Fluorescence study of thymus lymphocytes of X-irradiated mice and their progeny

The mechanisms of changes in the ultra-violet fluorescence (U.V.F.) intensity of mouse thymus lymphocytes 24 hours and 30 days after whole-body X-irradiation have been studied. The thymus lymphocytes of the first generation offspring (F1) from X-irradiated males and unirradiated females were also investigated. At 24 hours after irradiation the U.V.F. intensity decreased for small doses (50 and 65 rad) and increased for doses of more than 100 rad. The changes in U.V.F. intensity were related to a size-independent mechanism. It was found that the U.V.F. increase for doses of 100-700 rad was not connected with the appearance of non-viable (eosin test) cells. The changes in U.V.F. intensity and cellular composition of the thymus were the same 30 days after irradiation and for F1 mice. The increase in U.V.F. intensity was about 14% and did not depend on dose between 50 and 500 rad. About one-half of this increase was connected with an increase in the proportion of medium and large lymphocytes in the thymus. The rest of the effect was related to a size-independent mechanism.