconazole- and clobetasol-treated mouse OPCs compared with untreated cells, we identified differentially expressed genes (DEGs common to both drug treatments. Gene ontology analysis revealed that these DEGs are significantly associated with the sterol biosynthetic pathway, and further bioinformatics analysis suggested that sterol regulatory element binding factors (SREBFs might be key upstream regulators of the DEGs. In silico screening of a public database for chemicals associated with SREBF activation identified fenofibrate, a peroxisome proliferator-activated receptor α (PPARα agonist, as a drug that increases the expression of known SREBF targets, raising the possibility that fenofibrate may also stimulate myelination. To test this, we performed in vivo imaging of zebrafish expressing a fluorescent reporter protein under the control of the myelin basic protein (mbp promoter. Treatment of zebrafish with fenofibrate significantly increased expression of the fluorescent reporter compared with untreated zebrafish. This increase was attenuated by co-treatment with fatostatin, a specific inhibitor of SREBFs, confirming that the fenofibrate effect was mediated via SREBFs. Furthermore, incubation

Retinal glia promote dorsal root ganglion axon regeneration.

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Barbara Lorber

Full Text Available Axon regeneration in the adult central nervous system (CNS is limited by several factors including a lack of neurotrophic support. Recent studies have shown that glia from the adult rat CNS, specifically retinal astrocytes and Müller glia, can promote regeneration of retinal ganglion cell axons. In the present study we investigated whether retinal glia also exert a growth promoting effect outside the visual system. We found that retinal glial conditioned medium significantly enhanced neurite growth and branching of adult rat dorsal root ganglion neurons (DRG in culture. Furthermore, transplantation of retinal glia significantly enhanced regeneration of DRG axons past the dorsal root entry zone after root crush in adult rats. To identify the factors that mediate the growth promoting effects of retinal glia, mass spectrometric analysis of retinal glial conditioned medium was performed. Apolipoprotein E and secreted protein acidic and rich in cysteine (SPARC were found to be present in high abundance, a finding further confirmed by western blotting. Inhibition of Apolipoprotein E and SPARC significantly reduced the neuritogenic effects of retinal glial conditioned medium on DRG in culture, suggesting that Apolipoprotein E and SPARC are the major mediators of this regenerative response.

Analysis of axonal regeneration in the central and peripheral nervous systems of the NG2-deficient mouse

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Lieberman Alexander R

2007-09-01

Full Text Available Abstract Background The chondroitin sulphate proteoglycan NG2 blocks neurite outgrowth in vitro and has been proposed as a major inhibitor of axonal regeneration in the CNS. Although a substantial body of evidence underpins this hypothesis, it is challenged by recent findings including strong expression of NG2 in regenerating peripheral nerve. Results We studied axonal regeneration in the PNS and CNS of genetically engineered mice that do not express NG2, and in sex and age matched wild-type controls. In the CNS, we used anterograde tracing with BDA to study corticospinal tract (CST axons after spinal cord injury and transganglionic labelling with CT-HRP to trace ascending sensory dorsal column (DC axons after DC lesions and a conditioning lesion of the sciatic nerve. Injury to these fibre tracts resulted in no difference between knockout and wild-type mice in the ability of CST axons or DC axons to enter or cross the lesion site. Similarly, after dorsal root injury (with conditioning lesion, most regenerating dorsal root axons failed to grow across the dorsal root entry zone in both transgenic and wild-type mice. Following sciatic nerve injuries, functional recovery was assessed by analysis of the toe-spreading reflex and cutaneous sensitivity to Von Frey hairs. Anatomical correlates of regeneration were assessed by: retrograde labelling of regenerating dorsal root ganglion (DRG cells with DiAsp; immunostaining with PGP 9.5 to visualise sensory reinnervation of plantar hindpaws; electron microscopic analysis of regenerating axons in tibial and digital nerves; and by silver-cholinesterase histochemical study of motor end plate reinnervation. We also examined functional and anatomical correlates of regeneration after injury of the facial nerve by assessing the time taken for whisker movements and corneal reflexes to recover and by retrograde labelling of regenerated axons with Fluorogold and DiAsp. None of the anatomical or functional analyses

Axonal Membranes and Their Domains: Assembly and Function of the Axon Initial Segment and Node of Ranvier

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Andrew D. Nelson

2017-05-01

Full Text Available Neurons are highly specialized cells of the nervous system that receive, process and transmit electrical signals critical for normal brain function. Here, we review the intricate organization of axonal membrane domains that facilitate rapid action potential conduction underlying communication between complex neuronal circuits. Two critical excitable domains of vertebrate axons are the axon initial segment (AIS and the nodes of Ranvier, which are characterized by the high concentrations of voltage-gated ion channels, cell adhesion molecules and specialized cytoskeletal networks. The AIS is located at the proximal region of the axon and serves as the site of action potential initiation, while nodes of Ranvier, gaps between adjacent myelin sheaths, allow rapid propagation of the action potential through saltatory conduction. The AIS and nodes of Ranvier are assembled by ankyrins, spectrins and their associated binding partners through the clustering of membrane proteins and connection to the underlying cytoskeleton network. Although the AIS and nodes of Ranvier share similar protein composition, their mechanisms of assembly are strikingly different. Here we will cover the mechanisms of formation and maintenance of these axonal excitable membrane domains, specifically highlighting the similarities and differences between them. We will also discuss recent advances in super resolution fluorescence imaging which have elucidated the arrangement of the submembranous axonal cytoskeleton revealing a surprising structural organization necessary to maintain axonal organization and function. Finally, human mutations in axonal domain components have been associated with a growing number of neurological disorders including severe cognitive dysfunction, epilepsy, autism, neurodegenerative diseases and psychiatric disorders. Overall, this review highlights the assembly, maintenance and function of axonal excitable domains, particularly the AIS and nodes of

Enhanced uptake of multiple sclerosis-derived myelin by THP-1 macrophages and primary human microglia.

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Hendrickx, Debbie A E; Schuurman, Karianne G; van Draanen, Michael; Hamann, Jörg; Huitinga, Inge

2014-03-31

The pathological hallmark of multiple sclerosis (MS) is myelin phagocytosis. It remains unclear why microglia and macrophages demyelinate axons in MS, but previously found or yet-unknown changes in the myelin of MS patients could contribute to this process. We therefore studied whether myelin from normal-appearing white matter (NAWM) of MS donors is phagocytosed more efficiently than myelin from control donors. Myelin was isolated from 11 MS and 12 control brain donors and labeled with the pH-sensitive fluorescent dye pHrodo to quantify uptake in lysosomes. Phagocytosis by differentiated THP-1 macrophages and by primary human microglia was quantified with flow cytometry. Whereas myelin uptake by THP-1 macrophages reached a plateau after approximately 24 hours, uptake by primary human microglia showed an almost linear increase over a 72-hour period. Data were statistically analyzed with the Mann-Whitney U test. MS-derived myelin was phagocytosed more efficiently by THP-1 macrophages after 6-hour incubation (P = 0.001 for the percentage of myelin-phagocytosing cells and P = 0.0005 for total myelin uptake) and after 24-hour incubation (P = 0.0006 and P = 0.0001, respectively), and by microglia after 24-hour incubation (P = 0.0106 for total myelin uptake). This enhanced uptake was not due to differences in the oxidation status of the myelin. Interestingly, myelin phagocytosis correlated negatively with the age of myelin donors, whereas the age of microglia donors showed a positive trend with myelin phagocytosis. Myelin isolated from normal-appearing white matter of MS donors was phagocytosed more efficiently than was myelin isolated from control brain donors by both THP-1 macrophages and primary human microglia. These data indicate that changes in MS myelin might precede phagocyte activation and subsequent demyelination in MS. Identifying these myelin changes responsible for enhancing phagocytic ability could be an interesting therapeutic target to

Pathogenesis of axonal dystrophy and demyelination in alphaA-crystallin-expressing transgenic mice.

NARCIS (Netherlands)

Rijk, A. van; Sweers, M.A.; Merkx, G.F.M.; Lammens, M.M.Y.; Bloemendal, H.

2003-01-01

We recently described a transgenic mouse strain overexpressing hamster alphaA-crystallin, a small heat shock protein, under direction of the hamster vimentin promoter. As a result myelin was degraded and axonal dystrophy in both central nervous system (especially spinal cord) and peripheral nervous

Pericytes Stimulate Oligodendrocyte Progenitor Cell Differentiation during CNS Remyelination

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Alerie Guzman De La Fuente

2017-08-01

Full Text Available The role of the neurovascular niche in CNS myelin regeneration is incompletely understood. Here, we show that, upon demyelination, CNS-resident pericytes (PCs proliferate, and parenchymal non-vessel-associated PC-like cells (PLCs rapidly develop. During remyelination, mature oligodendrocytes were found in close proximity to PCs. In Pdgfbret/ret mice, which have reduced PC numbers, oligodendrocyte progenitor cell (OPC differentiation was delayed, although remyelination proceeded to completion. PC-conditioned medium accelerated and enhanced OPC differentiation in vitro and increased the rate of remyelination in an ex vivo cerebellar slice model of demyelination. We identified Lama2 as a PC-derived factor that promotes OPC differentiation. Thus, the functional role of PCs is not restricted to vascular homeostasis but includes the modulation of adult CNS progenitor cells involved in regeneration.

From the "little brain" gastrointestinal infection to the "big brain" neuroinflammation: a proposed fast axonal transport pathway involved in multiple sclerosis.

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Deretzi, Georgia; Kountouras, Jannis; Grigoriadis, Nikolaos; Zavos, Christos; Chatzigeorgiou, Stavros; Koutlas, Evangelos; Tsiptsios, Iakovos

2009-11-01

The human central nervous system (CNS) is targeted by different pathogens which, apart from pathogens' intranasal inoculation or trafficking into the brain through infected blood cells, may use a distinct pathway to bypass the blood-brain barrier by using the gastrointestinal tract (GIT) retrograde axonal transport through sensory or motor fibres. The recent findings regarding the enteric nervous system (often called the "little brain") similarities with CNS and GIT axonal transport of infections resulting in CNS neuroinflammation are mainly reviewed in this article. We herein propose that the GIT is the vulnerable area through which pathogens (such as Helicobacter pylori) may influence the brain and induce multiple sclerosis pathologies, mainly via the fast axonal transport by the afferent neurones connecting the GIT to brain.

Abbreviated exposure to hypoxia is sufficient to induce CNS dysmyelination, modulate spinal motor neuron composition, and impair motor development in neonatal mice.

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Jens O Watzlawik

Full Text Available Neonatal white matter injury (nWMI is an increasingly common cause of cerebral palsy that results predominantly from hypoxic injury to progenitor cells including those of the oligodendrocyte lineage. Existing mouse models of nWMI utilize prolonged periods of hypoxia during the neonatal period, require complex cross-fostering and exhibit poor growth and high mortality rates. Abnormal CNS myelin composition serves as the major explanation for persistent neuro-motor deficits. Here we developed a simplified model of nWMI with low mortality rates and improved growth without cross-fostering. Neonatal mice are exposed to low oxygen from postnatal day (P 3 to P7, which roughly corresponds to the period of human brain development between gestational weeks 32 and 36. CNS hypomyelination is detectable for 2-3 weeks post injury and strongly correlates with levels of body and brain weight loss. Immediately following hypoxia treatment, cell death was evident in multiple brain regions, most notably in superficial and deep cortical layers as well as the subventricular zone progenitor compartment. PDGFαR, Nkx2.2, and Olig2 positive oligodendrocyte progenitor cell were significantly reduced until postnatal day 27. In addition to CNS dysmyelination we identified a novel pathological marker for adult hypoxic animals that strongly correlates with life-long neuro-motor deficits. Mice reared under hypoxia reveal an abnormal spinal neuron composition with increased small and medium diameter axons and decreased large diameter axons in thoracic lateral and anterior funiculi. Differences were particularly pronounced in white matter motor tracts left and right of the anterior median fissure. Our findings suggest that 4 days of exposure to hypoxia are sufficient to induce experimental nWMI in CD1 mice, thus providing a model to test new therapeutics. Pathological hallmarks of this model include early cell death, decreased OPCs and hypomyelination in early postnatal life

Crystal structure of the extracellular domain of human myelin protein zero

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Liu, Zhigang; Wang, Yong; Yedidi, Ravikiran S.; Brunzelle, Joseph S.; Kovari, Iulia A.; Sohi, Jasloveleen; Kamholz, John; Kovari, Ladislau C. (WSU-MED); (NWU)

2012-03-27

different mutations in the MPZ gene leading to peripheral neuropathy in patients have been reported worldwide (http://www.molgen. ua.ac.be/CMTMutations). All identified mutations resulting in a change or deletion of amino acid residues in MPZ give rise to neuropathy with the exception of R215L, which instead causes a benign polymorphism. Furthermore, more detailed analysis has classified the MPZ mutations into two major groups. In the first group, the mutations disrupt the intracellular processing of MPZ and are primarily associated with early onset neuropathy. It has been proposed that the mutated MPZ is trapped inside the cell rather than being transported to the plasma membrane. However, other evidence suggests that the mutated MPZ protein is expressed on the plasma membrane, but dominant-negatively disrupts the structure of myelin. In the second group, the MPZ mutations are associated with late onset neuropathy as these mutations cause only mild demyelination. The underlying mechanism is elusive with the hypothesis being that the second group of mutations cause minor abnormalities in the myelin sheath that over time may lead to aberrant Schwann cell-axon interactions and subsequently to axonal degeneration. The crystal structure of the extracellular domain of human MPZ (hP0ex) fused with maltose binding protein (MBP) is reported at 2.1 {angstrom} resolution. While the crystal structure of rat MPZ extracellular domain (rP0ex) is available, the crystal structure of the human counterpart is useful for the analysis of the two homologs as well as a comparison between the two species. The hP0ex molecule reveals subtle structural variations between two homologs allowing comparison of the human myelin protein zero to that of the rat protein. The alignment of these homologs is shown in Figure 1(a).

Myelin repair by Schwann cells in the regenerating goldfish visual pathway: regional patterns revealed by X-irradiation

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Nona, S.N.; Stafford, C.A.; Cronly-Dillon, J.R. (Manchester Univ. (United Kingdom). Inst. of Science and Technology); Duncan, A. (Guy' s Hospital, London (United Kingdom). Dept. of Anatomy); Scholes, J. (University Coll., London (United Kingdom))

1994-07-01

In the regenerating goldfish optic nerves, Schwann cells of unknown origin reliably infiltrate the lesion site forming a band of peripheral-type myelinating tissue by 1-2 months, sharply demarcated form the adjacent new CNS myelin. To investigate this effect, we have interfered with cell proliferation by locally X-irradiating the fish visual pathway 24 h after the lesion. As assayed by immunohistochemistry and EM, irradiation retards until 6 months formation of new myelin by Schwann cells at the lesion site, and virtually abolishes oligodendrocyte myelination distally, but has little or no effect on nerve fibre regrowth. Optic nerve astrocyte processes normally fail to re-infiltrate the lesion, but re-occupy it after irradiation, suggesting that they are normally excluded by early cell proliferation at this site. Moreover, scattered myelinating Schwann cells also appear in the oligodendrocyte-depleted distal optic nerve after irradiation, although only as far as the optic tract. (Author).

Dual action of a dinoflagellate-derived precursor of Pacific ciguatoxins (P-CTX-4B) on voltage-dependent K(+) and Na(+) channels of single myelinated axons.

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Schlumberger, Sébastien; Mattei, César; Molgó, Jordi; Benoit, Evelyne

2010-10-01

The effects of Pacific ciguatoxin-4B (P-CTX-4B, also named gambiertoxin), extracted from toxic Gambierdiscus dinoflagellates, were assessed on nodal K(+) and Na(+) currents of frog myelinated axons, using a conventional voltage-clamp technique. P-CTX-4B decreased, within a few minutes, both K(+) and Na(+) currents in a dose-dependent manner, without inducing any marked change in current kinetics. The toxin was more effective in blocking K(+) than Na(+) channels. P-CTX-4B shifted the voltage-dependence of Na(+) conductance by about 14 mV towards more negative membrane potentials. This effect was reversed by increasing Ca(2+) in the external solution. A negative shift of about 16 mV in the steady-state Na(+) inactivation-voltage curve was also observed in the presence of the toxin. Unmodified and P-CTX-4B-modified Na(+) currents were similarly affected by the local anaesthetic lidocaine. The decrease of the two currents by lidocaine was dependent on both the concentration and the membrane potential during pre-pulses. In conclusion, P-CTX-4B appears about four times more effective than P-CTX-1B to affect K(+) channels, whereas it is about 50 times less efficient to affect Na(+) channels of axonal membranes. These actions may be related to subtle differences between the two chemical structures of molecules. Copyright 2009 Elsevier Ltd. All rights reserved.

Dynamics of oligodendrocyte responses to anterograde axonal (Wallerian) and terminal degeneration in normal and TNF-transgenic mice

DEFF Research Database (Denmark)

Drøjdahl, Nina; Fenger, Christina; Nielsen, Helle H

2004-01-01

degeneration and lesion-induced axonal sprouting in the hippocampal dentate gyrus in TNF-transgenic mice with the response in genetically normal mice. Transectioning of the entorhino-dentate perforant path axonal projection increased hippocampal TNF mRNA expression in both types of mice, but to significantly...... larger levels in the TNF-transgenics. At 5 days after axonal transection, numbers of oligodendrocytes and myelin basic protein (MBP) mRNA expression in the denervated dentate gyrus in TNF-transgenic mice had increased to the same extent as in nontransgenic littermates. At this time, transgenics showed...

Disruption of myelination by diagnostic US

International Nuclear Information System (INIS)

Ellisman, M.H.; Palmer, D.E.; Andre, M.P.

1986-01-01

In order to test for possible effects of US on myelination, the authors exposed 20 unanesthetized rat pups to US intensities consistent with those used for imaging a human fetus in utero. The rats were 3-5 days old and at a stage of myelination similar to that of a human fetus of about 4-5 months. Then animals were exposed for 30 minutes to the beam from a 3.5-MHz transducer (ADR 2130 real-time linear array, SPTA intensity of 0.4 mW/cm/sup 2/ and SATA intensity of 0.05 mW/cm/sup 2/). Control animals were bound and placed in the tank but not exposed for 30 minutes, and taken straight from the cage. Some animals were killed and tissues were processed for electron microscopy immediately after exposure, others were killed after recovery periods of up to 24 hours. Enlargements of the periaxonal space was visible with separation of adjacent paranodal loops and disruption of Schwann cell-axonal junctions in all exposed animals. Paranodal demyelination was also noted in several nodes. Nodes exhibiting this microedematous morphology were apparent even after a 24-hour recovery period but were not found in control preparations

Real-time CARS imaging reveals a calpain-dependent pathway for paranodal myelin retraction during high-frequency stimulation.

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Terry B Huff

2011-03-01

Full Text Available High-frequency electrical stimulation is becoming a promising therapy for neurological disorders, however the response of the central nervous system to stimulation remains poorly understood. The current work investigates the response of myelin to electrical stimulation by laser-scanning coherent anti-Stokes Raman scattering (CARS imaging of myelin in live spinal tissues in real time. Paranodal myelin retraction at the nodes of Ranvier was observed during 200 Hz electrical stimulation. Retraction was seen to begin minutes after the onset of stimulation and continue for up to 10 min after stimulation was ceased, but was found to reverse after a 2 h recovery period. The myelin retraction resulted in exposure of Kv 1.2 potassium channels visualized by immunofluorescence. Accordingly, treating the stimulated tissue with a potassium channel blocker, 4-aminopyridine, led to the appearance of a shoulder peak in the compound action potential curve. Label-free CARS imaging of myelin coupled with multiphoton fluorescence imaging of immuno-labeled proteins at the nodes of Ranvier revealed that high-frequency stimulation induced paranodal myelin retraction via pathologic calcium influx into axons, calpain activation, and cytoskeleton degradation through spectrin break-down.

Dynamic Changes of Neuroskeletal Proteins in DRGs Underlie Impaired Axonal Maturation and Progressive Axonal Degeneration in Type 1 Diabetes

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Hideki Kamiya

2009-01-01

Full Text Available We investigated mechanisms underlying progressive axonal dysfunction and structural deficits in type 1 BB/Wor-rats from 1 week to 10 month diabetes duration. Motor and sensory conduction velocities were decreased after 4 and 6 weeks of diabetes and declined further over the remaining 9 months. Myelinated sural nerve fibers showed progressive deficits in fiber numbers and sizes. Structural deficits in unmyelinated axonal size were evident at 2 month and deficits in number were present at 4 mo. These changes were preceded by decreased availability of insulin, C-peptide and IGF-1 and decreased expression of neurofilaments and β-III-tubulin. Upregulation of phosphorylating stress kinases like Cdk5, p-GSK-3β, and p42/44 resulted in increased phosphorylation of neurofilaments. Increasing activity of p-GSK-3β correlated with increasing phosphorylation of NFH, whereas decreasing Cdk5 correlated with diminishing phosphorylation of NFM. The data suggest that impaired neurotrophic support results in sequentially impaired synthesis and postranslational modifications of neuroskeletal proteins, resulting in progressive deficits in axonal function, maturation and size.

Tamoxifen Promotes Axonal Preservation and Gait Locomotion Recovery after Spinal Cord Injury in Cats

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Braniff de la Torre Valdovinos

2016-01-01

Full Text Available We performed experiments in cats with a spinal cord penetrating hemisection at T13-L1 level, with and without tamoxifen treatment. The results showed that the numbers of the ipsilateral and contralateral ventral horn neurons were reduced to less than half in the nontreated animals compared with the treated ones. Also, axons myelin sheet was preserved to almost normal values in treated cats. On the contrary, in the untreated animals, their myelin sheet was reduced to 28% at 30 days after injury (DAI, in both the ipsilateral and contralateral regions of the spinal cord. Additionally, we made hindlimb kinematics experiments to study the effects of tamoxifen on cat locomotion after the injury: at 4, 16, and 30 DAI. We observed that the ipsilateral hindlimb angular displacement (AD of the pendulum-like movements (PLM during gait locomotion was recovered to almost normal values in treated cats. Contralateral PLM acquired similar values to those obtained in intact cats. At 4 DAI, untreated animals showed a compensatory increment of PLM occurring in the contralateral hindlimb, which was partially recovered at 30 DAI. Our findings indicate that tamoxifen exerts a neuroprotective effect and preserves or produces myelinated axons, which could benefit the locomotion recovery in injured cats.

Growth of White Matter in the Adolescent Brain: Myelin or Axon?

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Paus, Tomas

2010-01-01

White matter occupies almost half of the human brain. It contains axons connecting spatially segregated modules and, as such, it is essential for the smooth flow of information in functional networks. Structural maturation of white matter continues during adolescence, as reflected in age-related changes in its volume, as well as in its…

Conduction of impulses by axons regenerated in a Schwann cell graft in the transected adult rat thoracic spinal cord.

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Pinzon, A; Calancie, B; Oudega, M; Noga, B R

2001-06-01

Central nervous system axons regenerate into a Schwann cell implant placed in the transected thoracic spinal cord of an adult rat. The present study was designed to test whether these regenerated axons are capable of conducting action potentials. Following the transection and removal of a 4- to 5-mm segment of the thoracic spinal cord (T8-T9), a polymer guidance channel filled with a mixture of adult rat Schwann cells and Matrigel was grafted into a 4- to 5-mm-long gap in the transected thoracic spinal cord. The two cut ends of the spinal cord were eased into the guidance channel openings. Transected control animals received a channel containing Matrigel only. Three months after implantation, electrophysiological studies were performed. Tungsten microelectrodes were used for monopolar stimulation of regenerated axons within the Schwann cell graft. Glass microelectrodes were used to record responses in the spinal cord rostral to the stimulation site. Evoked responses to electrical stimulation of the axon cable were found in two out of nine Schwann cell-grafted animals. These responses had approximate latencies in the range of those of myelinated axons. No responses were seen in any of the Matrigel-grafted animals. Histological analysis revealed that the two cases that showed evoked potentials had the largest number of myelinated axons present in the cable. This study demonstrates that axons regenerating through Schwann cell grafts in the complete transected spinal cord can produce measurable evoked responses following electrical stimulation. Copyright 2001 Wiley-Liss, Inc.

Spontaneous axonal regeneration in rodent spinal cord after ischemic injury

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von Euler, Mia; Janson, A M; Larsen, Jytte Overgaard

2002-01-01

cells, while other fibers were unmyelinated. Immunohistochemistry demonstrated that some of the regenerated fibers were tyrosine hydroxylase- or serotonin-immunoreactive, indicating a central origin. These findings suggest that there is a considerable amount of spontaneous regeneration after spinal cord......Here we present evidence for spontaneous and long-lasting regeneration of CNS axons after spinal cord lesions in adult rats. The length of 200 kD neurofilament (NF)-immunolabeled axons was estimated after photochemically induced ischemic spinal cord lesions using a stereological tool. The total...... length of all NF-immunolabeled axons within the lesion cavities was increased 6- to 10-fold at 5, 10, and 15 wk post-lesion compared with 1 wk post-surgery. In ultrastructural studies we found the putatively regenerating axons within the lesion to be associated either with oligodendrocytes or Schwann...

Spider silk constructs enhance axonal regeneration and remyelination in long nerve defects in sheep.

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Christine Radtke

Full Text Available BACKGROUND: Surgical reapposition of peripheral nerve results in some axonal regeneration and functional recovery, but the clinical outcome in long distance nerve defects is disappointing and research continues to utilize further interventional approaches to optimize functional recovery. We describe the use of nerve constructs consisting of decellularized vein grafts filled with spider silk fibers as a guiding material to bridge a 6.0 cm tibial nerve defect in adult sheep. METHODOLOGY/PRINCIPAL FINDINGS: The nerve constructs were compared to autologous nerve grafts. Regeneration was evaluated for clinical, electrophysiological and histological outcome. Electrophysiological recordings were obtained at 6 months and 10 months post surgery in each group. Ten months later, the nerves were removed and prepared for immunostaining, electrophysiological and electron microscopy. Immunostaining for sodium channel (NaV 1.6 was used to define nodes of Ranvier on regenerated axons in combination with anti-S100 and neurofilament. Anti-S100 was used to identify Schwann cells. Axons regenerated through the constructs and were myelinated indicating migration of Schwann cells into the constructs. Nodes of Ranvier between myelin segments were observed and identified by intense sodium channel (NaV 1.6 staining on the regenerated axons. There was no significant difference in electrophysiological results between control autologous experimental and construct implantation indicating that our construct are an effective alternative to autologous nerve transplantation. CONCLUSIONS/SIGNIFICANCE: This study demonstrates that spider silk enhances Schwann cell migration, axonal regrowth and remyelination including electrophysiological recovery in a long-distance peripheral nerve gap model resulting in functional recovery. This improvement in nerve regeneration could have significant clinical implications for reconstructive nerve surgery.

Transfer of vesicles from Schwann cell to axon: a novel mechanism of communication in the peripheral nervous system

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María Alejandra eLopez-Verrilli

2012-06-01

Full Text Available Schwann cells (SCs are the glial component of the peripheral nervous system, with essential roles during development and maintenance of axons, as well as during regenerative processes after nerve injury. SCs increase conduction velocities by myelinating axons, regulate synaptic activity at presynaptic nerve terminals and are a source of trophic factors to neurons. Thus, development and maintenance of peripheral nerves are crucially dependent on local signalling between SCs and axons. In addition to the classic mechanisms of intercellular signalling, the possibility of communication through secreted vesicles has been poorly explored to date. Interesting recent findings suggest the occurrence of lateral transfer mediated by vesicles from glial cells to axons that could have important roles in axonal growth and axonal regeneration. Here, we review the role of vesicular transfer from SCs to axons and propose the benefits of this means in supporting neuronal and axonal maintenance and regeneration after nerve damage.

Exposure to the Epstein–Barr Viral Antigen Latent Membrane Protein 1 Induces Myelin-Reactive Antibodies In Vivo

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Yakov Lomakin

2017-07-01

Full Text Available Multiple sclerosis (MS is an autoimmune chronic inflammatory disease of the central nervous system (CNS. Cross-reactivity of neuronal proteins with exogenous antigens is considered one of the possible mechanisms of MS triggering. Previously, we showed that monoclonal myelin basic protein (MBP-specific antibodies from MS patients cross-react with Epstein–Barr virus (EBV latent membrane protein 1 (LMP1. In this study, we report that exposure of mice to LMP1 results in induction of myelin-reactive autoantibodies in vivo. We posit that chronic exposure or multiple acute exposures to viral antigen may redirect B cells from production of antiviral antibodies to antibodies, specific to myelin antigen. However, even in inbred animals, which are almost identical in terms of their genomes, such an effect is only observed in 20–50% of animals, indicating that this change occurs by chance, rather than systematically. Cross-immunoprecipitation analysis showed that only part of anti-MBP antibodies from LMP1-immunized mice might simultaneously bind LMP1. In contrast, the majority of anti-LMP1 antibodies from MBP-immunized mice bind MBP. De novo sequencing of anti-LMP1 and anti-MBP antibodies by mass spectrometry demonstrated enhanced clonal diversity in LMP1-immunized mice in comparison with MBP-immunized mice. We suggest that induction of MBP-reactive antibodies in LMP1-immunized mice may be caused by either Follicular dendritic cells (FDCs or by T cells that are primed by myelin antigens directly in CNS. Our findings help to elucidate the still enigmatic link between EBV infection and MS development, suggesting that myelin-reactive antibodies raised as a response toward EBV protein LMP1 are not truly cross-reactive but are primarily caused by epitope spreading.

Exposure to the Epstein–Barr Viral Antigen Latent Membrane Protein 1 Induces Myelin-Reactive Antibodies In Vivo

Science.gov (United States)

Lomakin, Yakov; Arapidi, Georgii Pavlovich; Chernov, Alexander; Ziganshin, Rustam; Tcyganov, Evgenii; Lyadova, Irina; Butenko, Ivan Olegovich; Osetrova, Maria; Ponomarenko, Natalia; Telegin, Georgy; Govorun, Vadim Markovich; Gabibov, Alexander; Belogurov, Alexey

2017-01-01

Multiple sclerosis (MS) is an autoimmune chronic inflammatory disease of the central nervous system (CNS). Cross-reactivity of neuronal proteins with exogenous antigens is considered one of the possible mechanisms of MS triggering. Previously, we showed that monoclonal myelin basic protein (MBP)-specific antibodies from MS patients cross-react with Epstein–Barr virus (EBV) latent membrane protein 1 (LMP1). In this study, we report that exposure of mice to LMP1 results in induction of myelin-reactive autoantibodies in vivo. We posit that chronic exposure or multiple acute exposures to viral antigen may redirect B cells from production of antiviral antibodies to antibodies, specific to myelin antigen. However, even in inbred animals, which are almost identical in terms of their genomes, such an effect is only observed in 20–50% of animals, indicating that this change occurs by chance, rather than systematically. Cross-immunoprecipitation analysis showed that only part of anti-MBP antibodies from LMP1-immunized mice might simultaneously bind LMP1. In contrast, the majority of anti-LMP1 antibodies from MBP-immunized mice bind MBP. De novo sequencing of anti-LMP1 and anti-MBP antibodies by mass spectrometry demonstrated enhanced clonal diversity in LMP1-immunized mice in comparison with MBP-immunized mice. We suggest that induction of MBP-reactive antibodies in LMP1-immunized mice may be caused by either Follicular dendritic cells (FDCs) or by T cells that are primed by myelin antigens directly in CNS. Our findings help to elucidate the still enigmatic link between EBV infection and MS development, suggesting that myelin-reactive antibodies raised as a response toward EBV protein LMP1 are not truly cross-reactive but are primarily caused by epitope spreading. PMID:28729867

Exposure to the Epstein-Barr Viral Antigen Latent Membrane Protein 1 Induces Myelin-Reactive Antibodies In Vivo.

Science.gov (United States)

Lomakin, Yakov; Arapidi, Georgii Pavlovich; Chernov, Alexander; Ziganshin, Rustam; Tcyganov, Evgenii; Lyadova, Irina; Butenko, Ivan Olegovich; Osetrova, Maria; Ponomarenko, Natalia; Telegin, Georgy; Govorun, Vadim Markovich; Gabibov, Alexander; Belogurov, Alexey

2017-01-01

Multiple sclerosis (MS) is an autoimmune chronic inflammatory disease of the central nervous system (CNS). Cross-reactivity of neuronal proteins with exogenous antigens is considered one of the possible mechanisms of MS triggering. Previously, we showed that monoclonal myelin basic protein (MBP)-specific antibodies from MS patients cross-react with Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1). In this study, we report that exposure of mice to LMP1 results in induction of myelin-reactive autoantibodies in vivo . We posit that chronic exposure or multiple acute exposures to viral antigen may redirect B cells from production of antiviral antibodies to antibodies, specific to myelin antigen. However, even in inbred animals, which are almost identical in terms of their genomes, such an effect is only observed in 20-50% of animals, indicating that this change occurs by chance, rather than systematically. Cross-immunoprecipitation analysis showed that only part of anti-MBP antibodies from LMP1-immunized mice might simultaneously bind LMP1. In contrast, the majority of anti-LMP1 antibodies from MBP-immunized mice bind MBP. De novo sequencing of anti-LMP1 and anti-MBP antibodies by mass spectrometry demonstrated enhanced clonal diversity in LMP1-immunized mice in comparison with MBP-immunized mice. We suggest that induction of MBP-reactive antibodies in LMP1-immunized mice may be caused by either Follicular dendritic cells (FDCs) or by T cells that are primed by myelin antigens directly in CNS. Our findings help to elucidate the still enigmatic link between EBV infection and MS development, suggesting that myelin-reactive antibodies raised as a response toward EBV protein LMP1 are not truly cross-reactive but are primarily caused by epitope spreading.

Multiple sclerosis and anterograde axonal degeneration study by magnetic resonance. Asociacion de esclerosis multiple y degeneracion Walleriana estudio por resonancia magnetica

Energy Technology Data Exchange (ETDEWEB)

Martinez Pardo, P; Capdevila Cirera, A; Sanz Marin, P M; Gili Planas, J [Centro de Resonancia Magnetica de Barcelona (Spain)

1993-01-01

Multiple sclerosis (MS) is a disease of the central nervous system that affects specifically the myelin. Its diagnosis by imaging techniques is, since the development of magnetic resonance (MR), relatively simple, and its occasional association with anterograde axonal degeneration (WD) has been reported. In both disorders, there is a lengthening of the T1 and T2 relaxation times. In the present report, 76 patients with MS with less than 4 plaques in the typical periventricular position were studied retrospectively, resulting in a rate of association with anterograde axonal degeneration of 8%. We consider that in spite of their same behavior in MR,MS and WD, with moreover represent completely different pathologies, are perfectly differential by MR. The S-E images with longer repetition and echo times in the axial and coronal planes have proved to be those most sensitive for this differentiation. Given that MS is specific pathology of then myelin, the axonal damages in delayed until several plaques adjacent to an axon affect it. We consider that this, added to the restriction of our study group (less than 4 plaques), is the cause of the pow percentage of the MS-WD association in our study. (Author).

Single Cell Electroporation Method for Mammalian CNS Neurons in Organotypic Slice Cultures

Science.gov (United States)

Uesaka, Naofumi; Hayano, Yasufumi; Yamada, Akito; Yamamoto, Nobuhiko

Axon tracing is an essential technique to study the projection pattern of neurons in the CNS. Horse radish peroxidase and lectins have contributed to revealing many neural connection patterns in the CNS (Itaya and van Hoesen, 1982; Fabian and Coulter, 1985; Yoshihara, 2002). Moreover, a tracing method with fluorescent dye has enabled the observation of growing axons in living conditions, and demon strated a lot of developmental aspects in axon growth and guidance (Harris et al., 1987; O'Rourke and Fraser, 1990; Kaethner and Stuermer, 1992; Halloran and Kalil, 1994; Yamamoto et al., 1997). More recently, genetically encoded fluores cent proteins can be used as a powerful tool to observe various biological events. Several gene transfer techniques such as microinjection, biolistic gene gun, viral infection, lipofection and transgenic technology have been developed (Feng et al., 2000; Ehrengruber et al., 2001; O'Brien et al., 2001; Ma et al., 2002; Sahly et al., 2003). In particular, the electroporation technique was proved as a valuable tool, since it can be applied to a wide range of tissues and cell types with little toxicity and can be performed with relative technical easiness. Most methods, including a stand ard electroporation technique, are suitable for gene transfer to a large number of cells. However, this is not ideal for axonal tracing, because observation of individ ual axons is occasionally required. To overcome this problem, we have developed an electroporation method using glass micropipettes containing plasmid solutions and small current injection. Here we introduce the method in detail and exemplified results with some example applications and discuss its usefulness.

GABA and its B-receptor are present at the node of Ranvier in a small population of sensory fibers, implicating a role in myelination

DEFF Research Database (Denmark)

Corell, Mikael; Wicher, Grzegorz; Radomska, Katarzyna J

2015-01-01

throughout development and after injury. A small population of myelinated sensory fibers displayed all of these molecules at the node of Ranvier, indicating a role in axon-glia communication. Functional studies using GABAB receptor agonists and antagonists were performed in fetal DRG primary cultures...... to study the function of this receptor during development. The results show that GABA, via its B receptor, is involved in the myelination process but not in Schwann cell proliferation. The data from adult nerves suggest additional roles in axon-glia communication after injury.......The γ-aminobutyric acid (GABA) type B receptor has been implicated in glial cell development in the peripheral nervous system (PNS), although the exact function of GABA signaling is not known. To investigate GABA and its B receptor in PNS development and degeneration, we studied the expression...

Influence of myelin proteins on the structure and dynamics of a model membrane with emphasis on the low temperature regime

Energy Technology Data Exchange (ETDEWEB)

Knoll, W. [University Joseph Fourier, UFR PhiTEM, Grenoble (France); Institut Laue–Langevin, Grenoble (France); Peters, J. [University Joseph Fourier, UFR PhiTEM, Grenoble (France); Institut Laue–Langevin, Grenoble (France); Institut de Biologie Structurale, Grenoble (France); Kursula, P. [University of Oulu, Oulu (Finland); CSSB–HZI, DESY, Hamburg (Germany); Gerelli, Y. [Institut Laue–Langevin, Grenoble (France); Natali, F., E-mail: natali@ill.fr [Institut Laue–Langevin, Grenoble (France); CNR–IOM–OGG, c/o Institut Laue–Langevin, Grenoble (France)

2014-11-28

Myelin is an insulating, multi-lamellar membrane structure wrapped around selected nerve axons. Increasing the speed of nerve impulses, it is crucial for the proper functioning of the vertebrate nervous system. Human neurodegenerative diseases, such as multiple sclerosis, are linked to damage to the myelin sheath through demyelination. Myelin exhibits a well defined subset of myelin-specific proteins, whose influence on membrane dynamics, i.e., myelin flexibility and stability, has not yet been explored in detail. In a first paper [W. Knoll, J. Peters, P. Kursula, Y. Gerelli, J. Ollivier, B. Demé, M. Telling, E. Kemner, and F. Natali, Soft Matter 10, 519 (2014)] we were able to spotlight, through neutron scattering experiments, the role of peripheral nervous system myelin proteins on membrane stability at room temperature. In particular, the myelin basic protein and peripheral myelin protein 2 were found to synergistically influence the membrane structure while keeping almost unchanged the membrane mobility. Further insight is provided by this work, in which we particularly address the investigation of the membrane flexibility in the low temperature regime. We evidence a different behavior suggesting that the proton dynamics is reduced by the addition of the myelin basic protein accompanied by negligible membrane structural changes. Moreover, we address the importance of correct sample preparation and characterization for the success of the experiment and for the reliability of the obtained results.

Saltatory conduction in unmyelinated axons: Clustering of Na+ channels on lipid rafts allows micro-saltatory conduction in C-fibers

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Ali eNeishabouri

2014-10-01

Full Text Available The action potential (AP, the fundamental signal of the nervous system, is carried by two types of axons: unmyelinated and myelinated fibers. In the former the action potential propagates continuously along the axon as established in large-diameter fibers. In the latter axons the AP jumps along the Nodes of Ranvier – discrete, anatomically specialized regions which contain very high densities of sodium ion (Na + channels. Therefore saltatory conduction is thought as the hallmark of myelinated axons, which enables faster and more reliable propagation of signals than in unmyelinated axons of same outer diameter.Recent molecular anatomy showed that in C-fibers, the very thin (0.1 μm diameter axons of the peripheral nervous system, Nav1.8 channels are clustered together on lipid rafts that float in the cell membrane. This localized concentration of Na+ channels resembles in structure the ion channel organization at the Nodes of Ranvier, yet it is currently unknown whether this translates into equivalent phenomenon of saltatory conduction or related-functional benefits and efficiencies. Therefore, we modeled biophysically realistic unmyelinated axons with both conventional and lipid-raft based organization of Na+ channels. We find that action potentials are reliably conducted in a micro-saltatory fashion along lipid rafts.Comparing APs in unmyelinated fibers with and without lipid rafts did not reveal any significant difference in either the metabolic cost or AP propagation velocity. By investigating the efficiency of AP propagation over Nav1.8 channels, we find however that the specific inactivation properties of these channels significantly increase the metabolic cost of signaling in C-fibers.

Organophosphate-Related Alterations in Myelin and Axonal Transport in the Living Mammalian Brain

Science.gov (United States)

2014-10-01

stress, impairments of mitochondrial function, neuroinflammation, altered neurotrophin responses, etc. (reviewed, Soltaninejad and Abdollahi, 2009...Exposure to Chlorpyrifos in Rats: Protracted Effects on Axonal Transport, Neurotrophin Receptors, Cholinergic Markers, and Information Processing

Integration and long distance axonal regeneration in the central nervous system from transplanted primitive neural stem cells.

Science.gov (United States)

Zhao, Jiagang; Sun, Woong; Cho, Hyo Min; Ouyang, Hong; Li, Wenlin; Lin, Ying; Do, Jiun; Zhang, Liangfang; Ding, Sheng; Liu, Yizhi; Lu, Paul; Zhang, Kang

2013-01-04

Spinal cord injury (SCI) results in devastating motor and sensory deficits secondary to disrupted neuronal circuits and poor regenerative potential. Efforts to promote regeneration through cell extrinsic and intrinsic manipulations have met with limited success. Stem cells represent an as yet unrealized therapy in SCI. Recently, we identified novel culture methods to induce and maintain primitive neural stem cells (pNSCs) from human embryonic stem cells. We tested whether transplanted human pNSCs can integrate into the CNS of the developing chick neural tube and injured adult rat spinal cord. Following injection of pNSCs into the developing chick CNS, pNSCs integrated into the dorsal aspects of the neural tube, forming cell clusters that spontaneously differentiated into neurons. Furthermore, following transplantation of pNSCs into the lesioned rat spinal cord, grafted pNSCs survived, differentiated into neurons, and extended long distance axons through the scar tissue at the graft-host interface and into the host spinal cord to form terminal-like structures near host spinal neurons. Together, these findings suggest that pNSCs derived from human embryonic stem cells differentiate into neuronal cell types with the potential to extend axons that associate with circuits of the CNS and, more importantly, provide new insights into CNS integration and axonal regeneration, offering hope for repair in SCI.

The astrocyte/meningeal cell interface is a barrier to neurite outgrowth which can be overcome by manipulation of inhibitory molecules or axonal signalling pathways

NARCIS (Netherlands)

Shearer, Morven C; Niclou, Simone P; Brown, David; Asher, Richard A; Holtmaat, Anthony J D G; Levine, Joel M; Verhaagen, J.; Fawcett, James W

2003-01-01

Invading meningeal cells form a barrier to axon regeneration after damage to the spinal cord and other parts of the CNS, axons stopping at the interface between meningeal cells and astrocytes. Axon behavior was examined using an in vitro model of astrocyte/meningeal cell interfaces, created by

Myelination and myelin disorders

International Nuclear Information System (INIS)

Knaap, M.S. van der.

1991-01-01

The first part of this thesis contains the results of a study into the capabilities of MR in the assessment of normal cerebral development. The process of normal myelination under the age of 1 year is divided into stages with specific MRI characteristics. An indication of normal age limits for each stage is given. The relationships between changes in signal intensities and biochemical background, and between progress of myelination and psychomotor development are discussed. The latter in the light of a study performed in hydrocephalic children, prior to and repeatedly after shunt implantation. Normal changes in 1 H and 31 P spectra of the brain in infants and children are described. The relationship between observed spectral changes and cerebral maturational processes is discussed. The second part deals with assessment of myelin disorders with MRI. Basic information about demyelinating disorders and biochemical background are reviewed. A new classification of myelin disorders, underlying the development of an MRI pattern recognition scheme, is proposed based on the most recent scientific developments. Common histological characteristics are described for all main categories of myelin disorders. Extensive information is presented about MRI patterns of abnormalities in patients in whom the disease is predominantly or exclusively located in the white matter. On the basis of the data of these patients a global MRI pattern recognition scheme has been developed covering all white matter disorders that were encountered. Also an example of an in-depth pattern recognition in a circumscribed category of disorders is presented. Finally a study of MRS in demyelinating disorders as opposed to neuronal disorders is described. While MRI provides information about the extent of the process of demyelination and about the disease category, MRS turns out to provide information about the severity of the demyelination and of the concomitant neuronal damage. (H.W.). 725 refs.; 53 figs

Transient Hypothyroidism During Lactation Arrests Myelination in the Anterior Commissure of Rats. A Magnetic Resonance Image and Electron Microscope Study

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Federico S. Lucia

2018-04-01

Full Text Available Thyroid hormone deficiency at early postnatal ages affects the cytoarchitecture and function of neocortical and telencephalic limbic areas, leading to impaired associative memory and in a wide spectrum of neurological and mental diseases. Neocortical areas project interhemispheric axons mostly through the corpus callosum and to a lesser extent through the anterior commissure (AC, while limbic areas mostly project through the AC and hippocampal commissures. Functional magnetic resonance data from children with late diagnosed congenital hypothyroidism and abnormal verbal memory processing, suggest altered ipsilateral and contralateral telencephalic connections. Gestational hypothyroidism affects AC development but the possible effect of transient and chronic postnatal hypothyroidism, as occurs in late diagnosed neonates with congenital hypothyroidism and in children growing up in iodine deficient areas, still remains unknown. We studied AC development using in vivo magnetic resonance imaging and electron microscopy in hypothyroid and control male rats. Four groups of methimazole (MMI treated rats were studied. One group was MMI-treated from postnatal day (P 0 to P21; some of these rats were also treated with L-thyroxine (T4 from P15 to P21, as a model for early transient hypothyroidism. Other rats were MMI-treated from P0 to P150 and from embryonic day (E 10 to P170, as a chronic hypothyroidism group. The results were compared with age paired control rats. The normalized T2 signal using magnetic resonance image was higher in MMI-treated rats and correlated with the number and percentage of myelinated axons. Using electron microscopy, we observed decreased myelinated axon number and density in transient and chronic hypothyroid rats at P150, unmyelinated axon number increased slightly in chronic hypothyroid rats. In MMI-treated rats, the myelinated axon g-ratio and conduction velocity was similar to control rats, but with a decrease in conduction

Transient Hypothyroidism During Lactation Arrests Myelination in the Anterior Commissure of Rats. A Magnetic Resonance Image and Electron Microscope Study.

Science.gov (United States)

Lucia, Federico S; Pacheco-Torres, Jesús; González-Granero, Susana; Canals, Santiago; Obregón, María-Jesús; García-Verdugo, José M; Berbel, Pere

2018-01-01

Thyroid hormone deficiency at early postnatal ages affects the cytoarchitecture and function of neocortical and telencephalic limbic areas, leading to impaired associative memory and in a wide spectrum of neurological and mental diseases. Neocortical areas project interhemispheric axons mostly through the corpus callosum and to a lesser extent through the anterior commissure (AC), while limbic areas mostly project through the AC and hippocampal commissures. Functional magnetic resonance data from children with late diagnosed congenital hypothyroidism and abnormal verbal memory processing, suggest altered ipsilateral and contralateral telencephalic connections. Gestational hypothyroidism affects AC development but the possible effect of transient and chronic postnatal hypothyroidism, as occurs in late diagnosed neonates with congenital hypothyroidism and in children growing up in iodine deficient areas, still remains unknown. We studied AC development using in vivo magnetic resonance imaging and electron microscopy in hypothyroid and control male rats. Four groups of methimazole (MMI) treated rats were studied. One group was MMI-treated from postnatal day (P) 0 to P21; some of these rats were also treated with L-thyroxine (T4) from P15 to P21, as a model for early transient hypothyroidism. Other rats were MMI-treated from P0 to P150 and from embryonic day (E) 10 to P170, as a chronic hypothyroidism group. The results were compared with age paired control rats. The normalized T2 signal using magnetic resonance image was higher in MMI-treated rats and correlated with the number and percentage of myelinated axons. Using electron microscopy, we observed decreased myelinated axon number and density in transient and chronic hypothyroid rats at P150, unmyelinated axon number increased slightly in chronic hypothyroid rats. In MMI-treated rats, the myelinated axon g-ratio and conduction velocity was similar to control rats, but with a decrease in conduction delays. These

Structural characterization of the human cerebral myelin sheath by small angle x-ray scattering

International Nuclear Information System (INIS)

De Felici, M; Felici, R; Ferrero, C; Tartari, A; Gambaccini, M; Finet, S

2008-01-01

Myelin is a multi-lamellar membrane surrounding neuronal axons and increasing their conduction velocity. When investigated by small-angle x-ray scattering (SAXS), the lamellar quasi-periodical arrangement of the myelin sheath gives rise to distinct peaks, which allow the determination of its molecular organization and the dimensions of its substructures. In this study we report on the myelin sheath structural determination carried out on a set of human brain tissue samples coming from surgical biopsies of two patients: a man around 60 and a woman nearly 90 years old. The samples were extracted either from white or grey cerebral matter and did not undergo any manipulation or chemical-physical treatment, which could possibly have altered their structure, except dipping them into a formalin solution for their conservation. Analysis of the scattered intensity from white matter of intact human cerebral tissue allowed the evaluation not only of the myelin sheath periodicity but also of its electronic charge density profile. In particular, the thicknesses of the cytoplasm and extracellular regions were established, as well as those of the hydrophilic polar heads and hydrophobic tails of the lipid bilayer. SAXS patterns were measured at several locations on each sample in order to establish the statistical variations of the structural parameters within a single sample and among different samples. This work demonstrates that a detailed structural analysis of the myelin sheath can also be carried out in randomly oriented samples of intact human white matter, which is of importance for studying the aetiology and evolution of the central nervous system pathologies inducing myelin degeneration.

Cerebrospinal fluid analysis in the context of CNS demyelinating diseases

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Sandro Luiz de Andrade Matas

2013-09-01

Full Text Available The central nervous system demyelinating diseases are a group of disorders with different etiologies, characterized by inflammatory lesions that are associated with loss of myelin and eventually axonal damage. In this group the most studied ones are multiple sclerosis (MS, neuromyelitis optic (NMO and acute disseminated encephalomyelitis (ADEM. The cerebrospinal fluid is essential to differentiate between these different syndromes and to define multiple sclerosis, helping to assess the probability of Clinical Isolated Syndrome turn into multiple sclerosis.

Ischemic tolerance in pre-myelinated white matter: the role of astrocyte glycogen in brain pathology.

Science.gov (United States)

Fern, Robert

2015-06-01

In isolated white matter, ischemic tolerance changes dramatically in the period immediately before the onset of myelination. In the absence of an extrinsic energy source, postnatal day 0 to 2 (P0 to P2) white matter axons are here shown to maintain excitability for over twice as long as axons >P2, a differential that was dependent on glycogen metabolism. Prolonged withdrawal of extrinsic energy supply tended to spare axons in zones around astrocytes, which are shown to be the sole repository for glycogen particles in developing white matter. Analysis of mitochondrial volume fraction revealed that neither axons nor astrocytes had a low metabolic rate in neonatal white matter, while oligodendroglia at older ages had an elevated metabolism. The astrocyte population is established early in neural development, and exhibits reduced cell density as maturation progresses and white matter expands. The findings show that this event establishes the necessary conditions for ischemia sensitivity in white matter and indicates that astrocyte proximity may be significant for the survival of neuronal elements in conditions associated with compromised energy supply.

Acutely damaged axons are remyelinated in multiple sclerosis and experimental models of demyelination.

Science.gov (United States)

Schultz, Verena; van der Meer, Franziska; Wrzos, Claudia; Scheidt, Uta; Bahn, Erik; Stadelmann, Christine; Brück, Wolfgang; Junker, Andreas

2017-08-01

Remyelination is in the center of new therapies for the treatment of multiple sclerosis to resolve and improve disease symptoms and protect axons from further damage. Although remyelination is considered beneficial in the long term, it is not known, whether this is also the case early in lesion formation. Additionally, the precise timing of acute axonal damage and remyelination has not been assessed so far. To shed light onto the interrelation between axons and the myelin sheath during de- and remyelination, we employed cuprizone- and focal lysolecithin-induced demyelination and performed time course experiments assessing the evolution of early and late stage remyelination and axonal damage. We observed damaged axons with signs of remyelination after cuprizone diet cessation and lysolecithin injection. Similar observations were made in early multiple sclerosis lesions. To assess the correlation of remyelination and axonal damage in multiple sclerosis lesions, we took advantage of a cohort of patients with early and late stage remyelinated lesions and assessed the number of APP- and SMI32- positive damaged axons and the density of SMI31-positive and silver impregnated preserved axons. Early de- and remyelinating lesions did not differ with respect to axonal density and axonal damage, but we observed a lower axonal density in late stage demyelinated multiple sclerosis lesions than in remyelinated multiple sclerosis lesions. Our findings suggest that remyelination may not only be protective over a long period of time, but may play an important role in the immediate axonal recuperation after a demyelinating insult. © 2017 The Authors GLIA Published by Wiley Periodicals, Inc.

Role of calpains in the injury-induced dysfunction and degeneration of the mammalian axon.

Science.gov (United States)

Ma, Marek

2013-12-01

Axonal injury and degeneration, whether primary or secondary, contribute to the morbidity and mortality seen in many acquired and inherited central nervous system (CNS) and peripheral nervous system (PNS) disorders, such as traumatic brain injury, spinal cord injury, cerebral ischemia, neurodegenerative diseases, and peripheral neuropathies. The calpain family of proteases has been mechanistically linked to the dysfunction and degeneration of axons. While the direct mechanisms by which transection, mechanical strain, ischemia, or complement activation trigger intra-axonal calpain activity are likely different, the downstream effects of unregulated calpain activity may be similar in seemingly disparate diseases. In this review, a brief examination of axonal structure is followed by a focused overview of the calpain family. Finally, the mechanisms by which calpains may disrupt the axonal cytoskeleton, transport, and specialized domains (axon initial segment, nodes, and terminals) are discussed. © 2013.

A Comparative Morphometric Analysis of Three Cranial Nerves in Two Phocids: The Hooded Seal (Cystophora cristata) and the Harbor Seal (Phoca vitulina).

Science.gov (United States)

Wohlert, Dennis; Kröger, Jürgen; Witt, Martin; Schmitt, Oliver; Wree, Andreas; Czech-Damal, Nicole; Siebert, Ursula; Folkow, Lars; Hanke, Frederike D

2016-03-01

While our knowledge about the senses of pinnipeds has increased over the last decades almost nothing is known about the organization of the neuroanatomical pathways. In a first approach to this field of research, we assessed the total number of myelinated axons of three cranial nerves (CNs) in the harbor (Phoca vitulina, Pv) and hooded seal (Cystophora cristata, Cc). Axons were counted in semithin sections of the nerves embedded in Epon and stained with toluidine blue. In both species, the highest axon number was found within the optic nerve (Pv 187,000 ± 8,000 axons, Cc 481,600 ± 1,300 axons). Generally, considering absolute axon numbers, far more axons were counted within the optic and trigmenial nerve (Pv 136,700 ± 2,500 axons, Cc 179,300 ± 6,900 axons) in hooded in comparison to harbor seals. The axon counts of the vestibulocochlear nerve are nearly identical for both species (Pv 87,100 ± 8,100 axons, Cc 86,600 ± 2,700 axons). However, when comparing cell density, the cell density is almost equal for all nerves for both species except for the optic nerve in which cell density was particularly higher than in the other nerves and higher in hooded in comparison to harbor seals. We here present the first comparative analysis of three CNs in two phocid seals. While the CNs of these closely related species share some general characteristics, pronounced differences in axon numbers/densities are apparent. These differences seem to reflect differences in e.g. size, habitat, and/or functional significance of the innervated sensory systems. © 2015 Wiley Periodicals, Inc.

Regeneration of Drosophila sensory neuron axons and dendrites is regulated by the Akt pathway involving Pten and microRNA bantam

Science.gov (United States)

Song, Yuanquan; Ori-McKenney, Kassandra M.; Zheng, Yi; Han, Chun; Jan, Lily Yeh; Jan, Yuh Nung

2012-01-01

Both cell-intrinsic and extrinsic pathways govern axon regeneration, but only a limited number of factors have been identified and it is not clear to what extent axon regeneration is evolutionarily conserved. Whether dendrites also regenerate is unknown. Here we report that, like the axons of mammalian sensory neurons, the axons of certain Drosophila dendritic arborization (da) neurons are capable of substantial regeneration in the periphery but not in the CNS, and activating the Akt pathway enhances axon regeneration in the CNS. Moreover, those da neurons capable of axon regeneration also display dendrite regeneration, which is cell type-specific, developmentally regulated, and associated with microtubule polarity reversal. Dendrite regeneration is restrained via inhibition of the Akt pathway in da neurons by the epithelial cell-derived microRNA bantam but is facilitated by cell-autonomous activation of the Akt pathway. Our study begins to reveal mechanisms for dendrite regeneration, which depends on both extrinsic and intrinsic factors, including the PTEN–Akt pathway that is also important for axon regeneration. We thus established an important new model system—the fly da neuron regeneration model that resembles the mammalian injury model—with which to study and gain novel insights into the regeneration machinery. PMID:22759636

Orthodontic treatment for a patient with multiple sclerosis

Science.gov (United States)

Bakathir, Manal A

2017-01-01

Multiple sclerosis (MS) is a chronic, autoimmune inflammatory disorder of the central nervous system (CNS) that affects myelinated axons, destroying the myelin and damaging axons to varying degrees. The course of MS is highly varied and unpredictable. Metals used during orthodontic treatment can negatively affect imaging techniques used to diagnose and monitor the progression of MS, while medications used to treat MS can negatively affect orthodontic tooth movement. The present case report highlights some of the challenges encountered during orthodontic treatment of a patient with MS and how to overcome them. The patient was a 20-year-old woman with complaints of diastema and spacing in the upper arch. Although closing the spaces was challenging due to some of the MS medications, she was treated successfully, without complications, within 20 months using closing loops. PMID:28717636

Cellular and Axonal Diversity in Molecular Layer Heterotopia of the Rat Cerebellar Vermis

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Sarah E. Van Dine

2013-01-01

Full Text Available Molecular layer heterotopia of the cerebellar primary fissure are a characteristic of many rat strains and are hypothesized to result from defect of granule cells exiting the external granule cell layer during cerebellar development. However, the cellular and axonal constituents of these malformations remain poorly understood. In the present report, we use histochemistry and immunocytochemistry to identify neuronal, glial, and axonal classes in molecular layer heterotopia. In particular, we identify parvalbumin-expressing molecular layer interneurons in heterotopia as well as three glial cell types including Bergmann glia, Olig2-expressing oligodendrocytes, and Iba1-expressing microglia. In addition, we document the presence of myelinated, serotonergic, catecholaminergic, and cholinergic axons in heterotopia indicating possible spinal and brainstem afferent projections to heterotopic cells. These findings are relevant toward understanding the mechanisms of normal and abnormal cerebellar development.

Organophosphate Related Alterations in Myelin and Axonal Transport in the Living Mammalian Brain

Science.gov (United States)

2015-10-01

function, neuroinflammation, al- tered neurotrophin responses, etc. (reviewed, Soltaninejad and Abdollahi, 2009; Banks and Lein, 2012; Terry, 2012). Conflict...JN, Middlemore ML, Williamson LN, et al. Chronic, intermittent exposure to chlorpyrifos in rats: protracted effects on axonal transport, neurotrophin

Side-To-Side Nerve Bridges Support Donor Axon Regeneration Into Chronically Denervated Nerves and Are Associated With Characteristic Changes in Schwann Cell Phenotype.

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Hendry, J Michael; Alvarez-Veronesi, M Cecilia; Snyder-Warwick, Alison; Gordon, Tessa; Borschel, Gregory H

2015-11-01

Chronic denervation resulting from long nerve regeneration times and distances contributes greatly to suboptimal outcomes following nerve injuries. Recent studies showed that multiple nerve grafts inserted between an intact donor nerve and a denervated distal recipient nerve stump (termed "side-to-side nerve bridges") enhanced regeneration after delayed nerve repair. To examine the cellular aspects of axon growth across these bridges to explore the "protective" mechanism of donor axons on chronically denervated Schwann cells. In Sprague Dawley rats, 3 side-to-side nerve bridges were placed over a 10-mm distance between an intact donor tibial (TIB) nerve and a recipient denervated common peroneal (CP) distal nerve stump. Green fluorescent protein-expressing TIB axons grew across the bridges and were counted in cross section after 4 weeks. Immunofluorescent axons and Schwann cells were imaged over a 4-month period. Denervated Schwann cells dedifferentiated to a proliferative, nonmyelinating phenotype within the bridges and the recipient denervated CP nerve stump. As donor TIB axons grew across the 3 side-to-side nerve bridges and into the denervated CP nerve, the Schwann cells redifferentiated to the myelinating phenotype. Bridge placement led to an increased mass of hind limb anterior compartment muscles after 4 months of denervation compared with muscles whose CP nerve was not "protected" by bridges. This study describes patterns of donor axon regeneration and myelination in the denervated recipient nerve stump and supports a mechanism where these donor axons sustain a proregenerative state to prevent deterioration in the face of chronic denervation.

Possible Effects of Synaptic Imbalances on Oligodendrocyte-Axonic Interactions in Schizophrenia: a Hypothetical Model

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Bernhard Joseph Mitterauer

2011-04-01

Full Text Available AbstractA model of glial-neuronal interactions is proposed that could be explanatory for the demyelination identified in brains with schizophrenia. According to this model, receptors on astrocytes in glial-neuronal synaptic units are not functional, loosing their modulatory influence on synaptic neurotransmission. Hence, an unconstrained neurotransmission flux occurs that hyperactivates the axon and floods the cognate receptors of neurotransmitters on oligodendrocytes. The excess of neurotransmitters may have a toxic effect on oligodendrocytes and myelin, causing demyelination. In parallel, an increasing impairment of axons may disconnect neuronal networks. It is formally shown how oligodendrocytes normally categorize axonic information processing via their processes. Demyelination decomposes the oligodendrocyte-axonic system making it incapable to generate categories of information. This incoherence may be responsible for symptoms of disorganization in schizophrenia, such as thought disorder, inappropriate affect and incommunicable motor behavior. In parallel, the loss of oligodendrocytes affects gap junctions in the panglial syncytium, presumably responsible for memory impairment in schizophrenia.

Rational polypharmacology: systematically identifying and engaging multiple drug targets to promote axon growth

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Al-Ali, Hassan; Lee, Do-Hun; Danzi, Matt C.; Nassif, Houssam; Gautam, Prson; Wennerberg, Krister; Zuercher, Bill; Drewry, David H.; Lee, Jae K.; Lemmon, Vance P.; Bixby, John L.

2016-01-01

Mammalian Central Nervous System (CNS) neurons regrow their axons poorly following injury, resulting in irreversible functional losses. Identifying therapeutics that encourage CNS axon repair has been difficult, in part because multiple etiologies underlie this regenerative failure. This suggests a particular need for drugs that engage multiple molecular targets. Although multi-target drugs are generally more effective than highly selective alternatives, we lack systematic methods for discovering such drugs. Target-based screening is an efficient technique for identifying potent modulators of individual targets. In contrast, phenotypic screening can identify drugs with multiple targets; however, these targets remain unknown. To address this gap, we combined the two drug discovery approaches using machine learning and information theory. We screened compounds in a phenotypic assay with primary CNS neurons and also in a panel of kinase enzyme assays. We used learning algorithms to relate the compounds’ kinase inhibition profiles to their influence on neurite outgrowth. This allowed us to identify kinases that may serve as targets for promoting neurite outgrowth, as well as others whose targeting should be avoided. We found that compounds that inhibit multiple targets (polypharmacology) promote robust neurite outgrowth in vitro. One compound with exemplary polypharmacology, was found to promote axon growth in a rodent spinal cord injury model. A more general applicability of our approach is suggested by its ability to deconvolve known targets for a breast cancer cell line, as well as targets recently shown to mediate drug resistance. PMID:26056718

Association of a History of Child Abuse With Impaired Myelination in the Anterior Cingulate Cortex: Convergent Epigenetic, Transcriptional, and Morphological Evidence.

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Lutz, Pierre-Eric; Tanti, Arnaud; Gasecka, Alicja; Barnett-Burns, Sarah; Kim, John J; Zhou, Yi; Chen, Gang G; Wakid, Marina; Shaw, Meghan; Almeida, Daniel; Chay, Marc-Aurele; Yang, Jennie; Larivière, Vanessa; M'Boutchou, Marie-Noël; van Kempen, Léon C; Yerko, Volodymyr; Prud'homme, Josée; Davoli, Maria Antonietta; Vaillancourt, Kathryn; Théroux, Jean-François; Bramoullé, Alexandre; Zhang, Tie-Yuan; Meaney, Michael J; Ernst, Carl; Côté, Daniel; Mechawar, Naguib; Turecki, Gustavo

2017-12-01

Child abuse has devastating and long-lasting consequences, considerably increasing the lifetime risk of negative mental health outcomes such as depression and suicide. Yet the neurobiological processes underlying this heightened vulnerability remain poorly understood. The authors investigated the hypothesis that epigenetic, transcriptomic, and cellular adaptations may occur in the anterior cingulate cortex as a function of child abuse. Postmortem brain samples from human subjects (N=78) and from a rodent model of the impact of early-life environment (N=24) were analyzed. The human samples were from depressed individuals who died by suicide, with (N=27) or without (N=25) a history of severe child abuse, as well as from psychiatrically healthy control subjects (N=26). Genome-wide DNA methylation and gene expression were investigated using reduced representation bisulfite sequencing and RNA sequencing, respectively. Cell type-specific validation of differentially methylated loci was performed after fluorescence-activated cell sorting of oligodendrocyte and neuronal nuclei. Differential gene expression was validated using NanoString technology. Finally, oligodendrocytes and myelinated axons were analyzed using stereology and coherent anti-Stokes Raman scattering microscopy. A history of child abuse was associated with cell type-specific changes in DNA methylation of oligodendrocyte genes and a global impairment of the myelin-related transcriptional program. These effects were absent in the depressed suicide completers with no history of child abuse, and they were strongly correlated with myelin gene expression changes observed in the animal model. Furthermore, a selective and significant reduction in the thickness of myelin sheaths around small-diameter axons was observed in individuals with history of child abuse. The results suggest that child abuse, in part through epigenetic reprogramming of oligodendrocytes, may lastingly disrupt cortical myelination, a

Wnt3 and Gata4 regulate axon regeneration in adult mouse DRG neurons.

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Duan, Run-Shan; Liu, Pei-Pei; Xi, Feng; Wang, Wei-Hua; Tang, Gang-Bin; Wang, Rui-Ying; Saijilafu; Liu, Chang-Mei

2018-05-05

Neurons in the adult central nervous system (CNS) have a poor intrinsic axon growth potential after injury, but the underlying mechanisms are largely unknown. Wingless-related mouse mammary tumor virus integration site (WNT) family members regulate neural stem cell proliferation, axon tract and forebrain development in the nervous system. Here we report that Wnt3 is an important modulator of axon regeneration. Downregulation or overexpression of Wnt3 in adult dorsal root ganglion (DRG) neurons enhances or inhibits their axon regeneration ability respectively in vitro and in vivo. Especially, we show that Wnt3 modulates axon regeneration by repressing mRNA translation of the important transcription factor Gata4 via binding to the three prime untranslated region (3'UTR). Downregulation of Gata4 could restore the phenotype exhibited by Wnt3 downregulation in DRG neurons. Taken together, these data indicate that Wnt3 is a key intrinsic regulator of axon growth ability of the nervous system. Copyright © 2018 Elsevier Inc. All rights reserved.

HB-GAM (pleiotrophin) reverses inhibition of neural regeneration by the CNS extracellular matrix

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Paveliev, Mikhail; Fenrich, Keith K.; Kislin, Mikhail; Kuja-Panula, Juha; Kulesskiy, Evgeny; Varjosalo, Markku; Kajander, Tommi; Mugantseva, Ekaterina; Ahonen-Bishopp, Anni; Khiroug, Leonard; Kulesskaya, Natalia; Rougon, Geneviève; Rauvala, Heikki

2016-01-01

Chondroitin sulfate (CS) glycosaminoglycans inhibit regeneration in the adult central nervous system (CNS). We report here that HB-GAM (heparin-binding growth-associated molecule; also known as pleiotrophin), a CS-binding protein expressed at high levels in the developing CNS, reverses the role of the CS chains in neurite growth of CNS neurons in vitro from inhibition to activation. The CS-bound HB-GAM promotes neurite growth through binding to the cell surface proteoglycan glypican-2; furthermore, HB-GAM abrogates the CS ligand binding to the inhibitory receptor PTPσ (protein tyrosine phosphatase sigma). Our in vivo studies using two-photon imaging of CNS injuries support the in vitro studies and show that HB-GAM increases dendrite regeneration in the adult cerebral cortex and axonal regeneration in the adult spinal cord. Our findings may enable the development of novel therapies for CNS injuries. PMID:27671118

Axonal loss in the multiple sclerosis spinal cord revisited.

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Petrova, Natalia; Carassiti, Daniele; Altmann, Daniel R; Baker, David; Schmierer, Klaus

2018-05-01

Preventing chronic disease deterioration is an unmet need in people with multiple sclerosis, where axonal loss is considered a key substrate of disability. Clinically, chronic multiple sclerosis often presents as progressive myelopathy. Spinal cord cross-sectional area (CSA) assessed using MRI predicts increasing disability and has, by inference, been proposed as an indirect index of axonal degeneration. However, the association between CSA and axonal loss, and their correlation with demyelination, have never been systematically investigated using human post mortem tissue. We extensively sampled spinal cords of seven women and six men with multiple sclerosis (mean disease duration= 29 years) and five healthy controls to quantify axonal density and its association with demyelination and CSA. 396 tissue blocks were embedded in paraffin and immuno-stained for myelin basic protein and phosphorylated neurofilaments. Measurements included total CSA, areas of (i) lateral cortico-spinal tracts, (ii) gray matter, (iii) white matter, (iv) demyelination, and the number of axons within the lateral cortico-spinal tracts. Linear mixed models were used to analyze relationships. In multiple sclerosis CSA reduction at cervical, thoracic and lumbar levels ranged between 19 and 24% with white (19-24%) and gray (17-21%) matter atrophy contributing equally across levels. Axonal density in multiple sclerosis was lower by 57-62% across all levels and affected all fibers regardless of diameter. Demyelination affected 24-48% of the gray matter, most extensively at the thoracic level, and 11-13% of the white matter, with no significant differences across levels. Disease duration was associated with reduced axonal density, however not with any area index. Significant association was detected between focal demyelination and decreased axonal density. In conclusion, over nearly 30 years multiple sclerosis reduces axonal density by 60% throughout the spinal cord. Spinal cord cross sectional area

Investigation of sequential growth factor delivery during cuprizone challenge in mice aimed to enhance oligodendrogliogenesis and myelin repair.

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Jennifer K Sabo

Full Text Available Repair in multiple sclerosis involves remyelination, a process in which axons are provided with a new myelin sheath by new oligodendrocytes. Bone morphogenic proteins (BMPs are a family of growth factors that have been shown to influence the response of oligodendrocyte progenitor cells (OPCs in vivo during demyelination and remyelination in the adult brain. We have previously shown that BMP4 infusion increases numbers of OPCs during cuprizone-induced demyelination, while infusion of Noggin, an endogenous antagonist of BMP4 increases numbers of mature oligodendrocytes and remyelinated axons following recovery. Additional studies have shown that insulin-like growth factor-1 (IGF-1 promotes the survival of OPCs during cuprizone-induced demyelination. Based on these data, we investigated whether myelin repair could be further enhanced by sequential infusion of these agents firstly, BMP4 to increase OPC numbers, followed by either Noggin or IGF-1 to increase the differentiation and survival of the newly generated OPCs. We identified that sequential delivery of BMP4 and IGF-1 during cuprizone challenge increased the number of mature oligodendrocytes and decreased astrocyte numbers following recovery compared with vehicle infused mice, but did not alter remyelination. However, sequential delivery of BMP4 and Noggin during cuprizone challenge did not alter numbers of oligodendrocytes or astrocytes in the corpus callosum compared with vehicle infused mice. Furthermore, electron microscopy analysis revealed no change in average myelin thickness in the corpus callosum between vehicle infused and BMP4-Noggin infused mice. Our results suggest that while single delivery of Noggin or IGF-1 increased the production of mature oligodendrocytes in vivo in the context of demyelination, only Noggin infusion promoted remyelination. Thus, sequential delivery of BMP4 and Noggin or IGF-1 does not further enhance myelin repair above what occurs with delivery of Noggin

Networks of myelin covariance.

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Melie-Garcia, Lester; Slater, David; Ruef, Anne; Sanabria-Diaz, Gretel; Preisig, Martin; Kherif, Ferath; Draganski, Bogdan; Lutti, Antoine

2018-04-01

Networks of anatomical covariance have been widely used to study connectivity patterns in both normal and pathological brains based on the concurrent changes of morphometric measures (i.e., cortical thickness) between brain structures across subjects (Evans, ). However, the existence of networks of microstructural changes within brain tissue has been largely unexplored so far. In this article, we studied in vivo the concurrent myelination processes among brain anatomical structures that gathered together emerge to form nonrandom networks. We name these "networks of myelin covariance" (Myelin-Nets). The Myelin-Nets were built from quantitative Magnetization Transfer data-an in-vivo magnetic resonance imaging (MRI) marker of myelin content. The synchronicity of the variations in myelin content between anatomical regions was measured by computing the Pearson's correlation coefficient. We were especially interested in elucidating the effect of age on the topological organization of the Myelin-Nets. We therefore selected two age groups: Young-Age (20-31 years old) and Old-Age (60-71 years old) and a pool of participants from 48 to 87 years old for a Myelin-Nets aging trajectory study. We found that the topological organization of the Myelin-Nets is strongly shaped by aging processes. The global myelin correlation strength, between homologous regions and locally in different brain lobes, showed a significant dependence on age. Interestingly, we also showed that the aging process modulates the resilience of the Myelin-Nets to damage of principal network structures. In summary, this work sheds light on the organizational principles driving myelination and myelin degeneration in brain gray matter and how such patterns are modulated by aging. © 2017 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

Proliferation of Schwann cells induced by axolemmal and myelin membranes

International Nuclear Information System (INIS)

Dinneen, M.

1985-01-01

Purified Schwann Cells were cultured from neonatal rat sciatic nerve using a modification of the method of Brockes. Schwann cells and contaminating fibroblasts were unambiguously identified using fluorescent antibodies of 2'3' cyclic nucleotide 3'-phosphodiesterase and the thy 1.1 antigen respectively. The Schwann cells were quiescent unless challenged with mitogens. They proliferated rapidly in response to the soluble mitogen, cholera toxin, or to membrane fractions from rat CNS or PNS, prepared by the method of DeVries. Mitogenic activity was present in both axolemmal and myelin enriched fractions and promoted a 10-15 fold increase in the rate of 3 H-thymidine uptake. The axolemmal mitogen was sensitive to heat (80 0 C for 10 minutes), trypsin digestion (0.05% x 30 mins) or to treatment with endoglycosidase D, suggesting that it could be a glycoprotein. Fifty percent of the axolemmal mitogenic activity was solubilized in 1% octyl-glucoside. The solubilized material, however, was very unstable and further purification was not possible. The myelin associated mitogenic activity was markedly different. It was resistant to freeze thaw cycles, trypsin digestion of endoglycosidase treatment and the activity was actually enhanced by heating at 100 0 C for two hours. It is proposed that the axolemmal activity is responsible for Schwann cell proliferation during development and that the myelin associated activity promotes Schwann cell proliferation during Wallerian degeneration

After Nerve Injury, Lineage Tracing Shows That Myelin and Remak Schwann Cells Elongate Extensively and Branch to Form Repair Schwann Cells, Which Shorten Radically on Remyelination.

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Gomez-Sanchez, Jose A; Pilch, Kjara S; van der Lans, Milou; Fazal, Shaline V; Benito, Cristina; Wagstaff, Laura J; Mirsky, Rhona; Jessen, Kristjan R

2017-09-13

There is consensus that, distal to peripheral nerve injury, myelin and Remak cells reorganize to form cellular columns, Bungner's bands, which are indispensable for regeneration. However, knowledge of the structure of these regeneration tracks has not advanced for decades and the structure of the cells that form them, denervated or repair Schwann cells, remains obscure. Furthermore, the origin of these cells from myelin and Remak cells and their ability to give rise to myelin cells after regeneration has not been demonstrated directly, although these conversions are believed to be central to nerve repair. Using genetic lineage-tracing and scanning-block face electron microscopy, we show that injury of sciatic nerves from mice of either sex triggers extensive and unexpected Schwann cell elongation and branching to form long, parallel processes. Repair cells are 2- to 3-fold longer than myelin and Remak cells and 7- to 10-fold longer than immature Schwann cells. Remarkably, when repair cells transit back to myelinating cells, they shorten ∼7-fold to generate the typically short internodes of regenerated nerves. The present experiments define novel morphological transitions in injured nerves and show that repair Schwann cells have a cell-type-specific structure that differentiates them from other cells in the Schwann cell lineage. They also provide the first direct evidence using genetic lineage tracing for two basic assumptions in Schwann cell biology: that myelin and Remak cells generate the elongated cells that build Bungner bands in injured nerves and that such cells can transform to myelin cells after regeneration. SIGNIFICANCE STATEMENT After injury to peripheral nerves, the myelin and Remak Schwann cells distal to the injury site reorganize and modify their properties to form cells that support the survival of injured neurons, promote axon growth, remove myelin-associated growth inhibitors, and guide regenerating axons to their targets. We show that the

Caenorhabditis elegans VEM-1, a novel membrane protein, regulates the guidance of ventral nerve cord-associated axons.

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Runko, Erik; Kaprielian, Zaven

2004-10-13

In the developing CNS, pathfinding growth cones use intermediate target- and pioneer axon-associated guidance cues to navigate along stereotypical trajectories. We previously showed that the novel membrane-associated protein Vema is localized to the floor plate and the optic chiasm, intermediate targets located at the ventral midline of the spinal cord and diencephalon in the developing rodent CNS, respectively. Here, we report that the Caenorhabditis elegans ortholog of vema, vem-1, is expressed by the AVG pioneer midline neuron and by several neurons that extend longitudinally projecting axons into the ventral nerve cord (VNC). In vem-1 mutants and vem-1 (RNAi) animals, a subset of posteriorly projecting interneuron axons either fail to extend ventrally to the VNC and, instead, assume aberrant lateral positions or are inappropriately located in the left tract of the VNC. In addition, ventral motor neuron axons exhibit pathfinding errors within the VNC and along the dorsoventral body axis. The conserved UNC-40/DCC and SAX-3-/Robo receptors mediate signaling events that regulate axon guidance in a wide variety of systems. Double-mutant analyses reveal that vem-1 genetically interacts with unc-40 and is likely to function in parallel with sax-3 to regulate the guidance of a subset of VNC-associated interneuron and motor neuron axons. Consistent with these genetic data, we also show that VEM-1 is capable of physically interacting with UNC-40 but not SAX-3.

Axonal lesion-induced microglial proliferation and microglial cluster formation in the mouse

DEFF Research Database (Denmark)

Dissing-Olesen, L; Ladeby, R; Nielsen, Helle Hvilsted

2007-01-01

Microglia are innate immune cells and form the first line of defense of the CNS. Proliferation is a key event in the activation of microglia in acute pathology, and has been extensively characterized in rats, but not in mice. In this study we investigated axonal-lesion-induced microglial prolifer...

