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Biomedical subjects

M Murata

Publications and source records attributed to M Murata.

At least 199 records · Page 11Linked to original sources
PubMed1999

Mechanism of oxidative DNA damage induced by a heterocyclic amine, 2-amino-3,8-dimethylimidazo[4,5f]quinoxaline.

Adduct formation has been considered to be a major causal factor of DNA damage by carcinogenic heterocyclic amines. By means of experiments with 32P-labeled DNA fragments and an electrochemical detector coupled to a high-pressure liquid chromatograph, we investigated whether the N-hydroxy metabolite of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) can cause oxidative DNA damage or not. This metabolite [MeIQx(NHOH)] was found to cause Cu(II)-mediated DNA damage, including 8-oxo-7,8-dihydro-2'-deoxyguanosine formation. When an endogenous reductant, beta-nicotinamide adenine dinucleotide (NADH), was added, the DNA damage was greatly enhanced. Catalase and bathocuproine, a Cu(I)-specific chelator, inhibited the DNA damage, suggesting the involvement of H2O2 and Cu(I). MeIQx(NHOH) frequently induced DNA cleavage at thymine and cytosine residues in the presence of NADH and Cu(II). A UV-visible spectroscopic study showed that little decomposition of MeIQx(NHOH) occurred in the absence of Cu(II), whilst rapid spectral change was observed in the presence of Cu(II), suggesting that Cu(II) catalyzes the autoxidation. The addition of NADH reduced the oxidized product back to MeIQx(NHOH). These results suggest that a copper-peroxo intermediate, derived from the reaction of Cu(I) with H2O2, participates in Cu(II)-dependent DNA damage by MeIQx(NHOH), and NADH enhances the DNA damage via a redox cycle. We conclude that in addition to DNA adduct formation, oxidative DNA damage plays an important role in the carcinogenic process of MeIQx.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1999

Genotype difference of aldehyde dehydrogenase 2 gene in alcohol drinkers influences the incidence of Japanese colorectal cancer patients.

A case-control study was conducted to explore the possible etiologic role of alcohol and aldehyde dehydrogenase 2 (ALDH2) gene among Japanese colorectal cancer patients. Information on their drinking, smoking and dietary habits was collected from 265 colon and 164 rectum cancer patients, and 794 non-cancer patients as a control group. Genotypes of the ALDH2 gene at codon 487, glutamic acid (ALDH2*1) as a wild-type or lysine (ALDH2*2) as a mutated type with reduced enzyme activity, were analyzed by polymerase chain reaction in 160 colon and 110 rectum cancer patients and 121 control persons. Univariate analysis with the chi 2 statistical test showed that heavy alcohol drinking (P < 0.01), frequent meat intake (P < 0.001), and irregular (P < 0.01), hasty (P < 0.01) and excessive (P < 0.001) eating habits were associated with the incidence of both colon and rectum cancers, whereas heavier smoking (P < 0.05) and infrequent fish (P < 0.03) and fruit (P < 0.01) intake were solely associated with incidence of rectum cancer. Infrequent green vegetable intake was not correlated with the incidence of colorectal cancer. Multivariate unconditional logistic regression analysis confirmed the association of alcohol consumption (P < 0.01) and meat intake (P < 0.05). Homozygous and heterozygous carriers of ALDH2*2 allele tended to be found in colon (trend P = 0.04) but not in rectum cancer patients compared to controls. Risk elevation for colon cancer due to alcohol consumption was pronounced among the heterozygotes and it was statistically significant especially for distal colon cancer (trend P = 0.02). We conclude that alcohol consumption is a risk factor for colorectal cancer and the risk can be enhanced in ALDH2 heterozygotes.

Adult↗
PubMed1999

Indomethacin suppresses the growth of colon 26, Meth-A and FM3A tumors in mice by reducing the prostaglandin E2 content and telomerase activity in tumor tissues.

The antitumor effect of indomethacin on Colon 26, Meth-A and FM3A tumors was investigated in mice. The prostaglandin E2 content in tumor tissues was assayed to find out if indomethacin acts on tumors, and the telomerase activity in tumors and somatic tissues (testis, liver, spleen and colon) was also monitored during indomethacin treatment. Growth of Colon 26, Meth-A and FM3A tumors was significantly (P < 0.001-0.05) suppressed by indomethacin compared to the untreated controls. The prostaglandin E2 content in the three tumors was markedly (P < 0.001) reduced by indomethacin. Telomerase activity in Colon 26 and FM3A tumors was significantly (P < 0.001) lower than that of untreated tumors (80% and 45% decrease versus the controls, respectively), and the activity in Meth-A tumor was slightly decreased (10% decrease versus the control) by indomethacin. Telomerase activity in the somatic tissues was not significantly affected by indomethacin. In summary, this study shows the effectiveness of indomethacin as an antitumor agent against three types of tumors, and suggests that indomethacin affects telomerase activity in tumors in vivo.

Animals↗
PubMed1999

Prepulse-induced mode 2 gating behavior with and without beta-adrenergic stimulation in cardiac L-type Ca channels.

Mode 2 gating of L-type Ca channels is characterized by high channel open probability (NPo) and long openings. In cardiac myocytes, this mode is evoked physiologically in two apparently different circumstances: membrane depolarization (prepulse facilitation) and activation of protein kinase A. To examine whether the phosphorylation mechanism is involved during prepulse-induced facilitation of cardiac L-type Ca channels, we used isolated guinea pig ventricular myocytes to analyze depolarization-induced modal gating behavior under different basal levels of phosphorylation. In control, NPo measured at 0 mV was augmented as the duration of prepulse to +100 mV was prolonged from 50 to 400 ms. This was due to the induction of mode 2 gating behavior clustered at the beginning of test pulses. Analysis of open time distribution revealed that the prepulse evoked an extra component, the time constant of which is not dependent on prepulse duration. When isoproterenol (1 microM) was applied to keep Ca channels at an enhanced level of phosphorylation, basal NPo without prepulse was increased by a factor of 3.6 +/- 2.2 (n = 6). Under these conditions, prepulse further increased NPo by promoting long openings with the same kinetics of transition to mode 2 gating (tau congruent with 200 ms at +100 mV). Likewise, recovery from mode 2 gating, as estimated by the decay of averaged unitary current, was not affected after beta-stimulation (tau congruent with 25 ms at 0 mV). The kinetic behavior independent from the basal level of phosphorylation or activity of cAMP-dependent protein kinase suggests that prepulse facilitation of the cardiac Ca channel involves a mechanism directly related to voltage-dependent conformational change rather than voltage-dependent phosphorylation.

Adrenergic beta-Agonists↗
PubMed1999

Bone maturation reflects the secular trend in growth.

The aim of this study was to compare a series of X-rays from the mid-1990s with another taken in the mid-1980s in order to test the possibility that environmental causes affect the skeletal maturation. The first group of subjects included a total of 1,057 girls and 1, 055 boys participating in a project for Japan and China health research in 1986. The second group of subjects included a total of 382 girls and 629 boys participating in a project for bone mineral density research in 1996. The skeletal maturity score using the Tanner-Whitehouse 2-RUS method was used as the fundamental datum. This score was used to represent each group. The Wilcoxon's rank sum test was applied to examine the significance of the difference between the 1986 and the 1996 groups. The 1996 children had not matured more than the 1986 children; children in both groups reached the given scores at almost the same ages. In girls, there was little difference between the groups at 7 years of age, but it declined from 8 years of age onward. Some apparent differences arose at ages 14 and 15, but ceased by age 16 in girls. In boys, no differences were found in those aged from 7 to 17 years, except for 12-year-olds. We did not detect much of a difference in bone maturation between the 1986 and 1996 groups of children, and no differences in height during the same period. Our findings suggest that bone maturation reflects the secular trend in growth.

Adolescent↗
PubMed1999

Nuclear factor kappa B mediates interleukin-8 production in eosinophils.

BACKGROUND: Recent reports indicate that in response to various stimuli, eosinophils produce a variety of cytokines (e.g. IL-8) which play pivotal roles in allergic inflammation. In that regard, the transcription factor, nuclear factor, Kappa B (NF-kappaB), is an important activator of tumor-necrosis-factor-alpha (TNF-alpha)-induced IL-8 gene expression in monocytes, lymphocytes and neutrophils. We therefore investigated the role played by NF-kappaB in cytokine production induced by stimulation of eosinophils with the proinflammatory cytokines, granulocyte-monocyte colony-stimulating factor (GM-CSF) and TNF-alpha. METHODS: Peripheral blood samples were obtained from human subjects with slight to moderate eosinophilia. NF-kappaB activation elicited by exposing cells to GM-CSF and/or TNF-alpha was investigated using immunohistochemistry and gel shift assays. To functionally assess the effects of NF-kappaB translocation, IL-8 production was also examined using an enzyme-linked immunosorbent assay. RESULTS: Stimulation of eosinophils with GM-CSF + TNF-alpha induced significant increases in the synthesis and secretion of IL-8 which were associated with translocation of NF-kappaB p50 into the nucleus. The binding of NF-kappaB to the DNA was verified by the gel shift assays. IL-8 production was significantly inhibited by N-acetyl-L-cysteine, FK506 and MG-132, inhibitors of NF-kappaB activation and translocation. CONCLUSION: On the basis of our findings, we conclude that activation and translocation of NF-kappaB plays a crucial role in the signal-transduction pathway leading to the synthesis and release of IL-8 by eosinophils.

Acetylcysteine↗
PubMed1999

Effects of protein meals on the urinary excretion of various plasma proteins in healthy subjects.

To examine whether hemodynamic changes in response to acute protein loadings with different protein sources cause increases in urinary excretion of plasma proteins in healthy subjects, urinary excretions of various plasma proteins with various molecular radii and isoelectric points, namely albumin (Alb), IgG, IgG4, ceruloplasmin (CRL), and alpha2-macroglobulin (A2), were measured in healthy subjects after ingestion of a beef meal or of a tuna fish meal. Significant increases in urinary excretions of the negatively charged IgG4 and CRL and of the neutrally charged IgG were found in parallel with enhanced creatinine clearances after each protein ingestion. These renal responses returned to basal levels 9 h after the test. This finding suggests that in healthy subjects, the increase in glomerular filtration rate after acute protein loading caused selective enhancement of urinary excretions of plasma proteins with a molecular radius of approximately 55 A (the radius of IgG, IgG4, and CRL), irrespective of the charge barrier of the glomerulus. The increases in these three plasma proteins may be induced by leakage via the shunt pathway in the glomerulus, as proposed earlier (see text). In contrast, increases in urinary excretions of A2 and Alb were not found. The former finding may be explained by the possibility that A2 would not pass through this pathway, since the molecular radius of A2 (88 A) is larger than that of IgG, although the latter finding may be partially explained by preferential renal tubular reabsorption of Alb.

Adult↗
PubMed1999

An arrested late endosome-lysosome intermediate aggregate observed in a Chinese hamster ovary cell mutant isolated by novel three-step screening.

Chinese hamster ovary cell mutants defective in the post-uptake degradation of low-density lipoprotein (LDL) in lysosomes were selected from mutagenized cells by novel three-step screening. First, in the presence of LDL, clones sensitive to an inhibitor of the rate-limiting enzyme of the cholesterol biosynthetic pathway, 3-hydroxy-3-methylglutaryl-CoA reductase, were isolated. Second, from the selected clones, those lacking in the degradation of a constituent of a fluorescent LDL were qualitatively screened by microscopy. Third, the clones were further screened by previously established quantitative analytical flow cytometry that detects the early-phase disintegration of LDL by lysosomal acid hydrolases. One of the isolated mutant clones, LEX1 (Lysosome-Endosome X 1), was a recessive mutant, and exhibited a specific disorder in the late endocytic pathway. LEX1 cells showed an unusual perinuclear aggregate of vesicles, heterogeneously positive for lysosomal glycoprotein-B/cathepsin D and rab7, yet negative for the cation-independent mannose 6-phosphate receptor. The aggregate was formed around the microtubule organizing center, and was disrupted by nocodazole treatment. Internalized octadecyl rhodamine B-labeled LDL (R18-LDL) was accumulated in the perinuclear rab7-positive vesicles. In a Percoll density gradient, neither internalized R18-LDL nor internalized horseradish peroxidase was efficiently chased into heavy lysosomal fractions positive for beta-hexosaminidase. LEX1 cells showed differences in the activity and subcellular distribution of lysosomal enzymes. These characteristics of LEX1 cells are consistent with the ideas that the perinuclear vesicle aggregate is an arrested intermediate of direct fusion or divergence between lysosomes and rab7-positive, cation-independent mannose 6-phosphate receptor-negative late endosomes, and that equilibrium between the lysosomes and the late endosomes is shifted towards the late endosomes in LEX1 cells. Such fusion or divergence between the late endosomes and the lysosomes would determine an appropriate equilibrium between them, and might thereby play an important role for proper lysosomal digestive functions. LEX1 mutant cells would be helpful for the dissection of the as yet unrevealed details of the late endocytic membrane dynamics and for the identification of factors involved in the process arrested by the mutation.

