| Popis: |
The notion has grown in recent years that tne olastocyst may synthesize substances that participate actively in the process of implantation and in the maternal recognition of pregnancy. Deanesly (1967) showed in guinea pigs that fertilized eggs have “… a specific capacity to induce changes in the endometrium…” and that this property is appreciably greater than that of artificial traumatization. The difference in response was not affected by exogenous progesterone treatment. The capacity of the blastocyst to induce changes in the endometrium is also apparent from the localized increase in capillary permeability that occurs in close proximity to blastocysts in rats, hamsters, mice, and sheep (Psychoyos 1960; Orsini 1963; Finn and McLaren 1967; Boshier 1970). This increase in permeability occurs on the afternoon of day 5 in rats, on day 4 in hamsters and mice, and on day 15 in sheep, that is, about 20–24 h before morphological evidence of implantation. The nature of the stimulus given to the uterus by the blastocyst has been intensively studied in laboratory rodents, and experimentation has led to theories about the release of histamine from endometrial mast cells activated by the presence of the blastocyst (Shelesnyak 1960) and the local production of CO2 associated with the respiratory activity of the blastocyst (Menke and McLaren 1970a, b).These hypotheses, however, cannot explain the deciduagenic action of oil injected into the uterine lumen which Finn and Porter (1976) consider may be due to a complex molecular change at the epithelial cell surface. |
