Increase In Ca2 Research Articles

In situ determination of guard cell ion flux underpins the mechanism of ABA-mediated stomatal closure in barley plants exposed to PEG-induced drought stress

ABA regulates stomatal movement by affecting ion transport in guard cells; yet in situ measurement of ABA-mediated dynamics of guard cell ion transport and the involvement of other phytohormones in regulating stomatal aperture under drought stress are still lacking. In this study, hydroponically grown plants of wild type barley Steptoe (WT) and its correspondent ABA-deficient barley mutant Az34 were treated with 10% polyethylene glycol (PEG) 6000 for 0, 2, 4, and 24 h or 9 d to mimic short- and long-term drought stress. The K+, H+ and Ca2+ fluxes in the guard cell were monitored in situ by noninvasive micro-test technology. Upon 10% PEG treatment, leaf ABA concentration ([ABA]leaf) of both barley genotypes increased dramatically after 2 h and reached the highest level after the 24 h. Compared to the control, a significant increase in Ca2+ influx in both genotypes was observed after 2 h exposure to PEG, and reached the largest value after 4 h in WT. The increase of [ABA]leaf coincided with the increase of K+ efflux and Ca2+ influx and the decrease of stomatal conductance in WT under short-term drought stress, though the concentrations of IAA, GA3 and ZR in WT were all increased at 4 h. K+ efflux of guard cells was significantly greater in WT than in Az34 at 24 h after PEG treatment. The results elucidate the role of ABA in mediating ion transports in guard cells, hereby regulating the stomatal movement in barley exposed to drought stress.

Micropores and mass transfer in the formation of myrmekites

Abstract The formation process of myrmekites in granitic rocks can help us to understand the mass transfer between minerals and hydrothermal fluids during the deuteric stage. The Toki granite, central Japan, has three types of myrmekites. Type A myrmekite is defined as a single layer. Type B myrmekite shows a composite texture consisting of two layers, namely, a myrmekite layer and an albite (Ab)-rich layer that is free of vermicular quartz. Type C has a composite texture with the following three layers: two myrmekite layers separated by one Ab-rich layer. Micropores are found in these myrmekites in the undeformed granite, which enable quantitative determinations of the volume decrease during myrmekite formation by measurement of the area of micropores. The areal relationship between the micropores and vermicular quartz in the myrmekites exhibited a high correlation (R2 = 0.8352), thus indicating that the genesis of the micropores is evidently related to myrmekite formation. We derived the reaction equations for myrmekite formation based on the singular value decomposition method. The matrices for singular value decomposition involve the following volume factors: volume change during the reaction and volume ratios of the product minerals. The singular value decomposition indicates that the myrmekites are produced through the consumption of plagioclase and K-feldspar with an inflow of H4SiO4, Na+, and H+ from the hydrothermal fluid, accompanied by an outflow of Al3+, Ca2+, and K+ into the fluid, which constitute essential mass transfers during myrmekite formation. The difference of pH in the hydrothermal fluid and inflow amounts of H4SiO4 and Na+ can explain the reason why micropores occur in the myrmekites but not in the Ab-rich rim (layer); the smaller inflow of H4SiO4 and Na+ from the hydrothermal fluid with lower pH conditions yielded micropore production during myrmekitization, and the larger inflow of H4SiO4 and Na+ from the hydrothermal fluid with higher pH conditions yielded the formation of the Ab-rich rim (layer) with few micropores. The sequential variations in the chemical characteristics of the hydrothermal fluid during the sub-solidus conditions were characterized by a gradual decrease in H4SiO4 (Si4+), Fe2+, Mn2+, Mg2+, and Na+ and a gradual increase in Ca2+, K+, H+, and F–.

Uranium Distribution and Incorporation Mechanism in Deep-Sea Corals: Implications for Seawater [CO32–] Proxies

A conservative element in seawater, uranium is readily incorporated into the aragonitic skeletons of scleractinian corals, making them an important paleoclimate archive that can be absolutely dated with U-Th techniques. In addition, uranium concentrations (U/Ca ratios) in corals have been suggested to be influenced by the temperature and/or carbonate ion concentration of the ambient seawater based on empirical calibrations. Microsampling techniques have revealed strong heterogeneities in U/Ca within individual specimens in both surface and deep-sea corals, suggesting a biological control on the U incorporation into the skeletons. Here we further explore the mechanism of uranium incorporation in coral skeletons with the deep-sea species Desmophyllum dianthus, an ideal test organism for the biomineralization processes due to its relatively constant growth environment. We find a negative correlation between bulk coral U/Ca and temperature as well as ambient pH and [CO32–] that is consistent with previous studies. By sampling the growth bands of individual corals, we also find a twofold change in U/Ca within individual corals that is strongly correlated with the δ18O, δ13C, and other Me/Ca ratios of the bands. A similar correlation between U/Ca and stable isotopes as well as other Me/Ca ratios are observed in bulk deep-sea coral samples. With a numerical coral calcification model, we interpret the U/Ca-stable isotope correlation as a result of changes in uranium speciation in response to internal pH elevations in the extracellular calcifying fluid (ECF) of the corals, and suggest that the Ca2UO2(CO3)3(aq) complex, the dominant U species in seawater, may be the major species incorporated into the coral skeleton. Therefore, the correlation between U/Ca and ambient [CO32–] is likely a result of the response of the biomineralization process, especially the magnitude of internal pH elevation, to the growth environment of the corals. Our data suggest overall lower alkalinity pump rates in corals from low saturation seawater compared to those from high saturation seawater, and possible increases in Ca2+ supply from active pumping relative to seawater transport in response to the environmental stress of low saturation.

Chlorine isotope data of chlorides challenge the pore fluid paradigm

In order to examine the seawater-seafloor sediment interactions that influence the chemical composition of seawater through time, we examined hundreds of pore fluid geochemical analyses from 13 clay-rich sedimentary successions drilled by the ODP-IODP. Chemical trends such as monotonous increases in Ca2+, and decreases in Mg2+ and δ18O with depth are traditionally interpreted to result from water-rock interaction. In this view, the release of Ca2+ into fluids and the uptake of Mg2+ and 18O mainly results from the formation of low-temperature clays in the sediment and within underlying basalts. Chloride concentration profiles and isotopic compositions, however, suggest that different processes may influence pore water geochemistry. The data examined here show relatively constant chloride contents but with a systematic decrease in δ37Cl of chlorides with depth from 0 permil (the seawater value) down to −8.5 permil. The δ37Cl data are highly correlated with δ18O (with δ18O down to −5.7 permil).The δ37Cl-depletions of pore fluid chlorides are found in all studied sedimentary piles regardless of tectonic or sedimentary history. These trends cannot be explained by water–rock exchange reactions because minerals formed at low temperature have Cl contents that are too low to compensate for δ37Cl depletions observed in pore fluids. Accordingly, we hypothesize that fluid-specific processes are responsible for the δ37Cl-depletions of the fluids and that δ37Cl-enriched chlorides were expelled out of the sediments into the ocean. After reviewing the fluid-specific processes that are known to change the chlorine isotope ratios in chlorides, we rule out diffusion and gravitational isotope fractionations of chlorides could generate this isotope pattern. The flow of a δ37Cl -depleted fluid from the underlying basaltic basement into the sediments could explain the δ37Cl data. But the mechanism that produces depletion in δ37Cl of the fluid remains unknown. It cannot be chloride exchanges between fluids and rocks.Here we show that compaction-induced ion filtration of chlorides through clay-rich membranes can produce the observed pore fluid δ37Cl-depletions, with isotope fractionation factors ranging from 1.000 to 1.008 between the chlorides of the expelled fluid (the permeate) and those of the residual fluid (the retentate). We find that smectite-rich sediments are associated with higher isotopic fractionation factors, while illite/chlorite-rich sediments are associated with intermediate values and with clay-poor sediments associated with lower values. This suggests that chlorine isotope fractionation might be controlled by surface charge associated with specific clay minerals. Our calculations show that compaction-induced filtration has the capacity to produce 18O-depletion for oxygen isotope fractionation factors between the expelled fluid and the retentate ranging from 1.000 to 1.005. 18O-enrichment in the expelled fluid is in agreement with the experimental data of Haydon and Graf (1986). Overall, although further experimental work on both chlorine and oxygen isotopes is certainly needed, the results of this study indicate that ion-filtration should be considered as a potential mechanism for fractionating isotopic species in sediment pore waters, particularly for oxygen isotope ratios whose variations are often commonly attributed to water–rock exchange.

Dynamics of macroelements content in blood of foxes (Vulpes vulpes) with different genotypes in postnatal ontogenesis

The dynamics of macronutrients in blood of foxes (Vulpes vulpes L., 1758) of two coloring genotypes: silver-black (A/a b/b; a/a B/B) and Vyatka moth (A/A B/B) in postnatal ontogenesis - at the age of 2, 4, 6 and 12 (adults) months. Macronutrients were determined by the capacity of a semi-automatic biochemical analyzer “BioChem SA” (the USA) using reagent kits from High Technology (the USA). In growing young foxes of coloring genotypes: silver-black (A/a b/b; a/a B/B) and Vyatka moth (A/A B/B), the final profile of the content in the blood of macronutrients Ca2+, Mg2+ and phosphorus is formed by the age of 6 month. Moreover, only in Vyatka moth males (A/A B/B) at the age of 2 months a significant effect of the genotype on the increase in Ca2+ level was noted, in females of the same genotype at the age of 4 months – on the increase in the level of Mg2+. The obtained data can be used as reference values in the study of the etiology and pathogenesis of diseases accompanied by impaired metabolism of macroelements.

Mechanism of the adverse effect of hyaluronidase used for oocyte denudation on early development of bovine embryos.

Hyaluronidase is widely used in animal and human assisted reproductive technologies (ARTs) to remove cumulus cells around oocytes. However, adverse effects of hyaluronidase treatment, such as increased rates of degeneration and parthenogenesis, have been found after treatment of human and mouse oocytes. Currently, the mechanism(s) of the detrimental effects are unclear. The present study was initiated to identify the mechanism of adverse responses to hyaluronidase treatment in bovine oocytes and early embryos. Cumulus cells were removed from cumulus-oocyte complexes (COCs) with or without hyaluronidase and the oocytes were subjected to intracytoplasmic sperm injection (ICSI) or in vitro fertilization (IVF). Significantly lower rates of blastocyst formation were obtained in the hyaluronidase treatment group after ICSI (22.4%) and IVF (21.2%) compared with the non-hyaluronidase control groups: 36.1% after ICSI and 30.4% after IVF. Next, we examined the effect of hyaluronidase on parthenogenetic development rates and on the cytoplasmic levels of free calcium ions (Ca2+), reactive oxygen species (ROS) and reduced glutathione (GSH). No differences in parthenogenesis rates were found between treated and untreated groups. Ca2+ levels in oocytes from the hyaluronidase treatment group indicated using mean fluorescence intensity were significantly higher (68.8 ± 5.3) compared with in the control group (45.0 ± 2.5). No differences were found in the levels of ROS or GSH between the treated and untreated groups. We conclude that hyaluronidase might trigger an increase in Ca2+ levels in oocytes, resulting in a decreased potential for normal embryonic development.

The protective effects of curcumin in cerebral ischemia and reperfusion injury through PKC-θ signaling

ABSTRACT Ischemic stroke is a common cerebrovascular disease with the main cause considered to be cerebral ischemia and reperfusion (I/R), which exerts irreparable injury on nerve cells. Thus, the development of neuroprotective drugs is an urgent concern. Curcumin, a known antioxidant, has been found to have neuroprotective effects. To determine the protective mechanism of curcumin in ischemic stroke, oxygen and glucose deprivation/reoxygenation (OGD/R) was used to treat PC12 cells to mimic the cerebral I/R cell model. Curcumin (20 μM) was applied to OGD/R PC12 cells, followed by Ca2+ concentration, transepithelial electrical resistance (TEER), and cell permeability measurements. The results showed that OGD/R injury induced a decrease in TEER and increases in Ca2+ concentration and cell permeability. In contrast, curcumin alleviated these effects. The protein kinase C θ (PKC-θ) was associated with the protective function of curcumin in the OGD/R cell model. Moreover, the middle cerebral artery occlusion and reperfusion model (MCAO/R) was applied to simulate the I/R rat model. Our results demonstrated that curcumin could reverse the MCAO/R-induced increase in Ca2+ concentration and blood–brain barrier (BBB) disruption. Our study demonstrates the mechanisms by which curcumin exhibited a protective function against cerebral I/R through PKC-θ signaling by reducing BBB dysfunction.

Cobalt-containing calcium phosphate induces resorption of biomineralized collagen by human osteoclasts

BackgroundBiomineralized collagen, consisting of fibrillar type-I collagen with embedded hydroxyapatite mineral, is a bone-mimicking material with potential application as a bone graft substitute. Despite the chemical and structural similarity with bone extracellular matrix, no evidence exists so far that biomineralized collagen can be resorbed by osteoclasts. The aim of the current study was to induce resorption of biomineralized collagen by osteoclasts by a two-fold modification: increasing the calcium phosphate content and introducing cobalt ions (Co2+), which have been previously shown to stimulate resorptive activity of osteoclasts.MethodsTo this end, we produced biomineralized collagen membranes and coated them with a cobalt-containing calcium phosphate (CoCaP). Human osteoclasts, derived from CD14+ monocytes from peripheral blood, were differentiated directly on the membranes. Upon fluorescent staining of nuclei, F-actin and tartrate-resistant alkaline phosphatase, the cells were analyzed by laser confocal microscopy. Their resorption capacity was assessed by scanning electron microscopy (SEM), as well as indirectly quantified by measuring the release of calcium ions into cell culture medium.ResultsThe CoCaP coating increased the mineral content of the membranes by 4 wt.% and their elastic modulus from 1 to 10 MPa. The coated membranes showed a sustained Co2+ release in water of about 7 nM per 2 days. In contrast to uncoated membranes, on CoCaP-coated biomineralized collagen membranes, osteoclasts sporadically formed actin rings, and induced formation of resorption lacunae, as observed by SEM and confirmed by increase in Ca2+ concentration in cell culture medium. The effect of the CoCaP layer on osteoclast function is thought to be mainly caused by the increase of membrane stiffness, although the effect of Co2+, which was released in very low amounts, cannot be fully excluded.ConclusionsThis work shows the potential of this relatively simple approach to induce osteoclast resorption of biomineralized collagen, although the extent of osteoclast resorption was limited, and the method needs further optimization. Moreover, the coating method is suitable for incorporating bioactive ions of interest into biomineralized collagen, which is typically not possible using the common biomineralization methods, such as polymer-induced liquid precursor method.

Effect of temperature on mineral reactions and fines migration during low-salinity water injection into Berea sandstone

Recent experiments on sandstone rocks found more fines migration at higher temperature. They attributed this to temperature-dependent zeta potential. However, temperature also affects mineral reactions. The present study investigates the effect of temperature on both fines migration and mineral reactions.Two sets of single-phase injection experiments are performed using Berea sandstone sister plugs. In one set of experiments, solutions of NaCl brine are injected at a constant temperature of 25 °C, 50 °C, or 70 °C. In the other set, solutions of CaCl2 brine are injected at a constant temperature of 25 °C or 50 °C. All plugs are subjected to five sequential injections of the designated brine at salinities 0.684 mol/L, 0.171 mol/L, 0.043 mol/L, 0.0085 mol/L, and 0 mol/L. Permeability at each injection stage is calculated from pressure difference across the core. When NaCl brine is used, the percentage of permeability decrease is found to be 99% at 25 °C, 90% at 50 °C, and 40% at 70 °C. The lower permeability decrease at high temperature is found to be accompanied by a smaller concentration of produced fines. Comparison of scanning electron microscope images taken before and at the end of each experiment shows pore enlargement due to mineral reaction at high temperature, which further explains the lower permeability decrease. Ionic concentrations of Ca2+ and Mg2+ in the produced water are found to be greater at higher temperature, due to higher reaction rate. With CaCl2 brine, a 7% permeability decrease is observed at 25 °C, whereas a 20% permeability increase is observed at 50 °C. The observed fines concentration and increase in Ca2+ ion production are found to be lower than with NaCl brine, which is attributed to ion exchange between Na+ and Ca2+ with NaCl brine. Temperature affects both (1) permeability increase due to pore enlargement caused by mineral reactions, and (2) permeability decrease due to fines migration.

