The role of chemical speciation,chemical fractionation and calcium disruption in manganese-induced developmental toxicity in zebrafish (Danio rerio) embryos

Manganese (Mn) is an essential nutrient that can be toxic in excess concentrations, especially during early development stages. The mechanisms of Mn toxicity is still unclear, and little information is available regarding the role of Mn speciation and fractionation in toxicology. We aimed to investigate the toxic effects of several chemical forms of Mn in embryos of Danio rerio exposed during different development stages, between 2 and 122 h post fertilization. We found a stage-specific increase of lethality associated with hatching and removal of the chorion. Mn(II), ([Mn(H₂O)₆]²⁺) appeared to be the most toxic species to embryos exposed for 48 h, and Mn(II) citrate was most toxic to embryos exposed for 72 and/or 120 h. Manganese toxicity was associated with calcium disruption, manganese speciation and metal fractionation, including bioaccumulation in tissue, granule fractions, organelles and denaturated proteins.     

Influence of manganese deficiency and toxicity on isoprenoid syntheses

Twenty-eight day old wheat (Triticum aestivum L. cv Stacy) response to varying Mn concentration (10.1-10,000 micromolar) in nutrient solution was measured. Manganese concentrations in the most recently matured leaves (blade 1) were 0.21 to 19.03 mmol Mn per kilogram dry weight, respectively. Fresh and dry weights increased to a maximum at the 5 micromolar Mn nutritional level (0.37 millimole Mn per kilogram dry weight) and were decreased at Mn above and below this concentration. Blade 1 chloroplast pigment concentrations increased up to the 20 micromolar Mn nutritional level (1.98 millimole Mn per kilogram dry weight) and decreased at higher Mn concentrations. Thylakoid Mn content was above 1 mole Mn/100 mole chloroplast at Mn nutrition levels which resulted in greatly decreased plant growth. Total phytoene biosynthesis was decreased by Mn deficiency and toxicity. In vitro ent- kaurene synthesis was greatly influenced by Mn concentration with a maximal biosynthesis at 1 micromolar Mn and decreases at Mn levels above and below this concentration. In vivo blade 1 gibberellic acid equivalent concentrations were maximal at 20 parts per million Mn nutrition solution levels (1.98 millimole Mn per kilogram dry weight) and decreased at Mn tissue concentrations above and below this value; additionally, gibberellic acid concentrations were reciprocal to extracted C₂₀ alcohol concentrations. Mn influence on gibberellin and chloroplast pigment biosyntheses exactly matched the measured changes in growth.     

Predation behavior of Podisus nigrispinus on Spodoptera eridania

The behavior and effective predation time can affect the prey death in pest biological control programs. This work studied the Podisus nigrispinus (Dallas, 1851) (Heteroptera: Pentatomidae) behavior on Spodoptera eridania (Cramer, 1782) (Lepidoptera: Noctuidae) caterpillars, and its implications in case of prey escape. The preference bioassay (B1) aimed to verify the caterpillars body region (anterior: head and thorax; median and posterior) preferred by the predator and its implication in prey mortality. The predation duration bioassay considered the following effective predation times: 1, 2, 4, 8, 16, 32, 64 and 128 min; the caterpillars were removed after each predation time, to simulate prey escape, and the dead were counted until the seventh day. This experiment was performed in two ways: with randomly selected and not repeated predators (B2); and with the same predators in successive times (B3). The predator preferred to attack the caterpillars anterior region. The caterpillars mortality increased with increasing effective predation time. The mortality was 90% after 64 min under B2. This value was estimated for 16 min under B3. The P. nigrispinus prefers to attack the caterpillars anterior region and mortality of S. eridania caterpillars was favored in predators that have suffered predation interruption.     

