Specific degradation of keratin in Xenopus laevis egg extracts undergoing apoptosis

Cytochrome c activates apoptosis specific protease XCPP32 when being added to Xenopus laevis egg extracts, and induces apoptosis in this cell-free system. During apoptosis, cyto-skeleton proteins in egg extracts are degraded. Western blot assay indicates that 42-ku acidic keratin in egg extracts has been degraded by XCPP32. The degradation of 42-ku keratin may be crucial in apoptosis.     

Nicotiana ovule extracts in duce nuclear reconstitution of demembranated Xenopus sperm in cell-free system

s Nicotiana tabaccum ovule extracts induced nuclear reconstitution of demembranated Xenopus leavis sperm in a ceil-free system. Demembranated Xenopus sperm began to swell after 15 rmin of incubation with Nicotiana ovulde extracts. Accompanying the process of incubation,Xenopus sperm decondensed and their shapes changed gradually from long and ellipse to round. The completely decondensed chromatin was surrounded with membrane structure, which was a mixture envelope of a double membrane and a single membrane. Nucleosome assembly was verified by means of micrococcal nuclease digestion to reconstituted nuclei and DNA electrophoresis. Nicotiana ovule extracts supplied one more experimental model and system.The new system could promote powerfully the research on mechanisms of cell division and cell cycle regulation.     

Identification of inhibitor of apoptosis specific DNase in Xenopus egg extract

When added with cytochrome c, Xenopus laevis egg extract XS-150 can induce exogenous nuclei undergoing apoptosis. Apoptosis specific DNase XAD was activated during this process, and cut chromatin between nucleosome, leading to DNA Ladder in electrophoresis. Our results showed that an inhibitor of XAD, IXAD, exists abundantly in normal egg extract, its molecular weight is about 40 ku. Normally, IXAD exists either in the form of dimmer or in complex with XAD. It was degraded during apoptosis, releasing active XAD. The results of Western assay and cross-inhibition showed that IXAD was likely homologous to DFF45 in structure and function. At the same time, these results also indicated that the pathway in apoptosis was conserved in evolution.     

Identification of a DNase activated inXenopus egg extracts undergoing apoptosis

A cell-free apoptosis system was established by adding dATP and cytochrome c toXenopus laevis egg extracts S-150. Accompanied by an incubation process, an apoptosis-specific DNase was activated in egg extracts which depended on Mg²⁺ and inhibited by Zn²⁺. Two nucleases existing in egg extracts were revealed by in-gel nuclease assay. Further experiments showed that 27 ku nuclease which was different from other Ca²⁺ /Mg²⁺ -dependent nucleases was a possible candidate involved in apoptosis.     

Application of Xenopus laevis in ecotoxicology (I)—Introduction and quality control of laboratory animal

The aim of the series of papers is to discuss the application of Xenopus laevis, as model animal in biology, in ecotoxicology. X. laevis as model animal is wildly used in biological study and has provided a lot of relating data because of many advantages, such as living in water and being easily maintained, laying eggs in the whole year, and externally fertilizing and developing. Embryos and larvae of X. laevis like other amphibians are directly exposed in the aquatic environment and sensitive to pollutants. In addition, sex differentiation and sex organ development of X. laevis are sensitive to sex hormones and endocrine disruptors with sex hormone activities, which enable X. laevis to be used in studies on sex hormone disruption and reproductive toxicity of endocrine disruptors. Metamorphic development of X. laevis is very sensitive to thyroid hormones and thyroid disruptors, which enables X. laevis to be used for evaluating thyroid disruptors. Also, X. laevis ecotoxicology can be linked with amphibian population declines and malformed frog occurrence, being one of the hotspots in ecology. Thus, more and more laboratories have introduced X. laevis to ecotoxicological study. The quality of laboratory animals correlates with scientificity and reliability of results from animal experiments. It is especially important for toxicology. Quality control of X. laevis involving several factors such as water and food is discussed in this paper.     

Nicotiana ovule extracts induce nuclear reconstitution of demembranated Xenopus sperm in cell-free system

Nicotiana tabaccum ovule extracts induced nuclear reconstitution of demembranated Xenopus leavis sperm in a cell-free system. Demembranated Xenopus sperm began to swell after 15 min of incubation with Nicotiana ovule extracts. Accompanying the process of incubation, Xenopus sperm decondensed and their shapes changed gradually from long and ellipse to round. The completely decondensed chromatin was surrounded with membrane structure, which was a mixture envelope of a double membrane and a single membrane. Nucleosome assembly was verified by means of micrococcal nuclease digestion to reconstituted nuclei and DNA electrophoresis. Nicotiana ovule extracts supplied one more experimental model and system. The new system could promote powerfully the research on mechanisms of cell division and cell cycle regulation.     

