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Tetsuya Ishikawa

Publications and source records attributed to Tetsuya Ishikawa.

At least 37 records · Page 2Linked to original sources
PubMed2005

Wave-optical evaluation of interference fringes and wavefront phase in a hard-x-ray beam totally reflected by mirror optics.

The intensity flatness and wavefront shape in a coherent hard-x-ray beam totally reflected by flat mirrors that have surface bumps modeled by Gaussian functions were investigated by use of a wave-optical simulation code. Simulated results revealed the necessity for peak-to-valley height accuracy of better than 1 nm at a lateral resolution near 0.1 mm to remove high-contrast interference fringes and appreciable wavefront phase errors. Three mirrors that had different surface qualities were tested at the 1 km-long beam line at the SPring-8/Japan Synchrotron Radiation Research Institute. Interference fringes faded when the surface figure was corrected below the subnanometer level to a spatial resolution close to 0.1 mm, as indicated by the simulated results.

Journal Article↗
PubMed2005

Functional recovery of damaged skeletal muscle through synchronized vasculogenesis, myogenesis, and neurogenesis by muscle-derived stem cells.

BACKGROUND: Recent studies have shown that skeletal muscle-derived stem cells (MDSCs) can give rise to several cell lineages after transplantation. However, the potential therapeutic uses of MDSCs, the functional significance of the transplanted tissue, and vasculogenesis, myogenesis, and reconstitution of other tissues have yet to be investigated in detail. In addition, the relationship between MDSCs and mesenchymal bone marrow cells is of interest. METHODS AND RESULTS: We developed a severe-damage model of mouse tibialis anterior muscle with a large deficit of nerve fibers, muscle fibers, and blood vessels. We investigated the potential therapeutic use of freshly isolated CD34+/45- (Sk-34) cells. Results showed that, after transplantation, implanted cells give rise to myogenic, vascular (pericytes, vascular smooth muscle cells, and endothelial cells), and neural (Schwann) cells, as well as contributing to the synchronized reconstitution of blood vessels, muscle fibers, and peripheral nerves, with significant recovery of both mass and contractile function after transplantation. Investigation of Sk-34 cell transplantation to the renal capsule (nonmuscle tissue) and fluorescence in situ hybridization analysis for the transplanted muscle detecting the Y chromosome revealed the intrinsic plasticity of the Sk-34 cell population. In addition, there were no donor-derived Sk-34 cells in the muscle of lethally irradiated bone marrow-transplanted animals, indicating that the Sk-34 cells were not derived from bone marrow. CONCLUSIONS: These findings indicate that freshly isolated skeletal muscle-derived Sk-34 cells are potentially useful for reconstitution therapy of the vascular, muscular, and peripheral nervous systems. These results provide new insights into somatic stem and/or progenitor cells with regard to vasculogenesis, myogenesis, and neurogenesis.

Animals↗
PubMed2005

Quantitative image reconstruction of GaN quantum dots from oversampled diffraction intensities alone.

The missing data problem, i.e., the intensities at the center of diffraction patterns cannot be experimentally measured, is currently a major limitation for wider applications of coherent diffraction microscopy. We report here that, when the missing data are confined within the centrospeckle, the missing data problem can be reliably solved. With an improved instrument, we recorded 27 oversampled diffraction patterns at various orientations from a GaN quantum dot nanoparticle and performed quantitative image reconstruction from the diffraction intensities alone. This work in principle clears the way for single-shot imaging experiments using x-ray free electron lasers.

Journal Article↗
PubMed2005

Determination of the dynamic deformation tensor by time-resolved triple-crystal diffractometry.

Triple-crystal X-ray diffractometry has been combined with time-resolved measurement techniques. A simple time-resolved technique was employed by using a digital storage oscilloscope and a fast X-ray detector. The time dependence of the deformation tensor was determined for a gallium arsenide wafer after a flash of a 130 fs laser pulse. The laser pulse produced instantaneous expansion resulting in a localized convex surface. Time-resolved measurements showed that a flexural standing wave, explained well by the classical elasticity theory for thin plates, appeared in the relaxation process.

Journal Article↗
PubMed2005

On a phase problem of high-resolution Fourier transform X-ray spectroscopy.

