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S Yamada

Publications and source records attributed to S Yamada.

At least 55 records · Page 3Linked to original sources
PubMed2003

A repertoire of pyridinium-phenyl-methyl cross-talk through a cascade of intramolecular electrostatic interactions.

Direct intramolecular cation-pi interaction between phenyl and pyridinium moieties in 1a(+) has been experimentally evidenced through pH-dependent (1)H NMR titration. The basicity of the pyridinyl group (pK(a) 2.9) in 1a can be measured both from the pH-dependent chemical shifts of the pyridinyl protons as well as from the protons of the neighboring phenyl and methyl groups as a result of electrostatic interaction between the phenyl and the pyridinium ion in 1a(+) at the ground state. The net result of this nearest neighbor electrostatic interaction is that the pyridinium moiety in 1a becomes more basic (pK(a) 2.92) compared to that in the standard 2a (pK(a) 2.56) as a consequence of edge-to-face cation (pyridinium)-pi (phenyl) interaction, giving a free energy of stabilization (DeltaDeltaG(o)pKa) of -2.1 kJ mol(-1). The fact that the pH-dependent downfield shifts of the phenyl and methyl protons give the pK(a) of the pyridine moiety of 1a also suggests that the nearest neighbor cation (pyridinium)-pi (phenyl) interaction also steers the CH (methyl)-pi (phenyl) interaction in tandem. This means that the whole pyridine-phenyl-methyl system in 1a(+) is electronically coupled at the ground state, cross-modulating the physicochemical property of the next neighbor by using the electrostatics as the engine, and the origin of this electrostatics is a far away point in the molecule-the pyridinyl-nitrogen. The relative chemical shift changes and the pK(a) differences show that the cation (pyridinium)-pi (phenyl) interaction is indeed more stable (DeltaDeltaG(o)pKa = -2.1 kJ mol(-1)) than that of the CH (methyl)-pi (phenyl) interaction (DeltaDeltaG(o)pKa = -0.8 kJ mol(-1)). Since the pK(a) of the pyridine moiety in 1a is also obtained through the pH-dependent shifts of both phenyl and methyl protons, it suggests that the net electrostatic mediated charge transfer from the phenyl to the pyridinium and its effect on the CH (methyl)-pi (phenyl) interaction corresponds to DeltaG(o)pKa of the pyridinium ion (approximately 17.5 kJ mol(-1)), which means that the aromatic characters of the phenyl and the pyridinium rings in 1a(+) have been cross-modulated owing to the edge-to-face interaction proportional to this DeltaG(o)pKa change.

Journal Article↗
PubMed2003

Search for supernova relic neutrinos at Super-Kamiokande.

A search for the relic neutrinos from all past core-collapse supernovae was conducted using 1496 days of data from the Super-Kamiokande detector. This analysis looked for electron-type antineutrinos that had produced a positron with an energy greater than 18 MeV. In the absence of a signal, 90% C.L. upper limits on the total flux were set for several theoretical models; these limits ranged from 20 to 130 macro nu(e) cm(-2) s(-1). Additionally, an upper bound of 1.2 macro nu(e) cm(-2) s(-1) was set for the supernova relic neutrino flux in the energy region E(nu)>19.3 MeV.

Journal Article↗
PubMed2003

Indications of neutrino oscillation in a 250 km long-baseline experiment.

The K2K experiment observes indications of neutrino oscillation: a reduction of nu(mu) flux together with a distortion of the energy spectrum. Fifty-six beam neutrino events are observed in Super-Kamiokande (SK), 250 km from the neutrino production point, with an expectation of 80.1(+6.2)(-5.4). Twenty-nine one ring mu-like events are used to reconstruct the neutrino energy spectrum, which is better matched to the expected spectrum with neutrino oscillation than without. The probability that the observed flux at SK is explained by statistical fluctuation without neutrino oscillation is less than 1%.

Journal Article↗
PubMed2003

Reduced phosphorylation of cyclic AMP-responsive element binding protein in the postmortem orbitofrontal cortex of patients with major depressive disorder.

In this study, we examined the amounts of cAMP-responsive element binding protein (CREB) and its phosphorylated form in homogenate preparations from postmortem orbitofrontal cortices of antidepressant drug-free patients with major depressive disorder and age-matched controls by immunoblotting. Immunoreactivies of both CREB and phosphorylated CREB were significantly decreased in depressive subjects compared to controls. The immunoreactivity of phosphorylated CREB was diminished to a greater extent than that of CREB in depressive patients. It has been indicated from animal studies that a transcription factor likely mediates neural plasticity in the mammalian brain and neural tissues. Our results suggest that alterations in the cAMP signaling system, especially in CREB, may be involved in the pathophysiology of depression and be potential targets for antidepressant treatment.

