ULTRASTRUCTURE AND ENDOCRINOLOGICAL CORRELATES OF AN EARLY IMPLANTATION SITE IN THE RHESUS MONKEY

Abstract

Summary. An implanting blastocyst of a rhesus monkey killed on the 9th day after ovulation has been observed, using light- and electron-microscopy. The time of pregnancy was determined from the patterns of the circulating ovarian hormones and of LH from the beginning of the menstrual cycle to the day of autopsy. At this stage of implantation, the penetration of the epithelium by trophoblast cells had begun at a few sites along the area of attachment but the basement membrane was not reached. These events preceded measurable increments in circulating chronic gonadotrophin and the `rescue' of the corpus luteum.