Éditeur(s) : Springer
Résumé : The structure and summertime production of planktonic communities and the role of nondiatom planktonic cells were studied in coastal ponds, which are areas traditionally used for fattening and greening table-sized oysters. The abundance and biomass of nano-microplanktonic protists were determined at weekly intervals between February 1998 and February 1999 in a coastal pond without oysters in the French Atlantic coast near La Rochelle. The production of these microbiotas was determined in the summer period. The structure of plankton communities revealed the following observations: (1) microphytoplanktonic cells were mostly diatoms and dinoflagellates, (2) microzooplanktonic cells were mainly ciliates, and (3) nanoplanktonic cells were represented by pigmented (80-90% of the nanoplankton biomass) and colorless nanoflagellates. Diatoms were dominated by Naviculiineae. Dinoflagellates were dominated by Peridiniales. Oligotrichida were predominant in the ciliate community. Protist biomass levels were nine times higher from April to August (summer period 1033 mu g C L-1) than from September to March (winter period 114 mu g C L-1). Whatever the season, nanoflagellates were dominant in the water column (66 and 53% of the entire protist biomass in the summer and winter periods, respectively). Nanoflagellates represented the highest production of nano-microplanktonic communities (76% of carbon protist production) in the coastal pond in summer and showed the shortest generation time (7.1 h). Dinoflagellates came after nanoflagellates in production (19.5% of carbon protist production). Diatoms represented only a supplementary carbon resource available for higher trophic levels, whereas, until now, they were considered as the principal food of oysters in coastal ponds. Ciliates were a small source of carbon, but their growth rate was high. We suggest, first, that nanoflagellates represented the primary resource available in the pond and could constitute an important food resource for higher trophic levels, such as oysters, farmed in this type of pond. Overall, the system appeared to be more autotrophic than heterotrophic. Because inorganic nutrients are quickly exhausted in a semiclosed pond, pigmented flagellates dominated the carbon biomass, production and biomass of bacteria were high (thus, the microbial food web appeared to be active in this pond), and mixotrophy seemed to be an important trophic mode there.
Microbial Ecology (0095-3628) (Springer), 2007-05 , Vol. 53 , N. 4 , P. 537-548

Droits : 2007 Springer
http://archimer.ifremer.fr/doc/2007/publication-2641.pdf
DOI:10.1007/s00248-006-9087-z
http://archimer.ifremer.fr/doc/00000/2641/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Diploid budding yeast undergoes rapid mitosis when it ferments glucose, and in the presence of a non-fermentable carbon source and the absence of a nitrogen source it triggers sporulation. Rich medium with acetate is a commonly used pre-sporulation medium, but our understanding of the molecular events underlying the acetate-driven transition from mitosis to meiosis is still incomplete. We identified 263 proteins for which mRNA and protein synthesis are linked or uncoupled in fermenting and respiring cells. Using motif predictions, interaction data and RNA profiling we find among them 28 likely targets for Ume6, a subunit of the conserved Rpd3/Sin3 histone deacetylase-complex regulating genes involved in metabolism, stress response and meiosis. Finally, we identify 14 genes for which both RNA and proteins are detected exclusively in respiring cells but not in fermenting cells in our sample set, including CSM4, SPR1, SPS4 and RIM4, which were thought to be meiosis-specific. Our work reveals intertwined transcriptional and post-transcriptional control mechanisms acting when a MATa/α strain responds to nutritional signals, and provides molecular clues how the carbon source primes yeast cells for entering meiosis. Our integrated genomics study provides insight into the interplay between the transcriptome and the proteome in diploid yeast cells undergoing vegetative growth in the presence of glucose (fermentation) or acetate (respiration). Furthermore, it reveals novel target genes involved in these processes for Ume6, the DNA binding subunit of the conserved histone deacetylase Rpd3 and the co-repressor Sin3. We have combined data from an RNA profiling experiment using tiling arrays that cover the entire yeast genome, and a large-scale protein detection analysis based on mass spectrometry in diploid MATa/α cells. This distinguishes our study from most others in the field-which investigate haploid yeast strains-because only diploid cells can undergo meiotic development in the simultaneous absence of a non-fermentable carbon source and nitrogen. Indeed, we report molecular clues how respiration of acetate might prime diploid cells for efficient spore formation, a phenomenon that is well known but poorly understood.
ISSN: 1874-3919

hal-01122122
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01122122
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01122122/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01122122/file/Integrated%20RNA-%20and%20protein%20profiling%20of%20fermentation.pdf
DOI : 10.1016/j.jprot.2015.01.015

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Mechanical forces influence the growth and shape of virtually all tissues and organs. Recent studies show that increased cell contractibility, growth and differentiation might be normalized by modulating cell tensions. Particularly, the role of these tensions applied by the extracellular matrix during liver fibrosis could influence the hepatocarcinogenesis process. The objective of this study is to determine if 3D stiffness could influence growth and phenotype of normal and transformed hepatocytes and to integrate extracellular matrix (ECM) stiffness to tensional homeostasis. We have developed an appropriate 3D culture model: hepatic cells within three-dimensional collagen matrices with varying rigidity. Our results demonstrate that the rigidity influenced the cell phenotype and induced spheroid clusters development whereas in soft matrices, Huh7 transformed cells were less proliferative, well-spread and flattened. We confirmed that ERK1 played a predominant role over ERK2 in cisplatin-induced death, whereas ERK2 mainly controlled proliferation. As compared to 2D culture, 3D cultures are associated with epithelial markers expression. Interestingly, proliferation of normal hepatocytes was also induced in rigid gels. Furthermore, biotransformation activities are increased in 3D gels, where CYP1A2 enzyme can be highly induced/activated in primary culture of human hepatocytes embedded in the matrix. In conclusion, we demonstrated that increasing 3D rigidity could promote proliferation and spheroid developments of liver cells demonstrating that 3D collagen gels are an attractive tool for studying rigidity-dependent homeostasis of the liver cells embedded in the matrix and should be privileged for both chronic toxicological and pharmacological drug screening.
ISSN: 0730-2312

hal-01196600
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01196600
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01196600/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01196600/file/Increasing%203D%20Matrix%20Rigidity_accepted.pdf
DOI : 10.1002/jcb.25356

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Propagation energies for five examples of deformation bands in porous sandstones from four field sites in Nevada, Utah, and France were calculated by using the J-integral approach. Pure compaction bands that accommodate primarily closing displacements from the Valley of Fire (Nevada) site have a closing-mode band propagation energy of J I = 5.5 ± 1.6 kJ/m2. Shear-enhanced compaction bands having subequal amounts of normal (closing) and shear strains across them from the same site have propagation energies of J I = 6.11 ± 1.8 kJ/m2 and J II = 1.52 ± 0.5 kJ/m2 for closing and shearing modes respectively. Closing- and shearing-mode band propagation energies for shear-enhanced compaction bands from the Buckskin Gulch (Utah) site, 5.63 ± 1.7 and 1.91 ± 0.57 kJ/m2 and the Uchaux (France) site, 11.0 ± 3.3 and 2.35 ± 0.7 kJ/m2 respectively are comparable to the values for similar structures from the Valley of Fire site. Cataclastic deformation bands at the Orange (France) site accommodate significantly larger values of shear offset than do shear-enhanced compaction bands, with a ratio of shear to closing offset that exceeds 7. The calculated closing- and shearing-mode propagation energies for these shear bands, 17.8 ± 5.4 and 3.3 ± 1.0 kJ/m2 respectively are comparable to those for pure or shear-enhanced compaction bands deformed at approximately the same depth of burial. Strain softening of cataclastic compactional shear bands implies unstable shearing, whereas stable and perhaps strain-hardening shearing may be inferred for shear-enhanced compaction bands. Displacement-length scaling relations for shear-enhanced compaction bands of the form D∝L are consistent with the results and with suggestions of band thickening during growth obtained from bifurcation analyses and with field observations of shear zones in porous host rock.
ISSN: 0376-9429

hal-00750341
https://hal.archives-ouvertes.fr/hal-00750341
DOI : 10.1007/s10704-012-9730-2

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Iron is an essential micronutrient involved in many biological processes and is often limiting for primary production in large regions of the World Ocean. Metagenomic and physiological studies have identified clades or ecotypes of marine phytoplankton that are specialized in iron depleted ecological niches. Although less studied, eukaryotic picophytoplankton does contribute significantly to primary production and carbon transfer to higher trophic levels. In particular, metagenomic studies of the green picoalga Ostreococcus have revealed the occurrence of two main clades distributed along coast-offshore gradients, suggesting niche partitioning in different nutrient regimes. Here, we present a study of the response to iron limitation of four Ostreococcus strains isolated from contrasted environments. Whereas the strains isolated in nutrient-rich waters showed high iron requirements, the oceanic strains could cope with lower iron concentrations. The RCC802 strain, in particular, was able to maintain high growth rate at low iron levels. Together physiological and transcriptomic data indicate that the competitiveness of RCC802 under iron limitation is related to a lowering of iron needs though a reduction of the photosynthetic machinery and of protein content, rather than to cell size reduction. Our results overall suggest that iron is one of the factors driving the differentiation of physiologically specialized Ostreococcus strains in the ocean.
ISSN: 2045-2322

Droits : http://creativecommons.org/licenses/by/
hal-01502140
http://hal.upmc.fr/hal-01502140
http://hal.upmc.fr/hal-01502140/document
http://hal.upmc.fr/hal-01502140/file/acclimation.pdf
DOI : 10.1038/s41598-017-00216-6

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Ghrelin is a gut-brain peptide hormone, which binds to the growth hormone secretagogue receptor (GHS-R) to regulate a wide variety of biological processes in fish. Despite these prominent physiological roles, no studies have reported the anatomical distribution of preproghrelin transcripts using in situ hybridization in a non-mammalian vertebrate, and its mapping within the different encephalic areas remains unknown. Similarly, no information is available on the possible 24-h variations in the expression of preproghrelin and its receptor in any vertebrate species. The first aim of this study was to investigate the anatomical distribution of ghrelin and GHS-R1a ghrelin receptor subtype in brain and gastrointestinal tract of goldfish (Carassius auratus) using immunohistochemistry and in situ hybridization. Our second aim was to characterize possible daily variations of preproghrelin and ghs-r1 mRNA expression in central and peripheral tissues using real-time reverse transcription-quantitative PCR. Results show ghrelin expression and immunoreactivity in the gastrointestinal tract, with the most abundant signal observed in the mucosal epithelium. These are in agreement with previous findings on mucosal cells as the primary synthesizing site of ghrelin in goldfish. Ghrelin receptor was observed mainly in the hypothalamus with low expression in telencephalon, pineal and cerebellum, and in the same gastrointestinal areas as ghrelin. Daily rhythms in mRNA expression were found for preproghrelin and ghs-r1 in hypothalamus and pituitary with the acrophase occurring at nighttime. Preproghrelin, but not ghs-r1a, displayed a similar daily expression rhythm in the gastrointestinal tract with an amplitude 3-fold higher than the rest of tissues. Together, these results described for the first time in fish the mapping of preproghrelin and ghrelin receptor ghs-r1a in brain and gastrointestinal tract of goldfish, and provide the first evidence for a daily regulation of both genes expression in such locations, suggesting a possible connection between the ghrelinergic and circadian systems in teleosts
ISSN: 1932-6203

hal-01225511
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01225511
DOI : 10.1371/journal.pone.0141043
PUBMED : 26506093

Éditeur(s) : HAL CCSD Vsevolod Gurevich
Résumé : International audience
Chemotherapy is frequently used to treat primary or metastatic cancers, but intrinsic or acquired drug resistance limits its efficiency. Sphingolipids are important regulators of various cellular processes including proliferation, apoptosis, differentiation, angiogenesis, stress, and inflammatory responses which are linked to various aspects of cancer, like tumor growth, neoangiogenesis, and response to chemotherapy. Ceramide, the central molecule of sphingolipid metabolism, generally mediates antiproliferative and proapoptotic functions, whereas sphingosine-1-phosphate and other derivatives have opposing effects. Among the variety of enzymes that control ceramide generation, acid or neutral sphingomyelinases and ceramide synthases are important targets to allow killing of cancer cells by chemotherapeutic drugs. On the contrary, glucosylceramide synthase, ceramidase, and sphingosine kinase are other targets driving cancer cell resistance to chemotherapy. This chapter focuses on ceramide-based mechanisms leading to cancer therapy sensitization or resistance which could have some impacts on the development of novel cancer therapeutic strategies.
Handb Exp Pharmacol

inserm-00871347
http://www.hal.inserm.fr/inserm-00871347
PUBMED : 23563652
DOI : 10.1007/978-3-7091-1511-4_4

Éditeur(s) : HAL CCSD European Geosciences Union
Résumé : International audience
The production of aboveground soft tissue represents an important share of total net primary production in tropical rain forests. Here we draw from a large number of published and unpublished datasets (n = 81 sites) to assess the determinants of litterfall variation across South American tropical forests. We show that across old-growth tropical rainforests, litterfall averages 8.61±1.91Mgha−1 yr−1 (mean±standard deviation, in dry mass units). Secondary forests have a lower annual litterfall than old-growth tropical forests with a mean of 8.01±3.41Mgha−1 yr−1. Annual litterfall shows no significant variation with total annual rainfall, either globally or within forest types. It does not vary consistently with soil type, except in the poorest soils (white sand soils), where litterfall is significantly lower than in other soil types (5.42±1.91Mgha−1 yr−1). We also study the determinants of litterfall seasonality, and find that it does not depend on annual rainfall or on soil type. However, litterfall seasonality is significantly positively correlated with rainfall seasonality. Finally, we assess how much carbon is stored in reproductive organs relative to photosynthetic organs. Mean leaf fall is 5.74±1.83Mgha−1 yr−1 (71% of total litterfall). Mean allocation into reproductive organs is 0.69±0.40Mgha−1 yr−1 (9% of total litterfall). The investment into reproductive organs divided by leaf litterfall increases with soil fertility, suggesting that on poor soils, the allocation to photosynthetic organs is prioritized over that to reproduction. Finally, we discuss the ecological and biogeochemical implications of these results.
ISSN: 1726-4170

hal-00594514
https://hal.archives-ouvertes.fr/hal-00594514

Éditeur(s) : HAL CCSD Cambridge University Press (CUP)
Résumé : International audience
Leishmania parasites can escape the immune response by invading cell types lacking leishmanicidal mechanisms. Silent persistence of Leishmania parasites in the host organism is responsible for asymptomatic carriage and relapses after cured leishmaniasis. Here, we studied the interaction between Hepatic Stellate Cells (HSC) and Leishmania. An original model of human HSC in primary culture infected with L. donovani was developed. The presence of intracellular parasites was studied and quantified using optical and confocal microscopy. HSC characteristics were studied using microscopy, methylene blue assay, long-term cultures and qPCR. We showed for the first time that human HSC are permissive to L. donovani infection, with no modification of HSC survival, growth rate and proinflammatory and fibrogenic characteristics. Intracellular parasites did not replicate but HSC had no effect on their survival. Indeed, after a 40-day culture, infected HSC cultures transferred on NNN medium yielded new promastigotes that were able to proliferate and efficiently infect new cells. HSC are permissive to L. donovani, with neither parasite killing nor apparent cell damage. Thus, HSC could act as potent sanctuary cells for Leishmania in the liver, which could partially explain parasite reactivation after an asymptomatic carriage or a cured visceral leishmaniasis.
ISSN: 0031-1820

inserm-00825803
http://www.hal.inserm.fr/inserm-00825803
DOI : 10.1017/S0031182012001965
PUBMED : 23253952

Éditeur(s) : Université de la Méditerranée
Résumé : This study was supported by the Atlantic working site of the « Programme National d’Océanographie Côtière » (PNOC, PNEC since 1999). The objectives were (1) to check the existence and to understand the mechanisms of winter phytoplankton blooms in the bay of Biscay influenced by the Gironde waters (2) to determine the limiting nutrient of the primary production associated to these blooms and to follow the seasonal evolution of the limiting nutrient, (3) to understand the consequences of this early limitation on the structuration of algal populations in spring. Since phosphorus was supposed to be the major limiting nutrient of algal growth in the Gironde plume, the different forms of the phosphorus cycle as well as the bacterial compartment, central in this cycle, were also studied in term of stocks and fluxes. The sampling strategy consisted in three cruises in 1998, BIOMET 2 (January), BIOMET 3 (beginning of March), PEGASE (June) and six cruises in 1999, PLAGIA 1 to 6 (late February, late April, late May, late June, the middle of July and the beginning of October). Winter algal blooms, essentially diatoms, were actually observed both in the typical waters of the plume (S < 34.5) and at the limit of the plume and adjacent atlantic oceanic waters (S > 34.5) in the successives years 1998 and 1999. These blooms were initiated by the occurrence of short anticyclonic windows in winter, acting on physical processes which dominate the evolution and characteristics of the Gironde plume (runoff, wind direction and speed) and, ultimately, on the evolution of the depth of the mixed layer (haline stratification) and available light (decrease of turbidity). The algal growth was actually phosphorus limited in the typical waters of the plume at the end of the winter bloom, in spring and became nitrogen and phosphorus limited in summer until the first autumn gales restored the nutritive balance. More oceanic waters (S > 34.5) were probably N+P limited from the end of the winter-the beginning of spring to autumn. Phosphorus limitation of winter blooms, associated with girondine unbalanced nutritive supplies (high NO3/PO4 ratios) favoured the development of small cells at the beginning of spring and the later presence of spring blooms (June 1998, late May 1999) composed of pico and nanophytoplankton (nanoflagellates), instead of typical diatom spring blooms for temperate waters. This size reduction of algal communities is strongthened by the competition between phytoplankton and bacteria for the phosphate uptake, bacteria being more competitives at low concentrations and being phosphorus limited sometimes in spring. The decreasing size of algal cells probably acted on the structuration of the whole food web. The study of the different forms of phosphorus displayed the importance of the Dissolved Organic Phosphorus (DOP) pool. The potential biological lability and the capacity of algae and bacteria to use the DOP in spring when phosphate are undetectable was shown by the very high specific activities of alkaline phosphatases and the very rapid cycling of phosphate monoesters. According to the few estimations of actual phosphatasic activity and phosphate assimilation fluxes, the hydrolysis of DOP associated with the coupled assimilation of liberated phosphate would represent 91 to 99 % of the phosphorus fluxes into algal and bacterial cells when phosphate were exhausted. In such conditions DOP could satisfy most of microorganisms phosphorus needs.
Cette thèse s’inscrit dans le cadre du Chantier Atlantique du Programme National d’Océanographie Côtière (PNOC, PNEC depuis 1999). Les objectifs de ce travail étaient (1) de vérifier l’existence et comprendre le déterminisme de blooms phytoplanctoniques hivernaux dans les eaux du Golfe de Gascogne influencées par la Gironde, (2) de préciser le facteur limitant de la production primaire associée à ces blooms et de suivre l’évolution saisonnière de ce facteur et (3) de comprendre les conséquences de cette limitation précoce sur la structuration des populations algales au printemps. Le phosphore étant supposé être le principal élément limitant de la croissance algale dans le panache de la Gironde, les différentes composantes du cycle du phosphore ainsi que le compartiment bactérien, central dans ce cycle, ont été étudiés en terme de stock et de flux. La stratégie d’échantillonnage a consisté en trois campagnes en 1998, BIOMET 2 (janvier), BIOMET 3 (début mars), PEGASE (juin) et six campagnes en 1999, PLAGIA 1 à 6 (fin février, fin avril, fin mai, fin juin, mi-juillet et début octobre). Des efflorescences algales hivernales, constituées essentiellement de diatomées, ont effectivement été observées de façon récurrente dans les eaux typiques du panache (S < 34,5) et à la limite du panache et des eaux océaniques atlantiques adjacentes (S > 34,5) au cours des deux années successives 1998 et 1999. Ces blooms ont été engendrés par l’apparition de courtes fenêtres anticycloniques en période hivernale, ces fenêtres interférant sur les processus physiques qui prévalent sur l’évolution et les caractéristiques du panache de la Gironde (régime des débits, orientation et force du vent) et, de façon ultime, sur l’évolution de la profondeur de la couche de mélange (halostratification) et la disponibilité en lumière (diminution de la turbidité). La croissance algale était limitée par le phosphore dans les eaux typiques du panache à la fin du bloom hivernal, au printemps et devint limitée en azote et en phosphore en période estivale et ceci jusqu’à ce que les premières tempêtes automnales rétablissent l’équilibre nutritif des eaux. Les eaux à caractère plus océanique (S > 34,5) étaient plus probablement limitées par N+P dès la fin de l’hiverdébut du printemps et ce jusqu’à l’automne. La limitation des blooms hivernaux par le phosphore, associée à des apports nutritifs girondins déséquilibrés en phosphate (rapports NO3/PO4 élevés) a favorisé le développement de cellules de petite taille au début du printemps et la présence ultérieure de blooms printaniers (juin 1998, fin mai 1999) composés de pico- et de nanophytoplancton (nanoflagellés), blooms « atypiques » pour des eaux tempérées à cette saison. Cette structuration des communautés algales est renforcée par la compétition entre le phytoplancton et les bactéries pour l’acquisition du phosphate, les bactéries étant plus compétitives aux faibles teneurs en phosphate et pouvant être elles-mêmes limitées par le phosphore à certains moments du printemps. La diminution de taille des cellules algales a probablement une incidence sur la structure de taille de l’ensemble du réseau trophique. L’étude des différentes composantes du phosphore montre l’importance du pool de Phosphore Organique Dissous (POD), sa labilité biologique potentielle et la capacité des communautés algales et bactériennes à utiliser ce pool au printemps quand les phosphates sont indétectables (activités spécifiques des phosphatases alcalines très élevées, recyclage très rapide des monoesters de phosphate). Au vu des quelques estimations de l’activité phosphatasique réelle et des flux d’assimilation de phosphate, l’hydrolyse du POD associée à l’assimilation couplée du phosphate libéré représenterait 91 à 99 % des flux de phosphore vers les cellules algales et bactériennes, quand les phosphates du milieu sont déficients. Dans de telles conditions, le POD pourrait satisfaire l’essentiel des besoins des microorganismes en phosphore.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00013/12463/9298.pdf
http://archimer.ifremer.fr/doc/00013/12463/

