Denise,

The simplest way is to process the samples through to the final 
change in 100% EtOH, as for paraffin embedding. At this point, throw 
the samples dripping with EtOH into liquid nitrogen. Since there is 
no water in the samples, and since EtOH freezes vitreously, there is 
no freezing damage. Tightly grip a razor blade with a hemostat, put 
the edge of the blade on the skin when you wish to fracture and 
either press down or give the lock of the hemostat a sharp rap with a 
weighty rod (or the like). You will likely get many pieces, not just 
2.
Move the pieces to 100% EtOH, then process as usual.
The sample can also be placed in a "teabag" for processing -- I 
forget their official name, but they've been discussed on histonet 
before. But. The teabag will also fracture, making gathering up the 
pieces more entertaining.
Sometimes the sample has to be immersed in EtOH, not just soaking 
wet. In this case, make a pouch out of parafilm (cut out a rectangle 
just more than 2X the size of the sample, fold in half, crimp 3 edges 
tightly closed, fill with sample and 100% EtOH, crimp closed the 4th 
side) and throw this in the liquid nitrogen.
Ethanol cryofracture is discussed in EM texts and in the primary 
literature. Sorry, but I don't have any references to hand, just my 
quondum memory. A good source of of microscopy tips -- mostly EM, but 
still useful to light microscopists -- is this site from the Univ. of 
Florida:
Tips & Tricks of Microscopy
http://www.biotech.ufl.edu/~emcl/tips.html

Phil

Hi,
I've been asked to learn how to freeze fracture skin samples.  HELP!
Anybody out there know how to do this and can send me a protocol?
thanks a bunch,
Denise Long Woodward
Harvard Skin Disease Research Center
Brigham & Women's Hospital
Boston, MA


-- 
Philip Oshel
Supervisor, BBPIC microscopy facility
Department of Animal Sciences
University of Wisconsin
1675 Observatory Drive
Madison,  WI  53706 - 1284
voice: (608) 263-4162
fax: (608) 262-5157 (dept. fax)