Search PubMed⌕ Search

Biomedical subjects

M Brahic

Publications and source records attributed to M Brahic.

At least 91 records · Page 5Linked to original sources
PubMed1986

Theiler's virus genome is closely related to that of encephalomyocarditis virus, the prototype cardiovirus.

Theiler's virus causes a persistent demyelinating infection of the mouse central nervous system. Our study of the molecular mechanism of persistence led us to sequence 1925 nucleotides located at the 3' end of the viral genome. We observed extensive homologies between this region and the corresponding region of encephalomyocarditis virus, the prototype cardiovirus, and only some homologies with the 3' ends of foot-and-mouth disease virus, rhinovirus, and poliovirus genomes.

Amino Acid Sequence↗
PubMed1985

Theiler's virus RNA and protein synthesis in the central nervous system of demyelinating mice.

We studied Theiler's virus RNA and capsid protein synthesis in sections of mouse spinal cord using in situ hybridization coupled to immunoperoxidase. We found that the majority of infected cells contain 100 to 500 viral genomes and no detectable capsid antigens. Similarly, baby hamster kidney (BHK) cells, which are permissive to Theiler's virus, do not synthesize capsid if they contain less than 1000 viral genomes. Our results demonstrate that virus multiplication is restricted in vivo at the level of RNA replication. They suggest that RNA restriction is sufficient to explain the lack of capsid antigen synthesis.

Animals↗
PubMed1985

Combined macroscopic and microscopic detection of viral genes in tissues.

A hybridization technique has been devised for detecting and quantitating viral genes in tissues that combines macroscopic and microscopic analyses in the same section. The method is based on dual labeling virus-specific probes with 125I and 35S to generate signals that can be detected both with X-ray films and nuclear track emulsions. The regions of increased hybridization evident in the X-ray film serve as a guide to the portion of the section that warrants microscopic examination. Detection of viral RNA in tissues with visna virus and viral DNA with hepatitis B virus are illustrated, and potential applications of this technique in virology and other disciplines are discussed.

Animals↗
PubMed1985

Detection of two viral genomes in single cells by double-label hybridization in situ and color microradioautography.

Double labeling and color microradioautography were used in a new method of hybridization in situ to identify different genes in individual cells. The method is based on the unequal penetration of 3H and 35S into two layers of nuclear track emulsion separated by a thin barrier film. Hybridization of a 35S-labeled probe specific for one kind of gene results in silver grains over cells in both layers of emulsion; a 3H-labeled probe for a second gene provides grains only in the first layer of emulsion. Silver grains are converted to magenta-colored grains in the first layer and to cyan-colored grains in the second to facilitate enumeration of grains in each layer. This technique should be widely applicable in analyses of differential gene expression in single cells or in discrete populations of cells.

Autoradiography↗
PubMed1985

Detection of picornavirus sequences in nervous tissue of amyotrophic lateral sclerosis and control patients.

We used in situ hybridization to look for picornavirus ribonucleic acid (RNA) sequences in frozen sections of central nervous system (CNS) tissue of amyotrophic lateral sclerosis (ALS) and control patients. Using reconstruction experiments, we concluded that 30 copies of viral RNA per cell could be detected with the assay. RNA which hybridized to DNAs complementary (cDNAs) to both poliovirus and Theiler's virus was found at several levels in the CNS of 2 patients, 1 ALS patient, and 1 control. In transverse sections of the spinal cord, these sequences predominated in cells of the anterior horns. We assessed the specificity of hybridization by several criteria: no hybridization was observed with heterologous visna virus cDNA probes; hybridization was abolished by pretreatment of the sections with ribonuclease; chemography artifacts were ruled out; and the results were reproduced in three independent experiments. We concluded that RNA molecules, possibly belonging to a picornavirus having sequences in common with poliovirus and Theiler's virus, were present in the CNS of these 2 patients. On the other hand, 14 cases of classic ALS, 2 cases of Guamanian parkinsonian dementia, and 5 controls had negative results. However, the presence of picornavirus sequences in our series could be underestimated because in many cases autolysis times were 10 hours or longer.

Amyotrophic Lateral Sclerosis↗
PubMed1985

[Apropos of a family with Huntington's chorea].

The observed cases deal with six generations. The penetrance is there complete and the male diseases more frequent. The fifth generation shows infantile and youth disease that proceed from fatherly transmission during several generations. The anticipation is discussed, as well as possible genetic counselling and the psychological effects upon mothers.

Adolescent↗
PubMed1984

Simultaneous in situ detection of viral RNA and antigens.

We have combined in situ hybridization and immunocytochemistry to detect RNA and proteins in the same cell. We envision a wide range of applications for this method, and, as one example, we show that viral genomes and capsid antigens can be detected simultaneously in paraffin sections of the central nervous system of mice infected with Theiler's virus, the causative agent of a slow demyelinating disease.

Animals↗
PubMed1982

Detection of tissue culture-adapted Theiler's virus RNA in spinal cord white matter cells throughout infection.

The appearance of histological lesions and the localization of viral RNA in the central nervous system of mice infected with tissue culture-adapted Theiler's murine encephalomyelitis virus (WW strain) (TMEV-WW) was studied. Viral RNA was detected by autoradiography after in situ hybridization, using a (3)H-labeled DNA probe complementary to virion RNA, which was applied to deparaffinized sections of central nervous system tissues from infected mice. Subjacent histological sections of tissues were used to assess the location and extent of lesions. Lesions were first observed at 20 days post-inoculation and appeared to enlarge throughout infection. They consisted of infiltrates of mononuclear cells and lymphocytes in spinal cord white matter and leptomeninges; at 78 days post-inoculation severe necrotizing and demyelinative myelitis and gliosis were observed. In contrast to the pathogenesis of brain-derived TMEV-WW-infected mice, no lesions were found in the central nervous system gray matter of mice infected with tissue culture-adapted TMEV-WW at any time post-infection. Tissue culture-adapted viral RNA was found in the cells of spinal cord white matter throughout infection; only one neuron in close proximity to the injection site was found to contain viral RNA shortly after infection. At early times after infection, spinal cord white matter cells containing viral RNA were found before development of inflammatory lesions; at later days post-inoculation, positive cells were found within, at the periphery of, or at a distance from lesions. The number of infected cells and the amount of viral RNA per cell appeared to remain constant from 20 to 78 days post-inoculation despite the increasing intensity of the inflammatory response. The nearly exclusive spinal cord white matter tropism of tissue culture-adapted TMEV-WW appeared to directly correlate with the disease-inducing potential of this virus.

Animals↗
PubMed1981

Gene expression in visna virus infection in sheep.

Visna is a slow degenerative disease of the central nervous system (CNS) of sheep caused by a nontumorigenic retrovirus. During the course of this disease, visna virus establishes a persistent infection of the CNS, lung and haematopoietic system, despite a specific humoral and cellular immune response. We have studied visna virus life cycle at the single-cell level in choroid plexus of experimentally infected animals, using a very sensitive and quantitative in situ hybridization assay. We report here that although proviral DNA is synthesized in significant amounts, its expression is blocked at the transcriptional level. This restriction of proviral DNA transcription offers an explanation for the slowness of the disease and the persistence of the infection.

Animals↗
PubMed1981

Theiler's virus persists in glial cells during demyelinating disease.

Theiler's murine encephalomyelitis virus (T-MuEV) is the agent of a persistent, demyelinating infection of the central nervous system of mice, T-MuEV RNA was detected in histological sections of brain and spinal cord of experimentally infected animals by in situ hybridization. Both neurons and glial cells contained viral RNA during the early acute phase of the disease, The amount of viral RNA in neurons, however, was considerably higher than in glial cells. During the late demyelinating phase of the disease, viral RNA was found in low amounts only in glial cells of the white matter of spinal cord. At that stage, no viral RNA was found in neurons. These results demonstrate that T-MuEV persists in glial cells of the white matter. A reconstruction of the pathogenesis of this persistent infection is proposed, based on the different levels of virus replication in neurons and glial cells.

Animals↗
PubMed1981

Persistence and expression of Marek's disease virus DNA in tumour cells and peripheral nerves studied by in situ hybridization.

We have used cloned fragments of Marek's disease virus (MDV) DNA and in situ hybridization to search for virus DNA and study its expression in infected chick embryo fibroblasts (CEF), lymphoblastoid cell lines, tumours and neural lesions. DNA from the HPRS 16/att strain of MDV was cleaved with EcoRI endonuclease and several fragments were cloned in Escherichia coli using the vector PBR322. Seven fragments ranging in size from 2.6 to 11 kbp representing approx. 25% of the MDV genome were labelled in vitro and annealed to EcoRI digests of DNA from infected cells and tumours following separation and transfer according to the Southern blotting procedure. Most of the selected MDV DNA fragments hybridized to fragments of corresponding sizes in EcoRI digests of DNA from cell lines and tumours and failed to hybridize to digests of uninfected chick cell DNA. In situ hydridization using 3H-labelled DNA with specific activity of 10(8) d/min/microgram as probe showed intranuclear MDV DNA in infected CEF, in every cell of two lymphoblastoid cell lines and in the majority of infiltrating or proliferating lymphoid cells found in type 'A' lesions of grossly enlarged peripheral nerves. Both intranuclear and cytoplasmic RNA were detected in cells that contained virus DNA. However, comparatively little virus RNA appears to be transcribed in cell lines and in infected tissues from the regions of virus DNA (25% of genome) used as probe in this study. Our results favour the hypothesis that the accumulation of lymphoid cells in nerves is not the result of an inflammatory response to infected nerve cells but is rather the consequence of proliferating transformed cells.

