Search Results (55)

Nitrogen (N) critically regulates wheat growth and grain quality, yet the molecular mechanisms underlying foliar nitrogen application remain unclear. This study evaluated the effects of foliar nitrogen application (12.25 kg ha⁻¹) on the growth, grain yield, and quality of spring wheat, as well as its molecular mechanisms. The results indicated that N was absorbed within 3 h post-application, with leaf nitrogen concentration peaking at 12 h. The N treatment increased whole-plant dry matter accumulation and grain protein content by 11.34% and 6.8%, respectively. Amino acid content peaked 24 h post-application, increasing by 25.3% compared to the control. RNA-sequencing analysis identified 4559 and 3455 differentially expressed genes at 3 h and 24 h after urea treatment, respectively, these DEGs being primarily involved in nitrogen metabolism, photosynthetic carbon fixation, amino acid biosynthesis, antioxidant systems, and nucleotide biosynthesis. Notably, the plastidic glutamine synthetase gene (GS2) is crucial in the initial phase of urea application (3 h post-treatment). The pronounced downregulation of GS2 initiates a reconfiguration of nitrogen assimilation pathways. This downregulation impedes glutamine synthesis, resulting in a transient accumulation of free ammonia. In response to ammonia toxicity, the leaves promptly activate the GDH (glutamate dehydrogenase) pathway to facilitate the temporary translocation of ammonium. This compensatory mechanism suggests that GS2 downregulation may be a key switch that redirects nitrogen metabolism from the GS/GOGAT cycle to the GDH bypass. Additionally, the upregulation of the purine and pyrimidine metabolic routes channels nitrogen resources towards nucleic acid synthesis, and thereby supporting growth. Amino acids are then transported to the seeds, culminating in enhanced seed protein content. This research elucidates the molecular mechanisms underlying the foliar response to urea application, offering significant insights for further investigation. Full article

Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI) are powerful techniques that have been employed to analyze foodstuffs comprehensively. These techniques offer in-depth information about the chemical composition, structure, and spatial distribution of components in a variety of food products. Quantitative NMR is widely applied for precise quantification of metabolites, authentication of food products, and monitoring of food quality. Low-field ¹H-NMR relaxometry is an important technique for investigating the most abundant components of intact foodstuffs based on relaxation times and amplitude of the NMR signals. In particular, information on water compartments, diffusion, and movement can be obtained by detecting proton signals because of H₂O in foodstuffs. Saffron adulterations with calendula, safflower, turmeric, sandalwood, and tartrazine have been analyzed using benchtop NMR, an alternative to the high-field NMR approach. The fraudulent addition of Robusta to Arabica coffee was investigated by ¹H-NMR Spectroscopy and the marker of Robusta coffee can be detected in the ¹H-NMR spectrum. MRI images can be a reliable tool for appreciating morphological differences in vegetables and fruits. In kiwifruit, the effects of water loss and the states of water were investigated using MRI. It provides informative images regarding the spin density distribution of water molecules and the relationship between water and cellular tissues. ¹H-NMR spectra of aqueous extract of kiwifruits affected by elephantiasis show a higher number of small oligosaccharides than healthy fruits do. One of the frauds that has been detected in the olive oil sector reflects the addition of hazelnut oils to olive oils. However, using the NMR methodology, it is possible to distinguish the two types of oils, since, in hazelnut oils, linolenic fatty chains and squalene are absent, which is also indicated by the ¹H-NMR spectrum. NMR has been applied to detect milk adulterations, such as bovine milk being spiked with known levels of whey, urea, synthetic urine, and synthetic milk. In particular, T2 relaxation time has been found to be significantly affected by adulteration as it increases with adulterant percentage. The ¹H spectrum of honey samples from two botanical species shows the presence of signals due to the specific markers of two botanical species. NMR generates large datasets due to the complexity of food matrices and, to deal with this, chemometrics (multivariate analysis) can be applied to monitor the changes in the constituents of foodstuffs, assess the self-life, and determine the effects of storage conditions. Multivariate analysis could help in managing and interpreting complex NMR data by reducing dimensionality and identifying patterns. NMR spectroscopy followed by multivariate analysis can be channelized for evaluating the nutritional profile of food products by quantifying vitamins, sugars, fatty acids, amino acids, and other nutrients. In this review, we summarize the importance of NMR spectroscopy in chemical profiling and quality assessment of food products employing magnetic resonance technologies and multivariate statistical analysis. Full article

Aquaporins (AQPs) are a family of transmembrane water channel proteins facilitating the transport of water and, in some cases, small solutes such as glycerol, lactate, and urea. In the central nervous system (CNS), several aquaporins play crucial roles in maintaining water homeostasis, modulating cerebrospinal fluid (CSF) circulation, regulating energy metabolism, and facilitating neuroprotection under pathological conditions. Among them, AQP2, AQP4, AQP9, and AQP11 have been implicated in traumatic and non-traumatic brain injuries. The most abundant aquaporin (AQP) in the brain, AQP4, is essential for fluid regulation, facilitating water transport across the blood–brain barrier and glymphatic clearance. AQP2 is primarily known for its function in the kidneys, but it is also expressed in brain regions related to vasopressin signaling and CSF dynamics. AQP9 acts as a channel for glycerol and lactate, thus playing a role in metabolic adaptation during brain injury. AQP11, an intracellular aquaporin, is involved in oxidative stress responses and cellular homeostasis, with emerging evidence suggesting its role in neuroprotection. Aquaporins play a dual role in brain injury; while they help maintain homeostasis, their dysregulation can exacerbate cerebral edema, metabolic dysfunction, and inflammation. In traumatic brain injury (TBI), aquaporins regulate the formation and resolution of cerebral edema. In non-traumatic brain injuries, including ischemic stroke, aneurysmal subarachnoid hemorrhage (aSAH), and intracerebral hemorrhage (ICH), aquaporins influence fluid balance, energy metabolism, and oxidative stress responses. Understanding the specific roles of AQP2, AQP4, AQP9, and AQP11 in these brain injuries may lead to new therapeutic strategies to mitigate secondary damage and improve neurological outcomes. This review explores the function of the above aquaporins in both traumatic and non-traumatic brain injuries, highlighting their potential and limitations as therapeutic targets for neuroprotection and recovery. Full article

Background: Hyperuricemia (HUA) is a widespread metabolic disorder that arises from disruptions in purine metabolism, impaired kidney function, or both conditions. FPAW (Phe-Pro-Ala-Trp) is a novel peptide identified from Trachinotus ovatus with great XOD (xanthine oxidase) inhibitory activity (IC₅₀ = 3.81 mM), which can be developed as a potential active ingredient to relieve hyperuricemia. However, it remains unclear whether FPAW alleviates HUA in vivo or not. Methods: In this study, potassium-oxonate-induced hyperuricemic mice were used to evaluate the in vivo anti-hyperuricemic activity of FPAW. Some physiological parameters, such as serum uric acid (SUA), serum creatinine (SCR), blood urea nitrogen (BUN), and the activity of XOD and ADA (adenosine deaminase) in the liver were determined to evaluate the effect of reduced uric acid. The modulations in the gut microbiota and its metabolites (SCFAs) were analyzed by sequencing the V3-V4 region of the 16S rRNA gene and GC-MS in different fecal samples. Molecular docking was used to predict the interactions between the enzymes and FPAW. Results: The results showed that FPAW reduced the levels of serum uric acid, serum creatinine, and blood urea nitrogen, while also suppressing the activity of XOD in the livers of HUA mice. Moreover, the FPAW treatment alleviated gut microbiota dysfunction and increased the production of short-chain fatty acids to protect normal intestinal function and health of the host. Molecular docking simulations revealed that FPAW inhibited XOD activity by entering the hydrophobic channel and interacting with amino acid residues on the surface via hydrogen bonding and hydrophobic interactions. Conclusions: This study provides new candidates for the development of hypouricemic drugs. FPAW exhibited great potential to relieve hyperuricemia of mice induced by diet in the animal experiment. Full article

Fluorescent labeling of membrane proteins is essential for exploring their functions, signaling pathways, interaction partners, and structural dynamics. Organic fluorophores are commonly used for this purpose due to their favorable photophysical properties and photostability. However, a persistent challenge is the inaccessibility of the surface-exposed cysteine residues required for site-specific labeling, as these residues often become sequestered within detergent micelles during protein extraction. To address this limitation, we developed an approach based on polymer-encapsulated nanodiscs that preserves the protein’s native-like lipid-bilayer environment while ensuring the accessibility of surface-exposed cysteine residues. In this method, His-tagged proteins embedded in native nanodiscs are retained on a nickel affinity column, allowing for simultaneous purification and labeling by adding fluorescent dyes. This versatile technique was demonstrated with two challenging-to-label membrane proteins, the potassium channel KvAP and the urea channel HpUreI, for which detergent-based labeling had failed. This opens new possibilities for studying a wide range of fluorescently labeled membrane proteins in near-native states, advancing applications in biophysics, structural biology, and drug discovery. Full article

This study investigated the protective effect of selenium (Se) in a cadmium (Cd)-induced nephrotoxicity model in rats and the role of the TRPM2 channel in this mechanism. For this purpose, Cd (25 mg/kg orally), Se (0.5 mg/kg i.p.), and 2-aminoethoxydiphenyl borate (2-APB), a TRPM2 channel antagonist, (3 mg/kg i.p.) were administered to rats every day for 5 days. At the end of the study, kidney tissues were analysed using histological and biochemical methods. A histopathological examination revealed congestion, tubular degeneration, necrosis, and glomerular adhesion in the Cd group. However, these lesions were significantly reduced in the Cd + Se and Cd + 2-APB groups, while the Cd + Se + 2-APB group showed a histological appearance similar to the control group. Immunohistochemical analysis revealed that Caspase-3, Bax, and TRPM2 expression was higher in the Cd group, while these levels were lower in the Se and 2-APB treatment groups (p < 0.05). Among the groups that received Cd, urea, creatinine, TOS, TNF-α, and IL-1β levels were at the highest level in the Cd group, while TAS level was at the lowest level (p < 0.05). The Se and 2-APB treatment modulated these parameters; however, Se + 2-APB treatment reduced urea, creatinine, TOS, TNF-α, and IL-1β levels to the lowest level compared to the Cd groups and brought the TAS level closer to the control group (p < 0.05). These findings indicated that targeting TRPM2 channel inactivation together with the selenium treatment could alleviate Cd-induced nephrotoxicity. Full article

The previously available coding region for the spiny dogfish (Squalus acanthias) AQP3-2 gene was amplified from cDNAs using PCR. Agarose gel electrophoresis gave a band of the AQP3-2 coding region, as well as multiple smaller splice variant bands. The main AQP3-2 band and the largest and most fluorescently intense pair of these splice variant bands were cloned and sequenced. Amplifications were performed on a range of tissue cDNAs, but AQP3-2 was only expressed in the kidney and brain. Quantitative PCR amplifications using pre-existing kidney cDNA from an environmental salinity acclimation experiment showed that the abundance of mRNA from both the main AQP3-2 transcript and the largest splice variant (Splice Variant 1) was lower in 120% seawater (SW) acclimated fish, although only the values for Splice Variant 1 were statistically significant. A custom-made affinity-purified rabbit polyclonal AQP3-2 antibody was produced, and this gave four bands of around the correct sizes (which were 27 and 32 kDa) for the complete AQP3-2 and Splice Variant 1 proteins. Two of the bands may have been N-glycosylated forms of these proteins. Other bands were also present on the Western blot. No bands were present when the antibody was pre-blocked by the peptide antigen. In tissue sections of the dogfish kidney, immunohistochemical localization experiments showed that AQP3-2 was expressed in the early distal tubule (EDT) and late distal tubule (LDT) nephron segments. The results suggest that AQP3-2 may be involved in cell volume regulation in the EDT and water and urea absorption in the LDT nephron segment. Full article

Urea-based selective catalytic reduction (SCR) is highly efficient for NOx abatement within a diesel aftertreatment system. However, abnormally high NOx emissions in the aftertreatment system tailpipe during WHSC (World Harmonized Steady-State Cycle) evaluation have been observed due to insufficient urea decomposition or mixing, which cannot be predicted by the current uniform 1D (one-dimensional) modelling approach with different urea dosing ratios. As a result, a multi-channel model has been developed to investigate the effect of urea maldistribution on aftertreatment system performance, where the uniformity index (UI) is used as a characteristic parameter to describe urea mixing efficiency. It was found that NOx emissions at the tailpipe can be successfully described with the multi-channel model even with a relatively high UI (UI = 0.95). Additionally, an improved segment UI factor as a function of mass flow rate has also been applied for maldistribution description, wherein better correlation with the measured NOx emission can be obtained. Full article

We present the construction of an organic electrochemical transistor (OECT) based on poly(3,4-ethylendioxythiophene, PEDOT) and polyallylamine (PAH) and its evaluation as a bioelectronic platform for urease integration and urea sensing. The OECT channel was fabricated in a one-step procedure using chemical polymerization. Then, urease was immobilized on the surface by electrostatic interaction of the negatively charged enzyme at neutral pH with the positively charged surface of PEDOH-PAH channels. The real-time monitoring of the urease adsorption process was achieved by registering the changes on the drain–source current of the OECT upon continuous scan of the gate potential during enzyme deposition with high sensitivity. On the other hand, integrating urease enabled urea sensing through the transistor response changes resulting from local pH variation as a consequence of enzymatic catalysis. The response of direct enzyme adsorption is compared with layer-by-layer integration using polyethylenimine. Integrating a polyelectrolyte over the adsorbed enzyme resulted in a more stable response, allowing for the sensing of urine even from diluted urine samples. These results demonstrate the potential of integrating enzymes into the active channels of OECTs for the development of biosensors based on local pH changes. Full article

The eukaryotic microalga Nannochloropsis oceanica represents a promising bioresource for the production of biofuels and pharmaceuticals. Urea, a crucial nutrient for the photosynthetic N. oceanica, stimulates the accumulation of substances such as lipids, which influence growth and physiology. However, the specific mechanisms by which N. oceanica responds and adapts to urea addition remain unknown. High-throughput mRNA sequencing and differential gene expression analysis under control and urea-added conditions revealed significant metabolic changes. This involved the differential expression of 2104 genes, with 1354 being upregulated and 750 downregulated, resulting in the reprogramming of crucial pathways such as carbon and nitrogen metabolism, photosynthesis, and lipid metabolism. The results specifically showed that genes associated with photosynthesis in N. oceanica were significantly downregulated, particularly those related to light-harvesting proteins. Interestingly, urea absorption and transport may depend not only on specialized transport channels such as urease but also on alternative transport channels such as the ABC transporter family and the CLC protein family. In addition, urea caused specific changes in carbon and lipid metabolism. Genes associated with the Calvin cycle and carbon concentration mechanisms were significantly upregulated. In lipid metabolism, the expression of genes associated with lipases and polyunsaturated fatty acid synthesis was highly activated. Furthermore, the expression of several genes involved in the tricarboxylic acid cycle and folate metabolism was enhanced, making important contributions to energy supply and the synthesis and modification of genes and macromolecules. Our observations indicate that N. oceanica actively and dynamically regulates the redistribution of carbon and nitrogen after urea addition, providing references for further research on the effects of urea on N. oceanica. Full article

Background: Eryptosis stimulated by anticancer drugs can lead to anemia in patients. β-caryophyllene oxide (CPO) is an anticancer sesquiterpene present in various plants; however, its effect on the structure and function of human red blood cells (RBCs) remains unexplored. The aim of this study was to investigate the hemolytic and eryptotic activities and underlying molecular mechanisms of CPO in human RBCs. Methods: Cells were treated with 10–100 μM of CPO for 24 h at 37 °C, and hemolysis, LDH, AST, and AChE activities were photometrically assayed. Flow cytometry was employed to determine changes in cell volume from FSC, phosphatidylserine (PS) externalization by annexin-V-FITC, intracellular calcium by Fluo4/AM, and oxidative stress by 2′,7′-dichlorodihydrofluorescein diacetate (H₂DCFDA). Cells were also cotreated with CPO and specific signaling inhibitors and antihemolytic agents. Furthermore, whole blood was exposed to CPO to assess its toxicity to other peripheral blood cells. Results: CPO induced concentration-responsive hemolysis with LDH and AST leakage, in addition to PS exposure, cell shrinkage, Ca²⁺ accumulation, oxidative stress, and reduced AChE activity. The toxicity of CPO was ameliorated by D4476, staurosporin, and necrosulfonamide. ATP and PEG 8000 protected the cells from hemolysis, while urea and isotonic sucrose had opposite effects. Conclusions: CPO stimulates hemolysis and eryptosis through energy depletion, Ca²⁺ buildup, oxidative stress, and the signaling mediators casein kinase 1α, protein kinase C, and mixed lineage kinase domain-like pseudokinase. Development of CPO as an anticancer therapeutic must be approached with prudence to mitigate adverse effects on RBCs using eryptosis inhibitors, Ca²⁺ channel blockers, and antioxidants. Full article

Hyponatremia (hypo-osmolality) is a disorder of water homeostasis due to abnormal renal diluting capacity. The body limits the degree to which serum sodium concentration falls through a mechanism called “vasopressin escape”. Vasopressin escape is a process that prevents the continuous decrease in serum sodium concentration even under conditions of sustained high plasma vasopressin levels. Previous reports suggest that aldosterone may be involved in the vasopressin escape mechanism. The abilities of aldosterone synthase (Cyp11b2) knockout and wild-type mice to escape from vasopressin were compared. Wild-type mice escaped while the aldosterone synthase knockout mice did not. Both the water channel aquaporin 2 (AQP2) and the urea transporter UT-A1 protein abundances were higher in aldosterone synthase knockout than in wild-type mice at the end of the escape period. Vasopressin escape was also blunted in rats given spironolactone, a mineralocorticoid receptor blocker. Next, the role of the phosphatase, calcineurin (protein phosphatase 2B, PP2B), in vasopressin escape was studied since aldosterone activates calcineurin in rat cortical collecting ducts. Tacrolimus, a calcineurin inhibitor, blunted vasopressin escape in rats compared with the control rats, increased UT-A1, AQP2, and pS256-AQP2, and decreased pS261-AQP2 protein abundances. Our results indicate that aldosterone regulates vasopressin escape through calcineurin-mediated protein changes in UT-A1 and AQP2. Full article

