Overripeness of the egg as a cause of twinning and teratogenesis: a review.

Abstract

IV. Summary 1.The first part of this paper is a report on original experimental studies on frog eggs, relating to the effects of overripeness. Overripeness is produced by the forced retention of the unfertilized eggs in the uteri, over periods up to 10 days at room temperature. The following effects on development after delayed fertilization are described: a )Abnormalities of cleavage, gastrulation, and neurulation, leading often to dorsal asyntaxia (spina bifida and caudal duplication). b )Twinning and polymelia. c )Deficient organogenesis, particularly microcephaly and acephaly. d )Cellular pathology, incomplete or entirely lacking cellular and histologic differentiation. 2.Experiments on transplantation prove that the abnormal tissues, which usually die with the damaged embryos at an early stage, may survive and grow for months if transplanted into healthy larvae or frogs. The degree of malignancy of some such transplants must be determined in continued experiments. 3.The study of the carbohydrate metabolism confirms the discovery of Samassa of the capacity of frog eggs to survive and to develop through the entire cleavage period under anaerobic conditions. It further shows that uterine eggs store considerable amounts of CO 2 . Since other experimental series reveal a sensitivity of these eggs to high concentrations of CO 2 , it seems probable that this metabolite is the specific teratogenic agent of overripeness. The high R.Q. values observed in cultures from overripe eggs are an expression of general tissue damage, but support also the contention that some of the effects are of the nature of cancerous conversions. 4.The frequency of manifestation of damage by overripeness increases with the temperature and with the time of retention in the uterus. The special distribution pattern of the various grades of damage is discussed in connection with the interpretation of cancerogenic action. 5.The second part of the paper consists of a review of the literature on overripeness and a discussion of the mechanics of teratogenesis, based on the results of experimental investigations.