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Biomedical subjects

H Kawata

Publications and source records attributed to H Kawata.

At least 55 records · Page 3Linked to original sources
PubMed1998

Site specification on normal and magnetic XANES of ferrimagnetic Fe(3)O(4) by means of resonant magnetic Bragg scattering.

Resonant magnetic Bragg scattering (RMBS) for several reflections has been measured at the Fe K-edge in Fe(3)O(4). The normal and magnetic X-ray absorption near-edge structure (XANES) for two types of Fe ion site (tetrahedral and octahedral) were successfully determined from the analysis of DAFS and RMBS spectra on the assumption that there was an electric dipole transition. The obtained normal XANES for the octahedral site is well explained as a mixture of Fe(2+) and Fe(3+) ions, and the characteristic feature of the magnetic XANES at the pre-edge peak is mainly contributed from the Fe(3+) ion at the tetrahedral site.

Journal Article↗
PubMed1998

Development of an (X, eX) spectrometer for measuring the energies of the scattered photon and recoil electron.

The design and performance of a new spectrometer for coincidence measurements between the Compton scattered photon and the recoil electron are described. Coincidence measurements give direct information on the three-dimensional electron momentum density (EMD) of condensed matter. The present spectrometer measures energy spectra of both the photon and the electron. The energy spectrum of electrons is measured by a time-of-flight method using single-bunch operation at the Photon Factory Accumulator Ring (PF-AR). The energy resolution obtained for the recoil electron is 190 eV, which is better than that of the photon detector, so that a momentum resolution of the three-dimensional EMD of 0.3 atomic units can be achieved.

Journal Article↗
PubMed1998

Bent-crystal monochromators for high-energy synchrotron radiation.

Two kinds of monochromators covering the energy ranges 100-150 keV and approximately 300 keV have been designed for inelastic (Compton) scattering experiments at the elliptical multipole wiggler beamline, BL08W, of SPring-8. Finite-element analyses using ANSYS for bent crystals indicate that thermal problems are not serious for the 300 keV monochromator, while an energy spread of about 10(-3) for the 100-150 keV monochromator is possible in the centre of the crystal. Detailed calculations of X-ray interaction with the silicon crystal were performed. The results show that Compton scattering is a dominant process and deposits about 100 W continuously.

Journal Article↗
PubMed1998

A new water-cooled and doubly bent crystal monochromator for Compton scattering experiments.

The design and performance of a new water-cooled and doubly bent crystal monochromator for Compton scattering experiments are described. Its mechanical system is similar to that of a usual bent cylindrical X-ray mirror. A monolithic Si (111) crystal is mounted on a water-cooled and cylindrically polished copper crystal holder with liquid Ga-In alloy between them in order to obtain good thermal and mechanical contact. The sagittal bending radius of the holder, R(s), is 508 mm. The holder is mounted on a mechanical bender making a meridian radius, R(m), of 596 m. The performance of the monochromator, which has been installed at the Photon Factory Accumulator Ring beamline NE1, is as follows. The focused beam size, flux and energy resolution for 60 keV X-rays are 0.5 mm in height and 2.0 mm in width, 5 x 10(12) photons s(-1) and about 60 eV, respectively. The new monochromator gives one order higher brightness at the sample position and also better energy resolution than the previous monochromator. The overall momentum resolution for high-resolution Compton scattering experiments becomes 0.08 atomic units, and the background can be reduced by a third, because it is possible to insert a fine slit after the analyser crystal without losing any Compton scattering signal.

Journal Article↗
PubMed1998

High-pressure system for Compton scattering experiments.

High-pressure apparatus for Compton scattering experiments has been developed to study the momentum distribution of conduction electrons in metals and alloys at high pressure. This apparatus was applied to observe the Compton profile of metallic Li under pressure. It was found that the Compton profile at high pressure could be obtained within several hours by using this apparatus and synchrotron radiation. The result on the pressure dependence of the Fermi momentum of Li obtained here is in good agreement with that predicted from the free-electron model.

Journal Article↗
PubMed1998

Repair of left ventricular diverticulum with ventricular bigeminy in an infant.

Surgical repair of left ventricular diverticulum usually is not required in infancy even though it combines with other anomalies. In addition to prevention of rupture of the diverticulum and thrombus formation, treatment of combined ventricular tachycardia is thought to be an indication for resection of the diverticulum. We describe a successful repair performed by excising the isolated left ventricular diverticulum under cardiopulmonary bypass in a 9-day-old infant. The combined ventricular bigeminy has disappeared 9 months after the operation.

Cardiopulmonary Bypass↗
PubMed1998

Pulmonary and systemic arteriovenous fistulas in patients with left isomerism.

Hepatic venous blood has been thought to play some role as a vasoactive agent in the development of pulmonary arteriovenous fistulas in patients with congenital heart disease. During the last 15 years, we have observed pulmonary arteriovenous fistulas in 3, and systemic arteriovenous fistulas in 2, patients from our 16 cases of left isomerism. During the same period, neither pulmonary nor systemic arteriovenous fistulas were detected among 50 patients with right isomerism. Pulmonary arteriovenous fistulas had developed in the absence of surgery in 1 of the patients. Both pulmonary and systemic fistulas were detected in an another patient, in whom the hepatic venous blood bypassed the pulmonary circulation. The level of somatostatin, which is known to reduce splanchnic blood flow, was high in the systemic venous blood of this patient. Although the mechanism of development of the fistulas has yet to be clarified, we should be aware that not only pulmonary, but also systemic arteriovenous fistulas can be found in patients with left isomerism, even prior to any surgical intervention.

Angiography↗
PubMed1998

Biopsy sites suitable for the diagnosis of Helicobacter pylori infection and the assessment of the extent of atrophic gastritis.

OBJECTIVES: We performed this study to determine which biopsy sites in the stomach are suitable for the diagnosis of Helicobacter pylori infection and the assessment of the extent of atrophic gastritis. METHODS: Endoscopy was performed in 76 H. pylori-positive patients with histologically confirmed chronic gastritis. Biopsies were taken from the following six sites: the lesser curvatures of the mid-antrum (site 1), the angulus (site 2), the middle body (site 3), and the greater curvatures of the mid-antrum (site 4), the angulus (site 5), and the middle body (site 6) of the stomach. The extent of atrophic gastritis was assessed endoscopically as well as histologically, and patients were classified into five groups according to its extent. H. pylori status was assessed histologically. The histological severity of inflammation, activity, atrophy, and intestinal metaplasia was assessed according to the Updated Sydney System. The grades of these items were compared among the six biopsy sites in each group of patients. RESULTS: Site 6 was most reliable for the diagnosis of H. pylori infection, and site 4 was suitable for examining the status of H. pylori colonization in the antrum. Site 1, site 3, and site 6 were suitable for the assessment of the extent of atrophic gastritis. CONCLUSIONS: Our results indicate that for an accurate diagnosis and assessment, biopsies should be taken from the following four sites: the lesser curvatures of the mid-antrum (site 1) and middle body (site 3), and the greater curvatures of the mid-antrum (site 4) and middle body (site 6) of the stomach.

Adult↗
PubMed1998

[Legionella pneumonia caused by aspiration of hot spring water after sarin exposure].

A 72-year-old man was exposed to the sarin gas attack in a Tokyo subway on March 20 th, 1995. After exposure, he noticed eye discomfort, chest tightness, headache and weakness of the lower limbs and oropharyngeal muscles. Despite these symptoms, he visited a hot spring on the same day with his family. On March 25 th, his muscle weakness progressed, and a low grade fever appeared. His muscle weakness disappeared 8 days after exposure to sarin, but respiratory failure rapidly developed, necessitating artificial ventilation within four day after hospitalization on March 28th. Chemotherapy with erythromycin, imipenem/cilastatin, and steroid pulse therapy was begu. PCR and culture of sputum collected by bronchofiberscopy were positive for Legionella pneumophila, serogroup I. His respiratory state improved, but subsequent infection with Pseudomonous aeruginosa. Enterobacter cloacae, and Candida tropicalis/glabrata caused his death 71 days after admission. Oropharyngeal muscle weakness caused by sarin-mediated cholinesterase inhibition was strongly suspected as the cause of hot spring water aspiration. Transbronchial lung biopsy revealed organizing pneumonia with fibrosis. Bronchoscopic findings included redness, edema and fragility of all visible areas of the airway, which was thought to be due to bronchitis caused by Legionellosis.

Aged↗
PubMed1997

Interleukin-6 overexpression cannot generate serious disorders in severe combined immunodeficiency mice.

C57BL/6 human interleukin-6 (IL-6) transgenic mice develop mesangial proliferative glomerulonephritis with massive IgG1 plasmacytosis and die of renal failure in early life. To test whether the IL-6 overexpression could cause development of mesangial proliferative glomerulonephritis without plasmacytosis or promote proliferation of immature B cells that have not undergone immunoglobulin gene rearrangement, the IL-6 transgene was introduced into mice with severe combined immunodeficiency (SCID). In the immunocompetent littermate IL-6 transgenic mice, there were various symptoms such as plasmacytosis, nephropathy, anemia, and thrombocytosis, accompanied by marked increases in serum IL-6 levels as they aged. All these mice died by 25 weeks of age. In contrast, the SCID-IL-6 transgenic mice had no such abnormalities, except certain hematological changes, although the transgene was expressed in various tissues. In these mice, the serum IL-6 levels were 10- to 15-fold higher than those in the nontransgenic mice, and they remained constant throughout their lives. Furthermore, there were no signs of lymphoid development. This study demonstrates that deregulation of IL-6 expression does not stimulate cell growth or differentiation of immature B cells, and thus does not result in plasmacytosis and age-related increases in IL-6 production, and also does not generate mesangial proliferative glomerulonephritis.

Animals↗
PubMed1997

HLA-DRB4 genotyping by PCR-RFLP: diversity in the associations between HLA-DRB4 and DRB1 alleles.

The serologically defined HLA-DR53 antigen is associated with HLA-DR4, -DR7, and -DR9 antigens, and these haplotypes contain two functional genes, DRB1 and DRB4, and two pseudogenes, DRB7 and DRB8. The DRB4 gene encodes the DR53 antigen, and has been officially recognized to contain three allelic variants (DRB4*0101, 0102, and 0103). In this study, we have established the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method for DRB4 genotyping and analyzed genetic polymorphism of the DRB4 gene in Japanese population. DRB4*0101, DRB4*0102, and DRB4*0103 could be observed at the frequencies of 0.5%, 1.1% and 32.7%, respectively. The same DRB1 allele does not necessarily share an identical DRB4 allele. Further, a tight linkage disequilibrium was found between DRB4*0102 and DRB1*0401 in Japanese population, whereas DRB1*0401 was associated with DRB4*0101 or *0103 in Caucasian population. These findings reveal extensive diversity of the HLA-DRB1 and -DRB4 haplotypes and may have important implications for HLA-disease associations and donor selection in unrelated transplantation.

Alleles↗
PubMed1997

Triplet repeat polymorphism in the NOTCH4 gene with the human major histocompatibility complex in a healthy population and patients with a salivary gland tumor in Japan.

The NOTCH4 gene, the human counterpart of the mouse mammary tumor gene, int-3, has been recently localized near the boundary of the HLA class II and class III regions. This gene is one of candidates for development of salivary gland tumor. Microsatellite polymorphism of (CTG)n repeat in the signal peptide domain of NOTCH4 was analyzed in Japanese including the patients with salivary gland tumor. Four alleles consisting of 6, 9, 10 and 11 repetitions of CTG (Leu) were observed and found to be in linkage disequilibria with HLA class I and class II alleles. No significant association of this microsatellite polymorphism with the disease were observed in 26 samples of salivary gland tumor. In this neoplasia, neither large-scale deletion nor translocation was detected around the NOTCH4 gene using genomic Southern hybridization analysis by the NOTCH4 cDNA as a probe.

Alleles↗
PubMed1997

Participation of PKC in modulation of the excitation-contraction process of chick embryo cardiac muscle.

Phorbol esters are activators of protein kinase C (PKC) and have been widely used to study the function of this enzyme. We investigated the effect of phorbol ester, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), on tension responses and free cytosolic Ca in small strips of chick embryo ventricle and on the 45Ca influx in primary cultures of chick embryo ventricular cells. TPA (10(-8) M) decreased twitch tension about 40% when driven at 1 Hz. The free cytosolic Ca measured with fura-PE3 was rapidly increased in 110 mM KCl solution and this high K-induced increase was slightly inhibited by TPA (10(-8) M), by 12%. The resting 45Ca uptake in 5 mM KCl was slightly increased by a low concentration of TPA (10(-9) M), but high K-induced 45Ca uptake was decreased by TPA in a dose-dependent manner, but to 40% at the utmost. 4 alpha-Phorbol, an inactive phorbol ester, did not inhibit 45Ca uptake. These results indicate that TPA decreased the depolarization induced transsarcolemmal Ca uptake and thus the excitation-contraction process was attenuated, but to 40% at most. PKC may participate in the modulation of myocardial Ca homeostasis and contractile state.

Action Potentials↗
PubMed1996

Analysis of HLA-DM polymorphisms in sarcoidosis.

Sarcoidosis is a multisystemic granulomatous disorder showing significant increases in the HLA-DRB1*11, *12, *14 and *08 alleles in the Japanese population. To evaluate the role of polymorphism in the DMA and DMB genes in predisposition to sarcoidosis, seventy Japanese patients with sarcoidosis and 95 unrelated healthy controls were analyzed in the third exon polymorphisms within the DMA and DMB genes by the PCR-RFLP method. There were no differences in the distribution of DMA alleles between the patient and control groups. The frequency of DMB*0102 was higher (p < 0.05) and that of DMB*0101 was lower (p < 0.05) in the patients than in the healthy controls. However, this association and negative association could be explained by linkage disequilibrium with the disease-associated DRB1 alleles. The DMA and DMB genes do not primarily confer the susceptibility to sarcoidosis.

Adult↗
PubMed1996

cDNA cloning of the human homologues of the mouse Ke4 and Ke6 genes at the centromeric end of the human MHC region.

cDNA clones corresponding to the HKE4 and HKE6 genes at the centromeric end of the HLA region on human chromosome 6p21.3 were isolated and characterized. The predicted amino acid sequences of HKE4 and HKE6 exhibited 81.5 and 85.6% identity to the mouse homologues, Ke4 and Ke6, respectively. HKE4 may encode a membrane protein with histidine-rich charge clusters. HKE6 possesses remarkable amino acid sequence conservation with several bacterial proteins with oxidoreductase function and also shows significant homology with the two unique functional domains containing the nucleotide cofactor binding site and the consensus motif characteristic of the members of the superfamily of short-chain alcohol dehydrogenases such as human and rat steroid and prostaglandin dehydrogenases.

Amino Acid Sequence↗
PubMed1996

Surgical atrial septostomy without cardiopulmonary bypass.

Surgical atrial septostomy using a special atriotomy knife without cardiopulmonary bypass in patients with obstruction of the left-sided atrioventricular valve and complex cardiac anomalies is described. This procedure is effective, safe, and economical for patients in the acute stage after intracardiac repair, and available for patients with a closed fossa ovalis.

Cardiac Surgical Procedures↗
PubMed1996

The wavelength dependence of optically recorded action potentials in the atrial muscles of the bullfrog (Rana catesbeiana).

The action potentials from frog atrial muscles that had been stained with either merocyanine rhodanine or merocyanine oxazolone dyes were recorded optically. Then the dependence of the maximum rising phase of the optically recorded action potential on the wavelength of the incident beam was analyzed. The atrial muscle stained with two kinds of dyes showed no wavelength dependence in the duration of the rising phase (defined in Fig. 1) in the maximum rising phase of the action potential. These results were consistent with the structure of the membrane system of the frog heart. However, for the atrial muscles stained with merocyanine oxazolone dye, the optical signals recorded at 718 nm of the incident beam showed a second rising phase after the initial rapid rising phase of the optical signal, and this phase was not observed in the optical signals recorded at other wavelengths.

Action Potentials↗