Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Neurogenesis initiates during early development and it continues through later developmental stages and in adult animals to enable expansion, remodeling, and homeostasis of the nervous system. The generation of nerve cells has been analyzed in detail in few bilaterian model organisms, leaving open many questions about the evolution of this process. As the sister group to bilaterians, cnidarians occupy an informative phylogenetic position to address the early evolution of cellular and molecular aspects of neurogenesis and to understand common principles of neural development. Here we review studies in several cnidarian model systems that have revealed significant similarities and interesting differences compared to neurogenesis in bilaterian species, and between different cnidarian taxa. Cnidarian neurogenesis is currently best understood in the sea anemone Nematostella vectensis, where it includes epithelial neural progenitor cells that express transcription factors of the soxB and atonal families. Notch signaling regulates the number of these neural progenitor cells, achaete-scute and dmrt genes are required for their further development and Wnt and BMP signaling appear to be involved in the patterning of the nervous system. In contrast to many vertebrates and Drosophila, cnidarians have a high capacity to generate neurons throughout their lifetime and during regeneration. Utilizing this feature of cnidarian biology will likely allow gaining new insights into the similarities and differences of embryonic and regenerative neurogenesis. The use of different cnidarian model systems and their expanding experimental toolkits will thus continue to provide a better understanding of evolutionary and developmental aspects of nervous system formation.
ISSN: 1759-7692

Droits : http://creativecommons.org/licenses/by-nc/
hal-01405097
http://hal.upmc.fr/hal-01405097
http://hal.upmc.fr/hal-01405097/document
http://hal.upmc.fr/hal-01405097/file/Rentzsch_et_al-2016-Wiley_Interdisciplinary_Reviews__Developmental_Biology.pdf
DOI : 10.1002/wdev.257

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
CYLD is a tumour suppressor gene mutated in familial cylindromatosis, a genetic disorder leading to the development of skin appendage tumours. It encodes a deubiquitinating enzyme that removes Lys63- or linear-linked ubiquitin chains. CYLD was shown to regulate cell proliferation, cell survival and inflammatory responses, through various signalling pathways. Here we show that CYLD localizes at centrosomes and basal bodies via interaction with the centrosomal protein CAP350 and demonstrate that CYLD must be both at the centrosome and catalytically active to promote ciliogenesis independently of NF-κB. In transgenic mice engineered to mimic the smallest truncation found in cylindromatosis patients, CYLD interaction with CAP350 is lost disrupting CYLD centrosome localization, which results in cilia formation defects due to impairment of basal body migration and docking. These results point to an undiscovered regulation of ciliogenesis by Lys63 ubiquitination and provide new perspectives regarding CYLD function that should be considered in the context of cylindromatosis.
ISSN: 2041-1723

hal-01063915
https://hal.archives-ouvertes.fr/hal-01063915
DOI : 10.1038/ncomms5585
PUBMED : 25134987

Éditeur(s) : HAL CCSD Society for Molecular Biology and Evolution
Résumé : International audience
Although heterokaryons have been reported in nature, multicellular organisms are generally assumed genetically homogeneous. Here, we investigate the case of arbuscular mycorrhizal fungi (AMF) that form symbiosis with plant roots. The growth advantages they confer to their hosts are of great potential benefit to sustainable agricultural practices. However, measuring genetic diversity for these coenocytes is a major challenge: Within the same cytoplasm, AMF contain thousands of nuclei and show extremely high levels of genetic variation for some loci. The extent and physical location of polymorphism within and between AMF genomes is unclear. We used two complementary strategies to estimate genetic diversity in AMF, investigating polymorphism both on a genome scale and in putative single copy loci. First, we used data from whole-genome pyrosequencing of four AMF isolates to describe genetic diversity, based on a conservative network-based clustering approach. AMF isolates showed marked differences in genome-wide diversity patterns in comparison to a panel of control fungal genomes. This clustering approach further allowed us to provide conservative estimates of Rhizophagus spp. genomes sizes. Second, we designed new putative single copy genomic markers, which we investigated by massive parallel amplicon sequencing for two Rhizophagus irregularis and one Rhizophagus sp. isolates. Most loci showed high polymorphism, with up to 103 alleles per marker. This polymorphism could be distributed within or between nuclei. However, we argue that the Rhizophagus isolates under study might be heterokaryotic, at least for the putative single copy markers we studied. Considering that genetic information is the main resource for identification of AMF, we suggest that special attention is warranted for the study of these ecologically important organisms.
ISSN: 1759-6653

Droits : http://creativecommons.org/licenses/by/
hal-01224215
http://hal.upmc.fr/hal-01224215
http://hal.upmc.fr/hal-01224215/document
http://hal.upmc.fr/hal-01224215/file/Genome%20Biol%20Evol-2015-Boon-505-21.pdf
DOI : 10.1093/gbe/evv002

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
The evolutionary origin of teeth from dermal denticles (odontodes) that developed in the mouth cavity, designated as outside-in hypothesis, has long been undisputed. The outside-in hypothesis is based on the conclusion that dermal denticles and teeth fulfil the criteria of homology in an exemplary manner. Over the past 15 years, this hypothesis has been challenged. Proponents of the alternative inside-out hypothesis suggest that teeth did not evolve from dermal denticles, that they are of endodermal origin (forming in conjunction with neural crest-derived mesenchyme) and that they evolved several times independently in different lineages of vertebrates. Key arguments for the inside-out hypothesis are mineralized structures of conodonts that are accepted as teeth, the exclusive acceptance of placoderm pharyngeal denticles as teeth, together with the rejection of the presence of teeth in basal placoderms. We summarize the results of recent studies that have been triggered by the fruitful discussion between the two conflicting hypotheses. New findings support the traditional outside-in hypothesis: the mineralized elements of conodonts are not teeth, and the oral cusps in basal placoderms are true teeth. Furthermore, new developmental and molecular data clarify homology between teeth and dermal denticles. Today a new synthesis is emerging about the evolutionary origin of teeth from dermal denticles and about the unity of the elements of the dermal skeleton.
ISSN: 0175-8659

hal-01545480
https://hal.archives-ouvertes.fr/hal-01545480
DOI : 10.1111/jai.12532

Éditeur(s) : HAL CCSD American Association for the Advancement of Science
Résumé : International audience
DNA double-strand breaks (DSBs) are introduced in meiosis to initiate recombination and generate crossovers, the reciprocal exchanges of genetic material between parental chromosomes. Here, we present high-resolution maps of meiotic DSBs in individual human genomes. Comparing DSB maps between individuals shows that along with DNA binding by PRDM9, additional factors may dictate the efficiency of DSB formation. We find evidence for both GC-biased gene conversion and mutagenesis around meiotic DSB hotspots, while frequent colocalization of DSB hotspots with chromosome rearrangement breakpoints implicates the aberrant repair of meiotic DSBs in genomic disorders. Furthermore, our data indicate that DSB frequency is a major determinant of crossover rate. These maps provide new insights into the regulation of meiotic recombination and the impact of meiotic recombination on genome function.
ISSN: 0036-8075

hal-01123717
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01123717
PUBMED : 25395542
DOI : 10.1126/science.1256442

Éditeur(s) : HAL CCSD
Résumé : International audience
F.T. Kützing introduced Cocconeis molesta with only an uninformative description and a poor illustration: C. molesta has small, oblong valves and is an epiphyte. Another species, Cocconeis diaphana, described by William Smith, is said to have larger valves than C. molesta, with frustules that are relatively oblong. Smith described two forms: one with a distinct fascia on its raphe valve (var. β), the other without this feature. A third species, Cocconeis dirupta was described by Gregory, who expressed doubts that it differed from C. diaphana. Finally, Cocconeis molesta var. crucifera Grunow was first introduced in Van Heurck's Atlas but was subsequently treated by Van Heurck as a synonym of C. molesta. No previous account has examined the type material of these species. In this paper, we undertake that task and examine type slides and raw material in order to discriminate these different taxa. We conclude by recognizing three species: Cocconeis molesta Kütz., C. diaphana W.Sm. and C. dirupta W.Greg. Cocconeis diaphana var. β is considered to be a synonym of C. dirupta and C. molesta var. crucifera is considered to be a synonym of C. molesta. Lectotypes are designated for C. diaphana and C. dirupta.
ISSN: 2118-9773

Droits : http://creativecommons.org/licenses/by/
hal-01340453
https://hal-univ-perp.archives-ouvertes.fr/hal-01340453
https://hal-univ-perp.archives-ouvertes.fr/hal-01340453/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01340453/file/329-1709-1-PB.pdf
DOI : 10.5852/ejt.2016.204

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Sphingolipids, in particular ceramide, have been described as important components of cellular signalling pathways. Ceramide can be produced via multiple mechanisms including through the hydrolysis of sphingomyelin by acid and neutral sphingomyelinase or by a de novo synthesis pathway. Recent studies have identified sphingomyelinases and ceramide synthases as important targets for γ-irradiation and chemotherapeutic drugs. Likewise, common cancer treatment modalities, such as γ-irradiation and many chemotherapeutic agents, induce cell death via the generation of ceramide. This suggests that the manipulation of ceramide production and metabolism could offer promising a means for the enhancement of anti-tumor therapies. The focus of this mini-review will be to discuss contemporary evidence suggesting that ceramide forming pathways and ceramide itself are important targets for the treatment of tumors and the development of novel tumor treatment strategies.
ISSN: 0304-3835

hal-00682458
https://hal.archives-ouvertes.fr/hal-00682458
DOI : 10.1016/j.canlet.2011.07.010
PUBMED : 21862212

