Acetylcholine receptor at neuromuscular junctions by EM autoradiography using mask analysis and linear sources

Several methods of analyzing EM autoradiograms are now available. Two such procedures, the grain density distribution (or histogram) method and the mask method use the resolution of the EM autoradiographic technique to generate grain distributions expected from postulated sources, and compare these with the observed grains in the autoradiograms. These two methods are here compared in the analysis of label on linear sources: the distribution of labeled acetylcholine receptor (AChR) down the postjunctional folds of lizard and frog neuromuscular junctions. The receptors were labeled with I-25-α-bungarotoxin and the autoradiograms coated with the high resolution Kodak emulsion 129–01. We found that both methods gave similar results in confirming that the bulk of the AChR is concentrated on the thickened region of the membrane at the top ∼2000 A of the junctional folds, and that there may be a gradient of receptor concentration down the folds. The grain density distribution method is simpler, but does not lend itself easily to quantifying the extent of deviation from simple models. Although computer graphics is not necessary for either method, its use allows the expected grains from linear sources to be generated quickly, making the mask analysis a feasible routine method for assigning the extent of label in different membrane regions.     

A methodological basis for SEM autoradiography: biosynthesis and radioligand binding

A method is described for scanning electron microscope (SEM) autoradiography whereby preservation of high resolution cell surface details is retained together with degelatination of the emulsion without gross loss or redistribution of silver grains. This method should provide a convenient medium-sized marker for SEM (using secondary, backscattered electron and X-ray imaging) topographic studies of biosynthesized molecules, and of cell surface receptors and antigens, using indirect or direct labelling procedures with radio-labelled ligands.     

Image spread in dry-mounted tritium autoradiographs

A comparison has been made of autoradiographs prepared by conventional dipping methods and those prepared from the same material using a dry-mounting method developed for the study of receptor labelling. Resolution was found to be inferior, and image spread greater, in the dry-mounted preparations. The extent to which resolution and image spread were affected depended upon the distance between specimen and emulsion.     

雌激素受体电镜定位的微波照射技术

将微波照射与电镜细胞化学技术相结合确定雌激素受体在细胞内的位置。在样品的固定、包埋、聚合及孵育过程中,使用改进的微波照射技术,既提高了样品的制备质量,又将样品制备时间缩短到原来的1/3。     

Labelled-replica techniques: post-shadow labelling of intramembrane particles in freeze-fracture replicas

Three methods are described for direct post-fracture, post-shadow labelling of individual classes of intramembrane particles (IMPs) in freeze-fracture replicas of biological membranes. The P-face IMPs corresponding to the acetylcholine receptor complexes (AChRs) of vertebrate neuroeffector junctions are identified by post-replication labelling with ferritin-antibody complexes and with neurotoxin-biotin-avidin-colloidal gold affinity ligands. (The freeze-etch nomenclature of Branton et al., 1975, is used in this report.) These post-shadow labelling techniques resemble conventional en bloc labelling techniques except that the labelling reagents must penetrate a thin but discontinuous layer of platinum superimposed on the molecules of interest. In the ‘sectioned labelled-replica technique’, the replicated and labelled tissues are stained, embedded in plastic and sectioned parallel to the replica-tissue interfaces. In the direct ‘labelled-replica techniques’, the replicated and labelled samples are freeze-dried or critical point dried, the labelled surfaces are stabilized by carbon coating, and the underlying tissues are dissolved, allowing the labelled-replicas to be examined as conventional freeze-fracture replicas. The unshadowed side of each AChR IMP is shown to retain sufficient biochemical information to permit both immunospecific and neurotoxin specific labelling despite formaldehyde fixation, freezing, fracturing, platinum shadowing, and thawing in aqueous media. A new mixed ferricyanide-osmium staining method reveals electron opaque structures spanning the membrane bilayer in the same size, number and distribution as the labelled IMPs. These experiments demonstrate the feasibility of identifying individual IMPs in freeze-fracture replicas and may allow the identification of specific membrane lesions in human disease.     

