Biomedical subjects

M Tezuka

Publications and source records attributed to M Tezuka.

At least 37 records · Page 2Linked to original sources

PubMed1999

In vitro tests of 1,3-dithia-2-thioxo-cyclopent-4-ene to evaluate the mechanisms of its hepatoprotective action.

Some in vitro tests were performed using 1,3-dithia-2-thioxo-cyclopent-4-ene (DT827A) to evaluate its mode of action on hepatoprotection. Experiments with leucine, uridine and thymidine uptakes using L-132 cells showed no increase in leucine uptake, but did show a tendency toward increases in both uridine and thymidine uptakes, which suggested a stimulating effect on RNA and DNA synthesis in vitro. DT827A did not influence GSH levels in the HepG2 cultured cell system, and did not show inhibition of cytochrome P450 2El in microsomes obtained from mouse liver. There may be no possibility for DT827A to protect a liver injury through its influence on liver GSH levels and inhibiting metabolic activation of CCl4 in this in vitro system. However, the inhibitory effect of DT827A on lipid peroxidation was observed in vitro, the same as the observation in vivo. Furthermore, when DT827A was incubated with Alamar Blue in the presence of a mixture of mouse liver S9 and mitochondrial fractions for 20 hr, DT827A showed more reducibility than it did in a case of non-incubation, and it was suggested that DT827A would be metabolized in the S9-mitochondrial fraction in vitro to show an increase of Alamar Blue reducibility. The protective effect of DT827A on a liver injury is due neither to its influence on liver GSH levels nor inhibition of the metabolic activation of CCl4, but a possible mechanism of action for the DT827 series of compounds to indicate an antioxidative effect would be brought about by the role of the compounds as a radical scavenger as well as its reductive effect.

Animals↗

PubMed1999

Mutagenicity tests of 4-phenyl-1,3-dithia-2-thioxo-cyclopent-4-ene.

The mutagenicity of 4-phenyl-1,3-dithia-2-thioxo-cyclopent-4-ene (DT827B) was examined in reverse mutation tests using Salmonella typhimurium and Escherichia coli, in the chromosomal aberration test with Chinese hamster ovary (CHO) cells, and in the micronucleus test using mice bone-marrow. In reverse mutation assay on DT827B according to Ames' method, DT827B was not mutagenic to S. typhimurium or E. coli when tested in dimethylsulfoxide to the limit of its solubility where precipitation occurred. In chromosomal aberration assay using CHO cells, DT827B was not clastogenic to induce structural chromosomal aberration but capable of inducing polyploidy. In micronucleus test, DT827B did not show micronucleus-inducing potential at the maximum dose. In conclusion of the three mutagenicity studies, DT827B was considered to cause no mutagenicity under the conditions used in the present experiments except the increase in polyploidy, which probably is due to a toxic effect of the compound.

Animals↗

PubMed1998

Depletion of arylhydrocarbon receptor during adipose differentiation in 3T3-L1 cells.

Arylhydrocarbon receptor (AhR) is the receptor for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds. Although a physiological ligand for AhR has yet to be identified, several lines of evidence suggest that AhR may play an important role not only in the regulation of xenobiotic metabolism but also in the maintenance of homeostatic functions. When TCDD is administrated in vivo, this compound is primarily deposited in adipose tissue. Therefore, it is critical to know the states of AhR in adipose cells for assessing the expression of toxicities of TCDD and related compounds in vivo. In this report, we examined the levels of AhR protein and its associated protein (Arnt) during the adipose differentiation in 3T3-L1 cells. The level of AhR protein was found to decrease with ongoing adipose differentiation in 3T3-L1 cells. The binding activity to the xenobiotic response element and the cellular response to TCDD were also lowered as a result of adipose differentiation. These results indicate that the depletion of AhR is a novel event associated with adipose differentiation in 3T3-L1 cells and that the magnitude of the depletion of AhR is sufficient for 3T3-L1 cells to lose the functional response to xenobiotics. We also found a population of 3T3-L1 cells which have an adipose differentiation capability in the presence of high doses of TCDD. These cells lack nuclear AhR but not cytoplasmic AhR, suggesting a possible negative role of liganded nuclear AhR in adipose differentiation. The level of the Arnt protein also decreased as a result of the differentiation. However, the pattern of the depletion of the Arnt protein was distinct from that of the AhR protein. The data presented in this study will provide opportunities to carry out studies to better understand the roles of AhR in adipose cells which are the primary targets of TCDD.

