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Biomedical subjects

M Tada

Publications and source records attributed to M Tada.

At least 379 records · Page 21Linked to original sources
PubMed1991

Selective induction of rat urinary bladder tumors by simultaneous administration of 3,2'-dimethyl-4-aminobiphenyl (DMAB) and butylated hydroxyanisole or butylated hydroxytoluene is associated with increased DMAB-DNA adduct formation.

Modification of 3,2'-dimethyl-4-aminobiphenyl (DMAB) multi-organ carcinogenesis by simultaneous treatment with butylated hydroxyanisole (BHA) or butylated hydroxytoluene (BHT) was studied using young and old male F344 rats. Animals, 4 or 54 weeks old, were given DMAB (s.c. injection of 50 mg/kg body wt once a week for 10 weeks) along with BHA (2.0% in diet for 11 weeks) or BHT (1.0% in diet for 11 weeks). The experiments were terminated 55 weeks after the commencement. Combined administration of BHA or BHT with the carcinogen resulted in development of urinary bladder tumors in greater than 90% of both young and old rats thus treated, whereas no tumors were induced in animals given DMAB alone. In contrast, the appearance of preneoplastic lesions in the liver and pancreas was reduced by BHA or BHT treatment. Tumor development (less than 30% incidence) was also evident in the small and large intestines, prostate, preputial glands, skin/subcutis and ear duct, with no modification by BHA or BHT. No ageing effects were evident. The formations of DMAB-DNA adducts, evaluated by the enzyme-linked immunosorbent assay and immunohistochemical staining, correlated well with tumorigenesis in the urinary bladder, liver and pancreas. The selective enhancement of urinary bladder tumor induction by BHA and BHT appeared to be due to both increased DMAB-DNA adduct formation caused by metabolic alteration of DMAB in the liver and increased DNA synthesis in the urothelial cells.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1991

Studies on Phe-228 and Leu-307 recombinant mutants of porcine kidney D-amino acid oxidase: expression, purification, and characterization.

Two recombinant mutants of porcine kidney D-amino acid oxidase [EC 1.4.3.3, DAO], in which Tyr(228) and His(307) are replaced with Phe and Leu, respectively, have been expressed in Escherichia coli and purified to apparent homogeneity. The molecular size and amino-terminal sequence of the two mutants were the same as those of the native DAO. Kinetic analysis revealed that the Michaelis constants of the Phe-228 and Leu-307 mutants for D-alanine were 71- and 10-fold and the inhibition constants for benzoate, a potent competitive inhibitor, were 1,189- and 18-fold greater than those of the native DAO, respectively. The maximum velocities of the Phe-228 and Leu-307 mutants were 66 and 58% that of the native DAO. The kinetically estimated dissociation constant of the Leu-307 mutant for FAD was 28-fold greater than that of the native DAO, whereas the value of the Phe-228 mutant was comparable to that of the native DAO. The Leu-307 mutant and the recombinant wild-type DAO were inactivated by D-propargylglycine (D-PG), a suicide substrate. However, the Phe-228 mutant was resistant to the inactivation. Absorption peaks of the Phe-228 mutant were blue-shifted about 10 nm from the corresponding peaks of the wild-type DAO, and the oxidized form was fully reduced by D-alanine without appearance of the purple intermediate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

The existence of two different forms of apo-electron-transferring flavoprotein.

The association process of FAD and apo-electron-transferring flavoprotein (apoETF) from hog kidney was investigated. The reaction schemes which involve the association-dissociation of the protein species could be excluded by the light scattering data, which indicated that the molecular weights of apoETF and holoETF are identical. The binding reaction between FAD and a large excess of apoETF was monophasic and obeyed pseudo-first order kinetics. On the other hand, the reaction between apoETF and a large excess of FAD was biphasic: the fast phase obeyed a pseudo-first order reaction, and the rate of the slow phase was almost independent of FAD concentration. These results suggest the existence of two different forms of apoETF, as represented in the following reaction scheme: [formula: see text] where "F" is FAD, "H" is holoETF, and "A" and "A" are the different forms of apoETF. The kinetic parameters were determined as k-1 = 3.9 x 10(4) M-1.s-1, k-1 approximately 10(-5) s-1, k+2 = 1.0 x 10(-3) s-1, and k-2 = 3.1 x 10(-3) s-1, in 50 mM potassium phosphate buffer, pH 7.6, containing 0.3 mM EDTA, and 5% v/v glycerol, at 7 degrees C. The elution patterns of apoETF on molecular sieve chromatography were very different from that of holoETF although the true molecular weights were identical. This result suggests that the structure of apoETF differs greatly from that of holoETF.

