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  • 1
    ISSN: 1432-0533
    Keywords: Canine distemper virus ; Oligodendrocytes ; Myelin gene expression ; Demyelination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Canine distemper virus (CDV) induces oligodendroglial degeneration and multifocal demyelination in the central nervous system. The mechanism of oligodendrocyte degeneration is not understood but it has been shown that there is a restricted infection of these cells without viral protein production. Using a combination of immunocytochemistry and in situ hybridization we were able to demonstrate the transcription of the entire virus genome throughout the whole observation period (7–35 days after infection) in oligodendrocytes in CDV-infected brain cell cultures. Therefore, the lack of viral protein and particle production can not be explained on the basis of a defective viral transcription. The present study also shows that a restricted infection of oligodendrocytes with CDV down-regulates the transcription of the major myelin genes coding for proteolipid protein, myelin basic protein (MBP) and myelin-associated glycoprotein in a very similar way. Using densitometry for in situ hybridization products of MBP in populations of normal and infected oligodendrocytes, an effect could be observed long before morphological changes were detectable. The present results strongly suggest that demyelination in distemper is induced by a restricted CDV infection of oligodendrocytes which down-regulates the expression of a variety of cellular genes, in particular those coding for myelin proteins. Consequently, the infected cells are no longer able to synthesize all the membrane compounds which are necessary for maintaining their structural integrity.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0533
    Keywords: Key words Canine distemper virus ; Oligodendrocytes ; Myelin gene expression ; Demyelination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Canine distemper virus (CDV) induces oligodendroglial degeneration and multifocal demyelination in the central nervous system. The mechanism of oligodendrocyte degeneration is not understood but it has been shown that there is a restricted infection of these cells without viral protein production. Using a combination of immunocytochemistry and in situ hybridization we were able to demonstrate the transcription of the entire virus genome throughout the whole observation period (7–35 days after infection) in oligodendrocytes in CDV-infected brain cell cultures. Therefore, the lack of viral protein and particle production can not be explained on the basis of a defective viral transcription. The present study also shows that a restricted infection of oligodendrocytes with CDV down-regulates the transcription of the major myelin genes coding for proteolipid protein, myelin basic protein (MBP) and myelin-associated glycoprotein in a very similar way. Using densitometry for in situ hybridization products of MBP in populations of normal and infected oligodendrocytes, an effect could be observed long before morphological changes were detectable. The present results strongly suggest that demyelination in distemper is induced by a restricted CDV infection of oligodendrocytes which down-regulates the expression of a variety of cellular genes, in particular those coding for myelin proteins. Consequently, the infected cells are no longer able to synthesize all the membrane compounds which are necessary for maintaining their structural integrity.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0533
    Keywords: Key words Canine distemper virus ; T cells ; Acute demyelination ; Immunosuppression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The initial demyelinating lesions in canine distemper virus (CDV) infection develop during a period of severe immunosuppression in the absence of inflammation. In vitro and in vivo studies suggest that early demyelination is due to directly virus-induced oligodendroglial changes. In the present spatiotemporal study in experimentally CDV-infected dogs we observed diffuse up-regulation of T cells throughout the central nervous system (CNS) and T cell invasion in early demyelinating lesions. Invasion of T cells in the CNS occurred despite severe immunosuppression and without any perivascular cuffing. However, the major fraction of invading T cells correlated with sites of viral replication and coincided with the demonstration of an early immune response against the nucleocapsid protein of CDV. Activation of microglial cells was thought to have elicited the migration of T cells to the CNS by secretion of chemokines: marked IL-8 activity was found in the CSF of dogs with acute lesions. In areas of early demyelination, large numbers of CD3+ cells accumulated in the tissue in the absence of any morphological sign of inflammation. Whether the T cells at lesion sites contribute to the development of acute demyelination remains uncertain at this stage. Antiviral cytotoxicity was not apparent since viral clearance in demyelinating lesions is only effective when B cells and concurring antiviral antibody production appeared in the subacute and chronic inflammatory stage of the disease. CD3+ cells appear to persist for several weeks after infection since they were also found in recovered dogs that did not develop demyelination. Accumulation of immune cells, including a significant proportion of resting T cells (CD45RA+) in the CNS in the early stages of the disease may facilitate the later development of the intrathecal immune response and associated immunopathological complications.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0533
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In this report we document the results of several independent studies testing the sensitivity, specificity and reliability of the Prionics Western blotting (PWB) procedure to detect bovine and ovine disease-specific, protease-resistant prion protein (PrPSc). Validation of the technique was obtained by blind analysis of samples from cattle affected with bovine spongiform encephalopathy (BSE), clinically normal animals or cattle with neurological diseases unrelated to BSE. Overall, very high sensitivity, specificity and reliability was observed. It became clear that sampling of the correct brain region and the method used for protein extraction are important factors for correct diagnosis. Furthermore, we tested the usefulness of the PWB technique as an instrument for surveillance purposes. We analyzed animals from a culling scheme as well as older animals from abattoirs to determine the number of subclinical BSE cases detectable by histopathological examination, immunohistochemistry for PrPSc and PWB. In both studies, BSE-affected animals with no overt clinical symptoms were detected. These results demonstrate the usefulness of the PWB procedure in surveillance systems serving as a rapid diagnostic tool to identify animals subclinically infected with BSE.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 95 (1997), S. 71-77 
    ISSN: 1432-0533
    Keywords: Key words Canine distemper virus ; Oligodendrocytes ; In situ hybridization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Canine distemper virus (CDV) causes a multifocal demyelinating disease in dogs. The mechanism of acute demyelination in distemper is still poorly understood. The initial demyelinating lesion in distemper is directly virus induced, since there is a clear correlation between the occurrence of demyelination and CDV replication in the cells of the white matter. Yet, there is little evidence for oligodendroglial infection. Changes of these cells have been reported in vitro and in vivo. The in vitro studies showed that – in contrast to other cells such as astrocytes and macrophages – oligodendrocytes hardly express CDV protein. However, we could show that these cells underwent a restricted infection with transcription of CDV RNA and that this phenomenon correlated with down-regulation of myelin gene transcription. The extension of these in vitro findings in vivo was obscured by the lack of reliable oligodendrocyte labelling techniques in canine brain tissue sections. In this study we combined immunohistochemistry with in situ hybridization to examine oligodendrocytes in demyelinating lesions and to investigate the question of oligodendrocyte infection in vivo. We could demonstrate that CDV infection leads to massive down-regulation of myelin gene expression in demyelinating lesions and that this effect correlates in part with a restricted infection of oligodendrocytes.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 97 (1999), S. 279-287 
    ISSN: 1432-0533
    Keywords: Key words Canine distemper virus ; Oligodendrocytes ; Apoptosis ; Necrosis ; Demyelination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Canine distemper virus (CDV) causes a multifocal demyelinating disease in dogs. It was previously shown that the initial demyelinating lesions are directly virus induced since a correlation between the occurrence of demyelination and CDV replication in white matter cells was observed. During the course of infection oligodendrocytes undergo distinct morphological alterations, partly due to a restricted CDV infection of these cells, and eventually disappear from the lesions. This phenomenon has been described in vivo as well as in vitro. However, the reason for the morphological alterations and the following oligodendroglial depletion remained unclear. Since virus infection can induce cell death, it was investigated whether apoptosis or necrosis plays a role in the pathogenesis of demyelination in canine distemper. In brain tissue sections from dogs with acute distemper apoptotic cells were not detected within the demyelinating lesions using morphological and biochemical cell death criteria. In chronic distemper, apoptotic cells – presumably inflammatory cells – were seen within the perivascular cuffs. These in vivo findings were correlated to the in vitro situation using CDV-infected primary dog brain cell cultures as well as Vero cells. Infection with culture-adapted CDV lead to massive necrosis but not to apoptosis. After infection with virulent CDV neither apoptosis nor necrosis was a predominant feature in either culture system. These findings suggest that virus-induced demyelination in canine distemper is not the direct consequence of apoptosis or necrosis. It is speculated that another mechanism must be responsible for the observed morphological alterations of oligodendrocytes, ultimately leading to demyelination.
    Type of Medium: Electronic Resource
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