Carbohydrate Metabolism Is Essential for the Colonization of Streptococcus thermophilus in the Digestive Tract of Gnotobiotic Rats

Streptococcus thermophilus is the archetype of lactose-adapted bacterium and so far, its sugar metabolism has been mainly investigated in vitro. The objective of this work was to study the impact of lactose and lactose permease on S. thermophilus physiology in the gastrointestinal tract (GIT) of gnotobiotic rats. We used rats mono-associated with LMD-9 strain and receiving 4.5% lactose. This model allowed the analysis of colonization curves of LMD-9, its metabolic profile, its production of lactate and its interaction with the colon epithelium. Lactose induced a rapid and high level of S. thermophilus in the GIT, where its activity led to 49 mM of intra-luminal L-lactate that was related to the induction of mono-carboxylic transporter mRNAs (SLC16A1 and SLC5A8) and p27Kip1 cell cycle arrest protein in epithelial cells. In the presence of a continuous lactose supply, S. thermophilus recruited proteins involved in glycolysis and induced the metabolism of alternative sugars as sucrose, galactose, and glycogen. Moreover, inactivation of the lactose transporter, LacS, delayed S. thermophilus colonization. Our results show i/that lactose constitutes a limiting factor for colonization of S. thermophilus, ii/that activation of enzymes involved in carbohydrate metabolism constitutes the metabolic signature of S. thermophilus in the GIT, iii/that the production of lactate settles the dialogue with colon epithelium. We propose a metabolic model of management of carbohydrate resources by S. thermophilus in the GIT. Our results are in accord with the rationale that nutritional allegation via consumption of yogurt alleviates the symptoms of lactose intolerance

Axillary management after neoadjuvant treatment

Since its introduction nearly 30 years ago, sentinel lymph node biopsy (SLNB) has become the standard technique to stage the axilla for the great majority of patients with early breast cancer. While the accuracy of SLNB in clinically node-negative patients who undergo neoadjuvant chemotherapy (NAC) is similar to the upfront surgery setting, modifications of the technique to improve the false negative rate are necessary in node-positive patients at presentation. Currently, patients who present with matted nodes, cN1 patients who fail to downstage to cN0 with NAC and those with pathological residual disease have an indication to undergo axillary lymph node dissection. Ongoing trials will confirm if extensive nodal irradiation can replace surgery in patients with residual nodal disease after NAC and if nodal radiotherapy can be omitted in patients who achieve nodal pathological complete response. The aim of this review was to focus on the open questions on the management of the axilla after NAC

Comparison of Two Novel Solution-Based Routes for the Synthesis of Equiaxed ZnO Nanoparticles

Due to a dominant one-dimensional growth rate, nanoparticles of zinc oxide often show a rodlike morphology. As a result, the synthesis of small spherical nanoparticles of undoped ZnO remains challenging. This paper presents two procedures that successfully produce a powder consisting of equiaxed zinc oxide nanoparticles: one using a polyethylene glycol- (PEG-) assisted solvothermal method and the other by calcination of zinc oxalate obtained from a microemulsion-mediated method. In the latter, zinc-substituted aerosol OT (AOT) is used as a surfactant. The samples are characterized by inductively coupled plasma-atomic emission spectroscopy (ICP-AES), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), photon correlation spectroscopy (PCS), and photoluminescence (PL) spectroscopy. Both synthesis techniques produce nanoparticles with similar sizes in the range of 10 to 20 nm. Dense aggregates observed in the calcined powder are infrequent in the case of the solvothermal method

Silane ligand exchange to make hydrophobic superparamagnetic nanoparticles water-dispersible

Ferrite magnetic nanoparticles (MNPs) were functionalized with a variety of silanes bearing different functional endgroups to render them stable with respect to aggregation and keep them well-dispersed in aqueous media. The MNPs were prepared by the thermal decomposition method, widely used for the synthesis of monodisperse nanoparticles with controllable size. This method makes use of a hydrophobic surfactant to passivate the surface, which results in nanoparticles that are solely dispersible in nonpolar solvents. For use in biological applications, these nanoparticles need to be made water-dispersible. Therefore, a new procedure was developed on the basis of the exchange of the hydrophobic surface ligands with silanes bearing different endgroups to decorate ferrite magnetic nanoparticles with diverse functionalities . By this means, we could easily determine the influence of the endgroup on the nanoparticle stability and water-dispersibility. Amino-, carboxylic acid- and poly(ethylene glycol)-terminated silanes were found to render the MNPs highly stable and water-dispersible because of electrostatic and/or steric repulsion. The silane molecules were also found to form a protective layer against mild acid and alkaline environments. The ligand exchange on the nanoparticle surface was thoroughly characterized using SQUID, TEM, XPS, DLS, TGA, FTIR, UV-vis, and zeta potential measurements. The presented approach provides a generic strategy to functionalize magnetic ferrite nanoparticles and to form stable dispersions in aqueous media, which facilitates the use of these magnetic nanoparticles in biological applications.status: publishe

Study of interfacial reactions and phase stabilization of mixed Sc, Dy, Hf high-k oxides by attenuated total reflectance infrared spectroscopy

Grazing angle attenuated total reflectance Fourier transform infrared spectroscopy is applied to study ultrathin film Hf⁴⁺, Sc³⁺ and Dy³⁺ oxides, due to its high surface sensitivity. The (multi)metal oxides studied, are of interest as high-k dielectrics. Important properties affecting the permittivity, such as the amorphous or crystalline phase and interfacial reactions, are characterized. Dy₂O₃ is prone to silicate formation on SiO₂/Si substrates, which is expressed in DyScO₃ as well, but suppressed in HfDyOₓ. Sc₂O₃, HfScOₓ and HfO₂ were found to be stable in contact with SiO₂/Si. Deposition of HfO₂ in between Dy₂O₃ or DyScO₃ and SiO₂, prevents silicate formation, showing a buffer-like behavior for the HfO₂. Doping of HfO₂ with Dy or Sc prevents monoclinic phase crystallization. Instead, a cubic phase is obtained, which allows a higher permittivity of the films. The phase remains stable after anneal at high temperature.status: publishe

Synthesis and mechanical and tribological characterization of alumina-yttria stabilized zirconia (YSZ) nanocomposites with YSZ synthesized by means of an aqueous solution-gel. method or a hydrothermal route

In the present study, yttria stabilized zirconia (YSZ) nanoparticles, prepared by means of an aqueous solution–gel method or a hydrothermal route, are incorporated in a matrix of submicron alumina particles by wet mechanical milling. The microstructural characteristics and the mechanical and tribological properties of the obtained alumina–YSZ nanocomposites are evaluated as a function of different processing conditions like milling time, YSZ amount, sintering procedure and synthesis method of YSZ. It is noticed that the synthesis procedure and the agglomeration degree of the YSZ nanoparticles seriously affect the densification process of the alumina–YSZ nanocomposites and also their mechanical and tribological properties. The most probable cause for the difference is that the hydrothermally prepared YSZ nanoparticles are not as homogeneously distributed in the alumina matrix as the solution–gel prepared nanoparticles. Moreover the former nanoparticles have surface groups which release undesired gases during sintering. Thus to obtain a dense sample, nanocomposites with these nanoparticles require a higher sintering temperature and this has a negative effect on the mechanical and tribological properties of these materials.status: publishe

High flux composite PTMSP-silica nanohybrid membranes for the pervaporation of ethanol/water mixtures

Silica-filled poly(1-trimethylsilyl-1-propyne) (PTMSP) layers were successfully applied for the first time on top of ultrafiltration support membranes and applied in the pervaporative separation of ethanol/water mixtures. Reduction of the thickness of the separating PTMSP top layer and addition of hydrophobic silica particles resulted in a clear flux increase as compared to dense PTMSP membranes. With ethanol/water separation factors up to 12 and fluxes up to 3.5 kg m(-2) h(-1), the prepared supported PTMSP-silica nanohybrid membranes performed significantly better than the best commercially available organophilic pervaporation membranes. Characterization of a polyvinylidene fluoride (PVDF) and a polyacrylonitrile (PAN) support membrane revealed a more open, irregular and hydrophobic surface structure for the former membrane, thus explaining the higher fluxes of the PTMSP/PVDF composite membrane. Because of their promising flux-selectivity combination, the prepared membranes exhibit great potential in the removal of alcohols from aqueous mixtures. (C) 2010 Elsevier B.V. All rights reserved