You could avoid fixation entirely, snap freeze fresh tissue and section.
The sucrose is to cryoprotect the tissue, and water in fixative makes for
some crunchy sectioning after freezing, been there, fought with that,
morphology wasn't great. 

Some people dilute OCT with PBS, let fixed tissue sink to bottom, hopefully
to fulfill what sucrose is supposed to do.  The OCT componenets,
polyethylene glycol and polyvinyl alcohol,  molecular weights are
proprietary, so you will not know if they are large MW and not infiltrate
into tissue spaces (as sucrose would).  



At 02:53 PM 1/15/01 -0600, you wrote:
>Hi, I am doing cryo sections on animal tissue and will be doing snap
>freezing  with liquid nitrogen. The tissue specimens will be fixed before
>hand in 4% Para formaldehyde, I do not want to store in sucrose overnight
>because of the potential for interference with immunohistochemistry. Does
>anyone have any ideas on what I can use as substitute? Thanks Jenny.
>
>
>
Gayle Callis
Veterinary Molecular Biology
Montana State University
Bozeman MT 59717-3610
406 994-4705
406 994-4303