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Biomedical subjects

T Mikuni

Publications and source records attributed to T Mikuni.

At least 19 recordsLinked to original sources
PubMed1991

Production of the thiyl free radical by the reaction of N-methyl-N'-nitro-N-nitrosoguanidine with L-cysteine.

The thiyl free radical is formed in the L-cysteine/N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) system (pH 7.8) without exposure to light as detected by the ESR spin trapping technique. The formation of N-methyl-N'-nitroguanidine in the system is identified by thin-layer chromatography. The hypothesis that the thiyl radical is formed by the attack of the nucleophilic reagent L-cysteine on the nitroso group of MNNG is verified by these results.

Chromatography, Thin Layer↗
PubMed1989

Effects of propranolol and cimetidine on cysteamine inhibition of gastric carcinogenesis induced in Wistar rats by N-methyl-N'-nitro-N-nitrosoguanidine.

The effects of propranolol and cimetidine on inhibition by cysteamine (2-aminoethanethiol hydrochloride) of gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and on gastric acid secretion, serum gastrin level, and labelling index of the gastric mucosa were investigated in inbred Wistar rats. Rats received alternate-day injections of cysteamine (25 mg/kg body weight) with or without propranolol (dl-propranolol hydrochloride) (2 mg/kg bw) or cimetidine (50 mg/kg bw) in depot form after 25 weeks of oral treatment with MNNG. Prolonged administration of cysteamine significantly reduced the incidence of adenocarcinoma of the glandular stomach. A combination of cysteamine and propranolol significantly accelerated the inhibitory effect of cysteamine on gastric carcinogenesis. However, with concomitant administration of cysteamine and cimetidine, the incidence of adenocarcinoma was slightly but not significantly increased as compared to that after treatment with cysteamine alone. Administration of cysteamine caused a significant increase in gastric acid secretion and serum gastrin level, and a significant decrease in the labelling index of the antral mucosa. A combination of cysteamine and propranolol significantly increased gastric acid secretion by cysteamine alone and significantly decreased the labelling index of the antral mucosa. With this treatment, the serum gastrin level was significantly higher than the basal level, but the stimulated serum gastrin level was significantly lower than observed that after administration of cysteamine alone. In contrast, concomitant administration of cysteamine and cimetidine caused a significant decrease in gastric acid secretion and significant increase in the serum gastrin level as compared to the levels seen after treatment with cysteamine alone, but had no influence on the labelling index of the antral mucosa. These findings indicate that hypersecretion of acid, but not hypergastrinemia associated with hyposecretion of acid or achlorhydria, exerts a protective effect against gastric carcinogenesis, and that this effect may be related to its activity in decreasing proliferation of the antral mucosa.

Adenocarcinoma↗
PubMed1988

Inhibitory effect of prolonged administration of cysteamine on experimental carcinogenesis in rat stomach induced by N-methyl-N'-nitro-N-nitrosoguanidine.

The effect of cysteamine (2-aminoethanethiol hydrochloride) on the incidence and histology of gastric adenocarcinomas induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was investigated in inbred Wistar rats. Prolonged administration of 25 or 50 mg per kg body weight of cysteamine after treatment with MNNG for 25 weeks significantly reduced the incidence and number of adenocarcinomas of the glandular stomach. Histological examination showed that the adenocarcinomas that did develop in rats treated with these 2 doses of cysteamine had high mucin-producing activity. Furthermore, treatment with cysteamine caused significant increases in serum gastrin level and gastric acid secretion, together with significant decreases in the antral mucosal pH and the labelling indices of pyloric and oxyntic gland mucosae and gastric cancer. These findings indicate that cysteamine inhibits the development of gastric adenocarcinomas and that its effect may be related to decreasing proliferation of cells in the gastric mucosae.

Adenocarcinoma↗
PubMed1987

[A fundamental and clinical study of ferritin 'Eiken' radioimmunoassay kit].

We have measured serum ferritin level using double antibody radioimmunoassay kit (Eiken ICL) and evaluated the characteristics of the kit and clinical usefulness. Satisfactory results were observed in standard curve, reproducibility, dilution and recovery test. In clinical evaluation, we have measured in normal subjects and patients with various diseases. The range in normal males and females were 13.0-158.7 ng/ml and 7.3-73.0 ng/ml, respectively. Serum ferritin level was elevated in patients with hepatoma, biliary cancer, lung cancer and other malignant diseases. Measurement of serum ferritin value would be useful in the monitoring of cancer patients.

