Aspects géologiques et géomorphologiques de la Casamance : étude de la sédimentation actuelle

Après une synthèse des données géologiques et géomorphologiques de la région de Basse Casamance où il apparaît que les variations du niveau marin et les variations climatiques au cours du Quaternaire récent ont une part essentielle dans l'évolution du modelé des paysages, l'étude de la sédimentation actuelle est abordée à partir de prélèvement effectués sur une série de profils bathymétriques dans les cent derniers kilomètres du fleuve Casamance entre Adéane et l'embouchure. Cette approche nous permet de définir ensuite les principaux faciès et leurs aires de répartition. Trois zones apparaissent : un domaine maritime où domine un sable marin unimodal; un domaine intermédiaire où les apports marins et continentaux, brassés par les courants de marée donnent des sédiments plus hétérogènes souvent riches en sables grossiers dans les fonds de chenaux; et un domaine continental caractérisé par une dominance des limons fins. (Résumé d'auteur

Angular momentum evolution in laser-plasma accelerators

The transverse properties of an electron beam are characterized by two quantities, the emittance which indicates the electron beam extend in the phase space and the angular momentum which allows for non-planar electron trajectories. Whereas the emittance of electron beams produced in laser- plasma accelerator has been measured in several experiments, their angular momentum has been scarcely studied. It was demonstrated that electrons in laser-plasma accelerator carry some angular momentum, but its origin was not established. Here we identify one source of angular momentum growth and we present experimental results showing that the angular momentum content evolves during the acceleration

Campagne océanographique FLUPAC à bord du N.O. l'ATALANTE 23 septembre au 29 octobre 1994. Recueil des données. Tome 1 : météo, courantologie, hydrologie, données de surface

La campagne FLUPAC du N.O. L'Atalante, qui s'est déroulée du 23 septembre au 29 octobre 1994, s'est placée dans le cadre du programme international JGOFS (JOINT GLOBAL OCEAN FLUX STUDY). Elle a comporté deux radiales et deux stations équatoriales de 6-7 jours. La première radiale, le long de 165°E, a parcouru la zone comprise entre 20°S et 6°N. La seconde s'est déroulée le long de l'équateur entre 167°E et 150°W. Les deux stations de longue durée ont eu lieu à O°-167°E et 0°-150°W. Elles ont été l'occasion d'études détaillées des flux impliqués dans le cycle du carbone de la couche superficielle (0-500 m). Le premier tome du recueil de données présente des résultats, sous forme de graphiques et de tableaux, des paramètres enregistrés en continu et de ceux de la sonde CTD. Les paramètres chimiques, la chlorophylle "a" et les observations en cytomètrie de flux obtenus sur l'eau de la "rosette" couplée à la sonde CTD, sont également présentés. (Résumé d'auteur

A high-frequency, long-term data set of hydrology and sediment yield: the alpine badland catchments of Draix-Bléone Observatory

Draix-Bléone critical zone observatory was created in 1983 to study erosion processes in a mountainous badland region of the French Southern Alps. Six catchments of varying size (0.001 to 22 km2) and vegetation cover are equipped to measure water and sediment fluxes, both as bedload and suspended load. This paper presents the core dataset of the observatory, including rainfall and meteorology, high-frequency discharge and suspended-sediment concentration, and event-scale bedload volumes. The longest records span almost 40 years. Measurement and data-processing methods are presented, as well as data quality assessment procedures and examples of results. All the data presented in this paper are available on the open repository https://doi.org/10.17180/obs.draix (Draix-Bleone Observatory, 2015), and a 5-year snapshot is available for review at https://doi.org/10.57745/BEYQFQ (Klotz et al., 2023).</p

Innate Immune Function in Placenta and Cord Blood of Hepatitis C – Seropositive Mother-Infant Dyads

Vertical transmission accounts for the majority of pediatric cases of hepatitis C viral (HCV) infection. In contrast to the adult population who develop persistent viremia in ∼80% of cases following exposure, the rate of mother-to-child transmission (2–6%) is strikingly low. Protection from vertical transmission likely requires the coordination of multiple components of the immune system. Placenta and decidua provide a direct connection between mother and infant. We hypothesized that innate immune responses would differ across the three compartments (decidua, placenta and cord blood) and that hepatitis C exposure would modify innate immunity in these tissues. The study was comprised of HCV-infected and healthy control mother and infant pairs from whom cord blood, placenta and decidua were collected with isolation of mononuclear cells. Multiparameter flow cytometry was performed to assess the phenotype, intracellular cytokine production and cytotoxicity of the cells. In keeping with a model where the maternal-fetal interface provides antiviral protection, we found a gradient in proportional frequencies of NKT and γδ-T cells being higher in placenta than cord blood. Cytotoxicity of NK and NKT cells was enhanced in placenta and placental NKT cytotoxicity was further increased by HCV infection. HCV exposure had multiple effects on innate cells including a decrease in activation markers (CD69, TRAIL and NKp44) on NK cells and a decrease in plasmacytoid dendritic cells in both placenta and cord blood of exposed infants. In summary, the placenta represents an active innate immunological organ that provides antiviral protection against HCV transmission in the majority of cases; the increased incidence in preterm labor previously described in HCV-seropositive mothers may be related to enhanced cytotoxicity of NKT cells

CD160-Associated CD8 T-Cell Functional Impairment Is Independent of PD-1 Expression.

Expression of co-inhibitory molecules is generally associated with T-cell dysfunction in chronic viral infections such as HIV or HCV. However, their relative contribution in the T-cell impairment remains unclear. In the present study, we have evaluated the impact of the expression of co-inhibitory molecules such as 2B4, PD-1 and CD160 on the functions of CD8 T-cells specific to influenza, EBV and CMV. We show that CD8 T-cell populations expressing CD160, but not PD-1, had reduced proliferation capacity and perforin expression, thus indicating that the functional impairment in CD160+ CD8 T cells may be independent of PD-1 expression. The blockade of CD160/CD160-ligand interaction restored CD8 T-cell proliferation capacity, and the extent of restoration directly correlated with the ex vivo proportion of CD160+ CD8 T cells suggesting that CD160 negatively regulates TCR-mediated signaling. Furthermore, CD160 expression was not up-regulated upon T-cell activation or proliferation as compared to PD-1. Taken together, these results provide evidence that CD160-associated CD8 T-cell functional impairment is independent of PD-1 expression

Generation of a Novel Regulatory NK Cell Subset from Peripheral Blood CD34+ Progenitors Promoted by Membrane-Bound IL-15

BACKGROUND: NK cells have been long time considered as cytotoxic lymphocytes competent in killing virus-infected cells and tumors. However, NK cells may also play essential immuno-regulatory functions. In this context, the real existence of a defined NK subset with negative regulatory properties has been hypothesized but never clearly demonstrated. METHODOLOGY/PRINCIPAL FINDINGS: Herein, we show the in vitro generation from human peripheral blood haematopoietic progenitors (PB-HP), of a novel subset of non-cytolytic NK cells displaying a mature phenotype and remarkable immuno-regulatory functions (NK-ireg). The main functional hallmark of these NK-ireg cells is represented by the surface expression/release of HLA-G, a major immunosuppressive molecule. In addition, NK-ireg cells secrete two powerful immuno-regulatory factors: IL-10 and IL-21. Through these factors, NK-ireg cells act as effectors of the down-regulation of the immune response: reconverting mature myeloid DC (mDC) into immature/tolerogenic DC, blocking cytolytic functions on conventional NK cells and inducing HLA-G membrane expression on PB-derived monocytes. The generation of "NK-ireg" cells is obtained, by default, in culture conditions favouring cell-to-cell contacts, and it is strictly dependent on reciprocal trans-presentation of membrane-bound IL-15 forms constitutively and selectively expressed by human CD34(+) PB-HP. Finally, a small subset of NKp46(+) HLA-G(+) IL-10(+) is detected within freshly isolated decidual NK cells, suggesting that these cells could represent an in vivo counterpart of the NK-ireg cells. CONCLUSIONS/SIGNIFICANCE: In conclusion, NK-ireg cells represent a novel truly differentiated non-cytolytic NK subset with a self-sustainable phenotype (CD56(+) CD16(+) NKp30(+) NKp44(+) NKp46(+) CD94(+) CD69(+) CCR7(+)) generated from specific pSTAT6(+) GATA3(+) precursors. NK-ireg cells could be employed to develop new immuno-suppressive strategies in autoimmune diseases, transplant rejection or graft versus host diseases. In addition, NK-ireg cells can be easily derived from peripheral blood of the patients and could constitute an autologous biotherapic tool to be used combined or in alternative to other immuno-regulatory cells

Simulation of Postsynaptic Glutamate Receptors Reveals Critical Features of Glutamatergic Transmission

Activation of several subtypes of glutamate receptors contributes to changes in postsynaptic calcium concentration at hippocampal synapses, resulting in various types of changes in synaptic strength. Thus, while activation of NMDA receptors has been shown to be critical for long-term potentiation (LTP) and long term depression (LTD) of synaptic transmission, activation of metabotropic glutamate receptors (mGluRs) has been linked to either LTP or LTD. While it is generally admitted that dynamic changes in postsynaptic calcium concentration represent the critical elements to determine the direction and amplitude of the changes in synaptic strength, it has been difficult to quantitatively estimate the relative contribution of the different types of glutamate receptors to these changes under different experimental conditions. Here we present a detailed model of a postsynaptic glutamatergic synapse that incorporates ionotropic and mGluR type I receptors, and we use this model to determine the role of the different receptors to the dynamics of postsynaptic calcium with different patterns of presynaptic activation. Our modeling framework includes glutamate vesicular release and diffusion in the cleft and a glutamate transporter that modulates extracellular glutamate concentration. Our results indicate that the contribution of mGluRs to changes in postsynaptic calcium concentration is minimal under basal stimulation conditions and becomes apparent only at high frequency of stimulation. Furthermore, the location of mGluRs in the postsynaptic membrane is also a critical factor, as activation of distant receptors contributes significantly less to calcium dynamics than more centrally located ones. These results confirm the important role of glutamate transporters and of the localization of mGluRs in postsynaptic sites in their signaling properties, and further strengthen the notion that mGluR activation significantly contributes to postsynaptic calcium dynamics only following high-frequency stimulation. They also provide a new tool to analyze the interactions between metabotropic and ionotropic glutamate receptors