Biomedical subjects
Publications and source records attributed to H Yamaguchi.
Initial distributions of metastable antiprotonic (4)He and (3)He atoms over principal (n) and angular momentum (l) quantum numbers have been deduced using laser spectroscopy experiments. The regions n = 37-40 and n = 35-38 in the two atoms account for almost all of the observed fractions [(3.0 +/- 0.1)% and (2.4 +/- 0.1)%] of antiprotons captured into metastable states.
We hypothesized that reactive oxygen species play an important role in avascular/ischemic osteonecrosis. When isolated chick osteocytes were cultured with hydrogen peroxide, annexin V binding, which is the earliest marker of apoptosis, increased in a dose-dependent fashion. Hydrogen peroxide also induced the activation of caspase-3 and increase in cytosolic Ca2+. Treatment with BAPTA/AM (cheletor of cytosolic Ca2+) and Ac-DEVD-cho (caspase inhibitor) attenuated hydrogen peroxide-induced apoptosis. These data demonstrated the signal transduction pathways that participate in this hydrogen peroxide-induced cell damage.
To examine the regulation of amyloid secretion in more detail, Abeta sandwich ELISAs with high sensitivity and specificity were developed. Using this technique, we measured Abeta secreted from COS7 cells transiently transfected with APP C100 in the presence of LiCl, a potent glycogen synthase kinase (GSK)-3beta inhibitor. We found that both Abetax-40 and Abetax-42 secretion were reduced by LiCl treatment in a dose-dependent manner. Diminished amyloid secretion was associated with GSK-3beta activity. These results suggest that GSK-3beta might function as a possible mediator for regulating both amyloid deposition and tau pathology in Alzheimer's disease (AD), and that lithium should be re-evaluated as a candidate reagent for preventing AD pathology.
Combination of the superconductor and high conductive normal metal is now indispensable in the practical use of superconducting magnet. And the binding property of both materials is one of the key points whether superconductive characteristics are fully attained or the current fails prematurely in the practical magnet. But this binding evaluation is not so easy, because even in the mechanically well-jointed conductor, it often appears poor in electric and magnetic joint in cryogenic temperature. Since we have examined and reported fundamental AE properties of superconductor from UI-91, UI-93, UI-95, and UI-97, we have found the simple but important discovery for getting new information about the binding evaluation. Here we report a new technique for evaluating these bindings by observing ultrasonic spectra when a normal transition is propagated along the superconductor. We have discovered that a good contacting conductor has an emission of this sound with sharp resonating frequency peak or peaks at around the highest spectrum area; from 0.5 to 1.0 MHz. Our interpretation of the evaluations are so simple that we can say that binding degrees are best, good or bad, according to the resonating Q-value at around the highest spectrum of the ultrasonic sound.
Gardenia fruit (Gardenia jasminoides ELLIS) is widely used as a natural food colorant and as a traditional Chinese medicine for treatment of hepatic and inflammatory diseases. "Gardenia yellow" is a natural food colorant which is extracted by ethanol from gardenia fruit. The purpose of this study was to evaluate the genotoxicity of gardenia yellow. Genotoxicity of gardenia yellow and its components, crocetin, gentiobiose (a component of crocin), geniposide and genipin (formed by hydrolysis of geniposide), was studied by Ames test, rec-assay, and sister chromatid exchange (SCE) using V79 cells. Gardenia yellow and its components were found not to be mutagenic in the Salmonella reverse mutation assay. Gardenia yellow and genipin caused damage of DNA in rec-assay. Gardenia yellow induced a significant dose-dependent increase of SCE frequency (8.6 times at 1000 microg/ml as the value for the solvent control). Only genipin induced SCEs significantly among the components of gardenia yellow. Moreover, genipin induced a significant increase of tetraploids at all doses tested (95% at 8 microg/ml). Gardenia yellow preparation was analyzed by capillary electrophoresis (CE), and geniposide was detected. However, genipin was not observed. In conclusion, we have shown that genipin possesses genotoxicity. Furthermore, there were unidentified genotoxicants in gardenia yellow.
