CHROMOSOMES IN MURINE PRE-LEUKAEMIA 



P. L. T. ILBERY, P. A. MOORE, S. M. WINN 



Department of Preventive Medicine, University of Sydney, Australia 



AND C. E. FORDf 

 M.R.C. Radiobiological Research Unit, Hanvell, England 



SUMMARY 



Chromosome anomalies are frequent in our experience in established murine leukae- 

 mias. It seems that recognizable structural changes with excess, perhaps sometimes 

 deficiency, of total DNA (without consideration of gene mutation) are also often pre- 

 sent in the pre-leukaemic phase. It appears these changes are associated with an early 

 stage of leukaemia induction for transplantation of pre-leukaemic thymuses under 

 optimum conditions, with one exception in these experiments, failed. 



Abnormal chromosome combination formed the basis of Boveri's (1929) con- 

 cept of carcinogenesis. It is certain that altered chromosome karyotypes, in 

 which, parts of chromosomes or whole chromosomes are added to or subtracted 

 from the normal complement, have since been demonstrated in a variety of 

 established mammalian tumours. With improved techniques there has been 

 recognition of even less pronounced deviations from normal until, within the 

 framework of the somatic mutation theory, it is credible that a gradation of 

 genetic changes extends beyond optical limits to mutation of genes. If this 

 wide spectrum of genetic changes from point mutation to gross structural 

 changes can be responsible for neoplastic transformation it is perhaps note- 

 worthy, in the series of murine reticular neoplasms reported by the Harwell 

 group (Ford et al., 1958) and since extended, and in this present series, that 

 there is a heavy loading to the end where abnormalities of chromosome 

 number and/or form are visible. These cytogenetic abnormalities however 

 may be a reflection of more subtle initial genetic changes and become 

 manifest only at some point in time following the neoplastic transformation. 

 This report is then concerned with an attempt to locate the development of 

 malignancy in relation to the appearance of the altered karyotype. 



MATERIALS AND TECHNIQUES 



C57BL and DBA/2 mice inbred in this laboratory during the last 5 years 

 were used in the experiments. T6/T6 mice (Carter et al., 1955), homozygous 



t Guest Worker in the Department of Preventive Medicine during 1960 aided by the Post 

 Graduate Medical Foundation within the University of Sydney. 



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