Masters Theses

Date of Award

12-1988

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

James D. Godkin

Committee Members

W. Craig Cullen, Bert Erickson

Abstract

Stereologic techniques were used to quantify ultrastructural changes in ovine uterine epithelial cells in cyclic and early pregnant ewes. Three time periods were examined during early pregnancy. These included pre-attachment period (day 13), peri-attachment period (day 16) and post-attachment period (days 19 and 22). Tissue from day 13 nonpregnant ewes was used as a control. Uteri for stereological evaluation were perfused via the uterine artery with 3% glutaraldehyde and separated into proximal, middle and distal regions. Tissues from caruncular areas were processed for electron microscopy. Volume fractions (VV) of nuclei, mitochondria, lipid and secretory granules were estimated by point counting volumetry. Surface areas per unit tissue volume (SV) of mitochondrial membranes and cristae, golgi, plasmalemma, endoplasmic reticulum and nuclear membranes were estimated by line intersection counting.

The only statistical difference between pregnant and non-pregnant uterine epithelium at day 13, a time prior to attachment, was lower SV values of smooth endoplasmic reticulum (SER) in pregnant ewes. The mean SV of SER increased from day 13 of gestation to its highest value on day 16 of gestation followed by a significant decrease to its lowest value on day 22 of gestation. These changes in SER may reflect alterations in SER activities.

Lipid droplet VV was significantly decreased between days 13 and 16 of gestation. Implantation in the ewe does not occur until later in gestation. Lipid droplets, containing mainly triglycerides, may be used as a source of nutrition for the developing embryo. Utilization of the lipid droplets may be the reason for a significant reduction in the VV of this component.

There was a significant increase between days 13 and 16 of gestation in the SV of rough endoplasmic reticulum (RER), however the SV of RER was significantly lower between days 19 and 22 of gestation, which may indicate a decrease in RER activity.

Qualitative results confirm previous data indicating secretory granules are present in the syncytial mass. In this study, secretory granules were not observed in uterine epithelium during the pre and peri-attachment periods but were observed during the post-attachment period. The volume fraction of secretory granules was significantly increased from zero between days 16 and 19 of gestation. Surface per unit volume of golgi complex did not differ significantly between treatment groups, suggesting that secretory granules may be from trophoblastic binucleate cells.

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