The microtubule aster formation and its role in nuclear envelope assembly around the sperm chromatin in<Emphasis Type="Italic">Xenopus</Emphasis> egg extracts

Nuclear envelope separates cell genome from cyto-plasm in eucaryotic cells and plays a pivotal role in the cell life. The nuclear envelope is composed of two jointed membranes, the inner membrane and the out membrane, embedded the nuclear pore complexes. The out membrane is continuous with the endoplasmic reticulum (ER). The ARTICLES inner membrane faces to and connects with the chromatin through the nuclear lamina, an intermediate filamentous network thought to play a structural role for…     

全方位逃逸的第三宇宙速度蛋形曲面

由于地球的公转运动,从地球上向各方向发射宇宙火箭必与地球之间交换能量。火箭传递给地球的能量随着发射方向与公转速度的夹角而改变。其数值变化范围:(每公斤质量火箭)约从+1.14×10~8J,到-0.26×10~8J。速度矢径由最佳方向的16.7km/s变到相反方向的73km/s。全方位第三宇宙速度矢径,构成一个半径为43.5km/s的球面为基础的蛋形曲面。前端略尖,后部扁平。     

关于教学系统的信息分析

早在40年代,著名科学家申农(Shanon)就提出了信息量的概念,建立了编码理论,使信息论成为现代通信领域中的基本理论,并在实际生产中发挥了巨大的作用.现在人们所指的信息应同时涉及3个要素:信源、信道、信宿.信息应该是由信源发出,通过信道传输,最终为信宿接收的,能够去掉某种不确定性的量度.单独谈论信源发出多少信息是不完全的.在这种观点指导下,我们来分析教学过程.由教师、学生及教学环境组成的教学系统中各个元素之间的作用和交流主要是信息的交流.教学过程中所产生的信息不仅有知识信息,而且还有控制信息和反馈信息.知识信息是教学过程中的主要信息.通过这种信息流,学生掌握了技能与本领,这点已被人们重视,并进行了研究.在教学过程中影响学生学习效果的还有一类信息,它由教师的内容安排、讲课声调、手势等体现出来,这是控制信息.它对排     

校园计算机信息网络系统

计算机信息网络系统是院校现代化教育管理的重要手段,建立这种网络系统是一个庞大复杂的系统工程。本文明确提出了建立计算机信息网络系统的目的和意义,叙述了该系统的结构、功能、配置及发展趋势,并对其未来的效益作了评估。     

油桐尺蠖核型和木(木尞)尺蠖核型多角体病毒的限制性内切酶分析

油桐尺蠖核型多角体病毒(BsNPV)、木(木尞)尺蠖核型多角体病毒(CpNPV)和用CpNPV感染油桐尺蠖幼虫面得到的病毒CpNPV-Bs,三者经HaeⅢ酶解后的电泳图谱均一致,经HindⅢ酶解后,均获得11条片段。各病毒DNA的总分子量约为57.5×10~6D。本文初步认为BsNPV和CpNPV为同一种病毒。     

质子─核（~（208）Pb）弹性散射与核半径常数的确定

本文通过对动能为８００Ｍｅｖ的质子由基态铅核（２０８Ｐｂ）的弹性散射的角分布的分析给出了原子核半径（Ｒ）与核半径常数（ｒｏ）的值．这些值与从其它的测量原子核半径的方法所得到的结果符合得很好。     

低温高密度近似下核物质的热力学行为

本文对用Gogny有效势推得的核物质状态方程作低温高密度的极限过渡。温度T→0时,每核子的内能及压强均不为零,是明显的量子效应。     

计算机程序设计语言教学测评系统

本文报告如何充分利用计算机软件系统资源,经组合加工研制成的一个编译型高级语言的教学测评系统。     

大熊猫消化系统同工酶凝胶电泳分析

对身体瘦弱、无病,落水的大熊猫消化系统8种组织器官及1种消化液的LDH、酯酶及过氧化物酶等三种同工酶,进行了凝胶电泳分析,并从基因表达的角度讨论了LDH同工酶的变化.     

我国减灾管理体制及调整初探

我国减灾工作历史可分为经济性减灾，半经验半理论性减灾和综合减灾三个阶段。４０多年来逐步形成和发展的纵向分散减灾管理体制，取得了巨大的减灾成就，但现行减灾管理体制不能适应社会经济发展对减灾工作的需要，提出了调整设想。     

离散时间系统中一阶微分方程的建立与求解的新方法

引入了离散时间系统中微分与积分的新概念,讨论了该系统中一阶微分方程的建立与求解的方法,给出了相应的解表达式.按照本文的模式,离散函数空间中一切元素均无限次可微且无限次可积,灰色系统中GM(1.1)模型的解是离散函数一阶线性微分方程在特殊情形下的一个近似解.     

一般光路中的分数傅里叶变换的分析方法

在分数傅里叶变换的基本性质的基础,通过引入一个定标因子,通过两次切变操作来旋转ＷＤＦ,给了分数傅里叶变换的一种新的分析该方法可以将原有的分数傅里叶分析从对称光路扩展到的一般的光路。