Loss of the receptor tyrosine kinase Axl leads to enhanced inflammation in the CNS and delayed removal of myelin debris during Experimental Autoimmune Encephalomyelitis

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Prieto Anne L

2011-05-01

Full Text Available Abstract Background Axl, together with Tyro3 and Mer, constitute the TAM family of receptor tyrosine kinases. In the nervous system, Axl and its ligand Growth-arrest-specific protein 6 (Gas6 are expressed on multiple cell types. Axl functions in dampening the immune response, regulating cytokine secretion, clearing apoptotic cells and debris, and maintaining cell survival. Axl is upregulated in various disease states, such as in the cuprizone toxicity-induced model of demyelination and in multiple sclerosis (MS lesions, suggesting that it plays a role in disease pathogenesis. To test for this, we studied the susceptibility of Axl-/- mice to experimental autoimmune encephalomyelitis (EAE, an animal model for multiple sclerosis. Methods WT and Axl-/- mice were immunized with myelin oligodendrocyte glycoprotein (MOG35-55 peptide emulsified in complete Freund's adjuvant and injected with pertussis toxin on day 0 and day 2. Mice were monitored daily for clinical signs of disease and analyzed for pathology during the acute phase of disease. Immunological responses were monitored by flow cytometry, cytokine analysis and proliferation assays. Results Axl-/- mice had a significantly more severe acute phase of EAE than WT mice. Axl-/- mice had more spinal cord lesions with larger inflammatory cuffs, more demyelination, and more axonal damage than WT mice during EAE. Strikingly, lesions in Axl-/- mice had more intense Oil-Red-O staining indicative of inefficient clearance of myelin debris. Fewer activated microglia/macrophages (Iba1+ were found in and/or surrounding lesions in Axl-/- mice relative to WT mice. In contrast, no significant differences were noted in immune cell responses between naïve and sensitized animals. Conclusions These data show that Axl alleviates EAE disease progression and suggests that in EAE Axl functions in the recruitment of microglia/macrophages and in the clearance of debris following demyelination. In addition, these data

The Molecular and Cellular Mechanisms of Axon Guidance in Mossy Fiber Sprouting

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Ryuta Koyama

2018-05-01

Full Text Available The question of whether mossy fiber sprouting is epileptogenic has not been resolved; both sprouting-induced recurrent excitatory and inhibitory circuit hypotheses have been experimentally (but not fully supported. Therefore, whether mossy fiber sprouting is a potential therapeutic target for epilepsy remains under debate. Moreover, the axon guidance mechanisms of mossy fiber sprouting have attracted the interest of neuroscientists. Sprouting of mossy fibers exhibits several uncommon axonal growth features in the basically non-plastic adult brain. For example, robust branching of axonal collaterals arises from pre-existing primary mossy fiber axons. Understanding the branching mechanisms in adulthood may contribute to axonal regeneration therapies in neuroregenerative medicine in which robust axonal re-growth is essential. Additionally, because granule cells are produced throughout life in the neurogenic dentate gyrus, it is interesting to examine whether the mossy fibers of newly generated granule cells follow the pre-existing trajectories of sprouted mossy fibers in the epileptic brain. Understanding these axon guidance mechanisms may contribute to neuron transplantation therapies, for which the incorporation of transplanted neurons into pre-existing neural circuits is essential. Thus, clarifying the axon guidance mechanisms of mossy fiber sprouting could lead to an understanding of central nervous system (CNS network reorganization and plasticity. Here, we review the molecular and cellular mechanisms of axon guidance in mossy fiber sprouting by discussing mainly in vitro studies.

Reversible acute axonal polyneuropathy associated with Wernicke-Korsakoff syndrome: impaired physiological nerve conduction due to thiamine deficiency?

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Ishibashi, S; Yokota, T; Shiojiri, T; Matunaga, T; Tanaka, H; Nishina, K; Hirota, H; Inaba, A; Yamada, M; Kanda, T; Mizusawa, H

2003-05-01

Acute axonal polyneuropathy and Wernicke-Korsakoff encephalopathy developed simultaneously in three patients. Nerve conduction studies (NCS) detected markedly decreased compound muscle action potentials (CMAPs) and sensory nerve action potentials (SNAPs) with minimal conduction slowing; sympathetic skin responses (SSRs) were also notably decreased. Sural nerve biopsies showed only mild axonal degeneration with scattered myelin ovoid formation. The symptoms of neuropathy lessened within two weeks after an intravenous thiamine infusion. CMAPs, SNAPs, and SSRs also increased considerably. We suggest that this is a new type of peripheral nerve impairment: physiological conduction failure with minimal conduction delay due to thiamine deficiency.

Behaviour of oligodendrocytes and Schwann cells in an experimental model of toxic demyelination of the central nervous system Comportamento de oligodendrócitos e células de Schwann em modelo experimental de desmielinização tóxica do sistema nervoso central

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Dominguita Lühers Graça

2001-06-01

Full Text Available Oligodendrocytes and Schwann cells are engaged in myelin production, maintenance and repairing respectively in the central nervous system (CNS and the peripheral nervous system (PNS. Whereas oligodendrocytes act only within the CNS, Schwann cells are able to invade the CNS in order to make new myelin sheaths around demyelinated axons. Both cells have some limitations in their activities, i.e. oligodendrocytes are post-mitotic cells and Schwann cells only get into the CNS in the absence of astrocytes. Ethidium bromide (EB is a gliotoxic chemical that when injected locally within the CNS, induce demyelination. In the EB model of demyelination, glial cells are destroyed early after intoxication and Schwann cells are free to approach the naked central axons. In normal Wistar rats, regeneration of lost myelin sheaths can be achieved as early as thirteen days after intoxication; in Wistar rats immunosuppressed with cyclophosphamide the process is delayed and in rats administered cyclosporine it may be accelerated. Aiming the enlightening of those complex processes, all events concerning the myelinating cells in an experimental model are herein presented and discussed.Oligodendrócitos e células de Schwann realizam a produção e manutenção das bainhas de mielina, respectivamente no sistema nervoso central (SNC e periférico (SNP. As células de Schwann, à diferença dos oligodendrócitos, são capazes de invadir o SNC para remielinizar axônios desmielinizados, sempre que os astrócitos tenham sido destruídos. O brometo de etídio é uma droga gliotóxica usada para induzir desmielinização com o desaparecimento precoce de astrócitos, de modo que as células de Schwann têm liberdade para invadir o SNC. Em ratos Wistar normais, a remielinização é detectada treze dias após desmielinização; em ratos Wistar imunossuprimidos com ciclofosfamida a reparação do tecido é tardia, enquanto que em animais tratados com ciclosporina ela �

Recovery of function, peripheral sensitization and sensory neurone activation by novel pathways following axonal injury in Aplysia californica.

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Dulin, M F; Steffensen, I; Morris, C E; Walters, E T

1995-10-01

Recovery of behavioural and sensory function was examined following unilateral pedal nerve crush in Aplysia californica. Nerve crush that transected all axons connecting the tail to the central nervous system (CNS) eliminated the ipsilateral tail-evoked siphon reflex, whose sensory input travels in the crushed tail nerve (p9). The first reliable signs of recovery of this reflex were observed within 1 week, and most animals displayed tail-evoked siphon responses within 2 weeks. Wide-dynamic-range mechanosensory neurons with somata in the ventrocaudal (VC) cluster of the ipsilateral pleural ganglion exhibited a few receptive fields (RFs) on the tail 3 weeks after unilateral pedal nerve crush, indicating that the RFs had either regenerated or been reconnected to the central somata. These RFs were smaller and sensitized compared with corresponding RFs on the contralateral, uncrushed side. Centrally conducted axon responses of VC sensory neurones to electrical stimulation distal to the nerve crush site did not reappear until at least 10 days after the crush. Because the crush site was much closer to the CNS than to the tail, the failure of axon responses to be restored earlier than the behavioural responses indicates that early stages of reflex recovery are not due to regeneration of VC sensory neurone axons into the tail. Following nerve crush, VC sensory neurones often could be activated by stimulating central connectives or peripheral nerves that do not normally contain the sensory neurone's axons. These results suggest that recovery of behavioral function after nerve injury involves complex mechanisms, including regenerative growth of axotomized VC sensory neurones, sensitization of regenerating RFs and sprouting of VC sensory neurone fibres within the CNS. Furthermore, the rapidity of behavioural recovery indicates that its initial phases are mediated by additional mechanisms, perhaps centripetal regeneration of unidentified sensory neurones having peripheral

Mouse Intermittent Hypoxia Mimicking Apnea of Prematurity: Effects on Myelinogenesis and Axonal Maturation

OpenAIRE

CAI, JUN; TUONG, CHI MINH; ZHANG, YIPING; SHIELDS, CHRISTOPHER B.; GUO, GANG; FU, HUI; GOZAL, DAVID

2011-01-01

Premature babies are at high risk for both infantile apnea and long-term neurobehavioral deficits. Recent studies suggest that diffuse structural changes in brain white matter are a positive predictor of poor cognitive outcomes. Since oligodendrocyte maturation, myelination, axon development and synapse formation mainly occur in the 3rd trimester of gestation and 1st postnatal year, infantile apnea could lead to and/or exaggerate white matter impairments in preterm neonates. Therefore, we inv...

Role of T cell – glial cell interactions in creating and amplifying Central Nervous System inflammation and Multiple Sclerosis disease symptoms

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Eric S. Huseby

2015-08-01

Full Text Available Multiple Sclerosis (MS is an inflammatory disease of the Central Nervous System (CNS that causes the demyelination of nerve cells and destroys oligodendrocytes, neurons and axons. Historically, MS has been thought of as a T cell-mediated autoimmune disease of CNS white matter. However, recent studies have identified gray matter lesions in MS patients, suggesting that CNS antigens other than myelin proteins may be involved during the MS disease process. We have recently found that T cells targeting astrocyte-specific antigens can drive unique aspects of inflammatory CNS autoimmunity, including the targeting of gray matter and white matter of the brain and inducing heterogeneous clinical disease courses. In addition to being a target of T cells, astrocytes play a critical role in propagating the inflammatory response within the CNS through cytokine induced NF-ΚB signaling. Here, we will discuss the pathophysiology of CNS inflammation mediated by T cell – glial cell interactions and its contributions to CNS autoimmunity.

Myelin Formation during Development of the CNS Is Delayed in Matrix Metalloproteinase-9 and -12 Null Mice

DEFF Research Database (Denmark)

Larsen, Peter Hjørringgaard; DaSilva, Angelika G.; Conant, Kathrine

2006-01-01

was correlated with fewer mature oligodendrocytes, but similar precursor cell numbers, in MMP null animals compared with wild type. Because an important growth factor for oligodendrocyte maturation is insulin-like growth factor-1 (IGF-1), we addressed whether this was involved in the deficient myelination in MMP...

Myosin Va associates with mRNA in ribonucleoprotein particles present in myelinated peripheral axons and in the central nervous system.

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Calliari, Aldo; Farías, Joaquina; Puppo, Agostina; Canclini, Lucía; Mercer, John A; Munroe, David; Sotelo, José R; Sotelo-Silveira, José R

2014-03-01

Sorting of specific mRNAs to particular cellular locations and regulation of their translation is an essential mechanism underlying cell polarization. The transport of RNAs by kinesins and dyneins has been clearly established in several cell models, including neurons in culture. A similar role appears to exist in higher eukaryotes for the myosins. Myosin Va (Myo5a) has been described as a component of ribonucleoprotein particles (RNPs) in the adult rat nervous system and associated to ZBP1 and ribosomes in ribosomal periaxoplasmic plaques (PARPs), making it a likely candidate for mediating some aspects of RNA transport in neurons. To test this hypothesis, we have characterized RNPs containing Myo5a in adult brains of rats and mice. Microarray analysis of RNAs co-immunoprecipitated with Myo5a indicates that this motor may associate with a specific subpopulation of neuronal mRNAs. We found mRNAs encoding α-synuclein and several proteins with functions in translation in these RNPs. Immunofluorescence analyses of RNPs showed apparent co-localization of Myo5a with ribosomes, mRNA and RNA-binding proteins in discrete structures present both in axons of neurons in culture and in myelinated fibers of medullary roots. Our data suggest that PARPs include RNPs bearing the mRNA coding for Myo5a and are equipped with kinesin and Myo5a molecular motors. In conclusion, we suggest that Myo5a is involved in mRNA trafficking both in the central and peripheral nervous systems. Copyright © 2013 Wiley Periodicals, Inc.

Phosphorylation of myelin basic proteins and its relevance to myelin biogenesis

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Ulmer, J.B.

1985-01-01

Age-related differences in the in vivo incorporation of (32-P) into mouse myelin basic proteins (MBPs) of the central nervous system were observed. The resulting specific radioactivity (S.A.) of the MBPs appeared to be related to the S.A. of the acid-soluble pool of phosphates of myelin. In development, MBPs were phosphorylated in vivo prior to the onset of myelination in the brain, indicating that MBPs are phosphorylated prior to their deposition in the myelin sheath. The incorporation of (32-P) into MBPs and the turnover rates of MBP phosphates were studied in vivo in developmentally-related myelin compartments. The results suggest that there are two separate events in MBP phosphorylation and that the turnover rates of the MBP phosphates derived from these two events are different. A model for MBP phosphorylation, that could explain in these observations, is postulated and discussed in the light of existing information.

Wallerian degeneration: gaining perspective on inflammatory events after peripheral nerve injury

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Popovich Phillip G

2011-08-01

Full Text Available Abstract In this review, we first provide a brief historical perspective, discussing how peripheral nerve injury (PNI may have caused World War I. We then consider the initiation, progression, and resolution of the cellular inflammatory response after PNI, before comparing the PNI inflammatory response with that induced by spinal cord injury (SCI. In contrast with central nervous system (CNS axons, those in the periphery have the remarkable ability to regenerate after injury. Nevertheless, peripheral nervous system (PNS axon regrowth is hampered by nerve gaps created by injury. In addition, the growth-supportive milieu of PNS axons is not sustained over time, precluding long-distance regeneration. Therefore, studying PNI could be instructive for both improving PNS regeneration and recovery after CNS injury. In addition to requiring a robust regenerative response from the injured neuron itself, successful axon regeneration is dependent on the coordinated efforts of non-neuronal cells which release extracellular matrix molecules, cytokines, and growth factors that support axon regrowth. The inflammatory response is initiated by axonal disintegration in the distal nerve stump: this causes blood-nerve barrier permeabilization and activates nearby Schwann cells and resident macrophages via receptors sensitive to tissue damage. Denervated Schwann cells respond to injury by shedding myelin, proliferating, phagocytosing debris, and releasing cytokines that recruit blood-borne monocytes/macrophages. Macrophages take over the bulk of phagocytosis within days of PNI, before exiting the nerve by the circulation once remyelination has occurred. The efficacy of the PNS inflammatory response (although transient stands in stark contrast with that of the CNS, where the response of nearby cells is associated with inhibitory scar formation, quiescence, and degeneration/apoptosis. Rather than efficiently removing debris before resolving the inflammatory response as

A role of peripheral myelin protein 2 in lipid homeostasis of myelinating Schwann cells

NARCIS (Netherlands)

Zenker, J.; Stettner, M.; Ruskamo, S.; Domenech-Estevez, E.; Baloui, H.; Medard, J.J.; Verheijen, M.H.G.; Brouwers, J.F.; Kursula, P.; Kieseier, B.C.; Chrast, R.

2014-01-01

Peripheral myelin protein 2 (Pmp2, P2 or Fabp8), a member of the fatty acid binding protein family, was originally described together with myelin basic protein (Mbp or P1) and myelin protein zero (Mpz or P0) as one of the most abundant myelin proteins in the peripheral nervous system (PNS). Although

A role of peripheral myelin protein 2 in lipid homeostasis of myelinating Schwann cells.

NARCIS (Netherlands)

Zenker, Jennifer; ruskamo, salla; domenech-estevez, Enric; medard, jean-jacques; Verheijen, M.H.; Brouwers, Jos|info:eu-repo/dai/nl/173812694; Kursula, Petri; kieseier, bernd; Chrast, Roman

Peripheral myelin protein 2 (Pmp2, P2 or Fabp8), a member of the fatty acid binding protein family, was originally described together with myelin basic protein (Mbp or P1) and myelin protein zero (Mpz or P0) as one of the most abundant myelin proteins in the peripheral nervous system (PNS). Although

The age factor in axonal repair after spinal cord injury: A focus on neuron-intrinsic mechanisms.

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Geoffroy, Cédric G; Meves, Jessica M; Zheng, Binhai

2017-06-23

Age is an important consideration for recovery and repair after spinal cord injury. Spinal cord injury is increasingly affecting the middle-aged and aging populations. Despite rapid progress in research to promote axonal regeneration and repair, our understanding of how age can modulate this repair is rather limited. In this review, we discuss the literature supporting the notion of an age-dependent decline in axonal growth after central nervous system (CNS) injury. While both neuron-intrinsic and extrinsic factors are involved in the control of axon growth after injury, here we focus on possible intrinsic mechanisms for this age-dependent decline. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Conduction block of mammalian myelinated nerve by local cooling to 15–30°C after a brief heating

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Zhang, Zhaocun; Lyon, Timothy D.; Kadow, Brian T.; Shen, Bing; Wang, Jicheng; Lee, Andy; Kang, Audry; Roppolo, James R.; de Groat, William C.

2016-01-01

This study aimed at understanding thermal effects on nerve conduction and developing new methods to produce a reversible thermal block of axonal conduction in mammalian myelinated nerves. In 13 cats under α-chloralose anesthesia, conduction block of pudendal nerves (n = 20) by cooling (5–30°C) or heating (42–54°C) a small segment (9 mm) of the nerve was monitored by the urethral striated muscle contractions and increases in intraurethral pressure induced by intermittent (5 s on and 20 s off) electrical stimulation (50 Hz, 0.2 ms) of the nerve. Cold block was observed at 5–15°C while heat block occurred at 50–54°C. A complete cold block up to 10 min was fully reversible, but a complete heat block was only reversible when the heating duration was less than 1.3 ± 0.1 min. A brief (block at 50–54°C or 15 min of nonblock mild heating at 46–48°C significantly increased the cold block temperature to 15–30°C. The effect of heating on cold block fully reversed within ∼40 min. This study discovered a novel method to block mammalian myelinated nerves at 15–30°C, providing the possibility to develop an implantable device to block axonal conduction and treat many chronic disorders. The effect of heating on cold block is of considerable interest because it raises many basic scientific questions that may help reveal the mechanisms underlying cold or heat block of axonal conduction. PMID:26740534

Transient developmental Purkinje cell axonal torpedoes in healthy and ataxic mouse cerebellum

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Lovisa Ljungberg

2016-11-01

Full Text Available Information is carried out of the cerebellar cortical microcircuit via action potentials propagated along Purkinje cell axons. In several human neurodegenerative diseases, focal axonal swellings on Purkinje cells – known as torpedoes – have been associated with Purkinje cell loss. Interestingly, torpedoes are also reported to appear transiently during development in rat cerebellum. The function of Purkinje cell axonal torpedoes in health as well as in disease is poorly understood. We investigated the properties of developmental torpedoes in the postnatal mouse cerebellum of wildtype and transgenic mice. We found that Purkinje cell axonal torpedoes transiently appeared on axons of Purkinje neurons, with the largest number of torpedoes observed at postnatal day 11 (P11. This was after peak developmental apoptosis had occurred, when Purkinje cell counts in a lobule were static, suggesting that most developmental torpedoes appear on axons of neurons that persist into adulthood. We found that developmental torpedoes were not associated with a presynaptic GABAergic marker, indicating that they are not synapses. They were seldom found at axonal collateral branch points, and lacked microglia enrichment, suggesting that they are unlikely to be involved in axonal refinement. Interestingly, we found several differences between developmental torpedoes and disease-related torpedoes: developmental torpedoes occured largely on myelinated axons, and were not associated with changes in basket cell innervation on their parent soma. Disease-related torpedoes are typically reported to contain neurofilament; while the majority of developmental torpedoes did as well, a fraction of smaller developmental torpedoes did not. These differences indicate that developmental torpedoes may not be functionally identical to disease-related torpedoes. To study this further, we used a mouse model of spinocerebellar ataxia type 6 (SCA6, and found elevated disease

Depolarization and electrical stimulation enhance in vitro and in vivo sensory axon growth after spinal cord injury.

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Goganau, Ioana; Sandner, Beatrice; Weidner, Norbert; Fouad, Karim; Blesch, Armin

2018-02-01

Activity dependent plasticity is a key mechanism for the central nervous system (CNS) to adapt to its environment. Whether neuronal activity also influences axonal regeneration in the injured CNS, and whether electrical stimulation (ES) can activate regenerative programs in the injured CNS remains incompletely understood. Using KCl-induced depolarization, in vivo ES followed by ex-vivo neurite growth assays and ES after spinal cord lesions and cell grafting, we aimed to identify parameters important for ES-enhanced neurite growth and axonal regeneration. Using cultures of sensory neurons, neurite growth was analyzed after KCl-induced depolarization for 1-72h. Increased neurite growth was detected after short-term stimulation and after longer stimulation if a sufficient delay between stimulation and growth measurements was provided. After in vivo ES (20Hz, 2× motor threshold, 0.2ms, 1h) of the intact sciatic nerve in adult Fischer344 rats, sensory neurons showed a 2-fold increase in in vitro neurite length one week later compared to sham animals, an effect not observed one day after ES. Longer ES (7h) and repeated ES (7days, 1h each) also increased growth by 56-67% one week later, but provided no additional benefit. In vivo growth of dorsal column sensory axons into a graft of bone marrow stromal cells 4weeks after a cervical spinal cord lesion was also enhanced with a single post-injury 1h ES of the intact sciatic nerve and was also observed after repeated ES without inducing pain-like behavior. While ES did not result in sensory functional recovery, our data indicate that ES has time-dependent influences on the regenerative capacity of sensory neurons and might further enhance axonal regeneration in combinatorial approaches after SCI. Copyright © 2017 Elsevier Inc. All rights reserved.

Interaction between the C-terminal region of human myelin basic protein and calmodulin: analysis of complex formation and solution structure

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Hayashi Nobuhiro

2008-02-01

Full Text Available Abstract Background The myelin sheath is a multilamellar membrane structure wrapped around the axon, enabling the saltatory conduction of nerve impulses in vertebrates. Myelin basic protein, one of the most abundant myelin-specific proteins, is an intrinsically disordered protein that has been shown to bind calmodulin. In this study, we focus on a 19-mer synthetic peptide from the predicted calmodulin-binding segment near the C-terminus of human myelin basic protein. Results The interaction of native human myelin basic protein with calmodulin was confirmed by affinity chromatography. The binding of the myelin basic protein peptide to calmodulin was tested with isothermal titration calorimetry (ITC in different temperatures, and Kd was observed to be in the low μM range, as previously observed for full-length myelin basic protein. Surface plasmon resonance showed that the peptide bound to calmodulin, and binding was accompanied by a conformational change; furthermore, gel filtration chromatography indicated a decrease in the hydrodynamic radius of calmodulin in the presence of the peptide. NMR spectroscopy was used to map the binding area to reside mainly within the hydrophobic pocket of the C-terminal lobe of calmodulin. The solution structure obtained by small-angle X-ray scattering indicates binding of the myelin basic protein peptide into the interlobal groove of calmodulin, while calmodulin remains in an extended conformation. Conclusion Taken together, our results give a detailed structural insight into the interaction of calmodulin with a C-terminal segment of a major myelin protein, the myelin basic protein. The used 19-mer peptide interacts mainly with the C-terminal lobe of calmodulin, and a conformational change accompanies binding, suggesting a novel mode of calmodulin-target protein interaction. Calmodulin does not collapse and wrap around the peptide tightly; instead, it remains in an extended conformation in the solution structure

A Fat-Facets-Dscam1-JNK Pathway Enhances Axonal Growth in Development and after Injury

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Marta Koch

2018-02-01

Full Text Available Injury to the adult central nervous systems (CNS can result in severe long-term disability because damaged CNS connections fail to regenerate after trauma. Identification of regulators that enhance the intrinsic growth capacity of severed axons is a first step to restore function. Here, we conducted a gain-of-function genetic screen in Drosophila to identify strong inducers of axonal growth after injury. We focus on a novel axis the Down Syndrome Cell Adhesion Molecule (Dscam1, the de-ubiquitinating enzyme Fat Facets (Faf/Usp9x and the Jun N-Terminal Kinase (JNK pathway transcription factor Kayak (Kay/Fos. Genetic and biochemical analyses link these genes in a common signaling pathway whereby Faf stabilizes Dscam1 protein levels, by acting on the 3′-UTR of its mRNA, and Dscam1 acts upstream of the growth-promoting JNK signal. The mammalian homolog of Faf, Usp9x/FAM, shares both the regenerative and Dscam1 stabilizing activities, suggesting a conserved mechanism.

Evaluation of myelination and myelination disorders with turbo inversion recovery magnetic resonance imaging

International Nuclear Information System (INIS)

Daldrup, H.E.; Schuierer, G.; Link, T.M.; Moeller, H.; Bick, U.; Peters, P.E.; Kurlemann, G.

1997-01-01

The aim of our work was to determine the efficacy of turbo inversion recovery spin echo (TIRSE) pulse sequences in differentiating patients with normal and abnormal myelination. Twenty neurological normal children (aged 5 months to 12 years) as well as 65 children presenting clinically with neurologic developmental deficits (aged 2 months to 10 years) were examined using TIRSE, T1-weighted SE, and T2-weighted turbo SE pulse sequences. Contrast-to-noise-ratio (CNR) between myelinated white and gray matter was compared for the different pulse sequences. In addition, two readers analyzed all images qualitatively by consensus. The CNR values were significantly higher on TIRSE images as compared with conventional images (p < 0.05). Forty-two neurologically abnormal patients displayed a normal myelination on all sequences, whereas 23 showed an abnormal myelination. The TIRSE sequence provided a sensitive and specific depiction of an abnormal myelination in all of these patients. The TIRSE sequence provided additional information to conventional pulse sequences in determining myelination disorders in children, especially in children older than 2 years. (orig.)

Schwann cell-derived Apolipoprotein D controls the dynamics of post-injury myelin recognition and degradation

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Nadia eGarcía-Mateo

2014-11-01

Full Text Available Management of lipids, particularly signaling lipids that control neuroinflammation, is crucial for the regeneration capability of a damaged nervous system. Knowledge of pro- and anti-inflammatory signals after nervous system injury is extensive, most of them being proteins acting through well-known receptors and intracellular cascades. However, the role of lipid binding extracellular proteins able to modify the fate of lipids released after injury is not well understood.Apolipoprotein D (ApoD is an extracellular lipid binding protein of the Lipocalin family induced upon nervous system injury. Our previous study shows that axon regeneration is delayed without ApoD, and suggests its participation in early events during Wallerian degeneration. Here we demonstrate that ApoD is expressed by myelinating and non-myelinating Schwann cells and is induced early upon nerve injury. We show that ApoD, known to bind arachidonic acid (AA, also interacts with lysophosphatidylcholine (LPC in vitro. We use an in vivo model of nerve crush injury, a nerve explant injury model, and cultured macrophages exposed to purified myelin, to uncover that: (i ApoD regulates denervated Schwann cell-macrophage signaling, dampening MCP1- and Tnf-dependent macrophage recruitment and activation upon injury; (ii ApoD controls the over-expression of the phagocytosis activator Galectin-3 by infiltrated macrophages; (iii ApoD controls the basal and injury-triggered levels of LPC and AA; (iv ApoD modifies the dynamics of myelin-macrophage interaction, favoring the initiation of phagocytosis and promoting myelin degradation.Regulation of macrophage behaviour by Schwann-derived ApoD is therefore a key mechanism conditioning nerve injury resolution. These results place ApoD as a lipid binding protein controlling the signals exchanged between glia, neurons and blood-borne cells during nerve recovery after injury, and open the possibility for a therapeutic use of ApoD as a regeneration

Cdc42 and Rac1 signaling are both required for and act synergistically in the correct formation of myelin sheaths in the CNS

DEFF Research Database (Denmark)

Thurnherr, Tina; Benninger, Yves; Wu, Xunwei

2006-01-01

. This was characterized by the extraordinary enlargement of the inner tongue of the oligodendrocyte process and concomitant formation of a myelin outfolding as a result of abnormal accumulation of cytoplasm in this region. Ablation of Rac1 also resulted in the abnormal accumulation of cytoplasm in the inner tongue...... of the oligodendrocyte process, and we provide genetic evidence that rac1 synergizes with cdc42 in a gene dosage-dependent way to regulate myelination....

Botulinum toxin's axonal transport from periphery to the spinal cord.

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Matak, Ivica; Riederer, Peter; Lacković, Zdravko

2012-07-01

Axonal transport of enzymatically active botulinum toxin A (BTX-A) from periphery to the CNS has been described in facial and trigeminal nerve, leading to cleavage of synaptosomal-associated protein 25 (SNAP-25) in central nuclei. Aim of present study was to examine the existence of axonal transport of peripherally applied BTX-A to spinal cord via sciatic nerve. We employed BTX-A-cleaved SNAP-25 immunohistochemistry of lumbar spinal cord after intramuscular and subcutaneous hind limb injections, and intraneural BTX-A sciatic nerve injections. Truncated SNAP-25 in ipsilateral spinal cord ventral horns and dorsal horns appeared after single peripheral BTX-A administrations, even at low intramuscular dose applied (5 U/kg). Cleaved SNAP-25 appearance in the spinal cord after BTX-A injection into the sciatic nerve was prevented by proximal intrasciatic injection of colchicine (5 mM, 2 μl). Cleaved SNAP-25 in ventral horn, using choline-acetyltransferase (ChAT) double labeling, was localized within cholinergic neurons. These results extend the recent findings on BTX-A retrograde axonal transport in facial and trigeminal nerve. Appearance of truncated SNAP-25 in spinal cord following low-dose peripheral BTX-A suggest that the axonal transport of BTX-A occurs commonly following peripheral application. Copyright © 2012 Elsevier Ltd. All rights reserved.

γ-diketone central neuropathy: quantitative morphometric analysis of axons in rat spinal cord white matter regions and nerve roots

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LoPachin, Richard M.; Jortner, Bernard S.; Reid, Maria L.; Das, Soma

2003-01-01

A quantitative analytical method was used to measure myelinated axon morphometric parameters (e.g., axon area, ratio of axon area/fiber area, and index of circularity) in rat nervous tissue during intoxication with 2,5-hexanedione (HD). Parameters were assessed in nerve roots (dorsal and ventral) and in ascending (gracile fasciculus and spinocerebellar tract) and descending (corticospinal and rubrospinal tracts) spinal cord white matter tracts (L4-L5) of rats intoxicated with HD at two different daily dose-rates (175 or 400 mg HD/kg/day, gavage). For each dose-rate, tissue was sampled at four neurological endpoints: unaffected, slight, moderate, and severe toxicity, as determined by gait analysis and measurements of grip strength. Results indicate that, regardless of the HD dose-rate, axon atrophy (reduced axon area) was a widespread, abundant effect that developed in concert with neurological deficits. The atrophy response occurred contemporaneously in both ascending and descending spinal tracts, which suggests that loss of caliber developed simultaneously along the proximodistal axon axis. In contrast, swollen axons were a numerically small component and were present in nerve roots and spinal tracts only during subchronic intoxication at the lower HD dose-rate (i.e., 175 mg/kg/day). Intoxication at the higher dose-rate (400 mg/kg/day) produced neurological deficits in the absence of axonal swellings. These observations in conjunction with our previous studies of HD-induced peripheral neuropathy (Toxicol. Appl. Pharmacol. 135 (1995) 58; and Toxicol. Appl. Pharmacol. 165 (2000) 127) indicate that axon atrophy, and not axonal swelling, is a primary neuropathic phenomenon

Peptide mimetic of the S100A4 protein modulates peripheral nerve regeneration and attenuates the progression of neuropathy in myelin protein P0 null mice

DEFF Research Database (Denmark)

Moldovan, Mihai; Pinchenko, Volodymyr; Dmytriyeva, Oksana

2013-01-01

and mimicked the S100A4-induced neuroprotection in brain trauma. Here, we investigated a possible function of S100A4 and its mimetics in the pathologies of the peripheral nervous system (PNS). We found that S100A4 was expressed in the injured PNS and that its peptide mimetic (H3) affected the regeneration......, these effects were attributed to the modulatory effect of H3 on initial axonal sprouting. In contrast to the modest effect of H3 on the time course of regeneration, H3 had a long-term neuroprotective effect in the myelin protein P0 null mice, a model of dysmyelinating neuropathy (Charcot-Marie-Tooth type 1...... disease), where the peptide attenuated the deterioration of nerve conduction, demyelination and axonal loss. From these results, S100A4 mimetics emerge as a possible means to enhance axonal sprouting and survival, especially in the context of demyelinating neuropathies with secondary axonal loss...

Networks of myelin covariance

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Slater, David; Ruef, Anne; Sanabria‐Diaz, Gretel; Preisig, Martin; Kherif, Ferath; Draganski, Bogdan; Lutti, Antoine

2017-01-01

Abstract Networks of anatomical covariance have been widely used to study connectivity patterns in both normal and pathological brains based on the concurrent changes of morphometric measures (i.e., cortical thickness) between brain structures across subjects (Evans, 2013). However, the existence of networks of microstructural changes within brain tissue has been largely unexplored so far. In this article, we studied in vivo the concurrent myelination processes among brain anatomical structures that gathered together emerge to form nonrandom networks. We name these “networks of myelin covariance” (Myelin‐Nets). The Myelin‐Nets were built from quantitative Magnetization Transfer data—an in‐vivo magnetic resonance imaging (MRI) marker of myelin content. The synchronicity of the variations in myelin content between anatomical regions was measured by computing the Pearson's correlation coefficient. We were especially interested in elucidating the effect of age on the topological organization of the Myelin‐Nets. We therefore selected two age groups: Young‐Age (20–31 years old) and Old‐Age (60–71 years old) and a pool of participants from 48 to 87 years old for a Myelin‐Nets aging trajectory study. We found that the topological organization of the Myelin‐Nets is strongly shaped by aging processes. The global myelin correlation strength, between homologous regions and locally in different brain lobes, showed a significant dependence on age. Interestingly, we also showed that the aging process modulates the resilience of the Myelin‐Nets to damage of principal network structures. In summary, this work sheds light on the organizational principles driving myelination and myelin degeneration in brain gray matter and how such patterns are modulated by aging. PMID:29271053

Oxidative stress and proinflammatory cytokines contribute to demyelination and axonal damage in a cerebellar culture model of neuroinflammation.

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di Penta, Alessandra; Moreno, Beatriz; Reix, Stephanie; Fernandez-Diez, Begoña; Villanueva, Maite; Errea, Oihana; Escala, Nagore; Vandenbroeck, Koen; Comella, Joan X; Villoslada, Pablo

2013-01-01

Demyelination and axonal damage are critical processes in the pathogenesis of multiple sclerosis (MS). Oxidative stress and pro-inflammatory cytokines elicited by inflammation mediates tissue damage. To monitor the demyelination and axonal injury associated with microglia activation we employed a model using cerebellar organotypic cultures stimulated with lipopolysaccharide (LPS). Microglia activated by LPS released pro-inflammatory cytokines (IL-1β, IL-6 and TNFα), and increased the expression of inducible nitric oxide synthase (iNOS) and production of reactive oxygen species (ROS). This activation was associated with demyelination and axonal damage in cerebellar cultures. Axonal damage, as revealed by the presence of non-phosphorylated neurofilaments, mitochondrial accumulation in axonal spheroids, and axonal transection, was associated with stronger iNOS expression and concomitant increases in ROS. Moreover, we analyzed the contribution of pro-inflammatory cytokines and oxidative stress in demyelination and axonal degeneration using the iNOS inhibitor ethyl pyruvate, a free-scavenger and xanthine oxidase inhibitor allopurinol, as well as via blockage of pro-inflammatory cytokines using a Fc-TNFR1 construct. We found that blocking microglia activation with ethyl pyruvate or allopurinol significantly decreased axonal damage, and to a lesser extent, demyelination. Blocking TNFα significantly decreased demyelination but did not prevented axonal damage. Moreover, the most common therapy for MS, interferon-beta, was used as an example of an immunomodulator compound that can be tested in this model. In vitro, interferon-beta treatment decreased oxidative stress (iNOS and ROS levels) and the release of pro-inflammatory cytokines after LPS stimulation, reducing axonal damage. The model of neuroinflammation using cerebellar culture stimulated with endotoxin mimicked myelin and axonal damage mediated by the combination of oxidative stress and pro-inflammatory cytokines

An oral Na(V)1.8 blocker improves motor function in mice completely deficient of myelin protein P-0

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Rosberg, Mette R.; Alvarez Herrero, Susana; Krarup, Christian

2016-01-01

Mice deficient of myelin protein P0 are established models of demyelinating Charcot-Marie-Tooth (CMT) disease. Dysmyelination in these mice is associated with an ectopic expression of the sensory neuron specific sodium channel isoform NaV1.8 on motor axons. We reported that in P0+/−, a model of CMT......1B, the membrane dysfunction could be acutely improved by a novel oral NaV1.8 blocker referred to as Compound 31 (C31, Bioorg. Med. Chem. Lett. 2010, 20, 6812; AbbVie Inc.). The aim of this study was to investigate the extent to which C31 treatment could also improve the motor axon function in P0......-of-concept that treatment with oral subtype-selective NaV1.8 blockers could be used to improve the motor function in severe forms of demyelinating CMT....

Magnetic resonance imaging and myelin

International Nuclear Information System (INIS)

Adamsbaum, C.; Andre, C.; Rolland, Y.

1995-01-01

Postnatal development of the brain is characterized by growth and by myelination. Myelination of the brain normally extends from birth until about two years of age. MRI changes corresponding to the various myelination stages are due mainly to changes in the water content of the cerebral parenchyma. Myelination kinetics follow a fairly precise timetable, with variations across areas of the brain. Abnormalities of white matter are responsible for relatively stereotyped, nonspecific manifestations, which are mainly due to an increase in the amount of water contained in diseased white matter, whatever the cause of the disorder. Interpretation is based on the location, distribution, and progression of lesions. (authors). 7 refs., 5 figs

SAD kinases sculpt axonal arbors of sensory neurons through long and short-term responses to neurotrophin signals

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Lilley, Brendan N.; Pan, Y. Albert; Sanes, Joshua R.

2013-01-01

SUMMARY Extrinsic cues activate intrinsic signaling mechanisms to pattern neuronal shape and connectivity. We showed previously that three cytoplasmic Ser/Thr kinases, LKB1, SAD-A and SAD-B, control early axon-dendrite polarization in forebrain neurons. Here we assess their role in other neuronal types. We found that all three kinases are dispensable for axon formation outside of the cortex, but that SAD kinases are required for formation of central axonal arbors by subsets of sensory neurons. The requirement for SAD kinases is most prominent in NT-3 dependent neurons. SAD kinases transduce NT-3 signals in two ways through distinct pathways. First, sustained NT-3/TrkC signaling increases SAD protein levels. Second, short duration NT-3/TrkC signals transiently activate SADs by inducing dephosphorylation of C-terminal domains, thereby allowing activating phosphorylation of the kinase domain. We propose that SAD kinases integrate long- and short duration signals from extrinsic cues to sculpt axon arbors within the CNS. PMID:23790753

Retinal ganglion cell survival and axon regeneration after optic nerve injury in naked mole-rats.

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Park, Kevin K; Luo, Xueting; Mooney, Skyler J; Yungher, Benjamin J; Belin, Stephane; Wang, Chen; Holmes, Melissa M; He, Zhigang

2017-02-01

In the adult mammalian central nervous system (CNS), axonal damage often triggers neuronal cell death and glial activation, with very limited spontaneous axon regeneration. In this study, we performed optic nerve injury in adult naked mole-rats, the longest living rodent, with a maximum life span exceeding 30 years, and found that injury responses in this species are quite distinct from those in other mammalian species. In contrast to what is seen in other mammals, the majority of injured retinal ganglion cells (RGCs) survive with relatively high spontaneous axon regeneration. Furthermore, injured RGCs display activated signal transducer and activator of transcription-3 (STAT3), whereas astrocytes in the optic nerve robustly occupy and fill the lesion area days after injury. These neuron-intrinsic and -extrinsic injury responses are reminiscent of those in "cold-blooded" animals, such as fish and amphibians, suggesting that the naked mole-rat is a powerful model for exploring the mechanisms of neuronal injury responses and axon regeneration in mammals. J. Comp. Neurol. 525:380-388, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Schwann Cell Precursors from Human Pluripotent Stem Cells as a Potential Therapeutic Target for Myelin Repair.

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Kim, Han-Seop; Lee, Jungwoon; Lee, Da Yong; Kim, Young-Dae; Kim, Jae Yun; Lim, Hyung Jin; Lim, Sungmin; Cho, Yee Sook

2017-06-06

Schwann cells play a crucial role in successful nerve repair and regeneration by supporting both axonal growth and myelination. However, the sources of human Schwann cells are limited both for studies of Schwann cell development and biology and for the development of treatments for Schwann cell-associated diseases. Here, we provide a rapid and scalable method to produce self-renewing Schwann cell precursors (SCPs) from human pluripotent stem cells (hPSCs), using combined sequential treatment with inhibitors of the TGF-β and GSK-3 signaling pathways, and with neuregulin-1 for 18 days under chemically defined conditions. Within 1 week, hPSC-derived SCPs could be differentiated into immature Schwann cells that were functionally confirmed by their secretion of neurotrophic factors and their myelination capacity in vitro and in vivo. We propose that hPSC-derived SCPs are a promising, unlimited source of functional Schwann cells for treating demyelination disorders and injuries to the peripheral nervous system. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Autophagy is involved in the reduction of myelinating Schwann cell cytoplasm during myelin maturation of the peripheral nerve.

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So Young Jang

Full Text Available Peripheral nerve myelination involves dynamic changes in Schwann cell morphology and membrane structure. Recent studies have demonstrated that autophagy regulates organelle biogenesis and plasma membrane dynamics. In the present study, we investigated the role of autophagy in the development and differentiation of myelinating Schwann cells during sciatic nerve myelination. Electron microscopy and biochemical assays have shown that Schwann cells remove excess cytoplasmic organelles during myelination through macroautophagy. Inhibition of autophagy via Schwann cell-specific removal of ATG7, an essential molecule for macroautophagy, using a conditional knockout strategy, resulted in abnormally enlarged abaxonal cytoplasm in myelinating Schwann cells that contained a large number of ribosomes and an atypically expanded endoplasmic reticulum. Small fiber hypermyelination and minor anomalous peripheral nerve functions are observed in this mutant. Rapamycin-induced suppression of mTOR activity during the early postnatal period enhanced not only autophagy but also developmental reduction of myelinating Schwann cells cytoplasm in vivo. Together, our findings suggest that autophagy is a regulatory mechanism of Schwann cells structural plasticity during myelination.

[Regularities of fixation of brain serum antibodies from patients with lateral amyotrophic sclerosis in rabbit CNS].

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Musaeva, L S; Gannyshkina, I V; Zavalishin, I A; Markova, E D; Ivanova-Smolenskaia, I A

2002-01-01

Kuhns' indirect immunofluorescent test was used to study fixation of serum brain antibodies (Ab) of patients with bulbar, cervicothoracic, lumbosacral lateral amyotropic sclerosis (LAS) on brain sections of rabbits. The disease is characterized by formation of brain Ab complementary to various structures of nervous and glial cells, myelin of fibers from different conducting systems, vessels which exhibit both common and individual antigenic properties. It was found that fixation of antineuronal, antimyelin brain Ab of patients with bulbar, cervicothoracic and lumbosacral LAS in different CNS structures varies.

Sustained neonatal hyperthyroidism in the rat affects myelination in the central nervous system.

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Marta, C B; Adamo, A M; Soto, E F; Pasquini, J M

1998-07-15

We have carried out a study of the effects of sustained neonatal hyperthyroidism on myelin and on the oligodendroglial cells, in an effort to obtain further insight into the molecular mechanisms underlying the action of thyroid hormones on the central nervous system (CNS). Expression of the mRNAs of myelin basic protein (MBP) myelin proteolipid protein (PLP), 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase), transferrin, and c-Jun was investigated in 10- and 17-day-old normal and hyperthyroid rats, using Northern blot analysis. At 10 days of age, the levels of all the explored mRNAs were markedly higher in the experimental animals. The mRNA of transferrin showed a ninefold increase over control values, suggesting the possibility that this putative trophic factor might act as one of the mediators in the action of thyroid hormones. At 17 days of age on the other hand, the levels of all the mRNAs decreased markedly, reaching values below control, except for c-Jun, which remained higher than in normals. At 70 days of age, hyperthyroid rats showed clear evidence of myelin deficit, in agreement with previous results of our laboratories (Pasquini et al.: J Neurochem 57: Suppl S124, 1991). Immunocytochemistry of 70-day-old rat brain tissue sections showed a substantial reduction in the amount of MBP-reacting structures and a marked decrease in the number of oligodendroglial cells. Although the above-mentioned results could be the consequence, as proposed by Barres et al. (Development 120:1097-1108, 1994) and Baas et al. (Glia 19:324-332, 1997) of a premature arrest in oligodendroglial cell proliferation followed by early differentiation, the persistent high levels of expression of c-Jun, together with the dramatic decrease in the number of oligodendrocytes, suggested the possibility that prolonged hyperthyroidism could activate apoptotic mechanisms in the myelin forming cells. Using propidium iodide-labeled isolated oligodendroglial cells, we found, by flow cytometry

Reduced Synapse and Axon Numbers in the Prefrontal Cortex of Rats Subjected to a Chronic Stress Model for Depression

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Csabai, Dávid; Wiborg, Ove; Czéh, Boldizsár

2018-01-01

Stressful experiences can induce structural changes in neurons of the limbic system. These cellular changes contribute to the development of stress-induced psychopathologies like depressive disorders. In the prefrontal cortex of chronically stressed animals, reduced dendritic length and spine loss have been reported. This loss of dendritic material should consequently result in synapse loss as well, because of the reduced dendritic surface. But so far, no one studied synapse numbers in the prefrontal cortex of chronically stressed animals. Here, we examined synaptic contacts in rats subjected to an animal model for depression, where animals are exposed to a chronic stress protocol. Our hypothesis was that long term stress should reduce the number of axo-spinous synapses in the medial prefrontal cortex. Adult male rats were exposed to daily stress for 9 weeks and afterward we did a post mortem quantitative electron microscopic analysis to quantify the number and morphology of synapses in the infralimbic cortex. We analyzed asymmetric (Type I) and symmetric (Type II) synapses in all cortical layers in control and stressed rats. We also quantified axon numbers and measured the volume of the infralimbic cortex. In our systematic unbiased analysis, we examined 21,000 axon terminals in total. We found the following numbers in the infralimbic cortex of control rats: 1.15 × 109 asymmetric synapses, 1.06 × 108 symmetric synapses and 1.00 × 108 myelinated axons. The density of asymmetric synapses was 5.5/μm3 and the density of symmetric synapses was 0.5/μm3. Average synapse membrane length was 207 nm and the average axon terminal membrane length was 489 nm. Stress reduced the number of synapses and myelinated axons in the deeper cortical layers, while synapse membrane lengths were increased. These stress-induced ultrastructural changes indicate that neurons of the infralimbic cortex have reduced cortical network connectivity. Such reduced network connectivity is likely

Reduced Synapse and Axon Numbers in the Prefrontal Cortex of Rats Subjected to a Chronic Stress Model for Depression

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Dávid Csabai

2018-01-01

Full Text Available Stressful experiences can induce structural changes in neurons of the limbic system. These cellular changes contribute to the development of stress-induced psychopathologies like depressive disorders. In the prefrontal cortex of chronically stressed animals, reduced dendritic length and spine loss have been reported. This loss of dendritic material should consequently result in synapse loss as well, because of the reduced dendritic surface. But so far, no one studied synapse numbers in the prefrontal cortex of chronically stressed animals. Here, we examined synaptic contacts in rats subjected to an animal model for depression, where animals are exposed to a chronic stress protocol. Our hypothesis was that long term stress should reduce the number of axo-spinous synapses in the medial prefrontal cortex. Adult male rats were exposed to daily stress for 9 weeks and afterward we did a post mortem quantitative electron microscopic analysis to quantify the number and morphology of synapses in the infralimbic cortex. We analyzed asymmetric (Type I and symmetric (Type II synapses in all cortical layers in control and stressed rats. We also quantified axon numbers and measured the volume of the infralimbic cortex. In our systematic unbiased analysis, we examined 21,000 axon terminals in total. We found the following numbers in the infralimbic cortex of control rats: 1.15 × 109 asymmetric synapses, 1.06 × 108 symmetric synapses and 1.00 × 108 myelinated axons. The density of asymmetric synapses was 5.5/μm3 and the density of symmetric synapses was 0.5/μm3. Average synapse membrane length was 207 nm and the average axon terminal membrane length was 489 nm. Stress reduced the number of synapses and myelinated axons in the deeper cortical layers, while synapse membrane lengths were increased. These stress-induced ultrastructural changes indicate that neurons of the infralimbic cortex have reduced cortical network connectivity. Such reduced network

The Drosophila HEM-2/NAP1 homolog KETTE controls axonal pathfinding and cytoskeletal organization.

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Hummel, T; Leifker, K; Klämbt, C

2000-04-01

In Drosophila, the correct formation of the segmental commissures depends on neuron-glial interactions at the midline. The VUM midline neurons extend axons along which glial cells migrate in between anterior and posterior commissures. Here, we show that the gene kette is required for the normal projection of the VUM axons and subsequently disrupts glial migration. Axonal projection defects are also found for many other moto- and interneurons. In addition, kette affects the cell morphology of mesodermal and epidermal derivatives, which show an abnormal actin cytoskeleton. The KETTE protein is homologous to the transmembrane protein HEM-2/NAP1 evolutionary conserved from worms to vertebrates. In vitro analysis has shown a specific interaction of the vertebrate HEM-2/NAP1 with the SH2-SH3 adapter protein NCK and the small GTPase RAC1, which both have been implicated in regulating cytoskeleton organization and axonal growth. Hypomorphic kette mutations lead to axonal defects similar to mutations in the Drosophila NCK homolog dreadlocks. Furthermore, we show that kette and dock mutants genetically interact. NCK is thought to interact with the small G proteins RAC1 and CDC42, which play a role in axonal growth. In line with these observations, a kette phenocopy can be obtained following directed expression of mutant DCDC42 or DRAC1 in the CNS midline. In addition, the kette mutant phenotype can be partially rescued by expression of an activated DRAC1 transgene. Our data suggest an important role of the HEM-2 protein in cytoskeletal organization during axonal pathfinding.

Regeneration of Optic Nerve

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Kwok-Fai So

2011-05-01

Full Text Available The optic nerve is part of the central nervous system (CNS and has a structure similar to other CNS tracts. The axons that form the optic nerve originate in the ganglion cell layer of the retina and extend through the optic tract. As a tissue, the optic nerve has the same organization as the white matter of the brain in regard to its glia. There are three types of glial cells: Oligodendrocytes, astrocytes, and microglia. Little structural and functional regeneration of the CNS takes place spontaneously following injury in adult mammals. In contrast, the ability of the mammalian peripheral nervous system (PNS to regenerate axons after injury is well documented. A number of factors are involved in the lack of CNS regeneration, including: (i the response of neuronal cell bodies against the damage; (ii myelin-mediated inhibition by oligodendrocytes; (iii glial scarring, by astrocytes; (iv macrophage infiltration; and (v insufficient trophic factor support. The fundamental difference in the regenerative capacity between CNS and PNS neuronal cell bodies has been the subject of intensive research. In the CNS the target normally conveys a retrograde trophic signal to the cell body. CNS neurons die because of trophic deprivation. Damage to the optic nerve disconnects the neuronal cell body from its target-derived trophic peptides, leading to the death of retinal ganglion cells. Furthermore, the axontomized neurons become less responsive to the peptide trophic signals they do receive. On the other hand, adult PNS neurons are intrinsically responsive to neurotrophic factors and do not lose trophic responsiveness after axotomy. In this talk different strategies to promote optic-nerve regeneration in adult mammals are reviewed. Much work is still needed to resolve many issues. This is a very important area of neuroregeneration and neuroprotection, as currently there is no cure after traumatic optic nerve injury or retinal disease such as glaucoma, which

Immunological Demyelination Triggers Macrophage/Microglial Cells Activation without Inducing Astrogliosis

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Frank Cloutier

2013-01-01

Full Text Available The glial scar formed by reactive astrocytes and axon growth inhibitors associated with myelin play important roles in the failure of axonal regeneration following central nervous system (CNS injury. Our laboratory has previously demonstrated that immunological demyelination of the CNS facilitates regeneration of severed axons following spinal cord injury. In the present study, we evaluate whether immunological demyelination is accompanied with astrogliosis. We compared the astrogliosis and macrophage/microglial cell responses 7 days after either immunological demyelination or a stab injury to the dorsal funiculus. Both lesions induced a strong activated macrophage/microglial cells response which was significantly higher within regions of immunological demyelination. However, immunological demyelination regions were not accompanied by astrogliosis compared to stab injury that induced astrogliosis which extended several millimeters above and below the lesions, evidenced by astroglial hypertrophy, formation of a glial scar, and upregulation of intermediate filaments glial fibrillary acidic protein (GFAP. Moreover, a stab or a hemisection lesion directly within immunological demyelination regions did not induced astrogliosis within the immunological demyelination region. These results suggest that immunological demyelination creates a unique environment in which astrocytes do not form a glial scar and provides a unique model to understand the putative interaction between astrocytes and activated macrophage/microglial cells.

Analysis of the induction of the myelin basic protein binding to the plasma membrane phospholipid monolayer

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Zhang Lei; Hao Changchun; Feng Ying; Gao Feng; Lu Xiaolong; Li Junhua; Sun Runguang

2016-01-01

Myelin basic protein (MBP) is an essential structure involved in the generation of central nervous system (CNS) myelin. Myelin shape has been described as liquid crystal structure of biological membrane. The interactions of MBP with monolayers of different lipid compositions are responsible for the multi-lamellar structure and stability of myelin. In this paper, we have designed MBP-incorporated model lipid monolayers and studied the phase behavior of MBP adsorbed on the plasma membrane at the air/water interface by thermodynamic method and atomic force microscopy (AFM). By analyzing the pressure–area ( π – A ) and pressure–time ( π – T ) isotherms, univariate linear regression equation was obtained. In addition, the elastic modulus, surface pressure increase, maximal insertion pressure, and synergy factor of monolayers were detected. These parameters can be used to modulate the monolayers binding of protein, and the results show that MBP has the strongest affinity for 1,2-dipalmitoyl-sn-glycero-3- phosphoserine (DPPS) monolayer, followed by DPPC/DPPS mixed and 1,2-dipalmitoyl-sn-glycero-3-phospho-choline (DPPC) monolayers via electrostatic and hydrophobic interactions. AFM images of DPPS and DPPC/DPPS mixed monolayers in the presence of MBP (5 nM) show a phase separation texture at the surface pressure of 20 mN/m and the incorporation of MBP put into the DPPC monolayers has exerted a significant effect on the domain structure. MBP is not an integral membrane protein but, due to its positive charge, interacts with the lipid head groups and stabilizes the membranes. The interaction between MBP and phospholipid membrane to determine the nervous system of the disease has a good biophysical significance and medical value. (special topic)

Oxidative Stress and Proinflammatory Cytokines Contribute to Demyelination and Axonal Damage in a Cerebellar Culture Model of Neuroinflammation

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di Penta, Alessandra; Moreno, Beatriz; Reix, Stephanie; Fernandez-Diez, Begoña; Villanueva, Maite; Errea, Oihana; Escala, Nagore; Vandenbroeck, Koen; Comella, Joan X.; Villoslada, Pablo

2013-01-01

Background Demyelination and axonal damage are critical processes in the pathogenesis of multiple sclerosis (MS). Oxidative stress and pro-inflammatory cytokines elicited by inflammation mediates tissue damage. Methods/Principal Findings To monitor the demyelination and axonal injury associated with microglia activation we employed a model using cerebellar organotypic cultures stimulated with lipopolysaccharide (LPS). Microglia activated by LPS released pro-inflammatory cytokines (IL-1β, IL-6 and TNFα), and increased the expression of inducible nitric oxide synthase (iNOS) and production of reactive oxygen species (ROS). This activation was associated with demyelination and axonal damage in cerebellar cultures. Axonal damage, as revealed by the presence of non-phosphorylated neurofilaments, mitochondrial accumulation in axonal spheroids, and axonal transection, was associated with stronger iNOS expression and concomitant increases in ROS. Moreover, we analyzed the contribution of pro-inflammatory cytokines and oxidative stress in demyelination and axonal degeneration using the iNOS inhibitor ethyl pyruvate, a free-scavenger and xanthine oxidase inhibitor allopurinol, as well as via blockage of pro-inflammatory cytokines using a Fc-TNFR1 construct. We found that blocking microglia activation with ethyl pyruvate or allopurinol significantly decreased axonal damage, and to a lesser extent, demyelination. Blocking TNFα significantly decreased demyelination but did not prevented axonal damage. Moreover, the most common therapy for MS, interferon-beta, was used as an example of an immunomodulator compound that can be tested in this model. In vitro, interferon-beta treatment decreased oxidative stress (iNOS and ROS levels) and the release of pro-inflammatory cytokines after LPS stimulation, reducing axonal damage. Conclusion The model of neuroinflammation using cerebellar culture stimulated with endotoxin mimicked myelin and axonal damage mediated by the combination of

Myelin-specific T cells induce interleukin-1beta expression in lesion-reactive microglial-like cells in zones of axonal degeneration

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Grebing, Manuela; Nielsen, Helle H; Fenger, Christina D

2016-01-01

lesion-reactive CD11b(+) ramified microglia. These results suggest that myelin-specific T cells stimulate lesion-reactive microglial-like cells to produce IL-1β. These findings are relevant to understand the consequences of T-cell infiltration in white and gray matter lesions in patients with MS. GLIA...

Prolonged high frequency electrical stimulation is lethal to motor axons of mice heterozygously deficient for the myelin protein P0 gene

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Alvarez, Susana; Moldovan, Mihai; Krarup, Christian

2013-01-01

demyelinating neuropathy reminiscent of CMT Type 1b. Accumulating evidence suggests that impulse conduction can become lethal to acutely demyelinated central and peripheral axons. Here we investigated the vulnerability of motor axons to long-lasting, high-frequency repetitive stimulation (RS) in P₀+/- mice...... as compared to WT littermates at 7, 12, and 20 months of age. RS was carried out in interrupted trains of 200 Hz trains for 3h. Tibial nerves were stimulated at the ankle while the evoked compound muscle action potentials (CMAPs) and the ascending compound nerve action potentials (CNAPs) were recorded from...... aging and the dysmyelinating disease process may contribute to the susceptibility to activity-induced axonal degeneration. It is possible that in aging mice and in P₀+/- there is inadequate energy-dependent Na(+)/K(+) pumping, as indicated by the reduced post-stimulation hyperpolarization, which may...

SAD kinases sculpt axonal arbors of sensory neurons through long- and short-term responses to neurotrophin signals.

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Lilley, Brendan N; Pan, Y Albert; Sanes, Joshua R

2013-07-10

Extrinsic cues activate intrinsic signaling mechanisms to pattern neuronal shape and connectivity. We showed previously that three cytoplasmic Ser/Thr kinases, LKB1, SAD-A, and SAD-B, control early axon-dendrite polarization in forebrain neurons. Here, we assess their role in other neuronal types. We found that all three kinases are dispensable for axon formation outside of the cortex but that SAD kinases are required for formation of central axonal arbors by subsets of sensory neurons. The requirement for SAD kinases is most prominent in NT-3 dependent neurons. SAD kinases transduce NT-3 signals in two ways through distinct pathways. First, sustained NT-3/TrkC signaling increases SAD protein levels. Second, short-duration NT-3/TrkC signals transiently activate SADs by inducing dephosphorylation of C-terminal domains, thereby allowing activating phosphorylation of the kinase domain. We propose that SAD kinases integrate long- and short-duration signals from extrinsic cues to sculpt axon arbors within the CNS. Copyright © 2013 Elsevier Inc. All rights reserved.

Morphometric analysis of the diameter and g-ratio of the myelinated nerve fibers of the human sciatic nerve during the aging process.

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Ugrenović, Sladjana; Jovanović, Ivan; Vasović, Ljiljana; Kundalić, Braca; Čukuranović, Rade; Stefanović, Vladisav

2016-06-01

Myelinated nerve fibers suffer from different degrees of atrophy with age. The success of subsequent regeneration varies. The aim of this research was to analyze myelinated fibers of the human sciatic nerve during the aging process. Morphometric analysis was performed on 17 cases with an age range from 9 to 93 years. The outer and inner diameter of 100 randomly selected nerve fibers was measured in each of the cases evaluated, and the g-ratio (axonal diameter/outer diameter of the whole nerve fiber) of each was calculated. Scatter plots of the diameters and g-ratios of the analyzed fibers were then analyzed. Nerve fibers of each case were classified into three groups according to the g-ratio values: group I (g-ratio lower than 0.6), group II (g-ratio from 0.6 to 0.7) and group III (g-ratio higher than 0.7). Afterwards, nerve fibers of group II were further classified into small and large subgroups. The percentages of each group of nerve fibers were computed for each case and these values were used for correlational and bivariate linear regression analysis. The percentage of myelinated nerve fibers with large diameter and optimal g-ratio of the sciatic nerve declines significantly with age. This is accompanied by a simultaneous significant increase in the percentage of small myelinated fibers with g-ratio values close to 1 that occupy the upper left quadrant of the scatter plot. It can be concluded that aging of the sciatic nerve is associated with significant atrophy of large myelinated fibers. Additionally, a significant increase in regenerated nerve fibers with thinner myelin sheath is observed with age, which, together with the large myelinated fiber atrophy, might be the cause of the age-related decline in conduction velocity. A better understanding of the changes in aging peripheral nerves might improve interpretation of their pathological changes, as well as comprehension of their regeneration in individuals of different age.

MRI assessment of myelination: an age standardization

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Staudt, M. (Kinderklinik Dritter Orden, Passau (Germany)); Schropp, C. (Kinderklinik Dritter Orden, Passau (Germany)); Staudt, F. (Kinderklinik Dritter Orden, Passau (Germany)); Obletter, N. (Radiologische Praxis, Klinikum Ingolstadt (Germany)); Bise, K. (Neuropathologisches Inst., Muenchen Univ. (Germany)); Breit, A. (MR Tomographie, Klinikum Passau (Germany)); Weinmann, H.M. (Kinderklinik Schwabing, Muenchen (Germany))

1994-04-01

777 cerebral MRI examinations of children aged 3 days to 14 years were staged for myelination to establish an age standardization. Staging was performed using a system proposed in a previous paper, separately ranking 10 different regions of the brain. Interpretation of the results led to the identification of foue clinical diagnoses that are frequently associated with delays in myelination: West syndrome, cerebral palsy, developmental retardation, and congenital anomalies. In addition, it was found that assessment of myelination in children with head injuries was not practical as alterations in MRI signal can simulate earlier stages of myelination. Age limits were therefore calculated from the case material after excluding all children with these conditions. When simplifications of the definition of the stages are applied, these age limits for the various stages of myelination of each of the 10 regions of the brain make the staging system applicable for routine assessment of myelination. (orig.)

Peripheral myelin protein 22 alters membrane architecture

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Mittendorf, Kathleen F.; Marinko, Justin T.; Hampton, Cheri M.; Ke, Zunlong; Hadziselimovic, Arina; Schlebach, Jonathan P.; Law, Cheryl L.; Li, Jun; Wright, Elizabeth R.; Sanders, Charles R.; Ohi, Melanie D.

2017-01-01

Peripheral myelin protein 22 (PMP22) is highly expressed in myelinating Schwann cells of the peripheral nervous system. PMP22 genetic alterations cause the most common forms of Charcot-Marie-Tooth disease (CMTD), which is characterized by severe dysmyelination in the peripheral nerves. However, the functions of PMP22 in Schwann cell membranes remain unclear. We demonstrate that reconstitution of purified PMP22 into lipid vesicles results in the formation of compressed and cylindrically wrapped protein-lipid vesicles that share common organizational traits with compact myelin of peripheral nerves in vivo. The formation of these myelin-like assemblies depends on the lipid-to-PMP22 ratio, as well as on the PMP22 extracellular loops. Formation of the myelin-like assemblies is disrupted by a CMTD-causing mutation. This study provides both a biochemical assay for PMP22 function and evidence that PMP22 directly contributes to membrane organization in compact myelin. PMID:28695207

Are PrP(C)s involved in some human myelin diseases? Relating experimental studies to human pathology.

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Veber, Daniela; Scalabrino, Giuseppe

2015-12-15

We have experimentally demonstrated that cobalamin (Cbl) deficiency increases normal cellular prion (PrP(C)) levels in rat spinal cord (SC) and cerebrospinal fluid (CSF), and decreases PrP(C)-mRNA levels in rat SC. Repeated intracerebroventricular administrations of anti-octapeptide repeat-PrP(C)-region antibodies to Cbl-deficient (Cbl-D) rats prevent SC myelin lesions, and the administrations of PrP(C)s to otherwise normal rats cause SC white matter lesions similar to those induced by Cbl deficiency. Cbl positively regulates SC PrP(C) synthesis in rat by stimulating the local synthesis of epidermal growth factor (EGF), which also induces the local synthesis of PrP(C)-mRNAs, and downregulating the local synthesis of tumor necrosis factor(TNF)-α, thus preventing local PrP(C) overproduction. We have clinically demonstrated that PrP(C) levels are increased in the CSF of patients with subacute combined degeneration (SCD), unchanged in the CSF of patients with Alzheimer's disease and amyotrophic lateral sclerosis, and decreased in the CSF and SC of patients with multiple sclerosis (MS), regardless of its clinical course. We conclude that SCD (human and experimental) is a neurological disease due to excess PrP(C) without conformational change and aggregation, that the increase in PrP(C) levels in SCD and Cbl-D polyneuropathy and their decrease in MS CNS make them antipodian myelin diseases in terms of quantitative PrP(C) abnormalities, and that these abnormalities are related to myelin damage in the former, and impede myelin repair in the latter. Copyright © 2015 Elsevier B.V. All rights reserved.

The whole spectrum of alcohol-related changes in the CNS. Practical MR and CT imaging guidelines for daily clinical use

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Keil, V.C.; Greschus, S.; Hadizadeh, D.R.; Schild, H.H.; Schneider, C.

2015-01-01

Alcohol addiction is the most common drug addiction. Alcohol passes both the placenta as well as the blood-brain barrier and is in multiple ways neurotoxic. Liver diseases and other systemic alcohol-related diseases cause secondary damage to the CNS. Especially in adolescents, even a single episode of severe alcohol intoxication (''binge drinking'') may result in life-threatening neurological consequences. Alcohol-related brain and spinal cord diseases derive from multiple causes including impairment of the cellular metabolism, often aggravated by hypovitaminosis, altered neurotransmission, myelination and synaptogenesis as well as alterations in gene expression. Modern radiological diagnostics, MRI in particular, can detect the resulting alterations in the CNS with a high sensitivity. Morphological aspects often strongly correlate with clinical symptoms of the patient. It is less commonly known that many diseases considered as ''typically alcohol-related'', such as Wernicke's encephalopathy, are to a large extent not alcohol-induced. Visible CNS alterations are thus non-pathognomonic and demand careful evaluation of differential diagnoses. This review article elucidates the pathogenesis, clinical aspects and radiological image features of the most common alcohol-related CNS diseases and their differential diagnoses.

Excitability properties of motor axons in adults with cerebral palsy

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Cliff S. Klein

2015-06-01

Full Text Available Cerebral Palsy (CP is a permanent disorder caused by a lesion to the developing brain that significantly impairs motor function. The neurophysiological mechanisms underlying motor impairment are not well understood. Specifically, few have addressed whether motoneuron or peripheral axon properties are altered in CP, even though disruption of descending inputs to the spinal cord may cause them to change. In the present study, we have compared nerve excitability properties in seven adults with CP and fourteen healthy controls using threshold tracking techniques by stimulating the median nerve at the wrist and recording the compound muscle action potential (CMAP over the abductor pollicis brevis. The excitability properties in the CP subjects were found to be abnormal. Early and late depolarizing and hyperpolarizing threshold electrotonus was significantly larger (i.e., fanning out, and resting current-threshold (I/V slope was smaller, in CP compared to control. In addition resting threshold and rheobase tended to be larger in CP. According to a modeling analysis of the data, an increase in leakage current under or through the myelin sheath, i.e., the Barrett-Barrett conductance (GBB, combined with a slight hyperpolarization of the resting membrane potential, best explained the group differences in excitability properties. There was a trend for those with greater impairment in gross motor function to have more abnormal axon properties. The findings indicate plasticity of motor axon properties far removed from the site of the lesion. We suspect that this plasticity is caused by disruption of descending inputs to the motoneurons at an early age around the time of their injury.

An in vitro study of peptide-loaded alginate nanospheres for antagonizing the inhibitory effect of Nogo-A protein on axonal growth

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Zhai, Peng; Chen, X B; Schreyer, David J

2015-01-01

The adult mammalian central nervous system has limited ability to regenerate after injury. This is due, in part, to the presence of myelin-associated axon growth inhibitory proteins such as Nogo-A that bind and activate the Nogo receptor, leading to profound inhibition of actin-based motility within the growing axon tip. This paper presents an in vitro study of the use of a Nogo receptor-blocking peptide to antagonize the inhibitory effect of Nogo-A on axon growth. Alginate nanospheres were fabricated using an emulsion technique and loaded with Nogo receptor-blocking peptide, or with other model proteins. Protein release profiles were studied, and retention of the bioactivity of released proteins was verified. Primary dorsal root ganglion neurons were cultured and their ability to grow neurites was challenged with Nogo-A chimeric protein in the absence or presence of Nogo receptor antagonist peptide-loaded alginate nanospheres. Our results demonstrate that peptide released from alginate nanospheres could overcome the growth inhibitory effect of Nogo-A, suggesting that a similar peptide delivery strategy using alginate nanospheres might be used to improve axon regeneration within the injured central nervous system. (paper)

Involvement of both sodium influx and potassium efflux in ciguatoxin-induced nodal swelling of frog myelinated axons.

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Mattei, César; Molgó, Jordi; Benoit, Evelyne

2014-10-01

Ciguatoxins, mainly produced by benthic dinoflagellate Gambierdiscus species, are responsible for a complex human poisoning known as ciguatera. Previous pharmacological studies revealed that these toxins activate voltage-gated Na+ channels. In frog nodes of Ranvier, ciguatoxins induce spontaneous and repetitive action potentials (APs) and increase axonal volume that may explain alterations of nerve functioning in intoxicated humans. The present study aimed determining the ionic mechanisms involved in Pacific ciguatoxin-1B (P-CTX-1B)-induced membrane hyperexcitability and subsequent volume increase in frog nodes of Ranvier, using electrophysiology and confocal microscopy. The results reveal that P-CTX-1B action is not dependent on external Cl- ions since it was not affected by substituting Cl- by methylsulfate ions. In contrast, substitution of external Na+ by Li+ ions suppressed spontaneous APs and prevented nodal swelling. This suggests that P-CTX-1B-modified Na+ channels are not selective to Li+ ions and/or are blocked by these ions, and that Na+ influx through Na+ channels opened during spontaneous APs is required for axonal swelling. The fact that the K+ channel blocker tetraethylammonium modified, but did not suppress, spontaneous APs and greatly reduced nodal swelling induced by P-CTX-1B indicates that K+ efflux might also be involved. This is supported by the fact that P-CTX-1B, when tested in the presence of both tetraethylammonium and the K+ ionophore valinomycin, produced the characteristic nodal swelling. It is concluded that, during the action of P-CTX-1B, water movements responsible for axonal swelling depend on both Na+ influx and K+ efflux. These results pave the way for further studies regarding ciguatera treatment. Copyright © 2014 Elsevier Ltd. All rights reserved.

TREM2-transduced myeloid precursors mediate nervous tissue debris clearance and facilitate recovery in an animal model of multiple sclerosis.

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Kazuya Takahashi

2007-04-01

Full Text Available BACKGROUND: In multiple sclerosis, inflammation can successfully be prevented, while promoting repair is still a major challenge. Microglial cells, the resident phagocytes of the central nervous system (CNS, are hematopoietic-derived myeloid cells and express the triggering receptor expressed on myeloid cells 2 (TREM2, an innate immune receptor. Myeloid cells are an accessible source for ex vivo gene therapy. We investigated whether myeloid precursor cells genetically modified to express TREM2 affect the disease course of experimental autoimmune encephalomyelitis (EAE, an animal model of multiple sclerosis. METHODS AND FINDINGS: EAE was induced in mice by immunization with a myelin autoantigen. Intravenous application of TREM2-transduced bone marrow-derived myeloid precursor cells at the EAE peak led to an amelioration of clinical symptoms, reduction in axonal damage, and prevention of further demyelination. TREM2-transduced myeloid cells applied intravenously migrated into the inflammatory spinal cord lesions of EAE-diseased mice, showed increased lysosomal and phagocytic activity, cleared degenerated myelin, and created an anti-inflammatory cytokine milieu within the CNS. CONCLUSIONS: Intravenously applied bone marrow-derived and TREM2-tranduced myeloid precursor cells limit tissue destruction and facilitate repair within the murine CNS by clearance of cellular debris during EAE. TREM2 is a new attractive target for promotion of repair and resolution of inflammation in multiple sclerosis and other neuroinflammatory diseases.

Cerebrospinal fluid signs of neuronal damage after antiretroviral treatment interruption in HIV-1 infection

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Deeks Steven G

2005-08-01

Full Text Available Abstract Background The neurofilament is a major structural component of myelinated axons. Increased cerebrospinal fluid (CSF concentrations of the light chain of the neurofilament protein (NFL can serve as a sensitive indicator of central nervous system (CNS injury. To assess whether interrupting antiretroviral treatment of HIV infection might have a deleterious effect on the CNS, we measured NFL levels in HIV-infected subjects interrupting therapy. We identified subjects who had CSF HIV RNA concentrations below 50 copies/mL at the time combination antiretroviral therapy was interrupted, and for whom CSF samples were available before and after the interruption. Results A total of 8 subjects were studied. The median (range CSF NFL level at baseline was Conclusion These findings suggest that resurgence of active HIV replication may result in measurable, albeit subclinical, CNS injury. Further studies are needed to define the frequency and pathobiological importance of the increase in CSF NFL.

Ion channel density regulates switches between regular and fast spiking in soma but not in axons.

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Hugo Zeberg

2010-04-01

Full Text Available The threshold firing frequency of a neuron is a characterizing feature of its dynamical behaviour, in turn determining its role in the oscillatory activity of the brain. Two main types of dynamics have been identified in brain neurons. Type 1 dynamics (regular spiking shows a continuous relationship between frequency and stimulation current (f-I(stim and, thus, an arbitrarily low frequency at threshold current; Type 2 (fast spiking shows a discontinuous f-I(stim relationship and a minimum threshold frequency. In a previous study of a hippocampal neuron model, we demonstrated that its dynamics could be of both Type 1 and Type 2, depending on ion channel density. In the present study we analyse the effect of varying channel density on threshold firing frequency on two well-studied axon membranes, namely the frog myelinated axon and the squid giant axon. Moreover, we analyse the hippocampal neuron model in more detail. The models are all based on voltage-clamp studies, thus comprising experimentally measurable parameters. The choice of analysing effects of channel density modifications is due to their physiological and pharmacological relevance. We show, using bifurcation analysis, that both axon models display exclusively Type 2 dynamics, independently of ion channel density. Nevertheless, both models have a region in the channel-density plane characterized by an N-shaped steady-state current-voltage relationship (a prerequisite for Type 1 dynamics and associated with this type of dynamics in the hippocampal model. In summary, our results suggest that the hippocampal soma and the two axon membranes represent two distinct kinds of membranes; membranes with a channel-density dependent switching between Type 1 and 2 dynamics, and membranes with a channel-density independent dynamics. The difference between the two membrane types suggests functional differences, compatible with a more flexible role of the soma membrane than that of the axon membrane.

Data on the effect of in vivo knockdown using artificial ErbB3 miRNA on Remak bundle structure

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Yuki Miyamoto

2017-06-01

Full Text Available Mature Schwann cells, the peripheral nervous system (PNS glial cells, have two major roles for neuronal axons (Bunge, 1993 [1]. For large diameter axons, Schwann cells form myelin sheaths with multiple layers. For small diameter axons, they form Remak bundle composed only of single layer of the Schwann cell plasma membrane. In the PNS, ErbB3 forms a dimer with ErbB2 on the Schwann cell plasma membrane. ErbB3 plays a key role in myelination by myelinating Schwann cells, that is to say, its role in myelin thickness. Herein we provide the data regarding the effect of in vivo knockdown of ErbB3 on the thickness between an axon and a neighboring axon in Remak bundle, which is formed by non-myelinating Schwann cells. Since ErbB3 knockout mice are embryonically lethal, Schwann cell lineage-specific transgenic mice transcribing ErbB3 shRNA with an artificial miRNA backbone were generated and used in these experiments (Torii et al., 2014 [2].

Oligodendrocyte Injury and Pathogenesis of HIV-1-Associated Neurocognitive Disorders

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Han Liu

2016-07-01

Full Text Available Oligodendrocytes wrap neuronal axons to form myelin, an insulating sheath which is essential for nervous impulse conduction along axons. Axonal myelination is highly regulated by neuronal and astrocytic signals and the maintenance of myelin sheaths is a very complex process. Oligodendrocyte damage can cause axonal demyelination and neuronal injury, leading to neurological disorders. Demyelination in the cerebrum may produce cognitive impairment in a variety of neurological disorders, including human immunodeficiency virus type one (HIV-1-associated neurocognitive disorders (HAND. Although the combined antiretroviral therapy has markedly reduced the incidence of HIV-1-associated dementia, a severe form of HAND, milder forms of HAND remain prevalent even when the peripheral viral load is well controlled. HAND manifests as a subcortical dementia with damage in the brain white matter (e.g., corpus callosum, which consists of myelinated axonal fibers. How HIV-1 brain infection causes myelin injury and resultant white matter damage is an interesting area of current HIV research. In this review, we tentatively address recent progress on oligodendrocyte dysregulation and HAND pathogenesis.

Slowing of axonal regeneration is correlated with increased axonal viscosity during aging

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Heidemann Steven R

2010-10-01

Full Text Available Abstract Background As we age, the speed of axonal regeneration declines. At the biophysical level, why this occurs is not well understood. Results To investigate we first measured the rate of axonal elongation of sensory neurons cultured from neonatal and adult rats. We found that neonatal axons grew 40% faster than adult axons (11.5 µm/hour vs. 8.2 µm/hour. To determine how the mechanical properties of axons change during maturation, we used force calibrated towing needles to measure the viscosity (stiffness and strength of substrate adhesion of neonatal and adult sensory axons. We found no significant difference in the strength of adhesions, but did find that adult axons were 3 times intrinsically stiffer than neonatal axons. Conclusions Taken together, our results suggest decreasing axonal stiffness may be part of an effective strategy to accelerate the regeneration of axons in the adult peripheral nervous system.

Neural and Molecular Features on Charcot-Marie-Tooth Disease Plasticity and Therapy

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Paula Juárez

2012-01-01

Full Text Available In the peripheral nervous system disorders plasticity is related to changes on the axon and Schwann cell biology, and the synaptic formations and connections, which could be also a focus for therapeutic research. Charcot-Marie-Tooth disease (CMT represents a large group of inherited peripheral neuropathies that involve mainly both motor and sensory nerves and induce muscular atrophy and weakness. Genetic analysis has identified several pathways and molecular mechanisms involving myelin structure and proper nerve myelination, transcriptional regulation, protein turnover, vesicle trafficking, axonal transport and mitochondrial dynamics. These pathogenic mechanisms affect the continuous signaling and dialogue between the Schwann cell and the axon, having as final result the loss of myelin and nerve maintenance; however, some late onset axonal CMT neuropathies are a consequence of Schwann cell specific changes not affecting myelin. Comprehension of molecular pathways involved in Schwann cell-axonal interactions is likely not only to increase the understanding of nerve biology but also to identify the molecular targets and cell pathways to design novel therapeutic approaches for inherited neuropathies but also for most common peripheral neuropathies. These approaches should improve the plasticity of the synaptic connections at the neuromuscular junction and regenerate cell viability based on improving myelin and axon interaction.

Dynamics of target recognition by interstitial axon branching along developing cortical axons.

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Bastmeyer, M; O'Leary, D D

1996-02-15

Corticospinal axons innervate their midbrain, hindbrain, and spinal targets by extending collateral branches interstitially along their length. To establish that the axon shaft rather than the axonal growth cone is responsible for target recognition in this system, and to characterize the dynamics of interstitial branch formation, we have studied this process in an in vivo-like setting using slice cultures from neonatal mice containing the entire pathway of corticospinal axons. Corticospinal axons labeled with the dye 1,1'-dioctodecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (or Dil) were imaged using time-lapse video microscopy of their pathway overlying the basilar pons, their major hindbrain target. The axon shaft millimeters behind the growth cone exhibits several dynamic behaviors, including the de novo formation of varicosities and filopodia-like extensions, and a behavior that we term "pulsation," which is characterized by a variable thickening and thining of short segments of the axon. An individual axon can have multiple sites of branching activity, with many of the branches being transient. These dynamic behaviors occur along the portion of the axon shaft overlying the basilar pons, but not just caudal to it. Once the collaterals extend into the pontine neuropil, they branch further in the neuropil, while the parent axon becomes quiescent. Thus, the branching activity is spatially restricted to specific portions of the axon, as well as temporally restricted to a relatively brief time window. These findings provide definitive evidence that collateral branches form de novo along corticospinal axons and establish that the process of target recognition in this system is a property of the axon shaft rather than the leading growth cone.

Avaliação morfométrica de fibras nervosas do nervo ulnar após reparação cirúrgica com auto-enxerto e prótese tubular em cães

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Ângelo João Stopiglia

1998-01-01

Full Text Available The purpose of this study was to evaluate, by morphometric analysis, the regenerated nerve fibers of dogs, after 26 weeks of observation, in gaps of the ulnar nerves substituted by allografts and tubular prosthesis of silicone. The ulnar nerves of four dogs were processed for electron microscopic evaluation. Six fields, with 1750 µm², for each dog and each procedure, were photographed at 1880x. A morphometric computer based analysis (Sigma Scan - Jandel Co., USA resulted in the following numbers (average numbers in micrometers. 1. ulnar nerve with tubular prosthesis- a: myelinated fiber diameter-5.12 ± 1.67. b: myelinated axon diameter: 4.08 ± 1.52. c: myelin sheath thickness-0.52 ± 0.18. d: unmyelinated axon diameter: 0.98 ± 0.37. 2. ulnar nerve with allograft- a: myelinated fiber diameter: 6.04 ± 2.27. b: myelinated axon diameter: 4.59 ± 1.95. c: myelin sheath thickness: 0.72 ± 0.23. d: unmyelinated axon diameter: 0.96 ± 0.40. The morphometric analysis after 26 weeks of nerve repair didn’t show a significant difference between the two surgical procedures.

Cytokine and chemokine inter-regulation in the inflamed or injured CNS

DEFF Research Database (Denmark)

Owens, Trevor; Babcock, Alicia A; Millward, Jason M

2005-01-01

the expression of chemokines in the CNS, in the absence of any other inflammatory event, but the profiles differ from those induced by axotomy. Chemokines that bind the CCR2 receptor are implicated in traffic of macrophages and T cells to the denervated hippocampus. Innate responses in the immune system...... are directed by Toll-like receptors (TLR). Our recent studies focus on specific TLR signals as upstream on-switches for glial cytokine and chemokine responses. The biological activity of chemokines is regulated by matrix metalloproteinase enzymes (MMPs) and specific members of this family are expressed...... in response to axonal lesioning. These findings strengthen the case for the sharing of signals between the immune and nervous system....

The neuronal metabolite NAA regulates histone H3 methylation in oligodendrocytes and myelin lipid composition.

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Singhal, N K; Huang, H; Li, S; Clements, R; Gadd, J; Daniels, A; Kooijman, E E; Bannerman, P; Burns, T; Guo, F; Pleasure, D; Freeman, E; Shriver, L; McDonough, J

2017-01-01

The neuronal mitochondrial metabolite N-acetylaspartate (NAA) is decreased in the multiple sclerosis (MS) brain. NAA is synthesized in neurons by the enzyme N-acetyltransferase-8-like (NAT8L) and broken down in oligodendrocytes by aspartoacylase (ASPA) into acetate and aspartate. We have hypothesized that NAA links the metabolism of axons with oligodendrocytes to support myelination. To test this hypothesis, we performed lipidomic analyses using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and high-performance thin-layer chromatography (HPTLC) to identify changes in myelin lipid composition in postmortem MS brains and in NAT8L knockout (NAT8L -/- ) mice which do not synthesize NAA. We found reduced levels of sphingomyelin in MS normal appearing white matter that mirrored decreased levels of NAA. We also discovered decreases in the amounts of sphingomyelin and sulfatide lipids in the brains of NAT8L -/- mice compared to controls. Metabolomic analysis of primary cultures of oligodendrocytes treated with NAA revealed increased levels of α-ketoglutarate, which has been reported to regulate histone demethylase activity. Consistent with this, NAA treatment resulted in alterations in the levels of histone H3 methylation, including H3K4me3, H3K9me2, and H3K9me3. The H3K4me3 histone mark regulates cellular energetics, metabolism, and growth, while H3K9me3 has been linked to alterations in transcriptional repression in developing oligodendrocytes. We also noted the NAA treatment was associated with increases in the expression of genes involved in sulfatide and sphingomyelin synthesis in cultured oligodendrocytes. This is the first report demonstrating that neuronal-derived NAA can signal to the oligodendrocyte nucleus. These data suggest that neuronal-derived NAA signals through epigenetic mechanisms in oligodendrocytes to support or maintain myelination.

Analysis of the induction of the myelin basic protein binding to the plasma membrane phospholipid monolayer

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Zhang, Lei; Hao, Changchun; Feng, Ying; Gao, Feng; Lu, Xiaolong; Li, Junhua; Sun, Runguang

2016-09-01

Myelin basic protein (MBP) is an essential structure involved in the generation of central nervous system (CNS) myelin. Myelin shape has been described as liquid crystal structure of biological membrane. The interactions of MBP with monolayers of different lipid compositions are responsible for the multi-lamellar structure and stability of myelin. In this paper, we have designed MBP-incorporated model lipid monolayers and studied the phase behavior of MBP adsorbed on the plasma membrane at the air/water interface by thermodynamic method and atomic force microscopy (AFM). By analyzing the pressure-area (π-A) and pressure-time (π-T) isotherms, univariate linear regression equation was obtained. In addition, the elastic modulus, surface pressure increase, maximal insertion pressure, and synergy factor of monolayers were detected. These parameters can be used to modulate the monolayers binding of protein, and the results show that MBP has the strongest affinity for 1,2-dipalmitoyl-sn-glycero-3- phosphoserine (DPPS) monolayer, followed by DPPC/DPPS mixed and 1,2-dipalmitoyl-sn-glycero-3-phospho-choline (DPPC) monolayers via electrostatic and hydrophobic interactions. AFM images of DPPS and DPPC/DPPS mixed monolayers in the presence of MBP (5 nM) show a phase separation texture at the surface pressure of 20 mN/m and the incorporation of MBP put into the DPPC monolayers has exerted a significant effect on the domain structure. MBP is not an integral membrane protein but, due to its positive charge, interacts with the lipid head groups and stabilizes the membranes. The interaction between MBP and phospholipid membrane to determine the nervous system of the disease has a good biophysical significance and medical value. Project supported by the National Natural Science Foundation of China (Grant Nos. 21402114 and 11544009), the Natural Science Basic Research Plan in Shaanxi Province of China (Grant No. 2016JM2010), the Fundamental Research Funds for the Central

[Ultrastructural changes of myelinated fibers in the brain in continuous and attack-like paranoid schizophrenia].

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Uranova, N A; Kolomeets, N S; Vikhreva, O V; Zimina, I S; Rakhmanova, V I; Orlovskaya, D D

Previously the authors have reported the ultrastructural pathology of myelinated fibers (MF) in the brain in schizophrenia. The aim of the present study was to compare the effect of disease course on ultrastructural changes of MF. Postmortem electron microscopic morphometric study of MF was performed in the prefrontal cortex, caudate nucleus and hippocampus in 19 cases of paranoid schizophrenia. Fourteen cases of continuous schizophrenia, 5 cases of attack-like schizophrenia and 25 normal matched control cases were studied. The proportion (percentage) of pathological MF was estimated in the prefrontal cortex, layer 5, CA3 area of hippocampus, pyramidal layer, and in the head of the caudate nucleus. The percentage of MF having axonal atrophy and swelling of periaxonal oligodendrocyte process was significantly higher in both continuous and attack-like schizophrenia in all brain structures studied as compared to the control group. In the hippocampus and caudate nucleus, this parameter was increased significantly in attack-like schizophrenia as compared to continuous schizophrenia. In the prefrontal cortex. The percentage of the pathological MF having signs of deformation and destruction of myelin sheaths increased significantly only in continuous schizophrenia as compared to the control group. MF pathology is similar in attack-like and continuous paranoid schizophrenia but differ by the degree of severity of pathological MF. Abnormalities in MF contribute to the disconnectivity between the prefrontal cortex, caudate nucleus and hippocampus.

Curcumin-loaded nanoparticles ameliorate glial activation and improve myelin repair in lyolecithin-induced focal demyelination model of rat corpus callosum.

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Naeimi, Reza; Safarpour, Fatemeh; Hashemian, Mona; Tashakorian, Hamed; Ahmadian, Seyed Raheleh; Ashrafpour, Manouchehr; Ghasemi-Kasman, Maryam

2018-05-01

Curcumin has been introduced as effective anti-inflammatory agent in treatment of several inflammatory disorders. Despite the wide range pharmacological activities, clinical application of curcumin is restricted mainly due to the low water solubility of this substance. More recently, we could remarkably improve the aqueous solubility of curcumin by its encapsulation in chitosan-alginate-sodium tripolyphosphate nanoparticles (CS-ALG-STPP NPs). In this study, the anti-inflammatory and myelin protective effects of curcumin-loaded NPs were evaluated in lysolecithin (LPC)-induced focal demyelination model. Pharmacokinetic of curcumin was assessed using high performance liquid chromatography (HPLC). Local demyelination was induced by injection of LPC into corpus callosum of rats. Animals were pre-treated with intraperitoneal (i.p.) injections of curcumin or curcumin-loaded NPs at dose of 12.5 mg/kg, 10 days prior to LPC injection and the injections were continued for 7 or 14 days post lesion. Hematoxylin and eosin (H&E) staining and immunostaining against activated glial cells including astrocytes and microglia were carried out for assessment of inflammation level in lesion site. Myelin specific staining was performed to evaluate the effect of curcumin-loaded NPs on myelination of LPC receiving animals. HPLC results showed the higher plasma concentration of curcumin after administration of NPs. Histological evaluation demonstrated that, the extent of demyelination areas was reduced in animals under treatment of curcumin-loaded NPs. Furthermore, treatment with curcumin-loaded NPs effectively attenuated glial activation and inflammation in LPC-induced demyelination model compared to curcumin receiving animals. Overall; these findings indicate that treatment with curcumin-loaded NPs preserve myelinated axons through amelioration of glial activation and inflammation in demyelination context. Copyright © 2018 Elsevier B.V. All rights reserved.

Abundant extracellular myelin in the meninges of patients with multiple sclerosis.

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Kooi, E-J; van Horssen, J; Witte, M E; Amor, S; Bø, L; Dijkstra, C D; van der Valk, P; Geurts, J J G

2009-06-01

In multiple sclerosis (MS) myelin debris has been observed within MS lesions, in cerebrospinal fluid and cervical lymph nodes, but the route of myelin transport out of the brain is unknown. Drainage of interstitial fluid from the brain parenchyma involves the perivascular spaces and leptomeninges, but the presence of myelin debris in these compartments has not been described. To determine whether myelin products are present in the meninges and perivascular spaces of MS patients. Formalin-fixed brain tissue containing meninges from 29 MS patients, 9 non-neurological controls, 6 Alzheimer's disease, 5 stroke, 5 meningitis and 7 leucodystrophy patients was investigated, and immunohistochemically stained for several myelin proteins [proteolipid protein (PLP), myelin basic protein (MBP), myelin oligodendrocyte glycoprotein (MOG) and 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase)]. On brain material from MS patients and (non)neurological controls, PLP immunostaining was used to systematically investigate the presence of myelin debris in the meninges, using a semiquantitative scale. Extensive extracellular presence of myelin particles, positive for PLP, MBP, MOG and CNPase in the leptomeninges of MS patients, was observed. Myelin particles were also observed in perivascular spaces of MS patients. Immunohistochemical double-labelling for macrophage and dendritic cell markers and PLP confirmed that the vast majority of myelin particles were located extracellularly. Extracellular myelin particles were virtually absent in meningeal tissue of non-neurological controls, Alzheimer's disease, stroke, meningitis and leucodystrophy cases. In MS leptomeninges and perivascular spaces, abundant extracellular myelin can be found, whereas this is not the case for controls and other neurological disease. This may be relevant for understanding sustained immunogenicity or, alternatively, tolerogenicity in MS.

Evaluation of neuroprotection by melatonin against adverse effects of prenatal exposure to a nonsteroidal anti-inflammatory drug during peripheral nerve development.

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Keskin, Ilknur; Kaplan, Suleyman; Kalkan, Serpil; Sutcu, Mustafa; Ulkay, M Basak; Esener, O Burak

2015-04-01

The potential ability of melatonin to protect against impairment of the fetal peripheral nerve system due to maternal consumption of diclofenac sodium (DS) was investigated. Eighty-four pregnant rats were divided into seven groups: control (CONT), saline administered (PS), DS administered (DS), DS with low-dose melatonin administered (DS+MLT10), DS with high-dose melatonin administered (DS+MLT50), low-dose melatonin administered (MLT10), and high-dose melatonin administered (MLT50). After the pregnancy, six male newborn rats from each group were sacrificed at 4 and 20 weeks of age. Their right sciatic nerves were harvested, and nerve fibers were evaluated using stereological techniques. Mean numbers of myelinated axons, axon cross-section areas and the mean thickness of the myelin sheet were estimated. Four-week-old prenatally DS-exposed rats had significantly fewer axons, a smaller myelinated axonal area, and a thinner myelin sheath compared to CONT group (pmelatonin at both doses significantly increased axon numbers, only a high dose of melatonin increased the diameter of those axons (pmelatonin prophylaxis can prevent these effects. Copyright © 2014 Elsevier Ltd. All rights reserved.

Confocal mapping of myelin figures with micro-Raman spectroscopy

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Huang, Jung-Ren; Cheng, Yu-Che; Huang, Hung Ji; Chiang, Hai-Pang

2018-01-01

We employ confocal micro-Raman spectroscopy (CMRS) with submicron spatial resolution to study the myelin structures (cylindrical lamellae) composed of nested surfactant C12E3 or lipid DMPC bilayers. The CMRS mapping indicates that for a straight C12E3 myelin, the surfactant concentration increases with the myelin width and is higher in the center region than in the peripheral region. For a curved C12E3 myelin, the convex side has a higher surfactant concentration than the corresponding concave side. The spectrum of DMPC myelins undergoes a qualitative change as the temperature increases above 60 °C, suggesting that the surfactant molecules may be damaged. Our work demonstrates the utility of CMRS in bio-soft material research.

Encapsulated oligodendrocyte precursor cell fate is dependent on PDGF-AA release kinetics in a 3D microparticle-hydrogel drug delivery system.

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Pinezich, Meghan R; Russell, Lauren N; Murphy, Nicholas P; Lampe, Kyle J

2018-04-16

Biomaterial drug delivery systems (DDS) can be used to regulate growth factor release and combat the limited intrinsic regeneration capabilities of central nervous system (CNS) tissue following injury and disease. Of particular interest are systems that aid in oligodendrocyte regeneration, as oligodendrocytes generate myelin which surrounds neuronal axons and helps transmit signals throughout the CNS. Oligodendrocyte precursor cells (OPCs) are found in small numbers in the adult CNS, but are unable to effectively differentiate following CNS injury. Delivery of signaling molecules can initiate a favorable OPC response, such as proliferation or differentiation. Here, we investigate the delivery of one such molecule, platelet derived growth factor-AA (PDGF-AA), from poly(lactic-co-glycolic) acid microparticles to OPCs in a 3D polyethylene glycol-based hydrogel. The goal of this DDS was to better understand the relationship between PDGF-AA release kinetics and OPC fate. The system approximates native brain tissue stiffness, while incorporating PDGF-AA under seven different delivery scenarios. Within this DDS, supply of PDGF-AA followed by PDGF-AA withdrawal caused OPCs to upregulate gene expression of myelin basic protein (MBP) by factors of 1.6-9.2, whereas continuous supply of PDGF-AA caused OPCs to remain proliferative. At the protein expression level, we observed an upregulation in O1, a marker for mature oligodendrocytes. Together, these results show that burst release followed by withdrawal of PDGF-AA from a hydrogel DDS stimulates survival, proliferation, and differentiation of OPCs in vitro. Our results could inform the development of improved neural regeneration strategies that incorporate delivery of PDGF-AA to the injured CNS. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2018. © 2018 Wiley Periodicals, Inc.

Regeneration of peripheral nerve fibres following Haloxon-induced degeneration

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Maria Veronica de Souza

1996-12-01

Full Text Available Delayed neurotoxicity has been associated with organophosphorus poisoning for years. In order to study such condition in sheep, 11 animals were given either one or two high doses of Haloxon. Exposed sheep were observed daily and between 16 and 25 days after administration neurological signs as incoordination and ataxia were detected in six of them. Biopsies of tibial and laryngeal nerves were performed as soon as neurotoxicity was diagnosed, and after death fragments of selected nerves were collected together with CNS tissues for light and electron microscopy and teased fiber studies. Laryngeal, tibial and sciatic nerves showed the most pronouced changes, consisting chiefly of wallerian degeneration that was seen either as a single fiber or as a complete fascicle feature. Exams performed after death clearly showed regenerating fascicles with axonal sprouts growing within a Schwann cell old basal lamina, and some thinly myelinated axonal sprouts.

N,N-diethyldithiocarbamate promotes oxidative stress prior to myelin structural changes and increases myelin copper content

International Nuclear Information System (INIS)

Viquez, Olga M.; Lai, Barry; Ahn, Jae Hee; Does, Mark D.; Valentine, Holly L.; Valentine, William M.

2009-01-01

Dithiocarbamates are a commercially important class of compounds that can produce peripheral neuropathy in humans and experimental animals. Previous studies have supported a requirement for copper accumulation and enhanced lipid peroxidation in dithiocarbamate-mediated myelinopathy. The study presented here extends previous investigations in two areas. Firstly, although total copper levels have been shown to increase within the nerve it has not been determined whether copper is increased within the myelin compartment, the primary site of lesion development. Therefore, the distribution of copper in sciatic nerve was characterized using synchrotron X-ray fluorescence microscopy to determine whether the neurotoxic dithiocarbamate, N,N-diethyldithiocarbamate, increases copper levels in myelin. Secondly, because lipid peroxidation is an ongoing process in normal nerve and the levels of lipid peroxidation products produced by dithiocarbamate exposure demonstrated an unusual cumulative dose response in previous studies the biological impact of dithiocarbamate-mediated lipid peroxidation was evaluated. Experiments were performed to determine whether dithiocarbamate-mediated lipid peroxidation products elicit an antioxidant response through measuring the protein expression levels of three enzymes, superoxide dismutase 1, heme oxygenase 1, and glutathione transferase α, that are linked to the antioxidant response element promoter. To establish the potential of oxidative injury to contribute to myelin injury the temporal relationship of the antioxidant response to myelin injury was determined. Myelin structure in peripheral nerve was assessed using multi-exponential transverse relaxation measurements (MET 2 ) as a function of exposure duration, and the temporal relationship of protein expression changes relative to the onset of changes in myelin integrity were determined. Initial assessments were also performed to explore the potential contribution of dithiocarbamate

Increased Cx32 expression in spinal cord TrkB oligodendrocytes following peripheral axon injury.

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Coulibaly, Aminata P; Isaacson, Lori G

2016-08-03

Following injury to motor axons in the periphery, retrograde influences from the injury site lead to glial cell plasticity in the vicinity of the injured neurons. Following the transection of peripherally located preganglionic axons of the cervical sympathetic trunk (CST), a population of oligodendrocyte (OL) lineage cells expressing full length TrkB, the cognate receptor for brain derived neurotrophic factor (BDNF), is significantly increased in number in the spinal cord. Such robust plasticity in OL lineage cells in the spinal cord following peripheral axon transection led to the hypothesis that the gap junction communication protein connexin 32 (Cx32), which is specific to OL lineage cells, was influenced by the injury. Following CST transection, Cx32 expression in the spinal cord intermediolateral cell column (IML), the location of the parent cell bodies, was significantly increased. The increased Cx32 expression was localized specifically to TrkB OLs in the IML, rather than other cell types in the OL cell lineage, with the population of Cx32/TrkB cells increased by 59%. Cx32 expression in association with OPCs was significantly decreased at one week following the injury. The results of this study provide evidence that peripheral axon injury can differentially affect the gap junction protein expression in OL lineage cells in the adult rat spinal cord. We conclude that the retrograde influences originating from the peripheral injury site elicit dramatic changes in the CNS expression of Cx32, which in turn may mediate the plasticity of OL lineage cells observed in the spinal cord following peripheral axon injury. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Activation of MAPK overrides the termination of myelin growth and replaces Nrg1/ErbB3 signals during Schwann cell development and myelination

NARCIS (Netherlands)

M.E. Sheean (Maria); E. McShane (Erik); C. Cheret (Cyril); J. Walcher (Jan); T. Müller (Thomas); A. Wulf-Goldenberg (Annika); S. Hoelper (Soraya); A.N. Garratt (Alistair); M. Krüger (Markus); K. Rajewsky (Klaus); D.N. Meijer (Dies); W. Birchmeier (Walter); G.R. Lewin (Gary); M. Selbach (Matthias); C. Birchmeier (Carmen)

2014-01-01

textabstractMyelination depends on the synthesis of large amounts of myelin transcripts and proteins and is controlled by Nrg1/ErbB/Shp2 signaling. We developed a novel pulse labeling strategy based on stable isotope labeling with amino acids in cell culture (SILAC) to measure the dynamics of myelin

Deficiency of adaptive immunity does not interfere with Wallerian degeneration.

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Christopher R Cashman

Full Text Available Following injury, distal axons undergo the process of Wallerian degeneration, and then cell debris is cleared to create a permissive environment for axon regeneration. The innate and adaptive immune systems are believed to be critical for facilitating the clearance of myelin and axonal debris during this process. However, immunodeficient animal models are regularly used in transplantation studies investigating cell therapies to modulate the degenerative/regenerative response. Given the importance of the immune system in preparing a permissive environment for regeneration by clearing debris, animals lacking, in part or in full, a functional immune system may have an impaired ability to regenerate due to poor myelin clearance, and may, thus, be poor hosts to study modulators of regeneration and degeneration. To study this hypothesis, three different mouse models with impaired adaptive immunity were compared to wild type animals in their ability to degenerate axons and clear myelin debris one week following sciatic nerve transection. Immunofluorescent staining for axons and quantitation of axon density with nerve histomorphometry of the distal stump showed no consistent discrepancy between immunodeficient and wild type animals, suggesting axons tended to degenerate equally between the two groups. Debris clearance was assessed by macrophage density and relative myelin basic protein expression within the denervated nerve stump, and no consistent impairment of debris clearance was found. These data suggested deficiency of the adaptive immune system does not have a substantial effect on axon degeneration one week following axonal injury.

Dietary cholesterol promotes repair of demyelinated lesions in the adult brain.

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Berghoff, Stefan A; Gerndt, Nina; Winchenbach, Jan; Stumpf, Sina K; Hosang, Leon; Odoardi, Francesca; Ruhwedel, Torben; Böhler, Carolin; Barrette, Benoit; Stassart, Ruth; Liebetanz, David; Dibaj, Payam; Möbius, Wiebke; Edgar, Julia M; Saher, Gesine

2017-01-24

Multiple Sclerosis (MS) is an inflammatory demyelinating disorder in which remyelination failure contributes to persistent disability. Cholesterol is rate-limiting for myelin biogenesis in the developing CNS; however, whether cholesterol insufficiency contributes to remyelination failure in MS, is unclear. Here, we show the relationship between cholesterol, myelination and neurological parameters in mouse models of demyelination and remyelination. In the cuprizone model, acute disease reduces serum cholesterol levels that can be restored by dietary cholesterol. Concomitant with blood-brain barrier impairment, supplemented cholesterol directly supports oligodendrocyte precursor proliferation and differentiation, and restores the balance of growth factors, creating a permissive environment for repair. This leads to attenuated axon damage, enhanced remyelination and improved motor learning. Remarkably, in experimental autoimmune encephalomyelitis, cholesterol supplementation does not exacerbate disease expression. These findings emphasize the safety of dietary cholesterol in inflammatory diseases and point to a previously unrecognized role of cholesterol in promoting repair after demyelinating episodes.

Remarkable Stability of Myelinating Oligodendrocytes in Mice

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Richa B. Tripathi

2017-10-01

Full Text Available New myelin-forming oligodendrocytes (OLs are generated in the mouse central nervous system during adulthood. These adult-born OLs might augment the existing population, contributing to neural plasticity, or else replace OLs that die in use (turnover. To distinguish between these alternatives, we induced genetic labeling of mature myelinating OLs in young adult mice and tracked their subsequent survival. OL survival rates were region dependent, being higher in corpus callosum (∼90% survival over 20 months and motor cortex (∼70% survival than in corticospinal tract or optic nerve (50%–60% survival. Survival rates over the first 8 months were 90%–100% in all regions except the optic nerve. In the corpus callosum, new OLs accumulate during young adulthood and are therefore likely to participate in adaptive myelination. We also found that the number of myelin internodes maintained by individual cortical OLs is stable for at least 8 months but declines ∼12% in the following year.

Ascending Midbrain Dopaminergic Axons Require Descending GAD65 Axon Fascicles for Normal Pathfinding

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Claudia Marcela Garcia-Peña

2014-06-01

Full Text Available The Nigrostriatal pathway (NSP is formed by dopaminergic axons that project from the ventral midbrain to the dorsolateral striatum as part of the medial forebrain bundle. Previous studies have implicated chemotropic proteins in the formation of the NSP during development but little is known of the role of substrate-anchored signals in this process. We observed in mouse and rat embryos that midbrain dopaminergic axons ascend in close apposition to descending GAD65-positive axon bundles throughout their trajectory to the striatum. To test whether such interaction is important for dopaminergic axon pathfinding, we analyzed transgenic mouse embryos in which the GAD65 axon bundle was reduced by the conditional expression of the diphtheria toxin. In these embryos we observed dopaminergic misprojection into the hypothalamic region and abnormal projection in the striatum. In addition, analysis of Robo1/2 and Slit1/2 knockout embryos revealed that the previously described dopaminergic misprojection in these embryos is accompanied by severe alterations in the GAD65 axon scaffold. Additional studies with cultured dopaminergic neurons and whole embryos suggest that NCAM and Robo proteins are involved in the interaction of GAD65 and dopaminergic axons. These results indicate that the fasciculation between descending GAD65 axon bundles and ascending dopaminergic axons is required for the stereotypical NSP formation during brain development and that known guidance cues may determine this projection indirectly by instructing the pathfinding of the axons that are part of the GAD65 axon scaffold.

Drug-induced activation of SREBP-controlled lipogenic gene expression in CNS-related cell lines: Marked differences between various antipsychotic drugs

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Vik-Mo Audun O

2006-10-01

Full Text Available Abstract Background The etiology of schizophrenia is unknown, but neurodevelopmental disturbances, myelin- and oligodendrocyte abnormalities and synaptic dysfunction have been suggested as pathophysiological factors in this severe psychiatric disorder. Cholesterol is an essential component of myelin and has proved important for synapse formation. Recently, we demonstrated that the antipsychotic drugs clozapine and haloperidol stimulate lipogenic gene expression in cultured glioma cells through activation of the sterol regulatory element-binding protein (SREBP transcription factors. We here compare the action of chlorpromazine, haloperidol, clozapine, olanzapine, risperidone and ziprasidone on SREBP activation and SREBP-controlled gene expression (ACAT2, HMGCR, HMGCS1, FDPS, SC5DL, DHCR7, LDLR, FASN and SCD1 in four CNS-relevant human cell lines. Results There were marked differences in the ability of the antipsychotic drugs to activate the expression of SREBP target genes, with clozapine and chlorpromazine as the most potent stimulators in a context of therapeutically relevant concentrations. Glial-like cells (GaMg glioma and CCF-STTG1 astrocytoma cell lines displayed more pronounced drug-induced SREBP activation compared to the response in HCN2 human cortical neurons and SH-SY5Y neuroblastoma cells, indicating that antipsychotic-induced activation of lipogenesis is most prominent in glial cells. Conclusion Our present data show a marked variation in the ability of different antipsychotics to induce SREBP-controlled transcriptional activation of lipogenesis in cultured human CNS-relevant cells. We propose that this effect could be relevant for the therapeutic efficacy of some antipsychotic drugs.

CNPase Expression in Olfactory Ensheathing Cells

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Christine Radtke

2011-01-01

Full Text Available A large body of work supports the proposal that transplantation of olfactory ensheathing cells (OECs into nerve or spinal cord injuries can promote axonal regeneration and remyelination. Yet, some investigators have questioned whether the transplanted OECs associate with axons and form peripheral myelin, or if they recruit endogenous Schwann cells that form myelin. Olfactory bulbs from transgenic mice expressing the enhanced green fluorescent protein (eGFP under the control of the 2-3-cyclic nucleotide 3-phosphodiesterase (CNPase promoter were studied. CNPase is expressed in myelin-forming cells throughout their lineage. We examined CNPase expression in both in situ in the olfactory bulb and in vitro to determine if OECs express CNPase commensurate with their myelination potential. eGFP was observed in the outer nerve layer of the olfactory bulb. Dissociated OECs maintained in culture had both intense eGFP expression and CNPase immunostaining. Transplantation of OECs into transected peripheral nerve longitudinally associated with the regenerated axons. These data indicate that OECs in the outer nerve layer of the olfactory bulb of CNPase transgenic mice express CNPase. Thus, while OECs do not normally form myelin on olfactory nerve axons, their expression of CNPase is commensurate with their potential to form myelin when transplanted into injured peripheral nerve.

Action Potential Dynamics in Fine Axons Probed with an Axonally Targeted Optical Voltage Sensor.

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Ma, Yihe; Bayguinov, Peter O; Jackson, Meyer B

2017-01-01

The complex and malleable conduction properties of axons determine how action potentials propagate through extensive axonal arbors to reach synaptic terminals. The excitability of axonal membranes plays a major role in neural circuit function, but because most axons are too thin for conventional electrical recording, their properties remain largely unexplored. To overcome this obstacle, we used a genetically encoded hybrid voltage sensor (hVOS) harboring an axonal targeting motif. Expressing this probe in transgenic mice enabled us to monitor voltage changes optically in two populations of axons in hippocampal slices, the large axons of dentate granule cells (mossy fibers) in the stratum lucidum of the CA3 region and the much finer axons of hilar mossy cells in the inner molecular layer of the dentate gyrus. Action potentials propagated with distinct velocities in each type of axon. Repetitive firing broadened action potentials in both populations, but at an intermediate frequency the degree of broadening differed. Repetitive firing also attenuated action potential amplitudes in both mossy cell and granule cell axons. These results indicate that the features of use-dependent action potential broadening, and possible failure, observed previously in large nerve terminals also appear in much finer unmyelinated axons. Subtle differences in the frequency dependences could influence the propagation of activity through different pathways to excite different populations of neurons. The axonally targeted hVOS probe used here opens up the diverse repertoire of neuronal processes to detailed biophysical study.

Axon-Axon Interactions Regulate Topographic Optic Tract Sorting via CYFIP2-Dependent WAVE Complex Function.

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Cioni, Jean-Michel; Wong, Hovy Ho-Wai; Bressan, Dario; Kodama, Lay; Harris, William A; Holt, Christine E

2018-03-07

The axons of retinal ganglion cells (RGCs) are topographically sorted before they arrive at the optic tectum. This pre-target sorting, typical of axon tracts throughout the brain, is poorly understood. Here, we show that cytoplasmic FMR1-interacting proteins (CYFIPs) fulfill non-redundant functions in RGCs, with CYFIP1 mediating axon growth and CYFIP2 specifically involved in axon sorting. We find that CYFIP2 mediates homotypic and heterotypic contact-triggered fasciculation and repulsion responses between dorsal and ventral axons. CYFIP2 associates with transporting ribonucleoprotein particles in axons and regulates translation. Axon-axon contact stimulates CYFIP2 to move into growth cones where it joins the actin nucleating WAVE regulatory complex (WRC) in the periphery and regulates actin remodeling and filopodial dynamics. CYFIP2's function in axon sorting is mediated by its binding to the WRC but not its translational regulation. Together, these findings uncover CYFIP2 as a key regulatory link between axon-axon interactions, filopodial dynamics, and optic tract sorting. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Comparison of the fastest regenerating motor and sensory myelinated axons in the same peripheral nerve

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Moldovan, Mihai; Sørensen, Jesper; Krarup, Christian

2006-01-01

Functional outcome after peripheral nerve regeneration is often poor, particularly involving nerve injuries far from their targets. Comparison of sensory and motor axon regeneration before target reinnervation is not possible in the clinical setting, and previous experimental studies addressing...... the question of differences in growth rates of different nerve fibre populations led to conflicting results. We developed an animal model to compare growth and maturation of the fastest growing sensory and motor fibres within the same mixed nerve after Wallerian degeneration. Regeneration of cat tibial nerve...... after crush (n = 13) and section (n = 7) was monitored for up to 140 days, using implanted cuff electrodes placed around the sciatic and tibial nerves and wire electrodes at plantar muscles. To distinguish between sensory and motor fibres, recordings were carried out from L6-S2 spinal roots using cuff...

The structural and functional role of myelin fast-migrating cerebrosides

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Podbielska, Maria; Levery, Steven B; Hogan, Edward L

2011-01-01

A family of neutral glycosphingolipids containing a 3-O-acetyl-sphingosine galactosylceramide (3-SAG) has been characterized. Seven new derivatives of galactosylceramide (GalCer), designated as fast-migrating cerebrosides (FMCs) by TLC retention factor, have been identified. The simplest compounds...... myelin lipid biomarkers coappear with GalCer during myelinogenesis and disappear along with GalCer in de- or dys-myelinating disorders. Myelin lipid antigens, including FMCs, are keys to myelin biology, opening the possibility of new and novel immune modulatory tools for treatment of autoimmune diseases...

Staining Methods for Normal and Regenerative Myelin in the Nervous System.

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Carriel, Víctor; Campos, Antonio; Alaminos, Miguel; Raimondo, Stefania; Geuna, Stefano

2017-01-01

Histochemical techniques enable the specific identification of myelin by light microscopy. Here we describe three histochemical methods for the staining of myelin suitable for formalin-fixed and paraffin-embedded materials. The first method is conventional luxol fast blue (LFB) method which stains myelin in blue and Nissl bodies and mast cells in purple. The second method is a LBF-based method called MCOLL, which specifically stains the myelin as well the collagen fibers and cells, giving an integrated overview of the histology and myelin content of the tissue. Finally, we describe the osmium tetroxide method, which consist in the osmication of previously fixed tissues. Osmication is performed prior the embedding of tissues in paraffin giving a permanent positive reaction for myelin as well as other lipids present in the tissue.

Glia to axon RNA transfer.

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Sotelo, José Roberto; Canclini, Lucía; Kun, Alejandra; Sotelo-Silveira, José Roberto; Calliari, Aldo; Cal, Karina; Bresque, Mariana; Dipaolo, Andrés; Farias, Joaquina; Mercer, John A

2014-03-01

The existence of RNA in axons has been a matter of dispute for decades. Evidence for RNA and ribosomes has now accumulated to a point at which it is difficult to question, much of the disputes turned to the origin of these axonal RNAs. In this review, we focus on studies addressing the origin of axonal RNAs and ribosomes. The neuronal soma as the source of most axonal RNAs has been demonstrated and is indisputable. However, the surrounding glial cells may be a supplemental source of axonal RNAs, a matter scarcely investigated in the literature. Here, we review the few papers that have demonstrated that glial-to-axon RNA transfer is not only feasible, but likely. We describe this process in both invertebrate axons and vertebrate axons. Schwann cell to axon ribosomes transfer was conclusively demonstrated (Court et al. [2008]: J. Neurosci 28:11024-11029; Court et al. [2011]: Glia 59:1529-1539). However, mRNA transfer still remains to be demonstrated in a conclusive way. The intercellular transport of mRNA has interesting implications, particularly with respect to the integration of glial and axonal function. This evolving field is likely to impact our understanding of the cell biology of the axon in both normal and pathological conditions. Most importantly, if the synthesis of proteins in the axon can be controlled by interacting glia, the possibilities for clinical interventions in injury and neurodegeneration are greatly increased. Copyright © 2013 Wiley Periodicals, Inc.

Autoimmune reactions in patients with M-component and peripheral neuropathy

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Jønsson, V; Schrøder, H D; Trojaborg, W

1992-01-01

A study of 17 patients with autoimmune axonal or demyelinating peripheral neuropathy in combination with M-component is described. The M-component was associated with MGUS (monoclonal gammopathy of undetermined significance) in 12 patients, CLL in one patient, Waldenström's disease in one patient......, and myeloma in three patients. Immunohistological examination with direct and indirect fluorescence showed binding of antibodies to nerve structures of the same class and light chain as seen in the M-component. In five cases of IgM M-component, the demyelinating neuropathy was caused by binding of the IgM M......-protein and complement C3b to myelin-associated glycoproteins (MAG). In 12 cases with axonal neuropathy, binding of IgG to the connective tissue of the peri- and endoneurium was found in 50% of cases, IgM in five cases, and IgD in one case. None of the patients had central nervous system (CNS) symptoms. The clinical...

The genetics of axonal transport and axonal transport disorders.

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Jason E Duncan

2006-09-01

Full Text Available Neurons are specialized cells with a complex architecture that includes elaborate dendritic branches and a long, narrow axon that extends from the cell body to the synaptic terminal. The organized transport of essential biological materials throughout the neuron is required to support its growth, function, and viability. In this review, we focus on insights that have emerged from the genetic analysis of long-distance axonal transport between the cell body and the synaptic terminal. We also discuss recent genetic evidence that supports the hypothesis that disruptions in axonal transport may cause or dramatically contribute to neurodegenerative diseases.

Endogenous phosphorylation of basic protein in myelin of varying degrees of compaction

International Nuclear Information System (INIS)

Schulz, P.; Moscarello, M.A.; Cruz, T.F.

1988-01-01

Fractions containing myelin of varying degrees of compaction were prepared from human white matter. Protein kinase activity in these fractions was measured by using both endogenous and exogenous myelin basic protein (MBP) as substrates. In both cases, less compact myelin fractions possessed higher levels of protein kinase activity than the compact myelin fraction. In addition, the specific activity of phosphorylated basic protein was greater in the loosely compacted fractions than in compact multilamellar myelin. When basic protein in compact myelin or the myelin fractions was phosphorylated by the endogenous kinase, approximately 70% of the [ 32 P]phosphate was incorporated at a single site, identified as Ser-102. The remaining 30% was found in three other minor sites. Electron microscopy of less compact myelin showed it was composed of fewer lamellae which correlated with a relative decrease in the proportion of cationic charge isomers (microheteromers) when MBP was subjected to gel electrophoresis at alkaline pH. The shift in charge microheterogeneity of basic protein to the less cationic isomers in the less compact myelin fractions correlated with an increase in protein kinase activity and a greater specific activity of phosphorylated basic protein

Combining Quantitative Susceptibility Mapping with Automatic Zero Reference (QSM0) and Myelin Water Fraction Imaging to Quantify Iron-Related Myelin Damage in Chronic Active MS Lesions.

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Yao, Y; Nguyen, T D; Pandya, S; Zhang, Y; Hurtado Rúa, S; Kovanlikaya, I; Kuceyeski, A; Liu, Z; Wang, Y; Gauthier, S A

2018-02-01

A hyperintense rim on susceptibility in chronic MS lesions is consistent with iron deposition, and the purpose of this study was to quantify iron-related myelin damage within these lesions as compared with those without rim. Forty-six patients had 2 longitudinal quantitative susceptibility mapping with automatic zero reference scans with a mean interval of 28.9 ± 11.4 months. Myelin water fraction mapping by using fast acquisition with spiral trajectory and T2 prep was obtained at the second time point to measure myelin damage. Mixed-effects models were used to assess lesion quantitative susceptibility mapping and myelin water fraction values. Quantitative susceptibility mapping scans were on average 6.8 parts per billion higher in 116 rim-positive lesions compared with 441 rim-negative lesions ( P quantitative susceptibility mapping values of both the rim and core regions ( P Quantitative susceptibility mapping scans and myelin water fraction in rim-positive lesions decreased from rim to core, which is consistent with rim iron deposition. Whole lesion myelin water fractions for rim-positive and rim-negative lesions were 0.055 ± 0.07 and 0.066 ± 0.04, respectively. In the mixed-effects model, rim-positive lesions had on average 0.01 lower myelin water fraction compared with rim-negative lesions ( P quantitative susceptibility mapping scan was negatively associated with follow-up myelin water fraction ( P Quantitative susceptibility mapping rim-positive lesions maintained a hyperintense rim, increased in susceptibility, and had more myelin damage compared with rim-negative lesions. Our results are consistent with the identification of chronic active MS lesions and may provide a target for therapeutic interventions to reduce myelin damage. © 2018 by American Journal of Neuroradiology.

Nanoscale Correlated Disorder in Out-of-Equilibrium Myelin Ultrastructure.

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Campi, Gaetano; Di Gioacchino, Michael; Poccia, Nicola; Ricci, Alessandro; Burghammer, Manfred; Ciasca, Gabriele; Bianconi, Antonio

2018-01-23

Ultrastructural fluctuations at nanoscale are fundamental to assess properties and functionalities of advanced out-of-equilibrium materials. We have taken myelin as a model of supramolecular assembly in out-of-equilibrium living matter. Myelin sheath is a simple stable multilamellar structure of high relevance and impact in biomedicine. Although it is known that myelin has a quasi-crystalline ultrastructure, there is no information on its fluctuations at nanoscale in different states due to limitations of the available standard techniques. To overcome these limitations, we have used scanning micro X-ray diffraction, which is a unique non-invasive probe of both reciprocal and real space to visualize statistical fluctuations of myelin order of the sciatic nerve of Xenopus laevis. The results show that the ultrastructure period of the myelin is stabilized by large anticorrelated fluctuations at nanoscale, between hydrophobic and hydrophilic layers. The ratio between the total thickness of hydrophilic and hydrophobic layers defines the conformational parameter, which describes the different states of myelin. Our key result is that myelin in its out-of-equilibrium functional state fluctuates point-to-point between different conformations showing a correlated disorder described by a Levy distribution. As the system approaches the thermodynamic equilibrium in an aged state, the disorder loses its correlation degree and the structural fluctuation distribution changes to Gaussian. In a denatured state at low pH, it changes to a completely disordered stage. Our results aim to clarify the degradation mechanism in biological systems by associating these states with ultrastructural dynamic fluctuations at nanoscale.

Cell-type specific expression of constitutively-active Rheb promotes regeneration of bulbospinal respiratory axons following cervical SCI.

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Urban, Mark W; Ghosh, Biswarup; Strojny, Laura R; Block, Cole G; Blazejewski, Sara M; Wright, Megan C; Smith, George M; Lepore, Angelo C

2018-05-01

Damage to respiratory neural circuitry and consequent loss of diaphragm function is a major cause of morbidity and mortality in individuals suffering from traumatic cervical spinal cord injury (SCI). Repair of CNS axons after SCI remains a therapeutic challenge, despite current efforts. SCI disrupts inspiratory signals originating in the rostral ventral respiratory group (rVRG) of the medulla from their phrenic motor neuron (PhMN) targets, resulting in loss of diaphragm function. Using a rat model of cervical hemisection SCI, we aimed to restore rVRG-PhMN-diaphragm circuitry by stimulating regeneration of injured rVRG axons via targeted induction of Rheb (ras homolog enriched in brain), a signaling molecule that regulates neuronal-intrinsic axon growth potential. Following C2 hemisection, we performed intra-rVRG injection of an adeno-associated virus serotype-2 (AAV2) vector that drives expression of a constitutively-active form of Rheb (cRheb). rVRG neuron-specific cRheb expression robustly increased mTOR pathway activity within the transduced rVRG neuron population ipsilateral to the hemisection, as assessed by levels of phosphorylated ribosomal S6 kinase. By co-injecting our novel AAV2-mCherry/WGA anterograde/trans-synaptic axonal tracer into rVRG, we found that cRheb expression promoted regeneration of injured rVRG axons into the lesion site, while we observed no rVRG axon regrowth with AAV2-GFP control. AAV2-cRheb also significantly reduced rVRG axonal dieback within the intact spinal cord rostral to the lesion. However, cRheb expression did not promote any recovery of ipsilateral hemi-diaphragm function, as assessed by inspiratory electromyography (EMG) burst amplitudes. This lack of functional recovery was likely because regrowing rVRG fibers did not extend back into the caudal spinal cord to synaptically reinnervate PhMNs that we retrogradely-labeled with cholera toxin B from the ipsilateral hemi-diaphragm. Our findings demonstrate that enhancing neuronal

Intraspinal Delivery of Polyethylene Glycol-coated Gold Nanoparticles Promotes Functional Recovery After Spinal Cord Injury.

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Papastefanaki, Florentia; Jakovcevski, Igor; Poulia, Nafsika; Djogo, Nevena; Schulz, Florian; Martinovic, Tamara; Ciric, Darko; Loers, Gabrielle; Vossmeyer, Tobias; Weller, Horst; Schachner, Melitta; Matsas, Rebecca

2015-06-01

Failure of the mammalian central nervous system (CNS) to regenerate effectively after injury leads to mostly irreversible functional impairment. Gold nanoparticles (AuNPs) are promising candidates for drug delivery in combination with tissue-compatible reagents, such as polyethylene glycol (PEG). PEG administration in CNS injury models has received interest for potential therapy, but toxicity and low bioavailability prevents clinical application. Here we show that intraspinal delivery of PEG-functionalized 40-nm-AuNPs at early stages after mouse spinal cord injury is beneficial for recovery. Positive outcome of hind limb motor function was accompanied by attenuated inflammatory response, enhanced motor neuron survival, and increased myelination of spared or regrown/sprouted axons. No adverse effects, such as body weight loss, ill health, or increased mortality were observed. We propose that PEG-AuNPs represent a favorable drug-delivery platform with therapeutic potential that could be further enhanced if PEG-AuNPs are used as carriers of regeneration-promoting molecules.

A robust, efficient and flexible method for staining myelinated axons in blocks of brain tissue.

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Wahlsten, Douglas; Colbourne, Frederick; Pleus, Richard

2003-03-15

Previous studies have demonstrated the utility of the gold chloride method for en bloc staining of a bisected brain in mice and rats. The present study explores several variations in the method, assesses its reliability, and extends the limits of its application. We conclude that the method is very efficient, highly robust, sufficiently accurate for most purposes, and adaptable to many morphometric measures. We obtained acceptable staining of commissures in every brain, despite a wide variety of fixation methods. One-half could be stained 24 h after the brain was extracted and the other half could be stained months later. When staining failed because of an exhausted solution, the brain could be stained successfully in fresh solution. Relatively small changes were found in the sizes of commissures several weeks after initial fixation or staining. A half brain stained to reveal the mid-sagittal section could then be sectioned coronally and stained again in either gold chloride for myelin or cresyl violet for Nissl substance. Uncertainty, arising from pixelation of digitized images was far less than errors arising from human judgments about the histological limits of major commissures. Useful data for morphometric analysis were obtained by scanning the surface of a gold chloride stained block of brain with an inexpensive flatbed scanner.

Experimental Autoimmune Encephalomyelitis (EAE-Induced Elevated Expression of the E1 Isoform of Methyl CpG Binding Protein 2 (MeCP2E1: Implications in Multiple Sclerosis (MS-Induced Neurological Disability and Associated Myelin Damage

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Tina Khorshid Ahmad

2017-06-01

Full Text Available Multiple sclerosis (MS is a chronic neurological disease characterized by the destruction of central nervous system (CNS myelin. At present, there is no cure for MS due to the inability to repair damaged myelin. Although the neurotrophin brain derived neurotrophic factor (BDNF has a beneficial role in myelin repair, these effects may be hampered by the over-expression of a transcriptional repressor isoform of methyl CpG binding protein 2 (MeCP2 called MeCP2E1. We hypothesize that following experimental autoimmune encephalomyelitis (EAE-induced myelin damage, the immune system induction of the pathogenic MeCP2E1 isoform hampers the myelin repair process by repressing BDNF expression. Using an EAE model of MS, we identify the temporal gene and protein expression changes of MeCP2E1, MeCP2E2 and BDNF. The expression changes of these key biological targets were then correlated with the temporal changes in neurological disability scores (NDS over the entire disease course. Our results indicate that MeCP2E1 mRNA levels are elevated in EAE animals relative to naïve control (NC and active control (AC animals during all time points of disease progression. Our results suggest that the EAE-induced elevations in MeCP2E1 expression contribute to the repressed BDNF production in the spinal cord (SC. The sub-optimal levels of BDNF result in sustained NDS and associated myelin damage throughout the entire disease course. Conversely, we observed no significant differences in the expression patterns displayed for the MeCP2E2 isoform amongst our experimental groups. However, our results demonstrate that baseline protein expression ratios between the MeCP2E1 versus MeCP2E2 isoforms in the SC are higher than those identified within the dorsal root ganglia (DRG. Thus, the DRG represents a more conducive environment than that of the SC for BDNF production and transport to the CNS to assist in myelin repair. Henceforth, the sub-optimal BDNF levels we report in the SC

Experimental Autoimmune Encephalomyelitis (EAE)-Induced Elevated Expression of the E1 Isoform of Methyl CpG Binding Protein 2 (MeCP2E1): Implications in Multiple Sclerosis (MS)-Induced Neurological Disability and Associated Myelin Damage.

Science.gov (United States)

Khorshid Ahmad, Tina; Zhou, Ting; AlTaweel, Khaled; Cortes, Claudia; Lillico, Ryan; Lakowski, Ted Martin; Gozda, Kiana; Namaka, Michael Peter

2017-06-12

Multiple sclerosis (MS) is a chronic neurological disease characterized by the destruction of central nervous system (CNS) myelin. At present, there is no cure for MS due to the inability to repair damaged myelin. Although the neurotrophin brain derived neurotrophic factor (BDNF) has a beneficial role in myelin repair, these effects may be hampered by the over-expression of a transcriptional repressor isoform of methyl CpG binding protein 2 (MeCP2) called MeCP2E1. We hypothesize that following experimental autoimmune encephalomyelitis (EAE)-induced myelin damage, the immune system induction of the pathogenic MeCP2E1 isoform hampers the myelin repair process by repressing BDNF expression. Using an EAE model of MS, we identify the temporal gene and protein expression changes of MeCP2E1, MeCP2E2 and BDNF. The expression changes of these key biological targets were then correlated with the temporal changes in neurological disability scores (NDS) over the entire disease course. Our results indicate that MeCP2E1 mRNA levels are elevated in EAE animals relative to naïve control (NC) and active control (AC) animals during all time points of disease progression. Our results suggest that the EAE-induced elevations in MeCP2E1 expression contribute to the repressed BDNF production in the spinal cord (SC). The sub-optimal levels of BDNF result in sustained NDS and associated myelin damage throughout the entire disease course. Conversely, we observed no significant differences in the expression patterns displayed for the MeCP2E2 isoform amongst our experimental groups. However, our results demonstrate that baseline protein expression ratios between the MeCP2E1 versus MeCP2E2 isoforms in the SC are higher than those identified within the dorsal root ganglia (DRG). Thus, the DRG represents a more conducive environment than that of the SC for BDNF production and transport to the CNS to assist in myelin repair. Henceforth, the sub-optimal BDNF levels we report in the SC may arise

CNS role evolution.

Science.gov (United States)

Payne, J L; Baumgartner, R G

1996-01-01

THE CNS ROLE has been actualized in a variety of ways. Flexibility-inherent in the role-and the revolution in health care consciousness tend to place the CNS at risk for criticism regarding value to the organization. At Vanderbilt University Medical Center, a CNS task force evaluated the current reality of CNS practice and recommended role changes to include the financial analysis of patient care. After incorporating a financial perspective into our present practice, we have embarked on an interesting journey of post-Master's degree study, that of the tertiary care nurse practitioner. This practice option could elevated the clinical and financial aspects of providing cost-effective health care to a more autonomous role form; however, the transition has been challenging. Since 1990, the American Nurses Association has recommended that nursing school curricula change to meet the needs of the health care environment and provide increased career flexibility through creating one advanced degree incorporating both CNS and NP functions. Swiftly moving past differences and toward similarities will bridge the gap for advanced practice nurses in the future.

High-content phenotypic screening and triaging strategy to identify small molecules driving oligodendrocyte progenitor cell differentiation.

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Peppard, Jane V; Rugg, Catherine A; Smicker, Matthew A; Powers, Elaine; Harnish, Erica; Prisco, Joy; Cirovic, Dragan; Wright, Paul S; August, Paul R; Chandross, Karen J

2015-03-01

Multiple Sclerosis is a demyelinating disease of the CNS and the primary cause of neurological disability in young adults. Loss of myelinating oligodendrocytes leads to neuronal dysfunction and death and is an important contributing factor to this disease. Endogenous oligodendrocyte precursor cells (OPCs), which on differentiation are responsible for replacing myelin, are present in the adult CNS. As such, therapeutic agents that can stimulate OPCs to differentiate and remyelinate demyelinated axons under pathologic conditions may improve neuronal function and clinical outcome. We describe the details of an automated, cell-based, morphometric-based, high-content screen that is used to identify small molecules eliciting the differentiation of OPCs after 3 days. Primary screening was performed using rat CG-4 cells maintained in culture conditions that normally support a progenitor cell-like state. From a library of 73,000 diverse small molecules within the Sanofi collection, 342 compounds were identified that increased OPC morphological complexity as an indicator of oligodendrocyte maturation. Subsequent to the primary high-content screen, a suite of cellular assays was established that identified 22 nontoxic compounds that selectively stimulated primary rat OPCs but not C2C12 muscle cell differentiation. This rigorous triaging yielded several chemical series for further expansion and bio- or cheminformatics studies, and their compelling biological activity merits further investigation. © 2014 Society for Laboratory Automation and Screening.

Different Mechanisms of Inflammation Induced in Virus and Autoimmune-Mediated Models of Multiple Sclerosis in C57BL6 Mice

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Abhinoy Kishore

2013-01-01

Full Text Available Multiple sclerosis (MS is an inflammatory demyelinating disease of the human central nervous system (CNS. Neurotropic demyelinating strain of MHV (MHV-A59 or its isogenic recombinant strain RSA59 induces MS-like disease in mice mediated by microglia, along with a small population of T cells. The mechanism of demyelination is at least in part due to microglia-mediated myelin stripping, with some direct axonal injury. Immunization with myelin oligodendrocyte glycoprotein (MOG induces experimental autoimmune encephalomyelitis (EAE, a mainly CD4+ T-cell-mediated disease, although CD8+ T cells may play a significant role in demyelination. It is possible that both autoimmune and nonimmune mechanisms such as direct viral toxicity may induce MS. Our study directly compares CNS pathology in autoimmune and viral-induced MS models. Mice with viral-induced and EAE demyelinating diseases demonstrated similar patterns and distributions of demyelination that accumulated over the course of the disease. However, significant differences in acute inflammation were noted. Inflammation was restricted mainly to white matter at all times in EAE, whereas inflammation initially largely involved gray matter in acute MHV-induced disease and then is subsequently localized only in white matter in the chronic disease phase. The presence of dual mechanisms of demyelination may be responsible for the failure of immunosuppression to promote long-term remission in many MS patients.

Epizootic vacuolar myelinopathy of the central nervous system of bald eagles (Haliaeetus leucocephalus) and American coots (Fulica americana)

Science.gov (United States)

Thomas, N.J.; Meteyer, C.U.; Sileo, L.

1998-01-01

Unprecedented mortality occurred in bald eagles (Haliaeetus leucocephalus) at DeGray Lake, Arkansas, during the winters of 1994-1995 and 1996-1997. The first eagles were found dead during November, soon after arrival from fall migration, and deaths continued into January during both episodes. In total, 29 eagles died at or near DeGray Lake in the winter of 1994-1995 and 26 died in the winter of 1996-1997; no eagle mortality was noted during the same months of the intervening winter or in the earlier history of the lake. During the mortality events, sick eagles were observed overflying perches or colliding with rock walls. Signs of incoordination and limb paresis were also observed in American coots (Fulica americana) during the episodes of eagle mortality, but mortality in coots was minimal. No consistent abnormalities were seen on gross necropsy of either species. No microscopic findings in organs other than the central nervous system (CNS) could explain the cause of death. By light microscopy, all 26 eagles examined and 62/77 (81%) coots had striking, diffuse, spongy degeneration of the white matter of the CNS. Vacuolation occurred in all myelinated CNS tissue, including the cerebellar folia and medulla oblongata, but was most prominent in the optic tectum. In the spinal cord, vacuoles were concentrated near the gray matter, and occasional swollen axons were seen. Vacuoles were uniformly present in optic nerves but were not evident in the retina or peripheral or autonomic nerves. Cellular inflammatory response to the lesion was distinctly lacking. Vacuoles were 8-50 microns in diameter and occurred individually, in clusters, or in rows. In sections stained by luxol fast blue/periodic acid-Schiff stain, the vacuoles were delimited and transected by myelin strands. Transmission electron microscopy revealed intramyelinic vacuoles formed in the myelin sheaths by splitting of one or more myelin lamellae at the intraperiodic line. This lesion is characteristic of

Regeneration-associated macrophages: a novel approach to boost intrinsic regenerative capacity for axon regeneration

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Min Jung Kwon

2016-01-01

Full Text Available Axons in central nervous system (CNS do not regenerate spontaneously after injuries such as stroke and traumatic spinal cord injury. Both intrinsic and extrinsic factors are responsible for the regeneration failure. Although intensive research efforts have been invested on extrinsic regeneration inhibitors, the extent to which glial inhibitors contribute to the regeneration failure in vivo still remains elusive. Recent experimental evidence has rekindled interests in intrinsic factors for the regulation of regeneration capacity in adult mammals. In this review, we propose that activating macrophages with pro-regenerative molecular signatures could be a novel approach for boosting intrinsic regenerative capacity of CNS neurons. Using a conditioning injury model in which regeneration of central branches of dorsal root ganglia sensory neurons is enhanced by a preceding injury to the peripheral branches, we have demonstrated that perineuronal macrophages surrounding dorsal root ganglia neurons are critically involved in the maintenance of enhanced regeneration capacity. Neuron-derived chemokine (C-C motif ligand 2 (CCL2 seems to mediate neuron-macrophage interactions conveying injury signals to perineuronal macrophages taking on a soley pro-regenerative phenotype, which we designate as regeneration-associated macrophages (RAMs. Manipulation of the CCL2 signaling could boost regeneration potential mimicking the conditioning injury, suggesting that the chemokine-mediated RAM activation could be utilized as a regenerative therapeutic strategy for CNS injuries.

Rapid myelin water content mapping on clinical MR systems

International Nuclear Information System (INIS)

Tonkova, Vyara; Arhelger, Volker; Schenk, Jochen; Neeb, Heiko; Koblenz Univ.

2012-01-01

We present an algorithm for the fast mapping of myelin water content using standard multiecho gradient echo acquisitions of the human brain. The method extents a previously published approach for the simultaneous measurement of brain T 1 , T * 2 and total water content. Employing the multiexponential T * 2 decay signal of myelinated tissue, myelin water content was measured based on the quantification of two water pools ('myelin water' and 'rest') with different relaxation times. As the existing protocol was focussed on the fast mapping of quantitative MR parameters with whole brain coverage in clinically relevant measurement times, the sampling density of the T * 2 curve was compromised to 10 echo times with a T Emax of approx. 40 ms. Therefore, pool amplitudes were determined using a quadratic optimisation approach. The optimisation was constrained by including a priori knowledge about brain water pools. All constraints were optimised in a simulation study to minimise systematic error sources given the incomplete knowledge about the real pool-specific relaxation properties. Based on the simulation results, whole brain in vivo myelin water content maps were acquired in 10 healthy controls and one subject with multiple sclerosis. The in vivo results obtained were consistent with previous reports which demonstrates that a simultaneous whole brain mapping of T 1 , T * 2 , total and myelin water content is feasible on almost any modern MR scanner in less than 10 minutes. (orig.)

In vivo intracellular recordings from spinal lumbar motoneurones in P0-deficient mice indicate an activity-dependent axonal conduction failure in otherwise functional motoneurones

DEFF Research Database (Denmark)

Lehnhoff, Janna; Moldovan, Mihai; Hedegaard, Anne

2014-01-01

Mice deficient for the peripheral myelin binding protein zero (P0-/-) show a progressive dysmyelinating neuropathy phenotypically resembling severe forms of Charcot-Marie-Tooth (CMT) disease. Traditionally, the progression of the disease was attributed to axonal loss, but the effect of chronic...... dysmyelination remains poorly understood. In this study, in vivo electrophysiological recordings were used to assess the function of both central and axonal components of spinal lumbar motoneurones in adult P0-/- mice.Three month old P0-/- mice (n=7) and wild type (WT) littermate controls (n=5) were...... anaesthetized with Hypnorm (0.315 mg/mL fentanyl-citrate + 10 mg/mL fluanisone), Midazolam (5 mg/mL), and sterile water, mixed in the ratio 1:1:2 (induction: 0.15mL/25g, maintenance: 0.05 mL/20 minutes, S.C.). Anaesthesia during surgery was assessed by the lack of reflexes to a short noxious pinch on the hind...

Biology of the repair of central nervous system demyelinated lesions: an appraisal Biologia da reparação de lesões desmielinizantes do sistema nervoso central: uma avaliação

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L. A. V Peireira

1996-06-01

Full Text Available The integrity of myelin sheaths is maintained by oligodendrocytes and Schwann cells respectively in the central nervous system (CNS and in the peripheral nervous system. The process of demyelination consisting of the withdrawal of myelin sheaths from their axons is a characteristic feature of multiple sclerosis, the most common human demyelinating disease. Many experimental models have been designed to study the biology of demyelination and remyelination (repair of the lost myelin in the CNS, due to the difficulties in studying human material. In the ethidium bromide (an intercalating gliotoxic drug model of demyelination, CNS remyelination may be carried out by surviving oligodendrocytes and/or by cells differentiated from the primitive cell lines or either by Schwann cells that invade the CNS. However, some factors such as the age of the experimental animals, intensity and time of exposure to the intercalating chemical and the topography of the lesions have marked influence on the repair of the tissue.A integridade da bainha de mielina é fornecida pelos oligodendrócitos e pelas células de Schwann, no sistema nervoso central (SNC e no sistema nervoso periférico, respectivamente. O fenômeno de desmielinização refere-se à remoção das bainhas de mielina de axônios e este fato é característico na esclerose múltipla, a doença desmielinizante do SNC mais comum no homem. Muitos modelos experimentais têm sido utilizados para o estudo da biologia da desmielinização e remielinização no SNC, face à dificuldade de estudo de material humano. No modelo experimental da droga intercalate, gliotóxica, brometo de etídio, a remielinização do SNC pode ser efetuada por oligodendrócitos sobreviventes à lesão e/ou oriundos de diferenciação de linhagens celulares mais primitivas e por células de Schwann que invadem o SNC. No entanto, fatores como a idade dos animais, a intensidade, e o tempo de exposição ao agente intercalante e a

AKAP12 mediates barrier functions of fibrotic scars during CNS repair.

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Jong-Ho Cha

Full Text Available The repair process after CNS injury shows a well-organized cascade of three distinct stages: inflammation, new tissue formation, and remodeling. In the new tissue formation stage, various cells migrate and form the fibrotic scar surrounding the lesion site. The fibrotic scar is known as an obstacle for axonal regeneration in the remodeling stage. However, the role of the fibrotic scar in the new tissue formation stage remains largely unknown. We found that the number of A-kinase anchoring protein 12 (AKAP12-positive cells in the fibrotic scar was increased over time, and the cells formed a structure which traps various immune cells. Furthermore, the AKAP12-positive cells strongly express junction proteins which enable the structure to function as a physical barrier. In in vivo validation, AKAP12 knock-out (KO mice showed leakage from a lesion, resulting from an impaired structure with the loss of the junction complex. Consistently, focal brain injury in the AKAP12 KO mice led to extended inflammation and more severe tissue damage compared to the wild type (WT mice. Accordingly, our results suggest that AKAP12-positive cells in the fibrotic scar may restrict excessive inflammation, demonstrating certain mechanisms that could underlie the beneficial actions of the fibrotic scar in the new tissue formation stage during the CNS repair process.

Rapid myelin water content mapping on clinical MR systems

Energy Technology Data Exchange (ETDEWEB)

Tonkova, Vyara; Arhelger, Volker [Fachhochschule Koblenz, RheinAhrCampus Remagen (Germany); Schenk, Jochen [Radiologisches Institut, Koblenz (Germany); Neeb, Heiko [Fachhochschule Koblenz, RheinAhrCampus Remagen (Germany); Koblenz Univ. (Germany). Inst. for Medical Engineering and Information Processing - MTI Mittelrhein

2012-07-01

We present an algorithm for the fast mapping of myelin water content using standard multiecho gradient echo acquisitions of the human brain. The method extents a previously published approach for the simultaneous measurement of brain T{sub 1}, T{sup *}{sub 2} and total water content. Employing the multiexponential T{sup *}{sub 2} decay signal of myelinated tissue, myelin water content was measured based on the quantification of two water pools ('myelin water' and 'rest') with different relaxation times. As the existing protocol was focussed on the fast mapping of quantitative MR parameters with whole brain coverage in clinically relevant measurement times, the sampling density of the T{sup *}{sub 2} curve was compromised to 10 echo times with a T {sub Emax} of approx. 40 ms. Therefore, pool amplitudes were determined using a quadratic optimisation approach. The optimisation was constrained by including a priori knowledge about brain water pools. All constraints were optimised in a simulation study to minimise systematic error sources given the incomplete knowledge about the real pool-specific relaxation properties. Based on the simulation results, whole brain in vivo myelin water content maps were acquired in 10 healthy controls and one subject with multiple sclerosis. The in vivo results obtained were consistent with previous reports which demonstrates that a simultaneous whole brain mapping of T{sub 1}, T{sup *}{sub 2}, total and myelin water content is feasible on almost any modern MR scanner in less than 10 minutes. (orig.)

Studies in the development of a bridging device for guiding regenerating axons

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Wen, Xuejun

At present there is no clinically effective treatment for injuries or pathological processes that disrupt the continuity of axons in the mature central nervous system. However, a number of studies suggest that a tremendous potential exists for developing therapies. In particular biomaterials in the form of bridging substrates been shown to support at least some level of axonal regeneration across the lesion site, but display a limited capacity for directing axons toward their targets. To influence the directionality of the regeneration process filaments and tubes appear promising but the technology is far from optimized. As a step toward optimization, we investigated various components of a tissue-engineered bridging device consisting of numerous filaments surrounded by a semipermeable biodegradable hollow fiber membrane (HFM). In the first part of the thesis, we studied the influence of filament diameter and various extracellular matrix coatings on neuron regeneration suing a dorsal root ganglion explant model. We found that laminin surface treated filaments that approached the size of spinal axons support significantly longer regenerative outgrowth than similarly treated filaments of larger diameter, and exceed outgrowth distance on similarly sized filaments treated with fibronectin. Such substrates also consistently supported the attachment and alignment of glial cells and directed the outgrowth of regenerating axons along the long axis of the filaments. In the last part of the thesis, biodegradable hollow fiber membranes were fabricated and their physical, chemical and degradation properties were analyzed. We found that it is possible to use phase inversion methods to fabricate hollow fiber membranes of widely varying properties that degrade of the course of several months. We then evaluated the biocompatibility of the new materials after implantation in the CNS using an adult rat model. We found that the implants were well tolerated and elicited a reaction

Lipid metabolism in myelinating glial cells: lessons from human inherited disorders and mouse models.

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Chrast, Roman; Saher, Gesine; Nave, Klaus-Armin; Verheijen, Mark H G

2011-03-01

The integrity of central and peripheral nervous system myelin is affected in numerous lipid metabolism disorders. This vulnerability was so far mostly attributed to the extraordinarily high level of lipid synthesis that is required for the formation of myelin, and to the relative autonomy in lipid synthesis of myelinating glial cells because of blood barriers shielding the nervous system from circulating lipids. Recent insights from analysis of inherited lipid disorders, especially those with prevailing lipid depletion and from mouse models with glia-specific disruption of lipid metabolism, shed new light on this issue. The particular lipid composition of myelin, the transport of lipid-associated myelin proteins, and the necessity for timely assembly of the myelin sheath all contribute to the observed vulnerability of myelin to perturbed lipid metabolism. Furthermore, the uptake of external lipids may also play a role in the formation of myelin membranes. In addition to an improved understanding of basic myelin biology, these data provide a foundation for future therapeutic interventions aiming at preserving glial cell integrity in metabolic disorders.

Experimental Autoimmune Encephalomyelitis (EAE) as Animal Models of Multiple Sclerosis (MS).

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Glatigny, Simon; Bettelli, Estelle

2018-01-08

Multiple sclerosis (MS) is a multifocal demyelinating disease of the central nervous system (CNS) leading to the progressive destruction of the myelin sheath surrounding axons. It can present with variable clinical and pathological manifestations, which might reflect the involvement of distinct pathogenic processes. Although the mechanisms leading to the development of the disease are not fully understood, numerous evidences indicate that MS is an autoimmune disease, the initiation and progression of which are dependent on an autoimmune response against myelin antigens. In addition, genetic susceptibility and environmental triggers likely contribute to the initiation of the disease. At this time, there is no cure for MS, but several disease-modifying therapies (DMTs) are available to control and slow down disease progression. A good number of these DMTs were identified and tested using animal models of MS referred to as experimental autoimmune encephalomyelitis (EAE). In this review, we will recapitulate the characteristics of EAE models and discuss how they help shed light on MS pathogenesis and help test new treatments for MS patients. Copyright © 2018 Cold Spring Harbor Laboratory Press; all rights reserved.

Natalizumab therapy of multiple sclerosis.

LENUS (Irish Health Repository)

Hutchinson, Michael

2012-02-01

Multiple sclerosis (MS) is the commonest disabling neurological disease of young and middle-aged adults affecting 1 million persons world wide. The illness begins with a relapsing-remitting MS course in 85%-90% of patients; the other 10%-15% have a primary progressive onset MS. Our current understanding is that MS is an autoimmune disorder with an inflammatory T-cell attack on myelin or some component of the oligodendrocyte--myelin structure. Relapses of disease activity result in plaques of demyelination with destruction of myelin and, to a lesser, extent axons. Lymphocytes within the central nervous system tissue recruit more cells leading to an inflammatory cascade that causes myelin damage, axonal disruption, and neuronal death. If the plaque occurs in a vocal area of the central nervous system then symptoms relating to that area result. However, magnetic resonance imaging shows that approximately 10 times more lesions occur in asymptomatic areas of the brain. Recovery from an initial relapse may appear relatively complete but persistent inflammation results in axonal injury and residual disability results. With time and accumulated lesion load, secondary degeneration of denuded axons results in the phase of secondary progressive MS usually 15-20 years after onset.

In silico investigation of blast-induced intracranial fluid cavitation as it potentially leads to traumatic brain injury

Science.gov (United States)

Haniff, S.; Taylor, P. A.

2017-11-01

We conducted computational macroscale simulations predicting blast-induced intracranial fluid cavitation possibly leading to brain injury. To further understanding of this problem, we developed microscale models investigating the effects of blast-induced cavitation bubble collapse within white matter axonal fiber bundles of the brain. We model fiber tracks of myelinated axons whose diameters are statistically representative of white matter. Nodes of Ranvier are modeled as unmyelinated sections of axon. Extracellular matrix envelops the axon fiber bundle, and gray matter is placed adjacent to the bundle. Cavitation bubbles are initially placed assuming an intracranial wave has already produced them. Pressure pulses, of varied strengths, are applied to the upper boundary of the gray matter and propagate through the model, inducing bubble collapse. Simulations, conducted using the shock wave physics code CTH, predict an increase in pressure and von Mises stress in axons downstream of the bubbles after collapse. This appears to be the result of hydrodynamic jetting produced during bubble collapse. Interestingly, results predict axon cores suffer significantly lower shear stresses from proximal bubble collapse than does their myelin sheathing. Simulations also predict damage to myelin sheathing, which, if true, degrades axonal electrical transmissibility and general health of the white matter structures in the brain.

Estudo quantitativo do nervo frênico de rato albino em função do envelhecimento

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Romeu Rodrigues de Souza

1990-01-01

Full Text Available The phrenic nerve of albino rats was studied for age changes in number of fibres, myelin sheath thickness and axon calibre. Nerves were excised from three young and three aged rats. There is no significant morphological differences between nerves from young and aged rats and no difference with age was found in the number of fibres, myelin sheath thickness and axon calibre.

Isolated vasculitis of the CNS

International Nuclear Information System (INIS)

Block, F.; Reith, W.

2000-01-01

Vasculitis is a rare cause for disease of the CNS. The isolated vasculitis of the CNS is restricted to the CNS whereas other forms of vasculitis affect various organs including the CNS. Headache, encephalopathy, focal deficits and epileptic seizures are the major symptoms suggestive for vasculitis. One major criterion of the isolated vasculitis of the CNS is the lack of evidence for other vasculitis forms or for pathology of other organs. Angiography displays multifocal segmental stenosis of intracranial vessels. MRI demonstrates multiple lesions which in part show enhancement after gadolinium. A definite diagnosis can only be made on the grounds of biopsy from leptomeninges and parenchyma. Therapy consists of corticosteroids and cyclophosphamid. (orig.) [de

Signal propagation along the axon.

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Rama, Sylvain; Zbili, Mickaël; Debanne, Dominique

2018-03-08

Axons link distant brain regions and are usually considered as simple transmission cables in which reliable propagation occurs once an action potential has been generated. Safe propagation of action potentials relies on specific ion channel expression at strategic points of the axon such as nodes of Ranvier or axonal branch points. However, while action potentials are generally considered as the quantum of neuronal information, their signaling is not entirely digital. In fact, both their shape and their conduction speed have been shown to be modulated by activity, leading to regulations of synaptic latency and synaptic strength. We report here newly identified mechanisms of (1) safe spike propagation along the axon, (2) compartmentalization of action potential shape in the axon, (3) analog modulation of spike-evoked synaptic transmission and (4) alteration in conduction time after persistent regulation of axon morphology in central neurons. We discuss the contribution of these regulations in information processing. Copyright © 2018 Elsevier Ltd. All rights reserved.

A quantitative measure of myelination development in infants, using MR images

International Nuclear Information System (INIS)

Carmody, Dennis P.; Dunn, Stanley M.; Boddie-Willis, Akiza S.; DeMarco, J. Kevin; Lewis, Michael

2004-01-01

The objective of this study was to measure myelination of frontal lobe changes in infants and young children. Twenty-four cases of infants and children (age range 12-121 months) were evaluated by a quantitative assessment of T2-weighted MR image features. Reliable quantitative changes between white and gray matter correlated with developmental age in a group of children with no neurological findings. Myelination appears to be an increasing exponential function with the greatest rate of change occurring over the first 3 years of life. The quantitative changes observed were in accordance with previous qualitative judgments of myelination development. Children with periventricular leukomalacia (PVL) showed delays in achieving levels of myelination when compared to normal children and adjusted for chronological age. The quantitative measure of myelination development may prove to be useful in assessing the stages of development and helpful in the quantitative descriptions of white matter disorders such as PVL. (orig.)

A quantitative measure of myelination development in infants, using MR images

Energy Technology Data Exchange (ETDEWEB)

Carmody, Dennis P. [Robert Wood Johnson Medical School, New Brunswick, NJ (United States); Dunn, Stanley M.; Boddie-Willis, Akiza S. [The State University of New Jersey, Rutgers, New Brunswick, NJ (United States); DeMarco, J. Kevin [Laurie Imaging Center, New Brunswick, NJ (United States); Lewis, Michael [Robert Wood Johnson Medical School, New Brunswick, NJ (United States); Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Institute for the Study of Child Development, New Brunswick (United States)

2004-09-01

The objective of this study was to measure myelination of frontal lobe changes in infants and young children. Twenty-four cases of infants and children (age range 12-121 months) were evaluated by a quantitative assessment of T2-weighted MR image features. Reliable quantitative changes between white and gray matter correlated with developmental age in a group of children with no neurological findings. Myelination appears to be an increasing exponential function with the greatest rate of change occurring over the first 3 years of life. The quantitative changes observed were in accordance with previous qualitative judgments of myelination development. Children with periventricular leukomalacia (PVL) showed delays in achieving levels of myelination when compared to normal children and adjusted for chronological age. The quantitative measure of myelination development may prove to be useful in assessing the stages of development and helpful in the quantitative descriptions of white matter disorders such as PVL. (orig.)

Diversity of Internal Sensory Neuron Axon Projection Patterns Is Controlled by the POU-Domain Protein Pdm3 in Drosophila Larvae.

Science.gov (United States)

Qian, Cheng Sam; Kaplow, Margarita; Lee, Jennifer K; Grueber, Wesley B

2018-02-21

Internal sensory neurons innervate body organs and provide information about internal state to the CNS to maintain physiological homeostasis. Despite their conservation across species, the anatomy, circuitry, and development of internal sensory systems are still relatively poorly understood. A largely unstudied population of larval Drosophila sensory neurons, termed tracheal dendrite (td) neurons, innervate internal respiratory organs and may serve as a model for understanding the sensing of internal states. Here, we characterize the peripheral anatomy, central axon projection, and diversity of td sensory neurons. We provide evidence for prominent expression of specific gustatory receptor genes in distinct populations of td neurons, suggesting novel chemosensory functions. We identify two anatomically distinct classes of td neurons. The axons of one class project to the subesophageal zone (SEZ) in the brain, whereas the other terminates in the ventral nerve cord (VNC). We identify expression and a developmental role of the POU-homeodomain transcription factor Pdm3 in regulating the axon extension and terminal targeting of SEZ-projecting td neurons. Remarkably, ectopic Pdm3 expression is alone sufficient to switch VNC-targeting axons to SEZ targets, and to induce the formation of putative synapses in these ectopic target zones. Our data thus define distinct classes of td neurons, and identify a molecular factor that contributes to diversification of axon targeting. These results introduce a tractable model to elucidate molecular and circuit mechanisms underlying sensory processing of internal body status and physiological homeostasis. SIGNIFICANCE STATEMENT How interoceptive sensory circuits develop, including how sensory neurons diversify and target distinct central regions, is still poorly understood, despite the importance of these sensory systems for maintaining physiological homeostasis. Here, we characterize classes of Drosophila internal sensory neurons (td

Idiopathic acute onset myelopathy in cheetah (Acinonyx jubatus) cubs.

