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Biomedical subjects

T Oguma

Publications and source records attributed to T Oguma.

At least 19 recordsLinked to original sources
PubMed2006

Involvement of reduced sensitivity to Ca in beta-adrenergic action on airway smooth muscle.

BACKGROUND: It is well known that beta-adrenoceptor agonists (beta-agonists) cause relaxation in airway smooth muscle mediated by a reduction in the concentration of intracellular Ca2+ ([Ca2+](i)). However, little is currently known regarding whether reduced sensitization to Ca2+ is involved in the beta-adrenergic relaxation. OBJECTIVE: This study was designed to determine the intracellular mechanisms underlying suppression of Ca2+ sensitization in beta-adrenergic relaxation (Ca(2+)-independent relaxation by beta-agonists). Methods Isometric tension and [Ca2+](i) were simultaneously measured in fura-2-loaded strips isolated from guinea-pig tracheal smooth muscles. The relationships between tension and [Ca2+](i) were examined in the inhibitory action of isoprenaline (ISO) and other cAMP-related agents against methacholine-induced contraction. RESULTS: The concentration-inhibition curve for ISO against methacholine in tension was significantly dissociated from the curve for ISO in [Ca2+](i). In ISO-induced relaxation, a reduction in tension was significantly greater than that in [Ca2+](i.) This phenomenon was mimicked by other cAMP-related agents: forskolin and dibutyryl-cAMP. In contrast, the inhibitory action of SKF-96365, a non-selective inhibitor of Ca(2+) channels, was associated with that in [Ca2+](i). In the presence of Rp-cAMPS, an inhibitor of protein kinase A (PKA), ISO caused an equivalent relaxation with less reduction in [Ca2+](i). The effects of ISO were not affected by Y-27632, an inhibitor of Rho-kinase, or by bisindolylmaleimide, an inhibitor of protein kinase C. ISO failed to inhibit contraction elicited by calyculin A, an inhibitor of myosin phosphatase. Conclusion beta-Adrenergic action antagonizes not only Ca2+ mobilization but also Ca2+ sensitization in methacholine-induced contraction. The cAMP/PKA-independent, G(s)-direct action is more potent in Ca(2+)-independent relaxation by beta-agonists than the cAMP/PKA-dependent pathway. Moreover, myosin phosphatase is a fundamentally affected protein in the reduced response to Ca2+ mediated by beta-agonist. Our results may provide evidence that this Ca2+ desensitization is a novel target for a reliever medication using rapid-acting beta-agonists in acute asthma management.

Adrenergic beta-Agonists↗
PubMed2004

Phase I and pharmacokinetic study of TZT-1027, a novel synthetic dolastatin 10 derivative, administered as a 1-hour intravenous infusion every 3 weeks in patients with advanced refractory cancer.

BACKGROUND: TZT-1027 is a synthetic dolastatin 10 analog with antineoplastic properties in various cell lines and tumor xenografts. The purpose of this phase I study was to evaluate the safety and toxicity, maximum tolerated dose, pharmacokinetics and pharmacodynamics, clinical and metabolic antitumor activity of TZT-1027 when given as a 1-h intravenous infusion every 3 weeks in patients with refractory solid tumors. PATIENTS AND METHODS: Patients had a histologically verified refractory tumor with measurable disease, were > or = 18 years old, had an Eastern Cooperative Oncology Group performance status <2 and adequate bone marrow, liver, renal and cardiac function. Dose-limiting toxicity was defined as platelets <25 x 10(9)/l, neutrophils <0.5 x 10(9)/l for >5 days, febrile neutropenia > or = 38.5 degrees C with grade 4 (National Cancer Institute-common toxicity criteria) neutropenia, or grade 3/4 non-hematological toxicity excluding nausea and vomiting. The last dose was the dose where > or = 2 out of six patients experienced dose-limiting toxicity in cycle one. The maximum tolerated dose was one dose level below with less than two of six patients with dose-limiting events. RESULTS: Twenty-one non-selected, fully evaluable patients were enrolled. The majority were male (19) and the median age was 55 years (range 39-67). Dose levels of TZT-1027 ranged from 1.35 to 3.0 mg/m(2). The median number of cycles was two (range 1-4). Dose-limiting toxicities were observed in three patients at the 3.0 mg/m(2) dose level, including neutropenia, fatigue and a short lasting, reversible peripheral neurotoxic syndrome. The most common toxicities per patient were fatigue, anorexia, alopecia, nausea, constipation, leukopenia and neutropenia. Based on RECIST criteria, the best response was stable disease in seven patients. The pharmacokinetic evaluation revealed a T(1/2) of approximately 7 h and linear kinetics. CONCLUSIONS: The recommended dose of TZT-1027 for the 3-weekly administration is 2.7 mg/m(2). Neutropenia, fatigue and a reversible peripheral neurotoxic syndrome are dose-limiting with this schedule. TZT-1027 may be associated with neurological side-effects in patients previously exposed to neurotoxic compounds such as oxaliplatin.

