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Niladri Basu

Publications and source records attributed to Niladri Basu.

11 recordsLinked to original sources
USGS2024

Inconsistent transcriptomic responses to hexabromocyclododecane in Japanese quail: A comparative analysis of results from four different study designs

Efforts to use transcriptomics for toxicity testing have classically relied on the assumption that chemicals consistently produce characteristic transcriptomic signatures that are reflective of their mechanism of action. However, the degree to which transcriptomic responses are conserved across different test methodologies has seldom been explored. With increasing regulatory demand for New Approach Methods (NAMs) that use alternatives to animal models and high‐content approaches such as transcriptomics, this type of comparative analysis is needed. We examined whether common genes are dysregulated in Japanese quail ( Coturnix japonica ) liver following sublethal exposure to the flame retardant hexabromocyclododecane (HBCD), when life stage and test methodologies differ. The four exposure scenarios included one NAM: Study 1—early‐life stage (ELS) exposure via a single egg injection, and three more traditional approaches; Study 2—adult exposure using a single oral gavage; Study 3—ELS exposure via maternal deposition after adults were exposed through their diet for 7 weeks; and Study 4—ELS exposure via maternal deposition and re‐exposure of nestlings through their diet for 17 weeks. The total number of differentially expressed genes (DEGs) detected in each study was variable (Study 1, 550; Study 2, 192; Study 3, 1; Study 4, 3) with only 19 DEGs shared between Studies 1 and 2. Factors contributing to this lack of concordance are discussed and include differences in dose, but also quail strain, exposure route, sampling time, and HBCD stereoisomer composition. The results provide a detailed overview of the transcriptomic responses to HBCD at different life stages and routes of exposure in a model avian species and highlight certain challenges and limits of comparing transcriptomics across different test methodologies.

Environmental Toxicology and Chemistry↗
USGS2024

Global mercury concentrations in biota: Their use as a basis for a global biomonitoring framework

An important provision of the Minamata Convention on Mercury is to monitor and evaluate the effectiveness of the adopted measures and its implementation. Here, we describe for the first time currently available biotic mercury (Hg) data on a global scale to improve the understanding of global efforts to reduce the impact of Hg pollution on people and the environment. Data from the peer-reviewed literature were compiled in the Global Biotic Mercury Synthesis (GBMS) database (>550,000 data points). These data provide a foundation for establishing a biomonitoring framework needed to track Hg concentrations in biota globally. We describe Hg exposure in the taxa identified by the Minamata Convention: fish, sea turtles, birds, and marine mammals. Based on the GBMS database, Hg concentrations are presented at relevant geographic scales for continents and oceanic basins. We identify some effective regional templates for monitoring methylmercury (MeHg) availability in the environment, but overall illustrate that there is a general lack of regional biomonitoring initiatives around the world, especially in Africa, Australia, Indo-Pacific, Middle East, and South Atlantic and Pacific Oceans. Temporal trend data for Hg in biota are generally limited. Ecologically sensitive sites (where biota have above average MeHg tissue concentrations) have been identified throughout the world. Efforts to model and quantify ecosystem sensitivity locally, regionally, and globally could help establish effective and efficient biomonitoring programs. We present a framework for a global Hg biomonitoring network that includes a three-step continental and oceanic approach to integrate existing biomonitoring efforts and prioritize filling regional data gaps linked with key Hg sources. We describe a standardized approach that builds on an evidence-based evaluation to assess the Minamata Convention’s progress to reduce the impact of global Hg pollution on people and the environment.

Ecotoxicology↗
USGS2022

Mercury contamination and potential health risks to Arctic seabirds and shorebirds

Since the last Arctic Monitoring and Assessment Programme (AMAP) effort to review biological effects of mercury (Hg) on Arctic biota in 2011 and 2018, there has been a considerable number of new Arctic bird studies. This review article provides contemporary Hg exposure and potential health risk for 36 Arctic seabird and shorebird species, representing a larger portion of the Arctic than during previous AMAP assessments now also including parts of the Russian Arctic. To assess risk to birds, we used Hg toxicity benchmarks established for blood and converted to egg, liver, and feather tissues. Several Arctic seabird populations showed Hg concentrations that exceeded toxicity benchmarks, with 50 % of individual birds exceeding the “no adverse health effect” level. In particular, 5 % of all studied birds were considered to be at moderate or higher risk to Hg toxicity. However, most seabirds (95 %) were generally at lower risk to Hg toxicity. The highest Hg contamination was observed in seabirds breeding in the western Atlantic and Pacific Oceans. Most Arctic shorebirds exhibited low Hg concentrations, with approximately 45 % of individuals categorized at no risk, 2.5 % at high risk category, and no individual at severe risk. Although the majority Arctic-breeding seabirds and shorebirds appeared at lower risk to Hg toxicity, recent studies have reported deleterious effects of Hg on some pituitary hormones, genotoxicity, and reproductive performance. Adult survival appeared unaffected by Hg exposure, although long-term banding studies incorporating Hg are still limited. Although Hg contamination across the Arctic is considered low for most bird species, Hg in combination with other stressors, including other contaminants, diseases, parasites, and climate change, may still cause adverse effects. Future investigations on the global impact of Hg on Arctic birds should be conducted within a multi-stressor framework. This information helps to address Article 22 (Effectiveness Evaluation) of the Minamata Convention on Mercury as a global pollutant.

Science of the Total Environment↗
USGS2021

Sex- and developmental stage-related differences in the hepatic transcriptome of Japanese quail (Coturnix japonica) exposed to 17β-Trenbolone

Endocrine-disrupting chemicals can cause transcriptomic changes that may disrupt biological processes associated with reproductive function including metabolism, transport, and cell growth. We investigated effects from in ovo and dietary exposure to 17β-trenbolone (at 0, 1, and 10 ppm) on the Japanese quail ( Coturnix japonica ) hepatic transcriptome. Our objectives were to identify differentially expressed hepatic genes, assess perturbations of biological pathways, and examine sex- and developmental stage–related differences. The number of significantly differentially expressed genes was higher in embryos than in adults. Male embryos exhibited greater differential gene expression than female embryos, whereas in adults, males and females exhibited similar numbers of differentially expressed genes (>2-fold). Vitellogenin and apovitellenin-1 were up-regulated in male adults exposed to 10 ppm 17β-trenbolone, and these birds also exhibited indications of immunomodulation. Functional grouping of differentially expressed genes identified processes including metabolism and transport of biomolecules, enzyme activity, and extracellular matrix interactions. Pathway enrichment analyses identified as perturbed peroxisome proliferator–activated receptor pathway, cardiac muscle contraction, gluconeogenesis, growth factor signaling, focal adhesion, and bile acid biosynthesis. One of the primary uses of 17β-trenbolone is that of a growth promoter, and these results identify effects on mechanistic pathways related to steroidogenesis, cell proliferation, differentiation, growth, and metabolism of lipids and proteins.

Environmental Toxicology and Chemistry↗
USGS2019

Current state of knowledge on biological effects from contaminants on arctic wildlife and fish

Since the last Arctic Monitoring and Assessment Programme (AMAP) effort to review biological effects of the exposure to organohalogen compounds (OHCs) in Arctic biota, there has been a considerable number of new Arctic effect studies. Here, we provide an update on the state of the knowledge of OHC, and also include mercury, exposure and/or associated effects in key Arctic marine and terrestrial mammal and bird species as well as in fish by reviewing the literature published since the last AMAP assessment in 2010. We aimed at updating the knowledge of how single but also combined health effects are or can be associated to the exposure to single compounds or mixtures of OHCs. We also focussed on assessing both potential individual as well as population health impacts using population-specific exposure data post 2000. We have identified quantifiable effects on vitamin metabolism, immune functioning, thyroid and steroid hormone balances, oxidative stress, tissue pathology, and reproduction. As with the previous assessment, a wealth of documentation is available for biological effects in marine mammals and seabirds, and sentinel species such as the sledge dog and Arctic fox, but information for terrestrial vertebrates and fish remain scarce. While hormones and vitamins are thoroughly studied, oxidative stress, immunotoxic and reproductive effects need further investigation. Depending on the species and population, some OHCs and mercury tissue contaminant burdens post 2000 were observed to be high enough to exceed putative risk threshold levels that have been previously estimated for non-target species or populations outside the Arctic. In this assessment, we made use of risk quotient calculations to summarize the cumulative effects of different OHC classes and mercury for which critical body burdens can be estimated for wildlife across the Arctic. As our ultimate goal is to better predict or estimate the effects of OHCs and mercury in Arctic wildlife at the individual, population and ecosystem level, there remain numerous knowledge gaps on the biological effects of exposure in Arctic biota. These knowledge gaps include the establishment of concentration thresholds for individual compounds as well as for realistic cocktail mixtures that in fact indicate biologically relevant, and not statistically determined, health effects for specific species and subpopulations. Finally, we provide future perspectives on understanding Arctic wildlife health using new in vivo, in vitro, and in silico techniques, and provide case studies on multiple stressors to show that future assessments would benefit from significant efforts to integrate human health, wildlife ecology and retrospective and forecasting aspects into assessing the biological effects of OHC and mercury exposure in Arctic wildlife and fish.

Science of the Total Environment↗
USGS2018

Modulators of mercury risk to wildlife and humans in the context of rapid global change

Environmental mercury (Hg) contamination is an urgent global health threat. The complexity of Hg in the environment can hinder accurate determination of ecological and human health risks, particularly within the context of the rapid global changes that are altering many ecological processes, socioeconomic patterns, and other factors like infectious disease incidence, which can affect Hg exposures and health outcomes. However, the success of global Hg-reduction efforts depends on accurate assessments of their effectiveness in reducing health risks. In this paper, we examine the role that key extrinsic and intrinsic drivers play on several aspects of Hg risk to humans and organisms in the environment. We do so within three key domains of ecological and human health risk. First, we examine how extrinsic global change drivers influence pathways of Hg bioaccumulation and biomagnification through food webs. Next, we describe how extrinsic socioeconomic drivers at a global scale, and intrinsic individual-level drivers, influence human Hg exposure. Finally, we address how the adverse health effects of Hg in humans and wildlife are modulated by a range of extrinsic and intrinsic drivers within the context of rapid global change. Incorporating components of these three domains into research and monitoring will facilitate a more holistic understanding of how ecological and societal drivers interact to influence Hg health risks.

Ambio↗
USGS2015

Investigating endocrine and physiological parameters of captive American kestrels exposed by diet to selected organophosphate flame retardants

Organophosphate triesters are high production volume additive flame retardants (OPFRs) and plasticizers. Shown to accumulate in abiotic and biotic environmental compartments, little is known about the risks they pose. Captive adult male American kestrels (Falco sparverius) were fed the same dose (22 ng OPFR/g kestrel/d) daily (21 d) of tris(2- butoxyethyl) phosphate (TBOEP), tris(2-chloroethyl) phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCIPP), or tris(1,2-dichloro-2-propyl) phosphate (TDCIPP). Concentrations were undetected in tissues (renal, hepatic), suggesting rapid metabolism. There were no changes in glutathione status, indicators of hepatic oxidative status, or the cholinergic system (i.e., cerebrum, plasma cholinesterases; cerebrum muscarinic, nicotinic receptors). Modest changes occurred in hepatocyte integrity and function (clinical chemistry). Significant effects on plasma free triiodothyronine (FT3) concentrations occurred with exposure to TBOEP, TCEP, TCIPP, and TDCIPP; TBOEP and TCEP had additional overall effects on free thyroxine (FT4), whereas TDCIPP also influenced total thyroxine (TT4). Relative increases (32%−96%) in circulating FT3, TT3, FT4, and/or TT4 were variable with each OPFR at 7 d exposure, but limited thereafter, which was likely maintained through decreased thyroid gland activity and increased hepatic deiodinase activity. The observed physiological and endocrine effects occurred at environmentally relevant concentrations and suggest parent OPFRs or metabolites may have been present despite rapid degradation.

Environmental Science & Technology↗
USGS2014

Historic and contemporary mercury exposure and potential risk to yellow-billed loons ( Gavia adamsii ) breeding in Alaska and Canada

The Yellow-billed Loon (Gavia adamsii) is one of the rarest breeding birds in North America. Because of the small population size and patchy distribution, any stressor to its population is of concern. To determine risks posed by environmental mercury (Hg) loads, we captured 115 Yellow-billed Loons between 2002 and 2012 in the North American Arctic and sampled their blood and/or feather tissues and collected nine eggs. Museum samples from Yellow-billed Loons also were analyzed to examine potential changes in Hg exposure over time. An extensive database of published Hg concentrations and associated adverse effects in Common Loons (G. immer) is highly informative and representative for Yellow-billed Loons. Blood Hg concentrations reflect dietary uptake of methylmercury (MeHg) from breeding areas and are generally considered near background levels if less than 1.0 µg/g wet weight (ww). Feather (grown at wintering sites) and egg Hg concentrations can represent a mix of breeding and wintering dietary uptake of MeHg. Based on Common Loon studies, significant risk of reduced reproductive success generally occurs when adult Hg concentrations exceed 2.0 µg/g ww in blood, 20.0 µg/g fresh weight (fw) in flight feathers and 1.0 µg/g ww in eggs. Contemporary mercury concentrations for 176 total samples (across all study sites for 115 Yellow-billed Loons) ranged from 0.08 to 1.45 µg/g ww in blood, 3.0 to 24.9 µg/g fw in feathers and 0.21 to 1.23 µg/g ww in eggs. Mercury concentrations in blood, feather and egg tissues indicate that some individual Yellow-billed Loons in breeding populations across North America are at risk of lowered productivity resulting from Hg exposure. Most Yellow-billed Loons breeding in Alaska overwinter in marine waters of eastern Asia. Although blood Hg concentrations from most breeding loons in Alaska are within background levels, some individuals exhibit elevated feather and egg Hg concentrations, which likely indicate the uptake of MeHg originating from eastern Asia. Feather Hg concentrations tended to be highest in individuals overwintering farthest west (closer to Asia). A retrospective analysis of museum specimens (n = 25) found a two-fold increase in Yellow-billed Loon feather Hg concentrations from the pre-1920s (as early as 1845) to the present. The projected increase in Hg deposition (approximately four-fold by 2050) along with the uncertainty of Hg being released through the thawing of permafrost and Arctic sea ice suggest that Hg body burdens in Yellow-billed Loons may increase. These findings indicate that Hg is a current and potentially increasing environmental stressor for the Yellow-billed Loon and possibly other Nearctic-Palearctic migrant birds.

Alaska↗
USGS2012

Absence of fractionation of mercury isotopes during trophic transfer of methylmercury to freshwater fish in captivity

We performed two controlled experiments to determine the amount of mass-dependent and mass-independent fractionation (MDF and MIF) of methylmercury (MeHg) during trophic transfer into fish. In experiment 1, juvenile yellow perch ( Perca flavescens ) were raised in captivity on commercial food pellets and then their diet was either maintained on unamended food pellets (0.1 μg/g MeHg) or was switched to food pellets with 1.0 μg/g or 4.0 μg/g of added MeHg, for a period of 2 months. The difference in δ 202 Hg (MDF) and Δ 199 Hg (MIF) between fish tissues and food pellets with added MeHg was within the analytical uncertainty (δ 202 Hg, 0.07 ‰; Δ 199 Hg, 0.06 ‰), indicating no isotope fractionation. In experiment 2, lake trout ( Salvelinus namaycush ) were raised in captivity on food pellets and then shifted to a diet of bloater ( Coregonus hoyi ) for 6 months. The δ 202 Hg and Δ 199 Hg of the lake trout equaled the isotopic composition of the bloater after 6 months, reflecting reequilibration of the Hg isotopic composition of the fish to new food sources and a lack of isotope fractionation during trophic transfer. We suggest that the stable Hg isotope ratios in fish can be used to trace environmental sources of Hg in aquatic ecosystems.

Environmental Science & Technology↗
USGS2012

Ecotoxicology of mercury in fish and wildlife: Recent advances

A number of recent studies have documented subtle, yet potentially important effects of mercury on behavior, neurochemistry, and endocrine function in fish and wildlife at currently realistic levels of environmental exposure. Current levels of environmental methylmercury exposure are sufficient to cause significant biological impairment, both in individuals and in whole populations, in some ecosystems. Future toxicological studies on fish and wildlife will focus on linking biomarkers of methylmercury exposure and associated oxidative stress to effects on reproduction and population change; determining the genetic basis for mercury-related neurotoxic and other biological changes; determining the genetic basis for species differences in sensitivity to methylmercury; and linking toxic effects of methylmercury in individual animals to population-level changes.

Book chapter↗