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T Sakamoto

Publications and source records attributed to T Sakamoto.

At least 37 records · Page 2Linked to original sources
PubMed2005

A giant gamma-ray flare from the magnetar SGR 1806-20.

Two classes of rotating neutron stars-soft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars-are magnetars, whose X-ray emission is powered by a very strong magnetic field (B approximately 10(15) G). SGRs occasionally become 'active', producing many short X-ray bursts. Extremely rarely, an SGR emits a giant flare with a total energy about a thousand times higher than in a typical burst. Here we report that SGR 1806-20 emitted a giant flare on 27 December 2004. The total (isotropic) flare energy is 2 x 10(46) erg, which is about a hundred times higher than the other two previously observed giant flares. The energy release probably occurred during a catastrophic reconfiguration of the neutron star's magnetic field. If the event had occurred at a larger distance, but within 40 megaparsecs, it would have resembled a short, hard gamma-ray burst, suggesting that flares from extragalactic SGRs may form a subclass of such bursts.

Journal Article↗
PubMed2005

Sex-linked quantitative trait loci for thermotolerance and length in the rainbow trout.

We hypothesized that correlation between growth traits and upper thermal tolerance (UTT) in rainbow trout (Oncorhynchus mykiss) might be explained by quantitative trait loci (QTL) localized to the same linkage groups. Microsatellites on three autosomal linkage groups carrying UTT QTL in rainbow trout were tested for associations with fork length (FL) and condition factor (K) in half-sib families of outbred rainbow trout and in backcrosses of trout lines selected on UTT. Additionally, we used a sex-linked microsatellite (OmyFGT19TUF) to test for marker-trait associations at the sex chromosomes. The sex-linked marker OmyFGT19TUF was significantly associated with FL and UTT, accounting for up to 9.6% and 9.7% of variance in these traits, respectively. Male advantages in FL (and, to a lesser extent, UTT) relative to their female sibs were dependent on the origin of the Y chromosome and thus varied among grandsire lines. However, males had higher K in a manner unrelated to Y chromosomal origin, suggesting a partially sex-limited expression of this trait. Omy325UoG was significantly associated with K in one of the outbred half-sib families, but no other significant autosomal marker-trait associations were detected. Our findings illustrate minor evidence that correlation between UTT and FL is partially determined by one or more sex-chromosomal QTL.

Acclimatization↗
PubMed2005

Association analysis of tissue inhibitor of metalloproteinase2 gene polymorphisms with COPD in Egyptians.

Proteinase/antiproteinase imbalance is recognized to play an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD). A relative increase in the activities of matrix metalloproteinases might be caused by mutations of tissue inhibitor of metalloproteinase2 (TIMP2). Recently, two polymorphisms of the TIMP2 gene, +853 G/A and -418 G/C (+551 and -720 from the translation initiation site), have been shown to be associated with the development of COPD in the Japanese population. In this study, a case-control association analysis for these polymorphisms was conducted in the Egyptian population using 106 COPD patients and 72 healthy controls. The genotype frequency of +853 G/A was significantly different between the patient and the control groups (P = 0.029), although no significant difference was detected in the allele frequency between the two groups. These results suggest that the +853 G/A polymorphism of the TIMP2 gene might be associated with COPD across ethnicities. In contrast, neither the distributions of genotype nor allele frequencies of -418 G/C were significantly different between the two groups, raising the possibility that a combination of different genetic factors contributes to the development of COPD in different ethnic groups.

Case-Control Studies↗
PubMed2005

Impairment of conditioned freezing to tone, but not to context, in Fyn-transgenic mice: relationship to NMDA receptor subunit 2B function.

