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Biomedical subjects

A Tsukada

Publications and source records attributed to A Tsukada.

At least 19 recordsLinked to original sources
PubMed2006

Fluorescence X-ray absorption spectroscopy using a Ge pixel array detector: application to high-temperature superconducting thin-film single crystals.

A Ge pixel array detector with 100 segments was applied to fluorescence X-ray absorption spectroscopy, probing the local structure of high-temperature superconducting thin-film single crystals (100 nm in thickness). Independent monitoring of pixel signals allows real-time inspection of artifacts owing to substrate diffractions. By optimizing the grazing-incidence angle theta and adjusting the azimuthal angle phi, smooth extended X-ray absorption fine structure (EXAFS) oscillations were obtained for strained (La,Sr)2CuO4 thin-film single crystals grown by molecular beam epitaxy. The results of EXAFS data analysis show that the local structure (CuO6 octahedron) in (La,Sr)2CuO4 thin films grown on LaSrAlO4 and SrTiO3 substrates is uniaxially distorted changing the tetragonality by approximately 5 x 10(-3) in accordance with the crystallographic lattice mismatch. It is demonstrated that the local structure of thin-film single crystals can be probed with high accuracy at low temperature without interference from substrates.

Algorithms↗
PubMed2003

Magnetic penetration depth measurements of Pr2-xCexCuO4-delta films on buffered substrates: evidence for a nodeless gap.

We report measurements of the inverse squared magnetic penetration depth, lambda(-2)(T), in Pr(2-x)Ce(x)CuO(4-delta) (0.115< or =x < or =0.152) superconducting films grown on SrTiO3 (001) substrates coated with a buffer layer of insulating Pr2CuO4. lambda(-2)(0), T(c), and normal-state resistivities of these films indicate that they are clean and homogeneous. Over a wide range of Ce doping, 0.124< or =x < or =0.144, lambda(-2)(T) at low T is flat: it changes by less than 0.15% over a factor of 3 change in T, indicating a gap in the superconducting density of states. Fits to the first 5% decrease in lambda(-2)(T) produce values of the minimum superconducting gap in the range of 0.29< or =Delta(min)/k(B)T(c)< or =1.01.

Journal Article↗
PubMed2003

Magnetic-field dependence of the maximum supercurrent of La2-xCexCuO4-y interferometers: evidence for a predominant dx2-y2 superconducting order parameter.

We performed a phase-sensitive test of the symmetry of the superconducting order parameter of the electron doped cuprate La(2-x)Ce(x)CuO(4-y) using a superconducting quantum interferometer with spatially distributed Josephson junctions. The studies were made on a thin film grown on a SrTiO3 tetracrystal substrate. The superconducting transition temperature was about 29 K which indicates that the sample is close to optimal doping. The magnetic field dependence of the critical current gives strong evidence for a predominant dx(2)(-y(2)) order parameter symmetry of the sample measured. It also gives upper limits for the s-wave component in a mixed order parameter of the type s+idx(2)(-y(2)).

Journal Article↗
PubMed2003

Profiles of mRNA expression of genes related to sex differentiation of the gonads in the chicken embryo.

Sex is determined genetically in birds. The homogametic sex is male (ZZ), whereas the heterogametic sex is female (ZW). According to the genetic sex, gonads develop into testes or ovary. In this study, we performed experiments to reveal mRNA expression patterns in the gonad between d 5.5 and 8.5 of incubation and examined a possible role of Dss-Ahc critical region on the X chromosome 1 (Dax1), Steroidogenic factor 1 (Sf1), P450aromatase (P450arom), Estrogen receptor alpha (ER alpha), doublesex and mab3 related transcription factor 1 (Dmrt1), Sry-related HMG box gene 9 (Sox9), Gata binding protein 4 (Gata4), and anti-müllerian hormone (Amh) in sex differentiation in chicken embryonic gonads using RNase protection assay. In embryonic chicken gonads, Dax1 mRNA was expressed in both sexes but was higher in females than in males at d 6.5 and 7.5 of incubation. The Sf1 mRNA was expressed in both sexes, but it was expressed more in males at d 5.5 than in females but more in females than in males at d 7.5 and 8.5 of incubation. The P450arom mRNA was expressed only in female gonads from d 5.5 of incubation. The ER alpha mRNA was expressed in both sexes, but it did not show a sex difference. On the other hand, the Dmrt1 mRNA was expressed in both sexes, but it showed a male-specific expression pattern. The male-specific expression pattern was observed in Sox9 mRNA, but it was not expressed in female gonads. The Gata4 mRNA was expressed in both sexes, and sex differences were not revealed throughout the observational period. Amh mRNA was expressed in both sexes, but it had male-specific mRNA expression pattern at d 6.5 to 8.5 of incubation. These results indicate that Dax1, Sf1, and P450arom have possible roles in ovary formation, whereas Dmrt1, Sox9, and Amh are related to testis formation in differentiating chicken gonads at d 5.5 to 8.5 of incubation.

