Monitoring of Urinary Calcium and Phosphorus Excretion in Preterm Infants - Comparison of two Methods

OBJECTIVES: Premature babies require supplementation with calcium and phosphorus to prevent metabolic bone disease of prematurity. To guide mineral supplementation, two methods of monitoring urinary excretion of calcium and phosphorus are used: urinary calcium or phosphorus concentration and calcium/creatinine or phosphorus/creatinine ratios. We compare these two methods in regards to their agreement on the need for mineral supplementation. METHODS: Retrospective chart review of 230 premature babies with birthweight <1500 g, undergoing screening of urinary spot samples from day 21 of life and fortnightly thereafter. Hypothetical cut-off values for urine calcium or phosphorus concentration (1 mmol/l) and urine calcium/creatinine ratio (0.5 mol/mol) or phosphorus/creatinine ratio (4 mol/mol) were applied to the sample results. The agreement on whether or not to supplement the respective minerals based on the results with the two methods was compared. Multivariate general linear models sought to identify patient characteristic to predict disagreeing results. RESULTS: 24.8% of cases disagreed on the indication for calcium supplementation, 8.8% for phosphorus. Total daily calcium intake was the only patient characteristic associated with discordant results. CONCLUSIONS: With the intention to supplement the respective mineral, comparison of urinary mineral concentration with mineral/creatinine ratio is moderate for Calcium and good for Phosphorus. The results do not allow to identify superiority of either method on the decision which babies require calcium and/or phosphorus supplements.

Eliminating exposure to aqueous solvents is necessary for the early detection and ultrastructural elemental analysis of sites of calcium and phosphorus enrichment in mineralizing UMR106-01 osteoblastic cultures

The mechanism underlying the mineralization of bone is well studied and yet it remains controversial. Inherent difficulties of imaging mineralized tissues and the aqueous solubility of calcium and phosphate, the 2 ions which combine to form bone mineral crystals, limit current analyses of labile diffusible, amorphous, and crystalline intermediates by electron microscopy. To improve the retention of calcium and phosphorus, we developed a pseudo nonaqueous processing approach and used it to characterize biomineralization foci, extracellular sites of hydroxyapatite deposition in osteoblastic cell cultures. Since mineralization of UMR106-01 osteoblasts is temporally synchronized and begins 78 h after plating, we used these cultures to evaluate the effectiveness of our method when applied to cells just prior to the formation of the first mineral crystals. Our approach combines for the first time 3 well-established methods with a fourth one, i.e. dry ultrathin sectioning. Dry ultrathin sectioning with an oscillating diamond knife was used to produce electron spectroscopic images of mineralized biomineralization foci which were high-pressure frozen and freeze substituted. For comparison, cultures were also treated with conventional processing and wet sectioning. The results show that only the use of pseudo nonaqueous processing was able to detect extracellular sites of early calcium and phosphorus enrichment at 76 h, several hours prior to detection of mineral crystals within biomineralization foci.

The Efficacy of a Novel Microbial 6-Phytase Expressed in Aspergillus oryzae on the Performance and Phosphorus Utilization of Cold- and Warm-Water Fish: Rainbow Trout, Oncorhynchus mykiss , and Nile Tilapia, Oreochromis niloticus

The efficacy and tolerance of a novel microbial 6-phytase were investigated in rainbow trout, Oncorhynchus mykiss, and Nile tilapia, Oreochromis niloticus. Reference diets were sufficient in available phosphorus (P). The test diet limiting in available P was supplemented with phytase at 500, 1000, or 2000 phytase units/kg feed. The enzyme was effective in increasing total P apparent digestibility coefficient in relation to increasing the dose of phytase in rainbow trout and Nile tilapia. Zinc apparent digestibility improved in relation to phytase supplementation in rainbow trout. P release due to phytase supplementation ranged from 0.06 to 0.18% P/kg feed in rainbow trout and from 0.13 to 0.26% P/kg feed in Nile tilapia. A 58-d performance trial was conducted to evaluate tolerance of fish to phytase supplementation. Dietary treatments consisted of a basal diet without phytase or supplemented with 2000 and 200,000 phytase units/kg feed. Results indicate that this novel microbial 6-phytase is well tolerated by fish. Significant improvements for growth as well as feed conversion ratio were observed when the phytase was fed at 2000 phytase units/kg feed. This phytase is proven efficient in releasing P from phytate and could be added when plants are used for fish meal replacement in diets for salmonid and omnivorous fish.

[Osteoporosis diet]

Bone requires a wide variety of nutrients to develop normally and to maintain itself after growth. Most important--in the sense that bony abnormalities are associated with their deficiencies--are protein, calcium, phosphorus, vitamin D, C and K, zinc, manganese and copper. The nutrients most likely to be deficient in citizens of industrialized countries are calcium and vitamin D. In this review of the current literature about nutritional aspects of osteoporosis, we have focused on factors influencing calcium requirement: the principal interacting nutrients are sodium, protein, caffeine, fiber, oxalate, phytate, and the acid/alkaline ash character of the overall diet. Fiber and caffeine decrease calcium absorption from the gut and typically exert relatively minor effects, while sodium, protein and the acid/alkaline balance of the diet increase urinary excretion of calcium and are of much greater significance for the calcium homeostasis. Alkali buffers, whether vegetables or fruits reverse this urinary calcium loss. As long as accompanied by adequate calcium intake, protein-rich diet is not deleterious to bone: a calcium-to-protein ratio of 20:1 (mg calcium/g protein) is recommended. Whether a nutrition-based therapeutic approach to osteoporosis is feasible in the near future is yet unclear: at least there are some recent promising data from in-vitro as well as from rat studies showing that extracts taken from various vegetables, mainly from the onion family inhibit bone resorption in a dose-dependent manner.

Erosion in relation to nutrition and the environment.

When considering the erosive potential of a food or drink, a number of factors must be taken into account. pH is arguably the single most important parameter in determining the rate of erosive tissue dissolution. There is no clear-cut critical pH for erosion as there is for caries. At low pH, it is possible that other factors are sufficiently protective to prevent erosion, but equally erosion can progress in acid of a relatively high pH in the absence of mitigating factors. Calcium and phosphate concentration, in combination with pH, determine the degree of saturation with respect to tooth minerals. Solutions supersaturated with respect to enamel or dentine will not cause them to dissolve, meaning that given sufficient common ion concentrations erosion will not proceed, even if the pH is low. Interestingly, the addition of calcium is more effective than phosphate at reducing erosion in acid solutions. Today, several calcium-enriched soft drinks are on the market, and acidic products with high concentrations of calcium and phosphorus are available (such as yoghurt), which do not soften the dental hard tissues. The greater the buffering capacity of the drink or food, the longer it will take for the saliva to neutralize the acid. A higher buffer capacity of a drink or foodstuff will enhance the processes of dissolution because more release of ions from the tooth mineral is required to render the acid inactive for further demineralization. Temperature is also a significant physical factor; for a given acidic solution, erosion proceeds more rapidly the higher the temperature of that solution. In recent years, a number of interesting potentially erosion-reducing drink and food additives have been investigated.

A minimally destructive technique for removing the smear layer from dentine surfaces

OBJECTIVES: To develop a minimally destructive technique for removing the smear layer produced by cutting and polishing specimens of dentine prepared for use in experimental studies, e.g. on occlusion of dentinal tubules by oral health products. The aim was to avoid the damage caused by conventional techniques utilising short exposures to solutions with very low pH. METHODS: Two acetate buffers, pH 5.5, containing different concentrations of calcium and phosphate, with -log(ion activity product with respect to hydroxyapatite) (pI(HA)) of 55 or 56, were tested on slices of dentine using scanning electron microscopy (SEM). RESULTS: A solution which, from previous work, was slightly undersaturated with respect to dentine mineral, with a pI(HA) of 56, was found to remove smear layers produced by cutting and/or polishing after 15 min. However, to reliably remove debris occluding the tubules an exposure time of 2h, followed by brief ultrasonication, was necessary. After 2h treatment with this buffer, only a small amount of demineralization of the surface was detectable by SEM, while calcium and phosphorus were detectable by X-ray dispersive spectroscopy. CONCLUSION: It is possible to remove smear layers, and to open dentinal tubules, by a reasonably short exposure to an acidic buffer which is undersaturated with respect to dentine mineral.

Fruit yogurt: any erosive potential regarding teeth?

OBJECTIVE: The capability of drinks and foods to resist pH changes brought about by salivary buffering may play an important role in the dental erosion process in children. The aim of the present study was to test fruit yogurt, a popular snack for children, and the degrees of saturation (pK-pl) with respect to hydroxyapatite and fluorapatite to determine their erosive potential. METHOD AND MATERIALS: A variety of fruit yogurt was tested. To test the pH, 8 readings were taken with a pH electrode for each yogurt. Calcium content was detected by atomic absorption spectrophotometer, phosphorus by the inductively coupled plasma method, and fluoride content by ion chromatography. The degrees of saturation of hydroxyapatite and fluorapatite were calculated by use of a computer program. Statistical analysis was performed using 2-tailed analysis of variance (P < .05) and a post hoc test (Tukey) to determine differences between groups. RESULTS: The pH of each fruit concentrate was significantly different, except for banana yogurt. Except for the phosphorus content of raspberry yogurt, the calcium and phosphorus content for each fruit concentrate were significantly different. Fluoride levels were the same for all yogurts tested, and the degrees of saturation of hydroxyapatite and fluorapatite was positive, indicating supersaturation. CONCLUSION: It could be stated that fruit yogurt has no erosive potential.

Labeling the human skeleton with 41Ca to assess changes in bone calcium metabolism

Bone research is limited by the methods available for detecting changes in bone metabolism. While dual X-ray absorptiometry is rather insensitive, biochemical markers are subject to significant intra-individual variation. In the study presented here, we evaluated the isotopic labeling of bone using 41Ca, a long-lived radiotracer, as an alternative approach. After successful labeling of the skeleton, changes in the systematics of urinary 41Ca excretion are expected to directly reflect changes in bone Ca metabolism. A minute amount of 41Ca (100 nCi) was administered orally to 22 postmenopausal women. Kinetics of tracer excretion were assessed by monitoring changes in urinary 41Ca/40Ca isotope ratios up to 700 days post-dosing using accelerator mass spectrometry and resonance ionization mass spectrometry. Isotopic labeling of the skeleton was evaluated by two different approaches: (i) urinary 41Ca data were fitted to an established function consisting of an exponential term and a power law term for each individual; (ii) 41Ca data were analyzed by population pharmacokinetic (NONMEM) analysis to identify a compartmental model that describes urinary 41Ca tracer kinetics. A linear three-compartment model with a central compartment and two sequential peripheral compartments was found to best fit the 41Ca data. Fits based on the use of the combined exponential/power law function describing urinary tracer excretion showed substantially higher deviations between predicted and measured values than fits based on the compartmental modeling approach. By establishing the urinary 41Ca excretion pattern using data points up to day 500 and extrapolating these curves up to day 700, it was found that the calculated 41Ca/40Ca isotope ratios in urine were significantly lower than the observed 41Ca/40Ca isotope ratios for both techniques. Compartmental analysis can overcome this limitation. By identifying relative changes in transfer rates between compartments in response to an intervention, inaccuracies in the underlying model cancel out. Changes in tracer distribution between compartments were modeled based on identified kinetic parameters. While changes in bone formation and resorption can, in principle, be assessed by monitoring urinary 41Ca excretion over the first few weeks post-dosing, assessment of an intervention effect is more reliable approximately 150 days post-dosing when excreted tracer originates mainly from bone.

