Effects of Fetal or Maternal Hypophysectomy on Endocrine Organs and Body Weight in Infant Rhesus Monkeys (Macaca mulatta): With Particular Emphasis on Oogenesis

Abstract

The effects of fetal and maternal hypophysectomy on the development of the fetal endocrine glands in the rhesus monkey (Macaca mulatta), with particular emphasis on the progress of oogenesis is reported. Maternal hypophysectomy was performed between 58 and 71 days of gestation. Fetal hypophysectomy was performed between 114 and 117 days of pregnancy. Gravimetric data on body and organ weights were compiled on term infants. Completeness of hypophysectomy was confirmed by histological examination of the sella turcica from each operated animal. Morphological and quantitative studies were performed on serially sectioned ovaries of term infants. Maternal, but not fetal, hypophysectomy produced a generalized fetal growth retardation. Term infant mean adrenal, but not thyroid weight was elevated significantly (P<0.05) following maternal hypophysectomy. Conversely, mean ovarian, adrenal and thyroid weights were markedly reduced (P<0.05) in term infants following fetal hypophysectomy. Maternal hypophysectomy had no adverse effects on the morphology of term infant ovaries. In contrast, within ovaries of infants following ablation of the fetal hypophysis, the course of oogenesis was disordered and oocytes had undergone atresia. Quantitative data indicate that fetal hypophysectomy resulted in a reduction in total numbers of germ cells and a significant increase in the percentage of germ cells undergoing atresia. Although the total numbers of germ cells in ovaries of term infants in the absence of the maternal hypophysis was half that in intact controls, the percentage of atretic germ cells was similar to the controls. We conclude that a dynamic interaction of fetal and maternal hypothalamic-pituitary axes governs the development of the fetus and its endocrine organs. Survival of gametes within the fetal ovaries of these primates is dependent primarily on secretions of the fetal pituitary.