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T Tohyama

Publications and source records attributed to T Tohyama.

At least 19 recordsLinked to original sources
PubMed2006

Late flare-up of nephrotic lupus nephritis transforming histological pattern and autoantibody reactions.

A 15-year-old boy developed a nephrotic syndrome. At that time, autoantibodies related to systemic lupus erythematosus (SLE) had been persistently negative, even on repeated evaluation. C1q was normal, but C4, C3 and CH50 were low. Renal biopsy revealed membranous lupus nephritis (LN) based on the new classification of glomerulonephritis in SLE [Weenig et al. 2004]. We did not establish our diagnosis of SLE on the criteria of the American Rheumatism Association (ARA). The patient showed complete remission ofnephrotic syndrome treated with prednisolone and cyclophosphamide. Thereafter, he had no proteinuria and clinical evidence of SLE for 22 years. At the age of 37, however, he developed facial discoid eruption, proteinuria in the nephrotic range, hypocomplementemia and positive reaction to autoantibodies of SLE. Light microscopic findings of renal biopsy indicated mesangial LN, which showed "full-house" immunofluorescence and mesangial dense deposits associated with diffuse epithelial cell foot process effacement in electron microscopy. Steroid therapy was very effective. This case initially showed autoantibody-negative and hypocomplementemic LN with membranous type, and transformed to SLE with mesangial LN after a long interval.

Adolescent↗
PubMed2005

Momentum dependence of charge excitations in the electron-doped superconductor Nd1.85 Ce0.15 CuO4: a resonant inelastic x-ray scattering study.

We report a resonant inelastic x-ray scattering (RIXS) study of charge excitations in the electron-doped high-T(c) superconductor Nd1.85 Ce0.15 CuO4. The intraband and interband excitations across the Fermi energy are separated for the first time by tuning the experimental conditions properly to measure charge excitations at low energy. A dispersion relation with q-dependent width emerges clearly in the intraband excitation, while the intensity of the interband excitation is concentrated around 2 eV near the zone center. The experimental results are consistent with theoretical calculation of the RIXS spectra based on the Hubbard model.

Journal Article↗
PubMed2005

Mott gap excitations in twin-free YBa2Cu3O7-delta (Tc=93 K) studied by resonant inelastic x-ray scattering.

Mott gap excitations in the optimally doped high-T(c) superconductor YBa(2)Cu(3)O(7-delta) (T(c)=93 K) have been studied by the resonant inelastic x-ray scattering method. Anisotropic spectra in the ab plane are observed in a twin-free crystal. The excitation from the one-dimensional CuO chain is enhanced at 2 eV near the zone boundary of the b* direction, while the excitation from the CuO2 plane is broad at 1.5-4 eV and almost independent of the momentum transfer. Theoretical calculations based on the one-dimensional and two-dimensional Hubbard model reproduces the observed spectra when different values of the on-site Coulomb energy are assumed. The Mott gap of the CuO chain site is found to be much smaller than that of the CuO2 plane site.

Journal Article↗
PubMed2002

Resonant two-magnon Raman scattering and photoexcited States in two-dimensional mott insulators.

We investigate the resonant two-magnon Raman scattering in two-dimensional (2D) Mott insulators by using a half-filled 2D Hubbard model in the strong coupling limit. By performing numerical diagonalization calculations for small clusters, we find that the Raman intensity is enhanced when the incoming photon energy is not near the optical absorption edge but well above it, being consistent with experimental data. The absence of resonance near the gap edge is associated with the presence of background spins, while photoexcited states for resonance are found to be characterized by the charge degree of freedom. The resonance mechanism is different from those proposed previously.

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

Development of a cryopreservation procedure employing a freezer bag for pancreatic islets using a newly developed cryoprotectant.

One of the most important requirements for success in clinical islet transplantation is the use of a large number of viable donor islets. To achieve this, the ability to cryopreserve islets and to establish an islet bank are critical. Previously, we developed a two-step cryopreservation procedure with freezing tubes utilizing low and high concentrations of dimethyl sulfoxide (DMSO) and using a fully automated cryomachine for human pancreatic islets and porcine islet-like cell clusters (ICCs). Based on these experiments, we developed a simple and efficient cryopreservation procedure of a freezer bag for isolated islets using a fully automated computer-controlled cryomachine with a newly developed cryoprotectant consisting of ethylene glycol (EG) instead of DMSO for decreasing injury of the islets by freezing. A 250 ml Cryocyte blood freezer bag and our newly developed cryoprotectant containing ethylene glycol (EG) were used in the freezing procedure. The islets were frozen by a fully automated computer-controlled cryomachine (GE 9,000) with our original program of slow cooling. Nucleation occurred at -8 degrees C, and the frozen islets were stored at -196 degrees C in a liquid nitrogen tank. The frozen-stored islets were subsequently rapidly thawed in a 37 degrees C water bath and cultured before viability testing. In vitro function, the stimulation index of insulin release during the static incubation test for rat islets cryopreserved in a freezer bag vs. nonfrozen islets as control, was 2.13 +/- 0.42 and 2.02 +/- 0.38 (94.8% compared with control), respectively (n = 5, p = NS). The islet recovery compared with the nonfrozen control group was 85% (n = 5) in insulin content. When 1000 rat islets cryopreserved in a freezer bag were transplanted into the renal capsule of diabetic athymic mice, all the mice became normoglycemic within 7 days from transplantation. Before nephrectomy, the intravenous glucose torelance test (IVGTT) was performed. The fractional decay constant of the glucose level (K value) of the frozen-thawed group was 0.42 +/- 0.06%/min. A histological study of renal subcapsular grafts demonstrated the morphological integrity of the islets. These results demonstrate the utility of our cryopreservation procedure of a freezer bag for isolated islets using a fully automated computer-controlled cryomachine with a newly developed cryoprotectant for the maintenance of viability and function of frozen-stored islets both in culture and after transplantation. Cryopreservation using freezer bags with the new cryoprotectant is an effective and simple method for making an islet bank for clinical trials of islet transplantation.

Animals↗
PubMed2000

Electronic structure of mott insulators studied by inelastic X-ray scattering

The electronic structure of Mott insulators continues to be a major unsolved problem in physics despite more than 50 years of research. Well-developed momentum-resolved spectroscopies such as photoemission or neutron scattering cannot probe the full Mott gap. High-resolution resonant inelastic x-ray scattering revealed dispersive charge excitations across the Mott gap in a high-critical temperature parent cuprate (Ca(2)CuO(2)Cl(2)), shedding light on the anisotropy of the Mott gap. These charge excitations across the Mott gap can be described within the framework of the Hubbard model.

Journal Article↗
PubMed2000

[Histiocytic necrotizing lymphadenitis (Kikuchi-Fujimoto's disease) accompanied by hemophagocytosis and salivary gland swelling in a patient with systemic lupus erythematosus].

After 2 years of steroid therapy that had effectively controlled her systemic lupus erythematosus, a 37-year-old woman presented with fever, erythema (face, upper chest), and low CH50. Increased oral steroid (prednisolone from 15 mg to 40 mg) and intravenous methylprednisolone (mPSL) (80 mg for 3 days) alleviated these symptoms except for the fever. Subsequently, the patient's fever worsened and leukocytopenia, abnormal liver function, lymphadenopathy (neck, axilla), and salivary gland swelling developed. Lymph node histology revealed features characteristic of Kikuchi-Fujimoto's disease (KFD). Laboratory examinations showed WBC 600/microliter, Hb 9.5 g/dl, platelets 90,000/microliter, GOT 766 IU/l, GPT 646 IU/l, LDH 4,228 IU/l, TG 1,622 mg/dl, and ferritin 6,330 ng/ml. Serum interferon gamma was also elevated (673 U/ml). Because a bone marrow smear revealed hemophagocytosis, mPSL pulse therapy (1 g for 3 days) was started for treatment of hemophagocytic syndrome. The fever promptly disappeared, and the patient's clinical symptoms resolved within 2 weeks. The abnormal laboratory data related to KFD and hemophagocytosis returned to normal within 4 weeks after the initiation of mPSL pulse therapy. We speculated that the hemophagocytosis and salivary gland involvement in this patient were also symptoms of KFD. This case indicated that corticosteroid pulse therapy is effective for KFD with serious clinical symptoms.

Adult↗
PubMed1998

Stable integration of human immunodeficiency virus-based retroviral vectors into the chromosomes of nondividing cells.

