bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coating sections for electron microscopic autoradiography: a stripping technique using liquid emulsion
Authors: Burry Richard W. , Lasher Robert S. 
Published: August 2011

SUMMARYA coating technique for electron microscope autoradiography is described which combines the advantage of forming an emulsion film by a dipping method with the ease of coating sections already on grids. Sections are coated so that a formvar support film separates the section and the emulsion crystals. This intermediate layer of formvar ensures a random distribution of the emulsion crystals. Using light gold sections, Ilford L‐4 emulsion and Microdol‐X development, the resolution of this technique, as determined by the half distance method, was 150 nm. The additional layer of formvar slightly reduced the image quality with biological samples in the electron microscope. This technique has a minimal loss of resolution and image quality for moderate resolution electron microscope autoradiography.
A new method for comparative light and electron microscopic studies of individual cells, selected in the living state
Authors: van Ewijk W. , Hösli P. 
Published: August 2011

SUMMARYA method is described which permits comparative light and electronmicroscopic studies of cell cultures, cell spreads or single selected cells which have been kept in the Plastic Film Dish (PFD). The PFD is a versatile large surface tissue culture chamber which, for electron microscopy, is mounted with a transparent FEP‐Teflon film bottom. Cells are observed, selected and marked on the PFD‐bottom with a high power inverted light microscope. The cells are fixed and dehydrated with a semi‐automatic device while they are still in situ in the PFD. During the preparation steps for electron microscopy the topographical relationship between individual cells and between cells and cell support is accurately retained. After embedding and polymerization the Teflon film is easily peeled off the polymerized Epon, leaving a replica of the mark around the selected cell. This permits relocation of the selected cells for ultrathin sectioning in a plane plan‐parallel to the original cell support. To enable orientated sectioning of selected cells in a plane perpendicular to the cell support, cells are tagged with Letraset‐letters after original embedding and polymerization. Subsequently the re‐embedded polymerized specimens are orientated in the microtome in a position which permits controlled thin sectioning of the tagged cells in the previously selected plane.
A comparative study in the transmission electron microscope and scanning electron microscope of intracellular structures in sheep heart muscle cells
Authors: Myklebust Reidar , Dalen Helge , Saetersdal Thv. Selmer 
Published: August 2011

SUMMARYThe internal cellular structures of the sheep ventricular myocardium have been comparatively studied in the transmission electron microscope (TEM) and in the scanning electron microscope (SEM). For TEM studies the tissue was prepared according to standard methods. Thick sections (10 μm) of paraffin embedded material were, after they had been deparaffinized in toluene, critical point dried, coated with gold and examined in the SEM. The comparative TEM and SEM investigations revealed very good correspondence, and it is evident that the described preparation procedure for SEM has preserved the fine structures of myofibrils, mitochondria, T‐Tubules and sarcoplasmic reticulum in an excellent life‐like pattern. Of special interest was the three‐dimensional demonstration of triads and of circumferentially arranged T‐tubules.
Ice crystal growth in skeletal muscle fibres
Authors: Sjöström Michael 
Published: August 2011

SUMMARYIce crystal growth was studied in rapidly frozen skeletal muscle fibres which were treated with cryo‐protective additives (glycerol, DMSO, sucrose) or which were untreated. Freeze cleaving and etching was the basic method, with conventional plastic embedding and cryo‐ultramicrotomy as complementary techniques.Extensive crystal growth occurred during freezing in all unprotected fibres. Just below the fibre surface the crystals were numerous but small, while deeper in the fibre they were fewer but larger. The deeper within the specimen a fibre was located, the larger, in general, was the crystal size. The crystal volume density was about 55%, irrespective of crystal size. Ice recrystallization was practically absent at the temperature normally used in cryo‐sectioning (–70°C). Anti‐freeze treatment eliminated crystal growth. If the anti‐freeze agents were used in non‐toxic concentrations, however, their effect on crystal growth was very limited. ‘Dry’‐cut, freeze‐dried ultra‐thin cryosections of protected and unprotected fibres confirmed these observations, while sections obtained by ‘wet’ cryo‐cutting showed no apparent signs of crystal growth. In plastic sections of frozen and thawed fibres a previous occurrence of crystals was only slightly indicated.In interpreting the ultrastructure in ‘wet’‐cut cryo‐sections of unprotected frozen mucle fibres, the distorting effects of ice crystals through mechanical compression and alterations in sectioning conditions, must be taken into consideration. Crystal growth also strongly limits the possibilities of using ‘dry’‐cut sections of untreated frozen tissue for analytical electron microscopy; only the most superficial parts of the fibres seem to be suitable for microanalysis.
The relationship of plastic deformation in freeze‐etching to the orientation of a protein particle
Authors: Willison J. H. M. 
Published: August 2011

SUMMARYFreeze‐fracturing of face‐centred, cubically packed, intracellular crystals of fraction 1 protein result in two distinct fracture responses of the constituent particles, according to their orientation relative to the plane of fracture. If a square‐packed plane is revealed, fracture occurs either between particles or the particles plastically deform. Conversely, if a hexagonally‐packed plane is revealed, fracture occurs either between particles or cleanly at internal planes of the particles, without any plastic deformation. It is proposed that this information may be of value in determining the arrangement of the axes of the covalently bound polypeptide protomer chains which constitute the oligomer.
The effect of gas on the irradiation of aluminium inside a high voltage electron microscope
Authors: Mayer R. M. , Stobbs W. M. , Ward P. R. 
Published: August 2011

SUMMARYAn environmental cell was used in the high voltage electron microscope to observe the formation of radiation damage in aluminium and dilute aluminium alloys in the presence of gas atmospheres of hydrogen, helium and air. The types of defect produced under such conditions are classified and it is shown that the characteristic of electron irradiation in the presence of a gas is the promotion of void nucleation. The implication of this observation with regard to the design of reactor materials is discussed.
A multipurpose specimen‐carrier for handling small biological objects through critical point drying
Authors: Rostgaard J. , Christensen P. 
Published: August 2011

SUMMARYA specimen‐carrier for safely handling, protecting and drying minute biological specimens down to 1·0 μm in size during the various steps of the critical point drying procedure is described. Free, unattached cells or subcellular fragments can be processed without loss and without risk of unintentional air‐drying.
Quantitative analysis of micrographs by computer graphics*
Authors: Dunn Robert F. , O'Leary Dennis P. , Kumley Warren E. 
Published: August 2011

SUMMARYA computer‐aided graphical analysis system is presented which can be used to quantify several types of information from micrographs of cross‐sectioned peripheral nerves. A simple input consisting of eight points, corresponding to two diameters of each axon and two for each axon plus myelin, is used to compute statistical and numerical estimates of these diameters, the myelin thickness being expressed as a function of axon diameter, and both the spatial position and distribution of nerve fibres within the bundle. The computer programs presented and summarized here describe the procedure for digitizing the input data and the subsequent computations for editing and analysis. The general applicability of this approach for automated analyses of other anatomical areas is also presented.
The application of image pickup and storage‐display techniques to the high resolution electron microscope
Authors: Catto C. J. D. , Smith K. C. A. 
Published: August 2011

SUMMARYThe advantages of using image‐intensifiers and other image pickup systems as an aid to the observation of the image in the electron microscope have been known for many years, and a review of a number of the systems employed so far is presented here. The additional advantages to be gained by the use of a sensitive TV pickup tube in conjunction with a storage tube are discussed, with particular reference to a proposed system for use with a high voltage, high resolution, electron microscope. It is shown that the prime limitation to the signal‐to‐noise ratio obtainable in the image pickup‐display chain is due to the noise in the electron microscope signal itself, and that with the proposed pickup and storage tube arrangement a field of 800 by 600 picture points, with adequate signal‐to‐noise ratio, should be obtainable for a current density of 10−9 A/m2 in the image plane of the microscope if an integration period of about 3 s is used.
The effect of variations in objective focal length on electron microscope performance
Authors: Lovell D. J. , Chapman S. K. 
Published: August 2011

