Biomedical subjects

C Yang

Publications and source records attributed to C Yang.

At least 37 records · Page 2Linked to original sources

PubMed2005

Correlating gene expression with chemical scaffolds of cytotoxic agents: ellipticines as substrates and inhibitors of MDR1.

To facilitate a systematic study of chemoresistance across diverse classes of anticancer drug candidates, we performed correlation analyses between cytotoxic drug potency and gene expression in 60 tumor cell lines (NCI-60; NCI-National Cancer Institute). Ellipticine analogs displayed a range of correlation coefficients (r) with MDR1 (ABCB1, encoding multidrug resistance (MDR) protein MDR1 or P-glycoprotein). To determine MDR1 interactions of five ellipticines with diverse MDR1-r values, we employed MDR1-transport and cytotoxicity assays, using MDR1 inhibitors and siRNA-mediated MDR1 downregulation, in MDR1-overexpressing cells. Ellipticines with negative correlations-indicative of MDR1-mediated resistance-were shown to be MDR1 substrates, whereas those with neutral or positive correlations served as MDR1 inhibitors, which escape MDR1-mediated chemoresistance. Correlation with additional genes in the NCI-60 confirmed topoisomerases as ellipticine targets, but suggested distinct mechanisms of action and chemoresistance among them, providing a guide for selecting optimal drug candidates.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2005

Extracorporal liver support with molecular adsorbents recirculating system in patients with hepatitis B-associated fulminant hepatic failure.

Hepatitis B virus (HBV) infection is the most prevalent cause of fulminant hepatic failure (FHF) in the Far East. HBV-associated FHF is characterised by rapidly progressive end organ dysfunction/failure and a very poor prognosis. To investigate how molecular adsorbent recirculating system (MARS) treatment impacts multiple organ system function in HBV-associated FHF. Ten consecutive patients were treated with MARS in a period of 12 months. Clinical, biochemical and haemodynamic parameters were assessed before and after MARS. Various disease severity scoring systems including model for end-stage liver disease, APACHE II, APACHE III, sequential organ failure assessment and organ system failure scores were also assessed. There were significant improvements in hepatic encephalopathy grading (p < 0.001), mean arterial pressure (p < 0.001), plasma renin activity (p = 0.027), bilirubin (p < 0.001), ammonia (p = 0.001) and creatinine levels (p < 0.001). There were also significant improvements in all the scoring systems evaluated. Meanwhile, platelet count was significantly decreased (p < 0.001). One patient was successfully bridged to liver transplantation. Three patients were alive at 3 months of follow-up. MARS can improve multiple organ functions in HBV-associated FHF. On the basis of these findings, randomised controlled studies are indicated and justified.

Adult↗

PubMed2004

Destruction of organic pollutants in reusable wastewater using advanced oxidation technology.

This work studied the destruction of various M-EDTA complexes and trace organic pollutants in treated reusable wastewater under advanced oxidation using UV irradiation and ozonation. Effect of dosage of hydrogen peroxide and acidity of reaction matrices on oxidation efficiencies were investigated. The rate constant of mineralization presents a decreasing trend as Fe(III)-EDTA > Fe(II)-EDTA > Al(III)-EDTA > Pb(II)-EDTA > Na(I)-EDTA > Zn(II)-EDTA > Cu(II)-EDTA. The mineralization efficiencies using ozone alone are 15%, 40% and 15% for the water samples after reverse osmosis (RO), microfiltration (MF) and superfiltration (SF) processes, respectively. The presence of hydrogen peroxide in photochemical reaction matrixes can effectively enhance the mineralization of organic carbon species. When 150 mg l(-1) of H2O2 was added in the effluents, the mineralization markedly increased to 80%, 92% and 89%, respectively.

Edetic Acid↗

PubMed2004

Frequency-dependent laminar electroosmotic flow in a closed-end rectangular microchannel.

This article presents an analysis of the frequency- and time-dependent electroosmotic flow in a closed-end rectangular microchannel. An exact solution to the modified Navier-Stokes equation governing the ac electroosmotic flow field is obtained by using the Green's function formulation in combination with a complex variable approach. An analytical expression for the induced backpressure gradient is derived. With the Debye-Hückel approximation, the electrical double-layer potential distribution in the channel is obtained by analytically solving the linearized two-dimensional Poisson-Boltzmann equation. Since the counterparts of the flow rate and the electrical current are shown to be linearly proportional to the applied electric field and the pressure gradient, Onsager's principle of reciprocity is demonstrated for transient and ac electroosmotic flows. The time evolution of the electroosmotic flow and the effect of a frequency-dependent ac electric field on the oscillating electroosmotic flow in a closed-end rectangular microchannel are examined. Specifically, the induced pressure gradient is analyzed under effects of the channel dimension and the frequency of electric field. In addition, based on the Stokes second problem, the solution of the slip velocity approximation is presented for comparison with the results obtained from the analytical scheme developed in this study.

Journal Article↗

PubMed2004

Characterization and identification of the Detroit River mystery oil spill (2002).

In this paper, a case study of the Detroit River mystery oil spill (2002) is presented that demonstrates the utility of detailed and integrated oil fingerprinting in investigating unknown or suspected oil spills. The detailed diagnostic oil fingerprinting techniques include determination of hydrocarbon groups and semi-quantitative product screening, analysis of oil-characteristic biomarkers and the extended suite of parent and alkylated polycyclic aromatic hydrocarbons (PAHs), and quantitative determination of a variety of diagnostic ratios of "source-specific marker" compounds. The detailed chemical fingerprinting data and results highlight the followings: (1) The spill samples were largely composed of used lube oil mixed with smaller portion of diesel fuel. (2) The diesel in the samples had been weathered and degraded. (3) Sample 3 collected from N. Boblo Island on 14 April was more weathered (most probably caused by more evaporation and water-washing) than samples 1 and 2. (4) All fingerprinting results clearly demonstrated oils in three samples were the same, and they came from the same source. (5) Most PAH compounds were from the diesel portion in the spill samples, while the biomarker compounds were largely from the lube oil. (6) Input of pyrogenic PAHs to the spill samples was clearly demonstrated. The pyrogenic PAHs were most probably produced from combustion and motor lubrication processes, and the lube oil in these spill samples was waste lube oil.

Michigan↗

PubMed2004

Development of a recombinant human collagen-type III based hemostat.

Animal-tissue-derived collagen, containing mostly type I collagen with a minor amount of type III collagen, has been widely used in the production of hemostats for many decades, although it has been known for a long time that type III collagen is more likely to induce platelet aggregation in vitro. Because it is hard to purify type III from animal tissue, it has not been possible to correlate this finding with in vivo data. In this report, it is demonstrated that recombinant human collagen III fibrils are more capable of inducing platelet aggregation in vitro than those comprised of bovine collagen I, in agreement with previously published data on tissue-derived type III collagen. When formed into three-dimensional matrices, the use of type III collagen results in formulations with better mechanical integrity, larger surface area, and higher hemostatic activity in a rabbit spleen injury model as compared with commercially available hemostats formed from bovine type I collagen.

Animals↗

PubMed2004

Photochemical degradation of 1,3-dinitrobenzene in aqueous solution in the presence of hydrogen peroxide.

A study on the destruction of 1,3-dinitrobenzene (1,3-DNB) in aqueous solution was carried out under ultraviolet (UV) irradiation alone and UV irradiation in the presence of hydrogen peroxide (H2O2). The combination of UV and H2O2 is significantly effective in degrading 1,3-DNB in terms of initial reaction rate and the mineralization of organic carbons. The photodegradation process can be influenced in certain extent by increasing the content of H2O2 and the acidity of reaction matrices. It was found that a variety of phenolic intermediates and inorganic acid were formed via hydroxyl radicals attacking the parent compound. The UV/H2O2 oxidation of 1,3-DNB was characterized by pseudo-zero order reaction for the degradation of 1,3-DNB with a 20 times enhanced rate constant of 1.36 x 10(-7) Ms(-1) and the initial rate constant was dependent on the initial concentration of 1,3-DNB.

Chromatography, High Pressure Liquid↗

PubMed2004

Monitoring Aspergillus species by quantitative PCR during construction of a multi-storey hospital building.

