During early development, intracellular Ca2+ mobilization is not only essential for fertilization, but has also been implicated during other meiotic and mitotic events, such as germinal vesicle breakdown (GVBD) and nuclear envelope breakdown (NEBD). In this study, the roles of intracellular and extracellular Ca2+ were examined during meiotic maturation and reinitiation at parthenogenetic activa...

The tyrosine phosphorylation/dephosphorylation of p34cdc2 was estimated by immunoblotting with antiphosphotyrosine antibody during meiotic maturation of Xenopus oocytes. At the time of germinal vesicle breakdown (GVBD), p34cdc2 is tyrosine dephosphorylated whereas a p42 protein, which might correspond to a MAP2 kinase, becomes tyrosine phosphorylated. No modification in the level of tyrosine ph...

The role of Raf and MAPK (mitogen-activated protein kinase) during the maturation of Xenopus oocytes was investigated. Treatment of oocytes with progesterone resulted in a shift in the electrophoretic mobility of Raf at the onset of germinal vesicle breakdown (GVBD), which was coincident with the activation of MAPK. Expression of a kinase-defective mutant of the human Raf-1 protein (KD-RAF) inh...

The ability of different isoforms of follicle stimulating hormone (FSH) to induce the resumption of meiosis in cultured mouse oocytes was evaluated. Oocytes were cultured in the presence of hypoxanthine to prevent spontaneous resumption of meiosis. Using serial dilutions of the isoform fractions representing less acidic isoforms (pI 6. 43-5.69), mid-acidic (pI 5.62-4.96) and acidic (pI 4.69-3.7...

We have measured the levels of cyclin mRNAs and polypeptides during oogenesis, progesterone-induced oocyte maturation, and immediately after egg activation in the frog, Xenopus laevis. The mRNA for each cyclin is present at a constant level of approximately 5 x 10(7) molecules per oocyte from the earliest stages of oogenesis until after fertilization. The levels of polypeptides show more comple...

In mammalian cells, 5-methylcytosine (5-meC) can be transformed into 5-hydroxymethylcytosine (5-hmC) by the methylcytosine dioxygenase TET proteins (TET1, TET2 and TET3). Thymine DNA glycosylase (TDG), a downstream enzyme of TET proteins, not only functions in base excision repair, but also acts as a key enzyme that participates in active DNA demethylation. Here we microinjected exogenous TDG-m...

In Xenopus oocytes, the mos proto-oncogene product is required during meiosis I for the activation of maturation promoting factor (MPF) and the subsequent breakdown of the germinal vesicle (GVBD). In addition, the mos product has been shown to be a candidate "initiator" of meiotic maturation and is an active component of cytostatic factor (CSF), an activity responsible for metaphase II arrest. ...

Ovarian follicle maturation (OFM), including the resumption of meiosis in oocyte, is under hormonal regulation. Insulin-like growth factors (IGF) have been shown to participate regulation OFM with species-specific actions teleost fishes. In present study, vitro treatment rainbow trout ovarian follicles recombinant human insulin-like factor-1 (rhIGF1) or rhIGF2 did not induce germinal vesicle br...

background   objective:   materials and methods   results   conclusion   key words:   . vitrification, viability, in vitro maturation, gvbd, oocyte, mouse : these results suggest that step-wise vitrification of gvbd oocytes as compared to single step vitrification was better in the rate of survival and in vitro maturation of oocytes. : all non-vitrified oocytes were viable after 24 hr; however,...