bluuebunny/crossref_metadata_2025_split huggingface dataset:
The use of thin specimens for X‐ray microanalysis in biology
Authors: Hall T. A. , Anderson H. Clarke , Appleton T. 
Published: August 2011

SUMMARYThe quantitative X‐ray microanalysis of ultrathin biological sections is exemplified by a recent study of the distribution of calcium in mineralizing cartilage and bone. The determination of calcium mass‐fraction in one microarea of a vesicle within a section of rabbit epiphyseal plate cartilage is presented in detail in order to display all steps of the processing of the data. Mass fractions are obtained from an equation which is approximate but which is adequately accurate for most cases of interest, specifically for ultrathin biological sections where the analysed area consists predominantly of organic matrix. We shall examine the physical assumptions behind the computation, and the extent to which these assumptions have been verified in the analytical microscope.The purpose of this paper is to describe in detail the scheme of data collection and processing, which has now been in use for some years in the Cavendish Laboratory, for the measurement of local elemental mass fractions in thin biological specimens in instruments like the EMMA. After an outline of the physical theory we shall describe the handling of the data by means of working through an example of an actual measurement, and finally we shall add some comments, mainly precautions and reservations.
The application of analytical electron microscopy to the study of diseased biological tissue
Authors: Henderson W. J. , Chandler J. A. , Blundell G. , Griffiths C. , Davies J. 
Published: August 2011

SUMMARYA routine method is described for X‐ray microanalysis of thin specimens of biological tissue containing mineral particles in cancerous growths. Such a method allows information to be obtained that relates pathological history to histology, electron microscopy and X‐ray microanalysis.Classification of minerals is possible in a way that is not provided by bulk analysis.The technique provides baselines of elemental data of minerals from various sources that may be used to classify particles found present in certain tumour growths.
The quantitative morphology of anisotropic trabecular bone
Authors: Whitehouse W. J. 
Published: August 2011

SUMMARYDimensional measurements have been made on a small number of tracings of low magnification scanning electron micrographs of trabecular bone sections, using the Quantimet Image Analysing Computer, with a view to expressing the properties of the local bone pattern in a quantitative manner.Measurements of the orthogonally projected length of the boundary profile of the interface between bone and marrow were made as a function of the direction of projection, and these showed that the majority of the patterns were distinctly anisotropic.A formula is proposed for calculating the mean widths of the trabecular bands as they appear on the surfaces of the sections, from the mean area of bone and the boundary profile length. As the validity of this formula is not theoretically evident, the results have been compared with direct experimental measurements, and found to agree very well.The mean intercept lengths in the bone and in the marrow spaces have been calculated as a function of direction across the section. The polar diagrams of these lengths are found to have the shapes of ellipses, to an unexpected degree of accuracy. This makes it possible to express the departure from isotropy of the pattern by a single number, for instance by the ratio of the axes of the ellipse.The essential limitations of the methods used in these experiments are briefly discussed, in particular the impossibility of finding the exact symmetry properties of the surface patterns by experiments of this type.
A stereological method for calculating internal surface areas in structures which have become anisotropic as the result of linear expansions or contractions
Authors: Whitehouse W. J. 
Published: August 2011

SUMMARYIt is postulated that there may be classes of microstructures, having anisotropic internal features, which are related to internally isotropic structures by a coordinate transformation. Such structures are known to occur, for instance, in metallography when the bulk material has been subjected to deformation and there are many biological analogies.The simplest case of coordinate transformation is investigated theoretically in this paper; that of a linear transformation in one dimension. Formulae have been found for the numerical constant which allows the density of the internal surface which separates two components of the material to be calculated from the border profile density on a plane section through the material.Measurements on trabecular bone have suggested that it may be a structure of this type, and, on this assumption, the errors due to incorrectly assuming isotropy, when calculating the area of the surface which separates the bone from the marrow, are discussed.
A simple fracturing device for obtaining complementary replicas of freeze‐fractured and freeze‐etched suspensions and tissue fragments
Authors: Sleytr Uwe B. , Umrath Walter 
Published: August 2011

SUMMARYTechniques for obtaining complementary replicas have already been shown to be valuable in aiding the interpretation of electron micrographs of replicas of specimens prepared by freeze‐etching and freeze‐fracturing techniques, and in the recognition of artefacts. This paper describes a simple and efficient method of obtaining complementary pairs of replicas of all types of specimen. Ordinary hollow brass rivets are used as specimen holders and are frozen in an end‐to‐end position using a special pair of forceps. Up to six rivets are placed in a device consisting of a hinged plate held together with clamps against the force of small springs. When the clamps are released, the pair of rivets are separated, fracturing the specimens. The device is easily adapted for use in any type of freeze‐etching or high vacuum apparatus. On the example of Saccharomyces cerevisiae the application of the technique to the detection of artefacts in complementary replicas are described. It was shown that the fibrils observed on cross‐fractured cell walls are produced by plastic deformation of cell wall components.
A simple device for obtaining complementary fracture planes at liquid helium temperature in the freeze‐etching technique
Authors: Sleytr Uwe B. , Umrath Walter 
Published: August 2011

SUMMARYThis paper describes a simple technique for obtaining complementary replicas of specimens fractured under liquid helium. Ordinary hollow brass rivets are used as specimen holders and are frozen in an end‐to‐end position. The pairs of rivets are placed in a device consisting basically of two concentric steel tubes which can be twisted and moved relative to each other guided by a peg‐in‐slot mechanism. The rivets are inserted while the device is under liquid nitrogen, and the device is then transferred to liquid helium and the tubes are moved so that the upper rivet is knocked away and falls into a collector. The device is then transferred back to liquid nitrogen, the fracture faces being protected from contamination throughout the process. Replicas are then obtained by any of the standard methods for specimens fractured under liquid nitrogen. The device has been tested using yeast cells as a model system, and some typical results are presented and discussed.
The interpretation of freeze‐etch replicas from plant cell walls
Authors: Parish G. R. 
Published: August 2011

SUMMARYIf a freeze‐etch replica is not completely clean, some problems may arise concerned with interpretation. These can be particularly misleading in the case of freeze‐etched cellulose microfibrils. The interpretation of such replicas is discussed, and the method of image formation from a clean replica is demonstrated.
An illumination system for specimen block knife alignment with the LKB ultrotome ultramicrotome
Authors: Wyatt John H. 
Published: August 2011

SUMMARYThe principle of using reflected light to align knife to specimen block proposed by Gorycki (1965) is applied to the LKB ultrotome. A small mirror mounted on the knife holder base at an angle of 5° reflects light from the fluorescent lamp on to the front of the knife from where it is reflected on to the block face. The width of this band of reflected light at the bottom edge of the block is reduced as the knife approaches the block. At the point at which it is no longer visible the block is 2–3 μm from the knife. When the knife is parallel with the block in the cutting plane the line of reflection is parallel with the knife edge. Using reflected light facilitates alignment between block and knife and makes closing the gap prior to the initial cut a simple and certain operation.
A simple method of preparing 1–2 μm sections of large tissue blocks using glycol methacrylate
Authors: Sims B. 
Published: August 2011

SUMMARYThe method described allows the production of 1–2 μm sections of large tissue blocks. Sections can be obtained from conventional routine histological microtomes. The hydroxyethyl methacrylate is compatible with a wide range of fixatives and a variety of standard histological staining techniques may be applied. Small biopsies, e.g. renal, liver, jejunal etc., can be processed cut and stained within 24 h of receipt. Blocks and stained sections show no apparent deterioration over the 4 years in which the technique has been employed in this laboratory.
High voltage electron microscopy of wet whole cells
Authors: Parsons D. F. , Uydess I. , Matricardi V. R. 
Published: August 2011

SUMMARYFactors affecting the visibility of cell cytoplasmic structures and cell surface projections have been evaluated for examination of whole wet, unstained and unfixed cell preparations in the hydration chamber of a high voltage microscope.It was found that the thickness of the cells and that of the surrounding water layer were the most important factors affecting contrast and resolution of structures. One technique (surface spreading) flattened nuclei enough to see internal nuclear structure. Some washing and fixing (glutaraldehyde) methods caused regions of the grid of cultured cells to become hydrophobic with consequent improvement in contrast and resolution in these areas. Optimization of these factors appears feasible.The effects of cell freshness, blurring due to cell structure, vibration and Brownian movement, electron radiation and heat damage, microscope image mode, and photographic emulsion resolution are also discussed.Cell movements (e.g. cytoplasmic streaming) have not been observed to date, the possible reasons being radiation damage, cell bursting at lowered pressure, oxygen lack and concentration of metabolites on the grid surface.
Rapid freezing and electron microscopy for the arrest of physiological processes
Authors: Van Harreveld A. , Trubatch Janett , Steiner Jana 
Published: August 2011

SUMMARYAn apparatus for the rapid freezing of tissue is described, which can be used for the electron microscopy of arrested physiological processes. The material is frozen by bringing it in contact with a silver surface cooled to liquid nitrogen temperature at reduced pressure. The freezing surface is protected from condensation of moisture and gases from the air by a flow of helium gas. The cooling of the specimen during its descent through the cold helium is not large enough to interfere with physiological processes. Freezing occurs very rapidly in the surface but is retarded to about 8 msec at a depth of 10 μm. The apparatus was used to freeze frog muscle during contraction.
Current developments in high voltage electron microscopy
Authors: Cosslett V. E. 
Published: August 2011

SUMMARYIn respect of instrument design two main developments are taking place in high voltage electron microscopy: towards even higher operating voltages (3–5 MV) and towards higher resolving power at moderate voltages (250–600 kV). Applications of existing instruments (650 kV‐1.2 MV) are still primarily in metallurgy, especially for radiation damage studies, but their usefulness for biological research is now being actively explored. Microchambers have been developed for observing specimens, both metallurgical and biological, in a controlled gaseous or liquid environment. The prospects for observing living material, except at low magnifications, remain very doubtful on account of ionization effects, but informative work with wet specimens should be possible.
Scanning transmission electron microscopy*
Authors: Crewe Albert V. 
Published: August 2011

SUMMARYThe scanning transmission electron microscope is of quite recent origin, and it is only in the last few years that it has been shown that this instrument is capable of giving the same high resolution as the conventional electron microscope. In this article we examine the conditions necessary for the achievement of high resolution and also the various modes of contrast which can be obtained from this instrument. Finally, we suggest other ways in which the microscope can be used in future investigations.
Effect of fixatives on fracture plane in red blood cells
Authors: Nermut M. V. , WARD Barbara J. 
Published: August 2011

SUMMARYThe effect of various fixatives on the path of the fracture plane during freeze‐fracturing was studied in red blood cells. In unfixed cells the fracture plane ran between the leaflets of the plasma membrane (membrane‐fractured cells) in 66% of the cells and across the cells (cross‐fractured cells) in 34%. Formaldehyde fixation greatly increased the proportion of cross‐fractured cells (up to 80%) and osmium tetroxide acted in a similar manner (up to 90% cross‐fractured cells). With glutaraldehyde fixation, small, smooth patches of cross‐linked material were often seen on the convex (A) fracture faces. Holes were found on the corresponding concave (B) fracture faces. Uranyl acetate had no effect on the fracture plane or distribution of particles. Thus osmium and formaldehyde might be a useful means of altering the fracture plane of membranes (e.g. in bacteria or enveloped viruses).
A simple video method for the quantification of microscopic objects
Authors: Dvorak James A. , Schuette William H. , White‐House Willard C. 
Published: August 2011

SUMMARYThe design and operation of a simple, semi‐automatic video system for the analysis of geometric parameters of microscopic specimens is described. The system consists of standard video equipment and a custom built Electronic Integrator. The video signal from a camera attached to a microscope is mixed with the video signal from a second camera focused on a drawing board. A contour outline of the specimen to be analysed is drawn with the aid of a video monitor display of the combined images. The contour image is passed into the Electronic Integrator and analysed automatically. Logic circuitry in the Electronic Integrator permits analysis of complex contours independent of their orientation in the video raster. The area or volume of complex, overlapping specimens with restricted grey scale range can be rapidly analysed. The Electronic Integrator also is suitable for densitometric and specimen motion analyses.
An experimental study of coincidence grain boundary structure using displacement fringes
Authors: Pond R. C. , Smith D. A. , Clark W. A. T. 
Published: August 2011

SUMMARYThis paper describes how a transmission electron microscope may be used to study rigid body displacements between coincidence related grains. Computer calculations have predicted that such displacements reduce grain boundary internal energy in metals by relieving atomic over‐crowding. Displacements are revealed as fringe patterns by a Bloch wave interference mechanism resembling that which gives rise to stacking fault fringes. The sensitivity of the technique in detecting very small displacements and its potential applications are discussed.
Techniques for the observation of grain boundaries in an austenitic stainless steel
Authors: Howell P. R. , Jones A. R. , Ralph B. 
Published: August 2011

SUMMARYThis paper discusses methods of analysing grain boundary structure in a commercial alloy system using transmission electron microscopy of thin foils. The results illustrate how the fine scale structure of grain boundaries may be analysed by employing weak beam imaging techniques and grain boundary diffraction effects.
The annealing of dislocations in high angle grain boundaries and structural models
Authors: Pumphrey P. H. , Gleiter H. 
Published: August 2011

SUMMARYHot stage electron microscopy is used to study the annealing behaviour of lattice dislocations in high angle grain boundaries in nickel. The observations show that most boundaries can incorporate dislocations by increasing their core widths or splitting into partials with small Burgers vectors. The implications for models of grain boundary structure are discussed.
An observation of periodicity in grain boundaries
Authors: Bolin P. L. , Bayuzick R. J. , Ranganathan B. N. 
Published: August 2011

SUMMARYField ion microscopy and computer graphics techniques have been utilized in studying the topography of a grain boundary in a W‐1wt%ThO2 specimen. Perspective plots and Stereographic Pole Plots of the surface were obtained. An examination of the perspective plots of the boundary surface in conjunction with the Stereographic Pole Plot reveals a strong tendency towards periodicity in the grain boundary. Although no definite wavelength is noticed, an overall tendency towards periodicity is evident. Further the Stereographic Pole Plot indicates the nature of the inclinations in the grain boundary surface.
The topographical structure of grain boundaries in tungsten
Authors: Howell P. R. , Ralph B. 
Published: August 2011

SUMMARYThis paper discusses the observation of a variety of topographical defects in grain boundaries in tungsten as a function of thermomechanical treatment. It is shown that, for both cold worked and crept specimen material, the boundary topography is highly complex, whereas for secondary recrystallized specimen materials the boundaries approximate to that expected for an ‘equilibrium’ configuration. However, no evidence for any period step structure was observed in this specimen material although, in this and all specimen states, grain boundary dislocations were frequently observed.
The quantitative analysis of thin specimens
Authors: Cliff G. , Lorimer G. W. 
Published: August 2011

SUMMARYResults are reported concerning the use of an energy dispersive X‐ray detector to carry out the analysis of thin foils in the electron microscope. The combination of a thin specimen and the extreme stability of the energy dispersive X‐ray detector enables the experimental determination of a calibration curve of X‐ray production—detection efficiency vs characteristic X‐ray energy. Quantitative analysis can be carried out using the calibration curve without reference to standards at the time of analysis.
Radiation damage in stained catalase at low temperature
Authors: Glaeser Robert M. , Hobbs Linn W. 
Published: August 2011

SUMMARYRadiation damage, which occurs in the beam of the electron microscope, has been studied in uranyl acetate stained catalase crystals. Damage is observed in terms of the disappearance of higher orders of the electron diffraction pattern. In this study it has been found that the damage at very low specimen temperatures proceeds both more rapidly and to a greater final degree than is the case at room temperature.
Freeze‐fracturing and freeze‐etching of cardiac myosin filaments
Authors: Rayns David G. 
Published: August 2011

SUMMARYMyofilament structure was studied in freeze‐etch replicas of unfixed, glycerinated beef cardiac muscle. The information which is revealed depends upon the direction of metal shadowing in relation to the filament axis. Shadows oblique to this axis reveal that the outer surface of a longitudinal half of a thick filament comprises three, sometimes four, rows of myosin molecules. These molecules are generally assembled in a braided manner with both left and right‐handed helical components. Occasionally a more parallel arrangement is seen; this may represent a split filament. Shadows parallel to the myofilament axis reveal cross‐bridges linking thick and thin filaments. These bridges are readily detectable by optical diffraction techniques, giving an axial bridge spacing of approximately 40 nm. In unetched preparations cross bridges appear as vertical rows of beads. In all replicas the effects of plastic deformation of proteins must be considered.
X‐ray microradiography in the scanning electron microscope or microanalyser
Authors: Pugh D. J. , West P. D. 
Published: August 2011

SUMMARYA technique is described which enables microradiographic examination to be carried out in a scanning electron microscope (SEM) or X‐ray microanalyser. Comparison can readily be made between the radiographic image, a conventional scanning electron image or X‐ray image. A wide range of materials have been examined in a Cambridge Scientific Instruments Microanalyser Mark 1 and a Stereoscan S1 scanning electron microscope and a resolution of 1 μm has been consistently achieved.
A technique for processing mucous coated marine invertebrate spermatozoa for scanning electron microscopy
Authors: Atwood D. G. , Crawford B. J. , Braybrook G. D. 
Published: August 2011

SUMMARYA technique for preparing heavily mucous coated marine invertebrate spermatozoa for scanning electron microscopy (SEM) is described. This technique involves washing in 1500 NF units/ml hyaluronidase in millipored sea water to remove mucus, followed by fixation in glutaraldehyde and osmium tetroxide. Following primary fixation, spermatozoa are enclosed in Nuclepore membrane bags positioned within Teflon specimen capsules allowing them to be processed and critical point dried without excessive mechanical damage or loss.
The pore arrangement in the emu (Dromaius novæhollandiæ) eggshell as shown by plastic models
Authors: Board R. G. , Tullett S. G. 
Published: August 2011

SUMMARYPores arising in the cone layer merge with a plexus of tubules running just under and parallel to the outer surface of the emu eggshell. The outer surface of the shell is irregular due to dark green crystalline material arranged as flat domes. The plexus of tubules vent to the ambient environment via short pores opening in the valleys between these domes.
A technique for preparing human dermal and scar specimens for scanning electron microscopy
Authors: Sommerlad B. C. , Creasey J. M. 
Published: August 2011

SUMMARYThe aims in a current study of dermis and scar tissue using the scanning electron microscope are:

to maintain the orientation of the specimen
to preserve the in vivo architecture, and
to expose a satisfactory surface.

A technique which best fulfils these requirements involves glutaraldehyde fixation of a splinted specimen, freeze‐fracturing using a modified pair of pliers, freeze‐drying, incubation in a buffered saline solution of hyaluronidase and freeze‐drying again after washing.Consistently satisfactory specimens have been obtained, which provide information about fibre architecture and cell distribution.