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Lei Wang

Publications and source records attributed to Lei Wang.

At least 91 records · Page 5Linked to original sources
PubMed2006

Structural and genetic characterization of Shigella boydii type 17 O antigen and confirmation of two new genes involved in the synthesis of glucolactilic acid.

Shigella strains are human pathogens and normally identified based on their O antigens. The chemical structure and gene cluster of Shigella boydii type 17 O antigen were studied. As judged by sugar and methylation analyses along with NMR spectroscopy data, the O antigen of S. boydii type 17 has a linear trisaccharide O unit, which consists of two residues of N-acetylgalactosamine (GalNAc) and a 4-O-[(R)-1-carboxyethyl]-d-glucose (glucolactilic acid). The O antigen gene cluster of S. boydii type 17 was sequenced and genes encoding UDP-N-acetylglucosamine C4 epimerase for GalNAc synthesis, O unit flippase, O antigen polymerase, and glycosyltransferases were putatively identified based on sequence similarities and the presence of conserved motifs. Two genes, whose functions could not be clearly indicated by homology search, were confirmed to be involved in the synthesis of glucolactilic acid by mutation and structural verification of the O antigens from the mutants. To our knowledge, this is the first time that genes involved in the synthesis of glucolactilic acid have been reported. Two genes specific to S. boydii type 17 were also identified.

Amino Acid Motifs↗
PubMed2006

A multicenter observational study of the potential benefits of initiating combination antiretroviral therapy during acute HIV infection.

OBJECTIVE: Uncontrolled studies have suggested a benefit, after treatment discontinuation, of initiating highly active antiretroviral therapy (HAART) during primary human immunodeficiency virus (HIV) infection. We assessed whether initiation of HAART within 2 weeks of (acute treatment) or between 2 weeks and 6 months after (early treatment) HIV seroconversion was associated with improvements in the viral load and the CD4+ T cell count after discontinuation of treatment in an observational cohort. METHODS: Subjects from the multicenter Acute Infection and Early Disease Research Program cohort were enrolled in the present study within 6 months of HIV seroconversion and self-selected whether to initiate HAART. Subjects who received acute (n=13) or early (n=45) treatment received HAART for at least 12 weeks and then subsequently stopped treatment, whereas untreated subjects (n=337) declined treatment. HIV RNA levels and CD4+ T cell counts at 24, 48, and 72 weeks after treatment cessation in the 2 treatment groups were compared with those noted in the untreated group during the same periods of observation after enrollment. RESULTS: The acute treatment group had lower mean HIV RNA levels at 24 weeks without therapy (-0.48 log(10) copies/mL [95% confidence interval {CI}, -0.82 to -0.13 log(10) copies/mL]) and higher mean CD4+ T cell counts (112 cells/ mu L [95% CI, 20-205 cells/ microL]), compared with the untreated group at 24 weeks. The differences in the laboratory values for the acute treatment group versus the untreated group at 72 weeks without therapy were as follows: for the HIV RNA level, -0.35 log(10) copies/mL (95% CI, -0.91 to 0.21 log(10) copies/mL) and, for the CD4 T+ cell count, 112 cells/ microL (95% CI, -15 to 213 cells/ microL). The early treatment group had lower HIV RNA levels at 24 weeks than did the untreated group, but differences were no longer apparent by week 48; CD4+ T cell counts were higher in the early treatment group at week 24 (116 cells/ microL [95% CI, 75-157 cells/ microL]) and week 72 (70 cells/ microL [95% CI, 2-138 cells/ microL]). CONCLUSIONS: Initiation of HAART within 2 weeks of antibody seroconversion was associated with viral load and CD4+ T cell count benefits for 24 weeks after termination of HAART, with there being trends toward a longer-term benefit. Later initiation of HAART was associated with a persistent but decreasing CD4+ T cell count benefit and a loss of the viral load benefit by week 72 after discontinuation of treatment.

Acute Disease↗
PubMed2006

Development of a DNA microarray to identify the Streptococcus pneumoniae serotypes contained in the 23-valent pneumococcal polysaccharide vaccine and closely related serotypes.

Streptococcus pneumoniae is a major worldwide human pathogen. This investigation has developed a reliable and accurate DNA microarray method for inter-species differentiation of S. pneumoniae and intra-species differentiation of the 23 groups of S. pneumoniae including serotypes represented in the 23-valent pneumococcal vaccine and the other 20 closely related serotypes. In addition to 16S rDNA probes, serotype- or serogroup-specific probes targeting the capsular polysaccharide synthesis (cps) genes, wzy or capA were generated. We adopted a two-step multiplex PCR to improve the sensitivity of detection to a level of 10(5) cfu/ml in pure culture or 50 ng DNA. A total of 169 isolates (from China, Australia, Canada and New Zealand) including 147 belonging to 23-valent vaccine and closely related serotypes of S. pneumoniae, 11 belonging to other serotypes and 11 of different species commonly isolated from respiratory tract were tested to verify the method. The DNA microarray method developed provides a sensitive means to rapidly identify the members of the most common S. pneumoniae serotypes in patients and to monitor their distribution in different patient groups and geographic locations. Such information is needed for disease surveillance and to monitor vaccine efficacy.

Bacterial Proteins↗
PubMed2006

Diversity and evolution of conotoxins based on gene expression profiling of Conus litteratus.

Cone snails are attracting increasing scientific attention due to their unprecedented diversity of invaluable channel-targeted peptides. As arguably the largest and most successful evolutionary genus of invertebrates, Conus also may become the model system to study the evolution of multigene families and biodiversity. Here, a set of 897 expressed sequence tags (ESTs) derived from a Conus litteratus venom duct was analyzed to illuminate the diversity and evolution mechanism of conotoxins. Nearly half of these ESTs represent the coding sequences of conotoxins, which were grouped into 42 novel conotoxin cDNA sequences (seven superfamilies), with T-superfamily conotoxins being the dominant component. The gene expression profile of conotoxin revealed that transcripts are expressed with order-of-magnitude differences, sequence divergence within a superfamily increases from the N to the C terminus of the open reading frame, and even multiple scaffold-different mature peptides exist in a conotoxin gene superfamily. Most excitingly, we identified a novel conotoxin superfamily and three novel cysteine scaffolds. These results give an initial insight into the C. litteratus transcriptome that will contribute to a better understanding of conotoxin evolution and the study of the cone snail genome in the near future.

Amino Acid Sequence↗
PubMed2006

A cannabinoid receptor 1 mutation proximal to the DRY motif results in constitutive activity and reveals intramolecular interactions involved in receptor activation.

Activation of a G-protein-coupled receptor involves changes in specific microdomain interactions within the transmembrane region of the receptor. Here, we have focused on the role of L207, proximal to the DRY motif of the human cannabinoid receptor 1 in the interconversion of the receptor resting and active states. Ligand binding analysis of the mutant receptor L207A revealed an enhanced affinity for agonists (three- to six-fold) and a diminished affinity for inverse agonists (19- to 35-fold) compared to the wild-type receptor, properties characteristic of constitutive activity. To further examine whether this mutant adopts a ligand-independent, active form, treatment with GTPgammaS was used to inhibit G protein coupling. Under these conditions, the L207A receptor exhibited a 10-fold increase in affinity for the inverse agonist SR141716A, consistent with a shift away from an enhanced precoupled state. Analysis of the cellular activity of the L207A receptor showed elevated basal cyclic AMP accumulation relative to the wild type that is inhibited by SR141716A, consistent with receptor-mediated Gs precoupling. Using toxins to selectively abrogate Gs or Gi coupling, we found that CP55940 nonetheless induced only a Gi response suggesting a strong preference of this ligand-bound form for Gi in this system. Molecular dynamics simulations reveal that the single residue change of L207A impacts the association of TM3 and TM6 in the receptor by altering hydrophobic interactions involving L207, the salt bridge involving the Arg of the DRY motif, and the helical structure of TM6, consistent with events leading to activation. The structural alterations parallel those observed in models of a mutant CB(1) receptor T210I, with established constitutive activity (D'Antona, A.M., Ahn, K.H. and Kendall, D.A., 2006. Mutations of CB1 T210 produce active and inactive receptor forms: correlations with ligand affinity, receptor stability, and cellular localization. Biochemistry, 45, 5606-5617).

Amino Acid Motifs↗
PubMed2006

Synthesis and pore formation study of amorphous mesoporous aluminophosphates in the presence of citric acid.

Amorphous mesoporous aluminophosphates (AlPO) with high thermal stability were synthesized from Al(NO3)3 and H3PO4 in the presence of citric acid (CA). The effects of different synthetic conditions, such as pH value, citric acid content, and calcined temperature, on the formation of the mesoporous structure of AlPO materials were investigated. The results of N2 adsorption/desorption and other characterization means demonstrate that the presence of a certain amount of citric acid in the synthetic mixture can result in the formation of uniform mesoporous AlPO materials in a wide pH range from 3.5 to 10. Thermal gravimetry and differential thermal analysis suggest that the existence of a moderate interaction between citric acid and the AlPO network might be a critical factor in obtaining uniform mesostructure. Therefore, as an organic additive, citric acid can be regarded as a template for the mesopore formation of AlPO materials.

Aluminum Compounds↗
PubMed2006

MRI detects white matter reorganization after neural progenitor cell treatment of stroke.

We evaluated the effects of neural progenitor cell treatment of stroke on white matter reorganization using MRI. Male Wistar rats (n = 26) were subjected to 3 h of middle cerebral artery occlusion and were treated with neural progenitor cells (n = 17) or without treatment (n = 9) and were sacrificed at 5-7 weeks thereafter. MRI measurements revealed that grafted neural progenitor cells selectively migrated towards the ischemic boundary regions. White matter reorganization, confirmed histologically, was coincident with increases of fractional anisotropy (FA, P < 0.01) after stroke in the ischemic recovery regions compared to that in the ischemic core region in both treated and control groups. Immunoreactive staining showed axonal projections emanating from neurons and extruding from the corpus callosum into the ipsilateral striatum bounding the lesion areas after stroke. Fiber tracking (FT) maps derived from diffusion tensor imaging revealed similar orientation patterns to the immunohistological results. Complementary measurements in stroke patients indicated that FT maps exhibit an overall orientation parallel to the lesion boundary. Our data demonstrate that FA and FT identify and characterize cerebral tissue undergoing white matter reorganization after stroke and treatment with neural progenitor cells.

Algorithms↗
PubMed2006

Distribution and dissipation pathways of nonylphenol polyethoxylates in the Yellow River: Site investigation and lab-scale studies.

Spatial distribution of nonylphenol polyethoxylates (NPEOs) and nonylphenol (NP) was investigated in a field study in Lanzhou Reach of the Yellow River. NPEOs and their metabolites were found in the river, with the maximum dissolved concentrations of 6.38 nmol/L for NPEOs, 0.19 nmol/L for nonylphenol ethoxy acetic acids (NPECs) and 0.79 nmol/L for NP, respectively. The maximum concentrations in the sediment and suspended particle samples were 1.50 and 5.09 nmol/g for NPEOs and NP, respectively. The effects of particles, light and microorganism on the dissipation of NPEOs in the river water were investigated based on lab-scale experiments. When natural particles were removed, 72% and 22% degradation of NPEOs were achieved at 120 h in non-sterile and sterile conditions with light, respectively. Different concentrations of NPECs were also observed in these experiments. When suspended particle matters (SPMs) were present, about 38-50% of NPEOs were sorbed to the particulate phase in only 1 h. As a result, the degradation of NPEOs and production of NPECs were inhibited. However, the combined sorption and degradation in the presence of SPMs resulted in lower dissolved NPEO concentrations than those in the absence of SPMs. Biodegradation was the most important pathway for NPEOs degradation in the river water, while NPECs seemed to be produced through both biological and abiological pathways.

