Previous clinical and experimental studies have indicated that magnesium may prevent vascular calcification (VC), but mechanistic characterization has not been reported. This study investigated the influence of increasing magnesium concentrations on VC in a rat aortic tissue culture model. Aortic segments from male Sprague-Dawley rats were incubated in serum-supplemented high-phosphate medium for 10 days. The magnesium concentration in this medium was increased to demonstrate its role in preventing VC, which was assessed by imaging and spectroscopy. The mineral composition of the calcification was analyzed using Fourier transform infrared (FTIR) spectroscopic imaging, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) mapping. Magnesium supplementation of high-phosphate medium dose-dependently suppressed VC (quantified as aortic calcium content), and almost ablated it at 2.4 mm magnesium. The FTIR images and SEM-EDX maps indicated that the distribution of phosphate (as hydroxyapatite), phosphorus and Mg corresponded with calcium content in the aortic ring and VC. The inhibitory effect of magnesium supplementation on VC was partially reduced by 2-aminoethoxy-diphenylborate, an inhibitor of TRPM7. Furthermore, phosphate transporter-1 (Pit-1) protein expression was increased in tissues cultured in HP medium and was gradually-and dose dependently-decreased by magnesium. We conclude that a mechanism involving TRPM7 and Pit-1 underpins the magnesium-mediated reversal of high-phosphate-associated VC.
The preparation of so-called antimonic acid under various experimental conditions has been investigated in order to establish its usefulness as a chemically-stable cation-exchange material. In this experiment, the antimonic acid was mainly obtained by the hydrolysis of antimony pentachloride, and was rarely obtained from metallic antimony or potassium pyroantimonate. The hydrolyzed precipitate was amorphous at first, but it was gradually transformed into crystalline powder by keeping it in the mother liquor for a long time. The crystallization of the amorphous precipitate was facilitated by raising the temperature within a range of 0–80°C, and by increasing the concentration of strong mineral acid on aging, regardless of the kinds of starting antimony substances. The water-content of the air-dried samples is decreased by increasing the period of aging; the composition of the sample approximates Sb2O5·4H2O. The crystal of the antimonic acid is cubic and belong to the space group Oh7(Fd3m), with a lattice constant of 10.382 Å. The measurement of solubilities for the air-dried antimonic acid showed that both the amorphous and the glassy acids are soluble forms and that the crystalline is an insoluble form. The uptakes of potassium ions on these antimonic acids were little changed on the kinds of form; the uptake of lithium ions on the crystalline acid was very small as compared those on the amorphous and the glassy acids. This behavior may be attributed to the existence of different types of so-called antimonic acid, with different selectivities of their lithium ion adsorption, rather than to any difference in the size of the particle.
A new energy dispersive X-ray spectrometer (EDS) with a microcalorimeter detector equipped with a transmission electron microscope (TEM) has been developed for high- accuracy compositional analysis in the nanoscale. A superconducting transition-edge-sensor-type microcalorimeter is applied as the detector. A cryogen-free cooling system, which consists of a mechanical and a dilution refrigerator, is selected to achieve long-term temperature stability. In order to mount these detector and refrigerators on a TEM, the cooling system is specially designed such that these two refrigerators are separated. Also, the detector position and arrangement are carefully designed to avoid adverse affects between the superconductor detector and the TEM lens system. Using the developed EDS system, at present, an energy resolution of 21.92 eV full-width-at-half maximum has been achieved at the Cr K alpha line. This value is about seven times better than that of the current typical commercial Si(Li) detector, which is usually around 140 eV. The developed microcalorimeter EDS system can measure a wide energy range, 1-20 keV, at one time with this high energy resolution that can resolve peaks from most of the elements. Although several further developments will be needed to enable practical use, highly accurate compositional analysis with high energy resolution will be realized by this microcalorimeter EDS system.
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