Visualization Of Iron Research Articles

Rapid formation of iron monosulfide on Indicator of Reduction in Soil devices in S‐rich hydric soils

AbstractIndicator of Reduction in Soil (IRIS) devices are used to identify anaerobic conditions in soils for hydric soil and wetland identification purposes. IRIS devices quantify anaerobic conditions via the visualization of iron (Fe) reduction (e.g., orange Fe3+ paint reduces to soluble Fe2+, leaving behind the bare, white polyvinyl chloride device). Under stronger reducing conditions, sulfate (SO42−) reduction can occur, and sulfides (S2− and/or H2S) can react with the Fe3+ paint, resulting in the precipitation of black‐colored, reduced iron monosulfide (FeS). While these processes are well known, the rate of FeS formation remains relatively understudied and current IRIS methods may not capture these data accurately. This study investigated FeS formation on IRIS films to identify deployment times that capture the minimum and maximum precipitation of FeS. To determine the timing and magnitude of FeS‐precipitation on IRIS films, five replicate films were deployed in a wet, S‐rich soil, across 11 periods ranging from 2 min to 30 days. Results show that FeS precipitated on IRIS films in just 2 min, and the highest average amount of FeS (82%) precipitated in 1 day. After 1 day, the percentage of FeS decreased and a white color change became more apparent on IRIS films. Our results suggest that the recommended 30‐day deployment period is too long for accurately measuring FeS‐precipitation on IRIS devices deployed in wet, alkaline soils. These considerations should be incorporated into standard IRIS protocols used to quantify anaerobic conditions and other biogeochemical conditions (e.g., pore‐water sulfide levels) in S‐rich soils.

Perls Staining for Histochemical Detection of Iron in Plant Samples

Visualization of iron (Fe) localization in plants has greatly enhanced our understanding of plant Fe homeostasis. One of the relatively simple and yet powerful techniques is the classical Perls blue stain (Perls, 1867). The technique is based on the conversion of ferrocyanide to insoluble crystals of Prussian blue in the presence of Fe3+ under acidic conditions. It has been extensively used in animal and human histology (Meguro et al., 2007) and has recently gained popularity in plant research. For specific purposes, Fe signals may be additionally enhanced in the 3,3’-diaminobenzidine tetrahydrochloride (DAB) intensification procedure (Meguro et al., 2007). It has been demonstrated that this intensification results in the detection of both Fe2+ and Fe3+ ions (Roschzttardtz et al., 2009). The method has been successfully applied at the whole plant, organ and subcellular levels, both with (Roschzttardtz et al., 2011; Schuler et al., 2012; Roschzttardtz et al., 2013; Ivanov et al., 2014) and without intensification (Stacey et al., 2008; Long et al., 2010).Here, we present a full Perls staining and DAB intensification protocol, the way it is performed in our lab (Ivanov et al., 2014).

Hyperspectral fluorescence imaging for cellular iron mapping in thein vitromodel of Parkinson’s disease

Parkinson's disease (PD) is characterized by progressive dopaminergic cell loss in the substantia nigra (SN) and elevated iron levels demonstrated by autopsy. Direct visualization of iron with live imaging techniques has not yet been successful. The aim of this study is to visualize and quantify the distribution of cellular iron using an intrinsic iron hyperspectral fluorescence signal. The 1-methyl-4-phenylpyridinium (MPP+)-induced cellular model of PD was established in SHSY5Y cells exposed to iron with ferric ammonium citrate (FAC, 100 μM). The hyperspectral fluorescence signal of iron was examined using a high-resolution dark-field optical microscope system with signal absorption for the visible/near infrared spectral range. The 6-h group showed heavy cellular iron deposition compared with the 1-h group. The cellular iron was dispersed in a small particulate form, whereas the extracellular iron was aggregated. In addition, iron particles were found to be concentrated on the cell membrane/edge of shrunken cells. The iron accumulation readily occurred in MPP+-induced cells, which is consistent with previous studies demonstrating elevated iron levels in the SN. This direct iron imaging could be applied to analyze the physiological role of iron, and its application might be expanded to various neurological disorders involving metals, such as copper, manganese, or zinc.

Aluminum detoxication mechanism in Pseudomonas fluorescens is dependent on iron.

The soil microbe Pseudomonas fluorescens has been shown to detoxify aluminum by the elaboration of a soluble metabolite where the trivalent metal is sequestered [Appanna and St. Pierre, FEMS Microbiol. Lett. 24 (1994) 327-332]. The inclusion of 5 mM iron in the growth medium elicited an entirely disparate detoxification strategy. In this instance, the two trivalent metals were immobilized in a gelatinous lipid-rich residue. Dialysis and ultracentrifugation studies indicated that the test metals were being transformed from early stages of growth and were associated with phosphatidylethanolamine. However, at 45 h of cellular multiplication, most of the metals were deposited as an insoluble residue. X-ray fluorescence analyses identified the constituents of this mineral essentially as aluminum, iron and phosphorus. Scanning electron microscopy and energy dispersive X-ray microanalysis of the dialysate, isolated at 35 h of microbial growth, revealed thread-like structures associated with nodule-like bodies that were rich in the two test metals. Transmission electron microscopic studies aided in the visualization of iron and aluminum inclusions within the bacterial cells.

Aluminum detoxification mechanism in Pseudomonas fluorescens is dependent on iron

The soil microbe Pseudomonas fluorescens has been shown to detoxify aluminum by the elaboration of a soluble metabolite where the trivalent metal is sequestered [Appanna and St.Pierre, FEMS Microbiol. Lett. 24 (1994) 327–332]. The inclusion of 5 mM iron in the growth medium elicited an entirely disparate detoxification strategy. In this instance, the two trivalent metals were immobilized in a gelatinous lipid-rich residue. Dialysis and ultracentrifugation studies indicated that the test metals were being transformed from early stages of growth and were associated with phosphatidylethanolamine. However, at 45 h of cellular multiplication, most of the metals were deposited as an insoluble residue. X-ray fluorescence analyses identified the constituents of this mineral essentially as aluminum, iron and phosphorus. Scanning electron microscopy and energy dispersive X-ray microanalysis of the dialysate, isolated at 35 h of microbial growth, revealed thread-like structures associated with nodule-like bodies that were rich in the two test metals. Transmission electron microscopic studies aided in the visualization of iron and aluminum inclusions within the bacterial cells.

The Heterogeneous Distribution of Brain Transferrin

Immunocytochemistry with antisera to transferrin has often been used to identify oligodendroglia in tissue sections and cultures, but reaction product also occurs in blood vessel walls and nerve cells. There is considerable species variation. Serum transferrin is largely biosynthesized in the liver, and its established physiological role is the transport of iron to tissue sites and delivery of the metal to the interior of cells that have transferrin receptors on their surfaces. In sections of the central nervous system, the visualization of iron and transferrin generally does not coincide, and transferrin may have importance to normal brain function beyond iron transport. For a comparative analysis of transferrin in rabbit and rat brain, polyclonal antisera were raised against purified serum transferrins of these species. The antisera were used for transferrin immunocytochemistry on vibratome sections and for immunochemical detection on electroblots. Transferrin immunocytochemistry and iron histochemistry were compared. The electrophoretic separation of brain extracts and transfer to nitrocellulose membranes permitted the quantitation of the protein and the study of the carbohydrate chains of tissue-bound transferrins by biotinylated lectins. An unexpected result in the rabbit was the dense immunocytochemical reaction product in Bergmann glia and Golgi epithelial cells. Reaction in the cytoplasm of oligodendrocytes was relatively faint in this species except for some selected white matter tracts, e.g. the inferior cerebellar peduncles. In sections of rat brain, oligodendrocytes and vessel walls reacted vigorously in all locations. Transferrin levels in rat brain were substantially higher than in rabbit brain. In the rabbit, maximum transferrin levels occurred in the cerebellum.(ABSTRACT TRUNCATED AT 250 WORDS)

Visualization of iron in cultured macrophages with autometalography

Visualization of iron in cultured macrophages with autometalography