Although potassium sorbate (PS), ascorbic acid and ferric or ferrous salts (Fe-salts) are used widely in combination as food additives, the strong reactivity of PS and oxidative potency of ascorbic acid in the presence of Fe-salts might form toxic compounds in food during its deposit and distribution. In the present paper, the reaction mixture of PS, ascorbic acid and Fe-salts was evaluated for mutagenicity and DNA-damaging activity by means of the Ames test and rec-assay. Effective lethality was observed in the rec-assay. No mutagenicity was induced in either Salmonella typhimurium strains TA98 (with or without S-9 mix) or TA100 (with S-9 mix). In contrast, a dose-dependent mutagenic effect was obtained when applied to strain TA100 without S-9 mix. The mutagenic activity became stronger increasing with the reaction period. Furthermore, the reaction products obtained in a nitrogen atmosphere did not show any mutagenic and DNA-damaging activity. PS, ascorbic acid and Fe-salts were inactive when they were used separately. Omission of one component from the mixture of PS, ascorbic acid and Fe-salt turned the reaction system inactive. These results demonstrate that ascorbic acid and Fe-salt oxidized PS and the oxidative products caused mutagenicity and DNA-damaging activity.
Chronic myelogenous leukemia (CML) is characterized by the Philadelphia (Ph) chromosome and bcr/abl gene rearrangement which occurs in pluripotent hematopoietic progenitor cells expressing the c-kit receptor tyrosine kinase (KIT). To elucidate the biological properties of KIT in CML leukemogenesis, we performed analysis of alterations of the c-kit gene and functional analysis of altered KIT proteins. Gene alterations in the c-kit juxtamembrane domain of 80 CML cases were analyzed by reverse transcriptase and polymerase chain reaction-single strand conformation polymorphism (RT-PCR-SSCP). One case had an abnormality at codon 564 (AAT --> AAG, Asn --> Lys), and six cases had the same base abnormality at codon 541 (ATG --> CTG, Met --> Leu) in the juxtamembrane domain. Because the change from Met to Leu at codon 541 was a conservative one which was also observed in the normal population and normal tissues of CML patients, it probably represents a polymorphic variation. Although samples of hair roots and leukemic cells from the chronic phase of one CML patient showed no abnormality, an abnormality at codon 541 (ATG --> CTG, Met --> Leu) was found only at blastic crisis (BC) of this case. In the case with the abnormality at codon 564, the mutation was detected only in a sample of leukemic cells collected at BC. To examine the biological consequence and biological significance of these abnormalities, murine KIT(L540) and KIT(K563) expression vectors were introduced into interleukin-3 (IL-3)-dependent murine Ba/F3 cells to study their state of tyrosine phosphorylation and their growth rate. Ba/F3 cells expressing KIT(WT), KIT(L540) and KIT(K563) showed dose-dependent tyrosine phosphorylation after treatment with increasing concentrations of recombinant mouse stem cell factor (rmSCF). The cells expressing KIT(L540) and KIT(K563) were found to have greater tyrosine phosphorylation than cells expressing KIT(WT) at 0.1 and 1.0 ng/ml of rmSCF. The Ba/F3 cells expressing KIT(K563) proliferated in response to 0.1 and 1.0 ng/ml of rmSCF as well as IL-3. The Ba/F3 cells expressing KIT(L540)showed a relatively higher proliferative response to 0.1 ng/ml of rmSCF than the response of cells expressing KIT(WT). These mutations and in vitro functional analyses raise the possibility that the KIT abnormalities influence the white blood cell counts (P < 0.05) and survival (P < 0.04) of CML patients.
BACKGROUND: Excessive upregulation of gastric epithelial cell apoptosis is speculated to be associated with ulcerogenesis in Helicobacter pylori-positive peptic ulcer disease. H. pylori may have an ulcerogenic effect through induction of gastric epithelial cell apoptosis mediated by infiltrating T cells and their soluble products. METHODS: The contents of soluble Fas ligand (sFasL) and interferon-gamma (IFN-gamma) in organ cultures and the degree of apoptosis and the expression of apoptosis-related proteins in the gastric epithelium were examined using the mucosal tissues obtained from the antrum and the ulcer site in patients with H. pylori-positive gastric ulcer (GU). The molecular mechanisms of gastric epithelial cell apoptosis induced by sFasL and IFN-gamma were analyzed using epithelial cell lines, MKN 45 and KATO III. RESULTS: The mucosal tissues of the ulcer site had substantially higher contents of sFasL and IFN-gamma in organ cultures regardless of its healing stage in association with increased numbers of apoptotic cells and enhanced expression of proapoptotic proteins Bak and Bax in the surface foveolar epithelium as compared with the antral tissues in patients with H. pylori-positive GU. The addition of sFasL caused increases in cytotoxic cell death and caspase-3 activation in MKN 45 and KATO III cells in which IFN-gamma treated cells had more prominent effects than untreated cells. The expression of Bak in MKN 45 cells increased when they were treated with IFN-gamma. CONCLUSIONS: Upregulation of mucosal sFasL and IFN-gamma may be involved in ulcerogenesis in patients with H. pylori-positive GU through induction of gastric epithelial cell apoptosis.
Molecular dynamics simulations were performed for a dodecamer DNA containing a single strand break (SSB), which has been represented by a 3'-OH deoxyribose and 5'-OH phosphate in the middle of the strand. Molecular force field parameters of the 5'-OH phosphate region were determined from an ab initio calculation at the HF/6-31G level using the program package GAMESS. The DNA was placed in a periodic boundary box with water molecules and Na+ counter-ions to produce a neutralised system. After minimisation, the system was heated to 300 K, equilibrated and a production run at constant NTP was executed for 1 ns using AMBER 4.1. Snapshots of the SSB-containing DNA and a detailed analysis of the equilibrated average structure revealed surprisingly small conformational changes compared to normal DNA. However, dynamic properties calculated using the essential dynamics method showed some features that may be important for the recognition of this damage by repair enzymes.
Microdosimetric measurements of 19, 32, 43, 55, and 65 MeV protons were carried out with the A-150-walled low pressure proportional counter (LPPC). The spectra are deconvoluted into three components, which are energy loss by directly incident protons, secondary electrons, and scattered protons and heavy charged particle (including protons) produced by proton nuclear reactions with the TE wall. Dose-mean lineal energies of protons are large as usual, because larger lineal energies by proton reaction events are affected.
Single event spectra of a clinical carbon beam have been measured by an ultra-miniature tissue-equivalent proportional counter (UMC). In order to cover the energy range of the Bragg peak, the incident energy of the carbon beam was degraded by aluminium plates. Single event spectra for carbon-events incident to the UMC were analysed and selected at several carbon energies using thin scintillation counters. It was found that the dose weighted lineal energy distributions have a doublet peak structure due to incident carbon beam and fragment contributions.
OBJECTIVE: To determine the prevalence of mycoplasma pneumoniae in nasopharyngeal aspirates of children under five years of age suffering from pneumonia. DESIGN: Cross-sectional survey. METHODS: Two primer sets targeting the genes coding for adhesion protein and 16S rRNA were used in PCR and M. pneumoniae specific antibodies were detected using commercial article agglutination kit. Microbiological investigations to isolate common acute respiratory infectious pathogens were also carried out. RESULTS: M. pneumoniae was detected in nasopharyngeal aspirates of 33.7% of the cases by PCR while serology was positive in only 4.1%. M. pneumoniae alone (single detection) was detected in 25% of the cases while 75% occurred with other acute respiratory infectious (ARI) pathogens. However, the results did not correlate with clinical outcome or the severity of pneumonia. No significant aetiology was found in 28% of the cases investigated, however microbiological investigations by culture revealed the presence of other aetiological agents as follows: Streptococcus pneumoniae (26%), Klebsiella pneumoniae (1%), Staphylococcus aureus (3%), E. coli (2%), parainfluenza viruses (5%), Salmonella(1%), adenovirus (4%), RSV (22%) and Candida spp(13%), Mycoplasma pneumoniae was more prevalent in children aged between six months and three years. Cases of M. pneumoniae PCR positive and S. pneumoniae exhibited similar seasonal distribution with peaks in May and September. However, there was no relationship between M. pneumoniae PCR positive and the severity of pneumonia. CONCLUSION: More investigation is required to establish the significance of atypical pathogens in respiratory infections in Kenya.
This study aimed to determine whether sialyl Lewis(a) (Le(a)), sialyl Lewis(x )(Le(x)), or sialyl Tn antigen expression could identify a subset of node-negative colorectal cancer patients that are at high risk for recurrence after curative surgery. Tumor tissue samples from 90 patients with node-negative colorectal cancer, who had undergone surgical resection, were analyzed immunohistochemically for the expression of each antigen. Patients were classified as having low or high antigen expression depending on whether more or less than 40% of the field showed positive staining. The main outcome measure for each variable was disease-free interval. Sialyl Le(a), sialyl Le(x), and sialyl Tn antigens were expressed in 53 (58.9%), 41 (45.6%), and 34 (37.8%) carcinomas, respectively. The median follow-up was 83.5 months. Patients with high sialyl Le(x) expression had shorter disease-free intervals than those with low sialyl Le(x) expression (P = 0.0041); the expression of sialyl Le(a) or sialyl Tn antigens did not show a significant relationship with disease-free survival. Cox's regression analysis revealed that sialyl Le(x) expression was an independent predictor for disease-free survival, separate from T factor or tumor location. High sialyl Le(x) expression may be useful in identifying a subset of node-negative colorectal cancer patients who are at high risk for recurrence.
Early gastric cancer can be divided morphologically into two categories, penetrating growth type-A (Pen-A type) and other growth types (non-Pen-A types). Sialyl Lewis(x) antigen has been demonstrated to play an important role in tumor metastasis by serving as a functional ligand in the cell adhesion system. The aim of this study is to ascertain whether or not sialyl Le(x) antigen expression correlates with tumor growth patterns of early gastric carcinoma. An immunohistochemical assay was performed using monoclonal antibody CSLEX1 in 12 Pen-A type and 79 non-Pen-A type cancers. Scoring was based on the percentage of immunoreactive cells: negative, low expression (< or = 25%), and high expression (> 25%). Lymph node metastasis was found more frequently in Pen-A type than non-Pen-A type cancers (P=0.0004). Furthermore, sialyl Le(x) antigen high expression was detected more often in Pen-A type cancers (7 out of 12; 58.3%) than non-Pen-A type cancers (13 out of 79; 16.5%) (P=0.0036). Multivariate logistic regression analysis showed that these variables are related independently to the Pen-A type and the non-Pen-A type tumor growth patterns. These data suggest that the difference in sialyl Le(x) antigen expression between the Pen-A type and non-Pen-A type tumor growth patterns of early gastric cancer may, at least partially, reflect different biological behavior during tumor progression.
The thermal conductivity of organic superconductor kappa-(BEDT-TTF)2Cu(NCS)2 (Tc = 10.4 K) has been studied in a magnetic field rotating within the 2D superconducting planes with high alignment precision. At low temperatures ( T < or = 0.5 K), a clear fourfold symmetry in the angular variation, which is characteristic of a d-wave superconducting gap with nodes along the directions rotated 45 degrees relative to the b and c axes of the crystal, was resolved. The determined nodal structure is inconsistent with recent theoretical predictions of superconductivity induced by the antiferromagnetic spin fluctuation.
This study investigates the effects of candesartan, an angiotensin II type 1 receptor blockade, on carotid arterial intimal thickening and glucose tolerance in balloon-injured male Wistar fatty rats and their littermates (Wistar lean rats). Candesartan was orally administered to 12-week-old rats for 21 days, and age-matched rats without the agent were used as the respective controls. Balloon catheterization in the left common carotid artery was performed on day 7, and the artery was removed on day 14 for histological analysis. Compared with the area ratios of the neointima/media in fatty rats without treatment, the ratios in fatty rats treated with candesartan at 1 mg. kg(-1). d(-1) and lean rats without treatment were significantly decreased to 65%; on the other hand, the ratios of fatty rats treated with candesartan at 10 mg. kg(-1). d(-1) and lean rats treated with 1 mg. kg(-1). d(-1) were reduced to 35%, and those of lean rats treated with 10 mg. kg(-1). d(-1) were reduced to 28%. The administration of candesartan also decreased the level of plasma glucose time- and dose-dependently in fatty rats. In an intragastric glucose load, the levels of both glucose and insulin at 30 and 60 minutes were significantly decreased when fatty rats were treated with candesartan at 10 mg. kg(-1). d(-1). In cultured vascular smooth muscle cells from fatty rats, insulin-stimulated Akt (New England Biolabs) phosphorylation and 2-deoxy-D-glucose uptake were inhibited to 59% and 68%, respectively, by angiotensin II, but the effects were ameliorated by the addition of 10(-7) mol/L candesartan. We conclude that candesartan could be effective for the suppression of vascular smooth muscle cell growth dose-dependently in Wistar fatty and lean rats. Furthermore, the agent could improve insulin resistance in Wistar fatty rats.
Transport characteristics of grepafloxacin and levofloxacin across the apical membrane of Caco-2 cells were examined. Both grepafloxacin and levofloxacin uptakes increased rapidly, and were temperature-dependent. Grepafloxacin and levofloxacin uptakes showed concentration-dependent saturation with Michaelis constants of 3.9 and 9.3 mM, respectively. Uptake of grepafloxacin and levofloxacin increased in Cl(-)-free and ATP depleted conditions, suggesting the involvement of an efflux transport system different from the uptake mechanism. However, cyclosporin A, a typical inhibitor of P-glycoprotein, did not affect the uptake of these drugs. Unlabeled grepafloxacin, unlabeled levofloxacin and quinidine inhibited the uptake of grepafloxacin and levofloxacin under Cl(-)-free conditions. Tetraethylammonium, cimetidine, p-aminohippurate, probenecid, amino acids, beta-lactam antibiotic or monocarboxylates did not inhibit the uptake of grepafloxacin and levofloxacin under the same conditions. In conclusion, our results suggested that grepafloxacin and levofloxacin uptakes were mediated by a specific transport system distinct from those for organic cations and anions, amino acids, dipeptides and monocarboxylates.
The serine-threonine kinase Akt exerts its anti-apoptotic effects through several downstream targets, including the pro-apoptotic Bc1-2 family member Bad, Forkhead transcription factors, and the cyclic AMP response element-binding protein (CREB). In this report we demonstrate that Akt inhibits a conformational change in the pro-apoptotic Bax protein and its translocation to mitochondria, thus preventing the disruption of the mitochondrial inner membrane potential (DeltaPsi(m)), caspase-3 activation, and apoptosis in pre-B hematopoietic cells FL5.12 following interleukin-3 (IL-3) withdrawal. Inhibition of PI-3 kinase, but not MAPK kinase, promotes this conformational change in Bax. Moreover, overexpression of Akt suppresses the relocalization of GFP-Bax to mitochondria and apoptosis in Hela cells induced by the DNA-damaging agent methyl methanesulphonate. However, Akt does not abolish the ability of a conformationally changed Bax mutant, GFP-Bax (DeltaS184), to translocate to mitochondria and to induce apoptosis. These findings indicate that Akt exerts its anti-apoptotic effects in cells at a premitochondrial stage, at least in part, by inhibiting Bax conformational change and its redistribution to the mitochondrial membranes.