摘要:

AbstractWe employed two microelectrode current‐clamp and voltage‐clamp methods to examine the modulation of Ca++channels by norepinephrine and cyclic AMP (cAMP) in cultured astrocytes from the rat cerebral cortex. Currents owing to Ca++channels were maximized by replacing Ca++with Ba++in the extracellular solution and pharmacologically blocking K+and Na+currents. In current‐clamp experiments, we observed that norepinephrine, isoproternol (an agonist of β‐receptors for norepinephrine), or dibutyryl cAMP (dbcAMP, a membrane permeant analogue of cAMP) induced or enhanced slow Ba++‐dependent action potentials in the cells. In voltage‐clamp experiments, we confirmed that the slow action potentials were generated by a voltage‐activated and Ba++‐dependent inward current. This current was mediated by channels that resembled L‐type calcium channels (cf. McCleskey et al.,Journal of Experimental Biology124:177–190, 1986) in their voltage‐activation range, slow inactivation, and sensitivity to blockage by Co++, Cd++, and nifedipine. DbcAMP, or isoproterenol, enhanced the Ba++current. Modulation of Ca++channel function in glial cells could have f

ISSN:0894-1491    

DOI:10.1002/glia.440010602

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

年代:1988

数据来源: WILEY

摘要:

AbstractLactate released into the surrounding salt solution as well as the cellular lactate content were measured in cerebral primary cultures of mouse astrocytes and of mouse neurons. Any newly produced lactate was immediately released as lactic acid into the extracellular compartment via a lactate/proton cotransport. The astrocytic release was about 2,000 nmol × mg−1× hr−1; the neuronal release was about 300 nmol × mg−1× hr−1. However, if election transport was blocked with dinitrophenol, the neuronal lactate release was as high as the astrocytic one under normal conditions. High glucose (30 mM) and K+(60 mM) increased lactate release of astrocytes but not of neurons. In contrast it was found that insulin (1 μM) exposure mainly stimulated neuronal lactate release rather than glial release. Adenosine stimulated both neuronal and glial release. Neither intracellular lactate content nor concentration changed significantly in either cell type under any conditions tested. The pathophysiological implications of these measurements a

ISSN:0894-1491    

DOI:10.1002/glia.440010603

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

年代:1988

数据来源: WILEY

摘要:

AbstractLactic acid can permeate plasma membranes, causing intracellular acidosis. Gap junctions are sensitive to pHiand can be reversibly uncoupled by weak acids. In this study, dye coupling between in vitro astrocytes, presumably mediated by gap junctions, was measured in the absence and presence of lactic acid. Fluorescence recovery after laser photobleaching (gap‐FRAP analysis) was used to measure dye coupling. Astrocytes bathed in Eagle's minimum essential medium (EMEM) with lactic acid, pHo5.5–6, showed no difference in their dye coupling (mean recovery of fluorescence 30%) when compared to control astrocytes (mean recovery of fluorescence 26%). However, 24 mM lactic acid in EMEM, pHo4.5, decreased dye coupling (mean recovery of fluorescence 2.0%). This effect occurred within 5 min of treatment. When lactic acid‐EMEM, pH 4.5, was removed from astrocytes after 30 min and the cells were incubated in EMEM for 24 hr, decreased coupling was not reversed (mean recovery 4.0%). When lactic acid‐treated astrocytes were incubated in EMEM for 48 hr, the mean recovery of fluorescence increased to 15% (i.e., 42% of the recovery seen in controls). These observations suggest that brief exposure to high concentrations of lactic acid can have immediate and long‐lasting effects on glial gap junctional communication. Under pathological circumstances, such a sequence could be intiated, and this might impair astrocytic control of the central nervous system microenvironment mediated by spatial

ISSN:0894-1491    

DOI:10.1002/glia.440010604

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

年代:1988

数据来源: WILEY

摘要:

AbstractMany types of glial‐neuronal interactions occur during the development of the nervous system. To determine how such interactions might affect the development of autonomic ganglia, we compared the morphology of embryonic rat sympathetic neurons grown in the absence and in the presence of ganglionic nonneuronal cells in serum‐free medium. Dye injections, electron microscopy, and immunocytochemistry were used to distinguish axons from dendrites. In cultures without nonneuronal cells, most (<80%) sympathetic neurons extended only a single axonal process, and this unipolar state persisted for at least 8 weeks. Coculture with ganglionic nonneuronal cells caused sympathetic neurons to become multipolar and to extend multiple (range 1–17) dendrites. Morphometric measurements made after 1 month of coculture indicated that the amount of dendritic growth that occurred in vitro (mean number of dendrites/cell = 7.5; total dendritic length = 1,050 μm) was similar to that normally occurring during a comparable period in situ. In contrast to its prominent effects on dendritic growth, coculture did not cause chages in the number of axons/neuron or in the uptake of neurotransmitter. Cultures with ganglionic nonneuronal cells were immunostained for antigens present on the surfaces of fibroblasts (Thy‐1.1, fibronectin) and of glia of the peripheral nervous system (laminin). Fewer than 1% of the nonneuronal cells displayed immunoreactivity for fibroblastic antigens; in contrast, ≥99% reacted with antibody to laminin. Moreover, reconstitution experiments revealed that purified populations of laminin‐positive Schwann cells promoted dendritic growth. Fibroblasts and heart cells lacked this activity. These data indicate that glia selectively promote dendritic development in sympathetic neurons maintained in serum

