Ca Transport Research Articles

Binding Affinity of Serca Regulatory Complexes Quantified by Steered Molecular Dynamics Simulations

The regulatory peptide phospholamban (PLB) binds its target, the SERCA calcium pump, with high affinity when the pump is in a calcium-free conformation and with lower affinity when the Ca binding sites are occupied. To probe the energetics of PLB binding to the canonical (M6) binding site and several hypothetical alternative binding sites on SERCA, we performed steered molecular dynamics simulations. We measured the force required to rupture the regulatory complex as an index of PLB-SERCA binding affinity. Rupture force varied according to the binding site, the conformation of SERCA, and the axial rotation of the PLB transmembrane helix. We have previously hypothesized that PLB may bind to an alternative site on SERCA helix M9 in a configuration analogous to the complex of the Na+/K+-ATPase (NKA) with its regulatory partner FXYD2. Steered molecular dynamics results were not consistent with that hypothesis, as PLB interacted significantly more strongly with M6 than M9 for all SERCA conformations tested. We also evaluated a structural model of dwarf open reading frame (DWORF) bound to SERCA and observed that this non-inhibitory micropeptide binds with an apparent affinity that is comparable to PLB. The results provide insight into competitive binding of peptide regulators of SERCA, and reveals new information about dynamic changes in regulatory complex stability during the Ca transport cycle.

Chamber formation and trace element distribution in the calcite walls of laboratory cultured planktonic foraminifera ( Globigerina bulloides and Globigerinoides ruber )

Abstract Two species of spinose planktonic foraminifera (Globigerinoides ruber and Globigerina bulloides), cultured under controlled seawater temperatures (19, 21, 23, and 25 °C) with newly precipitated walls labeled with Ca isotopes, were subjected to quantitative analyses of Mg/Ca, Sr/Ca and Ba/Ca ratios at a spatial resolution of 2 μm. Mg mapping of calcite walls showed banding structures parallel to the wall surfaces for both species. Significant Mg accumulation was evident, particularly on walls precipitated at higher temperature, together with irregularly shaped chambers. Our experiment reproduced little cross-sectional variation in Sr/Ca, suggesting constant ratio levels in the calcification fluid and seawater. The Ba/Ca, however, showed different behavior in the two species: a relatively constant profile in Gs. ruber but a positive correlation with Mg/Ca in Ga. bulloides. The different geochemical properties in the two species cultured under the same conditions suggest different elemental regulation processes in the calcification sites. Positive coupling of Mg–Ba (but constant Sr/Ca) is unlikely to be explained only by a Mg-specific removal process, whereas Sr and Ca transport may follow a similar pathway.

Polyhalite as a multi nutrient fertilizer – potassium, magnesium, calcium and sulfate

Polyhalite is a hydrated sulfate of potassium (K), calcium (Ca) and magnesium (Mg) with the formula: K2Ca2Mg(SO4)4·2H2O. The main objective of the present study was to investigate and compare the efficiency of polyhalite as a fertilizer supplying K, Ca, Mg and sulfur (S) relative to equivalent soluble salts. The specific objectives were to investigate: 1. The release and transport of Ca, Mg, K and S in soil; 2. Uptake of these minerals by wheat plants and 3. Biomass production of wheat plants. To meet these objectives, two pot experiments (20 l pots filled with dune sand) were conducted in which the effects of four doses of polyhalite (0, 500, 1,500 and 2,500 kg/ha) and one dose of Ca, Mg and K sulfate salts (equivalent to the 1500 kg/ha polyhalite dose) were investigated. In a third experiment, residual effects of the fertilizers were studied using the pots from the first experiment. Different leaching fractions were used in the experiments (30% in the first one and 7–10% in the second and third experiments), to investigate the effect of water management on mineral transportation in the soil and plant uptake. Polyhalite was found to be a more efficient fertilizer for supplying K, Ca, Mg and S relative to equivalent soluble salts. To meet the plant required ratios for Ca, Mg and K, the polyhalite dose should be applied accordingly to provide sufficient Ca and Mg, and additional fertilizers should be used as a source of K. Transport and leaching of Ca, Mg, K and S in soil following polyhalite application was lower than following the application of the equivalent sulfate salts. The residual effect of polyhalite fertilizer on the subsequently grown crop was higher than the effect from the equivalent sulfate salts, especially regarding Ca, Mg and S. Irrigation management, as determined by the leaching fraction, has a strong impact on the efficiency of polyhalite as a source of K, Ca, Mg and S for plant nutrition.

