Decrease in Numbers of Mouse Spleen Nodules with Time Post-Irradiation. ∗

Abstract

Conclusion

The experiments discussed above serve to illustrate the fact that decreases in numbers of nodules can occur following irradiation of mice either a) to the whole body, or b) with the tail shielded. The phenomenon is as yet unexplained, and there is little evidence to indicate the nature of concomitant events at the cellular level.

These findings might conceivably be related to the “abortive rise” in numbers of cells in bone marrow and peripheral blood, seen following whole-body irradiation of mammals(5). The abortive rise is thought to be an expression of cellular radiation damage. As such, it might be related to the decrease found with endogenous nodules, but not to that found with tail shielding, in which case the nodules arise principally from cells in the shielded tail.

A second effect, which suggests itself as being relevant because of its resemblance to the slow growth found in endogenous nodules, is the “small colony formation” reported by Sinclair(6) for cultures of heavily irradiated mammalian cells. This effect appears not to be related to the main phenomenon, however, since it is not accompanied by any decrease in colony counts.

The author wishes to thank S. L. Commerford, J. L. Bateman, and V. P. Bond for helpful discussions and comment, and H. A. Johnson for help with morphology.