Development preimplantation embryos

In the present study, we were successfully able to develop preimplantation embryos after SCNT, the fused SCNT embryo being developed into 2-cell, 4-cell, 8-cell stage, morula and blastocysts (Fig. 11.3). 

Costanzi, C., Stein, P., Worrad, D.M., Schultz, R.M., and Pehrson, J.R. (2000) Histone macroH2Al is concentrated in the inactive X chromosome of female preimplantation embryos. Development 127, 2283-2289. 

The methylation of DNA at CpG islands has also turned out to be an important regulator for cell development, the differentiated proteome and the regulation of cell survival [237,238]. Indeed the implications of this chemical modification have been linked to DNA accessibility, chromatin fluidity and cell transformation [239,240]. DNA methylation is required for genomic stability and believed to act as an inert epigenetic marker in germinal cells and preimplantation embryos [238]. Presumably, DNA methylation is required for the heritable transmission of chromatin structure, which prevents the expression of terminally silenced genes in differentiated tissues, and provides a host-defense mechanism against parasitic transposable elements [241]. 

Treatment starts when the embryo is attached to the uterine wall and has completed the first stages of implantation. Therefore, pre-implantation development should be unaffected by the test substance. However, even in controls, not all fertilized oocytes develop to the hatched blastocyst stage. A loss of up to two preimplantation embryos per female can be considered a normal finding in rats and rabbits. In studies where exposure begins at or before fertilization a dose-dependent increase in the number of females that show larger differences between corpora lutea and implantation sites may indicate toxicity to pre-implantation embryos or the process of implantation itself. 

Paria, B. C., and Dey, S. K. (2000). Ligand-receptor signaling with endocannabinoids in preimplantation embryo development and implantation. Chem. Phys. Lipids 108, 211-220. 

The mouse preimplantation assay (MEPA) uses zygotes recovered from mated females, cultured in vitro for 7-10 days to assess embryo development, hatching, and survival that represent the toxicological endpoints [19]. The test is capable to assess toxic effects on preimplantation embryo development and survival in vitro up to hatching, a stage that precedes in vivo embryo implantation. It is a commercially available test, but still it has not been standardized and transferability to other laboratories must be addressed. 

Dooley, T., Miranda, M., Jones, N.C., and DePamphilis, ML. (1989). Transactivation of the adenovirus Ella promoter in the absence of adenovirus Ela protein is restricted to mouse oocytes and preimplantation embryos. Development 107 945-956. 

Rogers, M.B., Hosier, B.A., and Gudas, L.J. (1991). Specific expression of a retinoic acid-regulated, zinc-finger gene, Rex-1, in preimplantation embryos, trophoblast and spenriatocytes. Development 775 815-824. 

Worrad, D.M., Ram, P.T., and Schultz, R.M. (1994). Regulation of gene expression in the mouse oocyte and early preimplantation embryo Developmental changes in Spl and TATA box-binding protein, TBP. Development 120 2347-2357. 

Despite its autonomy, the preimplantation embryo, from the time of fertilization of the ovum to the time of entry into the uterus, is highly influenced by its external environment. Many preimplantation embryos already have their development program corrupted by genetics or environment or both and are not viable when they enter the uterus. Other embryos, for a variety of reasons, never achieve implantation in the uterine wall and are soon destroyed. The exact percentage of seriously defective early embryos is unknown. These embryos are usually lost before a woman realizes she s pregnant and the lost embryos remain undetected. The current estimate is that 50 percent of pregnancies end in spontaneous abortion. Only about half of these losses are the result of chromosomal abnormalities.9... 

A fertilized egg develops into a hatched blasto-cyte in vitro when cultured in a protein-free medium at a slower growth rate than that observed in vivo. Growth factors and cytokines appear to accelerate the zygotic development in both autocrine and paracrine manners. CDF/LIF is one of the factors produced by preimplantation embryos (Conquet and Brulet, 1990 Murray et al., 1990). The addition of hLIF to day-5 parthenogenetic bovine morulae produced in vitro stimulates their further development to blastocysts (Fukui et al., 1994). So far, studies of this process remain descriptive (Adamson, 1993) and hence the role of CDF/LIF is not well understood (see reviews by Lee, 1992 and Adamson, 1993). 

The expression of the CBj and to a lesser extent CBjR genes have been studied at different stages in development using brain tissues and preimplantation embryo and in the aging brain. CBjR gene expression can be detected in tissue from newborn infant (Mailleux et al., 1992). The ontogeny of rat CBR expression allows the receptor to be detected at postnatal day 2 and at even earlier time points in rat embryonic brains (McLaughlin and Abood, 1993 de Fonseca et al., 1993). 

Domaracky, M., P. Rehak, S. Juhas, and J. KoppeL 2007. Effects of selected plant essential oils on the growth and development of mouse preimplantation embryos in vioo. Physiol. Res. 56(1) 97-104. Drake, T.E., and H.I. Maibach. 1976. Allergic contact dermatitis and stomatitis caused by a cinnamic aldehyde-flavored toothpaste. Arch. Dermatol. 112(2) 202-203. 

Gutierrez-Pajares, J.L., L. Zuniga, and J. Pino. 2003. Ruta graveolens aqueous extract retards mouse preimplantation embryo development. Reprod. Toxicol. 17(6) 667-672. 

Il kova G, Rehak P, Vesela J, Cikos S, Fabian D, Czikkova S, Kop>p)el J (2004) Serotonin localization and its functional significance during mouse preimplantation embryo development. Zygote 12 205-213... 

Oxidative DNA damage and repair in teratogenesis and neurodevelopmental deficits. Birth Defects Res C Embryo Today. Vol. 90 No. 2 pp. 103-109 ISSN 1542-9768 Yukawa, M., Oda, S., Mitani, H., Nagata, M. and Aoki, F. (2007). Deficiency in the response to DNA double-strand breaks in mouse early preimplantation embryos. Biochem Biophys Res Commun. Vol. 358 No. 2 pp. 578-584 ISSN 0006-291X Zhao, T. and Xu, Y. (2010). p53 and stem cells new developments and new concerns. Trends Cell Biol. Vol. 20 No. 3 pp. 170-175 ISSN 1879-3088... 

Kawamura K, Ye Y, Kawamura N, Jing L, Groenen P, Gelpke MS, Rauch R, Hsueh AJ, Tanaka T. 2008. Completion of Meiosis I of preovulatory oocytes and facilitation of preimplantation embryo development by glial cell line-derived neurotrophic factor. Dev Biol 315(l) 189-202. 

Kawamura K, Kawamura N, Mulders SM, Sollewijn Gelpke MD, Hsueh AJ. 2005. Ovarian brain-derived neurotrophic factor (BDNF) promotes the development of oocytes into preimplantation embryos. Proc Natl Acad Sd USA 102(26) 9206-9211. 

Protocols and descriptions detailing the introduction of cells into mice by aggregation of ES cells with preimplantation embryos are provided elsewhere (40). Our own lab protocols can be obtained through the World Wide Web at http //www.mshri.on.ca/develop/nagy/nagy.htm. 

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