Biomedical subjects

T Tanabe

Publications and source records attributed to T Tanabe.

At least 163 records · Page 9Linked to original sources

PubMed1998

Development of an in-vacuum minipole undulator.

An in-vacuum minipole (short-period) insertion device has been developed in a collaboration between SPring-8 and the National Synchrotron Light Source (NSLS). The magnetic arrays were constructed by SPring-8 and were installed in a chamber with mechanical parts in the X-ray ring (E = 2.584 GeV) at the NSLS in May 1997. The device is made of permanent magnets with 30.5 periods and a period length of 11 mm. It is designed to produce fundamental radiation at 4.6 keV, and, with a modest value of deflection parameter (K = 0.7 at 3.3 mm gap), enables higher harmonics to be used for a variety of experiments.

Journal Article↗

PubMed1998

SPring-8 twin helical undulator.

There are several ways of producing circularly polarized light, such as using asymmetric devices, crossed undulators etc. The SPring-8 helical undulator introduces a simple way of producing both horizontal and vertical fields in one undulator. All the magnet arrays are arranged above and below the plane of the electron orbit, so there is no limitation of access from the sides of the undulator. For the SPring-8 BL25SU, two helical undulators will be installed in tandem, and the helicity of the polarization can be switched at up to 10 Hz using five kicker magnets.

Journal Article↗

PubMed1998

In-vacuum undulators of SPring-8.

Most of the SPring-8 insertion devices are in-vacuum undulators except for the soft X-ray devices and one elliptical wiggler. The standard-type SPring-8 in-vacuum undulator has a period of 32 mm and a minimum gap of 8 mm. The fundamental radiation energy ranges from 5.2 to 18.5 keV. Three standard in-vacuum undulators are already installed in the ring and are operating without any problems. The magnetic field correction, the vacuum system and the commissioning of the in-vacuum undulators are described in this paper.

Journal Article↗

PubMed1998

SPring-8 beamline control system.

The SPring-8 beamline control system is now taking part in the control of the insertion device (ID), front end, beam transportation channel and all interlock systems of the beamline: it will supply a highly standardized environment of apparatus control for collaborative researchers. In particular, ID operation is very important in a third-generation synchrotron light source facility. It is also very important to consider the security system because the ID is part of the storage ring and is therefore governed by the synchrotron ring control system. The progress of computer networking systems and the technology of security control require the development of a highly flexible control system. An interlock system that is independent of the control system has increased the reliability. For the beamline control system the so-called standard model concept has been adopted. VME-bus (VME) is used as the front-end control system and a UNIX workstation as the operator console. CPU boards of the VME-bus are RISC processor-based board computers operated by a LynxOS-based HP-RT real-time operating system. The workstation and the VME are linked to each other by a network, and form the distributed system. The HP 9000/700 series with HP-UX and the HP 9000/743rt series with HP-RT are used. All the controllable apparatus may be operated from any workstation.

Journal Article↗

PubMed1998

Development of an elliptical multipole wiggler at SPring-8.

An elliptical multipole wiggler (EMPW) based on a new concept has been installed on the SPring-8 storage ring. The EMPW, with a 120 mm period, has a critical energy of 50 keV at a gap of 20 mm. It will provide high-brilliance hard circularly polarized X-rays in the 100-300 keV range to the pilot beamline dedicated to materials science: the Compton scattering beamline. Field measurements, field integrals, the expected fluxes, polarization rates, power and power densities are presented for two operating gaps: 30 mm during commissioning, 20 mm later.

Journal Article↗

PubMed1998

Association of calcium channel alpha1S and beta1a subunits is required for the targeting of beta1a but not of alpha1S into skeletal muscle triads.

The skeletal muscle L-type Ca2+ channel is a complex of five subunits that is specifically localized in the triad. Its primary function is the rapid activation of Ca2+ release from cytoplasmic stores in a process called excitation-contraction coupling. To study the role of alpha1S-beta1a interactions in the incorporation of the functional channel complex into the triad, alpha1S and beta1a [or a beta1a-green fluorescent protein (GFP) fusion protein] were expressed alone and in combination in myotubes of the dysgenic cell line GLT. betaGFP expressed in dysgenic myotubes that lack the skeletal muscle alpha1S subunit was diffusely distributed in the cytoplasm. On coexpression with the alpha1S subunit betaGFP distribution became clustered and colocalized with alpha1S immunofluorescence. Based on the colocalization of betaGFP and alpha1S with the ryanodine receptor the clusters were identified as T-tubule/sarcoplasmic reticulum junctions. Expression of alpha1S with and without beta1a restored Ca2+ currents and depolarization-induced Ca2+ release. The translocation of betaGFP from the cytoplasm into the junctions failed when betaGFP was coexpressed with alpha1S mutants in which the beta interaction domain had been altered (alpha1S-Y366S) or deleted (alpha1S-Delta351-380). Although alpha1S-Y366S did not associate with betaGFP it was incorporated into the junctions, and it restored Ca2+ currents and depolarization-induced Ca2+ release. Thus, beta1a requires the association with the beta interaction domain in the I-II cytoplasmic loop of alpha1S for its own incorporation into triad junctions, but stable alpha1S-beta1a association is not necessary for the targeting of alpha1S into the triads or for its normal function in Ca2+ conductance and excitation-contraction coupling.

Animals↗

PubMed1998

Transcriptional role of the nuclear factor kappa B site in the induction by lipopolysaccharide and suppression by dexamethasone of cyclooxygenase-2 in U937 cells.

Cyclooxygenase-2 (COX-2), an inducible isozyme of cyclooxygenase, is selectively expressed in response to lipopolysaccharide (LPS) and its expression is suppressed by the glucocorticoid dexamethasone (DEX) in the monocytic differentiated U937 cells. However, COX-2 mRNA was not detected nor induced by LPS before the cells differentiated. To study the transcriptional role of the NF-kappa B site (nucleotides -223 to -214) in the COX-2 gene, the luciferase reporter vector driven by the COX-2 promoter region (nucleotides -327 to +59) mutated at both the cAMP response element and the NF-IL6 site was stably transfected into U937 cells. The substantial luciferase activity observed in the undifferentiated cells was not induced by LPS. However, after the cells had differentiated, luciferase activity was induced by LPS and its induction was suppressed by DEX. Moreover, a protein tyrosine kinase inhibitor herbimycin A suppressed both the expression of COX-2 mRNA and the luciferase activity induced by LPS. These results suggest that the NF-kappa B site is involved in both the LPS-induced expression of the COX-2 gene and its suppression by DEX and herbimycin A in a differentiation-dependent manner.

Benzoquinones↗

PubMed1998

Immunocytochemical localization of annexin 5, a calcium-dependent phospholipid-binding protein, in rat endocrine organs.

Annexin 5, a unique calcium- and phospholipid-binding protein, has been investigated for its specific distribution in rat endocrine organs by immunocytochemistry with a specific antiserum to recombinant rat annexin 5. Follicular epithelial cells and parafollicular cells of the thyroid gland, adrenocortical cells of the zona fasciculata and zona reticularis, luteal cells, testicular interstitial cells, and Sertoli cells were shown to contain annexin 5. To examine whether the synthesis of annexin 5 would be affected by a change in humoral signal, the distribution of annexin 5 in the anterior pituitary was examined three weeks after ovariectomy. The withdrawal of ovarian hormones induced huge castration cells in the anterior pituitary gland, which contained abundant annexin 5. Annexin 5 was not detected in the pineal gland, the parathyroid gland, the islet of Langerhans, the adrenal medulla, zona glomerulosa cells, and granulosa cells. Since annexin 5 was shown to exist in many of the endocrine tissues examined, to be localized in specific cell types, and to be abundant in castration cells, it is suggested that annexin 5 contributes to secretory cell functions, which may be common to endocrine cells secreting chemically different hormones.

Animals↗

PubMed1998

Immunocytochemical and immunochemical study of enamelins, using antibodies against porcine 89-kDa enamelin and its N-terminal synthetic peptide, in porcine tooth germs.

Enamelins comprise an important family of the enamel matrix proteins. Porcine tooth germs were investigated immunochemically and immunocytochemically using two antibodies: a polyclonal antibody raised against the porcine 89-kDa enamelin (89 E) and an affinity purified anti-peptide antibody against the porcine enamelin amino-terminus (EN). Immunochemical analysis of layers of immature enamel from the matrix formation stage detected immunopositive protein bands ranging from 10 kDa to 155 kDa in the outer layer enamel sample irrespective of the antibodies used. In contrast, the middle and inner enamel layer mainly contained lower molecular weight enamelins. In immunocytochemical analyses of the differentiation stage, 89 E stained enamel matrix islands around mineralized collagen fibrils of dentin, while EN stained both enamel matrix islands and stippled material. At the matrix formation stage, both antibodies intensely stained enamel prisms located in the outer layer. In the inner layer, 89 E moderately stained enamel matrix homogeneously, while EN primarily stained the prism sheath. The intense immunoreaction over the surface layer of enamel matrix at the matrix formation stage, following staining with 89 E and EN, disappeared by the end of the transition stage and the early maturation stage, respectively. The Golgi apparatus and secretory granules in the ameloblasts from the late differentiation stage to the transition stage were immunostained by both antibodies. These results suggest that expression of enamelin continues from late differentiation to the transition stage and the cleavage of N-terminal region of enamelin occurs soon after secretion. Some enamelin degradation products, which apparently have no affinity for hydroxyapatite crystals, concentrate in the prism sheaths during enamel maturation.

Amino Acid Sequence↗

PubMed1998

Portal vein reconstruction with conventional polytetrafluoroethylene grafts: an experimental study in dogs.

The purpose of this study was to examine the short- and long-term performance of conventional polytetrafluoroethylene (PTFE) grafts for portal vein reconstruction. The grafts were placed as a portal vein replacement in 11 mongrel dogs. At 1 month and 6 months, the grafts were then retrieved and examined for patency, while also undergoing a pathological analysis. During the observation period (at 55 days), one dog died of an unknown cause with a patent graft. The patency rates of the other 10 grafts were 83% (5/6) at 1 month and 100% (4/4) at 6 months. However, the neointima formation was incomplete even 6 months after implantation. In conclusion, although conventional PTFE grafts may be used as a synthetic alternative to autogenous vein grafts, every effort should be made to use autogenous vein grafts before considering conventional PTFE grafts.

Animals↗

PubMed1998

Surgery for thoracic empyema concurrent with rupture of lung abscesses in a child.

The authors report surgical treatment for thoracic empyema concurrent with rupture of lung abscesses and completely collapsed lung in a child. Right middle lobectomy for ruptured abscess, debridement and closure with interrupted sutures for another abscess in the lower lobe, and decortication were performed. Positive-pressure ventilation was needed to prevent reexpansion pulmonary edema because of long-term collapsed lobes. The patient is doing well with no recurrent empyema or thoracic deformity at 3 years postoperation.

Empyema, Pleural↗

PubMed1998

An electrophysiologic study of the guinea pig inner ear following low pressure barotrauma.

We examined electrophysiologic and morphologic changes following low pressure barotrauma in 25 guinea pigs. Compound action potentials (CAPs), cochlear microphonics (CMs), and transiently evoked otoacoustic emissions (TEOAEs) were elicited by tone bursts (1, 2, 4 and 8 kHz) or non-linear clicks immediately following barotrauma. CAP threshold elevations were observed in 19 out of 25 cochleas, mainly at lower stimulus frequencies. Furthermore, CM and TEOAE thresholds were significantly increased, while CAP and CM amplitudes demonstrated reductions at all stimulus frequencies and intensities. CAP N1 latencies exhibited slight elongations at all stimulus frequencies and intensities. The regression coefficient between the mean CAP thresholds of four stimulus frequencies and TEOAE thresholds was statistically significant. Scanning electron microscopy (SEM) study of six electrophysiologically abnormal cochleas revealed stereocilia morphology in four, but no changes in two. We hypothesize that low pressure barotrauma can injure inner ear hair cells through an early threshold shift secondary to dislocation of the basement membrane.

Acoustic Stimulation↗

PubMed1998

Establishment of novel cell lines derived from two patients with chronic myelogenous leukemia in blast crisis; IMS-BC1 and IMS-BC2 which exhibit markedly different sensitivity to apoptosis.

We established two novel cell lines, designated as IMS-BC1 and IMS-BC2, from two patients with chronic myelogenous leukemia in blast crisis. The two cell lines were positive for CD13 and CD33 and negative for CD34 and HLA-DR by surface marker analysis. IMS-BC1 had four Philadelphia (Ph1) chromosomes and a breakpoint within the 3'-portion of M-bcr, and IMS-BC2 had five Ph1 chromosomes and two breakpoints within the 3'- and 5'-portions of M-bcr. Both cell lines' growth activities were moderately suppressed by IFN-alpha. The proliferation of IMS-BC2 was inhibited by IFN-gamma and apoptosis was induced within 72 h, while IMS-BC1 was resistant to IFN-gamma. Fibronectin inhibited the proliferation of the two cell lines at higher than 10 micrograms/ml, but only IMS-BC2 showed apoptosis. Transforming growth factor-beta inhibited the proliferation of IMS-BC2 resulting in apoptosis, while it inhibited that of IMS-BC1 moderately but failed to induce apoptosis. All-trans retinoic acid (ATRA) inhibited the proliferation of IMS-BC2 at very low concentration (10(-17) mol/l) and induced apoptosis at doses higher than 10(-9) mol/l within 72 h without terminal differentiation, while IMS-BC1 was completely resistant to ATRA. The two cell lines showed different responses to growth inhibitory cytokines and factors. These cell lines should prove useful in the analysis of mechanisms of apoptosis induced by growth inhibitory cytokines and factors.

Adolescent↗

PubMed1998

A novel allosterically trans-activated ribozyme, the maxizyme, with exceptional specificity in vitro and in vivo.

We have constructed an allosterically controllable novel enzyme (designated maxizyme) that can be transcribed in vivo under the control of a human tRNA(Val) promoter. The maxizyme has sensor arms that can recognize target sequences, and in the presence of such a target sequence only, it can form a cavity that can capture catalytically indispensable Mg2+ ions. As a target for a demonstration of the potential utility of the maxizyme, we chose BCR-ABL mRNA, the translated products of which cause chronic myelogenous leukemia. Only the maxizyme (but not conventional ribozymes) had extremely high specificity and high-level activity, not only in vitro but also in cultured cells including BV173 cells derived from a patient with a Philadelphia chromosome. The maxizyme induced apoptosis only in leukemic cells with this chromosome.

Allosteric Regulation↗

PubMed1998

Disproportional response between refractory period and blood flow to alpha 1- and beta-adrenoceptor blockade in canine ischemic myocardium.

We investigated the response of refractory periods and blood flow to blockade of alpha 1- and beta-adrenoceptors alone, or in combination on endocardium and epicardium, during myocardial ischemia. Dogs were anesthetized with alpha-chloralose and divided into bunazosin (an alpha 1-blocking agent)-treated (0.1-0.2 mg/kg, i.v., n = 14), propranolol-treated (0.2 mg/kg, i.v., n = 12), and vehicle-control (n = 10) groups. The diagonal branches of the left anterior descending artery were ligated. The refractory period (ERP) and blood flow (RMBF) were determined by an S1-S2 extrastimulus method and a nonradioactive microsphere technique, respectively. The duration of regional electrograms (DRE) was measured in the endocardial and epicardial sites. Bunazosin alone reversed the ischemia-related shortening of ERPs at both the endocardial and epicardial sites, with a greater effect seen epicardially (P < .05). Subsequent administration of propranolol further prolonged ERPs in both sites, although the effect was greater in the epicardial surface (P < .05). Bunazosin reduced RMBF to a greater degree at the endocardial site than at the epicardial site in the ischemic zone (P < .01 and P < .05, respectively), but the magnitude of the reduction in RMBF and the difference in RMBF between sites were similar to the control group (P < .01). Propranolol alone and subsequent administration of bunazosin prolonged the ERP more at the epicardial site (P < .01) than at the endocardial sites in the ischemic zone. Propranolol produced no significant difference in RMBF between both sites. DREs in animals treated with bunazosin and propranolol alone, or in combination, were similar to those in animals treated with vehicle. These results suggest that differences in ERPs between endocardium and epicardium with blockade of alpha 1- and/or beta-adrenoceptor are not due to concomitant alterations in RMBF, but to differences in electrophysiological properties of the endocardial and epicardial cells during the acute phase of myocardial ischemia.

Adrenergic alpha-1 Receptor Antagonists↗

PubMed1998

Vaccine effect of granulocyte-macrophage colony-stimulating factor or CD80 gene-transduced murine hematopoietic tumor cells and their cooperative enhancement of antitumor immunity.

To develop immunogene therapy targeting minimal residual hematopoietic tumor cells in patients, we transduced murine GM-CSF or CD80 gene into murine WEHI 3B myelomonocytic leukemia and EL-4 thymic lymphoma cells using retroviral vectors and evaluated their effects on inducing antitumor responses in syngeneic host mice. Subcutaneously injected GM-CSF- and CD80 gene-transduced WEHI 3B (GMCSF/WEHI/3.2 or CD80/WEHI/1.8, respectively) cells lost their original tumorigenicity in immunocompetent syngeneic mice. Results from tumor inoculation experiments using athymic nude mice suggested that the rejection of GMCSF/WEHI/3.2 in immunocompetent mice depended fully on T cells and that of CD80/WEHI 1.8 depended partly on T cells and partly on NK cells. In both WEHI 3B and EL-4 models, irradiated GM-CSF gene-transduced cells provided strong immuno-protection against wild-type cells, but irradiated CD80 gene-transduced cells did not. A remarkably high cooperative effect was obtained when irradiated GMCSF/EL-4 and CD80/EL-4 were inoculated together. These results suggested that the tumor vaccine effect is efficiently enhanced by GM-CSF gene transduction and CD80 gene transduction induces some protective antitumor immunity in co-operation with GM-CSF gene transduction.

Animals↗

PubMed1998

Roles of the Ser146, Tyr159, and Lys163 residues in the catalytic action of 7alpha-hydroxysteroid dehydrogenase from Escherichia coli.

The Escherichia coli 7alpha-hydroxysteroid dehydrogenase (7alpha-HSDH; EC 1.1.1.159) has been the subject of our studies, including the cloning of its gene, and determination of the crystal structures of its binary and ternary complexes [J. Bacteriol. 173, 2173-2179 (1991); Biochemistry 35, 7715-7730 (1996)]. Through these studies, the Ser146, Tyr159, and Lys163 residues were found to be involved in its catalytic action. In order to clarify the roles of these residues, we constructed six single mutants of 7alpha-HSDH, Tyr159-Phe (Y159F), Tyr159-His (Y159H), Lys163-Arg (K163R), Lys163-Ile (K163I), Ser146-Ala (S146A), and Ser146-His (S146H), by site-directed mutagenesis. These mutants were overexpressed in E. coli WSD, which is a 7alpha-HSDH null strain, and the expressed enzymes were purified to homogeneity. The kinetic constants of the mutant enzymes were determined, and the structures of the Y159F, Y159H, and K163R mutants were analyzed by X-ray crystallography. The Y159F mutant showed no activity, while the Y159H mutant exhibited 13.3% of the wild-type enzyme activity. No remarkable conformational change between the Y159F (or Y159H) and wild-type proteins was detected on X-ray crystallography. On the other hand, the K163I mutant showed just 5.3% of the native enzyme activity, with a 8. 5-fold higher Kd. However, the K163R mutant retained 64% activity, and no remarkable conformational change was detected on X-ray crystallography. In the cases of the S146A and S146H mutants, the activities fairly decreased, with 20.3 and 35.6% of kcat of the wild-type, respectively. The data presented in this paper confirm that Tyr159 acts as a basic catalyst, that Lys163 binds to NAD(H) and lowers the pKa value of Tyr159, and that Ser146 stabilizes the substrate, reaction intermediate and product in catalysis.

Binding Sites↗

PubMed1998

Mechanism of HIV pathogenesis: role of superantigens in disease.

Initial infection with human immunodeficiency virus (HIV) results in a burst of viremia and an ensuing spread of virus to secondary lymphoid organs, after which a "latency" period occurs with little or no virus detectable in the circulation. The term latent period has been shown to be a misnomer, because substantial viral replication occurs during this time in lymph nodes, although clinically there appears to be few symptoms of disease. However, a telling indicator of active infection during this period is the initiation of decline in CD4+ T-cell numbers. A number of hypotheses have been postulated for the mechanism(s), as of yet not fully elucidated, by which T cells are depleted. Although quiescent cells can be infected, it has been shown that replication of HIV in CD4+ T cells requires cellular activation. The levels of viremia early in infection indicate that a large number of cells are actively infected, further suggesting that a mechanism must exist by which HIV activates a large pool of cells and ultimately causes their depletion. One possible mechanism for activation would be the presence of an HIV-encoded superantigen. Superantigens are proteins that are polyclonal stimulators of CD4+ T lymphocytes. This occurs as a result of their ability to form a trimolecular complex with MHC class II molecules on antigen-presenting cells and the Vbeta-specific region on the T-cell receptor. Thus, superantigen activation of T cells is antigen-nonspecific. The prototype superantigens are the staphylococcal enterotoxins. Putative viral superantigens include a protein from mouse mammary tumor virus and related retroviruses, rabies nucleocapsid, and the Nef protein of HIV. Nef is required for optimal HIV pathogenesis, and this may be due to its superantigen properties, where CD4 cells are transformed to the activated state for virus replication.

Animals↗