Section 16 — Human Cytogenetics 



Rat liver RNA inhibits the tumor growth in 

 transplantable rat liver mucous cancer obtained 

 by Maljugina (N. N. Aksenova, V. M. Bresler, 

 V. I. Vorobjev, J. M. Olenov). RNA-ase totally 

 inactivates the preparation. The action of RNA 

 from other tissues is less pronounced than the 

 action of liver RNA. 



The possibility to transform the nuclear cells 

 indicates the universality of this phenomenon. 

 Simultaneously, the result obtained proves the 

 transgenic origin of sarcolysine-resistant vari- 

 ant. The transformation frequency cannot be 

 determined exactly by studying of populations, 

 but it is likely to be small. The transformability 

 of non-haploid cells indicates the dominant or 

 semidominant nature of the marker. Unlike the 

 transforming activity of DNA, the antitumor 

 activity of RNA affects all or majority of cells 

 in the population — the change of some cells 

 would be ineffective. The paper deals with the 

 nature of normal tissue RNA antitumor action 

 (the templates controlling the protein synthe- 

 sis or repression and derepression of genes). 



There was no change in the normal diploid 

 chromosome count after 4 months of cultivation 

 (93 per cent diploid cells). The cells were then 

 exposed to 56C for one hour in an atmosphere 

 of 4.5 per cent CO2. Most of the cultures dis- 

 continued their growth, but a few surviving cells 

 were able to form new colonies. The chromo- 

 some number of these colonies was determined. 

 Shortly after recovery there were 52 per cent 

 polyploids, some octoploids included. After 

 6 months cultivation the chromosome number 

 changed again and there were now only 15 per 

 cent polyploids, 9 per cent subtetraploids and 

 76 per cent diploid cells. 



This change in chromosome number from 

 almost all diploid to more than 50 per cent 

 polyploid after heat shock and the slow decrease 

 of tetraploids, that is increase of diploid cells 

 and the almost absent fraction of subtetraploid 

 cells after 12 months of cultivation in Puck's 

 medium will be discussed. 



16.34. The Dependence of Molecular Weight of 

 DNA and RNA and Its Uptake by Mammalian 

 Cells. T. Wilczok (Gliwice, Poland). 



Ehrlich ascites carcinoma cells were used as 

 recipient cells for uptake studies of homologous 

 labeled DNA and RNA. The rate of incorpora- 

 tion was proportional to the molecular weight 

 of tracer nucleic acids; the lower molecular 

 weight, the lower adsorption and incorporation. 

 The highly polymerized polyanions such as 

 polyethylene sulphate compete with highly poly- 

 merized DNA and RNA in the process of its 

 uptake by recipient cells. DNA and RNA ad- 

 sorption on the surface of recipient cells pro- 

 ceeds instantly and this process is not time and 

 temperature dependent. The incorporation of 

 DNA into DNase resistant fraction of host 

 cell is higher at 0° than at 37° and reaches its 

 maximal level after 5 hours. The amount of 

 tracer DNA in DNase resistant fraction does 

 not increase when the exposure is performed 

 at 37°. 



16.35. The Change in Chromosome Number of 

 Human Cells in Culture after Heat Shock. W. 



Ostertag and H. Kruger (Munster, Ger- 

 many). 



The skin (epidermis) of a normal human male 

 was cultivated in modified Puck's medium. 



16.36. Alterations in Karyotype of Mammalian Cell 

 Populations Exposed to Antimetabolites. J. L. 

 Biedler (Rye, U.S.A.). 



Cytogenetic studies of transplantable mouse 

 neoplasms treated with several cancer chemo- 

 therapeutic agents were undertaken in a search 

 for possible specific relationships between anti- 

 metabolite, chromosomal alteration, and drug 

 resistance. Karyotype analyses were carried out 

 on sublines of sarcoma 180 and ascitic leukemia 

 L1210 continually exposed to amethopterin, 

 azaserine, 6-mercaptopurine, or 5-fluoruracil, 

 singly or in combination, over periods ranging 

 from a few weeks to several years. 



The modal chromosome numbers (70-71) and 

 4 bi-armed marker chromosomes of the untreated 

 sarcoma remained unaltered for 3 years. In 

 contrast, the modal number was reduced in 7 of 

 8 treated sublines. In all sublines there were 

 changes in or losses of one or more markers. 

 The disappearance of a small subtelocentric 

 chromosome was prevalent, and thus unrelated 

 to a specific antimetabolite. 



The modal chromosome number of the un- 

 treated leukemia remained 40-41 for 5 years. 

 Five of 12 variously treated sublines showed a 

 definite increase in number of chromosomes. In 

 early transplant generations of 6 of 13 amethop- 

 terin-treated sublines, a small proportion of cells 

 contained 2 characteristic subtelocentric marker 

 chromosomes instead of the usual 1. 



These results suggest that the antimetabolites 

 provoked mitotic non-disjunction, resulting in 

 decreases in numbers of chromosomes in the 



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