Éditeur(s) : HAL CCSD Royal Society of Chemistry
Résumé : International audience
Abstract View references (60)Here we show the long term performance at high temperatures of a multi-tube module containing 8 membranes in 4 parallel lines with a total of 545 cm 2 area. The membranes were prepared via thin film dip coating of cobalt oxide silica (CoO xSi) sol-gel on tubular alumina supports. A preliminary study found that the sol-gel containing 20 mol% cobalt oxide formed the best microporous structure with the highest surface area and pore volume. All resulting membranes delivered permeances of ∼1 × 10 -7 mol m -2 s -1 Pa -1 at 500 °C, indicating a high repeatability for the membrane fabrication process. The permselectivities of helium (He) and hydrogen (H 2) over carbon dioxide (CO 2) and nitrogen (N 2) increased from 10-20 at 100 °C to values close to 1000 at 500 °C. Additionally, the apparent energies of activation (E act) for the smaller kinetic diameter gases He and H 2 at 12.2 and 19.5 kJ mol -1 were high and contrary to the negative values for larger gases N 2 and CO 2 at -1.8 and -7.4 kJ mol -1. These remarkable results were attributed to the molecular sieving mechanism of the microporous silica which was enhanced by the embedding of cobalt oxide into the matrix, delivering structural control with an average pore size of 3 Å. The E act for H 2 permeance was higher than that of He, indicating that the cobalt oxide played an important role in H 2 transport. Two membrane lines performed exceptionally well for binary gas mixture processing with H 2 purity reaching values close to 100% in the permeate stream for argon (Ar) concentrations of up to 80% in the retentate stream. A major finding here is that the binary gas selectivity was independent of temperature, contrary to the permselectivity observed for single gas permeance. Further, the H 2 flow rate was greatly affected by the concentration of Ar in the mixture, while the temperature dependency played only a marginal role. In particular, competitive adsorption in the percolative pathways containing pore constrictions or bottlenecks of the anisotropic CoO xSi matrix allowed Ar to impede H 2 diffusion. Finally, the CoO xSi membranes proved thermally stable and robust for 2000 h of testing for various thermal cycles up to 500 °C. © The Royal Society of Chemistry 2012.
Energy & Environmental Science

hal-01683199
https://hal.univ-antilles.fr/hal-01683199
DOI : 10.1039/c2ee03247c

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Benzo[a]pyrene (B[a]P), the prototype molecule of polycyclic aromatic hydrocarbons, exhibits genotoxic and carcinogenic effects, which has led the International Agency for Research on Cancer to recognize it as a human carcinogen. Besides the well-known apoptotic signals triggered by B[a]P, survival signals have also been suggested to occur, both signals likely involved in cancer promotion. Our previous work showed that B[a]P induced an hyperpolarization of mitochondrial membrane potential (ΔΨm) in rat hepatic epithelial F258 cells. Elevated ΔΨm plays a role in tumor development and progression, and nitric oxide (NO) has been suggested to be responsible for increases in ΔΨm. The present study therefore aimed at evaluating the impact of B[a]P on NO level in F258 cells, and at testing the putative role for NO as a survival signal, notably in link with ΔΨm. Our data demonstrated that B[a]P exposure resulted in an NO production which was dependent upon the activation of the inducible NO synthase. This enzyme activation involved AhR and possibly p53 activation. Preventing NO production not only increased B[a]P-induced cell death but also blocked mitochondrial hyperpolarization. This therefore points to a role for NO as a survival signal upon B[a]P exposure, possibly targeting ΔΨm
ISSN: 0887-2333

hal-01163757
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01163757
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01163757/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01163757/file/Benzo%5Ba%5Dpyrene-induced%20nitric.pdf
DOI : 10.1016/j.tiv.2015.06.010

Éditeur(s) : HAL CCSD IOS Press
Résumé : International audience
Sickle cell anemia (SCA) is an inherited red blood cells (RBC) disorder characterized by significantly decreased RBC deformability. The present study aimed to assess whether modulation of RBC Nitric Oxide Synthase (RBC-NOS) activation could affect RBC deformability in SCA.Blood of twenty-five SCA patients was treated for 1 hour at 37°C with Phosphate Buffered Saline (PBS) or PBS containing 1% of Dimethylsulfoxyde as control, L-arginine or N(5)-(1-Iminoethyl)-L-ornithine (L-NIO) to directly stimulate or inhibit RBC-NOS, insulin or wortmannin to indirectly stimulate or inhibit RBC-NOS through their effects on the PI3 Kinase/Akt pathway, and sodium nitroprusside (SNP) and 2-(4-Carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) as NO donor and NO scavenger, respectively. RBC deformability was measured by ektacytometry at 3 Pa.RBC deformability significantly increased after insulin treatment and significantly decreased after L-NIO and wortmannin incubation. The other conditions did not affect deformability. Significantly increased nitrotyrosine levels, a marker of enhanced free radical generation, were detected by immunohistochemistry in SNP and insulin treated samples.These data suggest that RBC deformability of SCA can be modulated by RBC-NOS activity but also that oxidative stress may impair effectiveness of RBC-NOS produced NO.
ISSN: 1386-0291

hal-01669738
https://hal.univ-antilles.fr/hal-01669738
DOI : 10.3233/CH-162042

Éditeur(s) : HAL CCSD Elsevier
Résumé : Eperua falcata (Aublet), a late-successional species in tropical rainforest and one of the most abundant tree in French Guiana, has developed an original strategy concerning N-acquisition by largely preferring nitrate, rather than ammonium (H. Schimann, S. Ponton, S. Hattenschwiler, B. Ferry, R. Lensi, A.M. Domenach, J.C. Roggy, Differing nitrogen use strategies of two tropical rainforest tree species in French Guiana: evidence from N-15 natural abundance and microbial activities, Soil Biol, Biochem. 40 (2008) 487-494). Given the preference of this species for nitrate, we hypothesized that root exudates would promote nitrate availability by (a) enhancing nitrate production by stimulating ammonium oxidation or (b) minimizing nitrate losses by inhibiting denitrification. Root exudates were collected in situ in monospecific planted plots. The phytochemical analysis of these exudates and of several of their corresponding root extracts was achieved using UHPLC/DAD/ESI-QTOF and allowed the identification of diverse secondary metabolites belonging to the flavonoid family. Our results show that (i) the distinct exudation patterns observed are related to distinct root morphologies, and this was associated with a shift in the root flavonoid content, (ii) a root extract representative of the diverse compounds detected in roots showed a significant and selective metabolic inhibition of isolated denitrifiers in vitro, and (iii) in soil plots the abundance of nirK-type denitrifiers was negatively affected in rhizosphere soil compared to bulk. Altogether this led us to formulate hypothesis concerning the ecological role of the identified compounds in relation to N-acquisition strategy of this species. (C) 2013 Elsevier Masson SAS. All rights reserved.
ISSN: 0981-9428

hal-01032437
https://hal.archives-ouvertes.fr/hal-01032437
DOI : 10.1016/j.plaphy.2013.05.003

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Oxidative stress and haemolysis-associated nitric oxide (NO) depletion plays a crucial role in the development of vasculopathy in sickle cell anaemia (SS). However it remains unknown whether oxidative stress and haemolysis levels influence vascular function in patients with sickle haemoglobin C disease (SC). Microvascular response to heat (using Laser Doppler flowmetry on finger), oxidative stress biomarkers, NO metabolites, endothelin-1 and haematological parameters were compared between patients with SS and SC. Vascular function, oxidative and nitrosative markers were also measured in healthy (AA) children. SS and SC had increased plasma advanced oxidation protein products (AOPP), malondialdehyde, plasma antioxidant activities and NO end products, compared to AA. SC had lower catalase activity compared to AA and SS. Haemolytic rate, glutathione peroxidase and nitrotyrosine concentrations were significantly increased in children with SS compared to SC and AA. SS and SC had impaired microvascular reactivity compared to AA. In SS, the plateau phase of the response to local thermal heating was negatively associated with nitrotyrosine and AOPP. No association between vascular function parameters and oxidative stress markers was observed in SC. Mild haemolysis in SC, compared to SS, may limit oxidative and nitrosative stress and could explain the better preserved microvascular function in this group.
ISSN: 0007-1048

hal-01668314
https://hal.univ-antilles.fr/hal-01668314
DOI : 10.1111/bjh.14693

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
The shallow water bivalve Codakia orbicularis lives in symbiotic association with a sulfur-oxidizing bacterium in its gills. The endosymbiont fixes CO2 and thus generates organic carbon compounds, which support the host's growth. To investigate the uncultured symbiont's metabolism and symbiont-host interactions in detail we conducted a proteogenomic analysis of purified bacteria. Unexpectedly, our results reveal a hitherto completely unrecognized feature of the C. orbicularis symbiont's physiology: the symbiont's genome encodes all proteins necessary for biological nitrogen fixation (diazotrophy). Expression of the respective genes under standard ambient conditions was confirmed by proteomics. Nitrogenase activity in the symbiont was also verified by enzyme activity assays. Phylogenetic analysis of the bacterial nitrogenase reductase NifH revealed the symbiont's close relationship to free-living nitrogen-fixing Proteobacteria from the seagrass sediment. The C. orbicularis symbiont, here tentatively named `Candidatus Thiodiazotropha endolucinida', may thus not only sustain the bivalve's carbon demands. C. orbicularis may also benefit from a steady supply of fixed nitrogen from its symbiont-a scenario that is unprecedented in comparable chemoautotrophic symbioses.
ISSN: 2058-5276

hal-01545904
https://hal.archives-ouvertes.fr/hal-01545904
DOI : 10.1038/nmicrobiol.2016.193

Éditeur(s) : HAL CCSD
Résumé : International audience
In this work, a series of zinc partially substituted magnetite nanoparticles (Fe3-xZnxO4, 0 ≤ x ≤ 0.4), were synthesised through a facile precipitation-oxidation method. The partial substitution of zinc into the magnetite (Fe3O4) structure was confirmed by the collective findings of nitrogen sorption, XRD and TG-DTG analysis. It was found that the partial substitution of zinc slightly changed the textural properties of the resultant Fe3-xZnxO4 nanoparticles. From the XRD analysis, there was no visible formation of secondary phase or impurity peaks in the nanoparticles. These findings indicated the partial substitution of zinc into the Fe3O4 crystal structure with a good dispersion within the Fe3O4 matrix. © 2016 Author(s).
1st International Conference on Advanced Science,
Penang, Malaysia

hal-01683217
https://hal.univ-antilles.fr/hal-01683217

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : In French Guiana, the population growth will result in an increase in demand for agricultural products and thus, will lead to an increase in the amount of tropical forests converted into cropland or pasture. Impacts of different agricultural systems on greenhouse gas (GHG) fluxes have not been studied in French Guiana. In this context, the fire-free chop-and-mulch method was used to convert a tropical forest site to agriculture. This study focused on soil nitrous oxide (N2O) emissions and we compared four land uses: (1) the undisturbed tropical forest, (2) recently converted grassland and recently converted croplands (fertilized soybean/maize rotation) with either (3) disk tillage or (4) no tillage.N2O measurements were obtained through the chamber technique and conducted over a 1-year period (measurements began 19 months after the forest was cleared). N2O fluxes were related to soil parameters measured at each sampling date: nitrate and ammonium contents, gravimetric water content (GWC) and temperature.Through the entire period, the mean (±standard error) and median N2O fluxes were 3.8 ± 0.5 and 2.7 g N ha−1 day−1, respectively for undisturbed tropical forest and 2.4 ± 0.9 and 0.8 g N ha−1 day−1, respectively for grassland (mowed Brachiaria ruziziensis). For croplands, no significant difference was found for N2O emissions between both agricultural practices. The mean (±standard error) and median N2O fluxes were 8.5 ± 1.2 and 4.0 g N ha−1 day−1, respectively for disk tillage plots and 8.5 ± 1.3 and 3.6 g N ha−1 day−1, respectively for no tillage plots. Nitrogen inputs (due to the application of fertilizer or due to the mineralization of crop residues) led to higher N2O fluxes, resulting in significantly higher mean N2O emissions from croplands compared to the forest, when only considering land use effect on N2O fluxes in a statistical model. The soil nitrate content, GWC and temperature had a significant positive effect on N2O fluxes. Taking into account these soil parameters in another statistical model, N2O emissions from croplands were not higher than the natural N2O emissions from tropical forest soils. Our results suggest that, if more forest will have to be converted in the course of the expected population growth in French Guiana, it could have low impact on the soil N2O fluxes (similar to natural fluxes from forest) with the improving of farming techniques (for example modification of the splitting of N-fertilizer) in the cropping plots.
ISSN: 0167-8809

hal-01204228
https://hal.archives-ouvertes.fr/hal-01204228
DOI : 10.1016/j.agee.2015.04.004
PRODINRA : 307607

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
PurposeMarine mangrove sediments in the Manche-à-Eau lagoon (Guadeloupe, Caribbean Sea) harbor locally extensive, white microbial mats. These mats cover the surface of reduced sediments near the roots of red mangrove trees, Rhizophora mangle, and are mainly composed of sulfur-oxidizing bacteria belonging to the Beggiatoaceae family, with some filamentous cyanobacteria. The goal of this study was to investigate the possible influence of sediment characteristics on the presence of these microbial mats.Materials and methodsFour push cores were collected in April 2013, two from zones with microbial mats and two from zones without mats. Sediment characteristics (grain-size distribution, mineralogy, total organic carbon (TOC) and total nitrogen (TN) contents, atomic TOC/TN ratios, and organic matter (OM) δ13C values) were compared for all four cores.Results and discussionSignificant differences were observed between sediments below microbial mats and those without mats. Sediments with microbial mats contained greater amounts of clay, and higher TOC, TN, and TOC/TN ratios, with lower total carbonate content and δ13C values. The higher clay content most likely results from lower fluid flow velocity near to mangrove roots, while higher TOC/TN ratios and lower δ13C values indicate higher inputs of OM from mangrove trees. These results are consistent with the fact that microbial mats were observed near the roots of mangrove trees, which trap OM from terrestrial vegetation and fine sediments.ConclusionsThe grain-size distribution of sediment particles, the total carbonate content, and the δ13C values are the main parameters discriminating between zones with microbial mats and those without mats. Variations in total carbonate content, which is mainly of biogenic origin, result from conditions that are more favorable for benthic organisms in zones without microbial mats. Variations of the TOC/TN ratios are controlled by the presence of a non-negligible amount of inorganic nitrogen bound to surface clay mineral particles and/or by microbial processes.
ISSN: 1439-0108

hal-01545903
https://hal.archives-ouvertes.fr/hal-01545903
DOI : 10.1007/s11368-016-1555-6

Éditeur(s) : HAL CCSD IOS Press
Résumé : International audience
Vascular function has been found to be impaired in patients with sickle cell disease (SCD). The present study investigated the determinants of systemic vascular resistance in two main SCD syndromes in children: sickle cell anemia (SCA) and sickle cell-hemoglobin C disease (SCC). Nitric oxide metabolites (NOx), hematological, hemorheological, and hemodynamical parameters were investigated in 61 children with SCA and 49 children with SCC. While mean arterial pressure was not different between SCA and SCC children, systemic vascular resistance (SVR) was greater in SCC children. Although SVR and blood viscosity (ηb) were not correlated in SCC children, the increase of ηb (+18%) in SCC children compared to SCA children results in a greater mean SVR in this former group. SVR was positively correlated with ηb, hemoglobin (Hb) level and RBC deformability, and negatively with NOx level in SCA children. Multivariate linear regression model showed that both NOx and Hb levels were independently associated with SVR in SCA children. In SCC children, only NOx level was associated with SVR. In conclusion, vascular function of SCC children seems to better cope with higher ηb compared to SCA children. Since the occurrence of vaso-occlusive like complications are less frequent in SCC than in SCA children, this finding suggests a pathophysiological link between the vascular function alteration and these clinical manifestations. In addition, our results suggested that nitric oxide metabolism plays a key role in the regulation of SVR, both in SCA and SCC.
ISSN: 1386-0291

inserm-00849031
http://www.hal.inserm.fr/inserm-00849031
http://www.hal.inserm.fr/inserm-00849031/document
http://www.hal.inserm.fr/inserm-00849031/file/2013_Lamarre_-_Relationships_between_SVR_BR_and_NO_in_children_with_sickle_cell_anemia_or_sickle_cell-hemoglobin_C_disease.pdf
DOI : 10.3233/CH-121661

Éditeur(s) : HAL CCSD American Society for Microbiology
Résumé : International audience
Under physiological conditions, the liver sinusoidal endothelial cells (LSECs) mediate hepatic immune tolerance toward self or foreign antigens through constitutive expression of anti-inflammatory mediators. However, upon viral infection or Toll-like receptor 2 (TLR2) activation, LSECs can achieve proinflammatory functions, but their role in hepatic inflammation during acute viral hepatitis is unknown. Using the highly virulent mouse hepatitis virus type 3 (MHV3) and the attenuated variants 51.6-MHV3 and YAC-MHV3, exhibiting lower tropism for LSECs, we investigated in vivo and in vitro the consequence of LSEC infection on their proinflammatory profiles and the aggravation of acute hepatitis process. In vivo infection with virulent MHV3, in comparison to attenuated strains, resulted in fulminant hepatitis associated with higher hepatic viral load, tissue necrosis, and levels of inflammatory mediators and earlier recruitment of inflammatory cells. Such hepatic inflammatory disorders correlated with disturbed production of interleukin-10 (IL-10) and vascular factors by LSECs. We next showed in vitro that infection of LSECs by the virulent MHV3 strain altered their production of anti-inflammatory cytokines and promoted higher release of proinflammatory and procoagulant factors and earlier cell damage than infection by attenuated strains. This higher replication and proinflammatory activation in LSECs by the virulent MHV3 strain was associated with a specific activation of TLR2 signaling by the virus. We provide evidence that TLR2 activation of LSCEs by MHV3 is an aggravating factor of hepatic inflammation and correlates with the severity of hepatitis. Taken together, these results indicate that preservation of the immunotolerant properties of LSECs during acute viral hepatitis is imperative in order to limit hepatic inflammation and damage. IMPORTANCE Viral hepatitis B and C infections are serious health problems affecting over 350 million and 170 million people worldwide, respectively. It has been suggested that a balance between protection and liver damage mediated by the host's immune response during the acute phase of infection would be determinant in hepatitis outcome. Thus, it appears crucial to identify the factors that predispose in exacerbating liver inflammation to limit hepatocyte injury. Liver sinusoidal endothelial cells (LSECs) can express both anti- and proinflammatory functions, but their role in acute viral hepatitis has never been investigated. Using mouse hepatitis virus (MHV) infections as animal models of viral hepatitis, we report for the first time that in vitro and in vivo infection of LSECs by the pathogenic MHV3 serotype leads to a reversion of their intrinsic anti-inflammatory phenotype toward a proinflammatory profile as well to as disorders in vascular factors, correlating with the severity of hepatitis. These results highlight a new virus-promoted mechanism of exacerbation of liver inflammatory response during acute hepatitis.
ISSN: 0022-538X

hal-01390974
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01390974
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01390974/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01390974/file/Mouse%20Hepatitis%20Virus%20Infection_accepted.pdf
DOI : 10.1128/JVI.01069-16

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The chemical investigations of Dicorynia guianensis heartwood led to the isolation of four new indole alkaloids for the first time in this plant. Compound (1) identified as spiroindolone 20,30,40,90-tetrahydrospiro [indoline-3,10pyrido[3,4-b]-indol]-2-one, and compound (3) described as nitrone 1-methyl-4,9-dihydro-3H-pyrido [3,4-b] indole 2-oxide and were isolated for the first time as natural products. ABTS antioxidant activity guided their isolation.
ISSN: 1874-3900

hal-01138910
https://hal.archives-ouvertes.fr/hal-01138910
DOI : 10.1016/j.phytol.2015.03

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Nitro-polycyclic aromatic hydrocarbons (nitro-PAHs) are widespread environmental pollutants, generated from reactions between PAHs and nitrogen oxides during combustion processes. In the present study we have investigated the mechanisms of CXCL8 (IL-8) responses induced by 1-nitropyrene (1-NP) in human bronchial epithelial BEAS-2B cells, with focus on the possible importance of Ca(2+)-signaling and activation of β2-adrenergic receptors (β2AR). Ca(2+)-chelator treatment obliterated 1-NP-induced CXCL8 (IL-8) responses. 1-NP at 10μM (but not 1μM) induced a rapid and sustained increase in intracellular Ca(2+)-levels ([Ca(2+)]i). The early but not the later, sustained phase of 1-NP-induced [Ca(2+)]i was suppressed by beta-blocker treatment (carazolol). Moreover, inhibition of β2AR by blocking-antibody, beta-blocker treatment (ICI 118551) or siRNA transfection attenuated CXCL8 responses induced by 1-NP. The results confirm that PAHs may induce Ca(2+)-signaling also in BEAS-2B cells, at least partly through activation of β2AR, and suggest that both β2AR- and Ca(2+)-signaling may be involved in 1-NP-induced CXCL8 responses in bronchial epithelial cells.
ISSN: 0887-2333

hal-01058607
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01058607
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01058607/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01058607/file/Calcium_Signaling_and_I_2-Adrenergic_Receptors-final.pdf
DOI : 10.1016/j.tiv.2014.05.012

Résumé : Cette these etudie les effets de la conversion de la foret tropicale en parcelles agricoles, sur les emissions de n2o par les sols. Ce travail est realise a l’echelle du cycle cultural sur le dispositif experimental de combi (littoral guyanais), a l’aide de mesures in situ et de simulations (modele noe) des flux de n2o. La foret tropicale a ete comparee a des parcelles de foret converties en terres agricoles par la methode ‘chop-and-mulch’. La methode de deforestation ‘chop-and-mulch’ associe coupe mecanique de la vegetation, broyage puis enfouissement des residus forestiers dans le sol. Les terres agricoles etaient soient des parcelles de prairie non paturee soient des parcelles cultivees (maïs fertilise/soja) conduites en semis conventionnel (semis apres travail du sol, sans plante de couverture) ou en semis direct (sans travail du sol, avec plantes de couverture).Les principaux resultats de cette etude sont : le sol de la foret tropicale de combi est un faible emetteur de n2o ; la conversion par la methode ‘chop-and-mulch’ de cette foret en prairie ne conduit pas a une augmentation significative des emissions de n2o entre le 19eme et le 31eme mois suivant la conversion ; la conversion de la foret en parcelles cultivees induit une augmentation significative des emissions de n2o due a la fertilisation et a la modification des parametres edaphiques (densite apparente, temperature, humidite volumique) ; la technique sans travail du sol n’engendre pas de flux de n2o significativement plus eleves que la technique avec travail du sol ; l’introduction du phenomene d’hysterese hydrique dans le modele noe presente un reel potentiel pour l’estimation des emissions de n2o in situ.
This study investigates the effects of the conversion of tropical forest to cultivation on soil n2o emissions. The study was carried out over a complete crop cycle at the experimental site combi (french guianese coast). Nitrous oxide fluxes were obtained in the field and by conducting simulations with the noe model. Undisturbed tropical rainforest was compared to rainforest that had been converted to agricultural land using the ‘chop-and-mulch’ method. The ‘chop-and-mulch’ method is a fire-free method used for vegetation clearing combining the mechanical felling of trees with the mulching of small vegetation. Agricultural land included either mowed grassland or soybean/fertilised maize crop rotation. For croplands the two cultivation practices employed were: conventional seeding (using an offset disc harrow, without cover plants) or direct seeding (no till, with cover plants).The main results of this study are: rainforest soil at combi produced low n2o emissions; rainforest converted to mowed grassland using the 'chop-and-mulch’ method did not lead to a significant increase in n2o emissions between the 19th and 31st months after conversion; the conversion of rainforest to croplands induced a significant increase in soil n2o emissions due to the application of fertiliser and the modification of soil parameters (bulk density, temperature, volumetric moisture); n2o emissions from agricultural practices with no-till were no higher than those produced by conventional agricultural practices using an offset disc harrow; and, the introduction of an hydric hysteresis into the noe model constitutes a promising improvement to estimate in situ n2o emissions.

http://www.theses.fr/2013AGUY0610/document

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
In this work, we have studied quenching of the fluorescence of two well-known oxygen probes, 1-pyrene butyric acid (PBA) and tris(2,2'-bipyridine)ruthenium ([Ru(bpy)(3)](2+)) by reactive oxygen species (superoxide anion, nitric oxide derivative, hydrogen peroxide) and by the O(2) molecule. Both, time-resolved and steady state fluorescence measurements were performed in solution (ethanol, dimethyl sufoxide, water) and in micelles of Sodium Dodecyl Sulfate that serve as a model for membrane-containing biological structures. We have found that only the free radicals and O(2) can actively quench for the two probes, but not the diamagnetic H(2)O(2). Our data correspond to the classical Stern-Volmer equation. H(2)O(2) has an effect only at high molar concentrations (>0.1 M). In contrast, effective concentrations of free radicals and O(2) that lead to quenching are in millimolar range. In conclusion, our methods allows for detecting global ROS that are small free radicals without interference from the reactive hydroxyl radical. Our data suggest that the method can be used for the quantification of ROS in individual living cells based on the measurement of fluorescence lifetime of those probes
ISSN: 1053-0509

hal-01326234
https://hal.archives-ouvertes.fr/hal-01326234
DOI : 10.1007/s10895-008-0425-z

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Activation of cell signaling by reactive chemicals and pollutants is an important issue for human health. It has been shown that lipophilic nitro-benzoxadiazole (NBD) compounds rapidly move across the plasma membrane and enhance Epidermal Growth Factor Receptor (EGFR) tyrosine phosphorylation in cancer cells. Unlike ligand-dependent activation, the mechanism of this induction relies on the generation of hydrogen peroxide, which is involved in the activation of the catalytic site of the receptor and the inactivation of protein tyrosine phosphatase PTP-1B. Production of H2O2 during redox transformation of NBD compounds is associated with the transition of a monomeric form of Cu/Zn superoxide dismutase 1 (SOD1) to stable dimers. The highly stable and functionally active SOD1 dimer, in the absence of adequate activities in downstream reactions, promotes the disproportionate production and accumulation of intracellular hydrogen peroxide shortly after exposure to NBD compounds. The intrinsic fluorescence of small compounds was used to demonstrate their binding to SOD1. Our data indicate that H2O2 and concomitantly generated electrophilic intermediates behave as independent entities, but all contribute to the biological reactivity of NBD compounds. This study opens a promising path to identify new biomarkers of oxidative/electrophilic stress in the progression of cancer and other diseases
ISSN: 2045-2322

hal-01279094
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01279094
DOI : 10.1038/srep21088
PUBMED : 26883293

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Cyanobacteria are ubiquitous microorganisms considered as important contributors to the formation of Earth's atmosphere and nitrogen fixation. However, they are also frequently associated with toxic blooms. Indeed, the wide range of hepatotoxins, neurotoxins and dermatotoxins synthesized by these bacteria is a growing environmental and public health concern. This paper provides a state of the art on the occurrence and management of harmful cyanobacterial blooms in surface and drinking water, including economic impacts and research needs. Cyanobacterial blooms usually occur according to a combination of environmental factors e.g., nutrient concentration, water temperature, light intensity, salinity, water movement, stagnation and residence time, as well as several other variables. These environmental variables, in turn, have promoted the evolution and biosynthesis of strain-specific, gene-controlled metabolites (cyanotoxins) that are often harmful to aquatic and terrestrial life, including humans. Cyanotoxins are primarily produced intracellularly during the exponential growth phase. Release of toxins into water can occur during cell death or senescence but can also be due to evolutionary-derived or environmentally-mediated circumstances such as allelopathy or relatively sudden nutrient limitation. Consequently, when cyanobacterial blooms occur in drinking water resources, treatment has to remove both cyanobacteria (avoiding cell lysis and subsequent toxin release) and aqueous cyanotoxins previously released. Cells are usually removed with limited lysis by physical processes such as clarification or membrane filtration. However, aqueous toxins are usually removed by both physical retention, through adsorption on activated carbon or reverse osmosis, and chemical oxidation, through ozonation or chlorination. While the efficient oxidation of the more common cyanotoxins (microcystin, cylindrospermopsin, anatoxin and saxitoxin) has been extensively reported, the chemical and toxicological characterization of their by-products requires further investigation. In addition, future research should also investigate the removal of poorly considered cyanotoxins (β-methylamino-alanine, lyngbyatoxin or aplysiatoxin) as well as the economic impact of blooms.
Environment International

hal-00875835
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00875835
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00875835/document
DOI : 10.1016/j.envint.2013.06.013
PUBMED : 23892224

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Purpose: Marine mangrove sediments in the Manche-à-Eau lagoon (Guadeloupe, Caribbean Sea) harbor locally extensive, white microbial mats. These mats cover the surface of reduced sediments near the roots of red mangrove trees, Rhizophora mangle, and are mainly composed of sulfur-oxidizing bacteria belonging to the Beggiatoaceae family, with some filamentous cyanobacteria. The goal of this study was to investigatethe possible influence of sediment characteristics on the presence of these microbial mats. Materials and methods: Four push cores were collected in April 2013, two from zones with microbial mats and two from zones without mats. Sediment characteristics (grain-size distribution, mineralogy, total organic carbon (TOC) and total nitrogen (TN) contents, atomic TOC/TN ratios, and organic matter (OM) δ13C values) were compared for all four cores.Results and discussion: Significant differences were observed between sediments below microbial mats and those without mats. Sediments with microbial mats contained greater amounts of clay, and higher TOC, TN, and TOC/TN ratios, with lower total carbonate content andδ13C values. The higher clay content most likely results from lower fluid flow velocity near to mangrove roots, while higher TOC/TN ratiosand lower δ13C values indicate higher inputs of OM from mangrove trees. These results are consistent with the fact that microbial mats were observed near the roots of mangrove trees, which trap OM from terrestrial vegetation and fine sediments.Conclusions: The grain-size distribution of sediment particles, the total carbonate content, and the δ13C values are the main parameters discriminating between zones with microbial mats and those without mats. Variations in total carbonate content, which is mainly of biogenic origin, result from conditions that are more favorable for benthic organisms in zones without microbial mats. Variations of the TOC/TN ratios are controlled by the presence of a non-negligible amount of inorganic nitrogen bound to surface clay mineral particles and/or by microbial processes.
ISSN: 1439-0108

