bluuebunny/crossref_metadata_2025_split huggingface dataset:
A preparation method for observing intracellular structures by scanning electron microscopy
Authors: Tanaka Keiichi , Mitsushima Akira 
Published: August 2011

SUMMARYIn order to observe intracellular structures by scanning electron microscopy, excess cytoplasmic matrix must be removed from the fractured surface of cells. Previously we reported an Osmium‐DMSO‐Osmium method devised for this purpose. This method is very effective in revealing intracellular structures, but requires osmium tetroxide for initial fixation with some consequent disadvantages. In the present study, a revised Osmium‐DMSO‐Osmium method is reported, in which an aldehyde mixture is used as the initial fixative instead of osmium tetroxide. As fixation is carried out by perfusion in this revised method, better preservation of fine structures is achieved than by the original method, especially in the central nervous tissue which tends to suffer from post‐mortem degeneration. Moreover this method can be applied to cytochemical studies of intracellular structures with a scanning electron microscope (SEM). In this study, acid phosphatase of lysosomes is demonstrated in a coloured SEM micrograph.
A section press and low elemental support for enhanced preparation of freeze‐dried cryosections
Authors: Tvedt K. E. , Kopstad G. , Haugen O. A. 
Published: August 2011

SUMMARYA press‐ and specimen holder system is described, whereby thin, freeze‐dried cryosections can be obtained more conveniently and with greater protection against contamination and harmful temperature fluctuations. The use of a grid and retainer assembly as the basic working unit, greatly facilitates low temperature work particularly when delicate grids are preferable from an analytical point of view. A new press has been constructed in order to keep the sections permanently pressed during freeze‐drying and rewarming. The press also protects the sections during transfer to an external freeze‐dryer.
Methylamine tungstate and tannic acid in fixation for high contrast and preservation of fine structure: application to myxomycete plasmodia
Authors: Chestnut Matthew H. , Cohen Arthur L. 
Published: August 2011

SUMMARYThe effects of several fixation methods for electron microscopy were compared, using macro‐plasmodia of Badhamia utricularis (myxomycete) as test objects. A brief osmium tetroxide (Os) exposure followed by a mixture of glutaraldehyde (GA) and tannic acid (TA) with subsequent treatment with methylamine tungstate (MAT) overcame most commonly encountered difficulties in fixing these structures. Lead staining of the sections was necessary to bring out the range of densities inherent in the delicate detail of ground cytoplasm, membranes, and organelle structure retained by Os/GA‐TA/MAT. Microfilaments were well preserved with good contrast and little evidence of breakage. Although GA as the initial fixative gave good organelle preservation, Os pretreatment was required to prevent artefactual changes in plasmodial strand morphology. The several fixation procedures tested gave pronounced differences in mitochondrial appearance, in some cases giving a negative stained appearance to the cristae. Some advantages in interpretation may result from such reversed contrast. The high contrast and range of densities achieved following the Os/GA‐TA/MAT schedule permitted routine use of thin (silver‐grey) sections, thereby potentially increasing the resolution.
Automatic analysis of G‐banded human chromosomes by fast scanning microscope photometry. I. Basic principles and computer control
Authors: Wall W. J. , Butler L. J. 
Published: August 2011

SUMMARYA high resolution scanning microscope photometry system has been developed for use with standard G‐banded chromosome preparations. Various alternative scanning methods and their limitations are reviewed.The computer algorithms which we use are described for the manipulation of the digitized image as produced by the microscope photometer; these include noise reduction and contrast enhancement as well as altering the orientation of the chromosome.
Testing of detector strategies in scanning electron microscopy by isodensities
Authors: Lange M. , Reimer L. , Tollkamp C. 
Published: August 2011

SUMMARYThe dependence of the video signal of secondary electrons (SE) and backscattered electrons (BSE) on the local tilt angle φ and azimuth angle χ is important for the interpretation of micrographs and for comparing different detector strategies. The conventional Everhart‐Thornley detector (scintillator‐photomultiplier combination) has the disadvantage of collecting the SE with an efficiency which depends on too many geometric parameters of the specimen chamber.A more quantitative recording of SE and BSE can be realized by a multi‐detector system. For example, the signals A and B of two opposite detectors can be used to record the image with the difference signal A‐B or the sum signal A+B.Testing of these techniques requires a simple method of recording and comparing the dependence of the video signal on φ and χ for different detection modes and in different microscopes. This was tried by recording lines of equal video signal (isodensities) with a sphere as a test specimen.
A review of crystallographic calculational methods used in the RAD group of computer programs for analytical electron microscopy
Authors: Carr Martin J. , Chambers William F. 
Published: August 2011

SUMMARYRAD is a set of computer programs which has been developed to assist a microscopist who is doing electron diffraction analysis. The programs are designed to run on the computer which is normally supplied with a modern analytical electron microscope for X‐ray analysis. Matrix algebra methods are used to perform the crystallographic calculations; however, input and output are expressed in the familiar notational convention based on the Miller index system for directions and planes. Since all calculations are formulated for the most general crystal system (triclinic), they are applicable to all crystal types. Aspects of the Miller index system, vector analysis, and matrix algebra that pertain to the crystallographic calculations made by programs in the ‘RAD’ group are reviewed. Examples used to illustrate typical operations that can be easily accomplished by these methods include the calculation and plotting of stereographic projections and of electron diffraction patterns from single crystals, twinned crystals, and crystals containing oriented second phases.
Ultrastructural comparison of ion beam and radiofrequency plasma etching effects on biological tissue sections
Authors: Linton R. W. , Farmer M. E. , Ingram P. , Sommer J. R. , Shelburne J. D. 
Published: August 2011

SUMMARYThree dry etching techniques (Ar+ ion beam, O2+ ion beam, O2 radiofrequency electrodeless discharge) were compared with respect to preferential etching and damage to the ultrastructure of glutaraldehyde‐fixed Epon‐embedded frog skeletal muscle sections. SEM and TEM studies were performed on both unstained and stained (osmium tetroxide, uranyl acetate) sections. Etching effects were observed to differ for the various ion beam or plasma etching techniques. Whereas selective retention of electron dense structures (e.g. Z lines, nuclear heterochromatin) was observed for oxygen plasma etching, preferential etching of these components was observed using O2+ ion beam bombardment. Selectively etched Z lines and etch‐resistant nucleoli were observed for both reactive (O2+) and inert (Ar+) ion beam sputtering after sufficiently high ion doses. The above suggest that selective etching under keV ion beam irradiation is related more to physical sputtering processes (momentum transfer) than to the chemical reactivity of the incident ion. Heavy metal post‐fixation and staining had no qualitative effect on the nature of the selective etching phenomena. The above findings are significant in that they potentially influence both electron and ion microprobe measurements of etched biological specimens.
Beryllium coating for biological X‐ray microanalysis
Authors: Marshall A. T. , Carde D. 
Published: August 2011

SUMMARYBeryllium is ideal for coating biological specimens for light element X‐ray microanalysis at low temperature. It has higher electrical and thermal conductivity at 100 K and lower absorption of X‐rays of biological interest than carbon, aluminium or chromium. It produces no detectable characteristic X‐rays. When adequate precautions are taken beryllium is a valuable alternative to other coating materials. Because of its toxicity, however, it should not be used indiscriminately.
GRIDSS: an integrated suite of microcomputer programs for three‐dimensional graphical reconstruction from serial sections
Authors: Briarty L. G. , Jenkins P. H. 
Published: August 2011

SUMMARYA program for serial section reconstruction using computer graphics on a microcomputer is described, which uses freely available non‐specific hardware and software. Individual section data are input from a digitizer pad, and their reconstructed composite image can be displayed as if viewed from any direction.
Serial sectioning and digitization of porous media for two‐ and three‐dimensional analysis and reconstruction
Authors: Yanuka M. , Dullien F. A. L. , Elrick D. E. 
Published: August 2011

SUMMARYA procedure is proposed for serial sectioning of impregnated porous media, for photographing the sections under the microscope, and for digitizing the image using an IBM PC (XT) with a digitizing board.The result is a three‐dimensional matrix containing the enhanced digitized image in a binary form of O's and I's which represent solid and pore spaces respectively.The procedure was tested on three different porous materials: (1) a pack of glass beads, 170–350 μm; (2) Berca sandstone; and (3) Elora clay loam soil. Each of these was impregnated, forty‐six to eighty cross‐sections were prepared by close parallel polishing of 10–50 μm per section, and then the sections were photographed and digitized.Examples of the real and digitized cross‐sectioned samples are given as well as an example of reconstructed images in a plane perpendicular to the plane of sampling.It is proposed that the method of serial sectioning and automated digitization of porous media provides a powerful tool for further three‐dimensional geometrical and topological investigation of pore space to be used in models of fluid transport phenomena.
Influence of fixative osmolality on the morphometric determination of extracellular space in normal and reperfused ischaemic myocardium
Authors: Prickaerts J. P. , Wilson G. J. , Bayliss C. E. , Baffour R. 
Published: August 2011

SUMMARYMorphometric determination of extracellular space in control and post‐ischaemic reperfused rabbit myocardium was evaluated using two fixatives differing in their composition and total osmolality. Measurement of control extracellular space in an isotonic fixative (294 mOsm/kg water) was 20.8% and in a hypertonic fixative (1816 mOsm/kg water) was 22.2%. These values were not statistically different. Ischaemic durations of 15, 30, 60 and 90 min, followed by an equivalent period of reperfusion, created significant increases in extracellular space. The size of the extracellular space determined by both fixatives was found to be the same. Total fixative osmolality does not appear to influence morphometric evaluation of the extracellular space in control tissue or in tissue damaged by ischaemia and reperfusion.
Recent advances and applications of high resolution electron microscopy
Authors: Hutchison J. L. 
Published: August 2011

SUMMARYThis review covers several broad areas: firstly, recent developments in HREM instrumentation, and then novel techniques for imaging are discussed, including some of the problems of image interpretation. Applications of HREM techniques to a wide range of materials problems are described and include solid state chemistry, ceramics, semiconductors, metals and natural diamonds.The next generation of high resolution microscopes will operate in the 300–400 kV range, have low Cs objective lenses, and have sufficiently good vacuum to allow the combined use of CBED and EELS facilities with imaging in the sub‐2 Å range. Microprocessor control of instrumental parameters such as astigmatism, alignment and defocus are seen as an important way forward in achieving the optimum performance of these instruments.
Dynamical excitation of thermal diffuse scattering in crystals of rutile
Authors: Bursill L. A. , Rossouw C. J. 
Published: August 2011

SUMMARYObservations of thermal diffuse scattering (TDS) for the [001] projection of rutile are presented. New phenomena include: intense diffuse scattering directed inwards from {200} reflections, a sharply‐defined square of continuous intensity having {200} positions as vertices, relatively sharp <110> streaking along radial and non‐radial directions, and a distinct deficit scattering region surrounding the transmitted beam. Both the angular dependence of the TDS with respect to crystal tilts and the temperature variation of TDS in the range —180 <T < + 150°C are described.The observed features are interpreted using calculations of the site dependence, within the [001] projection of the rutile unit cell, of the electron current density and its strong dependence on crystal tilt. N‐beam dynamical interactions generate a sophisticated probe of the atomic sources of inelastic scattering within the unit cell, a detailed understanding of which is necessary also for further improvement of energy dispersive X‐ray and electron energy loss spectroscopic analysis.
The application of EDXS to the biological sciences
Authors: Hall T. A. , Gupta B. L. 
Published: August 2011

SUMMARYThe distribution of chemical elements in soft tissues may be faithfully preserved by very rapid freezing. Most often the material is then cryosectioned and the sections frozen‐dried prior to analysis, but direct analysis in the hydrated state is an established alternative.For bulk specimens, the shape of the analysed volume is uncertain. But whichever current model is accepted, analytical spatial resolution must generally be limited to the order of 1 μm. Such specimens can be suitable for the specific analysis of cytoplasm, cell nuclei and large extracellular spaces but not for study on a finer scale.Analytical spatial resolution in the range 200–500 nm is obtainable with sections cut ∼ 1 μm thick. In the frozen‐hydrated state, small extracellular spaces can be analysed but multiple scattering obscures intracellular detail in the STEM image. The irradiation required for an EDXS analysis, approximately 50 nanoCoulomb (50 nanoAmpere seconds), need not produce intolerable radiation damage when spread over an area 200 nm or more in diameter.Finer structure, for example mitochondria and regions of rough or smooth endoplasmic reticulum, can be identified and analysed in frozen‐dried cryosections cut ∼ 100 nm thick. Recently such features have been visualized in 100 nm frozen‐hydrated sections where the water is vitreous. This opens the prospect of analysing material where elemental distributions have been preserved on a very fine scale, since one might avoid even the ionic shifts from aqueous solution to supramolecular structures which must occur on freeze‐drying. But radiation damage may be prohibitive when an irradiation of 50 nanoCoulomb is concentrated into a hydrated area less than 200 nm in diameter.
On the use of ionization cross sections in analytical electron microscopy
Authors: Williams D. B. , Newbury D. E. , Goldstein J. I. , Fiori C. E. 
Published: August 2011

SUMMARYThere are two approaches to the utilization of the ionization cross section, Q, for use in the determination of kA B factors for quantitative microanalysis in the analytical electron microscope. The first approach is to interpolate a value of Q from experimentally determined kA B factors at a fixed accelerating voltage (kV). The second approach uses a theoretical parameterization of Q generated by fitting the fundamental Bethe expression to selected experimental values of Q over a wide range of kV. This paper discusses the relative merits of the two approaches.
Determination of UTW kXSi factors for seven elements from oxygen to iron
Authors: Cliff G. , Maher D. M. , Joy D. C. 
Published: August 2011

SUMMARYThis study reports k factors for an ultra‐thin window (UTW) Si(Li) energy dispersive (ED) X‐ray detector which extends the limit for X‐ray microanalysis in the analytical electron microscope (AEM) to elements below Na in the periodic table. The oxygen k factors reported for the UTW ED detector suggest that quantitative thin specimen X‐ray analysis can be extended to oxygen.
Correcting electron energy loss spectra for artefacts introduced by a serial data collection system
Authors: Craven A. J. , Buggy T. W. 
Published: August 2011

SUMMARYThe large range of signal intensities found in electron energy loss spectroscopy causes difficulty when trying to record the spectrum accurately. This paper describes a system which records the data serially as simultaneous pulse and analogue signals without the need for changing the gain of the photomultiplier tube during the scan. The effect of deadtime and dark current on the recorded signals is discussed and procedures for correcting the data for these effects are described. At the same time, it is possible to correct the data for stray signal in the spectrometer and non‐linearity in the photomultiplier head‐amplifier at high output signal levels. In addition to its use for electron energy loss spectroscopy, this system is ideal for recording other signals which have a wide dynamic range and change rapidly from point to point, e.g. energy filtered diffraction patterns from thin amorphous films.
Beam interactions, contrast and resolution in the SEM
Authors: Joy David C. 
Published: August 2011

SUMMARYBackscattered and secondary electrons are both used in the SEM for imaging purposes. The backscattered signal is the result of high angle elastic scattering events, while the secondary signal is the result of knock‐on inelastic collisions. The characteristic differences between images in the two modes arise from the details of the relevant interactions in the two cases. In order to examine this in a quantitative manner Monte Carlo electron trajectory simulation techniques have been used. Calculations of the ultimate resolution and depth of information of the secondary and backscattered images are presented, together with simulations of the edge brightness effect in high resolution secondary images and an analysis of the microanalytical application of atom number contrast in the backscattered mode.
A perimeter algorithm applied to lung pathology
Authors: Kemeny A. , Barres D. , Lafuma C. , Mignot J. , Robert A. M. 
Published: August 2011

SUMMARYA new image analyser, the NS 2000, explores the image using 256 photodiodes and, according to an adjustable threshold, converts it into a set of digital points of logical level 0 or 1. The method of fitting squares of increasing size consists of checking the presence of a square of a given size and of a given logical value throughout the image studied and gives the areas of successive erosions of the image. Using the parameters provided by the device one can obtain the total boundary BA per unit area for the phase studied, which is proportional to the number of squares having points of the two logical levels. Errors in length measurement as a function of orientation and for isotropic structures are compared to other automatic perimeter algorithms and to manual square grid measurement.Using the parameters provided by the device for the quantitative evaluation of lesions of elastase induced emphysema in hamster lungs, the values obtained for internal surface area (ISA) of alveoli, are lower by about 40% in elastase treated hamsters when compared to normal controls. This difference is highly significant (P < 0.001) and the results obtained by the described method are in good agreement with those obtained by the classical manual procedure. Efficiency, defined as the precision of the estimate per unit measurement time on a given set of sample units (pictures in this paper), is given for both NS 2000 and manual procedures. The results obtained show comparable values but the automatic procedure includes a statistical treatment and it is significantly faster on histological sections than on micrographs, which was not the case with the manual method.
Improved anticontaminator for cryo‐electron microscopy with a Philips EM 400
Authors: Homo Jean‐Claude , Booy Frank , Labouesse Patrick , Lepault Jean , Dubochet Jacques 
Published: August 2011

SUMMARYElectron microscopy of frozen‐hydrated specimens is frequently impaired by atmospheric humidity, introduced together with the cold specimen and subsequently condensing on it. This effect can be prevented in the Philips 400 electron microscope operating with the cold stage PW6591 by an improved anticontaminator described in this note. The retractable anticontaminator is formed by two adjustable liquid‐nitrogen cooled blades placed just above and below the specimen. It does not interfere with any other feature of the microscope.
On estimating freezing times during tissue rapid freezing
Authors: Jones G. J. 
Published: August 2011

SUMMARYFor the study of morphological changes that are associated with fast physiological processes, it is important to know the times at which the surface regions of specimens are frozen during rapid freezing. A simple physical model has been used to estimate the freezing times and the cooling rates at 10 μm depths in specimens. The calculations indicate that cooling rates in excess of 4 × 104 K s−1 are associated with freezing times of less than 0.5 ms. Using the same model, experimental measurements of freezing times at much larger depths have been extrapolated to a depth of 10 μm, the times obtained are 0.1‐0.6 ms for freezing by rapid immersion in cryogenic liquids, and 0.1 ms or less for freezing on a metal block. It is concluded that the delay time between contact with a cryogenic source and specimen freezing is less than 0.5 ms. The uncertainty in the time of freezing may be larger than this, because of an uncertainty of about ± 0.5 ms in determining the exact time of contact and, for freeze fracture studies, because of an uncertainty of up to 0.5 ms due to imprecision in the depth of fracture. At the same time it is estimated that the time during which freezing takes place may be as high as 250 μs, which can be taken as an upper limit for the resolution time for rapid freezing.
A simplified procedure for correction of errors in scanning stage absorbance photometry
Authors: de Vries Uwe , Schindler Joachim F. 
Published: August 2011

SUMMARYMeasurements with a scanning stage cytophotometer are subject to systematic errors. Residual distributional error, diffraction error and glare are due to physical limitations in measuring diaphragms and step width. These errors mainly depend on the ratio measuring stop/object size, mean local absorbance and shape of the measuring object. Small dense objects give rise to increasing inaccuracy. These errors were minimized by a set of easily handled equations, making use of the area and mean local absorbance only. These equations are easily incorporated in scanning programmes. The usefulness of this correction was demonstrated in Feulgen‐stained preparations.
A comparative study of softeners and catalyst systems upon dimensional changes and sectioning quality of glycol methacrylate sections
Authors: Gerrits P. O. , van Leeuwen M. B. M. 
Published: August 2011

SUMMARYIt is shown that softeners and temperature have an important influence upon the stretching parameters of glycol methacrylate sections. Also it is demonstrated that the catalyst system used may significantly interfere with section stretching.
The influence of tissue handling before fixation on the morphology of the chick blastoderm
Authors: Vanroelen Ch. , Vakaet L. 
Published: August 2011

SUMMARYThe morphology of cells and tissues of chick blastoderms handled before fixation in different ways, was compared. Blastoderms were fixed in ovo or after mounting on a glass ring (New, 1955). Differences in the morphology were observed.