Toxicity of two heavy rare earth elements to freshwater mussels Dreissena polymorpha.

Rare earth elements (REE) are essential components of many electronic devices that could end-up in solid waste disposal sites and inadvertently released in the environment. The purpose of this study was to examine the toxicity of two heavy REEs, erbium (Er) and lutetium (Lu), in freshwater mussels Dreissena polymorpha. Mussels were exposed to 14 days to increasing concentration (10, 50, 250, and 1250 µg/L) of either Er and Lu at 15 °C and analyzed for gene expression in catalase (CAT), superoxide dismutase (SOD), metallothionein (MT), cytochrome c oxidase (CO1), and cyclin D for cell cycle. In addition, lipid peroxidation (LPO), DNA damage (DNAd), and arachidonate cyclooxygenase were also determined. The data revealed that mussels accumulated Er and Lu similarly and both REEs induced changes in mitochondrial COI activity. Er increased cell division, MT, and LPO, while Lu increased DNAd and decreased cell division. Tissue levels of Er were related to changes in MT (r = 0.7), LPO (r = 0.42), CO1 (r = 0.69), and CycD (r = 0.31). Lu tissue levels were related to changes in CO1 (r = 0.73), CycD (r = - 0.61), CAT (r = 0.31), DNAd (r = 0.43), and SOD (r = 0.34). Although the lethal threshold was similar between Er and Lu, the threshold response for LPO revealed that Er produced toxicity at concentrations 25 times lower than Lu suggesting that Er was more harmful than Lu in mussels. In conclusions, the data supports that the toxicity pattern differed between Er and Lu although they are accumulated in the same fashion.

Form-Dependent Toxicity of Silver Nanomaterials in Rainbow Trout Gills.

The toxicity of the form of nanoparticles is presently not well understood. The purpose of this study consists in comparing the toxicity of various forms of silver nanoparticles (nAg) in juvenile rainbow trout Oncorhynchus mykiss. Juveniles were exposed to various forms of polyvinyl-coated nAg of similar size for 96 h at 15 °C. After the exposure period, the gills were isolated and analyzed for Ag uptake/distribution, oxidative stress, glucose metabolism, and genotoxicity. Higher levels of Ag were detected in gills in fish exposed to dissolved Ag followed by spherical, cubic, and prismatic nAg. Size-exclusion chromatography of gill fractions revealed that the dissolution of nAg was observed for all forms of nAg where prismatic nAg released more important levels of Ag in the protein pool as in fish exposed to dissolved Ag as well. The aggregation of nAg was more important for cubic nAg in respect of the other forms of nAg. The data revealed that lipid peroxidation was closely associated with protein aggregation and viscosity. Biomarkers revealed changes in lipid/oxidative stress and genotoxicity, which were related to the loss of protein aggregation and inflammation (NO2 levels), respectively. In general, the observed effects were found for all forms of nAg where the effects from prismatic nAg were generally higher than for spherical and cubic nAg. The strong relationship between genotoxicity and inflammation response suggests the participation of the immune system in the observed responses of juvenile fish gills.

Investigation on the Toxicity of Nanoparticle Mixture in Rainbow Trout Juveniles.

The environmental impacts of nanoparticle mixtures in the aquatic environment is not well understood. The purpose of this study examined the sub-lethal toxicity of low concentrations (ug/L range) of selected nanoparticles alone and in mixtures in juvenile trout. Fish were exposed to to individual and two environmentally relevant mixtures of silver (nAg), copper oxide (nCuO) and cerium oxide (nCeO) nanoparticles for 96 h at 15 °C. After the exposure period, fish were depurated overnight and tissue levels in Ag, Ce, Cu and Zn were determined along with a suite of effects biomarkers such as oxidative stress/inflammation, denatured protein tagging (ubiquitin), DNA strand breaks (genotoxicity) and acetylcholinesterase (AChE) activity. The data showed that these nanoparticles behaved as suspended matter but were nevertheless bioavailable for fish with bioconcentration factors of 6, 8 and 2 for nAg, nCeO and nCuO respectively. Only nCuO alone increased malonaldehyde (lipid peroxidation) contents but all nanoparticles increased DNA damage, protein-ubiquitin labeling, and decreased AChE activity. Globally, the toxicity of nCeO and nCuO was generally stronger than nAg, and antagonist effects were found in the mixtures. The interactions involved in these antagonisms are not well understood but do not involve the liberation of free ions and labile zinc in tissues. In conclusion, the bioavailability and toxicity of these nanoparticles are influenced by mixtures of nanoparticles, which is likely to occur in contaminated environments.

