44 Antoinette Pirie 



time that elapsed between irradiation and the measurement of 

 synthesis is unfortunately not given. Later, the bone marrow 

 decayed. We know that coenzyme A, the coenzyme concerned 

 in fatty acid formation, is normal after radiation and it appears 

 that the enzymes are activated at once, either directly or by 

 change in substrate concentration, or change in permeability 

 of the mitochondria which are the seat of fatty acid synthesis. 



This ties in with the work of Hevesy and Forssberg (1951) 

 who found that if mice given 2,000 r were then injected 

 immediately with ^^C-labelled glucose, and the exhaled CO 2 

 collected, starting 8 minutes later, the irradiated mice gave 

 ofP less CO 2 over the first hour than did the controls. There 

 was also increased ^*C in liver fats under these conditions. 



The synthesis of haemoglobin also appears to be stimulated 

 immediately. Richmond, Altman and Solomon (1951) again 

 using the rabbit and a whole body dose of 800 r, found that 

 bone marrow and spleen dispersions taken immediately after 

 radiation incorporated ^*C -labelled glycine into haemin and 

 globin with greater rapidity than the normal. Forty-eight 

 hours after radiation synthesis had declined. 



Similarly, Nizet, Lambert and Bacq (1954) found stimulation 

 of haemin synthesis in vitro by reticulocytes taken from a dog 

 30 minutes after a whole body dose of 500 r or by reticulocytes 

 irradiated in vitro. In three of four dogs tested it appeared 

 that plasma from the irradiated dog stimulated haemin forma- 

 tion in non-irradiated cells. This makes it appear that stimula- 

 ation of synthesis is not a direct or indirect effect on enzymes 

 of the red cell but a change in environment. 



On the other hand, Bonnichsen and Hevesy (1955), who 

 point out that "Haemoglobin is one of the comparatively few 

 molecular constituents of the adult organism that is formed in 

 close connection with cell division", found decreased haemo- 

 globin formation in irradiated guinea pigs which were in- 

 jected with ^^Fe 6 hours after X-ray and killed 17 hours later. 

 This decrease in synthesis did not take place immediately 

 after radiation and it is suggested that the red blood corpuscles 

 of the marrow which are in an advanced stage of maturation 



