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1.
Plant Mol Biol ; 102(6): 603-614, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32052233

RESUMO

The WRKY transcription factor family is involved in responding to biotic and abiotic stresses. Its members contain a typical WRKY domain and can regulate plant physiological responses by binding to W-boxes in the promoter regions of downstream target genes. We identified the sweet sorghum SbWRKY50 (Sb09g005700) gene, which encodes a typical class II of the WRKY family protein that localizes to the nucleus and has transcriptional activation activity. The expression of SbWRKY50 in sweet sorghum was reduced by salt stress, and its ectopic expression reduced the salt tolerance of Arabidopsis thaliana plants. Compared with the wild type, the germination rate, root length, biomass and potassium ion content of SbWRKY50 over-expression plants decreased significantly under salt-stress conditions, while the hydrogen peroxide, superoxide anion and sodium ion contents increased. Real-time PCR results showed that the expression levels of AtSOS1, AtHKT1 and genes related to osmotic and oxidative stresses in over-expression strains decreased under salt-stress conditions. Luciferase complementation imaging and yeast one-hybrid assays confirmed that SbWRKY50 could directly bind to the upstream promoter of the SOS1 gene in A. thaliana. However, in sweet sorghum, SbWRKY50 could directly bind to the upstream promoters of SOS1 and HKT1. These results suggest that the new WRKY transcription factor SbWRKY50 participates in plant salt response by controlling ion homeostasis. However, the regulatory mechanisms are different in sweet sorghum and Arabidopsis, which may explain their different salt tolerance levels. The data provide information that can be applied to genetically modifying salt tolerance in different crop varieties.


Assuntos
Homeostase , Tolerância ao Sal/fisiologia , Sorghum/genética , Sorghum/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Biomassa , Proteínas de Transporte , Proteínas de Transporte de Cátions/genética , Proteínas de Transporte de Cátions/metabolismo , Regulação da Expressão Gênica de Plantas , Germinação , Peróxido de Hidrogênio/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Raízes de Plantas/crescimento & desenvolvimento , Plantas Geneticamente Modificadas , Potássio/metabolismo , Regiões Promotoras Genéticas , Espécies Reativas de Oxigênio/metabolismo , Sementes , Sódio/metabolismo , Trocadores de Sódio-Hidrogênio/genética , Trocadores de Sódio-Hidrogênio/metabolismo , Estresse Fisiológico , Superóxidos/metabolismo , Simportadores/genética , Simportadores/metabolismo
2.
Cell Physiol Biochem ; 54(1): 27-39, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31935048

RESUMO

BACKGROUND/AIMS: To test whether the physiological regulation of the cardiac Kv4 channels by the Ca2+/calmodulin-dependent protein kinase II (CaMKII) is restricted to lipid rafts and whether the interactions observed in rat cardiomyocytes also occur in the human ventricle. METHODS: Ventricular myocytes were freshly isolated from Sprague-Dawley rats. Ito was recorded by the whole-cell Patch-Clamp technique. Membrane rafts were isolated by centrifugation in a discontinuous sucrose density gradient. The presence of the proteins of interest was analysed by western blot. Immunogold staining and electron microscopy of heart vibrosections was performed to localize Kv4.2/Kv4.3 and CaMKII proteins. Protein-protein interactions were determined by co-immunoprecipitation experiments in rat and human ventricular mycoytes. RESULTS: Patch-Clamp recordings in control conditions and after lipid raft or caveolae disruption show that the CaMKII-Kv4 channel complex must associate in non-caveolar lipid rafts to be functional. Separation in density gradients, co-immunoprecipitation and electron microscopy show that there are two Kv4 channel populations: one located in caveolae, that is CaMKII independent, and another one located in planar membrane rafts, which is bound to CaMKII. CONCLUSION: CaMKII regulates only the Kv4 channel population located in non-caveolar lipid rafts. Thus, the regulation of cardiac Kv4 channels in rat and human ventricle depends on their subcellular localization.


