Embryology term paper

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“Metformin has been used to treat an ovulation in women with polycystic ovarian syndrome (PCOS). Recent studies have suggested metformin may also decrease the higher miscarriage rates in these women. The mechanism for this event is unclear. Studies have shown that metformin activates AMP-kinase (AMPK) in rat and diabetic human muscle. Also, this activation stimulates muscle glucose uptake and meiotic maturation in mouse oocytes. Using a high insulin growth factor-1 (IGF-1) milieu model, to mimic PCOS, it has been previously demonstrated decreased insulin-stimulated glucose uptake in the mouse blastocyst, leading to increased apoptosis. One hypothesized metformin could override this phenomenon and increase insulin-stimulated glucose uptake in mouse blastocysts exposed to high IGF-1 media. Fertilized embryos were harvested from superovulated mice at the 2-cell stage and cultured in vitro for 72 hours in either control human tubal fluid, 25mcg/mL metformin, 130nM IGF-1, or metformin with IGF-1 media. Individual blastocysts were assayed for insulin-stimulated glucose transport by measuring nonradioactive deoxyglucose uptake via enzymatic cycling assays. Apoptosis was detected using a TUNEL assay and Topro-3 nuclear dye with confocal microscopy. Embryos were scored for %TUNEL positive divided by total nuclei. Analysts revealed a significant decrease of insulin-stimulated glucose uptake in IGF-1-exposed embryos when compared to control embryos (p < 0.01). Additionally, embryos co-exposed to IGF-1 and metformin showed a recovery of insulin-stimulated glucose uptake when compared to IGF-1-exposed embryos(p < 0.01). When evaluated for apoptosis, these metformin/IGF-1-exposed embryos also showed a significant decrease in %TUNEL positive nuclei when compared to IGF-1-treated embryos (p < 0.01). In conclusion, when compared to embryos cultured in high IGF-1 media, adding metformin improved embryonic insulin-stimulated glucose uptake. These same embryos demonstrated significantly less apoptosis. This improvement in insulin-stimulated glucose uptake with metformin may be a mechanism for improved pregnancy outcomes in PCOS patients treated with metformin.”
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“During this time the bilaminar germ disc grows, especially in the cephalo-caudal axis. At the beginning of the third week, a midline structure called the primitive streak appears in the epiblast, near the caudal end of the disc. Epiblast cells detach along the primitive streak and migrate into the space between the epiblast and hypoblast layers. This penetrating phenomenon is called gastrulation. This migration forms a third layer called the intra-embryonic mesoderm (in red) which goes to the cephalic end of the embryo. In this third layer, cellular groups, called blood islets, can be distinguished that form the shape of a horse shoe. At the cranial end of the embryo, the blood islets form the cardiogenic region. Laterally, the angioblastic cords coalesce. On day 17, the lateral layer divides into two layers: the ventral layer will produce a pair of endocardial tubes and the dorsal layer will produce the two aortae. Embryonic folding brings the endocardial tubes into the ventral thorax where they fuse to form a single primitive heart tube. At this stage of development, the embryo is 2-3 mm long.”
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“The idea of creating a child not only for its inherent worth, but also as a means to some practical end, intuitively induces unease about how parental attitudes to the donor child might be coloured and whether the welfare of the child might take second place to that of the patient. However, many parents whose children desperately need a compatible donor do try to provide one by having another child or two by natural means, despite a small and random chance of getting a suitable donor. With genetic disorders there is the added complication of avoiding having another affected child. PGD could reduce the uncertainty. A concern about using medical advances to select a child is how far parents might want these advances to be applied. There has been a rather extreme speculation about whether couples might consider aborting the fetus once it reaches the stage at which cord blood (or a desired organ) can be retrieved. Nevertheless, the chance to save a life and to relieve a family's anguish by PGD deserves consideration when prospects of successful tissue transplantation from other donors or of cure by other means are not in sight. Parents who opt for PGD rather than prenatal diagnosis generally do not favour abortion. And parents' capacity to love all their offspring equally however or why the children are conceived should not be underestimated-nor should health professionals' ability to gauge, or to learn to gauge, parents' likely attitude to the child.”
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