Vitamin D status in growing dairy goats and sheep: Influence of ultraviolet B radiation on bone metabolism and calcium homeostasis

The aim of this study was to investigate how controlled UVB irradiation in combination with reduced nutritional vitamin D (vitD) supply affects vitD status and Ca metabolism of growing goats and sheep. The hypothesis was that, like dairy cows, goats and sheep are able to compensate for the missing nutritional supply of vitD through endogenous production in the skin, with the consequence of a high vitD status and a balanced Ca homeostasis. Sixteen lambs and 14 goat kids aged 3 and a half months were housed in an UVB free environment and fed hay and a vitD-free concentrate over a period of 13 wk. One group of each species was exposed to UVB lamps daily during individual feeding; the other groups served as controls. Serum, urine, and feces samples were taken at the start and at a monthly interval. Serum was analyzed for vitD metabolites, bone markers, growth hormone, insulin-like growth factor I, Ca, and P. Apparent digestibility and urinary excretion of Ca and P were determined. The left metatarsus was analyzed by peripheral quantitative computer tomography for bone mineral density before starting and at the end of the trial. In wk 13, all animals were slaughtered and samples of skin, rumen, duodenum, kidney, and bone (metatarsus) were collected. Content of sterols of vitD synthesis in the skin, Ca flux rates in rumen and duodenum, expression of vitD receptor in duodenum and kidney, renal and intestinal gene expression of Ca transport proteins, and renal enzymes related to vitD metabolism were determined. The UVB exposure led to lower 7-dehydrocholesterol content in the skin and a better vitD status (higher serum 25-hydroxyvitamin D), but no signs of vitD deficiency were seen in the control groups and no effect of irradiation was detected in the analyzed parameters of Ca homeostasis. Differences between the 2 species were detected: lambs had a higher increase of bone mineral density, lower values of bone markers, growth hormone, and insulin-like growth factor I in serum and higher tachysterol and lower lumisterol content in skin compared with goat kids. The results indicated that growing lambs and goat kids are able to compensate for a vitD-reduced diet by cutaneous vitD synthesis when exposed to UVB irradiation and therefore to keep a high vitD status. In contrast, when a reduced vitD diet is combined with missing UVB exposure, the vitD status drops, but the experimental time was probably too short to induce a vitD deficiency or an effect on Ca homeostasis.

Intra-Amniotic Administration (Gallus gallus) of Cicer arietinum and Lens culinaris Prebiotics Extracts and Duck Egg White Peptides Affects Calcium Status and Intestinal Functionality.

Calcium (Ca) is one of the most abundant inorganic elements in the human body and has many important physiological roles. Prebiotics and bioactive peptides are two important substances used to promote calcium uptake. However, the difference in mechanisms of the calcium uptake from these two supplements is not clear. By using the Gallus gallus model and the intra-amniotic administration procedure, the aim of this study was to investigate whether Ca status, intestinal functionality, and health-promoting bacterial populations were affected by prebiotics extracted from chickpea and lentil, and duck egg white peptides (DPs). Eleven groups (non-injected; 18 MΩ H2O; 4 mmol/L CaCl2; 50 mg/mL chickpea + 4 mmol/L CaCl2; 50 mg/mL lentil + 4 mmol/L CaCl2; 40 mg/mL DPs + 4 mmol/L CaCl2; 5 mg/mL Val-Ser-Glu-Glu (VSEE) + 4 mmol/L CaCl2; 50 mg/mL chickpea; 50 mg/mL lentil; 40 mg/mL DPs; 5 mg/mL VSEE) were utilized. Upon hatch, blood, cecum, small intestine, liver and bone were collected for assessment of serum bone alkaline phosphate level (BALP), the relative abundance of intestinal microflora, expression of Ca-related genes, brush border membrane (BBM) functional genes, and liver and bone mineral levels, respectively. The BALP level increased in the presence of lentil, DPs and VSEE (p < 0.05). The relative abundance of probiotics increased significantly (p < 0.05) by VSEE + Ca and chickpea. The expression of CalbindinD9k (Ca transporter) increased (p < 0.05) in Ca, chickpea + Ca and lentil + Ca groups. In addition, the brush border membrane functionality genes expressions increased (p < 0.05) by the chickpea or lentil extracts. Prebiotics and DPs beneficially affected the intestinal microflora and duodenal villus surface area. This research expands the understanding of the prebiotics’ properties of chickpea and lentil extracts, and peptides’ effects on calcium metabolism and gut health.

Vitamin D metabolism in growing pigs: influence of UVB irradiation and dietary vitamin D supply on calcium homeostasis, its regulation and bone metabolism.

The aim of this study was to prove whether pigs are able to synthesize vitamin D (vitD) in the skin and to investigate the influence of ultraviolet irradiation (UVB) on vitD status and calcium (Ca) homeostasis of growing pigs. Thirty-two 11-week-old pigs were kept without access to sunlight and divided into four groups receiving the following treatment in a 2×2 factorial design: (i) UVB irradiation or not and (ii) vitD in feed or not. Blood, urine and faeces were sampled every third week. In serum, vitD metabolites, Ca, phosphorus (P), magnesium (Mg) and bone markers were analysed. Digestibility of Ca, P and Mg as well as urinary excretion of these minerals was analysed. After 14weeks, the animals were slaughtered, and samples of skin, intestines, kidneys and bones (metatarsus) were taken for further analyses: sterols of vitD synthesis in the skin, Ca flux rates in the intestines, expression of genes involved in Ca transport in the intestines and kidneys, bone mineral density (BMD) with the aid of peripheral quantitative computer tomography and bone mineral content by ashing the metatarsus. Irradiated animals showed higher levels of 7-dehydrocholesterol and tachysterol in the skin, higher levels of 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol in the serum and higher Ca net flux rates were determined in Ussing chambers. In contrast, the expression of genes involved in Ca transport in the intestines and kidneys was not altered. Similarly, the digestibility of Ca and P as well as the urinary excretion was not affected. With respect to the metatarsus, no differences in mineral contents and BMD were found between groups. At the end of the study, some subclinical signs of beginning vitD 'insufficiency' were observed in the group without access to vitD (represented by higher expression of 1α-hydroxylase in the kidney and increased parathyroid hormone in serum).

Differential effects of zinc exposure on male and female oysters (Crassostrea angulata) as revealed by label-free quantitative proteomics.

Oysters accumulate Zn as an adaptation to Zn exposure; however, it is not known whether male and female oysters respond differently to Zn exposure. Proteomic and real-time polymerase chain reaction analyses were used to investigate differential responses of male and female oysters (Crassostrea angulata) to Zn exposure. After exposure to 50 μg L-1 or 500 μg L-1 Zn for 30 d, gonads of female oysters accumulated more Zn than those of males, and gonadal development was accelerated in females but was abnormal in males. Differentially expressed proteins after exposure to Zn were identified and shown to function in Zn transport, Ca transport, phosphate metabolism, energy metabolism, immune regulation, oxidative stress responses, gene expression regulation, and fat metabolism. Proteins with functions in Zn transportation and storage, and multifunctional proteins, such as hemicentin-1 and histidinol dehydrogenase, were expressed at significantly higher levels in the gonads of female than male oysters after Zn exposure. Environ Toxicol Chem 2017;36:2602-2613. © 2017 SETAC.

Different oxidative status and expression of calcium channel components in stress-induced dysfunctional chicken muscle.

The objective of this study was to assess the effects of transport stress at high ambient temperatures on the oxidation status and the expression of essential elements responsible for the Ca transport (sarco- (endo-) plasmic reticulum Ca-ATPase (SERCA1) and the ryanodine receptor (RyR) in (PM) muscles of broilers. Briefly, Arbor Acres broiler chickens ( = 112) were randomly categorized into 2 treatments: unstressed control (C) and 0.5 h transport (T). Each treatment consisted of 8 replicates of 7 birds each. Birds were transported according to a designed protocol. PM muscle samples in T group were collected and classified as normal (T-NOR) or pale, soft, and exudative-like (T-PSE) using meat quality parameters. The results indicated that production of corticosterone (CORT) and reactive oxygen species (ROS) increased significantly after transportation ( < 0.05). Thiobarbituric acid reactive substance values and carbonyl contents increased significantly in the T group ( < 0.05). Moreover, the extent of lipid peroxidation and protein oxidation was more severe in the T-PSE group compared to the T-NOR group ( < 0.05). The mRNA and protein expression of SERCA1 and αRyR increased in the T-NOR group but decreased significantly in the T-PSE group compared to the CON group ( < 0.05). The mRNA expression of βRyR was found to be enhanced in the T-NOR group compared to the CON group, whereas there was no difference in the T-PSE group ( < 0.05). The results indicate that short-distance transport of broilers affects their physiological responses and biochemical changes which may lead to different oxidative states and, importantly, to different expressions of SERCA and RyR. These induced changes in abnormal sarcoplasmic Ca homeostasis have significant implications for the development of PSE-like meat.

Calcium isotope fractionation between aqueous compounds relevant to low-temperature geochemistry, biology and medicine

Stable Ca isotopes are fractionated between bones, urine and blood of animals and between soils, roots and leaves of plants by >1000 ppm for the 44Ca/40Ca ratio. These isotopic variations have important implications to understand Ca transport and fluxes in living organisms; however, the mechanisms of isotopic fractionation are unclear. Here we present ab initio calculations for the isotopic fractionation between various aqueous species of Ca and show that this fractionation can be up to 3000 ppm. We show that the Ca isotopic fractionation between soil solutions and plant roots can be explained by the difference of isotopic fractionation between the different first shell hydration degree of Ca2+ and that the isotopic fractionation between roots and leaves is controlled by the precipitation of Ca-oxalates. The isotopic fractionation between blood and urine is due to the complexation of heavy Ca with citrate and oxalates in urine. Calculations are presented for additional Ca species that may be useful to interpret future Ca isotopic measurements.

Role of LOTR1 in Nutrient Transport through Organization of Spatial Distribution of Root Endodermal Barriers

The formation of Casparian strips and suberin lamellae at the endodermis limits the free diffusion of nutrients and harmful substances via the apoplastic space between the soil solution and the stele in roots [1-3]. Casparian strips are ring-like lignin polymers deposited in the middle of anticlinal cell walls between endodermal cells and fill the gap between them [4-6]. Suberin lamellae are glycerolipid polymers covering the endodermal cells and likely function as a barrier to limit transmembrane movement of apoplastic solutes into the endodermal cells [7, 8]. However, the current knowledge on the formation of these two distinct endodermal barriers and their regulatory role in nutrient transport is still limited. Here, we identify an uncharacterized gene, LOTR1, essential for Casparian strip formation in Arabidopsis thaliana. The lotr1 mutants display altered localization of CASP1, an essential protein for Casparian strip formation [9], disrupted Casparian strips, ectopic suberization of endodermal cells, and low accumulation of shoot calcium (Ca). Degradation by expression of a suberin-degrading enzyme in the mutants revealed that the ectopic suberization at the endodermal cells limits Ca transport through the transmembrane pathway, thereby causing reduced Ca delivery to the shoot. Moreover, analysis of the mutants showed that suberin lamellae function as an apoplastic diffusion barrier to the steleat sites of lateral root emergence where Casparian strips are disrupted. Our findings suggest that thetransmembrane pathway through unsuberized endodermal cells, rather than the sites of lateral root emergence, mediates the transport of apoplastic substances such as Ca into the xylem.

Visualization of how light changes affect ion movement in rice plants using a real-time radioisotope imaging system

We developed a real-time radioisotope imaging system (RRIS) technique that can nondestructively visualize the element absorption and transport process in plants, using not only positron emitters but also commercially available radioisotopes. In this study, we applied RRIS to analyze light effects on ion movement in rice plants. As tracers, 28Mg, 32P, and 45Ca were used. During the first 5 h, dark/light cycle of 3/7 min were set up; the RRIS needs dark conditions during capturing. When the light was ceased 5 h after supplying each tracer, 32P transport from root to shoot decreased immediately. In contrast, 28Mg and 45Ca transport did not change with light conditions. These results suggest that the P transport is dependent on water flow, whereas Mg and Ca transport are independent of water flow.

