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Biomedical subjects

M Canivet

Publications and source records attributed to M Canivet.

At least 19 recordsLinked to original sources
PubMed1992

Human spumaretrovirus-related sequences in the DNA of leukocytes from patients with Graves disease.

Viruses, and more particularly retroviruses, have been postulated to play a role in the pathogenesis of autoimmune diseases. In a search for spumaretrovirus infection markers, we screened a group of 29 patients with Graves disease and a representative healthy population (23 subjects) as a control. Southern blot hybridization under stringent conditions, of patients' DNA extracted from peripheral blood lymphocytes, with a spumaretrovirus-specific genomic probe derived from the human spumaretrovirus (HSRV) prototype, gave a positive signal in 10 cases. Moreover, by PCR, HSRV-related sequences were detected in the DNA of 19 patients (66%). Positive DNA samples in Southern blots were also positive in PCR for all regions tested (gag, bel1, bel2, long terminal repeat). Amplified (gag and bel2) products were cloned and sequenced; they showed high homology with HSRV. On the other hand, all 23 control subjects were negative by both procedures. Sera from both populations were examined for the presence of antibodies reactive with antigens of the spumaretrovirus family. These sera were negative by several immunodetection techniques: ELISA, indirect immunofluorescence, serum neutralization, and Western blotting. These results strongly suggest the existence of an association between Graves disease and the presence of HSRV-related infection markers.

Animals↗
PubMed1992

Circulating interferon in cytomegalovirus infected bone-marrow-transplant recipients and in infants with congenital cytomegalovirus disease.

In a study concerning five CMV-infected bone-marrow-transplant recipients, five congenital CMV diseases and appropriate controls, presence of high levels of circulating interferon (IFN) was demonstrated exclusively during the course of CMV disease. This interferon was predominantly "immune" or gamma interferon (gamma-IFN). These results suggest that during CMV disease the interferon compartment of the immune response is modified.

Anemia, Aplastic↗
PubMed1991

Further characterization of the gapped DNA intermediates of human spumavirus: evidence for a dual initiation of plus-strand DNA synthesis.

We recently reported the presence of linear duplex DNA intermediates with a gap in the middle of the molecules in the replicative cycle of human (HSRV) and simian (SFV1) spumaviruses. The polypurine tract (PPT), at the 5' boundary of the 3' long terminal repeat, was found to be duplicated in the gap region. By molecular analysis of HSRV proviral DNA with region- and strand-specific probes, we have now determined that the gap is located on plus-strand DNA and that it is 120 bases long with the 3' end mapping at the duplicated PPT site. Kinetic analysis of proviral DNA provided evidence that the gap did not result from processing of a complete, full-length DNA molecule. These data strongly suggest that plus-strand DNA synthesis is initiated at both PPT sites.

Base Sequence↗
PubMed1990

Replication of HIV-1 in a wide variety of animal cells following phenotypic mixing with murine retroviruses.

Human T cells co-infected with the human immunodeficiency virus type 1 (HIV-1) and the xenotropic or dual-tropic mouse type C virus (MuLV) give rise, by phenotypic mixing, to progeny virus that can transfer HIV-1 into a wide variety of mammalian and avian cells. Differences in the extent of HIV-1 replication in these animal cells can be observed. Replication is best in human cells, but occurs substantially in cells from many animal species including mink, horse, and bush wallaby. Virus production in murine and avian cells is very limited. These results confirm that the major block to HIV-1 infection of animal cells is at the cellular surface but that intracellular regulation of viral replication is also involved. Moreover, an enhancement of HIV-1 cytopathic effects can be seen in human cells co-infected by MuLV. All these data suggest phenotypically mixed viruses might be useful for developing an animal model system for studying AIDS, and that the pathological expression of HIV-1 could be modified by the presence in cells of other retroviruses. They also indicate a potential mechanism by which HIV strains can be generated with an increased ability to spread in nature.

Acquired Immunodeficiency Syndrome↗
PubMed1990

In vitro induction of early mouse embryo intracisternal particles (epsilon particles) in cultured cell lines.

The experimental induction of epsilon particles, retrovirus-like structures corresponding to the small IA particles of the mouse, was studied by electron microscopy in rodent-cultured cell lines. Among the chemicals tested, only IdUr was shown to be an effective inducer, but not cycloheximide, puromycin , deoxy-fluorouracil or 5-azacytidine. However, only two mouse-derived cell lines: Ki-BALB and FG 10, among 27 cell lines of mouse, rat and mink origins tested, expressed epsilon particles upon IdUr treatment. Epsilon particles thus respond to chemical inducers very differently in comparison with large IAP. Moreover, the addition of interferon previously shown to attenuate IAP production, had no effect on that of epsilon particles.

Animals↗
PubMed1989

Electron microscopic characterisation of retrovirus and retrovirus-like particles induced by demethylating agents (5-azacytidine and 5-azadeoxycytidine) in Syrian hamster (Mesocricetus auratus) cells.

