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Results for “Embryo Implantation, Delayed”

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At least 19 recordsLinked to original sources
PubMed1996

Delayed embryo implantation following in vitro fertilization and embryo transfer (IVFET).

PURPOSE: Our goal was to compare serum human chorionic gonadotropin (hCG) levels in singleton pregnancies achieved following IVFET with those achieved following spontaneous conception. RESULTS: The mean serum hCG level of patients who became pregnant following IVFET lagged 1.5 days behind that of patients who became pregnant spontaneously. CONCLUSIONS: The use of gonadotropin releasing hormone analogue as part of the stimulation protocol leading to egg retrieval and IVFET results in a delay in embryo implantation.

Adult↗
PubMed1985

Actin mRNA content in normal and delayed implanting mouse embryos.

Actin mRNA levels were measured in mouse eggs, early embryos, and delayed implanting blastocysts by a homologous, cloned recombinant DNA probe and "dot" blot methodology. A maternal store of 431 fg of actin mRNA was observed in the unfertilized eggs. This mRNA pool decreased 12-fold by the mid-two-cell stage. Actin mRNA levels were then observed to increase progressively from the eight-cell to the blastocyst stage on a basis proportional to cell number. Late blastocysts contained 2400 fg actin mRNA per embryo (22 fg per cell). The cellular level decreased by about 20% in embryos induced into delay of implantation by ovariectomy of donor females. Reactivation of the delayed implanting blastocysts through hormonal manipulation in vivo or culture in vitro was accompanied by reestablishment of the level of cellular actin mRNA observed in normal blastocysts.

Actins↗
PubMed1981

Activation of 'delayed implanting' mouse embryos in vitro.

Blastocysts were recovered from mice with experimentally produced delay of implantation. The dormant embryos were incubated in vitro for up to 24 h in medium containing [3H]uridine and supplemented with mouse serum or bovine serum albumin. Outgrowth of the trophoblast cells occurred in the presence of serum but not with bovine serum albumin. In contrast, the rate of incorporation of [3H]uridine into RNA by the embryos increased steadily throughout the period of incubation and was not influenced by the presence of serum. The change in incorporation of [3H]uridine was due to an increase in the overall rate of RNA synthesis and serum therefore has not effect on this aspect of embryo activation. The observation that a stimulatory serum factor is necessary for outgrowth of dormant embryos in vitro, but is not required for increased metabolic activity, indicates that these two aspects of embryo activation are regulated differently in vivo. With the assumption that trophoblast outgrowth and the changes in metabolic activity in vitro are analogous to the events that occur when embryonic diapause is terminated in vivo, it is suggested that the process of embryo activation after delayed implantation proceeds in a stepwise fashion with each phase being controlled in different ways.

Animals↗
PubMed1993

Comparison of the ontogeny of specific cell surface determinants on normal and delayed implanting mouse embryos.

The ontogeny of immunospecific cell surface determinants on preimplantation mouse embryos was determined by means of an antibody-dependent complement-mediated cell lysis assay. The determinants conferring sensitivity to lysis in that assay were first observed at the late blastocyst stage on embryos recovered from normal pregnancy on day 5 or grown to an equivalent stage in vitro. Although blastocysts recovered during the dormant phase associated with delayed implantation were not lysed, those recovered following reactivation with an injection of oestrogen to the mother were sensitive. Furthermore, it was found that treating the dormant embryos with neuraminidase rendered them sensitive to lysis. These results demonstrate that the appearance of specific cell surface determinants on mouse embryos is temporally associated with the process of attachment to the uterus in both normal pregnancy and at termination of the dormant phase associated with delayed implantation. They also indicate that those determinants may be 'masked' with sialic acid during embryonic diapause. It is suggested that such cell surface determinants could be important for embryo attachment and that the mechanism responsible for their expression may explain some aspects of the synchronization between the preimplantation conceptus and its mother at the time of implantation.

Animals↗
PubMed1977

Uterine proteins and the activation of embryos from mice during delayed implantation.

Ovariectomy-induced delay of implantation was used to study the role of the uterine environment in controlling implantation in mice. Labelling studies in vivo showed that uterine protein synthesis and secretion is maximal 2-5 h and 24-30 h after the oestradiol injection which initiates implantation. Embryos removed from uteri 5,12 or 30 h after oestradiol injection were able to transport and utilize precursors of nucleic acids and proteins in short-term cultures at the same rate as normal embryos, although "delayed" embryos had low levels of activity. These results suggest that "delayed" embryos are metabolically activated within 5 h of release from delay, perhaps because of the hormonally-induced changes in uterine proteins which occur at this time.

Animals↗
PubMed1985

Changes in the rate of translation with reactivation of delayed implanting mouse embryos.

The transient embryonic diapause associated with delayed implantation in mice is characterized by decreases in the rates of synthesis of RNA and protein as well as a cessation of development. The present experiments were undertaken to examine the possibility that controls on protein synthesis at the level of translation of mRNA provide a regulatory mechanism in this situation. Rates of peptide chain elongation were determined in dormant embryos as well as in embryos that were reactivated either in vivo by estradiol-17 beta or by incubation in vitro. In dormant embryos the rate of peptide elongation was found to be approximately half that in active embryos. Although this change in translational efficiency appears to be sufficient to account for previously observed differences in overall rates of protein synthesis in dormant and reactivated embryos, the possibility that some changes also occur at the level of transcription during reactivation is not ruled out.

Animals↗
PubMed1987

Synthesis and secretion of stage-specific proteins by peri-implantation mouse embryos.

Blastocysts were recovered from intact mice at various times on the fourth and fifth days of pregnancy and incubated in vitro with 35S-methionine. Labeled proteins synthesized by the embryos and secreted into the medium were separated in two-dimensions on polyacrylamide gels by electrophoresis and localized by fluorography. The array of proteins synthesized and secreted by late stage blastocysts was found to be qualitatively and quantitatively different from those released by embryos at earlier stages of development. Similar changes were also observed in secreted proteins when delayed-implanting embryos were reactivated after an injection of estrogen. Furthermore, there was a temporal correlation between the appearance of certain proteins secreted by the embryos and changes in specific proteins synthesized and released by the uterus. It is suggested that these various secreted proteins constitute a signal-response mechanism that is important for the process of embryo implantation in mice.

Animals↗
PubMedDate not supplied

Assessment of estrogenicity by using the delayed implanting rat model and examples.

Endocrine disrupting chemicals have recently drawn increased interest. The delayed implanting rat model is a method that can identify and quantify the estrogenic activity of a chemical. In rats hypophysectomized after breeding, the administration of progesterone delays embryo implantation, and exposure to one dose of an estrogenic substance initiates implantation. Although methoxychlor was ineffective at dosages below 400 mg/kg when given by injection, the administration of the chemical by gavage resulted in an increase in the percent of fertilized rats exhibiting implantation sites. These results were statistically significant at dosages of 50, 100, 200, and 300 mg methoxychlor/kg. When bisphenol A was administered, by subcutaneous injection, dosages of 50, 100, and 200 mg/kg induced implantation. Only the 400 mg/kg dose of 4-tert-octylphenol was effective. Doses of beta-sitosterol up to 30 mg/kg failed to initiate implantation. These data confirm previous evidence of the availability of this model for evaluating estrogenic activity and provide estimates of the estrogenic potencies of several environmentally important chemicals.

Administration, Oral↗
PubMed1976

Repair of sublethal and potentially lethal radiation damage by rat embryos exposed to gamma rays or helium lons.

Embryonic survival was examined in rats exposed to a 24-hour split-dose regimen of gamma rays or extended-Bragg-peak (EBP) helium ions on the fifth and sixth days of gestation. The data indicate that EBP helium ions, which are known to have a single-dose relative biological effectiveness (RBE) of 1.0, exhibit a split-dose RBE of 1.5 with respect to embryo killing. Using an experimental rat embryo system, delayed implantation, it was also noted that the embryocidal damage induced by EBP helium ions contains a smaller potentially lethal component than that induced by gamma rays.

Animals↗
PubMed1981

Regional changes in the binding of [3H] concanavalin A to mouse blastocysts at implantation: an autoradiographic study.

Implanting and delayed-implanting mouse blastocysts were incubated in vitro with [3H] concanavalin A (Con A), and the distribution of binding on their surfaces was determined by light microscopic autoradiography. The density of binding was uniform on the trophectoderm of delayed-implanting embryos and was not changed on the polar surface of implanting embryos. However, binding was reduced on the proximal mural and distal mural trophectoderm of implanting blastocysts by 36% and 60%, respectively. These results suggest that there is a regional reduction in the density of mannose-like sugars on the surface of mouse blastocysts at the time of attachment and implantation.

Animals↗
PubMed1985

Effects of metabolic substrates and ionic environment on in-vitro activation of delayed implanting mouse blastocysts.

The possibility that the embryonic diapause associated with delayed implantation in mice is maintained by limitation of an essential amino acid, energy substrate or concentration of ions was examined by comparing the rates of DNA synthesis in delayed implanting embryos that were 'reactivated' by incubation in 'complete' medium or in one of several specially formulated 'deficient' media. It was found, in agreement with earlier observations, that an increase in the rate of DNA synthesis could be detected within 12 h and continued through 72 h in complete medium. An identical pattern was found when embryos were incubated in medium deficient in amino acids and vitamins. Similar patterns of activation were observed in the absence of all metabolizable substrates, a drastically reduced concentration of Na+, and even in a medium consisting only of 25 mM-bicarbonate buffer, NaCl and KCl. The embryos incubated in the more drastically deficient media appeared to be damaged after 18-24 h. Nevertheless, the observation that the rate of DNA synthesis did not remain depressed suggests that such deficiencies are not the means by which embryonic dormancy is maintained in utero.

Animals↗
PubMed1984

Transcriptional activity of blastomeres in mouse embryos during delayed implantation and after oestradiol benzoate-induced resumption of development.

The relative activities of endogenous DNA-bound RNA polymerases have been quantified in individual blastocysts of ovariectomized mice during delayed implantation and following oestradiol-induced resumption of development. Incorporation of [3H]UMP into an acid insoluble product was detected in the cell nuclei by autoradiography. Nucleolar polymerase I and the nucleoplasmic polymerase II were present in delayed blastocysts harvested from progesterone- or oil-treated ovariectomized females. However, the activities of these enzymes were considerably reduced in comparison with those of blastocysts of intact mice. A stimulation of transcription appeared to occur 18 h after oestradiol benzoate injection of progesterone-treated females but more rapidly in blastocysts from oil-treated females. The data indicate that progesterone may retard the rate of oestradiol-induced reactivation in delayed blastocysts.

Animals↗