Biomedical subjects

N Leblond-Bourget

Publications and source records attributed to N Leblond-Bourget.

3 recordsLinked to original sources

PubMed1999

Sequence and expression analysis of Nhlh1: a basic helix-loop-helix gene implicated in neurogenesis.

Nhlh1 is a basic helix-loop-helix (bHLH) gene that has been implicated in mouse neurogenesis. Previous studies have shown it to be expressed in regions in which there are differentiating neurons during late embryonic and fetal development, but detailed studies of the role of Nhlh1 earlier in embryonic development have not been performed. In this paper, we examine the expression of Nhlh1 transcripts at early embryonic stages (E8.5-E10.5), at the onset of neurogenesis, and compare the pattern of expression with that of Islet-1, a marker of postmitotic neurons. We show that Nhlh1 is expressed in early postmitotic neurons but is down-regulated as these cells migrate from the ventricular zone. We have also determined the genomic structure of mouse Nhlh1 and have characterised the promoter sequence, as a first step towards identifying factors that may control Nhlh1 expression. Nhlh1 has been implicated previously as a candidate for the neural tube defect mutant loop-tail (Lp); here, we present sequence and expression data indicating that Nhlh1 is unlikely to be responsible for the Lp mutation.

Amino Acid Sequence↗

PubMed1996

16S rRNA and 16S to 23S internal transcribed spacer sequence analyses reveal inter- and intraspecific Bifidobacterium phylogeny.

In the last few years many attempts have been made to differentiate more than 20 Bifidobacterium species. It has been recognized that identification of bifidobacterial species is problematic because of phenetic and genetic heterogeneities. In order to contribute to our understanding of Bifidobacterium taxonomy, we studied Bifidobacterium phylogeny by performing both 16S rRNA and 16S to 23S (16S-23S) internally transcribed spacer (ITS) sequence analyses. In this study, we determined 16S rRNA sequences of five Bifidobacterium strains representing four species, and compared them with the sequences available in the GenBank database, and used them to construct a distance tree and for a bootstrap analysis. Moreover, we determined the ITS sequences of 29 bifidobacterial strains representing 18 species and compared these sequences with each other. We constructed a phylogenetic tree based on these sequence data and compared this tree with the tree based on 16S rRNA sequence data. We found that the two trees were similar topologically, suggesting that the two types of molecules provided the same kind of phylogenetic information. However, while 16S rRNA sequences are a good tool to infer interspecific links, the 16S-23S rDNA spacer data allowed us to determine intraspecific relationships. Each of the strains was characterized by its own ITS sequence; hence, 16S-23S rRNA sequences are a good tool for strain identification. Moreover, a comparison of the ITS sequences allowed us to estimate that the maximum level of ITS divergence between strains belonging to the same species was 13%. Our data allowed us to confirm the validity of most of the Bifidobacterium species which we studied and to identify some classification errors. Finally, our results showed that Bifidobacterium strains have no tRNA genes in the 16S-23S spacer region.

Base Sequence↗

PubMedDate not supplied

Hydrogen peroxide effects on Streptococcus thermophilus CNRZ368 cell viability.

Streptococcus thermophilus CNRZ368 is an anaerobic aerotolerant bacteria and its ability to survive under aerobic growth conditions raises the question of the existence of a putative defence system against oxidative stress. Thus, survival of CNRZ368 in the presence of increasing concentrations of hydrogen peroxide was studied. Moreover, the influence of the physiologic state of the cells, as well as that of a preexposition with sublethal doses of hydrogen peroxide, upon S. thermophilus CNRZ368 survival were determined. The results suggest that S. thermophilus displays a defence system against oxidative stress and that this system is inducible.

Hydrogen Peroxide↗