Animals↗
PubMed1999

Setting up an automated system for evaluation of bone age.

The "Tanner-Whitehouse 2" method is the most popular in evaluating skeletal maturation, but this method has some inherent weak points. We therefore developed the new system to automatically evaluate the skeletal maturation of Japanese children by means of a personal computer. The subjects of this study were 318 healthy Japanese boys and 199 girls ranging from 2 to 15 years of age. The bone age was calculated by multiple regression analysis with parameters for the epiphysis and metaphysis. Successful automatic evaluation was about 80-90% on each phalanx. There was a significant correlation between chronological age and the ratio of epiphyseal width to metaphyseal width. The system developed in this study was useful for evaluating the skeletal maturation.

Adolescent↗
PubMed1999

Urinary excretion of ceruloplasmin is elevated in the subjects with "borderline glucose tolerance test".

To examine whether or not there are any renal alterations in subjects with borderline glucose tolerance and in patients with non-insulin dependent diabetes mellitus (NIDDM) classified by the criteria of Japan Diabetic Association, urinary excretions of plasma proteins including albumin, ceruloplasmin (Cerulo) and IgG were measured in timed overnight urine samples. Eighty middle-aged, non-obese, normotensive, untreated men with urinary albumin excretion rates below 20 microg/minutes, beta2-microglobulin excretion rates below 140 microg/minutes and creatinine clearance values exceeding 80 ml x min(-1) x (1.73 m2)(-1) were included in this study. Three groups were defined according to the results of 75 g oral glucose tolerance test (OGTT) as follows: D group, 10 subjects with NIDDM; B group, 40 subjects with "borderline glucose tolerance test" and N group, 30 subjects with normal glucose tolerance. The fractional clearance (theta) of Cerulo, but not albumin and IgG, was elevated in 37. 5% of the B group compared with the upper limit of that of the N group. Furthermore, theta-Cerulo and theta-IgG increased in the D group compared with those of the N and the B groups. Recently, we found that theta-Cerulo and theta-IgG increased in healthy volunteers when GFR was elevated by acute protein loading and that increase in theta-Cerulo is remarkable than increase in theta-IgG. The present result, taken together with our recent finding mentioned above, suggests that increases in theta-Cerulo and theta-IgG may not be due to an impairment of charge selectivity in the glomerular basement membrane, but due to an increase of intraglomerular hydraulic pressure.

Adult↗
PubMed1999

Effects of short-term glycemic control, low protein diet and administration of enalapril on renal hemodynamics and protein permselectivity in type 2 diabetic patients with microalbuminuria.

To determine whether each of glycemic control (GC), low protein diet (LPD) or administration of angiotensin converting enzyme inhibitor (ACEI) has beneficial effects on diabetic nephropathy through the different mechanisms, changes in charge and size selectivity of glomerulus and renal hemodynamics were analyzed in microalbuminuric type 2 diabetic patients after additive combination therapy (first period: GC only, second period: GC-LPD, third period: GC+LPD+ACEI). To detect improvement of the impairments of glomerular charge selectivity and size selectivity, changes in the ratio of the renal clearance of two plasma proteins with similar molecular radii and different isoelectric points (pIs) (ceruloplasmin and IgG: CRL/IgG) and changes in the ratio of the renal clearance of two plasma proteins with similar pIs and different molecular radii (alpha2-macroglobulin and albumin: alpha2/Alb) were examined before and after each therapy. Creatinine clearance decreased significantly in the first and third periods although slight but not significant decrease was detected in the second period. Filtration fraction was significantly decreased only in the third period. Although renal clearances of Alb, IgG and CRL were decreased in periods of all three therapies, that of alpha2-macroglobulin with a large molecular radius was decreased significantly only after the third therapy. Neither CRL/IgG nor alpha2/Alb changed during these three therapies. These findings suggest that each of three short-term therapies consisting of GC, GC+LPD and GC+LPD+ACEI, reduced proteinuria in microalbuminuric type 2 diabetic patients not through the improvement of renal size and charge selectivities, but through improvement of renal hemodynamics.

Adult↗
PubMed1999

Polyol formation and NADPH-dependent reductases in dog retinal capillary pericytes and endothelial cells.

PURPOSE: Dogs fed a diet containing 30% galactose experience retinal vascular changes similar to those in human diabetic retinopathy, with selective pericyte loss as an initial lesion. In the present study the relationship among reduced nicotinamide adenine dinucleotide phosphate (NADPH)-dependent reductases, polyol formation, and flux through the polyol pathway in cultured dog retinal capillary cells were investigated. METHODS: Pericytes and endothelial cells were cultured from retina of beagle dogs. NADPH-dependent reductases were characterized by chromatofocusing after gel filtration. Sugars in cultured cells were analyzed by gas chromatography, and flux through the polyol pathway was investigated by 19F nuclear magnetic resonance (NMR) with 3-fluoro-3-deoxy-D-glucose (3FG) as a substrate. The presence of aldose reductase and sorbitol dehydrogenase in these cells was examined by northern blot analysis. RESULTS: Two distinct peaks corresponding to aldose reductase and aldehyde reductase, the latter being dominant, were observed in pericytes by chromatofocusing. Culture in medium containing either 10 mM D-galactose or 30 mM D-glucose resulted in the accumulation of sugar alcohol in pericytes that was markedly reduced by aldose reductase inhibitors. 19F NMR spectra obtained from pericytes cultured for 5 days in medium containing 2 mM 3FG displayed the marked accumulation of 3-fluoro-deoxysorbitol but not 3-fluoro-deoxyfructose. No 3FG metabolism was observed in similarly cultured endothelial cells. With northern blot analysis, aldose reductase was detected in pericytes but not in endothelial cells. Sorbitol dehydrogenase was below the detectable limit in pericytes and endothelial cells. CONCLUSIONS: Aldose, aldehyde, and glyceraldehyde reductases are present in dog retinal capillary pericytes, with aldehyde reductase being the major reductase present. Polyol accumulation easily occurs in pericytes but not in endothelial cells.

Aldehyde Reductase↗
PubMed1999

Carrier-mediated lung distribution of HSR-903, a new quinolone antibacterial agent.

HSR-903 [(S)-(-)-5-amino-7-(7-amino-5-azaspiro[2. 4]hept-5-yl)-1-cyclopropyl-6-fluoro-1, 4-dihydro-8-methyl-4-oxoquinoline-3-carboxylic acid methanesulfonate] is a newly synthesized quinolone with a potent antibacterial activity and a low toxicity. The lung concentration of unchanged HSR-903 was about nine times higher than that in plasma after oral administration (5 mg/kg) in rats. In comparative studies, HSR-903 was accumulated more efficiently than levofloxacin, ciprofloxacin, and lomefloxacin in rat lung. To clarify the mechanism of the specific distribution of HSR-903 into the lung, the uptake of [14C]HSR-903 was studied using isolated rat lung cells and an isolated rat lung perfusion technique. Initial uptake of HSR-903 by isolated lung cells was temperature dependent, saturable, stereospecific, and Na+ and Cl- dependent. The Hill coefficients (1. 90 for Na+ and 1.13 for Cl-) suggest that two Na+ and one Cl- are associated with the transport of one HSR-903 molecule. The uptake of HSR-903 was inhibited by other quinolone antibacterial agents, grepafloxacin, and sparfloxacin. The extraction ratio of HSR-903 in isolated lung perfusion was temperature dependent and saturable. These findings suggest that HSR-903 is taken up by the lung cells via a carrier-mediated transport mechanism, resulting in a concentrative distribution into the lung.

Algorithms↗
PubMed1999

An HIV autopsy--characterization of zidovudine-resistant subtype E HIV-1 from autopsy tissue suggests the route of infection and an alternative protocol of therapy.

This CPC concerns a 47-year-old male patient with acquired immunodeficiency syndrome (AIDS). The patient became symptomatic when he developed Pneumocystis carinii pneumonia, but recovered sufficiently to be treated as an outpatient. Two years after falling ill, he developed septic shock and died within a short time. During this period, he failed to respond to HIV drugs, and there was no improvement in his immunodeficient status. The HIV retrieved from the patient's organs at autopsy was found to be type E and to have acquired resistance to Zidovudine. It was also possible to determine the route of infection. HIV treatment guidelines are continuously being revised on the basis of HIV research and the development of new treatment plans, and at the present time, when no definitive method of treatment has yet been established, it is essential for the clinician to keep abreast of the latest information. Since HIV patients are compromised hosts, it is important to diagnose and treat other infectious complications, not only complications unique to AIDS, and we have briefly described the latest HIV therapy.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Bone augmentation by recombinant human BMP-2 and collagen on adult rat parietal bone.

A composite of recombinant human bone morphogenetic protein-2 (rhBMP-2) and collagen was implanted beneath the cranial periosteum of 10-month-old rats to observe bone development and absorbent change of carrier collagen. The rhBMP-2/collagen onlay implant resulted in active bone formation and the augmented bone was connected directly with the original bone, whereas the collagen alone resulted in neither bone nor cartilage. The ossification process in the rhBMP-2/collagen occurred directly through bone formation, similar to intramembranous ossification. The carrier collagen fibers were found in the woven bone and were completely absorbed at 8 weeks in the presence of rhBMP-2, while the collagen alone implant remained encapsulated by a thin, fibrous connective tissue. Our results indicate that rhBMP-2/collagen is an effective material as a biological onlay implant, showing osteoinductive properties and being completely replaced by new bone. Carrier collagen not only plays a role in rhBMP-2 delivery, but also provides a cell anchorage for cell differentiation and remains as an artificial matrix in woven bone.

Absorbable Implants↗
PubMed1999

Efflux transport of a new quinolone antibacterial agent, HSR-903, across the blood-brain barrier.

The distribution of HSR-903, a new quinolone antibacterial agent, to the brain after i.v. administration to rats was low compared with that to other tissues. The blood-brain barrier permeability to HSR-903 determined by the brain perfusion method was low, and increased nonlinearly with increasing concentration of HSR-903 in the perfusate. When the brain-to-plasma concentration ratio (Kp, brain) was measured in mdr1a gene-knockout mice, the value was 8 times higher than that in normal mice. The uptake of [14C]HSR-903 by multidrug-resistant K562/ADM cells, which express P-glycoprotein (P-gp), was significantly lower than that by the drug-sensitive parent K562 cells. In addition, the uptake of [14C]HSR-903 by K562/ADM cells was significantly increased in the presence of cyclosporin A and ATP-depleting agents. These observations support the idea that P-gp participates in HSR-903 efflux from the brain. The steady-state uptake of HSR-903 by a monolayer of primary cultured bovine brain capillary endothelial cells was increased in the presence of several quinolone antibacterial agents or anionic compounds, such as 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid, and in bicarbonate ion-free medium, as well as by P-gp inhibitors (cyclosporin A and quinidine). These results suggested that the efflux of HSR-903 proceeds at least partly via an anion-sensitive efflux transport mechanism as well as via P-gp. In conclusion, the low brain distribution of the new quinolone antibacterial agent HSR-903 can be ascribed to multiple efflux mechanisms including P-gp and an unidentified anion-sensitive transporter operating in the brain capillary endothelial cells that constitute the blood-brain barrier.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