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 955 records · Page 53Linked to original sources

PubMed1996

Alpha- and beta-emitting radiolanthanides in targeted cancer therapy: the potential role of terbium-149.

The efficacy of systemic cancer therapy rests on the ability of a toxin to be preferentially located in cancer cells, so that cancer cell kill is maximized and normal tissue spared. This requires that the lifetime of the toxin be less than the lifetime of the carrier in the body, effectively ruling out chemical toxins, as they remain effective until excreted from the body. The requirement of localization of dose to the cancer cell makes radioactive beta-emitting radionuclides unattractive. Alpha-emitting radionuclides are much more appropriate toxins, as their efficacy depends on the high energy and short range of the alpha particles, and terbium-149 is shown to be the most efficacious of these. However, the merit of various alpha- and beta-emitting radionuclides depends on the stage and type of cancer. Recommendations are made with respect to the matching of the target cancer with required properties of the radiolabel and carrier.

Alpha Particles↗

PubMed1985

Reactivities of thiols in myosin rod: effect of magnesium and ionic strength.

There are six cysteines in each chain of myosin rod of rabbit skeletal muscle: three are in the S-2 portion, at residues 66, 108 and 410 (Lu, R.C. and Lehrer, S. (1984) Biochemistry 23, 5975-5981). The other three are in the light meromyosin portion, assigned at residues 572, 600 and 770 on the basis of homology between the amino acid sequence in the vicinity of these thiols and that of the rod of nematode myosin (McLachlan, A.D. and Karn, J. (1982) Nature 299, 226-231). Since the thiols are distributed in different regions of the rod, measuring their reactivities under various conditions may provide information on the conformations of these regions. Myosin rod was carboxymethylated with radioactive iodoacetic acid under various conditions. The cysteine-containing peptides were isolated using HPLC from the tryptic digests, and the radioactivity incorporated into each thiol was measured. In the denatured state all six thiols were equally reactive. In the native state, all thiols have low reactivity, the reactivity of Cys-108 or -410 is only 0.1% of that in the denatured state, Cys-600 exhibited the highest reactivity, about 20-times that of Cys-410; Cys-66, -572 and -770 had 2-4-times that of Cys-410. When the rods formed filaments, the reactivities of all cysteines further decreased: Cys-66, -108 and -770 were reduced to 50%, while Cys-410, -572 and -600, located in the middle of the rod, were reduced to 20-30% of their reactivities in the monomeric form. In the presence of Mg2+ the reactivity of Cys-108 increased by 20%, whereas Cys-572 decreased by 50%. The results are consistent with the view that metal ions affect the conformation of the rod. This may play a role in the mechanism of filament formation and the movement of crossbridges.

Animals↗

PubMed1994

Radiation chemistry in the 1990s: pressing questions relating to the areas of radiation biology and environmental research.

This preview discusses the possible future application of ionizing radiation in the study of the free-radical chemistry of some aqueous systems. With respect to the present state of knowledge in the area of chemistry related to radiobiology, ionizing-radiation damage to DNA will continue to be a major focus of radiobiological interest. It is noted that the purine-base, free-radical chemistry is still poorly understood, as is the chemistry of the direct effect of ionizing radiation on DNA. The role of transition metal ions, their interaction with hydrogen peroxide and the superoxide radical are areas of increasing interest, as are other reactions of the superoxide radical. The eventual chemical effects, on DNA, of the reactions of these species resemble those of the action of ionizing radiation and are therefore apt to be studied radiation-chemically. In contaminated water pollution control, procedures termed 'advanced oxidation processes' are gaining in importance. They are based on the action of the .OH radical. Radiation techniques will provide the tools for understanding the underlying reactions better.

Environmental Pollutants↗

PubMed2000

Radiolabeling brachytherapy sources with Re-188 through chelating microfilms: stents.

Rhenium-188 (Re-188, T(1/2) = 17 h) emits beta particles (E(max) = 2. 12 MeV) having an ideal range for intravascular brachytherapy and certain cancer brachytherapies. Re-188 was attached to metal wafers and stents via a chelating microfilm, and these brachytherapy sources characterized in vitro and in vivo. To prepare the sources, a siloxane film containing reactive amines was plasma deposited on the metal, a chelating microfilm conjugated to the amines, and the chelating microfilm used to attach Re-188. Re-188 was selectively bound to materials coated with the chelating microfilm. Binding correlated with the amount of radionuclide used. Wafers (1 cm(2)) bound up to 62.9 MBq (1.7 mCi) of Re-188 with yields generally near 30%. Stents bound up to 26.6 MBq (720 microCi). Typically, stents were labeled to bind 4-12 MBq and deposit 10-30 Gy at 2 mm in the arterial wall. In phantom studies, the longer nitinol stents deposited doses of 2.3 Gy/MBq (0.085 Gy/microCi), while shorter stainless steel stents deposited 4.62 Gy/MBq (0.171 Gy/microCi). After placement in arteries of pigs, only the Re-188-stents were detected by scintigraphy at times up to 24 h. Scintigraphy did not detect activity in other organs. Blood sampling (0.1-24 h) detected maximum radioactivity (up to 388 cpm/mL/100micro Ci) at 6 h. We conclude that on-demand radiolabeling of stents and other brachytherapy sources with Re-188 can be performed routinely.

Biocompatible Materials↗

PubMed1999

In search of spatial extremes.

In environmental studies attention increasingly focuses on identification of spatial extremes: locations with observations that are apparently higher than either a preset background threshold or neighbouring observations. We consider various procedures for identifying values and locations of these extremes: extreme value theory, conditionally simulated fields and disjunctive kriging. In a recent research project we studied the distribution of nine environmental pollutants (heavy metals, polyaromatic hydrocarbons and mineral oil) in a large industrial estate in the southern Netherlands. This area is interesting as it is influenced by three contaminating processes: inundation by the river Meuse, anthropogenic heightening with contaminated materials and local industrial activities. Concentrations are measured. In this paper the peaks over threshold method was useful for finding extremes for spatially uncorrelated variables, whereas conditional simulations applied in particular to areas with spatial dependence.

Animals↗

PubMed1996

Uranium in the environment: occurrence, transfer, and biological effects.

The assessment of uranium chemical and radiological consequences depends on the physicochemical properties of these radioelements and the knowledge of their environmental fate. Although uranium is the source of all these fissionable isotopes, its fate in ecosystems has been poorly investigated. In this review, we have updated information concerning the fate of uranium in the different compartments of the environment, the possibility of transfer to man through the food chain, and the biological and toxicological effects of this metal at cellular, tissular, or organism levels. The physicochemical characteristics of uranium, as well as its regulatory statutes, were reviewed. The fate of uranium in the environment was presented by indicating sources of uranium emission and the possible routes of transfer to man. The biological alterations caused by uranium exposure were discussed, and finally, we presented results collected during our recent study. Some propositions on research to be done to advance the understanding of uranium occurrence in the environment were also given.

Animals↗

PubMed1994

[Classification of mines in Poland by group radiation exposure of miners].

The computer data base on individual occupational exposure to ionizing radiation among miners (established at the Nofer Institute of Occupational Medicine, Lodz) was used to classify all Polish non-uranium mines (coal, copper, lead-zinc and chemical raw material mines) according to values of the so-called group radiation exposure (in man-sivert units). In total 72 coal mines, 13 chemical raw material mines and 10 metal ore mines employing 246,580, 3,080, 17,820 miners, respectively, were assessed. The analysis of individual annual miners exposures indicated the highest exposure to ionizing radiation in this group of workers in comparison with other occupational groups in Poland. An equivalent occupational group dose in Poland amounts to 1,480 man-siverts. Out of this dose 96.4% is received by miners, 2.5% by X-ray workers, 0.7% by workers of isotope laboratories and 0.1% by physiotherapeutists working in health resorts.

