I am fairly new to histochemical techniques, and
have some tissue storage questions. We are freezing whole rat embryo
heads/brains on the fast freeze shelf of a cryostat set to -35 C. Then we place
the frozen tissue in vac-u-pac bags, and store at -20 C, with the intent of
slicing the specimens within a few months. However, I'm now starting a project
where I may not be able to slice and process the tissue (for cytochrome
oxidase activity in the brain) for about a year. Concerning long term
1. What are the advantages/disadvantages of long
term storage in freezers at -20, versus -40, or -80 C?
2. Because I'm already storing the specimens in
vacuum sealed bags, would freezing & storing in OCT add any benefit? (I
have experienced OCT that has become "gummy" after more than a few days when
stored in a Ziploc bag at -20 C, but haven't tried it with the vacuum sealed
3. Would storage at colder temperatures necessitate
a different freezing protocol (e.g. slower or faster freezing)?
I appreciate any information you can give me on