1,721,105 research outputs found
Open versus closed systems for vitrification of human oocytes and embryos
No full textVitrification is now the dominant approach for cryopreservation of human oocytes and embryos; however, serious disagreement persists, particularly about biosafety issues. Techniques are categorized as either 'open' or 'closed' according to occurrence of direct contact between the medium and liquid nitrogen during cryopreservation. Advocates of closed systems emphasize the potential danger of disease transmission mediated through liquid nitrogen, and praise the safety of their approach; those who use the open systems refer to the lack of evidence of disease transmission and regard their systems as more consistent and efficient. The purpose of this review is to clarify whether open and closed systems are really open and closed; if closed systems are safe and free of any danger of contamination; if closed systems are equally efficient as open ones for cryopreservation of human embryos and oocytes by considering overall outcome; and finally, if ethical and legal concerns are sound when risks and benefits are considered in a broader sense. On the basis of these answers, implementation of rational measures to lower the theoretical danger of disease transmission are proposed while maintaining the achievements in cryopreservation that have contributed substantially to the advancement in assisted reproduction techniques during the past decade
Sperm DNA fragmentation to predict embryo development, implantation, and miscarriage: still an open question
No full textPredictive value of oocyte morphology in human IVF: a systematic review of the literature
No full textBackground: Non-invasive selection of developmentally competent human oocytes may increase the overall efficiency of human assisted reproduction and is regarded as crucial in countries where legal, social or religious factors restrict the production of supernumerary embryos. The purpose of this study was to summarize the predictive value for IVF success of morphological features of the oocyte that can be obtained by light or polarized microscopic investigations.
Methods: Studies about oocyte morphology and IVF/ICSI outcomes were identified by using a systematic literature search.
Results: Fifty relevant articles were identified: 33 analysed a single feature, 9 observed multiple features and investigated the effect of these features individually, 8 summarized the effect of individual features. Investigated structures were the following: meiotic spindle (15 papers), zona pellucida (15 papers), vacuoles or refractile bodies (14 papers), polar body shape (12 papers), oocyte shape (10 papers), dark cytoplasm or diffuse granulation (12 papers), perivitelline space (11 papers), central cytoplasmic granulation (8 papers), cumulus-oocyte complex (6 papers) and cytoplasm viscosity and membrane resistance characteristics (2 papers). None of these features were unanimously evaluated to have prognostic value for further developmental competence of oocytes.
Conclusions: No clear tendency in recent publications to a general increase in predictive value of morphological features was found. These contradicting data underline the importance of more intensive and coordinated research to reach a consensus and fully exploit the predictive potential of morphological examination of human oocytes
Oocyte and embryo cryopreservation in assisted reproductive technology: past achievements and current challenges
No full textPreincubation of human oocytes may improve fertilization and embryo quality after intracytoplasmic sperm injection
No full text: The aim of this study was to examine the relationship between different preincubation periods of oocytes and the outcome of intracytoplasmic sperm injection (ICSI). We analysed retrospectively 95 ICSI treatment cycles performed to alleviate severe male-factor infertility. Oocyte collection was performed approximately 36 h after human chorionic gonadotrophin administration. The cumulus-corona-oocyte complexes obtained were incubated until the moment of ICSI. Fertilization, embryo development and implantation rates were analysed in four groups, which were divided according to the time lapse between oocyte retrieval and ICSI: group I, 3-6-9-< or =12 h (11 cycles). Immediately before ICSI the cumulus and corona cells were removed from the oocytes. A total of 723 metaphase II oocytes were injected: 126 from group I, 380 from group II, 126 from group III and 91 from group IV. The fertilization rates obtained were 52.3, 66.8, 65.1 and 69.2% respectively [P < 0.05 (using the chi2 test) between group I and groups II, III and IV]. Cleavage rates were similar in all groups (68.1, 69.7, 79.2 and 79.3% respectively), but the proportion of good quality embryos (< or =20% fragmentation) was significantly lower (P < 0.05) in group I (24.2%) compared with groups II (39.8%) and IV (39.6%). However, no statistically significant differences were observed between the four groups with regard to implantation rates (11.7, 13.2, 10.4 and 20.4% respectively). The results suggest that a preincubation period between oocyte retrieval and ICSI can improve the fertilization rate and embryo quality. This period might be necessary for some oocytes to reach full cytoplasmic maturity, leading to a higher activation rate upon microinjection
Reply: 'Second stimulation in the same ovarian cycle', probably a terminology more appropriate than 'luteal phase stimulation' in the DuoStim protocol
No full textBreakthroughs in the human embryology laboratory... what are the real triggers?
Get PDFIn his article, Gabor Vajta elegantly describes how advances in mammalian embryology slow down for a number of reasons, including a lack of innovative thinking probably due to the lim- ited resources dedicated to “research and devel- opment” in this field. The picture he paints of IVF laboratory technologies “crystallized” at 20 years ago is harsh but accurate, especially when compared with other fields such as molecular genetics or mobile phones. In this scenario, the fascinating idea of a geneticist and an embryol- ogist from the early nineties time-travelling into this decade of the new century, with the geneti- cist lost in the new technology and the embryol- ogist perfectly capable of performing their usu- al lab routine, neatly gives the idea of how time has stopped in the IVF laboratory.
But, particularly in the field of human IVF, some changes have taken place in the last 20 years after the “ICSI revolution” during the early nineties, undoubtedly the major break- through in this field. And it is very interesting to observe that in some circumstances new tech- nologies or procedures were introduced not to improve the final result or to simplify the laboratory routine, but to overcome difficulties caused by strict legal requirements or for marketing reasons.
A striking example of the role indirectly played by legislative limitations is in the field of oocyte cryopreservation. This technique was only considered a safe procedure – and thus worth being marketed and used as a clinical tool – after a critical mass of information regarding its effi- ciency and safety had been gathered from the “Italian experience”. In 2012 the practice com- mittee of ASRM published its guidelines for oocyte cryopreservation, stating that it should no longer be considered experimental, replacing with this document the one previously published in 2008, in which they warned against the mar- keting and clinical use of oocyte and ovarian tis- sue cryopreservation. It is interesting to observe that 30% of the papers in the references were published by Italian groups, and the majority of these articles contain data collected from 2004 to 2009, the period of an abstruse, bizarre and exceedingly strict national IVF law, which was later, in 2009, declared unconstitutional and against human rights by the Italian Constitution- al Court.
This law (Law 40/04) was approved by the Ital- ian Parliament in February 2004 to regulate as- sisted reproduction technology. It infringed up- on basic human rights and the proper application of IVF technology because it mandated proce- dures that were against the best interest of the woman seeking pregnancy. The main point of controversy was the combination of a mandatory limit of three embryos for transfer, and an obligation to implant all embryos produced; cryopreservation of excess embryos was prohibited. Obviously, this decreased the chances for most women of achieving pregnancy, while at thesame increasing the number and complexity of procedures they needed to undergo and exposing some to an unacceptable risk of multiple pregnancy. This 2004 law was inspired by the desire to protect every newly produced embryo and deeply influenced by the way of think- ing of the Catholic Church. In this scenario, only the cryopreservation of gametes was allowed. This involved the female gamete despite the fact that at that time the majority of scientists and in- ternational scientific societies considered oocyte cryopreservation an experimental and unsafe technique.
On 8 May 2009, the Italian Constitutional Court declared that Law 40/04 was unconstitutional. The most important theoretical point made by the Court was that it did not provide protection to embryos, since it admitted that some of them may not produce a viable fetus. Embryo protection is therefore limited by the imperative to ensure a concrete possibility to achieve a success- ful pregnancy.
Owing to of this law, in Italy between 2004 and 2009 oocyte cryopreservation was used in addi- tion to conventional IVF techniques as a way to circumvent many of the regulative and ethical issues associated with embryo cryopreservation. This period saw the peak in the production of papers concerning oocyte cryopreservation by Italian groups, both basic science studies and clinical reports.
At the end of this period, the critical mass of clinical data obtained mainly from the “Italian experience” and a few other groups together with advances in vitrification technologies in the last 20 years, definitively boosted human oocyte cryopreservation, by demonstrating that vitrified oocytes perform as well as their fresh counterparts. Based on these stud- ies, international scientific societies finally took away the “experimental” label from this technology, which is nowadays used mostly for oocyte donation programmes (http://www.sart.org/). Other examples of new technologies which have been developed in the last 20 years of IVF in response to the introduction of strict laws or quality assurance programmes are the use of automatic witnessing/tracking systems, and improvements in lab environment sterility conditions and/or certification of aseptic procedures.
In tracking systems, time lapse microscopy (TLM) plays a crucial role. And one of the major factors in the massive increase in TLM culture systems in IVF labs in the last five years, must be the advances in computer/wireless and smartphone/tablet technology, which allow patients to see the footage of their growing embryo. So, despite the potential positive effect of TLM for embryo selection, it seems that the real trigger for the explosion of this technology in IVF units is much more related to customer service and marketing reasons
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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