Hydrogen peroxide stimulates rat colonic prostaglandin production and alters electrolyte transport.

The changes in short circuit current (electrogenic Cl- secretion) of rat colon brought about by xanthine/xanthine oxidase in the Ussing chamber were inhibited by catalase and diethyldithiocarbamate, but not by superoxide dismutase. These results, the reproduction of the response with glucose/glucose oxidase and with exogenous H2O2, and the lack of effect of preincubation with deferoxamine or thiourea implicate H2O2, and not O2- or OH., as the important reactive oxygen metabolite altering intestinal electrolyte transport. 1 mM H2O2 stimulated colonic PGE2 and PGI2 production 8- and 15-fold, respectively, inhibited neutral NaCl absorption, and stimulated biphasic electrogenic Cl secretion with little effect on enterocyte lactic dehydrogenase release, epithelial conductance, or histology. Cl- secretion was reduced by cyclooxygenase inhibition. Also, the Cl- secretion, but not the increase in prostaglandin production, was reduced by enteric nervous system blockade with tetrodotoxin, hexamethonium, or atropine. Thus, H2O2 appears to alter electrolyte transport by releasing prostaglandins that activate the enteric nervous system. The change in short circuit current in response to Iloprost, but not PGE2, was blocked by tetrodotoxin. Therefore, PGI2 may be the mediator of the H2O2 response. H2O2 produced in nontoxic concentrations in the inflamed gut could have significant physiologic effects on intestinal water and electrolyte transport

ALDH1A2 (RALDH2) genetic variation in human congenital heart disease

Abstract\ud \ud \ud \ud Background\ud \ud Signaling by the vitamin A-derived morphogen retinoic acid (RA) is required at multiple steps of cardiac development. Since conversion of retinaldehyde to RA by retinaldehyde dehydrogenase type II (ALDH1A2, a.k.a RALDH2) is critical for cardiac development, we screened patients with congenital heart disease (CHDs) for genetic variation at the ALDH1A2 locus.\ud \ud \ud \ud Methods\ud \ud One-hundred and thirty-three CHD patients were screened for genetic variation at the ALDH1A2 locus through bi-directional sequencing. In addition, six SNPs (rs2704188, rs1441815, rs3784259, rs1530293, rs1899430) at the same locus were studied using a TDT-based association approach in 101 CHD trios. Observed mutations were modeled through molecular mechanics (MM) simulations using the AMBER 9 package, Sander and Pmemd programs. Sequence conservation of observed mutations was evaluated through phylogenetic tree construction from ungapped alignments containing ALDH8 s, ALDH1Ls, ALDH1 s and ALDH2 s. Trees were generated by the Neighbor Joining method. Variations potentially affecting splicing mechanisms were cloned and functional assays were designed to test splicing alterations using the pSPL3 splicing assay.\ud \ud \ud \ud Results\ud \ud We describe in Tetralogy of Fallot (TOF) the mutations Ala151Ser and Ile157Thr that change non-polar to polar residues at exon 4. Exon 4 encodes part of the highly-conserved tetramerization domain, a structural motif required for ALDH oligomerization. Molecular mechanics simulation studies of the two mutations indicate that they hinder tetramerization. We determined that the SNP rs16939660, previously associated with spina bifida and observed in patients with TOF, does not affect splicing. Moreover, association studies performed with classical models and with the transmission disequilibrium test (TDT) design using single marker genotype, or haplotype information do not show differences between cases and controls.\ud \ud \ud \ud Conclusion\ud \ud In summary, our screen indicates that ALDH1A2 genetic variation is present in TOF patients, suggesting a possible causal role for this gene in rare cases of human CHD, but does not support the hypothesis that variation at the ALDH1A2 locus is a significant modifier of the risk for CHD in humans.Work supported by grants from Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) 01/000090; 00/030722; 01/142381; 02/113402; 03/099982; 04/116068; 04/157044 and Conselho Nacional de Desenvolvimento Científico e Tecnológico 481872/20078. We would like to thank the careful work and thoughtful suggestions of the two reviewers responsible for the reviewing editorial process.Work supported by grants from Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) 01/00009-0; 00/03072-2; 01/14238-1; 02/11340-2; 03/09998-2; 04/11606-8; 04/15704-4 and Conselho Nacional de Desenvolvimento Científico e Tecnológico 481872/2007-8. We would like to thank the careful work and thoughtful suggestions of the two reviewers responsible for the reviewing editorial process

Prostaglandin- and theophylline-induced Cl secretion in rat distal colon is inhibited by microtubule inhibitors

The aim of the present study was to examine the possible role of microtubules in chloride secretion by distal rat colon stimulated by prostaglandin (PGE 2 ) and theophylline. Distal colonic tissue from male rats was mounted in Ussing chambers, and short-circuit current (I sc ) was measured to assess chloride secretion. Three microtubule inhibitors, colchicine, nocodazole, and taxol, all inhibited the stimulated I sc and reduced the 60-min integrated secretory response to PGE 2 and theophylline (▪I sc dt) by 39–52%, whereas the inactive colchicine analog lumicolchicine did not. Atropine and tetrodotoxin had no effect on stimulated chloride secretion. To confirm the source of I sc , unidirectional 22 Na + and 36 Cl − fluxes were measured in tissues exposed to lumicolchicine (control) or colchicine. Control tissues absorbed both chloride [5.0 (1.1–8.6) (median and 95% confidence interval) μeq/cm 2 /hr] and sodium [2.8 (0.9–7.2) μeq/cm 2 /hr], and this net absorption was reduced by 96% and 79%, respectively, by treatment with PGE 2 and theophylline due to an increase in serosal-to-mucosal chloride and sodium movement. Colchicine-treated tissues exhibited similar net basal chloride and sodium absorption that was reduced by 71% and 75%, respectively, by treatment with PGE 2 and theophylline. Thus the PGE 2 - and theophylline-induced increase in chloride secretion was significantly reduced by colchicine ( P <0.05 by Wilcoxon rank-sum test), whereas colchicine had no effect on PGE 2 - and theophylline-induced changes in sodium fluxes. Furthermore, the colchinine-related changes in stimulated chloride secretion were numerically similar to colchicine-related changes in stimulated I sc . These findings indicate that microtubules are required for normal PGE 2 - and theophylline-induced chloride secretion in distal rat colon and suggest that induced chloride secretion may involve vesicular insertion of ion transporters into the plasma membrane or other microtubule-dependent regulatory processes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44414/1/10620_2005_Article_BF01299864.pd

Exchange Rate Regimes and Relative Prices: An Industry-Level Empirical Investigation

exchange rate policy, expenditure switching, pass-through, relative prices

Recipient-derived hepatocytes in sex-mismatched liver allografts after liver transplantation: Early versus late transplant biopsies

PubMed ID: 15591954Background. The presence of microchimerism in transplanted tissues is well defined; however, the timeframe of appearance and disappearance of engraftment in liver allograft is unknown. The aims of this study were to analyze for the presence of "recipient-derived cells" in sex-mismatched individuals after liver transplantation, comparing the frequency of "recipient-derived cell repopulation" in early versus late transplant biopsies and to evaluate the relationship between "recipient-derived cell repopulation" and the severity of graft injury. Methods. Paraffin-embedded liver biopsy samples of 18 recipients were reviewed. Sixteen of them were obtained from recipients with sex-mismatched donors. The remaining two were obtained from recipients with sex-matched donors and were used as controls. Immunohistochemistry and fluorescence in situ hybridization double-labeling method were performed on pretreated slides using anti-human hepatocyte antibody to identify hepatocytes, a mouse anti-human cytokeratin-7 to identify ductal epithelial cells, and using CEPX/Y DNA probes for visualizing X and Y chromosomes. The double-labeled slides were examined systematically using an image analyzer system. Results. The mean time from transplantation to biopsy was 8.1 months. Eleven of the 16 samples obtained from recipients with sex-mismatched grafts demonstrated "recipient-derived hepatocyte repopulation," comprising a mean of 2.1% of the hepatocytes. In the control biopsies, none of the cells demonstrated different nuclear signals from the donor's sex origin. The presence and proportion of "recipient-derived hepatocyte repopulation" rate were significantly higher in early transplant biopsies than in late transplant biopsies (P<0.05). Conclusion. Some hepatocytes of sex-mismatched liver grafts were replaced by "recipient-derived cells" during injury. Such repopulation is more common in the early liver-graft biopsies. The severity of acute cellular rejection appears to have no effect on the rate of recipient-derived repopulation

Hydrogen peroxide stimulates rat colonic prostaglandin production and alters electrolyte transport.

The changes in short circuit current (electrogenic Cl- secretion) of rat colon brought about by xanthine/xanthine oxidase in the Ussing chamber were inhibited by catalase and diethyldithiocarbamate, but not by superoxide dismutase. These results, the reproduction of the response with glucose/glucose oxidase and with exogenous H2O2, and the lack of effect of preincubation with deferoxamine or thiourea implicate H2O2, and not O2- or OH., as the important reactive oxygen metabolite altering intestinal electrolyte transport. 1 mM H2O2 stimulated colonic PGE2 and PGI2 production 8- and 15-fold, respectively, inhibited neutral NaCl absorption, and stimulated biphasic electrogenic Cl secretion with little effect on enterocyte lactic dehydrogenase release, epithelial conductance, or histology. Cl- secretion was reduced by cyclooxygenase inhibition. Also, the Cl- secretion, but not the increase in prostaglandin production, was reduced by enteric nervous system blockade with tetrodotoxin, hexamethonium, or atropine. Thus, H2O2 appears to alter electrolyte transport by releasing prostaglandins that activate the enteric nervous system. The change in short circuit current in response to Iloprost, but not PGE2, was blocked by tetrodotoxin. Therefore, PGI2 may be the mediator of the H2O2 response. H2O2 produced in nontoxic concentrations in the inflamed gut could have significant physiologic effects on intestinal water and electrolyte transport

Immune system control of rat and rabbit colonic electrolyte transport. Role of prostaglandins and enteric nervous system.

The role of the immune system in controlling intestinal electrolyte transport was studied in rat and rabbit colon in Ussing chambers. A phagocyte stimulus, the chemotactic peptide FMLP, and a mast cell stimulus, sheep anti-rat IgE, caused a brief (less than 10 min) increase in short-circuit current (Isc). Products of immune system activation, platelet-activating factor (PAF) and reactive oxygen species (ROS), caused a sustained, biphasic increase in the Isc. Ion replacement and flux studies indicated that these agonists stimulated electrogenic Cl secretion and inhibited neutral NaCl absorption; responses that were variably inhibited by the cyclooxygenase blockers indomethacin and piroxicam. Lesser degrees of inhibition by nordihydroguaiaretic acid could be accounted for by decreased prostaglandin synthesis rather than by lipoxygenase blockade. Tetrodotoxin, hexamethonium, and atropine also inhibited immune agonist-stimulated Isc, but had no effect on immune agonist-stimulated production of PGE2 or PGI2. These results indicate that immune system agonists alter intestinal epithelial electrolyte transport through release of cyclooxygenase products from cells in the lamina propria with at least 50% of the response being due to cyclooxygenase product activation of the enteric nervous system. The immune system, like the enteric nervous system and the endocrine system, may be a major regulating system for intestinal water and electrolyte transport in health and disease