HEMATOLOGIC EFFECTS OF RADIATION 



1045 



300 r and above. Lorenz (1951) has demonstrated that a severe thrombo- 

 cytopenia occurs in guinea pigs after exposure to 200 r. Mice, according, 

 to Jacobson, Robson, and Marks (1950) and Jacobson, Simmons, Bethard, 

 et al. (1950), are approximately equal in sensitivity in this respect to rats. 

 With 600 r the maximum reduction occurs at about 9 days after irradia- 

 tion (Fig. 16-10). Swine (Cronkite et al., 1949) and dogs (Allen and 

 Jacobson, 1947a, b; Prosser et al., 1947) are roughly comparable with 

 guinea pigs in sensitivity. In rabbits (Jacobson et al., 1947; Jacobson, 

 Marks, and Lorenz, 1949), platelets are markedly reduced after exposure 

 to 500 or 800 r. Recovery of the platelets to normal values in all these 

 species occurs by about the fourteenth to twenty-first day after LD 50 



n - 



10 

 9 



Q> 

 O 



\- 

 bJ 



< 



_J 

 CL 







3 

 TIME 



6 9 12 

 AFTER X RAY, 



19 



23 



15 

 days 



• • CONTROLS o--o OPERATED CONTROLS 



t-i600r WITH SPLEEN EXTERIORIZED 

 ♦— • 1025 r WITH SPLEEN EXTERIORIZED 



Fig. 16-10. Comparative effects of 600 and 1025 r of total-body roentgen irradiation 

 on the platelet values of CFi female mice. 



exposure. With doses above the LD 50 the recovery of platelet values is, 

 in general, a function of the dose. 



The factors concerned with the hemorrhage appearing in experimental 

 animals exposed to penetrating radiation may be multiple. With doses in 

 the LD 50 range or above in any of the species studied, a severe thrombo- 

 cytopenia occurs, but at this time it is not known with certainty whether 

 or not this single cellular reduction alone accounts for the widespread gross 

 and microscopic hemorrhage which occurs in many of these species but 

 which has been studied most extensively in the dog (Allen and Jacobson, 

 1947a, b; Allen, Moulder, and Enerson, 1951) and swine (Cronkite et al, 

 1949; Cronkite, 1950). Platelets are considered to have a number of 

 functions that are important in irradiation hemorrhage. Allen (1952) 

 lists these functions as follows: (1) platelet agglutination and adherence 

 to the site of vascular injury, (2) a source of thromboplastin, (3) an 