Éditeur(s) : HAL CCSD IWA Publishing
Résumé : International audience
The widely occurring degradation product aminomethylphosphonic acid (AMPA) is a result of glyphosate and amino-polyphosphonate degradation. Massive use of the parent compounds leads to the ubiquity of AMPA in the environment, and particularly in water. The purpose of this review is to summarize and discuss current insights into AMPA formation, transport, persistence and toxicity. In agricultural soils, AMPA is concentrated in the topsoil, and degrades slowly in most soils. It can reach shallow groundwater, but rarely managed to enter deep groundwater. AMPA is strongly adsorbed to soil particles and moves with the particles towards the stream in rainfall runoff. In urban areas, AMPA comes from phosphonates and glyphosate in wastewater. It is commonly found at the outlets of Wastewater Treatment Plants (WWTP). Sediments tend to accumulate AMPA, where it may be biodegraded. Airborne AMPA is not negligible, but does wash-out with heavy rainfall. AMPA is reported to be persistent and can be biologically degraded in soils and sediments. Limited photodegradation in waters exists. AMPA mainly has its sources in agricultural leachates, and urban wastewater effluents. The domestic contribution to urban loads is negligible. There is a critical lack of epidemiological data - especially on water exposure - to understand the toxicological effects, if any, of AMPA on humans. Fortunately, well operated water treatment plants remove a significant proportion of the AMPA from water, even though there are not sufficient regulatory limits for metabolites.
ISSN: 0043-1354

hal-01516026
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01516026
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01516026/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01516026/file/Grandcoin%20et%20al.%20-%20AminoMethylPhosphonic%20acid%20%28AMPA%29%20in%20natural%20water.pdf
DOI : 10.1016/j.watres.2017.03.055

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Polarization dependence second harmonic generation (P-SHG) microscopy is gaining increase popularity for in situ quantification of fibrillar protein architectures. In this report, we combine P-SHG microscopy, new linear least square (LLS) fitting and modeling to determine and convert the complex second-order non-linear optical anisotropy parameter ρ of several collagen rich tissues into a simple geometric organization of collagen fibrils. Modeling integrates a priori knowledge of polyhelical organization of collagen molecule polymers forming fibrils and bundles of fibrils as well as Poisson photonic shot noise of the detection system. The results, which accurately predict the known sub-microscopic hierarchical organization of collagen fibrils in several tissues, suggest that they can be subdivided into three classes according to their microscopic and macroscopic hierarchical organization of collagen fibrils. They also show, for the first time to our knowledge, intrahepatic spatial discrimination between genuine fibrotic and non-fibrotic vessels. CCl 4-treated livers are characterized by an increase in the percentage of fibrotic vessels and their remodeling involves peri-portal compaction and alignment of collagen fibrils that should contribute to portal hypertension. This integrated P-SHG image analysis method is a powerful tool that should open new avenue for the determination of pathophysiological and chemo-mechanical cues impacting collagen fibrils organization.
ISSN: 2045-2322

hal-01592192
https://hal.archives-ouvertes.fr/hal-01592192
https://hal.archives-ouvertes.fr/hal-01592192/document
https://hal.archives-ouvertes.fr/hal-01592192/file/s41598-017-12398-0.pdf
DOI : 10.1038/s41598-017-12398-0

Éditeur(s) : HAL CCSD American Society of Hematology
Résumé : International audience
Zika fever is an Aedes-borne disease caused by a flavivirus (Zika virus, ZIKV, genus Flavivirus). During the past years ZIKV spread in Polynesia, South-America and the Caribbean. Most ZIKV infections are asymptomatic or result in mild febrile disease with rash and conjunctivitis. Attention was recently drawn to non-vectored ZIKV transmission, including sexual, probable blood-borne and mother-to-fetus transmission, and to severe forms such as Guillain-Barré syndrome, acute neurological infections and fetal abnormalities (including microcephaly). Many aspects of Zika fever natural history remain unknown, e.g. the proportion of asymptomatic cases and the duration of viremia. Estimating the prevalence of Zika infections is difficult because a large proportion of infected individuals do not seek medical attention and seroprevalence studies are hampered by antigenic cross-reactivity with other flaviviruses, e.g. dengue virus. Here, we present a study of ZIKV infection in blooddonors from Martinique island (French West Indies, Caribbean region), with novel epidemiological, biological and clinical information that refine the picture of Zika fever in adults.
ISSN: 0006-4971

inserm-01415646
http://www.hal.inserm.fr/inserm-01415646
http://www.hal.inserm.fr/inserm-01415646/document
http://www.hal.inserm.fr/inserm-01415646/file/2016%2C%20Gallian%20et%20al%20-%20Zika%20virus%20in%20asymptomatic%20blood%20donors%2C%20Martinique%20%281%29.pdf
DOI : 10.1182/blood-2016-09-737981

Éditeur(s) : HAL CCSD Royal Society
Résumé : International audience
Trees control their posture by generating asymmetric mechanical stress around the periphery of the trunk or branches. This stress is produced in wood during the maturation of the cell wall. When the need for reaction is high, it is accompanied by strong changes in cell organization and composition called reaction wood, namely compression wood in gymnosperms and tension wood in angiosperms. The process by which stress is generated in the cell wall during its formation is not yet known, and various hypothetical mechanisms have been proposed in the literature. Here we aim at discriminating between these models. First, we summarize current knowledge about reaction wood structure, state and behaviour relevant to the understanding of maturation stress generation. Then, the mechanisms proposed in the literature are listed and discussed in order to identify which can be rejected based on their inconsistency with current knowledge at the frontier between plant science and mechanical engineering.
Journal of the Royal Society Interface

hal-01392832
https://hal.archives-ouvertes.fr/hal-01392832
https://hal.archives-ouvertes.fr/hal-01392832/document
https://hal.archives-ouvertes.fr/hal-01392832/file/AlmerasClair2016_JRSInterface_Critical%20review%20on%20the%20mechanisms%20of%20maturation%20stress%20generation%20in%20trees_HAL.pdf
DOI : 10.1098/rsif.2016.0550

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Growth series of Palaeozoic fishes are rare because of the fragility of larval and juvenile specimens owing to their weak mineralisation and the scarcity of articulated specimens. This rarity makes it difficult to describe early vertebrate growth patterns and processes in extinct taxa. Indeed, only a few growth series of complete Palaeozoic fishes are available; however, they allow the growth of isolated elements to be described and individual growth from these isolated elements to be inferred. In addition, isolated and in situ scales are generally abundant and well-preserved, and bring information on (1) their morphology and structure relevant to phylogenetic relationships and (2) individual growth patterns and processes relative to species ontogeny. The Late Devonian acanthodian Triazeugacanthus affinis from the Miguasha Fossil-Lagerstä tte preserves one of the best known fossilised ontogenies of early vertebrates because of the exceptional preservation, the large size range, and the abundance of complete specimens. Here, we present morphological, histological, and chemical data on scales from juvenile and adult specimens (scales not being formed in lar-vae). Histologically, Triazeugacanthus scales are composed of a basal layer of acellular bone housing Sharpey's fibers, a mid-layer of mesodentine, and a superficial layer of ganoine. Developmentally, scales grow first through concentric addition of mesodentine and bone around a central primordium and then through superposition of ganoine layers. Onto-genetically, scales form first in the region below the dorsal fin spine, then squamation spreads anteriorly and posteriorly, and on fin webs. Phylogenetically, Triazeugacanthus scales show similarities with acanthodians (e.g. " box-in-box " growth), chondrichthyans (e.g. squamation pattern), and actinopterygians (e.g. ganoine). Scale histology and growth are interpreted in the light of a new phylogenetic analysis of gnathostomes supporting acantho-dians as stem chondrichthyans.
ISSN: 1932-6203

Droits : http://creativecommons.org/licenses/by/
hal-01526367
http://hal.upmc.fr/hal-01526367
http://hal.upmc.fr/hal-01526367/document
http://hal.upmc.fr/hal-01526367/file/journal.pone.0174655.pdf
DOI : 10.1371/journal.pone.0174655

Éditeur(s) : HAL CCSD Wiley-Blackwell
Résumé : International audience
'Alarmins' are a group of proteins or molecules that are released from cells during cellular demise to alert the host immune system. Two of them, Interleukin-33 (IL-33) and high-mobility group box-1 (HMGB1), share many similarities of cellular localization, functions and involvement in various inflammatory pathologies including hepatitis. The expressions of IL-33 and HMGB1, and their receptors ST2 and receptor for advanced glycation end products (RAGE), are substantially up-regulated during acute and chronic hepatitis. Recent data evidence a possible protective role of IL-33/ST2 axis during liver injury. A contrast in expression of IL-33 and HMGB1 alarmins were associated with type of hepatocellular death mediated by immune cells or hepato-toxic agents. The massive release of active form of IL-33 from hepatocytes may affect the recruitment and activation of its ST2-positive target immune cells in the liver to confer its alarmin functions. This review highlights the emerging roles of alarmin proteins in various liver pathologies, by focusing on classical HMGB1 and a newly discovered alarmin, the IL-33.
ISSN: 1478-3223

hal-00874209
https://hal.archives-ouvertes.fr/hal-00874209
DOI : 10.1111/j.1478-3231.2012.02802.x
PUBMED : 22530772

