[Changes in the endometrical structure of cows during the estrous cycle]

Changes in the glycogen amount in alkaline phosphatase activity in the surface epithelium were regular during the estrous cycle, but changes in the thickness of the surface epithelium and in the size of cell nuclei were not statistically significant. The diameter of the uterine glands, the height of the glandular cells and the size of their nuclei, as well as alkaline phosphatase activity in the glandular cells decreased at proestrus in comparison with the preceding phase of the cycle (metestrus I and metestrus II). Mitosis of the glandular cells occurred only from the first to the twelfth day of the cycle (mitotic index 1.8%). An electron microscopic study showed that the glandular epithelium consists of ciliated and nonciliated cells, whereas the surface epithelium consists only of nonciliated cells. The number of neutrophils in the subepithelial layer of the endometrium was considerably greater at proestrus than at other phases of the estrus cycle. Changes in the number of the mast cells were not regular during the estrous cycle. The number of lymphocytes showed an increasing tendency in the follicular phase of the cycle.