>I think the problem is in the initial freezing of the brains. Ice crystals
>will grow if the tissue is not frozen fast enough i.e. snap frozen in liquid
>nitrogen.

Better in an isopentane slurry in LN2. The isopentane has less of an 
insulating effect when it evaporates than LN2 alone. The best way of 
course is to use a brain blower which can give homogenous water ice.

Bill
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Wm F Blank MD
Heartland Laboratory, Inc
Chaffee, MO 63740