Effects of sodium, potassium and calcium on salt-stressed barley

We grew barley ( Hordeum vulgare L. CM 72) for a 28-day period and sequentially harvested plants every 3 or 4 days. Plants were salt-stressed with either NaCl or KCl (125 m M ) with or without supplemental Ca (10 or 0.4 m M final concentration, respectively). We determined tissue concentrations of Na, Ca, Mg, K. S, P, Fe, Mn, Cu and Zn for each harvest date by inductively coupled plasma spectrometry. Uptake (specific absorption rate) was calculated from the element content and growth rates. Salinity had significant effects on the uptake and concentrations of most elements. Mg and Mn concentrations declined with time. The concentrations of all other elements determined increased over time. Element uptake on a root dry weight basis declined with time. Three variables were significantly affected by salinity and correlated with growth; 1) the Ca concentration, 2) the total sum of the cation concentration (TC), and 3) the Mn concentration of the shoot. Salinity reduced Ca uptake and concentrations. Supplemental Ca increased Ca concentrations and was positively correlated with growth during salt stress. Salinity doubled TC, which was negatively correlated with relative growth rate (RGR). Relative growth rate declined at TC values above 150 m M . Salinity reduced the uptake and concentration of Mn. Manganese concentrations in the shoot were highly correlated with RGR. Relative growth rate declined at Mn concentrations below 50 nmol (g fresh weight)⁻¹.     

Aluminium alleviates manganese toxicity to rice by decreasing root symplastic Mn uptake and reducing availability to shoots of Mn stored in roots

Background and Aims Manganese (Mn) and aluminium (Al) phytotoxicities occur mainly in acid soils. In some plant species, Al alleviates Mn toxicity, but the mechanisms underlying this effect are obscure.Methods Rice (Oryza sativa) seedlings (11 d old) were grown in nutrient solution containing different concentrations of Mn²⁺ and Al³⁺ in short-term (24 h) and long-term (3 weeks) treatments. Measurements were taken of root symplastic sap, root Mn plaques, cell membrane electrical surface potential and Mn activity, root morphology and plant growth.Key Results In the 3-week treatment, addition of Al resulted in increased root and shoot dry weight for plants under toxic levels of Mn. This was associated with decreased Mn concentration in the shoots and increased Mn concentration in the roots. In the 24-h treatment, addition of Al resulted in decreased Mn accumulation in the root symplasts and in the shoots. This was attributed to higher cell membrane surface electrical potential and lower Mn²⁺ activity at the cell membrane surface. The increased Mn accumulation in roots from the 3-week treatment was attributed to the formation of Mn plaques, which were probably related to the Al-induced increase in root aerenchyma.Conclusions The results show that Al alleviated Mn toxicity in rice, and this could be attributed to decreased shoot Mn accumulation resulting from an Al-induced decrease in root symplastic Mn uptake. The decrease in root symplastic Mn uptake resulted from an Al-induced change in cell membrane potential. In addition, Al increased Mn plaques in the roots and changed the binding properties of the cell wall, resulting in accumulation of non-available Mn in roots.     

Role of leaf apoplast in silicon-mediated manganese tolerance of Cucumis sativus L.

Silicon (Si) supplied as sodium silicate (1·8 mm ) clearly decreased symptoms of manganese (Mn) toxicity in Cucumis sativus L. (cv. Chinesische Schlange) grown in nutrient solution with low to elevated Mn concentrations (0·5–1000 µm ). Despite approximately the same total Mn content in the leaves, plants not treated with Si had higher Mn concentrations in the intercellular washing fluid (IWF) compared with plants treated with Si, especially in the BaCl₂‐ and DTPA‐exchangeable fraction of the leaf apoplast. The Mn concentration of the IWF correlated positively with the severity of Mn‐toxicity symptoms and negatively with the Si supply. Furthermore, in Si‐treated plants less Mn was located in the symplast (< 10%) and more Mn was bound to the cell wall (> 90%) compared with non‐Si‐treated plants (about 50% in each compartment). Manganese present in Si‐treated plants is therefore less available and for this reason less toxic than in plants not treated with Si. It is concluded that Si‐mediated tolerance of Mn in C. sativus is a consequence of stronger binding of Mn to cell walls and a lowering of Mn concentration within the symplast. These results support the role of Si as an important beneficial element in plant nutrition.     

Manganese exposure alters the expression of N‐methyl‐d‐aspartate receptor subunit mRNAs and proteins in rat striatum

Manganese is one of the ubiquitous environmental pollutants that can induce an indirect excitotoxicity caused by altered glutamate (Glu) metabolism. The present study has been carried out to investigate the effect of Mn on the expression of N‐methyl‐d ‐aspartate receptor (NR) subunit mRNAs and proteins in rat striatum when rats were in manganism. The rats were divided randomly into four groups of six males and six females each: control group (group 1) and 8, 40, and 200 μmol/kg Mn‐treated groups (groups 2–4). The control group rats were subcutaneously (s.c.) injected with normal saline. Manganese‐treated rats were s.c. injected with respectively 8, 40, and 200 μmol/kg of MnCl₂ · 6H₂O in normal saline. The administration of MnCl₂ · 6H₂O for 4 weeks significantly increased Mn concentration in the striatum. With the increase in administered MnCl₂ dosage, Glu concentration and cell apoptosis rate increased significantly. The relative intensity of NR2A mRNA decreased significantly in 8 μmol/kg Mn‐treated rats. However, relative intensities of NR1 and NR2B mRNAs decreased significantly in 40 μmol/kg Mn‐treated rats. Similarly, the relative intensity of NR2A protein showed a significant decrease in 40 μmol/kg Mn‐treated rats whereas those of NR1 and NR2B decreased significantly in 200 μmol/kg Mn‐treated rats. Therefore, the expression of NR2A mRNA and protein were much more sensitive to Mn than that of NR1 and NR2B. In conclusion, the results suggested that Mn induced nerve cell damage by increasing extracellular Glu level and altered expression of NR subunit mRNAs and proteins in rat striatum. © 2010 Wiley Periodicals, Inc. J Biochem Mol Toxicol 24:1–9, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jbt.20306     

Oxidative and nitrosative stress in frozen-thawed pig spermatozoa. II: Effect of the addition of saccharides to freezing medium on sperm function

Saccharides have bioprotective properties, with a high capacity to preserve biological proteins and membranes during sperm cryopreservation. The aim of this study was to evaluate how replacing the lactose of cryopreservation media by sucrose (SUC) or trehalose (TRE) at concentrations of 0.2 M (SUC-1 and TRE-1) and 0.25 M (SUC-2 and TRE-2) affects frozen/thawed pig spermatozoa. The media used were composed of medium A (saccharide/egg yolk) and B (saccharide/egg yolk/glycerol), their osmolality being determined prior to freezing. Cell viability, membrane lipid disorder, acrosome integrity, mitochondrial membrane potential (MMP), lipid peroxidation, thiol group oxidation, total reactive oxygen species (ROS), peroxynitrite and superoxide anion (O₂^●-) were determined through flow cytometry; total motility (TM), progressive motility (PM) and kinetic parameters motility were determined immediately after thawing (T0) and again 30 (T30) and 60 (T60) minutes later. The SUC-2 and TRE-2 groups maintained viability significantly and presented fewer lipid membrane disorders, respectively, both with a significant increase in MMP. The production of O₂^●- and peroxynitrite was lower in the TRE-2 groups compared to the control (P < 0.05). Total motility at T0 was greater in the TRE-2 group (P < 0.05). Sperm kinetics was not affected by the treatment. The use of saccharides SUC and TRE at a concentration of 0.25 M improves sperm quality, so that both non-penetrating cryoprotectants can be utilized in pig sperm freezing media.     

Accumulation and precipitation of Mn2+ by the cells of Oscillatoria terebriformis

The cyanobacterium Oscillatoria terebriformis was shown to exhibit resistance to high manganese concentrations, remaining viable at 2.5 mM MnCl₂ in the medium. Cyanobacterial cells were capable of considerable manganese consumption from the medium. The dynamics of Mn sorption by the cells were the same in all experimental variants, independent of the manganese concentration. Manganese concentration in the biomass peaked after 2–3 days and depended on Mn²⁺ concentration in the medium and on the amount of biomass introduced. In the case of O. terebriformis, manganese removed from the medium may be subdivided into Mn absorbed by the cell, Mn bound to the cell wall, Mn absorbed by the glycocalix, and chemically precipitated Mn. Of the total 21.25 ± 1.0 mg of consumed manganese, biological absorption and chemical precipitation were responsible for 11.78 ± 0.98 and 9.2 ± 0.8 mg, respectively. In the presence of cyanobacteria, Mn removal from the medium was 2.28 times higher than in the control. This process depended considerably on Mn sorption by exopolysaccharides. At 1.3 mM Mn²⁺, a lamellar mat was formed with interlayers of manganese carbonate.     

