Determination Of Radioactivity Research Articles

The determination of radioactivity in imported teas and vegetables

The determination of radioactivity in imported teas and vegetables

Radiological characteristics and investigation of the radioactive equilibrium in the ashes produced in lignite-fired power plants

Coal- and lignite-fired power plants produce significant amounts of ashes, which are quite often being used as additives in cement and other building materials. In many cases, coal and lignite present high concentrations of naturally occurring radionuclides, such as 238U, 226Ra, 210Pb, 232Th and 40K. During the combustion process, the produced ashes are enriched in the above radionuclides. The different enrichment of the various radionuclides within a radioactive series, such as that of 238U, results in the disturbance of radioactive secular equilibrium. An extensive research project for the determination of the natural radioactivity of lignite and ashes from Greek lignite-fired power plants is in progress in the Nuclear Engineering Department of the National Technical University of Athens (NED-NTUA) since 1983. This paper presents detailed results for the natural radioactivity, the secular radioactive equilibrium disturbance and the radon exhalation rate of the fly-ash collected at the different stages along the emission control system of a lignite-fired power plant as well as of the bottom-ash. From the results obtained so far, it may be concluded that 226Ra radioactivity of fly-ash in some cases exceeds 1 kBq kg −1, which is much higher than the mean 226Ra radioactivity of surface soils in Greece (25 Bq kg −1). Furthermore, the radioactivity of 210Pb in fly-ash may reach 4 kBq kg −1. These results are interpreted in relation to the physical properties of the investigated nuclides, the temperature in the flue-gas pathway, as well as the fly-ash grain size distribution. It is concluded that towards the coldest parts of the emission control system of the power plant, the radioactivity of some natural nuclides is gradually enhanced, secular radioactive equilibrium is significantly disturbed and the radon exhalation rate tends to increase.

Determination of natural radioactivity in Euphrates river

Levels of naturally occuring radionuclides (radium isotopes, U isotopes, 210Po and 210Pb) in water, sediments and biota samples collected from Euphrates river during the 1999–2000 period have been determined. Results have shown that the water contained relatively high levels of 226Ra; the largest value of 1150 mBq·l−1 was observed. These relatively high levels of 226Ra, which is one of the main radioactive contaminants in the oil industry, may be due to past discharges of production water from the oil fields situated near the river banks. 226Ra/238U activity ratio was found to be more than unity in all water samples varying between 13 and 242. In addition, the results of sediment analyses have also shown lower values for 228Ra/226Ra activity ratio than unity in those samples collected nearby the oil fields. Moreover, concentrations of other naturally occurring radionuclides such as uranium isotopes, 210Po and 210Pb for most samples (water, sediments and biota) were found to be within the natural levels and in agreement with those values reported for other local and international studies. Only mussel species were found to contain high levels of 210Po, about 1335 Bq·kg−1 dry mass was observed in Anodonta sp species. However, the results of this study can be considered a baseline for monitoring of future changes. A regional research project (including Turkey, Syria and Iraq) to study this river (from the Anatolia Mountains to the Arabian Gulf) is necessary to determine the impact of all potential sources of contaminants.

Measurement of escape energy from absorber in calorimetric determination of 192Ir radioactivity

An improved method for the measurement of the escape energy from the absorber is proposed, which is formulated based on the air kerma and the effective mass energy-absorption coefficients in air for the escape photon spectrum. By applying the method, the escape energy from the tungsten absorber with sealed 192Ir source in it was measured. The ion chamber-type detector was used to measure the air kerma rates due to the escape photons. From the energy spectrum obtained by means of HPGe spectrometry, the effective mass energy-absorption coefficient in air for the escape photons was evaluated. The proposed method can be used for any other radioactive sources.

Concentrations of heavy metal and radioactivity in surface water and sediment of Hazar Lake (Elazığ, Turkey)

Concentration of heavy metals and natural gross radioactivity were measured in the surface water and sediment of Hazar Lake (Elazığ, Turkey). Eight sampling sites were pre-defined in different locations of the lake. A preliminary study on heavy metals (Zn, Fe, Mn, Ni, Cu, Cr, Co and Pb), major elements (Na, K, Ca, Mg) concentrations and natural radioactivity related to 226Ra, gross-α and gross-β radiations in the surface water and deep sediments were determined. The obtained results showed that, in general, the heavy metals (Zn, Fe, Mn, Ni, Cu and Pb) and major elements (Na, K, Ca, Mg) concentrations in water did not exceed WHO (World Health Organization, 1999), EC (Europe Community, 1998), EPA (Environment Protection Agency, 2002) and TSE-266 (Turkish Standard, 1997) guidelines. Generally, heavy metals and major elements concentration of the sediments were found decrease in sequence of Fe > Mg > Ca > Mn > Zn > Ni > Cr > Cu > Co > Pb. The results of this study indicated that a general absence of serious pollution in the Hazar Lake. The results obtained from the radioactivity determination indicate that the surface water radioactivity concentration of 226Ra, gross-α and gross-β were ranging from 0.52 ± 0.02 to 2.02 ± 0.06 Bq/l and from 0.65 ± 0.03 to 2.52 ± 0.07 Bq/l and from 0.01 ± 0.01 to 0.14 ± 0.01 Bq/l, respectively. Deep sediment radioactivity concentrations of 226Ra is ranging from 0.07 ± 0.03 to 0.32 ± 0.07 Bq/g.

Differential effect of transforming growth factor beta (TGF-beta) on the genes encoding hyaluronan synthases and utilization of the p38 MAPK pathway in TGF-beta-induced hyaluronan synthase 1 activation.

Unfettered hyaluronan (HA) production is a hallmark of rheumatoid arthritis. The discovery of three genes encoding hyaluronan synthases (HASs) allows for the investigation of the signaling pathways leading to the activation of these genes. Our objective is to further understanding of the regulation of these genes as well as to find ways to prevent undesired gene activation. Human fibroblast-like synoviocytes were used in these experiments. mRNA levels of HAS were monitored by reverse transcriptase-PCR. A series of specific kinase inhibitors were used to investigate intracellular pathways leading to the up-regulation of HAS1. Our experiments, testing a series of stimuli including tumor necrosis factor alpha (TNFalpha), demonstrate that TGF-beta is the most potent stimulus for HAS1 transcription. TGF-beta activates HAS1 in a dose-dependent manner with a maximum effect at a concentration of 0.5-1 ng/ml. TGF-beta-induced HAS1 mRNA can be detected within 60 min and reaches maximal levels at 6 h. Furthermore, TGF-beta treatment leads to an increase in synthase activity as determined by HA ELISA and by in vitro HA synthase assays. In contrast to the activatory effect on HAS1, TGF-beta dose-dependently suppresses HAS3 mRNA. As to the mode of action of TGF-beta-induced HAS1 mRNA activation, our experiments reveal that blocking p38 MAPK inhibited the TGF-beta effect by 90%, blocking the MEK pathway led to an inhibition by 40%, and blocking the JNK pathway had no effect. The presented data might contribute to a better understanding of the role of TGF-beta and of HA in the pathology of diseases.

Long-lived unstable nuclei as microindicators for some processes of nature

137Cs and 90Sr are the long-lived radioactive isotopes generated from nuclear tests/accidents. These isotopes take part in various processes of nature. Radioactivities due to these isotopes in environmental samples relate closely not only to date, site, characteristics, etc. of nuclear tests/accidents, but also to mechanism of processes in which the isotopes are presented. Determination and analysis of 137Cs and 90Sr radioactivity of environmental samples would disclose interesting information of some natural processes and other relating issues. In this paper the following topics will be discussed: 1. 1. The radial distribution of 137Cs and 90Sr in annual tree rings. 2. 2. The relation with accumulative deposition of radioactive fallout. 3. 3. What would be the mechanism of internal transfer processes during tree aging.

1139. γ(HPGe)-γ(HPGe)同時計測法による体内放射能測定

1139. γ(HPGe)-γ(HPGe)同時計測法による体内放射能測定

Sedimentological study of a lagoon through natural radioactivity and 137Cs determinations

Profiles of artificial fallout (such as 137Cs) and natural radioactivity radionuclides in sediment cores are useful tools to study sedimentological properties of different aquatic environments as well as to evaluate average sedimentation rates. In the Portil lagoon, a small natural reservoir located in Huelva province (southwest of Spain), and through the analysis of 210Pb, 226Ra, 137Cs, 238U and 210Po vertical profiles in sediment cores, it is shown how the accumulative or transport character of the collection zones may be inferred. In the accumulation zone of the lagoon the influence of focusing effects has been analysed and an average sedimentation rate has been determined through 210Pb in one sediment core. This 210Pb-sedimentation rate is consistent with sediment dating based on the 137Cs data.

Phosphoenolpyruvate Carboxykinase Overexpression Selectively Attenuates Insulin Signaling and Hepatic Insulin Sensitivity in Transgenic Mice

The ability of insulin to suppress gluconeogenesis in type II diabetes mellitus is impaired; however, the cellular mechanisms for this insulin resistance remain poorly understood. To address this question, we generated transgenic (TG) mice overexpressing the phosphoenolpyruvate carboxykinase (PEPCK) gene under control of its own promoter. TG mice had increased basal hepatic glucose production (HGP), but normal levels of plasma free fatty acids (FFAs) and whole-body glucose disposal during a hyperinsulinemic-euglycemic clamp compared with wild-type controls. The steady-state levels of PEPCK and glucose-6-phosphatase mRNAs were elevated in livers of TG mice and were resistant to down-regulation by insulin. Conversely, GLUT2 and glucokinase mRNA levels were appropriately regulated by insulin, suggesting that insulin resistance is selective to gluconeogenic gene expression. Insulin-stimulated phosphorylation of the insulin receptor, insulin receptor substrate (IRS)-1, and associated phosphatidylinositol 3-kinase were normal in TG mice, whereas IRS-2 protein and phosphorylation were down-regulated compared with control mice. These results establish that a modest (2-fold) increase in PEPCK gene expression in vivo is sufficient to increase HGP without affecting FFA concentrations. Furthermore, these results demonstrate that PEPCK overexpression results in a metabolic pattern that increases glucose-6-phosphatase mRNA and results in a selective decrease in IRS-2 protein, decreased phosphatidylinositol 3-kinase activity, and reduced ability of insulin to suppress gluconeogenic gene expression. However, acute suppression of HGP and glycolytic gene expression remained intact, suggesting that FFA and/or IRS-1 signaling, in addition to reduced IRS-2, plays an important role in downstream insulin signal transduction pathways involved in control of gluconeogenesis and progression to type II diabetes mellitus.

Mixed waste reduction in radioactivity determination by using plastic scintillators

In this work, we tested whether plastic scintillation (PS) is a suitable alternative to liquid scintillation (LS) and Cerenkov techniques for beta emitter detection. The main advantage of this alternative is the reduction of mixed waste produced as consequence of the measurement process. In addition, the quality parameters obtained with PS are as reliable as those obtained with LS and allow determination, with a relative error <10%, for 90 Sr/ 90 Y in low level activity aqueous samples. Gamma and alpha emitters were also measured with plastic scintillators using linear and logarithmic amplified scintillation detectors.

Use of 5-[(76)Br]bromo-2'-fluoro-2'-deoxyuridine as a ligand for tumour proliferation: validation in an animal tumour model.

Uncontrolled cell proliferation is one of the prominent features in cancer development. Precise tools are needed for determination of the proliferation rate before, during and after treatment, thereby permitting assessment of treatment efficacy. The purpose of this study was to validate the use of 5-[(76)Br]bromo-2'-fluoro-2'-deoxyuridine ((76)Br-BFU) as a proliferation marker in an animal tumour model. Comparison was made with 2-[(14)C]thymidine ((14)C-TdR) incorporation and the labelling index assessed by bromodeoxyuridine (BrdUrd-LI). Fibrosarcoma (NFSA)-bearing mice were used for all experiments. Gemcitabine (dFdC), a potent inhibitor of DNA synthesis, was used to modulate cell proliferation. dFdC was injected intraperitoneally at a dose of 0.5 mg/kg or 40 mg/kg to induce partial ( approximately 50%) or complete inhibition of DNA synthesis, respectively. (76)Br-BFU (0.5-3 MBq per animal), (14)C-TdR (37-74 kBq per animal) and cold BrdUrd (60 mg/kg) were injected intraperitoneally in combination or alone. Animals were sacrificed at various times after tracer administration, and tumour and small intestine were removed for determination of radioactivity in whole tissue and the DNA fraction, as well as for LI assessment by flow cytometry. Cimetidine (6 mg/kg) was used to decrease (76)Br-BFU elimination and increase its bioavailability. The fraction of radioactivity associated with DNA increased with the time interval between tracer injection and tissue removal. At 6 h after injection, for both tracers, more than 95% of the radioactivity in the tumours was associated with the DNA fraction and an excellent correlation was observed with the LI. Similar findings were observed in the small intestine. Under all experimental conditions, (76)Br-BFU uptake was 4-10 times lower than (14)C-TdR uptake. Co-injection of cimetidine resulted in a three- to fourfold increase in (76)Br-BFU incorporation without affecting the effect of dFdC on DNA synthesis. (76)Br-BFU is a potentially good tracer for the assessment of tumour proliferation. It has all the specifications required of a PET tracer for clinical use. One limitation to its use is the necessity of co-injecting cimetidine to increase its bioavailability and hence its sensitivity for PET detection.

Analysis of a [14C]-labelled platinum anticancer compound in dosing formulations and urine using a combination of HPLC-ICPMS and flow scintillation counting

The use of high performance liquid chromatography with inductively coupled mass spectrometry (HPLC-ICPMS) in combination with on-line radioactivity determination is described for the analysis of ZD0573, a platinum anticancer drug. The technque was used to determine the purity of formulated material in oral and IV dosing solutions, and for the detection of Pt-containing metabolites in urine following IV administration to the dog. In addition to Pt, it was found possible to detect14C directly by ICPMS when analysis solutions containing [14C]-ZDO473.

Importância da preservação de tecido esplênico para a fagocitose bacteriana

OBJETIVO: O baço, como maior órgão linfóide do corpo humano, apresenta funções imunológicas relevantes, tais como depuração de bactérias da corrente sangüínea e produção precoce de anticorpos contra várias partículas antigênicas. Fígado, pulmão e baço apresentam mais de 95% da atividade fagocitária em humanos. MÉTODOS: Ratos jovens e adultos de ambos os sexos foram submetidos a esplenectomia total e comparados com animais não submetidos a tratamento cirúrgico, visando a avaliação dessa função. Após 16 semanas, os ratos de ambos os grupos foram inoculados, por via intravenosa, com suspensão de Escherichia coli marcada com tecnécio-99m, e depois de 20 minutos, foram mortos. Fígado, pulmão, baço e uma amostra de coágulo sangüíneo foram removidos para determinação da contagem radioativa. O estudo estatístico foi realizado pelo teste t de Student. RESULTADOS: Não ocorreram diferenças no percentual de captação obtido em ratos esplenectomizados jovens ou adultos. Entretanto, esses animais apresentaram contagens sangüíneas mais elevadas que os ratos do grupo controle (p&lt;0,0001), devido a maior remanescente bacteriano na corrente sangüínea. CONCLUSÃO: Esse achado sugere ocorrer alguma falha no sistema mononuclear fagocitário em sua adaptação à ausência do baço e ratifica a necessidade de desenvolvimento de técnicas cirúrgicas alternativas à esplenectomia total para emprego em pacientes em que seja necessária a remoção esplênica.

Bile salt-stimulated carboxyl ester lipase influences lipoprotein assembly and secretion in intestine: a process mediated via ceramide hydrolysis.

Bile salt-stimulated carboxyl ester lipase (CEL), also called cholesterol esterase, is one of the major proteins secreted by the pancreas. The physiological role of CEL was originally thought to be its mediation of dietary cholesterol absorption. However, recent studies showed no difference between wild type and CEL knockout mice in the total amount of cholesterol absorbed in a single meal. The current study tests the hypothesis that CEL in the intestinal lumen may influence the type of lipoproteins produced. A lipid emulsion containing 4 mm phospholipid, 13.33 mm [(3)H]triolein, and 2.6 mm [(14)C]cholesterol in 19 mm taurocholate was infused into the duodenum of lymph fistula CEL(+/+) and CEL(-/-) mice at a rate of 0.3 ml/h. Results showed no difference between CEL(+/+) and CEL(-/-) mice in the rate of cholesterol and triglyceride transport from the intestinal lumen to the lymph. However, CEL(-/-) mice produced predominantly smaller lipoproteins, whereas the CEL(+/+) mice produced primarily large chylomicrons and very low density lipoprotein. The proximal intestine of CEL(-/-) mice was also found to possess significantly less ceramide hydrolytic activity than that present in CEL(+/+) mice. By using Caco2 cells grown on Transwell membranes as a model, sphingomyelinase treatment inhibited the secretion of larger chylomicron-like lipoproteins without affecting total cholesterol secretion. In contrast, the addition of CEL to the apical medium increased the amount of large lipoproteins produced and alleviated the inhibition induced by sphingomyelinase. Taken together, this study identified a novel and physiologically significant role for CEL, namely the promotion of large chylomicron production in the intestine. The mechanism appears to be mediated through CEL hydrolysis of ceramide generated during the lipid absorption process.

Regulation of cytosolic phospholipase A2 activity in macrophages stimulated with receptor-recognized forms of alpha 2-macroglobulin: role in mitogenesis and cell proliferation.

Macrophages exposed to receptor-recognized forms of alpha(2)-macroglobulin (alpha(2)M*) demonstrate increased DNA synthesis and cell division. In the current study, we have probed the role of cytosolic phospholipase A(2) (cPLA(2)) activity in the cellular response to alpha(2)M*. Ligation of the alpha(2)M* signaling receptor by alpha(2)M*, or its receptor binding fragment, increased cPLA(2) activity 2-3-fold in a concentration and time-dependent manner. This activation required a pertussis toxin-insensitive G protein. Cellular binding of alpha(2)M* also induced transient translocation of cPLA(2) activity to nuclei and membrane fractions. Inhibition of protein kinase C activity or chelation of Ca(2+) inhibited alpha(2)M*-induced increased cPLA(2) activity. Binding of alpha(2)M* to macrophages, moreover, increased phosphorylation of MEK 1/2, ERK 1/2, p38 MAPK, and JNK. Incubation of macrophages with inhibitors of MEK 1/2 or p38 MAPK before stimulation with alpha(2)M* profoundly decreased phosphorylation of MAPKs, blocking cPLA(2) activation. alpha(2)M*-induced increase in [(3)H]thymidine uptake and cell proliferation was completely abolished if activation of cPLA(2) was prevented. The response of macrophages to alpha(2)M* requires transcription factors nuclear factor kappaB, and cAMP-responsive element-binding protein as well as expression of the proto-oncogenes c-fos and c-myc. These studies indicate that the activation of cPLA(2) plays a crucial role in alpha(2)M*-induced mitogenesis and cell proliferation.

Influence of viscosity and ionic strength on the reaction kinetics of aldosterone and androstendione and their specific antibodies.

This paper analyses the influence of viscosity and ionic strength on the kinetics and equilibrium of the reactions of (125)I labelled androstendione and aldosterone with their specific antibodies used in the radioactive immunoassay determination of such hormones. Bi-exponential and irreversible kinetics is found for androstendione, and single-exponential and reversible ones for aldosterone. The results of the viscosity analysis reflect clear negative influence on direct reaction rate. Ionic strength excerpts some influence but not in a significant way, which suggests that the variation resulting from the effect of the glycerol addition is not due to the influence of the dielectric constant of the solutions used. The apparent product of the electrical charges is 0.228 for aldosterone, and 0.230 and -0.230 for androstendione. Results show diffusive control for both cases.

Synthesis of 11C‐labelled acamprosate for PET studies

AbstractA method for labelling acamprosate (calcium N‐acetyl homotaurinate), an anti‐craving compound for ethanol, with 11C, has been developed for in vivo studies with positron emission tomography (PET). The synthesis was based on the acylation of homotaurinate using [11C]acetyl chloride as the labelling agent. Reversed‐phase HPLC in highly aqueous mobile phase conditions was used for product purification. The radiochemical yield achieved was about 1.14 GBq (31 mCi) with a specific radioactivity of 8.14 GBq/µmol (220 mCi/µmol). For the identification of 11C‐radioactivity and determination of specific radioactivities, HPLC and 1H‐NMR were used. Copyright © 2001 John Wiley &amp; Sons, Ltd.

2-Methoxyethanol metabolism, embryonic distribution, and macromolecular adduct formation in the rat: the effect of radiofrequency radiation-induced hyperthermia

Exposure of pregnant rats to the solvent 2-methoxyethanol (2ME) and radiofrequency (RF) radiation results in greater than additive fetal malformations (Nelson, B.K., Conover, D.L., Brightwell, W.S., Shaw, P.B., Werren, D.W., Edwards, R.M., Lary, J.M., 1991. Marked increase in the teratogenicity of the combined administration of the industrial solvent 2-methoxyethanol and radiofrequency radiation in rats. Teratology 43, 621–34; Nelson, B.K., Conover, D.L., Shaw, P.B., Werren, D.W., Edwards, R.M., Hoberman, A.M., 1994. Interactive developmental toxicity of radiofrequency radiation and 2-methoxyethanol in rats. Teratology 50, 275–93). The current study evaluated the metabolism of 14C-labeled 2ME and the distribution of methoxyacetic acid (MAA) in maternal and embryonic tissues of pregnant Sprague–Dawley rats either exposed to 10 MHz RF radiation or sham conditions. Additionally, adduct formation for both plasma and embryonic protein was tested as a possible biomarker for the observed 2ME/RF teratogenicity. Rats were administered [ethanol-1,2- 14C]-2ME (150 mg/kg, 161 μCi/rat average) by gavage on gestation day 13 immediately before RF radiation sufficient to elevate body temperature to 42°C for 30 min. Concurrent sham- and RF-exposed rats were sacrificed at 3, 6, 24 or 48 h for harvest of maternal blood, urine, embryos and extra-embryonic fluid. Tissues were either digested for determination of radioactivity or deproteinized with TCA and analyzed by HPLC for quantification of 2ME metabolites. Results show the presence of 2ME and seven metabolites, with the major metabolite, MAA, peaking at 6 h in the tissues tested. MAA, the proximal teratogen, was detectable in maternal serum, urine, embryo and extraembryonic fluid 48 h after dosing. Clearance of total body 14C was significantly reduced for the RF-exposed animals ( P<0.05) for the 24–48 h period, but MAA values for serum, embryos and extraembryonic fluid were similar for both sham- and RF-exposed rats. Additionally, no difference was noted for 2ME metabolite profiles in urine or tissue for sham- or RF-exposed rats, thus eliminating an effect of RF radiation on MAA production as a possible explanation for the reported RF-2ME synergism. Subsequently, serum and embryo protein-bound adducts were evaluated by analysis of covalently bound radioactivity. Serum protein binding was significantly higher for sham than RF rats at 3- and 6-h — highest for sham rats at 6 h (519±95 μg as parent 2ME/g of protein) whereas RF serum values were highest at 24 h (266±79 μg/g protein). Embryonic protein binding was significantly higher for sham rats at 6 h, but binding was highest for both groups at 24 h (sham=229±71 μg/g, RF=185±48 μg/g). Formation of protein adducts after 2ME is thought to be related to levels of methoxyacetaldehyde, a reactive intermediate in the formation of MAA. These results suggest that no direct relationship exists for covalent binding in the embryo which would explain RF-2ME synergistic malformations. In comparison with urinary metabolites, the relatively slow elimination of adducted serum 2ME indicates that analysis of protein-bound concentrations could be a potential tool for long- term biomonitoring of worker exposure.

Determination of natural radioactivity in public drinking water quality assessment

The determination of 90Sr and the gross α particleactivity originating from radium isotopes was performed on water samples atvarious stages of treatment taken from water treatment plants before distributionto the consumers.