I believe and it is my experience that the paraffin
and the state of the tissue (dehydrated) protects the
paraffin section from RNase activity.  I would worry
more about slides, waterbaths, hands, dust, and for
the most part reagents and clean technique.  Sections
are at greatest risk of contamination after
deparaffinization & rehydration.  I prefer to store my
paraffin unstained sections for ISH (DNA & RNA) in the
ribbon section with only air drying or at most 37C.  I
have experienced loss of reactivity of mRNA in
sections stored for several months after initial
58-62C drying.  This has also been observed with some
antigens for IHC, and some special histochemical
stains.  However, the worse threat to unstained
sections, as I once heard in a story from a person who
worked in Texas- was that the sections had been eaten
by cockroaches while being stored in a lab drawer.  My
advice is:  Feel free to huff & puff, keep the
sections in the paraffin until staining, practice good
clean lab technique, and watch out for the
cockroaches.

Tim Plummer

PS: I am a huffer & puffer and have passed it on to
several others. I learned the method during my student
internship from a Med. Tech who was a supervisor at
the Minneapolis VA.

--- ajennings@unmc.edu wrote:
> 
> Do any of you do RNA in situs? just wondering the
> affect of huffing on a
> block :-)
> 
> 


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