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Biomedical subjects

J Marchal

Publications and source records attributed to J Marchal.

35 records · Page 2Linked to original sources
PubMed1983

Functional aspects of bacterial polysomes during limited protein synthesis.

The effects of amino acid starvation on the metabolic behavior of polysomes and the size distribution of proteins have been studied in an otherwise isogenic pair of stringent (relA+) and relaxed (relA) strains of Escherichia coli. The stability of polysomes has been analyzed by using two different approaches. First, the process of their degradation has been followed after treating the cells with rifampicin, an inhibitor of the synthesis of all classes of RNA including messenger RNA. Secondly, the process of their assembly has been studied after their previous conversion to monosomes, as induced by glucose deprivation of cells. It is shown that, in either type of bacterial strain, polysomes are continually broken down and re-synthesized during amino acid starvation. However, such polysome turnover is then less rapid than in normally growing bacteria and, moreover, it seems amino acid specific since it occurs at a lower rate during arginine starvation than during histidine starvation, namely, in the relaxed strain. The molecular weight distribution of proteins has been determined after labeling of cells with radioactive methionine and separation of polypeptides by one-dimensional polyacrylamide gel electrophoresis. The average size of polypeptides synthesized in the stringent strain during starvation is quite similar to that measured during normal growth. By contrast, a significant shift towards smaller molecules is observed in the relaxed strain deprived of an essential amino acid. Here again, this reduction of the size of polypeptides seems amino acid specific since it is especially marked during arginine starvation. These results are discussed in terms of ribosomes translocation and premature peptide chain termination in connection with the accuracy of the translational process.

Bacterial Proteins↗
PubMed1983

[Curable asystole in an adult caused by a diffuse and complete arteriovenous aneurysm of the liver. Cure by ligation of the hepatic artery].

A case of cardiac failure in a 54 year old man with a diffuse total arteriovenous aneurysm of the liver is reported. The aneurysm was arteriolarvenous, without a wide bore localised fistula. It occupied the whole hepatic mass, including the territories of the right subphrenic and anterior collateral of the gastroduodenal artery. The cause of cardiac failure was the elevated cardiac output, 15 1/min, which fell to 6 1/min at each peroperative occlusion of the hepatic artery. After ligature of this vessel, the cardiac output stabilised at 9 1/min and remained at this value 4 months after surgical cure. This case is comparable to the neonatal cardiac failure due to multinodular hepatic angioma with respect to the clinical, angiographic and CAT scan characteristics, and the surgical cure of the high cardiac output syndrome. Some of the histological features were suggestive, in places, of the structure of hepatic cavernoma, which makes the exact pathological classification of this diffuse aneurysm difficult; the closest possibility being an involuted from of diffuse capillary hemangioma of childhood allowing such long survival and, occasionally taking on the appearances of a cavernoma. Permanent surgical cure by ligature of the hepatic artery was an additional rare feature of this case.

Age Factors↗
PubMed1980

[Level of polysomes in cells of Escherichia coli treated with sublethal doses of aminoglycosides].

Polysome level was measured in Escherichia coli cells grown in the presence of sublethal doses of four different aminoglycosides which all induce mistranslation: streptomycin, neomycin, kanamycin and gentamycin. No significant variation was noticed as referred to the level of polysomes in normally growing cells. This observation indicates that the erroneous incorporation of amino acids into polypeptide chains does not necessarily result in the release of ribosomes from messenger RNA molecules.

Aminoglycosides↗
PubMedDate not supplied

Cloning in cattle: from embryo splitting to somatic nuclear transfer.

The ability to obtain genetically identical offspring in cattle (clones) is useful for research and for potential applications to breeding schemes. Experimental possibilities for generating such animals have evolved considerably in the last two decades. Embryo splitting has become a relatively simple technique but is limited to twinning. Embryonic nuclear transfer has improved and is associated with sexing to generate sets of clones despite a great variability of results between parent embryos. The factors of progress are reviewed here. Recently, somatic cells used as a source of nuclei in bovine nuclear transfer has been demonstrated. Here we present the results of the developmental potential of nuclei from skin and muscle cells.

Animals↗
PubMedDate not supplied

Cytotoxic properties of a phosphoglycoconjugated derivative of 7 beta-hydroxycholesterol upon normal and tumor cells in culture.

The cytotoxic activity of a new hydrosoluble axysterol derivative, a phosphoric acid diester of 7 beta-hydroxycholesterol (7 beta-OHC, one of the most toxic oxysterol) and of galactose has been evaluated using cultured tumor cells of various origins, and compared with 7 beta-OHC. As its parent compound, XG-142 exhibits a significant cytotoxic activity against all the cell lines tested, but the IC50's were higher than those obtained with 7 beta-OHC. Moreover, the cytotoxicity was slower to appear than after a 7 beta-OHC treatment. Cell phase distribution was analysed, and revealed some differences between the two compounds. Both oxysterols induced apoptosis at micromolar concentrations, as evidenced by several methods including agarose gel electrophoresis of fragmented DNA and flow cytometry of propidium iodide labeled cells. Apoptosis was also obtained when 7 beta-OHC and XG-142 were combined at concentrations unable to induce this type of cell death when used separately. Upon normal murine spleen cells, XG-142 was found to be less toxic than 7 beta-OHC, and the capacity to respond to Con A stimulation was preserved. Therefore, XG-142 can be considered as a promising soluble analogue of 7 beta-OHC, and its application as anticancer agent should be considered.

Animals↗
PubMedDate not supplied

Assessment of apoptosis occurring in spleen cells from nitrogen mustard-treated or gamma-irradiated mice.

The short-term consequences on spleen cells of the intraperitoneal administration of nitrogen mustard (HN-2) to mice or of a whole-body gamma irradiation have been evaluated. Experiments were designed to assess the induction of apoptosis in spleen cells following exposure to these agents. The occurrence of this type of cell death was analysed by several methods, in particular the quantification in the blood of phosphotidylserine-bearing microparticles shed by apoptotic cells. In response to HN-2 or radiations, spleens undergo a rapid involution of their weight and cellularity. Ex vivo apoptosis occurs within 24 hours in cultured lymphocytes in a dose-dependent manner after both treatments. As compared with untreated controls, circulating microparticles increased 3-fold after the injection of 5 mg/kg of HN-2.

Animals↗