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A Terano

Publications and source records attributed to A Terano.

At least 145 records · Page 8Linked to original sources
PubMed1991

Beta-angonists modulate ACh-inhibition of a K current in intestinal smooth muscle cells.

ACh causes a long-lasting inhibition of STOCs via G proteins in intestinal smooth muscle cells. We examined the effects of isoproterenol (Iso) on the ACh-induced inhibition of STOCs in isolated ileal smooth muscle cells using the G omega-seal whole cell clamp technique. In control, ACh (1 microM) completely suppressed STOCs, which did not desensitize over a period lasting 20 minutes. When Iso (10 microM) was added to the bath in the presence of ACh, the ACh-induced inhibition of STOCs was gradually removed. This effect of Iso was prevented by propranolol (10 microM). Application of Db-cAMP (500 microM) mimicked the Iso effects. Intracellulary applied GTP-gamma S (100 microM) gradually suppressed STOCs in the absence of ACh, which could not be removed by either Iso or Db-cAMP. These results suggest that beta-adrenergic stimulation causes a removal of the muscarinic inhibition of STOCs via a cAMP-dependent process.

Acetylcholine↗
PubMed1991

Protective effect of tauroursodeoxycholate against chenodeoxycholate-induced damage to cultured rabbit gastric cells.

Ursodeoxycholate (UDC) and tauroursodeoxycholate (TUDC) have been reported to be protective against liver injury induced by other bile salts. UDC also has been shown to be effective against refluxed bile-induced gastritis after gastric surgery. However the mechanism of the therapeutic effect of UDC on gastric mucosa has not been known. In the present study, cytoprotective actions of UDC and TUDC against chenodeoxycholate (CDC)-induced gastric injury were investigated using rabbit gastric cell cultures without systemic factors. Rabbit gastric mucosal cells were cultured after the isolation of rabbit gastric cells with collagenase and ethylenediaminetetraacetic acid. Cytotoxicity was quantified by measuring 51Cr release from prelabeled cells and MTT assay. Prostaglandin (PG) E2 was assayed by radioimmunoassay. Concentrations of CDC greater than 0.5 mM or UDC greater than 5 mM caused cellular damage and increased 51Cr release in a dose-dependent and time-dependent fashion, while TUDC up to 10 mM did not. TUDC, but not UDC, showed a significant decrease of CDC (1.5 mM)-induced 51Cr release dose dependently. The protective effect of TUDC against CDC-induced damage was confirmed by MTT assay. On phase-contrast microscopy, disruption of monolayers induced by CDC (1.5 mM) was clearly protected by TUDC (10 mM). Free radical scavengers (500 units/ml of superoxide dismutase, 300 units/ml of catalase, and 100 mM of dimethyl sulfoxide) or a calcium blocker (10(-7)-10(-5) M verapamil) did not show significant protection against CDC-induced damage. Deprivation of Ca2+ in the media did not affect CDC-induced damage. Thus free radicals or Ca2+ might not be involved in the cell toxicity of CDC.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Characterization of a newly established cell line (JR-St) derived from human gastric signet ring cell cancer, producing tumor markers.

Despite the importance of in vitro study of gastric cancer, there are very few established cell lines derived from human gastric carcinoma. We have recently established a new cell line derived from human gastric cancer which has the ability to produce tumor markers. This cell line has been designated JR-St. This cell line was derived from the cerebrospinal fluid of a 37-yr-old female patient who had metastatic brain tumor of signet ring cell gastric adenocarcinoma. This cell line has been maintained for more than 24 months through 80 passages with stable growth. PAS staining showed intracellular mucin granules. Transmission and scanning electron microscopy revealed cells with numerous microvilli and fine projections as well as intracellular granules, indicating mucin. This cell line had the ability to produce high concentrations of tumor markers such as carcinoembryonic antigen (CEA) and carbohydrate antigen (CA) 19-9. Thus Thus this cell line should provide a very useful tool for the investigation of gastric cancer such as analysis of tumor markers as well as effects of anti-cancer drugs or growth factors.

Adenocarcinoma, Mucinous↗
PubMed1991

Endothelin-1 secretion from cultured rabbit gastric epithelial cells.

It has been shown that endothelin-1 (ET-1) is synthesized in various extraendothelial tissues. Although ET-1 has been reported to have potent ulcerogenic action in the stomach, the synthesis and physiological roles of ET-1 in the gastric mucosa are poorly understood. The aim of the present study was to investigate whether or not cultured gastric epithelial cells secrete ET-1 and possess autocrine functions. Gastric epithelial cells from rabbits were cultured in medium supplemented with 10% FBS after isolation. ET-1 was extracted by C18 columns from serum-free culture media and measured by radioimmunoassay (RIA). Effects of ET-1 on the intracellular concentration of calcium of the cultured cells were examined with Indo-1. Prostaglandin E2 (PGE2) was measured by RIA. Primary cultures of gastric epithelial cells were mainly composed of mucous cells. ET-1 was detected in the culture medium by RIA, and 70 pg/10(6) cells/24 h of ET-1 was secreted by cultured cells. Tumor growth factor-beta (4 ng/ml) and thrombin (8 U/ml) significantly increased ET-1 secretion. Exogenously administered ET-1 up to 10(-6) M neither modulated the intracellular calcium concentration nor affected PGE2 release by these cells. These results suggest that gastric mucous cells in culture secrete ET-1. Further studies are needed to explore the possible involvement of such paracrine function in the reported ulcerogenic action of ET-1.

Animals↗
PubMed1991

Role for iron in reactive oxygen species-mediated cytotoxicity to cultured rat gastric mucosal cells.

The gastric epithelium is exposed to oxygen species that are generated within the lumen. Reactive oxygen species, enzymatically generated, cause injury to cultured rat gastric mucosal cells. Much interest has been focused on the role of iron in producing oxidant-mediated injury to the gastric mucosa, because iron is a catalyst that promotes the production of .OH possibly from O2-. and H2O2 (Haber-Weiss reaction) or from H2O2 alone (Fenton reaction). With the use of an iron chelator and an iron binding protein, we examined the role of iron in producing oxidant-mediated injury to cultured gastric mucosal cells. Reactive oxygen species and H2O2 were generated by hypoxanthine-xanthine oxidase and glucose-glucose oxidase, respectively, in buffer without iron. Pretreatment with deferoxamine diminished hypoxanthine-xanthine oxidase-induced 51Cr release from prelabeled cells, dose dependently. Furthermore, addition of deferoxamine to the reactive oxygen species-generating system also protected against the injury. However, apotransferrin (which binds extracellular iron) failed to protect cells. Pretreatment with .OH scavengers was partially protective. Depletion of glutathione with diethyl maleate enhanced reactive oxygen species-mediated cytolysis; such cytolysis was inhibited by deferoxamine. Deferoxamine also decreased 51Cr release induced by glucose-glucose oxidase. We conclude that intracellular iron plays a crucial role in mediating oxygen radical damage to gastric mucosal cells. The .OH, produced from H2O2 by the iron-catalyzed Fenton reaction, seems to be the main mediator of oxidant-induced cytotoxicity to gastric mucosal cells in vitro.

Animals↗
PubMed1991

Reduced glutathione protects cultured gastric mucosal cells from suckling rats against acid.

We examined the role of reduced glutathione as a defense mechanism against acid-induced gastric mucosal cell damage in vitro. Cellular stores of reduced glutathione were depleted by reaction with diethyl maleate (DEM) or 1-chloro-2,4-dinitrobenzene (CDNB) and increased by reaction with L-cysteine. Depletion of cellular glutathione by reaction with DEM or CDNB potentiated gastric mucosal cell lysis by acid. Increase of cellular glutathione by L-cysteine decreased cell lysis by acid. Altering the cellular reduced-to-oxidized glutathione ratio by tert-butyl hydroperoxide or diamide increased cellular susceptibility to acid. Reduced glutathione is essential for glutathione peroxidase to catalyze hydrogen peroxide. We further studied whether oxygen free radicals were involved in the pathogenesis of acid-induced gastric mucosal injury in vitro. Neither superoxide dismutase, catalase, nor dimethyl sulfoxide decreased acid-induced gastric mucosal cell damage. We conclude that reduced glutathione plays an important role as a defense mechanism against acid-induced injury in cultured rat gastric mucosal cells. Production of oxygen radical in response to acid exposure may occur intracellularly, since exogenous oxygen radical scavengers, which do not gain access to the interior of cells, had no protective effect. Reduced glutathione might protect gastric mucosal cells by mechanisms other than the elimination of oxygen free radicals.

Acids↗
PubMed1991

Oxygen metabolites stimulate mucous glycoprotein secretion from cultured rat gastric mucous cells.

The aims of this study were to investigate the interaction between oxygen radicals and mucus secretion from cultured rat gastric mucous cells, and to assess the role of prostaglandin production in the modulation of mucus secretion in vitro. Xanthine oxidase in the presence of hypoxanthine caused a dose-dependent increase in the presence of hypoxanthine caused a dose-dependent increase of mucus secretion, as assessed by release of [3H]glucosamine from prelabeled cells, whereas xanthine oxidase or hypoxanthine alone did not. Xanthine oxidase (10 mU/ml) increased release of [3H]glucosamine by 57 +/- 6% compared with control values (P less than 0.001). Catalase (3,000 U/ml) inhibited xanthine oxidase-induced mucus secretion by 69 +/- 9% (P less than 0.01), whereas superoxide dismutase did not. Pretreatment with deferoxamine, an inhibitor of hydroxyl radical generation through chelating ferric ion, diminished oxygen radical-induced mucus release to control values. Xanthine oxidase dose dependently stimulated prostaglandin E2 (PGE2) production, which was blocked by catalase but not by superoxide dismutase. However, oxygen radical stimulation of mucus secretion was not inhibited by the addition of indomethacin. Moreover, PGE2, exogenously administered, did not significantly accelerate mucus secretion. Stimulation of mucus secretion by oxygen radicals was not accompanied by increased 51Cr release or by leakage of intracellular lactate dehydrogenase. These results suggest that oxygen species, particularly hydroxyl radical, stimulate mucous glycoprotein secretion from cultured rat gastric mucous cells. However, it seems unlikely that prostaglandin production mediates the oxygen species-induced stimulation of mucus secretion.

Animals↗
PubMed1991

Antioxidant defenses of cultured gastric cells against oxygen metabolites: role of GSH redox cycle and endogenous catalase.

Gastric mucous epithelial cells may represent a first line of defense against reactive oxygen species that are generated within the gastric lumen. However, little is known about their defenses against oxidant species. This study examined the importance of the glutathione (GSH) redox cycle and of endogenous catalase as antioxidant defenses in cultured gastric mucous cells. Cultured rat gastric mucous cells were exposed to H2O2 generated by glucose oxidase acting on glucose or to nascent H2O2 for 5 h. Cytotoxicity was quantified by measuring 51Cr release from prelabeled cells. The effects of inhibition of the GSH redox cycle and of endogenous catalase were examined. Glucose oxidase caused a dose-dependent increase of 51Cr release. Similarly, nascent H2O2 damaged the cells dose dependently. Pretreatment with 1,3-bis(chloroethyl)-1-nitrourea (inhibitor of GSH reductase) dose dependently increased glucose oxidase-induced 51Cr release. Preincubation with buthionine sulfoximine (inhibitor of gamma-glutamyl-cysteine synthetase), which lowered intracellular GSH content, enhanced glucose oxidase-induced damage in a dose-dependent manner. Pretreatment with diethyl maleate, which covalently binds GSH as catalyzed by GSH transferase, also enhanced the sensitivity to lysis by glucose oxidase. However, inhibition of endogenous catalase activity by 3-amino-1,2,4-triazole did not significantly alter glucose oxidase- or nascent H2O2-induced 51Cr release. These results suggest that the GSH redox cycle rather than endogenous catalase plays a critical role in intracellular antioxidant defense in cultured gastric mucous cells.

Animals↗
PubMed1991

Tetraprenylacetone promotes healing process of ethanol-induced gastric damage in the rat.

Tetraprenylacetone (TPA: teprenon, geranylgeranylacetone) is a novel anti-ulcer agent developed in Japan. The aim of this study was to test whether TPA has the ability to promote the healing process of rat gastric mucosal injury induced by absolute ethanol (ET). Fasted rats received orally 5 ml/kg of absolute ET. Sixty minutes later, TPA (200 mg/kg) or saline (control) was administered intragastrically. Thereafter, the same dose of TPA or saline was given orally every 8 hours. To investigate the role of endogenous prostaglandins, indomethacin was given intraperitoneally every 8 hours. Twenty four or 48 hours after the first administration of TPA or saline, rats were sacrificed and the stomachs were removed. Administration of TPA significantly reduced lesion indices from 100 +/- 12.9% (control) to 57.0 +/- 12.8% (24 hours, P less than 0.05) and from 100 +/- 15.3% (control) to 17.6 +/- 3.4% (48 hours, P less than 0.01). Addition of indomethacin did not significantly affect this effect of TPA. Ultrastructural studies revealed that TPA stimulated regeneration of gastric mucosa damaged by ET after 24 and 48 hours. These results indicate that TPA has the ability to promote the healing process of gastric mucosal damage induced by absolute ET. It is, however, unlikely that endogenous prostaglandins are involved in this promotive effect of TPA on the healing process of gastric injury.

Animals↗
PubMed1991

The effect of cimetidine on adaptive cytoprotection by mild irritant dose of HCl in the rat gastric mucosa.

While cimetidine (CIM) is strikingly effective in inhibiting gastric acid secretion, its effect on the defensive mechanisms of the gastric mucosa has been controversial. The aims of the present study were to test if administration of CIM at an antisecretory dose is protective against acid-induced injury and to assess its effect on adaptive cytoprotection induced by non-necrotizing concentrations of HCl in rats. A dose of 100 mg/kg of CIM was administered once, or twice a day for 5 days intraperitoneally. To study the effect of CIM on HCl-induced damage, 0.6 N HCl was given orally one hour after the last administration of CIM. To study the effect of CIM on adaptive cytoprotection, 0.35 N HCl was given orally one hour after the last administration of CIM. Fifteen minutes later, 0.6 N HCl was given orally. Thirty minutes after the administration of 0.6 N HCl, the stomach was removed and ulcer indices were calculated. Pretreatment with CIM did not prevent 0.6 N HCl induced gastric damage. Prior administration of 0.35 N HCl significantly reduced ulcer indices caused by 0.6 N HCl. Short or long term treatment with CIM did not have significant effects on the reduction of ulcer indices. These results suggest that CIM at an antisecretory dose neither acts as a protective agent nor modulates the protective process of the gastric mucosa.

Adaptation, Physiological↗
PubMed1990

Trimebutine maleate has inhibitory effects on the voltage-dependent Ca2+ inward current and other membrane currents in intestinal smooth muscle cells.

We examined effects of trimebutine maleate on the membrane currents of the intestinal smooth muscle cells by using the tight-seal whole cell clamp technique. Trimebutine suppressed the Ba2+ inward current through voltage-dependent Ca2+ channels in a dose-dependent manner. The inhibitory effect of trimebutine on the Ba2+ inward current was not use-dependent. It shifted the steady-state inactivation curve to the left along the voltage axis. Trimebutine also had inhibitory effects on the other membrane currents of the cells, such as the voltage-dependent K+ current, the Ca2(+)-activated oscillating K+ current and the acetylcholine-induced inward current. These relatively non-specific inhibitory effects of trimebutine on the membrane currents may explain, at least in part, the dual actions of the drug on the intestinal smooth muscle contractility, i.e. inhibitory as well as excitatory.

Animals↗
PubMed1990

Effect of vitamin K on carbon tetrachloride-induced cellular damage in primary cultured rat hepatocytes.

The effect of vitamin K on carbon tetrachloride-induced cellular damage of primary cultured hepatocytes was investigated by estimating prothrombin activity as a parameter of cellular function. Prothrombin activity was evaluated in primary cultured rat hepatocytes using synthetic fluorogenic peptide substrates (Boc-Val-Pro-Arg-MCA). Prothrombin activity significantly increased with the addition of vitamin K and decreased by the addition of warfarin (P less than 0.05). Carbon tetrachloride caused a significant decrease of prothrombin activity and cytotoxicity in a dose dependent manner. Prothrombin activity increased after addition of vitamin K when cells were previously exposed to carbon tetrachloride for a short period, but there was no change in cells treated for a long period. Carbon tetrachloride caused a modest increase of malondialdehyde formation after a short period of exposure and a significant increase following a long period of exposure. These results suggest that: 1) prothrombin activity is a good parameter for protein synthesis in cultured hepatocytes, 2) carbon tetrachloride-induced cytotoxicity results from different mechanisms in the early phase and the late phase of exposure, and 3) vitamin K has the ability to protect hepatocytes against the carbon tetrachloride-induced cellular damage in the early phase.

Animals↗
PubMed1990

A monolayer culture of gastric mucous cells from adult rabbits.

