INITIAL STEPS IN RADIATION DAMAGE TO 

 CHROMOSOMES AND MEANS OF PREVENTING 



THIS EFFECT 



ALEXANDER HOLLAENDER 



Biology Division, Oak Ridge National Lahoratonj, Oak Ridge, 



Tennessee, U.S.A.'\ 



SUMMARY 



Two approaches to the analysis of the initial steps in radiation damage are 

 discussed. 



The first is the use of very low radiation levels. Tluis the entire effect of small 

 doses of radiation on the grasshopper neuroblast can be reversed by immediate 

 treatment with hypertonic salt solution. X-ray-induced chromosomal aberra- 

 tions in Tradescantia pollen may be modified by pre- and post-treatment with 

 u.v. 



The second approach is the investigation of protection against radiation 

 damage. The killing of A. terreus cells and mutation are not interdependent. 

 Pre-mutation damage in Pornmecium can be repaired. 



All these studies establish that it is possible to manipulate living cells in regard 

 to sm'vival, mitosis, chromosome breaks and mutation production by radiation. 



The identitication of basic mechanisms involved in the initial effects 

 of radiation on living cells has been actively investigated in onr labora- 

 tory in the past few years. The emjjhasis, fitting into the general 

 programme of the laboratory, has been on cytological and genetic 

 effects. Some of onr projects, discnssed here, give a picture of what we 

 know about the effects of ionizing radiation on chromosomes and 

 suggest certain types of investigations which are essential. 



In an analysis of the initial steps involved in radiation damage, we 

 have used two approaches. One approach has persuaded us to go to 

 lower and lower radiation levels and search for effects which we can 

 determine quantitatively. Referred to here are only the iyiitial steps of 

 radiation damage. Of course, when massive doses of radiation are 

 administered many changes in living cells occur. But in this case steps 

 in damage follow each other so rapidly that it is usually not practicable 

 to analyse the initial steps since they are quickly obscured. 



The other approach is to investigate the areas where we can protect 

 against radiation damage. Special emphasis has been placed on what 

 can be done to help the cell repair the damage which radiation has 

 initiated before it becomes frozen or starts a chain reaction which 



t Operated by Union Carbide Corporation for the United States Atomic Energy Com. 

 missicai. 



201 



