Abstract
The embryo transfer technique is a very powerful tool for detecting intra-uterine effects of dams on prenatal growth of embryos. Embryos of DDD strain were transferred to a recipient of the same strain. Litter size, gestation period and birth weight of newbron offspring were measured. To examine the effect of embryo transfer on the prenatal growth of embryos, these results were compared with those of newborn DDD strain of mice that had developed from non-transferred embryos. Embryos of DDD strain were transferred to four strains of recipients (DDD/Qdj, C3H/Qdj, C57BL/Qdj and DBA/1J Sea) . Litter size, gestation period and birth weight of newborn offspring were measured. The four strains of recipients were compared to examine the effect of recipient strain on the prenatal growth of the embryos. The results were as follows. 1. There was no gender difference in birth weight of offspring. 2. A negative correlation (partial regression coefficients -0.024, P<0.001 in the transfer and non-transfer groups, and -0.058, P<0.001, in the four strains of recipients) was observed between litter size and birth weight of newborn offspring, while a positive correlation (partial regression coefficients: 0.068, P<0.001 in the transfer and non-transfer groups, and 0.071, P<0.001 in the four strains of recipients) was observed between gestation period and birth weight of newborn offspring. 3. Embryo transfer might affect the intra-uterine growth of transferred embryos. 4. The four different strains of recipients might contribute unequally to the prenatal growth of transferred embryos because of their different intra-uterine conditions. After statistically eliminating the effects of both litter size and gestation period, birth weight of newborn offspring that developed from the same DDD/Qdj strain of embryo increased significantly when developed in DDD/Qdj and C3H/Qdj, which had larger body weights than C57BL/Qdj and DBA/ 1J Sea.
