The Effect of Tritiated Thymidine on the Oocytes of Foetal Rats Following Maternal Infusion in Pregnancy

specific activity of 2 Ci/mM was given by continuous i.v. infusion from day 9 of pregnancy to term. The oocyte survival was scored in the offspring, killed at different ages from 0 to 70 days old. Four-month-old female Wistar rats, with an average body-weight of 180 g, were used. Their phase in the ovulatory cycle and the time of fertilization after mating with males of the same strain were determined by examination of vaginal smears (Preissecker 1958). From the 9th day of pregnancy until parturition, they were given continuous i.v. infusion H-TdR: in isotonic saline via a polyethylene catheter (Little, Brecher, Bradly and Rose) 1962 using a Havard pump, delivering 1 ml./day. 3 H-TdR was given at a daily dose of 290 pCi, with a specific activity of 2 Ci/mM. Rats of the same strain were killed 1, 3, 4, 7 and 28 days after birth to serve as untreated controls. The experimental design is illustrated in table 1. The right ovary was removed and fixed in formalin, and serial sections were cut at 5 , stained with Treatment of mother Number of female offspring killed at each interval after birth 3 H-TdRdose/day: 290 Ci Day Day Day Day Day Day Day Day Day Day 9th-22nd day of pregnancy 0 1 3 4 7 10 14 28 70 240