Zinc Availability Research Articles

Characterization of Global Gene Expression, Regulation of Metal Ions, and Infection Outcomes in Immune-Competent 129S6 Mouse Macrophages.

Nutritional immunity involves cellular and physiological responses to invading pathogens, such as limiting iron, increasing exposure to bactericidal copper, and altering zinc to restrict the growth of pathogens. Here, we examine infection of bone marrow-derived macrophages from 129S6/SvEvTac mice by Salmonella enterica serovar Typhimurium. The 129S6/SvEvTac mice possess a functional Slc11a1 (Nramp-1), a phagosomal transporter of divalent cations that plays an important role in modulating metal availability to the pathogen. We carried out global RNA sequencing upon treatment with live or heat-killed Salmonella at 2 h and 18 h postinfection and observed widespread changes in metal transport, metal-dependent genes, and metal homeostasis genes, suggesting significant remodeling of iron, copper, and zinc availability by host cells. Changes in host cell gene expression suggest infection increases cytosolic zinc while simultaneously limiting zinc within the phagosome. Using a genetically encoded sensor, we demonstrate that cytosolic labile zinc increases 45-fold at 12 h postinfection. Further, manipulation of zinc in the medium alters bacterial clearance and replication, with zinc depletion inhibiting both processes. Comparing the transcriptomic changes to published data on infection of C57BL/6 macrophages revealed notable differences in metal regulation and the global immune response. Our results reveal that 129S6 macrophages represent a distinct model system compared to C57BL/6 macrophages. Further, our results indicate that manipulation of zinc at the host-pathogen interface is more nuanced than that of iron or copper. The 129S6 macrophages leverage intricate means of manipulating zinc availability and distribution to limit the pathogen's access to zinc, while simultaneously ensuring sufficient zinc to support the immune response.

Zinc Complexes with 1,3-Diketones as Activators for Sulfur Vulcanization of Styrene-Butadiene Elastomer Filled with Carbon Black.

Zinc oxide nanoparticles (N-ZnO) and zinc complexes with 1,3-diketones of different structures were applied instead of microsized zinc oxide (M-ZnO) to activate the sulfur vulcanization of styrene-butadiene rubber (SBR). The influence of vulcanization activators on the cure characteristics of rubber compounds, as well as crosslink density and functional properties of SBR vulcanizates, such as tensile properties, hardness, damping behavior, thermal stability and resistance to thermo-oxidative aging was explored. Applying N-ZnO allowed to reduce the content of zinc by 40% compared to M-ZnO without detrimental influence on the cure characteristic and performance of SBR composites. The activity of zinc complexes in vulcanization seems to strongly depend on their structure, i.e., availability of zinc to react with curatives. The lower the steric hindrance of the substituents and thus the better the availability of zinc ions, the greater was the activity of the zinc complex and consequently the higher the crosslink density of the vulcanizates. Zinc complexes had no detrimental effect on the time and temperature of SBR vulcanization. Despite lower crosslink density, most vulcanizates with zinc complexes demonstrated similar or improved functional properties in comparison with SBR containing M-ZnO. Most importantly, zinc complexes allowed the content of zinc in SBR compounds to be reduced by approximately 90% compared to M-ZnO.

Molecular Insight into the Regulation of Vimentin by Cysteine Modifications and Zinc Binding.

