Effects of negative pi mesons on mouse bone marrow cells.

Mouse bone marrow cells exposed in vitro to graded doses of negative pi mesons at 3.5-6.0 rads/min. gave Do values of 160 rads in the plateau (0.6 and 12.0 cm), and 130 rads in the peak (16.5 and 18.4 cm). Survival curve shoulders were narrow, with Dq values of 25 and 15 rads for plateau and peak positions. Gamma rays from 60Co at 4.5 rads/min. produced a curve with wider shoulder but steeper slope such that the RBE was essentially 1 for single doses between 100-400 rads.