Biomedical subjects

H Murayama

Publications and source records attributed to H Murayama.

At least 19 recordsLinked to original sources

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↗

PubMed2005

Experimental investigation of geologically produced antineutrinos with KamLAND.

The detection of electron antineutrinos produced by natural radioactivity in the Earth could yield important geophysical information. The Kamioka liquid scintillator antineutrino detector (KamLAND) has the sensitivity to detect electron antineutrinos produced by the decay of 238U and 232Th within the Earth. Earth composition models suggest that the radiogenic power from these isotope decays is 16 TW, approximately half of the total measured heat dissipation rate from the Earth. Here we present results from a search for geoneutrinos with KamLAND. Assuming a Th/U mass concentration ratio of 3.9, the 90 per cent confidence interval for the total number of geoneutrinos detected is 4.5 to 54.2. This result is consistent with the central value of 19 predicted by geophysical models. Although our present data have limited statistical power, they nevertheless provide by direct means an upper limit (60 TW) for the radiogenic power of U and Th in the Earth, a quantity that is currently poorly constrained.

Journal Article↗

PubMed2005

Measurement of neutrino oscillation with KamLAND: evidence of spectral distortion.

We present results of a study of neutrino oscillation based on a 766 ton/year exposure of KamLAND to reactor antineutrinos. We observe 258 nu (e) candidate events with energies above 3.4 MeV compared to 365.2+/-23.7 events expected in the absence of neutrino oscillation. Accounting for 17.8+/-7.3 expected background events, the statistical significance for reactor nu (e) disappearance is 99.998%. The observed energy spectrum disagrees with the expected spectral shape in the absence of neutrino oscillation at 99.6% significance and prefers the distortion expected from nu (e) oscillation effects. A two-neutrino oscillation analysis of the KamLAND data gives Deltam(2)=7.9(+0.6)(-0.5)x10(-5) eV(2). A global analysis of data from KamLAND and solar-neutrino experiments yields Deltam(2)=7.9(+0.6)(-0.5)x10(-5) eV(2) and tan((2)theta=0.40(+0.10)(-0.07), the most precise determination to date.

Journal Article↗

PubMed2004

High sensitivity search for nu;e's from the sun and other sources at KamLAND.

Data corresponding to a KamLAND detector exposure of 0.28 kton yr has been used to search for nu;(e)'s in the energy range 8.3<E(nu;(e))<14.8 MeV. No candidates were found for an expected background of 1.1+/-0.4 events. This result can be used to obtain a limit on nu;(e) fluxes of any origin. Assuming that all nu;(e) flux has its origin in the Sun and has the characteristic 8B solar nu(e) energy spectrum, we obtain an upper limit of 3.7 x 10(2) cm(-2) s(-1) (90% C.L.) on the nu;(e) flux. We interpret this limit, corresponding to 2.8 x 10(-4) of the standard solar model 8B nu(e) flux, in the framework of spin-flavor precession and neutrino decay models.

Journal Article↗

PubMed2003

First results from KamLAND: evidence for reactor antineutrino disappearance.

KamLAND has measured the flux of nu;(e)'s from distant nuclear reactors. We find fewer nu;(e) events than expected from standard assumptions about nu;(e) propagation at the 99.95% C.L. In a 162 ton.yr exposure the ratio of the observed inverse beta-decay events to the expected number without nu;(e) disappearance is 0.611+/-0.085(stat)+/-0.041(syst) for nu;(e) energies >3.4 MeV. In the context of two-flavor neutrino oscillations with CPT invariance, all solutions to the solar neutrino problem except for the "large mixing angle" region are excluded.

Journal Article↗

PubMed2002

[Extraction of bisphenol-A from a cardiopulmonary bypass circuit].

We measured levels of bisphenol-A (BPA) in a priming solution and blood of a cardiopulmonary bypass (CPB) circuit. Eight circuits were used in the study of a priming solution. Blood samples were obtained from 6 patients who underwent open heart surgery after the commencement of CPB and at the termination of CPB. Another 3 samples were collected directly from the saline in a polyethylene container as a control. Then the concentrations of BPA in them were determined by means of gas chromatography. No detectable BPA was found in controls. However, a small amount was detected in the saline from the circuits (0.9 +/- 1.1 micrograms/l). A very small amount was also detected in the blood after the commencement and at the termination of CPB (0.3 +/- 0.2 microgram/l, and 0.4 +/- 0.3 microgram/l, respectively). BPA was considered to be leached from the circuit to the priming solution and the blood because the parts of the reservoir and the oxygenator were made of polycarbonate containing BPA. We suppose the BPA concentration is probably at a safe level. However, the data on the endocrinologically toxic level of blood BPA are insufficient. Therefore, the use of plastic in a circuit may require closer scrutiny to determine whether BPA contributes to exposure to xenoestrogens.

Benzhydryl Compounds↗

PubMed2002

[Repair of tetralogy of Fallot in an adult; the importance of preoperative examination for major aorto-pulmonary collateral arteries].

We report the repair of tetralogy of Fallot in a 51-year-old man. He underwent a left classical Blalock-Taussig (B-T) shunt when he was ten years old. Preoperative angiography showed a patent B-T shunt. Total corrective surgery was performed. Postoperatively, he suffered from left ventricular failure. Re-intubation was required three times. Postoperative catheterization showed excellent correction of the right ventricular system, however, descending aortography revealed a great many aorto-pulmonary collateral arteries, which caused the left ventricular failure. Coil embolization of these 13 collateral arteries was performed and he recovered from the left ventricular failure. We conclude that even in an elderly patient with tetralogy of Fallot, total correction should be performed, since the surgical risk is acceptable and the procedure improves the capacity for physical activity and quality of life. Preoperative examination of collateral arteries is important, especially in elderly patients, and coil embolization should be considered.

Aorta↗

PubMed2002

Total aortic arch graft replacement for recurrent aortic aneurysm.

We successfully performed a total aortic arch replacement for a recurrent aortic aneurysm following repair of an aortic dissection. A 59-year-old man underwent a patch aortoplasty through median sternotomy for Stanford type B aortic dissection in other hospital. Three years and 6 months later an aneurysm developed. Computed tomography and magnetic resonance imaging angiography demonstrated an enlargement of the aneurysm, resulting in a diagnosis of recurrent distal aortic arch aneurysm. A graft replacement of the total aortic arch with the aid of selective cerebral perfusion was performed through a median resternotomy and left lateral thoracotomy. Additional left lateral thoracotomy offered a sufficiently optimal operating field for distal anastomosis. However, care must be taken not to overlook the bleeding from intercostal arteries. Since aortoplasty may lead to subsequent dilation and aneurysmal formation, initial replacement of the segment of the aorta is recommended, and careful long-term follow-up of the patient is important.

Aorta, Thoracic↗

PubMed2001

Spontaneous nontraumatic rupture of the thoracic aorta: report of a case.

Spontaneous nontraumatic rupture of the thoracic aorta is a very rare, life-threatening condition for which emergency diagnostic and therapeutic measures are indicated. The patient reported herein suffered a spontaneous rupture of the thoracic descending aorta through an atheromatous plaque without aneurysmal formation. When acute intrapericardial, mediastinal, or intrapleural bleeding develops without any evidence of aortic aneurysm or dissection, the possibility of spontaneous rupture of the thoracic aorta should be considered in the differential diagnosis, and appropriate emergency surgery may be life-saving.

Aged↗

PubMed2001

Parathyroid hormone increases the expression level of matrix metalloproteinase-13 in vivo.

Parathyroid hormone (PTH) increases serum calcium (Ca) by enhancing bone resorption and renal Ca reabsorption. However, detailed mechanisms of enhanced bone resorption by PTH remain to be elucidated. Although PTH has been shown to increase the expression level of osteoblastic matrix metalloproteinase (MMP)-13 in vitro, only limited results are available regarding the in vivo regulation of MMP expression. In the present study, we have examined expression levels of MMPs in PTH-infused rats. Infusion of 1.5 or 2.0 nmol/kg/day rat PTH(1-34) for 3 days resulted in a dose-dependent increase in serum Ca. PTH infusion also decreased serum phosphate levels and increased urinary excretion of Ca and phosphate. Infusion of PTH for 7 days resulted in less severe hypercalcemia and hypophosphatemia. Urinary Ca and phosphate excretion in rats infused for 7 days was less than that in rats infused for 3 days. Northern blot analysis showed that PTH infusion increased the expression level of MMP-13 in calvaria, although it did not affect MMP-2 expression. Furthermore, the time-course and severity of hypercalcemia and hypercalciuria correlated with the expression level of MMP-13. In situ hybridization also showed that PTH infusion increased the expression level of MMP-13 in femora. These results indicate that PTH enhances MMP-13 expression in vivo and suggest that PTH stimulates bone resorption at least partly by enhancing MMP-13 expression.

Animals↗

PubMed2001

A useful ELISA system for human liver-type arginase, and its utility in diagnosis of liver diseases.

OBJECTIVES: To develop a new ELISA system for liver-type arginase using monoclonal antibodies against the enzyme, and to verify the utility of the arginase in diagnosis of hepatic disorders. DESIGN AND METHODS: We have developed an enzyme-linked immunosorbent assay (ELISA), using two kinds of monoclonal antibodies (Mo6G3 and Mo9C5) for human liver-type arginase as the first and second antibodies respectively. We have also developed a new method to eliminate the influence of erythrocyte-derived arginase contamination in hemolytic samples. This ELISA was applied to specimens received from patients with acute and chronic hepatic disease and also patients who had undergone partial hepatectomy. RESULTS: This assay is sensitive and reproducible for the measurement of liver-type arginase in the sera of patients with liver dysfunction, and enabled us to detect enzyme concentrations as low as 27 pmol/L without any processing of the samples. The assay showed within-run coefficients of variation (CV) ranging from 1.9 to 4.1% and between-day CV from 3.6 to 5.1% for arginase concentrations varying from 57.1 to 1200 pmol/L. The recovery was 113% (mean) with a range of 96 to 129%. These antibodies reacted strongly with both recombinant and native liver-type arginases, while, to some extent, with erythrocyte-derived arginase. Correction for erythrocyte-derived arginase contamination in hemolytic samples was, however, easily made by assaying peroxidase-like activity of hemoglobin. From the view of a limited localization of arginase in the liver, the marked increase of the enzyme in serum reflects initiation of liver injury, while the rapid decrease reflects termination of the damage. Such quick normalization in circulating liver-type arginase indicated another merit of the enzyme in diagnosis of liver diseases. CONCLUSIONS: The changes in circulating liver-type arginase level could be helpful not only in the diagnosis of liver diseases but also subsequent treatment of the patients with liver damage.

Acute Disease↗

PubMed2001

Aberrant growth plate development in VDR/RXR gamma double null mutant mice.

VDR forms heterodimers with one of three RXRs, RXR alpha, RXR beta, and RXR gamma, and it is thought that RXR ligands can also modulate the trans-activation function of VDR/RXR heterodimers. In the present study we generated VDR/RXR gamma double null mutant mice to examine the convergent actions of vitamin D and vitamin A signaling and to explore the possibility of a functionally redundant VDR. Although RXR gamma(-/-) mice exhibited no overt abnormalities, VDR(-/-)/RXR gamma(-/-) mice appeared similar to VDR(-/-) mice, showing features typical of vitamin D-dependent rickets type II, including growth retardation, impaired bone formation, hypocalcemia, and alopecia. However, compared to VDR(-/-) mice, growth plate development in VDR(-/-)/RXR gamma(-/-) mutant mice was more severely impaired. Normalizing mineral ion homeostasis through dietary supplementation with high calcium and phosphorous effectively prevented rachitic abnormalities, except for disarranged growth plates in VDR(-/-)/RXR gamma(-/-) mutant mice, and alopecia in both VDR(-/-) and VDR(-/-)/RXR gamma(-/-) mutant mice. Histological analysis of VDR(-/-)/RXR gamma(-/-) growth plates revealed that development of the hypertrophic chondrocytes was selectively impaired. Thus, our findings indicated that the combined actions of VDR- and RXR gamma-mediated signals are essential for the normal development of growth plate chondrocytes, and raised the possibility that a functionally redundant VDR is present on chondrocytes as a heterodimer with RXR gamma.

Animals↗

PubMed2001

[Extraction of di-2-ethylhexyl phthalate from a cardiopulmonary bypass circuit].

We measured levels of di-2-ethylhexyl phthalate (DEHP) in a priming solution of a cardiopulmonary bypass circuit. The circuit consisted of a venous reservoir, an oxygenator, and polyvinyl chloride (PVC) tubes. Eight circuits were used in this study. In 4 circuits a heparin-coating PVC tube was used and, in the others, a non-coating PVC tube. After they were primed with 1,500 ml of saline, the saline was circulated for 30 minutes at a rate of 6 l/min at 42 degrees C. Another four samples were collected directly from the saline in a polyethylene container as a control. Then the concentrations of DEHP in them were determined by means of gas chromatography. No detectable DEHP was found in controls. But, a small amount was detected in the saline from the circuits (2.75 +/- 4.27 ppb, and 3.75 +/- 4.99 ppb, respectively). DEHP was considered to be leached from the circuit to the priming solution because the tubes were made of PVC containing DEHP as a plasticizer. We suppose the DEHP concentration is probably at a safe level. However, the data on the endocrinologically toxic level of blood DEHP are insufficient. Therefore, the use of plastic in a circuit may require closer scrutiny to determine whether DEHP leached from PVC contributes to exposure to xenoestrogens.

Cardiopulmonary Bypass↗

PubMed2001

[A case of cardiac myxoma with multiple brain hemorrhage].

