X-Message-Number: 15420
From: 
Date: Mon, 22 Jan 2001 11:30:49 EST
Subject: Donaldson & "viability"

I believe that Dr. Thomas Donaldson is a member of the Board of Directors of 
the INC (Institute for Neural Cryobiology), which is one of the organizations 
involved with the rat hippocampal slice cryopreservation project. He is also 
a self-taught scholar in neuroscience and to some degree at least in 
cryobiology. 

There appears to be disagreement about how to interpret the "viability" of 
rat brain slices vitrified and then warmed, washed out, cultured or 
incubated, and tested for viability by the potassium/sodium ratio criterion. 
This ratio was reported as 53%--deemed very good compared to previous 
efforts-and then later improved to 66%. What does this mean?

One interpretation is that, in a sample containing many cells, the average 
K/Na ratio was 66% of normal, with the variance unknown or unreported. That 
is, it is unknown how many were dead or close to it by this criterion, and 
how many were normal or nearly so.

The other interpretation is that every individual cell was functioning at 66% 
normal, or very close to it, by this criterion. This latter seems very 
unlikely just as a matter of general experience with populations in 
statistical studies. Variance is hardly ever close to zero.

So that's the first question for Thomas. Which of these interpretations is 
right, or which is closer to being right?

Next, the K/Na criterion is said to be a good one for gauging overall cell 
life or function-if the K/Na ratio is near 100%, then most or all cell 
functions are close to normal. Is this really correct? How is that known? 
Which other parameters of cell function (neuron function especially) have 
been proven highly positively correlated with the K/Na ratio? If Thomas knows 
anything about this, then that's another question, or series of questions.

I remind readers that Suda in the Sixties got relatively good corticograms 
from glycerolized cat brains rewarmed after relatively short times at  
relatively high sub-zero temperatures. A couple of years ago Pichugin 
rewarmed frozen (not vitrified) glycerolized rabbit brain pieces from liquid 
nitrogen and obtained coordinated electrical activity in networks of neurons. 
This is surely an important marker of "viability" from the cryonics 
standpoint, and yet, as I understand it, the K/Na  test would not have given 
good results.

Any comments from Thomas would be welcome.

Robert Ettinger
Cryonics Institute
Immortalist Society
http://www.cryonics.org

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