bluuebunny/crossref_metadata_2025_split huggingface dataset:
A resin slide technique to select fixed embedded cells for transmission electron microscopy
Authors: Sigee D. C. 
Published: August 2011

SUMMARYA simple technique is described to resection, for electron microscopy, 2–6 μm sections that have been observed under the light microscope. The technique can be used to select cells on the basis of light microscope ultrastructure, histochemistry and autoradiography prior to electron microscopy.
An improved method for photographing fluorescent human chromosomes*
Authors: Verma Ram S. , Dosik Harvey 
Published: August 2011

SUMMARYIn the photography of sequentially QFQ and RFA banded chromosomes, the fading problem can be solved by reducing exposure time. This can be accomplished by choosing the right light source, filter combinations, type of film and developer. Three different systems were employed to record the exposure time during photography. A ‘Vertical Illuminator III RS’ with a 50 w/AC mercury burner equipped with 400–490, BG 12–BG 38 excitation filters and 510 barrier filter was found to be the most efficient and satisfactory. QFQ banded chromosomes can be photographed within 3–5 s and RFA banded chromosomes within 10–15 s with this system.
Image processing of electron micrographs of deformed filaments
Authors: Fraser R. D. B. , MacRae T. P. , Suzuki E. , Davey C. L. 
Published: August 2011

SUMMARYElectron micrographs of filaments are frequently unsuitable for image processing because they are not perfectly straight. Even minor departures from straightness result in appreciable deterioration of the Fourier transform and analysis of periodicities and subsequent image processing becomes difficult. A procedure is described for recovering the projection of a straight filament from that of an imperfectly straight filament.
Correction of stereological parameters from biased samples on nucleated particle phases
Authors: Orive Luis‐M. Cruz 
Published: August 2011

SUMMARYStereologists are aware that the experimental evaluation of component volume fractions and surface‐to‐volume ratios are subject to systematic errors whenever the requirements for cell identification impose the necessity for component‐biased sectioning. Mathematical corrections of biased volume proportion data have recently been published; these corrections assume that the components under analysis are spherical, and that the nucleated particle phase is monodispersed.In this report, general methods for obtaining corrections of biased nuclear volume fraction data are set out for polydispersed phases of nucleated particles, in terms of the relevant shapes and joint size distribution of nucleus and cell; the scope and limitations of these methods are thereby discussed.Explicit corrections of an immediate applicability are obtained, together with their standard errors, for monodispersed phases where nucleus and cell are two dissimilar biaxial ellipsoids (spheroids). When nucleus and cell are two concentric and similar convex bodies of a certain class—to which triaxial ellipsoids belong—the corrections are shown to be very simple.The corrections for the spheroid–spheroid systems are easily accessible with the aid of a small programmable calculator, whereas those for the sphere–spheroid models are directly obtainable from two nomograms.
Correction of stereological parameters from biased samples on nucleated particle phases
Authors: Orive Luis‐M. Cruz 
Published: August 2011

SUMMARYGeneral formulations for correcting component‐biased S/V estimates on poly‐dispersed phases of nucleated particles are set out. Direct application of these corrections to monodispersed phases where nucleus and cell are spheroids, yield explicit corrections. As a rule, the corrected specific surface area of the containing bodies equals the product of the nuclear‐biased estimate times a correction coefficient, which is bigger than one, and depends upon the shape of the components and the relative volume of nucleus‐in‐cell. Reference curves which allow a rapid obtention of the correction factor, are provided.Simple formulae for correcting biased surface density and surface‐to‐volume ratio estimates other than the specific surface area, are also given, together with the standard errors of the corrected parameters.
A programmable flying‐spot microscope and picture preprocessor
Authors: Eccles M. J. , McCarthy B. D. , Proffitt D. , Rosen D. 
Published: August 2011

SUMMARYA description is given of a system comprising a general purpose computer (PDP‐8E) and a special purpose computer controlling a flying‐spot microscope. Under program control, the system extracts data from a field of view on the microscope slide. Various operating features of the system are detailed and a general account is given of its design and construction. Experience of using the system is briefly discussed.
The spatial and grey‐level resolution of flying‐spot microscopes
Authors: Eccles M. J. , McCarthy B. D. , Proffitt D. , Rosen D. 
Published: August 2011

SUMMARYAn analysis is presented of the optimum number of points per line at which a flying‐spot microscope might work when used in a digital mode, and also of the maximum number of levels of light intensity which may be detected at any one point. In actual instruments, the parameters which appear in the resulting formulae will be determined by engineering considerations. In a practical case used as illustration, the upper limits are 563 points per line and eighty intensity levels at maximum microscope magnification (× 1200).
Compensator transducer increases ease, accuracy, and rapidity of measuring changes in specimen birefringence with polarization microscopy
Authors: Salmon E. D. , Ellis G. W. 
Published: August 2011

SUMMARYAn instrument has been designed to improve substantially the efficiency and convenience of measuring specimen birefringence retardation (BR) with a conventional Brace‐Köhler compensator. The design is based on the precise transduction of the angular position of the compensator's vernier dial to an easily visible red‐illuminated display on a digital voltmeter. The instrument display is accurate to within 0.1° over a range of ± 25° in the compensator vernier dial position which is similar to the precision obtainable with an ordinary vernier and the Brace‐Köhler method of measuring BR of biological specimens. For convenience in data reduction the display can also be read directly in nanometre units, with a similar precision for specimen BR in the range of 5 nm or less which is typical of birefringent fine structures in living cells.
Goethe's four microscopes in Weimar
Authors: Otto Ludwig 
Published: August 2011

SUMMARYFour microscopes that belonged to Johann Wolfgang von Goethe (1749–1832) are preserved in the instrument collection of the Goethe‐Haus, Weimar, D.D.R.; these are described and illustrated. The four instruments are: a simple and compound microscope by George Adams Sr, a compound microscope by L. F. Dellebarre, an unsigned solar microscope, and a universal microscope after W. F. von Gleichen‐Russworm.
EM autoradiography of non‐sectioned biological material
Authors: Haworth R. A. , Chapman J. A. 
Published: August 2011

SUMMARYMethods of EM autoradiography suitable for the study of non‐sectioned biological material deposited on a support film from suspension are described. The methods, which include modified procedures for specimen support and emulsion preparation, may also have advantages for the study of any specimen where physical separation of specimen and emulsion is desirable.In a study of the growth of 125I‐labelled collagen fibrils reconstituted from solution in vitro, these procedures have allowed the production of EM autoradiographs which show a high resolution and are free from stress artefacts and chemography.
High‐resolution autoradiography as a tool for the localization of nucleic acid synthesis and distribution in the mammalian cell nucleus
Authors: Fakan Stanislav 
Published: August 2011

SUMMARYSeveral examples of the application of high resolution autoradiography to the study of nucleic acid distribution in ultrathin sections of fixed and plastic embedded or frozen material are presented.Newly‐synthesized DNA, labelled by very short pulses of 3H‐thymidine is found to be localized throughout the nucleus.In the blastomeres of early mouse embryos developing after fertilization by 3H‐thymidine‐labelled spermatozoa, the labelled paternal DNA is distributed non‐homogeneously in the nucleus.Finally some results obtained by using a cytochemical enzymatic technique for visualization of DNA directly in ultrathin sections of fixed and embedded cells are demonstrated.Concerning the distribution of RNA, perichromatin localization of rapidly transcribed RNA is described in different cell systems. This label can be attributed to perichromatin fibrils. In cells labelled for longer periods of time, sometimes followed by prolonged postincubations, a residual label is always found over the nucleus. Clusters of interchromatin granules are usually only weakly labelled or unlabelled. These structures probably contain a limited amount of rather slowly labelled RNA.The present results are discussed in the context of some biochemical evidence and of the data described by other investigators.
Proliferative characteristics of epithelial cells in the pregnant rat uterus
Authors: Peel Sandra , Liddiard Barbara 
Published: August 2011

SUMMARYIn the pregnant rat, killed at about mid gestation and 1 h after injection of tritiated thymidine, 40% of the cells in the epithelium lining the uterine lumen at the implantation site were labelled. Between implantation sites fewer than 20% of the surface epithelial cells were labelled. A series of rats was given tritiated thymidine on day 12 of pregnancy and killed at intervals in the next 30 h. A percentage labelled mitoses analysis of the epithelium between implantation sites (interconceptual) and within the implantation site (conceptual) showed that cells in either region spent 7 h in DNA synthesis and 1.5 h in the G2 + ½ mitosis phases. The epithelial cells in the conceptual region spent 1.5 h in the G1 + ½ mitosis phases whereas cells in interconceptual regions spent at least 11.5 h in these phases. The average cycle times of cells in conceptual regions was 10 h: in interconceptual regions minimum cycle time was 20 h and the average appeared to be considerably longer. The grain count of the epithelial cells in the conceptual region was rapidly reduced during the 30 h after injection of tritiated thymidine suggesting successive rounds of cell division. In contrast the grain count distribution of cells in interconceptual regions changed only slowly during this time. The percentage of labelled epithelial cells was determined in the animals killed up to 30 h after injection of tritiated thymidine. In both conceptual and interconceptual regions these percentages increased initially as labelled cells produced labelled progeny. In the conceptual region the increase was not maintained after 7 h as cells initially in G1 divided to give unlabelled progeny. In the interconceptual region the increase in the percentage of labelled cells continued for 14 h; thereafter the percentage did not significantly alter.The interpretation of these results is discussed in relation to the differences in the kinetic characteristics of the epithelial cells in the two regions and in relation to the morphology of the epithelium lining the uterus during pregnancy.
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

SUMMARYA wide variety of plant and animal tissues were prepared for electron microscopy by freeze‐substitution, after rapid freezing on a liquid nitrogen cooled copper block by the van Harreveld method. Measurements were made of ice crystal size versus depth in tissues that had not been treated with any cryoprotectants. Ice crystal size increased exponentially with depth. It was confirmed that a narrow surface band (approximately 12 μm) was frozen sufficiently rapidly to prevent the formation of electron microscopically‐visible ice crystals.
Multiple‐Shockley unfaulting of single‐layer faulted defects
Authors: Ronander E. , Kritzinger S. 
Published: August 2011

SUMMARYThe general principles laid down by Swart & Kritzinger (1974a) in a paper dealing with the unfaulting of Frank dislocation loops by the simultaneous action of two shearing Shockley dislocations are applied to explain the structure and electron diffraction contrast behaviour of certain complex single‐layer dislocation configurations observed in quenched aluminium and dilute Al‐Mg alloys. In these cases the simultaneous operation of three Shockley dislocations is employed. It is also demonstrated that adequate stresses, such as those encountered during annealing at temperatures ∼150°C, serve to transform butterfly hexagons to normal hexagonal prismatic dislocation loops, confirming the expectation that the butterfly defects are in a metastable state.
A method for preparing absolute standards for quantitative calibration and measurement of section thickness with X‐ray microanalysis of biological ultrathin specimens in EMMA
Authors: Chandler J. A. 
Published: August 2011

SUMMARYSpecimen thickness is determined using X‐ray microanalysis in conjunction with atomic absorption spectrophotometry. Specimens of evaporated metal films and standards comprising fixed concentrations of elements (such as potassium) in organic media are used to determine elemental concentrations of endogenous elements in embedding resin, from which section thickness can also be determined. The method finally depends only on the single measurement of X‐ray emission of such an element in the specimen. Calibration of the X‐ray detector over the energy range with mineral salts enables the standard to be used for the quantitative analysis of any element under investigation.
Observations on the production of frozen‐dried thin sections for electron microscopy using unfixed fresh liver, fast‐frozen without cryoprotectants
Authors: Spriggs T. L. B. , Wynne‐Evans Daphne 
Published: August 2011

SUMMARYThin sections of unfixed liver, fast‐frozen without cryoprotectants, have been cut using conditions under which momentary thawing of the sections is unlikely to occur. A transfer stage which facilitates this procedure is described. Sections show hole damage probably due to ice‐crystal formation during the freezing process and have well defined edges, but despite hole damage, some morphological features of the cell are discernible. Presumptive mitochondria appear smaller in frozen sections than in conventional Araldite sections. Sections devoid of hole damage have indistinct edges and are presumed to have undergone transient thawing. Carbon coating of freeze‐dried sections to exclude atmospheric moisture during transference of sections to the electron microscope (EM) appear unnecessary as regards preservation of morphological structure. The results are discussed in relation to the limitations of the method and the potential value of the technique.
A study of the structure of reverse osmosis membranes by means of the scanning electron microscope
Authors: Mossa G. 
Published: August 2011

SUMMARYReverse osmosis, or hyperfiltration, is a desalination process that uses membranes through which brackish or sea water is passed under pressure. The desalination properties of the cellulose acetate reverse‐osmosis membranes are due to their particular structure.A study was made of the structure of the Loeb‐Sourirajan type cellulose acetate membranes by means of the scanning electron microscope (SEM). The specimens were prepared as follows: the samples were freeze‐dried and then fractured by applying a bending stress at liquid nitrogen temperature.Different results were obtained depending on which of the two surfaces of the membrane had been subject to bending stress. The scanning micrographs of membrane cross‐sections confirmed (Gittens et al., 1973), a three‐layer structure of the membranes: a first dense layer which is responsible for desalination, a second layer, and a porous sub‐layer which is a very good natural support for the dense one. The asymmetric morphology of the membrane was correlated with its particular transport properties. A study was also made of the influence that the conditions of preparation exerted on the structure of cellulose acetate asymmetric membranes; the micrographs confirmed that the evaporation step has a marked effect on the membrane morphology. The technique has been extended to observe the recently perfected, anisotropic polyamide membranes.
Atomic number intensity profiles in the scanning electron microscope—gold and aluminium
Authors: Robinson V. N. E. , George E. P. 
Published: August 2011

SUMMARYMonte Carlo computations were used to calculate the backscattered and secondary electron intensity profiles associated with a gold slice and gold cube in an aluminium matrix. The gold slice in an aluminium matrix was produced experimentally and the theoretical profiles show good agreement with the experimental profiles.
An efficient spectroscopic detection system for cathodoluminescence mode scanning electron microscopy (SEM)
Authors: Steyn J. B. , Giles† P. , Holt D. B. 
Published: August 2011

SUMMARYA detection system for analytical cathodoluminescence (CL) mode scanning electron microscopy (SEM) is described. This incorporates a cold stage, an efficient light collector, a monochromator and a photomultiplier and used the photon counting technique. The efficiency of the component subsystems was optimized and calibrated, and the performance of alternative light collecting and monochromating equipment is compared. The operation of the photon counter is discussed. The digital output of the photon counter was fed into a multichannel scaler and thence to a computer. This was used to correct the observed count rate with the calibrated spectral variations in the performance of the detection system.Spectra obtained at both room temperature and liquid nitrogen temperacure and monochromatic and panchromatic SEM micrographs are given as examples illustrating the value of this technique.The factors governing the performance of the system are discussed. The forms of noise in the signal and in the detection system are described and the means for minimizing, avoiding or correcting for them are dealt with. Sources of spurious signals in the SEM are treated.
Form and distribution of actin and myosin in non‐muscle cells: A study using cultured chick embryo fibroblasts
Authors: Buckley I. K. , Raju T. R. 
Published: August 2011

SUMMARYAttempting to throw light on the mechanical basis of movement of non‐muscle (cf. muscle) cells, the present work aims to determine the form and distribution of actin and myosin in chick embryo fibroblasts. These cells were cultured on formvar, fixed in glutaraldehyde then osmium tetroxide vapours, dehydrated, critical‐point dried and examined, in tow, in the electron microscope (EM). Stereoscopic pairs of micrographs were studied to define more exactly the form and distribution of cytoplasmic filaments topographically associated with deformations of the cell surface and with organelle movements through the cytoplasm. Permeating the cytoplasm, interconnecting long and short filaments closely surrounded all organelles, linked with microtubules and polyribosomes and joined to the plasma membrane. These filaments, which varied greatly in width (2–13 nm) were closely associated with large numbers of ‘comma‐shaped’ globoid bodies of ∼15 nm diameter. Attempting to establish the identity, form and distribution of cytoplasmic myosin, cultured cells were extracted with a cold (4°C) glycerol/pyrophosphate solution for 24 h before being fixed and critical‐point dried. EM examination of these cells revealed a residual three‐dimensional network of branching and anastomosing 4–13 nm diameter smooth filaments, devoid of fine (2 nm) filaments and globoid bodies. Examination of fixed, critical‐point dried, skeletal muscle heavy meromyosin showed globoid structures similar in form and size to the globoid bodies found in cultured fibroblasts. Similarly fixed and critical‐point dried paracrystals of actin, polymerized in the presence of Mg2+, appeared as branching interconnecting filaments which, in form and dimensions, resembled the network filaments observed in pyrophosphate‐extracted cells. It is concluded that the pyrophosphate‐extractable globoid bodies found in cultured fibroblasts represent monomers of myosin, that the broader filaments to which these attach represent actin in Mg2+ paracrystalline form and that the various subcellular movements are brought about by interactions between the two, analogous to those occurring in muscle cells.
Field‐ion microscopy of segregation to planar imperfections
Authors: Howell P. R. , Fleet D. E. , Hildon A. , Ralph B. 
Published: August 2011

SUMMARYThis paper investigates the segregation of solute to planar imperfections using field‐ion microscopy. Two major systems have been analysed, namely the segregation of chromium to grain boundaries in a tungsten‐chromium alloy, and the segregation of niobium to stacking faults in a cobalt‐niobium alloy.In both cases, the solute distributions within the planar faults were quantitatively analysed, and a strong tendency towards clustering of the niobium solute within the stacking faults of the cobalt alloy was observed.
Examining water trees in polythene using a flexible light source
Authors: Fursey Anita 
Published: August 2011

SUMMARYA battery powered flexible surgical light can be used as an inexpensive light source for transmission microscopy through 2 mm thick walls of polythene cups, where it is not possible to use a conventional condenser. With ASA 400 film photographic exposure times are 5–10 s. The illuminator has been used to study water trees in polythene.
Peculiar artefacts after fixation with glutaraldehyde and osmium tetroxide
Authors: Kuthy Enikö , Csapó Zsolt 
Published: August 2011

SUMMARYPeculiar electron dense granules were observed, in otherwise well preserved structures of the heart muscle and kidney of the rat after a 5–10 min perfusion, a 2 h fixation in the modified Karnovsky solution, followed by a postfixation in Millonig buffer containing 1% OsO4. The granules appeared most frequently on membranes, the surface of the red blood cells and in pinocytotic vacuoles, in stained and unstained sections alike. No artefacts were produced when the same buffer was used for both pre‐ and postfixation, or when the postfixative contained Veronal buffer.
The presentation of three‐dimensional reconstructions from serial sections
Authors: Jordan E. G. , Saunders A. M. 
Published: August 2011

SUMMARYA simple and effective way is described for showing particular structures in serial sections. By using waterproof inks and acetate sheets supported on a frame immersed in water and illuminated from beneath, the information from up to sixty sections can be easily visualized. This technique is particularly useful for displaying enclosed structures and by a suitable choice of colours enables special emphasis to be given to selected components. The information can be recorded simply through stereo photography.
Estimating aggregate and overall characteristics from thick sections by transmission microscopy
Authors: Miles R. E. 
Published: August 2011

SUMMARYThe random spatial structure considered is the union X of an aggregate of random opaque convex particles in transparent space, the particle centroids being sited at the points of a homogeneous Poisson process. The model is thus the union of an aggregate of non‐necessarily‐convex disjoint regions. Expressions are derived for the fundamental stereological quantities VV, SV, KV (integrated mean curvature density) and GV (integrated gaussian curvature density) for X; and for AA, LA and CA (integrated curvature density) for the projection of a slice of thickness t of this model onto a plane parallel to the slice, where t may take any non‐negative value. The estimates relevant to transmission microscopy suggested by this theory are presented.