Evaluation Studies as Topic↗
PubMed1987

Scavenging effect of butylated hydroxytoluene on the production of free radicals by the reaction of hydrogen peroxide with N-methyl-N'-nitro-N-nitrosoguanidine.

The scavenging effects of the antioxidant butylated hydroxytoluene (BHT) on a hydroxyl free radical (.OH) produced in the reaction of H2O2 with N-methyl-N'-nitro-N-nitrosoguanidine [(MNNG) CAS: 70-25-7] and on free radicals derived from MNNG (.MNNG) were examined by electron spin resonance with the use of the spin-trapping agent 5,5-dimethyl-1-pyrroline-1-oxide (DMPO). BHT was added to the H2O2-MNNG-DMPO system in 50% acetonitrile and exposed to a tungsten-halogen lamp at an intensity of 0.3 mW/cm2 for 3 minutes at 3 degrees C for the first 2 minutes of irradiation. The amounts of .OH and .MNNG in the system decreased and reached constant levels with increase in BHT concentration. The spectrum of the H2O2-MNNG-BHT system showed the specific signal of BHT, whereas the spectra of the BHT solution and the H2O2-MNNG system did not show any signal. These findings indicate that BHT scavenged .OH and .MNNG, and in its reaction with them formed a stable free radical.

Butylated Hydroxytoluene↗
PubMed1985

Production of hydroxyl-free radical by reaction of hydrogen peroxide with N-methyl-N'-nitro-N-nitrosoguanidine.

Production of a hydroxyl free radical (.OH) by reaction of hydrogen peroxide (H2O2) with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was examined by electron spin resonance using the X OH spin trapping agent 5,5-dimethyl-1-pyrroline-1-oxide (DMPO). The electron spin resonance spectra of the H2O2-MNNG-DMPO system after exposure to light at an intensity of 0.03 mW/cm2 for 5 min, and the DMPO- (.OH) spin adduct (2-hydroxy-5,5-dimethyl-1-pyrroline-1-oxide) generated by use of Fenton's reagent showed the same hyperfine structure and g-value. The signal of the DMPO adduct obtained in the H2O2-MNNG-DMPO system disappeared on addition of the .OH scavenger sodium benzoate. The addition of another .OH scavenger, ethanol, resulted in the appearance of a new signal due to trapping of the alpha-hydroxyethyl radical. These results show that .OH was formed in the H2O2-MNNG-DMPO system. The typical signal of the DMPO-(.OH) spin adduct was not observed in the system in the absence of light. The amount of DMPO-(.OH) spin adduct increased with increase in the concentration of H2O2 when the MNNG level was kept constant, and it changed with the concentration of MNNG at a constant H2O2 level, indicating that .OH was produced by the interaction of MNNG with H2O2. In the absence of H2O2, complicated trapped signals appeared in the spectrum of the MNNG-DMPO system in the light, but these signals were not observed when the system was kept in the dark. In the absence of MNNG, the H2O2-DMPO system did not show any signal, even in the light. These results indicate that interaction of free radicals derived from MNNG with H2O2 on exposure to light resulted in .OH production.

Chemical Phenomena↗
PubMed1984

[Clinical statistics on inpatients and operations in the Urological Department of the Wakayama Red Cross Hospital (April, 1979 to March, 1983)].

Statistical observations made on the 1,102 inpatients and 1,127 operations at our clinic between April 1979 and March 1983 were reviewed. The patients were most frequently in their sixties, and lately patients under 10 are increasing. The most frequent diseases of the inpatients were benign prostatic hypertrophies, ureteral calculi, undescended testicles and bladder tumors. The frequently performed operations were those for bladder tumors, phimosis and benign prostatic hypertrophies in order of frequency.

Adult↗
PubMed1984

[Gynecological urologic disease: a summary of clinical experience during the last 4 years at Wakayama Red Cross Hospital].

From April 1979 to March 1983, sixty seven patients with gynecological urologic disease were experienced at our department. Forty one of them were inpatients, i.e., 15.3% of the total number of female in patients admitted during the same period. Thirty three urologic operations were performed on them which corresponded to 16.1% of the total operations on female patients. Ten of these patients had ureteral obstruction following gynecological operation, 8 had ureteral fistula, 7 had vesicovaginal fistula, 11 had tumor invasion to urinary tract, 14 had radiation cystitis, 16 had neurogenic bladder dysfunction, and 1 had other complication. The treatment of these patients and the results are summarized and discussed.

