Fellow Histonetters,
I have a question regarding tissue fixation via perfusion. I have a PI who has, on two occcasions, submitted mouse tissue that has been perfused (liver, kidney, skin, small bowel-whole body perfusion). I have found on both occasions that the tissue (particularly the liver and kidney) seems very dry. I have processed other tissue for her that has not been perfused but fixed in 10% NBF  (Fisherbrand) with very good results using the same tissue processor and processing schedule.
My question is -could this perfusion technique be over fixing the tissue? I think she uses formalin (lab made from paraformaldehyde) for the perfusion then continues to fix the tissue in formalin (Fisherbrand) for 4 hours after harvesting it. Do I need to compensate for this procedure by shortening my tissue processing schedule? 
I have looked through the histonet archives and found some information. Any suggestions are greatly appreciated.
Thanks in advance,
Ron Martin, HTL (ASCP)HT
Research Associate