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Electrolyte Transport (electrolyte + transport)
Selected AbstractsGenome-wide gene expression differences in Crohn's disease and ulcerative colitis from endoscopic pinch biopsies: Insights into distinctive pathogenesisINFLAMMATORY BOWEL DISEASES, Issue 7 2007Feng Wu PhD Abstract Background: Ulcerative colitis (UC) and Crohn's disease (CD) are inflammatory bowel diseases (IBD) with variable, overlapping clinical features and complex pathophysiologies. Methods: To identify pathogenic processes underlying these disease subtypes, we used single endoscopic pinch biopsies to elucidate patterns of gene expression in active and inactive areas of UC and CD and compared these to infectious colitis and healthy control samples. Results: Unsupervised classification of a total of 36 samples yielded promising separation between the affected IBD, unaffected IBD, non-IBD colitis, and normal control samples, suggesting each sample type had a distinctive gene expression pattern. Genes differentially expressed in the CD samples compared to in the controls were related to IFN,-inducible TH1 processes (IFITM1, IFITM3, STAT1, and STAT3) and antigen presentation (TAP1, PSME2, PSMB8). The most noticeable change in the UC samples was reduced expression of genes regulating biosynthesis, metabolism, and electrolyte transport (HNF4G, KLF5, AQP8, ATP2B1, and SLC16A). Twenty-five percent of genes down-regulated in the UC samples were also down-regulated in the infectious colitis samples. Unaffected biopsy samples of IBD patients also registered differences expression of genes compared to in the normal controls. Of these differentially expressed genes, only 2 were up-regulated, PSKH1, a regulator of mRNA processing, and PPID, a suppressor of apoptosis. Conclusions: The study shows that the gene expression patterns of IBD, CD in particular, are quite different from those of infectious colitis, highlighting distinctive expression of genes and pathways in UC and CD. (Inflamm Bowel Dis 2007) [source] Modulation of Na+ transport across isolated rumen epithelium by short-chain fatty acids in hay- and concentrate-fed sheepJOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 11-12 2003S. K. Uppal Summary The effect of increasing concentrations of short-chain fatty acids [SCFA; mixture of the Na+ salts of acetic acid (62.5%), propionic acid (25.0%) and of butyric acid (12.5%)] on Na+ transport of sheep rumen epithelium was studied in vitro. The conventional Ussing chamber method was used for measuring Na+ transport rates (22Na+), short-circuit current (Isc) and tissue conductance (GT) of isolated rumen epithelium. SCFA in the buffer solution on the mucosal side caused a linear increase of Jnet Na+ from 1.14, to 1.22, 1.78 and 2.50 ,eq/cm2/h in hay-fed sheep at 0, 15, 40 and 80 mmol/l SCFA, respectively. In a second study, the effect of higher SCFA concentrations [0 (control), 80, 100 and 120 mmol/l] was investigated with epithelia from two groups of sheep. One group was subjected to hay ad libitum, whereas the other received concentrate feed (800 g/day in equal portions at 7.00 am and 3.00 pm) and hay ad libitum. Epithelia from concentrate-fed sheep again showed a significant (p < 0.05) and linear increase in Jnet Na+ at 80, 100 and 120 mmol/l. However, in hay-fed sheep, the difference in increase among 80, 100 and 120 mmol/l SCFA was not significant, indicating that, above 80 mmol/l SCFA Jms and Jnet exhibit saturation. Moreover, Na+ fluxes (Jms and Jnet) were generally higher in concentrate-fed than in hay-fed sheep at all SCFA concentrations and significant differences were observed at 100 and 120 mmol/l SCFA. The obtained results confirm the effect of SCFA on Na+ transport and are in agreement with studies regarding feeding regimes and electrolyte transport in the rumen. The important new observation is the increase of Na+ transport in concentrate-fed sheep even at high concentrations of SCFA (100 and 120 mmol/l). The enhanced activity of the Na+/H+ exchanger at these SCFA concentrations supports the assumption that the capacity for regulating the intracellular pH by extrusion of protons is increased, suggesting an adaptation in concentrate-fed sheep. This adaptation could prevent possible disturbances of epithelial functions (transport and barrier) under conditions of increased SCFA absorption. [source] Side chain contributions to the interconversion of the topological isomers of guanylin-like peptidesJOURNAL OF PEPTIDE SCIENCE, Issue 6 2005Dr Axel Schulz Abstract The peptide hormones guanylin and uroguanylin are ligands