X-Message-Number: 13993
Date: Fri, 23 Jun 2000 00:38:39 -0400
From: "Stephen W. Bridge" <>
Subject: Baboon freeze

To CryoNet
From Steve Bridge
In reply to:    Message #13985
                        From: "Dani Kollin" <>
                        Subject: Baboon freeze
                         Date: Wed, 21 Jun 2000 11:23:24 +0200

>Pardon my ignorance but why wasn't the baboon in the below article frozen
>for say, one year as opposed to only 55 minutes?
>Dani Kollin
>Berkeley, California, May 29 1992. BioTime Inc. has, for the first time,
>successfully revived a baboon following a procedure in which the animal's
>deep body temperature was lowered to near-freezing and its blood was
>replaced with BioTime's patent-pending blood- substitute solution.
>The animal was anesthetized, immersed in ice and cooled to below 2 degrees
>Celsius, using the BioTime solution with cardiopulmonary bypass
>After being bloodless and below 10 degrees Centigrade for 55 minutes, the
>animal was rewarmed and revived. The baboon is presently under study by
>BioTime scientists to determine any long-term physical effects.
>The company intends to conduct further experiments on primates, using its
>blood-substitute solutions.<

I think the key here is that the baboon was not "frozen;" it was "deeply
cooled."  Please note that the press release does NOT say either "frozen"
or "thawed."  It says "cooled" and "rewarmed."  It also says that the
animal's "deep body temperature was lowered to near-freezing."  The
cryobiology experts here (if they have time) will explain this in more
detail (and probably more accurately) than I can. 

Subjecting a large animal to slightly subzero temperatures for 55 minutes
does not freeze it to a significant extent, especially when the blood has
been replaced by protective chemicals.  I do not believe that BioTime's
blood substitute solution contains a cryoprotectant (which would bring up
an entirely different set of chemical issues).  BioTime is marketing this
as a blood-replacement fluid for surgery (and they already have FDA
approval for that), and freezing is not what they are after at this point. 
This length of time at this temperature level is probably about as long as
they can go.  

Still, this is a fairly significant accomplishment in cooling down to the
edge of freezing and may well lead BioTime to pursue actual freezing
experiments with cryoprotectants in the future.

Steve Bridge

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