HEMATOLOGIC EFFECTS OF RADIATION 1031 



30-day LD 50 exposure of rabbits to X rays. This information is fairly 

 complete for dosage ranges up to the LD 5 o, but more complete data are 

 needed for higher dosages. 



Correlation between the effects of these penetrating radiations on 

 blood-forming tissue and various hematologic constituents of the periph- 

 eral blood is generally good when the effects of dosages in the LD 5 o range 

 for any particular species are being considered. Major deviations, how- 

 ever, are recognized. With doses of 100 r or less there is a lack of correla- 

 tion because the changes that occur in the lymphatic tissue are difficult 

 to quantitate histologically. The lymphocytes in the peripheral blood 

 may be drastically reduced, although only equivocal changes are seen in 

 the lymphatic tissues. 



SINGLE EXPOSURE TO X RAYS 



Studies of the effects of a single total-body exposure to X rays indicate 

 that the rabbit (Hagen et al., 1944; Jacobson et al, 1947), rat (Steamer 

 et al., 1947a, b; Lawrence and Lawrence, 1936), monkey (Suter, 1947: 

 Ingram and Mason, 1950a), mouse (Henshaw, 1943-1944a; Bloom and 

 Bloom, 1947), chick (Murray et al, 1948), goat (Swift et al., 1946), pig 

 (Cronkite et al., 1949), guinea pig (Henshaw, 1943-1944b; Haley and 

 Harris, 1949; Lorenz, 1951; Brues and Rietz, 1948), and dog (Prosser 

 et al., 1947; Allen et al., 1948) show, in order, an increasing sensitivity to 

 radiation as measured by changes in the blood and blood-forming tissues. 

 As compared with the other species, it should be noted that the data on 

 the hematologic effects in monkeys are conspicuously inadequate. 



Effects on Leukocytes. The term "leukocyte" is applied to all the 

 white cells in the peripheral blood. In the species discussed in this 

 chapter the polymorphonuclear cells of the granulocyte series and the 

 lymphocytes are the predominant forms. These constituents are dis- 

 cussed individually. 



Aubertin and Beaujard (1908) first described the appearance of a 

 leukocytosis prior to leukopenia after total-body X irradiation. Actu- 

 ally, during the first 24 hours after exposure the total leukocyte count of 

 the peripheral blood reflects the rapidly changing status that may be 

 described briefly as follows: With doses of 500 r an initial significant 

 reduction occurs in the number of circulating leukocytes in the rabbit. 

 Since the number of heterophils remains constant during this period, the 

 reduction can be attributed to lymphocyte reduction which has been 

 initiated and continues. On the other hand, leukocytosis is apparent at 

 8 hours and again at about 24 hours. This leukocytosis, which is dis- 

 cussed in detail later, results entirely from an increased number of 

 heterophils. 



Effects on Lymphocytes. With the possible exception of erythrocyte 

 iron uptake, the most sensitive indicator of acute radiation effect that can 