SUMMARYStandard specimens were examined in a transmission electron microscope with a top entry stage. Using a range of objective focal lengths, measurements of contrast, resolution and magnification range were made. Focal lengths up to 14 mm were examined. The contrast was found to increase with increasing focal length, being twelve and a half times greater at 14 mm focal length than at the normal high resolution mode of 2 mm focal length. Resolution, determined by the fresnel fringe method decreased from 0·3 nm to 3·5 nm. The photographic image magnification was reduced from × 1000– × 500,000 at 2 mm focal length to ×100‐× 50,000 at 14 mm focal length.
A simple technique for the rapid preparation of freeze‐fracture replicas of plant nuclei
Authors: Severs N. J. , Jordan E. G. 
Published: August 2011

SUMMARYA rapid method of extracting nuclei in high yield from small quantities of plant material, for freeze‐fracture studies is described. The nuclei are gently isolated directly into buffered glutaraldehyde which ensures good preservation of ultrastructure. Removal of the cell wall allows rapid glycerination of the specimen and faster cleaning of the replica.
A container for handling small specimens during preparation and examination in the scanning electron microscope (SEM)
Authors: Taylor Peter G. 
Published: August 2011

SUMMARYThe difficulties of handling small specimens of < 1 mm3 are considerably reduced when the specimens are placed in a small container designed to be compatible with the dimensions of the preparatory instrumentation and of the microscope. The container described is unaffected by solvents used in the preparation of specimens for scanning electron microscopy.
Single atom image contrast: conventional dark‐field and bright‐field electron microscopy
Authors: Chiu Wah , Glaeser Robert M. 
Published: August 2011

SUMMARYSingle atom image intensities are calculated for bright‐field and various dark‐field modes, including the ideal beam stop, a wire beam stop, tilted illumination and a displaced aperture. Comparisons of scattering amplitudes and elastic scattering cross‐sections are made with different object potentials and scattering formulations. The image contrast for one mercury atom (Z = 80) on a column of carbon atoms (Z = 6) as the substrate is also discussed for both the bright‐field and the various dark‐field situations. A list of abbreviations to be used in the text is shown below.
A wet stage modification to a scanning electron microscope
Authors: Robinson V. N. E. 
Published: August 2011

SUMMARYA modification to the vacuum system of a JSM2 scanning electron microscope has enabled hydrated specimens to be placed inside the specimen chamber of the instrument and to be surrounded by water vapour at a pressure up to approximately 1.3 kPa (10 Torr). The surface topography was observed by detecting the backscattered electrons using a wide angle backscattered electron detector placed close to the specimen. The microscope was operated in the normal scanning mode which allowed the examination of the surface topography of the specimens, whilst still retaining the depth of focus which is a feature of the SEM.This modification has enabled a resolution of approximately 0.2 μm to be obtained from biological specimens partially immersed in water at temperatures just above 0°C.
Photographic aspects of scanning electron microscopy
Authors: Malin D. F. 
Published: August 2011

SUMMARYFactors governing photographic image quality in the scanning electron microscope are discussed with particular reference to the commonly used EXA camera on the Cambridge Stereoscan IIa. It is shown that the small image on the medium speed film suffers considerable loss of information due to the turbid nature of the photographic emulsion. Inexpensive modifications to the oscilloscope camera supplied with the Stereoscan are described which enable the superior quality of a larger format to be utilized. Appropriate settings of the brightness and contrast controls of the image tube with respect to the photographic system is discussed and the results illustrated in a series of micrographs.
Preparation of nematodes for scanning electron microscopy
Authors: Green C. D. , Stone A. R. , Turner R. H. , Clark S. A. 
Published: August 2011

SUMMARYNematodes from the orders Tylenchida and Rhabditida were fixed and processed in several different ways for examination with the scanning electron microscope (SEM). Four processes produced good preparations of fixed nematodes. Drying from acetone was the simplest of these techniques and most useful for regions of the tylenchid nematodes supported by skeletal tissue. Critical point drying, a more complicated procedure, gave good preparations but they required special care in processing. Nematodes infiltrated with glycerol and a conducting agent were the most life‐like but were difficult to examine. Specimens infiltrated with an epoxy resin looked natural and this was the most promising process tried.
Contrast enhancement by changing the objective lens focal length
Authors: Misell D. L. 
Published: August 2011

SUMMARYRecent experimental results on the variation of resolution and contrast of electron microscope images with objective lens focal length are compared with theory. Whereas there is agreement between theory and experiment for the normal range of focal lengths (2–6 mm), the experimental results indicate a far higher image contrast and inferior image resolution than predicted by theory for a very long focal length objective (12–14 mm).
Preparation of cultured cells for SEM: air drying from organic solvents
Authors: Albrecht R. M. , Rasmussen D. H. , Keller C. S. , Hinsdill R. D. 
Published: August 2011

SUMMARYAir evaporation from organic solvents of differing polarities and surface free energies was used in the preparation of cultured murine peritoneal macrophages for scanning electron microscopy (SEM). The surface structural features of these cells were compared to the surfaces of similar cells prepared by the critical‐point procedure. In general, all organic solvents produced a marked collapse of cell structure resulting in an increase in surface irregularity. Fracture surfaces and sharply defined contours including numerous flaps and ridges were characteristic of the non‐polar solvent dehydrated samples. Polar solvent dehydrated samples, including those dried from solvents of low surface free energy, exhibited a secondary flowing and settling of the cell membrane. Primary collapse was apparent but cell contours were smoothed and rounded. Overall cell shape and cell‐to‐cell relationships were retained regardless of solvent type.It is suggested that solvent evaporation may prove useful in certain cases, though investigators are advised to use caution when interpreting the results obtained by such procedures.
An aid to understanding differential interference contrast microscopy: computer simulation
Authors: Galbraith W. , David G. B. 
Published: August 2011

SUMMARYDifferential interference contrast (DIC) microscopy has been widely used for many years. However, many biologists employ DIC inefficiently and frequently misinterpret the resulting images. In an effort to improve the standard of use, a method of simulating DIC microscopy on the cathode‐ray tube (CRT) and x–y plotter of a computer was therefore developed. This paper describes the program and gives examples of its application, emphasizing some common errors of operation of the DIC microscope and interpretation of the image.Simulations are made for objects of negligible thickness, and in one azimuth of the microscope at a time. The method shows clearly the profiles of the phases and amplitudes of the interfering waves obtained for a variety of objects and demonstrates unequivocally the kinds of images obtained. It is possible to show very quickly how the image changes as instrumental parameters, such as phase‐bias, amplitude‐ratio, extinction factor, and beam‐splitter shear are altered.Simulation was found useful as a tool to learn DICM and as an aid to the interpretation of complicated images obtained with real objects. Examples of common errors in adjusting the microscope and interpreting images are given in this paper.The simulation program was developed for the computer of the Denver Universal Microspectroradiometer (David & Galbraith, 1975; Galbraith et al., 1975), but it can be used on a number of compatible computing systems. The program construction is explained to enable comparable programs to be written for different computers.
The nature of defocus fringes in scanning‐transmission electron microscope images
Authors: Joy David C. , Maher Dennis M. , Cullis Anthony G. 
Published: August 2011

SUMMARYExperimental observations have been made of the fringe contrast which appears at the terminating edges of thin objects in defocused, scanning‐transmission electron micrographs. In general only a single bright fringe is present and the displacement and width of this fringe was found to vary linearly with defocus, indicating the contrast does not result from simple‐Fresnel diffraction. A model for this contrast, based on the refraction of incident electrons by the object edge, is shown to explain the observed results.
Wholebody autoradiography: a β‐radioluminescence method for detecting tritium
Authors: Farebrother D. A. , Creasy Dianne M. 
Published: August 2011

SUMMARYA method of increasing the sensitivity of X‐ray film for the wholebody autoradiography of tritiated compounds is described. Thirty micrometre sections are sprayed with a scintillator, Diphenyl oxazole (PPO) and exposed to light sensitive (screen) X‐ray film at −70°C. The method permits a substantial reduction in the required dose of tritium and of the period of exposure of tissue sections.
Two‐Shockley unfaulting of two‐ and three‐layer faulted defects
Authors: Ronander E. , Kritzinger S. 
Published: August 2011

SUMMARYThe principles of butterfiy‐unfaulting of Frank dislocation loops, i.e. unfaulting by the simultaneous action of two Shockley partial dislocations (Swart & Kritzinger, 1974a), are applied to two‐layer faulted defects in thin foils of quenched aluminium to explain the structure and contrast behaviour of some dislocation configurations observed by transmission electron microscopy. Direct electron microscope evidence is presented for the butterfiy‐unfaulting of three‐layer faulted defects in the same specimens. Positive evidence is furnished that Shockley partial dislocations can be nucleated at sites in the stacking fault other than the hexagon corners of the defects.
Methods for the measurement of polarization optical properties: I. Birefringence
Authors: Taylor D. Lansing , Zeh Robert M. 
Published: August 2011

SUMMARYA simple birefringence detection system has been developed that can be used with any standard polarizing microscope. A Foster prism is utilized in separating the orthogonal components of the resultant linearly polarized light coming from a properly oriented λ/4 plate. The light intensities of the orthogonal components are measured simultaneously and a mathematical manipulation yields a direct read‐out of phase retardation (nm). The theory and practical use of this technique is discussed, as well as the present and future applications.
Modes of chromatin packing in Feulgen‐stained normal and malignant uro‐epithelial cell nuclei, and in lymphocytes, in relation to DNA content
Authors: Boss J. M. N. , Feneley R. C. L. , Mays R. G. W. 
Published: August 2011

SUMMARYBy a two‐step method of histogram densitometry it was found that the inhomogeneity of distribution of chromatin within a nucleus was similar in normal and malignant human bladder epithelium and in lymphocytes, despite the grossly abnormal range of DNA content of the carcinoma nuclei.
Modifications to an LKB Pyramitome
Authors: Dingemans K. P. , Lettinga K. P. 
Published: August 2011

SUMMARYModifications to an LKB Pyramitome and Target Marker are described which considerably increase both the accuracy and speed when preselected areas are trimmed out from larger tissue blocks. The modifications include: (a) a better viewing system which facilitates the movement of the specimen and the knife with respect to each other; (b) a movable light source which makes it possible to obtain a reflection image of the front face of the block in which many structural details are visible; (c) the possibility of introducing to the Target Marker system polaroid micrographs of light microscopic sections rather than the sections themselves. On the micrographs, the selected area and other desired features of the section can easily and clearly be marked; (d) a selected area marker with which the area to be trimmed out can be marked mechanically on the block with great accuracy; (e) various modifications to knobs, controls, etc., all aimed at higher speed and accuracy and greater convenience for the user. Whereas its basic working principles have remained unchanged, the modified instrument is much better suited for routinely executed high‐precision work than the original version.
A technique for electron microscope autoradiography (and X‐ray microanalysis) of diffusible substances using freeze‐dried fresh frozen sections
Authors: Baker J. R. J. , Appleton T. C. 
Published: August 2011

SUMMARYSeveral attempts have been made over the past few years to localize diffusible radioactive substances in tissues at the electron microscope level. The procedures employed hitherto have involved one or more aspects of the methods used in tissue preparation for conventional electron microscopy and as such are unlikely to be universally applicable for all classes of diffusible substance. The present paper shows that the use of ultrathin frozen sections of fresh unembedded biological material permits the ultrastructural localization by autoradiography and X‐ray microanalysis of highly soluble electrolytes.
Problems associated with particulate contamination of cell cultures with relation to ultra‐thin sectioning techniques
Authors: Smith K. , Luther P. D. 
Published: August 2011

SUMMARYHard foreign particles encountered in centrifuged pellets of cell cultures and other biological material can interfere with ultra‐thin sectioning. Factors which influence the presence of this contamination are considered and a technique is recommended for cell cultures which overcomes these difficulties.