摘要:

SUMMARYWe present a new reconstruction method that takes advantage of the fact that many biological macromolecular assemblies show a preferred orientation with respect to the plane of the specimen grid in the electron microscopic preparation. From one micrograph taken of such a specimen tilted by a large angle, a conical tilt series with random azimuthal angles can be extracted and used for a three‐dimensional reconstruction. Our technique allows the determination of the molecular structure under low‐dose conditions, which are not achievable with reconstruction methods that use conventional tilt series. The reconstruction method combines a number of existing image processing techniques with a newly developed weighted back‐projection algorithm designed for three‐dimensional reconstruction from projections taken with arbitrary projecting directions. The method is described as it was applied to the three‐dimensional reconstruction of the structure of the 50S ribosomal subunit ofEscherichia coli

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01333.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYA method is described for the production of stereo‐pair images in the tandem scanning reflected light microscope in which depths within the field imaged are coded in colour. The two images are recorded photographically whilst focusing vertically through the layer which is to be imaged. A horizontal component of motion is applied at the same time, but in opposing senses for the two images. Colour coding for depth is obtained by changing colour filters so that reflective features lying within different depth bands are imaged in corresponding colour

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01334.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYThe pH of sixteen different buffer vehicles is lowered by the addition of glutaraldehyde. This is the case even if the concentration of the buffer is as high as 0.2 m and that of the glutaraldehyde as low as 2%. Graphs are given which make it possible to determine which buffer has the highest buffering capacity at pH‐values between 6.5 and 8. Graphs illustrating the influence of concentrations of glutaraldehyde between 1% and 5% on the dissociation constant of these buffers make it possible to formulate a glutaraldehyde‐based fixative in which an optimally‐buffered vehicle can contribute to the attainment of an osmotically‐balanced f

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01335.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYA rapid clearing technique, involving methyl salicylate clearing and phase‐contrast microscopy, that enables large‐scale observations on meiosis and embryo sac development in intact ovules of potato, was developed. With high resolution phase‐contrast optics the details observed in cleared ovules were as well defined as in microtome sections and ‘abnormalities' associated with desynapsis and 2n‐megaspore formation were readily detected.In potato this ovule clearing technique offers certain advantages over earlier clearing and staining‐clearing techniques and permits bulk preparation of ethanol (70%) stored ovaries shortly (1·5–2 h) befo

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01336.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYIn order to evaluate the errors which can be introduced in the measurement of reflectance, we have made a study of data obtained for several minerals and in two immersion media on turning the microscope stage to a succession of positions relatively orientated by 45°. Fourier analysis of the results allows an estimate of the different errors as a function of the periodicity with which they appear on a full rotation of the stage.The mean magnitude of two of the Fourier coefficients is shown to provide a measure of the quality of the measurements further allowing evaluation of the equipment used, the orthogonality of the sample in relation to the incident light, and other errors of different periodicity

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01337.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Application of quantitative X‐ray imaging to frozen hydrated tissue sections has presented a number of major problems including lack of a suitable algorithm which could deal effectively with mass loss due to radiation damage, problems of low characteristic X‐ray signal to background ratios, and provide a means of analysis of the same location in both hydrated and dried states. This paper presents details of the application of our algorithm for analysis of frozen hydrated, then dried cryosections applied to quantitative X‐ray imaging, which provides relatively high precision quantitative measurement of elemental content (related to both wet and dry weight) and water content of each pixel. This algorithm largely circumvents many of the problems of analysis of frozen hydrated tissue sections. Our algorithm for X‐ray imaging obtains reasonably precise quantitative measurements coupled with morphological information by trading speed and image res

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01338.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYThe lymphocyte in Fig. 1 was incubated with a 1/10 dilution of a murine monoclonal antibody (Leu‐1) directed against a surface antigen expressed on circulating human T‐cells. It was labelled with a colloidal gold/immunoglobulin conjugate and examined with the scanning electron microscope (SEM) in the backscattered electron imaging (BEI) mode. It was easy to count the number of gold particles seen on this cell; actually, we counted 471 of them. For biologists, is this number relevant? We will discuss the principal factors involved in answering this quest

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01339.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYThe top hat filter is a computer algorithm that extracts small, compact or rounded objects from digital images. Examples show application of the filter to micrographs and electron diffraction patterns.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01340.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYA technique is described which allows quantification of specifically stained, intermingled vessel wall components in paraffin‐embedded tissue. The dissociation of elastic, muscular and connective tissue and the determination of their areal densities in the superior vena cava and in the ascending aorta of the dog, was performed by automated image analysis. The percentages of elastic+connective tissue, determined by this technique, correlated significantly with the data derived from biochemical measurements. It was further found that the structure of the vena cava wall was a function of the distance from the right atriu

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01341.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYComputer vision techniques have been developed for quantitative analysis of size and shape changes in cells frozen on a cryomicroscope. The analysis is based on implementation of standard serial edge detection algorithms in conjunction with a shape transform to isolate individual cells in complex scenes which may include adjacent and overlying ice crystals. In the present study the sensitivity of the automated analysis procedure is evaluated for images obtained by various microscope optical systems for progressive degrees of subject blurring by defocusing. Size measurements in calibration trials for freezing latex spheres with extracellular ice in the field of view were least sensitive for bright field images, although the most consistent data was obtained by differential interference contrast microscopy. In all cases phase contrast images produced the least accurate data. An example analysis is presented for the freezing of pancreas β‐cel

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01342.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY