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PubMed2003

Spatial variability of fallout-90Sr in soil and vegetation of an alpine pasture.

According to the soil-to-plant transfer concept generally used in dose assessment modeling, the plant uptake of a radionuclide should depend linearly on its concentration in the soil. In order to validate this concept for (90)Sr in a semi-natural ecosystem, plant and soil samples were taken at 100 plots of a 100 x 100 m(2) area within an alpine pasture near Berchtesgaden, Germany. At three plots, the vertical distribution of (90)Sr in the soil was determined in addition. A statistically significant correlation between the soil and plant concentration of (90)Sr was not detectable (Spearman correlation coefficient R=-0.116, p>0.05) within the range of the Sr-concentration covered (15-548 Bq kg(-1) dry soil and 17-253 Bq kg(-1) dry plant material). Thus, the prerequisite of the soil-to-plant transfer concept was not fulfilled for (90)Sr at this site. Organic carbon and total nitrogen were also determined in the soil samples. Both elements were highly correlated (R=0.912, p<0.001), their ratio being C/N=10.9+/-0.7. While C was positively correlated with the (90)Sr concentrations in the soil (R=0.342, p<0.001), negative correlations were observed for the plant concentrations (R=-0.286, p<0.01) and the concentration ratios (R=-0.444, p<0.001) of (90)Sr. These results are compared with those recently obtained for (137)Cs by Bunzl et al. (J Environ Radioactiv 48 (2000) 145).

Carbon↗

PubMed1988

Concentration factors used in the assessment of radiation dose to consumers of fish: a review of 27 radionuclides.

Concentration factors (CFs) for 27 radionuclides in marine and freshwater fish were reviewed, as were factors that may influence the dose commitment to man resulting from the consumption of fish. These factors include environmental partitioning, ecological trophic level discrimination and specific tissue accumulation (tropism). Our recommendations are based first on field data for radioisotopes of each element; second, on data for stable elements for which data on radioisotopes are lacking; and third, on the potential for bioaccumulation, which is influenced most by the established biological significance of the element or its chemical similarity to biologically active elements in the same chemical group. Only radionuclides of elements with known biological functions or their analogues accumulate to significant levels in fish tissue. The environmental data that exist for Cs, Sr, Co, Fe, Mn, I, P, Am, Cm, Np and Pu were used for adjusting CFs based on water quality or trophic status of fish. Separate CFs have been listed for particular groups of fish that showed a high propensity for certain radionuclides to accumulate in tissue at higher specific activity than that found in water.

Animals↗

PubMed2000

Quantitative analysis of DNA binding affinity and dimerization properties of wild-type and mutant thyroid hormone receptor beta1.

Thyroid hormone (triiodothyronine [T3]) actions are mediated through binding of thyroid hormone receptors (TRs) to specific DNA sequences (thyroid hormone response elements [TREs]) as monomers, homodimers, and heterodimers with thyroid hormone receptor auxiliary proteins (TRAPs). We quantitatively characterized dimerization of wild-type (WT) and mutant TRbetas by coimmunoprecipitation, and binding to DNA by electrophoretic gel mobility shift assays (EMSA). Binding affinities of TR retinoid X receptor-alpha (RXRalpha) heterodimers to DNA were determined by competing with excess nonradiolabeled TREs in EMSA. TRs in vitro synthesized in reticulocyte lysates (RL), and human RXRalpha expressed in a Sf9 cell-baculovirus system (BAC), were coincubated with 32P-labeled rat malic enzyme (ME), palindromic (PAL), or chicken lysozyme F2 (F2) TREs. The mutant TRbetas tested were R316H and G345R, which have nondetectable T3 binding and have previously been reported to show weak and potent dominant negative effect, respectively. Scatchard analysis showed no significant differences in Kas between WT and mutant TR-RXRalpha heterodimers binding to DNA. We measured affinity of heterodimerization between TRs and RXRalpha in solution in the absence of DNA, and by coimmunoprecipitation using anti-TRbeta1WT specific antibodies. 35S-labeled RL-RXRalpha was incubated with BAC-WT or TRbeta or R316H in the absence or presence of increasing amounts of nonlabeled BAC-RXRalpha. Displacement curves were obtained by counting radioactivity of precipitated 35S-RXRalpha, that was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and autoradiography. Kds of WT and TRbeta R316H heterodimerizing with RXRalpha were approximately the same. Binding affinity of TR homodimers for F2-TRE was studied because this TRE binds homodimers strongly. Scatchard analysis clearly showed that DNA binding affinity of BAC-WT homodimers did not differ with or without 100 nM T3, but maximal binding capacity (MBC) was reduced three-fold to fourfold in the presence of 100 nM T3. In contrast, BACTRbeta-R316H homodimers showed a fivefold reduction in DNA binding affinity for F2, both in the presence and absence of T3, and approximately the same MBC as WT in the absence of T3. Mutant RL-G345R homodimers showed approximately the same Ka as RL-WT homodimers for binding to F2 and the same MBC in the presence and absence of T3. These results indicate that (1) T3 reduced TRbeta homodimerization in solution but does not effect DNA binding of formed homodimers; (2) T3 does not influence DNA binding affinity of TR/RxR heterodimers; and (3) TRbeta mutant R316H homodimers have reduced DNA binding affinity but homodimerization and heterodimerization in solution does not differ from WT TRbeta.

Animals↗

PubMed2000

Quantification of local deposition patterns of inhaled radon decay products in human bronchial airway bifurcations.

Aerosol deposition studies with tracheobronchial casts and models have demonstrated that inhaled particles are preferentially deposited within transitional bifurcation zones, exhibiting hot spots in the vicinity of carinal ridges. The goal of the present study is to quantify the inhomogeneity of theoretically predicted deposition patterns by local deposition enhancement factors. First, inspiratory particle deposition patterns of unattached (1 nm), ultrafine (10 nm and 20 nm), and attached (100 nm and 200 nm) radon progeny within three-dimensional models of segmental bronchial airway bifurcations were simulated by a numerical fluid dynamics and particle trajectory model. Second, local deposition enhancement factors were computed by scanning along the surface of the bifurcation models with prespecified surface area elements. Maximum values and frequency distributions of local deposition enhancement factors of inhaled radon progeny were derived for different sizes of the scanning element in a "narrow" and a "physiologically realistic" bifurcation model and for two different flow rates (10 L min(-1) and 60 L min(-1) in the trachea). Computed enhancement factors indicate that cells located at carinal ridges may receive localized doses which are 20-40 times (1 nm) and 50-115 times higher (10 nm-200 nm), respectively, than the corresponding average doses. This may have important implications for the microdosimetry of inhaled radon progeny and the resulting lung cancer risk.

Aerosols↗

PubMed1993

Binding of an Escherichia coli double-stranded DNA virus PRD1 to a receptor coded by an IncP-type plasmid.

IncP plasmid RP1 Tra regions are needed to assemble the receptor for lipid-containing double-stranded DNA bacteriophage PRD1 on the cell surface. Using radioactively labeled phage and electron microscopic techniques, we showed that the surfaces of Salmonella typhimurium(RP1) and Escherichia coli(RP1) cells contained approximately 50 and 20 PRD1 binding sites, respectively. Expression of the receptor was growth phase dependent and was highest at late logarithmic or early stationary phase. The PRD1-resistant RP1 transposon mutants isolated were all Tra-, and the transposons were located in both the Tra1 and Tra2 regions.

Coliphages↗

PubMed2002

Composition of particulate and dissolved organic matter in a disturbed watershed of southeast Brazil (Piracicaba River basin).

The elemental and isotopic composition of particulate and dissolved organic matter was investigated in the Piracicaba River basin, São Paulo State, Brazil. Comparison of riverine organic matter from the Piracicaba River basin, a region where rivers and streams receive urban sewage and industrial effluents, with data reported for the pristine Amazon system revealed significant differences associated with anthropogenic impacts. One important difference was N enrichment in the particulate organic material of the Piracicaba basin rivers, due to (a) urban and industrial effluents, and (b) enhanced phytoplankton growth, which results from the combination of nutrient enrichment and damming of sections of the rivers. Radiocarbon concentrations were overall more depleted (older 14C age) in the Piracicaba basin rivers than in the Amazon, which may reflect the importance of soil erosion in the former. Analyses of stable and radioactive carbon isotopes and lignin-derived compounds indicated that coarse particulate organic material is composed of a mixture of soil particles and degraded organic matter from C3 and C4 vascular plants. Fine particulate organic material was composed mainly of soil particles and phytoplankton cell remains, the latter especially during low water. Ultrafiltered dissolved organic matter was the most degraded fraction according to its lignin oxidation products, and showed the greatest influence of C4 plant sources.

