Nonylphenol polyethoxylates as a possible endrocrine disrupter in the collapsing population of the bay scallop

Nonylphenol polyethoxylates (NPEO) are a group of non-ionic surfactants commonly used in industrial and consumer products. Previous research suggested that nonylphenol (NP), a degradation product of NPEO, can act as an estrogen-mimicking compound causing hermaphroditic tendencies in aquatic organisms. A study was carried out to evaluate the amount of NP bioaccumulated in the bay scallop (A. irradians) tissue under both static aqueous conditions and spiked sediment samples. This is an abstract of a paper presented at the 227th ACS National Meeting (Anaheim, CA 3/28/2004-4/1/2004)

Chronic Nanoparticulate Silver Exposure Results in Tissue Accumulation and Transcriptomic Changes in Zebrafish

Increasing utilization of metallic nanomaterials in recent years implies an increasing rate of release to the environment, with potentially serious adverse effects on environmentally important species. Previously, we demonstrated that exposure to nanoparticulate silver for 24–48 h results in dramatic alterations in global gene expression patterns and increased tissue burdens in zebrafish gills. The present study reports outcomes associated with chronic exposure to nanoparticulate silver in zebrafish. Adult female Danio rerio were exposed to 5, 15, 25, or 50 μg/L nanoparticulate silver in a time course up to 28 days. A soluble silver treatment (5 μg/L) was also included. Results indicate that use of flow-through systems for chronic nanometal studies is a viable concept; measured concentrations of approximately 60% of nominal values over the course of the 28-day exposure were observed. Dissolution of nanoparticulate silver was measured twice weekly throughout the exposure ranging between 0.5 and 1.0 μg/L, and was relatively consistent between nanoparticulate silver tanks, with no differences between treatments. Gill samples from the 28-day time point were analyzed for global gene expression patterns and histopathology. Tissue accumulation in both gill and eviscerated carcass was dose-dependent, and remained elevated 4 days after the silver was removed. Microarray analysis also revealed a dose-dependent response pattern, with the largest number of genes affected in the 50 μg/L AgNP exposure. Pathway analysis of affected genes identified a number of GO terms that were significantly over-represented in the high AgNP dataset. These terms are associated with DNA damage repair, cellular restructuring, and developmental processes

Overcoming qRT-PCR interference by select carbon nanotubes in assessments of gene expression

Nanomaterials (NMs) of various types, including carbon nanotubes (CNTs), can interfere with standard quantitative real-time PCR (qRT-PCR) assays, resulting in inaccurate gene expression measurements; however, the precise step in the qRT-PCR pipeline where this interference occurs has not been well described. Here, we investigated where in the process surface-oxidized multi-walled CNTs (oxMWNTs) inhibited qRT-PCR measurement of the expression of the housekeeping gene GAPDH and explored several strategies to minimize such inhibition. We determined that the interference occurred during the reverse transcription (RT) step and found that doubling reaction reagents or adding BSA successfully mitigated the inhibition. We observed assay interference in the presence of CNTs that were surface-oxidized, but pristine CNTs did not cause the same level of interference. These results highlight the importance of monitoring qRT-PCR assays for interference by CNTs that differ by surface chemistry, as these NMs are commonly used in gene expression assays at concentrations that we have shown to be inhibitory

Examination of Single-Walled Carbon Nanotubes Uptake and Toxicity from Dietary Exposure: Tracking Movement and Impacts in the Gastrointestinal System

Previous studies indicate that exposure of fish to pristine single-walled carbon nanotubes (SWCNTs) by oral gavage, causes no overt toxicity, and no appreciable absorption has been observed. However, in the environment, SWCNTs are likely to be present in dietary sources, which may result in differential impacts on uptake and biological effects. Additionally, the potential of these materials to sorb nutrients (proteins, carbohydrates, and lipids) while present in the gastrointestinal (GI) tract may lead to nutrient depletion conditions that impact processes such as growth and reproduction. To test this phenomenon, fathead minnows were fed a commercial diet either with or without SWCNTs for 96 h. Tracking and quantification of SWCNTs using near-infrared fluorescence (NIRF) imaging during feeding studies showed the presence of food does not facilitate transport of SWCNTs across the intestinal epithelia. Targeting genes shown to be responsive to nutrient depletion (peptide transporters, peptide hormones, and lipases) indicated that pept2, a peptide transporter, and cck, a peptide hormone, showed differential mRNA expression by 96 h, a response that may be indicative of nutrient limitation. The results of the current study increase our understanding of the movement of SWCNTs through the GI tract, while the changes in nutrient processing genes highlight a novel mechanism of sublethal toxicity in aquatic organisms

Influence of the Gastrointestinal Environment on the Bioavailability of Ethinyl Estradiol Sorbed to Single-Walled Carbon Nanotubes

Recent evidence suggests that, because of their sorptive nature, if single-walled carbon nanotubes (SWCNTs) make their way into aquatic environments, they may reduce the toxicity of other waterborne contaminants. However, few studies have examined whether contaminants remain adsorbed following ingestion by aquatic organisms. The objective of this study was to examine the bioavailability and bioactivity of ethinyl estradiol (EE2) sorbed onto SWCNTs in a fish gastrointestinal (GI) tract. Sorption experiments indicated that SWCNTs effectively adsorbed EE2, but the chemical was still able to bind and activate soluble estrogen receptors (ERs) <i>in vitro</i>. However, centrifugation to remove SWCNTs and adsorbed EE2 significantly reduced ER activity compared to that of EE2 alone. Additionally, the presence of SWCNTs did not reduce the extent of EE2-driven induction of vitellogenin 1 <i>in vivo</i> compared to the levels in organisms exposed to EE2 alone. These results suggest that while SWCNTs adsorb EE2 from aqueous solutions, under biological conditions EE2 can desorb and retain bioactivity. Additional results indicate that interactions with gastrointestinal proteins may decrease the level of adsorption of estrogen to SWCNTs by 5%. This study presents valuable data for elucidating how SWCNTs interact with chemicals that are already present in our aquatic environments, which is essential for determining their potential health risk