Stubbe's* experiments indicated that the genes 

 of Epilobium hirsutum have a greater frequency 

 of mutation when irradiated within the proto- 

 plasm of E. luteum than in their own protoplasm. 

 He conclu"ded that changes in interaction between 

 the nucleus and the cytoplasm revealed them- 

 selves in various reactions, which are regulated 

 sometimes by the nucleus and sometimes by the 

 cytoplasm. 



Changes in Chondriosomes and Plastids 



Improved microscopic techniques created a 

 new approach to the investigation of the effects 

 of X rays on cells. NUrnberger [1923] made a 

 major contribution to this problem. Basing his 

 work on a comparative investigation of normal 

 and irradiated ova of white mice, he came to 

 the conclusion that X rays can cause consider- 

 able injury to the body of the cell. The destruc- 

 tive action manifests itself in the accumulation 

 and rolling of the chondriosomes into tangled 

 balls with subsequent dissolution. For this 

 reason NUrnberger [1923] considers chondrio- 

 somes to be extremely delicate morphological 

 indicators of the condition of the cell. 



NUrnberger' s assumption was confirmed by 

 the work of Russian investigators (Nadson [and] 

 Rokhlina [1934]; Wail and Frenkel [1925]). On 

 the basis of their investigations, all of them 

 came to the conclusion that chondriosomes are 

 the most sensitive [parts of the cell]. In the 

 experiments of Nadson and Rokhlina [1934], the 

 length of irradiation ranged from 2. 5 minutes 

 (1 HED) to 60 minutes (24 HED). In the cells of 

 the epidermis of onion scales, the chondriomes 

 are small granular structures in the form of 

 chondriosomes. When the action of irradiation 

 is increased, the chondrioconts puff up unevenly 

 along their length, the irregularities of their 

 contours increase, the threads become stumpy 

 or assume the shape of tadpoles, spindles, and 

 sometimes of fragments or triangles. In cer- 

 tain places in the cell, the chondriosomes 

 gather in very large numbers reminiscent of 

 the agglutination of chloroplasts. When the 

 doses are increased still more, the chondrio- 

 somes undergo still greater changes: vacuoli- 

 zation, dissociation of monoproteins accompa- 

 nied by an increase in lipophanerosis, dissolu- 

 tion of albuminous compounds, and, finally, the 

 complete disappearance of the chondriomes. 



Wail and Frenkel (1925), studying the effects 

 of X rays on the cells of frog liver, established 

 that morphological changes first appear in the 

 chondriosomes and later in the nucleus. Tscha- 

 ssownikow (1928) came to a similar conclusion 

 for the same object. He fixed small pieces of 

 irradiated frog liver at intervals starting with 

 3 hours after irradiation and ending 6 days later, 

 and he observed that the chondriosomes were 

 the first to show the effect of X rays. However, 

 Tschassownikow points out that in observing 



chondriosomes one has to be extremely careful 

 in drawing conclusions because, in the first 

 place, chondriosomes can be injured traumat- 

 ically since in the surface of sections the chond- 

 rioconts fall apart into grains, and, secondly, 

 the effect of fixative agents on the surfaces has 

 to be kept in mind. Consequently, Tschassown- 

 ikow examined only such cells as could not have 

 been injured traumatically. It is for this reason, 

 he believes, that he did not observe the phenom- 

 ena described by Wail and Frenkel. In his ma- 

 terials the chondriosomes retain their normal 

 structure and position for 12, 24, and even 48 

 hours. Only after 48 to 72 hours and more did 

 Tschassownikow find truly degenerative changes 

 in the chondriosomes. The changes consisted 

 of disintegration of the chondriosomes into 

 granules, which then swelled into lumps. At 

 the same time changes took place in the plasma 

 and nucleus. Sometimes he observed necrosis 

 in the nucleus, although the chondriosomes were 

 still completely unaffected. In other cases clear 

 vacuoles appeared in the plasma alongside of 

 partially injured chondriosomes. Thus, we 

 have very few data about changes in chondrio- 

 somes due to influence of irradiation, and, 

 moreover, [these data] are contradictory. 

 Apparently, despite the detailed examinations 

 of Nadson and Rokhlina, this question has to be 

 taken up once more, especially since their 

 observations were made on living cells where 

 various destructive processes could take place 

 quite independently of the action of X rays. In 

 this respect we need merely mention one danger, 

 namely, the possibility of carbon dioxide poison- 

 ing in the humid chamber. 



Plastids have likewise been insufficiently 

 investigated to be able to come to definite con- 

 clusions about what effects X rays have on 

 them. Lopriore(l898, [1897?]) in the work 

 mentioned above, described the paling of chloro- 

 plasts in Valisneria spiralis that was induced by 

 high doses of X rays. Johnson (1936, [1936a])3 

 made the observation that chloroplasts develop 

 improperly. ToUenaar* and Hudson* in tobacco. 

 Stubbed in snapdragons, Stadler^ in barley and 

 corn, Lutkov* in barley, et al, all observed 

 changes in the green parts of plants due to irra- 

 diation. Certain of these changes were heredi- 

 tary (see Chapter 2). 



Knudson (1931 [1934?]), irradiating the 

 spores of Polypodium aureum , found giant, ir- 

 regular, amoeboid plastids in the prothallia, 

 especially in the peripheral cells. He assumed 

 that they arose as a result of the fusion of small 

 plastids. This explanation quite agrees with 

 SchUrhoff's* findings. The latter established that 

 under certain abnormal conditions the plastids 



'See References following Chapter 1. 

 ^See References following Ch^ter 2. 



63 



