动态STDP突触系统模型设计与验证

神经突触的STDP（Spike Timing Dependent Plasticity）机制被认为是脑神经网络中最重要的机制之一，最有效的模拟STDP神经突触的方法是建立神经突触的离子通道的动力学模型。目前的STDP突触系统建模均存在一定的缺陷，不能很好地解释STDP机制的细胞分子生物反应原理或者得到STDP的时间非对...     

突触信号传导的动态饱和模型研究

对一类动态饱和突触神经模型中信号传导性质进行了研究.模型的动态过程采用高阶Milstein随机微分方程解法进行求解,其信号输入输出特性用集平均互相关系数进行衡量.集平均互相关系数的数值分析结果表明,适宜的噪声能够增强信号传导,并且通过调节饱和势比值大小和突触神经群体数目,观测到噪声增强信号传导的非线性现象更加显著.     

果蝇幼虫神经肌肉突触电位反应的研究

实验采用电生理微电极胞内记录技术，研究了果蝇三龄幼虫腹纵肌细胞的静息电位与微兴奋性接点电位、神经－肌肉兴奋性接点电位的特点。研究结果显示：１、果蝇三龄幼虫的静息电位为－５３±５ｍＶ２．微兴奋性接点电位的波形与正常兴奋性接点电位相同，平均值为０．６ｍＶ．３．兴奋性接点电位在不同的刺激强度下有不同的值。     

玉米根细胞正面向外和内翻外质膜囊泡的分离

利用水双相分配分离法从玉米根细胞提取原生质膜囊泡。其质膜成分特异的K~+,Mg~(2+)—ATP酶活性比膜粗提液高1.67倍。其他细胞器标记酶活性在质膜组分中很低或没有。特异染色电镜形态学定量统计表明质膜组分中90％以上是质膜囊泡。去污剂刺激ATP酶活性实验证明,约92％囊泡是正面向外的。应用此法也证明NAD(P)H—氧化酶可能是跨膜存在的,其催化Fe~(3+)还原的位点可能在膜的内侧。应用高盐冻—融法并结合水双相分配分离法处理正面向外囊泡,可获得内翻外质膜囊泡,实验证明它不仅纯度高而且封闭。     

一维Theta神经网络微分方程模型的研究——多放电行波解的存在性

研究一维theta神经元网络的微分方程模型,对该网络模型从神经元生理运动特点和微分方程本身入手进行讨论.对模型中的输入形式加以简化,证明了对任意的传播速度c＞0,存在一个对应的耦合强度参数,使网络具有多放电行波解.     

Neurotrophic regulation of synapse development and plasticity

Neurotrophic factors are traditionally thought to be secretory proteins that regulate long-tern survival and differe, ntiation of neurons. Recent studies have revealed a previously unexpected role for these factors in synaptie de velopment ami plasticity in diverse neuronal populations. Here we review experimeuts carried oul in our own laboratory in the last few years.. We have made two important discoveries.First,we were among the first to report that brain-derived. neurotrophie faclor (BDNF) facilitates hippocampal hmg-term potentiation (LTP), a form of synaptic plaslicity believed to be involved in learning and memory. BDNF modulates LTP al CAI synapses by enhaneing synaptic responses to high frequency, tetanic slimulalion. This is achieved primafily by facilitating synaptie vesicle doeking, possibly due to an in crease in the levels of the vesicle prolein synaptobrevin and synaptoplysin in the nerve terminals. Gene knockout study demonstrates thai the effects of BDNF are primarily mediated through presynaptic mechanisms. Second, we demonstrated a form of long-term, neurotrophin-mediated synaptic regulation. We showed that long-term treatment of the neuromuscu lar synapses with neurotrophin-3 (NT3) resulted in an enhancement of both spontaneous and evoked synaptic currcuts, as well as profound changes in thc number of synaptic varicosities and syuaptic vesicle proteins in motoneurons, all of which are indicative of more mature synapses. Our current work addresses the following issues:(i) activity-dependent trafficking of neurotrophin receptors, and its role in synapse-specific modulation; (ii) signal transduction mechanisms medialing the acute enhancement of synaplic transmission by neurotrophins; (iii) acute and long-tenn synaptie actions of the GDNF family; (iv) role of BDNF in late-phase LTP and in the development of hippocampal circuit.     

整合发放神经元模型突触输入参数估计

文章针对突触输入和噪声共同作用下的整合发放神经元模型,在不考虑放电阈值前提下,采用最小二乘法估计突触输入参数;当考虑神经元放电阈值特性时,将放电阈值看成一个吸收边界,导出膜电位转移概率密度函数,再利用极大似然法估计突触输入参数。结果表明:最小二乘估计仅适合阈下活动的参数估计,而对阈上活动无效;极大似然估计适用于神经元放电的阈值行为;无论是从适用范围还是估计精度来说,极大似然估计都要优于最小二乘估计。     

Cholera toxin B-subunit incorporation into synaptic vesicles of the neuromuscular junction of the rat

Summary The B-subunit of cholera toxin, a nontoxic macromolecule which binds specifically to GM1 ganglioside, was conjugated to colloidal gold and injected into skeletal muscle of the rat. It was taken up rapidly in vesicles in the terminal axons at the neuromuscular junctions. Injection of albumin-colloidal gold conjugates resulted in an insignificant uptake. The results indicate that uptake of extracellular macromolecules into the terminal axon of the neuromuscular junction may be greatly enhanced by binding to gangliosides at the presynaptic membrane, and that it may occur without association with vesicular recycling related to transmitter release.The study was supported by grants from the Swedish Medical Research Council (proj. No. 07122).—Part of this study was performed at INSERM U-153, Paris, headed by Dr M. Fardeau.     

铜绿微囊藻气囊蛋白GvpW的异源表达纯化与晶体生长研究

铜绿微囊藻(Microcystisaeruginosa PCC 7806)是我国淡水湖泊生态系统季节性蓝藻水华爆发的最优势藻种,其爆发的机制之一在于气囊,它是一种充满气体的蛋白质性质的亚细胞器结构,可为藻细胞提供浮力,调节藻细胞在水体中的位置以利于生长和后续的生境殖民化。铜绿微囊藻的气囊合成涉及14个气囊蛋白,但大部分气囊蛋白在气囊合成过程中的具体分子功能尚不清楚。对其中一个气囊蛋白GvpW进行了分子克隆,利用原核表达系统在体外进行了异源表达,结合镍柱亲和层析和凝胶过滤层析纯化出了高纯度的GvpW,运用动态光散射和化学交联证实在体外纯化后的GvpW是呈单体状态,同时通过晶体初筛和优化获得了生长较好的蛋白质晶体。这为后续解析GvpW的三维结构及在分子水平直观探讨其在气囊合成中的生理功能奠定了基础。