[Histonet] RE: Tissue Freezing Medium

gayle callis gayle.callis <@t> bresnan.net
Thu Sep 17 12:43:36 CDT 2009

One has to be careful in calling ALL cryoembedding mediums OCT since this is
a trademarked product from Sakura Finetek, under the name Tissue Tek OCT.
If you use other than OCT, then you need to give the name and specify WHICH
brand you are using in order to lessen confusion.   


Out of curiosity and always shopping for a new product, we have tried as
many cryoembedding medias possible  and found them to be different from each
other e.g. none of them are exactly the same nor do they work for all
applications as in research where one may fill an intestine or lung with a
cryoembedding media.  The differences are the in the ingredients, what
molecular weights may be involved for the polyethylene glycol or polyvinyl
alcohols used or other ingredients that may be different.   Be sure to look
at the label and MSDS (hopefully tell the chemicals used!)  and if you know
which one you had success with to start with, I suggest going back to that
media.   The original Tissue Tek OCT has the ingredients written on the
bottle, but some information, the molecular weights of the PVA and PEG is
proprietary. - the only information is percentage of the ingredients listed.


As a side comment, I was fortunate to have a discussion about OCT with Dr.
McCormick who was involved with develop  OCT for Miles/Tissue Tek aka
Sakura.  He said he could make up different mixtures for use at whatever
cryosectioning temperature was desired.  


After trying a new (and graciously supplied by vendor) cryoembedding media
that did not work for our research application, I learned via the company
tech services  the product had only been tested on human tissues, and never
with research animal tissues. 


 Consequently,  we  continue to use Tissue Tek OCT  and at any temperature
we desire, from - 16C to -35C and at section thicknesses from 2 um up to 50
um or more.   It also worked perfectly for our human renal biopsy service
for over twelve years.   


The one message changing temperature according to tissue type is good
advice.  However, in a clinical diagnostic setting and under time
constraints, this could  be difficult unless a cryostat has two compressors
to speed up specimen temperature change.  There are other ways to cool a
sample - one suggestion from years ago was an awkward setup to let liquid
nitrogen fumes falling down and over the sample to cool it before sectioning
although some techs now spray Liq N2 on the sample.  Cryosprays are not
something I care to breathe however.   Also make sure your blade holders,
etc are tight, well adjusted - someone may have inadvertently changed
settings.  Or are you working with new brand of disposable blades - another
parameter to consider?     


Good luck on solving the problem 


Gayle M. Callis







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