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Diploid budding yeast undergoes rapid mitosis when it ferments glucose, and in the presence of a non-fermentable carbon source and the absence of a nitrogen source it triggers sporulation. Rich medium with acetate is a commonly used pre-sporulation medium, but our understanding of the molecular events underlying the acetate-driven transition from mitosis to meiosis is still incomplete. We identified 263 proteins for which mRNA and protein synthesis are linked or uncoupled in fermenting and respiring cells. Using motif predictions, interaction data and RNA profiling we find among them 28 likely targets for Ume6, a subunit of the conserved Rpd3/Sin3 histone deacetylase-complex regulating genes involved in metabolism, stress response and meiosis. Finally, we identify 14 genes for which both RNA and proteins are detected exclusively in respiring cells but not in fermenting cells in our sample set, including CSM4, SPR1, SPS4 and RIM4, which were thought to be meiosis-specific. Our work reveals intertwined transcriptional and post-transcriptional control mechanisms acting when a MATa/α strain responds to nutritional signals, and provides molecular clues how the carbon source primes yeast cells for entering meiosis. Our integrated genomics study provides insight into the interplay between the transcriptome and the proteome in diploid yeast cells undergoing vegetative growth in the presence of glucose (fermentation) or acetate (respiration). Furthermore, it reveals novel target genes involved in these processes for Ume6, the DNA binding subunit of the conserved histone deacetylase Rpd3 and the co-repressor Sin3. We have combined data from an RNA profiling experiment using tiling arrays that cover the entire yeast genome, and a large-scale protein detection analysis based on mass spectrometry in diploid MATa/α cells. This distinguishes our study from most others in the field-which investigate haploid yeast strains-because only diploid cells can undergo meiotic development in the simultaneous absence of a non-fermentable carbon source and nitrogen. Indeed, we report molecular clues how respiration of acetate might prime diploid cells for efficient spore formation, a phenomenon that is well known but poorly understood.
ISSN: 1874-3919

hal-01122122
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01122122
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01122122/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01122122/file/Integrated%20RNA-%20and%20protein%20profiling%20of%20fermentation.pdf
DOI : 10.1016/j.jprot.2015.01.015

Éditeur(s) : HAL CCSD
Résumé : Designing biodiversity conservation plans requires knowledge on the biogeographic distribution of taxabut also accurate estimates of species richness and diversification processes. However, measuring the phyleticrichness can be biased by the use of inappropriate taxonomical characters, leading to erroneous speciesdelimitation and diversity estimates.This work explores the phyletic richness at several taxonomic levels (generic, specific and intraspecific) ofthe hydrozoan family Aglaopheniidae (Marktanner-Turneretscher, 1890), with a particular focus on the South-Western Indian Ocean. Firstly, using several newly constructed phylogenies based on mitochondrial andnuclear markers, this study reveals that the phyletic diversity of this family is at underestimated by at least 50%:all studied genera are polyphyletic or with doubtful monophyletic status. Then, using several speciesdelimitation methods based on molecular markers, it sheds light on the richness of cryptic diversity of thisfamily, enlightening the potential of using an integrative taxonomic approach on these morphologically simpleorganisms. Finally, the population genetics of an Aglaopheniidae brooding species shows a high populationsstructuring with pervasive pattern of isolation by distance at several geographic scales (several to thousands ofkilometres), implying a potentially high cryptic diversity existing in this family.The results of this work provide new insights on Aglaopheniidae diversity, underlining the potentialinfluence of reproductive mode on the phyletic diversity and diversification processes of brooding hydrozoanbrooders. This thesis further highlights the relevance of using several complementary
La conservation et la gestion sur le long terme de la biodiversité nécessitent une connaissance de larépartition des taxons, mais également une estimation précise de leur diversité spécifique ainsi que desprocessus de spéciation ayant permis leur formation. Cependant, la mesure de la richesse phylétique peut êtrebiaisée par l’utilisation de caractères taxinomiques ne permettant pas de délimiter les espèces de manièreappropriée.Ce travail de thèse propose d’explorer la diversité phylétique à plusieurs niveaux taxinomiques(générique, spécifique et intra-spécifique) des Aglaopheniidae, une famille d’hydrozoaires, notamment présentedans le Sud-Ouest de l’océan Indien. Dans un premier temps, en utilisant des phylogénies basées sur plusieursmarqueurs (mitochondriaux et nucléaires), ce travail démontre que la diversité phylétique de cette famille est,au minimum, sous-estimée de moitié: tous les genres de la famille sont polyphyléthiques ou présentent un statutmonophylétique restant à confirmer. Dans un deuxième temps, l’utilisation de méthodes de délimitationd’espèces basées sur des données moléculaires met en évidence la diversité cryptique très élevée des morphoespècesétudiées, révélant l’intérêt potentiel des protocoles de taxinomie intégrative chez les organismesmorphologiquement simples. Enfin, l’étude de génétique des populations d’une espèce incubatriced’Aglaopheniidae révèle l’importance de la structuration des populations et de l’isolement par la distance chezcette espèce à plusieurs échelles géographiques (de quelques kilomètres à plusieurs milliers), impliquant unepotentielle diversité cryptique extrêmement élevée chez cette famille.L’ensemble des connaissances acquises lors de ce travail de thèse fournit un nouveau regard sur ladiversité de la famille des Aglaopheniidae, soulignant le potentiel impact du cycle de reproduction sur ladiversité phylétique et les processus de spéciation des hydrozoaires incubateurs. Cette thèse met en évidence lapertinence de l’utilisation de plusieurs procédures complémentaires de délimitation d’espèces pour étudier ladiversité des organismes morphologiquement simples.
https://hal.archives-ouvertes.fr/tel-01359424

tel-01359424
https://hal.archives-ouvertes.fr/tel-01359424
https://hal.archives-ouvertes.fr/tel-01359424/document
https://hal.archives-ouvertes.fr/tel-01359424/file/These%20manuscrit%20final.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We experimentally studied the predatory behavior of Polybia rejecta (Vespidae, Polistinae, Epiponini) towards 2-88 mm-long insects attracted to a UV light trap. Foragers, which began to hunt at 6:30, selected 4-14 mm-long prey insects. Prey detection by sight by hovering wasps was confirmed using decoys. After the wasps landed and walked along a sinuous path, prey were detected by contact or from a distance (1-3cm). This was followed by seizure, stinging (contrarily to most other known cases), prey manipulation and retrieval. Prey that flew off might be caught in flight. The prey load, representing 30.7% of a forager's weight, was optimized by capturing up to six small prey or two medium-sized prey successively (both of which might be consumed in situ). The foragers cut off the wings of larger prey or cut them into two pieces and returned to gather the second piece. The handling time increased exponentially with the weight of the prey. Partial loading (i.e., retrieving a load much inferior to the maximum possible) was likely related to social facilitation, a form of nest-based recruitment that was demonstrated through the experimental elimination of local enhancement by removing foragers (both mechanisms favor the exploitation of favorable patches).
ISSN: 0376-6357

hal-01533217
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01533217
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01533217/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01533217/file/Dejean%20et%20al.%20-%20The%20predatory%20behavior%20of%20the%20Neotropical%20social%20w.pdf
DOI : 10.1016/j.beproc.2017.05.011

Éditeur(s) : HAL CCSD Institut de Géographie Alpine
Résumé : International audience
The international symposium on «Urban Growth and Natural Hazards, in particular in Developing Countries» was held in the University Blaise Pascal, Clermont-Ferrand (France) on December 2 and 3, 1994. This meeting brought together about 70 research people, Ph.D. students, and professionals from France and 12 countries, representing universities, research agencies, as well as government and private companies. The symposium aimed to gather specialized people who are engaged and acting in programmes on hazard appraisal, risk prevention and urban management in city environment. These people aimed to compare experiences acquired in two different fields: on the one hand urban growth and its consequences, and on the other hand, natural hazards and effects, in particular in Developing Countries.Half-way through the International Decade for Natural Hazard Disaster Reduction, we strove to reconcile two points of view usually distincts: nature-oriented research and society-oriented research on hazards. These convergent approaches should merge, not only to improve knowledge of natural hazards and risks, but also to cope with hazard and risk situation on a day-basis in a city. We also choose to study both approaches in Developing Countries (DC) because most of the large cities of the world already are or will be located there in near future. In addition, city location in DC coincides with tropical areas where natural hazards are most frequent threats to life, in particular in mountains, on seashores, and on active convergent plate margins. We stress the fact that the 3 following topics are often lacking in studies which have been carried out on natural hazard appraisal and management. 1) How should we include social and economical factors, and particularly a sound analysis of vulnerability of people and values at risk ? 2) How should we cope with hazard management in large cities of Developing Countries ? 3) What is the specific task of research people in hazard case studies engaged in urban environment and management?Three themes correspond to the three sessions of the symposium. (1) Natural hazards and environmental factors : inventory, diagnostic and classification, (2) Vulnerability of urban society and environment : concepts, approaches, and classification, (3) Tools for urban risk prevention and risk management in case of crisis and catastrophes.
Ce numéro de la Revue de Géographie Alpine reprend une dizaine parmi les 41 contributions exposées par des chercheurs français et étrangers lors du colloque international « Croissance urbaine et risques naturels dans les pays en développement » qui s'est déroulé à l'Université Blaise Pascal, Clermont-Ferrand, les 2 et 3 décembre 1994. L'objectif général du colloque était de rassembler les diverses compétences existant en France et à l'étranger dans le domaine de l'évaluation et de la gestion des risques naturels et de confronter les expériences acquises à l'interface entre les villes en croissance et le champ d'action des phénomènes naturels créateurs de risques. Le colloque a donc réuni des chercheurs, des doctorants et des praticiens français et leurs collègues étrangers chargés de prévention, de gestion des risques naturels et de gestion urbaine, principalement dans les grandes villes des pays en développement (P.E.D.).Parvenus à mi-chemin de la Décennie Internationale pour la Prévention des Catastrophes Naturelles, nous avons porté des regards croisés sur les approches naturalistes et sociologiques des risques naturels. Il est maintenant nécessaire de faire converger ces approches, non seulement dans la connaissance des menaces et des risques, mais dans la gestion du risque quotidien en milieu urbain. Nous avons concentré ces approches dans les pays en développement ; en effet, le site de leurs grandes villes coïncide souvent avec le champ d'action des phénomènes naturels générateurs de risques, notamment dans la zone intertropicale et en particulier dans les marges continent ales actives (par exemple autour du Pacifique).Nous avons porté l'accent sur 3 points principaux, qui semblent en partie faire défaut dans les études et les méthodes actuellement mises en oeuvre dans la gestion des risques naturels : 1) comment prendre en compte les aspects socio-économiques, en particulier les types d'analyse des vulnérabilités ? 2) comment aborder la gestion des risques en milieu urbain dans les P.E.D. ? 3) quel rôle doit jouer le chercheur en Sciences de l'Homme, de la Société et de la Terre dans les analyses, les expertises consacrées aux risques et surtout dans leur gestion globale, à la charnière des sociétés citadines précaires et des milieux « naturels » contraignants ?Les contributions ont été regroupées, exposées et discutées lors du colloque sous forme de 3 thèmes. (1) Les phénomènes naturels créateurs de dommages (= menaces) : diagnostic, inventaire et typologie, (2) Les vulnérabilités des sociétés et des espaces urbanisés : concepts, typologie et modes d'analyse, (3) Les outils d'aide à la prévention et à la gestion du risque en milieu urbain.
Colloque international : "Croissance urbaine et risques naturels dans les pays en développement"
Clermont-Ferrand, Université Blaise Pascal, France

ISBN : 0035-1121
hal-01165252
https://hal.archives-ouvertes.fr/hal-01165252

Éditeur(s) : HAL CCSD
Résumé : Evolution of organisms, genomes and genes does not strictly follow a tree-like process; symbiosis, horizontal gene transfers and gene fusions build high level composite objects with components of phylogenetically distinct origins. Such processes have been called introgressive events and are significant in evolution. They are involved in some major evolutionary transitions such as eukaryogenesis, photosynthesis acquisition in eukaryotes and the origins of major archaeal clades. Eukaryogenesis would have involved (at least) two kinds of partners: an archaeon and an alpha-proteobacterium. Photosynthetic eukaryotes arose from the integration of a cyanobacterium into a eukaryotic cell and recent findings suggested that most archaeal lineages emerged after massive acquisitions of bacterial genes. These composite lineages carry highly chimeric genomes where genes from symbiotic partners co-localize into the same genome. During my PhD thesis, I used sequence similarity networks and phylogenetic methods in order to study reticulate evolution. My research specifically focused on a previously hidden component of composite genomes: symbiogenetic genes (S genes). These chimeric genes are found in genetic mergers, and originate from the association of genes of symbiotic partners. Some association rules have been discovered. In a broad perspective, the discovery of S-genes extends the concept of genome chimerism to the within-gene level.
L'évolution des organismes, des génomes et des gènes n'est pas strictement arborescente; les symbioses, les transferts horizontaux de gènes ou encore la fusion de gènes créent des objets composites formés de parties dont les histoires évolutives sont différentes. Ces processus non arborescents sont appelés introgressifs et ont un impact non négligeable en évolution. Ils sont à l'origine de transitions évolutives majeures comme l'émergence des eucaryotes, des eucaryotes photosynthétiques ou encore de nombreux groupes d'Archaea. Dans le cas des eucaryotes, l'association et la stabilisation d'une Archaea et d'une alpha-protéobactérie a permis l'émergence d'un nouveau groupe d'organismes composites aux propriétés émergentes. L'acquisition de la photosynthèse chez les eucaryotes s'est faite via l'endosymbiose d'une cyanobactérie et, bien que débattue, l'apparition des grands groupes d'Archaea semble être concomitante avec l'acquisition de nombreux gènes d'origine bactérienne. Ces superorganismes ont la particularité d'avoir des génomes composés de gènes de différents partenaires symbiotiques. L'objectif de mon travail de thèse a constitué à étudier l'aspect introgressif de l'évolution par des méthodes de réseaux de similarité de séquence et des méthodes phylogénétiques. Je me suis particulièrement focalisé sur la détection de nouveaux gènes chimériques nommés gènes symbiogénétiques (S-gènes) car composés de parties originaires des différents partenaires symbiotiques. De tels gènes existent dans les génomes et plusieurs règles d'association ont pu être mises en évidence. Plus généralement, la présence de S-gènes étend la notion de mosaïcisme génomique au niveau infra-génique.
https://tel.archives-ouvertes.fr/tel-01536344

