摘要:

SUMMARYEasy preparation of thin crystalline specimen supports for high resolution electron microscopy has been achieved by thermic exfoliation of vermiculite. The thinnest layers obtained appear to be 1·8 nm thick and show the expected hexagonal array with a 0·46 nm lattice spacing. This periodic background could be suppressed either by optical filtering or by putting a zero crossing of the respective transfer function of the electron microscope objective over the diffraction spots of the crysta

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03874.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYA method is described for making thin foil apertures by piercing a plastic film with a heated microneedle and subsequently metallizing the plastic film by vacuum evaporation. Apertures can be made with diameters from 5 μm to 100 μm. They are round and very sharp‐edged and can be made in various patterns and combinations of si

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03875.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY‘EM grade’ glutaraldehydes from three suppliers were tested for the following: (1) pH of stock solution, (2) 235/280 nm UV absorbance ratio, (3) milliosmolarity of 2% and 4% solutions, (4) quality of fixation produced in ovarian tissue by fixatives prepared from each stock solution. Low pH of the stock solution appeared to be the most detrimental factor in fixation. Fixatives with a low 235/280 nm ratio (between 0·18 and 0·67) did not give good fixation regardless of the pH of the stock solution. Fixatives made from stock solutions with a pH above 4 and a 235/280 nm ratio between 1 and 2 resulted in the best preservation of ultra‐structure. Variations in milliosmolarity from one batch of stock solution to another were encountered, but appeared to have no correlation with the quality of fixation.; Received 1 October 1973; revision received 20 Decem

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03876.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYThe nature of the reaction product and non‐specific staining obtained using lead salt methods, for localizing phosphatase activities, has been determined using energy dispersive X‐ray microanalysis. The detectability of ‘non‐electron dense’ elements has permitted the development of an alternative azo dye method involving the coupling of an enzymatically released, insoluble primary reaction product with the active diazotate of 2, 5‐dichloroaniline (Fast Scarlet GG). The resultant azo dye was detected in ultrathin cryosections. The localization achieved by this method and the advantages of combining ultracryotomy and X‐ray microanalysis with enzyme cytochemistry

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03877.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYDimensional measurements have been made on a small number of tracings of low magnification scanning electron micrographs of trabecular bone sections, using the Quantimet Image Analysing Computer, with a view to expressing the properties of the local bone pattern in a quantitative manner.Measurements of the orthogonally projected length of the boundary profile of the interface between bone and marrow were made as a function of the direction of projection, and these showed that the majority of the patterns were distinctly anisotropic.A formula is proposed for calculating the mean widths of the trabecular bands as they appear on the surfaces of the sections, from the mean area of bone and the boundary profile length. As the validity of this formula is not theoretically evident, the results have been compared with direct experimental measurements, and found to agree very well.The mean intercept lengths in the bone and in the marrow spaces have been calculated as a function of direction across the section. The polar diagrams of these lengths are found to have the shapes of ellipses, to an unexpected degree of accuracy. This makes it possible to express the departure from isotropy of the pattern by a single number, for instance by the ratio of the axes of the ellipse.The essential limitations of the methods used in these experiments are briefly discussed, in particular the impossibility of finding the exact symmetry properties of the surface patterns by experiments of this type.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03878.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYIt is postulated that there may be classes of microstructures, having anisotropic internal features, which are related to internally isotropic structures by a coordinate transformation. Such structures are known to occur, for instance, in metallography when the bulk material has been subjected to deformation and there are many biological analogies.The simplest case of coordinate transformation is investigated theoretically in this paper; that of a linear transformation in one dimension. Formulae have been found for the numerical constant which allows the density of the internal surface which separates two components of the material to be calculated from the border profile density on a plane section through the material.Measurements on trabecular bone have suggested that it may be a structure of this type, and, on this assumption, the errors due to incorrectly assuming isotropy, when calculating the area of the surface which separates the bone from the marrow, are discussed.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03879.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYTechniques for obtaining complementary replicas have already been shown to be valuable in aiding the interpretation of electron micrographs of replicas of specimens prepared by freeze‐etching and freeze‐fracturing techniques, and in the recognition of artefacts. This paper describes a simple and efficient method of obtaining complementary pairs of replicas of all types of specimen. Ordinary hollow brass rivets are used as specimen holders and are frozen in an end‐to‐end position using a special pair of forceps. Up to six rivets are placed in a device consisting of a hinged plate held together with clamps against the force of small springs. When the clamps are released, the pair of rivets are separated, fracturing the specimens. The device is easily adapted for use in any type of freeze‐etching or high vacuum apparatus. On the example ofSaccharomyces cerevisiaethe application of the technique to the detection of artefacts in complementary replicas are described. It was shown that the fibrils observed on cross‐fractured cell walls are produced by plastic deformation of cell wall

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03880.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYThis paper describes a simple technique for obtaining complementary replicas of specimens fractured under liquid helium. Ordinary hollow brass rivets are used as specimen holders and are frozen in an end‐to‐end position. The pairs of rivets are placed in a device consisting basically of two concentric steel tubes which can be twisted and moved relative to each other guided by a peg‐in‐slot mechanism. The rivets are inserted while the device is under liquid nitrogen, and the device is then transferred to liquid helium and the tubes are moved so that the upper rivet is knocked away and falls into a collector. The device is then transferred back to liquid nitrogen, the fracture faces being protected from contamination throughout the process. Replicas are then obtained by any of the standard methods for specimens fractured under liquid nitrogen. The device has been tested using yeast cells as a model system, and some typical results are presented and di

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03881.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYA simple anti‐roll plate has been designed for use in preparing ‘dry’ ultrathin frozen sections. The plate, which is made of a strip of a glass cover slip and attached close to the edge of a glass knife, prevents curling of the sec

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03882.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYIf a freeze‐etch replica is not completely clean, some problems may arise concerned with interpretation. These can be particularly misleading in the case of freeze‐etched cellulose microfibrils. The interpretation of such replicas is discussed, and the method of image formation from a clean replica is demonstra

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1974.tb03883.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY