Post-exposure Recovery Research Articles

Can acclimation of freshwater rotifers to silver nanoparticles or 5-fluorouracil influence their multi- and transgenerational effects?

Emerging chemical contaminants (ECCs) are among the major environmental threats in present century. A variety of ECCs is released into aquatic environments with little knowledge about their long-term impacts to organisms. We examined the role of acclimation of the freshwater rotifer Brachionus calyciflorus to silver nanoparticles (Ag-NPs) and 5-fluorouracil (5-FU) for determining their ability to deal with these ECCs individually and in mixtures along multiple generations. Additionally, transgenerational effects were also assessed during the recovery phase. Rotifers acclimated at EC10 of Ag-NPs along generations showed a higher ability to deal with higher concentrations of these nanoparticles or 5-FU along generations. Rotifers acclimated to EC10 of 5-FU showed varied responses, as their population growth rates were affected at the initial generations once exposed to higher concentration (EC50) of the same or a new contaminant; however, the rotifers acquired resistance in later generations. The exposure of generational Ag-NP-acclimated rotifers to the mixture of Ag-NPs and 5-FU at EC50 led to a shift from no effects to negative effects along successive generations, suggesting a decrease in resistance, which remained even in the post-exposure recovery phase. Similar transgenerational adverse effects were also observed for the generational Ag-NP-acclimated rotifers released from 5-FU. Rotifers acclimated to 5-FU showed a decrease in population growth rate at the first generation of recovery phase, possibly shifting their optimal environmental conditions when released from contaminants. Overall, our results suggest that rotifers had a high level of plasticity to ECC exposure in freshwaters; however, acclimation can be generic or contaminant dependent.

Effects of nutrition on recovery, mortality, and mobility of adult Tribolium castaneum after exposure to long-lasting insecticide-incorporated netting.

Long-lasting insecticide-incorporated netting (LLIN) has been used to deliver contact insecticides as an integrated pest management tool for stored product insect pests in food facilities. Although the presence of food is known to improve insect recovery after exposure, it is not clear whether food nutritional quality plays a role. Here, the red flour beetle Tribolium castaneum adults were exposed to two commercially available LLINs, Carifend (active ingredient α-cypermethrin) and D-Terrence (deltamethrin), then transferred to Petri dishes with foods with varying nutritional quality (e.g., 0-100% ratios of flour to non-nutritive cellulose). We investigated the effects of nutrition, LLIN type, and exposure time on post-exposure recovery, mortality, and mobility. After exposure for 2-168 h, the immediate mortality of T. castaneum adults ranged from 0.5% to 91.0% with Carifend and 0% to 75.3% with D-Terrence. Adult recovery and delayed mortality were significantly affected by nutritional quality, LLIN type, exposure time, and recovery time. For both LLINs, adult recovery increased over time, with a trend for higher recovery and lower mortality with increasing nutritional quality and decreasing exposure time. In addition, adult mobility decreased multiple-fold after Carifend or D-Terrence exposure for 30, 60 or 90 min compared to 10 min. This study shows nutrition significantly modulates the efficacy of LLIN against T. castaneum, and thus strengthens the rationale for implementing stringent sanitation protocols for food facility managers. © 2024 Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Acute toxicity and sublethal effects of phenol on hematological parameters of channel catfish Ictalurus punctatus and pacu Piaractus mesopotamicus

Phenol is an aromatic chemical commonly found in domestic and industrial effluents that represents a worldwide concern in toxicology. When it reaches aquatic environments, significant damage in fishes is observed. The first aim of this study was to investigate the acute toxicity levels of phenol in Ictalurus punctatus and Piaractus mesopotamicus. The second objective was to evaluate the hematological parameters of I. punctatus and P. mesopotamicus after 96 hours exposure to sublethal concentration of phenol (10% of 96-hour LC50) and after post-exposure recovery period of 7 days. The main hypothesis of the study was that even sublethal phenol concentration could cause hematological alterations in fish. For 96-hour LC50 tests, both fish species were exposed to several phenol concentrations (in the range between 5 and 50 mg L-1) and the mortality were recorded after 24, 48, 72 and 96 hours. Phenol was notably more toxic to I. punctatus than P. mesopotamicus and the 96-hour LC50 values were 15.08 and 32.56 mg L-1, respectively. Sublethal exposure to phenol in P. mesopotamicus resulted in significant higher hematocrit level (Ht), hemoglobin content (Hb) and red blood cell count (RBC) in comparison with control group. In I. punctatus, Ht, Hb and RBC remained constant after 96-hour sublethal exposure. However, after the recovery period of 7 days a significant increase of RBC followed by reduction in mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) were observed in I. punctatus. The sublethal responses to phenol revealed erythropoeisis in I. punctatus and respiratory distress in P. mesopotamicus. P. mesopotamicus presented excessive skin and gills mucus throughout the 96-hour LC50 tests. Acute toxicity tests and hematological responses after exposure to sublethal phenol concentration could be successfully used as a biomarker of stress in fish and may be applicable to investigate others toxic agents.

Noise-induced synaptic loss and its post-exposure recovery in CBA/CaJ vs. C57BL/6J mice

Acute noise-induced loss of synapses between inner hair cells (IHCs) and auditory nerve fibers (ANFs) has been documented in several strains of mice, but the extent of post-exposure recovery reportedly varies dramatically. If such inter-strain heterogeneity is real, it could be exploited to probe molecular pathways mediating neural remodeling in the adult cochlea. Here, we compared synaptopathy repair in CBA/CaJ vs. C57BL/6J, which are at opposite ends of the reported recovery spectrum. We evaluated C57BL/6J mice 0 h, 24 h, 2 wks or 8 wks after exposure for 2 h to octave-band noise (8–16 kHz) at either 90, 94 or 98 dB SPL, to compare with analogous post-exposure results in CBA/CaJ at 98 or 101 dB. We counted pre- and post-synaptic puncta in immunostained cochleas, using machine learning to classify paired (GluA2 and CtBP2) vs. orphan (CtBP2 only) puncta, and batch-processing to quantify immunostaining intensity. At 98 dB, both strains show ongoing loss of ribbons and synapses between 0 and 24 h, followed by partial recovery, however the extent and degree of these changes were greater in C57BL/6J. Much of the synaptic recovery is due to transient reduction in GluA2 intensity in synaptopathic regions. In contrast, CtBP2 intensity showed only transient increases (at 2 wks). Neurofilament staining revealed transient extension of ANF terminals in C57BL/6J, but not in CBA/CaJ, peaking at 24 h and reverting by 2 wks. Thus, although interstrain differences in synapse recovery are dominated by reversible changes in GluA2 receptor levels, the neurite extension seen in C57BL/6J suggests a qualitative difference in regenerative capacity.

Self-healing demonstration in imidacloprid toxicity with multibiomarkers and biologic pathways

Imidacloprid (IMI) pesticide has significant environmental and ecotoxicological pollution effects. Also, its high potential to enter the aquatic environment reveals the importance of early evaluation of the toxic effects of this compound. This study aimed to evaluate organ responses that can be associated with outcomes at higher levels of biological organization in fish. In this respect, the toxicity mechanism and recovery response process of IMI in rainbow trout (Oncorhyncus mykiss)’ s different tissues (blood, brain, gill and liver) were analyzed with important biomarkers [(hematological indices (RBC, WBC, Hg, Hct, MCV, MCH, MCHC), antioxidant enzyme activities (SOD, CAT, GPx, GSH), MDA, DNA damage (8-OHdG), apoptosis (caspase 3), AChE, TNF α, interleukin 6, Nrf-2, NF-kB activities, histopathological and immunofluorescence analyses (NeuN, BDNF, JNK and Nop10]. Exposure to different concentrations of IMI caused a decrease in RBC, WBC, Hg and Hct levels in O. mykiss. The effect of the same application on brain, gill and liver tissues was determined as inhibitions in antioxidant enzyme activities (SOD, CAT and GPx) and GSH level, inductions on MDA level, DNA damage, caspase-3, TNF α, IL- 6, Nrf-2 and NF-kB activities. As a result of three tissues’ histopathological examination; the degeneration, necrosis and hyperemia in the brain and liver, adhesion, desquamation and inflammation in the lamellar epitheliums has been determined in company with stress-induced responses inducing DNA damage. In the reflection of this situation on histomap results, increases were recorded in BDNF and NeuN levels. In the recovery response, tissue damage profile and detoxification process were differentiated according to dose and marker, and it manifested itself with moderate and mild symptoms. These findings revealed that IMI-mediated oxidative stress was effective in the Nrf-2/GSH/NF-kB pathways, showing strong hemato/hepato, and neurotoxic effects. It has become clear that the severity of the effects caused by IMI exposure is felt more in the brain and liver tissues, and that such contaminants should be taken into account in the risk assessment. During the post-exposure recovery period (after 15 days), AChE activity increased by 21% at high-dose administration. The recovery period was effective in regulating the oxidant/antioxidant balance of the organism by exhibiting serious induction/inhibition in each tissue and biomarker performance.

(113) Hydrophilic Inflatable Penile Prothesis (HC-IPP) Discs Inoculated With Aerobic and Anaerobic Bacteria and Fungal Species Dipped in 0.05% Chlorhexidine Gluconate (CHG) Irrigation Solution and Irrigated With the Device to Evaluate Real World Situations

Abstract Introduction Hydrophilic-coated implants have significantly decreased penile prosthesis infection (PPI) since their release in 2001. However, the microbial spectrum of PPI has significantly changed. Based on recent Next Generation Sequencing literature, gram negative and fungal species are now included in the three most common organisms isolated. The Titan (Coloplast, Minneapolis, MN, USA) implant enables surgeons to choose a dipping solution according to their local biogram and preference. Irrisept (Irrimax, Lawrenceville, GA, USA) is 0.05% chlorhexidine gluconate (CHG) solution and has an extensive profile for microbial kill, including many aerobic, anaerobic, and fungal species known to cause PPI. Objective Evaluate microbial reduction on HC-IPP material dipped and irrigated with 0.05% CHG irrigation device using a validated microbiological study design: microbial contamination with microbial reduction counts following treatment. Methods An In-Vitro evaluation of the ability of an irrigation device to reduce transient bacterial contamination from a Test Substrate - pre-cut discs prepared from a HC-IPP material. Seven common PPI microorganisms - Bacteroides fragilis (A TCC #25285), Candida albicans (A TCC #10231), Enterococcus faeca/is (A TCC #29212), Escherichia coli (A TCC #25922), Pseudomonas aeruginosa (ATCC #27853), Staphylococcus aureus (ATCC #29213) and Staphylococcus epidermidis (ATCC #12228) were used for this evaluation. For each challenge species, three discs of the implant material (i.e., carriers) were pre-conditioned by immersion in 0.9% Sodium Chloride Irrigation, USP (Baseline Controls), and six discs were pre-conditioned by immersion in the test irrigation solution, (Irrisept®; Test Carriers). The pre-conditioned carriers were allowed to dry for approximately 10 minutes prior to contamination with a suspension of each test strain. Following a 2-to-3-minute drying period at room temperature, the three contaminated Baseline Carriers were evaluated for viable microbial recoveries. Three of the contaminated and dried Test Carriers were evaluated for viable microbial recoveries with no additional treatment (Pre- Rinse Test Carriers). The three remaining Test Carriers were evaluated following a rinsing procedure using 200cc of Wound Irrigation Device/Solution (Post-Rinse Test Carriers) at three time points, mimicking an in-vivo practice. Results Table 1 presents the Initial population (CFU/mL), Mean Baseline Control Recovery (normal saline log10) and the mean Post-Exposure Recovery (0.05% CHG log10), and Mean Post-Exposure Reduction (0.05% CHG log10) following three separate 150cc irrigations (one full bottle/disk with 0.05% CHG irrigation device. (lrrisept 450mL [Lot #21HDB982]). Conclusions Dipped and irrigated HC-IPP material discs with the irrigation device containing 0.05% CHG results in clinically significant log10 reductions in tested microbial strains. All previous studies on this subject matter have used zone of inhibition (ZOI) testing only. This microbiological methodology is superior as it is quantitative not qualitative, and can evaluate bactericidal, viricidal and fungicidal activity. Disclosure Yes, this is sponsored by industry/sponsor: Irrimax Corporation, Coloplast Corporation Clarification Industry funding only - investigator initiated and executed study Any of the authors act as a consultant, employee or shareholder of an industry for: Coloplast, Irrimax.

Comparative Study of Time-Dependent Aluminum Exposure and Post-Exposure Recovery Shows Better Improvement in Synaptic Changes andNeuronal Pathology in Rat Brain After Short-Term Exposure.

Aluminum is a ubiquitous metal that causes multiple brain pathologies such as, cognitive dysfunction and Alzheimer's disease like symptoms. Exposure to aluminum through drinking water is responsible for hampering learning and memory. This study aimed to compare (1) the time-dependent effect of aluminum exposure (keeping total exposure of 5850mg/kg same) in two durations, 30 and 45days, and (2) to compare post-exposure self-recovery effect after 20days in both (30 and 45days exposure) groups. Rats were given 130 and 195mg/kg of AlCl3·6H2O for 45 and 30days respectively, to see the time-dependent exposure effect. At the end of exposure, rats were given distilled water and allowed to self-recover for 20days to study the recovery. Expressionlevelsof synaptic genes (Syp, SNAP25, Nrxn1/2, PSD95, Shank1/2, Homer1, CamkIV, Nrg1/2 and Kalrn) were measured using qPCR and compared in the exposure and recovery groups. Cellular morphology of the rat brain cortex and hippocampus was also investigated. Damage in lipid and protein profile was measured by employing FTIR. Results showed downregulation of mRNA expression of synaptic genes, plaques deposition, disorganization in lipid and protein profile by increasing membrane fluidity, and disorder and alteration of protein secondary structure after both exposure periods. However, better improvement/recovery in these parameters were observed in recovery group of 30days aluminum exposure compared to 45days aluminum exposure group. Taken together, these results suggested that short-term exposure resulted in better restoration of lipid and protein profile after time-dependent exposure of aluminum than prolonged exposure.

Identification and characterization of a novel SoxB2 gene in Litopenaeus vannamei and its potential roles in response to ammonia-N stress and post-exposure recovery

Increased concentrations of ammonia-N can cause seriously physiological harm to crustaceans, especially farmed shrimp (Litopenaeus vannamei). Ammonia-N is generally removed by water change, and will gradually accumulate for unconsumed feed. However, the underlying adaptation mechanism of shrimp under such environmental conditions is still not fully understood. A novel Sox gene expressed differentially in previous comparative transcriptome studies was characterized in this study, designated as LvSoxB2–1. The LvSoxB2–1 encodes a protein of 420 amino acids, sharing the highest identity with the Chinese mitten crab (Eriocheir sinensis) Sox14b. The expression level of LvSoxB2–1 was higher in fertilized egg and cleavage stage of early embryonic development and declined in the blastula stage, which showed no significant difference compared with the subsequent stage. During larval development, LvSoxB2–1 increased significantly in nauplius stage III and zoea stage I and then restored to the initial level. LvSoxB2–1 was highly expressed in the gills, followed by eyestalks and brain ganglion. Results of subcellular localization have shown that LvSoxB2–1 is a nuclear-localized protein. In the ammonia-N stress and post-exposure recovery experiments, LvSoxB2–1 mRNA significantly increased in the gills, hepatopancreas, and hemocytes. The total hemocyte counts (THC) of shrimp was decreased through LvSoxB2–1 RNA interference (RNAi). Moreover, the inhibition of LvSoxB2–1 significantly exacerbated the hepatopancreas pathology and reduced the survival rates of shrimp exposed to ammonia-N. Dual-luciferase reporter assay confirmed the activation of the Wnt/β-catenin pathway by LvSoxB2–1. Under ammonia-N stress and recovery after exposure, LvSoxB2–1 silencing could decrease the expression of Wnt/β-catenin signaling molecules (β-catenin and Pangolin) and Rh protein in L. vannamei, with the higher malonyldialdehyde (MDA) and protein carbonylation (PCO) levels and hemolymph ammonia-N and urea contents. These results suggested that LvSoxB2–1 played positive roles in oxidative stress responses and ammonia-N excretion through the Wnt/β-catenin pathway.

Immunological and hemato-biochemical effects on catfish (Clarias gariepinus) exposed to dexamethasone.

Dexamethasone (glucocorticoid) was recently shown to be a life-saving drug for the treatment of SARS-CoV-2 disease. Water and sediments can be contaminated by sewage treatment plants when this product is widely used. Accordingly, we evaluated the effects of dexamethasone as pharmaceutical residue on Clarias gariepinus, following exposure and post-exposure recovery on blood biochemical, antioxidant, and cytokine markers. Three experimental groups were examined. Control, fish exposed to 0.3 mg/L of dexamethasone, and fish exposed to 3 mg/L of dexamethasone for 7 days, followed by a 15-days recovery period. Hematological indices, such as red blood cell number, hemoglobin (Hb), platelets, mean corpuscular hemoglobin concentration, and large lymphocytes, were significantly declined following the exposure to dexamethasone compared to control. In contrast, hematocrit (Ht), mean corpuscular volume, monocytes, small lymphocytes, and mean corpuscular hemoglobin increased significantly depending on the dose–concentration. Liver and kidney functions, other biochemical parameters (albumin and globulin), cortisol, and cytokine (IL-1β and IL-6) concentrations increased significantly after exposure to dexamethasone compared to control. Antioxidants and acetylcholinesterase enzymes were significantly decreased in catfish treated with dexamethasone cumulatively with doses. After a recovery period, blood biochemical, antioxidant, and cytokine markers were still elevated compared with the control group. In conclusion, dexamethasone at concentrations present in water bodies causes deleterious effects on blood biomarkers, biochemical, and antioxidant as well as immune upregulation in catfish until after depuration period.

Immediate and Sustained Effects of Cobalt and Zinc-Containing Pigments on Macrophages.

Pigments are among the oldest nanoparticulate products known to mankind, and their use in tattoos is also very old. Nowadays, 25% of American people aged 18 to 50 are tattooed, which poses the question of the delayed effects of tattoos. In this article, we investigated three cobalt [Pigment Violet 14 (purple color)] or cobalt alloy pigments [Pigment Blue 28 (blue color), Pigment Green 14 (green color)], and one zinc pigment [Pigment White 4 (white color)] which constitute a wide range of colors found in tattoos. These pigments contain microparticles and a significant proportion of submicroparticles or nanoparticles (in either aggregate or free form). Because of the key role of macrophages in the scavenging of particulate materials, we tested the effects of cobalt- and zinc-based pigments on the J774A.1 macrophage cell line. In order to detect delayed effects, we compared two exposure schemes: acute exposure for 24 hours and an exposure for 24 hours followed by a 3-day post-exposure recovery period. The conjunction of these two schemes allowed for the investigation of the delayed or sustained effects of pigments. All pigments induced functional effects on macrophages, most of which were pigment-dependent. For example, Pigment Green 19, Pigment Blue 28, and Pigment White 4 showed a delayed alteration of the phagocytic capacity of cells. Moreover, all the pigments tested induced a slight but significant increase in tumor necrosis factor secretion. This effect, however, was transitory. Conversely, only Pigment Blue 28 induced both a short and sustained increase in interleukin 6 secretion. Results showed that in response to bacterial stimuli (LPS), the secretion of tumor necrosis factor and interleukin 6 declined after exposure to pigments followed by a recovery period. For chemoattractant cytokines (MCP-1 or MIP-1α), delayed effects were observed with a secretion decreased in presence of Pigment Blue 28 and Pigment violet 14, both with or without LPS stimuli. The pigments also induced persisting changes in some important macrophage membrane markers such as CD11b, an integrin contributing to cell adhesion and immunological tolerance. In conclusion, the pigments induced functional disorders in macrophages, which, in some cases, persist long after exposure, even at non-toxic doses.

Inhalation toxicity of copper compounds: Results of 14-day range finding study for copper sulphate pentahydrate and dicopper oxide and 28-day subacute inhalation exposure of dicopper oxide in rats

Inhalation exposure to copper may occur during a range of occupational activities and the purpose of this study was to characterise the toxicological response to repeated inhalation of two copper compounds, representative of copper substances in large-scale production/use. Crl:CD(SD) rats were repeatedly exposed to aerosols of dicopper oxide (Cu2O) or copper sulphate pentahydrate (CuSO4.5 H2O) for 14-days as part of a range finding study at normalised copper doses of 0.18, 0.71, 1.78 and 8.9 mg/m3 Cu. Within a 28-days main study (Cu2O only), animals were repeatedly exposed to 0.2, 0.4, 0.8 and 2.0 mg/m3 Cu2O following OECD TG 412. The main study also consisted of satellite groups exposed for 1-, 2- or 3- weeks as well as a 13-week post-exposure recovery period group. Repeated exposure for 14-days to both copper compounds, normalised for copper content, led to an acute influx of polymorphonuclear leukocytes (neutrophils) and macrophages whilst only CuSO4.5 H2O exposure resulted in epithelial hyperplasia. This differential response may reflect the highly dissolvable nature of CuSO4.5 H2O in lung lining fluid leading to a release of copper ions at the epithelial surface whilst Cu2O is relatively indissolvable at neutral pH. In the 28-day study with Cu2O, an increase in cellularity was also evident in both histological and BALF samples and was dose-related with minimal to mild (neutrophilic) inflammation observed > 0.4 mg/m3 in the lung tissue sections and significant increases from 0.2 mg/m3 in BALF. There were no minimal haematological findings, no clinical findings and systemic organs were unaffected by inhalation exposure to dicopper oxide. The lung cellular response was limited to alveolar histiocytosis and neutrophil influx with no evidence of epithelial hyperplasia or fibrosis and all lung biomarkers returned to control levels within the post-exposure recovery period. Interestingly, the satellite groups showed that this acute cellular response followed a biphasic rather than monotonic pattern with a peak in lung biomarkers between weeks 1–3 and reduction thereafter. This reduction in lung biomarkers occurred during continued exposure and may indicate an adaptive response to copper exposure. Overall, these results show that repeated exposure to copper compounds results in an acute cellular response with no associated pathology and which fully resolved after the cessation of exposure. Therefore, the cellular response is evidence of a controlled and adaptive response associated with the removal of Cu2O from the alveolar surface.

Effects of acute ammonia exposure and post-exposure recovery on nonspecific immunity in Clam Cyclina sinensis

This study aimed to assess the toxicity of ammonia on clam Cyclina sinensis and the post-exposure recovery. With increased exposure to TAN, the alkaline phosphatase (AKP) activities after exposure showed a trend of growing initially and subsequently decreasing, whereas the AKP activities after post-exposure recovery showed an increasing trend. The AKP activities after post-exposure recovery were significantly higher than those in control. The acid phosphatase (ACP) activities in T1 and T2 after post-exposure recovery were higher than those in the control, whereas the ACP activities in T3, T4, and T5 after post-exposure recovery were significantly higher than those in the control. The lysozyme (LZM) activities in T1 and T2 after exposure were significantly higher than those in control, whereas the LZM activities in T3, T4, and T5 after exposure were significantly lower than those in the control. Overall, ACP and LZM in the clams exposed to a low level of TAN (≤ 40 mg/L) can recover to the normal levels completely. However, a 48h recovery period scarcely seems adequate to compensate for AKP, ACP, and LZM activities in the clams exposed to a high level of TAN (> 40 mg/L).

Malathion-Induced Hematoxicity and Its Recovery Pattern in Barbonymus gonionotus.

An experiment was conducted to assess malathion-induced hematological responses of Barbonymus gonionotus (silver barb) and its recovery patterns in malathion-free water. Fish (45 days old) were exposed to two sublethal concentrations, namely, 25% and 50% (i.e., 3.78 and 7.56 ppm) of LC50 (15.13 ppm) of malathion for 28 days, followed by a postexposure recovery period for the same time. The hematological parameters were examined after 1, 7, 14, 21, and 28 days of exposure as well as after the postexposure recovery time. Except in the case of the control group (0% of malathion), the obtained results revealed that malathion exposure resulted in significantly (p < 0.05) higher prevalence and severity of micronucleus and lower values of Hb, PCV, and RBC and significantly higher values of WBC in a concentration- and time-dependent manner. The values of blood glucose, MCV, MCH, and MCHC showed mixed trends during the experiment. During the recovery period, all blood parameters (micronucleus, glucose, Hb, PCV, RBC, WBC, MCV, MCH, and MCHC) partially recovered, which means that the recovery period was not long enough for the organisms to recover from the previous exposure. The study thus confirms that hematology is a sensitive indicator for fish to detect toxicity caused by different chemicals. Changes in these parameters can provide useful information about environmental conditions and risk assessment of aquatic organisms.

On the intrusion and recovery of ocean-sourced 3H and 14C in coastal aquifers considering ocean-surge inundation

Human activities, such as discharging nuclear wastewater into the ocean, can put coasts in the risk of being exposed to radioactive contaminations. The radionuclides may potentially intrude into coastal aquifers from the ocean and endanger the groundwater resources, either laterally through subsurface or vertically through land surface during ocean surge induced inundation. This study attempted to investigate the temporal and spatial scales of these intrusion processes using an experimental site near Bremerhaven, northern Germany. A fully coupled surface–subsurface flow and transport model was employed to simulate the groundwater flow and the transport of TDS (total dissolved salt), 3H and 14C, under conditions with or without an ocean surge event. Scenarios of different exposure schemes were designed by varying the exposure duration and radionuclide concentrations. The intrusion and post-exposure recovery were assessed via contaminated volume and area, intrusion length, and recovery time. Results show that, depending on exposure duration, the intrusion of 3H and 14C can cause serious contamination in the coastal aquifer, with up to 18.9 km2 land area being contaminated and reaching up to 3.3 km landward from the shore. 3H shows a ‘harder intrusion, easier recovery’ pattern due to its higher decay rate. The full recovery may take up to 70 years and 217 years (considering 30-years-exposure) for 3H and 14C, respectively. An ocean surge event is more likely to exacerbate the intrusion, but it does not significantly change the full recovery time. Shorter exposure duration should be favored to minimize the influences on the coastal aquifer when the total exposure quantity is fixed. This study highlights the severity of radioactive contamination in coastal aquifers and the difficulty of recovery. Thus, cautious decision should be made concerning the possible impacts of releasing radioactive wastewater on coastal life and human beings.

Cochlear Synaptic Degeneration and Regeneration After Noise: Effects of Age and Neuronal Subgroup

In CBA/CaJ mice, confocal analysis has shown that acoustic overexposure can immediately destroy synapses between auditory-nerve fibers (ANFs) and their peripheral targets, the inner hair cells (IHCs), and that years later, a corresponding number of ANF cell bodies degenerate. In guinea pig, post-exposure disappearance of pre-synaptic ribbons can be equally dramatic, however, post-exposure recovery to near-baseline counts has been reported. Since confocal counts are confounded by thresholding issues, the fall and rise of synaptic ribbon counts could represent “regeneration,” i.e., terminal retraction, re-extension and synaptogenesis, or “recovery,” i.e., down- and subsequent up-regulation of synaptic markers. To clarify, we counted pre-synaptic ribbons, assessed their juxtaposition with post-synaptic receptors, measured the extension of ANF terminals, and quantified the spatial organization and size gradients of these synaptic elements around the hair cell. Present results in guinea pigs exposed as adults (14 months), along with prior results in juveniles (1 month), suggest there is post-exposure neural regeneration in the guinea pig, but not the CBA/CaJ mouse, and that this regenerative capacity extends into adulthood. The results also show, for the first time, that the acute synaptic loss is concentrated on the modiolar side of IHCs, consistent with a selective loss of the high-threshold ANFs with low spontaneous rates. The morphological similarities between the post-exposure neurite extension and synaptogenesis, seen spontaneously in the guinea pig, and in CBA/CaJ only with forced overexpression of neurotrophins, suggest that the key difference may be in the degree of sustained or injury-induced expression of these signaling molecules in the cochlea.

Retained particle surface area dose drives inflammation in rat lungs following acute, subacute, and subchronic inhalation of nanomaterials

BackgroundAn important aspect of nanomaterial (NM) risk assessment is establishing relationships between physicochemical properties and key events governing the toxicological pathway leading to adverse outcomes. The difficulty of NM grouping can be simplified if the most toxicologically relevant dose metric is used to assess the toxicological dose-response.Here, we thoroughly investigated the relationship between acute and chronic inflammation (based on polymorphonuclear neutrophil influx (% PMN) in lung bronchoalveolar lavage) and the retained surface area in the lung. Inhalation studies were performed in rats with three classes of NMs: titanium dioxides (TiO2) and carbon blacks (CB) as poorly soluble particles of low toxicity (PSLT), and multiwall carbon nanotubes (MWCNTs). We compared our results to published data from nearly 30 rigorously selected articles.ResultsThis analysis combined data specially generated for this work on three benchmark materials - TiO2 P25, the CB Printex-90 and the MWCNT MWNT-7 - following subacute (4-week) inhalation with published data relating to acute (1-week) to subchronic (13-week) inhalation exposure to the classes of NMs considered. Short and long post-exposure recovery times (immediately after exposure up to more than 6 months) allowed us to examine both acute and chronic inflammation.A dose-response relationship across short-term and long-term studies was revealed linking pulmonary retained surface area dose (measured or estimated) and % PMN. This relationship takes the form of sigmoid curves, and is independent of the post-exposure time. Curve fitting equations depended on the class of NM considered, and sometimes on the duration of exposure. Based on retained surface area, long and thick MWCNTs (few hundred nm long with an aspect ratio greater than 25) had a higher inflammatory potency with 5 cm2/g lung sufficient to trigger an inflammatory response (at 6% PMN), whereas retained surfaces greater than 150 cm2/g lung were required for PSLT.ConclusionsRetained surface area is a useful metric for hazard grouping purposes. This metric would apply to both micrometric and nanometric materials, and could obviate the need for direct measurement in the lung. Indeed, it could alternatively be estimated from dosimetry models using the aerosol parameters (rigorously determined following a well-defined aerosol characterization strategy).

Differential Recovery of Small Intestinal Segments after Partial-Body Irradiation in Non-Human Primates.

In the event of a radiological attack or accident, it is more likely that the absorbed radiation dose will be heterogeneous, rather than uniformly distributed throughout the body. This type of uneven dose distribution is known as partial-body irradiation (PBI). Partial exposure of the vital organs, specifically the highly radiosensitive intestines, may cause death, if the injury is significant and the post-exposure recovery is considerably compromised. Here we investigated the recovery rate and extent of recovery from PBI-induced intestinal damage in large animals. Rhesus macaques (Macaca mulatta) were randomly divided into four groups: sham-irradiated (0 Gy), 8 Gy PBI, 11 Gy PBI and 14 Gy PBI. A single dose of ionizing radiation was delivered in the abdominal region using a uniform bilateral anteroposterior and posteroanterior technique. Irradiated animals were scheduled for euthanasia on days 10, 28 or 60 postirradiation, and sham-irradiated animals on day 60. Intestinal structural injuries were assessed via crypt depth, villus height, and mucosal surface length in the four different intestinal regions (duodenum, proximal jejunum, distal jejunum and ileum) using H&E staining. Higher radiation doses corresponded with more injury at 10 days post-PBI and a faster recovery rate. However, at 60 days post-PBI, damage was still evident in all regions of the intestine. The proximal and distal ends (duodenum and ileum, respectively) sustained less damage and recovered more fully than the jejunum.

Stress and Recovery Responses of Microcystis aeruginosa Exposed to Extreme Light for Different Durations

Cyanobacterial growth is a significant problem in most parts of the world. Control measures are necessary to suppress cyanobacterial growth in natural water bodies. When the control measures were discontinued, cyanobacteria growth rebounded quickly. This study was conducted to provide insight into the stress and recovery responses of cyanobacteria. Microcystis aeruginosa was exposed to extreme light for 8 days, and the changes in response to the light exposure were observed. Post-exposure recovery performances were accessed by allowing Cyanobacteria to recover under optimum conditions for 8 days. Extreme light exposure causes stress on M. aeruginosa, but by adjusting the growth, pigmentation, chlorophyll fluorescence, and antioxidant levels, M. aeruginosa surpasses the stress. M. aeruginosa showed sudden changes in parameters on the eighth day of extreme light exposure. The post-stress recovery capacity of M. aeruginosa was positively correlated with the exposure duration. These findings suggest that exposure to light stress causes hardening of M. aeruginosa. The inter-parameter relationships differed between the stress and recovery phases. Besides, non-photochemical quenching was strongly correlated with cellular H2O2 content, which can indirectly explain the oxidative stress status of M. aeruginosa. This study highlights the research requirement on the post-stress recovery capacity of M. aeruginosa.

A comparison of black vs. yellow coat color on rectal and gastrointestinal temperature in Labrador retrievers

Although dark coat color in dogs has been theorized as a risk factor for heat injury, there is little evidence in the scientific literature to support that position. We utilized 16 non-conditioned Labradors (8 black and 8 yellow) in a three-phase test to examine effects of coat color on thermal status of the dog. Rectal, gastrointestinal (GI), and surface temperature using infrared thermography measured at the eye and abdomen, were measured along with respiration rate measured in breaths per minute (bpm), collected at three time points. Phase 1 (Baseline) – 30 minutes of crate rest in a climate-controlled room; Phase 2 (Walking in Sunlight) - 30-minute walk in an outdoor environment on a sunny day; and Phase 3 (Cooling) – 15 minutes of crate rest in climate-controlled room to determine post-exposure recovery temperatures. No effect of coat color was measured for rectal, gastrointestinal, surface temperature, or respiration rate (P > 0.05) in dogs following their 30-minute walk in sunlight. All temperatures measured increased similarly (rectal 1.86°C and 1.80°C; GI 1.92°C and 1.95°C; eye 2.8°C and 1.92°C; abdomen 2.91°C and 2.39°C) in black and yellow dogs respectively, following 30 in Sunlight (P > 0.05). Additionally, temperatures decreased in a similar fashion for both coat colors (rectal 0.84°C and 0.88°C; GI 1.48°C and 1.32°C; eye 1.49°C and 1.70°C; abdominal 1.75°C and 1.5°C) in black and yellow dogs respectively (P > 0.05) during Cooling. Respiration rate increased similarly for both coat colors, (147.2 bpm and 143.7 bpm for black and yellow respectively) when Baseline values were compared to Sunlight values and decreased similarly (28.8 bpm black; 60.2 bpm yellow after Cooling phase (P > 0.05). These novel data reveal a surprising lack of effect for black vs. yellow coat color on body temperature as measured by standard rectal thermometer, gastrointestinal thermistor, or infrared thermography in a population of Labrador retrievers.

Evaluation of the neurotoxic effects of engineered nanomaterials in C57BL/6J mice in 28-day oral exposure studies

In recent years, concerns have emerged about the potential neurotoxic effects of engineered nanomaterials (NMs). Titanium dioxide and silver are among the most widely used types of metallic NMs. We have investigated the effects of these NMs on behaviour and neuropathology in male and female C57BL/6J mice following 28-day oral exposure with or without a 14-day post-exposure recovery. The mice were fed ad libitum with food pellets dosed with 10 mg/g TiO2, 2 mg/g polyvinylpyrrolidone-coated Ag or control pellets. Behaviour was evaluated by X-maze, open field, string suspension and rotarod tests. Histological alterations were analysed by immunohistochemistry and brain tissue homogenates were investigated for markers of oxidative stress, inflammation and blood-brain barrier disruption. Effects of the NMs on tyrosine and serine/threonine protein kinase activity in mouse brains were investigated by measuring kinase activity on peptide microarrays.Markers of inflammation, oxidative stress and blood-brain barrier integrity were not significantly affected in the male and female mice following exposure to Ag or TiO2. Both types of NMs also revealed no consistent significant treatment-related effects on anxiety and cognition. However, in the Ag NM exposed mice altered motor performance effects were observed by the rotarod test that differed between sexes. At 1-week post-exposure, a diminished performance in this test was observed exclusively in the female animals. Cortex tissues of female mice also showed a pronounced increase in tyrosine kinase activity following 28 days oral exposure to Ag NM. A subsequent Inductively Coupled Plasma - Mass Spectrometry (ICP-MS) based toxicokinetic study in female mice revealed a rapid and persistent accumulation of Ag in various internal organs including liver, kidney, spleen and the brain up to 4 weeks post-exposure. In conclusion, our study demonstrated that subacute exposure to foodborne TiO2 and Ag NMs does not cause substantial neuropathological changes in mice. However, the toxicokinetic and specific toxicodynamic findings indicate that long-term exposures to Ag NM can cause neurotoxicity, possibly in a sex-dependent manner.