Search

A plant’s development is strongly linked to the water and carbon flows in the soil-plant-atmosphere continuum. Expected climate shifts will alter the water and carbon cycles and will affect plant phenotypes. Comprehensive models which simulate mechanistically and dynamically the feedback loops between a plant’s three-dimensional development and the water and carbon flows are useful tools to evaluate the sustainability of genotype-environment-management combinations which do not yet exist. In this study, we present the latest version of the open-source three-dimensional Functional-Structural Plant Model CPlantBox with PiafMunch and DuMuxcoupling. We simulated semi-mechanistically the development of generic C3 monocots from 10 to 25 days after sowing and undergoing an atmospheric dry spell of one week (no precipitation). We compared the results for dry spells starting on different days (day 11 or 18) and with different climates (wetter and colder against drier and warmer atmospheric and initial soil conditions). Compared with the wetter and colder climate, the dry spell with the drier and warmer climate led to a lower instantaneous water use efficiency. Moreover, the lower symplasm turgor for the drier and warmer climate limited the growth, which made the sucrose available for other processes, such as maintenance respiration. Both of these effects were stronger for the later dry spell compared with the early dry spell under the drier and warmer climate. We could thus use CPlantBox to simulate diverging emerging processes (like carbon partitioning) defining the plants’ phenotypic plasticity response to their environment.

International audience; With the advent of “New Space” and the explosion of nanosatellite missions, an extended latitude is offered for the emergence of innovative technological devices such as novel compact solid state UVC sensors. In this context, β-Ga2O3-based photodetectors are emerging as very promising candidates to overcome current technological limits for UVC detection in Space. Indeed, monitoring UVC solar radiation, and more specifically the Herzberg continuum (200-242nm), is fundamental to understand its’ impact on the earth’s climate and build better chemistry-climate models [1]. It is also, however, extremely challenging to achieve due to the harsh operating environment including large thermal variations, high energy particles, ionizing radiation and filter contamination due to satellite outgassing. The Ultra Wide Band Gap semiconductor, β-Ga2O3 (Eg ~ 4.9eV at 253nm), is intrinsically solar blind, radiation-hard and thermally-robust. Furthermore, the authors have recently shown that the bandgap can be engineered upwards through Al alloying so as to obtain optical transitions from 253 down to 200nm [2,3]. This allows the realization of β-Ga2O3-based photodetectors with peak operating wavelengths which capture the Herzberg continuum selectively and thus, dispenses with the need for short pass filters. Therefore, these β-Ga2O3-based photodetectors are excellent candidates to monitor the Herzberg continuum from Space. Hence, they have been selected to be integrated on the INSPIRE-Sat 7 (International Satellite Program in Research and Education) nanosatellite (“2U” CubeSat) which will monitor the Herzberg continuum on a low Earth orbit, following a prototype mission UVSQ-Sat (INSPIRE-Sat 5) successfully launched in January 2021 [4]. This work presents the realization of β-Ga2O3-based photodetectors going from the wafer to the final packaged sensors including device architecture development, photolithography, contacting, probing, singulation, packaging, stringent robustness testing (in a simulated environment) and performance binning, so as to obtain the final flight model photodetectors.

International audience; According to the literature, biological processes in the rhizosphere could play a role in the adaptation of plants to droughts under a changing climate. A previous study has identified significantly different productivity level and fruit quality for two tomato varieties under water deficit conditions. We conducted a field study, with and without water deficit, with these two varieties to examine whether microbiological activity and exopolysaccharides concentration could affect soil hydrophysical properties. The rhizosphere soil had indeed distinct bio-chemical and hydrophysical properties between the two cultivars and between the two water-related conditions. The quantity of soil exopolysaccharide and/or nitrogenous substances, and the activity of microorganisms (fungi in particular) explains part of the soil water retention measurements. In addition, these mechanisms are significantly accentuated for the cultivar with the best productive capability under water-limited condition—i.e. with commercial yield, fruit dry matter and water use efficiency which are respectively 35%, 28%, and 31% higher for the productive cultivar.

