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Biomedical subjects

S Uchida

Publications and source records attributed to S Uchida.

At least 37 records · Page 2Linked to original sources
PubMed2002

Generic values for soil-to-plant transfer factors of radiocesium.

There is a need for soil-to-plant transfer factors of radionuclides that take into account all possible crops on all soil varieties to support dose assessment studies. Because only limited experimental data exist for worldwide soil systems, such values should necessarily have a generic character. This paper describes a generic system for 137Cs, mainly based on a reference soil-to-plant transfer factor which depends solely on soil properties such as nutrient status, exchangeable K-content, pH and moisture content. Crops are divided into crop groups, cereals serving as reference group. The transfer of other crop groups can be calculated by multiplying data for cereals by a conversion factor. Existing data present in the IUR (International Union of Radioecologists) databank and in large part the work of a FAO (Food and Agriculture Organisation)/IAEA(International Atomic Energy Agency)/IUR project on tropical systems provided the basis for the derivation of the conversion factors and reference values.

Cesium Radioisotopes↗
PubMed2002

Calcifying tendonitis of the gastrocnemius. A report of three cases.

We describe the clinical features of calcifying tendonitis in the medial head of gastrocnemius in three elderly female patients. The presenting symptom was chronic pain in the posteromedial area of the knee in two patients and acute pain in the back of the knee in one. All had limitation of movement of the knee and marked tenderness in the region of the tendinous origin of the medial head of gastrocnemius with posterior knee pain induced by stretching the tendon. An injection of 1% lidocaine and steroid into the tendon resulted in temporary relief from pain and improved movement.

Aged↗
PubMed2001

[An international repatriation of a cervical cord injury patient who was under mechanical ventilation].

The patient was a 55-year old Japanese man, who had a traffic accident and suffered cervical cord injury in Thailand. Although he received an emergency operation and intensive care, he had respiratory paralysis and received a tracheostomy. One month after the accident, he still needed to receive mechanical ventilatory support. He and his wife hoped to return to Japan. We were asked to transport the patient from Bangkok to Tokyo. With some help from an assistance company, we could transport the patient safely from Bangkok to Tokyo on a commercial airline under mechanical ventilatory support. We experienced the several regulations and difficulties in performing medical treatment and transportation of a critical patient in a commercial airline.

Aircraft↗
PubMed2001

Spin dynamics of Sr14Cu24O41 two-leg ladder studied by Raman spectroscopy.

The two-magnon (2M) excitation at 3000 cm(-1) in Sr14Cu24O41 two-leg ladder is studied by Raman scattering. A slight anisotropy of the superexchange coupling J(perpendicular)/J(parallel) approximately 0.8 with J(parallel) = 110+/-20 meV is proposed from the analysis of the magnetic scattering. The resonant coupling across the charge transfer gap increases the 2M intensity by orders of magnitude. The anisotropy of Raman scattering is dependent upon the excitation energy. The 2M relaxation is found to be correlated with the temperature dependent electronic Raman continuum at low frequencies.

Journal Article↗
PubMed2001

Measurement of 240Pu/239Pu isotopic ratios in soils from the Marshall Islands using ICP-MS.

Nuclear weapons tests conducted by the United States in the Marshall Islands produced significant quantities of regional or tropospheric fallout contamination. Here we report on some preliminary inductively coupled plasma-mass spectrometry (ICP-MS) measurements of plutonium isolated from seven composite soil samples collected from Bikini, Enewetak and Rongelap Atolls in the northern Marshall Islands. These data show that 240Pu/239Pu isotopic signatures in surface soils from the Marshall Island vary significantly and could potentially be used to help quantify the range and extent of fallout deposition (and associated impacts) from specific weapons tests. 137Cs and 60Co were also determined on the same set of soil samples for comparative purposes.

Environmental Monitoring↗
PubMed2001

Microscopic electronic inhomogeneity in the high-Tc superconductor Bi2Sr2CaCu2O8+x.

The parent compounds of the copper oxide high-transition-temperature (high-Tc) superconductors are unusual insulators (so-called Mott insulators). Superconductivity arises when they are 'doped' away from stoichiometry. For the compound Bi2Sr2CaCu2O8+x, doping is achieved by adding extra oxygen atoms, which introduce positive charge carriers ('holes') into the CuO2 planes where the superconductivity is believed to originate. Aside from providing the charge carriers, the role of the oxygen dopants is not well understood, nor is it clear how the charge carriers are distributed on the planes. Many models of high-Tc superconductivity accordingly assume that the introduced carriers are distributed uniformly, leading to an electronically homogeneous system as in ordinary metals. Here we report the presence of an electronic inhomogeneity in Bi2Sr2CaCu2O8+x, on the basis of observations using scanning tunnelling microscopy and spectroscopy. The inhomogeneity is manifested as spatial variations in both the local density of states spectrum and the superconducting energy gap. These variations are correlated spatially and vary on the surprisingly short length scale of approximately 14 A. Our analysis suggests that this inhomogeneity is a consequence of proximity to a Mott insulator resulting in poor screening of the charge potentials associated with the oxygen ions left in the BiO plane after doping, and is indicative of the local nature of the superconducting state.

Journal Article↗
PubMed2001

Three families with autosomal dominant nephrogenic diabetes insipidus caused by aquaporin-2 mutations in the C-terminus.

The vasopressin-regulated water channel aquaporin-2 (AQP2) is known to tetramerize in the apical membrane of the renal tubular cells and contributes to urine concentration. We identified three novel mutations, each in a single allele of exon 4 of the AQP2 gene, in three families showing autosomal dominant nephrogenic diabetes insipidus (NDI). These mutations were found in the C-terminus of AQP2: a deletion of G at nucleotide 721 (721 delG), a deletion of 10 nucleotides starting at nucleotide 763 (763-772del), and a deletion of 7 nucleotides starting at nucleotide 812 (812-818del). The wild-type AQP2 is predicted to be a 271-amino acid protein, whereas these mutant genes are predicted to encode proteins that are 330-333 amino acids in length, because of the frameshift mutations. Interestingly, these three mutant AQP2s shared the same C-terminal tail of 61 amino acids. In Xenopus oocytes injected with mutant AQP2 cRNAs, the osmotic water permeability (Pf) was much smaller than that of oocytes with the AQP2 wild-type (14%-17%). Immunoblot analysis of the lysates of the oocytes expressing the mutant AQP2s detected a band at 34 kD, whereas the immunoblot of the plasma-membrane fractions of the oocytes and immunocytochemistry failed to show a significant surface expression, suggesting a defect in trafficking of these mutant proteins. Furthermore, coinjection of wild-type cRNAs with mutant cRNAs markedly decreased the oocyte Pf in parallel with the surface expression of the wild-type AQP2. Immunoprecipitation with antibodies against wild-type and mutant AQP2 indicated the formation of mixed oligomers composed of wild-type and mutant AQP2 monomers. Our results suggest that the trafficking of mutant AQP2 is impaired because of elongation of the C-terminal tail, and the dominant-negative effect is attributed to oligomerization of the wild-type and mutant AQP2s. Segregation of the mutations in the C-terminus of AQP2 with dominant-type NDI underlies the importance of this domain in the intracellular trafficking of AQP2.

Amino Acid Sequence↗
PubMed2001

Evidence for ubiquitous strong electron-phonon coupling in high-temperature superconductors.

Coupling between electrons and phonons (lattice vibrations) drives the formation of the electron pairs responsible for conventional superconductivity. The lack of direct evidence for electron-phonon coupling in the electron dynamics of the high-transition-temperature superconductors has driven an intensive search for an alternative mechanism. A coupling of an electron with a phonon would result in an abrupt change of its velocity and scattering rate near the phonon energy. Here we use angle-resolved photoemission spectroscopy to probe electron dynamics-velocity and scattering rate-for three different families of copper oxide superconductors. We see in all of these materials an abrupt change of electron velocity at 50-80 meV, which we cannot explain by any known process other than to invoke coupling with the phonons associated with the movement of the oxygen atoms. This suggests that electron-phonon coupling strongly influences the electron dynamics in the high-temperature superconductors, and must therefore be included in any microscopic theory of superconductivity.

Journal Article↗
PubMed2001

Molecular cloning and functional expression analysis of a cDNA for human hepassocin, a liver-specific protein with hepatocyte mitogenic activity.

By means of differential cDNA expression cloning, we earlier isolated a novel rat cDNA and its protein, named hepassocin, which is upregulated during liver regeneration. Using the rat cDNA as a probe, we have now isolated human hepassocin cDNA encoding a protein of 312 amino acids, which has 81.4% and 83.8% identity, respectively, to rat hepassocin before and after elimination of its signal peptide. Dot blot analysis revealed that hepassocin mRNA was strongly expressed in adult liver, fairly strongly in fetal liver, and weakly in pancreas, but not in other tissues. Recombinant human hepassocin produced in Chinese hamster ovary (CHO) cells by the dihydrofolate reductase-methotrexate (DHFR--MTX) gene amplification method is a homodimer (68 kDa) and has mitogenic activities in hepatocytes of various animal species including rat, mouse, rabbit and dog, and the activity was lost with 2-mercaptoethanol treatment. These results suggest that hepassocin is a potent regulator in liver cell growth not only in rats but also in humans. Computer searches revealed that human hepassocin as well as rat hepassocin has a characteristic disulfide structure close to that of fibrinogen-gamma. We assume that this newly identified growth factor exerts functions in association with an extracellular matrix such as fibrinogen.