Adult↗
PubMed2002

A formula for predicting optimal dosage of nedaplatin based on renal function in adult cancer patients.

PURPOSE: To predict the optimal dosage for nedaplatin ( cis-diammineglycolatoplatinum), an anticancer drug and a platinum derivative like cisplatin and carboplatin, a simple formula was developed based on renal function in Japanese adult cancer patients. PATIENTS AND METHODS: Unbound platinum concentrations in plasma after intravenous infusion of nedaplatin were measured for 187 courses in 145 patients with lung, esophageal, and cervical and ovarian cancer undergoing clinical treatment. The data were divided into two sets, a model development data set of 94 courses and a validation data set of 93 courses. Regression analysis was applied to the relationship between the unbound platinum clearance (CL) of nedaplatin and the patients' renal function. The predictability and usefulness of this formula were assessed by validation using the external data set of 93 courses obtained from 75 patients. RESULTS: A simple formula was obtained for predicting the platinum clearance using the creatinine clearance (CLcr): CL=0.0836xCLcr+3.45. Indices for the predictive performance for CL and the area under the plasma concentration curve (AUC) in the validation data were almost the same as those for the model development data. CONCLUSIONS: A formula for predicting the CL of unbound platinum after nedaplatin administration was developed, and only CLcr was found to be a significant covariate of the CL. This formula was useful for estimating the CL for the second as well as the first treatment with nedaplatin.

Adult↗
PubMed2002

Effect of short-term low-intensity exercise on insulin sensitivity, insulin secretion, and glucose and lipid metabolism in non-obese Japanese type 2 diabetic patients.

The aim of the present study was to investigate the effects of short-term physical exercise that did not change body mass on insulin sensitivity, insulin secretion, and glucose and lipid metabolism in 39 non-obese Japanese type 2 diabetic patients. Insulin sensitivity and insulin secretion were estimated with homeostasis model assessment insulin resistance (HOMA-IR) and HOMA-B-cell function proposed by Matthews et al., respectively. All patients were hospitalized and were engaged in low-intensity exercise that consisted of walking and dumbbell exercise for successive 7 days. There were no changes in hospital diet and the dose of any medications used throughout the study. Fasting glucose, insulin, and lipids were measured before and after exercise. After exercise, serum triglyceride levels significantly decreased, but no significant changes were observed in total and HDL cholesterol concentrations. Fasting glucose, insulin, and HOMA-IR levels significantly decreased after exercise, but HOMA-B-cell function did not change during the study. There was no significant difference between BMI levels before and after exercise. From these results, it can be concluded that short-term (7 days) low-intensity physical exercise combined with hospital diet reduces serum triglycerides, insulin resistance, and fasting glucose levels without affecting BMI in non-obese Japanese type 2 diabetic patients.

Adult↗
PubMed2001

Antitumor drugs possessing topoisomerase I inhibition: applicable separation methods.

