Éditeur(s) : HAL CCSD
Résumé : In a recent study based on a retrospective reconstruction of growth, we showed for Cecropia sciadophylla that branching and flowering processes, as well as alternation of long and short nodes were regularly spaced by ~23 nodes. We also found that this strong periodicity was related to an annual cycle of growth. Adult trees are successful individuals that have reached the canopy and our previous results were found in adult trees, suggesting that variability in the number of nodes produced per year is underestimated, because the degree of variation decreases with age. Here, we hypothesized that growth periodicity could be related to rainfall and we focus on two C. sciadophylla populations with contrasting precipitation seasonality. During 19 months and for 69 saplings, we measured growth at regular monthly intervals to test the intra-annual variability in the number of nodes produced per month and per year. We also characterized the intra-annual fluctuations in the number of present leaves in the main axis and internode lengths among months. We found that node elongation and number of present leaves in the main axis vary among months in the population subjected to a strong seasonal precipitation. In contrast, the population subjected to a non-seasonal precipitation showed smaller variation in node elongation and no variation in the number of leaves presented in the main axis among months. Regardless the population of origin, we also found that ~23 was the number of nodes produced per year and that the time required to produce a new node was ~15 days at any month of the year. The strong stability in the average number of nodes produced per month and per year among populations, suggests a genetically controlled trait. In spite of a strong genetic determination on the number of nodes produced per year, several environmental factors, including rainfall, could be the cause of the observed variation in elongation and number of present leaves in the main axis.INRAUM2
Botany 2010
Rhode Island, United States

hal-01191343
https://hal.archives-ouvertes.fr/hal-01191343
PRODINRA : 178581

Éditeur(s) : HAL CCSD Springer Verlag/EDP Sciences
Résumé : International audience
Key message: Genetic diversity appears to be unaffected by disturbance in a stand of the light-demanding Neotropical treeV. michelii. Although spatial genetic structure is modified in post-disturbance cohorts, mixing of seeds from different mother trees in canopy gaps appears to efficiently maintain genetic admixture. Context: The interplay between genetic and demographic processes has major consequences on population viability. Population size affects demographic trends, while genetic diversity insures viability by reducing risks of inbreeding depression and by maintaining adaptive potential. Yet, the consequences of increases in census size (as opposed to effective size) on genetic diversity of forest populations are poorly known. Aims: We have studied the structure of genetic diversity in populations of saplings of the light-responsive tree, Virola michelii (Myristicaceae, the nutmeg family), in two plots having undergone different levels of canopy-gap opening disturbance. This allowed us to test the “intermediate disturbance” hypothesis, which generally applies to species diversity, at the intra-specific scale. Methods: Levels and distribution of genetic diversity were compared between plots and between life stages. Sapling parentage was analysed to infer each adult tree’s contribution to regeneration. Results: Genetic diversity was higher, and spatial genetic structure was stronger in the post-disturbance than in the control seedling population. Parentage analysis suggested that a limited number of parents contributed to most of the regeneration, but that efficient mixing of their progeny may have enhanced the diversity of saplings occupying canopy gaps. Conclusion: A mixture of demo-genetic processes may contribute to maintain genetic diversity in spite of, or possibly due to, ecosystem disturbance in V. michelii.
ISSN: 1286-4560

hal-01502942
https://hal-agroparistech.archives-ouvertes.fr/hal-01502942
https://hal-agroparistech.archives-ouvertes.fr/hal-01502942/document
https://hal-agroparistech.archives-ouvertes.fr/hal-01502942/file/art_10.1007_s13595-015-0508-3-1_%7B869D58F4-272C-491F-A903-DAD6CDBDC042%7D.pdf
DOI : 10.1007/s13595-015-0508-3

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : Precise mapping of above-ground biomass (AGB) is a major challenge for the success of REDD+ processes in tropical rainforest. The usual mapping methods are based on two hypotheses: a large and long-ranged spatial autocorrelation and a strong environment influence at the regional scale. However, there are no studies of the spatial structure of AGB at the landscapes scale to support these assumptions. We studied spatial variation in AGB at various scales using two large forest inventories conducted in French Guiana. The dataset comprised 2507 plots (0.4 to 0.5 ha) of undisturbed rainforest distributed over the whole region. After checking the uncertainties of estimates obtained from these data, we used half of the dataset to develop explicit predictive models including spatial and environmental effects and tested the accuracy of the resulting maps according to their resolution using the rest of the data. Forest inventories provided accurate AGB estimates at the plot scale, for a mean of 325 Mg.ha^-1. They revealed high local variability combined with a weak autocorrelation up to distances of no more than10 km. Environmental variables accounted for a minor part of spatial variation. Accuracy of the best model including spatial effects was 90 Mg.ha^-1 at plot scale but coarse graining up to 2-km resolution allowed mapping AGB with accuracy lower than 50 Mg.ha^-1. Whatever the resolution, no agreement was found with available pan-tropical reference maps at all resolutions. We concluded that the combined weak autocorrelation and weak environmental effect limit AGB maps accuracy in rainforest, and that a trade-off has to be found between spatial resolution and effective accuracy until adequate “wall-to-wall” remote sensing signals provide reliable AGB predictions. Waiting for this, using large forest inventories with low sampling rate (<0.5%) may be an efficient way to increase the global coverage of AGB maps with acceptable accuracy at kilometric resolution
ISSN: 1932-6203

hal-01269305
https://hal.archives-ouvertes.fr/hal-01269305
DOI : 10.1371/journal.pone.0138456
PRODINRA : 326359

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Although ants may induce community-wide effects via changes in physical habitats in terrestrial environments, their influence on aquatic communities living in plant-held waters remains largely underexplored. The neotropical tank-bromeliad Aechmea mertensii (Bromeliaceae) occurs along forest edges in ant-gardens initiated by Camponotus femoratus or by Pachycondyla goeldii. Its leaves form wells that hold rainwater and provide suitable habitats for many aquatic organisms. We postulated that these ant-plant mutualisms indirectly affect the microbial community structure via changes in the environmental conditions experienced by the plants. To test this hypothesis, we analyzed the protist communities from 63 tank-bromeliads associated with either C. femoratus or P. goeldii (hereafter Cf-Aechmea and Pg-Aechmea) along a forest edge in French Guiana. For each plant, a large number of environmental variables (including habitat structure, food resources, incident radiation and the presence of aquatic invertebrates) were quantified to determine their relative importance in driving any observed differences across ant-associated plants. Pg-Aechmea are located in sun-exposed areas and hold low volumes of water and low amounts of detritus, whereas Cf-Aechmea are located in partially shaded areas and accumulate higher amounts of water and detritus. Protists (i.e., protozoa and algae) inhabiting Cf-Aechmea exhibit greater richness and abundances than those in Pg-Aechmea. Variations in detritus content, number of leaves, incident radiation, and the epiphyte richness of the ant-garden were the main factors explaining the variation in protist richness. A shift in the functional group composition of protists between bromeliads tended by different ant species suggested that mutualistic ants indirectly mediate changes in the microbial food web.
Basic and Applied Ecology

hal-00913126
https://hal.archives-ouvertes.fr/hal-00913126
https://hal.archives-ouvertes.fr/hal-00913126/document
DOI : 10.1016/j.baae.2012.10.002
OATAO : 10190

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The strikingly complex structural organization of the mammalian testis in vivo creates particular difficulties for studies of its organization, function and regulation. These difficulties are particularly pronounced for investigations of the molecular communication networks within the seminiferous tubules that govern spermatogenesis. The use of classical molecular and cell biology approaches to unravel this complexity has proved problematic, due to difficulties in maintaining differentiated germ cells in vitro, in particular. The lack of a suitable testing ground has led to a greater reliance on high-quality proteomic and genomic analyses as a prelude to the in vitro antx1d in vivo testing of hypotheses. In this study, we highlight the options currently available for research, as used in our laboratory, in which proteomic and integrative genomic strategies are applied to the study of spermatogenesis in mammals. We will comment on results providing insight into the molecular mechanisms underlying normal and pathological spermatogenesis and new perspectives for the treatment of male infertility in humans. Finally, we will discuss the relevance of our strategies and the unexpected potential and perspectives they offer to teams involved in the study of male reproduction, within the framework of the Human Proteome Project. SIGNIFICANCE: Integrative genomics is becoming a powerful strategy for discovering the biological significance hidden in proteomic datasets. This work introduces some of the integrative genomic concepts and works used by our team to gain new insight into mammalian spermatogenesis, a remarkably sophisticated process. We demonstrate the relevance of these integrative approaches to understand the cellular cross talks established between the somatic Sertoli cells and the germ cell lineage, within the seminiferous epithelium. Our work also contributes to new knowledge on the pathophysiology of testicular function, with promising clinical applications. This article is part of a Special Issue entitled: 20years of Proteomics in memory of Viatliano Pallini. Guest Editors: Luca Bini, Juan J. Calvete, Natacha Turck, Denis Hochstrasser and Jean-Charles Sanchez.
ISSN: 1874-3919

hal-01063931
https://hal.archives-ouvertes.fr/hal-01063931
DOI : 10.1016/j.jprot.2014.04.013
PUBMED : 24751586

Éditeur(s) : HAL CCSD Wiley
Résumé :  
Positive aboveground biomass trends have been reported from old-growth forests across the Amazon basin and hypothesized to reflect a large-scale response to exterior forcing. The result could, however, be an artefact due to a sampling bias induced by the nature of forest growth dynamics. Here, we characterize statistically the disturbance process in Amazon old-growth forests as recorded in 135 forest plots of the RAINFOR network up to 2006, and other independent research programmes, and explore the consequences of sampling artefacts using a data-based stochastic simulator. Over the observed range of annual aboveground biomass losses, standard statistical tests show that the distribution of biomass losses through mortality follow an exponential or near-identical Weibull probability distribution and not a power law as assumed by others. The simulator was parameterized using both an exponential disturbance probability distribution as well as a mixed exponential-power law distribution to account for potential large-scale blowdown events. In both cases, sampling biases turn out to be too small to explain the gains detected by the extended RAINFOR plot network. This result lends further support to the notion that currently observed biomass gains for intact forests across the Amazon are actually occurring over large scales at the current time, presumably as a response to climate change.
ISSN: 1354-1013

hal-01032162
https://hal.archives-ouvertes.fr/hal-01032162
DOI : 10.1111/j.1365-2486.2009.01891.x

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Plasma membrane is an early target of polycyclic aromatic hydrocarbons (PAH). We previously showed that the PAH prototype, benzo[a]pyrene (B[a]P), triggers apoptosis via DNA damage-induced p53 activation (genotoxic pathway) and via remodeling of the membrane cholesterol-rich microdomains called lipid rafts, leading to changes in pH homeostasis (non-genotoxic pathway). As omega-3 (n-3) fatty acids can affect membrane composition and function or hamper in vivo PAH genotoxicity, we hypothesized that addition of physiologically relevant levels of polyunsaturated n-3 fatty acids (PUFAs) might interfere with B[a]P-induced toxicity. The effects of two major PUFAs, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), were tested on B[a]P cytotoxicity in the liver epithelial cell line F258. Both PUFAs reduced B[a]P-induced apoptosis. Surprisingly, pre-treatment with DHA increased the formation of reactive B[a]P metabolites, resulting in higher levels of B[a]P-DNA adducts. EPA had no apparent effect on B[a]P metabolism or related DNA damage. EPA and DHA prevented B[a]P-induced apoptotic alkalinization by affecting Na(+)/H(+) exchanger 1 activity. Thus, the inhibitory effects of omega-3 fatty acids on B[a]P-induced apoptosis involve a non-genotoxic pathway associated with plasma membrane remodeling. Our results suggest that dietary omega-3 fatty acids may have marked effects on the biological consequences of PAH exposure.
ISSN: 0009-2797

hal-00950341
https://hal.archives-ouvertes.fr/hal-00950341
https://hal.archives-ouvertes.fr/hal-00950341/document
https://hal.archives-ouvertes.fr/hal-00950341/file/DENDELE_et_al_2013-unmarked.pdf
PUBMED : 24246761

Éditeur(s) : HAL CCSD John Libbey Eurotext
Résumé : International audience
Prostate cancer is the most frequent cancer affecting men in most Western countries. Certain risk factors have been identified (age, family history, ethnic origin), but the aetiology of this cancer remains largely unknown. However, a role for environmental factors is strongly suspected. Questions have been raised concerning the role of the chemical substances generated by human activities in the occurrence of this disease. Diverse studies have consistently demonstrated a higher risk of prostate cancer in agricultural populations than in the general population. The hypothesis that this higher risk is linked to the use of pesticides has been tested in a number of studies, mostly in North America and Europe. However, to date, with a few possible exceptions, it has been impossible to demonstrate a significant association between exposure to pesticides or a chemical family of pesticides and prostate cancer. In the face of these uncertainties, rigorous studies are required, with objective measurements of exposure, taking into account confounding factors and individual risk factors, making it possible to assess gene-environment interactions.
ISSN: 0007-4551

inserm-00504733
http://www.hal.inserm.fr/inserm-00504733
DOI : 10.1684/bdc.2008.0812
PUBMED : 19258224

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Chlordecone (CLD) was an organochlorine insecticide whose previous use resulted in an extensive pollution of the environment with severe health effects and social consequences. A closely related compound, 5b-hydrochlordecone (5b-hydroCLD), has been searched for and often detected in environmental matrices from the geographical area where CLD was applied. The current consensus considered that its presence was not the result of a biotic or abiotic dechlorination of CLD in these matrices but rather the consequence of its presence as impurity (synthesis by-product) in the CLD released into the environment. The aim of the present study was to determine if and to what extent degradation of CLD into 5b-hydroCLD occurred in the field. To test this hypothesis, the ratios of 5b-hydroCLD and CLD concentrations in a dataset of 810 soils collected between 2006 and 2012 in Martinique were compared to the ratios measured in 3 samples of the CLD dust commercial formulations applied in the banana fields of French West Indies (FWI) and 1 sample of the technical-grade CLD corresponding to the active ingredient used in such formulations. Soil data were processed with a hierarchical Bayesian model to account for random measurement errors and data censoring. Any pathway of CLD transformation into 5b-hydroCLD occurring over the long term in FWI soils would indeed change the ratio of 5b-hydroCLD/CLD compared to what it was in the initially applied formulations. Results showed a significant increase of the 5b-hydroCLD/CLD ratio in the soils-25 times greater in soil than in commercial formulations-which suggested that natural CLD transformation into 5b-hydroCLD over the long term occurred in these soils. Results from this study may impact future decisions for the remediation of the polluted areas.
ISSN: 0944-1344

hal-01347150
https://hal.archives-ouvertes.fr/hal-01347150
https://hal.archives-ouvertes.fr/hal-01347150/document
https://hal.archives-ouvertes.fr/hal-01347150/file/Devault_15973.pdf
DOI : 10.1007/s11356-015-4865-0

Éditeur(s) : Elsevier
Résumé : How users perceive the performance of Marine Protected Areas (MPAs) is fundamental for the social acceptance of these zones. Moreover, their perceptions may be relevant for monitoring the effects of MPAs on extractive activities. This study analyzes artisanal fishers' perceptions of the performance of a north-western Mediterranean coastal MPA, which encompasses two no-take zones (NTZs). Three viewpoints have been considered: the effect on the personal activity of fishers, the effect on the local fishery and the effect on the ecosystem. In order to test the hypothesis that biomass export (spillover) - which had previously been evidenced from the two NTZs - may influence fishers' perceptions of NTZ effects, fishers' perceptions were compared with both declared and observed fishing activity over an one-year period. The results show that negative perceptions of NTZs are either nil or are negligible. Most fishers are aware of the beneficial effects of NTZs on ecosystems and fisheries. However, they remain to be convinced of the beneficial effects of the NTZs on their own activity. For instance, the proximity of a NTZ appears never to be involved in the choice of a fishing spot. This partial lack of correspondence between scientific expectation and fishers' perceptions is discussed in the light of fishing habits in the zone adjacent to NTZs, and takes into account fishing grounds, targeted species and seniority (defined as the number of years the fisher has been fishing within the MPA). All three factors appear to influence fishers' perceptions. For example, having a positive perception about a NTZ and spending more time fishing in the adjacent zone are habits that can be associated with fishers with less seniority. Fishers' perceptions obviously indicate the social acceptance of the MPA and are an essential monitoring tool for MPA managers. However, perceptions cannot be seen as a substitute for scientific monitoring, as both approaches are clearly complementary. (C) 2011 Published by Elsevier Ltd.
Marine Policy (0308-597X) (Elsevier), 2012-03 , Vol. 36 , N. 2 , P. 414-422

Droits : 2011 Published by Elsevier Ltd.
http://archimer.ifremer.fr/doc/00060/17137/16442.pdf
DOI:10.1016/j.marpol.2011.06.002
http://archimer.ifremer.fr/doc/00060/17137/

Éditeur(s) : HAL CCSD Wiley
Résumé : In the Amazon basin and the Guiana Shield, white-sand (WS) forests are recognized as a low-resource habitat often composed by a distinct flora with many edaphic endemic plants. Small patches of nutrient-poor white-sand forests can pose a series of challenges to plants and animals. For plants, these challenges have been shown to function as strong filters that in turn drive taxonomic, functional and phylogenetic plant composition. However, very little is known about animal communities in WS forest and the effect that low-resource availability may have on higher trophic levels. Here, we investigate the diversity of both taxonomic and phylogenetic diversity of three Lepidoptera families' (Nymphalidae, Saturniidae, and Sphingidae) assemblages between low-resource (White-Sand Forest) and two adjacent high-resource habitats, terra firme clay and seasonally flooded forests. We found no clear effect of habitat type on taxonomic composition although butterfly and moth species abundance differed among the three contrasted habitats. The WS forest Lepidoptera community is significantly more phylogenetically overdispersed than expected by chance. We suggest that these low-resource habitats filter the number of plant lineages which, in turn, creates a bottom-up control structuring Lepidoptera phylogenetic structure. We recommend long-term sampling on Lepidoptera community both at larval and adult stages that may complement this study and test hypotheses linking herbivore phylogenetic structure to plant resource availability and trophic cascade theory.
ISSN: 0006-3606

hal-01532550
https://hal.archives-ouvertes.fr/hal-01532550
DOI : 10.1111/btp.12294
PRODINRA : 353400

Éditeur(s) : HAL CCSD American Society of Nephrology
Résumé : International audience
Since the recent publication of data showing favorable outcomes for patients with HIV-1 and ESRD, kidney transplantation has become a therapeutic option in this population. However, reports have documented unexplained reduced allograft survival in these patients. We hypothesized that the unrecognized infection of the transplanted kidney by HIV-1 can compromise long-term allograft function. Using electron microscopy and molecular biology, we examined protocol renal transplant biopsies from 19 recipients with HIV-1 who did not have detectable levels of plasma HIV-1 RNA at transplantation. We found that HIV-1 infected the kidney allograft in 68% of these patients. Notably, HIV-1 infection was detected in either podocytes predominately (38% of recipients) or tubular cells only (62% of recipients). Podocyte infection associated with podocyte apoptosis and loss of differentiation markers as well as a faster decline in allograft function compared with tubular cell infection. In allografts with tubular cell infection, epithelial cells of the proximal convoluted tubules frequently contained abnormal mitochondria, and both patients who developed features of subclinical acute cellular rejection had allografts with tubular cell infection. Finally, we provide a novel noninvasive test for determining HIV-1 infection of the kidney allograft by measuring HIV-1 DNA and RNA levels in patients' urine. In conclusion, HIV-1 can infect kidney allografts after transplantation despite undetectable viremia, and this infection might influence graft outcome.
ISSN: 1046-6673

hal-01121764
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01121764
DOI : 10.1681/ASN.2013050564
PUBMED : 24309185
PUBMEDCENTRAL : PMC3904571

Éditeur(s) : HAL CCSD Frontiers
Résumé : International audience
The generation of handwriting is a complex neuromotor skill requiring the interaction of many cognitive processes. It aims at producing a message to be imprinted as an ink trace left on a writing medium. The generated trajectory of the pen tip is made up of strokes superimposed over time. The Kinematic Theory of rapid human movements and its family of lognormal models provide analytical representations of these strokes, often considered as the basic unit of handwriting. This paradigm has not only been experimentally confirmed in numerous predictive and physiologically significant tests but it has also been shown to be the ideal mathematical description for the impulse response of a neuromuscular system. This latter demonstration suggests that the lognormality of the velocity patterns can be interpreted as reflecting the behavior of subjects who are in perfect control of their movements. To illustrate this interpretation, we present a short overview of the main concepts behind the Kinematic Theory and briefly describe how its models can be exploited, using various software tools, to investigate these ideal lognormal behaviors. We emphasize that the parameters extracted during various tasks can be used to analyze some underlying processes associated with their realization. To investigate the operational convergence hypothesis, we report on two original studies. First, we focus on the early steps of the motor learning process as seen as a converging behavior toward the production of more precise lognormal patterns as young children practicing handwriting start to become more fluent writers. Second, we illustrate how aging affects handwriting by pointing out the increasing departure from the ideal lognormal behavior as the control of the fine motricity begins to decline. Overall, the paper highlights this developmental process of merging toward a lognormal behavior with learning, mastering this behavior to succeed in performing a given task, and then gradually deviating from it with aging.
ISSN: 1664-1078

hal-01098124
https://hal.archives-ouvertes.fr/hal-01098124
DOI : 10.3389/fpsyg.2013.0094

Éditeur(s) : HAL CCSD Royal Society, The
Résumé : International audience
Coral spawning times have been linked to multiple environmental factors; however, to what extent these factors act as generalized cues across multiple species and large spatial scales is unknown. We used a unique dataset of coral spawning from 34 reefs in the Indian and Pacific Oceans to test if month of spawning and peak spawning month in assemblages of Acropora spp. can be predicted by sea surface temperature (SST), photosynthetically available radiation, wind speed, current speed, rainfall or sunset time. Contrary to the classic view that high mean SST initiates coral spawning, we found rapid increases in SST to be the best predictor in both cases (month of spawning: R2 = 0.73, peak: R2 = 0.62). Our findings suggest that a rapid increase in SST provides the dominant proximate cue for coral mass spawning over large geographical scales. We hypothesize that coral spawning is ultimately timed to ensure optimal fertilization success.
ISSN: 0962-8452

hal-01325704
https://hal-univ-perp.archives-ouvertes.fr/hal-01325704
DOI : 10.1098/rspb.2016.0011

Éditeur(s) : HAL CCSD Elsevier Elsevier Masson
Résumé : International audience
Prostate cancer is the most frequent cancer affecting men in most Western countries. Certain risk factors have been identified (age, family history, ethnic origin), but the aetiology of this cancer remains largely unknown. However, a role for environmental factors is strongly suspected. Questions have been raised concerning the role of the chemical substances generated by human activities in the occurrence of this disease. Diverse studies have consistently demonstrated a higher risk of prostate cancer in agricultural populations than in the general population. The hypothesis that this higher risk is linked to the use of pesticides has been tested in a number of studies, mostly in North America and Europe. However, to date, with a few possible exceptions, it has been impossible to demonstrate a significant association between exposure to pesticides or a chemical family of pesticides and prostate cancer. Studies have also been carried out on the role of exposure to trace metals, such as cadmium, or to pollutants from industry, such as polychlorobiphenyls. However, no firm conclusions have been drawn. Finally, the effect of chemical substances with endocrine disruptor activity on the occurrence of prostate cancer remains largely unexplored in epidemiological studies. In the face of these uncertainties, rigorous studies are required, with objective measurements of exposure, taking into account confounding factors and individual risk factors, making it possible to assess gene-environment interactions.
ISSN: 1297-9589

inserm-00524579
http://www.hal.inserm.fr/inserm-00524579
DOI : 10.1016/j.gyobfe.2008.07.005
PUBMED : 18693059

Éditeur(s) : HAL CCSD
Résumé : International audience
Extreme rainfall events can trigger numerous landslides in mountainous areas and a prolonged increase of river sediment load. The resulting mass transfer at the Earth surface in turn induces stress changes at depth, which could be sufficient to trigger shallow earthquakes. The 2009 Morakot typhoon represents a good case study as it delivered 3 m of precipitation in 3 days and caused some of the most intense erosion ever recorded. Analysis of seismicity time-series before and after the Morakot typhoon reveals a systematic increase of shallow (i.e. 0-15 km of depth) earthquake frequency in the vicinity of the areas displaying a high spatial density of landslides. This step-like increase in frequency lasts for at least 2-3 years and does not follow an Omori-type aftershock sequence. Rather, it is associated to a step change of the Gutenberg-Richter b-value of the earthquake catalog. Both changes occurred in mountainous areas of southwest Taiwan, where typhoon Morakot caused extensive landsliding. These spatial and temporal correlations strongly suggest a causal relationship between the Morakot-triggered landslides and the increase of earthquake frequency and their associated b-value. We propose that the progressive removal of landslide materials from the steep mountain landscape by river sediment transport acts as an approximately constant increase of the stress rate with respect to pre-typhoon conditions, and that this in turn causes a step-wise increase in earthquake frequency. To test this hypothesis, we investigate the response of a rate-and-state fault to stress changes using a 2-D continuum elasto-dynamic model. Consistent with the results of Ader et al. (2013), our preliminary results show a step-like increase of earthquake frequency in response to a step-like decrease of the fault normal stress. We also investigate the sensitivity of the amplitude and time-scale of the earthquake frequency increase to the amplitude of the normal stress change and to rheological parameters. Our study offers new insights on the potential influence of extreme erosional events on the short-time scale dynamics of faults and earthquakes.
American Geophysical Union Fall Meeting 2016
San Francisco, United States

insu-01416987
https://hal-insu.archives-ouvertes.fr/insu-01416987

Éditeur(s) : HAL CCSD IOS Press
Résumé : International audience
This study tested the hypothesis that trained sickle cell trait (SCT) carriers are not subjected to greater risk of rhabdomyolysis or renal failure in response to moderate submaximal exercise than subjects with normal hemoglobin (CONT). Blood markers in 11 trained SCT carriers and 12 control counterparts were measured before and after 40 min of exercise at 55% of peak power output (Ppeak) conducted in thermoneutral environment. Body weights decreased with exercise in the same proportion in the two groups (from 65.1 ± 7.0 kg to 64.1 ± 7.0 kg and from 70.2 ± 6.6 to 68.6 ± 6.6 kg at the end of exercise in SCT and CONT, respectively). Heart rate and rectal temperature increased in the two groups in response to exercise, but the groups remained closely matched. Serum urea, CRP, CK and LDH were similar in the two groups and remained unchanged in response to exercise. Creatinine, Na + , K + , Cl − and myoglobin concentrations increased above baseline in response to exercise, with changes of the same magnitude in the two groups. In summary, the results of the present study suggest that moderate submaximal exercise is not unsafe from a biochemical point of view for sportsmen carrying SCT.
ISSN: 1386-0291

hal-01163943
https://hal.univ-antilles.fr/hal-01163943
DOI : 10.3233/CH-2011-1524

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 Elsevier
Résumé : International audience
Although ants may induce community-wide effects via changes in physical habitats in terrestrial environments, their influence on aquatic communities living in plant-held waters remains largely underexplored. The neotropical tank-bromeliad Aechmea mertensii (Bromeliaceae) occurs along forest edges in ant-gardens initiated by Camponotus femoratus or by Pachycondyla goeldii. Its leaves form wells that hold rainwater and provide suitable habitats for many aquatic organisms. We postulated that these ant-plant mutualisms indirectly affect the microbial community structure via changes in the environmental conditions experienced by the plants. To test this hypothesis, we analyzed the protist communities from 63 tank-bromeliads associated with either C. femoratus or P. goeldii (hereafter Cf-Aechmea and Pg-Aechmea) along a forest edge in French Guiana. For each plant, a large number of environmental variables (including habitat structure, food resources, incident radiation and the presence of aquatic invertebrates) were quantified to determine their relative importance in driving any observed differences across ant-associated plants. Pg-Aechmea are located in sun-exposed areas and hold low volumes of water and low amounts of detritus, whereas Cf-Aechmea are located in partially shaded areas and accumulate higher amounts of water and detritus. Protists (i.e., protozoa and algae) inhabiting Cf-Aechmea exhibit greater richness and abundances than those in Pg-Aechmea. Variations in detritus content, number of leaves, incident radiation, and the epiphyte richness of the ant-garden were the main factors explaining the variation in protist richness. A shift in the functional group composition of protists between bromeliads tended by different ant species suggested that mutualistic ants indirectly mediate changes in the microbial food web.
ISSN: 1439-1791

hal-00817519
https://hal.archives-ouvertes.fr/hal-00817519