Intergrowth between the Oxynitride Perovskite SrTaO2N and the Ruddlesden-Popper Phase Sr2TaO3N.

Strontium tantalum oxynitrides were prepared within the nominal composition range of 1.0 ≤ x ≤ 2.0, where x = Sr/Ta atomic ratio. A gradual structural transition was observed between the perovskite SrTaO2N and the Ruddlesden-Popper phase Sr2TaO3N with increasing SrO content. X-ray diffraction analyses showed that a single-phase perovskite was obtained up to x = 1.1, after which Sr2TaO3N gradually appeared at x ≥ 1.25. High-resolution scanning transmission electron microscopy observations identified the gradual intergrowth of a Ruddlesden-Popper Sr2TaO3N type planar structure interwoven with the perovskite crystal lattice upon increasing x. The crystal lattice at x = 1.4 was highly defective and consisted primarily of perovskite intergrown with a large amount of the Ruddlesden-Popper phase structure. This Ruddlesden-Popper phase layer intergrowth is a characteristic of an oxynitride perovskite rather than the Ruddlesden-Popper defects previously reported in oxide perovskites. Partial substitution of Ta with Sr was also evident in this perovskite lattice. Just below x = 2, a perovskite-type structure was intergrown as defects in the Ruddlesden-Popper Sr2TaO3N. Characterization of Sr2TaO3N in ambient air was challenging due to its moisture sensitivity. Thermal analysis demonstrated that this material was relatively stable up to approximately 1400 °C in comparison with SrTaO2N perovskite, especially under nitrogen. Sr2TaO3N could keep its structure in a sealed tube, and some amount of SrCO3 was observed in XRD after 10 days of exposure to 75% relative humidity under prior ambient conditions. A compact of this material had a relative density of 96% after sintering at 1400 °C under 0.2 MPa of nitrogen, even though a drastic loss of nitrogen was previously reported for a SrTaO2N perovskite under these same conditions. Postammonolysis of the Sr2TaO3N ceramics was not required prior to studying its dielectric behavior. This is in contrast to the SrTaO2N perovskite, which requires postammonolysis to recover its stoichiometric composition and electrical insulating properties.

Effect of manganese and vanadium valences on microstructures and reliability of BaTiO3-based multi-layer ceramic capacitors.

The valences of manganese and vanadium oxides in multi-layer ceramic capacitors (MLCCs), sintered under a reducing atmosphere, were investigated using electron paramagnetic resonance; insulation resistance degradation was analyzed using impedance spectroscopy in highly accelerated lifetime tests to clarify the influences of manganese and vanadium on both the electrical properties and microstructure of MLCCs. The Mn(2+) was stable in the reducing-atmospheresintered MLCCs and formed a grain boundary. Vanadium mitigated insulation resistance degradation and increased the reliability of the MLCCs. Although V4+ was detected in MLCCs that had 0.20 mol% and 0.30 mol% of added vanadium, the electrical properties were dependent upon other ions, e.g., V(3+) or V(5+). All vanadium ions except for V(4+) decreased the insulation resistance of ceramic/electrode interface. This is because vanadium reduces electric field concentration at the ceramic/ electrode interface and delays the onset of oxygen vacancy migration in the early stages of a highly accelerated lifetime test.

Peroxiredoxin I protects gastric mucosa from oxidative injury induced by H. pylori infection.

BACKGROUND AND AIM: Helicobacter pylori (H. pylori) infection enhances the production of reactive oxygen species and peroxynitrite, thereby resulting in oxidative tissue damage. In this study, we examined the role of peroxiredoxin I (Prx I), a stress-induced antioxidant enzyme, in protecting gastric mucosa from H. pylori-induced gastric mucosal injury. METHODS: Wild type (Prx I(+/+)) and Prx I-deficient type (Prx I(-/-)) mice were maintained for 2 to 12 months with or without infection of H. pylori, Sydney strain-1. Gastric mucosal expression of Prx I was assessed by immunoblot analysis and immunohistochemistry. The degree of gastritis was evaluated by the updated Sydney system and by mucosal levels of inflammatory cytokines (MIP-2, IL-1beta, and TNF-alpha). Oxidative DNA injury and apoptosis were analyzed by mucosal level of 8-hydroxy-2'-deoxyguanosine, and the number of apoptotic cells stained with a single-stranded DNA antibody, respectively. RESULTS: H. pylori infection upregulated gastric mucosal Prx I expression in the Prx I(+/+) but not the Prx I(-/-) mice. H. pylori infection also induced more severe gastritis and a more prominent increase in MIP level, more marked oxidative DNA injury, and apoptosis in the Prx I(-/-) than the Prx I(+/+) mice. In the absence of H. pylori infection, no changes were demonstrated in gastric mucosa in either the Prx I(+/+) or the Prx I(-/-) mice. CONCLUSION: These data suggest that H. pylori infection upregulates gastric mucosal Prx I expression, and further, that Prx I plays an important role in gastric mucosal protection against oxidative injury induced by H. pylori infection.

