Approche multi-échelle du comportement mécanique des matériaux composites SiC/SiC : comportement élastique à l'échelle du toron

National audienceUne approche multi-échelle a été entreprise afin d'obtenir un modèle prédictif du comportement mécanique des composites SiC/SiC. L'étude du comportement élastique à l'échelle du toron (microstructure poreuse et hétérogène), réalisée sur des microstructures générées à partir des résultats de la caractérisation microstructurale, met en évidence un problème de séparabilité des échelles. Néanmoins, une estimation du comportement homogène équivalent est proposée en première approximation

Effects of differentiation on purinergic and neurotensin-mediated calcium signaling in human HT-29 colon cancer cells

Calcium signaling is a key regulator of processes important in differentiation. In colon cancer cells differentiation is associated with altered expression of specific isoforms of calcium pumps of the endoplasmic reticulum and the plasma membrane, suggesting that differentiation of colon cancer cells is associated with a major remodeling of calcium homeostasis. Purinergic and neurotensin receptor activation are known regulators of cytosolic free Ca2+ levels in colon cancer cells. This study aimed to assess changes in cytosolic free Ca2+ levels in response to ATP and neurotensin with differentiation induced by sodium butyrate or culturing post-confluence. Parameters assessed included peak cytosolic free Ca2+ level after activation; time to reach peak cytosolic free Ca2+ and the EC50 of dose response curves. Our results demonstrate that differentiation of HT-29 colon cancer cells is associated with a remodeling of both ATP and neurotensin mediated Ca2+ signaling. Neurotensin-mediated calcium signaling appeared more sensitive to differentiation than ATP-mediated Ca2+ signaling. (c) 2013 Elsevier Inc. All rights reserved

Optimisation de l'extraction, en réacteur "batch", de biomasse énergétique à l'aide d'émulsions ultrasoniques de solvants verts

L’industrie des biocarburants de deuxième génération utilise, entre autre, la biomasse lignocellulosique issue de résidus forestiers et agricoles et celle issue de cultures énergétiques. Le sorgho sucré [Sorghum bicolor (L.) Moench] fait partie de ces cultures énergétiques. L’intérêt croissant de l’industrie agroalimentaire et des biocarburants pour cette plante est dû à sa haute teneur en sucres (jusqu’à 60% en masse sèche). En plus de se développer rapidement (en 5-6 mois), le sorgho sucré a l’avantage de pouvoir croître sur des sols pauvres en nutriments et dans des conditions de faibles apports en eau, ce qui en fait une matière première intéressante pour l’industrie, notamment pour la production de bioéthanol. Le concept de bioraffinerie alliant la production de biocarburants à celle de bioénergies ou de bioproduits est de plus en plus étudié afin de valoriser la production des biocarburants. Dans le contexte d’une bioraffinerie exploitant la biomasse lignocellulosique, il est nécessaire de s’intéresser aux différents métabolites extractibles en plus des macromolécules permettant la fabrication de biocarburants et de biocommodités. Ceux-ci pouvant avoir une haute valeur ajoutée et intéresser l’industrie pharmaceutique ou cosmétique par exemple. Les techniques classiques pour extraire ces métabolites sont notamment l’extraction au Soxhlet et par macération ou percolation, qui sont longues et coûteuses en énergie. Ce projet s’intéresse donc à une méthode d’extraction des métabolites primaires et secondaires du sorgho sucré, moins coûteuse et plus courte, permettant de valoriser économiquement l’exploitation industrielle du de cette culture énergétique. Ce travail au sein de la CRIEC-B a porté spécifiquement sur l’utilisation d’une émulsion ultrasonique eau/carbonate de diméthyle permettant de diminuer les temps d’opération (passant à moins d’une heure au lieu de plusieurs heures) et les quantités de solvants mis en jeu dans le procédé d’extraction. Cette émulsion extractive permet ainsi de solubiliser à la fois les métabolites hydrophiles et ceux hydrophobes. De plus, l’impact environnemental est limité par l’utilisation de solvants respectueux de l’environnement (80 % d’eau et 20 % de carbonate de diméthyle). L’utilisation de deux systèmes d’extraction a été étudiée. L’un consiste en la recirculation de l’émulsion, en continu, au travers du lit de biomasse; le deuxième permet la mise en contact de la biomasse et des solvants avec la sonde à ultrasons, créant l’émulsion et favorisant la sonolyse de la biomasse. Ainsi, en réacteur « batch » avec recirculation de l’émulsion eau/DMC, à 370 mL.min[indice supérieur -1], au sein du lit de biomasse, l’extraction est de 37,91 % en 5 minutes, ce qui est supérieur à la méthode ASTM D1105-96 (34,01 % en 11h). De plus, en réacteur « batch – piston », où la biomasse est en contact direct avec les ultrasons et l’émulsion eau/DMC, les meilleurs rendements sont de 35,39 % en 17,5 minutes, avec 15 psig de pression et 70 % d’amplitude des ultrasons. Des tests effectués sur des particules de sorgho grossières ont donné des résultats similaires avec 30,23 % d’extraits en réacteur « batch » avec recirculation de l’émulsion (5 min, 370 mL.min[indice supérieur -1]) et 34,66 % avec le réacteur « batch-piston » (30 psig, 30 minutes, 95 % d’amplitude)

IL22 (interleukin 22)

Review on IL22 (interleukin 22), with data on DNA, on the protein encoded, and where the gene is implicated

Modulation of the texture of emulsified and acidified model systems by the addition of protein aggregates

Modulation of the texture of emulsified and acidified model systems by the addition of protein aggregates. Colloque Biopolymers 201

Gene Methylation and Silencing of WIF1 Is a Frequent Genetic Abnormality in Mantle Cell Lymphoma

We have previously shown that the Wnt canonical pathway (WCP) is constitutively active in most cases of mantle cell lymphoma (MCL). Here, we aimed to elucidate the mechanisms underlying this biochemical deregulation. We hypothesized that gene methylation/silencing of WIF1 (Wnt inhibitory factor-1), a physiologic inhibitor of WCP, contributes to the deregulation of WCP and promotes cell growth in MCL. In support of this hypothesis, we found that the expression of WIF1 was detectable in none of the 4 MCL cell lines, and in only 2 of 5 tumors (40%) examined. Using methylation-specific PCR, we found evidence of gene methylation of WIF1 in 4 of 5 cell lines (80%) and in 24 of 29 (82%) tumors. The addition of the demethylation agent 5-aza-2′-deoxycytidine to Mino and JeKo-1, two WIF1-negative cell lines, restored the expression of WIF1 mRNA in these cells. Gene transfection of WIF1 into JeKo-1 and Mino cells significantly reduced cell growth, and this finding correlated with substantial downregulations of various proteins in WCP, such as β-catenin and pGSK-3β. In conclusion, our results support the concept that gene methylation/silencing of WIF1 is a frequent event in MCL, and this abnormality contributes to the aberrant activation of WCP. These results have provided further evidence that aberrant Wnt signaling is pathogenetically important in MCL and it may represent a potential therapeutic target.publishedVersio

The stress response in Atlantic salmon (Salmo salar L.): identification and functional characterization of the corticotropin-releasing factor (crf) paralogs

Corticotropin-Releasing Factor (CRF) is one of the main mediators of the Hypothalamic-Pituitary–Interrenal (HPI) axis to stress response. In Atlantic salmon, a comparative understanding of the crf1 paralogs role in the stress response is still incomplete. Our database searches have identified four crf1 genes in Atlantic salmon, named crf1a1, crf1a2, crf1b1 and crf1b2. Brain distribution analysis revealed that the four crf1 paralogs were widely distributed, and particularly abundant in the telencephalon, midbrain, and hypothalamus of Atlantic salmon post-smolts. To increase the knowledge on crf1-mediated response to stress, Atlantic salmon post-smolts were exposed to either repeated chasing, hypoxia or a combination of chasing and hypoxia for eight days, followed by a novel-acute stressor, confinement. Cortisol, glucose, lactate, and creatinine levels were used as markers for the stress response.publishedVersio

Impact of long-term fasting on the stomach-hypothalamus appetite regulating genes in Atlantic salmon postsmolts

Atlantic salmon will experience periods of fasting during its lifecycle. In nature, prolonged fasting periods occur owing to seasonal fluctuations in available feeds, migration or in relation to reproduction. In a culture setting, salmon is fasted mainly as part of planned operational handling prior to vaccination, delousing, transfer etc., and where fasting may last up to nine days. The mechanisms regulating the appetite during long-term fasting may vary among fish species. Here, we studied the impact of long-term fasting on neuro-endocrine regulation of appetite through the stomach-hypothalamic axis in Atlantic salmon post smolts (1.2 kg, ∼46 cm), reared in two experimental conditions (Fed and Fasted; triplicated tanks), and sampled after 4 weeks and 6 weeks of fasting. Fasted fish showed lower condition factor and hepatosomatic index at both sampling points compared to Fed group. In qPCR analysis, hypothalamic relative mRNA expression of agouti-related protein 1 (agrp1) was upregulated in fasted group at both sampling points. Among neuropeptide Y (npy) paralogs, only npya1 at 4 weeks was upregulated by fasting. As for cocaine- and amphetamine-regulated transcripts (cart), cart2a was elevated at 4 weeks, and cart2b at both 4 and 6 weeks in fasted group, while cart3a and cart4 showed no response to fasting. The pro-opiomelanocortin (pomc) a1, a2 and melanocortin-4 receptor (mc4r) a2 increased only after 6 weeks of fasting, while mc4rb1 did not respond to fasting. In stomach, 6 weeks of fasting resulted in a decrease of ghrelin1 (ghrl1), while expression of mboat4 was unaffected. The elevated levels of hypothalamic agrp1 and npya1 in fasted group support orexigenic roles for these neuropeptides. In addition, upregulation of cart2a, cart2b, pomca1 and pomca2 indicate that these play vital roles in appetite regulation and that fasting may halt and/or counteract hunger signals (agrp1 and npya1) to save energy from foraging search activities during catabolic conditions. Another possibility is that these neuropeptides play a role in fasting-induced stress. Based on the drop in mRNA expression of ghrl under catabolic conditions, we hypothesize that Ghrl might return as hunger signal once feed becomes available. We also propose that agrp1 is a potential appetite biomarker gene under feed deprived conditions.publishedVersio

Publisher Correction:A DHODH inhibitor increases p53 synthesis and enhances tumor cell killing by p53 degradation blockage

The original PDF version of this Article listed the authors as "Marcus J.G.W. Ladds," where it should have read "Marcus J. G. W. Ladds, Ingeborg M. M. van Leeuwen, Catherine J. Drummond et al.#". Also in the PDF version, it was incorrectly stated that "Correspondence and requests for materials should be addressed to S. Lín.", instead of the correct "Correspondence and requests for materials should be addressed to S. Laín." This has been corrected in the PDF version of the Article. The HTML version was correct from the time of publication.</p