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A Kotani

Publications and source records attributed to A Kotani.

At least 19 recordsLinked to original sources
PubMed2006

Resonant inelastic x-ray scattering at the oxygen K resonance of NiO: nonlocal charge transfer and double-singlet excitations.

We report high-resolution polarization-dependent resonant inelastic x-ray scattering (RIXS) at the O K resonance of NiO showing a rich excitation spectrum. We perform multisite Ni6O19 cluster model calculations, revealing that solid state effects are substantial. We identify a nonlocal charge transfer excitation at 4-5 eV and double-singlet creation at 1.75 eV, both exhibiting significant scattering geometry dependence. Apart from an intense band of local charge transfer excitations (above 5 eV) also dd excitations at 1 eV are observed. Finally, we point out that O K RIXS of correlated metal oxides allows a quantitative and consistent determination of the charge transfer energy delta and the Hund coupling energy J(H).

Journal Article↗
PubMed2003

Autogenous osteochondral grafts for osteonecrosis of the femoral condyle.

PURPOSE: To evaluate the long-term outcome following use of osteochondral autografts for the treatment of osteonecrosis of the femoral condyle. METHODS: Clinical, radiographic and arthroscopic findings were evaluated at follow-up. Patients were 14 women and 2 men, with a mean age of 64.9 years (range, 58-74 years). The osteochondral lesion was equivalent to Lotke 1-B in 12 knees, and was equivalent to 1-C in 4 knees. Preoperative femoral tibia angle ranged from 178 degrees to 190 degrees. RESULTS: The follow-up period ranged from 28 months to 111 months (mean, 67 months). Functional scores improved from 60 to 75 preoperatively to 80 to 100 postoperatively, and the grafts were satisfactorily accepted. Patients with a femoral tibia angle of less than 180 degrees in particular were found to respond favourably. CONCLUSION: Transplant surgery using osteochondral autografting appeared effective for the treatment of osteonecrosis of femoral condyle.

Aged↗
PubMed2001

Correlation of peripheral blood OX40+(CD134+) T cells with chronic graft-versus-host disease in patients who underwent allogeneic hematopoietic stem cell transplantation.

There is no reliable laboratory indicator of the onset of chronic graft-versus-host disease (cGVHD). This study looks at whether the expression of OX40, a member of the tumor necrosis factor receptor family, is related to the development of cGVHD in patients who underwent allogeneic hematopoietic stem cell transplantation. Peripheral blood mononuclear cells from 22 patients after day 100 were subjected to multicolor flow cytometry. The percentages of both OX40+CD4+ and OX40+CD8+ T cells were significantly higher in patients with cGVHD than those without (P <.0001 and P =.001, respectively). Serial analyses showed that OX40+CD4+ T cells elevated before the onset of cGVHD and closely correlated with the therapeutic response. The expression of CD25, CD69, and HLA-DR was partially detectable on OX40+ T cells. These results indicate that serial measurement of OX40+ T cells is useful for predicting the onset as well as the therapeutic response of cGVHD and raise a possibility that the OX40/gp34 system is involved in the pathogenesis of cGVHD.

Anemia, Aplastic↗
PubMed2001

Magnetic circular dichroism of resonant X-ray emission spectra at L edges of rare-earth compounds.

We study the resonant x-ray emission spectroscopy (RXES) and the magnetic circular dichroism (MCD) at the L2,3 absorption edges of rare-earth elements, especially gadolinium ion. To this end, an atomic model is adopted and the multiplet coupling effect is taken into account. Using the formula of the coherent second order optical process which consists of the excitation process from the 2p core state to the empty 5d state and of the radiative decay from the 3d core state to the 2p core hole, we calculate RXES-MCD spectra. By inspection, we have confirmed that the enhancement of the 2p-5d dipole matrix element proposed for MCD of x-ray absorption spectroscopy. In addition, characteristic features of the spectra observed in gadolinium metallic compounds are reproduced by our calculations.

Journal Article↗
PubMed2001

Theory of resonant X-ray emission spectroscopy.

A short review is presented of recent topics in resonant X-ray emission spectroscopy (RXES), especially of the polarization dependence of RXES in d and f electron systems. Polarization-dependent RXES provides important information on the symmetry of electronic states. A scattering-angle dependence in the fluorescence yield of rare-earth metals, RXES in polarized and depolarized configurations of TiO2, and the magnetic circular dichroism in RXES of ferromagnetic systems are discussed together with typical experimental data.

Journal Article↗
PubMed2001

Calculation of rare-earth 4d giant-absorption spectra with multiplet effects and decay processes.

The total and partial photoelectron yield spectra of all the trivalent rare-earth ions in the 4d giant resonance region are calculated with full multiplet effects. The decay processes are treated as coherent processes following photoexcitation. The results reproduce the over all features of experiments. It is obtained that the character of the giant-absorption is different between the light and heavy rare-earths. The multiplet effects play an essential role in the decay processes.

Journal Article↗
PubMed2001

Polarization dependence of resonant X-ray emission spectra in early transition metal compounds.

We calculate the polarization dependent spectra of resonant X-ray emission in TiF3, VF3 and Cr2O3, which have one, two and three 3d electron(s) in the ground state, respectively. We study the detailed mechanism of the spectral structures, comparing with a previous result of TiO2. Then we discuss systematically the difference of spectra with the change of the 3d electron number from group theoretical consideration.

Journal Article↗
PubMed2001

Theory of oxygen 1s resonant X-ray emission spectroscopy in copper-based oxides.

Many-body effects on the oxygen 1s resonant x-ray emission spectrum (O 1s RXES) in copper-based oxides, such as Sr2CuO3 and La2CuO4, are discussed on the basis of cluster-model calculations. The Zhang-Rice singlet excitation, which is a typical many-body state in Cu-based oxide systems, can be detected at low temperatures where the antiferromagnetic correlation between the neighboring Cu spins is strong. Thus the present study emphasizes that the O 1s RXES can be a good tool to obtain information on the Cu 3d states. In particular the polarization-dependent RXES gives the symmetry-decomposed information.

Journal Article↗
PubMed2001

Successful resection of ampullary carcinoma in a father and adenoma in a daughter with familial adenomatous polyposis following detection by surveillance: report of two cases.

This report describes the successful resection of ampullary carcinoma in a 58-year-old man and an adenoma in his 28-year-old daughter after they had undergone proctocolectomy for familial adenomatous polyposis (FAP). Both patients had been monitored by surveillance endoscopy once a year since their proctocolectomy. The father was found to have an ampullary adenoma 26 years after proctocolectomy, and ampullary carcinoma was detected 2 years later, for which pancreatoduodenectomy was performed. Histological examination of the specimen revealed an ampullary carcinoma, 2.5 x 1.7 cm, that had invaded the submucosal layer, but no lymph node metastasis was found. The patient's daughter underwent endoscopy, which showed an ampullary polyp 6 years after total colectomy. Endoscopic mucosal resection of the periampullary lesion was performed, and histological examination revealed a dysplastic tubular adenoma 0.6 x 0.4 cm in diameter. This report reinforces the importance of long-term periodic surveillance of patients with FAP by gastroduodenal endoscopy.

Adenocarcinoma↗
PubMed2001

Histological and functional analysis of vascular smooth muscle cells in a novel culture system with honeycomb-like structure.

Vascular smooth muscle cells (SMCs) undergo phenotype change with the development of atherosclerosis. The phenotype changes of SMCs have been observed in various culture conditions, such as collagen-coated dishes. Here, we report the morphological and functional features of SMCs in a novel culture system using type I-collagen in a characteristic three-dimensional structure designated as honeycombs. The number of ribosome and mitochondria in SMCs cultured in honeycombs was one half or third of those cultured on collagen-coated plastic plates. DNA and protein synthesis of SMCs cultured in honeycombs were less than 1 and 30-40%, respectively, of those cultured on plastic plates. In addition, PDGF-BB did not increase the amount of DNA synthesis in SMCs in honeycombs. SMCs in honeycombs were shown to express several proteins, which are known to express in SMCs in medial layers of arteries. Particularly, caldesmon heavy chain was expressed in SMCs cultured in honeycombs, whereas not in those on plastic plates. Although focal adhesion kinase (FAK) was clearly detected in SMCs in honeycomb, the phosphotyrosine content of focal adhesion kin ase decreased in the process of culture. Immunoblot analysis showed dear different expression of ERK1 and ERK2 of mitogen-activated protein kinase in SMCs. SMCs in honeycombs expressed ERK2, more abundantly compared to ERK1, whereas SMCs in plates show the same levels of expressions for both proteins. Thus, the histological and functional feature of SMCs in the novel culture system is different from SMCs in plastic plates. The three-dimensional culture system described here may be indicating that cultured SMCs are able to express different proteins responding to the surrounding structures.

Animals↗
PubMed2001

Reconstruction of the anterior cruciate ligament using poly-L-lactide interference screws or titanium screws: a comparative study.

In the present clinical trial, interference screws, made of poly-L-lactic acid and applied in 46 knees, were compared to titanium screws employed in 45 knees for reconstructing the anterior cruciate ligament using bone-patellar tendon-bone. An identical surgical technique was applied to both groups; and neither group disclosed apparent side effects such as synovitis caused by hydrolysis of the PLLA or abnormal biochemical findings in the blood. There was no significant difference in the postoperative outcome between the two groups.

Adult↗
PubMed2001

Cerebral blood flow and tissue oxygen saturation in immediate and progressive ischemia in rat brain.

The aim of the present study was to investigate whether immediate ischemia is more harmful to the brain than progressive ischemia. To do so, we examined the correlation between the degree and the process of ischemia using hypobaric hypotension technique, which was used to reduce systemic blood pressure acutely or progressively below the lower threshold of CBF regulation, in rat brain. In Wistar rats (n = 21), global ischemia using bilateral carotid arteries occlusion coupled with hypobaric hypotension was induced by lowering mean arterial blood pressure (MABP) progressively to 55, 45 and 35 mmHg or immediately to 35 mm Hg. Local cerebral blood flow (ICBF) by laser Doppler (LD) flowmetry and tissue hemoglobin oxygen saturation (HbSO2) by a microspectrophotometric method were measured at 25 corresponding locations using a 'scanning' technique which employs a computer-controlled micromanipulator. Regional CBF (rCBF) and rHbSO2 were determined by calculation of the median value from the 25 ICBF and IHbSO2 data. In the 'progressive' group, rCBF and rHbSO2 decreased gradually and reached 12.2 +/- 15.8 LD-units and 44.9% +/- 13.4% at 35 mm Hg of MABP, respectively. In the 'immediate' group, both parameters dropped suddenly to 7.86 +/- 10.6 LD-units (p < 0.01 vs. CBF of the progressive group) and 22.5% +/- 15.5% (p < 0.001 vs. tissue HbSO2 of the progressive group) from the control at 35 mmHg. These data suggested that cerebral ischemia is better tolerated if it is induced gradually. CBF recorded by LD-scanning technique and HbSO2 value by microspectrophotometric method correlated well in the ischemic condition, indicating that HbSO2 can be preserved if CBF is decreased gradually.

Animals↗
PubMed2001

Relationship of electrochemical oxidation of catechins on their antioxidant activity in microsomal lipid peroxidation.

The oxidation potentials of catechins were measured by employing flow-through column electrolysis. The oxidation potentials of catechins were shown to depend on their structures. At the same time, the antioxidant activity of catechins on NADPH-dependent lipid peroxidation in rat liver microsomes was evaluated. Catechins showed a 50% inhibition of lipid peroxidation in the concentration range of 10-51 microM. Among those studied, galloylated catechins exhibited stronger antioxidant activities than those of nongalloylated catechins. A quantitative relationship has been obtained to describe the antioxidant activity of catechins: log IC50 (microM)= 1.56+2.49E1/2 (V)-0.29 logP (r=0.907), where IC50 represents the concentration for 50% inhibition of lipid peroxidation, E1/2 represents the half-wave potential of the first oxidation wave, and P represents the octanol/water partition coefficient. This relationship suggested two important characteristics determining catechin antioxidant activity, namely the ease of oxidation and the lipophilicity.

Animals↗
PubMed2001

Estimation of the antioxidant activities of flavonoids from their oxidation potentials.

A simple electrochemical method for estimating the antioxidant activity (AA) of flavonoids has been developed. The proposed method is based on a measurement of the half-wave potential (E1/2) of the first oxidation wave of flavonoids by using flow-through column electrolysis. At the same time, the lipid peroxidation (LPO) inhibiting effects of these flavonoids were determined. A quantitative structure-activity relationship was obtained to describe the AA of flavonoids: IC50(microM) = 30.36 + 151.50 E1/2 (V) -12.63 log P (r = 0.852), where IC50 represents the concentration for 50% inhibition of LPO, and P represents the octanol/water partition coefficient. This method is expected to be useful for the quick screening of flavonoid antioxidants, and evaluating the AA of flavonoid-containing foods and medicinal plants.

Animals↗
PubMed2001

Radiosurgery-induced brain tumor. Case report.

The authors describe a case of glioblastoma multiforme (GBM) associated with previous gamma knife radiosurgery for a cerebral arteriovenous malformation (AVM). A 14-year-old boy had undergone radiosurgery for an AVM, which was performed using a 201-source 60Co gamma knife system at another institution. The maximum and margin radiation doses used in the procedure were 40 and 20 Gy, respectively. One year after radiosurgery, the patient noticed onset of mild left hemiparesis due to radiation necrosis. Six and one-half years after radiosurgery, at the age of 20 years, the patient experienced an attack of generalized tonic-clonic seizure. Magnetic resonance (MR) imaging revealed the existence of a brain tumor in the right parietal lobe. The patient underwent an operation and the histological diagnosis of the lesion was GBM. Ten months following the operation, that is, 99 months postradiosurgery, this patient died. To the best of the authors' knowledge, this is the first reported case of a neoplasm induced by radiosurgery for an AVM and the second case in which it occurred following radiosurgery for intracranial disease.

Brain Neoplasms↗
PubMed2001

[Microcirculatory changes in the development of the cerebrovascular adaptation].

Recently, long-term cerebrovascular adaptations after unilateral carotid ligation that increase the tolerance of the brain to subsequent episode of ischemia was reported(J Cereb Blood Flow Metab, 1998). However, the pathophysiological mechanisms underlying the phenomenon was unknown. We examined regional cerebral blood flow(rCBF) before, during and after subsequent ischemia in the development of the adaptation. Male Wistar rats(n = 18) were used. Unilateral(right) carotid artery ligation was performed 3 hours(group A: n = 8), 3 days(group B: n = 10) before forebrain ischemia. With bilateral carotid arteries occlusion, mean arterial blood pressure(MABP) was reduced by hypobaric hypotension down to 50 mmHg and maintained constant for 30 min. After hypotension, the experiment continued for 90 min. Local CBF were registered at 25(5 x 5) identical locations by laser Doppler scanning in the cortex during the experiment in bilateral hemispheres(at control phase, after the left carotid artery ligation, during ischemia and after hypotension). The physiological variable such as blood pressure and gas analysis were within normal range in all groups. There were no differences of rCBF between the right and left hemispheres in group A during the experiment. In group A, rCBF of both hemispheres significantly decreased after the ligation of the left carotid artery, during the induced ischemia (P < 0.05), and recovered to the value of before ischemia. Whereas, in group B rCBF of the left side(non-occluded side) decreased after the ligation of the left carotid artery, during the induced ischemia(P < 0.05), and recovered to the value of before ischemia, but rCBF of the right side(occluded side) decreased only during the induced ischemia(P < 0.05) and rCBF of the right side was significantly higher than the left brain after ligation of the carotid artery, during ischemia and after hypotension(P < 0.05). On the basis of these data, we concluded that cerebrovascular adaptations can be acquired by 3 days after unilateral carotid artery occlusion and the tolerance phenomenon is certainly attributed to microcirculatory improvement.

Animals↗
PubMed2000

Determination of plasma free fatty acids by high-performance liquid chromatography with electrochemical detection.

Determination of free fatty acids (FFAs) in control serum and human plasma was carried out by high-performance liquid chromatography with electrochemical detection. Peak height for palmitic, palmitoleic, stearic, oleic, linoleic, and arachidonic acids at a detection potential of -415 mV vs a saturated calomel electrode showed a linear relation to acid amount in the range 50-1600 pmol. The present method for plasma free fatty acid determination required only 10 microL of plasma sample. The method is simple and the time for blood pretreatment is short. Change in plasma FFA with blood glucose level was monitored before and after meal ingestion by this method, using one male and one female subject. It was possible to rapidly reduce plasma FFA and increase blood glucose subsequent to the meal. The present method is thus shown to have potential for clinical application.

Adult↗