Relationship between action potential, contraction-relaxation pattern, and intracellular Ca2+ transient in cardiomyocytes of dogs with chronic heart failure

Abnormalities of contractile function have been identified in cardiomyocytes isolated from failed human hearts and from hearts of animals with experimentally induced heart failure (HF). The mechanism(s) responsible for these functional abnormalities are not fully understood. In the present study, we examined the relationship between action potential duration, pattern of contraction and relaxation, and associated intracellular Ca²⁺ transients in single cardiomyocytes isolated from the left ventricle (LV) of dogs (n = 7) with HF produced by multiple sequential intracoronary microembolizations. Comparisons were made with LV cardiomyocytes isolated from normal dogs. Action potentials were measured in isolated LV cardiomyocytes by perforated patch clamp, Ca²⁺ transients by fluo 3 probe fluorescence, and cardiomyocyte contraction and relaxation by edge movement detector. HF cardiomyocytes exhibited an abnormal pattern of contraction and relaxation characterized by an attenuated initial twitch (spike) followed by a sustained contracture ('dome') of 1 to 8 s in duration and subsequent delayed relaxation. This pattern was more prominent at low stimulation rates (58% at 0.2 Hz, n = 211, 21% at 0.5 Hz, n = 185). Measurements of Ca²⁺ transients in HF cardiomyocytes at 0.2 Hz manifested a similar spike and dome configuration. The dome phase of both the contraction/relaxation pattern and Ca²⁺ transients seen in HF cardiomyocytes coincided with a sustained plateau of the action potential. Shortening of the action potential duration by administration of saxitoxin (100 nM) or lidocaine (30 μM) reduced the duration of the dome phase of both the contraction/relaxation profile as well as that of the Ca²⁺ transient profile. An increase of stimulation rate up to 1 Hz caused shortening of the action potential and disappearance of the spike-dome profile in the majority of HF cardiomyocytes. In HF cardiomyocytes, the action potential and Ca²⁺ transient duration were not significantly different from those measured in normal cells. However, the contraction-relaxation cycle was significantly longer in HF cells (314 ± 67 ms, n = 21, vs. 221 ± 38 ms, n = 46, mean ± SD), indicating impaired excitation-contraction uncou pling in HF cardiomyocytes. The results show that, in cardiomyocytes isolated from dogs with HF, contractile abnormalities and abnormalities of intracellular Ca²⁺ transients at low stimulation rates are characterized by a spike-dome configuration. This abnormal pattern appears to result from prolongation of the action potential. Received 22 January 1998; received after revision 16 March 1998; accepted 27 March 1998     

抗性消声器中穿孔板结构的声传递特性

本文利用声波在管中粘滞阻尼方面的理论,研究了存在气流时穿孔板结构的声传递特性。研究表明:穿孔板的声阻与孔板厚度、孔径、穿孔数目、声波频率和气流速度等因素有关。     

卫星结构蜂窝夹层板的等效计算

在利用MSC／NASTRAN对卫星结构进行有限元计算时，必须对蜂窝夹层板进行预先的等效处理，等效处理的合理与否将直接影响到计算结果的可信度．为此，研究了3种不同的等效方法，即三明治夹心板理论、蜂窝板理论以及等效板理论，其中三明治夹心板理论方法只对蜂窝夹芯进行等效，而蜂窝板理论和等效板理论方法则是对整个蜂窝夹层板进行等效．分别采用这3种等效方法，对某铝蜂窝夹层板的2种工况进行了模态分析，并将计算结果进行了比较．结果表明，运用等效方法的计算结果非常接近于解析解，证实了等效处理方法的合理性和正确性．     

一种提高等离子体显示器分辨率和亮度的驱动技术

针对采用寻址与显示分离技术的传统彩色PDP应用于高清晰度显示时存在分辨率和子场数目的提高将导致亮度降低的问题，提出了一种新的复合型驱动方法，该方法采用电极等间距排列的PDP屏以及偶数行对奇数行图像数据的复制，将一帧图像分奇偶场交替显示，克服了传统PDP屏存在不发光电极间隙的缺点，使PDP屏所有电极间隙交替放光，提高了彩PDP的高度和分辨率，同时增加了子场数目，该方法还具有制屏工艺改动不大和电路成本无明显增加的优点，测量结果表明，采用复合型驱动技术的PDP，其峰值亮度可达到450cd/m^2.     

不完全面板数据随机效应的检验

主要考察了双向误差面板数据模型yi, t=α x′i, tβ ui, t,ui, t=μi λt νi, t在缺失数据下的统计性质,给出了检验随机效应是否存在的检验统计量,求出该检验统计量的大样本分布,并从数值实验上验证了上述检验统计量的统计性质.     

变孔径多孔集水管的水力设计

由于管壁的摩擦阻力和管内流体速度沿轴向增大 ,多孔集水管内的压力沿轴向减小 .基于水力学原理推导出多孔集水管内各种变量间的无量纲关系式 ,并给出了变孔径多孔集水管水力设计的一种简易方法 .     

高速公路收费站交通信号控制装置设计

对收费系统中3种交通信号设备进行了设计.设计重点是设备的基本功能和可靠性,根据实际工作条件尽可能选择简单的电路结构,以提高设备的性价比.可靠性设计主要包括自动故障测试、定位、报告和冗余备份.车辆金额显示板采用4个数码管8线复用的并行传输方式,对数码显示信号线的故障进行检测和报告.通行指示灯采用电流环光电隔离技术,设置了发光器件的冗余备份和自动切换功能,发生故障时能报告信息.自动挡车器由微处理器及其附属电路构成,可对闭环控制回路的故障进行检测、定位和指示.该设计不仅提高了设备的可靠性,而且使系统的在线维护工作更快捷,整体性能明显提高.     

一类化学反应流的传输问题的均匀化

研究了一类穿过具有周期分布的活性固体颗粒的区域外部,且在固体颗粒内部发生反应的化学反应流的均匀化问题.利用周期Unfolding方法,证明了均匀化结果,并在此基础上给出了矫正结果.这些结果完善了Conca,Diaz和Timofte的工作.     

基于一般速率模型的面板计数数据统计分析

在复发事件数据存在删失的情况下,对基准速率函数进行一般化调整之后建立了一般速率模型。同时,给出该模型中未知参数的极大似然估计,并且证明了这些参数估计的大样本性质,即相合性和渐近正态性。利用大量数值模拟验证了文中所提出的模型及参数估计方法的合理性。最后,通过对一组膀胱癌治疗的临床试验数据进行实例分析,刻画协变量对膀胱癌复发率的影响。     

安徽出口与经济增长关系的实证分析

文章从增长率的角度利用协整分析技术、格兰杰因果关系检验方法以及平行数据计量经济学模型,对安徽出口与经济增长关系进行了实证分析。结果表明,安徽出口增长与经济增长之间存在着协整关系,但出口增长还不是经济增长的原因,安徽出口弹性偏高,据此对进一步加大安徽出口工作力度,增强出口对经济增长的拉动作用,提出了相关的政策和建议。