Animals↗
PubMed1981

Detection of Theiler's virus RNA in mouse central nervous system by in situ hybridization.

The location and distribution of viral RNA were examined in the central nervous system tissues of weanling mice acutely infected with the GDVII strain of Theiler's murine encephalomyelitis virus. Viral RNA was detected by autoradiography following in situ hybridization of a 3H-labeled DNA synthesized in vitro complementary to purified viral RNA. Viral RNA was detected in pyramidal neurons of the hippocampus, cerebral cortex, brainstem nuclei, thalamus, basal ganglia, and spinal cord. Autoradiographic grains could be detected in the axonal and dendritic processes of many infected neurons. No viral RNA was detected in any cell of the cerebellum or white matter. In addition to demonstrating the location of viral RNA in infected central nervous system tissues, and hence the sites of viral replication during this acute polioencephalomyelitis, they indicate that necrosis of hippocampal neurons is due to lytic infection, rather than to hypoxia.

Animals↗
PubMed1979

Characterization of visna virus mRNA.

Visna virus is a retrovirus responsible for a classical slow infection of the central nervous system of sheep. In the present work we focused our attention on the viral mRNA's. We found that, during the acute infection in vitro, (i) viral mRNA's amount to only 0.1% of the total cytoplasmic RNA, (ii) 20% of the total cytoplasmic viral RNA is found in polyribosomes, and (iii) three viral mRNA's can be identified by sucrose gradient sedimentation or polyacrylamide gel electrophoresis. Their sedimentation coefficients are 36S, 27S, and 21S.

Animals↗
PubMed1978

Detection of viral sequences of low reiteration frequency by in situ hybridization.

The sensitivity of in situ hybridization has been increased at least 10-fold by hybridizing in cDNA excess, by increasing the diffusion of the cDNA through the cells, by hybridizing at optimum temperature, and by stabilizing hybrids during autoradiography. Saturation of intracellular RNA with [3H]cDNA has been achieved. The assay is quantitative. In situ hybridization has been used to detect and quantitate visna virus RNA in infected cells. By using [3H]cDNA with specific activity of 2 X 10(8) dpm/micrograms and conditions that reduce background to negligible levels, 10--20 copies of viral RNA per cell can be detected and quantitated after 2 days of autoradiographic exposure.

Animals↗
PubMed1978

Absence of circularly permuted and largely redundant sequences in the genome of visna virus.

A previous study of the infectivity of visna virus proviral DNA suggested that the genetic information of the virus is distributed over at least two of the RNA subunits. Because the genetic complexity of visna virus corresponds to the size of one subunit, this result may imply that sequence redundancies exist within each subunit. In the present article we have examined this question by constructing a map of the large RNase T1-resistant oligonucleotides of the viral genome. Our principal results are as follows: (i) all 36S RNA subunits have the same genetic content regardless of their polyadenylic acid [poly(A)] content; (ii) the poly(A) tract is present at the 3' end of the molecule; and (iii) the recoveries of 19 large RNase T1-resistant oligonucleotides from poly(A)-tagged RNA fragments of various sizes demonstrate that the oligonucleotides are organized in the same linear order within all subunits. Our results, therefore, exclude the existence of large sequence redundancies in the genome of visna virus.

Base Sequence↗
PubMed1977

Complexity and polyadenylic acid content of visna virus 60-70S RNA.

The genomic complexity of visna virus was measured by quantitative analysis of 18 RNase T1-resistant oligonucleotides from 60-70S RNA. T1-resistant oligonucleotides were separated by two-dimensional polyacrylamide gel electrophoresis. Visna virus had a genomic complexity of 3.6 X 10(6) daltons, very close to the size of a single 30-40S RNA subunit. It was therefore concluded that the visna virus genome is largely polyploid. Visna virus 60-70S RNA polyadenylic acid segment was purified by T1 RNase digestion followed by oligodeoxythymidylic acid-cellulose column chromatography. It contained over 99% AMP and had a size of about 200 nucleotides. The binding capacities on oligodeoxythymidylic acid-cellulose of native 60-70S RNA and purified 30-40S RNA subunits were examined. It was concluded that two out of three intact subunits contain a polyadenylic acid segment.

Avian Sarcoma Viruses↗