Evidence of selection in the uncoupling protein 1 gene region suggests local adaptation to solar irradiance in savannah monkeys (Chlorocebus spp.).

In the last 300 thousand years, the genus Chlorocebus expanded from equatorial Africa into the southernmost latitudes of the continent, where colder climate was a probable driver of natural selection. We investigated population-level genetic variation in the mitochondrial uncoupling protein 1 (UCP1) gene region-implicated in non-shivering thermogenesis (NST)-in 73 wild savannah monkeys from three taxa representing this southern expansion (Chlorocebus pygerythrus hilgerti, Chlorocebus cynosuros and Chlorocebus pygerythrus pygerythrus) ranging from Kenya to South Africa. We found 17 single nucleotide polymorphisms with extended haplotype homozygosity consistent with positive selective sweeps, 10 of which show no significant linkage disequilibrium with each other. Phylogenetic generalized least-squares modelling with ecological covariates suggest that most derived allele frequencies are significantly associated with solar irradiance and winter precipitation, rather than overall low temperatures. This selection and association with irradiance is demonstrated by a relatively isolated population in the southern coastal belt of South Africa. We suggest that sunbathing behaviours common to savannah monkeys, in combination with the strength of solar irradiance, may mediate adaptations to thermal stress via NST among savannah monkeys. The variants we discovered all lie in non-coding regions, some with previously documented regulatory functions, calling for further validation and research.

Assessment of the toxicity of a mixture of five rare earth elements found in aquatic ecosystems in Hydra vulgaris.

Rare earth elements (REEs) are considered critical elements for technology and their extraction through mining activities is expected to increase in the future. Due to their chemical similarities, they often co-occur in minerals and thus their ecotoxicity should be assessed as a group/family. However, the available ecotoxicological studies focused mainly on the evaluation of the potential toxicological impacts of individual REEs rather than their mixtures. The aim of this study was therefore to evaluate the toxicity of a representative mixture of five REEs (La, Ce, Pr, Nd and Sm) spanning environmentally relevant concentrations ranging from 0.05X (29 µg REEs L-1) to 5X (2926 µg REEs L-1) to the test organism, Hydra vulgaris, at the morphological, reproductive and regenerative levels. The data showed that lethality occurred at concentrations near (2.5 fold) to those inducing sublethal effects after chronic exposure of 7 days. The mixture affected reproduction and head regeneration and even lethality at concentrations even below those reported at environmental concentration (0.5X = 293 µg REEs L-1) in lakes. This suggests that REEs concentrations found in lakes near mining activities could disrupt regeneration and impair embryonic development. Our data also revealed that combining the 5 REEs results in an antagonistic effect, suggesting that those elements share the same receptor and that low molecular weight and high radius elements (approaching iron) were less toxic. Taken together, hydra could be used as a sensitive model organism for the assessment of aquatic ecotoxicological risks of REE mixtures but further analyses of biochemical and gene expressions should improve our understanding of the long-term effects of REEs mixtures.

Lanthanides Release and Partitioning in Municipal Wastewater Effluents.

The use of lanthanides is increasing in our society, whether in communication technologies, transportation, electronics or medical imaging. Some lanthanides enter urban wastewater and flow through municipal wastewater treatment plants (WWTPs). However, little is known about the effectiveness of treatment processes to remove these elements and the concentrations released in effluents to receiving waters. The main objective of this study was to investigate the fate of lanthanides in various wastewater treatment processes. A secondary objective was to better understand the fate of medical gadolinium (Gd) complexes; anthropogenic inputs were differentiated from geological sources using an approach based on concentration normalization with respect to chondrite Post-Archean Australian Shale (PAAS). The hypothesis was that most lanthanides, especially of geological origin, are associated with the particulate phase and could be efficiently removed by WWTPs. To monitor these elements in different WWTPs, various urban influents and effluents from simple aerated lagoons to advanced treatments were sampled in Canada. The results showed that the rates of lanthanide removal by treatment processes decrease with their atomic number; from 95% for cerium (Ce) to 70% for lutetium (Lu), except for Gd, which was minimally removed. The normalization approach permitted the determination of the origin of Gd in these wastewaters, i.e., medical application versus the geological background. By distinguishing the geogenic Gd fraction from the anthropogenic one, the removal efficiency was evaluated according to the origin of the Gd; nearly 90% for geogenic Gd and a rate varying from 15% to 50% in the case of anthropogenic Gd. The processes using alum as the flocculating agent had the highest removal efficiency from wastewater.

Evaluation of uptake of the cytostatic methotrexate in Elliptio complanata mussels by LC-MS/MS.

Aquatic organisms are continuously exposed to emerging contaminants coming from urban effluents of wastewater treatment plants. The contamination of surface water by those effluents poses a number of environmental risks, and pharmaceuticals are part of this class of effluent contaminants. Various classes of pharmaceuticals are not treated by wastewater treatment plants and anticancer drugs are part of them. The chemotherapy drug methotrexate (MTX) is an emerging contaminant and its growing use with the increase in cancer cases worldwide raises potential risk to aquatic organisms exposed to effluent discharges. However, chemical analyses in exposed freshwater aquatic organisms for ecotoxicological studies are rarely available and no studies have been done yet to accompany ecotoxicological data of exposed filter-feeding organisms. The purpose of this study was to develop a specific and sensitive analytical LC-MS/MS method for the quantification of methotrexate uptake in mussels exposed at different concentrations of the drug. A solid/liquid extraction followed by solid phase extraction (SPE) using an MCX phase purification scheme was optimized. The optimal recovery of 65% and matrix effect of 38% allowed to achieve a limit of quantification of 0.25 ng g-1, with an accuracy of 99-106%, a precision of no more than 3% RSD, and linearity ranging from 0.25 to 25 ng g-1. This methodology was tested with mussels exposed for 96 h at different concentrations (4 to 100 µg L-1) of MTX. The data revealed tissue uptake at concentrations ranging from 0 to 2.53 ng g-1. This suggests that this drug has low uptake potential and this methodology could be used to examine tissue levels of this drug in organisms continuously exposed to urban pollution.

Identifying congeners and transformation products of organic contaminants within complex chemical mixtures in impacted surface waters with a top-down non-targeted screening workflow.

Over 350,000 compounds are registered for production and use including a high number of congeners found in complex chemical mixtures (CCMs). With such a high number of chemicals being released in the environment and degraded into transformation products (TPs), the challenge of identifying contaminants by non-targeted screening (NTS) is massive. "Bottom-up" studies, where compounds are subjected to conditions simulating environmental degradation to identify new TPs, are time consuming and cannot be relied upon to study the TPs of hundreds of thousands of compounds. Therefore, the development of "top-down" workflows, where the structural elucidation of unknown compounds is carried directly on the sample, is of interest. In this study, a top-down NTS workflow was developed using molecular networking and clustering (MNC). A total of 438 compounds were identified including 176 congeners of consumer product additives and 106 TPs. Reference standards were used to confirm the identification of 53 contaminants among them lesser-known pharmaceuticals (aliskiren, sitagliptin) and consumer product additives (lauramidopropyl betaine, 2,2,4-trimethyl-1,2-dihydroquinoline). The MNC tools allowed to group similar TPs and congeners together. As such, several previously unknown TPs of pesticides (metolachlor) and pharmaceuticals (gliclazide, irbesartan) were identified as tentative candidates or probable structures. Moreover, some congeners that had no entry on global repositories (PubChem, ChemSpider) were identified as probable structures. The workflow worked efficiently with oligomers containing ethylene oxide moieties, and with TPs structurally related to their parent compounds. The top-down approach shown in this study addresses several issues with the identification of congeners of industrial compounds from CCMs. Furthermore, it allows elucidating the structure of TPs directly from samples without relying on bottom-up studies under conditions discussed herein. The top-down workflow and the MNC tools show great potential for data mining and retrospective analysis of previous NTS studies.

