CHAPTER 13 



The Effects of Radiation on Mammalian 

 Prenatal Development 1 



Liane Brauch Russell 

 Biology Division, Oak Ridge National Laboratory 



Introduction. Experimental findings: The ^reimplantation period — The period of 

 major organogenesis; Mortality, Body size, Sex ratio, Morphology — The period of the 

 fetus; Mortality, Morphology, Time of parturition. Isotope studies. Mechanisms of 

 radiation effect on the embryo: Influence of the maternal organism — Nature of the primary 

 damage and intermediate effects — Dosage relations; variability — Comparison with other 

 agents affecting development. Clinical literature on the effects of radiation on embryo 

 and fetus; human implications of experimental work. Summary. References. 



I. INTRODUCTION 



Studies on the effects of radiation on mammalian prenatal development 

 are of special interest not only because of their human and medical 

 implications but by virtue of their contributions to the fields of mam- 

 malian experimental embryology and of developmental mechanics in 

 general. 



Certain inherent peculiarities in the biological material set it apart 

 from the more conveniently studied invertebrates and lower vertebrates. 

 Since the mammalian embryo develops within the body of its mother and 

 cannot, in general, be irradiated without irradiating some maternal tis- 

 sues, the question of how much of the damage to the conceptus is direct 

 and how much is caused indirectly through damage to the mother must 

 always be in the background of an investigation and was, in fact, almost 

 the sole subject of much of the early work. The dependent nature of 

 mammalian development is, however, of some advantage for embryological 

 studies since it probably permits abnormal development to proceed to 

 more advanced stages than it would in the unprotected embryos of other 

 forms. Since the embryo is usually not observed at the time of irradia- 

 tion, its developmental stage can be designated only by its chronological 

 age, which — because of variations in rate between litters (especially of 

 different genetic backgrounds) and even within litters — provides only an 



1 Work at Oak Ridge and preparation of manuscript were performed under Con- 

 tract No. W-7405-eng-26 for the Atomic Energy Commission. 



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