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K Nakamura

Publications and source records attributed to K Nakamura.

At least 37 records · Page 2Linked to original sources
PubMed2006

Improved search for nu(mu) --> nu(e) oscillation in a long-baseline accelerator experiment.

We performed an improved search for nu(mu) --> nu(e) oscillation with the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment, using the full data sample of 9.2 x 10(19) protons on target. No evidence for a nu(e) appearance signal was found, and we set bounds on the nu(mu) --> nu(e) oscillation parameters. At Deltam(2)=2.8 x 10(-3) eV(2), the best-fit value of the K2Knu(mu) disappearance analysis, we set an upper limit of sin(2)2theta(mue) < 0.13 at a 90% confidence level.

Journal Article↗
PubMed2006

Heating by an electron Bernstein wave in a spherical tokamak plasma via mode conversion.

The first successful high power heating of a high dielectric constant spherical tokamak plasma by an electron Bernstein wave (EBW) is reported. An EBW was excited by mode conversion (MC) of an mode cyclotron wave injected from the low magnetic field side of the TST-2 spherical tokamak. Evidence of electron heating was observed as increases in the stored energy and soft x-ray emission. The increased emission was concentrated in the plasma core region. A heating efficiency of over 50% was achieved, when the density gradient in the MC region was sufficiently steep.

Journal Article↗
PubMed2006

Spreds, inhibitors of the Ras/ERK signal transduction, are dysregulated in human hepatocellular carcinoma and linked to the malignant phenotype of tumors.

Aberrant activation of the Ras/Raf-1/extracellular-regulated kinase (ERK) pathway has been shown to be involved in the progression of human hepatocellular carcinoma (HCC). However, the mechanism of dysregulation of ERK activation is poorly understood. Recently, we identified Sprouty-related protein with Ena/vasodilator-stimulated phosphoprotein homology-1 domain (Spred) as a physiological inhibitor of the Ras/Raf-1/ERK pathway. In this study, we found that the expression levels of Spred-1 and -2 in human HCC tissue were frequently decreased, comparing with those in adjacent non-tumorous tissue. Moreover, Spred expression levels in HCC tissue were inversely correlated with the incidence of tumor invasion and metastasis. Forced expression of Spred-1 inhibited HCC cell proliferation in vitro and in vivo, which was associated with reduced ERK activation. Spred-1 overexpression also reduced the secretion of matrix metalloproteinase-9 (MMP-9) and MMP-2, which play important roles in tumor invasion and metastasis. In addition, Spred-1 inhibited growth factor-mediated HCC cell motility. These data indicate that the reduction of Spred expression in HCC is one of the causes of the acquisition of malignant features. Thus, Spred could be not only a novel prognostic factor but also a new therapeutic target for human HCC.

Adaptor Proteins, Signal Transducing↗
PubMed2006

Search for the invisible decay of neutrons with KamLAND.

The Kamioka Liquid scintillator Anti-Neutrino Detector is used in a search for single neutron or two-neutron intranuclear disappearance that would produce holes in the -shell energy level of (12)C nuclei. Such holes could be created as a result of nucleon decay into invisible modes (inv), e.g., n--> 3v or nn--> 2v. The deexcitation of the corresponding daughter nucleus results in a sequence of space and time-correlated events observable in the liquid scintillator detector. We report on new limits for one- and two-neutron disappearance: tau(n--> inv) > 5.8 x 10(29) years and tau (nn--> inv) > 1.4 x 10(30) years at 90% C.L. These results represent an improvement of factors of approximately 3 and >10(4) and over previous experiments.

Journal Article↗
PubMed2006

Prognostic factors in node-positive patients with stage IB-IIB cervical cancer treated by radical hysterectomy and pelvic lymphadenectomy.

OBJECTIVE: The purpose of the present study was to identify prognostic factors in surgically treated patients with stage IB-IIB cervical cancers, who also presented with positive pelvic nodes. METHOD: The patient population consisted of 68 individuals presenting with stage IB-IIB cervical cancers and with histologically proven pelvic lymph nodes. RESULT: We found no association between the type of adjuvant therapy and patient outcome. Multivariate analysis revealed that non-squamous histology was an independent prognostic factor for disease-free and overall survival rates. In squamous cell carcinomas, the bilateral nature of the positive nodes was found to be a significant factor for disease-free survival rates. In non-squamous cell carcinomas, positive nodes of more than 2 cm in size were found to be a significant factor for disease-free survival rates. CONCLUSION: Non-squamous histology was an independent prognostic factor and chemoradiotherapy did not improve the survival outcomes of the patients in this study population.

Adenocarcinoma↗
PubMed2006

Staggered ladder spectra.

We exactly solve a Fokker-Planck equation by determining its eigenvalues and eigenfunctions: we construct nonlinear second-order differential operators which act as raising and lowering operators, generating ladder spectra for the odd- and even-parity states. The ladders are staggered: the odd-even separation differs from even-odd. The Fokker-Planck equation corresponds, in the limit of weak damping, to a generalized Ornstein-Uhlenbeck process where the random force depends upon position as well as time. The process describes damped stochastic acceleration, and exhibits anomalous diffusion at short times and a stationary non-Maxwellian momentum distribution.

Journal Article↗
PubMed2006

Writing 40 nm marks by using a beaked metallic plate near-field optical probe.

We have developed a near-field optical probe that uses a triangular metallic plate with a three-dimensionally tapered apex as a light source for thermally assisted magnetic recording. Numerical analysis using a finite-element method shows that the size of the optical spot generated at the apex is 15 nm x 20 nm, and the efficiency (defined as the ratio between the power of the optical near field at the surface of the recording medium and that of the incident light) is 15% when the incident light is focused by a lens with a numerical aperture of 0.8. The metallic plate was fabricated on the surface of a quartz slider and used for writing marks on a phase change recording medium. The marks were observed with a scanning electron microscope, and we confirmed that marks with a diameter of 40 nm were successfully written on the medium.

Journal Article↗
PubMed2006

An increase in the serum amylase level in patients after peroral double-balloon enteroscopy: an association with the development of pancreatitis.

BACKGROUND AND STUDY AIMS: Double-balloon enteroscopy (DBE) is a novel technique that allows the enteroscope to be inserted deep into the small intestine. The procedure has been thought to be safe, but cases of acute pancreatitis after peroral DBE have recently been observed. The aim of this study was to confirm the occurrence of hyperamylasemia after peroral DBE. PATIENTS AND METHODS: Peroral DBE was carried out in 13 patients from July 2005 to February 2006. Blood samples were taken before and 3 h after the procedure, and serum pancreatic amylase levels were measured. The patients were also evaluated for pancreatic-type abdominal pain after the procedure. Hyperamylasemia after peroral DBE was defined as an elevation of the serum pancreatic amylase level to more than the upper normal limit and twice the level before the procedure. Pancreatitis was diagnosed on the basis of both pancreatic-type abdominal pain and hyperamylasemia. RESULTS: Hyperamylasemia after peroral DBE occurred in six patients (46.2 %). One of the six patients with hyperamylasemia had pancreatic-type abdominal pain after the procedure and developed acute pancreatitis. The average procedure time was 105 min (range 65 - 155 min) in the patients with hyperamylasemia, and did not significantly differ from that in the group without hyperamylasemia (99 min). CONCLUSIONS: Hyperamylasemia after peroral DBE occurs frequently and may be associated with development of pancreatitis.

Adolescent↗
PubMed2006

Male New Zealand Black/KN mice: a novel model for autoimmune-induced permanent alopecia?

BACKGROUND: Irreversible, permanent and scarring alopecia is associated with several autoimmune diseases, including all autoimmune connective tissue disorders. The pathogenesis of autoimmune-induced permanent alopecia (APA) is still poorly understood, and instructive, simple mouse models for the study of APA are needed urgently. During the course of our studies in a well-established mouse model for chronic rheumatoid arthritis, the New Zealand Black/KN (NZB/KN) mouse, we noticed that ageing male NZB/KN mice developed spontaneous APA. OBJECTIVES: To study whether alopecia seen in ageing male NZB/KN mice displays key features of human APA and may, thus, be a useful new mouse model for clinically relevant APA research. METHODS: NZB/KN, the F1 hybrid of NZW/N Slc x NZB/KN (W/BKN F1), the F1 hybrid of NZB/KN x NZW/N Slc (BKN/W F1), and the F2 hybrid of W/BKN F1 x W/BKN F1 mice were employed in this study, in order to check which strain carries the highest risk of alopecia development. Besides routine histology, CD3, CD4 and CD8 expression as well as immunoglobulin (Ig) G and IgM deposition in hair follicles were investigated by immunohistology/immunofluorescence. Mast cell distribution/degranulation and Ki-67 (proliferation)/TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling) (apoptosis) positive cells were also analysed. RESULTS: Only F2 male NZB/KN mice were prone to develop alopecia, suggesting that Y chromosome-associated gene(s) are involved in the pathogenesis of APA, which incidence rises with increasing age. The lesional alopecia skin in 12-month-old male NZB/KN mice showed a sharp decline in hair follicle density, thus meeting a key criterion of permanent alopecia. Both macroscopically and histologically, the alopecia seen in these mice resembled in many respects different stages of clinical APA, such as alopecia associated with chronic discoid lupus erythematosus (DLE) in humans. Lesional APA hair follicles in mice displayed intrafollicular and perifollicular mononuclear cell infiltrates, as well as an increased number of activated (degranulated) perifollicular mast cells. In the fully developed lesion, many CD4+ cells were seen in perifollicular locations, including the epithelial stem cell region (bulge), and also contained a few CD8+ T cells. IgM deposits were found in the follicular basement membrane zone (BMZ). Both in the bulge and the hair matrix region of the affected anagen hair follicles, there were signs of massive keratinocyte apoptosis. CONCLUSIONS: Our currently available data suggest that male but not female NZB/KN mice may indeed represent a suitable mouse model for APA, with some similarities to the permanent alopecia seen in human DLE patients, although additional and confirmatory investigations are needed before this mouse strain can be accepted as a murine equivalent of APA in humans.

Aging↗
PubMed2006

Analysis of GM-CSF gene polymorphisms (3606T/C and 3928C/T) in Japanese patients with atopic dermatitis.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is thought to play an important role in the pathogenesis of atopic dermatitis. To examine whether GM-CSF single nucleotide polymorphisms (SNPs) are associated with susceptibility to atopic dermatitis, we investigated the genotype and allele frequencies of the SNPs 3606T/C and 3928C/T of the GM-CSF gene in 181 Japanese patients with atopic dermatitis and 100 controls, using a PCR restriction fragment length polymorphism method. A strong linkage disequilibrium existed between the polymorphisms 3606 and 3928, suggesting two common GM-CSF haplotypes, 3606*T-3928*C and 3606*C-3928*T. However, there was no significant difference in genotype or allele frequencies between patients with atopic dermatitis and controls for either of the two polymorphisms, thus GM-CSF SNPs do not appear to be associated with susceptibility to atopic dermatitis in Japanese patients. A large-scale study is necessary to confirm these findings.

Adolescent↗
PubMed2006

Pathology of fatal highly pathogenic H5N1 avian influenza virus infection in large-billed crows (Corvus macrorhynchos) during the 2004 outbreak in Japan.

Highly pathogenic H5N1 avian influenza viruses were isolated in 9 large-billed crows that died in Kyoto and Osaka prefectures in Japan from March to April in 2004. We studied 3 of the 9 crows using standard histologic methods, immunohistochemistry, and virus isolation. The most prominent lesions were gross patchy areas of reddish discoloration in the pancreas. The consistent histologic lesions included severe multifocal necrotizing pancreatitis, focal degeneration and necrosis of neuron and glial cells in the central nervous system, and focal degeneration of cardiac myocytes. All of these tissues contained immunohistochemically positive influenza viral antigens. The virus was isolated from the brain, lung, heart, liver, spleen, and kidney of the crows examined. Thus we concluded that highly pathogenic avian influenza virus was associated with clinical disease, severe pathologic changes, and death in the 3 crows.

Animals↗
PubMed2006

Risk factor analysis for ascending aorta and aortic arch repair using selective cerebral perfusion with open technique: role of open-stent graft placement.