Adult↗
PubMed1983

Protective effect of butylated hydroxytoluene against induction of gastric cancer by N-methyl-N'-nitro-N-nitrosoguanidine in Wistar rats.

The effects of butylated hydroxytoluene (BHT) on the incidence and histology of gastric cancers induced by oral administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in Wistar rats. Oral administration of 1.0% BHT in regular chow pellets during treatment with MNNG for 25 weeks significantly reduced the incidence of gastric cancers in experimental week 40. BHT had no influence on the histological type of adenocarcinomas induced in MNNG-treated rats. BHT alone induced slight glandular hyperplasia, but not moderate glandular hyperplasia or gastric cancer.

Animals↗
PubMed1983

Nuclear magnetic resonance studies on calmodulin: spectral assignments in the calcium-free state.

The 400-MHz proton magnetic resonance spectra of calcium-free scallop testis calmodulin (CaM) and pig brain CaM were observed. Detailed spectral assignments were made by resolution enhancement, spin decoupling, and nuclear Overhauser enhancement (NOE) experiments as well as pH titration. Comparison between spectra of scallop testis CaM and pig brain CaM were also utilized for the assignment. Previous assignments for tyrosine-99, histidine-107, epsilon-trimethyllysine-115, and tyrosine-138 [Seamon, K. B. (1980) Biochemistry 19, 207; Krebs, J., & Carafoli, E. (1982) Eur. J. Biochem. 124, 619] were confirmed. Phenylalanine-99 and threonine-143 of scallop testis CaM were identified. Sixteen methyl resonances from one isoleucine, two valines, nine methionines, and the amino-terminal acetyl group were identified. First-stage assignments were made of resonances arising from seven phenylalanines. The uniquely high field shifted phenylalanine resonance previously reported by Seamon was found to consist of two doublets from the two pairs of delta protons of two phenylalanines. The NOE experiments showed that the two phenylalanines are located closely to each other. The large high-field shifts of these phenylalanines were accounted for the ring-current effects due to their proximity. An isoleucine and a valine of which methyl resonances appear at high fields were found to be situated closely to each other. It was found that two delta protons and two epsilon protons of almost all aromatic residues are magnetically equivalent, suggesting that the local structure of aromatic residues is so flexible as to permit the rapid flipping motion of the ring.

Animals↗
PubMed1983

Nuclear magnetic resonance studies on calmodulin: calcium-induced conformational change.

The 400-MHz 1H nuclear magnetic resonance (NMR) studies were carried out on the Ca2+-induced conformational change of calmodulins (CaM's) isolated from scallop testis and pig brain. The resonances were found to be classified approximately into three groups. The resonances of group I, which are perturbed by the binding of Ca2+ to the high-affinity sites, include those of tyrosine-138, epsilon-trimethyllysine-115, histidine-107, tyrosine-99, etc. The previous assignments for tyrosine- (Tyr) 138 [Seamon, K. B. (1980) Biochemistry 19, 207] were corrected. The resonances of group II, which are affected by the binding of Ca2+ to the low-affinity sites, include those of a phenylalanine (Phe), a high field shifted methyl, and a low field shifted alpha-methine. Group III (related to the binding of Ca2+ to both the high-and low-affinity sites) includes the resonances of a Phe, a high field shifted methyl, and threonine-143. It is concluded that sites III and IV are the high-affinity sites. The off-rate of Ca2+ from the high-affinity sites is slower than 50 s-1 while the off-rate from the low-affinity sites is faster than 600 s-1. In the Ca2+-free state, there exists a hydrophobic region containing three phenylalanine (probably Phe-89, Phe-92, and Phe-141), a valine, and an isoleucine in the vicinity of sites III and IV. Tyr-138 is distant from these amino acids. Upon binding of Ca2+ to the high-affinity sites, one of the Phe residues and the valine approach Tyr-138. Similar structural changes were observed between CaM and troponin C when Ca2+ ions are bound to the high-affinity sites. CaM changes in a somewhat different way from troponin C when Ca2+ ions are bound to the low-affinity sites.

Animals↗