X-Message-Number: 7859
From: Brian Wowk <>
Date: Sun, 16 Mar 1997 00:11:30 -0600 (CST)
Subject: Reply to Jan Coetzee

"Jan Coetzee" <> writes:
	
>If so much repairing is going to be necessary why won't the cryonics
>organizations offer a formalin washout before freezing to save guard
>against equipment failure? Sure there are problems with formalin but I
>think on the whole it is saver on the long run!

	Experiments with fixation followed by freezing have shown
that fixation disrupts cell membranes so that ice (which normally
only forms outside cells) penetrates cells, causing intracellular
freezing.  Intracellar freezing is very damaging, and we want to
avoid it.

	Fixation and vitrification is an interesting idea (I believe
first proposed by Mike Darwin many years ago, and featured in
Drexler's book, "Engines of Creation").  Personally I'd rather
be just vitrified, and accept the risk of storage failure. 
Viable (or nearly viable) cells are going to be a lot easier to
repair than cells where everything has been cross-linked at the
molecular level (what a mess for future repair engineers!).

Re: Cryo Journal Club #5

	The size of cracks formed in vitrified solutions depends
on the temperature at which they crack.  If they crack near Tg,
cracks are large and few.  If they crack far below Tg (with large
accumulated stresses), vitrified solutions shatter into many
small pieces.  These tests have only been performed on pure
solutions; nobody knows if these same principles apply to organs.

***************************************************************************
Brian Wowk          CryoCare Foundation               1-800-TOP-CARE
President           Human Cryopreservation Services   
   http://www.cryocare.org/cryocare/

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