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K Furuya

Publications and source records attributed to K Furuya.

At least 19 recordsLinked to original sources
PubMed2006

NF-kappaB regulates the stability and activity of p73 by inducing its proteolytic degradation through a ubiquitin-dependent proteasome pathway.

Nuclear factor kappa B (NF-kappaB), which exists as heterodimeric complexes composed of p50 and p65, has been shown to play an important role in cell survival processes. In the present study, we found for the first time that NF-kappaB has an ability to induce the ubiquitin-dependent proteasomal degradation of proapoptotic p73alpha. The activation of NF-kappaB in tumor necrosis factor alpha (TNF-alpha)-stimulated H1299 cells resulted in a significant reduction in the amounts of the endogenous p73alpha. Consistent with these results, TNF-alpha-mediated downregulation of p73alpha was observed in wild-type (WT) mouse embryonic fibroblasts (MEFs) but not in p65-deficient MEFs. Ectopic expression of NF-kappaB decreased a half-life of p73alpha by increasing its ubiquitination levels, and thereby inhibiting the transcriptional activity as well as proapoptotic function of p73alpha, whereas NF-kappaB had undetectable effects on p53. Immunoprecipitation experiments demonstrated that, under our experimental conditions, NF-kappaB does not bind to p73alpha in mammalian cultured cells. In contrast to WT p65, the COOH-terminal deletion mutant of p65 (p65DeltaC) failed to reduce the expression levels of p73alpha, suggesting that NF-kappaB-mediated proteolytic degradation of p73alpha requires the transcriptional activity of NF-kappaB. Taken together, our present results imply that NF-kappaB-mediated degradation of proapoptotic p73 is a novel inhibitory mechanism of p73 that regulates cell survival and death.

Animals↗
PubMed2004

Dynamic profile calculation of deposition resolution by high-energy electrons in electron-beam-induced deposition.

The effect of the accelerating voltage of incident electrons on the resolution of electron-beam-induced deposition was investigated by a dynamic Monte Carlo profile simulator which includes the electron scattering in the already grown deposit structure. By simulating the deposition at two different accelerating voltages of 20 and 200 kV with an idealistic zero-diameter incident probe on a bulk substrate, it was revealed that the smaller size structures were attainable by 200 keV than by 20 keV. The effect of the substrate was also argued by comparing the above results with the simulation results obtained for a point-like starting substrate. Surprisingly, the shapes of the deposits grown on bulk substrates were reproduced well by the simulations starting from point-like substrates indicating the small effect of the substrate on the shape of deposits.

Journal Article↗
PubMed2004

Synchrotron X-ray and ab initio studies of beta-Si3N4.

Almost absorption- and extinction-free single-crystal synchrotron X-ray diffraction data were measured at 150, 200 and 295 K for beta-Si3N4, silicon nitride, at a wavelength of 0.7 A. The true symmetry of this material has been the subject of minor controversy for several decades. No compelling evidence favouring the low-symmetry P6(3) model was identified in this study.

Journal Article↗
PubMed2004

Observation of nanometer-Xe clusters embedded in Al crystals.

The structure of Xe precipitates with sizes in several nanometers embedded in Al is known to be stable and its structure is well confirmed. But knowledge about the structure of Xe precipitates with nanometer sizes is very limited. There are difficulties in observing such small structures embedded in a crystalline matrix. An off-Bragg condition is used to observe diffraction patterns, dark-field, and high-resolution transmission electron microscopy images. The structure of Xe precipitates with sizes of about 2 nm and smaller is observed and confirmed. They are in an fcc structure and their orientation relationship with the Al matrix is similar to that of larger crystalline Xe precipitates or in an undefined structure. The lattice spacing or atomic distance in such nanometer-sized Xe precipitates is smaller than those of larger Xe precipitates embedded in Al matrix. There is a trend that as the size becomes smaller, the precipitates are more likely to have an undefined structure.

Aluminum↗
PubMed2004

Application of transmission electron microscopes to nanometre-sized fabrication by means of electron beam-induced deposition.

Electron beam-induced deposition was carried out using a scanning transmission electron microscope with a field emission gun to fabricate nanometre-sized structures. A small amount of a metal-organic gas was introduced near the substrate in the microscope chamber, and focused electron beams were irradiated. Two- and three-dimensional structures were fabricated by scanning the beam position. The minimum line width of the freestanding structures was 8 nm at a constant gas flux used. This line width of 8 nm is considered to be achieved by employing a high accelerating voltage, which leads to a small probe size, and the optimum scanning speed.

