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Wei Yang

Publications and source records attributed to Wei Yang.

At least 145 records · Page 8Linked to original sources
PubMed2004

Molecularly imprinted sol-gel nanotubes membrane for biochemical separations.

In this study, we report a simple procedure for applying molecular imprinting functional groups to the inner surfaces of the template-synthesized sol-gel nanotubes for chemical separation of estrone. The silica nanotubes were synthesized within the pores of nanopore alumina template membranes using a sol-gel method by simultaneous hydrolysis of a silica monomer-imprinted molecule complex and tetraethoxysilane (TEOS). A covalent imprinting strategy was employed by generating a sacrificial spacer through the reaction of the isocyanate group of 3-(triethoxysilyl)propyl isocyanate and a phenol moiety of estrone to form a thermally cleavable urethane bond. This allowed us to remove the imprinted estrone by simple thermal reaction and to simultaneously introduce functional groups into the cavity formed by the silica nanotubes. Experiments indicated that estrone could be bound selectively by such an approach and have a binding affinity of 864 +/- 137 (n = 3).

Estrone↗
PubMed2004

Study on immune function of dendritic cells in patients with esophageal carcinoma.

AIM: To investigate the immune function of dendritic cells from both peripheral blood and operated tissues of esophageal carcinoma patients in order to find the relationship between the immune function of dendritic cells and the pathogenesis of esophageal carcinoma. METHODS: The expression of CD83, CD80, and CD86 on the surface of dendritic cells cultured from the peripheral blood of patients was detected compared with that from health donors using flow cytometry. The ability of dendritic cells to induce T lymphocyte proliferation was evaluated by a liquid scintillation counter. The expression of CD80, CD86, CD83, and S-100 proteins was assessed in esophageal carcinoma tissues using immunohistochemical method. RESULTS: Compared with those from healthy donors, dendritic cells cultured from the peripheral blood of patients expressed lower CD80 and CD86. Furthermore, the ability of dendritic cells in patients to induce T lymphocyte proliferation was significantly lower than that of the control group. Compared with the control group, the positive expression ratio and frequencies of CD80, CD86, and S-100 in esophageal carcinoma tissues were significantly down regulated. The expression of CD83 was up-regulated in the pericancerous tissues, but no expression was found in the cancerous nodules. CONCLUSION: The impaired immune function and the decreased number of dendritic cells cause pathogenesis and progression of esophageal carcinoma.

Aged↗
PubMed2004

Congenital malformations in births with orofacial clefts among 3.6 million California births, 1983-1997.

Few population-based epidemiologic data are available on malformation phenotypes that co-occur with orofacial clefts. We explored the occurrence of structural congenital malformations in offspring with cleft palate (CP) and in offspring with cleft lip with or without CP (CLP), using data from a population-based active surveillance system. Ascertainment was performed among 3548991 liveborn and 23239 stillborn offspring of California women who delivered in nonmilitary hospitals during the period, 1983-1997. Structural congenital malformations were found in 91888 births. Among them, 2343 had CP and 4072 had CLP. Malformations were grouped according to 3- and 4-digit codes of the British Pediatric Association (BPA). Prevalences of each malformation grouping, defined by these codes, were calculated among: (1). all births with CP; (2). all births with CLP; (3). all births without CP or CLP but with another structural malformation; and (4). all births in the population at risk. These various prevalence measures were the basis of estimating relative risks. Observed relative risks indicated that some phenotypes were more likely and some were less likely to co-occur with either CP or CLP, with relative risks ranging from 0.5 to 2.4. For both CP and CLP, estimated relative risks were highest for malformations involving the respiratory system and lowest for spina bifida. The exclusion of all births (n = 10702) with chromosomal anomalies from comparisons did not materially alter observed relative risk estimates. Computations extended to 4-digit level BPA codes revealed elevated risks for a number of more specific diagnoses seen within the larger (3-digit level) groupings defined as eye, ear, respiratory, upper alimentary tract, and other musculoskeletal anomalies. In this large population-based cohort of infants and fetuses with CLP or CP, we observed several noncleft malformation groupings to be more common and others to be less common in their co-occurrence with orofacial clefts relative to their co-occurrence with any other malformation. These observed patterns tended to be similar for CP and for CLP.

California↗
PubMed2004

Limb deficiency defects, MSX1, and exposure to tobacco smoke.