Absorption↗
PubMed2006

[Cultivation and identification of pancreatic endocrine progenitor cells].

OBJECTIVE: To develop an approach to cultivate pancreatic endocrine progenitor cells and evaluate the effect thereof. METHODS: The pancreatic tissues of newborn SD rats were digested by collagenase. The pancreatic endocrine progenitor cells thus obtained were cultured in medium with glucose of the concentration of 33.2 mmol/L for 3 - 4 generations and then in medium with glucose of the concentration of 13.2 mmol/L for 7 days. Electron microscopy was used to observe the ultramicroscopic structures. Dithizone staining was used to examine the expression of insulin. Immunohistochemistry was used to examine the expression of pancreatic-duodenal homebox 1 (Pdx1) and neurogenic 3 (Ngn3). Athymic nude mice of the line BALB/C underwent intraperitoneal injection of streptozotocin so as to establish model of diabetes. 1 x 10(5) pancreatic endocrine progenitor cells, cultured in the media with low or high glucose levels, were transplanted into the renal subcapsular space of the mice respectively. Mice without transplantation were used as controls (groups 1 - 3). The surviving status and blood glucose level were observed. Two weeks later the mice were killed and their kidneys were taken out, and underwent microscopy and immunohistochemistry to observe the expression of insulin. RESULTS: Islet of pancreas-like structures were formed with insulin-positive cells, 16% +/- 5% of Pdx1 positive cells, and 69% +/- 8% of Ngn3 positive cells. The rate of diathiazone positive cells in the low glucose level medium was 32% +/- 6%, significantly higher than that in the high glucose medium (10% +/- 3%). When the cells were cultured in the medium with the glucose level of 20 mmol/L, the insulin level in the culture fluid with low glucose level was 26.0 microU/ml +/- 2.2 microU/ml, significantly higher than that with high glucose level (22.7 microU/ml +/- 3.6 microU/ml, P < 0.05). Insulin-positive cells could be found among the transplanted pancreatic cells. The surviving times of the mice transplanted with the pancreatic endocrine progenitor cells, cultured in the media with low or high glucose levels, and the controls, were 10.0 days, 8.4 days, and 5.6 days respectively with a significant difference between the groups 1 and 3 (P < 0.05). CONCLUSION: Culture medium with a certain glucose level, is beneficial for the cultivation of pancreatic endocrine progenitor cells, especially the medium with a low level of glucose that promotes the maturation and differentiation of the pancreatic endocrine progenitor cells.

Animals↗
PubMed2006

Three options for citation tracking: Google Scholar, Scopus and Web of Science.

BACKGROUND: Researchers turn to citation tracking to find the most influential articles for a particular topic and to see how often their own published papers are cited. For years researchers looking for this type of information had only one resource to consult: the Web of Science from Thomson Scientific. In 2004 two competitors emerged--Scopus from Elsevier and Google Scholar from Google. The research reported here uses citation analysis in an observational study examining these three databases; comparing citation counts for articles from two disciplines (oncology and condensed matter physics) and two years (1993 and 2003) to test the hypothesis that the different scholarly publication coverage provided by the three search tools will lead to different citation counts from each. METHODS: Eleven journal titles with varying impact factors were selected from each discipline (oncology and condensed matter physics) using the Journal Citation Reports (JCR). All articles published in the selected titles were retrieved for the years 1993 and 2003, and a stratified random sample of articles was chosen, resulting in four sets of articles. During the week of November 7-12, 2005, the citation counts for each research article were extracted from the three sources. The actual citing references for a subset of the articles published in 2003 were also gathered from each of the three sources. RESULTS: For oncology 1993 Web of Science returned the highest average number of citations, 45.3. Scopus returned the highest average number of citations (8.9) for oncology 2003. Web of Science returned the highest number of citations for condensed matter physics 1993 and 2003 (22.5 and 3.9 respectively). The data showed a significant difference in the mean citation rates between all pairs of resources except between Google Scholar and Scopus for condensed matter physics 2003. For articles published in 2003 Google Scholar returned the largest amount of unique citing material for oncology and Web of Science returned the most for condensed matter physics. CONCLUSION: This study did not identify any one of these three resources as the answer to all citation tracking needs. Scopus showed strength in providing citing literature for current (2003) oncology articles, while Web of Science produced more citing material for 2003 and 1993 condensed matter physics, and 1993 oncology articles. All three tools returned some unique material. Our data indicate that the question of which tool provides the most complete set of citing literature may depend on the subject and publication year of a given article.

