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Biochimica Et Biophysica Acta.... Dec 2022The outstanding work of several eminent biophysicists has allowed the functional features of voltage-gated tetrameric ion channels to be disclosed using ingenious and... (Review)
Review
The outstanding work of several eminent biophysicists has allowed the functional features of voltage-gated tetrameric ion channels to be disclosed using ingenious and sophisticated electrophysiological techniques. However, the kinetics and mechanism underlying these functions have been heavily conditioned by an arbitrary interpretation of the groundbreaking results obtained by Hodgkin and Huxley (HH) in their investigation of sodium and potassium currents using the voltage clamp technique. Thus, the heavy parametrization of their results was considered to indicate that any proposed sequence of closed states terminates with a single open state. This 'dogma' of HH parametrization has influenced the formulation of countless mechanistic models, mainly stochastic, requiring a high number of free parameters and of often unspecified conformational states. This note aims to point out the advantages of a deterministic kinetic model that simulates the main features of tetrameric ion channels using only two free parameters by assuming their stepwise opening accompanied by a progressively increasing cation flow. This model exploits the electrostatic attractive interactions stemming from the charge distribution shared by all tetrameric ion channels, providing a close connection between their structure and function. Quite significantly, a stepwise opening of all ligand-gated tetrameric ion channels, such as glutamate receptors (GluRs), with concomitant ion flow, is nowadays generally accepted, not having been influenced by this dogma. This provides a unified picture of both voltage-gated and ligand-gated tetrameric ion channels.
Topics: Cations; Ion Channels; Ligands; Potassium; Sodium
PubMed: 36096197
DOI: 10.1016/j.bbamem.2022.184046 -
The Science of the Total Environment May 2023Livestock slurry has been reported to be a potential secondary raw material as it contains macronutrients ‑nitrogen, phosphorus and potassium-, which could be...
Livestock slurry has been reported to be a potential secondary raw material as it contains macronutrients ‑nitrogen, phosphorus and potassium-, which could be valorised as high-quality fertilizers if proper separation and concentration of valuable compounds is performed. In this work, pig slurry liquid fraction was assessed for nutrient recovery and valorisation as fertilizer. Some indicators were used to evaluate the performance of proposed train of technologies within the framework of circular economy. As ammonium and potassium species are highly soluble at the whole pH range, a study based on phosphate speciation at pH from 4 to 8 was assessed to improve the macronutrients recovery from the slurry, resulting in two different treatment trains at acidic and alkaline conditions. The acidic treatment system based on centrifugation, microfiltration and forward osmosis was applied to obtain a nutrient-rich liquid organic fertilizer containing 1.3 % N, 1.3 % PO and 1.5 % KO. The alkaline path of valorisation was composed by centrifugation and stripping by using membrane contactors to produce an organic solid fertilizer -7.7 % N, 8,0 % PO and 2.3 % KO-, ammonium sulphate solution -1.4 % N- and irrigation water. In terms of circularity indicators, 45.8 % of the initial water content and <50 % of contained nutrients were recovered - 28.3 % N, 43.5 % PO and 46.6 % KO - in the acidic treatment resulting in 68.68 g fertilizer per kg of treated slurry. 75.1 % of water was recovered as irrigation water and 80.6 % N, 99.9 % PO, 83.4 % KO was valorised in the alkaline treatment, as 219.60 g fertilizer per kg of treated slurry. Treatment paths at acidic and alkaline conditions yield promising results for nutrients recovery and valorisation as the obtained products (nutrient rich organic fertilizer, solid soil amendment and ammonium sulphate solution) fulfil the European Regulation for fertilizers to be potentially used in crop fields.
Topics: Swine; Animals; Fertilizers; Ammonium Sulfate; Nitrogen; Phosphorus; Acids; Potassium; Water; Nutrients
PubMed: 36870507
DOI: 10.1016/j.scitotenv.2023.162548 -
Nature Communications Dec 2023Cleavage and formation of phosphodiester bonds in nucleic acids is accomplished by large cellular machineries composed of both protein and RNA. Long thought to rely on a...
Cleavage and formation of phosphodiester bonds in nucleic acids is accomplished by large cellular machineries composed of both protein and RNA. Long thought to rely on a two-metal-ion mechanism for catalysis, structure comparisons revealed many contain highly spatially conserved second-shell monovalent cations, whose precise function remains elusive. A recent high-resolution structure of the spliceosome, essential for pre-mRNA splicing in eukaryotes, revealed a potassium ion in the active site. Here, we employ biased quantum mechanics/ molecular mechanics molecular dynamics to elucidate the function of this monovalent ion in splicing. We discover that the K ion regulates the kinetics and thermodynamics of the first splicing step by rigidifying the active site and stabilizing the substrate in the pre- and post-catalytic state via formation of key hydrogen bonds. Our work supports a direct role for the K ion during catalysis and provides a mechanistic hypothesis likely shared by other nucleic acid processing enzymes.
