Oocyte, fertilization

Borsuk E, Manka R 1988 Behavior of sperm nuclei in intact and bisected metaphase II mouse oocytes fertilized in the presence of colcemid. Gamete Res 20 365-376 Ciemerych MA 1995 Chromatin condensation activity and cortical activity during the first three cell cycles of mouse embryo. Mol Reprod Dev 41 416—424 Ciemerych MA, Kubiak JZ 1999 Transient reactivation of CSF in parthenogenetic one-cell mouse embryos. Biol Cell 91 641—647... 

The pattern of estradiol concentration during the days before hCG reflects the degree of maturity of the follicles (R7). When estradiol levels on the days before hCG administration plateau, significantly more oocytes are atretic and significantly fewer oocytes fertilize compared to those cycles where estradiol levels still increase (B7, L2). The percentage of pregnancies is not correlated to trend in estradiol concentration (B7). 

Bovine oocyte fertilization test Formation of female and male pronucleus after penetration of sperm into matured oocytes Hazard identification that could affect fertility... 

The impact in future offspring of fertilization with an injured DNA genome needs careful study. Many cells, and particularly oocytes, have the ability to repair DNA failures using specific pathways according to the nature of the insult (for example, simple or double strand breaks, base modifications, and base mismatch). The activation of these mechanisms has been noted in oocytes fertilized with frozen DNA cryodamaged sperm (Kopeika et al., 2004 Perez-Cerezales et al., 2010b), but this ability is limited and could introduce changes to the code, for which potential consequences should be evaluated. 

Suchanek E, Simunic V, Jurehc D, Grizelj V. Folhcular-fluid contents of hyaluronic-acid, follicle-stimulating-hormone and steroids relahve to the success of in-vitro feitihzation of human oocytes. Fertil Steril 1994 62 347-352. 

Xenobiotic induced disruption of female fertility follows essentially the same pattern as that of the male and can be caused by changes in pituitary-hypothalamic function, primary disruption of ovarian structure or hormone secretion, or changes in the rate of hormone deactivation. In addition, there may be changes in the synthesis of estrogen induced production of the yolk protein by the liver (vitellogenesis), which in turn can lead to failure to lay down sufficient yolk in the developing oocytes. Vitellogenesis provides a valuable biomarker for endocrine dysfunction in both sexes,but is more properly considered as part of the liver function. 

Chimeric DNA molecules are introduced into cells to make transfected cells or into the fertilized oocyte to make transgenic animals. 

Figure 1. Expression of c-mos in mouse oocytes, c-mos is transcribed during oocyte growth and transcripts with short poly(A) tails are accumulated in fully-grown germinal vesicle (GV) stage oocytes. These transcripts are polyadenylated and translated following the resumption of meiosis and then degraded following fertilization and cleavage to the two-cell stage.

FIG. 1. Schematic diagram of early Xenopus development. The figure shows relative levels of MPF (cyclin B/Cdc2) activity from the beginning of oocyte maturation until after fertilization. 

The first cell cycle of the mouse embryo differs in many respects from the second and the following cell cycles. It is characterized by a long Gl phase that starts after the penetration of the spermatozoon or artificial activation of the oocyte. During this period the chromatin of the oocyte completes the second meiotic division and forms the female pronucleus. At the same time, in the fertilized egg, the highly condensed chromatin of the sperm nucleus decondenses and sperm-specific proteins, protamines, are replaced by histones. After the initial sperm chromatin... 

FIG. 2. Relationship between activities of CSF, MPF and MAP kinase during the first 90 min after fertilization of the mouse oocyte. Data from Ciemerych Kubiak (1999), Szollosi et al (1993), Verlhac et al (1994). 

Pivotal pre-approval safety and efficacy was assessed in a randomized, open label, multicentre study of infertile females undergoing in vitro fertilization and embryo transfer. The primary efficacy parameter was the mean number of oocytes retrieved, which (at 13.6) was similar to the number retrieved when urinary-derived hCG was used. Serious potential side effects can include ovarian over/hyper-stimulation, sometimes with pulmonary or vascular complications. The product is marketed by Serono Inc. 

Fig. 1. Dynamics of DNA methylation levels during mouse development. The methylation patterns of the oocyte and the rapidly demethylated after fertilization sperm create the combined methylation patterns in the early mouse zygote. During the first two to three cleavage divisions, the 5mC levels decrease further and stay low through the blastula stage. Post-implantation, the mouse embryo genome is methylated de novo the CpG islands remain mostly unmethylated. The primordial germ cells remain unmethylated. During gametogenesis specific parental (maternal or paternal) patterns of DNA methylation are established at imprinted loci (for further details see Refs. [13, 14]) (re-drawn from Ref [4]).

In zebrafish, there is an initial endotrophic period, from fertilization to mouth opening, where the embryo and pre-feeding larvae use endogenous yolk nutrients previously accumulated in the oocyte. As the development and survival of fish... 

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