ISSN:0894-1491    

DOI:10.1002/glia.440010102

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe evolution of concepts concerning the identity and the functions of neuroglia is traced. Some of the main ideas in the works of Virchow, Deiters, Golgi, Lenhossék, Lugaro, Ramón y Cajal, del Río‐Hortega, Achúcarro, Penfield, and others are highli

ISSN:0894-1491    

DOI:10.1002/glia.440010103

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

年代:1988

数据来源: WILEY

摘要:

AbstractWhite matter is a compact structure consisting primarily of neuronal axons and glial cells. As in other parts of the nervous system, the function of glial cells in white matter is poorly understood. We have explored the electrophysiological properties of two types of glial cells found predominantly in white matter: type 2 astrocytes and oligodendrocytes. Whole‐cells and single‐channel patch‐clamp techniques were used to study these cell types in postnatal rat optic nerve cultures prepared according to the procedures of Raff et al. (Nature, 303:390–390, 1983b). Type 2 astrocytes in culture exhibit a “neuronal” channel phenotype, expressing at least six distinct ion channel types. With whole‐cell recording we observed three inward currents: a voltage‐sensitive sodium current qualitatively similar to that found in neurons and both transient and sustained calcium currents. In addition, type 2 astrocytes had two components of outward current: a delayed potassium current which activated at 0 mV and an inactivating calcium‐dependent potassium current which activated at −30 mV. Type 2 astrocytes in culture could be induced to fire single regenerative potentials in response to injections of depolarizing current. Single‐channel recording demonstrated the presence of an outwardly rectifying chloride channel in both type 2 astrocytes and oligodendrocytes, but this channel could only be observed in excised patches. Oligodendrocytes expressed only one other current: an inwardly rectifying potassium current that is mediated by 30‐ and 120‐pS channels. Because these channels preferentially conduct potassium from outside to inside the cell, and because they are open at the resting potential of the cell, they would be appropriate for removing potassium from the extracellular space; thus it is proposed that oligodendrocytes, besides myelinating axons, play an important role in potassium regulation in white matter. The conductances present in oligodendrocytes suggest a “modulated Boyle and Conway mechanism

ISSN:0894-1491    

DOI:10.1002/glia.440010104

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe structural plasticity of cerebral astroglia was investigated in vivo by implantation experiments. Immunocytochemical markers for glia filament protein were used to identify the astrocytes. First it was established that implanted nitrocellulose filters provided a substrate for astrocytes from different brain regions of young rats. Astrocytes attached to the filter and projected fine processes into it. Longer implantation times increased the density and length of glial processes within filter spaces. Astrocytes that penetrated the filters implanted in the tectum exhibited more processes than those in the cortex, suggesting regional differences of astrocyte distributions. Second it was observed that astrocyted that attached to the filter formed elongated processes when they were tethered within an expanding matrix. This was shown by implanting the nitrocellulose filter together with PC12 cells that continued to grow. The implantation of neither PC12 cells without filters nor nitrocellulose filters alone induced the formation of elongated astroglia with parallel aligned processes, resembling radial glia. Such glial forms only occurred in the filter/PC12 cell cografts. This indicates that processes of astrocytes adherent to nitrocellulose filters could be stretched in response to expansion of the surrounding tissue.

ISSN:0894-1491    

DOI:10.1002/glia.440010105

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

年代:1988

数据来源: WILEY

摘要:

AbstractOligodendrocytes generate myelin as extensions of the plasma membrane. Myelin has been well characterized, yet little is known concerning oligodendrocyte plasma membrane. We have developed a reproducible method for the isolation of an oligodendrocyte plasma membrane‐rich fraction (F2.2). F2.2 has a 25‐fold enrichment in K+‐dependent p‐nitrophenyl phosphatase, a plasma membrane marker. Impurities are composed of Golgi elements (8–12%), microsomes (4–6%), and lysosomal membranes (1–5%). Our starting material was oligodendrocytes kept in culture in a nonattached state for 3 to 5 d. After disrupting the cells and removing nuclei (P1), the supernatant (SP1) was fractionated on a self‐generating 20% Percoll gradient into three bands: F1, F2, and F3. F1 had only 3% of the applied protein and was not characterized. F2, with 11% of the protein, was fivefold enriched in plasma membrane. F3 had 27% of initial protein; it consisted of a crude mitochondrial and lysosomal fraction. F2 was further purified by first washing it hypotonically, treating it with Mg2+, and then fractionating it on a Ficoll step gradient that yielded F2.2 at the interphase. Morphologically F2.2 comprises (1) membranous sheets, often with more than one membrane in close apposition; (2) membrane vesicles of various sizes and shapes frequently filled with amorphous material; (3) Golgi elements; and (4) unrecognizable profiles. The sodium dodecyl sulfate‐polyacrylamide gel electrophoresis protein profile of F2.2 reveals CNPase as a major component in agreement with the high CNPase specific activity (3,860 μmol/mgP/h) found in F2.2 Other significant polypeptides have Mr= 170,000, 135,000, 108,000, 80,000, 53,000, 38,500,

ISSN:0894-1491    

DOI:10.1002/glia.440010106

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

年代:1988

数据来源: WILEY

摘要:

AbstractAn oligodendrocyte plasma membrane‐rich fraction, F2.2, was resolved by equilibrium density centrifugation on a linear sucrose gradient from 0.5 M to 1.3 M into three fractions, F2.2a, F.2.2b, F2.2c, and a pellet F2.2p. F2.2a and F.2.2b were enriched 1.5‐fold relative to F2.2 in plasma membrane markers at the expense of F2.2c and F2.2p, which became correspondingly impoverished. This gave F2.2a and F2.2b a 42‐fold and 37‐fold enrichment, respectively, in plasma membrane markers relative to the initial cell homogenate. F2.2c had a sevenfold enrichment in a Golgi marker; together with F2.2p, they contained all the Golgi marker initially present in F2.2. Preliminary data indicated that the F2.2‐subfractions differed from one another in their molar ratios of cholesterol to phospholipids and protein to lipids but had similar protein profiles when examined by sodium dodecylsulfate‐polyacrylamide gel electrophoresis. Their content of fucosylated glycoproteins appeared also to be different. Morphologically, F2.2a and F2.2b were very similar: they contained large membrane vesicles, membrane sheets, and vesicles entrapped within other vesicles. Membrane‐membrane interaction was apparent in these fractions. F2.2c had many of the same elements, but most of the membrane structures contained amorphous material. F2.2p differed morphologically from the other fractions in that it had principally electron‐dense structures. It is postulated that F2.2a, F2.2b, and perhaps F2.2c represent different domains of oligodendrocyte plasma membrane. Alternatively, these fractions might correspond to the plasma membrane of oligodend

ISSN:0894-1491    

DOI:10.1002/glia.440010107

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe characteristics of electrical coupling between astrocytes and between oligodendrocytes were analyzed in cell cultures derived from rodent central nervous system. Experiments were carried out by impaling one member of a glial pair with separate voltage recording and current passing electrodes (cell 1) and the other cell, a measured distance from the first, with a voltage‐recording electrode (cell 2). Astrocyte pairs within 300 μm of one another were always coupled. The coupling ratio was determined for 23 astrocytic pairs various distances apart, and decreased with distance in a roughly exponential manner. The average coupling ratio of astrocytes within 100 μm of each other was 0.44 ± 0.32. Oligodendrocytes were less strongly coupled to each other than astrocytes. Even cells immediately adjacent to one another were often uncoupled. Among coupled oligodendrocytes within 100 μm of each other, the average coupling ratio was 0.11 ± 0.1. Current passage between pairs of astrocytes and pairs of oligodendrocytes was nonrectifying. Application of 0.5 mM BaCl2or 44.6 mM CsCl (substituted for NaCl) depolarized and increased the input resistance of astrocytes and oligodendrocytes. These ions also increased the coupling ratio in astrocyte pairs and oligodendrocyte pairs; this effect was rapid in onset and completely reversible. Ba++and Cs+appear to block resting K+conductance in glia and probably increase the coupling ratio by increasing the effective length constant of the glial membrane without any direct effect on junctional resistance. In three cases, oligodendrocyte pairs that appear uncoupled in normal solution exhibited coupling in the presence of BaCl2or CsCl. This suggests that oligodendrocytes may be widely coupled by junctions that provide only weak electrical interaction; such junctions might be important for the exchange of small metabolically active molecules. The strong electrical coupling among astrocytes, in concert with their K+‐selective membrane conductance, would provide for an electrical syncytium well designed to transport K+away from areas of focal extracellular accumulation (i.e., the spatial buffer mechanism), and these cells, more than oligodendrocytes, may provide this

ISSN:0894-1491    

DOI:10.1002/glia.440010108

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

年代:1988

数据来源: WILEY

摘要:

AbstractIn the present study the distribution of astrocytes in the nerve fiber layer (NFL) has been studied in the sparsely vascularized retinae of the guinea pig and horse and in the richly vascularized retina of the Old World monkey (Cercopithecus aethiops) using immunocytochemical methods. In the guinea pig retina glial fibrillary acidic protein (GFAP)‐positive astrocytes could not be detected. They were found, however, in the myelinated region of the optic nerve. The optic nerve head and a small retinal region immediately adjacent to it contained few vimentin‐positive astrocytes. Histological sections confirmed the restriction of astrocytes to a small retinal region and showed that this is also the only retinal area that is vascularized. Astrocytes showing GFAP and vimentin immunoreactivity were absent from most of the horse retina. They were found only in a narrow zone close to the optic disc, which is also the only region of the horse retina that is vascularized. Thus, as in the rabbit retina (Schnitzer: J. Comp. Neurol. 240:128–142, 1985), in the guinea pig and horse retina astrocytes are not present ubiquitously in the NFL but coexist with blood vessels. In the monkey retina, GFAP‐positive astrocytes were found ubiquitously in the NFL. Astrocytes were absent from the avascular foveal region only. It is suggested that the concurrence of retinal astrocytes and intraretinal vascularization may be a feature common to many, if not all, mammalian

ISSN:0894-1491    

DOI:10.1002/glia.440010109

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

年代:1988

数据来源: WILEY

摘要:

AbstractGlial fibrillary acidic protein (GFAP) increases in astrocytes following axotomy of facial motoneurons. In the present study we quantified GFAP synthesis both in regenerating facial nuclei after nerve crush and in nonregenerating facial nuclei after nerve resection. An increase in GFAP synthesis during regeneration occurs as early as 24 h after the axotomy. Thus, the increase in the astrocytic GFAP synthesis seems to be the earliest glial response to retrograde changes in facial motoneurons.

ISSN:0894-1491    

DOI:10.1002/glia.440010110

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

年代:1988

数据来源: WILEY

摘要:

AbstractAstrocytes derived from the mouse brain mesencephalon and striatum regulate neuronal morphogenesis in a region‐specific manner in vitro. To begin defining molecular mechanisms that may underlie this functional heterogeneity, lectin probes were used to compare surface glycoproteins expressed by astrocytes from different brain regions. These experiments demonstrated marked differences in surface glycoproteins depending on the anatomic origin of the astrocytes. In particular, mesencephalic and cerebellar astrocytes express a fucosylated glycoprotein with and apparent molecular weight of 190 kD that is absent or rarely expressed by striatal or cortical astrocytes. These findings raise the possibility that carbohydrate diversity of astrocyte surface molecules may play a role in the heterogeneity of region‐specific neuron‐glial interac

ISSN:0894-1491    

DOI:10.1002/glia.440010111

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

年代:1988

数据来源: WILEY