Biomedical subjects

A Tanaka

Publications and source records attributed to A Tanaka.

At least 19 recordsLinked to original sources

PubMed2006

Spin state transition in LaCoO3 studied using soft x-ray absorption spectroscopy and magnetic circular dichroism.

Using soft x-ray absorption spectroscopy and magnetic circular dichroism at the Co-L(2,3) edge, we reveal that the spin state transition in LaCoO3 can be well described by a low-spin ground state and a triply degenerate high-spin first excited state. From the temperature dependence of the spectral line shapes, we find that LaCoO3 at finite temperatures is an inhomogeneous mixed-spin state system. It is crucial that the magnetic circular dichroism signal in the paramagnetic state carries a large orbital momentum. This directly shows that the currently accepted low- or intermediate-spin picture is at variance. Parameters derived from these spectroscopies fully explain existing magnetic susceptibility, electron spin resonance, and inelastic neutron data.

Journal Article↗

PubMed2006

K-ras mutations and cell kinetics in Helicobacter pylori associated gastric intestinal metaplasia: a comparison before and after eradication in patients with chronic gastritis and gastric cancer.

BACKGROUND: Helicobacter pylori related gastric intestinal metaplasia (IM) is considered to be a precancerous lesion. AIMS: To identify the effects of H pylori eradication on K-ras mutations, cell kinetics in IM and histological changes in patients with and without gastric cancers in a one-year prospective study. METHODS: Patients included group A (n = 39), chronic gastritis, and group B (n = 53), intestinal-type early gastric cancer patients who had all undergone endoscopic mucosal resection (n = 25) or surgical resection (n = 28). K-ras codon 12 mutations in IM were examined, followed by DNA sequencing analysis. Proliferating and apoptotic cells were detected with anti-Ki-67 antibody and using the TUNEL method, respectively. RESULTS: The incidence of K-ras mutations in the cancer was only 3.8%. The mutant K-ras in IM was observed more frequently in group A (46.2%) than in group B patients (1.9%) (p<0.005). After eradication, the K-ras mutations significantly declined to 12.8% in group A (p<0.005). The mutation pattern of K-ras codon 12 before eradication was that GGT was mainly changed to AGT (50%) in group A. AGT transformation was not affected by treatment. Apoptosis in IM showed an increase after H pylori eradication in both groups (p<0.05 in group A) although no histological improvement in IM was observed. The monocyte score was significantly higher in group A than in group B (p<0.05); the score improved significantly after eradication. CONCLUSIONS: K-ras mutations in IM do not always play a role in gastric carcinogenesis but cell kinetics, especially apoptosis, in IM may contribute to it. There are early events in K-ras mutations which are influenced by H pylori infection; some mutations may also be selected by eradication. These unstable K-ras mutations in IM may be related to lymphocyte infiltration caused by H pylori infection.

Apoptosis↗

PubMed2006

Orbitally driven spin-singlet dimerization in S=1 La4Ru2O10.

Using x-ray absorption spectroscopy at the Ru-L2,3 edge we reveal that the Ru4+ ions remain in the S=1 spin state across the rare 4d-orbital ordering transition and spin-gap formation. We find using local spin density approximation + Hubbard U band structure calculations that the crystal fields in the low-temperature phase are not strong enough to stabilize the S=0 state. Instead, we identify a distinct orbital ordering with a significant anisotropy of the antiferromagnetic exchange couplings. We conclude that La4Ru2O10 appears to be a novel material in which the orbital physics drives the formation of spin-singlet dimers in a quasi-two-dimensional S=1 system.

Journal Article↗

PubMed2006

Anti-parietal cell antibody and serum pepsinogen assessment in screening for gastric carcinoma.

BACKGROUND: Anti-parietal cell antibody is found in patients with Helicobacter pylori-positive gastritis and is related to atrophic gastritis and gastric carcinoma. AIM: To identify the characteristics of patients at high-risk for gastric carcinoma in terms of anti-parietal cell antibody and serum pepsinogen. PATIENTS AND METHODS: Subjects were 92 H. pylori-positive patients (54 men, 38 women; mean age, 57.9 years; range, 15-88 years). The serum concentrations of pepsinogen I and II were determined by radioimmunoassay, and the presence of anti-parietal cell antibody was assessed by enzyme-linked immunosorbent assay. Degrees of inflammation and atrophy in the corpus of the stomach were evaluated histologically. RESULTS: Patients were classified into four groups according to anti-parietal cell antibody status and pepsinogen I/II ratio. Anti-parietal cell antibody-negative/pepsinogen I/II-low patients had the highest risk for gastric carcinoma (prevalence of gastric carcinoma: 7/13=53.8%, odds ratio=7.6, 95% confidence interval, 1.2-48.0). Anti-parietal cell antibody titre was high when inflammation in the corpus was severe (p=0.06) and significantly low when atrophy in the corpus was severe (p=0.01). CONCLUSION: Our results showed that patients with a negative anti-parietal cell antibody titre and low pepsinogen I/II ratio are at high-risk for gastric carcinoma.

