Biomedical subjects

Yuxiang Zhou

Publications and source records attributed to Yuxiang Zhou.

11 recordsLinked to original sources

PubMed2006

Microelectrode array-based system for neuropharmacological applications with cortical neurons cultured in vitro.

Microelectrode arrays (MEAs) provide a means to investigate the electrophysiological behavior of neuronal systems through the measurements from neuronal culture preparations. Changes in activity patterns of neuronal networks are usually detected by applying neural chemicals. Because of the difficulties of fabricating the arrays, and the delicate and less reliable properties of cortical neurons, MEA-based systems with cortical neuronal networks for neurophamacological applications are technically difficult, therefore restricting their utility. Here, we report a new approach to the development of such MEA-based system with sensitive and durable MEAs conveniently fabricated and the culture conditions optimized. Upon growth differentiation, cortical neurons, cultured directly on MEAs, reach a developmentally stable and reliable activity state. With this system, we monitored the global spontaneous activities of neuronal networks and demonstrated the fine discrimination for specific substances and unique property of cortical neurons, which validated both the applicability and necessity of such system in pharmacological bioassay.

Action Potentials↗

PubMed2006

Cyclooxygenase-independent effects of aspirin on HT-29 human colon cancer cells, revealed by oligonucleotide microarrays.

Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) inhibit proliferation of human colon cancer cells in vitro. Transmission electron microscope detected morphological features of apoptosis in the aspirin-treated (5 mM, 72 h) HT-29 cells in which cyclooxygenoase-2 is catalytically inactive. We investigated aspirin-induced genome-wide expression changes in HT-29 cells and further studied the time- and concentration-dependent expression changes in 374 apoptosis-related genes, which is the first to show stimulation of genome-wide expression of HT-29 cells by aspirin. The most marked effects of aspirin are on ribosome assembly and rRNA metabolism, which could explain why the quasi-apoptotic morphological changes are not accompanied by a classical DNA ladder. These findings demonstrate that aspirin induces apoptosis in HT-29 cells, bolstering the hypothesis that apoptosis may be a mechanism by which NSAIDs inhibit colon carcinogenesis.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2006

Selective photoelectrochemical detection of DNA with high-affinity metallointercalator and tin oxide nanoparticle electrode.

Selective detection of double-stranded DNA (ds-DNA) in solution was achieved by photoelectrochemistry using a high-affinity DNA intercalator, Ru(bpy)2dppz (bpy = 2,2'-bipyridine, dppz = dipyrido[3,2-a:2',3'-c]phenazine) as the signal indicator and tin oxide nanoparticle as electrode material. When Ru(bpy)2dppz alone was irradiated with 470-nm light, anodic photocurrent was detected on the semiconductor electrode due to electron injection from its excited state into the conduction band of the electrode. The current was sustained in the presence of oxalate in solution, which acted as a sacrificial electron donor to regenerate the ground-state metal complex. After addition of double-stranded calf thymus DNA into the solution, photocurrent dropped substantially. The drop was attributed to the intercalation of Ru(bpy)2dppz into DNA and, consequently, the reduced mass diffusion of the indicator to the electrode, as well as electrostatic repulsion between oxalate anion and negative charges on DNA. The degree of signal reduction was a function of the DNA concentration, thus forming the basis for real-time DNA detection. The signal reduction was selective for ds-DNA, as no such effect was observed for single-stranded polynucleotides such as poly-G, poly-C, poly-A, and poly-U. The detection limit of calf thymus ds-DNA reached 1.8 x 10(-10) M in solution.

DNA↗

PubMed2006

Genomewide oligonucleotide microarray analysis on placentae of pre-eclamptic pregnancies.

