Exogenous Nitrate Research Articles

The acute effects of dietary nitrate supplementation on postmenopausal endothelial resistance to ischemia reperfusion injury: a randomized, placebo-controlled, double blind, crossover clinical trial.

Postmenopausal cardiovascular health is a critical determinant of longevity. Consumption of beetroot juice (BR) and other nitrate-rich foods is a safe, effective non-pharmaceutical intervention to increase systemic bioavailability of the vasoprotective molecule, nitric oxide, through the exogenous nitrate (NO3 -)-nitrite (NO2 -)-nitric oxide (NO) pathway. We hypothesized that a single dose of nitrate-rich beetroot juice (BRnitrate 600 mg NO3 -/140 mL, BRplacebo ∼ 0 mg/140 mL) would improve resting endothelial function and resistance to ischemia-reperfusion (IR) injury to a greater extent in early-postmenopausal (1-6 years following their final menstrual period (FMP), n=12) compared to late-postmenopausal (6+years after FMP, n=12) women. Analyses with general linear models revealed a significant (p<0.05) time*treatment interaction effect for brachial artery adjusted flow-mediated dilation (FMD). Pairwise comparisons revealed that adjusted FMD was significantly lower following IR-injury in comparison to all other time points with BRplacebo (early FMD 2.51±1.18%, late FMD 1.30±1.10, p<0.001) and was lower than post-IR with BRnitrate (early FMD 3.84±1.21%, late FMD 3.21±1.13%, p=0.014). A single dose of BRnitrate significantly increased resting macrovascular function in the late postmenopausal group only (p=0.005). Considering the postmenopausal stage-dependent variations in endothelial responsiveness to dietary nitrate, we predict differing mechanisms underpin macrovascular protection against IR injury.

Inflammation-induced sialin mediates nitrate efflux in dysfunctional endothelium affecting NO bioavailability

AimThe mechanism of NO bioavailability in endothelial dysfunction, the trigger for atherogenesis is still unclear as exogenous nitrate therapy fails to alleviate endothelial dysfunction. Recently, sialin, a nitrate transporter, has been linked to affect tissue nitrate/nitrite levels. Hence, we investigated the role of sialin in NO bioavailability in endothelial dysfunction. MethodsSerum-starved HUVECs were stimulated with either TNFα or AT-2 for 24 h either alone or in the presence of autophagy inducer or autophagy inhibitor alone. Nitric oxide, nitrite, and nitrate levels were measured in cell supernatant and cell lysate. Quantitative real-time PCR, Annexin V-PI, and monocyte adhesion assays were performed. Immunofluorescence staining for sialin, vWF, and LC3 was performed. STRING database was used to create protein interacting partners for sialin. ResultsSialin is strongly expressed in activated EC in vitro and atherosclerotic plaque as well as tumor neo-vessel ECs. Sialin mediates nitrate ion efflux and is negatively regulated by autophagy via mTOR pathway. Blocking sialin enhances NO bioavailability, autophagy, cell survival, and eNOS expression while decreasing monocyte adhesion. PPI shows LGALS8 to directly interact with sialin and regulate autophagy, cell-cell adhesion, and apoptosis. ConclusionSialin is a potential novel therapeutic target for treating endothelial dysfunction in atherosclerosis and cancer.

Response of microbial communities to exogenous nitrate nitrogen input in black and odorous sediment

Since nitrate nitrogen (NO3−-N) input has proved an effective approach for the treatment of black and odorous river waterbody, it was controversial whether the total nitrogen concentration standard should be raised when the effluent from the sewage treatment plant is discharged into the polluted river. To reveal the effect of exogenous nitrate (NO3−-N) on black odorous waterbody, sediments with different features from contaminated rivers were collected, and the changes of physical and chemical characteristics and microbial community structure in sediments before and after the addition of exogenous NO3−-N were investigated. The results showed that after the input of NO3−-N, reducing substances such as acid volatile sulfide (AVS) in the sediment decreased by 80 % on average, ferrous (Fe2+) decreased by 50 %, yet the changing trend of ammonia nitrogen (NH4+-N) in some sediment samples increased while others decreased. High-throughput sequencing results showed that the abundance of Thiobacillus at most sites increased significantly, becoming the dominant genus in the sediment, and the abundance of functional genes in the metabolome increased, such as soxA, soxX, soxY, soxZ. Network analysis showed that sediment microorganisms evolved from a single sulfur oxidation ecological function to diverse ecological functions, such as nitrogen cycle nirB, nirD, nirK, nosZ, and aerobic decomposition. In summary, inputting an appropriate amount of exogenous NO3−-N is beneficial for restoring and maintaining the oxidation states of river sediment ecosystems.

N-methyl pyrrolidone manufacturing wastewater as the electron donor for denitrification: From bench to pilot scale

Actual wastewater generated from N-methylpyrrolidone (NMP) manufacture was used as electron donor for tertiary denitrification. The organic components of NMP wastewater were mainly NMP and monomethylamine (CH3NH2), and their biodegradation released ammonium that was nitrified to nitrate that also had to be denitrified. Bench-scale experiments documented that alternating denitrification and nitrification realized effective total‑nitrogen removal. Ammonium released from NMP was nitrified in the aerobic reactor and then denitrified when actual NMP wastewater was used as the electron donor for endogenous and exogenous nitrate. Whereas TN and NMP removals occurred in the denitrification step, dissolved organic carbon (DOC) and CH3NH2 removals occurred in the denitrification and nitrification stages. The genera Thauera and Paracoccus were important for NMP biodegradation and denitrification in the denitrification reactor; in the nitrification stage, Amaricoccus and Sphingobium played key roles for biodegrading intermediates of NMP, while Nitrospira was responsible for NH4+ oxidation to NO3−. Pilot-scale demonstration was achieved in a two-stage vertical baffled bioreactor (VBBR) in which total‑nitrogen removal was realized sequential anoxic-oxic treatment without biomass recycle. Although the bench-scale reactors and the VBBR had different configurations, both effectively removed total nitrogen through the same mechanisms. Thus, an N-containing organic compound in an industrial wastewater could be used to drive total-N removal in a tertiary-treatment scenario.

Smoking and salivary microbiota: a cross-sectional analysis of an Italian alpine population

The oral microbiota plays an important role in the exogenous nitrate reduction pathway and is associated with heart and periodontal disease and cigarette smoking. We describe smoking-related changes in oral microbiota composition and resulting potential metabolic pathway changes that may explain smoking-related changes in disease risk. We analyzed health information and salivary microbiota composition among 1601 Cooperative Health Research in South Tyrol participants collected 2017–2018. Salivary microbiota taxa were assigned from amplicon sequences of the 16S-V4 rRNA and used to describe microbiota composition and predict metabolic pathways. Aerobic taxa relative abundance decreased with daily smoking intensity and increased with years since cessation, as did inferred nitrate reduction. Former smokers tended to be more similar to Never smokers than to Current smokers, especially those who had quit for longer than 5 years. Cigarette smoking has a consistent, generalizable association on oral microbiota composition and predicted metabolic pathways, some of which associate in a dose-dependent fashion. Smokers who quit for longer than 5 years tend to have salivary microbiota profiles comparable to never smokers.

The influence of different nitrate concentrations on aerobic sludge granulation and the role of extracellular polymeric substances

This study investigated the influence of nitrate on aerobic granular sludge (AGS) granulation. The introduction of nitrate at 5, 15 and 20 mg L−1 promoted AGS granulation, and the promoting effect was positively correlated with nitrate concentrations. Meanwhile, exogenous nitrate significantly increased denitrification rate in the AGS system. However, granular disintegration appeared at a long-term addition of nitrate. An in-deep analysis showed that nitrate stimulated the secretion of extracellular polymeric substances (EPS), especially the content of proteins, which might be the main reason for the AGS granulation. However, the rapid and excessive increase in EPS might cause granular disintegration, as excessive EPS blocked the transmission of substrates, leading to the increase of dead cells in the granules. Besides, nitrate also altered the hydrophobicity of EPS and the content of α-helix, 3-turned helix and polymeric chain that favored aggregation, which also affected AGS granulation. From the microbial community level, nitrate induced the enrichment of denitrifying bacteria, including those that also functioned as EPS producers, such as Micropruina and Flavobacterium, resulting in the rapid increase of functional enzymes associated with amino acid synthesis, thereby promoting the secretion of proteins in EPS. Conversely, disintegration caused by mass transfer blockage might lead to the loss of EPS producing bacteria and subsequent decrease in EPS content, further accelerating granular disintegration.

Nitrate reductase regulation in wheat seedlings by exogenous nitrate: A possible role in tolerance to salt stress

AbstractBackgroundSoil salinity is a major abiotic stress causing severe damage to plants. Thus, proper management approaches need to be developed to lessen the detrimental effect of salinity on crop growth and productivity.AimsThis study was conducted to investigate the putative role of nitrate (NO3−) and nitrate reductase (NR) in mitigating the adverse effects of salt stress on the growth of durum wheat seedlings.MethodsNitrogen nutrition has been modified, in the presence of 100 mM NaCl, either by increasing the NO3− availability, the deprivation of NO3− or by the addition of sodium tungstate—an inhibitor of NR—in the culture medium.ResultsObtained results showed that, in the presence of 2.5 mM NO3−, salt stress significantly decreased all studied growth traits (biomass production, relative growth rate, and water content). This was associated with a noteworthy reduction in total chlorophyll pigment, total carbohydrates, and protein contents. Concomitantly, NR activity was remarkably decreased. However, proline and malondialdehyde (MDA) were significantly accumulated. In the absence of NO3− as well as in the presence of tungstate, NR activities were noticeably reduced, and wheat seedling growth was further disturbed in comparison to salt‐stressed seedlings grown under 2.5 mM NO3−. Increasing the NO3− availability to 7.5 mM significantly restricted Cl− uptake, markedly increased root and leaf NR activities, and alleviated salt stress–induced seedling growth inhibition as compared to salt‐stressed seedlings grown under 2.5 mM NO3−. Such effects were associated with an increase in leaf chlorophyll and protein concentrations and in root and leaf carbohydrate concentrations. Nevertheless, MDA concentrations were sharply decreased.ConclusionsThis study provides strong arguments highlighting the potential role of NO3− reduction in mitigating the adverse effects of salt stress on the growth of wheat plants at the early seedling stage. The enhancement of the NR activity through increasing the NO3− availability may, therefore, represent a potential strategy to overcome the salinity‐mediated impairment of wheat seedlings to some extent.

Refining the role of nitrogen mineralization in mycorrhizal nutrient syndromes

Forest stands dominated by ectomycorrhizal (ECM) associated trees often have more closed nitrogen (N) cycling than stands dominated by arbuscular mycorrhizal (AM) associated trees, with slower N mineralization in ECM stands thought to suppress inorganic N cycling. However, most estimates of N mineralization come from measurements of net processes, which can lead to an incomplete view of ecosystem N retention and loss. To explore the mechanisms driving mycorrhizal N cycling syndromes, we measured gross N production and assimilation rates and net and potential N flux rates in paired N addition (from NH4SO4 and NaNO3) and control plots within ECM and AM-dominated stands. We observed greater gross N mineralization and microbial ammonium assimilation in ECM compared to AM stands, suggesting that increased microbial N demand drove lower net N mineralization rates in ECM stands. We found lower nitrification rates in ECM compared to AM stands and no effect of N addition on nitrification in ECM stands. Therefore, the low soil pH or high C:N ratios found in those stands, not limited ammonium supply, may have suppressed nitrification. Finally, potential denitrification rates and nitrous oxide fluxes were lower in ECM compared to AM stands with no effect of N addition, suggesting that denitrification is controlled by the endogenous supply of nitrate from nitrification, not exogenous nitrate inputs. Overall, we conclude that N mineralization may not play a central role in forming mycorrhizal nutrient syndromes, and that acidic conditions in ECM stands may ultimately control nitrification and the potential for ecosystem N loss.

