Impact Of Ca Research Articles

Impact of Zn and Ca on dissolution rate, mechanical properties and GFA of resorbable Mg–Zn–Ca metallic glasses

This article presents investigations utility of Mg-based metallic glasses for resorbable orthopedic implants. Exploration of biocompatible Mg–Zn–Ca alloys in order to determine Zn and Ca optimum concentration were conducted, based on three criteria: sufficiently high GFA (glass forming ability), sufficiently high tensile strength, microhardness and the suitable dissolution rate (corrosion rate) in Ringer's solution. Fulfillment of these criteria should ensure bone union before implant dissolution. The optimatization of Ca and Zn concentration in the range of 4–6at.% Ca and 28–32at.% Zn was executed. The samples in form of ribbons (0.02–0.05mm thickness) and rods (about diameter up to 4mm) with amorphous structure were produced. These investigations allowed to determine the GFA. The optimal results for Mg66Zn30Ca4 and Mg64Zn32Ca4 alloys: tensile strength: 191–166MPa, microhardness: 291–263 HV and volume of released hydrogen 0.04–0.12ml/cm2/h. The corrosion studies - immersion and potentiodynamic methods were conducted (including measurement specific corrosion current density for Mg alloys). Finally, a comparative analysis was performed, which indicated the impact of Ca and Zn concentration on: GFA, mechanical properties and dissolution rate of studied metallic glasses.

Is relative Si/Ca availability crucial to the performance of grassland ecosystems?

AbstractSpecies composition of grasslands and pastures is an important control on biomass production and ecological functioning, with a significant role of grasses and legumes. A change in composition of legumes/grasses abundance and biomass ratio results in altered nutrient cycling and composition of higher trophic‐level communities (e.g., grazers). However, in addition to pasturing and fire effects, other parameters may also potentially affect grassland composition. Grasses are known as silicon (Si) accumulators and legumes as calcium (Ca) accumulators. We propose a new testable hypothesis, and a conceptual model, on the role of Si/Ca availability in controlling legume/grass dominance/competition in grassland systems. Based on available literature, we argue that Si/Ca availability is an important trigger for shifts in abundance of both plant families. The differential uptake of Si and Ca by legumes and grasses affects grassland biogeochemistry and microbial (fungal) biomass. In addition, altered litter stoichiometry, through impact of Ca and Si uptake on N, C, and P turnover, affects the decomposition processes.

Age-dependent impact of CaV 3.2 T-type calcium channel deletion on myogenic tone and flow-mediated vasodilatation in small arteries.

Blood pressure and flow exert mechanical forces on the walls of small arteries, which are detected by the endothelial and smooth muscle cells, and lead to regulation of the diameter (basal tone) of an artery. CaV 3.2 T-type calcium channels are expressed in the wall of small arteries, although their function remains poorly understood because of the low specificity of T-type blockers. We used mice deficient in CaV 3.2 channels to study their role in pressure- and flow-dependent tone regulation and the possible impact of ageing on this role. In young mice, CaV 3.2 channels oppose pressure-induced vasoconstriction and participate in endothelium-dependent, flow-mediated dilatation. These effects were not seen in mature adult mice. The results of the present study demonstrate an age-dependent impact of CaV 3.2 T-type calcium channel deletion in rodents and suggest that the loss of CaV 3.2 channel function leads to more constricted arteries, which is a risk factor for cardiovascular disease. The myogenic response and flow-mediated vasodilatation are important regulators of local blood perfusion and total peripheral resistance, and are known to entail a calcium influx into vascular smooth muscle cells (VSMCs) and endothelial cells (ECs), respectively. CaV 3.2 T-type calcium channels are expressed in both VSMCs and ECs of small arteries. The T-type channels are important drug targets but, as a result of the lack of specific antagonists, our understanding of the role of CaV 3.2 channels in vasomotor tone at various ages is scarce. We evaluated the myogenic response, flow-mediated vasodilatation, structural remodelling and mRNA+protein expression in small mesenteric arteries from CaV 3.2 knockout (CaV 3.2KO) vs. wild-type mice at a young vs. mature adult age. In young mice only, deletion of CaV 3.2 led to an enhanced myogenic response and a ∼50% reduction of flow-mediated vasodilatation. Ni2+ had both CaV 3.2-dependent and independent effects. No changes in mRNA expression of several important K+ and Ca2+ channel genes were induced by CaV 3.2KO However, the expression of the other T-type channel isoform (CaV 3.1) was reduced at the mRNA and protein level in mature adult compared to young wild-type arteries. The results of the present study demonstrate the important roles of the CaV 3.2 T-type calcium channels in myogenic tone and flow-mediated vasodilatation that disappear with ageing. Because increased arterial tone is a risk factor for cardiovascular disease, we conclude that CaV 3.2 channels, by modulating pressure- and flow-mediated vasomotor responses to prevent excess arterial tone, protect against cardiovascular disease.

EGTA, a calcium chelator, affects cell cycle and increases DNA methylation in root tips of Triticum aestivum L.

In this study, when germinated <em>Triticum aestivum</em> L. seeds were treated with 0, 2, 4 and 6 mM ethyl glycol tetraacetic acid (EGTA), root growth was suppressed and the mitotic index decreased. These inhibitory effects were positively correlated with EGTA concentration. RT-PCR analysis revealed that the expression of several gene markers related to the G1/S transition of the cell cycle were significantly downregulated. Confocal microscopy of Fluo-3/AM-stained roots showed chelation of nearly all of the Ca<sup>2+</sup> within the root meristematic regions. Both random amplified polymorphic DNA (RAPD) and coupled restriction enzyme digestion-random amplification (CRED-RA) techniques showed significant increases in the levels of genomic DNA polymorphisms and degree of DNA methylation. The study provides information concerning the impact of Ca<sup>2+</sup> chelator, EGTA, on the growth, expression of cell cycle transition marker genes, and changes in DNA structure and methylation in the wheat roots.

Zn-doped CaTiO3:Eu(3+) red phosphors for enhanced photoluminescence in white LEDs by solid-state reaction.

Zn-doped CaTiO3:Eu(3+) red phosphors for enhanced photoluminescence in white light-emitting diodes (LEDs) were synthesized by a solid-state method. The structure and morphology of the obtained phosphor samples were observed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the impact of Ca, Zn and Eu content on their photoluminescence properties was studied. The results indicated that Zn not only participates in the formation of defects in suitable lattice matrices but also has a role in flux in the transformation from ZnO to Zn2TiO4, which is beneficial for the enhancement of photoluminescence properties. Photoluminescence test data showed that the Zn-doped phosphor is excited efficiently by near-ultraviolet (NUV) light at wavelengths around 398 nm and emits an intense red light with a broad peak around 616 nm corresponding to the (5) D0 →(7) F2 transition of Eu(3+). The intensity of this phosphor emission is three times stronger than that without Zn-doping. Furthermore, this phosphor has very good thermal stability, high color purity and a low sintered temperature, all of which suggest its potential as a promising red phosphor for white LEDs.

Abstract 11155: Impact of Serum Calcium Levels on Mortality of Patients With Heart Failure and Chronic Kidney Disease

Background: Chronic kidney disease-mineral and bone disorders (CKD-MBD) are associated with vascular calcification and abnormal electrolyte that lead to cardiovascular disease and mortality. CKD-MBD are identified by imbalances in serum calcium (Ca), phosphate, and parathyroid hormone (PTH). Although, the relation of phosphate and PTH to prognosis of HF patients has been reported, prognostic impact of Ca on patients with heart failure (HF) and CKD remains unclear. Methods and Results: Consecutive 191 patients admitted for HF and CKD (estimated GFR < 60 ml/min/1.73 m 2 ) were divided into 3 groups based on levels of corrected Ca: low Ca (Ca < 8.4 mg/dl, n = 32), normal Ca (8.4 ≤ Ca <10.0, n = 149), and high Ca (10.0 ≤ Ca, n = 10) groups. We compared echocardiographic findings and levels of hemoglobin, BNP, troponin T, CRP, estimated GFR, intact PTH, phosphate, zinc (Zn), and magnesium (Mg) among the three groups. Furthermore, we prospectively followed cardiac, non-cardiac, and all-cause mortality. The low Ca group, as compared to normal and high Ca groups, had lower levels of hemoglobin and Zn (hemoglobin: 11.2 vs. 12.4, 13.0 g/dl, P < 0.001; Zn: 58.1 vs. 70.1, 71.0 mg/dl, P = 0.003). Age, body mass index, BNP, troponin T, CRP, estimated GFR, intact PTH, phosphate, Mg, and left ventricular ejection fraction were similar among the three groups. Importantly, cardiac mortality (log-rank P = 0.003) and all-cause mortality (P < 0.001), but not non-cardiac mortality, were higher in low Ca group than in normal and high Ca groups in HF and CKD patients. In the multivariate Cox proportional hazard analyses, hypocalcemia was an independent predictor of cardiac (HR 2.34, P = 0.007) and all-cause mortality (HR 1.89, P = 0.027) in HF and CKD patients. Conclusions: Hypocalcemia was an independent predictor of cardiac and all-cause mortality in HF and CKD patients. Thus, taking appropriate management to control CKD-MBD balance may improve the prognosis of patients with HF and CKD.

ACTIVATION OF THE SIGMA-1 RECEPTOR BY SPECIFIC LIGANDS INHIBITS HUMAN INFLAMMATORY DENDRITIC CELL FUNCTIONS AND EFFECTOR T-LYMPHOCYTE RESPONSES

CN autoinhibitory domain located near the C terminus of the CN catalytic subunit. Commercially available antibodies that target the N terminus of the CN catalytic subunit reveal the presence of a highly-active 48 kDa proteolytic fragment in human brain tissue during early stages of cognitive decline and also in a variety of experimental models of neurodegeneration. While useful for determining the extent of CN proteolysis in Western blot applications, N terminus antibodies do not reveal the cellular location of the proteolysis. Knowing where CN is proteolyzed in nervous tissue seems critical to understanding the mechanistic basis of its many deleterious actions, particularly because CN is found in both neurons and glial cells where it is involved in different cellular functions.Methods: To address this gap in our understanding of CN regulation, we generated custom rabbit polyclonal antibodies to CNA based on previously identified calpain-dependent cleavage sites. One of these antibodies (referred to as “DCN48”) detects a 48 kDa fragment in Western blot assays, but does not detect full-length (60 kDa) CN. TheDCN48 antibody was then used for DAB immunohistochemical labeling of human brain sections characterized by AD andmixed AD/vascular pathologies. Results: The anatomical features labeled by the DCN48 antibody included astrocyte clusters and vascular-associated elements and/or processes. We also observed numerous DCN48-positive astrocytes associated with microinfarcts. Surprisingly, we have seen very little neuronal labeling with this antibody. Conclusions: The results suggest that astrocytes and, perhaps astrocyte end-feet, are a primary locus for CPdependent CN proteolysis in injured or diseased nervous tissue. CN proteolysis appears to be especially pronounced in astrocytes associated with vascular pathology. This work may provide new mechanistic insights into the impact of Ca 2+ dysregulation on neurodegenerative diseases.

Influence of Calcium Ions on Rhamnolipid and Rhamnolipid/Anionic Surfactant Adsorption and Self-Assembly

The impact of Ca(2+) counterions on the adsorption at the air-water interface and self-assembly in aqueous solution of the rhamnolipid biosurfactant and its mixture with the anionic surfactant sodium dodecylbenzenesulfonate, LAS, has been studied using neutron reflectometry and small-angle neutron scattering. The results illustrate how rhamnolipids are calcium tolerant and how their blending with conventional anionic surfactants improves the calcium tolerance of the anionic surfactant. Ca(2+) has relatively little effect upon the adsorption and self-assembly of the monorhamnose, R1, and dirhamnose, R2, rhamnolipids, even at high pH, due to their predominantly nonionic nature. For R1/R2 mixtures the addition of Ca(2+) has little impact upon the adsorbed amount or the surface composition. For R2/LAS mixtures the addition of Ca(2+) results in an increased adsorption and a surface slightly richer in R2. The weak binding of Ca(2+) to R1 and R2 does result in a change to the degree of ionization of the micelles and especially for mixed R1/R2 micelles at R1-rich solution compositions. The stronger binding of Ca(2+) to LAS results in the addition of Ca(2+) having a much greater impact on the self-assembly of R1/LAS and R2/LAS mixtures. For R1/LAS mixtures the addition of Ca(2+) promotes the formation of more planar structures, even at low surfactant concentrations where in the absence of Ca(2+) mixed globular micelle formation dominates. In R2/LAS mixtures, where there is a greater contrast between the high and low preferred curvatures associated with R2 and LAS, the addition of Ca(2+) results in a more complex evolution in micellar aggregation and the degree of ionization of the micelles. This results in variations in Ca(2+) binding that promotes micellar structures in which a spatial segregation of the two surfactant components within the micelle occurs.

Inhibition of hydrogen sulfide generation from disposed gypsum drywall using chemical inhibitors

Disposal of gypsum drywall in landfills has been demonstrated to elevate hydrogen sulfide (H 2S) concentrations in landfill gas, a problem with respect to odor, worker safety, and deleterious effect on gas-to-energy systems. Since H 2S production in landfills results from biological activity, the concept of inhibiting H 2S production through the application of chemical agents to drywall during disposal was studied. Three possible inhibition agents – sodium molybdate (Na 2MoO 4), ferric chloride (FeCl 3), and hydrated lime (Ca(OH) 2) – were evaluated using flask and column experiments. All three agents inhibited H 2S generation, with Na 2MoO 4 reducing H 2S generation by interrupting the biological sulfate reduction process and Ca(OH) 2 providing an unfavorable pH for biological growth. Although FeCl 3 was intended to provide an electron acceptor for a competing group of bacteria, the mechanism found responsible for inhibiting H 2S production in the column experiment was a reduction in pH. Application of both Na 2MoO 4 and FeCl 3 inhibited H 2S generation over a long period (over 180 days), but the impact of Ca(OH) 2 decreased with time as the alkalinity it contributed was neutralized by the generated H 2S. Practical application and potential environmental implications need additional exploration.

Changes in mitochondrial functionality and calcium uptake in hypertensive rats as a function of age

We studied whether mitochondrial functions and Ca 2+ metabolism were altered in Wistar Kyoto normotensive (WKY) and spontaneous hypertensive rats (SHR). Ca 2+ uptake was decreased in SHR compared to WKY rats. Accumulation of Ca 2+ was more efficient in WKY than in SHR rats. mΔΨ was lower in SHR compared to WKY rats. Basal complex IV activity was higher in SHR than WKY rats, whereas basal l-citrulline production, an indicator of nitric oxide synthesis, was decreased in SHR and dependent on Ca 2+ concentration ( p < 0.05). Impact of Ca 2+ was counteracted by EGTA. These data show an age-dependent decreased mitochondrial functions in brain mitochondria during hypertension.

Charge transfer at oxygen/zirconia interface at elevated temperatures: Part 11: Effect of surface doping with calcium

The present paper considers the effect of doping with Ca of the surface layer of yttria-stabilised (10 mol-%Y2O3) zirconia on its reactivity with oxygen and related charge transfer. Work function measurements were applied for in situ monitoring of charge transfer at the biphase oxygen/zirconia interface in the temperature range 973–1173 K. The work function data are considered in terms of the effect of Ca on reactivity between oxygen and zirconia. They indicate that Ca leads to the formation of a surface structure that decreases the surface charge produced by oxygen chemisorption. The observed effect is considered in terms of the impact of Ca on the performance of zirconia in electrochemical devices.

