Hi Terry- I've been doing in situ's off and on for the majority of my 
science career, using both oligo probes and riboprobes.  I've never 
used proteinase K in any of my protocols for frozen sections- during 
the fixing process, there is nomrally a delipidation step which 
normally facilitates probe entry into the cells prior to the 
alcohol-dehydration.

Our lab is quite interested in looking at how different stressors 
affect specific mRNA levels, therefore ISH is a reasonable choice as it 
allows you to look more carefully at particular tissue regions, rather 
than accept an overall mRNA level such as you would get from a Northern.

I realize this has been quite a general reply- I hope it's helped! ;)

Cheers,
Marcus

On Thursday, January 9, 2003, at 06:12  PM, Johnson, Teri wrote:

> Me again...
>
> I'd like to pick your collective brains again.  This time I'm looking 
> for
> information regarding doing ISH (RNA probes) on frozen section.
> Does anybody out there do them routinely, and if so, why?  Does one 
> still
> need to use Proteinase K to make the nucleic acids more accessible to 
> the
> probe?  What is your fixative of choice?  What other modifications to
> "standard" ISH protocols are made for frozen sections?  Anything else
> I've left out?
>
> Thanks for your advice!
>
> Teri Johnson
> Managing Director Histology Facility
> Stowers Institute for Medical Research
> 1000 E. 50th St.
> Kansas City, Missouri  64110
> tjj@stowers-institute.org
>
>
.:---------------------------:.
   Marcus Andrews, PhD.
   Department of Physiology,
   Faculty of Medicine,
   University of Toronto,
   1 King's College Circle,
   Toronto, Ontario,
   M5S 1A8
':---------------------------:'