Oxygen-deficient Conditions Research Articles

Combustion Temperature and Soil Organic Horizons Composition Influence on the PAHs Content (Laboratory Experiment Results)

Fire induced changes in the content and composition of polycyclic aromatic hydrocarbons (PAHs) in organic horizons of the boreal zone soils are considered. Experiment of combustion under oxygen deficient conditions were conducted. The organic horizons of soils as peat (sphagnum oligotrophic) and two types of forests (lichen pine and green-moss spruce) were selected. The PAHs content was determined by high-performance liquid chromatography. It was found that combustion conditions, composition of organic horizons and combustibility significantly affect the content and composition of PAHs. The formation of PAHs occurs to a greater extent at 300°C. Compared with the original samples, the content increases from 2.7 to 9.7 times. Compared with the peak PAHs content (in 300°C) samples, a decrease from 5.8 to 33.0 times is found at 500°C. It is likely that the significant decrease in the content of polycyclic aromatic hydrocarbons is due to the decomposition of substances to simpler ones. The ratio of low molecular to high molecular weight PAHs is indicated. The obtained ratio greater than 1.0 can serve as an indicator of pyrogenic origin of polyarenes.

High-Performance H2S Sensors to Detect SF6 Leakage.

Detecting H2S in oxygen-deficient conditions is vital for identifying leaks in SF6-insulated electrical equipment. Current infrared-based detection methods are expensive and sensitive to environmental conditions, highlighting the necessity for cost-effective and stable gas sensors. Existing gas sensors based on semiconducting metal oxides (SMOXs) are limited by redox reactions with oxygen and require high operating temperatures. Here, we introduce a room-temperature (RT) H2S sensor for oxygen-deficient environments using the intrinsic conducting two-dimensional (2D) metal-organic framework (MOF), Co1.8Ni1.2(hexaiminotriphenylene)2 [Co1.8Ni1.2(HITP)2], overcoming the limitations of SMOX gas sensors. Remarkably, Co1.8Ni1.2(HITP)2 sensors exhibit exceptional selectivity for H2S with negligible cross-responses and a sensitivity drift of less than 4.13% in an SF6 atmosphere over 60 days. The Co1.8Ni1.2(HITP)2 gas sensor shows significant promise for real-time and stable monitoring of H2S gas in oxygen-deficient environments.

Plasma-Enhanced Copper Sulfide/Oxide Electrode for Zinc-Air/Copper Dual Mode Battery

As search for novel electrochemical energy storage systems continues, metal-air batteries are one of the possible solution. Consisting of a metal anode and an air-breathing cathode, by design, they achieve much higher gravimetric energy density in theory. However, s-orbital metals suffer passivation issues and poses safety threats due to their reactivity with air and humidity. As a solution to this issue, safer d-block metals are being studied as an alternative. Zinc air batteries (ZABs) utilizes earth-abundant and cost-effective zinc as its anode, and has high theoretical capacity. At its cathode, oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) occur during charging and discharge processes. Sluggish kinetics of ORR degrades the discharge performance, and is the bottleneck in commercial application of the zinc air battery. Additionally, irreversibility of the cathode reaction results in dissatisfactory retention of battery capacity. Current state-of-the-art noble metal catalysts achieves nearly 80% of the theoretical capacity. However, its cycling stability is severely limited to less than 200 cycles despite low discharge rate applied.Herein, we present a nitrogen plasma-enhanced copper sulfide/oxide catalyst (referred to as N-CuS) that exhibits good catalytic activity for its application as the air-breathing cathode for ZABs. The material is grown directly on metal foam surface using anodization, which is then treated using nitrogen plasma. Anodization creates defect-rich flakes of copper sulfide on the oxide surface, highly increasing surface area and creating the active sites. The material has good electrical conductivity and highly open porous structure that alleviates mass transport issues. Additionally, nitrogen plasma treatment further increases the surface area about 80%, and is expected to introduce nitrogen dopants to the surface, enhancing conductivity of the material. ECSA estimated by measuring Cdl shows that each process increases the ECSA by over 40 times and about 1.8 times, respectively.LSV of CuS and N-CuS half-cells have been performed to measure and compare catalytic performance of the material. N-CuS shows far higher current density and better catalytic activity (35mV less overpotential) than CuS, and higher output voltage is observed with N-CuS cells with the same current density. By assessing the GCPL (potential limited galvanostatic cycling) results, it was concluded that N-CuS requires lower charging voltage and exhibits higher discharge voltages than CuS.The overall performance was evaluated in a stack cell configuration, utilizing thin zinc foil as its anode to minimize mass error. The measured specific capacity of the cell was 789.3 mA·h·g-1, which approximately is 85% of the theoretical specific capacity of zinc-air cells (820 mA·h·g-1). This cell yields gravimetric energy density of about 666 Wh·kg-1. It is notable that these ZAB characteristics are comparable to Pt/C, the state-of-the-art catalyst as of now. N-CuS may be a viable replacement for the Pt/C electrode, resulting in the cost-saving effect. The cycling stability of both N-CuS and Pt/C-based ZAB has been assessed to show that N-CuS-based ZAB has much prolonged (more than twice the cycles) cyclability compared to Pt/C-based ZAB (Fig. S11).Additionally, ZAB constructed using N-CuS can operate in oxygen-deficient environments. As the counter reaction it utilizes redox reaction of copper oxides (Zn-Cu mode) in the substrate when operating in anaerobic conditions. The reduction of divalent and monovalent copper oxides appears as plateaus at 1.1 V and 0.8 V versus the zinc anode during GCPL. Due to this alternate reaction, the cell can operate even at low concentrations of oxygen or even in its absence.DFT calculations have been performed to elucidate the reaction mechanism and the intrinsic catalytic activity of the material, and shows nitrogen dopants improve reactivity of the active sites, thus reducing the overpotential.In summary, we have synthesized N-CuS as the OER/ORR catalyst for ZAB. Through anodization the catalyst was directly grown on the substrate and nitrogen plasma treatment further enhances the catalyst properties to render it higher surface area, conductivity, and better stability. This allows better reversibility in the OER/ORR and results in enhanced cyclability of the overall cell. The constructed RZAB exhibited high specific capacity of 789.3 mA·h·g-1, which, has higher capacity than the analogue using Pt/C catalyst. In addition, N-CuS based RZAB is capable of operating under oxygen-deficient conditions utilizing the metal oxide substrate. This allows the dual mode operation of zinc-air and zinc-copper modes, and results in a more consistent output from the RZAB, as short-term air supply issues could be buffered by this effect. Figure 1

CFD modeling for hydrogen removal by a passive autocatalytic recombiner in oxygen-deficient conditions

This study aims to assess whether a computational fluid dynamics (CFD) approach effectively simulates hydrogen recombination characteristics by a passive autocatalytic recombiners (PAR) under oxygen-rich and lean conditions. Two PAR models were evaluated: one based on hydrogen recombination correlation provided by the manufacturer and another on hydrogen and oxygen mass diffusion rates. In the THAI-1 project, the experiments using an AECL PAR were performed to evaluate hydrogen recombination characteristics under oxygen-rich and lean conditions. In the CFD simulation of the HR18 test where oxygen was in surplus, both models predicted well the recombination rates. However, in simulations of the HR21 test under oxygen-starved conditions, the correlation-based PAR model significantly differed from experimental results. Conversely, the mass diffusion-based PAR model, incorporating oxygen diffusion to the catalytic surface, demonstrated greater accuracy than the correlation-based PAR model even with the recombination efficiency parameter used in the AREVA PAR correlation. These findings highlight the critical role of oxygen diffusion rates to catalytic surfaces in influencing hydrogen recombination rates, particularly in oxygen-starved conditions.

Emission of Intermediate Volatile Organic Compounds from Animal Dung and Coal Combustion and Its Contribution to Secondary Organic Aerosol Formation in Qinghai-Tibet Plateau, China.

Intermediate volatility organic compounds (IVOCs) are important precursors to secondary organic aerosols (SOAs), but they are often neglected in studies concerning SOA formation. This study addresses the significant issue of IVOCs emissions in the Qinghai-Tibetan plateau (QTP), where solid fuels are extensively used under incomplete combustion conditions for residential heating and cooking. Our field measurement data revealed an emission factor of the total IVOCs (EFIVOCs) ranging from 1.56 ± 0.03 to 9.97 ± 3.22 g/kg from various combustion scenarios in QTP. The markedly higher EFIVOCs in QTP than in plain regions can be attributed to oxygen-deficient conditions. IVOCs were dominated by gaseous phase emissions, and the primary contributors of gaseous and particulate phase IVOCs are the unresolved complex mixture and alkanes, respectively. Total IVOCs emissions during the heating and nonheating seasons in QTP were estimated to be 31.7 ± 13.8 and 6.87 ± 0.45 Gg, respectively. The estimated SOA production resulting from combined emissions of IVOCs and VOCs is nearly five times higher than that derived from VOCs alone. Results from this study emphasized the pivotal role of IVOCs emissions in air pollution and provided a foundation for compiling emission inventories related to solid fuel combustion and developing pollution prevention strategies.

Evidence for reversible oxygen ion movement during electrical pulsing: enabler of emerging ferroelectricity in binary oxides

Ferroelectric HfO2-based materials and devices show promising potential for applications in information technology but face challenges with inadequate electrostatic control, degraded reliability, and serious variation in effective oxide thickness scaling. We demonstrate a novel interface-type switching strategy to realize ferroelectric characteristics in atomic-scale amorphous binary oxide films, which are formed in oxygen-deficient conditions by atomic layer deposition at low temperatures. This approach can avoid the shortcomings of reliability degradation and gate leakage increment in scaling polycrystalline doped HfO2-based films. Using theoretical modeling and experimental characterization, we show the following. (1) Emerging ferroelectricity exists in ultrathin oxide systems as a result of microscopic ion migration during the switching process. (2) These ferroelectric binary oxide films are governed by an interface-limited switching mechanism, which can be attributed to oxygen vacancy migration and surface defects related to electron (de)trapping. (3) Transistors featuring ultrathin amorphous dielectrics, used for non-volatile memory applications with an operating voltage reduced to ±1 V, have also been experimentally demonstrated. These findings suggest that this strategy is a promising approach to realizing next-generation complementary metal-oxide semiconductors with scalable ferroelectric materials.

Biogeochemistry of dissolved trace metals in the Bay of Bengal

The pronounced seasonal variation over the Bay of Bengal affects trace metals concentration and distribution. Trace metals distribution in the Bay of Bengal has been best characterized during spring and fall intermonsoon, while limited studies were conducted during the southwest monsoon. This study reports the full-depth profiles of trace metals, including dissolved iron, manganese, lead, cadmium, copper, and zinc (Fe, Mn, Pb, Cd, Cu, and Zn) in the Bay of Bengal (BoB) during southwest monsoon, from July to August 2013. At coastal and ocean scales, transect observations covering the entire water depth provided a comprehensive picture of the circulation and biogeochemical cycles of these elements in seawater during the southwest monsoon. Water samples were obtained from one station in the northeastern Indian Ocean (NR-1) and from three shallow coastal stations with maximum depths <60 m (BA-1, BA-3, and BA-5), as well as from three offshore stations with maximum depths exceeding 2000 m (MY-7, MY-9, and MY-11). In the surface layer (5 m depth), the trace metal concentrations at the shallow near-coastal station BA-5 were higher than those at the ocean station NR-1. Surface trace metal concentrations in offshore regions encompassing stations MY-11, MY-9, and MY-7 were relatively higher than those reported for other seasons in a similar salinity region, indicating seasonal variation associated with freshwater intrusion and coastal-derived input. Below the mixed layer depth, the trace metal/phosphate (P) ratio was higher than that previously reported in the eastern Indian Ocean, suggesting an input from continental margins and mildly reducing sediments, particularly for Fe, Mn, and Cu. Moreover, at intermediate depths (190–800 m), where the North Indian Central Water (NICW) is the main water mass, the Cd/P ratio (0.55 ± 0.11 nmol/μmol) deviated from the global trend (∼0.3 nmol/μmol) owing to oxygen-deficient conditions. Intriguingly, at some stations, specifically MY-9 and MY-7, the intermediate dFe concentrations were relatively higher than those at station NR-1 at the same depth. Continental margin sediment, water mass movement, and ventilation may control the transport of Fe from locations with high Fe concentrations, including near the continental shelf (station MY-11 in this study) and the Andaman Sea.

Importance of the ECM-receptor interaction for adaptive response to hypoxia based on integrated transcription and translation analysis.

Low dissolved oxygen (LO) conditions represent a major environmental challenge to marine life, especially benthic animals. For these organisms, drastic declines in oxygen availability (hypoxic events) can trigger mass mortality events and thus, act as agents of selection influencing the evolution of adaptations. In sea cucumbers, one of the most successful groups of benthic invertebrates, the exposure to hypoxic conditions triggers adaptive adjustments in metabolic rates and behaviour. It is unclear, however, how these adaptive responses are regulated and the genetic mechanisms underpinning them. Here, we addressed this knowledge gap by assessing the genetic regulation (transcription and translation) of hypoxia exposure in the sea cucumber Apostichopus japonicus. Transcriptional and translational gene expression profiles under short- and long-term exposure to low oxygen conditions are tightly associated with extracellular matrix (ECM)-receptor interaction in which laminin and collagen likely have important functions. Finding revealed that genes with a high translational efficiency (TE) had a relatively short upstream open reading frame (uORF) and a high uORF normalized minimal free energy, suggesting that sea cucumbers may respond to hypoxic stress via altered TE. These results provide valuable insights into the regulatory mechanisms that confer adaptive capacity to holothurians to survive oxygen deficiency conditions and may also be used to inform the development of strategies for mitigating the harmful effects of hypoxia on other marine invertebrates facing similar challenges.