During the enlargement of an existing hospital, quantitative polymerase chain reaction (PCR) was used to monitor Aspergillus spp. populations within the construction site. The rapid availability of results meant that the construction schedule was largely uninterrupted, while assuring that the new construction was free from contamination by the targeted Aspergillus spp.

Aspergillus↗

PubMed2004

Efficient inhibition of multidrug-resistant human tumors with a recombinant bispecific anti-P-glycoprotein x anti-CD3 diabody.

Overexpressing of P-glycoprotein (Pgp) has been shown to be responsible for cancer resistance to multiple chemotherapeutic agents. Immunotherapy with biological agents, such as bispecific antibodies (BsAbs), may represent a promising approach to overcome the emergence of drug resistance. Here we constructed a recombinant BsAb, a diabody, with specificities to both CD3 on human T-lymphocyte and Pgp on cancer cells. The diabody was produced in Escherichia coli in a soluble functional form and purified by an affinity chromatography with a yield of >4 mg/l culture medium in shaker flask. The diabody binds to both CD3 on T-lymphocytes and Pgp on multidrug-resistant (MDR) tumor cells with affinities that are comparable to its respective parental single chain Fv molecules. In the presence of activated human peripheral blood lymphocytes (PBLs), the diabody mediates effectively the lysis of the Pgp-overexpressing human leukemia K562/A02 and epidermoid carcinoma KBv(200) cells, but is much less potent in mediating the lysis of the parent K562 and KB cells. Further, the diabody localized selectively within the K562/A02 xenografts in mice. When combined with activated PBL, the diabody significantly inhibited the growth of K562/A02 and KBv(200), but had no effect on K562 and KB xenografts. In contrast, treatment with doxorubicin, a standard chemotherapeutic agent, only inhibited the growth of K562 and KB, but had no effect on K562/A02 and KBv(200) xenografts. Taken together, our results suggest that the anti-Pgp x anti-CD3 diabody may have a great potential in the treatment of various MDR cancers.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2004

[Measurements of Gamma-Knife helmet output factors using a radiophotoluminescent glass rod dosimeter and a diode detector].

A radiophotoluminescent (RPL) glass rod dosimeter (GRD) and a small active volume p-type silicon diode detector (stereotactic field detector, SFD) were used for the measurement of Gamma-Knife output factors. All measurements were done using a 16 cm diameter spherical polystyrene phantom with the detector at the focal spot of Gamma-Knife. The GRD system consists of small rod-shaped glass chip detectors and an automatic readout device. The output factors measured with GRD of the 14, 8 and 4 mm helmets relative to the 18 mm helmet are 0.981, 0.942 and 0.877, respectively. Similarly, the corresponding output factors measured with SFD are 0.980, 0.949 and 0.867, respectively. These output factors are comparable with the values given in a recent publication and the values recommended by Elekta, the manufacture. The angular dependence of these detectors is also measured using a linear accelerator-based stereotactic radiosurgery system. For the Gamma-Knife angle ranging from 6 to 36 degrees from the vertical axis, the measured angular dependence of the GRD is approximately 1.0% at a 4 MV x-ray beam. The response of SFD indicates approximately 3-4% directional dependence for the same angle range for a 6 MV x-ray beam. The Gamma-Knife helmet output factors measured with SFD are corrected for angular dependence. In summary, GRD can be a good candidate in measuring small field output factor. Due to an angular dependence the small p-type diode detector needs care when calculating the Gamma-Knife dose.

Glass↗

PubMed2003

Progress in silicon-based quantum computing.

We review progress at the Australian Centre for Quantum Computer Technology towards the fabrication and demonstration of spin qubits and charge qubits based on phosphorus donor atoms embedded in intrinsic silicon. Fabrication is being pursued via two complementary pathways: a 'top-down' approach for near-term production of few-qubit demonstration devices and a 'bottom-up' approach for large-scale qubit arrays with sub-nanometre precision. The 'top-down' approach employs a low-energy (keV) ion beam to implant the phosphorus atoms. Single-atom control during implantation is achieved by monitoring on-chip detector electrodes, integrated within the device structure. In contrast, the 'bottom-up' approach uses scanning tunnelling microscope lithography and epitaxial silicon overgrowth to construct devices at an atomic scale. In both cases, surface electrodes control the qubit using voltage pulses, and dual single-electron transistors operating near the quantum limit provide fast read-out with spurious-signal rejection.

Journal Article↗

PubMed2003

Transmission confocal laser scanning microscopy with a virtual pinhole based on nonlinear detection.

We present a transmission-mode confocal laser scanning microscope system based on the use of second-harmonic generation (SHG) for signal detection. Our method exploits the quadratic intensity dependence of SHG to preferentially reveal unscattered signal light and reject out-of-focus scattered background. The SHG crystal acts as a virtual pinhole that remains self-aligned without the need for descanning.

Microscopy, Confocal↗

PubMed2003

Complete nucleotide sequence and genome organization of a Chinese isolate of tobacco bushy top virus.

The complete nucleotide sequence of a Chinese isolate of tobacco bushy top virus (TBTV), designated TBTV-Ch, was determined from cDNA generated from double-stranded RNA extracted from diseased tobacco. The genome is 4152 nucleotides (nt) in size, contains four putative open reading frames (ORFs) and untranslated regions of 10 nt and 645 nt at the 5' and 3' ends, respectively. In genome organization and in the amino acid sequence of its potential products, the RNA of TBTV-Ch is similar to other umbraviruses sequenced to date. The results suggested that TBTV should be regarded as a definitive species of the genus Umbravirus.

Base Sequence↗

PubMed2003

Card15 gene overexpression in mononuclear and epithelial cells of the inflamed Crohn's disease colon.

BACKGROUND: Crohn's disease is one of the principal human chronic inflammatory bowel diseases. Although its aetiology is still unknown, its complex pathogenesis has environmental, immunological, and genetic determinants. CARD15 is the first susceptibility gene implicated in the predisposition to Crohn's disease and is known to be expressed only in monocytes. However, its expression in situ has not yet been studied. AIMS: To analyse the tissue distribution of CARD15 and identify cells producing CARD15 in samples of colon from patients with Crohn's disease and control subjects. PATIENTS AND METHODS: We analysed CARD15 gene expression in surgical specimens of colon from eight children with Crohn's disease and nine controls by immunohistochemistry, in situ hybridisation, and reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: We showed that CARD15 was present only in the cytoplasm of macrophages in the normal colon. Increased CARD15 expression was detected in Crohn's disease lesions. There were more CARD15 positive cells in Crohn's disease lesions than in uninvolved areas. Both intestinal epithelial cells, macrophages, and their derivatives overproduced CARD15 in Crohn's disease. To further assess CARD15 expression by intestinal epithelial cells, we performed RT-PCR on freshly isolated intestinal epithelial cells, and showed that these cells isolated from Crohn's disease samples contained more CARD15 mRNA than intestinal epithelial cells from controls. CONCLUSIONS: We have demonstrated that colonic involvement in active Crohn's disease is associated with increased CARD15 gene expression in both macrophages and intestinal epithelial cells. Therefore, this deregulation can affect the host-environment interaction and thus contribute to the pathogenesis of this disease.

Acute Disease↗

PubMed2003

Destruction of model organic pollutants in water using ozone, UV and their combination (Part I).

The experimental results showed that ozone (O3) oxidation is an effective means to destroy phenolic organic pollutants present in water. High removal efficiencies can be readily achieved for most of the model compounds fortified in aqueous matrices within a reasonable time frame. This study also included the oxidation of phenolic compounds using ozone in combination with ultraviolet (UV) irradiation. The extent of mineralization measured in terms of the losses in total organic carbon is promoted by the joint action of ozone and UV in comparison with using ozone alone.

Organic Chemicals↗

PubMed2003

Biomass accumulation patterns for removing volatile organic compounds in rotating drum biofilters.

A rotating drum biofilter (RDB) with multi-layered foam media was developed for the improvement of current biofiltration technology. The biofilter was used to investigate the effects of organic loadings and influent volatile organic compound (VOC) concentrations on VOC removal efficiency and biomass accumulation. These effects were evaluated using diethyl ether and toluene separately as model VOCs at an empty bed contact time (EBCT) of 30 s. When the toluene loading increased from 2.0 to 4.0 and 8.0 kgCOD m(-3) day(-1), toluene removal efficiency of the biofilter decreased from over 99% to 78% and 74%, respectively. The biomass distribution was found to be more even within the medium when removing toluene than when removing diethyl ether. Higher organic loading also resulted in the more even distribution of the biomass. The ratios of biomass accumulation rates in the medium of the outermost, middle and innermost layers ranged from 1:0.11:0.02 when removing diethyl ether at 2.0 kgCOD m(-3) day(-1) to 1:0.69:0.51 when removing toluene at 8.0 kgCOD m(-3) day(-1). Review of these ratios revealed three biomass accumulation patterns: surface pattern, in-depth pattern and shallow pattern. Different patterns represent different removal mechanisms in the biofiltration process. Improved biofilter design and operation should be based on the biomass accumulation pattern.

Biodegradation, Environmental↗

PubMed2002

Integration of the information from gene expression and metabolic fluxes for the analysis of the regulatory mechanisms in Synechocystis.

Synechocystis was grown under autotrophic, mixotrophic and heterotrophic conditions, and the gene expression patterns at the mRNA and protein levels were measured by using semi-quantitative RT-PCR and two-dimensional electrophoresis (2DE), respectively. Moreover, the intracellular metabolic flux distributions in Synechocystis grown under different trophic conditions were also determined using the carbon isotope labeling technique. By combining the information obtained from the transcript levels, protein abundance and metabolic fluxes, the regulatory mechanisms of some enzymes involved in the central metabolism of Synechocystis during growth in the different culture conditions were analyzed. It was found that depending on the energy source available to cyanobacterial cells, the enzymes required for central metabolism were differently regulated according to different mechanisms. The expression of several genes, such as rbcLS and gap2, was light-regulated transcriptionally, while the gene gnd was regulated in response to an apparent flux requirement but by an unknown mechanism. The expression of other genes was independent of the presence of light. The reactions catalyzed by G6PDH, Fbp, PfkA and FbaA were not regulated through enzyme synthesis but by a change in metabolite concentrations. The enzyme PrK was post-translationally regulated by light, probably through the operation of ferredoxin/thioredoxin system. For the enzyme RubisCO, both transcriptional and post-translational regulation was observed. These findings demonstrate that the information obtained from the analysis of mRNA expression, protein expression, and metabolic flux distribution is necessary to understand the regulatory events in complex cellular networks.

Cyanobacteria↗

PubMed2002

Pharmacogenomic analysis: correlating molecular substructure classes with microarray gene expression data.

Genomic studies are producing large databases of molecular information on cancers and other cell and tissue types. Hence, we have the opportunity to link these accumulating data to the drug discovery processes. Our previous efforts at 'information-intensive' molecular pharmacology have focused on the relationship between patterns of gene expression and patterns of drug activity. In the present study, we take the process a step further-relating gene expression patterns, not just to the drugs as entities, but to approximately 27,000 substructures and other chemical features within the drugs. This coupling of genomic information with structure-based data mining can be used to identify classes of compounds for which detailed experimental structure-activity studies may be fruitful. Using a systematic substructure analysis coupled with statistical correlations of compound activity with differential gene expression, we have identified two subclasses of quinones whose patterns of activity in the National Cancer Institute's 60-cell line screening panel (NCI-60) correlate strongly with the expression patterns of particular genes: (i) The growth inhibitory patterns of an electron-withdrawing subclass of benzodithiophenedione-containing compounds over the NCI-60 are highly correlated with the expression patterns of Rab7 and other melanoma-specific genes; (ii) the inhibitory patterns of indolonaphthoquinone-containing compounds are highly correlated with the expression patterns of the hematopoietic lineage-specific gene HS1 and other leukemia genes. As illustrated by these proof-of-principle examples, we introduce here a set of conceptual tools and fluent computational methods for projecting directly from gene expression patterns to drug substructures and vice versa. The analysis is presented in terms of the NCI-60 cell lines and microarray-based gene expression patterns, but the concept and methods are broadly applicable to other large-scale pharmacogenomic database sets as well. The approach (SAT for Structure-Activity-Target) provides a systematic way to mine databases for the design of further structure-activity studies, particularly to aid in target and lead identification.

Algorithms↗