Uncovering transformation products of four organic contaminants of concern by photodegradation experiments and analysis of real samples from a local river.

In this study, photodegradation experiments simulating the exposure conditions of sunlight on the commonly detected in surface and wastewater contaminants atorvastatin (ATV), bezafibrate (BEZ), oxybenzone (OXZ), and tris(2-butoxyethyl)phosphate (TBEP) were conducted as the fate of these compounds and their transformation products (TPs) was followed. Then a nontargeted analysis was carried out on an urban river to confirm the environmental occurrence of the TPs after which the ECOSAR software was used to generate predicted effect levels of toxicity of the detected TPs on aquatic organisms. Five TPs of ATV were tentatively identified including two stable ones at the end of the experiment: ATV_TP557a and ATV_TP575, that were the product of hydroxylation. Complete degradation of OXZ was observed in the experiment with no significant TP identified. BEZ remained stable and largely undegraded at the end of the exposure. Five TPs of TBEP were found including four that were stable at the end of the experiment: TBEP_TP413, TBEP_TP415, TBEP_TP429, and TBEP_TP343. In the nontargeted analysis, ATV_TP557b, a positional isomer of ATV_TP557a, ATV_TP575 and the 5 TPs of TBEP were tentatively identified. The predicted concentration for effect levels were lower for ATV_TP557b compared to ATV indicating the TP is potentially more toxic than the parent compound. All the TPs of TBEP showed lower predicted toxicity toward aquatic organisms than their parent compound. These results highlight the importance of conducting complete workflows from laboratory experiments, followed by nontargeted analysis to confirm environmental occurrence to end with predicted toxicity to better communicate concern of the newfound TPs to monitoring programs.

Occurrence and size distribution of silver nanoparticles in wastewater effluents from various treatment processes in Canada.

The occurrence of silver (Ag) in urban effluents is partly associated with the increasing use of silver nanoparticles (Ag NPs) as an antiseptic agent in various consumer products. Distinction among Ag forms must be taken into account in the assessment of exposure and toxicological effects to aquatic organisms. Wastewater treatment processes effectively remove Ag particles and colloids (mostly > 95%), but this still leaves notable concentrations (in order of ng/L) escaping to effluent-receiving waters. Total suspended Ag concentrations in various studied effluents ranged from 0.1 to 6 ng/L. The purpose of this study was then to measure and characterize Ag NPs in urban effluents for their concentrations and size distribution using the single particle ICP-MS technique (SP-ICP-MS). Wastewater influents and effluents from various treatment plants-from aerated lagoons to advanced treatment technology-were collected for three sampling days. Our results showed the presence of Ag NP in all samples with concentrations reaching 0.5 ng/L on a mass basis. However, on a particle number basis, Ag NP concentrations (expressed in particle/mL) in the 20-34-nm fraction (up to 3400 particles/mL) were much more abundant (> 700%) than in the > 35-nm larger fraction. The proportion of Ag at the nanoscale (1-100 nm) represents less than 8% of the total suspended Ag for all effluent samples, regardless of their origins. A significant correlation (linear regression: r2 > 0.7) was observed between Ag NP and total suspended Ag concentrations in investigated effluents. Because Ag nanotoxicity is size dependent, the determination of size distribution and exposure concentration on a particle number basis is urgently needed for risk assessment of this class of nanoparticles.

Non-targeted screening of trace organic contaminants in surface waters by a multi-tool approach based on combinatorial analysis of tandem mass spectra and open access databases.

Non-targeted screening (NTS) in mass spectrometry (MS) helps alleviate the shortcoming of targeted analysis such as missing the presence of concerning compounds that are not monitored and its lack of retrospective analysis to subsequently look for new contaminants. Most NTS workflows include high resolution tandem mass spectrometry (HRMS2) and structure annotation with libraries which are still limited. However, in silico combinatorial fragmentation tools that simulate MS2 spectra are available to help close the gap of missing compounds in empirical libraries. Three NTS tools were combined and used to detect and identify unknown contaminants at ultra-trace levels in surface waters in real samples in this qualitative study. Two of them were based on combinatorial fragmentation databases, MetFrag and the Similar Partition Searching algorithm (SPS), and the third, the Global Natural Products Social Networking (GNPS), was an ensemble of empirical databases. The three NTS tools were applied to the analysis of real samples from a local river. A total of 253 contaminants were identified by combining all three tools: 209 were assigned a probable structure and 44 were confirmed using reference standards. The two major classes of contaminants observed were pharmaceuticals and consumer product additives. Among the confirmed compounds, octylphenol ethoxylates, denatonium, irbesartan and telmisartan are reported for the first time in surface waters in Canada. The workflow presented in this work uses three highly complementary NTS tools and it is a powerful approach to help identify and strategically select contaminants and their transformation products for subsequent targeted analysis and uncover new trends in surface water contamination.

Occurrence and ecotoxicity of cytostatic drugs 5-fluorouracil and methotrexate in the freshwater unionid Elliptio complanata.

Municipal effluents continuously release cytostatic drugs with unknown consequences in aquatic organisms. The purpose of the study was to examine the sublethal toxicity of 2 commonly-found cytostatic drugs 5-fluouracile (5-FLU) and methotrexate (MTX) to endemic Elliptio complanata freshwater mussels. The mussels were exposed of each drugs at 0, 4, 20 and 100 µg/L for 96 h t 15 °C. After the exposure period, glutathione S-transferase (GST) and dehydrofolate reductase (DHFR) activities, DNA damage and lipid peroxidation (LPO) were determined. The drugs were detected in mussel tissues with no evidence of accumulation with either drugs. The drug 5-FLU gave a larger spectrum of effects than MTX such as increased DHFR, decreased LPO and DNA strand breaks (repair activity) suggesting that the mussels were metabolically hindered and reduced DNA repair activity. The drug MTX only increased DHFR activity in the gonad. Hence, the data suggest that these drugs are biologically active in freshwater mussels and based on the reported maximum levels of these drugs in municipal effluents, the observed effects are likely in sessile freshwater mussel species downstream urban sources of pollution.

Elevated diversity in loci linked to facial morphology is consistent with the hypothesis that individual facial recognition is important across hominoids.

OBJECTIVES: The ability to use visual signals to identify individuals is an important feature of primate social groups, including humans. Sheehan and Nachman (2014) showed that loci linked to facial morphology had elevated levels of diversity and interpreted this as evidence that the human face is under frequency-dependent selection to enhance individual recognition (Nature Communications 5). In our study, we tested whether this pattern is found in non-human ape species, to help understand whether individual recognition might also play a role in species other than humans. MATERIALS AND METHODS: We examined levels of genetic diversity in an available population genomic dataset of humans, chimpanzees, bonobos, gorillas, and orangutans for three sets of loci, (1) loci linked to facial morphology, (2) loci linked to height, and (3) neutrally evolving regions. We tested whether loci linked to facial morphology were more variable than loci linked to height or neutrally evolving loci in each of these species. RESULTS: We found significantly elevated diversity in loci linked to facial morphology in chimpanzees, gorillas, and Sumatran and Bornean orangutans. DISCUSSION: Our findings closely parallel those of Sheehan and Nachman and are consistent with the idea that selection for facial diversity and individual recognition has not only shaped the evolution of the human face, but it has similarly shaped the evolution of most of our closest primate relatives. We also discuss alternative hypotheses for this pattern.

