Mineral Buffer Research Articles

An Oral Phosphate Challenge in Experimental CKD Reveals the Scope of Deficit in Calciprotein-Based Mineral Buffering Only If Both OsteoSense and T50 Are Used

An Oral Phosphate Challenge in Experimental CKD Reveals the Scope of Deficit in Calciprotein-Based Mineral Buffering Only If Both OsteoSense and T50 Are Used

Liver and spleen predominantly mediate calciprotein particle clearance in a rat model of chronic kidney disease.

Calciprotein particles (CPPs) provide an efficient mineral buffering system to prevent the complexation of phosphate and calcium in the circulation. However, in chronic kidney disease (CKD), the phosphate load exceeds the mineral buffering capacity, resulting in the formation of crystalline CPP2 particles. CPP2 have been associated with cardiovascular events and mortality. Moreover, CPP2 have been demonstrated to induce calcification in vitro. In this study, we examined the fate of CPP2 in a rat model of CKD. Calcification was induced in Sprague-Dawley rats by 5/6 nephrectomy (5/6-Nx) combined with a high-phosphate diet. Control rats received sham surgery and high-phosphate diet. Twelve weeks after surgery, kidney failure was significantly induced in 5/6-Nx rats as determined by enhanced creatinine and urea plasma levels and abnormal kidney histological architecture. Subsequently, radioactive and fluorescent (FITC)-labeled CPP2 ([89Zr]Zr-CPP2-FITC) were injected intravenously to determine clearance in vivo. Using positron emission tomography scans and radioactive biodistribution measurements, it was demonstrated that [89Zr]Zr-CPP2-FITC are mainly present in the liver and spleen in both 5/6-Nx and sham rats. Immunohistochemistry showed that [89Zr]Zr-CPP2-FITC are predominantly taken up by Kupffer cells and macrophages. However, [89Zr]Zr-CPP2-FITC could also be detected in hepatocytes. In the different parts of the aorta and in the blood, low values of [89Zr]Zr-CPP2-FITC were detectable, independent of the presence of calcification. CPP2 are cleared rapidly from the circulation by the liver and spleen in a rat model of CKD. In the liver, Kupffer cells, macrophages, and hepatocytes contribute to CPP2 clearance.NEW & NOTEWORTHY Calciprotein particles (CPPs) buffer calcium and phosphate in the blood to prevent formation of crystals. In CKD, increased phosphate levels may exceed the buffering capacity of CPPs, resulting in crystalline CPPs that induce calcification. This study demonstrates that labeled CPPs are predominantly cleared from the circulation in the liver by Kupffer cells, macrophages, and hepatocytes. Our results suggest that targeting liver CPP clearance may reduce the burden of crystalline CPP in the development of vascular calcification.

Accelerated calciprotein crystallization time (T50) is correlated with impaired lung diffusion capacity in systemic sclerosis.

Systemic sclerosis (SSc) is a complex auto-immune disease characterized by vascular damage, inflammation, fibrosis and calcinosis, where pulmonary involvement is the leading cause of mortality. Calciprotein particles (CPPs) are increasingly formed upon disbalance of the physiological mineral buffering system and induce pro-inflammatory effects. This exploratory study investigated whether functional indicators of the endogenous mineral buffering system are dysregulated in SSc and linked to disease activity. T50 (calciprotein crystallization test or serum calcification propensity) and hydrodynamic radius of secondary CPPs (CPP2) were determined in serum samples from 78 SSc patients and 44 controls without SSc, and were associated with disease activity markers of SSc. T50 was reduced and CPP2 radius was increased in SSc patients as compared to controls, indicating a deranged mineral buffering system. This was accompanied by slightly higher serum phosphate and PTH levels in SSc patients, while iFGF23 was not significantly modified. Longitudinally, all parameters remained unchanged over time in SSc patients, only iFGF23 increased. While the modified Rodnan skin score showed some inconsistent correlations with mineral buffering indicators, their association was not independent of other factors. However, lower T50 was significantly correlated to reduced lung diffusion capacity and this association remained significant in a multivariate linear regression model. This study provides indications for a disturbed mineral buffering system in SSc. Increased serum calcification propensity (lower T50) is correlated with impaired lung diffusion capacity, suggesting a possible role of deranged mineral buffering in disease progression. Further studies are required to confirm these observations in larger cohorts and to investigate a putative functional relevance.

Zircon trace-element and isotopes (U–Pb, Lu–Hf, δ 18 O) response to fluid-deficient metamorphism of a subducted continental terrane (North Muya, Eastern Siberia)

Abstract The orogenic continental crust of accretionary and collisional belts worldwide is dominated by felsic and metasedimentary rocks, which show variable responses to high-grade metamorphism. Transformation of felsic rocks is commonly limited as compared to that of the enclosed mafic rocks (including eclogites sensu stricto ), which is widely attributed to availability of H 2 O–CO 2 fluids, kinetically controlled growth of high-grade assemblages, and their preferential preservation in metabasites more competent to rehydration. We report on the results of studies of the geochemical behaviour of zircon (trace-element, U–Pb, Lu–Hf and δ 18 O) in three felsic samples (two metagranitoids and one paragneiss), which are spatially (geographically and at the outcrop-scale) juxtaposed with mafic eclogites within the North Muya block (Neoproterozoic Baikalides, northern Central Asian Orogenic Belt). The data imply that metagranitoids and metasediments within the buried continental lithosphere might follow a single subduction-related P – T – t trend, whereas contrasting degrees of mineralogical and zircon transformation were governed by mineral buffer reactions in the absence of external fluids. The latter was significant only in an H 2 O-enriched protolith of metasediments. The formation of 18 O-depleted zircon recrystallization rims together with Mn enrichment of garnet rims indicate a distinct metamorphic stage without or with minor localized fluid infiltration, most likely, related to peak temperature conditions during collision. Supplementary material: The data on the mineral composition, trace-element and U–Pb–Lu–Hf–O isotopic composition of zircon are available at https://doi.org/10.6084/m9.figshare.c.6794043

COUPLED SOLUBILITY OF Cu and Ag IN CHLORIDE-BEARING HYDROTHERMAL FLUIDS (350-650 °С, 1000 - 1500 BAR)

The coupled solubility of Cu(cr) and Ag(cr) was measured in acidic chloride solutions at 350 °С/1000 bar, 450 °С/1000 bar and 653 °С/1450 bar in a wide range of chloride concentrations (0.02m HCl + (0-15m) NaCl). The experiments were performed using autoclave (350, 450 °С) and ampoule (653 °С) techniques, the dissolved metal concentrations were measured after quenching the experimental system. The equilibrium constants of the reaction combining the dominant forms of transport of the metals are determinedCu(cr) + AgCl2- = Ag(cr) + CuCl2- K°(Cu-Ag) . The calculated reaction constant is independent of chloride concentration. It is known that AgCl2- predominates in the studied chloride concentration range. Therefore, the main cupper form of occurrence is CuCl2- in all experimental fluids with chloride content up to 47 wt.%, which is close to the NaCl saturation limit. The constant of the coupled Cu and Ag solubility was determined for the experimental PT-parameters as lg K°(Cu-Ag) = 2.65±0.20 (350 °С/1000 bar), 2.28±0.10 (450 °С/1000 bar), 1.49±0.34 (653 °С/1450 bar). These data, together with values from the literature for temperatures from 200 to 900 °С and pressure up to 2000 bar were fitted to the density model equation: lg K°(Сu-Ag) = 1.066 + 1.108∙103∙T(K)-1 + 3.585lgd(w) – 1.443∙lg d(w)103T(K)-1, where d(w) is the pure water density. According to these data, copper is much more soluble in chloride solutions compared to silver, but the difference in the solubility decreases with the temperature increase. Reliable literature data on the silver solubility constant allow to calculate the copper solubility oneCu(к) + HCl° + Cl- = CuCl2-+ 0.5H2(р-р) K°(Cu) ,lg K°(Cu) = 1.39±0.20 (350 °С, 1000 bar), 1.91±0.10 (450 °С, 1000 bar), 2.06±0.34 (653 °С, 1450 bar). The new values of K°(Cu) are combined with reliable literature data to calculate the density model parameters. The obtained density model equation can be used to calculate the copper solubility constant up to 800 °C and pressures to 2000 bar: lg K°(Сu) = 6.889 – 3.298∙103∙T(K)-1 + 8.694∙lg d(w) – 4.807∙lg d(w)∙103∙T(K)-1. The solubility of chalcopyrite in the system with mineral buffer assemblages pyrite-hematite-magnetite and K-feldspar-muscovite-quartz is discussed.

