[Histonet] tissue processing

Rittman, Barry R Barry.R.Rittman <@t> uth.tmc.edu
Tue Apr 24 07:53:36 CDT 2007

René raises an interesting point. 
While we all accept the 20:1 ratio for fixation as our standard to aim for, I do not believe that this has actually been studied or published as original paper. Please let me know if I am incorrect in this statement.
The 20:1 ratio is one of those items that are always passed along.
In fact it has been suggested that the concentration of the main fixing agent (within certain limits) and the time of fixation are more important considerations. This principal is used in tanning leather when the amount of glutaraldehyde is carefully matched to the quantity of the proteins in the leather. The aim is to have just the right amount of glutaraldehyde. Excess glutaraldehyde would end up permeating various parts of our anatomy close to the billfold for example.
In most labs we only carry out a partial fixation. This is necessitated by time constraints, immunohistochemistry etc.
An alternative to immersion fixation for small or thin sample sis vapor fixation. This has the added advantages that no carrier vehicle is necessary, small amount of sometimes expensive fixing agents can be used.

-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu [mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Rene J Buesa
Sent: Tuesday, April 24, 2007 7:18 AM
To: histonet <@t> lists.utsouthwestern.edu
Subject: Re: [Histonet] tissue processing

If you are using a tissue processor (TP) you do not have to worry about this problem but since you asked it seems that you are going to process manually.
  If that is the case you should maintain the same volume ratio of 20:1 as when fixing.
  The other thing (if processing tissue manually) is that you will not have agitation, pressure, vacuum or controlled temperature, so time has to be increased (as compared with an automatic TP) for each step.
  Volume alone will not determine proper processing without the other advantages of a TP and these disadvantages have to be compensated with longer steps.
  René J.
mwstarbu <@t> mdanderson.org wrote:

Is there a standard tissue volume to liquid volume ratio that you use when 
dehydrating samples with ethanol?
Thank you in advance.

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