Table 36 



The action of acute and fractionated (three fractions 



at 24 -hour intervals) doses of radiation of various qualities 



on the frequency of mutations in Antirrhinum majus L . 



(based on Stubbe's data, 1934) 



Stubbe explains this by the fact that the action 

 of large doses shakes up the structure of the 

 genes to an extent which cannot occur under 

 normal conditions or with weak doses. As a 

 consequence, after strong doses, even genes 

 that are distinguished in general by great sta- 

 bility undergo mutation. 



The majority of experiments in this area, 

 however, indicate that experimentally obtained 

 mutations do not in any way differ from spon- 

 taneous ones. If mutations appear after irradi- 

 ation that were not encountered previously, the 

 reason, in all probability, is that none of the 

 objects with spontaneously arising mutations 

 was sufficiently observed to uncover all the 

 possible mutations. In addition, we know that, 

 in every more or less thoroughly investigated 

 object, spontaneous mutations crop up from 

 time to time which had not been encountered 

 before in X-ray experiments. 



The regularity of distribution of experiment- 

 ally obtained chromosomal aberrations con- 

 firms the assumption concerning the lack of 

 specificity in the effects of short-wave radia- 

 tion, which should have been expected on the 

 basis of the physical properties of the rays. 



The following facts indicate that various 

 sectors of the wave spectrum do not produce 

 specific effects: 1) Stubbe's experiments which 

 were set up with an isolated segment of ultra- 

 violet rays; 2) the fact that as a consequence of 

 irradiation the same kinds of mutations arise 

 as are observed under natural conditions; ^ 



2 Recent findings indicate that the action of ultra- 

 violet rays does differ from the action of X rays. 



3) the appearance of reverse mutations due to 

 the action of short waves. 



The significant factor in the increase of mu- 

 tations is the amount of energy used (the num- 

 ber of r) and not the quality of the radiation 

 (voltage). The frequency of mutations rises in 

 direct proportion to the dose. 



VARIABLE SENSITIVITY OF ORGANISMS 

 TO X RAYS 



We pointed out in Chapter 1 that X rays have 

 a varying effect, not only on different species and 

 finer subdivisions of the classification system, 

 but also, frequently, on organisms of a single 

 species. Then we broached the question, in this 

 chapter we shall attempt to clarify it. The first 

 suggestion on this subject was expressed by 

 Bergonie and Tribandeau in 1906. They point 

 out in their article that according to the data of 

 all the physicians, irradiation, which induces 

 the death of neoplastic cells, leaves the immedi- 

 ately adjacent cells of the normal tissues, in- 

 cluding those of the tumor, uninjured. In addi- 

 tion, experiments with living tissues have indi- 

 cated that the rays have a selective action on 

 healthy tissues. These authors showed that X 

 rays destroyed the seminal cells of rat ova but 

 didnot affect the interstitial gland [cells?] . 

 Therefore, the authors assumed that it was pos- 

 sible to formulate the following law (which is 

 known as the Bergonie -Tribandeau Law): "X rays 

 act with greater intensity on those cells which 

 have a greater power of reproduction, on those 

 which have a longer karyokinetic future, on 

 those whose morphology and function are less 

 definitely fixed. " Hence, they have no difficulty 

 in understanding why irradiation destroys tum- 

 ors without affecting the healthy tissues. 



101 



