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Biomedical subjects

G Coste

Publications and source records attributed to G Coste.

17 recordsLinked to original sources
PubMed2004

Mismatch repair ensures fidelity of replication and recombination in the radioresistant organism Deinococcus radiodurans.

We have characterized the mismatch repair system (MMR) of the highly radiation-resistant type strain of Deinococcus radiodurans, ATCC 13939. We show that the MMR system is functional in this organism, where it participates in ensuring the fidelity of DNA replication and recombination. The system relies on the activity of two key proteins, MutS1 and MutL, which constitute a conserved core involved in mismatch recognition. Inactivation of MutS1 or MutL resulted in a seven-fold increase in the frequency of spontaneous RifR mutagenesis and a ten-fold increase in the efficiency of integration of a donor point-mutation marker during bacterial transformation. Inactivation of the mismatch repair-associated UvrD helicase increased the level of spontaneous mutagenesis, but had no effect on marker integration--suggesting that binding of MutS1 and MutL proteins to a mismatched heteroduplex suffices to inhibit recombination between non identical (homeologous) DNAs. In contrast, inactivation of MutS2, encoded by the second mutS -related gene present in D. radiodurans, had no effect on mutagenesis or recombination. Cells devoid of MutS1 or MutL proteins were as resistant to gamma-rays, mitomycin C and UV-irradiation as wild-type bacteria, suggesting that the mismatch repair system is not essential for the reconstitution of a functional genome after DNA damage.

Amino Acid Sequence↗
PubMed2002

Quantification of RecA protein in Deinococcus radiodurans reveals involvement of RecA, but not LexA, in its regulation.

RecA protein is essential for the very high level of resistance of Deinococcus radiodurans to DNA damage induced by ionizing radiation or other DNA-damaging agents. Since the mechanism(s) involved in the control of recA expression and the extent of RecA induction following DNA damage in this species are still unclear, we have performed a genetic analysis of the recA locus and quantified the basal and induced levels of RecA protein in wild type, recA, and lexA mutants. We found that the two genes upstream of recA in the predicted cinA ligT recA operon appear to have no role in the regulation of recA expression or function, despite the fact that the reading frames in the operon overlap. By using a translational fusion of recA to a lacZ reporter gene, we showed that induction began with no delay following exposure to gamma-radiation or treatment with mitomycin, and continued at a constant rate until it reached a plateau. The induction efficiency increased linearly with inducer dose, levelling off at a concentration fourfold above the background. The basal concentration of RecA protein measured by Western blotting corresponded to approximately 11,000 monomers per cell, and the induced concentration to around 44,000 monomers per cell. These levels remained unchanged upon disruption of the lexA gene, indicating that LexA does not plays a role in recA regulation. However, inactivation of lexA caused cells to aggregate, suggesting that LexA may control the activity or expression of as yet undefined membrane functions. Cells bearing the recA670 mutation showed an elevated constitutive expression of recA in the absence of DNA damage. This phenotype did not result from the defect in DNA repair associated with the RecA670 protein, since the increased basal level of recA expression was also found in recA670/ recA(+) diploid cells that are proficient in DNA repair. These results suggest that RecA may be involved in regulating its own expression, possibly by stimulating proteolytic modification of other regulatory proteins.

Bacterial Proteins↗
PubMed2000

Potent aroma compounds of two red wine vinegars.

Gas chromatography olfactometry (GCO) was used to determine key aroma compounds of two red wine vinegars. Sensory analysis was performed to choose the best neutralization agent of acetic acid (NaOH or MgO) and to test representativeness of four extracts obtained by different methods (dichloromethane extraction, XAD-2, mixture of XAD-2 and XAD-7, and Extrelut resins extraction). Neutralization with NaOH followed by dichloromethane extraction was selected to extract volatile compounds of vinegars. Key odorant compounds were determined by GCO based on detection frequency with 13 people. In the two red wine vinegars, 13 odors were perceived by at least 70% of the panelists, and 8 compounds among the 13 were identified: acetic acid, 3-methylbutyric acid, 2-phenyl-1-ethanol, 2, 3-butanedione, butyric acid, 2-methylbutyric acid, mixture of 2- and 3-methyl-1-butanol, and two newly identified compounds in vinegar, 3-hydroxy-2-pentanone and 3-(methylthio)-1-propanal. Quantification of all the volatile compounds was performed by GC-FID, and 10 other compounds were identified for the first time in wine vinegar.

Acetic Acid↗
PubMed2000

Specific amino acid changes enhance the anti-recombination activity of the UmuD'C complex.