Calciprotein Particles Cause Physiologically Significant Pro-Inflammatory Response in Endothelial Cells and Systemic Circulation

Calciprotein particles (CPPs) represent an inherent mineral buffering system responsible for the scavenging of excessive Ca2+ and PO43- ions in order to prevent extraskeletal calcification, although contributing to the development of endothelial dysfunction during the circulation in the bloodstream. Here, we performed label-free proteomic profiling to identify the functional consequences of CPP internalisation by endothelial cells (ECs) and found molecular signatures of significant disturbances in mitochondrial and lysosomal physiology, including oxidative stress, vacuolar acidification, accelerated proteolysis, Ca2+ cytosolic elevation, and mitochondrial outer membrane permeabilisation. Incubation of intact ECs with conditioned medium from CPP-treated ECs caused their pro-inflammatory activation manifested by vascular cell adhesion molecule 1 (VCAM1) and intercellular adhesion molecule 1 (ICAM1) upregulation and elevated release of interleukin (IL)-6, IL-8, and monocyte chemoattractant protein-1/ C-C motif ligand 2 (MCP-1/CCL2). Among the blood cells, monocytes were exclusively responsible for CPP internalisation. As compared to the co-incubation of donor blood with CPPs in the flow culture system, intravenous administration of CPPs to Wistar rats caused a considerably higher production of chemokines, indicating the major role of monocytes in CPP-triggered inflammation. Upregulation of sICAM-1 and IL-8 also suggested a notable contribution of endothelial dysfunction to systemic inflammatory response after CPP injections. Collectively, our results demonstrate the pathophysiological significance of CPPs and highlight the need for the development of anti-CPP therapies.

Effect of nutritional calcium and phosphate loading on calciprotein particle kinetics in adults with normal and impaired kidney function.

Plasma approaches metastability with respect to its calcium and phosphate content, with only minor perturbations in ionic activity needed to sustain crystal growth once nucleated. Physiologically, calcium and phosphate are intermittently absorbed from the diet each day, yet plasma concentrations of these ions deviate minimally post-prandially. This implies the existence of a blood-borne mineral buffer system to sequester calcium phosphates and minimise the risk of deposition in the soft tissues. Calciprotein particles (CPP), endogenous mineral-protein colloids containing the plasma protein fetuin-A, may fulfill this function but definitive evidence linking dietary mineral loading with their formation is lacking. Here we demonstrate that CPP are formed as a normal physiological response to feeding in healthy adults and that this occurs despite minimal change in conventional serum mineral markers. Further, in individuals with Chronic Kidney Disease (CKD), in whom mineral handling is impaired, we show that both fasting and post-prandial levels of CPP precursors are markedly augmented and strongly inversely correlated with kidney function. This study highlights the important, but often neglected, contribution of colloidal biochemistry to mineral homeostasis and provides novel insight into the dysregulation of mineral metabolism in CKD.

Deep-basin gas generation via organic–inorganic interactions: New insights from redox-controlled hydrothermal experiments at elevated temperature

Under hot, deep-basin conditions, hydrogen-to-carbon ratios of residual kerogen are low. Whether ubiquitous water in sedimentary environments contributes hydrogen directly to hydrocarbon gas formation through organic-inorganic interactions is, therefore, critical for natural gas generation. Accordingly, we conducted laboratory experiments on immature to overmature kerogens at 300–600°C and 700 bar to examine the chemical interactions between kerogens and fluid under varying redox states and hydrothermal conditions. Mineral buffers, comprised of magnetite-hematite, nickel‑nickel oxide, cobalt‑cobalt oxide, and molybdenum‑molybdenum trioxide, were added to the experiments to control the redox state of the fluid from geologically reasonable to generally excessive values. The kerogens and mineral buffers were spatially isolated using double-capsule techniques to prevent contact catalysis.Our results indicated that chemical interactions between kerogens and water depended strongly on the kerogen thermal maturity and fluid redox state. The chemical interactions of overmature kerogens with reducing water were stronger than those of immature kerogens, which could be ascribed to the weaker competitive transfer of hydrogen from organics to organics than from water to organics. Unexpectedly high amounts of hydrocarbon gas were generated by incorporating water-derived hydrogen in the pyrolysis of overmature kerogens, and the yields increased under low to high reducing fluid conditions for a given temperature. Along with the increasing thermal maturity, residual kerogen eventually became ineffective for hydrocarbon gas generation through reduction reactions. Demethylation, bridge bond cleavage reaction, aromatic structure ring opening reactions in residual kerogen and subsequent redox reaction of intermediate products with reducing fluids is evidenced as the possible reaction mechanisms. The produced hydrocarbon gas under fH2 level of oilfield water is characterized by high dryness (99 mol%) and more-enriched 13C in CH4 compared with precursors. Natural gas deep within the Sichuan and Appalachian basins with similar characteristics suggests that our simulated organic–inorganic interactions could occur widely under natural conditions. Consequently, a potentially prolific source of natural gas may be formed by the overmature source rocks in the deep basin and fluid redox should be considered for gas potential evaluation of overmature source rocks.

Compositional Analysis of Conventional and Unconventional Permian Basin-Produced Waters: A Simple Tool for Predicting Major Ion Composition

Summary Treatment methods for produced water (PW) are significantly affected by a high concentration of total dissolved solids (TDS), a summation of dissolved organic and inorganic compositions. Understanding the constituents of TDS to eliminate or prevent chemical reactions is critical in the design optimization of the treatment processes. In this paper, two PW geochemical data sets generated from conventional and unconventional reservoirs in the Permian Basin were analyzed to correlate constituents with TDS. Compositional data sets from over 115,000 PW samples originally reported by the U.S. Geological Survey (USGS) and 45 oil and gas operations were analyzed. Data preprocessing, culling, systematized- and meta-analysis, and statistical techniques were adapted to associate the data. Subcompositional geochemical data were transformed into isometric log ratios and are presented in bivariate and multivariate plots. Results indicate that Na+ and Ca2+ were the dominant cations and Cl− was the dominant anion. No observable trend differences in the Na+, Cl−, Ca2+, Mg+, and SO42− concentrations between PW from conventional and unconventional wells were registered. Variations in the isometric log ratio of Na/Cl and Ca/SO4 with TDS revealed that Na/Cl was nearly constant over the range of TDS, suggesting mineral buffering or a lack of significant water/rock reactions involving Na and Cl, and that Ca/SO4 increased with TDS, indicating that low-salinity fluids may have dissolved anhydrite producing a value near zero, with Ca gain and/or SO4 loss with increasing salinity. In all 10 counties and 8 formations investigated in this work, the ln (Ca/SO4) denotes Ca gain/SO4 loss relative to their composition in anhydrite or Permian seawater. Likely mechanisms leading to elevated ln (Ca/SO4) include sulfate reduction, dolomitization of calcite, Na/Ca cation exchange, albitization, and anhydrite precipitation from Ca-rich fluids. Results from this work are important as it is revealed that Ca/SO4 and Na/Cl can potentially be predicted from PW TDS concentrations. This information was combined to create a reservoir or location-specific model to estimate Na, Cl, Ca, and SO4 concentrations in Permian Basin PW, a powerful tool to improve treatment and reuse options in areas with few direct data.

Effects of Carbonate Minerals on Shale-Hydraulic Fracturing Fluid Interactions in the Marcellus Shale

Natural gas extracted from tight shale formations, such as the Marcellus Shale, represents a significant and developing front in energy exploration. By fracturing these formations using pressurized fracturing fluid, previously unobtainable hydrocarbon reserves may be tapped. While pursuing this resource, hydraulic fracturing operations leave chemically complex fluids in the shale formation for at least two weeks. This provides a substantial opportunity for the hydraulic fracturing fluid (HFF) to react with the shale formation at reservoir temperature and pressure. In this study, we investigated the effects of the carbonates on shale-HFF reactions with a focus on the Marcellus Shale. We performed autoclave experiments at high temperature and pressure reservoir conditions using a carbonate-rich and a decarbonated or carbonate-free version of the same shale sample. We observed that carbonate minerals buffer the pH of the solution, which in turn prevents clay dissolution. Carbonate and bicarbonate ions also scavenge reactive oxidizing species (ROS), which prevents oxidation of shale organic matter and volatile organic compounds (VOCs). Carbonate-free samples also show higher pyrite dissolution compared to the carbonate-rich sample due to chelation reactions. This study demonstrates how carbonate minerals (keeping all other variables constant) affect shale-HFF reactions that can potentially impact porosity, microfracture integrity, and the release of heavy metals and volatile organic contaminants in the produced water.

Soil Carbon Dioxide Flux Partitioning in a Calcareous Watershed With Agricultural Impacts

AbstractPredicting the partitioning between aqueous and gaseous C across landscapes is difficult because many factors interact to control carbon dioxide (CO2) concentrations and removal as dissolved inorganic carbon (DIC). For example, carbonate minerals buffer soil pH and allow CO2 dissolution in porewaters, but nitrification of fertilizers may decrease pH so that carbonate weathering results in a gaseous CO2 efflux. Here, we investigate CO2 partitioning in an agricultural, first‐order, mixed‐lithology humid, temperate watershed. We quantified soil mineralogy and measured porewater chemistry, soil moisture, and soil pCO2 and pO2 as a function of depth at three hillslope positions. Variation of soil moisture along the hillslope was the dominant control on the concentration of soil CO2, but mineralogy acted as a secondary control on the partitioning of CO2 between gaseous and aqueous phases. Regression slopes of pCO2 versus pO2 in the carbonate‐bearing soils indicate a deficit of aerobically respired CO2 relative to O2 (p < 0.05). Additionally, nitrification of upslope fertilizers did not lower soil pH and therefore did not cause a gaseous CO2 flux from carbonate weathering. We concluded that in the calcareous soils, up to 43% of respired C potentially dissolves and drains from the soil rather than diffusing out to the atmosphere. To explore the possible implications of the reactions we evaluated, we used databases of carbonate minerals and land uses to map types of soil degassing behaviors. Based on our maps, the partitioning of respired soil CO2 to the aqueous phase could be important in estimating ecosystem C budgets and models.

Experimental study on Fe solubility in vapor-rich hydrothermal fluids at 400–500 °C, 215–510 bar: Implication for Fe mobility in seafloor vent systems

In seafloor hydrothermal systems, vent fluids usually contain elevated dissolved iron (Fe) that is significantly enriched relative to deep ocean seawater. It is commonly thought that Fe is preferentially transported in dense Cl-rich fluids due to the formation of aqueous Fe-Cl complexes. However, Fe enrichment in vapor-rich low-density fluids with low Cl concentrations (<550 mmol/kg) underscores the efficacy of the low-Cl vapor-rich phase to transport Fe in both subaerial and submarine hydrothermal systems. Currently, transport of Fe in low-density vapor-rich fluids is poorly understood due to the lack of high temperature–pressure (T-P) solubility experiments and requisite thermodynamic data. Here, we report new data of Fe solubility from experiments conducted at 400–500 °C, 215–510 bar, targeting fluids with low-density (∼0.1–0.35 g/cm3). The experiments were performed in the KCl-H2O system with hematite-magnetite and K-feldspar-muscovite-quartz as mineral buffering assemblages. Our results show that Fe solubility positively correlates with density and fluid chlorinity, which are affected by temperature and pressure. The equilibrium constants (log Khm) for Fe-buffering reaction Fe3O4(s) + 2HCl(aq) = Fe2O3(s) + FeCl2(aq) + H2O were determined. The new data and the data calculated using Helgeson-Kirkham-Flowers (HKF) equation of state were fit into a density model to extrapolate log Khm for hematite-magnetite Fe buffering reaction over a wide T-P range. The density models for magnetite dissolution reaction and pyrite-pyrrhotite equilibrium were also fit based on HKF to allow redox constraints. We show that calculated Fe solubility are in good agreement with measured values in vapor-rich fluids formed via phase separation in mineral buffered and basalt alteration experiments at elevated T-P. The density model was further applied to model Fe transport in fluids at the Brandon hydrothermal field at East Pacific Rise (EPR) 21°S, with T-P constrained by Si-Cl geothermobarometer. The calculations suggest that the reported Fe concentrations of vent fluids at Brandon reflect phase separation occurring at depth in the seafloor, with T-P up to 450 °C, 400 bar, and redox conditions buffered by pyrite-pyrrhotite-magnetite equilibrium.

A Validated Non-compendial Method for Determination of Haemodialysis Concentrate’s Contents and its Comparison with Compendial Method: Application of ISO 13958:2014 Standard

Background: Haemodialysis is a process to remove the waste products and excess fluids that build up in the human body when kidneys stop working. Haemodialysis concentrate consists of two parts, acid concentrate (Part A) that contains mineral ions (Na, K, Mg and Ca) and buffering agent acetic acid /citric acid whereas basic concentrate (Part B) comprises sodium bicarbonate alone or in combination with sodium chloride. Aim: Present research aimed to develop and validate a rapid method for the determination of cations and anions in haemodialysis concentrates in solution and powder form by choosing one technique among various suggested in ISO 13958:2014. Methods: The analysis was done by flame emission (flame photometer), atomic absorption spectrometer (AAS), polarimetric and titrimetric techniques. ICH guidelines were followed for method validation by addressing the linearity, accuracy, precision and detection limits (LOD and LOQ). Results and Discussion: The calibration curves were linear for Mg, Ca, K and Na with coefficient of determination (R2) ≥ 0.9978 and regression data indicating the excellent linearity for the selected concentration range for each content. The recovery results were obtained between the ranges 96.9-102.5 % which were good enough to justify the suitability of the proposed method for its intended applications. Statistical analysis indicated that there was no significant difference was observed between the proposed and compendial method at 95 % confidence of interval. Conclusion: The advantage of the proposed method over the compendial method by virtue of its economy and fast with reliable results because more reagents and chemicals are consumed in the compendial method.

Deserpentinization in Subduction Zones as a Source of Oxidation in Arcs: a Reality Check

AbstractPrevious studies have concluded that dehydration of serpentinites in subduction zones produces oxidizing fluids that are the cause of oxidized arc magmas. Here, observations of natural samples and settings are combined with thermodynamic models to explore some of the factors that complicate interpretation of the observations that form the basis of this conclusion. These factors include the variability of serpentinite protoliths, the roles of carbon and sulfur in serpentinite evolution, variability in serpentinization in different tectonic settings, changes in the bulk compositions of ultramafic rocks during serpentinization, fundamental differences between serpentinization and deserpentinization, and the absence of precise geothermobarometers for ultramafic rocks. The capacity of serpentinite-derived fluids to oxidize sub-arc magma is also examined. These fluids can transport redox budget as carbon-, sulfur-, and iron-bearing species. Iron- and carbon-bearing species might be present in sufficient concentrations to transport redox budget deep within subduction zones, but are not viable transporters of redox budget at the temperatures of antigorite breakdown, which produces the largest proportion of fluid released by serpentinite dehydration. Sulfur-bearing species can carry significant redox budget, and calculations using the Deep Earth Water (DEW) model show that these species might be stable during antigorite breakdown. However, oxygen fugacities of ∼ΔFMQ + 3 (where FMQ refers to the fayalite–magnetite–quartz buffer, and ΔFMQ is log fO2 – log fO2, FMQ), which is close to, or above, the hematite–magnetite buffer at the conditions of interest, are required to stabilize oxidized sulfur-bearing species. Pseudosection calculations indicate that these conditions might be attained at the conditions of antigorite breakdown if the starting serpentinites are sufficiently oxidized, but further work is required to assess the variability of serpentinite protoliths, metamorphic pressures and temperatures, and to confirm the relative positions of the mineral buffers with relation to changes in fluid speciation.