Separation methods for antitumor drugs capable of topoisomerase I inhibition were reviewed in this study. Camptothecin (CPT) its related analogues seemed to be promising anticancer drugs that exhibit topoisomerase I inhibition. This group of compounds contain a closed alpha-hydroxy-delta-lactone ring (lactone form) that can undergo reversible hydrolysis to form the open-ring form (carboxylate form). In vitro pharmacological study showed that the antitumor activity of the lactone form was higher than that of the carboxylate form. Thus a quantitative method to separate these two forms is important to evaluate the pharmacokinetics and pharmacodynamics of these compounds. Nevertheless, current separation methods are complicated by the pH-dependent instability of the lactone moiety. High-performance liquid chromatography (HPLC) coupled with fluorometric detection has been widely used for the quantitation of the drug as the intact lactone form or as the total lactone carboxylate forms in biological matrices. In this report we reviewed current applicable chromatographic techniques for further bioanalytical studies of CPT derivatives including sample preparations, HPLC columns, mobile phases and additives.

Antineoplastic Agents↗
PubMed2001

Analytical method of heparan sulfates using high-performance liquid chromatography turbo-ionspray ionization tandem mass spectrometry.

We established a highly sensitive quantitative analytical method of heparan sulfates (HS) by LC-MS-MS. It became possible to determine the unsaturated disaccharides produced by the enzyme digestion of HS, and to perform the whole analyses on one sample within 3 min by use of a short column of CAPCELL PAK NH2 UG80 (35 mm x 2 mm I.D.). The assay method was validated and showed the satisfactory sensitivity, precision and accuracy, which enabled the quantitation up to picomol level. By employing this method, we performed the analyses of HS in mouse brain and liver, and tumor tissues of tumor-bearing mouse transplanted subcutaneously with Meth A fibrosarcoma cells. The compositions of the unsaturated disaccharide units derived from HS were found to be somewhat different among those tissues. It is assumed that the site of sulfation in HS may be controlled by certain regulatory mechanisms. The quantitative method developed in this study is believed to be a very useful method for the determination of compositional profiles of constitutive disaccharide units of tissue HS.

Animals↗
PubMed2001

Immobilization of cycloisomaltooligosaccharide glucanotransferase for the production of cycloisomaltooligosaccharides from dextran.

Immobilization of cycloisomaltooligosaccharide glucanotransferase (CITase) and its application in the production of cycloisomaltooligosaccharides (CIs) from dextran were studied. Among various carrier materials examined, the enzyme adsorbed physically on Chitopearl BCW-3505 showed the highest activity (1.75 U/ml carrier). The activity remaining was 35%. The maximum CI yield in batch reactions at 0.2, 2 and 10% dextran was 28, 24 and 12%, respectively. The maximum CI yield at 2% dextran (24%) was slightly less than that with the free enzyme under the same conditions (26%). The concentration of linear oligosaccharides, the byproducts in the reaction mixture, was greater with the immobilized CITase than the free enzyme. The immobilized CITase was less thermostable than the free enzyme by about 10 degrees C. The pattern of influence of Ca(2+) concentration on the thermostability differed between the free and immobilized CITase. A Ca(2+) concentration of 50-100 mM was optimum for the thermostability of the immobilized CITase, 10-50 mM for the free enzyme. CIs were produced continuously by a column system packed with the immobilized enzyme at 40 degrees C with a space velocity (SV) of 6 h(-1). The three quarters life time was 4 weeks. We think that relatively long life time at fast SV was accomplished and CI production cost by this method should be lower than the batch reaction. This is the first report on immobilization of CITase.

Journal Article↗
PubMed2001

Analytical method for keratan sulfates by high-performance liquid chromatography/turbo-ionspray tandem mass spectrometry.

We established a highly sensitive LC/MS/MS method for the analysis of the disaccharides produced from keratan sulfates (KS). It was revealed that the disaccharides produced by keratanase II enzymatic digestion of KS could be determined with high sensitivity by the negative-ion mode of multiple reaction monitoring. Furthermore, monosulfated and disulfated disaccharides can be separated using a short column of Capcell Pak NH2 UG80 (35 mm x 2 mm i.d.). The complete analysis of one sample can be performed within 5 min. The assay method was validated and showed satisfactory sensitivity, precision, and accuracy, which enabled quantitation at subpicomole levels. From the results of analyses of KS obtained from cornea, nasal cartilage, and brain, it was found that the degree of sulfation at the C-6 position of the galactose residues differed among those samples in the following order: nasal cartilage > cornea > brain. Our analytical method is very useful for the analyses of KS in various biological materials and for comparison of the degree of sulfation of KS from various biological samples.

