1,721,043 research outputs found
Origins and effects of oocyte quality in cattle
No full textOocyte quality is the resultant of multifactor interactions that should be carefully taken into account and used either for in vitro embryo production technologies or for studying follicle dynamics. Different approaches may be used to perform an analysis of variables related to oocyte quality which may focus on the ovary, the follicle, the cumulus-oocyte complex and, finally, the oocyte. The information obtained may answer key questions, such as what does the oocyte need to acquire meiotic competence and whether follicle activity can be manipulated to improve the in vitro embryo production efficiency. Although morphological evaluation represents the most common procedure used to discriminate the developmental potential of the oocyte and in spite of a good relationship that has been found between the quality of the oocyte and the atresia grade of the follicle that comprises it, there is not yet a clear correspondence between the visual criteria and the developmental competence of oocytes submitted to in vitro embryo production. New technologies have become available, including emerging ‘omics’ sciences that, through analysis of the cumulus cells, offer the opportunity, by a non-invasive method, to indirectly predict the developmental potential of the oocyte
Ovum Pick-up in cattle – a 25-yr retrospective analysis
Full text linkRepeated oocyte collection by transvaginal ultrasound-guided follicular puncture (Ovum Pick-Up, OPU), implicitly associated to in vitro embryo production (IVEP), has become alternative and competitive to superovulation for embryo production in cattle. It is alternative because it can be applied successfully irrespective of the reproductive status of the donor, i.e. in pregnant and acyclic animals, in those having patent tube or genital tract infections and in animals insensitive to superovulatory treatment. It is competitive because it can yield more transferable embryos per donor on a monthly basis. Through the years, the number of transferable embryos provided by OPU has significantly increased mainly due to the technological improvement of IVEP. However, limits to OPU application remain due to lower pregnancy rate of in vitro vs in vivo produced embryos or non optimal co-operation between OPU practitioners and IVF laboratories.
This review will focus on the technical modifications proposed for improving OPU efficiency, the analysis of the physiological parameters that affect OPU and IVEP efficiency and, finally, the use of OPU as a tool to study and manipulate reproductive activity in cattle
Heat stress, a serious threat to reproductive function in animals and humans
No full textGlobal warming represents a major stressful environmental condition that compromises the reproductive efficiency of animals and humans via a rise of body temperature above its physiological homeothermic point (heat stress [HS]). The injuries caused by HS on reproductive function involves both male and female components, fertilization mechanisms as well as the early and late stages of embryo-fetal development. This occurrence causes great economic damage in livestock, and, in wild animals creates selective pressure towards the advantages of better-adapted genotypes to the detriment of others. Humans undergo several types of stress, including heat, and these represent putative causes of ongoing progressive decay in procreation; an increasing number of remedies in the form of antioxidant preparations are now being proposed to counteract the effects of stress. This review aims to describe the results of the most recent studies that aimed to highlight these effects and to draw information on the mechanisms acting as the basis of this problem from a comparative analysis
Electrical events during gamete maturation and fertilization in animals and humans
No full textGamete cells are electrogenic, i.e. capable of responding to electrical stimuli and modifying their electrical properties
during the crucial periods of maturation and fertilization. Ion channels have been widely demonstrated on the
plasma membrane of the oocyte and spermatozoon in all animals studied, and electrical modifications in gametes
are due to ion currents that are modulated via these ion channels. The modification of intracellular calcium levels in
gametes has been extensively studied, and these modifications are recognized to be a second messenger system for
gamete maturation and fertilization. Other ions also move through the plasma membrane, either in association with
or independent of calcium, and these generate typical features such as fertilization currents and oscillation of resting
potential. These modifications were first studied in marine invertebrates, and the observations subsequently compared
with mammalian systems, including human. The precise role played by these currents in the processes of maturation
and fertilization is still poorly understood; however, recent research opens new frontiers for their clinical
and technological application
Kinetic activity, membrane mitochondrial potential, lipid peroxidation, intracellular pH and calcium of frozen/thawed bovine spermatozoa treated with metabolic enhancers
No full textOwing to the progressive decline of sperm motility during storage there is a need to find substances capable of enhancing sperm energy metabolism and motility and/or preserving it from oxidative damage. The aim of this study was to evaluate in frozen/thawed bovine spermatozoa the effect of several compounds, such as myo-inositol, pentoxifylline, penicillamine + hypotaurine + epinephrine mixture (PHE), caffeine and coenzyme Q10+ zinc + d-aspartate mixture (CZA), on either kinetic or metabolic parameters. Sperm kinetics was evaluated by Sperm Class Analyser whereas specific fluorochromes were used to evaluated mitochondrial membrane potential (MMP), intracellular pH, intracellular calcium concentration and lipid peroxidation. Lipid peroxidation was also evaluated by TBARS analysis. Treatments significantly affected total and progressive motility with different dynamics in relation to the incubation time. After the first hour of incubation, CZA treatment produced the best performance in total and progressive sperm motility as well as in curvilinear velocity, average path velocity and amplitude of head displacement, whereas pentoxifylline stimulated the highest straight-line velocity. MMP showed higher values (p < 0.01) after treatment with pentoxifylline and PHE. Intracytoplasmic calcium concentration and lipid peroxidation were significantly (p < 0.05) affected by the incubation time rather than the treatments. Intracellular pH varied significantly (p < 0.01) in relation to either the incubation time or treatments. In particular, it showed a progressive increase throughout incubation with values in control group significantly higher than in myo-inositol, PHE, caffeine, pentoxifylline and CZA groups (7.37 ± 0.03 vs. 7.29 ± 0.03, 7.28 ± 0.03, 7.26 ± 0.03, 7.22 ± 0.03 and 7.00 ± 0.03, respectively; p < 0.01).; however, among treatments, CZA displayed the lowest values. Significant correlations were found between sperm kinetic and metabolic parameters. These findings provide new comparative information on the effects of putative metabolic enhancers on kinetics and metabolic activities of bovine spermatozoa. In this study, a rapid methodological approach for evaluating sperm quality is proposed
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