ISSN:
0741-0581
Keywords:
Plastic flow
;
Section surface relief
;
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Natural Sciences in General
Notes:
The technology of ultramicrotomy is now well established, but the properties of the resin that determine the different forces needed to generate a section have been neglected, although this process could introduce artefacts in the thin sections. We have investigated the principal resin dependent factors involved in the sectioning process and determined the related mechanical properties. Tensile experiments have given the best correlation with the sectioning quality of the resin: the elastic (Young's) modulus value (depending on polymer structure or hardening mode), the presence of a short plastic flow for a controlled fracture and enough flexibility to minimize shearing, and internal cracks, appear to be the main characteristic parameters. The ultrathin section seems to be generated by a process close to cleavage, favoured by the relative hardness of the embedding media, while machining and “true” sectioning requires softer resins.Consequently, the rupture follows the path of least resistance in the specimen-resin composite, providing sections with a surface relief. Embedded biological material copolymerizes with polycondensed matrix (epoxy resins), and, by reducing the heterogeneity, gives smoother sections. Embedments hardened by radical polymerization provide a rougher relief, since almost no copolymerization occurs, offering to the microtome a heterogeneous block with two constituents of very different mechanical properties. The surface relief seems to be an important factor in labelling, staining, and imaging, and more attention has to be paid for some improvements of the quality of the information provided by electron microscopy.
Additional Material:
9 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jemt.1060060109
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