bluuebunny/crossref_metadata_2025_split huggingface dataset:
Critical evaluation of histogram densitometry of Feulgen‐stained normal human lymphocyte nuclei
Authors: Boss J. M. N. , Mays R. G. W. 
Published: August 2011

SUMMARYBy means of a Vickers M85 microdensitometer, combined with a histogram unit, the distribution of the coloured product of the Feulgen reaction in single nuclei of human lymphocytes was examined by taking the fraction of each nucleus occupied by DNA at different concentrations. Tchacarof's index of homogeneity, derived from these fractions, was found to rise with the mean nuclear DNA concentration, and the calculated linear relation between the index and the concentration was found, in a preliminary experiment, to be independent of the degree of flattening of the nuclei. Further analysis, of the contribution of more and less densely packed areas to differences in mean intranuclear DNA concentration, showed that these differences depended on differences in both denser and less dense areas. The effects of hydrolysis on homogeneity were controlled by the use of Tchacarof's index. The procedure for using the Vickers M86 microdensitometer, with histogram unit, for analyses such as those reported here was developed to become established critically.
Some methods for more efficient processing of SEM specimens
Authors: Sweney L. R. , Laible N. J. , Shapiro B. L. 
Published: August 2011

SUMMARYThree techniques are described for increasing the quantity of specimens which may be processed for SEM while maintaining the quality of the final product. They are: a simple stainless steel holder for safe manipulation of coverslips during incubation and fixation; a coverslip carrier which permits four or more coverslips to be dehydrated and critically point dried at the same time; and a simple pattern for making baskets to hold relatively large but delicate specimens during processing for SEM.Processing soft tissues for scanning electron microscopy (SEM) presents many problems depending on the size, shape and type of specimen. Cohen (1974) presented an overall view of this problem. Methods for handling cells in suspension have been suggested by Baker & Princen (1975), Newell & Roath (1975) and Rostgaard & Christensen (1975). Tissue culture specimens are also difficult to process for SEM. These may be long‐term cultures such as fibroblasts or kidney cells, or short‐term preparations such as the collecting of white blood cells or bacteria on coverslips. Nemanic (1972) described a method using Tygon tubing with slits to hold the coverslips after incubation. Perecko et al. (1973) gave details of a holder for processing six small (6 mm) coverslips after incubation. Rice et al. (1976) designed several complex multipurpose carriers for 9 × 22 mm coverslips and for cells on silver or cellulose membrane filters. Broers et al. (1975) used a mesh receptacle for bacteria attached to silicon dioxide slivers. Many investigators simply process pieces of plastic cut from the tissue culture dish itself. Using the plastic directly avoids the problems of incubating cells on glass coverslips. Coverslips are fragile and difficult to remove from the culture dish or flask. Each coverslip must be processed individually, increasing the risk of breakage and limiting the number which can be done at one time. For processing larger tissues there are commercial baskets available. Cohen (1974) illustrated mesh baskets for odd sizes and shapes of soft tissues.We have devised a simple holder which facilitates the use of 12 mm 0 grade coverslips in several types of culture dishes. We have developed a multipurpose carrier which increases the number of coverslips which can be processed for SEM and reduces the number of manipulations needed for each individual coverslip. This carrier can be used for histological and histochemical studies as well as SEM processing. We have modified Cohen's technique (1974) for mesh baskets for larger soft tissue specimens.
The application of optical microscopy to studies of dust filtration
Authors: Rothwell E. , Bickham D. R. 
Published: August 2011

SUMMARYNeedle‐felted fabrics which are used in modern continuously operated dust filter units comprise a loose assembly of synthetic fibres interlocked in the manufacturing process by the action of needle barbs, which pull tufts of fibres through the depth of the fabric; the high porosity of the fabrics and their lack of rigidity prevents their sectioning by conventional microtome techniques. Specimens for incident and transmitted light microscopy are prepared after vacuum impregnating with an embedding resin using modified metallographic preparation techniques. The advantages and limitations of these techniques in revealing details of the structure of needle‐felted fabrics are discussed and illustrated with typical photomicrographs.
A method of embedding tissue culture preparations in situ for transmission electron microscopy
Authors: Codling B. W. , Mitchell J. C. 
Published: August 2011

SUMMARYA method for embedding tissue culture preparations, grown on Millipore filters, in Araldite is described. Accurate light microscopic localization of areas suitable for ultrathin sectioning is possible. The plane of sectioning relative to the Millipore filter can be varied to suit individual experimental needs.
Suppression of background on stripping‐film autoradiographs: A review
Authors: Stevens G. W. W. 
Published: August 2011

SUMMARYSuppression of background in autoradiographic materials can be influenced by control in manufacture, transport and storage, and user handling. Fogging by radiation during transport and storage is a definite risk, but for some materials can be combated by latent‐image fading during storage before transfer to the specimen. Leaching out of emulsion constituents during transfer enhances the risk of background growth, and can be counteracted by transferring from a suitable solution. Background growth is positively promoted by chemographic agents derived from wood and other materials. The transfer solution helps to block chemographic action, as does storage of the transferred emulsion at a low temperature or in a non‐porous and photographically inert container.
Analysis of electron microscope autoradiographs using the hypothetical grain analysis method
Authors: Parry D. M. , Blackett N. M. 
Published: August 2011

SUMMARYCross‐fire between adjacent labelled sources can often introduce problems in the analysis of electron microscope autoradiographs. A general method is described which makes allowance for this cross‐fire and is then applied to the analysis of autoradiographs of 3H‐proline in the accessory olfactory bulb of the mouse.It is shown how the method allows estimates to be made of the radioactivity of the various cell types and the accuracy of these estimates and the errors in obtaining them are discussed.
High‐resolution autoradiography of 3H‐ouabain binding in salt transporting epithelia
Authors: Stirling C. E. 
Published: August 2011

SUMMARYThe distribution of salt transporting sites in epithelia is a problem of special interest to electrolyte metabolism. Autoradiography of freeze‐dried plastic embedded tissue was used to localize 3H‐ouabain in rabbit small intestine and renal medulla and gills of killifish. Resolution approaching theoretical limits for tritium at the light microscope level was achieved. The results of several tests are presented which demonstrate the resolution of the method and the specificity of the observed ouabain binding patterns. A large uptake of ouabain was found along the basolateral membranes of the enterocyte, thick ascending tubules and chloride cells (fish gill).
Autoradiographic studies of DNA synthesis in lymphoid tissues
Authors: Harris G. 
Published: August 2011

SUMMARYUsing long exposures of stripping film autoradiographs before processing, mixtures of weakly and strongly labelled nuclei were seen in different areas of the mouse spleen. Previous results (Harris et al., 1973) led to the conclusion that many cells, not in division cycle, were labelling with (3H) thymidine and that this process was important for the development of specific antibody‐producing cells following stimulation with an antigen such as sheep red cells (SRC). The present data are an analysis of the (3H) thymidine labelling kinetics in the spleens of mice reared in conventional or germ‐free conditions.The labelling seen in the 24 h following an injection of (3H) thymidine could best be interpreted on the basis of synthesis of unstable DNA. The changes in the pattern, and distribution of labelled nuclei as well as the intensity of their labelling was not compatible with cell division only, but was also the result of movement of labelled material between the lymphoid cells of the organ.Germ‐free mice were followed for 24 days following a single injection of (3H) thymidine. The rate of uptake of label into the spleen was much slower than has been found previously in mice reared in conventional conditions. When SRC were injected 2 h after giving (3H) thymidine the labelling of lymphoid cells in the spleen and blood was quite different to controls given (3H) thymidine alone. Detailed analysis indicated that turnover of labelled material, presumably DNA, as well as cells was involved. This turnover of DNA could be considered to be metabolic in the sense that renewal, increase in amount, loss, and transfer to other cells were involved. These, and other studies, in vivo (Harris & Olsen, 1973) and in vitro (Harris et al. 1975) indicate that such processes, involving DNA, are highly relevant to the development of antibody‐producing capacity by cells responding to antigenic challenge.
The possibility of electron microscopic autoradiography of steroids after freeze drying of unfixed testes
Authors: Frederik P. M. , Klepper D. 
Published: August 2011

