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Biomedical subjects

Qi Wang

Publications and source records attributed to Qi Wang.

At least 199 records · Page 11Linked to original sources
PubMed2003

[Synthesis and in vitro antibacterial activities of new 3,5-disubstituted oxazolidinone compounds].

AIM: To design and synthesize new oxazolidinone antibacterial agents. METHODS: The synthetic method reported in literature has been modified and new 3,5-disubstituted oxazolidinone compounds were synthesized on the basis of SAR reported in the literature and their antibacterial activities in vitro were determined. RESULTS: Eighteen new objective compounds were synthesized, and their structures were determined by IR, 1HNMR and FAB-MS. Within the eighteen new objective compounds, sixteen compounds showed antibacterial activity in vitro and compound 9, 10 and 10b showed better antibacterial activities in vitro than ciprofloxacin (CIP), sultamicillin (Sul) and vancomycin (VCO). Compounds 9a and 11c have no antibacterial activity in vitro at all. CONCLUSION: Compounds 9, 10 and 10b are worthy to be intensively studied.

Ampicillin↗
PubMed2003

[Comparison of optimum, RSA and GLUE methods in parameter identification of a nonlinear environmental model].

Parameter identification plays a key role in environmental model application. The optimization method is one of the earliest and most widely used methods. However, as the parameters by optimization may not fully fit the observations, there is a risk that the errors may be enhanced in the decision-make stage. With this deficiency in consideration, the RSA and GLUE algorithms search for the feasible parameters not only to the optimum but also around the neighbors. The difference between RSA and GLUE is that the RSA accepts the estimated parameters equally as the candidates for application; while the GLUE keeps the difference among the parameters as measured by likelihood. In addition for parameter identification, both RSA and GLUE are efficient tools for global sensitivity analysis.

Environment↗
PubMed2002

Wavelet transforming characteristic of a lens.

Based on the wave-front filtering concept of wavelet optics, which we proposed, here we consider that the wave fronts of a light wave are filtered by the lens when the wave fronts pass through the lens. After filtering, the weight of the light field is redistributed, and a Gaussian frequency-modulated complex-valued wavelet function is introduced with the weight function. Subsequent analysis indicates that the lens has a wavelet-transforming characteristic and that the introduction of a Gaussian frequency-modulated complex-valued wavelet function conforms to the actual lens.

Journal Article↗
PubMed2002

Symmetries of the Doi kinetic theory for nematic polymers of arbitrary aspect ratio: at rest and in linear flows.

The Doi theory has successfully modeled the monodomain shear flow problem for rigid, rodlike nematic polymers. Numerical simulations of the Smoluchowski equation for the orientational probability distribution function (PDF) predict monodomain attractors in regions of nematic concentration N and shear rate gamma. Theoretical work has focused on approximate constructions of PDF solutions in linear flow regimes. Here we develop a collection of simple observations, expressed by symmetries of the Smoluchowski equation, which imply global properties that all PDF solutions must obey. The well-known orientational degeneracy of quiescent nematics is a continuous O(3) symmetry. In simple shear, a discrete reflection symmetry survives that is evident in recent numerical simulations and implies bistability of out-of-plane attractors; and rodlike and discotic nematic liquids of reciprocal aspect ratio respond identically up to a fixed rotation of the PDF. Finally, we show the orientational effects due to varying molecular aspect ratio in any linear flow are equivalent to varying the straining component of the flow field.

Journal Article↗
PubMed2002

Rapid positive selection of stable integrants following transfection of Plasmodium falciparum.

With the near-completion of the genome sequence of Plasmodium falciparum, further understanding of this major human pathogen urgently requires more effective genetic tools. These must include faster and more reliable gene replacement or gene knockout techniques, essential for the analysis of gene function. We describe a serial system which uses the blasticidin S deaminase (bsd) gene of Aspergillus and the neomycin phosphotransferase II (neo) gene from transposon Tn5 as selectable markers for, respectively, transient transfection of malaria parasites and the selection of stable integrants. Challenge with blasticidin S (BS) enriches the parasite population transiently expressing the bsd gene, laying the foundation for the subsequent, much less frequent, integration event. Positive selection for this rare event is enormously facilitated by fusing the neo gene in frame to the replacement or knockout targeting gene. The sequence employed for the targeting (the polymorphic pppk-dhps gene of P. falciparum, as a model system) is truncated at the 5' end with no promoter located upstream, therefore neo cannot be expressed without specifically integrating within the genomic copy of the target gene. After BS selection, the culture is immediately exposed to geneticin (G418), leading to an apparently homogenous population of mutant parasites. As well as excluding spurious integrants at non-targeted sequences, this system greatly reduces the lengthy selection period for obtaining the desired mutants by eliminating the drug-on and drug-off cycles for the production of stable integrants, which are normally required by the single marker systems currently in use for transfection of malaria parasites.

Aminohydrolases↗
PubMed2002

Kinetic theory for flows of nonhomogeneous rodlike liquid crystalline polymers with a nonlocal intermolecular potential.

The Doi kinetic theory for flows of homogeneous, rodlike liquid crystalline polymers (LCPs) is extended to model flows of nonhomogeneous, rodlike LCPs through a nonlocal (long-range) intermolecular potential. The theory features (i) a nonlocal, anisotropic, effective intermolecular potential in an integral form that is consistent with the chemical potential, (ii) short-range elasticity as well as long-range isotropic and anisotropic elasticity, (iii) a closed-form stress expression accounting for the nonlocal molecular interaction, and (iv) an extra elastic body force exclusively associated with the integral form of the intermolecular potential. With the effective intermolecular potential, the theory is proven to be well posed in that it warrants a positive entropy production and thereby the second law of thermodynamics. Approximate theories are obtained by gradient expansions of the number density function in the free energy density.

Journal Article↗
PubMed2002

Construction and characterization of a chimeric virus (BIV/HIV-1) carrying the bovine immunodeficiency virus gag-pol gene.

HIV-1(HXB2) 5'LTR region, most of BIV(R29) gag-pol segment and HIV-1(HXB2) pol IN-3'LTR region were respectively amplified. A chimeric clone, designated as pHBIV(3753), was constructed by cloning three fragments sequentially into pUC18. MT4 cells were transfected with pHBIV3753. The replication and expressions of the chimeric virus (HBIV3753) were monitored by RT activity and IFA. The results firstly demonstrated that it is possible to generate a new type of the BIV/HIV-1 chimeric virus containing BIV gag-pol gene.

AIDS Vaccines↗
PubMed2002

Ordering in aqueous polysaccharide solutions. II. Optical rotation and heat capacity of aqueous solutions of a triple-helical polysaccharide schizophyllan.

Deuterium oxide solutions of schizophyllan, a triple-helical polysaccharide, undergoing an order-disorder transition centered at 17 degrees C, were studied by optical rotation (OR) and heat capacity (C(p)) to elucidate the molecular mechanism of the transition and water structure in the solution and frozen states. The ordered structure at low temperature consisted of the side chains and water in the vicinity forming an ordered hydrogen-bonded network surrounding the helix core and was disordered at higher temperature. In the solution state appeared clearly defined transition curves in both the OR and C(p) data. The results for three samples of different molecular weights were analyzed theoretically, treating this transition as a typical linear cooperative transition from the ordered to disordered states and explained quantitatively if the molecular weight polydispersity of the sample was considered. The excess heat capacity C(EX)(p) defined as the C(p) minus the contributions from schizophyllan and D(2)O was estimated. In the frozen state it increased with raising temperature above 150 K until the mixture melted. This was compared with the dielectric increment observed in this temperature range and ascribed to unfreezable water. From the heat capacity and dielectric data, unfreezable water is mobile but more ordered than free water. In the solution state, the excess heat capacity originates from the interactions of D(2)O molecules as bound water and structured water, and so forth. Thus the schizophyllan triple helix molds water into various structures of differing orders in solution and in the solid state.

Adjuvants, Immunologic↗
PubMed2002

Ordering in aqueous polysaccharide solutions. I. Dielectric relaxation in aqueous solutions of a triple-helical polysaccharide schizophyllan.

Deuterium oxide solutions of a triple-helical polysaccharide schizophyllan, undergoing an order-disorder transition centered around 17 degrees C, were studied by the time-domain reflectometry (TDR) to obtain dielectric dispersions in the solution and frozen states. In the solution state, the dispersion below the transition temperature is resolved in three dispersions (relaxation times at 0 degrees C) ascribed to side chain glucose residue (1; 102 ns), structured water (s; 2.0 ns) and bulk water (h), respectively, from low to high frequencies. Bulk water is divided into slow water (h2; 0.04 ns) and free or pure water (h1; 0.02 ns). Above the transition temperature structured water almost disappears and is compensated by slow water. Structured water is similar to bound water for proteins but different from it because of this transition behavior. Another dispersion (l) seen at the lowest frequency is assigned to the rotation of side-chain glucose residue coupled with hydrated water. Parts of this dispersion and structured water are suggested to constitute bound water. In the frozen state were observed a major dispersion (h; 0.14 ns) and a minor one (m; 28 ns), which were ascribed to considerably mobile and less mobile waters. They are similar to but not exactly the same as that for unfreezable water in bovine serum albumin solutions argued by Miura et al. (Biopolymers, 1995, Vol. 36, p. 9). Water is molded into different structures by the triple helix.

