Biomedical subjects

I Ishiguro

Publications and source records attributed to I Ishiguro.

At least 37 records · Page 2Linked to original sources

PubMed1999

Possible contribution of a decrease in serum albumin concentration to a low level of blood L-tryptophan in nephrotic rats.

In order to clarify whether or not a decrease in serum albumin concentration contributes to a low level of blood L-tryptophan (Trp) in nephrosis, blood Trp concentration at 30, 60, 90, and 120 min after oral administration of Trp (100 mumol/kg body weight) in the same rats injected once with puromycin aminonucleoside (PAN) (100 mg/kg body weight, i.p.), an inducer of nephrosis, was examined at different stages of nephrosis. The increase and decrease in blood Trp concentration after Trp administration were similar in the PAN-treated rats without nephrosis, the PAN-treated rats recovered from nephrosis, and untreated control rats. The maximum increase in blood Trp concentration at 30 min after Trp administration was lower in nephrotic rats than in control rats. In all rats treated with and without PAN, increased blood L-tryptophan concentrations at 30 min after L-tryptophan administration were positively correlated well with serum albumin concentrations (r = 0.88, p < 0.001). There was no difference in the intestinal absorption of the same dose of orally administered Trp between nephrotic and control rats. These results suggest that a decrease in serum albumin concentration may contribute to a low level of blood L-tryptophan in nephrosis.

Animals↗

PubMed1998

Protective and preventive effects of teprenone on gastric mucosal lesions in rats.

We have reported that neutrophil infiltration into gastric mucosa is closely related to gastric mucosal lesion development in rats with water immersion restraint stress. In this study, we examined the effect of teprenone, which is known to prevent gastric mucosal injury through stimulation of gastric mucus synthesis and secretion, on neutrophil infiltration into the gastric mucosa of rats with water immersion restraint stress. Pre- and post-administration of teprenone (200 mg/kg, p.o.) significantly attenuated the neutrophil infiltration into the gastric mucosa and the lesion development found at 6 h of water immersion restraint stress with preservation of gastric mucosal hexosamine and adherent mucus levels. These results indicate that teprenone exerts protective and preventive actions against water immersion restraint stress-induced gastric mucosal lesions in rats and suggest that these actions could be related to the preservation of gastric mucus synthesis and secretion and inhibition of neutrophil infiltration into the gastric mucosal tissue.

Animals↗

PubMed1998

Improved fluorometric enzymatic sorbitol assay in human blood.

Samples for use in the fluorometric enzymatic assay of sorbitol in erythrocytes are normally prepared using HClO4 and K2CO3. We have replaced these reagents with NaOH and ZnSO4. Human whole blood, erythrocyte and plasma samples prepared with NaOH and ZnSO4 are colorless and clear, while erythrocyte samples prepared with HClO4 and K2CO3 are a pale yellow-brown color. The sorbitol dehydrogenase reaction in the supernatant of the mixture of NaOH and ZnSO4 is inhibited, but ethylenediaminetetraacetate completely eliminates this effect. The sorbitol assay in erythrocytes prepared with NaOH and ZnSO4 shows higher sensitivity and reproducibility than did that with HClO4 and K2CO3. Recovery of sorbitol added to erythrocytes is similar in both assay methods. Concentrations of whole blood and erythrocyte sorbitol assayed by the present method are significantly higher in diabetics than in normals. Poorly controlled diabetics had higher whole blood and erythrocyte sorbitol than well-controlled diabetics. Whole blood sorbitol concentrations differed more between diabetic and normal subjects than did erythrocyte sorbitol concentrations.

Adult↗

PubMed1998

Preventive effect of gamma-glutamylcysteinylethyl ester on carbon tetrachloride-induced hepatic triglyceride accumulation in mice.

The effect of gamma-glutamylcysteinylethyl ester (gamma-GCE), which is a precursor of reduced glutathione (GSH), on carbon tetrachloride (CCl4)-induced hepatic triglyceride (TG) accumulation in mice was investigated in comparison with that of GSH. Administration of gamma-GCE (160 micromol/kg), but not GSH (160 micromol/kg), to mice at 3 h after CCl4 injection (1 ml/kg, i.p.) significantly attenuated an increase in hepatic TG concentration at 6, 12, and 24 h after the CCl4 injection. A decrease in hepatic GSH concentration after the CCl4 injection was significantly diminished by the gamma-GCE administration, but not by the GSH administration. The correlation coefficient between hepatic TG concentration and hepatic GSH concentration was -0.627 (P < 0.001) when the results of all mice were grouped together. These results indicate that gamma-GCE can attenuate CCl4-induced hepatic TG accumulation in mice through the maintenance of hepatic GSH level.

Animals↗

PubMed1998

Contribution of NO synthases to neutrophil infiltration in the gastric mucosal lesions in rats with water immersion restraint stress.

A decrease in constitutive NO synthase (cNOS) activity and an increase in inducible NO synthase (iNOS) activity occurred with an increase in myeloperoxidase (MPO) activity, an index of neutrophil infiltration, in the gastric mucosa of rats with water immersion restraint (WIR) stress. This increase in gastric mucosal MPO activity was enhanced by pretreatment with NG-monomethyl L-arginine, a non-selective NOS inhibitor, but was prevented with maintenance of gastric mucosal cNOS activity by pretreatment with aminoguanidine, a selective iNOS inhibitor. The MPO activity was negatively correlated with the cNOS activity in all WIR-stressed rats used (r=-0.723). These results suggest that a decrease in cNOS activity could contribute to an increase in neutrophil infiltration in the gastric mucosa of WIR-stressed rats.

Animals↗

PubMed1998

Gamma-glutamylcysteinylethyl ester attenuates progression of carbon tetrachloride-induced acute liver injury in mice.

We examined the effect of gamma-glutamylcysteinylethyl ester (gamma-GCE), which is readily transported into hepatocytes and increases hepatocellular reduced glutathione (GSH) levels, on the progression of carbon tetrachloride (CCl4)-induced liver injury in mice in comparison with that of GSH. Administration of more than 160 micromol/kg of gamma-GCE, but not GSH, to mice at 3 h after intraperitoneal injection of CCl4 (1 ml/kg) significantly attenuated increases in serum aspartate aminotransferase and alanine aminotransferase activities at 24 h after the CCl4 injection. Increases in hepatic lipid peroxide (LPO) concentrations and decreases in hepatic GSH concentrations after the CCl4 injection were significantly diminished by the gamma-GCE (160 micromol/kg) administration, but not by the same dose of GSH. Gamma-GCE, gamma-glutamylcysteine, and cysteine acted as substrates for glutathione peroxidases much less efficiently than GSH in the post-mitochondrial fraction of normal mouse liver cells. These results indicate that gamma-GCE attenuates the progression of CCl4-induced acute liver injury in mice through the maintenance of hepatic GSH levels, leading to inhibition of hepatic LPO formation, which could be due to an efficient utilization of GSH converted from gamma-GCE in the liver cells.

Animals↗

PubMed1998

Relation of inducible nitric oxide synthase activity to lipid peroxidation and nonprotein sulfhydryl oxidation in the development of stress-induced gastric mucosal lesions in rats.

We have reported that increases in lipid peroxide (LPO) formation, nonprotein sulfhydryl (NP-SH) oxidation, and inducible NO synthase (iNOS) activity and a decrease in constitutive NO synthase (cNOS) activity in the gastric mucosa of rats with water immersion restraint (WIR) stress are closely related to gastric mucosal lesion development. Peroxynitrite, which is produced by the reaction of nitric oxide (NO) with superoxide anion, can initiate intracellular LPO formation and NP-SH oxidation, resulting in producing an extreme cellular membrane damage. In this study, the relation of changes in cNOS and iNOS activities to LPO formation and NP-SH oxidation was examined in the gastric mucosa of rats with WIR stress. An increase in iNOS activity, but not a decrease in cNOS activity, correlated well with an increase in LPO concentration (r = 0.750) and NP-SH concentration (r = -0.808) in the gastric mucosa of rats with WIR stress. In addition, the above-mentioned changes in iNOS activity and LPO and NP-SH concentrations with lesion development in the gastric mucosa of rats with WIR stress were attenuated with both prevention of the lesion development and an increase in the concentration of gastric mucosal nitrite/nitrate, the breakdown products of NO, by pretreatment with aminoguanidine, a selective iNOS inhibitor. These results suggest that in the gastric mucosa of WIR-stressed rats, NO produced by increased iNOS could contribute to enhanced LPO formation and NP-SH oxidation, resulting in lesion development.

Animals↗

PubMed1998

Relationship between constitutive nitric oxide synthase activity and mucus level in the gastric mucosa of rats with stress.

A decrease in constitutive nitric oxide synthase (cNOS) activity occurred with decreases in hexosamine (an index of mucus synthesis) and adherent mucus (an index of mucus secretion) concentrations in the gastric mucosa of rats with water immersion restraint (WIR) stress. The decreases in gastric mucosal hexosamine and adherent mucus concentrations were enhanced with a further decrease in gastric mucosal cNOS activity by pretreatment with NG-monomethyl L-arginine, a non-selective NOS inhibitor, but were prevented with maintenance of the gastric mucosal cNOS activity by pretreatment with aminoguanidine, a selective inducible NO synthase inhibitor. In all WIR-stressed rats used in this study, gastric mucosal cNOS activity was well correlated with either gastric mucosal hexosamine or adherent mucus concentration (r=0.717 or 0.739, respectively). These results indicate that in the gastric mucosa of WIR-stressed rats, a decrease in cNOS activity is closely related to a decrease in mucus level due to impairment of its synthesis and secretion. (c) 1998 The Italian Pharmacological Society.

Animals↗

PubMed1998

Inhibitory effect of Oren-gedoku-to (Huanglian-Jie-Du-Tang) extract on hepatic triglyceride accumulation with the progression of carbon tetrachloride-induced acute liver injury in rats.

The inhibitory effect of Oren-gedoku-to (Huanglian-Jie-Du-Tang) extract (TJ-15) on hepatic triglyceride (TG) accumulation with the progression of acute liver injury was examined in rats intoxicated with carbon tetrachloride (CCl4). TJ-15 at a dose of 100, 250 or 500 mg/kg body weight (BW) was orally administered to male Wistar rats aged 7 weeks, 6 h after the intraperitoneal injection of CCl4 (1.0 ml/kg BW) at which time apparent liver injury and hepatic TG accumulation occurred. TJ-15 significantly prevented not only the progression of liver injury but also inhibited hepatic TG accumulation with the progression of the injury in a dose-dependent manner when these effects were examined 24 h after CCl4 injection. In CCl4-untreated rats with oral administration of TJ-15 at a dose of 100, 250 or 500 mg/kg BW, liver and serum TG concentrations decreased depending on the dose of the herbal medicine. These results indicate that in rats intoxicated once with CCl4, orally administered TJ-15 can inhibit hepatic TG accumulation with the progression of acute liver injury by its decreasing action on serum and liver TG levels, leading to a prevention of the progression of the liver injury.

Administration, Oral↗

PubMed1998

Teprenone, an anti-ulcer agent, increases gastric mucosal mucus level via nitric oxide in rats.

We examined whether the increasing action of teprenone (TP) on mucus synthesis and content in rat gastric mucosa is related to nitric oxide (NO) formation via NO synthase (NOS) in the tissue. TP (200 mg/kg)-induced increases in levels of gastric mucosal hexosamine and adherent mucus were inhibited with decreased gastric mucosal NOS activity and nitrite/nitrate concentration by co-administration of NG-monomethyl L-arginine (100 mg/kg), a NOS inhibitor, but not its D-isomer. These results suggest that TP exerts an increasing action on gastric mucus synthesis and content possibly under the condition of maintained NO production via NOS in gastric mucosal tissues, although the precise mechanisms for the action of TP is still unclear.

Animals↗

PubMed1998

Changes in nitric oxide production with lesion development in the gastric mucosa of rats with water immersion restraint stress.

In rats with gastric mucosal lesions induced by water immersion restraint (WIR) stress over a 6 h period, increases in the serum and gastric mucosal concentrations of nitrite/nitrate, the breakdown products of NO, occurred with a drastic increase in inducible NO synthase (iNOS) activity in the gastric mucosa. Pretreatment with aminoguanidine (100 mg/kg), a relatively selective iNOS inhibitor, attenuated not only gastric mucosal lesion development, but also increases in serum and gastric mucosal nitrite/nitrate concentrations with inhibition of increased gastric mucosal iNOS activity in rats with 6 h of WIR stress. A good positive correlation between either serum or gastric mucosal nitrite/nitrate concentration and gastric mucosal iNOS activity in all rats used (r = 0.741 or 0.842, respectively, p < 0.001) was found. These results suggest that in WIR-stressed rats, an increase in NO production via iNOS in the gastric mucosa could contribute to gastric mucosal lesion development.

Animals↗

PubMed1997

Chemical characterization of pheomelanogenesis starting from dihydroxyphenylalanine or tyrosine and cysteine. Effects of tyrosinase and cysteine concentrations and reaction time.

Two types of melanin pigment are produced in mammals; the brown-to-black eumelanins and the yellow-to-reddish-brown pheomelanins. The switch from one type of melanin to the other appears to be regulated by the levels of tyrosinase and thiols, such as cysteine and glutathione. This study examines the process of pheomelanin formation starting from dihydroxyphenylalanine (dopa) or tyrosine and cysteine. We prepared pheomelanins by tyrosinase oxidation of dopa or tyrosine in the presence of cysteine. Experimental variables were reaction time, tyrosinase concentration, and dopa or tyrosine to cysteine ratio. Following the reactions, we measured concentrations of tyrosine, dopa, cysteine and cysteinyldopas, amounts of total melanin (TM) by Soluene-350 solubilization and aminohydroxyphenylalanine (AHP), a specific indicator of pheomelanin, formed by hydriodic acid hydrolysis, and absorbance ratio, A650/A500. It was found that (1) mixed melanogenesis is a heterogeneous process in which pheomelanogenesis proceeds first, followed by eumelanogenesis, as shown by changes in the tyrosine and cysteinyldopa concentrations, the AHP/TM ratio, and the A650/A500 ratio during the course of melanogenesis and (2) lower tyrosinase concentration favors pheomelanogenesis even when the availability of cysteine is limited, as shown by AHP/TM ratios that were higher than the corresponding tyrosine to cysteine ratios. These results indicate that the switch from eumelanogenesis to pheomelanogenesis can be achieved by lowering the tyrosinase activity, which conforms to our proposal that tyrosinase activity is the major factor controlling the course of melanogenesis.

Cysteine↗

PubMed1997

Glycine facilitates gamma-glutamylcysteinylethyl ester-mediated increase in liver glutathione level.

gamma-Glutamylcysteinylethyl ester (gamma-GCE) increases reduced glutathione (GSH) levels in GSH-depleted rat hepatocytes. Because glycine, a constituent of GSH, exists at 0.3 to 0.4 mM in rat plasma, we examined the influence of glycine added to the medium on the action of gamma-GCE to increase GSH levels in the rat hepatocytes. Glycine (0.2-0.8 mM) dose-dependently enhanced gamma-GCE-mediated increase in intracellular GSH levels with an increase in intracellular gamma-GCE levels. These results indicate that exogenous glycine facilitates gamma-GCE-mediated increase in intracellular GSH levels in rat hepatocytes possibly by enhancing the uptake of gamma-GCE into the cells.

Animals↗

PubMed1997

Role of gastric mucosal constitutive and inducible nitric oxide synthases in the development of stress-induced gastric mucosal lesions in rats.

Changes in gastric mucosal constitutive NO synthase (cNOS) and inducible NO synthase (iNOS) activities with the development of gastric mucosal lesions induced by water immersion restraint (WIR) stress were investigated in rats pretreated with and without NOS inhibitors. A decrease in cNOS activity and an increase in iNOS activity in the gastric mucosa occurred with gastric mucosal lesion development. Pretreatment with N(G)-monomethyl L-arginine, a non-selective NOS inhibitor, enhanced gastric mucosal lesion development with inhibition of gastric mucosal cNOS and iNOS activities, although the inhibited iNOS activity was still higher than the normal level. Pretreatment with aminoguanidine, a selective iNOS inhibitor, prevented gastric mucosal lesion development with inhibition of iNOS activity and maintenance of cNOS activity in the gastric mucosa. These results indicate that in WIR-stressed rats, an increase in iNOS activity and a decrease in cNOS activity in the gastric mucosa are closely related to the development of gastric mucosal lesions.

Animals↗

PubMed1997

Chemical characterization of eumelanins with special emphasis on 5,6-dihydroxyindole-2-carboxylic acid content and molecular size.

Mammalian melanins exist in two chemically distinct forms; the brown to black eumelanins and the yellow to reddish pheomelanins. Eumelanins are derived from copolymerization of 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA). Eumelanins can be quantified by HPLC analysis of the oxidation product pyrrole-2,3,5-tricarboxylic acid (PTCA) and by our spectrophotometric method (Sp.EM). We also developed a spectrophotometric method for assaying the total amount of eu- and pheomelanins by dissolving them in Soluene-350 (TM). In addition, we previously showed that Sp.EM/TM and PTCA/TM ratios are significant parameters in characterizing eumelanins produced in follicular melanocytes. The objectives of this study were (1) to clarify the significance of Sp.EM/TM and PTCA/TM ratios in synthetic eumelanins and (2) to apply these methods to characterizing natural eumelanins with various DHI/ DHICA ratios and molecular sizes. The results obtained show that (1) the Sp.EM/TM ratio of synthetic eumelanins increases as polymerization proceeds, (2) the Sp.EM/TM and PTCA/TM ratios in copolymers of DHI and DHICA correlate to the percentage content of DHICA-derived units, and (3) combination of the Sp.EM/TM and PTCA/TM ratios serves to estimate the DHICA content and the degree of polymerization in natural eumelanins.

Animals↗

PubMed1997

Dihydro-1,4-benzothiazine-6,7-dione, the ultimate toxic metabolite of 4-S-cysteaminylphenol and 4-S-cysteaminylcatechol.

4-S-Cysteaminylphenol (4-S-CAP) and the corresponding catechol 4-S-cysteaminylcatechol (4-S-CAC) have been evaluated for melanocytotoxicity. It was shown recently that tyrosinase oxidation of these substrates produces a violet pigment, dihydro-1,4-benzothiazine-6,7-dione (BQ). In this study we examined whether BQ is the ultimate toxic metabolite produced in melanoma cells from 4-S-CAP/4-S-CAC. Biochemical experiments showed that (1) BQ was formed by autoxidation of 4-S-CAC as well as by tyrosinase oxidation of 4-S-CAP/4-S-CAC, (2) BQ reacted rapidly with thiols such as reduced glutathione (GSH), and (3) BQ inhibited the activity of alcohol dehydrogenase, an SH enzyme. In vitro experiments showed that (1) the cytotoxicity of 4-S-CAC was mostly prevented by catalase and superoxide dismutase, (2) BQ was highly cytotoxic to B16 melanoma cells (IC50 being 3.9 microM as compared with 507 microM for 4-S-CAP), (3) BQ was metabolized rapidly to a GSH adduct in melanoma cells, and (4) the same GSH adduct was also formed upon incubation of melanoma cells with 4-S-CAP, the reaction being tyrosinase dependent. In vivo experiments showed that intratumoral administration of BQ (0.5 micromol) inhibited the subcutaneous growth of B16 melanoma nearly as effectively as 4-S-CAP/4-S-CAC (20 micromol). These results indicate that BQ is the ultimate toxic metabolite produced by tyrosinase oxidation of 4-S-CAP/4-S-CAC. BQ deprives melanoma cells of GSH and may inactivate SH enzymes essential for DNA synthesis and cell proliferation by covalent binding through their cysteine residues, thereby exerting melanocytotoxicity. Cytotoxicity of 4-S-CAC depends mostly on autoxidation producing BQ and active oxygens.

Animals↗

PubMed1997

Modulating role of endogenous reduced glutathione in tert-butyl hydroperoxide-induced cell injury in isolated rat hepatocytes.