International audience; We investigated the current-induced domain-wall (DW) depinning for various applied magnetic fields on a well-indentified single pinning site in epitaxial Co/Ni-based spin-valve wire of micronic width. The DW depinning process occurs with thermal activation involving a single energy barrier associated with a single pinning site. By measuring the DW depinning probability for various positive and negative applied fields (H+,H−) and currents (I+,I−), we built a map highlighting regions where spin-transfer torque (STT) effect, Joule heating, and Oersted field dominate. We then propose a method to quantify characteristic parameters of both adiabatic and nonadiabatic components of STT despite the presence of other effects due to current injection. The suitability of the method is validated by the fact the extracted values are close to those obtained previously on single [Co/Ni] layer where Oersted field and Joule effects were negligible.

International audience; Low-temperature plasma enhanced atomic layer deposition (PE-ALD) was successfully used to grow silicon (Si) doped amorphous and microcrystalline gallium phosphide (GaP) layers onto p-type Si wafers for the fabrication of n-GaP/p-Si heterojunction solar cells. PE-ALD was realized at 380 °C with continuous H2 plasma discharge and the alternate use of phosphine and trimethylgallium as sources of P and Ga atoms, respectively. The layers were doped with silicon thanks to silane (SiH4) diluted in H2 that was introduced as a separated step. High SiH4 dilution in H2 (0.1%) allows us to deposit stoichiometric GaP layers. Hall measurements performed on the GaP:Si/p-Si structures reveal the presence of an n-type layer with a sheet electron density of 6–10 × 1013 cm−2 and an electron mobility of 13–25 cm2 V−1 s−1 at 300 K. This is associated with the formation of a strong inversion layer in the p-Si substrate due to strong band bending at the GaP/Si interface. GaP:Si/p-Si heterostructures exhibit a clear photovoltaic effect, with the performance being currently limited by the poor quality of the p-Si wafers and reflection losses at the GaP surface. This opens interesting perspectives for Si doped GaP deposited by PE-ALD for the fabrication of p-Si based heterojunction solar cells.

We investigate Titan's low-latitude and midlatitude surface using spectro-imaging near-infrared data from Cassini/Visual and Infrared Mapping Spectrometer. We use a radiative transfer code to first evaluate atmospheric contributions and then extract the haze and the surface albedo values of major geomorphological units identified in Cassini Synthetic Aperture Radar data, which exhibit quite similar spectral response to the Visual and Infrared Mapping Spectrometer data. We have identified three main categories of albedo values and spectral shapes, indicating significant differences in the composition among the various areas. We compare with linear mixtures of three components (water ice, tholin-like, and a dark material) at different grain sizes. Due to the limited spectral information available, we use a simplified model, with which we find that each albedo category of regions of interest can be approximately fitted with simulations composed essentially by one of the three surface candidates. Our fits of the data are overall successful, except in some cases at 0.94, 2.03, and 2.79 μm, indicative of the limitations of our simplistic compositional model and the need for additional components to reproduce Titan's complex surface. Our results show a latitudinal dependence of Titan's surface composition, with water ice being the major constituent at latitudes beyond 30°N and 30°S, while Titan's equatorial region appears to be dominated partly by a tholin-like or by a very dark unknown material. The albedo differences and similarities among the various geomorphological units give insights on the geological processes affecting Titan's surface and, by implication, its interior. We discuss our results in terms of origin and evolution theories. ©2018. American Geophysical Union. All Rights Reserved.

The design of enzymatic routes for the production of biosourced copolymers represents an attractive alternative to chemical synthesis from fossil carbon. In this paper, we explore the potential of glycosynthesizing enzymes to produce novel block copolymers composed of various covalently-linked α-glucans with contrasting structures and physicochemical properties. To this end, various glucansucrases able to synthesize α-glucans with different types of α-osidic bonds from sucrose were tested for their ability to elongate oligosaccharide and polysaccharide acceptors with different structures from the native polymer synthesized by each enzyme. We showed that two enzymes – namely, the alternansucrase from Leuconostoc mesenteroides NRRL B-1355 (specific for α(1 → 6)/α(1 → 3)-linked alternan synthesis) and the dextransucrase DSR-MΔ1 from Leuconostoc citreum NRRL B-1299 (specific for α(1 → 6)-linked dextran formation) – were able to elongate α(1 → 4)-linked amylose and α(1 → 6)/α(1 → 3)-linked alternan respectively. Carrying out stepwise acceptor reactions, and after optimization of the acceptor size and donor/acceptor ratio, two types of diblock copolymers were synthesized – a dextran-b-alternan and an alternan-b-amylose – as well as the triblock copolymer dextran-b-alternan-b-amylose. Their structural characterization, performed by combining chromatographic, NMR and permethylation analyses, showed that the copolymer polymerization degree ranged from 29 to 170, which is the highest degree of polymerization ever reported for an enzymatically synthesized polysaccharide-based copolymer. The addition of dextran and alternan blocks to amylose resulted in conformational modifications and related flexibility changes, as demonstrated by small angle X-ray scattering.

International audience; The combined effect of magnetic field and current on domain wall motion is investigated in epitaxial [Co/Ni] microwires. Both thermally activated and flow regimes are found to be strongly affected by current. All experimental data can be understood by taking into account both adiabatic and nonadiabatic components of the spin transfer torque, the parameters of which are extracted. In the precessional flow regime, it is shown that the domain wall can move in the electron flow direction against a strong applied field, as previously observed. In addition, for a large range of applied magnetic field and injected current, a stochastic domain wall displacement after each pulse is observed. Two-dimensional micromagnetic simulations, including some disorder, show a random fluctuation of the domain wall position that qualitatively matches the experimental results.

International audience; Thin layers of μc-GaP and a-GaP grown on n- type silicon wafers by plasmaenhanced atomic layer deposition at 380 C are characterized by space charge capacitance techniques, C-V profiling and deep level transient spectroscopy (DLTS). Two defect levels with activation energies of 0.30 eV and 0.80 eV were detected by DLTS in the μc-GaP/n-Si structure. Measurements performed on Schottky barriers formed on n-Si after selective etching of the GaPlayer did not reveal any defect level meaning that the observed defects in the μc-GaP/n-Si structure are related to μc-GaP layer.

Resume Introduction Les instillations endovesicales de BCG constituent le traitement de reference des TVNIM de risque intermediaire et eleve. Un traitement d’entretien est fortement recommande, neanmoins la frequence des effets secondaire responsable de l’arret du traitement d’entretien chez plus de quatre patients sur cinq avant la troisieme annee pourrait justifier une diminution voire un espacement des instillations. L’objectif de l’etude URO-BCG-4 etait l’evaluation d’un nouveau schema d’entretien par instillations endovesicales de BCG associant une diminution de dose (un tiers de dose) mais aussi une diminution du nombre d’instillation par cycle (deux ou trois). Patients et methodes Etude multicentrique du CCAFU (12 centres hospitalo-universitaires), randomisee, prospective, comparant le schema de reference de BCG-therapie d’entretien au un tiers de dose usuelle (groupe I) a un schema associant un tiers de dose et diminution du nombre d’instillations par cycle (deux au lieu de trois) (groupe II). Nous presentons les resultats preliminaires a un an de ce programme hospitalier de recherche clinique (2003-081 CHU de Rouen Promoteur). Resultats Le taux de recidive tumorale etait respectivement de 9 et 7 % ( p = 0,678) dans les groupes I et II. Le taux de progression tumorale etait de 3 et 2,8 % dans les groupes I et II ( p = 1). La tolerance des instillations endovesicales de BCG evaluee selon la classification OMS (Geneve 1979) etait comparable dans les deux groupes. Conclusion La diminution de la dose de BCG (un tiers de dose) et la modification du nombre et du rythme des instillations n’a pas modifie le taux de survie sans recidive tumorale. La toxicite des instillations endovesicales de BCG etait identique dans les deux groupes. L’utilisation de la classification OMS a montre ses limites dans l’etude des effets secondaires du BCG car trop complexe et souvent non exhaustive. Le taux de progression musculaire etait comparable dans les deux groupes neanmoins un recul clinique plus important est necessaire.

International audience; We demonstrate the ability to create, control the propagation, and annihilate domain walls in 25-nm thick Tb22Co78 ferrimagnetic alloy wires using a temperature gradient under a constant appliedfield. The temperature gradient is generated by passing a current through the wire, and the domainwall properties are imaged using Kerr microscopy. The manipulation of the domain wall is madepossible by creating a temperature gradient such that the temperature at one end of the wire isabove the compensation temperature for the TbCo alloy, while the other end remains below thecompensation temperature. By tuning the intensity of the applied magnetic field and the currentflowing inside the wire, it is possible to carefully control the domain wall position that can then bestabilized under zero applied field and current.

