【作者】 成波；

【导师】 杨玉星； 林家瑞；

【作者基本信息】 华中科技大学 ， 生物医学工程， 2007， 博士

【摘要】 生物电活动是生物体的一种重要的生命活动。神经元放电和膜片钳离子通道是电生理研究的两个重要领域。生物电活动既然是一种电,就必然受到外界电磁活动一定程度上的影响。目前采用磁场刺激神经细胞和肿瘤细胞是生物磁研究的两个重要课题,适当的磁场刺激对神经系统疾病起到一定的治疗作用,如帕金森症、神经性疼痛、癫痫、抑郁症、精神分裂症等,海马则是学习和记忆的重要脑区,特别是帕金森症的重要病灶区域。因此本文采用磁场刺激海马细胞,通过神经放电信号和钾离子通道信号分析研究其电生理特性的变化。该研究具有重要的理论意义与实际价值。本文首先设计了一款电生理磁刺激实验通用的极低频磁场发生器,该仪器能产生多种波形、频率、强度且空间分布均匀的磁场。然后通过神经元放电和膜片钳离子通道两种方法对大鼠海马细胞在极低频磁场作用前后的放电特性和离子通道特性分别进行了研究。最后分析了两种相互关联的研究方法下的结果。本研究工作主要获得了如下研究成果:(1)研制了一台适于生物磁刺激的多波形、多参数的磁场发生器。该仪器的特点是:a)强度从几个毫特斯拉(mT)提高到100 mT;b)通过硬件补偿和软件修正的方案,克服了通常随波形频率提高,磁场强度急剧递减的问题。产生从1 Hz到500 Hz,磁场强度均衡的磁场;c)针对三角波磁场能够产生恒定的感应电场的特征,也开发了一种三角波形的磁场发生器。(2)构造了一种适用于电生理信号的特定的小波降噪算法。在采用小波降噪中,针对电生理信号的两个特点:符合全或无定律;具有一定的不应期。采用方波haar函数作为母函数,构造了一种独特的小波降噪方法。通过检验,该方法较传统均值滤波效果有所提高。(3)提出了一种验证离子单通道降噪算法优劣的方法。针对离子单通道全或无的特点,通过原始信号,构造了一种标准波形来衡量降噪效果。(4)海马细胞在极低频磁场刺激作用下的放电信号更加具有节律性。通过自回归(Autoregressive,AR)模型谱分析表明,磁场刺激时的海马细胞放电信号的谱线更加光滑,说明高频率成分减少了,表明信号具有更好的节律性。(5)海马细胞在磁场刺激作用下其电生理活动更加活跃。采用AR模型谱分析方法研究表明,极低频磁场刺激海马细胞后,其AR频谱发生后移,电活动的频度增高了,表明电生理活动更加频繁。采用随机过程和统计学分析方法研究表明,极低频磁场刺激海马细胞时其发放动作电位的次数增加,峰峰间期(Inter Spike Interval, ISI)减小,钾离子通道的开放时间有所增加,静息时间有减小的趋势。这与有关文献报道的结论是一致的。本文采用的两种实验研究都得出特定磁场能够促进电生理活动的特性。从生理学分析,Na~+离子通道在神经元放电中承担主要角色,但是钾离子通道开放也会更加活跃,于是我们似乎可以得出如下推论:特定的磁场刺激对Na~+-K~+泵的活跃起到了一定的促进作用,虽然Na~+-K~+泵的K~+离子流动的方向与离子通道相反。这与文献报道磁场直接作用于Na~+-K~+泵并提高生物膜活性是相一致的,从而实验的角度印证磁场对神经系统疾病的治疗作用。更多还原

【Abstract】 Electrophysiological activity is an important activity of organisms. Neurons spark and ion channel in patch clamp are two important areas. Since electrophysiological activity is electricity; it will be some affected by external electromagnetic activity. Using electromagnetic fields to stimulate nerve cells and tumor cells are two important subjects in bioelectromagnetics research studies. The appropriate magnetic stimulation on diseases of the nervous system plays a certain role in treatment, such as Parkinson’s disease, neuropathic pain, epilepsy, depression, schizophrenia, etc. Hippocampal is an important region in brain for learning and memorization; it is very important lesions region in Parkinsson’s disease. In this paper we study hippocampal cells characteristics by magnetic field stimulation. Through research we had analyzed the potassium-ion-channel and neural discharge signals before and after magnetic stimulation to study the changes in its physiological characteristics. This study gave great theoretical and practical values.In this theses, at first we have designed a generic extremely low-frequency magnetic field generator for electrophysiology experiments in bioelectromagnetics. The equipment can generate a variety of waveforms, frequencies and intensities magnetic field which is constant distribution in spatial. Then we did the experiment on Rat hippocampal by two ways a) ion channel patch clamp b) and neurons spark. In this experiment some neurons has been stimulated by low-frequency magnetic fields, and the others haven’t stimulated. Finally we compared two results.The main research results we obtained are as follows:(1)A Low-frequency multi-waveform magnetic field stimulator has been developed, which Suitable for the bioelectromagnetics research studies. The apparatus is characterized by:a) Magnetic field strength has upgraded from several millitesla (mT) to 100 mT;b) Adoption of hardware and compensation software, to overcome the limitations of decreasing the intensity while increasing the frequency of the magnetic waveforms, producing constant magnetic field intensity from 1 Hz to 500 Hz;c) The Developed triangular magnetic field waveform can generate a short time constant electric field, which can be used for special researches.(2)A wavelet noise reduction algorithm has been created to do with specific electrophysiological signals. The electrophysiological signals have two characteristics: a11 or none law; it has short refractory period. In noise reduction methods we used a generating function called haar function as a wavelet basis function. Through testing, this method can enhance the effect significantly than the traditional of low-pass filter method.(3)An algorithm certification standards of ion single-channel noise reduction was been rose. Noting that ion channel has a characteristic of full or off. So we constructed a standard signal waveform to measure noise reduction effects.(4) Signals of discharge are more rhythm when hippocampus cells are stimulated by extremely low frequency magnetic field. The AR model spectrum analysis shows that signals spectrum of discharge are smoother when hippocampus cells stimulated by magnetic field, the decrease of the frequency components means signals are more rhythm.(5) The activities of the hippocampus cells electrophysiological become more active when they are stimulated by magnetic fields stimulation. Using AR model spectral analysis method we found that the electrophysiological signals in the AR spectrum will move to high frequency section. This means signals frequencies of electrophysiological activity are increased, the electrophysiological activities are more frequent. Stochastic processes and statistical analysis methods, which have been used showed that extremely low frequency magnetic stimulation hippocampus cells increased the number of action potentials, decreases ISI, increased the potassium channel opening time and decreased close time. These results are consistent with the conclusions of the relevant literature reported.In this paper, two experimental methods are used; concluded that the specific magnetic field can promote the activities of electrophysiological characteristics. From the view of physiology, Na~+ ion channels in the primary role of neurons discharge, but potassium channel opener will become more active. So it seems that we can draw the following inference: the specific magnetic stimulation played a role in promote Na~+-K~+ pump activity. Although K~+ flow the opposite direction in Na~+-K~+ pump flow and ion channels. This is consistent some literatures which reported magnetic field direct effect Na~+-K~+ pump activity and enhance membrane. By experiment we have proved in a certain way that the magnetic field can play a role in the treatment of nervous system diseases.更多还原