We previously demonstrated that transgenic mice overexpressing Fyn tyrosine kinase exhibit higher seizure susceptibility and enhanced tyrosine phosphorylation of several proteins, including the N-methyl-D-aspartate (NMDA) receptor subunit 2B (NR2B). In the present study, we analysed behavioural phenotypes, especially conditioned fear responses, of Fyn-transgenic (TG) mice to better understand the role of Fyn in learned emotional behaviour. Tone-dependent conditioned freezing was significantly attenuated in Fyn-TG mice, whereas context-dependent freezing was unaffected. Neither massed nor spaced conditioning ameliorated the attenuation of tone-dependent freezing. However, the selective NR2B antagonist ifenprodil, when administered before conditioning, restored tone-dependent freezing in Fyn-TG mice at a dose that did not affect freezing in wild-type (WT) mice. These results suggest that impairment of tone-dependent conditioned freezing in Fyn-TG mice is caused by disruption of the NR2B-containing NMDA receptor function. Tyrosine phosphorylation of brain proteins, including NR2B, was enhanced in Fyn-TG mice compared with that in WT mice. We also found that ifenprodil significantly suppressed the enhanced tyrosine phosphorylation. Thus, our data support the notion that NMDA receptor activity is tightly correlated with protein tyrosine phosphorylation, and Fyn might be one key molecule that controls tone-dependent conditioned freezing through the regulation of NMDA receptor function.

Acoustic Stimulation↗
PubMed2005

The characterisation of hyalocytes: the origin, phenotype, and turnover.

AIM: To determine the characterisation of hyalocytes: the origin, phenotype, and turnover in the rodent. METHODS: To characterise the ultrastructure and distribution of hyalocytes, transmission and scanning electron microscopy was performed in rat eyes. Immunophenotypical analysis was performed by either anti-ED1 or ED2 antibodies. To examine the origin of the hyalocytes, the chimeric mice were created and were used to transplant the bone marrow (BM) cells from enhanced green fluorescent protein (EGFP) transgenic mice. The turnover of hyalocytes was examined at 0, 4, 6, 7, and 12 months after BM transplantation. RESULTS: Hyalocytes were distributed especially in the vitreous cortex and had an irregular shape with a spherical granule. Immunophenotypical studies demonstrated that most of the hyalocytes in rat eyes expressed ED2 but not ED1. In the chimeric mice, the hyalocytes were GFP negative right after BM transplantation. Interestingly, more than 60% of hyalocytes were replaced within 4 months and approximately 90% within 7 months after BM transplantation. CONCLUSIONS: The rodent hyalocytes were shown to express tissue macrophage marker, were derived from BM, and totally replaced within 7 months. These data provide the characterisation of hyalocytes in physiological conditions, especially their origin, distribution, and turnover, and may contribute to the better understanding of the pathogenesis of vitreoretinal disease.

Animals↗
PubMed2005

Expression of prolactin-releasing peptide and prolactin in the euryhaline mudskippers (Periophthalmus modestus): prolactin-releasing peptide as a primary regulator of prolactin.

Prolactin (PRL)-releasing peptide (PrRP) is a strong candidate stimulator of pituitary PRL transcription and secretion in teleosts. However, the role in control of extrapituitary PRL expression is unclear even in mammals. To study the possible presence of PrRP-PRL axes not only in the brain-pituitary but also in peripheral organs, the expression patterns of PrRP, PRL and growth hormone (GH) were characterized in amphibious euryhaline mudskippers (Periophthalmus modestus). PrRP mRNA is abundantly expressed not only in the brain but also in the liver, gut and ovary, while less abundant expression was also detected in the skin and kidney. Corresponding to the distribution of PrRP mRNA, PRL mRNA was also detectable in these organs. During adaptation to different environments, the changes in mRNA levels of PrRP paralleled those in PRL in the brain-pituitary, liver and gut in an organ-specific manner. Brain PrRP mRNA and the pituitary PRL mRNA increased under freshwater and terrestrial conditions (P < 0.05); expression of PrRP and PRL in the gut of freshwater fish was higher (P < 0.05) than those in sea-water fish although there were no changes in fish kept out of water; no significant change was seen in the liver. Expressions of GH were not correlated with PrRP. In the gut, PrRP and PRL appear to be co-localized in the mucosal layer, especially in the mucous cells. Thus, PrRP may also be a local modulator of extrapituitary PRL expression and the PrRP-PRL axes in various organs may play an organ-specific role during environmental adaptation.

