Résumé : in mollusc hatcheries. Consequently, we assessed themost commonly used species to establish their growth and size profiles, their cytomorphological, biochemical, biomolecular identification as well as their cytometer signs, and also their ability to grow under extreme conditions of temperature and salinity. This work aimed at matching the conformity of the strains used in Argenton (dispatched to most of the French commercial hatcheries) to those of a referenced culture collection. A previous screening preceded this study, because of the 45 species and/or clones held originally, Argenton kept no more than 15 species. As most of the latter are also represented in referenced collection, our strains are therefore correctly identified. On the other hand, the combination of several approaches (characteristic of growth and size, cytomorphological description, establishment of biochemical and biomolecular profiles) to discriminate the different species was broadly successful. Nevertheless, flow cytometer measurements were extremely variable from sample to sample, dueto their high sensitivity to the microalga's physiological state. Accordingly, we have developed a method of identification which could be transferred at a national or international level, to the Institutions in charge of microalgae collections. Furthermore, we achieved relevant data to establish an identity card for each of the microalgae suitable for mollusc hatcheries.
La caractérisation des microalgues fourrage constituait l'un des points perfectibles au regard de ce qui est appliquée en microbiologie. Nous avons alors cherché à définir, pour les espèces les plus utilisées en écloserie, leurs profils de croissance et de taille, leur caractéristiques cytomorphologique, cytofluorimétrique, biochimique et biomoléculaire, et enfin, précisé leur aptitude au développement sous des conditions extrêmes de température et de salinité (écotolérance). Ce travail avait pour but de vérifier, d'une part, la conformité des souches utilisées à l'écloserie d'Argenton (auprès de laquelle se fournissent la plupart des écloseries commerciales françaises) en comparant les espèces utilisées à celles issues d'une collection référencée. Un premier balayage avait été réalisé avant la mise en place de cette étude puisque sur les 45 espèces et clones détenus originellement, Argenton ne possédait plus que 15 espèces. La plupart de ces dernières ayant leur équivalent en collection référencée notre souchier est désormais parfaitement identifiée. D'autre part, la confrontation de plusieurs approches, caractéristique de la croissance et de taille, description cytomorphologique, établissement des profils biochimique et biomoléculaire, écotolérance, signature cytofluorimétrique, pour discriminer les différentes espèces de microalgues fourrage a été globalement couronnée de succès. Seule cette dernière technique n'a pas permis de caractériser les espèces entre elles, les paramètres mesurés en cytométrie de flux étant particulièrement sensibles à l'état physiologique des microalgues, très variable d'un échantillon à un autre. Nous disposons dorénavant d'une méthode d'identification qu'il serait souhaitable de transférer, au niveau national voire international, auprès des organismes en charge des collections. De plus, nous disposons dorénavant de données pertinentes pour établir pour chacune des microalgues d'intérêt aquacole une véritable carte d'identité.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2004/rapport-1546.pdf
http://archimer.ifremer.fr/doc/00000/1546/

Éditeur(s) : HAL CCSD Springer-Verlag Berlin Heidelberg
Résumé : International audience
The main biological function of reaction wood is to act as " muscle " for trees, enabling them to control their posture. The key property to achieve this function is the development of high mechanical stress during the formation of reaction wood cells, called " maturation strains ". Actually, reaction wood formation is basically the asymmetric formation of wood around the tree circumference, with higher maturation strains on the side where reaction wood is formed than on the opposite side. This asymmetry enables stems to bend upward or to compensate for the downward bending induced by gravity. At the cross section level, the performance in this biological function is linked not only to the magnitude of this asymmetry but also to an effect of the cross-sectional size (diameter) of the stem. Eccentric growth and variations in wood mechanical stiffness are second order effects that can modify this performance. Differences in maturation strains between reaction and non-reaction woods are related to their specific cell wall structure and composition. The swelling of the cell wall matrix during maturation and the effect of microfibril angle explain the differences in maturation strains between normal and compression wood. However, this mechanism fails in explaining the high maturation shrinkage of tension wood, and several hypotheses at the molecular levels are still under debate. How trees perceive their gravitational disequilibrium is also an open question for physiologists. Integrative biomechanical modelling (from the polymer level to the cell wall, cross section and whole tree levels) enables defining key variables that explain the performance of reaction wood as a system that insures the stem motricity. Maturation strains can be precisely measured only in recently formed wood at the tree surface, but their changes during the whole tree life can also be estimated by retrospective dendrochronological analysis through structural markers of reaction wood. Lastly, wood in living trees ensures general storage, defence, vascular and skeletal functions, that ask general questions about synergies and trade-offs as the structural characteristics of reaction wood can affect all these functions.
The Biology of Reaction Wood

ISBN : 978-3-642-10813-6
hal-01452085
https://hal.archives-ouvertes.fr/hal-01452085
https://hal.archives-ouvertes.fr/hal-01452085/document
https://hal.archives-ouvertes.fr/hal-01452085/file/Chap_Gril_al_Biomechanical_action_biological_functions_2014.pdf

Éditeur(s) : HAL CCSD American Society for Biochemistry and Molecular Biology
Résumé : International audience
The budding yeast Saccharomyces cerevisiae is a major model organism for important biological processes such as mitotic growth and meiotic development, it can be a human pathogen, and it is widely used in the food-, and biotechnology industries. Consequently, the genomes of numerous strains have been sequenced and a very large amount of RNA profiling data is available. Moreover, it has recently become possible to quantitatively analyze the entire yeast proteome; however, efficient and cost-effective high-throughput protein profiling remains a challenge. We report here a new approach to direct and label-free large-scale yeast protein identification using a tandem buffer system for protein extraction, two-step protein prefractionation and enzymatic digestion, and detection of peptides by iterative mass spectrometry. Our profiling study of diploid cells undergoing rapid mitotic growth identified 86% of the known proteins and its output was found to be widely concordant with genome-wide mRNA concentrations and DNA variations between yeast strains. This paves the way for comprehensive and straightforward yeast proteome profiling across a wide variety of experimental conditions.
ISSN: 1535-9476

hal-00682837
https://hal.archives-ouvertes.fr/hal-00682837
DOI : 10.1074/mcp.M111.012682
PUBMED : 21997732

Éditeur(s) : HAL CCSD
Résumé : In Taiwan , the subduction of the Chinese continental margin under the Luzon arc results in the progressive growth of an active orogenic wedge. It is one of the best places to study the complex relationships that occurs between the tectonic processes controlling deformation (plate rheology and kinematics, metamorphism and magmatism) and surface processes (erosion and sedimentation). In order to study the kinematics of the present day convergence of Philippine Sea plate to the Asian continent around Taiwan, we perform 2D and 3D sandbox modeling and we analyzed the models with PIV (Particle Image Velocimetry) software. In 2D experiments, a model Coulomb wedge is submitted to erosion and sedimentation under topography and flux steady state conditions. The 3D experiments are mainly used to study the escape tectonics occurring in the middle west and southwest Taiwan. A wedge shaped indenter and a basement relief were used to simulate the mechanical plate boundary between Philippine Sea plate and Eurasia plate and the basement topography to the west of Taiwan respectively. We examine the exhumation patterns, the mode of fault propagation and displacement patterns by strain partitioning of vertical vs. horizontal displacement and convergent parallel vs. orogen parallel components. The preliminary conclusions are: 1. The interactions between tectonics, erosion and sedimentation control geometry and kinematics of the doubly vergent transpressional orogen. 2. Exhumation processes are controlled by the balance between erosion, frontal accretion and underplating in different structural domains of the wedge. 3. Retrowedge erosion favorites backfolding and backthrusting, induces flower structures and fan shaped cleavage distribution. 4. Sedimentation promotes underplating and out-of sequences thrusting. 5. Continental subduction or subduction of topographic highs will enhance underthrusting/underplating, thick-skin tectonics and inversion of sedimentary basin.
Bolletino di Geofisica teorica ed applicata

hal-00411133
https://hal.archives-ouvertes.fr/hal-00411133

Éditeur(s) : PSIC 11 - 11th Pacific Science Inter-Congress : Pacific Countries and their Ocean: Facing Local and Global Changes / 2nd Symposium on French Research in the Pacific. March 2 - 6, 2009 Tahiti, French Polynesia
Résumé : Shrimp farming in New Caledonia relies on the culture of a domesticated strain of Litopenaeus stylirostris introduced from Mexico at a time when genetic principles were of little or no consideration. Since then, advances in agriculture and for some aquatic species of importance led caledonian shrimp farmers to reconsider the appropriateness of a genetic improvement strategy adapted to local biotechnical and economical constraints. This questioning involves many different and interrelated aspects: scientific and technologic (genetics, biosecurity, quarantine, ), economic and organizational (financing, diffusion of genetic improvement) and pedagogic (awareness of farmers). Local institutions, producers associations, research centre and sanitary services associated to carry on the test of a first improvement strategy based on the crossing of different strains of L. stylirostris. This conceptually simple approach aimed at eliminating inbreeding, the first genetic limitating factor of improvement in captive populations. A second domesticated strain was obtained from Hawaii by the caledonian farmers, imported through a quarantine under the control of the zoosanitary local authorities, and reproduced and tested as pure or crossbred stocks by Ifremer within the framework of an interdisciplinary research project financed by caledonian institutions. Present results for hybrids (better growth and survival in the absence of virus) demonstrate the validity of this approach. They also bring out the importance to simultaneously integrate in a development scheme, a breeding centre to maintain and reproduce disease free breeders. This strategy and organization, tested in New Caledonia, could possibly be of benefit to other small scale aquaculture activities in the pacific islands.
La filière crevetticole de Nouvelle-Calédonie s’est développée jusqu’à aujourd’hui à partir d’un stock domestiqué de Litopenaeus stylirostris introduit d’Amérique à une époque où les principes de base en génétique n’étaient pas ou peu appliqués en aquaculture. Les avancées récentes en agriculture et chez quelques espèces aquacoles d’importance mondiale ont conduit les acteurs de cette filière à se poser la question de la mise en place d’une stratégie d’amélioration génétique adaptée aux contraintes biotechniques et économiques locales. Cette réflexion comportait à la fois des aspects scientifiques et technologiques (génétique, biosécurité, quarantaine, conservatoire), économiques et organisationnels (coût de l’opération, modalité de diffusion du progrès attendu), pédagogiques (sensibilisation des fermiers). Des acteurs d’horizons différents (institutions locales, association de producteurs, centre de recherche, police zoosanitaire) se sont associés pour monter une opération de testage d’une première stratégie d’amélioration par croisement de souches de la même espèce. Cette stratégie conceptuellement simple visait l’élimination du premier facteur génétique de limitation des performances d’élevage d’une population captive, à savoir une consanguinité d’autant plus élevée que le nombre de géniteurs fondateurs était faible. Une seconde souche domestiquée a ainsi été acquise à Hawaii par les producteurs calédoniens, contrôlée en quarantaine par les services vétérinaires calédoniens en charge de la réglementation sanitaire, reproduite et testée pure et en croisement par l’Ifremer dans le cadre d’un projet de recherche pluridisciplinaire plus large financé par les institutions du Pays. Les résultats obtenus démontrent l’intérêt de la démarche (meilleure croissance, meilleure survie en l’absence de virus). Mais ils montrent aussi l’utilité d’intégrer simultanément dans le plan de développement de la filière une stratégie de conservation des souches parentales afin de disposer de géniteurs exempts de pathogènes. Cette stratégie et cette organisation testées en Nouvelle-Calédonie pourraient vraisemblablement être profitables à d’autres filières aquacoles modestes, en particulier dans les pays insulaires du Pacifique.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00198/30879/29247.pdf
http://archimer.ifremer.fr/doc/00198/30879/

Éditeur(s) : HAL CCSD Instituto Oswaldo Cruz, Ministério da Saúde
Résumé : International audience
Leishmania are protozoan parasites that show remarkable diversity, as revealed by the various clinical forms of leishmaniasis, which can range from mild skin lesions to severe metastatic cutaneous/mucosal lesions. The exact nature and extent of Leishmania phenotypic diversity in establishing infection is not fully understood. In order to try to understand some aspects of this diversity, we subcutaneously infected BALB/c mice with first and second generation subclones of a L. amazonensis strain isolated from a patient (BA125) and examined in vivo lesion growth rate and antimony susceptibility. In vivo fast-, medium- and slow-growing subclones were obtained; moreover, fast-growing subclones could generate slow-growing subclones and inversely, revealing the continuous generation of diversity after passage into mice. No antimony-resistant subclone appeared, probably a rare occurrence. By tagging subclone cells with a L. amazonensis genomic cosmid library, we found that only a very small number of founding cells could produce lesions. Leishmania clones transfected with in vivo selected individual cosmids were also diverse in terms of lesion growth rate, revealing the cosmid-independent intrinsic characteristics of each clone. Our results suggest that only a few of the infecting parasites are able to grow and produce lesions; later, within the cell mixture of each lesion, there coexist several parasite populations with different potentialities to grow lesions during the next infection round. This may reflect a sort of programmed heterogeneity of individual parasites, favoring the survival of some individuals in various environmental conditions.
ISSN: 0074-0276

hal-01489009
https://hal-univ-perp.archives-ouvertes.fr/hal-01489009

Éditeur(s) : Wiley-blackwell
Résumé : Alexandrium tamarense (M. Lebour) Balech strains isolated in spring 2007 from a single bloom in Thau lagoon have been grown in nonaxenic artificial media. For three strains showing large oscillations in biomass (crashes followed by recoveries) on a scale of several days, a significant relationship was observed between changes in cell densities (as in vivo fluorescence) and changes in nitrate concentrations. Increases in cell densities were accompanied by decreases in nitrate, while decreases in cell densities corresponded to increases in nitrate, presumably due to nitrification. Net increases in nitrate could reach up to 15 mu mol N . L(-1) . d(-1) indicating a very active nitrifying archaeal/bacterial population. However, following population crashes, algal cells can recover and attain biomass levels similar to those reached during the first growth phase. This finding indicates that those archaea/bacteria do not compete for nutrients or do not hamper algal growth under those conditions. In contrast to diatoms, dinoflagellates such as A. tamarense do not excrete/exude dissolved organic matter, thus preventing excessive bacterial growth. This mechanism could help explain the recovery of this species in the presence of bacteria.
Journal Of Phycology (0022-3646) (Wiley-blackwell), 2011-10 , Vol. 47 , N. 5 , P. 1057-1062

Droits : 2011 Phycological Society of America
http://archimer.ifremer.fr/doc/00049/16046/13585.pdf
DOI:10.1111/j.1529-8817.2011.01031.x
http://archimer.ifremer.fr/doc/00049/16046/

Éditeur(s) : HAL CCSD Wiley-Blackwell
Résumé : International audience
Lawsonite pseudomorphs are used to identify and distinguish the kinematic records of subduction and exhumation in blueschist-facies rocks from Syros (Cyclades; Greece). Lawsonite is a hydrous mineral that crystallizes at high-pressure and low-temperature conditions. During decompression, lawsonite is typically pseudomorphed by an aggregate dominated by epidote and paragonite. Such aggregates are easily deformable and if deformation occurs after the lawsonite breakdown, the pseudomorphs are difficult to distinguish from the matrix. The preservation of the lawsonite crystal shape, despite complete retrogression, indicates therefore that the host blueschist rock has not been affected by penetrative deformation during exhumation, thus providing indication of strain-free conditions. Therefore, tracking the lawsonite growth and destabilization along the P-T path followed by the rocks during a subduction/exhumation cycle provides information about the subduction/exhumation-related deformation. Using microstructural observations and P-T pseudosections calculated with thermocalc, it is inferred that top-to-the-south sense of shear preserved in lawsonite pseudomorph-bearing blueschists on Syros occurred during the prograde metamorphic path within the lawsonite stability field, and is therefore associated with subduction. On the contrary, the deformation with a top-to-the-north sense of shear is observed in surrounding rocks, where lawsonite pseudomorphs are deformed or apparently lacking. This deformation occurred after the lawsonite breakdown during exhumation. At the regional scale, exhumation-related deformation is heterogeneous, allowing the preservation of lawsonite pseudomorphs in significant volumes of blueschists of the central and southern Cyclades. It is argued that such successive shearing deformation events with opposite senses more likely correspond to an exhumation process driven by slab rollback, in which subduction and exhumation are not synchronous
ISSN: 0263-4929

insu-00841214
https://hal-insu.archives-ouvertes.fr/insu-00841214
DOI : 10.1111/jmg.12035

Éditeur(s) : HAL CCSD Springer Verlag/EDP Sciences
Résumé :  
On 10 trees from 10 species of French Guyana tropical rainforest in a clear active process of restoring verticality growth strains were measured in situ in order to determine the occurrence of tension wood within samples. Wood specimens were cut in the vicinity of the growth strains measurements in order to measure some mechanical and physical properties. As suspected, tensile growth strains was very much higher in tension wood zone, because longitudinal modulus of elasticity was slightly higher. Longitudinal shrinkage was also much higher in tension wood than in opposite wood.
ISSN: 1286-4560

hal-01032110
https://hal.archives-ouvertes.fr/hal-01032110
DOI : 10.1051/forest:2007027

Éditeur(s) : HAL CCSD
Résumé : International audience
The search for safe antimalarial compounds acting against asexual symptom-responsible stages and sexual transmission-responsible forms of Plasmodium species is one of the major challenges in malaria elimination programs. So far, among current drugs approved for human use, only primaquine has transmission-blocking activity. The discovery of small molecules targeting different Plasmodium falcip-arum life stages remains a priority in antimalarial drug research. In this context, several independent studies have recently reported antiplasmodial and transmission-blocking activities of commonly used stains, dyes and fluorescent probes against P. falciparum including chloroquine-resistant isolates. Herein we have studied the antimalarial activities of dyes with different scaffold and we report that the triar-ylmethane dye (TRAM) Brilliant green inhibits the growth of asexual stages (IC 50 2 mM) and has exflagellation-blocking activity (IC 50 800 nM) against P. falciparum reference strains (3D7, 7G8) and chloroquine-resistant clinical isolate (Q206). In a second step we have investigated the antiplasmodial activities of two polysulfonated triarylmethane food dyes. Green S (E142) is weakly active against P. falciparum asexual stage (IC 50 x 17 mM) whereas Patent Blue V (E131) is inactive in both antimalarial assays. By applying liquid chromatography techniques for the culture supernatant analysis after cell washings and lysis, we report the detection of Brilliant green in erythrocytes, the selective uptake of Green S (E142) by infected erythrocytes, whereas Patent Blue V (E131) could not be detected within non-infected and 3D7-infected erythrocytes. Overall, our results suggest that two polysulfonated food dyes might display different affinity with transporters or channels on infected RBC membrane.
International journal for parasitology. Drugs and drug resistance

Droits : http://creativecommons.org/licenses/by-nc-sa/
pasteur-01614675
https://hal-pasteur.archives-ouvertes.fr/pasteur-01614675
https://hal-pasteur.archives-ouvertes.fr/pasteur-01614675/document
https://hal-pasteur.archives-ouvertes.fr/pasteur-01614675/file/Leba%20LJ-article%20colorant-version%20publiee.pdf
DOI : 10.1016/j.ijpddr.2017.07.002

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 Elsevier
Résumé : International audience
We conducted a laser-equipped analog experiment aimed at quasi-continuously monitoring the growth of a dense population of normal faults in homogeneous conditions. To further understand the way geological faults progressively gain in slip and length as they accumulate more strain, we measured with great precision the incremental slip and length changes that the analog faults sustain as they grow. These measurements show that the analog faults share common features with the natural ones. In particular, during their growth, the faults develop and maintain cumulative slip profiles that are generally triangular and asymmetric. The growth takes place through two distinct phases: an initial, short period of rapid lateral lengthening, followed by a longer phase of slip accumulation with little or no lengthening. The incremental slip is found to be highly variable in both space (along the faults) and time, resulting in variable slip rates. In particular, ‘short- and long-term' slip rates are markedly different. We also find that slip measurements at local points on fault traces do not contain clear information on the slip increment repeat mode. Finally, while the fault growth process is highly heterogeneous when considered at the scale of a few slip events, it appears homogeneous and self-similar at longer time scales which integrate many slip increments. This is likely to be the result of a feedback between stress heterogeneities and slip development. The long-term scale homogeneity also implies that the long-term faulting process is primarily insensitive to the short-term heterogeneities that are rapidly smoothed or redistributed. We propose a new conceptual scenario of fault growth that integrates the above observations and we suggest that faults grow in a bimodal way as a result of a self-driven and self-sustaining process.
ISSN: 0012-821X

Droits : info:eu-repo/semantics/OpenAccess
insu-00351998
https://hal-insu.archives-ouvertes.fr/insu-00351998
https://hal-insu.archives-ouvertes.fr/insu-00351998/document
https://hal-insu.archives-ouvertes.fr/insu-00351998/file/SchlagenhaufEtAl2008_EPSL_author.pdf
DOI : 10.1016/j.epsl.2008.06.042

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Transverse drying shrinkage was measured at microscopic and mesoscopic levels in poplar wood characterised by an increasing growth strain (GS), from normal to tension wood. Results show that: (a) The drying shrinkage, measured as a relative thickness decrease, was significantly higher for G-layer (GL) than the other layers (OL), GL shrinkage was not significantly correlated with GS and OL shrinkage was negatively correlated with GS. (b) In gelatinous fibre (G-fibre), lumen size increased during drying and this increase was positively related with GS, but in normal wood fibre lumen size decreased during drying. These findings suggest that GL shrank outwards, so that its shrinkage feebly affected the total cell shrinkage and the mesoscopic shrinkage was controlled by the OL shrinkage which shrank inwards. (c) Measurements done on 7×7 mm² thin sections evidenced a negative correlation between transverse shrinkage and GS, significant in T direction but weak in R direction. These observations at both levels allow to discuss the contribution of GL to the mesoscopic shrinkage of tension wood.
ISSN: 0043-7719

hal-00194930
https://hal.archives-ouvertes.fr/hal-00194930
https://hal.archives-ouvertes.fr/hal-00194930/document
https://hal.archives-ouvertes.fr/hal-00194930/file/WST_FANG2006.pdf
DOI : 10.1007/s00226-007-0148-3

Éditeur(s) : HAL CCSD Trans Tech Publications Inc.
Résumé : Two, high purity, Al-0.1 and 0.3wt%Mn alloys have been cold deformed in plane strain compression to strains of order 1.8 and the kinetics of subsequent recovery by sub-grain coarsening during annealing at 150-300°C measured by high resolution FEG-SEM EBSD. Accurate sub-grain size and misorientation distributions and their evolution with time and temperature have been determined. The average growth rates are then used to estimate the sub-grain boundary mobilities. Growth is analyzed by two well-known growth laws for the average sub-grain size δ (t): i) the standard relation for grain growth: where the exponent n takes values of 2-8 and ii) the relation proposed by Nes for dislocation climb in sub-grain walls: It is shown that the latter relation gives a better fit with the data in terms of the time and temperature dependence of the sub-grain sizes. In particular the activation energies for the logarithmic law are much closer to the values expected for solute-controlled movement of sub-boundaries.
Materials Science Forum

hal-00795441
https://hal.archives-ouvertes.fr/hal-00795441
DOI : 10.4028/www.scientific.net/MSF.715-716.725

Éditeur(s) : HAL CCSD American Geophysical Union (AGU)
Résumé : International audience
The Tian Shan Mountains constitute central Asia's longest and highest mountain range. Understanding their Cenozoic uplift history thus bears on mountain building processes in general, and on how deformation has occurred under the influence of the India-Asia collision in particular. In order to help decipher the uplift history of the Tian Shan, we collected 970 samples for magnetostratigraphic analysis along a 4571-m-thick section at the Jingou River (Xinjiang Province, China). Stepwise alternating field and thermal demagnetization isolate a linear magnetization component that is interpreted as primary. From this component, a magnetostratigraphic column composed of 67 polarity chrons are correlated with the reference geomagnetic polarity timescale between ~1 Ma and ~23.6 Ma, with some uncertainty below ~21 Ma. This correlation places precise temporal control on the Neogene stratigraphy of the southern Junggar Basin and provides evidence for two significant stepwise increases in sediment accumulation rate at ~16–15 Ma and ~11–10 Ma. Rock magnetic parameters also undergo important changes at ~16–15 Ma and ~11–10 Ma that correlate with changes in sedimentary depositional environments. Together with previous work, we conclude that growth history of the modern Tian Shan Mountains includes two pulses of uplift and erosion at ~16–15 Ma and ~11–10 Ma. Middle to upper Tertiary rocks around the Tian Shan record very young (<~5 Ma) counterclockwise paleomagnetic rotations, on the order of 15° to 20°, which are interpreted as because of strain partitioning with a component of sinistral shear that localized rotations in the piedmont.
ISSN: 0278-7407

insu-00376345
https://hal-insu.archives-ouvertes.fr/insu-00376345
https://hal-insu.archives-ouvertes.fr/insu-00376345/document
https://hal-insu.archives-ouvertes.fr/insu-00376345/file/2007TC002137.pdf
DOI : 10.1029/2007TC002137