Aged↗
PubMed2003

Prostaglandin E2 induced the differentiation of osteoclasts in mouse osteoblast-depleted bone marrow cells.

Prostaglandin (PG) E(2) is a known bone absorbing agent that acts on osteoblasts to facilitate osteoclastogenesis by increasing the secretion of RANKL. In the present study, we investigated the direct action of PGE(2) on osteoclastic progenitors that differentiate into TRAP-positive multinucleated cells. The hematopoietic stem cell obtained from murine bone marrow was purified by a Sephadex G-10 column, and cultured in the presence of CSF-1 and RANKL to facilitate cell differentiation. The introduction of low-density PGE(2) into the culture resulted in a drastic increase of TRAP-positive multinucleated cells, whereas the addition of high-density PGE(2) had the opposite effect. PCR analysis revealed increased level of EP3 mRNA in undifferentiated cells and reduced level after the development of osteoclast; EP1, EP2 and EP4 were constitutively expressed throughout the differentiation. Investigation of intracellular signaling verified that low-density PGE(2) suppressed PKA activity in undifferentiated cells, suggesting that PGE(2) acts on the osteoclastic cell lineage to facilitate cell differentiation by suppressing PKA in the presence of RANKL.

Animals↗
PubMed2003

Noninvasive, direct visualization of macro-reentrant circuits by using magnetocardiograms: initiation and persistence of atrial flutter.

AIMS: We analysed the cardiac magnetic fields on the body surface to visualize electrical currents noninvasively during reentrant arrhythmias. METHODS AND RESULTS: Seven patients with counterclockwise atrial flutter (AFL) were studied during 17 episodes of AFL using 64-channel magnetocardiograms (MCGs) and electrophysiological study. Eight of the episodes were paroxysmal AFL, in which MCGs were recorded from the time of spontaneous onset to the time of termination. We constructed iso-magnetic field maps of the tangential components and produced MCG animations. With respect to AFL initiation, an atrial premature complex induced AFL. Prior to the initiation of AFL, atrial fibrillation (AF) transiently occurred. The cardiac magnetic fields revealed a single peak during sinus rhythm or with premature complexes but a disorganized pattern during AF. When AF transformed to AFL, the magnetic fields changed from a disorganized pattern to a single peak at first and then evolved to a circular pattern. During persistent AFL, the magnetic source moved in a counterclockwise circuit. CONCLUSION: MCG animation can be used to visualize the sequence in which a premature complex transforms sinus rhythm to AFL via AF. Our findings indicate that MCGs can be used to identify noninvasively the mechanisms responsible for atrial tachyarrhythmias.

Atrial Fibrillation↗
PubMed2003

Dopamine stabilizes milrinone-induced changes in heart rate and arterial pressure during anaesthesia with isoflurane.

BACKGROUND AND OBJECTIVE: Phosphodiesterase-III inhibitors and dobutamine effectively improve cardiac function in patients with cardiac failure, but they are limited by possible hypotensive effects. We tested the hypothesis that dopamine contributes to stabilizing milrinone-induced haemodynamic changes. METHODS: Nine patients undergoing major surgery were anaesthetized using nitrous oxide and oxygen supplemented with isoflurane 1-2%. After baseline haemodynamics were recorded, milrinone (25 or 50 microg kg(-1)) was administered over 10min, followed by a continuous infusion (0.5 microg kg(-1) min(-1). The second set of haemodynamic values was measured 50 min after beginning the continuous infusion of milrinone. Dopamine (4 microg kg(-1) min(-1)) was then administered with milrinone. RESULTS: Milrinone significantly increased the heart rate from 81 +/- 8 to 102 +/- 16beats min(-1), but it decreased the mean arterial pressure from 83 +/- 10 to 66 +/- 10 mmHg and systemic vascular resistance (P < 0.05 for each). The pulmonary capillary wedge pressure, cardiac index and pulmonary vascular resistance did not change significantly. The addition of dopamine to the milrinone infusion significantly decreased the heart rate (94 +/- 12 beats min(-1)) and increased the mean arterial pressure (82 +/- 11 mmHg). Dopamine and milrinone, but not milrinone alone, significantly increased the cardiac index and the rate-pressure product. CONCLUSIONS: The combination regimen of milrinone and dopamine improved cardiac function, and changes in heart rate and mean arterial pressure induced by milrinone were attenuated by dopamine. The results suggest that a combination regimen of milrinone and dopamine rather than milrinone alone should be used to maintain arterial pressure.

Analysis of Variance↗
PubMed2003

Mineral characteristics of leaves of plants from different phylogeny grown in various soil types in the temperate region.

The objective of this research was to analyze selected minerals in leaves of plants, belonging to 166 species growing in alluvial, low pH, brown forest and serpentine soils. Mineral characteristics of the soils involved were also determined. For the macronutrients, in trees grown in alluvial soil, N, P, Ca, and Mg concentrations of leaves were higher in recently evolved plants than in plants with a longer period of evolution; K concentration remained constant regardless of evolution. In grasses grown in alluvial soil, it was difficult to detect the general tendency of mineral concentration. N, P, and K concentrations in alluvial soil were closely related to those in low pH and serpentine soils. Ca concentration in alluvial soil was lower than that in low pH and serpentine soils. Mg concentration in alluvial soils was higher than that in low pH soils, while lower than that in serpentine soil. Therefore, N, P, and K accumulated according to the plant characteristics for these elements, while Ca and Mg accumulation was strongly affected by the soil properties. For the micronutrients, in trees, Fe and Mn remained constant regardless of evolution; Zn concentration was lower in recently-evolved plants than in plants with a longer period of evolution. In grasses, Fe, Mn, and Zn concentrations in Caryophyllids were high. Except for Caryophyllids, Fe and Cu concentrations remained constant. Mn concentration decreased with evolution, Zn concentration was higher in recently-evolved plants than in plants with a longer period of evolution.

Calcium↗
PubMed2003

Mineral characteristics of the leaves of 166 plant species with different phylogeny in the temperate region.

The P-N regression coefficient was moderate in Magnoliales, Coniferopsidae, Pteridophyta, and Asterids, but very high in Caryophyllids, and very low in Rosids. The K-N regression coefficient in trees remained constant regardless of evolution, and that in grasses was high except for Rosids compared with that in trees. The coefficient was very high in Caryophyllids and was very low in Rosids. The N-Ca and N-Mg relationship was not estimated at all, suggesting that the mechanism of Ca and Mg accumulation was completely different from that of N related accumulation. The Zn and Cu concentrations were related to the N concentration. The Al concentration in leaves was negatively correlated with the N, P, K, Ca, Mg, Na, Cu, Zn, Mn, and Fe concentrations, while the N, P, K, and Mn concentrations in leaves increased slightly with the increase of Al concentration in the high Al concentration. The Na concentration in leaves related negatively to the P, Ca, Cu, Zn, Mn and Al concentration range. Thus, it was demonstrated that most of the minerals in leaves accumulate negatively Al and Na indicating that there are antagonistic mechanisms for mineral accumulation in leaves among Al or Na and other mineral elements.

Aluminum↗
PubMed2003

Laparoscopic radical nephrectomy for renal cell carcinoma.

PURPOSE: To estimate the efficacy of the laparoscopic radical nephrectomy we analyzed the clinical data of our series. PATIENTS AND METHODS: One hundred eighty five patients were enrolled in our laparoscopic radical nephrectomy program between July, 1992 and July, 2001. Of the 185 patients, 146 had small renal tumors (smaller than 5 cm in diameter) and 39 had large tumors (equal to or more than, 5 cm in diameter). Under a laparoscope the kidney, adrenal gland, and perirenal fatty tissue were dissected in an en bloc fashion. In case of taking out a small tumor, the specimen was fractionated within the sack to avoid an additional skin incision after entrapping in the laparoscopy sack in the working space. In case of a large tumor, regional lymph nodes dissection was done and the specimen was taken out intact in the sack through an enlarged incision. RESULTS: Our laparoscopic procedure was successful in 171 of the 185 cases; 14 patients required open surgery because of bleeding from an injured vessels or treatment for other injured organs. The mean operative time was 4.7 hours for both small and large tumors. Estimated blood loss was between 237 and 380 ml on average for small and large tumors, respectively. Full convalescence was achieved around 3 weeks after operation in both groups. Only one patient who had large tumor was found to have micrometastasis in 1 of 5 regional lymph nodes. Recurrences were observed in 4 cases of the small tumor group and in 2 cases of the large tumor group during 1 to 108 months of follow-up. CONCLUSION: Laparoscopic radical nephrectomy is a very useful and safe surgical procedure for renal cell carcinoma.

Carcinoma, Renal Cell↗
PubMed2003

A CYP2D6 phenotype-genotype mismatch in Japanese psychiatric patients.

The aim of the present study was to seek a CYP2D6 genotypic-phenotypic discordance possibility in Japanese patients under psychotropic drug treatment where the CYP2D6 status and pharmacodynamic responses differ from those in Caucasian psychiatric patients. Ninety drug-free, healthy volunteers and 14 patients undergoing psychotropic drug treatment were phenotyped for their individual CYP2D6 activity using dextromethorphan as a probe, and then the metabolic ratio (MR) was calculated. For the genotyping, eight mutant alleles of the CYP2D6 genes were identified. Serum concentrations of two frequently co-medicated psychotropic drugs, biperiden and levomepromazine, were determined by GC/MS. Genotyping revealed no poor metabolizers (PMs) enrolled in our study. Healthy volunteers exhibited an identical phenotype-genotype concordance, whereas 7 of the 14 patients had significantly high (p < 0.05) MRs compared with genotype-matched volunteers. Three of the patients who had the extensive metabolizer (EM) genotype had extremely high MRs and were classified as phenotypic PMs. Five patients plus all of the seven high MR patients were treated with levomepromazine and/or biperiden, respectively. Their mean serum steady-state concentrations were 27.4 and 7.6 ng/ml, respectively. A CYP2D6 phenotype-genotype mismatch (phenocopying) can occur in Japanese psychiatric patients receiving clinical doses of some psychotropic drugs where the prevalence of PMs is low and the pharmacodynamic responses to those drugs are enhanced compared to Caucasian patients.

Adult↗
PubMed2003

Relapsing herpes simplex encephalitis: pathological confirmation of viral reactivation.

This case is reported to raise awareness of herpes simplex encephalitis as a persisting brain disorder. A 66 year old immunocompetent man developed status epilepticus and died of pneumonia in the course of progressive hemiparesis, cognitive decline, and atrophy of the brain over a five year period after herpes simplex encephalitis. In addition to a completely destroyed left temporal lobe, necropsy revealed active encephalitis consisting of necrosis and lymphocyte infiltration with a large number of intranuclear inclusions in the neurones and glial cells in the markedly oedematous parenchyma of the right frontal and parietal lobes. Herpes simplex virus type 1 (HSV-1) antigen was detected by immunohistochemistry, HSV-1 DNA by in situ hybridisation, and herpes simplex virus nucleocapsids by electronmicroscopy. These clinical and pathological findings suggest that direct viral reactivation might result in a relapse of herpes simplex encephalitis, causing progressive clinical deterioration associated with the persistence of HSV-1 in the brain. This is the first case report demonstrating HSV-1 antigen, HSV-1 DNA, and herpes simplex virus nucleocapsids in a case of relapsing herpes simplex encephalitis.

Atrophy↗
PubMed2003

Involvement of CD73 (ecto-5'-nucleotidase) in adenosine generation by human gingival fibroblasts.

Adenosine has various biological effects on human gingival fibroblasts (HGF) and epithelial cells closely associated with inflammation, such as cytokine production and cell adhesion. However, the mechanism of adenosine formation in periodontal tissues is not yet defined. In this study, we examined the involvement of CD73 (ecto-5'-nucleotidase) in adenosine generation by HGF. CD73 was detected on in vitro-maintained HGF by immunocytochemistry and flow cytometric analysis. Adenosine production was observed following the addition of 5'-AMP, the substrate of CD73-associated ecto-5'-nucleotidase. Moreover, the addition of 5'-AMP to cultured HGF resulted in the elevation of cyclic adenosine monophosphate (cAMP). The 5'-AMP-induced increase in intracellular cAMP level was inhibited markedly by xanthine amine congener, an adenosine receptor antagonist, and partially by alpha,beta-methylene adenosine 5'-diphosphate, an ecto-5'-nucleotidase inhibitor. These results suggest that CD73 on HGF is a critical enzyme responsible for the generation of adenosine, an immunomodulator that activates adenosine receptors.

5'-Nucleotidase↗
PubMed2003

Initial medical management of patients severely irradiated in the Tokai-mura criticality accident.

