ELECTRONE MICROSCOPIC STUDIES OF THE HUMAN AND RAT ENDOMETRIUM

Abstract

Human and rat endometrium were electron microscopically examined for cyclic change, Arias-Stella atypia in ectopic pregnancy, and features in normal pregnancy (first trimester) and pseudopregnancy.
1. In the proliferative phase, glandular epithelium of human endometrium contains rich ribosomes, well-developed mitochondria and rough-surfaced endoplasmic reticulum, lysosome-like osmophilic granules, and microvilli on the free surface. In the secretory phase, ribosomes are decreased, development of Golgi apparatus is accompanied by small cystic distention of rough-surfaced endoplasmic reticulum, glycogen appears, and cell membrane processes on the free surface are protruded in a lingual or peninsular form. Apocrine is considered to be one of secretion types. Stroma cells in the secretory phase assume fibroblast-like morphology with well-developed rough-surfaced endoplasmic reticulum.
2. The cyclic changes are also observed in glandular epithelium of rat endometrium. During a period from proestrus to estrus, microvilli develop, ribosomes in cytoplasma proliferate markedly and rough-surfaced endoplasmic reticulum develop together with lysosome-like granules. From estrus to metestrus, Golgi vesicles appear in cytoplasma, rough-surfaced endoplasmic reticulum are enlarged in lumen, and vesicles are developed, thun indicating the presence of a secretory phenomenon. In the case of rat, eccrine is assumed to be the principal type of secretion.
3. In the early pregnancy, glandular epithelium of human endometrium is characterized by cytoplasmic hypertrophy, glycogen deposition and development of lamellar rough-surfaced endoplasmic reticulum, presnting a structure suggestive of Wessel's type I (helle glykogenhaltige Zellen).
4. Early human decidual cells have vast cytoplasma, in which glycogen is rich, rough-surfaced endoplasmic reticulum are well developed, and tonofibril-like fine fibrillar structures are visible. Cell membrane is covered with basement membrane-like homogeneous membrane, and in its interstices are obsered short or polyp-like processes, which contain homogeneous or nucleated osmophilic granules. There is “a nuclear body” in the nucleus of the decidual cell.
5. When a steroid preparation is administered to prolong the menstrual cycle, microvilli are developed on the free surface of cell membrane in the glandular epithelium of endometrium, and in the cytoplasma, organellas are rich, and lucent areas indicative of glycogen areas are visible. Also stroma cell are enlarged with cytoplasma containing markedly increased ribosomes and developed rough-surfaced endoplasmic reticulum. These features seem to indicate pseudopregnancy, induced by progesterone.
6. Arias-Stella atypia in ectopic pregnancy consists of glandular epithelium with irregular nuclei, and contains rich ribosomes and prominently developed lamellar rough-surfaced endoplasmic reticulum, wich have strong tendency of cystic distension. In lucent cells, frosted glass-like ground substance is visible, and organellas are lost. Glycogen is invisible. These findings, which indicate the effect of chorionic gonadotropin, is considered, on the basis of their ultrafine structure, to present “hypersecretion”. Also stroma cells have vast cytoplasma, and preset the essentially same appearance with glandular epithelium. The nucleus contains “a nuclear body”
7. On the free surface of glandular epithelium of pregnant rat's endometrium, long microvilli are densely grown. Occasionally osmophilic bodies are attached to luminal side of their free ends. Similar osmophilic bodies are also sporadically seen in cytoplasma just beneath the free surface. No glycogen is observed. Stroma cells posses polyp-form processes, but basement membrane is not seen on the surface of cell membrane.