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KBa(4)Bi(3)O crystallizes in the centrosymmetric tetragonal space group I4/mcm. In this compound, bismuth is present as two anionic species, i.e. Bi(2)(4-) dumbbells [Bi-Bi 3.113 (3) A] and isolated Bi(3-). Atom Bi1 (Bi(3-)) lies inside a bicapped square antiprism (2 x K and 8 x Ba). Atom Bi2, which forms the Bi(2)(4-) dumbbell, sits inside a bicapped distorted trigonal prism (2 x K and 6 x Ba). O atoms occupy tetrahedral voids between Ba atoms.
In dimethylformamide, the two carboxyl groups of bilirubin react with the bifunctional coupling agent, carbonyldimidazole, to form bilirubin diimidazole, which was isolated and crystallised. The bilirubin diimidazole, termed "activated bilirubin", was shown to react spontaneously with primary alcohols to form diesters of bilirubin. After addition of the tetrabutyl ammonium salt of glucuronic acid, compounds with chromatographic mobilities similar to those of bilirubin mono- and diglucuronides from bile were formed. Bilirubin diglucuronides were isolated by barium precipitation followed by solvent extraction. The bilirubin diglucuronides were considered to be a mixture of alpha and beta glucuronides esterified at positions 1,2,3, or 4 of glucuronic acid because the compound(s) was resistant to hydrolysis with glucuronidase and gave multiple sponts by chromatography after diazotization with ethyl anthranilate. The model compounds lauryl glucuronides were synthesized similarly; the most polar product by chromatography and had identical chromatographic mobility to synthetic lauryl 1-D-glucuronide prepared by reductive debenzylation of lauryl (benzyl (2,3,4-tri-O-benzyl))-D-glucuronide. It is concluded that bilirubin-1-di-beta-D-glucuronide can be synthesized when suitable protecting groups for the 2, 3, and 4 hydroxyl groups of glucuronic acid become available.
A method for determination of inorganic sulfate is described which represents the terminal step of an automated assay of organic sulfur compounds in biological fluids. Nanomole quantities of inorganic sulfate were applied to a barium chloranilate column. Corresponding amounts of chloranilate ion, released as a result of an exchange reaction, were then measured by uv absorption at 313 nm. The reproducibility and sensitivity of the method and a calibration curve are reported.
We describe the current performance of the prototype microcalorimeter energy-dispersive spectrometer (&mgr;cal EDS) developed at NIST for X-ray microanalysis. We show that the low-energy &mgr;cal EDS, designed for operation in the energy range 0.2-2 keV, offers significant advantages for low-beam-energy microanalysis. We present several examples in which the prototype &mgr;cal EDS has been used to solve problems in low-voltage microanalysis, including the analysis of tungsten silicide (WSi2), titanium nitride (TiN) and barium titanate (BaTiO3) and the measurement of chemical shifts in Fe and C compounds.
Micromonospora chalcea subsp. izumensis produces a novel beta-lactamase inhibitor izumenolide (EM4615). Isolation of izumenolide was performed by extraction into butanol under acidic conditions and then back extraction into water at neutrality. The compound was precipitated from the aqueous phase by the addition of calcium or barium salts. Further purification was achieved by distribution in BuOH - 1 N NaOH. Izumenolide is a macrolide containing sulfate ester groups.
Energy-dispersive x-ray analysis (EDXA) was used to study nine intraocular lenses from one manufacturer. Residual polishing compound was found on two of three dry-sterilized lenses from a "hot lot" associated with a high incidence of sterile hypopyon. Similar material was not present on normal lenses. This polishing compound was apparently fused to the lens surface, preventing its removal by ultrasonic cleaning. In addition, three wet-sterilized lenses were found to be covered with small crystals containing barium. These crystals apparently resulted from leaching of the glass storage vial by the caustic storage fluid. It is suggested that some cases of sterile hypopyon following intraocular lens surgery may be caused by residual polishing compound present on the lens surface.
A stingray pattern is adopted by Ba(2)Ag(8)S(7). Crystals of this compound were grown in a two-electrode chemical cell from a BaS(3)/ethylenediamine solution. In the pseudo-one-dimensional structure columns of (1)(infinity)[Ag(8)S(7)] (shown in the picture) are stacked head-to-tail to create voids where the barium atoms reside. The coexistence of S(2-) and S(2)(2-) indicates a reductive decomposition [Eq. (1)].
Enemas of various solutions were administered to rats to determine if Gastrografin was specifically irritating to the colonic mucosa. Gastrografin was found to cause considerably more inflammation than Hypaque-25, or barium sulfate. Further studies with hypertonic sorbitol, Renografin-76, and Tween 80 suggested that (a) neither hyperosmolality nor the diatrizoate compound itself were damaging to the colon, and (b) Tween 80 most likely plays a major role in Gastrografin's inflammatory effect.
Three kinds of diffusion samplers, conceived to perform long-term samplings in indoor sites are illustrated in this work. Two of them, in part deriving from the previous "Analyst for VOC" device, extend the field of application up to the semi-volatile organic compounds (SVOC), PAHs and nicotine in particular. A third device, which employs a basic barium hydroxide solution as an absorbing medium, is proposed for the determination of carbon dioxide levels which indicate the air change quality in the indoor sites. Laboratory and field experiments, performed in order to assess the reliability of the proposed devices, are shown. A monthly monitoring campaign, performed at three private apartments in Rome and its outskirts highlights that the indoor pollution levels are a complex function of various concurrent and opposite factors, like external air pollution, internal sources, air change rate and sink effect of surfaces, which contribute to depletion phenomena through adsorption and/or decomposition processes.
Elucidating the precise mechanism of intestinal ammonium transport is critical to the understanding of the acidosis associated with intestinal urinary diversion. Unfortunately, it is incompletely understood and controversial. Recently, we have shown that furosemide and Ba2+ significantly inhibit ammonium absorption in the ileum. On the basis of this and other data, we have suggested that ionized ammonium absorption occurs via K(+)-transport pathways. The present study examines intestinal ammonium absorption and its inhibition by K+ and Ba2+ utilizing a simplified in vivo system in rat distal ileum. Ammonium absorption demonstrates a tendency towards saturation at initial concentrations between 0 and 300 mM/l. Above 300 mM/l. there was a marked increase in ammonium absorption suggesting a possible biological effect of high NH4+ concentrations on the intestinal segment. Potassium inhibits ammonium absorption. K+ (50 mM/l.) significantly inhibited ammonium at an initial concentration of 100 mM/l. (p less than 0.05) and K+ (100 mM/l.) inhibited ammonium absorption at both 50 and 100 mM/l. (p less than 0.05 and p less than 0.01 respectively). Potassium inhibition of ammonium absorption was lost at concentrations above 200 mM/l. suggesting that K+ inhibition occurs via a competitive mechanism. Ba2+ (25 mM/l.) was shown to be a potent inhibitor of ammonium absorption. This significant inhibition persisted at high initial ammonium concentrations suggesting a complex, noncompetitive mechanism of inhibition. In conclusion, this study provides important data further suggesting that ammonium transport in the intestine occurs via K+ transport pathways, and suggests that the traditionally held mechanism of nonionic ammonium diffusion needs reevaluation.
The uptake of Ba(II) and Sr(II) by hydrous ferric oxide (HFO) was studied as a function of contact time, concentration, temperature and pH of the respective adsorptive solutions employing the 'radiotracer technique'. The uptake of both the ions was found to increase with the increase in concentration, temperature and pH of the adsorptive solutions. Concentration dependence data fitted well to the Freundlich adsorption isotherm over the entire range of concentration (10(-2)-10(-7) M) and the uptake process followed first-order rate kinetics. The desorption experiments demonstrate the irreversible nature of the uptake process, however, in the presence of H+ ions, i.e. on acidification, an appreciable amount of metal ions were removed in the bulk solution. The radiation stability of hydrous ferric oxide towards the uptake of Ba(II) and Sr(II) was also examined by using samples of hydrous ferric oxide irradiated by neutrons and gamma-rays prior to be employing as sorbents. The presence of some mono- and divalent co-ions along with the studied ions suppressed their removal appreciably.
We report the synthesis of the single enantiomers of permanently charged dihydropyridine derivatives (DHPs with alkyl linker lengths of two and eight carbon atoms) and their activities on cardiac and neuronal L-type calcium channels. Permanently charged chiral 1,4-dihydropyridines and methyl (omega)-trimethylalkylammonium) 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylate iodides were synthesized in high optical purities from (R)-(-) and (S)-(+)-1,4-dihydro-2,6-dimethyl-5-methoxycarbonyl-4-(3-nitrophenyl)-3-+ ++pyridinecarboxylic acid, obtained by resolution of racemic 1,4-dihydro-2,6-dimethyl-5-methoxycarbonyl-4-(3-nitrophenyl)-3-pyridi necarboxylic acid. Competition binding experiments with radioligand [3H]-(+)-PN200-110 and the block of whole cell barium currents through L-type calcium channels in GH4C1 cells show that the compounds with the eight-carbon alkyl linker optimally block the L-type Ca2+ channels, and that the S-enantiomer is more potent than the R-enantiomer.
[structure: see text] Tetrathiafulvalene redox-responsive ligands devoid of cis/trans isomerism containing the electroactive bis(pyrrolo[3,4-d])tetrathiafulvalene moiety and polyether subunits have been synthesized. One ligand exhibits high binding affinities for Pb2+ and Ba2+ cations as shown by independent methods (1H NMR, UV-vis spectroscopy, and cyclic voltammetry). The ability of this receptor to electrochemically recognize Pb2+ and Ba2+ is shown by cyclic voltammetry.
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The distal 2/3 of the opossum esophagus contains only smooth muscle. Manometry shows that the most distal 1-2 cm is the lower esophageal sphincter. We used a variety of agonists to seek differences between circular muscle from the sphincteric segment and more rostral levels. Isometric contractions of strips from the distal 6 cm were recorded in vitro in response to acetylcholine, carbachol, methacholine, nicotine. DMPP, norepinephrine, norepinephrine with propranolol, barium, atropine, and potassium. Significant differences in threshold concentration occurred for all drugs except barium, atropine, and potassium, the more distal strips being more sensitive. The gradient of threshold was much steeper for norepinephrine than for the other drugs. Maximal responses did not differ among levels for the choline esters or ganglionic stimulants, but showed proximal diminution for norepinephrine. These differences in threshold concentration could represent differences in distribution density of drug receptor sites, differences in affinity of receptors for the agonists, differences in rates of uptake of agonists, or differences in rates of enzymatic hydrolysis; or they may have no common basis. The sphincter is defined, at least in part, in the esophageal wall rather than in the central nervous system. The greater magnitude of the difference in sensitivity to norepinephrine than for the other agents suggests that the adrenergic innervation is important in defining the lower esophageal sphincter.
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PURPOSE: In addition to the CIE Lab color-difference formula (deltaE*ab), advanced formulas that include weighting functions have been introduced. The objectives of this study were to determine the correlations in color differences between different shade pairs of resin composites by different color formulas, and to determine whether the weighting functions included in the advanced formulas influenced the color-difference values. MATERIALS AND METHODS: Color was measured after polymerization of two resin composites in 26 shades, and color differences between shades were calculated by deltaE*ab, CIEDE 2000 (deltaE00), and DIN 99 (deltaE99) formulas. Regression analyses were performed between the color differences calculated by three formulas in each group divided by the differences in color parametric factors between the pairs compared. RESULTS: There were significant correlations between deltaEab and deltaE00, deltaEab and deltaE99, and deltaE99 and deltaE00 (r2 = .99, .89, and .90, respectively). The weighting functions in the CIEDE 2000 formula had influence on deltaE00 values when differences in chroma and hue between compared pairs were great. CONCLUSION: Differences in parametric factors between the pairs compared influenced the correlation between deltaE*ab and deltaE99 values (r2 = .25 to .97). As the CIEDE 2000 formula has been proven to be better matched to observer responses and showed significant involvement of weighting functions compared to CIE Lab color difference, this formula should be considered for evaluation of the color of resin composites.
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