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Biomedical subjects

M Yamazaki

Publications and source records attributed to M Yamazaki.

At least 469 records · Page 26Linked to original sources
PubMed1994

Study on hypomineralized areas in hamster molars.

Hypomineralized area (HMA) scores were determined for hamster molars during tooth maturation and fluoride treatment. It was found that the molars were maturing until the animals were 45 days old, but from 45 to 74 days of age the HMA scores remained constant. Fluoride treatment decreased the HMA score. The group with the lowest HMA score was fed a cariogenic diet, inoculated with Streptococcus mutans and received topical fluoride treatment.

Animals↗
PubMed1994

Effect of smear layer removal agent and/or fluoride on the surface of dentin.

A study was conducted to observe the effectiveness of an EDTA-based agent, Tubulicid Red, and a polyacrylic acid-based agent, Dentin Conditioner, for removal of the smear layer from a prepared dentin surface, with or without a fluoride dentin reinforcing agent, using the dye penetration test and scanning electron microscopy (SEM). Bovine mandibular first and second incisors were used. After removal of the enamel, the smear layer on the dentin surface was treated with 38% H3PO4, Tubulicid Red, Dentin Conditioner, 1% NaF, 1% SnF2, Tubulicid Red (including 1% SnF2), Dentin Conditioner (including 1% NaF) and Dentin Conditioner (including 1% SnF2). In the dye penetration test, Dentin Conditioner (including 1% SnF2) was the most effective agent for preventing dye penetration. SEM evaluation of the dentin surface after treatment with the smear layer removal agents and/or fluorides showed that the smear layer was removed by H3PO4 and Dentin Conditioner. However, dentinal plugs remained after treatment with Dentin Conditioner alone. The other agents left some layers on the dentin surface.

Acid Etching, Dental↗
PubMed1994

Effects of DX-9065a, an orally active, newly synthesized and specific inhibitor of factor Xa, against experimental disseminated intravascular coagulation in rats.

We investigated the protective effects of DX-9065a, an orally active, newly synthesized and specific inhibitor of factor Xa, against two kinds of experimental disseminated intravascular coagulation (DIC) in rats. Endotoxin-induced experimental DIC was induced by a 4-h sustained infusion of endotoxin at a dose of 100 mg/kg. Thromboplastin-induced experimental DIC was induced by a bolus injection of thromboplastin at a dose of 150 mg/kg. The rats were orally administered DX-9065a at 10, 30 or 100 mg/kg 30 min before endotoxin or thromboplastin injection. In both DIC models, DX-9065a showed a protective effect against DIC, at all doses and in all parameters, including fibrin/fibrinogen degradation products (FDP), fibrinogen level, prothrombin time, activated partial thromboplastin time, platelet count and the number of renal glomeruli with fibrin thrombi. When DX-9065a was orally administrated at 100 mg/kg without endotoxin or thromboplastin, no significant changes were seen in hemostatic parameters except PT and APTT, and no fibrin thrombi or abnormal bleeding were seen in renal specimens. These findings suggest that the new oral anti-Xa drug, DX-9065a, has an effect in reducing the severity of DIC. However, further dose-finding and safety studies of this drug have still to be assessed.

Administration, Oral↗
PubMed1994

Meeting report of the International Symposium of Molecular Cell Biology of Macrophages '94.

The International Symposium of Molecular Cell Biology of Macrophages '94 was held on February 10-11, 1994 at Kanazawa University, Kanazawa, Japan. Fifteen speakers including 4 speakers from Europe and the United States were invited to this symposium. In spite of unusual heavy snow and chilly weather, 150 macrophage scientists gathered and had hot discussions. In the meeting reception, a special recognition speech entitled "Dawn of Cytokines--Discovery of a Blastogenic Factor in the Early 1960's" was given by a discoverer of blastogenic factor, Dr. Shinpei Kasakura. This symposium was initiated in 1991 with the intention of bringing together experts of macrophage investigation once a year to discuss progress in the field of molecular cell biology of macrophages.

Animals↗
PubMed1994

The design of oral sustained-release theophylline dosing after conversion from intravenous to oral therapy.

We studied the design of oral sustained-release theophylline dosing after conversion from constant aminophylline infusion. Twelve children with bronchial asthma (9 boys and 3 girls) were evaluated in this study. Each patient received a constant intravenous administration of aminophylline for 4-10 days. Three hours after conversion from constant aminophylline infusion, they received oral sustained-release theophylline twice daily at 12-hour intervals. Blood samples were obtained at least once during the aminophylline infusion, just before conversion from the aminophylline infusion, and 0, 3 and 6 hours, and 4-5 days after administering oral theophylline. Pharmacokinetic parameters were estimated using the serum theophylline concentrations that were obtained during constant aminophylline infusion. These estimates of pharmacokinetic parameters were used to predict the serum theophylline concentrations during oral theophylline therapy. Predicted serum theophylline concentrations using individual pharmacokinetic parameters were fitted with actual measured values in this study. When switching a patient from intravenous aminophylline to sustained-release oral theophylline, the use of Bayesian analysis of serum theophylline concentration values obtained during intravenous therapy works well in predicting serum theophylline concentrations and in determining oral dosages that maximize the drug's effectiveness.

Administration, Oral↗
PubMed1994

[Characterization of infiltrating mononuclear cells in the spinal cords of Lewis rats with experimental autoimmune encephalomyelitis (EAE)].

Mononuclear cells (MNCs) infiltrating in spinal cords (SCs) of Lewis rats with EAE were isolated in order to permit flow cytometric (FCM) analysis of these cell populations, using monoclonal antibody to T cell, CD4, CD8. MHC class II antigen (Ia), intercellular adhesion molecule-1 (ICAM-1) and lymphocyte function associated antigen-1 (LFA-1). The number of MNCs isolated from SC varied from 5 to 620 x 10(4). They were increased and reached a peak on day 2 post clinical onset, and subsequently declined through the clinical course. The increase of infiltrating cells in SC paralleled the severity of the disease development. The surface phenotypes of MNCs from rats on the day of clinical onset were determined by flow cytometry. The phenotypes found in these rats were as follows: T cells (70.3%); CD4 + (58.3%); CD8 + (40.3%); Ia (51.9%); ICAM-1 (62.6%); LFA-1 (75.8%). These findings suggest that high proportion of ICMA-1 and LFA-1 expression may be important in antigen presentation in the inflammatory lesions of SC and in promoting lymphocyte extravasation across the blood-brain barrier during the disease. The approach we employed offered more sophisticated and quantitative analysis of CNS inflammatory cells, which is unobtainable by tissue section staining.

Animals↗
PubMed1994

Carrier-mediated active transport of histamine H2 receptor antagonists, cimetidine and nizatidine, into isolated rat hepatocytes: contribution of type I system.

The uptake rates of [3H]cimetidine and [14C]nizatidine into isolated rat hepatocytes were studied in order to identify the transport mechanism of histamine H2 receptor antagonists into the liver. In addition, the contributions of the uptake clearance to hepatic clearance for both drugs also were estimated. The uptakes of cimetidine and nizatidine achieved equilibrium in 5 min with cell-to-medium concentration ratios of 12.0 and 3.5, respectively. The uptake systems of both histamine H2 antagonists consisted of a saturable component and a nonsaturable component. The contributions of the carrier-mediated transport system for cimetidine and nizatidine at therapeutic concentrations (3 microM) were 86 and 70%, respectively. The uptakes of both drugs showed temperature dependency and were decreased significantly by various metabolic inhibitors and a sulfhydryl group modifying reagent. Only a slight effect was seen in the replacement of sodium with lithium on both uptakes. The uptake of cimetidine was reduced markedly in parallel with the reduction in the cellular ATP level and was inhibited by other histamine H2 antagonists and various organic cations. Furthermore, both nizatidine and quinidine competitively inhibited cimetidine's uptake. These results demonstrate that cimetidine and nizatidine are taken up into hepatocytes by a common Na(+)-independent transport system, namely the type I organic cation uptake system. By comparing the in vitro hepatic uptake clearance obtained from this study and the in vivo hepatic clearance from pharmacokinetic data, it is suggested that the rate-limiting step in hepatic clearance for cimetidine is drug metabolism, whereas for nizatidine, it is the uptake process.

Adenosine Triphosphate↗
PubMed1994

[Prevalence of specific IgE antibodies for Dermatophagoides farinae and six inhalants in the general population].

A seroepidemiologic study of house dust allergy and pollinosis was performed among a general population aged 17 to 69 in Aichi Prefecture, Japan. The prevalence of blood containing IgE antibodies to four perennial antigens and three seasonal antigens was examined among 198 persons whose serum total IgE antibodies were above 40 IU/ml. The prevalence of blood containing IgE antibodies was from 9 to 18 percent among perennial antigens and from 6 to 30 percent among seasonal antigens. These results show that Dermatophagoides farinae, Cryptomeria japonica pollen and Anthoxanthumodoratum pollen are important antigens in this population.

Adolescent↗
PubMed1994

Prediction of steady-state serum theophylline concentration in children by first-order and zero-order absorption models.

We estimated the pharmacokinetic characteristics of theophylline in children with bronchial asthma after multiple oral dosing of Theo-Dur, in order to determine whether the absorption of the drug is best described by a zero-order absorption kinetic model (0-order model) or a first-order absorption kinetic model (1-order model). Thirteen children with bronchial asthma were evaluated in this study. Each patient received Theo-Dur twice daily at 12-hour intervals. Blood samples were taken at 0, 3, 6, 9 and 12 hours after the administration; plasma theophylline concentration was determined by the fluorescence polarization immuno assay method. Pharmacokinetic parameters for each patient were estimated by a one-compartment open model with 0-order or 1-order absorption and 1-order elimination rate constants. The regression curve predicted using the 0-order model fitted well to the observed value. In contrast, the use of the 1-order model was overestimated considerably in the absorption phase the precision of the prediction using the 0-order model was better than the use of the 1-order model. This study suggests that the 0-order model gave better estimated pharmacokinetic parameters when applied to Theo-Dur than did the 1-order model in children.

Adolescent↗
PubMed1994

[TNF-alpha].

TNF-alpha, a cytokine with tumor necrosis activity produced by many types of cells including macrophages, was recently recognized as an important host defense factor that affects not only malignant cells, but many kinds of normal cells. Clinical applications of TNF-alpha are now limited, but local injection or local production of TNF-alpha should be given closer consideration in antitumor trials. Here we described the TNF receptor family and TNF-alpha-driven inflammation, and also discussed the physiological roles of TNF-alpha.

Animals↗
PubMed1994

[Effects of sevoflurane or halothane on contractile responses of isolated canine basilar artery].

Although volatile anesthetic is known as a cerebral vasodilator, its mechanism is not clear. The purpose of this study was to investigate effects of sevoflurane or halothane on contractions induced by high K+ and serotonin in the isolated canine basilar artery. Cylindrical segments of canine basilar artery were placed in Krebs solution oxygenated with 95% O2 and 5% CO2 at 37 degrees C. They were then constricted with cumulative administration of 10 to 60 mM KCl, or with 10(-9) to 10(-6) M serotonin and exposed to either sevoflurane or halothane at concentration of 1.0 and 2.0 MAC. Halothane and sevoflurane at concentration of 1.0 and 2.0 MAC decreased contractile responses evoked by KCl to a similar degree. The attenuation by either of the two anesthetics at concentration of 2.0 MAC were equivalent to the inhibitions by diltiazem 2 x 10(-7) M. Contractile responses to serotonin above 3 x 10(-7) M were depressed by halothane 1.0 MAC, but not by sevoflurane 1.0 MAC. Sevoflurane and halothane at concentration of 2.0 MAC decreased contractile responses evoked by serotonin at concentrations above 3 x 10(-8) M and 10(-8) M. Removal of the endothelium did not alter the response of the basilar artery contracted by serotonin to either anesthetic. These findings suggest that sevoflurane and halothane depress the voltage-dependent Ca2+ channels due to decreases of contractile responses to high K+. Our results also demonstrate that sevoflurane is a less potent vasodilator of the basilar artery contracted by serotonin than halothane.

Animals↗
PubMed1994

Plasma levels of lipoprotein(a) are elevated in patients with the antiphospholipid antibody syndrome.

The mechanisms underlying clinical abnormalities associated with the antiphospholipid antibody syndrome (APAS) have not been elucidated. We measured plasma levels of lipoprotein(a) [Lp(a)], the active form of plasminogen activator inhibitor (active PAI), thrombin-antithrombin III complex (TAT) and soluble thrombomodulin (TM), to investigate the relationship of these factors to thrombotic events in APAS. Mean plasma levels of Lp(a), TAT, active PAI and TM were all significantly higher in patients with aPL than in a control group of subjects. Plasma levels of Lp(a) and active PAI were significantly higher in patients with aPL and arterial thromboses than in patients with aPL but only venous thromboses. There was a significant correlation between plasma levels of Lp(a) and active PAI in patients with aPL. These findings suggest that patients with aPL are in hypercoagulable state. High levels of Lp(a) in plasma may impair the fibrinolytic system resulting in thromboses, especially in the arterial system.

Abortion, Habitual↗
PubMed1994

Expression of transforming growth factor-beta 1 and its relation to endomysial fibrosis in progressive muscular dystrophy.

Progressive muscular dystrophy is characterized by muscle fiber necrosis, regeneration, and endomysial fibrosis. Although absence of dystrophin has been known as the cause of muscle fiber degeneration, pathogenesis of interstitial fibrosis is still unknown. Transforming growth factor-beta 1 (TGF-beta 1) induces accumulation of extracellular matrix in various diseases, such as liver cirrhosis and interstitial pneumonitis. To investigate its function on the pathogenesis of progressive muscular dystrophy, it was necessary to determine the degree of TGF-beta 1 expression and the site of TGF-beta 1 immunoreactivity. In Duchenne muscular dystrophy and most of Becker muscular dystrophy, high TGF-beta 1 immunoreactivity expressed on muscle fibers and extracellular space. In other myopathies with endomysial fibrosis, however, TGF-beta 1 was seldom observed. We also examined the immunoreactivity of the latent TGF-beta binding protein, which is bound to the TGF-beta precursors. In all Duchenne muscular dystrophy and half of Becker muscular dystrophy cases, high latent TGF-beta 1 binding protein immunoreactivity was seen, but in other myopathies its immunoreactivity was seldom seen on muscle fibers or extracellular space. Therefore TGF-beta 1 may play an important role in synthesis and accumulation of extracellular matrix in progressive muscular dystrophy.

Animals↗
PubMed1993

Rapid determination of tetracycline antibiotics in serum by reversed-phase high-performance liquid chromatography with fluorescence detection.

A rapid and accurate determination of tetracycline antibiotics in human serum by reversed-phase high-performance liquid chromatography with fluorescence detection has been developed, based on protein precipitation in serum. Various reagents for precipitation were investigated, and 24% trichloroacetic acid in methanolic solution gave the maximum recovery (at least 94.3%) and interference-free chromatograms of different three tetracyclines. At a concentration of 0.5 micrograms/ml, the precision (relative standard deviation) ranged from 1.12 to 1.94%. In the range 0.04-10.0 micrograms/ml for oxytetracycline and chlorotetracycline and 0.01-10.0 micrograms/ml for tetracycline, linear responses were observed. The detection limits of this method were 10-35 ng/ml for all three antibiotics. The proposed method was applied to the determination of serum concentrations in subjects receiving tetracycline antibiotics.

Chromatography, High Pressure Liquid↗