Animals↗
PubMed2001

Validation study of assay method for DX-8951 and its metabolite in human plasma and urine by high-performance liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry.

A new liquid chromatographic/mass spectrometric assay has been developed for the determination of DX-8951, a new anti-tumor drug, and its 4-hydroxymethyl metabolite (UM-1) in human plasma and urine. Solid-phase extractions were used for sample preparation. A gradient reverse-phase HPLC separation was developed with mobile phases consisting of trifluoroacetic acid and methanol. The detection was conducted using atmospheric pressure chemical ionization tandem mass spectrometry in the selected reaction monitoring mode. A structural analog, camptothecin (CPT), was used as the internal standard. The assay was validated for the determination of DX-8951 and UM-1 in human plasma and urine. The lower limits of quantitation of DX-8951 and UM-1 were 0.1 ng/mL in plasma and 1 ng/mL in urine. The method showed a satisfactory sensitivity, precision, accuracy, recovery and selectivity.

Antineoplastic Agents↗
PubMed2001

Analytical method of chondroitin/dermatan sulfates using high performance liquid chromatography/turbo ionspray ionization mass spectrometry: application to analyses of the tumor tissue sections on glass slides.

We established a highly sensitive quantitative analytical method for chondroitin/dermatan sulfates by LC/MS method. By this method, the unsaturated disaccharides produced after the enzymatic digestion of chondroitin/dermatan sulfates can be determined in the amounts as low as 0.5 pmol levels. The use of tetrabutylammonium hydroxide as an ion-pair reagent for LC/MS allowed us to separate unsaturated 4-sulfated disaccharide and unsaturated 6-sulfated disaccharide. Furthermore, the peak areas of unsaturated disaccharides were increased almost 10 times by the postcolumn addition of acetonitrile. We applied this LC/MS method to the analyses of unsaturated disaccharides from chondroitin/dermatan sulfates in the tissues sections on glass slides, which were prepared from MethA tumor-bearing mice. This method brought about considerable reduction in the time distance from sample collection to preparation of analytical results.

Chondroitin Sulfates↗
PubMed2001

Differential expression of CCR3 ligand mRNA in guinea pig lungs during allergen-induced inflammation.

OBJECTIVE AND DESIGN: The gene expression profile of CCR3 ligands, eotaxin, RANTES, and monocyte chemoattractant protein-3 (MCP-3), was examined in normal and inflamed guinea pig lungs. MATERIAL: Male Hartley guinea pigs (n = 49). METHODS: Pulmonary mRNA was obtained from naive animals, animals treated with intravenous lipopolysaccharide administration, and animals repeatedly exposed to aerosolized allergen (ovalbumin). Northern analysis was performed to quantify pulmonary expression of eotaxin, RANTES, and MCP-3 mRNA. Pulmonary eosinophil peroxidase (EPO) activity was measured to quantify eosinophil accumulation. RESULTS: Eotaxin and RANTES mRNAs, but not MCP-3 mRNA, were constitutively expressed in guinea pig lungs. Lipopolysaccharide treatment increased MCP-3 mRNA expression, but not eotaxin or RANTES mRNA. In contrast, allergen exposure in sensitized animals caused an increase in eotaxin mRNA, which demonstrated good temporal and quantitative correlation with pulmonary EPO activity, but not in MCP-3 or RANTES mRNA. CONCLUSIONS: Guinea pig CCR3 ligands demonstrated different gene expression profiles in normal and inflamed airways, suggesting that they play different physiological and pathophysiological roles in the airway.

Allergens↗
PubMed2001

Urinary metabolites of DX-8951, a novel camptothecin analog, in rats and humans.

Urinary metabolites of DX-8951 ((1S,9S)-1-amino-9-ethyl-5-fluoro- 1,2,3,9,12,15-hexahydro-9-hydroxy-4-methyl-10H,13H- benzo[de]pyrano[3',4':6,7]indolizino[1,2-b]quinoline-10,13-dione, CAS 171335-80-1, exatecan) in rats and humans were identified. Rats were dosed with the drug, and two major metabolites (UM-1 and UM-2) in the urine were isolated and purified by using ion-exchange column and HPLC. From NMR and mass spectra, they are suggested to be 4-hydroxymethyl metabolite (UM-1) and 3-hydroxy metabolite (UM-2) of the drug. Their chemical structures were confirmed by comparing their NMR spectra with those of chemically synthesized metabolites. Two major metabolites were found in human urine obtained in phase I trial. They were also confirmed to be UM-1 and UM-2 by LC/MS/MS by comparing their mass fragment patterns with those of synthetic metabolites.