Effects of Ca addition on the uptake, translocation, and distribution of Cd in Arabidopsis thaliana

Cadmium (Cd) pollution poses a risk to human health for its accumulation in soil and crops, but this can be alleviated by calcium (Ca) addition. However, its mechanism remains unclear yet. In this study, Arabidopsis thaliana was used to explore the alleviating effects of Ca on Cd toxicity and its specific function during uptake, upward-translocation, and distribution of Cd. Supplementing plants with 5mM CaCl2 alleviated the intoxication symptoms caused by 50μM CdCl2, such as smaller leaves, early bolting and root browning. Ca addition decreased uptake of Cd, possibly by reducing the physical adsorption of Cd since the root cell membrane was well maintained and lignin deposition was decreased as well, and by decreasing symplastic Cd transport. Expression of the genes involved (AtZIP2 and AtZIP4) was also decreased. In addition, Ca accumulated in the plant shoot to help facilitating the upward-translocation of Cd, with evidence of higher translocation factor and expression of genes that were involved in Ca transport (AtPCR1) and Cd xylem loading (AtHMA2 and AtHMA4). Dithizone-staining of Cd in leaves showed that in Cd+Ca-treated plants, Ca addition initially protected the leaf stomata by preventing Cd from entering guard cells, but with prolonged Cd treatment facilitated the Cd accumulation around trichomes and maybe its excretion. We conclude that Ca promotes the upward-translocation of Cd and changes its distribution in leaves. The results may have relevance for bioremediation.

Fluid shear stress increases transepithelial transport of Ca2+ in ciliated distal convoluted and connecting tubule cells.

In kidney, transcellular transport of Ca2+ is mediated by transient receptor potential vanilloid 5 and Na+-Ca2+ exchanger 1 proteins in distal convoluted and connecting tubules (DCTs and CNTs, respectively). It is not yet understood how DCT/CNT cells can adapt to differences in tubular flow rate and, consequently, Ca2+ load. This study aims to elucidate the molecular mechanisms by which DCT/CNT cells sense fluid dynamics to control transepithelial Ca2+ reabsorption and whether their primary cilia play an active role in this process. Mouse primary DCT/CNT cultures were subjected to a physiologic fluid shear stress (FSS) of 0.12 dyn/cm2 Transient receptor potential vanilloid 5 and Na+-Ca2+ exchanger 1 mRNA levels were significantly increased upon FSS exposure compared with static controls. Functional studies with 45Ca2+ demonstrated a significant stimulation of transepithelial Ca2+ transport under FSS compared with static conditions. Primary cilia removal decreased Ca2+ transport in both static and FSS conditions, a finding that correlated with decreased expression of genes involved in transepithelial Ca2+ transport; however, FSS-induced stimulation of Ca2+ transport was still observed. These results indicate that nephron DCT and CNT segments translate FSS into a physiologic response that implicates an increased Ca2+ reabsorption. Moreover, primary cilia influence transepithelial Ca2+ transport in DCTs/CNTs, yet this process is not distinctly coupled to FSS sensing by these organelles.-Mohammed, S. G., Arjona, F. J., Latta, F., Bindels, R. J. M., Roepman, R., Hoenderop, J. G. J. Fluid shear stress increases transepithelial transport of Ca2+ in ciliated distal convoluted and connecting tubule cells.

Calcium improves apoplastic-cytosolic ion homeostasis in salt-stressed Vicia faba leaves.

Salinity disturbs both apoplastic and cytosolic Ca2+ and pH ([Ca2+]apo, [Ca2+]cyt, pHapo and pHcyt) homeostasis, and decreases plant growth. Seedlings of Vicia faba L. cv. Fuego were cultivated in hydroponics for 7 days under control, salinity (S), extra Ca (Ca) or salinity with extra Ca (S+Ca) conditions. The [Ca2+]apo, and pHapo in the leaves were then recorded in parallel by a pseudoratiometric method, described here for the first time. Lower [Ca2+]apo and higher pHapo were obtained under salinity, whereas extra Ca supply increased the [Ca2+]apo and acidified the pHapo. Moreover, the ratiometric imaging recorded that [Ca2+]cyt and pHcyt were highest in S+Ca plants and lowest in control plants. After all pretreatments, direct addition of NaC6H11O7 to leaves induced a decrease in [Ca2+]apo in control and S+Ca plants, but not in S and Ca plants, and only slightly affected pHapo. Addition of NaCl increased [Ca2+]cyt in protoplasts from all plants but only transiently in protoplasts from S+Ca plants. Addition of NaCl decreased pHcyt in protoplasts from Ca-pretreated plants. We conclude that Ca supply improves both apoplastic and cytosolic ion homeostasis. In addition, NaC6H11O7 probably causes transport of Ca from the apoplast into the cytosol, thereby leading to a higher resting [Ca2+]cyt.

