A detailed study of iron concentrations measured by the reducible, reactive ferrous, and extractable methods was conducted in Auke Bay, Alaska during June 1973 and in Hood Canal, Washington during October 1973 and April 1974. The concentrations by each method were generally highest at the bottom and decreased towards the surface with occasional pockets of high iron concentration water at the surface. In Hood Canal in October the maximum reactive ferrous iron concentration was observed at the bottom of the pycnocline. Large changes in the iron concentration were observed between successive surveys. The reducible iron method (range <0.8 to 187 μg Fe/L) measures colloidal ferric hydroxide plus easily dissolvable and reducible organically and inorganically bound iron. The reactive ferrous iron method (range <0.04 to 4.2 μg Fe/L) measures loosely bound organic and inorganic ferrous iron. The extractable iron method, as finally used, (range <4 to 170 μg Fe/L) measures that iron measured by reducible iron method plus up to twice the tightly bound organic iron. We have defined "available" iron (with quotes) as that iron which appears to be taken up by phytoplankton as determined by the correlation between the in situ iron concentration and the chlorophyll a concentration. Chlorophyll a concentration maxima generally occurred at the depth of the iron concentration minima, strongly supporting the idea that each method measures "available" iron. However, significant correlation coefficients for the regression of iron concentration versus chlorophyll a only support the "availability" of reactive ferrous iron and that phytoplankton prefer ferrous iron to ferric iron. This was one of the first extensive uses of Lewin and Chen's (1973) ferrous iron method and values observed were generally 2 to 100 times less than they reported. Changes occurring during water storage appear to be a function of p0₂. Major changes took place during the first five hours of storage. Interstitial water was greatly enriched in iron compared with the overlying water. The ferrous iron concentration was particularly high due to the low Eh of the sediments. Although the net flow of "available" iron is out of the sediment, the flux is small (approximately 3 x 10⁻⁵ μg Fe/m²sec). Most of the iron that appears to be coming from the sediment is probably being produced by bacterial decomposition as in the case of subsurface sources of iron associated with ammonia or urea maxima. Fresh water is a significant source of extractable and reactive ferrous iron into the well-mixed surface layer. Fresh water is also a source of organically bound iron. Zooplankton appear to produce "available" iron by eating or excretion. Light appears to cause the production of ferrous iron through an undetermined mechanism. / Graduation date: 1976

Call number: LD2668 .T4 1965 J79 / Master of Science

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A key mechanism utilized by plants to make iron (Fe) available for uptake is the reduction of Fe(III) to Fe(II) via an inducible, plasma membrane-bound Fe(III) reductase. Genes encoding such enzymes have not yet been isolated from plants; however, two Fe(III) reductases have been cloned from yeast. FRE1 and FRE2 account for the total membrane-associated Fe(III) reductase activity in Saccharomyces cerevisiae. If yeast reductase genes could be expressed in a plant system, root Fe(III) reduction may be enhanced, leading to a decrease in Fe chlorosis in transgenic plants. FRE1 and FRE2 were introduced into tobacco via Agrobacterium-mediated transformation. Fe(III) reductase activity was measured in homozygous transformants containing FRE1, FRE2, or both. The highest Fe(III) reduction levels were found in lines containing both FRE1 and FRE2. Liquid reductase assays showed three to four times more Fe(III) reduction in these transformants as compared to controls, and visual plate assays showed reduction along the entire length of the roots. One FRE1 containing line initially exhibited chlorosis on medium with low Fe at pH 7.5, but later recovered. Other transformants and the control remained chlorotic. Agrobacterium-mediated transformation often produces mutant phenotypes. A temperature-dependent morphological mutant was found among the progeny of tobacco transformed by Agrobacterium. The mutation is recessive and is expressed at low temperature (21��C). Mutant characteristics include formation of thick, narrow leaves with abnormal mesophyll cells and near absence of apical dominance. Also in the greenhouse (21-23��C), most plants remain vegetative, and the few flowers that are formed have petaloid stamens. High temperature (30��C) reverses the mutant phenotype, with formation of normal leaves and restoration of apical dominance. However, many flowers still have petaloid stamens. This mutant shares several phenotypic characteristics with transgenic tobacco plants overexpressing maize and Arabidopsis homeodomain proteins. / Graduation date: 1997

No description available.

No description available.

Both Immune cells and pathogenic microorganisms require iron for proliferation and multiplication. However, role of iron supplementation on immune function is still unclear. Studies show that iron-deficient mice are protected from developing Experimental Autoimmune Encephalomyelitis (EAE), an animal model of Multiple Sclerosis (MS) in humans. In this project, we developed a mice model of iron overload in (B6.Cg-Tg (Thy1-YFPH) 2Jrs/J mice). Seven mice were injected (ip), 100 μl iron dextran and seven with Phosphate buffered saline (PBS), five days/week for four weeks. Blood samples verified iron overload 170 versus 138μg/dl (P < 0.005). Flow Cytometry revealed high T-cells and low and CD8+ T-cell. Histological sections indicated perivascular immune cell infiltrations in the brain, but not in the spinal cord. Confocal microscopy of spinal cord sections showed myelinated axons with no breaks. The absence of demyelination and clinical signs, but high CD3+ with low CD4+ T-cells suggests an altered immune cell function in iron overload mice that needs further exploration. / Access to thesis permanently restricted to Ball State community only / Department of Physiology and Health Science

A number of neurodegenerative diseases like Multiple Sclerosis, Parkinson’s and Alzheimer’s have been linked with iron accumulation in the brain. Iron plays an important role in neural metabolism. However, mechanisms of neural degeneration in iron overload are complex and not clearly understood. We proposed that iron overload may lead to demyelination in B6.Cg-Tg (Thy1-YFPH) 2Jrs/J mice. These mice express spectral variants of GFP (yellow-YFP) at high levels in motor and sensory neurons. Serum iron levels were significantly higher in experimental versus control animals. Brain and spinal cords were harvested and fixed after 4 weeks of iron dextran injections. Tissue slices were stained with Prussian blue, H&E and fluromyelin for light and confocal microscopy. Immunological profile by Flow Cytometric analysis revealed significantly high numbers of CD3+T cells with no differences in CD4:CD8 ratio. This study indicates that iron overload caused a significant inflammation without demyelination in the CNS. / Department of Physiology and Health Science

published_or_final_version / abstract / Physiology / Master / Master of Philosophy