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Biomedical subjects

H Shirai

Publications and source records attributed to H Shirai.

At least 19 recordsLinked to original sources
PubMed2006

Phthalocyanine-dyed fibers adsorb allergenic proteins.

Phthalocyanine (Pc)-dyed fiber is reported to reduce atopic symptoms in some patients when they use underwear made of the fiber. We investigated the adsorption of allergens on Pc-fiber. Pc-fiber trapped house dust/pollen/food allergens with varied molecular weight and pI. The adsorbed allergens were released in the presence of mild detergent. Pc-fiber did not change the molecular weight or disulfide bonding of the allergens. These observations imply that Pc-fiber is applicable as an "allergen trap" for a wide variety of products.

Adsorption↗
PubMed2006

CLOCK is involved in obesity-induced disordered fibrinolysis in ob/ob mice by regulating PAI-1 gene expression.

BACKGROUND: An increased level of obesity-induced plasma plasminogen activator inhibitor-1 (PAI-1) is considered a risk factor for cardiovascular disease. AIM: The present study investigates whether the circadian clock component CLOCK is involved in obesity-induced PAI-1 elevation. METHODS: We examined plasma PAI-1 and mRNA expression levels in tissues from leptin-deficient obese and diabetic ob/ob mice lacking functional CLOCK protein. RESULTS: Our results demonstrated that plasma PAI-1 levels were augmented in a circadian manner in accordance with the mRNA expression levels in ob/ob mice. Surprisingly, a Clock mutation normalized the plasma PAI-1 concentrations in accordance with the mRNA levels in the heart, lung and liver of ob/ob mice, but significantly increased PAI-1 mRNA levels in adipose tissue by inducing adipocyte hypertrophy in ob/ob mice. The Clock mutation also normalized tissue PAI-1 antigen levels in the liver but not in the adipose tissue of ob/ob mice. CONCLUSION: These observations suggest that CLOCK is involved in obesity-induced disordered fibrinolysis by regulating PAI-1 gene expression in a tissue-dependent manner. Furthermore, it appears that obesity-induced PAI-1 production in adipose tissue is not closely related to systemic PAI-1 increases in vivo.

Adipose Tissue↗
PubMed2005

Measurement of turbulence decorrelation during transport barrier evolution in a high-temperature fusion plasma.

A low power polychromatic beam of microwaves is used to diagnose the behavior of turbulent fluctuations in the core of the JT-60U tokamak during the evolution of the internal transport barrier. A continuous reduction in the size of turbulent structures is observed concomitant with the reduction of the density scale length during the evolution of the internal transport barrier. The density correlation length decreases to the order of the ion gyroradius, in contrast with the much longer scale lengths observed earlier in the discharge, while the density fluctuation level remain similar to the level before transport barrier formation.

Journal Article↗
PubMed2002

Evolution of lower-hybrid-driven current during the formation of an internal transport barrier.

Evolution of the lower-hybrid(LH)-driven current profile was measured during the formation of an internal transport barrier (ITB) in a reversed magnetic shear discharge. As the ITB developed, the initially centrally peaked LH-driven current profile gradually turned hollow and was sometimes accompanied by an off-axis peak in the electron temperature profile. These observations indicate the concentration of LH power deposition to the ITB for this case as a result of nonlinear coupling between the LH waves and the target plasma.

Journal Article↗
PubMed2002

Effect of calcium supplementation on bone dynamics of the maxilla, mandible and proximal tibia in experimental osteoporosis.

