CRYOprotectants: More Replies to Sandberg

Twink (
Mon, 29 Dec 1997 00:01:29 -0500 (EST)

Note: cp = cryoprotectant

At 08:11 PM 12/28/97 +0100, Anders Sandberg <> wrote:
>> >> More than one cp?
>> >> Is a cp "cocktail" better than one cp?
>> >
>> >The problem is the combinatoric explosion of the search space.
>> Agreed, which is why it would be nice to have a model of what is going on
>> here so that one could use something like computer simulations with a GA
>> to narrow the search.
>Yes, that would be helpful. But simulating the interactions between
>arbitrary cps and a more or less living tissue is a *heavy*
>problem. Of course, some approximations could be done (such as a
>simple phenomenological model of crystal formation depending on some
>properties of the cps), and then more detailled studies could be done
>with the successful combinations, but I guess there will be a lot of
>both beneficial and problematic interactions that are very hard to
>deal with using general rules (cp X forms a complex with cp Y that
>limits perfusion, cp X, Y and Z appears to be very bad in simulations
>but due to serpendipity they interact with some body-chemicals to form
>a very good cryoprotectant solution).

Whatever happens, the point is we need a method which will work
well enough to get us better results than current research and
projections. If things then work out, more funding and effort might
be able to clean up some of these problems. Genetic algorithmn
searches, e.g., are not perfect, but they are often much better than
brute human engineering or trial and error.

>> It might be possible that some cps flow into tissue at different rates, in
>> which case, a cp cocktail might be made which can be administered
>> in the same way current ones are.
>One could also look at cps or additives that bind more or less
>strongly to certain tissues, "opening" or "closing" them for each
>other. Sounds complex but interesting (maybe something that opens the
>blood brain barrier first?)

Now we're getting somewhere!

>> Perhaps a multistage process might be used in which blood is removed
>> and cps are injected into the tissues rather than through the main
>> circulatory system.
>It is hard to get better access than the circulatory system - it is a
>spacefilling fractal.

Not exactly, but close enough.:) My notion was more like ~pull the blood
out through the circulatory system and perfuse through direct saturation."
This is just one example. Another might be to inject directly into the
target organ/tissue with a flow and temperature drop rate match so
that the cp works only on that organ/tissue and does not reach others
before vitrification.

>> (Stanislaw Lem's novel _Fiasco_ has cryonic suspension units inside
>> walkers on Titan, so that if the pilots of the walker wind up in a pinch,
>> they can suspend themselves. Early in the novel, there is no way to
>> revive people, but later on a means develops and one of the
>> preserved persons is revived.)
>Yes, it is a quite reasonable idea with emergency vitrification. A bit
>like an airbag...

Quite. No reason we can't draw up one for fun. Maybe someone else
might actually build one.

Daniel Ust