Insight into the effect of nitrate on AGS granulation: Granular characteristics, microbial community and metabolomics response

As a promising wastewater treatment technology, aerobic granular sludge (AGS) process is still hindered by slow granule formation and easy disintegration in the application. While nitrate, one of the target pollutants in wastewater, showed a potential effect on AGS granulation process. Herein, this study attempted to reveal the role of nitrate in AGS granulation. By adding exogenous nitrate (10 mg L−1), the AGS formation was markedly improved and accomplished at 63 d, while the control group achieved AGS formation at 87 d. However, a disintegration was observed under a long-term nitrate feeding. A positive correlation was observed among granule size, extracellular polymeric substances (EPS) and intracellular c-di-GMP level in both formation and disintegration phases. The subsequent static biofilm assays indicated that nitrate might upregulate c-di-GMP via denitrification-derived NO, and c-di-GMP further upregulated EPS, thereby promoting AGS formation. However, excessive NO probably caused disintegration by downregulating c-di-GMP and EPS. Microbial community showed that nitrate favored the enrichment of denitrifiers and EPS producing microbes, which were responsible for the regulation of NO, c-di-GMP and EPS. Metabolomics analysis showed that amino acid metabolism was the most affected metabolism by nitrate. Some amino acids, such as Arg, His and Asp, were upregulated in the granule formation phase and downregulated in the disintegration phase, indicating the potential contribution to EPS biosynthesis. This study provides metabolic insight into how nitrate promotes/inhibits granulation, which may contribute to unwrapping the mystery of granulation and overcoming the limitations of AGS application.

Administration of Nitrates After Spontaneous Delivery in Rheumatic Heart Disease

Introduction: Heart disease is one of the most common causes of maternal death. The incidence has increased since women with congenital and acquired heart disease reached fertile age. The circulation system changes during pregnancy which are induced by changes in the progesterone. The changes in progesterone levels increase heart work and cause death in pregnant women. Objective: This report aims to elaborate on the administration of nitrates as the management of labor in rheumatic heart disease (RHD). Case Report: A 27-year-old woman complained of shortness of breath and wanted to give birth. The patient was 38 weeks pregnant and had a history of heart disease. Antero-posterior chest radiography examination showed pulmonary edema and cardiomegaly. The patient was examined using echocardiography before spontaneous labor and was diagnosed as pregnant with rheumatic heart disease. As an emergency management, the patient was given painless spontaneous labor. The patient was given nitrates on the first day after delivery as a treatment for progesterone withdrawal syndrome in this case. After the delivery process was completed, the patient was admitted to the Intensive Care Unit (ICU). Discussion: Progesterone hormone produced by the corpus luteum and the placenta until the eighth week of pregnancy and before delivery, respectively, can reduce systemic vascular resistance. Progesterone hormone increase causes peripheral vasodilation by affecting the function of endothelial nitric oxide synthase (eNOS) and nitrite oxide (NO) production. Conclusion: A pregnant woman with rheumatic heart disease can be given exogenous nitrate. Administration of exogenous nitrates in this patient successfully prevent the reduction of peripheral vascular resistance and postpartum hemodynamic instability because it can replace the reduction in nitric oxide caused by progesterone withdrawal.

Transcriptional Regulation of zma-MIR528a by Action of Nitrate and Auxin in Maize.

In recent years, miR528, a monocot-specific miRNA, has been assigned multifaceted roles during development and stress response in several plant species. However, the transcription regulation and the molecular mechanisms controlling MIR528 expression in maize are still poorly explored. Here we analyzed the zma-MIR528a promoter region and found conserved transcription factor binding sites related to diverse signaling pathways, including the nitrate (TGA1/4) and auxin (AuxRE) response networks. Accumulation of both pre-miR528a and mature miR528 was up-regulated by exogenous nitrate and auxin treatments during imbibition, germination, and maize seedling establishment. Functional promoter analyses demonstrated that TGA1/4 and AuxRE sites are required for transcriptional induction by both stimuli. Overall, our findings of the nitrogen- and auxin-induced zma-MIR528a expression through cis-regulatory elements in its promoter contribute to the knowledge of miR528 regulome.

Nitrogen Application Alleviates the Adverse Effects of Defoliation Stress on Lolium perenne L. by Enhancing the Antioxidant System and Promoting Photosynthesis

Perennial grasses undergo compensatory growth after defoliation. Nitrate is the main nitrogen source for the growth of perennial ryegrass and plays a significant role in plant resistance to stress. The aim of the study was to understand the physiological mechanism of ryegrass in response to defoliation stress under different nitrate supplies and to explore possible ways to alleviate defoliation stress. We performed pot experiments where 12-week-old ryegrass plants grown in low (0.05 mM KNO3) or moderate nitrate (5 mM KNO3) conditions were defoliated and subsequently supplied with different concentrations of nitrate following defoliation treatments. During the regrowth stage, the regrowth rate, biomass, photosynthetic parameters, and the response of the antioxidant system to low or moderate nitrate supply of ryegrass were investigated. The results showed that moderate nitrate supply after defoliation increased the content of photosynthetic pigments in ryegrass and improved its photosynthetic efficiency. In addition, adding moderate nitrate after defoliation increased the activity of antioxidant enzymes and the accumulation of osmotic regulating substances, thereby enhancing plant resistance, effectively reducing the damage to plants caused by defoliation stress, and promoting plant regrowth, especially for plants grown in a low nitrate environment before defoliation. Therefore, this study showed that the addition of exogenous nitrate could counteract some of the adverse effects of defoliation stress on the growth and development of ryegrass.

Insights into integration of polyhydroxyalkanoates (PHAs) production into wastewater treatment: Comparison of different electron acceptors on system function and PHA-producer enrichment

Mixed microbial culture polyhydroxyalkanoates (MMC PHA) process combined with mainstream wastewater treatment is a competitive resource recovery integrated process in which economical non-oxygen electron acceptors can be used to enrich PHA-producer and reduce operating costs. Oxygen and three non-oxygen electron acceptors (endogenous nitrate, exogenous nitrate, and nitrite) were used and comprehensively compared in terms of PHA production ability and microbial community ecophysiology in this study. The results showed that the PHA production ability with exogenous nitrate was comparable to that of oxygen, which had a maximum PHA content of 64.0 wt% (versus 62.3% of oxygen), qPHA of 0.7 mg COD/mg Xa/h, as well as 99.1% denitrification efficiency. The non-oxygen acceptors delayed the time for Arcobacter to occupy the dominant niche in the community, and the environmental selection pressure produced was slightly lower than that of oxygen. The symbiotic community between denitrifying bacteria and PHA-producers ensured the high PHA production potential and denitrification efficiency of the non-oxygen system. An economic assessment showed that the integrated PHA production and nitrate removal process with the mainstream wastewater treatment process proposed in this study could reduce aeration energy by 64%, and PHA recovery yield was 0.1 kg CODPHA/kg CODWAS from waste activated sludge (WAS).

