固体颗粒诱导双亲分子自组装形成颗粒@囊泡复合体

固体颗粒可诱导两亲分子自组装形成囊泡及颗粒@囊泡复合体。该复合体在支撑双层膜的构筑、悬浮体的稳定、特殊结构材料的制备及药物输送-控释体系的构建等方面具有重要的应用前景,本文对此进行了综述。     

学习和记忆的突触模型:长时程突触可塑性

人类大脑是由上千亿神经元相互连接而组成一个高度复杂的神经网络,是认知、学习和意识等高级功能的重要基础。神经元之间通过特化的连接结构--“突触”而相互通讯。外界输入触发的神经元活动可特异性地持续改变突触的结构和功能,这种神经活动依赖的突触变化称之为长时程突触可塑性。大量实验证据表明突触可塑性是大脑学习和记忆的分子细胞学机制,了解突触可塑性的机制对阐明中枢神经系统性相关疾病（如老年痴呆症、药物成瘾等）的机理具有重要意义。本文简要地小结了长时程突触可塑性研究中的基本发现和新近进展。     

Novel Chitosan-based Biomaterials

1 Introduction Chitosan with two long side chains of N-alkyl group is an important amphiphilic material, which has potential application in tissue engineering and drug delivery system. In this paper the amphiphilic N, N-dilauryl chitosan has been prepared by the phase transfer catalysis. The π-A isotherms of the products were measured in order to find some fundamental data for making self-assembled vesicles out of this kind of material. The LB film experiment indicates that N, N-dilauryl …     

氧化锌/氧化钽双介质层忆阻器的突触特性分析

人工突触的开发是模拟人脑功能的关键。忆阻器由于具备独特的电阻记忆行为,在人工突触研究领域得到广泛的关注。氧化钽和氧化锌均是优良的忆阻器材料,鉴于有关ZnO/TaOx双介质忆阻器突触特性的研究较少,本文将氧化锌介质层引入Ti/TaOx/ITO忆阻器中拟改善其突触性能。研究发现,器件Ti/ZnO/TaOx/ITO在功耗和电导调制线性度方面皆有改善,并有着电阻渐变的行为,利于器件突触功能的实现及应用。为此对Ti/ZnO/TaOx/ITO双介质层器件进行了电压脉冲训练,并成功模拟了学习饱和、经验学习以及短时程记忆向长时程记忆转变等生物突触行为。     

大鼠海马结构内一氧化氮合酶阳性神经元在学习记忆时的形态学观察

用还原型烟酰胺腺嘌呤二核苷酸黄递酶（ＮＡＤＰＨ－ｄｉａｐｈｏｒａｓｅ）组织化学方法，检测空间辩别性学习记忆模型大鼠和对照大鼠的海马结构内一氧化氮合酶（ＮＯＳ）的活性，阳性细胞的分布、形态和数量等形态学指标．结果：（１）模型大鼠海马结构内ＮＯＳ阳性神经元的酶反应产物比对照大鼠的明显减少；（２）模型大鼠和对照大鼠海马结构内ＮＯＳ阳性神经元的分布未见组间差异，但均显示出明显的区间差异，即从ＣＡ４区向ＣＡ１区逐渐增多；（３）模型大鼠和对照大鼠海马结构内的ＮＯＳ阳性神经元的数量显示出明显的组间差异，即模型组比对照组的明显减少；（４）模型大鼠和对照大鼠海马结构内的ＮＯＳ阳性神经元形态主要有锥体形、颗粒形和纺锤形三种，但未见组间差异．据此，可认为大鼠海马结构内ＮＯＳ阳性神经元在空间辨别性学习记忆活动时发生了形态学可塑性．它提示一氧化氮可能作为信使参与信息的传递     

Synaptic dysfunction in Huntington’s disease: a new perspective

Huntington’s disease (HD) is caused by a polyglutamine expansion in the protein huntingtin and is characterized by intraneuronal inclusions and widespread neuronal death at the late stage of the disease. In research, most of the emphasis has been on understanding the cell death and its mechanisms. Until recently, it was believed that the vast majority, if not all, of the symptoms in HD are a direct consequence of neurodegeneration. However, increasing evidence shows that subtle alterations in synaptic function could underlie the early symptoms. It is of particular interest to understand the nature of this neuronal dysfunction. Normal huntingtin interacts with various cytoskeletal and synaptic vesicle proteins that are essential for exocytosis and endocytosis. Altered interactions of mutant huntingtin with its associated partners could contribute to abnormal synaptic transmission in HD. This review describes recent advances in understanding synaptic dysfunction in HD.Received 2 March 2005; received after revision 13 April 2005; accepted 19 April 2005     

The toxicity of twoBacillus thuringiensis δ-endotoxins to gypsy moth larvae is inversely related to the affinity of binding sites on midgut brush border membranes for the toxins

Summary The-endotoxin fromBacillus thuringiensis subspecieskurstaki strain HD1-9 is almost 400 times more potent than the-endotoxin from strain HD-73 as a gypsy moth larvicide. The two-endotoxins compete for a high-affinity binding site on the brush border membrane of larval gypsy moth midguts. The affinity for the-endotoxin from strain HD-73 is much greater than the affinity for the-endotoxin from strain HD1-9.     

Gamma-aminobutyric acid uptake by rat kidney brush-border membrane vesicles

Summary Brush-border membrane vesicles (BBMV) from rat kidney cortex possessed two uptake systems for -aminobutyric acid (GABA), a high affinity system (Km=10.9 M) and a low affinity system (Km=1203 M). Both uptake systems were inhibited by p-hydroxymercuribenzoic acid and ouabain, and by the action of neuraminidase, whereas the GABA analogs nipecotic acid, -alanine, 2,4-diaminobutyric acid and 4,5,6,7-tetrahydroisoxazolo-[4,5c]-pyridin-3-ol had no effect on the GABA uptake activity. The BBMW uptake systems were clearly different from the GABA transport systems present in brain tissue.     

Making more synapses: a way to store information?

Although information may be stored in the brain as changes in the strength of existing synapses, formation of new synapses has long been thought of as an additional substrate for memory storage. The identification of subcellular structural changes following learning in mammals poses a serious ‘needle-in-the-haystack’ problem. In most attempts to demonstrate structural plasticity during learning, animals have been exposed for prolonged periods to complex environments, where they are confronted with a variety of sensory, motor and spatial challenges throughout the exposure period. These environments are thought to promote several forms of learning. Repeated exposure to such environments has been shown to increase the density of spines and dendritic complexity in relevant brain structures. The number of neurons has also been reported to increase in some areas. It is not clear, however, whether the new synapses emerging from these forms of plasticity mediate specific information storage, or whether they reflect a more general sophistication of the excited parts of the network.     

Ca2+及cAMP调控的神经递质与激素释放

神经递质和激素的释放受胞内诸多信号通路的调控。这两种内源物质的释放都由依赖于Ca²⁺浓度的快速引发机制介导,相对于其他介导因素,[Ca²⁺]占主导地位。神经递质和激素释放的调控大多是通过调节释放小泡数量实现的。尽管在处于静息状态的神经末梢中,释放小泡的数量相对恒定,但当释放小泡被胞吐作用“消耗”后,其再生速度受调控作用介导而发生改变,从而导致小泡数量“稳中有变”的动态调控过程。这一动态调控作用表明了“消耗”与“再生”之间的平衡机制。