PATTERNS OF CELL DIVISION IN THE MOUSE UTERUS DURING EARLY PREGNANCY

Abstract

SUMMARY Estimates were made of the number and distribution of cells undergoing division in the mouse uterus during the first 6 days of pregnancy. There was a spectacular change in the distribution of mitoses between days 3 and 4. On day 3 large numbers of mitoses were present in the luminal and glandular epithelium, with few in the stroma, whereas on days 4 and 5 very large numbers were present in the stroma with few in the epithelia. On day 6 and late on day 5, in the vicinity of a blastocyst, the area containing decidual cells was free of mitoses. Many mitoses were found in the stroma immediately outside this area and there was evidence that the rate of division here was greater than in segments of the uterus unstimulated by a blastocyst.