Animals↗
PubMed2003

cDNA cloning of chicken orexin receptor and tissue distribution: sexually dimorphic expression in chicken gonads.

Orexin-A and -B are known to stimulate food intake in mammals. However, the critical roles of orexins in birds are not fully understood, since orexins have no stimulatory effect on food intake in the chicken. To understand the physiological role(s) of orexins in birds, we have cloned chicken orexin receptor (cOXR) cDNA by RT-PCR, and analysed the tIssue distribution of OXR mRNA in the chicken. The cOXR cDNA is 1869 bp long and encodes 501 amino acids. The cloned cDNA for cOXR corresponds to the type 2 OXR in mammals, and shows approximately 80% similarity to those of mammals at the amino acid level. Expression analysis by RNase protection assay revealed OXR mRNA was distributed widely in brain regions, and expression in the cerebrum, hypothalamus and optic tectum were abundant. In peripheral tIssues, OXR mRNA was expressed in the pituitary gland, adrenal gland and testis, but no mRNA expression was observed in other tIssues examined. Furthermore, we found that the amount of cOXR mRNA was different between testis and ovary, while prepro-orexin mRNA is equally expressed in the gonads of both sexes in the chicken. These data indicate that the orexins have neuroendocrine actions in chickens, which are mediated through hypothalamic receptors as has been observed in mammals. In addition, orexin may have specific role(s) in the regulation of gonadal function in which sex-dependent mechanisms could be involved.

Amino Acid Sequence↗
PubMed2001

Indirect arterial blood pressure measurement at the wrist using a pad-type square cuff and volume-oscillometric method.

Using theoretical and experimental approaches, we examined whether blood pressure at the wrist can be accurately measured by a volume-oscillometric method using a small pad-type square cuff placed above the radial artery (RA). Nuclear magnetic resonance imaging of the wrist allowed us to determine the geometry of two-dimensional (2-D) finite-element models. Finite-element method (FEM) analysis predicted that the pressure transmission ratio (calculated tissue pressure over externally applied pressure; square cuff to RA) was 98.8% for a cuff with a bladder sidelength 0.25 times the wrist diameter placed on the skin surface between the tendons of the brachioradialis muscle (Ta) and the flexor capri radialis muscle (Tb) and over the site (L) at which RA crosses the most protuberant spot on the volar aspect of the distal end of the radius. In addition, FEM analysis using a 3-D finite-element model (constructed by extending the 2-D finite-element model at site L in the longitudinal direction) showed that for all square cuffs with bladder sidelengths greater than or equal to 0.25 times the wrist diameter, the external pressure was transmitted almost completely to RA beneath the cuff center. Moreover, when the bladder sidelength was 0.44 times the wrist diameter, but not 0.29 times the wrist diameter, the mean blood pressure measured at site L in human subjects was similar to that measured at the upper arm. Taken together, the theoretical and the experimental results suggest that (i) blood pressure at the wrist can be measured accurately using a pad-type square cuff placed on the skin surface between Ta and Tb at site L, and (ii) the minimum bladder sidelength for accurate readings is somewhere between one-third and one-half of the wrist diameter.

Adult↗
PubMed2001

Intraosseous meningioma of the posterior fossa--Case report.

A 62-year-old male presented with a rare intraosseous meningioma with intradural extension manifesting as frequent vomiting and floating sensation that had persisted for 3 months. Neuroimaging detected a mass lesion that was mainly located extradurally in the right posterior fossa with a daughter lesion inside the dura. He underwent surgical excision of the mass lesion. Craniectomy exposed the main lesion of the tumor just beneath the thinned outer table of the skull, and in the extradural space, with the daughter lesion penetrating the dura. Both portions of the tumor were resected. There was no attachment to the adjacent dura mater. Histological examination showed meningotheliomatous meningioma containing scattered bony tissue. This intraosseous meningioma probably originated from the occipital bone with a small intradural extension caused by mechanical compression.

Cerebral Angiography↗
PubMed1999

Suitable location and optimum bladder width for the occluding cuff used for indirect arterial blood pressure measurements at the wrist.

Using a finite element method (FEM) and a volume oscillometric method with a photo-electric plethysmograph, we tried to determine which location(s) and which bladder width(s) of the occluding cuff would allow the most accurate indirect blood pressure measurements at the human wrist. Nuclear magnetic resonance imaging of the wrist allowed us to determine the geometry of two-dimensional (2D) finite element models. FEM analysis showed that the pressure transmission ratio (calculated tissue pressure: externally applied pressure) from the cuff to the radial artery (RA) was 100% when the cuff was placed over the site (L1) at which the RA crosses the most protuberant spot on the volar aspect of the distal end of the radius. In fact, the mean blood pressure (BPM) measured at this site in human subjects coincided with that measured at the upper arm (BPMA). In addition, a three-dimensional (3D) FEM was constructed by extending the 2D FEM at site L1 in the longitudinal direction to investigate the relation between pressure transmission to the RA and cuff bladder width. FEM analysis using the 3D finite element model showed that for all cuff widths greater than 0.25 times the diameter of the wrist, the external pressure was transmitted almost completely to the RA beneath the cuff center. Moreover, when the cuff width was as large as 0.45 times the diameter of the wrist, the BPM measured at site L1 in human subjects was similar to the BPMA. The theoretical and experimental results in the present study both suggest that for accurate indirect blood pressure measurements at the wrist, the L1 site is a suitable location for the occluding cuff and a cuff whose bladder width is more than one-third but less than one-half the wrist diameter can be used.

Adult↗
PubMed1998

Polyethylene wear from femoral bipolar neck-cup impingement as a cause of femoral prosthetic loosening.

A 33-year-old woman underwent an uncemented bipolar hip arthroplasty for osteoarthrosis of the left hip in 1985. Because of painful aseptic loosening, the bipolar implant was revised to a total hip prosthesis in 1994. Membranous tissues around the implant histologically presented foreign-body reaction against polyethylene debris. The retrieved implant showed polyethylene wear of the rim of the bipolar cup. Three-dimensional measurement of the surface configuration of the polyethylene of the cup indicated that wear debris had been generated almost exclusively from femoral bipolar neck-cup impingement. Volumetric wear in the articulating dome portion of the polyethylene was negligible. This report clearly illustrates how impingement of a bipolar cup on the femoral neck can be a major source of polyethylene wear debris which induces femoral osteolysis and subsequent stem loosening.

Adult↗
PubMed1998

Cloning and expression of pigeon growth hormone receptor cDNA in COS-7 monkey kidney cells.

Pigeon growth hormone receptor (pGHR) cDNA has been cloned, sequenced, characterized and expressed in COS-7 cells. The predicted pGHR preprotein was composed of 611 amino acids and contained a putative signal peptide, a single transmembrane region and the conserved proline-rich box 1 domain in the cytoplasmic region. A canonical polyadenylation signal was found in the extracellular region, as was observed in chicken growth hormone receptor cDNA. Northern blot analysis identified a single species of pGHR mRNA and its expression was widely observed in tissues in the young male pigeon. A pGHR expression vector was constructed and transfected into COS-7 cells. The transfected cells were specifically bound by 125I-labeled chicken GH and the binding was suppressed by the addition of excess amounts of unlabeled chicken GH.

Amino Acid Sequence↗
PubMed1998

Thyroid hormones are involved in insulin-like growth factor-I (IGF-I) production by stimulating hepatic growth hormone receptor (GHR) gene expression in the chicken.

Effect of thyroid status on IGF-I production in growing chickens was studied. Serum concentrations of GH were not affected by propylthiouracil (PTU) or thyroxine (T4) treatments, whereas serum IGF-I levels were significantly decreased in PTU-treated chickens. The lowered serum IGF-I levels in the PTU-treated group were completely restored to the control levels by T4 injections. In the liver, the messenger RNA (mRNA) expressions both for GH receptor (GHR) and IGF-I were significantly repressed by PTU treatment, and were restored again by T4 replacement. In addition, the results of analysis on radiolabelled GH binding to the liver membrane were consistent with the levels of hepatic GHR mRNA expression. Serum concentrations of IGF-I were positively correlated with hepatic IGF-I mRNA and GHR mRNA expressions. The correlation coefficient between serum T3 levels and hepatic IGF-I mRNA expressions was also significant. These results indicate that thyroid hormones regulate IGF-I production in the chicken by affecting hepatic GHR expression.

Animals↗
PubMed1998

Nontraumatic bilateral first rib fractures.

The authors report the case of a 21-year old woman who presented bilateral spontaneous fractures of the first ribs, in the posterior portion on the right side, in the anterior portion on the left side. The pathogenesis of spontaneous fractures of the first rib is discussed.

Adult↗
PubMed1996

[Simultaneous rupture of multiple intracranial aneurysms: a case report].

A rare case of simultaneous rupture of multiple aneurysms is reported. A 68-year-old man presented severe headache and vomiting and was transferred to our hospital. CT scan showed subarachnoid hemorrhage (SAH) in the interhemispheric fissure, the right basal cistern, the right sylvian fissure and intracerebral hemorrhage (ICH) in the paraventricle area. Continuation of the hemorrhage could not be detected between SAH and ICH on CT scan. Multiple aneurysms were detected by angiograms on the anterior communicating artery (A-com) and the bifurcation and the distal portion of the left middle cerebral artery (MCA). These findings suggested that SAH was due to a ruptured aneurysm of A-com, and ICH was due to a ruptured aneurysm of the distal portion of MCA. Simultaneous rupture of multiple aneurysms was confirmed by surgical findings. This case indicates that the usual assumption of a single aneurysm rupture in a patient with multiple aneurysms may be erroneous.

Adult↗
PubMed1995

Intrasyringal hemorrhage of the cervical cord associated with Chiari type I malformation--case report.

A 34-year-old male presented with intrasyringal hemorrhage associated with Chiari type I malformation manifesting as a history of repetitive severe pain around his neck and back and progressive sensory disturbance. Magnetic resonance imaging clearly demonstrated syringomyelia at the cervical region associated with Chiari type I malformation and hemorrhage in the syrinx which was strongly suggestive of bleeding into pre-existing syringomyelia or Gowers' syringal hemorrhage. Irrigation of the syrinx and syringosubarachnoid shunting were performed, but rebleeding occurred causing shunt malfunction. Shunt revision was performed, but a new cavity developed above the original syrinx. Foramen magnum decompression resulted in successful reduction of the new syrinx and subsequent neurological improvement. Simultaneous foramen magnum decompression and syrinx irrigation may be a better approach to treat this disease.

Adult↗
PubMed1995

Cerebral gumma mimicking glioblastoma on magnetic resonance images--case report.

A 39-year-old female presented with a syphilitic cerebral gumma mimicking small glioblastoma multiforme manifesting as visual impairment. Magnetic resonance imaging showed a low signal intensity area on T1-weighted images and marked small ring-like enhancement less than 1 cm in diameter following the administration of gadolinium. The symptoms and radiological abnormalities improved several weeks after penicillin therapy. The small ring-like enhancement was probably caused by inflammation associated with treponemal infection. A mass with a small ring-like enhancement less than 1 cm in diameter is a useful finding indicating an inflammatory lesion rather than a glial tumor.

Adult↗
PubMed1995

Effects of acidic fibroblast growth factor on neuronal activity of the parvocellular part in rat paraventricular nucleus.

The effects of acidic fibroblast growth factor (aFGF) and its amino-terminal and carboxyl-terminal fragments (aFGF(1-15) and aFGF(114-140), respectively were examined on the neuronal activity in the parvocellular part of the paraventricular nucleus. As well known, this part contains a lot of corticotropin-releasing factor (CRF)-immunoreactive neurons. Application of 1 pg/ml and 2 pg/ml aFGF produced responses in 29.7% and 46.7% of neurons tested, respectively. Half or more than half of the responding neurons increased their discharge rate. Application of 0.2 ng/ml and 0.4 ng/ml aFGF(1-15) (1-15) also elicited response in 46.2% and 68.8% of neurons tested, respectively. Of these responding neurons, more than two third increased their firing rate. However, most of neurons tested for 0.67 ng/ml and 1.33 ng/ml aFGF(114-140) did not respond. Results suggest that aFGF and aFGF(1-15) promote the release of CRF through the activation of CRF-containing neurons.

Animals↗