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Biomedical subjects

Peng Wang

Publications and source records attributed to Peng Wang.

At least 91 records · Page 5Linked to original sources
PubMed2005

Uncertainties of inherent optical properties obtained from semianalytical inversions of ocean color.

We present a method to quantify the uncertainties in the in-water constituent absorption and backscattering coefficients obtained from an inversion of remotely sensed reflectance (rrs). We first find a set of positive inversion solutions within a given uncertainty range around the values of the inverted rrs. The uncertainties of the solutions are then computed based on the statistics of these solutions. We demonstrate the uncertainty calculation algorithm using a specific semianalytic inversion model applied to both a field and a simulated data set. When the associated uncertainties are taken into account, the inverted parameters are generally within the uncertainties of the measured (or simulated) parameters, highlighting the success of the inversion and the method to obtain uncertainties. The specific inversion we use, however, fails to retrieve two spectral parameters within a usable range. The method presented is general and can be applied to all existing semianalytical inversion algorithms.

Journal Article↗
PubMed2005

Determination of desloratadine in drug substance and pharmaceutical preparations by liquid chromatography.

A simple and selective LC method is described for the determination of desloratadine in drug substance and pharmaceutical preparations. Chromatographic separation was achieved on a Diamonsil BDS C18 column using a mobile phase of a mixture of methanol, 0.03 mol/l heptanesulphonic acid sodium and glacial acetic acid (70:30:4, v/v) at a flow rate of 1.0 ml/min with detection at 247 nm. The developed method was validated in terms of selectivity, linearity, limit of quantitation, precision, accuracy and solution stability. The proposed LC method achieved satisfactory resolution between desloratadine and loratadine possibly present in desloratadine drug substance and other impurities in the mother liquor of the synthetic process. It can be used for the synthetic process control and determination of desloratadine in drug substance and pharmaceutical preparations.

Calibration↗
PubMed2005

Construction of a novel Shigella live-vector strain co-expressing CS3 and LTB/STm of enterotoxigenic E.coli.

AIM: To construct and evaluate a polyvalent recombinant vaccine strain Shigella flexneri 2a T32 against enterotoxigenic E.coli (ETEC). METHODS: By using a host-plasmid balanced lethal system based on asd gene, a polyvalent recombinant strain was constructed to highly express CS3 and regularly express fusion enterotoxin of LTB subunit and mutant ST (LTB/STm) in a vaccine strain Shigella flexneri 2a T32 with specific deletion of asd gene. Fimbria CS3 was observed by immunofluorescence and electron microscopy assay. The security of LTB/STm was examined by ileal loop assay and suckling mouse assay. To evaluate this new candidate vaccine, it was compared with a previous vaccine strain in plasmid and protein level, growth assay and immunogenicity in Balb/c mice. RESULTS: The newly constructed vaccine expressed CS3 and grew better than the previously constructed vaccine except for the lower expression of LTB/STm. Serum IgG and mucosal IgA against CS3, LTB, ST, and host lipopolysaccharide (LPS) were produced after immunization of Balb/c mice by oral route with the new strain. The titers were not significantly different from the Balb/c mice with the previous strain. CONCLUSION: This novel candidate diarrheal vaccine can effectively induce serum and mucosal antibody responses against ETEC and Shigella.

Animals↗
PubMed2005

Charge separation and efficient light energy conversion in sensitized mesoscopic solar cells based on binary ionic liquids.

A 7.4% power conversion efficiency at air mass (AM) 1.5 full sunlight was reached with a mesoscopic solar cell employing a new binary ionic liquid electrolyte composed of 1-propyl-3-methylimidazolium iodide and 1-ethyl-3-methylimidazolium tricyanomethanide in conjunction with the amphiphilic ruthenium complex NaRu(4-carboxylic acid-4'-carboxylate)(4,4'-dinonyl-2,2'-bipyridine)(NCS)(2), coded as Z-907Na. Ultramicroelectrode voltammetric, nanosecond laser transient absorbance, and photovoltaic measurements show that a high iodide concentration is required for dye regeneration to compete efficiently with charge recombination. A surprisingly fast reductive quenching process is turned on in pure iodide melts. This channel is unproductive, explaining the lower photocurrents observed under these conditions.