International audience; Extraordinary Hall Effect (EHE) based original concepts of a reconfigurable logic gate and a multibitlogic comparator are presented. They exploit the EHE voltage that develops on cross cells connectedin series that has no size limitation down to the nanometer scale. Experimental demonstrationsare performed on both micro- and nanometer lateral size crosses made of ferrimagnetic TbCo alloy.The simplicity of the device architecture and its robustness make it advantageous when comparedwith existing systems.

The control of magnetic domain wall (DW) motion under the action of an electrical current is of great interest for the development of new data storage electronic devices such as magnetic racetrack memories1 or logic devices2. In this context, materials with perpendicular magnetic anisotropy (PMA) are particularly attractive3,4 since they exhibit very narrow domain walls compatible with high density storage as well as spin-orbits effect that can improve the efficiency of current-induced domain wall motion5,6. However, even if the efficiency of current driven DW motion can be enhanced, the threshold current is still limited by the presence of structural defects in the materials. Particularly, the strong interaction of narrow DWs with random nanoscale inhomogeneities can lead to a so-called thermally activated creep motion for Hdep is the depinning field. This creep regime has been observed in various ultra thin films with PMA such as for instance Co/Pt7,8, CoFe or CoFeB9. Particularly, a ln(v) versus H−1/4 dependence has been found consistent with the propagation of a 1D domain wall in a 2D weak random disorder. As these films are usually deposited by sputtering, the random disorder originates in particular from crystalline texture, interface intermixing or grain boundaries, which induce a distribution of PMA on the nanoscale. In epitaxial systems, the nature, density and distribution of structural inhomogeneities can be very different, which may give rise to a different mechanism of domain wall motion. This has been shown for example in L 1 0 FePt films with PMA10 where extended 3D microtwins induced by a relaxation process generate a dendritic like motion distinct from the creep mechanism.

In French Atlantic coastal ponds of Charente, oysters can grow under conditions where phytoplankton production is limited by nutrients exhaustion. Such ponds typically show a high concentration of ciliates and flagellates during the growing season (1 x 104 to 3 x 105 cells l-1 in June 1997). In order to evaluate the importance of the "protozoan trophic link " for energy transfer from the " microbial food web" to large benthic suspension feeders, we offered a coastal pond community of ciliates and flagellates as potential prey to the oyster, Crassostrea gigas. Clearance rate, filtered particles and relative retention efficiency were evaluated. In the grazing experiment, 94 % of ciliates and 86 % of flagellates (size between 4 and 72 μm), were retained by the oyster. Whatever their size, protists were similarly retained by the oyster gills. In terms of carbon, oyster retain on average 126 μg carbon (C) h-1 g-1 dry weight, a value over 4 times higher than reported for phytoplankton. These results indicate that a field community of protists can contribute in coastal oyster rearing ponds to the energy requirements of the oyster Crassostrea gigas. We report here the first experimental evidence of a significant retention of a protist community by oysters, supporting the role of protists as a trophic link between picoplankton and benthic filter-feeding bivalves.

Équipe 101 : Nanomagnétisme et électronique de spin; International audience; We demonstrate an electrical control of an interfacial trapping effect for hot electrons injected in silicon by studying a magnetic tunnel transistor on wafer bonded Si substrate. Below 25 K, hot electrons are trapped at the Cu/Si interface, resulting in collector current suppression through scattering in both parallel and antiparallel magnetic configurations. Consequently, the magneto-current ratio strongly decreases from 300% at 27K to 30% at 22 K. The application of a relatively small electric field (similar to 333 V/cm) across the Cu/Si interface is enough to strip the trapped electrons and restore the magneto-current ratio at low temperature. We also present a model taking into account the effects of both electric field and temperature that closely reproduces the experimental results and allows extraction of the trapping binding energy (similar to 1.6meV).

