The strain effect of dam on intrauterine incisal growth in mouse fetuses

The embryo transfer technique was carried out to examine the strain effect of dams on the intrauterine incisal growth of mouse fetuses. A mean of nine DDD/Qdj embryos was transferred to each female recipient of the four strains (DDD/Qdj, C3H/Qdjl C57BL/Qdj, and DBA/IJ Sea). The dam's weight, the litter size, the gestation period and the newborn offspring weight were recorded. The mandibular incisal size of the newborn offspring was measured two-dimensionally by means of an image analyzing system. Statistical analyses of the incisal size of the DDD/Qdj newborn offspring delivered from the four strains of recipients showed the following results: 1) There were significant interstrain differences in the dam's weight and the newborn offspring weight, but not in the litter size and the gestation period among the four strains of recipients. 2) There was an inverse relation between the litter size and the mandibular incisal size while there were direct relations between the dam's weight and the mandibular incisal size, between the gestation period and the mandibular incisal size, and between the newborn offspring weight and the mandibular incisal size. 3) There was a significant strain effect of the dam on the mandibular incisal size of the newborn offspring. 4) After eliminating the effects of the litter size, the gestation period, and the newborn offspring weight on the mandibular incisal size of the DDD/Qdj newborn offspring developed in the four strains of dams, a significant interstrain difference in the adjusted mandibular incisal size was found (C3H/Qdj > DBA/1J Sea > C57BL/Qdj > DDD/Qdj), suggesting that the uteri of the C3H/Qdj strain of dams provided a more suitable environment for the intrauterine incisal growth than those of the other three strains of darns. Thus, it is concluded that the strain effect of dam played an important role in the intrauterine incisal growth of mouse fetuses.