Correct Calcium Research Articles

Comparison of the structure and function of phospholamban and the arginine-14 deficient mutant associated with dilated cardiomyopathy.

Phospholamban (PLB) is a pentameric protein that plays an important role in regulating cardiac contractility via a reversible inhibitory association with the sarcoplasmic reticulum Ca2+ATPase (SERCA), the enzyme responsible for maintaining correct calcium homeostasis. Here we study the functional and biophysical characteristics of a PLB mutant associated with human dilated cardiomyopathy (DCM), with a deletion of arginine at position 14 (PLBR14Δ). In agreement with recent findings, we find that PLBR14Δ has a reduced inhibitory effect on SERCA compared to wild type PLB (PLBWT) when reconstituted into lipid membranes. The mutation also leads to a large reduction in the protein kinase A-catalysed phosphorylation of Ser-16 in the cytoplasmic domain of PLBR14Δ. Measurements on SERCA co-reconstituted with an equimolar mixture of PLBWT and PLBR14Δ (representing the lethal heterozygous state associated with DCM) indicates that the loss-of-function mutation has a dominant effect on PLBWT functionality and phosphorylation capacity, suggesting that mixed PLBWT/PLBR14Δ pentamers are formed that have characteristics typical of the mutant protein. Structural and biophysical analysis of PLBR14Δ indicates that the mutation perturbs slightly the helical structure of the PLB cytoplasmic domain and reduces its affinity for the phospholipid bilayer surface, thereby altering the orientation of the cytoplasmic domain relative to the wild-type protein. These results indicate that the structure and function consequences of the R14 deletion have profound effects on the regulation of SERCA which may contribute to the aetiology of DCM.

Epigenetic regulation of microRNAs controlling CLDN14 expression as a mechanism for renal calcium handling.

The kidney has a major role in extracellular calcium homeostasis. Multiple genetic linkage and association studies identified three tight junction genes from the kidney--claudin-14, -16, and -19--as critical for calcium imbalance diseases. Despite the compelling biologic evidence that the claudin-14/16/19 proteins form a regulated paracellular pathway for calcium reabsorption, approaches to regulate this transport pathway are largely unavailable, hindering the development of therapies to correct calcium transport abnormalities. Here, we report that treatment with histone deacetylase (HDAC) inhibitors downregulates renal CLDN14 mRNA and dramatically reduces urinary calcium excretion in mice. Furthermore, treatment of mice with HDAC inhibitors stimulated the transcription of renal microRNA-9 (miR-9) and miR-374 genes, which have been shown to repress the expression of claudin-14, the negative regulator of the paracellular pathway. With renal clearance and tubule perfusion techniques, we showed that HDAC inhibitors transiently increase the paracellular cation conductance in the thick ascending limb. Genetic ablation of claudin-14 or the use of a loop diuretic in mice abrogated HDAC inhibitor-induced hypocalciuria. The genetic mutations in the calcium-sensing receptor from patients with autosomal dominant hypocalcemia (ADH) repressed the transcription of miR-9 and miR-374 genes, and treatment with an HDAC inhibitor rescued the phenotypes of cell and animal models of ADH. Furthermore, systemic treatment of mice with antagomiRs against these miRs relieved claudin-14 gene silencing and caused an ADH-like phenotype. Together, our findings provide proof of concept for a novel therapeutic principle on the basis of epigenetic regulation of renal miRs to treat hypercalciuric diseases.

SERCA2a: its role in the development of heart failure and as a potential therapeutic target

The complexity of heart physiology has delayed the implementation of efficient, feasible, and safe therapies to fight against heart diseases for many years. As knowledge of the precise mechanisms governing cardiac hypertrophy and heart failure development increases, the availability of new therapeutic alternatives also grows. Since the cardiomyocyte physiol- ogy deeply depends on the correct calcium handling, many efforts to describe accurately the excitation-contraction coupling process in the heart and the proteins involved have been made. Among the proteins participating in calcium handling, sarco/endoplasmic reticulum Ca 2+ adenosine triphosphatase-2a (SERCA2a), whose expression and function is decreased in heart failure, stands out because of its critical role regulating Ca 2+ concentration in the cardiomyocyte. The importance of SERCA2a has been reflected in numerous studies aimed to describe its expression and function. Recently, gene therapy to deliver SERCA2a has shown promising results in human clinical trials. This paper reviews the current literature knowledge exploring diverse approaches to rescue SERCA2a expression in heart failure. It also discusses some data suggesting other possible therapies that could improve SERCA2a expression and

Who should receive calcium and vitamin D supplementation?

Combined calcium and vitamin D supplementation is recommended in the prevention and treatment of osteoporosis. Until recently, supplementation was perceived as harmless without adverse effects. However, recent meta-analyses have provided evidence suggesting that calcium supplements, whether or not in combination with vitamin D, may be associated with cardiovascular risks. Although this finding constitutes a safety signal that has to be taken seriously, these data have to be interpreted with some caution. Current data do not allow definite conclusions to be drawn, but require further independent confirmation, since in numerous large studies, combined calcium and vitamin D supplementation did not increase cardiovascular events, even in the most frail and elderly populations. Nevertheless, it seems appropriate to correct calcium deficiency preferably by enhancing dietary intake and to target supplementation on individuals at high risk of fracture or in whom calcium and vitamin D deficiency is highly prevalent. Other trials have shown an increased risk of falls and fractures with annual oral administration of high dose of vitamin D. Therefore, supplementation with more frequent, lower doses is preferred. Yet, the optimal dosing schedule is unknown and needs further study. In order to correct age-associated secondary hyperparathyroidism and to prevent osteoporotic fractures, a daily dose of 1,000-1,200 mg calcium and 800 IU vitamin D is recommended in elderly or institutionalised people, patients with established osteoporosis and individuals on glucocorticoids.

The effect of acidification and oxalate concentration on urine calcium measurements in EQAS materials and patient samples

An increase in urine calcium compared to the consensus value was observed in some urine samples of the Dutch External Quality Assessment Scheme (EQAS). It appeared that the increase was due to the addition of oxalate by the EQAS organizers and preanalytical acidification of the samples by some of the participants. Because of this observation, the effect of urine acidification on urine calcium level in EQAS and patient samples with added oxalate was investigated. Twenty-four EQAS urine samples and 20 patient urine samples were subject to recovery measurements of urine calcium before and after addition of sodium oxalate and acidification. Differences in urine calcium between acidified and non-acidified samples up to 30.9% have been observed in EQAS samples with added oxalate. Patient samples show differences up to 80%. Differences between acidified and non-acidified samples are minimal for low calcium oxalate levels but increase with higher levels. Samples without added oxalate show equal urine calcium results between acidified and non-acidified samples. Urine calcium results are decreased in non-acidified samples with an excess of oxalate. In case of hyperoxaluria, acidification of patient urine collections and EQAS samples is recommended for correct urine calcium values.

Minireview: The Play of Proteins on the Parathyroid Hormone Messenger Ribonucleic Acid Regulates Its Expression

PTH regulates serum calcium and phosphate levels and bone strength. The parathyroid is unique in that the trigger for PTH secretion is a low extracellular calcium rather than high calcium as for other hormones. The parathyroid senses small changes in serum calcium through the seven-trans-membrane G protein-coupled calcium receptor to alter PTH secretion. PTH then acts on bone and kidney to correct serum calcium. Parathyroid cells have few secretory granules as compared with other endocrine cells, and therefore PTH production is regulated largely at the levels of PTH gene expression and parathyroid cell proliferation. The regulation of PTH gene expression by changes in calcium and phosphate and in chronic kidney failure is posttranscriptional involving the binding of trans-acting proteins to a defined cis element in the PTH mRNA 3'-untranslated region. These protein-PTH mRNA interactions are orchestrated by the peptidyl-prolyl isomerase Pin1. This review discusses the mechanisms of regulation of PTH mRNA stability determining serum PTH levels and mineral metabolism.