The linked concepts of 'microbial loop' and 'protozoan trophic link' have been very well documented in filter-feeding microzooplankton such as copepods, but have not been applied to energy transfer to benthic suspension-feeding macrofauna, with the exception of the recent demonstration of heterotrophic flagellate assimilation by mussels. The oyster Crassostrea gigas obtains energy resources by filtering microalgae (similar to 5 to 100 mu m). However, in turbid estuaries, light-limited phytoplanktonic production cannot entirely account for oyster energy requirements. Conversely, picoplankters (

Equipe 101 : Nanomagnétisme et électronique de spin; International audience; We have evidenced a new interfacial trapping phenomenon for hot electron injection in silicon by studying magnetic tunnel transistors (MTTs) with a MgO tunneling barrier emitter and a Cu/Si Shottky barrier collector. Transport measurements on hot electrons indicate that an interfacial charge trapping and a backscattering-induced collector current limitation take place with the MTT spin-valve base both in parallel and antiparallel states when the temperature is lower than 25 K, which results in a rapid decrease of the magnetocurrent ratio from similar to 2000% at 25K to 800% at 17 K. The binding energy of the trapped electron is estimated to be about 1.7 meV, which is also found to increase with the magnetic field. A simple analytic model considering the interfacial electron trapping and releasing is proposed to explain the experimental results.

Féral C, Le Gall S, Leymarie P. Angiotensin II modulates steroidogenesis in granulosa and theca in the rabbit ovary: its possible involvement in atresia. Eur J Endocrinol 1995;133:747–53. ISSN 0804–4643 Accumulating evidence has shown the ovary of mammals to contain an intrinsic renin–angiotensin system that has been ascribed an autocrine-paracrine role. The present study in the female rabbit ovary investigated the putative in vitro action of angiotensin II (A II) on basal and gonadotropin-induced steroidogenesis. Ovarian follicles from immature female rabbits treated with pregnant mare's serum gonadotropin (PMSG) were dissected out and a complete separation of the theca interna from the granulosa layer was performed, to demonstrate that A II affects separately the two individual cellular components of the follicular wall. We could show that theca is a source of estradiol whose production under human chorionic gonadotropin (hCG) stimulation was reduced by A II. At the same time, A II increased the in vitro hCG-stimulated secretion of testosterone by theca. In granulosa, A II decreased hCG-stimulated aromatization of androstenedione to estradiol but did not alter the release of hCG-stimulated progesterone production. These results suggest that A II could induce locally an increase in follicular fluid androgen/estrogen ratio and possibly participate in causing atresia. C. Féral, EP CNRS 009, Laboratoire de Biochimie, CHU Caen, F-14032 Caen Cedex, France

International audience; Using transport measurements and micromagnetic simulations we have investigated the domain wall motion driven by spin-transfer torques in all-perpendicular hexagonal nanopillar spin-valves. In particular, we probe domain walls nucleated in the free layer of the spin-valves, which are then pinned in the devices. We have determined both the field-current state diagrams for the domain-wall state and the thermally activated dynamics of the nucleation and depinning processes. We show that the nucleation process is well-described by a modified Néel-Brown model taking into account the spin-transfer torque, whereas the depinning process is independent of the current. This is confirmed by an analytical calculation which shows that spin-torques have no effect on the Arrhenius escape rate associated with thermally activated domain wall depinning in this geometry. Furthermore, micromagnetic simulations indicate that spin-transfer only weakly affects the domain wall motion, but instead modifies the inner domain wall structure.

Intravesical instillations of BCG remains the gold standard for intermediate and high risk NMIBC management. Maintenance treatment is recommended, however, the frequency of side effects responsible for the discontinuation of maintenance therapy over four out of five patients before the third year suggest a reduction or even spacing instillations. The objective of the study URO-BCG-4 was the evaluation of a new maintenance schedule by intravesical instillations of BCG combined reduced dose (third dose) and a decrease number of instillations per cycle (two or three).Multicenter study of the French Association Oncologic Committee (12 university hospital centers), randomized, prospective, comparing reference diagram of BCG maintenance therapy one third of usual dose (group I) to a regimen combining third dose and decrease the number of instillations per cycle (two instead of three) (group II). We present the preliminary results at 1year of this Program of Clinical Research (CHU Rouen Promoter 2003-081).The rate of recurrence was respectively 9 and 7% (P=0.678) in groups I and II. The rate of tumor progression are 3 and 2.8% in groups I and II (P=1). Tolerance of intravesical instillations of BCG scored according to the WHO classification (Geneva 1979) was similar in the two groups.The decrease in the BCG dose (third dose) and the changes in the number and rate of instillations did not alter free tumor recurrence survival. The toxicity of intravesical instillations of BCG was identical in both groups. The use of the WHO classification has shown its limitations in the study of side effects of BCG as too complex and often not exhaustive. The rate of increase muscle was comparable in the two groups; however, a larger clinical experience is required.

