Placental wet weight is increased by IGF-2 excess, as seen in Igf2r ko mice, and decreased by IGF-2 deficiency, as observed in Igf2 ko mice and this study). The mouse placenta is an anatomical unit in which maternal decidual tissue and conceptus components make contact and intermix; thus the total placenta fraction had a dual origin. As expected from its cellular composition, the total placenta had a significantly reduced wet weight when the trophoblast was Igf2 ko (data not shown). This reduction in wet weight was much lower than that seen when all parts of the conceptus lack active Igf2 genes. buy yasmin online
The fetal placenta was selected for study because it is the part of the placenta that is principally derived from the trophectoderm and that should, therefore, be most responsive to the genotype of the trophectoderm. The decidual base, invaded by extensive trophoblast giant cells, and the bulk of the spongiotrophoblast were removed from the total placenta to give the fetal placenta. The fetal placenta consisted of labyrinthine trophoblast decorated with small fragments of the spongiotrophoblast. This fetal placenta fraction was free of most maternal contamination, and similar dissections indicate that 80-90% is derived from the troph-ectoderm and 1-2% from maternal cells, with the rest made up from derivatives of the ICM, which include the sinuses of Duval.