Oxygen Flux Research Articles

Scalable Formation of Highly Viable and Functional Hepatocellular Carcinoma Spheroids in an Oxygen-Permeable Microwell Device for Anti-Tumor Drug Evaluation.

For high-throughput anti-cancer drug screening, microwell arrays may serve as an effective tool to generate uniform and scalable tumor spheroids. However, microwell arrays are commonly anchored in non-oxygen-permeable culture plates, leading to limited oxygen supply for avascular spheroids. Herein, a polydimethylsiloxane (PDMS)-based oxygen-permeable microwell device is introduced for generating highly viable and functional hepatocellular carcinoma (HCC) spheroids. The PDMS sheets at the bottom of the microwell device provide a high flux of oxygen like in vivo neighboring hepatic sinusoids. Owing to the better oxygen supply, the generated HepG2 spheroids are larger in size and exhibit higher viability and proliferation with less cell apoptosis and necrosis. These spheroids also exhibit lower levels of anaerobic cellular respiration and express higher levels of liver-related functions. In anti-cancer drug testing, spheroids cultured in PDMS plates show a significantly stronger resistance against doxorubicin because of the stronger stem-cell and multidrug resistance phenotype. Moreover, higher expression of vascular endothelial growth factor-A produces a stronger angiogenesis capability of the spheroids. Overall, compared to the spheroids cultured in conventional non-oxygen-permeable plates, these spheroids can be used as a more favorable model for early-stage HCCs and be applied in high-throughput anti-cancer drug screening.

Muscle Protein Oxidation and Functionality: A Global View of a Once-Neglected Phenomenon

Muscle is a highly organized apparatus with a hierarchic microstructure that offers the protection of cellular components against reactive oxygen species (ROS). However, fresh meat immediately postmortem and meat undergoing processing become susceptible to oxidation due to physical disruption and the influx of molecular oxygen. Upon the activation by endogenous prooxidants, oxygen species are rapidly produced, and both myofibrillar and sarcoplasmic proteins become their primary targets. Direct ROS attack of amino acid sidechains and peptide backbone leads to protein conformational changes, conversion to carbonyl and thiol derivatives, and subsequent aggregation and polymerization. Interestingly, mild radical and nonradical oxidation enables orderly protein physicochemical changes, which explains why gels formed by ROS-modified myofibrillar protein have improved rheological properties and binding potential in comminuted meat and meat emulsions. The incorporation of phenolic and other multifunctional compounds promotes gel network formation, fat emulsification, and water immobilization; however, extensive protein modification induced by high levels of ROS impairs protein functionality. Once neglected but now recognized to be a natural occurrence, protein oxidation has drawn much interest and is being intensively studied within the international community of meat science. This review describes the history and evolution of muscle protein oxidation, the mechanism and functionality impact hereof, and innovative oxidant/antioxidant strategies to control and manipulate oxidation in the context of meat processing, storage, and quality. It is hoped that the review will stimulate in-depth discussion of scientific as well as industrial relevance and importance of protein oxidation and inspire robust international collaboration in addressing this underappreciated challenge.

Effects of diet on feed intake, weight change, and gas emissions in beef cows.

The objective of this study was to examine the effects of diet energy density on ranking for dry matter intake (DMI), residual feed intake (RFI), and greenhouse gas emissions. Forty-two mature, gestating Angus cows (600 ± 69 kg body weight [BW]; body condition score [BCS] 5.3 ± 1.1) with a wide range in DMI expected progeny difference (-1.38 to 2.91) were randomly assigned to two diet sequences; forage then concentrate (FC) or concentrate then forage (CF). The forage diet consisted of long-stem native grass hay plus protein supplement (HAY; 1.96 Mcal ME/kg DM). The concentrate diet consisted of 35% chopped grass hay and 65% concentrate feeds on a dry matter basis (MIX; 2.5 Mcal ME/kg DM). The GreenFeed Emission Monitoring system was used to determine carbon dioxide (CO2), oxygen (O2), and methane (CH4) flux. Cow performance traits, ultrasound back fat and rump fat, feed DMI, and gas flux data were analyzed in a crossover design using a mixed model including diet, period, and sequence as fixed effects and pen and cow within sequence as random effects. For all measured traits excluding DMI, there was a diet × sequence interaction (P < 0.05). The correlation between MIX and HAY DMI was 0.41 (P = 0.067) and 0.47 (P = 0.03) for FC and CF sequences, respectively. There was no relationship (P > 0.66) between HAY and MIX average daily gain (ADG), regardless of sequence. Fifty-seven percent of the variation in DMI was explained by metabolic BW, ADG, and BCS for both diets during the first period. During the second period, the same three explanatory variables accounted for 38% and 37% of the variation in DMI for MIX and HAY diets, respectively. The negative relationship between BCS and DMI was more pronounced when cows consumed the MIX diet. There was no relationship between MIX and HAY RFI, regardless of sequence (P > 0.18). During the first period, correlations for CO2, CH4, and O2 with MIX DMI were 0.69, 0.81, and 0.56 (P ≤ 0.015), respectively, and 0.76, 0.74, and 0.64 (P < 0.01) with HAY DMI. During the second period, correlations for CO2, CH4, and O2 with MIX DMI were 0.62, 0.47, and 0.56 (P ≤ 0.11), respectively. However, HAY DMI during the second period was not related to gas flux (P > 0.47). Results from this experiment indicate that feed intake of two energy-diverse diets is moderately correlated while ADG while consuming the two diets is not related. Further experimentation is necessary to determine if gas flux data can be used to predict feed intake in beef cows.

CO2-stable and cobalt-free Ce0.8Sm0.2O2-δ-La0.8Ca0.2Al0.3Fe0.7O3-δ dual-phase hollow fiber membranes for oxygen separation

In this work, 60 wt% Ce0.8Sm0.2O2-δ-40 wt% La0.8Ca0.2Al0.3Fe0.7O3-δ (SDC-LCAF) dual-phase oxygen permeable hollow fiber membrane precursors were prepared via a combined sol–gel and phase inversion technique. Dual-phase SDC-LCAF hollow fiber membrane with compatible fluorite and perovskite phases was obtained after sintering at 1450 °C. The chemical compatibility, thermal expansion, conductivity, oxygen permeation, CO2 tolerance, and short-term regenerative durability regarding the phase structure and composition were systematically studied. The oxygen flux of the SDC-LCAF dual-phase membrane was significantly increased compared to that of LCAF single phase membrane. At 950 °C, the oxygen flux of the SDC-LCAF hollow fiber membrane reached 1.84 mL min−1 cm−2 when both the He sweep and the air feed flow rates were 100 mL min−1, and the dual-phase membrane exhibited stable oxygen permeation fluxes in pure CO2 atmosphere. When pure CO2 was used as the sweep gas in a 225-h short-term stability test, the oxygen permeation fluxes decreased slightly because of the inhibiting effect of CO2 on oxygen surface-exchange reaction. Nevertheless, the ability of the SDC-LCAF membrane to recover the original oxygen permeation performance indicated that the membrane surface did not react irreversibly with CO2. The CO2 stability was not reflected in the LCAF single phase membrane, thus indicating the superior membrane stability following the incorporation of the SDC phase.

Hyperoxia Reprogrammes Microvascular Endothelial Cell Response to Hypoxia in an Organ-Specific Manner.

Organ function relies on microvascular networks to maintain homeostatic equilibrium, which varies widely in different organs and during different physiological challenges. The endothelium role in this critical process can only be evaluated in physiologically relevant contexts. Comparing the responses to oxygen flux in primary murine microvascular EC (MVEC) obtained from brain and lung tissue reveals that supra-physiological oxygen tensions can compromise MVEC viability. Brain MVEC lose mitochondrial activity and undergo significant alterations in electron transport chain (ETC) composition when cultured under standard, non-physiological atmospheric oxygen levels. While glycolytic capacity of both lung and brain MVEC are unchanged by environmental oxygen, the ability to trigger a metabolic shift when oxygen levels drop is greatly compromised following exposure to hyperoxia. This is particularly striking in MVEC from the brain. This work demonstrates that the unique metabolism and function of organ-specific MVEC (1) can be reprogrammed by external oxygen, (2) that this reprogramming can compromise MVEC survival and, importantly, (3) that ex vivo modelling of endothelial function is significantly affected by culture conditions. It further demonstrates that physiological, metabolic and functional studies performed in non-physiological environments do not represent cell function in situ, and this has serious implications in the interpretation of cell-based pre-clinical models.

Altered nitrogen transformation pathways and a legacy of sediment organic matter enrichment

Estuaries are ecologically valuable ecosystems that process nutrients through complex biogeochemical processes. Here we identify drivers and inhibitors of nitrogen removal in unvegetated intertidal sandflats at six sites in Manukau Harbour (37° 2.00′S 174° 42.00′E) to quantify the exchange of solutes across the sediment-water interface, with nitrogen removal rates (NRR) measured at two contrasting sites (PI and CB) near and far, respectively, from an historical wastewater treatment plant. Solute fluxes were paired with sediment and macrofauna community data to identify drivers of ecosystem function. Fluxes of oxygen, nitrogen and phosphorous were found to vary among sites, with differences attributed to variation in sediment characteristics (grain size, chlorophyll a, organic content) and macrofauna community structure. Mean NRR was found to vary between sites (PI = 32.2 vs CB = 217.9 μmol N2/m2/h), with bioturbating macrofauna (bivalves Austrovenus stutchburyi and Macomona liliana), microphytobenthic biomass, and exposure to nutrients likely key contributing drivers.

Oxygen permeability and surface kinetics of composite oxygen transport membranes based on stabilized δ-Bi2O3

Composite ceramic membranes based on the ionic conducting Tm-stabilized δ-Bi2O3 (BTM) and the electronic conducting (La0.8Sr0.2)0.99MnO3-δ (LSM) exhibit among the highest oxygen flux values reported for Bi2O3-based membranes. Here, we use pulse-response isotope exchange (PIE) and oxygen flux measurements to elaborate on limiting factors for the oxygen permeation in BTM - 40-70 vol% LSM composites. Once both phases percolate, between 30 and 50 vol% BTM, the flux is essentially independent of the BTM/LSM volume ratio. The oxygen permeability is under mixed diffusion- and surface control, gradually becoming more bulk-limited with increasing temperature. The oxygen exchange coefficients of BTM-LSM are significantly higher than its constituent phases, revealing that a cooperative surface exchange mechanism enhances the kinetics. Some of the Tm was substituted with Pr to introduce electronic conductivity in BTM. (Bi0.8Tm0.15Pr0.05)2O3-δ (BTP) exhibits higher surface exchange coefficients compared to BTM, but the oxygen flux remains one order of magnitude lower than that of percolating BTM-LSM composites.

Optimization of active antireflection ZnO films for p-GaAs-based heterojunction solar cells

We have optimized the photovoltaic properties of active ZnO/p-GaAs heterojunction solar cells by pulsed laser deposition method by varying the oxygen pressure from 0 to 50 mTorr during the fabrication process. We observed the crystallinity and grain size of ZnO enhanced with increasing oxygen pressure from 0 to 30 mTorr. In addition, with this increase of oxygen flux, the intensity of E1(LO) modes obtained by Raman measurements declines significantly and almost disappears under an oxygen pressure of 50 mTorr. The change of intensity is assumed to be the change of oxygen vacancy and zinc interstitial concentrations in ZnO films with oxygen pressures. Current-voltage measurements and extractions show that ZnO grown at 30 mTorr displays the best performance with the ISC of 24.3 mA/cm2, the efficiency of 8.746 %, and FF0 of 68.73 %. The high performance of the heterojunction solar cell grown at the oxygen partial pressure of 30 mTorr might be due to the reduction of oxygen vacancies by increasing oxygen during the deposition. The results reveal the importance of the oxygen processing gas in promoting devices performance.

Stable, asymmetric, tubular oxygen transport membranes of (Sc2O3)0.10(Y2O3)0.01(ZrO2)0.89 – LaCr0.85Cu0.10Ni0.05O3-δ

Oxygen transport membranes have the potential to deliver pure and cheap oxygen to chemical reactors, combustors, gasifiers etc., given that geometry, microstructure and material properties are optimized. This work demonstrates the first successful preparation of dual-phase tubular, asymmetric oxygen transport membranes consisting of a new electronic conductor LaCr0.85Cu0.10Ni0.05O3-δ mixed with (Sc2O3)0.10(Y2O3)0.01(ZrO2)0.89 as ionic conductor. Challenges related to Cr-volatility were overcome by using Fe2O3 as a sintering aid. The sintering aid decreased mismatches in shrinkage and thermal expansion between the four layers in the asymmetric membrane and decreased the sintering temperature such that the Cr-volatility was suppressed. The membranes reached an oxygen flux of 0.28 ml∙min−1∙cm−2 in an air/N2 atmosphere at 950 °C. Furthermore, the membranes showed a stable oxygen flux after exposure to different atmospheres, including air/CO2 and air/H2 gradients. The successful fabrication of stable, asymmetric, tubular membranes opens the possibility for future integration in syngas or oxy-combustion applications.

Fundamental modeling and experimental validation of hydrogen and oxygen transport through mixed ionic and electronic conducting membranes

Hydrogen transporting mixed ionic and electronic membranes offer tremendous opportunities for process intensification and energy savings in various applications such as reaction chemistries and heat/energy generation. Over the past several decades there has been significant advancement in the membrane materials science to produce improved molecular transport, but commercial adoption is still limited. To escalate implementation, a fundamental understanding of the solid state membrane transport and the water splitting phenomenon would bridge the gap for process conceptualization and design. This work presents a fundamental transport model, which quantifies the contribution of the water splitting phenomenon to the overall observed apparent flux of hydrogen and oxygen through ionic and electronic conducting membranes. The model predictions are rigorously validated against experimental data gathered in parallel. Membranes tested were based on the composition La0.87Sr0.13CrO3-δ-La5.4WO12-δ. These measurements include both apparent hydrogen/oxygen fluxes and the water splitting contributions over a range of operating conditions that included varying temperatures, hydrogen partial pressures, and hydration gradients across the membrane.

(Invited) Photo-SECM Measurements of Water Splitting at Single Semiconductor Particles

Understanding and improving the properties of photocatalysts can have important implications for energy conversion and storage. Because the activity of heterogeneous catalysts depends strongly on local atomic structures, probing (photo)catalytic reactions at specific local sites is critically important. We have recently reported the use of scanning electrochemical microscopy (SECM) for nanoscale imaging of photoelectrochemical processes at semiconductor surfaces. To illuminate a microscopic portion of the substrate surface facing the SECM probe, a glass-sealed, polished Pt tip simultaneously serves as a nanoelectrode and a light guide. In this paper, we present the results of first nanoscale SECM and photo-SECM experiments with single BiVO4 and SrTiO3 particles. Local mapping of oxygen and hydrogen fluxes produced by water splitting at single semiconductor particles was carried out using chemically modified SECM nanotips.

Scanning Micropipette Contract Method Measurement of Aluminum Alloy: Effect of Approach Parameters on Corrosion Potential

Scanning electrochemical cell microscopy (SECCM) enables direct electrochemical measurements at microscopic sits by scanning a droplet cell over a substrate surface. Scanning micropipette contact method (SMCM) is a type of single-channel SECCM. It has been used to record the spatially resolved electrochemical activities across metal surfaces to investigate corrosion at the (sub)microscale. In SMCM, the applied potential during the approach of micropipette to the substrate (Eappr), generates a transient current upon droplet contact with the substrate. Once the transient current exceeds a set threshold, the micropipette is automatically halted. In the investigation of aluminum alloy, we found that Eappr affected the subsequent measurements of corrosion potential (Ecorr) in the open circuit potential (OCP) and potentiodynamic polarization (PDP), which was considered to be inconsequential previously. For aluminum alloys, the dense oxide film restricts the surface conductivity, increasing the difficulty of droplet landing. This leads to pipette-substrate contact and droplet-substrate contact landings using different Eappr. Additional oxygen flux from the droplet-oil interface in the droplet-substrate contact resulted in more positive Ecorr(OCP). In the anodic PDP at a high scan rate of 100 mV/s, Ecorr(PDP) moved away from Ecorr(OCP) to larger extent as Eappr increased to more cathodic values. The systematic interpretation of the effect of Eappr will promote the understanding of SMCM measurement especially in the field of metal corrosion.

PDIA2 Bridges Endoplasmic Reticulum Stress and Metabolic Reprogramming During Malignant Transformation of Chronic Colitis.

BackgroundChronic inflammation contributes to approximately 20% of cancers; the underlying mechanisms are still elusive. Here, using an animal model of colitis to colon-cancerous transformation, we demonstrated that endoplasmic reticulum (ER) stress couples with metabolic reprogramming to promote a malignant transformation of chronic inflammation.MethodsThe animal model for chronic colitis to colon-cancerous transformation was established in C57BL/6N mice by azoxymethane (AOM) and dextran sodium sulfate (DSS) treatments. The differential proteins in control and AOM/DSS-treated colon mucosa were determined using proteomic analysis; the kinetics of metabolic modifications were monitored by mitochondrial oxygen flux, extracellular acidification, and targeted metabolomics; the molecule linker between ER stress and metabolic modifications were identified by coimmunoprecipitation, KEGG pathway analysis, and the subcutaneous tumor model using gene-specific knockdown colon cancer cells. Tissue array analysis were used to evaluate the differential protein in cancer and cancer-adjacent tissues.ResultsAOM/DSS treatment induced 38 tumors in 10 mice at the 14th week with the mean tumor size 9.35 ± 3.87 mm2, which was significantly decreased to 5.85 ± 0.95 mm2 by the ER stress inhibitor 4-phenylbutyric acid (4PBA). Seven differential proteins were determined from control (1,067 ± 48) and AOM/DSS-treated mucosa (1,077 ± 59); the level of ER protein PDIA2 (protein disulfide isomerase-associated 2) was increased over 7-fold in response to AOM/DSS treatment. PDIA2 interacted with 420 proteins that were involved in 8 signaling pathways, in particular with 53 proteins in metabolic pathways. PDIA2 translocated from ER to mitochondria and interacted with the components of complexes I and II to inhibit oxophosphorylation but increase glycolysis. Knockdown PDIA2 in colon cancer cells restored the metabolic imbalance and significantly repressed tumor growth in the xenograft animal model. 4PBA therapy inhibited the AOM/DSS-mediated overexpression of PDIA2 and metabolic modifications and suppressed colon cancer growth. In clinic, PDIA2 was overexpressed in colon cancer tissues rather than cancer-adjacent tissues and was related with the late stages and lymph node metastasis of colon cancer.ConclusionsPersistent ER stress reprograms the metabolism to promote the malignant transformation of chronic colitis; PDIA2 serves as a molecule linker between ER stress and metabolic reprogramming. The inhibition of ER stress restores metabolic homeostasis and attenuates the cancerous transformation of chronic inflammation.

O-203 Live real-time determination of mitochondrial bioenergetics as a reliable tool to evaluate mitochondrial activity in mammalian oocytes

Abstract Study question Can live real-time determination of mitochondrial bioenergetics represent a reliable assay of the mitochondrial activity and bioenergetic metabolism in mouse oocytes? Summary answer We demonstrated that real-time determination of mitochondrial oxidative phosphorylation is a feasible method for the characterization of mitochondrial activity and adaptation capacity of mammalian oocytes. What is known already Mammalian oocytes possess about 300.000 mitochondria and their alterations represent the main factors underlying reduced oocyte competence. Mitochondrial oxidative phosphorylation, measured as the oxygen consumption rate (OCR) is the largest contributor to cellular ATP demand. Fine-tuning mitochondrial activity is required to sustain bioenergetics homeostasis and maintain physiological levels of ROS production in the female gamete. Despite numerous techniques have been used to measure OCR, the application in oocytes have remained infeasible. Recently the development of a non-invasive, real-time assay has provided a more comprehensive picture of OCR in terms of the components of mitochondrial oxygen flux. Study design, size, duration Mitochondrial bioenergetic profile was determined in GV oocytes from young unprimed and primed mice; MII oocytes from young hCG-primed mice; oocytes from aged hCG-primed mice; young MII oocytes from IVM; aged MII oocytes from IVM; MII oocytes from IVM following oxidative stress in the presence or absence of the NAD+ booster p7C3 or propionyl-L-carnitine (PLC). Mean values of basal oxygen consumption rate, maximal capacity, reserve capacity and non-mitochondrial sources on oxygen consumption were evaluated. Participants/materials, setting, methods Young (4-8 weeks) and aged (36-40weeks) CD-1 mice were employed. GV oocytes were isolated from PMSG-primed and unprimed mice. MII oocytes were retrieved from hCG-primed mice. Oxidative stress was induced by exposure to 25-100µM H2O2 for 10-30’. IVM was performed in M2 medium with/out 1-5 mM P7C3 or 0.2mg/ml PLC. SeahorseXFp96 Agilent was employed to measure OCR (pmol/min/oocytes/wells) in pools of 8 oocytes after establishment of mitochondrial inhibitors concentrations. SigmaStat was used for statistical analysis. Main results and the role of chance From the analysis of the parameters above described, GV oocytes from primed and unprimed mice showed different bioenergetic profiles revealing lower basal OCR in unprimed GV. When exposed to oxidative stress, GV oocytes exhibited of redox state alteration evidenced by the response to the different inhibitors. These effects were prevented by exposure to P7C3 or PLC. A similar profile was present in GV oocytes from aged oocytes. All classes of MII displayed an OCR lower than GV. Ovulated MII oocytes showed an OCR lower than MII from IVM oocytes. Moreover, the latter displayed an increased non-mitochondrial respiration as evidence of oxidative stress. IVM oocytes exposed to oxidative insult revealed increased proton leak associated with reduced ATP levels. The presence of P7C3 in the IVM medium reduced non-mitochondrial respiration and proton leak with positive effects on ATP production and IVM rate. MII oocytes from aged mice when compared with the young group showed a different bioenergetic profile revealing lower OCR in the aged MII along with reduced spare respiratory capacity and increased proton leak. These changes suggest decreased mitochondrial mass and/or altered integrity of ETC components. The presence of P7C3 during IVM allowed a partial recovery of these dysfunctions. Limitations, reasons for caution Results from animal studies should be extrapolated to humans with caution. Wider implications of the findings Live real-time analysis of mitochondrial bioenergetics can be a reliable approach for the study of mitochondrial dysfunctions linked with reduced oocyte competence associated with aging and other oxidative stress conditions. Thus, it could be employed to set up specific recovery strategies based on metabolic boosters to improve human IVF. Trial registration number not applicable

In-Situ Estimates of Net Ecosystem Metabolisms in the Rocky Habitats of Dokdo Islets in the East Sea of Korea

We measured oxygen (O2) fluxes in two major shallow subtidal benthic habitats (kelp bed (KB) and bare rock (BR) covered with crustose coralline algae) of Dokdo islet in the East Sea by applying noninvasive in-situ aquatic eddy covariance (AEC). The AEC device allows time series measurements (~24 h) of three-dimensional velocity (u, v, and w components) and high-resolution dissolved O2. This allows estimation of O2 exchange flux via benthic habitats. Local flow rates and irradiance levels were found to be major factors controlling O2 exchange flux in the rocky habitats. Gross primary production rates tended to be significantly higher in KB (163 mmol O2 m−2 d−1) than in BR (51 mmol O2 m−2 d−1). The net ecosystem metabolisms were assessed as opposite types, with 8 mmol O2 m−2 d−1 in KB (autotrophy) and –12 mmol O2 m−2 d−1 in BR (heterotrophy). Our results indicate that kelp beds are important for organic carbon cycling in rocky coastal waters and that AEC application to macroalgae habitats is a useful assessment approach.

Evidence of long term biogeochemical interactions in carbonate weathering: The role of planktonic microorganisms and riverine bivalves in a large fluviokarst system

The infiltration of organic-rich surface waters towards groundwaters, is known to play a significant role in carbonate weathering and in contributing to the atmospheric continental carbon sink. This paper investigated biogeochemical interactions in karst critical zones, with strong surface water /groundwater interactions, and in particular the role of planktonic microorganisms and riverine bivalves through the analysis of particulate organic matter (OM) oxidation on carbonate weathering. In the large Val d'Orléans fluviokarst aquifer (France), a 20-year monthly dataset of Nitrates, Dissolved Oxygen (DO), dissolved inorganic and organic Carbon (DIC and DOC) fluxes was gathered. The surface water-groundwater comparison of geochemical trends showed that planktonic microorganisms had drastically decreased in surface waters, related to the proliferation of Corbicula bivalves spreading and a decrease in nutrients. This decrease in planktonic microorganisms was followed by a DO increase and an DIC decrease at the karst resurgence. The degradation of planktonic microorganisms consumes DO and produces NO3, dissolved inorganic carbon (DIC) and a proton that in turn, dissolves calcite and produces DIC. Without the input from planktonic microorganisms, the fluviokarst has lost 29 % of this nitrification and 12 % of the carbonate dissolution capacities. Thus, the oxidation of particulate organic matter of planktonic microorganisms, which is part of heterotrophic respiration, appears to be a significant source of the inorganic carbon flux in riverine ecosystems. This shows how weathering can remain active under waters saturated versus calcite and suggests that the oxidation of organic matter can be a more appropriate mechanism than autotrophic respiration to explain the relationship between global warming and DIC flux change in rivers. Through the consumption of plankton, the animal life in rivers thus influences the inorganic carbon in groundwaters, creating a negative feedback in the carbon cycle.

Effects of Smart Drugs on Cholinergic System and Non-Neuronal Acetylcholine in the Mouse Hippocampus: Histopathological Approach.

In recent years, people in the United States and other countries have been using smart drugs, called nootropic or cognitive enhancers, to improve concentration and memory learning skills. However, these drugs were originally prescribed for attention-deficit hyperactivity disorder and dementia, and their efficacy in healthy people has not yet been established. We focused on acetylcholine in the hippocampus, which is responsible for memory learning, and elucidate the long-term effects of smart drugs on the neural circuits. Smart drugs were administered orally in normal young mice for seven weeks. The hippocampus was sectioned and compared histologically by hematoxylin and eosin (HE) staining, immunohistochemistry for acetylcholine, and immunoelectron microscopy. There were no significant changes in acetylcholinesterase staining. However, in HE, we found perivascular edema, and choline acetyltransferase staining showed increased staining throughout the hippocampus and new signal induction in the perivascular area in the CA3, especially in the aniracetam and α-glyceryl phosphoryl choline group. Additionally, new muscarinic acetylcholine receptor signals were observed in the CA1 due to smart drug intake, suggesting that vasodilation might cause neuronal activation by increasing the influx of nutrients and oxygen. Moreover, these results suggest a possible new mechanism of acetylcholine-mediated neural circuit activation by smart drug intake.

Impact of Variability in Precipitation Patterns on the Geochemistry of Pyritic Uranium Tailings Rehabilitated with Saturated Cover Technology

Increasing variability in precipitation patterns is expected to result from climate change in Canada. This effect has the potential to affect the performances of saturated covers in inhibiting acid rock drainage (ARD) and metal leaching (ML) processes. Because ARD and ML may cause the release of deleterious chemical species into the environment, such climate-change-driven impact was investigated using trickle leach columns. The physical, chemical, and mineralogical characteristics of the tailings as well as chemical composition of the leachate were measured before and after the column study. Results from the experiment showed that higher variability in precipitation regimes could enhance leaching of uranium. Leaching ranged from 67.1 to 90.1% of the total amount of U, with greater values associated with higher variability in precipitation patterns. Lower water levels and prolonged drought periods led to higher oxygen fluxes to the U tailings and dissolution of carbonate-bearing minerals. The release of carbonates could have enhanced uranium leaching through the formation of stable uranium-carbonate complexes in solution. Overall, this study shows that water level variation caused by varying precipitation patterns can significantly affect the drainage chemistry of saturated cover systems for which the level fluctuates freely near the tailings–cover interface.

No evidence for collateral effects of electromagnetic fields used to increase dissolved oxygen levels on the behavior and physiology of freshwater fishes.

Hypoxia in surface waters driven by warming climate and other anthropogenic stressors is a major conservation concern, and technological solutions for water quality remediation are sorely needed. One potential solution involves the use of low-intensity electromagnetic fields (EMFs) to increase dissolved oxygen levels, but potential collateral effects of the EMFs on aquatic animals have not been formally evaluated. We examined the effects of EMF exposure on wild-caught, captive sunfish (Lepomis spp.) over 8-day and 3-day exposures, with and without aeration in mesocosms and stock tanks (respectively). We also quantified ambient fish abundance in close proximity to EMF devices deployed in Opinicon Lake (ON). We found no significant differences in a suite of blood-based stress physiology biomarkers, behaviors, and putative aerobic capacities between EMF and control conditions over 8 days. Aerated mesocosms equipped with activated EMFs consistently had higher oxygen levels in the water than aerated controls. There were no differences in mortality during 3-day oxygen depletion trials under EMF or control conditions, and we detected no differences in fish abundance when the devices were activated in the lake. Our findings suggest that deploying EMF devices in field settings is not likely to exert negative effects on exposed fish populations. PRACTITIONER POINTS: Low-cost, low-energy technological solutions to remediate aquatic hypoxia are sorely needed Electromagnetic fields (EMFs) can increase oxygen flux across air/water interfaces and increase dissolved oxygen levels We found no evidence of negative effects of EMFs on fish physiology or behavior and our results support their use in alleviating hypoxic conditions.

Trawling effects on biogeochemical processes are mediated by fauna in high-energy biogenic-reef-inhabited coastal sediments

Abstract. Dynamic, sandy environments are generally less vulnerable to mechanical stress compared to silty, low-energy habitats. Biogenic reef communities, however, may provide an exception to this. This study explores the physical, biological, and biogeochemical effects of bottom trawl fishing on a coastal ecosystem dominated by the tube-building polychaete Lanice conchilega. Two specific gear types, both used to exploit North Sea sole (Solea solea), were compared: electric pulse trawls and tickler chain-rigged beam trawls. We detected a ∼1 cm bathymetric deepening after trawling associated with significant losses in benthic chlorophyll a caused by both fishing gears. Tickler chain trawls significantly reduced sediment oxygen consumption (57 %), total organic matter mineralization (56 %), denitrification (61 %), nitrification (60 %), and total benthos densities (52 %), while pulse trawls had no statistically significant impact on these parameters. Before trawling, significant relationships could be found between L. conchilega and very fine sand fractions, oxygen and nitrate fluxes, macrobenthos densities, and species richness; however, the trawl disturbances from both gears disrupted these connections. Our results suggest a reduced average effect for pulse compared to tickler chain beam trawls for several ecological and biogeochemical characteristics, though their impact was still significant for L. conchilega and associated species. This study also suggests that faunal-mediated ecosystem functions in habitats dominated by L. conchilega may be sensitive to relatively shallow sediment penetration from trawl gears and should be considered when assessing habitat vulnerability.