A case of cardiac myxoma with multiple brain hemorrhage is reported. A 57-year-old male had complained of lower abdominal pain, diarrhea and fever for 3 days. On admission, he was in a condition of disseminated intravascular coagulation and sepsis. An abdominal CT scan showed infarction in the right kidney and spleen and an echocardiogram also showed myxoma in the left atrium. Although he presented no neurological symptoms, the brain CT showed multiple brain hemorrhage in the bilateral brain hemispheres. Total resection of the tumor was carried out for the improvement of the patient's general condition. Vimentin, S-100 protein and neuron specific enolase was positive in immunological staining and the pathological diagnosis was myxoma. Postoperative recovery of consciousness was poor and left hemiparesis developed. CT showed the increase of hematoma but angiography showed no cerebral aneurysm. The symptoms improved with conservative therapy. However the enhanced lesion remained in the right parietal lobe and an operation was performed 5 months later. The myxoma cell could not be found in the pathological examination, so tumor embolism, cerebral infarction, hemorrhagic infarction due to DIC, hematoma enlargement caused by heparinization during operation were suspected to have occurred in this order without tumor growth.

Brain↗

PubMed2001

Right atrial myxoma associated with atrial septal defect: a case report and review of the literature.

We describe a case of right atrial myxoma with mild cyanosis due to a right-to-left shunt at the atrial level. The patient was a 31-year-old woman with a 10-month history of easy fatigability and shortness of breath. Echocardiography showed a right atrial tumor producing a partial dynamic tricuspid obstruction. Digital subtraction angiography via the superior vena cava disclosed a mass lesion which occupied the right atrium with early visualization of the ascending aorta. Successful excision of the tumor and repair of the atrial septal defect totally relieved her presenting symptoms. In a rare association of a right atrial myxoma with atrial septal defect, preoperative evaluation and operative management are discussed.

Adult↗

PubMed2001

[Reoperation for late postoperative right ventricular outflow tract obstruction].

Between February 1993 and July 2000, 18 patients with a mean age of 7.9 years underwent re-operation for critical stenosis of the right ventricular outflow tract. Their diagnoses of these patients included tetralogy of Fallot (n = 7), transposition of the great arteries (n = 6), truncus arteriosus communis (n = 3), and double outlet right ventricle with pulmonary stenosis (n = 2). The first operations were extracardiac conduit operations (n = 9), arterial switch operations (n = 6) and patch reconstruction of the right ventricular outflow tract (n = 3). At re-operation, the right ventricular outflow tract obstruction was released completely and reconstructed using a monocusp ventricular outflow patch (n = 14), valved pericardial roll (n = 2), or bovine pericardial patch sparing the native pulmonary valve annulus (n = 2). There were no early deaths, although one patient died of arrhythmia 2.6 years after re-operation. The pressure gradient across the right ventricular outflow tract, right ventricular systolic pressure, and right ventricle to systemic systolic pressure ratio were satisfactorily relieved (84.3 +/- 19.0 vs. 16.7 +/- 19.7 mmHg, 109.2 +/- 20.5 vs. 48.7 +/- 16.7 mmHg, 0.92 +/- 0.25 vs. 0.43 +/- 0.16; p < 0.001, p < 0.001, p < 0.001, respectively). The right ventricular end-diastolic volume index and right ventricular ejection fraction were also improved (166.3 +/- 85.2 vs. 105.6 +/- 28.8% of normal, 38.3 +/- 12.6 vs. 50.9 +/- 8.8%; p < 0.05, p < 0.005, respectively). Re-operation should be done before the development of marked right ventricular dysfunction, while it can still be performed at a low risk with satisfactory results.

Child↗

PubMed2000

New perspective on cosmic coincidence problems

Cosmological data suggest that we live in an interesting period in the history of the universe when rho(Lambda) approximately rho(M) approximately rho(R). The occurrence of any epoch with such a "triple coincidence" is puzzling, while the question of why we happen to live during this special epoch is the "Why now?" problem. We introduce a framework which makes the triple coincidence inevitable; furthermore, the "Why now?" problem is transformed and greatly ameliorated. The framework assumes that the only relevant mass scales are the electroweak scale M(EW), and the Planck scale M(Pl) and requires rho(1/4)(Lambda) approximately M(2)(EW)/M(Pl) parametrically. Assuming that the true vacuum energy vanishes, we present a simple model, where a false vacuum energy yields a cosmological constant of this form.

Journal Article↗

PubMed2000

Neutrino mass anarchy

What is the form of the neutrino mass matrix which governs the oscillations of the atmospheric and solar neutrinos? Features of the data have led to a dominant viewpoint where the mass matrix has an ordered, regulated pattern, perhaps dictated by a flavor symmetry. We challenge this viewpoint and demonstrate that the data are well accounted for by a neutrino mass matrix which appears to have random entries.

Journal Article↗