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Introduction: Post-ovulatory aging is a time-dependent deterioration of ovulated oocytes and a major limiting factor reducing the fitness of offspring. This process may lead to the activation of cell death pathways like apoptosis in oocytes. Methodology: We evaluated oocyte membrane integrity, egg developmental competency, and mRNA abundance of apoptosis-related genes by RT-qPCR. Oocytes from zebrafish Danio rerio were retained in vivo at 28.5°C for 24 h post-ovulation (HPO). Viability was assessed using trypan blue (TB) staining. The consequences of in vivo oocyte aging on the developmental competence of progeny were determined by the embryo survival at 24 h post fertilization, hatching, and larval malformation rates. Results: The fertilization, oocyte viability, and hatching rates were 91, 97, and 65% at 0 HPO and dropped to 62, 90, and 22% at 4 HPO, respectively. The fertilizing ability was reduced to 2% at 8 HPO, while 72% of oocytes had still intact plasma membranes. Among the apoptotic genes bcl-2 (b-cell lymphoma 2), bada (bcl2- associated agonist of cell death a), cathepsin D, cathepsin Z, caspase 6a, caspase 7, caspase 8, caspase 9, apaf1, tp53 (tumor protein p53), cdk1 (cyclin-dependent kinase 1) studied, mRNA abundance of anti-apoptotic bcl-2 decreased and proapoptotic cathepsin D increased at 24 HPO. Furthermore, tp53 and cdk1 mRNA transcripts decreased at 24 HPO compared to 0 HPO. Discussion: Thus, TB staining did not detect the loss of oocyte competency if caused by aging. TB staining, however, could be used as a simple and rapid method to evaluate the quality of zebrafish oocytes before fertilization. Taken together, our results indicate the activation of cell death pathways in the advanced stages of oocyte aging in zebrafish. [ABSTRACT FROM AUTHOR]

Post‐ovulatory oocyte ageing in fish is associated with limited fertilization rate, poor embryo development, larval malformation, ploidy anomalies and various other offspring abnormalities. Many studies have focused on morphological, physiological, biochemical and histological changes that occur during oocyte ageing. However, little is known about molecular changes associated with this process. This review covers the cellular and molecular characteristics of ageing oocytes with special focus on age‐associated changes affected by oxidative damage. The contribution of oxidative stress and mitochondrial dysfunction, as well as new insights into oocyte ageing in higher vertebrates, is discussed to provide direction for future studies. Investigating the genomics and proteomics of oocyte ageing, including underlying molecular mechanisms, could contribute valuable information on determinants of egg quality. Such knowledge can be translated into practical applications in aquaculture, such as supplementation of oocyte culture media with antioxidants and other agents as a means to inhibit or delay development of the aged oocyte phenotype. Identification of cellular and molecular markers associated with the oocyte ageing process will benefit such developments. [ABSTRACT FROM AUTHOR]

Abstract: The effect of in vitro storage of oocytes on embryos survival rate, egg oxidation status, antioxidant enzyme activities, lipid classes and fatty acid composition profile was investigated in common tench Tinca tinca. In order to identify the role of oxidative stress in the progress of oocyte ageing the levels of thiobarbituric acid reactive substances (TBARS) and carbonyls as indicators of lipid and protein oxidation were measured and the activity of antioxidant enzymes were examined. Stripped ova from six females were stored in cell culture plates at 20°C for up to 10 hr post‐stripping (HPS). The stored ova were fertilized and the embryo survival rates were assessed. The results indicated that tench eggs could be successfully stored in vitro for 4 hr after stripping at 20°C. Superoxide dismutase enzyme activity increased at 6 HPS, whereas glutathione peroxidase and glutathione reductase activities decreased in oocytes during in vitro storage (p < .05) at 4 and 8 HPSs, respectively. The level of malondialdehyde did not show any significant changes during the progress of oocyte ageing. Carbonyls increased up to 2 HPS and thereafter decreased significantly. However, ova ageing did not affect the main lipid class composition and the fatty acid composition of the eggs. Lower quality eggs exhibited lower levels of cholesterol but higher levels of triacylglycerol. [ABSTRACT FROM AUTHOR]

The time period during which oocyte and spermatozoa retain their fertilizing ability after contacting with water was evaluated in pikeperch (Sander lucioperca). In addition, success of in vitro fertilization was examined regarding to the sperm-to-oocyte ratio (SOR). In the first trial, oocytes were placed in Petri dishes containing 5 ml of the hatchery water, to which freshly collected and pooled sperm were added to each sample at 0, 15, 30, 60, 90, 120, 150 and 180 s post oocyte activation. The oocytes retained their fertility for at least 30 s after contacting with water. The second trial tested the maximum time period during which spermatozoa retained fertilizability after contacting with water. Milt (50 μl) was collected from each male and added to 5 ml of water in Petri dishes. Thereafter, oocytes were added at 0, 5, 15, 30, 60 and 75 s post-sperm activation. Delays exceeding 10 s affected negatively the fertilization success. The third trial examined the optimum SOR; in which was found that 100 × 103 spermatozoa per oocyte were the minimum ratio to ensure fertilization rates above 70%. Overall, the data clarified some biological interactions of gametes in the artificial propagation of pikeperch. [ABSTRACT FROM AUTHOR]

Abstract: Delayed fertilization following ovulation leads to the oocyte ageing which has been identified as the most important factor affecting egg quality after ovulation. Very little is known about the molecular changes associated with the progress of oocyte ageing. The present study monitored the egg viability rates during post‐stripping oocyte ageing in African catfish Clarias gariepinus. In addition the mRNA abundance of selected genes were studied during the progress of oocyte ageing by real time quantitative PCR. To study how maternal transcripts influence egg quality, expression levels were correlated with egg hatching rates. The highest embryo survival and hatching rates (88% and 81%, respectively) were obtained from eggs that were fertilized immediately after stripping. Complete loss of egg viability occurred at 16 and 24 hr Post Stripping (HPS) when eggs were stored at 25°C and 4°C respectively. Under both storage temperatures, the embryo mortality and larval malformation rates increased significantly over time and were the highest in the most aged oocytes. Genes indicating an upward trend in expression during ova ageing were determined to be related to oxidative injury and the stress response (hsp70), mitochondrial function (calmodulin), apoptosis (cathepsin D) and germ line speciation (vasa and sox9a). The results suggest that oxidative stress and mitochondrial dysfunction might be associated with post‐stripping ova ageing and the consequent induction of egg quality defects. The examined genes may be considered as candidate markers of egg quality associated with oocyte ageing in African catfish. [ABSTRACT FROM AUTHOR]

Ovulation, fertilization, and embryo development are orchestrated and synchronized processes essential for the optimal health of offspring. Post-ovulatory aging disrupts this synchronization and impairs oocyte quality. In addition, oocyte aging causes fertilization loss and poor embryo development. This investigation aimed to unravel the endpoint of in vitro oocyte aging in common carp (Cyprinus carpio) to understand the involvement of apoptosis in postovulatory oocyte death. It was observed that the fertilization ability significantly declined (p < 0.001) at 8 hours post-stripping (HPS), subsequently triggering apoptosis in the advanced stage of oocyte aging, i.e. 48 HPS. This process included an increase in proapoptotic transcripts (fas, bax, cathepsin D, caspase 8, caspase 9, and caspase 3a) (p < 0.05), elevated levels of caspase 3 protein (p < 0.05), and activation of caspase 3 enzyme (p < 0.001), a key player in apoptosis, in aging oocytes. Furthermore, the effects of oocyte aging on the embryonic apoptosis machinery were examined in embryos at 5 hours post-fertilization (HPF) and 24 HPF derived from fresh and aged oocytes. Expression of apoptotic genes and caspase enzyme activity remained at the basal level in 5 HPF (early blastula embryos) from both fresh and aged oocytes. In contrast, the zymogenic and active forms of caspase 3 increased in 24 HPF embryos from 8-h-aged oocytes (p < 0.01) compared to those from fresh oocytes. Thus, apoptosis intensified in 24 HPF embryos from aged oocytes without affecting the apoptotic machinery of early blastula embryos. Our findings demonstrate that apoptosis initiated by the Fas/FasL system is an important physiological process accompanying oocyte aging in common carp., (© The Author(s) 2025. Published by Oxford University Press on behalf of the American Society of Animal Science.)

Introduction: Post-ovulatory aging is a time-dependent deterioration of ovulated oocytes and a major limiting factor reducing the fitness of offspring. This process may lead to the activation of cell death pathways like apoptosis in oocytes., Methodology: We evaluated oocyte membrane integrity, egg developmental competency, and mRNA abundance of apoptosis-related genes by RT-qPCR. Oocytes from zebrafish Danio rerio were retained in vivo at 28.5°C for 24 h post-ovulation (HPO). Viability was assessed using trypan blue (TB) staining. The consequences of in vivo oocyte aging on the developmental competence of progeny were determined by the embryo survival at 24 h post fertilization, hatching, and larval malformation rates., Results: The fertilization, oocyte viability, and hatching rates were 91, 97, and 65% at 0 HPO and dropped to 62, 90, and 22% at 4 HPO, respectively. The fertilizing ability was reduced to 2% at 8 HPO, while 72% of oocytes had still intact plasma membranes. Among the apoptotic genes bcl-2 (b-cell lymphoma 2), bada (bcl2-associated agonist of cell death a), cathepsin D, cathepsin Z, caspase 6a, caspase 7, caspase 8, caspase 9, apaf1, tp53 (tumor protein p53), cdk1 (cyclin-dependent kinase 1) studied, mRNA abundance of anti-apoptotic bcl-2 decreased and pro-apoptotic cathepsin D increased at 24 HPO. Furthermore, tp53 and cdk1 mRNA transcripts decreased at 24 HPO compared to 0 HPO., Discussion: Thus, TB staining did not detect the loss of oocyte competency if caused by aging. TB staining, however, could be used as a simple and rapid method to evaluate the quality of zebrafish oocytes before fertilization. Taken together, our results indicate the activation of cell death pathways in the advanced stages of oocyte aging in zebrafish., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Konar, Mai, Brachs, Waghmare, Samarin, Policar and Samarin.)