Background HIV-specific CD8 T cells responses rely on the recognition of peptide-MHC-I complexes by cognate T cell receptors. HIV-derived MHC-I epitopes result from the degradation of viral proteins by the cellular processing machinery including proteasomes and aminopeptidases. Interferon gamma changes proteasome composition and peptidase activities. We hypothesize that HIV infection might affect the expression or activities of the antigen processing machinery, either through a direct effect of the virus or indirectly through cellular activation or from the release of cytokines by surrounding infected cells.

Background Whether HIV-infectable subsets, such as CD4 T cells, monocytes, macrophages and dendritic cells (DCs), have equivalent capacity to produce and present MHC-I restricted epitopes to HIV-specific CD8 T cells is unknown. MHC-I epitopes are processed by an intracellular degradation pathway involving multiple proteases. In this study we analyzed the effect of toll-like receptor (TLR) agonist-mediated maturation on the processing and presentation of HIV antigens in monocyte-derived DCs and macrophages.

International audience; Lichens are complex organisms resulting from the symbiosis between fungus, microalga and/or cyanobacteria and are source of metabolites of interest. As other living organisms harboring bacterial communities they could be considered as a mini-ecosystem. These bacterial communities most often belong to different phyla: Actinobacteria, Proteobacteria, with a dominance of Alphaproteobacteria and Firmicutes. In this study, we focused on the bacterial communities present on six lichens from Brittany coast (France) (Roccella fuciformis, R. phycopsis, Lichina confinis, L. pygmaea, Xanthoria aureola and X. calcicola). Abundance and diversity of these communities are dependent on several extrinsic factors (environmental) and/or intrinsic parameters including the chemical composition of their substrates (lichens). So, our aims are to elucidate the chemical composition of the studied lichens (extraction, isolation and structural identification) as well as those of associated bacterial communities. Some bacterial species were isolated from these lichens, identified by molecular fingerprints and their culture were optimized (media composition, pH and temperature). Due to the existence of chemical interactions between symbionts we target molecules with antibiotic properties.

International audience; The spin-torque switching of metallic nanopillar spin valves showing strong perpendicular anisotropy are studied. The magnetic states of the layers depend on extrinsic parameters such as the magnetic field and the dc current applied to the device. A state diagram presents a comprehensive graph of the role of those parameters on the spin-valve magnetic response. After explaining how state diagrams can be built and the different possible representation, experimental state diagrams are studied for perpendicular devices and the influence of lateral size, temperature, and field orientation are shown. An analytical model of a purely uniaxial system is presented. It is shown that this simple model does not properly reflect the experimental results, whereas if the symmetry is broken a qualitative agreement is obtained. Finally, the possible origins of the symmetry break are discussed in light of an analytical model and numerical simulations.

International audience; The transport mechanisms through MgO ultrathin layers (0.5-1.2 nm) deposited on n-type doped GaAs(001) layers have been studied. In order to favor field emission (FE) across the junctions, a high doping concentration layer in vicinity of the semiconductor surfaces has been included. Varying doping concentration of the underlying GaAs layer we find that the dominant transport mechanism is either the variable-range hopping mechanism or a thermionic emission-like process instead of the FE process. The observation of such mechanisms can be explained by the fact that during the MgO deposition, defect states are introduced in the semiconductor band gap.

The circulating reninangiotensin system (RAS) participates in the regulation of blood pressure and electrolyte metabolism. Renin, a proteolytic enzyme, synthesized in the kidney from its biological precursor, prorenin, cleaves its substrate angiotensinogen in the blood to form the active octapeptide, angiotensin II (AII). All the RAS components are present in the reproductive system of mammals. During pregnancy, the level of prorenin increases in the plasma. The ovary is the source of this prorenin during early pregnancy and maternal decidua later on. During the menstrual cycle, the thecal of preovulatory follicles synthesize prorenin, renin and AII. Thecal renin synthesis is controlled by LH/hCG as demonstrated in vivo and in vitro in the rabbit. Ovarian renin seems to be identical to kidney renin. Prorenin appears to be the major secretory product rather than renin, which remains intracellular. AT2-type angiotensin II-receptors are expressed in the rat on follicular granulosa cells and could be down-regulated by FSH. The bovine thecal cells also express AT2-receptors, up-regulated by LH. These data are consistent with an autrocrine or paracrine role for ovarian RAS. It has been implicated in neovascularization of the follicle and regulation of steroidogenesis by increasing the androgen/estrogen ratio, an index of follicular atresia.

