Intrafollicular overripeness and teratologic development

Abstract

Intrafollicular overripeness was studied in eggs of Xenopus which had been prevented from ovulating for extended periods. When ovulation was artificially induced, a number of eggs at various degrees were released. High mortality and malformation rates were recorded. Range and types of abnormalities were much like those in other amphibians developed from eggs affected by intrauterine overripeness. This suggests that the pathological change of the ovarian eggs is very similar to that of the uterine eggs. Effects on the meiotic spindle were studied in 353 externally normal eggs that were collected from various portions of the reproductive tract. In 179 eggs which were sectioned to show the maturation spindle in side view, 3 cases in first meiotic metaphase and 20 in second metaphase exhibited abnormal chromosomal behavior. This included precocious movement of one or two undivided tetrads and dyads to the outer or the inner spindle poles and loss of polarization of the displaced chromosomes. It was suggested that these might be caused by disintegration of the spindle fibers and related to the nondisjunction of the meiotic chromosomes. In obviously degenerating uterine eggs, disintegration of the spindle fibers was evidenced by the loss of connection of spindle fibers with the central body. Degeneration of chromosomes and hypertrophy of the spindle were also characteristic in these eggs. The importance of intrafollicular overripeness of ovocytes in the etiology of human spontaneous abortion and of congenital malformation is discussed.