The impact of CA 19-9 in therapy monitoring and follow up of locally advanced carcinoma of the exocrine pancreas treated with radiochemotherapy

The impact of CA 19-9 in therapy monitoring and follow up of locally advanced carcinoma of the exocrine pancreas treated with radiochemotherapy

Impact of Ca(OH)2 treatment on macroinvertebrate communities in eutrophic hardwater lakes in the Boreal Plain region of Alberta: in situ and laboratory experiments

Ca(OH)2 treatment has been recently used to remediate water quality problems associated with eutrophication in lakes on the Boreal Plain of western Canada. This study examines how Ca(OH)2 treatment affects the survival of Hyalella azteca and larvae of Chironomus spp. in laboratory microcosms and the abundance and seasonal dynamics of macroinvertebrates in two eutrophic hardwater lakes. Macroinvertebrate data for three reference lakes sampled during the same time period are also presented. Additions of 225 and 295 g Ca(OH)2·m-2 (74 and 107 mg·L-1) to two lakes resulted in lake water pH remaining within its natural range (&lt;10) and had no discernable effects on macroinvertebrate density or biomass up to 2 years after treatment. Macroinvertebrate response to Ca(OH)2 in hardwater lakes differed markedly from results reported for softwater lakes. After 4 days, no detectable influence was observed on survivorship of Chironomus spp. with laboratory dosages of 0-300 g Ca(OH)2·m-2 (0-1781 mg·L-1), but survivorship of H. azteca was reduced by &gt;= 50% at dosages that raised water pH to &gt;=10 (300 g Ca(OH)2·m-2). The sensitivity of H. azteca, but not Chironomus spp., could be a result of singular or combined effects of Ca(OH)2 levels, precipitate, or changes in pH. It may also reflect the greater dependence of H. azteca than Chironomus spp on the water above, rather than below, the sediment-water interface.

Impact of Ca(OH)&lt;sub&gt;2&lt;/sub&gt; treatment on macroinvertebrate communities in eutrophic hardwater lakes in the Boreal Plain region of Alberta: in situ and laboratory experiments

Impact of Ca(OH)&lt;sub&gt;2&lt;/sub&gt; treatment on macroinvertebrate communities in eutrophic hardwater lakes in the Boreal Plain region of Alberta: in situ and laboratory experiments

32 ADOLESCENTS WITH CANCER: PATIENT AND PARENT PERCEPTIONS OF IMPACT OF ILLNESS

Since parents are important sources of support for adolescents (adols) with cancer (ca), one needs to know if parents and their children share the same perceptions of illness-related problems. As part of our study of adols with ca, an impact of illness questionnaire was given to 23 patients (pts), 22 of their mothers (M), and 14 of their fathers (F) to determine: (1) the impact of ca on the pts reported by M, F, and pts and (2) the type of disruption seen by each. M and F each reported more illness-impact on the pts than did the pts themselves (p<.0001), while the difference between M and F was not significant. Of the impact-related items, the frequency of responses indicating treatment- and ca-related disruption of the pt was 52% by pts, 68% by M, and 73% by F. M, F, and pts all agreed in their perceptions that the adols were very hopeful and coped well with illness, in spite of the considerable impact reported. M, F, and pts agreed that ca interfered with the pts' popularity, freedom and physical appearance. M and pts agreed that treatments were worse than the illness itself, while F agreed with pts that ca caused general life disruption. The data suggest that parents believe that their adols experience more illness-related impact than is reported by these adols. Although parents and their children perceive ca as highly disruptive, all remain hopeful. Three areas of functioning ranked by M, F, and pts as highly disrupted were similar to findings of our previous study. These data have implications for helping families provide support for their adols with cancer.