3T3 Cells↗

PubMed1998

Effect of 4-phenyl-1,3-dithia-2-thioxo-cyclopent-4-ene on liver injury induced by repeated exposure to galactosamine plus carbon tetrachloride in rats.

The protective effects of 1,3-dithia-2-thioxo-cyclopent-4-ene (DT827A),4-phenyl-1,3-dithia-2-thioxo-cyclopent- 4-ene (DT827B) and 4-(4-fluorophenyl)-1,3-dithia-2-thioxo-cyclopent-4-ene (DT827C) on liver injury induced by D-galactosamine plus carbon tetrachloride (D-GalN + CCl4) and that of DT827B on liver injury induced by thioacetamide were studied using male rats. Out of the three DT827 series of compounds, DT827B was more effective on liver injury induced by the combination exposure to D-GalN + CCl4 for 4 weeks, and accordingly the following two experiments were carried out using DT827B only. Twelve-week administration of DT827B at dose levels of 5, 10 and 20 mg/kg/day revealed a therapeutic effect against liver injury induced by D-GalN + CCl4 dose-dependently, and another twelve-week administration of DT827B at the same three dose levels also revealed a therapeutic effect against liver injury induced by thioacetamide dose-dependently. A hepatoprotective potential of DT827B was suggested under the conditions of these studies.

Animals↗

PubMed1997

Cultured retinal pericytes stimulate in vitro angiogenesis of endothelial cells through secretion of a fibroblast growth factor-like molecule.

Interaction between cultured endothelial cells (EC) and pericytes (PC) was studied in vitro to clarify the mechanism of diabetic proliferative retinopathy. Conditioned medium (CM) from retinal PC strongly increased the proliferation and moderately stimulated migration of retinal EC. Moreover, CM from PC caused stimulation of angiogenesis of retinal EC and umbilical cord vein EC in vitro at the same extent as basic fibroblast growth factor (bFGF). PC also stimulated angiogenesis by EC in mixed cultures. The angiogenic, proliferative and migration activities in CM from PC were inhibited by an antibody to bFGF. These data suggest that PC play an important role in angiogenesis through secretion of an FGF-like molecule.

Animals↗

PubMed1997

Isolation and chemical-structural determination of a novel aromatic amine mutagen in water from the Nishitakase River in Kyoto.

Water samples from the Nishitakase River in Kyoto, Japan, especially taken at sites below sewage plants, show significantly high mutagenicity in the Ames test. In the present study, mutagens in the river water were adsorbed to 24 g of blue rayon, extracted, and separated by HPLC on ODS columns. Five mutagenic compounds (I-V) were isolated, and they accounted for 21%, 17%, 11%, 12%, and 6%, respectively, of the total mutagenicity of the blue rayon-adsorbed materials. With compound I obtained from adsorbate to 24 g of blue rayon as a marker, a large quantity (1.1 mg) of mutagenic compound I was isolated by Sephadex LH-20 column chromatography and HPLC on ODS columns from material adsorbed to 27 kg of blue cotton. X-ray crystal analysis was carried out with the debrominated derivative of compound I. Based on this X-ray crystallography data and the UV, mass, and 1H-NMR spectra of both the derivative and compound I, the structure of compound I was determined to be 2-[2-(acetylamino)-4-[bis(2-methoxyethyl)amino]-5-methoxyphenyl]-5-amino - 7-bromo-4-chloro-2H-benzotriazole (PBTA-1). PBTA-1 is a newly identified potent mutagen, inducing 1,200,000 revertants of Salmonella typhimurium YG1024 per microgram in the presence of S9 mix.

Amines↗

PubMed1997

Effect of 1,3-dithia-2-thioxo-cyclopent-4-ene and its derivatives on liver injury induced by carbon tetrachloride and orotic acid in rats.

The protective effect of 1,3-dithia-2-thioxo-cyclopent-4-ene (DT827A) and its two derivatives of 4-phenyl-1,3-dithia-2-thioxo-cyclopent-4-ene (DT827B) and 4-(4-fluorophenyl)-1,3-dithia-2-thioxo-cyclopent-4-ene (DT827C) on liver injury induced by carbon tetrachloride (CCl4) and orotic acid was studied using male rats. The approximate lethal doses were about 100 mg/kg for DT827A-treated animals and more than 800 mg/kg for the other two compounds-treated groups. Single oral administration of the three test compounds at the dose levels of 2 and 10 mg/kg 1 hour before CCl4 exposure revealed a protective effect on the findings of centrolobular necrosis, balloon cells and macrophage infiltration in histopathological findings in livers in the order of DT827B-treated rats > DT827A-treated rats > DT827C-treated rats. Repeated oral administration of the compounds at the dose levels of 2 and 10 mg/kg/day for 10 consecutive days revealed a protective effect against liver injury on the findings of centrolobular necrosis, balloon cells and macrophage infiltration in the order of DT827B-treated rats > DT827A-treated rats [symbol: see text] DT827C-treated rats. Simultaneous administration of the compounds at the dose level of 10 mg/kg/day together with a high sucrose diet containing orotic acid for 12 days revealed an inhibitory effect on fatty liver formation in the order of DT827B-treated rats > DT827C-treated rats > DT827A-treated rats. A hepatoprotective potential of the DT827 series compounds was suggested under the conditions of these studies, and DT827B was considered to be the most effective.

Administration, Oral↗

PubMed1996

Stimulation of interleukin-1beta-converting enzyme activity during growth inhibition by CPT-11 in the human myeloid leukemia cell line K562.

Camptothecin (CPT) was first extracted from Camptotheca acuminata and has a strong antitumor effect. Its water-soluble derivative, CPT-11, has higher therapeutic efficacy and less toxicity than CPT. Recently, CPT-treated cells have been shown to undergo apoptosis. However, the mechanism of induction of apoptosis by CPT has not been characterized in detail in any type of cells. On the other hand, interleukin-1beta-converting enzyme (ICE) is a mammalian homologue of CED3, a protein required for apoptosis in the nematode Caenorhabditis elegans. To determine how CPT-11 brings about cell death by apoptosis, we investigated the effects of CPT-11 on the expression of ICE activity in K562 cells, which represent human myeloid leukemia cells. The proliferation of K562 cells was shown to be inhibited by the presence of CPT-11 in the culture medium. We also found that the levels of mRNA for ICE in the cells were increased in the presence of CPT-11. Furthermore, we demonstrated that when CPT-11 was added to the culture medium, apoptosis of K562 cells was clearly detected in situ. These features suggested that CPT-11 enhances the apoptotic cell death in K562 cells and that a part of induction of apoptosis by CPT-11 may be correlated with the stimulation of the ICE activity.

Apoptosis↗

PubMed1995

Mechanism of angiogenic effects of saponin from ginseng Radix rubra in human umbilical vein endothelial cells.

1. The effects of saponin from Ginseng Radix rubra on angiogenesis (tube formation) and its key steps (protease secretion, proliferation and migration) in human umbilical vein endothelial cells (HUVEC) were examined to elucidate the mechanism of the tissue repairing effects of Ginseng Radix rubra. The effect on a wound healing model was also studied. 2. Tube formation was measured by an in vitro system. The activity and immunoreactivity of tissue-type plasminogen activator (tPA) as a protease for angiogenesis and the immunoreactivity of its inhibitor, plasminogen activator inhibitor-1 (PAI-1), were measured in conditioned medium of HUVEC stimulated for 24 h with saponin. Cell proliferation was measured by counting the cell numbers at 2-7 days after seeding. Migration was measured by Boyden's chamber method. The effect on wound healing was studied in the skin of diabetic rats. 3. Saponin at 10-100 micrograms ml-1 significantly stimulated tube formation by HUVEC in a dose-dependent manner. Saponin in a similar concentration-range increased the secretion of tPA from HUVEC as estimated by immunoreactivity and enzyme activity. On the other hand, PAI-1 immunoreactivity was slightly increased at 10 micrograms ml-1 of saponin, but then was significantly decreased at 50 and 100 micrograms ml-1. Cell proliferation was only slightly enhanced by 1-100 micrograms ml-1 of saponin, but migration was significantly enhanced by 10-100 micrograms ml-1 in a dose-dependent manner. Moreover, saponin stimulated wound healing with enhanced angiogenesis in vivo. 4. These results indicate that saponin stimulates tube formation mainly by modifying the balance of protease/protease inhibitor secretion from HUVEC and enhancing the migration of HUVEC, and that it is effective in vivo.

