Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Ecological signs of Earth's biosphere forewarn an alarming trajectory towards a global mass-extinction. Assessing species performance and susceptibilities to decline is essential to comprehend and reverse this trend. Yet it is challenging, given difficulties associated with quantifying individual and population processes that are variable across time, space, and life-stages. We describe a new approach to estimating and comparing species performances that combines empirical data, a novel theoretical consideration of population dynamics, and modern statistics. Our approach allows for a more realistic continuous representation of individual performances along development stages while taking into account non-linearity, and natural variability as captured by spatio-temporally replicated observations. We illustrate its application in a coral meta-assemblage composed of populations of the three major reef-building taxa Acropora, Pocillopora, Porites. Using a unique set of highly replicated observations of individual coral dynamics under various environmental conditions, we show how taxa differ in their investment in recruitment and size-specific aptitude for growth and survival, notably through different use of clonal shrinkage, fragmentation, fission, and fusion processes. Our results reveal contrasting life-history trade-offs among taxa which, along with differing patterns of density-dependent recruitment, modulate species responses to decline. These differences in coral life history traits reflect opposing life-strategies, imply regulation at differing life-stages, and explain divergence in species trajectories. Our findings indicate a high potential for resilience in Pocillopora and Porites populations, thanks respectively to a sustained recruitment that promotes demographic elasticity through replacement of individuals, and a steady resistance to mortality which confers persistence through lingering of individuals. Resilience in Acropora appears more arbitrary, given high susceptibility to perturbations and dependency of recruitment on presence of established local populations. We identify management actions that can complement Acropora's life history and benefit recovery of its populations following mortality events. Our regression-modelling approach to quantifying and comparing species performances in different population processes is applicable to all taxa, as illustrated even those with complex clonal life histories, and can be implemented at wide spatio-temporal and taxonomic coverage. It can promote more accurate representation of species dynamics in both descriptive and predictive modelling approaches. The semi-parametric contrast curve method we develop facilitates comparing response variables along continuous explicative metrics while accounting for multiple sources of complexity in empirical data. It should widely benefit investigations in ecology and quantitative science.
ISSN: 1476-945X

hal-01212337
https://hal-univ-perp.archives-ouvertes.fr/hal-01212337
DOI : 10.1016/j.ecocom.2015.07.003

Éditeur(s) : HAL CCSD Cambridge University Press (CUP)
Résumé : International audience
Leishmania parasites can escape the immune response by invading cell types lacking leishmanicidal mechanisms. Silent persistence of Leishmania parasites in the host organism is responsible for asymptomatic carriage and relapses after cured leishmaniasis. Here, we studied the interaction between Hepatic Stellate Cells (HSC) and Leishmania. An original model of human HSC in primary culture infected with L. donovani was developed. The presence of intracellular parasites was studied and quantified using optical and confocal microscopy. HSC characteristics were studied using microscopy, methylene blue assay, long-term cultures and qPCR. We showed for the first time that human HSC are permissive to L. donovani infection, with no modification of HSC survival, growth rate and proinflammatory and fibrogenic characteristics. Intracellular parasites did not replicate but HSC had no effect on their survival. Indeed, after a 40-day culture, infected HSC cultures transferred on NNN medium yielded new promastigotes that were able to proliferate and efficiently infect new cells. HSC are permissive to L. donovani, with neither parasite killing nor apparent cell damage. Thus, HSC could act as potent sanctuary cells for Leishmania in the liver, which could partially explain parasite reactivation after an asymptomatic carriage or a cured visceral leishmaniasis.
ISSN: 0031-1820

inserm-00825803
http://www.hal.inserm.fr/inserm-00825803
DOI : 10.1017/S0031182012001965
PUBMED : 23253952

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
The fitness landscapethe mapping between genotypes and fitnessdetermines properties of the process of adaptation. Several small genotypic fitness landscapes have recently been built by selecting a handful of beneficial mutations and measuring fitness of all combinations of these mutations. Here, we generate several testable predictions for the properties of these small genotypic landscapes under Fisher's geometric model of adaptation. When the ancestral strain is far from the fitness optimum, we analytically compute the fitness effect of selected mutations and their epistatic interactions. Epistasis may be negative or positive on average depending on the distance of the ancestral genotype to the optimum and whether mutations were independently selected, or coselected in an adaptive walk. Simulations show that genotypic landscapes built from Fisher's model are very close to an additive landscape when the ancestral strain is far from the optimum. However, when it is close to the optimum, a large diversity of landscape with substantial roughness and sign epistasis emerged. Strikingly, small genotypic landscapes built from several replicate adaptive walks on the same underlying landscape were highly variable, suggesting that several realizations of small genotypic landscapes are needed to gain information about the underlying architecture of the fitness landscape.
ISSN: 0014-3820

hal-01544760
https://hal.archives-ouvertes.fr/hal-01544760
DOI : 10.1111/evo.12545