Neoplastic transformation and induction of H+,K+ -adenosine triphosphatase by N-methyl-N'-nitro-N-nitrosoguanidine in the gastric epithelial RGM-1 cell line.

N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) induces gastric cancer in animal models. We established an MNNG-induced mutant of the rat murine RGM-1 gastric epithelial cell line, which we named RGK-1, that could be used as an in vitro model of gastric cancer. This cell line showed signs of neoplasia and transformation, in that it lost contact inhibition and formed tumors in nude mice. The mutant cells also expressed parietal cell-specific H(+),K(+)-adenosine triphosphatase (H(+),K(+)-ATPase), which parent RGM-1 did not. The results suggested that parent RGM-1 cells were gastric progenitor cells. This mutant RGK-1 cell line will contribute to future investigation on gastric carcinogenesis and to the development of other pathophysiologic fields.

Geranylgeranylacetone protects the human gastric mucosa from diclofenac-induced injury via induction of heat shock protein 70.

BACKGROUND/AIM: Geranylgeranylacetone (GGA) enhances gastric mucosal protection against nonsteroidal anti-inflammatory drugs by upregulating mucosal heat shock proteins (HSP), but the effects of GGA on the human gastric mucosa have not been well examined. This study was conducted to determine whether a clinical dose of GGA protects the human gastric mucosa from diclofenac (DIC)-induced gastric mucosal injury. METHODS: The study group comprised 40 healthy volunteers: 20 subjects were randomly assigned to take either placebo (lactose 1.5 g/day) or GGA (150 mg/day) for 2 weeks (study 1), and 20 subjects were assigned to take DIC (75 mg/day) plus placebo (lactose 1.5 g/day) or DIC (75 mg/day) plus GGA (150 mg/day) for 2 weeks (study 2). In both studies, gastroscopic biopsy specimens were obtained before and after treatment. Mucosal HSP70 expression and DNA damage were analyzed by measuring the levels of HSP70 and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-OHdG), respectively. RESULTS: In study 1, GGA increased the mucosal HSP70 expression without increasing the 8-OHdG production. In study 2, DIC treatment increased the 8-OHdG production, whereas the combination of GGA and DIC enhanced the HSP70 expression and attenuated the increase in 8-OHdG induced by DIC. CONCLUSION: The clinical dose of GGA enhanced the gastric mucosal HSP70 expression and inhibited the DIC-induced gastric mucosal damage in humans.

Hyperosmotic stress enhances interleukin-1beta expression in Helicobacter pylori-infected murine gastric epithelial cells in vitro.

BACKGROUND AND AIM: Gastric cancer is associated not only with Helicobacter pylori (H. pylori) infection, but also with the intake of a high salt diet. Interleukin-1beta (IL-1beta) is highly expressed in H. pylori-infected gastric mucosa. The aim of the present study was to determine if hyperosmotic stress induces IL-1beta expression in gastric epithelial cells in vitro. METHOD: Murine gastric epithelial cells, GSM06, were cultured with or without H. pylori (Sydney strain-1) at different osmolarities in the range of 300-450 mOsM. Expressions of IL-1beta mRNA and mature IL-1beta protein were evaluated by reverse transcription-polymerase chain reaction (RT-PCR) and an IL-1beta enzyme-linked immunosorbent assay (ELISA), respectively. IL-1beta converting enzyme (ICE) activity was measured by an ICE colorimetric assay. Apoptosis was evaluated by a single stranded-DNA assay. RESULTS: Addition of H. pylori at 300 mosM caused significant increases in IL-1beta mRNA, IL-1beta protein, ICE activity and apoptosis. Hyperosmotic stress alone also caused upregulation of IL-1beta mRNA and IL-1beta protein, enhanced ICE activity and accelerated apoptosis. Hyperosmotic stress accentuated the increases in IL-1beta mRNA, IL-1beta protein, ICE activity and apoptosis induced by H. pylori alone. Enhancement of IL-1beta protein release induced by hyperosmotic stress was significantly attenuated by an ICE inhibitor, Z-YVAD-FMK. CONCLUSIONS: Hyperosmotic stress enhances the release of bioactive mature IL-1beta protein in H. pylori-infected gastric epithelial cells, in part by upregulating IL-1beta mRNA expression, and in part by enhancing ICE activity. These results may explain the mechanisms by which chronic intake of a high salt diet increases the risk of gastric cancer among H. pylori-infected human subjects.

Influence of chemotherapeutic agents and cytokines on the expression of 5-fluorouracil-associated enzymes in human colon cancer cell lines.