The effect of calcium supplementation on the bone dynamics in the hard palate of the molar region (maxilla), mandible and proximal tibia in experimental osteoporotic rats was examined. Ninety ovariectomized (OVX) and 45 sham-OVX Wistar female rats were used in this study. All the rats received surgical operation at 6 weeks of age. Ovariectomized rats were fed on a low calcium diet (0.02%) for 12 weeks post-operation, and then randomly divided into the two following groups. One group was fed on high calcium diet (2.30%) (OVX-HCa) and the other group was remained on the low calcium diet (OVX-LCa). Sham-OVX rats were fed on regular calcium diet (1.15%) during the experimental period (Sham-OVX). Histomorphological analysis was carried out from 12 to 32 weeks post-operation. On undecalcified thin section, bone volume, eroded surface, osteoid surface and bone formation rate were calculated for cortical bone of the maxilla, and for cancellous bone of the mandible and proximal tibia. In the OVX-LCa group, compared with the Sham-OVX group, decrease of the bone volume and increase of the bone resorption and formation parameters were detected throughout the observation periods. In the OVX-HCa group, compared with the OVX-LCa group, increase of the bone volume and temporarily increased parameters of bone formation at 1 week after feeding on high calcium diet were observed in the maxilla, but these changes were not observed in the mandible and proximal tibia. Moreover, the bone resorption and formation parameters in the maxilla, mandible and proximal tibia in the OVX-HCa group became equivalent to the Sham-OVX levels with the passage of time.

Analysis of Variance↗
PubMed2001

Plasma equilibrium and confinement in a tokamak with nearly zero central current density in JT-60U.

A high confinement equilibrium with nearly zero toroidal current in the central region (a "current hole") has been observed for the first time to persist stably for several seconds in the JT-60U tokamak. This observation indicates the possibility of stable tokamak operation without central toroidal current; the central current has previously been believed to be necessary in tokamaks. The radius of the current hole extended up to 40% of the plasma minor radius. It was observed that the current hole was formed by the increase of the off-axis noninductive current.

Journal Article↗
PubMed2001

Elongation of the pi-system of phthalocyanines by introduction of thienyl substituents at the peripheral beta positions. Synthesis and characterization.

1,4,8,11,15,18,22,25-octabutoxyphthalocyanines ((OBu)8Pcs) having eight 2-thienyl (1) and [2,2'-bithiophene]-5-yl (2) groups at beta positions and their zinc(II) and cobalt(II) derivatives were prepared from 2-thienyl- (3) or [2,2'-bithiophene]-5-yl (4)-substituted phthalonitriles in moderate to good yields. The electronic absorption spectra of the Pcs showed red-shifted Q-bands relative to beta-unsubstituted (OBu)8Pcs. The longer substituent, the [2,2'-bithiophene]-5-yl group, is more effective than the 2-thienyl group in enlarging the pi-conjugated system of the Pcs. The ring oxidation potential obtained by cyclic voltammetry shifted cathodically with increasing chain length, indicating destabilization of the HOMOs. Due to the shift of the Q-band, 2-thienyl- and [2,2'-bithiophene]-5-yl-substituted Pcs exhibit a remarkable color change from the original green color.

Journal Article↗
PubMed2001

Synthesis of multicomponent systems composed of one phthalocyanine and four terpyridine ligands.

Two phthalocyanine-based multiple ligands were synthesized and characterized. Photochemical and electrochemical properties were measured for zinc(II) phthalocyanines covalently linked with four ruthenium(II) bisterpyridyl complexes. The absorption and electrochemical results are indicative of electronic interaction between two photoactive and redox-active components. Fluorescence spectroscopy of the five nuclear complexes provides evidence of an efficient photoinduced intramolecular energy transfer between the ruthenium-based metal-to-ligand charge-transfer (MLCT) chromophores and the zinc(II) phthalocyanine core. The absorption and fluorescence spectra of the phthalocyanine-based multiple ligands change dramatically as a result of the coordination of metal ions with peripheral terpyridine ligands. This change of fluorescence intensity upon addition of metal ions can apply to an output signal for metal ion sensing. The direct attachment of metal ion receptors with a zinc phthalocyanine core enhanced efficiency of the energy- and electron-transfer reaction from the core to the metal complexes.

Journal Article↗
PubMed2001

Quasisteady high-confinement reversed shear plasma with large bootstrap current fraction under full noninductive current drive condition in JT-60U.

