人工授精ならびに体外受精と早期胚異常

抄録

Artificial insemination (AI) has been widely applied in farm animals, especially cattle, for the efficient use of superior genes from male animals. The use of frozen semen for AI in cattle has been widespread. Although a relationship between the occurrence of congenital malformations and the use of frozen spermatozoa has not been demonstrated, it has been reported that aging of gametes, which would occur with the practice of AI, induces embryonic abnormalities which lead to early embryonic death. Successful fertilization in vitro has been reported for 14 mammalian species; newborn young have been obtained in the rabbit, rat, mouse and man after transfer of eggs fertilized in vitro into host females. In many species a high incidence of polyspermy is found during in vitro fertilization, inducing chromosomal abnormalities and leading to early embryonic loss after transfer. In one study, nearly half of the young derived from rat eggs fertilized in vitro showed some degree of microphthalmia. However, there was no clear evidence that the abnormality was directly caused by in vitro fertilization. We have observed no congenital malformation in three generations of rats derived from eggs fertilized in vitro; others have reported similar results in the second generation of mice after in vitro fertilization. We have reported the successful fertilization in vitro of cattle and pig oocytes, but transfer and in vivo development have not been investigated in these species.