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Y Shibata

Publications and source records attributed to Y Shibata.

At least 19 recordsLinked to original sources
PubMed2006

Functional characterization of Musca glutamate- and GABA-gated chloride channels expressed independently and coexpressed in Xenopus oocytes.

Ligand-gated chloride channels (LGICs) are important targets for insecticides and parasiticides. Genes encoding subunits of two LGICs, a glutamate-gated chloride channel (MdGluCl-alpha) and a gamma-aminobutyric acid (GABA)-gated chloride channel (MdRdl), were cloned from house-flies (Musca domestica L.). These genes were first expressed independently in Xenopus laevis oocytes by cRNA injection in order to investigate the pharmacology of these ligand-gated channels using two-electrode voltage-clamp electrophysiology. It was found that L-glutamate and GABA activated the MdGluCl-alpha homo-oligomers with an EC(50) value of 30 microM and the MdRdl homo-oligomers with an EC(50) value of 101 microM, respectively. Both channels were chloride ion-permeable, and the MdRdl channel was more sensitive to chloride channel blockers, such as gamma-hexachlorocyclohexane (gamma-HCH), fipronil and picrotoxinin, than the MdGluCl-alpha channel. MdGluCl-alpha required only 1-2 days of incubation after cRNA injection to be expressed in oocytes, whereas 4-7 days of incubation was necessary to achieve MdRdl expression. However, when the cRNA of MdGluCl-alpha was injected at a dose of 1% (w/w) 1 day after the injection of the cRNA of MdRdl, a significant increase in the current amplitude of responses to GABA was observed, and the incubation period necessary for MdRdl expression became shorter. These results suggest that MdGluCl-alpha assists in the expression of MdRdl when the two are coexpressed.

Animals↗
PubMed2006

Effect of mixed mutans streptococci colonization on caries development.

OBJECTIVE: To evaluate the clinical importance of mixed mutans streptococci colonization in predicting caries in preschool children. METHODS: Caries prevalence was examined twice, with a 6-month interval, in 410 preschool children aged 3-4 years at baseline. A commercial strip method was used to evaluate the mutans streptococci score in plaque collected from eight selected interdental spaces and in saliva. Mutans streptococci typing polymerase chain reaction (PCR) assays (Streptococcus sobrinus and Streptococcus mutans, including serotypes c, e, and f) were performed using colonies on the strips as template. RESULTS: Twenty variables were examined in a univariate analysis to predict caries development: questionnaire variables, results of clinical examination, mutans streptococci scores, and PCR detection of S. sobrinus and S. mutans (including serotypes c, e, and f). Sixteen variables showed statistically significant associations (P < 0.04) in the univariate analysis. However, when entered into a logistic regression, only five variables remained significant (P < 0.05): caries experience at baseline; mixed colonization of S. sobrinus and S. mutans including S. mutans serotypes; high plaque mutans streptococci score; habitual use of sweet drinks; and nonuse of fluoride toothpaste. CONCLUSION: 'Mixed mutans streptococci colonization' is a novel measure correlated with caries development in their primary dentition.

Beverages↗
PubMed2006

A marked decrease in heart rate variability associated with junctional rhythm during anesthesia with sevoflurane and fentanyl.

Heart rate variability (HRV) was investigated using a new technique for time series analysis combining the maximum entropy method and non-linear least squares method -- the 'MemCalc method' -- in patients undergoing general anesthesia with sevoflurane and fentanyl for elective surgery. As the occurrence of junctional rhythm coincided with the measurement of these variables in two patients, we successfully evaluated the entropy, low (LF) and high (HF) frequency component of the HRV during junctional rhythm and found that the occurrence of junctional rhythm is associated with marked decreases in the entropy, LF and HF of HRV. When evaluating autonomic control of the heart using HRV analysis, the decrease in HRV caused by the occurrence of junctional rhythm must be taken into account.

Adult↗
PubMed2006

Demonstration of inter- and intracellular distribution of boron and gadolinium using micro-proton-induced X-ray emission (Micro-PIXE).

Micro-proton-induced X-ray emission (Micro-PIXE) was applied to determine inter- and intracellular distribution of boron (10B) and gadolinium (157Gd), the capture atoms used to kill tumor cells in neutron capture therapy (NCT). Cultured 9L gliosarcoma cells on Mylar film were exposed to sodium borocaptate (BSH) and gadobenate dimeglumine (Gd-BOPTA). To analyze the inter- and intracellular distribution of 10B and 157Gd in 9L gliosarcoma cells, the cells were irradiated using a proton beam of 1.7 or 3 MeV energy collimated to 1 microm diameter and emission X-ray was detected. The distribution of 10B and 157Gd in 9L gliosarcoma cells was then examined. In this study, we could directly analyze the inter- and intracellular distribution of 10B and 157Gd elements in 9L gliosarcoma cells directly using Micro-PIXE. This is the first report on the distribution of 10B employing a method to detect gamma-rays resulting from the nuclear reaction of 10B using particle-induced gamma-ray emission (PIGE). These results show that the distribution of 157Gd elements was correctly measured using micro-PIXE. 157Gd should have the same tendency as 10B in cultured 9L gliosarcoma cells and agree with the distribution in 9L gliosarcoma cells. Further investigation is necessary for a higher spatial resolution and optimization of the measurement time or improvement of the sampling method. In the future, it will be possible to employ this method to analyze the intracellular microdistribution of the capture element and in the development of new drugs for NCT.

Boron↗
PubMed2005

Dipeptidyl peptidase IV of Streptococcus anginosus: purification and characterization.

We found that N-unblocked nine p-nitroanilde derivatives of amino acids or peptides were hydrolyzed by the crude cell extracts of Streptococcus anginosus NCTC 10713. Then dipeptidyl peptidase IV was purified 323-fold by the procedures including ammonium sulfate concentration, anion exchange chromatography (twice), gel filtration (twice), hydrophobic interaction chromatography, and isoelectric focusing. The molecular weight was calculated as 84 kDa, and the isoelectric point was 4.9. The enzyme hydrolyzed mainly dipeptides containing proline residues at P1 position. It was strongly inhibited by serine enzyme inhibitors. General protease inhibitors, metal chelators, thiol alkylating agent, reducing agent, and several metal ions had no effect on the enzyme activity. Optimum pH for the activity was found at 7.0. The enzyme was mostly inactivated by heating at 50 degrees C for 15 min.

Chromatography, Gel↗
PubMed2005

A searchable database for proteomes of oral microorganisms.

An online database of proteomes for two-dimensional electrophoresis (2DE) gel data was constructed and it is now freely accessible through a web-based interface. Proteins from three oral bacteria, Streptococcus mutans UA159, Actinobacillus actinomycetemcomitans HK1651, and Porphyromonas gingivalis W83, whose genome databases are freely available, were separated by 2DE, and protein spots were analyzed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and identified. About 1000 spots from the gels of P. gingivalis W83 were extracted and analyzed by MALDI-TOF, and 330 proteins were identified. In addition, 160 of 240 spots of A. actinomycetemcomitans and 158 of 356 spots of S. mutans were identified. Information such as spot coordinates on the gels, protein names (predicted functions), molecular weights, isoelectroric points, and links to online databases, including Oral Pathogen Sequence Databases of the Los Alamos National Laboratory Bioscience Division (ORALGEN) and National Center for Biotechnology Information (NCBI) or The Institute Genomic Research (TIGR), were stored in tables accessible through the relational database management system MySQL on an Apache web server. To test for functionality of this database system, responses of S. mutans to environmental changes were analyzed using the database and 21 spots on the gel were identified as proteins whose expression had been increased or decreased by environmental pH change without in-gel trypsin digestion, protein extraction, or MALDI-TOF/TOF-MS (mass spectrometer) analysis. The identified proteins are agreement with those reported in previous papers on acid tolerance of S. mutans, demonstrating the usefulness of the system. This database is available at http://www.myamagu.dent.kyushu-u.ac.jp/~bioinformatics/index.html or http://www.bipos.mascat.nihon-u.ac.jp/index.html.

