Labile Pool Research Articles

Changes in soil organic carbon pools in a long‐term trial with perennial fodder crops in acid soils of north‐east India

AbstractEfficient estimation of soil organic carbon (SOC) is vital for understanding and monitoring the effect of perennial fodder crops in conserving SOC. In subtropical regions, there is limited information on SOC accumulation and its allocation into different pools under long‐term grasses and legumes. Therefore, we investigated the dynamics of SOC in a 20‐year‐old field trial with seven perennial grass species and a legume in a Typic Paleudalf soil under subtropical climate in north‐east India by analysing oxidizable organic C (Coc) and its fractions of very labile (CVL), labile (CL), less labile (CLL) and non‐labile (CNL), microbial biomass C (Cmic) and mineralizable C (Cmin). Growing perennial fodder crops increased SOC in the 0–0.60 m soil depth from 19.9%–39.6% compared with the conventional cultivation with maize (Zea mays). The relative efficacy of the fodder species to SOC accumulation was Setaria sphacelata = Brachieria rosenesis > Panicum maximum cv. Makunia = Arachis pintoi > Panicum maximum cv. Hamil > Paspalam conjugalum = Pennisetum purpureum > Thysanolaena maxima. Among the analysed fractions, CVL, CL, CLL and Cmic were influenced most by the fodder crops and the active pools (CVL+CL) constituted 71.6% of the SOC. The results indicate that under the tested subtropical climate, soil under perennial grasses and legumes conserves organic C and that most of the SOC is in labile pools of short residence time.

Effects of snow absence on winter soil nitrogen dynamics in a subalpine spruce forest of southwestern China

The lack of snow cover due to winter climate change has great potential to impact winter soil nitrogen cycling in boreal forests. A snow manipulation was conducted in a Tibetan spruce forest to explore the effects of snow absence on winter soil nitrogen dynamics by shelter method. Snow absence on average reduced soil temperatures at the depths of 0cm and 5cm by 1.44°C and 0.33°C, respectively, throughout the winter. Moreover, snow absence increased soil frost and freeze-thaw cycles. Soil net nitrogen mineralization and labile nitrogen pools (ammonium, nitrate and dissolved organic nitrogen) were higher in the snow absence plots compared to control plots. Snow absence increased soil microbial biomass carbon but did not affect microbial biomass nitrogen. Nevertheless, soil enzyme activities involved in nitrogen cycles were often lowered by snow absence over the winter. The results noted in this study suggest that warming-induced absence in seasonal snowpack may stimulate winter soil nitrogen availabilities by changing soil microhabitats, which has important implications for soil biogeochemical cycles in the subalpine forest ecosystems on the eastern Tibetan Plateau.

Water-extractable organic matter in the profile of mineral and organic soils of Upper Dniester alluvial plane

Content of cold water extracted organic matter (CWEOM) in organic and mineral soils of Upperdniester alluvial plane was estimated. The largest CWEOM content (mg∙100 g-1) in the upper (10 cm) soil layers was found in peat soils – 105-135, and the smallest – 20-30– in arable sod and meadow soils. The highest CWEOM content was found in the lower horizons of peat soil, where it reaches 290 mg∙100 g-1. Strong correlation (r=0.81 -0.99; P<0.05) between CWEOM and TOC was found. It indicates the presence of dynamic equilibrium in the SOM system that supports certain level of labile pool compounds – the main source of bioavailable materials and energy.

Formation, reactivity and aging of amorphous ferric oxides in the presence of model and membrane bioreactor derived organics

