Fwd: Re: "Overprocessed tissue."

From:"Dr. Ian Montgomery"

        I buy Cedarwood oil from Merck in the UK but I'm sure there must be a US supplier. As for a schedule the best place is John Kiernan's book, Histological and Histochemical Methods. Chapter 4, Processing and mounting, gives details of clearing agents and  suitable schedules. John's book is one of these texts everyone should have, a mine of solid gold nuggets. Cedarwood oil is a bit expensive so you'd have to weigh the benefits before using heavily. I routinely use chloroform overnight for clearing with a final 15 minutes in xylene as the link agent with wax. If it's a tissue I know will be difficult then it gets cedarwood oil as the clearing agent.

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Date: Wed, 23 Jan 2002 15:53:01 -0700
To: "Dr. Ian Montgomery" <ian.montgomery@bio.gla.ac.uk>
From: Connie McManus <conmac@cc.usu.edu>
Subject: Re: "Overprocessed tissue."

I didn't know anyone still used cedarwood oil for clearing tissues!  Do you
know of a US supplier?  I have only heard of using this, never actually
experienced it.  I would love to try this... if it is economically
feasable.  I want to try it anyway.  Would you care to share your
processing schedule? 

much thanks from across the Pond
Connie McManus in Utah

At 01:40 PM 1/23/02 +0000, you wrote:
>>     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."

Veterinary Diagnostics Lab
Utah State University
Logan, UT
fax (435) 797-2805

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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