Biomedical subjects

M Nagao

Publications and source records attributed to M Nagao.

At least 19 recordsLinked to original sources

PubMed2006

Low-energy electrodynamics of superconducting diamond.

Heavily boron-doped, diamond films can become superconducting with critical temperatures Tc well above 4 K. Here we first measure the reflectivity of such a film down to 5 cm(-1), by also using coherent synchrotron radiation. We thus determine the optical gap 2Delta, the field penetration depth lambda, the range of action of the Ferrell-Glover-Tinkham sum rule, and the electron-phonon spectral function alpha2F(omega). We conclude that diamond behaves as a dirty BCS superconductor.

Journal Article↗

PubMed2006

Identification and phylogenetic analysis of hepatitis C virus in forensic blood samples obtained from injecting drug users.

Injecting drug users (IDUs) are a high-risk group for contracting hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV) infections. In Japan, data on the prevalence of those blood-borne viruses among IDUs are very limited. Blood samples were obtained from 12 cadavers of IDUs sent to Nagoya City University for the purpose of judicious autopsy and two alive IDUs with hepatitis C referred to a local hospital at the same period. The viruses were detected by polymerase chain reaction and phylogenetic analysis was performed. Two (16.6%) of the 12 autopsy cases were positive for HCV, but no case was positive for either HBV or HIV. Phylogenetic analysis of the two HCV isolates revealed that one was classified into genotype 1b and another was genotype 2b. Furthermore, nucleotide sequences of two isolates recovered from IDUs with hepatitis C were identical, that indicated the transmission of HCV between them, and those HCV were phylogenetically classified into genotype 2a. The prevalence of HCV infection among IDUs in Japan, despite the case of judicious autopsy, seems to be high, but HIV infection seems to be rare. The transmission of HCV between IDUs was demonstrated, and this indicates that phylogenetic analysis would applicable to also forensic analysis. HCV isolates identified in this study did not phylogenetically segregate, thus multiple transmission route of HCV among IDUs seems be exist in Japan.

Adult↗

PubMed2006

Small interfering RNA expression vector targeting hypoxia-inducible factor 1 alpha inhibits tumor growth in hepatobiliary and pancreatic cancers.

Hepatobiliary and pancreatic carcinomas are hypovascular tumors that can proliferate under hypoxic conditions. Recent reports have demonstrated that hypoxia-inducible factor 1 alpha (HIF1alpha) plays an important role in the survival of these cancers. Given these findings, the inhibition of the HIF1alpha pathway might prove to be a powerful tool in the treatment of these cancers. To inhibit HIF1alpha expression, we used small interference RNA (siRNA) expression vectors in this study. The transient transfection of siRNA expression vectors significantly reduced both HIF1alpha mRNA levels (13% of control) and protein levels (41% of control) and significantly inhibited the growth of cancer cell lines (P<0.05). VEGF, Glut1, and aldorase A expressions were also significantly reduced by transfection with these vectors (P<0.05), and we found that these vectors induced apoptosis but not cell cycle arrest. In a subcutaneous tumor model using nude mice, transfected MIA PaCa-2 cells, stably expressing siRNAs, barely formed tumors compared to control (P<0.05). This study thus demonstrates the usefulness of siRNA expression vector in targeting HIF1alpha and points to a potential clinical role in the treatment of pancreatic and hepatobiliary carcinomas.

Animals↗

PubMed2006

Comparison between intraperitoneal CO2 insufflation and abdominal wall lift on QT dispersion and rate-corrected QT dispersion during laparoscopic cholecystectomy.

This study compared the effect of intraperitoneal CO2 insufflation with abdominal wall lift on RR interval, QT interval, the rate-corrected QT (QTc) interval, QT dispersion (QTD), and the rate-corrected QTD (QTcD) using computerized measurement during laparoscopic cholecystectomy. Thirty patients scheduled for laparoscopic cholecystectomy were randomly assigned to 2 groups: intraperitoneal CO2 insufflation (CO2 group) or abdominal wall lift (lift group). A 12-lead electrocardiogram was monitored to measure parameters. The RR interval, QT interval, and QTc interval did not change significantly during the study in both groups. The QTD and QTcD in the CO2 group increased significantly during CO2 insufflation, and were significantly higher than those of the lift group. Statistically significant increases of QTD and QTcD, which are associated with an increased risk of arrhythmias and cardiac events, occur during CO2 insufflation, and QTD and QTcD in the CO2 group were significantly higher than those of the lift group.

Abdominal Wall↗

PubMed2005

Origin of the metallic properties of heavily boron-doped superconducting diamond.

The physical properties of lightly doped semiconductors are well described by electronic band-structure calculations and impurity energy levels. Such properties form the basis of present-day semiconductor technology. If the doping concentration n exceeds a critical value n(c), the system passes through an insulator-to-metal transition and exhibits metallic behaviour; this is widely accepted to occur as a consequence of the impurity levels merging to form energy bands. However, the electronic structure of semiconductors doped beyond n(c) have not been explored in detail. Therefore, the recent observation of superconductivity emerging near the insulator-to-metal transition in heavily boron-doped diamond has stimulated a discussion on the fundamental origin of the metallic states responsible for the superconductivity. Two approaches have been adopted for describing this metallic state: the introduction of charge carriers into either the impurity bands or the intrinsic diamond bands. Here we show experimentally that the doping-dependent occupied electronic structures are consistent with the diamond bands, indicating that holes in the diamond bands play an essential part in determining the metallic nature of the heavily boron-doped diamond superconductor. This supports the diamond band approach and related predictions, including the possibility of achieving dopant-induced superconductivity in silicon and germanium. It should also provide a foundation for the possible development of diamond-based devices.

Journal Article↗

PubMed2005

Macroscopic quantum tunneling in a d-wave high-TC Bi2Sr2CaCu2O8 + delta superconductor.

While Josephson-junction-like structures intrinsic to the layered cuprate high temperature superconductors offer an attractive stage for exploiting possible applications to new quantum technologies, the low energy quasiparticle excitations characteristically present in these d-wave superconductors may easily destroy the coherence required. Here we demonstrate for the first time the feasibility of macroscopic quantum tunneling in the intrinsic Josephson junctions of a high temperature superconductor Bi(2)Sr(2)CaCu(2)O(8 + delta), and find it to be characterized by a high classic-to-quantum crossover temperature and a relatively weak quasiparticle dissipation.

Journal Article↗

PubMed2005

Dynamics of deuterated polystyrene-protonated butadiene diblock copolymer micelles by neutron spin echo.

We report on neutron spin-echo (NSE) measurements on deuterated styrene-protonated butadiene diblock copolymer micelles in deuterated n-decane to investigate the dynamics of butadiene blocks in the corona. Before the NSE measurements, we performed small-angle neutron-scattering (SANS) measurements on the micelles to evaluate the structure to give a basis for the discussion of the dynamics. In the SANS study, we have estimated the form factor P(Q) in terms of a hard-core-shell model from the direct evaluation without curve-fitting procedure while a more flexible core-shell model with the structure factor S(Q) gives a better fit to the observed data. The observed normalized intermediate scattering function I(Q,t)/I(Q,0) by NSE does not show the collective motions corresponding to the so-called breathing mode but rather single chain motion (Zimm modes) for both the 2 and 20 wt % micelle solutions. The Zimm decay rate Gamma(z) in the micelle solution is slow compared with that in the homopolymer solution. This slowing down is assigned to the effective high concentration in the corona. The differences in Gamma(z) between concentrated solutions and the 20% micellar solution are attributed to end-tethering effect of the corona chains on the core surface. The possible reasons why the breathing mode was not observed in the present micelle system are discussed on the basis of chain density in the corona.

Journal Article↗

PubMed2005

Neutron spin-echo studies on dynamic and static fluctuations in two types of poly(vinyl alcohol) gels.

We report neutron spin-echo measurements on two types of poly(vinyl alcohol) (PVA) gels. The first is PVA gel in a mixture of dimethyl sulfoxide (DMSO) and water with volume ratio 60/40 , and the second is PVA gel in an aqueous borax solution. The observed normalized intermediate scattering functions I (Q,t) /I (Q,0) are very different between them. The former I (Q,t) /I (Q,0) shows a nondecaying component in addition to a fast decay, but the latter does not have the nondecaying one. This clearly indicates that the fluctuations in the former PVA gel consist of static and dynamic fluctuations whereas the latter PVA gel does include only the dynamic fluctuations. The dynamic fluctuations of the former and latter gels have been analyzed in terms of a restricted motion in the network and Zimm motion, respectively, and the origins of these motions will be discussed.

Journal Article↗

PubMed2005

Heterotopically transplanted hepatocyte survival depends on extracellular matrix components.

The novel approach of tissue engineering to treat many forms of liver diseases using hepatocytes requires sufficient numbers and sustained survival of the transplanted cells. It has been shown that providing extracellular matrix components extracted from Engelbreth-Holm-Swarm cells (EHS-ECMs) to heterotopically transplanted hepatocytes allows significantly greater hepatocyte survival. We investigated the survival and morphology of hepatocytes and EHS-ECMs transplanted under the kidney capsule compared with hepatocytes with growth factor-reduced EHS-ECMs in mice. Both the EHS-ECMs and growth factor-reduced EHS-ECMs showed a large number of surviving hepatocytes under the kidney capsule without any intergroup differences. Histologically, transplanted hepatocytes in both groups retained their characteristic morphologies and formed small liver tissues. These data indicate that extracellular matrix components are the predominant factor in EHS-ECMs required to maintain hepatocytes at heterotopic sites.

Animals↗

PubMed2005

Long-term results of rotational acetabular osteotomy for dysplasia of the hip in adult ambulatory patients with cerebral palsy.

We performed rotational acetabular osteotomy in order to treat dysplasia of the hip in five ambulatory adults with cerebral palsy. There was one man and four women, with a mean age of 21 years (16 to 27) who were followed up for a mean of 12 years and two months. The mean Sharp angle improved from 52 degrees to 43 degrees , the mean acetabular index from 30.2 degrees to 2.8 degrees , the mean centre-edge angle from -5.6 degrees to 29.2 degrees , and the mean acetabular head index from 49.2 to 88.2. There was no progression of joint degeneration and relief from pain was maintained. Our results suggest that rotational acetabular osteotomy is a valuable option for the treatment of acetabular dysplasia in adults with cerebral palsy who have incapacitating pain in the hip.

Adolescent↗

PubMed2004

Listeria monocytogenes isolated from cold-smoked fish products in Osaka City, Japan.

Listeria monocytogenes contamination of ready-to-eat seafood products commercially available in Osaka was examined between 1999 and 2000. L. monocytogenes was isolated from 12 (13%) of the 95 products tested. All positive samples were from cold-smoked fish with 9 being obtained during the summer. Thirteen isolates of L. monocytogenes were typed by pulsed-field gel electrophoresis (PFGE) and polymerase chain reaction (PCR)-based typing methods. Isolates of the same serotype originating from the same manufacturer gave similar DNA profiles, irrespective of the type of sample or date of isolation. The finding suggest that persistent strains in each manufacturing facility proliferate during the summer and contaminate products during manufacturing processes.

Animals↗

PubMed2004

Temperature and pressure effects on the bending modulus of monolayers in a ternary microemulsion.

We performed small-angle neutron scattering and neutron spin echo experiments on a ternary microemulsion composed of ionic surfactant AOT, water, and decane. Thermal fluctuations of monolayers have been investigated as a function of temperature and pressure. The amphiphilic monolayers become more flexible with increasing temperature and more rigid with increasing pressure. These results are consistent with the microscopic picture that the head-head repulsion of the AOT molecules is enhanced at high temperature while an attractive interaction between the hydrophobic tails of the AOT molecules increases at high pressure.

Journal Article↗

PubMed2004

Overview of mammalian zinc transporters.

In recent years, a number of mammalian zinc transporters have been identified, and candidate genes are rapidly growing. These transporters are classified into two families: ZIP (ZRT, IRT-like protein) and CDF (cation diffusion facilitator). ZIP members facilitate zinc influx into the cytosol, while CDF members facilitate its efflux from the cytosol. Molecular characterization of the transporters has brought about major advances in our understanding of their physiological functions. Zinc metabolism is regulated primarily through zinc-dependent control of transcription, translation, and intracellular trafficking of transporters. Analyses of mice whose zinc transporter genes have been genetically disrupted and of the naturally occurring mutant mice with symptoms related to abnormal zinc metabolism have provided compelling evidence that some zinc transporters play critical roles in zinc homeostasis. In this review, we review the literature of mammalian zinc transporters with emphasis on very recent findings and elicit integrative knowledge of zinc homeostasis.

Animals↗

PubMed2004

Prototype of simulation of orthognathic surgery using a virtual reality haptic device.

A maxillofacial simulator can support education and training. In the present study, cutting, separation, and quantitative rearrangement of bone during orthognathic surgery were simulated by means of a haptic device with virtual tactile perception. Computed tomographic (CT) images of two patients with severe jaw deformity, one women and one man, were input into the device. In the woman, Le Fort I osteotomy of the maxilla and sagittal splitting ramus osteotomy of the mandible were initially simulated. During surgery with the haptic device, separation and rearrangement of the maxilla and the ramus of the mandible were initially processed. However, there was discrepancy and overlapping of the ramus with the mandible. Intraoral vertical osteotomy of the right ramus was then performed, with satisfactory results and less discrepancy and interference. The simulation was referred to at surgery, and satisfactory surgical assistance was postoperatively confirmed on CT images. The male patient had severe jaw deformity due to unequal growth between the ramuses, resulting in anterior crossbite. Sagittal splitting ramus osteotomy with rotation of the mandible was successfully simulated. Because of its versatility and functions, the present device was found to be useful for simulating various procedures for orthognathic surgery and thereby three-dimensionally determine surgical movements.

Adult↗

PubMed2004

Time-frequency analysis for pulse driven ultrasonic microscopy for biological tissue characterization.

