Iron-rich Areas Research Articles

Iron concentration reduced in ventral pallidum, globus pallidus, and substantia nigra by GABA-transaminase inhibitor, gamma-vinyl GABA

Recent histochemical studies indicate that there is considerable overlap of brain areas accumulating iron in oligodendrocytes with those in which GABA neurons terminate. The ventral pallidum, globus pallidus, substantia nigra and cerebellar nuclei are iron-rich areas, receive GABA-containing efferents, and have high concentrations of gamma-aminobutyric acid (GABA) and glutamic acid decar☐ylase (GAD). The present study examines the efect of disruption of the metabolism of GABA on the accumulation of iron in GABAergic projection sites. Gamma-vinyl GABA, an enzyme activated inhibitor of GABA-transaminase, was injected unilaterally into the globus pallidus and adjacent striatum or into the substantia nigra of the rat brain. Additional animals received unilateral injections of saline into the same areas or an electrocoagulation lesion of the globus pallidus and surrounding striatum. Two days after injection or lesion all animals were perfused and 40 μm sections of the brain were processed with the Perls' + diaminobenzidine (DAB) histochemical method for iron. The intensity of iron stain was measured with densitometry. Gamma-vinyl GABA injection into the striatum/pallidum resulted in a significant reduction in iron concentration in the ipsilateral ventral pallidum, globus pallidus and substantia nigra. Gamma-vinyl GABA injected into the substantia nigra reduced iron in the injection site. This study provides evidence that the presence of iron in the brain is related to the utilization of GABA.

The use of in the x-ray photo-electron spectroscopy analyses of passive layers on stainless steel

The repassivation of a commercial grade 18% Cr 8% Ni austenitic stainless steel in low temperature, neutral, de-oxygenated water was studied by XPS, obtaining composition profiles by argon ion milling. Evaluation of the technique revealed negligible effect of sample transfer through air from the spectrometer to the corrosion cell, but photo-electron attenuation and reduction in peak definition resulted from organic carbon pick-up both from water and spectrometer vacuum. The passive layers contained chromium-rich and iron-rich areas. The Cr 3+, Fe 2+ and Fe 3+ cations are incorporated in layers containing both OH − and O 2− ions. The unreacted nickel of the alloy showed an attenuation of the 2p 3 2 signal with exposure which presented a unique opportunity to calculate film thickness. Increases in refreshment rate (1, 3 and 6 ml/h) at 313 K and 353 K respectively increased the film thickness (1.5–3.0 nm); possibly due to increased carbon accreation, incorporating hydrogen-bonded water into the film. The outer 33% of the film revealed (Fe 2+ + Fe 3+)/(Cr 3+) corresponding to alloy proportions, suggesting no overall selective oxidation or dissolution.

The mineralization and hardness of the radular teeth of the limpet Patella vulgata L.

A study of the Patella vulgata radula has been made using: the scanning electron microscope in its normal and compositional contrast modes of operation, the electron microprobe analyser, ion etching with argon ions and microhardness testing. Only iron, silicon and small amounts of sulphur were detected in the radula. The teeth can be subdivided into a cusp, a junctional area where the cusp is joined to the base, and the base which is embedded in the radular membrane. From a study of longitudinal vertical and transverse sections of the mature teeth it was found that the cusp could be subdivided into a posterior iron-rich area (44–51% Fe, 1–6% Si) and an anterior silicon-rich area (22–30% Fe, 27–32% Si). The junctional zone consisted of a poorly mineralised layer at its border with the cusp and an iron-rich layer where it joined the base. The upper part of the base (5% Fe, 16% Si) could be clearly differentiated from the silicon-rich anterior and lower parts of the base (3–4% Fe, 28–35% Si). No minerals were detected in the membrane. The changes in the mineral content of the teeth cusps along the length of the radula were studied. Iron appeared in the cusps at the 25th row and the concentration increased to 28% at the 50th row. The iron was here evenly distributed throughout the cusp. Silicon appeared in the anterior part of the cusp at the 50th row and as it increased in concentration so the iron was displaced, and at the same time the concentration of iron increased in the posterior part of the cusp. Mineralization appeared to be complete by the 150th row. The teeth cusps appear to consist of 800 A fibres grouped into 1μ thick bundles and the tooth appears to be covered by a thin enamel-like layer. It is suggested that the fibres contain the silicon-rich phase and the matrix the iron-rich phase. The significance of the arrangement of the fibres and the distribution of the minerals are discussed with relation to the function of the teeth.

Line Widths in Polycrystalline Yttrium Iron Garnet

The line widths at the half-power point for ferromagnetic resonance in a number of polycrystalline yttrium iron garnet samples have been measured at 16 kmc. It has been determined that, starting with mixtures of Y2O3 and Fe2O3, sound parts with small grain size and having line widths as low as 35 to 40 oersteds can be obtained on the iron-rich side of stoichiometry in Y3Fe5O12. However, narrower line widths (∼20 oersteds) in large grained materials are obtained by using less than the stoichiometric amount of iron and firing at temperatures higher than 1450°C. This is due to minimizing the disrupting influences of oxygen loss in iron-rich areas at high temperatures. Line widths do not appear to be broadened by the addition of small amounts of nickel, cobalt, or manganese to convert excess iron to high resistance forms of spinel in the iron-rich compositions.