40 Antoinette Pirie 



after radiation will remove the protective effects of anoxia or 

 of cysteine treatment (Patt, 1955). A low temperature also 

 seems to make the glycolytic enzyme systems of tumour and 

 retina more sensitive. 



One concept of the reason why it is difficult to find an 

 immediate change in enzymic activity is that radiation has a 

 greater effect on enzyme synthesis than on the enzymes them- 

 selves. The cell, therefore, may only gradually go down hill 

 as enzymes fail to be replaced; but in yeast and Escherichia 

 coli, which have been investigated, the ability to form 

 adaptive enzymes seems unimpaired immediately after a dose 

 of X-rays that has killed 90-99 per cent of the cells. Thus 

 Brandt, Foreman and Swenson (1951) find that yeast cultures 

 given 4,800 r, which kills 90 per cent of the cells, will still form 

 galactozymase. Spiegelman, Baron and Quastler (1951) 

 found both galactozymase and maltozymase formation un- 

 affected. Yanofsky (1953) found that Esch. coli could still form 

 lactase normally after a dose of 5,000-10,000 r and Billen and 

 Lichstein (1952) showed that hydrogenlyase formation by 

 Esch. coli was normal after 15,000 r, for 100 minutes, although 

 it then fell off. 



Concerning the effect of radiation on enzyme formation in 

 animal tissues Ranch and Stenstrom (1952) found that 

 400-000 r of X-radiation restricted to the pancreas, in dogs 

 w^ith pancreatic fistulae, caused a lowered secretion of amylase, 

 trypsin and lipase when tests were made 12 hours later. The 

 volume and pH of the secretion remained unchanged but the 

 enzyme content fell. The effect was reversible but could be 

 reproduced with further irradiation. The glands showed no 

 histological damage. Since the secretion of enzymes was not 

 studied at once after radiation we cannot say that this is an 

 initial effect, but it is an interesting approach. 



Therefore, as there is doubt in this last case, we can say 

 that irradiation with X-rays [ultraviolet does inhibit (Errera, 

 1955)] has no immediate effect on enzyme synthesis. Thus, a 

 bacterial cell can continue to maintain its integrity and to 

 synthesize some at least of its enzymes after an amount of 



