-70 or lower is always better, but if you can't access a lower temperature
freezer, it may be in your best interest to test antigenicity more
We use -80C and have found, with our murine tissue, snap frozen fresh and
embedded in OCT, the antigenicity was retained after 6 years of storage.
Our IHC staining was excellent. The frozen OCT/Tissue blocks were stored
in a screw top 50 ml centrifuge tube.
We avoid lower temperatures, and have a small under the counter freezer
adjusted to -30C for storage of biochemicals, serum, and staining reagents.
People have stored their OCT embedded tissues in this freezer, but not for 6
months. Personally, I have avoided this freezer for block storage mainly
since we have a -80C freezer always availabe. It is important that the
freezer is NOT a self defrosting freezer which I presume you are not using.
Also, are you saying that the vial also contains isopentane and stored in
this freezer? If so, you should not do this UNLESS the freezer is explosion
proof or you will end up like the U of Arkansas lab that blew up and burned
in the wee hours of the morning. Just store the frozen blocks in an
airtight container, i.e. your tube with OCT + tissue, frozen in the tube.
Bob Skinner wrote an article for HistoLogic (Sakura Finetek website) about
the this accident and the dangers of storing isopentane in an improper
There has been a great deal of discussion concerning frozen block storage on
Histonet, so you may want to research it a bit more.
Gayle M. Callis
Bozeman MT 59715
----- Original Message -----
From: "Cathy Malcontenti-Wilson"
Sent: Sunday, April 20, 2008 6:20 PM
Subject: [Histonet] Frozen sample storage
I would like some opinions on the storage of oct embedded tissues. These
samples of animal tissues are embedded into 1 x 1cm pieces of oct and
sit in a vial containing isopentane, and have been stored at -20 degrees
for around 6 months. The freezer is only used for long term storage and
so isn't opened very often (perhaps once per month). In the past I have
stored my oct embedded tissues like this at -70 degrees. What would be
your opinion of the antigenicity in these tissues if they were to be
used for immunohistochemistry??
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