Assuntos
Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/metabolismo , Microdomínios da Membrana/metabolismo , Miócitos Cardíacos/metabolismo , Canais de Potássio Shal/metabolismo , Animais , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/análise , Cavéolas/metabolismo , Células Cultivadas , Humanos , Transporte de Íons , Potássio/metabolismo , Mapas de Interação de Proteínas , Ratos Sprague-Dawley , Canais de Potássio Shal/análise
3.
Nat Commun ; 11(1): 547, 2020 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-31992706

RESUMO

TrkH is a bacterial ion channel implicated in K+ uptake and pH regulation. TrkH assembles with its regulatory protein, TrkA, which closes the channel when bound to ADP and opens it when bound to ATP. However, it is unknown how nucleotides control the gating of TrkH through TrkA. Here we report the structures of the TrkH-TrkA complex in the presence of ADP or ATP. TrkA forms a tetrameric ring when bound to ADP and constrains TrkH to a closed conformation. The TrkA ring splits into two TrkA dimers in the presence of ATP and releases the constraints on TrkH, resulting in an open channel conformation. Functional studies show that both the tetramer-to-dimer conversion of TrkA and the loss of constraints on TrkH are required for channel gating. In addition, deletion of TrkA in Escherichia coli depolarizes the cell, suggesting that the TrkH-TrkA complex couples changes in intracellular nucleotides to membrane potential.


Assuntos
Transportadores de Cassetes de Ligação de ATP/química , Transportadores de Cassetes de Ligação de ATP/metabolismo , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/metabolismo , Escherichia coli/metabolismo , Potenciais da Membrana/fisiologia , Canais de Potássio/química , Canais de Potássio/metabolismo , Transportadores de Cassetes de Ligação de ATP/genética , Difosfato de Adenosina , Trifosfato de Adenosina/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Transporte Biológico/fisiologia , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Modelos Moleculares , Mutagênese , Potássio/metabolismo , Canais de Potássio/genética , Conformação Proteica , Domínios e Motivos de Interação entre Proteínas , Deleção de Sequência , Vibrio parahaemolyticus/genética , Difração de Raios X
4.
J Chem Theory Comput ; 16(1): 738-748, 2020 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-31762275

RESUMO

Phosphatidylserine (PS) lipids are important signaling molecules and the most common negatively charged lipids in eukaryotic membranes. The signaling can be often regulated by calcium, but its interactions with PS headgroups are not fully understood. Classical molecular dynamics (MD) simulations can potentially give detailed description of lipid-ion interactions, but the results strongly depend on the used force field. Here, we apply the electronic continuum correction (ECC) to the Amber Lipid17 parameters of 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-l-serine (POPS) lipid to improve its interactions with K+, Na+, and Ca2+ ions. The partial charges of the headgroup, glycerol backbone, and carbonyls of POPS, bearing a unit negative charge, were scaled with a factor of 0.75, derived for monovalent ions, and the Lennard-Jones σ parameters of the same segments were scaled with a factor of 0.89. The resulting ECC-POPS model gives more realistic interactions with Na+ and Ca2+ cations than the original Amber Lipid17 parameters when validated using headgroup order parameters and the "electrometer concept". In ECC-lipids simulations, populations of complexes of Ca2+ cations with more than two PS lipids are negligible, and interactions of Ca2+ cations with only carboxylate groups are twice more likely than with only phosphate groups, while interactions with carbonyls almost entirely involve other groups as well. Our results pave the way for more realistic MD simulations of biomolecular systems with anionic membranes, allowing signaling processes involving PS and Ca2+ to be elucidated.


Assuntos
Cálcio/metabolismo , Bicamadas Lipídicas/metabolismo , Fosfatidilserinas/metabolismo , Potássio/metabolismo , Sódio/metabolismo , Cátions/metabolismo , Elétrons , Simulação de Dinâmica Molecular
5.
J Chem Theory Comput ; 16(1): 794-799, 2020 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-31809048

RESUMO

Ion permeation, selectivity, and the behavior of the K+ channel selectivity filter have been studied intensively in the previous two decades. The agreement among multiple approaches used to study ion flux in K+ channels suggests a consensus mechanism of ion permeation across the selectivity that has been put to the test in recent years with the proposal of an alternative way by which ions can cross the selectivity filter of K+ channels via direct Coulomb repulsion between contacting cations. Past experimental work by Zhou and MacKinnon (J. Mol. Biol. 2004, 338, 839) showed that mutation of the site S4 reduces the total occupancy of the selectivity filter to less than two ions on average by lowering the occupancy of the S2-S4 configuration without changing the S1-S3 configuration much, and this reduction of occupancy means that ion configurations different from the ones involved in the canonical mechanism are likely to be involved. At that time, calculations using complicated kinetic networks to relate occupancy to conduction did not provide deeper insight into the conduction mechanism. Here, to help solve this enigma, umbrella sampling simulations have been performed to evaluate the potential of mean force of two KcsA mutant channels where the S4 site is substituted. Our new results provide insights into the significance of threonine in this position, revealing the effect of substitution on the alternate mechanisms of conduction proposed, involving either water or vacant sites.


Assuntos
Proteínas de Bactérias/metabolismo , Canais de Potássio/metabolismo , Potássio/metabolismo , Streptomyces coelicolor/metabolismo , Proteínas de Bactérias/química , Sítios de Ligação , Cátions Monovalentes/metabolismo , Simulação por Computador , Cinética , Modelos Moleculares , Canais de Potássio/química , Conformação Proteica , Streptomyces coelicolor/química
6.
Plant Sci ; 290: 110267, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31779911

RESUMO

Both nitrogen (N) and potassium (K) have been widely studied in maintaining efficient photosynthesis and plant growth. However, the mechanisms underlying the photosynthetic response to their interaction remain unclear. This study assessed the effects of N and K supply on photosynthetic limitations and the corresponding changes in anatomical structures in leaves of rice (Oryza sativa L.) plants, grown hydroponically under different levels of N and K in a greenhouse. Results revealed that a suitable leaf N/K ratio (2.99-3.10) maintain a high rate of photosynthesis (A). The A under N and/or K deficiency was primarily limited by mesophyll conductance (gm) and RuBP carboxylation in biochemical processes. The decline of gm in N- or K-starved leaves was mostly resulted from low surface area of chloroplasts exposed to intercellular airspaces (Sc) and high mesophyll cell wall thickness. Synergistic effects of N and K on gm were reflected in leaf anatomical structure, especially their coordinated roles in enhancing Sc. The enhanced photosynthesis in plants with coordinated supply of N and K was caused by the balance of RuBP carboxylation and regeneration. These results highlight the synergistic effect of N and K on leaf photosynthesis, which are mainly reflected in facilitating anatomical-determined gm and carboxylation capacity.


Assuntos
Nitrogênio/metabolismo , Oryza/anatomia & histologia , Oryza/metabolismo , Fotossíntese , Potássio/metabolismo , Transporte Biológico , Dióxido de Carbono/metabolismo , Folhas de Planta/anatomia & histologia , Folhas de Planta/metabolismo
7.
J Sci Food Agric ; 100(1): 277-286, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31523836

RESUMO

BACKGROUND: Biodiversity-based agricultural systems can improve production efficiency and sustainability, with fewer negative environmental impacts and lower use of external inputs. Mixed-cropping and rice-duck co-culture have been shown to produce ecological benefits and to have positive effects on paddy soil. However, the effects of a combination of mixed cropping with different rice cultivars and duck co-culture on soil nutrients availability and grain yields have not been evaluated. A paddy field experiment was carried out over two rice growing seasons to test these effects. RESULTS: Several combinations of rice cultivars, when integrated with duck co-culture, significantly increased the soil organic matter and total nitrogen contents during the rice growing seasons, as compared to mono-cropping systems. In mixed-cropping combined with duck co-culture (MCDC) systems, the soil alkali-hydrolyzable nitrogen content ranged from 4.33% to 17.86% higher than that in mono-cropping systems. Similar increases were found for soil available phosphorus (8.71-15.91%) and soil available potassium (8.65-39.43%) contents. Furthermore, MCDC produced higher grain yields and harvest indexes for both study seasons. CONCLUSION: The integration of MCDC systems had positive effects on soil nutrient contents of paddy fields, which could, in turn, lead to yield enhancements, as well as additional income for farmers in the form of organic duck meat. © 2019 Society of Chemical Industry.


Assuntos
Produção Agrícola/métodos , Patos/crescimento & desenvolvimento , Oryza/crescimento & desenvolvimento , Solo/química , Animais , China , Fertilizantes/análise , Nitrogênio/análise , Nitrogênio/metabolismo , Oryza/metabolismo , Fósforo/análise , Fósforo/metabolismo , Potássio/análise , Potássio/metabolismo , Estações do Ano
8.
PLoS One ; 14(12): e0227020, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31887166

