Afternoon Listers,

I've had tissue stored in LN2 (immersed) freezer for 4+ years.  RNA
extractions and subsequent PCRs still work as they did in the beginning.  I
have not done quantitative PCR, and I have not tried these tissues for IHC,
but the RNA has apparently not degraded beyond recognition.

If one questions why, the answer lies in the difficulty in obtaining real,
control tissues.  these were harvested, with permission, from brain-dead
cadavers and frozen immediately by immersion in LN2.  They were shipped and
temporarily stored at -80oC before being placed for long-term in the LN2
freezer.

I have done IHC on control tissues embedded in OCT, quenched in LN2,
double-wrapped in heavy-duty Al foil, and stored separately in sealed, heavy
plastic bags up to 24 months after harvesting.  Good qualitative results.

Caveat:  as luck would have it, neither -80 (emergency power circuit) nor
LN2 freezer had a recorded mishap during that period. 

Regards,

Fred Monson

Frederick C. Monson, PhD   
Center for Advanced Scientific Imaging
Schmucker II Science Center
West Chester University
South Church Street and Rosedale
West Chester, Pennsylvania, USA, 19383
Phone:  610-738-0437
FAX:  610-738-0437
fmonson@wcupa.edu
CASI URL:  http://darwin.wcupa.edu/casi/
WCUPA URL:  http://www.wcupa.edu/
Visitors URL:  http://www.wcupa.edu/_visitors/