PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “METALS, RADIOACTIVE”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 847 records · Page 47Linked to original sources
PubMed1994

A biological method to evaluate bifunctional chelating agents to label antibodies with metallic radionuclides.

UNLABELLED: Since the lysosome is a common organelle for protein digestion, pursuing the fate of radiolabeled metabolites after lysosomal proteolysis in liver cells is ideal to evaluate bifunctional chelating agents (BCAs). METHODS: We used galactosyl-neoglycoalbumin (NGA) and mannosyl-neoglycoalbumin (NMA) as carrier proteins for hepatic parenchymal and nonparenchymal cells, respectively. These proteins were labeled with 111In using 1-(4-isothiocyanatobenzyl)ethylenediaminetetraacetic acid (SCN-Bz-EDTA) as a model. RESULTS: NGA-SCN-Bz-EDTA-111In exhibited rapid accumulation in the hepatic parenchymal cells, followed by hepatobiliary excretion of the metabolites with an elimination rate that was faster and much slower than that of NGA-DTPA-111In and NGA-131I, respectively. This metabolite represented all the radioactivity registered in the liver at 1 hr postinjection. Subcellular distribution studies indicated the metabolites were located only in the lysosome fraction, and the difference in elimination rates of the metabolites from the lysosome fraction was responsible for the variations in radioactivity clearance from the cells. CONCLUSION: The biological characteristics of radiolabeled metabolites play a critical role in eliminating the radiolabel from liver cells. The present method portrays a highly useful model to pursue the fate of radiolabeled metabolites in the liver.

Albumins↗
PubMed1997

Myelin basic protein is a zinc-binding protein in brain: possible role in myelin compaction.

The zinc-binding proteins (ZnBPs) in porcine brain were characterized by the radioactive zinc-blot technique. Three ZnBPs of molecular weights about 53 kDa, 42 kDa, and 21 kDa were identified. The 53 kDa and 42 kDa ZnBPs were found in all subcellular fractions while the 21 kDa ZnBP was mainly associated with particulate fractions. This 21 kDa ZnBP was identified by internal protein sequence data as the myelin basic protein. Further characterization of its electrophoretic properties and cyanogen bromide cleavage pattern with the authentic protein confirmed its identity. The zinc binding properties of myelin basic protein are metal specific, concentration dependent and pH dependent. The zinc binding property is conferred by the histidine residues since modification of these residues by diethyl-pyrocarbonate would abolish this activity. Furthermore, zinc ion was found to potentiate myelin basic protein-induced phospholipid vesicle aggregation. It is likely that zinc plays an important role in myelin compaction by interacting with myelin basic protein.

Animals↗
PubMed1974

Reverse transcriptase: correlation of zinc content with activity.

Evidence is presented that DNA polymerase of avian myeloblastosis virus has an obligatory zinc requirement for activity. Previous studies indicate that the purified polymerase contains zinc in a stoichiometry of about 1 g-atom/mole. We now find that the enzyme-bound zinc is exchangeable with radioactive (65)Zn; after isoelectric focusing, the radioactive (65)Zn is coincident with polymerase activity. Dialysis of the (65)Zn-labeled polymerase against the chelator, 1,10-phenanthroline, results in a progressive loss of radioactive (65)Zn and polymerase activity. Thereupon, incubation of the inactivated enzyme with Zn(2+) fully restores activity. Thus, the DNA polymerase present in an oncogenic RNA virus, like animal DNA polymerases, can be rigorously classified as a zinc metalloenzyme. DNA polymerase of avian myeloblastosis virus is inactivated by 1,10-phenanthroline at a much faster rate than the bacterial and animal DNA polymerases that have been tested. It may, therefore, be possible to inactivate selectively DNA polymerases from animal tumor viruses by brief exposure to appropriate metal chelators.

Avian Leukosis Virus↗
PubMed2006

Laboratory analyses of 60Co2+, 65Zn2+ and (55+59)Fe3+ radiocations uptake by Lemna minor.

The living Lemna minor vascular plant and two different sorbents obtained by chemical treatment of this plant were tested to study the removal process of 60Co2+, 65Zn2+ and (55+59)Fe3+ from low radioactive wastewaters. The most effective sorbent was the protonated biomass, indicating the decisive contribution of the complexation process in the assembly of the uptake mechanisms. The uptake performance of the biosorbent obtained from the L. minor can be increased with approximately 20% by treatment with 0.1 N HNO3. Concerning the metabolically active mechanism, it can be notice the slow elimination of 65Zn2+ and the continuously increase of (55+59)Fe3+ uptake degree. The Na2CO3 generated in situ in systems participates to a double exchange reaction with the metallic cations during the uptake. 60Co2+, 65Zn2+ and (55+59)Fe3+ radiocations prefer for coordination N-donor ligands at the expense O-donors ones.

Araceae↗
PubMed2002

The use of the Monte Carlo simulation technique for the design of an H*(10) dosemeter based on TLD-100.

The thermoluminescence (TL) detector material LiF:Mg,Ti (TLD-100) and appropriate filter materials were combined in order to design a passive dosemeter measuring the operational quantity ambient dose equivalent, H*(10), for monitoring low-dose external photon radiation fields. Using the Monte Carlo simulation technique, optimisations of energy dependent conversion coefficients from air kerma free-in-air compared to ICRU and ISO proposed values. h*K(10), were performed by varying dosemeter detector positioning. geometrical arrangements, and filter materials. Deviations smaller than 5% compared to h*K(10) between 30 keV and 2.5 MeV of primary photon energies were achieved by a dosemeter design consisting of a 15 microm Sn metal layer and a 5 mm PMMA layer surrounding the LiF detector. Subsequently performed free-air verification experiments carried out in well defined standard photon radiation fields showed an obviously TL-specific effect. An underestimation up to -15% of the modelled data at low photon energies was observed.

Air Pollutants, Radioactive↗
PubMed2005

Determination of phosphorus-, copper-, and zinc-containing human brain proteins by LA-ICPMS and MALDI-FTICR-MS.

Human brain proteins containing phosphorus, copper, and zinc were detected directly in protein spots in gels of a human brain sample after separation by two-dimensional gel electrophoresis using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). A powerful laser ablation system with cooled laser ablation chamber was coupled to a double-focusing sector field ICPMS. The separated protein spots in 2D gels were fast screened using the optimized microanalytical LA-ICPMS technique measured at medium mass resolution with a focused laser beam (wavelength, 213 nm; diameter of laser crater, 50 mum; and laser power density, 3 x 10(9) W cm(-2)) with respect to selected three essential elements. Of 176 protein spots in 2D gel from a human brain sample, phosphorus, copper, and zinc were detected in 31, 43, and 49 protein spots, respectively. For the first time, uranium as a naturally occurring radioactive element was found in 20 selected protein spots. The detection limits for P, S, Cu, Zn and U were determined in singular protein spots with 0.0013, 1.29, 0.029, 0.063, and 0.000 01 mg g(-1), respectively. A combination of LA-ICPMS with matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICR-MS) was applied for the identification of selected protein spots from human brain protein separated by 2D gel electrophoresis. Combining MALDI-FTICR-MS for the structure analysis of metal- and phosphorus-containing human brain proteins with LA-ICPMS, the direct analysis of heteroelements on separated proteins in 2D gels can be performed. For quantification of analytical LA-ICPMS data, the number of sulfur atoms per protein (and following the sulfur concentration) determined by MALDI-FTICR-MS was used for internal standardization. From the known sulfur concentration in protein, the concentration of other heteroelements was calculated. In addition, the number of phosphorylation and the phosphorylation sites of phosphorylated proteins in the human brain sample detected by LA-ICPMS were determined by MALDI-FTICR-MS. This technique allows the study of posttranslational modifications in human brain proteins.

Brain↗
PubMed1989

Presence of a particulate thyrotropin-releasing hormone-degrading pyroglutamate aminopeptidase activity in rat liver.

The data of this work describe the presence in the rat liver of a thyrotropin-releasing hormone (TRH)-degrading particulate metal-containing pyroglutamate aminopeptidase of high molecular weight. Following the fractionation of liver homogenate in 0.25 M sucrose, solubilization of the particulate fraction with papain and gel filtration on ACA34, an enzyme activity was detected which converts TRH into pyroglutamic acid and histidyl-proline diketopiperazine (cyclo[His-Pro]; cHP). [L-Histidine-2,5-3H]TRH and [L-proline-2,3-3H]TRH were used as a tracer. Products formed were separated by thin-layer chromatography, localized and quantified by scanning for radioactivity. Enzyme activities were tested using preferential site-directed inhibitors. Particulate pyroglutamate aminopeptidase activity was found to be sensitive to chelating agents. The physicochemical properties of this particulate aminopeptidase were distinct from the soluble pyroglutamate aminopeptidase from the same source. The particulate enzyme shared several similarities with particulate pyroglutamate aminopeptidase from adenohypophysis, brain and with serum enzyme, reported to have narrower specificity for TRH compared to the soluble pyroglutamate aminopeptidase from several tissues. The Km of the gel-filtrated enzyme is 27 microM and the specific activity 306 pmol.min-1.mg protein-1. Although no definite role has been established for this enzyme, it might be a potential determinant of cHP concentrations in liver. Furthermore, cHP is known to possess biological activities and specific binding sites in liver membranes. One of the major sites for TRH breakdown in vivo, the liver, probably represents a target tissue for TRH, especially for pancreatic TRH, and the particulate enzyme involved in the conversion of TRH into cHP may assume a specific function.

Aminopeptidases↗
PubMed2003

Plasma clearance of cadmium and zinc in non-acclimated and metal-acclimated trout.

Adult rainbow trout were pre-exposed to a sublethal concentration of waterborne cadmium (Cd, 26.7 nmol/l) or waterborne zinc (Zn, 2294 nmol/l) for 30 days to induce acclimation. A single dose of radiolabeled Cd (64.4 nmol/kg) or Zn (183.8 nmol/kg) was injected into the vascular system of non-acclimated and Cd- or Zn-acclimated trout through indwelling arterial catheters. Subsequently, repetitive blood samples over 10 h and terminal tissue samples (liver, heart, bile, stomach, intestine, kidney, gills, muscle, and spleen) were taken to characterize the effect of metal acclimation on clearance kinetics in vivo. Plasma clearance of Cd in Cd-acclimated fish (0.726+/-0.015 and 0.477+/-0.012 ml/min per kg for total and newly accumulated Cd, respectively), was faster than that in non-acclimated trout (0.493+/-0.013 and 0.394+/-0.009 ml/min per kg). Unlike plasma Cd, the levels of Cd in red blood cells (RBCs) were 1.2-2.2 times higher in Cd-acclimated fish than in non-acclimated fish. At 10 h post-injection, the liver accumulated the highest proportion ( approximately 22%) of the injected Cd dose in both non-acclimated and Cd-acclimated fish but did not account for the difference in plasma levels of Cd between two groups. Plasma clearance of Zn ( approximately 0.23 ml/min per kg for new Zn) was substantially lower than Cd clearance. Pre-acclimation to waterborne Zn reduced the new Zn levels in RBCs, but did not affect the clearance of Zn from blood plasma or tissue burdens of Zn in fish. Bile concentrations of both Cd and Zn were elevated in acclimated fish, but total bile burden accounted for <1% of the injected metal dose. The results suggest that the detoxification process of injected plasma Cd is stimulated by pre-acclimation to waterborne Cd, and that Zn levels are homeostatically controlled in both non-acclimated and acclimated trout.

Adaptation, Physiological↗
PubMed2003

Depleted uranium residual radiological risk assessment for Kosovo sites.

During the recent conflict in Yugoslavia, depleted uranium rounds were employed and were left in the battlefield. Health concern is related to the risk arising from contamination of areas in Kosovo with depleted uranium penetrators and dust. Although chemical toxicity is the most significant health risk related to uranium, radiation exposure has been allegedly related to cancers among veterans of the Balkan conflict. Uranium munitions are considered to be a source of radiological contamination of the environment. Based on measurements and estimates from the recent Balkan Task Force UNEP mission in Kosovo, we have estimated effective doses to resident populations using a well-established food-web mathematical model (RESRAD code). The UNEP mission did not find any evidence of widespread contamination in Kosovo. Rather than the actual measurements, we elected to use a desk assessment scenario (Reference Case) proposed by the UNEP group as the source term for computer simulations. Specific applications to two Kosovo sites (Planeja village and Vranovac hill) are described. Results of the simulations suggest that radiation doses from water-independent pathways are negligible (annual doses below 30 microSv). A small radiological risk is expected from contamination of the groundwater in conditions of effective leaching and low distribution coefficient of uranium metal. Under the assumptions of the Reference Case, significant radiological doses (>1 mSv/year) might be achieved after many years from the conflict through water-dependent pathways. Even in this worst-case scenario, DU radiological risk would be far overshadowed by its chemical toxicity.

Computer Simulation↗
PubMed1984

[14C]methylammonium transport by Frankia sp. strain CpI1.

We describe an NH4+-specific transport system in the N2-fixing symbiotic actinomycete Frankia sp. strain CpI1. [14C]methylammonium was used as an NH4+ analog. No specific transport process was detected when cells were grown on high concentrations of NH4+. A transport system with a high affinity for CH3NH3+ was synthesized after 3 to 4 h of nitrogen starvation. Methylammonium transport was not significantly inhibited by a variety of amino acids, primary amines, and polyamines. Ammonium completely eliminated CH3NH3+ transport. The Km for CH3NH3+ transport was around 2 +/- 1.8 microM with a Vmax of 4 to 5 nmol/min per mg of protein. The electron transport inhibitors cyanide and azide eliminated uptake, as did the uncoupler carbonyl cyanide-m-chlorophenylhydrazone. The sulfydryl reagent p-chloromercuribenzoic acid and the heavy metal thallium also inhibited uptake, suggesting the presence of an NH4+-specific permease. Concentration of CH3NH3+ across the membrane was demonstrated by conducting uptakes at low temperature to slow the metabolism of CH3NH3+ by glutamine synthetase. At 7 degrees C most of the label was concentrated inside the cells in a form that could be chased from the cells by adding excess NH4+ to the medium. At 30 degrees C most of the label was present as an impermeant metabolite. Thin-layer chromatography of cell extracts confirmed that the radioactivity inside the cells was mainly in the form of CH3NH3+ at 7 degrees C but was present as an unidentified metabolite at 30 degrees C. These studies demonstrate that Frankia sp. strain CpI1 has a high-affinity NH4+ transport system that is synthesized in response to NH4+ starvation.

Actinomycetales↗
PubMed2001

Measurement of stellar age from uranium decay.

The ages of the oldest stars in the Galaxy indicate when star formation began, and provide a minimum age for the Universe. Radioactive dating of meteoritic material and stars relies on comparing the present abundance ratios of radioactive and stable nuclear species to the theoretically predicted ratios of their production. The radioisotope 232Th (half-life 14 Gyr) has been used to date Galactic stars, but it decays by only a factor of two over the lifetime of the Universe. 238U (half-life 4.5 Gyr) is in principle a more precise age indicator, but even its strongest spectral line, from singly ionized uranium at a wavelength of 385.957 nm, has previously not been detected in stars. Here we report a measurement of this line in the very metal-poor star CS31082-001, a star which is strongly overabundant in its heavy elements. The derived uranium abundance, log(U/H) = -13.7 +/- 0.14 +/- 0.12 yields an age of 12.5 +/- 3 Gyr, though this is still model dependent. The observation of this cosmochronometer gives the most direct age determination of the Galaxy. Also, with improved theoretical and laboratory data, it will provide a highly precise lower limit to the age of the Universe.

Journal Article↗
PubMed1999

234Th and 7Be as tracers for transport and sources of particle-associated contaminants in the Hudson River Estuary.

The natural radionuclides 234Th and 7Be have known sources in estuaries and strongly and rapidly associate with particles. They are thus good tracers of the transport and sources of particles in the suspended sediment reservoir, and, by implication, of particle-associated contaminants such as heavy metals. In the Hudson River estuary, 234Th is produced from decay of dissolved 238U, which varies linearly with salinity, while 7Be is added directly to the estuary from the atmosphere. The 234Th/7Be activity ratio eliminates variations in radionuclide specific activities that result from changes in sediment grain size or composition. Sampling in the Hudson under conditions of low and high river flow shows that 234Th/7Be in suspended sediment increases from low salinity to higher salinity waters at all sampling times. The Th/Be activity ratio may thus be used as a tracer of where particles are labeled with these radionuclides in the estuary and of the relative importance of resuspension and particle transport through the estuary. The distribution of heavy metals in the suspended sediment reservoir can be compared with that of 234Th/7Be by normalizing the metals to Fe. Iron and Al are well correlated in suspended sediments of the Hudson, indicating that either element can be used to normalize grain size effects on specific concentrations of metals. Ratios of Ag and Pb to Fe in suspended particles generally increase down-estuary at all sampling times, whereas Cu, Zn and Cd-to-Fe ratios show more scatter and less consistency in trends. Both source(s) and chemical behavior affect the metal/Fe ratios. The strongest positive correlation with 234Th/7Be is seen for Ag/Fe, reflecting the dominance of lower estuary sources of this trace metal to the Hudson. Relationships between Pb/Fe, Cu/Fe and 234Th/7Be are less strong, reflecting multiple sources of these elements. No correlation is seen for Cd/Fe with 234Th/7Be, indicating either a source up-river or release of Cd as its Kd decreases with increasing salinity.

Beryllium↗
PubMed1971

Effect of stomatal opening on the transfer of 131I2 from air to grass.

The effect of stomatal opening on the air-to-trass transfer of molecular iodine gas (I2) was studied in a small environmental chamber with an airflow rate of about 1 m/sec above the grass. Measured stomatal densities and stomatal areas were used to determine the per cent of Bromegrass leaf area composed of stomatal openings (As). The transfer parameter Pt(g-1) (analogous to the normalized transfer velocity) was found to be directly dependent upon stomatal opening as measured by As: Pt = 2.21 X 10(-4) + (4.60 X 10(-4) As. The maximum value of Pt observed was 5.43 X 10(-4) g-1 or 2.4 times that observed for As approximately 0. This proportionality to pore area is in agreement with measured diffusion rates through perforated metal screens. It was also found that Bromegrass is far from a "perfect sink" for sorption of 131I2, a fact which must be considered in the development of models of radioiodine transfer. Retention of radioiodine by contaminated foliage is dependent on the radioiodine transfer process and the implications of the current results are indicated.

Air Pollution, Radioactive↗
PubMed2003

Surface-enhanced Raman scattering for cancer diagnostics: detection of the BCL2 gene.

A method of detection for cancer genes, such as B-cell lymphoma 2 gene, has been developed using surface-enhanced Raman scattering-active substrates. This method uses Raman active dye-labeled DNA gene probes and metallic nanostructures as surface-enhanced Raman scattering-active platforms. A self-assembled monolayer system composed of mercapto hexane-labeled, single-strand DNA (SH-(CH2)6-ssDNA/ 6-mercapto-1-hexanol) is formed on a silver surface. The Raman-active dye-labeled gene is hybridized with its complementary probe, which is immobilized on the silver surface. The surface-enhanced Raman gene probes in this study can be used to detect DNA targets via hybridization to complementary DNA probes. The probes do not involve the use of radioactive labels and have great potential to provide both sensitivity and selectivity. The utility of this approach is investigated.

DNA Probes↗
PubMed1992

Effects of complexed iron and aluminium on brain calcium.