In a framework of a study on retrovirus expression in Syrian hamster (mesocricetus auratus), three cell lines were examined by electron microscopy. As we had previously demonstrated the efficacy of demethylating drug in activating the formation of retroviral particles, we used 5-azacytidine to activate endogenous retrovirus expression. Proceeding to a more detailed survey we were able to observe various types of retrovirions. All of them were present in the different activated cell lines. They were: intracisternal R-type particles (IRP), intracisternal A-type particles (IAP), intracytoplasmic A-type particle (ICAP), intramitochondrial A-type particle (IMAP) and M-432 virus-like particles. Some of these particles have never been described before in Syrian hamster cells. The significance of their presence is discussed here.

Animals↗
PubMed1988

Evidence for a gapped linear duplex DNA intermediate in the replicative cycle of human and simian spumaviruses.

Two forms of linear DNAs have been found in simian (SFV1) and human (HSRV) spumaviruses: a linear duplex unsensitive to nuclease S1 and a sensitive structure with a single-stranded gap. Two nuclease S1 sensitive sites, mapping at the same position for both viruses, have been identified in the gapped structure. Using different molecular subgenomic clones of HSRV as probes in Southern blot analysis, one S1 site was localized in the 3'LTR and the other near the middle of the molecule at about 6.5 kbp from the 5' end of the viral genome. The latter site was shown to correspond to a single stranded region within the linear duplex DNA. Nucleotide sequence analysis revealed that the polypurine tract (PPT) usually found at the 5' boundary of the 3'LTR of retroviruses, is duplicated in HSRV at the 3' end of the pol gene, near the gap. This suggests that the synthesis of plus strand DNA is discontinuous, generating the gap.

Animals↗
PubMed1988

Dexamethasone stimulates expression of transposable type A intracisternal retroviruslike genes in mouse (Mus musculus) cells.

Dexamethasone treatment enhances expression of transposable intracisternal type A particles (IAP) at RNA and proteins levels in a murine retrovirus-transformed cell line (Ki-BALB). This effect was ascertained by electron microscopic numeration of IAP. By sequence comparison, we located glucocorticoid-responsive elements in IAP long terminal repeats. Their regulatory potential was tested on the promoter activity of an IAP long terminal repeat construct coupled with the chloramphenicol acetyltransferase gene. Our findings suggest that the IAP activation by dexamethasone occurs at the level of transcription.

Animals↗
PubMed1987

Interferon inducibility and sensitivity of human teratocarcinoma-derived cell lines.

Three cell lines tera I, tera II, and PA1, derived from human teratocarcinomas were tested for their capacity to produce interferon (IFN) and for their sensitivity to both human IFN-alpha and IFN-beta. When treated with Newcastle disease virus or Sendai virus, or a synthetic polyribonucleotide, poly(rI):poly(rC), tera I cells produced no IFN and the 2',5'-oligoadenylate (2-5A) synthetase enzymatic pathway was not activated, although there was an increase in protein kinase. In contrast, tera II and PA1 cells produced IFN and both enzymatic activities were detected. IFN treatment has no effect on the growth of any of the cell lines. Tera I and PA1 cells did not develop resistance to challenge with vesicular stomatitis virus or encephalomyocarditis virus, but the growth of a type-C baboon retrovirus was inhibited. Tera II cells were protected against all three viruses. It appears that human teratocarcinoma cell lines can thus differ greatly in their ability to produce IFN and to respond to it.

2',5'-Oligoadenylate Synthetase↗
PubMed1986

Simultaneous activation by 5-azacytidine of intracisternal R particles and murine intracisternal-A particle related sequences in Syrian hamster cells.

5-Azacytidine treatment of Syrian hamster (Mesocricetus auratus) cells, BHK21-cl.13, and primary embryo fibroblasts, activates the production of intracisternal type R particles (IRP) as ascertained by electron microscopy scanning and counting. Efficiency of the activation is dose- and time of treatment-dependent. The transcription of mouse intracisternal A particle (IAP) related sequences, which have been described in Syrian hamster genomic DNA, is increased at the same time. This correlates with demethylation of hamster IAP related genes, as shown by restriction of high molecular weight DNA from 5-azacytidine treated cells with methylation sensitive enzymes, and subsequent electrophoresis and molecular hybridization of the fragments with specific DNA probes. In 5-azacytidine treated cells derived from other hamster species (Cricetulus griseus and C. migratorius), intracisternal R particles were not induced, nor were mouse IAP-related RNAs detected.

Animals↗
PubMed1985

The interferon compartment of the immune response in human malaria: II. Presence of serum-interferon gamma following the acute attack.