BACKGROUND: Several studies have demonstrated that intratumoral expression of catabolizing and anabolizing enzymes for 5-fluorouracil (5-FU) is important in the response of cancers to 5-FU-based chemotherapy. We investigated the influence of other chemotherapeutic agents or cytokines, which are often administered for enhancing the efficacy of 5-FU, on the tumoral expression of 5-FU-associated enzymes, i.e., dihydropyrimidine dehydrogenase (DPD), thymidylate synthase (TS), orotate phosphoribosyl transferase (OPRT), and thymidine phosphorylase (TP). METHODS: Human colon cancer cell lines (HT-29, Caco-2, and DLD-1) were incubated with 5-FU and with 5-FU combined with cisplatin, camptothecin, paclitaxel, mitomycin C, interferon, or TNF-related apoptosis-inducing ligand. mRNA expression of 5-FU-associated enzymes was assessed by real-time PCR. Activity of each enzyme and intracellular 5-FU accumulation after incubation with such agents were also evaluated. RESULTS: Each agent had a synergistic effect on the cytotoxicity of 5-FU. All chemotherapeutic agents other than cytokines induced marked alteration of the mRNA expression profile of 5-FU-associated enzymes; depression of DPD, elevation of TS, and slight suppression of OPRT and TP. In accordance with mRNA expression, enzyme activity of DPD was significantly depressed by such agents. Furthermore, although 5-FU itself increased DPD mRNA expression, a mechanism considered to be related to the acquisition of 5-FU resistance, the addition of cisplatin or camptothecin significantly inhibited the 5-FU-induced elevation of DPD. CONCLUSIONS: 5-FU-associated enzymes in colon cancer cells were greatly influenced by various chemotherapeutic agents; in particular, DPD expression was depressed. These results appear important in planning chemotherapy and also in understanding the development of adverse effects of 5-FU.

Alteration of intestinal epithelial function by intraepithelial lymphocyte homing.

BACKGROUND: Intimate cross-talk may take place between intestinal epithelial cells and intraepithelial lymphocytes (IEL). The purpose of this study was to analyze the influence of lymphocyte migration into the epithelium on epithelial function, using an in vitro "IEL homing" model. METHODS: Molecular expression on epithelial cells was analyzed by flow cytometry. The barrier function of the epithelial monolayer was assessed by transepithelial electrical resistance. Cytokine production was measured by enzyme-linked immunosorbent assay (ELISA). RESULTS: (1) IEL homing into the epithelia induced significant phenotypic changes in epithelial cells; upregulation of MHC class I, and II, intercellular adhesion molecule (ICAM)-1, and CD44. IEL-derived interferon-gamma (IFN-gamma) could partially account for this alteration, as a neutralizing antibody (Ab) against IFN-gamma inhibited the upregulation of these molecules, except for CD44. (2) A marked fall in transepithelial electrical resistance was observed 4 h after IEL homing started, and Ab against IFN-gamma slightly inhibited this fall in resistance. (3) The production of interleukin (IL)-8 and IFN-gamma inducible protein-10 (IP-10), but not transforming growth factor (TGF)-beta1 or tumor necrosis factor (TNF)-alpha, in the epithelial monolayer was markedly induced after IEL homing in a basolaterally polarized fashion. IEL-conditioned media also induced the production of these cytokines in epithelial cells, thus suggesting that IEL-derived soluble factor(s) induce epithelial chemokine production. CONCLUSIONS: Under inflammatory conditions, IEL obviously interact with epithelial cells and upregulate adhesion molecules, alter barrier function, and enhance chemokine production. Because such alterations may increase epithelial permeability to luminal antigens or accelerate the migration of other inflammatory cells, our results suggest that IEL have a critical role in mucosal immunity.

Rebamipide significantly inhibits indomethacin-induced mitochondrial damage, lipid peroxidation, and apoptosis in gastric epithelial RGM-1 cells.

Nonsteroidal antiinflammatory drugs (NSAIDs) cause complications such as gastrointestinal injury. NSAIDs were recently reported to cause mitochondrial injury: to dissipate the mitochondrial transmembrane potential (MTP), and to induce mitochondrial permeability transition pore (PTP), which liberates cytochrome c. This enzyme generates reactive oxygen species (ROS) thereby triggers caspase cascade and cellular lipid peroxidation, resulting in cellular apoptosis. However, the mechanism of this NSAID-induced MTP's role in cellular apoptosis remains unknown. Rebamipide, an antiulcer drug, is reported to scavenge ROS and to show the protective effects on indomethacin-induced tissue peroxidations. Since cytochrome c and its generation of ROS are involved in indomethacin-induced cellular apoptosis, rebamipide may attenuate mitochondrial damage. The aim of this study was to elucidate whether indomethacin induces both the MTP decrease and cellular apoptosis, and the effect of rebamipide on these phenomena. We examined the effect of rebamipide on 1) MTP change, 2) lipid peroxidation, 3) apoptosis, and 4) caspase activation using gastric mucosal epithelial cell-line treated with indomethacin. With a specially designed fluorescence analyzing microscope system, MTP change, cellular lipid peroxidation, and cellular apoptosis were investigated with the small star, filled following fluorescent dyes, MitoRed, DPPP, and Hoechst 33,258, respectively. Indomethacin treatment decreased MTP but increased both cellular lipid peroxidation and cellular apoptosis via caspase 3 and 9 activation. Rebamipide clearly inhibited these phenomena {in vitro}. We demonstrated that fluorescent dyes such as MitoRed, DPPP, and Hoechst 33,258 are useful indicators for detecting oxidative cellular injuries in living cells. Rebamipide exerts a protective effect on mitochondrial membrane stability in gastric epithelial cells.

