Oxygenation through oral Ox66 in a two-hit rodent model of respiratory distress.

Acute respiratory distress syndrome (ARDS) is a complication of pulmonary disease that produces life-threatening hypoxaemia. Despite ventilation and hyperoxic therapies, undetected hypoxia can manifest in capillary beds leading to multi-organ failure. Ox66™ is an ingestible, solid-state form of oxygen designed to supplement oxygen deficits. Twenty-four anaesthetized rats underwent a two-hit model of respiratory distress (ARDS), where a single dose (5 mg/kg) of lipopolysaccharide (LPS) was given intratracheally, and then the respiratory tidal volume was reduced by 40%. After 60 min, animals were randomized to receive Ox66™, or normal saline (NS; vehicle control) via gavage or supplemental inspired oxygen (40% FiO2). A second gavage was administered at 120 min. Cardiovascular function and blood oximetry/chemistry were measured alongside the peripheral spinotrapezius muscle's interstitial oxygenation (PISFO2). ARDS reduced mean arterial pressure (MAP) and PISFO2 compared to baseline (BL) for all treatment groups. Treatment with Ox66 or NS did not improve MAP, but 40% FiO2 caused a rapid return to BL. PISFO2 improved after treatment with Ox66™ and 40% FiO2 and remained elevated for both groups against NS until study conclusion. Both oxygen treatments also suppressed the inflammatory response to LPS, suggesting that Ox66™ can deliver therapeutically-impactful levels of oxygen in situations of pulmonary dysfunction.

Suit Up: A Systematic Review of the Personal Protective Equipment (PPE) Recommended and Utilized by Various Classes of Responders to Nuclear Radiological Disasters at Nuclear Power Plants.

INTRODUCTION: Interest in nuclear power as a cleaner and alternative energy source is increasing in many countries. Despite the relative safety of nuclear power, large-scale disasters such as the Fukushima Daiichi (Japan) and Chernobyl (Ukraine) meltdowns are a reminder that emergency preparedness and safety should be a priority. In an emergency situation, there is a need to balance the tension between a rapid response, preventing harm, protecting communities, and safeguarding workers and responders. The first line of defense for workers and responders is personal protective equipment (PPE), but the needs vary by situation and location. Better understanding this is vital to inform PPE needs for workers and responders during nuclear and radiological power plant accidents and emergencies. STUDY OBJECTIVE: The aim of this study was to identify and describe the PPE used by different categories of workers and responders during nuclear and radiological power plant accidents and emergencies. METHODS: A systematic literature review format following the PRISMA 2020 guidelines was utilized. Databases SCOPUS, PubMed, EMBASE, INSPEC, and Web of Science were used to retrieve articles that examined the PPE recommended or utilized by responders to nuclear radiological disasters at nuclear power plants (NPPs). RESULTS: The search terms yielded 6,682 publications. After removal of duplicates, 5,587 sources continued through the systematic review process. This yielded 23 total articles for review, and five articles were added manually for a total of 28 articles reviewed in this study. Plant workers, decontamination or decommissioning workers, paramedics, Emergency Medical Services (EMS), emergency medical technicians, military, and support staff were the categories of responders identified for this type of disaster. Literature revealed that protective suits were the most common item of PPE required or recommended, followed by respirators and gloves (among others). However, adherence issues, human errors, and physiological factors frequently emerged as hinderances to the efficacy of these equipment in preventing contamination or efficiency of these responders. CONCLUSION: If worn correctly and consistently, PPE will reduce exposure to ionizing radiation during a nuclear and radiological accident or disaster. For the best results, standardization of equipment recommendations, clear guidelines, and adequate training in its use is paramount. As fields related to nuclear power and nuclear medicine expand, responder safety should be at the forefront of emergency preparedness and response planning.

Effects of short-chain per- and polyfluoroalkyl substances (PFAS) on toxicologically relevant gene expression profiles in a liver-on-a-chip model.