Animals↗
PubMed2004

Clinical implication of expression of cyclooxygenase-2 and peroxisome proliferator activated-receptor gamma in epithelial ovarian tumours.

Expression of cyclooxygenase (COX)-2 plays a key role in tumorigenesis and development and peroxisome proliferator-activated receptor gamma (PPARgamma) has been implicated in the control of COX-2 expression in some tissues. The aim of this study is to investigate (1) whether expression of COX-2 and PPARgamma is associated with ovarian carcinogenesis and progression of ovarian tumours and (2) whether COX-2 expression is controlled through ligand-mediated activation of PPARgamma in ovarian carcinoma cells. For this purpose, the presence of COX-2 and PPARgamma was immunohistochemically examined in 71 epithelial ovarian carcinomas, 18 borderline tumours and 23 benign tumours and the levels of COX-2 and PPARgamma proteins were determined by enzyme immunoassay in four benign tumours, three borderline tumours and 12 carcinomas. The frequency of COX-2 and PPARgamma detection was significantly increased and decreased as lesions progressed to carcinoma, respectively. The COX-2 protein was not detected in the three borderline tumours, whereas PPARgamma protein was detected in all of them. COX-2 protein was detected in eight of the 12 carcinomas, whereas PPARgamma protein was detected in only two cases. In addition, PPARgamma protein was not detected in all of the eight carcinomas in which COX-2 protein was detected, suggesting that expression of PPARgamma and COX-2 was in a reciprocal relationship. Furthermore, in cultured ovarian carcinoma cells, Western blot revealed that PPARgamma and COX-2 expression was regulated conversely as a result of stimulation by 15-deoxy-Delta(12, 14) PGJ(2) (15-PGJ(2)), a PPARgamma activator. In addition, 15d-PGJ(2) suppressed tumour necrosis factor-alpha-induced-COX-2 expression, confirming the reciprocal correlation between COX-2 and PPARgamma. From these results, it was suggested that PPARgamma activation might suppress COX-2 expression via the nuclear factor-kappaB pathway in the ovarian carcinoma cells and that low expression of PPARgamma and high expression of COX-2 might be involved in carcinogenesis and progression of ovarian tumours.

Adenocarcinoma↗
PubMed2004

Evidence for a role of basal ganglia in the regulation of rapid eye movement sleep by electrical and chemical stimulation for the pedunculopontine tegmental nucleus and the substantia nigra pars reticulata in decerebrate cats.

The present study was to determine how afferents from the substantia nigra pars reticulata (SNr) of the basal ganglia to the pedunculopontine tegmental nucleus (PPN) in the brainstem could contribute to the control of behavioral states. We used anesthetized and acutely decerebrated cats (n=22). Repetitive electrical stimulation (10-100 Hz, 20-50 microA, for 4-20 s) to the ventrolateral part of the PPN produced rapid eye movement (REM) associated with a suppression of postural muscle tone (REM with atonia). Although repetitive electrical stimuli (10-200 Hz, 10-60 microA, for 5-20 s) delivered to the dorsolateral part of the SNr did not evoke eye movements or muscular tonus in baseline conditions, it altered the PPN-induced REM with atonia. The following three types of effects were induced: (1) attenuation of the REM with atonia; (2) attenuation of muscular atonia without changes in REM (REM without atonia); and (3) attenuation of only REM. The optimal stimulus sites for these effects were intermingled within the lateral part of the SNr. The PPN-induced REM with atonia was abolished by an injection into the PPN of muscimol (1-15 mM, 0.1-0.25 microl), a GABAA receptor agonist, but not altered by an injection of baclofen (1-10 mM, 0.1-0.25 microl), a GABAB receptor agonist. Moreover, an injection of bicuculline (1-15 mM, 0.1-0.25 microl), a GABAA receptor antagonist, into the PPN, resulted in REM with atonia. On the other hand, an injection of muscimol into the dorsolateral part of the SNr (1-15 mM, 0.1-0.25 microl) induced REM with atonia, which was in turn eliminated by a further injection of muscimol into the PPN (5-10 mM, 0.2-0.25 microl). These results suggest that a GABAergic projection from the SNr to the PPN could be involved in the control of REM with atonia, signs which indicate REM sleep. An excessive GABAergic output from the basal ganglia to the PPN in parkinsonian patients may induce sleep disturbances, including a reduction of REM sleep periods and REM sleep behavioral disorders (REM without atonia).

