摘要:

AbstractIn order to study the voltage‐dependent ion channels in microglia, and their possible modulation by proinflammatory substances like lipopolysaccharide (LPS) and interferon‐γ (IFN‐γ) we employed the patch‐clamp technique on purified rat microglial cell subcultures grown for 1–5 days in control condition or after a 24 hour treatment with those agents. Regardless of the culture condition, almost 100% of the cells presented inward‐rectifying (IR) K+currents identified by the following features: (a) extracellular K+‐dependence of Vrevand whole‐cell conductance; (b) inward‐rectifying property; (c) channel blocking mechanism by Cs+; and (d) single channel conductance of 27 pS.A ‘n’ type outward‐rectifying (OR) K+current was present in 30% of the cells during the first 2 days of subcultivation. Its occurrence was strongly dependent on the preparation, varying from 0% to almost 80%, and it decreased to 13% of the cells after three days in culture. It showed the following features: (i) threshold of activation close to ‐30 mV; (ii) sigmoid current onset; (iii) voltage‐% kinetics; and (iv) sensitivity to 4‐aminopyridine (4‐AP) and tetraethylammonium (TEA). Furthermore, we detected two ion currents not previously described in microglia: (i) a slowly activating outward current which appeared at potentials more positive than +20 mV and with a reversal potential close to 0 mV, tentatively identified as a proton current; and (ii) a Cl−conductance identified in ion substitution experiments as the current sensitive to the Cl−channel blocker SITS.The two agents, LPS (20–2,000 ng/ml) and IFN‐γ (10–100 u/ml), shared the following effects: (a) enhancement of membrane capacitance, and (b) increase of OR current amplitude and frequency of occurrence. Moreover, IFN‐γ was also able to increase IR current density, especially in cells with ameboid morphology, while LPS was ineffective. We conclude that the voltage‐dependent ion channel pattern of microglia is more complex than previously thought and that activating agents such as LPS and IFN‐y share some electrophysiological ef

ISSN:0360-4012    

DOI:10.1002/jnr.490420402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractSingle‐channel activity was recorded from cell‐attached patches on skeletal muscle cells isolated from wild‐type mice and from mice carrying thedyormdxmutations. Spontaneous openings of the nicotinic acetylcholine receptor channel (nAChR) were detected in virtually all recordings from eitherdy/dyordy/ + myotubes, but only infrequently from wild‐type ormdxmyotubes. Spontaneous openings were also present in most recordings from undifferentiated myoblasts from all of the mouse strains studied. The biophysical properties of the spontaneous activity were similar to those of the embryonic form of the nAChR in the presence of acetylcholine (ACh). Examination of the single‐channel currents evoked by low concentrations of ACh showed a reduced sensitivity to the agonist in the dystrophicdyandmdxmyotubes, but not in wild type myotubes. The results suggest that alterations in nAChR function are associated with the pathogenesis of muscular dystir ophy in thedymouse. © 1995 Wiley

ISSN:0360-4012    

DOI:10.1002/jnr.490420403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractImmunofluorescence analysis was used to study the cellular localization of glucose transporters 1 and 3 (GLUT1 and GLUT3) in primary rat neuronal and glial cultures. In primary cultured cerebellar granule neurons and cortical neurons, GLUT3 was detected in a pattern consistent with a generalized cell surface distribution. GLUT3 distribution corresponded most closely with the neural cell adhesion molecule (NCAM), and showed overlapping but distinct distributions compared to synaptophysin, microtubule‐associated protein 2 (MAP2), neurofilament protein, and growth‐associated protein (GAP43). Culture of neurons in the presence of glia did not alter the cellular localization of GLUT3. GLUT1 was detectable in primary cerebellar granule neurons both at the cell surface and in the cytoplasm, and appeared decreased in neurons cocultured with glia. GLUT1, but not GLUT3, was detected in glial fibrillary acidic protein (GFAP)‐positive astrocytes present in mixed neuronal‐glial cultures derived from cerebellum and cerebral cortex, as well as in cortical astrocyte cultures. GLUT1, but not GLUT3, was also detected in microglia and oligodendrocytes present in these cultures. This study indicates a generalized cell surface expression of the glucose transporters expressed in neurons and glia, rather than selective targeting to different cellular domains or subcellular locations. © 1995 Wiley‐Liss, Inc.This article is a US Government work and, as such, is in the public domain in the United States

ISSN:0360-4012    

DOI:10.1002/jnr.490420404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe response of olfactory Schwann cells was assessed at 2, 4, and 7 days following intranasal zinc sulfate irrigation in 1‐month‐old mice. Ultrastructural and immunohistochemical observations showed dramatic differences between experimental and control mice which had been washed with saline intranasally. Two days after zinc sulfate treatment, many olfactory nerve bundles contained patchy areas of axonal degeneration, while the cell bodies of the olfactory Schwann cells appeared to have increased in electron density and to have shifted peripherally. Some of the cell bodies protruded from the surface of the axon fascicle, suggesting that the olfactory Schwann cells were in the initial process of migrating away. On the fourth day when most of the olfactory axons had degenerated, some olfactory Schwann cells were aligned immediately beneath the basal lamina of the olfactory epithelium. These cells were immunopositive for the S‐100 protein and possessed an expanded perinuclear space. Many olfactory Schwann cells were present in the region beneath the cribriform plate, while some appeared to have passed through the gaps between the bony plates to reach the olfactory bulb. Hence, the results showed that many olfactory Schwann cells migrated towards the olfactory bulb following loss of axonal contact. Furthermore, on the seventh day following zinc sulfate treatment, some olfactory Schwann cells in the vicinity of the olfactory bulb appeared phagocytic, as indicated by their extension of processes around fragments of cell debris and the presence of lysosome‐like organelles in the perikaryon. The control mice which had been intranasally irrigated with saline did not demonstrate massive olfactory axonal degeneration, and the morphology of the nasal cavity region was similar to that of normal mice. © 1995 Wiley

ISSN:0360-4012    

DOI:10.1002/jnr.490420405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractWe have previously shown that rat perinatal exposure to morphine causes dopaminergic and met‐enkephalin (ME) and substance P (SP) changes in the striatum during the early postnatal period (Tenconi et al.: Int J Dev Neurosci 10:517‐526, 1992); in addition it increases the susceptibility to neurotoxic lesions and impairs regenerative capacity of the serotoninergic system (Gorio et al.: J Neurosci Res 34: 462‐471, 1993). Our study shows that ME and SP levels increase postnatally in several areas of the rat brain, reaching the highest values between 30 and 60 days, after which the peptide content subsides to lower levels. Perinatal exposure to morphine increases such ME and SP levels during the early stages of postnatal life. No effect of morphine on 5‐HT and NE is observed, while the dopaminergic system is mainly affected in the mesencephalon. The pre‐ and postnatal brain expression of synapsin I mRNA is gradually and progressively localized in discrete areas of the brain. In the brain of rats perinatally exposed to morphine, the abundance of synapsin I mRNA expression is markedly reduced. Therefore, perinatal exposure to morphine affects early postnatal synaptic development in the brain as shown by the altered peptidergic and monoaminergic content and by the reduced synapsin I mRNA expression. © 1995 Wiley

ISSN:0360-4012    

DOI:10.1002/jnr.490420406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractWe investigated the immunohistochemical localization of epidermal growth factor (EGF) in the developing human brain from 6 weeks of gestation to 3 months postpartum. EGF‐like immunoreactivity varied in its localization and intensity according to the stage of development. At 10‐20 weeks of gestation, EGF‐like immunoreactivity appeared in proliferating and migrating cells in the cerebrum, disappeared thereafter, and appeared again in cortical neurons after 27 weeks of gestation. Astrocytes also showed EGF‐like immunoreactivity from 27 weeks of gestation. These results suggest developmental regulation of EGF expression in the human brain, suggesting Its physiological role in both neuronal and glial cells. © 1995 Wiley

ISSN:0360-4012    

DOI:10.1002/jnr.490420407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractProlongation of the action potential duration of dorsal root ganglion (DRG) neurons by low (nM) concentrations of opioids occurs through activation of excitatory opioid receptors that are positively coupled via Gsregulatory protein to adenylate cyclase. Previous results suggested GM1 ganglioside to have an essential role in regulating this excitatory response, but not the inhibitory (APD‐shortening) response to higher (μM) opioid concentrations. Furthermore, it was proposed that synthesis of GM1 is upregulated by prolonged activation of excitatory opioid receptor functions. To explore this possibility we have utilized cultures of hybrid F11 cells to carry out closely correlated electrophysiological and biochemical analyses of the effects of chronic opioid treatment on a homogeneous population of clonal cells which express many functions characteristic of DRG neurons. We show that chronic opioid exposure of F11 cells does, in fact, result in elevated levels of GM1 as well as cyclic adenosine monophosphate (AMP), concomitant with the onset of opioid excitatory supersensitivity as manifested by naloxone‐evoked decreases in voltage‐dependent membrane K+currents. Such elevation of GM1 would be expected to enhance the efficacy of excitatory opioid receptor activation of the Gs/adenylate cyclase/cyclic AMP system, thereby providing a positive feedback mechanism that may account for the remarkable supersensitivity of chronic opioid‐treated neurons to the excitatory effects of opioid agonists as well as antagonists. These in vitro findings may provide novel insights into the mechanisms underlying naloxone‐precipitated withdrawal syndromes and opioid‐induced hyperalgesia after chronic opiatf addiction in vivo. © 1995 Wi

ISSN:0360-4012    

DOI:10.1002/jnr.490420408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractCell‐type‐specific reagents have proven useful in the analysis of central nervous system (CNS) development and function. Most markers of oligodendrocytes are components of myelin sheath, which in the CNS is the specific product of oligodendrocytes. We have isolated a novel monoclonal antibody termed 2B10 which was raised against embryonic rat spinal cord tissue. In adult rat cerebrum, cerebellum, and spinal cord, 2B10 immunoreactivity is predominantly localized in white matter. 2B10 immunoreactivity is absent from peripheral nerve, suggesting that in the nervous system the 2B10 antigen is restricted to the CNS. Dissociated cell culture studies indicate that 2B10 labels a cell surface molecule, and its cellular distribution is coincident with O1 and myelin basic protein‐positive oligodendrocytes. By contrast, 2B10 does not label GFAP‐positive astrocytes. These data suggest that in the CNS the 2B10 antigen is expressed specifically on oligodendrocytes. Biochemical analysis indicates that 2B10 recognizes a protein with an apparent molecular weight of approximately 79,000 in reducing sodium dodecyl sulfate‐polyacrylamide gel electrophoresis. Developmentally, 2B10 immunoreactivity is detectable in rat spinal cord at as early as embryonic day 14. The relative abundance of this molecule decreases during myelination, but is maintained at a sustained level throughout adulthood. The 2B10 antigen appears not to be a myelin‐associated protein since it is not detected in purified myelin fractions. 2B10 immunoreactivity is not detectable in extracts of rat sciatic nerve, heart, kidney, muscle, and skin, but is detectable in extracts of spleen and thymus. These data suggest that the 2B10 antigen is a novel cell surface molecule that is expressed on oligodendrocyte lineage cells throughout development. © 1995 Wil

ISSN:0360-4012    

DOI:10.1002/jnr.490420409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractInsulin‐like growth factors IGF‐I and IGF‐II are potent inducers of oligodendrocyte development. Because IGF‐I is produced, in some cases, by the same cells that respond to it (autocrine/paracrine action), we examined the possibility that IGF‐I is expressed by developing oligodendroglial cells. We employed a sensitive method, reverse transcriptase‐polymerase chain reaction (RT‐PCR), to detect IGF‐I mRNA in purified populations of oligodendroglial cells isolated from rat brain during the period of oligodendrocyte development. Cells were purified by fluorescence activated cell sorting (FACS), using antibodies to the cell surface antigenic markers 04 and galactocerebroside (GC). RNA was isolated from the sorted cells, reverse‐transcribed, and PCR‐amplified, using a strategy that recognizes IGF‐I mRNA but not DNA. The amplified band was identified as IGF‐I by size, hybridization to an IGF‐I‐specific antisense probe, and restriction analysis. IGF‐I mRNA was detected in O4‐positive/ GC‐negative oligodendrocyte precursors and, more weakly, in GC‐positive oligodendrocytes. IGF‐I mRNA could be detected reproducibly in RNA extracted from 100‐cell samples of O4‐positive cells, making it unlikely that the mRNA was derived from contaminants in the FACS‐sorted cell populations. We conclude that IGF‐I is expressed by developing oligodendroglia. Autocrine expression of IGF‐I by developing oligodendroglial cells suggests that oligodendrocyte development is,

ISSN:0360-4012    

DOI:10.1002/jnr.490420410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractAlpha‐ and β‐dystroglycan (α‐ and β‐DG) are members of a dystrophin‐associaced glycoprotein complex (DGC) in skeletal muscle which binds to agrin and laminin, and has been postulated to be involved in myoneural synapse formation. The absence of functional dystrophin in Duchenne muscular dystrophy (DMD) and in one of its animal models, themdxmouse, leads to a reduction of α‐ and β‐DG in muscle, and is often associated with mental retardation and abnormal retinal synaptic transmission in DMD. Using immunohistochemistry, we find that a‐ and β‐DG are expressed in the outer plexiform layer of both wild type andmdxretina, where both dystrophin and dystrophin‐related protein (DRP), but not laminin are present. In situ hybridization identifies two neuronal populations, photoreceptors and retinal ganglion cells, that express DG mRNA. α‐ and β‐DG are also expressed in the inner limiting membrane and around blood vessels where they colocalize with laminin and DRP. Western blot analysis revealed the expression of several dystrophin isoforms in wild type andmdxretina, possibly explaining the unaltered expression of α‐ and β‐dystroglycan in themdxcentral nervous system (CNS). Our results support the hypothesis that a‐ and β‐DG can interact with dystrophin and DRP in the CNS and perform functions analogous to those of

ISSN:0360-4012    

DOI:10.1002/jnr.490420411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY