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Biomedical subjects

Y Lorch

Publications and source records attributed to Y Lorch.

27 records · Page 2Linked to original sources
PubMed1987

Fractionation of Theiler's virus-infected BHK21 cell homogenates: isolation of virus-induced membranes.

A purified fraction containing unique membranes entrapping virions was isolated from homogenates of cells infected with the DA strain of Theiler's virus, after high-speed centrifugation through a sucrose gradient. This fraction, sedimented at 45-50% sucrose, was only found in cells infected with the DA strain but not in cells infected with the GDVII strain of Theiler's virus or in mock-infected cells. Immunogold staining of the membranes entrapping virions, using antivirus IgG antibodies, revealed that the membranes entrapping virions did not incorporate viral capsid antigens.

Animals↗
PubMed1987

Monoclonal anti-I-A antibody reverses chronic paralysis and demyelination in Theiler's virus-infected mice: critical importance of timing of treatment.

Susceptibility to demyelination caused by the WW isolate of Theiler's murine encephalomyelitis viruses is linked to class II genes of the major histocompatibility complex. SJL/J (H-2s) mice, expressing only I-As class II gene products of the major histocompatibility complex, are highly susceptible to Theiler's murine encephalomyelitis virus infection with the WW virus isolate, with chronic paralysis and severe inflammation and demyelination in the central nervous system. The effect of in vivo administration of anti-I-As monoclonal antibodies on Theiler's murine encephalomyelitis virus infection was observed. SJL/J mice were treated in various protocols pre- or postinfection. Anti-I-As monoclonal antibody reversed chronic paralysis and reduced inflammation and demyelination when given after the establishment of persistent infection. The effect was long lasting, but clinical signs, inflammation, and demyelination recurred 2 months after treatment ceased. Anti-I-As antibodies had no effect on viral titers within the central nervous system. The timing of the administration of monoclonal antibodies was critical. Administration of anti-I-As before the establishment of the persistent infection resulted in fatal encephalitis.

Animals↗
PubMed1985

A region flanking the GAL7 gene and a binding site for GAL4 protein as upstream activating sequences in yeast.

A region of DNA 116 to 271 base-pairs upstream from the GAL7 gene of Saccharomyces cerevisiae activates transcription from a heterologous promoter and does so in either orientation, showing that the GAL7 upstream region contains an upstream activating sequence (UAS). The level of transcription obtained with two GAL7 UAS's in tandem was only 1.3 times that with one. Previous studies of the GAL1-GAL10 intergenic region were indicative of two binding sites for the GAL4 positive regulatory protein; we find that a single (synthetic) site is capable of gene activation. The level of transcription obtained with the intact GAL1-GAL10 UAS was five times that with the single site.

Base Sequence↗
PubMed1984

Electron microscopic study of the development of Theiler's murine encephalomyelitis viruses propagated in vitro.

The changes occurring in the nuclei and cytoplasms of BHK21 cells during infection with the two subgroups of Theiler's murine encephalomyelitis viruses were studied by electron microscopy. The nuclear alterations include: formation of clumps and margination of chromatin, enlargement of perinuclear spaces, deformation and displacement of the nucleus. The cytoplasmic alterations include: increase in the number of ribosomes, extensive proliferation of smooth membranes at the centrosphere of infected cells, appearance of electron-dense bodies, and decrease in number and swelling of mitochondria. At late stages of infection, GDVII and FA viruses which represent the virulent subgroup, form crystalline arrays in the cytoplasm of infected cells. A few mechanisms by which these crystals may be formed are discussed. The later stages of TO viruses infection, which cause a persistent infection in mice, differed markedly from those of GDVII and FA viruses. TO viruses were found to be arranged in a single file between two sheets of membranes. A model for this unique structure is presented.

Animals↗
PubMed1984

Persistent and acute central nervous system infections are caused by Theiler's murine encephalomyelitis viruses which differ in RNA composition but code for only slightly different proteins.

The RNA and proteins for four representatives of the two subgroups of Theiler's murine encephalomyelitis viruses were studied. The large RNase T1-resistant oligonucleotides, when mapped along the RNA molecules, were found to be differently distributed in the two subgroups. Replicative form RNAs of two representatives were partially denatured, and the denaturation maps obtained were found to be similar but not identical. In addition, the analysis of the tryptic maps of the capsid proteins of all four isolates revealed that only small differences in the peptide map patterns exist among these viruses. The correlation of these findings with the pathogenicity of Theiler's viruses is discussed.

Animals↗
PubMed1983

Proteins induced in tissue culture by four isolates of Theiler's murine encephalomyelitis virus.

The proteins specified by four Theiler's murine encephalomyelitis virus isolates in infected BHK-21 cells were studied. Their processing, sensitivity to trypsin, and the changeover after viral infection from synthesis of cellular proteins to synthesis of viral proteins were determined by one- and two-dimensional gel electrophoreses. The molecular weights and isoelectric points of the structural and nonstructural proteins of DA and WW isolates, which represent the less virulent subgroup of Theiler's murine encephalomyelitis virus, and of GDVII and FA isolates, which represent the virulent subgroup, were found to be the same. The sensitivity of DA and GDVII isolates to trypsin, as purified virions, and in infected cell extracts was similar. The shut-off of cellular protein synthesis in cells infected with the same two isolates and the changeover to the synthesis of viral proteins appeared to have the same pattern. These findings are interesting since the two subgroups of Theiler's murine encephalomyelitis virus differ in their pathogenicity, intracellular development in infected BHK-21 cells, and RNA composition, as determined by RNase T1 fingerprinting analysis.

Animals↗
PubMed1983

GDVII and DA isolates of Theiler's virus: proteins attached to the 5' end of the RNA are bound covalently to the same nucleotides.

GDVII and DA picornaviruses, which represent two biologically distinct subgroups of Theiler's murine encephalomyelitis viruses, were analyzed to detect the presence of a RNA-linked protein, VPg. It was found that the single-stranded RNA genomes isolated from the virions of both viruses contain a protein of approximately 7,000 daltons, which is covalently linked to the 5' end of the RNA. Like in other picornaviruses (e.g., poliovirus and encephalomyocarditis virus), the terminal nucleotide adjacent to the protein was found to be pUp. The possibility that differently charged VPg species exist is also mentioned.

Base Sequence↗
PubMed1981

Theiler's murine encephalomyelitis virus group includes two distinct genetic subgroups that differ pathologically and biologically.

The intracellular development and RNA composition of Theiler's murine encephalomyelitis virus (TMEV) isolates were determined by electron microscopy, sucrose gradient centrifugation, and RNase T1 fingerprinting. Replication of FA virus, a virulent strain of TMEV, was characterized by the appearance of viral crystalline arrays in the cytoplasm of infected cells. In contrast, cells infected with the less virulent isolates (WW, TO4, BeAn 8386, and Yale) showed no crystalline arrays; instead, virions were found to be arranged between two layers of membranes in the cytoplasm of infected cells. Analysis of the RNAs of TMEV isolates showed that the RNAs were single-stranded molecules having sedimentation coefficients of 35S. RNase T1 fingerprinting of TMEV RNA revealed that striking differences between the virulent and less virulent TMEV isolates existed. Moreover, base composition analysis of RNase T1-resistant oligonucleotides of two TMEV isolates which represented the two subgroups indicated that there were no substantial oligonucleotides common to both subgroups. Based on these findings and the known difference in virulence, we suggest that the TMEV group contains two genetically district subgroups of viruses.

Animals↗