Intragastric bile acid concentrations are unrelated to symptoms of flatulent dyspepsia in patients with and without gallbladder disease and postcholecystectomy

It has been proposed that duodenogastric reflux may be the basic underlying mechanism which gives rise to symptoms of flatulent dyspepsia. Fasting and postprandial gastric juice bile acid concentrations were measured in patients with flatulent dyspepsia with and without gall bladder disease and postcholecystectomy. There were 13 patients with gall bladder disease, 12 with normal gall bladders and 13 postcholecystectomy. Gastric juice was obtained by intubation. Bile acid concentrations were compared with 21 controls and 15 asymptomatic subjects with gall bladder disease. For 21 patients with gall bladder disease who underwent cholecystectomy, levels were again assessed postoperatively to allow correlation with outcome. The occurrence of reflux and the resultant gastric juice bile acids did not correlate with symptoms. Concentrations postcholecystectomy, including asymptomatic subjects were significantly higher than controls (p less than 0.01). It is concluded that limited duodenogastric reflux is common and need not be associated with symptoms even when the resultant intra-gastric concentrations are higher than normal.

The geometry of unstented and stented pig common carotid artery bypass grafts

The long-term success of arterial bypass grafting with autologous saphenous veins is limited by neointimal hyperplasia (NIH), which seemingly develops preferentially at sites where hydrodynamic wall shear is low. Placement of a loose-fitting, porous stent around end-to-end, or end-to-side, autologous saphenous vein grafts on the porcine common carotid artery has been found significantly to reduce NIH, but the mechanism is unclear. In a preliminary study, we implanted autologous saphenous vein grafts bilaterally on the common carotid arteries of pigs, placing a stent around one graft and leaving the contralateral graft unstented. At sacrifice 1 month post implantation, the grafts were pressure fixed in situ and resin casts were made. Unstented graft geometry was highly irregular, with non-uniform dilatation, substantial axial lengthening, curvature, kinking, and possible long-pitch helical distortion. In contrast, stented grafts showed no major dilatation, lengthening or curvature, but there was commonly fine corrugation, occasional slight kinking or narrowing of segments, and possible long-pitch helical distortion. Axial growth of grafts against effectively tethered anastomoses could account for these changes. CFD studies are planned, using 3D MR reconstructions, on the effects of graft geometry on the flow. Abnormality of the flow could favour the development of vascular pathology, including NIH.

A single-component multidrug transporter of the major facilitator superfamily is part of a network that protects Escherichia coli from bile salt stress

Resistance to high concentrations of bile salts in the human intestinal tract is vital for the survival of enteric bacteria such as Escherichia coli. Although the tripartite AcrAB-TolC efflux system plays a significant role in this resistance, it is purported that other efflux pumps must also be involved. We provide evidence from a comprehensive suite of experiments performed at two different pH values (7.2 and 6.0) that reflect pH conditions that E. coli may encounter in human gut that MdtM, a single-component multidrug resistance transporter of the major facilitator superfamily, functions in bile salt resistance in E. coli by catalysing secondary active transport of bile salts out of the cell cytoplasm. Furthermore, assays performed on a chromosomal ΔacrB mutant transformed with multicopy plasmid encoding MdtM suggested a functional synergism between the single-component MdtM transporter and the tripartite AcrAB-TolC system that results in a multiplicative effect on resistance. Substrate binding experiments performed on purified MdtM demonstrated that the transporter binds to cholate and deoxycholate with micromolar affinity, and transport assays performed on inverted vesicles confirmed the capacity of MdtM to catalyse electrogenic bile salt/H(+) antiport.

Measurement of the Electrogenicity of Bile Salt/H+ Antiport in Escherichia coli

The transmembrane proton gradient (ΔpH) is the primary source of energy exploited by secondary active substrate/H+ antiporters to drive the electroneutral transport of substrates across the Escherichia coli (E. coli) inner membrane. Such electroneutral transport results in no net movement of charges across the membrane. The charge on the transported substrate and the stoichiometry of the exchange reaction, however, can result in an electrogenic reaction which is driven by both the ΔpH and the electrical (∆Ψ) components of the proton electrochemical gradient, resulting in a net movement of electrical charges across the membrane. We have shown that the major facilitator superfamily transporter MdtM - a multidrug efflux protein from E. coli that functions physiologically in protection of bacterial cells against bile salts - imparts bile salt resistance to the bacterial cell by coupling the exchange of external protons (H+) to the efflux of bile salts from the cell interior via an electrogenic antiport reaction (Paul et al., 2014). This protocol describes, using fluorometry, how to detect electrogenic antiport activity of MdtM in inverted membrane vesicles of an antiporter-deficient strain of E. coli TO114 cells by measuring transmembrane ∆Ψ. The method exploits changes that occur in the intensity of the fluorescence signal (quenching and dequenching) of the probe Oxonol V in response to changes in membrane potential due to the MdtM-catalysed sodium cholate/H+ exchange reaction. The protocol can be adapted to detect activity of any secondary active antiporter that couples the electrogenic translocation of H+ across a biological membrane to that of its counter-substrate, and may be used to unmask otherwise camouflaged transport activities and physiological roles.

Genome wide interactions of wild-type and activator bypass forms of σ54

Enhancer-dependent transcription involving the promoter specificity factor σ54 is widely distributed amongst bacteria and commonly associated with cell envelope function. For transcription initiation, σ54-RNA polymerase yields open promoter complexes through its remodelling by cognate AAA+ ATPase activators. Since activators can be bypassed in vitro, bypass transcription in vivo could be a source of emergent gene expression along evolutionary pathways yielding new control networks and transcription patterns. At a single test promoter in vivo bypass transcription was not observed. We now use genome-wide transcription profiling, genome-wide mutagenesis and gene over-expression strategies in Escherichia coli, to (i) scope the range of bypass transcription in vivo and (ii) identify genes which might alter bypass transcription in vivo. We find little evidence for pervasive bypass transcription in vivo with only a small subset of σ54 promoters functioning without activators. Results also suggest no one gene limits bypass transcription in vivo, arguing bypass transcription is strongly kept in check. Promoter sequences subject to repression by σ54 were evident, indicating loss of rpoN (encoding σ54) rather than creating rpoN bypass alleles would be one evolutionary route for new gene expression patterns. Finally, cold-shock promoters showed unusual σ54-dependence in vivo not readily correlated with conventional σ54 binding-sites.

Comparison of DES predictions of turbulent flow and heat transfer in a 45° ribbed duct

Numerical predictions of the turbulent flow and heat transfer of a stationary duct with square ribs 45° angled to the main flow direction are presented. The rib height to channel hydraulic diameter is 0.1, the rib pitch to rib height is 10. The calculations have been carried out for a bulk Reynolds number of 50,000. The flows generated by ribs are dominated by separating and reattaching shear layers with vortex shedding and secondary flows in the cross-section. The hybrid RANS-LES approach is adopted to simulate such flows at a reasonable computation cost. The capability of the various versions of DES method, depending the RANS model, such as DES-SA, DES-RKE, DES-SST, have been compared and validated against the experiment. The significant effect of RANS model on the accuracy of the DES prediction has been shown. The DES-SST method, which was able to reproduce the correct physics of flow and heat transfer in a ribbed duct showed better performance than others.

Congenital nasolacrimal duct obstruction:Comparison of two different treatment algorithms

Purpose: To clarify the most appropriate treatment regimen for congenital nasolacrimal duct obstruction (CNLDO). Methods: A retrospective observational analysis was performed of patients undergoing probing with or without intubation to treat CNLDO in a single institution (Royal Victoria Hospital, Belfast) from 2006 to 2011. Results: Based on exclusion criteria, 246 eyes of 177 patients (aged 0 to 9.8 years with a mean age of 2.1 years) were included in this study: 187 (76%) eyes had successful outcome at first intervention with primary probing, whereas 56 (23%) eyes underwent secondary intervention. There were no significant differences by gender, age, or obstruction complexity between the successful and unsuccessful patients with first intervention. For those patients requiring secondary intervention, 16 of 24 (67%) eyes had successful probing, whereas 22 of 24 (92%) had successful intubation. Patients with intubation as a secondary procedure were significantly more likely to have a successful outcome (P = .037). Statistical analysis was performed using the Fisher's exact test and Barnard's exact test. Conclusions: Primary probing for CNLDO has a high success rate that is not adversely affected by increasing age. This study also indicates that if initial probing is unsuccessful, nasolacrimal intubation rather than repeat probing yields a significantly higher success rate.

