Neon isotopic composition of the mantle constrained by single vesicle analyses

© The Author(s), 2016. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Earth and Planetary Science Letters 449 (2016): 145-154, doi:10.1016/j.epsl.2016.05.052.The origin of volatiles on Earth is still a matter of debate. Noble gases are an efficient geochemical tool to constrain Earth formation processes due to their inertness. Several studies have focused on the neon isotopic composition of the lower mantle because the 20Ne/22Ne ratio is thought to reflect that of Earth’s primordial components. Two models to explain the origin of light noble gases on Earth have been proposed: either solar wind implantation onto the Earth's solid precursors or dissolution into the mantle of a primordial atmosphere captured from solar nebula gas. In order to test these two models, we analyzed the noble gas compositions (helium, neon and argon) of two submarine oceanic island basalt glasses from Fernandina volcano (Galápagos archipelago), which have among the most primitive/unradiogenic terrestrial helium and neon isotopic compositions. Several sample pieces are studied both by step-crushing and by laser ablation analyses of single vesicles. Results of step-crushing are consistent with those of laser ablation analyses, but the latter results provide new insights into the origin of atmospheric contamination. The single-vesicle laser-ablation measurements overlap with the step crushing results, but have systematically higher 40Ar/36Ar, and 3He/36Ar, suggesting less atmospheric contamination using this method. The single vesicle data therefore suggest that atmospheric contamination is introduced by exposure to the modern atmosphere, after sample collection. 3He/4He values are about 23 times the atmospheric ratio (R/Ra) for the two Fernandina (Galápagos) samples, in agreement with previous studies. We obtain 20Ne/22Ne and 40Ar/36Ar isotopic ratios as high as 12.91 and 9400, respectively, for the mantle source of the Galápagos hotspot. The new data show that step-crushing and laser ablation analyses are complementary methods that should be used together to derive the noble gas ratios in uncontaminated samples. The results of neon compositions are consistent with previous hotspot studies and support the model of solar wind implantation associated with sputtering to explain helium and neon origins on Earth.M.D.K. acknowledges support from NSF OCE in collecting the samples and allowing his participation in this study (OCE-1259218 and OCE-1232985). M.M. acknowledges the financial support from the UnivEarthS Labex program of Sorbonne Paris Cité (ANR-10-LABX-0023 and ANR-11-IDEX-0005-02).2018-06-0

Reconstruction of the birth of a male sex chromosome present in Atlantic herring

The mechanisms underlying sex determination are astonishingly plastic. Particularly the triggers for the molecular machinery, which recalls either the male or female developmental program, are highly variable and have evolved independently and repeatedly. Fish show a huge variety of sex determination systems, including both genetic and environmental triggers. The advent of sex chromosomes is assumed to stabilize genetic sex determination. However, because sex chromosomes are notoriously cluttered with repetitive DNA and pseudogenes, the study of their evolution is hampered. Here we reconstruct the birth of a Y chromosome present in the Atlantic herring. The region is tiny (230 kb) and contains only three intact genes. The candidate male-determining gene BMPR1BBY encodes a truncated form of a BMP1B receptor, which originated by gene duplication and translocation and underwent rapid protein evolution. BMPR1BBY phosphorylates SMADs in the absence of ligand and thus has the potential to induce testis formation. The Y region also contains two genes encoding subunits of the sperm-specific Ca2+ channel CatSper required for male fertility. The herring Y chromosome conforms with a characteristic feature of many sex chromosomes, namely, suppressed recombination between a sex-determining factor and genes that are beneficial for the given sex. However, the herring Y differs from other sex chromosomes in that suppression of recombination is restricted to an similar to 500-kb region harboring the male-specific and sex-associated regions. As a consequence, any degeneration on the herring Y chromosome is restricted to those genes located in the small region affected by suppressed recombination

Origin of terrestrial volatile elements : constraints from noble gases

L’origine des éléments volatils, éléments avec des températures de condensation très basses comme l’eau, l’azote, le carbone et les gaz rares, sur Terre et sur les autres planètes telluriques reste mal comprise. Comprendre comment ces éléments sont arrivés sur Terre permettra de mieux appréhender les mécanismes de formation du système solaire. De par leur caractère inerte, les gaz rares (He, Ne, Ar, Kr, Xe) constituent des traceurs uniques des sources d’éléments volatils. L’étude de la composition en gaz rares du manteau terrestre s’avère donc essentielle afin de déterminer l’origine de ces éléments. L’objectif de ces travaux était de mesurer précisément la composition des isotopes stables et non-radiogéniques des gaz rares dans le manteau à partir de verres basaltiques. Ces derniers étant très souvent contaminés par l’air, des techniques d’analyse des gaz rares ont été mises en place pour s’affranchir de cette contamination. Des échantillons du volcan Fernandina du point chaud des Galápagos ont été étudiés par ablation laser. Les résultats montrent que le rapport 20Ne/22Ne des bulles est en moyenne de 12,65 ± 0,04 (1σ), ce qui est proche de la valeur estimée pour le pôle d’implantation du vent solaire (~ 12,7). Cette étude suggère donc que l’implantation du vent solaire sur les grains précurseurs de la Terre serait à l’origine des éléments volatils légers du manteau.Des données d’échantillons de popping rocks, aussi analysés par cette technique, indiquent que le manteau supérieur est hétérogène à petite échelle et pourraient impliquer le recyclage de gaz rares dans le manteau, y compris He, Ne, lors de la subduction. Un nouveau protocole d’analyse du Kr et Xe a été développé. Les résultats montrent les plus forts excès en 124Xe, 126Xe et 128Xe mesurés pour le manteau et suggèrent une source chondritique. Les isotopes fissiogéniques du xénon ont permis de dater le début du recyclage des éléments volatils dans le manteau aux alentours de 3 Ga.The origin of volatiles, elements with low condensation temperatures such as water, nitrogen, carbon and noble gases, on Earth and other terrestrial planets is still misunderstood. Determining how these elements were delivered to the Earth will allow a better understanding of the processes of solar system formation. Due to their inertness, noble gases (He, Ne, Ar, Kr, Xe) constitute unique tracers of volatiles sources. Studying the noble gas composition of the Earth’s mantle is hence critical to unravel volatile origin. The aim of this PhD was to measure precisely the composition of non-radiogenic, stable noble gas isotopes in the mantle from basaltic glasses. The latter being very often contaminated by air, analytical techniques were thus set up to overcome this contamination.Samples from Fernandina volcano from the Galápagos hotspot were studied with laser ablation. The results show that the mean 20Ne/22Ne ratio in the vesicles is 12.65 ± 0.04 (1σ), close to the estimated value of the solar wind implanted end-member (~ 12,7). This study suggests that light volatiles in the mantle would originate from implantation of solar wind on the Earth’s precursors grains. Data from popping rock samples, also analyzed with this technique, indicate that the upper mantle is heterogeneous at small scale and that noble gases, included He, Ne, could be recycled into the mantle in subduction zones. A new protocol to analyse Kr and Xe was set up. The results show the highest measured excess in 124Xe, 126Xe and 128Xe for the mantle and suggest a chondritic source. The xenon fissiogenic isotopes allowed us to constrain the onset of volatile recycling in the mantle to around 3 Ga

ETUDE SUR LES ADMISSIONS INJUSTIFIEES AUX URGENCES MEDICALES ADULTES DU CENTRE HOSPITALO-UNIVERSITAIRE DE NANTES

NANTES-BU Médecine pharmacie (441092101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Origin of Light Noble Gases (He, Ne, and Ar) on Earth: A Review

We review the different scenarios for the origin of light noble gases (He, Ne, and Ar) on Earth. Several sources could have contributed to the Earth's noble gas budget: implanted solar wind, solar nebula gas, chondrites, and comets. Although there is evidence for solar-like neon in the Earth's mantle, questions remain as to its origin. A new compilation of noble gas data in lunar soils, interplanetary dust particles, micrometeorites, and solar wind allows examination of the implanted solar wind composition, which is key to understanding the solar-like mantle neon isotope composition. We show that lunar soils that reflect this solar-wind-implanted signature have a Ne-20/Ne-22 ratio very close to that of ocean island basalts. New data and calculations illustrate that the measured plume source Ne-20/Ne-22 ratio is close to the primitive mantle ratio, when taking into account mixing with the upper mantle (that has lower Ne-20/Ne-22 ratio). This favors early solar wind implantation to account for the origin of light volatiles (He, Ne, and possibly H) in the Earth's mantle: they were incorporated by solar wind irradiation into the Earth's precursor grains during the first few Myr of the solar system's formation. These grains must have partially survived accretion processes (only a few percent are needed to satisfy the Earth's budget of light volatiles). As for the atmosphere, the neon isotope composition can be explained by mixing 36% of mantle gases having this solar-wind-implanted signature and 64% of chondritic gases delivered in a late veneer phase

Transcriptomic Analysis of Trout Gill Ionocytes in Fresh Water and Sea Water Using Laser Capture Microdissection Combined with Microarray Analysis.

Fish gills represent a complex organ composed of several cell types that perform multiple physiological functions. Among these cells, ionocytes are implicated in the maintenance of ion homeostasis. However, because the ionocyte represents only a small percent of whole gill tissue, its specific transcriptome can be overlooked among the numerous cell types included in the gill. The objective of this study is to better understand ionocyte functions by comparing the RNA expression of this cell type in freshwater and seawater acclimated rainbow trout. To realize this objective, ionocytes were captured from gill cryosections using laser capture microdissection after immunohistochemistry. Then, transcriptome analyses were performed on an Agilent trout oligonucleotide microarray. Gene expression analysis identified 108 unique annotated genes differentially expressed between freshwater and seawater ionocytes, with a fold change higher than 3. Most of these genes were up-regulated in freshwater cells. Interestingly, several genes implicated in ion transport, extracellular matrix and structural cellular proteins appeared up-regulated in freshwater ionocytes. Among them, several ion transporters, such as CIC2, SLC26A6, and NBC, were validated by qPCR and/or in situ hybridization. The latter technique allowed us to localize the transcripts of these ion transporters in only ionocytes and more particularly in the freshwater cells. Genes involved in metabolism and also several genes implicated in transcriptional regulation, cell signaling and the cell cycle were also enhanced in freshwater ionocytes. In conclusion, laser capture microdissection combined with microarray analysis allowed for the determination of the transcriptional signature of scarce cells in fish gills, such as ionocytes, and aided characterization of the transcriptome of these cells in freshwater and seawater acclimated trout

Wheat value: improvements by feed technology, plant breeding and animal genetics

International audienc

Approche de la vulnérabilité du territoire D’Orly Rungis et Seine Amont (94) aux risques d’inondations, et orientations d’aménagement

L’approche de la vulnérabilité du territoire Orly Rungis et Seine Amont aux risques d’inondations vise à apprécier la vulnérabilité d’un territoire étendu, fortement inondable, sur lequel sont projetés de grands aménagements dans le cadre d’une Opération d’Intérêt National. Fondée sur une approche systémique et développée à partir des données accessibles, cette approche conduit à appréhender le territoire comme un système d’éléments (biens, activités et espaces physiques…) liés entre eux par différentes relations. L’analyse, dont certains extraits sont présentés dans cet article, s’appuie sur celle d’enjeux liés à l’occupation du sol (statiques) et celle d’enjeux majeurs, essentiels pour le fonctionnement du territoire (notion de dépendance et de transmission de vulnérabilité à l’ensemble d’un territoire). Au-delà d’une appréciation de la vulnérabilité du territoire à une inondation type 1910 ou d’occurrence plus fréquente, cette démarche amène à questionner ou renforcer les orientations à mettre en oeuvre dans les projets d’aménagement engagés, voire de proposer de nouveaux aménagements, pour porter une politique de maîtrise et de réduction de la vulnérabilité, y compris de l’existant, à de multiples échelles et partagée entre les différents acteurs

Regulation of the corticosteroid signalling system in rainbow trout HPI axis during confinement stress

This study aims to shed light on corticosteroid regulation of stress in teleost fish with focus on the corticosteroid signalling system. The role of the mineralocorticoid-like hormone 11-deoxycorticosterone (DOC) in fish is still enigmatic, as is the function of the mineralocorticoid receptor, MR. Low plasma DOC levels and ubiquitous tissue distribution of MR question the physiological relevance of the mineralocorticoid-axis. Furthermore, the particular purpose of each of the three corticosteroid receptors in fish, the glucocorticoid receptors, GR1 and GR2, and the MR, is still largely unknown. Therefore we investigate the regulation of cortisol and DOC in plasma and mRNA levels of MR, GR1 and GR2 in the HPI-axis tissue (hypothalamus, pituitary and interrenal gland) during a detailed confinement stress time-course. Here we show a sustained up-regulation of plasma DOC levels during a confinement stress time-course. However, the low DOC levels compared to cortisol measured in the plasma do not favour an activity of DOC through MR receptors. Furthermore, we show differential contribution of the CRs in regulation and control of HPI axis activity following confinement stress. Judged by the variation of mRNA levels negative feedback regulation of cortisol release occurs on the level of the pituitary via MR and on the level of the interrenal gland via GR2. Finally, as a significant effect of confinement stress on CR expressions was observed in the pituitary gland, we completed this experiment by demonstrating that corticosteroid receptors (GR1, GR2 and MR) are co-expressed in the ACTH cells located in the adenohypophysis. Overall, these data suggest the involvement of these receptors in the regulation of the HPI axis activity by cortisol