摘要:

AbstractYoung freshTradescantia reflexastamen hair cells were used to clarify the optimal conditions for direct viewing and taking photographs with a scanning electron microscope (SEM) equipped with a cryo‐system. The rate of protoplasmic streaming in the cells was measured under an optical microscope after examining and photographing them in the SEM over a period of a few minutes. Almost the same rate of streaming (5.5 μm/second, 20°C) was observed in nonirradiated control cells and irradiated cells photographed in the SEM using an accelerating voltage of 10 kV with the cryo‐stage at a temperature of – 15°C. (The specimen holder and specimen were not at this temperature, but, rather, probably somewhat higher.) Fresh plant organs, tissues, and cells were also tested under the same conditions. The fine structure was well preserved in detail. The procedures were as follows: (1) prompt attachment of fresh plant materials on an aluminum specimen holder with double‐faced adhesive Scotch tape or a small amount of plastic adhesive for woodcraft; (2) setting the holder on the cryo‐stage cooled to –15°C in advance and rapid evacuation; and (3) quick SEM examination and photography (within several minutes). The advantages of this method are summarized as follows: (1) high possibility of viewing living materials; (2) minimal artifacts: freedom from chemical fixation and additional procedures utilized in ordinary SEM specimen preparation; and (3) simplicity, speediness, and economy in preparation for viewing. Since the specimens were not likely to be frozen during quick examination and photography, this method might well be called “low‐temperature SEM” (LT‐SEM) as distin

ISSN:0741-0581    

DOI:10.1002/jemt.1060020101

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

年代:1985

数据来源: WILEY

摘要:

AbstractFold or wrinkles appear frequently in thin sections cut from botanical material embedded in epoxy resin such as Epon 812 (Polysciences) or EM‐bed‐812 (Electron Microscopy Sciences). Small wrinkles may occur more or less perpendicular to the cutting direction and mostly across the cell wall, causing problems in the examination of the ultrastructure. We studied the occurrence of wrinkles and folds by methodological sectioning, with regard to block hardness, use of Formvar‐support film, and chloroform vapor. Methodological sectioning or changing the block hardness did not reduce the occurrence of wrinkles in sections. Chloroform vapor improved the result as did also the use of uncoated grid. Wrinkles and folds could be avoided completely by embedding the specimens in LX‐112 (Ladd) or ERL‐4206 (Polysciences) low‐viscosity epoxy resins, in which case Formvar‐coated grids could be used, and chloroform vapor was

ISSN:0741-0581    

DOI:10.1002/jemt.1060020102

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

年代:1985

数据来源: WILEY

摘要:

AbstractMany transmission electron microscopes are available which can be used to examine biological material in 0.25–0.50‐μm‐thick sections. When compared to the traditional thin section, these “semithick” sections possess a number of inherent advantages: They can be screened for content with the phase contrast light microscope, they facilitate many types of studies requiring an analysis of serial sections, and they are frequently the optimum thickness for stereomicroscopy. Structures such as microtubule‐associated components, as well as structural relationships between cellular constituents, may also be clearly visible in semithick sections which are not visible, or go unnoticed, in thin sections. Together these advantages enable an investigator to obtain a more complete three‐dimensional picture of a cell or cell component in a significantly (i.e., up to 90%) shorter period of time than would be required if thin sections were used. Semithick sections may, therefore, make a study feasible which is not approachable, or which is approachable only with great difficulty, by conventional thin section

ISSN:0741-0581    

DOI:10.1002/jemt.1060020103

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

年代:1985

数据来源: WILEY

摘要:

AbstractA technique was developed to aid in the interpretation of nucleation and growth characteristics of otherwise electron‐opaque Al2O3particles. The technique involved embedding a dense collection of particles in an Epon mixture and sectioning with a diamond knife on an ultramicrotome. Serial sections were utilized to obtain three‐dimensional information. It was found that ultramicrotomy does not introduce artifacts in ceramics which would otherwise affect measurements of the crystallite size or phase fraction, nor does it affect the crystallographic data significantly.It was observed that α‐Al2O3nucleated at the surface of isolated particles and in the neck region of sintered particles. Other data, obtained from diffraction and in situ hot‐stage studies, indicated that each polycrystalline α‐Al2O3particle transformed to a nearly single crystal of γ‐Al2O3, which extended into adjacent particles under favorable

ISSN:0741-0581    

DOI:10.1002/jemt.1060020104

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

年代:1985

数据来源: WILEY

摘要:

