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T Yamabe

Publications and source records attributed to T Yamabe.

At least 19 recordsLinked to original sources
PubMed2002

Nitridation of Si(100)-( 2x1) surface by NH3: a quantum chemical cluster model study.

Based on density functional cluster model calculations, we present the first detailed mechanisms for the complete decomposition of NH3 to NHx(a) (x = 0-2) on the Si(100)-(2x1) surface. Three kinds of elementary processes, namely, N-H bond cleavage, NHx(a) insertion into the Si-Si surface dimer bond or backbond, and H2 libration, are investigated. A plausible microscopic mechanism for the nitridation of Si(100)-(2x1) surface by NH3 is proposed.

Journal Article↗
PubMed2001

First observation of clusters for solvated tropylium ions.

We have first observed clusters for solvated tropylium ions (Tr+(ROH)n) which were isolated from ROH-CH3CN (1:1 by vol.; R = Me, Et, and Prn) solutions by using a specially designed mass spectrometer and found the clear-cut essential features concerning the solvation structure around Tr+.

Journal Article↗
PubMed2000

Synthesis, structure, and H2O2-dependent catalytic functions of disulfide-bridged dicopper(I) and related thioether-copper(I) and thioether-copper(II) complexes.

A disulfide-bridged dicopper(I) complex, [Cu2(Py2SSPy2)](ClO4)2 (1) (Py2SSPy2 = bis(2-[N,N-bis(2-pyridylethyl)-amino]-1,1- dimethylethyl)disulfide), a thioether-copper(I) complex, [Cu(iPrSPy2)](ClO4) (2) (iPrSPy2 = N-(2-isopropylthio-2-methyl)propyl-N,N-bis-2-(2-pyridyl)ethylamine, and a thioether-copper(II) complex, [Cu-(PheSPy2)(H2O)](ClO4)2 (3) (PheSPy2 = N-(2-methyl-2-phenethylthio)propyl-N,N-bis-2-(2- pyridyl)ethylamine), were newly synthesized by the reactions of Cu(ClO4)2.6H2O with a thiol ligand of Py2SH (N,N-bis[2-(2-pyridyl)-ethyl]-1,1-dimethyl-2- mercaptoethylamine) and thioether ligands of iPrSPy2 and PheSPy2, respectively. For complexes 1 and 2, X-ray analyses were performed. Complex 1 crystallizes in the triclinic space group P1, and complex 2 crystallizes in the orthorhombic space group Pbca with the following unit cell parameters: for 1, a = 15.165 (3) A, b = 22.185 (4) A, c = 14.989 (3) A, alpha = 105.76 (1) degrees, beta = 90.82 (2) degrees, gamma = 75.23 (1) degrees, and Z = 2; for 2, a = 17.78 (2) A, b = 17.70 (1) A, c = 15.75 (1) A, and Z = 8. Complex 1 is the first structurally characterized example obtained by the redox reaction Cu(II) + RSH-->Cu(I) + RSSR and has two independent structures (1a, 1b) which mainly differ in S-S bond distances, Cu(I)...Cu(I) separations, and C-S-S-C dihedral angles of the disulfide units. The S-S bond distances of 2.088(7) A in 1a and 2.070(7) A in 1b are indicative of significant activation of the S-S bonds by the dicopper centers. Fragment molecular orbital (FMO) analyses and molecular orbital overlap population (MOOP) analyses based on the extended Hückel method clarify the preferable formation of the disulfide S-S bond in 1 rather than the formation of a thiolate-copper(II) complex within the Py2S- ligand framework. Catalytic functions of complexes 1-3 were investigated with peroxides (H2O2 and tBuOOH) as oxidants. Complex 1 catalyzed the selective oxidation of cyclohexane to cyclohexanol and mediated the cyclohexene epoxidation in the presence of H2O2. A transient dark green intermediate observed in the reaction of 1 with H2O2 is characterized by UV-vis, EPR, and resonance Raman spectroscopies, identifying it as a Cu(II)-OOH species, 1(OOH). The resonance Raman features of the nu(O-O) bands at 822 and 836 cm-1, which are red-shifted to 781 and 791 cm-1, respectively, upon introduction of H2(18)O2, are indicative of formation of two kinds of Cu-OOH species rather than the Fermi doublet and the significant weakening of the O-O bonds. These mechanistic studies demonstrate that by virtue of the electron-donating ability of the disulfide unit the Cu-OOH species can be actually activated for one-electron oxidation, which has been reported so far unfavorable for other vibrationally characterized Cu-OOH species.

Journal Article↗
PubMed1999

Triplet state of Würster's blue-based di(cation radical).

[reaction: see text] N,N-bis[4-(dimethylamino)phenyl]-N,N'-dimethyl-1,3-benzenediamine was prepared in order to investigate the corresponding Würster blue-based di(cation radical). The generated diradical was found to be a ground-state triplet, and moreover, the observed ESR spectrum had no definite fine structure, suggesting a mixture of some conformers.

Journal Article↗
PubMed1999

Micelle Formation of Anionic Surfactant with Divalent Counterion of Separate Electric Charge.

The critical micelle concentration (CMC) of the anionic surfactant, 1,1'-(1,omega-decanediyl) bispyridinium hexadecane-1-sulfonate (C10BP(C16)2) was determined by electrical conductivity measurements at various temperatures. The degree of counterion binding to micelles was evaluated from the change in CMC with total counterion concentration. The molecular weight of the micelles was determined by static light scattering. The mass action model was applied to micelle formation in order to calculate the three micellization parameters, the micellization constant, the micelle aggregation number, and the number of counterions per micelle. Thermodynamic parameters (DeltaG0, DeltaH0, -TDeltaS0) for the micellization were evaluated by their temperature dependence. The findings were: (1) Micelle formation was entropy-driven over the whole temperature range examined. (2) C10BP(C16)2 had a higher degree of counterion binding to micelles compared with those of monovalent counterion. (3) The plots of log CMC against the carbon number of the homologous surfactant ions gave a straight line, indicating that free energy change per methylene group for micelle formation was -1.18RT for surfactant ions. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Intestinal absorption of calcium from calcium ascorbate in rats.

The intestinal absorption of calcium (Ca) from Ca ascorbate (Ca-AsA) was investigated in normal rats. Each animal was perorally administered either 5mg (low dose) or 10mg (high dose) of Ca in 1ml of distilled water as Ca-AsA, Ca carbonate (CaCO3), or Ca chloride (CaCl2), which were intrinsically labeled with 45Ca using 45CaCl2. The amount of radioactivity in plasma was measured periodically up to 34h after dosing, and pharmacokinetic parameters were calculated from the radioactivity in plasma. The time taken to reach the maximum 45Ca level (Tmax) did not differ among the three groups. The area under the plasma 45Ca level/time curve (AUCinfinity) value for the Ca-AsA group was significantly higher than those for the CaCO3 and the CaCl2 groups. The radioactivity at Tmax (Cmax) for the Ca-AsA group was significantly higher than those for the CaCO3 and the CaCl2 groups for the low dose, and comparable with or significantly higher than those for the CaCl2 and CaCO3 groups for the high dose. Similar results were observed for whole-body 45Ca retention. Radioactivity in the femur 34h after dosing was the highest in the Ca-AsA group and the lowest in the CaCO3 group. The rank order of solubility in water, the first fluid (pH 1.2, JP-1) of JPXIII disintegration medium, acetate buffer solution (pH 4.0), triethanolamine-malate buffer solution (pH 7.0) and ammonium chloride buffer solution (pH 10.0) at 37 degrees C was CaCl2 > Ca-AsA > CaCO3. In contrast, the rank order of the solubility in the second fluid (pH 6.8, JP-2) of JPXIII disintegration medium at 37 degrees C was Ca-AsA > CaCl2 > CaCO3. These results indicate that the absorbability of Ca from Ca-AsA is almost comparable with, or higher than, that from CaCl2 and significantly higher than that from CaCO3 because of its high degree of solubility in the intestine. Therefore, Ca-AsA would be useful as a Ca supplement with relatively high absorption from intestine.

Animals↗
PubMed1999

Direct participation of potassium ion in the catalysis of coenzyme B(12)-dependent diol dehydratase.

The direct ion-dipolar interactions between potassium ion (K(+)) and the two hydroxyl groups of the substrate are the most striking feature of the crystal structure of coenzyme B(12)-dependent diol dehydratase. We carried out density-functional-theory computations to determine whether K(+) can assist the 1,2-shift of the hydroxyl group in the substrate-derived radical. Between a stepwise abstraction/recombination reaction proceeding via a direct hydroxide abstraction by K(+) and a concerted hydroxyl group migration assisted by K(+), only a transition state for the latter concerted mechanism was found from our computations. The barrier height for the transition state from the complexed radical decreases by only 2.3 kcal/mol upon coordination of the migrating hydroxyl group to K(+), which corresponds to a 42-fold rate acceleration at 37 degrees C. The net binding energy upon replacement of the K(+)-bound water for substrate was calculated to be 10.7 kcal/mol. It can be considered that such a large binding energy is at least partly used for the substrate-induced conformational changes in the enzyme that trigger the homolytic cleavage of the Co-C bond of the coenzyme and the subsequent catalysis by a radical mechanism. We propose here a new mechanism for diol dehydratase in which K(+) plays a direct role in the catalysis.

Catalysis↗
PubMed1998

Comparative study of dobutamine stress electron-beam computed tomography and exercise thallium scintigraphy in the diagnosis of patients with suspected coronary artery disease.

To evaluate the diagnostic value of dobutamine stress electron-beam computed tomography (EBCT) as compared with exercise stress thallium-201 single-photon emission computed tomography (201T1-SPECT) for the detection of myocardial ischemia, 10 patients with proven or suspected coronary artery disease underwent both tests. Nine of the 10 patients also underwent coronary angiography. EBCT images were analyzed objectively to evaluate systolic wall thickening and analyzed segmentally to determine the distribution of the coronary arteries. Dobutamine stress EBCT revealed the presence of ischemia in 59 segments, whereas exercise stress 201T1-SPECT revealed ischemia in 51 segments (agreement = 73%). The advantage of dobutamine stress EBCT was demonstrated in the inferior/posterior segments as compared with the results of exercise stress 201T1-SPECT. The overall sensitivity for detecting ischemic regions supplied by coronary arteries with significant stenosis (diameter stenosis > 50%) was 83% for dobutamine stress EBCT and 79% for exercise stress 201T1-SPECT (p = NS), with specificities of 75% and 82% (p = NS). Thus, dobutamine stress EBCT presents a reasonable alternative to exercise stress 201T1-SPECT for the objective assessment of patients with suspected coronary artery disease.

Adult↗
PubMed1998

[Early phase II trial of oral etoposide administered for 21 consecutive days in patients with cervical or ovarian cancer. ETP 21 Study Group--Cervical-Ovarian Cancer Group].

We conducted multi-site early phase II trial or oral etoposide administered for 21 consecutive days in patients with cervical or ovarian cancer in cooperation with 19 institutes. Fifty mg/body of oral etoposide was administered daily for 21 consecutive days. Cycles were repeated every 28 days. In cervical cancer, 24 patients were enrolled and 17 of them were evaluated. The overall response rate including CR and PR was 23.5% (4/17). In ovarian cancer, 18 patients out of 21 enrolled were evaluated. The overall response rate was 16.7% (3/18). The primary toxicity observed was myelosuppression such as leukopenia, neutropenia, hemoglobin decrease and thrombocytopenia. Other adverse effects were anorexia, nausea, vomitting, fatigue, alopecia and stomatitis. From these results we concluded that oral etoposide administered for 21 consecutive days was effective against cervical cancer.

Administration, Oral↗
PubMed1998

[Late phase II trial of oral etoposide administered for 21 consecutive days in patients with cervical cancer. ETP 21 Study Group--Cervical Cancer Group].

We conducted a multi-site late phase II trial of oral etoposide administered for 21 consecutive days in patients with cervical cancer in cooperation with 32 institutes. Fifty mg/body of oral etoposide was administered daily for 21 consecutive days. Treatment cycles were to be repeated at 4- to 5-week intervals. Eighty patients were enrolled and 70 patients were evaluated. The overall response rate (95% CI), including one complete response patient and 18 partial response patients, was 27.1% (19/70). The most commonly observed toxicity was myelosuppression such as leukopenia, neutropenia, hemoglobin decrease and thrombocytopenia. Other adverse effects were gastrointestinal toxicities such as anorexia, nausea, stomatitis and vomiting, as well as fatigue and alopecia. These adverse effects were well tolerated and controlled with medications. From these results we concluded oral etoposide administered for 21 consecutive days was an effective drug against cervical cancer.

Adenocarcinoma↗
PubMed1997

Expression of estrogen and progesterone receptors in endometrium and peritoneal endometriosis: an immunohistochemical and in situ hybridization study.

OBJECTIVE: To clarify the role of ovarian steroids in the development and progression of endometriosis, estrogen receptors (ERs) and progesterone receptors (PRs) were localized by immunohistochemistry, and ER messenger RNA (mRNA) was detected by in situ hybridization in the uterine endometrium and in normal and altered pelvic peritoneum. DESIGN: Retrospective and prospective study. SETTING: Nagasaki University School of Medicine, Nagasaki, Japan. PATIENT(S): A retrospective study of 61 formalin-fixed uterine endometria and normal and altered pelvic peritonea from patients suffering from various gynecologic diseases was conducted. In addition, in 22 fresh frozen tissue specimens, ER mRNA expression was evaluated prospectively. MAIN OUTCOME MEASURE(S): In formalin-fixed tissues, ER and PR were localized immunohistochemically. The results of immunohistochemical staining were scored from 0 to 4, depending on the signal intensity and frequency of positive cells. In fresh frozen specimens, ER mRNA expression was assessed by nonradioactive in situ hybridization using thymine-thymine dimerized oligonucleotide probes. RESULTS: The highest score of ERs and PRs was observed in the epithelial and stromal cells of the normal uterine endometrium at the early proliferative phase of the menstrual cycle. The ER and PR scores declined throughout the secretory phase. In typical endometriotic lesions, the ER and PR scores were constantly high independent of the menstrual cycle. The expression pattern of ER mRNA was mostly in parallel with that of ERs. In typical endometriosis, ERs and PRs were found in both glandular epithelial cells and their surrounding stromal cells. Expression of ER mRNA was found in typical endometriotic peritonea and in pelvic peritoneum with columnar epithelial cells, but not in normal pelvic peritoneum (mesothelium). Estrogen receptors and PRs were negative in mesothelium, but were positive in the nuclei of fibroblasts in the connective tissue. CONCLUSION(S): We demonstrated the expression of ERs, ER mRNA, and PRs in the columnar cells in pelvic peritonea and typical endometriosis, but not in normal mesothelium. These results suggest that endometriosis may originate from the columnar cells with ERs and PRs in the pelvic peritoneal lining.

Endometriosis↗
PubMed1997

Induction of the 2B9 antigen/dipeptidyl peptidase IV/CD26 on human natural killer cells by IL-2, IL-12 or IL-15.

Activation of human natural killer (NK) cells involves sequential events including cytokine production and induction of cell surface molecules, resulting in the enhancement of cytolytic activity. To delineate the activation process of NK cells, we generated murine monoclonal antibodies (mAbs) against YT, a human large granular lymphocyte/natural killer (LGL/NK) cell line. Among the mAbs reactive with YT cells, one mAb, termed 2B9, was noted because of the lack of reactivity with most of the human T- and B-cell lines tested. In fresh peripheral blood mononuclear cells (PBMC), however, the majority of cells expressing this antigen (Ag) were T cells but not CD16+ nor CD56+ NK cells. Since YT cells showed an activated phenotype expressing interleukin-2 (IL-2) receptor alpha chain, we examined whether 2B9 Ag could be induced on normal human peripheral blood NK cells by cytokines known to activate NK cells. The 2B9 Ag was induced on NK cells by IL-2, IL-12 or IL-15 while no induction was observed by interferon-gamma (IFN-gamma). Biochemical analysis showed that anti-2B9 mAb recognized a 115 kDa molecule in YT cells. A cDNA clone encoding the 2B9 Ag was isolated from a cDNA expression library of YT cells and its sequence was identical to CD26 cDNA although it was not of full length. Transient expression of the 2B9 cDNA on COS-7 cells revealed that this cDNA encodes the antigenic epitope(s) recognized by anti-2B9 mAb as well as Ta1, an anti-CD26 mAb. These results showed that the 2B9 Ag is identical to CD26, and demonstrated that CD26 is an activation antigen on CD16+ CD56+ NK cells inducible by IL-2, IL-12 or IL-15.

Antibodies, Monoclonal↗
PubMed1997

Primary prevention of HTLV-1 in Japan.

The Nagasaki Prefecture, Japan (population: 1.5 million), is one of the hot endemic foci of Human T-lymphotropic virus type 1 (HTLV-1). Prevalence of HTLV-1 carriers are approximately 10% in the age group over 40 years old (40,000 individuals), approximately 10 times of the national average. Annual registry of adult T-cell leukemia (ATL) in the Prefecture is approximately 60 cases (estimated incidence: 100 cases), or a half percent of total deaths. A effective measure to control the endemic cycle of HTLV-1 has been imperative, since practical ways to prevent or control ATL are not available. A prefecture wide intervention at Nagasaki by refrain from breast-feeding blocked approximately 80% of mother-to-child transmission of HTLV-1.

Adult↗
PubMed1996

Change in fetal urine production rate in growth-restricted fetuses after maternal meal ingestion.

OBJECTIVE: To determine if fetal urine production is affected by maternal meal ingestion in growth-restricted fetuses. METHODS: We studied 25 normal-growth fetuses in uncomplicated pregnancies and 15 growth-restricted fetuses, all after 30 weeks' gestation. Serial fetal bladder volume measurements were obtained at 2-3 minute intervals with ultrasonography 2 hours before and 2 hours after maternal breakfast. The hourly fetal urine production rate in each maternal state was calculated from the bladder volume measurements. The amniotic fluid index (AFI) and the pulsatility index of both umbilical and fetal middle cerebral arteries were also measured. RESULTS: Two of the 15 growth-restricted fetuses were excluded from analysis, one because it was anomalous and the other because it was not small for gestational age at birth. In the normal-growth fetuses, the hourly fetal urine production rate increased significantly after maternal breakfast (mean +/- standard deviation 30.2 +/- 11.7 versus 41.1 +/- 14.6 mL/hour, P < .001). In contrast, in the growth-restricted fetuses, the rate did not change after maternal breakfast (24.6 +/- 6.2 versus 24.9 +/- 5.7 mL/hour). Although the urine production rate before breakfast did not differ between groups, 2 hours after maternal breakfast it was significantly lower in the growth-restricted fetuses than in the control group (normal-growth) (P < .001). The AFI also was significantly lower in the growth-restricted fetuses than in the control group (15.0 +/- 3.5 versus 18.6 +/- 5.0 cm, P < .04). There were no significant differences in the pulsed Doppler studies. CONCLUSION: In contrast to normal-growth fetuses, maternal meal ingestion for growth-restricted fetuses does not increase fetal urine production. Decreased fetal urine production in the maternal fed state may lead to decreased amniotic fluid volume in growth-restricted fetuses without obvious hypoxia.

Amniotic Fluid↗