Animals↗
PubMed2001

Genetic polymorphisms of CC chemokine receptor 3 in Japanese and British asthmatics.

Whole genome scan analyses have revealed that chromosomal region 3p21-24, which contains a gene cluster of CC chemokine receptors such as CCR3, is possibly linked to asthma. Because CCR3 ligands play a pivotal role in the selective recruitment and activation of inflammatory cells in the asthmatic airway, the authors examined whether there is any association between asthma and the CCR3 gene polymorphisms. Three polymorphisms were identified using the single stranded conformational polymorphism method in Japanese (Asian) and British (Caucasian) subjects; one silent mutation T51C and two missense mutations G824A and T971C. These polymorphisms were examined in 391 Japanese subjects (210 asthmatics and 181 nonasthmatic controls) and 234 British subjects (142 asthmatics and 92 nonasthmatic controls). Asthma diagnosis was based on episodic symptoms, documented wheeze, and the presence of reversible airflow limitation. CCR3 T51C demonstrated a significant association with the diagnosis of asthma in the British population (odds ratio 2.35, p<0.01), but not in the Japanese population. Multiple logistic regression analysis also showed that CCR3 T51C was associated with asthma (odds ratio 2.83, p < 0.02), independent of atopic phenotypes such as high levels of total or house dust mite-specific immunoglobulin-E in serum. In conclusion, a significant association between asthma and CCR3 T51C polymorphism localized on chromosome 3p21 was found.

Alleles↗
PubMed2001

Evaluation of Bayesian predictability of vancomycin concentration in patients with various degrees of renal function.

To assess the usefulness of the population pharmacokinetic parameters of vancomycin (VCM) based on a two-compartment model in Japanese adult patients, predictability by a Bayesian method was evaluated using a concentration time course after single dosing to 22 patients with various degrees of renal function. Using one or two points from the observed data for each patient, the concentrations predicted by a Bayesian method were compared with the observed data for each sampling time. The patients were separated into five groups based on their renal functions indicated by creatinine clearance, and the mean prediction error (MPE) and root mean squared error (RMSE) were calculated for each group as measures of accuracy and precision, respectively. In both one- and two-point methods, the absolute MPE values at each sampling time in the elimination phase were less than 2.5 microg/ml, and the RMSE values were also small. No clear differences were found in MPE and RMSE among the groups. In the distribution phase, the MPE and RMSE were somewhat greater, and RMSE in some groups was around 15 microg/ml when trough data was used to predict the peak concentration. Also, the theoretical RMSE using this population parameter setting could well explain the observed RMSE. These results confirmed this population parameter setting is useful for at least predicting concentration in the elimination phase after single dosing, and the predictability was independent of renal function.

Adult↗
PubMed2001

High-Performance liquid chromatographic analysis of lactone and hydroxy acid of new antitumor drug, DX-8951 (exatecan), in mouse plasma.

A sensitive high-performance liquid chromatographic (HPLC) method has been developed and validated for the determination of lactone and total drug (lactone plus hydroxy-acid) of DX-8951 in mouse plasma. Solid-phase extraction by C18 cartridge separated lactone from total drug of DX-8951. Analysis was performed using a reverse-phase ODS column with a mobile phase consisting of acetonitrile/0.05 M potassium dihydrogen phosphate (pH 3) (18: 82, v/v) at a flow rate of 1 ml/min. The limits of quantitation of lactone and total drug were 3 ng/ml in plasma and a linear range of determination were observed over the concentration of 3 to 500 ng/ml. This method was applied to pharmacokinetic study in male mice treated with a single intravenous administration of either lactone or hydroxy-acid of DX-8951. The plasma concentrations of lactone from 2 to 6 h after dosing were similar regardless of the form of DX-8951 administered.

Animals↗