Role of the HTLV-III/LAV envelope in syncytium formation and cytopathicity

Acquired immune deficiency syndrome (AIDS) is characterized by marked depletion of the T4+ helper subset of T cells. The aetiological agent of the disease, the human T-lymphotropic virus type III (HTLV-III)/lymphadenopathy-associated virus (LAV), specifically kills T4+ cells in vitro. Part of this specificity for the T4+ population residues in the relative efficiency with which HTLV-III infects these cells, as a result of a specific interaction between the T4 molecule and the virus envelope glycoprotein. In addition, the cytotoxic consequences of HTLV-III replication are dependent on cell type, as certain lymphoid and myeloid cells can be productively infected without notable cytopathic effect. Here we investigate the basis for the specific cytotoxicity of the virus, and report that high-level expression of the HTLV-III envelope gene induces syncytia and concomitant cell death in T4+ cell lines but not in a B-lymphocyte line. Syncytium formation depends on the interaction of envelope-expressing cells with neighbouring cells bearing surface T4 molecules. These results explain, at least in part, the specific cytopathic effect of HTLV-III infections.     

A soluble CD4 protein selectively inhibits HIV replication and syncytium formation

The CD4 (T4) molecule is expressed on a subset of T lymphocytes involved in class II MHC recognition, and is probably the physiological receptor for one or more monomorphic regions of class II MHC (refs 1-3). CD4 also functions as a receptor for the human immunodeficiency virus (HIV) exterior envelope glycoprotein (gp120) (refs 4-9), being essential for virus entry into the host cell and for membrane fusion, which contributes to cell-to-cell transmission of the virus and to its cytopathic effects. We have used a baculovirus expression system to generate mg quantities of a hydrophilic extracellular segment of CD4. Concentrations of soluble CD4 in the nanomolar range, like certain anti-CD4 monoclonal antibodies, inhibit syncytium formation and HIV infection by binding gp120-expressing cells. Perhaps more importantly, class II specific T-cell interactions are uninhibited by soluble CD4 protein, whereas they are virtually abrogated by equivalent amounts of anti-T4 antibody. This may reflect substantial differences in CD4 affinity for gp120 and class II MHC.     

Structure-based design of non-natural amino-acid inhibitors of amyloid fibril formation

Many globular and natively disordered proteins can convert into amyloid fibrils. These fibrils are associated with numerous pathologies as well as with normal cellular functions, and frequently form during protein denaturation. Inhibitors of pathological amyloid fibril formation could be useful in the development of therapeutics, provided that the inhibitors were specific enough to avoid interfering with normal processes. Here we show that computer-aided, structure-based design can yield highly specific peptide inhibitors of amyloid formation. Using known atomic structures of segments of amyloid fibrils as templates, we have designed and characterized an all-D-amino-acid inhibitor of the fibril formation of the tau protein associated with Alzheimer's disease, and a non-natural L-amino-acid inhibitor of an amyloid fibril that enhances sexual transmission of human immunodeficiency virus. Our results indicate that peptides from structure-based designs can disrupt the fibril formation of full-length proteins, including those, such as tau protein, that lack fully ordered native structures. Because the inhibiting peptides have been designed on structures of dual-β-sheet 'steric zippers', the successful inhibition of amyloid fibril formation strengthens the hypothesis that amyloid spines contain steric zippers.     

论牛顿环干涉法测定液体折射率

普通物理实验中,牛顿环干涉实验只考虑在凸透镜与平面玻璃之间形成空气薄膜下的干涉现象。而该文讨论牛顿环所形成的是一般透明介质下的干涉现象,改进牛顿环实验,使之有更大的适用性,并提出一种测量液体折射率的新方法。     

基于UG二次开发的A级曲面拟合与边界裁剪方法

点云数据的曲面建模是反求建模的核心技术之一.在介绍Bézier曲面的拟合理论及相关二次开发函数用法的基础上,利用VC++编程,在UG软件中集成了点云拟合及边界裁剪的功能模块,有利于点云数据曲面建模的自动化实现.实例表明,该方法可行有效.     

Lense-Thirring场同电磁场耦合产生的干涉相移

以Lense－Thirring场为例，讨论其引力场同电磁场耦合的干涉相移，特别是在Lense-Thirring场同磁场矢势耦合情况下，得到了干涉相移同天体旋转角动量的直接显式。     

重组腺病毒介导RNA干扰人DLK1基因表达的研究

构建抑制人DLK1基因表达的重组腺病毒载体,利用腺病毒载体介导的RNA干扰技术评价其在肝癌细胞株中的基因沉默效应.将针对人DLK1基因的RNAi寡核苷酸序列,连接到腺病毒穿梭质粒中,在含有腺病毒骨架质粒pAdEasy-1的大肠杆菌BJ5183内进行同源重组.重组腺病毒载体在HEK-293细胞中包装扩增,得到高滴度的重组腺病毒.通过绿色荧光蛋白示踪腺病毒的感染效果,并通过荧光实时RT-PCR,western blot的方法证实重组腺病毒能够显著抑制DLK1基因在肝癌细胞株中的表达.     

火焰原子吸收光谱法测钙时磷酸根离子的干扰及消除研究

研究了用火焰原子吸收光谱法测钙时PO4^3-对测定的干扰情况，分别单独运用La（NO3）3、EDTA以及联合运用二者来消除其干扰进行了实验研究，并对有关问题作了讨论．实验结果表明，联合运用干扰抑制剂来消除PO4^3-的干扰具有显著效果，特别是当[EDTA]／[La^3＋]为160时更有效地消除了PO4^3-的干扰．     

黑曲霉发酵粉中一种β-葡萄糖苷酶的分离纯化与表征

黑曲霉发酵酶粉通过硫酸铵分级沉淀、SephadexG-25脱盐、再通过两步DEAE-TOYOPEARL650M弱阴离子交换色谱,分离得到一个新的电泳纯的β-葡萄糖苷酶.该酶对水杨素的比活力为597.12IU mg,并对其专一,不能水解棉花和羧甲基纤维素钠;DTT处理前后分子量均为117.5kDa;最适pH和温度分别为4 5和70℃;在pH5.0、50℃下对水杨素钠的米氏常数Km为3.73mg mL,最大反应速率Vm为0.088mg葡萄糖 (mL·min).     

一类潜伏期具有传染性的流行病模型的稳定性

研究一类潜伏期和染病期均具有传染性和康复可能的SEIQ流行病模型,确定了疾病流行与否的阈,利用Routh-Hurwitz判据和LaSalle不变集原理得到无病平衡点的全局渐近稳定性,并借助广义Bendixson-Dulac定理得到地方病平衡点的全局渐近稳定性,最后将隔离率作为控制变量,用范数指标函数作为衡量控制变量的标准,得出该模型最优控制元的存在惟一性.     

一类带投资和干扰的双险种风险模型

在进入过程模型的基础上,讨论了带投资和干扰的双险种风险模型的破产概率.首先得到该模型的盈余过程具有平稳独立增量性;其次,利用鞅方法获得了该模型破产概率的显式表达式以及它的一个上界估计.     

参数控制噪声干扰下的动态电路混沌控制

提出一种基于调制器参数控制噪声干扰下的混沌控制方法，通过利用一种混沌系统驱动另一种混沌系统产生出理想的输出波形，将这种控制方法用于混沌数字通信控制，根据噪声干扰下的系统方程构造出状态调制器，并将其用于具有测量噪声和输人噪声干扰下的混沌系统的控制，改变调制器的作用范围，可以将混沌系统稳定到一定的区域内．仿真结果证实了该方法的有效性．     

在时间分离操作中对干扰和抑制关系的研究

选择性注意的研究是当今信息加工理论框架的一个中心概念，而抑制是当前选择性注意研究的前沿焦点．作为注意的机制——抑制在注意选择中对分心物是如何起作用的，抑制和干扰是一种什么关系?笔者采用负启动实验范式，利用目标、分心物呈现时间先后来分离分心物的干扰作用．实验结果表明，抑制和干扰间是一种正相关．抑制随干扰的变化而变化．     

用线阵CCD测量干涉条纹间距

介绍采用ＣＣＤ、单片机组成的测量系统自动检测等间距干涉条纹的间距量，系统运用ＦＦＴ方法把干涉条纹间距量变换为频域量，有效地排除了散斑噪声干扰，方便准确地得到了干涉条纹的间距。