Utilization of tmRNA sequences for bacterial identification

In recent years, molecular approaches based on nucleotide sequences of ribosomal RNA (rRNA) have become widely used tools for identification of bacteria [1-4]. The high degree of evolutionary conservation makes 16S and 23S rRNA molecules very suitable for phylogenetic studies above the species level [3-5]. More than 16,000 sequences of 16S rRNA are presently available in public databases [4,6]. The 16S rRNA sequences are commonly used to design fluorescently labeled oligonucleotide probes. Fluorescence in situ hybridization (FISH) with these probes followed by observation with epifluorescence microscopy allows the identification of a specific microorganism in a mixture with other bacteria [2-4]. By shifting probe target sites from conservative to increasingly variable regions of rRNA, it is possible to adjust the probe specificity from kingdom to species level. Nevertheless, 16S rRNA sequences of closely related strains, subspecies, or even of different species are often identical and therefore can not be used as differentiating markers [3]. Another restriction concerns the accessibility of target sites to the probe in FISH experiments. The presence of secondary structures, or protection of rRNA segments by ribosomal proteins in fixed cells can limit the choice of variable regions as in situ targets for oligonucleotide probes [7,8]. One way to overcome the limitations of in situ identification of bacteria is to use molecules other than rRNA for phylogenetic identification of bacteria, for which nucleotide sequences would be sufficiently divergent to design species specific probes, and which would be more accessible to oligonucleotide probes. For this purpose we investigated the possibility of using tmRNA (also known as 10Sa RNA; [9-11]). This molecule was discovered in E. coli and described as small stable RNA, present at ~1,000 copies per cell [9,11]. The high copy number is an important prerequisite for FISH, which works best with naturally amplified target molecules. In E. coli, tmRNA is encoded by the ssrA gene, is 363 nucleotides long and has properties of tRNA and mRNA [12,13]. tmRNA was shown to be involved in the degradation of truncated proteins: the tmRNA associates with ribosomes stalled on mRNAs lacking stop codons, finally resulting in the addition of a C-terminal peptide tag to the truncated protein. The peptide tag directs the abnormal protein to proteolysis [14,15]. 165 tmRNA sequences have so far (August 2001; The tmRNA Website: http://www.indiana.edu/~tmrna/) been determined [16,17]. The tmRNA is likely to be present in all bacteria and has also been found in algae chloroplasts, the cyanelle of Cyanophora paradoxa and the mitochondrion of the flagellate Reclinomonas americana[10,17,18]

Types de familles, conditions de vie, fonctionnement du système familial et inadaptation sociale au cours de la latence et de l’adolescence dans les milieux défavorisés

Les données manquent concernant l'impact de certains types de familles, et les résultats sont souvent discordants concernant l'inadaptation. Après avoir décrit les variations de l'activité délictueuse et des troubles de comportement selon les types de familles, nous analysons les difficultés de fonctionnement du système familial. Six types de familles sont comparés pour 763 garçons de 10 ans, 319 adolescentes et 426 adolescents de 14 et 15 ans: les familles intactes, les familles monoparentales patricentriques et matricentriques, les familles recomposées patricentriques et matricentriques et les familles substituts. Les données présentées montrent qu'en cette fin des années 1980, près de 40 % des enfants et des adolescents des quartiers à faible statut socio-économique de Montréal vivent dans des familles désunies. Les données confirment en outre une observation classique: les familles désunies, en comparaison aux familles intactes, sont défavorisées sur le plan des conditions de vie, déficientes sur le plan du fonctionnement psychosocial et propices aux troubles de comportement et à l'activité délictueuse. Par ailleurs, il est établi que certains types de familles désunies constituent un facteur de risque considérable. L'effet dommageable de la structure de la famille s'accroît dans l'ordre suivant: familles intactes, familles monoparentales matricentriques, familles recomposées matricentriques, familles substituts, familles recomposées patricentriques et familles monoparentales patricentriques. Pour terminer, quelques pistes d'intervention pour la prévention des difficultés comportementales et familiales sont proposées.Available data on the impact of certain types of families is lacking, and the results are often misleading with respect to maladjustment. Following a description of variations in delinquent activity and behaviour problems according to family type, the authors analyse the difficulties in the operation of family systems. Comparisons of six family types apply to data from 763 boys aged 10, 319 female and 426 male adolescents, aged 14 and 15: intact families, father-based and mother-based single- parent families, father-based and mother-based reconstituted families and substitute families. The article's data show that in the late eighties, nearly 40 per cent of children and adolescents living in low-income districts in Montreal belonged to disunited families. In addition, the data confirm a classic observation: in comparison with intact families, disunited families are underprivileged in relation to living conditions, deficient in relation to psychosocial functioning, and propitious to behaviour problems and delinquent activity. In addition, it has been established that certain disunited family types represent a considerable risk factor. The damaging effect of family structure increases in the following order: intact families, mother-based single-parent families, mother-based reconstituted families, substitute families, father-based reconstituted families and father-based single-parent families. Finally, certain intervention methods are suggested to help prevent behaviour and family problems

Peut-on utiliser des algues marines pour améliorer la qualité de l'eau des bassins d'exposition du Biodôme de Montréal?

Affiche présentée dans le cadre du Colloque de l'ARC, «La relève scientifique et la recherche collégiale : pratiques inspirantes au regard des chercheuses et chercheurs, et enjeux spécifiques à la formation des étudiantes et étudiants», dans le cadre du 84e Congrès de l'Acfas, Université du Québec à Montréal, Montréal, le 10 mai 2016.Dans les bassins d’eau recyclée du Biodôme de Montréal, le contrôle de l’azote et du phosphore dissous est essentiel, car leur accumulation peut dégrader la qualité de l’eau et devenir une source de stress pour les organismes aquatiques. Or, certaines algues marines ont la capacité d’absorber ces polluants tout en produisant de l’oxygène. L’objectif de notre  projet mené à l’École des pêches et de l’aquaculture du Québec était de développer un prototype de filtre biologique à base d’algues cultivées, efficace en termes d’absorption et de séquestration du nitrate et du phosphate dissous. Pour ce faire, les performances de deux espèces d’algues marines du golfe du Saint-Laurent, Palmaria palmata et Ulva lactuca, ont été évaluées dans des conditions similaires à celles des bassins du Biodôme de Montréal, soit deux températures (5 °C et 10 °C) et trois combinaisons de nutriments N-NO3- : P-PO43- (40:6, 50:7,5, 60:9 mg/L). Les résultats indiquent qu’aux densités testées (7 et 3 g AF/L; AF = algues fraîches), au bout de six jours, 10,2 ± 1,5 % du nitrate et 13,83 ± 9,0 % du phosphate présents dans l’eau ont été enlevés par P. palmata tandis que U. lactuca a enlevé 12,7 ± 3,3 % du nitrate et 13,01 ± 9,8 % du phosphate. La vitesse moyenne d’absorption journalière de l’azote par P. palmata était de 0,12 mg N/g AF  vs 0,34 mg N/g AF pour U. lactuca. Si les deux espèces montrent une bonne capacité d’épuration de l’eau, c’est U. lactuca qui absorbe l’azote le plus efficacement

Caribou herd dynamics : impacts of climate change on traditional and sport harvesting

Caribou (Rangifer tarandus) are a key species in Arctic ecosystems including northern Québec and Labrador. They play a central role in the ecology of predators and the structure of Arctic plant communities. In addition, caribou provide socioeconomic and cultural benefits from subsistence and sport hunting activities. Changes in the distribution and abundance of caribou due to global climate change would have serious biological, societal, and economic implications. Direct and indirect consequences of climate change on migratory caribou herds may include alteration in habitat use, migration patterns, foraging behaviour and demography. For example, caribou may experience a further northerly shift in distribution due to several factors including longer ice-free periods, increases in snowfall and extreme weather events, alterations in the fire regime, and changes in the distribution of insects and predators. Future research by Caribou Ungava, a research group interested in the ecology of migratory caribou in the context of climate change, will address the factors outlining variations in the population dynamics of caribou, implications for survival and reproduction, as well as the response of caribou habitat to different climate change scenarios. Management efforts focusing on mitigating greenhouse gases to reduce the potential effects of climate change, preserving high quality habitat, limiting anthropogenic landscape disturbances, and managing hunting in a sustainable manner, could alleviate stressors on migratory caribou of the QuébecLabrador peninsula

Conductance Distributions in Random Resistor Networks: Self Averaging and Disorder Lengths

The self averaging properties of conductance $g$ are explored in random resistor networks with a broad distribution of bond strengths P(g)\simg^{\mu-1}. Distributions of equivalent conductances are estimated numerically on hierarchical lattices as a function of size $L$ and distribution tail parameter $\mu$. For networks above the percolation threshold, convergence to a Gaussian basin is always the case, except in the limit $\mu$ --> 0. A {\it disorder length} $\xi_D$ is identified beyond which the system is effectively homogeneous. This length diverges as $\xi_D \sim |\mu|^{-\nu}$ ($\nu$ is the regular percolation correlation length exponent) as $\mu$-->0. This suggest that exactly the same critical behavior can be induced by geometrical disorder and bu strong bond disorder with the bond occupation probability $p$$\mu$. Only lattices at the percolation threshold have renormalized probability distribution in a {\it Levy-like} basin. At the threshold the disorder length diverges at a vritical tail strength $\mu_c$ as $|\mu-\mu_c|^{-z}$, with $z=3.2\pm 0.1$, a new exponent. Critical path analysis is used in a generalized form to give form to give the macroscopic conductance for lattice above $p_c$.Comment: 16 pages plain TeX file, 6 figures available upon request.IBC-1603-01

Superconductivity close to the Mott state: From condensed-matter systems to superfluidity in optical lattices

Since the discovery of high-temperature superconductivity in 1986 by Bednorz and Mueller, great efforts have been devoted to finding out how and why it works. From the d-wave symmetry of the order parameter, the importance of antiferromagnetic fluctuations, and the presence of a mysterious pseudogap phase close to the Mott state, one can conclude that high-Tc superconductors are clearly distinguishable from the well-understood BCS superconductors. The d-wave superconducting state can be understood through a Gutzwiller-type projected BCS wave-function. In this review article, we revisit the Hubbard model at half-filling and focus on the emergence of exotic superconductivity with d-wave symmetry in the vicinity of the Mott state, starting from ladder systems and then studying the dimensional crossovers to higher dimensions. This allows to confirm that short-range antiferromagnetic fluctuations can mediate superconductivity with d-wave symmetry. Ladders are also nice prototype systems allowing to demonstrate the truncation of the Fermi surface and the emergence of a Resonating Valence Bond (RVB) state with preformed pairs in the vicinity of the Mott state. In two dimensions, a similar scenario emerges from renormalization group arguments. We also discuss theoretical predictions for the d-wave superconducting phase as well as the pseudogap phase, and address the crossover to the overdoped regime. Finally, cold atomic systems with tunable parameters also provide a complementary insight into this outstanding problem.Comment: 98 pages and 18 figures; Final version (references added and misprints corrected

Regulation of pituitary MT1 melatonin receptor expression by gonadotrophin-releasing hormone (GnRH) and early growth response factor-1 (Egr-1) : in vivo and in vitro studies

Copyright: © 2014 Bae et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was funded by the UK Biotechnology and Biological Sciences Research Council (BBSRC; grant BB/F020309/1; http://www.bbsrc.ac.uk/home/home.aspx). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

Organic matter remineralization in marine sediments : A Pan-Arctic synthesis

Natural Environment Research Council (GrantNumber(s): NE/J023094/1; Grant recipient(s): Ursula Witte) ArcticNet (GrantNumber(s): Hotspot biodiversity project; Grant recipient(s): Philippe Archambault)Peer reviewedPublisher PD

Genetic regulation of pituitary gland development in human and mouse

Normal hypothalamopituitary development is closely related to that of the forebrain and is dependent upon a complex genetic cascade of transcription factors and signaling molecules that may be either intrinsic or extrinsic to the developing Rathke’s pouch. These factors dictate organ commitment, cell differentiation, and cell proliferation within the anterior pituitary. Abnormalities in these processes are associated with congenital hypopituitarism, a spectrum of disorders that includes syndromic disorders such as septo-optic dysplasia, combined pituitary hormone deficiencies, and isolated hormone deficiencies, of which the commonest is GH deficiency. The highly variable clinical phenotypes can now in part be explained due to research performed over the last 20 yr, based mainly on naturally occurring and transgenic animal models. Mutations in genes encoding both signaling molecules and transcription factors have been implicated in the etiology of hypopituitarism, with or without other syndromic features, in mice and humans. To date, mutations in known genes account for a small proportion of cases of hypopituitarism in humans. However, these mutations have led to a greater understanding of the genetic interactions that lead to normal pituitary development. This review attempts to describe the complexity of pituitary development in the rodent, with particular emphasis on those factors that, when mutated, are associated with hypopituitarism in humans