Biomedical subjects

M B Parr

Publications and source records attributed to M B Parr.

62 records · Page 4Linked to original sources

PubMed1982

Effects of ovarian hormones on endocytosis at the basal membranes of rat uterine epithelial cells.

Ovariectomized rats treated with progesterone and estradiol-17 beta in sequences that prepared the uterus for implantation showed marked increases in the number of endocytotic invaginations in the basal membranes of luminal epithelial cells and in the amount of intravenously administered horseradish peroxidase taken into the cells. Tight junctions between the epithelial cells blocked the direct passage of horseradish peroxidase into the uterine lumen. The number of basal pinocytotic invaginations in glandular epithelial cells was relatively small and did not increase following hormonal stimulation. The probable occurrence of a pathway for the transepithelial transport of macromolecules from the blood or stroma into the uterine lumen, and its sensitivity to stimulation by ovarian hormones, suggests a likely mechanism for altering the molecular environment of the embryo during the implantation period.

Animals↗

PubMed1982

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

The luminal surfaces of non-ciliated uterine epithelial cells of 17 rabbits on Days 4--6 of 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.

Animals↗

PubMed1980

Endocytosis at the basal and lateral membranes of rat uterine epithelial cells during early pregnancy.

By 20 min after intravenous injection of horseradish peroxidase on Day 5 of pregnancy the tracer was present between the lateral epithelial cell membranes, in coated and non-coated invaginations in the lateral and basal membranes of epithelial cells, and in pinocytotic vesicles at the periphery of epithelial cells. By 60 min after injection the tracer was also distributed in vesicles throughout the epithelial cell cytoplasm. By 2 h the tracer was present only in a few vesicles in the apical region of epithelial cells, and some of these vesicles appeared to be fusing with the apical cell membrane. Pinocytotic invaginations in the basal membrane of uterine epithelial cells were 4--5-fold more numerous on Day 5 of pregnancy than on Days 1--4 and 7, suggesting a specific role for this activity during early pregnancy. The observations show that uterine epithelial cells can pinocytose substances derived from blood, transport them to the apical cytoplasm, and release them into the uterine lumen by exocytosis.

Animals↗

PubMed1978

Uptake and fate of ferritin in the uterine epithelium of the rat during early pregnancy.

The ingestion of ferritin injected into the uterine lumen for 20 min was followed by light and electron microscopy. Uptake occurred on Days 4 to 6, with a distinct peak of activity on Day 5 when blastocysts are present in the uterine lumen. At this time, the antimesometrial cells took up more tracer than those on the mesometrial side. The ferritin was located in various types of organelles which contained acid phosphatase, indicating that the tracer entered the lysosomal system. Ferritin-containing lysosomes were essentially all located in the apical half of the cells at 1 h after the injection, but thereafter were distributed throughout the cell. There appeared to be some digestion of ferritin by 48 h, but no evidence for exocytosis of the tracer at the base of the cells was found with light or electron microscopy.

Acid Phosphatase↗

PubMed1978