1,720,974 research outputs found
Breakthroughs in the human embryology laboratory... what are the real triggers?
Full text linkIn 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
Full text linkThe 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
EFFICACY AND EFFICIENCY OF THE "UNIVERSAL WARMING PROTOCOL'': MULTICENTER RANDOMIZED CONTROLLED STUDY ON HUMAN SLOW FROZEN OOCYTES.
No full textImpact of medically assisted fertility on preterm birth.
No full textPreterm birth is a frequent problem in women who undergo treatment for infertility. Many factors appear to contribute to the occurrence of this complication. Infertile women seem to have a predisposition to giving birth preterm and to having low birthweight babies. These complications also occur in women with a history of infertility who achieve pregnancy without treatment and who have singleton pregnancies. Assisted reproduction patients treated with in vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI) have a disproportionately high occurrence of preterm births even with singleton pregnancies. Spontaneous preterm labour may be related to underlying medical conditions of the female partner, as its occurrence is not increased in subjects treated with ICSI (i.e. when the infertility problem is associated with male reproductive dysfunction in normal female partners). Multiple pregnancy is the factor most likely to be related to preterm birth in infertile women. The administration of drugs to induce ovulation either alone or combined with intrauterine insemination causes a significant increase in multiple pregnancies. The occurrence of higher order multiple pregnancy is also increased. Multiple pregnancy in women undergoing IVF or ICSI is related to the number of embryos transferred at the end of treatment. The transfer of more than two embryos in women under 35 is not associated with an increased chance of conception, while the occurrence of multiple pregnancy is significantly increased. Women over 40 may benefit from the transfer of more than two embryos, with fewer risks of multiple pregnancy. Single embryo transfer is increasingly considered a workable clinical option, particularly in young women. Hopefully, a more cautious approach to infertility management will reduce the occurrence of multiple pregnancy, spontaneous preterm labour and the high number of low birthweight infants born after treating these women
Efficacy of low-dose human chorionic gonadotropin alone to complete controlled ovarian stimulation.
No full textOBJECTIVE: To prove that low-dose hCG alone can be clinically used to replace FSH-containing gonadotropins to complete controlled ovarian hyperstimulation (COH). DESIGN: Controlled, prospective, randomized study. SETTING: Academic center. PATIENT(S): Infertile patients who are candidates for assisted reproduction. INTERVENTION(S): Patients received [1] recombinant FSH or hMG throughout COH (group A); [2] ovarian priming with recombinant FSH/hMG followed by low-dose hCG (200 IU/day) alone (group B). MAIN OUTCOME MEASURE(S): Medication consumption; daily serum and follicular fluid (FF) measurements of LH, FSH, hCG, E2, P, T, and androstenedione (A); number and size of follicles; intracytoplasmic sperm injection (ICSI) outcome. RESULT(S): In group B: [1] duration and dose of recombinant FSH/hMG administration were reduced; [2] preovulatory serum hCG, E2, and T were higher, whereas FSH was lower; [3] FF hCG, E2, T levels, and E2/T, E2/A, and E2/P ratios were higher, whereas A was lower; [4] small but not large preovulatory follicles were reduced; [5] fertilization rates were higher; and [6] serum and FF P levels, and ICSI outcome did not differ. CONCLUSION(S): Low-dose hCG alone in the late COH stages: [1] reduced recombinant FSH/hMG consumption whereas ICSI outcome was comparable to traditional COH regimens; [2] stimulated follicle growth and maturation independent of FSH administration; [3] was associated with a reduced number of small preovulatory follicles; [4] did not cause premature luteinization; [5] resulted in a more estrogenic intrafollicular environment
Variations on the Author
Full text link“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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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