Imaging, Three-Dimensional↗
PubMed2004

Structure of nanometre-sized Xe particles embedded in Al crystals.

The structure and lattice parameters of Xe particles about 1 nm to about 6 nm in size embedded in Al were investigated with off-Bragg condition high-resolution transmission electron microscopy. An Xe particle about 1 nm in size had different structural properties from those 2-6 nm in sizes. Some 1-nm Xe particles had an face-centred cubic (f.c.c.) structure with the same orientation as the Al matrix, whereas others of the same size had a non-f.c.c. structure. The lattice parameters of a 1-nm f.c.c. Xe particle were about 20% smaller than the average value obtained from electron diffraction, i.e. the particle was compressed by about 80%. The lattice parameters of Xe crystals about 2 nm to about 6 nm in size were almost the same as those obtained from diffraction results. One of the reasons for the extra compression seen with a 1-nm Xe particle is the increase in pressure inside an Xe particle with decreasing particle size.

Journal Article↗
PubMed2003

Ordered quantization and the Ehrenfest time scale.

We propose a prescription to quantize classical monomials in terms of symmetric and ordered expansions of noncommuting operators of a bosonic theory. As a direct application of such quantization rules, we quantize a classically time evolved function O(q,p,t), and calculate its expectation value in coherent states. The result can be expressed in terms of the application of a classical operator that performs a Gaussian smoothing of the original function O evaluated at the center of the coherent state. This scheme produces a natural semiclassical expansion for the quantum expectation values at a short time scale. Moreover, since the classical Liouville evolution of a Gaussian probability density gives the same form for the classical statistical mean value, we can calculate the first-order correction in h entirely from the associated classical time evolved function. This allows us to write a general expression for the Ehrenfest time in terms of the departure of the centroid of the quantum distribution from the classical trajectory, provided we start with an initially coherent state for each subsystem. In order to illustrate this approach, we have calculated analytically the Ehrenfest time of a model with N-coupled nonlinear oscillators with nonlinearity of even order.

Journal Article↗
PubMed2003

In situ observation of the formation of Fe3O4 in Fe4N (001) due to electron irradiation.

gamma(')-Fe4N was subjected to electron irradiation with the dose rate of 6.8 x 10(23)e m(-2) s(-1) in a 400 kV transmission electron microscope. The first in situ observation of the formation of Fe3O4 (O) on Fe4N (gamma(')) with the orientation relationship of [100](O) parallel [100](gamma(')) and <001>(O) parallel <001>(gamma(')) has been made inside the microscope with the basic column vacuum of (5-6) x 10(-5) Pa. A mechanism is proposed involving the electron-stimulated dissociation of Fe-N chemical bonds, desorption of nitrogen from the surface, adsorption of oxygen to the surface, and the oxidization of excessive metallic iron on the surface.

Journal Article↗
PubMed2003

Layer-doubling method in ADF-STEM image simulation.

A layer-doubling method developed in LEED calculation is applied to the ADF-STEM image simulation. This approach makes it possible to simulate image intensities of systems having a repeated slab structure, such as embedded precipitates or defects, with a much higher efficiency because it does not require the diagonalization of repeated slabs. As a simple example of this method, channeling effects are calculated for a system with embedded crystalline displaced slabs for various different slab thicknesses.

Journal Article↗
PubMed2001

Whole genome sequencing of meticillin-resistant Staphylococcus aureus.

