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Biomedical subjects

X Zhao

Publications and source records attributed to X Zhao.

At least 37 records · Page 2Linked to original sources
PubMed2005

Charge-transfer excitations in the model superconductor HgBa(2)CuO(4+delta).

We report a Cu -edge resonant inelastic x-ray scattering (RIXS) study of charge-transfer excitations in the 2-8 eV range in the structurally simple compound HgBa(2)CuO(4+delta) at optimal doping (T(c)=96.5 K). The spectra exhibit a significant dependence on the incident photon energy which we carefully utilize to resolve a multiplet of weakly dispersive (<0.5 eV) electron-hole excitations, including a mode at 2 eV. The observation of this 2 eV excitation suggests the existence of a remnant charge-transfer gap deep in the superconducting phase. Quite generally, our results, which include additional data for the Mott insulator La(2)CuO(4), demonstrate the importance of exploring the incident photon-energy dependence of the RIXS cross section.

Journal Article↗
PubMed2005

Effects of cassia oil on serum and hepatic uric acid levels in oxonate-induced mice and xanthine dehydrogenase and xanthine oxidase activities in mouse liver.

We investigated the hypouricemic effects of cassia oil extracted from Cinnamomum cassia using hyperuricemic mice induced by potassium oxonate, and its inhibitory actions against liver xanthine dehydrogenase (XDH) and xanthine oxidase (XOD) activities. Oral administration of cassia oil significantly reduced serum and hepatic urate levels in hyperuricemic mice in a time- and dose-dependent manner. At doses of 450 mg/kg of cassia oil or above, serum urate levels of the oxonate-pretreated mice were not different from the normal control mice. Cassia oil at 600 mg/kg was found to be as potent as allopurinol, which reduced hepatic urate levels to lower than normal. In normal mice, urate levels in liver, but not in serum, were altered with dose-dependent decrease after cassia oil treatment. Furthermore, the ratio, liver uric acid/serum uric acid, was determined after cassia oil administration with time- and dose-dependent decreases in hyperuricemic mice. The positive dose-dependent decrease ratio was also observed after cassia oil treatment in the normal animals. The decreased extent of ratio elicited by cassia oil in normal mice appeared to be greater than that in the hyperuricemic animal. In addition, cassia oil significantly exhibited marked reductions in liver XDH/XOD activities, with an apparent dose-dependence in the normal and hyperuricemic mice. The onset of inhibition in enzyme activities elicited by allopurinol was much higher than that elicited by cassia oil. These results suggested that hypouricemic effects of cassia oil could be explained, at least partly, by inhibiting liver in vivo activities of XDH/XOD.

Administration, Oral↗
PubMed2005

Quantitative determination and structural characterization of isoflavones in nutrition supplements by liquid chromatography-mass spectrometry.

In this paper, an accurate and route method was developed to quantitative determine daidzein, genistein, glycitein, daidzin, glycitin, 6"-O-acetyldaidzin, 6"-O-acetylglycitin and 6"-O-acetylgenistin contents in selected high and low isoflavones in nutrition supplements by on line liquid chromatography-atmospheric pressure chemical ionisation mass spectrometry (LC-APCI-MS). Improved extraction and hydrolysis methods of the isoflavones from three nutrition supplements were also studied and a rapid extraction method was developed. Comparison of different MS2 and MS3 spectra of isoflavones and some unknown compounds were also explored and proposed pathway fragments of nine isoflavones were first systematically suggested.

Chromatography, High Pressure Liquid↗
PubMed2005

Assessment of PCBs and PCDD/Fs along the Chinese Bohai Sea coastline using mollusks as bioindicators.

Mollusk samples such as bivalves and gastropods were collected from eight sampling sites along Bohai Sea coastline from northeastern China. The samples were analyzed for polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) by high-resolution gas chromatography/high-resolution mass spectrometry (HRGC-HRMS) to elucidate bioaccumulation of persistent organic pollutants in benthon. Residue levels of sigmaPCBs and sigmaPCDD/Fs were in the ranges of 66.1 to 583.6 ng/g and 0.9 to 15317 pg/g on a lipid-weight basis, respectively, The pollution source was identified using principal component analysis (PCA) in some coastal areas. It indicated that the typical pollution sources were characterized by PCB3, which was one Chinese technical product of PCBs. PCA also revealed the similarity patterns of PCBs between identical species collected from the different sites. The higher gastropod PCB concentrations were related to a former capacitor factory and the paint factories in some coastal areas, but this was not the case with the bivalves. The results of this study suggest that some gastropod species may be a potential bioindicator or "sentinel" organism for marine PCBs monitoring.

Animals↗
PubMed2005

Analysis of the Candida albicans Als2p and Als4p adhesins suggests the potential for compensatory function within the Als family.

The ALS (agglutinin-like sequence) gene family encodes eight large cell-surface glycoproteins. The work presented here focuses on Als2p and Als4p, and is part of a larger effort to deduce the function of each Als protein. Both ALS4 alleles were deleted from the Candida albicans genome and the phenotype of the mutant strain (als4Delta/als4Delta; named 2034) studied. Loss of Als4p slowed germ tube formation of cells grown in RPMI 1640 medium and resulted in decreased adhesion of C. albicans to vascular endothelial cells. Loss of Als4p did not affect adhesion to buccal epithelial cells, biofilm formation in a catheter model, or adhesion to or destruction of oral reconstituted human epithelium (RHE). Although deletion of one ALS2 allele was achieved readily, a strain lacking the second allele was not identified despite screening thousands of transformants. The remaining ALS2 allele was placed under control of the C. albicans MAL2 promoter to create an als2Delta/PMAL2-ALS2 strain (named 2342). Real-time RT-PCR analysis of strain 2342 grown in glucose-containing medium (non-inducing conditions) showed that although ALS2 transcript levels were greatly reduced compared to wild-type cells, some ALS2 transcript remained. The decreased ALS2 expression levels were sufficient to slow germ tube formation in RPMI 1640 and Lee medium, reduce adhesion to vascular endothelial cells and to RHE, decrease RHE destruction, and impair biofilm formation. Growth of strain 2342 in maltose-containing medium (inducing conditions) restored the wild-type phenotype in all assays. Real-time RT-PCR analysis demonstrated that in maltose-containing medium, strain 2342 overexpressed ALS2 compared to wild-type cells; however no overexpression phenotype was apparent. Microarray analysis revealed little transcriptional response to ALS4 deletion, but showed twofold up-regulation of orf19.4765 in the glucose-medium-grown als2Delta/PMAL2-ALS2 strain. orf19.4765 encodes a protein with features of a glycosylated cell wall protein with similarity to Saccharomyces cerevisiae Ccw12p, although initial analysis suggested functional differences between the two proteins. Real-time RT-PCR measurement of ALS2 and ALS4 transcript copy number showed a 2.8-fold increase in ALS2 expression in the als4Delta/als4Delta strain and a 3.2-fold increase in ALS4 expression in the als2Delta/PMAL2-ALS2 strain, suggesting the potential for compensatory function between these related proteins.

Biofilms↗
PubMed2005

"Lineage addiction" in human cancer: lessons from integrated genomics.

Genome-era advances in the field of oncology endorse the notion that many tumors may prove vulnerable to targeted therapeutic avenues once their salient molecular alterations are elucidated. Accomplishing this requires both detailed genomic characterization and the ability to identify in situ the critical dependencies operant within individual tumors. To this end, DNA microarray platforms such as high-density single-nucleotide polymorphism (SNP) arrays enable large-scale cancer genome characterization, including copy number and loss-of-heterozygosity analyses at high resolution. Clustering analyses of SNP array data from a large collection of tumor samples and cell lines suggest that certain copy number alterations correlate strongly with the tissue of origin. Such lineage-restricted alterations may harbor novel cancer genes directing genesis or progression of tumors from distinct tissue types. We have explored this notion through combined analysis of genome-scale data sets from the NCI60 cancer cell line collection. Here, several melanoma cell lines clustered on the basis of increased dosage at a region of chromosome 3p containing the master melanocyte regulator MITF. Combined analysis of gene expression data and additional functional studies established MITF as an amplified oncogene in melanoma. MITF may therefore represent a nodal point within a critical lineage survival pathway operant in a subset of melanomas. These findings suggest that, like oncogene addiction, "lineage addiction" may represent a fundamental tumor survival mechanism with important therapeutic implications.

Chromosomes, Human, Pair 3↗
PubMed2005

Identification of an HLA-B*07 allele variant (B*0740) in the Chinese Han population.

A novel HLA-B*07 allele, B*0740, has been identified by sequence-based typing (SBT) in the Chinese Han population. This new allele is identical to B*0705 and B*0706 for exons 2, 3, and 4, except for a single nucleotide at position 605 of codon 202 in exon 3 (AAG-->ATG) leading to an amino acid change from lysine to methionine. SBT was performed following allele separation using the Haploprep method. The serological equivalence of B*0740 to the B7 antigen did not change.

Alleles↗
PubMed2005

A novel HLA allele, DRB1*1609, identified in the Chinese Han population*.

A novel human leucocyte antigen-DRB1*16 (HLA-DRB1*16) allele (DRB1*1609) has been identified by sequencing-based typing (SBT) in Chinese Han population. This new allele has identical nucleotide sequence to DRB1*160101 in exon 2, except for a single-nucleotide substitution from A to T at position 127. This change leads to an amino acid change from tyrosine to phenylalanin at residue 47 (Y47F). SBT was performed for cloned DRB1*16-specific polymerase chain reaction fragment. The serological phenotype of DRB1*1609 is equivalent to DR16 antigen.

Alleles↗
PubMed2005

Effects of anticoagulant treatment on intestinal ischaemia and reperfusion injury in rats.

BACKGROUND: In recent years it has become increasingly clear that a cross-talk between the inflammatory response and blood coagulation exists, although many of the underlying mechanisms remain unclear. In the present study we investigated the potential anti-inflammatory properties of two different anticoagulant compounds, i.e. active-site inactivated FVIIa (FVIIai) and fondaparinux sodium, a selective FXa inhibitor, administered as pretreatment in a model of intestinal I/R in rats. METHODS: Endothelial barrier permeability was assessed using the vascular leakage of radiolabelled human serum albumin, tissue neutrophil sequestration was quantitated by myeloperoxidase (MPO) activity, and plasma levels of macrophage inflammatory protein (MIP)-2 were examined using an enzyme-linked-immuno-sorbent assay after 40 min of intestinal ischaemia and 6 h of reperfusion in the rat (n = 34). Pretreatment with FVIIai or fondaparinux sodium was administered 90 min before initiation of ischaemia. RESULTS: Endothelial-barrier permeability in all examined organs, myeloperoxidase activity in the lungs, and ileum and MIP-2 levels in plasma increased after intestinal I/R. Pretreatment with FVIIai decreased the endothelial barrier permeability and MPO activity in the ileum, and a tendency towards decreased permeability was also observed in the lungs. Fondaparinux did not affect the endothelial barrier permeability or MPO activity. Both FVIIai and fondaparinux decreased the MIP-2 levels in plasma after intestinal I/R. CONCLUSIONS: Inhibition of the TF-FVIIa complex by FVIIai can attenuate inflammatory responses in connection with intestinal I/R-injury and could represent a potentially important therapeutic strategy for the prevention of organ dysfunction. Potential anti-inflammatory properties of fondaparinux and other inhibitors of FXa are not excluded and need further investigation.

Animals↗
PubMed2005

Proteases involved in mammary tissue damage during endotoxin-induced mastitis in dairy cows.

During and after diapedesis, milk polymorphonu-clear neutrophils (PMN) release many proteases that have the potential of degrading extracellular matrix proteins and milk proteins. However, the kinetics of milk proteolysis during inflammation and the underlying mechanisms are poorly defined. The enzymes involved in bovine mammary tissue destruction were investigated in this study using an endotoxin-induced mastitis model. Using zymography techniques, the proteolytic activity of milk and mammary tissue during mastitis was examined. Mastitic milk produced 6 caseolysis bands, 4 of which differed from the ones produced by plasmin. Peak proteolytic activity, bovine serum albumin contents, and mammary tissue damage occurred between 6 and 12 h postchallenge. Mastitic milk proteases hydrolyzed casein, gelatin, collagen, hemoglobin, mammary gland membrane proteins, and lactoferrin. These results confirm that mastitic milk proteases have a broad spectrum of activity. The hydrolytic activity of mastitic milk was partially inhibited by aprotinin, EDTA, 1,10-phenanthroline, leupeptin, and pefabloc. When cocultured with normal mammary tissue, mastitic milk, but not normal milk, caused mammary tissue degradation. In situ zymography of mammary gland showed increased proteolytic activity in mastitic tissue compared with normal tissue. The similarity of zymograms of mastitic milk, blood PMN, milk somatic cells, and PMN strongly suggests that proteases in mastitic milk mainly originate from milk PMN. These results suggest that proteases released by PMN are actively involved in udder tissue damage during mastitis.

Animals↗
PubMed2005

Antioxidants to prevent bovine neutrophil-induced mammary epithelial cell damage.

Activated neutrophils are able to produce a large quantity of bactericidal molecules such as reactive oxygen species that have been associated with tissue damage in several inflammation models. The protective effects of antioxidants in a context of neutrophil-induced damage to mammary epithelial cells were first evaluated in vitro using a coculture model of activated bovine neutrophils and a bovine mammary epithelial cell line (MAC-T cells). Cell damage was determined by quantifying the release of lactate dehydrogenase by MAC-T cells in culture medium. Morphological observation of cells stained with acridine orange was used to visualize the extent of cell damage. When incubated with neutrophils activated by lipopolysaccharides and phorbol 12-myristate 13-acetate, MAC-T cells released large amounts of lactate dehydrogenase indicating significant cell damage. The addition of dimethylthiourea or bathocuproine disulfonic acid did not reduce the damage whereas catechin, deferoxamine or glutathione ethyl ester significantly reduced neutrophil-induced cytotoxicity in a dose-dependent manner. The effect of deferoxamine, an iron chelator, on the growth of Escherichia coli and the ability of bovine neutrophils to phagocytose these bacteria were then assessed in vitro. Our data showed that deferoxamine did not interfere with the phagocytic activity of neutrophils but inhibited growth of the bacteria. Overall, our results suggest that antioxidants may be effective tools for protecting mammary tissue against neutrophil-induced oxidative stress during bovine mastitis.

Animals↗
PubMed2005

Effect of a trivalent vaccine against Staphylococcus aureus mastitis lymphocyte subpopulations, antibody production, and neutrophil phagocytosis.

The effect of a novel bovine mastitis trivalent vaccine, containing Staphylococcus aureus capsular polysaccharide type 5 (T5), 8 (T8), and 336 (T336), on lymphocyte subpopulations, antibody production, and neutrophil phagocytosis was evaluated. Twenty pregnant heifers were immunized with either the trivalent alone, trivalent emulsified in Freund's incomplete adjuvant (FICA), trivalent in aluminum hydroxide, or adjuvant only (FICA). Immunization was done 30 d before the expected calving date followed by 2 boosts in a 2-week interval. Compared to FICA, serum antigen-specific immunoglobulin (Ig)G1 and IgG2 were significantly increased in all the vaccinated groups before parturition and sustained until 3 wk postpartum. In comparison with the trivalent alone, formulation with either adjuvant enhanced production of IgG2, but not IgG1. Immune sera, which contained the highest amount of antibodies, slightly increased neutrophil phagocytosis to the 3 serotypes of killed S. aureus, but most of the differences were not significant due to large variation between the cows. The percentage of CD4+ lymphocyte was significantly higher in vaccinated groups than that of FICA 4 wk after the primary immunization. In comparison with FICA, cows inoculated with trivalent vaccine and adjuvants had an increased percentage of CD8+ lymphocytes at 2 time points, 2 wk before and after calving. Our results indicated that the whole cell trivalent vaccine, with or without adjuvants, is able to elicit antibody responses specific to the 3 capsular polysaccharide antigens. The increase of T8-specific IgG2 was more noticeable when the vaccine was emulsified with adjuvants.

Animals↗
PubMed2004

A universal scaling relation in high-temperature superconductors.

Since the discovery of superconductivity at elevated temperatures in the copper oxide materials there has been a considerable effort to find universal trends and correlations amongst physical quantities, as a clue to the origin of the superconductivity. One of the earliest patterns that emerged was the linear scaling of the superfluid density (rho(s)) with the superconducting transition temperature (T(c)), which marks the onset of phase coherence. This is referred to as the Uemura relation, and it works reasonably well for the underdoped materials. It does not, however, describe optimally doped (where T(c) is a maximum) or overdoped materials. Similarly, an attempt to scale the superfluid density with the d.c. conductivity (sigma(dc)) was only partially successful. Here we report a simple scaling relation (rho(s) proportional, variant sigma(dc)T(c), with sigma(dc) measured at approximately T(c)) that holds for all tested high-T(c) materials. It holds regardless of doping level, nature of dopant (electrons versus holes), crystal structure and type of disorder, and direction (parallel or perpendicular to the copper-oxygen planes).

Journal Article↗
PubMed2004

Formation of nitro musk adducts of rainbow trout hemoglobin for potential use as biomarkers of exposure.

The high use of nitro musk xylene (MX) and musk ketone (MK) as fragrances, and their persistence and bioaccumulation potential make them ubiquitous environmental contaminants. The 4-amino-MX (AMX) and 2-amino-MK (AMK) metabolites have been detected in trout fish hemoglobin (Hb) samples by gas chromatography-ion trap-mass spectrometry (GC-MS). Twelve Hb samples prepared from rainbow trout that were exposed to MX and MK, over a period of 24 and 72 h, were analyzed. Amino metabolites were liberated by basic hydrolysis and extracted from the fish Hb into n-hexane. The extract was concentrated, analyzed, and spiked with a standard solution (80 pg/microl) of AMX or AMK and reanalyzed. Concentrations of AMX from 10 to 25 ng/g were detected in Hb from fish taken 24 and 72 h after MX exposure. At 24 and 72 h after MK exposure, the concentration of AMK was found to be 25-51 ng/g and 9.5-25 ng/g, respectively. Concentrations of AMK in Hb from two of the three trout were substantially lower after 72 h compared with 24 h exposure. The AMX and AMK metabolites were not detected in four control samples. Average recoveries exceeding 89 and 86% could be achieved for AMX and AMK, respectively, with a coefficient of variation (CV) around 5%.

Animals↗
PubMed2004

Genomewide linkage analysis of bipolar disorder by use of a high-density single-nucleotide-polymorphism (SNP) genotyping assay: a comparison with microsatellite marker assays and finding of significant linkage to chromosome 6q22.

We performed a linkage analysis on 25 extended multiplex Portuguese families segregating for bipolar disorder, by use of a high-density single-nucleotide-polymorphism (SNP) genotyping assay, the GeneChip Human Mapping 10K Array (HMA10K). Of these families, 12 were used for a direct comparison of the HMA10K with the traditional 10-cM microsatellite marker set and the more dense 4-cM marker set. This comparative analysis indicated the presence of significant linkage peaks in the SNP assay in chromosomal regions characterized by poor coverage and low information content on the microsatellite assays. The HMA10K provided consistently high information and enhanced coverage throughout these regions. Across the entire genome, the HMA10K had an average information content of 0.842 with 0.21-Mb intermarker spacing. In the 12-family set, the HMA10K-based analysis detected two chromosomal regions with genomewide significant linkage on chromosomes 6q22 and 11p11; both regions had failed to meet this strict threshold with the microsatellite assays. The full 25-family collection further strengthened the findings on chromosome 6q22, achieving genomewide significance with a maximum nonparametric linkage (NPL) score of 4.20 and a maximum LOD score of 3.56 at position 125.8 Mb. In addition to this highly significant finding, several other regions of suggestive linkage have also been identified in the 25-family data set, including two regions on chromosome 2 (57 Mb, NPL = 2.98; 145 Mb, NPL = 3.09), as well as regions on chromosomes 4 (91 Mb, NPL = 2.97), 16 (20 Mb, NPL = 2.89), and 20 (60 Mb, NPL = 2.99). We conclude that at least some of the linkage peaks we have identified may have been largely undetected in previous whole-genome scans for bipolar disorder because of insufficient coverage or information content, particularly on chromosomes 6q22 and 11p11.

Bipolar Disorder↗