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : A hypothetical mechanism for the generation of maturation stress in wood was tested experimentally. The hypothesis was that the maturation stress could partly originate in a physical mechanism related to daily changes in water pressure and associated diurnal strains. The matrix of lignin and hemicellulose, deposited in the cell wall during the night, would be put in compression by the effect of water tension during the next day. The cellulose framework, crystallizing during the day, would be put in tension by the decrease in tension at night and subsequent cell-wall swelling. This was tested on young saplings of sugi and beech. Half of the saplings were submitted to continuous lighting, which canceled diurnal strains. Saplings were tilted 40 degrees, and their uprighting movement was measured. The uprighting movement is directly due to the production of reaction wood and the concomitant development of large longitudinal maturation stress. It occurred in the continuously lighted plants at least as much as in control plants. We conclude that the generation of longitudinal maturation stress in tension or compression wood is not directly related to variations in water pressure and diurnal strains.
ISSN: 1435-0211

hal-01031891
https://hal.archives-ouvertes.fr/hal-01031891
DOI : 10.1007/s10086-005-0788-6

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Chromatin modification enzymes are important regulators of gene expression and some are evolutionarily conserved from yeast to human. Saccharomyces cerevisiae is a major model organism for genome-wide studies that aim at the identification of target genes under the control of conserved epigenetic regulators. Ume6 interacts with the upstream repressor site 1 (URS1) and represses transcription by recruiting both the conserved histone deacetylase Rpd3 (through the co-repressor Sin3) and the chromatin-remodeling factor Isw2. Cells lacking Ume6 are defective in growth, stress response, and meiotic development. RNA profiling studies and in vivo protein-DNA binding assays identified mRNAs or transcript isoforms that are directly repressed by Ume6 in mitosis. However, a comprehensive understanding of the transcriptional alterations, which underlie the complex ume6Δ mutant phenotype during fermentation, respiration, or sporulation, is lacking. We report the protein-coding transcriptome of a diploid MAT a/α wild-type and ume6/ume6 mutant strains cultured in rich media with glucose or acetate as a carbon source, or sporulation-inducing medium. We distinguished direct from indirect effects on mRNA levels by combining GeneChip data with URS1 motif predictions and published high-throughput in vivo Ume6-DNA binding data. To gain insight into the molecular interactions between successive waves of Ume6-dependent meiotic genes, we integrated expression data with information on protein networks. Our work identifies novel Ume6 repressed genes during growth and development and reveals a strong effect of the carbon source on the derepression pattern of transcripts in growing and developmentally arrested ume6/ume6 mutant cells. Since yeast is a useful model organism for chromatin-mediated effects on gene expression, our results provide a rich source for further genetic and molecular biological work on the regulation of cell growth and cell differentiation in eukaryotes.
ISSN: 1617-4615

hal-01151619
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01151619
DOI : 10.1007/s00438-015-1051-5
PUBMED : 25957495

Éditeur(s) : HAL CCSD American Society for Microbiology
Résumé :  
We report the isolation and identification of a new quassinoid named simalikalactone E (SkE), extracted from a widely used Amazonian antimalarial remedy made out of Quassia amara L. (Simaroubaceae) leaves. This new molecule inhibited the growth of Plasmodium falciparum cultured in vitro by 50%, in the concentration range from 24 to 68 nM, independently of the strain sensitivity to chloroquine. We also showed that this compound was able to decrease gametocytemia with a 50% inhibitory concentration sevenfold lower than that of primaquine. SkE was found to be less toxic than simalikalactone D (SkD), another antimalarial quassinoid from Q. amara, and its cytotoxicity on mammalian cells was dependent on the cell line, displaying a good selectivity index when tested on nontumorogenic cells. In vivo, SkE inhibited murine malaria growth of Plasmodium vinckei petteri by 50% at 1 and 0.5 mg/kg of body weight/day, by the oral or intraperitoneal routes, respectively. The contribution of quassinoids as a source of antimalarial molecules needs therefore to be reconsidered.
ISSN: 0066-4804

hal-01032126
https://hal.archives-ouvertes.fr/hal-01032126
DOI : 10.1128/AAC.00951-09