NNT : 2016PA066534
tel-01536344
https://tel.archives-ouvertes.fr/tel-01536344
https://tel.archives-ouvertes.fr/tel-01536344/document
https://tel.archives-ouvertes.fr/tel-01536344/file/2016PA066534.pdf

Éditeur(s) : HAL CCSD European Centre for Disease Prevention and Control
Résumé : International audience
In 2002, the French Food Safety Agency drew attention to the lack of information on the prevalence of human cryptosporidiosis in the country. Two years later, the ANOFEL Cryptosporidium National Network (ACNN) was set up to provide public health authorities with data on the incidence and epidemiology of human cryptosporidiosis in France. Constituted on a voluntary basis, ACNN includes 38 hospital parasitology laboratories (mainly in university hospitals). Each laboratory is engaged to notify new cases of confirmed human cryptosporidiosis, store specimens (e.g. stools, duodenal aspirates or biopsies) and related clinical and epidemiological data, using data sheet forms. From January 2006 to December 2009, 407 cryptosporidiosis cases were notified in France and 364 specimens were collected. Of the notified cases, 74 were children under four years of age, accounting for 18.2%. HIV-infected and immunocompetent patients represented 38.6% (n=157) and 28% (n=114) of cases, respectively. A marked seasonal pattern was observed each year, with increased number of cases in mid to late summer and the beginning of autumn. Genotyping of 345 isolates from 310 patients identified C. parvumin 168 (54.2%) cases, C. hominis in 113 (36.4%) and other species in 29 (9.4%), including C. felis (n=15), C. meleagridis (n=4), C. canis (n=4), Cryptosporidium chipmunk genotype (n=1), Cryptosporidium rabbit genotype (n=1) and new Cryptosporidium genotypes (n=4). These data represent the first multisite report of laboratory-confirmed cases of cryptosporidiosis in France.
ISSN: 1560-7917

hal-00926813
https://hal-unilim.archives-ouvertes.fr/hal-00926813
PUBMED : 20739000

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
: Previously, we demonstrated that eicosapentaenoic acid enhanced ethanol-induced oxidative stress and cell death in primary rat hepatocytes via an increase in membrane fluidity and lipid raft clustering. In this context, another n-3 polyunsaturated fatty acid, docosahexaenoic acid (DHA), was tested with a special emphasis on physical and chemical alteration of lipid rafts. Pretreatment of hepatocytes with DHA reduced significantly ethanol-induced oxidative stress and cell death. DHA protection could be related to an alteration of lipid rafts. Indeed, rafts exhibited a marked increase in membrane fluidity and packing defects leading to the exclusion of a raft protein marker, flotillin. Furthermore, DHA strongly inhibited disulfide bridge formation, even in control cells, thus suggesting a disruption of protein-protein interactions inside lipid rafts. This particular spatial organization of lipid rafts due to DHA subsequently prevented the ethanol-induced lipid raft clustering. Such a prevention was then responsible for the inhibition of phospholipase C-γ translocation into rafts, and consequently of both lysosome accumulation and elevation in cellular low-molecular-weight iron content, a prooxidant factor. In total, the present study suggests that DHA supplementation could represent a new preventive approach for patients with alcoholic liver disease based upon modulation of the membrane structures.
ISSN: 0278-6915

hal-00860153
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00860153
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00860153/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00860153/file/Sergent-et-al-incl-figures-accepted.pdf
DOI : 10.1016/j.fct.2013.07.061