Tubular (T-) System SOCE-PMCA Balance Is Regulated by RyR Leak in Resting Skeletal Muscle

Skeletal muscle possesses a unique, rapidly activating store-operated Ca2+ entry (SOCE) mechanism. SOCE is activated when the activity of the ryanodine receptors increase, following action potential-induced Ca2+release or even increased RyR Ca2+ leak (Koenig et al 2018, Comm Biol; Cully et al 2018, PNAS). The role of SOCE in muscle remains poorly defined, but a role in calcium content regulation is likely, which means it must work in concert with fibre Ca2+ extrusion mechanisms for balance. Kinetics of Ca2+ movements in imaging experiments performed with high spatiotemporal resolution have shown that the t-system PMCA exists in the same microdomain as RyRs and the SOCE protein components; and all components are equally distributed throughout the muscle fibre (Cully et al 2012, AJP). We studied RyR mutant mice (RyR KI; Lopez et al 2018, BJA) and calsequestrin 1 null (CSQKO) mice (Paolini et al 2007, J.Physiol) to examine the regulatory relationship of RyR Ca2+ leak with SOCE and PMCA activity using mechanically skinned fibres. We determined that RyR Ca2+ leak increased in the order WT<RyR KI HET<RyR KI HOM<CSQKO. This leak caused a steady state reduction in SR calcium content, which we quantified in absolute terms. We found PMCA activity to be increased in same order as increased RyR Ca2+ leak, where CSQKO muscle showed the most rapid rate of Ca2+ extrusion when [Ca2+]t-sys was initially 0.1 mM and [Ca2+]cyto was varied between 28-1342 nM. The increase in Ca2+ extrusion was offset by increasing SOCE so that physiological, mM [Ca2+]t-sys levels were maintained. Our data conform with Cell Boundary Theorem (Rios, 2010, J.Physiol Sci), providing a platform to explain the increased [Ca2+]cyto in resting intact fibres (Lopez et al 2018) in the presence of increased RyR Ca2+ leak.

High glucose induces Drp1-mediated mitochondrial fission via the Orai1 calcium channel to participate in diabetic cardiomyocyte hypertrophy

Mitochondrial dysfunction and impaired Ca2+ handling are involved in the development of diabetic cardiomyopathy (DCM). Dynamic relative protein 1 (Drp1) regulates mitochondrial fission by changing its level of phosphorylation, and the Orai1 (Ca2+ release-activated calcium channel protein 1) calcium channel is important for the increase in Ca2+ entry into cardiomyocytes. We aimed to explore the mechanism of Drp1 and Orai1 in cardiomyocyte hypertrophy caused by high glucose (HG). We found that Zucker diabetic fat rats induced by administration of a high-fat diet develop cardiac hypertrophy and impaired cardiac function, accompanied by the activation of mitochondrial dynamics and calcium handling pathway-related proteins. Moreover, HG induces cardiomyocyte hypertrophy, accompanied by abnormal mitochondrial morphology and function, and increased Orai1-mediated Ca2+ influx. Mechanistically, the Drp1 inhibitor mitochondrial division inhibitor 1 (Mdivi-1) prevents cardiomyocyte hypertrophy induced by HG by reducing phosphorylation of Drp1 at serine 616 (S616) and increasing phosphorylation at S637. Inhibition of Orai1 with single guide RNA (sgOrai1) or an inhibitor (BTP2) not only suppressed Drp1 activity and calmodulin-binding catalytic subunit A (CnA) and phosphorylated-extracellular signal-regulated kinase (p-ERK1/2) expression but also alleviated mitochondrial dysfunction and cardiomyocyte hypertrophy caused by HG. In addition, the CnA inhibitor cyclosporin A and p-ERK1/2 inhibitor U0126 improved HG-induced cardiomyocyte hypertrophy by promoting and inhibiting phosphorylation of Drp1 at S637 and S616, respectively. In summary, we identified Drp1 as a downstream target of Orai1-mediated Ca2+ entry, via activation by p-ERK1/2-mediated phosphorylation at S616 or CnA-mediated dephosphorylation at S637 in DCM. Thus, the Orai1–Drp1 axis is a novel target for treating DCM.

Cardiac Mineralocorticoid Receptor and the Na+/H+ Exchanger: Spilling the Beans.

Current evidence reveals that cardiac mineralocorticoid receptor (MR) activation following myocardial stretch plays an important physiological role in adapting developed force to sudden changes in hemodynamic conditions. Its underlying mechanism involves a previously unknown nongenomic effect of the MR that triggers redox-mediated Na+/H+ exchanger (NHE1) activation, intracellular Na+ accumulation, and a consequent increase in Ca2+ transient amplitude through reverse Na+/Ca2+ exchange. However, clinical evidence assigns a detrimental role to MR activation in the pathogenesis of severe cardiac diseases such as congestive heart failure. This mini review is meant to present and briefly discuss some recent discoveries about locally triggered cardiac MR signals with the objective of shedding some light on its physiological but potentially pathological consequences in the heart.

Sorption of tetrabromobisphenol A onto microplastics: Behavior, mechanisms, and the effects of sorbent and environmental factors

Microplastics (MPs) and halogenated organic pollutants coexist in ambient water and MPs tend to sorb organic pollutants from surrounding environments. Herein, a study on the sorption behavior of tetrabromobisphenol-A (TBBPA) onto four different MPs, namely, polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC) was carried out. Effects of MPs properties and environmental factors, including the type, surface charge and pore volume as well as the ionic strength (Ca2+) and humic acid (HA) on the sorption of TBBPA were discussed. Results showed that the sorption of TBBPA onto the MPs could reached an equilibrium within 24 h, and the sorption capacities decreased in the following order —PVC (101.85 mg kg-1) >PS (78.95 mg kg-1) >PP (58.57 mg kg-1) >PE (49.43 mg kg-1). Adsorption kinetics data fitted by intraparticle diffusion model revealed both surface sorption and intraparticle diffusion contributed, in the interfacial diffusion stage approximately 11–29% of TBBPA slowly diffused onto the surface of the MPs, and finally, in the intraparticle diffusion stage. The increase of Ca2+ concentration could promote the sorption of TBBPA by PE, PP, and PS, but no significant alteration for PVC. For all the four MPs, HA was found to exert a negative effect on TBBPA sorption. The adsorption was mainly driven by hydrophobic partition and electrostatic interactions.

Requirement of the Ca2+ channel β2 subunit for sympathetic PKA phosphorylation

Facilitation of cardiac function in response to signals from the sympathetic nervous system is initiated by the phosphorylation of L-type voltage-dependent Ca2+ channels (VDCCs) by protein kinase A (PKA), which in turn is activated by β-adrenoceptors. Among the five subunits (α1, β, α2/δ, and γ) of VDCCs, the α1 subunit and the family of β subunits are substrates for PKA-catalyzed phosphorylation; however, the subunit responsible for β-adrenergic augmentation of Ca2+ channel function has yet to be specifically identified. Here we show that the VDCC β2 subunit is required for PKA phosphorylation upon sympathetic acceleration. In mice with β2 subunit-null mutations, cardiac muscle contraction in response to isoproterenol was reduced and there was no significant increase in Ca2+ channel currents upon PKA-dependent phosphorylation. These findings indicate that within the sympathetic nervous system the β2 subunit of VDCCs is required for physiological PKA-dependent channel phosphorylation.

Involvement of TRPM2 Channel on Hypoxia-Induced Oxidative Injury, Inflammation, and Cell Death in Retinal Pigment Epithelial Cells: Modulator Action of Selenium Nanoparticles.

