Exchangeable Pool Research Articles

Assessing chromium mobility in natural surface waters: Colloidal contribution to the isotopically exchangeable pool of chromium (EwCr value)

The labile pool of chromium (Cr), ECr value for soils and EwCr value for suspended particulate matter (SPM) in water, can be efficiently assessed in different environmental compartments through the use of isotopic dilution techniques. The overall objective of this work was to evaluate Cr availability based on the suspended particle matter size range and, more specifically, to determine the role of colloids in the calculation of the EwCr value. Surface water samples were collected from ponds and streams at the active nickel mine of Barro Alto (Goiás State, Brazil). Two isotopic exchange (spiking) experiments were performed: #E1, the water samples were either spiked before cascade filtration (0.7 μm, 0.2 μm, 500 kDa and 1 kDa) or, #E2, according to the range of particle sizes (>0.7 μm, 0.2–0.7 μm, 500 kDa–0.2 μm and 1–500 kDa). This study showed that: 1) mining activities in ultramafic environments locally increase the presence of particulate matter and colloids containing Cr-bearing phases, mainly iron oxy(hydroxides); 2) in the pristine area, chromium was mainly associated with colloids (1 kDa–500 kDa), while mining activities increase the amount of large particles (>0.2 μm) containing chromium in the impacted area, and 3) there is an overestimation of the exchangeable pool of chromium (EWCr value) due to the presence of organic and inorganic colloids containing non-exchangeable chromium. A correction to overcome this discrepancy was proposed.

Measuring Plant-Available Mg, Ca, and K Pools in the Soil—An Isotopic Dilution Assay

In many forest ecosystems, plant-available pools of Mg, Ca, and K are assumed to be stored in the soil as exchangeable cations adsorbed on the cation exchange complex (exchangeable pools). However, between soil minerals and exchangeable cations exists a gradient of Mg, Ca, and K storage forms that have not been fully characterized and may play an important role in plant nutrition and biogeochemical cycles. We hypothesize that sources of Mg, Ca, and K in the soil other than the conventionally measured exchangeable pools are plant-available on very short time scales (<1 day). In the present study, we developed and applied an isotopic dilution technique using the stable isotopes 26Mg, 44Ca, and 41K to trace and quantify the pools of Mg, Ca, and K (isotopically exchangeable pools) in the soil of a hardwood forest that contribute directly to equilibrium processes between the soil water and the soil. We characterize the equilibrium between the soil and soil solution using both a batch approach and a flow-through approach in order (i) to develop and determine the best routine method to measure the isotopically exchangeable pools and (ii) to further the characterization of the forms of storage of Mg, Ca, and K in the isotopically exchangeable pools. We first show that the flow-through reactor approach (equilibrium in unsaturated soil columns) is the most adequate to measure the isotopically exchangeable pools with the fewest equilibrium disturbances. We then show that isotopically exchangeable pools of Mg, Ca, and K are greater than traditionally measured exchangeable pools. The isotopically exchangeable pools of Mg, Ca, and K are mainly composed of traditionally measured exchangeable pools (88.8–98.5% for Mg, 74.7–97.7% for Ca, and 68.7–77.1% for K) but are also composed of pools extracted with the Tamm reagent (oxalic acid, pH 3) and nitric acid (1 mol·L–1): 1.5–11.2% for Mg, 2.3–25.3% for Ca, and 22.9–31.3% for K. Storage forms of Mg, Ca, and K in the isotopically exchangeable pool could include chelation with soil organic matter, retention on soil aluminum and iron oxides and hydroxides through phosphate and/or organic acid bridges and site-specific adsorption. The isotopic dilution method is a relevant tool to quantify the plant-available pools of Mg, Ca, and K on short time scales (source and sink pools) and is a very promising approach to characterize and quantify the processes responsible for the depletion and/or replenishment of these pools over longer time scales.

Recycling of waste biomass and mineral powder for preparation of potassium-enriched compost

An attempt was made to recycle waste biomass and mineral powder (waste mica) as an alternative source of potassium (K) through composting technology. Two different waste biomass, isabgol straw and palmarosa distillation waste along with two levels of waste mica (2 and 4% as K) were used for preparation of enriched composts. A notable decrease of C:N ratio was observed at the end of the composting (150 days) as an indicator of compost maturity. The mature composts were evaluated for K-supplying capacity through laboratory leaching and soil incubation study. Significantly higher water-soluble K released initially followed by a sharp decrease up to 21 days of leaching thereafter gradually decreased up to 35 days of leaching. Water-soluble K was released from K-enriched (mica charged) compost significantly higher than the ordinary compost throughout the leaching period. Soil incubation study also revealed that application of K-enriched compost greatly improved the available K (water soluble and exchangeable) pools in K-deficient soil which indicated that a considerable amount of K releases during composting. Therefore, K-enriched compost could be an effective alternative of costly commercial K fertilizer and eco-friendly approach to utilize low-cost waste mineral powder and plant residue.

Монополия внешней торговли в политике РСФСР в 1917-1922 гг. и борьба тенденций в организации международной филателии

Examines the main trends in the development of Russian philately in the formation of nationality of the course of the RSFSR and the monopoly of foreign trade as an instrument of the foreign exchange pool spas the state.

Towards speciation of organically bound tritium and deuterium: Quantification of non-exchangeable forms in carbohydrate molecules

An original methodology to quantitatively explore exchangeability of hydrogen isotopes in carbohydrate molecules is proposed. To access the speciation of organically bound hydrogen isotopes, isotopic exchanges were carried out under a soft path regime in the vapor phase at 20 °C with set (D,T/H) vapor pressure ratios. When steady states were reached, the fraction of exchangeable hydrogen of microcrystalline cellulose, alpha-cellulose and wheat grains were obtained and ranged from 13 to 31% (versus a theoretical value of 30%). In cellulose, and more specifically in microcrystalline cellulose, the molecular hydrogen bonds as well as the different conformations of the network seemed to decrease the hydroxyl groups of glucose units available for isotopic exchange. On the contrary, the assumed enzymatic hydrolysis of the constitutive molecules of wheat starch into low-molecular weight carbohydrate molecules enhanced the exchangeable pool. An average value of the activity between non-exchangeable organically bound tritium (NE-OBT) and non-exchangeable organically bound hydrogen was calculated for wheat grains, (TH)NE = 0.55 ± 0.03 Bq.g−1 of hydrogen atoms.

Long-term effects of forest liming on mineral soil, organic layer and foliage chemistry: Insights from multiple beech experimental sites in Northern France

Abstract Most forest ecosystems grow on acid and nutrient poor soils. In many cases, a slow degradation of forest soil chemical fertility due to increasing external pressures (decreasing atmospheric inputs, intensification of biomass harvesting and silvicultural practices) has been observed and is a growing concern in the international forest community. When the pressure endured by low fertility forest ecosystems is too intense, nutrient losses and ecosystem function losses may occur, forest decline being the ultimate stage of this process. In such cases, forest liming with a carbonate product is a solution to restore soil fertility and reduce soil acidity, globally improve the ecosystem functioning and compensate for nutrient losses caused by biomass harvest and exportation. However, the effects of liming on ecosystem processes and the biogeochemical cycling of nutrients in forest ecosystems are still unclear. We studied the dynamics of magnesium and calcium originating from the dissolution of liming products in the different compartments (organic and mineral soil layers and, aboveground biomass) of five long-term (20 to 40 years) monitoring beech (Fagus sylvatica L.) plots located in Northern France from ecosystem magnesium and calcium budgets. Compared to the control plots, soil exchangeable pools of Mg and Ca in the 0–15 cm mineral soil layer increased during the first decade after liming but these differences rapidly decreased after 20–30 years. The effect of liming on foliar concentrations and tree growth was still observed after 40 years, most probably because the biological cycling of these elements was more dynamic in the limed plots. Liming increased the decomposition rate of the soil organic layer but the pools of Mg and Ca in this layer remained relatively stable over time, probably because Mg and Ca concentrations in foliage and litterfall increased after the liming. Liming effects varied between sites depending on the liming product and amount, and the initial chemical fertility level of the soil. Although liming operations may help improve forest soil fertility, they may also generate nutrient deficiencies and/or imbalances for nutrients that are poorly available in the soil. The planning of liming operations therefore necessitates a thorough soil chemical fertility diagnosis.

An Isotopic Dilution Approach for Quantifying Mercury Lability in Soils

The accurate estimation of soil mercury lability is crucial for risk assessment. In comparison to chemical fractionation and speciation, isotopic dilution (ID) offers precise definition of labile mercury fractions while maintaining the natural equilibrium. We developed and applied an ID protocol with 199Hg to estimate the soil mercury (Hg) isotopically exchangeable (labile) pool or HgE using a range of industrially contaminated soils in Switzerland. The measured HgE values were consistent for the same soil against different spike levels (50, 100, and 200% of native 199Hg), indicating that the spiked and soil isotopes achieved required dynamic equilibrium at the soil–water interface. Total soil Hg (THg; mg kg–1) was the best predictor of HgE (mg kg–1) and %HgE and accounted for 96 and 63% of the variance, respectively. Nonetheless, despite the wide range of THg values (0.37–310 mg kg–1) in the studied soils, Hg lability spanned a narrow range (∼12–25% of THg), highlighting the large capacity of soils to se...

Kidney exchange simulation and optimization

One of the challenges in a kidney exchange program (KEP) is to choose policies that ensure an effective and fair management of all participating patients. In order to understand the implications of different policies of patient allocation and pool management, decision makers should be supported by a simulation tool capable of tackling realistic exchange pools and modeling their dynamic behavior. In this paper, we propose a KEP simulator that takes into consideration the wide typology of actors found in practice (incompatible pairs, altruistic donors, and compatible pairs) and handles different matching policies. Additionally, it includes the possibility of evaluating the impact of positive crossmatch of a selected transplant, and of dropouts, in a dynamic environment. Results are compared to those obtained with a complete information model, with knowledge of future events, which provides an upper bound to the objective values. Final results show that shorter time intervals between matches lead to higher number of effective transplants and to shorter waiting times for patients. Furthermore, the inclusion of compatible pairs is essential to match pairs of specific patient–donor blood type. In particular, O-blood type patients benefit greatly from this inclusion.

Invasive earthworms change nutrient availability and uptake by forest understory plants

Assess whether invasive earthworms alter nutrient dynamics in habitats they colonize. We investigated nutrient dynamics of forest soils and three native plant species (Acer saccharum, Polygonatum pubescens, Polystichum acrostichoides) along four earthworm invasion gradients in central New York. Earthworm biomass (a proxy for earthworm impact) was related to distribution and concentration of soil and plant nutrients. At shallower depths, earthworms were associated with lower total and exchangeable P, but higher Ca, K, Mg and Mn. Earthworm-invaded plots showed higher soil Ca and higher foliar Ca in A. saccharum and P. acrostichoides, and lower soil P with lower foliar P in P. pubescens. Presence of earthworms substantially decreased rooting volume in the A horizon, co-occurring with a build up of exchangeable nutrient concentrations and pools. Overall, earthworm biomass was a better predictor of foliar nutrient concentrations than either exchangeable or total nutrient concentrations and pools. Earthworms may create stressful rooting conditions, limiting rooting of native plants in the A horizon. The resulting plant-accessible nutrient pool that builds up in the A horizon of earthworm-invaded soils could provide a mechanism for the invasive success of non-indigenous plants that have an evolutionary association with earthworms in the native range and that follow earthworm invasions.

Distribution and isotopic composition of trimethylamine, dimethylsulfide and dimethylsulfoniopropionate in marine sediments

Abstract Methylated amines and sulfides are ubiquitous organic nitrogen and sulfur compounds in the marine environment and could serve as important energy substrates to methanogens inhabiting anoxic sediments. However, their abundance and isotopic values remain largely unconstrained in marine sediments. In this study, we investigated the distribution of trimethylamine (TMA), dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) in Aarhus Bay, Denmark and provided the first report for their stable carbon isotopic composition. Simultaneous measurement of those two compounds in small volumes of pore waters and sediments was accomplished with gas chromatography in combination with either a purge and trap system for quantification or a headspace method for carbon isotopic analysis. TMA in the solid phase (exchangeable pool, 0.3–6.6 μmol kg −1 wet sediment; base-extractable pool, 2–18 μmol kg −1 ) was much more abundant than the dissolved pool ( −1 ) than the dissolved pool of DMS(P)d in the pore water (including DMS and dissolved DMSP; 1–12 nM). TMA and DMS(P) contents in the solid phase peaked in the surface sediment, consistent with their phytodetrital origin. TMA was more 13 C-depleted than DMS(P) (TMA: −36.4‰ to −39.2‰; DMS: −18.6‰ to −23.4‰), presumably due to different biological or biosynthetic origins of the respective methyl groups. Both compounds showed a downcore decrease in their solid-phase concentration, a feature that was attributed to microbial degradation, but progressive enrichment in 13 C (up to 4‰) with depth was observed only for DMS(P). The considerable pool size of TMA and DMS(P) outlined in this study and geochemical evidence of their degradability suggested these two compounds could be potentially important substrates for methane production in sulfate-reducing environments.

Coupling between phosphate and calcium homeostasis: a mathematical model

We developed a mathematical model of calcium (Ca) and phosphate (PO4) homeostasis in the rat to elucidate the hormonal mechanisms that underlie the regulation of Ca and PO4 balance. The model represents the exchanges of Ca and PO4 between the intestine, plasma, kidneys, bone, and the intracellular compartment, and the formation of Ca-PO4-fetuin-A complexes. It accounts for the regulation of these fluxes by parathyroid hormone (PTH), vitamin D3, fibroblast growth factor 23, and Ca2+-sensing receptors. Our results suggest that the Ca and PO4 homeostatic systems are robust enough to handle small perturbations in the production rate of either PTH or vitamin D3 The model predicts that large perturbations in PTH or vitamin D3 synthesis have a greater impact on the plasma concentration of Ca2+ ([Ca2+]p) than on that of PO4 ([PO4]p); due to negative feedback loops, [PO4]p does not consistently increase when the production rate of PTH or vitamin D3 is decreased. Our results also suggest that, following a large PO4 infusion, the rapidly exchangeable pool in bone acts as a fast, transient storage PO4 compartment (on the order of minutes), whereas the intracellular pool is able to store greater amounts of PO4 over several hours. Moreover, a large PO4 infusion rapidly lowers [Ca2+]p owing to the formation of CaPO4 complexes. A large Ca infusion, however, has a small impact on [PO4]p, since a significant fraction of Ca binds to albumin. This mathematical model is the first to include all major regulatory factors of Ca and PO4 homeostasis.

Information and Optimal Trading Strategies with Dark Pools

We study how asymmetric information affects market participants’ choice of trading venue (either an exchange or dark pool), and the optimal submission strategies in a sequential trading game. The exchange is organized as a fully transparent limit order book, and the dark pool is an opaque venue where orders are continuously executed at the midpoint of the bid and ask prices that prevail in the exchange. We find that when the limit order book conveys no information rational uninformed traders never trade in the dark pool due to price risk. However, price risk may be reduced when the information in the book induces an uninformed buyer (seller) to believe that the value of the asset is high (low) since the order was previously submitted by an informed buyer (seller). The optimal strategy of an informed trader takes into account the information leakage, and the strategic response of each type of trader in the subsequent stages. Our main finding is that, adding a dark pool alongside an exchange, may divert the informed trader from the exchange to the dark pool. When the execution risk in the dark pool is low, the informed trader decides to trade in the dark pool. In this case the adverse selection problem in the exchange reduces and consequently, the uninformed trader decides to switch from no trade to placing a limit order in the exchange.

Calcium is cycled tightly in Cryptomeria japonica stands on soils with low acid buffering capacity

Calcium (Ca) is a key cation in the soil acidification process and in the fertility of forest soils. We investigated total concentrations of Ca, magnesium (Mg), and potassium (K) in both soil and fresh leaf litter in eight plantation stands of Cryptomeria japonica divided into two groups of highly contrasting soil acid buffering capacity (ABC). In addition to conventional methods, we used a double-crystal high resolution X-ray fluorescence (HRXRF) spectrometer to determine Ca fractions in soils with low and high ABC. Total Ca had accumulated in the 0–10cm depth horizons of the high-ABC soils, but not in the low-ABC soils. The exchangeable Ca concentration was correlated with total Ca concentration in the 0–10cm depth of the low-ABC soils. Calcium-Kα1,2 emission spectra of the 0–10cm soils obtained by HRXRF spectrometry separated the total Ca into two fractions, suggesting that the predominant Ca constituents had either passed through biological processes or were derived from weathering hydration in both the high- and low-ABC soils. Calcium concentration in the fresh leaf litter was significantly lower in the stands with low-ABC soil than in those with high-ABC soil and was positively correlated with soil exchangeable Ca concentration in the low-ABC stands; no such correlation was observed in the high-ABC stands. Exchangeable Ca pools in the 0–10cm depth range were equal to or less than the annual input of Ca via leaf litterfall in the low-ABC stands, but were seven times the annual input in the high-ABC soils. These results suggested that the accumulation of Ca in the upper soil occurs via the process of Ca circulation within C. japonica ecosystems, and that sufficient supply of Ca for tree needs was accompanied by the large accumulation of available Ca by C. japonica in the high-ABC soils. Nevertheless, it is likely that only small amounts of Ca were circulated in the stands on low-ABC soil. The lack of Ca accumulation in the surface soil and the accompanying tight circulation of Ca in the plant–soil system may explain the observed positive feedback in which ABC is gradually reduced in low-ABC soils.

Filling the gap in Ca input-output budgets in base-poor forest ecosystems: The contribution of non-crystalline phases evidenced by stable isotopic dilution

In terrestrial ecosystems, plant-available pools of magnesium and calcium are assumed to be stored in the soil as exchangeable cations adsorbed on the surface of mineral and/or organic particles. The pools of exchangeable magnesium and calcium are measured by ion-exchange soil extractions. These pools are sustained in the long term by the weathering of primary minerals in the soil and atmospheric inputs. This conceptual model is the base of input-output budgets from which soil acidification and the sustainability of soil chemical fertility is inferred. However, this model has been questioned by data from long-term forest ecosystem monitoring sites, particularly for calcium. Quantifying the contribution of atmospheric inputs, ion exchange and weathering of both primary, secondary and non-crystalline phases to tree nutrition in the short term is challenging.In this study, we developed and applied a novel isotopic dilution technique using the stable isotopes of magnesium and calcium to study the contribution of the different soil phases to soil solution chemistry in a very acidic soil. The labile pools of Mg and Ca in the soil (pools in equilibrium with the soil solution) were isotopically labeled by spraying a solution enriched in 26Mg and 44Ca on the soil. Labeled soil columns were then percolated with a dilute acid solution during a 3-month period and the isotopic dilution of the tracers was monitored in the leaching solution, in the exchangeable (2 sequential 1molL−1 ammonium acetate extractions) and non-crystalline (2 sequential soil digestions: oxalic acid followed by nitric acid) phases.Significant amounts of Mg and Ca isotope tracer were recovered in the non-crystalline soil phases. These phases represented from 5% to 25% and from 24% to 50%, respectively, of the Mg and Ca labile pools during the experiment. Our results show that non-crystalline phases act as both a source and a sink of calcium and magnesium in the soil, and contribute directly to soil solution chemistry on very short-term time scales. These phases are very abundant in acid soils and, in the present study, represent a substantial calcium pool (equivalent in size to the Ca exchangeable pool). The gradual isotopic dilution of Mg and Ca isotope ratios in the leaching solution during the experiment evidenced an input flux of Mg and Ca originating from a pool other than the labile pool. While the Mg input flux originated primarily from the weathering of primary minerals and secondarily from the non-crystalline phases, the Ca input flux originated primarily from the non-crystalline phases. Our results also show that the net calcium release flux from these phases may represent a significant source of calcium in forest ecosystems and actively contribute to compensating the depletion of Ca exchangeable pools in the soil. Non-crystalline phases therefore should be taken into account when computing input-output nutrient budgets and soil acid neutralizing capacity.

Drinking and water permeability in the Pacific hagfish, Eptatretus stoutii

Hagfish are osmoconformers, maintaining an internal osmolality that matches their seawater habitats. Hagfish would, therefore, appear to have no physiological need to drink, but previous studies are equivocal regarding whether drinking in hagfish occurs. The current study addressed this knowledge gap, by examining drinking and water permeability in the Pacific hagfish, Eptatretus stoutii. One-third of analysed hagfish were shown to accumulate radiolabelled drinking rate markers (tritiated inulin and polyethylene glycol-4000) in their gut tissues; however, this was attributed to the presence of markers in the blood perfusing the digestive tract, following absorption through paracellular pathways at the gill. No accumulation of marker was observed in hagfish subjected to more dilute (75% seawater) or more concentrated (125% seawater) media. Diffusive water efflux, measured by tritiated water washout, was shown to be very high, with 50% of body water exchanged within 14 to 16min, depending on exposure salinity. In full-strength seawater, the total exchangeable pool of water was 78% of hagfish mass. We conclude that hagfish do not drink, and their high water permeability is likely to result in rapid osmotic equilibration under circumstances where perturbations may occur.

Supplemental Zinc Decreases Fractional Zinc Absorption and Increases Lean Tissue Mass among Vietnamese Children with Tuberculosis

Childhood tuberculosis (TB) is a major health concern in Vietnam. Dietary Zn absorption is greater in children recovering from TB, possibly due to increased demand of Zn for immune function. Zn supplementation, therefore, may improve the effectiveness of TB treatment. Our objective was to determine changes in Zn homeostasis in response to Zn supplements among children admitted for treatment of TB at the National Lung Hospital in Hanoi, Vietnam.After baseline, children matched by sex were randomized to 10 mg Zn/d (n=10) or placebo (n=11) for the first 2 mo of TB treatment. At baseline and after 2 mo, fractional Zn absorption (FZA) and exchangeable Zn pool size (EZP) were determined using Zn stable isotopes during an 8 d controlled‐diet metabolic study. After each of 3 meals on d 2, the child received 0.33 mg 67Zn orally and, 1 h following dinner, 0.1 mg 70Zn intravenously. FZA was determined from urinary Zn tracer‐tracee ratios (TTRs) in samples collected 5–7 d post isotope administration. EZP was estimated from the y‐intercept of the log‐transformed linear regression of urinary 70Zn TTRs. Height, weight, body mass index (BMI), mid‐upper arm circumference (MUAC), triceps skinfold thickness (TSK), and subscapular skinfold thickness (SSK) were determined. Mid‐upper arm muscle area (MUAM) and mid‐upper arm fat area (MUAF) were derived from MUAC and TSK.21 children 9 to 15 y, 11 male and 10 female, enrolled. 14 had pulmonary TB. Height‐ and BMI‐for‐age z‐scores were −1.2 (−1.9, −0.6) and −1.7 (−2.4, −1.0), respectively. After 2 mo, controlling for baseline values, FZA was significantly lower among Zn‐supplemented children vs. placebo: 25.8% (21.5, 30.1%) vs. 32% (27.7, 36.3%), p &lt; 0.05. EZP tended to be higher with Zn compared with placebo: 83.3 mg (69.2, 97.5 mg) vs. 70.1 mg (55.2, 85 mg), p = 0.19 (NS). No differences in weight, height, or BMI were observed. MUAC was higher among Zn supplemented, 21.1 cm (20.2, 22 cm), vs. placebo, 19.5 cm (18.7, 20.3 cm), p &lt; 0.05. MUAM was also higher among Zn supplemented, 19.6 cm2 (17.3, 22.2 cm2) vs. 15.7 cm2 (13.9, 17.6 cm2) placebo, p &lt; 0.05.In sum, 10 mg Zn/d led to a homeostatic response and improved lean tissue gain in Vietnamese children with TB, and thus should further be evaluated as part of their treatment. Given the sensitivity of MUAC and MUAM, these indicators should be included for monitoring the TB recovery process in future studies.Support or Funding InformationInternational Atomic Energy Agency, Contract 15859

Renal Handling of Ketones in Response to Sodium-Glucose Cotransporter 2 Inhibition in Patients With Type 2 Diabetes.

Pharmacologically induced glycosuria elicits adaptive responses in glucose homeostasis and hormone release, including decrements in plasma glucose and insulin levels, increments in glucagon release, enhanced lipolysis, and stimulation of ketogenesis, resulting in an increase in ketonemia. We aimed at assessing the renal response to these changes. We measured fasting and postmeal urinary excretion of glucose, β-hydroxybutyrate (β-HB), lactate, and sodium in 66 previously reported patients with type 2 diabetes and preserved renal function (estimated glomerular filtration rate ≥60 mL · min-1 · 1.73 m-2) and in control subjects without diabetes at baseline and following empagliflozin treatment. With chronic (4 weeks) sodium-glucose cotransporter 2 inhibition, baseline fractional glucose excretion (<2%) rose to 38 ± 12% and 46 ± 11% (fasting vs. postmeal, respectively; P < 0.0001) over a range of BMIs (range 23-41 kg/m2) and creatinine clearance (65-168 mL · min-1 · m-2). Excretion of β-HB (median [interquartile range]: 0.08 [0.10] to 0.31 [0.43] µmol · min-1), lactate (0.06 [0.06] to 0.28 [0.25] µmol · min-1), and sodium (0.27 [0.22] to 0.36 [0.16] mEq · min-1) all increased (P ≤ 0.001 for all) and were each positively related to glycosuria (P ≤ 0.001). These parameters changed in the same direction in subjects without diabetes, but changes were smaller than in the patients with diabetes. Although plasma N-terminal pro-B-type natriuretic peptide levels were unaltered, plasma erythropoietin concentrations increased by 31 (64)% (P = 0.0078). We conclude that the sodium-glucose cotransporter 2 inhibitor-induced increase in β-HB is not because of reduced renal clearance but because of overproduction. The increased lactate excretion contributes to lower plasma lactate levels, whereas the increased natriuresis may help in normalizing the exchangeable sodium pool. Taken together, glucose loss through joint inhibition of glucose and sodium reabsorption in the proximal tubule induces multiple changes in renal metabolism.

Eight-year long potassium fertilization effects on quantity/intensity relationship of soil potassium under double rice cropping

Present research was undertaken to understand the effect of long-term potassium (K) fertilization @ 0kg (K0) and 80kg (K80)Kha−1 on the quantity/intensity (Q/I) parameters for K in soil and characterize the Aeric Haplaquept soil for K supplying capacity under long-term continuous rice cropping. The study involved laboratory experiments on Q/I parameters of the soils in different depths (0–75cm depth) from long-term K management experimental field. The Q/I parameters showed a linear relationship for both K omission and K fertilized soils at different depths. Omission of K decreased the equilibrium K concentration ratio (CR0K) compared to K applied to the soil and slightly decreased the labile K (KL) and non-specifically available K (-ΔK0) but had no effect on specifically available K (KX). The K omission increased the potential buffering capacity (PBCK) compared to K fertilized soil. Potassium management had little effect on equilibrium exchangeable K (EK0), magnitude of the conversion of added K to exchangeable pool (α) and non-exchangeable pool (β). However, equilibrium solution K (CK0) in K omission soil was lower than K applied soil. β was higher than α in both the K management conditions. The PBCK for non-exchangeable pool was also higher than exchangeable pool both in K omission and K fertilized soils. Potassium management influenced critical solution K (CKr) and critical exchangeable K (EKr) but had no effect on minimum exchangeable K (Emin). Since the exchangeable K (EK), EKr and EK0 is very close to Emin it is concluded that EKr and Emin should be consider in interpreting the K fertility specially the EK of soil under long-term wetland double rice cultivation.

Using isotope dilution assays to understand speciation changes in Cd, Zn, Pb and Fe in a soil model system under simulated flooding conditions

Flooded soils are systems with complex chemistry and understanding the mechanisms that control the mobility and bioavailability of metals in these soils is important for their management. This work uses stable metal multi-element isotopic dilution combined with sequential extraction assays to help understand the changes in solid and solution speciation of Cd, Fe, Pb and Zn in a contaminated soil following submergence. However, it is necessary to ensure that the isotopic dilution principles, originally developed for aerobic soils, are not compromised; in particular due to the presence of non-labile colloids in the solution phase. In particular, no studies examining the validity of these assays in systems where rapid pH and Eh changes are occurring due to fermentation reactions have been published. Thus sucrose (0.42% and 1.26% added C) was used as a carbon source to stimulate bacterial mediated fermentation reactions allowing changes in Cd, Zn, Fe and Pb isotopic exchangeability, speciation and solution chemistry to be examined after 10, 20 and 42days of submergence. Without the addition of added C, submergence for 42days only produced minor changes in the speciation of the metals in solid or solution phases. However, the presence of easily labile carbon produced significant responses depending on the quantity of C added. Assessments of whether fermentation products caused over-estimation of the isotopically exchangeable pool of metals (E-values) were made by measuring concentrations with and without a resin purification step. Results showed generally good agreement over a pH range of 4–7 for Pb, Cd, Zn and Fe and demonstrate that fermentation by-products do not induce the formation of non-exchangeable metal colloids. E-value concentrations were compared with fractions extracted using a modified Tessier sequential extraction. With no carbonate phases present in the soils, the E-values for Cd, Zn, Fe and Pb compared favourably with the concentrations of metal present in the combined solution, exchangeable and specifically adsorbed fractions. This provided additional evidence that the conditions for the isotopic dilution assays were not violated as these fractions should be isotopically exchangeable. Combining results from the different treatments and stages of the reduction process, strong pH dependence was found for the isotopically exchangeable and the solution pools of Cd, Zn and Pb.

Predictors of the Size of the Exchangeable Zinc Pool Differ between Children and Adults

BackgroundThe size of the rapidly exchanging pool of body zinc has been suggested as having potential utility as a biomarker of zinc status. Knowledge of the relations of exchangeable zinc pool (EZP) size to relevant variables is necessary to adequately evaluate its use as a biomarker. ObjectiveWe used regression analysis to investigate associations of EZP with age, sex, body size, and zinc nutrition variables. MethodsData were compiled from 18 isotope tracer studies of zinc absorption in 247 children and adults (248 observations) in which EZP and relevant variables (e.g., weight, age, absorbed zinc) were measured. Linear regression analyses were performed separately on data from adults and children. ResultsIn children, EZP was most strongly associated with weight (r = 0.78). The best-fitting regression models of EZP (R2 ≥ 0.68) had weight or age and weight-for-age z score as predictors. Other variables had little effect on EZP when controlling for weight. Absorbed zinc was observed to be a predictor of EZP only in zinc intervention trials of infants. The mean EZP/wt was 4 mg/kg between 8 and 120 mo of age. In adults, EZP was observed to vary in a complex manner with (in order of importance) age, absorbed zinc, weight, sex, and plasma zinc concentration. EZP data from zinc-deprived subjects were lower than the 95% prediction interval of a model of normative data. ConclusionsEZP was observed to maintain a constant size relative to weight and was influenced only slightly by other factors in children. In contrast, EZP in adults varied with several factors, including absorbed zinc, and was statistically smaller in zinc-deprived individuals. The findings suggest that EZP may have utility as an indicator of zinc status in adults, but there is less evidence for this in children. Additional data are needed to reach a definitive conclusion.