Animals↗

PubMed1995

In vitro effect of chromium and other trace metals on mouse hepatotoxicity induced by carbon tetrachloride exposure.

Using primary cultured mouse hepatocytes, in vitro study was performed to discuss the effect of Cr(III) and several other trace metals, Cr(VI), Mn(II), Zn(II), Co(II), Cu(II), Ni(II), and Ga(III) on acute liver damage induced by CCl4 exposure. 1) The LDH activity 60 min after CCl4 exposure increased dose-dependently with CCl4 concentrations in all of the trace metal pretreatment groups, except for the Cr(VI) pretreatment group, which showed a significant protective effect even after 30 min of CCl4 exposure. 2) LDH leakage was not observed 10 min after CCl4 exposure at 3 or 5 mM, while lipid peroxidation was increased dose-dependently with CCl4 concentrations in all groups except the Cr(VI) pretreatment group, in which the production of peroxidated lipid was significantly inhibited. 3) Similarly to the pretreatment with Cr(VI), LDH leakage 30 min after exposure to 5 mM CCl4 was inhibited by pretreatment with such antioxidants as N,N'-diphenyl-p-phenylenediamine or DL-alpha-tocopherol. 4) The Cr(VI) uptake was about 50% of the added amount, whereas the Cr(III) uptake was only 5% of the added amount. 5) 90% or more of the intracellular chromium was reduced to Cr(III) 10 min after Cr(VI) treatment. The results suggested that the in vitro protective effect of pretreatment with Cr(VI) was due to a rapid reduction of Cr(VI) to Cr(III), and the radical scavenger-like effect of the produced Cr(III) was the same effect as in vivo Cr(III); it therefore suggests that Cr(III) contributes to protective effect on CCl4-induced hepatotoxicity.

Animals↗

PubMed1995

DNA-strand breaks induced by dimethylarsinic acid, a metabolite of inorganic arsenics, are strongly enhanced by superoxide anion radicals.

We previously reported that dimethylarsinic acid (DMAA), a major metabolite of inorganic arsenics, induced DNA single-strand breaks (ssb) both in vivo and in cultured alveolar type II (L-132) cells in vitro, possibly via the production of dimethylarsenic peroxyl radicals. Here, the interaction of superoxide anion radicals (O2-) in the induction of ssb in L-132 cells was investigated using paraquat, an O2(-)-producing agent. A significant enhancement of ssb formation was observed in the DMAA-exposed cells when coexposed to paraquat. This enhancement occurred even when post-exposed to DMAA after washing, suggesting that the DMAA exposure caused some modification of DNA such as DNA-adducts, which was recognized by active oxygens to form ssb. An experiment with UV-irradiation, which was likely to induce ssb at the modified region, supported the possibility of DNA modification by DMAA exposure. An ESR study indicated that O2- produced by paraquat in DMAA-exposed cells was more consumed than in non-exposed cells, assumingly through the reaction with the dimethylarsenic-modified region of DNA. The species of active oxygens were estimated by using diethyldithiocarbamate, aminotriazole, diethylmaleate, hydrogen peroxide (H2O2), gamma-irradiation and ethanol. O2- but neither H2O2 nor hydroxyl radicals was very likely to contribute to the ssb-enhancing action of paraquat.