Acids↗
PubMed2005

Anode glow discharge plasma treatment of titanium plates facilitates adsorption of extracellular matrix proteins to the plates.

Glow discharge plasma (GDP) supplied to an anode (GDP+) promotes calcium phosphate adsorption onto titanium better than that supplied to a cathode (GDP-). However, the adsorption of extracellular matrix (ECM) proteins is crucial for cell adhesion to titanium. Since GDP+ induced both inorganic adsorption and cell adhesion, we hypothesized that the inorganic adsorption in a culture medium might affect the adsorption of the ECM proteins. In this study, ECM proteins adsorbed on titanium with and without GDP were examined by x-ray photoelectron spectroscopy. After 1 hr of incubation, increasing sodium adsorption on GDP+ specimens induced adsorption of ECM proteins as shown by NH(+) and COO(-) signals without calcium adsorption. In contrast, since no specific adsorption of sodium on GDP-specimens was detected, GDP-did not contribute to the adsorption of ECM proteins. Thus, promotion of sodium adsorption of GDP+ was effective, at least in the initial ECM protein adsorption on a titanium surface.

Adsorption↗
PubMed2005

Colloidal beta-tricalcium phosphate prepared by discharge in a modified body fluid facilitates synthesis of collagen composites.

The development of hydroxyapatite/collagen composites that are naturally synthesized and need no additional treatment is required for use in bone repair. Since reducing the diameter can increase the specific surface area of calcium phosphate particles that can conjugate collagen molecules, we expected colloidal calcium phosphates of submicron diameter obtained by discharge to be effective in formulating these composites. Additionally, since biodegradable beta-tricalcium phosphate has better osteoconductivity than hydroxyapatite, this study aimed to investigate the synthesis of colloidal hydroxyapatite and beta-tricalcium phosphate/collagen composites. Collagen molecules were tightly polymerized in the beta-tricalcium phosphate/collagen composite by catalysis of the generated -P-O-P- polyphosphate chain. Bonding strength between collagen NH+ amino groups and -P-O-P-, and cross-linking of the Ca++-RCOO- in the collagen were increased compared with those in the hydroxyapatite/collagen composite. These chemical reactions due to colloidal beta-tricalcium phosphate might play a key role in the synthesis of collagen composites.

Biocompatible Materials↗
PubMed2005

Cloning, expression and characterization of three types of 17beta-hydroxysteroid dehydrogenases from the Nile tilapia, Oreochromis niloticus.

In order to elucidate the roles of 17beta-HSDs in fish gonadal steroidogenesis, three types of 17beta-HSDs (17beta-HSD1, 17beta-HSD8 and putative 17beta-HSD12) were cloned and characterized from the Nile tilapia, Oreochromis niloticus. The cloned cDNAs of 17beta-HSD type 1, 8 and 12 were 1504, 1006 and 1930 bp long, with open reading frames encoding proteins of 289, 256 and 314 aminoacids, respectively. Tissue distribution pattern analyzed by RT-PCR and Northern blot showed that 17beta-HSD1 was dominantly expressed in the ovary, while the putative 17beta-HSD12, one of the two duplicates found in fish, is a male specific enzyme and expressed exclusively in testis (detected by RT-PCR only). On the other hand, 17beta-HSD8 was expressed in the brain, gill, heart, liver, intestine, gonad, kidney and muscle of both male and female. Enzymatic assays of the three types of 17beta-HSDs were performed using recombinant proteins expressed in E. coli or HEK 293 cells. Tilapia 17beta-HSD1 expressed in E. coli had the preference for NADP(H) as cofactor and could catalyze the inter-conversion between estrone and estradiol efficiently as well as the inter-conversion between androstenedione and testosterone, but less efficiently. Tilapia 17beta-HSD8 recombinant protein expressed in HEK 293 cells could catalyze the conversion of testosterone to androstenedione, as well as the inter-conversion between estrone and estradiol. However, the putative 17beta-HSD12 expressed in E. coli or in HEK 293 cells showed no conversion to any of the four substrates tested in this study. Based on enzyme characterization and tissue distribution, it is plausible to attribute crucial roles to 17beta-HSDs in the gonadal steroidogenesis of teleosts.

