Comparison of 99mTc complexes for renal imaging.
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The distribution of 17 different agents for renal imaging was compared in the rabbit by organ radioassay at 1 hr. Similarly, 99mTc complexes of iron-ascorbate, glucoheptonate (GHA) and 2,3-dimercaptosuccinic acid (DMS), and 203Hg-chlormerodrin were compared in the dog. The distribution of 99mTc-GHA and DMS was assessed in the human by blood and urinary clearance, external renal measurements, and scintillation camera imaging, and compared with older renal radiopharmaceuticals. Radiation dose estimates, based chiefly on human data, were calculated. Technetium-99m-DMS reaches a high concentration in the renal cortex and its urinary excretion rate and blood clearance are slow. It is excellent for imaging the renal parenchyma without activity in pelvocalyceal collecting system. However, it readily oxidizes and must be used within 30 min of preparation. The biologic distribution of 99mTc-GHA is similar to gluconate and iron-ascorbate complex. Its renal concentration is not as great as that of DMS but its blood and urinary clearances are much faster, resulting in lower radiation doses to most organs. Early camera images with this agent usually demonstrate both the renal parenchyma and collecting system. In later images, ther is excellent demonstration of the parenchyma alone, superior to that obtained with 99mTc-Sn-DTPA. It is a very stable complex and may be used for at least 5 hr after preparation. All radioactive renal agents examined to date have a significant concentration in the liver, making an accurate quantitative comparison between the two kidneys difficult. (+info)
Combination of renal and adrenal scanning in the diagnosis of renovascular hypertension: case report.
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Superimposition of an adrenal scan on a renal scan revealed a kidney defect not appreciated on the renal scan alone. The defect proved to be ischemia of the upper pole of the kidney. Resection of the lesion alleviated the patient's hypertension. (+info)
Evaluation of radiopharmaceuticals sequestered by acutely damaged myocardium.
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Eighteen radiopharmaceuticals were screened in a small-animal model as potential infarct-localizing agents. Twelve of the 18 compounds were labeled with 99mTc, four with 203Hg, one with 131I, and one with either 203Hg or 125I. The model used heat-induced myocardial lesions in the rat. The absolute concentration within the lesion and also the activity ratios of injured myocardium to normal heart tissue, blood, and muscle were determined for all compounds. Among the 99mTc-labeled agents, two bone-seekers [pyrophosphate (PPi) and 1-hydroxyethylidine-1,1-diphosphonate (HEDP)] showed the most promise; these were followed by 99mTc-tetracycline analogs and 99mTc-glucoheptonaate. The tracer showing the most favorable concentration in the lesion and the best target-to-nontarget ratios was an iodinated derivatives of hydroxymercurifluorescein labeled with either 125I or 203Hg. Consideration of the structure of these compounds suggests that the presence of mercury or of a polycyclic aromatic structure, such as that found is tetracycline and fluorescein, was associated with localization in damaged myocardial tissue. Mercury bound to such an aromatic moiety may produce an additive or even a synergistic effect. (+info)
Mercuric reductase activity and evidence of broad-spectrum mercury resistance among clinical isolates of rapidly growing mycobacteria.
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Resistance to mercury was evaluated in 356 rapidly growing mycobacteria belonging to eight taxonomic groups. Resistance to inorganic Hg2+ ranged from 0% among the unnamed third biovariant complex of Mycobacterium fortuitum to 83% among M. chelonae-like organisms. With cell extracts and 203Hg(NO3)2 as the substrate, mercuric reductase (HgRe) activity was demonstrable in six of eight taxonomic groups. HgRe activity was inducible and required NADPH or NADH and a thiol donor for optimai activity. Species with HgRe activity were also resistant to organomercurial compounds, including phenylmercuric acetate. Attempts at intraspecies and intragenus transfer of HgRe activity by conjugation or transformation were unsuccessful. Mercury resistance is common in rapidly growing mycobacteria and appears to function via the same inducible enzyme systems already defined in other bacterial species. This system offers potential as a strain marker for epidemiologic investigations and for studying genetic systems in rapidly growing mycobacteria. (+info)
Myocardial infarct imaging agents. III. Synthesis and evaluation of [203Hg] hydroxymercuriphthaleins.
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Four Hg-203-mercurated phthaleins were prepared, purified, and compared with [203Hg] mercuric nitrate, [3H] phenolphthalein [203Hg] hydroxymercurifluorescein and Tc-99m-pyrophosphate in a rat model of myocardial necrosis to determine their specificities for damaged myocardium. The ratios of damaged myocardium to normal myocardium, and to blood, for the [203Hg] hydroxymercuriphthaleins (20.7-34.1 and 12.1-20.1, respectively) were somewhat lower than those reported previously for [203Hg] hydroxymercurifluorescein, but were higher than those found with [203Hg] mercuric nitrate, [3H] phenolphthalein, and Tc-99m pyrophosphate. Both the hydroxymercuri- functional group and the phthalein moiety are required for selectivity. The removal of the oxygen bridge present in fluorescein, and the replacement of carboxylic acid by sulfonic acid, had no significant effects on the sequestration process in damaged tissue. (+info)
Dental "silver" tooth fillings: a source of mercury exposure revealed by whole-body image scan and tissue analysis.
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Mercury (Hg) vapor is released from dental "silver" tooth fillings into human mouth air after chewing, but its possible uptake routes and distribution among body tissues are unknown. This investigation demonstrates that when radioactive 203Hg is mixed with dental Hg/silver fillings (amalgam) and placed in teeth of adult sheep, the isotope will appear in various organs and tissues within 29 days. Evidence of Hg uptake, as determined by whole-body scanning and measurement of isotope in specific tissues, revealed three uptake sites: lung, gastrointestinal, and jaw tissue absorption. Once absorbed, high concentrations of dental amalgam Hg rapidly localize in kidneys and liver. Results are discussed in view of potential health consequences from long-term exposure to Hg from this dental material. (+info)
A multidetector scintillation camera with 254 channels.
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A computer-based scintillation camera has been designed for both dynamic and static radionuclide studies. The detecting head has 254 independent sodium iodide crystals, each with a photomultiplier and amplifier. In dynamic measurements simultaneous events can be recorded, and 1 million total counts per second can be accommodated with less than 0.5% loss in any one channel. This corresponds to a calculated deadtime of 5 nsec. The multidetector camera is being used for 133Xe dynamic studies of regional cerebral blood flow in man and for 99mTc and 197 Hg static imaging of the brain. (+info)
Interaction of alkylmercuric compounds with sodium selenite. II. Metabolism of methylmercuric chloride administered alone and in combination with sodium selenite in rats.
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Repeated doses of sodium selenite (Se) were administered to rats receiving repeated (IV or PO) doses of 0.25 or 2.5 mg Hg/kg methylmercuric chloride (Me2(203)Hg). Se (0.5 mg/kg) was observed to alter the distribution of Me203Hg among tissues as well as among subcellular fractions of kidneys and liver. An excess of selenium resulted in a twofold decrease in the mercury content of kidneys and a similar increase in the mercury content of brain. (+info)