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PubMed1999

Synthesis, Structure, and Magnetism of Mono- and Binuclear Manganese(II) Compounds of Nitronyl Nitroxide Substituted Phosphine Oxides.

Complexes of manganese(II)-containing aminoxyl radical substituted phosphine oxide ligands are reported. The compounds [(o-nitronyl nitroxide-phenyl)diphenylphosphine oxide]bis(hexafluoroacetylacetonato)manganese(II), 3, and bis{[(p-nitronyl nitroxide-phenyl) diphenylphosphine oxide]bis(hexafluoroacetylacetonato)manganese(II)}, 4, prepared by addition of the free radical phosphine oxides to Mn(hfac)(2), were structurally characterized. Complex 3 is mononuclear, containing an O,O-chelating ortho-substituted radical phosphine oxide ligand, while in 4 the para-substituted ligands bridge two Mn(hfac)(2) units to yield a binuclear molecular rectangle. The magnetic behavior of both systems is dominated by a strong antiferromagnetic Mn(II)-aminoxyl interaction (J = -213 (3), -218 (4) cm(-)(1) with H = -JS(Mn).S(rad)) to give effective S = 2 ground state units. The S = 3 excited state is populated at high temperatures. At low temperatures a decrease in chi(M)T in both complexes is attributable primarily to inter- or intramolecular antiferromagnetic interactions rather than zero-field splitting (ZFS) of the S = 2 ground state. For the bimetallic compound, the magnetic data indicate that ligand-mediated interactions between the Mn(II) spin carriers are weak. The powder EPR spectra of both systems have been recorded and successfully simulated, giving a ZFS parameter D = 0.112 cm(-)(1). Crystals of 3 are triclinic, space group P&onemacr; with a = 10.6672(19) Å, b = 13.270(6) Å, c = 15.363(3) Å, alpha = 93.84(2) degrees, beta = 108.054(16) degrees, gamma = 105.69(3) degrees, and Z = 2. Crystals of 4 are monoclinic, space group P2(1)/a with a = 12.463(6) Å, b = 19.315(3) Å, c = 17.084(9) Å, alpha = 90 degrees, beta = 98.49(2) degrees, gamma = 90 degrees, and Z = 2.

Journal Article↗
PubMed1994

Mechanism of manganese peroxidase compound II reduction. Effect of organic acid chelators and pH.

The effect of oxalate, malonate, lactate, and succinate chelators on the reduction of Phanerochaete chrysosporium manganese peroxidase compound II by MnII was investigated using stopped-flow techniques. All rate data were collected from single-turnover experiments under pseudo-first-order conditions. With oxalate, the reduction of compound II by MnII exhibited saturation behavior when the observed pseudo-first-order rate constants were plotted against oxalate concentration. The plots passed through the origin, indicating that the reduction by MnII is irreversible at all concentrations of oxalate. Maximal stimulation of the rate of compound II reduction occurred at 2 mM oxalate, the concentration of oxalate found in the extracellular medium of agitated cultures of this fungus. In contrast, maximal stimulation of the reduction of compound II by MnII only was observed at high (> 20 mM) nonphysiological concentrations of malonate and lactate. Furthermore, at low concentrations of malonate and lactate, the reduction of compound II appeared to be reversible. These results suggest that at physiological concentrations oxalate chelates and stabilizes MnIII, enhancing its efficient removal from the enzyme. The rate constants for compound II reduction exhibited bell-shaped curves as a function of pH and had optima at pHs 5.0-5.4. In the presence of succinate, triphasic kinetics were observed for compound II reduction by MnII. In contrast to the reduction of compound II by MnII, various chelators had no observable effect on the formation of compound I. However, they did affect the steady-state oxidation of 2,6-dimethoxyphenol.

Basidiomycota↗
PubMed2003

Novel transition metal oxalatophosphates with a two-dimensional honeycomb structure: (H3TREN)[M2(HPO4)(C2O4)2.5] x 3H2O (M = Mn(II) and Fe(II), TREN = tris(2-aminoethyl)amine).

Two new layered transition metal oxalatophosphates, (H(3)TREN)[M(2)(HPO(4))(C(2)O(4))(2.5)].3H(2)O (M = Mn(II) and Fe(II)), have been synthesized by hydrothermal methods in the presence of a structure-directing organic amine, tris(2-aminoethyl)amine, and characterized by single-crystal X-ray diffraction and magnetic susceptibility. They are the first metal oxalatophosphates which adopt a two-dimensional honeycomb structure with the organic cations and water molecules intercalated in between. Within a layer, there are 12-membered pores made from 6 Mn, 1 phosphate, and 5 oxalate units. Measurements of field dependence of magnetization and variable-temperature susceptibilities under different fields were performed on a polycrystalline sample of the manganese compound. The results indicate a phase transition from a paramagnetic to an antiferromagnetic coupled state at about 12 K. Crystal data for the manganese compound follow: triclinic, space group Ponemacr; (No. 2), a = 8.8385(6) A, b = 9.0586(6) A, c = 16.020(1) A, alpha = 77.616(1) degrees, beta = 83.359(1) degrees, gamma = 68.251(1) degrees, and Z = 2. Crystal data for the iron compound are the same as those for the manganese compound except a = 8.7776(9) A, b = 8.9257(9) A, c = 15.884(2) A, alpha = 78.630(2) degrees, beta = 84.018(2) degrees, and gamma = 67.372(2) degrees.

Journal Article↗
PubMed2000

Oxidative neuropathology and putative chemical entities for Alzheimer's disease: neuroprotective effects of salen-manganese catalytic anti-oxidants.

Considerable evidence exists that the brains of individuals with Alzheimer's disease are subject to elevated levels of oxidative stress, particularly in regions exhibiting pathological damage. A major contributor to this oxidative stress appears to be the inflammatory process. Activation of rodent microglial cells by LPS or beta-amyloid peptide results in a marked up-regulation of inducible nitric oxide synthase (iNOS) and corresponding nitric oxide (NO) production. Elevated levels of iNOS are also observed in the brains of Alzheimer patients. The reaction of NO with superoxide leads to the generation of the highly reactive and damaging peroxynitrite free radical species. Peroxynitrite appears to play a key role in the generation of an oxidative stress in the Alzheimer brain as evidenced by widespread nitrotyrosine immunoreactivity. We have employed SIN-1 as a peroxynitrite generating system in cell cultures in order to characterize the effects of this free radical on neurons. SIN-1 treatment of primary rat hippocampal neurons in culture results in neurotoxicity by a necrosis mechanism according to electron microscopic criteria. One approach to limiting peroxynitrite mediated damage is to limit superoxide production. An approach we have evaluated is treatment with salen manganese compounds, a class of catalytic antioxidant compounds which behave as superoxide dismutase (SOD)/catalase mimetics to detoxify superoxide. A number of such salen manganese compounds, including EUK-8 and EUK-134, can markedly protect primary rat cortical neurons from hydrogen peroxide mediated oxidative stress. Such salen manganese compounds can similarly afford marked neuroprotection to an oxidative stress imposed by SIN-1, potentially attributable at least in part to their inherent SOD activity. The salen manganese SOD/catalase mimetics represent a promising class of catalytic antioxidant for attenuating oxidative stress.

Journal Article↗
PubMed2005

Recycling spent zinc manganese dioxide batteries through synthesizing Zn-Mn ferrite magnetic materials.

A novel process to reclaim spent zinc manganese dioxide batteries (SDBs) through synthesizing Zn-Mn ferrite magnetic materials is present. Firstly, the dismantling, watering, magnetism, baking and griddling steps were consecutively carried out to obtain iron battery shells, zinc grains and manganese compounds using the collected SDBs, and then these separated substances were dissolved with 4 mol L(-1) H(2)SO(4) to prepare FeSO(4), ZnSO(4) and MnSO(4) reactant solutions. Secondly, Zn-Mn ferrites with stoichiometric ratio of Mn(0.26)Zn(0.24)FeO(2) were synthesized using chemical co precipitation process with ammonium oxalate precipitator. The XRD results showed that the obtained Zn-Mn ferrites had spinel structure and high purity at the calcining temperatures of 850-1250 degrees C. With the increase of calcining temperature, the finer crystalline structure could be formed, and their intensity of saturation magnetization reached the highest value at 1150 degrees C. The magnetization performances of Zn-Mn ferrites prepared from the SDBs were similar to that of from analysis reagents, suggesting the feasibility to synthesize Zn-Mn ferrites with high properties from SDBs.

Conservation of Natural Resources↗
PubMed1987

Electron paramagnetic resonance and spectrophotometric studies of the peroxide compounds of manganese-substituted horseradish peroxidase, cytochrome-c peroxidase and manganese-porphyrin model complexes.

Peroxide compounds of manganese protoporphyrin IX and its complexes with apo-horseradish peroxidase and apocytochrome-c peroxidase were characterized by electronic absorption and electron paramagnetic resonance spectroscopies. An intermediate formed upon titration of Mn(III)-horseradish peroxidase with hydrogen peroxide exhibited a new electron paramagnetic resonance absorption at g = 5.23 with a definite six-lined 55Mn hyperfine (AMn = 8.2 mT). Neither a porphyrin pi-cation radical nor any other radical in the apoprotein moiety could be observed. The reduced form of Mn-horseradish peroxidase, Mn(II)-horseradish peroxidase, reacted with a stoichiometric amount of hydrogen peroxide to form a peroxide compound whose electronic absorption spectrum was identical with that formed from Mn(III)-horseradish peroxidase. The electronic state of the peroxide compound of manganese horseradish peroxidase was thus concluded to be Mn(IV), S = 3/2. Mn(III)-cytochrome-c peroxidase reacted with stoichiometry quantities of hydrogen peroxide to form a catalytically active intermediate. The electronic absorption spectrum was very similar to that of a higher oxidation state of manganese porphyrin, Mn(V). Since the peroxide compound of manganese cytochrome-c peroxidase retained two oxidizing equivalents per mol of the enzyme (Yonetani, T. and Asakura, T. (1969) J. Biol. Chem. 244, 4580-4588), this peroxide compound might contain an Mn(V) center.

Cytochrome-c Peroxidase↗
PubMed1998

Enzymatic Combustion of Aromatic and Aliphatic Compounds by Manganese Peroxidase from Nematoloma frowardii.

The direct involvement of manganese peroxidase (MnP) in the mineralization of natural and xenobiotic compounds was evaluated. A broad spectrum of aromatic substances were partially mineralized by the MnP system of the white rot fungus Nematoloma frowardii. The cell-free MnP system partially converted several aromatic compounds, including [U-C]pentachlorophenol ([U-C]PCP), [U-C]catechol, [U-C]tyrosine, [U-C]tryptophan, [4,5,9,10-C]pyrene, and [ring U-C]2-amino-4,6-dinitrotoluene ([C]2-AmDNT), to CO(2). Mineralization was dependent on the ratio of MnP activity to concentration of reduced glutathione (thiol-mediated oxidation), a finding which was demonstrated by using [C]2-AmDNT as an example. At [C]2-AmDNT concentrations ranging from 2 to 120 muM, the amount of released CO(2) was directly proportional to the concentration of [C]2-AmDNT. The formation of highly polar products was also observed with [C]2-AmDNT and [U-C]PCP; these products were probably low-molecular-weight carboxylic acids. Among the aliphatic compounds tested, glyoxalate was mineralized to the greatest extent. Eighty-six percent of the COOH-glyoxalate and 9% of the CHO-glyoxalate were converted to CO(2), indicating that decarboxylation reactions may be the final step in MnP-catalyzed mineralization. The extracellular enzymatic combustion catalyzed by MnP could represent an important pathway for the formation of carbon dioxide from recalcitrant xenobiotic compounds and may also have general significance in the overall biodegradation of resistant natural macromolecules, such as lignins and humic substances.

Journal Article↗
PubMed2003

Reaction of [60]fullerene with free radicals generated from active methylene compounds by manganese(III) acetate dihydrate.

The reaction of [60]fullerene with dimethyl malonate and diethyl malonate in the presence of manganese(III) acetate dihydrate (Mn(OAc)3.2H2O) for 20 min afforded singly bonded [60]fullerene dimers 1a and 1b in a 1,4-addition pattern. When the reaction time was extended to 1 h, 1,4-bisadducts 2a and 2b were obtained. Unsymmetrical 1,4-adduct 5 and C2 symmetrical 1,16-bisadduct 6 were obtained when diethyl bromomalonate was used as the active methylene compound. Reaction of [60]fullerene with malononitrile and ethyl cyanoacetate with the aid of Mn(OAc)3.2H2O produced methanofullerenes 7 and 8. It is proposed that all these products were formed the addition of free radicals from the active methylene compounds generated by Mn(OAc)3.2H2O.

Acetates↗
PubMed2005

Involvement of lipid peroxidation in the degradation of a non-phenolic lignin model compound by manganese peroxidase of the litter-decomposing fungus Stropharia coronilla.

Culture liquids of the litter-decomposing basidiomycete Stropharia coronilla showed pro-oxidant activity promoting the peroxidation of linoleic acid. This activity depended on the presence of manganese peroxidase (MnP) in the fungal culture. Pro-oxidant activity maxima coincided with maximum MnP activities during the separation of extracellular proteins by anion-exchange chromatography. Purified MnP1 showed substantial pro-oxidant activity in the presence of acetate and Mn2+ ions, even without the addition of hydrogen peroxide. A non-phenolic beta-O-4 lignin model compound [LMC; 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)-1,3-dihydroxypropane] was partially oxidized in an in vitro reaction system developing MnP-dependent lipid peroxidation. The chelating organic acids malonate and tartrate noticeably inhibited both the peroxidation of linoleic acid and the conversion of LMC in the system. The major product of the LMC oxidation was 1-(3,4-dimethoxyphenyl)-1-oxo-2-(2-methoxyphenoxy)-3-hydroxypropane; in addition, small amounts of 3,4-dimethoxybenzaldehyde (veratraldehyde) and 3,4-dimethoxybenzoic (veratric) acid were detected. Thus, MnP-initiated lipid peroxidation may be involved in the degradation of recalcitrant non-phenolic lignin substructures by litter-decomposing fungi similar to MnPs of wood-decaying fungi.

Basidiomycota↗
PubMed2004

Chloride ligation in inorganic manganese model compounds relevant to photosystem II studied using X-ray absorption spectroscopy.

Chloride ions are essential for proper function of the photosynthetic oxygen-evolving complex (OEC) of Photosystem II (PS II). Although proposed to be directly ligated to the Mn cluster of the OEC, the specific structural and mechanistic roles of chloride remain unresolved. This study utilizes X-ray absorption spectroscopy (XAS) to characterize the Mn-Cl interaction in inorganic compounds that contain structural motifs similar to those proposed for the OEC. Three sets of model compounds are examined; they possess core structures Mn(IV)(3)O(4)X (X=Cl, F, or OH) that contain a di-micro-oxo and two mono-micro-oxo bridges or Mn(IV)(2)O(2)X (X=Cl, F, OH, OAc) that contain a di-micro-oxo bridge. Each set of compounds is examined for changes in the XAS spectra that are attributable to the replacement of a terminal OH or F ligand, or bridging OAc ligand, by a terminal Cl ligand. The X-ray absorption near edge structure (XANES) shows changes in the spectra on replacement of OH, OAc, or F by Cl ligands that are indicative of the overall charge of the metal atom and are consistent with the electronegativity of the ligand atom. Fourier transforms (FTs) of the extended X-ray absorption fine structure (EXAFS) spectra reveal a feature that is present only in compounds where chloride is directly ligated to Mn. These FT features were simulated using various calculated Mn-X interactions (X=O, N, Cl, F), and the best fits were found when a Mn-Cl interaction at a 2.2-2.3 A bond distance was included. There are very few high-valent Mn halide complexes that have been synthesized, and it is important to make such a comparative study of the XANES and EXAFS spectra because they have the potential for providing information about the possible presence or absence of halide ligation to the Mn cluster in PS II.

Chlorides↗
PubMed1999

High-Dimensional Manganese(II) Compounds with Noncovalent and/or Covalent Bonds Derived from Flexible Ligands: Self-Assembly and Structural Transformation.

A hydrogen- and covalent-bonded 3D array, [Mn(bpe)(H(2)O)(4)](n)()(ClO(4))(2)(n)()(bpe)(4)(n)()(H(2)O)(2)(n)() (2) [bpe = 1,2-bis(4-pyridyl)ethane], a covalent-bonded 3D network, [Mn(bpe)(1.5)(H(2)O)(tp)](n)()(H(2)O)(n)() (3) [tp = terephthalate], and a covalent-bonded 2D sheet, [Mn(bpe)(N(3))(2)](n)() (4), have been synthesized and characterized by spectroscopic data and single-crystal X-ray diffraction studies. Complex 2 contains two types of packing bpe molecules: One type of bpe molecules (=N31-bpe and symmetry-related bpe) run along the chain direction, and the other type of bpe molecules (=N11-bpe and N21-bpe) are slanted to the chain linked by bridging bpe (=N1-bpe). The chain is coupled with hydrogen bonds via N31-bpe, while hydrogen bonds through packing bpe molecules of N11- and N21-bpe sew the chains, leading to a 3D interlocking network structure. The bpe ligands in 3 have an anti conformation for the bridging bpe and a gauche conformation for the capping bpe with a dihedral angle between the two pyridyl rings of 44.5 degrees. The tp ligand acts as a linker of three metal ions through the unidentate and bridging modes, leading to the formation of a 2D layer. The final molecular dimensionality in 3 is determined from adding bpe ligands to the 2D sheet connected by tp ligands, resulting in a covalent-bonded 3D array where the bridging bpe ligands link the tp-bridged layers. The manganese(II) center in 4 consists of four equatorial azido nitrogen atoms and two axial bpe nitrogen atoms. The one-dimensional chains formed by two azido bridging ligands are interconnected by bpe ligands, each of which has two pyridyl rings with a dihedral angle of 67 degrees, leading to a two-dimensional sheet. Variable-temperature magnetic susceptibility data of 2 and 4 have been fitted to the infinite-chain model (H = -J summation operatorS(A)(i)().S(A)(i)()(+1)) derived by Fisher under the molecular field approximation (J '). Obtained exchange parameters are J = -0.083 cm(-)(1), g = 2.0 for 2 and J = -12.5 cm(-)(1), g = 2.0, J ' = 1.3 cm(-)(1) for 4. In the case of 3, the magnetic nature was interpreted by the dimer model (H = -JS(1).S(2)), affording parameters J = -0.96 cm(-)(1), g = 1.99, J ' = -0.005 cm(-)(1). MO calculations on a hypothetical dimeric unit (NH(3))(5)Mn-bpe-Mn(NH(3))(5) are discussed to evaluate the magnetic nature for the bpe-bridged system 4.

Journal Article↗
PubMed1989

Thiol-mediated oxidation of nonphenolic lignin model compounds by manganese peroxidase of Phanerochaete chrysosporium.

In the presence of MnII, H2O2, and glutathione (GSH), manganese peroxidase oxidized veratryl alcohol (I) to veratraldehyde (IV). Anisyl alcohol (II) and benzyl alcohol (III) were also oxidized by this system to their corresponding aldehydes (V and VI). In the presence of GSH, chemically prepared MnIII or gamma-irradiation also catalyzed the oxidation of I, II, and III to IV, V, and VI, respectively. GSH and dithiothreitol rapidly reduced MnIII to MnII in the absence of aromatic substrates and the dithiothreitol was oxidized to its disulfide (4,5-dihydroxyl-1,2-dithiane). These results indicate that the thiol is oxidized by enzyme-generated MnIII to a thiyl radical. The latter abstracts a hydrogen from the substrate, forming a benzylic radical which reacts with another thiyl radical to yield an intermediate which decomposes to the benzaldehyde product. In the presence of MnII, GSH, and H2O2, manganese peroxidase also oxidized 1-(4-ethoxy-3-methoxy-phenyl)-2-(4'-hydroxymethyl-2'-methoxyphenoxy)- 1,3-dihydroxypropane (XII) to yield vanillyl alcohol (VII), vanillin (VIII), 1-(4-ethoxy-3-methoxyphenyl)-1,3-dihydroxypropane (XVI), 1-(4-ethoxy-3-methoxyphenyl)-1-oxo-3-hydroxypropane (XIX), and several C alpha oxidized dimeric products. Abstraction of the C alpha (A ring) hydrogen of the dimer (XII) yields a benzylic radical, leading to C beta oxygen ether cleavage. The resultant intermediates yield the ketone (XIX) and vanillyl alcohol (VII) or vanillin (VIII). Alternatively, benzylic radical formation at the C' alpha position (B ring) leads to radical cleavage, yielding a quinone methide and a C beta radical, which yield vanillin and the 1,3-diol (XVI), respectively. In these reactions, MnIII oxidizes a thiol to a thiyl radical which subsequently abstracts a hydrogen from the substrate to form a benzylic radical. The latter undergoes nonenzymatic reactions to yield the final products.

Aerobiosis↗
PubMed2001

Correlation of structure and triboluminescence for tetrahedral manganese(II) compounds.

To investigate the structural basis of triboluminescence, several known tetrahedrally coordinated Mn(II) complexes have been synthesized according to literature methods and their crystal structures have been determined by X-ray diffraction. Among them, (MePh(3)P)(2)[MnCl(4)] (2), a = 15.4804(4) A, cubic, space group P2(1)3, Z = 4; (Et(4)N)(2)[MnBr(4)] (4), a = 13.362(1) A, c = 14.411(1) A, tetragonal, space group P42(1)m, Z = 4; MnBr(2)(OPPh(3))(2) (7), a = 9.974(1) A, b = 10.191(3) A, c = 10.538(2) A, alpha = 65.32(1) degrees, beta = 63.49(1) degrees, gamma = 89.44(2) degrees, triclinic, space group P1, Z = 1; and MnBr(2)(OAsPh(3))(2) (10), a = 17.816(3) A, b = 10.164(1) A, c = 18.807(3) A, orthorhombic, space group Pca2(1), Z = 4 were reported to be triboluminescent and (Me(4)N)(2)[MnCl(4)] (3), a = 9.016(3) A, b = 36.90(2) A, c = 15.495(3) A, beta = 90.72(3) degrees, monoclinic, space group P2(1)/n, Z = 12, and MnI(2)(OAsPh(3))(2) (11), a = 10.094(4) A, b = 10.439(2) A, c = 34.852(2) A, alpha = 83.17(4) degrees, beta = 86.09(2) degrees, gamma = 75.16(3) degrees, triclinic, space group P1, Z = 4, were reported to be not triboluminescent. The result supports the correlation between space group acentricity and triboluminescence activity.

Journal Article↗
PubMed2004

Manganese distribution in the brain and neurobehavioral changes following inhalation exposure of rats to three chemical forms of manganese.

The central nervous system is an important target for manganese (Mn) intoxication in humans; it may cause neurological symptoms similar to Parkinson's disease. Manganese compounds emitted from the tailpipe of vehicles using methylcyclopentadienyl manganese tricarbonyl (MMT) are primarily Mn phosphate, Mn sulfate, and Mn phosphate/sulfate mixture. The purpose of this study is to compare the patterns of Mn distribution in various brain regions (olfactory bulb, frontal parietal cortex, globus pallidus, striatum and cerebellum) and other tissues (lung, liver, kidney, testis) and the neurobehavioral damage following inhalation exposure of rats to three Mn species. Rats (n=15 rats per Mn species) were exposed 6 h per day, 5 days per week for 13 consecutive weeks to metallic Mn, Mn phosphate or Mn phosphate/sulfate mixture at about 3000 microgm(-3) and compared to controls. At the end of the exposure period, spontaneous motor activity was measured for 36 h using a computerized autotrack system. Mn in tissues was determined by instrumental neutron activation analysis (INAA). The Mn concentrations in the brain were significantly higher in rats exposed to Mn phosphate and Mn phosphate/sulfate mixture than in control rats or rats exposed to metallic Mn. Exposure to Mn phosphate/sulfate mixture caused a decrease in the total ambulatory count related to locomotor activity. Our results confirm that Mn species and solubility have an influence on the brain distribution of Mn in rats.

Animals↗
PubMed2005

The Manganese Health Research Program (MHRP): status report and future research needs and directions.

The manganese (Mn) research health program (MHRP) symposium was a full day session at the 22nd International Neurotoxicology Conference. Mn is a critical metal in many defense and defense-related private sector applications including steel making and fabrication, improved fuel efficiency, and welding, and a vital and large component in portable power sources (batteries). At the current time, there is much debate concerning the potential adverse health effects of the use of manganese in these and other applications. Due to the significant use of manganese by the Department of Defense, its contractors and its suppliers, the Manganese Health Research Program (MHRP) seeks to use the resources of the federal government, in tandem with manganese researchers, as well as those industries that are involved with manganese, to determine the exact health effects of manganese, as well as to devise proper safeguard measures for both public and private sector workers. Humans require manganese as an essential element; however, exposure to high levels of this metal is sometimes associated with adverse health effects, most notably within the central nervous system. Exposure scenarios vary extensively in relation to geographical location, urban versus rural environment, lifestyles, diet, and occupational setting. Furthermore, exposure may be brief or chronic, it may be to different types of manganese compounds (aerosols or salts of manganese with different physical and/or chemical properties), and it may occur at different life-stages (e.g., in utero, neonatal life, puberty, adult life, or senescence). These factors along with diverse genetic composition that imposes both a background and disease occurrence likely reflect on differential sensitivity of individuals to manganese exposure. Unraveling these complexities requires a multi-pronged research approach to address multiple questions about the role of manganese as an essential metal as well as its modulation of disease processes and dysfunction. A symposium on the Health Effects of Manganese (Mn) was held on Wednesday, September 14, 1005, to discuss advances in the understanding on role of Mn both in health and disease. The symposium was sponsored by the Manganese Health Research Program (MHRP). This summary provides background on the MHRP, identifies the speakers and topics discussed at the symposium, and identifies research needs and anticipated progress in understanding Mn health- and disease-related issues.

Biomedical Research↗