The intermediate filament protein vimentin is involved in essential cellular processes, including cell division and stress responses, as well as in the pathophysiology of cancer, pathogen infection, and autoimmunity. The vimentin network undergoes marked reorganizations in response to oxidative stress, in which modifications of vimentin single cysteine residue, Cys328, play an important role, and is modulated by zinc availability. However, the molecular basis for this regulation is not fully understood. Here, we show that Cys328 displays a low pKa, supporting its reactivity, and is readily alkylated and oxidized in vitro. Moreover, combined oxidation and crosslinking assays and molecular dynamics simulations support that zinc ions interact with Cys328 in its thiolate form, whereas Glu329 and Asp331 stabilize zinc coordination. Vimentin oxidation can induce disulfide crosslinking, implying the close proximity of Cys328 from neighboring dimers in certain vimentin conformations, supported by our computational models. Notably, micromolar zinc concentrations prevent Cys328 alkylation, lipoxidation, and disulfide formation. Moreover, zinc selectively protects vimentin from crosslinking using short-spacer cysteine-reactive but not amine-reactive agents. These effects are not mimicked by magnesium, consistent with a lower number of magnesium ions hosted at the cysteine region, according to molecular dynamics simulations. Importantly, the region surrounding Cys328 is involved in interaction with several drugs targeting vimentin and is conserved in type III intermediate filaments, which include glial fibrillary acidic protein and desmin. Altogether, our results identify this region as a hot spot for zinc binding, which modulates Cys328 reactivity. Moreover, they provide a molecular standpoint for vimentin regulation through the interplay between cysteine modifications and zinc availability.

Regulation of zinc homeostatic genes by environmental pH in the filamentous fungus Aspergillus fumigatus.

Aspergillus fumigatus can grow over a broad range of pH values even though zinc availability is greatly conditioned by ambient pH. It has been previously shown that regulation of zinc homeostatic genes in this fungus relies on the transcription factor ZafA. In addition, their expression is further modulated by the transcription factor PacC depending on ambient pH, which allows this fungus to grow in diverse types of niches, including soils and the lungs of immunosuppressed hosts. In this work the regulation by PacC of genes zrfB and zrfC that are expressed, respectively, under acidic and alkaline zinc-limiting conditions have been analysed in detail. Thus, data that extend the current model for PacC function, including the role of the full-length PacC72 protein and the PacC processed forms (PacC53 and PacC27 ) on gene expression has been provided, and a new mechanism for the repression of acid-expressed genes in alkaline media based on interference with the start of transcription has been described. Moreover, it was proposed that the transcription of both acid-expressed and alkaline-expressed genes under zinc-limiting conditions might also rely on a third factor (putatively Pontin/Reptin), which may be required to integrate the action of PacC and ZafA into gene specific transcriptional responses.

Zinc and the Zinc Transporter SLC39A10/ZIP10 Are Required for Heme Synthesis in Developing Erythroid Progenitors

ObjectivesZinc is an essential nutrient for diverse biological processes in the body. Cellular zinc homeostasis is established through differential expressions of the transmembrane zinc transporter proteins, ZnTs and ZIPs. The aims of the current studies were to elucidate the roles of cellular zinc in erythrocyte maturation, and to determine the zinc transporters essential to erythroid zinc homeostasis. MethodsG1E-ER4 mouse cells were employed as an in vitro study model of terminal erythroid differentiation. A cell-impermeable zinc chelator, diethylenetriamine pentaacetate (DTPA), was used to limit extracellular zinc availability. For gene silencing, gene-specific siRNAs were introduced to cells via Nucleofection. Functional impacts of zinc and gene deficiency were assessed via ICP-MS-based metal quantitation, heme assays, and gene expression assays using RNA-seq, qPCR, and western analyses. ResultsG1E-ER4 cells featured a 1.7-fold increase in total cellular zinc contents after 48 h of differentiation. Restriction of zinc import by 50 μM of DTPA led to less red coloration and lower increases in mean corpuscular hemoglobin contents by development. The heme deficiency by DTPA was fully restored by the addition of equimolar zinc, and was not due to changes in cellular iron contents. Zinc-deficient G1E-ER4 cells differentiated with normal Alas2 and Hbb-b1 transcript responses, but less Alad and alpha-globin expressions. Among the 24 zinc transporter genes, Zip10 produced the most prominent response to zinc restriction in differentiating erythroid cells. ZIP10-deficient G1E-ER4 cells were less efficient than control cells in hemoglobin production under zinc restriction. ZIP10 deficiency alone had no effects on the molecular indices of red cell hemoglobinization. ConclusionsOur studies characterize zinc as a nutrient essential to normal erythroid maturation and heme synthesis. Moreover, we have identified a compensatory role of ZIP10 for erythroid zinc homeostasis during zinc restriction. Thus, poor zinc status and ZIP10 mutations might serve as potential risk factors and thus new therapeutic targets for anemia and other erythrocyte-related disorders. Funding SourcesSupported by CFANS Graduate Fellowship to JK, and the Allen Foundation, Inc. and USDA NIFA Hatch Funds to M-SR.