hal-01682110
https://hal.univ-antilles.fr/hal-01682110
DOI : 10.1007/s11368-016-1555-6

Éditeur(s) : HAL CCSD
Résumé : International audience
Traffic air pollution is a major health problem and is recognized as an important risk factor for cardiovascular disease. Even so the role of particles-induced adverse health effects is well established, recent studies outlined the contribution of nitrogen dioxide (NO2) in these effects, in particular on the cardiovascular function. The main sources of this pollutant are oxidation catalysts used to reduce emissions of carbon monoxide and non-methane hydrocarbons from the exhaust of diesel engines and also to facilitate filter regeneration. However, the contribution of NO2 compared to other gaseous and particulate pollutants remains unknown. Consequently, the main objective of this study was to analyze the specific contributions of NO2 in the traffic-related air pollution-induced cardiovascular adverse effects. For this, Wistar rats were exposed for 3 weeks (3h/day, 5 days/week) to either a continuous flow of catalyzed diesel exhaust (DE), particle free or whole DE (particles concentration 2mg/m3), either to a continuous flow of NO2 used at a concentration identical to that measured in the exhaust line. The composition of the emission and the NO2 analyses were monitored on-line during the whole experiment. We evaluated cardiac function and biological effects after 16h recovery in clean air. DE or NO2 exposures induced a modest cardiac dysfunction characterized by an increase in left ventricular diameters and a decrease in fractional shortening. In the case of DE, the presence of particles did not worsen the impairment of cardiac function. In parallel to this effect, mitochondrial function was altered as illustrated by the reduction of the oxygen consumption and of the ATP production. Mitochondrial reactive oxygen species was increased only by the NO2 exposure. In conclusion, these results suggest that DE-induced cardiac dysfunction is due to, at least in part, to NO2 present in DE.
Archives of Cardiovascular Diseases Supplements
Toulouse, France

hal-01150495
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01150495
DOI : 10.1016/S1878-6480(15)30036-7

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
This study, conducted in the brain of a perciform fish, the European sea bass, aimed at raising antibodies against the precursor of the kisspeptins in order to map the kiss systems and to correlate the expression of kisspeptins, kiss1 and kiss2, with that of kisspeptin receptors (kiss-R1 and kiss-R2). Specific antibodies could be raised against the preprokiss2, but not the preoprokiss1. The data indicate that kiss2 neurons are mainly located in the hypothalamus and project widely to the subpallium and pallium, the preoptic region, the thalamus, the pretectal area, the optic tectum, the torus semicircularis, the mediobasal medial and caudal hypothalamus, and the neurohypophysis. These results were compared to the expression of kiss-R1 and kiss-R2 messengers, indicating a very good correlation between the wide distribution of Kiss2-positive fibers and that of kiss-R2 expressing cells. The expression of kiss-R1 messengers was more limited to the habenula, the ventral telencephalon and the proximal pars distalis of the pituitary. Attempts to characterize the phenotype of the numerous cells expressing kiss-R2 showed that neurons expressing tyrosine hydroxylase, neuropeptide Y and neuronal nitric oxide synthase are targets for kisspeptins, while GnRH1 neurons did not appear to express kiss-R1 or kiss-R2 messengers. In addition, a striking result was that all somatostatin-positive neurons expressed-kissR2. These data show that kisspeptins are likely to regulate a wide range of neuronal systems in the brain of teleosts.
ISSN: 1932-6203

hal-00877315
https://hal.archives-ouvertes.fr/hal-00877315
https://hal.archives-ouvertes.fr/hal-00877315/document
https://hal.archives-ouvertes.fr/hal-00877315/file/Expressionsur Kisspeptins-accepted.pdf
DOI : 10.1371/journal.pone.0070177