Fig. 5. Defective postimplantation developments in Pla2g4a^–/– mice. (A) A composite photograph of uteri in wild-type and Pla2g4a^–/– mice on day 12 of pregnancy. Resorption sites were often noted (arrows) and many implantation sites were closely apposed and even conjoined (brackets) to each other in Pla2g4a^–/– mice. (B) Median weights of implantation sites and their embryos on day 12. The implantation sites without embryos (resorption sites) were excluded from this computation. (C) Photographs of embryos isolated from implantation sites of one representative wild-type and two Pla2g4a^–/– mice on day 12. Note retarded and asynchronous development of embryos in Pla2g4a^–/– mice. (D) Histological examination of day 12 implantation sites in Pla2g4a^–/– mice. Feto-placental units from Pla2g4a^–/– mice were examined on day 12. Embryos and placentas show defective development with a preponderance of trophoblast giant cells. Arrowheads and an arrow indicate trophoblast giant cells and degenerating embryo, respectively. (c,d) Higher magnifications of a,b, respectively. la, labyrinthine trophoblast; sp, spongiotrophoblast; dec, decidua. (E) Distribution of embryonic weights on day 12 (n=60-75). The horizontal orange lines represent median values of embryonic weights. Pla2g4a^–/– mice were given the vehicle or PGs at 10:00 and 18:00 hours on day 4 of pregnancy and killed on day 12. Note a reduction in numbers of retarded embryos in the PG-treated group. (F) Representative photographs of conjoined embryos in a placenta (a,c) and three embryos in the same decidual envelope (b,d) from Pla2g4a^–/– mice on day 12. (c) A histological section of (a) with two embryos; embryos shown in (d) are from (b). Yellow arrows indicate the source of the embryos from the decidual envelope.

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