RESUMO

The heterogeneous distribution of soil salinity across the rhizosphere can moderate salt injury and improve sorghum growth. However, the essential molecular mechanisms used by sorghum to adapt to such environmental conditions remain uncharacterized. The present study evaluated physiological parameters such as the photosynthetic rate, antioxidative enzyme activities, leaf Na+ and K+ contents, and osmolyte contents and investigated gene expression patterns via RNA sequencing (RNA-seq) analysis under various conditions of nonuniformly distributed salt. Totals of 5691 and 2047 differentially expressed genes (DEGs) in the leaves and roots, respectively, were identified by RNA-seq under nonuniform (NaCl-free and 200 mmol·L-1 NaCl) and uniform (100 mmol·L-1 and 100 mmol·L-1 NaCl) salinity conditions. The expression of genes related to photosynthesis, Na+ compartmentalization, phytohormone metabolism, antioxidative enzymes, and transcription factors (TFs) was enhanced in leaves under nonuniform salinity stress compared with uniform salinity stress. Similarly, the expression of the majority of aquaporins and essential mineral transporters was upregulated in the NaCl-free root side in the nonuniform salinity treatment, whereas abscisic acid (ABA)-related and salt stress-responsive TF transcripts were more abundant in the high-saline root side in the nonuniform salinity treatment. In contrast, the expression of the DEGs identified in the nonuniform salinity treatment remained virtually unaffected and was even downregulated in the uniform salinity treatment. The transcriptome findings might be supportive of the increased photosynthetic rate, reduced Na+ levels, increased antioxidative capability in the leaves and, consequently, the growth recovery of sorghum under nonuniform salinity stress as well as the inhibited sorghum growth under uniform salinity conditions. The increased expression of salt resistance genes activated in response to the nonuniform salinity distribution implied that the cross-talk between the nonsaline and high-saline sides of the roots exposed to nonuniform salt stress is potentially regulated.


Assuntos
Raízes de Plantas/fisiologia , Estresse Salino , Tolerância ao Sal/genética , Solo/química , Sorghum/fisiologia , Ácido Abscísico/metabolismo , Aquaporinas/metabolismo , Proteínas de Transporte/metabolismo , Produção Agrícola , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Regulação da Expressão Gênica de Plantas/fisiologia , Fotossíntese/efeitos dos fármacos , Fotossíntese/genética , Folhas de Planta/química , Folhas de Planta/metabolismo , Raízes de Plantas/química , Raízes de Plantas/efeitos dos fármacos , Potássio/análise , Potássio/metabolismo , Rizosfera , Salinidade , Sódio/análise , Sódio/metabolismo , Cloreto de Sódio/efeitos adversos
9.
BMC Plant Biol ; 19(1): 469, 2019 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-31690290

RESUMO

BACKGROUND: Soybean (Glycine max (L.)) is one the most important oil-yielding cash crops. However, the soybean production has been seriously restricted by salinization. It is therefore crucial to identify salt tolerance-related genes and reveal molecular mechanisms underlying salt tolerance in soybean crops. A better understanding of how plants resist salt stress provides insights in improving existing soybean varieties as well as cultivating novel salt tolerant varieties. In this study, the biological function of GmNHX1, a NHX-like gene, and the molecular basis underlying GmNHX1-mediated salt stress resistance have been revealed. RESULTS: We found that the transcription level of GmNHX1 was up-regulated under salt stress condition in soybean, reaching its peak at 24 h after salt treatment. By employing the virus-induced gene silencing technique (VIGS), we also found that soybean plants became more susceptible to salt stress after silencing GmNHX1 than wild-type and more silenced plants wilted than wild-type under salt treatment. Furthermore, Arabidopsis thaliana expressing GmNHX1 grew taller and generated more rosette leaves under salt stress condition compared to wild-type. Exogenous expression of GmNHX1 resulted in an increase of Na+ transportation to leaves along with a reduction of Na+ absorption in roots, and the consequent maintenance of a high K+/Na+ ratio under salt stress condition. GmNHX1-GFP-transformed onion bulb endothelium cells showed fluorescent pattern in which GFP fluorescence signals enriched in vacuolar membranes. Using the non-invasive micro-test technique (NMT), we found that the Na+ efflux rate of both wild-type and transformed plants after salt treatment were significantly higher than that of before salt treatment. Additionally, the Na+ efflux rate of transformed plants after salt treatment were significantly higher than that of wild-type. Meanwhile, the transcription levels of three osmotic stress-related genes, SKOR, SOS1 and AKT1 were all up-regulated in GmNHX1-expressing plants under salt stress condition. CONCLUSION: Vacuolar membrane-localized GmNHX1 enhances plant salt tolerance through maintaining a high K+/Na+ ratio along with inducing the expression of SKOR, SOS1 and AKT1. Our findings provide molecular insights on the roles of GmNHX1 and similar sodium/hydrogen exchangers in regulating salt tolerance.