Journal Article↗
PubMed2005

Stereoselective kinetic study of hexaconazole enantiomers in the rabbit.

Hexaconazole [(RS)-2-(2,4-dichlorophenyl)-1-(1H-1,2,4-triazol-1-yl)hexan-2-ol] is a potent triazole fungicide. The (-) isomer accounts for most of the fungicidal activity. The stereo- and/or enantioselective kinetics of hexaconazole were investigated in rabbits by intravenous injection. The concentrations of (-)- and (+)-hexaconazole in plasma, liver, and kidney tissue were determined by HPLC with a cellulose tris(3,5-dimethylphenylcarbamate)-based chiral stationary phase and by gas chromatography-mass spectrometry. After intravenous administration of racemic hexaconazole (rac-hexaconazole) at 30 mg/kg, plasma, liver, and kidney levels of the (+)-enantiomer decreased more rapidly than those of the (-)-enantiomer. The (-)-/(+)-enantiomer ratio of the area under the concentration-time curve (AUC(0-infinity)) was 1.35. The total plasma clearance value (CL) of (+)-enantiomer was more than 1.3-fold higher than that of the (-)-hexaconazole. The enantiomeric ratio (ER) increased with time in plasma, liver, and kidney. Other pharmacokinetic parameters of the enantiomers were also different. These results indicate substantial stereoselectivity in the kinetics of hexaconazole enantiomers in rabbits.

Animals↗
PubMed2005

Optimization of purine based PDE1/PDE5 inhibitors to a potent and selective PDE5 inhibitor for the treatment of male ED.

In search of a PDE5 inhibitor for erectile dysfunction, an SAR was developed from a PDE1/PDE5 purine series of leads, which had modest PDE5 potency and poor isozyme selectivity. A compound (41) with PDE5 inhibition and in vivo activity similar to sildenafil was discovered from this effort. In addition, purine 41 demonstrated superior overall PDE isozyme selectivity when compared to the approved PDE5 inhibitors sildenafil, vardenafil, and tadalafil, which may result in a more favorable side-effect profile.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2005

Determination of ibuprofen in dog plasma by liquid chromatography and application in pharmacokinetic studies of an ibuprofen prodrug in dogs.

A liquid chromatography (LC) method for the determination of ibuprofen in dog plasma is described. Chromatographic separation was performed on a Diamonsil C18 column with a C18 guard column using a binary mixture of acetonitrile and 0.02 mol/l phosphate buffer (pH 6.5) (35:65, v/v) delivered at a flow rate of 1.2 ml/min. The linear range for ibuprofen was from 1.0 to 40.0 microg/ml with a limit of quantitation of 1.0 microg/ml. Within-run accuracy and precision ranged from -0.1% to 4.0% and from 1.1% to 5.5% and between-run accuracy and precision ranged from -1.1% to 4.7% and from 1.3% to 7.0%, respectively. The mean extraction recoveries of ibuprofen determined over the concentrations of 1.0, 10.0, and 40.0 microg/ml were (100.5+/-1.8)%, (99.8+/-1.0)%, and (99.2+/-2.3)%. The developed LC method greatly simplified the sample preparation and adopted mild conditions to prevent the possible hydrolysis of the prodrug and was successfully applied to the pharmacokinetic studies of an ibuprofen prodrug in dogs.

Animals↗
PubMed2005

Phylogenetic analysis of Archaea in the deep-sea sediments of west Pacific Warm Pool.

Archaea are known to play important roles in carbon cycling in marine sediments. The main compositions of archaeal community in five deep-sea sediment samples collected from west Pacific Warm Pool area (WP-0, WP-1, WP-2, WP-3, WP-4), and in five sediment layers (1 cm-, 3 cm-, 6 cm-, 10 cm-, 12 cm- layer) of the 12 cm sediment core of WP-0 were checked and compared by denaturing gradient gel electrophoresis and 16 S rRNA gene sequencing. It was revealed that all the deep-sea sediment samples checked contained members of non-thermophilic marine group I crenarchaeota as the predominant archaeal group. To further detect groups of archaea possibly relating with C1 metabolism, PCR amplification was carried out using primers targeting methane-oxidizing archaea. Although no methane-oxidizing archaea was detected, a group of novel archaea (named as WPA) was instead identified from all these five WP samples by clone analysis. They could be placed in the euryarchaeota kingdom, separated into two distinct groups, the main group was peripherally related with methanogens, the other group related with Thermoplasma. The vertical distributions of WPA, archaea and bacteria along the WP-0 sediment column were determined by quantitative-PCR. It was found that bacteria dominated at all depths, the numbers of bacteria were 10-10(4) times more than those of archaea. The proportion of archaea versus bacteria had a depth related increasing tendency, it was lowest at the first layer (0.01%), reached highest at the 12 cm- layer (10%). WPA only constituted a small proportion of the archaeal community (0.05% to 5%) of west Pacific Warm Pool sediment.

Archaea↗
PubMed2005

Overexpression of 5-lipoxygenase and cyclooxygenase 2 in hamster and human oral cancer and chemopreventive effects of zileuton and celecoxib.

PURPOSE: Previous studies have suggested an important role of aberrant arachidonic acid metabolism, especially the cyclooxygenase (Cox) pathway, in oral carcinogenesis. However, it is unknown whether the 5-lipoxygenase (5-Lox) pathway contributes to oral carcinogenesis, and whether combination of inhibitors of both pathways may have synergistic or additive effects of chemoprevention. EXPERIMENTAL DESIGN: 5-Lox expression was examined in 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster and human oral cancer tissues by immunohistochemistry, and Cox2 expression was investigated in hamster oral tissues using in situ hybridization. Zileuton (a specific 5-Lox inhibitor) and celecoxib (a specific Cox2 inhibitor), either alone or in combination, were investigated for their chemopreventive effects on the DMBA-induced hamster model at the post-initiation stage through topical application. RESULTS: 5-Lox was overexpressed during oral carcinogenesis in hamsters and humans, as well as Cox2 in the hamster tissues. In a chemoprevention study using the post-initiation DMBA model, incidence of hamster oral squamous cell carcinoma was reduced from 76.9% (20 of 26) to 45.8% (11 of 24, P < 0.05) and 32.1% (9 of 28, P < 0.01) by 3% and 6% topical zileuton, respectively; and to 57.6% (15 of 26, P > 0.05) and 50% (12 of 24, P < 0.05) by 3% and 6% topical celecoxib, respectively. When used in combination, celecoxib and zileuton (3% of each) had an additive inhibitory effect on the incidence of squamous cell carcinoma (36%, 9 of 25, P < 0.01). Other pathologic variables and the levels of leukotriene B4 and prostaglandin E2 of the hamster tissues were reduced as well. CONCLUSIONS: The results clearly showed that both 5-Lox and Cox2 played important roles in oral carcinogenesis. Zileuton and celecoxib prevented oral carcinogenesis at the post-initiation stage through their inhibitory effects on arachidonic acid metabolism.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2005

Algorithm for near-field reconstruction based on radial-shearing interferometry.

A new iterative algorithm to be used to precisely reconstruct near-field distribution from an interferogram of a laser output generated by a cyclic radial-shearing interferometer is proposed. First, by use of a window function around the zero-frequency part of the Fourier transform of the interferogram and calculation of the inverse Fourier transform of the zero-frequency part, we obtain the background intensity distribution of the interferogram. Then, according to the iterative algorithm, the near-field distribution of the laser output is precisely reconstructed from the background intensity distribution obtained in the first step. A numerical simulation and an actual experiment of the near-field reconstruction of the laser output with arbitrary amplitude distribution are implemented successfully.

Journal Article↗
PubMed2005

Interferon gamma induces neurite outgrowth by up-regulation of p35 neuron-specific cyclin-dependent kinase 5 activator via activation of ERK1/2 pathway.

Interferon gamma (IFN-gamma) is a cytokine predominantly involved in antiproliferative and antiviral responses, immune surveillance, and tumor suppression. However, it has been shown that IFN-gamma is also involved in central nervous system development. Here we studied the underlying mechanism for IFN-gamma-induced neuronal differentiation using the human neuroblastoma Paju cell line. Our results indicate that IFN-gamma treatment led to neurite outgrowth followed by growth arrest in the G1 phase of the cell cycle. IFN-gamma induced ERK1/2 phosphorylation and subsequently the transcription factor early gene response 1, which in turn up-regulated p35 expression and increased cyclin-dependent kinase 5 (Cdk5) activity. IFN-gamma-induced neurite outgrowth was abolished by the treatment of MEK1/2 kinase inhibitors, such as U0126 and PD98059, which inhibit the ERK1/2 activation and subsequently prevent the up-regulation of p35 expression and Cdk5 activity. In agreement with the role of p35-Cdk5 in neuronal differentiation, small interfering RNA targeting Cdk5 abrogate the IFN-gamma-induced neurite outgrowth. Together, these results demonstrate for the first time that IFN-gamma-triggered neuronal differentiation mediated through the up-regulation of p35-associated Cdk5 depends on the activation of the ERK1/2 pathway. Therefore, the present study suggests that IFN-gamma is not only involved in tumorigenicity but also involved in neurogenesis by regulating cell proliferation and differentiation.

Antibodies, Monoclonal↗
PubMed2005

Quantitative evaluation of protein-DNA interactions using an optimized knowledge-based potential.

Computational evaluation of protein-DNA interaction is important for the identification of DNA-binding sites and genome annotation. It could validate the predicted binding motifs by sequence-based approaches through the calculation of the binding affinity between a protein and DNA. Such an evaluation should take into account structural information to deal with the complicated effects from DNA structural deformation, distance-dependent multi-body interactions and solvation contributions. In this paper, we present a knowledge-based potential built on interactions between protein residues and DNA tri-nucleotides. The potential, which explicitly considers the distance-dependent two-body, three-body and four-body interactions between protein residues and DNA nucleotides, has been optimized in terms of a Z-score. We have applied this knowledge-based potential to evaluate the binding affinities of zinc-finger protein-DNA complexes. The predicted binding affinities are in good agreement with the experimental data (with a correlation coefficient of 0.950). On a larger test set containing 48 protein-DNA complexes with known experimental binding free energies, our potential has achieved a high correlation coefficient of 0.800, when compared with the experimental data. We have also used this potential to identify binding motifs in DNA sequences of transcription factors (TF). The TFs in 79.4% of the known TF-DNA complexes have accurately found their native binding sequences from a large pool of DNA sequences. When tested in a genome-scale search for TF-binding motifs of the cyclic AMP regulatory protein (CRP) of Escherichia coli, this potential ranks all known binding motifs of CRP in the top 15% of all candidate sequences.

Base Sequence↗
PubMed2005

Upregulation of phosphodiesterase-4 in the lung of allergic rats.

Inhibitors of phosphodiesterase-4 (PDE4) are efficacious for allergic asthma in animal models and have shown some efficacy in human asthma. Regulation of PDE4 in allergy and asthma has been widely investigated in blood leukocytes, with discrepant results. This study investigated PDE4 regulation in the lung in a rat model of allergic asthma. Ovalbumin sensitization and challenge significantly increased pulmonary resistance and lung interleukin (IL)-4 production. The increases in pulmonary resistance and IL-4 production were both suppressed by the PDE4-selective inhibitor rolipram or the corticosteroid drug dexamethasone. Furthermore, cAMP-PDE enzyme activity in the lung was also significantly increased by the sensitization and challenge. mRNA analysis confirmed that PDE4 gene expression was increased in the lung of the allergic rats. A highly significant correlation was observed between the increases in PDE activity and IL-4 production. Our data suggest, for the first time, that PDE4 may be upregulated in the lung and play a role in the pathogenesis of allergic asthma.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2005

Direct enantiomeric resolutions of chiral triazole pesticides by high-performance liquid chromatography.

Cellulose-tris (3,5-dimethylphenylcarbamate; CDMPC) was synthesized and coated on aminopropylsilica to prepare chiral stationary phase (CSP). Normal-phase high-performance liquid chromatography (HPLC) methods for the resolutions of five chiral triazole pesticides, diniconazole, tebuconazole, hexaconazole, triadimefon and flutriafol, on the CSP were developed. Several operating parameters such as mobile phase composition, modifier and column temperature were studied for the optimization of the resolutions. Better separations were achieved using 2% iso-butanol for diniconazole, 2% ethanol for tebuconazole, 2% iso-propanol for hexaconazole, 1% n-butanol for triadimefon and 2% n-propanol for flutriafol as modifiers in n-hexane at 0 degrees C with the resolution factors (Rs) of 1.62, 1.66, 2.46, 1.68 and 1.98, respectively. Low temperature was better for the resolutions. Validation of the methods included linearity and precision.

Chromatography, High Pressure Liquid↗
PubMed2005

Effect of alcohols and temperature on the direct chiral resolutions of fipronil, isocarbophos and carfentrazone-ethyl.

The enantiomeric separations of three pesticides fipronil (asymmetric nitrogen), isocarbophos (asymmetric phosphorus) and carfentrazone-ethyl (asymmetric carbon) were studied on cellulose-tri(3,5-dimethylphenylcarbamate) chiral stationary phase using high-performance liquid chromatography under normal phase. The mobile phase was n-hexane with alcohols including ethanol, n-propanol, iso-propanol, n-butanol and iso-butanol as polar modifiers. The flow rate was 1.0 mL/min with UV detection at 280, 225 and 230 nm for fipronil, isocarbophos and carfentrazone-ethyl respectively. The influence of the modifiers and their volume content and temperature from 0 to 50 degrees C on the separations was investigated. The chiral stationary phase showed excellent stereoselectivity for the two enantiomers of fipronil and isocarbophos and certain chiral recognition for carfentrazone-ethyl. Iso-propanol was more suitable for the chiral separation of isocarbophos and carfentrazone-ethyl, and iso-butanol was better for fipronil. The resolutions increased with the decreasing modifier content and temperature for all the three chiral pesticides.

Alcohols↗
PubMed2005

Identification of a trace colored impurity in drug substance by preparative liquid chromatography and mass spectrometry.

6-(Nitrooxy)hexyl-(2z)-4-(acetyloxy)-3-[4-(methylsulfonyl)phenyl]-2-phenylbut-2-enoate (enoate 1) was investigated as a novel therapy for pain relief. In a recent manufacturing run at the pilot plant scale, the enoate drug substance was found to have a yellowish color not observed previously. An unknown impurity at trace level was detected by high-performance liquid chromatographic (HPLC) analysis and found to be the primary cause for the color of the drug substance. The colored impurity was enriched by preparative HPLC and structurally elucidated by liquid chromatography/tandem mass spectrometry (LC/MS/MS). It was found that the colored impurity was derived from the product of oxidative dimerization of rofecoxib, an impurity present in the enoic acid intermediate. It was further revealed by the photodiode array and LC/MS/MS data that the colored impurity exists in the drug substance as a pair of double-bond isomers with one isomer at majority. These findings were also confirmed by synthesizing the colored impurity through the proposed pathway.

Butyrates↗
PubMed2005

Immortalized rat astrocyte strain genetically modified by rat preprogalanin gene.

To construct an immortalized rat astrocyte strain genetically modified by rat preprogalanin gene (IAST/GAL) and detect its galanin (GAL) expression and secretion, a cDNA fragment of rat GAL in plasmid of pBS KS(+)-GAL was inserted into eukaryotic expression vector pcDNA3.1 (+) by DNA recombinant technology, then the restriction enzyme digestion and DNA sequencing were carried out to evaluate the recombinant. The pcDNA3.1 (+)-GAL and pcDNA3.1 (+) construct were transfected into immortalized rat astrocyte strain (IAST) by lipofectamine and the population of cells which stably integrated the construct was selected with 600 microg/mL G418. Individual clones were screened and expanded into clonal cell strains. Detection of Neo gene was used to validate the success of the transfection. Immunocytochemical staining, RT-PCR and radioimmunoassay were used to detect the expression and secretion level of GAL. The recombinant had been successfully constructed by restriction enzyme digestion and DNA sequencing. Detection of Neo gene showed that the pcDNA3.1 (+)-GAL and pcDNA3.1 (+) have been successfully transfected into IAST. After selection by using G418, IAST/GAL and IAST/Neo cell strains were obtained. IAST/GAL, IAST/Neo and IAST were immunostained positively for GAL, but the GAL average optical density of IAST/GAL was significantly higher than that of IAST/Neo and IAST (P< 0.01). The level of GAL mRNA expression and the supernatant concentration of GAL in cultured IAST/GAL were significantly higher than those of IAST and IAST/Neo (P<0.01), but no significant differences were found between the IAST and IAST/Neo (P>0.05). It was concluded that IAST/GAL strain was constructed successfully and it might provide a basis for the further study of pain therapy.

Animals↗