Biomedical subjects

H Yamaguchi

Publications and source records attributed to H Yamaguchi.

At least 73 records · Page 4Linked to original sources

PubMed2001

Local density of states in zero-dimensional semiconductor structures.

The local density of states (LDOS) within tetrahedral InAs structures, formed at the surface of InAs/GaAs(111)A, has been characterized using low-temperature scanning tunneling microscopy. The LDOS of the lowest four zero-dimensional (0D) discrete levels have been imaged in structures with a comparable size to the electron wavelength. The LDOS inside the structures is observed to be higher than that of the surrounding area at intervals of the level separation. This feature indicates the singularity of the LDOS close to the 0D resonant levels.

Journal Article↗

PubMed2001

A comparison of myocardial function after primary cardiac and primary asphyxial cardiac arrest.

Although myocardial dysfunction after resuscitation from ventricular fibrillation (VF) has been extensively investigated, less is known of the function of the myocardium after asphyxial cardiac arrest. The present experimental study was designed to compare postresuscitation left ventricular (LV) function after cardiac arrest caused by asphyxia with that of cardiac arrest induced by dysrhythmia. Four groups of Sprague-Dawley rats, which included eight animals in each group, were investigated. In the first two groups, cardiac arrest followed asphyxia produced by neuromuscular blockade with and without airway obstruction. In a third group, cardiac arrest was induced by electrical fibrillation of the ventricle. The fourth group represented animals in which the duration of asphyxial cardiac arrest was maintained for a time interval corresponding to that of the VF group. The fourth group received approximately the same number of electrical shocks as the third (VF) group. All animals were successfully resuscitated with precordial compression and mechanical ventilation. Postresuscitation measurements, including cardiac output, LV end-diastolic pressure (LVEDP), rate of pressure rise at LV pressure of 40 mm Hg (LV dP/dt40), and negative LV dP/dt, demonstrated decreased myocardial function in each group. No differences in cardiac function were observed between the animals with primary respiratory arrest whether or not the airway was obstructed. However, disproportionate and consistently greater impairment in myocardial function followed primary cardiac arrest due to VF when compared with equal duration of asphyxial cardiac arrest. We conclude that in this healthy animal model, asphyxial cardiac arrest resulted in significantly lesser impairment of postresuscitation myocardial function when compared with cardiac arrest caused by VF.

Animals↗

PubMed2001

DNA microarray analysis of Bacillus subtilis DegU, ComA and PhoP regulons: an approach to comprehensive analysis of B.subtilis two-component regulatory systems.

We have analyzed the regulons of the Bacillus subtilis two-component regulators DegU, ComA and PhoP by using whole genome DNA microarrays. For these experiments we took the strategy that the response regulator genes were cloned downstream of an isopropyl-beta-D-thiogalactopyranoside-inducible promoter on a multicopy plasmid and expressed in disruptants of the cognate sensor kinase genes, degS, comP and phoR, respectively. The feasibility of this experimental design to detect target genes was demonstrated by the following two results. First, expression of lacZ fusions of aprE, srfA and ydhF, the target genes of DegU, ComA and PhoP, respectively, was stimulated in their cognate sensor kinase-deficient mutants upon overproduction of the regulators. Secondly, by microarray analysis most of the known target genes for the regulators were detected and, where unknown genes were found, the regulator dependency of several of them was demonstrated. As the mutants used were deficient in the kinase genes, these results show that target candidates can be detected without signal transduction. Using this experimental design, we identified many genes whose dependency on the regulators for expression had not been known. These results suggest the applicability of the strategy to the comprehensive transcription analysis of the B.subtilis two-component systems.

Bacillus subtilis↗

PubMed2001

Expression of multiple cancer-testis antigen genes in gastrointestinal and breast carcinomas.

Cancer-testis antigens (CTAs) such as MAGE are selectively expressed in various types of human neoplasms but not in normal tissues other than testis. This characteristic feature of CTAs makes them promising antigens for cancer-specific immunotherapy. A critical requirement for this therapy is identification of promising antigens. In this study, we investigated the expression of 6 genes recently identified by serological analysis of antigens by recombinant expression (SEREX) libraries: NY-ESO-1, LAGE-1, SCP-1, SSX-1, SSX-2, and SSX-4, in many surgical samples of gastrointestinal and breast carcinomas using reverse transcription-polymerase chain reaction. We found relatively high expression of SCP-1 (23.5%) and SSX-4 (20.6%) in gastric carcinoma, LAGE-1 (39.1%) and NY-ESO-1 (23.9%) in oesophageal carcinoma, and SCP-1 (34.1%) in breast carcinoma. We also found frequent synchronous expression with MAGE, including LAGE-1 (46.2%) in oesophageal carcinoma, SSX-4 (46.7%) in gastric carcinoma, and SCP-1 (38.3%) in breast carcinoma. Immunohistochemical analysis of the tumour samples expressing both MAGE-4 and NY-ESO-1 genes demonstrated differences in distribution between MAGE-4 and NY-ESO-1 in serial sections. We concluded that NY-ESO-1, LAGE-1, SCP-1 and SSX-4 genes may be promising candidates for cancer-specific immunotherapy in addition to MAGE, and that polyvalent cancer vaccines may be useful in cases of heterogeneous expressions of CTA genes in gastrointestinal and breast carcinomas.

Antigens, Neoplasm↗

PubMed2001

Sub-ppm laser spectroscopy of antiprotonic helium and a CPT-violation limit on the antiprotonic charge and mass.

Six laser-resonant transitions have been detected in metastable antiprotonic helium atoms produced at the CERN Antiproton Decelerator. They include UV transitions from the last metastable states in the v = n-l-1 = 0 and 1 cascades. Zero-density frequencies were obtained from measured pressure shifts with fractional precisions between 1.3 x 10(-7) and 1.6 x 10(-6). By comparing these with QED calculations and the antiproton cyclotron frequency, we deduce that the antiproton and proton charges and masses agree to within 6 x 10(-8) with a confidence level of 90%.

Journal Article↗

PubMed2001

Limbic encephalitis associated with recurrent thymoma: a postmortem study.

The authors report an autopsied patient with limbic encephalitis and recurrent thymoma. The immunohistochemical study showed selective depositions of immunoglobulin G on the neurons in the limbic system and the tumor cells of the recurrent thymoma. The immunoblotting study detected two types of antibodies that react with the human brain, rat brain, and rat thymus.

Brain↗

PubMed2001

Angular position of nodes in the superconducting gap of quasi-2D heavy-fermion superconductor CeCoIn5.

The thermal conductivity of the heavy-fermion superconductor CeCoIn5 has been studied in a magnetic field rotating within the 2D planes. A clear fourfold symmetry of the thermal conductivity which is characteristic of a superconducting gap with nodes along the ( +/- pi,+/- pi) directions is resolved. The thermal conductivity measurement also reveals a first-order transition at H(c2), indicating a Pauli limited superconducting state. These results indicate that the symmetry most likely belongs to d(x(2)-y(2)), implying that the anisotropic antiferromagnetic fluctuation is relevant to the superconductivity.

Journal Article↗

PubMed2001

Imaging of Friedel oscillation patterns of two-dimensionally accumulated electrons at epitaxially grown InAs(111) A surfaces.

The local density of states (LDOS) at the epitaxially grown InAs surface on a GaAs(111) A substrate were characterized using low-temperature scanning tunneling microscopy. Using dI/dV signal mapping, LDOS standing waves were clearly imaged at point defects and within nanostructures. Measurement of the wavelength as a function of bias voltage showed a nonparabolic dispersion relation for the conduction band. The observed wave features originate from the Friedel oscillations of the two-dimensional electron gas in the semiconductor surface accumulation layer.

Journal Article↗

PubMed2001

Requirement of the basic region of N-WASP/WAVE2 for actin-based motility.

WASP family proteins activate nucleation by the Arp2/3 complex, inducing rapid actin polymerization in vitro. Although the C-terminal portion of WASP family proteins (VCA) activates nucleation by the Arp2/3 complex in pure systems, we find that this fragment lacks activity in cell extracts. Thus, polystyrene beads coated with VCA did not move in brain cytosol, while beads coated with N-WASP or WAVE2 did move. The basic clusters between the WH1 domain and the CRIB domain of N-WASP were critical for movement since beads coated with N-WASP or WAVE2 constructs missing the basic clusters (Delta basic) also did not move. Furthermore, VCA and N-WASP/WAVE2 Delta basic constructs were much less able than wild-type N-WASP and WAVE2 to induce actin polymerization in cytosol. All of the proteins, with or without the basic domain, were potent activators of nucleation by purified Arp2/3 complex.

Actins↗

PubMed2001

Molecular cloning and characterization of Bif-1. A novel Src homology 3 domain-containing protein that associates with Bax.

Bax is a proapoptotic member of the Bcl-2 protein family that commits the cell to undergo programmed cell death in response to apoptotic stimuli. To gain further insights into Bax mechanisms, we have identified a novel Bax-binding protein, termed Bif-1, by using a yeast two-hybrid cloning technique. Bif-1 is an evolutionarily conserved cytoplasmic protein that contains a predicted Src homology 3 (SH3) domain located near its C terminus but shares no significant homology with members of the Bcl-2 family. A Northern blot analysis indicates that Bif-1 is expressed in most tissues with abundant expression in heart and skeletal muscle. Bif-1 is capable of interacting with Bax as demonstrated by yeast two-hybrid, coimmunoprecipitation, and immunofluorescence studies. Induction of apoptosis in murine pre-B hematopoietic cells FL5.12 by interleukin-3 withdrawal results in increased association of Bax with Bif-1, which is accompanied by a conformational change in the Bax protein. Overexpression of Bif-1 promotes Bax conformational change, caspase activation, and apoptotic cell death in FL5.12 cells following interleukin-3 deprivation. Bif-1 thus represents a new type of regulator of Bax-mediated signaling pathways for apoptosis.

Adaptor Proteins, Signal Transducing↗

PubMed2001

Superconducting gap structure of spin-triplet superconductor Sr2RuO4 studied by thermal conductivity.

To clarify the superconducting gap structure of the spin-triplet superconductor Sr2RuO4, the in-plane thermal conductivity has been measured as a function of relative orientations of the thermal flow, the crystal axes, and a magnetic field rotating within the 2D RuO2 planes. The in-plane variation of the thermal conductivity is incompatible with any model with line nodes vertical to the 2D planes and indicates the existence of horizontal nodes. These results place strong constraints on models that attempt to explain the mechanism of the triplet superconductivity.

Journal Article↗

PubMed2001

XAFS study on gallium ions implanted in silicon carbide.

Local structure of gallium ions implanted in silicon carbide has been investigated using extended X-ray absorption fine structure on the Ga K-edge. The crystallinity of the implantation layer is compared in the samples prepared under several different conditions of implantation temperature and post-implantation annealing. It is found that significant damage is induced by the implantation at room temperature, but the crystallinity recovers by the subsequent annealing at high temperature at 1600 degrees C. On the other hand, the best crystallinity is obtained by the implantation at high temperature of 500 degrees C. but the annealing results in degrading the crystallinity. This indicates an influence of the post-implantation annealing at high temperature on the crystallinity in atomic level, which relates to the secondary defects in lattice observed by electron microscope.

Journal Article↗

PubMed2001

Enhancer regions of ovine interferon-tau gene that confer PMA response or cell type specific transcription.