Vibration and noise in brake systems of vehicles. Part 2: Theoretical investigation techniques

The paper reviews theoretical research into vibroacoustic phenomena in transport brake systems. The mechanisms of occurrence of different types of noise and vibration in brakes are described. Analytical, numerical, and experiment-calculated methods for studying brake noise are discussed and their disadvantages from the point of view of obtaining adequate calculation models are analyzed. The results of prediction of the vibroacoustic activity of friction units based on calculation methods are considered.     

Anterograde tracing in the brain using autoradiography and HRP-histochemistry. A comparison at the ultrastructural level

The present paper decribes the use of ³H-leucine and WGA-HRP as anterograde tracers in the brain at the ultrastructural level. In addition the different aspects of the two tracing techniques are compared, including the analysis of the results, the reliability and relative efficiency.     

Simultaneously identifying S-phase labelled cells and immunogold-labelling of vinculin in focal adhesions

A new combination of autoradiography and immunolabelling techniques is presented that allows the simultaneous identification of both S‐phase cells and their focal adhesions using scanning electron microscopy. The technique allows both labels to be discerned visually by their unique shapes and location within and on the cell. S‐phase cells were radio‐labelled with a pulse of tritiated thymidine, selectively incorporated into synthesizing DNA. The cells were then immunogold‐labelled for the focal adhesion protein, vinculin, prepared for autoradiography, and embedded in resin. The resin was then polymerized before removing the substrate, to expose the embedded cell undersurface. Electron‐energy ‘sectioning’ of the sample by varying the accelerating voltage of the electron beam allowed separate S‐phase cell identification in one electron‐energy ‘section’ and visualization of immunogold label in another ‘section’, within the same cell. As a result of applying this technique it was possible to positively identify S‐phase cells and immunogold‐labelled focal adhesions on the same cell simultaneously, which could be used to quantify focal adhesion sites on different substrates.     

对城市暴雨洪水利用有关问题的探讨

解决城市暴雨问题,过去一味强调疏与排,这样做的结果是大量雨水从城市排水系统流走了.雨洪过后,城市依然喊渴.现在人们逐渐发现,城市其实非常需要雨水,城市暴雨洪水完全可以收集和利用,这是解决城市排水和缺水问题的有效途径.     

实物逆向工程中的关键技术及其最新发展

逆向工程是将实物转变为CAD模型相关的数字化技术、几何模型重构技术和产品制造技术的总称。在各工业领域有广泛的应用。总结了逆向工程中的数据获取、数据预处理、曲面重建等主要技术,分析了一些比较典型的方法,并就其在国内、外最新的研究进展进行了介绍。     

Receptor binding occurrence and plasma levels of natriuretic peptides in response to sympathectomy

In the present investigation the relationship between the sympathetic nervous system and the endocardial levels of receptor binding sites for natriuretic peptides and the plasma content of atrial natriuretic peptide were analyzed in rats. In order to destruct the cardiac sympathetic nerve terminals, chemical sympathectomy with 6-hydroxydopamine was made in parallel with intravenous measurements of blood pressure and heart frequency. By use of immunohistochemical and enzyme-linked-immunosorbent techniques the expression of tyrosine hydroxylase-positive sympathetic nerve terminals and plasma levels of pro-atrial natriuretic peptide were determined, respectively. The occurrence of receptor binding sites for natriuretic peptides was examined by in vitro receptor autoradiography. In contrast to the marked occurrence of natriuretic peptide receptor binding sites seen in the ventricular endocardium of control rats, the sympathectomized rats exhibited a decreased number of binding sites for natriuretic peptides in the endocardium of both the right and left chambers. Interestingly, this was found in parallel with a significant decrease of systolic and diastolic blood pressure and increased plasma levels of pro-atrial natriuretic peptide in the treated group of rats. These findings, together with those in previous studies, give support to an idea that one part of the blood pressure-decreasing effects, seen in patients treated with beta-adrenergic blockade, might be through a reduction of the natriuretic clearance receptor C, then giving rise to increased levels of atrial natriuretic peptide.     

Triboelectrochemical techniques and interpretation methods in tribocorrosion: A comparative evaluation

Tribocorrosion is a material deterioration or transformation resulting from simultaneous action of wear and corrosion. Tribocorrosion is found in many engineering applications but the involved mechanisms are still little understood. The investigation of tribocorrosion requires the control of the chemical conditions during a wear test. In aqueous electrolytes, this is achieved by using different types of electrochemical-controlled wear experiments (triboelectrochemical experiments). This paper presents a critical appraisal of the main electrochemical techniques and evaluation methods used in tribocorrosion research with special emphasis on sliding and fretting situations involving passive metals.     

Scanning and detection techniques used in a confocal scanning laser microscope

A two-mirror scanning mechanism for confocal microscopy is described. No optical components, in addition to the scanning mirrors, are used. Design criteria and performance of the scanner are discussed. The photometric linearity of a detector unit incorporating a photomultiplier tube is reported, and a dual detector unit with tunable split wavelength is described.     

流动分析技术及其在海水营养盐自动检测中的应用

海水营养盐是海洋初级生产力和食物链的基础,营养盐的测定对海洋学的研究至关重要。流动分析技术由于其自动化、低耗以及重现性高等优点,在海水的营养盐自动检测中有着广泛的应用。本文对流动分析技术的发展进行了归纳总结,对流动分析技术在海水营养盐自动检测中的应用进行了讨论,并对流动分析技术在海水营养盐检测中的总体发展方向进行了展望。     

Scope of in-process measurement, monitoring and control techniques in machining processes—Part 3: In-process techniques for cutting processes and machine tools

In-process techniques for cutting processes and machine tools are surveyed through representative examples. Detection of cutting force and chatter vibration are especially important in cutting processes. As for machine tools, four measuring items will be important which include the driving system, the bearing and rotating systems, the temperature control system, and the monitoring system. They are the primary factors to be taken into consideration for achieving high machining accuracy.     

快速换模技术在大中型客车行业冲压加工中的应用

以1030T压力机为例,对其在精益生产的推进过程中进行分析,应用了快速换模技术,通过使内换模和外换模分离、缩短内换模时间等步骤,使换模时间由原来的34min减少为13min,设备利用率由45.9%提高到75%.     

电热膜采暖系统中能量转换和利用状况的探讨

简述了低温辐射电热膜采暖的优点和存在的问题,从热工学理论出发,基于能量转换和利用的知识,对低温辐射电热膜采暖系统中能量形式的转换和利用的实际情况进行了探讨,初步论证了低温辐射电热膜采暖的可能性与可行性。在采暖方式的选择及系统节能方面具有一定的指导意义。     

水体沉积物和土壤中多环芳烃的分析方法研究

简单论述水体沉积物和土壤中多环芳烃的来源及危害,系统综述国内外分析多环芳烃的前处理和检测方法的研究进展,对微波辅助萃取、超声波提取、快速溶剂革取、超临界流体萃取、固相萃取、固相微苹取等前处理技术在水体沉积物和土壤中的应用进行概述和比较,对气相色谱质谱联用、高效液相色谱、高效液相色谱质谱联用等测定方法分别进行归纳和对比,并对多环芳烃的分析方法进行展望。     

虚拟现实技术在工程制图实验系统中的应用研究

这里阐述了虚拟现实技术的特点,并进一步探讨了基于网络的工程制图实验系统中,虚拟现实动画及其交互的实现技术以及在Web界面中的具体应用。     

港口输送系统钢栈桥及转载房焊接工艺

为适应货源改变的格局,提高泊位利用率,使泊位效益最大化,湛江港对300号和301号泊位装卸储运系统进行技术改造。整个技术改造工程中固定带式输送机的支撑是钢结构栈桥及转载房,介绍钢结构栈桥及转载房的焊接工艺。