AIM: The present study was designed to identify risk factors that may induce adverse outcome defined as permanent neurological dysfunction and mortality after aortic arch surgery using selective cerebral perfusion by logistic regression analysis and to reveal the role of open stent-graft placement. METHODS: One hundred and nineteen consecutive patients underwent ascending aorta and/or aortic arch operation with open technique between 1995 and 2005 were examined. Ascending aorta and/or hemiarch was replaced in 28 patients, total arch in 75 patients, and proximal or distal aortic arch replacement in 16 patients. Open stent-graft placement was used in 25 patients. RESULTS: The in-hospital mortality rate was 9.2%. Permanent neurological dysfunction occurred in 10 patients (8.4%). Thoracotomy (P=0.0331) and cardiopulmonary bypass time (P=0.0238) were significant risk factors for permanent neurological dysfunction. Preoperative shock (P=0.0266) was significant independent risk factor for mortality. Emergent operation (P=0.0454), thoracotomy (P=0.0232), and cardiopulmonary bypass time (P=0.0379) were significant independent risk factors for adverse outcome. The duration of selective cerebral perfusion was not associated with adverse outcome. Open stent-graft placement has no need of thoracotomy for aneurysm extending descending thoracic aorta and time variables concerning the operation were significantly shorter in the patients with open stent-graft placement than in patients with standard operation for total arch replacement. RESULTS: Thoracotomy was significant risk factor for adverse outcome after aortic arch repair using selective cerebral perfusion. Total arch replacement with open stent-graft placement can avoid the need of thoracotomy and reduce time variables concerning the operation to improve the surgical

Adult↗
PubMed2005

Search for coherent charged pion production in neutrino-carbon interactions.

We report the result from a search for charged-current coherent pion production induced by muon neutrinos with a mean energy of 1.3 GeV. The data are collected with a fully active scintillator detector in the K2K long-baseline neutrino oscillation experiment. No evidence for coherent pion production is observed, and an upper limit of is set on the cross section ratio of coherent pion production to the total charged-current interaction at 90% confidence level. This is the first experimental limit for coherent charged pion production in the energy region of a few GeV.

Journal Article↗
PubMed2005

Differential susceptibility of equine and mouse brain microvascular endothelial cells to equine herpesvirus 1 infection.

Equine herpesvirus 1 (EHV-1) shows endotheliotropism in the central nervous system (CNS) of infected horses. However, infection of endothelial cells has not been observed in the CNS of infected mice. To explore the basis for this difference in endotheliotropism, we compared the susceptibility of equine brain microvascular endothelial cells (EBMECs) and mouse brain microvascular endothelial cells (MBMECs) to EHV-1 infection. The kinetics of viral growth in EBMECs was typical of a fully productive infection whereas viral infection in MBMECs seemed to be nonproductive. Immunofluorescence microscopy using anti-EHV-1 polyclonal antibody demonstrated viral antigen in infected EBMECs, but not infected MBMECs. EHV-1 immediate early (IE), early (ICP0), and late (gB, gD and gK) transcripts were expressed in infected EBMECs. However, none of these genes was detected in infected MBMECs by reverse transcription-polymerase chain reaction. Electron microscopic examination at the stage of viral entry showed that viral particles were present within uncoated vesicles in the cytoplasm of EBMECs, but absent from those of MBMECs. These results suggest that viral entry is an important determinant of the susceptibility of EBMECs and MBMECs to EHV-1 infection.

Animals↗
PubMed2005

A new method for measurement of bone deformation by echo tracking.

No method has been available to noninvasively detect bone deformation or strain under loading in vivo. We focused on ultrasonic measurement of the displacement at a certain point on a bone using the echo-tracking method (ET). To develop a method that can noninvasively detect bone deformation in vivo, a preliminary investigation was performed. We investigated the accuracy of measuring displacement with our echo tracking system by using a flat metal panel and found that the method could measure displacement with a precision of a few microns. A three-point bending test of a porcine tibia with both ends fully constrained was performed to measure bone surface displacement, and simultaneous measurement of the surface strain was done using two strain gauges. The correlation between the displacement measured by ET and the strain gauge readings was completely linear (r=0.999), showing that the method could precisely detect bone deformation. The loads versus displacement curves obtained with cyclic loading were typical hysteresis loops that showed viscoelastic properties of the measured bone. We also improved a multi-ET system capable of simultaneously tracking multiple points to detect deformation of the bone surface. Measurement by this echo tracking system was also compared with strain gauge readings during a three point bending test with both ends of the tibia supported. The linearity of both methods was very high (r=0.998). Our ET method might have considerable potential for noninvasive measurement of bone viscoelasticity and plasticity.

Aluminum↗