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N Hamasaki

Publications and source records attributed to N Hamasaki.

At least 37 records · Page 2Linked to original sources
PubMed2001

[Effects of preserved erythrocytes and activated-preserved erythrocytes with phosphoenolpyruvate on energy metabolism in rat ischemic brain tissue].

The effects of erythrocyte function on cerebral ischemia were studied from the perspective of filtration capability (deformability) and total oxygen delivery. Erythrocytes of Wistar rats were divided into three groups: fresh blood, preserved blood, and activated preserved blood (preserved erythrocytes in which total oxygen delivery was increased with phosphoenolpyruvate). Filtration capability was calculated and evaluated by a filtration technique, while total oxygen delivery was evaluated by calculating the efficiency of oxygen delivery from an oxygen dissociation curve. Exchange transfusion was performed in spontaneously hypertensive rats with each of these groups at the same hemoglobin concentration. Bilateral carotid arteries were then ligated for one hour, and, cerebral blood flow and concentrations of adenine nucleotide and lactic acid in cerebral tissue were measured. The filtration capability of both preserved blood and activated preserved blood decreased to about one-third that of fresh blood. The efficiency of oxygen delivery after blood transfusion decreased to 17% with preserved blood, which was about half that (35%) with fresh blood. In the group of with activated preserved blood, this rate increased to 52%. The adenylate energy charge (E.C.) in brain tissue markedly decreased to 0.27 with preserved blood, which was much lower than the value (0.74) with fresh blood. With activated preserved blood, the E.C. value was 0.39. Thus, the decrease in E.C. was mild. With regard to the lactic acid concentration in brain tissue, the value with fresh blood was 12 mumoles/g tissue, while that with preserved blood was 24 mumoles/g tissue, and that with activated preserved blood was 18 mumoles/g tissue. With respect to cerebral blood flow, the values with preserved blood and activated preserved blood decreased to about one-half that with fresh blood. These results suggest that an increase in total oxygen delivery by erythrocytes contributes to improving energy metabolism in brain tissue during cerebral ischemia, and particularly during poor microcirculation.

Animals↗
PubMed2001

[Clinical enzymology].

Clinical Enzymology is an important discipline of Clinical Chemistry and Laboratory Medicine. We review the significant aspect of clinical enzymology from the theoretical as well as the empirical points of view.

Biomarkers↗
PubMed2000

Augmentation of signal transducer and activation of transcription (STAT)6 and STAT3 expression in stimulated B and T cells.

Signal transducer and activation of transcription (STAT)6 has a central role in the signal transduction of interleukin (IL)-4 and IL-13. It has recently been revealed that STAT3 is also involved. STAT6 and STAT3 are expressed ubiquitously; however, it remains unknown how STAT6 and STAT3 expression is regulated. In this study, we found that STAT6 expression was augmented at the transcription level in B and T cells stimulated with anti-IgM antibody and anti-CD40 antibody or PMA and ionomycin, respectively, and that STAT3 expression was similarly augmented in the stimulated B cells. The stimulated B and T cells showed enhancement of STAT6 activation and CD23 expression induced by IL-4 and IL-13. Augmentation of STAT6 and STAT3 would be a mechanism of the amplification of the IL-4 and IL-13 signals in stimulated B and T cells.

B-Lymphocytes↗
PubMed2000

Structure and calcium-binding properties of Frq1, a novel calcium sensor in the yeast Saccharomyces cerevisiae.

