scholarly journals Octopaminergic modulation of the membrane potential of the Schwann cell of the squid giant nerve fibre

1986 ◽  
Vol 121 (1) ◽  
pp. 421-443 ◽  
Author(s):  
V. Reale ◽  
P. D. Evans ◽  
J. Villegas
Keyword(s):  
Schwann Cell ◽  
Schwann Cells ◽  
Nerve Fibre ◽  
High Frequency ◽  
Cell Activity ◽  
Physiological Role ◽  
Giant Axon ◽  
Octopamine Receptors ◽  
Low Concentrations

The actions of octopamine on the Schwann cells of the giant nerve fibre of the tropical squid are described. The pharmacology of the receptors mediating the actions of octopamine has been investigated in terms of stereospecificity, amine specificity and interactions with a range of agonists and antagonists. The receptors are maximally activated by D(−)-octopamine and share many of the characteristics of OCTOPAMINE2 class receptors in other preparations. The octopamine receptors appear to mediate their actions by increasing the intracellular levels of cyclic AMP in the Schwann cells. Low concentrations of octopamine potentiate the actions of the nicotinic cholinergic activation system of the Schwann cells. The results are discussed in terms of the possible physiological role of octopamine in the modulation of Schwann cell activity during stressful conditions when the giant axon system is likely to be used at a high frequency to facilitate the escape response of the squid.

scholarly journals Fibronectin promotes rat Schwann cell growth and motility.

1982 ◽  
Vol 93 (1) ◽  
pp. 211-216 ◽  
Author(s):  
A Baron-Van Evercooren ◽  
H K Kleinman ◽  
H E Seppä ◽  
B Rentier ◽  
M Dubois-Dalcq
Keyword(s):  
Schwann Cell ◽  
Schwann Cells ◽  
Tritiated Thymidine ◽  
Primary Cultures ◽  
Boyden Chamber ◽  
Low Concentrations ◽  
And Migration ◽  
Thymidine Autoradiography ◽  
Double Immunolabeling

Techniques are now available for culturing well characterized and purified Schwann cells. Therefore, we investigated the role of fibronectin in the adhesion, growth, and migration of cultured rat Schwann cells. Double-immunolabeling shows that, in primary cultures of rat sciatic nerve, Schwann cells (90%) rarely express fibronectin, whereas fibroblasts (10%) exhibit a granular cytoplasmic and fibrillar surface-associated fibronectin. Secondary cultures of purified Schwann cells do not express fibronectin. Exogenous fibronectin has a small effect on promoting the adhesion of Schwann cells to the substrate and does not significantly affect cell morphology, but it produced a surface fibrillar network on fibronectin on the secondary Schwann cells. Tritiated thymidine autoradiography revealed that addition of fibronectin to the medium, even at low concentrations, markedly stimulates Schwann cell proliferation, in both primary and secondary cultures. In addition, when cell migration was measured in a Boyden chamber assay, fibronectin was found to moderately, but clearly, stimulate directed migration or chemotaxis.

scholarly journals The effect of a glutamate uptake inhibitor on axon-Schwann cell signalling in the squid giant nerve fibre.

1992 ◽  
Vol 173 (1) ◽  
pp. 251-260
Author(s):  
P D Evans ◽  
V Reale ◽  
R M Merzon ◽  
J Villegas
Keyword(s):  
Membrane Potential ◽  
Schwann Cell ◽  
Glutamate Receptors ◽  
Schwann Cells ◽  
Nerve Fibre ◽  
Glutamate Uptake ◽  
Cell Signalling ◽  
Giant Axon ◽  
Uptake System ◽  
Extracellular Level

The glutamate uptake blocker p-chloromercuriphenylsulphonic acid (PCMS) (100 mumol l-1) does not block any of the membrane potential changes induced by the application of L-glutamate to the adaxonal Schwann cells of the giant axon of the tropical squid Sepioteuthis sepioidea. This indicates that these potential changes are not due to the activation of an electrogenic glutamate uptake system and supports the idea that they are due to the activation of specific glutamate receptors. The presence of PCMS (100 mumol l-1) reduces the activity of the glutamate uptake system sufficiently for the extracellular level of axonally released glutamate to exceed the threshold for the activation of the NMDA-type glutamate receptors in this preparation.

A comparison of the release of a vasoactive-intestinal-peptide-like peptide and acetylcholine in the giant axon-Schwann cell preparation of the tropical squid Sepioteuthis sepioidea

1999 ◽  
Vol 202 (4) ◽  
pp. 417-428
Author(s):  
P.D. Evans ◽  
V. Reale ◽  
R.M. Merzon ◽  
J. Villegas
Keyword(s):  
Schwann Cell ◽  
Vasoactive Intestinal Peptide ◽  
Schwann Cells ◽  
Recovery Time ◽  
Cell Signalling ◽  
Giant Axon ◽  
Direct Application ◽  
Cell Preparation ◽  
Signalling Molecule ◽  
Release Of Acetylcholine

A vasoactive intestinal peptide (VIP)-like peptide is released by axonal stimulation in the giant axon-Schwann cell preparation from the tropical squid Sepioteuthis sepioidea. It is also released by direct application of l-glutamate, the giant axon-Schwann cell signalling molecule in this preparation. The release of the peptide parallels the release of acetylcholine from the Schwann cells themselves in this preparation in a number of different ways. The release of both acetylcholine and the VIP-like peptide have the same threshold (between 2×10(−10) and 5×10(−10)mol l-1) for l-glutamate application and the same recovery time after inhibition of release by exposure of the preparation to a prolonged pulse of l-glutamate. A prolonged l-glutamate pulse of 10(−8)mol l-1 releases both substances for as long as the pulse is applied to the preparation, whereas a prolonged pulse of 10(−9)mol l-1 l-glutamate releases acetylcholine in the same way but releases the VIP-like peptide only transiently. The VIP-like peptide is likely to be co-released with acetylcholine from the Schwann cells.

scholarly journals Grayanotoxin, veratrine, and tetrodotoxin-sensitive sodium pathways in the Schwann cell membrane of squid nerve fibers.

1976 ◽  
Vol 67 (3) ◽  
pp. 369-380 ◽  
Author(s):  
J Villegas ◽  
C Sevcik ◽  
F V Barnola ◽  
R Villegas
Keyword(s):  
Membrane Potential ◽  
Cell Membrane ◽  
Schwann Cell ◽  
Nerve Fiber ◽  
Schwann Cells ◽  
Giant Axon ◽  
Nerve Fibers ◽  
Resting Membrane Potential ◽  
External Application ◽  
Axon Membrane

The actions of grayanotoxin I, veratrine, and tetrodotoxin on the membrane potential of the Schwann cell were studied in the giant nerve fiber of the squid Sepioteuthis sepioidea. Schwann cells of intact nerve fibers and Schwann cells attached to axons cut lengthwise over several millimeters were utilized. The axon membrane potential in the intact nerve fibers was also monitored. The effects of grayanotoxin I and veratrine on the membrane potential of the Schwann cell were found to be similar to those they produce on the resting membrane potential of the giant axon. Thus, grayanotoxin I (1-30 muM) and veratrine (5-50 mug-jl-1), externally applied to the intact nerve fiber or to axon-free nerve fiber sheaths, produce a Schwann cell depolarization which can be reversed by decreasing the external sodium concentration or by external application of tetrodotoxin. The magnitude of these membrane potential changes is related to the concentrations of the drugs in the external medium. These results indicate the existence of sodium pathways in the electrically unexcitable Schwann cell membrane of S. sepioidea, which can be opened up by grayanotoxin I and veratrine, and afterwards are blocked by tetrodotoxin. The sodium pathways of the Schwann cell membrane appear to be different from those of the axolemma which show a voltage-dependent conductance.

Charcot–Marie–Tooth type 4B demyelinating neuropathy: deciphering the role of MTMR phosphatases

2007 ◽  
Vol 9 (25) ◽  
pp. 1-16 ◽  
Author(s):  
Stefano C. Previtali ◽  
Angelo Quattrini ◽  
Alessandra Bolino
Keyword(s):  
Schwann Cell ◽  
Schwann Cells ◽  
Autosomal Recessive ◽  
Protein Tyrosine Phosphatases ◽  
Vesicular Trafficking ◽  
Demyelinating Neuropathy ◽  
Charcot Marie Tooth ◽  
Catalytically Active ◽  
Tooth Type

AbstractCharcot–Marie–Tooth type 4B (CMT4B) is a severe autosomal recessive neuropathy with demyelination and myelin outfoldings of the nerve. This disorder is genetically heterogeneous, but thus far, mutations in myotubularin-related 2 (MTMR2) and MTMR13 genes have been shown to underlie CMT4B1 and CMT4B2, respectively. MTMR2 and MTMR13 belong to a family of ubiquitously expressed proteins sharing homology with protein tyrosine phosphatases (PTPs). The MTMR family, which has 14 members in humans, comprises catalytically active proteins, such as MTMR2, and catalytically inactive proteins, such as MTMR13. Despite their homology with PTPs, catalytically active MTMR phosphatases dephosphorylate both PtdIns3P and PtdIns(3,5)P2 phosphoinositides. Thus, MTMR2 and MTMR13 may regulate vesicular trafficking in Schwann cells. Loss of these proteins could lead to uncontrolled folding of myelin and, ultimately, to CMT4B. In this review, we discuss recent findings on this interesting protein family with the main focus on MTMR2 and MTMR13 and their involvement in the biology of Schwann cell and CMT4B neuropathies.

scholarly journals SoxD transcription factor deficiency in Schwann cells delays myelination in the developing peripheral nervous system

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ella Ittner ◽  
Anna C. Hartwig ◽  
Olga Elsesser ◽  
Hannah M. Wüst ◽  
Franziska Fröb ◽  
...  
Keyword(s):  
Nervous System ◽  
Schwann Cell ◽  
Peripheral Nervous System ◽  
Schwann Cells ◽  
Terminal Differentiation ◽  
Factor Deficiency ◽  
Schwann Cell Development ◽  
The Central Nervous System ◽  
Brain And Spinal Cord

AbstractThe three SoxD proteins, Sox5, Sox6 and Sox13, represent closely related transcription factors with important roles during development. In the developing nervous system, SoxD proteins have so far been primarily studied in oligodendroglial cells and in interneurons of brain and spinal cord. In oligodendroglial cells, Sox5 and Sox6 jointly maintain the precursor state, interfere with terminal differentiation, and thereby ensure the proper timing of myelination in the central nervous system. Here we studied the role of SoxD proteins in Schwann cells, the functional counterpart of oligodendrocytes in the peripheral nervous system. We show that Schwann cells express Sox5 and Sox13 but not Sox6. Expression was transient and ceased with the onset of terminal differentiation. In mice with early Schwann cell-specific deletion of both Sox5 and Sox13, embryonic Schwann cell development was not substantially affected and progressed normally into the promyelinating stage. However, there was a mild and transient delay in the myelination of the peripheral nervous system of these mice. We therefore conclude that SoxD proteins—in stark contrast to their action in oligodendrocytes—promote differentiation and myelination in Schwann cells.

scholarly journals Nitrite Transport Activity of the ABC-Type Cyanate Transporter of the Cyanobacterium Synechococcus elongatus

2009 ◽  
Vol 191 (10) ◽  
pp. 3265-3272 ◽  
Author(s):  
Shin-ichi Maeda ◽  
Tatsuo Omata
Keyword(s):  
Nitrogen Deficiency ◽  
Physiological Role ◽  
Synechococcus Elongatus ◽  
Transport Activity ◽  
High Affinity ◽  
Low Concentrations ◽  
Cyanobacterial Species ◽  
Relative Specificity ◽  
Nitrite Transport

