Search results for "Radioisotope"
showing 10 items of 300 documents
A laboratory study of the mineralization and binding of 14C-labeled herbicide rimsulfuron in a rendzina soil
1999
Abstract The fate of pyrimidine-2- 14 C-rimsulfuron in a rendzina soil was investigated using a laboratory microcosm approach. Measurement of CO 2 evolution suggested that rimsulfuron applied at 5 times the recommended dose did not affect soil respiration. Under abiotic conditions, no mineralization of 14 C-rimsulfuron into 14 C-CO 2 occured and under biotic ones it was very low reaching 0.75 % of the applied 14 C-rimsulfuron after 246 days of incubation. The analysis of data showed that a three-half order model provided the best fit for the mineralization curve. Extractable 14 C-residues decreased over time to 70 – 80% of the applied 14 C-rimsulfuron at the end of the incubation. After 246…
Cysteine-Specific Radioiodination of Proteins with Fluorescein Maleimide
1997
A protocol is described for coupling of carrier-free iodine to protein sulfhydryl groups via fluorescein maleimide. 125I is first coupled to fluorescein maleimide in the presence of chloramine T. Iodination is stopped with sodium thiosulfate, and the iodine-substituted fluorescein maleimide is reacted with free cysteines of the protein. Excess label is then removed by gel-permeation chromatography. The procedure avoids exposition of the protein to oxidative conditions and does not require purification of the labeled carrier reagent. Suitability of the method for a given protein can be evaluated spectrophotometrically without employing radioactivity. It can be applied under denaturing condit…
An ethoxylated surfactant enhances the penetration of the sulfated laminarin through leaf cuticle and stomata, leading to increased induced resistanc…
2016
International audience; Some β-1,3-glucans and particularly sulfated laminarin (PS3) are known as resistance inducers (RIs) in grapevine against the downy mildew. However, their efficacy in vineyard is still often too low, which might be caused by a limited penetration through the leaf cuticle following spray application. We used (14) C-sucrose uptake experiments with grapevine leaves in order to select a surfactant as saccharide penetration enhancer. Our results showed that though sucrose foliar uptake was low, it was strongly enhanced by Dehscofix CO125 (DE), a highly ethoxylated surfactant. Fluorescent saccharides were then produced and laser scanning microscopy was used to analyze their…
Evidence of chloroethylene oxide being the reactive metabolite of vinyl chloride towards DNA: comparative studies with 2,2′ -dichloro-diethylether
1983
The roles of chloroethylene oxide (CEO) and chloroacetaldehyde (CAA) in carcinogenicity of vinyl chloride (VC) have been studied by comparing biological effects of VC exposure with those of 2,2'-dichlorodiethylether (bis(chloroethyl)ether, BCEE) as a metabolic precursor of CAA. Biological end-points investigated were covalent protein binding, nucleic acid (RNA and DNA) alkylation and the potency of the two chemicals to induce preneoplastic ATPase-deficient foci in rat liver. After exposure of rats to [1-14C]BCEE, BCEE derived radioactivity was bound to liver proteins. Analysis of hydrolysates of liver RNA and DNA gave no indication for the formation of either 7-N-(2-oxoethyl)guanine, 1,N6-e…
Evaluation of P-glycoprotein (abcb1a/b) modulation of [18F]fallypride in MicroPET imaging studies
2012
[(18)F]Fallypride ([(18)F]FP) is an important and routinely used D2/D3 antagonist for quantitative imaging of dopaminergic neurotransmission in vivo. Recently it was shown that the brain uptake of the structurally related [(11)C]raclopride is modulated by P-glycoprotein (P-gp), an important efflux transporter at the blood-brain barrier. The purpose of this study was to determine whether the brain uptake of [(18)F]FP is influenced by P-gp. For examination of this possible modulation microPET studies were performed in a rat and a mouse model. Hence, [(18)F]FP was applied to Sprague Dawley rats, half of them being treated with the P-gp inhibitor cyclosporine A (CsA). In a second experimental s…
18F-labeling of peptides by means of an organosilicon-based fluoride acceptor.
2006
Fluorine-18 is among the most commonly used radionuclides for positron emission tomography (PET). This non-invasive imaging technique is capable of providing in vivo information about the distribution of radiolabeled biomolecules by 1808 coincidence detection of two simultaneously emitted photons from positron–electron annihilation. Although a number of different radiotracers have been successfully employed in PET, only a few, such as 2-[F]fluoro-2-deoxy-d-glucose (FDG) and [F]fluorodopa, have gained widespread application in nuclear medicine. The reason for this is that the regioselective introduction of F into tracer molecules is often non-specific and radiochemical yields (RCY) of the Fl…
Synthesis and preliminary evaluation of (R,R)(S,S) 5-(2-(2-[4-(2-[18F]fluoroethoxy)phenyl]-1-methylethylamino)-1-hydroxyethyl)-benzene-1,3-diol ([18F…
2003
The 18 F-labeled b2-adrenergic receptor ligand (R,R)(S,S) 5-(2-(2-(4-(2-( 18 F)fluoroethoxy)phenyl)-1-methylethylamino)-1- hydroxyethyl)-benzene-1,3-diol, a derivative of the original highly selective racemic fenoterol, was synthesized in an overall radio- chemical yield of 20% after 65 min with a radiochemical purity higher than 98%. The specific activity was in the range of 50-60 GBq/mmol. In vitro testing of the non-radioactive fluorinated fenoterol derivative with isolated guinea pig trachea was conducted to obtain an IC50 value of 60 nM. Preliminary ex vivo organ distribution and in vivo experiments with positron emission tomography (PET) on guinea pigs were performed to study the biod…
Synthesis and evaluation of (S)-2-(2-[18F]fluoroethoxy)-4-([3-methyl-1-(2-piperidin-1-yl-phenyl)-butyl-carbamoyl]-methyl)-benzoic acid ([18F]repaglin…
2004
18F-labeled non-sulfonylurea hypoglycemic agent (S)-2-(2-[(18)F]fluoroethoxy)-4-((3-methyl-1-(2-piperidin-1-yl-phenyl)-butylcarbamoyl)-methyl)-benzoic acid ([(18)F]repaglinide), a derivative of the sulfonylurea-receptor (SUR) ligand repaglinide, was synthesized as a potential tracer for the non-invasive investigation of the sulfonylurea 1 receptor status of pancreatic beta-cells by positron emission tomography (PET) in the context of type 1 and type 2 diabetes. [(18)F]Repaglinide could be obtained in an overall radiochemical yield (RCY) of 20% after 135 min with a radiochemical purity higher than 98% applying the secondary labeling precursor 2-[(18)F]fluoroethyltosylate. Specific activity w…
Improved automated synthesis of [18F]fluoroethylcholine as a radiotracer for cancer imaging.
2007
[(18)F]Fluoroethylcholine has been recently introduced as a promising (18)F-labelled analogue of [(11)C]choline which had been previously described as a tracer for metabolic cancer imaging with positron emission tomography (PET). Due to the practical advantages of using the longer-lived radioisotope (18)F (t(1/2)=110 min), offering the opportunity of a more widespread clinical application, we established a reliable, fully automated synthesis for its production using a modified, commercially available module. [(18)F]Fluoroethylcholine was prepared from N,N-dimethylaminoethanol by iodide catalyzed alkylation with 1-[(18)F]fluoro-2-tosylethane as alkylating agent, resulting in a total radioche…