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Trabajo presentado en Satellite Activity of the UN Ocean Decade: Clean Ocean Laboratory, celebrado online del 17 al 19 de noviembre de 2021, This poster emphasizes relevant values to build research links between EU and US within the scope of marine pollution data policies. It interprets ocean literacy in the special data case of the global risks posed by plastics (which call for citizen science based tools that can help fill data gaps relevant for policy). And it seeks to demonstrate that the effects of the US interdisciplinary and multiregional collaboration, regarding plastics data on the European partners, respond to the needs of the 21st Century paradigm concerning information. A proposal for a permanent access to marine plastic data is advanced.

11 pages; International audience; Freshwater ecosystems play an important role in transporting and accumulating microplastics. Spatial and temporal variability in microplastic pollution can create critical spots and moments of elevated pollution, however, the consequences of their interaction are still poorly understood. This study aimed to assess the interaction between urbanization and flood episodes on river microplastic pollution. The water surface was sampled in two sites of the Garonne River, upstream and downstream a large urban area, during two flood episodes. Samples were chemically digested to facilitate particles isolation, and microplastics (700 μm-5 mm) were characterized through infrared spectroscopy (ATR-FTIR). Microplastic concentration increased by 5-8 fold during flood episodes, driven by river discharge. This increase was more significant in the downstream site. During the flood, there was an overall increase of larger particles on water surface, but only in the downstream site microplastic colours and polymeric compositions significantly varied. Principal component analysis of infrared spectra from polyethylene microplastics revealed that the main variance in the spectral region corresponded to hydroxyl and carbonyl groups. The carbonyl content in microplastics was significantly higher for particles collected during the flood, likely indicating a higher level of degradation. Urbanization modulates freshwater microplastic pollution during floods, and changes in microplastic physicochemical profile should be further integrated within toxicity studies to evaluate risks potentially elevated to animal and human health.

International audience; Nowadays, environmental pollution by microplastics (

SUMMARY Afferent responses to the fish's own electric organ discharge were explored in the electrosensory lobe of the mormyrid fish Gnathonemus petersii. In order to understand the neural encoding of natural sensory images,responses were examined while objects of different conductivities were placed at different positions along the skin of the fish, i.e. at different points within, and also outside, peripheral receptive fields. The presence of an object in the fish's self-generated electric field produces local modulation of transcutaneous current density. Measurement of the local electric organ discharge shows that object images formed at the electroreceptive sensory surface have an opposing center-surround, `Mexican hat' profile. This is a pre-receptor phenomenon intrinsic to the physical nature of the sensory stimulus that takes place prior to neural lateral inhibition and is independent of such central inhibition. Stimulus intensity is encoded in the latency and number of action potentials in the response of primary afferent fibers. It is also reflected in changes in the amplitude and area of extracellular field potentials recorded in the deep granular layer of the electrosensory lobe. Since the object image consists of a redistribution of current density over the receptive surface,its presence is coded by change in the activity of receptors over an area much larger than the skin surface facing the object. We conclude that each receptor encodes information coming from the whole scene in a manner that may seem ambiguous when seen from a single point and that, in order to extract specific object features, the brain must process the electric image represented over the whole sensory surface.

In order to understand the sensitivity of alveolar macrophages (AMs) to substrate properties, we have developed a new model of macrophages cultured on substrates of increasing Young's modulus: (i) a monolayer of alveolar epithelial cells representing the supple (approximately 0.1 kPa) physiological substrate, (ii) polyacrylamide gels with two concentrations of bis-acrylamide representing low and high intermediate stiffness (respectively 40 kPa and 160 kPa) and, (iii) a highly rigid surface of plastic or glass (respectively 3 MPa and 70 MPa), the two latter being or not functionalized with type I-collagen. The macrophage response was studied through their shape (characterized by 3D-reconstructions of F-actin structure) and their cytoskeletal stiffness (estimated by transient twisting of magnetic RGD-coated beads and corrected for actual bead immersion). Macrophage shape dramatically changed from rounded to flattened as substrate stiffness increased from soft ((i) and (ii)) to rigid (iii) substrates, indicating a net sensitivity of alveolar macrophages to substrate stiffness but without generating F-actin stress fibers. Macrophage stiffness was also increased by large substrate stiffness increase but this increase was not due to an increase in internal tension assessed by the negligible effect of a F-actin depolymerizing drug (cytochalasine D) on bead twisting. The mechanical sensitivity of AMs could be partly explained by an idealized numerical model describing how low cell height enhances the substrate-stiffness-dependence of the apparent (measured) AM stiffness. Altogether, these results suggest that macrophages are able to probe their physical environment but the mechanosensitive mechanism behind appears quite different from tissue cells, since it occurs at no significant cell-scale prestress, shape changes through minimal actin remodeling and finally an AMs stiffness not affected by the loss in F-actin integrity.

Letter to the Editors; International audience; No abstract is available for this article

International audience; The uptake of iron (III) mediated by lactotransferrin to human biopsies from upper intestine has suggested the presence of specific receptors for human lactotransferrin at the brush border (Cox, T., Mazurier, J., Spik, G., Montreuil, J. and Peters, T.J. (1979) Biochim. Biophys. Acta 588, 120-128). In the present data, using 125I-radiolabeled transferrins, we have demonstrated that a preparation of microvillous membrane vesicles, from rabbit jejunal brush-border specifically binds human lactotransferrin. This binding is specific, saturable and calcium dependent. Scatchard plots analysis of lactotransferrin binding indicates 1.5 X 10(13) sites per mg of membrane proteins with an equilibrium constant of 1.2 X 10(6) M-1. Sodium dodecyl sulfate solubilization of the brush-border proteins allows the lactotransferrin receptor to retain its binding activity. Moreover, the ligand blotting of the detergent solubilized membrane proteins on nitrocellulose sheet and after incubation with 125I-labeled lactotransferrin, has shown that the receptor is a protein of about 100 kDa. In the same experimental conditions, the rabbit microvillous membrane vesicles do not specifically bind rabbit serotransferrin indicating the absence of serotransferrin receptors at the brush border.