BACKGROUND: Staphylococcus aureus is one of the major causes of community-acquired and hospital-acquired infections. It produces numerous toxins including superantigens that cause unique disease entities such as toxic-shock syndrome and staphylococcal scarlet fever, and has acquired resistance to practically all antibiotics. Whole genome analysis is a necessary step towards future development of countermeasures against this organism. METHODS: Whole genome sequences of two related S aureus strains (N315 and Mu50) were determined by shot-gun random sequencing. N315 is a meticillin-resistant S aureus (MRSA) strain isolated in 1982, and Mu50 is an MRSA strain with vancomycin resistance isolated in 1997. The open reading frames were identified by use of GAMBLER and GLIMMER programs, and annotation of each was done with a BLAST homology search, motif analysis, and protein localisation prediction. FINDINGS: The Staphylococcus genome was composed of a complex mixture of genes, many of which seem to have been acquired by lateral gene transfer. Most of the antibiotic resistance genes were carried either by plasmids or by mobile genetic elements including a unique resistance island. Three classes of new pathogenicity islands were identified in the genome: a toxic-shock-syndrome toxin island family, exotoxin islands, and enterotoxin islands. In the latter two pathogenicity islands, clusters of exotoxin and enterotoxin genes were found closely linked with other gene clusters encoding putative pathogenic factors. The analysis also identified 70 candidates for new virulence factors. INTERPRETATION: The remarkable ability of S aureus to acquire useful genes from various organisms was revealed through the observation of genome complexity and evidence of lateral gene transfer. Repeated duplication of genes encoding superantigens explains why S aureus is capable of infecting humans of diverse genetic backgrounds, eliciting severe immune reactions. Investigation of many newly identified gene products, including the 70 putative virulence factors, will greatly improve our understanding of the biology of staphylococci and the processes of infectious diseases caused by S aureus.

Animals↗
PubMed2001

Lipopolysaccharide-induced ischemic tolerance is associated with increased levels of ceramide in brain and in plasma.

Intravenous administration of lipopolysaccharide (LPS) (0.9 mg/kg) has been shown to induce ischemic tolerance in spontaneously hypertensive rats (SHR). TNF-alpha is believed to play a crucial role in preconditioning as its inhibition with TNF-alpha-binding protein abolished tolerance. Our recent studies (Liu et al., Am. J. Physiol. 278 C144, 2000) have demonstrated that ceramide, a downstream messenger in TNF-alpha signaling, is a mediator of hypoxia-induced tolerance in neuronal cells. To test the hypothesis that ceramide contributes to LPS-induced tolerance in vivo, SHR were injected intravenously with either LPS or saline and the levels of ceramide in brain and in plasma were determined by reversed phase HPLC. LPS injection resulted in a significant increase of ceramide in plasma with a maximum at 24 h (8.32+/-1.14 pmol/microl (LPS) vs. 2.65+/-0.62 pmol/microl (saline)). LPS also induced ceramide upregulation in brain cortex, which started between 6 and 12 h and remained elevated up to 48 h after LPS injection. Fluorescent NBD-C6 ceramide was able to cross blood-brain barrier and was found in brain vessels, perivascular cells and in brain parenchyma 30 min after intravenous injection. These findings demonstrate that LPS preconditioning leads to elevation of ceramide in brain and plasma and, in conjunction with previous work, suggests that ceramide plays a role in LPS-induced protection against brain ischemic injury in vivo.

4-Chloro-7-nitrobenzofurazan↗
PubMed2001

Rho-associated kinase phosphorylates MARCKS in human neuronal cells.

Myristoylated alanine-rich C kinase substrate (MARCKS) is a filamentous actin bundling protein and has multiple sites for phosphorylation, by which the biochemical function is negatively regulated. However, the role of such phosphorylation in physiological functions, particularly in neuronal functions, is not well understood. Using a phosphorylation-site specific antibody, we detected the phosphorylation of MARCKS at Ser159 by various protein kinases. Rho-kinase, protein kinase A, and protein kinase C, could introduce (32)P into human recombinant MARCKS in vitro and the phosphorylation site was confirmed to be the Ser159 residue. In human neuronal teratoma (NT-2) cells, lysophosphatidic acid (LPA) induced MARCKS phosphorylation dose- and time-dependently. This phosphorylation was sensitive to Rho-kinase inhibitor HA1077. However, the phosphorylation induced by PDBu was lesser sensitive. In a skinned NTera-2 cell system, Ca(2+)-independent and GTP gamma S/ATP-stimulated phosphorylation at Ser159 was also sensitive to pre-treatment C3 toxin and HA1077. These findings suggest that the Ser159 residue of MARCKS is a target of LPA-stimulated Rho-kinase in neuronal cells.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed2001

Parathyroid hormone-induced bone resorption does not occur in the absence of osteopontin.