The role of endogenous reduced glutathione (GSH) in tert-butyl hydroperoxide (TBHP)-induced cell injury was examined in isolated rat hepatocytes. When liver cell injury was estimated from release of transaminases from hepatocytes into the incubation medium, cell injury in hepatocytes (2 x 10(6) cells/ml) incubated in Hanks' balanced salt solution (pH 7.2) containing 1.0 mM TBHP at 37 degrees C was potentiated with enhanced lipid peroxidation by prior depletion of intracellular GSH which was induced by diethylmaleate, a GSH depletor. GSH-depleted hepatocytes were incubated with gamma-glutamylcysteinylethyl ester (gamma-ECOEt), which is known to be converted to GSH via glutathione synthetase after its hydrolysis by esterase, at concentrations of 1.0 to 10 mM in order to replenish intracellular GSH. Although TBHP-induced cell injury and lipid peroxidation were enhanced in GSH-depleted hepatocytes, these enhancements were prevented with the consumption of intracellular GSH in GSH-depleted hepatocytes pretreated with 5.0 mM gamma-ECOEt. These preventive effects were observed at any time point during the TBHP treatment over a 60 min period and depended on the concentration of gamma-ECOEt used. But, no preventive effect was found in GSH-depleted hepatocytes pretreated with 5.0 mM GSH. No prevention of the potentiation of TBHP-induced cell injury found in GSH-depleted hepatocytes occurred in GSH-depleted hepatocytes pretreated with both 5.0 mM gamma-ECOEt and 250 microM bis-(p-nitrophenyl)phosphate, a nonspecific esterase inhibitor. gamma-ECOEt treatment caused an increase in intracellular GSH content in GSH-depleted hepatocytes, while treatments of both gamma-ECOEt and the esterase inhibitor caused no increase in intracellular GSH content in the cells. These results indicate that endogenous GSH modulates TBHP-induced cell injury and lipid peroxidation in isolated rat hepatocytes. The present results suggest that endogenous GSH should play a critical role in TBHP-induced cell injury in isolated rat hepatocytes and that in rat hepatocytes treated with TBHP, enhanced lipid peroxidation with the consumption of intracellular GSH could be associated with the initiation of cell injury.

Alanine Transaminase↗

PubMed1997

Relationship between changes of active oxygen metabolism and blood flow and formation, progression, and recovery of lesions is gastric mucosa of rats with a single treatment of compound 48/80, a mast cell degranulator.

The relationship between the changes of active oxygen metabolism and blood flow and the formation, progression, and recovery of lesions was examined in the gastric mucosa of rats treated once with compound 48/80, a mast cell degranulator. Gastric mucosal lesions appeared 0.5 hr after compound 48/80 treatment, became worst at 3 hr, and recovered fairly well at 12 hr. Increases in gastric mucosal lipid peroxide content and xanthine oxidase and myeloperoxidase activities and decreases in gastric mucosal vitamin E and hexosamine contents and Se-dependent glutathione peroxidase activity occurred with the formation and progression of gastric mucosal lesions. These changes were attenuated with the recovery of the lesion. Gastric mucosal nonprotein SH content decreased with the formation of gastric mucosal lesions, and this decreased SH content returned to near the original level with lesion progression. No changes in gastric mucosal superoxide dismutase and catalase activities occurred with the formation, progression, and recovery of gastric mucosal lesions. Gastric mucosal blood flow decreased with the formation of gastric mucosal lesions, and this decreased blood flow recovered with lesion progression. Serum serotonin concentration, an index of mast cell degranulation, increased with the formation of gastric mucosal lesions, and this increased serotonin level was attenuated with lesion progression and recovery. Pretreatment with ketotifen, a connective tissue mast cell stabilizer, prevented the formation of gastric mucosal lesions, the increases of gastric mucosal lipid peroxide content, xanthine oxidase and myeloperoxidase activities, and serum serotonin level; and the decreases of gastric mucosal nonprotein SH content, glutathione peroxidase activity, and blood flow found at 0.5 hr after compound 48/80 treatment. These results indicate that the changes of gastric mucosal active oxygen metabolism and blood flow are closely related to the formation, progression, and recovery of gastric mucosal lesions in rats with a single compound 48/80 treatment. The present results also suggest that this compound 48/80-induced gastric mucosal injury could be a kind of ischemia-reperfusion-induced injury occurring through degranulation of connective tissue mast cells.

Animals↗