Animals↗
PubMed2004

Improvement of dermatitis by iontophoretically delivered antisense oligonucleotides for interleukin-10 in NC/Nga mice.

IL-10 is overexpressed in skin lesions of atopic dermatitis (AD) patients and believed to be an important factor in the pathogenesis of the disease. Thus the regulation of IL-10 production is a potential solution for immunotherapeutic intervention in AD. We examined the topical delivery of an antisense oligonucleotide for mouse IL-10 (AS6) and the therapeutic effect on the skin lesions of NC/Nga mice, a human AD model. Using an iontophoresis system, about 30% of the applied dose of AS6 penetrated the skin and was distributed in the epidermis and upper dermis. Topically delivered AS6 decreased the levels of mRNA and protein of IL-10 in the lesions of NC/Nga mice, with no effect on IL-4 levels. The dorsal lesions of NC/Nga mice disappeared with repeated topical application of AS6. Topically delivered AS6 showed an inhibitory effect on the production of IL-10 in the skin lesions of NC/Nga mice and had a therapeutic effect on the established dermatitis.

Animals↗
PubMed2004

[Cholesterol crystal embolization exacerbated after the off-pump coronary artery bypass; report of a case].

A 66-year-old man with left main trunk disease was treated under a diagnosis of acute myocardial infarction based on coronary angiography by off-pump coronary artery bypass (OPCAB). About 1 month after operation, his renal function deteriorated and purpura appeared on both feet, especially at the toe tips. In this case, steroid therapy was performed and the patient survived. Cholesterol embolism rarely occurs after angiographic procedure or cardiovascular surgery. In general, it is associated with high morbidity and mortality, but no optimal treatment has yet been developed. This underlines the importance of careful observation and skin biopsy for early diagnosis.

Aged↗
PubMed2003

A cold-adapted endo-arabinanase from Penicillium chrysogenum.

Previously, three arabinan-degrading enzymes were isolated from Penicillium chrysogenum 31B. Here we describe another arabinan-degrading enzyme, termed Abnc, from the culture filtrate of the same organism. Analysis of the reaction products of debranched arabinan by high-performance anion-exchange chromatography (HPAEC) revealed that Abnc cleaved the substrate in an endo manner and that the final major product was arabinotriose. The molecular mass of Abnc was estimated to be 35 kDa by SDS-PAGE. Enzyme activity of Abnc was highest at pH 6.0 to 7.0. The enzyme was stable up to 30 degrees C and showed optimum activity at 30 to 40 degrees C. Compared with a mesophilic counterpart from Aspergillus niger, Abnc exhibited a lower thermal stability and optimum enzyme activity at lower temperatures. Production of Abnc in P. chrysogenum was found to be strongly induced by arabinose-containing polymers and required a longer culture time than did other arabinanase isozymes in this strain.

Amino Acid Sequence↗
PubMed2003

Polarization-mode dispersion measurement by an optical time-domain reflectometer with polarimetry assuming backscattering by randomly oriented nonspherical particles.

In previous work on polarization-mode dispersion (PMD) measurement with an optical time-domain reflectometer with polarimetry (p-OTDR), scatterers were assumed to be a cloud of small spherical particles in a fiber. We have found that the p-OTDR waveforms were fitted well by modified Mueller matrices, assuming scattering by a cloud of nonspherical particles. We realized a PMD measurement based on the p-OTDR Jones matrix eigenanalysis (JME) method. The measured PMD was consistent with that of JME standard measurement with transmission-type polarimetry.