Adolescent↗

PubMed2006

Hypothalamic-pituitary-adrenocortical axis: the hidden gold in gastric mucosal homeostasis.

The results overviewed in the present article suggest that glucocorticoids released during acute activation of hypothalamic-pituitary-adrenocortical (HPA) axis are important gastroprotective factors, allowing us to re-evaluate the traditional point of view about their ulcerogenic role. It has been shown that various ulcerogenic stimuli induce an increase in glucocorticoid production that in turn helps the gastric mucosa to resist against a harmful action of ulcerogenic stimuli. Glucocorticoids released in response to mild stress contribute to adaptive gastric cytoprotection. The gastroprotective action of glucocorticoids is accounted for by maintaining the local defensive factors and inhibiting the pathogenic elements. Maintenance of glucose and temperature homeostasis as well as systemic blood pressure by glucocorticoid hormones could be a fundamental of their beneficial action on various gastric targets. Thus, glucocorticoids released during activation of HPA axis may contribute to the gastric mucosal homeostasis through their contribution to general body homeostasis.

Animals↗

PubMed2006

Comparison of activities of enzymes related to energy metabolism in peripheral leukocytes and livers between Holstein dairy cows and ICR mice.

Activities of enzymes related to energy metabolism and isoenzyme patterns of lactate dehydrogenase (LDH) were determined in peripheral leukocytes and livers of Holstein dairy cows and Institute of Cancer Research (ICR) mice. In dairy cow liver, activities of enzymes in glycolysis, malate-aspartate shuttle and lipogenesis were lower, but activities of glucose-6-phosphatase in gluconeogenesis were higher than those in mouse liver. Glucokinase activities were below detection limit in leukocytes and liver of the cows. Dairy cow leukocytes and liver showed the isoenzyme patterns with dominance of LDH-1, -2 and-3, whereas mouse leukocytes and liver showed that LDH-5 was dominant. The LDH isoenzyme patterns were very similar between leukocytes and liver in each animal species. Some enzymes in leukocytes may reflect those enzymes activities in liver and be a useful indicator for energy metabolism in animals.

Animals↗

PubMed2006

Semi-purification of the immunoglobulin E-sweat antigen acting on mast cells and basophils in atopic dermatitis.

BACKGROUND: Sweating aggravates the symptoms of atopic dermatitis (AD). We have recently reported positive skin reactions and histamine release from basophils in response to autologous sweat in patients with AD. OBJECTIVE: To characterize the biochemical and immunological properties of the substance in sweat that evokes histamine release and to study the usability of the basophil-histamine release test with the sweat antigen for AD. METHODS: Sweat collected from healthy volunteers was purified using chromatographies. Serum immunoglobulin (Ig)E of four patients with AD were purified using an affinity-chromatography column with anti-IgE antibodies. The amount of semi-purified sweat antigen (138 ng protein/ml) that induced a half-maximum reaction of basophils of a patient with AD was utilized for the basophil histamine release test. The involvement of specific IgE and high-affinity IgE receptor (FcepsilonRI) in the reactions was examined using basophils of healthy volunteers, a human mast cell line (LAD2), and a rat basophilic leukemia cell line transfected with human alpha-subunit of FcepsilonRI (RBL-48). RESULTS: The semi-purified sweat antigen induced histamine release from the basophils of 47 of 61 (74.6%) patients with AD and four of 46 (8.7%) healthy controls. Both basophils and mast cells sensitized with the patient-derived IgE showed degranulation upon stimulation with the sweat antigen. However, no reaction was observed when cells were sensitized with myeloma IgE or the antigen was treated with proteases. CONCLUSION: The semi-purified standardized sweat antigen consists of a protein that induces degranulation of basophils and mast cells via antigen-specific IgE and FcepsilonRI in patients with AD.