There is increasing evidence from epidemiologic studies that genetic susceptibilities may modify the teratogenic effects of smoking. A previous study suggested that maternal smoking in the presence of a dinucleotide repeat polymorphism for MSX1 produced an almost fivefold increased risk for limb anomalies, providing evidence for a gene-environment interaction. The current study examined this potential interaction, using case-control data with several methodologic improvements, including a larger sample size and more detailed information on cigarette smoke exposures. Cases (n = 92) were ascertained from pregnancies ending in 1987-1989, and controls (n = 180) were randomly selected from eligible liveborn infants. In telephone interviews, women reported smoking behaviors during the month before pregnancy through the end of the first trimester. Odds ratios (OR) for maternal and paternal smoking ranged from 1.0 to 1.4, risk estimates were imprecise; for example, the OR for maternal smoking >or=20 cigarettes per day, versus none, was 1.3 (95% confidence interval (CI) 0.5-3.4). Relative to the homozygous wildtype, the OR was 1.5 (95% CI 0.7-3.5) for the homozygous variant genotype and 0.8 (95% CI 0.5-1.4) for the heterozygous variant genotype. There was no evidence that maternal smoking or both parents smoking, in combination with a susceptible MSX1 genotype, conferred an additional increase in risk of limb defects. This study did not find a gene-environment interaction between maternal smoking, infant MSX1 CA repeat polymorphism, and risk of limb deficiency defects. This finding contrasts with results of a previous study, which provided initial evidence for such an interaction. Several important methodological differences may have contributed to the differences in findings between the two studies.

Adult↗
PubMed2004

Snapshots of replication through an abasic lesion; structural basis for base substitutions and frameshifts.

Dpo4 from S. Solfataricus, a DinB-like Y family polymerase, efficiently replicates DNA past an abasic lesion. We have determined crystal structures of Dpo4 complexed with five different abasic site-containing DNA substrates and find that translesion synthesis is template directed with the abasic site looped out and the incoming nucleotide is opposite the base 5' to the lesion. The ensuing DNA synthesis generates a -1 frameshift when the abasic site remains extrahelical. Template realignment during primer extension is also observed, resulting in base substitutions or even +1 frameshifts. In the case of a +1 frameshift, the extra nucleotide is accommodated in the solvent-exposed minor groove. In addition, the structure of an unproductive Dpo4 ternary complex suggests that the flexible little finger domain facilitates DNA orientation and translocation during translesion synthesis.

Amino Acid Substitution↗
PubMed2004

Activation of integrin beta-subunit I-like domains by one-turn C-terminal alpha-helix deletions.

Integrins contain two structurally homologous but distantly related domains: an I-like domain that is present in all beta-subunits and an I domain that is present in some alpha-subunits. Atomic resolution and mutagenesis studies of alpha I domains demonstrate a C-terminal, axial displacement of the alpha7-helix that allosterically regulates the shape and affinity of the ligand-binding site. Atomic resolution studies of beta I-like domains have thus far demonstrated no similar alpha7-helix displacement; however, other studies are consistent with the idea that alpha I and beta I-like domains undergo structurally analogous rearrangements. To test the hypothesis that C-terminal, axial displacement of the alpha7-helix, coupled with beta6-alpha7 loop reshaping, activates beta I-like domains, we have mimicked the effect of alpha7-helix displacement on the beta6-alpha7 loop by shortening the alpha7-helix by two independent, four-residue deletions of about one turn of alpha-helix. In the case of integrin alphaLbeta2, each mutant exhibits constitutively high affinity for the physiological ligand intercellular adhesion molecule 1 and full exposure of a beta I-like domain activation-dependent antibody epitope. In the case of analogous mutants in integrin alpha4beta7, each mutant shows the activated phenotype of firm adhesion, rather than rolling adhesion, in shear flow. The results show that integrins that contain or lack alpha I domains share a common pathway of beta I-like domain activation, and they suggest that beta I-like and alpha I domain activation involves structurally analogous alpha7-helix axial displacements.

Allosteric Regulation↗
PubMed2004

Crystal structure of a benzo[a]pyrene diol epoxide adduct in a ternary complex with a DNA polymerase.

The first occupation-associated cancers to be recognized were the sooty warts (cancers of the scrotum) suffered by chimney sweeps in 18th century England. In the 19th century, high incidences of skin cancers were noted among fuel industry workers. By the early 20th century, malignant skin tumors were produced in laboratory animals by repeatedly painting them with coal tar. The culprit in coal tar that induces cancer was finally isolated in 1933 and determined to be benzo[a]pyrene (BP), a polycyclic aromatic hydrocarbon. A residue of fuel and tobacco combustion and frequently ingested by humans, BP is metabolized in mammals to benzo[a]pyrene diol epoxide (BPDE), which forms covalent DNA adducts and induces tumor growth. In the 70 yr since its isolation, BP has been the most studied carcinogen. Yet, there has been no crystal structure of a BPDE DNA adduct. We report here the crystal structure of a BPDE-adenine adduct base-paired with thymine at a template-primer junction and complexed with the lesion-bypass DNA polymerase Dpo4 and an incoming nucleotide. Two conformations of the BPDE, one intercalated between base pairs and another solvent-exposed in the major groove, are observed. The latter conformation, which can be stabilized by organic solvents that reduce the dielectric constant, seems more favorable for DNA replication by Dpo4. These structures also suggest a mechanism by which mutations are generated during replication of DNA containing BPDE adducts.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed2004

Intersubunit signal transmission in integrins by a receptor-like interaction with a pull spring.

The function of some multidomain proteins is regulated by interdomain communication. We use second-site suppressor cysteine mutations to test a hypothesis on how the inserted (I)-like domain in the integrin beta-subunit regulates ligand binding by the neighboring I domain in the integrin alpha-subunit [Huth, J. R., Olejniczak, E. T., Mendoza, R., Liang, H., Harris, E. A., et al. (2000) Proc. Natl. Acad. Sci. USA 97, 5231-5236; and Alonso, J. L., Essafi, M., Xiong, J. P., Stehle, T. & Arnaout, M. A. (2002) Curr. Biol. 12, R340-R342]. The hypothesis is that an interaction between the beta I-like metal ion-dependent adhesion site (MIDAS) and an intrinsic ligand in the linker following the alpha I domain, Glu-310, exerts a pull that activates the alpha I domain. Individual mutation of alpha(L) linker residue Glu-310 or beta(2) MIDAS residues Ala-210 or Tyr-115 to cysteine abolishes I domain activation, whereas the double mutation of alpha(L)-E310C with either beta(2)-A210C or beta(2)-Y115C forms a disulfide bond that constitutively activates ligand binding. The disulfide-bonded mutant is resistant to small molecule antagonists that bind to the beta I-like domain near its interface with the alpha I domain and inhibit communication between these domains but remains susceptible to small molecule antagonists that bind underneath the I domain alpha 7-helix and certain allosteric antagonistic antibodies. Thus, the alpha 7-helix and its linker are better modeled as a pull spring than a bell rope. The results suggest that alpha(L) residue Glu-310, which is universally conserved in all I domain-containing integrins, functions as an intrinsic ligand for the beta I-like domain, and that when integrins are activated, the beta I-like MIDAS binds to Glu-310, pulls the spring, and thereby activates the alpha I domain.

Animals↗
PubMed2004

Free energy simulations: use of reverse cumulative averaging to determine the equilibrated region and the time required for convergence.

A method is proposed for improving the accuracy and efficiency of free energy simulations. The essential idea is that the convergence of the relevant measure (e.g., the free energy derivative in thermodynamic integration) is monitored in the reverse direction starting from the last frame of the trajectory, instead of the usual approach, which begins with the first frame and goes in the forward direction. This simple change in the use of the simulation data makes it straightforward to eliminate the contamination of the averages by contributions from the equilibrating region. A statistical criterion is introduced for distinguishing the equilibrated (production) region from the equilibrating region. The proposed method, called reverse cumulative averaging, is illustrated by its application to the well-studied case of the alchemical free energy simulation of ethane to methanol.

Computer Simulation↗
PubMed2004

[Mathematical protocol for radiofrequency ablation of liver tumors and its clinical application].

OBJECTIVE: To develop a preoperative protocol for ultrasonography-guided percutaneous radiofrequency ablation (RFA) on liver tumors larger than 3.5 cm in diameter based on mathematical models and clinical experience, and to evaluate its ablated effect compared to the previous non-math method. METHODS: One hundred and twenty-five patients with 80 primary and 55 secondary liver tumors (4.7 +/- 0.9 cm in diameter, ranged from 3.6 - 7.0 cm) were enrolled in this study, of which the first 22 patients (23 tumors) had been treated empirically before the mathematical model was set up and were referred as the non-math group. The rest 103 patients (112 tumors) were treated based on the mathematical model and referred as the math group. Based on principle of overlapping spheres, a mathematical analysis was performed to investigate how multiple ablation spheres could overlap and cover larger tumors most efficiently. Some mathematical models such as regular prism and regular polyhedron model were chosen to estimate the mathematical protocol which included least ablation (sphere) number and optimal overlapping mode required to adequately ablate a large and spherical target lesion. The target volume consisted of the tumor plus a 0.5 - 1 cm tumor-free margin. The operation method for electrode placement was also described. RESULTS: The procedure success rate for the math group was 88.4% (99/112), local recurrence rate and estimated mean time until local recurrence were 25.9% (29/112) and 17.5 months, respectively. While for the non-math group the results were 52.2% (12/23) (P < 0.01), 56.5% (13/23) (P < 0.05) and 11.9 months (P < 0.05), respectively. The therapy results in the math group were much better than in the non-math group. CONCLUSION: This study provides theoretic basis and clinical guidance for RFA therapy for liver tumors larger than 3.5 cm. These results could be used to reduce local recurrence rate and improve treatment response.

