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Now showing items 1 - 16 of 92

  • Experimental investigation on a two-stage CO2 compressor with high back pressure

    Qi, Z.   Yang, J.   Chen, J.   Zhang, H.   Zhang, L.  

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  • Local Structure of Nanocrystalline Lu2O3:Eu Studied by X-ray Absorption Spectroscopy

    Qi, Z.   Liu, M.   Chen, Y.   Zhang, G.   Xu, M.   Shi, C.   Zhang, W.   Yin, M.   Xie, Y.  

    Eu-doped nanocrystalline Lu 2O 3 with different particle sizes was prepared by combustion synthesis. The local structures around the rare-earth Lu and Eu ions were studied by using both Lu and Eu L 3 edge X-ray absorption spectroscopy. According to the extended X-ray absorption fine structure (EXAFS) analysis, detailed local structure information such as coordination numbers, bonding length, and disorder has been obtained. The results showed that the samples with a particle size larger than 5 nm keep the cubic structure and the disorder increases with decreasing size. However, when the particle size is smaller than 5 nm, the existence of considerable amorphous components accounts for the rough interface and the obvious change of the local structure around the rare-earth ions. A new type of coordination environment around Eu was formed, and the most probable symmetry of the Eu 3+ site was determined by combining the real-space self-consistent field full multiple scattering X-ray absorption near edge structure (XANES) calculation and the EXAFS result. The local structure information obtained from EXAFS and XANES was used to explain the size-dependent luminescent properties of the nanocrystalline Lu 2O 3:Eu. The decreasing intensity ratio between the host absorption band and the Eu 3+-O 2- charge-transfer state (CTS) band with decreasing particle size can be attributed to a larger disorder and more defects in the small sized samples, while the red shift of the CTS band in the smaller size particles can be ascribed to the longer Eu-O bond length and the higher coordination number
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  • Differentiation of Cyclooxygenase 1- and 2-Derived Prostanoids in Mouse Kidney and Aorta

    Qi, Z.   Cai, H.   Morrow, J. D.   Breyer, M. D.  

    Accumulating evidence indicates cyclooxygenase (COX) 1 and COX2 differentially regulate cardiovascular and renal function. We have demonstrated previously in mice that COX2 inhibition enhances angiotensin II-induced hypertension, and COX1 inhibition attenuates the pressor effect of angiotensin II. To further elucidate the mechanism underlying the functional difference of COX1 versus COX2 inhibition, the present studies examined the prostaglandin (PG) profiles derived in COX1- or COX2-inhibited mouse kidney and aorta using gas chromatographic/mass spectrometric assays. PGE(2) is the most abundant prostanoid in both renal cortex and medulla in normal C57BL/6J mice, followed by PGI(2), PGF(2 alpha) and thromboxane A(2). In contrast PGI(2) was most abundant in aorta followed by thromboxane A(2), PGE(2), and PGF(2 alpha). PGD(2) was undetectable in control kidney or aorta. At baseline, inhibition of COX 1 decreased total prostaglandins in renal cortex, medulla, and aorta, whereas COX2 inhibition decreased total prostaglandins only in renal medulla. Angiotensin II infusion significantly increased COX2-dependent/COX1-independent PGE(2) and PGI(2) in renal cortex and medulla. Anciotensin II also significantly increased renal PGF(2 alpha) in cortex, but not in medulla, through both COX1- and COX2-dependent mechanisms. These studies demonstrate that although COXI primarily contributes to basal prostanoid production in the kidney and aorta, angiotensin 11 increases renal vasodilator prostanoids predominately via COX2 activity. These effects may contribute to the specific effect of COX2 inhibitors to increase blood pressure.
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  • Hyperresponse to T-Cell Receptor Signaling and Apoptosis of Id1 Transgenic Thymocytes

    Qi, Z.   Sun, X.-H.  