A nuclear criticality accident occurred in Japan on September 30, 1999, which resulted in severe exposure of three victims to mixed flux of neutrons and gamma-rays. Estimated average doses for the three victims were 5.4 Gy of neutrons and 8.5 Gy of gamma-rays for Patient A, 2.9 Gy of neutrons and 4.5 Gy of gamma-rays for Patient B, and 0.81 Gy of neutrons and 1.3 Gy of gamma-rays for Patient C. They then suffered the consequences of the effects of ionizing radiation resulting in acute radiation syndrome. In Patients A and B, bone marrow failure was so severe that they received haematopoietic stem cell transplantation. The graft initially took successfully in both patients, although in Patient B it was later taken over by his own haematopoietic cells. They also suffered from severe skin lesions, later exhibited gastrointestinal bleeding and eventually died of multiple organ failure 82 and 210 days after the accident, respectively. The survival of these patients beyond the period of agranulocytosis means that bone marrow failure per se caused by exposure to ionizing radiation may now be overcome. Patient C also developed bone marrow failure and was treated with granulocyte colony-stimulating factor as well as supportive care. He recovered without major complications and is now under periodical follow-up. Remarkably, during the prodromal phase, all the patients exhibited hypoxaemia, two of whom also showed interstitial oedema of the lungs. In Patient C these manifestations improved within a week. The circumstances of the accident and the initial medical treatment of the victims are described.

Adult↗
PubMed2003

Genetic differences in interleukin-1 betapolymorphisms among four Asian populations: an analysis of the Asian paradox between H. pylori infection and gastric cancer incidence.

The prevalence of Helicobacter pylori infection is high among Asian populations, but the incidences of gastric cancer differ greatly among northern and southern Asian populations. Here, we studied histopathological findings in stomach tissue using an updated Sydney System and the frequencies of interleukin (IL)-1betapolymorphisms, thought to be associated with an increased risk of gastric cancer, in four Asian populations. Endoscopic-guided biopsies from three regions of the stomach and the -511 T-to-C polymorphism in the IL-1betagene were examined in 228 Japanese, 116 Chinese, 159 Thai and 83 Vietnamese patients with gastric diseases. H. pylori colonization, inflammation and activity were more severe in the Japanese and Thai populations than in the Chinese and Vietnamese populations and these scores were more antrum-predominant in the Thai and Vietnamese populations than in the Japanese and Chinese populations, with the most severe degree of atrophy and intestinal metaplasia occurring in the angulus region of the Japanese population. The IL-1betapolymorphisms did not differ among the four populations overall, but in cases with severe mucosal atrophy (pepsinogen I/II ratio <3.0), the CC polymorphism was dominant in the Japanese population and the TT+TC polymorphism was dominant in the Chinese population; no difference in C and T allele frequencies was found in the Thai and Vietnamese populations. In conclusion, the incidence of gastric cancer is extremely low, but the prevalence of H. pylori infection is high in the Thai population (Asian paradox). In the Thai population, the scores for corpus gastritis and intestinal metaplasia, which are associated with a high risk of gastric cancer, were low in comparison with the Japanese population. IL-1betapolymorphisms were correlated with mucosal atrophy in the Japanese and Chinese populations, but not in the Thai and Vietnamese populations.

Adolescent↗
PubMed2002

Immunocytochemical observation of ghrelin-containing neurons in the rat arcuate nucleus.

Ghrelin is a novel peptide that stimulates the release of growth hormone from the pituitary and is involved in hypothalamic feeding regulation. A pre-embedding immunostaining technique was used to study the ultrastructure and synaptic relationships of ghrelin-containing neurons in the rat arcuate nucleus (ARC). Ghrelin-like immunoreactive (ghrelin-LI) neurons were found in the ARC, and were especially abundant in its ventral part. At the electron microscopic level, ghrelin-LI neurons received afferent synapses from many unknown axon terminals. Ghrelin-LI products in the immunoreactive cell bodies, processes, and axon terminals were detected mainly in dense granular vesicles about 110 nm in diameter. Ghrelin-LI presynaptic axon terminals often made synapses with unknown immunonegative neurons. These results suggest that ghrelin acts to regulate food intake through synaptic connections in hypothalamic neuronal networks.

Animals↗
PubMed2002

Charge/orbital ordering structure of Pr(1-x)Ca(x)MnO(3)(x = 3/8) examined by low-temperature transmission electron microscopy.

The structural phase transition of Pr(1-x)Ca(x)MnO(3)(x = 3/8) was investigated by means of low-temperature transmission electron microscopy. Superlattice reflection spots with a modulation wave vector q(1) = (0,1/2,0) appeared below 230 K, indicating formation of the d(3x(2-r(2))/d(3y(2)-r(2)) type of charge/orbital ordering. Below 150 K, a new series of superlattice reflection spots with a modulation wave vector q(2) = (1/4,1/4,1/2) appeared, suggesting an additional ordering of excess 1/8 Mn(3+), necessary due to the deviation of x from 1/2, with the occupation of the d(3z(2-r(2)) type of e(g) orbital.

Journal Article↗