Iron salts are routinely dosed in wastewater treatment as a means of achieving effluent phosphorous concentration goals. The iron oxides that result from addition of iron salts partake in various reactions, including reductive dissolution and phosphate adsorption. The reactivity of these oxides is controlled by the conditions of formation and the processes, such as aggregation, that lead to a reduction in accessible surface sites following formation. The presence of organic compounds is expected to significantly impact these processes in a number of ways. In this study, amorphous ferric oxide (AFO) reactivity and aging was investigated following the addition of ferric iron (Fe(III)) to three solution systems: two synthetic buffered systems, either containing no organic or containing alginate, and a supernatant system containing soluble microbial products (SMPs) sourced from a membrane bioreactor (MBR). Reactivity of the Fe(III) phases in these systems at various times (1–60 min) following Fe(III) addition was quantified by determining the rate constants for ascorbate-mediated reductive dissolution over short (5 min) and long (60 min) dissolution periods and for a range (0.5–10 mM) of ascorbate concentrations. AFO particle size was monitored using dynamic light scattering during the aging and dissolution periods. In the presence of alginate, AFO particles appeared to be stabilized against aggregation. However, aging in the alginate system was remarkably similar to the inorganic system where aging is associated with aggregation. An aging mechanism involving restructuring within the alginate-AFO assemblage was proposed. In the presence of SMPs, a greater diversity of Fe(III) phases was evident with both a small labile pool of organically complexed Fe(III) and a polydisperse population of stabilized AFO particles present. The prevalence of low molecular weight organic molecules facilitated stabilization of the Fe(III) oxyhydroxides formed but subsequent aging observed in the alginate system did not occur. The reactivity of the Fe(III) in the supernatant system was maintained with little loss in reactivity over at least 24 h. The capacity of SMPs to maintain high reactivity of AFO has important implications in a reactor where Fe(III) phases encounter alternating redox conditions due to sludge recirculation, creating a cycle of reductive dissolution, oxidation and precipitation.

A Tough Nut to Crack: Intracellular Detection and Quantification of Heme in Malaria Parasites by a Genetically Encoded Protein Sensor.

How free is heme? A fluorescent sensor has been used by Niles and co-workers to detect heme in P. falciparum. ECFP and EYFP were attached to its termini to give a FRET signal that was quenched by heme binding. The sensor was used to investigate alterations in the labile heme pool during the parasite's life cycle as well as under the influence of the drug chloroquine.

Cadmium Accumulation Risk in Vegetables and Rice in Southern China: Insights from Solid-Solution Partitioning and Plant Uptake Factor.

Solid-solution partitioning coefficient (Kd) and plant uptake factor (PUF) largely determine the solubility and mobility of soil Cd to food crops. A four-year regional investigation was conducted in contaminated vegetable and paddy fields of southern China to quantify the variability in Kd and PUF. The distributions of Kd and PUF characterizing transfers of Cd from soil to vegetable and rice are probabilistic in nature. Dynamics in soil pH and soil Zn greatly affected the variations of Kd. In addition to soil pH, soil organic matter had a major influence on PUF variations in vegetables. Heavy leaching of soil Mn caused a higher Cd accumulation in rice grain. Dietary ingestion of 85.5% of the locally produced vegetable and rice would have adverse health risks, with rice consumption contributing 97.2% of the risk. A probabilistic risk analysis based on derived transfer function reveals the amorphous Mn oxide content exerts a major influence on Cd accumulation in rice in pH conditions below 5.5. Risk estimation and field experiments show that to limit the Cd concentration in rice grains, soil management strategies should include improving the pH and soil Mn concentration to around 6.0 and 345 mg kg-1, respectively. Our work illustrates that re-establishing a balance in trace elements in soils' labile pool provides an effective risk-based approach for safer crop practices.

Identification, evolution and functional characterization of two Zn CDF-family transporters of the ectomycorrhizal fungus Suillus luteus.

Two genes, SlZnT1 and SlZnT2, encoding Cation Diffusion Facilitator (CDF) family transporters were isolated from Suillus luteus mycelium by genome walking. Both gene models are very similar and phylogenetic analysis indicates that they are most likely the result of a recent gene duplication event. Comparative sequence analysis of the deduced proteins predicts them to be Zn transporters. This function was confirmed by functional analysis in yeast for SlZnT1. SlZnT1 was able to restore growth of the highly Zn sensitive yeast mutant Δzrc1 and localized to the vacuolar membrane. Transformation of Δzrc1 yeast cells with SlZnT1 resulted in an increased accumulation of Zn compared to empty vector transformed Δzrc1 yeast cells and equals Zn accumulation in wild type yeast cells. We were not able to express functional SlZnT2 in yeast. In S. luteus, both SlZnT genes are constitutively expressed whatever the external Zn concentrations. A labile Zn pool was detected in the vacuoles of S. luteus free-living mycelium. Therefore we conclude that SlZnT1 is indispensable for maintenance of Zn homeostasis by transporting excess Zn into the vacuole.

Effects of snow removal on soil labile nitrogen in a subalpine spruce forest of western Sichuan, China

Warming-induced decrease in seasonal snow cover has a great potential to affect soil nitrogen cycle in alpine cold forest ecosystems. In this study, a wooden-shelter method was used to remove the snow accumulation. Soil nitrogen pools and mineralization rates in the snow removal and control plots were measured synchronously in three critical periods (early snow cover, deep snow cover and snow cover melting) in a subalpine spruce forest of western Sichuan, China. Seasonal snow cover kept soil from cold air temperature. Snow removal decreased average and minimum soil temperatures (5 cm) by 0.33 and 1.17 ℃, respectively. In addition, snow removal caused a positive effect on soil frost depth and freeze-thaw cycle. There was a significant dynamic in soil labile nitrogen pool among different periods. Snow removal on average increased NH4+-N, NO3--N and dissolved organic nitrogen (DON) contents by 38.6%, 23.5% and 57.3%, respectively, over the winter. Moreover, snow removal increased soil net nitrification and mineralization rates in the snow co-ver melting period. Overall, warming-induced decrease in snow cover could stimulate winter soil nitrogen cycle of subalpine forests.

Intracellular zinc flux causes reactive oxygen species mediated mitochondrial dysfunction leading to cell death in Leishmania donovani.

Leishmaniasis caused by Leishmania parasite is a global threat to public health and one of the most neglected tropical diseases. Therefore, the discovery of novel drug targets and effective drug is a major challenge and an important goal. Leishmania is an obligate intracellular parasite that alternates between sand fly and human host. To survive and establish infections, Leishmania parasites scavenge and internalize nutrients from the host. Nevertheless, host cells presents mechanism like nutrient restriction to inhibit microbial growth and control infection. Zinc is crucial for cellular growth and disruption in its homeostasis hinders growth and survival in many cells. However, little is known about the role of zinc in Leishmania growth and survival. In this study, the effect of zinc on the growth and survival of L.donovani was analyzed by both Zinc-depletion and Zinc-supplementation using Zinc-specific chelator N, N, N', N'–tetrakis (2-pyridylmethyl) ethylenediamine (TPEN) and Zinc Sulfate (ZnSO4). Treatment of parasites with TPEN rather than ZnSO4 had significantly affected the growth in a dose- and time-dependent manner. The pre-treatment of promastigotes with TPEN resulted into reduced host-parasite interaction as indicated by decreased association index. Zn depletion resulted into flux in intracellular labile Zn pool and increased in ROS generation correlated with decreased intracellular total thiol and retention of plasma membrane integrity without phosphatidylserine exposure in TPEN treated promastigotes. We also observed that TPEN-induced Zn depletion resulted into collapse of mitochondrial membrane potential which is associated with increase in cytosolic calcium and cytochrome-c. DNA fragmentation analysis showed increased DNA fragments in Zn-depleted cells. In summary, intracellular Zn depletion in the L. donovani promastigotes led to ROS-mediated caspase-independent mitochondrial dysfunction resulting into apoptosis-like cell death. Therefore, cellular zinc homeostasis in Leishmania can be explored for new drug targets and chemotherapeutics to control Leishmanial growth and disease progression.

Transformation kinetics of corn and clover residues in mineral substrates of different composition

Mineralization kinetics of corn and clover residues in quartz sand, loam, sand + 15% bentonite, and sand + 30% kaolinite have been studied. A scheme has been proposed for the transformation of plant residues in mineral substrates. Kinetic parameters of mineralization have been calculated with the use of a first-order two-term exponential polynomial. It has been shown that the share of labile organic carbon pool in the clover biomass is higher (57–63%) than in the corn biomass (47–49%), which is related to the biochemical composition of plant residues. The mineralization constants of clover residues generally significantly exceed those of corn because of the stronger stabilization of the decomposition products of corn residues. The turnover time of the labile clover pool (4–9 days) in all substrates and that of the labile corn pool (8–10 days) in sands and substrates containing kaolinites and bentonite are typical for organic acids, amino acids, and simple sugars. In the loamy substrate, the turnover time of labile corn pool is about 46 days due to the stronger stabilization of components of the labile pool containing large amounts of organic acids. The turnover time of the stable clover pool (0.95 years) is significantly lower than that of the stable corn pool (1.60 years) and largely corresponds to the turnover time of plant biomass.

Two‐stage metabolism inferred from diel oxygen dynamics in aquatic ecosystems

AbstractDynamics of dissolved oxygen in aquatic ecosystems reflect the biological, physical, and chemical processes that regulate ecosystem metabolism. Organic matter that supports ecosystem respiration (ER) is produced both by in situ photosynthesis and via loading from terrestrial ecosystems. Terrestrial‐derived organic matter is relatively recalcitrant and its availability is stable at diel time scales relative to substrates produced through photosynthesis, which are more labile and often show distinct diel changes in availability. Here, we explored whether the contributions of these two sources of organic matter to ecosystem metabolism could be quantified by a process model of photosynthesis and ER fit to high‐frequency observations of oxygen concentration in streams. We found that a two‐stage model of respiration provided a better fit to diel oxygen dynamics in most streams than a model assuming that the substrates supporting ER were one temporally stable pool. Two‐stage models estimated peak daytime respiration rates that were ~2.9× higher on average than nighttime rates, but this increase was variable and ranged from 1.1 to 11.6×. Estimates of gross primary production were 1.35× higher, on average, (range = 1.04–7.91×) compared to estimates generated by a single‐stage model. Streams draining watersheds with less than about 7% gradient exhibited oxygen dynamics that provided comparable statistical support for single‐stage metabolism, likely due to the higher loading of allochthonous organic matter that swamped metabolism based on autochthonous production in these streams. Ecosystem metabolism in streams draining steeper watersheds was best characterized by two‐stage metabolism, reflecting the greater importance of autochthonous contributions to labile organic carbon pools in these ecosystems.

Interactions of cisplatin and the copper transporter CTR1 in human colon cancer cells.

There is much interest in understanding the mechanisms by which platinum-based anticancer agents enter cells, and the copper transporter CTR1 has been the focus of many recent studies. While there is a clinical correlation between CTR1 levels and platinum efficacy, cellular studies have provided conflicting evidence relating to the relationship between cisplatin and CTR1. We report here our studies of the relationship between cisplatin and copper homeostasis in human colon cancer cells. While the accumulation of copper and platinum do not appear to compete with each other, we did observe that cisplatin perturbs CTR1 distribution within 10min, a far shorter incubation time than commonly employed in cellular studies of cisplatin. Furthermore, on these short time-scales, cisplatin caused an increase in the cytoplasmic labile copper pool. While the predominant focus of studies to date has been on CTR1, these studies highlight the importance of investigating the interaction of cisplatin with other copper proteins.

Cell death induced by mitochondrial complex I inhibition is mediated by Iron Regulatory Protein 1

Mitochondrial dysfunction and oxidative damage, often accompanied by elevated intracellular iron levels, are pathophysiological features in a number of neurodegenerative processes. The question arises as to whether iron dyshomeostasis is a consequence of mitochondrial dysfunction. Here we have evaluated the role of Iron Regulatory Protein 1 (IRP1) in the death of SH-SY5Y dopaminergic neuroblastoma cells subjected to mitochondria complex I inhibition. We found that complex I inhibition was associated with increased levels of transferrin receptor 1 (TfR1) and iron uptake transporter divalent metal transporter 1 (DMT1), and decreased levels of iron efflux transporter Ferroportin 1 (FPN1), together with increased 55Fe uptake activity and an increased cytoplasmic labile iron pool. Complex I inhibition also resulted in increased oxidative modifications and increased cysteine oxidation that were inhibited by the iron chelators desferoxamine, M30 and Q1. Silencing of IRP1 abolished the rotenone-induced increase in 55Fe uptake activity and it protected cells from death induced by complex I inhibition. IRP1 knockdown cells presented higher ferritin levels, a lower iron labile pool, increased resistance to cysteine oxidation and decreased oxidative modifications. These results support the concept that IRP1 is an oxidative stress biosensor that mediates iron accumulation and cell death when deregulated by mitochondrial dysfunction. IRP1 activation, secondary to mitochondrial dysfunction, may underlie the events leading to iron dyshomeostasis and neuronal death observed in neurodegenerative disorders with an iron accumulation component.

Why does carbon increase in highly weathered soil under no-till upon lime and gypsum use?

Field experiments have been used to explain how soil organic carbon (SOC) dynamics is affected by lime and gypsum applications, however, how SOC storage occurs is still debatable. We hypothesized that although many studies conclude that Ca-based soil amendments such as lime and gypsum may lead to SOC depletion due to the enhancement of microbial activity, the same does not occur under conservation agriculture conditions. Thus, the objective of this study was to elucidate the effects of lime and gypsum applications on soil microbial activity and SOC stocks in a no-till field and in a laboratory incubation study simulating no-till conditions. The field experiment was established in 1998 in a clayey Oxisol in southern Brazil following a completely randomized blocks design with a split-plot arrangement and three replications. Lime and gypsum were surface applied in 1998 and reapplied in 2013. Undisturbed soil samples were collected before the treatments reapplications, and one year after. The incubation experiment was carried out during 16months using these samples adding crop residues on the soil surface to simulate no-till field conditions. Lime and gypsum applications significantly increased the labile SOC stocks, microbial activity and soil fertility attributes in both field and laboratory experiments. Although the microbial activity was increased, no depletion of SOC stocks was observed in both experiments. Positive correlations were observed between microbial activity increase and SOC gains. Labile SOC and Ca2+ content increase leads to forming complex with mineral soil fractions. Gypsum applications performed a higher influence on labile SOC pools in the field than in the laboratory experiment, which may be related to the presence of active root system in the soil profile. We conclude that incubation experiments using lime and gypsum in undisturbed samples confirm that soil microbial activity increase does not deplete SOC stocks under conservation agriculture.

Soil biological properties and carbon dynamics subsequent to organic amendments addition in sodic black soils

ABSTRACTThe field experiments on calcareous sodic Vertisols were conducted on farmer’s fields in Purna valley of Vidarbha region of Maharashtra. The treatments comprised of different green manures (GMs); crop residues (CRs); gypsum. The chemical and biological properties after 2 years experiment showed that the application of gypsum recorded significant drop in pH and exchangeable sodium percentage (ESP) as compared to organic amendments. But later has outperformed with respect to biological activities viz., dehydrogenase activity (DHA) and microbial respiration and carbon sequestration by enhancing soil organic carbon (SOC), soil organic carbon (SOC) stock, soil microbial biomass carbon (SMBC) and labile carbon pool (POXC). Among the different organic amendments the application of dhaincha improved SMBC by 90%, microbial respiration by 104%, POXC by 59% and DHA by 265% as compare to control. High ESP of these soils showed negative relationship with microbial respiration and POXC (r = 0.48 and r = 0.43, p = < 0.05). While addition of biomass showed positive relationship with SMBC, microbial respiration, POXC and DHA (r = 0.93, r = 0.81, r = 0.83 and r = 0.91 p = < 0.01). The results of study showed green manuring in sodic black soil found to be alternative choice to gypsum, which besides gradual reclamation also enhance biological properties and carbon sequestration.

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.

Can Carbon Fluxes Explain Differences in Soil Organic Carbon Storage under Aspen and Conifer Forest Overstories?

Climate- and management-induced changes in tree species distributions are raising questions regarding tree species-specific effects on soil organic carbon (SOC) storage and stability. Quaking aspen (Populus tremuloides Michx.) is the most widespread tree species in North America, but fire exclusion often promotes the succession to conifer dominated forests. Aspen in the Western US have been found to store more SOC in the mineral soil than nearby conifers, but we do not yet fully understand the source of this differential SOC accumulation. We measured total SOC storage (0–50 cm), characterized stable and labile SOC pools, and quantified above- and belowground litter inputs and dissolved organic carbon (DOC) fluxes during snowmelt in plots located in N and S Utah, to elucidate the role of foliage vs. root detritus in SOC storage and stabilization in both ecosystems. While leaf litterfall was twice as high under aspen as under conifers, input of litter-derived DOC with snowmelt water was consistently higher under conifers. Fine root (&lt;2 mm) biomass, estimated root detritus input, and root-derived DOC fluxes were also higher under conifers. A strong positive relationship between root and light fraction C content suggests that root detritus mostly fueled the labile fraction of SOC. Overall, neither differences in above- and belowground detritus C inputs nor in detritus-derived DOC fluxes could explain the higher and more stable SOC pools under aspen. We hypothesize that root–microbe–soil interactions in the rhizosphere are more likely to drive these SOC pool differences.

Speciation and reactivity of lead and zinc in heavily and poorly contaminated soils: Stable isotope dilution, chemical extraction and model views

Correct characterization of metal speciation and reactivity is a prerequisite for the risk assessment and remedial activity management of contaminated soil. To better understand the intrinsic reactivity of Pb and Zn, nine heavily and poorly contaminated soils were investigated using the combined approaches of chemical extractions, multi-element stable isotopic dilution (ID) method, and multi-surface modelling. The ID results show that 0.1–38% of total Pb and 3–45% of total Zn in the studied soils are isotopically exchangeable after a 3-day equilibration. The intercomparison between experimental and modelling results evidences that single extraction with 0.43 M HNO3 solubilizes part of non-isotopically exchangeable fraction of Pb and Zn in the studied soils, and cannot be used as a surrogate for ID to assess labile Pb and Zn pools in soil. Both selective sequential extraction (SSE) and modelling reveal that Mn oxides are the predominant sorption surface for Pb in the studied soils; while Zn is predicted to be mainly associated with soil organic matter in the soil with low pH and Fe/Mn oxides in the soils with high pH. Multi-surface modelling can provide a reasonable prediction of Pb and Zn adsorption onto different soil constituents for the most of the studied soils. The modelling could be a promising tool to decipher the underlying mechanism that controls metal reactivity in soil, but the submodel for Mn oxides should be incorporated and the model parameters, especially for the 2-pK diffuse layer model for Mn oxides, should be updated in the further studies.

Effects of Hepcidin on Zinc Homeostasis in HepG2 cells

Hepcidin, a peptide hormone produced by theliver in response to iron loading and inflammation, regulates body iron storesby inhibiting iron transporter function. Recently, hepcidin was shown toinhibit zinc efflux in intestinal epithelial cells. The objective of this study was to determine whether hepcidin affects hepatic zinc homeostasis. Human HepG2cells were treated ± 1μM hepcidin for 24 h. Labile zinc pools were labeled with the zinc‐specific fluoroionophore FluoZin‐3‐AM (Kd 15 nM) and visualized and quantified using confocal microscopy and a fluorescent platereader. Expression of metallothionein, ZIP14, and ZnT1 was determined by Western blot. Intracellular zinc in control cells was localized to vesiclesdispersed throughout the cytoplasm; however, the number of vesicles and intensity of FluoZin‐3 fluorescence decreased by 38% in cells treated with hepcidin for 24 h (34.0 ± 11.3 and 21.0 ± 11.2 RFU/OD 562 nm; P&lt;0.05). Metallothionein expression increased in cells treated with hepcidin as compared to control cells(P&lt;0.05). ZIP14 expression remained unchanged (P&gt;0.05), whereas hepcidin increased ZnT1 expression (P&lt;0.05) as compared to control cells. These data suggest that hepcidin may affect zinc homeostasis in liver cells. Understanding the mechanism and role of hepcidin in zinc homeostasis may provide insight in to the hypozincemia associated with inflammation and infection.Support or Funding InformationThe views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government. Support provided by USAMRMC.

Tillage effects on labile pools of soil organic nitrogen in a semi-humid climate of Argentina: A long-term field study

Tillage systems strongly affect nitrogen (N) mineralization. However, there is still only limited information on the relationship between N in labile soil organic matter (SOM) fractions and crop N uptake under different tillage systems in areas with poor water availability. This study discusses the long-term effect of two tillage systems on i) the N-content in labile organic matter fractions and their relationship with the N mineralization potential at three depths (0–5; 0–10 and 0–20cm), ii) the factors that affect the N mineralization potential, and iii) the relationship between potentially mineralizable N (N0) and crop N uptake in a semi-humid climate. In a long-term experiment, a Typic Argiudoll was sampled under two contrasting tillage systems: no-tillage (NT) and conventional tillage (CT). The soil sampling was performed over four years of the crop sequence (2003, 2009, 2010 and 2011) when the plots were sown with winter wheat (Triticum aestivum L.). They were analyzed for N0 in the form of anaerobic N, soil organic nitrogen (SON), physically separated SOM fractions and crop N uptake. Higher values of SON and labile soil N fractions were observed under NT at all three depths. Significant differences in N0 were found between the tillage systems, with greater values under NT. Significant (P<0.05) and positive correlations between N0 and fine particulate organic carbon (fPOM-C) (r≥0.66) were found in CT and in NT at the three depths, whereas highly significant (P<0.001) and negative relationships between N0 and fine particulate organic N (fPOM-N) (r≥−0.83) were found under both tillage systems at 0–5 and 0–10cm. The most pronounced difference in these relationships between tillage systems was observed at the 0–5cm soil depth. Significant correlations of N0 with residue input from previous crops and the fallow period were observed under both tillage systems and for all three depths. Regarding the relationships between N0 and wheat N uptake, no significant correlations were found for any tillage system or depth. Soil organic N fractions were shown to be strongly influenced by the residue input from the previous crop and by variable weather conditions during the fallow period. The higher content of SON fractions under NT was associated with a higher N mineralization potential, however, it did not result in increased N availability and N uptake by wheat, because of climatic conditions during the crop growing season.