Abstract 378: PHD3 dependent stabilization of β3-adrenoceptor induces HIF-1αactivation in Ewing sarcoma

Abstract Hypoxia is a condition of oxygen deficiency which occurs in most growing solid tumors and stimulates a cascade of cell signals through a family of transcription factors named as hypoxia inducible factors (HIFs) that transactivate several regulatory genes involved in tumor proliferation. β3-adrenoceptors (β3-ARs) are involved in several hypoxic scenarios and in pathological conditions where hypoxia leads to important steps for cancer progression. Studies showed that β-AR blockade of mice suppressed hypoxia induction of renal HIF-1α accumulation, erythropoietin production, and erythropoiesis in vivo. In this work we assumed that through PHD3 activity, β3-AR mediates hypoxia sensing needed for HIF-1α stabilization, thus we investigated a putative correlation between β3-AR/HIF-1α and PHD3. Data showed a similar outcome of β3-ARs and HIF-1α at short time of hypoxia, and that β3-AR antagonist, SR59230A reduced HIF-1α protein expression under hypoxia. β3-AR silencing under hypoxia revealed an evident reduction of HIF-1α protein expression that confirmed the β3-AR modulation of HIF-1α expression. SR59230A treatment strongly reduced the HIF-1α target genes as GLUT1, HK-2 and HIF-1α expression at long time treatment confirming the β3-AR modulation of HIF-1α transcriptional activity. Conversely, the HIF-1α-transcriptional inhibitor Topotecan did not affect β3-AR expression confirming that β3-AR mediates HIF-1α activation. Immunofluorescence and nuclear-cytoplasmic fragmentation showed that β3-AR co-localized with the nucleus under hypoxia, more than normoxia, and presence of both β3-AR and HIF-1α in the nucleus. Co-immunoprecipitation of β3-AR/HIF-1α revealed that under hypoxia, HIF-1α dissociates from β3-AR binding, but this process was abrogated by SR59230A. HIF-1α, released under hypoxia from the link with β3-AR, can play its transcriptional activity in the nucleus, while the binding with β3-AR blocks its transcriptional activity. Moreover, the β3-AR upregulation under hypoxia occurs trough an early inhibition of PHD3 activity that did not influence HIF-1α expression. Hypoxic PHD2 inhibition results after PHD3 leading to HIF-1α upregulation. Moreover, the blockade β3-AR by SR59230A, inhibited HIF-1α upregulation by increasing PHD2 activity. Citation Format: Amada Pasha, Laura Zocca, Francesco Carrozzo, Cristina Banella, Rachele Amato, Annalisa Tondo, Claudio Favre, Maura Calvani. PHD3 dependent stabilization of β3-adrenoceptor induces HIF-1αactivation in Ewing sarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 378.

Redirecting the electron flow to coordinate oxidation and reduction reactions for efficient photocatalytic H2O2 production

Energy-efficient photocatalytic production of H2O2 from water holds the potential to replace the anthraquinone process. However, the impracticality of oxygen bubbling in such processes necessitates addressing the H2O2 production in oxygen-deficient environments. Here, we demonstrated the generation of singlet oxygen (1O2) as a highly active water oxidation derivative that redirects the electron flow for H2O2 production in oxygen-deficient environments. Ground-state oxygen was in-situ generated on photocatalysts and undergoes transition to 1O2, surpassing other competitive electron-consuming reactions. Self-generated 1O2 undergoes preferential photo-reduction to H2O2, benefiting from a small activation energy (0.2 eV), facilitated electron trapping rate, adjacent oxidation/reduction sites and suppressed competitive energy transfer from excited-states to air 3O2. A remarkable solar-to-chemical conversion (SCC) efficiency of 0.25 % was obtained for H2O2 generation in oxygen-deficient conditions. This work unveils a novel concept of redirecting electron flow towards H2O2 production, taking advantage of highly active in-situ generated 1O2.

Molecular Mechanism of RNA Polymerase II Transcriptional Mutagenesis by the Epimerizable DNA Lesion, Fapy·dG.

Oxidative DNA lesions cause significant detrimental effects on a living species. Two major DNA lesions resulting from dG oxidation, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-OxodGuo) and formamidopyrimidine (Fapy·dG), are produced from a common chemical intermediate. Fapy·dG is formed in comparable yields under oxygen-deficient conditions. Replicative bypass of Fapy·dG in human cells is more mutagenic than that of 8-OxodGuo. Despite the biological importance of transcriptional mutagenesis, there are no reports of the effects of Fapy·dG on RNA polymerase II (Pol II) activity. Here we perform comprehensive kinetic studies to investigate the impact of Fapy·dG on three key transcriptional fidelity checkpoint steps by Pol II: insertion, extension, and proofreading steps. The ratios of error-free versus error-prone incorporation opposite Fapy·dG are significantly reduced in comparison with undamaged dG. Similarly, Fapy·dG:A mispair is extended with comparable efficiency as that of the error-free, Fapy·dG:C base pair. The α- and β-configurational isomers of Fapy·dG have distinct effects on Pol II insertion and extension. Pol II can preferentially cleave error-prone products by proofreading. To further understand the structural basis of transcription processing of Fapy·dG, five different structures were solved, including Fapy·dG template-loading state (apo), error-free cytidine triphosphate (CTP) binding state (prechemistry), error-prone ATP binding state (prechemistry), error-free Fapy·dG:C product state (postchemistry), and error-prone Fapy·dG:A product state (postchemistry), revealing distinctive nucleotide binding and product states. Taken together, our study provides a comprehensive mechanistic framework for better understanding how Fapy·dG lesions impact transcription and subsequent pathological consequences.

Tracing the geochemical imprints of Maastrichtian black shales in southern Tethys, Egypt: Assessing hydrocarbon source potential and environmental signatures

This study conducted comprehensive bulk and molecular geochemical analyses, as well as elemental investigations, on seventeen black shale samples collected from the Upper Cretaceous sediments on the western margin of the Red Sea. The primary objective is to assess the hydrocarbon generation potential, maturity, source input, biodegradation levels, and depositional environment characteristics within the Lower Maastrichtian interval near the Safaga area. Lower Maastrichtian black shales demonstrate very good to excellent source rock generative potential based on pyrolysis data. The prevalent kerogen type in the older black shale at the Heweitat mine is Type II, whereas within the younger units at the Queih mine, it predominantly exhibits Type II/III kerogen. These Maastrichtian black shales remain thermally immature, as evidenced by vitrinite reflectance (VRr < 0.5%), pyrolysis data, and biomarker proxies.The studied black shales show that the organic matter input comprises bacterial and algal biomass with minor terrigenous contributions. Additionally, there is no evidence of significant biodegradation in the studied samples based on molecular fossils data. Microscopic analysis and various bulk and molecular characteristics, in conjunction with major and trace element profiles, collectively indicate a marine depositional environment with oxygen-deficient bottom water conditions during source rock deposition. The presence of isorenieratene and aryl isoprenoids suggests persistent and episodic photic zone anoxia during the Maastrichtian period. Elevated nutrient inputs and paleobioproductivity were recorded in the older black shale at the Heweitat mine compared to the younger one at the Queih mine. Paleoproductivity and oxygen depletion emerge as pivotal factors influencing the accumulation and preservation of organic matter within the black shales. These findings provide valuable insights into the environmental conditions prevailing during the deposition of Maastrichtian sediments in the Eastern Desert.

Methylomonadaceae was the active and dominant methanotroph in Tibet lake sediments.

Methane (CH4), an important greenhouse gas, significantly impacts the local and global climate. Our study focused on the composition and activity of methanotrophs residing in the lakes on the Tibetan Plateau, a hotspot for climate change research. Based on the field survey, the family Methylomonadaceae had a much higher relative abundance in freshwater lakes than in brackish and saline lakes, accounting for ~92% of total aerobic methanotrophs. Using the microcosm sediment incubation with 13CH4 followed by high throughput sequencing and metagenomic analysis, we further demonstrated that the family Methylomonadaceae was actively oxidizing CH4. Moreover, various methylotrophs, such as the genera Methylotenera and Methylophilus, were detected in the 13C-labeled DNAs, which suggested their participation in CH4-carbon sequential assimilation. The presence of CH4 metabolism, such as the tetrahydromethanopterin and the ribulose monophosphate pathways, was identified in the metagenome-assembled genomes of the family Methylomonadaceae. Furthermore, they had the potential to adapt to oxygen-deficient conditions and utilize multiple electron acceptors, such as metal oxides (Fe3+), nitrate, and nitrite, for survival in the Tibet lakes. Our findings highlighted the predominance of Methylomonadaceae and the associated microbes as active CH4 consumers, potentially regulating the CH4 emissions in the Tibet freshwater lakes. These insights contributed to understanding the plateau carbon cycle and emphasized the significance of methanotrophs in mitigating climate change.

Metals and biogenic substances’ migration ability in the «bottom sediments – water» system under natural and experimental conditions

&#x0D; &#x0D; &#x0D; The paper considers the results of long-term studies on some chemical elements’ migration (Al, Fe, Ti, Mn, Cu, Zn, Pb, N, P, Si) in the «bottom sediments – water» system of surface water bodies under the effect of different aquatic environment factors. The greatest effect is made by water bodies’ oxygen regime, pH, and presence of dissolved organic substances, in particular humic substances. The migration of manganese, iron, inorganic nitrogen and phosphorus from bottom sediments is controlled mostly by oxygen regime. Migration of these chemical elements significantly increases, when there is oxygen deficiency and anaerobic conditions are formed in the bottom water layer. It has been observed in both natural and experimental conditions. Man- ganese concentration increases in bottom water in 25–50 times, iron – in 1.3–13, inorganic nitrogen – in 5.3–19.3, and inorganic phosphorus – in 2.8–23 times. The dissolved oxygen concentration hardly has any effect on the migration of aluminium, titanium, copper, zinc, lead, and silicon from bottom sediments into the water. The chemical elements’ migration is significantly affected by a decrease in pH of water contacting with bottom sediments and the presence of humic substances in it. High humic substances concentrations promote a reduction in water pH and oxygen content, which is consumed for their oxidation. A case study of several water bodies illustrates the cumulative effect of water pH lowering, anaerobic conditions at the solid and liquid phases’ interface, as well as complexation with humic substances on chemical elements’ migration from bottom sediments. Experimental modeling has shown that the metal migration from bottom sediments occurs both due to their labile fractions and complex compounds with dissolved organic matter, especially with humic substances of low molecular weight (≤2.0 kDa). The share of the metal labile fraction gets higher, when water pH decreases. Under recent climate change, the probability of water’s secondary pollution with different chemicals increases significantly in summer. This is mainly caused by oxygen deficiency, water pH lowering, and reducing conditions at the «bottom sediments – water» interface with hydrogen sulphide being formed. This is especially true for highly eutrophic water bodies subject to human impact. The aquatic environment toxicity can get considerably higher due to the migration of chemicals with strong toxic properties from bottom sediments, as well as labile metal fractions, marked by higher bioavailability for hydrobionts.&#x0D; &#x0D; &#x0D;

Centella asiatica extract ameliorates deoxygenation-induced neurological dysfunction in zebrafish larvae

Background: Oxygen deprivation (OD) is a critical condition that can lead to brain damage and even death. Current hypoxia management approaches are limited in effectiveness. Centella asiatica, known for its neuroprotective properties, offers a potential alternative for OD treatment. Aim: This study aims to investigate the neuroprotective effects of Centella asiatica (CA) on the expression of Brain-Derived Neurotrophic Factor (BDNF) and Vesicular Glutamate Transporter 1 (VGLUT1) in zebrafish larvae under oxygen-deficient conditions. Methods: Zebrafish embryos were subjected to low oxygen levels (1.5 mg/L) 0-2 hours post-fertilization (hpf) until three days post-fertilization (dpf), simulating the early stages of OD. Subsequent treatment involved varying concentrations of CA (1.25-5 µg/ml) up to nine days post-fertilization. The expression levels of BDNF and VGLUT1 were measured using PCR methods. Statistical analysis was conducted using Two-way ANOVA to evaluate the impact of CA on the expression of BDNF and VGLUT1 in zebrafish larvae aged 3 and 9 dpf in oxygen-deprived conditions. Results: CA significantly influenced the expression of BDNF and VGLUT1 under oxygen deprivation (p&lt;0.001). An increase in BDNF expression (p&lt;0.001) and a decrease in VGLUT1 (p&lt;0.01) were observed in zebrafish larvae experiencing OD and treated with CA. There was no significant difference in BDNF and VGLUT1 expression across age variations in zebrafish larvae at 3 dpf and 9 dpf in the treatment groups (p&gt;0.05). CA concentration of 2.5 µg/ml effectively enhanced BDNF and reduced VGLUT1 in 3-9 dpf zebrafish larvae. Conclusion: CA demonstrates potential as a neuroprotective agent, modulating increased BDNF expression and reduced VGLUT1 under OD conditions. These findings lay a foundation for further research in developing therapies for oxygen deficiency.

Thin layer chromatography of plant phospholipids of Zea mays (L.) un-der the action of the phytohormone kinetin in different aeration condi-tions

Under extreme weather conditions, crops are exposed to excess rainfall, causing the acute oxygen starvation of plants. The treatment of plants with phytohormones started in order to increase plant resistance to stresses. Using thin layer chromatography, the effect of the phytohormone kinetin on the content of plant phospholipids was studied under different aeration conditions. A kinetin solution (10 mg l-1) was injected into the etiolated maize seedlings separated from the roots by the suction method with a transpiration current and seedlings were transferred to aeration conditions, hypoxia or carbon dioxide (9 hours). Control plants were not treated with kinetin. Samples were fixed with boiling isopropanol and extracted with a hexane:isopropanol mixture (3:2). After purification from non-lipid impurities, lipids were evaporated and dissolved in chloroform. Phospholipids were isolated on silica gel W plates and further separated into classes on silica gel 60G plates. (“Merk”, Germany). It was found that the content of total phospholipids in maize seedlings decreased to 84.9% under hypoxic conditions and to 54.5% in CO2. If plants were pre-treated with kinetin, the content of total phospholipids practically did not change (96.2%), and in CO2 it increased to 88.5%. When plants were treated with kinetin under aeration conditions, the content of phosphatidylcholine (PC), phosphatidylserine (PS) and phosphatilylethanolamium (PEA) increased, and phosphatidylglycerol (PG) decreased by almost 40%. Under conditions of oxygen deficiency, changes in the composition of phospholipids were different. The content of PS and PC in seedlings increased by1.5-2.0 times, and the content of PG and PEA decreased to 27.2% and 20.0% of the control. Treatment of maize seedlings with kinetin reduced the effect of gaseous media on the content of all analysed classes of phospholipids in plants, this was especially evident in CO2. Thus, it can be considered proven that the protective effect of kinetin is realized due to the ability of this phytohormone to maintain the optimal content and ratio of phospholipid components characteristic of a given tissue in plants exposed to various unfavourable environmental factors, including oxygen deficiency and high concentrations of carbon dioxide.

Chemo- and bio-stratigraphic constraints on Cretaceous-Paleocene biotic turnover in the southern Tethys low-oxygen margin, Egypt

The late Cretaceous-Danian (K-Pg) organic-rich sequence is a global archive that witnessed abrupt paleo-condition changes during a high sea-level. In Egypt, this sequence is present in the Duwi and Dakhla formations as an E-W belt from the Red Sea to the Western Desert. We analyzed elemental and isotopic distributions in an age-constrained core from the Quseir area to understand paleoclimatic and paleoenvironmental factors influencing its deposition. Calcareous nannofossil and the chemical index of alteration (CIA) confirm a global cooling trend during the late Cretaceous, with two warming episodes indicating early phases of the Deccan volcanism. The Danian stage experienced a warm climate and intense chemical weathering. Mo-U enrichment factors covariation suggest deposition under oxygen-deficient conditions with evident watermass restrictions. High-productivity-indicating taxa were more abundant in Danian strata than in late Cretaceous strata, consistent with organic carbon characteristics. The δ13COrg-δ15N data show temporal heterogeneity due to organic matter type, redox conditions, preservation, stratigraphic condensation, and recycling of isotopically-light CO2. The negative δ13COrg shift around the K-Pg transition is globally correlative. Dynamic pyrite δ34S distribution resulted from variation in riverine influx, degree of pore-water openness, sulfate reduction rate, and diagenetic disproportionation of sulfur intermediates. Generally, radiogenic 187Os/188Os values were observed that were seemingly influenced by continental weathering and subsequent runoff influx of 187Os/188Os under a greenhouse climate. A positive 187Os/188Os shift to 3.68 (187Os/188Osi of 0.74) occurred at the onset of the Dakhla organic-rich spike. However, without a precise correlative stratigraphic framework, a global or regional seawater isotopic shift cannot be confirmed. We suggest that temporal variations in organic matter composition, redox, watermass conditions, and isotope fractionation of the K-Pg sequence in the study area were driven by discrepancies in climate, sea-level, and tectonic uplift. Further integrated approaches are needed to explore the geospheric drivers of this organic-rich sequence in time-equivalent sections.

Load of nutrients and organic substances of the Don River basin (Severskyi Donets sub-basin)

Formulation of the problem. The main danger of organic substances is the use of large amounts of oxygen for its oxidation. As a result, there are conditions of oxygen deficiency in polluted water sometimes to the formation of hypoxia. It leads to significant violations of biological groups and the death of certain species. The increase of nutrients leads to the uncontrolled development of higher aquatic plants and algae. It caused to undesirable imbalance of organisms in the water body and to decrease in water quality. So, control over the content of nutrients and organic substances in water is one of the important factors to ensure the proper functioning of aquatic ecosystems and maintain water quality. The Severskiy Donets river basin is a quite difficult water object with a variety of natural conditions. Water resources of the Severskyi Donets River serve to provide drinking and industrial water supply, agricultural needs and recreation function. Aim of the research is to determine the peculiarities of loading rivers of the Severskyi Donets basin with nutrients and organic substances. Methods. For the purpose of research, the state register 2TP-Vodhosp was used. It contains information about removal of pollutants from utilities and industrial enterprises. Statistical data about the number of population and settlements, distribution by the territory of the basin were borrowed from the database of the State Statistics Service of Ukraine and the Institute of Demography and Social Research. Scientific novelty of the work is that for the first time the loading of nutrients and organic substances for all first-order tributaries in the Severskyi Donets basin was calculated. Practical value. Analys of the main anthropogenic loads in the Severskyi Donets river basin and their impacts can be used for composition of the River Basin Management Plan as an important component. It may serve as a basis for the development of measures for surface water bodies and the river basin as a whole in order to achieve defined environmental goals. Results. The main load of nutrients and organic compounds is caused by cities with a population equivalent (PE) more than 100 thousand people. The rivers of the Uda sub-basin are the most polluted by these compounds (as a part of municipal sewage) mainly due to the influence of Kharkiv city. The amount of organic matter that enters with the industrial wastewater is also the largest for the Uda sub-basin. Among the industrial enterprises within the Severskyi Donets basin, the largest number of nutrients was diverted by PJSC NKMZ in Kramatorsk city to the rivers of the Kazenny Torets sub-basin and PJSC Severodonetsk Association "Azot" directly to the Severskyi Donets River. The main role in organic pollution from the rural population is played by 5 sub-basins: Velyka Kamyanka, Kazenny Torets, Severskyi Donets, Udy, Aidar. In general, they form 59% of the total organic substances load. The largest inflow of nitrogen and phosphorus compounds is observed to the sub-basins of the rivers Luhan, Kazennyi Torets, Udy, Aidar, Oskol and the Severskyi Donets.

Histological and cytochemical analysis of the brain under conditions of hypobaric hypoxia-induced oxygen deficiency in albino rats

High altitude sickness is a life-threatening disease that occurs among acclimatized individuals working or living at a high altitude accompanied by hypobaric hypoxia exposure. The prolonged influence of hypobaric hypoxia on the brain may trigger neuronal damage and cell death due to an oxygen deficiency. The purpose of the current study was to investigate the histomorphological changes in the hippocampus, cerebral cortex, cerebellar cortex, and striatum of the rat’s brain following chronic hypobaric hypoxia. Fourteen albino rats were used for this investigation. The animals were exposed to chronic hypobaric hypoxia in the special decompression chamber at an altitude of 7000 m for 7 days. The histological analysis was conducted via toluidine staining and silver impregnation. DNA damage and cell apoptosis were assessed via Feulgen staining. The histochemical assessment revealed increased dark neurons in the hippocampus with cell swelling. Silver impregnation showed increased argyrophilic neurons in the cerebellar cortex, striatum, CA1 subfield of the hippocampus, and cerebral cortex. The cytochemical analysis determined the increased apoptotic cells with hyperchromatic condensation and pyknosis in the hippocampus subfields and cerebral cortex. In addition, it has been observed that hypoxia has resulted in small hemorrhages and perivascular edema within the cerebellar and cerebral cortex.The results indicate brain injury observed in the various parts of the brain towards hypobaric hypoxia, however, the hippocampus showed greater vulnerability against hypoxic exposure in comparison to the striatum, cerebellum, and cerebral cortex. These changes support our insights regarding brain intolerance under conditions of hypoxia-induced oxygen deficiency and its histomorphological manifestations.

THE CATALYTIC PROPERTIES OF LACTATE DEHYDROGENASE IN SKELETAL MUSCLES AND LIVER OF THE MARSH FROG (PELOPHYLAX RIDIBUNDUS) DEPEND ON ITS ECOLOGICAL AND GEOGRAPHICAL LOCATION

The marsh frog (Pelophylax ridibundus) has a widespread distribution range, which is due to a variety of adaptations that contribute to the development of tolerance to a wide range of physicochemical environmental factors. Of particular interest are the adaptations of these animals to different levels of oxygen in mid- and high-altitude conditions. In this work, a comparative analysis of the kinetic parameters of lactate dehydrogenase (LDH) in the liver of marsh frogs living in the mountainous and lowland regions of Dagestan was carried out. Animals caught in their habitats were decapitated, the liver and calf muscles were isolated, and they were placed in liquid nitrogen. In the laboratory, the selected tissues were homogenized and mitochondria-free cytosol was obtained by differential centrifugation, in which LDH activity was determined. It was found that LDH activity is significantly higher in the tissues of frogs from mountainous regions: by 42.4% in the muscles and 2.38 times in the liver (p 0.05). The high efficiency of catalysis is ensured due to significant changes in the catalytic parameters of the enzyme: an increase in Vmax (50.9% in muscles and 70% in the liver (p 0.05)) and a decrease in Km. (45.9% in muscles and 69% in liver, (p 0.05)). A more pronounced difference, compared to muscles, between LDH activity in the liver of foothill and lowland populations of frogs suggests that the sensitivity of liver LDH to changes in oxygen tension is higher. The vector of a number of other kinetic parameters of LDH (Ki, Sopt, Δ) in the liver of animals from mountainous landscapes is absolutely opposite to that of skeletal muscles. High activity and modifications of the catalytic properties of LDH in the tissues of marsh frogs living in mid-mountain areas may play an important role in the adaptation of these animals to conditions of oxygen deficiency.