Adjustment for body mass index and calcitrophic hormone levels improves the diagnostic accuracy of the spot urine calcium-to-creatinine ratio

Providers diagnose hypercalciuria using a 24-hour or random urine samples. We compared calcium measurements from paired 24-hour and morning urine samples; measurements correlated poorly. We developed a formula to correct random urine calcium levels. Corrected levels showed excellent agreement with 24-hour measurements. Until validation, providers should diagnose hypercalciuria using 24-hour tests. Hypercalciuria is a risk factor for osteoporosis and nephrolithiasis. The 24-hour urine calcium (24HUC) measurement is the gold standard to diagnose hypercalciuria, but the spot urine calcium-to-creatinine ratio (SUCCR) is more convenient. Although authors claim they are interchangeable, we observed inconsistencies during the conduct of a clinical trial. Therefore, we systematically evaluated agreement between the tests. During a 28-inpatient calcium absorption studies in 16 postmenopausal women, we simultaneously collected paired fasting morning and 24-hour urine specimens. We found moderate correlation between paired SUCCR and 24HUC specimens (r = 0.57, p = 0.002), but the SUCCR underestimated 24HUC by a mean of 83 mg (Bland-Altman). We diagnosed hypercalciuria (24HUC >250 mg) in eight specimens using the 24HUC, but only in two specimens using the SUCCR (25% sensitivity). We developed a regression model to predict 24HUC using SUCCR, parathyroid hormone, body mass index, and 1,25(OH)(2)D. The model improved diagnostic sensitivity to 100% and decreased Bland-Altman bias of the SUCCR to +0.06 mg/kg/24-hour. We conclude that the SUCCR underestimates urine calcium loss and does not reliably diagnose hypercalciuria. A formula derived from multivariate regression incorporating other readily measurable variables greatly improved the SUCCR's accuracy. Future studies must verify this correction before clinical implementation.

A cyclic nucleotide‐gated channel is necessary for optimum fertility in high‐calcium environments

* Arabidopsis cngc2 plants are hypersensitive to external calcium and exhibit reduced plant size and fertility, especially when they are treated with elevated but physiologically relevant levels of calcium. This report focuses on the role of cyclic nucleotide-gated channel 2 (CNGC2) in plant fertility. * To determine the cause of the reduced fertility, we investigated the flower structure and growth potential of both male and female reproductive organs in cngc2 plants grown in high-calcium conditions. * cngc2 mutants had short stamens that may limit pollen deposition and pistils that were not conducive to pollen tube growth. * Our data indicate that sporophytic, but not gametophytic, defects are the main cause of the observed reduction in seed yield in cngc2 plants, and suggest that correct cyclic nucleotide and calcium signaling are important for cell elongation and pollen tube guidance.

Estrogen Receptor-alpha Genotype Affects Exercise And Nutrient Intake-related Change Of Bone Mass.

Bone mass is affected not only by environment factors, e.g., physical activities and foods, but also by gene polymorphism. PURPOSE: The present study was to determine whether gene polymorphism in the estrogen receptor (ER) alpha gene (ESR1) affect bone mass. And, the interaction between genes and physical activities and/or dietary intakes on bone mass in young women. METHODS: Seventy 20-23 years old Japanese women were chosen for the study. They wee euther very active physically (exercise three times per week) or not active. Food frequency questionnaires were used to estimate calcium intake. Bone mass was measured by quantitative ultrasound measurement (QUS). Genomic DNA was extracted from buccal cell. The ESR1 polymorphisms at intron I (Pvu II for a T/C substitution and Xba I for an A/G substitution) were genotyped using the PCR-RFLP. The relationships between ER1 genotype and physical activity, and/or dietary were evaluated. RESULTS: There were no significant differences between bone mass and ER1 genotypes. However, body weight, BMI and high physical activity showed the positive correlation with bone mass in the Pp heterozygote (P < 0.01). Furthermore, bone mass was higher in the individual who eats fish (three times per week) in the Xx heterozygote (P < 0.01). CONCLUSIONS: Our data suggested that physical exercise or a correct calcium intake is more important to bone mass for young women with Pp heterozygote or Xx heterozygote of ER alpha gene, respectively.

Plasma calcium in haemodialysis patients: total calcium or ionized calcium? Should we systematically provide a value of total corrected calcium on our protocols?

Ionized calcium is the only physiologically active form of calcium. Because of the variation of albumin, pH and haemoconcentration observed during haemodialysis session in patients with chronic renal failure, measure of total calcium does not reflect the real variation of ionized calcium. However, many formulae to correct total calcium by albumin have been proposed but none of them has been validated in dialysis patients. At present time, computing progress permit laboratory to systematically provide a value of corrected total calcium on protocols but is it really indicated? Our results showed that any of those formulae allows obtaining a value of total calcium that possesses a significant critical difference in relation to total calcium. Thus, correction formulae must be abandoned in aid of ionized calcium in haemodialysis patients.

Effect of housing system on the calcium requirement of laying hens and on eggshell quality

The effects of housing systems on the calcium requirement for eggshell production, eggshell quality and on the breaking strength of the hen’s tibia were evaluated. Unenriched cages (UN) (24 laying hens), enriched cages (EN) (16 laying hens) and floor system (FS) (24 laying hens) were used in this experiment. The eggshell production of laying hens from 19 to 66 weeks of age was higher (&lt;I&gt;P&lt;/I&gt; &lt; 0.01) in the cage systems (UN 39.6 g/hen/week and EN 39.2 g/hen/week) than it was in FS (35.0 g/hen/week). Consequently, the amount of calcium deposited in the eggshells (g/hen/week) was higher (&lt;I&gt;P&lt;/I&gt; &lt; 0.01) in the cage systems (14.2 and 14.0 g/hen/week) than in FS (12.6 g/hen/week). Despite of the same calcium intake of the hens housed in EN and FS the eggshell thickness (0.39 and 0.38 mm, respectively) and eggshell strength (38.04 and 36.43 N respect.) were higher (&lt;I&gt;P&lt;/I&gt; &lt; 0.01 and &lt;I&gt;P&lt;/I&gt; &lt; 0.001 respectively) in EN. The tibia breaking strength was higher (&lt;I&gt;P&lt;/I&gt; &lt; 0.05) in FS (156.6 N) in comparison with UN (92.7 N). The rate of calcium intake deposited in the eggshells was higher in the cage systems than in FS, namely by 1.7 to 8.9% depending on the age of laying hens. When determining the correct calcium requirements in the diets of laying hens, the housing system should be taken into account.

Lait et produits laitiers dans la prévention et le traitement des maladies par carence

Milk and dairy products are the main sources of calcium in western countries. In contrast, most calcium ingested in eastern and black African countries comes from vegetables and fish. Calcium is necessary for optimal bone metabolism and for many other biological systems. Recommended daily calcium intake differs among countries and even among institutions. Daily intake should be at least 1000 mg after the age of 10-12 years, and 1200-1500 mg/day for adolescents (14-18 years), pregnant women, and men over 65. There is no added benefit beyond 2000 mg, but intake should not fall below 700-800 mg/day. Three servings of dairy products are needed to meet recommended daily calcium intake. The importance of calcium in the management of osteoporosis is controversial. However, experts agree on the need to correct calcium deficiency, especially when associated with vitamin D deficiency Calcium and vitamin D supplementation is essential to prevent fractures in deficient elderly subjects. Calcium and vitamin D should be systematically added to treatments for patients with established osteoporosis and for those with risk factors.

Accelerated Bone Resorption, Due to Dietary Calcium Deficiency, Promotes Breast Cancer Tumor Growth in Bone

The skeleton is a major site of breast cancer metastases. High bone turnover increases risk of disease progression and death. However, there is no direct evidence that high bone turnover is causally associated with the establishment and progression of metastases. In this study, we investigate the effects of high bone turnover in a model of breast cancer growth in bone. Female nude mice commenced a diet containing normal (0.6%; 'Normal-Ca') or low (0.1%; 'Low-Ca') calcium content. Mice were concurrently treated with vehicle or osteoprotegerin (1 mg/kg/d s.c; n = 16 per group). Three days later (day 0), 50,000 Tx-SA cells (variant of MDA-MB-231 cells) were implanted by intratibial injection. On day 0, mice receiving Low-Ca had increased serum parathyroid hormone (PTH) and tartrate-resistant acid phosphatase 5b levels, indicating secondary hyperparathyroidism and high bone turnover, which was maintained until day 17. Osteoprotegerin increased serum PTH but profoundly reduced bone resorption. On day 17, in mice receiving Low-Ca alone, lytic lesion area, tumor area, and cancer cell proliferation increased by 43%, 24%, and 24%, respectively, compared with mice receiving Normal Ca (P < 0.01). Osteoprotegerin treatment completely inhibited lytic lesions, reduced tumor area, decreased cancer cell proliferation, and increased cancer cell apoptosis. Increased bone turnover, due to dietary calcium deficiency, promotes tumor growth in bone, independent of the action of PTH. Breast cancer patients frequently have low dietary calcium intake and high bone turnover. Treatment to correct calcium insufficiency and/or treatment with antiresorptive agents, such as osteoprotegerin, may be of benefit in the adjuvant as well as palliative setting.

Cation exchange capacity methodology III: Correct exchangeable calcium determination of calcareous clays using a new silver–thiourea method

Cation exchange capacity (CEC) is a fundamental property of clays and soils. Determination of CEC for samples that contain Ca-carbonate minerals, such as calcite and dolomite, is problematic because Ca 2+ released by dissolution of carbonates during CEC determinations interferes with the accuracy of CEC values. This paper describes a new method for the determination of correct exchangeable Ca 2+ values of calcareous clays and soils. For the method, a silver–thiourea exchange solution is saturated with Ca 2+ by treatment with fine-grained calcite prior to the start of the exchange procedure. Using this exchange solution, calcite in the sample can no longer be dissolved but exchangeable Ca 2+ is desorbed quantitatively. The case for dolomite is similar, because dissolution of dolomite is minimised. However, the determination of reasonable exchangeable Ca 2+ values for samples containing gypsum is not possible because gypsum is soluble in the exchange solution.

Caring for HIV-Positive and Aging Patients With Associated Facial Lipoatrophy

Facial lipoatrophy is characterized by fat loss and redistribution. It is a natural, biological phenomenon that occurs over time, presenting as mild-to-moderate volume depletion that gives the skin the appearance of sagging. More recently, highly active antiretroviral therapy, introduced for the management of human immunodeficiency virus, has been associated with moderate-to-severe facial lipoatrophy, and is characterized by sunken cheeks, accentuated nasolabial folds, and protruding musculature and bones. Furthermore, the consequences of facial lipoatrophy have been found to substantially impact patient quality of life. Nurses play an integral role in the treatment of facial lipoatrophy by educating the patients on available therapies and assisting them in making informed treatment decisions. It is important that treating nurses conduct a well-organized interview to understand patient treatment goals. This article will discuss several treatment options available to correct facial lipoatrophy-associated volume deficits, including collagen, hyaluronic acid, calcium hydroxylapatite, poly-L-lactic acid, and permanent implants and injectables.

Influence of dietary factors on calcium bioavailability: a brief review.

There are several factors that affected calcium bioavailability, such as physiological and dietary factors. These dietary factors help to achieve an appropiate status of calcium for a correct bone mineralization. In this pathway, recently some compounds present in milk that seem improve calcium absorption such as lactose and certain caseinophosphopeptides formed during digestion of caseins have been studied. On the other hand, the possible inhibitatory effect of fiber has been also studied, without conclusive results between in vitro and in vivo studies and the role of phytic acid on impairs calcium bioavailability could be prevented by using fructo-oligosaccharides, which cannot be digested in the small intestine and arrive practically intact to the colon, where are fermented. Finally, calcium fortification must be executed by suitable compounds with high bioavailability, better technological properties, and a correct calcium:phosphorus ratio. For that reason, the objective of the present article is to review the influence of all these conditional factors on calcium bioavailability.

Movimentação de cátions em amostras de um Latossolo Vermelho-Amarelo incubadas com duas fontes de cálcio

Estudou-se a movimentação de cátions alcalinos e alcalinos terrosos (CAAT) em colunas de solo arranjadas com amostras de Latossolo Vermelho-Amarelo, álico, coletadas a profundidade de 0 a 5cm sob dois tipos distintos de cobertura, floresta secundária e grama batatais (Paspalum notatum L.), as quais foram superpostas em potes plásticos à amostras do horizonte Bw, da mesma unidade de solo. Aplicaram-se carbonato de cálcio, sulfato de cálcio ou a mistura das duas fontes de cálcio às amostras superficiais, as quais foram colocadas a incubar e depois submetidas a sete aplicações de água destilada, na taxa de 1 volume-poro por semana, durante sete semanas consecutivas. O lixiviado foi recolhido semanalmente e analisado para cálcio, magnésio, potássio e sulfato solúveis. Nos solos, fizeram-se determinações dos teores de cálcio, magnésio e potássio trocáveis, e a determinação da acidez potencial a pH 7,0. A aplicação de sulfato de cálcio favoreceu o processo de lixiviação de potássio e magnésio, enquanto que a aplicação de carbonato de cálcio minimizou a lixiviação. Concluiu-se que a utilização de sulfato de cálcio para a correção da deficiência de cálcio em subsolos ácidos deve ser acompanhada necessariamente da aplicação de carbonato.

Functional identification of calcium binding residues in bovine alpha-lactalbumin.

The functional role of previously identified calcium binding residues in alpha-lactalbumin (alpha-LA) was investigated by site-directed mutagenesis. Mutation of D82 to alanine did not effect the binding affinity for calcium, the protein structure, or its function in the lactose synthase assay, suggesting that this aspartate side chain is not essential for calcium binding or structural stabilization. In contrast, mutation of either D87 or D88 to alanine completely eliminated the strong calcium binding and altered alpha-LA as shown by several spectroscopically derived properties such as near- and far-UV CD and intrinsic fluorescence studies. These latter two mutants displayed significantly reduced abilities to stimulate lactose synthase activity (<3.5% of the maximal rate). Additionally, residues K79 and D84, which chelate calcium by backbone carbonyls, were mutated to alanine. K79A lost approximately 50% of its tertiary structure and stability (as determined by CD) but retained full calcium binding activity, indicating that at least the lysine side chain does not influence the carbonyl-mediated calcium coordination. In contrast, D84A lost approximately 25% of its tertiary structure and stability which was accompanied by a modest reduction in calcium affinity. Both mutants were able to stimulate normal lactose synthase activity. The triple mutant, D82A/D87A/D88A alpha-LA, lost its ability to bind calcium, similar to D87A and D88A. These studies clearly demonstrate the importance and variation of side chain interactions, which might be the seminal event in the establishment of the correct calcium binding loop conformation, possibly to stabilization and final folding of the overall protein structure.

The clinical spectrum of hypocalcaemia associated with bone metastases

Malignancy-related hypocalcaemia has received less attention in the literature than the opposite perturbation, hypercalcaemia. Only, scarce and contradictory data exist about hypocalcaemia associated with bone metastases (BMH). We have reviewed the clinical records of 155 patients with bone metastases of solid tumours, 122 of which were followed during the whole course of the disease until death. The frequency of hypocalcaemia ranged from 5 to 13%, depending on the formula used to correct calcium values for protein concentration. BMH was almost exclusively limited to patients with osteoblastic metastases. The frequency of BMH among patients with prostate carcinoma was 13-27%, depending on the formula used. Only two of 60 patients with lytic bone lesions presented hypocalcaemia, and in both cases it was rather mild. The development of hypocalcaemia did not seem to imply a worse prognosis, at least in patients with carcinoma of the prostate. Thus, the prevalence of BMH appears to be higher than is usually considered. Adequate attention should be given to this disorder because of the potentially deleterious effects on several organ systems.

Ease of extraction of calcium from ash of cucurbitamaximaandcucurbita andreanaembryos following dry ashing at different temperatures

Abstract While occlusion of the elements in the carbonaceous ash residue has been found to be a problem, calcium is more readily extracted from the black ash containing 11% carbon than from the light gray, carbon free ash of Cucurbita maxima and Cucurbita andreana embryos. The temperature of 600° C seems to be the point at which a change in the ash occurs. At and above 600° C ash samples require additional digestion with dilute nitric and hydrochloric acids before giving the correct calcium levels. Plant materials such as NBS Tomato Leaves and Wheat Flour standards do not show a change in ash solulility at higher ashing temperatures.