The outer-membrane protease family of omptins in Uropathogenic «Escherichia coli»

Uropathogenic Escherichia coli (UPEC) causes approximately 85% of community acquired urinary tract infections (UTIs). In order to cause infection in the urinary tract, UPEC must overcome innate immune defenses such as antimicrobial peptides (AMPs). Antimicrobial peptides have both antibacterial and immunomodulatory properties that keep the bladder epithelium free of bacterial colonization. OmpT, an outer-membrane protease that plays a role in AMP resistance, has previously been identified as a UPEC virulence factor. We assessed OmpT activity in a collection of 58 UPEC clinical isolates of increasing disease severities. The activity was significantly higher in symptomatic groups compared to fecal isolates. Since the ompT gene is present in 85-97% of UPEC clinical isolates, we screened for the presence of ompT and other possible members of the OmpT subfamily such as ompP and arlC. This screen revealed the presence of arlC in eight symptomatic isolates while ompP was not found in any isolates. Heterogeneity of OmpT activity was due to differential gene expression of both ompT and arlC in clinical isolates causing cystitis. Furthermore, OmpT and ArlC showed different substrate specificities towards known AMPs of the urinary tract. Finally, arlC, and potentially ompP, should also be included as UPEC virulence genes and be screened for in newly isolated bacterial strains.Les Escherichia coli uropathogènes causent approximativement 85% des infections urinaires acquises dans la communauté. Pour causer des infections urinaires, les E. coli uropathogènes doivent surmonter les défenses innées du système immunitaire telles que les peptides antimicrobiens. Les peptides antimicrobiens ont à la fois des propriétés antimicrobiennes et des propriétés immunomodulatoires. OmpT, une protéase de la membrane externe qui joue un rôle dans la défense contre les peptides antimicrobiens, a précédemment été identifiée comme un facteur de virulence chez les E. coli uropathogènes. Nous avons évalué l’activité de la protéase OmpT dans une collection de 58 isolats cliniques causant des infections de sévérité croissante. L’activité était signicativement plus élevée dans les groupes symptomatiques comparativement aux isolats provenant des excréments. Étant donné que le gène ompT est présent dans 85-97% des E. coli uropathogènes, nous avons investigué pour la présence de ce gène ainsi que pour la présence des autres membres de la famille OmpT tels qu’ ompP et arlC. Ce dépistage a révélé la présence de arlC dans huit isolats symptomatiques alors que ompP n’as pu être repéré dans aucun isolat de notre collection. L’ hétérogénétité de l’activité de OmpT est due à la différente expression des gènes ompT et arlC dans les isolats cliniques causant des cystites. En outre, OmpT et ArlC ont démontrés différentes spécificités de substrat envers des peptides antimicrobiens connus des voies urinaires. Finalement, arlC, et potentiellement ompP, devraient être inclus dans la caractérisation des E. coli uropathogènes en tant que gènes de virulence

Etude de l'hygroexpansion du carton plat par une méthode de corrélation d'images obtenues par MEB environnemental et microtomographie aux rayons X = Analysis of paperboard hygroexpansion by digital correlation of images obtained by ESEM and X-ray microtomography

National audienceLe carton plat est un matériau stratifié. Ses couches ont une structure anisotrope et sont formées par des fibres de bois issues de pâtes à papier de différents types. Au cours de sa transformation et de son utilisation, le carton plat est soumis à des variations d'humidité relative de l'air ambiant. Celles-ci peuvent occasionner des problèmes de stabilité dimensionnelle telles que des pertes de planéité du carton et une décohésion de ses couches. Ce phénomène est anisotrope. Assez bien décrit dans le plan, mais assez peu selon l'épaisseur du carton, il est ici étudié au moyen d'outils classiques donnant accès à des coefficients d'hygroexpansion macroscopiques selon les directions d'anisotropie du carton. Une analyse, plus fine, par méthode de corrélation d'images, obtenues par MEB environnemental ou microtomographie aux rayons X au cours desquels l'humidité relative a été contrôlée, a permis de déterminer les champs de déformation hygroscopiques au travers de l'épaisseur du carton. Ceux-ci présentent de fortes hétérogénéités qui peuvent être reliées à une évolution spécifique de la porosité de certaines couches. Par ailleurs, il est possible de distinguer un comportement différent des couches selon la nature de leurs fibres, fonction des caractéristiques des pâtes chimiques ou mécaniques dont elles proviennent

Transfert d'aluminium (cas des matériaux pour contact alimentaire)

