摘要:

SUMMARYA method for the detection and characterization of clusters of particles observed in section with the electron microscope is presented. Cluster analysis is performed by the division method described by Berthetet al.(1976). Starting from a single cluster, profiles from each electron micrograph are successively classified in sets containing an increasing number of clusters. The decrease in the mean free distance, Λ, between profiles in the clusters, is used for terminating the subdivision procedure. The function relating the mean free distance with the number of clusters is evaluated in each subdivision set. The actual number of clusters is selected on the basis of the slope of that function, at a point where Λ has a value close to the average profile diameter. The method assumes a convex shape for the clusters; the salient feature is that it provides a physical delineation of clusters in the section. Hence, an evaluation of some characteristics of clusters in the three‐dimensional sample may be obtained by using standard stereological procedures. Characterization of the volume to which the individual particles of a population are eventually restricted can as a result be performed.Practical problems in the acquisition of the data needed for cluster analysis are discussed and a system using for that purpose a Quantimet 720 image analyser in a basic configuration, connected on line with a PDP 11/10 minicomputer, is presented. Application of the method is illustrated by the analysis of lysosomes in cultured hepatoma (HTC) cells, at the end of mitosis and during the S phase. Cluster analysis shows that in mitotic cells, lysosomes are confined within 3·7% of the total cellular volume, while in cells actively synthesizing DNA they are grouped in clusters representing 5·7% of the cellular volume. Moreover, the average number of particles per cluster falls from a minimum of thirteen at mitosis to only six at the S

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1979.tb00148.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

SUMMARYThis report deals with the reconstruction of the distribution of membrane thicknessTfrom that of orthogonal intercept lengthL0, measured in random section planes. In such planes the membrane appears as a band and the linear distance from one of its boundaries perpendicular to the opposite one is the length of the orthogonal intercept. Using a membrane model, an integral equation relating the probability density functions of orthogonal intercept lengthf(l0) and membrane thicknessg(τ) is derived. Relations between moments are derived and the analytic solution to the problem of reconstructingg(τ) fromf(l0) is given. The parametric approach by which it is assumed thatg(τ) has some known analytic form with unknown parameters is considered, and the use of a suggested analytic form for describing the thickness distribution of the human glomerular basement membrane is discuss

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1979.tb00149.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

SUMMARYThis study was undertaken with the aim of identifying the different cell types found in human bone marrow by examining their surface morphology. In an attempt to obtain a homogeneous cell population, cells were both fractionated by discontinuous albumin density gradient centrifugation (DADGC) and selectively grown in nutrient agar. Both cell preparations underwent the critical point drying technique before examination under both the scanning electron microscope (SEM) and subsequently the light microscope (LM). When the SEM image of individual cells was compared with the corresponding LM image, it was not easy to identify the different cell types, because of the shrinkage and distortion that occurred during their preparation. The shrinkage observed under the SEM amounted to a 45% reduction in mean cell diameter. This shrinkage was confirmed by comparing the SEM and LM images of the same cell. Although shrinkage occurred throughout the dehydration sequence, critical point drying was responsible for a 25% reduction in mean cell diameter. Furthermore, direct observation under LM of fixed cells drying in air from ethanol, revealed visible contraction of the cell and distortion of the cell membrane. We assume that a similar morphological change occurred during critical point drying. We conclude that the shrinkage and distortion, caused by the dehydration process involved in SEM preparation, severely limit the value of a study of surface morphology by SEM in the identification of the different cell types found in human bone marrow.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1979.tb00150.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

SUMMARYThe size‐distribution of normal human lymphocytes growing in tissue culture was measured with a Quantimet 720 image‐analysing computer. The proportion of cells undergoing volumetric growth after phytohaemagglutinin (PHA) stimulation was derived from a simple mathematical model describing the growth patterns of the cells up to the first mitotic division. The approach may have general application in biology as a method for measuring the proportion of growing cells by microsc

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1979.tb00151.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

SUMMARYPrevious work, at foreign laboratories, essentially based on electron microscopy of longitudinal sections, has suggested a radial morphology for the aromatic poly‐amide high modulus fibres; the present paper gives direct evidence of such a morphology, thanks to a special preparation technique which allows a great improvement in the quality of the cross‐sections of these fibres.This is demonstrated for both a commercial ‘Du Pont de Nemours’ yarn sample ‘Kevlar 29’, and an experimental high modulus aramid RPT (Rhǒne Poulenc Textile) yarn. In the first case, Ag2S insertion technique was used and permitted one to see, on the cross‐sections, an alternation of dark and clear radial bands, again with a tendency towards tangential splitting. In the second case the fibres were included into an amorphous polymer, a sample preparation technique which greatly enhances the quality of the cross‐sections; optical microscopy showed the radial morphology fairly well; dark‐field transmission electron microscopy—using the equatorial doublet of the electron diffraction pattern—allowed satisfactory resolution: both the radial, and occasionally the tangential, splitting, and the size of the cross‐sectioned crystallites were easily revealed: these crystallites appear as isodiametric bright particle

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1979.tb00152.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

SUMMARYA dual purpose stage has been constructed for an EM6G 100 kV transmission electron microscope. With this stage the composition of thin films and bulk specimens can be determined by X‐ray microanalysis. With thin films a change of specimen cartridge then enables a full analysis of crystal defects in the film to be made using tilt controls incorporated in the stage. Modifications to the stage to reduce background effects in X‐ray microanalysis spectra are also described.The alternative use of this system in the bulk analysis of specimens by an X‐ray fluorescence technique is also disc

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1979.tb00153.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

SUMMARYA technique is described for arresting rapid movement of living cells and preserving their fine surface structures for scanning electron microscopy. Rapid freezing is recommended as the method of immobilization and freeze substitution has been employed to fix and dehydrate the specimens; this technique is more reliable than osmium fixation, both in terms of obtaining a much higher proportion of good results and in the improved preservation of detail. Various techniques of substitution have been investigated for best preservation, and the roles of the constituents of the substitution mixture have been discussed.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1979.tb00154.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

SUMMARYA method is described for transmission electron microscopy which allows high resolution mapping of three lectin receptors on the same cell. As a model, receptors for Concanavalin A, soya bean and wheat germ agglutinins have been simultaneously localized on human erythrocytes using lectin‐labelled gold markers of different sizes (5, 17 and 26 nm, respectively). Quantitative binding data and examination of stereoscopic micrographs of thin sections of marked erythrocytes indicated that the greatest part of these lectin markers was bound by receptors spatially separated. As gold granules are electron dense and uniform in size, they are well suited for multiple marking of cell surface components. The method is simple and leads to a better understanding of the topography of cell membrane

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1979.tb00155.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

SUMMARYIdentifying marks can be made around specific cells on the culture surface of plastic tissue culture dishes. When the cultures are embeddedin situand the plastic dish is split away, the marks are reproduced around the cells. The marks permit trimming and complete serial sectioning of specific cells in the vertical plane.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1979.tb00156.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

SUMMARYDeposits of silver chloride made on the surface of animal tissue are visible by reflected light after osmication. When the tissue is flat embedded, the deposits permit precise relocation and thin sectioning of specific identified cells.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1979.tb00157.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY