Relationship of apical domes in the rabbit uterine epithelium during the peri-implantation period to endocytosis, apocrine secretion and fixation

Abstract

Summary. The luminal surfaces of non-ciliated uterine epithelial cells of 17 rabbits on Days 4\p=n-\6of pregnancy were studied histologically with light microscopy, transmission and scanning electron microscopy. The luminal surfaces of most epithelial cells exhibited short microvilli and did not project into the uterine lumen. However, the surfaces of some cells showed fewer microvilli and bulged out into the uterine lumen, giving the cells a dome-like appearance. The domes appeared most frequently on Day 6 of pregnancy and contained a few ribosomes, mitochondria, and membranous elements; large vacuoles and granules were absent.The domes were not involved in endocytosis. Ferritin introduced into the uterine lumen was incorporated into the cells by coated micropinocytotic invaginations at the base of the microvilli, rather than by any activity of the domes. There was also no indication that the domes pinched off to produce an apocrine secretion. The size and frequency of domes were, however, clearly related to the fixation procedure. Epithelial cells from uteri fixed by vascular perfusion showed fewer and less prominent domes, while cells from uteri fixed by immersion displayed a larger number of domes that projected further into the uterine lumen. The domes in the rabbit epithelium therefore differ structurally and functionally from the apical projections (pinopods) that occur in the uterine epithelium of the rat and mouse during the peri-implantation period.

Conceptus Influences the Distribution of Uterine Leukocytes During Early Porcine Pregnancy1

“…In sections of zinc-fixed tissues, the compressed appearance of the deep uterine glands relative to those in paraformaldehyde-fixed sections suggested that the zinc fixative had not penetrated as well as had the paraformaldehyde. Blebbing on the apical surfaces of some luminal epithelium cells resembled the apical domes described by Parr and Parr in the rabbit uterus, which were artifacts of fixation (perfusion versus immersion) [26]. Despite the slight compromise in morphology, zinc fixation was clearly superior for immunostaining; no specific staining was detectable in tissue fixed with paraformaldehyde, ethanol, or Zenker solution, but strong positive staining was obtained in zinc-fixed sections.…”

Alterations in epithelial glycocalyx of rabbit uteri during early pseudopregnancy and pregnancy, and following ovariectomy

“…These alterations could be accomplished through several mechanisms, including 1) membrane turnover during endo-and exocytotic activity, 2) enzyme activity of uterine secretions, 3) a change in glycosylation activity of luminal epithelium in response to progesterone, or 4) a dilution of surface anionic sites to levels undetectable by PCF binding due to extensive epithelial proliferation during early pregnancy or pseudopregnancy. That luminal membrane glycoproteins present in uteri from nonpregnant females are replaced through membrane turnover during endocytotic and exocytotic activity is unlikely since these events are not characteristic of the rabbit luminal epithelium during the progestational period (Parr and Parr, 1982). This may contribute to reduction in negativity in the rat uterus where endocytosis is a predominant feature of hormonal stimulation Parr, 1974, 1977;Williams and Rogers, 1980).…”

Relación Útero-Embrionaria Y Su Variación Morfológica Durante El Período Implantacional en Conejo

“…En nuestro trabajo no observamos estructuras semejantes ni el desarrollo de proyecciones apicales, debido a que en los días estudiados la fase receptiva ha terminado y está comenzando el periodo implantacional (días 7 al 10 post coito). Los estudios realizados en conejo por Lescoat et al, (1982) y Parr & Parr, (1982), y en rata por Bansode et al, (1998), fueron realizados durante el período de máxima sensibilidad endometrial (días 4 al 6pc).…”