Éditeur(s) : Elsevier Sci Ltd
Résumé : Time-series studies have reported trophic cascades in land, freshwater and marine environments in many geographic areas. However, the spatial extent of habitats, a key metric of ecosystem structure, has not been mapped in these studies. Marine reserves can provide experimental, before-after and inside-outside (control-impacted), situations for assessing the impact of fishing on ecosystems. We mapped seabed habitats and their associated communities (biotopes) in New Zealand's oldest marine reserve for comparison with pre-reserve maps created about 30 years previously. Areas grazed bare by sea urchins were entirely replaced in the centre of the reserve by kelp, or alga turf, an intermediate biotope between heavily grazed encrusting algae and lightly grazed kelp. Urchins declined following increased abundance and body size of spiny (rock) lobsters and fish (especially snapper) in the reserve but maintained bare rock outside. While this gradient in habitat change matched the gradient of predator abundance, it also matched the extent of reef habitat area. Thus the trophic cascade may be influenced by the effect of habitat on the abundance and behavioural interactions of urchins and their predators. Further ecosystem changes may arise should the abundance of mega-predators, such as seals, cetaceans and large sharks, increase in the region; if parasites become pathogenic; and/or when invasive species reach the reserve. No-take marine reserves provide real-world experiments that show the importance of species in food webs, and the consequences of fishing for ecosystems. Because these changes in ecosystem structure may continue, and will vary with environment, climate and species distributions, reserves need to be permanent and replicated geographically. Habitat maps should be produced for all reserves to enable ecological changes in the ecosystem to be spatially quantified. (C) 2012 Elsevier Ltd. All rights reserved.
Biological Conservation (0006-3207) (Elsevier Sci Ltd), 2012-10 , Vol. 155 , P. 193-201

Droits : 2012 Elsevier Ltd. All rights reserved
http://archimer.ifremer.fr/doc/00107/21842/20067.pdf
DOI:10.1016/j.biocon.2012.05.009
http://archimer.ifremer.fr/doc/00107/21842/

Éditeur(s) : HAL CCSD BMJ Publishing Group
Résumé : International audience
OBJECTIVES: Many women who work during pregnancy are occupationally exposed to toxicants. The developing central nervous system is highly vulnerable to neurotoxicants such as solvents. Although the neurotoxicity of solvents to adults is well established, very few studies have examined their effects on children's behaviour following prenatal exposure. METHODS: Women from the Perturbateurs endocriniens: Étude Longitudinale sur les Anomalies de la Grossesse, l'Infertilité et l'Enfance (PELAGIE) mother-child cohort (including 3005 working women) were recruited in Brittany (France) between 2002 and 2006, at the beginning of pregnancy, to assess occupational exposure to solvents at that time. Child behaviour was documented at age 2 by mothers (n=1278) assessing components of attention deficit/hyperactivity, aggression, opposition and emotionality. We used a multiple linear regression analysis to evaluate the association between occupational solvent exposure and children's behaviour. Complementary sensitivity analyses allowed us to handle missing data, due mostly to attrition. RESULTS: 20% of women reported occasional exposure and 31% regular exposure to solvents. Children prenatally exposed were more likely to have higher scores of attention deficit/hyperactivity and aggression, and dose-response relations were observed. CONCLUSIONS: The dose-response effect and the high prevalence of children potentially exposed to solvents from their mother's workplace exposure underline the public health relevance of this result. Our results should be replicated in further studies designed to identify which solvents are most deleterious and to assess child behaviour at school age.
ISSN: 1351-0711

inserm-00795043
http://www.hal.inserm.fr/inserm-00795043
http://www.hal.inserm.fr/inserm-00795043/document
http://www.hal.inserm.fr/inserm-00795043/file/Occupationnal_solvent_exposure_child_behavior_HAL.pdf
DOI : 10.1136/oemed-2012-100892

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
The shallow-water bivalve Codakia orbiculata which harbors gill-endosymbiotic sulfur-oxidizing ?-proteobacteria can lose and acquire its endosymbionts throughout its life. Long-term starvation and recolonization experiments led to changes in the organization of cells in the lateral zone of gill filaments. This plasticity is linked to the presence or absence of gill-endosymbionts. Herein, we propose that this reorganization can be explained by three hypotheses: (a) a variation in the number of bacteriocytes and granule cells due to proliferation or apoptosis processes, (b) a variation of the volume of these two cell types without modification in the number, and (c) a combination of both number and cell volume variation. To test these hypotheses, we analyzed cell reorganization in terms of proliferation and apoptosis in adults submitted to starvation and returned to the field using catalyzed reporter deposition fluorescence in situ hybridization, immunohistochemistry, and structural analyses. We observed that cell and tissue reorganization in gills filaments is due to a variation in cell relative abundance that maybe associated with a variation in cell apparent volume and depends on the environment. In fact, bacteriocytes mostly multiply in freshly collected and newly recolonized individuals, and excess bacteriocytes are eliminated in later recolonization stages. We highlight that host tissue regeneration in gill filaments of this symbiotic bivalve can occur by both replication of existing cells and division of undifferentiated cells localized in tissular bridges, which might be a tissue-specific multipotent stem cell zone.
ISSN: 1059-910X

hal-01545915
https://hal.archives-ouvertes.fr/hal-01545915
DOI : 10.1002/jemt.22041

Éditeur(s) : Co-tutelle Al Centro de Investigaciones Biológicas del Noroeste - Université de Bretagne occidentale
Résumé : The interest in probiotics for aquaculture is increasing rapidly. In the present work we evaluated the potential of some yeast to induce the larvae gut maturation in sea bass larvae Dicentrarchus labrax. The production of polyamines putrescine, spermidine and spermine was quantified in ten yeast strains using high performance liquid chromatography (HPLC). Afterwards, fluorescently labelled yeast adhesion to the intestine of sea bass larvae and the spotted sand bass (Paralabrax maculatofasciatus) was evaluated by fluorescent microscopy. Two of them, CBS 8339 strain (Debaryomyces hansenii) and X2180 strain (Saccharomyces cerevisiae) produce the polyamines of our interest. The same strains showed the best adhering capabilities to the sea bass and spotted sand bass intestine. Both strains were selected and introduced by pulverization into the diet of larvae. The larvae fed with CBS 8339 strain, increase survival in 8.3% but not in their weight. The secretion of trypsin and amylase as well as those from the brush border membrane: alkaline phosphatase, maltase and leucine aminopeptidase, are incresed at 27 days after hatching (dah). At 42 dah difference in the enzyme activity of the different groups does not exist, suggesting a maturation of the digestive system in early stages of larval development. A second experiment was carried out to know the effect of different levels of incorporation into the diet of CBS 8339 strain: 1.1% and 5.7%. The minimum level, 1.1% of yeast produce best growth and survival rates, as well as lower deformed larvae than those obtained by 5.7% and the control one. Both level of yeast inclusion favored the trypsin secretion and lipase activity at 26 dah. Whereas mRNA levels for trypsin and amylase were influenced by both yeast concentrations at 26 and 36 dah, which suggest a development of digestive capacity of larvae as a result of the presence of polyamines secreted by the yeast.
Les probiotiques ont été définis comme des préparations microbiennes vivantes utilisées comme additif alimentaire, et qui ont une action bénéfique sur l'animal hôte en améliorant la digestion et l'hygiène intestinale. L'application de tels traitements aux productions aquacoles suscite un intérêt qui s'accroît rapidement. Dans ce travail, nous avons étudié l'effet de souches de levures sur la maturation de l'intestin des larves du bar Dicentrarchus labrax. Ces souches produisent des polyamines qui sont impliquées dans la réplication et la différentiation cellulaire, ainsi que dans la synthèse des protéines et des acides nucléiques. Dix souches de levures ont été testées pour leur production de polyamines (putrescine, spermidine et spermine), et pour leur adhérence à la paroi intestinale du bar et la cabrilla (Paralabrax maculatofasciatus). La production des polyamines a été analysée en utilisant la chromatographie liquide à haute performance (HPLC). Les levures selectionées ont été marquées avec un composé fluorescent pour tester leur adhérence a l'intestin de larves de bar et de juvéniles de cabrilla. L'adhérence a pu ainsi être evaluée par observation microscopique en épifluorescence. Les souches CBS 8339 (Debaryomyces hansenii) et X2180 (Saccharomyces cerevisiae) ont été choisies pour leur forte production de spermidine et de spermine, respectivement, et pour leur capacité d'adhérence à l'intestin du bar et de la cabrilla. Les deux souches ont été ajoutées par pulvérisation au régime des larves. Nous avons observé une augmentation de 8.3% du taux de survie avec les larves alimentées avec la souche CBS 8339, mais le poids moyen de ces larves était inférieur à celui obtenu sans ajout de levure. Une augmentation de l'activité de la trypsine et de l'amylase, aussi bien que des activités enzymatiques dans la bordure en brosse, aminopeptidase, phosphatase alkaline et maltase, ont été observées dans les larves âgées de 27 jours alimentées avec la souche CBS 8339. Au jour 42, il n'existait plus de différence d'activité enzymatique entre les larves traitées ou non avec la levure. Ces résultats suggèrent que la maturation du système digestif a été accélérée chez les larves nourries avec la levure, la maturation étant achevée chez les larves de 42 jours, qu'elles aient reçu l'un ou l'autre régime. Une deuxième expérience a été effectuée pour étudier l'effet de différents niveaux d'incorporation dans le régime contenant 1,1% et 5,7% de levure CBS 8339. L'incorporation de 1,1% a induit une augmentation du poids moyen et du taux de survie des larves, ainsi qu'une réduction du taux de malformation de la colonne vertébrale, par rapport aux résultats obtenus avec 0 ou 5,7% de levure. Les deux niveaux d'incorporation de la levure ont favorisé l'activité de la trypsine et de la lipase au jour 26. Les niveaux d'ARNm codant pour la synthèse de la trypsine et de l'amylase ont été influencés par les deux doses de levure aux jours 26 et 36. Ces résultats suggèrent qu'une faible dose de levure améliore le développement et la capacité digestive des larves, et nous formulons l'hypothèse que cette efficacité est due à la production de polyamines in situ. Le rôle des polyamines est particulièrement important pendant les phases de forte croissance comme les stades larvaires, mais elles peuvent être toxiques à dose trop élevée. L'incorporation de levure dans l'aliment destiné aux larves semble donc une excellente méthode pour délivrer les polyamines chez l'animal hôte.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2002/these-103.pdf
http://archimer.ifremer.fr/doc/00000/103/

Éditeur(s) : HAL CCSD
Résumé : Neotropical forests shelter an astonishing and underrated biodiversity. The integrity and stability of these natural ecosystems are threatened by human-induced environmental changes. Therefore, highlighting the determinants of ecosystem functioning, be they natural or anthropogenic, is a daunting but paramount scientific challenge. The intrinsic complexity of highly diversified ecosystems arouses both conceptual and logistical difficulties, which we handle, by manipulating tiny ecosystems, the tank bromeliads. The leaves of tank bromeliads form wells that hold rainwater and intercept leaf litter, allowing for a simple invertebrate aquatic community to thrive. These plants can be exhaustively sampled, are naturally replicated, and widely distributed.From local to biogeographic scales, this thesis aims at understanding how these communities respond to the natural heterogeneity of Amazonian forests, and at predicting the impacts of human-induced disturbances on the structure and functioning of these communities, using in situ and lab experiments. Particular focus is attributed to the influence of some aspects of climate changes (e.g., warming, and various precipitations scenarios) on individual physiology, behavior, and trophic interactions.
Les forêts néotropicales accueillent une importante biodiversité encore méconnue. L’intégrité des écosystèmes naturels est menacée par les changements environnementaux (e.g., réchauffement climatique, destruction des habitats), par conséquent, identifier les facteurs structurants, naturels et anthropiques, du fonctionnement des écosystèmes, représente un défi scientifique crucial. L’inhérente complexité de ces milieux diversifiés pose de nombreux problèmes conceptuels et logistiques comme un échantillonnage exhaustif et/ou l’identification des espèces. Les broméliacées à réservoirs sont des écosystèmes miniatures adéquats pour pallier ces difficultés, car elles retiennent de l’eau de pluie et accumulent de la matière organique au creux de leurs feuilles, permettant ainsi de supporter des réseaux trophiques simples d’invertébrés aquatiques. Elles peuvent être échantillonnées exhaustivement, ont une forte abondance locale, et une large aire de répartition. De l’échelle locale à biogéographique, les travaux de cette thèse visent d’abord à comprendre comment ces communautés se structurent en réponse à l’hétérogénéité naturelle des forêts amazoniennes (e.g., ouverture de la canopée, fluctuations climatiques saisonnières), puis tente de prédire, par le biais d’expérimentations in situ et au laboratoire les réponses structurelles et fonctionnelles de ces communautés à divers scénarios de changement climatique. Une attention particulière a été portée sur l’impact de la température et des précipitations sur la physiologie et le comportement d’espèces clefs, et sur les interactions trophiques au sein des communautés.
https://tel.archives-ouvertes.fr/tel-01405025

NNT : 2015YANE0003
tel-01405025
https://tel.archives-ouvertes.fr/tel-01405025
https://tel.archives-ouvertes.fr/tel-01405025/document
https://tel.archives-ouvertes.fr/tel-01405025/file/These-DEZERALD-Diffusion.pdf

Éditeur(s) : HAL CCSD Oxford University Press (OUP): Policy C - Option B
Résumé : International audience
We report the characterization of a DNA primase/ polymerase protein (PolpTN2) encoded by the pTN2 plasmid from Thermococcus nautilus. Sequence analysis revealed that this protein corresponds to a fusion between an N-terminal domain homologous to the small catalytic subunit PriS of heterodimeric archaeal and eukaryotic primases (AEP) and a C-terminal domain related to their large regulatory subunit PriL. This unique domain configuration is not found in other virus-and plasmid-encoded primases in which PriS-like domains are typically fused to different types of helicases. PolpTN2 exhibited primase, polymerase and nucleotidyl transferase activities and specifically incorporates dNTPs, to the exclusion of rNTPs. PolpTN2 could efficiently prime DNA synthesis by the T. nautilus PolB DNA polymerase, suggesting that it is used in vivo as a primase for pTN2 plasmid replication. The N-terminal PriS-like domain of PolpTN2 exhibited all activities of the full-length enzyme but was much less efficient in priming cellular DNA polymerases. Surprisingly, the N-terminal domain possesses reverse transcriptase activity. We speculate that this activity could reflect an ancestral function of AEP proteins in the transition from the RNA to the DNA world.
ISSN: 0305-1048

Droits : http://creativecommons.org/licenses/by/
hal-01332620
http://hal.upmc.fr/hal-01332620
http://hal.upmc.fr/hal-01332620/document
http://hal.upmc.fr/hal-01332620/file/Nucl.%20Acids%20Res.-2014-Gill-3707-19.pdf
DOI : 10.1093/nar/gkt1385

Éditeur(s) : HAL CCSD BMJ Publishing Group
Résumé : International audience
OBJECTIVES: Social position and social mobility are associated with cancer incidence and mortality, yet little is known about their association with mediating factors such as occupational exposures to carcinogens. Our aim was to assess the association between the type of professional trajectory and multiple occupational exposure profiles. METHOD: Data were extracted from the Giscop93 study (n = 1 009), which is a cohort of cancer patients with (mainly) respiratory tumours. Job histories were reconstructed through interview, then a multi-disciplinary expert group examined the probability of occupational exposure to a list of 54 potentially carcinogenic agents. The typology of professional trajectories was built based on employment stability, employment continuity, job qualification trend, and multiple skills through Multiple Correspondence Analysis followed by Ascending Hierarchical Classification. Association with multiple-exposure profiles was then assessed through multiple logistic regression. RESULTS: Men and women differed in terms of predominant job category over the lifecourse (68,2% of blue-collar-workers among men, 57,3% of employees among women, p extless 0.0001). Professional trajectories were grouped in four classes as "stable qualified, employee" (21,3%), "stable manual, independent blue-collar-worker" (24,4%), "stable tiring, no gain in qualification" (30,5%), and "very unstable, precarious" (23,8%). Among men, the last two categories were associated with exposure to at least five different occupational carcinogens (ORstable_tiring/stable_qualified=2,0 [1,3;3,1], ORvery_unstable/stable_qualified=2,6 [1,6;4,2]). No such association was found among women. CONCLUSIONS: The association found between the type of professional trajectory and multiple occupational exposures among men should be replicated among people not suffering cancer. Forthcoming analysis will investigate the gendered differences observed.
ISSN: 1351-0711

hal-01063899
https://hal.archives-ouvertes.fr/hal-01063899
DOI : 10.1136/oemed-2014-102362.266

Éditeur(s) : HAL CCSD
Résumé : National audience
Traditional network generation models attempt to replicate global structural properties (degree distribution, average distance, clustering coefficient, communities, etc.) through synthetic link formation mechanisms such as triadic closure or preferential attachment. In this work, we study the evolution of a very big communication network coming from mobile telephony and we analyse the link formation process. A first study conducted on the standard mechanisms allows observing that several mechanisms are responsible for the properties observed in this network. In a second study, we characterize more precisely the link formation process by searching for correlations between the probability of creating a new link and some individual properties such as the degree, the clustering coefficient and the age of the nodes.
Conférence sur les modèles et l'analyse des réseaux : Approches mathématiques et informatiques
Saint-Etienne, France

hal-00873990
https://hal.archives-ouvertes.fr/hal-00873990

Éditeur(s) : HAL CCSD Springer
Résumé : International audience
Playbacks are a useful tool for conducting well-controlled and replicated experiments on the effects of anthropogenic noise, particularly for repeated exposures. However, playbacks are unlikely to fully reproduce original sources of anthropogenic noise. Here we examined the sound pressure and particle acceleration of boat noise playbacks in a field experiment and reveal that although there remain recognized limitations, the signal-to-noise ratios of boat playbacks to ambient noise do not exceed those of a real boat. The experimental setup tested is therefore of value for use in experiments on the effects of repeated exposure of aquatic animals to boat noise.
The Effects of Noise on Aquatic Life II

ISBN : 978-1-4939-2980-1 (Print) 978-1-4939-2981-8 (Online)
hal-01270660
https://hal-univ-perp.archives-ouvertes.fr/hal-01270660
DOI : 10.1007/978-1-4939-2981-8_55

Éditeur(s) : HAL CCSD Oxford University Press
Résumé : International audience
Type IB DNA topoisomerases can eliminate torsional stresses produced during replication and transcription. These enzymes are found in all eukaryotes and a short version is present in some bacteria and viruses. Among prokaryotes, the long eukaryotic version is only observed in archaea of the phylum Thau-marchaeota. However, the activities and the roles of these topoisomerases have remained an open question. Here, we demonstrate that all available thaumar-chaeal genomes contain a topoisomerase IB gene that defines a monophyletic group closely related to the eukaryotic enzymes. We show that the topIB gene is expressed in the model thaumarchaeon Ni-trososphaera viennensis and we purified the recom-binant enzyme from the uncultivated thaumarchaeon Candidatus Caldiarchaeum subterraneum. This enzyme is active in vitro at high temperature, making it the first thermophilic topoisomerase IB characterized so far. We have compared this archaeal type IB enzyme to its human mitochondrial and nuclear counterparts. The archaeal enzyme relaxes both negatively and positively supercoiled DNA like the eukaryotic enzymes. However, its pattern of DNA cleavage specificity is different and it is resistant to camptothecins (CPTs) and non-CPT Top1 inhibitors, LMP744 and lamellarin D. This newly described ther-mostable topoisomerases IB should be a promising new model for evolutionary, mechanistic and structural studies.
ISSN: 0305-1048

Droits : http://creativecommons.org/licenses/by/
hal-01327354
http://hal.upmc.fr/hal-01327354
http://hal.upmc.fr/hal-01327354/document
http://hal.upmc.fr/hal-01327354/file/Nucl.%20Acids%20Res.-2016-Dahmane-2795-805.pdf
DOI : 10.1093/nar/gkw097

Éditeur(s) : HAL CCSD Elsevier
Résumé : The Authors. Published by Elsevier Masson SAS on behalf of Institut Pasteur. This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/)
Ehrlichia is a large genus of obligate intracellular Gram-negative bacteria transmitted by ticks that cause several emerging infectious diseases in humans and are pathogenic on rodents, ruminants, and dogs. Ehrlichia spp. invade and replicate either in endothelial cells, white blood cells, or within midgut cells and salivary glands of their vector ticks. In this review, we discuss the insights that functional studies are providing on how this group of bacteria exploits their host by subverting host innate immunity and hijacking cellular processes.
ISSN: 1286-4579

hal-01512099
https://hal.archives-ouvertes.fr/hal-01512099
https://hal.archives-ouvertes.fr/hal-01512099/document
https://hal.archives-ouvertes.fr/hal-01512099/file/Moumene%202016%20Microbes%20and%20Infection_%7BEFBE9395-9C1F-4C96-A09E-A017DC15F940%7D.pdf
DOI : 10.1016/j.micinf.2015.11.001

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
A thorough phytochemical study of Stereocaulon evolutum was conducted, for the isolation of structurally related atranorin derivatives. Indeed, pilot experiments suggested that atra-norin (1), the main metabolite of this lichen, would interfere with the lifecycle of hepatitis C virus (HCV). Eight compounds, including one reported for the first time (2), were isolated and characterized. Two analogs (5, 6) were also synthesized, to enlarge the panel of atra-norin-related structures. Most of these compounds were active against HCV, with a half-maximal inhibitory concentration of about 10 to 70 µM, with depsides more potent than monoaromatic phenols. The most effective inhibitors (1, 5 and 6) were then added at different steps of the HCV lifecycle. Interestingly, atranorin (1), bearing an aldehyde function at C-3, inhibited only viral entry, whereas the synthetic compounds 5 and 6, bearing a hydroxy-methyl and a methyl function, respectively, at C-3 interfered with viral replication.
ISSN: 1932-6203

hal-01134343
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01134343
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01134343/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01134343/file/Depsides-PloS.pdf
DOI : 10.1371/journal.pone.0120405

Éditeur(s) : HAL CCSD Wiley-Blackwell
Résumé : International audience
The shallow-water bivalve Codakia orbiculata which harbors gill-endosymbiotic sulfur-oxidizing g-proteobacteria can lose and acquire its endosymbionts throughout its life. Longterm starvation and recolonization experiments led to changes in the organization of cells in the lateral zone of gill filaments. This plasticity is linked to the presence or absence of gill-endosymbionts. Herein, we propose that this reorganization can be explained by three hypotheses: (a) a variation in the number of bacteriocytes and granule cells due to proliferation or apoptosis processes, (b) a variation of the volume of these two cell types without modification in the number, and (c) a combination of both number and cell volume variation. To test these hypotheses, we analyzed cell reorganization in terms of proliferation and apoptosis in adults submitted to starvation and returned to the field using catalyzed reporter deposition fluorescence in situ hybridization, immunohistochemistry, and structural analyses. We observed that cell and tissue reorganization in gills filaments is due to a variation in cell relative abundance that maybe associated with a variation in cell apparent volume and depends on the environment. In fact, bacteriocytes mostly multiply in freshly collected and newly recolonized individuals, and excess bacteriocytes are eliminated in later recolonization stages. We highlight that host tissue regeneration in gill filaments of this symbiotic bivalve can occur by both replication of existing cells and division of undifferentiated cells localized in tissular bridges, which might be a tissue-specific multipotent stem cell zone.
Microscopy Research and Technique

hal-00743036
https://hal-uag.archives-ouvertes.fr/hal-00743036

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
The regulatory mechanisms involved in the acquisition of thermal tolerance are unknown in insects. Reversible phosphorylation is a widespread post-translational modification that can rapidly alter proteins function(s). Here, we conducted a large-scale comparative screening of phosphorylation networks in adult Drosophila flies that were cold-acclimated versus control. Using a modified SIMAC method followed by a multiple MS analysis strategy, we identified a large collection of phosphopeptides (about 1600) and phosphoproteins (about 500) in both groups, with good enrichment efficacy (80%). The saturation curves from the four biological replicates revealed that the phosphoproteome was rather well covered under our experimental conditions. Acclimation evoked a strong phosphoproteomic signal characterized by large sets of unique and differential phosphoproteins. These were involved in several major GO superclusters of which cytoskeleton organization, positive regulation of transport, cell cycle, and RNA processing were particularly enriched. Data suggest that phosphoproteomic changes in response to acclimation were mainly localized within cytoskeletal network, and particularly within microtubule associated complexes. This study opens up novel research avenues for exploring the complex regulatory networks that lead to acquired thermal tolerance.
ISSN: 2045-2322

hal-01532256
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01532256
DOI : 10.1038/s41598-017-01974-z
PUBMED : 28490779