Journal Article↗
PubMed2003

Modulation of the onset age in primary dystonia by APOE genotype.

APOE polymorphisms were studied in 200 unrelated patients with primary dystonia as well as 300 age-matched control subjects. Although no difference was found in APOE genotype between the patients with dystonia and the controls, APOE-epsilon4 carriers developed the disease on average approximately 10 years earlier than APOE-epsilon4 noncarriers (p = 0.0012). This suggests that APOE-epsilon4 genotype affects the clinical presentation of primary dystonia.

Adolescent↗
PubMed2003

A new approach for studying interaction of the polygalacturonase-inhibiting proteins with pectins.

A method for determination of the interaction between pectins and proteins was developed using cross-linked polygalacturonic acid (CLPG) as the pectic substrate and polygalacturonase-inhibiting proteins (PGIPs). Defined water-insoluble pectins were prepared by chemical substitutions with acetyl or methoxyl groups on CLPG. In the presence of 0.1 M NaCl, PGIPs fully bound to CLPG but not to cross-linked alginic acid (CLAL), which had a similar pK(a) to CLPG, suggesting that the inhibitor was not simply bound to the substrate by nonspecific electrostatic interaction. Optimum binding of PGIPs to CLPG occurred at pH 2.4 to 4.7. The binding ability of the inhibitor to CLPGs with degree of methylation (DM) of 66% or degree of acetylation (DAc) of 133% was not significantly changed. In contrast, the DM of 82% or 95% decreased the binding. These results indicated that the carboxylic groups of galacturonic acid residues were involved in the recognition of the substrate by PGIPs.

Cross-Linking Reagents↗
PubMed2003

Purification and properties of two type-B alpha-L-arabinofuranosidases produced by Penicillium chrysogenum.

Two distinct extracellular alpha-L-arabinofuranosidases (AFases; EC 3.2.1.55) were purified from the culture filtrate of Penicillium chrysogenum 31B. The molecular masses of the enzymes were estimated to be 79 kDa (AFQ1) and 52 kDa (AFS1) by SDS-PAGE. Both enzymes had their highest activities at 50 degrees C and were stable up to 50 degrees C. Enzyme activities of AFQ1 and AFS1 were highest at pH 4.0 to 6.5 and pH 3.3 to 5.0, respectively. Addition of 10 mg/ml arabinose to the reaction mixture decreased the AFS1 activity but hardly affected AFQ1. Both enzymes displayed broad substrate specificities; they released arabinose from branched arabinan, debranched arabinan, arabinoxylan, arabinogalactan, and arabino-oligosaccharides. AFS1 also showed low activity towards p-nitrophenyl-beta-D-xylopyranoside. An exo-arabinanase, which catalyzes the release of arabinobiose from linear arabinan at the nonreducing terminus, acted synergistically with both enzymes to produce L-arabinose from branched arabinan.

Amino Acid Sequence↗
PubMed2003

Intra-arterial injection of prolactin-releasing peptide elevates prolactin gene expression and plasma prolactin levels in rainbow trout.

Prolactin-releasing peptide (PrRP), recently isolated from the brain of mammals and teleosts, is a strong candidate for being a stimulatory hormone of pituitary prolactin secretion. The present study examined whether or not PrRP is capable of inducing prolactin gene expression and elevating plasma prolactin levels in vivo in cannulated rainbow trout. Following a single intra-arterial injection of chum salmon PrRP (40 nmol kg(-1)) through a dorsal aorta catheter, plasma prolactin levels increased (P<0.05) rapidly (2 min and 30 min), and prolactin mRNA levels were elevated (P<0.05) in pituitaries sampled 8 h after the injection. In contrast, plasma levels of somatolactin were decreased (P<0.05) and growth hormone and somatolactin mRNA levels were not significantly affected by PrRP. Thus, PrRP appears to be a potent prolactin secretagogue as well as prolactin transcription inducer in vivo in the rainbow trout.

Animals↗