Timing of ICSI with Respect to Meiotic Spindle Status.

The aim of this study was to evaluate the efficiency of using meiotic spindle (MS) visibility and relative position to the polar body (PB) as indicators of oocyte maturation in order to optimize intracytoplasmic sperm injection (ICSI) timing. This was a cohort study of patients younger than 40 years with planned ICSI, the timing of which was determined by MS status, compared with those without MS evaluation. The angle between PB and MS and MS visibility were evaluated by optical microscope with polarizing filter.

Important parameters affecting quality of vitrified donor oocytes.

For group of 281 oocytes obtained from 43 stimulated donors and cryopreserved by vitrification protocol using Cryotop and Kitazato medium we determined important parameters of oocytes collection and vitrification processes which strongly affect the probability that warmed oocytes will produce high-quality embryos for transfer. The probability to obtain high-quality embryos for transfer from vitrified and warmed oocytes was highest when two conditions were fulfilled: 1. oocytes were incubated before vitrification for 7-10 h and 2.

Chromatin architecture changes and DNA replication fork collapse are critical features in cryopreserved cells that are differentially controlled by cryoprotectants.

In this work, we shed new light on the highly debated issue of chromatin fragmentation in cryopreserved cells. Moreover, for the first time, we describe replicating cell-specific DNA damage and higher-order chromatin alterations after freezing and thawing. We identified DNA structural changes associated with the freeze-thaw process and correlated them with the viability of frozen and thawed cells.

DNA methylation pattern in human zygotes and developing embryos.

We report on observations of the global methylation/demethylation pattern of both pronuclei in human zygotes and in early embryos up to the blastocyst stage. Our results demonstrate that in about half of the zygotes examined the paternal chromatin was less methylated than the maternal chromatin. In the other half, both pronuclei exhibited the same intensity of labeling.