Abundant Cation Research Articles

Electrochemical Synthesis of Cation Vacancy-Enriched Ultrathin Bimetallic Oxyhydroxide Nanoplatelets for Enhanced Water Oxidation.

Metal cation vacancies, a kind of structural defect, are viewed as a promising strategy for regulating the electronic properties to enhance the catalytic activity. However, the effective introduction of cation vacancies into electrocatalysts still remains a challenge. Herein, we present and elucidate a facile "fast reduction and in situ phase transformation" strategy at room temperature to simultaneously introduce abundant metal cation vacancies (cobalt vacancies and iron vacancies) into Co0.5Fe0.5OOH electrocatalysts. The incorporation of the Fe element could tailor the micrometer-sized ultrathin CoOOH platelets into nanometer-sized ultrathin Co0.5Fe0.5OOH platelets, and the tailoring process is accompanied with the generation of numerous cation vacancies. The defect degree of CoOOH could be effectively tuned by the incorporation of Fe, resulting in more active sites and lower energy barrier, and thereby the intrinsic catalytic activity of electrocatalysts was further enhanced. Compared to CoOOH, the optimized nanometer-sized ultrathin Co0.5Fe0.5OOH platelets (Co0.5Fe0.5OOH-NSUPs) require a smaller overpotential of 220 mV at a current density of 20 mA cm-2, lower Tafel slope of 38.2 mV dec-1, and better long-term durability without obvious decay for more than 200 h at a high current density of 40 mA cm-2. The electrochemical performances are equal to or better than that of the reported first-class electrocatalysts. More importantly, this work provides new perspective for designing and fabricating efficient multimetal electrocatalysts in large scale.

High concentration magnesium inhibits extracellular matrix calcification and protects articular cartilage via Erk/autophagy pathway

The significant cytopathological changes of osteoarthritis are chondrocyte hypertrophy, proteoglycan loss, extracellular matrix (ECM) calcification, and terminally, the replacement of cartilage by bone. Meanwhile, magnesium ion (Mg2+ ), as the second most abundant divalent cation in the human body, has been proved to inhibit the ECM calcification of hBMSCs (human bone marrow stromal cells), hVSMCs (Human vascular smooth muscle cells), and TDSCs (tendon-derived stem cells) in vitro studies. The ATDC5 cell line, which holds chondrocyte characteristics, was used in this study as an in vitro subject. We found that Mg2+ can efficiently suppress the ECM calcification and downregulate both hypertrophy and matrix metalloproteinase-related genes. Meanwhile, Mg2+ inhibits the formation of autophagy by inhibiting Erk phosphorylation signaling and lowers the expression of LC3, and eventually effectively reduces the formation of ECM calcification in vitro. In this study, we also used destabilization of the medial meniscus (DMM)-induced osteoarthritis (OA) animal model to further confirm the protective effect of Mg2+ on articular cartilage. Compared with the control group (saline-injected), continuous intra-articular magnesium chloride (MgCl2 ) injection can significantly alleviate the severity of cartilage calcification in OA animal model. Immunofluorescence staining also revealed that saline-injected DMM group had a higher positive rate of LC3 expression in cartilage chondrocytes, compared with MgCl2 -injected DMM group. In general, Mg2+ can significantly downregulate the hypertrophic gene Runx2, MMP13, and Col10α1, upregulate the chondrogenic genes Sox9 and Col1α1, inhibit the Erk phosphorylation signaling, reduce the expression of autophagy protein LC3, and effectively inhibit the ECM calcification of ATDC5. In vivo study also proved that intra-articular injection of Mg2+ protected knee cartilage by inhibiting the autophagy formation.

Hypomagnesemia as a predictor of mortality in critically ill pediatric patients in picu using prism score