Environmental Monitoring↗

PubMed2006

Structural study of trivalent lanthanide and actinide complexes formed upon solvent extraction.

The coordination of the trivalent 4f ions, Ln = Nd3+, Eu3+ and Yb3+, as well as the trivalent 5f ion, Am3+, with diamide and dialkylphosphoric acid extractants, individually and in combination, was studied by use of X-ray absorption spectroscopy. These studies provide metrical information about the interatomic interactions between the f-ions (M3+) and the ligands, dihexylphosphoric acid (HDHP) and N,N'-dimethyl-N,N'-dioctylhexylethoxymalonamide (DMDOHEMA), that is of practical relevance to the control of metal-ligand binding in liquid-liquid extraction systems for the separation of trivalent actinide ions, An3+, from trivalent lanthanide ions, Ln3+. Through systematic variations of extraction conditions and extractant combinations, we have found that the HDHP complexes with M3+ involve MO6 coordination and distant M...P interactions, whereas the DMDOHEMA complexes with M3+ involve MO8 coordination. The combination of the EXAFS results with ancillary extraction data and IR results facilitates descriptions of the stoichiometries and structures of the molecular species formed in solution upon liquid-liquid extraction and leads to a new understanding of the binary extraction systems in terms of the strength and selectivity of An3+- vs. Ln3+-ligand interactions. This fundamental structure information affords insight into solvent extraction processes that are of contemporary and practical importance in heavy element chemistry and to environmentally related issues arising from the separation and disposal of radioactive materials, particularly actinides and selected fission products, in the field of nuclear waste reprocessing research.

Journal Article↗

PubMed2003

DOTA alpha-melanocyte-stimulating hormone analogues for imaging metastatic melanoma lesions.

Scintigraphic imaging of metastatic melanoma lesions requires highly tumor-specific radiopharmaceuticals. Because both melanotic and amelanotic melanomas overexpress melanocortin-1 receptors (MC1R), radiolabeled analogues of alpha-melanocyte-stimulating hormone (alpha-MSH) are potential candidates for melanoma diagnosis. Here, we report the in vivo performance of a newly designed octapeptide analogue, [betaAla(3), Nle(4), Asp(5), D-Phe(7), Lys(10)]-alpha-MSH(3-10) (MSH(OCT)), which was conjugated through its N-terminal amino group to the metal chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) to enable incorporation of radiometals (e.g., indium-111) into the peptide. DOTA-MSH(OCT) displayed high in vitro MC1R affinity (IC(50) 9.21 nM). In vivo [(111)In]DOTA-MSH(OCT) exhibited a favorable biodistribution profile after injection in B16-F1 tumorbearing mice. The radiopeptide was rapidly cleared from blood through the kidneys and, most importantly, accumulated preferentially in the melanoma lesions. Lung and liver melanoma metastases could be clearly imaged on tissue section autoradiographs 4 h after injection of [(111)In]DOTA-MSH(OCT). A comparative study of [(111)In]DOTA-MSH(OCT) with [(111)In]DOTA-[Nle(4), D-Phe(7)]-alpha-MSH ([(111)In]-DOTA-NDP-MSH) demonstrated the superiority of the DOTA-MSH(OCT) peptide, particularly for the amount of radioactivity taken up by nonmalignant organs, including bone, the most radiosensitive tissue. These results demonstrate that [(111)In]DOTA-MSH(OCT) is a promising melanoma imaging agent.

Animals↗

PubMed1990

Review of biotechnology applications to nuclear waste treatment.

This paper gives an overview of the feasibility of the application of biotechnology to nuclear waste treatment. The contents are based on a report which PA Technology carried out for the Department of the Environment (DoE Reference: DoE/RW/88.008 Sector No 2.3). Many living and dead organisms accumulate heavy metals and radionuclides. The controlled use of this phenomenon forms the basis for the application of biotechnology to the removal of radionuclides from nuclear waste streams. Indeed, biotechnology offers a series of new opportunities for removal of radionuclides from dilute aqueous process effluents. Such technology is already used for heavy metal removal on a commercial basis and could be optimised for radionuclide removal. An overview of biotechnology areas, namely the use of biopolymers and biosorption using biomass applicable to the removal of radionuclides from industrial nuclear effluents is given. The potential of biomagnetic separation technology, genetic engineering and monoclonal antibody technology is also to be examined. The most appropriate technologies to develop for radionuclide removal in the short term appear to be those based on biosorption of radionuclides by biomass and the use of modified and unmodified biopolymers in the medium term.

Biotechnology↗

PubMedDate not supplied

Metabolism and renal clearance of 111In-labeled DOTA-conjugated antibody fragments.

Radiometal-labeled antibody fragments are promising reagents for radioimmunotherapy due to their high tumor uptake and rapid pharmacokinetics, but their therapeutic potentials are limited by high uptake and retention in the kidney. Identification of metabolic products is a first step in designing rationale approaches to lower kidney uptake. Previous studies in rats have shown that 111In-labeled DTPA-conjugated antibody fragments (via lysine residues) were degraded to an DTPA-epsilon-amino-lysine derivative and retained in the lysosomal compartments of the liver and kidney [Rogers et al. (1995) Cancer Res. 55, 5714s-5720s]. To determine the metabolic profile of another widely used metal-chelate, [111In]DOTA conjugated to lysines in antibody fragments via active ester chemistry, we analyzed kidney homogenates from nude mice injected with an [111In]DOTA-Fab generated enzymatically from the anti-lymphoma intact antibody Rituxan. The major kidney metabolite was identified as [111In]DOTA-epsilon-amino-lysine by comparison to an authentic synthetic standard. This end product was also identified in the urine, along with relatively small amounts of [111In]DOTA-Fab. Since injection of [111In]DOTA-epsilon-amino-lysine into nude mice resulted in rapid clearance into the urine without kidney retention, it is likely that the renal retention observed was due to kidney uptake of [111In]DOTA-Fab, followed by lysosomal degradation to [111In]DOTA-epsilon-amino-lysine, which is only slowly cleared from this compartment. This observation is supported by autoradiographs of the kidney showing rapid localization of radioactivity into the distal regions of the kidney cortex. To extend this analysis to clinical trials, we have also analyzed urine taken from a patient injected with the intact antibody [111In]DOTA-cT84.66. In that example, we found that the major radioactive species was also [111In]DOTA-epsilon-amino-lysine.

Animals↗

PubMed2006

Application of a high-density oligonucleotide microarray approach to study bacterial population dynamics during uranium reduction and reoxidation.

Reduction of soluble uranium U(VI) to less-soluble uranium U(IV) is a promising approach to minimize migration from contaminated aquifers. It is generally assumed that, under constant reducing conditions, U(IV) is stable and immobile; however, in a previous study, we documented reoxidation of U(IV) under continuous reducing conditions (Wan et al., Environ. Sci. Technol. 2005, 39:6162-6169). To determine if changes in microbial community composition were a factor in U(IV) reoxidation, we employed a high-density phylogenetic DNA microarray (16S microarray) containing 500,000 probes to monitor changes in bacterial populations during this remediation process. Comparison of the 16S microarray with clone libraries demonstrated successful detection and classification of most clone groups. Analysis of the most dynamic groups of 16S rRNA gene amplicons detected by the 16S microarray identified five clusters of bacterial subfamilies responding in a similar manner. This approach demonstrated that amplicons of known metal-reducing bacteria such as Geothrix fermentans (confirmed by quantitative PCR) and those within the Geobacteraceae were abundant during U(VI) reduction and did not decline during the U(IV) reoxidation phase. Significantly, it appears that the observed reoxidation of uranium under reducing conditions occurred despite elevated microbial activity and the consistent presence of metal-reducing bacteria. High-density phylogenetic microarrays constitute a powerful tool, enabling the detection and monitoring of a substantial portion of the microbial population in a routine, accurate, and reproducible manner.

Bacteria↗

PubMed1979

[Method for the determination of alpha radiation potential energy of radon decay products occurring as free ions].

The paper presents a simple method of measuring the concentration of alpha radiation potential energy of radon decay products occurring as free ions in the air. This method consists in deposition of free ions of radon decay products on the surface of metal plates in so called impactor, which is constructed by an appropriate selection of shapes and mutual arrangement of the plates. The paper presents an improved system of calibration of impactor, which continuously produces free ions in the tube, through which the filtered air containing radon is being passed. The least concentration of alpha radiation potential energy of radon decay products free ions, detactable by this method, when 1 liter of air is passed through the impactor, is 10(3) MeV liter-1). This method may be applied in laboratory and environmental measurements.

Air Pollutants↗

PubMedDate not supplied

Origins of biliary copper.

We tested the hypothesis that the copper present in bile--the major route of elimination of the metal from the body--is derived exclusively from hepatocytes by administering radiocopper (64Cu or 67Cu)-labeled ionic Cu, desialylated (AsCPN) or intact human ceruloplasmin (CPN), intravenously, to rats with cannulated bile ducts. The rates of appearance and the total amounts of radiolabeled isotope recovered in bile were measured. The three vehicles chosen for the delivery of radiocopper interact differently with hepatocytes: ionic Cu is taken up by a passive process (Schmitt, R. C. et al., Am. J. Physiol. 1983; 244:G183-G191); AsCPN is promptly cleared from the circulation by specific receptor-mediated endocytosis, and CPN largely remains in the circulation for the duration of the experiment. Similar amounts of radiocopper were recovered following injections of ionic Cu (3.1%) or CPN (2%), but substantially larger amounts (8.1%) were excreted after administration of AsCPN. Using an antibody to CPN which reacts also with AsCPN, we found about 70% of the bile radioactivity to be immunoprecipitable following injections of either glycoprotein, indicating that a fraction of these copper proteins had entered the bile essentially unmodified. Our observations indicate that in addition to the lysosomal compartment which catabolizes a portion of the AsCPN in hepatocytes, there appears to be a direct route for AsCPN from hepatocellular sinusoids to the bile canaliculi. Since CPN does not interact significantly with hepatocytes, its presence in bile suggests transcytosis via the biliary epithelium.

Animals↗

PubMed1995

Technetium-99m chelators in nuclear medicine. A review.

Nuclear medicine is a branch of medical imaging that uses radioactive tracers to examine the function of body systems. The radionuclide used in about 90% of all examinations is 99Tcm, which is available from 99Mo/99Tcm generators at most nuclear medicine departments. In aqueous medium, technetium is chemically stable as pertechnetate, 99TcmO4-. Injected into the human body, pertechnetate will be absorbed by the thyroid gland because of the similarity to iodide in its radius and charge. To reach targets in the human body other than glandula thyreoidea, 99Tcm needs a carrier molecule, usually a chelating agent. Many chelators that form stable complexes with 99Tcm have affinities for certain tissues in the human body. Other chelators can be manipulated by pharmaceutical formation to be retained in certain body systems. In order to form bonds with technetium, the chelator must contain electron donors like nitrogen, oxygen and sulfur. Space between multiple electron donor atoms is required to allow several bonds to form with the central metal. The stability of the complex increases with increasing number of bonds. Today, chelators for the use with 99Tcm exist for a number of highly sensitive scintigraphic studies of the brain, heart, skeleton, kidneys, hepatobiliary system and lungs. This includes chelators such as dimercaptosuccinic acid, 1,2-ethylenediylbis-L-cysteine diethyl ester, methylenediphosphonate, hexamethylpropyleneamineoxime and hexakis(methoxy isobutyl isonitrile).

Chelating Agents↗

PubMed1987

Paper disk assay for glycosaminoglycan sulfotransferases.

A method is described for the assay of sulfotransferases, which transfer sulfate from 3'-phosphoadenosine-5'-phosphosulfate (PAPS) to glycosaminoglycan acceptors. Following the sulfation reactions, the [35S]sulfate-labeled products are precipitated and then separated from a sulfate donor ([35S]PAPS) and its degradation products by a paper disk method, and then the radioactivity remaining on the paper disk is subsequently determined by liquid scintillation counting. The rapidity and simplicity of the method are advantageous for multiple assays and have allowed us to establish assay conditions for serum sulfotransferases which introduce sulfate at position 6 of the internal N-acetylgalactosamine units of chondroitin, position 2 (amino group) of the glucosamine units of heparan sulfate and sugar units of keratan sulfate, respectively. The assay method will be applicable with modification to the assay of other glycosaminoglycan sulfotransferases and glycoprotein sulfotransferases.

Animals↗

PubMed2004

Use of spectroscopic techniques for uranium(VI)/montmorillonite interaction modeling.

To experimentally identify both clay sorption sites and sorption equilibria and to understand the retention mechanisms at a molecular level, we have characterized the structure of hexavalent uranium surface complexes resulting from the interaction between the uranyl ions and the surface retention groups of a montmorillonite clay. We have performed laser-induced fluorescence spectroscopy (LIFS) and X-ray photoelectron spectroscopy (XPS) on uranyl ion loaded montmorillonite. These structural results were then compared to those obtained from the study of uranyl ions sorbed onto an alumina and also from U(VI) sorbed on an amorphous silica. This experimental approach allowed for a clear determination of the reactive surface sites of montmorillonite for U(VI) sorption. The lifetime values and the U4f XPS spectra of uranium(VI) sorbed on montmorillonite have shown that this ion is sorbed on both exchange and edge sites. The comparison of U(VI)/clay and U(VI)/oxide systems has determined that the interaction between uranyl ions and montmorillonite edge sites occurs via both [triple bond]AlOH and [triple bond]SiOH surface groups and involves three distinct surface complexes. The surface complexation modeling of the U(VI)/montmorillonite sorption edges was determined using the constant capacitance model and the above experimental constraints. The following equilibria were found to account for the uranyl sorption mechanisms onto montmorillonite for metal concentrations ranged from 10(-6) to 10(-3) M and two ionic strengths (0.1 and 0.5 M): 2[triple bond]XNa + UO2(2+) <==> ([triple bond]X)2UO2 + 2Na+, log K0(exch) = 3.0; [triple bond]Al(OH)2 + UO2(2+) <==> [triple bond]Al(OH)2UO2(2+), log K0(Al) = 14.9; [triple bond]Si(OH)2 + UO2(2+) <==> [triple bond]SiO2UO2 + 2H+, log K0(Si1) = -3.8; and [triple bond]Si(OH)2 + 3UO2(2+) + 5H2O <==> [triple bond]SiO2(UO2)3(OH)5- + 7H+, log K0(Si2) = -20.0.

Bentonite↗

PubMed2004

Optimization of parameters for semiempirical methods IV: extension of MNDO, AM1, and PM3 to more main group elements.

The NDDO semiempirical methods MNDO, AM1, and PM3 have been extended to all the remaining non-radioactive elements of the main group, excluding the noble gases. Most of the new elements are of Groups I and II. 44 sets of parameters are presented for the following methods and elements. MNDO: Na, Mg, K, Ca, Ga, As, Se, Rb, Sr, In, Sb, Te, Cs, Ba, Tl, and Bi; AM1: Li, Be, Na, Mg, K, Ca, Ga, As, Se, Rb, Sr, In, Sn, Sb, Te, Cs, Ba, Tl, Pb, and Bi; PM3: B, Na, K, Ca, Rb, Sr, Cs, and Ba. Average errors are presented for heats of formation, molecular geometries, etc.

Chemistry, Inorganic↗