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At least 739 records · Page 41Linked to original sources
PubMed1991

Usefulness of a small scale indirect 125I-labelled protein A binding assay for detection of monoclonal antibodies against hematopoietic cell surface antigens.

We describe a small-scale solid-phase indirect 125iodine protein A binding assay (IPA) and discuss its usefulness for detection of hematopoietic cell surface antigens and for screening hybridoma clones producing monoclonal antibodies (McAbs) against K562 cell surface antigens correlated with differentiation induced by 12-O-tetradecanoyl phorbol-13-acetate (TPA). This assay was performed in polystyrene Terasaki microtest plates instead of 96-well microtiter plates, using hematopoietic cells attached to the wells by air drying. This method facilitates washing procedures and reduces the radioactive waste. The specificity of this IPA method is as high as those of RIAs and ELISAs generally used. Titration curves of a McAb, My7, specific for CD13 on HL60 and TPA-treated HL60 (HL60-TPA) cells, were linear between the 10(-1) and 10(-4) dilutions. A difference in the CD13 expression between HL60 and HL60-TPA cells could be detected by both IPA and flow cytometry using My7 at 10(-1)-10(-3) dilutions. At the 10(-3) dilution, however, CD13 expressed on HL60 cells was detected by the IPA method but not by flow cytometry. These results show that the sensitivity of IPA is superior to that of flow cytometry. By screening hybridoma clones with this IPA method, we succeeded in producing three interesting and useful McAbs (21H73, 37G7 and 49C12) against K562 cell surface antigens whose expression was altered after the differentiation induced by TPA. We also demonstrated that the IPA method is suitable for cell surface marker analysis of leukemia cells freshly isolated from patients.

Animals↗
PubMed1987

Mutagenicity of chlorinated polycyclic aromatic compounds.

The catalytic chlorination of polycyclic aromatic hydrocarbons leads to the formation of complex mixtures of isomers analogous to those found in fly ash samples of an incineration plant for radioactive waste. Therefore chlorination mixtures of chrysene, pyrene, and fluoranthene were analyzed and characterized by gas chromatography-mass spectrometry. Determination of the exact position of each chlorosubstituent within the molecule was not possible either by mass spectrometry or by comparison with well-defined methyl analogs. The toxic as well as mutagenic effects of such mixtures of isomers was compared with those of their parent hydrocarbons in the microtiter fluctuation test using Salmonella typhimurium TA 98 and TA 100 in a concentration range of 0.5 to 5.0 microgram/ml. No toxic effect could be observed, but the chlorinated products in contrast to their parent compounds were found to be strong mutagens to the S. typhimurium test strains and showed a positive response even without enzymatic activation. Frameshift mutations as well as base pair alterations were detected.

Animals↗
PubMed1989

Paraffin scintillator for radioassay of solid support samples.

A new paraffin scintillator used for solid support sample counting has been proposed, and its composition and various characteristics are described. The solid support sample treated with this scintillator can be easily handled because of rigid sample conditions. This technique provides great advantages such as the elimination of a large volume of scintillator and little radioactive waste material by using an economical polyethylene bag instead of the conventional counting vial.

Chromatography↗
PubMed2004

Lanthanide-based time-resolved fluorescence of in cyto ligand-receptor interactions.

A lanthanide-based assay for ligand-receptor interactions provides an attractive alternative to the traditional radiolabeled determinations in terms of sensitivity, throughput, and biohazards. We designed and tested peptide ligands modified with an Eu-DTPA chelate. These labeled ligands were used in competitive binding assays with results comparable to those obtained using the traditional radiolabeled binding assays. The sensitivity of time-resolved fluorescence is sufficient to detect attomoles of europium, allowing assays in 96-well plates, compared with 30-mm dishes for (125)I binding assays to whole cells. We verified binding of Eu-DTPA-NDP-alpha-MSH to cells overexpressing the human melanocortin-4 receptor. The Eu-labeled ligand bound to these cells with an affinity similar to that of unlabeled NDP-alpha-MSH and was used to optimize a competitive binding assay. The lanthanide-based assays provided superior results with higher throughput and eliminated the need for radioactive waste disposal. This assay is appropriate for high-throughput screening of ligand libraries.

Binding, Competitive↗
PubMed2005

Development of a lanthanide-based assay for detection of receptor-ligand interactions at the delta-opioid receptor.

A lanthanide-based assay for ligand-receptor interactions provides an attractive alternative to the traditional radiolabeled determinations in terms of sensitivity, throughput, and biohazards. We designed and tested five peptide ligands for the delta-opioid receptor that were modified with a europium (Eu)-containing chelate. These labeled ligands were tested for their binding affinities and compared with the unlabeled parental ligands. The Eu-diethylenetriaminepentaacetic acid (DTPA)-[D-Pen(2),l-Cys(5)] enkephalin (DPLCE) ligand bound to Chinese hamster ovary (CHO) cells overexpressing the human delta-opioid receptor with affinity similar to the unlabeled ligand. This ligand was used in competitive binding assays with results comparable to those obtained using the traditional radiolabeled binding assays. These lanthanide-based assays provide superior results with higher throughput and eliminate the need for radioactive waste disposal; hence, they are appropriate for high-throughput screening of ligand libraries.

Animals↗
PubMed2004

Non-destructive 10B analysis in neutron transmission experiments.

Boron alloyed stainless-steel sheets are predominantly used in nuclear engineering as neutron shielding for radioactive waste disposal equipment. The neutron absorption depends strongly on the amount and the distribution of the 10B isotope. A systematic transmission study of 10B enriched steel plates by means of neutron time-of-flight and neutron radiography experiments was performed. The 10B content was analyzed with accuracy up to 5 x 10(-3) wt% using monochromatic beams and a linear increase of the macroscopic cross section with the 10B content was found even for strong absorbers. Then we extended the transmission analysis to "white" thermal neutron beams where large deviations from the exponential transmission law are observed. The influence of the spectral width is discussed in more detail because beam hardening causes an elevation of the effective transmission through strong absorbing materials, an effect which is crucial for the design of neutron shielding.

Journal Article↗
PubMed2005

Effect of pH, ionic strength and fulvic acid on the sorption and desorption of cobalt to bentonite.

Humic substances and bentonite have attracted great interest in radioactive waste management. Here the sorption of cobalt on bentonite in the presence and absence of fulvic acid (FA) under ambient conditions was studied. The effects of pH, ionic strength, FA and solution concentrations on cobalt sorption to bentonite were also investigated using batch techniques. The results indicate that the sorption of cobalt is strongly dependent on pH and is independent of ionic strength under our experimental conditions. Surface complexation is considered the main mechanism of cobalt sorption to bentonite. In the presence of FA, little effect of FA on cobalt sorption was found at pH<6; a positive effect of FA on cobalt sorption was found for pH 6-8; and a negative effect of FA on cobalt sorption was found at pH>8. The addition sequences of FA/Co(2+) to the bentonite suspension on the sorption of cobalt to FA-coated bentonite were also studied. The results indicated that the sorption is not influenced by the addition sequences. Some possible mechanisms are discussed.

Journal Article↗
PubMed2005

Radioactive byproducts in [18O]H2O used to produce 18F for [18F]FDG synthesis.

Potential radioactive byproducts in [(18)O]H(2)O irradiated with 9.6 MeV protons to produce (18)F were analyzed theoretically and experimentally. Twenty two nuclear reaction cross sections included in the National Nuclear Data Center's (NNDC) data base were selected from the possible nuclear reactions between 9.6 MeV protons and a silver havar target. Ten radionuclides: (52)Mn, (55)Fe, (55)Co, (56)Co, (57)Co, (58)Co, (59)Ni, (95)Tc, (96)Tc and (109)Cd were detected experimentally in [(18)O]H(2)O by using high purity germanium semiconductor detectors. The activities of the 10 radionuclides were distributed between 4B q and 1.2k Bq. These activities were less than the reference values given in the International Basic Safety Standards. The radionuclides derived from nuclear reactions between a silver target body and 9.6 MeV protons at a beam current 25 microA for 60 min irradiation would be exempt from restrictions for radioactive waste. The purified [(18)F]FDG prepared from (18)F produced by irradiating a silver havlar target with 9.6 MeV protons was not contaminated by the radionuclides.

Drug Contamination↗
PubMed2006

Detection of spallation neutrons and protons using the (nat)Cd activation technique in transmutation experiments at Dubna.

Various spallation sources have been used to transmute long-lived radioactive waste, mostly making use of the wide energy neutron fluence. In addition to neutrons, a large number of protons and gamma rays are also emitted from these sources. In this paper (nat)Cd is proved to be a useful activation detector for determining both thermal-epithermal neutron as well as secondary proton fluences. The fluences measured with (nat)Cd compared with other experimental data and calculations of DCM-DEM code were found to be in reasonable agreement. An accumulation of thermal-epithermal neutrons around the center of the target (i.e. after approx. 10 cm) and of secondary protons towards the end of the target is observed.

Journal Article↗
PubMed2006

Preparation and activity measurement of electrodeposited alpha-emitting sources.

Alpha-emitting 238Pu and 241Am sources on stainless steel substrates have been prepared using a new electrodeposition method based on an ammonium oxalate-ammonium sulfate electrolyte containing diethyl triamino pentaacetic acid. The deposition yield is determined by measuring the activity of the sources using a high-efficiency 2pi alpha proportional counter and a backscattering chamber designed and fabricated for this purpose. Optimal electrodeposition parameters have been determined for 241Am, enabling manufacture of standard alpha-emitting sources with minimal radioactive waste.

Alpha Particles↗
PubMed2006

A theoretical model for the production of Ac-225 for cancer therapy by photon-induced transmutation of Ra-226.

Radium needles that were once implanted into tumours as a cancer treatment are now obsolete and constitute a radioactive waste problem, as their half-life is 1600 years. We are investigating the reduction of radium by transmutation on a small scale by bombarding Ra-226 with high-energy photons from a medical linear accelerator (linac) to produce Ra-225, which subsequently decays to Ac-225, which can be used as a generator to produce Bi-213 for use in 'targeted alpha therapy' for cancer. This paper examines the possibility of producing Ac-225 with a linac using an accurate theoretical model in which the bremsstrahlung photon spectrum at 18 MV linac electron energy is convoluted with the corresponding photonuclear cross sections of Ra-226. The total integrated yield can then be obtained and is compared with a computer simulation. This study shows that at 18 MV, the photonuclear reaction on Ra-226 can produce low activities of Ac-225 with a linac. However, a high power linac with high current, pulse length and frequency is needed to produce practical amounts of Ac-225 and a useful reduction of Ra-226.

Actinium↗
PubMed2006

The uncertainties associated with the application of batch technique for distribution coefficients determination--a case study of cesium adsorption on four different bentonites.

The uncertainties associated with the batch method used often as adsorption data source for performance assessments of radioactive waste repositories have been analyzed and evaluated. The adsorption of cesium on four different bentonites (two Na- and two Ca-bentonites) using a radiotracer ((137)Cs) technique has been studied to evaluate experimental uncertainties and compare their effects on calculated distribution coefficients (K(d)s). Three main factors influencing uncertainty of K(d) at given conditions were identified-the radiotracer operation (mainly tracer addition to experimental systems), the phase separations efficiency and the mineralogical heterogeneity of samples. It was found that the determination of quantitative contributions of the last two factors to the uncertainty of K(d) is difficult, depending on input material and conditions. The centrifugation and ultrafiltration method has been tested for removing colloids in sample solutions, but the results obtained were disputable. The mineral heterogeneity (complex mineral composition) effect has been identified mainly in kinetics of cesium adsorption where three different trends were described. This has important influence on the time-scale of the experiment's planning and equilibrium time estimation or identification. It has been concluded that experimental procedure may represent important uncertainty source of calculated K(d). In performance assessment studies, this uncertainty of K(d) given by the appropriate experimental procedure should be taken into account and properly evaluated.

Journal Article↗
PubMed2006

The risks of risk-based regulation: insights from the environmental policy domain.

Risk-based regulation has become increasingly popular in recent years. Proponents argue that it facilitates robust governance, contributing to efficient and effective use of regulatory resources and delivering interventions in proportion to risk. Critics contend that the challenges of operationalising risk-based governance mitigate its potential benefits. In this paper we start by considering what we mean by risk-based governance and discuss some of the factors shaping the adoption of such strategies. We then consider the development and operation of risk-based approaches in the environmental policy domain, focusing specifically on the regulation of contaminated land and radioactive waste. We argue that whilst risk-based approaches can offer important benefits, they face a range of epistemic, institutional and normative challenges that can play an important role in shaping the way that organisations manage both risks to society and their own institutional risks. This has profound implications for achieving regulatory objectives and, for this paper, the environmental outcomes that the regulations are designed to deliver.

Environment↗
PubMed2006

Control of pertechnetate sorption on activated carbon by surface functional groups.

The isotope 99Tc is highly soluble and poorly adsorbed by natural materials under oxidizing conditions, thus being of particular concern for radioactive waste disposal. Activated carbon can potentially be used as an adsorbent for removing Tc from aqueous solutions. We have tested six commercial activated carbon materials for their capabilities for sorption of pertechnetate (TcO4-). The tested materials can be grouped into two distinct types: Type I materials have high sorption capabilities with the distribution coefficients (Kd) varying from 9.5 x 10(5) to 3.2 x 10(3) ml/g as the pH changes from 4.5 to 9.5, whereas type II materials have relatively low sorption capabilities with Kd remaining more or less constant (1.1 x 10(3)-1.8 x 10(3) ml/g) over a similar pH range. The difference in sorption behavior between the two types of materials is attributed to the distribution of surface functional groups. The predominant surface groups are identified as carboxylic and phenolic groups. The carboxylic group can be further divided into three subgroups, A, B, and C, in the order of increasing acidity. The high sorption capabilities of type I materials are found to be caused by the presence of a large fraction of carboxylic subgroups A and B, while the low sorption capabilities of type II materials are due to the exclusive presence of phenolic and carboxylic subgroup C. Therefore, the performance of activated carbon for removing TcO4- can be improved by enhancing the formation of carboxylic subgroups A and B during materials processing.

Journal Article↗
PubMed2006

A temperature-profile method for estimating flow in geologic heat pipes.

Above-boiling temperature conditions, as encountered, for example, in geothermal reservoirs and in geologic repositories for the storage of heat-producing radioactive wastes, may induce strong liquid and gas flow processes in porous subsurface environments. The magnitude of these flow processes is extremely hard to measure in the field. We therefore propose a simple temperature-profile method that uses high-resolution temperature data for deriving such information. The energy that is transmitted with the vapor and water flow creates a nearly isothermal zone maintained at about the boiling temperature, referred to as a heat pipe. Characteristic features of measured temperature profiles, such as the differences in the gradients inside and outside of the heat-pipe regions, are used to derive the approximate magnitude of the liquid and gas fluxes in the subsurface.

Air Movements↗
PubMed2006

A simple and rapid radiochemical choline acetyltransferase (ChAT) assay screening test.

A simple radiochemical choline acetyltransferase (ChAT) assay screening test was developed by measuring for [(3)H]acetylcholine ([(3)H]ACh) formed from 0.2 mM [(3)H]acetyl-coenzyme A ([(3)H]acetyl-CoA) and 1 mM choline by 0.2 mg of rat brain homogenates containing ChAT into 96-well microplates. A simple and rapid procedure for isolating [(3)H]ACh from the incubation mixture into 96-well microplates was achieved by using a sodium tetraphenylboron (Kalibor) solution (in ethyl acetate, 0.75%, w/v) and a hydrophobic liquid scintillator mixture (1:5, v/v, 0.2 mL) as an extraction solvent. The benefits of this radiochemical method using 96-well microplates are as follows: (1) this method is reliable and reproducible; (2) many samples can be examined at the same time by this method; (3) this method is economical and effective in reducing radioactive waste. The development of a new simple radiochemical ChAT assay screening test is the first stage of development of radiolabeled ChAT mapping agent.

Acetylcholine↗
PubMed2006

Cement/clay interactions-- a review: experiments, natural analogues, and modeling.

The concept of storing radioactive waste in geological formations calls for large quantities of concrete that will be in contact with the clay material of the engineered barriers as well as with the geological formation. France, Switzerland and Belgium are studying the option of clayey geological formations. The clay and cement media have very contrasted chemistries that will interact and lead to a degradation of both types of material. The purpose of this review is to establish an exhaustive list of laboratory experiments so as to identify the reaction sequences in the evolution of both the clay minerals and accessory minerals during their alteration in an alkaline environment. We review the data on clay dissolution kinetics in this environment, and include an invaluable study of natural analogues that allow one to correlate the phenomena in time. The available data and experiments make it possible to construct predictive numerical models. However, as the quality of the data is inhomogeneous, we recommend a continuation of the thermodynamic and kinetic data acquisition. It is obvious that the numerical modeling of the alkaline disturbance will be more relevant if it can combine the advantages of the different detailed models: mineralogical completeness, combined modeling of the clay and cement media, evolution of the porosity, consideration of the pCO2 and all the surface reactions.

Aluminum Silicates↗