The effect of pre-fertilization maternal irradiation on prenatal, perinatal and postnatal survival in the albino rat.

Abstract

The rats usad were from a highly inbred stock (F-1) developed in a selection experiment for high and low ovarian response to a gonadotro’phic hormone (KYLE and CHAPMAN 1953; CHUNG and CHAPMAN 19%). Two “lines”, designated as control (C) and irradiated (R), were formed by random selection within litters of the inbred stock. These “lines“ were maintained for 13 generatims (0 through 12) by restricted random matings, the restriction being that the mated individuals should ;have no grandparents in common. The offspring from these matings are referred to as “outbreds”. The quotation marks refer to the fact that the outbreeding was within the highly inbred i(F’+l) stock. Part of the animals in generations 3, 4, 5, 7, 10 and 12 were produced by full-sib matings and are referred to as “inbreds”. They were not irradiated or allowed to reproduce. The design and mating procedure is as illustrated in Figure 1 of HAVENSTEIN et al. (1968). Full-sib mating pairs were selected at random from the “outbred” litters of the previous generation. Because the litters from which they came had to contain at least one male and one female, individuals from small litters and litters with no males or no females were eliminated from baing parents of the “inbred” group. This may have resulted in some bias in the results if the number of induced mutations which was put to test by the full-sib matings was dependent on the size of the litter from which the sib pairs were obtained. The “outbred” females of the irradiated group were exposed to 100, 150 and 2OOr doses of whole-body X rays at 10, 32 and 14 weeks 01 age, respectively, in generations 0 through 7 and in generation 9. In some generations the animals were remated. Their litters were referred to as “mating group (2)”. Further details of the experimental design and procedures have been published by CHAPMAN et al. (1964) and by HAVENSTEIN et al. (1968).