ABSTRACT In addition to the ATP-binding cassette (ABC)-type nitrate/nitrite-bispecific transporter, which has a high affinity for both substrates (Km , ∼1 μM), Synechococcus elongatus has an active nitrite transport system with an apparent Km (NO2 −) value of 20 μM. We found that this activity depends on the cynABD genes, which encode a putative cyanate (NCO−) ABC-type transporter. Accordingly, nitrite transport by CynABD was competitively inhibited by NCO− with a Ki value of 0.025 μM. The transporter was induced under conditions of nitrogen deficiency, and the induced cells showed a V max value of 11 to 13 μmol/mg of chlorophyll per h for cyanate or nitrite, which could supply ∼30% of the amount of nitrogen required for optimum growth. Its relative specificity for the substrates and regulation at transcriptional and posttranslational levels suggested that the physiological role of the bispecific cyanate/nitrite transporter in S. elongatus is to allow nitrogen-deficient cells to assimilate low concentrations of cyanate in the medium. Its contribution to nitrite assimilation was significant in a mutant lacking the ABC-type nitrate/nitrite transporter, suggesting a possible role for CynABD in nitrite assimilation by cyanobacterial species that lack another high-affinity mechanism(s) for nitrite transport.

scholarly journals Biological Role of Dystroglycan in Schwann Cell Function and Its Implications in Peripheral Nervous System Diseases

2010 ◽  
Vol 2010 ◽  
pp. 1-17 ◽  
Author(s):  
Toshihiro Masaki ◽  
Kiichiro Matsumura
Keyword(s):  
Schwann Cell ◽  
Schwann Cells ◽  
Cell Function ◽  
Cell Polarization ◽  
Targeted Mutagenesis ◽  
Biological Role ◽  
Central Component ◽  
Molecular Architecture ◽  
Loss Of Function

Dystroglycan is a central component of the dystrophin-glycoprotein complex (DGC) that links extracellular matrix with cytoskeleton, expressed in a variety of fetal and adult tissues. Dystroglycan plays diverse roles in development and homeostasis including basement membrane formation, epithelial morphogenesis, membrane stability, cell polarization, and cell migration. In this paper, we will focus on biological role of dystroglycan in Schwann cell function, especially myelination. First, we review the molecular architecture of DGC in Schwann cell abaxonal membrane. Then, we will review the loss-of-function studies using targeted mutagenesis, which have revealed biological functions of each component of DGC in Schwann cells. Based on these findings, roles of dystroglycan in Schwann cell function, in myelination in particular, and its implications in diseases will be discussed in detail. Finally, in view of the fact that understanding the role of dystroglycan in Schwann cells is just beginning, future perspectives will be discussed.

High conductance anion-selective channels in rat cultured Schwann cells

1984 ◽  
Vol 221 (1225) ◽  
pp. 395-409 ◽  
Keyword(s):  
Schwann Cells ◽  
Physiological Role ◽  
Potential Range ◽  
Patch Clamp Technique ◽  
Bathing Medium ◽  
Voltage Dependent ◽  
Cultured Schwann Cells ◽  
Inside Out ◽  
High Conductance

Anion-selective channels, with very large single unit conductances, are present in the cell membrane of rat cultured Schwann cells measured with the patch-clamp technique. In inside-out membrane patches, channels with a conductance of about 450 pS (in symmetrical 150 mM NaCl) were observed. These channels did not become active until several minutes after the cytoplasmic surface had been exposed to the bathing medium, suggesting that these channels may normally be kept in an inactive state by some as yet unknown internal factor. The channel opened over a relatively small potential range ( — 10 mV to + 20 mV) and closed rapidly at more positive and more negative potentials with voltage-dependent kinetics. Although the channels showed a slight permeability towards small cations the major permeability was to anions. The order of permeability was: I > Br > Cl > methyl SO 4 > SO 4 > acetate = isethionate. Aspartate and glutamate were not detectably permeant. The physiological role of these channels remains unknown.

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