Background Extensive research toward creating a biological pacemaker by enhancement of inward depolarizing current has been performed. However, studies have mainly focused on inducing spontaneous activity and have not...Background Extensive research toward creating a biological pacemaker by enhancement of inward depolarizing current has been performed. However, studies have mainly focused on inducing spontaneous activity and have not adequately addressed ways to improve pacemaker function. In this study we attempted to improve pacemaker function by altering connexin expression in rat mesenchymal stem cells （MSCs） to a phenotype similar to native sinus node pacemaker cells. Methods To generate a biological pacemaker, MSCs were transduced with a cardiac pacemaker gene- hyperpolarization-activated cyclic nucleotide-gated channel 4 （HCN4）, via transfection with a lentiviral vector. Funny current （If） in HCN4~ MSCs was recorded by voltage-clamp. Overexpression of connexin 45 （gene Gja7） in MSCs was achieved by transfection with the plasmid pDsRED2-N1-Gja7-RFP. Double-immunolabelling with anti-connexin 43 and anti-connexin 45 antibodies were used to identify the gap junction channels. The effects of the genetically modified MSCs on cardiomyocyte excitability were determined in MSCs cocultured with neonatal rat ventricular myocytes. Spontaneous action potentials of neonatal rat ventricular myocytes were recorded by current-clamp. Results High level time- and voltage-dependent inward hyperpolarization current that was sensitive to 4 mmol/L Cs＋ was detected in HCN4＋ MSCs, confirming that HCN4 acted as Ir channels in MSCs. Connexin 43 and connexin 45 were simultaneously detected in CX45＋ MSCs. Beating frequency was （82±8） beats per minute （n=-5） in myocytes cocultured with non-transfected control MSCs, versus （129±11） beats per minute （n=-5） in myocytes cocultured with HCN4＋ MSCs. Myocytes cocultured with MSCs cotransfected with HCN4 and connexin 45 had the highest beating frequency at （147±9） beats per minute （n=5）. Conclusion These findings demonstrate that overexpression of connexin 45 and subsequent formation of heteromeric connexin 45/connexin 43 gap junction channels in HCN4 express展开更多
In this paper,we aim to design a practical low complexity low-density parity-check(LDPC)coded scheme to build a secure open channel and protect information from eavesdropping.To this end,we first propose a punctured L...In this paper,we aim to design a practical low complexity low-density parity-check(LDPC)coded scheme to build a secure open channel and protect information from eavesdropping.To this end,we first propose a punctured LDPC coded scheme,where the information bits in a codeword are punctured and only the parity check bits are transmitted to the receiver.We further propose a notion of check node type distribution and derive multi-edge type extrinsic information transfer functions to estimate the security performance,instead of the well-known weak metric bit error rate.We optimize the check node type distribution in terms of the signal-to-noise ratio(SNR)gap and modify the progressive edge growth algorithm to design finite-length codes.Numerical results show that our proposed scheme can achieve a lower computational complexity and a smaller security gap,compared to the existing scrambling and puncturing schemes.展开更多
目的分解单通道表面肌电信号(surface electromyography,sEMG),获得组成肌电信号的运动单元动作电位(motor unit action potential,MUAP)的波形及发放频率。方法首先对单通道的sEMG信号进行候选MUAP信号段检测,然后使用基于模糊K-均值...目的分解单通道表面肌电信号(surface electromyography,sEMG),获得组成肌电信号的运动单元动作电位(motor unit action potential,MUAP)的波形及发放频率。方法首先对单通道的sEMG信号进行候选MUAP信号段检测,然后使用基于模糊K-均值聚类的Gap Statistic聚类分析处理获取参与肌肉活动的运动单元发放的模板MUAP,最后使用广义互相关求时延的方法完成对低收缩水平的表面肌电信号的分解,并获得所有模板MUAP的发放频率。结果对模拟的单通道表面肌电信号进行分解,MUAP的准确识别率可达80%以上;并对真实采集的低收缩水平的等长收缩表面肌电信号进行分解,得到了MUAP波形和发放信息。结论本文提出的方法能够有效的对单通道表面肌电信号进行分解,具有较好的分解效果。展开更多
文摘Background Extensive research toward creating a biological pacemaker by enhancement of inward depolarizing current has been performed. However, studies have mainly focused on inducing spontaneous activity and have not adequately addressed ways to improve pacemaker function. In this study we attempted to improve pacemaker function by altering connexin expression in rat mesenchymal stem cells （MSCs） to a phenotype similar to native sinus node pacemaker cells. Methods To generate a biological pacemaker, MSCs were transduced with a cardiac pacemaker gene- hyperpolarization-activated cyclic nucleotide-gated channel 4 （HCN4）, via transfection with a lentiviral vector. Funny current （If） in HCN4~ MSCs was recorded by voltage-clamp. Overexpression of connexin 45 （gene Gja7） in MSCs was achieved by transfection with the plasmid pDsRED2-N1-Gja7-RFP. Double-immunolabelling with anti-connexin 43 and anti-connexin 45 antibodies were used to identify the gap junction channels. The effects of the genetically modified MSCs on cardiomyocyte excitability were determined in MSCs cocultured with neonatal rat ventricular myocytes. Spontaneous action potentials of neonatal rat ventricular myocytes were recorded by current-clamp. Results High level time- and voltage-dependent inward hyperpolarization current that was sensitive to 4 mmol/L Cs＋ was detected in HCN4＋ MSCs, confirming that HCN4 acted as Ir channels in MSCs. Connexin 43 and connexin 45 were simultaneously detected in CX45＋ MSCs. Beating frequency was （82±8） beats per minute （n=-5） in myocytes cocultured with non-transfected control MSCs, versus （129±11） beats per minute （n=-5） in myocytes cocultured with HCN4＋ MSCs. Myocytes cocultured with MSCs cotransfected with HCN4 and connexin 45 had the highest beating frequency at （147±9） beats per minute （n=5）. Conclusion These findings demonstrate that overexpression of connexin 45 and subsequent formation of heteromeric connexin 45/connexin 43 gap junction channels in HCN4 express
文摘In this paper,we aim to design a practical low complexity low-density parity-check(LDPC)coded scheme to build a secure open channel and protect information from eavesdropping.To this end,we first propose a punctured LDPC coded scheme,where the information bits in a codeword are punctured and only the parity check bits are transmitted to the receiver.We further propose a notion of check node type distribution and derive multi-edge type extrinsic information transfer functions to estimate the security performance,instead of the well-known weak metric bit error rate.We optimize the check node type distribution in terms of the signal-to-noise ratio(SNR)gap and modify the progressive edge growth algorithm to design finite-length codes.Numerical results show that our proposed scheme can achieve a lower computational complexity and a smaller security gap,compared to the existing scrambling and puncturing schemes.
