Bifidobacterium longum and Lactobacillus helveticus synergistically suppress stress-related visceral hypersensitivity through hypothalamic-pituitary-adrenal axis modulation

Visceral pain and hypothalamic-pituitary-adrenal axis (HPA) dysregulation is a common characteristic in irritable bowel syndrome (IBS) patients. Previously, we reported that a probiotic formulation (Lactobacillus helveticus R0052 and Bifidobacterium longum R0175) prevents chronic stress-mediated brain function abnormalities by attenuating the HPA axis response. Here, we compared the effect between different probiotic treatments on the perception of visceral pain during colorectal distension (CRD) following a chronic stress and the consequences to the activity of the HPA axis. After a 2-week treatment with a combined probiotic formulation, or L. helveticus or B. longum alone in stressed mice, the visceral pain in response to CRD was recorded. The expression of glucocorticoid receptors was determined in the different brain areas involved in the stress response (hypothalamus, hippocampus, and prefrontal cortex). The plasma levels of stress hormones were also measured. A pretreatment using the combination of probiotic formulation significantly reduces the chronic stress-induced visceral hypersensitivity respectively at 0.06, 0.08, and 0.10 mL CRD volume. However, a single probiotic (B. longum or L. helveticus) administration is less effective in reducing visceral pain in stressed mice. Moreover, the expression of the glucocorticoid receptor mRNA was consistently up-regulated in several brain areas after pretreatment with a combined probiotic, which correlated with the normalization of stress response compared to the inconsistent effects of a single probiotic. The combination of L. helveticus and B. longum is more effective in regulating glucocorticoid negative feedback on the HPA axis than probiotic alone and subsequently in treating stress-induced visceral pain

Interactions between Biocide Cationic Agents and Bacterial Biofilms

The resistance of bacterial biofilms to physical and chemical agents is attributed in the literature to various interconnected processes. The limitation of mass transfer alters the growth rate, and physiological changes in the bacteria in the film also appear. The present work describes an approach to determination of the mechanisms involved in the resistance of bacteria to quaternary ammonium compounds (benzalkonium chloride) according to the C-chain lengths of those compounds. For Pseudomonas aeruginosa CIP A 22, the level of resistance of the bacteria in the biofilm relative to that of planktonic bacteria increased with the C-chain length. For cells within the biofilm, the exopolysaccharide induced a characteristic increase in surface hydrophilicity. However, this hydrophilicity was eliminated by simple resuspension and washing. The sensitivity to quaternary ammonium compounds was restored to over 90%. Staphylococcus aureus CIP 53 154 had a very high level of resistance when it was in the biofilm form. A characteristic of bacteria from the biofilm was a reduction in the percent hydrophobicity, but the essential point is that this hydrophobicity was retained after the biofilm bacteria were resuspended and washed. The recovery of sensitivity was thus only partial. These results indicate that the factors involved in biofilm resistance to quaternary ammonium compounds vary according to the bacterial modifications induced by the formation of a biofilm. In the case of P. aeruginosa, we have underlined the involvement of the exopolysaccharide and particularly the three-dimensional structure (water channels). In the case of S. aureus, the role of the three-dimensional structure is limited and drastic physiological changes in the biofilm cells are more highly implicated in resistance

Molecular and morphological systematics of the sandfly Sergentomyia (Sintonius) clydei Sinton, 1928 and questions about its record in the Seychelles

In the Phlebotomine sandflies, a few molecular studies related on the genus Sergentomyia have been published. The present study explored the genetic variability within Sergentomyia (Sintonius) clydei ( Diptera, Psychodidae). The sampling included 15 populations originating from 12 countries. A morphological approach was coupled to the sequencing of two molecular markers (cytochrome b mtDNA and cacophony nuclear DNA). The most variable morphological characters resided in the cibarium of the females, especially (i) the pigment patch pattern and (ii) the number of cibarial teeth and denticles in the armature. However this morphological approach was unable to individualize any population within S. clydei. The NJ trees based on both molecular markers individualized the specimens from the Aldabra group of islands in the Seychelles. Surprisingly, cyt b variability was not compatible with the known data about the complete submersion of Aldabra occurring relatively recently some 125,000 years ago. The settlement of these islands by S. clydei from continental Africa, the Middle East or Asia, and the value of mtDNA markers are discussed

Dynamics and Site Isolation : Keys to High Propane Dehydrogenation Performance of Silica-Supported PtGa Nanoparticles

Nonoxidative dehydrogenation of light alkanes has seen a renewed interest in recent years. While PtGa systems appear among the most efficient catalyst for this reaction and are now implemented in production plants, the origin of the high catalytic performance in terms of activity, selectivity, and stability in PtGa-based catalysts is largely unknown. Here we use molecular modeling at the DFT level on three different models: (i) periodic surfaces, (ii) clusters using static calculations, and (iii) realistic size silica-supported nanoparticles (1 nm) using molecular dynamics and metadynamics. The combination of the models with experimental data (XAS, TEM) allowed the refinement of the structure of silica-supported PtGa nanoparticles synthesized via surface organometallic chemistry and provided a structure-activity relationship at the molecular level. Using this approach, the key interaction between Pt and Ga was evidenced and analyzed: the presence of Ga increases (i) the interaction between the oxide surface and the nanoparticles, which reduces sintering, (ii) the Pt site isolation, and (iii) the mobility of surface atoms which promotes the high activity, selectivity, and stability of this catalyst. Considering the complete system for modeling that includes the silica support as well as the dynamics of the PtGa nanoparticle is essential to understand the catalytic performances

A Robust and Efficient Propane Dehydrogenation Catalyst from Unexpectedly Segregated Pt2Mn Nanoparticles

The increasing demand for short chain olefins like propene for plastics production and the availability of shale gas make the development of highly performing propane dehydrogenation (PDH) catalysts, robust towards industrially applied harsh regeneration conditions, a highly important field of research. A combination of surface organometallic chemistry (SOMC) and thermolytic molecular precursor (TMP) approach was used to prepare a nanometric, bimetallic Pt-Mn mate-rial (3 wt% Pt, 1.3 wt% Mn) supported on silica via consecutive grafting of a Mn and Pt precursor on surface OH groups present on the support surface, followed by a treatment under a H2 flow at high temperature. The material exhibits a 70% fraction of the overall Mn as MnII single sites on the support surface; the remaining Mn is incorporated in segregated Pt2Mn nanoparticles. The material shows great performance in PDH reaction with a low deactivation rate. In particular, it shows outstanding robustness during repeated regeneration cycles, with conversion and selectivity stabilizing at ca. 37% and 98%, respectively. Notably, a material with a lower Pt loading of only 0.05 wt% shows an outstanding catalytic per-formance – initial productivity of 4523 gC3H6/gPt h and an extremely low kd of 0.003 h-1 under a partial pressure of H2 – ranging among the highest reported productivities. A combined in situ XAS, STEM, EPR and metadynamics at the DFT level study could show that the strong interaction between the MnII decorated support and the unexpectedly segregated Pt2Mn particles is most likely responsible for the outstanding performance of the investigated materials

A Robust and Efficient Propane Dehydrogenation Catalyst from Unexpectedly Segregated Pt2Mn Nanoparticles

The increasing demand for short chain olefins like propene for plastics production and the availability of shale gas make the development of highly performing propane dehydrogenation (PDH) catalysts, robust toward industrially applied harsh regeneration conditions, a highly important field of research. A combination of surface organometallic chemistry and thermolytic molecular precursor approach was used to prepare a nanometric, bimetallic Pt-Mn material (3 wt % Pt, 1.3 wt % Mn) supported on silica via consecutive grafting of a Mn and Pt precursor on surface OH groups present on the support surface, followed by a treatment under a H-2 flow at high temperature. The material exhibits a 70% fraction of the overall Mn as Mn-II single sites on the support surface; the remaining Mn is incorporated in segregated Pt2Mn nanoparticles. The material shows great performance in PDH reaction with a low deactivation rate. In particular, it shows outstanding robustness during repeated regeneration cycles, with conversion and selectivity stabilizing at ca. 37 and 98%, respectively. Notably, a material with a lower Pt loading of only 0.05 wt % shows an outstanding catalytic performance -initial productivity of 4523 g(C3H6)/gPt h and an extremely low kd of 0.003 h(-1) under a partial pressure of H-2, which are among the highest reported productivities. A combined in situ X-ray absorption spectroscopy, scanning transmission electron microscopy, electron paramagnetic resonance, and metadynamics at the density functional theory level study could show that the strong interaction between the Mn-II-decorated support and the unexpectedly segregated Pt2Mn particles is most likely responsible for the outstanding performance of the investigated materials.ISSN:0002-7863ISSN:1520-512