Role Of Calcium Ions Research Articles

Agglomeration of Ag and TiO2 nanoparticles in surface and wastewater: Role of calcium ions and of organic carbon fractions

This study aims to investigate factors leading to agglomeration of citrate coated silver (AgNP-Cit), polyvinylpyrrolidone coated AgNPPVP and titanium dioxide (TiO2) nanoparticles in surface waters and wastewater. ENPs (1 mg/L) were spiked to unfiltered, filtered, ultrafiltered (<10 kDa and <1 kDa) samples. Z-average particle sizes were measured after 1 h, 1 day and 1 week. AgNP-PVP was stable in all fractions of the samples and kept their original size around 60 nm over 1 week. Agglomeration of AgNP-Cit and TiO2 was positively correlated with Ca2+ concentration, but dissolved organic carbon concentrations > 2 mg/L contributed to stabilizing these NP. Moreover, agglomeration of AgNP-Cit in the various organic matter fractions showed that high molecular weight organic compounds such as biopolymers provide stabilization in natural water. A generalized scheme for the agglomeration behavior of AgNP-Cit, AgNP-PVP and TiO2 in natural waters was proposed based on their relation with Ca2+, Mg2+ and DOC concentration.

In vivo Temperature Sensitivity of the Calcium Affinity of fluo-5F and mag-fluo4

The role of calcium ion (Ca2+) in diverse cellular signaling pathways has been identified and investigated principally by using fluorescent chelators as indicators. Using the biophysical characteristics of a fluorescent Ca2+ indicator allows investigators to convert measured fluorescence intensity into values of free Ca2+ concentration ([Ca2+]). Troublingly, the characteristics of Ca2+-indicators are dependent on numerous environmental factors. Determining the behavior of each indicator in vivo under comparable experimental conditions is necessary for quantitative measurements. Temperature is one environmental factor that strongly affects Ca2+ indicator behavior. A change in temperature can change the intrinsic physical characteristics of the indicator (e.g., Ca2+ affinity, quantum efficiency, and fluorescence lifetime), as well as change the cellular processes that affect indicator performance (e.g., extrusion by transporters, cellular pH). Therefore, experiments were designed to estimate the disassociation constants (KD) of the Ca2+ indicators fluo-5F and mag-fluo4 (loaded into the cytosol and sarcoplasmic reticulum, respectively) at room and physiological temperatures in murine ventricular myocytes. Ca2+ access to cytosolic compartment was established using a Ca2+ ionophore, while sarcoplasmic reticulum (SR) access was established by sarcolemma permeabilization with saponin in the presence of caffeine. Once access was established, buffers with known [Ca2+] were rapidly applied using a micro-perfusion system with temperature feedback control. We observed that, increasing from room temperature to 36°C caused a modest decrease in the KD of both fluo-5F and mag-fluo4. Both indicators also displayed a decrease in dynamic range when heated. Additionally, temperature-dependent extrusion was observed for indicators loaded into the cytosol, but not those loaded into the SR. These findings are important in enabling quantitative interpretation of measurements in living cells under physiological conditions.

Evolution of Ca2+-signaling mechanisms: The role of Ca2+ in regulation of specialized cardiomyocyte functions in chronic heart diseases

This review considers the role of calcium ions in regulation of the specialized cardiomyocyte (CM) functions in heart diseases and disorders. It covers some issues of Ca2+-dependent signaling mechanisms that lead to pathological cardiac hypertrophy, arrhythmogenesis and heart failure. The authors pay special attention to the analysis of Ca2+-dependent molecular mechanisms resulting in remodeling of contractile proteins, apoptosis and pathological CM growth.

Calcium Ion – The Key Player in Cerebral Ischemia

Role of calcium ion (Ca2+) in the functioning of neurons from their naïve state to mature state is of vital importance. It controls functions such as neuronal functioning, neuronal ATP production, central nervous system migration and many others. Failure in Ca2+ homeostasis mechanisms and the resulting cellular Ca2+ ion load initiates a cascade of reactions involving various cytosolic enzymes and proteins. This total mechanism leads to the neuronal death. The ability of neurons to resist such death mechanisms fails as a result of extensive cell death signaling cascade reactions and later brings brain damage. The role of neuronal endoplasmic reticulum and protein channels like CaVs, TRP channels, and NMDAR as the mediators of cell damage and death has been evaluated in the studies related to cerebral ischemia. Here, we portray Ca2+ ion as one of the role players in neuronal death and cerebral damage following ischemia. The role of Ca2+ in neuronal functioning, its regulatory mechanisms and the failure of homeostatic mechanisms are discussed in detail.

Ca2+ as an Air Impurity in Polymer Electrolyte Membrane Fuel Cells

Cationic contamination is known to cause performance degradation and reduced lifetime in polymer electrolyte based electrochemical systems. Calcium is an important cationic impurity due to its prevalence in roadside particulates and as an airborne contaminant. The role of calcium ion (Ca2+) is investigated in-situ by injecting a solution of calcium sulfate (CaSO4) in deionized (DI) water into the cathode of a polymer electrolyte membrane (PEM) fuel cell through a nebulizer. Stability tests are conducted to determine the effects at various current densities with various Ca2+ concentrations. It is found that 5 parts per million (ppm, molar ratio) eq. Ca2+ in air is sufficient to lead to high cell performance loss at 1 A/cm2 as well as severe membrane degradation. Precipitation of CaSO4 is found at the contact regions between the gas diffusion layers (GDL) and bipolar plates of the cathode at all test conditions. The amount of precipitation becomes sufficient to cause mass transport issues.

Role of Calcium in Glucagon Secretion

The role of calcium ions in the process by which nutrients affect glucagon secretion by pancreatic islet α-cells remains the matter of an apparently endless debate. In the prolongation of recent articles dealing with this matter, the present review draws attention to the dual role of Ca2+ as revealed by prior publications. In such a perspective, emphasis is placed on the increase in glucagon output in response to the omission of extracellular Ca2+ as recorded in the presence of D-glucose or 2-ketoisocaproate, the permissive role of extracellular Ca2+ in the positive secretory response to arginine or a mixture of fumarate, glutamate and pyruvate, and the effects of an organic calcium-antagonist on glucagon output. Considering the role currently ascribed to Ca2+ in the activation of motile events involved in stimulus-secretion coupling, attention is also given to the effects of cytochalasin B, D2O and mitotic-spindle inhibitors upon the secretory response of α-cells exposed to D-glucose in the absence or presence of arginine.

High-throughput fluorescence assay for membrane-protein interaction

Membrane-protein interaction plays key roles in a wide variety of biological processes. Although various methods have been employed to measure membrane binding of soluble proteins, a robust high-throughput assay that is universally applicable to all proteins is lacking at present. Here we report a new fluorescence quenching assay utilizing enhanced green fluorescence protein (EGFP)-fusion proteins and a lipid containing a dark quencher, N-dimethylaminoazobenzenesulfonyl-phosphatidylethanolamine (dabsyl-PE). The EGFP fluorescence emission intensity showed a large decrease (i.e., >50%) when EGFP-fusion proteins bound the vesicles containing 5 mol% dabsyl-PE. This simple assay, which can be performed using either a cuvette-based spectrofluorometer or a fluorescence plate reader, allowed rapid, sensitive, and accurate determination of lipid specificity and affinity for various lipid binding domains, including two pleckstrin homology domains, an epsin N-terminal homology domain, and a phox homology domain. The assay can also be applied to high-throughput screening of small molecules that modulate membrane binding of proteins.

Permeabilization of mercury-supported biomimetic membranes by amphotericin B and the role of calcium ions

The mechanism of membrane permeabilization by the antifungal heptaene macrolide amphotericin B (AmB) was investigated by using two different mercury-supported biomimetic membranes, namely a lipid self-assembled monolayer and a lipid bilayer tethered to the mercury surface through a hydrophilic spacer (tethered bilayer lipid membrane: tBLM). The disruptive permeabilization of a sterol-free mercury-supported lipid monolayer by low AmB concentrations, after a sufficiently long exposure to the macrolide, suggests a similar effect on the distal lipid monolayer of vesicular or bilayer lipid membranes. The notable permeabilization of a tBLM to Cd(II), with amalgam formation, by 0.6μM AmB complexed with sterols in a 1:3 molar ratio, as compared with the absence of any effect in the absence of sterols, suggests a direct participation of sterols in ion channel formation. The fact that the tBLM permeabilization requires the presence in solution of a freshly added AmB–sterol mixture and of Cd(II) or Ca2+ ions points out the notable role played by these divalent inorganic ions in the formation of AmB ion channels. Ion channels formed in a tBLM by AmB–ergosterol complexes are stable at physiological transmembrane potentials, whereas those formed by AmB–cholesterol complexes require application of non-physiological transmembrane potentials for their stability.

Effect of calcium ions and pH on the structure and rheology of carrot-derived suspensions

In the present work, the role of calcium ions (Ca2+) in the rheological behaviour of carrot-derived purées was investigated. Therefore, purées based on carrots containing pectin with different degree of methoxylation were prepared and the effects of Ca2+ addition in excess on the rheological properties of these purées were studied at different pH. More specifically, it was assessed if the purée stiffness and strength could be influenced by Ca2+ addition. Ion addition caused a decrease in both network stiffness and strength, in particular at pH values above 4.5. By separating the particle phase from the serum, and characterizing the rheology of both phases as a function of pectin degree of methoxylation, Ca2+ addition in excess and pH, it was concluded that the particle phase rather than the serum phase is affected by ion addition. Immunolabeling of the carrot-derived particles with anti-pectin antibodies showed the presence of non-methoxylated residues at the particle surfaces, which will be charged at specific pH. Hence, the calcium ions may compress the electrical double layer around the particles whereby they can approach each other more closely. The latter mechanism was confirmed by the relation between the phase volume and the rheological parameters. Rather than being involved in Ca2+ cross-link formation thus enhancing the pectin network in carrot-derived purées, it turned out that Ca2+ screens the negatively charged pectin at the surface of the particles whereby the rheological characteristics of these suspensions, such as the yield stress and storage modulus, are reduced and the flow is facilitated.

Spheroid Formation and Enhanced Cardiomyogenic Potential of Adipose-Derived Stem Cells Grown on Chitosan

Mesenchymal stem cells may differentiate into cardiomyocytes and participate in local tissue repair after heart injury. In the current study, rat adipose-derived adult stem cells (ASCs) grown on chitosan membranes were observed to form cell spheroids after 3 days. The cell seeding density and surface modification of chitosan with Arg-Gly-Asp–containing peptide had an influence on the sizes of ASC spheroids. In the absence of induction, these spheroids showed an increased level of cardiac marker gene expression (Gata4, Nkx2-5, Myh6, and Tnnt2) more than 20-fold versus cells on the tissue culture polystyrene (TCPS) dish. Induction by 5-azacytidine or p38 MAP kinase inhibitor (SB202190) did not further increase the cardiac marker gene expression of these spheroids. Moreover, the enhanced cardiomyogenic potential of the spheroids was highly associated with the chitosan substrates. When ASC spheroids were plated onto TCPS with either basal or cardiac induction medium for 9 days, the spheroids spread into a monolayer and the positive effect on cardiomyogenic marker gene expression disappeared. The possible role of calcium ion and the up-regulation of adhesion molecule P-selectin and chemokine receptor Cxcr4 were demonstrated in ASC spheroids. Applying these spheroids to the chronic myocardial infarction animal model showed better functional recovery versus single cells after 12 weeks. Taken together, this study suggested that the ASC spheroids on chitosan may form as a result of calcium ion signaling, and the transplantation of these spheroids may offer a simple method to enhance the efficiency of stem cell–based therapy in myocardial infarction.

Protective role of calcium ion against stress-induced osmotic fragility of red blood cells in patients with type 2 diabetes mellitus

Type 2 diabetes mellitus can increase osmotic fragility of red blood cells. Osmotic fragility test is an index of the function of cytoskeletal proteins and of the calcium pump activity in RBC membrane. The aim of this study is to determine the effect of physiological calcium supplement on red blood cell osmotic fragility of patients with type 2 diabetes mellitus. Osmotic fragility of red cells was determined for 30 healthy subjects and 30 patients in a NaCl gradient medium. 5 mg/dl of calcium was added to media and the osmotic fragility were evaluated for RBCs of patients and healthy subjects. Comparison of patients and control group showed higher sensitivity of red cells of patients to osmotic fragility upon exposure to higher sodium chloride concentrations. Comparison of initial, fifty percent and total hemolysis showed significant difference on initial and fifty percent hemolysis between two groups (P < 0.001). In healthy subjects, Fifty percent hemolysis index showed a smaller change after addition of calcium, from 4.1 ± 0.22 to 3.9 ± 0.2 (P < 0.05). Fifty percent hemolysis index for patients significantly decreased from 4.45 ± 0.17 to 4 ± 0.17 after addition of calcium (P < 0.001). Osmotic fragility increases in patients with diabetes. The role of calcium in cell membrane integrity was more prominent in the patients with diabetes than the healthy subjects, emphasizing the role of calcium on the membrane stability. We showed for the first time that controlling calcium ion concentration in patients with diabetes could exert a protective and beneficial role against membrane-affecting conditions.

Protein Kinase Cθ C2 Domain Is a Phosphotyrosine Binding Module That Plays a Key Role in Its Activation

Protein kinase Cθ (PKCθ) is a novel PKC that plays a key role in T lymphocyte activation. To understand how PKCθ is regulated in T cells, we investigated the properties of its N-terminal C2 domain that functions as an autoinhibitory domain. Our measurements show that a Tyr(P)-containing peptide derived from CDCP1 binds the C2 domain of PKCθ with high affinity and activates the enzyme activity of the intact protein. The Tyr(P) peptide also binds the C2 domain of PKCδ tightly, but no enzyme activation was observed with PKCδ. Mutations of PKCθ-C2 residues involved in Tyr(P) binding abrogated the enzyme activation and association of PKCθ with Tyr-phosphorylated full-length CDCP1 and severely inhibited the T cell receptor/CD28-mediated activation of a PKCθ-dependent reporter gene in T cells. Collectively, these studies establish the C2 domain of PKCθ as a Tyr(P)-binding domain and suggest that the domain may play a major role in PKCθ activation via its Tyr(P) binding.

Calcium is omnipresent in the physiology and pathophysiology of heart disease

Calcium is omnipresent in the physiology and pathophysiology of heart disease 277 1 3 In western industrialized nations, the burden of cardiovascular disease is increasing steadily. Despite numerous pharmacological, interventional, and surgical therapeutic options and promising novel additions to the field, cardiovascular disease remains the leading cause of death. The physiology of the healthy human heart has been characterized well in vivo and in vitro. However, to develop novel therapeutic and diagnostic tools, it is necessary to transfer our physiological perceptions into the field of pathophysiology. In human physiology, the role of calcium ions is ubiquitous. In particular, skeletal and cardiac muscles depend on calcium as their main effectors of contraction, but calcium is also essential in vascular function, neural transduction, endocrinological processes, and several other physiological functions of the human body. Similarly, the role of calcium is ubiquitous in the human heart. Not only it is an essential effector of the most obvious of all cardiac functions—contractility—but it also plays important roles in regulating and generating heart rhythm and metabolism. Thus, the contemplation of calcium handling in the development and maintenance of cardiac disease can of course not be limited to a single cardiac disease entity. Instead, one has to discuss the role of calcium in several cardiac disease categories such as arrhythmia, heart failure, and cardiac ischemia. One also has to be aware that these disease entities mutually depend on one another reciprocating their development and maintenance. In any of these three pathological entities—arrhythmia, heart failure, and ischemia—aberrations of calcium handling may not always be cause but can also be consequence of the disease mechanism in the sense of adaptive or maladaptive mechanisms. This thematic issue of the Wiener Medizinische Wochenschrift aims at adding to the translational research process by presenting a collection of papers that review specific cardiac disease entities in light of their associated aberrations of cardiac calcium handling. To begin with, Bogeholz et al. will give a brief overview on physiologi cal calcium handling, i.e. as it occurs in the healthy human heart. Next, Frommeyer et al. and Heijman et al. are going to review the growing field of research on calcium handling in life threatening ventricular arrhythmias and atrial fibrillation, respectively. Closely related to this field, Kochhauser et al. give an overview on mutations of calcium handling proteins and the associated disease categories. Reuter and Schwinger will review the topic of calcium handling in heart failure while Kleinbongard et al. give an overview on the role of calcium antagonists in ischemic heart disease. Finally, Vogler et al. will add a digest on established and novel pharmacological agents that can influence specific targets of cardiac calcium handling.

The role of calcium ions for the stability of Sonic Hedgehog protein

The role of calcium ions for the stability of Sonic Hedgehog protein

Weak Carbohydrate-Carbohydrate Interactions Measured by Colloidal Probe Microscopy

The weak calcium mediated interaction between membrane based carbohydrates derived from the marine sponge Microciona prolifera has been investigated by colloidal probe microscopy. An in situ synthesis of glycolipids was employed to measure the dynamic strength of homomeric self-association between sulfated and non-sulfated oligosaccharides. For this purpose an in situ protocol has been developed to entirely rely on a defined synthetic system with adjustable composition and physical properties. Since thermal undulation of membranes renders analysis of binding affinity cumbersome we rely on solid supported membranes with preserved fluidity and minimal non-specific interaction. We investigate the attraction of carbohydrates derived from Microciona prolifera with a focus on the role of calcium ions, the necessity of the sulfate group, membrane fluidity, and loading rate. Membrane fluidity is of particular interest considering that lateral organization of ligand-receptors into small-scale clusters as a result of competition between binding enthalpy and mixing entropy is only possible in laterally mobile matrices.We found that nanoclusters consisting of 4-8 homomeric bonds were formed in the contact area between colloidal probe and solid supported membrane. Depletion of calcium or removal of the sulfato group resulted both in a disappearance of specific interactions.

Role of calcium ions in photosignaling processes in a plant cell

Ca2+ is an important structural and functional component of plant cells. During the last decade, Ca2+ attracted attention as a secondary messenger in signaling processes in plants to mediate the action of abiotic and biotic signals including light. The structural basis for Ca2+ signaling in plants, the generation of Ca2+ signatures and of nature of Ca2+ sensors are considered in relation to the functioning of plant photoreceptors phytochromes, cryptochromes, and phototropins. Special attention was focused upon genetic factors controlling the expression of light-inducible genes being closely related to above photoreceptors. The analysis of the achievements in the field of plant photoreceptor signal transduction and suggestions of some prospects for the future research were done.

Роль ионов кальция в патологических состояниях нервной системы

Роль ионов кальция в патологических состояниях нервной системы

The role of calcium ions in the stability and instability of a thermolysin‐like protease

Thermolysin and other secreted broad-specificity proteases, such as subtilisin or alpha-lytic protease, are produced as pre-pro-proteins that stay at least partially unfolded while in the cytosol. After secretion, the pro-proteases fold to their active conformations in a process that includes the autolytic removal of the pro-peptide. We review the life cycle of the thermolysin-like protease from Bacillus stearothermophilus in light of the calcium dependent stability and instability of the N-terminal domain. The protease binds calcium ions in the regions that are involved in the autolytic maturation process. It is generally assumed that the calcium ions contribute to the extreme stability of the protease, but experimental evidence for TLP-ste indicates that at least one of the calcium ions plays a regulatory role. We hypothesize that this calcium ion plays an important role as a switch that modulates the protease between stable and unstable states as appropriate to the biological need.

Nutrient Balance at Integrated Nutrient Management on Lowland Rice Which is Dominated by 1:1 Clay Mineral for High Potential Rice Yields

Nutrient Balance at Integrated Nutrient Management on Lowland Rice Which is Dominated by 1:1 Clay Mineral for High Potential Rice Yields

The role of calcium ions in the interactions of PrP106-126 amide with model membranes

In this work, we investigated the interactions of PrP106-126 amide with 1-palmitoyl-2-oleoyl-3-phosphocholine (POPC) and POPC/bovine brain sphingomyelin (BSM) membranes in the presence of calcium ions by in situ time-lapse atomic force microscopy (AFM) and circular dichroism (CD). The CD results show that Ca 2+ has no obvious effects on the random coil conformation of PrP106-126 amide. The tapping mode AFM results demonstrate that electrostatic interaction decreases the measured heights of supported lipid bilayers (SLBs) in HBS–Ca 2+ solution. Electrostatic interaction analysis also can be used to determine the applied force in liquid tapping mode AFM. The interactions of PrP106-126 amide with membranes by AFM demonstrate the following: (i) Ca 2+ inhibits the interaction of PrP106-126 amide with POPC lipid and (ii) the co-interaction between Ca 2+ and BSM increases the poration ability of PrP106-126 amide. These results imply that the main role of Ca 2+ in the interactions of PrP106-126 amide with membranes is changing the surface properties of the membranes.