摘要:

SUMMARYExamples of plastic deformation are illustrated from a wide range of specimens that have been prepared for electron microscopic examination by fracturing at low temperature prior to replication of the frozen surface. Deformation has been shown to occur in some specimens when fractured at temperatures as low as 4 K.Plastic deformation is recognized in non‐biological polymers such as polystyrene and polyacrylate latex spheres, as well as in similar biological molecules such as poly‐β‐hydroxybutyrate (PHB). However, it is also demonstrated that plastic deformation occurs widely in more complex biological systems, including membranes and protein macromolecules.The interpretation of the structure of fracture faces of frozen membranes, and particularly the lack of complementarity on opposing fracture faces, is discussed in relation to deformation artifacts.It is concluded that very considerable energy must be dissipated as heat during the cleavage process. In the case of some of the latex spheres, the glass transition temperature(Tg)of the bulk polymer can be more than 200 K above the cleavage temperature, and yet plastic deformation still occurs.Once a molecule has deformed, its appearance in the final replica may be significantly changed by heating during evaporation of the replica. An empirical attempt has been made to define the factors leading to the ‘survival’ of a deformed particle.Although the evidence in this review has been drawn from freeze‐fracture and freeze‐etching studies, it is emphasized that the process of cleaving at low temperature—whether in freeze‐fracture techniques or in cryoultramicrotomy—is essentially the same. Therefore the interpretation of structure in ultra‐thin frozen sections will also need to allow for the possibility of

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00009.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYIt is described how inference concerning the geometrical structure of a two‐phase specimen may be carried out on the basis of sampling subregions or ‘quadrats’. Two basically different situations are considered—firstly when the specimen itself is the centre of interest, and secondly when the specimen is only part of a larger body of interest Weighted random quadrats are shown to be useful in the first case. Serial and multistage sectioning, and the incorporation of supplementary information via Monte Carlo techniques, are also di

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00010.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYAn improved anodization technique for the production of thin samples of GaAs and other III‐V semiconductors which are suitable for TEM studies is describe

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00011.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYThe critical point drying method of preparing samples for scanning electron microscopy is associated with a variable amount of specimen shrinkage. We studied the causes of this phenomenon in isolated mouse hepatocyte nuclei and in human erythrocytes and found that the critical point drying process itself caused most of the shrinkage that we observed (a 25–30% reduction in diameter in both specimens). Glutaraldehyde fixation and ethanol dehydration caused only minimal size reduction, prior to critical point drying. Substitution of an inert (ethylene glycol‐ethylene glycol monethyl ether) dehydration technique did not alter the final result. Previous studies in our laboratory using high resolution SEM and correlative transmission microscopy of isolated nuclei have demonstrated that the shrinkage represents a miniaturization of the organelles in which all structural components retain their usual relationsh

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00012.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYThree improvements, which we have investigated, promise to lead to a scanning ion microprobe with a space resolution of about 15 nm. The improvements are: (1) use of a field‐evaporation (EHD) ion source with liquid gallium to give a brightness exceeding 1010A m−2sr1at 21 keV, (2) a high efficiency (10%) collecting system for secondary ions, and (3) enhancement of the secondary‐ion yield by cesium deposition. With this instrument, tracing with stable isotopes would offer a number of advantages over autoradiog

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00013.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYEpoxy‐embedded blocks of glutaradehyde and OsO4fixed adenohypophyseal tissue were immersed in performic acid, rinsed and sectioned for electron microscopy. Sections exhibited a general image intensity equivalent to control sections but their stainability with both uranyl acetate and lead citrate stains was increased. It was concluded that osmium was not removed by performic acid oxidation.Membranes of endoplasmic reticulum and the Golgi apparatus were not visible, and other components (acidophil granules, in particular) were markedly distorted in shape after oxidation. Such changes, however, were not evident in specimens previously exposed to uranyl acetate during ethanol dehydratio

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00014.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYThe ligand osmium binding technique utilizing thiocarbohydrazide has been a successful alternative to evaporation or sputter coating of botanical specimens. A modification to this technique is presented which we have found successful in our laboratory for the preparation of a variety of specimens. This technique permits an overall reduction in the quantity of osmium necessary to provide conductivity. Further, dehydration time and specimen handling is reduced by the complete chemical dehydration of the tissue utilizing 2‐2‐dimethoxyprop

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00015.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYA technique is described for obtaining clean cut surfaces on wood samples prepared for the scanning‐electron microscop

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00016.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYThe silhouette system, although requiring a darkroom, gives the experimenter a powerful method of recording the biological populations in large samples of water with great depth‐of‐field. The short exposure also effectively stops the motions of the subjects. No optics are required for the initial exposure but are required for enlargeme

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00017.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Book reviewed in this article:Principles and Techniques of Electron Microscopy: Biological Applications, Vol. 6. Edited by M. A. Hayat.Electron Microscopy in Mineralogy. Coordinating Editor: H.‐R.Wenk. Editorial Board: P. E. Champness, J. M. Christie, J. M. Cowley, A. H. Heuer, G. Thomasand N. J. Tighe.Basic Biology Course, Unit 1, Microscopy and its Application to Biology: Book 1, Light Microscopy. By M. A. Tribe, M. R. Erautand R. K. Snook.Basic Biology Course, Unit 1, Microscopy and its Application to Biology: Book 2, Electron Microscopy and Cell Structure. By M. A. Tribe, M. R. Erautand R. K. Snoo

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb00018.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY