Study of the cholesterol transportation mechanism in embryo

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Changes in cell size of preimplantation mouse embryos and the influences of low density lipoprotein on the development of embryos. The total cell volume (TV) in an embryo, calculated by the diameters of cells, decreased of 29.1% but the total cell surface area (TA) did not change during the first cell division. During 2 to 8 cell stage TV was constant but TA increased of 24-26% after each division. Low density lipoprotein (LDL) in the culture media did not improve the blastocyst rates of embryos cultured from 1 cell stage, but significantly increased the area of trophoblast outgrowth cultured after the early blastocyst stage. However the cell surface area incresae during preimplantation embryogenesis, the development improving effect of LDL were observed only after the blastocyst stage.The concentration and distribution of F4/80-positive macrophages and BM8-positive macro-phages in the uterus of mice during the preimplantation period (between day 1 and 14 of pregnancy) were assessed immunohistochemically. In the endometrium, macrophages were found diffusely on day 0-1 and the number of these cells increased on the lumen side on day 2 and 3.Upon initiation of implantation (day 3-7), significant numbers of macrophages were found on the outside of the decidua formed around the implantation site, but macrophages were not found within the decidua. In the endo-metrium without decidualization, macrophages were found diffusely on day 0-1.Furthermore, this study demonstrates that, during pregnancy, macrophages are not present within the early stage of decidua-lization, but they migrate from a deep layer of the endometrium following the proliferation of the decidua.