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The lifespans of proteins range from minutes to years within mammalian tissues. Protein lifespan is relevant to organismal aging, as long‐lived proteins accrue damage over time. It is unclear how protein lifetime is shaped by tissue context, where both cell turnover and proteolytic degradation contribute to protein turnover. We develop turnover and replication analysis by 15N isotope labeling (TRAIL) to quantify protein and cell lifetimes with high precision and demonstrate that cell turnover, sequence‐encoded features, and environmental factors modulate protein lifespan across tissues. Cell and protein turnover flux are comparable in proliferative tissues, while protein turnover outpaces cell turnover in slowly proliferative tissues. Physicochemical features such as hydrophobicity, charge, and disorder influence protein turnover in slowly proliferative tissues, but protein turnover is much less sequence‐selective in highly proliferative tissues. Protein lifetimes vary nonrandomly across tissues after correcting for cell turnover. Multiprotein complexes such as the ribosome have consistent lifetimes across tissues, while mitochondria, peroxisomes, and lipid droplets have variable lifetimes. TRAIL can be used to explore how environment, aging, and disease affect tissue homeostasis. Synopsis: A new 15N metabolic labeling method for parallel quantification of cell and protein turnover rates in mouse tissues illustrates the variable influence of "nature" versus "nurture" on protein turnover rates in vivo. The median proteome turnover rate and the identity of the longest‐ and shortest‐lived proteins vary across tissues.Protein turnover and cell turnover occur at similar rates in proliferative tissues, but protein turnover outpaces cell turnover in less proliferative tissues.Sequence features such as hydrophobicity, disorder, and isoelectric point contribute to protein turnover rate only in less proliferative tissues.Protein and organelle turnover rates remain very different from tissue to tissue even after correcting for cell turnover rates. [ABSTRACT FROM AUTHOR]

Abstract: Benthic periphytic biofilms are important food sources at the base of aquatic ecosystems. These biofilms also sit at the interface of oxic waters and hypoxic sediments, and can be influenced by or influence trace element speciation. In the present study, we compared arsenic (As) enrichment in periphyton exposed to arsenate (As[V]) or arsenite (As[III]) (20 μg/L, static renewal, 7 d), and we found similar accumulation patterns of total As (101 ± 27 and 88 ± 22 mg kg−1 dry wt, respectively). Periphyton As was 6281‐ and 6684‐fold higher than their aqueous exposures and occurred primarily as As(V). When these biofilms were fed to larval mayflies, similar total As tissue concentrations (13.9 and 14.6 mg kg−1 dry wt, respectively) were observed, revealing significant biodilution (∼ 10% of their dietary concentrations). Finally, we investigated the influence of aeration and periphyton presence on As speciation in solutions and solid phases treated with As(III). Predominantly As(III) solutions were slowly oxidized over a 7‐d time period, in the absence of periphyton, and aeration did not strongly affect oxidation rates. However, in the presence of periphyton, solution and solid‐phase analyses (by microscale x‐ray absorption spectroscopy) showed rapid As(III) oxidation to As(V) and an increasing proportion of organo‐As forming over time. Thus periphyton plays several roles in As environmental behavior: 1) decreasing total dissolved As concentrations via abiotic and biotic accumulation, 2) rapidly oxidizing As(III) to As(V), 3) effluxing organo‐As forms into solution, and 4) limiting trophic transfer to aquatic grazers. Environ Toxicol Chem 2018;37:903–913. © 2017 SETAC [ABSTRACT FROM AUTHOR]

To determine whether the bioavailability of trace elements derived from coal ash leachates varies with the geochemical conditions associated with their formation, we quantified periphyton bioaccumulation and subsequent trophic transfer to the mayfly Neocloeon triangulifer. Oxic ash incubations favored periphyton uptake of arsenic, selenium, strontium, and manganese, whereas anoxic incubations favored periphyton uptake of uranium. Mayfly enrichment was strongest for selenium, whereas biodilution was observed for strontium, uranium, and arsenic. Environ Toxicol Chem 2017;36:2991-2996. © 2017 SETAC [ABSTRACT FROM AUTHOR]

The development of water quality criteria (WQC) for the protection of aquatic life is a fundamental component of the Clean Water Act-the primary US legislation responsible for protecting aquatic ecosystems from pollution. Water quality criteria define acceptable levels of contamination in the environment and thus play an important role in society. Rules for how science is used to develop WQC were created in 1985. Most rely on only data and knowledge obtained through a single methodology, the single-species laboratory toxicity test. Since 1985, understanding of the fate and effects of environmental contaminants has advanced markedly from multiple perspectives and disciplines. However, many of these advances are routinely discarded in WQC development because they do not adhere to data limits imposed by the 1985 guidelines. The present Focus article outlines how multiple lines of inquiry have played important roles in improving understanding of the ecological implications of environmental contaminants. The authors focus on gains in understanding that would not have been possible through traditional toxicity bioassays alone and argue that more robust scientific understanding can be used to modernize WQC development. In particular, the present article highlights ways to increase the relevance of toxicity testing (at different spatiotemporal scales) and incorporate all relevant lines of evidence into WQC modernization. Environ Toxicol Chem 2017;36:285-291. © 2017 SETAC [ABSTRACT FROM AUTHOR]

Many environmental stressors manifest their effects via physiological processes (traits) that can differ significantly among species and species groups. We compiled available data for three traits related to the bioconcentration of the toxic metal cadmium ( Cd) from 42 species representing the aquatic insect orders Ephemeroptera (mayflies), Plecoptera (stoneflies) and Trichoptera (caddisflies). These traits included the propensity to take up Cd from water (uptake rate constant, ku), the ability to excrete Cd (efflux rate constant, ke) and the net result of these two processes (bioconcentration factor)., Ranges in these Cd bioaccumulation traits varied in magnitude across clades (some clades had a greater tendency to bioaccumulate Cd than others). Overlap in the ranges of trait values among different clades was common and highlights situations where species from different lineages can share a similar trait state, but represent the high end of possible physiological values for one clade and the low end for another., Variance around the mean trait states differed widely across clades, suggesting that some groups (e.g. Ephemerellidae) are inherently more variable than others (e.g. Perlidae). Thus, trait variability/lability is at least partially a function of lineage., Akaike information criterion comparisons of statistical models were more often driven by lineage than by the other tested potential biological or ecological explanations. Lineage-driven models generally improved with increasing taxonomic resolution., Together, these findings suggest that lineage provides context for the analysis of species traits and that failure to consider lineage in community-based analysis of traits may obscure important patterns of species responses to environmental change. [ABSTRACT FROM AUTHOR]

In previous laboratory chronic 7-d toxicity tests conducted with the cladoceran Ceriodaphnia dubia, surface waters collected from Appalachian sites impacted by coal mining have shown toxic effects associated with elevated total dissolved solids (TDS). The objective of the present study was to evaluate the effects of elevated major ions in chronic laboratory tests with C. dubia (7-d exposure), a unionid mussel ( Lampsilis siliquoidea; 28-d exposure), an amphipod ( Hyalella azteca; 28-d exposure), and a mayfly ( Centroptilum triangulifer; 35-d exposure) in 3 reconstituted waters designed to be representative of 3 Appalachian sites impacted by coal mining. Two of the reconstituted waters had ionic compositions representative of alkaline mine drainage associated with mountaintop removal and valley fill-impacted streams (Winding Shoals and Boardtree, with elevated Mg, Ca, K, SO4, HCO3), and a third reconstituted water had an ionic composition representative of neutralized mine drainage (Upper Dempsey, with elevated Na, K, SO4, and HCO3). The waters with similar conductivities but, with different ionic compositions had different effects on the test organisms. The Winding Shoals and Boardtree reconstituted waters were consistently toxic to the mussel, the amphipod, and the mayfly. In contrast, the Upper Dempsey reconstituted water was toxic to the mussel, the amphipod, and the cladoceran but was not toxic to the mayfly. These results indicate that, although elevated TDS can be correlated with toxicity, the specific major ion composition of the water is important. Moreover, the choice of test organism is critical, particularly if a test species is to be used as a surrogate for a range of faunal groups. Environ Toxicol Chem 2013;32:2826-2835. © 2013 SETAC [ABSTRACT FROM AUTHOR]

A key challenge in ecotoxicology is to assess the potential risks of chemicals to the wide range of species in the environment on the basis of laboratory toxicity data derived from a limited number of species. These species are then assumed to be suitable surrogates for a wider class of related taxa. For example, Daphnia spp. are used as the indicator species for freshwater aquatic invertebrates. Extrapolation from these datasets to natural communities poses a challenge because the extent to which test species are representative of their various taxonomic groups is often largely unknown, and different taxonomic groups and chemicals are variously represented in the available datasets. Moreover, it has been recognized that physiological and ecological factors can each be powerful determinants of vulnerability to chemical stress, thus differentially influencing toxicant effects at the population and community level. Recently it was proposed that detailed study of species traits might eventually permit better understanding, and thus prediction, of the potential for adverse effects of chemicals to a wider range of organisms than those amenable for study in the laboratory. This line of inquiry stems in part from the ecology literature, in which species traits are being used for improved understanding of how communities are constructed, as well as how communities might respond to, and recover from, disturbance (see other articles in this issue). In the present work, we develop a framework for the application of traits-based assessment. The framework is based on the population vulnerability conceptual model of Van Straalen in which vulnerability is determined by traits that can be grouped into 3 major categories, i.e., external exposure, intrinsic sensitivity, and population sustainability. Within each of these major categories, we evaluate specific traits as well as how they could contribute to the assessment of the potential effects of a toxicant on an organism. We then develop an example considering bioavailability to explore how traits could be used mechanistically to estimate vulnerability. A preliminary inventory of traits for use in ecotoxicology is included; this also identifies the availability of data to quantify those traits, in addition to an indication of the strength of linkage between the trait and the affected process. Finally, we propose a way forward for the further development of traits-based approaches in ecotoxicology. Integr Environ Assess Manag 2011;7:172-186. © 2011 SETAC [ABSTRACT FROM AUTHOR]

Aquatic insects have evolved diverse respiratory strategies that range from breathing atmospheric air to breathing dissolved oxygen. These strategies result in vast morphological differences among taxa in terms of exchange epithelial surface areas that are in direct contact with the surrounding water that, in turn, affect physiological processes. This paper examines the effects of acute temperature shifts on water permeability and chlorpyrifos uptake in aquatic insects with different respiratory strategies. While considerable differences existed in water permeability among the species tested, acute temperature shifts raised water influx rates similarly in air-breathing and gill-bearing taxa. This contrasts significantly with temperature-shift effects on chlorpyrifos uptake. Temperature shifts of 4.5°C increased 14C-chlorpyrifos accumulation rates in the gill-bearing mayfly Cinygma sp. and in the air-breathing hemipteran Sigara washingtonensis. However, the temperature-induced increase in 14C-chlorpyrifos uptake after 8 h of exposure was 2.75-fold higher in Cinygma than in Sigara. Uptake of 14C-chlorpyrifos was uniformly higher in Cinygma than in Sigara in all experiments. These findings suggest that organisms with relatively large exchange epithelial surface areas are potentially more vulnerable to both osmoregulatory distress as well as contaminant accumulation. Temperature increases appear more likely to impact organisms that have relatively large exchange epithelial surface areas, both as an individual stressor and in combination with additional stressors such as contaminants. [ABSTRACT FROM AUTHOR]

The ternary complex factors (TCFs) Net, Elk-1 and Sap-1 regulate immediate early genes through serum response elements (SREs) in vitro, but, surprisingly, their in vivo roles are unknown. Net is a repressor that is expressed in sites of vasculogenesis during mouse development. We have made gene-targeted mice that express a hypomorphic mutant of Net, Netδ, which lacks the Ets DNA-binding domain. Strikingly, homozygous mutant mice develop a vascular defect and up-regulate an immediate early gene implicated in vascular disease, egr-1. They die after birth due to respiratory failure, resulting from the accumulation of chyle in the thoracic cage (chylothorax). The mice have dilated lymphatic vessels (lymphangiectasis) as early as E16.5. Interestingly, they express more egr-1 in heart and pulmonary arteries at E18.5. Net negatively regulates the egr-1 promoter and binds specifically to SRE-5. Egr-1 has been associated with pathologies involving vascular stenosis (e.g. atherosclerosis), and here egr-1 dysfunction could possibly be associated with obstructions that ultimately affect the lymphatics. These results show that Net is involved in vascular biology and egr-1 regulation in vivo. [ABSTRACT FROM AUTHOR]

One of the critical first steps in the knowledge management area is to conduct a knowledge audit. Some people view the knowledge audit as being the business needs assessment, cultural assessment, and an examination of what knowledge is needed, available, missing, applied, and contained. In the same manner that a manufacturing company will first inventory its physical assets, an aspiring 'knowledge organization' should also inventory its intellectual capital assets. This paper will focus on the third strand of the knowledge audit described above, namely determining what knowledge is needed, what is available and missing, who needs this knowledge, and how it will be applied. Then, a case study will be discussed where the knowledge audit instrument was used. [ABSTRACT FROM AUTHOR]

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The influence of metal exposure history on rates of aqueous Cd accumulation, elimination, and subcellular distribution was examined in the aquatic insect Hydropsyche californica. Specimens were obtained from a reference site and a metal-contaminated site and returned to the laboratory where they were continuously exposed to aqueous Cd (518 ng/L, nominal) for 6 d, followed by 9 d of depuration. Rates of Cd accumulation and elimination were similar in insects from the two sites. Efflux rate constants, ke, ranged from 0.20 to 0.24/d (t1/2 3 d). Immediately following exposure, the cytosol accounted for 40% of the body burden in insects from both sites; however, 89 ± 2% of the cytosolic Cd was associated with metallothionein-like proteins (MTLP) in insects from the contaminated site, compared to 60 ± 0% in insects from the reference site. The concentration of Cd bound to non-MTLPs (representing potentially Cd-sensitive proteins) was significantly greater in the insects from the reference site (134 ± 7 ng/g) than in those from the contaminated site (42 ± 2 ng/g). At the end of the depuration period, 90% of the accumulated Cd body burden had been eliminated, and Cd concentrations in MTLPs and non-MTLPs were similar between the sites. Results suggested that differences in exposure history had no influence on the bioaccumulation of Cd, but did affect the concentrations of Cd bound to MTLP during Cd exposure in these insects. [ABSTRACT FROM AUTHOR]