Journal Article↗
PubMed2006

Hapten synthesis and development of polyclonal antibody-based multi-sulfonamide immunoassays.

This paper reports the synthesis of five sulfonamide derivatives, the production of broad-specificity polyclonal antibodies for immunoassay of sulfonamides, and the analysis of milk samples by developed assay. The three-step synthesis procedure reported in most of the literature was adopted and modified in this study. In the procedure, the purification of the intermediate was avoided and the time of synthesis was shortened from >20 to 6-9 h with improved yields. This method is generally applicable to the synthesis of haptens containing the common structure of sulfonamides. Three haptens were coupled to keyhole limpet hemocyanin, and polyclonal antibodies were obtained from rabbits immunized with these conjugates. Using the antibodies obtained, from one of these was developed an enzyme-linked immunosorbent assay (ELISA) based on the competition between free sulfonamides and the hapten-horseradish peroxidase (HRP) conjugates. The hapten-HRP conjugate giving the best competitive results and 11 structurally different sulfonamides showed 50% inhibition at concentrations of <100 ng mL(-1). After removal of the protein with acetone, milk samples were analyzed by ELISA directly; a matrix effect could be avoided when a 1:20 dilution with phosphate-buffered saline was used, and 104-131% recoveries of spiked samples were obtained. The developed immunoassay is suitable to determine sulfisozole, sulfathiazole, sulfameter, sulfamethoxypyridazine, sulfapyridine, and sulfamethizole below the maximum residue limit in milk (100 ng mL(-1) of total sulfonamides) rapidly and reliably.

Animals↗
PubMed2006

Discovery of a novel class of conotoxin from Conus litteratus, lt14a, with a unique cysteine pattern.

Conus litteratus is a worm-hunting cone snail with a highly sophisticated neuropharmacological defense strategy using small peptides in its venom. By analyzing different clones in the cDNA library of venom ducts from C. litteratus, we identified the peptide lt14a which displays a characteristic signal peptide sequence in its precursor and a unique arrangement of Cys residues (-C-C-C-C-) in its mature peptide region. RT-PCR analysis suggested that lt14a is abundantly expressed throughout the whole venom duct. An intensive analysis in sequence suggested that lt14a is similar to alpha-conotoxin qc1.1 cloned from Conus quercinus. We conducted the chemical synthesis of lt14a. The synthetic lt14a has a remarkable biological activity to suppress pain and inhibits the neuronal-type nicotinic acetylcholine receptors.

Amino Acid Sequence↗
PubMed2006

Structure of a teichoic acid-like O-polysaccharide of Escherichia coli O29.

A teichoic acid-like O-polysaccharide was isolated by mild acid degradation of the lipopolysaccharide (LPS) of Escherichia coli O29. The O-polysaccharide and an oligosaccharide obtained by dephosphorylation of the O-polysaccharide were studied by sugar analysis along with 1H and 13C NMR spectroscopy. The following structure of the branched oligosaccharide repeating unit, containing five monosaccharide residues and glycerol 1-phosphate (D-Gro-1-P), was established: [carbohydrate structure: see text].

Carbohydrate Sequence↗
PubMed2006

Structure-directing role of amines in the ionothermal synthesis.

The structure-directing effect of amine has been observed in the ionothermal synthesis of aluminophosphate molecular sieves in 1-butyl-3-methylimidazolium bromide ionic liquid. The seven different amines we tested have an influence on the crystallization dynamics and the final product, leading to the formation of pure AFI and ATV structures.

