Biomedical subjects

V Boivin-Jahns

Publications and source records attributed to V Boivin-Jahns.

4 recordsLinked to original sources

PubMed1997

A dileucine motif in the C terminus of the beta2-adrenergic receptor is involved in receptor internalization.

The cytoplasmic C terminus of the beta2-adrenergic receptor and many other G protein-coupled receptors contains a dileucine sequence that has been implicated in endosome/lysosome targeting of diverse proteins. In the present study, we provide evidence for an essential role of this motif in the agonist-induced internalization of the beta2-adrenergic receptor. Mutation of Leu-339 and/or Leu-340 to Ala caused little changes in surface expression, ligand binding, G protein coupling, and signaling to adenylyl cyclase, when these receptors were transiently or stably expressed in CHO or HEK-293 cells. However, agonist-induced receptor internalization was markedly impaired in the L339,340A double mutant and reduced in the two single mutants. This impairment in receptor internalization was seen by using various approaches to determine internalization: binding of hydrophobic vs. hydrophilic ligands, loss of surface beta2-adrenergic receptor immunoreactivity, and immunofluorescence microscopy. The selective effects of these mutations suggest that the C-terminal dileucine motif is involved in agonist-induced internalization of the beta2-adrenergic receptor.

Amino Acid Substitution↗

PubMed1996

Bacterial diversity in a deep-subsurface clay environment.

The presence of bacteria in a deep clay sediment was analyzed in a 20-m-long core horizontally drilled from a mine gallery at a depth of 224 m in the Boom clay formation (Mol, Belgium). This clay deposit is the result of a marine sedimentary process that occurred 35 million years ago. Bacterial activities were estimated by measuring respiration on [14C]glucose. Using the same samples, universal primers for the genes coding for eubacterial 16S rRNA were used to amplify extracted DNA. PCR products were then cloned, sequenced, and analyzed by molecular phylogeny. Our data showed a decrease in bacterial densities as a function of distance from the gallery, with few bacteria detectable by culture at more than 80 cm from the gallery wall. PCR experiments showed the presence of bacteria in all samples, and phylogenetic analyses were then used to tentatively identify these organisms. Because of low bacterial densities in deep clay samples, direct counts and enumeration of viable bacteria on diverse culture media remained negative. All experiments, both cultures and PCR, demonstrated the difficulty of analyzing samples that contain only a few poorly active bacteria as it is difficult to avoid a small contamination by active bacteria during sampling. Since the porosity of the Boom clay formation is less than the expected size of bacteria, it is possible that some of the bacteria present in this 35-million-year-old deep clay deposit derive from cells initially trapped during the sedimentation process.

Bacteria↗

PubMed1995

Comparison of phenotypical and molecular methods for the identification of bacterial strains isolated from a deep subsurface environment.

Vol. 61, no. 9, p. 3406: the Acknowledgments should read as follows. "This work was supported by the CNRS and by grants of the European Community and ANDRA as part of the project Archimede-Argiles and of the Direction de la Recherche et des Etudes Doctorales. V.B. was a recipient of a CIFRE fellowship." [This corrects the article on p. 3400 in vol. 61.].

Journal Article↗

PubMed1995

Comparison of phenotypical and molecular methods for the identification of bacterial strains isolated from a deep subsurface environment.

Seventy-four bacterial strains were freshly isolated from a mine gallery. Using these bacteria, we have investigated how a molecular identification based on the analysis of small subunit rDNA sequences would compare in terms of precision and reliability to a more classical comparison of phenotypical descriptions (100 morphological and physiological traits). Our data clearly showed that a phylogenetic analysis of small subunit rDNA sequences is more efficient than classical phenotypic methods for the identification of bacterial strains freshly isolated from a natural environment, because occurrences of misidentification are very much decreased by this method. The lack of rDNA sequences for many described species is probably the major cause of a few failures in molecular identification, as the completeness of the database of small subunit rDNA sequences holds much importance in the degree of uncertainty in such identifications.

Journal Article↗