Biomedical subjects

Wen Yang

Publications and source records attributed to Wen Yang.

At least 37 records · Page 2Linked to original sources

PubMed2005

Echinococcus shiquicus, a new species from the Qinghai-Tibet plateau region of China: discovery and epidemiological implications.

In Shiqu County of the Qinghai-Tibet plateau, many wild and domestic mammals are involved in the transmission cycles of Echinococcus spp. Echinococcus multilocularis and Echinococcus granulosus genotype G1 (sheep strain) are sympatrically distributed in the plateau. In 1995, we identified a unique strobilate stage of Echinococcus from the Tibetan fox, Vulpes ferrilata, but considered it to be a variant of E. multilocularis. Subsequent molecular genetic studies revealed that a hydatid cyst from the plateau pika, Ochotona curzoniae, had unique mitochondrial DNA sequences which are dissimilar to any published sequences of Echinococcus. The same sequences were subsequently found in adult worms from Tibetan foxes. Morphological, genetic and ecological features of the cestode led us to designate a new species Echinococcus shiquicus. E. shiquicus has been found at other areas surveyed on the plateau; however, no infections in humans caused by E. shiquicus have been yet identified.

Animals↗

PubMed2005

Small interfering RNA and gene expression analysis using a multiplex branched DNA assay without RNA purification.

The authors have developed a novel multiplex detection system that quantitatively measures the expression level of 11 messenger RNAs (mRNAs) directly from cell lysates or tissue homogenates without RNA purification. The system incorporates branched DNA (bDNA) technology from Bayer and a multiplex bead array platform from Luminex. In this study, a 21-nt synthetic small interfering RNA (siRNA; specifically designed to knockdown interleukin-8 [IL-8] expression) was delivered into HeLa cells. Using the multiplex bDNA assay, gene expression levels were measured simultaneously from cell lysates for 11 genes. After treating the HeLa cells for 20 h with phorbol myristate acetate (PMA), IL-8 mRNA levels were induced by almost 50-fold; transfection with 30 nM IL-8-specific siRNA reduced the PMA-induced IL-8 mRNA by 80%. In addition, PMA induced mRNA expression in IL-1alpha (3-fold) and IL-6 (4-fold); however, the IL-8 siRNA did not affect the expression of either of these 2 cytokine genes, indicating that the siRNA was selective for IL-8 mRNA expression. Three housekeeping genes' expression levels were measured under all conditions tested. The multiplex bDNA assay provides a powerful tool for quantitative multiplex gene expression analysis directly from cell lysates, which could be extremely valuable for conservation of rare or difficult-to-obtain samples.

Cytokines↗

PubMed2005

Decreased stability of photosystem I in dgd1 mutant of Arabidopsis thaliana.

The dgd1 mutant of Arabidopsis thaliana provides us with a powerful tool for revealing the specific role of digalactosyldiacylglycerol (DGDG) in photosynthesis. Blue-native polyacrylamide gel electrophoresis analysis revealed that photosystem I (PSI) subunits are assembled into a PSI complex, and that a PSI subcomplex lacking stroma side subunits was also present. PSI subunits in the dgd1 mutant were decreased to a similar level compared with that in the wild type (WT) Arabidopsis. Further experiments showed that PSI subunits in the stroma side, PsaD and PsaE, in the dgd1 mutant were more susceptible to removal by chaotropic agents than those in the WT plant, indicating that the stability of PsaD and PsaE is impaired in the dgd1 mutant. These results provide evidence that DGDG is important for the stability of the PSI complex.

Arabidopsis↗

PubMed2005

Echinococcus shiquicus n. sp., a taeniid cestode from Tibetan fox and plateau pika in China.

The taeniid cestode Echinococcus shiquicus n. sp. was found from the Tibetan fox Vulpes ferrilata and the plateau pika Ochotona curzoniae in the Qinghai-Tibet plateau region of China. In the adult stage, E. shiquicus from the foxes is morphologically similar to Echinococcus multilocularis. However, the new species is differentiated by its smaller rostellar hooks, fewer segments, distinct position of genital pore in the mature segment and fewer eggs in the gravid segment. Hydatid cysts of E. shiquicus found in the livers from the pikas were essentially unilocular but an oligovesicular cyst was also found. The data of mitochondrial and nuclear DNA sequences proved E. shiquicus to be a valid taxon.

Amino Acid Sequence↗

PubMed2005

Synthesis of SiC nanowires with in-situ deposition of carbon coating.

SiC nanowires are effective reinforcement materials in ceramic matrix composites. A compliant coating such as carbon on nanowires is necessary in order to moderate the nanowire/matrix interfacial bounding for taking the most advantages of SiC nanowires. SiC nanowires with an in-situ deposition of carbon shell coating were fabricated by a novel chemical vapor growth process. Highresolution transmission electron microscopy examinations showed that the nanowires consisted of a single crystal beta-SiC core with an amorphous carbon shell 2-5 nm in thickness. The nanowires were straight with a length generally over 10 microm and a diameter 15-150 nm. The growth direction of the core SiC nanowires is (111). A simple three-step growth model for SiC nanowires was proposed based on a vapor-solid growth mechanism. Because the carbon-coated nanowires were grown directly on continuous Tyranno-SA SiC fibers, in-situ application of the present technique on the fabrication of SiC nanowire-reinforced SiC/SiC composites is expected.

Carbon↗

PubMed2004

Perturbed homeostasis of peripheral T cells elicits decreased susceptibility to anti-CD3-induced apoptosis in prediabetic nonobese diabetic mice.

Activation-induced cell death (AICD) plays a key role in the homeostasis of the immune system. Autoreactive T cells are eliminated through AICD both from the thymus and periphery. In this study, we show that NOD peripheral T cells, especially CD8(+) T cells, display a decreased susceptibility to anti-CD3-induced AICD in vivo compared with T cells from diabetes-resistant B6, nonobese diabetes-resistant, and NOD.B6Idd4 mice. The susceptibility of NOD CD8(+) T cells to AICD varies in an age- and dose-dependent manner upon stimulation in vivo with either a mitogenic or nonmitogenic anti-CD3. NOD T cells preactivated by anti-CD3 in vivo are less susceptible than B6 T cells to TCR-induced AICD. Treatment of NOD mice with a mitogenic anti-CD3 depletes CD4(+)CD25(-)CD62L(+) but not CD4(+)CD25(+)CD62L(+) T cells, thereby resulting in an increase of the latter subset in the spleen. Treatment with a nonmitogenic anti-CD3 mAb delays the onset of T1D in 8.3 TCR transgenic NOD mice. These results demonstrate that the capacity of anti-CD3 to protect NOD mice from T1D correlates with its ability to perturb T cell homeostasis by inducing CD8(+) T cell AICD and increasing the number of CD4(+)CD25(+)CD62L(+) T cells in the periphery.

Aging↗

PubMed2004

Inhibition of polyglutamine aggregate cytotoxicity by a structure-based elongation inhibitor.

Huntington's disease and other expanded CAG repeat diseases are associated with the expression of proteins containing polyglutamine (polyGln) tracts expanded beyond a pathological repeat length threshold of approximately 38. Aggregation of these expanded polyGln proteins may trigger disease by recruiting and sequestering other polyGln-containing proteins in the cell, depriving the cellular environment of critical protein activities. We describe here proline-containing polyGln peptide sequences that are effective inhibitors of the ability of polyGln aggregates to be elongated by recruiting additional polyGln monomers. These peptides are also effective inhibitors of polyGln aggregate toxicity in a cell culture model based on delivery of preassembled polyGln aggregates into the cell nucleus. These results are not only consistent with a role for polyGln aggregates in the disease mechanisms of expanded CAG repeat disorders, but also directly implicate the elongation phase of aggregate growth in the toxicity mechanism, supporting the recruitment-sequestration model for polyGln toxicity. These results may be related to the ability of the glutamine/proline-rich protein PQE-1 to protect C. elegans against polyglutamine toxicity. Inhibition of aggregate elongation is a therapeutic strategy that, based on our results, may be effective even in neurons already compromised by polyGln aggregates.

Amino Acid Sequence↗

PubMed2004

Fenced pasture: a possible risk factor for human alveolar echinococcosis in Tibetan pastoralist communities of Sichuan, China.

Alveolar echinococcosis, infection caused by the parasitic helminth Echinococcus multilocularis, is a zoonosis strongly linked to climatic and ecological factors. Cross-sectional survey data were used to test a hypothesis that partial fencing of pastures could promote alveolar echinococcosis transmission in semi-nomadic pastoral communities of the Tibetan plateau, PR China. Using multiple stepwise logistic regression with consideration of factors of age and gender, it was shown that partial fencing around the settlements in winter pasture was significantly and independently associated with the risk of human alveolar echinococcosis in the surveyed villages (P = 0.021). The underlying reason may lie in overgrazing, an assumed cause of population outbreaks of small mammal intermediate hosts of the parasite on the Tibetan plateau. Overgrazing may have been exacerbated by the reduction of communal pastures nearby the settlements due to introduction of partial fencing around group tenure pastures acquired by Tibetan pastoralist families.

Adolescent↗

PubMed2004

[Application of image correction in 3D reconstruction of mandible from CT slices].

Precision registration of serial sections is an important step for 3-D image reconstruction. It directly affects the accuracy of the reconstructed result and parameter computation. This problem has been studied and demonstrated by many investigators, but the whole process has not yet reached good performance. In this paper, we discussed the registration of serial sections image of mandible and put forward a method of the soft registration-based transformation on the basis of the hard registration in consideration of the speciality of 3-D image reconstruction for the serial sections of mandible. Employing control points and using Affine Transformation and Extended Hough Transformation, we solved the problem of displacement on 3-D image reconstruction for serial secons and paved the way for reconstructing the mandible microstructure with reality. The results of experiments indicate that the 3D image reconstructed after registration has only a little distortion.

Humans↗

PubMed2003

Study of the mechanism of TCR antagonism using dual-TCR-expressing T cells.

The mechanism of action of TCR antagonists is incompletely understood. T cells expressing two distinct TCRs have been used to test competition for TCR occupancy as a potential mechanism. Previous studies with CD4 T cells showed that an antagonist for one TCR inhibited the response to the other TCR (cross-antagonism), whereas studies with CD8 cells failed to demonstrate cross-antagonism. To determine whether CD4 and CD8 cells were intrinsically different or whether the differences were the result of the use of different effector assays, we studied both CD4 and CD8 dual-TCR-expressing T cells. In the CD4 system, consistent with previous reports, cross-antagonism of proliferation was observed. In the CD8 system, cross-antagonism was observed using proliferation as readout but not when target cell cytolysis was used. These results suggest that different mechanisms may be involved in the inhibition of proliferation and inhibition of cytotoxic effector function, the latter only involving competition for TCR occupancy. Inhibition of proliferation appears to be more complex and other mechanisms such as sequestration of signaling molecules or negative signaling may be involved. The fact that 10- to 20-fold more antagonist was needed to achieve cross-antagonism compared with inhibition of the cognate TCR is consistent with the hypothesis that competition for TCR occupancy is also a major, albeit not sole, mechanism of antagonism of the proliferative responses of CD4 and CD8 cells.

Amino Acid Sequence↗

PubMed2003

Improved recursive algorithm for light scattering by a multilayered sphere.

An improved recurrence algorithm to calculate the scattering field of a multilayered sphere is developed. The internal and external electromagnetic fields are expressed as a superposition of inward and outward waves. The alternative yet equivalent expansions of fields are proposed by use of the first kind of Bessel function and the first kind of Hankel function instead of the first and the second kinds of Bessel function. The final recursive expressions are similar in form to those of Mie theory for a homogeneous sphere and are proved to be more concise and convenient than earlier forms. The new algorithm avoids the numerical difficulties, which give rise to significant errors encountered in practice by previous methods, especially for large, highly absorbing thin shells. Various calculations and tests show that this algorithm is efficient, numerically stable, and accurate for a large range of size parameters andrefractive indices.

Journal Article↗

PubMed2003

Effects of carboxymethylcellulose and carboxypolymethylene on morphology of Aspergillus fumigatus NRRL 2346 and fumagillin production.

Aspergillus fumigatus NRRL 2346 is the producer of fumagillin, an antitumor antibiotic that inhibits angiogenesis. This strain is very difficult to grow reproducibly in shake flasks owing to an extreme form of pellet growth and extensive wall growth. The effects of carboxymethylcellulose (CMC) and carboxypolymethylene (Carbopol) on growth and fumagillin production by A. fumigatus were investigated. By adding the polymers to the fermentation medium, the growth form of the mold was changed from a single large glob to small reproducible pellets, and wall growth was diminished to a minimum. Carbopol, at a lower concentration, was more effective than CMC in improving both morphology and production. Small pellets were produced which favored fumagillin biosynthesis. 1.5% (wt/vol) CMC and 0.3% (wt/vol) Carbopol were found to be the optimum concentrations; higher levels increased viscosity to an unacceptable level.

Acrylic Resins↗

PubMed2003

Carbon and nitrogen source nutrition of fumagillin biosynthesis by Aspergillus fumigatus.

The carbon and nitrogen source requirements of Aspergillus fumigatus NRRL 2436 for growth and production of the angiogenesis inhibitor fumagillin were studied in chemically defined media. Both carbon and nitrogen sources strongly influenced fumagillin formation. Two out of 29 carbon sources tested interfered with fumagillin biosynthesis. The best combination of two carbon sources was 30 g L(-1) xylan and 50 g L(-1) mannose. Of fifteen nitrogen sources tested, three ammonium salts (chloride, sulfate, and dibasic phosphate) failed to support fumagillin formation, presumably due to the low pH which developed. The dosage-response study of the best nitrogen source, L-glutamic acid, revealed that 9 g L(-1) was optimal. Volumetric production of fumagillin was increased by 15-fold over that in the starting (Peterson-Goldstein) medium as a result of these findings.

Aspergillus fumigatus↗

PubMed2003

Evidence of a novel isoform of placenta growth factor (PlGF-4) expressed in human trophoblast and endothelial cells.

Placenta growth factor (PlGF), a homodimeric glycoprotein that is homologous to vascular endothelial growth factor (VEGF), is mitogenic to endothelial cells and protects trophoblast from apoptosis. Alternative splicing of mature mRNA gives rise to three known isoforms of PlGF. PlGF is expressed by human trophoblast during normal pregnancy, however, it is not known which isoforms are produced. We have utilized RT-PCR to characterize PlGF isoform expression in normal human trophoblast and umbilical vein endothelial cells (HUVEC). Our results show that PlGF-1, PlGF-2, and PlGF-3 isoforms are expressed by trophoblast and HUVECs. In addition, both cell types also express a novel variant of PlGF, tentatively termed PlGF-4, which has not been previously reported. PlGF-4 consists of the same sequence of PlGF-3, plus the heparin binding domain previously thought to be present only in PlGF-2. Presence of the heparin binding domain in PlGF-4 suggests that this variant would remain cell membrane-associated and thus could influence trophoblast and endothelial cells in an autocrine manner.

Alternative Splicing↗

PubMed2003

A Schistosoma japonicum very low-density lipoprotein-binding protein.

Schistosomes acquire fatty acids from their hosts, although how these parasites bind human low-density lipoproteins (LDL) and like molecules that transport fatty acids is not understood. Because parasite surface-bound host LDL may provide the schistosome with cholesterol and other lipids, as well as aid immune avoidance, understanding this process may provide fundamental insights into lipid metabolism and host defense in schistosomes. To investigate molecular aspects of lipid acquisition by schistosomes, transcripts encoding a very (V)LDL-receptor ligand binding, cysteine-rich repeat-containing protein were isolated from Schistosoma japonicum cDNAs. The deduced amino acid sequence included 207 residues with an NH2-terminal LDL ligand-binding Cys-rich motif and a COOH-terminal transmembrane (TM) domain. The ligand-binding domain was similar in sequence and structure to ligand-binding Cys-rich repeat domains from mammalian very low-density lipoprotein (VLDL) and LDL receptors, which are multi-domain proteins. This putative VLDL binding protein, designated S. japonicum very low-density lipoprotein binding protein (SVLBP), appeared to be membrane-associated, sensitive to reducing conditions, and included intra-molecular disulfide linkages. A three-dimensional (3D) model suggested that two of the three Cys residues form intra- and/or inter-molecular disulfide bridges that contribute to a patch of negative charge on the molecular surface, assumed to be associated with VLDL binding activity. SVLBP in membrane-associated and soluble fractions of adult schistosomes bound human plasma VLDL in vitro, and VLDL bound to recombinant SVLBP inhibited the binding of anti-recombinant SVLBP antibodies. Immunolocalization of SVLBP revealed prominent expression in the tegument and sub-tegument of adult male schistosomes. SVLBP may play a key role in lipid acquisition by S. japonicum.