Éditeur(s) : HAL CCSD
Résumé : International audience
The main biological function of reaction wood is to act as “muscle” for trees, enabling them to control their posture and right stems when they are permanently disturbed from their set-point inclination by gravity or winds. The key property to achieve this function is the development of high mechanical stress during the formation of reaction wood cells, called “maturation strains”. Moreover, this function is basically performed through the asymmetric formation of wood (in quantity or quality) around the tree circumference. This asymmetry enables stems to bend upward or to compensate for the downward bending induced by gravity, as an asymmetric force associated to maturation strains creates a bending moment (i.e. one side of the stem “pulls” the other one). We will discuss the traits (cross sectional size and shape, wood features as G fibers or microfibril angle, eccentric growth even in usual or extreme cases as buttresses, total biomass growth and height of center of mass, stem lean and set-point angle) involved to understand how the posture control works. We will give simple formulas to estimate a “muscle efficiency” from biomechanical modeling. We will give practical methods to estimate all the involved traits, especially maturation strains from direct and indirect measurements, in peripheral functional wood or by retrospective dendrochronological analysis. Then, we will illustrate how tree stem tropisms and especially gravitropism, widely studied by physiologists, are key processes in natural ecosystems, through practical examples from tropical rainforest tree communities and regeneration of European mixed beech forests. Using the previous definition of postural control efficiency, we will show that the cross section size is rapidly a limiting factor, opposing the extreme strategies of flexible small stems, which bend easily but also right themselves quickly, to stiff big stems. Lastly, as wood in living trees ensures general storage, defence, vascular and skeletal functions, we will ask general questions about synergies and trade-offs between posture control and other functions.
Botany 2014 : new frontiers in botany
Boise, United States

hal-01627031
https://hal.archives-ouvertes.fr/hal-01627031

Éditeur(s) : HAL CCSD
Résumé : Background and objectives.[br/] Dairy propionibacteria are isolated from various ecological niches, including soil, grass, silage, rumen, raw milk and dairy plants, showing great adaptability and robustness. Used as ripening starters in Swiss type cheeses, these food grade bacteria are described as nutraceutical producers and they release into the external medium short chain fatty acids (SCFA), folic acid, cobalamin and the bifidogenic 1,4- dihydroxy-2-naphthoic acid (DHNA). These compounds are known to play a pivotal role in the modulation of intestinal physiology through diet. Considering the pro-apoptotic potential of some of these metabolites, we investigated the potential of dairy products fermented by the main species, Propionibacterium freudenreichii, to prevent colon carcinogenesis. Methods.[br/] We developed a new fermented milk. Taking advantage of milk fractions, high and stable populations of P. freudenreichii were obtained in this product. It was tested in vitro on gastric HGT-1 and colic HT-29 cells with respect to the typical hallmarks of apoptosis. In vivo, the fermented milk was evaluated in piglets with respect to general health parameters and in human microbiota-associated rats, treated or not with dimethylhydrazine (DMH), with respect to intestinal proliferation and apoptosis. Results. Fermented milk induced cell death in both gastric and colon cancer cells. Cellular and molecular characterization of cells dying in response to SCFA treatment revealed cell cycle arrest, drop in intracellular ATP, depolarization of mitochondria, translocation of key apoptosis proteins, processing of caspases and fragmentation of the nucleus. Interestingly, the new fermented milk was shown to potentiate the cytotoxic effect of molecules used in cancer chemotherapy. In accordance, it modulated expression of key apoptotic proteins. In vivo, the fermented milk was evaluated in piglets. Daily oral gavage led to high colic P. freudenreichii populations, to modulation of the intestinal microbiota and modulation of intestinal cytokines. Promotion of piglets’ growth also revealed general probiotic effects of fermented milk. Considering that propionibacteria were metabolically active in the intestine, we further investigated their impact on colon carcinogenesis (induced by dimethylhydrazine, DMH) in human microbiota-associated rats. Consumption of selected strains of propionibacteria resulted in enhanced apoptotic depletion of DMH damaged epithelial cells, yet had no effect on neither proliferation nor apoptosis in healthy rats. Conclusions and perspectives.[br/] These results open new perspectives in the field of colon cancer cells prevention and/or treatment. The synergy with pro-apoptotic chemotherapy molecules suggests that such a fermented product may be proposed as a food supplement to enhance the effects of anticancer treatments.
colloque international « Nutrition and Cancer : Hot topics from biology to public health issues »
Paris, France

hal-01190452
https://hal.archives-ouvertes.fr/hal-01190452
PRODINRA : 201853