Adult↗
PubMed2004

Soluble fibrin augments spreading of fibroblasts by providing RGD sequences of fibrinogen in soluble fibrin.

We previously reported that fibroblasts were found to spread far more avidly on NaBr-solubilized fibrin monomer (FM) monolayers than on immobilized fibrinogen (Fbg), indicating that removal of fibrinopeptides by thrombin is a prerequisite for the fibrin-mediated augmentation of cell spreading [J. Biol. Chem. 272 (1997) 8824-8829]. Soluble fibrin (SF), a 1:2 complex of fibrin-monomer and fibrinogen, is known to be present in the circulating blood under the pathological condition in which blood coagulation is activated. However, its physiological roles are still incompletely known. Fibroblasts spread on immobilized purified soluble fibrin. Cells spreading on immobilized soluble fibrin were blocked by the exogenous addition of soluble fibrin and glycine-arginine-glycine-aspartic acid-serine-phenylalanine (GRGDSP)-synthetic peptide but not by the addition of fibrinogen or fibrin monomer. However, cell spreading activity was decreased in the surfaces coated with fragment X, whose Aalpha-chains lack carboxyl-terminal segments including arginine-glycine-aspartic acid (RGD)-2 domain, fibrin monomer complexes. It suggests that the RGD-2 domain of fibrinogen after being complexed with fibrin monomer plays a pivotal role for soluble fibrin-dependent cell spreading. Soluble fibrin in plasma derived from the patients of disseminated intravascular coagulation (DIC) was immuno-purified using the monoclonal antibody (mAb) which specifically recognizes the Ca(++)-dependent conformer of fibrinogen. The purified soluble fibrin consisted of desAA-fibrin monomer and two fibrinogen molecules and did show the cell spreading activity. Thus, soluble fibrin in plasma plays a role as the modulator of thrombogenic process in vivo.

Cell Adhesion↗
PubMed2004

Molecular characterization of benzimidazole resistance in Helicobacter pylori.

A family of benzimidazole derivatives (BI) was shown to possess potent and selective activity against Helicobacter pylori, although the precise cellular target of the BIs is unknown. Spontaneous H. pylori mutants were isolated as resistant to a representative BI (compound A). Genomic DNA was isolated from a BI-resistant mutant, transformed into a BI-sensitive strain, and found to be sufficient to confer BI resistance. The resistance determinant was localized to a 17-kb clone after screening a lambda-based genomic library constructed from the BI-resistant strain. Upon sequencing and mapping onto the H. pylori strain J99 genome, the 17-kb clone was shown to contain the entire nuo operon (NADH:ubiquinone oxidoreductase). Further subcloning and DNA sequencing revealed that a single point mutation in nuoD was responsible for BI resistance. The mutation resulted in a G398S amino acid change at the C terminus of NuoD. Thirty-three additional spontaneous BI-resistant mutants were characterized. Sequencing of nuoD from 32 isolated mutants revealed three classes of missense mutation resulting in amino acid changes in NuoD: G398S, F404S, and V407M. One BI-resistant isolate did not have a mutation in nuoD. Instead, a T27A amino acid change was identified in NuoB. MIC testing of the wild-type H. pylori strain and four classes of nuo mutants revealed that all NuoD mutant classes were hypersensitive to rotenone, a known inhibitor of complex I (NADH:ubiquinone oxidoreductase) suggested to bind to NuoD. Further, a nuoD knockout verified that it is essential in H. pylori and may be the target of the BI compounds.

Anti-Bacterial Agents↗
PubMed2004

Use of the riboflavin synthase gene (ribC) as a model for development of an essential gene disruption and complementation system for Haemophilus influenzae.

