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Biomedical subjects

Yi Wang

Publications and source records attributed to Yi Wang.

At least 37 records · Page 2Linked to original sources
PubMed2007

Nonspecific cellular accumulation of 99mTc-labeled oligonucleotides in culture is influenced by their guanine content.

Specific accumulation of radiolabeled antisense oligonucleotides as a result of binding by an antisense mechanism to target mRNAs in tumor has been repeatedly observed. However, the mechanisms responsible for nonspecific cellular accumulation remain almost completely unexplored. We have occasionally observed in cell culture nonspecific accumulations of 99mTc-labeled sense, scrambled or random control oligonucleotides in tumor cells comparable to or even higher than those of the corresponding antisense oligonucleotides. We have also observed that these nonspecific accumulations of control oligonucleotides are sequence dependent. To explore the influence of base composition on nonspecific accumulation, we used MCF-7 breast cancer cells, along with 10 uniform phosphorothioates and 5 uniform phosphodiesters oligonucleotides. Three of the phosphorothioates were antisense against different sites within the survivin mRNA, and two were the corresponding sense and scrambled controls. In addition, the accumulations in MCF-7 cells of radiolabeled poly A, poly C, poly T and poly GGGA phosphorothioate oligonucleotides were also studied to explore the influence of each nitrogenous base on the nonspecific cell accumulations of phosphorothioate oligonucleotides. Our results show that guanine content is an important determinant of nonspecific cellular accumulations under the conditions of this investigation. If this observation can be shown to be universally applicable to other cell types, then the selection of control sequences in studies of antisense tumor targeting should avoid those that are guanine rich, if possible.

Breast Neoplasms↗
PubMed2006

Mechanism of dihydroneopterin aldolase: functional roles of the conserved active site glutamate and lysine residues.

Dihydroneopterin aldolase (DHNA) catalyzes the conversion of 7,8-dihydroneopterin (DHNP) to 6-hydroxymethyl-7,8-dihydropterin (HP) in the folate biosynthetic pathway. There are four conserved active site residues at the active site, E22, Y54, E74, and K100 in Staphylococcus aureus DHNA (SaDHNA), corresponding to E21, Y53, E73, and K98, respectively, in Escherichia coli DHNA (EcDHNA). The functional roles of the conserved glutamate and lysine residues have been investigated by site-directed mutagenesis in this work. E22 and E74 of SaDHNA and E21, E73, and K98 of EcDHNA were replaced with alanine. K100 of SaDHNA was replaced with alanine and glutamine. The mutant proteins were characterized by equilibrium binding, stopped-flow binding, and steady-state kinetic analyses. For SaDHNA, none of the mutations except E74A caused dramatic changes in the affinities of the enzyme for the substrate or product analogues or the rate constants. The Kd values for SaE74A were estimated to be >3000 microM, suggesting that the Kd values of the mutant are at least 100 times those of the wild-type enzyme. For EcDHNA, the E73A mutation increased the Kd values for the substrate or product analogues neopterin (MP), monapterin (NP), and 6-hydroxypterin (HPO) by factors of 340, 160, and 5600, respectively, relative to those of the wild-type enzyme. The K98A mutation increased the Kd values for NP, MP, and HPO by factors of 14, 3.6, and 230, respectively. The E21A mutation increased the Kd values for NP and HPO by factors of 2.2 and 42, respectively, but decreased the Kd value for MP by a factor of 3.3. The E22 (E21) and K100 (K98) mutations decreased the kcat values by factors of 1.3-2 x 10(4). The E74 (E73) mutation decreased in the kcat values by factors of approximately 10. The results suggested that E74 of SaDHNA and E73 of EcDHNA are important for substrate binding, but their roles in catalysis are minor. In contrast, E22 and K100 of SaDHNA are important for catalysis, but their roles in substrate binding are minor. On the other hand, E21 and K98 of EcDHNA are important for both substrate binding and catalysis.

Aldehyde-Lyases↗
PubMed2006

Comparison of linear and nonlinear analysis in estimating the Thomas model parameters for methylene blue adsorption onto natural zeolite in fixed-bed column.

Comparison analysis of linear least square method and nonlinear least square method for estimating the kinetic parameters was made using the experimental column data of methylene blue (MB) adsorption onto zeolite at different flow rates and initial concentration. The data were fitted to Thomas model equations using linear and nonlinear regressive analysis, respectively. The error analysis was performed. Present investigation showed that the linear and nonlinear methods are both suitable to predict the breakthrough curves using Thomas model parameters and the nonlinear method is better.

Adsorption↗
PubMed2006

Removal of low-concentration ammonia in water by ion-exchange using Na-mordenite.

Removal of low-concentration ammonia (2-10ppm) in water by ion exchange with Na-form zeolites was investigated using a flow system at 278-333K. Results indicated that Na-mordenite was the most efficient cation-exchanger (compared with Na-ferrierite, Na-ZSM-5, Na-beta, and Na-Y, as well as the K- and H-form mordenite) for the removal of low-concentration ammonia. The ammonia uptake and the ion-exchange level achieved using mordenite with NH(4)(+) for removal of 10ppm ammonia at 333K were 1.21mmolg(-1) and 79.1%, respectively. The high efficiency of Na-mordenite for removal of low-concentration ammonia in water is due to the strong acidity of the corresponding H-form mordenite as demonstrated by ammonia temperature-programmed desorption. Ammonia uptake on the Na-mordenite was minimally influenced by operating temperature in the range of 278-333K. The coexistent K(+) and Na(+) in water had little influence on ammonia uptake of the Na-mordenite. In contrast, coexistent Ca(2+) and Mg(2+) significantly lowered the efficiency of the Na-mordenite for ammonia removal.

Aluminum Silicates↗
PubMed2006

Effect of mu-opioid receptor gene polymorphisms on heroin-induced subjective responses in a Chinese population.

BACKGROUND: Genetic factors that influence subjective responses to drug use (such as euphoria) contribute to the risk of addiction. mu-opioid receptor is the molecular target of heroin mediating its effects in both pain relief and euphoria. METHODS: To evaluate the association of mu-opioid receptor gene (OPRM1) variants with heroin-induced positive responses on first use, we studied 336 Chinese Han heroin addicts recruited in Shanghai and divided heroin addicts into two groups (positive vs. negative) according to the self-reporting feeling on first use. Association analyses with the genotypes and alleles in nine tagging single nucleotide polymorphisms (tSNPs) in OPRM1 with subjective responses were performed. Similar analysis with haplotypes of these tSNPs was also performed. RESULTS: Allele frequencies of three tSNPs were significantly different between the positive and negative groups. They were rs696522 (odds ratio [OR] = 3.06, p = .0013), rs1381376 (OR = 3.16, p = .0008), and rs3778151 (OR = 3.12, p = .0004). Such association remains after adjustment for demographic covariates and for multiple testing. The subjects with heroin-induced positive responses on first use consumed more drugs than the negative group (Mann-Whitney U = 224.0, Wilcoxon W = 16334.0, p <or= .0001). CONCLUSIONS: Self-reported positive responses on first use of heroin were found to be associated with OPRM1. The findings suggest that heroin-induced positive responses are likely associated with more heroin consumption.

Adult↗
PubMed2006

Imaging using parallel integrals in optical projection tomography.

We develop and demonstrate improved image-forming optics for optical projection tomography (OPT), with which the parallel integral throughout an object can be obtained. This method results in an improved resolution for OPT images, especially for the cross sections far from the optical axis of the image-forming optics. We find the optimal configuration used in our OPT system by use of a point spread function and simulation technique. The new method is validated by both numerical simulations and experimental results. The spatial resolution of the OPT system presented is approximately 40 microm.

Animals↗
PubMed2006

Characterization of the nuclear import pathways of galectin-3.

Galectin-3 (Gal-3), a pleiotropic beta-galactoside-binding protein, was shown to be involved in several nuclear-dependent functions, including up-regulation of transcriptional factors, RNA processing, and cell cycle regulation. Gal-3 compartmentalization in the nucleus versus the cytoplasm affects, in part, the malignant phenotype of various cancers. However, to date, the mechanism by which Gal-3 translocates into the nucleus remains debatable. Thus, we have constructed and expressed a variety of fusion proteins containing deletion mutants of Gal-3 fused with monomers, dimers, and trimers of enhanced green fluorescent protein and searched for the Gal-3 sequence motifs essential for its nuclear localization in vivo. In addition, a digitonin-permeabilized, cell-free transport in vitro assay was used to directly examine the mechanism of Gal-3 nuclear import. Partial deletions of the COOH-terminal region (114-250) of the human Gal-3 significantly decreases its nuclear translocation, whereas a peptide (1-115) was transported to the nuclei. The in vitro nuclear import assay revealed that there are at least two independent nuclear pathways for shuttling Gal-3 into the nucleus: a passive diffusion and an active transport. This is the first article providing direct evidence for the nuclear import mechanisms of Gal-3 and suggests that Gal-3 nuclear translocation is governed by dual pathways, whereas the cytoplasmic/nuclear distribution may be regulated by multiple processes, including cytoplasmic anchorage, nuclear retention, and or nuclear export. These results may lead to the development of a therapeutic modality aiming at abrogating Gal-3 translocation into the nucleus and thus hampering its activity during cancer progression and metastasis.

Active Transport, Cell Nucleus↗
PubMed2006

A point mutation converts dihydroneopterin aldolase to a cofactor-independent oxygenase.

Dihydroneopterin aldolase (DHNA) catalyzes the conversion of 7,8-dihydroneopterin (1) to 6-hydroxymethyl-7,8-dihydropterin (4) in the folate biosynthetic pathway. Substitution of a conserved tyrosine residue at the active site of DHNA by phenylalanine converts the enzyme to a cofactor-independent oxygenase, which generates mainly 7,8-dihydroxanthopterin (6) rather than 4. 6 is generated via the same enol intermediate as in the wild-type enzyme-catalyzed reaction, but this species undergoes an oxygenation reaction to form 6. The conserved tyrosine residue plays only a minor role in the formation of the enol reaction intermediate but a critical role in the protonation of the enol intermediate to form 4.

Aldehyde-Lyases↗
PubMed2006

A simple, two-step, site-specific preparation of fluorinated naphthalene and phenanthrene derivatives from fluorobromo-substituted alkenes.

A facile two-step procedure for the site-specific preparation of fluorinated naphthalene and phenanthrene derivatives is described. The Sonogashira reaction of bromofluoro-substituted alkenes with terminal alkynes, followed by base-catalyzed cyclization in refluxing N-methyl-2-pyrrolidinone (NMP), affords the corresponding fluorinated naphthalene and phenanthrene derivatives in good yields.

Journal Article↗
PubMed2006

A rationally designed agonist antibody fragment that functionally mimics thrombopoietin.

By using rational design, antibody fragments (Fabs) that mimic thrombopoietin (TPO) were created. A peptide with cMpl receptor-binding capability was grafted into different complementarity-determining regions of a fully human Fab scaffold. Functional presentation of the peptide was optimized by using phage display and cell-based panning. Select antibodies and fragments containing two grafted peptides were assayed for their ability to stimulate the cMpl receptor in vitro. Several candidates demonstrated agonist activity in an in vitro cMpl receptor signaling reporter assay, including Fab59, which was estimated to be equipotent to TPO. Fab59 additionally was able to effectively stimulate platelet production in normal mice. These rationally designed mimetic Fabs may provide a therapeutic intervention for thrombocytopenia while avoiding the potential generation of neutralizing antibodies to endogenous TPO. Furthermore, this study demonstrates a method by which short-lived linear peptides with binding activity may be converted to more stable and potent agonists capable of activating cell surface receptors.

Animals↗
PubMed2006

Identification of hepatitis C virus (HCV) 2a-derived epitope peptides having the capacity to induce cytotoxic T lymphocytes in human leukocyte antigen-A24+ and HCV2a-infected patients.

Since virus-specific cytotoxic T lymphocytes (CTLs) play a critical role in preventing the spread of hepatitis C virus (HCV), vaccine-based HCV-specific CTL induction could be a promising strategy to treat HCV-infected patients. In this study, we tried to identify HCV2a-derived epitopes, which can induce human leukocyte antigen (HLA)-A24-restricted and peptide-specific CTLs. Peripheral blood mononuclear cells of HCV2a-infected patients or healthy donors were stimulated in vitro with HCV2a-derived peptides, which were prepared based on the HLA-A24 binding motif. As a result, three peptides (HCV2a 576-584, HCV2a 627-635, and HCV2a 1085-1094) efficiently induced peptide-specific CTLs from HLA-A24(+) HCV2a-infected patients as well as healthy donors. The cytotoxicity was exhibited by peptide-specific CD8(+) T cells in an HLA-A24-restricted manner. In addition, the HCV2a 627-635 peptide was frequently recognized by immunoglobulin G of HCV2a-infected patients. These results indicate that the identified three HCV2a peptides might be applicable to peptide-based immunotherapy for HLA-A24(+) HCV2a-infected patients.

Cell Line, Tumor↗
PubMed2006

DNA repair protein involved in heart and blood development.

Apurinic/apyrimidinic endonuclease 1, a key enzyme in repairing abasic sites in DNA, is an embryonic lethal in mice. We are examining its role in embryogenesis in zebra fish. Zebra fish contain two genomic copies (zfAPEX1a and zfAPEX1b) with identical coding sequences. zfAPEX1b lacks introns. Recombinant protein (ZAP1) is highly homologous with and has the same enzymatic properties as its human orthologue. ZAP1 is highly expressed throughout development. Embryos microinjected with morpholino oligonucleotide (MO) targeting the translation start site die at approximately the midblastula transition (MBT) without apoptosis. They are rescued with mRNA for human wild-type APEX1 but not for APEX1 encoding endonuclease-defective protein. Rescued embryos develop dysmorphic hearts, pericardial edema, few erythrocytes, small eyes, and abnormal notochords. Although the hearts in rescued embryos form defective loops ranging from no loop to one that is abnormally shaped, cardiac myosin (cmlc2) is present and contraction occurs. Embryos microinjected with MO targeting zfAPEX1a intron-exon junctions also pass the MBT with similar abnormalities. We conclude that AP endonuclease 1 is involved in both repairing DNA and regulating specific early stages of embryonic development.

Amino Acid Sequence↗
PubMed2006

Phosphotyrosine profiling identifies the KG-1 cell line as a model for the study of FGFR1 fusions in acute myeloid leukemia.

The 8p11 myeloproliferative syndrome (EMS) is associated with translocations that disrupt the FGFR1 gene. To date, 8 fusion partners of FGFR1 have been identified. However, no primary leukemia cell lines were identified that contain any of these fusions. Here, we screened more than 40 acute myeloid leukemia cell lines for constitutive phosphorylation of STAT5 and applied an immunoaffinity profiling strategy to identify tyrosine-phosphorylated proteins in the KG-1 cell line. Mass spectrometry analysis of KG-1 cells revealed aberrant tyrosine phosphorylation of FGFR1. Subsequent analysis led to the identification of a fusion of the FGFR1OP2 gene to the FGFR1 gene. Small interfering RNA (siRNA) against FGFR1 specifically inhibited the growth and induced apoptosis of KG-1 cells. Thus, the KG-1 cell line provides an in vitro model for the study of FGFR1 fusions associated with leukemia and for the analysis of small molecule inhibitors against FGFR1 fusions.

Apoptosis↗
PubMed2006

Stability of entomopathogenic bacteria, Xenorhabdus nematophila and Photorhabdus luminescens, during in vitro culture.

The entomopathogenic nematode-bacteria complexes Heterorhabditis bacteriophora/Photorhabdus luminescens and Steinernema carpocapsae/Xenorhabdus nematophila are mass produced for use as biological insecticides. Stability of the bacterial partner in culture is essential for maintaining traits important for both biological control and production. Two geographically distinct strains of each bacterial species were isolated from their nematode partners and serially subcultured on in vitro media to assess trait stability. Subculturing resulted in a shift to secondary cell production in one P. luminescens strain and both X. nematophila strains within ten in vitro culture cycles. However, when cell phenotypic variation was controlled in X. nematophila strains by regular selection for primary variants, no trait change was detected in the primary variant after prolonged subculture. When P. luminescens cell phenotypic variation was controlled by selection for primary variants, changes in the primary variant of both strains were noted including reductions in cell and inclusion body size and inclusion body prevalence. Bacterial ability to cause lethal infections following injection into the hemocoel of Tenebrio molitor larvae declined by more than half in primary variants of one P. luminescens strain. Conversely, yield was enhanced, with the subcultured P. luminescens strains showing 53.5 and 75.8% increases in primary cell density. Field adapted traits of primary variant P. luminescens strains tend to deteriorate during in vitro culture as tradeoffs for gains in yield. In vitro producers of the P. luminescens/H. bacteriophora complex must weigh the need for superior bacterial yield against the need to preserve traits important for biological control.

Animals↗
PubMed2006

In-situ incorporation of gold nanoparticles of desired sizes into three-dimensional macroporous matrixes.

We present here a facile route to the incorporation of gold nanoparticles (GNPs) with desired sizes into three-dimensionally ordered macroporous (3DOM) matrixes. Our route combined the first attachment of small GNPs to the silica colloidal crystal templates as precursors and their subsequent controlled growth by the in-situ chemical reduction method. The desired enlargement of GNPs was acquired via their alternating and repeated exposure to solutions of auric salts and reducing agent NH(3)OH. Such gold-decorated silica templates were also converted into self-sustained polystyrene (PS) macroporous films with GNPs embedded in their wall structures. The growth of gold seeds can be easily followed by their UV-vis absorbance spectra. The route provides an alternative way to incorporate GNPs with predetermined sizes into 3DOM matrixes without destroying their ordered structures. A highlight of our approach is that it obviates the need for the preformation of various-sized GNPs, which is an indispensable step in many other approaches.

Colloids↗
PubMed2006

MPS1-dependent mitotic BLM phosphorylation is important for chromosome stability.

Spindle assembly checkpoint (SAC) ensures bipolar attachment of chromosomes to the mitotic spindle and is essential for faithful chromosome segregation, thereby preventing chromosome instability (CIN). Genetic evidence suggests a causal link between compromised SAC, CIN, and cancer. Bloom syndrome (BS) is a genetic disorder that predisposes affected individuals to cancer. BS cells exhibit elevated rates of sister chromatid exchange, chromosome breaks, and CIN. The BS gene product, BLM, is a member of the RecQ helicases that are required for maintenance of genome stability. The BLM helicase interacts with proteins involved in DNA replication, recombination, and repair and is required for the repair of stalled-replication forks and in the DNA damage response. Here we present biochemical evidence to suggest a role of BLM phosphorylation during mitosis in maintaining chromosome stability. BLM is associated with the SAC kinase MPS1 and is phosphorylated at S144 in a MPS1-dependent manner. Phosphorylated BLM interacts with polo-like kinase 1, a mitotic kinase that binds to phosphoserine/threonine through its polo-box domain (PBD). Furthermore, BS cells expressing BLM-S144A show normal levels of sister chromatid exchange but fail to maintain the mitotic arrest when SAC is activated and exhibit a broad distribution of chromosome numbers. We propose that MPS1-dependent BLM phosphorylation is important for ensuring accurate chromosome segregation, and its deregulation may contribute to cancer.

Adenosine Triphosphatases↗
PubMed2006

SOX13 exhibits a distinct spatial and temporal expression pattern during chondrogenesis, neurogenesis, and limb development.

SOX13 is a member of the SOX family of transcription factors. SOX proteins play essential roles in development, and some are associated with human genetic diseases. SOX13 maps to a multi-disease locus on chromosome 1q31-32, yet its function is unknown. Here we describe the temporal and spatial expression of SOX13 protein during mouse organogenesis. SOX13 is expressed in the three embryonic cell lineages, suggesting that it may direct various developmental processes. SOX13 is expressed in the developing central nervous system including the neural tube and the developing brain. Expression is also detected in the condensing mesenchyme and cartilage progenitor cells during endochondral bone formation in the limb as well as the somite sclerotome and its derivatives. SOX13 is also detected in the developing kidney, pancreas, and liver as well as in the visceral mesoderm of the extra-embryonic yolk sac and spongiotrophoblast layer of the placenta.

Animals↗