AbstractWe have found that ultrathin Formvar films are easily and reliably made at an air‐water interface by the drop method. By varying the concentration of Formvar in the drop, films of different characteristics can be obtained. Concentrations of 0.25–0.4% in ethylene dichloride produce extremely flat, ultrathin, and stable films that are especially suited for shadowed and negatively stained preparations. Low concentrations (⩽ 0.1%) produce nets consisting of many tiny holes which, after carbon stabilization, are ideal for supporting high‐resolution samples. Above 0.5%, films made by the drop method develop bubbles, and this bubble defect makes them unsuitable for section support.For section support, Formvar films made by the stripping method off mica are far superior to those made off glass. The films are more uniform in surface contour and thickness. They are less readily attacked by alcohols. Consequently, they are more resistant to staining procedures involving organic solvents and continue to be strong and uniform for section

ISSN:0741-0581    

DOI:10.1002/jemt.1060020105

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

年代:1985

数据来源: WILEY

摘要:

AbstractFore‐vacuum (pressure ≥ 3 Pa) evaporation of carbon fibers and rods to thin films has been tested and the resulting thicknesses recorded. A modified sputter coater was used as a vacuum evaporator. The quality of the carbon films was evaluated by bright‐field and dark‐field electron microscopy. Although high‐vacuum‐evaporated carbon films are superior in quality, low‐vacuum‐evaporated carbon films were found fully acceptable for routine work in bright field, for both TEM and SEM purposes. Apart from being time‐saving, the method presented has the obvious advantage, in SEM preparations, that carbon coating and metal sputtering can be carried out in the same unit without br

ISSN:0741-0581    

DOI:10.1002/jemt.1060020106

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe cold stage specimen surface in our Balzer's 300 Freeze‐etch instrument, averages 29–43°C warmer than the reading on the GA‐1 stage temperature control unit. By introduction of Indium foil seals above and below the stainless steel plug in the stage tower, the specimen cold stage surface temperatures were still 9–10°C warmer than the GA‐1 reading. After replacing the stainless steel plug with a copper plug and using Indium seals, the cold stage specimen surface was brought within 2.6°C of the GA‐1 temperature reading. In addition, the copper plug, Indium seal modified stage cools about two times faster in going from –100°C to –150°C than the normal stainless steel stage modifi

ISSN:0741-0581    

DOI:10.1002/jemt.1060020107

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

年代:1985

数据来源: WILEY

摘要:

AbstractA major difficulty in preparing frozen‐hydrated specimens from solutions is to control an optimal thickness of water remaining on the EM grid just before it is immersed in liquid nitrogen. In this report, we describe a modification of the fatty acid monolayer technique for preparing frozen‐hydrated specimens. With the use of this technique, all excess solvent is removed when a behenic acid (a fatty acid) monolayer film is picked up over the surface of the electron microscope grid. Low‐dose electron diffraction patterns and optical diffraction patterns of low‐dose micrographs of bacteriorhodopsin (bR) ofHalobacterium halobiumthus prepared show strong reflection orders at a resolution of ∽4 Å and ∽10 Å, respectively. Because the preparation of thin, hydrated specimens by the behenic acid monolayer technique does not depend upon evaporation of water, a dramatic change of ion concentration and pH is not expected to occur. The method should be applicable to specimens which need to be kept in a specific buffer and/or at a specific i

ISSN:0741-0581    

DOI:10.1002/jemt.1060020108

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

年代:1985

数据来源: WILEY

摘要:

AbstractRecently we have been making extensive use of TEM observations of grain boundaries in a research program concerned with the deformation behavior of tungsten bicrystals. A major problem in this research involved the preparation of thin foils which contained the grain boundary in the electron tranparent region, since standard cell type electrojetpolishing techniques do not allow adequate control of the placement of the thin area. Since the grain boundary comprises a very small percentage of a foil, good thin area placement control is critical to obtaining useful samples consistently. Masking techniques which use electrically insulating lacquers are not precise enough to guarantee the position of the thin area. However, we have found that one can use the dishing characteristic of the jetpolisher (i.e., the fact that the center of the foil thins faster than the perimeter) in conjunction with the masking technique to predict the position of the thin area within a preferentially thinned region created by the masking procedure outlined below. This is the essence of the procedure outlined below.

ISSN:0741-0581    

DOI:10.1002/jemt.1060020109

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

年代:1985

数据来源: WILEY

ISSN:0741-0581    

DOI:10.1002/jemt.1060020110

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

年代:1985

数据来源: WILEY