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Biomedical subjects

Y Taguchi

Publications and source records attributed to Y Taguchi.

At least 37 records · Page 2Linked to original sources
PubMed2001

Doping dependence of pseudogap and related charge dynamics in Nd2-xCexCuO4.

A notable pseudogap ( Delta(PG) as large as 0.2-0.4 eV) has been found below a characteristic temperature T(*) in the optical conductivity spectrum for metallic but nonsuperconducting crystals of Nd2-xCexCuO4 (x<0.15). The Delta(PG) and T(*) decrease with doping x, holding the relation of Delta(PG) approximately 10k(B)T(*). The Drude-like component is observed to evolve concomitantly with the pseudogap. The T(*) almost coincides with another characteristic temperature T0 that scales the Hall coefficient. These results indicate that the charge transport in the underdoped region is under the strong influence of the pseudogap state.

Journal Article↗
PubMed2001

Large third-order optical nonlinearity of Cu-O chains investigated by third-harmonic generation spectroscopy.

Spectra of the third-order nonlinear susceptibility chi((3)) have been investigated for one-dimensional Mott insulators, Sr(2)CuO(3) and Ca(2)CuO(3), by applying the third-harmonic generation (THG) spectroscopy on their single-crystalline thin films. The three-photon resonance to the lowest charge-transfer (CT) state with odd parity strongly enhances chi((3)), which is of the order of 10(-9) esu. The two-photon resonant structure unravels the even-CT state, located close to the odd-CT state. Two types of chi((3)) spectra obtained from THG and the electroreflectance measurements are explained based on the concept of spin-charge separation.

Journal Article↗
PubMed2001

Anomalous electronic structure and pseudogap effects in Nd1.85Ce0.15CuO4.

We report a high-resolution angle-resolved photoemission spectroscopic study of the electron-doped ( n-type) cuprate superconductor Nd1.85Ce0.15CuO4. We observe regions along the Fermi surface where the near- E(F) intensity is suppressed and the spectral features are broad in a manner reminiscent of the high-energy "pseudogap" in the underdoped p-type (hole doped) cuprates. However, instead of occurring near the (pi,0) region, as in the p-type materials, this pseudogap falls near the intersection of the underlying Fermi surface with the antiferromagnetic Brillouin zone boundary.

Journal Article↗
PubMed2001

Spin chirality, Berry phase, and anomalous Hall effect in a frustrated ferromagnet.

An electron hopping on non-coplanar spin sites with spin chirality obtains a complex phase factor (Berry phase) in its quantum mechanical amplitude that acts as an internal magnetic field, and is predicted to manifest itself in the Hall effect when it is not cancelled. The present combined work of transport measurement, neutron scattering, and theoretical calculation provides evidence that the gigantic anomalous Hall effect observed in Nd2Mo2O7, a pyrochlore ferromagnet with geometrically frustrated lattice structure, is mostly due to the spin chirality and the associated Berry phase originating from the Mo spin tilting.

Journal Article↗
PubMed2001

Mouse CD94 participates in Qa-1-mediated self recognition by NK cells and delivers inhibitory signals independent of Ly-49.

Inhibitory receptors expressed on NK cells recognize MHC class I molecules and transduce negative signals to prevent the lysis of healthy autologous cells. The lectin-like CD94/NKG2 heterodimer has been studied extensively as a human inhibitory receptor. In contrast, in mice, another lectin-like receptor, Ly-49, was the only known inhibitory receptor until the recent discovery of CD94/NKG2 homologues in mice. Here we describe the expression and function of mouse CD94 analyzed by a newly established mAb. CD94 was detected on essentially all NK and NK T cells as well as small fractions of T cells in all mouse strains tested. Two distinct populations were identified among NK and NK T cells, CD94(bright) and CD94(dull) cells, independent of Ly-49 expression. The anti-CD94 mAb completely abrogated the inhibition of target killing mediated by NK recognition of Qa-1/Qdm peptide on target cells. Importantly, CD94(bright) but not CD94(dull) cells were found to be functional in the Qa-1/Qdm-mediated inhibition. In the presence of the mAb, activated NK cells showed substantial cytotoxicity against autologous target cells as well as enhanced cytotoxicity against allogeneic and "missing self" target cells. These results suggest that mouse CD94 participates in the protection of self cells from NK cytotoxicity through the Qa-1 recognition, independent of inhibitory receptors for classical MHC class I such as Ly-49.

Animals↗
PubMed2001

Superconducting gap anisotropy in Nd1.85Ce0.15CuO4: results from photoemission.

We have performed angle resolved photoelectron spectroscopy on the electron doped cuprate superconductor Nd1.85Ce0.15CuO4. A comparison of the leading edge midpoints between the superconducting and normal states reveals a small, but finite shift of 1.5-2 meV near the ( pi,0) position, but no observable shift along the zone diagonal near ( pi/2, pi/2). This is interpreted as evidence for an anisotropic superconducting gap in the electron doped materials, which is consistent with the presence of d-wave superconducting order in this cuprate superconductor.

Journal Article↗
PubMed2001

Electrocochleogram after transection of vestibulo-cochlear nerve in a patient with a large acoustic neurinoma.

This study reports pre- and post-operative compound action potentials (CAPs) that were recorded from a 27-year-old woman with an acoustic neurinoma. During surgery it was necessary to totally sever her vestibulo-cochlear nerve to excise a large tumor. A pure tone audiogram changed to the scale-out pattern immediately after operation. However, CAP, the waveform of which was broadened, has been recorded 3 years post-operatively with a threshold elevation of 10 dB over the pre-operative threshold. This phenomenon suggests that CAP may originate from the extreme periphery of the auditory nerve within the cochlea. The broadening of the CAP was assumed to result from enhancement of the negative summating potential included in the CAP. We studied the effect of preceding stimulus on CAP using paired click stimuli pre- and post-operatively. A reduction of CAP amplitude in response to the second click of paired clicks was markedly suppressed in the inter-click interval between 3 and 80 ms post-operatively. We speculate that depletion of adaptation induced the abnormal CAP recovery described above and that the lateral efferent nerve system was involved in abnormal CAP adaptation with transection of the vestibulo-cochlear nerve in this case.

Action Potentials↗
PubMed2001

Eruption disturbances of mandibular permanent canines in Japanese children.

OBJECTIVES: The purpose of this study was to clarify the cause and prognosis of eruption disturbance of mandibular permanent canines. SAMPLE AND METHODS: Fifteen Japanese children who visited Niigata University Dental Hospital between 1979 and 1997 with unerupted and/or impacted mandibular permanent canines were examined. RESULTS: All cases showed unilateral disturbances. The eruption disturbance of 6 mandibular canines was associated with a calcified obstacle such as an odontoma (5 cases) or a supernumerary tooth (1 case). After removal of the obstacle, 5 canines were aligned within the dentition. Out of 10 cases, where the permanent canine germ showed malpositioning or aberrant eruption path, 5 primary predecessors had undergone endodontic treatment. In these 10 cases, 6 canines erupted after treatment, two were extracted and the remaining two were left in their impacted position. CONCLUSIONS: The present results suggest that it is relatively easy for the position of unerupted mandibular canines associated with calcified obstacles to be improved by removal of the obstacle, but that it is more difficult for teeth showing anomaly in the position of the canine germ to be aligned within the dentition.

Adolescent↗
PubMed2001

Existence of alpha(1A)- and alpha(1B)-adrenoceptor subtypes in canine mandibular alveolar arteries.

1. The present study attempted to pharmacologically characterize the alpha-adrenoceptor subtypes mediating vasoconstriction in canine isolated and perfused mandibular alveolar artery (MAA). 2. Noradrenaline (NA) and phenylephrine (PE) induced a strong vasoconstriction in a dose-dependent manner. The PE-induced vascular constriction was significantly inhibited by treatment with prazosin. Xylazine evoked a moderate vascular constriction and the xylazine-induced response was suppressed by rauwolscine. The NA-induced response was partially inhibited by rauwolscine and the remaining response to NA was abolished by subsequent administration of prazosin. 3. Treatment of MAA with WB4101 produced a dose-dependent inhibition of NA-induced vasoconstriction. Pretreatment of tissues with 10 micromol/L chloroethylclonidine produced a slight and statistically significant inhibition of NA-induced responses. BMY 7378, a selective alpha(1D)-adrenoceptor antagonist, failed to significantly affect vasoconstrictor responses to NA. 4. The present results suggests that: (i) both alpha(1)- and alpha(2)-adrenoceptors are involved in vasoconstrictor responses in the canine MAA; and (ii) the alpha(1)-adrenoceptors involved in the vasoconstrictor responses in the MAA are characterized as mainly of the alpha(1A)- and partially of the alpha(1B)-adrenoceptor subtype.

Adrenergic alpha-Agonists↗
PubMed2001

Eruption disturbances of mandibular permanent incisors.

In this study, we analyzed 7 eruption disturbance cases of mandibular permanent incisors (5 males and 2 females), aged 5y9m to 10y4m. The etiology was divided into 3 categories: traumatic injuries (3 cases), odontomas (2 cases), supernumerary teeth (2 cases). The procedures such as removal of cause (4 cases), surgical exposure (5 cases) and traction (1 case) were done.

Child↗
PubMed2001

[Anti-ulcer therapy after eradication of Helicobacter pylori].