Evaluation of general stress, detoxification pathways, and genotoxicity in rainbow trout exposed to rare earth elements dysprosium and lutetium.

Rare earth elements (REEs) have been recently identified as emergent contaminants because of their numerous and increasing applications in technology. The impact of REEs on downstream ecosystems, notably aquatic organisms, is of particular concern, but has to date been largely overlooked. The purpose of this study was thus to evaluate the toxicity of lanthanide metals, lutetium (Lu) and dysprosium (Dy) in rainbow trout after 96 h of exposure. The lethal concentration (LC50) was determined and the expression of 14 genes involved in different pathways such as oxidative stress, xenobiotic detoxification, mitochondrial respiration, DNA repair, protein folding and turnover, inflammation, calcium binding and ammonia metabolism were quantified in surviving fish. In parallel, lipid peroxidation (LPO), DNA damage (DSB), metallothionein level (MT) and cyclooxygenase activity (COX) were examined. The acute 96 h-LC50 data revealed that Lu was more toxic than Dy (1.9 and 11.0 mg/L, respectively) and was able to affect all investigated pathways by changing the expression of the studied genes, to the exception of superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST). It also induced a decrease in DNA repair at concentrations 29 times below the LC50. This suggests that Lu could trigger a general stress to disrupt the cell homeostasis leading to genotoxicity without promoting oxidative stress. However, Dy induced modulation in the expression of genes involved in the protection against oxidative stress, detoxification, mitochondrial respiration, immunomodulation, protein turnover and an increase in the DNA strand breaks at concentrations 170 times lower than LC50. Changes in mRNA level transcripts could represent an early signal to prevent against toxicity of Dy, which exhibited inflammatory and genotoxic effects. This study thus provides useful knowledge enhancing our understanding of survival strategies developed by rainbow trout to cope with the presence of lanthanides in the environment.

Effects of climate and atmospheric deposition on a boreal lake chemistry: A synthesis of 36 years of monitoring data.

Reduction in SO42- and NO3- atmospheric deposition in the past decades has improved surface water quality in several catchments but recent studies suggest an increasing influence of climate and dissolved organic carbon (DOC). Here, we report on long-term trends in climate variables, strong acid anions and base cations concentrations in precipitation and at the lake outlet (stream) of a boreal catchment in Québec, Canada, and assess the combined effects of these trends on stream chemistry. Annual SO42- and NO3- depositions respectively decreased by ~85% (from 23 to ~3 kg ha-1) and ~70% (from 18 to ~5 kg ha-1 yr-1) from 1981 to 2016. As a response, stream SO42- and Ca2+ concentrations decreased by 50% (from 3.9 to 1.9 mg L-1) and ~35% (from 2.4 to 1.5 mg L-1), respectively. Stream NO3- concentration decreased by ~89% (from 0.6 to 0.07 mg L-1) mainly due to the decline in NO3- deposition and possibly to increased vegetation N uptake. Unexpectedly, stream alkalinity decreased, likely due to the decline in Ca2+ concentration and to an increase in DOC concentration. Variations in stream pH and Na+ concentrations were best explained by climatic changes than by changes in acid deposition, likely reflecting the effect of climate change on chemical weathering in the region. In addition, the average daily temperature between May and September had a strong influence on stream Ca2+ concentration in the last two decades (negative relationship), suggesting an increasing vegetation nutrient uptake caused by improved growth conditions. Overall, decreased acidic deposition resulted in a general recovery of surface water although the parallel increase in DOC concentration prevented from an increase in water alkalinity. Our data also indicate an increasing influence of climate on water chemistry at the study site, probably mediated by increasing weathering rate and vegetation nutrient uptake.

Evaluation of ELISA-based method for total anabaenopeptins determination and comparative analysis with on-line SPE-UHPLC-HRMS in freshwater cyanobacterial blooms.

Anabaenopeptins (APs) are bioactive cyanopeptides of emerging concern produced by cyanobacteria. The research for analytical development has recently gained in importance due to their abundance in toxic cyanobacterial blooms. A new commercial enzyme-linked immunosorbent assay kit for the determination of total APs (APtot ELISA) has been released promising a rapid response with good cost efficiency for the routine monitoring of uncommon cyanopeptides. The present study explores the suitability of this new kit in comparison with a validated quantitative analytical method based on liquid chromatography coupled to mass spectrometry (LC-MS). The validation results were comparable with both methods for accuracy, precision, and calibration. Method detection limits were more sensitive using LC-MS specifically evaluated at 0.011 and 0.013 µg L-1 for AP-A and B respectively, compared to APtot ELISA evaluated at 0.10 µg L-1 for total of the two. For APtot ELISA, results were independent from the matrix; however, a systematic signal response was measured in blanks, requiring a blank subtraction in data treatment. Cross-reactivity of APtot ELISA was investigated by analyzing ten cyanopeptides selected for their abundance and diversity. Cyanopeptolin A (CP-A), nodularin-R (NOD), microcystin (MC)-RR, [Asp3]RR, and HilR showed cross-reactivity with an average overestimation going from 25 to 66%. Considering the contribution of cross-reactive cyanopeptides, thirteen lake samples out of fifteen showed higher concentrations using APtot ELISA with overestimation values up to 2261% compared to LC-MS. In light of this study results, LC-MS should still be preconized for the study and monitoring of APs when sensitivity and specificity are needed.

The effects of low intensity focused ultrasonic stimulation on dorsal root ganglion neurons and Schwann cells in vitro.

Satisfactory treatment of peripheral nerve injury (PNI) faces difficulties owing to the intrinsic biological barriers in larger injuries and invasive surgical interventions. Injury gaps >3 cm have low chances of full motor and sensory recovery, and the unmet need for PNI repair techniques which increase the likelihood of functional recovery while limiting invasiveness motivate this work. Building upon prior work in ultrasound stimulation (US) of dorsal root ganglion (DRG) neurons, the effects of US on DRG neuron and Schwann cell (SC) cocultures were investigated to uncover the role of SCs in mediating the neuronal response to US in vitro. Acoustic intensity-dependent alteration in selected neuromorphometrics of DRG neurons in coculture with SCs was observed in total outgrowth, primary neurites, and length compared to previously reported DRG monoculture in a calcium-independent manner. SC viability and proliferation were not impacted by US. Conditioned medium studies suggest secreted factors from SCs subjected to US impact DRG neuron morphology. These findings advance the current understanding of mechanisms by which these cell types respond to US, which may lead to new noninvasive US therapies for treating PNI.

Cyanotoxin release from the benthic, mat-forming cyanobacterium Microseira (Lyngbya) wollei in the St. Lawrence River, Canada.

Benthic cyanobacterial mats occurring in the St. Lawrence River fluvial lakes Saint-Louis and Saint-Pierre are dominated by Microseira (Lyngbya) wollei which produce several cyanotoxins including LWTX-1 that is characteristic of Microseira wollei. This cyanotoxin is not only present in the filaments forming benthic mats, but was also measured in the water overlying the mats. LWTX-1 was found in all cyanobacterial filament samples (75.29-103.26 ng mg-1) and all overlying water samples (3.01-11.03 ng L-1). Toxin concentrations measured in overlying water and dry biomass were strongly correlated (r = 0.94). Furthermore, LWTX-1 concentration in water was positively correlated with the dissolved organic carbon in water (r = 0.74) and % nitrogen content in cyanobacterial filaments (r = 0.52). A preliminary study was conducted to determine the release and degradation rates of LWTX-1 from a M. wollei mat kept under laboratory conditions over a 3-month period. Toxin measurements revealed an early, massive toxin release followed by a typical decaying function, with a half-life in the order of 17 days. Our results raise concerns about the occurrence and downstream advection of dissolved cyanotoxins from Microseira mats in the aquatic environment. Graphical abstract.