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A Derrien

Publications and source records attributed to A Derrien.

14 recordsLinked to original sources
PubMed2002

Occurrence of pathogenic vibrios in coastal areas of France.

AIMS: This study was carried out to investigate the occurrence of potentially pathogenic species of Vibrio in French marine and estuarine environments. METHODS AND RESULTS: Samples of coastal waters and mussels collected between July and September 1999 were analysed by culture, using selective media including thiosulphate-citrate-bile salts-sucrose and modified cellobiose-polymixin B-colistin agar. Presumptive Vibrio colonies were isolated and identified using selected biochemical tests. Specific primers based on flanking sequences of the cytolysin, vvhA gene, pR72H DNA fragment and 16S-23S rRNA intergenic spacer region (ISR) were used in a polymerase chain reaction (PCR) to confirm the identification of Vibrio vulnificus, V. parahaemolyticus and V. cholerae, respectively. In this study, V. alginolyticus (99 of 189) was the predominant species, followed by V. parahaemolyticus (41 of 189), V. vulnificus (20 of 189) and non-O1/non-O139 V. cholerae (three of 189). All 20 V. vulnificus isolates showed PCR amplification of the vvhA gene, 16 of which had been isolated from estuarine water. The PCR amplification of the pR72H DNA fragment in 41 V. parahaemolyticus isolates generated two unique amplicons of 387 and 320 bp. The latter, present in 24.4% of these isolates, had not previously been found in V. parahaemolyticus strains examined to date. Amplification of the trh gene in two of the isolates suggested these to be virulent strains. Three strains identified as V. cholerae by amplification of the 16S-23S rRNA ISR were confirmed to be non-cholera (non-O1/non-O139) strains. CONCLUSIONS: The results of this study demonstrated the presence of pathogenic Vibrio species in French coastal waters. Furthermore, the PCR approach proved useful for the rapid and reliable confirmation of species identification. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings indicate the potential sanitary risk associated with the presence of pathogenic Vibrio spp. in cultivated mussels and in the aquatic environment. The PCR can be used to detect pathogenic vibrios directly in environmental samples.

Animals↗
PubMed2001

RGS16 function is regulated by epidermal growth factor receptor-mediated tyrosine phosphorylation.

Galpha(i)-coupled receptor stimulation results in epidermal growth factor receptor (EGFR) phosphorylation and MAPK activation. Regulators of G protein signaling (RGS proteins) inhibit G protein-dependent signal transduction by accelerating Galpha(i) GTP hydrolysis, shortening the duration of G protein effector stimulation. RGS16 contains two conserved tyrosine residues in the RGS box, Tyr(168) and Tyr(177), which are predicted sites of phosphorylation. RGS16 underwent phosphorylation in response to m2 muscarinic receptor or EGFR stimulation in HEK 293T or COS-7 cells, which required EGFR kinase activity. Mutational analysis suggested that RGS16 was phosphorylated on both tyrosine residues (Tyr(168) Tyr(177)) after EGF stimulation. RGS16 co-immunoprecipitated with EGFR, and the interaction did not require EGFR activation. Purified EGFR phosphorylated only recombinant RGS16 wild-type or Y177F in vitro, implying that EGFR-mediated phosphorylation depended on residue Tyr(168). Phosphorylated RGS16 demonstrated enhanced GTPase accelerating (GAP) activity on Galpha(i). Mutation of Tyr(168) to phenylalanine resulted in a 30% diminution in RGS16 GAP activity but completely eliminated its ability to regulate G(i)-mediated MAPK activation or adenylyl cyclase inhibition in HEK 293T cells. In contrast, mutation of Tyr(177) to phenylalanine had no effect on RGS16 GAP activity but also abolished its regulation of G(i)-mediated signal transduction in these cells. These data suggest that tyrosine phosphorylation regulates RGS16 function and that EGFR may potentially inhibit Galpha(i)-dependent MAPK activation in a feedback loop by enhancing RGS16 activity through tyrosine phosphorylation.

Amino Acid Sequence↗
PubMed1999

Angiotensin II inhibits insulin-induced egr-1 expression in mesangial cells.

The gene early growth response gene-1 (egr-1) encodes a zinc transcription factor involved in cell proliferation. Increased expression of egr-1 has been linked to heart and kidney disease. In mouse mesangial cells, insulin stimulated egr-1 expression more than angiotensin II, suggesting that insulin may play an important role in stimulating cell proliferation, leading to glomerulonephritis and diabetic nephropathy. Angiotensin II inhibited insulin-induced egr-1 expression but not c-fos expression, and the decrease in egr-1 expression was concurrent with a decrease in insulin receptor substrate-1 (IRS-1) tyrosine phosphorylation. These results suggest that insulin-induced egr-1 expression in mouse mesangial cells is downstream of tyrosine phosphorylation of IRS-1 and activation of the MAP kinase pathway and that crosstalk between angiotensin II and insulin signaling pathways led to an inhibition of IRS-1 tyrosine phosphorylation and egr-1 expression.

Angiotensin II↗
PubMed1997

Salmonella DNA persistence in natural seawaters using PCR analysis.

The risks of false-positive responses were examined when using the polymerase chain reaction (PCR) method for the detection of Salmonella in the marine environment (water and shellfish). The degradation rates of DNA, both free and from dead Salmonella, were evaluated in natural seawaters maintained at 10 degrees and 20 degrees C, using PCR with Vir and invA primers. The DNA of dead Salmonella was detected up to 55 d in seawater collected in winter and stored at 10 degrees C. But in summer, the persistence was shorter: 10 d or even 2 d for a smaller inoculum (3 x 10(3) Salmonella ml-1). The role of the planktonic organisms present in spring and summer was pinpointed. For free DNA, the persistence times were shorter: from 2 to 4 d at 20 degrees C, and from 3 to 8 d at 10 degrees C showing that the nuclease activity of marine organisms is higher at warm temperatures. These data led us to recommend careful interpretations of direct PCR results, especially during cold periods and for samples collected close to terrestrial discharges of high concentrations of live, dead or lysed Salmonella. PCR is a rapid, specific and sensitive method, but should be applied with care to marine samples, in order to avoid false-positive responses.

Animals↗
PubMed1996

Expression and regulation of G alpha q and G alpha 11 mRNAs and proteins in bovine adrenal cells.

Bovine adrenal cortical cells (BAC) express corticotropin (ACTH) and angiotensin II (AngII) receptors (AT1 subtype), which are coupled to adenylate cyclase and phosphoinositide pathways, respectively. The coupling of AT1 to phosphoinositide breakdown is mainly pertussis toxin-insensitive suggesting that this receptor is coupled to Gaeq/Gae11. In the present work we have demonstrated that BAC express G alpha q and G alpha 11 mRNA and proteins, and their variation during culture as well as their regulation by ACTH and AngII is different. ACTH enhanced G alpha q mRNA levels mainly by increasing the transcription rate. In addition, ACTH increased both G alpha q and G alpha 11 proteins without changing their half-lives. In contrast, AngII reduced both G alpha q mRNA and protein and increased G alpha 11 mRNA but not G alpha 11 protein. The decrease of G alpha q mRNA levels was mainly due to a marked reduction of its half-life. These changes in G alpha q/G alpha 11 proteins induced by both hormones were associated with an enhanced AngII-induced inositol phosphate accumulation, more marked after stimulation with ACTH than after AngII pretreatment. In summary, the present results demonstrated that BAC express both G alpha q and G alpha 11 and their regulations are different and in contrast to other cell types these regulations do not involve changes in the half-life of G alpha q/G alpha 11 proteins.

Adrenocorticotropic Hormone↗
PubMed1996

Differentiation of the "Ascochyta complex" fungi of pea by biochemical and molecular markers.

Isolates of three closely related pea pathogens, Ascochyta pisi, Ascochyta pinodes (teleomorph Mycosphaerella pinodes) and Phoma medicaginis var. pinodella, were compared by means of isozyme analysis and restriction fragment length polymorphisms (RFLP) of amplified rDNA spacers. Three enzyme systems differentiated A. pisi from M. pinodes and P. m. pinodella. The internal transcribed spacers (ITSs) of the three fungi showed no intraspecific and very little interspecific variation after digestion with 12 endonucleases. Digestion of the intergenic spacer (IGS) with HinfI, and Sau3A revealed uniformity in A. pisi patterns which consistently differed from those of M. pinodes and P. m. pinodella. No clear distinction could be made between the latter two fungi which both showed intraspecific variability. Both biochemical and molecular markers thus discriminated between two Ascochyta species. The results also indicated a closer relationship between two organisms belonging to different genera (Ascochyta and Phoma) than between two species of the same genus (Ascochyta).

Alcohol Oxidoreductases↗
PubMed1996

Retention of enteropathogenicity by viable but nonculturable Escherichia coli exposed to seawater and sunlight.

The effect of natural sunlight on culturability and persistence of pathogenicity of Escherichia coli was examined in the field, i.e., in the Morlaix Estuary, France, using an enterotoxigenic strain of Escherichia coli H10407. Results showed that E. coli responds to the estuarine diurnal solar cycle by entering the viable but nonculturable state upon exposure to sunlight. That is, direct counts of viable cells remained stable without significant change, but E. coli cells remained fully culturable only when exposed to seawater in control chambers in the dark, i.e., without solar irradiation. The effect of sunlight on the pathogenicity of E. coli H10407 was studied, using both the rabbit intestinal loop assay and ganglioside-enzyme-linked immunosorbent assay (GM1-ELISA), a sensitive procedure for testing for production of enterotoxin. Results of the GM1-ELISA demonstrated that strains of E. coli, after exposure to sunlight and entering the viable but nonculturable state, as well as culturable E. coli, retained pathogenicity, i.e., produced enterotoxin. The GM1-ELISA is concluded to be more sensitive than the rabbit intestinal loop assay for analysis of enterotoxin in natural water samples.

Animals↗
PubMed1995

Osmoregulation by trehalose synthesis in Salmonella manhattan after exposure to waste waters.

A 24 h period in waste waters improved the subsequent survival of Salmonella in oligotrophic sea water, at 20 degrees C, compared to a direct input control. The main osmoprotective compound accumulated, investigated by 1H-NMR spectroscopy (nuclear magnetic resonance), after 6 d in sea water was trehalose. Taking into account these observations, this paper put forward the following explanation concerning the survival mechanism: (1) stress in waste waters induces the endogenous synthesis of trehalose via the activation of the gene kat F; (2) when exposed to an osmotic stress, two degradative cytoplasmic enzymes are repressed and the bacteria accumulate trehalose which acts as an osmoprotectant. The succession of the two steps enables Salm. manhattan to immediately resist to the high salinity of oligotrophic seawater.

Adaptation, Physiological↗
PubMed1994

Regulation by growth factors of angiotensin II type-1 receptor and the alpha subunit of Gq and G11 in bovine adrenal cells.

In the present work we have investigated the effects of several growth factors on the expression of Angiotensin II (A-II) receptors subtype AT1 and their pertussis toxin-insensitive coupling to G-proteins in bovine adrenal fasciculata-reticularis cells (BAC). Insulin, Insulin-like growth factor and basic Fibroblast growth factor increased AT1 receptors (mRNA and binding sites) as well as the alpha subunit of Gq (mRNA and protein) and G11 (protein). These changes were associated with an enhanced A-II-induced inositol phosphate accumulation and cortisol production. In contrast, Transforming growth factor beta 1, which reduced slightly AT1 binding sites, but not the level of alpha q or alpha 11 proteins, did not change the A-II-induced inositol phosphate accumulation. However, this factor, as previously reported, markedly reduced cortisol production.

Adrenal Glands↗
PubMed1989

Production of 4-methylumbelliferyl heptanoate hydrolase by Escherichia coli exposed to seawater.

The production of an enzyme, 4-methylumbelliferyl heptanoate hydrolase, in Escherichia coli exposed to enriched and nonenriched seawater was studied. In all media, except for seawater with no or very small amounts of organic material and seawater enriched with peptone, 4-methylumbelliferyl heptanoate hydrolase activity increased by 2 to 3 orders of magnitude within 2 days. Increased enzyme activity was assumed to be related to cells not undergoing lysis but adapting to conditions of nutrient limitation.

Colony Count, Microbial↗
PubMedDate not supplied

[Extensive scabies in a baby (author's transl)].

The authors are reporting a new case of widespread scabies in a baby. They take this opportunity to emphasize on the atypical erythematous and excoriated papular rash which sometimes may be vesicular and hyper-keratotic. This widespread eruption may mimic generalised dermatitis, pustular psoriasis and even histiocytosis X. They also underline importancy of longlasting ointment with fluorinated steroid being responsible for this widespread eruption.

Administration, Topical↗