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Search Results: 1 - 10 of 78058 matches for " Chen Yanxin "
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A Routing Strategy with Link Disruption Tolerance for Multilayered Satellite Networks  [PDF]
Gang Zheng, Yanxin Guo
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2010, DOI: 10.4236/ijcns.2011.311113
Abstract: Link disruption has a considerable impact on routing in multilayered satellite networks, which includes predictable disruption from the periodic satellite motion and unpredictable disruption from communication faults. Based on the analysis on the predictability of satellite links, a link disruption routing strategy is proposed for multilayered satellite networks, where, a topology period is divided into non-uniform slots, and a routing table in each slot is calculated by the topology predictability of satellite networks, and a congestion control mechanism is proposed to ensure the reliable transmission of packets, and a flooding mechanism is given to deal with the routes selection in the case of unpredictable link disruption. This routing strategy is implemented on the satellite network simulation platform, the simulation results show that the strategy has less delay and higher link utilization, and can meet the routing requirements of multilayered satellite networks.
Homocysteine Induces Apoptosis of Rat Hippocampal Neurons by Inhibiting 14-3-3ε Expression and Activating Calcineurin
Jing Wang, Xue Bai, Yongxing Chen, Yanxin Zhao, Xueyuan Liu
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0048247
Abstract: A high level of plasma homocysteine (Hcy) increases the risk for neurodegenerative diseases. One such disorder is Alzheimer’s disease, which involves marked neuronal apoptosis of unknown etiology. This study shows that Hcy inhibits expression of 14-3-3ε and activates calcineurin in rat hippocampal neurons in a dose-dependent manner. Calcineurin-mediated Bad dephosphorylation, which is blocked by calcineurin inhibition and Ca2+ chelation, causes mitochondrial translocation of Bad and apoptosis; this step in the apoptotic pathway is synergistically blocked by calcineurin inhibition and overexpression of 14-3-3ε. These findings demonstrated that calcineurin activation and downregulation of 14-3-3ε may be one of the mechanisms of Hcy-induced apoptosis of hippocampal neurons.
PepMapper: A Collaborative Web Tool for Mapping Epitopes from Affinity-Selected Peptides
Wenhan Chen, William W. Guo, Yanxin Huang, Zhiqiang Ma
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0037869
Abstract: Epitope mapping from affinity-selected peptides has become popular in epitope prediction, and correspondingly many Web-based tools have been developed in recent years. However, the performance of these tools varies in different circumstances. To address this problem, we employed an ensemble approach to incorporate two popular Web tools, MimoPro and Pep-3D-Search, together for taking advantages offered by both methods so as to give users more options for their specific purposes of epitope-peptide mapping. The combined operation of Union finds as many associated peptides as possible from both methods, which increases sensitivity in finding potential epitopic regions on a given antigen surface. The combined operation of Intersection achieves to some extent the mutual verification by the two methods and hence increases the likelihood of locating the genuine epitopic region on a given antigen in relation to the interacting peptides. The Consistency between Intersection and Union is an indirect sufficient condition to assess the likelihood of successful peptide-epitope mapping. On average from 27 tests, the combined operations of PepMapper outperformed either MimoPro or Pep-3D-Search alone. Therefore, PepMapper is another multipurpose mapping tool for epitope prediction from affinity-selected peptides. The Web server can be freely accessed at: http://informatics.nenu.edu.cn/PepMapper?/
Activation of GSK3β by Sirt2 Is Required for Early Lineage Commitment of Mouse Embryonic Stem Cell
Xiaoxing Si, Wen Chen, Xudong Guo, Long Chen, Guiying Wang, Yanxin Xu, Jiuhong Kang
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0076699
Abstract: Sirt2, a member of the NAD+-dependent protein deacetylase family, is increasingly recognized as a critical regulator of the cell cycle, cellular necrosis and cytoskeleton organization. However, its role in embryonic stem cells (ESCs) remains unclear. Here we demonstrate that Sirt2 is up-regulated during RA (retinoic acid)-induced and embryoid body (EB) differentiation of mouse ESCs. Using lentivirus-mediated shRNA methods, we found that knockdown of Sirt2 compromises the differentiation of mouse ESCs into ectoderm while promoting mesoderm and endoderm differentiation. Knockdown of Sirt2 expression also leads to the activation of GSK3β through decreased phosphorylation of the serine at position 9 (Ser9) but not tyrosine at position 216 (Tyr216). Moreover, the constitutive activation of GSK3β during EB differentiation mimics the effect of Sirt2 knockdown, while down-regulation of GSK3β rescues the effect of Sirt2 knockdown on differentiation. In contrast to the effect on lineage differentiation, Sirt2 knockdown and GSK3β up-regulation do not change the self-renewal state of mouse ESCs. Overall, our report reveals a new function for Sirt2 in regulating the proper lineage commitment of mouse ESCs.
Epitope Prediction Based on Random Peptide Library Screening: Benchmark Dataset and Prediction Tools Evaluation
Pingping Sun,Wenhan Chen,Yanxin Huang,Hongyan Wang,Zhiqiang Ma,Yinghua Lv
Molecules , 2011, DOI: 10.3390/molecules16064971
Abstract: Epitope prediction based on random peptide library screening has become a focus as a promising method in immunoinformatics research. Some novel software and web-based servers have been proposed in recent years and have succeeded in given test cases. However, since the number of available mimotopes with the relevant structure of template-target complex is limited, a systematic evaluation of these methods is still absent. In this study, a new benchmark dataset was defined. Using this benchmark dataset and a representative dataset, five examples of the most popular epitope prediction software products which are based on random peptide library screening have been evaluated. Using the benchmark dataset, in no method did performance exceed a 0.42 precision and 0.37 sensitivity, and the MCC scores suggest that the epitope prediction results of these software programs are greater than random prediction about 0.09–0.13; while using the representative dataset, most of the values of these performance measures are slightly improved, but the overall performance is still not satisfactory. Many test cases in the benchmark dataset cannot be applied to these pieces of software due to software limitations. Moreover chances are that these software products are overfitted to the small dataset and will fail in other cases. Therefore finding the correlation between mimotopes and genuine epitope residues is still far from resolved and much larger dataset for mimotope-based epitope prediction is desirable.
Decreased Extracellular Adenosine Levels Lead to Loss of Hypoxia-Induced Neuroprotection after Repeated Episodes of Exposure to Hypoxia
Mei Cui, Xue Bai, Tianfu Li, Fangzhe Chen, Qiang Dong, Yanxin Zhao, Xueyuan Liu
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0057065
Abstract: Achieving a prolonged neuroprotective state following transient ischemic attacks (TIAs) is likely to effectively reduce the brain damage and neurological dysfunction associated with recurrent stroke. HPC is a phenomenon in which advanced exposure to mild hypoxia reduces the stroke volume produced by a subsequent TIA. However, this neuroprotection is not long-lasting, with the effects reaching a peak after 3 days. Therefore, in this study, we investigated the use of multiple episodes of hypoxic exposure at different time intervals to induce longer-term protection in a mouse stroke model. C57BL/6 mice were subjected to different hypoxic preconditioning protocols: a single episode of HPC or five identical episodes at intervals of 3 days (E3d HPC) or 6 days (E6d HPC). Three days after the last hypoxic exposure, temporary middle cerebral artery occlusion (MCAO) was induced. The effects of these HPC protocols on hypoxia-inducible factor (HIF) regulated gene mRNA expression were measured by quantitative PCR. Changes in extracellular adenosine concentrations, known to exert neuroprotective effects, were also measured using in vivo microdialysis and high pressure liquid chromatography (HPLC). Neuroprotection was provided by E6d HPC but not E3d HPC. HIF-regulated target gene expression increased significantly following all HPC protocols. However, E3d HPC significantly decreased extracellular adenosine and reduced cerebral blood flow in the ischemic region with upregulated expression of the adenosine transporter, equilibrative nucleoside transporter 1 (ENT1). An ENT1 inhibitor, propentofylline increased the cerebral blood flow and re-established neuroprotection in E3d HPC. Adenosine receptor specific antagonists showed that adenosine mainly through A1 receptor mediates HPC induced neuroprotection. Our data indicate that cooperation of HIF-regulated genes and extracellular adenosine is necessary for HPC-induced neuroprotection.
Analysis of the Long-Term Trend of the Exchange Rate of RMB Based on ICP’s Datum in 2011 Year  [PDF]
Hua Niu Niu, Yanxin Ma, Xiaoyuan Chu
Theoretical Economics Letters (TEL) , 2015, DOI: 10.4236/tel.2015.53045
Abstract: This paper analyzes and compares the purchasing power parity (PPP) and exchange rate worldwide based on the datum of International Comparison Program (ICP) in the year 2005 and 2011. The results indicate that developing countries have been experiencing more substantial currency devaluation, while currency appreciation occurs mainly in high-income countries. After analyzing the relative price levels for 2011 and per capita income, we find that the relative price level is above 1.5 in most countries worldwide, while the relative price level is between 0.5 and 1 in a few high-income countries. When the per capita income is around $3000, the peering relationships of purchasing power parity and exchange rates are the most obvious.
Study on the Fluctuation of Purchasing Power Parity  [PDF]
Hua Niu, Xiaoyuan Chu, Yanxin Ma
Open Journal of Business and Management (OJBM) , 2016, DOI: 10.4236/ojbm.2016.41008
Abstract: This paper tests the effect of per capita income, exchange rate, foreign direct investment inflows, net trade condition index and the final consumption expenditure growth rate on the fluctuation of purchasing power parity basing on panel fixed effects model during the period of 2000-2013 of 62 countries (religions). Empirical results show that the fluctuation of per capita income and exchange rate are the key factors to explain the fluctuation of purchasing power parity, however, purchasing power parity (PPP) fluctuation is influenced by the five variables has some differences in terms of magnitude and direction between different economies. The effect of the foreign investment on purchasing power parity is negative in low income economies, but other economies are the opposite, at the same time, the estimated coefficient of high income is lower than upper & middle income economies. The growth of final consumption expenditure is helpful to improve the purchasing power parity of low income and high income economies. It is surprising that the increase in per capita income will reduce the purchasing power of some developed economies. In China, purchasing power parity will continue a growth trend in future.
HBx Sensitizes Cells to Oxidative Stress-induced Apoptosis by Accelerating the Loss of Mcl-1 Protein via Caspase-3 Cascade
Liang Hu, Lei Chen, GuangZhen Yang, Liang Li, HanYong Sun, YanXin Chang, QianQian Tu, MengChao Wu, HongYang Wang
Molecular Cancer , 2011, DOI: 10.1186/1476-4598-10-43
Abstract: Although expression of HBx itself did not activate apoptotic signaling, it significantly enhanced oxidative stress-induced cell death both in vitro and in vivo. Interestingly, this phenomenon was associated with a pronounced reduction of protein levels of Mcl-1, but not other anti-apoptotic Bcl-2 members. Importantly, enforced expression of Mcl-1 prevented HBx-triggered cell apoptosis; conversely, specific knockdown of Mcl-1 exacerbated HBx-induced apoptosis upon exposure to oxidative stress. Furthermore, inhibition of caspase-3 not only abrogated HBx-triggered apoptotic killing but also blocked HBx-induced Mcl-1 loss. Additionally, expression of HBx and Mcl-1 was found to be inversely correlated in HBV-related hepatocellular carcinogenesis (HCC) tissues.Our findings indicate that HBx exerts pro-apoptotic effect upon exposure to oxidative stress probably through accelerating the loss of Mcl-1 protein via caspase-3 cascade, which may shed a new light on the molecular mechanism of HBV-related hepatocarcinogenesis.Chronic Hepatitis B virus (HBV) infection is a major risk factor of human chronic liver disease and is strongly associated with hepatocellular carcinogenesis (HCC). Among the HBV encoding proteins, HBV X protein (HBx) is considered as a critical viral protein that exhibits multifunctional activities in modulating gene transcription, protein degradation, signal transduction, cell proliferation, cell cycle progress, senescence, autophagy and apoptosis [1-4].Since apoptosis has been implicated as an important mechanism for liver injury [5,6], much effort has been made to understand the role of HBx in the regulation of apoptosis and its contribution to HCC. To date, the reported effects of HBx on apoptosis are controversial. As reported previously, the discrepancy of the role of HBx on cell apoptosis may be due to the different culture conditions and experimental systems used in these studies. Nevertheless, majority of these studies demonstrated that HBx can indu
Expression of human soluble TRAIL in Chlamydomonas reinhardtii chloroplast
Zongqi Yang,yinü Li,Feng Chen,Dong Li,Zhifang Zhang,Yanxin Liu,Dexian Zheng,Yong Wang,Guifang Shen
Chinese Science Bulletin , 2006, DOI: 10.1007/s11434-006-2041-0
Abstract: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces selectively apoptosis in various tumor cells and virus-infected cells, but rarely in normal cells. A chloroplast expression vector, p64TRAIL, containing the cDNA coding for the soluble TRAIL (sTRAIL), was constructed with clpP-trnL-petB-chlL-rpl23-rpl2 as Chlamydomonas reinhardtii plastid homologous recombinant fragments and spectinomycin-resistant aadA gene as a select marker. The plasmid p64TRAIL was transferred into the chloroplast genome of C. reinhardtii by the biolistic method. Three independently transformed lines were obtained by 100 mg/L spectinomycin selection. PCR amplification, Southern blot analysis of the sTRAIL coding region DNA and cultivation cells in the dark all showed that the exogenous DNA had been integrated into chloroplast genome of C. reinhardtii. Western blot analysis showed that human soluble TRAIL was expressed in C. reinhardtii chloroplast. The densitometric analysis of Western blot indicated that the expressed human sTRAIL protein in the chloroplasts of C. reinhardtii accounted for about 0.43%–0.67% of the total soluble proteins. These experimental results demonstrated the possibility of using transgenic chloroplasts of green alga as bioreactors for production of biopharmaceuticals.
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