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Kazuhiro Imai

Publications and source records attributed to Kazuhiro Imai.

At least 19 recordsLinked to original sources
PubMed2006

Nonlinear finite element model predicts vertebral bone strength and fracture site.

STUDY DESIGN: A study on computed tomography (CT)-based finite element (FE) method that predicts vertebral strength and fracture site using human cadaveric specimens. OBJECTIVE: To evaluate the accuracy of the nonlinear FE method by comparing the predicted data with those of mechanical testing. SUMMARY OF BACKGROUND DATA: FE methods may predict vertebral strength and fracture site but the prediction has been difficult because of a complex geometry, elastoplasticity, and thin cortical shell of the vertebra. METHODS: FE models of the 12 thoracolumbar vertebral specimens were constructed. Nonlinear FE analyses were performed, and the yield load, the fracture load, the sites where elements failed, and the distribution of minimum principal strain were evaluated. A quasi-static uniaxial compression test for the same specimens was conducted to verify these analyses. RESULTS: The yield loads, fracture loads, minimum principal strains, and fracture sites of the FE prediction significantly correlated with those measured. CONCLUSIONS: Nonlinear FE model predicted vertebral strength and fracture site accurately.

Adult↗
PubMed2006

Tumor-derived TGFbeta-1 induces dendritic cell apoptosis in the sentinel lymph node.

Lymphatic flux from a primary tumor initially flows into a tumor-draining lymph node (LN), the so-called sentinel LN (SLN). Carried by the lymph fluid are a variety of mediators produced by the tumor that can influence immune responses within the SLN, making it a good model with which to investigate tumor-related immunology. For instance, dendritic cell (DC) numbers are reduced in SLNs from melanoma and breast cancer patients. In the present study, we investigated the mechanism by which DC numbers were reduced within SLNs from patients with non-small cell lung cancer. We found that the incidence of apoptosis among DCs was higher in SLNs than in non-SLNs, as were levels of TGFbeta-1. In contrast, levels of TGFbeta-1 mRNA did not differ between SLNs and non-SLNs, but were 30 times higher in tumors than in either LN type. In vitro, incubation for 2 days with TGFbeta-1 induced apoptosis among both cultured DCs and DCs acutely isolated from normal thoracic LNs, effects that were blocked by the TGFbeta-1 inhibitor DAN/Fc chimera. Taken together, these results suggest that tumor-derived TGFbeta-1 induces immunosuppression within SLNs before the movement of tumor cells into the SLNs, thereby facilitating metastasis within those nodes.

Apoptosis↗
PubMed2006

Synthesis of the isotope-labeled derivatization reagent for carboxylic acids, 7-(N,N-dimethylaminosulfonyl)-4-(aminoethyl)piperazino-2,1,3-benzoxadiazole (d6) [DBD-PZ-NH2 (D)], and its application to the quantification and the determination of relative amount of fatty acids in rat plasma samples by high-performance liquid chromatography/mass spectrometry.

The isotope-labeled benzofurazan derivatization reagent for carboxylic acids, 7-(N,N-dimethylaminosulfonyl)-4-(aminoethyl)piperazino-2,1,3-benzoxadiazole (d6) [DBD-PZ-NH2 (D)] was synthesized. DBD-PZ-NH2 (D) was used for the accurate quantification of fatty acids by liquid chromatography/mass spectrometry (LC/MS). The standard fatty acids were derivatized with DBD-PZ-NH2 (D) to the stable isotope-labeled compounds for the fatty acids derivatives of DBD-PZ-NH2 and used for the internal standards. The obtained calibration curves for fatty acids were linear over the range 0.1-200 microM (r2 > 0.999). Fatty acids in plasma samples were determined after derivatization with DBD-PZ-NH2 and analyzed by LC/MS using standard fatty acid DBD-PZ-NH2 (D) derivatives as internal standards. Furthermore, the relative amounts of fatty acids in two plasma samples were determined after derivatization with DBD-PZ-NH2 and DBD-PZ-NH2) (D). The isotope-labeled derivatization reagent was useful for accurate quantification and the determination of relative amounts of the metabolites in biological samples having the target functional group.

Animals↗
PubMed2006

A further study on the combined use of internal standard and isotope-labeled derivatization reagent for expansion of linear dynamic ranges in liquid chromatography-electrospray mass spectrometry.

The combined use of a so-called internal standard and the isotope-labeled derivatization reagent for the quantification of analytes for liquid chromatography-mass spectrometry (LC/MS) was further studied. The sample solution (containing the analytes and an internal standard) was derivatized with the light form of the derivatization reagent, 7-(N,N-dimethylaminosulfonyl)-4-(aminoethyl)piperazino-2,1,3-benzoxadiazole (DBD-PZ-NH(2)) or 7-(N,N-dimethylaminosulfonyl)-4-piperazino-2,1,3-benzoxadiazole (DBD-PZ). A standard solution of the analytes (containing an internal standard) was derivatized with the isotope (d(6))-labeled derivatization reagent, DBD-PZ-NH(2) (D) or DBD-PZ (D), and served as the isotope-labeled internal standards. The peak heights of the targeted analytes derivatives in the sample solution were corrected using those of the internal standard and the heavy form derivatives of the standards, and the calibration curves were constructed. The curve bending of the calibration curves caused by the ion suppression at the ion source was suppressed and the linear dynamic ranges of the calibration curves were expanded. The derivatives of DBD-PZ-NH(2) were about 10 times more sensitively detected than those of DBD-PZ derivatives and, therefore, DBD-PZ-NH(2) might be suitable for sensitive detection.

Chromatography, Liquid↗
PubMed2006

Intraoperative sentinel lymph node mapping using a new sterilizable magnetometer in patients with nonsmall cell lung cancer.

PURPOSE: We recently developed a novel method for sentinel lymph node mapping using magnetic force. However, problems with the sterility and sensitivity of the magnetometer made intraoperative sentinel lymph node mapping impossible. The purpose of this study was to test the utility of a new, more sensitive, sterilizable magnetometer developed in our institute for in vivo sentinel lymph node mapping in patients with nonsmall cell lung cancer. DESCRIPTION: Ferumoxides (magnetite) served as the tracer. Twenty patients with nonsmall cell lung cancer participated in the study. Each received 5 mL of ferumoxides, which were injected around their tumor. Magnetic force was then measured intraoperatively using the new sterilizable magnetometer. EVALUATION: The in vivo sentinel lymph node detection rate was 80.0% (16 of 20). The accuracy, sensitivity, and false-negative rates were 100% (16 of 16), 100% (4 of 4) and 0% (0 of 12), respectively. Our preliminary study indicates that our new magnetometer enables in vivo sentinel lymph node mapping in patients with nonsmall cell lung cancer. CONCLUSIONS: This device safely and accurately detected sentinel lymph nodes in nonsmall cell lung cancer patients.

Aged↗
PubMed2006

Low catechol-O-methyltransferase activity in the brain and blood pressure regulation.

Catecholamines (CAs) are important hormones in regulating blood pressure both in centrally and peripheral sympathetic nerve endings. Production of CAs, release and inactivation are three components to regulate CAs level. We have reported that the inactivation of CAs by catechol-O-methyltransferase (COMT) in the liver is important in high blood pressure in spontaneously hypertensive rats (SHR). In the present study, we investigated central role of COMT in hypertension. We investigated COMT activities in cerebral cortex, cerebellum, hippocampus, brain stem, hypophysis, and hypothalamus of SHR and Wistar-Kyoto (WKY) rats. COMT activities were assessed by measuring normetanephrine with the use of norepinephrine as an endogenous substrate. Membrane-bound COMT activities in cerebral cortex were significantly reduced in SHR (19.1+/-1.8 pmol/min/mg protein) compared with WKY rats (25.0+/-3.3 pmol/min/mg protein). The ratio of concentrations of normetanephrine/norepinephrine in cerebral cortex was also lower in SHR than in WKY rats. Our results suggest that there is an association between MB-COMT in cerebral cortex and blood pressure regulation.

Animals↗
PubMed2005

Catecholamine analysis with microcolumn LC-peroxyoxalate chemiluminescence reaction detection.

BACKGROUND: Plasma catecholamines (CAs) are widely used as an index of sympathetic nervous system activity. In addition, CAs are known to be metabolized by catechol-O-methyltransferase (COMT) to produce their 3-O-methyl metabolites. We previously established a sensitive determination method of CAs and their 3-O-methyl metabolites using HPLC-peroxyoxalate chemiluminescence (POCL) reaction detection system. In this study, a microcolumn (100 x 1.0 mm I.D.) was used for separation to obtain higher sensitivity and shorter analysis time. METHODS: The system included automated precolumn ion-exchange extraction of amines, followed by separation on an ODS column, coulometric oxidation, fluorescence derivatization with ethylenediamine, and finally POCL reaction detection. RESULTS: The detection limits for CAs and their 3-O-methyl metabolites were 0.3-2.0 fmol. The analysis time was about 35 min, about half that of previously reported results. The method developed was used in monitoring changes in CAs and 3-O-methyl metabolite concentrations in human plasma during exercise. CONCLUSION: The simultaneous determination method for concentrations of CAs and their 3-O-methyl metabolites in human plasma was developed using micro LC-peroxyoxalate chemiluminescence detection. We were successful in quantitating the changes in plasma CAs and their 3-O-methyl metabolites during exercise.

Blood Pressure↗
PubMed2005

High performance liquid chromatography post-column chemiluminescence determination of sulfonamide residues in milk at low concentration levels using bis[4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl] oxalate as chemiluminescent reagent.

The determination of seven sulfonamides by means of HPLC with chemiluminescence detection is proposed for the first time. The analytes are derivatized with fluorescamine, separated and subsequently they participate in the post-column chemiluminescence (CL) peroxyoxalate system using imidazole as a catalyst. Among the different peroxyoxalates tested, bis[4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl] oxalate provides higher sensitivities and stabilities, avoiding precipitation problems. A rigorous optimization of the significant variables by means of experimental designs has been developed in order to reconcile the chromatographic conditions with the CL reaction. The method provides detection limits in the low microgl(-1) range and has been satisfactorily applied to the analysis of spiked raw milk samples.

Animals↗
PubMed2005

Cationic starch derivatives as dynamic coating additives for protein analysis in capillary electrophoresis.

Positively charged starch derivatives were used to modify the inner surface of fused-silica capillaries by addition to running buffer, which were subsequently employed in capillary electrophoresis (CE). Capillaries coated with the cationic starch derivatives were shown to generate a stable, reversed electroosmotic flow (EOF) in the investigated pH range of 3-9. The presented coating procedure was fast, based on a simple rinsing protocol where the polymer created a physically adsorbed, cationic polymer layer. Among the additives studied, a quaternary ammonium starch derivative showed a fast EOF mobility and effectively suppressed the adsorption of proteins. The intra- and inter-day reproducibility of the coating referring to the EOF mobility were satisfactory with relative standard deviation (RSD) of 0.27 and 1.67%, respectively. The coating enabled separation of some protein mixtures including basic proteins within l3 min with efficiencies up to 280,000 plates/m. In addition, this cationic starch derivative possessed a good solubility (about 100mg/mL), and it does not significantly contribute to the background adsorption in the UV region of 190-400 nm.

Cations↗
PubMed2005

Improved assay for catechol-O-methyltransferase activity utilizing norepinephrine as an enzymatic substrate and reversed-phase high-performance liquid chromatography with fluorescence detection.

We have previously established a rapid catechol-O-methyltransferase (COMT) assay using norepinephrine (NE) as a natural substrate and flow-injection analysis. In this study, the method is improved for screening of COMT inhibitors or activators using reversed-phase high-performance liquid chromatographic separation with fluorescence detection. The excess substrate, NE, was removed by the addition of borate in the eluent for HPLC to make an ionic complex with NE, which was eluted faster than the enzymatic product, normetanephrine. The method had good precision and accuracy, and was able to assay one sample in 5 min, showing the usability for screening of COMT inhibitors or activators.

Animals↗
PubMed2005

Rapid assay for catechol-O-methyltransferase activity by high-performance liquid chromatography-fluorescence detection.

A rapid assay for measuring the activities of catechol-O-methyltransferase (COMT) is described. The method is based on high-performance liquid chromatography (HPLC)-fluorescence detection, and includes on-line extraction of catecholamines with a precolumn, separation of norepinephrine (NE) and normetanephrine (NMN) on an ODS column, electrochemical oxidation, and post-column fluorogenic derivatization using ethylenediamine. The method took less than 25 min for one sample, which is half that of the previous method and the sensitivity was similar. The intra-day assay precisions were 0.52-1.6%, and the inter-day assay precisions were 3.6-5.8% for rat liver and cerebral cortex (n = 5). The method is suitable for the rapid measurement of COMT activities of many biological samples.

Animals↗
PubMed2005

High-performance liquid chromatographic assay of N(G)-monomethyl-L-arginine, N(G),N(G)-dimethyl-L-arginine, and N(G),N(G)'-dimethyl-L-arginine using 4-fluoro-7-nitro-2, 1,3-benzoxadiazole as a fluorescent reagent.

N(G)-Monomethyl-L-arginine (L-NMMA), N(G),N(G)-dimethyl-L-arginine (ADMA), and N(G),N(G)'-dimethyl-L-arginine (SDMA) are emerging cardiovascular risk factors. A high-performance liquid chromatographic method with fluorescence detection for the simultaneous determination of L-NMMA, ADMA and SDMA is described. The assay employed 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) as a fluorescent derivatization reagent. After solid phase extraction with cation-exchange column, the methylated arginines were converted to fluorescent derivatives with NBD-F, and the derivatives were separated within 32 min on a reversed-phase column. Nomega-Propyl-L-arginine was Used as an internal standard. Extrapolated detection limits were 12 nM (12 fmol per injection) for L-NMMA and 20 nM (20 fmol per injection) for ADMA and SDMA, respectively, with a signal-to-noise ratio of 3. The calibration curves for L-NMMA, ADMA and SDMA were linear within the range of 50-5000 fmol. The method was applied to the quantitative determination of L-NMMA, ADMA and SDMA in 200 microl of rat plasma. The concentrations of L-NMMA, ADMA and SDMA in rat plasma were 0.16 +/- 0.03, 0.80 +/- 0.25 and 0.40 +/- 0.21 microM, respectively (n = 5).

4-Chloro-7-nitrobenzofurazan↗
PubMed2005

An improved method for proteomics studies in C. elegans by fluorogenic derivatization, HPLC isolation, enzymatic digestion and liquid chromatography--tandem mass spectrometric identification.

An improved method for proteomics studies, which includes the fluorogenic derivertization of protein mixtures with 7-chloro-4-(dimethylaminoethylaminosulfonyl)-2,1,3-benzoxadiazole (DAABD-Cl), followed by HPLC isolation, enzymatic digestion and identification of the derivatized proteins by HPLC-electrospray ionization (ESI)-MS/MS with the probability-based protein identification algorithm, identified 103 proteins in the soluble extract (10 microg protein) of Caenorhabditis elegans.

Algorithms↗
PubMed2005

Development of an HPLC-fluorescence determination method for carboxylic acids related to the tricarboxylic acid cycle as a metabolome tool.

We report the simultaneous determination of the carboxylic acids related to the tricarboxylic acid (TCA) cycle, which plays an important role in producing adenosine triphosphate (ATP) and generating energy in mitochondria. Seven carboxylic acids from the TCA cycle, and pyruvic acid and 2-methylsuccinic acid, as an internal standard, were derivatized with a fluorescent reagent for carboxyl groups, 4-N,N-dimethylaminosulfonyl-7-piperazino-2,1,3-benzoxadiazole (DBD-PZ), in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and 4-N,N-dimethyaminopyridine as the coupling reagents, at 60 degrees C for 120 min. Subsequently, the excess DBD-PZ was removed efficiently using a cation-exchange cartridge, SDB-RPS (Empore). These fluorescent derivatives were separated well from each other on an octadecyl silica column (TSKgel ODS-80Ts, 250 x 4.6 mm, i.d.) with an eluent of acetonitrile-water containing 1% formic acid at a flow rate of 0.8 mL/min, and were detected fluorometrically at 560 nm, with excitation at 450 nm. The validation data were satisfactory in the range of 2.5-100 microm citric acid, isocitric acid, 2-oxoglutaric acid, succinic acid and fumaric acid. The detection limit (S/N = 3) for citric acid was 2 fmol on the column. The structures of these derivatives were confirmed by high-performance liquid chromatography-mass spectrometry, which proved that their carboxylic groups were completely labeled with DBD-PZ, except for oxaloacetic acid. This HPLC method was successfully applied to the analysis of TCA cycle metabolites in rat urine. The method will also be useful for metabolome research, such as for target analyses of metabolites with carboxyl groups, not only in urine but also in cells and organs.