Relationships between Yield, Mineral Content of Fruits, and Sap Bleeding Rate in Dutch and Japanese Tomato Cultivars

We present the relationship between yield, mineral content, and the sap bleeding rate (SBR) caused by root pressure as an indicator of root activity in eight Dutch and eight Japanese tomato cultivars (including popular Japanese cultivar ‘Momotaro’) grown in a hydroponic system. Root dry weight in the rockwool slab was positively correlated with stem and leaf fresh weight. In the Dutch cultivars, the SBR remained high (over 20 mL∙h-1) as the root dry weight increased. In contrast, the SBR of Japanese ‘Momotaro’ series cultivars decreased. Ca in the tomato fruits and the SBR were higher in the Dutch cultivars than in the ‘Momotaro’ series. The SBR was found to positively correlate with fruit or total fresh weight. The higher SBR, which supports Ca transport to the fruits, probably led to the higher yields. The SBR might be a simplified indicator of selecting high-yielding cultivars in long-term cultivation.

Reduced Protein Expression of the Na+/Ca2++K+-Exchanger (SLC24A4) in Apical Plasma Membranes of Maturation Ameloblasts of Fluorotic Mice

Exposure of forming enamel to fluoride results into formation of hypomineralized enamel. We tested whether enamel hypomineralization was caused by lower expression of the NCKX4/SLC24A4 Ca2+-transporter by ameloblasts. Three commercial antibodies against NCKX4 were tested on enamel organs of wild-type and Nckx4-null mice, one of which (a mouse monoclonal) was specific. This antibody gave a prominent staining of the apical plasma membranes of maturation ameloblasts, starting at early maturation. The layer of immuno-positive ameloblasts contained narrow gaps without immunostaining or with reduced staining. In fluorotic mouse incisors, the quantity of NCKX4 protein in ameloblasts as assessed by western blotting was not different from that in non-fluorotic ameloblasts. However, immunostaining of the apical plasma membranes of fluorotic ameloblasts was strongly reduced or absent suggesting that trafficking of NCKX4 to the apical membrane was strongly reduced. Exposure to fluoride may reduce NCKX4-mediated transport of Ca2+ by maturation stage ameloblasts which delays ameloblast modulation and reduces enamel mineralization.

Milestones and recent discoveries on cell death mediated by mitochondria and their interactions with biologically active amines

Mitochondria represent cell "powerhouses," being involved in energy transduction from the electrochemical gradient to ATP synthesis. The morphology of their cell types may change, according to various metabolic processes or osmotic pressure. A new morphology of the inner membrane and mitochondrial cristae, significantly different from the previous one, has been proposed for the inner membrane and mitochondrial cristae, based on the technique of electron tomography. Mitochondrial Ca(2+) transport (the transporter has been isolated) generates reactive oxygen species and induces the mitochondrial permeability transition of both inner and outer mitochondrial membranes, leading to induction of necrosis and apoptosis. In the mitochondria of several cell types (liver, kidney, and heart), mitochondrial oxidative stress is an essential step in the induction of cell death, although not in brain, in which the phenomenon is caused by a different mechanism. Mitochondrial permeability transition drives both apoptosis and necrosis, whereas mitochondrial outer membrane permeability is characteristic of apoptosis. Adenine nucleotide translocase remains the most important component involved in membrane permeability, with the opening of the transition pore, although other proteins, such as ATP synthase or phosphate carriers, have been proposed. Intrinsic cell death is triggered by the release from mitochondria of proteic factors, such as cytochrome c, apoptosis inducing factor, and Smac/DIABLO, with the activation of caspases upon mitochondrial permeability transition or mitochondrial outer membrane permeability induction. Mitochondrial permeability transition induces the permeability of the inner membrane in sites in contact with the outer membrane; mitochondrial outer membrane permeability forms channels on the outer membrane by means of various stimuli involving Bcl-2 family proteins. The biologically active amines, spermine, and agmatine, have specific functions on mitochondria which distinguish them from other amines. Enzymatic oxidative deamination of spermine by amine oxidases in tumor cells may produce reactive oxygen species, leading to transition pore opening and apoptosis. This process could be exploited as a new therapeutic strategy to combat cancer.

Calcium and ATP control multiple vital functions.

Life on Planet Earth, as we know it, revolves around adenosine triphosphate (ATP) as a universal energy storing molecule. The metabolism of ATP requires a low cytosolic Ca(2+) concentration, and hence tethers these two molecules together. The exceedingly low cytosolic Ca(2+) concentration (which in all life forms is kept around 50-100 nM) forms the basis for a universal intracellular signalling system in which Ca(2+) acts as a second messenger. Maintenance of transmembrane Ca(2+) gradients, in turn, requires ATP-dependent Ca(2+) transport, thus further emphasizing the inseparable links between these two substances. Ca(2+) signalling controls the most fundamental processes in the living organism, from heartbeat and neurotransmission to cell energetics and secretion. The versatility and plasticity of Ca(2+) signalling relies on cell specific Ca(2+) signalling toolkits, remodelling of which underlies adaptive cellular responses. Alterations of these Ca(2+) signalling toolkits lead to aberrant Ca(2+) signalling which is fundamental for the pathophysiology of numerous diseases from acute pancreatitis to neurodegeneration. This paper introduces a theme issue on this topic, which arose from a Royal Society Theo Murphy scientific meeting held in March 2016.This article is part of the themed issue 'Evolution brings Ca(2+) and ATP together to control life and death'.

The Effect of Dietary Protein and Insulin on Calciuria

This review covers papers looking at the mechanism of dietary protein induced hypercalciuria and in particular looking at the mechanism of the effect that insulin has in varying calciuria. Consideration is also given to the role of pH. ammoniagenesis, gluconeogenesis, ammonia and dietary lipids. Examination of the mechanism of dietary protein induced hypercalciuria is shown to be significant and that insulin can have a significant effect on modifying the level of calciuria. The effect of insulin was shown to work via its inhibition of gluconeogenesis so that ATP is made more available for active transport of Ca. Consideration was also given to the role of pH that can result from a high protein meal and it was demonstrated to work by stimulating ammoniagenesis coupled to gluconeogenesis thus reducing the availability of ATP. The membrane transport of ammonia that is also produced by ammoniagenesis was examined to see if it could have a direct inhibitory effect on Ca transport. It is shown to change its molecular configuration to a non-polar form and diffuse through membranes in a manner that would have no effect on Ca transport. Dietary lipids are also considered in regard to possible effect on calciuria and they were shown to have no significant effect on calciuria.

Sine-wave electrical stimulation initiates a voltage-gated potassium channel-dependent soft tissue response characterized by induction of hemocyte recruitment and collagen deposition.

Soft tissue repair is a complex process that requires specific communication between multiple cell types to orchestrate effective restoration of physiological functions. Macrophages play a critical role in this wound healing process beginning at the onset of tissue injury. Understanding the signaling mechanisms involved in macrophage recruitment to the wound site is an essential step for developing more effective clinical therapies. Macrophages are known to respond to electrical fields, but the underlying cellular mechanisms mediating this response is unknown. This study demonstrated that low‐amplitude sine‐wave electrical stimulation (ES) initiates a soft tissue response in the absence of injury in Procambarus clarkii. This cellular response was characterized by recruitment of macrophage‐like hemocytes to the stimulation site indicated by increased hemocyte density at the site. ES also increased tissue collagen deposition compared to sham treatment (P < 0.05). Voltage‐gated potassium (KV) channel inhibition with either 4‐aminopyridine or astemizole decreased both hemocyte recruitment and collagen deposition compared to saline infusion (P < 0.05), whereas inhibition of calcium‐permeable channels with ruthenium red did not affect either response to ES. Thus, macrophage‐like hemocytes in P. clarkii elicit a wound‐like response to exogenous ES and this is accompanied by collagen deposition. This response is mediated by KV channels but independent of Ca2+ channels. We propose a significant role for KV channels that extends beyond facilitating Ca2+ transport via regulation of cellular membrane potentials during ES of soft tissue.