SIX FIGURES
C'ysteine has been shown to diminish many of the biological effects of x-irradiation, e.g., lethality of bacteria (Forssberg, '50 ; Hollaender, Stapleton and Burnett, 'Sl), isolated cells Patt, Blackford and Straube, '52), tissues (Hall, '52), and animals (Patt et al., '49, '50; Smith et al., '50) ; epilation (Forssberg, '50) ; greying of hair (Kulwin, '52) ; lenticular opacities (Von Sallmann, '52) ; leucopenia and anemia (Patt, Smith and Jackson, '50). Thus, it would appear that cysteine may raise the threshold for x-radiation effects generally, with the probable exception of those attributable to direct ionization or excitation. Hypoxia (Thoday and Read, '47 ; Dowdy, Bennett and Chastain, '50) probably belongs in the same category in contrast with more specific procedures such as estrogen pretreatnient (Treadwell, Gardner and Lawrence, '43 ; Patt et al., '49), spleen shielding (Jacobson et al., '49, '50), and bone marrow injection (Lorenz et al., '51). The present experiments were designed to determine primarily whether (1) cysteine results in a uniform dose reduction f o r several radiobiological effects in the mammal, i.e., lethality, lymphopenia, granulocytopenia, and splenic involution and (2) dose reduction consists, in effect, of the deletion of a fixed o r proportional amount of the radiation.
Methods
Female C F no. 1 mice, 10 to 1 2 weeks of age and weighing 19 to 25 gm, were used in these studies. Animals were main-327 .