摘要:

AbstractWe studied the distribution of voltage‐gated Ca2+channels in cells of the oligodendrocyte lineage from retinal and cortical cultures. Influx Of ca2+via voltagegated channels was activated by membrane depolarization with elevated extracellular K+concentration ([K+]e) and local, subcellular increases in cytosolic free Ca2+concentration ([Ca2+]in) could be monitored with a fluometric system connected to a laser scanning confocal microscope. In glial precursor cells from both retina and cortex, small depolarizations (with 10 or 20 mM K+) activated Ca2+transients in processes indicating the presence of low‐voltage‐activated Ca2+channels. Larger depolarizations (with 50 mM K+) additionally activated high‐voltage‐activated Ca2+channels in the soma. An uneven distribution of Ca2+channels was also observed in the mature oligodendrocytes; Ca2+trasients in processes were considerably larger. Recovery of Ca2+levels after the voltage‐induced influx was achieved by the activity of the plasmalemmal Ca2+pump, while mitochondria played a minor role to restore2+levels after an influx through voltageoperated channels. During the development of white matter tracts, cells of the oligodendrocyte lineage contact axons to form myelin. Neuronal activity is accompanied by increases in [K+]e; this may lead to Ca2+changes in the processes and the Ca2+increase might be a signal for the glial precursor cell to start myelin formation. © 1995 Wil

ISSN:0894-1491    

DOI:10.1002/glia.440130102

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

年代:1995

数据来源: WILEY

摘要:

AbstractA recent study has shown that ramified microglia in the adult rat optic nerve express the ganglioside GD3[Wolswijk Glia 10:244–249, 1994], thereby raising the possibility that some GD3+in the developing rat central nervous system (CNS) belong to the microglial lineage rather than to the oligodendrocyte lineage, as previously thought. To examine this possibility, sections of postnatal and adult cerebellum were doublelabelled with markers for rat microglia [the B4isolectin derived fromGriffonia simplicifolia(GSI‐B4), the ED1 monoclonal antibody (mAb), and the OX‐42 mAb] and anti‐GD3mAbs (the mAbs R24 and LB1). These immunolabellings showed that ramified microglia as well as amoeboid microglia are strongly GD3+in vivo. Moreover, most, if not all, cells that express high levels of GD3in sections of developing cerebellum appear to belong to the microglial lineage. These observations contradict previous suggestions that the strongly GD3+cells in the putative white matter regions of the developing brain are oligodendrocyte‐type‐2 astrocyte (0–2A) progenitor cells; the cells that give rise to oligodendrocytes in the CNS. The present study did, however, confirm that some 0–2A progenitor cells in sections of postnatal cerebellum are weakly GD3+in vivo. Amoeboid microglia are present in areas of the developing cerebellum where newly generated oligodendrocytes are found, suggesting that these cells play a role in the phagocytosis of the large numbers of oligodendrocytes that die as part of CNS development. © 1995

ISSN:0894-1491    

DOI:10.1002/glia.440130103

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

年代:1995

数据来源: WILEY

摘要:

AbstractSchwann cells freshly isolated from the sciatic nerves of neonatal rats respond to exogenously applied ATP with a rapid increase in cytosolic calcium. This increase in [Ca2+]i is mediated by a P2Y‐purinergic pathway (Lyons et al.: J. Neurochem. 63:552–560, 1994) and was measured using the calcium indicator dye, fura‐2/AM, and a video‐enhanced calcium imaging system. The ability to respond to ATP with increases in intracellular calcium is lost over a period of several days in culture; this loss can be prevented or reversed by application of cAMP analogs in a defined medium. We now demonstrate that the direct contact of Schwann cells with neurons also induces and stabilizes this ATP responsiveness. The induction of ATP responsiveness was observed among all Schwann cells contacting neurites, including those forming myelin, and regardless of whether the source of neurons was dorsal root ganglion neurons or superior cervical ganglion neurons. Approximately 85% of Schwann cells responded to ATP over the time studied (72 d in coculture). Addition of axolemma to Schwann cell cultures did not induce ATP responsiveness. We also examined the ATP responsiveness of Schwann cells in situ (excised nerves) using laser‐scanning confocal microscopy and the calcium indicator dye, fluo‐3/AM. Schwann cells in intact sciatic nerve segments isolated from neonatal and 16–day‐old rats exhibited ATP‐mediated [Ca2+]i increases. We conclude that neuronal contact is necessary for the expression of the ATP‐mediated calcium responses in Schwann cells and that these responses are independent of myelin formation or maintenance. Copy 1

ISSN:0894-1491    

DOI:10.1002/glia.440130104

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe in vitro properties of the CG4 cell line have led to its increasing use as a cell line with which to study the behaviour of the O‐2A progenitor cell. In this study we have examined the in vivo behaviour of the CG4 cell line following transplantation into areas of adult rat spinal cord white matter which have been permanently depleted of glial cells by the combination of local X‐irradiation and direct injection of 0.1% ethidium bromide. Twenty‐one days after transplantation, both myelin‐forming oligodendrocytes and glial fibrillary acidic protein‐positive astrocytes were identified within the lesion, indicating that the CG4 cell line has bipotential differentiation properties when introduced into a pathological environment consisting of demyelinated axons but devoid of oligodendrocytes or astrocytes. In this respect, the CG4 cell line resembles other glial progenitor cell lines that have been transplanted into similar lesions. In some areas of the lesion, remyelination was observed that was similar in extent to that achieved by growth factor‐expanded populations of O‐2A progenitor cells. The transplant origin of the cell types within the lesion was confirmed by retroviral incorporation of thelacZmarker gene, the expression of which allowed their identification by histochemistry. In conclusion, the in vivo properties of the CG4 cell line make it a highly suitable line with which to study the behaviour of O‐2A progenitors following transplantation into normal and damaged CNS. © 1995