Animals↗
PubMed1991

Molecular weight determination of phospholamban oligomer in the presence of sodium dodecyl sulfate: application of low-angle laser light scattering photometry.

The number of polypeptides constituting the oligomeric structure of canine phospholamban (a putative regulator of Ca(2+)-ATPase of cardiac sarcoplasmic reticulum) stable even in the presence of sodium dodecyl sulfate was estimated through determination of the molecular weight of the oligomer. Owing to the small molecular size, the low UV-absorptivity and the limited availability, the molecular weight determination required very sophisticated application of the following technique, used as the only recourse: low-angle laser light scattering measurement combined with high-performance gel chromatography. The molecular weight of phospholamban oligomer was found to be 30,400 and the number of subunits was concluded to be five after correction for the dependence of the apparent molecular weights on the protein concentration.

Animals↗
PubMed1991

Evaluation of peptic ulcer healing with a highly magnifying endoscope: potential prognostic and therapeutic implications.

Gastric and duodenal ulcer healing and scarring were evaluated with a highly magnifying endoscope. The appearance of scar was classified into three types: Sa, with a depression at the center; Sb, with a pattern of regenerated mucosa reaching the center; and Sc, with a uniform pattern throughout. The relationship between regenerative mucosal patterns and histologic findings of biopsy specimens was investigated in 58 patients with gastric ulcer. Mucosal regeneration was sufficient in 26.7% of patients with Sa pattern, 79.2% of patients with Sb pattern, and 100% with Sc pattern. From prospective endoscopic follow-up observations, the relationship between endoscopic findings of ulcer scars and ulcer relapses was investigated in 80 patients with gastric ulcer and 56 patients with duodenal ulcer. As a result, patients who completed the cycle of ulcer healing from Sa pattern through Sb to Sc patterns had rarely relapse. In contrast, patients with a Sa pattern of mucosal scar showed a high rate of recurrence: 88.8% for gastric ulcer, and 88.0% for duodenal ulcer. Our method of evaluation of gastric and duodenal ulcer healing with a highly magnifying endoscope may have important prognostic and therapeutic implications. It may indicate a population of patients (with Sa scarring pattern) with a high risk of ulcer recurrence and therefore requiring prolonged prophylactic treatment.

Cicatrix↗
PubMed1991

Neutrophil-induced myocardial cell damage and active oxygen metabolites.

Free radicals derived from polymorphonuclear leukocytes (PMN) have been suggested to play an important role in myocardial ischemia-reperfusion injury. To define the mechanism by which activated PMN exacerbate ischemic myocardial damage, we investigated the extent of cell injury, free radical generation and lipid peroxidation in embryo mouse myocardial cells co-incubated with activated PMN. The generation of free radicals derived from PMN correlated with the extent of myocardial cell injury. Among the cell sheets preconditioned with hypoxic and glucose free medium, PMN-adhered myocardial cells were initially injured after adding PMN activator, extending to adjacent cells. Chemiluminescence emission and thiobarbituric acid reactive substance in the co-incubated cells were markedly increased and sustained compared with those in each cell monoincubation. The augmented lipid peroxidation was related to the progression of myocardial cell injury. These results indicate that PMN-derived free radicals cause membrane disruption, contributing to the progression of myocardial injury.

Animals↗
PubMed1991

[A case-control study of ulcerative colitis].

In order to evaluate the epidemiological characteristics of ulcerative colitis, we conducted a matched case-control study of ulcerative colitis. Fifty patients with ulcerative colitis diagnosed at three hospitals in Kyoto, Osaka and Hyogo Prefectures in Japan during 1984 and 1987 were interviewed about their habitual and pre-illness diets, personal habits, past histories and family histories. The results were compared to those for fifty healthy controls who were matched for sex and age (+/- 2 years) and participated in health-screening examinations in Kyoto or Osaka during the same period. Frequent intake of rice (4 or more bowls a day), bread (3 or more times a week), and green tea (7 or more cups a day) significantly increased the relative risk of ulcerative colitis. However, a past history of appendectomy was negatively correlated with the disease. There were no relationships between ulcerative colitis and consumption of animal foods and tobacco.

Adolescent↗
PubMed1991

Antiproliferative effect of trapidil on PDGF-associated growth of human glioma cell lines in vitro.

The effects of trapidil on platelet-derived growth factor (PDGF)-associated growth of glioblastoma cells were studied. The assessment using PDGF-dependent rat lung endothelium cells revealed secretion of a PDGF-like factor from SF-126 cell line but not from SF-188. Human recombinant PDGF stimulated proliferation of both these glioblastoma cell lines. The anti-PDGF monoclonal antibody inhibited the growth of SF-126 more than SF-188. The results suggest the presence of an autocrine growth mechanism in SF-126 cells mediated by PDGF. The growth of both SF-126 and SF-188 cells was suppressed by trapidil, a specific PDGF antagonist, at 10 and 50 micrograms/ml, respectively. The proliferative response to exogenous PDGF and the antagonistic effect of trapidil were greater in the SF-126 cell line. In addition, trapidil markedly reduced production of prostaglandin E2 in both glioblastoma cell lines. This anti-proliferative effect on malignant glioma cells suggests that trapidil might be a new therapeutic agent for malignant gliomas.

Animals↗
PubMed1991

DNA polymerase action blocked by adenine adducts induced by 5-hydroxymethylchrysene sulfate.

Modification of M13mp10 single-stranded DNA with 5-hydroxymethylchrysene (5HCR) sulfate, the ultimate carcinogenic metabolite of 5-methylchrysene, resulted in formation of N6[(chrysen-5-yl)methyl]adenine and N2[(chrysen-5-yl)methyl]-guanine at the ratio of 2.7:1. Measurement of DNA synthesis using this modified template and E.coli DNA polymerase I (Klenow fragment) demonstrated that increasing levels of adducts caused a progressive decline in replication. Analysis of reaction products on DNA-sequence gels revealed DNA elongation to be arrested exclusively at adenine adducts in -AAAGGA- and -AACA- sequences.

Adenine↗
PubMed1991

Cadmium injury of cultured human vascular endothelial cells.

The effect of cadmium chloride (CdCl2) on cultured human vascular endothelial (HVE) cells and cultured human fibroblasts (HAIN-55 cells) was investigated. Umbilical vein-derived HVE cells were collected by enzymatic digestion with collagenase. At the concentration of 0-10 microM, Cd had hardly any effect on the cell viability of either cells. The viability of HVE cells decreased markedly at 100 microM, but not that of HAIN-55 cells. Morphologic examination by phase contrast microscopy revealed a more damaging effect of Cd on HVE cells than on HAIN-55 cells. These results suggest that Cd is more cytotoxic to HVE cells than HAIN-55 cells.

Cadmium↗
PubMed1991

Tracer feasibility for monitoring tumor radiotherapy: a quadruple tracer study with fluorine-18-fluorodeoxyglucose or fluorine-18-fluorodeoxyuridine, L-[methyl-14C]methionine, [6-3H]thymidine, and gallium-67.

In a rat AH109A tumor model, metabolic tracers for glucose, amino acid, and nucleic acid metabolisms (2-deoxy-2-[18F]fluoro-D-glucose (18FDG), L-[methyl-14C]methionine (14C-Met), [6-3H]thymidine (3H-Thd), and 2'-deoxy-5-[18F]fluorouridine (18FdUrd], and the conventional radionuclide 67Ga-citrate were used to assess the feasibility of monitoring tumor radiotherapy using a quadruple tracer technique. Two combinations of four tracers (18FDG or 18FdUrd, 14C-Met, 3H-Thd and 67Ga) were compared in a time-course study after single-dose irradiation (20 Gy) and were also used in a dose-dependency study performed 6 days after 5, 10, 15, or 20 Gy of irradiation. Fluorine-18-FDG showed a large change in uptake and a steady response to radiotherapy. Fluorodeoxyuridine showed a rapid decrease after radiotherapy, but the range of change in uptake was narrow. Gallium-67 could not detect tumor response early after treatment, but showed a marked change in uptake later. [6-3H]Thd and 14C-Met showed a rapid response to irradiation and a high sensitivity for monitoring radiotherapy, suggesting that they may be feasible for PET studies.

Animals↗