PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Elements, 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 487 records · Page 27Linked to original sources
PubMed1986

Radioisotopic method for measuring cell division rates of individual species of diatoms from natural populations.

Silicon is an essential element for diatom frustule synthesis and is usually taken up only by dividing cells. With Ge, a radioactive analog of Si, the cell cycle marker event of frustule formation was identified for individual species of diatom. The frequency of cells within a population undergoing this division event was estimated, and the cell division rate was calculated. In laboratory cultures, these rates of cell division and those calculated from changes in cell numbers were similar. By dual labeling with Ge(OH)(4) and NaHCO(3), rates of cell division and photosynthesis were coincidently measured for diatoms both in laboratory cultures and when isolated from natural populations in estuarine, offshore, and polar environments. These techniques permit the coupling between photosynthesis and cell division to be examined in situ for individual species of diatom.

Journal Article↗
PubMedDate not supplied

Application of beryllium antibodies in risk assessment and health surveillance: two case studies.

This paper demonstrates that current standards used by the Occupational Safety and Health Administration (OSHA) to establish an area free from potential beryllium contamination may be inadequate. Using the Beryllium Antibody Assay, it was shown that workers exposed to former beryllium work areas, thought to be sanitized and to meet OSHA standards, experienced statistically significant rises in blood beryllium antibody titers. This finding raises the question of whether the equipment currently required to protect workers in beryllium-laden environments is sufficient. The project mission of decommissioning/decontaminating the former nuclear weapons plant at Rocky Flats Environmental Technology Site (RFETS), instituted in 1992, has necessitated development of new technology directed toward safe and responsible cleanup. Challenges have been posed not only by the need to dispose of radioactive and chemical waste, but also by the problem of cleaning up hazardous metals such as the element beryllium. Beryllium was used extensively in research and the manufacture of nuclear weapons components at Rocky Flats for over 40 years. Since inhalation of this element can induce chronic beryllium disease (Eisenbud and Lisson, 1983), an antibody assay was developed to screen workers for internal exposure to beryllium. Exposure is indicated by a titer of antibodies greater than two standard deviations above a normal population control (defined as the mean titer of pooled samples from 51 individuals with no known exposure to beryllium) and a p-value of < 0.05. This paper describes two new applications for the assay: risk assessment and health surveillance. Case study 1 involves a team of three workers who cleaned a beryllium plenum and whose beryllium antibody titers provided a quantitative assessment of their exposure. Case study 2 describes the use of the antibody assay to determine the probable manner in which one worker was exposed to beryllium while performing his duties as an architectural engineer.

Air Pollutants, Occupational↗
PubMed1989

Strontium and bromide as tracers in X-ray microanalysis of biological tissue.

Since energy dispersive X-ray microanalysis cannot distinguish between isotopes of the same element, alternative methods have to be used to get information similar to that obtained in experiments with radioactive tracers. In the present study, strontium was used as a tracer for calcium, and bromide as a tracer for chloride. Rats were injected with strontium chloride in vivo, and the uptake of strontium in the acinar cells of the submandibular gland was studied. Eventually a Sr/Ca ratio of 0.3 was reached. In some animals, secretion of mucus had been elicited by stimulation with isoproterenol 4 h prior to injection of strontium chloride. Exchange of calcium for strontium was enhanced by prior injection with isoproterenol. In a second experiment, rats were injected with sodium bromide, and the uptake of bromide by the submandibular acinar cells was followed in time, both in pilocarpine-stimulated and unstimulated glands. Under the experimental conditions, bromide was rapidly taken up by the cells, and the cellular Br/Cl ratio was close to that found in serum. Submandibular glands take up Br somewhat faster than other tissues (liver, heart muscle, skeletal muscle). The uptake of Br in pancreatic acinar cells was studied in vitro. These experiments showed a 1:1 ratio (molar) exchange of Cl for Br.

Animals↗
PubMed1997

Radiation doses to critical groups since the early 1950s due to discharges of liquid radioactive waste from Sellafield.

First, some of the early work is reviewed on exposure pathways in connection with proposed and early liquid radioactive waste discharges from Sellafield. The main historical features of these discharges, affected by relevant plant operations, are then briefly described. The important radiological exposure pathways resulting from the discharges and people's consumption and occupancy habits are considered. To place the changing scenario onto a consistent basis using present-day methodology, a reconstruction of exposures has been carried out using environmental monitoring data and models. The three major pathways are examined of Porphyra/laverbread consumption in South Wales, fish and shellfish consumption near Sellafield, and external exposure over local and more distant sediments. The results show that over the period 1952 to about 1970 the laverbread pathway was probably critical, taking a cautious approach. Effective dose rates fluctuated at around 1 mSv y(-1) from about 1956 to 1971. From about 1970 to 1985, the fish and shellfish pathway was likely to have been critical, with effective dose rates peaking at about 2 mSv y(-1) in 1975-1976. External exposure was likely to have been of lesser importance than the other two pathways until about 1985, when with the retention of previously-released radiocesium on sediments it has become dominant. This phenomenon applies particularly further afield where radiocesium concentrations have been slower to decline; in the Ribble estuary, houseboat dwellers have been the critical group from about 1985. Effective doses have been at about 0.3 mSv y(-1) and declining; they are due to the effects of radiocesium discharges in earlier years. Dose rates have remained within contemporary ICRP dose limits.

Actinoid Series Elements↗
PubMed2005

Influence of antipyretic drugs on the labeling of blood elements with technetium-99m.

Acetaminophen (AAP), acetylsalicylic acid (ASA) and dipyrone (DIP) are antipyretic and analgesics drugs that have wide use in health sciences. Some drugs can modify the labeling of blood elements with technetium-99m (99mTc). This work has evaluated the effect of AAP, ASA and DIP on the labeling of the blood elements with 99mTc. Blood was incubated with different concentrations of the drugs before the 99mTc-labeled process. Plasma (P), blood cells (BC), insoluble (IF-P, IF-BC) and soluble (SF-P, SF-BC) fractions were separated and percentage of radioactivity (%ATI) in each fraction was determined. Data have shown that the antipyretic drugs used in this study did not significantly modify the fixation of 99mTc on the blood elements when the experiments were carried out with the doses usually used in human beings. Although the experiments were carried out with rats, it is possible to suggest that AAP, ASA or DIP should not interfere with the procedures in nuclear medicine involving the labeling of blood elements with 99mTc.

Acetaminophen↗
PubMed1985

Effect of linear gramicidin on sporulation and intracellular ATP pools of Bacillus brevis.

When Bacillus brevis ATCC 8185 was subjected to nutritional shiftdown from a rich medium to one completely devoid of a nitrogen source, sporulation could be stimulated by the addition of linear gramicidin. Gramicidin-induced sporulation occurred after a considerably longer lag period than the earlier described tyrocidine-induced process (Ristow and Paulus 1982) but involved similar associated biochemical changes, such as extracellular protease production, rapid incorporation of radioactive precursors into RNA, and dipicolinate synthesis. The increased incorporation of [3H]leucine into tyrocidine was a characteristic element in gramicidin-induced sporulation, not being observed when spore formation was accelerated by limited nitrogen supplementation. Nitrogen supplementation (0.02-0.01% nutrient broth) caused a slow and gradual increase in dipicolinate production, in contrast to the sudden, rapid rise of dipicolinate synthesis provoked by the addition of gramicidin or tyrocidine. The induction of sporulation by gramicidin occurred at very low peptide concentrations (0.03 microM), which also brought about an acute depletion of intracellular ATP. In sporulation accelerated by nutrient broth, no depression of ATP level was observed and nonionophoric analogues of gramicidin were unable to substitute for gramicidin in inducing sporulation.

Adenosine Diphosphate↗
PubMed2006

Affinity labeling of the rabbit 12/15-lipoxygenase using azido derivatives of arachidonic acid.

Lipoxygenases are lipid-peroxidizing enzymes, which have been implicated in the pathogenesis of important diseases. They consist of a single polypeptide chain, which is folded into a two-domain structure. The large catalytic domain contains the putative substrate-binding pocket and the catalytic non-heme iron. To identify structural elements of the rabbit 12/15-lipoxygenase that are involved in enzyme/substrate and/or enzyme/product interaction, we synthesized a set of radioactively labeled lipoxygenase substrates carrying a photoreactive azido group (17-azido-ETE, 18-azido-ETE, 19-azido-ETE) and used these compounds as affinity probes. After photoaffinity labeling, the enzyme was digested proteolytically and modified tryptic cleavage peptides were identified by a combination of radio-HPLC and mass spectral analysis. Following this strategy, we observed covalent linkage of a cleavage peptide that contained Ile593, which has previously been identified as the sequence determinant for the positional specificity. These data are consistent with the previous suggestion that this peptide lines the substrate-binding pocket. Surprisingly, we also observed strong labeling of cleavage peptides originating from the N-terminal beta-barrel domain, and our mass spectral data suggested covalent linkage of oxidized affinity probes. Taken together, these results confirm the previous conclusion that Ile593 and surrounding amino acids are constituents of the active site, but they also implicate the N-terminal beta-barrel in enzyme/substrate and/or enzyme/product interaction.

Affinity Labels↗
PubMedDate not supplied

Grid resolution study of ground water flow and transport.

Three-dimensional grids representing a heterogeneous, ground water system are generated at 10 different resolutions in support of a site-scale flow and transport modeling effort. These grids represent hydrostratigraphy near Yucca Mountain, Nevada, consisting of 18 stratigraphic units with contrasting fluid flow and transport properties. The grid generation method allows the stratigraphy to be modeled by numerical grids of different resolution so that comparison studies can be performed to test for grid quality and determine the resolution required to resolve geologic structure and physical processes such as fluid flow and solute transport. The process of generating numerical grids with appropriate property distributions from geologic conceptual models is automated, thus making the entire process easy to implement with fewer user-induced errors. The series of grids of various resolutions are used to assess the level at which increasing resolution no longer influences the flow and solute transport results. Grid resolution is found to be a critical issue for ground water flow and solute transport. The resolution required in a particular instance is a function of the feature size of the model, the intrinsic properties of materials, the specific physics of the problem, and boundary conditions. The asymptotic nature of results related to flow and transport indicate that for a hydrologic model of the heterogeneous hydrostratigraphy under Yucca Mountain, a horizontal grid spacing of 600 m and vertical grid spacing of 40 m resolve the hydrostratigraphic model with sufficient precision to accurately model the hypothetical flow and solute transport to within 5% of the value that would be obtained with much higher resolution.

Finite Element Analysis↗
PubMed2003

Stability of peroxide-containing uranyl minerals.

Minerals containing peroxide are limited to studtite, (UO2)O2(H2O)4, and metastudtite, (UO2)O2(H2O)2. High-temperature oxide-melt solution calorimetry and solubility measurements for studtite (standard enthalpy of formation at 298 kelvin is -2344.7 +/- 4.0 kilojoules per mole from the elements) establishes that these phases are stable in peroxide-bearing environments, even at low H2O2 concentrations. Natural radioactivity in a uranium deposit, or the radioactivity of nuclear waste, can create sufficient H2O2 by alpha radiolysis of water for studtite formation. Studtite and metastudtite may be important alteration phases of nuclear waste in a geological repository and of spent fuel under any long-term storage, possibly at the expense of the commonly expected uranyl oxide hydrates and uranyl silicates.

Journal Article↗
PubMed1992

New nonradioactive microspheres and more sensitive X-ray fluorescence to measure regional blood flow.