The FRQ1 gene is essential for growth of budding yeast and encodes a 190-residue, N-myristoylated (myr) calcium-binding protein. Frq1 belongs to the recoverin/frequenin branch of the EF-hand superfamily and regulates a yeast phosphatidylinositol 4-kinase isoform. Conformational changes in Frq1 due to N-myristoylation and Ca(2+) binding were assessed by nuclear magnetic resonance (NMR), fluorescence, and equilibrium Ca(2+)-binding measurements. For this purpose, Frq1 and myr-Frq1 were expressed in and purified from Escherichia coli. At saturation, Frq1 bound three Ca(2+) ions at independent sites, which correspond to the second, third, and fourth EF-hand motifs in the protein. Affinity of the second site (K(d) = 10 microM) was much weaker than that of the third and fourth sites (K(d) = 0.4 microM). Myr-Frq1 bound Ca(2+) with a K(d)app of 3 microM and a positive Hill coefficient (n = 1.25), suggesting that the N-myristoyl group confers some degree of cooperativity in Ca(2+) binding, as seen previously in recoverin. Both the NMR and fluorescence spectra of Frq1 exhibited very large Ca(2+)-dependent differences, indicating major conformational changes induced upon Ca(2+) binding. Nearly complete sequence-specific NMR assignments were obtained for the entire carboxy-terminal domain (residues K100-I190). Assignments were made for 20% of the residues in the amino-terminal domain; unassigned residues exhibited very broad NMR signals, most likely due to Frq1 dimerization. NMR chemical shifts and nuclear Overhauser effect (NOE) patterns of Ca(2+)-bound Frq1 were very similar to those of Ca(2+)-bound recoverin, suggesting that the overall structure of Frq1 resembles that of recoverin. A model of the three-dimensional structure of Ca(2+)-bound Frq1 is presented based on the NMR data and homology to recoverin. N-myristoylation of Frq1 had little or no effect on its NMR and fluorescence spectra, suggesting that the myristoyl moiety does not significantly alter Frq1 structure. Correspondingly, the NMR chemical shifts for the myristoyl group in both Ca(2+)-free and Ca(2+)-bound myr-Frq1 were nearly identical to those of free myristate in solution, indicating that the fatty acyl chain is solvent-exposed and not sequestered within the hydrophobic core of the protein, unlike the myristoyl group in Ca(2+)-free recoverin. Subcellular fractionation experiments showed that both the N-myristoyl group and Ca(2+)-binding contribute to the ability of Frq1 to associate with membranes.

Amino Acid Sequence↗
PubMed2000

Membrane integration of the second transmembrane segment of band 3 requires a closely apposed preceding signal-anchor sequence.

We have investigated the topogenic rules of multispanning membrane proteins using erythrocyte band 3. Here, the fine structural requirements for the correct disposition of its second transmembrane segment (TM2) were assessed. We made fusion proteins where TM1 and the loop sequence preceding TM2 were changed and fused to prolactin. They were expressed in a cell-free system supplemented with rough microsomal membrane, and their topologies on the membrane were assessed by protease sensitivity and N-glycosylation. TM1 was demonstrated to be a signal-anchor sequence that mediates translocation of the downstream portion, and thus TM2 should be responsible to halt the translocation to acquire TM topology. When the loop between TM1 and TM2 was elongated, however, TM2 was readily translocated through the membrane and not integrated. For the membrane integration of TM2, TM2 must be in close proximity to TM1. The TM1 can be replaced with another signal-anchor sequence with a long hydrophobic segment but not with a signal sequence with shorter hydrophobic stretch. The length of the hydrophobic segment affected final topology of TM2. We concluded that the two TM segments work synergistically within the translocon to acquire the correct topology and that the length of the preceding signal sequence is critical for stable transmembrane assembly of TM2. We propose that direct interaction among the TM segments is one of the critical factors for the transmembrane topogenesis of multispanning membrane proteins.

Amino Acid Sequence↗
PubMed2000

Binding of human mitochondrial transcription factor A, an HMG box protein, to a four-way DNA junction.

Mitochondrial transcription factor A (mtTFA), the only known transcription factor in mitochondria, is also implicated in maintenance of mitochondrial genome although little is elucidated about its molecular basis. mtTFA is a member of HMG box proteins family. Some HMG proteins bind with high affinity to four-way DNA junctions that mimic a Holliday structure, a putative intermediate in DNA recombination. To explore possible involvement of a Holliday-like structure in the maintenance of mitochondrial genome, we examine the binding of recombinant human mtTFA to a synthetic four-way DNA junction. The human mtTFA binds to the four-way DNA junction with an approximately 10-fold higher affinity than to the corresponding linear duplex DNA and with essentially the same affinity as to a 40-mer DNA containing the human mitochondrial light strand promoter sequence. The mtTFA binds to the four-way as a monomer. Both of the two HMG box domains of human mtTFA are required for the high affinity binding to the four-way junction.

Base Sequence↗
PubMed2000

Accumulation of adenine DNA glycosylase-sensitive sites in human mitochondrial DNA.

The mitochondrial respiratory chain inevitably produces reactive oxygen species as byproducts of aerobic ATP synthesis. Mitochondrial DNA (mtDNA), which is located close to the respiratory chain, is reported to contain much more 8-oxoguanine (8-oxoG), an oxidatively modified guanine base, than nuclear DNA. Despite such a high amount of 8-oxoG in mtDNA (1-2 8-oxoG/10(4) G), mtDNA is barely cleaved by an 8-oxoG DNA glycosylase or MutM, which specifically excises 8-oxoG from a C:8-oxoG pair. We find here that about half of human mtDNA molecules are cleaved by another 8-oxoG-recognizing enzyme, an adenine DNA glycosylase or MutY, which excises adenine from an A:8-oxoG pair. The cleavage sites are mapped to adenines. The calculated number of MutY-sensitive sites in mtDNA is approximately 1.4/10(4) G. This value roughly corresponds with the electrochemically measured amount of 8-oxoG in mtDNA (2.2/10(4) G), raising the possibility that 8-oxoG mainly accumulates as an A:8-oxoG pair.

