Hi Nicola,
You haven't given any details about how your blocks were 
prepared, so I will just jump into some suggestions (you may 
already be doing some of these things). I apologize in advance for 
the lengthy reply!

My absolute preferred way to get excellent frozen sections is using 
a system I came up with a number of years ago (it was an original 
idea at the time, but I'm sure others have worked out similar 
protocols for themselves). 

I used the old Peel-away embedding moulds, (I think they are still 
available in many different shapes and sizes). I like these because 
you can write on them, and if you are careful about taking your 
blocks out, you can reuse them. I would put enough OCT in the 
mould to cover the bottom. Then orient the tissue in the mould as 
you would for paraffin sectioning. I would also have a shallow 
styofoam box (a shipping container is all I used-shallow enough to 
to able to reach in and out of easily) with an aluminum foil "boat" 
floating in liquid nitrogen. I then placed the Peel-Away moulds on 
the floating foil boat and watch for the OCT to start to freeze. Once I 
know the freezing has reached the tissue, but before the rest of the 
OCT has frozen, I top up the OCT enough to cover the tissue (this is 
important- don't let all the OCT freeze before covering the tissue, or 
your block will break apart into an upper and lower half). I like the 
tissue to freeze to the bottom first so that I know it will not float up. 
This is particularly useful with lungs or with any this tissues that tend 
to fall over when you are trying to get them to stand on their edge.

I then place the frozen blocks for each case in their own Whirl-Pak 
bag label it (watch your fingers!), and place them either in the 
cryostat or in the freezer. They will keep for years like this because 
"freezer-burn" is no longer an issue. 

When it is time to cut, if you just warm the sides of the mould slightly 
with your fingers, you can squeeze the sides of the mould and the 
block will pop out. Now, put a few drops of OCT on a warm (room 
temp) mount (or chuck, or whatever it's called?) and press your 
block in place while it freezes. Now when you cut your sections, 
there will be OCT on all sides of the tissue, so that not only is the 
tissue supported on all sides, you can use your brush to guide the 
section down on to the knife without pulling or tearing your tissue.

After you (hopefully) have cut your beautiful sections, cover the cut 
surface of the bock with OCT and allow to freeze. Now remove the 
block from the mount and store it, sealed in its Whirl-Pak bag. This 
will keep the tissue from drying out, and they will keep for years.

If you are still having trouble getting the sections to stay together, 
you are correct to try different cutting temperatures. If the knife 
angle was okay for other tissues you have cut, then it should be 
okay for these skin samples. Sometimes in desperation, I will lightly 
rub my thumb over the cut surface of the block and then quickly try 
to get the next section. 

Good luck with it!
Greg  

Date sent:      	Mon, 26 May 2003 11:29:35 +0100
From:           	ncragg 
Subject:        	Problems cryosectioning skin
To:             	'HistoNet Server' 

> Please can someone advise me on how to cut good cryosections of skin? I am 
> having real trouble getting good mouse sections, the tissue tears and 
> separates from the OCT as I'm cutting it. I've tried changing the 
> temperature, from -20 to -15, as the manual for the cyrostat seem to be 
> saying the temperature was too cold, changing the clearance angle, new 
> blades, changing the speed - I'm exasperated. I know it does take a lot of 
> practice to get the technique right, I learnt this with paraffins, but I 
> really don't know what I'm doing wrong. Please help!! I have 200 samples to 
> cut!!!
> Yours desperately,
> Nicola Cragg
> 
> 
> 
> 


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Greg Dobbin
Pathology Lab
Atlantic Veterinary College, U.P.E.I.
550 University Ave.
Charlottetown, P.E.I.
Canada,  C1A 4P3
Phone: (902)566-0744
Fax: (902)566-0851
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"A farmer is a person outstanding in their field."