Résumé : The dynamism of small-scale fishing since the end of the sixties was able to slow the fall in employment observed since after the war in the fishing sector. If changes in the number of small-scale fishermen correspond to those of the entire primary sector, two contrasted examples, that of Martinique's small-scale fishing and that of the Boulonnais sole trammel netters, will bring out the influence of the peculiarities of this sector as well as that of the general economic environment on employment. After the first section devoted to the general evolution of employment in the fishing sector, the second section will focus on studying the influence of public assistance on the situation of Martinique's fishing industry. The third section will be devoted to the growth of coastal fishing in the Boulogne region with the sole trammel netters. The conclusion will place these two examples side by side in order to emphasize the whole of the factors to be taken into account to analyse employment in this business sector.
Le dynamisme de la pêche artisanale depuis la fin des années soixante-dix a permis de ralentir la chute de l'emploi observée depuis l'après-guerre dans le secteur de la pêche. Si l'évolution du nombre de pêcheurs artisans correspond à celle de l'ensemble du secteur primaire, deux exemples contrastés, celui de la pêche artisanale martiniquaise et celui des trémailleurs à sole boulonnais, permettront de mettre en relief l'influence des particularités de ce secteur ainsi que celle de l'environnement économique général sur l'emploi. Après une première section consacrée à l'évolution générale de l'emploi dans le secteur de la pêche, la seconde section s'attachera à étudier l'influence des aides publiques sur la situation de la pêche martiniquaise. La troisième section sera consacrée au développement de la petite pêche dans la région de Boulogne avec les trémailleurs à sole. La conclusion mettra en parallèle ces deux exemples afin de souligner l'ensemble des éléments à prendre en compte pour analyser l'emploi dans ce secteur d'activité.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/1989/rapport-2482.pdf
http://archimer.ifremer.fr/doc/00000/2482/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
To constrain the relations between deformation and metasomatism in the subcratonic lithospheric mantle, we have analyzed the microstructures and crystal preferred orientations in 50 mantle xenoliths from the Kaapvaal craton. Water contents in olivine and pyroxenes were measured in 14 samples equilibrated at different depths. Coarse-granular microstructures recording deformation by dislocation creep followed by annealing predominate. Mylonitic (sheared) peridotites with partially or totally recrystallized microstructures are however common below 140 km. Refractory compositions predominate, but multiple metasomatic events resulted in orthopyroxene enrichment or secondary crystallization of clinopyroxene and phlogopite. Coherent orthopyroxene and olivine CPO in most coarse-grained peridotites implies in pre- to syn-kinematic orthopyroxene enrichment or epitaxial growth on primary orthopyroxene. Undeformed, interstitial orthopyroxene, clinopyroxene, and phlogopite with random orientations in coarse-grained peridotites record post-kinematic modal metasomatic events. Deformation of these phases in the sheared peridotites implies that mylonitization results from a later event, which affected locally the deep cratonic lithosphere. Olivine CPO recording dominant [100] glide predominate at all depths. Only two samples, equilibrated at ~ 3.3 GPa show olivine [001] and orthopyroxene [001] axes subparallel, suggesting dominant [001] glide. Water contents in olivine are maximum (150 wt. ppm H2O) in peridotites equilibrated at ~ 160 km depth. Peridotites equilibrated below 180 km depth are, in contrast, almost dry. Lack of correlation between olivine mg# and water content indicates that the high water contents in olivine record re-hydration after the extensive partial melting, which produced the cratonic root. The vertical variation in water contents in olivine observed in the Kaapvaal peridotites may result from hydrogen addition or loss during extraction by the kimberlites. Comparison with magnetotelluric electrical conductivity data suggests, however, that the observed vertical variation of water contents in olivine may be representative of the present-day state of the Kaapvaal mantle, implying that extensive metasomatism resulted in hydration of the cratonic mantle at intermediate depths. The annealed microstructures of Kaapvaal peridotites indicate however that this metasomatism was not followed by remobilization of the cratonic root.
ISSN: 0024-4937

hal-00750328
https://hal.archives-ouvertes.fr/hal-00750328
DOI : 10.1016/j.lithos.2012.05.001

