bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stereo‐scanning electron microscopy of desmids
Authors: Pickett‐Heaps Jeremy D. 
Published: August 2011

SUMMARYStereo‐pairs of scanning electron micrographs are presented of two species of Staurastrum, one species of Cosmarium and two species of Micrasterias, including the triradiate, diploid variant of M. thomasiana. Techniques for processing these cells are discussed and some typical morphological variations encountered in cultures are illustrated; the methods are reasonably quick and reliable and may prove useful in taxonomic studies of desmids.
Wetting agents for biological electron microscopy
Authors: Gregory D. W. , Pirie B. J. S. 
Published: August 2011

SUMMARYThe most frequently used method of enabling aqueous suspensions of small, particulate, biological specimens to spread on the hydrophobic support films required for electron microscopy, is to add a surface‐active compound to the suspensions. The requirements of an ideal wetting agent for use in this situation are outlined. The polypeptide bacitracin has been found to meet all these requirements, and it is superior to the commonly‐used bovine serum albumin (BSA) in several respects. Bacitracin molecules are much smaller than those of BSA, and unlike BSA molecules they are not visualized by negative staining. Thus bacitracin produces a very even background against which the fine details of a specimen can be more easily interpreted. It facilitates the penetration of negative stain into small crevices and it produces a smaller halo of negative stain around specimen particles. Its use for spreading electron dense specimens is also demonstrated. Bacitracin is compatible with at least five commonly‐used negative stains, namely ammonium molybdate, potassium phosphotungstate (KPT), potassium silicotungstate, sodium tungstate and uranyl acetate. It is also biologically acceptable for use with a wide range of specimens. There is no evidence of bacitracin causing damage to specimens examined representing macromolecules, animal, plant and bacterial viruses, bacteria and subcellular organelles.
A computer system for the measurement of cell and nuclear sizes*
Authors: Cowan W. M. , Wann F. 
Published: August 2011

SUMMARYA semi‐automated system has been developed for the measurement of cell (perikaryal), nuclear and nucleolar areas. The system consists essentially of a Graf/Pen data tablet (with its associated acoustical stylus and tablet electronics), an optical input system such as a camera lucida, and a small digital computer. The perikaryal, nuclear and nucleolar outlines are traced in sequence with the stylus which, on contacting the tablet surface, emits a high frequency acoustic wave that is sensed by X and Y strip microphones along the left and upper edges of the tablet. The acoustic signal is converted by a simple program into a series of X and Y coordinates which are sampled at several points around the perimeter of the profile. When the stylus tip re‐enters a 1 mm stationary window set up around the starting point, the measurement is automatically terminated and the data for this profile is printed out and stored in memory for subsequent statistical analysis. The system has an overall accuracy of about 1% and in practice it has been possible to measure objects at least ten times more rapidly than by any of the other currently available methods. The hardware and software features of the system are detailed and a number of additional uses for the system are described.
A practical device for processing Polaroid 55 P/N film used with scanning electron microscopes
Authors: Thurston E. Laurence , Scott James R. , McKee Thomas R. 
Published: August 2011

SUMMARYA device to improve the awkward handling and processing of Polaroid type 55 P/N film used with scanning electron microscopes can be constructed from Plexiglass and 1, 2 dichloroethane.
The application of cryo‐ultramicrotomy in the study of the fine structure of myofilaments
Authors: Sjöström M. , Thornell L. E. , Cedergren E. 
Published: August 2011

SUMMARYThe possibility of using sections obtained by cryo‐ultramicrotomy in the study of the fine structure of myofilaments was explored. Heart and skeletal muscles were stabilized for 5–15 min in 2.5% glutaraldehyde. Neither cryo‐protection, encapsulation nor any other chemical treatment preceded the freezing in Freon‐12 cooled by liquid nitrogen. ‘Wet’ sectioning was performed using dimethyl sulphoxide (50% in water) in the knife trough. The sections were stained using either positive or negative contrasting techniques.The results showed that sections prepared by cryo‐ultramicrotomy permit high resolution studies, especially if negatively stained. By eliminating several steps of specimen preparation that destroy the native configuration of biopolymers, the method promises to make it possible to study well‐preserved myofilaments and their fine structure, both in longitudinal and cross‐section, in situ. It is not yet certain, however, that new sources of artefacts are not introduced.
A preliminary field‐ion atom‐probe investigation of competitive carbide formation in ferritic steels
Authors: Youle A. , Turner P. J. , Ralph B. 
Published: August 2011

SUMMARYA combined field‐ion microscope and field‐ion atom‐probe study has been made of the early stages of precipitation in an Fe—V—Mo—C alloy. Crystallo‐graphic analysis showed that precipitates based on both molybdenum and vanadium carbide structures were present. Atom probe analysis showed that individual carbides ∼15 nm in size contained both molybdenum and vanadium, while for smaller sizes a considerable amount of iron was present in the precipitates.
Morphometrics of living specimens. A methodology for the quantitative three‐dimensional study of growing microscopic embryos
Authors: Prothero John W. , Tamarin Arnold , Pickering Ruth 
Published: August 2011

SUMMARYA methodology is described which permits quantitative three‐dimensional studies of growing microscopic (and substantially transparent) animals to be made. The methodology has been applied in a limited way to the study of blastula formation in sand dollar embryos. A preliminary analysis has been made of the errors likely to arise (see Appendix).It was observed that the total blastomeric (cellular) volume decreased somewhat at the time of the second cleavage, and that the volume of the blastocoel simultaneously increased by about the same amount. It is suggested on the basis of this and other evidence that the blastocoel material is initially secreted by the blastomeres and that the blastocoel may subsequently innate, perhaps as a result of the imbibition of fluid from the extrablastular space. Further study will be required to confirm or invalidate this hypothesis.A study of plexiglas reconstructions suggests that formation of the blastular epithelium is the result of a coordinated pattern of cell cleavages and cell displacements. It is suggested that cell displacements may be the result of localized intracellular constrictions and/or changes in surface adhesion. Further study will also be required to confirm or invalidate this hypothesis.The methodology described in this paper is considered to be complementary to one previously described by Hou, Veress & Prothero (1970) for application to similar problems at the macroscopic level of resolution.
A comparative survey of techniques for preparing plant surfaces for the scanning electron microscope
Authors: Parsons Elizabeth , Bole Barbara , Hall D. J. , Thomas W. D. E. 
Published: August 2011

SUMMARYA comparative investigation of techniques for the preparation of soft botanical tissue for the scanning electron microscope has been carried out using the leaves and petals of Pelargonium zonale as test specimens. Twelve different preparative procedures involving combinations of fixation, dehydration, air drying, freeze drying, critical point drying, coating methods, replicas and a temperature controlled specimen stage were tested.
Preparation of tough, fibrous material for examination in the scanning electron microscope
Authors: Barlow John R. 
Published: August 2011

SUMMARYA simple method has been devised which minimizes distortion of fibrous material during the cutting needed for examination of cross‐sections in the SEM. Camphene, suggested for use in ‘freeze‐drying’ at room temperature (Watters & Buck, 1971) is used as an embedding material with a surrounding layer of ice for reinforcement and sectioning can then be carried out. The technique has been successfully applied to hides and skins in several stages of processing to leather, i.e. in both wet and dry initial states.
Suppression of lattice periods in vermiculite single crystal specimen supports for high resolution electron microscopy*
Authors: Baumeister W. , Hahn M. H. 
Published: August 2011

SUMMARYEasy preparation of thin crystalline specimen supports for high resolution electron microscopy has been achieved by thermic exfoliation of vermiculite. The thinnest layers obtained appear to be 1·8 nm thick and show the expected hexagonal array with a 0·46 nm lattice spacing. This periodic background could be suppressed either by optical filtering or by putting a zero crossing of the respective transfer function of the electron microscope objective over the diffraction spots of the crystal.
A comparison of three different electron microscopical grade glutaraldehydes used to fix ovarian tissue
Authors: Weakley Brenda S. 
Published: August 2011

SUMMARY‘EM grade’ glutaraldehydes from three suppliers were tested for the following: (1) pH of stock solution, (2) 235/280 nm UV absorbance ratio, (3) milliosmolarity of 2% and 4% solutions, (4) quality of fixation produced in ovarian tissue by fixatives prepared from each stock solution. Low pH of the stock solution appeared to be the most detrimental factor in fixation. Fixatives with a low 235/280 nm ratio (between 0·18 and 0·67) did not give good fixation regardless of the pH of the stock solution. Fixatives made from stock solutions with a pH above 4 and a 235/280 nm ratio between 1 and 2 resulted in the best preservation of ultra‐structure. Variations in milliosmolarity from one batch of stock solution to another were encountered, but appeared to have no correlation with the quality of fixation.; Received 1 October 1973; revision received 20 December 1973
The use of X‐ray microanalysis to investigate problems encountered in enzyme cytochemistry*
Authors: Ryder T. A. , Bowen I. D. 
Published: August 2011

SUMMARYThe nature of the reaction product and non‐specific staining obtained using lead salt methods, for localizing phosphatase activities, has been determined using energy dispersive X‐ray microanalysis. The detectability of ‘non‐electron dense’ elements has permitted the development of an alternative azo dye method involving the coupling of an enzymatically released, insoluble primary reaction product with the active diazotate of 2, 5‐dichloroaniline (Fast Scarlet GG). The resultant azo dye was detected in ultrathin cryosections. The localization achieved by this method and the advantages of combining ultracryotomy and X‐ray microanalysis with enzyme cytochemistry is discussed.
Microscopical communication
Authors: Turner G. L'E. 
Published: August 2011

SummaryMicroscopy poses special problems of communication because it reveals completely unfamiliar images to the eye. During the eighteenth century, scientific societies, private letters and the sale of standard specimens satisfied the largely amateur interest in microscopy. The need to illustrate texts came rather later than might be expected, however, because the development of the optics of the instrument was very slow between its invention in about 1600 and the discoveries of J. J. Lister in the 1830s. In the second half of the nineteenth century the microscope increased in scientific importance, creating a need for rapid and efficient means of communicating results, to which photography and new printing techniques were essential. This development is illustrated with special reference to the publications of the Royal Microscopical Society.
Ultrastructure research in biology before the introduction of the electron microscope
Authors: Frey‐Wyssling A. 
Published: August 2011

SummaryBefore the introduction of the electron microscope for cytological research around 1940, indirect methods were used for disclosing sublight‐microscopic structures. The results obtained by macromolecular chemistry were combined with those from investigations made with polarized light and by X‐ray diffraction. The application of Wiener's theory of composite bodies proved the presence of rodlet and lamellar ultrastructures, and the X‐ray analysis gave information on the crystallinity and the size of the components of such structures.Both methods are based upon regular periodicities in the object investigated, so that their application is limited. Nevertheless, most of the conclusions concerning ultrastructural morphology gained with these techniques were corroborated when direct images of the relevant ultrastructures could be produced by electron microscopy.
A cryostat approach to ultrathin ‘dry’ frozen sections for electron microscopy: a morphological and X‐ray analytical study
Authors: Appleton T. C. 
Published: August 2011

SummaryConventional preparative procedures for the examination of tissues in the electron microscope involve the use of fixatives, dehydration in alcohol or acetone, embedding in plastics and staining. Such procedures remove soluble components and are therefore often unsuitable for chemical analysis of naturally occurring electrolytes. Ultrathin frozen sections of unfixed, unembedded biological tissue can be cut onto dry glass knives, freeze‐dried and viewed in the electron microscope without staining. Morphological detail is sufficient to identify cell types and ultrastructure. X‐ray microanalysis in the analytical electron microscope (EMMA‐4) has shown that highly soluble electrolytes can be detected and that intracellular compartments are retained.
Measurement of the top bottom effect in scanning transmission electron microscopy of thick amorphous specimens
Authors: Gentsch P. , Gilde H. , Reimer L. 
Published: August 2011

SummaryIn Scanning Transmission Electron Microscopy (STEM) details at the top of thick specimens can be imaged with a better resolution than those at the bottom, because the scanning electron probe is broadened by multiple scattering. For quantitative measurement we used a test specimen consisting of a substrate film with an island‐structured indium film and coated with polystyrene spheres of different diameters up to 1.1 μm. The fine detail contained in the indium film was observed and the beam broadening was that caused by the polystyrene spheres. This specimen was imaged with the spheres both above and below the layer, in a JEOL 100B electron microscope with a scanning device. Electron energies from 20 to 100 keV were used. Images with the sphere below show a higher resolution than those with the sphere above and also those of conventional electron microscopical images at 100 kV and 200 kV. The broadening of the edges on the photographic film was recorded with a microdensitometer. The results can be compared with theoretical calculations by a Monte Carlo method. There is a good agreement with the experiments if one uses an effective aperture obtained by transmission experiments.
A precise stage arrangement for correlative microscopy for specimens mounted on glass slides, stubs or EM grids
Authors: Geissinger H. D. 
Published: August 2011

SummaryThe instrumentation necessary for precise and fast correlation of images derived from a light optical microscope (LM) and a scanning electron microscope (SEM) operated in the reflective mode, is described. The specimens can be mounted on standard microscope slides (25 × 75 mm), SEM‐stubs (12 mm ø), or on transmission EM grids (3 mm ø). The instrumentation consists of two parts: an attachable precision stage for an LM, and an attachable slide carrier for the stage of an SEM. By taking into account the vernier readings of the stages of both microscopes (LM and SEM), identical particles in a specimen can be found instantaneously under either microscope. Therefore it is concluded that the use of this instrumentation in correlative microscopy (LM → SEM → LM) is time saving, and especially recommended on fragile biological specimens, which may deteriorate rapidly under the electron beam of an SEM.
Advances in atom‐probe field ion microscopy*
Authors: Müller Erwin W. 
Published: August 2011

SUMMARYThe ToF atom‐probe FIM is a microanalytical tool of ultimate sensitivity. Design and performance of the three presently operating instruments are described, including applications to metallurgical problems and contributions to basic effects in field ion microscopy. Up to four‐fold ionic charges of metals, field adsorption of noble gases, and the occurrence of metal‐helide ions have been surprising results. The mass resolution of present atom‐probes is marginal due to random ion energy deficits. A new energy deficit compensated atom‐probe offers a very satisfactory mass resolution of 1/1000.
A note on Aherne's method of counting tissue components in relatively thick sections
Authors: Freedman L. S. 
Published: August 2011

SUMMARYAherne's method of estimating the number of components NV per unit volume in relatively thick sections is briefly described. Next, formulae are given which lead to an unbiased estimate of NV when the components are identical spheres. This is done for the situations (i) where there is perfect contrast and (ii) where there is contrast deficiency. Aherne's approximation for small objects is compared to the unbiased estimates, to give an idea of its accuracy. The results are used as a guide to the accuracy of Aherne's approximation in more general situations. A summary of recommendations to the experimenter, as to when it is satisfactory to use Aherne's method, is given.
On the sub‐nanometre structure visible in high‐resolution dark‐field electron microscopy
Authors: Brakenhoff G. J. 
Published: August 2011

SUMMARYIn high‐resolution dark‐field microscopy thin carbon films present an appearance with many bright spots with sizes down to 0.3–0.5 nm which, by their presence, seriously interfere with the extraction of biological information. The nature of these spots has so far remained unexplained. It is shown that these spots are sharpest at an overfocus of about 275 nm with respect to the bright‐field focus condition. An explanation is presented here which accounts for both the focus difference and the otherwise inexplicable phenomenon of the small size of the spots. In the proposed model the bright spots are associated with small crystals present in the carbon film which give rise to Bragg reflection of electrons into the acceptance angle of the dark‐field geometry. Due to a constructive interference the Bragg‐reflected coherent electron wave fronts produce, behind the object, high‐intensity maxima with sizes equal to about × 1/5 the diameter of the scattering crystals. These maxima are now thought to produce the bright spots usually observed in dark‐field electron microscopy. The interference effect is illustrated with pictures of an optical analogue.
Quantitative analysis of mast cell structure
Authors: Helander Herbert F. , Bloom Gunnar D. 
Published: August 2011

SUMMARYFixed and embedded normal rat peritoneal mast cells were studied by light and electron microscopy, utilizing stereological methods to obtain quantitative data on their structure. The diameters of the mast cells and their nuclei averaged 10.9 and 5.8 μm respectively. The volume of the individual mast cell granule was estimated to 0.3 μm3. About 53% of the cytoplasmic volume was occupied by granules, and 2% by mitochondria. 11% of the cell volume was taken up by the nucleus. The average number of granules per cell was calculated to about 1020. Quantitative biochemical data on mast cells, extrapolated from the literature and applied to the calculated figures above, yield the following results with respect to mast granule contents‐heparin: 95 × 10−3 pg, histamine: 30 × 10−3 pg and 5‐hydroxytryptamine: 1.3 × 10−3 pg per mast cell granule.
High resolution in‐focus Lorentz electron microscopy
Authors: Podbrdský Josef 
Published: August 2011

SUMMARYThe Foucault in‐focus method for viewing magnetic domains in a conventional electron microscope has been modified. The main feature of our modification is to introduce an aperture below the intermediate lens and to use it for stopping out one part of the split central spot instead of the objective aperture. This arrangement substantially reduces the axial astigmatism due to the objective aperture and makes it possible to reach the point resolution 5–6 nm in both light and dark domains. The image resolution is limited by the small image magnification achieved using the three‐stage optical system of a Tesla BS 413 microscope.
Towards higher resolution in electron beam sensitive specimens of biological origin
Authors: Dobb M. G. , Murray R. 
Published: August 2011

SUMMARYThe resolution of structurally significant detail in electron micrographs of organic polymers is limited by damage to the specimen during electron irradiation. The factors affecting the kinetics of the degradation of characteristic high angle reflections in the electron diffraction patterns of Cellulose I and II have been studied in an attempt to determine quantitatively the conditions under which meaningful high resolution micrographs may be recorded.In Cellulose I it was established that the decay of the 002 reflection during irradiation (in the range 0.6‐6.0 Am−2) is independent of dose‐rate. Moreover the meridional 040 and equatorial 002 reflections were found to decay at different rates. This latter finding indicates the importance of selecting the appropriate conditions for imaging a particular structural repeat in a specimen. Perhaps the most significant conclusion arising from this work is that specimen cooling in conjunction with low‐beam densities may be used to considerable advantage in obtaining meaningful higher resolution images than hitherto possible in beam‐sensitive materials.
Reproducibility of electron microscope magnifications with digital display of individual lens currents
Authors: Dunn Robert F. , Preiss Guenther W. B. 
Published: August 2011

SUMMARYQuantitative measurements on electron micrographs with less than 10% error require precise calibration of all lenses contributing to the final image magnification. Calibration of the magnification to approximately 1.5% is easily attained by using simple statistical methods and a digital display milliampere meter capable of measuring the objective, intermediate and projector lens currents independently. The method detailed, readily adaptable to other electron microscopes, requires the projector lens current be held constant, with the magnification determined by varying the intermediate lens current and corrections made on the basis of calibrated objective lens current effect. The errors of magnification, approximately 1.5%, are the same range as the test grid variation which appears to be the limiting factor. Even with this limitation, magnifications have been determined reproducible to within less than 0.2% in daily use over a 6 month period.
A modified specimen stub for the scanning electron microscope
Authors: Peat C. J. 
Published: August 2011

SUMMARYThe standard ‘Stereoscan’ specimen stub has been modified to permit palynological acid‐maceration techniques to be performed under aseptic conditions. It is hoped that this adaptation will also be of use where contaminant‐free pure culture preparations are required, where delicate specimens are being treated, or where it is desirable to examine the precipitated products of chemical reactions.