Mechanism and relationship between dehydration and freezing injury recorded by calorimetric apparatu

Meryman, H. T.

English

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Ik, George Jacobs 
Chief, P Q m i a l  Biology 
b t i o n a l  Aeronautics and Space AdBlinistration 
4OO I y h s r y l s n a  Avenue, S.W, 
Washington, I), C, 
Bar Doctor Jacobs: 
!Ibis letter will confirm our telephone conversation i n  which I in- 
dicated that Contract R-63, Freezing and Drying of Living Cells, will 
be financed internal ly  i n  the future and that it will not be necessary 
fo r  us t o  rgqnest renewal following the termination of the present con- 
t r a c t  on June 30, 1%. I enclose a copy of a momorandmn front the H e a d  
of the Tissue Btmk which w i l l  amplify the circumstances leading to t h i s  
decision. 
During a 
Asys?nLpAsA, uar 
blind U e p ,  
and drying resistance in the nenstOde which terminated unproductively 
Wi th  the  departure of Dr. Burns. 
the ultimate outcome has been a l l  that  I could have wished. lche design 
and construction of continuously recording calorimetric apparatus, com- 
pleted under ou1 HASA contract, enabled us t o  demnstrate a consistent 
r eh i ionsh ip  between c3ehyciration and freezing injury and to rule out 
previous theories regarding the atechanical effects of i c e  crystals which 
have dominated cryobiology for  m y  years. 
orimetric measurements, w e  have been able to assemble a hypothesis fo r  
the mechanism of freezing injury and its prevention by cryoprotective 
agents, and we can now explain the influence of various freezing rates 
and cryoprotective a g e n t s  on the  basis of their effects on cell &hydra- 
tion. 
n which we have received f inancial  assistance 
ea8 &as been uneven and we have expLsred 
% g i n  relation to the i n i t i a l  study of freezing 
However, I am pleased to  report thst 
., 
Based largely on these c a b  
'Ihis hypothesis has led u8 to a series of experiments ai& have 
demonstrated that, contrary to previous assumptions, a substantial  pro- 
portion of the freezing injury seen w i t h  l o w  concentrations of cryo- 
protective agent can be prevented by very slow freezing and thawing. 
W i t h  our bet ter  understanding of the  mechanism of freezing injury we 
have ident i f ied two new approaches to l o w  temperature preservation. 
%e first of these is the use of low concentrations of cryoprotective 
agents which would be inadequately protective a t  very low temperature 
but uhich afgord good storage at moderately low temperatures of the 
order of -20 C. atere appear to be applications fo r  this compromise 
approach in materials wbich are injured by the high concentration of 
, 
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cryoprotective agents usually necessary to achieve very low temperature 
preservation- 
’ !  
Since preliminary supercooling and the lowering of the supercooling 
temperature through solutes has been a v i t a l  element in our hypothesis 
of injury, we have been led to f’urther investigation of supercooling 
and its control. 
of -100 C can be easily achieved and indefinitely maintained using a 
variety of solutes which do not have the toxicity of the cryoprotective 
agents and, in many situations, do not penetrate the cell. Even these 
modest reductions in temperature have been found to confer a substantial 
fneresse in +&e hratios  cf s?;=page c9= ?x %hieye&. We =re ex- 
ploring the application of these t w o  preservation techniques to leulm- 
cytes and platelets and to certain of the protozoa which are of practical. 
importance but for which no satisfactory preservation method has yet been 
devised. 
director of research grants arid I w i l l  see that you also receive a copy- 
We find that supercooling to temperatures of the order 
I am preparing an extensive report of our progress for the 
There is no question but that these theoretical and practical de- 
velopments have been to a great extent made possible by the support that 
we have received from NASA. I particularly appreciate the fact that you 
have not hounded us for a continual flow of tangible results but have had 
sufficient confidence to p e r m i t  our investigations to progress free of 
pressure. 
than justified confidence. 
I feel that the developments surnnarized above w i l l  have more 
Very sincerely yours, 
HAROLD T. MEZ”, MOD. 
Tissue Preservation Research Division 
Encl: 
(1) Copy of Memo 
2 


Experimental investigation of the mechanism by which freezing or drying and associated effects affect living cells

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