Interferon-tau (IFNtau), produced by the trophectoderm of peri-implantation conceptuses in ruminant ungulates, attenuates the uterine production of a luteolytic factor, prostaglandin F(2alpha), resulting in the maintenance of corpus luteum function. However, molecular mechanisms regulating the temporal/spatial expression of IFNtau gene are not clearly understood. The 5'-upstream region of the sheep IFNtau (oIFNtau) gene was examined for its transcriptional regulation in two different cell types; JEG3 cells supported the transactivation of oIFNtau-reporter construct, but HeLa cells did not. In a heterologous SV40 enhancer-oIFNtau promoter or oIFNtau enhancer-SV40 promoter systems, elements required for such cell specific transactivation were localized between -654 and -555 bases, the enhancer, but not the basal promoter region of the oIFNtau gene. In these combinations, high degrees of transactivation were observed in JEG3 cells and the activity was further enhanced by the addition of phorbol 12-myristate 13-acetate (PMA), while those responses were absent in HeLa cells. To identify nucleotide sequences responsible for cell specific expression, transient transfection studies with sequential point mutations in the enhancer elements were executed. Transactivation of oIFNtau enhancer-reporter constructs was primarily regulated by three regions containing AP-1 site, GATA like sequence and site(s) unidentified. In gel mobility shift assays (GMSAs), the AP-1 site located in the enhancer region was recognized by nuclear extracts from both cell types. However, one of the GMSA probes containing GATA-like sequence exhibited different DNA-protein complex patterns in JEG3 and HeLa cells. Observations, in which the same upstream sequence behaved differently due possibly to kinds of nuclear factors available in these cell lines, suggest that such a sequence may be involved in cell specific transactivation of the oIFNtau gene. Furthermore, the same enhancer sequences were also recognized by nuclear extracts from sheep trophoblasts, suggesting that the enhancer sequences between -654 and -555 bases of oIFNtau gene may be functioning in vivo.

Animals↗

PubMed2001

Combined transcriptome and proteome analysis as a powerful approach to study genes under glucose repression in Bacillus subtilis.

We used 2D protein gel electrophoresis and DNA microarray technologies to systematically analyze genes under glucose repression in B:acillus subtilis. In particular, we focused on genes expressed after the shift from glycolytic to gluconeogenic at the middle logarithmic phase of growth in a nutrient sporulation medium, which remained repressed by the addition of glucose. We also examined whether or not glucose repression of these genes was mediated by CcpA, the catabolite control protein of this bacterium. The wild-type and ccpA1 cells were grown with and without glucose, and their proteomes and transcriptomes were compared. 2D gel electrophoresis allowed us to identify 11 proteins, the synthesis of which was under glucose repression. Of these proteins, the synthesis of four (IolA, I, S and PckA) was under CcpA-independent control. Microarray analysis enabled us to detect 66 glucose-repressive genes, 22 of which (glmS, acoA, C, yisS, speD, gapB, pckA, yvdR, yxeF, iolA, B, C, D, E, F, G, H, I, J, R, S and yxbF ) were at least partially under CcpA-independent control. Furthermore, we found that CcpA and IolR, a repressor of the iol divergon, were involved in the glucose repression of the synthesis of inositol dehydrogenase encoded by iolG included in the above list. The CcpA-independent glucose repression of the iol genes appeared to be explained by inducer exclusion.

Amino Acid Sequence↗

PubMed2001

Establishment of a cell line with AML1-MTG8, TP53, and TP73 abnormalities from acute myelogenous leukemia.

Gene alterations accumulate during the progression of acute myelogenous leukemia (AML) to a malignant clone. Here, a new myeloid cell line, designated YSK-21, with the balanced t(8;21)(q22;q22) and the unbalanced der(1)t(1;17)(p36;q21), was established. YSK-21 grows well in a medium containing recombinant human granulocyte colony-stimulating factor (rhG-CSF), granulocyte-macrophage colony-stimulating factor (rhGM-CSF), or interleukin-3 (rhIL-3). Molecular analysis using the reverse transcriptase-polymerase chain reaction (RT-PCR) and fluorescence in situ hybridization (FISH) revealed that t(8;21)(q22;q22) resulted in an AML1-MTG8 fusion transcript. FISH and spectral karyotyping (SKY) in conjunction with G-banding analysis revealed a der(1)t(1;17)(p36;q21) chromosomal translocation, which appeared in the clone developed from the original leukemic cells. Molecular analysis of the TP73 gene on 1p36 and the TP53 gene revealed a deletion of one-allele in TP73 with partial demethylation of another allele in the initial clone of YSK, and a point mutation consisting of an A-->T substitution in codon 288 of the TP53 gene in the developed clone of YSK-21. YSK-21 cells, expressing aberrant AML1-MTG8, TP53, and TP73 protein molecules, may be useful for elucidating the pathophysiology of these aberrant proteins and for studying the der(1)t(1;17)(p36;q21) chromosomal translocation.

