900 RADIATION BIOLOGY 



already commenced before injection, is greatly modified; (3) newly 

 differentiated cells are more radiosensitive as shown by greater damage in 

 the second than the first molar and by effects within different cell layers 

 of each tooth; (4) doses of 10-17 /zc/g produce general postnatal growth 

 retardation which is' greater for earlier than for later injections. 



Finkel (1947) injected Sr 89 and plutonium into pregnant females 

 (stages not stated). While very little plutonium reached the fetus, Sr 89 

 concentration in the fetus actually exceeded that of the mother if injec- 

 tion was shortly before term. Both treatments increased the percentage 

 of stillbirths, and Sr 89 produced retardation of growth, fragility, bending 

 and shortening of the long bones, anemia, and osteogenic sarcoma. 



III. MECHANISMS OF RADIATION EFFECT 

 ON THE MAMMALIAN EMBRYO AND FETUS 8 



A. INFLUENCE OF THE MATERNAL ORGANISM 



One question that has been raised several times in the literature is 

 whether radiation affects the conceptus directly or produces an altered 

 condition in the maternal organism which indirectly damages the embryo 

 or fetus. Archangelsky (1923) suggested that this altered condition 

 might consist of changes in uterine tissues, alterations of hormonal output 

 of the ovaries, or the production of "roentgen leukotoxins" first postu- 

 lated by Linser and Helber (1905). Obviously, any debilitated condition 

 of the mother could affect viability of the embryo, and several reports 

 from the early investigations in this field — when preoccupation with this 

 particular point was greatest — seem indeed to indicate an indirect influ- 

 ence on viability of the embryo. In most of this early work, however, the 

 doses were extremely high, often high enough to kill the mother before 

 expected term, and factors of shielding may have been incompletely 

 understood. Fellner and Neumann (1907) and Saretzky (1908), who 

 shielded the uterus and irradiated the ovaries of rabbits in the first half of 

 pregnancy, both reported death of embryos (resorption and abortion, 

 respectively). Von Hippel and Pagenstecher (1907) obtained almost as 

 poor a yield of living young at term when the abdomen was shielded as 

 when total-body irradiation was given to rabbits 7-12 days pregnant. 

 They also injected blood from an irradiated animal into one nonirradiated 

 doe presumed to be 9 days pregnant and report that no young were born 

 and that maternal toxins were therefore responsible for prenatal death. 

 Cohn (1907) shielded all but the head of rabbits 10-20 days pregnant and 



8 Since this chapter went to press, the mechanisms of radiation effect on the mam- 

 malian embryo have been more extensively and systematically discussed in another 

 publication (L. B. Russell and W. L. Russell, 1954). 