RELATIONSHIPS AMONG GROWTH RATE,CELLULAR MANGANESE CONCENTRATIONS AND MANGANESE TRANSPORT KINETICS IN ESTUARINE AND OCEANIC SPECIES OF THE DIATOM THALASSIODIRA1

Growth rate, cellular manganese concentration and mangfanese uptake kinetics were measured as functions of the free manganese ion concentration in the medium for two centric diatoms. Thalassiodira oceanica Hasle, isolated from a lou'-managanese oceanic enviorment. was capable of better growth at low manganese ion concentrations that T. pseudonana hasle and Heimdal, islated from higt.manganese estuatine waters. This was dur to the oceanic species’ greater avility to accumulate manganese at low free ion concentrations and to grow well at lower cellular manganese concentions. Manganese up take in both species followed classical saturation kinestics, and V_max but not K, Uaried with the managanese ion concentration in the growth medium. The K_s of managanese uptake for T. Oceanica (10^-795 M) was one-seventh of that for T. Pseudonana. accouning for T. oceanica's greater ablility to accumulate managaese at low gree ion concentrations.V_max appeared to be under negative feedback control in both species and six- to twelve-fold variations in this parameter allowed cells to regulate cellular managanese at nearly constant valies at manganese ion concentrations in the vicinity of and somewhat below K_r The range in free manganese ion concenteations over which regukation occurred was diffrent for the two species, and coincided with the in free manganese ion concentrations of the natural habitat of each species.     

Effect of High Dietary Manganese on the Immune Responses of Broilers Following Oral Salmonella typhimurium Inoculation

Manganese (Mn) is an essential nutrient for both host and pathogen. Recent studies have demonstrated the nutritional immunity of Mn against Salmonella infection in mammals. To investigate the effect of high dietary Mn on immune responses of broilers following Salmonella challenge, 144 1-day-old male broilers were fed a basal diet (containing 20.04 mg Mn/kg) plus an additional 40 (the control group) or 400 mg Mn/kg (the H-Mn group) for 7 days. The 72 broilers in each group were then orally inoculated with 5 × 10⁷ CFUs of Salmonella typhimurium (ATCC#14028) or phosphate-buffered saline. Peripheral blood, spleens, cecal tonsils, and bursa of Fabricius were collected from Salmonella-inoculated and Salmonella-noninoculated broilers (n = 6) at 2 days post inoculation (2 DPI) and 7 days post inoculation (7 DPI). Peripheral blood lymphocyte subpopulations were determined by flow cytometry. The messenger RNA (mRNA) abundance of genes was determined by quantitative real-time polymerase chain reaction. Salmonella counts were higher (P < 0.05) in the H-Mn group than that in the control group at 2 DPI in the cecal contents of Salmonella-inoculated broilers. High dietary Mn increased CD3⁺CD4⁺ and CD3⁺CD8⁺ percentages in the peripheral blood of Salmonella-inoculated broilers at 2 DPI. Salmonella inoculation increased interleukin (IL)-6 mRNA expression in spleens and bursa of Fabricius at 2 DPI and increased IL-1β and IL-6 mRNA expression in cecal tonsils at 7 DPI in the H-Mn group. These changes were not observed in the control group. High dietary Mn increased interferon-γ (IFN-γ) in spleens and decreased IFN-γ and IL-12 mRNA expression in cecal tonsils of Salmonella-inoculated broilers at 2 DPI. High dietary Mn decreased IL-17 mRNA expression in the bursa of Fabricius at 7 DPI, but increased this expression in cecal tonsils at 2 and 7 DPI in Salmonella-inoculated broilers. These results suggested that dietary Mn level affected T helper (Th) 1-cytokine reaction in spleens and cecal tonsils, and Th17-mediated immunity in cecal tonsils and the bursa of Fabricius of broilers when challenged with Salmonella.

