采样参数设置对小鼠心电图波形的影响

目的探讨采样参数设置对小鼠心电图波形的影响。方法选用C57小鼠,戊巴比妥钠麻醉,四肢皮下插针式电极,连接RM6240BD型多道生理信号采集处理系统,选择不同的采样参数设置,对心电图进行采样、记录和分析。结果采样速率、低通滤波、时间常数和陷波滤波等采样参数设置均对心电图波形有影响,部分参数会导致心电图不同形式的变形和失真。结论小鼠的心电图实验中应选择合适的采样参数设置,通过操作技术的改进来提高心电图的稳定性,尽量避免或减少滤波的使用,以获得准确的心电图实验结果。     

高频电刺激改变神经元锋电位的波形

为了正确检测和研究高频电刺激(high frequencystimulation,HFS)期间神经元的动作电位发放活动,进而深入揭示深部脑刺激治疗神经系统疾病的机制,本课题研究HFS期间锋电位波形的变化.在麻醉大鼠海马CA1区的输入神经通路Schaffer侧支上,施加1~2 min时长的100或者200 Hz顺向高频刺激(orthodromic-HFS,O-HFS),利用微电极阵列采集刺激下游神经元的多通道锋电位信号,并获得由O-HFS经过单突触传导激活的中间神经元的单元锋电位波形及其特征参数.结果表明,O-HFS使得锋电位的幅值明显减小而半高宽明显增加,以基线记录为基准计算百分比值,O-HFS期间锋电位的降支幅值和升支幅值分别可减小20%和40%左右,半高宽则增加10%以上.并且,在大量神经元同时产生动作电位期间,或者在比200 Hz具有更大兴奋作用的100 Hz刺激期间,锋电位波形的改变更多,幅值的减小可达50%,宽度的增加可达20%.可以推测,高频电刺激对于神经元的兴奋作用可能升高细胞膜电位,从而改变细胞膜离子通道的活动特性,导致动作电位波形的改变.这些结果支持深部脑刺激具有兴奋性调节作用的假说,对于正确分析高频电刺激期间神经元锋电位活动具有指导意义,也为进一步研究深部脑刺激(DBS)治疗脑神经系统疾病的机制提供了重要线索.     

应用数字滤波器消除神经放电中的噪声

本研究目的在于应用高通—低通数字滤波器消除神经放电中的噪声。数字滤波器通带频率500～1000Hz,其高通和低通阻带截止频率分别为300和2000Hz,阻带衰减大于25dB。以6阶和4阶Butterworth模拟滤波器变换为数字高通及低通滤波器,并在Apple—Ⅱ和MCS—51系列微机上得以实现。在消除家兔神经动作电位波形的噪声信号时取得了满意的结果。     

镉对大鼠心室肌细胞动作及L-型钙电流的影响

目的:探讨镉(Cd)对大鼠心室肌细胞动作电位(AP)及L-型钙电流(ICa-L)影响。方法:用常规微电极和全细胞膜片钳技术记录心肌细胞动作电位和ICa-L。结果:①不同浓度的CdCl2可降低大鼠心肌细胞动作电位幅值(APA),缩短复极化时程(APD)。②不同浓度的CdCl2明显抑制大鼠心室肌细胞钙通道电流。结论:CdCl2抑制大鼠心室肌细胞动作电位和ICa-L,可能是Cd对心肌毒性的重要机制之一。     

海葵毒素对心肌钠通道开放模式、动作电位及心电图QT间期的影响

应用膜片箝技术记录游离豚鼠心肌细胞钠通道电流, 细胞内微电极技术记录心室乳头肌的动作电位和心电图机记录豚鼠的心电图。使用与心肌细胞钠通道有高度亲和力的海葵毒素(sea anemone toxin, ATXⅡ)改变钠通道开放的动力过程, 从三个水平来研究钠通道、动作电位、心电图变化的关系, 并试图探讨长QT综合征(long QT syndrome, LQTs)的发病机制。结果显示: ATXⅡ使钠通道的开放频率增加, 钠通道中“长时间开放模式”的开放时间常数增大, 动作电位的持续时间APD50和APD90也分别增加了23%和27%。 ATXⅡ使动物心电图QT间期延长18.6%, QTc (校正的QT间期)增大18.9%。这些结果提示, 钠通道动力过程的变化对动作电位和心电图QT间期有重要影响, 钠通道功能或结构的变异可能是临床上部分长QT综合征产生的原因。     

东亚钳蝎蝎毒成分BmK—9及其次级提取物对心肌细胞电活动的影响

培养小鼠的心肌细胞,用微电极胞内引导快反应心肌细胞动作电位。以五项除极化参数ＡＰＡ,ＯＳ,ＭＤＰ,ＴＰ,Ｖｍａｘ和波宽参数ＡＰＤ５０为指标,发现东亚钳蝎蝎毒三级提取物ＢｍＫ－９－（３）、ＢｍＫ－９－（４）、ＢｍＫ－９－（５）３μｇ／ｍｌ使除极有关参数全部减小,而不影响动作电位波宽。表明它们可能是蝎毒中单纯阻滞钠通道的活性成分。     

培养大鼠搏动心肌细胞在缺氧和复氧时的电生理观察

应用细胞内微电极技术记录到37个培养大鼠搏动心肌细胞充氮前后和复氧后的电活动参数。结果提示:充氮10min后,最大舒张电位(MDP),最大除极速度(V_(max)),动作电位振幅(APA)和动作电位时程(APD)等参数明显降低;自发节律增快,并出现多种形式的节律失常。83.8％细胞在充氮后30min内停搏,16.2％在50min左右停搏。复氧后,86.5％细胞在5min内复跳,13.5％未能复跳;12.5％复跳细胞在复跳10min内再次停搏。复跳细胞的各项电活动参数在30min内未能恢复到充氮前水平(p<0.05),且呈现不同程度的各类异常电活动。本结果对进一步研究心肌细胞缺氧和复氧损伤有一定意义。     

培养新生大鼠心肌细胞的电信号传导：多电极记录研究

利用多电极阵列同步记录技术对培养的新生大鼠单层心肌细胞的电活动进行胞外记录,观察心肌细胞在自发搏动和电刺激情况下信号在细胞间的传导模式。通过对记录信号的处理和分析,能获得诸如起搏细胞的数量和位置、动作电位的传导速度和途径以及不同起搏细胞间的相互影响等信息。研究还发现,心肌细胞阈下刺激会影响细胞的搏动和信号传导。     

一种稳定的心肌细胞电位与心肌收缩力的同时记录方法

同时记录心肌细胞动作电位与收缩力能较全面地分析神经递质、药物或病理因素(如缺氧、心律失常等)对心肌功能的影响。目前国内学者多采用标准微电极在豚鼠离体心脏乳头肌标本上同时记录心肌细胞电与机械活动,在需要较长时间观察递质、药物等因素的作用,或是在观察药物的多个剂量效应时,微电     

白介素-2对离体右心室乳头肌的作用及其机制

目的 :研究白介素 2 (IL 2 )对心肌跨膜电位和收缩作用的影响及其可能机制。方法 :在离体灌流大鼠右心室乳头肌标本上 ,采用常规细胞内玻璃微电极技术 ,观察IL 2 (0 .5～ 2 0 0u/ml)灌流 10min对心肌细胞跨膜电位的影响 ,并记录乳头肌收缩力变化。结果 :IL 2缩短心肌动作电位时程 (APD50 和APD80 ) ,但对静息电位、动作电位 0期去极化幅度及其速度无明显影响。IL 2呈剂量依赖性地抑制心肌收缩力 ,0 .5、2 .5、10、5 0和 2 0 0u/ml的IL 2分别使乳头肌收缩力下降至加药前的 94 .8%± 6 .8%、85 .8%± 6 .5 %、76 .3%± 7.8%、6 9.3%± 9.5 %和 5 2 .5 %±11.0 %。L NAME(10 -4mol/L)预处理 10min ,完全阻断较低浓度 (u/ml)IL 2 (0 .5、2 .5、10 )的心肌抑制作用 ,部分阻断高浓度IL 2 (5 0u/ml和 2 0 0u/ml)的作用。结论 :IL 2对离体右心室乳头肌的动作电位时程和收缩力有抑制作用 ,其负性变力作用与NO途径有关     

Ventricular slices of adult mouse hearts--a new multicellular in vitro model for electrophysiological studies.

AIM: We established a preparation of adult murine ventricular slices suitable for electrophysiological recordings as a new in vitro model of adult myocardium with preserved in vivo tissue structure. METHODS: Short axis slices (thickness: 150 microm) of adult murine ventricles were prepared with a microtome. Sharp glass electrodes were used for measurements of action potentials (APs) at stimulation frequencies of 2 Hz and 10 Hz. Field potential (FP) recordings by means of microelectrode arrays (MEAs) were performed to map excitation spread. RESULTS: APs showed the characteristics of adult murine ventricular APs: (i) a stable resting membrane potential, (ii) a fast upstroke and (iii) a fast phase 1 repolarization. Application of the Na+ channel blocker lidocaine (30 microM) led to a decline of upstroke slope, amplitude and conduction speed. The unspecific K+ channel blocker 4-aminopyridine (5 mM) caused a prolongation of APD50. The excitation spread was homogenous throughout the ventricular wall. CONCLUSION: Adult murine ventricular slices are electrophysiologically intact and respond physiologically to cardioactive drugs. Thus, they provide a new multicellular in vitro model of adult cardiac tissue suitable for electrophysiological investigations, which in future could be used to study the functional integration of stem cells transplanted in infarcted hearts in vivo.     

Calcium-sensitive action potential of long duration in the fertilized egg of the ctenophore Mnemiopsis leidyi

The membrane properties of fertilized eggs of the ctenophore Mnemiopsis leidyi were studied using standard microelectrode techniques. The resting potential was approximately -80 mV, and was dependent on the extracellular K concentration. Depolarizing current injections elicited an action potential with an initial peak amplitude of +20 to +40 mV (duration about 5 sec) and a long lasting (duration 3 to 10 min) plateau phase. The depolarizing phase and the plateau phase appeared to have different ionic mechanisms. The entire action potential could be prevented by removal of extracellular Ca, but only the amplitude of the depolarizing phase, not the plateau phase, was dependent on the extracellular Ca concentration. The plateau phase was not observed in the absence of Ca, but in the presence of Ca its duration was dependent on the external Ca concentration. The data suggest that the plateau phase is activated as a consequence of Ca influx during the initial depolarizing phase. Removal of external Na resulted in only minor changes in the waveform of repolarization. The action potential was resistant to low concentrations of Mn and Cd in the presence of Ca. The role of this action potential in ctenophore development is not known, but in its waveform and duration it resembles the sperm-gated potentials that have been seen in eggs of other phyla. These experiments show ctenophore embryos to be excitable at very early stages, and suggest their utility in the study of the differentiation of cellular electrical properties.     

Magnetic field of a single muscle fiber. First measurements and a core conductor model.

We present the first measurements of the magnetic field from a single muscle fiber of the frog gastrocnemius, obtained by using a toroidal pickup coil coupled to a room-temperature, low-noise amplifier. The axial currents associated with the magnetic fields of single fibers were biphasic and had peak-to-peak amplitudes ranging between 50 and 100 nA, depending primarily on the fiber radius. With an intracellular microelectrode, we measured the action potential of the same fiber, which allowed us to determine that the intracellular conductivity of the muscle fiber in the core conductor approximation was 0.20 +/- 0.09 S/m. Similarly, we found that the effective membrane capacitance was 0.030 +/- 0.011 F/m2. These results were not significantly affected by the anisotropic conductivity of the muscle bundle. We demonstrate how our magnetic technique can be used to determine the transmembrane action potential without penetrating the membrane with a microelectrode, thereby offering a reliable, stable, and atraumatic method for studying contracting muscle fibers.     

Sensitivity analysis for an improved estimation of respiratory mechanics parameters

In this paper a respiratory mechanics model is considered, which is characterized by a biquadratic input impedance, and a sensitivity analysis has been carried out to determine the influence of experimental conditions on parameter estimation. This analysis was effected with data obtained experimentally, in three different patients under intermittent positive pressure ventilation. In all three cases, the model's input impedance demonstrated a maximum sensitivity in relation to the various parameters included in the field of frequencies from 0 to 10 Hz. This seems to suggest therefore, that the use of a low-pass filter with a cut-off frequency equal to 10 Hz could improve the signal/noise ratio and, consequently, the accuracy of the estimation of the parameters. Furthermore, the use of a system input with a bandwidth of 0–10 Hz provides the experimental conditions, under which good estimates of the parameters can be obtained. This conclusion has also been confirmed by simulation studies which have been conducted with different types of input signals.     

迷走神经对家兔在体心脏心室肌细胞跨膜电位的影响

本研究观察了电刺激迷走神经对家兔在体心脏心室肌细胞跨膜电位的作用及钾通道阻滞剂氯化四乙基铵对这一作用的影响。结果表明,在自然心率条件下,迷走神经刺激可使静息电位(RP)、动作电位振幅(APA)和0相最大上升速率(dv/dt)_(max)增加,动作电位时程(APD)缩短。冠脉注射氯化四乙基铵使心室肌细胞复极过程明显延长,迷走神经刺激不再引起 RP、APA 增大,动作电位时程不再缩短,(dv/dt)_(max)反而减小。这些结果提示,迷走神经刺激对正常心室肌细胞跨膜电位的影响可能是通过外向 K~ 流增加引起的。     

Electrophysiological effects of agmatine on human atrial fibers

The objective of the present study was to study the electrophysiological effects of agmatine on human atrial fibers obtained at cardiac surgery using standard microelectrode techniques. Agmatine (1 to approximately 10 mM) decreased the action potential amplitude (APA), maximum upstroke velocity of phase 0 depolarization (Vmax), velocity of diastolic (phase 4) depolarization (VDD), rate of pacemaker firing (RPF), and action potential duration at 50 and 90% of repolarization (APD(50-90)) in a concentration-dependent manner. Pretreatment with N(G)-nitro-L-arginine methyl ester (L-NAME, 0.5 mM), a NOS inhibitor, did not affect the electrophysiological effects of agmatine (5 mM) on human atrial fibers. The effects of agmatine (5 mM) could be blocked completely by pretreatment with idazoxan (0.1 mM), an alpha-2 adrenergic receptor (alpha2-AR) and imidazoline receptor (IR) antagonist. All these results indicate that the effects of agmatine on human atrial fibers are likely due to a decrease of intracellular calcium mediated by IR and/or alpha2-AR.     

Squid Axon Membrane Response to White Noise Stimulation

The current from a white noise generator was applied as a stimulus to a space-clamped squid axon in double sucrose gap. The membrane current and the voltage response of the membrane were then amplified, recorded on magnetic tape, and the stimulus was cross-correlated with the response. With subthreshold stimuli, a cross-correlation function resembling that obtained from a resonant parallel circuit is obtained. As the intensity of the input noise is increased, the cross-correlation function resembles that obtained from a less damped oscillatory circuit. When the noise intensity is further increased so that an appreciable frequency of action potentials is observed, an additional component appears in the experimental cross-correlogram. The subthreshold cross-correlogram is analyzed theoretically in terms of the linearized Hodgkin-Huxley equations. The subthreshold axon approximates a parallel resonant circuit. The circuit parameters are temperature dependent, with resonant frequency varying from approximately 100 Hz at 10°C to approximately 250 Hz at 20°C. The Q₁₀ of the resonant frequency is equal to 1.9. These values are in agreement with values found previously for subthreshold oscillations following a single action potential.     

An Assessment of the Double Sucrose-Gap Voltage Clamp Technique as Applied to Frog Atrial Muscle

The homogeneity of voltage clamp control in small bundles of frog atrial tissue under double sucrose-gap voltage clamp conditions was assessed by intracellular microelectrode potential measurements from cells in the test node region. The microelectrode potential measurements demonstrated that (1) good voltage control of the impaled cell existed in the absence of the excitatory inward currents (e.g., during small depolarizing clamp pulses of 10-15 mV), (2) voltage control of the impaled cell was lost during either the fast or slow excitatory inward currents, and (3) voltage control of the impaled cell was regained following the inward excitatory currents. Under nonvoltage clamp conditions the transgap recorded action potential had a magnitude and waveform similar to the intracellular microelectrode recorded action potentials from cells in the test node. Transgap impedance measured with a sine-wave voltage of 1,000 Hz was about 63% of that measured either by a sine-wave voltage of 10 Hz or by an action potential method used to determine the longitudinal resistance through the sucrose-gap region. The action potential data in conjunction with the impedance data indicate that the extracellular resistance (R_s) through the sucrose gap is very large with respect to the longitudinal intracellular resistance (R_i); the frequency dependence of the transgap impedance suggests that at least part of the intracellular resistance is paralleled by a capacitance. The severe loss of spatial voltage control during the excitatory inward current raises serious doubts concerning the use of the double sucrose-gap technique to voltage clamp frog atrial muscle.     

缺血对心室浦肯野纤维跨膜电位和起搏离子流的影响

采用细胞内微电极和双微电极电压箝制术观察缺血对绵羊心室浦肯野纤维跨膜电位和起搏离子流（Ｉｆ）的影响。结果：模拟缺血液灌流３０ｍｉｎ,浦肯野纤维最大舒张电位（ＭＤＰ）、动作电位幅度（ＡＰＡ）明显减少;动作电位时程ＡＰＤ５０,ＡＰＤ９０明显缩短（ｎ＝１５Ｐ＜０．０１）;起搏离子流（Ｉｆ）,幅度降低,激活曲线向超极化方向移位,最大激活时间及半最大激活时间延长（ｎ＝１３Ｐ＜０．００１）。上述结果表明：心肌缺血时,心室浦肯野细胞跨膜电位及正常起搏活动不是增强,而是减弱。提示缺血性室性心律失常不是由于正常心室自律活动异常增强引起     

Voltage clamping with a single microelectrode.

A technique is described which allows neurons to be voltage clamped with a single microelectrode, and the advantages of this circuit with respect to conventional bridge techniques are discussed. In this circuit, the single microelectrode is rapidly switched from a current passing to a recording mode. The circuitry consists of: (1) an electronic switch; (2) a high impedance, ultralow input capacity amplifier; (3) a sample-and-hold module; (4) conventional voltage clamping circuitry. The closed electronic switch allows current to flow through the electrode. The switch then opens, and the electrode is in a recording mode. The low input capacity of the preamplifier allows the artifact from the current pulse to rapidly abate, after which time the circuit samples the membrane potential. This cycle is repeated at rates up to 10 kHz. The voltage clamping amplifier senses the output of the sample-and-hold module and adjusts the current pulse amplitude to maintain the desired membrane potential. The system was evaluated in Aplysia neurons by inserting two microelectrodes into a cell. One electrode was used to clamp the cell and the other to independently monitor membrane potential at a remote location in the soma.