Non-Mendelian development defects: animal models and implications for research into human disease.

The major groups of malformations in man are polygenic in origin but this review deals only with defects due to non-Mendelian factors. Animal models that help in identifying the causes and in understanding the numerous and often subtle mechanisms of human malformations are of particular value. Many chemicals, physical agents, and nutritional deficiencies affect experimental species but few are teratogenic for domestic animals and even fewer for man. The known fetopathic viruses of animals and man cross the placenta to cause chronic, nonlethal fetal damage without harm to the mother. Ionizing radiations are teratogenic for all species and hyperthermia for many, but the role of the latter in human development is uncertain. The identification of more animal species with spontaneous or induced defects comparable to those found in man and of additional causative teratogens will increase the resources available for research into the causes and mechanisms of abnormal development in man. No animal species is ideal in teratological research but each has its virtues. This report comments on the present status of research in teratology and the trends that might profitably be followed in the future.