Iron-Responsive Olfactory Uptake of Manganese Improves Motor Function Deficits Associated with Iron Deficiency

Iron-responsive manganese uptake is increased in iron-deficient rats, suggesting that toxicity related to manganese exposure could be modified by iron status. To explore possible interactions, the distribution of intranasally-instilled manganese in control and iron-deficient rat brain was characterized by quantitative image analysis using T1-weighted magnetic resonance imaging (MRI). Manganese accumulation in the brain of iron-deficient rats was doubled after intranasal administration of MnCl2 for 1- or 3-week. Enhanced manganese level was observed in specific brain regions of iron-deficient rats, including the striatum, hippocampus, and prefrontal cortex. Iron-deficient rats spent reduced time on a standard accelerating rotarod bar before falling and with lower peak speed compared to controls; unexpectedly, these measures of motor function significantly improved in iron-deficient rats intranasally-instilled with MnCl2. Although tissue dopamine concentrations were similar in the striatum, dopamine transporter (DAT) and dopamine receptor D1 (D1R) levels were reduced and dopamine receptor D2 (D2R) levels were increased in manganese-instilled rats, suggesting that manganese-induced changes in post-synaptic dopaminergic signaling contribute to the compensatory effect. Enhanced olfactory manganese uptake during iron deficiency appears to be a programmed “rescue response” with beneficial influence on motor impairment due to low iron status

Fine-Scale in Situ Measurement of Riverbed Nitrate Production and Consumption in an Armored Permeable Riverbed

Alteration of the global nitrogen cycle by man has increased nitrogen loading in waterways considerably, often with harmful consequences for aquatic ecosystems. Dynamic redox conditions within riverbeds support a variety of nitrogen transformations, some of which can attenuate this burden. In reality, however, assessing the importance of processes besides perhaps denitrification is difficult, due to a sparseness of data, especially in situ, where sediment structure and hydrologic pathways are intact. Here we show in situ within a permeable riverbed, through injections of 15N-labeled substrates, that nitrate can be either consumed through denitrification or produced through nitrification, at a previously unresolved fine (centimeter) scale. Nitrification and denitrification occupy different niches in the riverbed, with denitrification occurring across a broad chemical gradient while nitrification is restricted to more oxic sediments. The narrow niche width for nitrification is in effect a break point, with the switch from activity “on” to activity “off” regulated by interactions between subsurface chemistry and hydrology. Although maxima for denitrification and nitrification occur at opposing ends of a chemical gradient, high potentials for both nitrate production and consumption can overlap when groundwater upwelling is strong

Assessing the Seasonal Dynamics of Nitrate and Sulfate Aerosols at the South Pole Utilizing Stable Isotopes

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Brain iron loading impairs DNA methylation and alters GABAergic function in mice.

Iron deficiency is closely associated with altered GABA metabolism and affective behavior. While mutation in the hemochromatosis ( HFE) gene disrupts iron homeostasis and promotes oxidative stress that increases the risk of neurodegeneration, it is largely unknown whether HFE mutation modifies GABAergic homeostasis and emotional behavior. The goal of our study was to investigate the impact of HFE on GABAergic neurochemistry and redox-epigenetic regulation in the brain using H67D HFE-mutant mice that recapitulates the H63D-HFE mutation in humans. H67D mice displayed elevated redox-active iron levels in the brain by 32% compared to age-matched wild-type mice. Moreover, the H67D brain had increased isoprostane and decreased glutathione, indicating elevated oxidative stress. Additionally, the H67D brain had decreased global methylation and attenuated DNA methyltransferase (DNMT) activity. Direct addition of iron to purified DNMT in vitro decreased enzyme activity in a concentration-dependent manner. Last, H67D mice exhibited decreased anxiety-like behavior, which was associated with increased expression of the GAB

Effect of iron deficiency and manganese instillation on the expression of dopamine transporters and receptors in the striatum.

<p>Rats intranasally instilled with MnCl₂ (6×10 mg/kg) were euthanized and striatal tissues were collected and homogenized to determine the expression levels of dopamine transporter (DAT; <b>A</b>), dopamine receptor D₁ (D1R; <b>B</b>), and dopamine receptor D₂ (D2R; <b>C</b>). Relative intensities of protein bands normalized to actin were determined using Odyssey software (version 2.1). Empty and closed bars represent water-instilled and MnCl₂-instilled rats, respectively. Data were presented as mean ± SEM (N = 3–4 per group) and were analyzed using two-way ANOVA.</p