[Histonet] freezing mouse embryos

[Rita Angel]

Hi all,

I was wondering what is the preferred method for freezing mouse embryos. I 
have a researcher here that said he has previously fixed his embryos 
(13.5d) in 4% paraformaldehyde o/n then placed in 30% sucrose until the 
tissue sank. He then embedding in a mold with oct in liquid nitrogen. He 
said the morphology on these were very good.

However, he brought some today that were not fixed, just frozen fresh in 
oct in liquid nitrogen. The morphology was very poor, and we were unable to 
see tissue structure very well. He thought it was because the tissue was 
not fixed before freezing. I'm wondering if perhaps the embryo was 
necrotic. I asked him if this was possible and he said he didn't think so.

Has anyone done a comparison before? And has anyone had any problems with 
morphology when the embryos were just snap-frozen?

Thank you for your help. I did find a few responses in the archives, but 
not very many.

Rita Angel