Éditeur(s) : HAL CCSD American Society for Microbiology
Résumé : International audience
Coronaviruses (CoVs) have shown neuroinvasive properties in human and animal secondary to replication in peripheral organ but the mechanism of neuroinvasion is unknown. The major aim of our work was to evaluate the ability of CoVs to enter the central nervous system (CNS) through the blood brain barrier (BBB). Using the high hepatotropic mouse hepatitis virus (MHV) type 3, its attenuated variant 51.6-MHV3, showing low tropism for endothelial cells, and the low hepatotropic MHV-A59 strains from murine coronavirus group, we investigated the viral-induced dysfunctions of BBB in vivo and in brain microvascular endothelial cells (BMECs) in vitro. We report here a MHV strain-specific ability to cross the BBB during acute infection according to their virulence for liver. Brain invasion was only observed in MHV3-infected mice and correlated with enhanced BBB permeability associated with decreased expression of ZO-1, VE-cadherin and occludin but not claudin-5 in the brain or in cultured BMECs. BBB breakdown in MHV3 infection was not related to production of barrier-dysregulating inflammatory cytokines or chemokines by infected BMECs but rather to a downregulation of barrier protective IFN-β production. Our findings highlight the importance of IFN-β production by infected BMECs in preserving BBB function and preventing access of blood-borne infectious viruses to the brain. IMPORTANCE: Coronaviruses (CoVs) infect several mammals including humans and are associated with respiratory, gastrointestinal and/or neurological diseases. Some evidences suggest that human respiratory CoVs may show neuroinvasive properties. Indeed, the SARS-CoV, causing severe acute respiratory syndrome, and the CoVs OC43 and 229E were found in the brains of SARS and multiple sclerosis patients respectively. These finding suggest that hematogenous spread CoVs may gain access to CNS at the BBB level. Herein we report for the first time that CoVs exhibit ability to cross the BBB according to strain virulence. BBB invasion by CoVs correlates with viral-induced disruption of tight junctions on BMECs, leading to BBB dysfunction and enhanced permeability. We provide evidence that production of IFN-β by BMECs during CoV infection may prevent BBB breakdown and brain viral invasion
ISSN: 0022-538X

hal-01187308
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01187308
DOI : 10.1128/JVI.01501-15
PUBMED : 26202229

Éditeur(s) : HAL CCSD Springer
Résumé : International audience
Traditional network generation models aim to replicate global structural properties observed on various real-world networks through synthetic link formation mechanisms such as triadic closure or preferential attachment. Nowadays, the large amount of data available allow to study more precisely the link formation processes and to compare models with real situations. In this work, we analyze the network formed by the communication activities of the users of a telephony operator for studying the link formation process. Our goal is to identify the underlying formation mechanisms and checking if they match those proposed in traditional models. Indeed, the communications emitted and received by users are strong indicators for understanding the underlying patterns of the link formation process and highlighting how some individual properties induce the formation process in such a network. In a first study conducted at a global level, we show that the traditional mechanisms commonly used in network generation models cannot reproduce alone the link formation in this network. In a second study, we adopt a new point of view and analyze locally the link formation process by searching for correlations between some user attributes and the formation of the new links. The results obtained show that a very strong percentage of new links are formed between individuals with strong similarity.
ISSN: 1869-5450

hal-01312310
https://hal.univ-antilles.fr/hal-01312310
DOI : 10.1007/s13278-015-0304-y

Éditeur(s) : HAL CCSD American Society for Investigative Pathology (ASIP)
Résumé : International audience
Semen represents the main vector of HIV dissemination worldwide, yet the origin of HIV in semen remains unclear. Viral populations distinct from those found in blood have been observed in semen, indicating local viral replication within the male genital tract. The seminal vesicles, the secretions of which constitute more than 60% of the seminal fluid, could represent a major source of virus in semen. This study is the first to investigate the susceptibility of human seminal vesicles to HIV infection both in vitro and in vivo. We developed and characterized an organotypic culture of human seminal vesicles to test for target cells and HIV infection, and, in parallel, analyzed the seminal vesicle tissues from HIV-infected donors. In vitro, in contrast to HIV-1 X4, HIV-1 R5 exposure induced productive infection. Infected cells consisted primarily of resident CD163(+) macrophages, often located close to the lumen. In vivo, HIV protein and RNA were also detected primarily in seminal vesicle macrophages in seven of nine HIV-infected donors, some of whom were receiving prolonged suppressive highly active antiretroviral therapy. These results demonstrate that human seminal vesicles support HIV infection in vitro and in vivo and, therefore, have the potential to contribute virus to semen. The presence of infected cells in the seminal vesicles of treated men with undetectable viremia suggests that this organ could constitute a reservoir for HIV.
American Journal of Pathology

inserm-00626549
http://www.hal.inserm.fr/inserm-00626549
DOI : 10.1016/j.ajpath.2011.08.005
PUBMED : 21925468