Hypoxia (HYPX) in several eye diseases such as glaucoma and diabetic retinopathy causes oxidative cell death and inflammation. TRPM2 cation channel is activated by HYPX-induced ADP-ribose (ADPR) and oxidative stress. The protective role of selenium via inhibition of TRPM2 on the HYPX-induced oxidative cytotoxicity and inflammation values in the human kidney cell line was recently reported. However, the protective role of selenium nanoparticles (SeNP) on the values in the retinal pigment epithelial (ARPE-19) cells has not been clarified yet. In the current study, we investigated two subjects. First, we investigated the involvement of TRPM2 channel on the HYPX-induced oxidative injury, inflammation, and apoptosis in the ARPE-19 cells. Second, we investigated the protective role of SeNP via inhibition of TRPM2 channel on the HYPX-induced oxidative injury and apoptosis in the ARPE-19 cells. For the aims, the ARPE-19 cells were divided into four main groups as follows: Control (Ctr), SeNP (2.5 μg/ml for 24 h), HYPX (200 μM CoCl2 for 24 h), and HYPX+SeNP. The TRPM2 current density and Ca2+ fluorescence intensity with an increase of mitochondrial membrane depolarization and oxygen free radical (OFR) generations were increased in the ARPE-19 cells by the treatment of HYPX. There was no increase of Ca2+ fluorescence intensity in the pre-treated cells with PARP-1 inhibitors (DPQ and PJ34) or in the presence of Ca2+-free extracellular buffer. When HYPX-induced TRPM2 activity was treated by SeNP and TRPM2 (2-APB and ACA) blockers, the increases of OFR generation, cytokine (TNF-α and IL-1β) levels, TRPM2, and PARP-1 expressions were restored. In conclusion, the exposure of HYPX caused mitochondrial oxidative cell cytotoxicity and cell death via TRPM2-mediated Ca2+ signaling and may provide an avenue for treating HYPX-induced retinal diseases associated with the excessive OFR and Ca2+ influx.

Heat stability and rheology of high-calorie whey protein emulsion: Effects of calcium ions

In this study, the effect of calcium ions (Ca2+) on the heat stability and rheology of high-calorie (>1.0 kcal/mL) whey protein emulsion (HCWPE) was investigated. The mass fractions of carbohydrate, lipid and protein in the emulsions were 20, 6, and 6 wt%, respectively. It was found that there was little difference in stability and rheology between emulsions (unheated) of different concentrations of Ca2+. However, after high-temperature sterilization (121 °C for 15 min), Ca2+ had a significant effect on the stability of HCWPE. The particle size and flocculation degree increased rapidly when the Ca2+ concentration was above 1.5 mM, and absolute ζ-potential decreased. The change of 3-week particle size and backscattering showed that the emulsion had better storage stability when the Ca2+ concentration was below 1.5 mM. Another interesting result was that after the high temperature sterilization, the rheological behavior of HCWPE changed from shear-thickening to shear-thinning with increase in Ca2+ concentration. It could be explained that free Ca2+ continued to bind with protein during the shearing process. The present study would provide a theoretical reference for calcium fortified functional drinks.

Membrane excitabilities in neonatal rat mesencephalic trigeminal neurons under dietary zinc deficiency.

The present study aimed to evaluate the effects of zinc deprivation on the properties of membrane and spike-discharge features of mesencephalic trigeminal neurons (MTNs), which are important sensory neurons for oral-motor reflexes and rhythmical jaw movements. Neonatal Sprague Dawley rats (P10-12) were distributed equally into a normal diet group and a zinc-deficient diet (ZD) group. Whole cell patch-clamp recordings were obtained from MTNs from coronal brain slices. Passive membrane properties showed a modest depolarized membrane potential and decreased cell capacitance in the ZD group. Zinc deprivation decreased the minimal current amplitude, which induced an action potential and increased the amplitude of afterhyperpolarization following the action potential. Negligible changes were observed for other action potential properties. A decreased burst duration was observed, accompanied by hastened spike frequency adaptation in the burst discharge. There was no difference in the resonant properties at both the subthreshold depolarized potential and hyperpolarized membrane potential between the control and ZD groups. These results suggests that neither the persistent sodium conductance nor slow inwardly rectifying conductance were altered; however, there appeared to be an increase in Ca2+-dependent K+ conductance in zincdeficient MTNs.

Exercise-induced alterations of myocardial sarcomere dynamics are associated with hypophosphorylation of cardiac troponin I.

Although the knowledge of sports cardiology advanced significantly in the recent years, the molecular mechanisms by which exercise training augments cardiac performance is poorly understood. Here we aimed at determining left ventricular (LV) myocardial sarcomeric protein modifications in a rat model of exercise training and detraining. Young male Wistar rats were divided into exercised (Ex) and control (Co) groups. Trained rats swam 200 min/day for 12 weeks. Detrained (DEx) and control (DCo) rats remained sedentary for 8 weeks after completion of the 12-week-long protocol. Ca2+-regulated active force production (Fa⁢c⁢t⁢i⁢v⁢e), its Ca2+-sensitivity (pCa50) and Ca2+-independent passive tension (Fp⁢a⁢s⁢s⁢i⁢v⁢e) were determined in isolated permeabilized cardiomyocytes and phosphorylation levels of sarcomeric proteins were assayed by biochemical methods. Means of maximal Ca2+-activated isometric force (Fm⁢a⁢x) and pCa50 values were higher (p < 0.05) in the Ex group (28.0 ± 1.4 kN/m2 and 5.91 ± 0.03, respectively, mean ± SEM) than those in the Co group (15.8 ± 0.8 kN/m2 and 5.81 ± 0.03, respectively). Fp⁢a⁢s⁢s⁢i⁢v⁢e did not differ between these two groups. The level of cardiac troponin I (cTnI) phosphorylation decreased upon exercise (from 1.00 ± 0.02 to 0.66 ± 0.06, p < 0.05; in relative units). Site specific phosphorylation assays revealed cTnI hypophosphorylations at the protein kinase A (PKA)-specific Ser-22/23 sites and at the protein kinase C (PKC)-specific Thr-143 site. Mechanical and biochemical parameters of the DEx and DCo groups did not differ from each other following the detraining period. Exercise-induced hypertrophy is associated with reversible increases in Ca2+-dependent force production and its Ca2+-sensitivity in LV cardiomyocytes, which can be associated with changes in cTnI phosphorylation.

TSPAN-7 as a key regulator of glucose-stimulated Ca2+ influx and insulin secretion.

TSPAN-7 as a key regulator of glucose-stimulated Ca2+ influx and insulin secretion.

Mitochondria-localizing curcumin-cryptolepine Zn(II) complexes and their antitumor activity

Many metal complexes are potent candidates as mitochondrial-targeting agents. In this study, four novel Zn(II) complexes, [Zn(BPQA)Cl2] (Zn1), [Zn(BPQA)(Curc)]Cl (Zn2), [Zn(PQA)Cl2] (Zn3), and [Zn(PQA)(Curc)]Cl (Zn4), containing N,N-bis(pyridin-2-ylmethyl)benzofuro[3,2-b]quinolin-11-amine (BPQA), N-(pyridin-2-ylmethyl)benzofuro[3,2-b]quinolin-11-amine (PQA), and curcumin (H-Curc) were synthesized. An MTT assay showed that Zn1–Zn4 had strong anticancer activities against SK-OV-3/DDP and T-24 tumor cells with IC50 values of 0.03–6.19 μM. Importantly, Zn1 and Zn2 displayed low toxicities against normal HL-7702 cells. Mechanism experiments demonstrated that probe Zn2 showed appreciable fluorescence in the red region of the spectrum, and substantial accumulation of Zn2 occurred in the mitochondria after treatment, indicating increases in Ca2+ and reactive oxygen species levels, loss of the mitochondrial membrane potential, and consequent induction of mitochondrial dysfunction at low concentrations. In addition, the probe Zn2 effectively (50.7%) inhibited the growth of T-24 bladder tumor cells in vivo. The probe Zn2 shows potential for use in cancer therapy while retaining the H-Curc as an imaging probe.