Cryptomelane formation from nanocrystalline vernadite precursor: a high energy X-ray scattering and transmission electron microscopy perspective on reaction mechanisms

International audienceBackground:Vernadite is a nanocrystalline and turbostratic phyllomanganate which is ubiquitous in the environ‑ment. Its layers are built of (MnO6)8− octahedra connected through their edges and frequently contain vacancies and(or) isomorphic substitutions. Both create a layer charge deficit that can exceed 1 valence unit per layer octahedron and thus induces a strong chemical reactivity. In addition, vernadite has a high affinity for many trace elements (e.g., Co, Ni, and Zn) and possesses a redox potential that allows for the oxidation of redox sensitive elements (e.g., As, Cr, Tl). As a result, vernadite acts as a sink for many trace metal elements. In the environment, vernadite is often found associated with tectomanganates (e.g., todorokite and cryptomelane) of which it is thought to be the precursor. The transformation mechanism is not yet fully understood however and the fate of metals initially contained in vernadite structure during this transformation is still debated. In the present work, the transformation of synthetic vernadite (δ‑MnO2) to synthetic cryptomelane under conditions analogous to those prevailing in soils (dry state, room tempera‑ture and ambient pressure, in the dark) and over a time scale of ~10years was monitored using high‑energy X‑ray scattering (with both Bragg‑rod and pair distribution function formalisms) and transmission electron microscopy

Solubilisation, purification et reconstitution de la H"+-ATPase du plasmalemme de racine de maies (Zea mays L.)

CNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

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Membrane phospholipid composition of hemocytes in the Pacific oyster Crassostrea gigas and the Manila clam Ruditapes philippinarum

International audienceThe detailed sterol (free sterol proportions and compositions) and phospholipid (PL) compositions (relative proportions of PL classes and subclasses and their respective fatty acid (FA) compositions) of hemocyte membranes were investigated in two bivalve mollusks: the Pacific oyster Crassostrea gigas and the Manila clam Ruditapes philippinarum. Hemocyte membrane lipids of both species revealed similar general composition: i) their free sterol/PL ratio was above 0.4 and ii) their PL were predominated by the diacyl + alkyl forms of glycerophosphatidylcholine (PC), the plasmalogen form of glycerophosphatidylethanolamine (PE) and ceramide aminoethylphosphonate (CAEP). Free sterols were predominated by cholesterol in both species. Plasmalogen forms of PE and glycerophosphatidylserine (PS) represented 82-83% and 46-55% of total PE and PS, respectively. When compared to their respective diacyl + alkyl forms, plasmalogen forms of PE and PS were specifically enriched in non-methylene-interrupted (NMI) FA and 20:1n-11, suggesting a functional significance of these PL molecular species in bivalve hemocytes. Lysoglycerophosphatidylcholine (LysoPC) levels were found to be fairly high in hemocytes, accounting for about 8% of the PL Some species-specific features were also found. LysoPC and glycerophosphatidylinositol (PI) FA compositions differed between Ruditapes philippinarum and Crassostrea gigas. CAEP proportion was higher in R. philippinarum than in C. gigas (14.5% and 27.9% of the PL respectively). Hemolymph cell monolayer observations and flow-cytometric analyses revealed species-specific hemocyte morphology and sub-populations which could account for some of the observed species-specific membrane lipid compositions

Altered membrane lipid composition and functional parameters of circulating cells in cockles (Cerastoderma edule) affected by disseminated neoplasia

International audienceMembrane lipid composition and morpho-functional parameters were investigated in circulating cells of the edible cockle (Cerastoderma edule) affected by disseminated neoplasia (neoplastic cells) and compared to those from healthy cockles (hemocytes). Membrane sterol levels, phospholipid (PL) class and subclass proportions and their respective fatty acid (FA) compositions were determined. Morpho-functional parameters were evaluated through total hemocyte count (THC), mortality rate, phagocytosis ability and reactive oxygen species (ROS) production. Both morpho-functional parameters and lipid composition were profoundly affected in neoplastic cells. These dedifferentiated cells displayed higher THC (5×), mortality rate (3×) and ROS production with addition of carbonyl cyanide m-chloro phenylhydrazone (1.7×) but lower phagocytosis ability (½×), than unaffected hemocytes. Total PL amounts were higher in neoplastic cells than in hemocytes (12.3 and 5.1 nmol × 10-6 cells, respectively). However, sterols and a particular subclass of PL (plasmalogens; 1-alkenyl-2-acyl PL) were present in similar amounts in both cell type membranes. This led to a two times lower proportion of these membrane lipid constituents in neoplastic cells when compared to hemocytes (20.5% vs. 42.1% of sterols in total membrane lipids and 21.7% vs. 44.2% of plasmalogens among total PL, respectively). Proportions of non-methylene interrupted FA- and 20:1n-11-plasmalogen molecular species were the most impacted in neoplastic cells when compared to hemocytes (⅓× and ¼×, respectively). These changes in response to this leukemia-like disease in bivalves highlight the specific imbalance of plasmalogens and sterols in neoplastic cells, in comparison to the greater stability of other membrane lipid components

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Disseminated Neoplasia in the Soft-Shell Clam Mya arenaria: Membrane Lipid Composition and Functional Parameters of Circulating Cells.

International audienceIn a previous study we compared lipid composition and functional parameters of circulating cells from Cerastoderma edule affected or not by disseminated neoplasia (neoplastic cells vs hemocytes) (Le Grand et al. Chem Phys Lipids 167:9-20 2013). Neoplastic cells presented morpho-functional modifications concomitant to striking membrane lipid alterations: the proportion of particular plasmalogen molecular species was drastically decreased. We wanted to test whether this pattern was representative of bivalve neoplastic cells. For the purpose, a similar study was conducted on another bivalve species affected by disseminated neoplasia, the soft-shell clam (Mya arenaria). Although total reactive oxygen species production was unaffected, M. arenaria neoplastic cells presented some functional alterations: phagocytosis activity was reduced by 33 %. However, lipid compositions were not drastically altered. Particularly, sterol and plasmalogen levels did not differ between both cell types (about 43 % of membrane lipids and 35 % of phospholipids, respectively in hemocytes and neoplastic cells). This could be related to the fact that disseminated neoplasia was not related to hemolymph cell proliferation in M. arenaria (0.9 ± 0.2 10(6)cell mL(-1), considering both healthy and neoplastic clams, n = 6). Nevertheless this study highlighted minor but specific alterations of membrane lipid composition in M. arenaria neoplastic cells. The only phospholipid subclass in which the fatty acid profile strongly differed between both cell types was serine plasmalogen (PlsSer), with neoplastic cells presenting lower specific enrichment of 20:1n-11 in PlsSer. Such specific alteration of membrane lipid composition strengthened the assumption of an implication of key plasmalogen molecular species in this leukemia-like disease in bivalves

Le système agro-alimentaire. Un découplage progressif de la production et de la consommation

International audienceUn aspect fondamental du fonctionnement d’un territoire est la manière dont ses habitants organisent l’espace pour produire ou se procurer leur subsistance alimentaire. Tout territoire est profondément structuré par l’ensemble des activités et des services par lesquels la société assure la production, la transformation, la distribution et la consommation de sa nourriture, mais aussi comment elle garantit sur le long terme la pérennité de la fertilité des sols. Tout cela définit le système agro-alimentaire dont les bases de l’analyse ont été édifiées par les traités d’économie agro-alimentaire établis autour de L. Malassis (1973 ; 1986 ; 1997a ; 1997 b ; Rastoin & Ghersi, 2010)

Analyser une transition agro-alimentaire par les flux d'azote : Aussois un cas d'étude du découplage progessif de la production et de la consommation

International audienceWe reconstructed the one-century evolution of the agri-food system of the municipality of Aussois. We considered the nitrogen and money flows. Two periods are distinguished: from 1925 to 1965, characterized by autonomous agro-pastoral systems, while the second period from 1965 to the present, is defined by specialized and intensive grazing systems with an autonomy of 67%. Nitrogen use efficiency almost no changes between the two periods. Only 10% of nitrogen inputs are fixed in the products of the first period and 11% for the second period. Productivity, or the amount of products produced by surface is multiplied by 2.5 to reach today 7.2 kg N/ha/year. Finally, there is an opening of the nitrogen cycle and an economic transition from a low cash flow closely linked to nitrogen flow, to a significant cash flows independent of nitrogen flow.Nous reconstituons l’évolution du système agro-alimentaire de la commune d’Aussois, en considérant les flux d’azote et de monnaie au cours du XXe siècle. Deux périodes sont distinguées : de 1925 à 1965, cette période est caractérisée par des systèmes agro-pastoraux vivriers et autonomes, tandis que la seconde période de 1965 à nos jours, se définit par des systèmes agro-pastoraux spécialisés et plus intensifs avec une autonomie de 67 %. L’efficacité d’utilisation de l’azote n’évolue pas : seul 10 % de l’azote des intrants est fixé dans les produits sur la première période et 11 % pour la deuxième période. La productivité, soit la quantité d’azote produit par hectare, est multipliée par 2,5 pour atteindre aujourd’hui 7,2 kg N par hectare et par an. Enfin, on montre une ouverture du cycle d’azote et le passage d’une situation de flux monétaires faibles, intimement liés aux flux d’azote, à des flux monétaires importants et indépendants des flux d’azote

Le système agro-alimentaire. Un découplage progressif de la production et de la consommation

International audienceUn aspect fondamental du fonctionnement d’un territoire est la manière dont ses habitants organisent l’espace pour produire ou se procurer leur subsistance alimentaire. Tout territoire est profondément structuré par l’ensemble des activités et des services par lesquels la société assure la production, la transformation, la distribution et la consommation de sa nourriture, mais aussi comment elle garantit sur le long terme la pérennité de la fertilité des sols. Tout cela définit le système agro-alimentaire dont les bases de l’analyse ont été édifiées par les traités d’économie agro-alimentaire établis autour de L. Malassis (1973 ; 1986 ; 1997a ; 1997 b ; Rastoin & Ghersi, 2010)