Efficacy of endoscopic nasobiliary drainage for the prevention of pancreatitis after papillary balloon dilatation: a pilot study.

OBJECTIVE: Endoscopic papillary balloon dilatation (EPBD) has been reported to increase the risk of post-endoscopic retrograde cholangiopancreatography (ERCP) pancreatitis (4%-11%). Based on the hypothesis that performing endoscopic nasobiliary drainage (ENBD) could prevent this complication, we performed EPBD combined with ENBD (EPBD/ENBD) and analyzed the risk of pancreatitis. METHODS: Thirty-four patients underwent EPBD followed by ENBD for common bile duct stone(s). Serum amylase levels the following morning and incidence of pancreatitis were compared with those previously reported and with complications of simple diagnostic ERCP performed in our institution. RESULTS: After EPBD/ENBD, amylase levels the following morning were 214.5 +/- 152.9 U/L, and no cases developed pancreatitis or hyperamylasemia (>3 times normal). These outcomes were favorable compared with previous EPBD reports. Furthermore, despite the stress of EPBD/ENBD after ERCP, these outcomes were better, even compared with simple ERCP performed at our institution [amylase levels: 318.7 +/- 475.2 U/L; hyperamylasemia: 16.5% (P = 0.006); pancreatitis: 7.1%]. CONCLUSION: Although EPBD has been regarded as a risk factor for post-ERCP pancreatitis, our results suggest the possibility that application of ENBD after EPBD decreases the incidence of pancreatitis and should be studied further. We speculate that ENBD itself prevents pancreatic duct obstruction by residual stones or papillary edema.

Ammonia-induced apoptosis is accelerated at higher pH in gastric surface mucous cells.

Gastric luminal ammonia produced by Helicobacter pylori has been shown to cause gastric mucosal injury. This study was conducted to examine the mechanisms by which gastric luminal ammonia causes apoptosis of gastric epithelial cells. Monolayers of GSM06 cells, developed from murine gastric surface mucous cells, were cultured in the absence or presence of 10-30 mM NH(4)Cl at ambient pH of 5.0, 6.0, and 7.0. In the presence of luminal NH(4)Cl, GSM06 cells showed 1) cell shrinkage and nuclear chromatin condensation, 2) DNA fragmentation into oligonucleosomes, 3) leakage of cytochrome c into cytosolic fraction without affecting bax expression, and 4) increases in activity of caspases-3 and -9. These changes were accentuated when the cells were cultured at pH 7.0. In the absence of NH(4)Cl, none of these changes was detected at any pH examined. These results suggest that gastric luminal ammonia, at concentrations detected in H. pylori-infected subjects, induces apoptosis of gastric epithelial cells by release of cytochrome c from mitochondria, followed by activation of caspases-9 and -3, especially at higher ambient pH.

EGF promotes gastric mucosal restitution by activating Na(+)/H(+) exchange of epithelial cells.

This study was conducted to determine whether the contributions of epidermal growth factor (EGF) to gastric mucosal restitution after injury are mediated by stimulation of Na(+)/H(+) exchangers in surface mucous cells (SMC). Intact sheets of guinea pig gastric mucosae were incubated in vitro. Intracellular pH (pH(i)) in SMC was measured fluorometrically, using 2',7'- bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein. Restitution after Triton X-100-induced injury was evaluated by recovery of electrical resistance. At neutral luminal pH, exogenous EGF (ex-EGF) increased pH(i) and enhanced restitution in the absence but not in the presence of serosal HCO. During exposure to luminal acid, ex-EGF not only prevented intracellular acidosis but also promoted restitution. These effects of ex-EGF were blocked by serosal amiloride or anti-EGF-receptor antibody. In the absence of ex-EGF, restitution was inhibited by replacement of luminal and serosal solutions with fresh solutions and was blocked more completely by serosal anti-EGF-receptor antibody. These results suggest that both endogenous and ex-EGF contribute to restitution via basolateral EGF receptors, with effects mediated, at least in part, by stimulation of basolateral Na(+)/H(+) exchangers.