ISSN:0894-1491    

DOI:10.1002/glia.440130105

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

年代:1995

数据来源: WILEY

摘要:

AbstractActivated microglia may contribute to two opposite effects during inflammation within the central nervous system: host defense against microorganisms and neuronal injury. Each of these processes may be mediated by the generation of reactive oxygen intermediates by activated microglia. We investigated the effects of two proinflammatory cytokines, interferon (IFN)‐β and tumor necrosis factor (TNF)‐α, and of the anti‐inflammatory cytokine, transforming growth factor (TGF)‐β, on murine microglial cell superoxide (O2) production upon stimulation with phorbol myristate acetate (PMA). Priming of microglia with IFN‐β or TNF‐α resulted in a dose‐dependent enhancement of O2release in response to PMA. The priming effects of these two cytokines were additive, suggesting that they acted by independent mechanisms. We also found that IFN‐β and TNF‐β stimulated the release of bioactive TGF‐β and that treatment of microglial cell cultures with TGF‐β antagonized the priming effects of IFN‐β and TNF‐α on O2production. The results of this study have implications for understanding the mechanisms by which cytokines and microglia may contribute to host defense as well as to injury

ISSN:0894-1491    

DOI:10.1002/glia.440130106

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

年代:1995

数据来源: WILEY

摘要:

AbstractN‐ethyl‐N‐nitrosourea (ENU)‐induced gliomas, animal models of human gliomas, are most frequently oligodendrocytic, while human gliomas tend to be astrocytic. To facilitate a detailed study of human glial carcinogenesis, we developed an in vitro system using type 1 astrocyte transformation with ENU. Type 1 astrocytes from fetal Wistar rat brain were treated by a single dose of ENU. Transformed colonies appeared 50 days after exposure to single doses of ENU greater than 150 μg/mL. Cloned cells from these colonies retained the immunohistochemical characteristics of type 1 astrocytes. They showed rapid growth and high saturation densities, colony formation in low (2%) serum medium and gave rise to tumors when injected into nude mice. When p53expression was studied at each passage, a single cell positive for mutant p53protein emerged 40 days after ENU treatment. In the next 1–3 passages, the mutant p53positive cell formed piled‐up colonies and exhibited dominant growth. Northern blot analysis showed markedly increased accumulations of p53mRNA in transformed cells. This in vitro transformation system of type 1 astrocytes provides a valuable tool for further investigations of astrocyte carcinogenesis. © 1995 Wi

ISSN:0894-1491    

DOI:10.1002/glia.440130107

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

年代:1995

数据来源: WILEY

摘要:

AbstractAttachment sites and biological functions of laminin isolated from murine EHS sarcoma have been well studied. Recently several variants of laminin including human placental laminin have been shown to be distinct from EHS‐laminin. This study was undertaken to determine attachment, proliferation, and migration phenomena of human astrocytoma cell lines to human and murine sarcoma EHS‐laminin. Using short‐term attachment assays human placental laminin was shown to be the better substrate for cell adhesion. EHS‐laminin mediated approximately 30–50% of the effect observed on human laminin. The astrocytoma cells expressed β1, β3, and β4 subunit mRNA as determined by RT‐PCR. Anti‐β antibodies blocked adhesion to EHS‐laminin, but antibodies against β1, β4, and αvsubunits were all ineffective in blocking adhesion to human laminin. A migration assay showed that astrocytoma cells on human laminin dispersed from a central seeding area, while cells on EHS‐laminin remained where they were seeded. The pattern of dispersion could not be accounted for by changes in growth rates of astrocytoma cells on the different proteins, since both cell lines grew equally well on the two laminins. We conclude that unique epitopes on human laminin are recognized by novel receptors on human astrocytoma cells which confer a migratory phenotype to the cells

ISSN:0894-1491    

DOI:10.1002/glia.440130108

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe transforming growth factors type β (TGF‐β) have been implicated in regulation of peripheral nervous system inflammation and regeneration. Here we demonstrate expression of a TGF‐β‐related bone morphogenetic protein, the vgr (BMP‐6, DVR‐6) in Schwann cells of the rat peripheral nervous system. The expression of vgr in the peripheral nervous system suggests that this factor and probably other TGF‐β‐related bone morphogenetic proteins might participate in Schwann cell function during aspects of peripheral nervous system physiology and pathology. However, we did not observe changes in expression patterns in response to autoimmune inflammation (experimental autoimmune neuritis) of the peripheral nervous system. © 19

ISSN:0894-1491    

DOI:10.1002/glia.440130109

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

年代:1995

数据来源: WILEY

ISSN:0894-1491    

DOI:10.1002/glia.440130101

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

年代:1995

数据来源: WILEY