Re: formalin substitutes

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From:"J. A. Kiernan" <>
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On Wed, 7 Jun 2000 wrote:

> What non-formaldeyde based fixers are people using to preserve antigens in
> paraffin sections? I have been using zinc formalin with little improvement
> and am looking for something else. Does anyone used Shandon's Glyo-Fixx?
> Are there tried and true ones out there?

  The only reasonable answer to your question is that you should
  try some alternatives. This is the only way to find out if the
  immunoreactivity of an antigen to a particular serum or
  monoclonal is preserved. For preservation of structure, there's
  a large body of peer-reviewed literature, much of which has
  been summarized in textbooks. The following paragraph makes a
  case for trying an extremely simple fixative that's been
  around for a long time. 

  If you are going to cut paraffin sections an acidic and 
  predominantly coagulant fixative may provide better
  antigenic and structural preservation than a neutral buffered 
  aqueous formaldehyde mixture. A very simple one that's been
  around for 149 years is Clarke's fluid: 3 volumes of alcohol
  (95% or 100%) and one volume of glacial acetic acid. These
  ingredients penetrate rapidly and coagulate proteins and
  nucleic acids (respectively) on contact. A 5 mm cube is
  fixed in about 6 hours and can then be moved into 95% alcohol.
  Don't fix for too long, or there will be some extraction of
  RNA and this will spoil any conventional staining method that
  makes use of a basic dye. 
  It's important to know the exact composition of any fixative
  you use, and the action of each ingredient. Fixation affects 
  immunostaining and conventional staining more than any other 
  preparative event.

 John A. Kiernan,
 Department of Anatomy & Cell Biology,
 The University of Western Ontario,
 LONDON,  Canada  N6A 5C1

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