     

Differences in pupal cold hardiness and larval food consumption between overwintering and non‐overwintering generations of the common yellow swallowtail,Papilio machaon (Lepidoptera: Papilionidae), from the Osaka population

To clarify differences in pupal cold hardiness and larval food consumption between overwintering and non‐overwintering generations of the common yellow swallowtail, Papilio machaon, we reared larvae from the Osaka population under photoperiods of 16 h light : 8 h dark (LD 16:8) (long day) or LD 12:12 (short day) at 20°C. We examined the relationship between food consumption and weight during the final larval stadium and pupae, and measured the pupal supercooling point (SCP). Although the ratio of assimilation to consumption did not differ significantly between photoperiods, the ratio of assimilation to pupal weight differed significantly between individuals reared under long and short days. All diapausing pupae were brown, whereas 56% of non‐diapausing pupae were green with the remainder brown. The mean pupal body length (L), dorsal width (W₁) and lateral width (W₂) were larger in non‐diapausing than in diapausing pupae, and the W₁/L and W₁/W₂ ratios differed significantly between non‐diapausing and diapausing pupae. SCP was approximately –20°C and did not differ among pupae 5, 15 and 30 days after pupation under long‐day conditions. However, under short‐day conditions, mean SCP gradually decreased, stabilizing at approximately –24 to –25°C by 30 days after pupation. After freezing, some diapausing pupae emerged as adults, whereas all non‐diapausing pupae died. Both egestion and assimilation were greater under long‐day conditions. The results revealed that pupae of this papilionid exhibit seasonal polyphenism in physiological and morphological traits. Energy from food appears to be expended on increasing cold hardiness in the overwintering generation and on reproduction in the non‐overwintering generation.     

Silicon dioxide in the defence induction of soybean against Spodoptera frugiperda

Silicon can increase the natural defence of plants against stresses including herbivorous insects. Silicon dioxide (SiO₂) is one of the forms of silicon, and despite its wide use in the industrial sector, its use in agriculture is still poorly adopted. The aim of this study was to evaluate the effectiveness of foliar application of SiO₂ in inducing defence against Spodoptera frugiperda in soybean. The experiments were conducted in a completely randomised design with four treatments (0%, 1%, 2.5%, and 5% of SiO₂). The effect on cannibalism, biological parameters (mortality, duration of the larval stage, duration of the pupal stage and pupal weight) and wear on the mandible of S. frugiperda were evaluated. The foliar silicon content was also determined. The supply of SiO₂ prolonged the duration of the larval and pupal stages of the S. frugiperda by 0.56 and 0.17 days for each 1% of SiO₂ applied, respectively. The use of SiO₂ at 5% increased the mortality rate of caterpillars in the larval stage by approximately 25%. There was no effect of SiO₂ application on cannibalism and weight of S. frugiperda pupae. There was wear on the caterpillars' jaws in the third and fourth instar at the highest SiO₂ concentration. The application of SiO₂ promoted greater accumulation of silicon in soybean leaves. It is concluded that the foliar application of SiO₂ affects the biological performance of S. frugiperda through the induction of defence in the soybean crop and presents itself as a promising strategy in integrated pest management programmes.     

Does a polyphagous caterpillar have the same gut microbiota when feeding on different species of food plants?

We used classical culture techniques to explore gut bacteria and changes associated with dietary change in the highly polyphagous, tropical caterpillar Automeris zugana (Saturniidae). Fifty-five third instar wild-caught sibs feeding on Annona purpurea (Annonaceae) in the Area de Conservación Guanacaste (ACG) in northwestern Costa Rica were divided into eight groups. Each of seven groups was reared to the ultimate instar on another species of food plant normally used by A. zugana. Some pupae were also analyzed for the presence of bacteria. Aerobic bacterial cultures were obtained from all 33 caterpillar guts and the eight pupae inventoried. There was no clear pattern in species composition of cultivated bacteria among the eight diets, and each caterpillar on a given food plant carried only a small fraction of the total set of species isolated from the set of caterpillars feeding on that food plant. Taken as a whole, the larvae and pupae contained 22 species of cultivable bacteria in 12 genera. Enterobacter, present in 81.8% of the samples, was the genus most frequently isolated from the caterpillars, followed by Micrococcus and Bacillus. Bacillus thuringiensis was isolated from 30.3% of the dissected caterpillars, but found in caterpillars feeding on only half of the species of food plants.     