Entanglement distribution with global control in a star-shaped multi-splitter

Distributed quantum information processing (QIP) is a promising way to bypass problems due to unwanted interactions between elements. However, this strategy presupposes the engineering of protocols for remote processors. In many of them, pairwise entanglement is a key resource. We study a model which distributes entanglement among elements of a delocalized network without local control. The model is efficient both in finite- and infinite-dimensional Hilbert spaces. We suggest a setup of electromechanical systems to implement our proposal.

Particle Image Velocimetry Investigation of a finite amplitude pressure wave

Particle image velocimetry is used to study the motion of gas within a duct subject to the passage of a finite amplitude pressure wave. The wave is representative of the pressure waves found in the exhaust systems of internal combustion engines. Gas particles are accelerated from stationary to 150 m/s and then back to stationary in 8 ms. It is demonstrated that gas particles at the head of the wave travel at the same velocity across the duct cross section at a given point in time. Towards the tail of the wave viscous effects are plainly evident causing the flow profile to tend towards parabolic. However, the instantaneous mean particle velocity across the section is shown to match well with the velocity calculated from a corresponding measured pressure history using 1D gas dynamic theory. The measured pressure history at a point in the duct was acquired using a high speed pressure transducer of the type typically used for engine research in intake and exhaust systems. It is demonstrated that these are unable to follow the rapid changes in pressure accurately and that they are prone to resonate under certain circumstances.

Induction of tetraploidy through loss of p53 and upregulation of Plk1 by Human Papillomavirus type-16 E6

Cancer cells are insensitive to many signals that inhibit growth of untransformed cells. Here, we show that primary human epithelial cells expressing human papillomavirus (HPV) type-16 E6/E7 bypass arrest caused by the DNA-damaging drug adriamycin and become tetraploid. To determine the contribution of E6 in the context of E7 to the resistance of arrest and induction of tetraploidy, we used an E6 mutant unable to degrade p53 or RNAi targeting p53 for knockdown. The E6 mutant fails to generate tetraploidy; however, the presence of E7 is sufficient to bypass arrest while the p53 RNAi permits both arrest insensitivity and tetraploidy. We published previously that polo-like kinase 1 (Plk1) is upregulated in E6/E7-expressing cells. We observe here that abnormal expression of Plk1 protein correlates with tetraploidy. Using the p53 binding-defective mutant of E6 and p53 RNAi, we show that p53 represses Plk1, suggesting that loss of p53 results in tetraploidy through upregulation of Plk1. Consistent with this hypothesis, overexpression of Plk1 in cells generates tetraploidy but does not confer resistance to arrest. These results support a model for transformation caused by HPV-16 where bypass of arrest and tetraploidy are separable consequences of p53 loss with Plk1 required only for the latter effect.

Cyclooxygenase-2 and inducible nitric oxide synthase gene polymorphisms and risk of reflux esophagitis, Barrett's Esophagus, and esophageal adenocarcinoma

The incidence of esophageal adenocarcinoma has increased in recent years, and Barrett's esophagus is a recognized risk factor. Gastroesophageal reflux of acid and/or bile is linked to these conditions and to reflux esophagitis. Inflammatory disorders can lead to carcinogenesis through activation of "prosurvival genes," including cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS). Increased expression of these enzymes has been found in esophageal adenocarcinoma, Barrett's esophagus, and reflux esophagitis. Polymorphic variants in COX-2 and iNOS genes may be modifiers of risk of these conditions. In a population-based case-control study, we examined associations of the COX-2 8473 T>C and iNOS Ser 608 Leu (C>T) polymorphisms with risk of esophageal adenocarcinoma, Barrett's esophagus, and reflux esophagitis. Genomic DNA was extracted from blood samples collected from cases of esophageal adenocarcinoma (n = 210), Barrett's esophagus (n = 212), and reflux esophagitis (n = 230) and normal population controls frequency matched for age and sex (n = 248). Polymorphisms were genotyped using TaqMan allelic discrimination assays. Odds ratios and 95% confidence intervals were obtained from logistic regression models adjusted for potential confounding factors. The presence of at least one COX-2 8473 C allele was associated with a significantly increased risk of esophageal adenocarcinoma (adjusted odds ratio, 1.58; 95% confidence interval, 1.04-2.40). There was no significant association between this polymorphism and risk of Barrett's esophagus or reflux esophagitis or between the iNOS Ser 608 Leu polymorphism and risk of these esophageal conditions. Our study suggests that the COX-2 8473 C allele is a potential genetic marker for susceptibility to esophageal adenocarcinoma.

A modified commercial DRIFTS cell for kinetically relevant operando studies of heterogeneous catalytic reactions

This paper discusses a number of checks that should be carried out to ensure that the kinetic and spectroscopic measurements made using a DRIFTS cell are meaningful. The observations reported here demonstrate how an appropriately modified commercial DRIFTS cell can provide pertinent kinetic information about both gaseous products and the related surface intermediates. The oxidation of CO with 02 was used as a test to assess the catalyst bed bypass by the reaction mixture. Full CO conversion was obtained after the light-off temperature in the case of the modified cell, contrary to the case of the original cell, for which 80% of the reaction mixture bypassed the catalyst bed. The water-gas shift reaction over a Pt/CeO2 catalyst was used as a model reaction to further characterize the behavior of the cell under reaction conditions. The catalyst bed was shown not to be a dead-zone and was purged in essentially the same time as that needed to purge the cell. The reaction chamber globally operated in a quasi plug-flow mode and the gas composition in the thin catalyst bed appears to be homogeneous when operated under differential conditions. The production of the gas-phase reaction product CO2 could be simultaneously followed both by mass spectrometry and DRIFTS, both techniques leading to identical results. Various IR bands integration methods were discussed to allow a precise and accurate determination of the surface concentration of adsorbates during isotopic exchange. (c) 2008 Elsevier B.V. All rights reserved.

Measurement of Quenching Coefficients and Developement of Calibration Methods for Quantitative Spectroscopy of Plasma at Elevated Pressures

Measurements of collisional de-excitation (quenching) coefficients required for the interpretation of emission and fluorescence spectroscopic measurements are reported. Particular attention is turned on argon transitions which are of interest for actinometric determinations of atomic ground state populations and on fluorescence lines originating from excited atoms and noble gases in connection with two-photon excitation (TALIF) of atomic radicals. A novel method is described which allows to infer quenching coefficients for collisions with molecular hydrogen of noble gas states in the energy range up to 24 eV. The excitation is performed in these experiments by collisions of energetic electrons in the sheath of an RF excited hydrogen plasma during the field reversal phase which lasts about 10 ns. We describe in addition a calibration method - including quenching effects - for the determination by TALIF of absolute atomic radical densities of hydrogen, nitrogen and oxygen using two-photon resonances in noble gases close by the resonances of the species mentioned. The paper closes with first ideas on a novel technique to bypass quenching effects in TALIF by introducing an additional, controllable loss by photoionization that will allow quenching-free determination of absolute atomic densities with prevalent nanosecond laser systems in situations where collisional de-excitation dominates over spontaneous emission.

Combined inhibition of FLIP and XIAP induces Bax-independent apoptosis in type II colorectal cancer cells.

Death receptors can directly (type I cells) or indirectly induce apoptosis by activating mitochondrial-regulated apoptosis (type II cells). The level of caspase 8 activation is thought to determine whether a cell is type I or II, with type II cells less efficient at activating this caspase following death receptor activation. FLICE-inhibitory protein (FLIP) blocks death receptor-mediated apoptosis by inhibiting caspase 8 activation; therefore, we assessed whether silencing FLIP could convert type II cells into type I. FLIP silencing-induced caspase 8 activation in Bax wild-type and null HCT116 colorectal cancer cells; however, complete caspase 3 processing and apoptosis were only observed in Bax wild-type cells. Bax-null cells were also more resistant to chemotherapy and tumor necrosis factor-related apoptosis inducing ligand and, unlike the Bax wild-type cells, were not sensitized to these agents by FLIP silencing. Further analyses indicated that release of second mitochondrial activator of caspases from mitochondria and subsequent inhibition of X-linked inhibitor of apoptosis protein (XIAP) was required to induce full caspase 3 processing and apoptosis following FLIP silencing. These results indicate that silencing FLIP does not necessarily bypass the requirement for mitochondrial involvement in type II cells. Furthermore, targeting FLIP and XIAP may represent a therapeutic strategy for the treatment of colorectal tumors with defects in mitochondrial-regulated apoptosis.