摘要:

SummaryA coherent detection system using a two‐mode optical fibre is described which permits confocal, differential amplitude contrast and differential phase contrast images to be obtained simultaneously from a scanning optical microscope. The direction of differentiation may be chosen arbitrarily. The differential imaging modes possess an optical sectioning propert

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1994.tb04782.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryA novel method ofZ‐contrast imaging in the scanning transmission electron microscope (STEM) is presented. The technique relies on the element dependence of the angular distribution of the scattered electrons, and is realized with a detector consisting of a set of concentric rings. It is possible to discriminate 9‐nm colloidal gold and silver specifically distributed on thin sections. In addition to this practical work, numerical evaluations are used to assess the method. With two smaller markers, this approach will be useful in discriminating closely spaced antigenic sites when steric hindrance occurs with double‐labelling using probes of different

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1994.tb04783.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryA powerful new method is used to investigate the correlation between light microscopic and acoustic properties of biological tissues. Specimens of liver were sectioned into successive slices, 250 μm and 10 μm thick. The thick sections were investigated acoustically, the thin sections by means of light microscopy. Markers that could be detected and located, both optically and acoustically, were used to find and reconstruct corresponding regions in the acoustic and optical sections (2·5 × 2·5 mm).Parameter images were reconstructed from the sections investigated acoustically. The acoustic parameters were attenuation at 30 MHz, the slope of the attenuation spectrum (between 10 and 50 MHz), backscattering at 30 MHz, the slope of the backscattering spectrum (between 10 and 50 MHz) and the local ultrasound velocity. Acoustic images were obtained in the frequency range from 10 to 50 MHz, yielding a lateral resolution of about 50 μm.The sections for light microscopy were stained according to the Goldner trichrome staining technique. The histological composition was determined quantitatively, using digital image segmentation techniques. The percentage of collagen‐rich fibrous tissue, luminal structure and interstitial spaces, and the number of nuclei were calculated for regions of 250 × 250 μm. These histological features were correlated with the acoustic parameters obtained from the corresponding regions in adjacent sections. It was thus possible to find the histological components responsible for acoustic p

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1994.tb04784.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryA procedure for efficient cryoimmobilization of large volumes of cell suspensions or micro‐organisms by high‐pressure freezing is described. This procedure uses transparent, porous cellulose capillary tubes with an inner diameter of 200 μm, into which the suspensions are drawn by capillary action. The tubes are processed by high‐pressure freezing and freeze‐substitution as if they were tissue samples. Centrifugation of suspensions at low temperatures is no longer necessary and cryopreparation is greatly facilitated.A very high yield of adequately frozen specimens is obtained due to the constant, defined sample geometry. This approach can also be used to process suspensions by conventional chemical fixation, eliminating the need to embed pellets in low‐melting‐point agarose, for example, prior to chemical fixation.The preparation procedure is demonstrated with suspensions of nematodes, paramecia

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1994.tb04785.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryDetailed chemical maps of BrdU‐labelled polytene chromosomes ofDrosophila melanogaster, obtained by imaging secondary ion mass spectrometry, reveal separately the distribution of DNA and proteins in the chromosomes. The thymidine‐analogue BrdU within the chromosomal DNA is localized by detecting the Br−secondary ion signal, while both nucleic acid and protein content are mapped through the abundantly emitted CN−signal. This novel approach supercedes, and helps explain the origin of, the banding patterns that are observed by conventional staining techniques. The high spatial resolution and chemical and isotopic sensitivity of this technique should enhance the localization of specific genes byin situhybridization in mitotic chro

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1994.tb04786.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryIn the study of the lichen‐rock interface, light microscopy, scanning electron microscopy (SEM) in secondary emission mode and transmission electron microscopy are the most commonly used techniques. As these methods have some limitations, there is a need to explore other techniques for observation of the lichen‐substrate interface. One of the most promising methods is the application of SEM in the back‐scattered electron (BSE) emission mode.The thallus ofAspicilia intermutans(Nyl.) Arn. growing on granitic rock was examined by SEM in BSE mode. The detailed preparation of transverse sections of the lichen‐rock contact zone is presented. The BSE scanning images of the lichen‐rock interface obtained present new insights into the ultrastructural features of the biological components, providing more information about the biogeophysical and biogeochemical weatherin

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1994.tb04787.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryThe distribution of the lengths of airspace chords in pulmonary parenchyma characterizes many architectural features of the alveoli and alveolar ducts. Laborious to obtain manually, the distributions and density functions may be acquired semi‐automatically by video microscopy, digitization and image processing. The accuracy of the estimation is influenced by the microscopical methods and also by the techniques used (i) to convert the digitized grey‐scale picture to a two‐valued image, (ii) to collect the chord lengths and (iii) to compensate for finite field widths. The last problem arises because some chords are completely visible within a field while others are only partially seen, since one of the two air‐tissue boundaries lies outside the field of view. This error systematically biases the observed distribution. This paper contains solutions to hardware, software and analytic problems encountered while developing the capability to measure airspace chord length density functions semi‐automatically. Formulas for estimating the true chord length density function from samples of observed chord lengths are presented. Also given are formulas for the estimation of the first and second moments of the true chord length distribution from the means of observed chord lengths. These techniques of image preparation and analysis should be suitable for characterizing particle, grain or cell size distributions, especially where many profiles fall partially outside the fiel

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1994.tb04788.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryAn algorithm is presented which offers an alternative approach for measuring volume‐ and number‐weighted mean volume and standard deviation of particles. Using a computer‐assisted manual method the following intermediate steps are performed automatically: generation of linear probes emanating from the sampling point of the object and intersecting the profile periphery, measurement of their lengths, and measurement of the area of the transect required for estimating the standard deviation of the volume‐weighted mean volume. By first tracing manually the outline of the periphery of the object with a cursor, on a magnetic tablet or on an image acquired into the computer with a video camera, the location of all pixels of the periphery is registered and the area of the transect is measured concurrently. The computer is informed of the coordinates of the selection point in the uniform random (UR) sampling grid by clicking the cursor. All ensuing operations are automatic. In the case of isotropic UR (IUR) sections the algorithm traces a series of uniform systematic random linear probes between the sampling point and the object profile periphery emanating from this selection point, radiating at angular intervals of 29–30° to the periphery. In the case of vertical sections, similar lines are generated at intervals where the sine of the angle changes by a value of 0·33. The volume‐weighted mean volume of the object is estimated from the average of all the products, wherelrepresents the length of each individual random linear probe. As the periphery is traced, the algorithm can automatically determine the area of the cross‐section of the object, from which the standard deviation of the volume‐weighted mean volume can be calculated. Some elements of the above algorithm are also used for the measurement of the number‐weighted mean volume. The latter procedure is facilitated using an acoustic vertical depth monitor attached to the microscope. The impact of truncation (‘lost caps’) on the precision of the measurements is discussed. The algorithm is of particular use in light microscopy for measuring cell nuclei by direct visual inspection of the microscopic field using a side‐arm mirror assembly interfac

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1994.tb04789.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryMicrospectroscopy is used to investigate optical properties of haemoglobin‐free perfused rat liver. Visible spectra of 20 μm diameter spot size were measured in transmission and/or reflection modes as a function of the thickness (<1200 μm) of the liver‐edge. Optical density (OD) in transmission mode increased with the increasing liver thickness, whereas in reflection modeODdecreased but became almost constant above a certain thickness (c. 600 μm) of the liver. The Kubelka‐Munk (KM) two‐flux model, with a minor modification, was applied successfully to the analysis of the changes inODas a function of the thickness. This approach estimates the KM absorption coefficient (EKM), KM scattering coefficient (SKM) and effective penetration depth (δeff) of the liver. The optical properties were similar to reported values, obtained with differ

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1994.tb04790.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1994.tb04791.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY