ANHYDRIOBIOSIS 



19 



10 20 30 40 50 60 

 Minutes after thawing lysozime added 



Fig. 3. Sensitivity to lysis by lysozyme of frozen and thawed E. co/i, following 

 starvation or KCN treatment. E. coli starved by aeration in phosphate 



buffer for 20 min before freezing (A A), or 0.005 M KCN added 



20 min before freezing (D D). Each point represents % lysis in 



20 min due to lysozyme added after thawing, at times indicated 2. 



Control: O O. 



leave enough space to accomodate the bacteria and prevent them 

 from being crushed. We shall see later that these colloids have 

 no action in protecting bacteria from death due to drying during 

 the process of freeze-drying or after it. 



A very important chance discovery made first by Rostand in 

 1946, and later, independently by Parkes^^. was that the addition 

 of glycerol to animal cells (fowl sperm) protected them from the 

 injurious and lethal effects of freezing. Bull semen has been 

 successfully preserved in the frozen state for several years and 

 calves have been produced by semen from a bull that had died 

 three years previously. Thus a practical method was devised for 

 freezing and storing semen, red blood cells, tissue culture cells 

 and lately bone marrow cells. Recent information^^ indicates 

 that bone marrow cells suspended in glycerol (10%) or frozen in 

 glycerol are much more resistant to ionizing radiation than in 

 the absence of glycerol. The effect of glycerol may be compared 

 to the effect of drying since glycerol is a dehydrating agent. 



References p. 29 



