Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Adult fish exhibit a strong neurogenic capacity due to the persistence of radial glial progenitor cells. In zebrafish, radial glial cells display well-established markers such as the estrogen-synthesizing enzyme (AroB) and the brain lipid binding protein (Blbp), which is known to strongly bind omega-3 polyunsaturated fatty acids such as docosahexaenoic acid (DHA). While Blpb is mainly described in the telencephalon of adult zebrafish, its expression in the remaining regions of the brain is poorly documented. The present study was designed to further investigate Blbp expression in the brain, its co-expression with AroB, and its link with radial glial cells proliferation in zebrafish. We generated a complete and detailed mapping of Blbp expression in the whole brain and show its complete co-expression with AroB, except in some tectal and hypothalamic regions. By performing PCNA and Blbp immunohistochemistry on cyp19a1b-GFP (AroB-GFP) fish, we also demonstrated preferential Blbp expression in proliferative radial glial cells in almost all regions studied. To our knowledge, this is the first complete and detailed mapping of Blbp-expressing cells showing strong association between Blbp and radial glial cell proliferation in the adult brain of fish. Given that zebrafish is now recognized models for studying neurogenesis and brain repair, our data provide detailed characterization of Blbp in the entire brain and open up a broad field of research investigating the role of omega-3 polyunsaturated fatty acids in neural stem cell activity in fish
ISSN: 1567-133X

hal-01237088
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01237088
DOI : 10.1016/j.gep.2015.11.003
PUBMED : 26611722

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
BACKGROUND: The use of pesticides and the related environmental contaminations can lead to human exposure to various molecules. In early-life, such exposures could be responsible for adverse developmental effects. However, human health risks associated with exposure to complex mixtures are currently under-explored. OBJECTIVE: THIS PROJECT AIMS AT ANSWERING THE FOLLOWING QUESTIONS: What is the influence of exposures to multiple pesticides on the metabolome? What mechanistic pathways could be involved in the metabolic changes observed? METHODS: Based on the PELAGIE cohort (Brittany, France), 83 pregnant women who provided a urine sample in early pregnancy, were classified in 3 groups according to the surface of land dedicated to agricultural cereal activities in their town of residence. Nuclear magnetic resonance-based metabolomics analyses were performed on urine samples. Partial Least Squares Regression-Discriminant Analysis (PLS-DA) and polytomous regressions were used to separate the urinary metabolic profiles from the 3 exposure groups after adjusting for potential confounders. RESULTS: The 3 groups of exposure were correctly separated with a PLS-DA model after implementing an orthogonal signal correction with pareto standardizations (R2 = 90.7% and Q2 = 0.53). After adjusting for maternal age, parity, body mass index and smoking habits, the most statistically significant changes were observed for glycine, threonine, lactate and glycerophosphocholine (upward trend), and for citrate (downward trend). CONCLUSION: This work suggests that an exposure to complex pesticide mixtures induces modifications of metabolic fingerprints. It can be hypothesized from identified discriminating metabolites that the pesticide mixtures could increase oxidative stress and disturb energy metabolism.
ISSN: 1932-6203

inserm-00863407
http://www.hal.inserm.fr/inserm-00863407
http://www.hal.inserm.fr/inserm-00863407/document
http://www.hal.inserm.fr/inserm-00863407/file/journal.pone.0064433.pdf
PUBMED : 23704985

Éditeur(s) : HAL CCSD
Résumé : International audience
(Guava (Psidium guajava L.) is a tropical fruit widely consumed around the world. The study wascarried out on four selected guava varieties grown in Martinique. Two fruit harvests were gathered at two-yearintervals, at the green/yellow color change maturity stage. First, we established the homogeneity of all fruitbatches by bootstrapping, ANOVA, box plot and multiple comparison statistical analysis on physicalparameters. Red Supreme Ruby clearly differs from the other three varieties, whereas the results for CentenoProlific are between Beauséjour and Enana Cuba. We determined on puree obtained from a homogeneousbatch of each variety the physicochemical and functional properties as well as the antioxidant properties. Ourresults show that the combination of lycopene and vitamin C, and their synergistic mechanisms in the fruitextracts may be responsible for the high antioxidant activity of guava puree, and we demonstrate a statisticallysignificant positive correlation between EC50 and lycopene.
IOSR Journal of Environmental Science, Toxicology and Food Technology (IOSR-JESTFT)

hal-01672064
https://hal.univ-antilles.fr/hal-01672064
DOI : 10.9790/2402-1109015767