In addition to being an essential component of trans-lesion synthesis, the UmuD'C complex is an antagonist of RecA-mediated homologous recombination. When constitutively expressed at an elevated concentration, the UmuD'C complex sensitizes recA+ bacteria to DNA damage, whereas it has no effect on bacteria expressing a RecA [UmuR] protein that overcomes recombination inhibition. Using as a genetic screen enhanced cell killing on mitomycin plates, we isolated novel umuD' and umuC mutations that restored mitomycin sensitivity to recA D112G [UmuR] bacteria overproducing the UmuD'C complex. The mutations were named [Rin++] because a characterization in a recA+ as well in a recA D112G background showed that they enhanced UmuD'C-promoted recombination inhibition in two assays, conjugational recombination and recombinational repair of palindrome-containing DNA. The [Rin++] mutations affect five amino acids, G25D, S28T, P29L, E35K, and T95R, in UmuD' and seven, F10L, Y270C, K277E, F287L, F287S, K342Q and F351I, in UmuC. These amino acids might play a key role in the UmuD'C anti-recombination activity. None of the [Rin++] mutations enhanced UmuD'C-promoted mutagenic bypass of UV lesions, in contrast, several lead to a defect in this process. In this study, we discuss a few molecular mechanisms that could account for the recombination and mutagenesis phenotypes of a mutant UmuD'C [Rin++] complex.

Amino Acids↗
PubMed1995

[Conformal radiation therapy. Fédération nationale des centres de lutte contre le cancer (FNCLCC)].

The authors present the summary of a workshop of a group of radiation oncologists and radiation physicists on three dimensional treatment planning and conformal radiation therapy with multileaf collimator. It appears that this technic must be considered as experimental and that it cannot be promoted in all radiotherapy departments without scientific and clinical evaluation.

Evaluation Studies as Topic↗
PubMed1989

[A case of parathyroid adenoma localized in the middle mediastinum].

The discovery of a parathyroid adenoma in the middle mediastinum is exceptional and fewer than 10 cases have been reported. On the basis of a new case, the authors propose several pathogenic hypotheses: this adenoma develops and/or migrates from the fourth branchial pouch. Preoperative imaging is very useful for guiding the operation via sternotomy. The absence of any CT signs in the present case caused us to explore the retro-aortico-caval region. Sternotomies performed for the treatment of primary hyperparathyroidism are unsuccessful in one third of patients. In more than 30% of cases, the cause for this failure is related to the persistence of a cervical adenoma: when the pathological gland is actually located in the mediastinum, the possibility of middle mediastinal ectopia should be considered when investigation of the classical sites in the neck and mediastinum remains negative.

Adenoma↗
PubMed1987

Cloning and characterization of the immunity region of phage phi 80.

The immunity region of phage phi 80 has been localized. It codes for at least three proteins: a protein of 34 kDa which has the biological properties of the phage repressor, and two other proteins of 9 kDa and 18 kDa which are the first proteins on the rightward operon. These two proteins are negatively regulated by the 34 kDa protein at a divergent promoter site. By position analogy with phage lambda, but not by its biological activity, the 9 kDa protein could be the cro product. The 18 kDa protein is able to block totally UV induction of phage phi 80.

Cloning, Molecular↗
PubMed1984

[Generalized peritonitis of non-traumatic colonic origin. Reflexions on 62 cases].

The authors analyze sixty-two cases of acute generalized peritonitis with a non-traumatic colonic etiology. They point out that the prognosis depends on three main factors: the age of the patient, the time spent in diagnosis and the therapeutic difficulties. They recommend a gastrographin colonic enema to obtain earlier diagnosis, in the absence of radiological evidence of pneumoperitoneum, in elderly patients presenting with abdominal signs. They also recommend multistage surgical management combining effective drainage of the abdominal cavity with resection of the perforated segment of the colon, whenever there is extensive damage to the colon, or in the presence of a tumor. In their view, conservative surgery should be confined to strictly selected cases not involving tissue resection. These indications are essential if a satisfactory result is to be achieved.

Adult↗
PubMed1984

[Pancreatitis: a little-known cause of ureteral obstruction].

Left ureteral stenosis induced by pancreatitis was observed in one case. Five similar cases have been reported in the literature. Ureteral obstructions may be found in two clinical contexts--patent pancreatitis or retroperitoneal fibrosis. The ureter may be simply compressed mechanically, or there may also be enzymatic or ischemic necrosis. The clinical approach should be directed towards treating primarily the pancreatitis and secondarily the urological pathology. As regards the urological treatment, ureterolysis or ilio-ureteroplasty are indicated in cases of organized irreversible ureteral stenosis.

Adult↗
PubMed1980

[Thoracic ectopic kidney (author's transl)].

On the basis of a case of thoracic ectopic kidney, discovered following trauma and diagnosed at laparotomy (since it was confused with rupture of the left diaphragm) the authors review certain data concerning this rare malformation (150 published cases). --The site of origin of the renal artery may be used to distinguish on the one hand between true intra renal ectopic kidney with the renal artery arising from the aorta and secondly trans-diaphragmatic herniation of a kidney with a kidney with a normal vascular pedicle through a hernia, most often congenital, and equally often right as left. --Clinically, at the time of a routine examination or following trauma, chest X-ray reveals an opacity at the base of the thorax, the low and posterior topography of which is suggestive of the diagnosis and and IVP is then indicated. In the absence of violent trauma, the diagnosis of traumatic hernia is eliminated. The distinction between true ectopic kidney and congenital trans-diaphragmatic hernia becomes a false problem since there is no need for treatment in either case.

Child↗