88 p. L. T. ILBERY, P. A. MOORE, S. M. WINN, AND C. E. FORD 



A (C57BL X T6)Fi$ received 4 x 180 rads y-irradiation. One hundred 

 and nineteen days later, this pre-leukaemic mouse was sacrificed after the 

 administration of Colcemid (Ciba) 1 hour before death. The thymus weighed 

 50 mg. Of 63 cells analysed 8 from the thymus contained 40 chromosomes and 

 7,41 with an Sii/iii marker chromosome present as well as T6. Forty-one cells 

 from the bone-marrow and 7 from spleen contained 40 chromosomes. Bone- 

 marrow from this mouse in dosage of 0-2 ml containing 2 x 10^ cells was 

 given to each of 5 C57BL $ mice irradiated with 900 rads ^^Co y-rays. Two 

 radiation chimaeras received one-quarter thymus each as a subcutaneous 

 graft in the ear, one a graft of spleen, one a graft of lymjjh gland, all grafts 

 from the pre-leukaemic mouse; one chimaera was ungrafted. One thymic 

 grafted chimaera died from the radiation syndrome on the 14th day. The other 

 thymic grafted mouse developed a soft whitish tumour about the ear. The 

 remaining chimaeras survived to one year and at sacrifice at that time no 

 abnormality was seen. The C57BL/C57BL x T6 radiation chimaera carrymg 

 the ear tumour was sacrificed following the prior administration of Colcemid 

 32 days from grafting. There was a tumour underlying the right ear measur- 

 ing 3 cm X 2 cm x 2 cm; the right axillary node was enlarged one plus, but 

 there was nothing else. The cytogenic data from this mouse showed sixteen 

 cells of 42 and 14 ceUs of 41 in the tumour, T6 present in aU and Sii/iii 

 frequently; in the lymph gland 11 cells of 41 (one with a Sii/iii), 11 cells of 40 

 1 of 42, T6 present in aU; and cells of 41 were seen in spleen and bone-marrow. 

 The tumour itself had shown progression to a mode of 42. The tumour was 

 passed by Bashford needle to 4 C57BL and 4 C6 mice. Two of the C6 grew 

 the tumour progressively and 1 mouse showed further progression in the 

 tumour to 14 cells of 42, 11 of 43, and 8 of 44. 



This exception to the failure of all other pre-leukaemic organs to trans- 

 plant is interesting because it shows that transplantation is possible before 

 overt signs of malignancy or spread have appeared; that is the cell containing 

 the altered karyotype is not necessarily still dependent simply because 

 dissemination in other organs or local infiltration has not been observed. The 

 exception involved transplantation of thymic tissue with a mode of 40 but 

 with a clone of 30% of cells with 41. Four other pre-leukaemias with a mode 

 of 40 and significant clones of 41 or 42 and four pre-leukaemias with modes of 

 41 did not transplant. 



DISCUSSION 



It is difficult not to associate the observed chromosome phenomena in 

 some way with leukaemia-induction, although there are cases of leukaemia 

 without observable changes. No consistent abnormality of chromosome 

 morphology has been identifiable by other groups (Kaplan, 1959). However, 



