Effect of fixation protocols on muscle preservation and in situ diffusion distances

In order to examine the effects of various methods for tissue preparation on ultrastructural analyses, and hence standardize reported values, six commonly used fixatives were examined for their quantitative effect on muscle fibre size and capillary dimensions. Both the composition and osmolarity of fixatives affected structural indices significantly, producing a range of values of similar magnitude to that presented in reports of structural adaptations. When comparing data from different studies, therefore, it is essential to establish that dissimilar values reflect different tissue composition, rather than methodologies. The method of choice for quantitative analysis of intracellular diffusion pathways uses a combined aldehyde fixative with a metabolic poison, and an isotonic buffer as vehicle.