Background: Magnesium is the fourth most abundant cation in the human body and the second most abundant intracellular cation after potassium. A potential relationship between low magnesium levels and increased mortality has been suggested in the literature. The objectives were to detect prevalence of hypomagnesemia in critically ill children, its association with sepsis and to correlate this with mortality.Methods: This study was an observational study done on 100 children who met the inclusion criteria, admitted to the PICU of Kempegowda Institute of Medical Sciences, Bangalore, Karnataka, India. Patients under the study were managed and treated according to their clinical status and supportive traditional treatment.Results: Prevalence of hypomagnesemia in critically ill pediatric patients was 53%. In this study, majority of the cases admitted to PICU were dengue (19%) and bronchopneumonia (15%) which were significantly associated with hypomagnesemia as p value was less than 0.05. As regard prognosis, Mg had an AUC of 0.576 for prediction of mortality whereas the AUC for PRISM score was 0.811. Logistic regression analysis showed that hypomagnesemia is a significant predictor for mortality among critically ill children (p value=0.028) and OR=3.180 (0.854-7.965).Conclusions: Present study has found high prevalence of hypomagnesemia in critically ill patients. Hypomagnesemia was associated with a higher mortality rate in critically ill patients and commonly associated with infections and respiratory diseases. Hypomagnesemia indicated poor outcome and higher mortality rates in critically ill patients.

The KupA and KupB Proteins of Lactococcus lactis IL1403 Are Novel c-di-AMP Receptor Proteins Responsible for Potassium Uptake.

Cyclic di-AMP (c-di-AMP) is a second messenger involved in diverse metabolic processes, including osmolyte uptake, cell wall homeostasis, and antibiotic and heat resistance. In Lactococcus lactis, a lactic acid bacterium which is used in the dairy industry and as a cell factory in biotechnological processes, the only reported interaction partners of c-di-AMP are the pyruvate carboxylase and BusR, the transcription regulator of the busAB operon for glycine betaine uptake. However, recent studies uncovered a major role of c-di-AMP in the control of potassium homeostasis, and potassium is the signal that triggers c-di-AMP synthesis. In this study, we have identified KupA and KupB, which belong to the Kup/HAK/KT family, as novel c-di-AMP binding proteins. Both proteins are high-affinity potassium transporters, and their transport activities are inhibited by binding of c-di-AMP. Thus, in addition to the well-studied Ktr/Trk potassium channels, KupA and KupB represent a second class of potassium transporters that are subject to inhibition by c-di-AMP.IMPORTANCE Potassium is an essential ion in every living cell. Even though potassium is the most abundant cation in cells, its accumulation can be toxic. Therefore, the level of potassium has to be tightly controlled. In many Gram-positive bacteria, the second messenger cyclic di-AMP plays a key role in the control of potassium homeostasis by binding to potassium transporters and regulatory proteins and RNA molecules. In the lactic acid bacterium Lactococcus lactis, none of these conserved c-di-AMP-responsive molecules are present. In this study, we demonstrate that the KupA and KupB proteins of L. lactis IL1403 are high-affinity potassium transporters and that their transport activity is inhibited by the second messenger c-di-AMP.

Biochemical and biophysical characterization of a prokaryotic Mg2+ ion channel: Implications for cost-effective purification of membrane proteins

Although magnesium is the second most abundant cation present in the cell, the transport mechanism of Mg2+ across membranes is poorly understood. Importantly, the prokaryotic MgtE Mg2+ channel is related to mammalian SLC41A1 transporters and, therefore, biochemical and biophysical characterization of MgtE and its orthologs assumes significance. To date, the purification and structure determination of MgtE from Thermus thermophilus has been carried out using the widely used nonionic detergent, n-dodecyl-β-d-maltopyranoside (DDM). However, DDM is an expensive detergent and alternative methods to produce high-quality proteins in stable and functional form will be practically advantageous to carry out structural studies in a cost-effective manner. In this work, we have utilized ‘dual-detergent strategy’ to successfully purify MgtE channel in a stable and functional form by employing relatively inexpensive detergents (Triton X-100 and Anzergent 3–14) for membrane solubilization and subsequently changed to DDM during purification. Our results show that Triton X-100 and Anzergent 3–14 extract MgtE well and the quality of purified protein is comparable to DDM-extracted MgtE. Interestingly, addition of high concentration of salt and glycerol during solubilization does not significantly affect the quantity and quality of MgtE. Importantly, limited proteolysis assay, circular dichroism spectroscopy and ensemble tryptophan fluorescence strongly support the use of Triton X-100, in particular, as an inexpensive, alternative detergent for the purification of MgtE without compromising the structural integrity of the channel and Mg2+-induced gating-related conformational dynamics. Overall, these results are relevant for the cost-effective purification of stable and functional membrane proteins in general, and magnesium channels, in particular.

Controllable Eu2+-Doped Orthophosphate Blue-/Red-Emitting Phosphors: Charge Compensation and Lattice-Strain Control.

Cation-substitution-induced controllable luminescence tuning could efficiently optimize and improve the luminescence performances of novel phosphor materials for realizing high-quality lighting. As important members of the orthophosphate family, ABPO4 (A = alkali metal Li, Na, K, Rb, Cs; B = alkali earth metal Mg, Ca, Sr, Ba) offers an abundant cation lattice environment for rare earth ions. Herein, we successfully prepared a broad-band red-emitting CsMgPO4:Eu2+ phosphor with an emission peak at 628 nm (fwhm = 118 nm). A series of cation-substitution strategies are designed to adjust and enhance its luminescence performances. The corresponding mechanisms are also investigated and proposed reasonably. A charge-compensation strategy of [Eu2+-Si4+] → [Cs+-P5+] could dramatically enhance the quenching concentration from 0.04 to 0.30, which is attributed to the decrease of Eu3+. Two cation-substitution strategies of larger Ba2+ (Sr2+) ions for Mg2+ ions could achieve superior emission adjustment of Eu2+ ions from the red to blue (yellow) region due to local lattice distortion. Interestingly, a consecutive emission adjustment from the red to blue region by simply changing the annealed temperature is reported for the first time, and the possible emission tuning mechanism is revealed based on a local lattice-strain control. This study could serve as a guide in developing Eu2+-activated ABPO4 phosphors with improving luminescence performance and controllable luminescence adjustment based on charge compensation and lattice-strain control through various cation substitutions.

Magnesium: The Forgotten Electrolyte-A Review on Hypomagnesemia.

Magnesium is the fourth most abundant cation in the body and the second most abundant intracellular cation. It plays an important role in different organ systems at the cellular and enzymatic levels. Despite its importance, it still has not received the needed attention either in the medical literature or in clinical practice in comparison to other electrolytes like sodium, potassium, and calcium. Hypomagnesemia can lead to many clinical manifestations with some being life-threatening. The reported incidence is less likely than expected in the general population. We present a comprehensive review of different aspects of magnesium physiology and hypomagnesemia which can help clinicians in understanding, identifying, and treating this disorder.

Contribution of Mg2+ and Solute Carrier Family 41 to Pulmonary Hypertension in Rat Models

Pulmonary hypertension (PH) is a debilitating disease and characterized by profound vascular remodeling. Many studies indicate that it is related in part to the alterations of Ca2+ homeostasis in pulmonary arterial smooth muscle cells (PASMCs). Mg2+ ion is closely related to Ca2+ ion and is the second‐most abundant divalent cation in animal cells. It is required for the regulation of diverse cellular functions, including cell growth, proliferation, and migration. The Solute Carrier 41 family (SLC41) members including A1, A2 and A3 are Mg2+ transporters, and they have been identified in lung vascular tissue. However, the changes in their expression and functions of SLC41 transporters in PH have not been examined. The present study was designed to investigate whether Mg2+ and its transporters are involved in PH development. PH rats were established by a single injection of MCT or exposed to normobaric hypoxia (CH, 10% O2) for 21 days. Another set of animals received the same treatment were fed with Mg2+ diet supplement (10 mL/kg/d) for 21 days. The expression of SLC41A1/2/3 mRNA and protein in PAs of control and PH rats with or without Mg2+ supplement were determined by Q‐PCR and Western blot. SLC41A1‐2 expressions were significantly increased in PAs of MCT or CH‐treated rats, while mRNA and protein of SLC41A3 were decreased in PH rats. Moreover, PH was attenuated and the changes in SLC41A1‐3 expression were reversed in rats treated with Mg2+ diet supplement. The roles of Mg2+ and SLC41 proteins in PASMCs proliferation and migration were further examined in PASMCs isolated from control rat. They were treated with a control sequence or a SLC41A1/2 targeting siRNA and cultured under low (0.15 mM), normal (1.2 mM) and high (4.8 mM) level of Mg2+. PASMC proliferation monitored using MTS reagent or EdU staining and, migration assessed with Transwell or wound healing assay were markedly inhibited after incubation with high Mg2+ for 48h. Furthermore, siRNA targeting SLC41A1/2 attenuated PASMC proliferation. Our results, hence, clearly show that the SLC41 transporters contribute to PH, and Mg2+ diet supplement could effectively alleviate PH; In addition, Mg2+ and SLC41A1/2 actively participate in PASMC proliferation and migration. These results provide the basis for future study on the roles of Mg2+ and its transporters in PH development.Support or Funding InformationThis work was supported by grants from the National Natural Science Foundation of China NSFC31571179 and NSFC31371165This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Mg2+ homeostasis and transport in cyanobacteria - at the crossroads of bacterial and chloroplast Mg2+ import.

Magnesium cation (Mg2+) is the most abundant divalent cation in living cells, where it is required for various intracellular functions. In chloroplasts and cyanobacteria, established photosynthetic model systems, Mg2+ is the central ion in chlorophylls, and Mg2+ flux across the thylakoid membrane is required for counterbalancing the light-induced generation of a ΔpH across the thylakoid membrane. Yet, not much is known about Mg2+ homoeostasis, transport and distribution within cyanobacteria. However, Mg2+ transport across membranes has been studied in non-photosynthetic bacteria, and first observations and findings are reported for chloroplasts. Cyanobacterial cytoplasmic membranes appear to contain the well-characterized Mg2+ channels CorA and/or MgtE, which both facilitate transmembrane Mg2+ flux down the electrochemical gradient. Both Mg2+ channels are typical for non-photosynthetic bacteria. Furthermore, Mg2+ transporters of the MgtA/B family are also present in the cytoplasmic membrane to mediate active Mg2+ import into the bacterial cell. While the cytoplasmic membrane of cyanobacteria resembles a 'classical' bacterial membrane, essentially nothing is known about Mg2+ channels and/or transporters in thylakoid membranes of cyanobacteria or chloroplasts. As discussed here, at least one Mg2+ channelling protein must be localized within thylakoid membranes. Thus, either one of the 'typical' bacterial Mg2+ channels has a dual localization in the cytoplasmic plus the thylakoid membrane, or another, yet unidentified channel is present in cyanobacterial thylakoid membranes.

Role of magnesium in heart diseases among elderly

Magnesium constitutes fourth most abundant cation in human body. It plays important role in the electrical stability of the conduction system of the heart. Measure of total serum magnesium correlates with ionized and intracellular levels of magnesium in human cells. Both low and high levels of magnesium are associated with cardiac disorders especially in older people. The hypomagnesemia contributes to atherosclerosis which in turn is a risk factor for Hypertension and cardiovascular diseases. The magnesium in diet is often not sufficient to meet the daily needs in older people hence they are prone for developing complication of cardiovascular events. This review relooks at the role of magnesium in causing cardiovascular diseases and its complications. Keywords: Magnesium, Elderly, Heart Disease.

Structural Modulation of RyR1 by MgATP and Free Mg2+ in Lipid Membrane using CryoEM

Mg2+ is the most abundant divalent cation in living cells. In the skeletal muscle cytosol, out of the total Mg2+ concentration of 8 mM, around 1 mM is free Mg2+ and around 5 mM exists in the form of MgATP, the biological active form of cellular ATP. Mg2+ is constitutively bound to RyR1 in its free and complexed forms. In fact, preferential binding of Mg2+ to the acidic side chains with similar coordination geometry as Ca2+, allows it to be a potential antagonistic cation of Ca2+, which has much lower cytoplasmic concentrations (<1 μM - 100 μM). Free Mg2+ is thought to inhibit RyRs through its association with Ca2+ binding sites at cytoplasmic or luminal regions, while the effect of MgATP per se is novel in the context of excitation-contraction coupling. We studied the effect of free Mg2+ and MgATP on RyR1 bound to a POPC bilayer enclosed by membrane scaffold protein (nanodisc). CryoEM reconstructions of RyR1 nanodiscs complexed with MgAMPPCP at ∼3.8 Å resolution show that in the absence of any detergents or FKBP, the RyR1 assumes a closed conformation with a pore radius that makes impermeant to Ca2+ ions. Discernible densities for nanodisc and MgATP were observed. Binding of MgATP involves global motion of the central and cytoplasmic domains towards the T-tubule and the fourfold axis with reorganization of the P2 domain. Local motion of the TM helices, U-motif, VSC and EF hands were also observed with concomitant closure of the ATP cavity at the intersubunit interface. With the cryoEM structure of RyR1-MgATP, we seek to explain the mechanistic basis of RyR1 inhibition during the physiological resting state of skeletal muscle. Supported by grants AHA 14GRNT19660003, MDA352845, NIH R01 AR068431, and NIH U24GM116789.

Characteristics of Mineral Fluids and Geothermal Reservoir in Changbai Mountain, Northeast of China

Changbai Mountain in China has been explored as a potential area for enriching mineral fluids including thermal springs and cold springs mineral water. The hydrogeochemical characteristics and reservoir temperatures of the nine thermal springs and fifteen cold springs were evaluated by hydrogeochemical analysis, statistical analysis and geothermometry analysis. The results showed that the concentrations of ions of thermal springs were higher than those of cold springs. $${\text{HCO}}_{3}^{ - }$$ and Na+ were the most abundant anion and cation in the thermal springs, and hydrochemical type was Na–HCO3. While the cold springs were enriched in Ca2+, Mg2+, $${\text{HCO}}_{3}^{ - }$$ and $${\text{SO}}_{4}^{{2 - }}$$ , and hydrochemical types were Ca · Mg–HCO3 · SO4, Ca–HCO3, Ca · Mg · Na–HCO3 and Ca · Mg · Na–SO4 · HCO3. The age of thermal springs were larger than 62 years. Olivine and pyroxene were under-saturated for all thermal springs; and olivine, pyroxene, dolomite and fluorite were under-saturated for all cold springs. All the thermal and cold springs samples can be divided into three groups by cluster test, and all the thermal spring samples fell into the part of immature waters, the mixing ration of cold and hot water ranged 12.70 to 36.95%. The reservoir temperatures of WQ1 to WQ9 were between 96.88 and 174.28°C using silica geothermometry.

Hydrogeochemical Characteristics and Genesis Model of Jinjiang and Julong Hot Springs in Changbai Mountain, Northeast China

Changbai Mountain in China has been explored as a potential area for its rich hot springs including the Jinjiang and Julong hot spring groups. The hydrogeochemical characteristics and conceptual genesis models of the Jinjiang and Julong hot springs were evaluated by hydrogeochemical analysis, isotope analysis, rock sample analysis, hydrogeochemistry simulation, and geophysical exploration method. The results showed that HCO3− and Na+ were the most abundant anion and cation in the hot springs, and the hydrochemical type was Na-HCO3. And the hot springs are enriched with trace components such as H2SiO3 and Sr. The major gas composition of the Jinjiang hot springs and Julong hot springs were CO2, N2, and CH4, which were derived from the mantle. The chemical compositions were produced by feldspar and pyroxene mineral hydrolysis. The recharge source of the hot springs was atmospheric precipitation and was also influenced by evaporation, and the genetic models for the Jinjiang hot springs and Julong hot springs were as follows: the heat source of both was a magma body and heat was mainly migrated in the form of thermal conduction. The cap rocks were both composed of trachyte of Baitoushan formation, basalt of Junjianshan formation, and rhyolitic pyroclastic rocks of Changbai formation. The geothermal reservoir of both hot springs was a fracture zone with the lithology of volcanic breccia, sand, and gravel and volcanic breccia and marble, respectively.

An observational study on effects of hypomagnesemia among critically ill patients at a tertiary care hospital

Background: Magnesium is the fourth abundant cation in the human body and second most abundant intracellular cation after potassium and also serving as cofactor in more than 300 enzymatic reactions. Magnesium deficiency is the most commonly overlooked condition in critically ill patients and associated with other coexisting electrolyte abnormalities. The aim of the present study was to evaluate serum magnesium levels in critically ill patients and to correlate with patient outcome and other parameters like length of stay in ICU, ventilator support, APACHE-II score and duration and mortality.Methods: A two years observational study after ethical committee approval was conducted at a tertiary care hospital among critically ill patients admitted in ICU. Serum magnesium levels and other relevant investigations were performed within 24 hours of admission. Patients management and progress were followed till the outcome. The data was analysed by using SPSS software version 16.0 for windows.Results: Total of 150 patients with 102 males and 48 females were enrolled. 97 cases (64.7%) of hypomagnesemia were observed and 11 cases of hypermagnesemia and 42 cases with normal serum magnesium levels were observed. Hypomagnesemia cases were compared with normal cases and found that: Hypomagnesemia cases had higher mortality rate, higher APACHE II score, more length of hospital stay and ventilator duration. Significant association was identified with diabetes and chronic alcoholism (p valve &lt;0.05).Conclusions: Monitoring of magnesium levels in critically ill patients has several prognostic and therapeutic implications and should be recommended as a regular parameter as it is commonly out looked condition. Statistically significant association of hypomagnesaemia was found with hypocalcaemia, hypoalbuminaemia, septicaemia, diabetes and chronic alcoholism. Higher APACHE II score is associated with higher mortality and more length of stay in ICU among the cases of hypomagnesaemia.

The Arabidopsis thaliana K+-Uptake Permease 5 (AtKUP5) Contains a Functional Cytosolic Adenylate Cyclase Essential for K+ Transport.

Potassium (K+) is the most abundant cation in plants, and its uptake and transport are key to growth, development and responses to the environment. Here, we report that Arabidopsis thaliana K+ uptake permease 5 (AtKUP5) contains an adenylate cyclase (AC) catalytic center embedded in its N-terminal cytosolic domain. The purified recombinant AC domain generates cAMP in vitro; and when expressed in Escherichia coli, increases cAMP levels in vivo. Both the AC domain and full length AtKUP5 rescue an AC-deficient E. coli mutant, cyaA, and together these data provide evidence that AtKUP5 functions as an AC. Furthermore, full length AtKUP5 complements the Saccharomyces cerevisiae K+ transport impaired mutant, trk1 trk2, demonstrating its function as a K+ transporter. Surprisingly, a point mutation in the AC center that impairs AC activity, also abolishes complementation of trk1 trk2, suggesting that a functional catalytic AC domain is essential for K+ uptake. AtKUP5-mediated K+ uptake is not affected by cAMP, the catalytic product of the AC, but, interestingly, causes cytosolic cAMP accumulation. These findings are consistent with a role for AtKUP5 as K+ flux sensor, where the flux-dependent cAMP increases modulate downstream components essential for K+ homeostasis, such as cyclic nucleotide gated channels.

Plant Calcium Signaling in Response to Potassium Deficiency.

Potassium (K+) is an essential macronutrient of living cells and is the most abundant cation in the cytosol. K+ plays a role in several physiological processes that support plant growth and development. However, soil K+ availability is very low and variable, which leads to severe reductions in plant growth and yield. Various K+ shortage-activated signaling cascades exist. Among these, calcium signaling is the most important signaling system within plant cells. This review is focused on the possible roles of calcium signaling in plant responses to low-K+ stress. In plants, intracellular calcium levels are first altered in response to K+ deficiency, resulting in calcium signatures that exhibit temporal and spatial features. In addition, calcium channels located within the root epidermis and root hair zone can then be activated by hyperpolarization of plasma membrane (PM) in response to low-K+ stress. Afterward, calcium sensors, including calmodulin (CaM), CaM-like protein (CML), calcium-dependent protein kinase (CDPK), and calcineurin B-like protein (CBL), can act in the sensing of K+ deprivation. In particular, the important components regarding CBL/CBL-interacting protein kinase (CBL/CIPK) complexes-involved in plant responses to K+ deficiency are also discussed.

Molecular expression of Mg2+ regulator TRPM7 and CNNM4 in rat odontoblasts

ObjectiveMagnesium, the second most abundant cation in cellular fluid, is critical for mineralization of hard tissues. Among the molecules involved in cellular Mg2+ homeostasis, functional impairment of Mg2+ permeable ion channel TRPM7 or Mg2+ transporter CNNM4 have been found to result in severe hypomineralization of the enamel and dentin. However, molecular expressions of TRPM7, CNNM4 and their respective homologues have not been fully investigated in adult odontoblasts. DesignExpressions of TRPM6, TRPM7, CNNM1, CNNM2, CNNM3, CNNM4 were screened in acutely dissociated rat odontoblasts by single cell RT-PCR. Among these candidates, expression levels of TRPM7 and CNNM4 were compared along the odontoblast layer by immunohistochemical analysis. Finally, the coexpression pattern of TRPM7 and CNNM4 in subcellular regions was examined by immunocytochemical analysis. ResultsScRT-PCR revealed high expression rate of TRPM7 and CNNM4 in odontoblasts, with CNNM4 detected almost exclusively in TRPM7-positive odontoblasts. However, CNNM2 and CNNM3 were detected in only a small population of odontoblasts, and TRPM6 and CNNM1 were not detected even in the pulp tissue. Immunohistochemical analysis revealed higher CNNM4 expression in the apical odontoblast layer than the coronal area, in contrast to the ubiquitous expression of TRPM7. Lastly, immunocytochemical analysis revealed colocalization of CNNM4 with TRPM7 in the odontoblastic process. ConclusionsCNNM4 and TRPM7 may serve as main Mg2+ regulators in odontoblasts, possibly with selective involvement of CNNM4 in apical dentin formation or mineralization. Colocalization of TRPM7 and CNNM4 in the odontoblastic process suggest functional coupling of these two molecules to maintain Mg2+ homeostasis.

Multiparametric quantification of heterogeneity of metal ion concentrations, as demonstrated for [Mg2+] by way of 31P MRS

Magnesium(II) is the second most abundant intracellular cation in mammals. Non-invasive 31P MRS is currently used to measure intracellular free Mg2+ levels in studies of magnesium deficiency disorders. However, this technique only provides one [Mg2+] value for a given tissue volume (or voxel), based on the chemical shift of the ATP-β (or NTP-β) resonance. We present here an approach for quantifying tissue heterogeneity in regard to [Mg2+], by way of multiple 31P MRS-derived descriptors characterizing the statistical intra-volume distribution of free [Mg2+] values. Our novel paradigm exploits the fact that the lineshape of the ATP-β 31P MRS resonance reflects the statistical distribution of [Mg2+] values within the observed volume (or voxel). Appropriate lineshape analysis reveals multiple quantitative statistical parameters (descriptors) characterizing the [Mg2+] distribution. First, the ATP-β 31P MRS resonance is transformed into a [Mg2+] curve that is used to construct a histogram with our specially developed algorithms. From this histogram, at least eight [Mg2+] descriptors are computed: weighted mean concentration and median concentration, standard deviation of concentration, range of concentration, concentration mode(s), concentration kurtosis, concentration skewness, and concentration entropy. Comprehensive evaluation based on in silico and experimental models demonstrates the validity of this new method. This basic feasibility study should open new avenues for future in vivo studies in physiology and medicine.

Genome-Wide Analysis of Potassium Transport-Related Genes in Chickpea (Cicer arietinum L.) and Their Role in Abiotic Stress Responses

Potassium is the most abundant inorganic cation that constitutes up to 10% of the total plant dry weight and plays a prominent role in plant growth and development. Plants exhibit a complex but highly organized system of channels and transporters, which are involved in absorption and distribution of K+ from soil to different parts of plants. In this study, we explored the K+ transport system in chickpea genome and identified 36 genes encoding potassium channels and transporters. The identified genes were further classified on the basis of their domain structure and conserved motifs. It includes K+ transporters (23 genes: 2 HKTs, 6 KEAs, and 15 KUP/HAK/KTs) and K+ channels (13 genes: 8 Shakers and 5 TPKs). Chromosomal localization of these genes demonstrated that various K+ transporters and channels are randomly distributed across all the eight chromosomes. Comparative phylogenetic analysis of K+ transport system genes from Arabidopsis thaliana, Glycine max, Medicago truncatula, and Oryza sativa revealed their strong conservation in different plant species. Similarly, gene structure analysis displayed conservation of family-specific intron/exon organization in the K+ transport system genes. Evolutionary analysis of these genes suggested the segmental duplication as principal route of expansion for this family in chickpea. Several abiotic stress-related cis-regulatory elements were also identified in promoter regions suggesting their role in abiotic stress tolerance. Expression analysis of selected genes under drought, heat, osmotic, and salt stress demonstrated their differential expression in response to these stresses. This signifies the importance of these genes in the modulation of stress response in chickpea. Present study provides the first insight into K+ transport system in chickpea and can serve as a basis for their functional analysis.

Magnesium Balance and Measurement.

Magnesium is an essential ion in the human body, playing an important role in practically every major metabolic and biochemical process, supporting and maintaining cellular processes critical for human life. Magnesium plays an important physiological role, particularly in the brain, heart, and skeletal muscles. As the second most abundant intracellular cation after potassium, it is involved in over 600 enzymatic reactions including energy metabolism and protein synthesis. Magnesium has been implicated in and used as treatment of several diseases. Although the importance of magnesium is widely acknowledged, routine serum magnesium levels are not routinely evaluated in clinical medicine. This review provides a discussion as to where magnesium is stored, handled, absorbed, and excreted. We discuss approaches for the assessment of magnesium status.