RADIATION IN PRENATAL DEVELOPMENT 



867 



earliest stages were most sensitive, the average number of living embryos 

 per treated female being only about 20 per cent of the controls in groups 

 irradiated on days Y 2 , \\i, or 2 l / 2 , but 31 and 57 per cent following treat- 

 ment on days %y 2 and 4y 2 , respectively (Fig. 13-la). Mortality between 

 days 103^ and 13>£ and between days 13>2 and term was no higher than 

 in controls and radiation-induced death, therefore, occurred entirely 

 before day 10> 2 , m fact, so long before that stage that abnormalities, if 



lOOi 



80- 



,_ 60- 



z 



UJ 



o 

 cc 



Lid 



°- 40- 



20- 



10.0- 



(a) 



-r 



°7777?% 



.POSTIMPL^DEAT 



y/y//jyy- 



\POSTIMPLANTATION DEATHnX 



(b) 



I 



(O) 



h — A 



~J Z -r 2 2 'g 



DAY IRRADIATED (POSTCOPULATION) 



(b) 



3* 



H 



YIELD 0FL1VE EMBRYOS PER 

 TREATED FEMALE, % OF 

 CONTROLS 



PROPORTION OF MATINGS 

 RESULTING IN ANY IMPLANTS, 

 % OF CONTROL PROPORTION 



O O IMPLANTS PER CONTROL 



A A IMPLANTS PER IRRADIATED FEMALE 



•-- -• LIVING EMBRYOS PER CONTROL 

 A- — A LIVING EMBRYOS PER IRRADIATED 



FEMALE 

 SPACE BETWEEN SOLID LINES REPRESENTS PRE- 

 IMPLANTATION DEATH OF INDIVIDUALS 



Fig. 13-1. Effects of irradiation with 200 r during the preimplantation stages of the 

 mouse embryo. All observations are made on days 10}-^ or 13} 4 postcopulation, and 

 points are based on a total of 521 implants in the controls, 310 in the irradiated groups. 

 Fig. (b) based on pregnant females only. (Russell and Russell, 1950a.) 



any were produced, could no longer be recognized at the time of observa- 

 tion. More specifically, three groups of deaths can be recognized: (1) 

 Preimplantation death of entire litters, i.e., very early termination of 

 pregnancy, is indicated by the excess of nonpregnant females at the time 

 of dissection (see Fig. 13-la). The percentage of copulations resulting in 

 implants observable on days 10^ and 13>^ is 79 in controls and 44-67 in 

 different irradiated groups (average, 56 per cent). As a whole, the reduc- 

 tion is highly significant but fluctuations among the different irradiated 

 groups are probably random. Therefore, on the average, about 29 per 

 cent of the embryos irradiated in preimplantation stages are lost in whole- 



