696 RADIATION BIOLOGY 



mitotic prophases in the amount and type of chromosomal ribonucleic 

 acid (Kaufmann, McDonald, and Gay, 1948). 



Since in the living cell nucleic acids exist in association with proteins, 

 the possible effects of ionizing radiations on proteins and nucleoproteins 

 must also be assessed. Changes occur in the viscosity of solutions of 

 gelatin, egg albumin, and serum albumin exposed to X rays or radium 

 (see, for example, the review of Arnow, 1936). The action of X rays in 

 lowering the viscosity of a solution of nucleohistone is shown in Table 

 9-16. When nucleoproteins prepared from chicken erythrocytes and 

 carp spermatozoa in the form of stiff gels were irradiated, the gels gradu- 

 ally liquefied (Errera, 1946). If the cells were first subjected to intense 

 irradiation (50,000 r), and the nucleoproteins were then extracted, the 

 latter formed liquid solutions rather than gels. Von Euler and Hahn 

 (1946) irradiated nuclei isolated from calf thymus with 65,000 r but did 

 not detect any change in the nucleoproteins. Cytological examination 

 of cells of the testis of the salamander, Triturus, that had been irradiated 

 with heavy doses of X rays (from 5,000 to 50,000 r) revealed chromosomal 

 material that had spread out along the spindle fibers (Rugh, 1950). It 

 was suggested that denaturation of protein might have been responsible 

 for the lowered viscosity leading to this dislocation. 



In the light of these various lines of experimental evidence it is apparent 

 that a satisfactory understanding of the action of ionizing radiations on 

 the materials of the chromosome must await the accumulation of informa- 

 tion about the types and patterns of association of nucleic acids, proteins, 

 and related materials during the various phases of the mitotic cycle. 



REFERENCES 



Information regarding availability of government reports indicated by an asterisk 

 may be obtained from the Office of Technical Services, Department of 



Commerce, Washington, D.C. 



Alberti, W., and G. Politzer (1923) tJber den Einfluss der Rontgenstrahlen auf die 



Zellteilung. Arch, mikroskop. Anat. Entwicklungsmech., 100: 82-109. 

 and (1924) Uber den Einfluss der Rontgenstrahlen auf die Zellteilung. 



Arch. Entwicklungsmech. Organ., 103: 284-307. 

 Allsopp, C. B. (1948) Theories of the biological action of ionizing radiations. Brit. J. 



Radiology, 21: 72-74. 

 and D. G. Catcheside (1948) Chemical breakage of chromosomes. Nature, 



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(1925b) The proportion of exceptions in the offspring of exceptional females 



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