Browsing by Subject "Bisphenol A"
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Item Biodegradation of bisphenol a and ibuprofen by ammonia oxidizing bacteria(Texas A&M University, 2007-09-17) Subramanya, Nethra T.Bisphenol A (BPA) is a compound that is commonly used in the manufacture of epoxy resins and plastics. Because of large scale production and widespread usages, BPA is released into the atmosphere through air, land, and water. BPA is weakly estrogenic in animals and has acute aquatic toxicity even at low concentrations of 1- 10????g/L. Ibuprofen is a widely used analgesic and antipyretic. Ibuprofen and its metabolites are mainly released into the environment by human urinary excretion. Ibuprofen has been detected at low concentrations in surface and waste waters. The environmental and health effects at such concentrations are unclear. The high removal of BPA and ibuprofen in the wastewater treatment plants (WWTPs), suggest that biodegradation might be responsible for the removal of these compounds. Several bacterial strains, isolated from waste water, are known to degrade BPA and ibuprofen. No studies, however, have reported using ammonia oxidizing bacteria for this purpose. Ammonia oxidizing bacteria (AOB) are an important group of microorganisms in nitrifying activated sludge of WWTPs. AOB are known to express ammonia monooxygenase (AMO) to degrade many different aromatic and aliphatic organics via cometobolic degradation (non beneficial mechanism). Nitrosomonas europaea is a widely studied AOB found to degrade synthetic estrogen by a study. This study aims to characterize the biodegradation of BPA and ibuprofen by AOB. The biodegradation ability of N.europaea with respect to BPA and ibuprofen was examined. Experiments were conducted in the presence/absence of the AMO inhibitor (allylthiourea), an external reducing energy source (sodium formate) and different primary substrate (ammonia) concentrations. The second part of the study comprises of biodegradation tests on BPA and ibuprofen using activated sludge from two WWTPs, one with one-sludge activated sludge system and the other one with two-sludge nitrification system. From the experiments conducted BPA at a concentration of 1.6 mg/L was degraded to 0.12 mg/L by N.europaea. BPA at concentrations of 1.0 mg/L and 0.75 mg/L was completely degraded by the cells. Resting cells of N.europaea were, however, unable to degrade BPA. Also ibuprofen of two concentrations, 0.42 mg/L and 0.8 mg/L, were not degraded by the culture. BPA at a concentration of 1 mg/L was degraded to 0.2 mg/L and ibuprofen at 0.5 mg/L was completely degraded by the activated sludge from the combined reactor. The activated sludge from the nitrification tank degraded BPA of concentration 1 mg/L and ibuprofen of concentration 0.5 mg/L completely. Hence, it can be summarized that Bisphenol A was degraded by N.europaea and also by the activated sludge obtained from the WWTPs. Ibuprofen was found incapable of inhibiting ammonia oxidizing bacteria in the case of the pure culture while it was successfully degraded by the mixed culture.Item Bisphenol A, and three related alkylphenols exert rapid estrogenic actions on zebrafish (Danio rerio) oocytes to maintain meiotic arrest(2014-12) Fitzgerald, Amanda Crane; Thomas, P. (Peter)Bisphenol A (BPA) is an alkylphenol compound used in plastic manufacturing, which enters the aquatic environment through wastewater treatment plants and landfill leachates. Exposure of fish to BPA results in developmental defects, decreased hatching, and increased occurrence of the egg yolk precursor protein vitellogenin in male fish. BPA is an estrogenic like compound (xenoestrogen) that can bind and activate the nuclear estrogen receptors, ERα and ERβ, causing changes in gene transcription (genomic mechanism). However, the ability of BPA to activate rapid estrogen signaling and to disrupt nongenomic physiological responses to estrogens is not known. One important nongenomic estrogen action in fish is to maintain meiotic arrest of oocytes and to prevent precocious oocyte maturation through activation of the transmembrane G-protein coupled estrogen receptor (Gper). Binding of estrogens to Gper on zebrafish oocytes results in rapid activation of epidermal growth factor receptor (Egfr) signaling and subsequent Mapk3/1 activation. We show here that BPA and three structurally-related chemicals, tetrachlorobisphenol A, tetrabromobisphenol A and nonylphenol, can mimic estrogen by activating this mechanism of meiotic arrest through Gper in zebrafish (Danio rerio). BPA bound to zebrafish Gper and inhibited spontaneous oocyte maturation (OM) of denuded oocytes. Treatment of oocytes with Actinomycin D did not block the effects of BPA, suggesting that this inhibition of OM is through a nongenomic mechanism. Incubation of oocytes with a selective GPER antibody and the specific GPER antagonist G-15 blocked the effects of BPA on OM, further suggesting that BPA inhibition of OM is through its interaction with the receptor. Various inhibitors of the EGFR pathway were utilized to determine if the inhibition of OM by BPA is mediated through this mechanism. BPA activation of the Egfr pathway resulted in Mapk3/1 (also known as Erk 1/2) phosphorylation. The results show that BPA disrupts oocyte maturation through a novel mechanism involving activation of a Gper/Egfr/Mapk3/1 pathway with potential adverse impacts on reproductive success.Item Effect of bisphenol A on stress-induced premature senescence(2016-11-11) Alper, Samantha J.; Haper, James M.; Gaillard, Anne R.; Haines, Donovan C.; Lynne, Aaron M.Plastics are used for a wide variety of commercial applications all over the world, but recently a number of health risks have been linked to plastics and plastic products. For example, bisphenol A (BPA) is a plasticizer used in the production of plastics such as storage containers, plastic bottles, adhesives, and many other everyday objects. BPA-containing plastics are subject to degradation, resulting in the ingestion of BPA from many different sources. BPA has been shown to cause negative side-effects once ingested due to its ability to act as an estrogen mimic, along with being implicated in the formation of cancers and the metabolic syndrome. BPA has also been linked to inducing oxidative stress, which can lead to damaged DNA, promote tumorigenesis, and can cause cell death in extreme cases. On the other hand, little is known about the effect of BPA on cellular senescence, a state of irreversible cell cycle arrest and a recognized barrier to cancer progression. Because of its pro-oxidizing role, it was hypothesized that BPA could increase the likelihood of cells becoming senescent. To test this, cells were exposed to a variety of experimental conditions for varying lengths of time; they were then stained for β-galactosidase, a widely used biomarker of senescence, and interleukin-6, a pro-inflammatory cytokine linked to senescence. It was found that, although BPA may not have a direct effect on senescence induction in a dose dependent manner, dimethyl sulfoxide (DMSO), the vehicle used to dissolve BPA in this experiment, could have an effect on senescence induction at very low doses.