We previously reported that, in cultured hepatocytes, mitochondrial aquaporin-8 (AQP8) channels facilitate the conversion of ammonia to urea and that the expression of human AQP8 (hAQP8) enhances ammonia-derived ureagenesis. In this study, we evaluated whether hepatic gene transfer of hAQP8 improves detoxification of ammonia to urea in normal mice as well as in mice with impaired hepatocyte ammonia metabolism. A recombinant adenoviral (Ad) vector encoding hAQP8, AdhAQP8, or a control Ad vector was administered via retrograde infusion into the bile duct of the mice. Hepatocyte mitochondrial expression of hAQP8 was confirmed using confocal immunofluorescence and immunoblotting. The normal hAQP8-transduced mice showed decreased plasma ammonia and increased liver urea. Enhanced ureagenesis was confirmed via the NMR studies assessing the synthesis of ¹⁵N-labeled urea from ¹⁵N-labeled ammonia. In separate experiments, we made use of the model hepatotoxic agent, thioacetamide, to induce defective hepatic metabolism of ammonia in mice. The adenovirus-mediated mitochondrial expression of hAQP8 was able to restore normal ammonemia and ureagenesis in the liver of the mice. Our data suggest that hAQP8 gene transfer to mouse liver improves detoxification of ammonia to urea. This finding could help better understand and treat disorders with defective hepatic ammonia metabolism. Full article

Crystalline/crystalline blends of polymer have shown advantages in the preparation of new polymeric materials. However, the regulation of co-crystallization in a blend is still full of challenges due to the preferential self-crystallization driven by thermodynamics. Here, an inclusion complex approach is proposed to facilitate the co-crystallization between crystalline polymers, because the crystallization process displays a prominent kinetics advantage when polymer chains are released from the inclusion complex. Poly(butylene succinate) (PBS), poly(butylene adipate) (PBA) and urea are chosen to form co-inclusion complexes, where PBS and PBA chains play as isolated guest molecules and urea molecules construct the host channel framework. The coalesced PBS/PBA blends are obtained by fast removing the urea framework and systematically investigated by differential scanning calorimetry, X-ray diffraction, proton nuclear magnetic resonance and Fourier transformation infrared spectrometry. It is demonstrated that PBA chains are co-crystallized into PBS extended-chain crystals in the coalesced blends, while such a phenomenon has not been detected in simply co-solution-blended samples. Though PBA chains could not be totally accommodated in the PBS extended-chain crystals, their co-crystallized content increases with the initial feeding ratio of PBA. Consequently, the melting point of the PBS extended-chain crystal gradually declines from 134.3 °C to 124.2 °C with an increasing PBA content. The PBA chains playing as defects mainly induce lattice expansion along the a-axis. In addition, when the co-crystals are soaked in tetrahydrofuran, some of the PBA chains are extracted out, leading to damage to the correlative PBS extended-chain crystals. This study shows that co-inclusion complexation with small molecules could be an effective way to promote co-crystallization behavior in polymer blends. Full article

We previously showed that the phosphatases PP1/PP2A and PP2B dephosphorylate the water channel, AQP2, suggesting their role in water reabsorption. In this study, we investigated whether protein phosphatase 2A (PP2A) and protein phosphatase 2B (PP2B or calcineurin), which are present in the inner medullary collecting duct (IMCD), are regulators of urea and water permeability. Inhibition of calcineurin by tacrolimus increased both basal and vasopressin-stimulated osmotic water permeability in perfused rat IMCDs. However, tacrolimus did not affect osmotic water permeability in the presence of aldosterone. Inhibition of PP2A by calyculin increased both basal and vasopressin-stimulated osmotic water permeability, and aldosterone reversed the increase by calyculin. Previous studies showed that adrenomedullin (ADM) activates PP2A and decreases osmotic water permeability. Inhibition of PP2A by calyculin prevented the ADM-induced decrease in water reabsorption. ADM reduced the phosphorylation of AQP2 at serine 269 (pSer269 AQP2). Urea is linked to water reabsorption by building up hyperosmolality in the inner medullary interstitium. Calyculin increased urea permeability and phosphorylated UT-A1. Our results indicate that phosphatases regulate water reabsorption. Aldosterone and adrenomedullin decrease urea or osmotic water permeability by acting through calcineurin and PP2A, respectively. PP2A may regulate water reabsorption by dephosphorylating pSer269, AQP2, and UT-A1. Full article