The present study concerns the monitoring of serum-interferon (serum-IFN) levels among 189 patients followed after and sometimes during an acute episode of malaria due mainly to Plasmodium falciparum (P. falciparum). Of these patients, 110 known to have no other parasitic or infectious disease were followed in France; 79 were from Thailand, among which 25 cases of neuromalaria were diagnosed. In a first four-month survey conducted in France, among 100 patients seen after the acute attack, serum-IFN-gamma was characterized among 87% cases for which at least two sera were controlled, whereas in a healthy population no serum-IFN was present. When efforts were concentrated on screening ten cases during the first 48 h of the febrile attack, serum-IFN-alpha was mainly characterized, whereas serum-IFN-gamma was present only once. Elevated leukocyte 2',5' oligoadenylate synthetase levels were found among several IFN-alpha positive patients of this study group. A peculiarity pertaining to the patients from Thailand was that one-third (25 cases) were cerebral malaria cases. Among these, 15 were followed under hospitalization during the first 96 h. In this study group, the onset of circulating immune interferon was found to be preceded or accompanied by that of IFN-alpha. Thus, if serum-IFN-gamma is largely characterized among malaria patients followed after the acute attack, it is possible that the onset of circulating immune interferon is generally preceded by that of IFN-alpha.

2',5'-Oligoadenylate Synthetase↗
PubMed1985

Interferon-mediated regulation of myc and Ki-ras oncogene expression in long-term-treated murine viral transformed cells.

Long-term treatment of a murine retroviral-transformed cell line (Ki-Balb) with 50 units/ml of interferon (IFN) resulted in a morphological reversion. The effects of IFN on myc and Ki-ras oncogene expression were examined after 6 months of treatment. mRNA dot and Northern blots hybridization analysis reveal that the expression of c-myc at the RNA level decreases by about fourfold. This reduction in the c-myc mRNA appears to be selective since in the same cells v-Ki-ras and an endogenous retroviral gene, intracisternal A particles (IAP), are increased four- and threefold, respectively. No significant inhibition of cellular growth and cell-cycle distribution was observed in IFN-Ki-Balb-treated cells.

Animals↗
PubMed1984

Regulation of intracisternal A particles in mouse teratocarcinoma cells: involvement of DNA methylation in transcriptional control.

The methylation state of Intracisternal A Particle (IAP) genes in mouse teratocarcinoma cell lines has been investigated as an approach to study the regulation of the expression of these particles. Treatment of the cells with the methylation inhibitor 5-azacytidine induces the production of the particles in all the cells; the induction is particularly striking in an embryonal carcinoma cell line which is normally devoid of IAPs. The induction is accompanied by decrease in DNA methylation as demonstrated by using the methylation sensitive isoschizomer enzymes MspI and HpaII. Hypomethylation of the IAP genes correlates with accumulation of IAP, specific polyadenylated RNA reinforcing the hypothesis that methylation plays an important role in the control of IAP expression.

Animals↗
PubMed1983

Activation of intracisternal a particles by 5-azacytidine in mouse Ki-BALB cell line.

5-Azacytidine activates the production of intracisternal A particles (IAPs) in mouse Ki-BALB cell line as ascertained by electron microscopy scanning and numeration. Efficiency of the activation is higher than that obtained with iododeoxyuridine. The increase in particle production is concentration and time dependent. The results obtained in our system correlate the high IAP expression after drug treatment with a demethylation of IAP-related genes sequences.

Animals↗
PubMed1983

Circulating interferon in cytomegalovirus infected bone-marrow-transplant recipients and in infants with congenital cytomegalovirus disease.

In a study concerning five CMV-infected bone-marrow-transplant recipients, five congenital CMV diseases and appropriate controls, presence of high levels of circulating interferon (IFN) was demonstrated exclusively during the course of CMV disease. This interferon was predominantly "immune" or gamma interferon (gamma-IFN). These results suggest that during CMV disease the interferon compartment of the immune response is modified.

Adult↗
PubMed1983

Effect of human interferon on type D retroviruses multiplication in chronically infected cell lines.

A study was made on the effect of human interferon (HuIFN) on the synthesis and release of type D viruses (MPMV and SMRV) by chronically infected human lines. Interferon at concentrations of 50 IU/ml lead to an inhibition of the extracellular virus production by about 50%-80% as measured by virus-associated reverse transcriptase activity, by metabolic labeling of the virus with (3H) uridine or (3H) amino acids, or by electron microscopy counting of particles. The profiles of intracellular viral proteins, as visualized by radioimmunoprecipitation and electrophoresis, were not different in control or IFN-treated cells and the yield of intracellular protein p27 stayed unchanged or was slightly increased. Electron microscopy of thin sections taken from the control and IFN-treated cells revealed no difference in any subcellular structures including that of the viruses. However, electron microscopic examination of IFN-treated cells showed an increased number of either budding particles and intracytoplasmic precursors (two- to five-fold) or mature virus particles (four- to ten-fold) on the cell surface of the IFN-treated cells. These results indicate that IFN inhibits further developments of MPMV and SMRV replication as was described for type C and B retroviruses.

Animals↗