Analyse génomique de la sélection spatialement variable chez l'anguille d'Amérique (Anguilla rostrata)

L'anguille d'Amérique est un poisson avec un cycle de vie très particulier. En effet, elle occupe une aire de répartition qui s'étire du Groenland aux Caraïbes, mais tous les individus se reproduisent dans la mer des Sargasses. Après la reproduction, les larves sont dispersées de façon aléatoire jusqu'aux côtes. Ce lieu de reproduction unique fait en sorte que tous les individus de l'espèce appartiennent à la même population. Par contre, les conditions environnementales varient grandement au sein de l'aire de répartition, puisque celle-ci s'étend de régions subarctiques à des régions subtropicales, ce qui confronte les individus à des conditions différentes selon l'endroit jusqu'où ils dérivent et peut entraîner la sélection d'allèles différents selon les régions. Les objectifs de cette étude étaient d'identifier les régions du génome soumises au phénomène de sélection spatialement variable et quels mécanismes sont affectés par la sélection. Pour ce faire, 710 individus en provenance de 13 sites différents représentant une grande partie de l'aire de répartition de l'espèce ont été séquencés. Un total de 12 098 SNP a été obtenu. Des méthodes d'association environnementale et d'analyse de redondance ont été employées pour identifier des marqueurs potentiellement sous sélection spatialement variable. Un total de 183 marqueurs a été identifié comme étant sous sélection spatialement variable. L'interaction entre les différentes régions sous sélection a également été évaluée en utilisant des scores polygéniques additifs. Des corrélations significatives entre ces scores polygéniques et la latitude, la longitude et la température ont été identifiées. Finalement, nous avons identifié les gènes à proximité des marqueurs potentiellement sous sélection. Parmi ces gènes, le mécanisme de réponse à l'insuline était le seul mécanisme significativement enrichi. Cette étude a permis de mieux documenter l'étendue de la sélection spatialement variable chez l'anguille d'Amérique en montrant qu’il semble y avoir de la sélection dans de nombreuses régions du génome.The American eel is a fish with a complex life cycle. The eel occupy a wide species range from Greenland to the Caribbean, but all eels reproduce in the Sargasso Sea. After the reproduction, the larvea are advected randomly to the coast by ocean currents. Because of this reproduction mode, all the American Eel are in the same population. On the other hand, the range is extending from subarctic to subtropical regions and the eels occupying these different regions are facing really different environmental conditions. These differents conditions could result in the selection of different alleles. The objective of this study was to identify the different regions of the genome that are affected by this phenomenon of spatially-varying selection and which mecanisms are affected by selection. A total of 710 glass eels captured in 12 different sites representing an important part of the species range were sequenced to reach these objectives. After sequencing, 12 098 SNPs were conserved for further analysis. Using environmental association and redundancy analyses approaches, 183 of these markers were identified to be potentially under spatially-varying selection. The interaction between these differents regions was analyzed using additive polygenic scores. Significant correlations were identified between these polygenic scores and the latitude, longitude and temperature. Genes close to outliers were identified and gene ontology analyses were made. The only significantly enriched pathway was the insuline signalling pathway. With this study our understanding of the spatially-varying selection in the American Eel has been increased

The Uptake and Distribution of Diethyltoluenediamine in the Male Sprague Dawley Rat.

Diethyltoluenediamine (CAS 68479-98-1) is a ring-ethylated analog of toluenediamine (TDA) and like TDA, consists of the 2,4- and 2,6-diamine isomers. DETDA was developed by Albermarle Corporation as a substitute for TDA in some applications. To determine the uptake and distribution of 2,4- and 2,6-DETDA, 5 groups of 4 adult male Sprague Dawley rats were gavaged at 179 $\mu$mol/kg body weight with (\sp3H) -2,4- or (\sp3H) -2,6-DETDA. Multiple tissues were collected at 1, 4, 8, 24 and 48 hours. Very high levels of label occurred in the gastrointestinal system and bladder during the first 8 hours while liver and kidney exhibited moderate levels. The concentration of radioactivity in most tissues except the stomach, duodenum, caecum, colon, bladder and thyroid was greatest at the 4 hour time point. Thyroid levels, at the 24 and 48 hour time points, were the highest of all tissues examined. By 8 hours, urinary excretion became the primary route of elimination. By 24 hours, over 60% of the labeled compound had been excreted and by 6 days less than 4% of label remained in the tissues. Low levels of residual label was found in all tissues examined at day 6. To determine urinary and fecal excretion patterns of 2,4- and 2,6-DETDA, 5 adult male Sprague Dawley rats were gavaged at 179 $\mu$mol/kg body weight of (\sp3H) -2,4- or (\sp3H) -2,6-DETDA. Urine and feces were collected for 6 days then blood and tissues were collected at euthanasia on day 6. Excretion data revealed that the primary route of elimination of DETDA was the urinary system with the majority of label being excreted in the first 24 hours. Compared to the 2,4-isomer, 2,6-DETDA exhibited a higher rate of urinary excretion. Both 2,4- and 2,6-DETDA demonstrated covalent binding to rat liver DNA and liver protein

Intermittency and regularity issues in 3D Navier-Stokes turbulence

Two related open problems in the theory of 3D Navier-Stokes turbulence are discussed in this paper. The first is the phenomenon of intermittency in the dissipation field. Dissipation-range intermittency was first discovered experimentally by Batchelor and Townsend over fifty years ago. It is characterized by spatio-temporal binary behaviour in which long, quiescent periods in the velocity signal are interrupted by short, active `events' during which there are violent fluctuations away from the average. The second and related problem is whether solutions of the 3D Navier-Stokes equations develop finite time singularities during these events. This paper shows that Leray's weak solutions of the three-dimensional incompressible Navier-Stokes equations can have a binary character in time. The time-axis is split into `good' and `bad' intervals: on the `good' intervals solutions are bounded and regular, whereas singularities are still possible within the `bad' intervals. An estimate for the width of the latter is very small and decreases with increasing Reynolds number. It also decreases relative to the lengths of the good intervals as the Reynolds number increases. Within these `bad' intervals, lower bounds on the local energy dissipation rate and other quantities, such as \|\bu(\cdot, t)\|_{\infty} and \|\nabla\bu(\cdot, t)\|_{\infty}, are very large, resulting in strong dynamics at sub-Kolmogorov scales. Intersections of bad intervals for $n\geq 1$ are related to Scheffer's potentially singular set in time. It is also proved that the Navier-Stokes equations are conditionally regular provided, in a given `bad' interval, the energy has a lower bound that is decaying exponentially in time.Comment: 36 pages, 3 figures and 6 Table