High Levels Of Mn Research Articles

Variability and Site Dependence of Grain Mineral Contents in Tetraploid Wheats

Crop production and natural resource use, especially in developing countries, represents one of the most important food sources for humans. In particular, two wheat species (tetraploid, which is mostly used for pasta and hexaploid, which is primarily used for bread) account for about 20% of the whole calories consumed worldwide. In order to assess the mineral accumulation capability of some popular tetraploid wheat genotypes, a metabolomic (metallomic) approach was used in this study. The metallomic profile related to micro- (Zn, Fe, Cu, Mn, Ni and Cr), macro- (Ca, Mg and K) and toxic trace elements (Cd and Pb) was obtained by ICP-AES analysis in a large set of tetraploid wheat genotypes (Triticum turgidum L.) that were grown in two different experimental fields. Correlations and multivariate statistical analyses were performed, grouping the samples under two wheat sets, comprising cultivated durum cultivars (T. turgidum subsp. durum) and wild accessions (T. turgidum subsp. dicoccum and subsp. dicoccoides). The site dependence ranking for the selected genotypes with the highest nutrient accumulation was obtained. The significantly higher content of Mg (among the macronutrients) and the highest levels of Mn, Fe and Zn (among the micronutrients) were found for wild accessions with respect to durum cultivars. Moreover, the former genotypes were also the ones with the lowest level of accumulation of the trace toxic elements, in particular Cd. According to the performed statistical analyses, the wild accessions appeared also to be less influenced by the different environmental conditions. This is in accord with literature data, indicating the superiority of “old” with respect to modern wheat cultivars for mineral content. Although further studies are required on a wider range of genotypes to confirm these findings, the obtained results could be used to better select the less demanding and better performing cultivars in specific target wheat growing environments.

Vetiver grass is a potential candidate for phytoremediation of iron ore mine spoil dumps

Vetiver grass, Chrysopogon zizaniodes (L.) Roberty, is a perennial C4 grass, valued for its aromatic essential oil in the roots. Vetiver attracted global attention as a natural means for diverse environmental applications including detoxification of degraded soil and water. A pilot study was conducted to investigate its potential to rehabilitate iron ore spoil dumpsites generated from the Joda East Iron mine located in Odisha, India. Four diverse genotypes of vetiver: S2 (diploid variety), S4 (tetraploid derivative of S2), TH (originated from Thailand), BL (a broad leaf) were grown over a period of 12 months to observe their growth performance, metal tolerance and metal uptake. The shoot/root length, photosynthetic pigments – chlorophyll, carotenoid and biomass production of plants grown on iron mine soil decreased initially as compared to the control plants grown on garden soil. At the end of 12 month the plants showed evidence of normal growth and appeared healthy. Scanning electron microscopy (SEM) and Perl’s Prussian blue stain confirmed the uptake and localization of Fe in the roots and shoots of the plants grown on mine soil. In addition Zn, Mn, Cr and Cu, was detected in the plant tissues. Such accumulation of metals in plant tissues led to oxidative damage induced by reactive oxygen species (ROS). As a consequence the activities of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPOD), glutathione reductase (GR) and glutathione peroxidase (GPX) were increased. Based on the results it can be inferred that vetiver grass per se can tolerate high concentrations of Fe along with other heavy metals in its tissues. Such potential vary across the four genotypes, and the genotype BL followed by S4 can be claimed of paramount importance in terms of phytoremediation. Thus vetiver grass can be effectively used for rehabilitation and soil stabilization of sites contaminated with high levels of heavy metals, particularly Fe, Mn, Zn and Cr.

Strengthening from Cu Addition in 0.2C-(1-2)Mn Steels during Tempering.

The strengthening effects of Cu and Mn were studied in steels, which contained 0.2% C and were micro-alloyed with B and Ti. The experimental steels were austenitized and quenched in order to take Mn and Cu into solid solution. The subsequent tempering of martensitic structures resulted in higher strengths in the materials alloyed with Cu than in the steel without Cu addition. Tensile testing and metallographic analyses were performed. The kinetics and magnitude of precipitation strengthening were measured for different tempering temperatures and times. Presumed synergistic effects between Cu precipitation strengthening and higher levels of Mn were observed.

Butyrylcholinesterase-a potential plasma biomarker in manganese-induced neurobehavioral changes.

Groundwater particularly drinking water contamination with metals has created an environmental disaster in Bangladesh. Manganese (Mn), an essential trace element, plays a key role in the development and function of the brain. Excess Mn exposure is reported to be associated with complex neurological disorders. Here, we have found a notably large extent of Mn above the permissive limit in the tube-well water of Rajshahi and Naogaon districts in Bangladesh. Higher levels of Mn in hair and nail samples, and a decreasing level of butyrylcholinesterase (BChE) activity were detected in plasma samples of the human subjects recruited from Naogaon district. Mn concentrations in water, hair, and nails were negatively correlated with the plasma BChE levels in Mn-exposed populations. To compare and validate these human studies, an animal model was used to determine the in vivo effects of Mn on neurobehavioral changes and blood BChE levels. In elevated plus maze, the time spent was significantly reduced in open arms and increased in closed arms of Mn-exposed mice compared to control group. The mean latency time to find the platform was declined significantly in control mice compared to Mn-treated group during 7days in Morris water maze test, and Mn-exposed group also spent significantly less time in the desired quadrant as compared to the control group in probe trial. BChE activity was significantly reduced in Mn-exposed mice compared to control mice. Taken together, these results suggest that plasma BChE levels may serve as reliable biomarker of Mn-induced neurotoxicity related to behavioral changes.

Assessment of Physico-Chemical Parameters and Their Pollution Implications on the Major Dams in Ekiti State

The study was aimed at assessing the Physico-chemical parameters namely, temperature, electrical conductivity (EC), pH, turbidity, total alkalinity (TA), total hardness (TH), total dissolved solids (TDS), dissolved oxygen (DO2); total solids (TS), total suspended solids (TSS) colour, potassium, Zinc, Copper, total Iron, BOD, COD etc. in three dams in Ekiti State, South-West Nigeria. The seasonal variations in the physicochemical parameters of water of the dams were studied from November, 2017 to October, 2018. Water samples were collected from the dams on monthly basis and analyzed for 26 water physico-chemical parameters by using standard methods. The standards for the drinking water recommended by the Indian Council of Medical Research (ICMR), World Health Organization (WHO), Nigerian Industrial Standard (NIS), National Environmental Standards and Regulations Enforcement Agency (NESREA) and Bureau of Indian standards (BIS) were used in this study. The comparison of the physico-chemical parameters values with the standard values of WHO guidelines and other international standards revealed the high level of BOD, COD, turbidity, DO2, pH, colour, K, Fe, Mn, Cu, Zn, Pb and Cd in the water content. There were significant differences (p > 0.05) between the seasons (dry and wet) values of some of the physicochemical parameters in Egbe dam, Ureje dam and Ero dam. pH, DO2, TSS, EC, TDS and TS had higher values in the rainy season while Temperature, BOD, COD, NO3, Alkalinity, NO2 and PO4 had higher values during the dry season in the dams with few exemptions. The accumulation of these parameters in high values may render the dams’ water unsuitable for drinking. In this study, it was observed that most of the physico-chemical parameters except metals were higher in Ureje dam than Egbe dam and Ero dam. This might be due to population increase, indiscriminate dumping of refuse around the dam, urbanization, domestic effluents and other attendant problems of the State capital where the dam is located and thus indicate that Ureje dam was more contaminated than Egbe and Ero dams in terms of anthropogenic contamination. Conclusively, the water from Egbe, Ureje and Ero dams may support fish production but is not fit for domestic and drinking purpose without adequate treatment.

First records of metal concentrations in the Pacific oyster (Crassostrea gigas) from a Southwest Atlantic estuary.

The Pacific oyster (Crassostrea gigas) is one of the world's most widespread bivalves and a suitable species for biomonitoring metals in coastal environments. In the present research, wild individuals were collected from an Argentinian estuary and the coastal beaches nearby. The concentrations of eight metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn)were quantified in the soft tissues of the Pacific oyster. Among the metals, Cu, Fe and Zn reached the highest concentrations in the soft tissues over the rest of the elements. The results showed the highest values to be estuary related, with the beach site achieving the lowest values. These results possibly lie on the impact of human activities surrounding the estuary, as well as streams and rivers that outflow within it. Higher Cu and Zn levels, both port related, were mainly found toward the outer estuary. On the other hand, high levels of Cr, Fe and Mn were found toward the inner zone of the estuary, an area with sewage sludge from the cities located on the margins of the BBE. Regarding the potential risk to public health, Cu and Zn levels found in C. gigas were above national and international safety guidelines in 100% and 11% of the samples, respectively.

Correction: Bacterial diversity of bat guano from Cabalyorisa Cave, Mabini, Pangasinan, Philippines: A first report on the metagenome of Philippine bat guano.

[This corrects the article DOI: 10.1371/journal.pone.0200095.].

Metal/metalloid levels in urine and seminal plasma in relation to computer-aided sperm analysis motion parameters

BackgroundExposure to high levels of metals/metalloids may impair semen quality. Computer-aided sperm analysis (CASA) can be used for kinematic analysis of spermatozoa, which provides additional insights into sperm motion characteristics. ObjectiveTo explore the associations of urinary and seminal plasma metal/metalloid concentrations with CASA motion parameters and assess the degree of correspondence between the two sample types. MethodsEighteen metals/metalloids in seminal plasma and repeated urine samples were determined among 746 men recruited from a reproductive center. We assessed their associations with 6 CASA motion parameters [i.e., straight-line velocity (VSL), curvilinear velocity (VCL), average path velocity (VAP), linearity (LIN), straightness (STR) and amplitude head displacement (ALH)] using multivariable linear regression models. ResultsWe found significantly inverse dose-dependent relationships between seminal plasma arsenic (As) and VSL, VCL and VAP, between seminal plasma selenium (Se) and VSL and VAP, between seminal plasma zinc (Zn) and STR and LIN, and between seminal plasma manganese (Mn) and LIN in single-metal models [all false discovery rate (FDR) adjusted P for trend < 0.05]. These dose-response relationships remained statistically significant based on multiple-metal models and restricted cubic spline functions. Metal/metalloid concentrations in urine poorly predicted the same-day seminal plasma concentrations [coefficient of determination (R2) < 0.15]. We didn't find any significant associations between urinary metal/metalloid concentrations and the CASA motion parameters. ConclusionExposure to high levels of As, Se, Mn and Zn may impair sperm motion capacity. Concentrations of metals/metalloids in spot urine samples cannot accurately predict same-day seminal plasma exposure levels.

Morphophysiological responses and tolerance mechanisms of Xanthium strumarium to manganese stress

Effective phytoremediation of manganese (Mn) requires the careful selection of a species that has a relatively high manganese tolerance. Exploring the physiological mechanisms related to Mn stress responses is crucial for identifying and employing species for Mn phytoremediation. Xanthium strumarium is a species that can accumulate high levels of Mn, thus it is a candidate species for Mn-phytoremediation. To reveal the tolerance mechanisms of this species to manage Mn stress, the morphological, physiological, and biochemical responses of seedlings grown in water cultures under six different Mn concentrations were analyzed. The results showed that X. strumarium can accumulate high levels of Mn, even as plant growth was inhibited by rising Mn concentrations. Malondialdehyde (MDA) content increased and catalase (CAT) activity decreased along with the increased Mn concentrations, while soluble protein and proline content, as well as the superoxide dismutase (SOD) and peroxidase (POD) enzymes, all increased initially and then declined. The highest value of POD, SOD, soluble protein and proline all occurred at 5000 µM of Mn stress, which means that X. strumarium can adapt to low concentration of Mn stress. The net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci) and transpiration rate (Tr) decreased, and the stomatal limitation (Ls) increased in response to Mn stress. Furthermore, water use efficiency (WUE) and intrinsic water use efficiency (WUEi) increased first under low concentration of Mn, and then reduced as the concentration of Mn increased. The maximum quantum efficiency of PSII photochemistry (Fv/Fm), efficiency of excitation capture by open PSII reaction centers (Fv′/Fm′), electron transport rate (ETR) declined as Mn concentration increased. In conclusion, the above results showed that X. strumarium can be effectively used for phytoremediation of Mn-contaminated soils.

Use of CALPUFF to predict airborne Mn levels at schools in an urban area impacted by a nearby manganese alloy plant

Children are susceptible to the health effects derived from elevated manganese (Mn) environmental exposure; residents living in urban areas where ferromanganese alloy plants are located are usually exposed to high Mn levels. In this work, a dispersion model developed by the USEPA, CALPUFF, has been used to estimate the airborne Mn levels near educational centers located in Santander bay, Northern Spain, an urban area where high Mn levels have been measured in the last decade. The CALPUFF model was validated in a previous work from a multi-site one-year observation dataset. Air manganese levels in 96 primary, secondary and high schools located in Santander bay were estimated using the CALPUFF model for two months corresponding to warm and cold periods using real meteorological data and Mn emission rates corresponding to different emission scenarios. Results show that when the emission scenario that best represented the observations dataset is used, the air Mn levels exceed the WHO guideline (i.e. 150 ng Mn/m3) in 24% and 11% of the studied schools in the cold and warm periods respectively. These exceedances depend on the distance from the FeMn alloy plant and the direction of the prevailing winds. Additional emission scenarios based on the implementation of preventive and corrective measures are simulated and analysed in terms of the number of exceedances of the WHO guideline. The age range of children has been also considered in the analysis.

Manganese-mediated immobilization of arsenic by calcifying macro-algae, Chara braunii

The restoration capability of charophyte Chara braunii was studied in arsenic-polluted water in the context of biogenic calcium and manganese depositions on the plant. In addition to calcite encrustation, formation of craterlike shape deposits of manganese oxides (MnOx) with diameters of 5–10 μm was detected on the cell walls of the plants grown in Mn-rich media. Relative proportions of arsenic taken up by the plant biomass to those incorporated into the calcium and manganese biominerals were determined using a modified sequential chemical extraction method. The mean total arsenic recovery from water reached its highest value at 375 mg kg−1 in treatment with HCO3− and high concentrations of Ca and Mn (40 and 2 mg L−1, respectively). The percentage of arsenic associated with the manganese deposits in the plants exposed to 0.5 mg L−1 As(III) increased from 16.3% to 51.7% of the total arsenic accumulation at low and high Mn levels (<0.05 and 2 mg L−1, respectively), that accounted for the highest Mn-bound arsenic contribution. Surface oxidation of As(III) by MnOx and subsequent precipitation-adsorption of the formed As(V) onto the evolving structure of MnOx could be a plausible mechanism for arsenic removal. The presence, and in some cases dominance of arsenic bound to the biogenic Ca and Mn deposits on the studied aquatic plant may contribute to preservation of arsenic in sediments in a less bioavailable form upon its senescence and decomposition.

Bacterial diversity of bat guano from Cabalyorisa Cave, Mabini, Pangasinan, Philippines: A first report on the metagenome of Philippine bat guano.

Bats are highly diverse and ecologically valuable mammals. They serve as host to bacteria, viruses and fungi that are either beneficial or harmful to its colony as well as to other groups of cave organisms. The bacterial diversity of two bat guano samples, C1 and C2, from Cabalyorisa Cave, Mabini, Pangasinan, Philippines were investigated using 16S rRNA gene amplicon sequencing. V3-V4 hypervariable regions were amplified and then sequenced using Illumina MiSeq 250 PE system. Reads were processed using Mothur and QIIME pipelines and assigned 12,345 OTUs for C1 and 5,408 OTUs for C2. The most dominant OTUs in C1 belong to the Proteobacteria (61.7%), Actinobacteria (19.4%), Bacteroidetes (4.2%), Firmicutes (2.7%), Chloroflexi (2.5%), candidate phylum TM7 (2.3%) and Planctomycetes (1.9%) while Proteobacteria (61.7%) and Actinobacteria (34.9%) dominated C2. Large proportion of sequence reads mainly associated with unclassified bacteria indicated possible occurrence of novel bacteria in both samples. XRF spectrophotometric analyses of C1 and C2 guano revealed significant differences in the composition of both major and trace elements. C1 guano recorded high levels of Si, Fe, Mg, Al, Mn, Ti and Cu while C2 samples registered high concentrations of Ca, P, S, Zn and Cr. Community structure of the samples were compared with other published community profiling studies from Finland (SRR868695), Meghalaya, Northeast India (SRR1793374) and Maharashtra State, India (CGS). Core microbiome among samples were determined for comparison. Variations were observed among previously studied guano samples and the Cabalyorisa Cave samples were attributed to either bat sources or age of the guano. This is the first study on bacterial diversity of guano in the Philippines through high-throughput sequencing.

Competitive inhibition of cobalt uptake by zinc and manganese in a pacificProchlorococcusstrain: Insights into metal homeostasis in a streamlined oligotrophic cyanobacterium

AbstractIn order to satisfy metabolic requirements for growth, marine cyanobacteria such asProchlorococcusmust acquire cobalt from seawater and synthesize cobalamin cofactors. Through a series of experiments withProchlorococcusstrain MIT 9215 under cobalt limiting conditions, the mechanism ofProchlorococcus' cobalt uptake was investigated. Due to low quotas,ProchlorococcusMIT 9215 can maintain growth at extremely slow rates of cobalt uptake, circa 1 atom per cell per hour. Cobalt quotas were linearly related to the concentration of inorganic cobalt species, Co′, indicating that the metal binding sites on the transporter are strongly unsaturated with respect to cobalt. When limited by cobalt,Prochlorococcusgrowth rates decreased at high levels of both Zn and Mn, suggesting that both metals compete with cobalt for the same transporter. This effect was not observed under a wide range of Fe, Cu, and Ni concentrations, although the onset of exponential growth was delayed at high Ni. These observations agree with prior characterizations of the periplasmic manganese binding protein MntC, which is probably the main pathway for inorganic cobalt uptake and the locus for Mn and Zn competitive inhibition. The toxicity of zinc toward cobalt limitedProchlorococcusMIT 9215 contrasts with the observation of cobalt‐zinc substitution in eukaryotic phytoplankton and is expected to occur at environmentally relevant concentrations of free zinc and cobalt ions. Thus, the ecological success ofProchlorococcusin the modern ocean may depend on access to cobalt complexed by strong organic ligands that are not subject to competitive inhibition by other metals.

High waterborne Mg does not attenuate the toxic effects of Fe, Mn, and Ba on Na+ regulation of Amazonian armored catfish tamoatá (Hoplosternum litoralle).

Formation water (FoW) is a by-product from oil and gas production and usually has high concentrations of soluble salts and metals. Calcium (Ca) and magnesium (Mg) have been shown to reduce the toxicity of metals to aquatic animals, and previous study showed that high waterborne Ca exerts mild effect against disturbances on Na+ regulation in Amazonian armored catfish tamoatá (Hoplosternum littorale) acutely exposed to high Fe, Mn, and Ba levels. Here, we hypothesized that high Mg levels might also reduce the toxic effects of these metals on Na+ regulation of tamoatá. The exposure to 5% FoW promoted an increase in Na+ uptake and a rapid accumulation of Na+ in all tissues analyzed (kidney<plasma<gills<carcass<liver), besides increasing the branchial activity of both NKA and v-type H+-ATPase in fish. High waterborne Mg lowered Na+ efflux rates and markedly inhibited Na+ uptake, and also reduced both NKA activity and newly Na+ accumulation in gills of fish. High Fe levels increased Na+ net losses and inhibited Na+ uptake in tamoatá. The diffusive Na+ losses and the newly accumulated Na+ in gills were reduced in fish exposed to high Mn and Ba. High waterborne Ba also inhibited NKA in gills, while both high Mn and Ba inhibited v-type H+-ATPase in kidney of tamoatá. High Mg did not lessen the toxic effect of Fe on Na+ net fluxes, and reduced even more Na+ uptake and the newly Na+ accumulation in gills and plasma, and did not prevent the inhibition of both NKA and v-type H+-ATPases in kidney. Furthermore, Mg did not attenuate the effect of Mn on inhibition Na+ uptake, keeping the activity of v-type H+-ATPase in kidney significantly lowered. High Mg levels mildly attenuated the effects of Ba in Na+ balance by increasing the new accumulation of Na+ in liver, and restore the activity of both NKA and v-type H+-ATPase in gills of tamoatá. Overall, high waterborne Mg does not have a strong contribution to, or have only minor effects, in protecting tamoatá against disruptions in Na+ regulation mediated by high Fe, Mn, and Ba levels.

Involvement of gap junctions in astrocyte impairment induced by manganese exposure

Glutamate excitotoxicity, characterized as excessive glutamate stress, is considered to be involved in cerebral ischaemia, brain trauma, and neurodegenerative diseases such as Parkinson’s disease and Alzheimer's disease. Glutamate homeostasis disruption was highlighted in Mn neurotoxicity caused by high levels of Mn. Astrocytes, accounting for approximately 50% of the neuronal cells in the central nervous system and maintain glutamate homeostasis, are sensitive to neurotoxicity induced by Mn exposure. Astrocytes are tightly coupled with gap junctions (GJ), which are comprised of connexins, mainly connexin43 (Cx43). The gap junctional intercellular communication (GJIC) pathway allows small signal molecules, such as glutamate, ATP (adenosine triphosphate, ATP) and tropic factors, etc., to transfer between adjacent cells. Evidence has shown that astrocytes execute the bystander effect during cell death through the GJIC pathway. However, the pathogenic mechanism of the gap junction underlying glutamate neurotoxicity induced by manganese exposure has not been elucidated yet. In the present study, primary astrocytes were cultured and then exposed to different levels of Mn (ranging from 0 to 1000 μM) for 4/16 h to investigate the function of the GJIC in apoptosis induced by Mn. The cellular toxicity was confirmed by cell viability and apoptotic percentage through MTT assay and flow cytometry (FC). The levels of intracellular/extracellular glutamate were measured by high-performance liquid chromatography (HPLC). The fluorescent dye, Lucifer Yellow (LY), was used to assess the status of gap junctions among astrocytes after Mn exposure. The protein/gene expression of major gap junctional forming protein, Cx43, was also investigated. Cell viability was distinctly reduced when exposed to 500 and 1000 μM MnCl2 compared with control cells at both time points. The percentage of apoptosis was significantly increased among all detected Mn levels (125, 500 and 1000 μM MnCl2) of exposure (p < 0.05) with a concentration-dependent manner at either time point. Mn administration for 4/16 h also caused a remarkable intracellular/extracellular glutamate increase in a concentration-dependent manner for extracellular glutamate levels (p < 0.01). Gap junctions were prominently inhibited by Mn with Cx43 protein shown as shortening of the LY dye transfer distance at both time points. In-cell western blot indicated that Mn caused a decrease in Cx43 protein/gene expression in a dose-dependent manner. These results suggested that the gap junction intercellular communication and its forming protein, Cx43, are likely involved in glutamate excitotoxicity induced by Mn exposure.

Lithogenic and Anthropogenic Components in Surface Sediments from Lake Limboto as Shown by Magnetic Mineral Characteristics, Trace Metals, and REE Geochemistry

Lake Limboto is one of the major lakes in Sulawesi, Indonesia. It is currently undergoing serious degradation due to population pressure. As more residential areas have been established around the lake, the sedimentation rate has increased because of the contribution of anthropogenic particles. In this study, the lithogenic and anthropogenic components in surface sediments from 17 points in the lake were studied and identified using a combination of magnetic and geochemical analyses. The results showed that although the magnetic susceptibility values in R (residential) and NR (non-residential) areas were relatively similar, the values of saturation isothermal remanent magnetization (SIRM) as well as those of SIRM/χLF differed significantly, implying that the magnetic characteristics of the lithogenic component (in the NR area) differ from those of the anthropogenic component (in the R area). The discrepancy between the anthropogenic and lithogenic contributions was further supported by trace metals and rare earth element (REE) contents. Sediment samples in the R area contained higher levels of Mn, La, Pr, and Gd, while in the NR area they contained higher levels of Fe, Sc, Nd, and Ce. The magnetic susceptibility also correlated strongly with Fe, Cu, Zn, and Mn contents in the NR area. A similar correlation was not observed in the R area. The results above imply that a combination of magnetic and geochemical analyses can successfully differentiate lithogenic and anthropogenic components or contributions in lake sediments.

The Impact of Environmental Mn Exposure on Insect Biology.

Manganese (Mn) is an essential trace element that acts as a metal co-factor in diverse biochemical and cellular functions. However, chronic environmental exposure to high levels of Mn is a well-established risk factor for the etiology of severe, atypical parkinsonian syndrome (manganism) via its accumulation in the basal ganglia, pallidum, and striatum brain regions, which is often associated with abnormal dopamine, GABA, and glutamate neural signaling. Recent studies have indicated that chronic Mn exposure at levels that are below the risk for manganism can still cause behavioral, cognitive, and motor dysfunctions via poorly understood mechanisms at the molecular and cellular levels. Furthermore, in spite of significant advances in understanding Mn-induced behavioral and neuronal pathologies, available data are primarily for human and rodents. In contrast, the possible impact of environmental Mn exposure on brain functions and behavior of other animal species, especially insects and other invertebrates, remains mostly unknown both in the laboratory and natural habitats. Yet, the effects of environmental exposure to metals such as Mn on insect development, physiology, and behavior could also have major indirect impacts on human health via the long-term disruptions of food webs, as well as direct impact on the economy because of the important role insects play in crop pollination. Indeed, laboratory and field studies indicate that chronic exposures to metals such as Mn, even at levels that are below what is currently considered toxic, affect the dopaminergic signaling pathway in the insect brain, and have a major impact on the behavior of insects, including foraging activity of important pollinators such as the honey bee. Together, these studies highlight the need for a better understanding of the neuronal, molecular, and genetic processes that underlie the toxicity of Mn and other metal pollutants in diverse animal species, including insects.

Maternal second trimester blood levels of selected heavy metals in pregnancies complicated with neural tube defects

Purpose: Neural tube defects (NTDs) are the most common malformations of the central nervous system (CNS). There is continuing research for the identification of risk factors and interventions for prevention of NTDs. The aim of this study was to investigate the maternal second trimester blood levels of selected heavy metals namely, arsenic (As), cadmium (Cd), mercury (Hg), manganese (Mn), nickel (Ni), and lead (Pb) and their possible relation with the occurrence of NTDs.Methods: Twenty-one healthy second trimester pregnant women with fetuses affected with NTD (cases) were matched with 21 healthy pregnant women with unaffected fetuses (controls) with respect to age, body mass index (BMI), and gestational age. Maternal blood levels of heavy metals were measured after an overnight fasting period.Results: No significant differences were observed in terms of maternal blood levels of As, Cd, Hg, and Ni between NTD-affected and unaffected pregnancies. The blood Pb and Mn levels were found to be higher in pregnant women with a fetus affected with NTD when compared with pregnant women with unaffected fetuses (for Pb, in cases 12.3 ± 5.5 µg/L, in controls 7.8 ± 2.4 µg/L; for Mn in cases 3.6 ± 1.4 µg/L, in controls 2.4 ± 1.0 µg/L, p < .05).Conclusions: High maternal second trimester blood levels of Pb and Mn during pregnancy are associated with NTDs in the newborn.

Environmental manganese exposure and associations with memory, executive functions, and hyperactivity in Brazilian children

Manganese (Mn) is an essential element, however high levels of Mn have been associated with lower neuropsychological performance and behavioral problems in children. We investigated the associations between hair Mn concentrations and neuropsychological and behavioral performances among children with long-term exposure to airborne Mn aged between 7 and 12 years. Neuropsychological performance included tests of: verbal memory, inhibitory control, cognitive flexibility, verbal fluency, and motor function. We used the Conners Abbreviated Rating Scale for teachers to assess students’ behaviors of hyperactivity. Hair manganese (MnH) concentrations in children and exposure to airborne manganese from a ferro-manganese alloy plant were analyzed and correlated with tests scores. Multivariable linear models adjusting for potential confounders showed that elevated levels of MnH were associated with lower performance in verbal memory, as measured by the free recall after interference (β = – 1.8; 95% CI: – 3.4, – 0.2), which indicates susceptibility to interference, and Delayed Effect (β = –2.0; 95% CI: –3.7, – 0.2), representing a loss of information over time. Additionally, we found patterns of effect modification by sex in three subtests measuring verbal memory: the free recall after interference score, Interference Effect, and Delayed Effect (all at p < 0.10). Overall, the results suggest that long-term airborne Mn exposure may be associated with lower performance in verbal memory, and hyperactivity behaviors.

Variation in the Determination of Macronutrient Absorption by Micronutrients in Certain Stionic Combinations of Grape

Investigations were carried out through a survey of vineyards of Thompson Seedless and 2A clone on their own root and Dog Ridge rootstock to identify those micronutrients which have positive relationship with major nutrient absorption and the stionic combinations in which such relationship exists. Relationship of major nutrient absorption with micronutrient status was highly complex, which could be attributed to variation in their absorption due to their relative abundance, variety and rootstock, and interactions among them. Results of the investigations indicated that none of the micronutrients could influence the absorption of N in any stionic combination. Fe, Mn, Zn and Cu together determined the absorption of Na highest in 2A clone on Dog Ridge rootstock, followed by the determination of P and S in Thompson Seedless on Dog Ridge. Mn contributed most towards the determination of P, K, Ca, Mg, S and Na across the stionic combinations. P absorption increased with higher levels of Mn and Cu respectively above 66.0 and 111.9 ppm, but decreased above 121.1 ppm of Zn in TS/DR. It increased with increasing levels of Mn above 129.8 ppm in 2A/OR and Zn levels above 121.2 ppm in 2A/DR. Higher levels of petiole Cu above 105.4 ppm and of Mn below 435.9 ppm increased K absorption in TS/DR. Levels of Mn above 210.2 ppm in 2A/OR, of Cu above 155.6 ppm and Mn at any level in 2A/DR were also associated with higher absorption of K. Calcium absorption increased with Fe levels above 116.7 ppm and Mn levels above 106.3 ppm in TS/OR. The increase in Ca absorption was limited to 466.7 and 500 ppm respectively of Fe and Mn in 2A/DR. Fe levels above 100 ppm resulted in increased Ca absorption in 2A/OR. Increased Mg absorption was associated with petiole Zn levels above 65.2 ppm in TS/OR, with any level of Mn and Zn levels up to 96.7 ppm in 2A/OR. It also increased with Zn levels above 112.9 ppm, but Mn levels up to 650 ppm in 2A/DR. Sulphur absorption increased with increasing contents of petiole Mn to any level and Cu levels above 149.3 ppm, but its increase was limited to 118.8 ppm of Zn in 2A/OR. Reduced absorption of Na was associated with increasing levels of Mn above 209.6 ppm in TS/OR, and with increasing levels of Fe, Mn and Zn respectively above 63.6, 257.1 and 117.1 ppm in 2A/OR. Increasing levels of Fe an Mn respectively above 516.6 and 380.8 ppm, but Zn levels below 66.7 ppm also reduced Na absorption in 2A/DR. Management of micronutrient levels above their threshold levels and below optimum levels corresponding to major nutrient absorption could help in increased absorption of P, K, Ca, Mg and S but reduced absorption of Na in different stionic combinations.