Amino Acid Sequence↗

PubMed2003

Deficient activation and resistance to activation-induced apoptosis of CD8+ T cells is associated with defective peripheral tolerance in nonobese diabetic mice.

Activation-induced cell death (AICD) is a mechanism of homeostasis that limits the clonal expansion of autoreactive T cells and regulates central and peripheral tolerance. In nonobese diabetic (NOD) mice, defects in central and peripheral tolerance are associated with a proliferative hyporesponsiveness of thymocytes and peripheral T cells elicited upon TCR activation. We investigated whether these defects in tolerance induction and hyporesponsiveness of NOD T cells manifest in an altered susceptibility to TCR-induced AICD. TCR-activated NOD splenic CD4+ and CD8+ T cells are more resistant to AICD than control strain C57BL/6, BALB/c, and NOR T cells. NOR CD4+ but not CD8+ T cells are resistant to TCR-induced AICD. Whereas c-FLIP expression is reduced in activated T cells from control strains, it persists in activated NOD CD8+ T cells and is accompanied by diminished activity of caspase-3 and -8. IL-4 reduces this c-FLIP expression and increases caspase-3 and -8 activity in activated NOD CD8+ T cells. Moreover, IL-4 and CD28 costimulation restores the susceptibility of NOD CD8+ T cells to AICD, and this is associated with increased expression of CD25, CD95, CD95L, and TNFR2. Thus, deficient activation of CD8+ T cells and their greater resistance to TCR-induced AICD may mediate defective peripheral tolerance and the development of T1D in NOD mice.

Animals↗

PubMed2003

[Study on the diagnostic test with C-reactive protein in elderly patients with infections].

OBJECTIVE: To evaluate the value of C-reactive protein (CRP) to diagnostic test in elderly patients with infections. METHODS: C-reactive protein were investigated in 142 elderly patients with infections and 216 elderly patients without. CRP 7 - 20, 21 - 40 and 41 - 60 mg/L were stratified, the index of diagnostic test counted. RESULTS: Concentrations of CRP in patients with different diseases were upper respiratory tract infection 36.9 mg/L +/- 28.9 mg/L, acute bronchitis 30.1 mg/L +/- 28.1 mg/L, pneumonia 55.9 mg/L +/- 32.9 mg/L, urinary infection 49.0 mg/L +/- 27.6 mg/L and enteritis 39.3 mg/L +/- 35.6 mg/L. They were all higher than those in control group (5.2 mg/L +/- 2.9 mg/L, P < 0.001). Stratified analysis disclosed that the specificity of CRP was 83.3% - 99.0% for diagnostic infection disease. The positive likelihood ratio (LR) of 7 - 20, 21 - 40 and 41 - 60 mg/L were 3.6, 27.0 and 128.0, respectively. CONCLUSION: C-reactive protein was an important marker to diagnose elderly patients with infections.

Aged↗

PubMed2002

Aggregated polyglutamine peptides delivered to nuclei are toxic to mammalian cells.

A number of observations point to the aggregation of expanded polyglutamine [poly(Q)]-containing proteins as playing a central role in the etiology of Huntington's disease (HD) and other expanded CAG-repeat diseases. Transfected cell and transgenic animal models provide some of this support, but irrefutable data on the cytotoxicity of poly(Q) aggregates is lacking. This may be due in part to difficulties in observing all aggregated states in these models, and in part to the inability to conclusively rule out the role of monomeric states of the poly(Q) protein. To address these questions, we produced aggregates of simple poly(Q) peptides in vitro and introduced them to mammalian cells in culture. We find that Cos-7 and PC-12 cells in culture readily take up aggregates of chemically synthesized poly(Q) peptides. Simple poly(Q) aggregates are localized to the cytoplasm and have little impact on cell viability. Aggregates of poly(Q) peptides containing a nuclear localization signal, however, are localized to nuclei and lead to dramatic cell death. Amyloid fibrils of a non-poly(Q) peptide are non-toxic, whether localized to the cytoplasm or nucleus. Nuclear localization of an aggregate of a short, Q(20), poly(Q) peptide is just as toxic as that of a long poly(Q) peptide, supporting the notion that the influence of poly(Q) repeat length on disease risk and age of onset is at the level of aggregation efficiency. The results support a direct role for poly(Q) aggregates in HD-related neurotoxicity.

Animals↗