Microbial Manganese and Sulfate Reduction in Black Sea Shelf Sediments

The microbial ecology of anaerobic carbon oxidation processes was investigated in Black Sea shelf sediments from mid-shelf with well-oxygenated bottom water to the oxic-anoxic chemocline at the shelf-break. At all stations, organic carbon (C_org) oxidation rates were rapidly attenuated with depth in anoxically incubated sediment. Dissimilatory Mn reduction was the most important terminal electron-accepting process in the active surface layer to a depth of ~1 cm, while SO₄²⁻ reduction accounted for the entire C_org oxidation below. Manganese reduction was supported by moderately high Mn oxide concentrations. A contribution from microbial Fe reduction could not be discerned, and the process was not stimulated by addition of ferrihydrite. Manganese reduction resulted in carbonate precipitation, which complicated the quantification of C_org oxidation rates. The relative contribution of Mn reduction to C_org oxidation in the anaerobic incubations was 25 to 73% at the stations with oxic bottom water. In situ, where Mn reduction must compete with oxygen respiration, the contribution of the process will vary in response to fluctuations in bottom water oxygen concentrations. Total bacterial numbers as well as the detection frequency of bacteria with fluorescent in situ hybridization scaled to the mineralization rates. Most-probable-number enumerations yielded up to 10⁵ cells of acetate-oxidizing Mn-reducing bacteria (MnRB) cm⁻³, while counts of Fe reducers were <10² cm⁻³. At two stations, organisms affiliated with Arcobacter were the only types identified from 16S rRNA clone libraries from the highest positive MPN dilutions for MnRB. At the third station, a clone type affiliated with Pelobacter was also observed. Our results delineate a niche for dissimilatory Mn-reducing bacteria in sediments with Mn oxide concentrations greater than ~10 μmol cm⁻³ and indicate that bacteria that are specialized in Mn reduction, rather than known Mn and Fe reducers, are important in this niche.     

Manganese induces oxidative stress, redox state unbalance and disrupts membrane bound ATPases on murine neuroblastoma cells in vitro: protective role of silymarin

Manganese (Mn) is an essential trace element required for ubiquitous enzymatic reactions. Chronic overexposure to this metal may promote potent neurotoxic effects. The mechanism of Mn toxicity is not well established, but several studies indicate that oxidative stress play major roles in the Mn-induced neurodegenerative processes. Silymarin (SIL) has antioxidant properties and stabilizes intracellular antioxidant defense systems. The aim of this study was to evaluate the toxic effects of MnCl₂ on the mouse neuroblastoma cell lines (Neuro-2A), to characterize the toxic mechanism associated with Mn exposure and to investigate whether SIL could efficiently protect against neurotoxicity induced by Mn. A significant increase in LDH release activity was observed in Neuro-2A cells associated with a significant decrease in cellular viability upon 24 h exposure to MnCl₂ at concentrations of 200 and 800 μM (P < 0.05) when compared with control unexposed cells. In addition, exposure cells to MnCl₂ (200 and 800 μM), increases oxidant biomarkers and alters enzymatic and non enzymatic antioxidant systems. SIL treatment significantly reduced the levels of LDH, nitric oxide, reactive oxygen species and the oxidants/antioxidants balance in Neuro-2A cells as compared to Mn-exposed cells. These results suggested that silymarin is a powerful antioxidant through a mechanism related to its antioxidant activity, able to interfere with radical-mediated cell death. SIL may be useful in diseases known to be aggravated by reactive oxygen species and in the development of novel treatments for neurodegenerative disorders such as Alzheimer or Parkinson diseases.     

Repellency of the oily extract of neem seeds (<Emphasis Type="Italic">Azadirachta indica</Emphasis>) against <Emphasis Type="Italic">Varroa destructor</Emphasis> (Acari: Varroidae)

A crude oil extract of neem seed (Azadirachta indica, Sapindales: Meliaceae) was evaluated for repellency on Varroa destructor Anderson and Trueman. Burgerjon’s tower was used to spray worker bee pupae with 0.0, 0.3, 0.7, 1.3, 2.6, 5.3, 10.6 and 21.1% neem extract concentrations. Sprayed pupae were attached to observation arenas and incubated at 32 ± 2°C and 70 ± 10% RH. The ability of V. destructor to locate and feed on treated and untreated pupae was monitored from 30 min to 72 h after spray. Higher and more stable repellency was achieved with 2.6, 5.3, 10.6 and 21.1% neem extract. At the highest concentration, 98% of V. destructor were prevented to settle on bee pupae, resulting in 100% V. destructor mortality at 72 h.     

Nutritional aspects of manganese homeostasis

Manganese (Mn) is an essential mineral. It is present in virtually all diets at low concentrations. The principal route of intake for Mn is via food consumption, but in occupational cohorts, inhalation exposure may also occur (this subject will not be dealt with in this review). Humans maintain stable tissue levels of Mn. This is achieved via tight homeostatic control of both absorption and excretion. Nevertheless, it is well established that exposure to high oral, parenteral or ambient air concentrations of Mn can result in elevations in tissue Mn levels. Excessive Mn accumulation in the central nervous system (CNS) is an established clinical entity, referred to as manganism. It resembles idiopathic Parkinson's disease (IPD) in its clinical features, resulting in adverse neurological effects both in laboratory animals and humans. This review focuses on an area that to date has received little consideration, namely the potential exposure of parenterally fed neonates to exceedingly high Mn concentrations in parenteral nutrition solutions, potentially increasing their risk for Mn-induced adverse health sequelae. The review will consider (1) the essentiality of Mn; (2) the concentration ranges, means and variation of Mn in various foods and infant formulas; (3) the absorption, distribution, and elimination of Mn after oral exposure and (4) the factors that raise a theoretical concern that neonates receiving total parenteral nutrition (TPN) are exposed to excessive dietary Mn.     

Manganese species from human serum,cerebrospinal fluid analyzed by size exclusion chromatography-, capillary electrophoresis coupled to inductively coupled plasma mass spectrometry

Manganese (Mn) at high concentrations can have adverse effects on health, mainly because of its toxicity to the central nervous system. Health impacts of Mn are known mostly from occupational health studies, but the exact mechanisms how Mn, being bound to transferrin (TF) in the blood, enters the brain – are unknown. Mn speciation at the neural barriers can help to obtain more information about the pathways and carriers. This paper summarizes investigations on the size distribution of Mn carriers (e.g. proteins, peptides, carbonic acids) in serum before the neural barriers and in cerebrospinal fluid (CSF) behind them as a first characterization step of the Mn carriers being involved in moving Mn across the neural barriers. Further identification of Mn-species in CSF was successfully achieved by CZE–inductively coupled plasma (ICP)–dynamic reaction cell (DRC)–mass spectrometry (MS). Serum samples showed Mn mean concentrations of 1.7±0.8 μg L⁻¹. The size distribution of Mn-carriers showed a main peak in the TF/albumin size fitting to the known physiological ligands. However, also an increasing Mn peak at 700 Da with increasing total Mn concentration was seen. Samples of CSF showed Mn mean concentrations of 2.6 μg L⁻¹=48 nM. In CSF Mn was found to be mostly bound to low-molecular-mass (LMM)-Mn carriers in the range of 640–680 Da. This is similar to the LMM compound in serum and to Mn–citrate complexes suggested to be present in body fluids. Citrate concentration was 573 μM, thus being in huge excess compared to Mn. CSF was further analyzed by CZE–ICP–DRC–MS. Several Mn-species were monitored and mostly identified. The most abundant Mn-species was Mn–citrate at a concentration of around 0.7 μg Mn L⁻¹.     

Effect of Meloidogyne incognita on Plant Nutrient Concentration and Its Influence on the Physiology of Beans

Phaseolus vulgaris plants, 3, 8, 11, and 13 days old, were inoculated with 0, 2,000, 4,000, or 8,000 second-stage Meloidogyne incognita larvae and maintained under controlled conditions. The photosynthetic rate and the shoot and root concentration of K, Ca, Mn, Fe, Cu, and Zn were determined by destructive assay at 1-27-day intervals and by nondestructive assay of leaves, stems, and roots at 27 or 28 days after inoculation. In the destructive assay, the concentration of the elements in the plant tissues did not change until 1 week after inoculation. Thereafter, the trend was mostly decreasing for shoot K and Fe and increasing in the root, whereas Ca had the opposite trend in the shoots. Manganese, Cu, and Fe showed variable trends. Generally, the concentration of K and Mn increased, whereas Ca and Fe decreased, with duration of infection in all treatments. Zinc and Cu decreased in the highest nematode treatments. The overall elemental content generally decreased with level of infection from 1 week after inoculation. Photosynthetic rate based on shoot K concentration significantly decreased with level of infection. In most of the nondestructive assays, the concentrations of shoot K, Zn, and Mn decreased, whereas Ca increased with increasing nematode treatment. One of the first effects of the nematode on host physiology appears to be a change in concentration of nutrient elements in the host plant.