Phylogeny of Efflux-Mediated Tetracycline Resistance Genes and Related Proteins Revisited

A SRS search in the GenBank/EMBL databases for entire genes encoding efflux-mediated resistance allocated to a recognized tetracycline determinant revealed the existence of at least 87 genes. DNA-based and protein sequence analyses of representatives from the different efflux-mediated tetracycline determinant groups were performed and allowed us to propose a revision of the current grouping on the basis of our new evolutionary trees. On the other hand, similarity, topology, and hydropathy analyses of some representatives from 12-transmembrane segments (TMS) and 14-TMS proteins lead us to perform meaningful sequence alignments of recognized or putative 12-TMS and 14-TMS proteins truncated to their first 200 amino acids (α-domain of the protein). For all aligned truncated proteins, including old and recently discovered tetracycline resistance determinants, significant similarities along this segment were demonstrated and three new conserved motifs identified, reinforcing the hypothesis of a common ancestry for the α-domain of all tetracycline-efflux pumps.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Le « génie orienté produit » appliqué à l’élaboration de matrices poreuses pour l’ingénierie tissulaire.

peer reviewedCe travail vise à appliquer une approche « génie-orienté produit » à la fabrication de matrices poreuses synthétiques (scaffolds) susceptibles d’être utilisées en ingénierie tissulaire. Parmi les différents polymères biosourcés et biodégradables déjà utilisés pour la fabrication de scaffolds, l’acide polylactique (PLA) a été choisi. Des matrices poreuses ont été obtenues par un procédé de moussage par lyophilisation puis leur microstructure 2D/3D a été caractérisée par microtomographie à rayons X avant d’être mise en lien avec les conditions d’élaboration testées. La diminution de la porosité ainsi que l’augmentation de l’épaisseur des parois avec l’augmentation de rapport polymère/solvant ont été confirmées

"Product-oriented engineering" applied to the development of porous scaffolds for tissue engineering.

This work applies a “product-oriented engineering” approach to the development of porous scaffolds for tissue engineering. Polylactic acid scaffolds were obtained by a freeze-drying process. Their 2D/3D microstructure was characterized by X-ray microtomography and related to the operating conditions used. Two types of scaffold end-use properties were characterized in relation to their microstructure: the mechanical and the transport properties. Scaffold young's modulus was computed from data measured on tension-compression devices. To evaluate the permeability, Darcy’s experiments were carried out. The obtained results allowed highlighting the quantitative relationships existing between elaboration conditions, microstructure and end use properties of the fabricated PLA scaffolds

FDC-B1, a new monoclonal antibody directed against bovine follicular dendrititic cells.

Follicular dendritic cells (FDCs) are unique immunological accessory cells located in the light and dark zones of the germinal centres in lymph follicles. Characterized by long branching processes forming a three-dimensional network, FDCs create particular microenvironments for germinal centre B and T cells and contribute to the maturation of B cells into memory cells. An involvement of the FDCs is suspected in various disorders affecting lymphoid tissues, malignant lymphoma or in some viral diseases. Moreover, in prion diseases, FDCs seem to be the major sites of extraneuronal cellular prion protein expression and the principal sites of the infectious agent accumulation in lymph organs. Because no antibody commercially available was specific to bovine FDCs, a new monoclonal antibody directed against bovine FDCs (FDC-B1) has been produced and characterized in our laboratory. The antigen detected by FDC-B1 is expressed on FDC surfaces in ruminant (bovine, ovine and caprine) lymphoid organs. This protein seems to be a membrane glycoprotein of more or less 28 kDa whose sequence will be soon determined. Moreover, FDC-B1 can be used in various applications: immunofluorescence, immunoperoxidase, immunogold labellings and western blotting. FDCs are potential targets for therapy or prophylaxis in natural TSEs, such as bovine spongiform encephalopathies and scrapie. Thus, it appears of great interest to identify bovine and ovine FDCs in routine lymphoid tissues sections. An other application of this antibody to immunofluorescence histochemistry techniques will enable the study of possible direct contacts between bovine FDCs and nerve endings and thus clarify prions neuroinvasion scheme in the case of BSE and scrapie

Acid acting as redispersing agent to form stable colloids from photoactive crystalline aqueous sol–gel TiO2 powder

In this work, the redispersion of three nanocrystalline TiO2 colloids is studied: one pure and two Fe-doped titania. These three colloids are produced by an easy aqueous sol-gel synthesis using precipitation-acidic peptization of Ti precursor. For the two Fe-doped TiO2, one is doped during synthesis (primary doping) and the other is doped after the synthesis (secondary doping). The initial colloids are composed of crystalline TiO2 particles around 7 nm with good photocatalytic properties, tested on PNP degradation under visible light (wavelength > 390 nm). The powders obtained by air drying of these three colloids are redispersed in water to produce colloids which are compared to the initial colloid produced. For each colloid, 5 cycles of drying-redispersion are achieved. The colloids are characterized by dynamic light scattering, zeta potential measurements, inductively coupled plasma–atomic emission spectroscopy, X-ray diffraction, nitrogen adsorption-desorption measurements, Mössbauer spectroscopy, diffuse reflectance spectroscopy, and photocatalytic tests. The results show that similar products are obtained between the cycles, maintaining homologous properties of colloids. This property of redispersion is mainly due to the acid (HNO3, HCl, or H2SO4) which protonates the surface of the TiO2 nanoparticle leading to high surface charges and electrostatic repulsions between aggregates. This property can be very useful for industrial applications of this synthesis, especially as it allows the volume and weight to be reduced for transportation and storage. Moreover, results show that the pure TiO2 powder can be doped during its redispersion step. The redispersion of the TiO2 developed here is possible without surface functionalization or multiple step processes, contrary to commercial Degussa P25. A two year stability study of all the produced colloids has been performed by following the evolution of the macroscopic aspect and the physico-chemical properties of these sols. This study showed high stability of the produced colloids

FDC-B1: a new monoclonal antibody directed against bovine follicular dendritic cells

Follicular dendritic cells (FDCs) are a unique population of accessory cells located in the light zone of the germinal centres of lymphoid follicles. Their involvement in the generation of Immoral immune responses implies a potential role for these cells in many disorders. Indeed, in prion diseases, FDCs seem to be the major sites of extraneuronal cellular prion protein expression and the principal sites of the infectious agent accumulation in lymphoid organs. The identification of FDC is useful for the analysis of their distribution in reactive lymphoid tissue as well as in pathological conditions. The production and characterisation of a new mouse monoclonal antibody directed against bovine follicular dendritic cells (FDC-B1) is reported. The antigen detected by FDC-B1 is expressed exclusively on the surface of FDCs in ruminant lymphoid organs. The antigen has an approximate molecular weight of 28 kDa. (C) 2003 Elsevier B.V. All rights reserved

Microplastics in air: Are we breathing it in?

The annual production of plastic textile fibers has increased by more than 6% per year, reaching 60 million metric tons, about 16% of world plastic production. The degradation of these fibers produces fibrous microplastics (MPs). Such MPs have been observed in atmospheric fallouts, as well as in indoor and outdoor environments. Some fibrous MPs may be inhaled. Most of them are likely to be subjected to mucociliary clearance; however, some may persist in the lung causing localized biological responses, including inflammation, especially in individuals with compromised clearance mechanisms. Associated contaminants such as Polycyclic Aromatic Hydrocarbons (PAHs) could desorb and lead to genotoxicity while the plastic itself and its additives (dyes, plasticizers) could lead to health effects including reproductive toxicity, carcinogenicity and mutagenicity