We developed new nonradioactive microspheres and used more sensitive X-ray fluorescence spectrometers than used previously to measure regional blood flow in the heart and other organs. We demonstrated the chemical stability of eight kinds of heavy element-loaded microspheres and validated their use for regional blood flow measurement by comparing duplicate flows measured with radioactive and/or nonradioactive microspheres in both acute and chronic dog experiments. The wavelength-dispersive spectrometer (Philips PW 1480) has a higher sensitivity than the previously described X-ray fluorescent system and reduced the number of microspheres required for accurate measurement. The fine energy resolution of this system makes it possible to increase the numbers of different kinds of microspheres to be quantitated, but at present only eight kinds are available. We also used a synchrotron radiation-excited energy dispersive spectrometer. The monochromatic synchrotron radiation allowed us to obtain much higher signal-to-background ratios of X-ray fluorescence spectra than with the wavelength-dispersive system (50 dB more for Zr-loaded microspheres) and will enable analysis of fluorescent activity in smaller regions (< 20 mg) than the radioactive method does.

Animals↗
PubMed1992

Transfer of bilirubin covalently bound to 125I-albumin from blood to brain in the Gunn rat newborn.

Transfer of bilirubin covalently bound to albumin (Alb.B) from blood into brain was examined in Gunn rats at postnatal day 3, 7, 14, 28 or 70. The ratio of the 125I-Alb.B concentration in the brain to that in the plasma 2 h after the injection (RAB) was used as a criterion for Alb.B transfer. RAB in brain decreased with age until day 28. Significant correlations were indicated between 125I-Alb.B plasma levels and those in the brain at days 7 and 14, but not at day 28. These results suggested that 125I-Alb.B could transfer from the blood to the brain until day 14. Comparison of the relative amount of radioactivity accumulated in the brain by a 125I-Alb.B injection with that of 125I-albumin alone revealed higher radioactivity in the former than the latter only at day 14, suggesting a transient appearance of particular cellular elements with high affinity to bilirubin in the developmental stage of the brain.

Aging↗
PubMedDate not supplied

[Radionuclides 90Sr and 137Cs in the benthos near the nuclear submarine "Komsomolets"].

We have analyzed the content of radionuclides 90Sr and 137Cs in the benthofauna and deposits near the nuclear submarine "Komsomolets." Analysis was performed on the basis of the materials of the 31st (1993) and 36th (1995) voyages of R/V "Akademik Mstislav Keldysh" in correspondence with the system of monitoring the state of the abiotic and biotic situation near the nuclear submarine "Komsomolets" (Norwegian Sea). Whereas during the 33rd voyage of this vessel (1994) the content of these elements in the benthic animals at stations located close to the submarine somewhat exceeded the background level of radioactivity (Kuznetsov et al., 1996), no such excess was found during the 31st and 36th voyages. Meanwhile, radioactive cobalt (60Co) was found in representatives of three groups of animals during the 31st voyage at two stations located near the submarine.

Animals↗
PubMed2000

Pneumotoxic effects of radioactive dust (RD) from a nuclear power plant in Kozloduy, Bulgaria.

BACKGROUND: Airborne radioactive particles isolated from the reactor halls of nuclear power plants are a potential risk to the respiratory system of the working staff. Such radioactive dust (RD) from the Nuclear Power Plant, Kozloduy, Bulgaria was investigated. METHODS: The RD was administered intratracheally to 60 male Wistar rats as an aqueous suspension and the biological effects are estimated, using sensitive biological markers in bronchoalveolar lavage fluid (BALF) and important parameters of the pulmonary antioxidant defense. RESULTS: The results obtained show that RD increases the total cell number, the activities of the lactate dehydrogenase and alkaline phosphatase as well as the protein content in BALF. The activities of superoxide dismutase and catalase in lung homogenate are decreased while activity of the glutathione peroxidase and the content of non-protein sulfhydrils is elevated. CONCLUSIONS: It is concluded that the RD causes transitory toxic effect on lung tissue and changes the correlation between the elements of the pulmonary antioxidative defense.

Air Pollutants, Radioactive↗