Short-chain per- and polyfluoroalkyl substances (PFAS) are highly stable and widely used environmental contaminants that pose potential health risks to humans. Aggregating reliable mechanistic information for safety assessments necessitates physiologically relevant high-throughput screening approaches. Here, we demonstrated the utility of a liver-on-a-chip model to investigate the effects of five short-chain PFAS at low (1 nM) and high (1 µM) concentrations on toxicologically-relevant gene expression profiles using the QuantiGene® Plex Assay. We found that the short-chain PFAS tested in this study modulated the expression of ABCG2, a gene encoding for the breast cancer resistance protein (BCRP), with marked and significant upregulation (up to 4-fold) observed for all but one of the short-chain PFAS tested. PFBS and HFPO-DA repressed SLCO1B3 expression, a gene that encodes for an essential liver-specific organic anion transporter. High concentrations of PFBS, PFHxA, and PFHxS upregulated the expression of genes encCYP1A1,CYP2B6 and CYP2C19 with the same treatments resulting in the repression of the expression of the gene encoding CYP1A2. This dysregulation could have consequences for the clearance of endogenous compounds and xenobiotics. However, we acknowledge that increased expression of genes encoding for transporters and biotransformation enzymes may or may not indicate changes to their protein expression or activity. Overall, our study provides important insights into the effects of short-chain PFAS on liver function and their potential implications for human health. The use of the liver-on-a-chip model in combination with the QuantiGene® Plex Assay may be a valuable tool for future high-throughput screening and gene expression profiling in toxicology studies.

Evaluating the effect of acute diesel exhaust particle exposure on P-glycoprotein efflux transporter in the blood-brain barrier co-cultured with microglia.

A growing public health concern, chronic Diesel Exhaust Particle (DEP) exposure is a heavy risk factor for the development of neurodegenerative diseases like Alzheimer's (AD). Considered the brain's first line of defense, the Blood-Brain Barrier (BBB) and perivascular microglia work in tandem to protect the brain from circulating neurotoxic molecules like DEP. Importantly, there is a strong association between AD and BBB dysfunction, particularly in the Aß transporter and multidrug resistant pump, P-glycoprotein (P-gp). However, the response of this efflux transporter is not well understood in the context of environmental exposures, such as to DEP. Moreover, microglia are seldom included in in vitro BBB models, despite their significance in neurovascular health and disease. Therefore, the goal of this study was to evaluate the effect of acute (24 hr.) DEP exposure (2000 µg/ml) on P-gp expression and function, paracellular permeability, and inflammation profiles of the human in vitro BBB model (hCMEC/D3) with and without microglia (hMC3). Our results suggested that DEP exposure can decrease both the expression and function of P-gp in the BBB, and corroborated that DEP exposure impairs BBB integrity (i.e. increased permeability), a response that was significantly worsened by the influence of microglia in co-culture. Interestingly, DEP exposure seemed to produce atypical inflammation profiles and an unexpected general downregulation in inflammatory markers in both the monoculture and co-culture, which differentially expressed IL-1ß and GM-CSF. Interestingly, the microglia in co-culture did not appear to influence the response of the BBB, save in the permeability assay, where it worsened the BBB's response. Overall, our study is important because it is the first (to our knowledge) to investigate the effect of acute DEP exposure on P-gp in the in vitro human BBB, while also investigating the influence of microglia on the BBB's responses to this environmental chemical.

Comparative cytotoxicity of seven per- and polyfluoroalkyl substances (PFAS) in six human cell lines.

Human exposures to perfluoroalkyl and polyfluoroalkyl substances (PFAS) have been linked to several diseases associated with adverse health outcomes. Animal studies have been conducted, though these may not be sufficient due to the inherent differences in metabolic processes between humans and rodents. Acquiring relevant data on the health effects of short-chain PFAS can be achieved through methods supported by in vitro human cell-based models. Specifically, cytotoxicity assays are the crucial first step to providing meaningful information used for determining safety and providing baseline information for further testing. To this end, we exposed human cell lines representative of six different tissue types, including colon (CaCo-2), liver (HepaRG), kidney (HEK293), brain (HMC-3), lung (MRC-5), and muscle (RMS-13) to five short-chain PFAS and two legacy PFAS. The exposure of the individual PFAS was assessed using a range of concentrations starting from a low concentration (10-11 M) to a high concentration of (10-4 M). Our results indicated that CaCo-2 and HEK293 cells were the least sensitive to PFAS exposure, while HMC-3, HepaRG, MRC-5, and RMS-13 demonstrated significant decreases in viability in a relatively narrow range (EC50 ranging from 1 to 70 µM). The most sensitive cell line was the neural HMC-3 for all short- and long-chain PFAS (with EC50 ranging from 1.34 to 2.73 µM). Our data suggest that PFAS do not exert toxicity on all cell types equally, and the cytotoxicity estimates we obtained varied from previously reported values. Overall, this study is novel because it uses human cell lines that have not been widely used to understand human health outcomes associated with PFAS exposure.

Evaluation of an Injectable, Solid-State, Oxygen-Delivering Compound (Ox66) in a Rodent Model of Pulmonary Dysfunction-Induced Hypoxia.

INTRODUCTION: Pulmonary dysfunction (PD) and its associated hypoxia present a complication to the care of many service members and can arise intrinsically via comorbidities or extrinsically by infection or combat-related trauma (burn, smoke inhalation, and traumatic acute lung injury). Current supportive treatments (e.g., ventilation and supplemental oxygen) relieve hypoxia but carry a significant risk of further lung injury that drives mortality. Ox66 is a novel, solid-state oxygenating compound capable of delivering oxygen via intravenous infusion. MATERIALS AND METHODS: Male Sprague Dawley rats (N = 21; 250-300 g) were surgically prepared for cardiovascular monitoring, fluid infusion, mechanical ventilation, and intravital and phosphorescence quenching microscopy (interstitial oxygen tension; PISFO2) of the spinotrapezius muscle. Baselines (BL) were collected under anesthesia and spontaneous respiration. PD was simulated via hypoventilation (50% tidal volume reduction) and was maintained for 3 hours. Groups were randomized to receive Ox66, normal saline (NS; vehicle control), or Sham (no treatment) and were treated immediately following PD onset. Arterial blood samples (65 µL) and intravital images were taken hourly to assess blood gases and chemistry and changes in arteriolar diameter, respectively. Significance was taken at P < .05. RESULTS: PD reduced PISFO2 for all groups; however, by 75 minutes, both NS and Sham were significantly lower than Ox66 and remained so until the end of PD. Serum lactate levels were lowest in the Ox66 group-even decreasing relative to BL-but only significant versus Sham. Furthermore, all Ox66 animals survived the full PD challenge, while one NS and two Sham animals died. No significant vasoconstrictive or vasodilative effect was noted within or between experimental groups. CONCLUSION: Treatment with intravenous Ox66 improved interstitial oxygenation in the spinotrapezius muscle-a recognized bellwether for systemic capillary function-suggesting an improvement in oxygen delivery. Ox66 offers a novel approach to supplemental oxygenation that bypasses lung injury and dysfunction.

Gavage approach to oxygen supplementation with oxygen therapeutic Ox66™ in a hypoventilation rodent model of respiratory distress.

Acute respiratory distress syndrome (ARDS) features pulmonary dysfunction capable of causing life-threatening hypoxaemia. Ventilation and hyperoxic therapies force oxygen through dysfunctional alveoli but risk exacerbating damage. Ox66™ is an ingestible, solid-state oxygen product designed for oxygen supplementation. Eighteen anaesthetized, ventilated rats were subjected to a 40% reduction in tidal volume to produce a hypoventilatory simulation of the hypoxia in ARDS (HV-ARDS). After 60 min, animals were randomized to receive either normal saline (Saline; volume control) or Ox66™ gavage. Cardiovascular function and blood oximetry/chemistry were measured alongside interstitial oxygenation (PISFO2) of the peripheral spinotrapezius muscle. HV-ARDS reduced mean arterial pressure by ∼20% and PISFO2 by ∼35% for both groups. Ox66™ gavage treatment at 60 min improved PISFO2 over Saline (p < .0001), restoring baseline values, however, the effect was temporary. A second bolus at 120 min repeated the OX66™ PISFO2 response, which remained elevated over Saline (p < .01) until study end and was supported by systemic parameters of lactate, PaO2, SO2, and base deficit. Saline remained hypotensive, whereas Ox66™ became normotensive. Vasoconstriction was observed in the Saline, but not Ox66™ group. Supplemental oxygenation through Ox66™ gavage increased peripheral tissue oxygenation, warranting further study for disorders featuring dysfunction of pulmonary perfusion like ARDS.

Evaluating the endothelial-microglial interaction and comprehensive inflammatory marker profiles under acute exposure to ultrafine diesel exhaust particles in vitro.

Exposure to combustion-derived particulate matter (PM) such as diesel exhaust particles (DEP) is a public health concern because people in urban areas are continuously exposed, and once inhaled, fine and ultrafine DEP may reach the brain. The blood-brain barrier (BBB) endothelial cells (EC) and the perivascular microglia protect the brain from circulating pathogens and neurotoxic molecules like DEP. While the BBB-microglial interaction is critical for maintaining homeostasis, no study has previously evaluated the endothelial-microglial interaction nor comprehensively characterized these cells' inflammatory marker profiles under ultrafine DEP exposures in vitro. Therefore, the goal of this study was to investigate the in vitro rat EC-microglial co-culture under acute (24 h.) exposure to ultrafine DEP (0.002-20 µg/mL), by evaluating key mechanisms associated with PM toxicity: lactate dehydrogenase (LDH) leakage, reactive oxygen species (ROS) generation, cell metabolic activity (CMA) changes, and production of 27 inflammatory markers. These parameters were also evaluated in rat microglial and endothelial monocultures to determine whether the EC-microglial co-culture responded differently than the cerebrovasculature and microglia alone. While results indicated that ultrafine DEP exposure caused concentration-dependent increases in LDH leakage and ROS production in all groups, as expected, exposure also caused mixed responses in CMA and atypical cytokine/chemokine profiles in all groups, which was not expected. The inflammation assay results further suggested that the microglia were not classically activated under this exposure scenario, despite previous in vitro studies showing microglial activation (priming) at similar concentrations of ultrafine DEP. Additionally, compared to the cerebrovasculature alone, the EC-microglia interaction in the co-culture did not appear to cause changes in any parameter save in pro-inflammatory marker production, where the interaction appeared to cause an overall downregulation in cytokine/chemokine levels after ultrafine DEP exposure. Finally, to our knowledge, this is the first study to evaluate the influence of microglia on the BBB's ultrafine DEP-induced cytotoxic and inflammatory responses, which are heavily implicated in the pathogenesis of PM-related cerebrovascular dysfunction and neurodegeneration.

A quantitative and non-invasive method for nanoparticle translocation and toxicity evaluation in a human airway barrier model.

Human exposure to environmental nanoparticles (NPs) may result in systemic distribution and accumulation of NPs. Depending on exposure conditions and their physiochemical properties, NPs could cross biological barriers and reach vital organs. This method describes an analytical technique that quantifies the nanoparticles' translocation through a sample human airway barrier. Silver nanoparticles (AgNPs) were used as the example nanoparticles due to their common use in nanotechnology. The analytical method introduced in this study allows mass measurements of both cellular uptake and translocation of AgNPs through the modeled barrier. Additionally, cytotoxicity was evaluated using a convenient assay to investigate adverse effects from AgNPs treatment. The assay measures cellular injury from each layer in the barrier independently. The assay does not engage cells physically for chemical reaction, therefore it is non-destructive to the model, and the model can be used for other purposes subsequently. To conclude, this study provides researchers with measurable tools for evaluating the translocation, cellular trafficking, uptake and toxic effects of metallic nanoparticles in the in vitro barrier format.•Quantitative evaluation of nanoparticles translocation through human airway barrier•Non-invasive and quantifiable toxicity evaluation for co-culture models.

Assessing the translocation of silver nanoparticles using an in vitro co-culture model of human airway barrier.

The lung has been recognized as one of the main target organs for nanoparticles (NPs) exposure. Cellular uptake of nanoparticles into pulmonary components has been routinely evaluated in the conventional monoculture format, which lacks relevant cell to cell communications and interactions that are vital in the physiological environment. A more physiologically relevant co-culture model has thus been developed and described here to study the translocation of NPs across human airway barrier. The model consists of human bronchial epithelial cells (Calu-3), endothelial cells (EA.hy926) and macrophage-like cells (differentiated Thp-1) in a two-chamber system. Silver nanoparticles (AgNPs) coated with tannic acid were used as an example nanoparticle. These AgNPs were applied to the co-culture system where their movement and resultant toxicity were monitored. Cellular uptake and translocation of AgNPs through the modeled barrier were confirmed using analytical methods. Mild cytotoxicity at the given dosage levels was also observed, accompanied by reduced secretion of interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor-alpha (TNF-α). This human airway model provides researchers with an alternative method for the quantitative evaluation of uptake, translocation and toxicity of aerosol contaminants or nano-sized drug delivery systems in a more relevant in vitro format.

Oral ingestion of a novel oxygenating compound, Ox66™, is non-toxic and has the potential to increase oxygenation.

Ox66™ is a novel solid state oxygenating compound. In order to support the use of Ox66™ as a potential oxygenating supplement to injured cells, this study evaluated the safety of Ox66™, its ability to withstand the conditions in the digestive tract, and its potential to increase oxygenation in the mesentery in rats. The toxicity of Ox66™ was evaluated by performing acute (10-day) and chronic (90-day) feeding studies on rats, the stability of the compound in the digestive tract was evaluated via ex vivo simulated digestion and subsequent CFDA viability assay on gut epithelial cells, and its capacity for oxygenation in the mesenteric microcirculation was determined by interstitial fluid pressure (PISF) O2 measurements upon injection into the small intestine of rats. No toxicity was found associated with acute or chronic oral administration of the compound in rats, and the compound was able to withstand the environment of the digestive tract in vitro. Based on the acute animal feeding study, the NOAEL was considered to be 1000 mg/kg/day. This proof-of-concept study further demonstrates the potential of Ox66™ to function as an oxygenating supplement that might be useful for treating either pathological hypoxic-related conditions or to improve oxygenation levels during or after exercise under healthy conditions.

Evaluating a novel oxygenating therapeutic for its potential use in the advancement of wound healing.

Non-gaseous oxygen therapeutics are emerging technologies in regenerative medicine that aim to sidestep the undesirable effects seen in traditional oxygen therapies, while enhancing tissue and wound regeneration. Using a novel oxygenating therapeutic (Ox66™) several in vitro models including fibroblast and keratinocyte monocultures were evaluated for potential drug toxicity, the ability of cells to recover after chemical injury, and cell migration after scratch assay. It was determined that in both cell lines, there was no significant cytotoxicity found after independent treatment with Ox66™. Similarly, after DMSO-induced chemical injury, the health parameters of cells treated with Ox66™ were improved when compared to their untreated counterparts. Particles were also characterized using scanning electron microscopy and electron dispersive spectroscopy both individually and in conjunction with fibroblast growth. The data in this study showed that the novel wound healing therapeutic has potential in advancing the treatment of various types of acute and chronic wounds.

Evaluation of Common Use Brominated Flame Retardant (BFR) Toxicity Using a Zebrafish Embryo Model.

Brominated flame retardants (BFRs) are used to reduce the flammability of plastics, textiles, and electronics. BFRs vary in their chemical properties and structures, and it is expected that these differences alter their biological interactions and toxicity. Zebrafish were used as the model organism for assessing the toxicity of nine structurally-diverse BFRs. In addition to monitoring for overt toxicity, the rate of spontaneous movement, and acetylcholinesterase and glutathione-S-transferase (GST) activities were assessed following exposure. The toxicities of BFRs tested can be ranked by LC50 as tetrabromobisphenol A (TBBPA) < 4,4'-isopropylidenebis[2-(2,6-dibromophenoxyl)ethanol] (TBBPA-OHEE) < Pentabromochlorocyclohexane (PBCH) < 2-ethylhexyl 2,3,4,5-tetrabromobenzoate (TBB) < hexabromocyclododecane (HBCD) < hexabromobenzene (HBB) < Tetrabromophthalic anhydride (PHT4). No adverse effect was observed in di(2-ethylhexyl) tetrabromophthalate (TBPH) or dibromoneopentyl glycol (DBNPG)-treated embryos. The rate of spontaneous movement was decreased in a concentration-dependent manner following exposure to four of the nine compounds. GST activity was elevated following treatment with PBCH, TBBPA, HBCD, and HBB. The results indicate that exposure to several BFRs may activate an antioxidant response and alter behavior during early development. Some of the BFRs, such as TBBPA and TBBPA-OHEE, induced adverse effects at concentrations lower than chemicals that are currently banned. These results suggest that zebrafish are sensitive to exposure to BFRs and can be used as a comparative screening model, as well as to determine alterations in behavior following exposure and probe mechanisms of action.

Binary Mixtures of Polycyclic Aromatic Hydrocarbons Display Nonadditive Mixture Interactions in an In Vitro Liver Cell Model.

Polycyclic aromatic hydrocarbons (PAHs) have been labeled contaminants of concern due to their carcinogenic potential, insufficient toxicological data, environmental ubiquity, and inconsistencies in the composition of environmental mixtures. The Environmental Protection Agency is reevaluating current methods for assessing the toxicity of PAHs, including the assumption of toxic additivity in mixtures. This study was aimed at testing mixture interactions through in vitro cell culture experimentation, and modeling the toxicity using quantitative structure-activity relationships (QSAR). Clone-9 rat liver cells were used to analyze cellular proliferation, viability, and genotoxicity of 15 PAHs in single doses and binary mixtures. Tests revealed that many mixtures have nonadditive toxicity, but display varying mixture effects depending on the mixture composition. Many mixtures displayed antagonism, similar to other published studies. QSARs were then developed using the genetic function approximation algorithm to predict toxic activity both in single PAH congeners and in binary mixtures. Effective concentrations inhibiting 50% of the cell populations were modeled, with R(2) = 0.90, 0.99, and 0.84, respectively. The QSAR mixture algorithms were then adjusted to account for the observed mixture interactions as well as the mixture composition (ratios) to assess the feasibility of QSARs for mixtures. Based on these results, toxic addition is improbable and therefore environmental PAH mixtures are likely to see nonadditive responses when complex interactions occur between components. Furthermore, QSAR may be a useful tool to help bridge these data gaps surrounding the assessment of human health risks that are associated with PAH exposures.

Neuroimaging and traumatic brain injury: State of the field and voids in translational knowledge.

Traumatic brain injury (TBI) is a leading cause of death and disability in every developed country in the world and is believed to be a risk factor in the later development of depression, anxiety disorders and neurodegenerative diseases including chronic traumatic encephalopathy (CTE), Alzheimer's Disease (AD), Parkinson's Disease (PD), and amyotrophic lateral sclerosis (ALS). One challenge faced by those who conduct research into TBI is the lack of a verified and validated biomarker that can be used to diagnose TBI or for use as a prognostic variable which can identify those at risk for poor recovery following injury or at risk for neurodegeneration later in life. Neuroimaging continues to hold promise as a TBI biomarker but is limited by a lack of clear relationship between the neuropathology of injury/recovery and the quantitative and image based data that is obtained. Specifically lacking is the data on biochemical and biologic changes that lead to alterations in neuroimaging markers. There are multiple routes towards developing the knowledge required to more definitively link pathology to imaging but the most efficient approach is expanded leveraging of in vivo human blood, serum, and imaging biomarkers with both in vivo and ex vivo animal findings. This review describes the current use and limitations of imaging in TBI including a discussion of currently used animal injury models and the available animal imaging data and extracted markers that hold the greatest promise for helping translate alterations in imaging back to injury pathology. Further, it reviews both the human and animal TBI literature supporting current standards, identifies the remaining voids in the literature, and briefly highlights recent advances in molecular imaging. This article is part of a Special Issue entitled 'Traumatic Brain Injury'.

Particle uptake efficiency is significantly affected by type of capping agent and cell line.

Surface-functionalized silver nanoparticles (AgNPs) are the most deployed engineered nanomaterials in consumer products because of their optical, antibacterial and electrical properties. Almost all engineered nanoparticles are coated with application-specific capping agents (i.e. organic/inorganic ligands on particle surface) to enhance their stability in suspension or increase their biocompatibility for biomedicine. The aim of this study was to investigate the contribution of the selected capping agents to their observed health impacts using realistic dose ranges. AgNPs capped with citrate, polyvinylpyrrolidone (PVP) and tannic acid were studied with human bronchoalveolar carcinoma (A549) and human colon adenocarcinoma (Caco-2) cell lines and compared against exposures to Ag ions. Cellular uptake and cytotoxicity were evaluated up to 24 h. Tannic acid capped AgNPs induced higher cellular uptake and rate in both cell lines. Citrate-capped and PVP-capped AgNPs behaved similarly over 24 h. All three of the capped AgNPs penetrated more into the A549 cells than Caco-2 cells. In contrast, the uptake rate of Ag ions in Caco-2 cells (0.11 ± 0.0001 µg h(-1) ) was higher than A549 cells (0.025 ± 0.00004 µg h(-1) ). The exposure concentration of 3 mg l(-1) is below the EC50 value for all of the AgNPs; therefore, little cytotoxicity was observed in any experiment conducted herein. Exposure of Ag ions, however, interrupted cell membrane integrity and cell proliferation (up to 70% lysed after 24 h). These findings indicate cellular uptake is dependent on capping agent, and when controlled to realistic exposure concentrations, cellular function is not significantly affected by AgNP exposure.

Comparison of PBDE congeners as inducers of oxidative stress in zebrafish.

A proposed primary pathway through which polybrominated diphenyl ethers (PBDEs) disrupt normal biological functions is oxidative stress. In the present study, 4 PBDE congeners were evaluated for their potential to initiate oxidative stress in zebrafish during development: BDE 28, BDE 47, BDE 99, and BDE 100. N-acetylcysteine (NAC) was used to increase intracellular glutathione concentrations and only decreased the effects of BDE 28 at 10 ppm and 20 ppm and BDE 47 at 20 ppm. N-acetylcysteine coexposure did not alter the rates of mortality or curved body axis compared with PBDE exposure alone. The activity of glutathione-S-transferase (GST) was not altered at 24 h postfertilization (hpf), but increased following 10 ppm BDE 28 exposure at 120 hpf. Transcription of several genes associated with stress was also evaluated. At 24 hpf, cytochrome c oxidase subunit 6a (COX6a) transcription was up-regulated in embryos exposed to BDE 99, and BDE 28 exposure up-regulated the transcription of Glutathione-S-transferase-pi (GSTpi). At 24 hpf, glutamate-cysteine ligase (GCLC) was slightly down-regulated by all congeners evaluated. At 120 hpf, TNF receptor-associated protein 1 (TRAP1) and COX6A were up-regulated by all congeners, however GSTpi was down-regulated by all congeners. The results of quantitative real-time transcription polymerase chain reaction are mixed and do not strongly support a transcriptional response to oxidative stress. According to the authors' data, PBDEs do not induce oxidative stress. Oxidative stress may occur at high exposure concentrations; however, this does not appear to be a primary mechanism of action for the PBDE congeners tested.

Uptake and metabolism of individual polybrominated diphenyl ether congeners by embryonic zebrafish.

Embryonic zebrafish were used to compare the uptake and metabolism of six polybrominated diphenyl ether (PBDE) congeners (BDEs 28, 47, 99, 100, 153, and 183) and identified metabolites from static exposures at 24 and 120 h postfertilization (hpf). An inverse relationship was observed between uptake of PBDEs and their octanol-water partitioning coefficients (uptake of BDEs 28 and 47>99 and 100>153 and 183). Debromination metabolites were identified in all congeners (excluding BDE 28) tested in the 120-hpf tissue samples. Interestingly, BDE 153 underwent meta-debromination, forming BDEs 47 and 99. Gene transcription analysis was conducted at 120 hpf to identify potential metabolic pathways for the PBDEs examined in the present study (gstpi, deiodinases 1 and 2, cyp1a1, cyp1b1, and ugt5g). The greatest induction was of ugt5g for all congeners and deiodinase transcription was also upregulated by BDEs 28, 47, and 183. The cyp1a1 and cyp1b1 were upregulated by BDEs 28, 47, 99, and 183. The least alterations in gene transcription were in the BDE 153-exposed embryos. A clear primary pathway of debromination metabolism was not identified; however, upregulation of these different genes indicated that fish were responding to exposure of PBDEs. Furthermore, the present study demonstrated that the most bioavailable congeners are also those with the highest reported toxicity.

Non-specific interactions between soluble and induce irreversible changes in the properties of bilayers.

Soluble in the extracellular matrix experience a crowded environment. However, most of the biophysical studies performed to date have focused on concentrations within the dilute regime (well below the mM range). Here, we systematically studied the interaction of model cell membrane systems (giant unilamellar vesicles and supported bilayers) with soluble globular , bovine serum albumin, and lysozyme at physiologically relevant concentrations. To mimic the extracellular environment more closely, we also used fetal bovine serum as a good representative of a biomimetic mixture. We found that regardless of the used (and thus of their biological function), the interactions between a model cell membrane and these are determined by their physico-chemical characteristics, mainly their dipolar character (or charged patches). In this paper we discuss the specificity and reversibility of these interactions and their potential implications on the living cells. In particular, we report initial evidence for an additional role of in cell membranes: that of reducing the effects of non-specific of soluble on the cell membrane.

Hydroxylated PBDEs induce developmental arrest in zebrafish.

The ubiquitous spread of polybrominated diphenyl ethers (PBDEs) has led to concerns regarding the metabolites of these congeners, in particular hydroxylated PBDEs. There are limited studies regarding the biological interactions of these chemicals, yet there is some concern they may be more toxic than their parent compounds. In this study three hydroxylated PBDEs were assessed for toxicity in embryonic zebrafish: 3-OH-BDE 47, 5-OH-BDE 47, and 6-OH-BDE 47. All three congeners induced developmental arrest in a concentration-dependent manner; however, 6-OH-BDE 47 induced adverse effects at lower concentrations than the other congeners. Furthermore, all three induced cell death; however apoptosis was not observed. In short-term exposures (24-28 hours post fertilization), all hydroxylated PBDEs generated oxidative stress in the region corresponding to the cell death at 5 and 10 ppm. To further investigate the short-term effects that may be responsible for the developmental arrest observed in this study, gene regulation was assessed for embryos exposed to 0.625 ppm 6-OH-BDE 47 from 24 to 28 hpf. Genes involved in stress response, thyroid hormone regulation, and neurodevelopment were significantly upregulated compared to controls; however, genes related to oxidative stress were either unaffected or downregulated. This study suggests that hydroxylated PBDEs disrupt development, and may induce oxidative stress and potentially disrupt the cholinergic system and thyroid hormone homeostasis.