Fiberoptic system for recording dendritic calcium signals in layer 5 neocortical pyramidal cells in freely moving rats

Calcium influx into the dendritic tufts of layer 5 neocortical pyramidal neurons modifies a number of important cellular mechanisms. It can trigger local synaptic plasticity and switch the firing properties from regular to burst firing. Due to methodological limitations, our knowledge about Ca2+ spikes in the dendritic tuft stems mostly from in vitro experiments. However, it has been speculated that regenerative Ca2+ events in the distal dendrites correlate with distinct behavioral states. Therefore it would be most desirable to be able to record these Ca2+ events in vivo, preferably in the behaving animal. Here, we present a novel approach for recording Ca2+ signals in the dendrites of populations of layer 5 pyramidal neurons in vivo, which ensures that all recorded fluorescence changes are due to intracellular Ca2+ signals in the apical dendrites. The method has two main features: 1) bolus loading of layer 5 with a membrane-permeant Ca2+ dye resulting in specific loading of pyramidal cell dendrites in the upper layers and 2) a fiberoptic cable attached to a gradient index lens and a prism reflecting light horizontally at 90 degrees to the angle of the apical dendrites. We demonstrate that the in vivo signal-to-noise ratio recorded with this relatively inexpensive and easy-to-implement fiberoptic-based device is comparable to conventional camera-based imaging systems used in vitro. In addition, the device is flexible and lightweight and can be used for recording Ca2+ signals in the distal dendritic tuft of freely behaving animals.

Added value of coronary artery calcium score as an adjunct to gated SPECT for the evaluation of coronary artery disease in an intermediate-risk population

The coronary artery calcium (CAC) score is a readily and widely available tool for the noninvasive diagnosis of atherosclerotic coronary artery disease (CAD). The aim of this study was to investigate the added value of the CAC score as an adjunct to gated SPECT for the assessment of CAD in an intermediate-risk population. METHODS: Seventy-seven prospectively recruited patients with intermediate risk (as determined by the Framingham Heart Study 10-y CAD risk score) and referred for coronary angiography because of suspected CAD underwent stress (99m)Tc-tetrofosmin SPECT myocardial perfusion imaging (MPI) and CT CAC scoring within 2 wk before coronary angiography. The sensitivity and specificity of SPECT alone and of the combination of the 2 methods (SPECT plus CAC score) in demonstrating significant CAD (>/=50% stenosis on coronary angiography) were compared. RESULTS: Forty-two (55%) of the 77 patients had CAD on coronary angiography, and 35 (45%) had abnormal SPECT results. The CAC score was significantly higher in subjects with perfusion abnormalities than in those who had normal SPECT results (889 +/- 836 [mean +/- SD] vs. 286 +/- 335; P < 0.0001). Similarly, with rising CAC scores, a larger percentage of patients had CAD. Receiver-operating-characteristic analysis showed that a CAC score of greater than or equal to 709 was the optimal cutoff for detecting CAD missed by SPECT. SPECT alone had a sensitivity and a specificity for the detection of significant CAD of 76% and 91%, respectively. Combining SPECT with the CAC score (at a cutoff of 709) improved the sensitivity of SPECT (from 76% to 86%) for the detection of CAD, in association with a nonsignificant decrease in specificity (from 91% to 86%). CONCLUSION: The CAC score may offer incremental diagnostic information over SPECT data for identifying patients with significant CAD and negative MPI results.

Comparative study of biphasic calcium phosphates with different HA/TCP ratios in mandibular bone defects. A long-term histomorphometric study in minipigs

Three biphasic calcium phosphate (BCP) bone substitute materials with hydroxyapatite (HA)/tricalcium phosphate (TCP) ratios of 20/80, 60/40, and 80/20 were compared to coagulum, particulated autogenous bone, and deproteinized bovine bone mineral (DBBM) in membrane-protected bone defects. The defects were prepared in the mandibles of 24 minipigs that were divided into four groups of six with healing times of 4, 13, 26, and 52 weeks, respectively. The histologic and histomorphometric evaluation focused on differences in amount and pattern of bone formation, filler degradation, and the interface between bone and filler. Collapse of the expanded polytetrafluoroethylene barrier membrane into the coagulum defects underlined the necessity of a filler material to maintain the augmented volume. Quantitatively, BCP 20/80 showed bone formation and degradation of the filler material similar to autografts, whereas BCP 60/40 and BCP 80/20 rather equaled DBBM. Among the three BCP's, the amount of bone formation and degradation of filler material seemed to be inversely proportional to the HA/TCP ratio. The fraction of filler surface covered with bone was highest for autografts at all time points and was higher for DBBM than BCP 80/20 and 60/40 at the early healing phase. TRAP-positive multinucleated cells were identified on BCP and DBBM surfaces without showing typical signs of resorption lacunae.

Gender modulates the expression of calcium-regulating proteins in pediatric atrial myocardium

A differential expression of sarcoplasmic reticulum calcium-ATPase (SERCA2a) and phospholamban (PLB) characterizes the remodeling process in heart failure and atrial arrhythmias in adult patients. Gender is known to modulate the course and prognosis of different forms of heart disease. We hypothesized that gender plays a role in molecular changes of myocardial calcium regulating components already in childhood. Moreover, we studied the influence of volume overloaded (VO) on SERCA2a and PLB in pediatric patients. Quantitative reverse transcription-polymerase chain reaction was used to measure mRNA expression of SERCA2a and PLB in atrial myocardium from 30 pediatric patients (12 girls, 18 boys). Eighteen patients had VO right atria, and 12 patients had not-overloaded atria (NO). Protein expression was studied by Western blot. In the entire population, SERCA2a and PLB expression was not different between girls and boys. If hemodynamic overload was taken into account, SERCA2a mRNA expression was significantly reduced in the VO group compared with the NO group (P = 0.021). The VO versus NO difference was restricted to boys, which corresponds to a highly significant interaction of gender versus VO status (P = 0.002). The PLB to SERCA2a protein ratio was significantly lower in girls (P = 0.028). The decrease in SERCA2a mRNA expression in VO atrial myocardium and the PLB to SERCA2a ratio of protein expression was modulated by gender in this pediatric population. To our knowledge, this study is the first to show the impact of gender on the differential expression of calcium-regulating components in pediatric cardiac patients.

Automatic Labeling of Software Components and their Evolution using Log-Likelihood Ratio of Word Frequencies in Source Code

As more and more open-source software components become available on the internet we need automatic ways to label and compare them. For example, a developer who searches for reusable software must be able to quickly gain an understanding of retrieved components. This understanding cannot be gained at the level of source code due to the semantic gap between source code and the domain model. In this paper we present a lexical approach that uses the log-likelihood ratios of word frequencies to automatically provide labels for software components. We present a prototype implementation of our labeling/comparison algorithm and provide examples of its application. In particular, we apply the approach to detect trends in the evolution of a software system.

PTH-related protein is released into the mother's bloodstream during location: evidence for beneficial effects on maternal calcium-phosphate metabolism