OBJECTIVE: Human placentae from normal and pre-eclamptic pregnancies were evaluated for possible changes in gene expression by microarray analysis to uncover new clues for the research of the etiology of pre-eclampsia. METHODS: Placentae from five normal pregnancies and five pregnancies complicated by pre-eclampsia were collected. mRNA levels of five pre-eclamptic placentae were examined using genome-wide 70-mer oligonucleotide microarrays (CapitalBio, Beijing, China) in comparison with the pooled control consisting of total RNA from five normotensive placentae. RESULTS: Ninety-six genes were found consistently down- or up-regulated in at least four pre-eclamptic samples. Most of them were related to an imbalance of reactive oxygen metabolites in placenta, abnormal trophoblast invasion, disorders of lipoprotein metabolism and signal transduction, or some that have been reported to have close correlation to the pathology of pre-eclampsia. The microarray data were also confirmed by the measurement of real-time PCR. CONCLUSION: DNA microarray is a high throughput and time-saving method to monitor altered gene expression. The results could provide interesting clues to the etiology of pre-eclampsia and lead to further studies in a more targeted fashion.

Adult↗

PubMed2006

Genome-wide analysis of the expression profile of Saccharomyces cerevisiae in response to treatment with the plant isoflavone, wighteone, as a potential antifungal agent.

The limitations of currently available antifungal agents and the rapid emergence of drug-resistant strains necessitate more efficient approaches to screening and developing novel antifungal drugs. The antifungal activity of the natural products of a series of plants was evaluated and wighteone, 5, 7, 4'-trihydroxy-6-(gamma,gamma-dimethylallyl)isoflavone showed excellent anti-yeast activity (MIC against Saccharomyces cerevisiae was 4 microg/ml). Transcriptome profiling of wighteone-treated S. cerevisiae indicated that wighteone is different from commonly used antifungal compounds in its mode of action.

Antifungal Agents↗

PubMed2005

Genomic analysis of anti-hepatitis B virus (HBV) activity by small interfering RNA and lamivudine in stable HBV-producing cells.

Hepatitis B virus (HBV) causes acute and chronic hepatitis and hepatocellular carcinoma. Small interfering RNA (siRNA) and lamivudine have been shown to have anti-HBV effects through different mechanisms. However, assessment of the genome-wide effects of siRNA and lamivudine on HBV-producing cell lines has not been reported, which may provide a clue to interrogate the HBV-cell interaction and to evaluate the siRNA's side effect as a potential drug. In the present study, we designed seven siRNAs based on the conserved HBV sequences and tested their effects on the expression of HBV genes following sorting of siRNA-positive cells. Among these seven siRNAs, siRNA-1 and siRNA-7 were found to effectively suppress HBV gene expression. We further addressed the global gene expression changes in stable HBV-producing cells induced by siRNA-1 and siRNA-7 by use of human genome-wide oligonucleotide microarrays. Data from the gene expression profiling indicated that siRNA-1 and siRNA-7 altered the expression of 54 and 499 genes, respectively, in HepG2.2.15 cells, which revealed that different siRNAs had various patterns of gene expression profiles and suggested a complicated influence of siRNAs on host cells. We further observed that 18 of these genes were suppressed by both siRNA-1 and siRNA-7. Interestingly, seven of these genes were originally activated by HBV, which suggested that these seven genes might be involved in the HBV-host cell interaction. Finally, we have compared the effects of siRNA and lamivudine on HBV and host cells, which revealed that siRNA is more effective at inhibiting HBV expression at the mRNA and protein level in vitro, and the gene expression profile of HepG2.2.15 cells treated by lamivudine is totally different from that seen with siRNA.

Antiviral Agents↗

PubMed2004

Direct detection of 16S rRNA using oligonucleotide microarrays assisted by base stacking hybridization and tyramide signal amplification.

A simple method has been developed and validated for direct, sensitive detection and specific identification of 16S rRNA. We first report our direct investigation of discrimination efficiency for sequence variations in RNA using oligonucleotide microarrays assisted by base stacking hybridization, and demonstrate that the sequence variations of double base substitution, single base substitution and single base deletion in RNA could be directly identified. With the help of tyramide signal amplification (TSA), the detection sensitivity of this method for four clinically important bacterial species was below 0.5, 5, 1 and 1 ng of total RNA, which are 100-1000 fold more sensitive than the published methods.

DNA Probes↗

PubMed2003

The polymorphisms of intron1 sequences of HLA-A and -B.

Human leucocyte antigen (HLA) class I antigens are highly polymorphic membrane glycoproteins present on most nucleated cells. The polymorphism region is mainly located in exons 2 and 3 of HLA class I genes, which is flanked by introns 1 and 3. Thus, the sequence information of introns 1 and 3 is important for the genotyping of HLA. However, the information about them has not been extensively reported by now. In this work, the intron 1 sequences of HLA-A and -B of 51 standard genomic DNAs provided by the 13th International Histocompatibility Work Group (IHWG) were cloned and sequenced. The polymorphism of the intron sequences were also analyzed by the software Clustal W 1.82. Some sequences were chosen to compare with the standard sequences published in National Center for Biotechnology Information (NCBI). The comparison showed that all the sequences matched exactly with the standard sequences. The knowledge of intron 1 sequences could be very important not only for developing DNA-based typing strategies for the HLA-A and -B alleles but also for establishing an understanding of the evolutionary mechanisms involved in the polymorphism generation of HLA class I alleles.

HLA-A Antigens↗

PubMed2003

Detection of known mutations in hypertrophic cardiomyopathy using oligonucleotide microarrays assisted by improved base stacking hybridization.

With the assistance of improved base stacking hybridization, a low-density microarray, containing 12 capture probes, was used to identify 7 known hypertrophic cardiomyopathy-related mutations in the gene of MYH7 (beta-myosia heavy chain). The hybridization targets, amplified from 11 plasmids containing wild type or mutation sequences of MYH7 and healthy genomic DNA, were prepared by single-step fluorescence labeled asymmetric PCR. Six single base substitutions and a trinucleotide deletion were identified unambiguously, and the average discrimination ratio (Qmut) for artificial heterozygous samples was as high as 16.2.

Base Sequence↗

PubMed2002

Expression profiling of the response of Saccharomyces cerevisiae to 5-fluorocytosine using a DNA microarray.

5-Fluorocytosine is a commonly used antifungal agent. It acts by inhibiting the synthesis of fungal DNA and protein. In order to understand the global response of Saccharomyces cerevisiae to changes in DNA and protein synthesis caused by 5-fluorocytosine, genome-wide transcript profiling following 5-fluorocytosine exposure was obtained. A total of 96 genes were identified as responsive to 25 microg/ml fluorocytosine treatment for 90 min, which caused approximately 17% specific growth inhibition. The transcript levels of 57 genes were increased more than 2-fold, while it was found that the transcript levels of the other 39 genes decreased to a similar extent. Genes involved in DNA repair, synthesis and replication represented the highest proportion of induced genes identified, which may account for the easily acquired resistance to 5-fluorocytosine. Two enzyme encoding genes CTS1 and EGT2, which function in the separation of daughter cells from their mother cells, were down-regulated by a factor of 3.7 and 10.2, respectively, indicating that 5-fluorocytosine may also inhibit the separation of fungal cells.

Antifungal Agents↗

PubMed2002

Response of gene expression in Saccharomyces cerevisiae to amphotericin B and nystatin measured by microarrays.

The response of the yeast Saccharomyces cerevisiae to two polyene antibiotics, amphotericin B and nystatin, was studied by genomic expression profiling. The two agents produced highly similar expression pattern changes, which was consistent with their known identical mechanisms of action on cell membranes. Detailed analysis was focused on the amphotericin B-treated sample in this study. Our data showed that genes involved in mitochondrial ribosomal protein synthesis were more severely repressed than those in the cytoplasm, which might contribute to the cytotoxicity of amphotericin B. To counteract the leakage of intracellular nutrients and ions from the pores in the cell membrane caused by amphotericin B, c. 17 genes involved in transport facilitation were induced, presumably to allow more efficient uptake of nutrients and ions. The expression level of five genes involved in ergosterol synthesis dropped and three genes related to cell wall biogenesis were induced, indicating that the cell membrane and cell wall were also affected by the presence of polyene antibiotics. It was observed that the pleiotropic drug resistance network in yeast cells was activated after exposure to amphotericin B, possibly contributing to the acquisition of amphotericin B resistance. Part of the gene expression alteration measured by microarray was confirmed by quantitative RT-PCR.

Amphotericin B↗