Main factors causing ultrastructural preservation artefact

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Below is a summary of the common factors that negatively affect the performance of the examination and/or interpretation of EM results:

  • Delayed fixation: Detrimental ultrastructural changes begin immediately upon removal of blood supply. The longer the delay: the more significant the ultrastructural artefact. Note: Although the use of saline may advantageous from the point of view of preventing the tissue drying out, it does not provide fixation and therefore has an overall detrimental effect for electron microscopy.
  • Inadequate fixation: This can affect a sample even if immediately placed into fixative and be caused by multiple factors including:

– sample size too large
– fixation time too short
– fixative to weak
– wrong fixative

  • Defective buffer: A suboptimal pH of the buffer can lead to significant artefactual changes to tissue ultrastructure. The effect is time dependant.
  • Dewaxed samples: The ultrastructure of tissue samples that are embedded in paraffin wax and subsequently dewaxed and reprocessed into resin for electron microscopy is significantly affected by the stresses afforded to it by the process involved. The ultrastructural appearances of dewaxed samples are unreliable and potentially misleading in certain diagnostic scenarios

(Last reviewed 19th June 2018)