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Biomedical subjects

A Maeda

Publications and source records attributed to A Maeda.

At least 19 recordsLinked to original sources
PubMed2005

Nanoscale friction: kinetic friction of magnetic flux quanta and charge density waves.

In analogy with the standard macroscopic friction, here we present a comparative study of the friction force felt by moving vortices in superconductors and charge density waves. Using experiments and a model for this data, our observations (1) provide a link between friction at the micro- and macroscopic scales, (2) explain the roundness of the static-kinetic friction transition in terms of thermal fluctuations, particle interactions, and system size (critical-phenomena view), and (3) explain the crossing of the kinetic friction F(k) versus velocity V for our pristine (high density of very weak defects) and our irradiated samples (with lower density of deeper pinning defects).

Journal Article↗
PubMed2005

Large optical nonlinearity of semiconducting single-walled carbon nanotubes under resonant excitations.

We measured third-order nonlinear susceptibility (chi(3)) spectra in semiconducting single-walled carbon nanotubes (SWNTs) by the Z-scan method. |Imchi(3)| is remarkably enhanced under resonant excitation to the lowest interband transition, reaching 4.2 x 10(-6) esu and 1.5 x 10(-7) esu in SWNTs grown by the laser ablation and HiPco methods, respectively. A comparison of the transient absorption changes evaluated by degenerate and nondegenerate pump-probe measurements suggests that the resonant enhancement of |Imchi(3)| is dominated by a coherent process rather than by saturation of absorption.

Journal Article↗
PubMed2004

Modification of endothelial cell functions by Hantaan virus infection: prolonged hyper-permeability induced by TNF-alpha of hantaan virus-infected endothelial cell monolayers.

Serious vascular leakage is central to the pathogenesis of hantavirus infections. However, there is no evidence suggesting the hantavirus infection of endothelial cells directly causes obvious cell damage or morphological alteration either in vivo or in vitro. In this study, we examined whether Hantaan virus (HTNV) infection modifies the barrier function of endothelial cell monolayers upon the exposure to pro-inflammatory cytokines. Low levels (1 ng/ml) of tumor necrosis factor-alpha initially increased the permeability in both HTNV-infected and uninfected monolayers similarly. Thereafter, however, these monolayers showed significant difference. The HTNV-infected monolayers remained irreversibly hyper-permeable during the experimental period up to 4 days, while the uninfected monolayers completely recovered the barrier function. The prolonged hyper-permeability of HTNV-infected monolayers was not associated with cell death or gap formation in the monolayers, and was independent from their nitric oxide or prostaglandin production. These results are the first evidence that hantavirus infection modifies barrier function of endothelial cell monolayers and suggest that HTNV-infection of endothelial cells may contribute to the increased vascular leakage through the prolonged response to cytokines.

Boron Compounds↗
PubMed2004

Low-molecular weight dextran sulfate abrogates the instant blood-mediated inflammatory reaction induced by adult porcine islets both in vitro and in vivo.

BACKGROUND: One of the main obstacles to clinical application of islet xenotransplantation is the injurious inflammatory reaction elicited by porcine islets when they are exposed to fresh human blood in vitro and in vivo. This instant blood-mediated inflammatory reaction (IBMIR) causes rapid binding of platelets to the islet surface, activation of the coagulation and complement systems, and leukocyte infiltration of the islets. As a consequence of IBMIR, morphological destruction of porcine islets occurs within the first few hours after transplantation. MATERIALS AND METHODS: In the present study, by analyzing the plasma samples and performing immunohistochemical investigation, we assessed the effect of adding low-molecular weight dextran sulfate (LMW-DS) at 0.01-1 mg/mL to an in vitro tubing loop assay in which porcine islets were exposed to fresh human blood. The effect of LMW-DS also was investigated in an in vivo model using diabetic athymic mice, which provides an innate inflammatory milieu without influence of T cells. The possible toxicity of LMW-DS was assessed by culturing pig islets in the presence or absence of LMW-DS for 3 days. RESULTS: In the in vitro study, in the presence of LMW-DS at 0.01 mg/mL, platelet consumption, coagulation, and complement activation were reduced, and, at 0.1 mg/mL, LMW-DS totally prevented IBMIR. Immunohistochemical investigation showed that leukocyte infiltration was totally abrogated at the highest dose. A similar finding was observed in the in vivo study. No adverse effect of LMW-DS was observed on the quality of the islets. CONCLUSIONS: LMW-DS appears to be an effective drug candidate that is able to control the strong innate immune response induced by pig islets in contact with human blood.

