X-Message-Number: 4951
Date: Mon, 9 Oct 1995 14:48:27 -0700 (PDT)
From: Doug Skrecky <>
Subject: variations on a straight freeze

 In message 4946 the American Cryonics Society makes the following
 interesting observations: 
 >>
 Necessity has also required that we all be in the "straight freeze" 
 business. The American Cryonics Society makes a commitment to its members
 to follow their wishes on such questions as: "Under what conditions of
 delay, destruction, and deterioration, do you want to be suspended?" With
 many circumstances of death the circulatory system can't be used. I
 expect that as many as half of the patients now in suspension were
 suspended without cryoprotective perfusion. If that is the reality,
 perhaps research should center more on methods of reducing damage in such
 cases and less on "ideal case" scenarios. 
 <<
 Note: Permission is here given for the following to be reprinted in any
 cryonics related publication that wishes to do so: 

                    VARIATIONS ON A STRAIGHT FREEZE
                           By Doug Skrecky

     With the circulatory system being unavailable in many cases for
 cryoprotective perfusion what are the available options? Here's the way I
 see it: 

 1. Hamburger technique: Pretend that cryoprotectants were used and do the
 usual slow freeze. The result is hamburger. 

 2. Salami technique: Cut the brain into slices 5 mm thick. 
 Cryoprotectants can rapidly diffuse into thin slices of tissue, thus
 preserving them well when they are frozen. The result is a Dagwood
 sandwich. (Cryobiology 24:120-134 1987)

 3. Microwave technique: Microwaves can rapidly penetrate and fix tissue. 
 Pack the brain with ice and place in a microwave. Cook until well done. 
 Treat brain with cryoprotectants by storing it in a concentrated
 cryoprotectant solution for a week. Store in freezer until needed. 
 (Journal of Neuroscience Methods 53:81-85 1994)

 4. Freeze Substitution technique: Freeze brain at -1 C to limit ice
 crystal damage. Pickel brain in an alcohol based cryoprotectant solution
 such as Kryofix till ice has all melted. Baste in liquid nitrogen. 

 5. Quick Freeze technique: Freeze brain at -1 C to partly dehydrate cells
 and reduce subsequent intracellular ice crystal formation. Then dunk in
 liquid propane cooled with dry ice. Rapid freezing limits extracellular
 ice crystal growth. Then slowly cool further with liquid nitrogen vapour
 to limit the formation of cracks due to increased tissue brittleness. 
 (Biophysical Journal Vol.64 1908-1921 1993 & Cryobiology Vol.31 506-515
 1994)

     Based on my expectations of the quality of the treated tissue I group
 these 5 techniques in the following order of increasing merit: 

           WORST:  1. Hamburger
           INTERMEDIATE: 3. Microwave & 4. Freeze Substitution
           BEST:  2. Salami & 5. Quick Freeze


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