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  • Calcium Entry Mediated by GLR3.3, an Arabidopsis Glutamate Receptor with a Broad Agonist Profile

    Qi, Z.   Stephens, N. R.   Spalding, E. P.  

    The amino acids glutamate (Glu) and glycine (Gly) trigger large, rapid rises in cytosolic Ca(2+) concentration and a concomitant rise in membrane potential (depolarization) in plants. The possibility that plant homologs of neuronal ionotropic glutamate receptors mediate these neuron-like ionic responses was tested in Arabidopsis (Arabidopsis thaliana) seedlings using a combination of Ca(2+) measurements, electrophysiology, and reverse genetics. The membrane depolarization triggered by Glu was greatly reduced or completely blocked in some conditions by mutations in GLR3.3, one of the 20 GLR genes in Arabidopsis. The same mutations completely blocked the associated rise in cytosolic Ca(2+). These results genetically demonstrate the participation of a glutamate receptor in the rapid ionic responses to an amino acid. The GLR3.3-independent component of the depolarization required Glu concentrations above 25 mu M, did not display desensitization, and was strongly suppressed by increasing extracellular pH. It is suggested to result from H(+)-amino acid symport. Six amino acids commonly present in soils (Glu, Gly, alanine, serine, asparagine, and cysteine) as well as the tripeptide glutathione (gamma-glutamyl-cysteinyl-Gly) were found to be strong agonists of the GLR3.3-mediated responses. All other amino acids induced a small depolarization similar to the non-GLR, putative symporter component and in most cases evoked little or no Ca(2+) rise. From these results it may be concluded that sensing of six amino acids in the rhizosphere and perhaps extracellular peptides is coupled to Ca(2+) signaling through a GLR-dependent mechanism homologous to a fundamental component of neuronal signaling.
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  • A three-dimensional coupled dynamics model of the air spring of a high-speed electric multiple unit train

    Qi, Z.   Li, F.   Yu, D.  

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  • Association of Neurofilament Proteins with Neuronal Cdk5 Activator

    Qi, Z.   Tang, D.   Zhu, X.   Fujita, D. J.   Wang, J. H.  

    Cdk5 exists in brain extracts in multiple forms, one of which is a macromolecular protein complex comprising Cdk5, neuron-specific Cdk5 activator p35nck5a and other protein components (Lee, K.-Y., Rosales, J. L., Tang, D., and Wang, J. H. (1996) J. Biol. Chem. 271,1538-1543). The yeast two-hybrid system was employed to identify p35nck5a-interacting proteins from a human brain cDNA library. One of the isolated clones encodes a fragment of glial fibrillary acidic protein, which is a glial-specific protein. Sequence alignment revealed significant homology between the p35nck5a-binding fragment of glial fibrillary acidic protein and corresponding regions in neurofilaments. The association between p35nck5a and neurofilament medium molecular weight subunit (NF-M) was confirmed by both the yeast two-hybrid assay and direct binding of the bacteria-expressed proteins. The p35nck5a binding site on NF-M was mapped to a carboxyl-terminal region of the rod domain, in close proximity to the putative Cdk5 phosphorylation sites in NF-M. A region immediately amino-terminal to the kinase-activating domain in p35nck5a is required for its binding with NF-M. In in vitro binding assays, NF-M binds both monomeric p35nck5a and the Cdk5/p35nck5a complex. The binding of NF-M has no effect on the kinase activity of Cdk5/p35nck5a.
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  • Combinations of bacterial species associated with symptomatic endodontic infections in a Chinese population

    Qi, Z.   Cao, H.   Jiang, H.   Zhao, J.   Tang, Z.  

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  • Computational Modeling of Synaptic Neurotransmission as a Tool for Assessing Dopamine Hypotheses of Schizophrenia

    Qi, Z.   Miller, G.   Voit, E.  

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  • Blockade of type ? transforming growth factor signaling prevents liver fibrosis and dysfunction in the rat

    Qi, Z.   Atsuchi, N.   Ooshima, A.   Takeshita, A.   Ueno, H.  

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  • Recombinant Covalently Closed Circular Hepatitis B Virus DNA Induces Prolonged Viral Persistence in Immunocompetent Mice

    Qi, Z.   Li, G.   Hu, H.   Yang, C.   Zhang, X.   Leng, Q.   Xie, Y.   Yu, D.   Zhang, X.   Gao, Y.   Lan, K.   Deng, Q.  

    It remains crucial to develop a laboratory model for studying hepatitis B virus (HBV) chronic infection. We hereby produced a recombinant covalently closed circular DNA (rcccDNA) in view of the key role of cccDNA in HBV persistence. A loxP-chimeric intron was engineered into a monomeric HBV genome in a precursor plasmid (prcccDNA), which was excised using Cre/loxP-mediated DNA recombination into a 3.3-kb rcccDNA in the nuclei of hepatocytes. The chimeric intron was spliced from RNA transcripts without interrupting the HBV life cycle. In cultured hepatoma cells, cotransfection of prcccDNA and pCMV-Cre (encoding Cre recombinase) resulted in accumulation of nuclear rcccDNA that was heat stable and epigenetically organized as a minichromosome. A mouse model of HBV infection was developed by hydrodynamic injection of prcccDNA. In the presence of Cre recombinase, rcccDNA was induced in the mouse liver with effective viral replication and expression, triggering a compromised T-cell response against HBV. Significant T-cell hyporesponsiveness occurred in mice receiving 4 mu g prcccDNA, resulting in prolonged HBV antigenemia for up to 9 weeks. Persistent liver injury was observed as elevated alanine transaminase activity in serum and sustained inflammatory infiltration in the liver. Although a T-cell dysfunction was induced similarly, mice injected with a plasmid containing a linear HBV replicon showed rapid viral clearance within 2 weeks. Collectively, our study provides an innovative approach for producing a cccDNA surrogate that established HBV persistence in immunocompetent mice. It also represents a useful model system in vitro and in vivo for evaluating antiviral treatments against HBV cccDNA. IMPORTANCE (i) Unlike plasmids that contain a linear HBV replicon, rcccDNA established HBV persistence with sustained liver injury in immunocompetent mice. This method could be a prototype for developing a mouse model of chronic HBV infection. (ii) An exogenous intron was engineered into the HBV genome for functionally seamless DNA recombination. This original approach could be also extended to other viral studies. (iii) rcccDNA was substantially induced in the nuclei of hepatocytes and could be easily distinguished by its exogenous intron using PCR. This convenient model system affords the opportunity to test antivirals directly targeting HBV cccDNA.
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  • Heme is an effector molecule for iron-dependent degradation of the bacterial iron response regulator (Irr) protein

    Qi, Z.   Hamza, I.   O\"Brian, M. R.  

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  • Molecular cloning and characterization of the glyceraldehyde-3-phosphate dehydrogenase gene from Penicillium expansum PE-12

    Zhang, T.   Qi, Z.   Yu, Q.S.   Tang, K.X.  

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  • Significant Contribution of Ion-water Interaction to the Ion Selectivity of a de novo Synthesized Hydrophobic Channel

    Qi, Z.   Sokabe, M.  

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  • Surface treatment of carbonyl nickel powder: Z. Qi, (Peoples\" Republic of China)

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  • Acquisition of Maternal Antibodies both from the Placenta and by Lactation Protects Mouse Offspring from Yersinia pestis Challenge

    Qi, Z.   Zhao, H.   Zhang, Q.   Bi, Y.   Ren, L.   Zhang, X.   Yang, H.   Yang, X.   Wang, Q.   Li, C.   Zhou, J.   Xin, Y.   Yang, Y.   Yang, H.   Du, Z.   Tan, Y.   Han, Y.   Song, Y.   Zhou, L.   Zhang, P.   Cui, Y.   Yan, Y.   Zhou, D.   Yang, R.   Wang, X.  

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