X-Message-Number: 20291
From: 
Date: Sat, 12 Oct 2002 10:56:20 EDT
Subject: I freeze human cells every week....

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> The difference between successful cryopreservation and failure lies with
> size and achievable cooling rates. A single cell survives freezing if it
> cools so last that the entire cell freezes at once. Such cooling must take
> place at around 1000C per minute, even when using cryoprotectants.

  ?? We routinely freeze many different types of human cells in the 
Shay-Wright lab. We make a 10% DMSO/90% fetal calf serum freezing media, and 
then we put the cryovials in special freeze boxes full of isopropanol which 
SLOW DOWN the rate of cooling to roughly one degree Celsius per minute until 
they reach -80 Celsius. Then we throw them into the -150 for long-term 
storage. This is how cells have been frozen for over thirty years.
  What, exactly, was the source for the -1000C per minute figure?  -Bill 
Walker


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