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Physiological Reviews Jul 2019Oligodendrocytes generate multiple layers of myelin membrane around axons of the central nervous system to enable fast and efficient nerve conduction. Until recently,... (Review)
Review
Oligodendrocytes generate multiple layers of myelin membrane around axons of the central nervous system to enable fast and efficient nerve conduction. Until recently, saltatory nerve conduction was considered the only purpose of myelin, but it is now clear that myelin has more functions. In fact, myelinating oligodendrocytes are embedded in a vast network of interconnected glial and neuronal cells, and increasing evidence supports an active role of oligodendrocytes within this assembly, for example, by providing metabolic support to neurons, by regulating ion and water homeostasis, and by adapting to activity-dependent neuronal signals. The molecular complexity governing these interactions requires an in-depth molecular understanding of how oligodendrocytes and axons interact and how they generate, maintain, and remodel their myelin sheaths. This review deals with the biology of myelin, the expanded relationship of myelin with its underlying axons and the neighboring cells, and its disturbances in various diseases such as multiple sclerosis, acute disseminated encephalomyelitis, and neuromyelitis optica spectrum disorders. Furthermore, we will highlight how specific interactions between astrocytes, oligodendrocytes, and microglia contribute to demyelination in hereditary white matter pathologies.
Topics: Aging; Animals; Central Nervous System; Demyelinating Diseases; Humans; Myelin Sheath
PubMed: 31066630
DOI: 10.1152/physrev.00031.2018 -
Cold Spring Harbor Perspectives in... Jun 2015Myelinated nerve fibers have evolved to enable fast and efficient transduction of electrical signals in the nervous system. To act as an electric insulator, the myelin... (Review)
Review
Myelinated nerve fibers have evolved to enable fast and efficient transduction of electrical signals in the nervous system. To act as an electric insulator, the myelin sheath is formed as a multilamellar membrane structure by the spiral wrapping and subsequent compaction of the oligodendroglial plasma membrane around central nervous system (CNS) axons. Current evidence indicates that the myelin sheath is more than an inert insulating membrane structure. Oligodendrocytes are metabolically active and functionally connected to the subjacent axon via cytoplasmic-rich myelinic channels for movement of macromolecules to and from the internodal periaxonal space under the myelin sheath. This review summarizes our current understanding of how myelin is generated and also the role of oligodendrocytes in supporting the long-term integrity of myelinated axons.
Topics: Axons; Glycolysis; Models, Biological; Myelin Sheath; Oligodendroglia; Synaptic Transmission
PubMed: 26101081
DOI: 10.1101/cshperspect.a020479 -
Molecular Neurobiology Aug 2009Fast-transmitting vertebrate axons are electrically insulated with multiple layers of nonconductive plasma membrane of glial cell origin, termed myelin. The myelin... (Review)
Review
Fast-transmitting vertebrate axons are electrically insulated with multiple layers of nonconductive plasma membrane of glial cell origin, termed myelin. The myelin membrane is dominated by lipids, and its protein composition has historically been viewed to be of very low complexity. In this review, we discuss an updated reference compendium of 342 proteins associated with central nervous system myelin that represents a valuable resource for analyzing myelin biogenesis and white matter homeostasis. Cataloging the myelin proteome has been made possible by technical advances in the separation and mass spectrometric detection of proteins, also referred to as proteomics. This led to the identification of a large number of novel myelin-associated proteins, many of which represent low abundant components involved in catalytic activities, the cytoskeleton, vesicular trafficking, or cell adhesion. By mass spectrometry-based quantification, proteolipid protein and myelin basic protein constitute 17% and 8% of total myelin protein, respectively, suggesting that their abundance was previously overestimated. As the biochemical profile of myelin-associated proteins is highly reproducible, differential proteome analyses can be applied to material isolated from patients or animal models of myelin-related diseases such as multiple sclerosis and leukodystrophies.
Topics: Animals; Demyelinating Diseases; Humans; Myelin Proteins; Myelin Sheath; Proteolipids; Proteomics
PubMed: 19452287
DOI: 10.1007/s12035-009-8071-2 -
Journal of Integrative Neuroscience Mar 2011Recently, patients with chronic demyelinating neuropathies have demonstrated significant abnormalities in their multiple nerve excitability properties measured by a... (Review)
Review
Recently, patients with chronic demyelinating neuropathies have demonstrated significant abnormalities in their multiple nerve excitability properties measured by a non-invasive threshold tracking technique. In order to expand our studies on the possible mechanisms underlying these abnormalities, which are not yet well understood, we investigate the contributions of the aqueous layers within the myelin sheath on multiple membrane properties of simulated fibre demyelinations. Four degrees of systematic paranodal demyelinations (two mild demyelinations termed PSD1 and PSD2, without/with aqueous layers respectively, and two severe demyelinations termed PSD3 and PSD4, with/without aqueous layers, respectively) are simulated using our previous multi-layered model of human motor nerve fibre. We studied the following parameters of myelinated axonal function: potentials (intracellular action, electrotonic-reflecting the propagating and accommodative fibre processes, respectively) and strength-duration time constants, rheobases, recovery cycles (reflecting the adaptive fibre processes). The results show that each excitability parameter is markedly potentiated when the aqueous layers within their paranodally demyelinated sheaths are taken into account. The effect of the aqueous layers is significantly higher on the propagating processes than on the accommodative and adaptive processes in the fibres. The aqueous layers restore the action potential propagation, which is initially blocked when they are not taken into account. The study provides new and important information on the mechanisms of chronic demyelinating neuropathies, such as chronic inflammatory demyelinating polyneuropathy (CIDP).
Topics: Animals; Chronic Disease; Demyelinating Diseases; Humans; Membrane Potentials; Motor Neurons; Myelin Sheath; Polyneuropathies; Water
PubMed: 21425485
DOI: 10.1142/S0219635211002646 -
Yakugaku Zasshi : Journal of the... 2022Myelin is a multilamellar membrane structure formed by oligodendrocytes in the central nervous system (CNS) and Schwann cells in the peripheral nervous system (PNS). It... (Review)
Review
Myelin is a multilamellar membrane structure formed by oligodendrocytes in the central nervous system (CNS) and Schwann cells in the peripheral nervous system (PNS). It has been recognized as an insulator that is essential for the rapid and efficient propagation of action potentials by saltatory conduction. However, recently many studies have shown that myelin and myelin-forming cells interact with axons and regulate the nervous system far more actively than previously thought. For example, myelination changes axons dynamically and divides them into four distinct functional domains: node of Ranvier, paranode, juxtaparanode, and internode. Voltage-gated Na channels are clustered at the node, while K channels are at the juxtaparanode, and segregation of these channels by paranodal axoglial junction is necessary for proper axonal function. My research experience began at the neurology ward of the Niigata University Medical Hospital, where I saw a patient with peripheral neuropathy of unknown etiology more than 37 years ago. In the patient's serum, we found an autoantibody against a glycolipid enriched in the PNS. Since then, I have been interested in myelin because of its beautiful structure and unique roles in the nervous system. In this review, our recent studies related to CNS and PNS myelin are presented.
Topics: Autoantibodies; Axons; Central Nervous System; Humans; Myelin Sheath; Ranvier's Nodes; Schwann Cells
PubMed: 35908945
DOI: 10.1248/yakushi.21-00224 -
Current Opinion in Neurobiology Oct 2000During the past few years, significant advances have been made in elucidating the mechanisms by which point mutations and altered gene dosages in tetraspan genes cause... (Review)
Review
During the past few years, significant advances have been made in elucidating the mechanisms by which point mutations and altered gene dosages in tetraspan genes cause neurological disease. In addition, several new myelin tetraspans have been identified that are involved in adhesion, molecular trafficking, growth regulation, and migration of oligodendrocytes and Schwann cells.
Topics: Animals; Humans; Myelin Sheath; Nerve Tissue Proteins; Proteolipids
PubMed: 11084316
DOI: 10.1016/s0959-4388(00)00125-2 -
Physiological Reviews Jan 1968
Review
Topics: Animals; Cats; Dogs; Microscopy, Electron; Myelin Sheath; Neuroglia
PubMed: 4866614
DOI: 10.1152/physrev.1968.48.1.197 -
Aging May 2018
Topics: Animals; Humans; Lipids; Myelin Sheath
PubMed: 29788000
DOI: 10.18632/aging.101458 -
Brain : a Journal of Neurology Nov 2001
Topics: Animals; Humans; Myelin Sheath; Regeneration
PubMed: 11673315
DOI: 10.1093/brain/124.11.2129 -
Journal of Addictions Nursing May 2012As concern grows over the impact that accidental chemical exposures may have on the long term health of individuals, our young people are deliberately exposing... (Review)
Review
As concern grows over the impact that accidental chemical exposures may have on the long term health of individuals, our young people are deliberately exposing themselves to the effect of neurotoxic chemicals with the intent of feeling high. Over time the result of inhaling these chemicals is often the development of symptoms and behavior that may suggest serious physiological damage. Research is being conducted to examine what the exact nature of the damage might be, especially the impact of inhaled lipophilic chemicals on structures in the brain and other parts of the nervous system. Healthcare professionals responsible for assessing adolescents in all settings need to be aware of the prevalence of inhalant abuse, as well as the chemicals, terminology, and potential symptomatology in order to intervene in the behavior and provide diagnosis and treatment as indicated. Some implications for nursing are included.
Topics: Adolescent; Demyelinating Diseases; Humans; Inhalant Abuse; Myelin Sheath
PubMed: 22471781
DOI: 10.3109/10884602.2012.669422