X-Message-Number: 9837
Date: Mon, 1 Jun 1998 08:31:12 -0700 (PDT)
From: Doug Skrecky <>
Subject: Life on Ice

New Scientist May 2,1998: 24-28

"Life on Ice"

Various quoted snippets:

   "Wood frogs, it turns out, only look frozen solid. In reality, the water
in between their cells freezes, but not the water within them. To achieve
this semi-frozen state, the frogs adopt two main strategies. First their
blood contains ice nucleating proteins - molecules that actually encourage
ice to grow by mimicking its crystal lattice. "If you could fly over a
nucleating protein in a miniature airplane," story says, "its surface would
look like ice." With so many nucleators in the blood, no one crystal ever
gets big enough to damage tissue.
    Glucose is the second trick. Just as the extremities begin to get icy,
the frog's liver starts churning out glucose, which circulates round its
body. "The frogs start out with the same amount of glucose we have," says
Storey, "then go right to being diabetic." Glucose in the cells has the
same effect as antifreeze in a car radiator - it drives the freezing
temperature down. Consequently, the cells' syrupy insides stay liquid even
while the remaining 65 per cent of the water in the frog has turned to ice.
   <snip>
   Just as frogs use glucose, Arctic brine shrimp and many cold-tolerant
insects use a sugar called trehalose, which forms a syrup as thick as
stretchy toffee, is even better at lowering freezing points and stopping
dehydration than glycerol or glucose. But just like glucose, it crosses
membranes slowly. How then to get it into the cells so that it can work its
magic? The answer, Beattie says, is to take advantage of the cold-induced
leaky membranes. She and her UCSD colleague Alberto Hayek slowly cooled
human insulin-producing cells in a trehalose solution, and just as the
lipid membrane started to congeal at around 5 C, the trehalose leaked in.
Then Beattie plunged the cells into liquid nitrogen to rapidly finish the
freezing process.
    <snip>
    Given the progress that's been made, is there any hope of freezing and
reviving a whole human? Barring some unforeseen breakthrough, such
cryogenic time capsules will very likely remain impossible, according to
most experts. Scaling up techniques that work on bits of humans won't work
for the whole thing. high levels of sugar trigger diabetic shock, for
instance, and glycerol would be toxic when you thawed out and started to
metabolise it. And even if we could handle such chemicals, getting them
inside all the cells in the body would be problematic.
    That's not to say that people like Storey don't wish they could freeze
humans. "If by magic I could fill you with high levels of sugar and put
nucleating proteins in your blood," says Storey, "then I could freeze you."
unfortunately, the operative word, he says, is magic"."

Suggestion by poster:

    Try sorbitol instead. This sugar penetrates cell membranes much better
than glucose or trehalose, and is nontoxic.

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