HAL-Université de Bretagne Occidentale
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Télégraphes de l'Utopie. L'art des avant-gardes en Europe centrale, 1918-1939
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Testing the use of southern France and Cyprus mouflons as a reference to reconstruct birth season in sheep from oxygen isotope analysis in teeth
No full textInternational audienceReconstructing past sheep birth seasons relies on oxygen isotope analysis in dental enamel, using modern reference datasets with known birth seasons for comparison. However, the comparability of dental growth calendar between modern and ancient sheep remains uncertain. The current mouflons in Europe, descended from Neolithic domestic sheep that later became feral in Corsica, Sardinia, and Cyprus, are amongst the closest living relatives of Neolithic sheep. Their suitability as references for the estimation of the birth season was explored by analysing the third molar of individuals from two populations giving birth in the spring: Cyprus mouflons (n = 7) and Mediterranean mouflons from southern France (n = 10). Results from oxygen isotope analysis of dental enamel reflect environmental and management differences (e.g., wild vs. captive conditions, local climate and seasonal temperature fluctuations). Isotopic sequence modelling indicated a good agreement between the Mediterranean mouflons from southern France and previously published western European sheep references. However, a radical shift in the record of the δ 18 O values of the seasonal cycle between the Cyprus mouflon and the sheep references has been observed. This divergence suggests distinct dental growth calendars between the Cyprus mouflons and the remaining Ovis included in the study, which may be attributed to a different genetic lineage, reduced genetic diversity in Cyprus mouflons due to one or more founder events-potentially leading to the expression of traits not present or rarely present in the source population-and/or long-term isolation resulting in phylogenetic drift.These findings suggest that Mediterranean mouflons from southern France are as suitable as modern sheep breeds as references for reconstructing past birth seasons in Western Europe. In contrast, the use of the Cyprus mouflons as a reference requires further investigation, both in the context of Cyprus and more broadly across the Near East
Toward a Taxol-producing microbial cell factory
No full textInternational audienceScedosporium species are opportunistic filamentous fungi found in human-impacted areas. Clinically relevant species, such as S. apiospermum, rank as the second most frequent colonizers of the airways of patients with cystic fibrosis (CF), which are characterized by persistent oxidative stress. This raises the question of how Scedosporium species abate conditions imposed in hostile environments. Since the High Osmolarity Glycerol (HOG) pathway plays a central role in fungal adaptation to stress, we aimed to pheno-profile the involvement of the pathway in response to stress in S. apiospermum using Western blot. We show for the first time that a wide range of stress distinctively activates the HOG pathway in S. apiospermum, including oxidants (H2O2, menadione, cumene hydroperoxide, diamide, paraquat, and honokiol), osmotic agents (sorbitol and KCl), cell-wall stress agents (caffeine, calcofluor white, and Congo Red), heavy metals (cadmium and arsenite), fungicides (fludioxonil and iprodione), antifungals (voriconazole and amphotericin B), and acid stress (pH 4). We suggest that the function of the HOG pathway as a general stress regulator is also conserved in S. apiospermum
Enseigner-apprendre la sociologie au lycée.: Un cadre théorique pour saisir l'articulation sens-commun savoirs sociologiques.
No full textInternational audienceIn our thesis, we analyze a lesson in which 10th-grade students study a statistical table showing how women and men divide their time (Ricroch, 2012). Teachers expect students to identify differences in behavior and then explain them using the concept of socialization (the set of processes through which individuals incorporate dispositions to act, think, and feel in a certain way in a certain context). We apply the intermediate model of history appropriation (Lautier, 1997) from history teaching, which is based on Moscovici's theory of social representations (Moscovici, 2004; Moscovici & Hewstone, 2017). We show that, as in history class, students learn by spontaneously connecting knowledge with common sense, transforming it to give it meaning. As in history class, the socialization of knowledge is accompanied by a phase of rationalization in which teachers lead a collective examination of spontaneous connections. In history classes, teachers use historicization techniques: source criticism, periodization, etc. (Cariou, 2012). This parallel invites us to focus our research on the sociological processes of distancing ourselves from common sense.Dans notre travail de thèse nous analysons une séance où les élèves, en classe de seconde, étudient un tableau statistique représentant la façon dont les femmes et les hommes répartissent leur temps (Ricroch, 2012). Les professeur.e.s attendent que les élèves établissent la différenciation des comportements puis l’expliquent en s’appuyant sur le concept de socialisation (ensemble des processus au cours desquels les individus incorporent des dispositions à agir, penser et sentir d’une certaine manière dans un certain contexte). Nous mettons au travail le modèle intermédiaire de l’appropriation de l’histoire (Lautier, 1997) issu de la didactique de l’histoire qui prend appui sur la théorie des représentations sociales de Moscovici (Moscovici, 2004; Moscovici & Hewstone, 2017). Nous montrons que, comme en classe d’histoire, les élèves apprennent en rapprochant spontanément le savoir du sens commun, en le transformant pour lui donner une signification. Comme en classe d’histoire, la socialisation du savoir s’accompagne d’une phase de rationalisation où les professeur.e.s dirigent l’examen collectif des rapprochements spontanés. En classe d’histoire les professeur.e.s mobilisent des opérations d’historicisation : la critique des sources, la périodisation, etc. (Cariou, 2012). Le parallèle invite à axer notre recherche sur les procédés sociologiques de mise à distance du sens commun
Trenches apart, yet worm to worm: inter- and intra-trench comparisons reveal divergent and convergent dynamics in hadal nematode biodiversity
No full textInternational audienceThe hadal zone, the deepest part of the global ocean, encompasses several extreme ecosystems with elevated biological activity, contrasting the general trend of declining biomass and biodiversity with increasing water depth. These bathymetrically isolated habitats act as depocenters and are characterized by high hydrostatic pressure and unique environmental conditions that provide an opportunity to fundamentally explore biogeographic patterns and the genetic diversity of deep-sea meiofauna, which remain poorly understood. In this study, we compared nematode communities in two geographically distant trench systems, the Aleutian Trench (North Pacific) and the South Sandwich Trench (South Atlantic), separated by 17 000 km. Environmental DNA (eDNA) sequencing targeting the ribosomal 18S region was combined with a metaphylogeography approach. Comparative analyses were performed for intra- and inter-trench, biodiversity and genetic differentiation across environmentally characterised trench-specific habitats. Our findings reveal evidence for the meiofauna paradox in hadal settings, demonstrating distinct nematode communities that appear to be shaped by availability and quality of food. Furthermore, environmental filtering appeared to contribute to assembly of habitat specific communities according to localised environmental condition. Finally, we observed shared haplotypes among some dominating nematode genera, suggesting potential connectivity between habitats associated within or even across hadal trenches might exist. Overall, this study provides valuable insights on how environmental factors drive nematode biodiversity and genetic diversity in the hadal realm. Environmental heterogeneity plays a pivotal role in shaping nematode communities, influencing their population structure and connectivity by creating spatially variable habitats that drive diversification, local adaptation, and gene flow patterns
Cytotoxicity of polystyrene nanoplastics involves mitochondrial dysfunction and DNA damage in hemocytes of the Pacific oyster
No full textInternational audienceNanoplastics represent an increasing ecological threat to marine ecosystems, with the potential to disrupt immune responses, oxidative stress pathways, and bioenergetics. We employed an in vitro cellular bioassay to investigate the distribution, metabolic disruption, and genotoxicity resulting from 24 hours of exposure to polystyrene nanoplastics (NanoPS, approximately 90 nm) in the hemocytes of the Pacific oyster (Crassostrea gigas). Transmission electron microscopy suggested the internalization and distribution of NanoPS within vesicles, the cytosol, and the nuclei of exposed hemocytes. Cytotoxicity assays revealed that metabolic activity (resazurin assay, LC50 = 91.6 mg/L) was more sensitive than lysosomal integrity (neutral red assay, LC50 = 252.3 mg/L). Exposure to NanoPS also increased the levels of reactive oxygen species and DNA damage as low as 1.2 mg/L. Metabolic assays revealed that enhancing mitochondrial metabolism through galactose supplementation increased the cytotoxicity and DNA damage caused by NanoPS. Conversely, promoting anaerobic metabolism with glucose supplementation reduced these effects. Co-exposures with the mitochondrial uncoupler FCCP did not decrease cellular viability but elevated DNA damage. We suggest that mitochondria are a sensitive target of nanoplastics in bivalve hemocytes, highlighting the importance of considering aerobic metabolism in assessing nanoplastic toxicity. The strong correlation with the published in vivo effects of this same NanoPS highlights the biological relevance of this cellular toxicity assessment. This research supports the use of hemocyte-based cellular assays to complement in vivo studies for characterizing nanoplastic toxicity mechanisms in marine organisms
Mass Spectrometry for In-Depth Study and Discovery of Marine Bioactive Metabolites
No full textInternational audienceThis chapter examines the use of mass spectrometry as an effective tool for the detailed study and discovery of bioactive metabolites of marine origin. The seas and oceans are full of organisms that generate a significant variety of natural compounds with pharmacological, cosmetic, and nutraceutical effects. Thanks to its high sensitivity and analytical resolution, mass spectrometry is able to identify, characterize, and quantify these molecules, even when they are found in complex matrices. This chapter discusses the main categories of marine metabolites, methods frequently used in mass spectrometry, and approaches for discovering new bioactive substances. It also highlights contemporary issues and future directions concerning the sustainable use of these natural resources in research and industry
PROSE+ project: offshore seismic measurements on the seabed to test the ability to assess the spatial variation of the small-strain shear modulus in the subsurface environment
No full textInternational audienceThe increase in the number of offshore wind farm siting projects, combined with the multiplicity of developments in anchoring techniques, means that foundations and anchors need to be optimized for the conditions of the offshore subsurface, requiring precise knowledge of the mechanical characteristics of the medium. According to the recommendations of the CFMS (French committee of Soils Mechanics), detailed geophysical reconnaissance is then necessary during the project phase (design and execution) to obtain the most accurate information possible at the locations of the structures. In this context, the PROSE+ project aims to increase knowledge and provide new methodological and technical elements, based on surface seismic and geoelectrical techniques. This will make possible to approach heterogeneous environments in a quantitative and non-destructive way, thereby reducing the number of costly and invasive geotechnical surveys. To this end, we developed numerically a 2D seismic inversion technique using Surface Seismic Waves based on Particle Swarm optimization methods. In order to validate it on experimental data, we carried out measurements off Concarneau using 70 4-components sensors (GPR -Sercel nodes) placed on the seabed, in an unprecedented manner. 241 seismic shots were fired over this sensor's network using an air gun at variable water depth. Finally, the sensors were left recording on the seafloor for 28 days. The recorded seismic data allow to test the capacity of both active and passive seismic imaging process to assess the shear modulus in a 2D medium under seabed
