Uteri Of Day Research Articles

Does "blastocyst estrogen" initiate implantation?

Fertilized eggs were incubated for 2 hours in a medium containing estradiol-17beta and then transferred into the uteri of day 5 pseudopregnant rats. These eggs, but not estrogen-free control eggs, induced a local increase in capillary permeability. We suggest that the blastocyst factor which induces the local increase in capillary permeability during early pregnancy is estrogen synthesized by the blastocyst.

Ultrastructural studies of frozen-thawed 8-cell mouse embryos

Survival of frozen 8-cell mouse embryos transferred directly upon thawing to the uteri of Day 3 pseudopregnant foster mothers was significantly lower (26%) than the survival of unfrozen 8-cell embryos transferred immediately after collection (73%). When frozen-thawed 8-cell embryos were cultured for 20-24 hr before transfer survival was similar to that of unfrozen 8-cell embryos transferred after 20-24 hr inculture (65% and 73%, respectively). Ultrastructural examination of the frozen-thawed 8-cell embryos revealed no obvious damage to protoplasmic components.

Ontogeny of uterine responsiveness to estrogen during early development in the rat

1. 1. Uterine responsiveness to exogenous estradiol was studied in rats of 5–23 days of age in terms of several known estrogen-dependent parameters — induction of the synthesis of a specific uterine estrogen-induced protein, IP, and increased glucose metabolism, two temporally early responses to estrogen, and increased uterine weight at 1 day and at 3 days after hormone, two later estrogen-induced responses. 2. 2. Induced protein (IP) synthesis can be induced, and induced nearly maximally on a per cell basis in uteri of day 5 rats. The IP to DNA ratio remains nearly constant from day 5 through day 15–18 and drops at day 23. At all ages, IP represents 1.6–3.1% of the newly labeled soluble uterine protein. 3. 3. In contrast to the early uterine responsiveness in terms of IP synthesis, maximal stimulation of 2-deoxyglucose metabolism is not obtained until day 12–15 and maximal increases in the 24 h estradiol-induced uterine wet weight are not obtained until day 12. Likewise, a maximal 3 day uterine growth response cannot be induced until day 20 although some minimal response can be obtained to the 3 daily injections even in the day 5 uterus. 4. 4. These studies indicate that the uterus can respond partially to exogenous estrogen very early (by day 5), but that full responsiveness develops over a further period of approximately two weeks. Further, the induction of IP synthesis is itself not sufficient for induction of the full complement of responses culminating in uterine growth.

Hormonal requirements for the transformation of morula to blastocyst in the rat: Effects of long-term ovariectomy

Morulae were transferred into the uteri of recipient rats whose ovaries had been removed 30 days earlier. Three days after transfer, the eggs were recovered as blastocysts and retransferred into the uteri of day 4 pseudopregnant, definitive recipients, which were killed 14 days later. The 69 blastocysts transferred into the uteri of 11 definitive recipients yielded 27(39%) normal, live fetuses. The results demonstrate that morula to blastocyst transformation can occur in the absence of the ovarian hormones.