ISSN:0894-1491    

DOI:10.1002/glia.440010605

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

年代:1988

数据来源: WILEY

摘要:

AbstractDopamine (D1) receptors were demonstrated to be present on astroglial cells from striatum in primary culture. In a cocultivation system, the astrocytes were influenced by neurons from one of their natural projection areas (substantia nigra) to increase the efficacy and potency of second messenger (cyclic AMP) from the dopamine receptor. This provides evidence for a heterogeneity among astroglia from the various brain regions with respect to the expression of receptors.

ISSN:0894-1491    

DOI:10.1002/glia.440010606

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe possible relation betweeen glial fibers and the formation of longitudinal granule cell migration patterns that occur in the cerebellar anlage of the chicken was investigated by immunocytochemistry of vimentin (monoclonal antibody) and glial fibrillary acidic protein (polyclonal antibody against GFAP, PGF) on fixed and unfixed brain tissues. In addition, neuronal development was studied with a monoclonal antibody for neurofilament. Vimentin was present in radial and tangential fibers in the cerebellar anlage during granule cell migration in almost all parts of the anlage. However, no specific topographic relation of vimentin and GFAP to the migration pattern of granule cells was observed. In adults, Bergmann fibers and astroglia were stained with vimentin antiserum and not with GFAP antiserum. Conclusions are that radial fibers do not determine the formation of longitudinal cytoarchitectonic patterns in the chick cerebellum and that vimentin is the main cytoskeletal component of Bergmann fibers and astroglial cells in embryonic and adult chicken cerebellum.

ISSN:0894-1491    

DOI:10.1002/glia.440010607

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

年代:1988

数据来源: WILEY

摘要:

AbstractEnriched preparations of oligodendrocytes, isolated either from adult bovine brain or from 30‐day‐old rat brain, eventually yield cultures in MEM‐15% calf serum that contain, in addition to oligodendrocytes, proliferating astrocytes and variable numbers of fibroblast‐like cells. If these cultures are switched to a serum‐free defined medium during the 1st week, mixed cultures containing only oligodendrocytes and astrocytes are obtained. Bovine cultures can be replated and purified by selective adhesion to yield cultures that are<99% astrocytes; similar procedures were not successful with rat cultures. Cytoskeletal preparations of the purified astrocyte cultures from mature bovine brain contain both vimentin and glial fibrillary acidic protein (GFAP), but vimentin is by far the major intermediate filament protein. Thus, the intermediate filament composition of these astrocytes is similar to that of astrocytes in primary cultures obtained from neonatal rat brain. Immunofluorescent studies of these cultures at 24 hr in vitro show that there are no GFAP+ cells in cultures of either species; the bovine cultures contain<95% GC+ cells; and the rat cultures contain 90% GC+ cells. After a few days in vitro flat cells appear that are vimentin+/GFAP–/GC–. In serum‐free medium these cells eventually become vimentin+/GFAP+. We propose that the astrocytes that grow in these cultures arise from a population of glial precursor cells, which are present even in adult brain and are isolated together with oligodendroglia, and that they do not derive from contaminating mature astrocytes. Thus, the astrocytes in our cultures may have the same origin as astrocytes grown in culture from dissociated

ISSN:0894-1491    

DOI:10.1002/glia.440010608

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

年代:1988

数据来源: WILEY

摘要:

AbstractIn the present study we have analyzed the membrane currents of mature oligodendrocytes in cultures from dissociated fetal mouse cerebral hemispheres and explant cultures from fetal mouse spinal cord. Both types of oligodendrocytes showed large voltage‐dependent, but time‐independent inward and outward currents that were partially blocked by Ba2+. In addition, time‐ and voltage‐dependent inward and outward currents were observed in a minority of oligodendrocytes from spinal cord. All voltage‐dependent currents were completely blocked by Ba2+, and inward currents were completely blocked by Cs+, suggesting that they are mediated by K+channels. Current‐voltage curves of mouse spinal cord oligodendrocytes varied from being linear to outwardly or inwardly rectifying. In contrast, oligodendrocytes cultured from mouse brain always showed an inward rectification of the current voltage relation and a lack of time‐dependent currents. It thus appears that mature oligodendrocytes in explant cultures of mouse spinal cord, in contrast to oligodendrocytes from dissociated brain, consist of different cell populations that are distinguished by their expression by their expression or active state

ISSN:0894-1491    

DOI:10.1002/glia.440010609

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

年代:1988

数据来源: WILEY

ISSN:0894-1491    

DOI:10.1002/glia.440010601

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

年代:1988

数据来源: WILEY