We retain cut blocks for years, some recently cut after 6 years storage, no
loss of antigenicity.

After sectioning, we reseal with a thin layer of OCT, wrap the block with
foil (can be labelled with sharpie marker), placed into a 50 ml centrifuge
tube, tight lid at -80C. Have used zip lock bags for short term storage,
not tried these for years.

Uncut blocks remain in Tissue Tek disposable molds (edges are cut off to
facilitate better snap freeze and fit into 50 ml tubes, also stored for 6
years without problems.   

I think sealing your tissues in foil would be important, to try and avoid
exposure air in -80C freeze, I have seen poorly sealed blocks where tissue
looks freezer "burned" as observed in a home freezer with steaks left too
long (forgotten! in back), turns white, very dry to cut also. One can
always protect tissue a bit before freezing WITHOUT actual embedding  by a
brief soak in diluted OCT or 4% polyvinyl alcohol, water soluble from Sigma
30,000-70,000 MW.  This gives a very thin outer layer around sample. When
you need to section, just embed in OCT (a double embedding method).  We do
this with snap frozen bone, undecalcified, fresh (Dodds et al) without
problems.  

What about using a seal a meal bag, or you can use the seal a meal device
and seal baggies, have done it! to exclude any air for "bare" frozen
tissue.  The whirl pak bags, cut off top and make them smaller for this
purpose, the plastic is heavier, sturdy for banging around in a freezer,
seal a meal tight! This would minimize freezer burn/air exposure.  

 At 09:01 AM 9/20/02 -0400, you wrote:
>We would like to know how long other people/companies retain their frozen
>tissue for (at -80 degrees).  Some tissue would be in OTC and other tissue
>would just be in a plastic bag or tinfoil without any embedding media. 
>
>Thanks
>
>
>Richard Rodriguez
>Schering-Plough Research Institute
>973-940-4282
>
>
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Gayle Callis
MT,HT,HTL(ASCP)
Research Histopathology Supervisor
Veterinary Molecular Biology - Marsh Lab
Montana State University - Bozeman
19th and Lincoln St
Bozeman MT 59717-3610

406 994-6367 (lab with voice mail)
406 994-4303 (FAX)

email: gcallis@montana.edu