The authors have proposed a new type of ultrasonic microscopy for biological tissue characterization. The system is driven by a nanosecond pulse voltage, the generated acoustic wave being reflected at the front and rear side of the sliced tissue. In this report, a time-frequency analysis was applied to determine the sound speed thorough the tissue. Frequency dependence of sound speed was obtained with a myocardium of a rat sliced into 10 microm. As the reflected waveform had a significant amount of oscillating component, the waveform was once subjected to the deconvolution process. As the result, two reflections were clearly separated in time domain. Then these two reflections were separately analyzed by time-frequency analysis. Each reflection was extracted by using a proper window function. Phase angles of these reflections at the same frequency were compared. A sound speed micrograph at an arbitrary frequency in between 50 and 150 MHz was successfully obtained. A tendency was found that the sound speed slightly increases with frequency.

Animals↗

PubMed2004

Computer-assisted morphological analysis of dental casts with maxillary prognathism and reversed occlusion.

The morphologic characteristics of the dentition with maxillary prognathism and reversed occlusion were examined by a computer-assisted dental cast analysing system. Dental casts with normal occlusion, maxillary prognathism and reversed occlusion were selected and measured by a 3D shape measuring system. The dental arches and anteroposterior occlusal curves were approximated numerically by the polynomial expression with a fourth order and second order coefficients, respectively. The coefficients were analysed statistically. Maxillary dental arches with mandibular prognathism showed a more acuminate shape (V-shape) with a significant larger second order coefficient, while arches with reversed occlusion showed more angulate shapes (U-shape) with significantly smaller second order coefficients compared with arches with normal occlusions. However, a notable difference in the shape of the mandibular dental arches was not observed. The mandibular dental arches with maxillary prognathism were positioned backward relative to maxillary dental arches, while the arches with reversed occlusion were positioned forward. The anteroposterior occlusal curves with maxillary prognathism showed larger curvatures in maxilla and mandible, while the curves with reversed occlusion showed smaller curvatures in mandible comparing with the curves with normal occlusion. These results suggest that the present method could offer a useful and objective examination technique for the diagnosis of malocclusion.

Adolescent↗

PubMed2003

A preliminary report on a computer-assisted dental cast analysis system used for the prosthodontic treatment.

To accomplish computerized 3D morphological analyses of maxillary and mandibular casts with malocclusions on the same co-ordinate system, a new reference co-ordinate located on soft tissue has been proposed consisting of the top of maxillary bilateral tubercles and incisive papilla on the maxillary cast. To test the validity of this co-ordinate system, the angles of the occlusal plane in this system were examined on 10 subjects with normal occlusion. In addition, to analyse maxillary and mandibular casts on the same co-ordinate system, a bite block was made under the intercuspal position. The maxillary cast was measured by 3D measuring system, then, the bite block was placed on maxillary casts, and measured similarly. To examine the position reproducibility of this method, 3D co-ordinates of the apex of the buccal cusp of the mandibular pre-molar in five bite blocks were determined. The angles formed of the occlusal plane were 1.3 +/- 1.3 degrees and 0.2 +/- 1.1 degrees on the sagittal and frontal base plane, respectively. This co-ordinate system had enough stability to replace the occlusal plane. By the measurement of bite blocks, the co-ordinates of the mandibular cusp tips were determined within the deviation of 0.2 mm.

Dental Casting Technique↗

PubMed2002

Liver fibrosis increases the risk of intrahepatic recurrence after hepatectomy for hepatocellular carcinoma.

BACKGROUND: Hepatocellular carcinoma (HCC) commonly develops in patients with chronic hepatitis. Intrahepatic recurrence after hepatectomy often includes nodules of new tumour in the liver remnant. The aim of this study was to examine hepatitis-related factors that might predict this type of recurrence. METHODS: The influence of various hepatitis-related factors on intrahepatic recurrence of HCC was studied by multivariate analysis in 138 patients who underwent curative resection and were followed for more than 2 years. RESULTS: The Cox proportional hazard model showed that histological evidence of fibrosis of the underlying liver was the most significant predictive factor for intrahepatic recurrence (P = 0.001). Serum albumin level was also significantly associated with recurrence (P = 0.038). The relative risks of histological fibrosis and low serum albumin levels were 8.9 and 1.7 respectively. Among tumour-related factors, only tumour size was significantly associated with recurrence (P = 0.017). Major hepatectomy was also an independent risk factor for intrahepatic recurrence (P = 0.004). CONCLUSION: Histological evidence of fibrosis and low serum albumin levels are useful predictors of intrahepatic recurrence after hepatectomy, presumably owing to metachronous multifocal tumour in the liver remnant.

Adolescent↗