Éditeur(s) : HAL CCSD
Résumé : International audience
Effective and sustainable prevention of work-related musculoskeletal disorders (WR-MSDs) remains a challenge for preventers and policy makers. Coordination of stakeholders involved in the prevention of WR-MSDs is a key factor that requires greater reflection on common knowledge and shared representation of workers’ activities among stakeholders. Information on workers’ strategies and operational leeway should be the core of common representations, since it places workers at the center of the “work situation system” considered by the intervention models. Participatory ergonomics permitting debates among stakeholders about workers’ activity and strategies to cope with the work constraints in practice could help them to share representations of the “work situation system” and cooperate. Sharing representation therefore represents a useful tool for prevention, and preventers should provide sufficient space and time for dialogue and discussion of workers’ activities among stakeholders during the conception, implementation and management of integrated prevention programs
Safety and Health at Work

hal-01279095
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01279095
DOI : 10.1016/j.shaw.2016.02.001
PUBMED : 27340607

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
BackgroundTo date, all studies conducted on breast cancer diagnosis have focused on the expression of the full-length 66-kDa estrogen receptor alpha (ERα66). However, much less attention has been paid to a shorter 46-kDa isoform (ERα46), devoid of the N-terminal region containing the transactivation function AF-1. Here, we investigated the expression levels of ERα46 in breast tumors in relation to tumor grade and size, and examined the mechanism of its generation and its specificities of coregulatory binding and its functional activities.MethodsUsing approaches combining immunohistochemistry, Western blotting, and proteomics, antibodies allowing ERα46 detection were identified and the expression levels of ERα46 were quantified in 116 ERα-positive human breast tumors. ERα46 expression upon cellular stress was studied, and coregulator bindings, transcriptional, and proliferative response were determined to both ERα isoforms.ResultsERα46 was expressed in over 70% of breast tumors at variable levels which sometimes were more abundant than ERα66, especially in differentiated, lower-grade, and smaller-sized tumors. We also found that ERα46 can be generated via internal ribosome entry site-mediated translation in the context of endoplasmic reticulum stress. The binding affinities of both unliganded and fully-activated receptors towards co-regulator peptides revealed that the respective potencies of ERα46 and ERα66 differ significantly, contributing to the differential transcriptional activity of target genes to 17β estradiol (E2). Finally, increasing amounts of ERα46 decrease the proliferation rate of MCF7 tumor cells in response to E2.ConclusionsWe found that, besides the full-length ERα66, the overlooked ERα46 isoform is also expressed in a majority of breast tumors. This finding highlights the importance of the choice of antibodies used for the diagnosis of breast cancer, which are able or not to detect the ERα46 isoform. In addition, since the function of both ERα isoforms differs, this work underlines the need to develop new technologies in order to discriminate ERα66 and ERα46 expression in breast cancer diagnosis which could have potential clinical relevance.
ISSN: 1465-5411

inserm-01412032
http://www.hal.inserm.fr/inserm-01412032
http://www.hal.inserm.fr/inserm-01412032/document
http://www.hal.inserm.fr/inserm-01412032/file/13058_2016_Article_780.pdf
DOI : 10.1186/s13058-016-0780-7

Éditeur(s) : HAL CCSD Lippincott, Williams & Wilkins
Résumé : International audience
Objectives: Lung cancer risk associated with occupational cleaning activities has been investigated in the population-based case-control study ICARE. Methods: Occupational history was collected by standardized interviews. Jobs were first defined according to the International Standard Classification of Occupations (ISCO) codes and then categorized according to activity sectors. Adjusted odds ratios (ORs) were estimated by unconditional logistic regression, separately for women (619 cases and 760 controls) and men (2265 and 2780). Results: Thirty percent of women and 2.3% of men controls ever held a cleaner or care job. Women who worked as housemaids longer than 7 years showed an OR of 1.76 [95% confidence interval (95% CI) 1.09 to 2.87] with respect to controls. Women employed in domestic service sector for a long time had an OR of 2.06 (95% CI 1.15 to 3.66). Conclusion: We confirmed and redefined the association of lung cancer with occupational cleaning, which concerns a considerable proportion of women workers.
ISSN: 1076-2752

hal-01359564
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01359564
DOI : 10.1097/JOM.0000000000000722
PUBMED : 27206119

Éditeur(s) : HAL CCSD Rockefeller University Press
Résumé : International audience
Accumulation of type I collagen fibrils in tumors is associated with an increased risk of metastasis. Invadosomes are F-actin structures able to degrade the extracellular matrix. We previously found that collagen I fibrils induced the formation of peculiar linear invadosomes in an unexpected integrin-independent manner. Here, we show that Discoidin Domain Receptor 1 (DDR1), a collagen receptor overexpressed in cancer, colocalizes with linear invadosomes in tumor cells and is required for their formation and matrix degradation ability. Unexpectedly, DDR1 kinase activity is not required for invadosome formation or activity, nor is Src tyrosine kinase. We show that the RhoGTPase Cdc42 is activated on collagen in a DDR1-dependent manner. Cdc42 and its specific guanine nucleotide-exchange factor (GEF), Tuba, localize to linear invadosomes, and both are required for linear invadosome formation. Finally, DDR1 depletion blocked cell invasion in a collagen gel. Altogether, our data uncover an important role for DDR1, acting through Tuba and Cdc42, in proteolysis-based cell invasion in a collagen-rich environment.
ISSN: 0021-9525

hal-01118481
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01118481
PUBMED : 25422375
DOI : 10.1083/jcb.201404079
PUBMEDCENTRAL : PMC4242841

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The 90-kDa heat shock protein (Hsp90) is a highly flexible dimer able to self-associate in the presence of divalent cations or under heat shock. In a previous work, we focused on the Mg2 +-induced oligomerization process of Hsp90, and characterized the oligomers. Combining analytical ultracentrifugation, size-exclusion chromatography coupled to multi-angle laser light scattering and high-mass matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, we studied the interaction of p23 with both Hsp90 dimer and oligomers. Even if p23 predominantly binds the Hsp90 dimer, we demonstrated, for the first time, that p23 is also able to interact with Hsp90 oligomers, shifting the Hsp90 dimer-oligomers equilibrium toward dimer. Our results showed that the Hsp90:p23 binding stoichiometry decreases with the Hsp90 oligomerization degree. Therefore, we propose a model in which p23 would act as a “protein wedge” regarding the Hsp90 dimer closure and the Hsp90 oligomerization process
ISSN: 1570-9639

hal-01174219
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01174219
DOI : 10.1016/j.bbapap.2015.07.003
PUBMED : 26151834

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : Active mechanisms of re-orientation are necessary to maintain the verticality of tree stems. They are achieved through the production of reaction wood, associated with circumferential variations of three factors related to cambial activity: maturation strain, longitudinal modulus of elasticity (MOE) and eccentric growth. These factors were measured on 17 mature trees from different botanical families and geographical locations. Various patterns of circumferential variation of these factors were identified. A biomechanical analysis based on beam theory was performed to quantify the individual impact of each factor. The main factor of re-orientation is the circumferential variation of maturation strains. However, this factor alone explains only 57% of the re-orientations. Other factors also have an effect through their interaction with maturation strains. Eccentric growth is generally associated with heterogeneity of maturation strains, and has an important complementary role, by increasing the width of wood with high maturation strain. Without this factor, the efficiency of re-orientations would be reduced by 31% for angiosperms and 26% for gymnosperms. In the case of angiosperms, MOE is often larger in tension wood than in normal wood. Without these variations, the efficiency of re-orientations would be reduced by 13%. In the case of gymnosperm trees, MOE of compression wood is lower than that of normal wood, so that re-orientation efficiency would be increased by 24% without this factor of variations.
ISSN: 0931-1890

hal-01031825
https://hal.archives-ouvertes.fr/hal-01031825
DOI : 10.1007/s00468-005-0407-6

Éditeur(s) : HAL CCSD
Résumé : National audience
The last study describing the epidemiology of malaria in French Guiana was published 20 years ago. Yet French Guiana in the Americas along with Mayotte in the Indian Ocean is the only French territory with persisting endemic malaria. The purpose of this study is to provide an update based on official malaria surveillance data as well as on information from hospital records and various field surveys that have been carried out in recent years. Due to recurrent problems in collecting thorough, continuous, and consistent data, exact determination of incidence by plasmodium species has always been difficult in French Guiana. These problems include not only the remote location of endemic areas and intense unpredictable migration patterns but also poor data collection methods that do not always ensure consistency and homogeneity. Another factor hindering thorough collection of conventional epidemiological data is the requirement for rapid effective treatment in remote regions. The overall incidence of malaria in French Guiana appears to have remained stable since the beginning of the decade with an average of 3,920 case reports per year for an incidence rate of 20 per thousand, noting that three fourths of the 206,000 inhabitants of French Guiana live outside of endemic areas. Overall involvement of P. falciparum and P. vivax appears to be equal with P. malariae accounting for only 2.6% of cases. Trends in recent years indicate an increase in the number of cases involving P. vivax especially in the eastern zones, i.e. in the Oyapock focus where annual incidences in children have reached up to 500 per thousand and in the whole region located between Saint Georges and Cayenne. Conversely a decrease in endemic levels has been observed in western areas, especially for P. falciparum in the upper and middle focuses of the Maroni. Most zones now causing problems are located near migration points, particularly in relation with clandestine gold panning activities. In the coastal strip where the three main cities with most of the population are located, most reported cases are imported but local cases may occur. In general local transmission in these areas has been promptly controlled but trends indicate that incidence of these events may be rising. Anopheles darlingi is still recognized as the main vector but its role in transmission is less obvious in eastern areas where increasing evidence suggests that other species may contribute to maintaining endemic levels. These findings indicate that the extensive resources deployed in this French territory (public financing, health care network, public awareness campaigns, and training of health care personnel in diagnosis and treatment of malaria) have helped reduce the number of severe cases in an unfavorable epidemiological setting.
Médecine tropicale : revue du Corps de santé colonial

pasteur-00583514
https://hal-riip.archives-ouvertes.fr/pasteur-00583514
PUBMED : 19499726

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Polycyclic aromatic hydrocarbons (PAHs), such as benzo[a]pyrene (B[a]P), are widely distributed environmental contaminants exerting toxic effects such as genotoxicity and carcinogenicity, mainly associated with aryl hydrocarbon receptor (AhR) activation and the subsequent induction of cytochromes P-450 (CYP) 1-metabolizing enzymes. We previously reported an up-regulation of AhR expression and activity in primary cultures of human T lymphocyte by a physiological activation. Despite the suggested link between exposure to PAHs and the risk of lymphoma, the potential of activated human T lymphocytes to metabolize AhR exogenous ligands such as B[a]P, and produce DNA damage has not been investigated. In the present study, we characterized the genotoxic response of primary activated T lymphocytes to B[a] P. We demonstrated that, following T lymphocyte activation, B[a]P treatment triggers a marked increase in CYP1 expression and activity generating, upon metabolic activation, DNA adducts and double-strand breaks (DSBs) after a 48-h treatment. At this time point, B[a]P also induces a DNA damage response with ataxia telangiectasia mutated kinase activation, thus producing a p53-dependent response and T lymphocyte survival. B[a]P activates DSB repair by mobilizing homologous recombination machinery but also induces gene mutations in activated human T lymphocytes which could consequently drive a cancer process. In conclusion, primary cultures of activated human T lymphocytes represent a good model for studying genotoxic effects of environmental contaminants such as PAHs, and predicting human health issues.
ISSN: 0006-2952

hal-01560145
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01560145
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01560145/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01560145/file/Liamin%20et%20al.%20-%20Benzo%5Ba%5Dpyrene-induced%20DNA%20damage%20associated%20with%20.pdf
DOI : 10.1016/j.bcp.2017.04.025

Éditeur(s) : HAL CCSD
Résumé : International audience
Home health care workers interventions have been implemented in western countries to improve health status of patients with respiratory diseases especially asthma and allergic illnesses. Twenty-six controlled studies dealing with prevention and control of these diseases through home environmental interventions were reviewed. After a comprehensive description of the characteristics of these studies, the effectiveness of each intervention was then evaluated in terms of participants' compliance with the intervention program, improvement of quality of the indoor environment, and finally improvement of health outcomes, in detailed tables. Limitations and biases of the studies are also discussed. Overall, this review aims at giving a toolbox for home health care workers to target the most appropriate measures to improve health status of the patient depending on his and/or her environment and disease. Only a case-by-case approach with achievable measures will warrant the efficacy of home interventions. This review will also provide to the research community a tool to better identify targets to focus in future evaluation studies of home health care workers action.
Journal of allergy and clinical immunology. In practice

hal-01477202
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01477202
DOI : 10.1016/j.jaip.2016.07.011
PUBMED : 27665387

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
In cyclic females, FSH stimulates ovarian estradiol (E2) production and follicular growth up to the terminal stage. A transient elevation in circulating FSH and E2 levels occurs shortly after birth. But what could be the action of FSH on the ovary during this period, and in particular how it stimulates ovarian steroidogenesis without supporting terminal follicular maturation is intriguing. By experimentally manipulating FSH levels, we demonstrate in mice that the mid-infantile elevation in FSH is mandatory for E2 production by the immature ovary, but that it does not stimulate follicle growth. Importantly, FSH increases aromatase expression to stimulate E2 synthesis, however it becomes unable to induce cyclin D2, a major driver of granulosa cell proliferation. Besides, although FSH prematurely induces luteinizing hormone (LH) receptor expression in granulosa cells, LH pathway is not functional in these cells to induce their terminal differentiation. In line with these results, supplying infantile mice with a superovulation regimen exacerbates E2 production, but it does not stimulate the growth of follicles and it does not induce ovulation. Overall, our findings unveil a regulation whereby high postnatal FSH concentrations ensure the supply of E2 required for programming adult reproductive function without inducing follicular maturation before puberty.
ISSN: 2045-2322

hal-01516023
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01516023
DOI : 10.1038/srep46222
PUBMED : 28397811
PUBMEDCENTRAL : PMC5387682

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
The status of ethnic minority has been reported to be associated with a tendency toward sedentary behavior. The Guadeloupean population is composed of Afro-Caribbeans and an Asian Indian minority. This study examined the association of ethnicity and physical activity on the island. Energy expenditures (EE), energy intakes (EI), and macronutrient intakes of 122 Guadeloupean workers (60 Indians and 62 controls) were assessed by three consecutive 24-h recalls. Two-way analyses of variance were conducted to test the hypothesis of an effect of ethnicity, taking the potential effect of sex into account, on these variables. Asian Indians reported lower EE (P=0.011), lower EE/EI ratios (P=0.001), and lower physical activity (P=0.003) than their Afro-Carribean counterparts. Their food intakes were not different in terms of EI or macronutrient intake. No sex × ethnicity interactions were significant. The present study reports a tendency toward physical inactivity in Asian Indians of Guadeloupe associated with EI similar to those of controls. Sedentary lifestyles and energetic imbalances are well-documented risk factors for several diseases, including type 2 diabetes and cardiovascular disease, both major public health concerns in Guadeloupe. Strategies to prevent sedentary lifestyles should be considered for Asian Indian Guadeloupeans.
ISSN: 0905-7188

hal-00706161
https://hal.univ-antilles.fr/hal-00706161
DOI : 10.1111/j.1600-0838.2007.00743.x

Éditeur(s) : HAL CCSD PubMed
Résumé : International audience
The aim of this study was to measure the heart rate (HR) response of eight elite water polo players during the four 7-min quarters of the game and to check for relationships with the physiological parameters of performance ( ·VO2max, Th1vent, Th2vent). Each athlete performed a ·VO2max treadmill test and played a water polo game wearing a heart rate monitor. The game fatigue index was calculated as the ratio of the fourth-quarter HR to the first-quarter HR: HR4/HR1. The results showed a slight decrease in fourth-quarter HR compared with the first quarter, with the mean four-quarter HR equal to 79.9 ± 4.2% of HRmax. Stepwise multiple regression analysis showed ·VO2max to be the main explanatory factor of game intensity, i.e. game HR expressed in %HRreserve (R=0.88, P<0.01). We observed that higher aerobic capacity resulted in higher game intensity. We also observed a decrease in the playing intensity in the fourth quarter compared with the first, likely due to very high game involvement. We concluded that high aerobic capacity seems necessary to ensure high game intensity in water polo. This suggests that coaches should encourage their athletes to reach a minimum level of ·VO2max and that HR monitoring could be of great interest in the control of water polo training sessions.
ISSN: 0860-021X

hal-01158208
https://hal.univ-antilles.fr/hal-01158208
DOI : 10.5604/20831862.1083277

Éditeur(s) : HAL CCSD
Résumé : International audience
The aim of this study was to examine the heart rate (HR) response to Olympic windsurfing competition and to check if there was any correlation between racing HR, performance, and the variables measured during laboratory maximal exercise. Ten elite windsurfers [age: 20.93 (3.46) years; height: 178.10 (6.34) cm; body mass: 66.79 (5.90) kg] performed a laboratory maximal oxygen consumption (VO2max) trial and national windsurf competitions wearing a HR monitor. One hundred and forty-three individual races were examined. Racing HR was expressed as a percentage of (1) HRmax (maximal treadmill HR) and (2) HRreserve (HRmax)HRrest). The performance (racing classification: RC, which is inversely proportional to performance) was significantly correlated to the racing HR response in both light wind (LW): LW)RC=)0.12(%HRreserve)+13.03; r=)0.71, r2=0.50, p<0.001, and medium wind (MW): MW)RC=)0.11(%HRreserve)+10.99; r=)0.66, r2=0.43, p<0.001. The results showed similar correlations between performance and %HRmax. Post racing lactate concentration was higher in LW compared to MW [7.14 (0.21) and 5.18 (2.02) mmolÆl)1, respectively]. There was a negative correlation between the highest racing HR (%HRreserve) of each athlete and the second ventilatory threshold expressed as a percentage of VO2max (r=-0.71, p<0.05). To summarize, this study showed that light and medium wind Olympic windsurfing performances are highly dependent on the capacity of the athlete to maintain a high HR for long periods of time. Furthermore, windsurfing is highly dependent on the athlete's physical fitness level as shown by the correlations between racing HRs and laboratory physiological variables.
EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY

hal-00720564
https://hal.univ-antilles.fr/hal-00720564
https://hal.univ-antilles.fr/hal-00720564/document
https://hal.univ-antilles.fr/hal-00720564/file/Chamari_Wind_surf_and_Heart_rat.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The biogeochemistry of sulfur and carbon during early-diagenetic processes within organic-rich marine mangrove sediments was studied in the “Manche à Eau” lagoon, Guadeloupe, West Indies. These sediments are characterized by a total organic carbon content (TOC) mostly above 11 wt%, δ13CTOC below − 25‰ VPDB and C/Nmolar ratios exceeding 15. Rates of mangrove-derived organic carbon accumulation vary between ~ 200 and 400 gOC·m− 2·yr− 1, with highest rates at the shore of the lagoon. On the lagoon border, where colorless filamentous sulfur-oxidizing bacteria colonize the sediments, active sulfate reduction within the upper 20 cm, with a net removal rate of ~ 0.5 μmol·cm− 3·d− 1, is assumed to be essentially driven by organic carbon oxidation. This is expressed by relatively low apparent sulfur isotope fractionation (34εnet = − 33‰) and a gentle δ18O/δ34Ssulfate apparent slope of 0.36 ± 0.03 (2s). Further inside the lagoon, in the absence of sulfur-oxidizing bacteria, higher apparent sulfur isotope fractionation and a steeper δ18O/δ34Ssulfate slope (0.67 ± 0.20) suggest an overall lower sulfate removal rate that may be coupled to minor sulfur disproportionation. Spatial and vertical variation in sulfur cycling, reflected by oxygen and sulfur isotopic characteristics, seem to be mainly controlled by unsteady to relatively steady organic matter deposition and its reactivity. In all sediments, δ34S values of pyrite are positively correlated with the TOC/TS ratio and negatively correlated with δ13CTOC; suggesting a primary control of the quantity and quality of organic matter on the pyrite isotope records, despite potential iron-limiting conditions for the most active sites. Our results provide insights into the role of organic carbon input on sulfur cycling; stimulating sulfate reduction and in turn the presence of sulfur-oxidizing microbial mats, resulting in an intense cycling of both carbon and sulfur in these marine mangrove sediments.
ISSN: 0009-2541

hal-01507696
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01507696
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01507696/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01507696/file/Cr%C3%A9mi%C3%A8re%20et%20al.%20-%20Sulfur%20diagenesis%20under%20rapid%20accumulation%20of%20orga.pdf
DOI : 10.1016/j.chemgeo.2017.02.017

Éditeur(s) : HAL CCSD American Physiological Society
Résumé : International audience
Zidi-Yahiaoui N, Callebaut I, Genetet S, Le Van Kim C, Cartron JP, Colin Y, Ripoche P, Mouro-Chanteloup I. Functional analysis of human RhCG: comparison with E. coli ammonium transporter reveals similarities in the pore and differences in the vestibule. Am J Physiol Cell Physiol 297: C537–C547, 2009. First published June 24, 2009; doi:10.1152/ajpcell.00137.2009.—Rh glycoproteins are members of the ammonium transporter (Amt)/methylamine permease (Mep)/Rh family facilitating movement of NH3 across plasma membranes. Homology models constructed on the basis of the experimental structures of Escherichia coli AmtB and Nitrosomonas europaea Rh50 indicated a channel structure for human RhA (RhAG), RhB (RhBG), and RhC (RhCG) glycoproteins in which external and internal vestibules are linked by a pore containing two strictly conserved histidines. The pore entry is constricted by two highly conserved phenylalanines, “twin-Phe.” In this study, RhCG function was investigated by stopped-flow spectrofluorometry measuring kinetic pH variations in HEK293E cells in the presence of an ammonium gradient. The apparent unitary NH3 permeability of RhCG was determined and was found to be close to that of AmtB. With a site-directed mutagenesis approach, critical residues involved in Rh NH3 channel activity were highlighted. In the external vestibule, the importance of both the charge and the conformation of the conserved aspartic acid was shown. In contrast to AmtB, individual mutations of each phenylalanine of the twin-Phe impaired the function while the removal of both resulted in recovery of the transport activity. The impact of the mutations suggests that, although having a common function and a similar channel structure, bacterial AmtB and human Rh vary in several aspects of the NH3 transport mechanisms.
ISSN: 0363-6143

hal-00417492
https://hal.archives-ouvertes.fr/hal-00417492
DOI : 10.1152/ajpcell.00137.2009.

Éditeur(s) : HAL CCSD Springer Verlag/EDP Sciences
Résumé : International audience
In the dense tropical rainforest understorey, saplings exhibit different growth strategies aiming at reaching light levels better fitting their ecology. Investing mainly in height growth, at the expense of their width, a lot are close to mechanical instability. Tachigali melinonii, a long living heliophilic tree species, is frequently observed to be extremely slender and supported by neighbours. Such observations suggest an active growth control through the perception of mechanical environment. * Mechanical environment or light availability, which one is the most influent on growth and slenderness (H/D)? To test this question, we recorded growth of control and staked saplings of two species with contrasting habits and ecology: T. melinonii, and Dicorynia guianensis, along a natural light gradient. * Dicorynia, the more stable, responded more clearly to the staking treatment, showing slenderness increase when light is available, whereas for Tachigali, only light availability governed growth. * For Tachigali, growth allocation is mainly governed by light availability and ontogeny, whereas Dicorynia is probably similar to the average tree strategy, using the thigmomorphogenetic physiological process to control its stability.
ISSN: 1286-4560

hal-00534019
https://hal.archives-ouvertes.fr/hal-00534019
DOI : 10.1051/forest/2009104

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Cell death of hepatocytes is a prominent characteristic in the pathogenesis of liver disease, while hepatolysis is a starting point of inflammation in hepatitis and loss of hepatic function. However, the precise molecular mechanisms of hepatocyte cell death, the role of the cytokines of hepatic microenvironment and the involvement of intracellular kinases, remain unclear. Tumor necrosis factor alpha (TNF-α) is a key cytokine involved in cell death or survival pathways and the role of RIPK1 has been associated to the TNF-α-dependent signaling pathway. We took advantage of two different deficient mouse lines, the RIPK1 kinase dead knock-in mice (Ripk1K45A) and the conditional knockout mice lacking RIPK1 only in liver parenchymal cells (Ripk1LPC-KO), to characterize the role of RIPK1 and TNF-α in hepatitis induced by concanavalin A (ConA). Our results show that RIPK1 is dispensable for liver homeostasis under steady-state conditions but in contrast, RIPK1 kinase activity contributes to caspase-independent cell death induction following ConA injection and RIPK1 also serves as a scaffold, protecting hepatocytes from massive apoptotic cell death in this model. In the Ripk1LPC-KO mice challenged with ConA, TNF-α triggers apoptosis, responsible for the observed severe hepatitis. Mechanism potentially involves both TNF-independent canonical NF-κB activation, as well as TNF-dependent, but canonical NF-κB-independent mechanisms. In conclusion, our results suggest that RIPK1 kinase activity is a pertinent therapeutic target to protect liver against excessive cell death in liver diseases. © The Author(s) 2016.
ISSN: 2041-4889

hal-01414916
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01414916
DOI : 10.1038/cddis.2016.362
PUBMED : 27831558