A phase problem is discussed for high-resolution Fourier transform X-ray spectroscopy where the phase of the interferogram is missing. A numerical iterative method and an analytic logarithmic Hilbert transform method were tested for recovery of the missing phase information from the modulus of the interferogram. These methods were applied to measured data of the Si 14 6 0 back reflection and a calculated interferogram from an X-ray Fabry-Perot interferometer. The iterative method experienced an ambiguity of reconstruction; however, the ambiguity was relatively small and may be acceptable. The logarithmic Hilbert transform method gave a poorer reconstruction for the measured data owing to a lower signal-to-noise ratio, whereas it recovered the original spectrum from the calculated data without noise.

Artifacts↗
PubMed2005

Element array by scanning X-ray fluorescence microscopy after cis-diamminedichloro-platinum(II) treatment.

Minerals are important for cellular functions, such as transcription and enzyme activity, and are also involved in the metabolism of anticancer chemotherapeutic compounds. Profiling of intracellular elements in individual cells could help in understanding the mechanism of drug resistance in tumors and possibly provide a new strategy of anticancer chemotherapy. Using a recently developed technique of scanning X-ray fluorescence microscopy (SXFM), we analyzed intracellular elements after treatment with cis-diamminedichloro-platinum(II) (CDDP), a platinum-based anticancer agent. The images obtained by SXFM (element array) revealed that the average Pt content of CDDP-resistant cells was 2.6 times less than that of sensitive cells, and the zinc content was inversely correlated with the intracellular Pt content. Data suggested that Zn-related detoxification is responsible for resistance to CDDP. Of Zn-related excretion factors, glutathione was highly correlated with the amount of Zn. The combined treatment of CDDP and a Zn(II) chelator resulted in the incorporation of thrice more Pt with the concomitant down-regulation of glutathione. We propose that the generation of an element array by SXFM opens up new avenues in cancer biology and treatment.

Antineoplastic Agents↗
PubMed2005

Rebamipide enemas-new effective treatment for patients with corticosteroid dependent or resistant ulcerative colitis.

In this study we investigated the effect of rebamipide enema in patients with steroid-resistant and/or dependent ulcerative colitis. Rebamipide enemas were administered twice daily for a 12-week period; this treatment was further continued longer in patients who requested this. Disease activity index as reflecting the clinical condition and endoscopic index with histological grading were determined before and after the treatment period. Nine of 11 (81.8%) patients on 12-week treatment with rebamipide approved and were classified as colitis in remission. Moreover, seven of 11 patients requested long-term medication, the longest medication term being 80 weeks. These results medicated that rebamipide enemas may be effective in patients with steroid-resistant and/or dependent ulcerative colitis.

Adolescent↗
PubMed2005

Evaluation of the cross-bridge-dependent change in the Ca2+ affinity of troponin C in aequorin-injected ferret ventricular muscles.

Ca2+ affinity of cardiac troponin C (TnC) is regulated by the active cross-bridges (downstream-dependent mechanism). In the present study, we showed one of the methods to evaluate the downstream-dependent change in the Ca2+ affinity of TnC during contraction using the aequorin-injected ferret papillary muscle. For this purpose, the tension-dependent change in the extra-Ca2+ (a transient increase in the intracellular Ca2+ concentration ([Ca2+]i) in response to a quick length reduction) was measured under various conditions. We examined whether the regression line between the magnitude of tension reduction and the magnitude of the normalized extra-Ca2+ (the extra-Ca2+ was divided by [Ca2+]i immediately before length change) (the normalized extra-Ca2+-tension relation) in twitch contraction can be used for the estimation of the downstream-dependent change in the Ca2+ affinity of TnC. The normalized extra-Ca2+-tension relation became shallow by EMD 57033 (EMD) (one of the Ca2+ sensitizers) and by an increase in Ca2+ concentration in the solution ([Ca2+]o) in a concentration-dependent manner. However, 2,3-butanedione monoxime (BDM) (one of the desensitizers) antagonized the effects of EMD and higher [Ca2+]o in a concentration-dependent manner. These effects of EMD and BDM were also observed in the normalized extra-Ca2+-tension relation in tetanic contraction. The normalized extra-Ca2+-tension relation became steep by shortening the initial muscle length before contraction in tetanic contraction. Length-tension relation in twitch contraction was significantly shifted upward by higher [Ca2+]o and EMD, but BDM showed the opposite effects on them in a concentration-dependent manner. Thus, the downstream-dependent change in the Ca2+ affinity of TnC which physiologically functions in intact cardiac muscle can be evaluated using the normalized extra-Ca2+-tension relation.

Aequorin↗
PubMed2005

Changes in natural killer T cells subsets during therapy in type C hepatitis and hepatocellular carcinoma.

Natural killer T (NKT) cells share features of both classical T cells and NK cells. NKT are heterogenous populations, and recognize glycolipids associated with CD1d molecule. We investigated Th1/Th2 cytokine production as well as frequency and phenotype of circulating NKT cells in 14 healthy subjects and in patients during therapy with type C chronic hepatitis (CH; 14 cases) and hepatocellular carcinoma (HCC; 13 cases). Peripheral blood mononuclear cells (PBMC) were obtained before and 2 weeks later interferon (IFN)/ribavirin and radiofrequency ablation therapy for CH and HCC, respectively. PBMC were cultured for 10 days with alpha-galactosylceramide (alpha-GalCer) and interleukin-2 (IL-2). Frequencies and IFN-gamma/IL-4 production of NKT cells were analyzed using flow cytometry. Intrahepatic lymphocytes were analyzed in seven CH patients with liver biopsy specimen. Prevalence of circulating Valpha24+CD3+ T cells was 0.9+/-0.9% of PBMC for controls and increased to 8.5+/-8.9% (p<0.001) in response to alpha-GalCel. Similar frequency and expansion were noted in CH. The frequency increased during therapy. The prevalence in HCC tended to be high compared to controls and response to alpha-GalCel was well. Although frequency of Valpha24+Vbeta11+CD3+ T cells was low in all groups, the distribution pattern was similar to Valpha24+Vbeta11-CD3+ T cells. Prevalence of CD56+CD3+ T cells was low independent of therapy in CH (2-3%) compared to 5.0+/-4.0% of controls, although response to alpha-GalCel was not impaired. IFN-gamma production of Valpha24+CD3+ T cells did not differ among groups, but became greater after treatment in contrast to lowered IL-4 production. Frequencies of NKT populations were higher in liver than in peripheral blood. Our study suggests that CD1d-reactive T cells have distinct distribution in different populations and therapy for patients alters cytokine response of NKT cells.

Journal Article↗
PubMed2005

Deteriorative effect of smoking on target lesion revascularization after implantation of coronary stents with diameter of 3.0 mm or less.

BACKGROUND: Although smoking cessation is widely encouraged because of the associated risk of cardiovascular events, the impact of smoking on target lesion revascularization (TLR) after percutaneous coronary intervention (PCI) is controversial. Therefore, the present study retrospectively investigated the effect of smoking on TLR after plain-old balloon angioplasty (POBA; n=376) and stenting (STENT; n=434) in patients undergoing secondary coronary angiography at a single center. METHODS AND RESULTS: A smoker was defined as current smoking or quitting within 2 years of the first PCI. In the POBA group, the predictors for TLR, as calculated by multiple logistic regression analysis, were a complex type of lesion (p<0.0001) and the left anterior descending artery (LAD) as affected vessel (p<0.05). In the STENT group, the predictors were the final % diameter of stenosis after stenting, measured by quantitative coronary arteriography (p<0.0005), LAD (p<0.01), and smoking (p=0.049). When the STENT group was divided into 2 groups according to the diameter of the implanted stent, smoking was a predictive factors for TLR in the group that received relatively small stents (diameter < or =3.0 mm) (p<0.02), but not in the group that received larger stents (diameter > or =3.5 mm). CONCLUSION: Smoking has a deteriorative effect on TLR after implantation of relatively small coronary stents with a diameter of 3.0 mm or less.

Angioplasty, Balloon, Coronary↗
PubMed2004

Valence transition of YbInCu4 observed in hard X-ray photoemission spectra.

Yb 3d and valence-band photoemission spectra of the first-order valence-transition compound YbInCu4 have been measured with hard x ray at an excitation energy of 5.95 keV. Abrupt changes are clearly observed in both spectra around the transition temperature T(V)=42 K, in comparison with ultraviolet and soft x-ray photoemission (VUV-PES and SX-PES) spectra. From the Yb 3d spectra, the Yb valence has been estimated to be approximately 2.90 from 220 down to 50 K and approximately 2.74 at 30-10 K. We propose that Yb 3d hard x-ray photoemission spectroscopy is a very powerful method to estimate the valence of Yb with high accuracy. On the other hand, the Yb2+ 4f-derived peaks in the valence-band spectra exhibit a remarkable enhancement below T(V). The shape of the valence-band spectra is different from those of the VUV-PES and SX-PES spectra above T(V), reflecting the In 5s and 5p contributions.

Journal Article↗
PubMed2004

An X-ray BBB Michelson interferometer.

A new X-ray Michelson interferometer based on the BBB interferometer of Bonse and Hart and designed for X-rays of wavelength approximately 1 A was described in a previous paper. Here, a further test carried out at the SPring-8 1 km beamline BL29XUL is reported. One of the BBB's mirrors was displaced by a piezo to introduce the required path-length difference. The resulting variation of intensity with piezo voltage as measured by an avalanche photodiode could be ascribed to the phase variation resulting from the path-length change, with a small additional contribution from the change of the position of the lattice planes of the front mirror relative to the rest of the crystal. This 'Michelson fringe' interpretation is supported by the observed steady movement across the output beam of the interference fringes produced by a refractive wedge when the piezo voltage was ramped. The front-mirror displacement required for one complete fringe at the given wavelength is only 0.675 A; therefore, a quiet environment is vital for operating this device, as previous experiments have shown.

Journal Article↗
PubMed2004

Image quality improvement in a hard X-ray projection microscope using total reflection mirror optics.

A new figure correction method has been applied in order to fabricate an elliptical mirror to realize a one-dimensionally diverging X-ray beam having high image quality. Mutual relations between figure errors and intensity uniformities of diverging X-ray beams have also been investigated using a wave-optical simulator and indicate that figure errors in relatively short spatial wavelength ranges lead to high-contrast interference fringes. By using a microstitching interferometer and elastic emission machining, figure correction of an elliptical mirror with a lateral resolution close to 0.1 mm was carried out. A one-dimensional diverging X-ray obtained using the fabricated mirror was observed at SPring-8 and evaluated to have a sufficiently flat intensity distribution.

Equipment Design↗
PubMed2004

A case report of late coronary stent thrombosis manifested as acute myocardial infarction 19 months after stenting.

A 63-year-old Japanese man was readmitted to our hospital due to acute broad-anterior myocardial infarction (AMI). The proximal left anterior descending artery (LAD) at the prior stent, which was implanted 19 months earlier and in which no angiographic restenosis was recognized 13 months before the second study, was totally occluded. After crossing a guide wire and balloon angioplasty, angiographic radiolucency was observed at the prior stent, suggesting that AMI was induced by late coronary stent thrombosis. Intravascular ultrasound performed 19 days after the onset of AMI revealed superficial calcification without significant stenosis and an atherosclerotic plaque distal to the stent that was not significantly changed compared to 19 months previously, consistent with the culprit lesion being an intrastent site. AMI may thus be induced by late coronary stent thrombosis during long-term clinical follow-up without clinical symptoms or angiographic restenosis at the second study.

Angioplasty, Balloon, Coronary↗
PubMed2004

Usefulness of a 6 fr right judkins catheter for mechanically extracting a massive intracoronary thrombus from an ectasic right coronary artery: a report on two different cases of thrombectomy.

In order to bail out the slow-flow phenomenon (slow flow) created by a massive thrombus in an ectasic right coronary artery, a thrombus was mechanically extracted with a 6 Fr right Judkins (JR) catheter, which proved to be more useful than a usual thrombectomy using a Rescue PT system catheter (Rescue). In case 1, the Rescue was used in combination with thrombolysis but failed to alleviate the slow flow that was implicated in a large infarction. On the other hand, in case 2, aggressive thrombectomy with a 6 Fr JR catheter with an 8 Fr Amplatz guiding catheter successfully extracted the massive intracoronary thrombus, restoring good coronary flow. Therefore, mechanical extraction with a 6 Fr JR catheter is safe and useful in cases of massive thrombus when diffuse coronary artery ectasia complicates an acute myocardial infarction. In addition, this method should be applicable to cases of acute coronary syndrome with massive thrombus.

Adult↗
PubMed2004

[Survivor of cardiogenic shock following acute myocardial infarction with Churg-Strauss syndrome: first angiographic documention of coronary recanalization of infarct-related arteries: a case report].

A 42-year-old man was treated under a diagnosis of Churg-Strauss syndrome with predonisolone pulse therapy. Three days later, he developed cardiogenic shock following acute myocardial infarction. Coronary angiography showed total occlusions in three peripheral coronary vessels. Intraaortic balloon pumping was used to maintain hemodynamics and predonisolone pulse therapy was repeated. However, he developed cardiogenic shock again after the second pulse therapy and needed percutaneous cardiopulmonary support and intraaortic balloon pumping. Accordingly, combination therapy of predonisolone and cyclophosphamide was given. He then recovered. Follow-up angiography showed recanalization of the infarct-related arteries.

Adult↗