1,720,973 research outputs found
A novel method for transmission electron microscopy study of cytoplasmic fragments from preimplantation human embryos
Full text linkTransmission electron microscopy (TEM) is the main tool for exploring the intracellular damage and organelle distribution. The cause of producing embryo cytoplsamic fragmentation is not completely understood. Since the fragments have detrimental effects on embryo development, the ultrastructural analysis of fragments may play an important role in fragmentation etiology and in embryo development as well. There are no studies regarding the ultrastructure of fragments in transferable embryos, because the preparation for TEM is not vital and embryos are discarded inevitably. This study aims to introduce a new method for ultrastructural evaluation of fragments without damaging the human cleaving embryos
Contribution of human oocyte architecture to success of in-vitro maturation technology
No full textThe use of ovarian stimulation for infertility treatment is associated with side effects
of ovarian hyperstimulation syndrome (OHSS) and potential cancer risk. This is also
true in high risk women such as those polycystic with ovary (PCO) and polycystic
ovarian syndrome (PCOS). In-vitro maturation (IVM) of oocytes was primarily
developed to make IVF safe for women with PCO and at high risk of OHSS. The
application of IVM of oocytes to assist clinical infertility treatment remains poor
because of the reduced developmental competence of oocytes after IVM, despite
several decades of research. Reduced meiotic maturation and fertilization rates, as
well as low blastocyst production reveal short-term developmental insufficiency of
oocytes when compared with in vivo-matured counterparts. In this review, the
structural role of human oocytes, revealed by different technical approaches, to the
success of IVM technology is highlighted
Cleavage-stage embryo micromanipulation in the clinical setting
No full textEmbryo micromanipulation was developed after introduction of microinjection to overcome infertility. Embryo micromanipulation may be performed at any embryo stage from pronuclear to blastocyst. The technique started out as basic and turned out to be increasingly more complex. Embryo micromanipulation at the cleavage-stage includes a wide range of techniques, from opening the zona pellucida in order to improve the chance of implantation, to removing detrimental components from the embryo to enhance embryo development or blastomeres for preimplantation genetic diagnosis and embryo splitting. Evaluating the impact(s) of different micromanipulation techniques on epigenetics of the embryo and considering quality control during these techniques are important issues in this regard. This review aims to discuss the micromanipulation of cleavage-stage embryos in clinical assisted reproductive technology (ART)
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
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
Human cumulus cell sensitivity to vitrification, an ultrastructural study
No full textAbstract
Cumulus cells (CCs) play an important role in the regulation of female gamete development, meiotic maturation, oocyte-sperm interaction, capacitation and acrosome reaction. However, their role in maintaining oocyte competence after vitrification is unclear as controversial data on their protecting action against oocyte cryoinjuries are available. Here we described the effects of vitrification on the ultrastructure of human CCs collected from women undergoing assisted reproductive technologies (ARTs). In total, 50 patches of CCs, sampled from high-quality human cumulus-oocyte complexes, were randomly allocated into two groups after patient informed consent: 1, fresh CCs (controls, n = 25); 2, vitrified CCs (n = 25). Samples were then prepared and observed by transmission electron microscopy. In fresh CCs, in which small cell clusters were visible, cell membranes were joined by focal gap junctions. Microvilli were rare and short. Nuclei, mitochondria, smooth endoplasmic reticulum (SER), Golgi apparatus and lipid droplets appeared well preserved; vacuoles were scarce. After vitrification, we observed two populations of CCs: light CCs, with a smooth appearance and few short microvilli; and dark CCs, with numerous and long microvilli. In both, most of the organelles appeared similar to those of fresh CCs. Lipid droplets were denser and more numerous, with respect to fresh CCs. They were mainly located in the peri-nuclear and sub-plasmalemmal regions. Numerous packed electron-negative vacuoles were visible. The vitrification procedure did not cause alterations in the fine structure of major organelles, except for an increased amount of lipid droplets and vacuoles. This specific sensitivity of human CCs to vitrification should be considered during ARTs
Cosmetic micromanipulation of vitrified-warmed cleavage stage embryos does not improve ART outcomes: an ultrastructural study of fragments
No full textAbstract
The aim was to study the ultrastructure of cytoplasmic fragments along with the effect of cosmetic micromanipulation (CM) on the morphology and development of vitrified-warmed embryos as well as assisted reproductive technology (ART) outcomes. A total of 96 frozen embryo transfer (FET) cycles were included in this prospective randomized study. They were divided into three groups of CM (n=32), sham (n=32) and control (n=32). In the CM group, the vitrified- warmed embryos were subjected to fragments and coarse granules removal (cosmetic micromanipulation) after laser assisted zona hatching (LAH); sham group subjected only to LAH and no intervention was taken for the control group. Fragmented embryo was evaluated by transmission electron microscopy (TEM). Significant improvement was observed in the morphological parameters, such as fragmentation degrees, evenness of the blastomeres and embryo grade during the subsequent development, after applying cosmetic micromanipulation, when compared to sham or control groups (P=0.00001). However, there were no differences in the clinical outcomes amongst the three studied groups e.g. the rates of clinical, ongoing and multiple pregnancies, implantation, delivery and live birth. In fine structure view, fragments exhibited uniform cytoplasmic texture containing majority of organelles that were observed in normal blastomeres including mitochondria. In conclusion, application of cosmetic micromanipulation in low-grade vitrified-warmed embryos showed significant improvement on embryo morphology parameters; however, did not result in noticeable improvements in clinical outcomes of the patients undergoing ART program. In addition, embryo vitrification had no adverse effects on fine structure of the fragments
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
In-vitro application of pentoxifylline preserved ultrastructure of spermatozoa after vitrification in asthenozoospermic patients
Full text linkAbstract
PURPOSE:
To evaluate the effect of in vitro application of pentoxifylline (PX) on sperm parameters and ultrastructure after vitrification in asthenozoospermic patients.
MATERIALS AND METHODS:
A total of 30 asthenozoospermic semen samples (aged 25-45 years) were divided into four groups before vitrification, after vitrification, control (without PX) and experimental (with PX). In experimental group, each sample was exposed for 30 min to 3.6mmol/l PX and the control group without any treatment apposing in 370C for 30 min. After incubation, the samples were washed and analyzed again. Vitrification was done according to straw method. Eosin-nigrosin and Papanicolaou staining were applied for assessment of sperm viability and morphology, respectively. The samples without PX and post treatment with PX were assessed by transmission electron microscopy (TEM).
RESULTS:
A significant decrease in sperm motility (P ≤ .001), morphology (11.47 ± 2.9 versus 6.73 ± 2.01) and viability (73.37 ± 6.26 versus 54.67 ± 6.73) was observed post vitrification, but sperm motility (19.85 ± 4.75 versus 32.07 ± 5.58, P ≤ .001) was increased significantly following application of PX. This drug had no significant (P >.05) detrimental neither negative effect on ultrastructure acrosome, plasma membrane and coiled tail statues of spermatozoa.
CONCLUSION:
Vitrification had detrimental effects on sperm parameters, but PX reversed detrimental effects on sperm motility. However, PX had no alteration on ultrastructure morphology of human spermatozoa after vitrification
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