We have developed a system for rapid and reliable assessment of gene essentiality in Haemophilus influenzae Rd strain KW20. We constructed two "suicide" complementation vectors (pASK5 and pASK6) containing 5' and 3' regions of the nonessential ompP1 gene flanking a multiple cloning site and a selectable marker (a chloramphenicol resistance gene or a tetracycline resistance cassette). Transformation of H. influenzae with the complementation constructs directs chromosomal integration of a gene of interest into the ompP1 locus, where the strong, constitutive ompP1 promoter drives its expression. This single-copy, chromosome-based complementation system is useful for confirming the essentiality of disrupted genes of interest. It allows genetic analysis in a background free of interference from any upstream or downstream genetic elements and enables conclusive assignment of essentiality. We validated this system by using the riboflavin synthase gene (ribC), a component of the riboflavin biosynthetic pathway. Our results confirmed the essentiality of ribC for survival of H. influenzae Rd strain KW20 and demonstrated that a complementing copy of ribC placed under control of the ompP1 promoter reverses the lethal phenotype of a strain with ribC deleted.

Bacterial Proteins↗
PubMed2004

Silica-hemin composite nanoparticles as new biocatalyst to highly sensitive determination of glucose in human serum.

The preparation and utilization of a novel composite silica-hemin nanoparticles (CSHNs) as mimetic peroxidase are reported in this article. Experimental results showed that the composite nanoparticles had unique advantages over free hemin molecules in good stability and highly catalytic activity. By employing these nanoparticles as biocatalyst, we developed a new spectrofluorometric method for the determination of trace level glucose. The calibration graph for glucose was linear over the range 4.0 x 10(-7) mol/L - 7.0 x 10(-5) mol/L, with a detection limit of 1.0 x 10(-7) mol/L. The proposed method has been successfully applied to the determination of glucose in serum samples and offers the advantages of being rapid, stable, sensitive, and renewable.

Blood Glucose↗
PubMed2004

[Identification of a recurrent mutation in the ROR2 gene in a Chinese family with brachydactyly type B].

OBJECTIVE: To identify the disease-causing mutation in a Chinese family with brachydactyly type B (BDB). METHODS: Genomic DNA was extracted from peripheral blood samples of family members. Exons 8 and 9 of the ROR2 gene were amplified by polymerase chain reaction (PCR) and sequenced directly. Furthermore, the PCR products showing mutation were cloned into pMD18T vector and the insert fragments were sequenced. RESULTS: A 1398-1399 insA heterozygous mutation was detected in the patient. This mutation had been found in German families with BDB. CONCLUSION: To the authors' knowledge, it is the first report on identification of the ROR2 pathogenic mutation in Chinese patients with BDB.

Amino Acid Sequence↗
PubMed2004

[Effects of high frequency vibration on expression of myosin heavy chain (MHC) in intrafusal and extrafusal fibers in soleus muscles of tail-suspended rats].

OBJECTIVE: To study the effects of high frequency vibration on expression of myosin heavy chain (MHC) in intrafusal and extrafusal fibers in soleus muscles of tail-suspended rats. METHOD: Weightlessness was simulated by tail suspension of female rats. Using immunohistochemistry technique, changes of expression of MHC in intrafusal and extrafusal fibers of soleus muscles were detected. RESULT: Expression of fast MHC in intrafusal and extrafusal fibers of soleus muscles increased during 7 d of simulated weightlessness, whereas during 7 d of tail suspension plus high frequency vibration, these changes were not detected. CONCLUSION: High frequency vibration can counteract the changes in expression of MHC in intrafusal and extrafusal fibers of rats soleus under muscles of rats in simulated weightlessness situation.

Animals↗
PubMed2003

Tetramerization and DNA ligase IV interaction of the DNA double-strand break repair protein XRCC4 are mutually exclusive.

The XRCC4 protein is of critical importance for the repair of broken chromosomal DNA by non-homologous end joining (NHEJ). The absence of XRCC4 abolishes chromosomal NHEJ almost completely. One reason for this severe phenotype is that XRCC4 binds and modulates the stability and activity of the NHEJ-specific ligase, DNA ligase IV. XRCC4 in solution is in equilibrium between the dimeric and tetrameric forms. Previous structural studies have shown that the interface between dimers is located in the same region as that implicated in DNA ligase IV interaction. With the use of equilibrium sedimentation analysis, we show here that only the XRCC4 dimer can associate with DNA ligase IV, forming a monodisperse complex of 2:1 stoichiometry in solution. In addition, physical analysis of XRCC4/DNA ligase IV complex formation, combined with mutational analysis of XRCC4, indicates that tetramerization and DNA ligase IV binding are mutually exclusive. We propose that the putative function of the XRCC4 tetramer is distinct from its DNA ligase IV-associated function.

Animals↗