Effects of carbon load on nitrate reduction during riverbank filtration: Field monitoring and batch experiment

Riverbank filtration (RBF) is a well-established technique worldwide, and is critical for the maintenance of groundwater quality and production of clean drinking water. Evaluation of the decay of exogenous nitrate (NO3−) in river water and the enrichment of ammonium (NH4+) in groundwater during RBF is important; these two processes are mainly influenced by denitrification (DNF) and dissimilatory nitrate reduction to ammonium (DNRA) controlled by the groundwater carbon load. In this study, the effects of carbon load (organic carbon [OC]: NO3−) on the competing nitrate reduction (DNRA and DNF) were assessed during RBF using field monitoring and a laboratory batch experiment. Results show the groundwater OC: NO3− ratio did not directly affect the reaction rate of DNRA and DNF, however, it could control the competitive partitioning between the two. In the near-shore zone, the groundwater OC: NO3− ratio shows significant seasonal variations along the filtration path owing to the changing conditions of redox, OC-rich, and NO3−-limited. A greater proportion of NO3− would be available for DNRA in the wet season with higher OC: NO3− ratio (> 10), resulting in a significantly NH4+-N enrichment rate (from 1.43 × 10−3 to 9.54 × 10−4 mmol L−1 d−1) in the near-shore zone where the zone of Mn (IV) oxide reduction. However, the activity of DNRA was suppressed with lower OC: NO3− ratio (< 10) in the dry season, resulting in a stable NH4+-N enrichment rate (from 3.12 × 10−4 to 1.30 × 10−4 mmol L−1 d−1). Benefiting from seasonal variation of OC-rich and NO3−-limited conditions, DNRA bacteria outcompeted denitrifiers, which eventually led to seasonal differences in NO3− reduction in the near-shore zone. Overall, under the effect of DNRA induced by continuous high carbon load in RBF systems, nitrogen input is not permanently removed but rather retained in groundwater during RBF.

Nitrate enhances the secondary growth of storage roots in Panax ginseng

BackgroundNitrogen (N) is an essential macronutrient for plant growth and development. To support agricultural production and enhance crop yield, two major N sources, nitrate and ammonium, are applied as fertilizers to the soil. Although many studies have been conducted on N uptake and signal transduction, the molecular genetic mechanisms of N-mediated physiological roles, such as the secondary growth of storage roots, remain largely unknown. MethodsOne-year-old P. ginseng seedlings treated with KNO3 were analyzed for the secondary growth of storage roots. The histological paraffin sections were subjected to bright and polarized light microscopic analysis. Genome-wide RNA-seq and network analysis were carried out to dissect the molecular mechanism of nitrate-mediated promotion of ginseng storage root thickening. ResultsHere, we report the positive effects of nitrate on storage root secondary growth in Panax ginseng. Exogenous nitrate supply to ginseng seedlings significantly increased the root secondary growth. Histological analysis indicated that the enhancement of root secondary growth could be attributed to the increase in cambium stem cell activity and the subsequent differentiation of cambium-derived storage parenchymal cells. RNA-seq and gene set enrichment analysis (GSEA) revealed that the formation of a transcriptional network comprising auxin, brassinosteroid (BR)-, ethylene-, and jasmonic acid (JA)-related genes mainly contributed to the secondary growth of ginseng storage roots. In addition, increased proliferation of cambium stem cells by a N-rich source inhibited the accumulation of starch granules in storage parenchymal cells. ConclusionThus, through the integration of bioinformatic and histological tissue analyses, we demonstrate that nitrate assimilation and signaling pathways are integrated into key biological processes that promote the secondary growth of P. ginseng storage roots.

