bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preliminary oxidation in histochemical staining methods for cholesterol
Authors: Adams C. W. M. , High O. B. Bayliss 
Published: August 2011

SUMMARYThe need for preliminary oxidation with histochemical methods for cholesterol was investigated on silica‐coated sheets and in tissue sections. The techniques used were the Schultz reaction, perchloric acid‐naphthoquinone (PAN), Lewis & Lobban's ferric alum‐sulphuric acid reagent and Okamoto's iodine‐sulphuric acid. The oxidants assessed were ferric chloride, ferric alum, potassium permanganate, ammonium sulphamate and ultraviolet light. The best combinations amongst those tested in order of reactivity were FeCl3‐PAN, ferric alum‐Schultz, Lewis‐Lobban (no additional oxidant), iodine‐sulphuric acid (no additional oxidant). Authentic preparations of cholesterol oxidation products were stained with these methods, but the nature of the oxidized product in the preliminary stage could not be determined.
Transmission electron microscopy of organic pigments
Authors: Fryer J. R. 
Published: August 2011

SUMMARYPreparative techniques and electron microscopy applicable to organic pigments have been illustrated by the phthalocyanines, also showing that particle ablation and changes in shape occur before extensive lattice degradation. Similar radiation damage mechanisms are shown by both the transmission electron microscope and the scanning transmission electron microscope. Lattice resolution in phthalocyanines permits a definition of the primary particle in pigment agglomerates.
Morphological characterization of liposome suspensions by stereological analysis of freeze‐fracture replicas from spray‐frozen samples
Authors: Guiot Pierre , Baudhuin Pierre , Gotfredsen Carsten 
Published: August 2011

SUMMARYA method for size distribution analysis of liposome suspensions is described. Spray‐freezing was used in order to avoid cryoprotectants and fixatives. Light scattering showed that, depending on their composition, liposomes can be modified by the spraying procedure. Dipalmitoylphosphatidylcholine liposome suspensions display large modifications of light scattering upon spraying. The commonly used unilamellar phosphatidylserine/phosphatidylcholine (1:4) liposomes, with or without cholesterol, are, however, only slightly affected by the spraying procedure.For liposome suspensions stable upon spraying, size distribution analysis can be performed on freeze‐fracture replicas by standard procedures and average size, area and volume of particles are obtained. The number of particles per unit volume cannot be determined by stereological procedures, since the fracture face does not correspond to a plane section through the sample. By combining stereological data with phospholipid mass and specific molecular area of phospholipids, abundance of particles, fractional volume and total membrane area can nevertheless be evaluated.Data on small unilamellar liposomes prepared by sonication are presented as an illustration of the method. In suspensions obtained by this procedure, vesicles may be considered at thermodynamic equilibrium in the aqueous phase. The experimental size distribution compared favourably with that obtained from self‐assembly theory for liposomes, considering natural lecithin heterogeneity. For comparison purposes, data on large unilamellar liposomes, obtained by reverse‐phase evaporation, are also presented.
A cathodoluminescent study of quartz sand grains
Authors: Tovey N. K. , Krinsley D. H. 
Published: August 2011

SUMMARYSurfaces and cross sections of individual quartz sand grains have been examined in both the emissive and cathodoluminescent (CL) modes using a scanning electron microscope. The cathodoluminescent micrographs reveal sub‐surface information not seen in the emissive mode micrographs. The CL features are generally associated with previous stressing, fracturing or abrasion of the grains, and are probably related to the formation of disrupted‐lattice and/or amorphous quartz. The sequence of events during the formation of these features can be identified on many grains by studying the spatial distribution of the most common form of CL contrast—narrow dark bands. On other grains, irregularly distributed dark patches are generally observed to be a surface phenomenon, but the distribution, depth and intensity of these features can be studied by examining cross sections of grains. While it is common for the banded features to cross the entire specimen, it is rare for the diffuse areas to penetrate more than 30 μm. Some grains when experimentally heated above the α‐β transition temperature show a marked change and even a complete reversal in CL contrast.Such studies of grains in cathodoluminescence can supplement the environmental information obtained from emissive mode micrographs of geological materials.
Improvement in microscope photometry by voltage to frequency conversion: analogue measurement and digital processing
Authors: Freitas M. I. , Giordano P. A. , Bottiroli G. 
Published: August 2011

SUMMARYA system for digital measurement of microscope photometric signals, based on Voltage to Frequency Conversion (VFC) and suitable for automatic data processing, has been devised.Advantages and disadvantages are illustrated with special emphasis on the comparison between photocurrent measuring and photon counting techniques. A statistical analysis of the results allows the calibration of VFC net counts versus detected photons. A biological application is reported; this shows the suitability of the system even to low light levels.
Stereological meaning of the inflection point count
Authors: DeHoff R. T. 
Published: August 2011

SUMMARYThe relationship between the inflection point count on a representative microsection and the integral‐asymptotoic line curvature of saddle surface in the system constitutes a new fundamental stereological equation. While the geometric meaning of this quantity cannot be readily visualized, it is unambiguous, and general for all structures. Combinations of the inflection point count with other descriptors of two‐dimensional structures provide potentially useful descriptors of particle roughness, scale, and some aspects of shape. Like all measures of boundary properties, the inflection point count is sensitive to resolution; it is thus essential to report the level of resolution in conjuction with any experimental determination of IA.
Electron beam current measurement in the electron microscope
Authors: Nicholson W. A. P. 
Published: August 2011

SUMMARYTwo devices for measuring the beam current in an electron microscope are described; a Faraday cage rod for accurate absolute measurements in the specimen position and a collector plate mounted in the viewing chamber, which may be used continuously during experiments, for relative current measurements. Results of experiments to determine the effect of secondary electrons on, and choice of material of, the collector plate are presented. An example of the use of the collector plate as a photometer is given.
Some modifications on freeze‐fracture replica preparation
Authors: Bosch M. Van den , Jacob W. 
Published: August 2011

SUMMARYFreeze‐fracture replicas are freed from lipid material by saponification in a hot sodium hydroxide solution and subsequently rinsed with 10% ethanol in distilled water. All manipulations are carried out with a glass bead fashioned onto a pasteur pipette. A stable, two‐layered plastic support film has been developed to allow the use of grids with larger openings so that more of the specimen is observable.
Stereological estimation of volume ratios by systematic sections
Authors: Cruz‐Orive L. M. , Myking A. O. 
Published: August 2011

SUMMARYTwo related problems are explored. Firstly, a single opaque solid Ω1 of arbitrary size and shape, containing an arbitrarily shaped phase Ω2, is considered. The problem is to estimate the minimum number of systematic sections m, necessary to estimate the volume ratio v = V(Ω2)/V(Ω1) with a coefficient of error of at most γ0 with a probability 1 ‐ α. Secondly, we consider a population of such specimens. The second problem is to estimate the optimum number n of specimens to be sampled and the number m of systematic sections per specimen in order to estimate the mean volume ratio of the population with a relative error of at most ∍0 with a probability 1 ‐ α.General guidelines for solving the two problems are presented. Practical results applicable to two populations of mouse and guinea‐pig lymph nodes, exhibiting a wide variation in size and shape, are obtained.
Trace fossils as revealed by staining: a light microscope/scanning electron microscope study of the ancient microbiota from carbonate matrix
Authors: Karkhanis Suresh N. 
Published: August 2011

SUMMARYPreviously invisible fossil remains of ancient iron‐bearing microbiota from the carbonate matrix have been detected by staining the petrographic thin sections by weakly acidic solutions of potassium ferricyanide. The chemical staining technique imparts a deep blue colour—Turnbull's blue—in the presence of ferrous iron to these fossil remains, which are considered to be an example of authigenic preservation process, whereby the microbiota are preserved as carbonate molds or casts.The technique was found to be suitable for Proterozoic rocks and has been further extended to Archaean rocks. Hence its universality.
The myosin filament
Authors: Ashton Francis T. , Pepe Frank A. 
Published: August 2011

SUMMARYDifferent multistage fixation procedures patterned after the procedure described by Reedy (1976) have been evaluated with regard to preservation of subfllament structural organization along the length of the vertebrate skeletal myosin filament. The criteria used for evaluation of structural preservation include (a) the precision of subfllament organization as reflected by the quality of the optical diffraction patterns obtained from images of transverse sections of the myosin filament and (b) the clarity with which structural differences in serial transverse sections along the myosin filament could be defined.
Scanning immuno‐electron microscopy of human leukaemia and lymphoma cells: a comparative study of techniques using immunolatex spheres as markers
Authors: Gamliel Haim , Leizerowitz Rachel , Gurfel Dorit , Polliack Aaron 
Published: August 2011

SUMMARYIn this study scanning immuno‐electron microscopic (SIEM) techniques were used to identify human leukaemia‐lymphoma cells. Monodispersed polystyrene (latex) beads were conjugated to specific antisera using glutaraldehyde, in an attempt to detect surface antigenic components on a variety of cells of known origin. Antisera, mostly immunoglobulin fractions, against human thymus (T) derived cells, common type acute lymphoblastic leukaemia cells (C/ALL) and surface immunoglobulin (sIg) bearing cells were used to coat latex spheres, while rabbit anti‐mouse Thy‐1 antiserum or whole human‐IgG (γ‐globulin) bound to latex were used as controls in some experiments. The use of SIEM techniques in the direct mode as a simple and sensitive method for labelling surface antigens is described. The disadvantages of the SIEM methodology are also summarized while the requirements for optimal cell preparation using this technique are stressed. The experiments were designed to ascertain whether prolonged fixation of cells could be used prior to incubation of the cells with the marker. In this respect, repeated neutralization of the glutaraldehyde with glycine is essential. SIEM labelling of cells is random and unreliable without adequate quenching with glycine. The heteroantisera used in this study proved to be adequate and insignificant non‐specific attachment and cross reactivity were seen. SIEM adds a further dimension to ultrastructural aspects of immunology and is a potentially useful tool in the study and identification of leukaemia and lymphoma cells.
Use of a multichannel pulse height analyser for the analysis of back‐scattered SEM images
Authors: Hall M. G. , Skinner G. K. 
Published: August 2011

SUMMARYThe use of a simple electronic switch to convert the video signal from a scanning electron microscope to a series of pulses is described. A multichannel pulse height analyser may then be used to perform quantitative image analysis. Examples are given showing how composition analysis, area fraction measurement and image contouring may be performed using the atomic number contrast signal from a back‐scattered electron detector. Other detector systems such as scintillators or specimen current imaging could also be used.
The calibration of standards for the measurement of specular reflectance with a microscope photometer
Authors: Piller Horst 
Published: August 2011

SUMMARYSolid standards with reliable reflectance references are of fundamental importance for exact measurements of specular reflectances of microscopical objects. The liquid surface is the utopia of surfaces sought as reference for the calibration of solid standards. However, there are difficulties in setting the measuring equipment and adjusting the liquid surface for the comparison with the solid body. In this paper, the ‘liquid’ method is described clearly for microscopists to consider.
Application of morphometrical methods in studies of the mandibular condyle
Authors: Luder H. U. , Weilenmann W. , Schroeder H. E. 
Published: August 2011

SUMMARYTwo mandibular condyles of a growing monkey (Macaca fascicularis) were used for developing and testing a morphometrical model system suitable for generating quantitative data about the structure of and the growth activities in the articulating surface layers. The animal received 3H‐proline (1 mCi/kg body weight) 24 h and 3H‐thymidine (0.5 mCi/kg body weight) 3 h prior to killing. Using standardized conditions, 1–2 μm thick histological sections were processed for autoradiography. The morphometrical analysis was carried out using light microscopy at two levels of magnification. Sampling of tissue fields was performed at twenty‐four (level I) and twelve (level II) different sites, respectively. These sites were distributed systematically in the anteroposterior and lateromedial dimension of the cartilaginous condylar covering. Using a multivariate analysis of variance, a parameter comparison revealed significant differences between single sampling sites in the anteroposterior as well as in the lateromedial direction, suggesting that the articulating condylar surface is inhomogeneous with respect to both structures and growth activities. The sampling mode eventually arrived at in this study was shown to be sufficient for the recording of gradients within the condylar surface layers. The model system presented permits simultaneous quantitative characterization of structure and growth activities such as mitotic cell division and extracellular matrix production of the condylar cartilage including the zone of its replacement by bone.
Propane jet‐freezing: A valid ultra‐rapid freezing method for the preservation of temperature dependent lipid phases
Authors: van Venetië R. , Hage W. J. , Bluemink J. G. , Verkleij A. J. 
Published: August 2011

SUMMARYWe have developed a temperature controlled specimen stage on the existing jet‐freezing apparatus, in order to quench samples from elevated temperatures up to 330 K. We have shown that the phase transition both from the liquid‐crystalline to solid phase for pure phosphatidylcholines and from hexagonal II to lamellar phase for phosphatidylethanolamine/4% egg phosphatidic acid is prevented. Moreover, cooling rates exceeding 10,000 K s—1 were recorded indicative of ultra‐rapid freezing capacity. Cryoprotectants can be omitted, since phase separation due to ice crystal growth does not occur.
An electron microprobe study of the influence of beam current density on the stability of detectable elements in mixed‐salts (isoatomic) microdroplets
Authors: Morgan A. J. , Davies T. W. 
Published: August 2011

SUMMARYThis paper shows that a means of accurately measuring beam current during microprobe analysis of inorganic fluid microdroplets is essential, since certain elements were sublimated from such specimens under easily achieved beam current densities, i.e. S at 1·8 nA/μm2, K at 2·5 nA/μm2, Na at 3·5 nA/μm2, P at 5·3 nA/μm2. In comparison, Cl was volatilized even under the mildest conditions used (0·35 nA/μm2), and Ca, Mg and Co were stable under the severest operating conditions (7·1 nA/μm2). Elements were less stable in large (3 μm diameter) droplets than in small (1 μm) droplets under identical irradiation conditions. The onset of volatilization is a direct function of the current delivered per unit area and not of the total integrated dose.The addition of 50 g/l of urea to the mixed‐salts (isoatomic) solution, or (a) the mounting of the droplets so that the carbon‐celloidin support film was interposed between them and the electron source, and (b) top‐coating the droplets with carbon, did not, in general, raise the threshold of volatilization of a given element, but did effectively retard the rate of loss at current densities above the volatilization threshold. A literature survey confirmed that similar losses can occur from biological tissue specimens, albeit at higher beam current densities.Finally, the possibility that local specimen heating during electron/specimen interaction is a cause of element loss during microprobe analysis is discussed.
Cryopreparation of mammalian tissue for X‐ray microanalysis in STEM
Authors: Zierold Karl 
Published: August 2011

SUMMARYA cryopreparation technique for studies of ultrastructure and distribution of diffusible elements in biological tissue is described. Electron microscopical contrast and characteristic X‐ray spectra are found to be poor in completely frozen‐hydrated ultrathin cryosections of fresh chemically untreated tissue. Both STEM contrast and detection of characteristic X‐rays are enhanced by careful freeze‐drying in the microscope. Although the ultrastructure is affected by ice crystals, intracellular compartments can be identified by STEM without staining and studied by X‐ray microanalysis.
Intramembrane particle movement revealed by study of an intercellular junction
Authors: Green Colin R. 
Published: August 2011

SUMMARYComparison of results from thin section and freeze‐fracture techniques on the echinoderm epidermal septate junction has shown that a large degree of intramembrane particle translocation is possible during fixation and cryoprotection. The intramembrane and intermembrane components of the junction are apparently separated from each other in the process. Lanthanum tracer studies show that septa of this junction are double, straight, unbranched structures running around the cell apex. Freeze‐fracture of fixed tissue reveals junctional particles or pits in a broad band, also around the apical circumference of cells. However, they do not line up as would be expected after viewing septa in tangential sections and form a belt of randomly dispersed structures. In contrast, replicas of unfixed tissue show particles that clearly align in rows, often double, as are the septa in tangential views. It appears that intramembrane structural changes revealed by freeze‐fracture do not necessarily reflect corresponding intercellular changes.
Specimen preparation for electron microscopy using low temperature embedding resins
Authors: Armbruster B. L. , Carlemalm E. , Chiovetti R. , Garavito R. M. , Hobot J. A. , Kellenberger E. , Villiger W. 
Published: August 2011