Osteopontin is an RGDS-containing protein that acts as a ligand for the alpha(v)beta(3) integrin, which is abundantly expressed in osteoclasts, cells responsible for bone resorption in osteopenic diseases such as osteoporosis and hyperparathyroidism. However, the role of osteopontin in the process of bone resorption has not yet been fully understood. Therefore, we investigated the direct function of osteopontin in bone resorption using an organ culture system. The amount of (45)Ca released from the osteopontin-deficient bones was not significantly different from the basal release from wild type bones. However, in contrast to the parathyroid hormone (PTH) enhancement of the (45)Ca release from wild type bones, PTH had no effect on (45)Ca release from organ cultures of osteopontin-deficient bones. Because PTH is located upstream of receptor activator of NF-kappaB ligand (RANKL), that directly promotes bone resorption, we also examined the effect of RANKL. Soluble RANKL with macrophage-colony stimulating factor enhanced (45)Ca release from the bones of wild type fetal mice but not from the bones of osteopontin-deficient mice. To obtain insight into the cellular mechanism underlying the phenomena observed in osteopontin-deficient bone, we investigated the number of tartrate-resistant acid phosphatase (TRAP)-positive cells in the bones subjected to PTH treatment in cultures. The number of TRAP-positive cells was increased significantly by PTH in wild type bone; however, no such PTH-induced increase in TRAP-positive cells was observed in osteopontin-deficient bones. These results indicate that the absence of osteopontin suppressed PTH-induced increase in bone resorption via preventing the increase in the number of osteoclasts in the local milieu of bone.

Animals↗
PubMed2001

Synergistic effects of ATP on oxytocin-induced intracellular Ca2+ response in mouse mammary myoepithelial cells.

An increase in intracellular Ca2+ ([Ca2+]i) is essential for mammary myoepithelial cells to contract, leading to milk ejection during lactation. In this study, the intracellular signaling leading to the increase in [Ca2+]i in cultured myoepithelial cells from mouse lactating mammary glands was investigated using fura-2 fluorescence ratiometry. [Ca2+]i increased in cultured myoepithelial cells in response to either oxytocin (1 nM) or ATP (10 microM), and the cells then contracted. These [Ca2+]i responses were diminished by treatment with an inhibitor of phospholipase C (> or = 1 microM U73122). Intracellular application of inositol 1,4,5-trisphosphate (IP3: 10 or 100 microM) increased [Ca2+]i. Pretreatment with pertussis toxin (PTX: 0.1 or 1 microgram/ml) inhibited the [Ca2+]i response to ATP, but had less of an effect on the response to oxytocin. These results indicate that oxytocin and purinergic receptors are coupled to PTX-insensitive and PTX-sensitive G proteins, respectively, and that their activation leads to the increase in [Ca2+]i through the release of Ca2+ from IP3-sensitive intracellular stores via the inositol-phospholipid signaling pathway. Furthermore, we found that the [Ca2+]i responses to oxytocin at physiological doses (0.01-0.1 nM) were augmented in the presence of a sub-responsive dose of ATP (1 microM). The activation of purinergic receptors may facilitate myoepithelial cell contraction in milk-ejection responses.

Adenosine Triphosphate↗
PubMed2001

Molecular characterization of Cryptosporidium isolates obtained from human and bovine infections in Japan.

Cryptosporidium oocysts, morphologically identified as Cryptosporidium parvum, were isolated from 22 human and 14 bovine cases in Japan, and were genotyped by means of a PCR/RFLP analysis of the polythreonine gene. DNA profiles of human isolates gave three distinct genotypes, namely an anthroponotic genotype 1, zoonotic genotype 2 and a new genotype. Isolates from bovine samples gave zoonotic genotype 2. The unusual genotype of Cryptosporidium was isolated from the feces of three immunologically healthy adults, and was further characterized by the sequence analysis of the 18S rRNA gene. The third genotype was identified as Crypto sporidium meleagridis, demonstrating that C. meleagridis, which occurs worldwide, has the potential to infect humans regardless of their immunological condition.

Animals↗
PubMed2001

Isolation and identification of a diuretic hormone from Zootermopsis nevadensis.

A diuretic hormone (DH) was isolated from extracts of heads of Zootermopsis nevadensis, a dampwood termite. The peptide has 46 residues, M(r) = 5,328.2 Da, with the sequence TGAVPSLSIVNPLDVLRQRLLLEIARRRMRQSQDQIQANREMLQTI-NH(2,) showing it to be a CRF-related DH. This peptide increases cyclic AMP production in Malpighian tubules of Manduca sexta. We detected another factor in the head extracts which behaved as a more basic peptide on ion exchange chromatography. The latter factor also stimulated cyclic AMP production in the bioassay, but two large scale attempts to isolate this peptide were unsuccessful. We believe the second peptide is acid labile.

Amino Acid Sequence↗