Co-variation of hydrochemistry, inorganic nitrogen, and microbial community composition along groundwater flowpath: A case study in Linzhou-Anyang area, Southern North China plain

The exogenous input of nitrate in groundwater may change microbial community, and in turn, the change of microbial community affects the biogeochemical transformation of nitrate. However, how this mutual interaction varies along the groundwater flowpath remains poorly understood. Herein, we investigated the co-variation of hydrochemical characteristics and microbial community compositions in nitrate-contaminated groundwater along a generalized flowpath in Linzhou-Anyang area, southern North China Plain. The groundwater-rock interactions and human activities collectively controlled the transition patterns of hydrogeochemical conditions. Along the groundwater flowpath, the nitrate, ammonia, major ions, total organic carbon (TOC), C/N, and relative abundance of Proteobacteria and Epsilonbacteraeota subsequently increased, while nitrite, oxidation reduction potential (ORP), and overall microbial diversity decreased. Both microbial community composition and microbial co-occurrence network were primarily governed by the levels of TOC, nitrate, and nitrite, a sum of which explained 48.4% variance of community compositions, greater than the effect of water-rock interaction (basically ion contents, 12.9%) and ORP (4%), suggesting the dominant role of exogenous nitrate and organic carbon inputs in shaping microbial community. Accordingly, the variations of keystone bacterial lineages, e.g., Vogesella sp., Acinetobacter sp., Rhodoferax sp., Pseudomonas sp., and Flavobacterium sp., and archaeal lineage Candidatus Nitrosoarchaeum along the groundwater flowpath were putatively involved in the dissimilatory nitrate reduction, indicating the potential role of heterotrophic nitrate reducers in nitrate transformation. Our findings suggest that microbial community distribution along groundwater flowpath is intimately related to exogenous nitrate and organic carbon inputs, which likely outweigh the effect of groundwater circulation or water-rock interaction. This study could help us to better understand the inter-relationship between hydrochemical environments and microbial communities in nitrate-polluted groundwater.

Effect of nitrate administration on plasma nitric oxide levels in patients with peripheral arterial disease at Dr. Sardjito General Hospital, Yogyakarta

Peripheral arterial disease (PAD) is a disease involving reduction of blood flow to the inferior extremity associated with atherosclerotic lesions. In 2010, more than 200 million people with PAD were reported globally, including 54.8 million in Southeast Asia. The high prevalence of PAD causes its management become challenging for clinicians. Nitric oxide (NO) has a role in endothelial function that is associated with the appearance of symptoms in PAD patients. Exogenous nitrate is usually used as a primary vasodilator in the treatment of angina pectoris and Prinzmetal angina. However, information concerning the role of nitrate administration to improve symptomatic PAD patients is limited. This study aimed to evaluate the effectiveness of exogenous nitrates in increasing plasma NO levels and improving PAD patients. A prospective pre-post clinical trial involving PAD patients who were registered in the vascular registry at Dr. Sardjito General Hospital, Yogyakarta was conducted. Primary endpoint was the change in plasma NO levels after short term administration of nitroglycerin oral 2.5 mg once daily (4 h) and long term (7 d). Analysis of variance test with Bonferroni posttest was used for statistical hypothesis testing. Among 33 subjects who completed this study, no negative side effects, and only one hypotensive patient was reported at the first follow-up after 4 h of the nitroglycerin administration. Plasma NO levels increased in the post 4 h and in the post 7 d administration. However, no statistically significant was observed (p &gt; 0.05). Administration of exogenous nitrates in patients with PAD increases the plasma NO levels, even though it is not statistically significant.

Factor affecting nitrate in a mixed land-use watershed of southern China based on dual nitrate isotopes, sources or transformations?

River nitrate (NO3–) pollution is ubiquitous and has attracted worldwide attention. The continuous increase nitrate flux in the river system is mainly caused by inputs of exogenous nitrate sources or nitrogen transformations. In this study, coupled nitrogen and oxygen isotopes of nitrate were used to identify sources and transformations of nitrate in a mixed land use watershed of southern China (the Beijiang River basin), aimed at evaluating the impacts of sources or transformations on nitrate pollution and provide guidance for aquatic environment management. The results showed that the NO3–-N flux in the Beijiang River Basin was 9.37 × 104 tons in 2015; isotopic evidence indicated that the impacts of nitrogen transformations in the river on the removal and production of nitrate were not significant, and the increased NO3–-N concentration along the river was caused by inputs of exogenous nitrate sources. The isotope-based source apportionment revealed that approximately 52% of the influx NO3–-N was contributed by synthetic fertilizer, 27% by soil nitrogen and 21% by domestic sewage. There was no significant temporal variations in source apportionment; however, significant spatial variations were found across the study area. The spatial variations were mainly affected by the different land use patterns. With the increasing percentage of urbanized areas, the proportional contributions of domestic sewage have increased, which has resulted in an increased NO3–-N concentration. In addition, the relationships between the land use index and proportional contributions of different nitrate sources suggested that the effect of urbanized area might be more pronounced on nitrate pollution in a mixed land use watershed. Therefore, the results of this study suggested that land use should be considered in nitrate pollution management strategies and reducing inputs of nitrate sources to river water is crucial to reducing nitrate pollution in mixed land use watersheds.

CALMODULIN-LIKE-38 and PEP1 RECEPTOR 2 integrate nitrate and brassinosteroid signals to regulate root growth.

Plants exhibit remarkable developmental plasticity, enabling them to adapt to adverse environmental conditions such as low nitrogen (N) in the soil. Brassinosteroids (BRs) promote root foraging for nutrients under mild N deficiency, but the crosstalk between the BR- and N-signaling pathways in the regulation of root growth remains largely unknown. Here, we show that CALMODULIN-LIKE-38 (CML38), a calmodulin-like protein, specifically interacts with the PEP1 RECEPTOR 2 (PEPR2), and negatively regulates root elongation in Arabidopsis (Arabidopsis thaliana) in response to low nitrate (LN). CML38 and PEPR2 are transcriptionally induced by treatments of exogenous nitrate and BR. Compared with Col-0, the single mutants cml38 and pepr2 and the double mutant cml38 pepr2 displayed enhanced primary root growth and produced more lateral roots under LN. This is consistent with their higher nitrate absorption abilities, and their stronger expression of nitrate assimilation genes. Furthermore, CML38 and PEPR2 regulate common downstream genes related to BR signaling, and they have positive roles in BR signaling. Low N facilitated BR signal transmission in Col-0 and CML38- or PEPR2-overexpressing plants, but not in the cml38 and pepr2 mutants. Taken together, our results illustrate a mechanism by which CML38 interacts with PEPR2 to integrate LN and BR signals for coordinating root development to prevent quick depletion of N resources in Arabidopsis.

The effect of antioxidants on xanthine oxidase activity in fresh ovine milk

In the present, the consequences of nitrate pollution of the environment are very pronounced. In humans and animals, microorganisms can reduce nitrates to nitrites, which cause cancer. Purified and homogeneous xanthine oxidase (XO) of cow's milk can restore these compounds, which makes the article extremely relevant. The purpose of the article is to determine the effect of antioxidants on the activity of xanthine oxidase in fresh ovine milk. Various natural and artificial antioxidants were examined for the detection of xanthine oxidase (XO) activity in ovine milk. Among the natural antioxidants, L-cysteine was more effective in the stabilization of XO in heated milk. XO of sheep milk activated by heat treatment in the presence of cysteine and molybdenum became able to convert nitrate and nitrite to nitric oxide (NO). Therefore, L-cysteine was used for double purposes: as the protector of enzyme active center against the oxidation during heat treatment of milk and as a reagent for S-nitrosothiol formation. Hypoxanthine, as a natural substrate of XO, is an effective electron donor for nitrate reductase (NR) and nitrite reductase (NiR) activities. Heat treatment of the milk in the presence of exogenous lecithin increased the activity of NR and NiR of XO and CysNO formation. Thus, during the heat treatment: a) excess of exogenous phospholipids disintegrates the structure of milk fat globule membrane (MFGM) and b) enzyme molecules denatured partially and their active center became available for exogenous cysteine, molybdenum, hypoxanthine, and nitrate or nitrite.