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Le roman Look at Me d’Anita Brookner, publie en 1983, raconte l’histoire de Frances Hinton, bibliothecaire documentaliste dans un institut medical. La tâche de Frances consiste a archiver des reproductions d’œuvres d’art depeignant les pathologies a travers les âges, veritable « encyclopedie de la maladie et de la mort », pour reprendre sa propre formulation. A mesure que se developpe l’intrigue, centree sur les interactions de Frances avec les autres personnages de la bibliotheque, le roman lui-meme devient une veritable encyclopedie de la maladie et de la mort dans laquelle les images picturales fonctionnent comme des metaphores de la desintegration physique et mentale de Frances. Apres etre passee tres pres de la mort, Frances reussit a creer les conditions d’une retraite therapeutique qui va lui permettre de se lancer dans son grand projet, l’ecriture d’un roman autobiographique base sur l’institut, en d’autres termes, l’ecriture du roman meme que nous venons de lire. En s’inspirant des travaux de philosophes et de critiques litteraires tels que Kristeva, Derrida, Hirsch, Woolf, Caws et Restuccia, ainsi que de specialistes de Brookner telles que Bowen, Williams-Wanquet et Stetz, cet essai explore la maniere dont la peinture et l’ecriture, qui permettent a Frances de controler sa vie et celle des autres, peuvent etre vues comme des cadres metaphoriques contre la terreur, selon une perspective ontologique aussi bien qu’historique.

Forty per cent of French subjects over 65 years old with Alzheimer's disease and related disorders (ADRD) are chronically exposed to antidepressants, suggesting an overuse of these drugs. The main objective of our study was to estimate the prevalence of the overuse of antidepressants in this population and the factors associated with this. METHODOLOGY a single-centre, prospective, cross-sectional study carried out at the Bretonneau outpatient department between 1st December 2014 and 31st May 2015. All patients aged 70 and above, suffering from ADRD (according to DSM IV criteria) and currently being prescribed an antidepressant were eligible. "Overuse" was defined as off-label prescriptions or prescriptions that went beyond the recommended duration of treatment. This was assessed by the geriatrician in charge and validated by an expert committee, who were blind to the geriatrician's assessment. RESULTS Fifty-four patients were included in the study (mean age: 82.9 years (± 5.4); 70.4% women; 60% with mild to moderate dementia). The main indication of antidepressant treatment was a major depressive episode (59.3%). The geriatrician could not reach a conclusion on overuse in 10 cases (18.5%). Inter-rater agreement between geriatricians and the expert committee was good (kappa coefficient: 0.73 [0.5-0.95]). Finally, 33 (61%) of these patients were overusing antidepressants: a third had an off-label prescription and two thirds had exceeded the recommended treatment duration. The only factor associated with this overuse was co-prescription of psychotropic drugs (p = 0.009). CONCLUSIONS the overuse of antidepressants is common in older patients with dementia, particularly overuse due to exceeding the treatment duration. This is significantly associated with co-prescription with another psychotropic drug, suggesting that this represents a more global problem of the overuse of psychotropic drugs.

Here, multivalent functions have been successfully integrated on a single core-shell type nanostructure, for remote-controlled and receptor-targeted intracellular delivery of doxorubicin (DOX) to breast cancer cells that overexpress biotin receptors.

Extracellular vesicles (EVs) are emerging as crucial mediators in cell-to-cell communication. Stik et al. provide evidence that EVs released by supportive stromal cells target hematopoietic stem and progenitor cells in vivo and in vitro and influence their gene expression and potential., Extracellular vesicles (EVs) have been recently reported as crucial mediators in cell-to-cell communication in development and disease. In this study, we investigate whether mesenchymal stromal cells that constitute a supportive microenvironment for hematopoietic stem and progenitor cells (HSPCs) released EVs that could affect the gene expression and function of HSPCs. By taking advantage of two fetal liver–derived stromal lines with widely differing abilities to maintain HSPCs ex vivo, we demonstrate that stromal EVs play a critical role in the regulation of HSPCs. Both supportive and nonsupportive stromal lines secreted EVs, but only those delivered by the supportive line were taken up by HSPCs ex vivo and in vivo. These EVs harbored a specific molecular signature, modulated the gene expression in HSPCs after uptake, and maintained the survival and clonogenic potential of HSPCs, presumably by preventing apoptosis. In conclusion, our study reveals that EVs are an important component of the HSPC niche, which may have major applications in regenerative medicine.

Summary The cardinal property of bone marrow (BM) stromal cells is their capacity to contribute to hematopoietic stem cell (HSC) niches by providing mediators assisting HSC functions. In this study we first contrasted transcriptomes of stromal cells at different developmental stages and then included large number of HSC-supportive and non-supportive samples. Application of a combination of algorithms, comprising one identifying reliable paths and potential causative relationships in complex systems, revealed gene networks characteristic of the BM stromal HSC-supportive capacity and of defined niche populations of perivascular cells, osteoblasts, and mesenchymal stromal cells. Inclusion of single-cell transcriptomes enabled establishing for the perivascular cell subset a partially oriented graph of direct gene-to-gene interactions. As proof of concept we showed that R-spondin-2, expressed by the perivascular subset, synergized with Kit ligand to amplify ex vivo hematopoietic precursors. This study by identifying classifiers and hubs constitutes a resource to unravel candidate BM stromal mediators., Graphical Abstract, Highlights • A correlation network with predictor genes for the BM HSPC-supportive stromal niche • An information theoretic network for the supportive perivascular stromal niche • Wnt facilitator Rspo2 together with SCF to amplify ex vivo hematopoietic precursors • Resource combining bioinformatics algorithms to search for novel stromal mediators, Cell Biology; Stem Cells Research; Bioinformatics

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It is well established that haematopoietic stem and progenitor cells (HSPCs) are generated from a transient subset of specialized endothelial cells termed haemogenic, present in the yolk sac, placenta and aorta, through an endothelial-to-haematopoietic transition (EHT). HSPC generation via EHT is thought to be restricted to the early stages of development. By using experimental embryology and genetic approaches in birds and mice, respectively, we document here the discovery of a bone marrow haemogenic endothelium in the late fetus/young adult. These cells are capable of de novo producing a cohort of HSPCs in situ that harbour a very specific molecular signature close to that of aortic endothelial cells undergoing EHT or their immediate progenies, i.e., recently emerged HSPCs. Taken together, our results reveal that HSPCs can be generated de novo past embryonic stages. Understanding the molecular events controlling this production will be critical for devising innovative therapies.

Cet article étudie trois œuvres littéraires et cinématographiques publiées dans les années 1980 : le film muet Le Bal (1983) du cinéaste italien Ettore Scola, le roman Family and Friends (1985) de la romancière britannique contemporaine Anita Brookner, et le film Distant Voices, Still Lives (1988) du réalisateur britannique Terence Davies. En dépit des différences de nature entre texte et film, on est frappé, dans ces trois œuvres, non pas tant par leur technique narrative similaire (avec l’utilisation de la photographie et de l’image fixe ainsi que de chants et de danses), que par leur manière d’explorer la cyclicité ou « danse » de l’histoire en des termes qui font écho aux concepts postmodernes de trauma et de déshistoricisation. L’article se fonde sur un certain nombre de critiques du postmodernisme ainsi que sur les théories poststructuralistes de la photographie pour montrer comment, dans ces trois œuvres qui explorent les notions de temporalité, de mémoire et de nostalgie, les photographies, utilisées à la fois comme ressort narratif et comme témoignage historique, représentent bien plus qu’une simple tentative de fixer et de contenir le cours du temps. En faisant la chronique de la seconde moitié du vingtième siècle, marquée par la rupture épistémologique de la Seconde Guerre mondiale (présente dans les trois œuvres) et de la Shoah (omniprésente dans le roman de Brookner même si elle y est à peine évoquée), elles offrent une vision de l’histoire qui, dès lors, ne peut plus être appréhendée que comme un éternel retour dénué de sens, dans lequel les personnages, quels que soient les liens (fragiles ou intenses) qu’ils entretiennent avec leurs familles (réelles ou métaphoriques), semblent irrémédiablement voués à l’aliénation et à la solitude absolue. This essay examines three literary and cinematic works which were all released in the 1980s: Italian director Ettore Scola’s 1983 silent film Le Bal (Ballando… Ballando); contemporary British novelist Anita Brookner’s 1985 novel Family and Friends; and British filmmaker Terence Davies’s 1988 film Distant Voices, Still Lives. What is striking about these three works, despite their different textual and visual nature, is not so much their similar narrative techniques, with their use of photographs and stilled images as well as songs and dances, but the way in which they explore the cyclicality or “dance” of history in terms that resonate with the postmodern concepts of trauma and dehistorization. Borrowing from a number of critics of postmodernism as well as poststructuralist theorists of the photograph, this essay will show how, in these three works which explore the notions of temporality, memory, and nostalgia, the photographs, which are used as both narrative device and historical evidence, represent far more than just an attempt at fixating and containing the passing of time. By chronicling the second half of a twentieth century marked by the epistemological rupture of the Second World War—present in all three works—and the Holocaust—barely alluded to, and yet omnipresent, in Brookner’s novel—they provide a view of history which, from then on, can only be apprehended as an endless and meaningless cyclical return, in which the characters, despite the frail or strong cohesion of actual or metaphorical families, seem forever doomed to alienation and utter solitude.

His mother wrapped him up in a shawl and gave him a passport photograph of herself as a student. She told him to turn to the picture whenever he felt the need to do so. His parents both promised him that they would come and find him and bring him home after the war. (Dori Laub 1992) Survival, testimony, and witness The 1992 coauthored collection Testimony by Shoshana Felman and Dori Laub became a groundbreaking work in trauma studies largely due to its ability to situate trauma within a post-...

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Summary Fanconi anemia (FA) causes bone marrow failure early during childhood, and recent studies indicate that a hematopoietic defect could begin in utero. We performed a unique kinetics study of hematopoiesis in Fancg−/− mouse embryos, between the early embryonic day 11.5 (E11.5) to E12.5 developmental window (when the highest level of hematopoietic stem cells [HSC] amplification takes place) and E14.5. This study reveals a deep HSC defect with exhaustion of proliferative and self-renewal capacities very early during development, together with severe FA clinical and biological manifestations, which are mitigated at E14.5 due to compensatory mechanisms that help to ensure survival of Fancg−/− embryos. It also reports that a deep HSC defect is also observed during human FA development, and that human FA fetal liver (FL) HSCs present a transcriptome profile similar to that of mouse E12.5 Fancg−/− FL HSCs. Altogether, our results highlight that early mouse FL could represent a good alternative model for studying Fanconi pathology., Highlights • Deep HSC defect in FL and Pl very early during Fancg−/− development • Functional and molecular compensation in Fancg−/− FL HSCs at E14.5 • Deep HSC defect also observed during human FA development • E12.5 Fancg−/− FL could represent a good model for studying Fanconi pathology, A deep HSC defect is present very early during Fancg−/− mouse embryonic development, and is also reported for the first time during human Fanconi anemia development. At E14.5, functional and molecular compensation in Fancg−/− FL HSCs help ensure the survival of Fancg−/− embryos. Altogether E12.5 Fancg−/− FL could represent a good model for studying Fanconi pathology.

International audience; Based on specific interactions taking place between poly(N,N-dimethylacrylamide) [PDMA] and silica nanoparticles, two strategies were used to improve the viscoelastic properties of aqueous formulations. First, PDMA oligomers were grafted onto a non-adsorbing poly(acrylamide-co-sodium acrylate) backbone. With this architecture, the binding process of PDMA side-chains with silica nanoparticles was shown to proceed very similarly to free PDMA chains and to promote the formation of hybrid physical networks. The viscoelastic properties of these systems are controlled by the concentration of inorganic cross-links and the fraction of adsorbing grafts involved in the formation of bridges between particles. An optimum weight ratio between silica and grafts was found for the viscoelastic properties, in agreement with the saturation of silica beads by the PDMA precursor. While the homogeneous formation of such hybrid assemblies remains limited to mixtures involving low polymer concentrations (≤ 2 wt%), we show that homogeneous hybrid networks can be readily prepared by direct polymerization of DMA monomer (≥ 5 wt%), with or without chemical cross-linker, in a suspension of silica nanoparticles. In this case, the specific interactions taking place between the silica filler and the whole polymer network give rise to a very unusual combination of properties where elasticity, dissipation, strength and strain at failure are enhanced simultaneously. While the intrinsic structure of the network can be controlled by the level of chemical cross-linking, physical interactions dominate the dissipation process with a dramatic time dependence of the mechanical properties.

Contemporary British writer Anita Brookner was for some thirty years a world-renowned art historian specializing in 18th-century French painting—she has published extensively on Watteau, Ingres, Greuze, and Fragonard, among other artists—before she became a prolific novelist. It is therefore hardly a surprise that painting should play such a prominent part in the novels that she wrote later in her life, only a few years before the end of her long professional career as an art historian. And yet, despite the wealth of pictorial images contained in her fiction, Brookner provides a somewhat unexpected and ambivalent discourse on the image, oscillating between iconophilia and iconophobia, which resonates with W.J.T. Mitchell’s analysis of the “pictorial” turn in postmodern culture. In the vast “textual art museum,” or “museum of words,” of Brookner’s fiction, the pictorial image serves a function which is primarily didactic, metaphorical, and allegorical. Brookner’s use of the image strictly in absentia, thro...

Chantier qualité GA; International audience; DNA double-strand breaks (DSBs) represent a serious threat for hematopoietic stem cells (HSCs). How cytokines and environmental signals integrate the DNA damage response and contribute to HSC-intrinsic DNA repair processes remains unknown. Thrombopoietin (TPO) and its receptor, Mpl, are critical factors supporting HSC self-renewal and expansion. Here, we uncover an unknown function for TPO-Mpl in the regulation of DNA damage response. We show that DNA repair following gamma-irradiation (gamma-IR) or the action of topoisomerase-II inhibitors is defective in Mpl(-/-) and in wild-type mouse or human hematopoietic stem and progenitor cells treated in the absence of TPO. TPO stimulates DNA repair in vitro and in vivo by increasing DNA-PK-dependent nonhomologous end-joining efficiency. This ensures HSC chromosomal integrity and limits their long-term injury in response to IR. This shows that niche factors can modulate the HSC DSB repair machinery and opens new avenues for administration of TPO agonists for minimizing radiotherapy-induced HSC injury and mutagenesis.

Summary: The adsorption process onto a silica surface of oligomers from three different monomers, N,N-dimethylacrylamide (DMA), N-isopropyiacrylamide (NIPA) and ethylene oxide (EO), was studied. From the adsorption isotherms and calorimetric experiments, it was shown that N-alkylacrylamide derivatives strongly interact with silica nanoparticles. At low coverage (Γ < 0. 5 mg m -2 ), the polymers were adsorbed in a flat conformation with a high proportion of trains, while for higher coverages (Γ = 0.5 - 1 mg m -2 ), the adsorption of new chains proceeded by chain displacement, forming an increasing proportion of loops and tails. Similarly, PEO chains readily interacted with silica nanoparticles but showed a lower affinity with an adsorbed amount (T ≅ 0.6 mg m -2 ) that was approximately half of the value obtained for both PDMA and PNIPA. When these oligomers were grafted onto a non-adsorbing poly(acrylamide-co-sodium acrylate) backbone (PAMH), the binding process of these adsorbing side-chains with silica nanoparticles proceeded very similarly and gave rise to the formation of hybrid hydrogels above critical copolymer and silica concentrations. The viscoelastic properties of these networks were controlled by the concentration of inorganic cross-links and the fraction of adsorbing grafts that participated in the formation of bridges between particles, the others being involved in inelastic loops or pendant chains. For all the hybrid mixtures investigated, an optimum weight ratio between silica and grafts was found for the viscoelastic properties, which was in agreement with the saturation of silica beads by the graft precursors. Due to the temperature-dependence of the solubility of the PNIPA side-chains in aqueous solutions, the PAMH-g-PNIPA copolymer was also able to self-assemble with temperature, giving rise to a hybrid conetwork in the presence of added silica.

Hematopoietic stem cells (HSCs) arise first in the third week of human ontogeny inside yolk sac developing blood vessels, and independently, from the wall of the embryonic aorta and vitelline arteries one week later. HSCs produced in the yolk sac and in the embryonic truncal arteries migrate to and transiently colonize the embryonic liver (EL), and thereafter the bone marrow (BM), their permanent site of residence. At the moment, the origin of human HSCs is still controversial; one of the main hypotheses being that they are generated by hemogenic endothelial cells (ECs). To proove definitively the endothelial origin of HSCs that arise within the human embryo, we previously purified ECs from either the yolk sac or the truncal arteries and reported that they were able to produce blood cells in vitro. We then found that some of the HSCs present in the human EL were co-expressing vascular endothelial (VE)-cadherin, an endothelial marker, CD45, a pan-hematopoietic marker, and CD34, a common endothelial and hematopoietic marker, and demonstrated that these HSCs bearing a dual hemato-endothelial phenotype were endowed with remarkably high self renewal and proliferative potentials. Furthermore, a transgenic mouse model based on the VE-cadherin cis-regulating elements that we engineered to trace the fate of the first VE-cadherin expressing cells allowed us to clearly demonstrate that a majority of adult BM HSCs derived from a VE-cadherin ancestor. Altogether our studies strongly suggest that at least a part of both the human and the murine hematopoietic systems arise from an endothelium-like ancestor.

Critics and photographers insist on the lethal and petrifying power of the photographic act, through which the subject becomes reified and disincarnated in a "micro-experience of death," as Barthes puts it in Camera Lucida {La Chambre claire 14). The photographic act seen as an "embalming" is such that the subject photographed "truly [becomes] a specter," Barthes goes on to say (14), thus taking up again almost word for word Susan Sontag's analysis in On Photography for whom photographic images are "ghost images," "death masks," and even "memento mori" (84, 168, 26). Conversely, the photographic image whether its referent in the real world is already dead or still alive has this quasi-magical power of maintaining it in an illusion of perpetual life, as it is cut off from time, and therefore of endowing it with a spectral quality. Photography as the trace of a body without a body, a "paradoxical incorporation" (Derrida 6) or the "tangible intangibility of a proper body without flesh" (7), as Derrida puts it, thus corresponds to the definition of the specter as a "phenomenal and carnal form of the spirit" that he gives in Specters of Marx (6). Much has been said about the literary use of photography for realistic purposes photography being on the side of evidence, of authenticity because of its indexicality or illusionistic ones photography being a construct, and as such capable of lying and deceiving. Less has perhaps been made of its spectral nature and the fictional games made possible by what Regis Durand calls the "photo

In a previous study, we underlined the functional role of the TPO receptor, Mpl, in the establishment of definitive mouse hematopoiesis, by demonstrating that the lack of Mpl led to a delayed production of definitive hematopoietic cells in the aorta-gonad-mesonephros (AGM) region, and resulted in the production of hematopoietic stem cells (HSCs) with an impaired activity at E11.5. In order to more accurately estimate the role of Mpl during generation of HSCs in the aorta, we performed an analysis of these AGMs at the time of the first HSC emergence (E10.5). Our results indicated that while Mpl-/- AGMs were found to contain more hematopoietic cells (HC) than C57Bl6 AGMs at E10.5, a defect in the expansion process of the HC/HSCs was detected in explant cultures of these AGMs, likely due to an increased apoptosis of these cells. To determine the molecular mechanisms by which invalidation of Mpl receptor affects the temporal distribution and expansion of HC/HSCs in the AGM, a study of the transcription level of of Mpl target genes was conducted. Expression of Runx1, a master transcription factor for the formation of hematopoietic progenitor (HP) cells and HSCs from the vasculature, as well as expression of Meis1 and HoxB4, known to play a role in self-renewal and expansion of HSCs, were found to be down regulated in E10.5 Mpl-/- AGMs. Our data indicate that Mpl is an active player during the first steps of definitive hematopoiesis establishment through direct regulation of the expression of transcription factors or genes important for the self-renewal, proliferation and apoptosis of HSCs.

Dicarboxylic acids have been recently found to provide a significant improvement of the mechanical properties of hard materials such as bitumen when added at low concentration. To understand such properties, periodic DFT calculations combined with empirical van der Waals corrections have been performed on crystals of dicarboxylic acid molecules with various chain lengths. Our calculations allow us to understand the interactions governing the cohesive energy of the crystal and to qualitatively correlate diacid transition phase properties (fusion, vaporization, and sublimation) to their behavior when mixed in bitumen. The molecules are distorted because of structural constraints in the crystal packing and that distortion is found to be larger for odd diacids than for even diacids, explaining the usual odd−even alternation of their properties related to the solid state. In particular, the relative fusion temperature of diacids as a function of chain length is dominated by distortion effects. In contrast, mos...

The first coordination sphere of trivalent lanthanum in a highly concentrated (14 M) lithium chloride solution is studied with a combination of classical molecular dynamics and density functional theory based first principle molecular dynamics. This method enables us to obtain a solvation shell of La3+ containing 2 chloride ions and 6 water molecules. After refinement using first principle molecular dynamics, the resulting cation-water and cation−anion distances are in very good agreement with experiment. The 2 Cl− and the 6 water molecules arrange in a square antiprism around La3+. Exchange of water molecules was also observed in the first-principle simulation, with an intermediate structure comprising 7 water molecules stable for 2.5 ps. Finally, evaluation of dipole moments using maximally localized Wannier functions shows a substantial polarization of the choride anions and the water molecules in the first solvation shell of trivalent lanthanum.

A new neutral gene vector, based on a lipopolythiourea N-(2-(3-[2-(2-(3-[2-(3-methyl-thioueido)-ethyl] -thioureido)-ethylamino)-ethyl]-thioureido)-ethyl)- N′, N′- ditetradecyl-succinamide (DTTU) has recently been synthetized but its behavior is difficult to study at the experimental level. Density functional theory (DFT) calculations have thus been performed to predict its interaction mode with B-DNA. Its acidic properties are first computed and suggest that DTTU should be non-charged when interacting with DNA. Different ways of DTTU/DNA associations based on hydrogen bonding–namely external and groove-binding interactions—are then investigated. Our calculations clearly point out that external interaction is preferred with respect to groove-binding, due to three bifurcated hydrogen bonds between DTTU thiourea groups and DNA phosphates. Such results can be explained by the absence of charged groups in groove-binding whereas the negative charge of DNA phosphates deeply strengthens hydrogen bonds.

The quantum chemical study presented here shows various aspects of the bonding of lanthanide (La 3+ , Gd 3+ ) and actinide (U 3+ , Am 3+ , Cm 3+ ) ions with N -heterocyclic ligands (polyazines, BTP: bis(1,2,4-triazinyl)-2,6-pyridine). Several families of complexes, differing by their coordination sphere, have been examined. Clearly, the lanthanide complexes always show a purely ionic bonding. The behaviour of U(III) is also well defined with a more or less strong backbonding interaction whatever the complex is. In contrast, the heavy actinides (Am 3+ and Cm 3+ ) are changeable, with a weak covalent character, going from donation to backdonation, depending on the coordination sphere of the complex.

The calculation of the absorption spectra of four families of transition-metal complexes (Ni(CO)4, MnO4(-), MF6 (M = Cr, Mo, W) and CpM(CO)2 (M = Rh, Ir)) has been undertaken to unravel the influence of basis sets onto excitation energies, oscillator strengths, and assignments. Three among the most common pseudopotentials, with the corresponding valence basis sets, and two all-electron basis sets have been used for the metal center description in the framework of the time dependent Density Functional Theory (TD-DFT). Our results show that this approach does not particularly depend on the basis set used on the metal atoms. Furthermore, the chosen functional PBE0 provides transitions in good agreement with experiments, and it provides an accuracy of about 0.3 eV, comparable to that of refined post-Hartree-Fock methods.

The properties of a highly concentrated aqueous lithium chloride solution (|LiCl| = 14 mol L(-1)) are investigated using Car-Parrinello molecular dynamics. The coordination spheres of lithium ions, chloride ions, and water molecules are described successively. On the whole, our simulation provides results-distances and coordination numbers-in very good agreement with experimental data. The lithium solvation shell is found to exhibit a tetrahedral configuration on average, with three stable clusters observed during the simulation: Li(+)-4H2O, Li(+)(H2O)3Cl(-), and Li(+)(H2O)2(Cl(-))2. The chloride coordination sphere is logically formed by strong Cl-H hydrogen bonds with neighboring water molecules, for a mean coordination number of 4.4. The structuring of water molecules is strongly affected by the high concentration in LiCl. The hydrogen bond network is globally broken down, but little variation is calculated on water dipoles (μ = 3.07 D) because of the strong polarization from Li(+) and Cl(-) ions. We also point out some of the characteristic features of such a highly concentrated solution: water bridging between Li(+) and Cl(-) hydration spheres, Li(+)-Cl(-) ion-pairing, and intermediate behavior between dilute solutions and molten salts. Finally, the reliability of our simulation to describe ion-pairing is discussed.

Fanconi anemia (FA) is a genetic disorder due to mutations in one of the sixteen FANC genes involved in DNA repair. Many FA patients develop bone marrow failure (BMF) during childhood, and FA strongly predisposes to myelodysplasia syndrome and/or acute myeloid leukaemia. The pathogenesis of the BMF remains uncompletely understood. Low hematopoietic progenitor cell (HPCs) counts observed early in life and preceeding the onset of blood cytopenia in patients led we, and other, to hypothesize that the hematopoietic development might be abnormal in the FA embryo. Indeed, unlike adult hematopoietic stem cells (HSCs) which are quiescent in the BM niche, during embryonic life HSCs are in active proliferation in sites of expansion such as fetal liver and placenta, where they get amplified and acquire properties of adult HSC .We hypothesized that in FA, the FA defect in response to the replicative stress could impair the expension of the HSC pool.In order to investigate this hypothesis, we carried out studies in Fancg-/- knock out mice and in human FA fetuses obtained with informed consent from medical abortion. In Fancg-/- mice, FACS analysis revealed a 1,5- to 3-fold deficiency in hematopoietic stem and progenitor cells (HSPC) very early during embryonic development (i.e 11.5 days of gestation - E11.5) in fetal liver (FL) and placenta (Pl) (p In vivo long-term hematopoietic reconstitution (LTR) assays confirmed a deficit of the HSC enriched LSA population of E14.5 Fancg-/- FL. Indeed, although the percentage of mice reconstituted was as good as that obtained with the same number of WT LSA, the CD45 Ly5.2 chimerism was reduced (49±20% vs 84±4% for 1000 LSA injected, and 56±12% vs 87±2% for 5000 LSA). Interestingly, bone marrow analysis of mice reconstituted with Fancg-/- LSA 22 weeks after injection showed a level of CD45 Ly5.2 chimerism 3-fold lower than that found in blood, spleen and thymus, as well as a very low chimerism for myeloid GEM lineages, contrasting with a high chimerism for B and T lymphoid lineages. Moreover, we were able to demonstrate that this deficit is already present at E12.5, both in Fancg-/- FL and Pl. Indeed, no mice reconstituted with 3.105 total Fancg-/- fetal liver cells, while 100% injected with the same number of WT FL cells got reconstituted with a chimerism of 59,5±5%. For Pl, when 500 000 cells were injected, reconstitution was observed in only 1 out of 3 mice for Fancg-/- (29% chimerism), and in 3 out of 3 mice for WT (88±4% chimerism). In human FA FL of 14 weeks of gestation, we also observed a 4-fold defect of HSPC with a total lack of in vitro amplification compared to control, in agreement with the mice data. Taken together, these data demonstrate that a profound deficit of HSCs and progenitors cells is present since the earlier stages of embryonic development in FA. In addition, using organotypic cultures of E11 aortas, we could show that this defect of amplification is already present in HSCs emerging from Fancg-/- aorta, which showed a 2-fold lower rate of amplification compared to WT. More importantly, our results show for the first time exhaustion in myeloid lineage of FA, in agreement with what is observed in children with FA disease. Altogether, our work suggests a role of the FA pathway during the development of the hematopoietic system leading to a deficit of amplification of HSC. Comparison of FA HSC transcriptome with that of control HSC in FL and Pl is in progress. It should allow to identify the key pathways involved in the embryonic HSC amplification that are deregulated in FA, and hopefully getting more insights in the pathogenesis of the BMF and leukemogenesis in FA patients. Disclosures No relevant conflicts of interest to declare.

Hematopoietic stem cells (HSCs) are identified by their ability to self-renew and to differentiate into all blood cell lineages. In vivo, hematopoietic stem/progenitor cells (HSPCs) are in close association with stromal cells that constitute a supportive microenvironment also called niche. Recently, exosomes that are small microvesicles enclosed by a lipid bilayer and enriched in cytoplasmic proteins, mRNAs, microRNAs, have emerged as major communication mediators between cells. However, their implication in the cross-talk between HSCs and stromal cells is still largely unknown. This study aims to assess the existence and the functionality of stromal cell-derived exosomes in the HSPC support. To address this issue, we used two murine stromal cell lines derived from the fetal liver and with differing capacity to maintain HSPCs ex vivo as revealed by repopulation assay and long-term cultures. AFT024 (AFT) harbors a potent HSPC supporting capacity in vitro whereas BFC012 (BFC) is non supportive. For each cell line, the exosome fractions were isolated from culture supernatant by ultra-centrifugation. Electron microscopy, western blot, and flow cytometry analyses revealed that both AFT and BFC stromal cells secrete exosomes. Interestingly, using PKH67 stained exosomes, we demonstrated that bone marrow Lin-Sca-1+c-kit+ (LSK) cells preferentially uptake AFT-derived exosomes. This observation might be related to the different tetraspanin compositions of AFT and BFC derived exosomes as observed by flow cytometry. We then showed an increase in cell viability and clonogenic potential when LSK cells were exposed to AFT-derived exosomes for 96 hours in cytokine-free medium as compared to controls. Moreover, cultures with AFT-derived exosomes exhibited a 3.5 fold increase in the number of LSK cells as compared to untreated conditions. We then used high-throughput sequencing to explore the molecular signatures of AFT and BFC derived exosomes, as well as their cells of origin. We identified a list of 394 mRNAs and 6 microRNAs specifically expressed in exosomes and correlated to the HSPC support. Gene ontology analysis revealed that the apoptotic regulation, cell survival and proliferation pathways were significantly enriched in the AFT-derived exosomal signature. In addition, we showed the transfer of mRNAs involved in these pathways from the AFT-exosomes to the LSK recipient cells. Together with our observation of a decrease in the LSK apoptotic cells after co-culture with AFT-derived exosomes, these data suggest that exosomes released by AFT cells may protect HSPCs from apoptosis. Collectively, our results revealed an important role for exosomes in the HSPC supporting capacity of stromal cells. This work provides new insights in our understanding of the molecular and cellular mechanisms involved in the cross-talk between HSPCs and their niches. It may also have interesting applications in regenerative medicine, regarding the ex vivo manipulation of HSCs in stromal-free conditions for cell therapy. Disclosures No relevant conflicts of interest to declare.

As Marianne Hirsch explains in Family Frames: Photography, Narrative and Postmemory, family pictures, by displaying the cohesion of the family in conventional postures, perpetuate dominant mytholog...

Responsive thickeners have been obtained by grafting onto poly(sodium acrylate) [PAA] macromolecular stickers characterized by a lower critical solution temperature (LCST) in water: poly(N-isopropylacrylamide) [PNIPA] or poly(ethylene oxide-co-propylene oxide) [PPO]. As these LCST polymeric side chains are able to interact specifically with silica surfaces, while the macromolecular backbone does not, the aim of the present work was to study the formation of hybrid self-assemblies in aqueous solutions between inorganic nano-particles and copolymers. Despite very strong electrostatic repulsions taking place between silica beads and PAA chains at pH 8, specific interactions were clearly evidenced for all organic/inorganic mixtures and their properties were studied by rheology and calorimetry. At low temperature, PNIPA side-chains strongly adsorb on silica surfaces and promote the formation of hybrid networks with viscoelastic properties close to chemical gels. The 3D structure is very stable, even in the presence of salt ([NaCl] = 0.1 mol/l), and thermothickening properties are observed above the LCST of PNIPA due to self-assembling of non-adsorbed stickers. PAAgPPO solutions display a similar behaviour with thermothickening properties in the presence of added nanoparticles. Nevertheless the association between PPO and silica are weaker and the hybrid network is no longer stable at high ionic strength.

A theoretical study on a family of divalent transition metal bacteriochlorin complexes (M-BC, where M = Mn, Fe, Co, Ni Cu, and Zn) has been carried out to elucidate their potentialities as active molecules in photodynamic therapy (PDT). To draw a complete picture of their electronic properties, both for the ground and excited states, these complexes have been studied by the means of density functional theory (DFT). The time-dependent DFT (TDDFT) approach was used to interpret the electronic spectra, while solvent effects were taken into account by explicitly considering both two water molecules coordinated to the central metal atom and the contribution from the solvent bulk. Particular attention has been devoted to the analysis of the so-called Q bands, since these can be particularly important for medical applications. Metal substitution and environment (solvent) effects have been analyzed, and good agreement is found between computed and available UV-vis spectra. These theoretical data, especially those relative to the metallobacteriochlorins not yet completely characterized at the experimental level, could give some hints for future medical applications.

Several reports have demonstrated that the pineal hormone, melatonin, plays an important role in body mass regulation in mammals. To date, however, the target tissues and relevant biochemical mechanisms involved remain uncharacterized. As adipose tissue is the principal site of energy storage in the body, we investigated whether melatonin could also act on this tissue. Semiquantitative RT-PCR analysis revealed the expression of MT1 and MT2 melatonin receptor mRNAs in the human brown adipose cell line, PAZ6, as well as in human brown and white adipose tissue. Binding analysis with 2-[(125)I]iodomelatonin ((125)I-Mel) revealed the presence of a single, high affinity binding site in PAZ6 adipocytes with a binding capacity of 7.46 +/- 1.58 fmol/mg protein and a K(d) of 457 +/- 5 pM. Both melatonin and the MT2 receptor-selective antagonist, 4-phenyl-2-propionamidotetraline, competed with 2-[(125)I]iodomelatonin binding, with respective K(i) values of 3 x 10(-11) and 1.5 x 10(-11) M. Functional expression of melatonin receptors in PAZ6 adipocytes was indicated by the melatonin-induced, dose-dependent inhibition of forskolin-stimulated cAMP levels and basal cGMP levels with IC(50) values of 2 x 10(-9) and 3 x 10(-10) M, respectively. Modulation of the cGMP pathway by melatonin further supports functional expression of MT2 receptors, as this pathway was shown to be specific for that subtype in humans. In addition, long-term melatonin treatment of PAZ6 adipocytes was found to decrease the expression of the glucose transporter Glut4 and glucose uptake, an important parameter of adipocyte metabolism. These results suggest that melatonin may act directly at MT2 receptors on human brown adipocytes to regulate adipocyte physiology.

Two cDNAs encoding novel isoforms of Xenopus laevis melatonin receptors were cloned using PCR primers specific for the X. laevis-melanophore Mel1c melatonin receptor described in a recent publication. The novel isoforms were highly homologous to the described frog Mel1c cDNA, although the C-terminal tail of both was shorter by 65 amino acid residues. Nucleotide sequences of these novel isoforms, called Mel1c(alpha) and Mel1c(beta), differed from each other by only 35 nucleotides and six amino acid residues. Studies on several animals of various Xenopus species indicate that Mel1c(alpha) and Mel1c(beta) receptors may correspond to allelic variants of the same locus. Studies on cells transfected with both receptor cDNAs showed the expression of high-affinity 2-[125I]iodomelatonin binding sites. Agonist stimulation of Mel1c(alpha) receptor was associated with the inhibition of cAMP accumulation stimulated by forskolin (IC50 approximately 10(-10) M) in HeLa, Ltk-, and human embryonic kidney 293 (HEK 293) cells. Mel1c(beta) receptor modulated cAMP in HeLa and HEK 293 cells but not in Ltk- cells. Both receptors inhibited, in a dose-dependent manner, cGMP accumulation in all three cell lines incubated with a phosphodiesterase inhibitor. This effect was localized upstream of soluble guanylyl cyclase and was blocked by pertussis toxin treatment. However, IC50 values (approximately 10(-10) M for Mel1c(beta) and 10(-9) to 10(-7) M for Mel1c(alpha)) and maximal inhibition levels showed that Mel1c(alpha) receptors are much less efficiently coupled to the cGMP pathway. Coupling differences may be explained by the fact that five of the six amino acid substitutions between Mel1c(alpha) and Mel1c(beta) receptors are located within cytoplasmic regions potentially involved in signal transduction. The existence of coupling differences is in agreement with the observation that expression of both receptors is evolutionally conserved in native tissue. In conclusion, two novel, potentially allelic, isoforms of Xenopus Mel1c melatonin receptors display identical ligand-binding characteristics, but different potencies in modulating cAMP and cGMP levels through G(i)/G(o)-dependent pathways. Furthermore, to our knowledge, this study provides the first data on the modulation of intracellular cGMP levels by cloned melatonin receptors.

Combinatorial peptide libraries are a new source of compounds from which a large number of pharmacological leads will emerge in the next few years. A large body of literature shows that this approach is of considerable interest in many areas of biological sciences for the search of enzyme substrates and inhibitors, of receptor agonists or antagonists, or of antigen sequences. Nevertheless, the analytical investigation of such complex mixtures as libraries which contain up to millions of individual molecules is still poorly documented. In this work, we present analytical solutions for their characterization. NMR and tandem mass spectrometry (MS/MS) can provide an in deep description of any type of combinatorial libraries, while MS and high-performance capillary electrophoresis can bring a rapid and overall information at the routine level, sufficient to ensure a first assessment of their composition. MS in the fast atom bombardment mode was used to describe the libraries O1X2X3X4X5 or O1X2X3X4 (Oiand Xiare fixed and random residue in positioni, respectively). Advantage was taken of the high proton affinity of arginine and of its induction of charge remote fragmentation to interpret the MS spectra of whole libraries and neutral losses (MS/MS) in the model sublibraries ArgGlyX3X4 and NipValX3X4 (Nip, 4-nitrophenylalanine). Two-dimensional NMR allowed the incorporation of the individual residues during synthesis to be tested in 24 sublibraries O1X2X3X4. While from the pharmacological point of view, impressive discoveries made with combinatorial peptide libraries have already been reported, our results show that they should be complemented by appropriate analytical tools, crucial for the proper characterization and exploitation of these libraries.

Abstract 3447 Radiation-induced double-strand breaks (DSBs) represent a serious threat to the preservation of genetic information when it reaches hematopoietic stem cells (HSCs). Residual loss of HSC functions and increased risk of developing hematopoietic malignancies are two concerning complications of anti-cancer radiotherapy. Management of acute myelosuppression following radio- or chemotherapy has been significantly improved in recent years by the use of growth factors. However, how cytokine/environmental signals integrate the DNA damage responses in HSCs and regulate the long-term residual HSC defects following radio-or chemotherapy is unknown. Notably, the contribution of cytokines regulating HSC functions to HSC intrinsic DNA damage repair processes remains to be delineated. Thrombopoietin (TPO) and its receptor, Mpl, are critical factors supporting HSC self-renewal, survival and expansion posttransplantation. In this study, we uncover an unknown and unique function for TPO/Mpl in the regulation the DNA damage response. We show that DSB repair, measured by both γH2Ax foci resolution and neutral comet assays, following γ-irradiation (IR) or topoisomerase II inhibitor treatments, is defective in Mpl−/− and Mpl+/− HS and progenitor cells (HSPCs). Similar defects were found in wild-type cells treated in the absence of TPO. This indicates that the impaired DNA repair of Mpl−/− and Mpl+/− cells results from a specific loss of TPO-mediated DNA damage response signaling at the time of IR rather than from intrinsic constitutive differences. TPO stimulates DNA repair by increasing IR-induced DNA-PK phosphorylation at Ser2056 and Thr2609 and non-homologous end joining (NHEJ) efficiency in both HSPCs and the human UT7-Mpl cell line. This is to our knowledge the first demonstration that a cytokine involved in the homeostatic maintenance of HSCs may also regulate their response to external DNA damaging insults by controlling the DSB repair machinery. Short TPO treatment in vitro or single TPO injection to TPO/Mpl proficient mice prior to sublethal total body IR reduced IR-induced HSC genomic instability and loss of long-term reconstitution ability. This may open new avenues for administration of TPO agonists before radiotherapy to minimize radiation-induced HSC injury and mutagenesis. In addition, since Mpl is haploinsufficient in the regulation of DNA damage repair, these data suggest that Mpl might also act as a tumor suppressor in response to radiotherapy. Disclosures: No relevant conflicts of interest to declare.