Amino Acid Sequence↗
PubMed2001

Interplay of magnetism and high-Tc superconductivity at individual Ni impurity atoms in Bi2Sr2CaCu2O8+delta.

Magnetic interactions and magnetic impurities are destructive to superconductivity in conventional superconductors. By contrast, in some unconventional macroscopic quantum systems (such as superfluid 3He and superconducting UGe2), the superconductivity (or superfluidity) is actually mediated by magnetic interactions. A magnetic mechanism has also been proposed for high-temperature superconductivity. Within this context, the fact that magnetic Ni impurity atoms have a weaker effect on superconductivity than non-magnetic Zn atoms in the high-Tc superconductors has been put forward as evidence supporting a magnetic mechanism. Here we use scanning tunnelling microscopy to determine directly the influence of individual Ni atoms on the local electronic structure of Bi2Sr2CaCu2O8+delta. At each Ni site we observe two d-wave impurity states of apparently opposite spin polarization, whose existence indicates that Ni retains a magnetic moment in the superconducting state. However, analysis of the impurity-state energies shows that quasiparticle scattering at Ni is predominantly non-magnetic. Furthermore, we show that the superconducting energy gap and correlations are unimpaired at Ni. This is in strong contrast to the effects of non-magnetic Zn impurities, which locally destroy superconductivity. These results are consistent with predictions for impurity atom phenomena derived from a magnetic mechanism.

Journal Article↗
PubMed2001

Dual nature of the electronic structure of (La(2--x--y)Nd(y)Sr(x))CuO(4) and La(1.85)Sr(0.15)CuO(4).

High resolution angle-resolved photoemission measurements have been carried out on (La(1.4--x)-Nd(0.6)Sr(x))CuO(4), a model system with static one-dimensional (1D) charge ordering (stripe), and (La(1.85)-Sr(0.15))CuO(4), a high temperature superconductor (T(c) = 40 K) with possible dynamic stripes. In addition to the straight segments near ( pi,0) and ( 0,pi) antinodal regions, we have identified the existence of spectral weight along the [1,1] nodal direction in the electronic structure of both systems. This observation of nodal state, together with the straight segments near antinodal regions, reveals the dual nature of the electronic structure of stripes due to the competition of order and disorder.

Journal Article↗
PubMed2001

Monozygotic twins incompletely concordant for narcolepsy.

BACKGROUND: Among 15 monozygotic twin pairs described in the literature, only four pairs were considered to be concordant. There is no detailed report of HLA-DRB1*1501/DQB1*0602 positive monozygotic twins concordant for narcolepsy, with marked difference in the age of onset. METHODS: We compared a pair of female narcoleptic twins clinically. RESULTS: Diagnosis of narcolepsy and monozygosity of the twins were confirmed. The second-born twin demonstrated a typical course of narcolepsy, whereas the first-born twin had a very late onset of recurrent daytime sleep episodes at age 45 and cataplexy at age 50 years, which was apparently triggered by chronic emotional stresses and sleep insufficiency. CONCLUSIONS: The atypical course of narcolepsy in the first-born twin supports the multifactorial model for the development of narcolepsy. It was noted that cataplexy was preceded by sustained polyphasic sleep conditions. Our observation implies that the unaffected co-twins in discordant pairs could develop narcolepsy in stressful situations later in their lives.

Cytochrome P-450 Enzyme System↗
PubMed2001

Transverse josephson plasma mode in T* cuprate superconductors.

A transverse optical plasma mode is observed at far-infrared frequencies within the superconducting gap region by measuring the c-axis optical reflectivity for single crystals of T* cuprate superconductors SmLa0.85Sr0.15CuO4-delta and Nd1.4Sr0.4Ce0.2CuO4-delta. These T* cuprates have two different insulating layers sandwiching the superconducting CuO2 planes, leading to two longitudinal plasmons. Also, the transverse mode is directly observed due to the coupling of the infrared radiation with the current perpendicular to the superconducting layers which are regarded as an alternating array of two inequivalent Josephson junctions.

Journal Article↗
PubMed2001

Two-photon resonant third-harmonic generation in La2CuO4.

Combining linear absorption and nonlinear third harmonic generation (THG) experiments, we investigate details of the electronic structure of the highly correlated electronic system in La2CuO4. We demonstrate strong THG mainly due to the charge transfer excitation from O (2p(sigma)) to Cu (3d(x2-y2)). The THG spectrum shows pronounced features due to three-photon and two-photon resonance enhancement as well as quantum interference effects. We obtain excellent agreement with a THG spectrum calculated in terms of the excitonic cluster model and can identify both odd and even symmetry excitation modes.

Journal Article↗
PubMed2001

A method for standardizing jaw displacements in the horizontal plane while recording single motor unit activity in the human lateral pterygoid muscle.

The normal function of the lateral pterygoid muscle is not well understood although this muscle is thought to play an important role in the control of jaw and jaw-joint function and is implicated in temporomandibular disorders (TMD). The lack of a validated method for standardization of jaw movement in studies of lateral pterygoid function has contributed to the lack of understanding of the normal function of this muscle. An improved understanding of normal function will allow valid comparisons to be made with TMD patients in order to identify whether purported differences in activity actually exist. This paper describes a methodology for standardizing command jaw movements in the horizontal plane, together with reliable recordings of single-motor-unit (SMU) activity. In six human participants, jaw movements were standardized by having participants track a linear bank of light-emitting diodes (LEDs) aligned on a monitor displaying the mid-incisor point (MIPT). In all participants, the MIPT target (i.e. an illuminated LED) could be tracked, according to a pre-determined criterion, during single- and multiple-step displacements at different rates (1.3--6.5 mm/s at MIPT) and magnitudes (0.65--12 mm) of movement. SMU activity from the superior (SHLP) or inferior (IHLP) head of the lateral pterygoid muscle could be reliably discriminated during repeated trials of these defined tasks. This methodology establishes a reliable technique for characterizing the firing properties of SMUs within the lateral pterygoid, and has implications for analogous studies in other jaw muscles.

Adult↗
PubMed2001

Cortical oscillations in human medial temporal lobe during wakefulness and all-night sleep.

We have recorded human medial temporal lobe electrocorticogram during wakefulness and natural sleep in epileptic patients with subdural electrodes. From these recordings, we have found gamma (30-150 Hz) [Neuroscience 90 (1999) 1149] and beta-1 (10-20 Hz) [NeuroReport 10 (1999) 3055] activities during wakefulness in human medial temporal lobe. In this paper, we will report changes of these frequencies across wake and natural sleep. Electrocorticograms during wake, slow wave sleep and rapid eye movement (REM) sleep were subjected to fast Fourier transformation analysis. During wake two spectral enhancements, beta-1 and gamma, were consistently observed across subjects. In the raw signal, beta-1 was observed as a regular rhythmic oscillation. In slow wave sleep, the beta-1 peak disappeared but gamma remained, although slightly reduced in power. During REM sleep, beta-1 appeared again, but the peak frequency was significantly lower than during wake (mean frequency: wake=16.6, REM=12.8 Hz). The gamma peak was also present in REM sleep. It has been known that the rhythmic slow activity (RSA) or theta is observed in some animals. However, it is unclear whether the human hippocampus displays similar activity. Since human beta-1 appears during wake and REM sleep when RSA is observed in other species, and since beta-1 is also a regular rhythmic oscillation, we propose that beta-1 may be the functional equivalent of hippocampal RSA (theta) observed in some animals. Functional significances of the gamma activity should be further investigated.

Adult↗
PubMed2001

Therapeutic potential of ex vivo expanded endothelial progenitor cells for myocardial ischemia.

BACKGROUND: We investigated the therapeutic potential of ex vivo expanded endothelial progenitor cells (EPCs) for myocardial neovascularization. METHODS AND RESULTS: Peripheral blood mononuclear cells obtained from healthy human adults were cultured in EPC medium and harvested 7 days later. Myocardial ischemia was induced by ligating the left anterior descending coronary artery in male Hsd:RH-rnu (athymic nude) rats. A total of 10(6) EPCs labeled with 1,1'-dioctadecyl-1 to 3,3,3',3'-tetramethylindocarbocyanine perchlorate were injected intravenously 3 hours after the induction of myocardial ischemia. Seven days later, fluorescence-conjugated Bandeiraea simplicifolia lectin I was administered intravenously, and the rats were immediately killed. Fluorescence microscopy revealed that transplanted EPCs accumulated in the ischemic area and incorporated into foci of myocardial neovascularization. To determine the impact on left ventricular function, 5 rats (EPC group) were injected intravenously with 10(6) EPCs 3 hours after ischemia; 5 other rats (control group) received culture media. Echocardiography, performed just before and 28 days after ischemia, disclosed ventricular dimensions that were significantly smaller and fractional shortening that was significantly greater in the EPC group than in the control group by day 28. Regional wall motion was better preserved in the EPC group. After euthanization on day 28, necropsy examination disclosed that capillary density was significantly greater in the EPC group than in the control group. Moreover, the extent of left ventricular scarring was significantly less in rats receiving EPCs than in controls. Immunohistochemistry revealed capillaries that were positive for human-specific endothelial cells. CONCLUSIONS: Ex vivo expanded EPCs incorporate into foci of myocardial neovascularization and have a favorable impact on the preservation of left ventricular function.

Animals↗