Cell Culture Techniques↗

PubMed2001

Vascular endothelial growth factor C gene expression is closely related to invasion phenotype in gynecological tumor cells.

OBJECTIVE: The correlation between the gene expression of various angiogenic factors and in vitro invasive activity in 16 human gynecological cancer cell lines was investigated. METHODS: Semiquantitative reverse transcription polymerase chain reaction analysis was performed to investigate the mRNA expression levels of vascular endothelial growth factors (VEGF-A, -B, -C, and -D), basic fibroblast growth factor (bFGF), and matrix metalloproteinase (MMP)-2 with beta-actin coamplified as an internal standard. Tumor cell migration along a gradient of substratum-bound fibronectin and invasion into reconstituted basement membrane were evaluated by haptotactic migration and invasion assay. RESULTS: Expression of VEGF-A mRNA was detected in all 16 cell lines, whereas the relative expression levels of other VEGF family members and bFGF, differed markedly among the cell lines. There was a statistical correlation between VEGF-C gene expression and the number of cells that migrated and invaded (P < 0.01). However, expression of mRNAs of other angiogenic factors did not correlate with motility and invasive activity of the cells. Moreover, there was a close correlation between VEGF-C and MMP-2 gene expression levels (P < 0.05). CONCLUSION: Tumor cells that produce VEGF-C may have a higher invasive and metastatic potential because of their capacity to pass through tissue barriers.

DNA, Neoplasm↗

PubMed2001

Nitric oxide regulates smooth-muscle-specific myosin heavy chain gene expression at the transcriptional level-possible role of SRF and YY1 through CArG element.

Nitric oxide (NO) plays an important role in vascular regulation through its vasodilatory, antiatherogenic, and antithrombotic properties. NO inhibits platelet adhesion and aggregation and modulates smooth muscle cell (SMC) proliferation and migration. In animals with experimentally induced vascular injury, ec-NOS gene transfection not only restored NO production to normal levels but also increased vascular reactivity of the injured vessels. However, it is unclear whether NO regulates smooth-muscle-specific gene expression. We report here that addition of PDGF-BB to vascular smooth muscle cells suppressed SM-MHC expression but treatment with the NO donors FK409 and SNAP restored SM-MHC mRNA/protein expression. In vitro transfection and subsequent CAT assays demonstrated that exogenous NO can restore PDGF-BB-induced suppression of SM-MHC promoter activity. Promoter deletion analysis revealed that a CArG-3 box located at -1276 bp in the SM-MHC promoter was important for NO-dependent promoter regulation and as well as high level promoter activity. Gel mobility shift assays showed that CArG-3 contained the SRF binding site and a binding site for YY1, a nuclear factor which acts as a negative regulator on muscle-specific promoters. Interestingly, NO donor FK409 reduced YY1 binding to the CArG-3 element but increased SRF binding, suggesting that these two factors bind competitively to the overlapping sites. We also found that mutation to the YY1 binding site in the CArG-3 element resulted in a loss of PDGF-BB-induced suppression of the SM-MHC promoter activity. These findings indicate that NO regulates SM-MHC gene expression at the transcriptional level at least partially through the regulation of transcription factor binding activities on the CArG element. Thus we propose that NO plays a positive role in maintaining the differentiated state of VSMCs.

Animals↗

PubMed2001

Formation of filamentous tau aggregations in transgenic mice expressing V337M human tau.

Formation of neurofibrillary tangles (NFTs) is the most common feature in several neurodegenerative diseases, including Alzheimer's disease (AD). Here we report the formation of filamentous tau aggregations having a beta-sheet structure in transgenic mice expressing mutant human tau. These mice contain a tau gene with a mutation of the frontotemporal dementia parkinsonism (FTDP-17) type, in which valine is substituted with methionine residue 337. The aggregation of tau in these transgenic mice satisfies all histological criteria used to identify NFTs common to human neurodegenerative diseases. These mice, therefore, provide a preclinical model for the testing of therapeutic drugs for the treatment of neurodegenerative disorders that exhibit NFTs.

Animals↗