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Analytica Chimica Acta Aug 2024Potassium isotopic analysis is increasingly performed in both geological and biological contexts as a result of the introduction of MC-ICP-MS instrumentation either...
High-precision K isotopic analysis of cerebrospinal fluid and blood serum microsamples via multicollector inductively coupled plasma-mass spectrometry equipped with 10 Ω faraday cup amplifier resistors.
BACKGROUND
Potassium isotopic analysis is increasingly performed in both geological and biological contexts as a result of the introduction of MC-ICP-MS instrumentation either equipped with a collision/reaction cell or having the capability of working at "extra-high" mass resolution in order to deal with spectral interference caused by argon hydride (ArH) ions. Potassium plays an important role in the central nervous system, and its isotopic analysis could provide an enhanced insight into the corresponding processes, but K isotopic analysis of cerebrospinal fluid is challenging due to the small volume, a few microliter only, typically available. This work aimed at developing a method for determining the K isotopic signature of serum and cerebrospinal fluid at a final K concentration of 25 ng mL using Faraday cup amplifiers equipped with a 10 Ω resistor.
RESULTS
Potassium isotope ratios obtained for reference materials measured at a final K concentration of 25 ng mL were in excellent agreement with the corresponding reference values and the internal and external precision for the δK value was 0.11 ‰ (2SE, N = 50) and 0.10 ‰ (2SD, N = 6), respectively. The robustness against the presence of matrix elements and the concentration mismatch between sample and standard observed at higher K concentrations is preserved at low K concentration. Finally, K isotopic analysis of serum and cerebrospinal fluid (3-12 μL of sample) of healthy mice of both sexes was performed, revealing a trend towards an isotopically lighter signature for serum and cerebrospinal fluid from female individuals, however being significant for serum only.
SIGNIFICANCE
This work provides a robust method for high-precision K isotopic analysis at a concentration of 25 ng mL. By monitoring both K isotopes, K and K, with Faraday cups connected to amplifiers with 10 Ω resistors, accurate K isotope ratio results are obtained with a two-fold improvement in internal and external precision compared to those obtained with the set-up with traditional 10 Ω resistors. The difference in the K isotope ratio in CSF and serum between the sexes, is possibly indicating an influence of the sex or hormones on the fractionation effects accompanying cellular uptake/release.
Topics: Animals; Potassium; Female; Mass Spectrometry; Male; Mice; Isotopes; Humans
PubMed: 38879212
DOI: 10.1016/j.aca.2024.342812 -
Plant Physiology and Biochemistry : PPB Jun 2024Grasslands, the largest carbon pool in China, possess enormous potential for carbon sequestration. Increasing the stomatal aperture to increase the CO absorption...
Grasslands, the largest carbon pool in China, possess enormous potential for carbon sequestration. Increasing the stomatal aperture to increase the CO absorption capacity is a potential method to improve plant photosynthetic efficiency and ultimately enhance the carbon sequestration capacity of grass plants. Research on stomatal aperture regulation has focused mostly on Arabidopsis or crops, while research on grass plants in these areas is scarce, which seriously restricts the implementation of this grassland carbon sequestration strategy. Here, a widely used ecological grass, centipedegrass, was used as the experimental material. First, a convenient method for observing the stomatal aperture was developed. The leaves were floated in a potassium ion-containing open solution (67 mM KCl, pH 6.0) with the adaxial surface rather than the abaxial surface in contact with the solution and were cultivated under light for 1.5 h. Then, nail polish was applied on the adaxial surface, and a large number of open stomata were imprinted. Second, with the help of this improved method, the concentration‒response characteristics of the stomatal aperture to eleven environmental stimuli were tested. The stomatal aperture is dependent on these environmental stimuli in a concentration-dependent manner. The addition of 100 μM brassinolide led to the maximal stomatal aperture. This study provided a technical basis for manipulating stomatal opening to increase the carbon sequestration capacity of centipedegrass.
PubMed: 38878388
DOI: 10.1016/j.plaphy.2024.108838 -
Ecotoxicology and Environmental Safety Jul 2024The combined cadmium (Cd) and acid rain pollution poses a significant threat to the global ecological environment. Previous studies on the combined adverse effects have...
The combined cadmium (Cd) and acid rain pollution poses a significant threat to the global ecological environment. Previous studies on the combined adverse effects have predominantly focused on the aboveground plant physiological responses, with limited reports on the microbial response in the rhizosphere soil. This study employed Populus beijingensis seedlings and potting experiments to simulate the impacts of combined mild acid rain (pH=4.5, MA) or highly strong acid rain (pH=3.0, HA), and soil Cd pollution on the composition and diversity of microbial communities, as well as the physiochemical properties in the rhizosphere soil. The results showed that Cd decreased the content of inorganic nitrogen, resulting in an overall decrease of 49.10 % and 46.67 % in ammonium nitrogen and nitrate nitrogen, respectively. Conversely, acid rain was found to elevate the content of total potassium and soil organic carbon by 4.68 %-6.18 % and 8.64-19.16 %, respectively. Additionally, simulated acid rain was observed to decrease the pH level by 0.29-0.35, while Cd increased the pH level by 0.11. Moreover, Cd alone reduced the rhizosphere bacterial diversity, however, when combined with acid rain, regardless of its intensity, Cd was observed to increase the diversity. Fungal diversity was not influenced by the acid rain, but Cd increased fungal diversity to some extend under HA as observed in bacterial diversity. In addition, composition of the rhizosphere bacterial community was primarily influenced by the inorganic nitrogen components, while the fungal community was driven mainly by soil pH. Furthermore, "Metabolism" was emerged as the most significant bacterial function, which was markedly affected by the combined pollution, while Cd pollution led to a shift from symbiotroph to other trophic types for fungi. These findings suggest that simulated acid rain has a mitigating effect on the diversity of rhizosphere bacteria affected by Cd pollution, and also alters the trophic type of these microorganisms. This can be attributed to the acid rain-induced direct acidic environment, as well as the indirect changes in the availability or sources of carbon, nitrogen, or potassium.
Topics: Cadmium; Soil Microbiology; Populus; Acid Rain; Soil Pollutants; Seedlings; Rhizosphere; Nitrogen; Soil; Microbiota; Hydrogen-Ion Concentration; Bacteria; Fungi
PubMed: 38878333
DOI: 10.1016/j.ecoenv.2024.116583 -
The Journal of Physiology Jun 2024Large trans-sarcolemmal ionic shifts occur with fatiguing exercise or stimulation of isolated muscles. However, it is unknown how resting membrane potential (E) and...
Large trans-sarcolemmal ionic shifts occur with fatiguing exercise or stimulation of isolated muscles. However, it is unknown how resting membrane potential (E) and intracellular sodium concentration ([Na]) change with repeated contractions in living mammals. We investigated (i) whether [Na] (peak, kinetics) can reveal changes of Na-K pump activity during brief or fatiguing stimulation and (ii) how resting E and [Na] change during fatigue and recovery of rat soleus muscle in situ. Muscles of anaesthetised rats were stimulated with brief (10 s) or repeated tetani (60 Hz for 200 ms, every 2 s, for 30 s or 300 s) with isometric force measured. Double-barrelled ion-sensitive microelectrodes were used to quantify resting E and [Na]. Post-stimulation data were fitted using polynomials and back-extrapolated to time zero recovery. Mean pre-stimulation resting E (layer 2-7 fibres) was -71 mV (surface fibres were more depolarised), and [Na] was 14 mM. With deeper fibres, 10 s stimulation (2-150 Hz) increased [Na] to 38-46 mM whilst simultaneously causing hyperpolarisations (7.3 mV for 2-90 Hz). Fatiguing stimulation for 30 s or 300 s led to end-stimulation resting E of -61 to -53 mV, which recovered rapidly (T, 8-22 s). Mean end-stimulation [Na] increased to 86-101 mM with both fatigue protocols and the [Na] recovery time-course (T, 21-35 s) showed no difference between protocols. These combined findings suggest that brief stimulation hyperpolarises the resting E, likely via maximum Na-induced stimulation of the Na-K pump. Repeated tetani caused massive depolarisation and elevations of [Na] that together lower force, although they likely interact with other factors to cause fatigue. [Na] recovery kinetics provided no evidence of impaired Na-K pump activity with fatigue. KEY POINTS: It is uncertain how resting membrane potential, intracellular sodium concentration ([Na]), and sodium-potassium (Na-K) pump activity change during repeated muscle contractions in living mammals. For rat soleus muscle fibres in situ, brief tetanic stimulation for 10 s led to raised [Na], anticipated to evoke maximal Na-induced stimulation of the Na-K pump causing an immediate hyperpolarisation of the sarcolemma. More prolonged stimulation with repeated tetanic contractions causes massive elevations of [Na], which together with large depolarisations (via K disturbances) likely reduce force production. These effects occurred without impairment of Na-K pump function. Together these findings suggest that rapid activation of the Na-K pump occurs with brief stimulation to maintain excitability, whereas more prolonged stimulation causes rundown of the trans-sarcolemmal K gradient (hence depolarisation) and Na gradient, which in combination can impair contraction to contribute to fatigue in living mammals.
PubMed: 38877870
DOI: 10.1113/JP285870 -
Journal of Applied Microbiology Jun 2024Study of rhizospheric microbiome-mediated plant growth promotional attributes currently highlighted as a key tool for the development of suitable bio-inoculants for...
AIMS
Study of rhizospheric microbiome-mediated plant growth promotional attributes currently highlighted as a key tool for the development of suitable bio-inoculants for sustainable agriculture purposes. In this context, we have conducted a detailed study regarding the characterization of phosphate solubilizing potential by plant growth-promoting bacteria that have been isolated from the rhizosphere of a pteridophyte Dicranopteris sp., growing on the lateritic belt of West Bengal.
METHODS AND RESULTS
We have isolated three potent bacterial strains, namely DRP1, DRP2, and DRP3 from the rhizoids-region of Dicranopteris sp. Among the isolated strains, DRP3 is found to have the highest phosphate solubilizing potentiality and is able to produce 655.89 and 627.58 µg ml-1 soluble phosphate by solubilizing tricalcium phosphate (TCP) and Jordan rock phosphate, respectively. This strain is also able to solubilize Purulia rock phosphate moderately (133.51 µg ml-1). Whole-genome sequencing and further analysis of the studied strain revealed the presence of pyrroloquinoline quinone (PQQ)-dependent glucose dehydrogenase gdh gene along with several others that were well known for their role in phosphate solubilization. Further downstream, quantitative reverse transcriptase PCR-based expression study revealed 1.59-fold upregulation of PQQ-dependent gdh gene during the solubilization of TCP. Root colonization potential of the studied strain on two taxonomically distinct winter crops viz. Cicer arietinum and Triticum aestivum has been checked by using scanning electron microscopy. Other biochemical analyses for plant growth promotion traits including indole acetic acid production (132.02 µg ml-1), potassium solubilization (3 mg l-1), biofilm formation, and exopolymeric substances productions (1.88-2.03 µg ml-1) also has been performed.
CONCLUSION
This study highlighted the active involvement of PQQ-dependent gdh gene during phosphate solubilization from any Enterobacter group. Moreover, our study explored different roadmaps for sustainable farming methods and the preservation of food security without endangering soil health in the future.
Topics: Phosphates; Enterobacter; Rhizosphere; Soil Microbiology; Crops, Agricultural; Solubility; Plant Development; Plant Roots; Phylogeny; Calcium Phosphates; Indoleacetic Acids
PubMed: 38877666
DOI: 10.1093/jambio/lxae146 -
Scientific Reports Jun 2024Neuronal activity is accompanied by a net outflow of potassium ions (K) from the intra- to the extracellular space. While extracellular [K] changes during neuronal...
Neuronal activity is accompanied by a net outflow of potassium ions (K) from the intra- to the extracellular space. While extracellular [K] changes during neuronal activity are well characterized, intracellular dynamics have been less well investigated due to lack of respective probes. In the current study we characterized the FRET-based K biosensor lc-LysM GEPII 1.0 for its capacity to measure intracellular [K] changes in primary cultured neurons and in mouse cortical neurons in vivo. We found that lc-LysM GEPII 1.0 can resolve neuronal [K] decreases in vitro during seizure-like and intense optogenetically evoked activity. [K] changes during single action potentials could not be recorded. We confirmed these findings in vivo by expressing lc-LysM GEPII 1.0 in mouse cortical neurons and performing 2-photon fluorescence lifetime imaging. We observed an increase in the fluorescence lifetime of lc-LysM GEPII 1.0 during periinfarct depolarizations, which indicates a decrease in intracellular neuronal [K]. Our findings suggest that lc-LysM GEPII 1.0 can be used to measure large changes in [K] in neurons in vitro and in vivo but requires optimization to resolve smaller changes as observed during single action potentials.
Topics: Animals; Potassium; Neurons; Mice; Biosensing Techniques; Action Potentials; Cells, Cultured; Fluorescence Resonance Energy Transfer; Optogenetics
PubMed: 38877089
DOI: 10.1038/s41598-024-62993-1 -
The Journal of Biological Chemistry Jun 2024The voltage-gated potassium ion channel K11.1 plays a critical role in cardiac repolarization. Genetic variants that render Kv11.1 dysfunctional cause Long QT Syndrome...
The voltage-gated potassium ion channel K11.1 plays a critical role in cardiac repolarization. Genetic variants that render Kv11.1 dysfunctional cause Long QT Syndrome (LQTS), which is associated with fatal arrhythmias. Approximately 90% of LQTS-associated variants cause intracellular protein transport (trafficking) dysfunction, which pharmacological chaperones like E-4031 can rescue. Protein folding and trafficking decisions are regulated by chaperones, protein quality control factors, and trafficking machinery comprising the cellular proteostasis network. Here, we test whether trafficking dysfunction is associated with alterations in the proteostasis network of pathogenic Kv11.1 variants and whether pharmacological chaperones can normalize the proteostasis network of responsive variants. We used affinity-purification coupled with tandem mass tag-based quantitative mass spectrometry to assess protein interaction changes of wild-type (WT) K11.1 or trafficking-deficient channel variants in the presence or absence of E4031. We identified 572 core K11.1 protein interactors. Trafficking-deficient variants K11.1-G601S and K11.1-G601S-G965* had significantly increased interactions with proteins responsible for folding, trafficking, and degradation compared to WT. We confirmed previous findings that the proteasome is critical for K11.1 degradation. Our report provides the first comprehensive characterization of protein quality control mechanisms of K11.1. We find extensive interactome remodeling associated with trafficking-deficient K11.1 variants, and with pharmacological chaperone rescue of K11.1 cell surface expression. The identified protein interactions could be targeted therapeutically to improve K11.1 trafficking and treat Long QT Syndrome.
PubMed: 38876300
DOI: 10.1016/j.jbc.2024.107465 -
Food Chemistry Jun 2024A novel approach for simultaneous detection of iron and potassium via a smartphone-based potentiometric method is proposed in this study. The screen printed electrodes...
A novel approach for simultaneous detection of iron and potassium via a smartphone-based potentiometric method is proposed in this study. The screen printed electrodes were modified with carbon black nanomaterial and ion selective membrane including zinc (II) phtalocyanine as the ionophore. The developed Fe-selective electrode and K-selective electrode exhibited detection limits of 1.0 × 10 M and 1.0 × 10 M for Fe and K ions, respectively. The electrodes were used to simultaneously detect Fe and K ions in apple juice, skim milk, soybean and coconut water samples with recovery values between 90%-100.5%, and validated against inductively coupled plasma-optical emission spectrometry. Due to the advantageous characteristics of the sensors and the portability of Near Field Communication potentiometer supported with a smartphone application, the proposed method offers sensitive and selective detection of iron and potassium ions in food and beverage samples at the point of need.
PubMed: 38876060
DOI: 10.1016/j.foodchem.2024.139971 -
MBio Jun 2024Lymphocytic choriomeningitis virus (LCMV) is an enveloped and segmented negative-sense RNA virus classified within the family of the order. LCMV is associated with...
Lymphocytic choriomeningitis virus (LCMV) is an enveloped and segmented negative-sense RNA virus classified within the family of the order. LCMV is associated with fatal disease in immunocompromised populations and, as the prototypical arenavirus member, acts as a model for the many highly pathogenic members of the family, such as Junín, Lassa, and Lujo viruses, all of which are associated with devastating hemorrhagic fevers. To enter cells, the LCMV envelope fuses with late endosomal membranes, for which two established requirements are low pH and interaction between the LCMV glycoprotein (GP) spike and secondary receptor CD164. LCMV subsequently uncoats, where the RNA genome-associated nucleoprotein (NP) separates from the Z protein matrix layer, releasing the viral genome into the cytosol. To further examine LCMV endosome escape, we performed an siRNA screen which identified host cell potassium ion (K) channels as important for LCMV infection, with pharmacological inhibition confirming K channel involvement during the LCMV entry phase completely abrogating productive infection. To better understand the K-mediated block in infection, we tracked incoming virions along their entry pathway under physiological conditions, where uncoating was signified by separation of NP and Z proteins. In contrast, K channel blockade prevented uncoating, trapping virions within Rab7 and CD164-positive endosomes, identifying K as a third LCMV entry requirement. K did not increase GP-CD164 binding or alter GP-CD164-dependent fusion. Thus, we propose that K mediates uncoating by modulating NP-Z interactions within the virion interior. These results suggest K channels represent a potential anti-arenaviral target.IMPORTANCEArenaviruses can cause fatal human disease for which approved preventative or therapeutic options are not available. Here, using the prototypical LCMV, we identified K channels as critical for arenavirus infection, playing a vital role during the entry phase of the infection cycle. We showed that blocking K channel function resulted in entrapment of LCMV particles within late endosomal compartments, thus preventing productive replication. Our data suggest K is required for LCMV uncoating and genome release by modulating interactions between the viral nucleoprotein and the matrix protein layer inside the virus particle.
PubMed: 38874413
DOI: 10.1128/mbio.01684-23 -
Frontiers in Chemistry 2024Traumatic brain injury (TBI) is a global public health problem with 50-60 million incidents per year, most of which are considered mild (mTBI) and many of these...
Traumatic brain injury (TBI) is a global public health problem with 50-60 million incidents per year, most of which are considered mild (mTBI) and many of these repetitive (rmTBI). Despite their massive implications, the pathologies of mTBI and rmTBI are not fully understood, with a paucity of information on brain lipid dysregulation following mild injury event(s). To gain more insight on mTBI and rmTBI pathology, a non-targeted spatial lipidomics workflow utilizing high resolution mass spectrometry imaging was developed to map brain region-specific lipid alterations in rats following injury. Discriminant multivariate models were created for regions of interest including the hippocampus, cortex, and corpus callosum to pinpoint lipid species that differentiated between injured and sham animals. A multivariate model focused on the hippocampus region differentiated injured brain tissues with an area under the curve of 0.99 using only four lipid species. Lipid classes that were consistently discriminant included polyunsaturated fatty acid-containing phosphatidylcholines (PC), lysophosphatidylcholines (LPC), LPC-plasmalogens (LPC-P) and PC potassium adducts. Many of the polyunsaturated fatty acid-containing PC and LPC-P selected have never been previously reported as altered in mTBI. The observed lipid alterations indicate that neuroinflammation and oxidative stress are important pathologies that could serve to explain cognitive deficits associated with rmTBI. Therapeutics which target or attenuate these pathologies may be beneficial to limit persistent damage following a mild brain injury event.
PubMed: 38873407
DOI: 10.3389/fchem.2024.1394064