How badly antigens get crosslinked and then how hard they are to retrieve
depends on a lot of issues, but in essence, the answer is yes, some are
harder to retrieve. For instance, some antigens (like actin, if you're
looking for smooth muscle cells, or many keratins), are located inside
the cell and are present in whopping amounts. That makes them very hard
to hide, even after extensive crosslinking. Others, like cell membrane
markers, have less signal to begin with and are much more subject to
being crosslinked and made unavailable for localization.
When I don't know exactly what I might be looking for, I would say be
conservative, within reason. I used to work at a place that required
(after an 8-hour perfusion experiment, thank you) samples to be split and
fixed in formalin, Karnovsky's, Trumps, PVA/Paraformaldehyde, and fresh
frozen. This made for very late nights and was overkill. Formalin with
zinc is probably a good compromise for most things.

Jeffrey Crews, HTL (ASCP)

PS Did I mention that we had to go through 3 buffer rinses after 1 hour
in the PVA/PF? But I'm not bitter about it.   jc




On Tue, 11 Jul 2000 15:16:40 -0500 DELONG_CYNTHIA_A@LILLY.COM writes:
>Hello everyone,
>
>I have a fixation question regarding saline perfused brains.   What is 
>the
>difference in drop fixing brains in zinc formalin vs 4% 
>Parafomaldehyde?
>Or is there?      These are then cryo protected and froze in liquid
>nitrogen.   It seems as though zinc produces the same results.  Are 
>certain
>antigens harder to retrieve?
>
>Just curious
>Cindy
>
>
>

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