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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 11 (1999), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Entorhinal cortex lesion of adult rats induces glial activation and proliferation in the deafferented dentate molecular layer. Double-labelling immunocytochemistry for the astrocyte-specific antigen glial fibrillary acidic protein or the microglial cell marker Griffonia simplicifolia isolectin B4 with bromodeoxyuridine detection revealed that microglia counts and the proliferation rate in the ipsilateral dentate gyrus reached a maximum in the molecular layer at 3 days post-lesion (dpl) and returned to control levels by 30 dpl. Astrocyte counts in the ipsilateral dentate gyrus peaked at 30 dpl, with maximum proliferation at 7 dpl. At 100 dpl the astrocyte count had reverted to control levels. Glial proliferation was not restricted to the ipsilateral molecular layer but also occurred to some degree in the granule cell layer and the contralateral dentate gyrus. Thus entorhinal cortex lesion induces a rapid microglia reaction and long-lasting astrocyte activation in the deafferented termination zone of the perforant path. We conclude that glial proliferation after entorhinal cortex lesion follows a complex temporal and spatial pattern that coincides with processes of neuronal and axonal reorganization.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 9 (1997), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Microglial cells with their characteristic ramified morphology are exclusively found in healthy CNS tissue, whereas various pathologies are associated with the occurrence of amoeboid, macrophage-like cells. It is still a matter of discussion whether amoeboid cells are blood-derived macrophages, or whether a characteristic change in morphology, reflecting activation of previously ramified microglia, takes place. Cells in dissociated microglia culture obtained from healthy rat brains, inevitably developing this amoeboid morphology, were labelled with a fluorescent dye and transferred onto organotypic hippocampal slice cultures. Prelabelled cells with amoeboid morphology invaded these slice cultures and had, after 9 days in vitro, gradually transformed into highly ramified cells. Our findings strengthen the hypothesis that the observed amoeboid and ramified cells belong to a single population of microglia, appearing with different morphologies depending on the presence of stimuli provided by the CNS microenvironment. Microglial cells obviously appear in different shapes and can switch from immunologically resting to activated modes and vice versa.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In this study we investigated whether treatment with the immunosuppressant mycophenolate mofetil (MMF) has beneficial effects on neuronal damage after excitotoxic injury. Organotypic hippocampal slice culture (OHSC), lesioned by the application of N-methyl-d-aspartate (NMDA) after 6 days in vitro, showed an improved preservation of the hippocampal cytoarchitecture after continuous treatment with MMF for 3 further days (10 or 100 µg/mL). Treatment with NMDA and MMF (100 µg/mL) reduced the number of damaged propidium iodide (PI)+ neurons by 50.7% and the number of microglial cells by 52%. Continuous treatment of lesioned OHSCs with MMF for 3 days almost abrogated the glial proliferative response, reflected by the 91.5% reduction in the number of bromo-desoxy-uridine (BrdU)-labelled microglial cells and astrocytes. Microglial cells in MMF-treated OHSCs contained fragmented nuclei, indicating apoptotic cell death, an effect which was also found in isolated microglial cells treated with MMF. The beneficial effect of MMF on neuronal survival apparently does not reflect a direct antiexcitotoxic effect, as short-term treatment of OHSCs with NMDA and MMF for 4 h did not reduce the number of PI+ neurons. In conclusion, MMF inhibits proliferation and activation of microglia and astrocytes and protects neurons after excitotoxic injury.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The aim of this study was to analyse microglial reactions to excitotoxic N-methyl-d-aspartic acid (NMDA)-induced degeneration of rat dentate and hippocampal neurons in vitro. We used a migration model combining the techniques of microglial single cell culture and organotypic hippocampal slice culture (OHSC). Site-specific oxidative damage in OHSCs was induced by pretreatment with 50 μm NMDA. Neuronal injury determined by propidium iodide (PI) uptake included the hippocampal cell layers of the dentate gyrus (DG) and the cornu ammonis (CA). Fluorescence-prelabelled microglial cells with ameboid morphology were transferred onto the OHSC and migrated predominantly to the prelesioned cell layers of DG and CA when compared with unlesioned areas of the OHSC. In NMDA pretreated slices, microglial cells clustered around degenerating granule cells in the DG and pyramidal cells in the CA. This effect was significantly inhibited in unlesioned slice cultures and in NMDA-exposed cultures that were pretreated with the NMDA-antagonist MK-801. Our observations suggest that microglia – attracted by the presence of stimuli provided by NMDA-induced neuronal death – migrate specifically towards these lesioned neurons.