Visualizing the Dynamic Metalation State of New Delhi Metallo-β-lactamase-1 in Bacteria Using a Reversible Fluorescent Probe.

New Delhi metallo-β-lactamase (NDM) grants resistance to a broad spectrum of β-lactam antibiotics, including last-resort carbapenems, and is emerging as a global antibiotic resistance threat. Limited zinc availability adversely impacts the ability of NDM-1 to provide resistance, but a number of clinical variants have emerged that are more resistant to zinc scarcity (e.g., NDM-15). To provide a novel tool to better study metal ion sequestration in host-pathogen interactions, we describe the development of a fluorescent probe that reports on the dynamic metalation state of NDM within Escherichia coli. The thiol-containing probe selectively coordinates the dizinc metal cluster of NDM and results in a 17-fold increase in fluorescence intensity. Reversible binding enables competition and time-dependent studies that reveal fluorescence changes used to detect enzyme localization, substrate and inhibitor engagement, and changes to metalation state through the imaging of live E. coli using confocal microscopy. NDM-1 is shown to be susceptible to demetalation by intracellular and extracellular metal chelators in a live-cell model of zinc dyshomeostasis, whereas the NDM-15 metalation state is shown to be more resistant to zinc flux. The development of this reversible turn-on fluorescent probe for the metalation state of NDM provides a new tool for monitoring the impact of metal ion sequestration by host defense mechanisms and for detecting inhibitor-target engagement during the development of therapeutics to counter this resistance determinant.

Calprotectin-Mediated Zinc Chelation Inhibits Pseudomonas aeruginosa Protease Activity in Cystic Fibrosis Sputum.

Pseudomonas aeruginosa induces pathways indicative of low zinc availability in the cystic fibrosis (CF) lung environment. To learn more about P. aeruginosa zinc access in CF, we grew P. aeruginosa strain PAO1 directly in expectorated CF sputum. The P. aeruginosa Zur transcriptional repressor controls the response to low intracellular zinc, and we used the NanoString methodology to monitor levels of Zur-regulated transcripts, including those encoding a zincophore system, a zinc importer, and paralogs of zinc containing proteins that do not require zinc for activity. Zur-controlled transcripts were induced in sputum-grown P. aeruginosa compared to those grown in control cultures but not if the sputum was amended with zinc. Amendment of sputum with ferrous iron did not reduce expression of Zur-regulated genes. A reporter fusion to a Zur-regulated promoter had variable activity in P. aeruginosa grown in sputum from different donors, and this variation inversely correlated with sputum zinc concentrations. Recombinant human calprotectin (CP), a divalent-metal binding protein released by neutrophils, was sufficient to induce a zinc starvation response in P. aeruginosa grown in laboratory medium or zinc-amended CF sputum, indicating that CP is functional in the sputum environment. Zinc metalloproteases comprise a large fraction of secreted zinc-binding P. aeruginosa proteins. Here, we show that recombinant CP inhibited both LasB-mediated casein degradation and LasA-mediated lysis of Staphylococcus aureus, which was reversible with added zinc. These studies reveal the potential for CP-mediated zinc chelation to posttranslationally inhibit zinc metalloprotease activity and thereby affect the protease-dependent physiology and/or virulence of P. aeruginosa in the CF lung environment. IMPORTANCE The factors that contribute to worse outcomes in individuals with cystic fibrosis (CF) with chronic Pseudomonas aeruginosa infections are not well understood. Therefore, there is a need to understand environmental factors within the CF airway that contribute to P. aeruginosa colonization and infection. We demonstrate that growing bacteria in CF sputum induces a zinc starvation response that inversely correlates with sputum zinc levels. Additionally, both calprotectin and a chemical zinc chelator inhibit the proteolytic activities of LasA and LasB proteases, suggesting that extracellular zinc chelators can influence proteolytic activity and thus P. aeruginosa virulence and nutrient acquisition in vivo.

