Section 16 — Human Cytogenetics 



In order to estimate damage from various 

 dosages, frequency curves have been compiled 

 for some of these nuclear aberrations (binucleate 

 cells and pyknotic leukocytes) using normal 

 leukocyte cultures irradiated with different 

 dose levels of X-rays up to 100 r. In addition, 

 other cultures were supplemented with radio- 

 sulphur (S 35 ) and radiophosphorus(P 32 )(togive 

 accumulated doses up to 200 rad). These experi- 

 ments were repeated for different culture times. 

 A correlation was found to exist between the 

 number of these aberrant forms, increasing 

 radiation dosage and increasing culture time. 

 The results with X-ray and S 35 were comparable 

 but P 32 gave an enhancing effect due to its 

 incorporation and subsequent transmutation in 

 vital cellular components. 



16.31. Chromosome Aberration Rates in Human 

 Somatic Cells Irradiated in Vivo. M. A. Bender 

 and P. C. Gooch (Oak Ridge, U.S.A.). 



Although a fairly large body of data has 

 accumulated on the induction of somatic 

 chromosomal aberrations in human cells by 

 ionizing radiation, the work has necessarily 

 been done by irradiation of cells /'// vitro. The 

 recent development of a technique for the initi- 

 ation of mitosis in human peripheral leukocytes, 

 however, permits the examination of the chromo- 

 somes of irradiated humans in the first division 

 following irradiation. We have examined such 

 material from a number of normal persons who 

 received whole-body irradiation. One group of 

 three men received doses of mixed gamma and 

 fission neutron radiation estimated at 19, 43, 

 and 110 rem (estimating the RBE for the 

 neutrons as 2). A second group of three men 

 received doses of y-rays estimated at 17, 22, and 

 57 rad. The frequencies of aberrations observed 

 in samples obtained immediately after irradiation 

 were consistent with the coefficients of aberration 

 production obtained previously for irradiation 

 of leukocytes in vitroS 1 ) Aberration frequencies 

 remained at essentially the same frequency until 

 about 4 weeks, and the aberrations seen provided 

 evidence that the cells had not divided in vivo 

 after irradiation. In later samples, however, 

 aberration frequencies fell, and many of the cells 

 sampled had evidently undergone division in 

 vivo. Dicentric chromosomes, symmetrical trans- 

 locations, and deleted chromosomes continue 

 to be seen many months after irradiation. 



1. Bender and Gooch, Proc. Natl. Acad. Sci. 

 U.S. 48, 522, 1962. 



16.32. Action of X-rays on Transformation of Normal 

 Cells into Malignant in vitro. Ju. B. Vakhtin 

 (Leningrad, U.S.S.R.). 



It is known that attempts to accelerate the 

 process of malignant transformation of mono- 

 layer cell cultures by means of chemical cancer- 

 ogens were unsuccessful. The cancerogenic 

 action of ionizing radiation on cell cultures 

 inducing the high percent of mutations and 

 chromosome aberrations has not yet been 

 investigated. 



Fibroblasts isolated by tripsinization from 

 subcutaneous connective tissue of newborn rats 

 were cultured in the synthetic medium 199 or 

 0.5 per cent lactalbumin hydrolysate with 20 

 per cent of horse or bovine serum. Just after 

 explantation cells of each culture have been 

 divided into five variants. Four of them were 

 treated with 10 r 10, 100 r, 100 r 5 and 

 500 r of X-rays and control variant was not 

 irradiated. Cultures were maintained for 2-15 

 months (6-26 passages) and implanted regularly 

 into newborn rats and adults of the same strain 

 (1-5 x 10 6 cells in each inoculum, subcutaneous- 

 ly and interperitoneally). 



No malignization took place in variants of 

 cultures maintained for 2-8 months. All of these 

 cultures consisted mainly of cells with diploid 

 and near-diploid chromosome complements. 



Malignant transformation has been found 

 within the only culture in the control variant and 

 the variant irradiated with the dose of lOOr 

 after 12 months of the cultivation. As implanted 

 into rats these variant cells give rise to transplant- 

 able sarcomas. 



Results obtained are compared with our data 

 of caryological studies of cell cultures and tu- 

 mours developed. The importance of genetic and 

 epigenetic variations for evolution of cell popu- 

 lations in vitro is discussed. 



16.33. The Changes in Somatic (Tumour) Cells 

 Induced by Specific DNA and RNA. J. M. 



Olenov (Leningrad, U.S.S.R.). 



Tumor cells are suitable objects for study of the 

 action of nucleic acids for a selective back- 

 ground can be applied in experiments in vivo. 



The treatment of the sarcolysine-sensitive 

 variant of the rat sarcoma 45 with DNA from 

 the sarcolysine-resistant variant of the same 

 sarcoma causes the transformation of the for- 

 mer cells (D. Podgajeckaja, V. Bresler, J. Olenov). 

 DNA-ase inactivates the activity of the prepara- 

 tion. The transformants retain their properties 

 in subsequent passages. 



309 



