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A variant of the FitzHugh-Nagumo model is proposed in order to fully make use of the computational properties of intraneuronal dynamics. The mechanisms of threshold and refractory periods resulting from the double dynamical processes are qualitatively studied through computer simulation. The results show that the variant neuron model has the property that its threshold, refractory period and response amplitude are dynamically adjustable. This paper has also discussed some problems relating to collective property, learning and implementation of the neural network based on the neuron model proposed. It is noted that the implicit way to describe threshold and refractory period is advantageous to adaptive learning in neural networks and that molecular electronics probably provides an effective approach to implementing the above neuron model. 相似文献
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人睫状神经营养因子的原核表达,纯化及其生物效应 总被引:2,自引:0,他引:2
人睫状神经营养因子(hCNTF)克隆入pBV220中,在DH5α菌株中表达,重组蛋白以包含体的形式存在,表达量为菌体总蛋白的50%左右。经比较发现用2mol/L脲洗涤包含体可溶解大量可溶性细菌蛋白,且包含体损失较小。在高浓度变性剂条件下进行sepharcylS-200凝胶过滤,解决了纯化中hCNTF易聚合的问题,在低浓度变性剂条件下进行DEAE离子交换,有利于蛋白活性的保持。经两步纯化后得到均一性hCNTF,纯度达95%以上。在自然状态下使hCNTF复性。纯化复性后的hCNTF对无血清培养的鸡胚背根节神经元和脊髓腹角运动神经元有明显的维持存活和促进生长发育的生物效应。 相似文献
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本文讨论了不同条件下苋菜红在银基汞膜电极上的伏安行为.发现在 pH=4时,苋菜红在-0,24V 处有很灵敏的检出信号,在此条件下,汞膜电极有良好的再现性和使用寿命;在10-100ppb 范围内,还原电流与浓度呈良好的线性关系. 相似文献
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Abstract: Elevated concentrations of extracellular K+ increased inositol phosphate accumulation in primary cultures of chick retinal photoreceptors and multipolar neurons. K+ -evoked stimulation of inositol phosphate accumulation was greater in photoreceptor-enriched cell cultures than in cultures where multipolar neurons were the predominant cell type. Destroying multipolar neurons, but not photoreceptors, with kainic acid and N -methyl- d -aspartate did not reduce the K+ -evoked stimulation of inositol phosphate accumulation. Both of these observations indicate that the observed effects occur in photoreceptor cells. The K+ -evoked stimulation of inositol phosphate accumulation was blocked by omitting Ca2+ from the incubation medium or by adding the dihydropyridine-sensitive Ca2+ -channel antagonists, nitrendipine and nifedipine. Bay K 8644, a dihydropyridine agonist, stimulated inositol phosphate accumulation and enhanced the effect of K+ . ω-Conotoxin GVIA, an inhibitor of N-type Ca2+ channels, had no significant effect on K+ -stimulated inositol phosphate accumulation. Pretreatment with pertussis toxin neither blocked K+ -evoked inositol phosphate accumulation nor altered the inhibitory effect of nifedipine. K+ -evoked inositol phosphate accumulation appears to reflect activation of phosphatidylinositol-specific phospholipase C, as it is inhibited by U-73122. These results indicate that Ca2+ influx through voltage-gated, dihydropyridine-sensitive channels activates phospholipase C in photoreceptor inner segments and/or synaptic terminals. 相似文献
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Plant and Soil - Agricultural practices often have persistent effects on soil physicochemical properties and soil biota, which can feedback to influence plant performance. We investigated... 相似文献
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Sample preparation is key to the success of proteomics studies. In the present study, two sample preparation methods were tested for their suitability on the mature, recalcitrant leaves of six representative perennial plants (grape, plum, pear, peach, orange, and ramie). An improved sample preparation method was obtained: Tris and Triton X-100 were added together instead of CHAPS to the lysis buffer, and a 20% TCA-water solution and 100% precooled acetone were added after the protein extraction for the further purification of protein. This method effectively eliminates nonprotein impurities and obtains a clear two-dimensional gel electrophoresis array. The method facilitates the separation of high-molecular-weight proteins and increases the resolution of low-abundance proteins. This method provides a widely applicable and economically feasible technology for the proteomic study of the mature, recalcitrant leaves of perennial plants. 相似文献
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The monocarboxylate (pyruvate) carrier from bovine heart mitochondria was extracted from submitochondrial particles with Triton X-114 in the presence of cardiolipin. By a single hydroxylapatite chromatography step a 125-fold purification of the carrier protein could be achieved. High pyruvate/pyruvate-exchange activity was recovered, when the protein was reconstituted into phospholipid vesicles. No transport activity was observed, when the isolation occurred in the absence of phospholipids. The 2-cyano-4-hydroxycinnamate sensitive pyruvate exchange reaction was strongly temperature sensitive and dependent on the amount of protein reconstituted. Other 2-ketoacids caused competitive inhibition of the pyruvate uptake. Inhibitors of other mitochondrial carries, however, had very low or no effect on the monocarboxylate exchange. The influence of different -SH group reagents on the measured pyruvate/pyruvate-exchange in the reconstituted system was similar to the one observed with intact mitochondria. It is concluded that the described procedures for extraction, purification and reconstitution of the mitochondrial monocarboxylate carrier conserved the functional properties of the protein. 相似文献