Biopolymers↗
PubMed2002

Overexpression of a stabilized mutant form of the cyclin-dependent kinase inhibitor p27(Kip1) inhibits cell growth.

OBJECTIVE: The purpose of this study was to test the hypothesis that the expression of the mutant p27(Kip1) protein enhances cell growth inhibition and is more stable than that of the wild-type p27(Kip1). METHODS: Site-directed mutagenesis was used to mutate threonine 187 to an alanine residue, generating the mutant p27(Kip1). To study the effects of the p27(Kip1) mutant on cell growth, luciferase assays were performed. Cells were transiently transfected with the Renilla luciferase reporter construct and empty vector, wild-type p27(Kip1), or mutant p27(Kip1) using Fugene 6. The transfected cells were lysed and assayed for luciferase activity 24 h later with a dual-luciferase reporter assay system. To further assess the effects of the p27(Kip1) mutant on cell growth, colony count assays were performed. The experiments were repeated in duplicate and a standard two-tailed Student t test was use to analyze the data. RESULTS: Wild-type p27(Kip1) protein has a half-life of approximately 2 h while the p27(Kip1) mutant has a half-life of greater than 12 h. Furthermore, the p27(Kip1) mutant retained the ability to inhibit CDK2-associated H1 kinase activity. Cells expressing the p27(Kip1) mutant had an 88% reduction in luciferase activity compared to cells expressing the wild-type p27(Kip1) (P = 0.001). Colony assays revealed that cells expressing the p27(Kip1) mutant had fewer colonies compared to cells expressing the wild-type p27(Kip1) (P = 0.04). CONCLUSIONS: These data are consistent with the hypothesis that the mutated form of p27(Kip1) is more effective in cell growth inhibition than the wild-type p27(Kip1) protein.

Amino Acid Sequence↗
PubMed2002

A new haplogroup pattern displayed in Fujian Han in China.

Human Y-chromosomal binary polymorphisms have been considered to preserve the paternal genetic legacy and provide evidence on human evolution and the genetic relationships among and demographic history of different populations. To reveal the genetic origin and immigration of the Fujian Han, 13 binary markers on the Y chromosome were used to screen Fujian Han by allele-specific polymerase chain reaction. The results indicated that the M9G marker was highly prevalent (96.20%), suggesting a significant genetic drift. In addition, M122C frequency was only 22.78%, and M45A and M103T were default. The distinctive haplogroup frequencies (H1, H5, and H6/7/8) imply that the haplogroup pattern is a relatively ancestral and interim type.

Asian People↗
PubMed2002

Intestinal apolipoprotein B secretion is inhibited by the flavonoid quercetin: potential role of microsomal triglyceride transfer protein and diacylglycerol acyltransferase.

Recent studies have yielded evidence that plant flavonoids reduce hepatic lipid and apolipoprotein B (apoB) secretion. However, the possible role of flavonoids in regulating lipid and apoB secretion by the intestine has not been studied. The purpose of our study was to examine the effects of quercetin, a common dietary flavonoid, on TAG and apoB secretion in a human intestinal cell-line, CaCo-2. Differentiated postconfluent CaCo-2 cells grown on filters and pretreated with quercetin for 8 h were shown by ELISA to inhibit basolateral apoB secretion in a dose-dependent manner. At 15 microM, the secretion of both apoB-100 and apoB-48 were inhibited similarly. This effect was shown to be specific, as quercetin did not affect the incorporation of [35S]methionine/cysteine into secreted TCA-precipitable proteins. To determine the mechanism underlying this inhibitory effect, we examined two regulatory points: TAG availability and lipid transfer to the lipoprotein particle. Quercetin inhibited TAG synthesis under both basal and lipid-rich conditions, indicating that lipid availability is a determining factor in the regulation of apoB secretion by quercetin. The reduction was due at least in part to a decrease in diacylglycerol acyltransferase activity. We next examined lipid transfer or lipidation of the lipoprotein particle by analyzing microsomal TAG transfer protein (MTP) activity. Quercetin decreased MTP activity moderately. In summary, the data demonstrated that pharmacological concentrations of quercetin are a potent inhibitor of intestinal apoB secretion and that reduced lipid availability and lipidation in the lipoprotein assembly step are the mechanism for the suppression of apoB-containing lipoprotein secretion by quercetin in CaCo-2 cells.

Acyltransferases↗
PubMed2002

Survey on cystic echinococcosis in Tibetans, West China.

Human cystic echinococcosis (CE) is a serious public health problem in West China. The Tibetan has a nature relation with these definitive and intermediate hosts in West China. Although Tibet is CE endemic, a few community studies have been reported. Eight hundred and eighty two Tibetans residing in the three rural communes of Tianzhu County, Gansu province of West China were investigated by serology and ultrasound scanning. 11.2% serum antibody positive rate in ELISA test was found out, and a 12.1% ultrasound rate of hepatic CE was found in the sero-positive population. Seropositivity rates varied for communes between 7.6 and 13.7%. Overall, females had a significantly greater risk of infection than males-ratio was about 2:1. The local behaviors were investigated and showed that family dog and grazing could not effect the infectious rates, but the number of sheep owned a family had a positive correlation with the infection rates. The infectious rate of hunting population was significantly higher than that of no-hunting population. The educated level of Tibetans in school had no effect on the infected rates.

Adolescent↗
PubMed2002

Reconstitution of G protein-coupled receptors with recombinant G protein alpha and beta gamma subunits.

The methods outlined in this article describe experiments that can probe the first steps in receptor:G protein interaction using defined, recombinant receptors and G proteins. The protocols have the advantages that the receptors are inserted properly in a cell membrane and that the investigator has complete control of the proteins reconstituted with the receptor. Specific mutations in the receptors or G proteins are studied easily and the protocols allow precise examination of the stoichiometry of the receptor:alpha:beta gamma interaction.

Animals↗
PubMed2002

Polymerization rate and mechanism of ultrasonically initiated emulsion polymerization of n-butyl acrylate.

The factors affecting the induction period and polymerization rate in ultrasonically initiated emulsion polymerization of n-butyl acrylate (BA) were investigated. The induction period takes only an instant in ultrasonically initiated emulsion polymerization of BA without any added initiator by enhancing the N2 flow rate. Increasing temperature, power output and SDS concentration, decreasing the monomer concentration results in further decreasing induction period and enhanced polymerization rate. Under optimized reaction conditions the conversion of BA reaches 92% in 11 min. The polymerization rate can be controlled by varying reaction parameters. The apparatus of ultrasonically initiated semi-continuous and continuous emulsion polymerization were set up and the feasibility was first studied. Based on the experimental results, a free radical polymerization mechanism for ultrasonically initiated emulsion polymerization was proposed, including the sources of the radicals, the process of radical formation, the locus of polymerization and the polymerization process. Compared with conventional emulsion polymerization, where the radicals come from thermal decomposition of a chemical initiator, ultrasonically initiated emulsion polymerization has attractive features such as no need for a chemical initiator, lower reaction temperature, faster polymerization rate, and higher molecular weight of the polymer prepared.

Journal Article↗
PubMed2002

Green tea catechins decrease apolipoprotein B-100 secretion from HepG2 cells.

To understand the hypocholesterolemic activity of green tea, our in vitro studies screened the relative efficacy of two structurally distinct green tea catechins, epicatechin (EC) and epigallocatechin gallate (EGCG), on apolipoprotein B-100 (apoB) and lipid production using a well established human hepatoma cell-line, HepG2, as the model system. This study showed that HepG2 cells pretreated with EC and EGCG for 8 h exerted a dose-dependent inhibitory effect on apoB secretion. Total protein and albumin synthesis and secretion were unaffected indicating the effects on apoB secretion to be specific. Under lipid-rich conditions, apoB secretion was markedly reduced by EGCG and to a lesser extent by EC at 50 microM. Mechanistic study showed that tea catechins inhibited apoB secretion via a proteasome-independent pathway as indicated by a lack of response to N-acetyl-leucyl-leucyl-norleucinal (ALLN), a proteasome inhibitor. The effect on apoB secretion was also found to be independent of lipid biosynthesis. In summary, the data suggest that EGCG in contrast to EC is a potent inhibitor of apoB secretion. The results indicate that the gallate moiety in the catechin molecule may result in a beneficial effect on lipid metabolism in terms of apoB secretion.

Anticholesteremic Agents↗