L aluminium est le 3ème élément présent à la surface de la terre et le plus utilisé dans l industrie, ainsi que dans le monde de la fabrication des ustensiles de cuisine et des emballages alimentaires, en particulier pour leur stockage et leur préparation. L exposition de l homme est donc inévitable et chaque jour, des taux modérés de ce métal pénètrent dans l organisme et sont capables de s accumuler dans certains organes. Longtemps considérée comme inoffensif, l aluminium est considéré aujourd hui comme un métal toxique. Le but de notre étude a été de vérifier s il y avait une migration de l aluminium dans les aliments, lors de leur stockage ou de leur cuisson, dans des matériaux à base d aluminium ; d évaluer la dose libérée d aluminium, et de la comparer à la dose maximum admissible pour préserver la santé des populations afin d apprécier si cette utilisation domestique de l aluminium pouvait présenter un risque toxique potentiel en santé publique. Nous avons confirmé la libération de l aluminium mise en contact avec des molécules chélatrices, présentes dans les aliments et testées en milieu simple ; et nous avons montré que cette solubilisation pouvait être très importante et était fonction de la nature de la molécule chélatrice, de sa concentration, de sa forme chimique et surtout de la température. Les formes salifiés étudiées (sels de K+, Na+ et Li+ de l acide citrique, de l acide oxalique et de l acide lactique) nous ont permis de comprendre comment la modification d une molécule pouvait changer la libération de l aluminium soit par modification du pH, soit par modification de la réactivité. Nous avons également évalué l impact de la matrice alimentaire sur la quantité d aluminium relarguée à partir d ustensiles de cuisine utilisés pour la conservation ou la cuisson. Différents aliments, ont été sélectionnés en fonction de leur composition en molécules chélatrices de l aluminium. Le relargage de l aluminium est fonction de l aliment, de la localisation du prélèvement de l échantillon, de la température, du temps et du type de contenant. En confrontant nos résultats aux différentes données de la littérature et en les intégrant dans le contexte des apports quotidiens et des limites de sécurité nous avons essayé de modéliser l implication de l aluminium, en fonction des quantités relarguées, dans notre nutrition. Ce travail nous a permis d identifier d éventuelles habitudes à risque, de proposer des recommandations concernant l utilisation des ustensiles de cuisine en aluminium, de proposer un modèle cinétique et de découvrir une méthode de prétraitement permettant de réduire le transfert d aluminium.Aluminium is the third element present at the surface of the earth and more used in industry, like the world of manufacture of the kitchen utensils and food packing, in particular for their storage and their preparation. Thus, the exposure of the man is inevitable and each day, the moderate rates of this metal penetrate in the organism and be able to accumulate in certain organs. For long time was as inoffensive, aluminium is today as a toxic metal. The aim of our study is to check if there are a migration of aluminium in food, at the time of their storage, or their cooking, in materials based on aluminium; to evaluate the released aluminium amount, and to compare it with the permissible maximum amount to preserve pubic health in order to appreciate if this use domesticates aluminium could present a potential toxic risk in public health. We confirmed the release of aluminium put in contact with molecules chelating, present in food and tested in simple medium; and we showed that this solubilization could be very important and was a function of the nature of the chelating molecule, its concentration, its chemical form and especially of the temperature. The studied salts forms (salts of K+, Na+ and Li+ of the citric acid, the oxalic acid and the lactic acid) enabled us for understand how the modification of a molecule could change the release of aluminium either by modification of the pH, or by modification of the reactivity. We also evaluated the impact of the food matrix on the quantity of aluminium leaching starting from kitchen utensils used for the storage or cooking. Various foods are selected according to their composition in chelating molecules of aluminium. The release of aluminium is a function of food, localization, temperature, time and the type sampling of container. By confronting our results with the various data of the literature and by integrating them in the context of the daily contributions and the safety limits we tried to model the implication of aluminium, according to the released quantities, in our nutrition. This work enabled us to identify possible practices at the risk, to propose recommendations concerning the use of the kitchen utensils of aluminium, to propose a kinetic model and to discover a pretreatment method for reducing the leachability of aluminium.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Microfibrillated cellulose coatings as new release systems for active packaging

International audienceIn this work, a new use of microfibrillated cellulose (MFC) is highlighted for high-added-value applications. For the first time, a nanoporous network formed by MFC coated on paper is used for a controlled release of molecules. The release study was carried out in water with caffeine as a model molecule. The release process was studied by means of (i) continuous, and (ii) intermittent diffusion experiments (with renewal of the medium every 10 min). The effect of the MFC was first observed for the samples impregnated in the caffeine solution. These samples, coated with MFC (coat weight of about 7 g/m2), released the caffeine over a longer period (29 washings compared with 16), even if the continuous diffusions were similar for both samples (without and with MFC coating). The slowest release of caffeine was observed for samples coated with the mixture (MFC + caffeine). Moreover, the caffeine was only fully released 9 h after the release from the other samples was completed.This study compared two techniques for the introduction of model molecules in MFC-coated papers. The latter offers a more controlled and gradual release. This new approach creates many opportunities especially in the food-packaging field. A similar study could be carried out with an active species

A simple pre-treatment of aluminium cookware to minimize aluminium transfer to food

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Microfibrillated cellulose – Its barrier properties and applications in cellulosic materials: A review

International audienceInterest in microfibrillated cellulose (MFC) has been increasing exponentially. During the last decade, this bio-based nanomaterial was essentially used in nanocomposites for its reinforcement property. Its nano-scale dimensions and its ability to form a strong entangled nanoporous network, however, have encouraged the emergence of new high-value applications. In previous years, its mode of production has completely changed, as many forms of optimization have been developed.New sources, new mechanical processes, and new pre- and post-treatments are currently under development to reduce the high energy consumption and produce new types of MFC materials on an industrial scale. The nanoscale characterization possibilities of different MFC materials are thus increasing intensively. Therefore, it is critical to review such MFC materials and their properties. Moreover, very recent studies have proved the significant barrier properties of MFC. Hence, it is proposed to focus on the barrier properties of MFC used in films, in nanocomposites, or in paper coating

Printing stiffeners on the surface of corrugated boards: a bio-inspirated approach to lighten packaging and optimize resource consumption

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Steel versus Paper : The Conservation of a Piece of Modern Art Consisting of a Rust Print on Paper

International audienceThe experimentation with new ideas and techniques in contem-p o r a ry art can lead to substantial conservation issues in the near f u t u re, especially when the artist tries to fuse two incompatible materials into one object. This is the case with the 'Print of thre e rusted iron plates', created by the French contemporary art i s t B e rn a rd Pagès and now in the Museum of Modern Art, Saint Etienne, France. Although contemporary, this print alre a d y shows serious damage caused by the presence of iron in the p a p e r. It was so brittle that it could no longer be handled nor be displayed. This type of artefact raises fundamental questions for paper conservators: its degradation is extremely rapid and inherent to the combination of its constituents (iron compounds and paper) that obviously cannot be separated. It also necessitates investigation into the possibilities of using available chemical t reatments in order to limit the degradation mechanisms while keeping in mind that the visual appearance should re m a i n unchanged. Historical Background 'Print of three rusted iron plates' is one of the series of prints and drawings created in the 1970's by Bern a rd Pagès while he was working under the influence of the avant-garde, Support s / S u r-faces' gro u p (Abadie 1999; Exhibition catalogue, 19 91, 2002). A s an established sculptor, he worked with raw materials and tried to escape from personal expression by using printing methods that place the object in the centre of the creation process. These methods consisted of etching a hydrochloric acid solution on steel plates in order to encourage the formation of rust. These plates were then pressed on the paper, producing prints of ru s t. F i n a l l y, the artwork was completed with graphite pencil and black ink lines that emphasised the borders of the central plate (Fig 1). Description of the Arte f a c t F rom a chemical point of view, the work is in fact a thick ru s t layer embedded in a contemporary wove paper, commonly known as 'Vélin d'Arches' and manufactured by C a n s o n. One edge features a watermark, 'Dessin-Ja-Arches-France'. The paper is now very brittle and fractured in many places. Two pieces are missing. The sharpness of the edges shows that the frac-t u res are due to loss of paper flexibility. Raking light observ a t i o n revealed undulations. Unprinted areas are light brown and hig-' E m p reinte de trois plaques de fer rouillées' (Print of three ru s t e d i ron plates) was produced in the 1970's by the artist Bern a rd Pagès according to a specific protocol: steel plates were etched with a hydrochloric acid solution then pressed onto paper to create ru s t prints. Although contemporary, this work of art already shows serious damage caused by the presence of iron in the paper. Various conservation treatment possibilities were explored to pre-s e rve the artefact. Replicas were made and used to evaluate the dif-f e rent options. The application of the calcium phytate tre a t m e n t , initially developed for iron gall ink corroded manuscripts, was investigated and it turned out to be efficient in preventing degradation of the replicas. The addition of alcohol to the treatment solutions was also considered, but was eventually not tested, as it tends to decrease the treatment effectiveness. It was finally decided to use pure aqueous solutions and to float the artefact during the treatment. The treatment was undertaken twice without inducing any visual changes to the artefact. Some free iron (II) still remained in the paper after treatment but to a much lesser extent than before treatment. This suggests that the intervention was at least partially effective. As the artefact re q u i red consolidation and lining, the capabilities of several commonly used adhesives that change paper sensitivity to water were evaluated and compare d. Gelatine was finally chosen for consolidation as it renders the paper the most hydrophobic compared with starch, hydro x y p ro-pylcellulose or methylcellulose. After lining, the artefact was mounted in a frame specially designed for safe display

Antibacterial paperboard packaging using microfibrillated cellulose

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