RESUMO
Mammalian oocytes undergo maturation and fertilization in the low-oxygen (O2) environment of the oviduct. To evaluate the effect of O2 tension during in vitro maturation and fertilization on embryo yield, quality, cryotolerance, and gene expression, we matured and fertilized bovine cumulus-oocyte complexes under low (5%) or high (20%) O2 tension. Presumptive zygotes from both groups were cultured at 5% O2 for 8 days. Blastocysts were vitrified, and then warmed, and cultured for further 24 h to assess their cryotolerance. Our findings indicate that low O2 during maturation and fertilization enhances embryo development and cell count in both fresh and vitrified/warmed blastocysts. In this study, the interaction of O2 tension and status (fresh or vitrified/warmed) affected the transcript abundance of SOD2, AQP3, and BAX in blastocysts. These results highlight the role of low O2 tension during bovine maturation and fertilization and provide support to using 5% O2 throughout all stages of bovine in vitro embryo production.
Assuntos
Fertilização in vitro , Vitrificação , Bovinos , Animais , Fertilização in vitro/veterinária , Fertilização in vitro/métodos , Oócitos , Blastocisto , Oxigênio/farmacologia , Criopreservação/veterinária , Criopreservação/métodos , MamíferosRESUMO
The use of α-tocopherol during in vitro maturation (IVM) is an alternative to minimize the adverse effects of heat stress on oocyte competence. However, α-tocopherol is diluted in ethanol, which can induce oocyte parthenogenetic activation (PA). This study aimed to evaluate the role of ethanol concentration on PA and the effect of α-tocopherol supplementation during IVM on the developmental competence and the expression of key genes in blastocysts derived from summer-collected oocytes. All in vitro embryo production was conducted at 5% O2, 5% CO2 at 38.5 °C. Experiment 1: oocytes were cultured with or without 0.05% ethanol. As positive PA control matured oocytes were subjected to 3% or 7% ethanol for 7 min. Oocytes from all groups were placed in fertilization medium (22 h) and culture medium (9 days). Ethanol at 0.05% during IVM did not induce oocyte PA, however, 3% and 7% ethanol were effective parthenogenetic inductors. Experiment 2: oocytes were cultured in maturation medium supplemented with 0, 50, 100 and 200 µM α-tocopherol, diluted in 0.05% ethanol. After in vitro fertilization and embryo culture, we assessed blastocyst apoptotic index and the transcription of a panel of genes. The results showed that supplementation with 100 µM α-tocopherol reduced apoptotic index and increased the expression of SOD2. In conclusion, 100 µM α-tocopherol, diluted in 0.05% ethanol, can be used during IVM to embryonic quality.
Assuntos
Suplementos Nutricionais , Etanol/farmacologia , Oócitos/efeitos dos fármacos , Oócitos/fisiologia , Partenogênese/efeitos dos fármacos , alfa-Tocoferol/farmacologia , Animais , Biomarcadores , Bovinos , Diferenciação Celular , Células Cultivadas , Fertilização in vitro , Regulação da Expressão Gênica no Desenvolvimento , Oócitos/citologiaRESUMO
Beef cows and ewes grazing native pastures are exposed to cycles of undernutrition that reflect the seasonal variations of biomass production. In grazing dairy cows, the physiological undernutrition during early lactation due to increased demands for lactation and low dry matter intake is exacerbated by the need to get sufficient intake from pasture and the extra grazing energy costs. Undernutrition has profound impacts on reproduction by affecting multiple reproductive processes at different levels of the reproductive axis. The objective of this paper is to review the influence of undernutrition on reproductive events of the adult female ruminant, with emphasis on both grassland and mixed rain-fed grazing farming systems. The comparative endocrinology and reproductive biology among ewes, beef and dairy cows may provide a comprehensive knowledge of the metabolic and reproductive adaptation to feed restriction. Understanding the critical underlying physiological mechanisms by which nutrition affects reproduction is the base of focus feeding strategy to improve the reproductive performance of the female ruminant.
RESUMO
Naïve female mice are usually described as spontaneously maternal. We investigated how many exposures to pups (15 min vs. 1 hr) were needed to induce full maternal behavior (FMB) in 20-22, 30-35, 60-65-days-old naïve female mice (C57BL/6), and how cohabitation with the parturient mother and newborn siblings facilitated juvenile maternal behavior (MB). Only 20% of the adults displayed FMB immediately after the first exposure to pups. Incomplete MB was present in 11%, 20%, and 30% of juveniles, adolescents and adults, respectively. Three-sixty minute exposures to pups induced FMB in all adult subjects. All naïve juveniles that were not exposed to their siblings and maternal fluids failed to show maternal behavior. In contrast, more than half of the juveniles present at their homecage during delivery of a second litter showed incomplete MB (34.5%) or FMB (21.5%) when tested individually housed in a novel cage. This study suggests that most adult female mice are not spontaneously maternal but gradually sensitized. Besides, naïve juveniles could be inhibited or not motivated to show MB, but display adult-like behavior toward pups if previously exposed to newborn siblings and maternal fluids.