Elevated Ammonia Concentrations Research Articles

Management implications following the reconstruction of the small and shallow Lake Mustijärv (Estonia)

Lake Mustijärv was reconstructed by sediment removal following an almost complete siltation. Here we evaluate challenges and opportunities for the management of the lake. We focused on the stream discharging to the lake (i.e., external loading), sediment retention in accumulation basins (i.e., internal processes) as well as the ecosystem-level response to stressors based on biological variables (phyto- and zooplankton, macrophytes, fishes and zoobenthos). Urban and agricultural inputs elevated ammonium and total phosphorus concentrations in the lake, challenging lake reconstruction efforts. Sediment transport highly increased the risk of faster filling of the lake, associated with upstream streambed excavation. Sediments trapped at the accumulation basins release nutrients that enhance eutrophication. We, however, observed a rapid recovery in fish, macrophytes, and zoobenthos, despite the significant disturbances. Lake Mustijärv is in eutrophic condition, reflected by phytoplankton (Pseudanabaena, Closteriopsis dominance) and zooplankton (Keratella, Polyarthra dominance) composition. To improve lake water quality will require controlling external nutrient inputs, underlining the importance of better coordinated activities between the local (lake restoration) and regional (catchment use) scales.

Evaluating Groundwater Quality for Drinking and Irrigation Purposes and Health Risk Assessment in West Midnapore District of West Bengal, India

Groundwater quality in the West Midnapore district of West Bengal, India is affected by anthropogenic activities as well as by water quality of Subarnarekha and Kangsabati rivers. This study aims to assess quality of groundwater and river water for drinking and irrigation usage, and assess the health risks of the people consuming the water across the rivers. The study also explores the groundwater-river water interaction. The river water and groundwater samples were collected three times during monsoon season from 14 sites across the rivers. The samples were analyzed for 11 water quality parameters, i.e., pH, total dissolved solids (TDS), total hardness (TH), major anions and cations, and iron (Fe). The groundwater was found slightly acidic (mean pH ~ 6.71) and correlated with nitrate concentrations. Most of the water quality parameters were found within their permissible limits of drinking water. However, elevated concentrations of potassium (K), ammonium (NH4), magnesium (Mg), phosphate (PO4), sodium (Na), and Fe were detected at some places, which were likely due to use of fertilizers. Water quality index (WQI), sodium absorption ratio (SAR), and percentage Na values were computed to evaluate the groundwater quality. The mean WQI value of 37.07 showed that the majority of groundwater samples met drinking water standards. Groundwater was also found suitable for irrigation (SAR ~ 0.26 to 1.62 meq L-1 and percentage Na ~ 13.10% to 78.12%). Health risk assessments suggested minimal immediate risks, though high Na levels in certain areas raised concerns. Piper plot showed that increased calcium concentrations in groundwater were mainly due to interactions between river water and groundwater. Overall, groundwater quality did not present any harmful health hazards to the community. The findings of this study can be instrumental for groundwater managers in identifying potential areas for treating groundwater quality.

Adaptation of the anammox process for high ammonium photovoltaic wastewater treatment

Tunnel Oxide Passivating Contacts (TOPcon) battery in the photovoltaic industry generates high ammonium wastewater during the production process, the adaptability of using the anaerobic ammonia oxidation (Anammox) process for photovoltaic wastewater (PVW) treatment is a research hotspot. Based on the analysis of photovoltaic wastewater quality, the effectiveness of nitrogen removal, sludge characteristics and microbial communities were examined. The results showed that when the influent NH4+-N concentration of PVW was lower than 150 mg·L−1, the nitrogen removal efficiency (NRE) was almost 100 %. In addition, the NRE decreased from 74 % sharply to 20 % when the NH4+-N concentration was increased from 175 mg·L−1 to 200 mg·L−1. The extracellular polymeric substances (EPS) content increased with elevated ammonium concentration in the influent, indicating that microorganisms secreted more EPS to resist elevated nitrogen loading. The main functional populations were Candidatus Kuenenia (0–24 %). The influent ammonium concentration is recommended to be < 200 mg·L−1.

Recovery of ecosystems pollution by contaminants of potential concern using phytoremediation techniques.

Phytoremediation is a technology that uses plants to break down, remove, and immobilize contaminants in surface water, shallow groundwater, and sediment to achieve cost savings compared with conventional treatments. This study describes a marshy land on an explosives manufacturing site in India that consistently reported elevated concentrations of nitrates, nitrites, ammonia, perchlorate, and lead (contaminants of potential concern-CoPC). The study also illustrates the potential for addressing the human health and environmental risks associated with the explosives manufacturing industrsy in India using innovative, sustainable, and carbon-neutral techniques. This work focuses on reconstructed marshy lands, desedimentation, microwatershed management, and phytoremediation using Phragmites and Vetiveria species (also known as vetiver) to reduce contaminants in surface water and groundwater, improve stormwater management and carbon capture, and increase natural capital like biodiversity. The results obtained during the trial indicate that the selected indigenous species are effective and can be used to remediate sediment and shallow groundwater for many CoPC in tropical climates. Integr Environ Assess Manag 2024;20:1987-2002. © 2024 SETAC.

Unveiling ammonium concentration ranges that determine competition for mineral nitrogen among soil nitrogen transformations under increased carbon availability

Globally, approximately 50% of nitrogen (N) fertilizer applied in agricultural practices escapes into the environment, resulting in water and air pollution and ozone depletion. Soil N transformation processes determine the chemical form of N and the amount of the various N forms, controlling where N fertilizer goes and how much of it is lost. Therefore, a comprehensive understanding of soil N transformation responses to N fertilizer is critical for developing effective management strategies to improve soil N retention capacity and minimize soil N losses. Using 15N tracing techniques with acetylene inhibition, three ranges for ammonium concentration in fertilizer were identified (I: 14–16, II: 46–59, and III: 90–115 mg N kg−1, depending on type of organic materials added) that determine competition for mineral N among N transformation processes under increased carbon availability in an agricultural soil. Increasing ammonium concentration caused a shift from a nitrate assimilation-dominated (<I) to an equally ammonium assimilation- and nitrification-dominated (I-II) to nitrification-dominated (II-III), and finally to nitrification-predominant (>III) period in organic amendment addition treatments. Structural equation modeling revealed that ammonium addition inhibited soil nitrate assimilation by enhancing nitrification and ammonium assimilation, resulting in the shift. Consequently, the ratios of nitrification to ammonium assimilation and to gross N assimilation (nitrate assimilation + ammonium assimilation) increased significantly in response to elevated ammonium concentration with organic amendment addition, indicating lower N retention capacity and higher potential risks of N loss. Overall, we present a comprehensive picture of how concurrent gross N transformation processes interact to compete for mineral N in response to ammonium-forming fertilizer application, and demonstrate that nitrification and ammonium assimilation weaken the stimulating effect of organic amendment on nitrate assimilation with increasing ammonium concentration.

The protein nutritional status affects hope of patients in the terminal phase of cancer

Progressive destruction of the patient’s body in the terminal phase of cancer intensifies the breakdown of muscle tissue proteins, producing neurotoxic ammonia and urea. These metabolites negatively affect the brain function and are more difficult to remove from the cancer-ravaged body than from better-nourished patients. Developing cachexia impairs the functioning of all body organs, including the excretory function of the kidneys, including the removal of neurotoxic metabolites. Elevated concentrations of ammonia and urea in the brain leads to cerebral dysfunction involving a spectrum of neuropsychiatric and neurological symptoms. This may negatively affect the perception of patient’s existential situation, and the experience of hope. Improving the protein nutritional status of patients in the terminal phase of cancer may decrease the muscle tissue breakdown, improve the functioning of internal organs and the efficiency of removing neurotoxic metabolites from the body. According to this, we hypothesize that the hope of patients in the terminal phase of cancer may significantly depend on their protein nutritional status. Patients less malnourished with protein experience greater hope and cope better with their existential situation than those more malnourished. We propose a clinical trial to investigate the relation between protein nutritional status and hope experience in patients in the terminal phase of cancer. The verification of this hypothesis may contribute to better and more holistic patients’ care, both professional and non-professional, which may improve the quality of their life in the last days.

Assessment of a sustainable multigeneration system integrating supercritical CO2 Brayton cycle and LNG regasification: Thermodynamic and exergoeconomic evaluation

This study proposes a cost-effective multigeneration system that integrates a supercritical carbon dioxide (sCO2) power cycle with a liquefied natural gas (LNG) regasification process. The system aims to deliver electricity, cooling, heating, and hydrogen simultaneously. Utilizing the temperature difference between the sCO2 cycle and the LNG thermal sink, an ammonia-water-based absorption refrigeration cycle (ARC) recovers waste heat from the sCO2 power cycle, producing cooling. The elevated ammonia concentration at the ARC's condenser outlet is leveraged by a heat pump system for heating production. Concurrently, cold energy from LNG is used to recover latent heat from the condenser and heat rejected from the sCO2 power cycle, providing inputs for additional electrical power through an NG turbine. The system incorporates a PEM electrolyzer (PEME) for hydrogen production. A comprehensive examination, including energy, exergy, and exergoeconomic analyses, evaluates system performance. A sensitivity analysis illustrates the impacts of key parameters. In the baseline scenario, the system achieves energy and exergy efficiencies of 62.79% and 54.89%, with a low product unit cost of 11.35 ($/GJ). The system demonstrates substantial net power output (259.184 MW), cooling capacity (88.938 MW), heating capacity (2.839 MW), and hydrogen production (391.68 kg/h). This robust performance, coupled with cost-effectiveness, positions the proposed system as a versatile and impactful solution for sustainable and environmentally friendly energy applications.

Ammonium Removal in Wastewater Treatments by Adsorbent Geopolymer Material with Granite Wastes: Full-Scale Validation

Elevated ammonium (NH4+) concentrations in untreated waterways contribute to eutrophication and dissolved oxygen depletion. Geopolymer (GP) materials are introduced as sustainable, straightforward operation and low-cost option for pollutant adsorption through ion exchange mechanism. In the present study, a porous metakaolin-based geopolymer with granite waste additions was synthetized, characterised and validated as adsorbent material for NH4+ pollution in water. At this point, treatments to reduce GP alkalis leaching were also considered to comply with the water discharge regulations. The adsorption mechanism was analysed by Redlich-Peterson isotherm model concluding that NH4+ was disposed on the GP surface as a monolayer with strong physical-chemical attraction between molecules. Kinetics of the process followed the Weber-Morris rate equation being the intraparticle diffusion the limiting process. Continuous experiments at lab-scale suggested a maximum removal of 97% during the first hours and an adsorption capacity (q) of 25.24 mg/g. Additionally, as a main novelty of the work, the GP was validated in a full-scale pilot plant monitoring pH, electrical conductivity and NH4+ concentration. The obtained data revealed that the GP is high selective in a real wastewater stream and removed 81% of NH4+, higher adsorption values than those reported for natural and some synthetic zeolites.

Tropical bloom-forming mesoalgae Cladophoropsis sp. and Laurencia sp.-responses to ammonium enrichment and a simulated heatwave.

Algal blooms are increasing worldwide, driven by elevated nutrient inputs. However, it is still unknown how tropical benthic algae will respond to heatwaves, which are expected to be more frequent under global warming. In the present study, a multifactorial experiment was carried out to investigate the potential synergistic effects of increased ammonium inputs (25 μM, control at 2.5 μM) and a heatwave (31°C, control at 25°C) on the growth and physiology (e.g., ammonium uptake, nutrient assimilation, photosynthetic performance, and pigment concentrations) of two bloom-forming algal species, Cladophoropsis sp. and Laurencia sp. Both algae positively responded to elevated ammonium concentrations with higher growth and chlorophyll a and lutein concentrations. Increased temperature was generally a less important driver, interacting with elevated ammonium by decreasing the algaes'%N content and N:P ratios. Interestingly, this stress response was not captured by the photosynthetic yield (Fv/Fm) nor by the carbon assimilation (%C), which increased for both algae at higher temperatures. The negative effects of higher temperature were, however, buffered by nutrient inputs, showing an antagonistic response in the combined treatment for the concentration of VAZ (violaxanthin, antheraxanthin, zeaxanthin) and thalli growth. Ammonium uptake was initially higher for Cladophoropsis sp. and increased for Laurencia sp. over experimental time, showing an acclimation capacity even in a short time interval. This experiment shows that both algae benefited from increased ammonium pulses and were able to overcome the otherwise detrimental stress of increasingly emerging temperature anomalies, which provide them a strong competitive advantage and might support their further expansions in tropical marine systems.

Pore-water nutrient concentrations variability under different oxygen regimes: A case study in Elefsis Bay, Greece

Anthropogenic pressures considerably affect coastal areas, increasing nitrogen and phosphorous loads that lead to eutrophication. Eutrophication sometimes results in hypoxic and/or anoxic conditions near the bottom water. Dissolved oxygen (DO) concentrations influence redox-sensitive nutrients, which can alter the benthic flux of nutrients. We retrieved sediment cores from two sites in the eastern and western parts of Elefsis Bay, a semi-enclosed area of the Eastern Mediterranean, Greece, during winter and summer. In the western part, seasonally hypoxic or anoxic conditions occurred. We analysed pore-water samples under normoxic, hypoxic and anoxic bottom water conditions to study the pore-water nutrient concentrations variability under different oxygen regimes. Ex situ incubation experiments were conducted at the site experiencing oxygen deficiency by manipulating the DO concentrations. The pore-water nutrient concentrations showed higher variability at the site experiencing oxygen deficiency. Notably, elevated ammonium concentrations were observed in the pore water during anoxic conditions, in the 2–20-cm sediment layer. However, the benthic fluxes of ammonium and phosphate at the 0–2-cm sediment layer were comparable under hypoxic and anoxic conditions. The results of the incubation experiments demonstrate a direct decrease in nitrate concentrations as the DO concentrations diminished in the overlying water. The incubations after re-oxygenating the overlying water show that phosphate was more efficiently scavenged when anoxic conditions prevailed in the bottom water. The incubation experiments indicate the rapid response of the seafloor to oxygen availability, particularly concerning processes that influence nitrate and phosphate concentrations. These observations highlight the dynamic nature of nutrient cycling in shallow, seasonally anoxic environments, such as Elefsis Bay, and emphasise the sensitivity of the seafloor ecosystem to changes in bottom water oxygen availability.

Bio-chemical treatment of landfill leachates with high load of organic and nitrogen compounds

This research encompassed an 8-month investigation to evaluate the biological treatment of complex landfill leachates. The primary objectives were the removal of organic and nitrogen compounds, as well as the mitigation of H2S and VOC emissions. Biological treatment was conducted within a sequencing batch reactor (SBR), incorporating aerobic, anaerobic, and anoxic stages. The results indicate that biological treatment is indeed effective in eliminating biodegradable organic matter, with an average removal rate of 84.5% for BOD5, 42.7% for COD, and 40.9% for TOC. Nonetheless, it is imperative to integrate supplementary processes to enhance organic removal. It is worth noting that biological nitrification proved inadequate for sufficiently reducing elevated ammonia concentrations, achieving only a 23.2% reduction. In controlled laboratory conditions, the utilization of chemical precipitation, employing either MgO+H3PO4 or MgCl2.6 H2O+Na2HPO4.7 H2O in an equimolar ratio of Mg:NH4:PO4, exhibited substantial ammonia removal rates of 76.8 ± 6.4% and 80.7 ± 4.5%, respectively. Additionally, the incorporation of an anoxic stage in reactor operation demonstrated its effectiveness in achieving proficient denitrification, with an 80% removal rate for nitrates present in the raw leachates. These findings underscore the potential for optimizing the efficiency of biological leachate treatment processes through strategic modifications and the integration of additional treatment steps.

Sanitary-Hygienic Research to Ensure State Sanitary-Epidemiological Surveillance in the Republic of Kazakhstan.

There are numerous factors that impact human health. Sanitary and hygienic conditions in the workplace and living environments, the state of the environment, and nutrition levels play a significant role in determining environmental quality. An integral part is also the organization of effective treatment and preventive health care services for the population. The purpose of this study is to analyze the sanitary and hygienic situation in the Republic of Kazakhstan. The methodological framework employed general theoretical methods, statistical analysis, and techniques for systematizing information. During the study, it was determined that in several cities, high levels of respiratory and skin morbidity are recorded, linked to elevated concentrations of dust, ammonia, hydrogen fluoride, and nitrogen dioxide. As a consequence of chemical contamination of drinking water sources, there is an escalation in the incidence of nephritis and hepatitis, an upsurge in the number of toxicosis cases among pregnant women, and congenital anomalies. The sanitary condition of settlements greatly impacts the development of satisfactory living conditions. Therefore, this research holds significant practical relevance, and the findings can be utilized by specialists in relevant fields to analyze and address the identified problems, as safeguarding public health, development, and improvement of its protection system is currently becoming one of the paramount tasks.

Oxidation of Ammonia in Fish Ponds to Nitrates Using Free and Immobilized Nitrifying Bacteria

In fish farming, ammonia stands out as detrimental toxicant, with the potential to significantly impede growth and even lead to fish mortality. The adverse effects of ammonia exposure in aquatic environments primarily stem from elevated concentrations of unionized ammonium (NH3), which can readily permeate gill membranes. This study aimed at assessing the capability of free and mobilized forms of nitrifying bacteria in converting ammonia to nitrates. Nitrifying bacteria were isolated from water samples, resulting in the identification of two Pseudomonas species and two Bacillus species. The Bacillus sp., designated with the isolate code, B4 which exhibited the ability to convert ammonia to both nitrite and nitrate while demonstrating resilience to high ammonia concentrations. When Pseudomonas sp. (C4) and Bacillus sp. (B4) were utilized, the total ammonia concentration was reduced from 2 mg/L to 1.4 mg/L and 1.3 mg/L, respectively. Moreover, the immobilized forms of Pseudomonas sp. C4 and Bacillus sp. B4 achieved a more substantial reduction (75%), lowering the total ammonia concentration from 2 mg/L to 0.5 mg/L within 5-days period. Both nitrifying bacteria not only exhibited ammonia removal capabilities but also demonstrated their proficiency in transforming ammonia into nitrate. Immobilization proved effective in enhancing microbial tolerance to high ammonia concentrations, ultimately leading to improved water quality and the preservation of aquatic animal health.

Decoding Microbial Responses to Ammonia Shock Loads in Biogas Reactors through Metagenomics and Metatranscriptomics.

The presence of elevated ammonia levels is widely recognized as a significant contributor to process inhibition in biogas production, posing a common challenge for biogas plant operators. The present study employed a combination of biochemical, genome-centric metagenomic and metatranscriptomic data to investigate the response of the biogas microbiome to two shock loads induced by single pulses of elevated ammonia concentrations (i.e., 1.5 g NH4+/LR and 5 g NH4+/LR). The analysis revealed a microbial community of high complexity consisting of 364 Metagenome Assembled Genomes (MAGs). The hydrogenotrophic pathway was the primary route for methane production during the entire experiment, confirming its efficiency even at high ammonia concentrations. Additionally, metatranscriptomic analysis uncovered a metabolic shift in the methanogens Methanothrix sp. MA6 and Methanosarcina flavescens MX5, which switched their metabolism from the acetoclastic to the CO2 reduction route during the second shock. Furthermore, multiple genes associated with mechanisms for maintaining osmotic balance in the cell were upregulated, emphasizing the critical role of osmoprotection in the rapid response to the presence of ammonia. Finally, this study offers insights into the transcriptional response of an anaerobic digestion community, specifically focusing on the mechanisms involved in recovering from ammonia-induced stress.

Impaired enzymatic antioxidant defense in erythrocytes of rats with ammonia-induced encephalopathy: role NMDA receptors

Hepatic encephalopathy (HE), a medical term that deals with a neuropsychiatric disorder seen in patients with severe hepatic dysfunction, has been known for more than a century, however, pathogenetic mechanisms underlying cerebral dysfunction during conditions of liver disease are still not entirely understood. There is a consensus that an accumulation of ammonia in brain as a result of impaired detoxification capacity of the liver or the appearance of a portosystemic shunt is a primary cause of HE. Current evidence suggests that ammonia toxicity is mediated by hyperactivation of glutamate receptors, mainly N-methyl-D-aspartate receptors (NMDA-R) and affects many processes of aerobic metabolism that provides energy for a myriad of specific functions and viability of nerve cells. Recent reports on the presence of functional NMDA receptors in erythrocytes and deviations from normal ranges in many blood test parameters that was indicative of impaired hemodynamics and reduced carrying capacity for oxygen in erythrocytes in most patients with HE implicate the relationship between “erythrocyte damage” and cerebral dysfunction. In order to understand how, during hyperammonemia, disturbances in energy metabolism in brain that needs a constant supply of a high level of oxygen in the blood lead to encephalopathy, it is necessary to reveal ammonia-induced disorders in energy metabolism and antioxidant defense system of erythrocytes and explore the potential role of ammonia in reduced brain oxygenation. To detect the said missing link, the activities of erythrocyte antioxidant enzymes and concentrations of GSH, GSSG and H2O2 were measured in animals with hyperammonemia by using MK-801, a powerful noncompetitive NMDA receptor antagonist. It was found that the accumulation of ammonia in the blood of animals with hyperammonemia occurs within rat erythrocytes in large amounts and makes these cells which do not contain enzymes for the removal of ammonia, more susceptible to a prooxidant environment of ammonia created during oxidative stress that was completely or partially inhibited with the help of MK-801. Data obtained provide a support to identification of extra risk factors in cognitive disorders and in the prediction of unfavorable outcome with hypoperfusion in patients with elevated concentrations of ammonia in the blood.

Groundwater nutrient loading into the northern Indian River lagoon: measurements and modeling

The Indian River Lagoon System (IRLS) has been impacted by the surrounding development, leading to excessive nutrient loads that have resulted in frequent and prolonged phytoplankton blooms in the northern reaches. Our study focused on estimating terrestrial groundwater discharge (TGD) and associated nutrient loads by combining field measurements and hydrogeologic modeling at four transects: Eau Gallie (EGT), River Walk (RWT), Banana River (BRT), and Mosquito Lagoon (MLT) across the IRLS. Multiple monitoring stations were installed to collect groundwater and surface water levels, salinity, and nutrient concentrations during 2014-2015. Samples were analyzed for dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP). Numerical modeling was accomplished using SEAWAT to simulate TGD rates, whereas nutrient loads were calculated by multiplying simulated TGD by measured concentrations. TGD rates and nutrient loads were also estimated specifically for the “near-shore zone” along each transect. The effect of recharge from underlying Hawthorn Formation was also evaluated by incorporating estimated recharge rates into the models. Porewater and lagoon water samples showed that ammonium predominated over (NO2+NO3) and PO4 at all sites, resulting in DIN/DIP ratio surpassing the Redfield ratio. Low nitrite/nitrate, coupled with elevated ammonium concentrations at RWT, BRT, and MLT, may be attributed to biogeochemical transformations catalyzed by mangroves and wetlands. Simulated TGD showed mild temporal but significant spatial variation, especially between EGT and RWT compared to BRT and MLT. The highest average TGD of 0.73 and 0.77 m3/d.m occurred at RWT and EGT, respectively, whereas the lowest rates were predicted at BRT and MLT. The highest estimated average DIN loads of 507 and 428 g/yr.m were received at EGT and RWT, respectively, whereas MLT and BRT exhibited lower loads. The DIP loads were remarkably lower than the DIN loads and were significantly different in space and time between sites. Elevated DIN combined with reduced DIP resulted in DIN/DIP exceeding the Redfield ratio, thereby encouraging the blooming of harmful algae. Although the majority of seepage occurs through the near-shore zone, small amounts are received along the entire transect at all sites. The Hawthorn Formation does not contribute significant recharge to the aquifer at the transect locations.

Understanding photochemical adaptations of microalgal ammonium extremophiles to elevated ammonium concentrations in abattoir anaerobic digestate

Identifying microalgal species with outstanding environmental resistance to NH4+ toxicity is critical to developing effective algal-based anaerobic effluent treatment. This is the case for two microalgal NH4+ extremophiles, Chlorella sp. MUR269 and Scenedesmus sp. MUR270 well suited to treat high nitrogen digestates. However, their exact tolerance mechanisms to high NH4+ conditions still need to be understood. A chlorophyll fluorescence approach based on high-throughput pulse amplitude-modulated fluorimetry was used to understand the photochemical adaptations of these species under increasing NH4+ concentrations (0, 100, 200 mgNL−1) derived from abattoir anaerobic digestate. Both species tolerated 200 mgN-NH4+L−1 in the digestate by exhibiting different photochemical mechanisms. Chlorella decreased its PSII primary photochemistry efficiency (Fq′/FM′) and maximum electron transport (rETRmax) immediately after exposure to the treatment conditions. In contrast, Scenedesmus maintained unaltered Fq′/FM′ regardless of NH4+-N concentration, while rETRmax was significantly reduced to a level of Chlorella at 200 mgNL−1. Energy transduction parameters showed Chlorella increased the size of its reaction centre antennae to capture more photons, which increased the trapping flux ratio and maintained efficient dissipation of excess energy. Conversely, Scenedesmus displayed reductions in the absorbed, trapped and dissipated energy fluxes, though its transported flux for photochemical energy production was similar to Chlorella sp. The energetic communication and connectivity between Chlorella PSII units went up by 47 % and 40 % when the NH4+-N level increased from 50 to 100 and N200 mgL−1, respectively, while Scenedesmus exhibited a dose-dependent decrease in the connectivity between its PSII components. The photosynthetic performance index revealed that the overall energetic flux processing efficiency by Scenedesmus was 86 % (50 mgNL−1), 73 % (100 mgNL−1) and 91 % (200 mgNL−1) higher than Chlorella sp. Thus, the two chlorophytes maintained their overall photochemical capacity by simple, economic biological mechanisms involving adjustments of antenna size and energetic communications between PSII neighbour units.

Impaired Enzymatic Antioxidant Defense in Erythrocytes of Rats with Ammonia-Induced Encephalopathy: Role of NMDA Receptors.

Hepatic encephalopathy (HE), a neuropsychiatric disorder developing in patients with severe hepatic dysfunction, has been known for more than a century. However, pathogenetic mechanisms of cerebral dysfunction associated with liver disease are still poorly understood. There is a consensus that the primary cause of HE is accumulation of ammonia in the brain as a result of impaired liver detoxification capacity or the portosystemic shunt. Current evidence suggests that ammonia toxicity is mediated by hyperactivation of glutamate receptors, mainly N-methyl-D-aspartate receptors (NMDARs), and affects brain aerobic metabolism, which provides energy for multiple specific functions and neuronal viability. Recent reports on the presence of functional NMDARs in erythrocytes and the data on the deviations of blood parameters from their normal ranges indicate impaired hemodynamics and reduced oxygen-carrying capacity of erythrocytes in most patients with HE, thus suggesting a relationship between erythrocyte damage and cerebral dysfunction. In order to understand how hyperammonemia (HA)-induced disturbances in the energy metabolism in the brain (which needs a constant supply of large amounts of oxygen in the blood) lead to encephalopathy, it is necessary to reveal ammonia-induced impairments in the energy metabolism and antioxidant defense system of erythrocytes and to explore a potential role of ammonia in reduced brain oxygenation. To identify the said missing link, the activities of antioxidant enzymes and concentrations of reduced glutathione (GSH), oxidized glutathione (GSSG), and H2O2 were measured in the erythrocytes of rats with HA that were injected with the noncompetitive NMDAR antagonist MK-801. We found that in rats with HA, ammonia was accumulated in erythrocytes (cells lacking ammonia removal enzymes), which made them more susceptible to the prooxidant environment created during oxidative stress. This effect was completely or partially inhibited by MK-801. The data obtained might help to identify the risk factors in cognitive disorders and facilitate prediction of unfavorable outcomes of hypoperfusion in patients with a blood elevated ammonia concentration.

The effects of acutely elevated ammonia concentrations on haemolymph parameters in the Mediterranean mussel, Mytilus galloprovincialis

In aquaculture systems, ammonia nitrogen is a major component of waste products arising from the metabolism of cultured organisms and can significantly affect the quality of the rearing environment. The purpose of the current study was to determine modulation of the haemocyte population and selected haemolymph biochemical parameters of the Mediterranean mussel Mytilus galloprovincialis (Lamarck, 1919) exposed to acutely elevated ammonia concentrations.In order to investigate the extent and dynamics of an expected reduction of physiological fitness and survival rate of cultured mussels the stress-on-stress test was conducted combining ammonia and air exposure. The latter test illustrated the extent of reduced mussel physiological fitness and survival rate upon 72 h exposure to 10 and 30 mM NH4Cl in experimental tanks followed by additional exposure to air. Mussels cultured for up to 48 h in experimental tanks comprising 5, 10 and 30 mM NH4Cl, revealed dose and time dependent increase in haemolymph enzyme lactate dehydrogenase levels, urea, and uric acid metabolite levels, as well as the corresponding redistribution in haemocyte population profiles, indicating an inherent response of this organism to ammonia. Finally, a significant negative linear correlation between the mussel hyalinocytes subpopulation and the mean urea levels was observed. The obtained result suggests a possible function of basophilic and acidophilic granulocyte subpopulations in ammonia metabolism leading to urea synthesis by means of surplus ammonium ions are sequestered and extracted from the body. Therefore, defined modulation of the mussel haemocyte population structure may serve as an accurate bioindicator of mussels exposure to acutely elevated ammonia concentrations in environmental and aquaculture biomonitoring studies.

Case report: therapeutic monitoring of vancomycin in an acute liver failure patient with anuria under high-flow continuous hemodiafiltration

BackgroundHigh-flow continuous hemodiafiltration (HF-CHDF) combines diffusive and convective solute removal and is employed for artificial liver adjuvant therapy. However, there is no report on dosage planning of vancomycin (VCM) in patients with acute liver failure under HF-CHDF.Case presentationA 20-year-old woman (154 cm tall, weighing 50 kg) was transferred to the intensive care unit (ICU) with acute liver failure associated with autoimmune liver disease. On the following day, HF-CHDF was started due to elevated plasma ammonia concentration. On ICU day 8, VCM was started for suspected pneumonia and meningitis (30 mg/kg loading dose, then 20 mg/kg every 12 hrs). However, on ICU day 10, VCM blood concentration was under the limit of detection (< 3.0 μg/mL) and the patient developed anuria. The VCM dose was increased to 20 mg/kg every 6 hrs. Calculation with a one-compartment model using the HF-CHDF blood flow rate as a surrogate for VCM clearance, together with hematocrit and protein binding ratio, predicted a trough VCM blood concentration of 15 μg/mL. The observed concentration was about 12 μg/mL. The difference may represent non-HF-CHDF clearance. Finally, living donor liver transplantation was performed.ConclusionWe report an acute liver failure patient with anuria under HF-CHDF in whom VCM administration failed to produce an effective blood concentration, likely due to HF-CHDF-enhanced clearance. VCM dosage adjustment proved successful, and was confirmed by calculation using a one-compartment model.