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Acute CNS lesions lead to neuronal injury and a parallel glial activation that is accompanied by the release of neurotoxic substances. The extent of the original neuronal damage can therefore be potentiated in a process called secondary damage. As astrocytes are known to secrete immunomodulatory and neuroprotective substances, we investigated whether astrocytic factors can attenuate the amount of neuronal injury as well as the degree of microglial activation in a model of excitotoxic neurodegeneration. Treatment of organotypic hippocampal slice cultures with N-methyl-d-aspartate (NMDA) resulted in a reproducible loss of viable granule cells, partial destruction of the regular hippocampal cytoarchitecture and a concomitant accumulation of amoeboid microglial cells at sites of neuronal damage. Astrocyte-conditioned media reduced the amount of NMDA-induced neuronal injury by 45.3%, diminished the degree of microglial activation and resulted in an improved preservation of the hippocampal cytoarchitecture. Transforming growth factor (TGF)-β failed to act as a neuroprotectant and even enhanced the amount of neuronal injury by 52.5%. Direct effects of astrocytic factors on isolated microglial cells consisted of increased microglial ramification and down-regulated expression of intercellular adhesion molecule-1, whereas incubation with TGF-β had no such effects. In summary, our findings show that hitherto unidentified astrocyte-derived factors that are probably not identical with TGF-β can substantially enhance neuronal survival, either by eliciting direct neuroprotective effects or by modulating the microglial response to neuronal injury.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 11 (1999), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Morphological, immunophenotypical and electrophysiological properties were investigated in isolated cultured murine microglia before and after exposure to astrocyte-conditioned medium (ACM). Following application of ACM, microglial cells underwent a dramatic shape transformation from an amoeboid appearance to a ramified morphology. In parallel to morphological changes, a downregulation of macrophage surface antigens was observed in microglia exposed to ACM. Staining intensities for major histocompatibility complex (MHC) class II molecules and for the adhesion molecules leukocyte function-associated antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1) were significantly decreased in ramified microglia 5 days after exposure to ACM. In microglial cells treated daily with ACM over a period of 5 days, the smallest staining intensities for all surface antigens as well as the smallest ramification index as a measure for the highest degree of ramification were determined. In addition, upregulation of delayed rectifier K +  currents was observed in microglia exposed to ACM for 1 day or treated daily with ACM for 5 days. In contrast, untreated amoeboid microglia or ramified microglia analysed 5 days after exposure to ACM did not express delayed rectifier K +  currents. Analyses of the resting membrane potential and expression levels and properties of inward rectifier K +  currents did not reveal any differences between untreated and ACM-treated microglia. It is suggested that electrophysiological properties of microglia do not strongly correlate with the morphology or the immunophenotype of microglial cells.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The effects of interleukin (IL)-1β and IL-1 receptor antagonist (IL-1ra) on neurons and microglial cells were investigated in organotypic hippocampal slice cultures (OHSCs). OHSCs obtained from rats were excitotoxically lesioned after 6 days in vitro by application of N-methyl-d-aspartate (NMDA) and treated with IL-1β (6 ng/mL) or IL-1ra (40, 100 or 500 ng/mL) for up to 10 days. OHSCs were then analysed by bright field microscopy after hematoxylin staining and confocal laser scanning microscopy after labeling of damaged neurons with propidium iodide (PI) and fluorescent staining of microglial cells. The specificity of PI labeling of damaged neurons was validated by triple staining with neuronal and glial markers and it was observed that PI accumulated in damaged neurons only but not in microglial cells or astrocytes. Treatment of unlesioned OHSCs with IL-1β did not induce neuronal damage but caused an increase in the number of microglial cells. NMDA lesioning alone resulted in a massive increase in the number of microglial cells and degenerating neurons. Treatment of NMDA-lesioned OHSCs with IL-1β exacerbated neuronal cell death and further enhanced microglial cell numbers. Treatment of NMDA-lesioned cultures with IL-1ra significantly attenuated NMDA-induced neuronal damage and reduced the number of microglial cells, whereas application of IL-1ra in unlesioned OHSCs did not induce significant changes in either cell population. Our findings indicate that: (i) IL-1β directly affects the central nervous system and acts independently of infiltrating hematogenous cells; (ii) IL-1β induces microglial activation but is not neurotoxic per se; (iii) IL-1β enhances excitotoxic neuronal damage and microglial activation and (iv) IL-1ra, even when applied for only 4 h, reduces neuronal cell death and the number of microglial cells after excitotoxic damage.
    Type of Medium: Electronic Resource
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