Recent studies have indicated that parathyroid hormone-related protein (PTHrP) may have important actions in lactation, affecting the mammary gland, and also calcium metabolism in the newborn and the mother. However, there are as yet no longitudinal studies to support the notion of an endocrine role of this peptide during nursing. We studied a group of 12 nursing mothers, mean age 32 years, after they had been nursing for an average of 7 weeks (B) and also 4 months after stopping nursing (A). It was assumed that changes occurring between A and B correspond to the effect of lactation. Blood was assayed for prolactin (PRL), PTHrP (two-site immunoradiometric assay with sheep antibody against PTHrP(1-40), and goat antibody against PTHrP(60-72), detection limit 0.3 pmol/l), intact PTH (iPTH), ionized calcium (Ca2+), 25-hydroxyvitamin D3 (25(OH)D3) and 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), alkaline phosphatase (alkP), as well as for creatinine (Cr), protein, phosphorus (P), and total calcium (Ca). Fasting 2-h urine samples were analyzed for Ca excretion (CaE) and renal phosphate threshold (TmP/GFR). PRL was significantly higher during lactation than after weaning (39 +/- 10 vs. 13 +/- 9 micrograms/l; p = 0.018) and so was PTHrP (2.8 +/- 0.35 vs. 0.52 +/- 0.04 pmol/l; p = 0.002), values during lactation being above the normal limit (1.3 pmol/l) in all 12 mothers. There was a significant correlation between PRL and PTHrP during lactation (r = 0.8, p = 0.002). Whole blood Ca2+ did not significantly change from A (1.20 +/- 0.02 mmol/l) to B (1.22 +/- 0.02, mmol/l), whereas total Ca corrected for protein (2.18 +/- 0.02 mmol/l) or uncorrected (2.18 +/- 0.02 mmol/l) significantly rose during lactation (2.31 +/- 0.02 mmol/l, p = 0.003 and 2.37 +/- 0.03 mmol/l, p = 0.002, respectively). Conversely, iPTH decreased during lactation (3.47 +/- 0.38 vs. 2.11 +/- 0.35 pmol/l, A vs. B, p = 0.02). Serum-levels of 25(OH)D3 and 1,25(OH)2D3 did not significantly change from A to B (23 +/- 2.3 vs. 24 +/- 1.9 ng/ml and 29.5 +/- 6.0 vs. 21.9 +/- 1.8 pg/ml, respectively). Both TmP/GFR and P were higher during lactation than after weaning (1.15 +/- 0.03 vs. 0.86 +/- 0.05 mmol/l GF, p = 0.003 and 1.25 +/- 0.03 vs. 0.96 +/- 0.05 mmol/l, p = 0.002, respectively) as was alkP (74.0 +/- 7.1 vs. 52.6 +/- 6.9 U/l, p = 0.003). CaE did not differ between A and B (0.015 +/- 0.003 vs. 0.017 +/- 0.003 mmol/l GF, A vs. B, NS). We conclude that lactation is accompanied by an increase in serum PRL. This is associated with a release of PTHrP into the maternal blood circulation. A rise in total plasma Ca ensues, probably in part by increased bone turnover as suggested by the elevation of alkP. PTH secretion falls, with a subsequent rise of TmP/GFR and plasma P despite high plasma levels of PTHrP.

Effect of oral calcium loading on intact PTH and calcitriol in idiopathic renal calcium stone formers and healthy controls

The calciuric response after an oral calcium load (1000 mg elemental calcium together with a standard breakfast) was studied in 13 healthy male controls and 21 recurrent idiopathic renal calcium stone formers, 12 with hypercalciuria (UCa x V > 7.50 mmol/24 h) and nine with normocalciuria. In controls, serum 1,25(OH)2 vitamin D3 (calcitriol) remained unchanged 6 h after oral calcium load (50.6 +/- 5.1 versus 50.9 +/- 5.0 pg/ml), whereas it tended to increase in hypercalciuric (from 53.6 +/- 3.2 to 60.6 +/- 5.4 pg/ml, P = 0.182) and fell in normocalciuric stone formers (from 45.9 +/- 2.6 to 38.1 +/- 3.3 pg/ml, P = 0.011). The total amount of urinary calcium excreted after OCL was 2.50 +/- 0.20 mmol in controls, 2.27 +/- 0.27 mmol in normocalciuric and 3.62 +/- 0.32 mmol in hypercalciuric stone formers (P = 0.005 versus controls and normocalciuric stone formers respectively); it positively correlated with serum calcitriol 6 h after calcium load (r = 0.392, P = 0.024). Maximum increase in urinary calcium excretion rate, delta Ca-Emax, was inversely related to intact PTH levels in the first 4 h after calcium load, i.e. more pronounced PTH suppression predicted a steeper increase in urinary calcium excretion rate. Twenty-four-hour urine calcium excretion rate was inversely related to the ratio of delta calcitriol/deltaPTHmax after calcium load (r = -0.653, P = 0.0001), indicating that an abnormally up-regulated synthesis of calcitriol and consecutive relative PTH suppression induce hypercalciuria.(ABSTRACT TRUNCATED AT 250 WORDS)