摘要:

SUMMARYImage analysis methods are first classified into four groups of theories related to optics, after which the associate hypotheses, the structures, the laboratory equipment and the mathematical framework for one of them, better known by the term ofmorphological optics, are studied in detail. Conclusions are drawn as to the role played by hypotheses in image analysis.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01312.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYWe have studied the method of projections on to convex sets (POCS) for the restoration of three‐dimensional signals, especially applied for the degraded information obtained in three‐dimensional (3‐D) reconstructions by electron microscopy due to the limited tilting angular range of the sample that is obtainable in practice. A computer generated specimen has been used as a test object. Several noise levels were added to the specimen, obtaining signal‐to‐noise ratios (signal power/noise power) of between 12 and 0·5 dB. Different missing data angular regions of 30° and 10° zenithal angle have been considered. Our results illustrate the possibilities of POCS to restore incomplete 3‐D data in the absence and the presence of noise, and offer ways for further applications to improve the quality of 3‐D reconstructions ba

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01313.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYIn situoxidation and reduction of the oxides of cerium, praseodymium and terbium in a controlled atmosphere and temperature have been studied utilizing a high‐voltage electron microscope. Experiments were carried out in the environmental cell of the Berkeley KRATOS EM 1500 HVEM at temperatures between 298 K and 1023 K in an atmosphere of oxygen, hydrogen or vacuum. Electron diffraction patterns revealed the course of small fragments of the crystalline oxides. In nearly all cases, the degree of reduction recorded was greater than expected from equilibrium tensimetric studies in the absence of an electron beam. Furthermore, reoxidation appeared to be more sluggish and to a lesser extent than is observed in specimens outside the microscop

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01314.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYThe direction of the crystal optical axis of a uniaxial microscopic object is determined on the basis of the known correlation between this direction, the displacement of isogyres of the conoscopic figure, and the rotation of the microscope stage. It is shown that the use of photoelectric equipment for indicating the displacement, a stepping motor controlled by a microprocessor for rotating the stage, and a desk calculator for processing the photometric data provides a more convenient and accurate determination than classicial procedures, involving visual inspection and manual operation. The method is particularly suitable for uniaxial crystals of the size and shape of precious stones.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01315.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYA long chain amphiphilic molecule—the phospholipid 1,2‐dihexadecylsnglycerophosphoethanolamine—has been crystallized epitaxially so that the interlamellar molecular periodicity is parallel to the substrate and hence normal to the electron beam in the electron microscope. This has permitted the direct resolution of the 55·6 Å lamellae in unstained crystals at room temperature.The lattice images have shown the presence of line dislocations and lenticular cracks in the crystals. Of significance to their biological properties is that the lattice is undulating with a periodicity of 0·1–0·5 μm. This would also account for the difficulties encountered by X‐ray and electron diffraction techniques when examining

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01316.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYThe occurrence of more than one nucleolus within the cellular nucleus (polynucleolarity) is a well‐known phenomenon during the proliferative cell cycle, both under normal and pathological conditions (e.g. neoplasia). It can also be observed in neuronal nuclei at early stages of their maturation. Polynucleolarity merits investigation for cytological reasons.In an histological section, the observed number of nucleoli in a nucleus may be smaller than the actual number. In order to estimate the true distribution of the number of nucleoli per nucleus from the observed distribution, the mathematical relation between these distributions is derived (Section 4) on the basis of rather restrictive (Sections 3 and 11) stereological assumptions (Section 2). It is indicated how these distributions can be estimated from the data available and how the statistical uncertainties involved can be expressed (Sections 5, 6 and 7).This paper arose from making cell counts (Section 1). Two methods may be applied: (1) all visible nuclear profiles are counted, (2) nuclear profiles are only included if at least one nucleolus is visible in the section. We recommend a combination of these two methods (Section 8). An advantage of our theory for determining cell number (Section 9) is that one can often manage without the rather restrictive stereological assumptions needed hitherto.The advantage of expressing statistical uncertainties in estimated nucleolar multiplicity probabilities and cell numbers is indicated (Section 10

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01317.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYCoolants used for freezing biological specimens were tested for cooling performance in the continuous plunge mode. Results from bare thermocouples showed that ethane cooled faster than propane or a propane: pentane mixture, even when warmed to 25 K above its freezing point. Propane coolants were more efficient than Freon 22 and the slowest cooling occurred in boiling liquid nitrogen. Hydrated gelatin specimens showed similar results with ethane cooling about 33% faster than propane. Epoxy resin specimens cooled faster than hydrated gelatin specimens of similar size. Hydrated and resin specimens cooled over increasing distances as plunge velocity increased. A bare thermocouple, however, cooled over a constant distance when plunged above a critical velocity. This phenomenon may reflect vapour formation and its suppression at high plunge velocities. The rate of cooling in hydrated specimens is shown to have an absolute limit and cannot be modelled by bare thermocouples or resin specimens.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01318.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYWe describe a method for the structural analysis and identification of viruses, without purification or concentration steps which could alter virus morphology. Virus‐infected cells grown on carbon‐Parlodion‐coated electron microscope grids release large numbers of progeny viruses which adsorb to the surface of the grid and are revealed by negative staining. The technique is rapid, sensitive and can be used at three levels. (1) Negative staining of whole cell preparations revealed both extracellular and intracellular viruses or nucleocapsids beneath the plasma membrane; (2) non‐ionic detergent extraction of cells infected with certain viruses reveals cytoskeleton‐associated, virus‐specific structures normally only observed after thin sectioning; (3) cultures prepared by either procedure are suitable for colloidal gold immunological studies. Extracellular and cytoskeletal‐associated viruses were heavily and specifically labelled with gold. The results indicate that the technique may be used to rapidly identify unknown viruses on the basis of size, topography, morphology and mode of maturation from the infected cell, as well as the presence of characteristic intracellular cytoskeletal‐associated structures. The technique also has potential use in the sero‐grouping and sero‐typing of viruses with specific mo

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01319.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYThis paper reports the dimensional changes occurring in the different steps of the histoprocessing of tissues for light microscopy. Two water‐miscible methacrylates used for embedding, namely 2‐hydroxyethyl methacrylate and 2‐hydroxypropyl methacrylate, were investigated. It was found that during stretching on the water bath and in the mounting step considerable size changes occur, which are of the same magnitude as during the dehydration step of histoprocessing. The final dimensions of the sections and of microscopic images are dependent on the response to surface tension at the water surface and mounting of the glycol and hydroxypropyl methacrylate sections, respectively. Between the two resins under study, significant differences in the size of the resin sections, with and without embedded liver tissue, were found. It is shown that the temperature at which the sections are mounted is of great importance. These observations indicate the importance of standardizing histotechniques if morphometry is to be ap

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01320.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYA simple method of preparing ‘swiss rolls' from strips of tissue up to 500 mm in length is described. This procedure has been applied to a variety of tissues and is suitable for the preparation of both paraffin‐ and methacrylate‐embedded spec

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01321.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY