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Biomedical subjects

M Cornet

Publications and source records attributed to M Cornet.

At least 55 records · Page 3Linked to original sources
PubMed1992

[Description of a tissue culture technique using tissue from mussel (Mytilus edulis) for the preparation of chromosomes].

Explants from mantle and foot tissues of adult mussel were grown in culture tubes containing a medium composed of Eagle's Basal Medium supplemented with salts, Hepes buffer, egg yolk and antibiotics. The cultures were maintained at 18 degrees C and pH 7.50, without medium renewal. After 6-7 days, the cultures were stopped and harvested for slide preparation. Numerous metaphase spreads that were good enough for karyotyping were consistently obtained. This method may prove to be a reliable source of actively dividing cells that is a prerequisite for extensive chromosome structure analyses in the bivalves.

Animals↗
PubMed1991

In vitro biotransformation of 2-methylpropene (isobutene): epoxide formation in mice liver.

Until now, no data are available concerning the biotransformation and toxicity of 2-methylpropene (or isobutene), a gaseous alkene widely used in industry (rubber, fuel additives, plastic polymers, adhesives, antioxidants). In this work, the biotransformation of 2-methylpropene (MP) has been studied, using total liver homogenates of mice, supplemented with a NADPH-generating system. In analogy to other olefins, 2-methylpropene is metabolized to its epoxide 2-methyl-1,2-epoxypropane (MEP), as proved by the identification by gas chromatography coupled with mass spectrometry. The epoxidation is cytochrome P-450 dependent, as shown by experiments in the absence of the NADPH-generating system and in the presence of various concentrations of metyrapone and SKF 525-A, two known inhibitors of the mono-oxygenases. A simple gas chromatographic headspace method has been developed for the quantitative determination of the epoxide formed. The formation of MEP is never linear in function of time and it reaches a maximum after 20 min. Thereafter is decreases continuously to undetectable levels. This observation can be explained by the immediate action of epoxide hydrolase and glutathione S-transferase, converting the epoxide to 2-methyl-1,2-propanediol and to the glutathione conjugate respectively. The involvement of both enzymes has been demonstrated by the addition of 3,3,3-trichloropropene oxide and indomethacin. These inhibitors of, respectively, epoxide hydrolase and glutathione S-transferase increase the epoxide formation in a significant way. The actual concentration of MEP is therefore not only dependent on its formation by cytochrome P-450 dependent mono-oxygenases, but also on its conversion by epoxide hydrolase and glutathione S-transferase, both very active in liver tissue.

Alkenes↗
PubMed1991

Investigation of species differences in isobutene (2-methylpropene) metabolism between mice and rats.

Metabolism of isobutene (2-methylpropene) in rats (Sprague Dawley) and mice (B6C3F1) follows kinetics according to Michaelis-Menten. The maximal metabolic elimination rates are 340 mumol/kg/h for rats and 560 mumol/kg/h for mice. The atmospheric concentration at which Vmax/2 is reached is 1200 ppm for rats and 1800 ppm for mice. At steady state, below atmospheric concentrations of about 500 ppm the rate of metabolism of isobutene is direct proportional to its concentration. 1,1-Dimethyloxirane is formed as a primary reactive intermediate during metabolism of isobutene in rats and can be detected in the exhaled air of the animals. Under conditions of saturation of isobutene metabolism the concentration of 1,1-dimethyloxirane in the atmosphere of a closed exposure system is only about 1/15 of that observed for ethene oxide and about 1/100 of that observed for 1,2-epoxy-3-butene as intermediates in the metabolism of ethene or 1,3-butadiene.

Administration, Inhalation↗
PubMed1991

Volume regulation in rat pheochromocytoma cultured cells submitted to hypoosmotic conditions.

The mechanisms at work in cell volume regulation have been studied in PC12 cultured cells. Results show, for the first time to our knowledge, that the volume readjustment process occurring after application of a hypoosmotic saline is sensitive to amiloride, IBMX and forskoline. The process is also inhibited by quinine hydrochloride and trifluoperazine. Volume readjustment is concomtant with a decrease in K+ and Cl- intracellular levels. The decrease in K+ level can be related to an assymetrical change in the fluxes in and out of the ion as shown by flux kinetics studies using Rb86. These results are interpreted considering that the control of the activity of the ion channel pathways associated with volume readjustment in PC12 cells may implicate the Ca(2+)-calmodulin - cAMP system.

1-Methyl-3-isobutylxanthine↗
PubMed1990

Phase I and phase II xenobiotic biotransformation in cultures and co-cultures of adult rat hepatocytes.

The aim of this study was to measure the activity of phase I and II key enzymes in the biotransformation of xenobiotics and their inducibility by phenobarbital (2 mM) in two currently used in vitro models, namely adult rat hepatocytes, conventionally cultured or co-cultured with rat epithelial cells derived from primitive biliary duct cells. For phase I, the cytochrome P450 content and the enzymic activities of 7-ethoxycoumarin O-deethylase and aldrin epoxidase have been determined, for phase II glutathione S-transferase activity was measured. In conventional cultures, all phase I parameters investigated declined continuously as a function of culture time. Two mM phenobarbital had inducing effects on 7-ethoxycoumarin O-deethylase and glutathione S-transferases but not on aldrin epoxidase. In co-cultures, after an initial decrease, a steady state situation developed for all the parameters measured, lasting for at least 10 days. The cytochrome P450 content, the 7-ethoxycoumarin O-deethylase, aldrin epoxidase and glutathione S-transferase activities were maintained from 3 to 4 days on at 25, 100, 15 and 50%, respectively, of their corresponding value obtained for freshly isolated hepatocytes. After phenobarbital treatment, the parameters mentioned were significantly increased with the exception of the aldrin epoxidase activity of which the inducibility was nearly completely lost.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1988

Relations between cell volume control, microfilaments and microtubules networks in T2 and PC12 cultured cells.

The possible relations between cell volume, microfilaments and microtubules networks have been studied in cultured mice fibrosarcoma cells of line T2 and rat pheochromocytoma cells of line PC12. The obtained results show that: 1. Changes in volume induced by application of hypo-osmotic medium are concomitant with a modification in the organization of the microfilaments network as visualized by immunocytochemistry. The microtubules lattice is not affected in these conditions. 2. Disruption of the microfilaments network by cytochalasin B causes a significant decrease in cell volume in isosmotic conditions. It also deeply affects the volume regulation response of cells swollen in hypo-osmotic media. 3. Disruption of the microtubules lattice by colchicine has no effect on volume in isosmotic conditions nor on the volume regulation that follows application of hypo-osmotic shock. The possible role of microfilaments in cell volume control is discussed.

Actin Cytoskeleton↗
PubMed1986

Isolation of dengue 2 and dengue 4 viruses from patients in Senegal.

Dengue 2 and dengue 4 viruses were isolated and re-isolated by inoculation into Aedes pseudoscutellaris continuous cell line (Mos 61) and/or Toxrhynchites brevipalpis. The strain of dengue 2 had been isolated from a patient returning from Casamance (south-western Senegal) and two strains of dengue 4 from patients who lived in Dakar and had not been outside the town in the 15 days before becoming ill. Serological evidence of dengue 4 infection was found in another patient living in Casamance.

Antibodies, Viral↗
PubMed1986

[Dengue 2 in eastern Senegal: serologic survey in simian and human populations. 1974-85].

After the previously reported isolations of dengue 2 virus in eastern Senegal in 1974 and 1981-1982, a retrospective serological study on simian and human populations was carried out in the same area. We investigated 1,095 simian sera collected at regular intervals between 1974 and 1984 from wild caught monkeys and 1,783 human sera from young children less than 11 years old collected during punctual surveys after the rainy season from 1976 to 1985. Sera were tested using HAI test, CF test and for someone's ELISA for specific IgM antibodies. Serological data from monkeys corroborated the virus isolations and demonstrated the existence of two epizootics in 1974-1975 and 1981-1982. No CF antibodies were detected in children sera up to 1981 epizootic when about 11% of tested sera showed a probable infection by dengue 2 virus, no clinical dengue infections were notified by the medical staff. After 1982, serological results showed that the virus maintained in the same area until 1985. The mechanism of the circulation of dengue 2 virus in eastern Senegal is discussed on the basis of these serological results.

Animals↗
PubMed1985

Homogeneity among Senegalese strains of yellow fever virus.

A series of 16 yellow fever (YF) viruses isolated from mosquitoes, monkeys and humans in different epidemiological contexts in Senegal and The Gambia between 1976 and 1983, was analyzed by T1 RNase oligonucleotide fingerprints of the genomic 32P-labeled RNA, by SDS-polyacrylamide gel electrophoresis of the intracellular virus-specified polypeptides, by peptide mapping of the envelope E glycoprotein and by immunological reactivities with monoclonal antibody fluids (MAF's) against the E glycoprotein. These strains had not been passed in suckling mice and were isolated in Aedes pseudoscutellaris Mos 61 cultured cells. These strains showed no virulence in three-week-old Swiss mice when injected intraperitoneally. Direct comparison of the large T1 RNase-resistant oligonucleotide maps indicated a relative genetic stability (92%-100%). A greater change was observed when these strains were compared with an epidemic YF strain isolated in 1965 with an oligonucleotide fingerprint map sharing 82%-88% similarity. The YF-specified proteins were identical in their molecular weight, and the fragments obtained after limited proteolysis of the envelope protein using protease V8 or alphachymotrypsine indicated that the strains were chemically similar. Only a few differences were observed when the strains were seroneutralized with MAF's, but no relation could be made with genetic or biological data. This suggested that the YF virus strains isolated from the same geographic area and during a short period of time had evolved slowly. Moreover, all the viruses were closely related and no correlation could be established with the apparent variations in virulence in nature.

Aedes↗
PubMed1981

Seroepidemiologic studies of acute hemorrhagic conjunctivitis virus (enterovirus type 70) in West Africa. III. Studies with animal sera from Ghana and Senegal.

One hundred and thirty-nine bovine sera collected in Senegal in 1968 and 1969, before the human pandemic of acute hemorrhagic conjunctivitis (AHC), and 145 sera collected in 1977, seven years after the introduction of AHC, were tested for virus neutralizing (VN) titers against enterovirus 70 (EV70) in neutralization tests. Positive rates of VN titers (1:16) were fairly constant (about 40%) in 1968 and 1969 but the proportion of positives from the 1977 collection was significantly higher (61%). The proportion of Ghanaian bovine sera positive in 1977 (39%) was comparable with those collected earlier in Senegal but the proportion was lower in sera of calves (7%). Similar studies were performed on sheep sera collected in 1966, 1967, 1968, and 1969 in Senegal. The proportions positive and the geometric mean titers (GMTs) peaked in alternate years: the proportions were 43% and 54% in 1966 and 1968 but dropped to 12% and 5% in 1967 and 1969, respectively. The prevalence rate for Ghanaian sheep sera in 1977 was comparable to the earlier figures in Senegal. The prevalence of VN (83%) and the GMT (1:27.28) in swine sera in Ghana in 1977 were much higher than those seen in chickens and dogs. However, 87 sera of wild monkeys caught in Senegal after 1970 were negative in neutralization tests. The VN substance detected in these domestic animals was found to be 2-mercaptoethanol sensitive; hence it is considered to belong to IgM. The results seem to favor the hypothesis that enterovirus type 70 (EV70) evolved from an animal enterovirus which shares a common antigen with EV70.

Animals↗