In vitro Production of Nucleolar Channel System by Progesterone in Human Endometrium

Abstract

ELECTRON microscope examination of normal human endometrium during the midsecretory phase of the menstrual cycle demonstrates that the nucleolus of the epithelial cell differentiates into an organelle variously termed a nucleolar canalicular system¹, a nucleolar basket² or a nucleolar channel system³. Such a structure appears if ovulation has occurred. Nucleolar baskets have been seen as early as the sixteenth day of a normal 28 day cycle. After this they may increase in number, reaching a maximum around the twentieth day and then disappear, not being found later in the cycle. They have not been seen in the proliferative phase of the cycle or in early pregnancy.