Pig oocytes in different maturational stages--germinal vesicle (GV), metaphase I (MI) and metaphase II (MII)--were cultured in vitro with [3H]-fucose. The incorporation of the precursor was followed by LM or EM autoradiography on air-dried preparations and on semithin or thin sections. The cumulus cells connected with the oocytes at the GV stage were intensely labelled, while the labelling of t...

Egg activation is a universal process that includes a series of events to allow the fertilized egg to complete meiosis and initiate embryonic development. One aspect of egg activation, conserved across all organisms examined, is a change in the intracellular concentration of calcium (Ca(2+)) often termed a 'Ca(2+) wave'. While the speed and number of oscillations of the Ca(2+) wave varies betwe...

Vertebrate oocytes proceed through the first and the second meiotic division without an intervening S-phase to become haploid. Although DNA replication does not take place, unfertilized oocytes acquire the competence to replicate DNA one hour after the first meiotic division by accumulating an essential factor of the replicative machinery, Cdc6. Here, we show that the turnover of Cdc6 is precis...

The fully grown mammalian oocyte is transcriptionally quiescent and utilizes only transcripts synthesized and stored during early development. However, we find that an abundant RNA population is retained in the oocyte nucleus and contains specific mRNAs important for meiotic progression. Here we show that during the first meiotic division, shortly after nuclear envelope breakdown, translational...

After becoming competent for resuming meiosis, fully developed mammalian oocytes are maintained arrested in prophase I until ovulation is triggered by the luteotropin surge. Meiotic pause has been shown to depend critically on maintenance of cAMP level in the oocyte and was recently attributed to the constitutive Gs (the heterotrimeric GTP-binding protein that activates adenylyl cyclase) signal...

Maturation of vertebrate oocytes into haploid gametes relies on two consecutive meioses without intervening DNA replication. The temporal sequence of cellular transitions driving eggs from G2 arrest to meiosis I (MI) and then to meiosis II (MII) is controlled by the interplay between cyclin-dependent and mitogen-activated protein kinases. In this paper, we propose a dynamical model of the molec...

Oocytes develop the competence for meiosis and early embryogenesis during their growth. Setdb1 is a histone H3 lysine 9 (H3K9) methyltransferase required for post-implantation development and has been implicated in the transcriptional silencing of genes and endogenous retroviral elements (ERVs). To address its role in oogenesis and pre-implantation development, we conditionally deleted Setdb1 i...

the present study investigated serum cortisol in response to postpartum ovarian resumption and luteal function. postpartum ovarian resumption was detected based on a rise in progesterone (p4) concentrations during three weeks after calving. twenty two holstein cows in a semi-closed dairy farm in qena city, egypt were used. the study was carried out from late march to early june; the period char...

After a long period of quiescence at dictyate prophase I, termed the germinal vesicle (GV) stage, mammalian oocytes reenter meiosis by activating the Cdc2-cyclin B complex (maturation-promoting factor [MPF]). The activity of MPF is regulated by Wee1/Myt1 kinases and Cdc25 phosphatases. In this study, we demonstrate that the sequestration of components that regulate MPF activity in distinct subc...

Cyclin B1, the regulatory component of M phase-promoting factor (MPF), is degraded during the metaphase-anaphase transition in an anaphase-promoting complex/cyclosome (APC/C)-dependent process. MPF activity is stable in eggs, and a sperm-triggered Ca(2+) signal is needed to promote cyclin degradation. In frogs, a single Ca(2+) spike promotes cell cycle resumption, but, in mammals, the Ca(2+) si...