Adolescent↗

PubMed2006

Inhibitory effects of fluvastatin on cytokine and chemokine production by peripheral blood mononuclear cells in patients with allergic asthma.

BACKGROUND: Statins have anti-inflammatory effects on immune cells. OBJECTIVE: To investigate the immunomodulatory effects of fluvastatin on peripheral blood mononuclear cells (PBMCs) after allergen-specific and non-allergen-specific stimulation in patients with asthma and in healthy subjects. METHODS: PBMCs from seven patients with asthma who showed elevated immunoglobulin (Ig)E to house dust mite were isolated and stimulated with Dermatofagoides farinae, purified protein derivative, and phytohaemagglutinin (PHA) in the presence or absence of fluvastatin. PBMCs from seven healthy subjects were stimulated with PHA. The effects of fluvastatin on cell proliferation and production of cytokines (interferon [IFN]-gamma and interleukin [IL]-5) and chemokines (chemokine CXC motif, ligand [CXCL10], and CC chemokine ligand [CCL17]) were measured. Migration of T helper (Th)1 and Th2 cell lines was also investigated. The expression of CXCR3 and CCR4 was analysed with flow cytometry. Steroid-insensitive PBMCs induced by preculture with IL-2 and IL-4 were also evaluated. Some experiments were performed in the presence of mevalonic acid. RESULTS: Fluvastatin inhibited the proliferation of PBMCs and decreased the production of IL-5, IFN-gamma, CCL17, and CXCL10 after allergen-specific and non-allergen-specific stimulation; all these effects, except for decreased CXCL10 production, were partially reversed by mevalonic acid. Culture supernatants obtained in the presence of fluvastatin prevented the migration of Th1 and Th2 cell lines in a dose-dependent manner. In addition, CCR4 and CXCR3 expression on CD4(+) T cells was not affected by the presence of fluvastatin. Fluvastatin inhibited the proliferative response of steroid-insensitive PBMCs to phytohaemagglutinin. CONCLUSION: Fluvastatin has inhibitory effects on cytokine and chemokine production, and thus might be used as a potential therapeutic agent in severe asthma.

Adult↗

PubMed2006

Association between lipid peroxidation and inflammation in obstructive sleep apnoea.

In the present study, the authors examined the relationship between lipid peroxidation and inflammation in patients with obstructive sleep apnoea (OSA). A total of 40 obese patients with OSA were studied, along with 18 obese and 12 lean subjects without OSA. Overnight excretion of 8-isoprostane in urine and serum levels of high-sensitivity C-reactive protein (hsCRP) were measured. In addition, the effects of 3 months' treatment with nasal continuous positive airway pressure (nCPAP) were studied in 20 obese patients with moderate-to-severe OSA. Overnight urinary excretion of 8-isoprostane and serum levels of hsCRP were significantly higher in patients with moderate-to-severe OSA compared with patients with mild OSA and obese or lean subjects without OSA. Overnight urinary excretion of 8-isoprostane significantly correlated with apnoea-hypopnoea index, duration of hypoxia during sleep, body mass index, and serum levels of hsCRP in patients with OSA. The severity of OSA was an independent factor predicting the urinary excretion of 8-isoprostane. nCPAP significantly decreased urinary excretion of 8-isoprostane and serum levels of hsCRP. In conclusion, these results suggest that both obstructive sleep apnoea severity and obesity can independently contribute to elevations in urinary excretion of 8-isoprostane. Therefore, obstructive sleep apnoea may increase the risks of cardiovascular morbidity in obese patients.

C-Reactive Protein↗

PubMed2006

Spontaneous improvement of persistent ulceration after carotid artery stenting.

BACKGROUND AND PURPOSE: Because carotid plaque ulceration is associated with an increased risk of cerebral embolism, residual carotid plaque ulceration directly around a stent (persistent ulceration) after carotid angioplasty and stent placement (CAS) could still be a risk factor for a stroke. The purpose of this study is to understand the morphologic and clinical prognosis of persistent ulceration. PATIENTS AND TECHNIQUES: CAS was attempted on 91 consecutive stenotic lesions (80 patients). Of these, 54 lesions (48 patients) had ulceration before CAS. Angiograms were evaluated immediately after the procedure. Persistent ulceration was found in 34 lesions (30 patients). The mean depth and length of persistent ulcers were 2.1 mm (range, 1-4.7 mm) and 8.9 mm (range, 1.5-22 mm), respectively. All patients with persistent ulceration were followed with antiplatelet therapy. RESULTS: No ischemic event due to the lesions occurred during the mean follow-up period of 25.5 months (range, 3-48 months). Angiography on 25 lesions (21 patients) at a mean of 5.8 months (range, 1-21 months) after CAS showed that persistent ulceration disappeared in 12 lesions (48%), improved in 11 lesions (44%), and remained unchanged in 2 lesions (8%). Nine lesions (36%) showed restenosis, which were < or =30% and did not require any additional intervention. New ischemic lesions were not detected in any of the 14 patients (17 lesions) who underwent follow-up MR imaging at a mean of 9 months (range, 1-32 months) after CAS. CONCLUSION: We conclude that persistent ulceration after CAS improves spontaneously and is not a risk factor for cerebral embolism.

Aged↗

PubMed2006

Cerebral hemodynamics in Moyamoya disease: correlation between perfusion-weighted MR imaging and cerebral angiography.

BACKGROUND AND PURPOSE: In Moyamoya disease, the relationship between cerebral hemodynamics and angiographic findings has not been fully evaluated. The purpose of this study is to evaluate hemodynamics in Moyamoya disease with perfusion-weighted MR imaging (PWI) and cerebral angiography. METHODS: Twenty patients with Moyamoya disease were the subjects. Mean transit time (MTT) derived from PWI was calculated in the medial frontal lobes, the posterior frontal lobes, the occipital lobes, and the basal ganglia. From the angiographies, we classified the degrees of internal carotid artery (ICA) and posterior cerebral artery (PCA) stenoses as well as the degrees of Moyamoya vessels and leptomeningeal anastomosis (LMA). MTT in each region was compared with the angiographic findings. RESULTS: MTT positively correlated with the degree of ICA stenosis in the medial frontal (P < .01), posterior frontal (P < .001), and occipital (P < .001) lobes, as well as in the basal ganglia (P < .001). MTT correlated with the degree of PCA stenosis in the medial frontal (P < .001), posterior frontal (P < .001), and occipital (P < .001) lobes, as well as in the basal ganglia (P < .001). MTT correlated with the degree of Moyamoya vessels in the medial frontal (P < .05) and posterior frontal (P < .01) lobes. A multivariate analysis revealed that ICA and PCA stenoses and Moyamoya vessels were independent factors that prolonged MTT. CONCLUSION: Both ICA and PCA stenoses may influence overall cerebral perfusion in Moyamoya disease. The development of Moyamoya vessels may indicate hemodynamic impairment.

Adolescent↗

PubMed2006

Direct carotid puncture for the endovascular treatment of anterior circulation aneurysms.

We report the usefulness of Guglielmi detachable coil (GDC) embolization by direct carotid puncture for anterior circulation aneurysms. For all 27 patients, GDC embolization by direct carotid puncture was safely performed by using a 5F sheath introducer 5 cm long and a Tracker-38 catheter. Neurologic deficits and hemorrhage were not found in any patient during the follow-up period. If the transfemoral approach cannot be applied, GDC embolization should be considered as an alternative method.

Aged↗

PubMed2006

The significance of incomplete stent apposition in patients undergoing stenting of internal carotid artery stenosis.

BACKGROUND AND PURPOSE: Incomplete stent apposition after carotid angioplasty and stent placement (CAS) is often seen but little is known about how the incomplete attachment goes after stent placement. For example, some may change into restenosis around the stent edge and some may remain unchanged. The purpose of this study is to clarify the morphologic prognosis of an incomplete stent apposition at the stent edge. METHODS: CAS was attempted on 135 consecutive stenotic lesions (124 patients). Angiograms were then evaluated immediately after the procedure. An incomplete stent apposition at stent edge was found in 15 patients, and all of them were followed up by angiography and MR imaging with antiplatelet therapy. RESULTS: No ischemic event caused by the lesions occurred during the mean follow-up period of 11 months (from 4 to 32 months). The angiography findings of 15 lesions at a mean of 8.8 months (from 2 to 28 months) after CAS showed that all remained unchanged. No patients required any additional intervention. No new ischemic lesions were detected in any of the 15 patients who underwent follow-up MR imaging at a mean of 10 months (from 2 to 32 months) after CAS. CONCLUSION: In this study, the existence of a segment of incomplete stent apposition had no adverse morphologic or clinical effect.