Helicobacter pylori (H. pylori) infection is the cause of the frequent relapse of peptic ulcer disease. Successful eradication therapy of H. pylori is associated with a decline in the recurrence of peptic ulcer. In this paper, we discussed the significance of anti-ulcer therapy after H. pylori eradication therapy. In patients with duodenal ulcer, maintenance therapy for preventing ulcer recurrence is not necessary because the rate of ulcer recurrence after eradication therapy is very low. However, in patients with gastric ulcer, the rate of ulcer relapse and reflux esophagitis ranges between 5-10% in the Japanese population even after successful eradication therapy; therefore, maintenance therapy for 1 year may be permissible in patients with gastric ulcer even after successful eradication therapy.

Anti-Ulcer Agents↗
PubMed2001

[A case of Miller Fisher syndrome with pharyngeal palsy as an initial symptom].

We report herein a rare case of Miller Fisher syndrome with pharyngeal palsy as an initial symptom. A 68-year-old man admitted to our hospital with pharyngeal palsy two weeks after a respiratory infection. He subsequently developed ataxic gait, paresthesia in the upper limbs and ophthalmoplegia. Double-filtrated-plasmapheresis had been performed four times and all the symptoms subsided within two months. In the acute phase of the disease, the titers of anti-GQ1b and GT1a antibodies were elevated. The titer of anti-GT1a antibody was higher than that of anti-GQ1b antibody. Recently, the activity of serum anti-GT1a antibody has been supposed to be associated with pharyngeal palsy. In the present case, higher titer of anti-GT1a antibody compared with that of anti-GQ1b antibody could possibly cause pharyngeal palsy as an initial symptom of Miller Fisher syndrome.

Aged↗
PubMed2001

[A case of craniopharyngioma with chemical meningitis as an initial symptom].

We reported a rare case of craniopharyngioma with chemical meningitis due to spontaneous rupture of the tumor. A 50-year-old woman was admitted with high fever, headache, and nausea. On physical examination, she had nuchal rigidity. The examination of her cerebral spinal fluid(CSF) revealed pleocytosis(mononuclear cell dominant), low value of glucose level and high content of protein. The feature of her CSF findings suggested tuberculosis or fungal meningitis, but bacteriologic culture of the CSF was negative. The CT scan showed an isodensity mass in the suprasellar region and a spotty calcification in the third ventricle. The MRI with gadolinium enhancement suggested that the tumor must be craniopharyngioma and that meningitis was a type of chemical meningitis due to spontaneous rupture of craniopharyngioma. The corticosteroid therapy was rather effective to the symptoms of fever and headache. Then the operation was performed by neurosurgeons, and the diagnosis of craniopharyngioma was pathologically confirmed. Spontaneous rupture of craniopharyngioma rarely occurred and was followed by chemical meningitis. This case was an extremely rare condition that presented with chemical meningitis as an initial symptom.

Craniopharyngioma↗
PubMed2001

[Occurrence of BOOP outside radiation field after radiation therapy for small cell lung cancer].

We report a case of bronchiolitis obliterans organizing pneumonia (BOOP) that occurred outside the radiation field after radiation therapy for small cell lung cancer. A 74-year-old woman received chemotherapy and a total of 60 Gy of radiation therapy to the right hilum and mediastinum for small cell carcinoma of the suprahilar area of the right lung. Radiation pneumonitis developed within the radiation port 3 months after the completion of radiation therapy. She complained of cough and was admitted 7 months after completion of the radiation therapy. Chest radiography and computed tomography demonstrated peripheral alveolar opacities outside the radiation field on the side contralateral to that receiving the radiation therapy. Bronchoalveolar lavage showed that the total cell count was increased, with a markedly increased percentage of lymphocytes. Transbronchial lung biopsy revealed a histologic pattern consistent with BOOP. Treatment with corticosteroids resulted in rapid improvement of the symptoms and complete resolution of the radiographic abnormalities of the left lung. Although some cases of BOOP following radiation therapy for breast cancer have been reported, none of BOOP after radiation therapy for lung cancer have appeared in the literature.

Aged↗
PubMed2000

Spin dynamics and orbital state in LaTiO3

A neutron scattering study of the Mott-Hubbard insulator LaTiO3 ( T(N) = 132 K) reveals a spin wave spectrum that is well described by a nearest-neighbor superexchange constant J = 15.5 meV and a small Dzyaloshinskii-Moriya interaction ( D = 1.1 meV). The nearly isotropic spin wave spectrum is surprising in view of the absence of a static Jahn-Teller distortion that could quench the orbital angular momentum, and it may indicate strong orbital fluctuations. A resonant x-ray scattering study has uncovered no evidence of orbital order in LaTiO3.

Journal Article↗