RE: [Histonet] tissue processing

From:LuAnn Anderson

Sheehan states "at least 15 to 20 volumes of 
fixative should be used for every volume of tissue"
pg. 49---in the  "Tissue-Handling fixation chart".

At 07:53 AM 4/24/2007, Rittman, Barry R wrote:
>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-----
>[] On Behalf Of Rene J Buesa
>Sent: Tuesday, April 24, 2007 7:18 AM
>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.
> wrote:
>   Hello,
>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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