SUMMARYA technique has been developed for the autoradiographic localization of steroids in testes at the light and possibly electron microscope level. During processing of the tissue there is no contact of tissue with water up to the moment of photographic development of the autoradiographs.Tritium labelled steroids have been introduced into the testis through perfusion of the isolated organ. Small tissue samples were rapidly frozen, freeze dried and fixed with osmium vapour. The fixed tissue was embedded in Epon and thin sections could be cut from this material on an ultra‐cryotome without the aid of floatation liquids. Results with light microscopic autoradiography indicate the potential of this technique. This procedure which avoids any contact of the tissue with water offers good prospects for autoradiography of steroids and other soluble compounds at the electron microscope level. A comparison is made with other proposed techniques for steroid autoradiography.
A copper block method for freezing non‐cryoprotected tissue to produce ice‐crystal‐free regions for electron microscopy
Authors: Dempsey G. P. , Bullivant S. 
Published: August 2011

SUMMARYTwo methods are described for fracturing unfixed, uncryoprotected mouse liver that had been frozen by contact with a copper block at liquid nitrogen temperature. The best method involved precise fracturing of a few microns of surface tissue with a cooled glass knife, using the Cryokit attachment of the LKB III ultramicrotome. The resulting replicas were free from electron microscopically‐visible ice crystals. A noticeable feature of replicas from unfixed, uncryoprotected tissue was the extent of plastic deformation of certain cellular structures. Cytoplasmic macromolecules, and to a lesser extent intramembranous particles, often appeared to be ‘stretched’ to form fibrils.
Electron microscope image contrast with double beam illumination from crystal supports
Authors: Hines R. L. 
Published: August 2011

SUMMARYWhen a cluster of atoms on the bottom side of a crystal is viewed in the vicinity of a bend contour, a double image of the cluster is formed. The crystal acts as a beam splitter so that an object on the bottom of the crystal is illuminated by two coherent but non‐parallel electron waves. The possibility of using double beam illumination to enhance the contrast of amorphous phase objects is discussed. Experimental results are presented for the image contrast of clusters formed by evaporating gold and aluminium on to the bottom side of graphite and silicon crystals.
The application of X‐ray analysis in the transmission electron analytical microscope (T.E.A.M.) to the quantitative bulk analysis of biological microsamples
Authors: Davies T. W. , Morgan A. J. 
Published: August 2011

SUMMARYThis paper describes: (a) methods for the high and low temperature ashing of biological tissue samples about 10−4–10−5 g in weight; (b) a method of spraying the solubilized ash on to specimen grids which produces droplets of a size convenient for their quantitative analysis in a transmission electron analytical microscope (T.E.A.M.), but without the need to know the actual volume of individual droplets; (c) the construction of standard curves for determining the absolute concentration of Na, Mg, P, S, K, and Ca simultaneously in a given sample. For most of the elements the error in analysis was about 5% or less. It was proposed that the technique is useful for detecting local element‐compartments in complex tissues, and thus may be an important aid in the interpretation of the results of point analyses performed on sections taken from adjacent micro‐volumes.
X‐ray microanalysis of ultrathin frozen and freeze‐dried sections of human sperm cells
Authors: Chandler J. A. , Battersby S. 
Published: August 2011

SUMMARYX‐ray microanalysis of air dried and ultrathin frozen and frozen dried sections of human sperm cells has indicated a large deviation of elemental composition between cells in a single sample and between samples. Analysis of air dried cells indicates a similar subcellular elemental distribution to that found in sectioned material. Sodium to potassium ratios are found to be similar in both preparations. Air drying is considered a valid method for the preparation of sperm cells for analysis.
An improved culture flask for photographic and visual observation of living cell cultures
Authors: Fox Cecil H. , Chaconas Peter G. , Sanford Katherine K. 
Published: August 2011

SUMMARYA new type of culture vessel is described, identical in shape to the classic T15 vessel but with the advantage of optical surfaces that allow photography at medium resolution (with numerical apertures of 0.60–1.0). Details of flask manufacture are given.
Characterization of particulate material in very pure waters
Authors: Biddle P. , Miles J. H. 
Published: August 2011

SUMMARYTechniques are described which enable exceptionally pure waters to be handled without contamination. The solids content which may be less than 1 part/108, can be obtained on the electron microscope grid and transmission electron micrographs and diffraction patterns obtained. X‐ray spectra obtained using a Li drifted Si detector attached to a scanning electron microscope (SEM), are enhanced by use of an auxiliary circuit, which causes the electron beam to dwell on the particle surface much longer than over blank film. The problems involved in converting X‐ray count rates into an analysis are discussed. The analyses gave valuable information on the origin of the particulate material.Paper presented to the symposium on the ‘Use of the microscope in studies on air and water pollution’. Royal Microscopical Society, University of York, 17 December 1974.
The effect of the electron beam on various mounting and coating media in the SEM. II
Authors: Rampley D. N. 
Published: August 2011

SUMMARYThe results given in this paper supplement those reported in Muir & Rampley (1969). The effect of the electron beam on eight uncoated and eight differently coated specimen adhesives is investigated. The results are reported in tabular form. The investigation was carried out to determine the most beam damage‐resistant combination of adhesive and coating. It must be kept in mind that for certain investigations the choice of adhesive is limited by one or more factors, which may be unrelated to beam damage resistance.
The electron‐beam induced monomerization of di‐p‐anthracene
Authors: Jones William 
Published: August 2011

SUMMARYThe electron beam stability of di‐para‐anthracene has been investigated with regard to the study, in situ, of the mechanism of photodimerization of anthracene and related materials. It is found that the electron beam converts di‐para‐anthracene to anthracene, the process taking place in a single crystal to single crystal manner. Electron doses greater than 6.0 × 10−5 C mm−2 result in a diffraction pattern corresponding to the anthracene lattice.
Errors in area measurement in thick sections, with special reference to trabecular bone
Authors: Whitehouse W. J. 
Published: August 2011

SUMMARYA formula is derived for the errors caused by section thickness in the measurement of the mean cross‐sectional areas of opaque material embedded in a transparent medium. There are some simplifying assumptions which can only be justified by limiting the maximum thickness of the section, but no restriction whatever is placed upon the shape of the opaque material.For isotropic materials a very simple formula is found, relating the relative error in cross‐sectional area to measurements of area and boundary profile length on the section surface. The effect of anisotropy in the material may be very large. To illustrate this, numerical calculations are made for two particular classes of simple anisotropic material, those which might be made from isotropic materials by linear distortions.
The use of freeze‐substitution in the preparation of plant tissue for ion localization studies
Authors: Harvey Diana M. R. , Hall J. L. , Flowers T. J. 
Published: August 2011

SUMMARYA method, utilizing freeze substitution, is described for the preparation of plant tissue for analytical electron microscopy. The fine structure of the cytoplasm was adequately preserved after freezing leaf tissue in 2‐methylbutane at −170°C. Furthermore, following substitution in ether, losses of sodium and potassium from the tissue were less than 4% of the original ion content and the loss of chloride was less than 1%. The merits of the procedure as a means of tissue preparation for ion localization studies are discussed.
Stereological method for estimating relative membrane surface area in freeze‐fracture preparations of subcellular fractions*
Authors: Weibel Ewald R. , Losa G. , Bolender R. P. 
Published: August 2011

SUMMARYMicrosomal fractions from liver cells are a mixture of vesicles derived from a number of different cellular membranes. These can be differentiated on freeze‐fracture preparations by their characteristic density of intramembranous particles. A stereological method is developed which allows the estimation of the relative membrane surface of the various membrane types by using freeze‐fracture preparations. The sample is restricted to concave profiles without cast shadow. The numerical frequency distribution of vesicles with respect to particle density is determined. The estimation of relative surface area must consider the effects on sampling of (a) variable size distributions of vesicles and (b) loss of small profiles. Correction coefficients are derived which allow a differential vesicle count to be transformed into an estimate of relative membrane surface.
Application of various stereological methods to the study of the grain and the crack structure of concrete
Authors: Stroeven Piet 
Published: August 2011

SUMMARYVarious statistico‐geometrical as well as deterministic stereological methods have been applied to study the structure and the structural defects in plain concrete, subjected to a compressive loading. Up till now use has been made of an artificial spherical single‐sized ceramic aggregate instead of coarse gravel for most of the investigations. Crack patterns which have been visualized with the help of the filtered particle method (based on fluorescence), have been analysed by means of the method of directed secants. Apart from structural information and results for engineering applications, this approach facilitated a mutual comparison of various stereological techniques in this field of materials science.
Estimation of linear functionals by maximum likelihood*
Authors: Nicholson W. L. 
Published: August 2011

SUMMARYA classical problem of stereology is estimation of linear functionals of particle size distributions from intersections on planar probes. The maximum likelihood method of estimation is outlined and compared with classical linear methods and with numerical interpolation methods.A population of spherical particles is distributed in an infinite matrix with position defined by a Poisson field. Diameters of circular intersections on a planar probe constitute a generalized Poisson process. Maximum likelihood theory fits a parametric family of planar density functions to observed diameter frequency data. The integral of an appropriate kernel with respect to the fitted density function is the linear functional estimate.The approach can handle composite data involving observation at several magnifications. Estimation of complementary cumulative density of pores in uranium oxide fuel pellets illustrates the maximum likelihood method of data collected with two microscopes at four magnifications.
Cell and organelle shrinkage during preparation for scanning electron microscopy: effects of fixation, dehydration and critical point drying
Authors: Gusnard Debra , Kirschner Robert H. 
Published: August 2011

SUMMARYThe critical point drying method of preparing samples for scanning electron microscopy is associated with a variable amount of specimen shrinkage. We studied the causes of this phenomenon in isolated mouse hepatocyte nuclei and in human erythrocytes and found that the critical point drying process itself caused most of the shrinkage that we observed (a 25–30% reduction in diameter in both specimens). Glutaraldehyde fixation and ethanol dehydration caused only minimal size reduction, prior to critical point drying. Substitution of an inert (ethylene glycol‐ethylene glycol monethyl ether) dehydration technique did not alter the final result. Previous studies in our laboratory using high resolution SEM and correlative transmission microscopy of isolated nuclei have demonstrated that the shrinkage represents a miniaturization of the organelles in which all structural components retain their usual relationships.
Some proposed improvements in the scanning ion microprobe
Authors: Krohn V. E. , Ringo G. R. 
Published: August 2011

SUMMARYThree improvements, which we have investigated, promise to lead to a scanning ion microprobe with a space resolution of about 15 nm. The improvements are: (1) use of a field‐evaporation (EHD) ion source with liquid gallium to give a brightness exceeding 1010 A m−2 sr1 at 21 keV, (2) a high efficiency (10%) collecting system for secondary ions, and (3) enhancement of the secondary‐ion yield by cesium deposition. With this instrument, tracing with stable isotopes would offer a number of advantages over autoradiography.
Thiocarbohydrazide binding for botanical specimens for scanning electron microscopy: a modification
Authors: Postek Michael T. , Tucker Shirley C. 
Published: August 2011

SUMMARYThe ligand osmium binding technique utilizing thiocarbohydrazide has been a successful alternative to evaporation or sputter coating of botanical specimens. A modification to this technique is presented which we have found successful in our laboratory for the preparation of a variety of specimens. This technique permits an overall reduction in the quantity of osmium necessary to provide conductivity. Further, dehydration time and specimen handling is reduced by the complete chemical dehydration of the tissue utilizing 2‐2‐dimethoxypropane.