Probiotic-induced changes in the intestinal epithelium: Implications in gastrointestinal disease

There is resurgent interest in the use of probiotics to maintain gastrointestinal and systemic health, driven by recent advances in knowledge of bacterial interactions with the epithelium and innate immune system of the intestine. The effects of probiotic bacteria on the intestinal epithelium and their downstream consequences are reviewed. Probiotics prevent pathogen adherence and invasion of the epithelium, partly by blocking adherence sites but also by upregulating gene expression of MUC2 and of antimicrobial peptides. Metabolic effects of probiotics on the intestinal epithelium include production of short chain fatty acids which influence epithelial cell metabolism, turnover and apoptosis. Bacterial metabolism of unabsorbed dietary constituents with production of free radicals and phenolic metabolites can lead to DNA damage and cancer; probiotics restore eubiosis and potentially prevent this. Probiotics alter expression and redistribution of tight junction proteins and reduce intestinal permeability limiting absorption of noxious molecules from the gut lumen. Most studied are the effects of probiotics on epithelial cells which are the first line of innate immune-capable cells that encounter luminal flora. Probiotics, through secreted molecules, influence the innate inflammatory response of epithelial cells to stimuli from the gut lumen, and reduce mucosal inflammation. Through effects on dendritic, and possibly epithelial, cells they influence naïve T cells in the lamina propria of the gut and thus influence adaptive immunity. These varied effects of probiotics have implications for the treatment of several gastrointestinal diseases including antibiotic-associated colitis, acute gastroenteritis, inflammatory bowel disease, colon cancer, and irritable bowel syndrome

Near Field Lenses in Two Dimensions

It has been shown that a slab of materials with refractive index = -1 behaves like a perfect lens focussing all light to an exact electromagnetic copy of an object. The original lens is limited to producing images the same size as the object, but here we generalise the concept so that images can be magnified. For two dimensional systems, over distances much shorter than the free space wavelength, we apply conformal transformations to the original parallel sided slab generating a variety of new lenses. Although the new lenses are not `perfect' they are able to magnify two dimensional objects. The results apply equally to imaging of electric or magnetic sub wavelength objects in two dimensions. The concepts have potential applications ranging from microwave frequencies to the visible.Comment: PDF fil

Master’s of Science Programs in Information Systems: Match Between the Model Curriculum and Existing Programs

In a rapidly changing Information Systems (IS) field, the marketability of students from IS programs is partly related to the responsiveness of the programs to changing market conditions. Thus, curriculum development and periodic finetuning plays a very important role. This paper is an attempt to evaluate the current status of Master’s of Science programs in IS and to study their fit with the recently proposed MSIS 2000 model curriculum. We studied 86 Master’s of Science programs in IS and mapped them onto the proposed curriculum structure. Matches and mismatches with the proposed model curriculum are reported in our results. The results indicate the fit to be somewhat mixed. We have also presented some implications for university administrators and faculty for using the findings of this study and also for further curriculum research

Effects of enteropathogenic bacteria & lactobacilli on chemokine secretion & Toll like receptor gene expression in two human colonic epithelial cell lines

Background & objectives: The intestinal epithelium is part of the innate immune system responding to contact with pathogenic or commensal bacteria. The objective of this study was to compare innate responses of intestinal epithelial cell lines to pathogenic bacteria and to lactobacilli. Methods: Two human intestinal epithelial cell lines, HT29 (enterocyte-like) and T84 (crypt-like), were exposed to pathogenic bacteria representative of non invasive (Vibrio cholerae O1 and O139), adherent (enterohaemorrhagic Escherichia coli, EHEC) or invasive (Salmonella Typhimurium and Shigella flexneri) phenotypes and to non pathogenic Lactobacillus rhamnosus GG or Lactobacillus plantarum. Interleukin-8 (IL-8) was measured in culture supernatant by ELISA, while mRNA from cells was subjected to quantitative reverse transcriptase PCR for several other chemokines (CXCL1, CCL5 and CXCL5) and for Toll-like receptors (TLR) 2, 4, 5 and 9. Results: V. cholerae, S. Typhimurium, S. flexneri and EHEC induced IL-8 secretion from epithelial cells into the medium. Salmonella, Shigella and EHEC, but not V. cholerae, significantly increased mRNA expression of CXCL1. None of the pathogens induced CCL5 or CXCL5. Salmonella and Vibrio significantly increased TLR4 expression, while Vibrio and EHEC decreased TLR5 expression. EHEC also decreased TLR9 expression. Lactobacilli attenuated the IL-8 response of the cell lines to V. cholerae, Salmonella, and EHEC but did not significantly change the IL-8 response to Shigella. Interpretation amp; conclusions: Distinct patterns of epithelial cell chemokine responses were induced by the bacterial pathogens studied and these were modulated by commensal lactobacilli. Alterations in TLR expression by these pathogens are likely to be important in pathogenesis

Resistant starch-an adjunct to oral rehydration solution: not yet ready for prime time

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Imaging the Near Field

In an earlier paper we introduced the concept of the perfect lens which focuses both near and far electromagnetic fields, hence attaining perfect resolution. Here we consider refinements of the original prescription designed to overcome the limitations of imperfect materials. In particular we show that a multi-layer stack of positive and negative refractive media is less sensitive to imperfections. It has the novel property of behaving like a fibre-optic bundle but one that acts on the near field, not just the radiative component. The effects of retardation are included and minimized by making the slabs thinner. Absorption then dominates image resolution in the near-field. The deleterious effects of absorption in the metal are reduced for thinner layers.Comment: RevTeX, (9 pages, 8 figures

Impact of heavy metals on water, fish (Cyprinus carpio) and sediments from a water tank at Tumkur, India

This study was carried out to assess the concentrations of various heavy metals and their distribution in a hyper-eutrophic urban Tumkur tank system, which is being polluted from industrial, domestic and sewage effluents. Samples of water, fish and soil sediment were analyzed for the concentration of seven heavy metals (iron, zinc, copper, nickel, chromium, lead and cadmium) using atomic absorption spectrophotometry. The water-soluble (bioavailable) fractions of heavy metals correlated positively with their total concentration, exhibiting the following sequence of bioavailability: Zn > Cd > Ni > Pb > Cu > Cr > Fe. Cyprinus carpio exhibited a maximum bioaccumulation factor for copper (5500). The mean values of all types of collected samples were correlated with the corresponding mean values in a control tank (Teetha tank). The sequence of the order of the concentration of the metals in water, fish and sediment samples exhibiting higher values than those observed in the control tank was as follows: Cr > Pb > Cu ≈ Ni > Fe > Cd > Zn, Cr > Cd > Cu ≈ Zn > Pb > Fe ≈ Ni and Fe > Pb > Cr > Cu > Ni > Zn > Cd, respectively. The geoaccumulation indices of the heavy metals revealed that the tank is moderately to strongly contaminated. As Cyprinus carpio is extensively used for human consumption, there is a growing health risk that these metals could find their way into the human food chain

Extreme nonlinear electrodynamics in metamaterials with very small linear dielectric permittivity

We consider a sub-wavelength periodic layered medium whose slabs are filled by arbitrary linear metamaterials and standard nonlinear Kerr media and we show that the homogenized medium behaves as a Kerr medium whose parameters can assume values not available in standard materials. Exploiting such a parameter availability, we focus on the situation where the linear relative dielectric permittivity is very small thus allowing the observation of the extreme nonlinear regime where the nonlinear polarization is comparable with or even greater than the linear part of the overall dielectric response. The behavior of the electromagnetic field in the extreme nonlinear regime is very peculiar and characterized by novel features as, for example, the transverse power flow reversing. In order to probe the novel regime, we consider a class of fields (transverse magnetic nonlinear guided waves) admitting full analytical description and we show that these waves are allowed to propagate even in media with $\epsilon0$ since the nonlinear polarization produces a positive overall effective permittivity. The considered nonlinear waves exhibit, in addition to the mentioned features, a number of interesting properties like hyper-focusing induced by the phase difference between the field components.Comment: 12 pages, 7 figure