Topics: Spliceosomes; RNA; RNA Splicing; Catalysis; Metals; Potassium; Chelating Agents; Nucleic Acid Conformation; Binding Sites; Cations, Monovalent
PubMed: 38123540
DOI: 10.1038/s41467-023-44174-2 -
The Plant Cell Mar 2023Nitrogen (N) and potassium (K) are essential macronutrients for plants. Sufficient N and K uptake from the environment is required for successful growth and development....
Nitrogen (N) and potassium (K) are essential macronutrients for plants. Sufficient N and K uptake from the environment is required for successful growth and development. However, how N and K influence each other at the molecular level in plants is largely unknown. In this study, we found loss-of-function mutation in SLAH3 (SLAC1 HOMOLOGUE 3), encoding a NO3- efflux channel in Arabidopsis thaliana, enhanced tolerance to high KNO3 concentrations. Surprisingly, slah3 mutants were less sensitive to high K+ but not NO3-. Addition of NO3- led to reduced phenotypic difference between wild-type and slah3 plants, suggesting SLAH3 orchestrates NO3--K+ balance. Non-invasive Micro-test Technology analysis revealed reduced NO3- efflux and enhanced K+ efflux in slah3 mutants, demonstrating that SLAH3-mediated NO3- transport and SLAH3-affected K+ flux are critical in response to high K +. Further investigation showed that two K+ efflux channels, GORK (GATED OUTWARDLY-RECTIFYING K+ CHANNEL) and SKOR (STELAR K+ OUTWARD RECTIFIER), interacted with SLAH3 and played key roles in high K+ response. The gork and skor mutants were slightly more sensitive to high K+ conditions. Less depolarization occurred in slah3 mutants and enhanced depolarization was observed in gork and skor mutants upon K+ treatment, suggesting NO3-/K+ efflux-mediated membrane potential regulation is involved in high K+ response. Electrophysiological results showed that SLAH3 partially inhibited the activities of GORK and SKOR in Xenopus laevis oocytes. This study revealed that the anion channel SLAH3 interacts with the potassium channels GORK and SKOR to modulate membrane potential by coordinating N-K balance.
Topics: Arabidopsis; Potassium Channels; Arabidopsis Proteins; Membrane Potentials; Anions; Homeostasis; Plants; Potassium; Ion Channels
PubMed: 36653170
DOI: 10.1093/plcell/koad014 -
Journal of Feline Medicine and Surgery Dec 2022The aim of this study was to evaluate the magnitude, duration and significance of postprandial changes to select serum biochemistry analytes in healthy adult cats in the...
OBJECTIVES
The aim of this study was to evaluate the magnitude, duration and significance of postprandial changes to select serum biochemistry analytes in healthy adult cats in the 12 h period after a meal.
METHODS
Nine adult research cats fed commercial food were included. Blood samples were taken after a 12 h fast (hour 0), cats were offered and consumed a meal, and postprandial samples were obtained over a 12 h period starting 2 h after the baseline blood draw (hours 2, 4, 6, 8, 10 and 12). Serum samples were run on a Roche Cobas C501 chemistry analyzer to obtain concentrations of blood urea nitrogen (BUN), creatinine, phosphorus, total calcium, bicarbonate, cholesterol, magnesium, sodium, potassium and chloride. Serum concentrations of each analyte at hours 2, 4, 6, 8, 10 and 12 were compared with concentrations prior to feeding.
RESULTS
Serum concentration for at least one postprandial time point was different from baseline fasted concentration for BUN (hour 2, = 0.006; hour 4, <0.0001; hour 6, = 0.002; hour 8, = 0.026), phosphorus (hour 2, = 0.019), bicarbonate (hours 2, 4, 6, 8 and 10; all <0.01), glucose (hour 12, = 0.014), magnesium (hour 10, = 0.029) and chloride (hour 2, = 0.026; hour 4, = 0.044; hour 12, = 0.019). No significant difference was seen at any postprandial sampling point compared with baseline for serum creatinine, total calcium, cholesterol, sodium or potassium concentrations.
CONCLUSIONS AND RELEVANCE
Short-term postprandial serum concentrations of BUN, phosphorus, bicarbonate and chloride differed at multiple time points within a 12 h period compared with the fasted state at baseline, with most values remaining within the reference intervals. Veterinarians should be aware of these alterations, though they are unlikely to be mistaken for pathological disease states in healthy adult cats.
Topics: Cats; Animals; Bicarbonates; Chlorides; Magnesium; Calcium; Sodium; Potassium
PubMed: 36219454
DOI: 10.1177/1098612X221121929 -
BMC Nephrology Oct 2017Dietary modification is an important component of the management of end stage kidney disease (ESKD). The diet for ESKD involves modifying energy and protein intake, and... (Review)
Review
BACKGROUND
Dietary modification is an important component of the management of end stage kidney disease (ESKD). The diet for ESKD involves modifying energy and protein intake, and altering sodium, phosphate, potassium and fluid intake. There have been no comprehensive reviews to date on this topic. The aims of this integrative review were to (i) describe the methods used to measure dietary adherence (ii) determine the rate of dietary adherence and (iii) describe factors associated with dietary adherence in ESKD.
METHODS
The Web of Science and Scopus databases were searched using the search terms 'adherence' and 'end stage kidney disease'. Of the 787 potentially eligible papers retrieved, 60 papers of 24,743 patients were included in this review. Of these papers, 44 reported the rate of dietary adherence and 44 papers described factors associated with adherence.
RESULTS
Most of the evidence regarding dietary adherence is derived from studies of hemodialysis patients (72% of patients). The most common method of measuring dietary adherence in ESKD was subjective techniques (e.g. food diaries or adherence questionnaires). This was followed by indirect methods (e.g. serum potassium, phosphate or interdialytic weight gain). The weighted mean adherence rate to ESKD dietary recommendations was 31.5% and 68.5% for fluid recommendations. Adherence to protein, sodium, phosphate, and potassium recommendations were highly variable due to differences in measurement methods used, and were often derived from a limited evidence base. Socioeconomic status, age, social support and self-efficacy were associated with dietary adherence. However, factors such as taste, the impact of the diet on social eating occasions; and dietetic staffing also appear to play a role in dietary adherence.
CONCLUSION
Dietary adherence rates in people with ESKD are suboptimal. Further research is required on dietary adherence in patients with ESKD from different social, educational, economic and ethnic groups. This research may identify other factors which may impact upon adherence, and could be used to inform the design of future strategies to improve dietary adherence. Future research that reports not just the rate of adherence to individual components of the nutrient prescription but also the overall quality of the diet would be useful.
Topics: Age Factors; Diet; Diet Records; Drinking; Humans; Kidney Failure, Chronic; Patient Compliance; Phosphates; Potassium; Renal Dialysis; Self Efficacy; Social Participation; Social Support; Socioeconomic Factors; Surveys and Questionnaires; Weight Gain
PubMed: 29061163
DOI: 10.1186/s12882-017-0734-z -
JCI Insight Mar 2023Dietary potassium (K+) supplementation is associated with a lowering effect in blood pressure (BP), but not all studies agree. Here, we examined the effects of short-...
Dietary potassium (K+) supplementation is associated with a lowering effect in blood pressure (BP), but not all studies agree. Here, we examined the effects of short- and long-term K+ supplementation on BP in mice, whether differences depend on the accompanying anion or the sodium (Na+) intake and molecular alterations in the kidney that may underlie BP changes. Relative to the control diet, BP was higher in mice fed a high NaCl (1.57% Na+) diet for 7 weeks or fed a K+-free diet for 2 weeks. BP was highest on a K+-free/high NaCl diet. Commensurate with increased abundance and phosphorylation of the thiazide sensitive sodium-chloride-cotransporter (NCC) on the K+-free/high NaCl diet, BP returned to normal with thiazides. Three weeks of a high K+ diet (5% K+) increased BP (predominantly during the night) independently of dietary Na+ or anion intake. Conversely, 4 days of KCl feeding reduced BP. Both feeding periods resulted in lower NCC levels but in increased levels of cleaved (active) α and γ subunits of the epithelial Na+ channel ENaC. The elevated BP after chronic K+ feeding was reduced by amiloride but not thiazide. Our results suggest that dietary K+ has an optimal threshold where it may be most effective for cardiovascular health.
Topics: Mice; Animals; Blood Pressure; Sodium Chloride Symporters; Potassium, Dietary; Sodium Chloride; Epithelial Sodium Channels; Sodium; Thiazides; Dietary Supplements
PubMed: 36719746
DOI: 10.1172/jci.insight.156437 -
Scientific Reports Aug 2020Analyzing electrolytes in urine, such as sodium, potassium, calcium, chloride, and nitrite, has significant diagnostic value in detecting various conditions, such as...
Analyzing electrolytes in urine, such as sodium, potassium, calcium, chloride, and nitrite, has significant diagnostic value in detecting various conditions, such as kidney disorder, urinary stone disease, urinary tract infection, and cystic fibrosis. Ideally, by regularly monitoring these ions with the convenience of dipsticks and portable tools, such as cellphones, informed decision making is possible to control the consumption of these ions. Here, we report a paper-based sensor for measuring the concentration of sodium, potassium, calcium, chloride, and nitrite in urine, accurately quantified using a smartphone-enabled platform. By testing the device with both Tris buffer and artificial urine containing a wide range of electrolyte concentrations, we demonstrate that the proposed device can be used for detecting potassium, calcium, chloride, and nitrite within the whole physiological range of concentrations, and for binary quantification of sodium concentration.
Topics: Biosensing Techniques; Calcium; Decision Making; Early Diagnosis; Electrolytes; Humans; Miniaturization; Nitrites; Potassium; Smartphone
PubMed: 32788641
DOI: 10.1038/s41598-020-70456-6 -
European Journal of Applied Physiology Mar 2021To reduce the need for invasive and expensive measures of human biomarkers, sweat is becoming increasingly popular in use as an alternative to blood. Therefore, the...
PURPOSE
To reduce the need for invasive and expensive measures of human biomarkers, sweat is becoming increasingly popular in use as an alternative to blood. Therefore, the (in)dependency of blood and sweat composition has to be explored.
METHODS
In an environmental chamber (33 °C, 65% relative humidity; RH), 12 participants completed three subsequent 20-min cycling stages to elicit three different local sweat rates (LSR) while aiming to limit changes in blood composition: at 60% of their maximum heart rate (HR), 70% HR and 80% HR, with 5 min of seated-rest in between. Sweat was collected from the arm and back during each stage and post-exercise. Blood was drawn from a superficial antecubital vein in the middle of each stage. Concentrations of sodium, chloride, potassium, ammonia, lactate and glucose were determined in blood plasma and sweat.
RESULTS
With increasing exercise intensity, LSR, sweat sodium, chloride and glucose concentrations increased (P ≤ 0.026), while simultaneously limited changes in blood composition were elicited for these components (P ≥ 0.093). Sweat potassium, lactate and ammonia concentrations decreased (P ≤ 0.006), while blood potassium decreased (P = 0.003), and blood ammonia and lactate concentrations increased with higher exercise intensities (P = 0.005; P = 0.007, respectively). The vast majority of correlations between blood and sweat parameters were non-significant (P > 0.05), with few exceptions.
CONCLUSION
The data suggest that sweat composition is at least partly independent of blood composition. This has important consequences when targeting sweat as non-invasive alternative for blood measurements.
Topics: Adult; Ammonia; Chlorides; Exercise; Female; Glucose; Humans; Lactic Acid; Male; Potassium; Sodium; Sweat
PubMed: 33355715
DOI: 10.1007/s00421-020-04562-8 -
Nutrients Jul 2022The excess sodium (Na) intake and insufficient potassium (K) intake are frequently observed all over the world, including Indonesia. This study explored the dietary...
The excess sodium (Na) intake and insufficient potassium (K) intake are frequently observed all over the world, including Indonesia. This study explored the dietary patterns of Indonesian people and evaluated their associations with Na and K intakes. Na and K intakes were assessed by repeated 24-h urine collection. The dietary patterns of the previous month were extracted by factor analysis using the Indonesian Food Frequency Questionnaire. The participants were community-dwelling Indonesian men and women (n = 479) aged 20 years and over. We identified four dietary patterns in each sex. After controlling for confounding factors, the high quantile of ‘Noodle, oil, and salty sea products’ pattern was associated with the high Na intake in both men and women (p = 0.02 and <0.001, respectively). The ‘Meat, vegetable, oil, and fruit’ pattern statistically significantly contributed to the high K intake in men (p = 0.04), but not in women (p = 0.26). The ‘Vegetable, non-oil, and milk’ pattern in men and ‘Meat, vegetable, and fruit’ pattern in women were associated with low Na:K ratios (p = 0.03 and 0.01, respectively). Neither ‘bread’ nor ‘fish’ appeared as a major determinant of any dietary patterns in this population. The ‘Noodle, oil, and salty sea products’ pattern should be avoided to reduce sodium intake.
Topics: Adult; Diet; Female; Humans; Indonesia; Ions; Male; Potassium; Potassium, Dietary; Sodium; Sodium, Dietary; Urine Specimen Collection; Vegetables
PubMed: 35889861
DOI: 10.3390/nu14142905