230 research outputs found
RIENZI
No full textTranscript of RIENZI by anonymous author, appearing in LE GAULOIS, 8 avril 1869, p. 3
Views and reviews: fertility preservation from different perspectives
No full text: Fertility preservation for different conditions provides women the chance to buy time that can be invested in improving their well-being, by curing their condition from a holistic perspective, in line with the precepts of modern medicine
Mosaicism between trophectoderm and inner cell mass
No full textDefining the actual incidence and prevalence of mosaicism in human blastocysts still remains a difficult task. The small amount of evidence generated by animal and human studies does not support the existence of mechanisms involved in developmental arrest, clonal depletion, or aneuploidy rescue for abnormal cells in euploid/aneuploid embryos during preimplantation development. However, studies in humans are mainly descriptive and lack functional evidence. Understanding the biological mechanisms that beset preimplantation differentiation holds the potential to reveal the role of aneuploidies and gene dosage imbalances in cell fate decision, providing important clues on the origin and evolution of embryonic mosaicism. The evidence on human blastocysts suggests that a mosaic euploid/aneuploid configuration is detected in around 5% of embryos. This figure supports the extremely low level of mosaicism reported in natural and IVF pregnancies. Similarly, the clinical management of patterns consistent with the presence of mosaicism in a trophectoderm biopsy during preimplantation genetic diagnosis cycles (PGD-A) is still a controversial issue. Despite the facts that some contemporary comprehensive chromosomal screening platforms can detect mosaic samples in cell mixture models with variable accuracy and many reproductive genetics laboratories are now routinely including embryonic mosaicism on their genetic reports, a diagnosis of certainty for mosaicism in PGD-A cycles is conceptually impracticable. Indeed, several technical and biological sources of errors clearly exist when trying to estimate mosaicism from a single trophectoderm biopsy in PGD-A cycles and must be understood to adequately guide patients during clinical care. (C) 2017 by American Society for Reproductive Medicine
New approaches for multifactor preimplantation genetic diagnosis of monogenic diseases and aneuploidies from a single biopsy
No full textSperm DNA fragmentation to predict embryo development, implantation, and miscarriage: still an open question
No full textChapter 10 Human Oocyte Vitrification
No full textDiscovery and widespread application of successful cryopreservation methods for MII-phase oocytes was one of the greatest successes in human reproduction during the past decade. Although considerable improvements in traditional slow-rate freezing were also achieved, the real breakthrough was the result of introduction of vitrification. Here we describe the method that is most commonly applied for this purpose, provides consistent survival and in vitro developmental rates, results in pregnancy and birth rates comparable to those achievable with fresh oocytes, and does not result in higher incidence of gynecological or postnatal complications
The daunting goal to rescue oocytes collected immature in conventional ovarian stimulation cycles
No full textThe final maturation of the preovulatory oocyte is only a short chapter of the book of oogenesis. Yet, it is crucial for the oocyte to achieve full developmental competence. In preparation for fertilization and preimplantation development, meiotic maturation is accomplished, while the cytoplasm undergoes major rearrangements. Cumulus cells are key to maturation, supporting the oocyte with regulative and metabolic cues. For reasons not entirely understood, a minority of oocytes are still immature when collected from stimulated ovaries in assisted reproductive technology treatment. In intracytoplasmic sperm injection this material is discarded, as most oocytes are mature and in general sufficient for treatment. However, in selected cases in which the yield of mature oocytes is low, immature oocytes could be rescued by pursuing in vitro maturation. Indeed, animal and human studies have shown that oocyte in vitro maturation is not a “mission impossible”. Major hurdles, however, persist. Crucially, in the intracytoplasmic sperm injection procedure, cumulus cells are removed; with them, essential support to cytoplasmic maturation is also lost. So, while meiotic maturation may well occur in vitro, achievement of full developmental competence in a cumulus cell-free system remains a daunting task
Oocyte and embryo cryopreservation in assisted reproductive technology: past achievements and current challenges
No full textCryopreservation has revolutionized the treatment of infertility and fertility preservation. This review summarizes the milestones that paved the way to the current routinary clinical implementation of this game-changing practice in assisted reproductive technology. Still, evidence to support "the best practice" in cryopreservation is controversial and several protocol adaptations exist that were described and compared here, such as cumulus-intact vs. cumulus-free oocyte cryopreservation, artificial collapse, assisted hatching, closed vs. open carriers, and others. A last matter of concern is whether cryostorage duration may impact oocyte/embryo competence, but the current body of evidence in this regard is reassuring. From social and clinical perspectives, oocyte and embryo cryopreservation has evolved from an afterthought when assisted reproduction was intended for immediate pregnancy with supernumerary embryos of secondary interest to its current purpose, which primarily is to preserve fertility long-term and more comprehensively allow for family planning. However, the initial consenting process, which still is geared to short-term fertility care, may no longer be relevant when the individuals that initially preserved the tissues have completed their reproductive journey. A more encompassing counseling model is required to address changing patient values over time
- …