17-Hydroxysteroid Dehydrogenases↗
PubMed2004

Observation of millimeter-wave radiation generated by the interaction between an electron beam and a photonic crystal.

We observed directional light emission in the millimeter-wave region when a high-energy (150 MeV) electron beam passes just above a photonic crystal made of polytetrafluoroethylene beads ( approximately 3.2 mm in diameter). The relation between the momentum and the energy of the emitted photons strongly suggests that the observed light is generated by the umklapp scattering process that changes the evanescent waves emitted by the electron beam into observable ones. By comparing the observed spectra with calculated ones based on the photonic band structure, we found that generated photons excite the photonic band modes making them observable as enhanced fine structures in the emission spectra.

Journal Article↗
PubMed2004

Preliminary treatment planning and dosimetry for a clinical trial of neutron capture therapy using a fission converter epithermal neutron beam.

A Phase I/II clinical trial of neutron capture therapy (NCT) was conducted at Harvard-MIT using a fission converter epithermal neutron beam. This epithermal neutron beam has nearly ideal performance characteristics (high intensity and purity) and is well-suited for clinical use. Six glioblastoma multiforme (GBM) patients were treated with NCT by infusion of the tumor-selective amino acid boronophenylalanine-fructose (BPA-F) at a dose of 14.0 g/m(2) body surface area over 90 min followed by irradiation with epithermal neutrons. Treatments were planned using NCTPlan and an accelerated version of the Monte Carlo radiation transport code MCNP 4B. Treatments were delivered in two fractions with two or three fields. Field order was reversed between fractions to equalize the average blood boron concentration between fields. The initial dose in the dose escalation study was 7.0 RBEGy, prescribed as the mean dose to the whole brain volume. This prescription dose was increased by 10% to 7.7 RBEGy in the second cohort of patients. A pharmacokinetic model was used to predict the blood boron concentration for determination of the required beam monitor units with good accuracy; differences between prescribed and delivered doses were 1.5% or less. Estimates of average tumor doses ranged from 33.7 to 83.4 RBEGy (median 57.8 RBEGy), a substantial improvement over our previous trial where the median value of the average tumor dose was 25.8 RBEGy.

Aged↗
PubMed2004

Current clinical results of the Tsukuba BNCT trial.

Nine high grade gliomas (5 glioblastomas and 4 anaplastic astrocytomas) were treated with BSH-based intaoperative boron neutron capture therapy (IOBNCT). BSH (100 mg/kg body weight) was intravenously injected, followed by single fraction irradiation using the mixed thermal/epithermal beam of Japan Research Reactor 4. The blood boron level at the time of irradiation averaged 29.9 (18.8-39.5)microg/g. The peak thermal neutron flux as determined by post-irradiation measurements varied from 1.99 to 2.77x10(9) n cm(-2)s(-1). No serious BSH-related toxicity was observed in this series. The interim survival data in this study showed median survival times of 23.2 months for glioblastoma and 25.9 months for anaplastic astrocytoma, results which are consistent with the current conventional radiotherapy with/without boost radiation. Of the 4 residual tumors, 2 showed complete response (CR) and 2 showed partial response (PR) within 6 months following BNCT. No linear correlation was proved between the dose and the occurrence of early neurological events. The maximum boron dose of 11.7-12.2 Gy in the brain related to the occurrence of radiation necrosis. The clinical application of a mixed thermal/epithermal beam and JRR-4 facilities on BSH-based IOBNCT proved to be safe and effective in this series.

Adult↗