bluuebunny/crossref_metadata_2025_split huggingface dataset:
Liquid propane jet‐freezing, freeze‐drying and rotary replication of the cytoskeleton and plasma membrane associated structures in human monocytes
Authors: Espevik Terje , Elgsaeter Arnljot 
Published: August 2011

SUMMARYWe have studied the cytoskeleton and plasma membrane associated structures of human monocytes using liquid propane jet‐freezing, freeze‐drying and rotary replication. We find that the cytoskeleton of these cells consists mainly of actin filaments. The actin filaments were identified by their ability to bind myosin sub‐fragment S1. A large fraction of these actin filaments radiates from dense cytoskeletal foci. The presence of such actin filament rich foci also in unfrozen cells was demonstrated using immunofluorescence light microscopic techniques. In addition to coated pits a network of thin fibrils (diameter 4–5 nm) were observed on the protoplasmic side of the plasma membrane facing the substrate. These results indicate that liquid propane jet‐freezing may represent a simple, inexpensive alternative to impact freezing at liquid helium temperature for obtaining the high cooling rate necessary for successful freeze‐drying and rotary replication of cytoskeletal structures.
Extraction of lipids during freeze‐substitution of Acholeplasma laidlawii‐cells for electron microscopy
Authors: Weibull C. , Villiger W. , Carlemalm E. 
Published: August 2011

SUMMARYCells of the bacterium Acholeplasma laidlawii were rapidly frozen against a copper block cooled by liquid helium. The frozen cells were transferred to liquid nitrogen and subsequently to acetone or methanol at 183 K. After 24 h the cells were infiltrated at 203 K with a non‐polar methacrylate resin of the same type as Lowicryl HM20. The resin was cured at the same temperature. Acetone extracted approximately 5% of the lipid content of the cells, methanol 15–45% and the resin only negligible amounts. Similar results were obtained with A. laidlawii‐ghosts. The cells appeared well preserved when examined in the electron microscope.
Descriptors of flatness and roughness
Authors: Serra J. 
Published: August 2011

SUMMARYThe two notions of flatness and roughness refer to local properties of the profiles and of the surfaces. They are defined in two‐ and three‐dimensional spaces. Flatness is the ratio of the measure of the surface divided by its projection, and roughness the average of the square of the mean curvature of the surface per unit area. Whatever the number of dimensions of the space is, both parameters are accessible from vertical plane sections. The problem of their digital version is discussed, and algorithms are given. The approach also applies for grey tone functions, in R2 and in R3. Finally the results are extended to the n‐dimensional case.
Measurement of cellular elastic properties by acoustic microscopy
Authors: Hildebrand J. A. , Rugar D. 
Published: August 2011

SUMMARYThe acoustic microscope is used to investigate the elastic properties of living biological cells. A quantitative model is developed relating acoustic microscope image contrast to cellular elastic properties. Cytoplasmic acoustic attentuation is measured by focusing the acoustic microscope on the surface of the underlying substrate. Cytoplasmic acoustic impedance is measured by focusing the acoustic microscope on the top surface of the cell. The model allows the acoustic microscope to give quantitative information about cellular elasticity on a subcellular scale.
Specimen holder design for X‐ray microanalysis of thin films in the TEM: reduction of spurious X‐rays
Authors: Ryan K. G. , Flower N. E. , Presland M. R. 
Published: August 2011

SUMMARYSpurious Cu and Fe peaks were observed during energy dispersive X‐ray spectroscopy of thin resin sections or of thin gold films in a Philips EM400T. Since our field of interest lies in the distribution of Cu in thin sections, experiments were aimed at the elimination of this peak. Replacement of the low background specimen holder with one fashioned from a small strip of Al foil established that the source of the Cu was the Cu alloy of the specimen holder. Tests showed that the incident beam was well collimated and that the fluorescence of the holder was due to X‐rays scattered from the analysed volume.We have made a new low background specimen holder from an Al alloy (6351 T6) containing 1% Si, 1% Mg, 0·7% Mn and 0·4% Cu. Although the tensile strength of this material is only two‐thirds that of the Cu alloy, it is still sufficient for a mechanically robust holder. The spurious CuKα peak was not observed in the X‐ray spectrum when analyses were performed with this holder and when the beryllium top plate on the holder was doubled in thickness, no other peaks were introduced to the spectrum. The importance of eliminating spurious peaks is discussed.
A clearing method for the observation of lateral root primordia
Authors: Casero V. J. , Lloret P. G. , Vidal M. R. , Abadía‐Fenoll F. 
Published: August 2011

SUMMARYA clearing method is described to show the adventitious root tissues of Allium cepa by transparency. This method allows the lateral root primordia to be observed in situ, and enables them to be dissected out more easily. The histological sections show that both the tissues of the adventitious and lateral root primordia are perfectly preserved so that it is possible to carry out morphological observations.
Electron phase‐contrast imaging of melamine‐embedded, unstained horse‐spleen ferritin
Authors: Westphal C. , Bachhuber K. , Frösch D. 
Published: August 2011

SUMMARYA pellet of aldehyde‐fixed horse‐spleen ferritin was embedded in a water‐soluble melamine resin for ultrathin sectioning. Overfocused electron micrographs of individual molecules show the four‐lobed iron‐core and the peripheral protein subunits in great detail. They confirm earlier X‐ray diffraction data of hydrated horse‐spleen apoferritin (Hoare et al., Nature, 255, 653, 1975), which postulate a molecule with twenty‐four protein subunits occupying octahedral lattice sites around the iron‐core.
An improved detection system for electrical microcharacterization in a scanning electron microscope
Authors: Lesniak M. , Unvala B. A. , Holt D. B. 
Published: August 2011

SUMMARYAn improved, modular detection system for conductive mode, charge collection (CC) microscopy and electrical microcharacterization in a scanning electron microscope is reported. It makes possible the recording of both the short‐circuit current (EBIC) and the open‐circuit voltage (EBIV) generated by the barrier or the bulk electron voltaic effect even in the presence of biases up to 700 V. The constant‐current β‐conductivity voltage signal and the constant‐voltage β‐conductivity current signal can also both be recorded.The design of the system emphasizes noise minimization, a wide range of operating characteristics all independently controllable, quantitative monitoring and simple signal processing. An interface to a microcomputer is provided for more detailed quantitative analyses of the signals. The system has been calibrated so the accuracy of the measurements is known.The potential of this detection system is illustrated by means of a number of applications.
Design and application of a freeze‐fracture stage with a cleaver device for Balzers ‘freeze‐etching’ apparatus
Authors: Stolinski C. , Landmann L. , Abt H. 
Published: August 2011

SUMMARYA fracturing mechanism in the form of a double‐wedged cleaver, used previously on other freeze‐fracture machines, has been incorporated in the Balzers BAF 400 D apparatus. The design of the stage, with the cleaver, is explained and its performance and advantages are outlined. By minimizing mechanical damage to the exposed surface of the frozen specimen and reducing contamination by effective shrouding, an improvement in the quality of the replicas is achieved. The suitability of this mechanism for the fracturing of tough tissues such as skin is also outlined.
Stereological estimation of average cell volume in monolayer culture by combined light and electron microscopy
Authors: Halgunset Jostein 
Published: August 2011

SUMMARYIn order to convert stereological ratio estimates into ‘absolute’ values (‘per cell’ values) the average cell volume must be estimated. The present paper describes a stereological method based on well‐known point counting procedures for the estimation of average cell volumes in monolayer cultures fixed in situ. This method involves estimation of the average attachment area per cell by light microscopy combined with estimation of the attachment membrane surface density by electron microscopy. There is no need for any assumption as to cellular or nuclear shape.The method has been tested on an established cell line, NHIK 3025, and shows a good accuracy. It has also been used to analyse the volume changes that take place in human monocytes during monolayer culture, demonstrating a 28‐fold increase of the average cell volume over 10 days.
An improved approach to the analysis of autoradiographs containing isolated sources of simple shape: Method, theoretical basis and reference data
Authors: Downs A. M. , Williams M. A. 
Published: August 2011

SUMMARYThere are circumstances in which, by assuming that a high proportion of the radioactivity in a biological specimen is associated with certain well‐dispersed structures of simple shape, a relatively simple and effective objective analysis can be carried out. The usefulness of this type of restricted analysis has previously been severely limited by the requirement that all the profiles of interest should be of roughly the same size, which is rarely the case. A procedure is proposed which, by appropriately combining image spread functions for profiles of the same shape but of various sizes, allows realistic hypothesis testing in such circumstances. Details for the practical application of the method are offered and criteria for assessing the feasibility of applying the method in particular circumstances are discussed.The necessary backup information to the method is supplied in the form of the derivation of the fundamental image spread function, the introduction of a coherent notation and reference data quantitatively describing the image spread around certain extended sources of simple shape.
New classification methods of branching patterns
Authors: van Pelt J. , Verwer R. W. H. 
Published: August 2011

SUMMARYBinary branching patterns are described in this paper by their topological structure. The statistical properties of these structures appear to be highly dependent on their growth patterns. As such, observed trees may be used for testing growth models. This paper describes three options in the construction of frequency distributions of topological parameters and their corresponding probability distributions, arising from the terminal and segmental growth models. The construction of these distributions makes the analysis of observed tree structures possible in those experimental conditions where small numbers of observations or differing sizes of trees would form serious obstacles to alternative analytical procedures.
Low voltage scanning electron microscopy
Authors: Pawley James 
Published: August 2011

SUMMARYThe scanning electron microscope (SEM) is usually operated with a beam voltage, V0, in the range of 10–30 kV, even though many early workers had suggested the use of lower voltages to increase topographic contrast and to reduce specimen charging and beam damage. The chief reason for this contradiction is poor instrumental performance when V0=1–3 kV, The problems include low source brightness, greater defocusing due to chromatic aberration greater sensitivity to stray fields, and difficulty in collecting the secondary electron signal. Responding to the needs of the semiconductor industry, which uses low V0 to reduce beam damage, considerable efforts have been made to overcome these problems. The resulting equipment has greatly improved performance at low kV and substantially removes the practical deterrents to operation in this mode. This paper reviews the advantages of low voltage operation, recent progress in instrumentation and describes a prototype instrument designed and built for optimum performance at 1 kV. Other limitations to high resolution topographic imaging such as surface contamination, the de‐localized nature of the inelastic scattering event and radiation damage are also discussed.
Locational stereology performed within sampling fields in rat aortic wall, a polarized tissue
Authors: Guyton John R. 
Published: August 2011

SUMMARYOne‐dimensional structural localization on a scale approximating the sizes of the structures themselves is accomplished for polarized tissue by a new microcomputer‐based stereological method The tissue of interest is the inner rat aortic wall, viewed by transmission electron microscopy. Particular attention is given to the interface between intima and media. Locational analysis of smooth muscle cells, elastin, collagen and other structures near this interface can be performed. The key to accomplishing the analysis within a reasonable time rests with a microcomputer program which simultaneously records structure codes from the microcomputer keyboard and X, Y‐coordinates from an electronic digitizing board. The stereological solution to this problem is applicable to a wide range of situations with polarized geometries.
A methodological basis for SEM autoradiography: biosynthesis and radioligand binding
Authors: Cheng G. , Hodges G. M. , Trejdosiewicz L. K. 
Published: August 2011

SUMMARYA method is described for scanning electron microscope (SEM) autoradiography whereby preservation of high resolution cell surface details is retained together with degelatination of the emulsion without gross loss or redistribution of silver grains. This method should provide a convenient medium‐sized marker for SEM (using secondary, backscattered electron and X‐ray imaging) topographic studies of biosynthesized molecules, and of cell surface receptors and antigens, using indirect or direct labelling procedures with radio‐labelled ligands.
Polyethylene glycol embedding of plant tissues for transmission electron microscopy
Authors: Hawes C. R. , Horne J. C. 
Published: August 2011

SUMMARYThe use of high molecular weight polyethylene glycol as an embedding medium for the production of resin‐free sections of plant cells is described. Specimens can be observed at a range of accelerating voltages, are high in contrast and require no heavy metal staining. All the major organelles appear intact and a three‐dimensional network of filaments in the cytoplasm and nucleoplasm is reported.
Measurement of the width of thin, cylindrical, transparent objects by phase contrast light microscopy6
Authors: Knight Peter , Parsons Nick 
Published: August 2011

SUMMARYMeasurement of the width of a thin, cylindrical, transparent object by phase contrast light microscopy has been frustrated by the absence of an established relationship between the true width of the object and its apparent width in the phase contrast image. We have solved this problem by devising a simple method by which individual glass fibres may be measured using both phase contrast light microscopy and electron microscopy. Using this method we have constructed calibration curves relating the diameter measured by phase contrast microscopy to the real diameter of the fibres. These curves are linear in the range 0.10‐2.5 μm real diameter, with slopes close to unity and intercepts of about 0.2 μm. Thus widths of such objects are overestimated. The precise value of the intercept is related to the overall numerical aperture of the optical system. Each calibration curve permits the true width of a cylindrical object to be estimated by phase contrast microscopy with an accuracy of better than ±0.05 μm. We have found that greater precision is obtained by taking measurements of light micrographs subjectively using a microcomparator rather than objectively using a microdensitometer.
Weighted least squares estimation of background in EELS imaging
Authors: Pun Thierry , Ellis James R. , Eden Murray 
Published: August 2011

SUMMARYIn quantitative Electron Energy Loss Spectrometry, a weighted least squares estimation should theoretically be used to estimate the background law below core edge energy, since the variances of the data vary. However, it is found that proper weighting makes the above edge signal‐to‐noise ratio decrease rather than increase. This result is discussed, and the influence of the bias introduced by the logarithmic transformation of the data is quantified.
Automated recognition of atypical nuclei in breast cancer cytology specimens by iterative image transformations
Authors: Cornelisse C. J. , van Driel‐Kulker A. M. J. , Meyer F. , Ploem J. S. 
Published: August 2011

SUMMARYIn order to develop an objective grading system for nuclear atypia in breast cancer, an image analysis technique has been applied for the automated recognition of enlarged and hyperchromatic nuclei in cytology specimens. The image segmentation algorithm, based on the ‘top hat’ image transformation developed in mathematical morphology, is implemented on the LEYTAS automated microscope system. The performance of the segmentation algorithm has been evaluated for fifty malignant and eighty‐five benign breast lesions by visual inspection of the displayed ‘flagged’ objects. The mean number of flagged objects per 1600 image fields for breast cancers was 887 (range 0–7920) of which 87% consisted of single, atypical nuclei. For benign lesions the mean number was 30 (range 0–307) of which 20% were single nuclei. By adaptation of the ‘top hat’ parameter values, a more extreme subpopulation of atypical nuclei could be discriminated. The large interspecimen variation in the breast cancer results was related to differences in DNA content distribution and mean nuclear area, determined independently with scanning cytophotometry, and to some extent with the histological type.
Systematic inquiry in tests of negative/positive replica combinations for SEM
Authors: Bromage Timothy G. 
Published: August 2011

SUMMARYHigh resolution replica materials are routinely used in scanning electron microscopy. A systematic evaluating procedure for replica combinations is proposed which details fourteen points to be recorded. These points include quantitative and qualitative information useful when assessing a replica combination for a particular research problem. A case study employing one silicone‐based impression material and one epoxy resin is performed as an example of the procedure.
Digital mapping of metal‐bearing amoebocytes in tissue sections of the Pacific oyster by scanning microphotometry
Authors: Lytton D. G. , Eastgate A. R. , Ashbolt N. J. 
Published: August 2011

