Frank,
we do a lot of mouse embryo's here at Curis (used to be Ontogeny).
Most of our tissues are fixed first, then placed in 30% sucrose for 1hr, 
then OCT for a few hrs. Embryo's are then frozen in OCT using a dry 
ice/acetone slush.
Sections look fantastic, up to e18 are no problem.

On ocassion, we must cut unfixed embryo's (e12.5). In this case, we 
freeze again in the dry ice/acetone slush insteadof LN2, and the box temp 
is raised to -16c (from -20c).
Sections are placed on PLUS slides.
We've had good success with this method also, but one thing we noticed 
for sagg. sections - orient the emryo vertically on the chuck so the tail 
is cut first, head last and it will cut better.

good luck,
John

--------
Anybody have any tips on sectioning whole mouse embryos?  I'm embedding 
them 
in OCT at -20 C and they are sectioning OK, but the sections don't stay 
together. They split and do not remain contiguous.  This isn't a knife 
nick 
problem, but probably results from the different densities of the various 
organs.
Could someone send me info on the tape transfer system?


John Lydon
jlydon@curis.com, jlydon@ziplink.net