IN VITRO PROTEIN SOLUBILITY AND SOLUBILIZATION OF SELECTED FEEDSTUFFS FOR RUMINANT FEEDING

Protein solubility in mineral buffer, and protein degradability with bacterial protease, of condensed distillers solubles, distillers dried grains, brewers dried grains, raw, roasted and extruded soybeans, corn silage, haycrop silage, hay, corn gluten feed, multiage solulac and lactosy-urea (Ewoplus) were in­vestigated for use in ruminant feeding. The proteins of distillers dried grains, brewers dried grains, roasted and extruded soybeans and corn gluten meal were highly Insoluble in mineral buffer with average solubilities of 4.50%, 10.47%, 8.07%, 13.12% and 5.40% respectively. Lactosyl­urea (Ewoplus) was 100% soluble. The protease of streptomyces griseus was used to determine protein degradability. The degradable proteins of distillers grains, brewers grains, raw and roasted soybeans, and corn gluten meal were resis­tant to protease action. Extruded soybeans, distillers solubles, forage feedstuffs and Ewoplus were readily degradable.

Inflammation: a putative link between phosphate metabolism and cardiovascular disease.

Dietary habits in the western world lead to increasing phosphate intake. Under physiological conditions, extraosseous precipitation of phosphate with calcium is prevented by a mineral buffering system composed of calcification inhibitors and tight control of serum phosphate levels. The coordinated hormonal regulation of serum phosphate involves fibroblast growth factor 23 (FGF23), αKlotho, parathyroid hormone (PTH) and calcitriol. A severe derangement of phosphate homeostasis is observed in patients with chronic kidney disease (CKD), a patient collective with extremely high risk of cardiovascular morbidity and mortality. Higher phosphate levels in serum have been associated with increased risk for cardiovascular disease (CVD) in CKD patients, but also in the general population. The causal connections between phosphate and CVD are currently incompletely understood. An assumed link between phosphate and cardiovascular risk is the development of medial vascular calcification, a process actively promoted and regulated by a complex mechanistic interplay involving activation of pro-inflammatory signalling. Emerging evidence indicates a link between disturbances in phosphate homeostasis and inflammation. The present review focuses on critical interactions of phosphate homeostasis, inflammation, vascular calcification and CVD. Especially, pro-inflammatory responses mediating hyperphosphatemia-related development of vascular calcification as well as FGF23 as a critical factor in the interplay between inflammation and cardiovascular alterations, beyond its phosphaturic effects, are addressed.

Role of CO2 in low to medium enthalpy geothermal systems in the Central Betic Cordillera (Spain)

There is growing interest in geothermal energy, which is considered as an efficient energy solution to mitigate rising atmospheric CO2. Besides known high enthalpy geothermal systems, increasing attention is paid to low temperature geothermal systems, as they are suitable for local use. Although geothermal production seems to be an environmentally advantageous renewable energy, it might result in significant CO2 emissions. In this study, we investigate the relationship between temperature, fugacity of CO2 (fCO2), and mineral buffers in the reservoir conditions, taking the low- to medium- enthalpy thermal waters in the Central Betic Cordillera as case study. Using geochemical modeling, three main groups of waters have been identified depending on temperature, buffering mineral assemblage, and fCO2 in their reservoir. A group of waters with a reservoir temperature ranging from 70 to 90 °C and located in the intramountain sedimentary basins shows a fCO2 in depth ranging from ~6 × 10−2 and 6 × 10−1. The reservoir chemistry of this water group seems to be mainly controlled by carbonates and evaporites displaying a fCO2 variation between depth and surface (ΔfCO2) of 10−1. Another intermediate group of waters, located in an active extension zone, displays lower temperature (50–60 °C) and fCO2 in the reservoir (from 10−3 to 10−2). Finally, the third group of waters, located on the metamorphic complexes contacts, show the highest estimated temperatures (130–140 °C) and fCO2 in the reservoir (1 to 102). The two latter groups suggest increasing buffering effect of alumino-silicates, in addition to carbonates and quartz. Therefore, we evidenced a strong relationship between temperature and fCO2 in the reservoir as well as the potential mineral buffers. We discussed the potential of geothermal systems as clean energy source based on the estimation of the CO2 emissions generated by the investigated thermal systems for a practical case of household heating.

Ideas and perspectives: Development of nascent autotrophic carbon fixation systems in various redox conditions of the fluid degassing on early Earth

Abstract. The origin and development of the primary autotrophic metabolism on early Earth were influenced by the two main regimes of degassing of the Earth – reducing (predominance CH4) and oxidative (CO2). Among the existing theories of the autotrophic origin of life in hydrothermal environments, CO2 is usually considered to be the carbon source for nascent autotrophic metabolism. However, the ancestral carbon used in metabolism may have been derived from CH4 if the outflow of magma fluid to the surface of the Earth consisted mainly of methane. In such an environment, the primary autotrophic metabolic systems had to be methanotrophic. Due to the absence of molecular oxygen in the Archean conditions, this metabolism would have been anaerobic; i.e., oxidation of methane must be realized by inorganic high-potential electron acceptors. In light of the primacy and prevalence of CH4-dependent metabolism in hydrothermal systems of the ancient Earth, we propose a model of carbon fixation where the methane is fixed or transformed in a sequence of reactions in an autocatalytic methane–fumarate cycle. Nitrogen oxides are thermodynamically the most favorable among possible oxidants of methane; however, even the activity of oxygen created by mineral buffers of iron in hydrothermal conditions is sufficient for methanotrophic acetogenesis. The hydrothermal system model is considered in the form of a phase diagram, which demonstrates the area of redox and P and T conditions favorable for the development of the primary methanotrophic metabolism.

Phosphate, Calcification in Blood, and Mineral Stress: The Physiologic Blood Mineral Buffering System and Its Association with Cardiovascular Risk.

Phosphate is an important cardiovascular risk factor and lowering elevated blood phosphate concentrations is a main therapeutic target in kidney patients. Phosphate is subject to the blood mineral buffering system which controls the precipitation of calcium and phosphate. Calciprotein particles (CPP), self-assembling complexes of calcium phosphate and serum proteins, are the nanomorphological correlates of this system. CPP1 are spherical, 50-100 nm in diameter, and contain amorphous mineral. CPP2 are oblongated, 100-200nm in the long axis, and they contain a crystalline mineral core. The relative abundance and biological activity of these particles are a matter of intense research, because they can cause oxidative stress, inflammation, and calcification in cellular assay. Therapeutically reducing this endogenous stressor by prolonging crystal formation time might improve patient outcome. This concise review article summarizes our current knowledge about the blood mineral buffering system and proposes Mineral Stress as a novel modifiable cardiovascular risk factor. It furthermore outlines possible implications this might have for improving patient care.

Development of nascent autotrophic carbon fixation systems in various redox conditions of the fluid degassing in early Earth

&lt;p&gt;&lt;strong&gt;Abstract.&lt;/strong&gt; Strategies for the origin and development of primary metabolism on early Earth were determined by the two main regimes of degassing of Earth in the form of CO&lt;sub&gt;2&lt;/sub&gt; or CH&lt;sub&gt;4&lt;/sub&gt; fluid impulses. Among the existing theories of the autotrophic origin of the life, CO&lt;sub&gt;2&lt;/sub&gt; is usually considered the carbon source for nascent autotrophic metabolism. However, the ancestral carbon used in metabolism may have been derived from CH&lt;sub&gt;4&lt;/sub&gt; if the outflow of magma fluid to the surface of the Earth consisted mainly of methane. Primary biochemical systems are present in methane degassing regimes developed in an environment of high partial pressure of methane, which is a source of carbon for nascent metabolic systems. Due to the absence of molecular oxygen in the Archaean conditions, this metabolism would have been anaerobic, i.e., oxidation of methane must be realized by inorganic high-potential electron acceptors. In light of the primacy and predominance of CH&lt;sub&gt;4&lt;/sub&gt;-dependent metabolism in hydrothermal systems of the ancient Earth, we propose a model of carbon fixation, which is a sequence of reactions in a hypothetical methane-fumarate (MF) cycle. Thermodynamics calculations showed a high efficiency of oxidation of methane to acetate (methanotrophic acetogenesis) by oxidized nitrogen compounds in hydrothermal systems. Thermodynamically favorable were also reactions involving the introduction of carbon methane into the intermediates of the proposed MF cycle. The methane oxidation reactions with the use of oxygen of iron mineral buffers are closer to the equilibrium state, which apparently determines the possibilities of primordial cycle flow in the forward or reverse directions.&lt;/p&gt;