摘要:

AbstractUsing the whole‐cell patch‐clamp technique, at least three types of voltage‐gated currents expressed by cultured rat microglia were identified: an inward rectifier K+current, a delayed rectifier K+current (IK), and a Na+current activated by depolarization. The inward rectifier conductance was activated by hyperpolarization to potentials more negative than −80 mV, depended on the external K+concentration, and declined over time during whole cell recording, as the cell was internally dialyzed. The delayed rectifier current was activated by depolarization to potentials more positive than −40 mV and the rates of activation and deactivation showed a voltage‐dependence similar to such currents seen in other preparations. An inward current possibly carried by Na+was seen in a small percentage of cells. Recordings had been made from two morphological cell types, namely process‐bearing (“ramified”) and non‐process‐bearing (“ameboid”). Each of these currents was present in microglia of both morphological types. However, microglial morphology, which is thought to represent different states of activation, was significantly related to the types of combinations of currents expressed in a given cel

ISSN:0894-1491    

DOI:10.1002/glia.440060202

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe neurokinin‐1 (NK‐1, substance P) receptor belongs to the class of seven transmembrane domain (7‐TM) receptors that interact with cellular effector systems via guanine nucleotide binding regulatory proteins (G‐proteins). In this study, coupling mechanisms of functional NK‐1 receptoirs endogenously expressed in a human astrocytoma cell line (U373MG) were analyzed. Stimulation with substance P (SP) resulted in 1) a rapid increase in inositol 1,4,5‐trisphosphate (IP3) synthesis; 2) a rise in cytosolic free calcium concentration ([Ca2+]); 3) induction of immediate early gene transcription as monitored byc‐fosandc‐junexpression; and 4) a significant increase in de novo DNA synthesis. Thus, the functional responses induced by stimulation of NK‐1 receptors on U373MG strongly correlate with those observed after treatment of primary astrocytes with SP and make U373MG cells a useful in vitro model system for the analysis of NK‐1 receptor function on astrocytes in vivo. ©

ISSN:0894-1491    

DOI:10.1002/glia.440060203

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

年代:1992

数据来源: WILEY

摘要:

AbstractExposure of the rat lumbar spinal cord to X‐rays during the early postnatal period results in a marked reduction in the glial populations within the irradiated region. The present study was undertaken to determine what effects this reduction of glia, particularly astrocytes, has on the pattern and characteristics of the scar formation that follows root injury in the normal spinal cord. Morphological assessments 60 days following injury of the right L4 dorsal root revealed a distinct difference in the extent of the astrocyte response between the irradiated and the nonirradiated rats. In the nonirradiated animals, a thick astrocytic scar composed of multiple layers of astrocyte processes formed over the dorsal horn and adjacent portions of the dorsal surface of the cord. This astrocytic response was not confined to the surface of the spinal cord but extended also into the root, i.e., into regions normally considered as PNS. In irradiated rats, the astrocytes did not form a thick scar nor did they extend into the injured root. Instead, they formed a glia limitans and were at most only one or two layers thick over the region of cord comparable to that occupied by the thick astrocytic scar in the nonirradiated rats. Mechanisms involved in the glial response of the irradiated spinal cord to dorsal root injury are discussed, particularly with regard to the possible positive effect that this reduction in scar formation may have on regrowth of injured dorsal root axons into the spinal cord environment. © 1992 Wiley‐Liss,

ISSN:0894-1491    

DOI:10.1002/glia.440060204

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

年代:1992

数据来源: WILEY

摘要:

AbstractAttempts to show the distribution of adrenergic receptors (ARs) in autoradiographs of a brainstem motor nucleus following elimination of motor neurons yielded the unexpected result of an increase in β‐AR density. This increase was related to the gliosis accompanying the motor neuron degeneration. To determine the cells on which the AR subtypes were located, we dissociated cells from various regions of the adult rat brain and subsequently identified astrocytes by glial fibrillary acidic protein (GFAP) immunofluorescence. Slides containing the astrocytes were prepared for autoradiography using the nonselective β ligand125I‐iodocyanopindolol (125ICYP) or the α1ligand125IBE 2254 (125I‐HEAT). The addition of the selective β1blocker betaxolol or the β2blocker ICI 118.551 to the incubation medium to displace125ICYP binding was used to determine the binding of β‐AR subtypes.The great majority (>88%) of isolated astrocytes sampled from the trigeminal motor nucleus, cerebral cortex, striatum, and cerebellum showed β‐AR binding. Astrocytes from the first three regions had similar average densities of β‐ARs, whereas the density in cerebellar astrocytes was 2‐ to 3‐fold greater. The β2‐AR subtypes was proportionally greater than the β1subtype in each region. Reactive astrocytes isolated from the trigeminal motor nucleus after degeneration of motor neurons showed a β‐AR density nearly 2‐fold greater than resting astrocytes from the same region, with the β1subtype showing the greater proportional increase. There was no β‐AR binding on trigeminal motor neurons.Astrocytes also showed a significant level of α1‐AR binding. No differences in α1‐AR binding were found in normal astrocytes isolated from the different regions, nor was there an increase in reactive astrocytes. In contrast, trigeminal motor neurons had an α1‐AR density nearly 10 times greater than astrocytes.In terms of the NE modulation of synaptic responses in motor neurons, the distribution of ARs would permit NE to act indirectly through α1and β receptors on astrocytes and directly through α1re

ISSN:0894-1491    

DOI:10.1002/glia.440060205

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

年代:1992

数据来源: WILEY

摘要:

AbstractWhole‐cell membrane currents and imaging of intracellular calcium concentrations ([Ca2+]i) were used to investigate the role of calcium in a response to serotonin of C6 glioma cells. Activation of a high‐affinity serotoinin receptor induced a transient rise in calcium concentration in these cells and activated a predominantly potassium conductance, with a small chloride component. Perfusion of the cytoplasm with an internal solution containing high calcium concentration induced similar but prolonged increase of membrane conductance. The responsiveness of C6 cells to serotonin was negatively correlated with the concentration of the unbound calcium chelator BAPTA when BAPTA‐buffered calcium‐containing intracellular solutions were used. Responses to serotonin persisted in the absence of external calcium, decreased gradually, and then recovered partially after replenishment of extracellular calcium. These findings substantiate the direct role of intracellular calcium in mediating the serotonin response, and indicate that serotonin‐induced release of calcium from intracellular stores is sufficient for the activation of conductance in the C6 glioma cell line. © 1992 Wiley

ISSN:0894-1491    

DOI:10.1002/glia.440060206

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

年代:1992

数据来源: WILEY

摘要:

AbstractIntercellular coupling among astrocytes was studied in rat visual cortex slices from animals aged 1 week to 4 months. Cell coupling via gap junctions was determined by the dye spread of the low molecular weight dye Lucifer Yellow CH injected into electrophysiologically identified cells to adjacent cells. Coupling among glial cells was first detected at postnatal day 11 and was thereafter consistently observed until adulthood. Dye spread was observed up to 300 μm radially from the injected cell covering multiple cortical layers. Following dye injection into a single cell up to several hundred Lucifer Yellow‐positive cells could be observed. Quantitative analysis revealed a similar extent of dye spread at different developmental stages including a quite constant number of dye‐coupled astrocytes from the end of the second postnatal week to adulthood. Double labelling of Lucifer Yellow‐filled cells with an antiserum against the glial fibrillary acidic protein confirmed the astrocytic nature of the injected and coupled cells. Comparison of the density of dye‐coupled cells in a given area and the total number of astrocytes as revealed by immunocytochemical staining suggests that dye‐coupling includes the entire local astrocytic population. It is concluded that coupling among astrocytes via gap junctions in rat visual cortex occurs shortly after birth and reflects one of the first steps in astroglial maturation. © 1992 Wile

ISSN:0894-1491    

DOI:10.1002/glia.440060207

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe monoclonal antibody Rip recognizes an antigen specific to oligoderdrocytes and their processes (Friedman et al: Gila 2:380, 1989). We have used this antibody to document the appearance of oligodendrocytes and the sequence of ensheathment of axons along the optic tract (OT) and within its major target areas in neonatal (P3–P21) and adult hamsters.Myelination of axons in the visual pathway follows an overall proximo‐distal gradient. On P3, immunopositive, pre‐ensheathing oligodendrocytes are detected in the OT ventral to the lateral geniculate body (LGB) whereas myelin segments are present around OT axons by P5. The first pre‐ensheathing oligodendrocytes are detected medially in the LGB on P7 and myelinated axons in the overlying OT by P11. In the superior colliculus, pre‐ensheathing oligodendrocytes are prsent in the optic fiber layer (SO) on P7, but not in the superficial gray layer (SGS) until P11. Myelination of axons within SO proceeds along a marked rostro‐caudal gradient. On P14, axons in rostral SO are heavily myelinated; thereafter, ensheathment continues caudally within the SO and the SGS.The progressive invasion of oligodendrocytes along the proximo‐distal axis of the optic pathway, and the corresponding myelination of OT axons, are discussed in the context of a possible inhibitory role of oligodendrocytes in regulating the regenerative propensity of retinotectal axons. © 1992 W

ISSN:0894-1491    

DOI:10.1002/glia.440060208

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

年代:1992

数据来源: WILEY

摘要:

AbstractImmuno‐electron microscopy was used to localize the distribution of vimentin and glial fibrillary acidic protein (GFAP) in mouse astrocytes and their precursor cells in primary cultures. In astroblasts and astrocytes, vimentin and GFAP form intermediate filaments (IF), which are heteropolymers, as previously observed in gliomas. Astrocytes and their precursor cells may have IF composed of GFAP‐vimentin heteropolymer or vimentin alone, but IF composed of GFAP only were not seen. It seems that the formation of IF that are GFAP‐vimentin heteropolymers is a feature of normal astroglia development and that the ratio of GFAP to vimentin in these IF reflects the degree of differentiation and functional state of the cell. © 1992 Wiley‐L

ISSN:0894-1491    

DOI:10.1002/glia.440060209

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

年代:1992

数据来源: WILEY

摘要:

AbstractCo‐localization of glial fibrillary acidic protein (GFAP) and radioactivity was examined after intraventricular injection of [3H]5‐HT in adult rat brains. Radioactivity localized over GFAP‐positive astrocytes was seen, especially when image‐enhancing techniques were applied to the data. Also slices prepared from astrogliotic hippocampi of rats pretreated with kainic acid showed a twofold increased uptake of [3H]5‐HT compared to control slices. This indicates that the uptake of [3H]5‐HT seen in primary astrocyte cultures also occurs for astrocytes in situ. Also, as with astrocyte cultures, only some of the GFAP(+) astrocytes in situ showed localization of radioactivity, supporting the concept of intraregional heterogeneity of astrocyte functions. © 1992 Wil

ISSN:0894-1491    

DOI:10.1002/glia.440060210

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

年代:1992

数据来源: WILEY

ISSN:0894-1491    

DOI:10.1002/glia.440060201

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

年代:1992

数据来源: WILEY