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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Temporal alterations in bovine placental capacity during compromised pregnancies

Contreras, Zully E 06 August 2021 (has links)
The circadian rhythms are not solely regulated by photoperiod but are also influenced by feed regimen. Therefore, maternal nutrient restriction during gestation could potentially impact the fetal circadian rhythm. Melatonin, a circadian rhythm modulator hormone, has shown to act as an antioxidant reducing reactive oxygen species during stress exposure; and two potential mechanisms have been proposed for melatonin causing vasoconstriction and vasodilation regulating blood flow. In livestock species, nutrient restriction during gestation reduces uterine blood flow, limiting nutrients availability to the fetus for growth and development. Therefore, this project aimed to use beef heifers to evaluate the maternal nutrient restriction and/ or melatonin supplementation in (1) temporal transcript abundance of clock genes, angiogenic factors and nutrient sensing genes in bovine placenta, (2) temporal alterations of uteroplacental blood flow, vaginal temperatures, and placentome vascularization, and (3) fetal morphometrics. Early maternal nutrient restriction did not alter placental explants gene expression. Furthermore, the maternal portion of the placentome exhibited limit temporal variation, while the fetal tissue exhibited a clear temporal rhythm in the mRNA relative abundance of the genes measured. Additionally, melatonin supplementation during late gestation, showed to increased uterine blood flow, reduced vaginal temperatures, and rescued fetal weights during compromised pregnancies in a season dependent manner. In conclusion, the bovine placenta exhibited an autonomous circadian rhythm, while the fetal and maternal circadian rhythms appeared to be independent systems. Future research should examine the effects of melatonin supplementation in fetal organ development.

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