Brazil↗

PubMed1983

Uptake and retention of [3H]adrenaline by central monoaminergic neurons: a light- and electron-microscope radioautographic study after intraventricular administration in the rat.

Paraventricular and paracisternal regions of adult rat central nervous system were investigated by light- and electron-microscope radioautography after intraventricular administration of tritiated adrenaline. In tissue primarily fixed by glutaraldehyde perfusion and post-fixed by immersion in osmium tetroxide, there were no aggregates of silver grains indicative of intraneuronal accumulation of the tracer, except over perivascular nerve terminals at the base of the brain. In contrast, when both fixation and postfixation were carried out by rapid vascular perfusion, preferentially labeled nerve cell bodies and axonal varicosities (i.e. terminals) were detected in various anatomical areas known to contain dopaminergic and/or noradrenergic neurons. Serotoninergic axonal varicosities in the supraependymal plexus and subcommissural organ, as well as a small group of nerve cell bodies of undetermined chemical identity in the n. paraventricularis thalami were also found to be labeled. Addition of a ten-fold higher concentration of non-radioactive serotonin to the solution of [3H]adrenaline suppressed the reactivity in the subcommissural organ and the supraependymal plexus but had no such effect elsewhere in brain. Lesioning of the nigrostriatal dopaminergic system with 6-hydroxydopamine prior to [3H]adrenaline injection eradicated axon terminal labeling in the ipsilateral neostriatum. Electron-microscopic examination of [3H]adrenaline-labeled varicosities in the neostriatum, lateral septum, arcuate nucleus and median eminence extended earlier observations on the ultrastructure of the catecholaminergic innervation of these regions. It was concluded that both dopaminergic and noradrenergic neurons as well as certain serotonin-containing axon terminals can take up and retain [3H]adrenaline, although they probably have lesser affinity for this amine than for their own transmitter. Due to the fact that presumptive adrenergic neurons are intermingled with dopaminergic and noradrenergic elements, further work will be needed to determine to which extent they also contributed to [3H]adrenaline uptake in the present experimental conditions.

Animals↗

PubMed2000

Living on a high sugar diet: the fate of sucrose ingested by a phloem-feeding insect, the pea aphid Acyrthosiphon pisum.

The natural diet of aphids, plant phloem sap, generally contains high concentrations of sucrose. When pea aphids (Acyrthosiphon pisum) were fed on chemically defined diets containing sucrose radiolabelled in the glucose or fructose moiety, 2 to 12-fold and 87 to 110-fold more radioactivity was recovered from the tissues and honeydew, respectively, of aphids that ingested [U-(14)C-glucose]-sucrose than from those ingesting [U-(14)C-fructose]-sucrose. The total radioactivity recovered was 70% of the ingested [U-(14)C-glucose]-sucrose and <5% of ingested [U-(14)C-fructose]-sucrose. The dominant honeydew sugars produced by aphids feeding on 0.75 M sucrose diets were oligosaccharides comprising glucose. In vitro the guts of pea aphids had high sucrase activity, 1-5 U mg(-1) protein, generating equimolar glucose and fructose except at high sucrose concentrations where glucose production was inhibited (K(si)=0.1 M). These data suggest that the fructose moiety of ingested sucrose is assimilated very efficiently and may be preferentially respired by the aphid, and that the glucose moiety of sucrose is incorporated into oligosaccharides by the transglucosidase activity of the gut sucrase at high sucrose concentrations. These differences in the fate of sucrose-derived glucose and fructose are important elements in both the carbon nutrition and osmoregulation of aphids.

Journal Article↗

PubMed1992

Behavior of Chernobyl fallout radionuclides in peat combustion.

The fallout from the explosion and fire at the Chernobyl nuclear power plant concentrated levels of up to 10 kBq 137Cs kg-1 dry weight in the fuel peat harvested during the summer of 1986 in Finland. We investigated the behavior of fallout radionuclides 137Cs, 134Cs, 106Ru, 144Ce, 125Sb, 95Zr, and 110mAg together with naturally occurring 210Pb and 226Ra in the combustion of this contaminated peat in four different power plants. The elements antimony, ruthenium, lead, and cesium were enriched on the smallest particles, indicating that they were in a volatile chemical form, while cerium, zirconium, and radium were nonvolatile at the combustion temperatures. This result confirms the previous finding that ruthenium is volatile in combustion. Although metallic ruthenium requires 2,310 degrees C to melt, some of its oxides melt and evaporate at much lower temperatures.

Accidents↗

PubMed1989

Tellurium-induced neuropathy: metabolic alterations associated with demyelination and remyelination in rat sciatic nerve.

Rats fed a diet containing 1.25% elemental tellurium initiated on postnatal day 20 undergo a transient neuropathy characterized by synchronous demyelination of peripheral nerves. In sciatic nerve, the extent of demyelination was maximal after 5 days of tellurium exposure; there was a loss of 25% of the myelin, as assayed by concentration of myelin-specific P0 protein. Tellurium-induced alterations in the metabolic capacity of Schwann cells were examined by measuring the synthesis of myelin lipids in vitro in isolated sciatic nerve segments. Exposure to tellurium resulted in an early marked decrease of approximately 50% in overall incorporation of [14C]acetate into lipids, with a preferential depression in synthesis of cerebrosides, cholesterol, and ethanolamine plasmalogens (components enriched in myelin). Most dramatically, within 1 day of initiation of tellurium exposure, there was a profound increase in [14C]acetate-derived radioactivity in squalene; 23% of incorporated label was in this intermediate of cholesterol biosynthesis, compared to less than 0.5% in controls. In association with the remyelinating phase seen after 5 days of tellurium exposure, synthesis of myelin components gradually returned to normal levels. After 30 days, metabolic and morphologic alterations were no longer apparent. We suggest that the sequence of metabolic events in sciatic nerve following tellurium treatment initially involves inhibition of the conversion of squalene to 2,3-epoxysqualene, and that this block in the cholesterol biosynthesis pathway results, either directly or indirectly, in the inhibition of the synthesis of myelin components and breakdown of myelin.

Acetates↗

PubMed2005

Optimization of dynamic measurement of receptor kinetics by wavelet denoising.

The most important technical limitation affecting dynamic measurements with PET is low signal-to-noise ratio (SNR). Several reports have suggested that wavelet processing of receptor kinetic data in the human brain can improve the SNR of parametric images of binding potential (BP). However, it is difficult to fully assess these reports because objective standards have not been developed to measure the tradeoff between accuracy (e.g. degradation of resolution) and precision. This paper employs a realistic simulation method that includes all major elements affecting image formation. The simulation was used to derive an ensemble of dynamic PET ligand (11C-raclopride) experiments that was subjected to wavelet processing. A method for optimizing wavelet denoising is presented and used to analyze the simulated experiments. Using optimized wavelet denoising, SNR of the four-dimensional PET data increased by about a factor of two and SNR of three-dimensional BP maps increased by about a factor of 1.5. Analysis of the difference between the processed and unprocessed means for the 4D concentration data showed that more than 80% of voxels in the ensemble mean of the wavelet processed data deviated by less than 3%. These results show that a 1.5x increase in SNR can be achieved with little degradation of resolution. This corresponds to injecting about twice the radioactivity, a maneuver that is not possible in human studies without saturating the PET camera and/or exposing the subject to more than permitted radioactivity.

Algorithms↗

PubMed1995

[The progress in radiopharmaceuticals in Japan--In connection with the 100-year anniversary after Prof. Röntgen discovered X-ray in 1895].

This year is the 100-year anniversary after Prof. W.K. Röntgen discovered X-rays in 1895. In connection with this point, I studied the history of radiopharmaceuticals (RP) in Japan. In 1937, the first cyclotoron was established by Dr. Yoshio Nishina in Tokyo and researches for radioisotope (RI) were started in the medical field in Japan. After the Second World War, RI research in the medical field started again using imported RI from U.S.A. in 1950. The National Institute of Radiological Sciences was established by the Japanese Government in Chiba-city in 1957 and the RP law was enacted by the Ministry of Health and Welfare of Japan. Twenty-five nuclear elements were regulated as RP by the Pharmaceutical Law in 1959. Five RP products were included for the first time in the Japanese Pharmacopoeia (JP), 7th Edition, in 1961. The Japan Radioisotope Association (JRIA) was established in 1951 for the purpose of importing and distributing RI, technical training for safety operation, collecting the RI wastes and so on. The JRIA is playing an important role in the progress of RP. Now, RP were separated officially for in vivo use and in vitro use in Japan.

History, 20th Century↗

PubMed1975

Determining liver retention of transuranium elements in living beagles.

A method has been developed whereby the liver content of photon-emitting transuranium elements can be determined in living beagles by a combination of total-body and partial-body counting. Calibration of the system was accomplished through the photon counting of intact dogs and also of the parts of the same animals following autopsy. A determination of the calibration factors for 252Cf, 247Cf, 243Cm, 237Pu, and 241Am has been made. The special case of 252Cf was treated in which a significant fraction of the high energy fission gamma-ray spectrum penetrates the Pb shield employed in partial-body counting, and methods were developed which allow for this effect in the calculation of liver content. Some uniformity of response in the system was evident for all of the emitters which were considered. It is proposed that similar techniques could be applied in the determination of selected organ radioactivity in other species including man.

Americium↗

PubMed1998

Antiproliferative effect of deferiprone on the Hep G2 cell line.

Iron is an essential element in cellular metabolism and the growth of all living species, and is involved in DNA replication. The risk of hepatocellular carcinoma development is associated with an increase in iron availability. The aim of the present work was to investigate the effect of an oral iron chelator, deferiprone (CP20), on HepG2 cell-line proliferation in culture. HepG2 cell cultures were maintained in the absence of fetal calf serum (FCS) and in the presence or not (control cultures) of CP20 at the concentrations of 50 or 100 microM; deferoxamine (DFO) was used as an iron chelator reference. Cell proliferation was investigated by the analysis of DNA synthesis using [3H] methyl-thymidine incorporation and of the cell cycle by flow cytometry. Iron chelation efficiency in the culture model was studied by analyzing the effect of CP20 on radioactive iron uptake, intracellular ferritin level, and transferrin receptor expression. CP20, at the concentration of 50 or 100 microM, inhibited DNA synthesis after 48 hr of incubation and induced an accumulation of the cells in the S phase of the cell cycle. Iron chelators inhibited cellular iron uptake, decreased intracellular ferritin level, and increased transferrin receptor protein and mRNA levels. Our results show that CP20 as well as deferoxamine inhibit HepG2 cell proliferation and block cell cycle in the S phase.

Cell Cycle↗

PubMed1998

Magnesium transport in freshwater teleosts

The magnesium handling of freshwater teleost fish is discussed, with an emphasis on the role of branchial, intestinal and renal transport. In response to the eminent threat of constant diffusive losses of minerals such as magnesium, freshwater fish have developed efficient mechanisms for magnesium homeostasis. Magnesium losses are overcome by the uptake of magnesium from the food, making the intestine an important route for magnesium uptake. Some evidence suggests that intestinal magnesium uptake in fish is a regulated, cellular process. The ambient water is an additional magnesium source for fish, implicating the gills as a secondary route for magnesium uptake. Certainly, in some species, direct uptake from the water, probably via branchial routes, ameliorates the effects of a low-magnesium diet. The hard tissues, representing over 50 % of the total body magnesium pool, form a reservoir from which magnesium can be recruited to perform its functions in the cellular metabolism of soft tissues such as muscle. In fish, as in terrestrial vertebrates, the balance of a variety of elements becomes disturbed when the magnesium homeostasis of the soft tissues is disrupted. However, fish appear to be less sensitive than terrestrial vertebrates to these perturbations. Magnesium is reabsorbed in the kidneys to minimise losses. For renal cells, part of a cellular pathway has been elucidated that would allow absorptive magnesium transport (a magnesium conductive pathway in renal brush-border membranes). In some euryhaline teleosts, the kidneys appear to switch instantaneously to rapid magnesium secretion upon magnesium loading, a response common to marine fish that are threatened by diffusive magnesium entry. This enigmatic mechanism underlies the capacity of some euryhaline species to acclimate rapidly to sea water. Despite the progress made over the last decade, much of the cellular and molecular basis of magnesium transport in the gills, intestine and kidneys remains obscure. The application of fluorescent, radioactive and molecular probes, some of which have only recently become available, may yield rapid progress in the field of magnesium research.