Adenine↗
PubMed2000

Genetic variants of IL-13 signalling and human asthma and atopy.

Asthma and atopy show epidemiological association and are biologically linked by T-helper type 2 (T(h)2) cytokine-driven inflammatory mechanisms. IL-4 operates through the IL-4 receptor (IL-4R, a heterodimer of IL-4Ralpha and either gammac or IL-13Ralpha1) and IL-13 operates through IL-13R (a heterodimer of IL-4Ralpha and IL-13Ralpha1) to promote IgE synthesis and IgE-based mucosal inflammation which typify atopy. Recent animal model data suggest that IL-13 is a central cytokine in promoting asthma, through the stimulation of bronchial epithelial mucus secretion and smooth muscle hyper-reactivity. We investigated the role of common genetic variants of IL-13 and IL-13Ralpha1 in human asthma, considering IgE levels. A novel variant of human IL-13, Gln110Arg, on chromosome 5q31, associated with asthma rather than IgE levels in case-control populations from Britain and Japan [peak odds ratio (OR) = 2.31, 95% CI 1.33-4.00]; the variant also predicted asthma and higher serum IL-13 levels in a general, Japanese paediatric population. Immunohistochemistry demonstrated that both subunits of IL-13R are prominently expressed in bronchial epithelium and smooth muscle from asthmatic subjects. Detailed molecular modelling analyses indicate that residue 110 of IL-13, the site of the charge-modifying variants Arg and Gln, is important in the internal constitution of the ligand and crucial in ligand-receptor interaction. A non-coding variant of IL-13Ralpha1, A1398G, on chromosome Xq13, associated primarily with high IgE levels (OR = 3. 38 in males, 1.10 in females) rather than asthma. Thus, certain variants of IL-13 signalling are likely to be important promoters of human asthma; detailed functional analysis of their actions is needed.

Adult↗
PubMed2000

Ten-years clinical follow-up following successful percutaneous transvenous mitral commissurotomy: single-center experience.

The purpose of this study is to report the long-term follow-up outcome of patients undergoing percutaneous transvenous mitral commissurotomy (PTMC). The follow-up of 68 of 82 (83%) consecutive patients undergoing successful PTMC (mitral valve area of more than 1.5 cm(2) without major complications) in 1987 using the Inoue balloon was analyzed. The mean age at the time of PTMC was 52 +/- 11 years and 81% were female patients. The mean follow-up interval was 98 +/- 37 months (6 to 123). Actuarial survival rate was 98%, 97%, and 86% at 1, 5, and 10 years, respectively; the event-free (death, mitral valve replacement, and repeat PTMC) survival rate was 90%, 85%, and 66% at 1, 5, and 10 years, respectively. According to the echocardiographic findings, patients could be divided into three groups: pliable valve, semipliable valve, and rigid valve. Multivariable analysis identified echocardiographic subgrouping as the major significant predictor of any event: the event-free survival rate being 70% in group 1, 66% in group 2, and 20% in group 3 (P < 0.05). Echocardiographic follow-up was available in 49 of 68 patients (72%); the mitral valve area changed from 1.4 +/- 0.5 before to 2.1 +/- 0.4 immediately post-PTMC, and 1.8 +/- 0.4 cm(2) 10 years after the procedure. The long-term follow-up outcome following successful PTMC was favorable and seems to support it as a viable alternative to surgical commissurotomy in selected patients. Patients with rigid valves should be selected very carefully.

Adult↗
PubMed2000

Clinical and angiographic follow-up after single long GFX coronary stent implantation.

In order to identify predictors of late restenosis after GFX stent implantation, procedural and 6-month clinical and angiographic follow-up data of prospectively entered 141 consecutive lesions treated with a single long (24 or 30 mm) GFX stent were compared to 66 consecutive lesions requiring a single short (12 or 18 mm) stent. The initial clinical success rate of 97% and thrombosis rate of 1.4% with long stents were similar to 97% and 0% with short stents (P = NS). Their respective binary restenosis rates were 34.7% and 23.3% for long and short stents as a whole (P = NS), but being 10.0% for 12 mm, 26.0% for 18 mm, 31.3% for 24 mm, and 39.2% for 30 mm. When proximal and distal reference diameters at baseline were compared between the lesions with and without restenosis, proximal reference diameters were not statistically different (3.02+/-0.42 mm vs. 3.18+/-0.62 mm) and the restenosis group had significantly smaller distal reference diameters (2.15+/-0.48 mm vs. 2.55+/-0.53 mm, P<0.0001). The treatment of long lesions with single long-stent implantation can be accomplished with high success and low complication rates. Single long-stent implantation may be effective, if the distal reference size of the long narrowing is big enough to accept the stent.

Aged↗
PubMed2000

The D-loop structure of human mtDNA is destabilized directly by 1-methyl-4-phenylpyridinium ion (MPP+), a parkinsonism-causing toxin.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine has been reported to cause parkinsonism via its neurotoxic form, 1-methyl-4-phenylpyridinium ion (MPP+), which inhibits complex I of the mitochondrial respiratory chain. Its parkinsonism-causing mechanisms attract a great deal of interest as a model of the disease. Recently, we reported that MPP+ strongly decreases the amount of mtDNA independent of the inhibition of complex I. Maintenance of a proper amount of mtDNA is essential for the normal function of mitochondria as exemplified in many mitochondrial diseases. The most characteristic feature in vertebral mtDNA replication is that H-strand synthesis proceeds displacing the parental H-strand as a long single strand. It forms the D-loop, a triplex replication intermediate composed of the parental L-strand, nascent H-strand and displaced H-strand. Here we show that MPP+ does not inhibit DNA synthesis by DNA polymerase gamma, but rather releases the nascent H-strands from mtDNA both in organello and in vitro. This indicates that MPP+ directly destabilizes the D-loop structure, thereby inhibiting replication. This study raises a new mechanism, i.e. destabilization of replication intermediates, for depletion of mtDNA.

1-Methyl-4-phenylpyridinium↗
PubMed2000

Atopy and the human IL-4 receptor alpha chain.

BACKGROUND: Atopy is a common inherited disorder characterized by increased IgE responsiveness, but no functional analysis of the candidate genes related to atopy has been performed. IL-4 is important for B-cell production of IgE, and the human IL-4 receptor alpha chain (hIL-4Ralpha) is crucial for the binding and signal transduction of IL-4, so hIL-4Ralpha may be a candidate gene related to atopy. OBJECTIVE: We examined the relationship between the variation at amino acid 50 of hIL-4Ralpha and atopic asthma. METHODS: We performed a genetic study to investigate the relationship between the variation of amino acid 50 (isoleucine [Ile(50)] or valine [Val(50)]) and atopic asthma in a Japanese population and a functional study with the use of transfectants that expressed hIL4Ralpha bearing either Ile(50) or Val(50). Furthermore, we analyzed CD23 expression and IgE synthesis after IL-4 stimulation of peripheral blood mononuclear cells bearing either Ile(50) or Val(50). RESULTS: The prevalence of Ile(50) was higher than that of Val(50) in individuals with atopic asthma, especially during childhood. In transfectants, germline epsilon transcription activity and Stat6 activity were upregulated by the Ile(50) variant, compared with Val(50), but receptor affinity for IL-4 was similar between the two. CD23 expression and IgE synthesis in response to IL-4 were augmented in Ile(50)-expressing peripheral mononuclear blood cells compared to cells expressing Val(50). CONCLUSION: The Ile(50) variant of hIL-4Ralpha may be related to atopic asthma, particularly in children.

Amino Acid Substitution↗
PubMed2000

Characterization of IL-4 and IL-13 signals dependent on the human IL-13 receptor alpha chain 1: redundancy of requirement of tyrosine residue for STAT3 activation.

IL-4 and IL-13 are pleiotropic cytokines whose biological activities overlap with each other. IL-13 receptor alpha chain 1 (IL-13R alpha 1) is necessary for binding to IL-13, and the heterodimer composed of IL-13R alpha 1 and IL-4R alpha chain transduces IL-13 and IL-4 signals; however, the functional mapping of the intracellular domain of IL-13R alpha 1 is not fully understood. In this study, we constructed wild and mutated types of human IL-13R alpha 1, and analyzed IL-4 and IL-13 signals using an IL-13R alpha 1-transfected human B cell line. Expression of IL-13R alpha 1 evoked STAT3 activation by IL-4 and IL-13, and in stimulated human B cells, on which IL-13R alpha 1 was highly expressed, IL-4 and IL-13 induced STAT3 activation. Replacement of the two tyrosine residues completely abolished STAT3 activation, although replacing either tyrosine residue alone retained it. Furthermore, we found that the Box1 region and the C-terminal tail of IL-13R alpha 1 were critical for binding to Tyk2, and activation of Jak1, Tyk2, the insulin receptor substrate-1 and STAT6 respectively. These results suggest that STAT3 activation is involved with IL-4 and IL-13 signals in human B cells along with the activation of STAT6, and that there is a unique sequence in IL-13R alpha 1 to activate STAT3.

Animals↗
PubMed2000

Highly selective antibacterial activity of novel alkyl quinolone alkaloids from a Chinese herbal medicine, Gosyuyu (Wu-Chu-Yu), against Helicobacter pylori in vitro.

To elucidate the antibacterial activity of Gosyuyu, the crude extract from the fruit of Evodia rutaecarpa, a Chinese herbal medicine, has been fractionated chromatographically, and each fraction was assayed for antibacterial activity against Helicobacterpylori (H. pylori) in vitro. As the result, a single spot having marked antibacterial activity against H. pylori was obtained and the chemical structure was analyzed. The isolated compound was revealed to be a novel alkyl quinolone alkaloid based on the solubility, IR spectra, NMR analysis and mass spectrometric data after purification by TLC of silica. We compared the antimicrobial activity of this compound with that of other antimicrobial agents and examined susceptibility of various intestinal pathogens. As the result, the new quinolone compounds obtained from Gosyuyu extracts were found to be a mixture of two quinolone alkaloids, 1-methyl-2-[(Z)-8-tridecenyl]-4-(1H)-quinolone and 1-methyl-2-[(Z)-7-tridecenyl]-4-(1H)-quinolone (MW: 339), reported previously. The minimum inhibitory concentration (MIC) of these compounds against reference strains and clinically isolated H. pylori strains were less than 0.05 microg/ml, which was similar to the MIC of amoxicillin and clarithromycin that are used worldwide for the eradication of H. pylori, clinically. Furthermore, it was noted that the antimicrobial activity of these compounds was highly selective against H. pylori and almost non-active against other intestinal pathogens. The above results showed that these alkyl methyl quinolone (AM quinolones) alkaloids were useful for the eradication of H. pylori without affecting other intestinal flora.

Alkaloids↗
PubMed2000

In vivo administration of mycobacterial cord factor (Trehalose 6, 6'-dimycolate) can induce lung and liver granulomas and thymic atrophy in rabbits.

Trehalose 6,6'-dimycolate (TDM) is a cell surface molecule of Mycobacterium tuberculosis. TDM induced a loss of body weight and prominent granulomas in the liver and lungs by the intravenous injection of TDM into rabbits. TDM also induced atrophy of the thymus and spleen due to apoptosis. By contrast, sulfolipid (2,3,6, 6'-tetraacyl trehalose 2'-sulfate) induced neither toxicity, nor granuloma formation, nor atrophy of the thymus and spleen. In rabbits the histopathological changes were more dramatic than in mice. The rabbit model may be more sensitive and may provide more information on the beneficial or pathological effects of TDM.

Animals↗
PubMed2000

Childhood atopic asthma: positive association with a polymorphism of IL-4 receptor alpha gene but not with that of IL-4 promoter or Fc epsilon receptor I beta gene.

We examined the relative contributions of three representative candidate genes for atopy (Fc epsilon receptor I beta, IL-4, and IL-4 receptor alpha) to the development of atopic asthma. Four polymorphisms of the three candidate genes including Ile50Val and Gln551Arg of IL-4 receptor alpha, -590C/T of IL-4 promoter and Glu237Gly of Fc epsilon receptor I beta were studied in 100 patients with atopic asthma and 100 nonatopic controls in the northern Kyushu area in Japan. Among the four polymorphisms of the three candidate genes, the Ile50 allele of the IL-4 receptor alpha chain gene demonstrated an association with atopic asthma subjects (p = 0.044), especially in patients with onset at 2 years of age or earlier (p = 0.034) and in patients with moderate to severe atopic asthma (p = 0. 031). Gln551Arg of IL-4 receptor alpha, -590C/T of IL-4 promoter and Glu237Gly of Fc epsilon receptor I beta showed no association with atopic asthma. A slight linkage disequilibrium between Ile50Val and Gln551Arg polymorphisms of the IL-4 receptor alpha chain gene was observed in both patients and nonatopic controls. The identification of additional atopy genes in areas with a certain genetic background is essential for genetic diagnosis and to establish new therapeutic modalities for atopic asthma.

Adolescent↗