Science.gov (United States)

Walzer, Christian; Url, Angelika; Robert, Nadia; Kübber-Heiss, Anna; Nowotny, Norbert; Schmidt, Peter

2003-03-01

Numerous cases of ataxia, hind limb paresis, and paralysis have occurred in cheetah (Acinonyx jubatus) cubs over the past 10 yr within the European Endangered Species Program population, including 12 in mainland Europe, two in the British Isles, one in Namibia, and one in Dubai. The condition is the most important medical factor limiting European cheetah population growth. Eight cubs at the Salzburg Zoo, Austria, were affected. They demonstrated upper motor neuron lesions when alive and bilateral, symmetrical myelin degeneration of the spinal cord on necropsy. Ballooning of myelin sheaths surrounded mostly preserved axons, and no spheroids, characteristic of acute axonal degeneration, were found. Myelin loss markedly exceeded axonal degeneration. The syndrome's etiology is unclear, although viral, bacterial, parasitic, genetic, nutritional-metabolic, toxic, and physical causes have been considered.

The CNS connectome of a tadpole larva of Ciona intestinalis (L.) highlights sidedness in the brain of a chordate sibling.

Science.gov (United States)

Ryan, Kerrianne; Lu, Zhiyuan; Meinertzhagen, Ian A

2016-12-06

Left-right asymmetries in brains are usually minor or cryptic. We report brain asymmetries in the tiny, dorsal tubular nervous system of the ascidian tadpole larva, Ciona intestinalis . Chordate in body plan and development, the larva provides an outstanding example of brain asymmetry. Although early neural development is well studied, detailed cellular organization of the swimming larva's CNS remains unreported. Using serial-section EM we document the synaptic connectome of the larva's 177 CNS neurons. These formed 6618 synapses including 1772 neuromuscular junctions, augmented by 1206 gap junctions. Neurons are unipolar with at most a single dendrite, and few synapses. Some synapses are unpolarised, others form reciprocal or serial motifs; 922 were polyadic. Axo-axonal synapses predominate. Most neurons have ciliary organelles, and many features lack structural specialization. Despite equal cell numbers on both sides, neuron identities and pathways differ left/right. Brain vesicle asymmetries include a right ocellus and left coronet cells.

Differentiating between axonal damage and demyelination in healthy aging by combining diffusion-tensor imaging and diffusion-weighted spectroscopy in the human corpus callosum at 7 T.

Science.gov (United States)

Branzoli, Francesca; Ercan, Ece; Valabrègue, Romain; Wood, Emily T; Buijs, Mathijs; Webb, Andrew; Ronen, Itamar

2016-11-01

Diffusion-tensor imaging and single voxel diffusion-weighted magnetic resonance spectroscopy were used at 7T to explore in vivo age-related microstructural changes in the corpus callosum. Sixteen healthy elderly (age range 60-71 years) and 13 healthy younger controls (age range 23-32 years) were included in the study. In healthy elderly, we found lower water fractional anisotropy and higher water mean diffusivity and radial diffusivity in the corpus callosum, indicating the onset of demyelination processes with healthy aging. These changes were not associated with a concomitant significant difference in the cytosolic diffusivity of the intra-axonal metabolite N-acetylaspartate (p = 0.12), the latter representing a pure measure of intra-axonal integrity. It was concluded that the possible intra-axonal changes associated with normal aging processes are below the detection level of diffusion-weighted magnetic resonance spectroscopy in our experiment (e.g., smaller than 10%) in the age range investigated. Lower axial diffusivity of total creatine was observed in the elderly group (p = 0.058), possibly linked to a dysfunction in the energy metabolism associated with a deficit in myelin synthesis. Copyright © 2016 Elsevier Inc. All rights reserved.

Axons take a dive

Science.gov (United States)

Tong, Cheuk Ka; Cebrián-Silla, Arantxa; Paredes, Mercedes F; Huang, Eric J; García-Verdugo, Jose Manuel; Alvarez-Buylla, Arturo

2015-01-01

In the walls of the lateral ventricles of the adult mammalian brain, neural stem cells (NSCs) and ependymal (E1) cells share the apical surface of the ventricular–subventricular zone (V–SVZ). In a recent article, we show that supraependymal serotonergic (5HT) axons originating from the raphe nuclei in mice form an extensive plexus on the walls of the lateral ventricles where they contact E1 cells and NSCs. Here we further characterize the contacts between 5HT supraependymal axons and E1 cells in mice, and show that suprependymal axons tightly associated to E1 cells are also present in the walls of the human lateral ventricles. These observations raise interesting questions about the function of supraependymal axons in the regulation of E1 cells. PMID:26413556

Central connectivity of transient receptor potential melastatin 8-expressing axons in the brain stem and spinal dorsal horn.

Directory of Open Access Journals (Sweden)

Yun Sook Kim

Full Text Available Transient receptor potential melastatin 8 (TRPM8 ion channels mediate the detection of noxious and innocuous cold and are expressed by primary sensory neurons, but little is known about the processing of the TRPM8-mediated cold information within the trigeminal sensory nuclei (TSN and the spinal dorsal horn (DH. To address this issue, we characterized TRPM8-positive (+ neurons in the trigeminal ganglion and investigated the distribution of TRPM8+ axons and terminals, and their synaptic organization in the TSN and in the DH using light and electron microscopic immunohistochemistry in transgenic mice expressing a genetically encoded axonal tracer in TRPM8+ neurons. TRPM8 was expressed in a fraction of small myelinated primary afferent fibers (23.7% and unmyelinated fibers (76.3%, suggesting that TRPM8-mediated cold is conveyed via C and Aδ afferents. TRPM8+ axons were observed in all TSN, but at different densities in the dorsal and ventral areas of the rostral TSN, which dominantly receive sensory afferents from intra- and peri-oral structures and from the face, respectively. While synaptic boutons arising from Aδ and non-peptidergic C afferents usually receive many axoaxonic contacts and form complex synaptic arrangements, TRPM8+ boutons arising from afferents of the same classes of fibers showed a unique synaptic connectivity; simple synapses with one or two dendrites and sparse axoaxonic contacts. These findings suggest that TRPM8-mediated cold is conveyed via a specific subset of C and Aδ afferent neurons and is processed in a unique manner and differently in the TSN and DH.

Role of motoneuron-derived neurotrophin 3 in survival and axonal projection of sensory neurons during neural circuit formation.

Science.gov (United States)

Usui, Noriyoshi; Watanabe, Keisuke; Ono, Katsuhiko; Tomita, Koichi; Tamamaki, Nobuaki; Ikenaka, Kazuhiro; Takebayashi, Hirohide

2012-03-01

Sensory neurons possess the central and peripheral branches and they form unique spinal neural circuits with motoneurons during development. Peripheral branches of sensory axons fasciculate with the motor axons that extend toward the peripheral muscles from the central nervous system (CNS), whereas the central branches of proprioceptive sensory neurons directly innervate motoneurons. Although anatomically well documented, the molecular mechanism underlying sensory-motor interaction during neural circuit formation is not fully understood. To investigate the role of motoneuron on sensory neuron development, we analyzed sensory neuron phenotypes in the dorsal root ganglia (DRG) of Olig2 knockout (KO) mouse embryos, which lack motoneurons. We found an increased number of apoptotic cells in the DRG of Olig2 KO embryos at embryonic day (E) 10.5. Furthermore, abnormal axonal projections of sensory neurons were observed in both the peripheral branches at E10.5 and central branches at E15.5. To understand the motoneuron-derived factor that regulates sensory neuron development, we focused on neurotrophin 3 (Ntf3; NT-3), because Ntf3 and its receptors (Trk) are strongly expressed in motoneurons and sensory neurons, respectively. The significance of motoneuron-derived Ntf3 was analyzed using Ntf3 conditional knockout (cKO) embryos, in which we observed increased apoptosis and abnormal projection of the central branch innervating motoneuron, the phenotypes being apparently comparable with that of Olig2 KO embryos. Taken together, we show that the motoneuron is a functional source of Ntf3 and motoneuron-derived Ntf3 is an essential pre-target neurotrophin for survival and axonal projection of sensory neurons.

Schwann cell autophagy, myelinophagy, initiates myelin clearance from injured nerves

NARCIS (Netherlands)

Gomez-Sanchez, Jose A.; Carty, Lucy; Iruarrizaga-Lejarreta, Marta; Palomo-Irigoyen, Marta; Varela-Rey, Marta; Griffith, Megan; Hantke, Janina; Macias-Camara, Nuria; Azkargorta, Mikel; Aurrekoetxea, Igor; de Juan, Virginia Gutiérrez; Jefferies, Harold B. J.; Aspichueta, Patricia; Elortza, Félix; Aransay, Ana M.; Martínez-Chantar, María L.; Baas, Frank; Mato, José M.; Mirsky, Rhona; Woodhoo, Ashwin; Jessen, Kristján R.

2015-01-01

Although Schwann cell myelin breakdown is the universal outcome of a remarkably wide range of conditions that cause disease or injury to peripheral nerves, the cellular and molecular mechanisms that make Schwann cell-mediated myelin digestion possible have not been established. We report that

Engineering Biomaterials to Influence Oligodendroglial Growth, Maturation, and Myelin Production.

Science.gov (United States)

Russell, Lauren N; Lampe, Kyle J

2016-01-01

Millions of people suffer from damage or disease to the nervous system that results in a loss of myelin, such as through a spinal cord injury or multiple sclerosis. Diminished myelin levels lead to further cell death in which unmyelinated neurons die. In the central nervous system, a loss of myelin is especially detrimental because of its poor ability to regenerate. Cell therapies such as stem or precursor cell injection have been investigated as stem cells are able to grow and differentiate into the damaged cells; however, stem cell injection alone has been unsuccessful in many areas of neural regeneration. Therefore, researchers have begun exploring combined therapies with biomaterials that promote cell growth and differentiation while localizing cells in the injured area. The regrowth of myelinating oligodendrocytes from neural stem cells through a biomaterials approach may prove to be a beneficial strategy following the onset of demyelination. This article reviews recent advancements in biomaterial strategies for the differentiation of neural stem cells into oligodendrocytes, and presents new data indicating appropriate properties for oligodendrocyte precursor cell growth. In some cases, an increase in oligodendrocyte differentiation alongside neurons is further highlighted for functional improvements where the biomaterial was then tested for increased myelination both in vitro and in vivo. © 2016 S. Karger AG, Basel.

Distribution of elements in rat peripheral axons and nerve cell bodies determined by x-ray microprobe analysis

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LoPachin, R.M. Jr.; Lowery, J.; Eichberg, J.; Kirkpatrick, J.B.; Cartwright, J. Jr.; Saubermann, A.J.

1988-09-01

X-ray microprobe analysis was used to determine concentrations (millimoles of element per kilogram dry weight) of Na, P, Cl, K, and Ca in cellular compartments of frozen, unfixed sections of rat sciatic and tibial nerves and dorsal root ganglion (DRG). Five compartments were examined in peripheral nerve (axoplasm, mitochondria, myelin, extraaxonal space, and Schwann cell cytoplasm), and four were analyzed in DRG nerve cell bodies (cytoplasm, mitochondria, nucleus, and nucleolus). Each morphological compartment exhibited characteristic concentrations of elements. The extraaxonal space contained high concentrations of Na, Cl, and Ca, whereas intraaxonal compartments exhibited lower concentrations of these elements but relatively high K contents. Nerve axoplasm and axonal mitochondria had similar elemental profiles, and both compartments displayed proximodistal gradients of decreasing levels of K, Cl, and, to some extent, Na. Myelin had a selectively high P concentration with low levels of other elements. The elemental concentrations of Schwann cell cytoplasm and DRG were similar, but both were different from that of axoplasm, in that K and Cl were markedly lower whereas P was higher. DRG cell nuclei contained substantially higher K levels than cytoplasm. The subcellular distribution of elements was clearly shown by color-coded images generated by computer-directed digital x-ray imaging. The results of this study demonstrate characteristic elemental distributions for each anatomical compartment, which doubtless reflect nerve cell structure and function.

Dynamics and heterogeneity of brain damage in multiple sclerosis

KAUST Repository

Kotelnikova, Ekaterina

2017-10-26

Multiple Sclerosis (MS) is an autoimmune disease driving inflammatory and degenerative processes that damage the central nervous system (CNS). However, it is not well understood how these events interact and evolve to evoke such a highly dynamic and heterogeneous disease. We established a hypothesis whereby the variability in the course of MS is driven by the very same pathogenic mechanisms responsible for the disease, the autoimmune attack on the CNS that leads to chronic inflammation, neuroaxonal degeneration and remyelination. We propose that each of these processes acts more or less severely and at different times in each of the clinical subgroups. To test this hypothesis, we developed a mathematical model that was constrained by experimental data (the expanded disability status scale [EDSS] time series) obtained from a retrospective longitudinal cohort of 66 MS patients with a long-term follow-up (up to 20 years). Moreover, we validated this model in a second prospective cohort of 120 MS patients with a three-year follow-up, for which EDSS data and brain volume time series were available. The clinical heterogeneity in the datasets was reduced by grouping the EDSS time series using an unsupervised clustering analysis. We found that by adjusting certain parameters, albeit within their biological range, the mathematical model reproduced the different disease courses, supporting the dynamic CNS damage hypothesis to explain MS heterogeneity. Our analysis suggests that the irreversible axon degeneration produced in the early stages of progressive MS is mainly due to the higher rate of myelinated axon degeneration, coupled to the lower capacity for remyelination. However, and in agreement with recent pathological studies, degeneration of chronically demyelinated axons is not a key feature that distinguishes this phenotype. Moreover, the model reveals that lower rates of axon degeneration and more rapid remyelination make relapsing MS more resilient than the

Dynamics and heterogeneity of brain damage in multiple sclerosis

KAUST Repository

Kotelnikova, Ekaterina; Kiani, Narsis A.; Abad, Elena; Martinez-Lapiscina, Elena H.; Andorra, Magi; Zubizarreta, Irati; Pulido-Valdeolivas, Irene; Pertsovskaya, Inna; Alexopoulos, Leonidas G.; Olsson, Tomas; Martin, Roland; Paul, Friedemann; Tegner, Jesper; Garcia-Ojalvo, Jordi; Villoslada, Pablo

2017-01-01

Multiple Sclerosis (MS) is an autoimmune disease driving inflammatory and degenerative processes that damage the central nervous system (CNS). However, it is not well understood how these events interact and evolve to evoke such a highly dynamic and heterogeneous disease. We established a hypothesis whereby the variability in the course of MS is driven by the very same pathogenic mechanisms responsible for the disease, the autoimmune attack on the CNS that leads to chronic inflammation, neuroaxonal degeneration and remyelination. We propose that each of these processes acts more or less severely and at different times in each of the clinical subgroups. To test this hypothesis, we developed a mathematical model that was constrained by experimental data (the expanded disability status scale [EDSS] time series) obtained from a retrospective longitudinal cohort of 66 MS patients with a long-term follow-up (up to 20 years). Moreover, we validated this model in a second prospective cohort of 120 MS patients with a three-year follow-up, for which EDSS data and brain volume time series were available. The clinical heterogeneity in the datasets was reduced by grouping the EDSS time series using an unsupervised clustering analysis. We found that by adjusting certain parameters, albeit within their biological range, the mathematical model reproduced the different disease courses, supporting the dynamic CNS damage hypothesis to explain MS heterogeneity. Our analysis suggests that the irreversible axon degeneration produced in the early stages of progressive MS is mainly due to the higher rate of myelinated axon degeneration, coupled to the lower capacity for remyelination. However, and in agreement with recent pathological studies, degeneration of chronically demyelinated axons is not a key feature that distinguishes this phenotype. Moreover, the model reveals that lower rates of axon degeneration and more rapid remyelination make relapsing MS more resilient than the

The whole spectrum of alcohol-related changes in the CNS. Practical MR and CT imaging guidelines for daily clinical use; Alkoholinduzierte ZNS-Veraenderungen in der bildgebenden Diagnostik. Ein CT- und MRT-Leitfaden fuer die klinische Praxis

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Keil, V.C.; Greschus, S.; Hadizadeh, D.R.; Schild, H.H. [University Hospital Bonn (Germany). Dept. of Radiology; Schneider, C. [University Hospital Bonn (Germany). Dept. of Neurology

2015-12-15

Alcohol addiction is the most common drug addiction. Alcohol passes both the placenta as well as the blood-brain barrier and is in multiple ways neurotoxic. Liver diseases and other systemic alcohol-related diseases cause secondary damage to the CNS. Especially in adolescents, even a single episode of severe alcohol intoxication (''binge drinking'') may result in life-threatening neurological consequences. Alcohol-related brain and spinal cord diseases derive from multiple causes including impairment of the cellular metabolism, often aggravated by hypovitaminosis, altered neurotransmission, myelination and synaptogenesis as well as alterations in gene expression. Modern radiological diagnostics, MRI in particular, can detect the resulting alterations in the CNS with a high sensitivity. Morphological aspects often strongly correlate with clinical symptoms of the patient. It is less commonly known that many diseases considered as ''typically alcohol-related'', such as Wernicke's encephalopathy, are to a large extent not alcohol-induced. Visible CNS alterations are thus non-pathognomonic and demand careful evaluation of differential diagnoses. This review article elucidates the pathogenesis, clinical aspects and radiological image features of the most common alcohol-related CNS diseases and their differential diagnoses.

Nanomedicines for the Treatment of CNS Diseases.

Science.gov (United States)

Reynolds, Jessica L; Mahato, Ram I

2017-03-01

Targeting and delivering macromolecular therapeutics to the central nervous system (CNS) has been a major challenge. The blood-brain barrier (BBB) is the main obstacle that must be overcome to allow compounds to reach their targets in the brain. Therefore, much effort has been channelled into improving transport of therapeutics across the BBB and into the CNS including the use of nanoparticles. In this thematic issue, several reviews and original research are presented that address "Nanomedicines for CNS Diseases." The articles in this issue are concentrated on either CNS-HIV disease or CNS tumors. In regards to CNS-HIV disease, there are two reviews that discuss the role of nanoparticles for improving the delivery of HIV therapeutics to the CNS. In addition, there are two original articles focusing on therapies for CNS-HIV, one of them uses nanoparticles for delivery of siRNA specific to a key protein in autophagy to microglia, and another discusses nanoparticle delivery of a soluble mediator to suppress neuroinflammation. Furthermore, a comprehensive review about gene therapy for CNS neurological diseases is also included. Finally, this issue also includes review articles on enhanced drug targeting to CNS tumors. These articles include a review on the use of nanoparticles for CNS tumors, a review on functionalization (ligands) of nanoparticles for drug targeting to the brain tumor by overcoming BBB, and the final review discusses the use of macrophages as a delivery vehicle to CNS tumors. This thematic issue provides a wealth of knowledge on using nanomedicines for CNS diseases.

The Changes in Rats with Sciatic Nerve Crush Injury Supplemented with Evening Primrose Oil: Behavioural, Morphologic, and Morphometric Analysis

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Danial Ramli

2017-01-01

Full Text Available Nerve crush injuries are commonly used models for axonotmesis to examine peripheral nerve regeneration. As evening primrose oil (EPO is rich in omega-6 essential fatty acid component and gamma-linolenic acid, studies have shown the potential role of EPO in myelination. Seventy-two healthy adult Sprague-Dawley rats were classified into three groups: normal group, control group, and experimental group. The result indicates that there was significant difference in toe-spreading reflex between the normal and the control groups (1.9±0.031, p<0.05 and the normal and the EPO groups (0.4±0.031, p<0.05 and significant difference between EPO and the control groups (1.5±0.031, p<0.05. Regeneration of axons and myelin in nerve fibre in the EPO-treated group developed better and faster than in the control group. In the control group, the shape of the axon was irregular with a thinner myelin sheath. In the experimental group, the shape of the axons, the thickness of the myelin sheath, and the diameter of the axons were almost the same as in the normal group. In conclusion, EPO supplementation may be beneficial as a therapeutic option for disturbances of nerve interaction.

Severe diffuse axon injury in chronic alcoholic rat medulla oblongata following a concussion blow.

Science.gov (United States)

Luo, Jianming; Chen, Guang; Wei, Lai; Qian, Hong; Lai, Xiaoping; Wang, Dian; Lv, Junyao; Yu, Xiaojun

2014-01-01

We investigated the axonal morphological changes and expression of both tau protein and β-APP following concussion to the medulla oblongata, in a rat model of chronic alcoholism. Fifty-nine male Sprague-Dawley rats were randomly divided into EtOH, EtOH-TBI and control groups (water group, water-TBI group). To establish chronic alcoholic rats, rats were intragastrically given edible spirituous liquor twice daily. Rats also received a blow on the occipital tuberosity with an iron pendulum. Morphological changes and expression of tau and β-APP proteins in the medulla oblongata were examined. (a) Nerve fibre thickening and twisting were observed in alcoholic rats, with nerve fibre changes becoming more significant following a concussion blow, which leads to some nerve fibres fracturing. (b) Transmission electron microscopy revealed that the nerve fibre myelin became loosened and displayed lamellar separation, which became more significant following concussion. (c) The integral optical density (IOD) sum value of β-APP of the EtOH-TBI group was lower than that in the EtOH group (P Chronic alcoholism caused nerve fibre and neuronal morphology damage in the rat medulla oblongata, with structural damage becoming more significant following concussion. (b) Concussion changed the expression of β-APP and tau protein in chronic alcoholic rat medulla oblongata, suggesting that chronic alcoholism can lead to severe axonal injury following a concussion blow. (c) The effect of chronic alcoholism may be synergistic the concussion blow to promote animal injury and death.

Studies of axon-glial cell interactions and periaxonal K+ homeostasis--II. The effect of axonal stimulation, cholinergic agents and transport inhibitors on the resistance in series with the axon membrane.

Science.gov (United States)

Hassan, S; Lieberman, E M

1988-06-01

The small electrical resistance in series with the axon membrane is generally modeled as the intercellular pathway for current flow through the periaxonal glial (Schwann cell) sheath. The series resistance of the medial giant axon of the crayfish, Procambarus clarkii, was found to vary with conditions known to affect the electrical properties of the periaxonal glia. Series resistance was estimated from computer analysed voltage waveforms generated by axial wire-constant current and space clamp techniques. The average series resistance for all axons was 6.2 +/- 0.5 omega cm2 (n = 128). Values ranged between 1 and 30 omega cm2. The series resistance of axons with low resting membrane resistance (less than 1500 omega cm2) increased an average of 30% when stimulated for 45 s to 7 min (50 Hz) whereas the series resistance of high membrane resistance (greater than 1500 omega cm2) axons decreased an average of 10%. Carbachol (10(-7) M) caused the series resistance of low membrane resistance axons to decrease during stimulation but had no effect on high membrane resistance axons. d-Tubocurare (10(-8) M) caused the series resistance of high membrane resistance axons to increase during stimulation but had no effect on low membrane resistance axons. Bumetanide, a Na-K-Cl cotransport inhibitor and low [K+]o, prevented the stimulation-induced increase in series resistance of low membrane resistance axons but had no effect on the high membrane resistance axons. The results suggest that the series resistance of axons varies in response to the activity of the glial K+ uptake mechanisms stimulated by the appearance of K+ in the periaxonal space during action potential generation.(ABSTRACT TRUNCATED AT 250 WORDS)

Axodendritic sorting and pathological missorting of Tau are isoform-specific and determined by axon initial segment architecture.

Science.gov (United States)

Zempel, Hans; Dennissen, Frank J A; Kumar, Yatender; Luedtke, Julia; Biernat, Jacek; Mandelkow, Eva-Maria; Mandelkow, Eckhard

2017-07-21

Subcellular mislocalization of the microtubule-associated protein Tau is a hallmark of Alzheimer disease (AD) and other tauopathies. Six Tau isoforms, differentiated by the presence or absence of a second repeat or of N-terminal inserts, exist in the human CNS, but their physiological and pathological differences have long remained elusive. Here, we investigated the properties and distributions of human and rodent Tau isoforms in primary forebrain rodent neurons. We found that the Tau diffusion barrier (TDB), located within the axon initial segment (AIS), controls retrograde (axon-to-soma) and anterograde (soma-to-axon) traffic of Tau. Tau isoforms without the N-terminal inserts were sorted efficiently into the axon. However, the longest isoform (2N4R-Tau) was partially retained in cell bodies and dendrites, where it accelerated spine and dendrite growth. The TDB (located within the AIS) was impaired when AIS components (ankyrin G, EB1) were knocked down or when glycogen synthase kinase-3β (GSK3β; an AD-associated kinase tethered to the AIS) was overexpressed. Using superresolution nanoscopy and live-cell imaging, we observed that microtubules within the AIS appeared highly dynamic, a feature essential for the TDB. Pathomechanistically, amyloid-β insult caused cofilin activation and F-actin remodeling and decreased microtubule dynamics in the AIS. Concomitantly with these amyloid-β-induced disruptions, the AIS/TDB sorting function failed, causing AD-like Tau missorting. In summary, we provide evidence that the human and rodent Tau isoforms differ in axodendritic sorting and amyloid-β-induced missorting and that the axodendritic distribution of Tau depends on AIS integrity. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Slit stimulation recruits Dock and Pak to the roundabout receptor and increases Rac activity to regulate axon repulsion at the CNS midline.

Science.gov (United States)

Fan, Xueping; Labrador, Juan Pablo; Hing, Huey; Bashaw, Greg J

2003-09-25

Drosophila Roundabout (Robo) is the founding member of a conserved family of repulsive axon guidance receptors that respond to secreted Slit proteins. Here we present evidence that the SH3-SH2 adaptor protein Dreadlocks (Dock), the p21-activated serine-threonine kinase (Pak), and the Rac1/Rac2/Mtl small GTPases can function during Robo repulsion. Loss-of-function and genetic interaction experiments suggest that limiting the function of Dock, Pak, or Rac partially disrupts Robo repulsion. In addition, Dock can directly bind to Robo's cytoplasmic domain, and the association of Dock and Robo is enhanced by stimulation with Slit. Furthermore, Slit stimulation can recruit a complex of Dock and Pak to the Robo receptor and trigger an increase in Rac1 activity. These results provide a direct physical link between the Robo receptor and an important cytoskeletal regulatory protein complex and suggest that Rac can function in both attractive and repulsive axon guidance.

Variation in myelin lipid composition induced by change in environmental temperature of goldfish (Carassius auratus L. )

Energy Technology Data Exchange (ETDEWEB)

Selivonchick, D.P.; Roots, B.I.

1976-04-01

Goldfish (Carassius auratus L.) were acclimated to 5, 15, and 30/sup 0/C, and the lipid and protein composition of brain and spinal cord myelin was determined. Goldfish myelin contains less galactolipid, but more protein and phospholipid than mammalian and bird myelin. Phosphatidyl choline was the predominant phospholipid in both brain and spinal cord myelin. Fish myelin also showed a greater plasmalogen content with an average ethanolamine plasmalogen/total phosphatidyl ethanolamine ratio of 0.84. Total brain and myelin lipids, with the exception of plasmalogens, showed a resistance to change with thermal acclimation. Differences between brain and spinal cord myelin protein and phospholipids were not observed. It is suggested that temperature acclimation in poikilotherms may be used as a tool in the study of membrane adaptability.

Sleeve bridging of the rhesus monkey ulnar nerve with muscular branches of the pronator teres: multiple amplification of axonal regeneration

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Yu-hui Kou

2015-01-01

Full Text Available Multiple-bud regeneration, i.e., multiple amplification, has been shown to exist in peripheral nerve regeneration. Multiple buds grow towards the distal nerve stump during proximal nerve fiber regeneration. Our previous studies have verified the limit and validity of multiple amplification of peripheral nerve regeneration using small gap sleeve bridging of small donor nerves to repair large receptor nerves in rodents. The present study sought to observe multiple amplification of myelinated nerve fiber regeneration in the primate peripheral nerve. Rhesus monkey models of distal ulnar nerve defects were established and repaired using muscular branches of the right forearm pronator teres. Proximal muscular branches of the pronator teres were sutured into the distal ulnar nerve using the small gap sleeve bridging method. At 6 months after suture, two-finger flexion and mild wrist flexion were restored in the ulnar-sided injured limbs of rhesus monkey. Neurophysiological examination showed that motor nerve conduction velocity reached 22.63 ± 6.34 m/s on the affected side of rhesus monkey. Osmium tetroxide staining demonstrated that the number of myelinated nerve fibers was 1,657 ± 652 in the branches of pronator teres of donor, and 2,661 ± 843 in the repaired ulnar nerve. The rate of multiple amplification of regenerating myelinated nerve fibers was 1.61. These data showed that when muscular branches of the pronator teres were used to repair ulnar nerve in primates, effective regeneration was observed in regenerating nerve fibers, and functions of the injured ulnar nerve were restored to a certain extent. Moreover, multiple amplification was subsequently detected in ulnar nerve axons.

Sleeve bridging of the rhesus monkey ulnar nerve with muscular branches of the pronator teres: multiple amplification of axonal regeneration.

Science.gov (United States)

Kou, Yu-Hui; Zhang, Pei-Xun; Wang, Yan-Hua; Chen, Bo; Han, Na; Xue, Feng; Zhang, Hong-Bo; Yin, Xiao-Feng; Jiang, Bao-Guo

2015-01-01

Multiple-bud regeneration, i.e., multiple amplification, has been shown to exist in peripheral nerve regeneration. Multiple buds grow towards the distal nerve stump during proximal nerve fiber regeneration. Our previous studies have verified the limit and validity of multiple amplification of peripheral nerve regeneration using small gap sleeve bridging of small donor nerves to repair large receptor nerves in rodents. The present study sought to observe multiple amplification of myelinated nerve fiber regeneration in the primate peripheral nerve. Rhesus monkey models of distal ulnar nerve defects were established and repaired using muscular branches of the right forearm pronator teres. Proximal muscular branches of the pronator teres were sutured into the distal ulnar nerve using the small gap sleeve bridging method. At 6 months after suture, two-finger flexion and mild wrist flexion were restored in the ulnar-sided injured limbs of rhesus monkey. Neurophysiological examination showed that motor nerve conduction velocity reached 22.63 ± 6.34 m/s on the affected side of rhesus monkey. Osmium tetroxide staining demonstrated that the number of myelinated nerve fibers was 1,657 ± 652 in the branches of pronator teres of donor, and 2,661 ± 843 in the repaired ulnar nerve. The rate of multiple amplification of regenerating myelinated nerve fibers was 1.61. These data showed that when muscular branches of the pronator teres were used to repair ulnar nerve in primates, effective regeneration was observed in regenerating nerve fibers, and functions of the injured ulnar nerve were restored to a certain extent. Moreover, multiple amplification was subsequently detected in ulnar nerve axons.

Acute nutritional axonal neuropathy.

Science.gov (United States)

Hamel, Johanna; Logigian, Eric L

2018-01-01

This study describes clinical, laboratory, and electrodiagnostic features of a severe acute axonal polyneuropathy common to patients with acute nutritional deficiency in the setting of alcoholism, bariatric surgery (BS), or anorexia. Retrospective analysis of clinical, electrodiagnostic, and laboratory data of patients with acute axonal neuropathy. Thirteen patients were identified with a severe, painful, sensory or sensorimotor axonal polyneuropathy that developed over 2-12 weeks with sensory ataxia, areflexia, variable muscle weakness, poor nutritional status, and weight loss, often with prolonged vomiting and normal cerebrospinal fluid protein. Vitamin B6 was low in half and thiamine was low in all patients when obtained before supplementation. Patients improved with weight gain and vitamin supplementation, with motor greater than sensory recovery. We suggest that acute or subacute axonal neuropathy in patients with weight loss or vomiting associated with alcohol abuse, BS, or dietary deficiency is one syndrome, caused by micronutrient deficiencies. Muscle Nerve 57: 33-39, 2018. © 2017 Wiley Periodicals, Inc.

Effect of anti-GM2 antibodies on rat sciatic nerve: electrophysiological and morphological study.

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Ortiz, Nicolau; Sabaté, M Mar; Garcia, Neus; Santafe, Manel M; Lanuza, M Angel; Tomàs, Marta; Tomàs, Josep

2009-03-31

We found that a monoclonal human IgM anti-GM2 was fixed in rat sciatic axons and Schwann cells and was able to activate human complement. The passive transfer of IgM and complement in sciatic nerves can induce an acute alteration in nerve conduction. When the transfer of IgM plus complement was repeated for 10 days, the compound action motor potential amplitude was very low and the morphological study showed axons and myelin damage. Without human complement, IgM can only slightly disorganize the myelin by separating some layers, probably by interfering with the functional role of gangliosides in the myelin package.

Patchy distributions of myelin and vesicular glutamate transporter 2 align with cytochrome oxidase blobs and interblobs in the superficial layers of the primary visual cortex

Directory of Open Access Journals (Sweden)

Rockoff EC

2014-09-01

Full Text Available Emily C Rockoff,1 Pooja Balaram,1 Jon H Kaas1,2 1Department of Psychology, 2Department of Cell and Molecular Biology, Vanderbilt University, Nashville, TN, USA Abstract: Blobs are a modular component of the primary visual cortex (area 17 of all primates, but not of other mammals closely related to primates. They are characterized as an even distribution of patches, puffs, or blobs of dense cytochrome oxidase (CO expression in layer III of area 17, and are now known to differ from surrounding, nonblob cortex in thalamic, intrinsic, and extrastriate connections. Previous studies have also recognized a blob-like pattern of myelin-dense patches in layer III of area 17 of primates, and more recently the vesicular glutamate transporter (VGLUT-2 isoform of the VGLUT family has been found to selectively distribute to layer III patches in a similar blob-like pattern. Here, we sought to determine if the blob-like patterns all identify the same modular structures in area 17 of primates by staining alternate brain sections cut parallel to the surface of area 17 of a prosimian primate (Otolemur garnettii for CO, myelin, and VGLUT2. By aligning the sections from the three preparations, we provide clear evidence that the three preparations all identify the same modular blob structures. The results provide a further understanding of the functional nature of the blobs by demonstrating that their higher level of CO activity is related to thalamic inputs from the lateral geniculate nucleus that use VGLUT2 as their main glutamate transporter, and via myelinated axons. Keywords: columns, modules, visual cortex, primates, prosimians

Motor axon excitability during Wallerian degeneration

DEFF Research Database (Denmark)

Moldovan, Mihai; Alvarez, Susana; Krarup, Christian

2008-01-01

Axonal loss and degeneration are major factors in determining long-term outcome in patients with peripheral nerve disorders or injury. Following loss of axonal continuity, the isolated nerve stump distal to the lesion undergoes Wallerian degeneration in several phases. In the initial 'latent' phase......, action potential propagation and structural integrity of the distal segment are maintained. The aim of this study was to investigate in vivo the changes in membrane function of motor axons during the 'latent' phase of Wallerian degeneration. Multiple indices of axonal excitability of the tibial nerve...

Rapid simultaneous high-resolution mapping of myelin water fraction and relaxation times in human brain using BMC-mcDESPOT.

Science.gov (United States)

Bouhrara, Mustapha; Spencer, Richard G

2017-02-15

A number of central nervous system (CNS) diseases exhibit changes in myelin content and magnetic resonance longitudinal, T 1 , and transverse, T 2 , relaxation times, which therefore represent important biomarkers of CNS pathology. Among the methods applied for measurement of myelin water fraction (MWF) and relaxation times, the multicomponent driven equilibrium single pulse observation of T 1 and T 2 (mcDESPOT) approach is of particular interest. mcDESPOT permits whole brain mapping of multicomponent T 1 and T 2 , with data acquisition accomplished within a clinically realistic acquisition time. Unfortunately, previous studies have indicated the limited performance of mcDESPOT in the setting of the modest signal-to-noise range of high-resolution mapping, required for the depiction of small structures and to reduce partial volume effects. Recently, we showed that a new Bayesian Monte Carlo (BMC) analysis substantially improved determination of MWF from mcDESPOT imaging data. However, our previous study was limited in that it did not discuss determination of relaxation times. Here, we extend the BMC analysis to the simultaneous determination of whole-brain MWF and relaxation times using the two-component mcDESPOT signal model. Simulation analyses and in-vivo human brain studies indicate the overall greater performance of this approach compared to the stochastic region contraction (SRC) algorithm, conventionally used to derive parameter estimates from mcDESPOT data. SRC estimates of the transverse relaxation time of the long T 2 fraction, T 2,l , and the longitudinal relaxation time of the short T 1 fraction, T 1,s , clustered towards the lower and upper parameter search space limits, respectively, indicating failure of the fitting procedure. We demonstrate that this effect is absent in the BMC analysis. Our results also showed improved parameter estimation for BMC as compared to SRC for high-resolution mapping. Overall we find that the combination of BMC analysis

Npn-1 contributes to axon-axon interactions that differentially control sensory and motor innervation of the limb.

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Rosa-Eva Huettl

2011-02-01

Full Text Available The initiation, execution, and completion of complex locomotor behaviors are depending on precisely integrated neural circuitries consisting of motor pathways that activate muscles in the extremities and sensory afferents that deliver feedback to motoneurons. These projections form in tight temporal and spatial vicinities during development, yet the molecular mechanisms and cues coordinating these processes are not well understood. Using cell-type specific ablation of the axon guidance receptor Neuropilin-1 (Npn-1 in spinal motoneurons or in sensory neurons in the dorsal root ganglia (DRG, we have explored the contribution of this signaling pathway to correct innervation of the limb. We show that Npn-1 controls the fasciculation of both projections and mediates inter-axonal communication. Removal of Npn-1 from sensory neurons results in defasciculation of sensory axons and, surprisingly, also of motor axons. In addition, the tight coupling between these two heterotypic axonal populations is lifted with sensory fibers now leading the spinal nerve projection. These findings are corroborated by partial genetic elimination of sensory neurons, which causes defasciculation of motor projections to the limb. Deletion of Npn-1 from motoneurons leads to severe defasciculation of motor axons in the distal limb and dorsal-ventral pathfinding errors, while outgrowth and fasciculation of sensory trajectories into the limb remain unaffected. Genetic elimination of motoneurons, however, revealed that sensory axons need only minimal scaffolding by motor axons to establish their projections in the distal limb. Thus, motor and sensory axons are mutually dependent on each other for the generation of their trajectories and interact in part through Npn-1-mediated fasciculation before and within the plexus region of the limbs.

Uniformity and Deviation of Intra-axonal Cross-sectional Area Coverage of the Gray-to-White Matter Interface

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Stefan Sommer

2017-12-01

Full Text Available Diffusion magnetic resonance imaging (dMRI is a compelling tool for investigating the structure and geometry of brain tissue based on indirect measurement of the diffusion anisotropy of water. Recent developments in global top-down tractogram optimizations enable the estimation of streamline weights, which characterize the connection between gray matter areas. In this work, the intra-axonal cross-sectional area coverage of the gray-to-white matter interface was examined by intersecting tractography streamlines with cortical regions of interest. The area coverage is the ratio of streamline weights divided by the surface area at the gray-to-white matter interface and assesses the estimated percentage which is covered by intra-axonal space. A high correlation (r = 0.935 between streamline weights and the cortical surface area was found across all regions of interest in all subjects. The variance across different cortical regions exhibits similarities to myelin maps. Additionally, we examined the effect of different diffusion gradient subsets at a lower, clinically feasible spatial resolution. Subsampling of the initial high-resolution diffusion dataset did not alter the tendency of the area coverage at the gray-to-white matter interface across cortical areas and subjects. However, single-shell acquisition schemes with lower b-values lead to a steady increase in area coverage in comparison to the full acquisition scheme at high resolution.

EFA6 regulates selective polarised transport and axon regeneration from the axon initial segment

Czech Academy of Sciences Publication Activity Database

Eva, R.; Koseki, H.; Kanamarlapudi, V.; Fawcett, James

2017-01-01

Roč. 130, č. 21 (2017), s. 3663-3675 ISSN 0021-9533 Institutional support: RVO:68378041 Keywords : axon regeneration * axon transport * neuronal polarisation Subject RIV: FH - Neurology OBOR OECD: Neuroscience s (including psychophysiology Impact factor: 4.431, year: 2016

Dynamics of mitochondrial transport in axons

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Robert Francis Niescier

2016-05-01

Full Text Available The polarized structure and long neurites of neurons pose a unique challenge for proper mitochondrial distribution. It is widely accepted that mitochondria move from the cell body to axon ends and vice versa; however, we have found that mitochondria originating from the axon ends moving in the retrograde direction never reach to the cell body, and only a limited number of mitochondria moving in the anterograde direction from the cell body arrive at the axon ends of mouse hippocampal neurons. Furthermore, we have derived a mathematical formula using the Fokker-Planck equation to characterize features of mitochondrial transport, and the equation could determine altered mitochondrial transport in axons overexpressing parkin. Our analysis will provide new insights into the dynamics of mitochondrial transport in axons of normal and unhealthy neurons.

