μM Zn Research Articles

N-Acetylcysteine as Modulator of the Essential Trace Elements Copper and Zinc.

N-acetylcysteine (NAC) is a frequently prescribed drug and known for its metal chelating capability. However, to date it is not well characterized whether NAC intake affects the homeostasis of essential trace elements. As a precursor of glutathione (GSH), NAC also has the potential to modulate the cellular redox homeostasis. Thus, we aimed to analyze effects of acute and chronic NAC treatment on the homeostasis of copper (Cu) and zinc (Zn) and on the activity of the redox-sensitive transcription factor Nrf2. Cells were exposed to 1 mM NAC and were co-treated with 50 μM Cu or Zn. We showed that NAC treatment reduced the cellular concentration of Zn and Cu. In addition, NAC inhibited the Zn-induced Nrf2 activation and limited the concomitant upregulation of cellular GSH concentrations. In contrast, mice chronically received NAC via drinking water (1 g NAC/100 mL). Cu and Zn concentrations were decreased in liver and spleen. In the duodenum, NQO1, TXNRD, and SOD activities were upregulated by NAC. All of them can be induced by Nrf2, thus indicating a putative Nrf2 activation. Overall, NAC modulates the homeostasis of Cu and Zn both in vitro and in vivo and accordingly affects the cellular redox balance.

The Evaluation of the Effects of Nanoemulsion Formulations Containing Boron and/or Zinc on the Wound Healing in Diabetic Rats.

Wound healing remains a challenging clinical problem, especially in the presence of diabetes. Diabetic patients have the impaired ability to fight infection and insufficient inflammatory response. The aim of this study was to evaluate the effects of boronophenylalanine (BFA) and/or Zn-containing nanoemulsion (NE) formulations on wound healing in diabetic rats. MTT and scratch assays were performed to evaluate the proliferative effects of BFA and/or Zn on human dermal fibroblast (HDF) cells and the migration of these cells, respectively. The BFA and/or Zn-NE were prepared, and the effects of NEs on wound healing in diabetic rats were evaluated by applying once a day for 14 days. MTT assay showed that 10 to 25 µM BFA and/or 50 µM Zn had very significant positive effects on cell proliferation. In the scratch assay, 10 µM BFA significantly increased the migration of HDF cell compared with control. The droplet sizes of all the NEs were <115 nm and their zeta potential values were in range of (-) 23.9 ± 2.356 to (-) 33.1 ± 1.438 mV. There was a significant reduction in the wound contraction values (%) of the groups treated with the BFA and/or Zn-NE on the 14th day compared with the untreated diabetic rats group. According to histopathological findings, wound healing was nearly complete in BFA and/or Zn-NE compared with untreated diabetic rats. Especially, the group treated with the NE containing the low concentration of BFA showed highly promising results in wound healing of diabetic rats within 14 days with complete epithelialization and the completely closed wound area.

The Expressions of Small Ubiquitin-like Modifier (SUMO) Related Genes Under Metal (Cu, Zn and Fe) Stress in Arabidopsis thaliana

Aim of this work was to investigate effects of Cu, Zn and Fe treatments on small ubiquitin-like modifier (SUMO) machinery of Arabidopsis thaliana. SUMO is a 100-115 amino acid post-translational modifier that can regulate stability, activity or sub-cellular localization of target proteins. A. thaliana plants were treated with 50 µM Cu, 700 µM Zn and 400 µM Fe for 7 d and then expressions of genes related to SUMOylation and deSUMOylation of target proteins were measured with qRT-PCR. Only Cu treatment was able to induce genes related to SUMOylation (SUM3, SAE2, SIZ1) of target proteins, while all of the three metal used in this study was effective in inducing a deSUMOylation related gene. Results of this study indicated that deSUMOylation of proteins might be a part of plant response to metal toxicity.

Direct inhibition of photosynthesis by Cd dominates over inhibition caused by micronutrient deficiency in the Cd/Zn hyperaccumulator Arabidopsis halleri

This work reveals, by imaging in vivo measurements in the Cd/Zn hyperaccumulator Arabidopsis halleri, in how far Cd stress affects macronutrient (Ca, K) and micronutrient (Fe, Zn) distribution in the leaves. We directly correlate these changes with biophysics of the photosynthetic light reactions. Plants were grown for 2 months at 10 μM Zn (=control), and supplemented with 10, 15, 50 or 75 μM Cd. Direct imaging of OJIP transients revealed that bundle sheath cells were more sensitive to Cd toxicity than mesophyll cells further from the vein. Progressive inhibition of photosystem (PS) II reaction centres and decrease in quantum yield of electron transport between QA and QB and further to PSI acceptors was observed. This was correlated with the decreased dynamics of QA re-oxidation and lower operating efficiency of PSII. Analysis by a benchtop micro X-ray fluorescence device showed that Cd mostly accumulated in the veins, and restricted Fe and Zn distribution from the veins, especially in the 75 μM Cd, while K concentration increased in the whole leaf. Calcium distribution was apparently not affected by Cd, but Cd excess inhibited trichome formation and thereby diminished total Ca concentration in the leaves. The results point to differential tissue sensitivity to Cd, evident by heterogeneous inhibition of photosynthesis. Part of this may be a result of selective disturbances in the leaf nutrient homeostasis. The better photosynthetic performance away from the veins compared to the bundle sheath cells, however, indicates that direct inhibition of photosynthesis by Cd dominates over inhibition caused by micronutrient deficiency.

Intra-specific variation in zinc, cadmium and nickel hypertolerance and hyperaccumulation capacities in Noccaea caerulescens

The study aimed at characterizing the patterns of natural variation in the tolerance and accumulation capacities for zinc (Zn), cadmium (Cd), and nickel (Ni) between and within edaphic ecotypes of the Zn/Cd/Ni hyperaccumulator, Noccaea caerulescens. Tolerance was assessed in a hydroponic ‘sequential exposure’ test, using the lowest concentration that completely arrested root growth as an end point. Accumulation was measured as the foliar metal concentration after six weeks of growth at 5 µM Zn, 2 µM Cd, or 1 µM Ni. Zn and Cd tolerance were positively correlated, and highest in the calamine ecotype. Ni tolerance was without significant ecotypic variation. The ultramafic ecotype was as Zn-tolerant as the non-metallicolous one, but much more sensitive to Cd. The accumulation capacities for Zn, Cd and Ni were all positively correlated and without significant ecotypic variation. Zn hyperaccumulation capacity was species-wide, but Cd and Ni hyperaccumulation capacities were lacking in four populations (all calamine). There is considerable independent variation among populations regarding their Zn, Cd, and Ni accumulation capacities. This variation is most pronounced within the calamine ecotype, because some populations apparently had adopted an exclusion strategy for Zn or Cd hypertolerance, whereas others had not.

Contribution of NtZIP1-like, NtZIP11 and a WAK-pectin based mechanism to the formation of Zn-related lesions in tobacco leaves

Previous studies on tobacco (Nicotiana tabacum var. Xanthi) have shown that in the presence of 200 μM Zn, lesions develop on the leaf blades from Zn accumulating mesophyll cells. This was interpreted as a tolerance mechanism against high Zn, protecting non-accumulating photosynthesizing cells. Underlying this phenomenon is the distinct capacity of mesophyll cells for Zn accumulation. To learn more about the involved mechanisms, here we searched for two key elements. First, for Zn transporters contributing to Zn accumulation in groups of mesophyll cells. Tissue-specific expression of two ZIP transporters previously identified in the leaves of tobacco plants exposed to high Zn was examined. Transgenic tobacco lines expressing GUS reporter gene under 2156 bp and 1922 bp of the promoter region of NtZIP1-like and NtZIP11, respectively, were used for analysis. Promoter activity of both genes in the leaves of high Zn-exposed plants was detected in groups of mesophyll cells, which correlates with the pattern of Zn accumulation. Second, we searched for putative components signalling the status of the cell wall. The WAKs/WAKLs and pectin fractions were the focus in the study, as it was known that upon binding pectin, WAK/WAKLs directly signals from the cell wall to the cytoplasm. Pectin microarray identified rhamnogalacturonan I (RG I) as the only pectin fraction that increased in the apoplast at high Zn (relative to control conditions), and immunocytochemistry demonstrated its presence in groups of cells. This was accompanied by increased expression of NtWAK2P-2 (putative NtWAK2), NtWAK4P-4, and NtWAK4P-2. Based on these data, a hypothesis was forwarded that RG I generated in the cell wall upon exposure to high Zn might bind to the extracellular domain of NtWAK2P-2, NtWAK4P-4, and/or NtWAK4P-2, which subsequently could transmit a signal on Zn status into the cytoplasm. It was also considered that regulation of NtZIP1-like and NtZIP11 expression by Zn availability might depend on the interaction between the RG I and/or NtWAK2P-2-, NtWAK4P-4, NtWAK4P-2.

Bionanopolymeric film for the electroanalytical detection of zinc, cadmium and lead ions

ABSTRACT An electrochemical gold nanoparticle sensor was developed for the detection of zinc, cadmium and lead ions, due to its electronic properties provided by the large surface/volume ratio and its easy surface modification. Linear ranges for Zn2+, Cd2+ and Pb2+ solutions were 0.469–3.051 µM, 3.968–68.970 µM and 7.937–137.900 µM, respectively. Sensitivity values were superior for electrode modified with chitosan, melamine and gold nanoparticles, and its microamperes/micromoles ratio were 5.7887 [µA/(µM)], 0.8915 [µA/(µM)] and 0.2221 [µA/(µM)], for Zn2+, Cd2+ and Pb2+ solutions, respectively. Synthetic sample solutions with concentrations higher than 1.481 µM Pb2+/L, 37.04 µM Cd2+/L and 74.07 µM Zn2+/L were analysed with high selectivity for the three ions in the mixed water samples. The results showed relevant enhancement of the electrochemical response signals for the ion-selective membrane sensor when the AuNPs added to the composite, a suitable resolution was reached leading to higher selectivity and better accuracy.

Differential Aquaporin Response to Distinct Effects of Two Zn Concentrations after Foliar Application in Pak Choi (Brassica rapa L.) Plants

Zinc (Zn) is considered an essential element with beneficial effects on plant cells; however, as a heavy metal, it may induce adverse effects on plants if its concentration exceeds a threshold. In this work, the effects of short-term and prolonged application of low (25 µM) and high (500 µM) Zn concentrations on pak choi (Brassica rapa L.) plants were evaluated. For this, two experiments were conducted. In the first, the effects of short-term (15 h) and partial foliar application were evaluated, and in the second a long-term (15 day) foliar application was applied. The results indicate that at short-term, Zn may induce a rapid hydraulic signal from the sprayed leaves to the roots, leading to changes in root hydraulic conductance but without effects on the whole-leaf gas exchange parameters. Root accumulation of Zn may prevent leaf damage. The role of different root and leaf aquaporin isoforms in the mediation of this signal is discussed, since significant variations in PIP1 and PIP2 gene expression were observed. In the second experiment, low Zn concentration had a beneficial effect on plant growth and specific aquaporin isoforms were differentially regulated at the transcriptional level in the roots. By contrast, the high Zn concentration had a detrimental effect on growth, with reductions in the root hydraulic conductance, leaf photosynthesis rate and Ca2+ uptake in the roots. The abundance of the PIP1 isoforms was significantly increased during this response. Therefore, a 25 µM Zn dose resulted in a positive effect in pak choi growth through an increased root hydraulic conductance.

CAN COPPER AND ZINC IN DIFFERENT CHEMICAL FORMS CAN IMPROVE IRON DEFICIENT IN PHASEOLUS PLANT

This study was aimed to compare between the effects of different chemical forms of Zn and cupper[ionic forms (CuSO4), (Zn SO4) and chelated forms of [Cu Zn (II) HEDTA and Cu (II) HEDTA], whereas, HEDTA is N-(hydroxyethyl) ethylenediamine triacetic acid, applied at micromolar concentrations in the nutrient solution] of Phaseolus Vulgaris plants grown hydroponically under conditions of iron deficiency (- Fe) were investigated. Plant variants (– Fe + 2 µM Cu2+) and (– Fe+ 20 µM Zn2+) with extremely strong chlorosis were examined for investigations to take after the recuperation of leaf greening after treatment with Cu(II)HEDTA created leaf greening in the two variations, particularly strong for the recently which created leaf, as it appeared with chlorophyll estimations. Changes of plasma membrane reductase movement (PMRA) in roots after treatment with ionic or chelated copper were followed in (+Fe) and (– Fe) plants. The results show the increment of ferric-chelate reductase action (with substrate of Fe (III) HEDTA). Then, the cupric-chelate Cu (II) HEDTA, connected at similar level in arrangements with (– Fe) plants, kept up the high encouragement of plasma membrane ferric-chelate reductase activity. It can be concluded that the treatment with Cu (II) HEDTA enhanced the development and root plasma membrane reductase activity (PMRA) and additionally iron deficiency reactions of phaseolus plants. Regard to cell compounds increase, measurements of 20 μM of Zn altogether developed the action of the protein superoxide dismutase and peroxidase.

The effect of silicon (Si) on the growth and nutritional status of Schizolobium amazonicum seedlings subjected to zinc toxicity

Zinc is an essential element to plants. However, excessive zinc levels can severely damage them. Schizolobium amazonicum is an Amazon native species that presents desirable features to remediate environments contaminated with heavy metals. Silicon has the beneficial effect of reducing the toxicity of different contaminants. The aim of the current study is to investigate the effect of Si on the growth and nutritional status of S. amazonicum seedlings subjected to zinc toxicity. The study followed a completely randomized design at 4 x 2 factorial arrangement based on four zinc (1, 150, 300 and 600 μM) and two silicon (0 and 1.5 mM) concentrations with five repetitions for 30 days. Increasing Zn concentrations in the nutrient solution reduced the growth of the plant and Ca, P, Mg, Fe, Mn and Cu contents in plant tissues, increased S concentrations and led to higher toxicity in the roots than shoot of S. amazonicum plants. Si addition to the nutrient solution increased plant growth and the absorption of the evaluated macro and micronutrients. Si increased plant tolerance level from 42.8 to 41.3% at 600 µM Zn, which suggested that this element mitigated the phytotoxic effects of the excess of zinc. Based on the tolerance index, the species presented medium and high tolerance to the evaluated zinc doses. Bioconcentration and translocation factors have indicated the low Zn-phytoextraction capacity of S. amazonicum and suggested that the species may be promising for Zn phytostabilization purposes.

Morpho-physiological and transcriptome analysis provide insights into the effects of zinc application on nitrogen accumulation and metabolism in wheat (Triticum aestivum L.)

Nitrogen (N) is the essential nutrient for wheat growth and development, its accumulation and metabolism controlled by many other elements. Zinc (Zn) is one of the important elements which tends to have effects on plant N homeostasis. Here in our study, 0 μM and 5 μM Zn was applied to the wheat seedlings culturing in 5 mM (+N) and 0.5 mM (-N) N treatments, respectively. The results showed that the shoot and root length growth performance, total N, NO3−, and amino acid concentrations, glutamine synthetase (GS) activity of wheat were facilitated by 5 μM Zn application under + N and –N conditions. Quantitative real-time PCR (qRT-PCR) analysis indicated that several NO3− transporters genes (TaNRT2.1, TaNPF7.1 and TaNPF7.2) and the genes encoding GS (TaGS1 and TaGS2) were induced by 5 μM Zn. In addition, transcriptional changes in wheat shoots and roots with Zn application were tested by RNA-seq techniques. A total of 147/551 induced and 36/2162 reduced differentially expression genes (DEGs) was detected in wheat shoots/roots, respectively. GO and KEGG enrichment analyses showed that 5 μM Zn mainly affected the glutathione (GSH) metabolism, phenylpropanoid biosynthesis and amino acid metabolism, involving in N homeostasis. Furthermore, the relative expression of genes related to phenylalanine, cysteine and methionine metabolism was induced by 5 μM Zn to promote the amino acid accumulation. Overall, these results highlight the facilitating of N accumulation by low level Zn, and provide an insight into the effects of Zn on N metabolism in wheat.

Interactive Effects of Zinc and Zilpaterol Hydrochloride on Bovine &amp;lt;i&amp;gt;β&amp;lt;/i&amp;gt;-Adrenergic Receptors

The objective of this study was to determine if the addition of zinc (Zn) in combination with zilpaterol HCL (ZH) affected the interaction of ZH with the beta2-adrenergic receptor (β-AR) by altering cAMP production, gene expression, and protein abundance in cultured skeletal muscle cells. Cultures of muscle bovine satellite cells were established and treated at 120 h with: 1) 0 μM Zn/zilpaterol hydrochloride (ZH; CON); 2) 0 μM Zn/10 μM ZH (ZH); 3) 1 μM Zn from Zn chloride/0 μM ZH (Zn); 4) 1 μM Zn from Zn chloride/10 μM ZH (ZN/ZH) in differentiation media for an additional 0, 6, 24, 48 and 96 h. Protein and mRNA were isolated and quantified at 24 and 96 h, and cAMP was measured at 0, 6, 24, 48 and 96 h. At 0, 24, 48 and 96 h, no differences (P > 0.05) were detected in cAMP production. At 6 h, Zn cells had the greatest concentration of cAMP (P P > 0.05) were detected in mRNA abundance at 24 h. At 96 h, 0 μM Zn/10 μM ZH cells had an increased abundance of myosin heavy chain (MHC)-I mRNA (P P P P > 0.05) were detected in the protein abundance of β1AR and the β2AR. These results indicated Zn and ZH in combination did not have an additive effect on β2-AR function as indicated by cAMP concentrations.

RUDERAL VERBASCUM OLYMPICUM BOISS.UN FOTOSENTETIK PIGMENT VE ANTIOKSIDATIF ENZIM AKTIVITESINDE YUKSEK KONSANTRASYONLARDA ÇINKONUN ETKISI

Verbascum olympicum Boiss. is dominated in disturbed areas of Uludağ Mountain/Turkey. It is a special species that is subject to phytoremediation due to its heavy metal accumulation, high biomass production and its ability to live in degraded areas. But, it is not known what its photosynthetic and antioxidative responses to high Zn concentrations that increased with anthropogenic activities such as mining, sewage sludge. Thus, in the present study we investigated photosynthetic pigments (chlorophyll a and b) and antioxidative enzymatic system of ruderal Verbascum olympicum grown in three different Zn levels (50, 250 and 500 µM) as zinc sulfate during 1, 3 and 10 days. The activity of antioxidative enzymes [superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX)] and photosynthetic pigment contents (chlorophyll a and b) was determined in the 8-week-old seedlings. Also, lipid peroxidation was measured as the amount of malondialdehyde (MDA) and, the cell membrane integrity and permeability was determined. Results were subjected to two-way ANOVA according to different Zn concentration treatments and exposed periods. It was determined an increase tendency up to 200 µM Zn treatment in antioxidative enzyme activities depending on increasing Zn concentrations and duration of exposure. This situation indicates that Verbascum olympicum has a strong antioxidative defense system for scavenging Zn-induced oxidative stress. But 500 µM Zn treatment had a destructive effect in photosynthetic pigment content and antioxidative enzymatic activities of V. olympicum. These results contribute to the understanding of survival success of Verbascum olympicum in degraded areas.

Visible cellular distribution of cadmium and zinc in the hyperaccumulator Arabidopsis halleri ssp. gemmifera determined by 2-D X-ray fluorescence imaging using high-energy synchrotron radiation.

The striking sub-cellular distribution of cadmium (Cd) and zinc (Zn) in the Cd and Zn hyperaccumulator Arabidopsis halleri ssp. gemmifera was revealed by microbeam X-ray microfluorescence analysis (μ-XRF) using high-energy synchrotron radiation. Plants were grown in hydroponics with various Cd and Zn concentrations. The concentration of Cd in the aerial portions of the plants increased with increasing Zn exposure and the transportation efficiency of Cd from the root to the shoot was affected by both the Cd and Zn concentrations in the nutrient solution. The μ-XRF imaging clearly showed that Cd and Zn were preferentially accumulated in trichomes on the leaf, while the distribution of Cd in the leaf was changed by Zn treatment. It was observed that Cd treated with a higher Zn concentration (20 μM Cd + 100 μM Zn) was distributed in the mesophyll tissue at high concentrations. In addition, μ-XRF imaging clarified that the distribution of Zn inside the leaf was different from that of Cd at a cellular level. Zn was primarily distributed in the mesophyll tissue of the leaf blade. In contrast, Cd was localized in the vascular bundle of the main vein. That is, Zn was transported to mesophyll tissue from the vascular bundle more efficiently than Cd. As seen above, we were able to study the difference of the distribution of Cd and Zn, which are congeners and behave similarly, inside the plant body at the cellular level in detail by high-energy μ-XRF.

Differential partitioning of thiols and glucosinolates between shoot and root in Chinese cabbage upon excess zinc exposure

Zinc (Zn) is one of the important elements of plant growth, however, at elevated level it is toxic. Exposure of Chinese cabbage to elevated Zn2+ concentrations (5 and 10 μM ZnCl2) resulted in enhancement of total sulfur and organic sulfur concentration. Transcript level of APS reductase (APR) as a key enzyme in biosynthesis of primary sulfur compounds (cysteine and thiols), was up-regulated in both shoot and root upon exposure to elevated Zn2+, which was accompanied by an increase in the concentration of cysteine in both tissues. In contrast, the concentration of thiols increased only in the root by 5.5 and 15-fold at 5 and 10 μM Zn2+, respectively, which was in accompanied by an upregulation of ATP sulfurylase, an enzyme responsible for activation of sulfate. An elevated content of glucosinolates, mostly indolic glucosinolates, only in the shoot of plants exposed to excess level of Zn2+ coincided with an increase in gene expression of key biosynthetic enzymes and regulators (CYP79B3, CYP83B1, MYB34). Thus distinct acuumulation patterns of sulfur containing compounds in root and shoot of Chinese cabbage may be a strategy for Chinese cabbage to combat with exposure to excess Zn.

Molecular characterization of ten zinc (Zn) transporter genes and their regulation to Zn metabolism in freshwater teleost yellow catfish Pelteobagrus fulvidraco

BackgroundZn is an essential trace element for vertebrates, and Zn uptake and transport is related with the ZIP family of Zn transporters. Meantime, Zn also influenced the expression of ZIP family members. MethodsWe cloned and characterized the full-length cDNA sequences of ten Zn transport-relevant genes (ZIP1, ZIP3, ZIP6, ZIP7, ZIP8, ZIP9, ZIP10, ZIP11, ZIP13 and ZIP14) from yellow catfish Pelteobagrus fulvidraco, investigated their mRNA tissue expression. These ZIP mRNA expression was also assessed in the primary hepatocytes and intestinal epithelial cells of yellow catfish in response to three Zn levels (0, 30 μM and 60 μM, respectively). ResultsAll these genes shared the similar domains with the corresponding members in mammals. The mRNA expression of the ten ZIP genes was detected in nine-tested tissues, but variable among these tissues. Flow cytometry analysis and confocal microscopy observation indicated that intracellular free Zn2+ concentration in hepatocytes and intestinal epithelial cells increased with increasing Zn incubation concentration at both 24 h and 48 h. Zn incubation differentially influenced mRNA levels of ZIP transporters in the hepatocytes and intestinal epithelial cells, in a time- and cells-dependent manners. In the hepatocytes, at 24 h, compared to the control, Zn addition down-regulated mRNA levels of ZIP1, ZIP3, ZIP6, ZIP7, ZIP8, ZIP9, ZIP11 and ZIP14; however, ZIP10 mRNA levels were lower in 60 μM Zn group than those in the control and 30 μM Zn group. At 48 h, mRNA levels of ZIP1, ZIP6, ZIP7, ZIP9, ZIP10 and ZIP14 declined with increasing Zn incubation concentrations; ZIP3 mRNA levels were the lowest in 60 μM Zn group and showed no significant differences between the control and 30 μM Zn group. In the intestinal epithelial cells, at 24 h, Zn addition down-regulated mRNA levels of ZIP1, ZIP6, ZIP7, ZIP8, ZIP9, ZIP10, ZIP11, ZIP13 and ZIP14; ZIP3 mRNA levels were lower in 60 μM Zn group than those in the control and 30 μM Zn group. At 48 h, Zn addition up-regulated mRNA levels of ZIP6 and ZIP9, but down-regulated mRNA levels of ZIP8, ZIP10 and ZIP13. ZIP7, ZIP11 and ZIP14 mRNA abundances were the lowest in 60 μM Zn group and showed no significant differences between the control and 30 μM Zn group. ConclusionFor the first time, our study characterized ten ZIP family members in yellow catfish, explored their mRNA tissue expression. Their regulation to Zn addition were also investigated in the hepatocytes and intestinal epithelial cells of yellow catfish. Our study revealed the mechanism of cells exposed to Zn addition and provided novel insights for the regulatory mechanism of Zn homeostasis.

Joining of AA 6061/Ti–6Al–4V with zinc interlayer using friction welding process

The formation of intermetallic phases consisting of intermetallic compounds during welding of aluminium/titanium joints is a challenge to the welding processes, in the last two decades. Friction welding is attempted to reduce the formation of intermetallic phases through inserting the interlayer material. In recent years, the number of approaches has been used to insert the interlayer material to avoid metallurgical phases at the weld interface. In this paper, the new technique of electrodeposited zinc coating on titanium substrate acted as an interlayer. Different welding joints were made by varying the interlayer thickness, and henceforth, the characterization is almost done against the mechanical and microstructure of the weld interface. The result shows that the specimen joint having 5 µm Zn interlayer has higher mechanical strength when compared to the specimen joints having 2 µm and 3 µm Zn interlayer. The results of the EDAX line scan concentration profile reveal that across the joint interface there is diffusion of the zinc interlayer into the aluminium zone. The microstructural investigation has been carried out at the joint interface of titanium and aluminium alloy with zinc as an interlayer. It is revealed that the formation of the thin interfacial reaction layer occurs in between the zinc and titanium zone. The intermetallic compounds are formed here in this region, and they are identified as secondary phases of the reaction between zinc and titanium.

24-Epibrassinolide Improves Root Anatomy and Antioxidant Enzymes in Soybean Plants Subjected to Zinc Stress

The aim of this research was to determine whether 24-epibrassinolide can mitigate oxidative stress in soybean plants subjected to different zinc levels; to examine this, we evaluated the possible repercussions on anatomical, nutritional, biochemical, physiological and morphological behaviours. The experiment followed a completely randomized factorial design with two concentrations of 24-epibrassinolide (0 and 100 nM EBR, described as - EBR and + EBR, respectively) and three zinc supplies (0.2, 20 and 2000 μM Zn, described as low, control and a high supply of Zn). In general, low and high zinc supplies produced deleterious effects. However, plants exposed to high zinc +100 nM EBR presented increases of 25%, 7%, 9% 29% and 69% for root epidermis, root endodermis, root cortex, vascular cylinder and metaxylem, respectively, when compared to the same treatment without the steroid. The steroid spray alleviated the impact produced by zinc stress on nutritional status, and these results were intrinsically linked to incremental changes in root structure, mainly vascular cylinder and metaxylem. Antioxidant enzymes play crucial roles in the photosynthetic machinery of plants treated with 24-epibrassinolide and stressed by high and low zinc supply, modulating reactive oxygen species scavenging and protecting the chloroplast membranes, with clear positive repercussions on photosystem II efficiency and photosynthetic pigments. The stimulation induced by this steroid on gas exchange can be explained by the favourable conditions detected in stomatal performance and leaf anatomy, thus enhancing the diffusion of carbon dioxide.

Zinc effects on cadmium toxicity in two wheat varieties (Triticum aestivum L.) differing in grain cadmium accumulation

Presence of cadmium (Cd) in food poses serious risks to human health. Understanding the effects of zinc (Zn) on Cd absorption by crops could help provide a theoretical basis for the treatment with Zn on contaminated soils. In this study, two wheat varieties, differing in grain-Cd accumulation ability (L979, a Cd low-accumulation variety, and H27, a high-accumulation variety) were selected to investigate the effect of Zn addition on Cd toxicity. Cd was applied to nutrient solutions at 0 and 10 μM, and added Zn were 0, 50 and 100 μM. Zn supplements alleviated decreases in biomass induced by Cd toxicity for both varieties, and both varieties had different reduced concentrations of Cd in their shoots. Application of 50 μM Zn to H27 resulted in a 17% decrease in Cd concentrations. When treated with 100 μM Zn, only L979 showed a reduction in Cd concentration. The higher proportion of Cd in the soluble fraction was found in L979. In addition, ion-selective scanning at the root-surface indicated that Zn supplements reduced net root Cd2+ flux by 55% for L979, and 69% for H27. These mitigating effects of Zn in both varieties involved mechanisms related to photosynthesis, root growth, and antioxidant production. Additionally, both Zn available in the medium and absorbed in plant tissue causes antagonistic effects on Cd absorption for wheat. It seemed that vacuolar compartmentation could contribute Cd detoxification especially for low accumulation variety.

Waterborne zinc induced lobe-dependent effect on oxidative stress and energy metabolism in hepatopancreas of Larimichthys crocea

The study aimed to compare differences in oxidative stress and energy metabolism between the left and right lobe of hepatopancreas in large yellow croaker Larimichthys crocea exposed to 0 (control), 20, and 100 μM Zn for 96 h. Tipical biomarkers were examined including the proportion of white hepatopancreas, lipid content, malondialdehyde (MDA) level, glutathione (GSH) content, activity levels of enzymes (Cu/Zn-superoxide dismutase, Cu/Zn-SOD; catalase, CAT; glutathione peroxidase, GPx; glutathione reductase, GR; mitochondrial ATP synthase, F-ATPase; malate dehydrogenase, MDH; succinate dehydrogenase, SDH; hepatic lipase, HTGL; lipoprotein lipase, LPL), mRNA levels of genes encoding these enzymes (sod1, cat, gpx1a, gr, atp5b, mdh, sdh, htgl, and lpl), and gene expression of signaling molecules the NF-E2-related nuclear factor 2 (nrf2) and Kelch-like ECH-associated protein 1 (keap1). A whitish color in the left lobe of hepatopancreas was observed in the control and Zn-exposed fish. Contrarily, the right lobe of hepatopancreas tended towards red with increasing Zn levels. The phenomenon was further confirmed by that lipid content was reduced in the right lobe and was not significantly affected in the left lobe by Zn. The right lobe showed higher energy consumption than the left lobe as reflected by the up-regulation of activity levels of HTGL, LPL, F-ATPase, MDH, and SDH. Lipid peroxidation declined by 20 μM Zn and was unchanged by 100 μM Zn in both lobes, which could be explained by increased activity levels of Cu/Zn-SOD and GPx. However, the magnitude of increase in Cu/Zn-SOD activity was greater in the right lobe than that in the left one. The difference in enzyme activity between two lobes may be involved in changes in mRNA levels of sod1, gr, atp5b, sdh, htgl, lpl, and nrf2, which was further confirmed by positive relationships between enzyme activity and gene expression. Our data also showed positive correlations between nrf2 expression and mRNA levels of its target genes, suggesting that Nrf2 was required for the protracted induction of these genes. Our results demonstrated the potential molecular mechanism of Zn-induced differences between lobes of hepatopancreas, suggesting that the sampling part of hepatopancreas should be considered with caution when assessing metal contamination.