International audience; We report on ballistic electron-emission spectroscopy on high-quality Au(110)/GaAs(001) and Fe(001)/GaAs(001) Schottky contacts. For the Au(110)/GaAs(001) interface, the ballistic current is characterized by a strong electron injection in the L valley of the GaAs conduction band. This remarkable spectroscopic feature is absent for the Fe(001)/GaAs(001) interface. These observations are explained by the different electronic structures in the two metal layers, assuming conservation of the electron transverse momentum at the metal/semiconductor epitaxial interfaces. Conversely, this comparative study suggests that the technique can be used for the analysis of local electronic states propagating in the metal films.

Hypermutation is an important mechanism used by different Salmonella enterica subspecies enterica to regulate genetic stability in adaptation to changing environments, including antimicrobial treatments and industrial processes. Strong hypermutator strains generally contain a mutation in genes of the methyl mismatch repair (MMR) system and have mutation frequencies up to 1000-fold higher than wild type strains. The objectives of this study were to determine the distribution of mutation frequencies from a collection of 209 Salmonella strains, to genetically characterize a strong mutator, and to study MMR mutated protein-DNA binding interactions. Only one strain of S. Heidelberg was determined to have a hypermutator phenotype by virtue of its high mutation rate. Sequencing of genes of the MMR system showed a 12bp deletion in the mutS gene was present. The MMR mutated protein-DNA binding interactions were studied by bioanalysis, using the available crystal structure of a similar MutS protein from Escherichia coli. This analysis showed the small deletion in the Salmonella MutS was localized within the core domain. A retardation assay with MutS from hypermutable and wild type strains showed this mutation has no effect on MutS DNA binding. A better understanding of the genetic mechanisms of hypermutation will help to anticipate the behavior of hypermutator strains in various conditions.

The origin of ovarian renin and its regulation by hCG were investigated in rabbit periovulatory follicles and cultured preovulatory follicular cells. Intracellular content of renin in thecal cells was 8-fold greater than of granulosa cells. In vivo, administration of hCG increased intracellular content of renin in thecal but not granulosa cells. Similar results were obtained for cultured follicular cells, from which renin was partly released into the medium. In vitro, hCG increased intracellular renin content of thecal but not granulosa cells, without obvious effect on release. Approximately 95% of ovarian renin was inactive, but could be activated by trypsin. Thecal renin was antagonized in vitro by renin antiserum, indicating a specific renin activity. Our study establishes in the rabbit the thecal cell origin of ovarian inactive renin and demonstrates hCG regulation of its synthesis.

International audience; The electrical properties of Au/MgO/n-GaAs(001) tunnel structures have been investigated with capacitance-voltage and current-voltage measurements at room temperature with various MgO thicknesses between 0.5 and 6.0nm. For an oxide thickness higher than 2nm and for low bias voltages, the voltage essentially drops across the oxide and the structure progressively enters the high-current mode of operation with increasing reverse bias voltage, the property sought in spin injection devices. In this mode, we demonstrate that a large amount of charge accumulates at the MgO/GaAsinterface in interface traps located in the semiconductor band gap.

International audience; 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) microzooplank-tonic 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 mg C L _ 1) than from September to March (winter period 114 mg 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 hetero-trophic. 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.

The Nef protein from the human immunodeficiency virus (HIV) induces CD4 cell surface downregulation by interfering with the endocytic machinery. It has been recently proposed that binding of HIV type 1 Nef to the β subunit of COPI coatomers participated in the Nef-induced CD4 downregulation through recognition of a novel diacidic motif found in the C-terminal disordered loop of Nef (V. Piguet, F. Gu, M. Foti, N. Demaurex, J. Gruenberg, J. L. Carpentier, and D. Trono, Cell 97:63–73, 1999). We have mutated the glutamate residues which formed this motif in order to document this observation. Surprisingly, mutation of the diacidic sequence of Nef did not significantly affect its ability (i) to interact with β-COP, (ii) to downregulate CD4 cell surface expression, and (iii) to address an integral resident membrane protein containing Nef as the cytoplasmic domain to the endocytic pathway. Our results indicate that these acidic residues are not involved in the connection of Nef with the endocytic machinery through binding to β-COP. Additional studies are thus required to characterize the residues of Nef involved in the binding to β-COP and to evaluate the contribution of this interaction to the Nef-induced perturbations of membrane trafficking.

