摘要:

AbstractAgarose, agar, and gelatin were initially compared as encapsulation media for 3 structurally diverse particulate specimens: bacteria, yeast, and mitochondria. Agarose proved superior to both gelatin and agar for ease of handling and overall image quality (minimum background). All sample types exhibited high quality fixation and structural detail with no heat damage from the agarose medium. Based on this finding, we further characterized agarose encapsulation as affected by post‐fixation, en bloc staining and resin type. Osmium tetroxide post‐fixation, followed by en bloc uranyl acetate staining, could be performed without an increase in the electron density of the encapsulation medium. Agarose proved successful as an encapsulation medium regardless of the resin type or preparation protocol, thus providing flexibility in experimental design and excellent results over a range of variables. © 1993 Wiley‐Lis

ISSN:1059-910X    

DOI:10.1002/jemt.1070250402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe localization of calcium inToxoplasma gondiitachyzoites was studied at the ultrastructural level, with a cytochemical pyroantimonate precipitation method (PA) and controlled by EGTA chelating and EDX and EELS microanalyses. Appropriate conditions for material preparation, fixation and embedding, were defined. The proportion of precipitates that were either free or inside vacuoles and their distribution insideToxoplasmaappeared to be PA dose‐dependent. Precipitation mainly occurred in the anterior pole of the Epon‐embedded tachyzoites. EDX and EELS analyses showed that out of 30 PA precipitates inside tachyzoites, 78% contained Ca. In Melamine sections, 96% of the tachyzoites had intracellular precipitates and the membrane complex was stained; 25% of the tachyzoites inside host cells contained PA‐Ca precipitates, but most of them were retained in the reticular network of the parasitophorous vacuole. Melamine embedding appeared to improve the preservation of calcium pyroantimonate precipitates. © 1993 Wiley‐L

ISSN:1059-910X    

DOI:10.1002/jemt.1070250403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractTritrichomonas foetus, a pathogenic protozoan, was used as a model to analyse microwave‐stimulated fixation as a procedure of preparation of biological samples for electron microscopy of thin sections and freeze‐fracture replicas. Good preservation of the protozoan structure was achieved by microwave‐stimulated fixation and Epon polymerization. The membrane structure, as visualized in freeze‐fracture replicas, was well preserved. © 1993 Wiley

ISSN:1059-910X    

DOI:10.1002/jemt.1070250404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractA new method of thin section preparation of III–‐V semiconductors and multilayers for transmission electron microscopy (TEM) is presented that exhibits considerable advantages over conventional methods such as ion beam milling and jet thinning. GaAs thin films and multilayers of GaAs/InxGa1‐xAs/GaAs are grown over an etch release layer of AlAs on GaAs substrates by molecular beamepitaxy (MBE). Planar TEM sections prepared by selective etching from these samples show improved ability to image film morphology and dislocation arrangements, and the resulting large thin electron transparent areas facilitate dislocation density measurements and detection of spatial variations. Avoidance of radiation effects and wedge shaping, both common to ion milled samples, allows this method to be used to prepare uniform thickness standards of single layer GaAs films for EDS analysis or lattice imaging. © 1993 Wiley‐L

ISSN:1059-910X    

DOI:10.1002/jemt.1070250405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThis study was designed to investigate patterns of fibrils organization in histochemically stained otoconia. Transmission electron microscope and video imaging were used. These data indicate that otoconia of the chick (Gallus domesticus) inner ear may have central cores in vivo. The data also show that the ultrastructural organization of fibrils fixed with aldehydes and histochemical stains follows trajectories that conform to the hexagonal shape of otoconia. These changes in direction may contribute to the formation of a central core. The existence of central cores is important for the in vivo buoyancy of otoconia. Packing of fibrils is tighter after phosphotungstic acid (PTA) stained otoconia than with other histochemical stains, which usually produce looser packing of fibrils and seemingly larger central core. TEM of tilted and untilted material showed that turning of fibrils occurs at the points where the face angles of otoconia form and where central cores exist. Video image processing of the images allowed reconstructing a template which, if assumed to repeat and change trajectories, would fit the pattern of fibrils seen in fixed otoconia. Since it is highly unlikely that aldehyde primary fixation or PTA stain caused such drastic change in the direction of fibrils, the template derived from these results may closely approximate patterns of otoconia fibrils packing in vivo. However, if the above is correct, the perfect crystallographic diffraction pattern of unfixed otoconia do not correspond to patterns of fixed fibrils. © 1993 Wiley‐Liss, I

ISSN:1059-910X    

DOI:10.1002/jemt.1070250406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractA well‐deserved criticism of stereology is that it is often too difficult to understand and use. Nevertheless, it is rapidly becoming one of the most effective ways of collecting and interpreting structural data in experimental biology. Recent breakthroughs in theory have produced a remarkable set of tools that can be used to engineer new methods. The dilemma remains, however, in that some of these new methods continue to be too difficult to understand and use. One solution to this growing problem of technology transfer might be to simplify the methods with computer software. To test this idea, programs were written for quantitative immunogold and in situ hybridization. Simulators were used to develop and test new experimental designs, which, in turn, were translated into step‐by‐step laboratory toolkits. This paper shows how these toolkits can turn two‐dimensional section data into estimates for the number of labeled molecules in three‐dimensional organelles, cells, tissues, and organs. The results indicate that software can identify the key data of an experiment and reduce the computational requirements of a new stereological method to entering constants and variables into data entry forms. © 1993 Wiley

ISSN:1059-910X    

DOI:10.1002/jemt.1070250407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractWe describe MS‐DOS software for the optical volume fractionator (OVF), a stereological method combining the principles of the optical disector (Gundersen et al.: Acta Pathol. Microbiol. Immunol. Scand., 96:857–881, 1988) and fractionator (Gundersen: J. Microsc., 143:3–45, 1986). The OVF program estimates the volume of a fixed and embedded structure, the numerical density of cells, and the total number of cells in a structure. The hardware requirements include a PC computer (386 or 486 with VGA graphics) and a conventional light microscope fitted with a rotating stage, extension tube, and length gauge. The software includes an introduction, tutorial, simulator, laboratory toolkit, and report generator. The toolkit improves the efficiency of gathering stereological data with light microscopy and offers a convenient link between the data of light and electron microscopy. A novel algorithm, based on fractionator sampling, gives the volume of a fixed and embedded structure from the same set of sections used for cell counting. A laboratory example illustrates the operation of the software. © 1993 Wiley‐L

ISSN:1059-910X    

DOI:10.1002/jemt.1070250408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractNatural (molybdenite) and synthesized molybdenum disulfide crystals have been studied by high‐resolution transmission electron microscopy. The image simulation demonstrates that the [0001] and [0110] HRTEM images of hexagonal and rhombohedral MoS2crystals hardly disclose their stacking sequences, and that the [2110] images can distinguish the Mo and S columns along the incident electron beam and enable one to determine not only the crystal structure but also the fault structure. Observed [0001]images of cleaved molybdenite and synthesized MoS2crystals, however, reveal the strain field around partial dislocations limiting an extended dislocation. A cross‐sectional image of a single molecular (S‐Mo‐S) layer cleaved from molybdenite has been observed. Synthesized MoS2flakes which were prepared by grinding have been found to be rhombohedral crystals containing many stacking faults caused by glides between S/S layers. © 1993 Wiley

ISSN:1059-910X    

DOI:10.1002/jemt.1070250409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe cores of human and simian immunodeficiency viruses (HIV and SIV) were observed by negative staining after isolation of the core with Nonidet P40 and glutaraldehyde. Four kinds of cores were found: asymmetric and symmetric sectoral shapes, a bar shape, and a triangular shape. These results were confirmed by the examination of ultrathin sections of whole virions. In some virions, the connection between the core and the envelope was observed after freeze fracturing. Its structure was considered to be characteristic of an intermediate stage of viral maturation. The HIV‐1 core was reacted with anti‐HIV‐1 p24 mouse monoclonal antibody. © 1993 Wiley‐L

ISSN:1059-910X    

DOI:10.1002/jemt.1070250410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractA simplified mode of differential phase contrast Lorentz microscopy for the study of magnetic domain structures in thin films is proposed and demonstrated. This mode employs a single annular detector in a scanning transmission electron microscope rather than the specialized split detectors that have been previously used. The resulting signal is sufficiently linear with magnetic field strength to allow quantitative data to be obtained on the domain configurations and the natures of the domain walls. © 1993 Wiley‐Liss, I

ISSN:1059-910X    

DOI:10.1002/jemt.1070250411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY