I do this all the time and it is worth it to get better sections.
As I just mentioned to Rich Cartun, I remove the frozen block from the freezer
and place it directly in to RT fixative, let it melt and change the fixative
solution a few times to wash out the melted OCT or sucrose, then proceed as
with fresh tissue.  You will probably get really good morphology since the
samples were perfused fixed in the first place.
Patsy

"Trenton R. Schoeb" wrote:

> I've received an unusual request from a PI who wants to have HE sections
> made from some mouse tissues. The mice were perfused with paraformaldehyde.
> The tissues were then treated with 3 changes of 30% sucrose buffer, then
> frozen for cryosectioning. He uses this method for studies of the brain. He
> wants to look at the rest of the mouse to see if there are any other
> manifestations of the mutation he's studying. The tissues he has are
> already prepared like the brains (perfused, soaked in sucrose, and frozen).
> We could do HE stained frozens, but I wonder if we can get better fine
> detail if we paraffin embed the tissues. So, my question is, has anyone
> tried paraffin embedding and sectioning fixed frozen tissues such as these,
> and, if so, was it worth the effort? (I expect we'll have to remove the
> sucrose first.)
>
> --------------------------------------------------
> Trenton R. Schoeb, DVM, PhD, Diplomate ACVP
> Professor, Department of Genomics and Pathobiology
> University of Alabama at Birmingham
> trs@uab.edu
> 205-934-2288
> Department office: 205-934-2117
> Fax: 205-975-4418
>
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