Biomedical subjects

Y L Yang

Publications and source records attributed to Y L Yang.

At least 19 recordsLinked to original sources

PubMed2007

Midazolam vs ondansetron for preventing postoperative nausea and vomiting: a randomised controlled trial.

We compared the prophylactic anti-emetic efficacy of midazolam and ondansetron in 90 patients scheduled for minor gynaecological (hysteroscopy) or urological (ureteroscopy) procedures planned to last 1-2 h under sevoflurane anaesthesia with spontaneous ventilation of the lungs via a laryngeal mask airway. Midazolam 2 mg or ondansetron 4 mg were administered intravenously 30 min before the end of surgery. The proportions of patients who experienced postoperative nausea and vomiting in the first 24 h (30% and 27% for the midazolam and ondansetron groups, respectively) were similar in the two groups. The incidence of postoperative nausea and vomiting was significantly smaller in both groups than predicted according to the patients' underlying risks (midazolam group: p = 0.018; ondansetron group: p = 0.017). There were no significant differences in average sedation scores or pain scores. Treatment using ondansetron for anti-emetic prophylaxis did not provide a superior benefit compared to midazolam in the present study.

Adjuvants, Anesthesia↗

PubMed2006

Self-assembled pattern formation of block copolymers on the surface of the sphere using self-consistent field theory.

The spherical surface is spatially discretized with triangular lattices to numerically calculate the Laplace-Beltrami operator contained in the self-consistent field theory (SCFT) equations using a finite volume method. Based on this method we have developed a spherical alternating-direction implicit (ADI) scheme for the first time to help extend real-space implementation of SCFT in 2D flat space to the surface of the sphere. By using this method, we simulate the equilibrium microphase separation morphology of block copolymers including AB diblocks, ABC linear triblocks and ABC star triblock copolymers occurred on the spherical surface. In general, two classes of microphase separation morphologies such as striped patterns for compositionally symmetric block copolymers and spotted patterns for asymmetric compositions have been found. In contrast to microphase separation morphology in 2D flat space, the geometrical characteristics of a sphere has a large influence on the self-assembled morphology. For striped patterns, several of spiral-form and ring-form patterns are found by changing the ratio of the radius of a sphere to the averaging width of the stripes. The specific pattern such as the striped and spotted pattern with intrinsic dislocations or defects stems from formed periodic patterns due to microphase separation of block copolymers arranged on the curved surface.

Adsorption↗

PubMed2006

Preferential infection of dividing cells by Cryptosporidium parvum.

In spite of its limitations, the culture of Cryptosporidium parvum in monolayers of epithelial cells is a suitable model to study the interaction of this protozoan parasite with the host cell, to assay oocyst infectivity, and to screen drugs for anti-cryptosporidial activity. For unknown reasons, growth of Cryptosporidium in culture is limited in time and generally does not lead to the production of significant numbers of oocysts. In monolayers infected with high doses of oocysts, we observed that many cells remain uninfected, suggesting that some cells are less susceptible to the infection. Since C. parvum and the related species C. hominis lack many essential biosynthetic pathways, we tested whether the dependence of the parasite on host cell metabolites may favour the infection of cells in mitosis. The proportion of monolayer cells in stationary (G0/G1) phase and in mitosis (S/G2/M) was determined and the prevalence of infected cells in each subpopulation was quantified. Although C. parvum infects and develops in dividing and stationary cells, a significant preference for cells in S/G2/M phase was observed. Consistent with previous observations showing that C. parvum induces apoptosis in cell monolayers, infection was accompanied by a significant increase in the proportion of mitotic cells.

Animals↗

PubMed2006

Molecular epidemiology of long-term colonization of Candida albicans strains from HIV-infected patients.

Twenty-one Candida albicans isolates from three HIV-infected patients were collected over a period of 3 years and characterized for fluconazole susceptibility, infectivity and genetic relatedness. Fluconazole resistance was found in five isolates, four exhibited dose-dependent susceptibility and the remainder were fully susceptible to this agent. Pulsed-field gel electrophoresis of SfiI restriction digests of the genomic DNA from the isolates revealed that isolates from the same swab specimen were identical despite differences in susceptibility to fluconazole and isolates recovered over time from the three patients retained clonally related DNA fingerprints within each patient. This small-scale study confirms the persistence of oral colonization of C. albicans strains in HIV-infected patients. Clinical data also suggests that the primary infecting strain may become a persistent colonist in the oral cavity once the immune function of the patient has been restored.

Adult↗

PubMed2005

Facilitation of conditioned fear extinction by d-cycloserine is mediated by mitogen-activated protein kinase and phosphatidylinositol 3-kinase cascades and requires de novo protein synthesis in basolateral nucleus of amygdala.

Recent results showed that either systemic or intra-amygdala administration of d-cycloserine, a partial agonist at the glycine modulatory site on the glutamate N-methyl-d-aspartate receptor facilitates the extinction of conditioned fear. Here we evaluated the role of mitogen-activated protein kinase and phosphatidylinositol 3-kinase in the basolateral nucleus of amygdala on the effect of d-cycloserine. The facilitation effect of d-cycloserine on fear extinction and mitogen-activated protein kinase activation was completely blocked by intra-amygdala administration of mitogen-activated protein kinase inhibitor PD98059 (500 ng/side, bilaterally) or U0-126 (20 microM/side, bilaterally). Furthermore, phosphatidylinositol 3-kinase inhibitor (wortmannin, 5.0 microg/side, bilaterally) infused into the basolateral nucleus of amygdala significantly reduced both facilitation effect of d-cycloserine and phosphatidylinositol 3-kinase activation. Intra-amygdala administration of a transcription inhibitor (actinomycin D, 10 microg dissolved in 1.6 microl vehicle; 0.8 microl per side) and a translation inhibitor (anisomycin, 125 microg dissolved in 1.6 microl vehicle; 0.8 microl per side) completely blocked the facilitation effect of d-cycloserine. Control experiments indicated the blockage by actinomycin D or anisomycin were not due to lasting damage to the basolateral nucleus of amygdala or state dependency. In addition, none of the active drugs used here altered the expression of conditioned fear. These results suggested that phosphatidylinositol 3-kinase and mitogen-activated protein kinase-dependent signaling cascades and new protein synthesis within the basolateral nucleus of amygdala played important roles in the d-cycloserine facilitation of the extinction of conditioned fear.

Amygdala↗

PubMed2005

Distribution and susceptibility to amphotericin B and fluconazole of Candida spp. isolated from Taiwan.

Susceptibilities to amphotericin B and fluconazole of 628 clinical yeast strains collected from 22 hospitals in Taiwan were determined. A total of 53 isolates (8.4%) were resistant to fluconazole. Each hospital had different resistance rate to fluconazole ranging from 0% to 24%. None of the 186 isolates from eight of the 22 hospitals was resistant to fluconazole. In contrast, isolates from nine of the remaining 14 hospitals had greater than 10% resistance rate to fluconazole. Consistently, 88.9% (8/9) fluconazole-resistant C. albicans isolates were from hospitals having a high resistance rate to fluconazole. The prevalence of various Candida spp. in each hospital was different. A positive association was found between the prevalence of C. tropicalis and the resistance rate to fluconazole for individual hospitals. Although only three isolates (0.5%) were resistant to amphotericin B, a co-resistance to both amphotericin B and fluconazole was observed, which highlights the emerging problem of drug resistance.

Amphotericin B↗

PubMed2003

Iron-mediated inhibition of H+-ATPase in plasma membrane vesicles isolated from wheat roots.

The mechanisms of iron-mediated inhibition of the H(+)-ATPase activity of plasma membrane (PM) vesicles isolated from wheat roots were investigated. Both FeSO(4) and FeCl(3) significantly inhibited PM H(+)-ATPase activity, and the inhibition could be reversed by the addition of the metal ion chelator EDTA-Na(2) or a specific Fe(2+) chelator, indicating that the inhibitory effect was due to specific action of Fe(2+) or Fe(3+). Measurement of the extent of lipid peroxidation showed that oxidative damage on the PM caused by Fe(2+) or Fe(3+) seemed to be correlated with the inhibition of PM H(+)-ATPase activity. However, prevention of lipid peroxidation with butylated hydroxytoluene did not affect iron-mediated inhibition in the PM H(+)-ATPase, suggesting that the inhibition of the PM H(+)-ATPase was not a consequence of lipid peroxidation caused by iron. Investigation of the effects of various reactive oxygen species scavengers on the iron-mediated inhibition of H(+)-ATPase activity indicated that hydroxyl radicals (*OH) and hydrogen peroxide (H(2)O(2)) might be involved in the Fe(2+)-mediated decrease in PM H(+)-ATPase activity. Moreover, iron caused a decrease in plasma protein thiol (P-SH), and Fe(3+) brought a higher degree of oxidation in thiol groups than Fe(2+) at the same concentration. Modification of the thiol redox state in the PM suggested that reducing thiol groups were essential to maintain PM H(+)-ATPase activity. Incubation of the specific thiol modification reagent 5,5-dithio-bis(2-nitrobenzoic acid) with the rightside-out and inside-out PM revealed that thiol oxidation occurred at the apoplast side of the PM. Western blotting analysis revealed a decrease in H(+)-ATPase content caused by iron. Taken together, these results suggested that thiol oxidation might account for the inhibition of PM H(+)-ATPase caused by iron, and that *OH and H(2)O(2) were also involved in Fe(2+)-mediated inhibition.

Cell Membrane↗

PubMed2001

Identification of three novel 6-pyruvoyl-tetrahydropterin synthase gene mutations (226C>T, IVS3+1G>A, 116-119delTGTT) in Chinese hyperphenylalaninemia caused by tetrahydrobiopterin synthesis deficiency.

The enzyme 6-Pyruvoyl-tetrahydropterin synthase (PTS) deficiency is the major cause of BH(4)-deficient HPA. The frequency of BH(4)-deficient HPA was estimated to be around 30% among Chinese HPA population in Taiwan, which is much higher than that in Caucasian population (1.5-2% of HPA). Approximately 86% of Chinese BH(4)-deficient HPA was found to be caused by PTS-deficiency. Seven mutations - namely R25G, N52S, V56M, V70D, P87S, D96N, and T106M - had been identified in Chinese PTS-deficient patients previously. In this study, five additional mutations in the PTS gene, namely 200C>T (T67M), 226C>T (L76F), IVS3+1G>A (K54X), 116-119delTGTT (K38X) and 169-171delGTG (V57del), were identified by PCR and DNA sequencing in Chinese PTS-deficient patients. The 116-119delTGTT introduces a frameshift stop after lysine of codon 38 (K38X). The G-to-A transition at the consensus sequence of splicing donor site of exon 3 (IVS3+1G>A) resulted in exon 3 skipping of the PTS transcript and caused a frameshift stop after lysine of codon 54 (K54X). The T67M and V57del mutations have been found in Caucasian PTS deficient patients, while the L76F, IVS3+1G>A, and K38X mutations are novel. None of 100 normal alleles screened was found to have the L76F substitution, which indicated that the L76F substitution is a mutation causing PTS deficiency. Hum Mutat 18:83, 2001.

Alleles↗

PubMed2001

[Permeabilization of yeast Trigonopsis variabilis FA10 cells for enhancing apparent activity of D-amino acid oxidase].

D-amino acid oxidase(DAO) is an intracellular enzyme in Trigonopsis variabilis FA10. The whole cells of yeast exhibited very low DAO activity. Various treatment with physical and chemical agents, such as, freezing and thawing, acetone, butanol and cetyltrimethylammoinium bromide altered membrane permeability and increased cellular DAO activity. It was demonstrated that the performance of acetone was dependent on the concentration of the solvent, the incubation time and the temperature. Maximum enzyme activity of the cells was achieved with 30-35% acetone, between 4 degrees C and 28 degrees C. The process was very quick and permeabilization occurred in 5 minutes or less. On the other hand, the thermostability of DAO in permeabilized cells was higher than in cell extract. It was proved that Cephalosporin C could be effectively converted to glutaryl-7ACA by permeabilized Trigonopsis variabilis cells with 83% yield.

D-Amino-Acid Oxidase↗

PubMed2001

[Enzymatic conversion of cephalosporin C to glutaryl-7-aminocephalosporanic acid using whole cells of the yeast Trigonopsis variabilis FA10].

A process for the production of glutaryl-7-aminocephalosporanic acid (GL-7ACA) from cephalosporin C(CPC) using permeabilized cells of yeast Trigonopsis variabilis FA10 containing D-amino acid oxidase (DAO) is described. It was found that the bioconversion of CPC to GL-7ACA was interfered by the catalase activity presented in the cells that hydrolyzed the hydrogen peroxide and resulted in the accumulation of alpha-keto-adipyl-7-ACA (AKA-7ACA) and decrease of GL-7ACA yield. the methods to overcome this problem including the addition of extra H2O2 and use of catalase inhibitor, NaN3, were developed and the rate of GL-7ACA from CPC were 73% and 70.1%, respectively. Another alternative method was to incubate the permeabilized FA10 cells at pH10.5-11.0 for 30 minutes at 20 degrees C which served to selectively inactivate the catalase. In the bioconversion of CPC to GL-7ACA using pH10.5-treated cells without catalase activity, the high reaction yield of GL-7ACA(84%) was achieved.

Cephalosporins↗

PubMed2001

Mechanisms of antifungal agent resistance.

During the past decade, yeast infections have had an important role in nosocomial infections due to alterations in the immune status of patients. Coincidentally with the increased usage of antifungal agents, the number of reports of drug resistance has increased, which highlights the need for understanding the molecular mechanisms of antifungal agent resistance. This review describes the mechanisms of action of antifungal agents, cellular factors contributing to drug resistance, the known molecular mechanisms of drug resistance, and proposed but unproved molecular mechanisms of drug resistance. This review also proposes possible strategies for preventing drug resistance.

ATP-Binding Cassette Transporters↗

PubMed2001

[Establishment of detective systems for GL-7ACA acylase expression].

Glutaryl-7-amino cephalosporanic acid (GL-7ACA) acylase catalyzes the conversion of GL-7ACA to 7-amino cephalosporanic acid (7-ACA). The product 7-ACA is a starting compound for semi-synthetic cephalosporin antibiotics in industry. In order to detect the expression and specific activity of protein-engineered GL-7ACA acylase accurately, two useful detective systems for its expression has been established, in which reporter genes xylE and lacZ were fused to the downstream the GL-7ACA acylase gene acy respectively and the activity of catechol dioxygenase or beta-galactosidase could indicate the amount of acy expression.

Catechol 2,3-Dioxygenase↗

PubMed2001

Mutagenesis of N-terminal Amino Acid Residues in beta-subunit of Glutaryl-7-amino-cephalosporanic Acid Acylase C130.

In many GL-7ACA acylases, the first Ser residue at the N-terminal of beta-subunit is the catalytic center. In order to investigate relationship between the N-terminal structure and catalytic activities, peptide replacement and site-directed mutagenesis were performed at the N-terminal of beta-subunit of GL-7ACA acylase C130. When the N-terminal 8 amino acid residues of C130 were replaced by the corresponding sequence of penicillin acylases PAC and PGA, respectively, the first mutant B8PAC lost the activity of the acylase, and the second mutant B8PGA had lower activity with the K(m) value increasing from 0.44x10(-3)mol.L(-1) to 0.55x10(-3) mol.L(-1), and the k(cat) decreasing from 4.92 s(-1) to 1.64 s(-1). Although the substitution of Trp (beta4) by Tyr did not change the K(m) value, the k (cat) decreased to 2.29 s(-1). When the Trp was substitued by Leu, both the K ( m ) and k ( cat ) values decreased. Compared with the wild type, mutations of Ser (beta3) to Met, Ala and Cys caused decrease of K(m) values by 52.27%, 43.18% and 38.64%, respectively. Mutation of Asn (beta2) to Gln caused the K ( m ) value being increased by 5-fold, and k ( cat ) decreased by 10-fold. These results suggested that the N-terminal amino acid residues of beta-subunit in GL-7ACA acylase C130 are important for enzyme function.

Journal Article↗

PubMed2001

[Synthesis, characterization and fluorescence property of europium ternary complex p-nitrophenylacetic acid and 1, 10-phenanthroline].

The europium ternary solid complex containing p-nitrophenylacetic acid and 1, 10-phenanthroline was synthesized in this work, and the chemical formula of this compound was determined to be EuL3 phen by elemental analysis. The complex has been characterized by analysis of molar conductivity, TG-DTA, IR and UV. The fluorescence spectra of this Eu3+ complex has been investigated also in this paper.

Chelating Agents↗

PubMed2000

Negative regulation of CD8+ T cell function by the IFN-induced and double-stranded RNA-activated kinase PKR.

The IFN-induced and dsRNA-activated kinase (PKR) mediates the antiviral and antiproliferative effects of IFN-alpha and IFN-gamma. Despite these findings, PKR:(-/-) mice have no overt immunological phenotype. Here we tested the role of PKR in cellular immunity by determining the induction and elicitation of contact hypersensitivity in PKR:(-/-) mice, a model of T cell-mediated immunity. When compared with wild type, the magnitude of contact hypersensitivity responses in PKR:(-/-) mice were 2-fold higher and of extended duration. This was also observed when naive recipients of immune CD8(+) T cells from sensitized PKR:(-/-) and CD4(+) T cells from sensitized wild-type PKR:(+/+) or PKR:(-/-) mice were challenged with hapten, indicating a regulatory defect intrinsic to the CD8(+) T cell population. Isolated lymph node T cells from PKR:(-/-) mice were hyperproliferative during Con A-mediated stimulation. These results implicate PKR for the first time in the growth control of mature T lymphocytes and give insight into the negative regulation of CD8(+) T cell-mediated immune responses.

Adoptive Transfer↗

PubMed2000

Fluorescence property on solutions of zwitterionic surfactant tetradecylbetaine in the presence of macromolecules.

The fluorescence property of zwitterionic surfactant tetradecylbetaine (C14BE) solutions in the presence of polyvinylpyrrolidone (PVPk30 and PVPk90), or Xanthan (Xc) have been investigated by steady-state fluorescence probe. The intensity ratio of the first and third peaks (I1/I3) of the monomer and that of the excimer to monomer (Ie/Im), and the aggregation number of the aggregates have been monitored. The results showed that C14BE/PVP and C14BE/Xc interactions mostly occur at the micelle surface. The C14BE clusters or micelles are bound to macromolecule chains by electrostatic force for PVP and by hydrogen-bonding for Xc, respectively.

Betaine↗

PubMed2000

Expression in Escherichia coli, purification and kinetic analysis of the aspartokinase and aspartate semialdehyde dehydrogenase from the rifamycin SV-producing Amycolatopsis mediterranei U32.

The operon encoding aspartokinase and aspartate semialdehyde dehydrogenase was cloned and sequenced from rifamycin-SV-producing Amycolatopsis mediterranei U32 previously. In the present work, these two genes were introduced into the auxotrophic Escherichia coli strain CGSC5074 (ask-) and E. coli X6118 (asd-), respectively. The A. mediterranei U32 asparto-kinase and aspartate semialdehyde dehydrogenase genes can be functionally expressed in E. coli and the gene products are able to substitute for the E. coli enzymes. Histidine-tagged aspartokinase and aspartate semialdehyde dehydrogenase were partially purified from E. coli cellular extracts and their kinetic characteristics were studied. Both aspartokinase and aspartate semialdehyde dehydrogenase showed typical Michaelis-Menten type substrate saturation patterns. Aspartokinase has Km values of 3.4 mM for aspartate and 2.3 mM for ATP, while aspartate semialdehyde dehydrogenase has Km values of 1.25 mM for DL-aspartate semialdehyde and 0.73 mM for NADP, respectively. Aspartokinase was inhibited by L-threonine, L-lysine, and L-methionine, but not by L-isoleucine and diaminopimelate. Aspartate semialdehyde dehydrogenase was not inhibited by any of the end-product amino acids at a concentration of less than 5 mM. Hill plot analysis suggested that asparto-kinase was subject to allosteric control by L-threonine. Repression of both aspartokinase and aspartate semi-aldehyde dehydrogenase gene transcription in A. mediterranei U32 by L-lysine, L-methionine, L-threonine, and L-isoleucine were found. The network of regulation of aspartokinase and aspartate semialdehyde dehydrogenase in rifamycin SV-producing A. mediterranei U32 is presented.

Actinomycetales↗

PubMed2000

The IAP family: endogenous caspase inhibitors with multiple biological activities.

IAPs (inhibitors of apoptosis) are a family of proteins containing one or more characteristic BIR domains. These proteins have multiple biological activities that include binding and inhibiting caspases, regulating cell cycle progression, and modulating receptor-mediated signal transduction. Our recent studies found the IAP family members XIAP and c-IAP1 are ubiquitinated and degraded in proteasomes in response to apoptotic stimuli in T cells, and their degradation appears to be important for T cells to commit to death. In addition to three BIR domains, each of these IAPs also contains a RING finger domain. We found this region confers ubiquitin protease ligase (E3) activity to IAPs, and is responsible for the auto-ubiquitination and degradation of IAPs after an apoptotic stimulus. Given the fact that IAPs can bind a variety of proteins, such as caspases and TRAFs, it will be of interest to characterize potential substrates of the E3 activity of IAPs and the effects of ubiquitination by IAPs on signal transduction, cell cycle, and apoptosis.

Animals↗