Failure of syngeneic bone marrow cells to protect against MC-induced lymphoma in dba-2 mice

The D4Mit12 locus on mouse chromosome 4 provides susceptibility to both gamma-ray-induced and N-methyl-N-nitrosourea-induced thymic lymphomas

Low-penetrance genes control different susceptibilities to gamma-ray-induced thymic lymphomas in mouse strains. Our previous genetic analyses with backcross mice between BALB/c and MSM strains and congenic lines localized one such gene near the D4Mit12 locus on chromosome 4. N-Methyl-N-nitrosourea (MNU) is a guanine base-alkylating agent and differs from gamma-radiation in its mechanism of mutagenic action. Accordingly, in this study, we examined whether or not the locus also provides susceptibility to MNU-induced thymic lymphomas using 84 offsprings derived from congenic mice for D4Mit12. Association analysis provided a suggestive linkage at D4Mit12 (P = 0.0075) and the linkage was sustained by the peak of likelihood ratio statistical values being at the same position as that for the gamma-ray-induced lymphomas. The results strongly suggest that the BALB/c allele near D4Mit12 is associated with susceptibility to lymphomas induced by two carcinogenic agents having different mechanisms of mutagenic action.

Effects of Syngeneic Bone Marrow Cells on Mice Given a Leukemogenic Treatment with Urethan

A leukemogenic treatment with urethan in infant (SWR x C57BL)F1 mice (1 mg/g body weight, 5 times, once every second day) induced a marked reduction of the thymus and spleen weight, of the number of RBC, WBC, and bone marrow cells, with an inverted lymphoid/myeloid cell ratio in the bone marrow. An analysis of the bone marrow population showed that the carcinogen acted selectively on the lymphoid cells and, to a lesser extent, on the erythroblastic ones, while the myeloid cells did not appear to be involved. The damage was still present 10 days after the end of treatment. A single intracardiac inoculum of 15–20 × 106 syngeneic normal bone marrow cells, 3 days after the last urethan injection, determined a recovery of the spleen weight and of the cell ratio in the bone marrow, whereas the thymus weight and the blood and bone marrow cell counts were uneffected. Moreover the bone marrow inoculum failed to inhibit the induction of thymic lymphosarcomas.