Cellular Mn/Zn Ratio Influences Phosphoglucomutase Activity and Capsule Production in Streptococcus pneumoniae D39.

Capsular polysaccharide (CPS) is a major virulence determinant for many human-pathogenic bacteria. Although the essential functional roles for CPS in bacterial virulence have been established, knowledge of how CPS production is regulated remains limited. Streptococcus pneumoniae (pneumococcus) CPS expression levels and overall thickness change in response to available oxygen and carbohydrate. These nutrients in addition to transition metal ions can vary significantly between host environmental niches and infection stage. Since the pneumococcus must modulate CPS expression among various host niches during disease progression, we examined the impact of the nutritional transition metal availability of manganese (Mn) and zinc (Zn) on CPS production. We demonstrate that increased Mn/Zn ratios increase CPS production via Mn-dependent activation of the phosphoglucomutase Pgm, an enzyme that functions at the branch point between glycolysis and the CPS biosynthetic pathway in a transcription-independent manner. Furthermore, we find that the downstream CPS protein CpsB, an Mn-dependent phosphatase, does not promote aberrant dephosphorylation of its target capsule-tyrosine kinase CpsD during Mn stress. Together, these data reveal a direct role for cellular Mn/Zn ratios in the regulation of CPS biosynthesis via the direct activation of Pgm. We propose a multilayer mechanism used by the pneumococcus in regulating CPS levels across various host niches. IMPORTANCE Evolving evidence strongly indicates that maintenance of metal homeostasis is essential for establishing colonization and continued growth of bacterial pathogens in the vertebrate host. In this study, we demonstrate the impact of cellular manganese/zinc (Mn/Zn) ratios on bacterial capsular polysaccharide (CPS) production, an important virulence determinant of many human-pathogenic bacteria, including Streptococcus pneumoniae. We show that higher Mn/Zn ratios increase CPS production via the Mn-dependent activation of the phosphoglucomutase Pgm, an enzyme that functions at the branch point between glycolysis and the CPS biosynthetic pathway. The findings provide a direct role for Mn/Zn homeostasis in the regulation of CPS expression levels and further support the ability of metal cations to act as important cellular signaling mediators in bacteria.

Trace Element Content in the Soils of the Forest-Steppe of Western Siberia

This research is based on local monitoring in 1994-2018 on reference plots of agricultural lands and materials of a large-scale agrochemical survey. The research examined the soils of the forest-steppe zone of the Omsk Region: ordinary chernozem low-power low-humus heavy loamy soil; meadow-chernozem medium-thick medium-humus heavy loamy soil; and solonetz meadow chernozemic deep low humus clay soil. It was found that almost the entire surveyed area of arable land in the forest-steppe zone of the Omsk Irtysh Land (98.1 %) had low mobile zinc availability with an average level of 0.85 mg/kg. 41.1% of arable land had low mobile manganese availability, 41.3% had medium and 17.6% had high availability; the weighted average was 13.0 mg/kg. Most of the arable land was characterized by a low degree of mobile copper content security (81.2%), while 18.3% of the land had soil with an average content, and only 0.5% of the land had high mobile copper content. The average concentration was 20.0 mg/kg. The soil levels of mobile molybdenum availability wereas follows: 71.6% of land had medium availability, 26.5% had high, and only 1.9% had low; the weighted average concentration was 0.20 mg/kg. All soils had a high degree of mobile forms of boron, while the weighted average was 2.69 mg/kg of soil. 67.8% of the area had low mobile cobalt availability, 31.6% had average availability, and 0.5 % had high availability, with an average concentration of 0.16 mg/kg in the zone. The reference plots did not differ in terms of their content of mobile zinc, copper, and cobalt, ordinary chernozems, meadow chernozem soils, and deep solonetz. Movable connections of molybdenum, manganese, and boron in ordinary chernozem were lower than in meadow chernozem soil, and the maximum ones were observed in solonetz meadow chernozemic deep.
 Keywords: trace elements, content, soil, survey, dynamics, Omsk region

Carbapenem Use Is Driving the Evolution of Imipenemase 1 Variants.

Metallo-β-lactamases (MBLs) are a growing clinical threat because they inactivate nearly all β-lactam-containing antibiotics, and there are no clinically available inhibitors. A significant number of variants have already emerged for each MBL subfamily. To understand the evolution of imipenemase (IMP) genes (blaIMP) and their clinical impact, 20 clinically derived IMP-1 like variants were obtained using site-directed mutagenesis and expressed in a uniform genetic background in Escherichia coli strain DH10B. Strains of IMP-1-like variants harboring S262G or V67F substitutions exhibited increased resistance toward carbapenems and decreased resistance toward ampicillin. Strains expressing IMP-78 (S262G/V67F) exhibited the largest changes in MIC values compared to IMP-1. In order to understand the molecular mechanisms of increased resistance, biochemical, biophysical, and molecular modeling studies were conducted to compare IMP-1, IMP-6 (S262G), IMP-10 (V67F), and IMP-78 (S262G/V67F). Finally, unlike most New Delhi metallo-β-lactamase (NDM) and Verona integron-encoded metallo-β-lactamase (VIM) variants, the IMP-1-like variants do not confer any additional survival advantage if zinc availability is limited. Therefore, the evolution of MBL subfamilies (i.e., IMP-6, -10, and -78) appears to be driven by different selective pressures.

Influence of zinc nutrition on zinc availability, uptake and crop yield of rainfed maize-pea sequence in Northwestern Himalaya

Field experiments were conducted during summer (kharif) and winter (rabi) seasons from 2014-2016 at the experimental farm of Hill Agricultural Research and Extension Center, Bajaura, Kullu to study the influence of zinc nutrition on its availability, uptake and crop yield of rainfed maize-pea sequence in Northwestern Himalaya. Different levels of zinc (Zn) priming (water soaking- without zinc, 1%, 2% and 3% ZnSO4), were applied to the seeds of maize and pea for three priming durations (4, 8 and 12 h). The outcomes were compared with the basal dose of recommended NPK + ZnSO4 @ 25 kg ha−1 and farmers’ practice (40% N of recommended dose of fertilizer + unprimed seed- control). The availability of Zn content in soil was significantly improved with the increasing levels of priming and its durations. The maximum available Zn content in soil was recorded from the application of ZnSO4 and minimum with water soaking- without zinc. The Zn uptake by pea pods, maize grains and stover of both crops was found maximum in priming with 2% ZnSO4 at the priming duration of 12 h. The yield of green peas and pea stover were maximum with 1% ZnSO4 at the priming duration of 12 h, however, maize grain and stover yield were highest with a treatment combination of 2% ZnSO4 with 12 h duration of seed priming. The results revealed the positive effect of ZnSO4 seed priming on zinc availability its uptake and crop yield at the different extent in rainfed maize-pea sequence. The seed priming to maize -pea sequence can be applied in nutrients deficient areas to improve crop yield and avoid severe health complications from Zn malnutrition.

Role of zinc in female reproduction.

Zinc is a critical component in a number of conserved processes that regulate female germ cell growth, fertility, and pregnancy. During follicle development, a sufficient intracellular concentration of zinc in the oocyte maintains meiotic arrest at prophase I until the germ cell is ready to undergo maturation. An adequate supply of zinc is necessary for the oocyte to form a fertilization-competent egg as dietary zinc deficiency or chelation of zinc disrupts maturation and reduces the oocyte quality. Following sperm fusion to the egg to initiate the acrosomal reaction, a quick release of zinc, known as the zinc spark, induces egg activation in addition to facilitating zona pellucida hardening and reducing sperm motility to prevent polyspermy. Symmetric division, proliferation, and differentiation of the preimplantation embryo rely on zinc availability, both during the oocyte development and post-fertilization. Further, the fetal contribution to the placenta, fetal limb growth, and neural tube development are hindered in females challenged with zinc deficiency during pregnancy. In this review, we discuss the role of zinc in germ cell development, fertilization, and pregnancy with a focus on recent studies in mammalian females. We further detail the fundamental zinc-mediated reproductive processes that have only been explored in non-mammalian species and speculate on the role of zinc in similar mechanisms of female mammals. The evidence collected over the last decade highlights the necessity of zinc for normal fertility and healthy pregnancy outcomes, which suggests zinc supplementation should be considered for reproductive age women at risk of zinc deficiency.

Zinc limitation in Klebsiella pneumoniae profiled by quantitative proteomics influences transcriptional regulation and cation transporter-associated capsule production

BackgroundMicrobial organisms encounter a variety of environmental conditions, including changes to metal ion availability. Metal ions play an important role in many biological processes for growth and survival. As such, microbes alter their cellular protein levels and secretion patterns in adaptation to a changing environment. This study focuses on Klebsiella pneumoniae, an opportunistic bacterium responsible for nosocomial infections. By using K. pneumoniae, we aim to determine how a nutrient-limited environment (e.g., zinc depletion) modulates the cellular proteome and secretome of the bacterium. By testing virulence in vitro, we provide novel insight into bacterial responses to limited environments in the presence of the host.ResultsAnalysis of intra- and extracellular changes identified 2380 proteins from the total cellular proteome (cell pellet) and 246 secreted proteins (supernatant). Specifically, HutC, a repressor of the histidine utilization operon, showed significantly increased abundance under zinc-replete conditions, which coincided with an expected reduction in expression of genes within the hut operon from our validating qRT-PCR analysis. Additionally, we characterized a putative cation transport regulator, ChaB that showed significantly higher abundance under zinc-replete vs. -limited conditions, suggesting a role in metal ion homeostasis. Phenotypic analysis of a chaB deletion strain demonstrated a reduction in capsule production, zinc-dependent growth and ion utilization, and reduced virulence when compared to the wild-type strain.ConclusionsThis is first study to comprehensively profile the impact of zinc availability on the proteome and secretome of K. pneumoniae and uncover a novel connection between zinc transport and capsule production in the bacterial system.

Cattle manure loadings and legacy effects on copper and zinc availability under rainfed and irrigated conditions

Long-term cattle manure applications build up nutrient pools and can lead to trace element enrichments in soils. The objectives of this study were to evaluate copper (Cu) and zinc (Zn) loadings in the soil during continuous annual cattle manure applications and determine the time required for soil to return to its pre-manure available Cu and Zn levels after manure is discontinued. The manure application rates were 0, 30, 60, and 90 Mg·ha−1 for rainfed and 0, 60, 120, and 180 Mg·ha−1 (wet weight) for irrigated plots. Although manure was applied for 45 yr in some plots, applications were terminated in one subset of treatments after 14 yr and in another subset after 30 yr to study legacy effects after 31 and 15 yr, respectively. Soil samples were collected in the fall of 2003, 2008, 2013, and 2018 and analyzed for available Cu and Zn. Crops were grown in all years continuously with Cu and Zn concentrations measured in both silage and grains harvested. The regression model developed using data collected suggests long legacy effects with recovery time to pre-manure levels ranging from 10 to 20 yr for Cu and 23 to 41 yr for Zn at irrigated and 10–24 for Cu and 21–32 yr for Zn under rainfed, respectively. Long-term applications of cattle manure could lead to accumulation of Cu and Zn, creating long-lasting legacy effects in soils with the increased environmental risk of leaching to groundwater.

Zrg1, a cryptococcal protein associated with regulation of growth in nutrient deprivation conditions

Cryptococcus gattii is one of the causes of cryptococcosis, a life-threatening disease generally characterized by pneumonia and/or meningitis. Zinc is an essential element for life, being required for the activity of many proteins with catalytic and structural roles. Here, we characterize ZRG1 (zinc-related gene 1), which codes a product involved in zinc metabolism. Transcriptional profiling revealed that zinc availability regulated the expression of ZRG1, and its null mutants demonstrated impaired growth in zinc- and nitrogen-limiting conditions. Moreover, zrg1 strains displayed alterations in the expression of the zinc homeostasis-related genes ZAP1 and ZIP1. Notably, cryptococcal cells lacking Zrg1 displayed upregulation of autophagy-like phenotypes. Despite no differences were detected in the classical virulence-associated traits; cryptococcal cells lacking ZRG1 displayed decreased capacity for survival inside macrophages and attenuated virulence in an invertebrate model. Together, these results indicate that ZRG1 plays an important role in proper zinc metabolism, and is necessary for cryptococcal fitness and virulence.

Plant Available Zinc Is Influenced by Landscape Position in the Amhara Region, Ethiopia

Zinc (Zn) is an important element determining the grain quality of staple food crops and deficient in many Ethiopian soils. However, farming systems are highly variable in Ethiopia due to different soil types and landscape cropping positions. Zinc availability and uptake by plants from soil and fertilizer sources are governed by the retention and release potential of the soil, usually termed as adsorption and desorption, respectively. The aim of this study was to characterize the amount of plant available Zn at different landscape positions. During the 2018/19 cropping season, adsorption-desorption studies were carried out on soil samples collected from on-farm trials conducted at Aba Gerima, Debre Mewi and Markuma in the Amhara Region. In all locations and landscape positions, adsorption and desorption increased with increasing Zn additions. The amount of adsorption and desorption was highly associated with the soil pH, the soil organic carbon concentration and cation exchange capacity, and these factors are linked to landscape positions. The Freundlich isotherm fitted very well to Zn adsorption (r2 0.87–0.99) and desorption (r2 0.92–0.99), while the Langmuir isotherm only fitted to Zn desorption (r2 0.70–0.93). Multiple regression models developed by determining the most influential soil parameters for Zn availability could be used to inform Zn fertilizer management strategies for different locations and landscape positions in this region, and thereby improve plant Zn use efficiency.

Steel mill waste effects on rice growth: comparison of chemical extractants on lead and zinc availability.

Zinc deficiency is widespread in cultivated soils, limiting the grain crop production and the adequate human nutrition. Several wastes from metallurgical activity can be used as Zn source, but these materials generally also have other potentially toxic elements, such as Pb, that can be highly toxic for plants and humans. This study aimed to evaluate the efficiency of five chemical extractors (water, citric acid, DTPA, Mehlich 1, and USEPA 3051A) in better correlating with the bioavailable contents of Zn and Pb in soils treated with steel mill wastes (metallurgic press residue (MPR), filter press mud (FPM), and phosphate mud (PM)). Rice plants were cultivated in pots with 4 kg of a Haplic Eutrophic Gleisol and steel mill wastes were applied in soil at increasing doses (0, 0.5, 1, 2, 4, 8, and 16 t ha-1). The availability of the potentially toxic elements Zn and Pb was assessed as total contents in rice shoots, grains, husks, and roots. The results showed that the USEPA 3051A method extracted greater contents of Zn and Pb from soil compared with other extractants. Due to their greater natural Pb and Zn contents, MPR and PM promoted higher contents of these elements in soils, respectively. Doses of PM influenced Zn contents in grains. After adding 16 t ha-1 of PM, Zn content in rice grains was 0.1 mg kg-1. However, at doses 0.5, 1, 2, and 4 t ha-1, the average concentration of Zn in the grains was 40 mg kg-1. The wastes MPR and FPM at 16 t ha-1 promoted Zn concentration in grains of 42 and 45 mg kg-1, respectively. The greatest contents of Pb in grains were found after addition of FPM at doses 0.5, 1, and 2 t ha-1: 6.67, 4.96, and 0.45 mg kg-1, respectively, and above 4 t ha-1 (4, 8, and 16 t ha-1); Pb content in grains was less than 0.3 mg kg-1. The content of Pb in roots at 16 t ha-1 of PM, MPR, and FPM was 18, 25, and 155 mg kg-1, respectively, and for Zn, under the same conditions, 100, 255, and 813 mg kg-1 for MPR, FPM, and PM, respectively. USEPA 3051A can be used to assess Pb and Zn available contents, and positive correlations with bioavailable contents of these elements in roots prove its feasibility. Further studies are necessary to state the safety of using steel mill application, including the use of other crop species, but PM is a promising waste for soil Zn fertilization.

The modulation effects of dietary zinc on reproductive performance and gonadotropins’ (FSH and LH) expression in threatened Asian catfish, Clarias magur (Hamilton, 1822) broodfish

The availability of zinc has been correlated with reproductive performance. To validate the hypothesis, a 60-day feeding trial was conducted to evaluate the effect of dietary zinc on reproductive performance and gonadotropin gene (FSH and LH) expression in threatened Clarias magur brooder. Four isonitrogenous (35%) and iso-energetic (372.18 ± 1.73 k cal/100 g) diets were prepared with zinc acetate as control (100 mg/kg diet normal requirement), T1 (50 mg/kg diet, low zinc), T2 (200 mg/kg diet, medium zinc) and T3 (300 mg/kg diet, high zinc). The weight gain % and specific growth rate were significantly (p < 0.05) decreased with the increased dietary zinc level. The pituitary mRNA levels of FSH were assessed during the reproductive cycle of female C. magur, and the FSH expression was increased which was significantly (p < 0.05) highest in T1 group. Similarly, LH expression was revealed to be highest. In all treatment groups except T1, GTH expression reduced significantly by increasing zinc inclusion in the diet. GSI and fecundity were lowest during initial sampling and start to increase was observed. The highest GSI and fecundity were recorded in the T1; however, GSI and fecundity significantly (p < 0.05) reduced with increasing the zinc level. Reproductive parameters like spawning fecundity, fertilization rate, hatching rate and larval survival were found to be dose-dependent of zinc. This revealed that 50 mg/kg zinc was optimum for enhanced reproductive performance; therefore, the present study proposed that 50 mg/kg of zinc could be supplemented for flexible enhanced reproductive performance in threatened Asian catfish, C. magur.

Effect of high dietary potassium chloride or potassium citrate on growth and zinc availability in rats

Effect of high dietary potassium chloride or potassium citrate on growth and zinc availability in rats

Improvement in paddy management: an assessment of copper and zinc concentration in paddy cultivated area

Copper and zinc play an essential part for paddy growth. This study was conducted to identify the amount of copper and zinc availability from three locations and compare the factors that contribute to the accumulation of copper and zinc in soil. Samples were collected from locations that were cultivated by paddy which was an industrial area, a roadside area and an urban area. The soil series that were taken from the industrial and roadside area were labelled as Kuala Kedah series and the urban area as urban series. The mean availability of copper at the industrial, roadside and urban area was 1.052 ppm, 0.905 ppm and 0.326 ppm respectively, whereas the mean availability of zinc at those sites was 1.258 ppm, 5.038 ppm and 1.705 ppm accordingly. The result showed that the content of copper and zinc in those areas were according to the standard and did not exceed the MAL of heavy metal in soil.