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Influence of ROS on Ovarian Functions
No full textHigh level of ROS (Reactive Oxygen Species), due to an increased production of oxidant species and/or a decreased efficacy of antioxidant system, can lead to oxidative stress (OS) an emerging health risk factor involved in the aging and in many diseases, either in humans or in animals. ROS are a double-edged sword – they serve as key signal molecules in physiological processes, but also have a role in pathological processes involving the female reproductive tract.ROS affect multiple physiological processes in reproduction and fertility, from oocyte maturation to fertilization, embryo development and pregnancy. Several studies indicate that follicular atresia in mammalian species due to the accumulation of toxic metabolites often results from oxidative stress. It has been suggested that ROS under moderate concentrations play a role in signal transduction processes involved in growth and protection from apoptosis. Conversely, increase of ROS levels is primarily responsible for the alteration of macromolecules, such as lipids, proteins and nucleic acids, that lead to significant damage of cell structures and thereby cause oxidative stress. To prevent damage due to ROS, cells possess a number of non-enzymatic and enzymatic antioxidants. Non-enzymatic antioxidants include vitamin C, glutathione and vitamin E. Enzymatic antioxidants consist of superoxide dismutases (MnSOD and Cu/ZnSOD) that convert superoxide into hydrogen peroxide; glutathione peroxidase (GPX) and catalase (CAT) which neutralize hydrogen peroxide. Intracellular homeostasis is ensured by the complex interaction between pro-oxidants and antioxidants.This chapter describes gathering evidence that oxidative stress is involved in ovarian physio-pathology caused by diverse stimuli. There is strong evidence that ROS are involved in initiation of apoptosis in antral follicles caused by several chemical and physical agents, in the fluid follicular environment, influencing the folliculogenesis and the steroidogenesis. Although less attention has been focused on the roles of ROS in primordial and primary follicle death, several studies have shown protective effects of antioxidants and/or evidence of oxidative damage, suggesting that ROS may play a role in these smaller follicles as well. Oxidative damage to lipids in the oocyte has been implicated as a cause of persistently poor oocyte quality. Developing germ cells in the fetal ovary have also been shown to be sensitive to toxicants and ionizing radiation, which induce oxidative stress. Recent studies have begun to elucidate the mechanisms by which ROS mediate ovarian toxicity. It has been investigated the role of antioxidant enzymes, such as catalase, glutathione peroxidase and the SOD isoforms in maintaining low levels of oxidative stress.The literature provides some evidence of oxidative stress influencing the entire reproductive cycle. OS plays a role in multiple physiological processes from oocyte maturation to fertilization and embryo development. An increasing number of published studies have pointed towards increased importance of the role of OS in female reproduction. Of course, there is much to learn about this topic, whereby it cannot be underestimated
IMPIEGO DI SPERMATOZOI EPIDIDIMALI CRIOCONSERVATI PER LA FECONDAZIONE IN VITRO DI OVOCITI DI GATTO DOMESTICO “Felis catus”.
No full textEFFECTS OF ANTIOXIDANT SUPPLEMENTATION TO IN VITRO MATURATION MEDIUM ON OOCYTE DEVELOPMENT OF DOMESTIC CAT (FELIS CATUS).
No full textMammalian oocytes require a variable period of in vitro maturation (IVM) to develop to metaphase II stage.
Oocytes recovered from preovulatory follicles show a reduction in cleavage frequency and blastocyst
development of cat embryos produced. It was demonstrated that high oxygen concentration compromises
nuclear maturation rates and worsens the oxidative stress during IVM. Incubated oocytes show severely
high quantities of superoxide dismutase (SOD), glutathione reductase (GSR), glutathione peroxidase (GPX1)
and catalase (CAT) mRNA and this effect results in a protective mechanism against oxidative stress.
Examining the follicular fluid oxidants and antioxidants it is possible to understand the composition changes
in vivo and optimize the conditions of IVM. To improve the development of cat oocyte, we studied the
effects of the addition of SOD and CAT to IVM medium on developmental competence and embryo
production.
Cat oocytes were collected from fresh excised ovaries and cultured in a maturation medium supplemented
without (untreated group) or with (treated group) SOD (25UI/ml) and CAT (50UI/ml) for 24h. Both groups
were subjected to fertilization in vitro (IVF) with fresh epididymal sperm extracts for 12h. After IVF, the
zygotes were cultured in a synthetic oviduct fluid medium for 8 days.
There were no significant difference in the maturation rates (86.4% vs 87.6%) between the groups,
nevertheless antioxidant supplementation. The frequency of blastocyst development from oocytes of
treated group (36.0%) was higher (p<0.05) than untreated group (28.4%).
Our data indicate that the supplementation of SOD and CAT into IVM medium may improve blastocyst
development of cat oocytes after IVF.
Gupta S, Choi A, Yu HY, Czerniak SM, Holick EA, Paolella LJ, Agarwal A, Combelles CM. Fluctuations in total
antioxidant capacity, catalase activity and hydrogen peroxide levels of follicular fluid during bovine
folliculogenesis. Reprod Fertil Dev. 2011;23(5):673-80.
Luu VV, Hanatate K, Tanihara F, Sato Y, Do LT, Taniguchi M, Otoi T. The effect of relaxin supplementation of
in vitro maturation medium on the development of cat oocytes obtained from ovaries stored at 4°C
Fertility cryopreservation
Full text linkThe cryobiology is the science of low temperature biology. Fertility cryopreservation is a vital branch of reproductive science and involves the preservation of gametes (sperm and oocytes), embryos, and reproductive tissues (ovarian and testicular tissues) for use in assisted reproduction techniques (ART). The cryopreservation of reproductive cells is the process of freezing, storage, and thawing of spermatozoa or oocytes. It involves an initial exposure to cryoprotectants, cooling to subzero temperature, storage, thawing, and finally, dilution and removal of the cryoprotectants, when used, with a return to a physiological environment that will allow subsequent development. Proper management of the osmotic pressure to avoid damage due to intracellular ice formation is crucial for successful freezing and thawing procedure. Management of non-cryopreserved reproductive cells (i.e., spermatozoa or oocytes) and tissues (i.e., testicular tissue or ovarian tissue) is problematic due to difficulties in donor-recipient synchronization and the potential for transmission of infectious pathogens, which cumulatively limits widespread application of these techniques. Cryopreserved cells and tissues can endure storage for centuries with almost no change in functionality or genetic information, making this storage a method highly attractive. There is a pressing need for the development of optimum cryopreservation methods for reproductive cells and tissues from many species. There are two major techniques for cryopreservation: freeze-thaw processes and vitrification. The major difference between them is the total avoidance of ice formation in vitrification. However, the biotechnology of the reproduction, although widely implemented, has generated protocols currently used to cryopreserve bovine sperm or oocytes, for example, that are still suboptimal, and cannot readily be extrapolated to other species' gametes. ART provide an ensemble of strategies for preserving fertility in patients and commercially valuable or endangered species. Nevertheless, it is very difficult to successfully cryopreserve. Currently, there is a growing interest to understand the underlying cryobiological fundamentals responsible for low survival rates in an effort to develop better cryopreservation. The key factors that affect the life-span of spermatozoa are the combinations of storage temperature, cooling rate, chemical composition of the extender, cryoprotectant concentration, reactive oxygen species (ROS), seminal plasma composition and hygienic control. Sperm preservation protocols vary among animal species owing to their inherent particularities that change extenders used for refrigeration and freezing. On the other hand, oocytes are available only in limited number as compared to spermatozoa, therefore, a cryopreservation protocol must allow a high rate of viability maintenance when they are employed in practical application in ART programs. One of the key factors that influence the freezing process is the ratio of surface area to volume. The oocytes require a longer time to reach osmotic balance with the cryoprotectant solution than the spermatozoa, due to their bigger volume. Then, during cooling of oocytes, various forms of cellular damage may occur, including cytoskeleton disorganization, chromosome and DNA abnormalities, spindle disintegration, plasma membrane disruption and premature cortical granule exocytosis with its related hardening of the zona pellucida. Therefore, animal gametes have been shown to survive storage at low temperatures, and recent results are very encouraging, although reproducible methods have yet to be obtained in many species
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
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
Cryopreservation of feline epididymal spermatozoa from dead and alive animals and its use in assisted reproduction.
No full textCryopreservation of gametes is an important tool in assisted reproduction programmes; long-term
storage of oocytes or spermatozoa is necessary when in vitro fertilization (IVF) or artificial insemination
is to be performed at a future date. Cryopreservation of epididymal spermatozoa offers a potential
tool for rescuing genetic material from males of endangered populations. The objectives of this work
were to: (1) examine sperm motility, viability, abnormality and acrosome integrity of frozen–thawed
domestic cat epididymal spermatozoa; and (2) evaluate the same cryopreservationmethod onwild feline
spermatozoa, needed to preserve their genetic resources. Epididymides were collected from 20 domestic
cats during routine neutering procedure and from two wild felines at autopsy. The sperm samples,
diluted with 4% glycerol/Tris/egg yolk, were loaded into 0.25 ml mini-straws, exposed to nitrogen
vapour and stored in liquid nitrogen. After 4 weeks, samples were thawed and re-evaluated. The quality
of each fresh and frozen–thawed sperm sample was tested by determining the motility (54.7±11.3%
and 32±13.1% respectively for cat spermatozoa; 38.3±18.7% and 21.5±16.8% respectively for tiger
spermatozoa), viability (74.3±8.6% and 45.2±9.4% respectively for cat spermatozoa; 42.4±14.5% and
33.5±12.9% respectively for wild felid spermatozoa), morphology and acrosomal status. The present
study showed that feline epididymal spermatozoa can be frozen in egg-yolk extender with 4.0% glycerol
in 0.25 ml straws. The procedure used in the present study for epididymal cat sperm cryopreservation
may be applied to bank the genetic resources of wild felid species
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