X-Message-Number: 6031
Date: Fri, 5 Apr 1996 21:28:08 -0800 (PST)
From: Doug Skrecky <>
Subject: Cryonet Gulch II

                         CRYONET GULCH II
        (From the November 1995 issue of Canadian Cryonics News)
                         By Doug Skrecky
      Big Mike eased the mug down on the bar and put his arm around this
 pretty young thing who cooed about his prowess at perfusion. Someone
 ordered a round of glycerol on the house and Mike of course got the
 refill first. Life was good. 
      Then the doors to the saloon burst open and a stranger walked in and
 ordered a glass of sorbitol. The saloon fell silent. Ben Best, the
 bartender cautioned "We serve only glycerol here, stranger". Mike, being
 engaged in perfusion preparation, paid no attention. Spurs clicking
 Thomas Donaldson put down his five aces on the table, sidled up to the
 bar and whispered to Mike "The fool's here". Reluctantly Big Mike got up,
 leaving his lass at the bar and wiped the lipstick stain off his cheek. 
 He looked at the stranger and nodded outside. Thomas eyed the stranger,
 measuring him up for the box. The stranger left, as did Mike. 
      Big Mike was in a good mood. Well, well what have we here, the
 Sorbitol Kid? I heard you were coming to town to avenge the death of your
 brother, the Sucrose Kid. Let's call it a draw and you can walk out of
 town right now.  The stranger positioned himself down the main street
 and turned around to face the most experienced cryonics man in town. He
 worked his fingers a bit to loosen them up. A wind passed by, but the
 stranger's face was perspiring.  Mike nodded again and let loose: I've
 got 500 research reports on the effect of glycerol on cryopreservation. 
 What have you got on sorbitol? 
      The Kid looked uncomfortable, but gamely fired back: Glycerol is
 unsafe mister. At even dry ice temperatures glycerolized bone marrow
 disintegrated after just 3 years of storage. *1 Glycerol is unsafe! 
      Mike looked puzzled: That's why we use liquid nitrogen instead of
 dry ice. What's your point? 
      The Kid fired back: With glycerol you are locked into expensive
 liquid nitrogen storage. Nothing else will do. Not so with sorbitol. With
 an annealed glass transition temperature (Tg') above that of dry ice
 sorbitolized tissue could be stored using cheaper dry ice instead. 
       Mike shrugged: If we are forced to cut costs in the future we could
 pool our patients with those of the other cryonics towns and use a single
 large containment system to reduce boiloff. If it really came down to it
 I suppose we would reluctantly behead our frozen patients and cut costs
 further by a factor of ten. Do you have any PROOF that sorbitolized
 tissue could be stored safely at dry ice temperatures? A single
 experiment, give me a single experiment! 
       The Kid looked a little singed but replied: Deterioration of frozen
 surimi stored at -20 C is slower when sorbitol is mixed with it than when
 glycerol is used. *2 However the big advantage of sorbitol is that unlike
 glycerol, which has a dry Tg of -93 C, sorbitolized tissue could be
 usefully freeze-dried since it has a dry Tg of -9 C. *3 *4 Then merely
 refridgerated storage at say -20 C should be enough. The expense of even
 dry ice could be dispensed with. 
       Big Mike shook his head and then blasted back: Do you or do you not
 have a single experiment on freeze-drying of sorbitolized brain tissue? 
 Aw, it looks like you're bleeding! 
       The Kid shook, but returned fire: Sorbitol has been found to
 stabilize cell membranes even at room temperature, while glycerol
 actually destabilizes them. *5 I don't know exactly how much safer than
 glycerol, sorbitol is, but it sure as shooting is a heck of a lot more
 stable. With sorbitol there is at least the possibility of alternatives
 to liquid nitrogen. With glycerol there is none. 
       Mike looked surprised, but not particularly worried: Ok so sorbitol
 might be a wee bit safer in the long run. I'll grant that. I have 500
 research reports on glycerol. What have you got? 
       The Kid took his best shot: The problem with sugars is that human
 cell membranes are virtually impermeable to them. Animals capable of
 surviving dry storage or anhydrobiosis have special sugar transporting
 molecules on their cell membranes such as trehalose transferase. This
 deficiency in human cell membranes is not operative with regard to
 sorbitol as this can (slowly) penetrate these membranes. Rat embryos
 actually have a higher survival rate when treated with 0.3 M sorbitol
 (58%) than with glycerol (16%) or sucrose (0%). *6
       Mike noticed the bullet impacting the ground about 10 feet away,
 listened to a strange thumping sound then blasted back: In case nobody
 ever told you, with human bodies, the high cooling rates required to
 enable cells treated with 0.3 M of any cryoprotectant to survive are not
 possible. We have no option but to use slow cooling rates and as a result
 we also have to use 7 M glycerol. Concentrated sorbitol solutions put
 cells into osmotic shock and revival rates are reduced when high molar
 sorbitol is used instead of glycerol. *7 You're toast mister... 
       Just then the Eveready Energiser Battery Bunny thumped into view. 
 With vicious looks both the Kid and Big Mike laced the main street with
 gunfire. The Bunny exploded and the thumping mercifully stopped. 
       Mike pointed his gun at the Kid: In all the excitement I forgot how
 many shots I fired. Well, Do you feel lucky, punk? 
       The Kid gritted his teeth and carefully eyed the barrel of his own
 gun. Slowly he lowered the gun and put it into his holster. Bleeding, he
 got on his horse and rode up to Mike: You're right I don't have 500
 research reports to match yours. I couldn't hit the broad side of a barn
 with the number of reports I do have, but the gun is a good one. By
 gradually ramping up the concentration maybe osmotic shock might be
 avoided. If this could be avoided the greater safety of sorbitol in the
 long-term would make it a good replacement for glycerol. 
       The Kid rode off into the sunset for a minute, then fell from his
 horse. Thomas, the funeral director ambled over, but looked disappointed. 
 Mike motioned to MaryLoo to go get him and patch him up. 
       The Kid paid for MaryLoo's administrations by giving her his gun. 
 Mike bought the gun from MaryLoo and added it to his collection, thinking
 that maybe there was something in what the kid said afterall. 
 *1 "Long-term Storage of Bone Marrow Cells at Liquid Nitrogen and Dry Ice
 Temperatures" 65-69 No.1 1970 Cryobiology
 *2 "Cryoprotective Effects of Some Materials on Cod-Surimi Proteins
 During Frozen Storage" 1222-1227 Vol.55 No.5 1990 Journal of Food Science
 *3 "Beyond Water Activity: Recent Advances Based on an Alternative
 Approach to the Assessment of Food Quality and Safety" 115-360 Vol.30
 No.2-3 1991 Critical Reviews in Food Science and Nutrition
 *4 "Melting and Glass Transitions of Low Molecular Weight Carbohydrates" 
 39-48 Vol.238 1993 Carbohydrate Research
 *5 "Effects of Carbohydrates on Membrane Stability at Low Water
 Activities" 141-150 Vol.769 1984 Biochimca et Biophysica Acta
 *6 "Cryoprotective Effect of Polyols on Rat Embryos During Two-Step
 Freezing" 332-341 Vol.29 1992 Cryobiology
 *7 "Evidence that Membrane Stress Contributes More Than Lipid
 Peroxidation to Sublethal Cryodamage in Cryopreserved Human Sperm: 
 Glycerol and Other Polyols as Sole Cryoprotectant" 199-209 Vol.14 No.3
 1993 Journal of Andrology

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