Journal Article↗

PubMed1983

[Application of PIXE (particle-induced x-ray emission) method to the cytolytic test of tumor cells].

Immunological studies have often been based on the results of cytolytic assay in which cells labelled with radioactive 51Cr are usually employed. The replacement of the radioactive isotope by a stable one is obviously desirable in order to eliminate the problem of radiation hazard and to prevent environmental contamination. We applied PIXE (particle induced X-ray emission) method for the detection of stable chromium (Cr). MM46 cells labelled with natural Cr were treated with anti-MM46 serum and a rabbit complement. The remaining Cr was filtered. The released Cr was precipitated with ethanol and deposited on the filter. The specimens were bombarded with proton beams from a Van de Graaff accelerator and the X-rays produced were detected with a Si(Li) detector. The Cr peaks appeared clearly. One of the main advantages of the application of the PIXE method is its high sensitivity. Another merit of the present method is that it can easily compare the remaining ratio of several elements in cellular materials after lytic treatment. This information may be used as a parameter indicating differences in the process of cytolysis.

Animals↗

PubMed1993

[35S]cysteamine: facile synthesis, in vivo biokinetics, and subcellular distribution.

Whereas chemical radioprotection against external beams of ionizing radiation is well studied in radiobiology, the aspects relating to tissue incorporated radionuclides have received little attention. The increased use of radionuclides in diagnostic and therapeutic nuclear medicine, as well as the presence of both manmade and natural radioactivity in the environment, indeed call for such investigations. Our ongoing work on a variety of radioprotectors has revealed that cysteamine (MEA), S-2-aminoethylisothio uroniumbromide hydrobromide (AET), and others (e.g. ascorbic acid), protect spermatogonial cells in mouse testis from the effects of chronic irradiation with intratesticularly localized radionuclides. In these experiments, dose modification factors ranging from 2 to 4 and 10 to 14 were obtained using spermhead survival and induction of spermhead abnormalities, respectively, as the biological end points. Similar experiments were carried out by changing the mode of administration of cysteamine to oral intubation. In these studies a dose modification factor of approximately 3 was observed in the spermhead survival assay. In an effort to understand the protection offered by MEA, the present work describes a one-pot synthesis of high specific activity [35S]cysteamine from elemental [35S]sulphur and its use in determining the biokinetics and biodistribution of MEA following intratesticular (i.t.) or oral administration in mice.

Administration, Oral↗

PubMed1981

Mathematical analysis of the chemosmotic polar diffusion of auxin through plant tissues.

Equations have been developed to describe the diffusional movement of a weak acid such as the auxin indoleacetic acid through a long file of vacuolated cells, where cellular accumulation is driven by the pH gradients across the cell membranes. If the permeability to the auxin anion is greater at one end of the cell than at the other, diffusional movement takes the form of polar transport, which exhibits: a nearly constant velocity either for the front or for a pulse of radioactive auxin, the capacity to move auxin against an external gradient of concentration, and a polar ratio that increases exponentially with the length of the section. The determinants of velocity include both diffusion through the vacuole and permeation steps at the cell membranes. Except for the permeabilities of the membranes to the anion, values are now available for all of the physical parameters in the equations. With reasonable estimates of permeability coefficients for the anion, the equations predict a velocity of transport of about 1 cm hr(-1), which agrees well with measured values. The analysis indicates, however, that the underlying cellular polarity may be greater than has been heretofore assumed. We thus demonstrate that the hypothesis of chemosmotic polar diffusion is capable of accounting quantitatively for the major features of auxin transport and provides a theoretical framework whose elements can be tested in future experiments.

Journal Article↗