Aged↗

PubMed2005

Orbital-assisted metal-insulator transition in VO2.

We found direct experimental evidence for an orbital switching in the V 3d states across the metal-insulator transition in VO2. We have used soft-x-ray absorption spectroscopy at the V L2,3 edges as a sensitive local probe and have determined quantitatively the orbital polarizations. These results strongly suggest that, in going from the metallic to the insulating state, the orbital occupation changes in a manner that charge fluctuations and effective bandwidths are reduced, that the system becomes more one dimensional and more susceptible to a Peierls-like transition, and that the required massive orbital switching can only be made if the system is close to a Mott insulating regime.

Journal Article↗

PubMed2005

Controlling orbital moment and spin orientation in CoO layers by strain.

We have observed that CoO films grown on different substrates show dramatic differences in their magnetic properties. Using polarization dependent x-ray absorption spectroscopy at the Co L2,3 edges, we revealed that the magnitude and orientation of the magnetic moments strongly depend on the strain in the films induced by the substrate. We presented a quantitative model to explain how strain together with the spin-orbit interaction determine the 3d orbital occupation, the magnetic anisotropy, as well as the spin and orbital contributions to the magnetic moments. Control over the sign and direction of the strain may, therefore, open new opportunities for applications in the field of exchange bias in multilayered magnetic films.

Journal Article↗

PubMed2005

Relation between aortic stiffness and coronary flow reserve in patients with coronary artery disease.

OBJECTIVES: To investigate the relation between aortic stiffness and coronary flow reserve (CFR) in patients with coronary artery disease (CAD). DESIGN: Observational study. SETTING: Coronary care unit of a primary care hospital. PATIENTS: 192 consecutive patients who underwent coronary angiography. MAIN OUTCOME MEASURE: Brachial-ankle pulse wave velocity (ba-PWV), CFR, and severity of CAD. RESULTS: According to the angiographic findings, patients were divided into four subgroups: patients without significant stenosis (normal coronary artery (NCA) group, n = 28) and those with one vessel disease (1VD group, n = 92), two vessel disease (2VD group, n = 50), or three vessel disease (3VD group, n = 22). ba-PWV increased with the number of diseased vessels and was significantly correlated with the number of diseased vessels (NCA group v 1VD group v 2VD group v 3VD group: 1481 (252) v 1505 (278) v 1577 (266) v 1727 (347) cm/s, p < 0.001). CFR had a significant negative correlation with ba-PWV (r = -0.45, p < 0.0001). The diastolic to systolic velocity ratio obtained in 45 patients also was significantly correlated with ba-PWV (r = -0.35, p < 0.05). Multiple regression analysis showed that ba-PWV was an independent determinant of CFR (p < 0.01). CONCLUSIONS: Coronary flow is altered with aortic stiffening in patients with CAD. These results suggest one possible mechanism for recent reports that aortic stiffness is a key cardiovascular risk factor.

Ankle↗

PubMed2005

Spectroscopy of stripe order in La1.8Sr0.2NiO4 using resonant soft x-ray diffraction.

Strong resonant enhancements of the charge-order and spin-order superstructure-diffraction intensities in La1.8Sr0.2NiO4 are observed when x-ray energies in the vicinity of the Ni L2,3 absorption edges are used. The pronounced photon-energy and polarization dependences of these diffraction intensities allow for a critical determination of the local symmetry of the ordered spin and charge carriers. We found that not only the antiferromagnetic order but also the charge-order superstructure resides within the NiO2 layers; the holes are mainly located on in-plane oxygens surrounding a Ni2+ site with the spins coupled antiparallel in close analogy to Zhang-Rice singlets in the cuprates.

Journal Article↗

PubMed2005

Macroscopic quantum tunneling in a d-wave high-TC Bi2Sr2CaCu2O8 + delta superconductor.

While Josephson-junction-like structures intrinsic to the layered cuprate high temperature superconductors offer an attractive stage for exploiting possible applications to new quantum technologies, the low energy quasiparticle excitations characteristically present in these d-wave superconductors may easily destroy the coherence required. Here we demonstrate for the first time the feasibility of macroscopic quantum tunneling in the intrinsic Josephson junctions of a high temperature superconductor Bi(2)Sr(2)CaCu(2)O(8 + delta), and find it to be characterized by a high classic-to-quantum crossover temperature and a relatively weak quasiparticle dissipation.

Journal Article↗