Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The mycotoxin alternariol (AOH), a frequent contaminant in fruit and grain, is known to induce cellular stress responses such as reactive oxygen production, DNA damage and cell cycle arrest. Cellular stress is often connected to autophagy, and we employed the RAW264.7 macrophage model to test the hypothesis that AOH induces autophagy. Indeed, AOH treatment led to a massive increase in acidic vacuoles often observed upon autophagy induction. Moreover, expression of the autophagy marker LC3 was markedly increased and there was a strong accumulation of LC3-positive puncta. Increased autophagic activity was verified biochemically by measuring the degradation rate of long-lived proteins. Furthermore, AOH induced expression of Sestrin2 and phosphorylation of AMPK as well as reduced phosphorylation of mTOR and S6 kinase, common mediators of signaling pathways involved in autophagy. Transmission electron microscopy analyzes of AOH treated cells not only clearly displayed structures associated with autophagy such as autophagosomes and autolysosomes, but also the appearance of lamellar bodies. Prolonged AOH treatment resulted in changed cell morphology from round into more star-shaped as well as increased β-galactosidase activity. This suggests that the cells eventually entered senescence. In conclusion, our data identify here AOH as an inducer of both autophagy and senescence. These effects are suggested to be to be linked to AOH-induced DSB (via a reported effect on topoisomerase activity), resulting in an activation of p53 and the Sestrin2-AMPK-mTOR-S6K signaling pathway.
ISSN: 0300-483X

hal-01117627
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01117627
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01117627/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01117627/file/Autophagy%20and%20senescence_accepted.pdf
PUBMED : 25456271

Éditeur(s) : HAL CCSD
Résumé : soutenue le 09 juin 2008
Intrinsic tribological properties of lamellar compounds are usually attributed to the presence of van der Waals gap in their structure. The controled variation of the graphite's crystal and electronic structure by intercalation processes of different species (electrophile, nucleophile ...) give a possibility to study in a more deeply way the friction reduction processes for low dimensional compounds. Three groups of intercalant are studied and tribological properties are correlated to structural and chemical evolutions.
Les propriétés tribologiques intrinsèques des composés lamellaires sont généralement attribuées à la présence de gap de van der Waals dans leur structure. La possibilité de faire varier de manière contrôlée la structure cristalline et la structure électronique du graphite par processus d'intercalation de différentes espèces chimiques (électrophile, nucléophile ...) sont utilisées pour étudier de façon plus approfondie les processus de réduction du frottement par les composés de basse dimensionnalité. Trois familles d'intercalants sont étudiées et les propriétés tribologiques sont corrélées aux évolutions structurales et chimiques.
https://tel.archives-ouvertes.fr/tel-00431713

Droits : info:eu-repo/semantics/OpenAccess
tel-00431713
https://tel.archives-ouvertes.fr/tel-00431713
https://tel.archives-ouvertes.fr/tel-00431713/document
https://tel.archives-ouvertes.fr/tel-00431713/file/These-DELBE_Karl.pdf

Éditeur(s) : HAL CCSD
Résumé : International audience
It is classically admitted that the goodfriction properties of lamellar compounds are strongly related to their anisotropic structure and especially to the existence of weak interlayer interactions through the van der Waals gap separating the basal layers. As it is also known, the presence of the van der Waals gap in the structure of lamellar compounds will allow lot of chemical species to be intercalated in the structure leading both to the expansion of structure parameters and inter layer interactions modifications. The present work is concerned with the experimental and theoretical study of friction propertiesof Graphite Intercalated Compounds (GICs) in order to better understand thetribologiclamellar compounds. In order to modulate the interlayer interactions, two types of intercalated species were used, electrophylic species (AlCl3, FeCl3, SbCl5) and nucleophilic species (Li, K, Rb).
40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013
Lyon, France

Droits : info:eu-repo/semantics/OpenAccess
hal-00926509
https://hal.archives-ouvertes.fr/hal-00926509
https://hal.archives-ouvertes.fr/hal-00926509/document
https://hal.archives-ouvertes.fr/hal-00926509/file/Delbe_9781.pdf
OATAO : 9781

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Intrinsic tribological properties of lamellar compounds are usually attributed to the presence of van der Waals gaps in their structure through which interlayer interactions are weak. The controlled variation of the distances and interactions between graphene layers by intercalation of electrophilic species in graphite is used in order to explore more deeply the friction reduction properties of low-dimensional compounds. Three graphite intercalation compounds with antimony pentachloride, iron trichloride and aluminium trichloride are studied. Their tribological properties are correlated to their structural parameters, and the interlayer interactions are deduced from ab initio bands structure calculations.
ISSN: 1023-8883

hal-00767639
https://hal.archives-ouvertes.fr/hal-00767639
https://hal.archives-ouvertes.fr/hal-00767639/document
https://hal.archives-ouvertes.fr/hal-00767639/file/Delbe_6330.pdf
DOI : 10.1007/s11249-012-9981-0

Éditeur(s) : HAL CCSD
Résumé : International audience
In boundary lubrication regime, friction reduction and antiwear processes are associated to the presence of additives in the lubricating oils or greases. These processes are due to the formation of protective tribofilms resulting from chemical reactions between the additives and the sliding surfaces, in the physico-chemical conditions of the sliding contact. Conventional antiwear additives mainly consist of transition metal organo phosphate or thiophosphates which present a remarkable efficiency in the case of contacts between ferrous alloys. In the case of non reacting surfaces, these additives become inactive. Recently developped lubrication strategies consist in the use of dispersion in oils of nano additives able to build the protective tribofilm in the sliding contact without reaction with the surfaces. Carbon fluorinated phases, due to their lamellar structure and their high chemical stability even at relatively high temperature (400°C) represent interesting candidates as lubricant nano-additives subjected to present friction reduction, anti wear and anti corrosion actions. This work presents the tribologic behaviour of some carbon fluorinated derivatives such as graphite fluorides, fluorinated carbon nanofibers, fluorinated carbon nanodiscs and fluorinated carbon blacks. The influence, on the tribologic performances, of the structure of the initial carbon phases, of the fluorination rate (0
World Tribology Congress 2013
Torino, Italy

Droits : info:eu-repo/semantics/OpenAccess
hal-00926514
https://hal.archives-ouvertes.fr/hal-00926514
https://hal.archives-ouvertes.fr/hal-00926514/document
https://hal.archives-ouvertes.fr/hal-00926514/file/Delbe_9783.pdf
OATAO : 9783

Éditeur(s) : HAL CCSD
Résumé : International audience
Abstract View references (38)This work presents a facile, scalable method for the fabrication of graphene oxide-iron oxide (GO-Fe3O4) nanocomposites produced by co-precipitation of iron ions onto the GO surfaces in basic aqueous media. FTIR and XRD characterisation suggests that Fe3O4 was chemically anchored to the GO sheets, possibly via the carboxyl and hydroxyl groups. Small GO loadings of 0.5 and 1 wt% were not sufficient to alter the Fe3O4 structures. However, increasing the GO loading to 5 and 10 wt% resulted in significant loss in pore volume, thus suggesting the lamellar GO sheets decorated with Fe3O4 were assembling into GO-Fe3O4 nanocomposite stacks. It was found that the GO-Fe3O4 nanocomposites had an enhanced catalytic activity in the heterogeneous Fenton-like oxidation of Acid Orange 7 (AO7) compared to pure GO flat sheets and Fe3O4 nanoparticles. Interestingly, the GO-Fe3O4 nanocomposite with 5 wt% loading ratio exhibited the best catalytic activity with 76% degradation of AO7 dye observed within 90 min of reaction. This was attributed to the synergistic effect of GO by enriching the adsorbed AO7 molecules onto the nanocomposite to be further oxidised in the vicinities of active sites. This finding suggests the promising employment of GO-Fe3O4 nanocomposites in removing organic dyes from polluted water by heterogeneous Fenton-like reaction. © 2014 by American Scientific Publishers.
SCIENCE OF ADVANCED MATERIALS

hal-01683207
https://hal.univ-antilles.fr/hal-01683207
DOI : 10.1166/sam.2014.1812

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
The extinct Odontopterygiformes are the sole birds known to possess strong and sharp bony pseudoteeth, the shape and location of which are closely mimetic of real teeth. The structure of the pseudoteeth is investigated here in a late Pliocene/early Pleistocene species, Pelagornis mauretanicus, using X-ray microtomography and thin sections. The results are interpreted with regard to the pseudotooth mode of growth, and have implications concerning aspects of Pelagornis ecology. The larger pseudoteeth are hollow and approximately cone-shaped, and the smaller ones are rostro-caudally constricted. The walls of pseudoteeth are composed of bone tissue of the fibro-lamellar type, which is intensively remodeled by Haversian substitution. The jaw bones display the same structure as the pseudoteeth, but their vascular canals are oriented parallel to the long axis of the bones, whereas they are perpendicular to this direction in the pseudoteeth. There is no hiatus or evidence of a fusion between the pseudoteeth and the jaw bones. Two possible models for pseudotooth growth are derived from the histological data. The most plausible model is that pseudotooth growth began after the completion of jaw bone growth, as a simple local protraction of periosteal osteogenic activity. Pseudotooth development thus occurred relatively late during ontogeny. The highly vascularized structure and the relative abundance of parallel-fibered bone tissue in the pseudoteeth suggest poor mechanical capabilities. The pseudoteeth were most likely covered and protected by the hardened, keratinized rhamphotheca in the adult during life. The late development of the pseudoteeth would involve a similarly late and/or partial hardening of the rhamphotheca, as displayed by extant Anseriformes, Apterygiformes and some Charadriiformes. This would add support to the hypothesis of a close phylogenetic relationship between Odontopterygiformes and Anseriformes. The late maturation of the Pelagornis feeding apparatus, and hence the delayed capability for efficient prey catching, suggests that Pelagornis was altricial.
ISSN: 1932-6203

hal-01545486
https://hal.archives-ouvertes.fr/hal-01545486
DOI : 10.1371/journal.pone.0080372

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
In order to progress in the understanding of mechanical stress generation, the mesoporosity of the cell wall and its changes during maturation of poplar (Populus deltoides x P. nigra) tension wood (TW) and opposite wood (OW) were measured by nitrogen adsorption–desorption. Variations in the thickness of the gelatinous layer (G-layer) were also measured to clarify whether the mesoporosity change simultaneously with the deposition of the G-layer in TW. Results show that mesoporous structures of TW and OW were very similar in early development stages before the deposition of G-layers. With the formation of the S2 layer in OW and the G-layer in TW, the mesopore volume decreased steeply before lignification. However, in TW only, the decrease in mesopore volume occurred together with the pore shape change and a progressive increase in pore size. The different patterns observed in TW revealed that pores from G-layers appear with a different shape compared to those of the compound middle lamella, and their size increases duringthe maturation process until stabilising in mature wood. This observation strongly supports the hypothesis of the swelling of the G-layer matrix during maturation as the origin of maturation stress in poplar tension wood.
ISSN: 0028-646X

hal-01081834
https://hal.archives-ouvertes.fr/hal-01081834
https://hal.archives-ouvertes.fr/hal-01081834/document
https://hal.archives-ouvertes.fr/hal-01081834/file/Chang_al_Mesoporosity_changes_New-Phyto._2015.pdf
DOI : 10.1111/nph.13126

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The mycotoxin enniatin B (EnnB) is predominantly produced by species of the Fusarium genera, and often found in grain. The cytotoxic effect of EnnB has been suggested to be related to its ability to form ionophores in cell membranes. The present study examines the effects of EnnB on cell death, differentiation, proliferation and pro-inflammatory responses in the murine monocyte-macrophage cell line RAW 264.7. Exposure to EnnB for 24 h caused an accumulation of cells in the G0/G1-phase with a corresponding decrease in cyclin D1. This cell cycle-arrest was possibly also linked to the reduced cellular ability to capture and internalize receptors as illustrated by the lipid marker ganglioside GM1. EnnB also increased the number of apoptotic, early apoptotic and necrotic cells, as well as cells with elongated spindle-like morphology. The Neutral Red assay indicated that EnnB induced lysosomal damage; supported by transmission electron microscopy (TEM) showing accumulation of lipids inside the lysosomes forming lamellar structures/myelin bodies. Enhanced levels of activated caspase-1 were observed after EnnB exposure and the caspase-1 specific inhibitor ZYVAD-FMK reduced EnnB-induced apoptosis. Moreover, EnnB increased the release of interleukin-1 beta (IL-1β) in cells primed with lipopolysaccharide (LPS), and this response was reduced by both ZYVAD-FMK and the cathepsin B inhibitor CA-074Me. In conclusion, EnnB was found to induce cell cycle arrest, cell death and inflammation. Caspase-1 appeared to be involved in the apoptosis and release of IL-1β and possibly activation of the inflammasome through lysosomal damage and leakage of cathepsin B.
ISSN: 0041-008X

inserm-00871698
http://www.hal.inserm.fr/inserm-00871698
DOI : 10.1016/j.taap.2012.03.014
PUBMED : 22483798