Cacodylic Acid↗

PubMed1995

[Reconstruction of pulmonary trunk in pulmonary atresia and tetralogy of Fallot utilizing autologous tissue].

Establishment of right ventricular-pulmonary arterial continuity with autologous tissue, avoiding the use of prosthetic conduit, is presented. From February 1992 through March 1993, 22 patients with pulmonary atresia and tetralogy of Fallot underwent reparative operation at The Heart institute of Japan. In 20 patients out of the 22 patients, the right ventricular-pulmonary arterial continuity was successfully established with either direct anastomosis or insertion of tailored autologous pericardial tube. The morphology of the right ventricular-pulmonary arterial discontinuity comprised of valvular and infundibular atresia in seven, truncal atresia in nine, and failed extracardiac conduit in four. In patients with relatively short distance between right ventricle and pulmonary artery, the pulmonary artery was retracted and anastomosed directly to the cranial margin of the ventriculotomy incision to serve as a smooth floor made of autologous tissue. In patients with long distance, tailored autologous pericardial tube was interposed between right ventricle and pulmonary artery instead of using prosthetic conduit. Both techniques were completed by mono- or bicuspid anterior patch made of equine pericardial conduit. There were no early and late deaths. Postoperative catheterization data showed satisfactory reduction of right ventricular pressure with the right-to-left ventricular systolic pressure ratio ranging from 0.42 to 0.69 (average 0.52) in direct anastomosis group and 0.43 to 0.48 (average 0.45) in autologous pericardial tube group, and the pressure gradient across right ventricular outflow tract ranged from 1 to 15 (average 8) mmHg and 1 to 15 (average 5.8), respectively. The distributing frequency of late complication, mainly conduit obstruction, of prosthetic materials prompted us to use autologous tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1995

[Mitral valve reconstruction: for ruptured chordae to the posteromedial commissural scallop].

The advantages of mitral valve repair for pure mitral incompetence are established. It is necessary for us to describe suture points more detailed. This article presents our standardized maneuver for mitral regurgitation due to ruptured chordae to the posteromedial commissural scallop. The first step in the repair is placement of a temporary suture in the annulus at attachment of posterior commissural chordae and one of posterior cleft chordae. After measuring the annular diameter and estimating coaptation, this suture is removed. Secondary, rupture of chordae tendinease and adjacent margin of posteromedial commissural scallop are resected. Then, one end of a thread is passed through the margin at end of this untethered segment of leaflet, and another end is passed through the margin of leaflet at opposite end of this segment. Finally, a mattress suture using 3-0 Prolene with pledget is placed as a temporary suture. Between April 1993 and December 1994, four patients underwent reconstruction of mitral regurgitation with ruptured chordae to the posteromedial commissural scallop. Left ventriculogram 4 weeks postoperatively showed no regurgitant jet in all patients.

Aged↗

PubMed1994

Migratory and proliferative effect of platelet-derived growth factor in rabbit retinal endothelial cells: evidence of an autocrine pathway of platelet-derived growth factor.

Angiogenesis is a crucial event in the progression of diabetic retinopathy. Migration and proliferation of endothelial cells (EC) are important steps in angiogenesis and are caused by angiogenic factors such as basic fibroblast growth factor (bFGF). In this work, capillary EC were isolated from rabbit retinal tissues and rabbit retinal EC (RREC) were found to secrete a migration factor for RREC in conditioned medium (CM). The activity was inhibited by an anti-platelet-derived growth factor (PDGF) antibody, but not by an anti-bFGF antibody. We also found that RREC showed a migratory response to PDGF. The response was induced by PDGF-BB and PDGF-AB dose dependently, but not by PDGF-AA, indicating that it was mediated by PDGF-beta receptor-dependent pathways, and that the PDGF-like factor was PDGF-BB or -AB. In addition, PDGF-BB induced the proliferation of RREC as well as bFGF. These data indicate that RREC have an autocrine pathway of PDGF by the secretion of and the response to PDGF. PDGF may play significant parts in angiogenesis in the progression of diabetic retinopathy.

Animals↗

PubMed1994

Diabetic control and progression of retinopathy in elderly patients: five-year follow-up study.

OBJECTIVE: To assess whether control of diabetes mellitus is as important in the elderly as in young and middle-aged diabetic patients in terms of progression of retinopathy. DESIGN: A 5-year longitudinal cohort study. SETTING: Outpatient diabetic clinic. PATIENTS: One hundred fourteen non-insulin-dependent diabetic patients (30 males, 84 females) > or = 60 years of age. MEASUREMENTS: Retinopathy was checked at the beginning and end of the follow-up period. During the 5-year follow-up period, demographic variables, body mass index, HbA1c, blood pressure, and plasma lipids were monitored. Retinopathy was classified as follows: grade 0, no lesion; grade 1, non-proliferative retinopathy; grade 2, pre-proliferative retinopathy; grade 3, proliferative retinopathy. Progression of retinopathy during the 5-year follow-up was defined as an increase in its grade. RESULTS: At the start of the study, 13% of the patients already had retinopathy, all of grade 1. The 5-year follow-up study showed that progression of retinopathy was 23.6% in all cases, 22.2% in those with grade 0 initially, and 33.3% in those with grade 1 initially. The progression rates of retinopathy as a function of the mean HbA1c during the follow-up were as follows: lower than 7%, 2%; 7-8%, 20%; 8-9%, 40%; more than 9%, 61%. Multiple logistic regression analysis showed that, of the parameters examined, only HbA1c was a significant risk factor for progression of retinopathy. CONCLUSIONS: Control of diabetes mellitus is the most important factor associated with prevention of progression of retinopathy in elderly patients.

Aged↗

PubMed1993

Angiogenic effects of advanced glycation end products of the Maillard reaction on cultured human umbilical cord vein endothelial cells.

The effects of advanced glycation end products (AGE) of the Maillard reaction on proliferation, migration and angiogenesis of cultured human umbilical vein endothelial cells (HUVEC) were studied. In an in vitro angiogenesis system, tube formation of HUVEC was dose-dependently stimulated by AGE at 0.5-50 micrograms/ml. Migration of HUVEC was also stimulated by AGE in a similar concentration range, and checkerboard analysis revealed that AGE were chemotactic but not chemokinetic. Proliferation of HUVEC was not affected by AGE. These data provide evidence that AGE are angiogenic.

Cell Movement↗

PubMed1993

Gene damage induced in human alveolar type II (L-132) cells by exposure to dimethylarsinic acid.

To analyze the mechanisms of arsenic-induced gene damage, found previously in lungs of mice and rats orally administered dimethylarsinic acid (DMAA), a major metabolite of inorganic arsenics, we employed an in vitro system using human alveolar type II (L-132) cells. The exposure to 10 mM DMAA for 10 hr caused significant single-strand breaks in DNA of the cells. At an earlier period of the exposure, the replicative DNA synthesis was markedly suppressed, and the chain length of the nascent DNA was shorter than that of the control, suggesting that the template DNA received some modification other than strand breaks. The modification, being repairable, was sensitive to ultraviolet irradiation to cause strand breaks. These results suggest the possibility of DNA-adduct formation at the early period of DMAA exposure in L-132 cells.

Cacodylic Acid↗

PubMed1993

Crosslink formation between DNA and nuclear proteins by in vivo and in vitro exposure of cells to dimethylarsinic acid.

DNA damage induced by arsenics, particularly by dimethylarsinic acid (DMAA), a main metabolite of inorganic arsenics in mammals, was investigated. DNA-protein crosslinks, similarly to DNA single-strand breaks, were induced in mouse and human culture cells by the treatment with DMAA. The crosslinks were sensitive to treatment with guanidine and hydroxylamine, suggesting that the DNA linkage sites in proteins were serine and threonine residues of H1 histone and of nonhistone proteins and that the linkage occurred through a phospho-nitrogen bond. The type of crosslinks was different from that induced by X-ray radiation. Of the radicals produced in the further metabolic processing of DMAA, the dimethylarsenic peroxyl radical rather than the superoxide anion radical is likely responsible for the formation of crosslinks, similar to the case of DNA single-strand breaks.

Animals↗