of the intestinal guanylyl cyclase-C (GC-C) that is involved in the regulation of epithelial water and electrolyte transport. The small peptides contain 15 and 16 amino acids, respectively, and two disulfide bonds with a 1,3/2,4 connectivity. This structural feature causes the unique existence of two topological isoforms for each peptide in an approximate 3:2 ratio, with only one of the isoforms exhibiting GC-C-activating potential. The two uroguanylin isomers can be separated by HPLC and are of sufficient stability to be studied separately at ambient temperatures while the two guanylin isomers are rapidly interconverting even at low temperatures. Both isomers show clearly distinguishable 1H chemical shifts. To investigate the influence of certain amino acid side chains on this isomerism and interconversion kinetics, derivatives of guanylin and uroguanylin (L -alanine scan and chimeric peptides) were designed and synthesized by Fmoc solid-phase chemistry and compared by HPLC and 2D 1H NMR spectroscopy. Amino acid residues with the most significant effects on the interconversion kinetics were predominantly identified in the COOH-terminal part of both peptides, whereas amino acids in the central part of the peptides only moderately affected the interconversion. Thus, the conformational conversion among the isomers of both peptides is under the control of a COOH-terminal sterical hindrance, providing a detailed model for this dynamic isomerism. Our results demonstrate that kinetic control of the interconversion process can be achieved by the introduction of side chains with a defined sterical profile at suitable sequence positions. This is of potential impact for the future development of GC-C peptide agonists and antagonists. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd. [source] Standardized procedure for measurement of nasal potential difference: An outcome measure in multicenter cystic fibrosis clinical trials,PEDIATRIC PULMONOLOGY, Issue 5 2004Thomas A. Standaert PhD Abstract Patients with cystic fibrosis (CF) can be discriminated from healthy subjects by measurement of the nasal potential difference, which has become a useful outcome measure for therapies directed toward correcting defective electrolyte transport in CF. A standard operating procedure was developed by a CF Foundation clinical trials network, to be followed by all sites performing collaborative studies. Key variables in the measurement included type of voltmeter, exploring probe, reference electrodes, and solutions used to assess both sodium transport and chloride conductance. Eight sites submitted data on 3,8 normal and 4,5 CF subjects. Baseline voltage, an index of sodium transport, was ,18.2,±,8.3 mV (mean,±,SD) for normals, and ,45.3,±,11.4 mV for CF patients. There was no CFTR-mediated chloride secretion in CF subjects, as evidenced by the lack of response to perfusion with zero chloride,+,beta agonist solutions (+3.2,±,3.5 mV) vs. that in normals (,23.7,±,10.2 mV). The standardized nasal potential difference measurement minimizes variability between operators and study sites. Valid and consistent results can be attained with trained operators and attention to technical details. These data demonstrate the procedure to be sufficient for multicenter studies in the CF Foundation network. Pediatr Pulmonol. 2004; 37:385,392. © 2004 Wiely-Liss, Inc. [source] The antidiarrhoeal activity of Alchornea cordifolia leaf extractPHYTOTHERAPY RESEARCH, Issue 11 2004Gabriel A. Agbor Abstract Diarrhoea is a public health problem in developing countries. It is therefore important and useful to identify plants with antidiarrhoeal activity. Alchornea cordifolia is quoted by many traditional healers as a plant with this activity. The antidiarrhoeal activity of its leaf extract was investigated against castor oil induced diarrhoea in mice, using morphine as the standard reference drug. A signi,cant (p < 0.01) dose related (100 mg/kg, 200 mg/kg, 400 mg/kg, 800 mg/kg) antidiarrhoeal activity of A. cordifolia leaf ethanol extract was observed with 800 mg/kg extract being the most effective. It delayed mouse intestinal transit accelerated by castor oil, inhibited the production of diarrhoeal faeces and modi,ed the ,uid and electrolyte transport across the colonic mucosa when administered intraluminally. Phytochemical screening revealed the presence of tannins and ,avonoids which may account for the increased colonic water and electrolyte reabsorption, a mechanism suggested for the antidiarrhoeal activity of A. cordifolia. Copyright © 2004 John Wiley & Sons, Ltd. [source] | ||||||||||