摘要:

SUMMARYMagnetite crystals inside coccoid magnetotactic bacteria found in lagoons near Rio de Janeiro city were examined by electron microscopy (EM) and atomic force microscopy (AFM). For AFM, ultrathin sections of bacteria embedded in Epon resin were etched with an ethanolic NaOH solution and observed both in the height and in the force modes. Comparative electron microscope images were useful for identifying crystalline reliefs in the etched sections. Different situations representing particular arrangements of crystal chains were observed by AFM. The majority of the bacteria examined presented unusually large magnetite crystals which remained strongly attached in linear chains even after the laboratory procedures for their isolation. This behaviour is different from all other biogenic magnetite crystals isolated so far. It is suggested that this attachment is due to the strong field between individual crystals as well as to the contact areas, which are the largest observed until now. The correct identification of a particular topography by AFM as a crystal relief may be critical when crystals are not aligned in chains; in these cases the linear dimensions and the presence of well‐defined edges and faces are important features to be taken into account. Characterization of the crystal faces is important for the study of magnetotactic micro‐organisms since the crystalline habits seem to be species‐specific. Observation of etched sections proved to be a helpful approach for crystal relief observation, especially when small amounts of bacteria were avai

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1994.tb03423.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SUMMARYThe development of a parallel electron energy‐loss spectrum imaging system is presented. The analytical performance of the imaging technique was investigated and the system applied to materials science problems. The system, which allows acquisition and storage of a parallel electron energy‐loss spectrum at each pixel of an image, was developed by interfacing a multichannel analyser and a microscope to a computer workstation. In the experimental conditions used for imaging, detection limits and quantification errors were large and varied as a function of spatial resolution and the range of chemical elements of interest in the image. Applications of this imaging technique in materials science showed that quantitative chemical information is provided by the system and that the use of relative thickness maps and detailed statistical analysis of the spectrum‐image allowed an unbiased interpretation of the images. As energy‐loss spectra are available after processing, spectroscopic information about the analysed material can be used to provide supplementary info

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1994.tb03424.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SUMMARYA method for reflectancein situhybridization (RISH) is presented. The importance of the method is demonstrated by results obtained on cytological and histological breast cancer specimens.Scattering reflectance signals from 1‐nm colloidal‐gold particles after RNA/RNAin situhybridization, using digoxigenin‐labelled riboprobes, were detected by confocal scanning laser microscopy.The mRNA expression of two ras‐related genes, rho B and rho C, was analysed in human histological breast cancer specimens and in human breast cancer cell lines. Horizontal (x, y) and vertical (z) optical sections after three‐dimensional imaging were used for visualization.A marked heterogeneity (between individual cells and between specimens) was noted for the expression of the rho B gene, both in cytological and in histological samples. On the other hand, rho C was always expressed and showed no heterogeneity.This method allows the identification of several cellular constituents in an heterogeneous tissue structure, as demonstrated by the simultaneous detection of rho B (or rho C) by reflectance and of DNA, cytokeratin and/or vimentin by flu

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1994.tb03425.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SUMMARYVariable‐angle total internal reflection fluorescence microscopy (VA‐TIRFM) allows controlled variation of the illumination depth with the potential of measuring both membrane/substrate separation distances and sizes of focal contacts. VA‐TIRFM images are collected from well‐spread bovine aortic endothelial cells (BAEC) stained with a membrane‐bound carbocyanine dye. Quantitative determination of absolute membrane/substrate separation distances and individual focal contact area are attempted using a simplified model of TIRFM optics. For angles slightly greater than the critical angle of 64°, both the dorsal and ventral membranes were illuminated, while images excited above 66° illuminated only focal contacts. Above 74° the fluorescence of focal contacts was dominated by background noise. Direct application of the simplified optical model without accounting for background intensity was unsatisfactory. However, correction for background fluorescence and nonlinear regression of the untransformed data over the working range yielded focal contact separation distances of 24 ± 13 nm. Focal contact areas estimated by TIRFM (1·3 ± 0·7 μm2) agreed closely with areas observed by immunofluorescence staining of vinculi

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1994.tb03426.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SUMMARYSemiautomated methods are used to measure elongated, curved and complex branching profiles and isolated perimeter segments in monochrome video images with a general‐purpose analysis system. These methods are used to make the major primary measurements of bone histomorphometry. Accuracy and reproducibility of the image acquisition, processing and measurement system is documented by measuring a semicircular standard of known dimensions. Semiautomated applications of the Ar/Le method for measuring areas and perimeters, and calculating lengths and widths of osteoid seams, lengths of mineralization labels and mineral apposition rate, wall width, indirect measurements of eroded, osteoclastic and osteoblastic perimeters without tracing, and measurement of mineralized or total cancellous bone area and perimeter gave values comparable to measurements of the same parameters by tracing or grid counting techniques with equal or better reproducibility and much greater efficiency. Intraindividual variation in measuring multiple bone biopsies was comparable to that reported with current standard methods. Major sources of variability for semiautomated methods were image magnification and selection of profile edges by thresholding, and sources of variability for manual methods are image magnification, numbers of orthogonal intercepts, tracing speed and accuracy of the algorithm used to measure traced pixels. Semiautomated methods are accurate, reproducible and rapid methods suitable for bone histomorphometr

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1994.tb03427.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SUMMARYA set of three line grids in three orthogonal directions is called a spatial grid. This spatial grid can be used for surface area estimation by counting the number of intersection points of a surface with the grid lines. If direction and localization of the spatial grid are suitably randomized, the expectation of this number is proportional to the surface area of interest. The method was especially developed for cases where the surface to be measured is embedded in a medium, which is the usual case in microscopical applications, and where a stack of serial optical sections of the surface is available.The paper presents an improvement of an earlier version of the counting rule for intersection points. Furthermore, if the direction of sectioning is not uniform random, a bias results. This bias is calculated for a disc as a perfectly anisotropic object. A generalization of the estimator is considered by introducing a weighted mean instead of the usual arithmetic mean. The variance due to the randomized direction is investigated depending on the weights, and the minimum of this variance is derived. The relationship between the covariogram and the variance of the surface area estimated with the spatial grid is considered.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1994.tb03428.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SUMMARYThe use of the ‘point‐sampled intercepts’ method on histopathological material is evaluated for the main purpose of comparing different methods of intercept length measurements. The volume‐weighted mean nuclear volume—nuclear—of the carcinoma of the ampulla of Vater is calculated using three methods for measuring intercept lengths: a semiautomatic image analyser, an equidistantIo‐ruler and a logarithmic‐ruler. Rulers of several classes and lengths are used, and the results of the nuclearestimations are compared. The equidistantIo‐ruler is more accurate than the logarithmic‐ruler. With a greater number of ruler classes and with adjustment of ruler length to the greatest nuclear intercept lengths, the systematic deviation from the true value of the nuclearis smaller. The nuclearparameter has great power to differentiate intestinal carcinoma

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1994.tb03429.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SUMMARYA method to calibrate current density ratios for the determination of specimen thickness is presented. This method uses a tilt series from a single noncrystalline specimen to create different thicknesses; these are used to generate data points to establish the relationship between specimen thickness and current density ratio. The actual specimen thickness at 0° tilt was determined to an accuracy of 5 nm by a parallax method. From the calibration curves obtained, we observed that the current density ratio was sensitive to relative thickness changes on the same section of less than 1 nm when a 50‐μm objective aperture was u

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1994.tb03430.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SUMMARYA novel method of attaching a fine mesh filter to the end of a disposable plastic pipette is described. Such a pipette filter can be used to exclude specimen uptake during specimen preparation procedures, particularly when processing small or transparent materials. The pipette filter‐tip does not interfere with fluid exchange and is non‐reactive with normal processing flu

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1994.tb03431.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY