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作为老年性痴呆的主要类型,阿尔茨海默病(Alzheimer disease,AD)的病理特征包括大脑局部,尤其是海马和皮层神经元退行性病变化,细胞内神经原纤维缠结和细胞外老年斑沉淀(淀粉样斑块).其中淀粉样斑块的核心是β淀粉样蛋白(amyloid β-peptide,Aβ).随着对AD研究的深入,越来越多的证据显示Aβ可能是AD发生的原发性病理因子.由于Aβ产生和清除之间的平衡逐渐改变,聚集态的Aβ累积引发连串的复杂反应,最终出现神经元功能失调,死亡,斑块形成,神经原纤维缠结等病理现象.但Aβ究竟是通过什么样的分子途径引发AD的,Aβ作用的部位在哪里,Aβ毒性与其聚集状的关系等等问题还未能完全揭示.结合近年来实验和模拟的结果,综述了Aβ最新的研究进展. 相似文献
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本试验以苜蓿为原料,水为提取溶剂,采用盐析和热絮凝相结合的方法提取苜蓿叶蛋白。单因素试验设计分别考察料液比、加盐量、提取液pH值和絮凝温度对可溶性蛋白提取率的影响。以单因素试验结果为依据,采用L9(3^3)正交试验对料液比、加盐量、pH值进行工艺优化。试验结果表明:影响可溶性蛋白提取率的因素依次为料液比〉加盐量〉pH,絮凝温度70℃、时间10min时最佳工艺条件组合为料液比1:20,加盐量4%、pH值为5,在此条件下可溶性蛋白的提取率达29.58%,叶蛋白中可溶性蛋白含量可达52.71%。 相似文献
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为探讨免疫球蛋白对Aβ的拮抗作用,我们用20μmol/L的Aβ和5、10、15μl/L的人免疫球蛋白处理原代培养的昆明胎鼠大脑皮层细胞,用MTT法和PI-Hochest双染色法分析细胞的成活率.实验结果显示,人免疫球蛋白能有效地提高Aβ处理过的神经细胞成活率,说明免疫球蛋白对Aβ有一定的拮抗作用,对神经细胞有保护功能. 相似文献
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Xi-ming LI Ming-tao SHAO Jian-juan WANG Yue-lan WANG 《Journal of Zhejiang University. Science. B》2014,(10)
研究目的:探讨腹腔镜胰体尾切除术患者术后认知功能障碍(POCD)的发生与脑氧饱和度(rSO2)及血浆β-淀粉样蛋白(Aβ)水平的相关性。创新要点:POCD的发生机制与rSO2及Aβ有一定的相关性;rSO2较基础值下降的最大百分数(rSO2,%max)10.2%有可能发生POCD,因此,rSO2监测可能是预测POCD发生的有效工具;Aβ可能是发生POCD敏感的生化预警指标。研究方法:择期行腹腔镜胰十二指肠切除术患者50例,于术前1天和术后7天分别行简明精神状态量表(MMSE)、数字广度、数字符号、循迹连线、词汇流畅性(VFT)和单词辨认神经心理测验。分别于麻醉诱导前(t0)、气腹开始前(t1)、气腹120 min(t2)、气腹240 min(t3)、气腹480 min(t4)、气腹结束(t5)及术毕24 h,抽取颈内静脉血3 ml,采用酶联免疫法(ELISA)方法测定Aβ含量。术中利用近红外光谱技术(NIRS)连续监测rSO2,并计算术中rSO2平均值(2rSO)、术中rSO2最小值(rSO2,min)和rSO2,%max。重要结论:POCD的发生与rSO2及Aβ有关;危险因素可能有老年、低教育水平、较高基础体温、rSO2下降、CO2蓄积、血浆Aβ升高等;rSO2监测有可能是POCD的有效预测工具之一;Aβ有可能是发生POCD敏感的生化预警标志物之一。 相似文献
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饱和苯酚氯仿法提取Tg2576转基因鼠基因组DNA,PCR法扩增编码β-淀粉样蛋白的目的基因,利用基因克隆技术构建以β-淀粉样蛋白为靶的表达载体pcDNA3.1-Aβ42×2,应用酶切及测序鉴定表达载体.相应的双酶酶切能够获得插入的目的基因片段(为269bp),测序未发现突变,表达载体构建成功. 相似文献
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喻祖文 《当代教育理论与实践》2011,3(3):174-176
分别以无水乙醇、纯水以及乙醇与水的混合溶剂作提取剂,采用微波加热的方式,对茶叶中的茶多酚进行提取。实验结果表明,在同等操作条件下,以乙醇与水的混合溶剂作提取剂时提取率最高,以无水乙醇作提取剂时提取率最低;采用乙醇与水的混合溶剂进行提取时,以(NH4)2SO4作析相盐,使之形成双水相体系,此时提取率比未使用析相盐时明显提高。 相似文献
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新鲜蔬菜中β-胡萝卜素提取和测定的研究 总被引:4,自引:0,他引:4
用三种不同方法提取不同新鲜蔬菜中的β-胡萝卜素,并对β-胡萝卜素含量进行测定.结果表明,比较优先的β-胡萝卜素提取方法是:试样用4%Na0H甲醇溶液在60℃-70℃皂化1 h,用3:7(v/v)的丙酮-石油醚混合溶剂提取,以MgO为吸附剂,丙酮一石油醚为洗脱剂分离,提取液用紫外分光光度计在波长447 nm,1cm比色皿条件下测定,得出蔬菜中β-胡萝卜素含量:胡萝卜为0.134 mg·g-1,红椒为0.0863 mg·g-1,菠菜为0.0426 mg·g-1.该方法工艺简单,提取率较高. 相似文献
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This paper presents a new molecular connectivity wherein the atomic delta value is weighted by the Mulliken bond order, and
thus connects effectively the molecular orbital theory with the topological theory and converts the molecular connectivity
method into a novel quantum-topology method. Comparison of the atomic delta value of the molecular connectivity with the value
of the Mulliken bond order, showed that they have similar physical meanings. The calculated new molecular connectivity indexes
of some typical hydrocarbons showed good correlatin with their volumes, hydrophobic constants and thermodynamic properties,
respectively. 相似文献
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This paper presents a novel micro fabrication method based on the laminar characteristics of micro-scale flows. Therein the separator and etchant are alternatively arranged in micro channels to form multiple laminar streams, and the etchant is located at the site where the reaction is supposed to occur. This new micro fabrication process can be used for the high aspect ratio etching inside a microchannel on glass substrates. Furthermore, the topography of microstructure patterned by this method can be controlled by changing the flow parameters of the separator and etchant. Experiments on the effects of flow parameters on the aspect ratio, side wall profile and etching rate were carried out on a glass substrate. The effect of flow rates on the etching rate and the micro topography was analyzed. In addition, experiments with dynamical changes of the flow rate ratio of the separator and etchant showed that the verticality of the side walls of microstructures can be significantly improved. The restricted flowing etching technique not only abates the isotropic effect in the traditional wet etching but also significantly reduces the dependence on expensive photolithographic equipment. 相似文献
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INTRODUCTION Automatic face recognition has become a very active research area in the last decade due to the new interest in, and need for, surveillance and security, telecommunication and digital libraries, hu-man-computer intelligent interaction, and smart en-vironments. The small sample size (SSS) problem is often encountered because the number of the samples is much smaller than the dimension of the sample space in face recognition. It results in the singularity of the within-class … 相似文献
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《中国科技论文》2019,(12)
针对传统无监督图像显著性目标检测鲁棒性不强、学习算法复杂度高的问题,提出了一种新的鲁棒无监督显著性目标检测方法——三元结构化矩阵分解目标检测。该方法利用低秩矩阵三元分解降低奇异值分解(singular value decomposition)的算法复杂度,结合高层先验知识,提升复杂背景下的显著性目标检测性能。通过分层稀疏正则化和构造索引树,解决显著图的细节缺失问题。在3种标准多目标数据集上对主流无监督显著性目标检测方法进行了实验对比,结果表明,所提方法学习时间最多可以降低40%,并且F-measure指标在超过50%的阈值范围内鲁棒性优于当前最好的无监督检测算法。 相似文献
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INTRODUCTIONObjecttrackingisachallengingandimpor tanttaskincomputervision .Someofthemorepopularapplicationsincludevideosurveillanceinstrument,roboticcontrol,andautonomousve hicularnavigation .Trackingalgorithmsfindhowanimageregionmovesfromoneframetothenext.Thisimpliestheexistenceofanerrorfunc tiontobeminimized ,suchasthesumofsquareddifferences (SSD)betweenthetwoimagere gions.Thiserrorfunctionistheresultofmakingthe“constantbrightnessassumption” .Yet,quiteoftenweareinterestedintrackinga… 相似文献
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Dynamic equivalence of the wind farm is a fundamental problem in the simulation of a power system connected with wind farms because it is unpractical to model every generator in a wind farm in detail. In this paper, an Equivalence Method based on the Output Characteristics (EMOC) is proposed, with which the wind farm composed of Squirrel-Cage Induction Generators (SCIGs) can be equivalent to one generator. By considering the diversity of wind generators and special operating characteristics of a wind farm, the equivalent generator based on EMOC responds accurately in various faults. No matter whether the wind farm is integrated in grid or just programmed, EMOC can be used to acquire an accurate equivalent generator. Simulation of the dynamic equivalence of an SCIG wind farm validated the method. 相似文献