Animals↗
PubMed2003

Ultrafast optical switching to a metallic state by photoinduced mott transition in a halogen-bridged nickel-chain compound.

We demonstrate the ultrafast photoinduced Mott transition from a charge transfer insulator to a metal in a halogen-bridged Ni-chain compound by pump-probe reflection spectroscopy. Upon the irradiation of a 130-femtosecond laser pulse, the spectral weight of the gap transition is transferred to the inner-gap region. When the photoexcitation density exceeds 0.1/Ni site, the Drude-like high-reflection band appears in the infrared region, signaling the formation of a metallic state. The photogeneration of the metallic state and the subsequent recovery to the original gapped state occur within a few picoseconds.

Journal Article↗
PubMed2003

Immunosuppression with FTY720 and cyclosporine A inhibits rejection of adult porcine islet xenografts in rats.

BACKGROUND: Our aim was to evaluate the effect of FTY720 in discordant islet xenotransplantation. METHODS: Fetal porcine islet-like cell clusters (ICCs) were transplanted into normoglycemic rats that were either left untreated or treated with FTY720 only, with FTY720 plus cyclosporine A (CsA) or with CsA only. Twelve or 24 days after transplantation, graft morphology was evaluated immunohistochemically. Furthermore, adult porcine islets (APIs) were transplanted into diabetic rats immunosuppressed with FTY720 plus CsA. Blood glucose and porcine C-peptide levels were monitored. RESULTS: In untreated rats, the ICC xenografts were completely rejected after 12 days. Treatment with CsA had only a marginal effect on the rejection. In animals given FTY720, only the number of infiltrating cells was somewhat reduced. However, at 12 days, no intact ICCs remained. Immunosuppression with FTY720 plus CsA had a marked inhibitory effect on islet xenograft rejection and plentiful morphologically intact ICCs remained. Twelve days after transplantation, only occasional macrophages and T cells could be detected. At 24 days after transplantation, the findings were similar. Furthermore, diabetic rats transplanted with APIs and immunosuppressed with FTY720 plus CsA remained normoglycemic for 53.0+/-15.8 days. In fact, one animal remained normoglycemic for more than 100 days. Serum levels of porcine C-peptide remained at levels similar to those for human C-peptide in healthy individuals. CONCLUSIONS: Immunosuppression with FTY720 plus CsA inhibited almost all morphological signs of pig-to-rat islet xenograft rejection for up to 24 days after transplantation. Diabetic rats transplanted with APIs and immunosuppressed with FTY720 plus CsA remained normoglycemic for 53.0+/-15.8 days.

Animals↗
PubMed2002

Evidence for insulating behavior in the electric conduction of (NH(3))K(3)C(60) systems.

Microwave study using the cavity perturbation technique revealed that the conductivity of the antiferromagnet (NH(3))K(3-x)Rb(x)C(60) at 200 K is already 3-4 orders of magnitude smaller than those of superconductors, K(3)C(60) and (NH(3))(x)NaRb(2)C(60), and that the antiferromagnetic compounds are insulators below 250 K without metal-insulator transitions. The striking difference in the magnitude of the conductivity between these materials strongly suggests that the Mott-Hubbard transition in the ammoniated alkali fullerides is driven by a reduction of lattice symmetry from face-centered-cubic to face-centered-orthorhombic, rather than by the magnetic ordering.

Journal Article↗
PubMed2001

PD-1 immunoreceptor inhibits B cell receptor-mediated signaling by recruiting src homology 2-domain-containing tyrosine phosphatase 2 to phosphotyrosine.

PD-1 is an immunoreceptor that belongs to the immunoglobulin (Ig) superfamily and contains two tyrosine residues in the cytoplasmic region. Studies on PD-1-deficient mice have shown that PD-1 plays critical roles in establishment and/or maintenance of peripheral tolerance, but the mode of action is totally unknown. To study the molecular mechanism for negative regulation of lymphocytes through the PD-1 receptor, we generated chimeric molecules composed of the IgG Fc receptor type IIB (Fc gamma RIIB) extracellular region and the PD-1 cytoplasmic region and expressed them in a B lymphoma cell line, IIA1.6. Coligation of the cytoplasmic region of PD-1 with the B cell receptor (BCR) in IIA1.6 transformants inhibited BCR-mediated growth retardation, Ca(2+) mobilization, and tyrosine phosphorylation of effector molecules, including Ig beta, Syk, phospholipase C-gamma 2 (PLC gamma 2), and ERK1/2, whereas phosphorylation of Lyn and Dok was not affected. Mutagenesis studies indicated that these inhibitory effects do not require the N-terminal tyrosine in the immunoreceptor tyrosine-based inhibitory motif-like sequence, but do require the other tyrosine residue in the C-terminal tail. This tyrosine was phosphorylated and recruited src homology 2-domain-containing tyrosine phosphatase 2 (SHP-2) on coligation of PD-1 with BCR. These results show that PD-1 can inhibit BCR signaling by recruiting SHP-2 to its phosphotyrosine and dephosphorylating key signal transducers of BCR signaling.

Animals↗
PubMed2001

Promoter structure and transcription initiation sites of the human death receptor 5/TRAIL-R2 gene.

The death receptor 5 (DR5) is a receptor for tumor necrosis factor-related apoptosis-inducing ligand and is able to induce apoptosis in various tumor cells. The expression of DR5 is up-regulated at the transcriptional level by p53, genotoxic stress and so on. To investigate the structure of the DR5 gene promoter, we screened and sequenced a genomic clone containing the 5'-flanking region of the DR5 gene. RNase protection assays showed two major transcription start sites around -122 and -137 upstream of the translation initiation codon ATG. Transient transfections with serial 5'-deletion mutants identified the minimal promoter element spanning -198 to -116. Site-directed mutagenesis demonstrated that the DR5 gene promoter has no typical TATA-box, but has two Sp1 sites responsible for the basal transcription activity of the DR5 gene promoter.

5' Flanking Region↗
PubMed2001

Intranuclear localization of the transcription coadaptor CBP/p300 and the transcription factor RBP-Jk in relation to EBNA-2 and -5 in B lymphocytes.

We have studied the expression and the localization of the cellular proteins CBP/p300 and RBP-Jk in in vitro EBV-infected human B lymphocytes in relation to the EBNA-2 and EBNA-5 proteins. We found that the level of CBP/p300 was elevated drastically by EBV infection and also after activation by CD40 ligation. Thus the increase in CBP/p300 expression in the EBV-infected cells is related to the virus-induced activation and proliferation of the cells. EBNA-2 and RBP-Jk colocalized in the nucleoplasm, which is in accordance with their functional interaction. We confirmed earlier reports about the presence and colocalization of EBNA-5 and CBP in the nuclear POD bodies. On the other hand, neither EBNA-2 nor p300 was detected in the PODs. The expression of these two proteins overlapped in some distinct dots of the nucleoplasm. Taken together, the different patterns of CBP and p300 expression and their different localization in relation to the PML bodies and two EBV-encoded proteins in the B cells may provide some clue to their distinct functional roles.

B-Lymphocytes↗
PubMed2001

EBNA promoter usage in EBV-negative Burkitt lymphoma cell lines converted with a neomycin-resistant EBV strain.

Latent Epstein-Barr virus (EBV) uses two alternative strategies to express the Epstein-Barr nuclear antigens (EBNAs). Resting normal B cells harboring latent virus and Burkitt's lymphoma (BL) cells use monocistronic messages generated from the Q promoter (restricted strategy). EBV-transformed immunoblasts express all EBNAs by using giant messages generated from the W/C promoter (full program). Whether the virus establishes the restricted program on primary infection of a BL cell (or its progenitor) or, alternatively, whether such cells are generated by phenotypic down-regulation from the immunoblast is unclear. We found previously that conversion of EBV-negative BL lines to EBV-positive sublines required repeated exposure to large virus doses. The converted sublines used the full program. However, the possibility that cells with a full program had a selective advantage during the long period of in vitro passage could not be excluded. We therefore infected EBV-negative BL lines with recombinant EBV carrying a neomycin resistance marker. Most convertants of the 12 lines tested were positive for YUK splicing, indicative of the full program, but some were also positive for the restricted QUK splice program. One convertant DG75 line showing both YUK and QUK was cloned and gave rise to stable QUK users. We conclude that EBV infection of established BL lines can give rise to subclones with either the full or the restricted program. The fact that all EBVs carrying BL lines use the restricted program in vitro may be a consequence of immunoselection.

Anti-Bacterial Agents↗
PubMed2001

Disseminated scleroderma of a Japanese patient successfully treated with bath PUVA photochemotherapy.

BACKGROUND: Localized scleroderma is known to be resistant to therapies. Recently, it has been reported that bath PUVA photochemotherapy is effective for treating this dermatosis. OBJECTIVES: Although according in earlier reports mainly white populations have been treated successfully with bath PUVA therapy, there is little knowledge of whether it is effective in treating colored populations. We treated a 64-year-old Japanese woman suffering from disseminated scleroderma with bath PUVA photochemotherapy to see its effects. CONCLUSION: Although rather high cumulative UVA doses were required for this patient compared with those needed in earlier reports, no adverse effects were observed. The lesions were markedly improved, suggesting that this therapeutic modality is well-tolerated and useful for colored patients such as the Japanese. Furthermore, it turns out that the thermographical assessment is useful to estimate clinical improvement of this sclerosing skin disorder.

Asian People↗
PubMed2001

Membrane topology of coronavirus E protein.

Coronavirus small envelope protein E has two known biological functions: it plays a pivotal role in virus envelope formation, and the murine coronavirus E protein induces apoptosis in E protein-expressing cultured cells. The E protein is an integral membrane protein. Its C-terminal region extends cytoplasmically in the infected cell and in the virion toward the interior. The N-terminal two-thirds of the E protein is hydrophobic and lies buried within the membrane, but its orientation in the lipid membrane is not known. Immunofluorescent analyses of cells expressing biologically active murine coronavirus E protein with a hydrophilic short epitope tag at the N-terminus showed that the epitope tag was exposed cytoplasmically. Immunoprecipitation analyses of the purified microsomal membrane vesicles that contain the same tagged E protein revealed the N-terminal epitope tag outside the microsomal membrane vesicles. These analyses demonstrated that the epitope tag at the N-terminus of the E protein was exposed cytoplasmically. Our data were consistent with an E protein topology model, in which the N-terminal two-thirds of the transmembrane domain spans the lipid bilayer twice, exposing the C-terminal region to the cytoplasm or virion interior.

Animals↗
PubMed2001

Association between a single-nucleotide polymorphism in the promoter of the human interleukin-3 gene and rheumatoid arthritis in Japanese patients, and maximum-likelihood estimation of combinatorial effect that two genetic loci have on susceptibility to the disease.

Genetic variants of interleukin-3 (IL-3), a well-studied cytokine, may have a role in the pathophysiology of rheumatoid arthritis (RA); but reports on this association sometimes conflict. A case-control study was designed to investigate association between RA and a single-nucleotide polymorphism (SNP) in the IL-3 promoter region. Comparison of cases of RA versus control individuals yielded a chi(2) value of 14.28 (P=.0002), with a genotype odds ratio of 2.24 (95% confidence interval [95%CI] 1.44-3.49). When female cases with earlier onset were compared with female control individuals, the SNP revealed an even more significant correlation, with chi2=21.75 (P=.000004) and a genotype odds ratio of 7.27 (95%CI 2.80-18.89). The stronger association that we observed in this clinically distinct subgroup (females with early onset), within a region where linkage disequilibrium was not significantly extended, suggested that the genuine RA locus should locate either within or close to the IL-3 gene. Combined genotype data on SNPs on eight other candidate genes were combined with our IL-3 results, to estimate relationships between pairs of loci and RA, by maximum-likelihood analysis. The utility of combining the genotype data in this way to identify possible contributions of various genes to this disease is discussed.

Age of Onset↗
PubMed2001

Identification of human antitumor cytotoxic T lymphocytes epitopes of recoverin, a cancer-associated retinopathy antigen, possibly related with a better prognosis in a paraneoplastic syndrome.

Cancer-associated retinopathy (CAR) is a rare paraneoplastic syndrome, and the recoverin-specific autoantibody is suggested to contribute to the pathogenesis of retinopathy, including apoptosis of retinal cells. Because it is known that CAR(+) cancer patients have a preferable prognosis, we hypothesized that aberrantly expressed recoverin in cancer cells can become a target of cytotoxic T lymphocytes (CTL). Here we tested nine recoverin-derived HLA-A24-binding peptides for their capacity to elicit antitumor CTL. We observed recoverin-specific CTL responses in two HLA-A24(+) CAR(+) cancer patients. In addition, the CTL responses were obtained from three of ten CAR(-) cancer patients and two of six healthy individuals. The CTL precursor frequency of CAR(+) cancer patients and that of CAR(-) cancer patients was higher than that of healthy individuals. Of nine recoverin peptides, R49 (QFQSIYAKF), R49.2 (QFQSIYAKFF), and R64 (AYAQHVFRSF) were discovered to induce the peptide-specific CTL. Taken together, our present data suggest that peripheral activation of recoverin-specific antitumor CTL is likely to contribute to the preferable prognosis of CAR(+) cancer patients. Moreover, in cases other than CAR(+) cancer patients, recoverin may offer the opportunity to design epitope-based immunotherapeutic approaches for treating HLA-A24(+) cancer patients with a recoverin-expressing tumor.

Antigens, Neoplasm↗
PubMed2001

Diurnal variations in alpha power density and subjective sleepiness while performing repeated vigilance tasks.

OBJECTIVE: Diurnal variations in EEG activity and subjectively rated sleepiness while performing repeated vigilance tasks were examined. METHODS: Nine diurnally active healthy males underwent repeated vigilance tasks at 08:00, 11:00, 14:00, 17:00 and 20:00 h. An electroencephalogram (EEG) was taken while the subjects performed the tasks with their eyes open. The alpha power spectra (8.6-13.3 Hz) of EEG was integrated. Subjectively rated sleepiness, reaction time and oral temperature were also measured. RESULTS: Significant diurnal variations were found for alpha power, subjectively rated sleepiness and oral temperature. The alpha power was significantly smaller at 08:00 than at 11:00, 14:00, 17:00 and 20:00 h. The subjectively rated sleepiness was significantly larger at 08:00 than at 11:00, 17:00 and 20:00 h. The diurnal variation in alpha power did not correspond to that in subjectively rated sleepiness. On the other hand, repeated vigilance tasks increased the alpha power, subjectively rated sleepiness and reaction time at each time of day. The increase in alpha power was significantly greater at 14:00 than at 08:00 and 20:00 h. CONCLUSIONS: The diurnal variation was found in alpha power while performing vigilance tasks. Furthermore, the increase in alpha power with repetition of the task depended on the time of day.

Adult↗