Guanine nucleotides stimulate hydrolysis of phosphatidyl inositol bis phosphate in human myelin membranes

International Nuclear Information System (INIS)

Boulias, C.; Moscarello, M.A.

1989-01-01

Phosphodiesterase activity was stimulated in myelin membranes in the presence of guanine nucleotide analogues. This activity was reduced in myelin membranes which had been adenosine diphosphate ribosylated in the presence of cholera toxin which ADP-ribosylated three proteins of Mr 46,000, 43,000 and 18,500. Aluminum fluoride treatment of myelin had the same stimulatory effects on phosphodiesterase activity as did the guanine nucleotides

Axonal transmission in the retina introduces a small dispersion of relative timing in the ganglion cell population response.

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Günther Zeck

Full Text Available BACKGROUND: Visual stimuli elicit action potentials in tens of different retinal ganglion cells. Each ganglion cell type responds with a different latency to a given stimulus, thus transforming the high-dimensional input into a temporal neural code. The timing of the first spikes between different retinal projection neurons cells may further change along axonal transmission. The purpose of this study is to investigate if intraretinal conduction velocity leads to a synchronization or dispersion of the population signal leaving the eye. METHODOLOGY/PRINCIPAL FINDINGS: We 'imaged' the initiation and transmission of light-evoked action potentials along individual axons in the rabbit retina at micron-scale resolution using a high-density multi-transistor array. We measured unimodal conduction velocity distributions (1.3±0.3 m/sec, mean ± SD for axonal populations at all retinal eccentricities with the exception of the central part that contains myelinated axons. The velocity variance within each piece of retina is caused by ganglion cell types that show narrower and slightly different average velocity tuning. Ganglion cells of the same type respond with similar latency to spatially homogenous stimuli and conduct with similar velocity. For ganglion cells of different type intraretinal conduction velocity and response latency to flashed stimuli are negatively correlated, indicating that differences in first spike timing increase (up to 10 msec. Similarly, the analysis of pair-wise correlated activity in response to white-noise stimuli reveals that conduction velocity and response latency are negatively correlated. CONCLUSION/SIGNIFICANCE: Intraretinal conduction does not change the relative spike timing between ganglion cells of the same type but increases spike timing differences among ganglion cells of different type. The fastest retinal ganglion cells therefore act as indicators of new stimuli for postsynaptic neurons. The intraretinal dispersion

Loss of Local Astrocyte Support Disrupts Action Potential Propagation and Glutamate Release Synchrony from Unmyelinated Hippocampal Axon Terminals In Vitro.

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Sobieski, Courtney; Jiang, Xiaoping; Crawford, Devon C; Mennerick, Steven

2015-08-05

Neuron-astrocyte interactions are critical for proper CNS development and function. Astrocytes secrete factors that are pivotal for synaptic development and function, neuronal metabolism, and neuronal survival. Our understanding of this relationship, however, remains incomplete due to technical hurdles that have prevented the removal of astrocytes from neuronal circuits without changing other important conditions. Here we overcame this obstacle by growing solitary rat hippocampal neurons on microcultures that were comprised of either an astrocyte bed (+astrocyte) or a collagen bed (-astrocyte) within the same culture dish. -Astrocyte autaptic evoked EPSCs, but not IPSCs, displayed an altered temporal profile, which included increased synaptic delay, increased time to peak, and severe glutamate release asynchrony, distinct from previously described quantal asynchrony. Although we observed minimal alteration of the somatically recorded action potential waveform, action potential propagation was altered. We observed a longer latency between somatic initiation and arrival at distal locations, which likely explains asynchronous EPSC peaks, and we observed broadening of the axonal spike, which likely underlies changes to evoked EPSC onset. No apparent changes in axon structure were observed, suggesting altered axonal excitability. In conclusion, we propose that local astrocyte support has an unappreciated role in maintaining glutamate release synchrony by disturbing axonal signal propagation. Certain glial cell types (oligodendrocytes, Schwann cells) facilitate the propagation of neuronal electrical signals, but a role for astrocytes has not been identified despite many other functions of astrocytes in supporting and modulating neuronal signaling. Under identical global conditions, we cultured neurons with or without local astrocyte support. Without local astrocytes, glutamate transmission was desynchronized by an alteration of the waveform and arrival time of axonal

Electrical stimulation enhanced remyelination of injured sciatic nerves by increasing neurotrophins.

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Wan, L D; Xia, R; Ding, W L

2010-09-01

Previous studies have demonstrated that electrical stimulation (ES) enhances axonal regeneration following central and peripheral nerve injury. However, the effect of ES on peripheral remyelination after nerve damage has been investigated less, and the mechanism underlying its action remains unclear. In the present study, neuron/Schwann cell (SC) co-cultures in vitro and crush-injured sciatic nerves in rats were subjected to 1 h of continuous ES (20 Hz, 100 micros, 3 V). Electron microscopy and nerve morphometry were performed to investigate the extent of regenerated nerve myelination. The expression profiles of P0, Par-3 and brain-derived neurotrophic factor (BDNF) in vitro and in vivo were examined by western blotting. We reported that 20 Hz ES increased the number of regenerated and myelinated axons at 4 and 8 weeks after injury. P0 level in the ES-treated groups, as well as myelin sheath thickness, were enhanced compared with the controls. The earlier peak Par-3 in the ES-treated groups indicated earlier initiation of SC myelination. Moreover, the similar results were achieved in the cell co-culture. Additionally, brief ES significantly elevated BDNF expression in co-cultured cells and nerve tissues. In conclusion, ES of the site of nerve injury potentiates axonal regrowth and myelin maturation during peripheral nerve regeneration. Further, the therapeutic actions of ES on myelination that is mediated via enhanced BDNF signals, which driving the promyelination effect on SCs at the onset of myelination. Copyright (c) 2010 IBRO. Published by Elsevier Ltd. All rights reserved.

Myelination Is Associated with Processing Speed in Early Childhood: Preliminary Insights.

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Nicolas Chevalier

Full Text Available Processing speed is an important contributor to working memory performance and fluid intelligence in young children. Myelinated white matter plays a central role in brain messaging, and likely mediates processing speed, but little is known about the relationship between myelination and processing speed in young children. In the present study, processing speed was measured through inspection times, and myelin volume fraction (VFM was quantified using a multicomponent magnetic resonance imaging (MRI approach in 2- to 5-years of age. Both inspection times and VFM were found to increase with age. Greater VFM in the right and left occipital lobes, the body of the corpus callosum, and the right cerebellum was significantly associated with shorter inspection times, after controlling for age. A hierarchical regression showed that VFM in the left occipital lobe predicted inspection times over and beyond the effects of age and the VFM in the other brain regions. These findings are consistent with the hypothesis that myelin supports processing speed in early childhood.

Single myelin fiber imaging in living rodents without labeling by deep optical coherence microscopy

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Ben Arous, Juliette; Binding, Jonas; Léger, Jean-François; Casado, Mariano; Topilko, Piotr; Gigan, Sylvain; Claude Boccara, A.; Bourdieu, Laurent

2011-11-01

Myelin sheath disruption is responsible for multiple neuropathies in the central and peripheral nervous system. Myelin imaging has thus become an important diagnosis tool. However, in vivo imaging has been limited to either low-resolution techniques unable to resolve individual fibers or to low-penetration imaging of single fibers, which cannot provide quantitative information about large volumes of tissue, as required for diagnostic purposes. Here, we perform myelin imaging without labeling and at micron-scale resolution with >300-μm penetration depth on living rodents. This was achieved with a prototype [termed deep optical coherence microscopy (deep-OCM)] of a high-numerical aperture infrared full-field optical coherence microscope, which includes aberration correction for the compensation of refractive index mismatch and high-frame-rate interferometric measurements. We were able to measure the density of individual myelinated fibers in the rat cortex over a large volume of gray matter. In the peripheral nervous system, deep-OCM allows, after minor surgery, in situ imaging of single myelinated fibers over a large fraction of the sciatic nerve. This allows quantitative comparison of normal and Krox20 mutant mice, in which myelination in the peripheral nervous system is impaired. This opens promising perspectives for myelin chronic imaging in demyelinating diseases and for minimally invasive medical diagnosis.

Single myelin fiber imaging in living rodents without labeling by deep optical coherence microscopy.

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Ben Arous, Juliette; Binding, Jonas; Léger, Jean-François; Casado, Mariano; Topilko, Piotr; Gigan, Sylvain; Boccara, A Claude; Bourdieu, Laurent

2011-11-01

Myelin sheath disruption is responsible for multiple neuropathies in the central and peripheral nervous system. Myelin imaging has thus become an important diagnosis tool. However, in vivo imaging has been limited to either low-resolution techniques unable to resolve individual fibers or to low-penetration imaging of single fibers, which cannot provide quantitative information about large volumes of tissue, as required for diagnostic purposes. Here, we perform myelin imaging without labeling and at micron-scale resolution with >300-μm penetration depth on living rodents. This was achieved with a prototype [termed deep optical coherence microscopy (deep-OCM)] of a high-numerical aperture infrared full-field optical coherence microscope, which includes aberration correction for the compensation of refractive index mismatch and high-frame-rate interferometric measurements. We were able to measure the density of individual myelinated fibers in the rat cortex over a large volume of gray matter. In the peripheral nervous system, deep-OCM allows, after minor surgery, in situ imaging of single myelinated fibers over a large fraction of the sciatic nerve. This allows quantitative comparison of normal and Krox20 mutant mice, in which myelination in the peripheral nervous system is impaired. This opens promising perspectives for myelin chronic imaging in demyelinating diseases and for minimally invasive medical diagnosis.

A Laminin-2, Dystroglycan, Utrophin Axis is Required for Compartmentalization and Elongation of Myelin Segments

OpenAIRE

Court, Felipe A.; Hewitt, Jane E.; Davies, Kay; Patton, Bruce L.; Uncini, Antonino; Wrabetz, Lawrence; Feltri, M. Laura

2009-01-01

Animal and plant cells compartmentalize to perform morphogenetic functions. Compartmentalization of myelin-forming Schwann cells may favor elongation of myelin segments to the size required for efficient conduction of nerve impulses. Compartments in myelinated fibers were described by Ramon-y-Cajal and depend on periaxin, mutated in the hereditary neuropathy Charcot-Marie-Tooth 4F. Lack of periaxin in mice causes loss of compartments, formation of short myelin segments (internodes) and reduce...

Exploitation of detergent thermodynamics in the direct solubilization of myelin membrane proteins for two-dimensional gel electrophoresis for proteomic analysis.

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Nair, Sreepriya; Xavier, Tessy; Kumar, Madathiparambil Kumaran Satheesh; Saha, Sharmistha; Menon, Krishnakumar N

2011-12-01

Performing 2-DE of lipid-rich multilamellar membranes like myelin is a cumbersome task. However, for understanding its molecular organization and changes during diseases, identification of proteins of myelin is essential. Although the 2-D-proteomic approach of myelin has been employed to understand the myelin proteome, representation of myelin proteins in its entirety is still a challenge. 2-DE profiling of myelin proteins is very important for the detection of immuno-reactivity to myelin proteins from various biological fluids following Western blotting in diseases like multiple sclerosis. Here we developed a novel approach by exploiting the thermodynamic principles behind detergent-mediated solubilization of myelin membranes without any conventional processing of myelin involving precipitation of myelin proteins. We show that the addition of myelin to ASB-14-4 resulted in significant increase in protein representation of myelin in 2-DE compared with the addition of ASB-14-4 to myelin. Moreover, the number and resolution of spots are significantly higher in myelin to ASB-14-4 strategy than other strategies of myelin sample processing such as ASB-14-4 to myelin or ethanol or acetone or methanol-ammonium acetate precipitation of myelin proteins. In addition, the step involves no precipitation that selective removal of any proteins as a result of precipitation is nil and a qualitative representation of myelin proteins in a 2-D gel is achieved. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Formation of longitudinal axon pathways in Caenorhabditis elegans.

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Hutter, Harald

2017-11-18

The small number of neurons and the simple architecture of the Caenorhabditis elegans (C. elegans) nervous system enables researchers to study axonal pathfinding at the level of individually identified axons. Axons in C. elegans extend predominantly along one of the two major body axes, the anterior-posterior axis and the dorso-ventral axis. This review will focus on axon navigation along the anterior-posterior axis, leading to the establishment of the longitudinal axon tracts, with a focus on the largest longitudinal axon tract, the ventral nerve cord (VNC). In the VNC, axons grow out in a stereotypic order, with early outgrowing axons (pioneers) playing an important role in guiding later outgrowing (follower) axons. Genetic screens have identified a number of genes specifically affecting the formation of longitudinal axon tracts. These genes include secreted proteins, putative receptors and adhesion molecules, as well as intracellular proteins regulating the cell's response to guidance cues. In contrast to dorso-ventral navigation, no major general guidance cues required for the establishment of longitudinal pathways have been identified so far. The limited penetrance of defects found in many mutants affecting longitudinal navigation suggests that guidance cues act redundantly in this process. The majority of the axon guidance genes identified in C. elegans are evolutionary conserved, i.e. have homologs in other animals, including vertebrates. For a number of these genes, a role in axon guidance has not been described outside C. elegans. Taken together, studies in C. elegans contribute to a fundamental understanding of the molecular basis of axonal navigation that can be extended to other animals, including vertebrates and probably humans as well. Copyright © 2017. Published by Elsevier Ltd.

Use of self-complementary adeno-associated virus serotype 2 as a tracer for labeling axons: implications for axon regeneration.

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Yingpeng Liu

Full Text Available Various types of tracers are available for use in axon regeneration, but they require an extra operational tracer injection, time-consuming immunohistochemical analysis and cause non-specific labeling. Considerable efforts over the past years have explored other methodologies, especially the use of viral vectors, to investigate axon regeneration after injury. Recent studies have demonstrated that self-complementary Adeno-Associated Virus (scAAV induced a high transduction efficiency and faster expression of transgenes. Here, we describe for the first time the use of scAAV2-GFP to label long-projection axons in the corticospinal tract (CST, rubrospinal tract (RST and the central axons of dorsal root ganglion (DRG in the normal and lesioned animal models. We found that scAAV2-GFP could efficiently transduce neurons in the sensorimotor cortex, red nucleus and DRG. Strong GFP expression could be transported anterogradely along the axon to label the numerous axon fibers from CST, RST and central axons of DRG separately. Comparison of the scAAV2 vector with single-stranded (ss AAV2 vector in co-labeled sections showed that the scAAV2 vector induced a faster and stronger transgene expression than the ssAAV2 vector in DRG neurons and their axons. In both spinal cord lesion and dorsal root crush injury models, scAAV-GFP could efficiently label the lesioned and regenerated axons around the lesion cavity and the dorsal root entry zone (DREZ respectively. Further, scAAV2-GFP vector could be combined with traditional tracer to specifically label sensory and motor axons after spinal cord lesion. Thus, we show that using scAAV2-GFP as a tracer is a more effective and efficient way to study axon regeneration following injury.

Axon-glial disruption: the link between vascular disease and Alzheimer's disease?

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Horsburgh, Karen; Reimer, Michell M; Holland, Philip; Chen, Guiquan; Scullion, Gillian; Fowler, Jill H

2011-08-01

Vascular risk factors play a critical role in the development of cognitive decline and AD (Alzheimer's disease), during aging, and often result in chronic cerebral hypoperfusion. The neurobiological link between hypoperfusion and cognitive decline is not yet defined, but is proposed to involve damage to the brain's white matter. In a newly developed mouse model, hypoperfusion, in isolation, produces a slowly developing and diffuse damage to myelinated axons, which is widespread in the brain, and is associated with a selective impairment in working memory. Cerebral hypoperfusion, an early event in AD, has also been shown to be associated with white matter damage and notably an accumulation of amyloid. The present review highlights some of the published data linking white matter disruption to aging and AD as a result of vascular dysfunction. A model is proposed by which chronic cerebral hypoperfusion, as a result of vascular factors, results in both the generation and accumulation of amyloid and injury to white matter integrity, resulting in cognitive impairment. The generation of amyloid and accumulation in the vasculature may act to perpetuate further vascular dysfunction and accelerate white matter pathology, and as a consequence grey matter pathology and cognitive decline.

Application of empowerment theory for CNS practice.

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Carlson-Catalano, J M

1993-11-01

Power is necessary for the clinical nurse specialist (CNS) to successfully conduct objectives of practice in bureaucratic hospital settings. To obtain power, the CNS could use strategies of an empowerment theory to fully operationalize roles in hospitals. This article will discuss how the CNS may be empowered utilizing strategies in four empowering categories. In addition, the many benefits of empowering the CNS are reviewed.

Disruption of spinal cord white matter and sciatic nerve geometry inhibits axonal growth in vitro in the absence of glial scarring

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Crutcher Keith A

2001-05-01

Full Text Available Abstract Background Axons within the mature mammalian central nervous system fail to regenerate following injury, usually resulting in long-lasting motor and sensory deficits. Studies involving transplantation of adult neurons into white matter implicate glial scar-associated factors in regeneration failure. However, these studies cannot distinguish between the effects of these factors and disruption of the spatial organization of cells and molecular factors (disrupted geometry. Since white matter can support or inhibit neurite growth depending on the geometry of the fiber tract, the present study sought to determine whether disrupted geometry is sufficient to inhibit neurite growth. Results Embryonic chick sympathetic neurons were cultured on unfixed longitudinal cryostat sections of mature rat spinal cord or sciatic nerve that had been crushed with forceps ex vivo then immediately frozen to prevent glial scarring. Neurite growth on uncrushed portions of spinal cord white matter or sciatic nerve was extensive and highly parallel with the longitudinal axis of the fiber tract but did not extend onto crushed portions. Moreover, neurite growth from neurons attached directly to crushed white matter or nerve tissue was shorter and less parallel compared with neurite growth on uncrushed tissue. In contrast, neurite growth appeared to be unaffected by crushed spinal cord gray matter. Conclusions These observations suggest that glial scar-associated factors are not necessary to block axonal growth at sites of injury. Disruption of fiber tract geometry, perhaps involving myelin-associated neurite-growth inhibitors, may be sufficient to pose a barrier to regenerating axons in spinal cord white matter and peripheral nerves.

Myelin Basic Protein synthesis is regulated by small non-coding RNA 715

NARCIS (Netherlands)

Bauer, N.M.; Moos, C.; van Horssen, J.; Witte, M.E.; van der Valk, P.; Altenhein, B.; Luhmann, H.J.; White, R.

2012-01-01

Oligodendroglial Myelin Basic Protein (MBP) synthesis is essential for myelin formation in the central nervous system. During oligodendrocyte differentiation, MBP mRNA is kept in a translationally silenced state while intracellularly transported, until neuron-derived signals initiate localized MBP

Hypothyroidism coordinately and transiently affects myelin protein gene expression in most rat brain regions during postnatal development.

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Ibarrola, N; Rodríguez-Peña, A

1997-03-28

To assess the role of thyroid hormone on myelin gene expression, we have studied the effect of hypothyroidism on the mRNA steady state levels for the major myelin protein genes: myelin basic protein (MBP), proteolipid protein (PLP), myelin-associated glycoprotein (MAG) and 2':3'-cyclic nucleotide 3'-phosphodiesterase (CNP) in different rat brain regions, during the first postnatal month. We found that hypothyroidism reduces the levels of every myelin protein transcript, with striking differences between the different brain regions. Thus, in the more caudal regions, the effect of hypothyroidism was extremely modest, being only evident at the earlier stages of myelination. In contrast, in the striatum and the cerebral cortex the important decrease in the myelin protein transcripts is maintained beyond the first postnatal month. Therefore, thyroid hormone modulates in a synchronous fashion the expression of the myelin genes and the length of its effect depends on the brain region. On the other hand, hyperthyroidism leads to an increase of the major myelin protein transcripts above control values. Finally, lack of thyroid hormone does not change the expression of the oligodendrocyte progenitor-specific gene, the platelet derived growth factor receptor alpha.

Watery and dark axons in Wallerian degeneration of the opossum's optic nerve: different patterns of cytoskeletal breakdown?

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MARCELO S. NARCISO

2001-06-01

Full Text Available In this paper we report a qualitative morphological analysis of Wallerian degeneration in a marsupial. Right optic nerves of opossums Didelphis marsupialis were crushed with a fine forceps and after 24, 48, 72, 96 and 168 hours the animals were anaesthetized and perfused with fixative. The optic nerves were immersed in fixative and processed for routine transmission electron microscopy. Among the early alterations typical of axonal degeneration, we observed nerve fibers with focal degeneration of the axoplasmic cytoskeleton, watery degeneration and dark degeneration, the latter being prevalent at 168 hours after crush. Our results point to a gradual disintegration of the axoplasmic cytoskeleton, opposed to the previous view of an "all-or-nothing'' process (Griffin et al 1995. We also report that, due to an unknown mechanism, fibers show either a dark or watery pattern of axonal degeneration, as observed in axon profiles. We also observed fibers undergoing early myelin breakdown in the absence of axonal alterations.Neste trabalho, relatamos uma análise morfológica qualitativa da degeneração Walleriana em um marsupial. Os nervos ópticos direito de gambás da espécie Didelphis marsupialis foram esmagados com uma pinça fina. Após 24, 48, 72, 96 e 168 horas, os animais foram anestesiados e perfundidos com fixador. A seguir, os nervos foram imersos em fixador e processados para microscopia eletrônica de rotina. Entre as alterações precoces típicas da degeneração, observamos fibras nervosas com degeneração focal do citoesqueleto axoplasmático, degeneração aquosa e degeneração escura, com o último tipo prevalente às 168 horas após esmagamento. Nossos resultados indicam uma desintegração gradual do citoesqueleto axoplasmático, oposta à prévia visão de um processo "tudo-ou-nada''. Relatamos também que, devido a um mecanismo desconhecido, as fibras mostram ou um padrão aquoso ou um padrão escuro de degeneração axonal

Central Nervous System (CNS Disease Triggering Takotsubo Syndrome

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Josef Finsterer

2016-01-01

Full Text Available Takotsubo syndrome (TTS is usually triggered by psychological or physical stress. One of the many physical sources of stress are central nervous system (CNS disorders. CNS disorders most frequently triggering TTS include subarachnoid bleeding, epilepsy, ischemic stroke, migraine, and intracerebral bleeding. More rare CNS-triggers of TTS include posterior reversible encephalopathy syndrome (PRES, amyotrophic lateral sclerosis, encephalitis, or traumatic brain or spinal cord injury. TTS triggered by any of the CNS disorders needs to be recognized since adequate treatment of TTS may improve the general outcome from the CNS disorder as well. Neurologists need to be aware of TTS as a complication of specific CNS disorders but TTS may be triggered also by CNS disorders so far not recognised as causes of TTS.

Cargo distributions differentiate pathological axonal transport impairments.

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Mitchell, Cassie S; Lee, Robert H

2012-05-07

Axonal transport is an essential process in neurons, analogous to shipping goods, by which energetic and cellular building supplies are carried downstream (anterogradely) and wastes are carried upstream (retrogradely) by molecular motors, which act as cargo porters. Impairments in axonal transport have been linked to devastating and often lethal neurodegenerative diseases, such as Amyotrophic Lateral Sclerosis, Huntington's, and Alzheimer's. Axonal transport impairment types include a decrease in available motors for cargo transport (motor depletion), the presence of defective or non-functional motors (motor dilution), and the presence of increased or larger cargos (protein aggregation). An impediment to potential treatment identification has been the inability to determine what type(s) of axonal transport impairment candidates that could be present in a given disease. In this study, we utilize a computational model and common axonal transport experimental metrics to reveal the axonal transport impairment general characteristics or "signatures" that result from three general defect types of motor depletion, motor dilution, and protein aggregation. Our results not only provide a means to discern these general impairments types, they also reveal key dynamic and emergent features of axonal transport, which potentially underlie multiple impairment types. The identified characteristics, as well as the analytical method, can be used to help elucidate the axonal transport impairments observed in experimental and clinical data. For example, using the model-predicted defect signatures, we identify the defect candidates, which are most likely to be responsible for the axonal transport impairments in the G93A SOD1 mouse model of ALS. Copyright © 2012 Elsevier Ltd. All rights reserved.

Acrolein-mediated conduction loss is partially restored by K+ channel blockers

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Yan, Rui; Page, Jessica C.

2015-01-01

Acrolein-mediated myelin damage is thought to be a critical mechanism leading to conduction failure following neurotrauma and neurodegenerative diseases. The exposure and activation of juxtaparanodal voltage-gated K+ channels due to myelin damage leads to conduction block, and K+ channel blockers have long been studied as a means for restoring axonal conduction in spinal cord injury (SCI) and multiple sclerosis (MS). In this study, we have found that 100 μM K+ channel blockers 4-aminopyridine-3-methanol (4-AP-3-MeOH), and to a lesser degree 4-aminopyridine (4-AP), can significantly restore compound action potential (CAP) conduction in spinal cord tissue following acrolein-mediated myelin damage using a well-established ex vivo SCI model. In addition, 4-AP-3-MeOH can effectively restore CAP conduction in acrolein-damaged axons with a range of concentrations from 0.1 to 100 μM. We have also shown that while both compounds at 100 μM showed no preference of small- and large-caliber axons when restoring CAP conduction, 4-AP-3-MeOH, unlike 4-AP, is able to augment CAP amplitude while causing little change in axonal responsiveness measured in refractory periods and response to repetitive stimuli. In a prior study, we show that 4-AP-3-MeOH was able to functionally rescue mechanically injured axons. In this investigation, we conclude that 4-AP-3-MeOH is an effective K+ channel blocker in restoring axonal conduction following both primary (physical) and secondary (chemical) insults. These findings also suggest that 4-AP-3-MeOH is a viable alternative of 4-AP for treating myelin damage and improving function following central nervous system trauma and neurodegenerative diseases. PMID:26581866

Axon initial segment Kv1 channels control axonal action potential waveform and synaptic efficacy

NARCIS (Netherlands)

Kole, Maarten H. P.; Letzkus, Johannes J.; Stuart, Greg J.

2007-01-01

Action potentials are binary signals that transmit information via their rate and temporal pattern. In this context, the axon is thought of as a transmission line, devoid of a role in neuronal computation. Here, we show a highly localized role of axonal Kv1 potassium channels in shaping the action

Elucidation of axonal transport by radioautography

International Nuclear Information System (INIS)

Droz, Bernard.

1979-01-01

Radioautography permits to distinguish various pathways within the axons: the axoplasm which includes soluble enzymes and constituents of the cytoskeleton moving with slow axoplasmic flow; the mitochondria which are conveyed as organelles; the smooth endoplasmic reticulum which ensures the fast axonal transport of membrane constituents delivered to axolemma, synaptic vesicles, presynaptic membranes or mitochondria. Furthermore radioautography makes it possible to visualize intercellular exchanges of molecules between axon and glia

The formation of lipid droplets favors intracellular Mycobacterium leprae survival in SW-10, non-myelinating Schwann cells.

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Jin, Song-Hyo; An, Sung-Kwan; Lee, Seong-Beom

2017-06-01

Leprosy is a chronic infectious disease that is caused by the obligate intracellular pathogen Mycobacterium leprae (M.leprae), which is the leading cause of all non-traumatic peripheral neuropathies worldwide. Although both myelinating and non-myelinating Schwann cells are infected by M.leprae in patients with lepromatous leprosy, M.leprae preferentially invades the non-myelinating Schwann cells. However, the effect of M.leprae infection on non-myelinating Schwann cells has not been elucidated. Lipid droplets (LDs) are found in M.leprae-infected Schwann cells in the nerve biopsies of lepromatous leprosy patients. M.leprae-induced LD formation favors intracellular M.leprae survival in primary Schwann cells and in a myelinating Schwann cell line referred to as ST88-14. In the current study, we initially characterized SW-10 cells and investigated the effects of LDs on M.leprae-infected SW-10 cells, which are non-myelinating Schwann cells. SW-10 cells express S100, a marker for cells from the neural crest, and NGFR p75, a marker for immature or non-myelinating Schwann cells. SW-10 cells, however, do not express myelin basic protein (MBP), a marker for myelinating Schwann cells, and myelin protein zero (MPZ), a marker for precursor, immature, or myelinating Schwann cells, all of which suggests that SW-10 cells are non-myelinating Schwann cells. In addition, SW-10 cells have phagocytic activity and can be infected with M. leprae. Infection with M. leprae induces the formation of LDs. Furthermore, inhibiting the formation of M. leprae-induced LD enhances the maturation of phagosomes containing live M.leprae and decreases the ATP content in the M. leprae found in SW-10 cells. These facts suggest that LD formation by M. leprae favors intracellular M. leprae survival in SW-10 cells, which leads to the logical conclusion that M.leprae-infected SW-10 cells can be a new model for investigating the interaction of M.leprae with non-myelinating Schwann cells.

The axonal cytoskeleton : from organization to function

NARCIS (Netherlands)

Kevenaar, Josta T; Hoogenraad, Casper C

The axon is the single long fiber that extends from the neuron and transmits electrical signals away from the cell body. The neuronal cytoskeleton, composed of microtubules (MTs), actin filaments and neurofilaments, is not only required for axon formation and axonal transport but also provides the

Quantification of myelin in children using multiparametric quantitative MRI: a pilot study

International Nuclear Information System (INIS)

Kim, Hyun Gi; Choi, Jin Wook; Moon, Won-Jin; Han, JinJoo

2017-01-01

The purpose of this study was to evaluate the usefulness of multiparametric quantitative MRI for myelination quantification in children. We examined 22 children (age 0-14 years) with multiparametric quantitative MRI. The total volume of myelin partial volume (Msum), the percentage of Msum within the whole brain parenchyma (Mbpv), and the percentage of Msum within the intracranial volume (Micv) were obtained. Four developmental models of myelin maturation (the logarithmic, logistic, Gompertz, and modified Gompertz models) were examined to find the most representative model of the three parameters. We acquired myelin partial volume values in different brain regions and assessed the goodness of fit for the models. The ranges of Msum, Mbpv, and Micv were 0.8-160.9 ml, 0.2-13%, and 0.0-11.6%, respectively. The Gompertz model was the best fit for the three parameters. For developmental model analysis of myelin partial volume in each brain region, the Gompertz model was the best-fit model for pons (R"2 = 74.6%), middle cerebeller peduncle (R"2 = 76.4%), putamen (R"2 = 95.8%), and centrum semiovale (R"2 = 77.7%). The logistic model was the best-fit model for the genu and splenium of the corpus callosum (R"2 = 79.7-93.6%), thalamus (R"2 = 81.7%), and frontal, parietal, temporal, and occipital white matter (R"2 = 92.5-96.5%). Multiparametric quantitative MRI depicts the normal developmental pattern of myelination in children. It is a potential tool for research studies on pediatric brain development evaluation. (orig.)

Quantification of myelin in children using multiparametric quantitative MRI: a pilot study

Energy Technology Data Exchange (ETDEWEB)

Kim, Hyun Gi; Choi, Jin Wook [Ajou University School of Medicine, Ajou University Medical Center, Department of Radiology, Suwon (Korea, Republic of); Moon, Won-Jin [Konkuk University Hospital, Konkuk University School of Medicine, Department of Radiology, Seoul (Korea, Republic of); Han, JinJoo [Ajou University School of Medicine, Office of Biostatistics, Department of Humanities and Social Medicine, Suwon (Korea, Republic of)

2017-10-15

The purpose of this study was to evaluate the usefulness of multiparametric quantitative MRI for myelination quantification in children. We examined 22 children (age 0-14 years) with multiparametric quantitative MRI. The total volume of myelin partial volume (Msum), the percentage of Msum within the whole brain parenchyma (Mbpv), and the percentage of Msum within the intracranial volume (Micv) were obtained. Four developmental models of myelin maturation (the logarithmic, logistic, Gompertz, and modified Gompertz models) were examined to find the most representative model of the three parameters. We acquired myelin partial volume values in different brain regions and assessed the goodness of fit for the models. The ranges of Msum, Mbpv, and Micv were 0.8-160.9 ml, 0.2-13%, and 0.0-11.6%, respectively. The Gompertz model was the best fit for the three parameters. For developmental model analysis of myelin partial volume in each brain region, the Gompertz model was the best-fit model for pons (R{sup 2} = 74.6%), middle cerebeller peduncle (R{sup 2} = 76.4%), putamen (R{sup 2} = 95.8%), and centrum semiovale (R{sup 2} = 77.7%). The logistic model was the best-fit model for the genu and splenium of the corpus callosum (R{sup 2} = 79.7-93.6%), thalamus (R{sup 2} = 81.7%), and frontal, parietal, temporal, and occipital white matter (R{sup 2} = 92.5-96.5%). Multiparametric quantitative MRI depicts the normal developmental pattern of myelination in children. It is a potential tool for research studies on pediatric brain development evaluation. (orig.)

Action potential propagation: ion current or intramembrane electric field?

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Martí, Albert; Pérez, Juan J; Madrenas, Jordi

2018-01-01

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.

The MR evaluation of normal children and disorders of neuronal migration and myelination

International Nuclear Information System (INIS)

Miyamachi, Keikichi; Miyasaka, Kazuo; Abe, Hiroshi

1990-01-01

Magnetic resonance imaging (MRI) scans were available for review in 10 healthy children (aged one month-4 years) and 5 pediatric patients with disorders of neuronal migration and myelination during the developing process (aged 2-10 years). Such disorders in the 5 patients were megalencephaly, pachygyria, heterotopia, delayed myelination, and dysmyelinating disease. In the heathy group, myelination was matured during the first two years on MRI. This was depicted earlier on T1-weighted images than T2-weighted images (7 months vs one year and 9 months after birth). Abnormality in myelination was clearly visualized on T2-weighted images. Furthermore, MRI had the ability to detect morphologically the associated brain malformations. Thus, MRI may be a promising diagnostic procedure of choice in pediatric brain abnormality. (N.K.)

The axon-protective WLD(S) protein partially rescues mitochondrial respiration and glycolysis after axonal injury.

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Godzik, Katharina; Coleman, Michael P

2015-04-01

The axon-protective Wallerian degeneration slow (WLD(S)) protein can ameliorate the decline in axonal ATP levels after neurite transection. Here, we tested the hypothesis that this effect is associated with maintenance of mitochondrial respiration and/or glycolysis. We used isolated neurites of superior cervical ganglion (SCG) cultures in the Seahorse XF-24 Metabolic Flux Analyser to determine mitochondrial respiration and glycolysis under different conditions. We observed that both mitochondrial respiration and glycolysis declined significantly during the latent phase of Wallerian degeneration. WLD(S) partially reduced the decline both in glycolysis and in mitochondrial respiration. In addition, we found that depleting NAD levels in uncut cultures led to changes in mitochondrial respiration and glycolysis similar to those rescued by WLD(S) after cut, suggesting that the maintenance of NAD levels in Wld(S) neurites after axonal injury at least partially underlies the maintenance of ATP levels. However, by using another axon-protective mutation (Sarm1(-/-)), we could demonstrate that rescue of basal ECAR (and hence probably glycolysis) rather than basal OCR (mitochondrial respiration) may be part of the protective phenotype to delay Wallerian degeneration. These findings open new routes to study glycolysis and the connection between NAD and ATP levels in axon degeneration, which may help to eventually develop therapeutic strategies to treat neurodegenerative diseases.

MR imaging of the various stages of normal myelination during the first year of life

International Nuclear Information System (INIS)

Knaap, M.S. van der; Valk, J.

1990-01-01

The normal process of myelination of the brain mainly occurs during the first year of life. This process as known from histology can be visualized by MRI. Because of the very long T1 and T2 of immature brain tissue it is necessary to use adjusted pulse sequences with a long TR in order to obtain sufficient tissue contrast. With long TR SE images five stages can be recognized in the process of normal myelination and brain maturation. During the first month of life long TR short TE SE images show what are believed to be myelinated structures by correlation with published histological studies with a high signal intensity, unmyelinated white matter with a low signal intensity and gray matter with an intermediate signal intensity. The signal intensity of unmyelinated and myelinated white matter is reversed on long TR long TE SE images. In the course of a few weeks the signal intensity of unmyelinated white matter becomes high and the signal intensity of myelinated white matter becomes low also on long TR short TE SE images. These changes are believed to be caused by a loss of water and a change in chemical composition of brain tissue just prior to the onset of a wave of myelination. With progression of myelination the signal intensity of white matter changes from high to intermediate to low. These changes result in stages of isointensity, first in the central parts of the brain, later in the lobar parts. At the end of the first year the adult contrast pattern is reached in all parts of the brain. IR images are also able to depict the progress of myelination, but appear to be less sensitive to subtle changes in the degree of myelination. The precise normal values for the five stages depend on the magnetic field strength and the pulse sequences used. (orig.)

A single dose of a neuron-binding human monoclonal antibody improves brainstem NAA concentrations, a biomarker for density of spinal cord axons, in a model of progressive multiple sclerosis.

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Wootla, Bharath; Denic, Aleksandar; Watzlawik, Jens O; Warrington, Arthur E; Rodriguez, Moses

2015-04-29

Intracerebral infection of susceptible mouse strains with Theiler's murine encephalomyelitis virus (TMEV) results in chronic demyelinating disease with progressive axonal loss and neurologic dysfunction similar to progressive forms of multiple sclerosis (MS). We previously showed that as the disease progresses, a marked decrease in brainstem N-acetyl aspartate (NAA; metabolite associated with neuronal integrity) concentrations, reflecting axon health, is measured. We also demonstrated stimulation of neurite outgrowth by a neuron-binding natural human antibody, IgM12. Treatment with either the serum-derived or recombinant human immunoglobulin M 12 (HIgM12) preserved functional motor activity in the TMEV model. In this study, we examined IgM-mediated changes in brainstem NAA concentrations and central nervous system (CNS) pathology. (1)H-magnetic resonance spectroscopy (MRS) showed that treatment with HIgM12 significantly increased brainstem NAA concentrations compared to controls in TMEV-infected mice. Pathologic analysis demonstrated a significant preservation of axons in the spinal cord of animals treated with HIgM12. This study links drug efficacy of slowing deficits with axon preservation and NAA concentrations in the brainstem in a model of progressive MS. HIgM12-mediated changes of NAA concentrations in the brainstem are a surrogate marker of axon injury/preservation throughout the spinal cord. This study provides proof-of-concept that a neuron-reactive human IgM can be therapeutic and provides a biomarker for clinical trials.

An Experimental Infarct Targeting the Internal Capsule: Histopathological and Ultrastructural Changes

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Chang-Woo Han

2017-05-01

Full Text Available Background Stroke involving the cerebral white matter (WM has increased in prevalence, but most experimental studies have focused on ischemic injury of the gray matter. This study was performed to investigate the WM in a unique rat model of photothrombotic infarct targeting the posterior limb of internal capsule (PLIC, focusing on the identification of the most vulnerable structure in WM by ischemic injury, subsequent glial reaction to the injury, and the fundamental histopathologic feature causing different neurologic outcomes. Methods Light microscopy with immunohistochemical stains and electron microscopic examinations of the lesion were performed between 3 hours and 21 days post-ischemic injury. Results Initial pathological change develops in myelinated axon, concomitantly with reactive change of astrocytes. The first pathology to present is nodular loosening to separate the myelin sheath with axonal wrinkling. Subsequent pathologies include rupture of the myelin sheath with extrusion of axonal organelles, progressive necrosis, oligodendrocyte degeneration and death, and reactive gliosis. Increase of glial fibrillary acidic protein (GFAP immunoreactivity is an early event in the ischemic lesion. WM pathologies result in motor dysfunction. Motor function recovery after the infarct was correlated to the extent of PLIC injury proper rather than the infarct volume. Conclusions Pathologic changes indicate that the cerebral WM, independent of cortical neurons, is highly vulnerable to the effects of focal ischemia, among which myelin sheath is first damaged. Early increase of GFAP immunoreactivity indicates that astrocyte response initially begins with myelinated axonal injury, and supports the biologic role related to WM injury or plasticity. The reaction of astrocytes in the experimental model might be important for the study of pathogenesis and treatment of the WM stroke.