"Overprocessed tissue."

From:"Dr. Ian Montgomery"

        Recently there has been series of postings regarding overprocessed tissue that have left me totally confused. The object in processing and embedding in paraffin wax is the complete removal of water from tissue and it's replacement by wax. Therefore if overprocessing has occurred  tissue has been lost and replaced by wax. If that is what's meant then the overprocessed tissue is only fit for the rubbish bin. I really think that the term overprocessing should be dropped and replaced by something more suitable and probably more accurate such as under processed, mis-processed, it wasn't me it was the machine and so forth. From the descriptions people give I think water is still present in the tissue or users have moved away from "proper" clearing agents and rely on xylene or a substitute as the agent of choice which can result in "crumbly" blocks. I still use chloroform, cedarwood oil etc., "real" clearing agents and when the tissue has been thoroughly dehydrated, cleared and embedded the resulting blocks are a dream.
        Then we have the next wee problem. "How long did you fix the tissue." "Oh, not very long, it's only been in Bouin for a couple of months. That's alright, isn't it."

Dr. Ian Montgomery,
Microscopy Service Unit,
Graham Kerr Building,
Institute of Biomedical & Life Sciences,
University of Glasgow,
G12 8QQ.
Tel: 0141 332 8855 Extn.6644.
e-mail: ian.montgomery@bio.gla.ac.uk

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