SUMMARYAutomated scanning microphotometry provides an objective assessment of the distribution of metal‐bearing (MB) amoebocytes in various tissues of the Pacific oyster, Crassostrea gigas. Silver‐staining of these cells in paraffin‐embedded sections gave good histochemical enhancement for effective photometric discrimination. Metal‐associated pixel fractions (MAPF) for 0.41 mm2 tissue‐fields were calculated from the results of microphotometric scans, giving an estimate of the metal content and an expression of the population density of MB cells. Gut‐associated MB cells in oysters obtained from two geographically‐separate metalliferous estuaries had similar distribution patterns, with MAPF values that correlated with metal concentrations in visceral mass determined by atomic absorption spectrophotometry (AAS). The metal content of other tissues varied by two orders of magnitude, the gill having the highest MAPF values. Intermediate MAPF values were found for digestive diverticula and the lowest values in the gonad. There was little difference between gut‐associated MB cell populations in oysters from the two collection sites, despite differences in size, glycogen content and gonadal maturation. This non‐destructive method of tissue microanalysis may provide a better way of assessing tissue metal‐load in individual organisms, and one that is independent of physiological variables.
A microcomputer based digital imaging system for ion microanalysis
Authors: Bryan S. R. , Woodward W. S. , Griffis D. P. , Linton R. W. 
Published: August 2011

SUMMARYA microcomputer based digital imaging system was developed for a Cameca IMS‐3f ion microscope permitting real‐time digital acquisition of secondary ion images. Image signal‐to‐noise enhancement results from random noise reduction by real‐time ensemble averaging and from a reduction of pattern noise in the charge injection device (CID) array by subtraction of blank frames. Acquired images comprise 244times248 pixel arrays with 8‐bit intensity resolution. Images are displayed on a colour monitor in a grey scale or pseudo‐colour using one of four programmable lookup tables. Image processing software permits off‐line ion image enhancement and manipulation as well as multitechnique digital image correlations. System capability is illustrated by a biological example involving digital imaging studies of Al distribution in osteomalacic bone tissue, including correlative light microscopy and ion microanalysis.
Differences in apparent elemental composition of tissues and cells using a fully quantitative X‐ray microanalysis system
Authors: Kendall Marion D. , Warley Alice , Morris I. W. 
Published: August 2011

SUMMARYThe elemental composition of tissues and cells in suspension was studied using fully quantitative X‐ray microanalysis. Quantitation was achieved using a commercially available program with reference to gelatin standards. Results showed that cells isolated in suspension differed in composition from those in the corresponding tissue. Elevated concentrations of Na, P, S and Cl were found in the cells in suspension. Concentrations of K and Mg were affected to a lesser extent and concentrations of Fe, Zn and Ca were unaffected by the suspension procedures.
Inaccuracies with the Hall technique due to continuum variation in the analytical microscope
Authors: Warner R. R. , Myers M. C. , Taylor D. A. 
Published: August 2011

SUMMARYWe have identified a source of extraneous (non‐sample) continuum in analytical microscopes with high‐angle EDS detectors. The extraneous continuum is generated by specimen‐scattered electrons but is not associated with a characteristic peak. This peakless continuum varies in magnitude with position across a grid and can cause large errors in quantitation with the Hall technique. The use of a modified specimen holder and an objective lens with a widened exit bore in the lower pole piece reduces the peakless continuum to acceptable levels in our instrument. Peripheral standards attached to the specimen can further reduce the impact of this extraneous continuum. Analytical microscopes with horizontal EDS detectors can also have serious problems with continuum variation across a grid, although the effect is likely due to X‐ray absorption by the specimen holder rather than extraneous continuum.
Effect of glutaraldehyde on the osmolarity of the buffer vehicle
Authors: Coetzee J. , van der Merwe C. F. 
Published: August 2011

SUMMARYThe osmolarity of four different buffers (Na‐cacodylate, PIPES, Na‐K‐phosphate and Na‐Na‐phosphate) at different pH‐values and molarities was measured. On the addition of glutaraldehyde to these buffers, an increase in osmolarity was observed. This increase was more than could be explained by the numerical addition of the osmolar values of the glutaraldehyde and of the buffer. The increase is due to a higher buffer dissociation constant. On the addition of 5% glutaraldehyde to a 0.05 M buffer, the increase in buffer osmolarity may be as much as 107 mOsm. Graphs are given to allow the determination of K‐values for these four buffers at different molarities and pH‐values. The effect of different glutaraldehyde concentrations on these K‐values is presented graphically. The time‐dependent increase in osmolarity of glutaraldehyde solutions in water is described.