Animals↗
PubMed2005

Synthesis of benzofurazan derivatization reagents for carboxylic acids and its application to analysis of fatty acids in rat plasma by high-performance liquid chromatography-electrospray ionization mass spectrometry.

The derivatization regents for carboxylic acids, DAABD-AE (4-[2-(N,N-dimethylamino)ethylaminosulfonyl]7-(2-aminoethylamino)-2,1,3-benzoxadiazole), MePZBD-AE ([4-(4-N-methyl)piperazinosulfonyl]-7-(2-aminoethylamino)-2,1,3-benzoxadiazole) and APZBD-NHMe ([4-(4-N-aminoethyl)piperazinosulfonyl]-7-methylamino-2,1,3-benzoxadiazole) were developed for electrospray ionization-mass spectrometry (ESI-MS). The derivatization reaction with fatty acids was completed at 60 degrees C within 30 min. The derivatives of fatty acids were separated on a reversed-phase column and detected with ESI-MS. The detection limits attained for fatty acids were femtomol range and the calibration curves were linear over the range from 0.1 to 100 pmol (r2 > 0.992) for DAABD-AE and MePZBD-AE. DAABD-NHMe was applied to the analysis of fatty acids in rat plasma samples.

Animals↗
PubMed2005

Intraoperative detection of lymph node micrometastasis with flow cytometry in non-small cell lung cancer.

OBJECTIVE: We sought to determine whether cytokeratin-positive cells can be detected as markers of lymph node metastasis by using flow cytometry within a time frame suitable for intraoperative decision making in non-small cell lung cancer. METHODS: Five lymph nodes from each of 20 patients with non-small cell lung cancer were randomly selected for study. Each node was divided longitudinally into 3 pieces: one piece for flow cytometry, one for immunohistochemical staining, and the last for conventional hematoxylin and eosin staining. In both flow cytometry and immunohistochemistry, cytokeratin-positive cells were detected with the fluorescein isothiocyanate-conjugated anti-cytokeratin antibody AE1/AE3. RESULTS: Cytokeratin-positive nodes were detected by means of flow cytometry within 40 minutes. Eight (8%) of the 100 lymph nodes from 4 (20%) of the 20 patients were deemed positive for metastasis on the basis of conventional histologic examination. By contrast, 33 (33%) lymph nodes from 13 (65%) patients were deemed positive on the basis of immunohistochemical cytokeratin staining, and 38 (38%) lymph nodes from 14 (70%) patients were deemed positive on the basis of flow cytometric cytokeratin-positive cell detection. All nodes deemed positive for metastasis on the basis of conventional and immunohistochemical methods were also positive on flow cytometry. CONCLUSIONS: Flow cytometry enables rapid intraoperative diagnosis of nodal metastasis in patients with non-small cell lung cancer. Flow cytometric detection of cytokeratin-positive cells within lymph nodes correlates with their immunohistochemical detection, and its level of sensitivity is greater than that of conventional histologic staining and about equal to that of immunohistochemical staining.

Biomarkers, Tumor↗
PubMed2005

Effect of vascularity on canine distracted tibial callus consolidation.

In the consolidation period of distraction osteogenesis, mineralization occurs before corticalization. We hypothesized that the increased rate of bone mineral density correlates to the density of vascularity in the callus. We unilaterally lengthened the tibia in eight adult beagles. After a waiting period of 7 days, tibiae were lengthened for 30 days. After a consolidation period of an additional 60 days, all animals were euthanized. Just before euthanasia, blood vessels were perfused with 50% w/v barium sulfate solution, and soft radiographs of the distracted callus and the control tibiae were taken. Bone mineral density of the regenerated bones was measured preoperatively by quantitative computed tomography on Days 37, 68, and 98. Increases of the percent bone mineral density (from Day 37 to Day 98 and from Day 68 to Day 98) correlated with the blood vessel volume density ratios on Day 98. Our results suggest that preservation of the higher density of blood vessels in the consolidation period could lead to the better mineralization of the distracted callus.

Angiography↗