Human immunodeficiency virus type 1 (HIV-1)-based vectors are thought to be useful for gene transfer into nondividing cells. We examined whether HIV vectors can really integrate into the chromosomes of nondividing cells. CD4+HeLa cells arrested at the G2 or G1/S phase were incubated with the HIV vector pseudotyped with the HIV envelope. The transduction efficiency of the HIV vector in these nondividing cells was comparable to that in proliferating cells. Sequencing of the polymerase chain reaction-amplified fragments containing the junction sites showed that the HIV vector was stably integrated into the chromosomal DNA. It was also demonstrated that terminally differentiated human macrophages and nonproliferating NT neurons could be transduced by the HIV vector after adenovirus-mediated expression of CD4. These results suggest that the HIV vector may be useful not only for gene therapy of AIDS but also for a variety of gene therapy protocols targeting nondividing cells.

Adenoviridae↗
PubMed1997

Human herpesvirus 7 infection of lymphoid and myeloid cell lines transduced with an adenovirus vector containing the CD4 gene.

It has been reported recently that CD4 is a major component of the receptor for human herpesvirus 7 (HHV-7), which has been newly identified as a T-lymphotropic virus. To investigate further the role of CD4 in HHV-7 infection, we examined the susceptibility to HHV-7 infection of various CD4-negative or weakly positive cell lines into which the cDNA for CD4 was transferred using an adenovirus vector (Adex1CACD4). Of 13 cell lines transduced with Adex1CACD4, including T-lymphoid, B-lymphoid, monocytoid, and myeloid cell lines, one T-lymphoid cell line, one monocytoid cell line, and two cell lines established from the blast crisis of chronic myelogenous leukemia showed high susceptibility to HHV-7 infection. Taken together with the results of previous studies, these data suggest strongly that CD4 is a major component of the binding receptor for HHV-7. This study also shows that HHV-7 may be able to infect CD4-positive hematopoietic precursor cells as well as T lymphocytes.

Adenoviridae↗
PubMed1996

Two-step gene transfer using an adenoviral vector carrying the CD4 gene and human immunodeficiency viral vectors.

Human immunodeficiency virus-1 (HIV-1) belongs to the lentivirus subfamily of retroviruses and has several interesting features, including T cell tropism and the ability to infect nondividing cells. Replication-incompetent HIV vectors were developed and were shown to be capable of targeted gene transfer into CD4+T cells. This strict T cell tropism may be important for the development of gene therapy of acquired immunodeficiency syndrome (AIDS), but it hampers the use of the HIV vector for other gene transfer applications. To expand the host range of the HIV vector, we established the two-step gene transfer system, which allows us to transduce non-T cells stably. In the first step, the CD4 gene was introduced into target cells using a replication-defective adenoviral vector. Transient but high-level expression of CD4 molecules was detected in both adherent and floating cells. In the subsequent step, the cells were incubated with HIV vectors. Stable integration of the HIV vector was demonstrated in cells transduced with the adenoviral vector. These results indicate that transient expression of CD4 molecules by the adenoviral vector is sufficient to render non-T cells susceptible to HIV-mediated gene transfer. This two-step gene transfer strategy may be used as a general method to transduce various types of human cells stably including nondividing cells.

Adenoviridae↗
PubMed1996

A distribution study of 11C platelet-activating factor (PAF) analogs in normal and tumor-bearing mice.

As a preliminary study to image platelet-activating factor (PAF) receptors in vivo, comparative study of biodistribution between 1-O-hexadecy1-2-O-N, N-dimethylcarbamoyl-sn-glycero-3-phosphocholine [choline-methyl-11C](L-[11C]dimethylcarbamoyl-PAF) and nonspecific PAF analog, 3-O-hexadecyl-2-O-N,N-dimethylcarbamoyl-sn-glycero-1-phosphocholine [choline-methyl-11C](D-[11C]-dimethylcarbamoyl-PAF) was carried out in both normal and tumor-bearing mice. Higher accumulation of L-[11C]dimethylcarbamoyl-PAF than D-[11C]dimethylcarbamoyl-PAF was observed in normal mice spleen. The co-administration of PAF antagonists dose-dependently reduced the radioactivity level of the L-isomer only in the spleen. In mice bearing Ehrlich tumors and Sarcoma 180, more L-than the D-[11C]-isomer was accumulated in the tumor and spleen. We found that specific accumulation sites for L-[11C]dimethylcarbamoyl-PAF exist in the spleen and tumors than in other tissues. Moreover, the comparison of accumulation between L- and D-[11C] dimethylcarbamoyl-PAF would be a useful procedure for estimation of PAF receptors in vivo.

Animals↗