A quasisteady reversed shear plasma with a large bootstrap current fraction ( approximately 80%) has been obtained for the first time in the JT-60U tokamak. The shrinkage of reversed shear region was suppressed by the bootstrap current peaked at the internal transport barrier (ITB) layer and the ITBs at a large radius were sustained, which, by combination with an H-mode edge pedestal, resulted in a high confinement or 2.2 times the H-mode scaling for 6 times energy confinement time or 2.7 s. Furthermore, a full noninductive current drive was obtained by the bootstrap current and the beam driven current.

Journal Article↗
PubMed2001

Construction of regulated nanospace around a porphyrin core.

A series of 1,3,5-phenylene-based rigid dendritic porphyrins were synthesized by Suzuki coupling between a porphyrin core and dendron units. The intramolecular energy transfer was studied by absorption and fluorescence spectroscopies. The encapsulation of the porphyrin core within the 1,3,5-phenylene dendron units was found to provide highly efficient energy transfer from the dendron units to the porphyrin core. The dendritic wedge structure affected the energy transfer efficiency. The 1,3,5-phenylene-based rigid dendron units act as highly efficient light-harvesting antennae. These dendritic porphyrins have also been examined as C(60) hosts and substrate-selective oxidation catalysts. The attachment of the second generation of 1,3,5-phenylene-based dendron units with the porphyrin core enabled a stable inclusion of C(60) in toluene. Furthermore, the size and shape of the nanospace in the rigid dendritic porphyrins were found to affect the selectivity of substrates in the catalytic olefin oxidations.

Energy Transfer↗
PubMed2001

A role of the third complementarity-determining region in the affinity maturation of an antibody.

We recently found that there are two distinct antibody maturation pathways for the immune response of C57BL/6 mice to (4-hydroxy-3-nitrophenyl) acetyl and that a junctional amino acid introduced at a point far in advance of somatic hypermutation determined which pathway of affinity maturation was used. We describe here the structural basis for this aspect of maturation using recently developed H3 rules, which allow for reliable identification of the conformation of the third complementarity-determining region of the heavy chain (CDR-H3) from the primary amino acid sequences only. By the application of these rules, the anti-(4-hydroxy-3-nitrophenyl) acetyl antibodies examined here were classified into two major groups on the basis of their CDR-H3 structure, and these groups were found to be consistent with the maturation pathways. In addition, circular dichroism measurements revealed that the versatile nature of the antigen binding of the antibodies was significantly influenced by the pathway employed. We postulated in this study that flexibility in the CDR-H3 structure in the antigen-combining site could facilitate efficient antibody maturation supported by a plurality of possible antigen binding modes.

Animals↗
PubMed2001

Large vortex-like structure of dipole field in computer models of liquid water and dipole-bridge between biomolecules.

We propose a framework to describe the cooperative orientational motions of water molecules in liquid water and around solute molecules in water solutions. From molecular dynamics (MD) simulation a new quantity "site-dipole field" is defined as the averaged orientation of water molecules that pass through each spatial position. In the site-dipole field of bulk water we found large vortex-like structures of more than 10 A in size. Such coherent patterns persist more than 300 ps although the orientational memory of individual molecules is quickly lost. A 1-ns MD simulation of systems consisting of two amino acids shows that the fluctuations of site-dipole field of solvent are pinned around the amino acids, resulting in a stable dipole-bridge between side-chains of amino acids. The dipole-bridge is significantly formed even for the side-chain separation of 14 A, which corresponds to five layers of water. The way that dipole-bridge forms sensitively depends on the side-chain orientations and thereby explains the specificity in the solvent-mediated interactions between biomolecules.

Amino Acids↗
PubMed2001

Synthesis and antifungal activities of novel 1,3-beta-D-glucan synthase inhibitors. Part 1.

Highly potent 1,3-beta-D-glucan synthase inhibitors 10, 11 and 13 have been identified by the chemical modification of the fungicidal macrocyclic lipopeptidolactone, RO-09-3655 (1), isolated from the cultured broth of Deuteromycotinia spp. D-Ornithine derivative (10) showed improved antifungal activity in the systemic candidiasis model in mice and reduced hepatotoxicity in vitro, as compared with 1.

Animals↗