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Voltage-gated calcium currents are important for the survival and growth of embryonic cockroach brain neurons in primary culture. In the present experiments, we have studied, using the patch-clamp technique, the evolution with time in culture of the voltage-dependency and of the pharmacological properties of the calcium conductance of these neurons during the formation of a network. We have observed a progressive increase of the high-voltage-activated calcium conductance and a 10mV shift of the voltage-dependency of activation towards more negative potentials. The proportion of the R-like calcium current component increased during network formation. At the same time, the highly omega-AgaTxIVA-sensitive P-like component of the current is progressively replaced by a component which is less sensitive to the toxin. The origin and functional implications of these modifications are discussed.
ISSN: 0304-3940

hal-00982273
https://hal.archives-ouvertes.fr/hal-00982273
DOI : 10.1016/j.neulet.2004.05.002
PUBMED : 15246554

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The contourite depositional system (CDS) along the southwestern Iberian Margin (SIM), within the Gulf of Cadiz and offshore areas of western Portugal bear the unmistakable signal of Mediterranean Outflow Water (MOW) exiting the Strait of Gibraltar. This locality records key information concerning the effects of tectonic activity on margin sedimentation, the effects of MOW dynamics on Atlantic circulation, and how these factors may have influenced global climate. Over the last four decades, numerous studies have been conducted on the late Miocene, Pliocene and Quaternary sedimentary stacking pattern of Neogene basins along the SIM for both academic and resources exploration purposes. However, understanding of the region rests primarily on basic seismic stratigraphy calibrated with limited data from only a few exploration wells. The Integrated Ocean Drilling Program (IODP) Expedition 339 recently drilled five sites in the Gulf of Cadiz and two sites on the western Iberian margin. The integration of core and borehole data with other geophysical databases leads us to propose a new stratigraphic framework. Interpretation of IODP Exp. 339 data along with that from industry sources and onshore outcrop analysis helps refine our understanding of the SIM's sedimentary evolution.We identify significant changes in sedimentation style and dominant sedimentary processes, coupled with widespread depositional hiatuses along the SIM within the Cadiz, Sanlucar, Doñana, Algarve and Alentejo basins. Following the 4.5 Ma cessation of a previous phase of tectonic activity related to the Miocene–Pliocene boundary, tectonics continued to influence margin development, downslope sediment transport and CDS evolution. Sedimentary features indicate tectonic pulses of about 0.8–0.9 Ma duration with a pronounced overprint of ~ 2–2.5 Ma cycles. These more protracted cycles relate to the westward rollback of subducted lithosphere at the convergent Africa-Eurasia plate boundary as its previous NW–SE compressional regime shifted to a WNW–ESE direction. Two major compressional events affecting to the Neogene basins at 3.2–3 Ma and 2–2.3 Ma help constrain the three main stages of CDS evolution. The stages include: 1) the initial-drift stage (5.33–3.2 Ma) with a weak MOW, 2) a transitional-drift stage (3.2–2 Ma) and 3) a growth-drift stage (2 Ma-present time) with enhanced MOW circulation into the Atlantic and associated contourite development due to greater bottom-current velocity. Two minor Pleistocene discontinuities at 0.7–0.9 Ma and 0.3–0.6 Ma record the effects of renewed tectonic activity on basin evolution, appearing most prominently in the Doñana basin. Several discontinuities bounding major and minor units appear on seismic profiles. Quaternary records offer the clearest example of this, with major units of about 0.8–0.9 Ma and sub-units of 0.4–0.5 Ma. Sedimentation is controlled by a combination of tectonics, sediment supply, sea-level and climate. This research identifies time scales of tectonic controls on deep-marine sedimentation, specifically over periods of 2.5–> 0.4 Ma. Shorter-term climatic (orbital) mechanisms control sedimentation at time scales of ≤ 0.4 Ma. The role of bottom water circulation and associated processes in shaping the seafloor and controlling the sedimentary stacking pattern on continental margins has to be seriously reconsidered in future multidisciplinary studies. This is not only because of the common occurrence of sandy contourite deposits in deep water setting and their economic interest for hydrocarbon exploration, but principally because they archive the heartbeat of the interior Earth and therefore have important sedimentary and paleoceanographic implications.
ISSN: 0025-3227

hal-01356166
https://hal.archives-ouvertes.fr/hal-01356166
DOI : 10.1016/j.margeo.2015.09.013

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Cyanobacteria are ubiquitous microorganisms considered as important contributors to the formation of Earth's atmosphere and nitrogen fixation. However, they are also frequently associated with toxic blooms. Indeed, the wide range of hepatotoxins, neurotoxins and dermatotoxins synthesized by these bacteria is a growing environmental and public health concern. This paper provides a state of the art on the occurrence and management of harmful cyanobacterial blooms in surface and drinking water, including economic impacts and research needs. Cyanobacterial blooms usually occur according to a combination of environmental factors e.g., nutrient concentration, water temperature, light intensity, salinity, water movement, stagnation and residence time, as well as several other variables. These environmental variables, in turn, have promoted the evolution and biosynthesis of strain-specific, gene-controlled metabolites (cyanotoxins) that are often harmful to aquatic and terrestrial life, including humans. Cyanotoxins are primarily produced intracellularly during the exponential growth phase. Release of toxins into water can occur during cell death or senescence but can also be due to evolutionary-derived or environmentally-mediated circumstances such as allelopathy or relatively sudden nutrient limitation. Consequently, when cyanobacterial blooms occur in drinking water resources, treatment has to remove both cyanobacteria (avoiding cell lysis and subsequent toxin release) and aqueous cyanotoxins previously released. Cells are usually removed with limited lysis by physical processes such as clarification or membrane filtration. However, aqueous toxins are usually removed by both physical retention, through adsorption on activated carbon or reverse osmosis, and chemical oxidation, through ozonation or chlorination. While the efficient oxidation of the more common cyanotoxins (microcystin, cylindrospermopsin, anatoxin and saxitoxin) has been extensively reported, the chemical and toxicological characterization of their by-products requires further investigation. In addition, future research should also investigate the removal of poorly considered cyanotoxins (β-methylamino-alanine, lyngbyatoxin or aplysiatoxin) as well as the economic impact of blooms.
Environment International

hal-00875835
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00875835
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00875835/document
DOI : 10.1016/j.envint.2013.06.013
PUBMED : 23892224

Résumé : Introduction: To develop its 2005-2009 strategic plan, IFREMER made two prospective analysis studies in 2003: a thematic prospective analysis and a sectorial prospective analysis. The "aquafarming" sectorial prospective analysis, based primarily on an IFREMER idea, particularly brought to light the difference in nature of problems posed by the future evolution of shellfish farming, fish farming and other stockbreeding (pearl farming and shrimp farming). In addition, the prospective analyses made on an international scale by the FAO (2002, 2004) and the IFPRI (2003) emphasise that the development of aqua farming is the required condition for satisfying world demand of consumer aquatic products, given the foreseeable weak growth, indeed, the stagnation of caught-fish production. Considering the weak development of sea fish farming in France, a country with a long tradition of shellfish farming, it has seemed necessary to deepen the thinking about the prospective analysis devoted to sea fish farming by widening it to include all players interested in this production sector. The goal is to ensure that the strategic plan's objectives, stated in the 2005-2008 four-year contract, define a strategy fully compliant with one of IFREMER's three missions in particular: Contribute to the economic development of the maritime world.
Introduction : Pour élaborer son plan stratégique 2005-2009, l'Ifremer a réalisé en 2003 deux exercices de prospective : une prospective thématique, et une prospective sectorielle. La prospective sectorielle « aquaculture », fondée essentiellement sur une réflexion Ifremer, a mis notamment en évidence la différence de nature des problèmes posés par les évolutions futures de la conchyliculture, de la pisciculture et des autres élevages (perliculture et crevetticulture). Par ailleurs, les prospectives réalisées à l'échelle internationale par la FAO (2002, 2004) et l'IFPRI (2003) soulignent que le développement de l'aquaculture est la condition nécessaire de satisfaction de la demande mondiale d'approvisionnement en produits aquatiques de consommation, compte tenu de la prévisible faible croissance, voire stagnation, de la production des pêches de capture. Considérant le faible développement de la pisciculture marine en France, pays de longue tradition conchylicole, il est apparu nécessaire d'approfondir la réflexion prospective consacrée à la pisciculture marine, en l'élargissant à tous les acteurs concernés par ce secteur de production. Le but est de s'assurer que les objectifs du plan stratégique, déclinés dans le contrat quadriennal 2005-2008, définissent une stratégie pleinement conforme à l'une des trois missions de l'Ifremer : contribuer au développement économique du monde maritime.

Droits : 2006 Ifremer
http://archimer.ifremer.fr/doc/2006/rapport-1506.pdf
http://archimer.ifremer.fr/doc/00000/1506/

Éditeur(s) : HAL CCSD
Résumé : 1 p.
International audience
The 12th May 2008 Wenchuan earthquake in the Longmen Shan occurred on a large thrust fault largely inherited from an Indosinian structure itself probably controlled by an older structural heritage of the South China block continental margin. Within the whole northeast Tibet region, such a structural inheritance has had a major impact on the Tertiary deformation. It appears of primary importance to assess the pre-Tertiary tectonic evolution of the main blocks involved to understand the actual deformation in the eastern edge of Tibet. Over the past decades, the Proterozoic to Cenozoic tectonic, metamorphic and geochronologic history of the Longmen Shan and Songpan Garzê area have been largely studied. We present a synthesis of the tectonic evolution of the Songpan Garzê fold and thrust belt from Triassic to present. The Songpan-Garzê belt was formed during closure of a wide oceanic basin ?lled with a thick (5 to 15 km) sequence of Triassic ?yschoid sediments. Closure of the basin due to Triassic subduction involved strong shortening, intense folding and faulting of the Triassic series. A large-scale décollement, that presently outcrops along the eastern boundary of the belt (Danba area), allowed the growth of a wide and thick accretionary wedge. It develops in the Paleozoic and Triassic series and separates the accretionary prism from an autochthonous crystalline basement which shares many similarities with the basement of the Yangtze Craton (0.7-0.9 Ga). To the north and northwest, below the thickened Triassic series of the belt, the composition (oceanic or continental) of the basement remains unknown. During the Indosinian orogeny the emplacement of orogenic granites (220 - 150 Ma) was associated to crustal thickening. The isotopic composition of granitoids shows that their magma source were predominantly derived from melting of the proterozoic basement with varying degrees of sedimentary material and negligible mantle source contribution. In the Danba area, the décollement outcrops in a large tertiary antiform with a NNW-SSE axis. It has been exhumed too in the hanging wall of the NE-SW faults of the Tertiary Longmen-Shan belt that marks the present day transition from the Tibetan plateau to the Sichuan basin. These faults have episodically absorbed signi?cant shortening since the Late Triassic. The amount and precise timing of post-triassic deformation are dif?cult to constrain especially because of the dif?culty to isolate the tertiary thermochronological signal from the protracted late Triassic - Cretaceous thermal history. Nonetheless it is generally accepted that Jurassic - Cretaceous tectonism did not modi?ed the general Triassic architecture of eastern Tibet contrarily to the Tertiary deformation. The long-term cooling histories obtained on Mesozoic granites and on the metamorphic series of the Danba dome are very similar showing a very slow and regular cooling during Jurassic andCretaceous, con?rming the absence of major tectonic event between c.a. 150 and 30 Ma. Low temperature thermochronology data indicate that ?nal exhumation and cooling occurred in theTertiary with an acceleration between 10 and 5 Ma along the major tectonic structures. Within the Longmen Shan range, a total denudation of 7 to 10 km is estimated for the late Cenozoic period. Similar amounts of late Tertiary denudation have been estimated along an east-west section across the Xianshuihe fault
Asian climate and tectonics seminar
Utrecht, Netherlands

insu-00610298
https://hal-insu.archives-ouvertes.fr/insu-00610298
DOI : 10.1016/j.jseaes.2010.03.008

Éditeur(s) : HAL CCSD American Academy of Pediatrics
Résumé : International audience
Vitamin D is an essential hormone for calcium gut absorption. It is also involved in child growth, cancer prevention, immune system responses, and tooth formation. Due to inadequate vitamin D intake and/or decreased sunlight exposure, vitamin D deficiency has resurfaced in developed countries despite known inexpensive and effective preventive methods. Vitamin D deficiency is a common cause of rickets, a condition that affects bone development in children and that can have serious dental complications. Deficiency during pregnancy can cause enamel hypoplasia of primary teeth. Enamel regeneration is currently impossible; hypoplasia is therefore irreversible, and once affected, teeth are prone to fast caries development. Deficiency during early childhood can affect permanent teeth and ensuing caries can sometimes lead to tooth loss at a young age. Oral manifestations of rickets should be diagnosed early by both physicians and dentists to prevent severe dental complications. This case study presents 2 young girls with rickets in early childhood who suffered from subsequent serious tooth decay.
ISSN: 0031-4005

hal-01545477
https://hal.archives-ouvertes.fr/hal-01545477
DOI : 10.1542/peds.2013-0733

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Carbonation of peridotite is a widespread process in nature, with emerging societal and environmental implications through geological storage of CO2. We studied the micro- and nano-scale structures associated with the carbonation of peridotite pervaded by a CO2-rich water and the induced changes of its hydrodynamic properties. Focused ion beam (FIB) nanotomography was coupled with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. An experimental sample of dunite core percolated by a CO2-rich fluid (pCO2 = 11 MPa) at 160 °C was compared with a naturally carbonated sample from the Atlantic Ridge (Exp. IODP 304). Results of the 8-days percolation experiment show continuous alteration of olivine into magnesite locally associated with a poorly crystalline serpentine-type mineral referred to as proto-serpentine. The experiment is also characterized by an overall decrease in rock porosity (from 7.7 to 6.4%) and permeability (from 8.5 × 10− 16 to 1.7 × 10− 16 m2). The primary inter-granular porosity (1 to 10 μm) is progressively filled with magnesite, leading to the overall decrease of permeability. At the same time, a secondary small-scale porosity (10 nm to 1 μm) is created at the tip of the dissolution features along the (010) cleavage planes of olivine grains. Carbonate crystals grow within these etch-pit structures behind the dissolution front. Dissolution and precipitation occur at a relative rate that maintains the secondary porosity over the timescale of the experiment (i.e. carbonate growth has to be the slowest one). This process is interpreted as an interface coupled dissolution-precipitation mechanism of olivine carbonation. Proto-serpentine is only formed in highly reduced flow areas, such as small olivine etch-pits (10 to 500 nm wide), which are more isolated from CO2 input. SEM-FIB analyses show the 3D preferential orientation of the dissolution-precipitation planes within a given olivine grain. It suggests the formation of lateral connections between the etch-pits (infra-micrometric “channels”) providing access to reactants and removing reaction products at the reaction sites. The experimental results show that olivine dissolution and magnesite precipitation converge to a quasi-steady state resulting in a constant carbonation rate controlled by reaction kinetics and not by mass transfer for this flow regime. The system self-regulates, independently of the porosity change at least during this incipient stage of olivine carbonation. Similar textures are observed in natural samples collected at 170 m-depth in the vicinity of veinlets driving late fluids down into the cooling oceanic lithosphere. This suggests that similar mechanisms are active in nature and can play an important role in the late, low temperature alteration stages of fractured peridotite. These results also highlight the critical role of nm-scale spatial arrangement of dissolution and precipitation features on mass transfers and on the sustainability of olivine carbonation through coupled dissolution-precipitation processes.
ISSN: 0009-2541

hal-01684733
https://hal.archives-ouvertes.fr/hal-01684733
DOI : 10.1016/j.chemgeo.2017.11.013