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Articles by Wei Chen
Total Records ( 13 ) for Wei Chen
  Wei Chen , Xiaowei Song and Steven Beyea
  Recent research has demonstrated that brain circulation abnormalities, either during task-induced neural activity or at rest, are more commonly associated with Alzheimer's disease (AD) than was previously thought. This is consistent with the increasing attention to the early involvement of vascular risk factors in the development of AD, in addition to the dominating neurodegenerative pathology. Early detection of cerebral perfusion changes could help advance diagnosis and intervention therapies. The present article reviews advances in perfusion magnetic resonance imaging in the study of AD. In general, there are consistent accounts of cerebral hypoperfusion in the temporal and parietal lobes in people with clinically diagnosed AD. In the early stages of the disease, transient hyperperfusion may occur particularly in the prefrontal cortex, possibly as a compensatory effect. Nevertheless, significant variability in the details of perfusion patterns is present in the early phases, making the use of these methods in early diagnosis difficult. Noninvasive perfusion-weighted magnetic resonance imaging methods have advantages over nuclear medicine imaging, especially for safe usage in long-term follow-up studies. Optimization of perfusion-weighted imaging techniques is crucial for any future clinical application. Additional studies are needed with optimization likely to come with 3T and higher field strength magnets.
  Guo-Feng Fang , Wei Chen , Shou-Dong Wang , Yan-Dong Wang , Chuan-Hao Li , Hong-Lei Zhu , Hui Wang and Yong-Qing Zeng
  Background: Intramuscular fat (IMF) is one of the most important traits affecting meat quality such as tenderness, juiciness and flavor. Phosphotyrosine interaction domain containing 1 (PID1) gene has been reported as a candidate gene for fat deposition. Therefore, an overexpression of PID1 gene in pigs could be of great benefit to the swine industry and consumers. Materials and Methods: In this study, the PID1-transgenic pigs were produced by sperm mediated gene transfer and magnetic nanoparticles with high efficiency. Real-time fluorescence quantitative PCR and Southern blot methods were employed to identify PID1-transgenic pigs. The copy numbers of exogenous gene in transgenic pigs were estimated by Southern blot analysis. Results: Twenty four live piglets were born from the two sows by natural delivery. Eleven piglets were positive in the PCR amplifications (45.83%). These PCR-positive pigs were further identified by Southern-blot analysis, out of which 7 pigs were positive in both Southern blotting and PCR (29.16%), others were positive only in PCR. In addition, the PID1 expression levels in the liver and longissimus dorsi muscle tissue were higher than wild-type ones (p<0.05), whereas the levels in backfat and kidney were similar to wild-type ones in transgenic pigs. Conclusion: The results suggest that magnetic nanoparticles can be used to efficiently introduce a transgene into animals via sperm mediated gene transfer, the PID1-transgenic pig model could further serve to study obesity and the mechanism of IMF deposition.
  Wei Chen , Hao Luo , Min Zhou , Zhe-Ming Lu , Yong-Heng Shang and Fa-Xin Yu
  In this study a level converter based on GaAs pHEMT technology for a MFC (Multifunctional Chip) is designed, simulated and tested for the application of T/R (Transmit/Receive) module for an X band phase array radar system. It has the advantages of smaller chip size, lower power consumption, higher efficiency, lower cost and high stability. The circuit design is based on a feedback and feed-forward network which compensates the chip process variations during the wafer fabrication and operation temperature changing. It results the designed chip has a high stability. Its supply voltage is -5 v with a shared bias generator, this allows reducing the power consumption compared with the other design at -7.5 v in the literature. The testing results have shown that the proposed novel design has met all the specifications given in this project.
  Jian Luo , Liu Yu , Dafang Zhang , Zhen Xia and Wei Chen
  Efficient, accurate, real-time and stable link quality estimation is essential to guarantee the upper layer protocol performance in wireless sensor network. This study expounds a new LQI-based (Based on Link Quality Indicator) link quality estimation mechanism for wireless sensor networks, which takes the lost packets and error packets into account. Based on real platform, we carry out a large number of experiments. After being analyzed the collected data, a new link evaluation model between LQI and PRR (Packet Received Ratio) is established. Experiment results have validated the correctness of the LQI-PRR model and the results also show that compared with traditional assessment methods, the mechanism proposed in this study improves the accuracy of the assessment and is more useful. At last, we analyze BER (Bit Error Ratio) and draw a relationship between LQI-PER (Packet Error Ratio), LQI-BER in order to get a further understands of the link quality.
  Wei Chen , Zhongqiang Tang and Houliang Qian
  Precision of three-dimensional space plays a vital role for the robot to perform tasks accurately. This study designs a camera image acquisition system by using rotating linear laser beam. First, the control of actuator is realized by serial communication and the 2D image is captured from lines to surface, then denoise processing calibration is carried out by using Open CV. By using Irrlicht3D engine, the point cloud data is to be rendered to convert the 2D images to the 3D effect. Robot’s collection on external image is achieved through the study of Open CV learning that combined with VC2008.
  Wei Chen , Houliang Qian , Hanqi Yu , Hu Feng and Gui Tong
  In order to solve the high frequency oscillation generated from the video signal of the camera, the paper proposes a method to improve the stability of high frequency oscillation of common sensor signal which means the high frequency oscillation signal generated from the sensor module can increase the phase margin of the unstable signal through PD controller, thus produces a stable video signal and then through the circuit of AGC (Automatic Gain Control), the automatic compensation of the frequency can be achieved and finally the fourth-order low-pass circuit is used to meet the requirement of cutoff frequency of the sensor signal processing and the stability of the signal and the high frequency performance can be ultimately improved.
  Wei Chen , Xiuqin Xu , Hui Xu , Ming Hong , Zhiyu Wang , Yongheng Shang , Dongdong Liu , Min Zhou , Zhengliang Huang and Faxin Yu
  This study presents the temporal Coupled-Mode Theory (CMT) analysis of a K-band MMIC (Microwave Monolithic Integrated Circuit) bandpass filter with dual orthogonal resonant modes. Two test methods are applied and compared in the filter response measurement. The dimensions of the MMIC filter, whose chip size is 1.9×1.35 mm, are optimized based on the FEM (Finite Element Method) simulation assisted temporal coupled-mode theory. As a two-port reciprocal system, the transmission and reflection responses of the filter are deduced. GaAs MMIC IPD (Integrated Passive Device) technology is applied for chip fabrication. The test results using a probe station fit well with the simulation results. A testing fixture is introduced to model the practical application scenario, whose measurement results, after de-embedment, have shown consistency with the simulation and the probe station test results.
  Wei Chen , Jinghua Ma , Hui Zhang , Dan Li and Xianfu Zhang
  The Red-crowned crane (Grus japonensis) is one of the largest birds in East Asia which is among the rarest and endangered cranes in the world. In order to enhance population management and further conservation of Red-crowned cranes, researchers compared behavioural changes from wild population to captive population. Meanwhile, researchers also compared the artificial inbred population with the natural normal populations. In this research, five main behavioural patterns of Red-crowned cranes include resting, moving, preening, feeding and alerting were identified by all occurrence sampling and instantaneous scanning sampling methods with 5-10 min intervals. The referred wild and captive populations were concluded from the previous publications and the artificial inbred populations were observed in Hangzhou Wildlife Park (China) during August and September, 2009. As a result, researchers found the difference (p>0.05) between wild and captive populations is not significant. However, preening in captive population is higher than in wild population. The wild population spent more time for resting compared to captive population yet feeding is the most time-spent behaviours for both populations. Furthermore, behavioural patterns between normal and inbred populations are found significantly different (p<0.05). Alerting and resting behaviours are significantly higher in the normal population than in inbred population. Moreover, moving is the dominant behaviour of inbred population but feeding is taken the most time by normal population.
  Huichun Tong , Wei Chen , Wenyuan Shi , Fengxia Qi and Xiuzhu Dong
  We previously demonstrated that Streptococcus oligofermentans suppressed the growth of Streptococcus mutans, the primary cariogenic pathogen, by producing hydrogen peroxide (H2O2) through lactate oxidase activity. In this study, we found that the lox mutant of S. oligofermentans regained the inhibition while growing on peptone-rich plates. Further studies demonstrated that the H2O2 produced on peptone by S. oligofermentans was mainly derived from seven L-amino acids, i.e., L-aspartic acid, L-tryptophan, L-lysine, L-isoleucine, L-arginine, L-asparagine, and L-glutamine, indicating the possible existence of L-amino acid oxidase (LAAO) that can produce H2O2 from L-amino acids. Through searching the S. oligofermentans genome for open reading frames with a conserved flavin adenine dinucleotide binding motif that exists in the known LAAOs, including those of snake venom, fungi, and bacteria, a putative LAAO gene, assigned as aaoSo, was cloned and overexpressed in Escherichia coli. The purified protein, SO-LAAO, showed a molecular mass of 43 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and catalyzed H2O2 formation from the seven L-amino acids determined above, thus confirming its LAAO activity. The SO-LAAO identified in S. oligofermentans differed evidently from the known LAAOs in both substrate profile and sequence, suggesting that it could represent a novel LAAO. An aaoSo mutant of S. oligofermentans did lose H2O2 formation from the seven L-amino acids, further verifying its function as an LAAO. Furthermore, the inhibition by S. oligofermentans of S. mutans in a peptone-rich mixed-species biofilm was greatly reduced for the aaoSo mutant, indicating the gene`s importance in interspecies competition.
  Rima Kossah , Consolate Nsabimana , Jianxin Zhao , Haiqin Chen , Fengwei Tian , Hao Zhang and Wei Chen
  In this article, two different sumac species, namely Syrian sumac (Rhus coriaria L.) and Chinese sumac (Rhus typhina L.) were investigated in order to determine and compare the chemical compositions of their fruits. The proximate analysis revealed a significant difference (p<0.05) between the two sumac species, with Chinese sumac exhibiting higher contents in ash, protein, fat and fiber. Gas Chromatography (GC) revealed that Chinese sumac contains higher percentage of total unsaturated fatty acids than that of Syrian sumac, with oleic and linoleic acids being predominant. The amounts of potassium and calcium were found to be higher in the fruit of Syrian sumac than in that of Chinese sumac. However, both sumac fruits exhibited also appreciable quantities of magnesium, phosphorous, sodium and iron. Syrian sumac contained much more vitamins than that of Chinese sumac, which in contrast exhibited higher amounts of essential and non-essential amino acids than that of Syrian sumac. High-Performance Liquid Chromatography (HPLC) indicated that Syrian sumac contains higher concentrations of organic acids than Chinese sumac and malic acid is the most abundant. Results from this study suggested that both Syrian and Chinese sumac fruits are potential sources of food ingredients and/or additives.
  Wei Chen , Ting Huang , Jin Dai , Wenting Liu , Julong Cheng and Yunfeng Wu
  Tobacco mosaic virus (TMV) and Potato virus Y (PVY) are two destructive plant viruses which cause significant economic losses to tobacco. Breeding resistant cultivars is one of the most important strategies to control these viruses. In this study, the responses to TMV and PVY of 22 tobacco cultivars were evaluated based on resistance index and virus titre obtained from ELISA in both greenhouses and fields during five years (2007-2011). Nicotiana glutinosa resistant to TMV and Virgin A Mutant resistant to PVY were used as resistant checks; NC89 susceptible to both TMV and PVY was used as the susceptible check. The results showed that there were significant differences in disease index and ELISA value among the 22 tobacco cultivars after inoculation. Specifically, 2 cultivars (Coker86 and Jiyan5) were identified to be resistant or moderate resistant to TMV and 3 cultivars (Liaoyan8, Jinxing6007 and Qinyan98) to PVY, while the other cultivars were susceptible or moderate susceptible to TMV or PVY. The resistant cultivars may be used as resistant resources to TMV and PVY in future breeding projects.
  Wei Chen , Methode Bacanamwo and David G. Harrison
  Previous studies have shown that the acute stimulation of endothelial nitric-oxide synthase (eNOS) mRNA transcription by laminar shear stress is dependent on nuclear factor ĸ B (NFĸB) subunits p50 and p65 binding to a shear stress response element (SSRE) in the human eNOS promoter and that mutation of the SSRE abrogates the shear-stimulated increase in eNOS promoter activity. In the present study, we found that although shear markedly increased eNOS mRNA, the increase in nuclear translocation of p50 and p65 caused by shear was only 2-fold, suggesting that shear has additional effects on NFĸB cofactor activity beyond nuclear translocation. Chromatin immunoprecipitation assays showed that virtually no p50 or p65 was bound to the eNOS promoter at base line but that shear increased the binding of these subunits to the human eNOS SSRE by 10- to 20-fold. Co-immunoprecipitation studies demonstrated during the first 30 min of shear p300 bound to p65. Shear also increased p300 histone acetyltransferase (HAT) activity by 2.5-fold and increased acetylation of p65. The increase in eNOS mRNA caused by shear was completely blocked by pharmacological inhibition of p300/HAT activity with curcumin or by p300 small interfering RNA. Chromatin immunoprecipitation assays also showed that shear stimulated acetylation of histones 3 and 4 at the region of the eNOS promoter SSRE and extended 3’ toward the eNOS coding region. This was associated with opening of chromatin at the SSRE. In conclusion, these studies reveal a previously unknown role of p300/HAT activation as a very early response to shear that is essential for increasing eNOS mRNA levels.
  Yong Jun Yang , Wei Chen , Svetlana O. Carrigan , Wei-Min Chen , Kristy Roth , Taishin Akiyama , Jun-ichiro Inoue , Jean S. Marshall , Jason N. Berman and Tong-Jun Lin
  TRAF6 (tumor necrosis factor-associated factor 6) is an essential adaptor downstream from the tumor necrosis factor (TNF) receptor and Toll-like receptor superfamily members. This molecule is critical for dendritic cell maturation and T cell homeostasis. Here we show that TRAF6 is important in high affinity IgE receptor, FcεRI-mediated mast cell activation. In contrast to dendritic cells and T cells, TRAF6-deficient mast cells matured normally and showed normal IgE-dependent degranulation. Importantly, TRAF6-deficient mast cells showed impaired production of cytokine interleukin-6, CCL-9, interleukin-13, and TNF following FcεRI aggregation. Chromatin immunoprecipitation assay showed decreased NF-κB p65 binding to CCL-9 and TNF promoters in TRAF6-deficient mast cells. Antigen and IgE-induced IκB phosphorylation and NF-κB p65 translocation to the nucleus were diminished in TRAF6-deficient mast cells. NF-κB luciferase activity in response to antigen and IgE stimulation was severely impaired in TRAF6-deficient mast cells. In addition, antigen and IgE-induced phosphorylation of mitogen-activated protein kinase p38 and JNK, but not ERK1/2, was significantly reduced in TRAF6-deficient mast cells. These results identified TRAF6 as an important signal transducer in FcεRI-mediated signaling in mast cells. Our findings implicate TRAF6 as a new adaptor/regulator molecule for allergen-mediated inflammation in allergy.
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