To review cases of alcoholic ketoacidosis in order to better ascertain therapeutic management.The medical files of 32 alcoholic patients with ketoacidosis hospitalized in the Saint-Pierre general hospital of the Reunion island from January 1, 1991 through 31 August 1994 were analyzed.There were 18 women and 14 men, mean age 47 years. The first clinical signs were predominated by digestive (n = 22) or neurological disorders (n = 10). Acidosis was severe (mean pH = 7.12) and always associated with a wide anion gap (mean anion gap = 35). There were 3 types of glycemic status: hypoglycemia 10 cases, normal or subnormal glycemia in 19 cases (mean glycemia = 9.3 mmol/l) and hyperglycemia above 20 mmol/l in 3 cases. Hypophosphatemia, elevated serum lactate levels and cytolytic hepatitis were the main abnormalities associated.Short-term outcome was favorable in all cases after rehydration. The use of insulin may be dangerous and needs to be avoided.

Background Epitopes displayed by MHC-I come from the multistep degradation of proteins by intracellular peptidases such as proteasome and aminopeptidases or cathepsins in the exogenous pathway. We hypothesize that due to structural homologies HIV protease inhibitors (PIs) used in antiretroviral therapies may affect activities of cellular peptidases involved in epitope processing and may affect epitope presentation to immune cells. Methods Using a fluorogenic assay the effect of 5 HIV-1 PIs (Ritonavir, Saquinavir, Nelfinavir, Indinavir, Atazanavir) on proteasome, aminopeptidase and cathepsin activities was tested in PBMCs from at least 6 healthy donors. Using PBMC cytosol as a source of peptidases and HPLC and mass spectrometry to define and quantify the degradation products, the effect of HIV PIs on HIV peptide processing kinetics and HIV epitope half-life was assessed. Finally we assessed the impact of PIs on the endogenous processing and presentation of epitopes by infected cells to CD8 T cells using a fluorescence-based cytotoxicity assay. Results HIV PIs variably altered proteasome, post-proteasomal aminopeptidases and cathepsin activities. Depending on the PI, some activities were inhibited (from 1.1 to 5 folds, p

The circulating reninangiotensin system (RAS) participates in the regulation of blood pressure and electrolyte metabolism. Renin, a proteolytic enzyme, synthesized in the kidney from its biological precursor, prorenin, cleaves its substrate angiotensinogen in the blood to form the active octapeptide, angiotensin II (AII). All the RAS components are present in the reproductive system of mammals. During pregnancy, the level of prorenin increases in the plasma. The ovary is the source of this prorenin during early pregnancy and maternal decidua later on. During the menstrual cycle, the thecal of preovulatory follicles synthesize prorenin, renin and AII. Thecal renin synthesis is controlled by LH/hCG as demonstrated in vivo and in vitro in the rabbit. Ovarian renin seems to be identical to kidney renin. Prorenin appears to be the major secretory product rather than renin, which remains intracellular. AT2-type angiotensin II-receptors are expressed in the rat on follicular granulosa cells and could be down-regulated by FSH. The bovine thecal cells also express AT2-receptors, up-regulated by LH. These data are consistent with an autrocrine or paracrine role for ovarian RAS. It has been implicated in neovascularization of the follicle and regulation of steroidogenesis by increasing the androgen/estrogen ratio, an index of follicular atresia.

Background HIV-1 Nef is a multifunctional protein frequently targeted by host CD8+ T cell responses in early and chronic phases of HIV-1 infection. In vivo reversions of CTL escape mutations within Nef have been reported, suggesting a possible impact of immune-selected mutations in Nef on viral fitness. The goal of this work was to determine whether CD8+ T cell selected mutations in regions outside of Gag, such as in Nef, also impair viral replication and may thus contribute to early immune control of HIV-1.