Journal Article↗
PubMed2006

Seasonal and spatial distribution of nonylphenol in Lanzhou Reach of Yellow River in China.

Nonylphenol (NP) is known as an endocrine disruptor and consequently has drawn much environmental concern. This study focused on seasonal variation and spatial distribution of NP in various matrices including water, suspended particles, and sediment taken from Lanzhou Reach of Yellow River in China. NP was measured in July and November in 2004. Concentrations of NP in water ranged from 34.2 to 599.0 ng/l, in suspended particles from 49.6 to 2835.2 ng/g dry wt, and in sediment from 38.4 to 863.0 ng/g dry wt. In terms of most water and suspended particles samples, concentrations were higher in warmer seasons than in colder seasons. Good linear correlations (R(2)=0.90 in July, R(2)=0.97 in November) were obtained for NP concentrations between water and suspended particles. In terms of sediment samples, concentrations were higher in November than in July, probably due to greater deposition of suspended particles. Reasonable linear correlations (R(2)=0.60 in July, R(2)=0.79 in November) were obtained for NP concentrations between water and sediment.

China↗
PubMed2006

Structural and molecular characterization of Shigella boydii type 16 O antigen.

Shigella is a well-known human pathogen causing dysentery and their typing is solely based on the O antigens. We investigated the chemical structure and gene cluster of Shigella boydii type 16 O antigen. As judged by sugar and methylation analyses along with NMR spectroscopy data, the O antigen has an O-acetylated branched pentasaccharide repeating O unit, which consists of two D-mannose residues (D-Man), one residue each of d-glucuronic acid (D-GlcA), N-acetylglucosamine (D-GlcNAc) and D-galactose (D-Gal), and the structure of the O unit was established. The O antigen gene cluster of S. boydii type 16 was identified and shown to contain putative genes for the synthesis of GDP-D-Man, genes encoding sugar transferases, O unit flippase (Wzx) and O antigen polymerase (Wzy) as expected. The function of the wzy gene was characterized by mutation test. Genes specific to S. boydii type 16 O antigen gene cluster were identified by screening 186 Escherichia coli and Shigella type strains, and can be used to develop PCR assays for detection of type 16 strains.

Base Sequence↗
PubMed2006

Dopachrome tautomerase (Dct) regulates neural progenitor cell proliferation.

DOPAchrome tautomerase (Dct) functions downstream of tyrosinase in the biosynthetic pathway of eumelanin by catalyzing the conversion of dopachrome to 5,5-dihydroxyindole-2-carboxylic acid (DHICA) in pigment cells. Dct transcription is regulated directly or synergistically by Pax3, Sox10 and microphthalmia transcription factor (MITF). Using Dct-lacZ transgenic mice, we measured the spatial and temporal pattern of Dct expression in vivo during neocortical neurogenesis in the brain. Dct was expressed in all layers of the dorsal telencephalon in E10.5. At E15.5 and E17.5 when cortical neurogenesis occurs, expression of Dct was primarily localized to the ventricular zone (VZ) where neuronal stem cells reside. Blocking endogenous Dct by RNAi decreased proliferation of embryonic cortical neural progenitor cells (by 48%, P < 0.05), as determined by BrdU incorporation. In adult brain, Dct/Dct expression decreased in the subventricular zone (SVZ), dentate gyrus and olfactory bulb (OB). However, strong expression of Dct was observed in rostral migratory stream (RMS) and septum. Overexpression of Dct in SVZ cells derived from the adult mice significantly increased the number of cells by 260%, whereas silencing Dct by RNAi decreased cell numbers by 25.8% at 48 h post-nucleofection (P < 0.05). The results of RT-PCR analysis revealed that Dct in the brain lacks exon 7 and is identical to the form of Dct found in neural-crest-derived melanocytes. Our data indicate that Dct, previously known as a melanoblast marker, regulates neural progenitor cell proliferation.

Animals↗