Ferric lactate increases Ca(2+)-uptake by Ehrlich carcinoma ascites cells as well as in vitro and in vivo Ca(2+)-uptake by the liver. Iron and aluminium are increased in the substantia nigra of patients with Parkinson's disease and aluminium is suspected to be involved in the pathophysiology of Alzheimer's disease. This study was conducted to determine if there is any relationship between iron and aluminium uptake and a possible calcium influx into brain tissue. Groups of Swiss mice were injected in the tail vein with 100 microliters of 0.05 M ferric lactate plus 2 microCi45CaCl2, or 100 microliters of 0.05 M aluminium lactate plus 2 microCi45CaCl2, or 100 microliters of saline plus 2 microCi45CaCl2. Twenty-four hr later they were sacrificed by decapitation. Samples of blood and the total brain were weighed and ashed. The ashes were dissolved and the solution transferred to counting vials evaporated to dryness. A scintillation solution was added to the vials and the radioactivity was counted. To accurately assess brain uptake in each animal the value of brain specific activity was related to blood specific activity. When compared to those of control animals, these values gave the 24 hr increase of 45Ca-uptake by brain of ferric lactate or aluminium lactate-treated animals. A significant increase of 45Ca-uptake was observed for ferric lactate (136% of control value, p less than 0.005), which is more important for aluminium lactate (163% of control value, p less than 0.001). The nature of the complexed metal-brain tissue interaction is not known, several mechanisms are discussed.

Animals↗
PubMed1980

The inhibition of cerebral high affinity receptor sites by lead and mercury compounds.

The effect of various concentrations of several lead and mercury compounds upon various high affinity receptor sites within discrete brain regions has been measured. The specific binding of radioactive spiroperidol and quinuclidinyl benzilate to striatal and cortical membranes respectively, was much more severely inhibited in the presence of tri-n-butyl lead acetate than by lead acetate. This suggested that the hydrophobic organic lead derivative was able to interfere with receptor structure more readily than the lead acetate. On the other hand mercuric chloride was more effective in blocking these two neurotransmitter receptor sites than was the organic methylmercuric chloride. This implied that sulfhydryl groups may be within, or proximal to the allosteric binding site. The relative ineffectiveness of all heavy metal compounds studied in blocking the glycine. GABA or the diazepam receptors indicated that the mechanism of binding may not be similar with different receptor proteins. Since micromolar concentrations of some lead and mercury compounds suffice to severely inhibit neurotransmitter binding sites, such a direct interference with postsynaptic events may in part account for the neurological consequences of heavy metal poisoning.

Animals↗
PubMed2003

Removal and recovery of metals and other materials by supported liquid membranes with strip dispersion.

This paper reviews recent advances in supported liquid membranes (SLMs) with strip dispersion for removal and recovery of metals including chromium, copper, zinc, and strontium; it also discusses potential applications of SLMs for removal and recovery of other materials, including cobalt and penicillin G. The technology for chromium that we developed, not only removes the Cr(VI) from about 100-1,000 ppm to less than 0.05 ppm in the treated effluent allowable for discharge or recycle, but also recovers the chromium product at a high concentration of about 20% Cr(VI) (62.3% Na(2)CrO(4)) suitable for resale or reuse. In other words, we have achieved the goals of zero discharge and no sludge. The stability of the SLM is ensured by a modified SLM with strip dispersion, where the aqueous strip solution is dispersed in the organic membrane solution in a mixer. The strip dispersion formed is circulated from the mixer to the membrane module to provide a constant supply of the organic solution to the membrane pores. The copper SLM system that we have identified, not only removed the copper from 150 ppm in the inlet feed to less than 0.15 ppm in the treated feed, but also recovered the copper at a high concentration of greater than 10,000 ppm in the strip solution. For the zinc SLM system identified, zinc at an inlet feed concentration of 550 ppm was removed to less than 0.3 ppm in the treated feed, whereas a high zinc concentration of more than 17,000 ppm was recovered in the strip solution. For strontium removal, we synthesized a family of new extractants, alkyl phenylphosphonic acids. The SLM removed radioactive (90)Sr to the target of 8 pCi/L or lower from feed solutions of 300-1,000 pCi/L. The SLM removed cobalt from about 525 ppm to 0.7 ppm in the treated feed solution, concentrating it to at least 30,000 ppm in the aqueous strip solution. Concerning penicillin G recovery, the SLM removed penicillin G from a feed of 8,840 ppm and concentrated it to a high concentration of 41,011 ppm in the aqueous strip solution with a high recovery of about 93%.

Adhesives↗