I haven't cut fish embryos but I have had the experience with salamanders. 
They too have a "yolky" part that is difficult to cut. I use a shortened 
processing schedule and soak the paraffin blocks in room temp water while 
sectioning. I try to cut the blocks at close to room temperature because I 
often need serial sections. This helps the whole thing stay together and 
not shatter. Sometimes I embed in histogel before processing but process 
and cut the same way. The specimens are very fragile.
Likewise I have not cut frozen fish embryos but have cut other embryos and 
also oocytes. The same holds true for these in that the "yolky" part always 
wants to shatter. This is where making a couple quick passes with the 
gloved thumb over the tissue giving it a gentle rub helps a lot. Sometimes 
no matter what you do the sections will still shatter and then I try 
warming up the cryostat a few degrees.
Andi Grantham




At 09:38 AM 5/30/2003 +0200, you wrote:
>Dear list members
>
>On the question of embryos I have to add that she has tried cutting fixed 
>and unfixed in cryostat. She wants to study lipids.
>
>jose luis

.....................................................................
: Andrea Grantham, HT(ASCP)     Dept. of Cell Biology & Anatomy     :
: Sr. Research Specialist       University of Arizona               :
: (office:  AHSC 4212)          P.O. Box 245044                     :
: (voice:  520-626-4415)        Tucson, AZ  85724-5044    USA       :
: (FAX:  520-626-2097)          (email:  algranth@u.arizona.edu)       :
:...................................................................:
           http://www.cba.arizona.edu/histology-lab.html