SUMMARYStudies using polar and non‐polar methacrylate‐based resins (Lowicryl® K4M and HM20) suitable for low temperature embedding are described. We present the first applications of the system to various membrane structures in glutaraldehyde‐fixed, uranyl acetate‐stained thin sections of bacteria, mitochondria and cell‐cell contact regions.
Freezing patterns in quench frozen, freeze‐dried polyvinylpyrrolidone (PVP)
Authors: Scheie Paul , Dalen Helge , Saetersdal Thorvald , Myklebust Reidar 
Published: August 2011

SUMMARYAn SEM investigation of the effects of freezing and freeze‐drying on 2 mm diameter columns as well as on 10 mm diameter thick discs of PVP was carried out using standard techniques of quench freezing and cryofracturing followed by freeze‐drying. Quench freezing in liquid Freon 12 or liquid propane led to patterns of ice formation that depended on the position in the sample, the orientation of the fracture plane observed relative to the geometry of the sample and the concentration of PVP. Vitrification did not occur. Quench freezing in liquid N2 resulted in larger ice crystals and the pattern of the crystals was much less predictable.
Transfer, observation and analysis of frozen hydrated specimens
Authors: Hax Werner M. A. , Lichtenegger Siegfried 
Published: August 2011

SUMMARYHitherto, the observation of frozen hydrated specimens in transmission electron microscopes has been inhibited due to the technical difficulties experienced in transferring the specimen to the microscope and maintaining it at a low temperature during observation. This has resulted in loss of the primary advantage of freezing since the frozen water had to be removed from the specimen before it could be introduced into the electron microscope.The cryo‐transfer system overcomes these objections and provides a means to transfer frozen hydrated specimens from any preparation equipment into the microscope without ice condensation on the specimen. The cryo‐transfer system consists of a cryo‐transfer unit, a cryo‐specimen holder and a temperature control unit.
A television system for point counting morphometry in high resolution light microscopy
Authors: Nielsen H. Winther 
Published: August 2011

SUMMARYHigh resolution light microscopical images that can be superimposed on a test system for the estimation of stereological parameters are obtained by a television system modified for point‐counting morphometry. The full resolving power of the light microscope is exploited and a test system applied in the same plane as the microscopical image displayed on the monitor screen. Volume fraction estimates of nuclei and zymogen granules from the rat pancreas made with the television microscopical system and with electron‐microscopic micrographs rendered the same precision, and showed that the volume fraction of objects as small as zymogen granules was measurable with the light microscope. The measuring with the television microscopical system was about 15 times faster than with electron‐microscopic micrography and about 5 times faster than with conventional photomicrography and the light microscope.
Multiple image integration: a new method in electron microscopy
Authors: Wrigley N. G. , Chillingworth R. K. , Brown Elaine , Barrett A. N. 
Published: August 2011

SUMMARYAn optical ‘flicker’ method is described for the precise azimuthal and translational co‐registration of many noisy but identical molecular images. Starting with a real micrograph of known biological objects showing no visible detail below 4 nm, a lattice of images of individual objects was synthesized by computer and translationally filtered, using real experimental data throughout. Detail was recovered conforming with known structural features of the object down to about 1·5 nm, and rotational analysis showed that the registration accuracy of the lattice elements was better than 0·5 nm on the object. Application to the straightening of real two‐dimensional lattices with long‐range distortion is discussed.
Point projection imaging of unstained ferritin molecules on tungsten*
Authors: Panitz J. A. , Ghiglia D. C. 
Published: August 2011

SUMMARYPoint‐projection microscopy has been used to obtain the first images of closely spaced (but isolated) unstained ferritin molecules on a tungsten substrate. The microscopy, in conjunction with a digital processing algorithm, produces images which display a striking three‐dimensional quality usually associated with scanning electron micrographs. From these images, an apoferritin diameter of 13 nm has been deduced. This is identical to the diameter of apoferritin obtained from a reconstruction of the molecule using X‐ray coordinate data, but almost 70% larger than that deduced from TEM images of ferritin in which only its iron rich core can be seen.