Assuntos
Proteínas de Plantas/metabolismo , Tolerância ao Sal/genética , Plantas Tolerantes a Sal/metabolismo , Trocadores de Sódio-Hidrogênio/metabolismo , Soja/metabolismo , Arabidopsis/genética , Inativação Gênica , Proteínas de Plantas/genética , Potássio/metabolismo , Plantas Tolerantes a Sal/genética , Sódio/metabolismo , Trocadores de Sódio-Hidrogênio/genética , Soja/genética , Estresse Fisiológico/genética , Regulação para Cima , Vacúolos/metabolismo
10.
Biochemistry (Mosc) ; 84(11): 1280-1295, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31760918

RESUMO

Maintenance of non-equilibrium Na+ and K+ distribution between cytoplasm and extracellular medium suggests existence of sensors responding with conformational transitions to the changes of these monovalent cations' intracellular concentration. Molecular nature of monovalent cation sensors has been established in Na,K-ATPase, G-protein-coupled receptors, and heat shock proteins structural studies. Recently, it was found that changes in Na+ and K+ intracellular concentration are the key factors in the transcription and translation control, respectively. In this review, we summarize results of these studies and discuss physiological and pathophysiological significance of Na+i,K+i-dependent gene expression regulation mechanism.


Assuntos
Potássio/metabolismo , ATPase Trocadora de Sódio-Potássio/metabolismo , Sódio/metabolismo , Animais , Cátions Monovalentes/química , Citoplasma/metabolismo , Proteínas de Choque Térmico/metabolismo , Potássio/química , Biossíntese de Proteínas , Sódio/química , Transcrição Genética
11.
Dtsch Med Wochenschr ; 144(22): 1576-1584, 2019 11.
Artigo em Alemão | MEDLINE | ID: mdl-31658482

RESUMO

Hyperkalemia increases morbidity and mortalilty risk in both in- and outpatients. Common causes are decreased renal excretion, excess intake or potassium shifting from the intra- to the extracellular space in combination with reduced renal excretion or impairment of regulation. Hyperkalemia may alter the cellular transmembrane potential and cause life-threatening arrhythmias. Heart failure patients with comorbid renal insufficiency and/or diabetes mellitus are at increased risk of developing hyperkalemia, which thus constitutes a common reason for insufficient up-titration, down-titration or discontinuation of prognostically relevant heart failure medications predisposing to hyperkalemia (e. g. angiotensin-converting-enzyme inhibitors, angiotensin-receptor blockers and mineralocorticoid receptor antagonists). New oral potassium binders may enhance treatment opportunities in this respect.


Assuntos
Hiperpotassemia , Comorbidade , Insuficiência Cardíaca/complicações , Humanos , Hiperpotassemia/diagnóstico , Hiperpotassemia/etiologia , Hiperpotassemia/fisiopatologia , Hiperpotassemia/terapia , Potássio/sangue , Potássio/metabolismo , Insuficiência Renal/complicações
12.
J Physiol Pharmacol ; 70(3)2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31566191

RESUMO

We hypothesized that the repolarization phase of action potentials (APs) in mammals with large body mass and high cardiac output could not be reliably controlled by only one of the delayed rectifier potassium IK current components. To test this hypothesis experimentally, we performed a comparative study of the response of AP phases to the rapid IKr channels blocker E-4031 and slow IKs blocker chromanol 293B in APs spontaneously generated in strips of sinoauricular (SA) tissue from mouse, guinea pig, and pig hearts. Application of a slow channels blocker chromanol 293B caused a decrease of Aps generation frequency in SA area strips from mouse, guinea-pig and pig by 5.3, 16, and 18% compared to the control. Treatment with the IKr blocker E-4031 caused a significant reduction of APs generation frequency in the mouse, guinea pig, and pig SA strips by 24, 26, and 36%, respectively, compared to the control values. These results suggest that the rapid IKr current is the key component responsible for AP generation in sinoauricular node cells of the pig heart.


Assuntos
Potenciais de Ação/efeitos dos fármacos , Canais de Potássio/metabolismo , Potássio/metabolismo , Nó Sinoatrial/fisiologia , Animais , Cromanos/farmacologia , Cobaias , Masculino , Camundongos , Bloqueadores dos Canais de Potássio/farmacologia , Nó Sinoatrial/metabolismo , Sulfonamidas/farmacologia , Suínos
13.
Bioelectromagnetics ; 40(8): 578-587, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31642089

RESUMO

A sub-acute electromagnetic field (EMF) biological effect study was carried out on rats exposed in the Transverse ElectroMagnetic exposure chamber at 171 MHz Continuous Wave (CW). The experiments involved three exposure levels (15, 25, and 35 V/m) for 15 days with triplicate parallel sham-exposed controls in each series. All exposure conditions were simulated for the evaluation of the electromagnetic energy distribution and specific absorption rate (SAR) in the rat phantoms. Studies have shown a biphasic biological response depending on time and absorbed electromagnetic energy. Under low SAR, approximately 0.006 W/kg, EMF exposure leads to the stimulation of adrenal gland activity. This process is accompanied by an initial increase of daily excretion of corticosterone and Na+ , which is seen as a higher Na+ /K+ ratio, followed by a decrease of these parameters over time. It is possible that EMF exposure causes a stress response in animals, which is seen as an increased adrenal activity. Bioelectromagnetics. 2019;40:578-587. © 2019 Bioelectromagnetics Society.


Assuntos
Glândulas Suprarrenais/metabolismo , Campos Eletromagnéticos/efeitos adversos , Glucocorticoides/metabolismo , Mineralocorticoides/metabolismo , Animais , Corticosterona/metabolismo , Masculino , Potássio/metabolismo , Ratos , Ratos Wistar , Sódio/metabolismo
14.
Arch Anim Nutr ; 73(6): 505-516, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31617788

RESUMO

A growth trial was performed to optimise the inclusion of potassium (K) in feeds of Heteropneustes fossilis (body weight [BW] 6.92 ± 0.1 g). Eight isonitrogenous and isoenergetic diets with varying dietary K levels were prepared by supplementing 0, 1.91, 3.82, 5.73, 7.64, 9.55, 11.46 and 13.37 g KCl/kg basal diet. Analysed dietary K levels were 0.16, 1.12, 2.08, 3.19, 4.18, 5.16, 6.11, 7.14 and 8.16 g/kg dry matter. BW gain, feed conversion ratio (FCR), protein gain (PG) and gill Na+/K+-ATPase activity were best in fish fed 4.18 g K/kg diet. The K concentrations in the whole body and vertebrae increased linearly with the increase up to 5.16 g K/kg diet and reached then a plateau. The K-retention [%] was highest in fish fed the basal diet and decreased with the further inclusion of dietary K up to 2.08 g/kg followed by no change up to diet containing 4.18 g K/kg and then declined further in fish fed higher levels of dietary K. Serum alkaline phosphatase activity was found to increase up to 4.18 g K/kg diet. Regression of BW gain, PG, gill Na+/K+-ATPase and vertebrae K concentration against varying levels of dietary K using broken-line model indicated that an inclusion of 5.44 g K/kg diet is the optimum for maximising growth and mineralisation of H. fossilis.


Assuntos
Peixes-Gato/fisiologia , Proteínas de Peixes/genética , Potássio/metabolismo , ATPase Trocadora de Sódio-Potássio/genética , Ração Animal/análise , Fenômenos Fisiológicos da Nutrição Animal/efeitos dos fármacos , Animais , Composição Corporal/efeitos dos fármacos , Peixes-Gato/crescimento & desenvolvimento , Dieta/veterinária , Suplementos Nutricionais/análise , Relação Dose-Resposta a Droga , Proteínas de Peixes/metabolismo , Potássio/administração & dosagem , ATPase Trocadora de Sódio-Potássio/metabolismo
15.
Phys Rev E ; 100(2-1): 022406, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31574673

RESUMO

Ion channels regulate the flux of ions through cell membranes and play significant roles in many physiological functions. Most of the existing literature focuses on computational approaches based on molecular dynamics simulation or numerical solution of the modified Poisson-Nernst-Planck (PNP) system. In this paper, we present an analytical and computational study of a mathematical model of the KcsA potassium channel, including the effects of ion size (Bikerman model) and solvation energy (Born model). Under equilibrium conditions, we obtain an analytical solution of our modified PNP system, which is used to explain selectivity of KcsA of various ions (K^{+}, Na^{+}, Cl^{-}, Ca^{2+}, and Ba^{2+}) due to negative permanent charges inside the filter region and the effect of ion sizes. Our results show that K^{+} is always selected over Na^{+}, as smaller Na^{+} ions have larger solvation energy. As the amount of negative charges in the filter exceeds a critical value, divalent ions (Ca^{2+} and Ba^{2+}) can enter the filter region and block the KcsA channel. For the nonequilibrium cases, due to difficulties associated with a pure analytical or numerical approach, we use a hybrid analytical-numerical method to solve the modified PNP system. Our predictions of selectivity of KcsA channels and saturation phenomenon of the current-voltage (I-V) curve agree with experimental observations.


Assuntos
Modelos Biológicos , Canais de Potássio/metabolismo , Potássio/metabolismo , Sódio/metabolismo , Especificidade por Substrato
16.
EMBO J ; 38(19): e101468, 2019 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-31506973

RESUMO

Excitatory amino acid transporters (EAATs) mediate glial and neuronal glutamate uptake to terminate synaptic transmission and to ensure low resting glutamate concentrations. Effective glutamate uptake is achieved by cotransport with 3 Na+ and 1 H+ , in exchange with 1 K+ . The underlying principles of this complex transport stoichiometry remain poorly understood. We use molecular dynamics simulations and electrophysiological experiments to elucidate how mammalian EAATs harness K+ gradients, unlike their K+ -independent prokaryotic homologues. Glutamate transport is achieved via elevator-like translocation of the transport domain. In EAATs, glutamate-free re-translocation is prevented by an external gate remaining open until K+  binding closes and locks the gate. Prokaryotic GltPh contains the same K+ -binding site, but the gate can close without K+ . Our study provides a comprehensive description of K+ -dependent glutamate transport and reveals a hitherto unknown allosteric coupling mechanism that permits adaptions of the transport stoichiometry without affecting ion or substrate binding.


Assuntos
Proteínas de Transporte de Glutamato da Membrana Plasmática/química , Proteínas de Transporte de Glutamato da Membrana Plasmática/metabolismo , Potássio/metabolismo , Regulação Alostérica , Transporte Biológico , Células HEK293 , Humanos , Modelos Moleculares , Simulação de Dinâmica Molecular , Conformação Proteica , Transmissão Sináptica
17.
Cell Physiol Biochem ; 53(3): 532-549, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31512466

RESUMO

BACKGROUND/AIMS: Silver nanoparticles (AgNPs) are the most frequently used nanomaterials in industrial and biomedical applications. Their functionalization significantly impacts their properties and potential applications. Despite the need to produce, investigate and apply them, not much is known about the toxicity of silver nanoparticles to and their interaction with blood components, such as erythrocytes. Here, we report on the effect of two negatively charged AgNPs (Creighton, and Lee-Meisel) on ion transport in human red blood cells (HRBCs). METHODS: HRBCs were obtained from blood of adult donors, which was either expired, fresh or refrigerated for variable lengths of time, and from fresh or refrigerated cord blood. Rb+ and K+ ions were measured by atomic emission and absorption spectrophotometry, respectively. Erythrocyte hemoglobin optical density (Hbc OD), was determined at 527 nm to estimate RBC volume in the same tubes in which Rb+ and K+ were measured. Cellular Rb+ uptake and intracellular K+ concentrations, [K]i, were calculated in mmol/L of original cells (LOC) per time. Rubidium, a potassium ion (K+) congener used to measure K+ influx, [K]i, and Hbc ODs were determined in the presence and absence of several concentrations (0-150 µg mL-1) of spherical AgNPs of an average diameter of 10 nm, at different time points (0-60 min). RESULTS: Creighton AgNPs inhibited Rb+ influx and depleted the cells of K+ independently of the source and in a time and dose-dependent manner. In contrast, Lee-Meisel AgNPs caused ~ 50 % Rb+ influx inhibition and ~ 15 % K+ loss with larger interindividual variability than Creighton AgNPs. The loss of K+ from HRBCs was entirely accounted for by an increase in extracellular K+ concentration, [K]o. Enhanced dark field optical microscopy in conjunction with CytoViva® hyperspectral imaging helped visualize AgNPs internalized by HRBCs, thus pointing to a potential cause for their cytotoxic effects. CONCLUSION: These findings indicate that HRBC K+ homeostasis is an early and sensitive biomarker for AgNPs toxicity and is a function of their surface functionalization.


Assuntos
Eritrócitos/efeitos dos fármacos , Eritrócitos/metabolismo , Transporte de Íons/efeitos dos fármacos , Nanopartículas Metálicas/química , Prata/química , Prata/farmacologia , Células Cultivadas , Humanos , Tamanho da Partícula , Potássio/metabolismo , Rubídio/metabolismo
18.
Microbes Environ ; 34(4): 347-355, 2019 Dec 27.
Artigo em Inglês | MEDLINE | ID: mdl-31527341

RESUMO

To develop biofertilizers for rice in Afghanistan, 98 plant growth-promoting rhizobacteria were isolated from rice plants and their morphological and physiological characteristics, such as indole-3-acetic acid production, acetylene reduction, phosphate and potassium solubilization, and siderophore production, were evaluated. The genetic diversity of these bacteria was also analyzed based on 16S rRNA gene sequences. Of 98 bacteria, 89.7% produced IAA, 54.0% exhibited nitrogenase activity, and 40% showed phosphate solubilization and siderophore production. Some isolates assigned to Pseudomonas (brassicacearum, chengduensis, plecoglossicida, resinovorans, and straminea) formed a relationship with rice, and P. resinovorans and P. straminea showed nitrogen fixation. Rhizobium borbori and R. rosettiformans showed a relationship with rice plants and nitrogen fixation. Among the isolates examined, AF134 and AF137 belonging to Enterobacter ludwigii and P. putida produced large amounts of IAA (92.3 µg mL-1) and exhibited high nitrogenase activity (647.4 nmol C2H4 h-1), respectively. In the plant growth test, more than 70% of the inoculated isolates showed significantly increased root and shoot dry weights. Highly diverse bacterial isolates showing promising rice growth-promoting traits were obtained from Afghanistan alkaline soils.


Assuntos
Bactérias/isolamento & purificação , Oryza/microbiologia , Afeganistão , Bactérias/classificação , Bactérias/genética , Bactérias/metabolismo , Ácidos Indolacéticos/metabolismo , Fixação de Nitrogênio , Nitrogenase/metabolismo , Oryza/classificação , Oryza/crescimento & desenvolvimento , Fosfatos/metabolismo , Filogenia , Raízes de Plantas/classificação , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/microbiologia , Potássio/metabolismo , RNA Ribossômico 16S/genética , Sideróforos/metabolismo , Microbiologia do Solo
19.
Cell Physiol Biochem ; 53(4): 638-647, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31556253

RESUMO

BACKGROUND/AIMS: Prolonged hyperosmotic shrinkage evokes expression of osmoprotective genes via nuclear factor NFAT5-mediated pathway and activates Na+ influx via hypertonicity-induced cation channels (HICC). In human umbilical vein endothelial cells (HUVEC) elevation of intracellular sodium concentration ([Na+]i) triggers transcription of dozens of early response genes (ERG). This study examined the role of monovalent cations in the expression of Na+i-sensitive ERGs in iso- and hyperosmotically shrunken HUVEC. METHODS: Cell volume was measured by 3D reconstruction of cell shape and as 14C-urea available space. Intracellular Na+ and K+ content was measured by flame atomic absorption spectrometry. ERG transcription was estimated by RT-PCR. RESULTS: Elevation of medium osmolality by 150 mM mannitol or cell transfer from hypo- to isosmotic medium decreased cell volume by 40-50%. Hyperosmotic medium increased [Na+]i by 2-fold whereas isosmotic shrinkage had no impact on this parameter. Hyperosmotic but not isosmotic shrinkage increased up-to 5-fold the content of EGR1, FOS, ATF3, ZFP36 and JUN mRNAs. Expression of these ERGs triggered by hyperosmotic shrinkage and Na+,K+-ATPase inhibition by 0.1 µM ouabain exhibited positive correlation (R2=0.9383, p=0.0005). Isosmotic substitution of NaCl by N-methyl-D-glucamine abolished an increment of [Na+]i and ERG expression triggered by mannitol addition. CONCLUSION: Augmented expression of ERGs in hyperosmotically shrunken HUVEC is mediated by elevation of [Na+]i.


Assuntos
Tamanho Celular , Sódio/metabolismo , Tamanho Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Proteína 1 de Resposta de Crescimento Precoce/genética , Proteína 1 de Resposta de Crescimento Precoce/metabolismo , Células Endoteliais da Veia Umbilical Humana , Humanos , Meglumina/farmacologia , Ouabaína/farmacologia , Potássio/metabolismo , Cloreto de Sódio/farmacologia , ATPase Trocadora de Sódio-Potássio/antagonistas & inibidores , ATPase Trocadora de Sódio-Potássio/metabolismo , Tristetraprolina/genética , Tristetraprolina/metabolismo
20.
Br J Hosp Med (Lond) ; 80(9): 525-529, 2019 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-31498679

RESUMO

Noise-induced hearing loss is sensory deafness caused by long-term exposure of the auditory system to a noisy environment. Auditory fatigue is an early symptom of noise-induced hearing loss, and hearing can gradually recover after people leave a noisy environment. However, if people remain in a noisy environment for a prolonged period of time, their hearing will be permanently impaired. Societal changes mean that people are more likely to be exposed to noise. The hearing loss and tinnitus caused by noise seriously affect people's quality of life and lead to huge economic loss. The pathogenesis of noise-induced hearing loss is complex. Various theories try to explain this, such as the oxidative stress theory, but none perfectly explains the occurrence of noise-induced hearing loss. There is no treatment which can completely reverse the damage. More research is required to explore the pathogenesis and to better guide clinical practice. Preventative strategies, such as educating the public about hearing health, should be adopted to reduce the harm of noise-induced hearing loss.


Assuntos
Cóclea/lesões , Perda Auditiva Provocada por Ruído/fisiopatologia , Estresse Oxidativo , Cálcio/metabolismo , Educação em Saúde , Perda Auditiva Provocada por Ruído/metabolismo , Perda Auditiva Provocada por Ruído/prevenção & controle , Perda Auditiva Provocada por Ruído/terapia , Humanos , Potássio/metabolismo
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