Structure of the Sagittarius dwarf galaxy at low Galactic latitudes

We report the detection of $\sim$ 1500 RR Lyrae of Bailey type ab located in the Sagittarius dwarf galaxy (Sgr). These variables have been detected on two ESO Schmidt fields centred on (l,b)=(3.1 deg,-7.1 deg) and (6.6 deg, -10.8 deg), covering an area of $\sim$50 square degree. We present a surface density map of Sgr based on the spatial distribution of these RRab, allowing us to trace its structure in a region that was still almost unexplored between b=-14 deg and b=-4 deg. We present the results of the fit of different models to the density profile of Sgr. The best fit to the core of Sgr is an exponential with a scale length of 4.1 deg along the major axis. When we look at the extension of Sgr we find a break (significant at the $\sim2\sigma$ level) in the slope of the surface density along the main axis of Sgr. The nearly flat (or at least very slowly decreasing) profile in the outer region of Sgr shows that this dwarf galaxy is probably extending even further out our fields.Comment: 11 pages, 11 figures, accepted for publication in A&

Minimal lensing solutions in the singular perturbative approach

This paper analyse the properties of minimal solutions for the reconstruction of the lens potential in the singular perturbative approach. These minimal solutions corresponds to an expansion with a minimal degree in Fourier expansion of the perturbative fields. Using these minimal solutions prevent spurious physically meaningless terms in the reconstruction of the fields. In effect a perturbative analysis indicates that a small change in the source model will corresponds to the higher order terms in the expansion of the fields. The results of the perturbative analysis are valid not only for slightly non-circular sources but also for more distorted sources to order two. It is thus of crucial importance to minimize the number of terms used in the modelling of the lens. Another important asset of the minimal solutions is that they offers a de-coupling between the source and lens model and thus help to break the source lens degeneracy issue. The possible drawback of minimal solutions is to under-estimate the higher order terms in the solution. However this bias has its merit since the detection of higher order terms using this method will ensure that these terms are real. This type of analysis using minimal solutions will be of particular interest when considering the statistical analysis of a large number of lenses, especially in light of the incoming satellite surveys.Comment: 15 pages, 7 figure

The Age and Structure of the Galactic Bulge from Mira Variables

We report periods and JHKL observations for 648 oxygen-rich Mira variables found in two outer bulge fields at b=-7 degrees and l=+/-8 degrees and combine these with data on 8057 inner bulge Miras from the OGLE, Macho and 2MASS surveys, which are concentrated closer to the Galactic centre. Distance moduli are estimated for all these stars. Evidence is given showing that the bulge structure is a function of age. The longer period Miras (log P > 2.6, age about 5 Gyr and younger) show clear evidence of a bar structure inclined to the line of sight in both the inner and outer regions. The distribution of the shorter period (metal-rich globular cluster age) Miras, appears spheroidal in the outer bulge. In the inner region these old stars are also distributed differently from the younger ones and possibly suggest a more complex structure. These data suggest a distance to the Galactic centre, R0, of 8.9 kpc with an estimated uncertainty of 0.4 kpc. The possible effect of helium enrichment on our conclusions is discussed.Comment: Accepted for MNRAS, 12 pages, 12 figure

Autoantibodies to Endothelial Cell Surface ATP Synthase, the Endogenous Receptor for Hsp60, Might Play a Pathogenic Role in Vasculatides

International audienceBACKGROUND: Heat shock protein (hsp) 60 that provides "danger signal" binds to the surface of resting endothelial cells (EC) but its receptor has not yet been characterized. In mitochondria, hsp60 specifically associates with adenosine triphosphate (ATP) synthase. We therefore examined the possible interaction between hsp60 and ATP synthase on EC surface. METHODOLOGY/PRINCIPAL FINDINGS: Using Far Western blot approach, co-immunoprecipitation studies and surface plasmon resonance analyses, we demonstrated that hsp60 binds to the β-subunit of ATP synthase. As a cell surface-expressed molecule, ATP synthase is potentially targeted by anti-EC-antibodies (AECAs) found in the sera of patients suffering vasculitides. Based on enzyme-linked immunosorbent assay and Western blotting techniques with F1-ATP synthase as substrate, we established the presence of anti-ATP synthase antibodies at higher frequency in patients with primary vasculitides (group I) compared with secondary vasculitides (group II). Anti-ATP synthase reactivity from group I patients was restricted to the β-subunit of ATP synthase, whereas those from group II was directed to the α-, β- and γ-subunits. Cell surface ATP synthase regulates intracellular pH (pHi). In low extracellular pH medium, we detected abnormal decreased of EC pHi in the presence of anti-ATP synthase antibodies, irrespective of their fine reactivities. Interestingly, soluble hsp60 abrogated the anti-ATP synthase-induced pHi down-regulation. CONCLUSIONS/SIGNIFICANCE: Our results indicate that ATP synthase is targeted by AECAs on the surface of EC that induce intracellular acidification. Such pathogenic effect in vasculitides can be modulated by hsp60 binding on ATP synthase which preserves ATP synthase activity

Edge contrast does not modulate edge effect on plants and pollinators

Edge contrast, is one of the main determinants of edge effects. This study examines the response of plant and pollinator diversity (bees and butterflies) to forest edge contrast, i.e. the difference between forests and adjacent open habitats with different disturbance regimes. We also investigated a potential cascading effect from plants to pollinators and whether edge structure and landscape composition mediate the relationship between edge contrast and beta diversity of pollinators. We sampled 51 lowcontrast edges where forests were adjacent to habitats showing low levels of disturbance (i.e. grey dunes, mowed fire-breaks, orchards, grasslands) and 29 high-contrast edges where forests were adjacent to more intensively disturbed habitats (i.e. tilled firebreaks, oilseed rape) in three regions of France. We showed that plant diversities were higher in edges than in adjacent open habitat, whatever the edge contrast. However, plant beta diversity did not differ significantly between low and highcontrast edges. While we observed higher pollinator diversities in adjacent habitats than in low-contrast edges, there were no significant differences in pollinator beta diversity depending on edge contrast. We did not observe a cascading effect from plants to pollinators. Plant and bee beta diversities were mainly explained by local factors (edge structure and flower cover) while butterfly beta diversity was explained by surrounding landscape characteristics (proportion of land cover in grassland)

A chemical survey of exoplanets with ARIEL

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25–7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10–100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed – using conservative estimates of mission performance and a full model of all significant noise sources in the measurement – using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL – in line with the stated mission objectives – will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.Peer reviewedFinal Published versio

Genome sequencing and analysis of the versatile cell factory Aspergillus niger CBS 513.88

The filamentous fungus Aspergillus niger is widely exploited by the fermentation industry for the production of enzymes and organic acids, particularly citric acid. We sequenced the 33.9-megabase genome of A. niger CBS 513.88, the ancestor of currently used enzyme production strains. A high level of synteny was observed with other aspergilli sequenced. Strong function predictions were made for 6,506 of the 14,165 open reading frames identified. A detailed description of the components of the protein secretion pathway was made and striking differences in the hydrolytic enzyme spectra of aspergilli were observed. A reconstructed metabolic network comprising 1,069 unique reactions illustrates the versatile metabolism of A. niger. Noteworthy is the large number of major facilitator superfamily transporters and fungal zinc binuclear cluster transcription factors, and the presence of putative gene clusters for fumonisin and ochratoxin A synthesis

Les auto-anticorps anti-cellules endothéliales (détermination des récepteurs de la b2glycoprotéine 1 et de l HSP60, deux cibles solubles, et identification de l'ATP synthase, une nouvelle cible membranaire)

Les Anticorps anti-cellules endothéliales (AACE) regroupent des anticorps (Ac) reconnaissant des protéines exprimées par les cellules endothéliales (CE). Nous avons cherché à préciser les mécanismes impliqués dans les effets de deux AACE reconnaissant des protéines solubles les Ac antibeta2GPl et les M anti-HSP6O. Dans le syndrome de Hugues, les Ac anti-beta2GPl activent les CE qui deviennent alors pro-coagulante. Cette activation dépend d un récepteur protéique. Lors de ce travail, nous avons mis fin à une dizaine d année de débat sur la nature de ce récepteur en mettant en évidence le rôle d TLR2 dans ce processus. La seconde cible d AACE étudiée est l HSP6O. Sa reconnaissance sur des CE stressées provoque l apoptose des CE en activant un récepteur jusqu alors non identifié. Dans un premier temps nous avons pu observer que l HSP6O se fixée à la mortaline à la surface des CE. Puis nous avons montré que la reconnaissance de complexe induit l apoptose des CE en activant le récepteur CCR5. Nous avons ensuite étudié un récepteur de i HSP6O sur les CE non stressées l ecto-ATP synthase. Nous avons montré que l KSP60 protége la fonction de régulation du pH intracellulaire de l ecto-ATP synthase. Puis, nous avons mis en évidence que l ecto-ATP synthase est une des cibles d AACE. Ces AACE perturbent la régulation du pH intracellulaire des cellules, fragilisant les CE. En conclusion les AACE participent aux lésions auto-immunes en reconnaissant des complexes protéiques à la surface des CE. Ces Complexes peuvent contenir des protéines solubles.et/ou d origine intracellulaire, ce qui souligne la complexité de la localisation des protéines dans les CE.Anti.endothelial cells auto-antibodies (AECA) are a pool of antibodies (Ab) that recognize endothelial cells (EC) proteins. In this work, we planed to precise the mechanism involve in the effect of two AECA that recognize soluble targets beta2 GPI and HSP6O. Anti-beta2GPJ Ah are found in anti-phospholipid syndrom. The recognition of beta2GPl on the endothelial cell surface promotes a procoagulant cellular phenotype. This EC s activation needs a receptor. The Toll-like receptors (TLR) 2 and 4 were the two main candidates. Our results incriminate TLR2, and exclude the participation ofTLR4 in this process. The second AECA s target studied was HSP6O protein. Anti-HSP60 ab recognize HSP60 on the surface of stressed EC, This recognition triggers EC apoptosis through an unknown receptor. We found that HSP6O interacted with mortalin on EC cell surface. The complex can mediate an apoptotic response by activation of the CCR5 receptor. As HSP6O cm he expressed at non-stressed EC surface, we found also that ecto-ATP synthase cm bind HSP6O. This interaction seemed to be a protective process of ecto ATP-synthase-dependent regulation of intracellular pH (pHi). Furthermore, we identified ecto-ATP synthase as another target of AECA. Theses AECA could block the pHi regulation of the cells, altering the EC survival. In conclusion, AECA participate to auto-immune injury by targeting different protein complexes on the EC surface. Theses complexes can contain soluble proteins and/or protein originated from intracellular localization. This data underline the complexity of protein localization in EC.BREST-BU Médecine-Odontologie (290192102) / SudocSudocFranceF

TLR2 is one of the endothelial receptors for beta 2-glycoprotein I.

International audienceDuring the antiphospholipid syndrome, beta2-gpI interacts with phospholipids on endothelial cell (EC) surface to allow the binding of autoantibodies. However, induced-pathogenic intracellular signals suggest that beta2-gpI associates also with a receptor that is still not clearly identified. TLR2 and TLR4 have long been suspected, yet interactions between TLRs and beta2-gpI have never been unequivocally proven. The aim of the study was to identify the TLR directly involved in the binding of beta2-gpI on EC surface. beta2-gpI was not synthesized and secreted by ECs in vitro, but rather taken up from FCS. This uptake occurred through association with TLR2 and TLR4 which partitioned together in the lipid rafts of ECs. After coimmunoprecipitation, mass-spectrometry identification of peptides demonstrated that TLR2, but not TLR4, was implicated in the beta2-gpI retention. These results were further confirmed by plasmon resonance-based studies. Finally, siRNA were used to obtain TLR2-deficient ECs that lost their ability to bind biotinylated beta2-gpI and to trigger downstream phosphorylation of kinases and activation of NFkappaB. TLR4 may upregulate TLR2 expression, thereby contributing to beta2-gpI uptake. However, our data demonstrate that direct binding of beta2-gpI on EC surface occurs through direct interaction with TLR2. Furthermore, signaling for anti-beta2-gpI may be envisioned as a multiprotein complex concentrated in lipid rafts on the EC membrane