EFFECT OF THE DAM STRAIN ON THE SPONTANEOUS INCIDENCE OF CLEFT-LIP AND PALATE AND INTRAUTERINE GROWTH OF CL FR MOUSE FETUSES/

Purpose: The effects of dam strain on the spontaneous incidence of the cleft lip and palate (CLP) and the intra-uterine growth of transferre d CLP-susceptible CL/Fr embryos were examined with an embryo transfer technique. The CL/Fr strain of embryos at the early blastocyst stage w as transferred to the same dam strain and also to the CLP-resistant C5 7BL dam strain. A laparotomy was done on the 18th gestational day at w hich time the number of fetuses, the resorption sites and the fetus we ight were recorded, Each fetus was checked for the presence of CLP. Fi ve criteria to assess the reproduction and fertility as well as the fe tus weight were then compared between both dam strains. Results: The d am pregnancy rate and the fetus survival rate in the CL/Fr dam strain were both significantly lower than those in the C57BL dam strain. The resorption rate in the CL/Fr dam strain was significantly higher than that in the C57BL dam strain. The spontaneous incidence rate of CLP in the CL/Fr dam strain was also significantly higher than that in the C 57BL dam strain. The fetus weight of the CL/Fr fetuses developed in th e CL/Fr dam strain was significantly lighter than that of the CL/Fr fe tuses developed in the C57BL dam strain. Conclusion: The results indic ated that the CLP-susceptible CL/Fr dam strain provided a less favorab le uterine environment for the implantation, survival and intrauterine growth of the transferred CL/Fr embryos and also caused a higher spon taneous incidence rate of CLP. Thus, it can be concluded that the effe ct of the dam strain appears to play an important role on the spontane ous incidence of CLP and the intraauterine growth of the CLI Fr strain embryos transferred to both CL/Fr and C57BL dam strains.