A new method for the primary monolayer cultures of adult rabbit gastric mucous cells has been developed. Rabbit gastric mucosal cells were isolated with etylenediaminetetraacetic acid and collagenase. Cells were cultured in Coon's modified Ham's F-12 medium supplemented with 10% fetal bovine serum, 15mM HEPES buffer, antibiotics, and antimycotic. The cells reached confluency on days 3-4. Histochemically 92% of the cells contained PAS positive gramules (mucous cells), 3% of cells showed a strong reaction for succinic dehydrogenase activity (parietal cells), 2% of the cells showed positive granules by Bowie staining (chief cells), and G6PDH staining was positive in 5% of the cells (surface mucous cells). Fibroblasts were rarely seen until day 7 (less than 1%). Thus rabbit cultured gastric cells were considered to be mainly comosed of mucous neck cells. These cells produced prostaglandin (PG) E2 and PGI2. Quantitatively cultured cells synthesized 1.475 +/- 0.039 ng/mg protein/hour of PGE2 and 0.244 +/- 0.042 pg/mg protein/hour of PGI2. This relatively simple and convenient technique provides a useful model for the study of cellular functions of gastric mucosa.

6-Ketoprostaglandin F1 alpha↗
PubMed1990

Protective role of intracellular glutathione against ethanol-induced damage in cultured rat gastric mucosal cells.

This study investigated whether intracellular glutathione is cytoprotective against ethanol-induced injury to cultured rat gastric mucosal cells in vitro. Secondly, it investigated whether reduced glutathione or oxidized glutathione is responsible for this cytoprotection. Cytolysis was quantified by measuring 51Cr release from prelabeled cells. Concentrations of ethanol greater than 12% caused cell damage and increased 51Cr release in a dose-dependent and time-related fashion. When a substrate for glutathione synthesis, N-acetyl-L-cysteine, was provided to cultured cells for 4 h before challenge with ethanol, cytolysis was significantly decreased corresponding with an increase in cellular glutathione content. Pretreatment with diethyl maleate, which depletes reduced glutathione without forming oxidized glutathione, potentiated ethanol-induced cell damage in a dose-dependent manner with the decrease of cellular glutathione content. The administration of tert-butyl hydroperoxide (which is specifically reduced by glutathione peroxidase to generate oxidized glutathione from reduced glutathione) or diamide (which nonenzymatically oxidizes reduced glutathione to oxidized glutathione) enhanced ethanol injury. We conclude that in cultured gastric mucosal cells, (a) intracellular glutathione maintains integrity of gastric mucosal cells against ethanol in vitro; and (b) reduced glutathione rather than oxidized glutathione is responsible for this cytoprotection. We postulate that the presence of reduced glutathione is essential to allow glutathione peroxidase to catalyze the ethanol-generated toxic oxygen radical, hydrogen peroxide.

Acetylcysteine↗
PubMed1990

Role of oxygen radicals in ethanol-induced damage to cultured gastric mucosal cells.

We have examined the role of oxygen radicals in ethanol-induced damage to cultured rat gastric mucosal cells. Cultured cells exposed to ethanol produced superoxide anion, as assessed by the reduction of cytochrome c, in a time-related fashion. The production of superoxide anion increased dose dependently as the concentration of ethanol increased. Cellular damage increased in a similar fashion to the production of superoxide anion. Both superoxide dismutase (SOD) and catalase diminished ethanol-induced injury dose dependently. SOD and catalase were able to maintain their enzymatic activities in the presence of 15% ethanol, respectively. Pretreatment with deferoxamine, an iron-chelating agent, decreased ethanol-induced injury dose dependently. Furthermore, dimethyl sulfoxide decreased ethanol-induced damage dose dependently. We conclude that cultured gastric mucosal cells exposed to ethanol generate oxygen radicals and that the production of oxygen radicals is closely linked with ethanol-induced damage to the cells. Hydroxyl radical, produced by the iron-catalyzed Haber-Weiss reaction, seems to be the main mediator of ethanol-induced damage to gastric mucosal cells in vitro.

Animals↗
PubMed1990

Glibenclamide specifically blocks ATP-sensitive K+ channel current in atrial myocytes of guinea pig heart.

Effects of glibenclamide on the control membrane ionic currents, acetylcholine or adenosine-induced K+ current, and nicorandil-induced K+ current were examined in single atrial myocytes of guinea pig heart. The nystatin-whole cell clamp technique was used. Nicorandil evoked the time-independent K+ current which is probably the current through the ATP-sensitive K+ channel. Glibenclamide inhibited this current in a concentration-dependent fashion, although it had no effect on the other currents. We concluded that glibenclamide specifically inhibits the ATP-sensitive K+ channel current in cardiac myocytes.

Adenosine Triphosphate↗