OBJECTIVE To evaluate the developmental competence of vitrified human oocytes thawed using two different methods to establish an effective cryopreservation protocol. DESIGN In vitro model study. SETTING University-affiliated hospital. PATIENT(S) Patients who underwent a long protocol of ovarian stimulation with GnRH and gonadotropins. INTERVENTION(S) Vitrified oocytes from the patients ...

The highly condensed chromatin of mammalian spermatozoa is usually considered to be biologically inert before fertilization. However, we have demonstrated that even in this compacted state, sperm chromatin is subject to degradation at open configurations associated with the nuclear matrix through a process we have termed sperm chromatin fragmentation (SCF). This suggests that a mechanism exists...

Microscope observations of rabbit zygotes demonstrate that a sperm aster forms in association with the male pronucleus approximately 1 h postinsemination and consists of two regions. One, the centrosphere, contains a dense aggregation of cisternae of smooth endoplasmic reticulum and microtubules. The second consists of fascicles of microtubules which emanate from the centrosphere. Fertilized ra...

Covalent modification of cytosine nucleotides within the genome encode essential epigenetic information, with methylation (5meC) and hydroxymethylation (5hmC) having received most attention. It has been proposed that the formation of 5hmC is an intermediate in the active demethylation of 5meC. Some reports show that global loss of 5meC in the newly fertilised embryo is accompanied by increased ...

The most popular approach for generating transgenic mammals is the direct injection of transgenes into one pronucleus of a fertilized oocyte. In the past 15 years microinjection has been successfully applied in laboratory as well as in farm animals. The frequency of transgenic founders, although highly different between the species, is efficient enough to render this technique applicable to a w...

Aim To determine whether there are differences in size between the male and female pronuclei immediately before the pronuclear membrane breakdown (PNMBD) and to evaluate whether pronuclear size differences influence normal birth rates. Methods Time-lapse photography was used to measure the size of each pronucleus, while the outcome of 71 frozen-thawed single blastocyst transfers in patients r...

Embryonic development is a complex and dynamic process with frequent changes in gene expression, ultimately leading to cellular differentiation and commitment of various cell lines. These changes are likely preceded by changes to signaling cascades and/or alterations to the epigenetic program in specific cells. The process of epigenetic remodeling begins early in development. In fact, soon afte...

Major epigenetic modifications apparently occur during early development in the mouse. The factors that induce such modifications are complex and may involve the various components of a zygote. We have started to explore whether changes in the nucleocytoplasmic composition brought about by micromanipulation can induce phenotypic effects through epigenetic modifications. Nucleocytoplasmic hybrid...

Tri-methylated lysine 20 on histone H4 (Me(3)K20H4) is a marker of constitutive heterochromatin in murine interphase and metaphase cells. Heterochromatin marked by Me(3)K20H4 replicates late during S phase of the cell cycle. Serum starvation increases the number of cells that exhibit high levels of Me(3)K20H4 at constitutive heterochromatin. Me(3)K20H4 is also present at the centromeric heteroc...

Global demethylation of DNA which marks the onset of development occurs asynchronously in the mouse; paternal DNA is demethylated at the the zygote stage, whereas maternal DNA is demethylated later in development. The biological function of such asymmetry and its underlying mechanisms are currently unknown. To test the hypothesis that the early demethylation of male DNA may be associated with p...