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At least 73 records · Page 4Linked to original sources
PubMed1992

Probes for narcotic receptor mediated phenomena. 18. Epimeric 6 alpha- and 6 beta-iodo-3,14-dihydroxy-17-(cyclopropylmethyl)-4,5 alpha-epoxymorphinans as potential ligands for opioid receptor single photon emission computed tomography: synthesis, evaluation, and radiochemistry of [125I]-6 beta-iodo-3,14-dihydroxy-17-(cyclopropylmethyl)-4,5 alpha-epoxymorphinan.

The epimeric 6 beta- and 6 alpha-iodo-3,14-dihydroxy-17-(cyclopropylmethyl)-4,5 alpha-epoxymorphinans (1, ioxy) and (2, epioxy), respectively, were each synthesized in five steps starting with naltrexone. The configuration of the 6-iodo group of 1 was unequivocally determined to be beta-based on single crystal X-ray analysis of its precursor 3-acetoxy-6 beta-iodo-14-hydroxy-17-(cyclopropylmethyl)-4,5 alpha-epoxymorphinan (10). Both 1 and 2 as well as their corresponding 3-O-acetates 10 and 11 were found to readily cross the blood-brain barrier and completely reverse the analgesic effects of a 10 mg/kg intraperitoneal dose of morphine sulfate as determined by the paw withdrawal latency test. Compounds 1 and 2 were found to bind with high affinity to mu, delta, and kappa receptors in vitro. In general, 1 and 2 exhibited higher affinity for mu and kappa receptors than naltrexone while the 6 beta-iodo epimer 1 (ioxy) was more potent than its epimer 2. In a comparison of the 6 beta-halogen substituent on binding affinity across opioid receptor subtypes, it was generally found that I greater than Br greater than F. On the basis of the results of in vitro and in vivo testing, 1 was selected as a target for radioiodination and evaluation as a potential single photon emission computed tomography imaging agent for opioid receptors. Carrier-free [125I]-1 was synthesized in near quantitative yield by the sequence of reaction of excess 3-acetoxy-6 alpha-[[(trifluoromethyl)sulfonyl]oxy]-14-hydroxy-17- (cyclopropylmethyl)-4,5 alpha-epoxymorphinan (8) with anhydrous Na125I in dry acetonitrile for 90 min at 76 degrees C followed by deacetylation of the product with 1:1 aqueous ammonia/acetonitrile at 25 degrees C. The potential of [125I]-1 as an in vivo imaging agent for opioid receptors is evaluated and discussed.

Animals↗
PubMed2004

Comparative in vivo behavior studies of cyclen-based copper-64 complexes: regioselective synthesis, X-ray structure, radiochemistry, log P, and biodistribution.

The in vivo behavior of copper(II)-cyclen complexes was modified via substitution of the parent ligand with two different substituents, 4-tert-butylbenzyl and acetate. This was achieved by using same synthetic strategy (regioselective protection/first alkylation/deprotection/second alkylation) to give nine cyclen derivatives. The X-ray structure of [Cu(2c)Cl]+ (2c = 1-(4-tert-butylbenzyl)-1,4,7,10-tetraazacyclododecane) showed that the chlorine ion from the reaction mixture occupied the remaining apical position of a square pyramidal coordination environment of these Cu-cyclen complexes. Eight out of nine compounds were labeled with 64Cu in high radiochemical purity. log P measurements showed that the lipophilicities of the copper complexes were increased dramatically by attaching hydrophobic substituents on the nitrogen atoms of cyclen. Conversely, as the number of acetate groups increased, the lipophilicity was decreased. The biodistribution of Cu-cyclen complexes was found to be influenced mostly by the overall charge of the complexes rather than their lipophilicity. Positively charged (+2) complexes showed high blood retention at early time points with sluggish clearance from liver by 24 h. The attachment of even one acetate group onto cyclen accelerated blood and liver clearance dramatically compared to +2 charged Cu(II) complexes. Neutral trans-substituted Cu-4 showed the best clearance and lowest retention of doses from all organs most time, followed by -1 charged complex Cu-2. Trans-substituted complexes structure isomers Cu-3 and Cu-4 showed better clearance and lower retention from all organs than their cis-counterparts Cu-5 and Cu-6.

Animals↗
PubMedDate not supplied

[Radiochemistry of polysaccharides (review)].

Data on the radiolysis of polysaccharides (in the form of aqueous solutions in liquid or frozen states, and native "dry" preparations) is surveyed to explore the possibility of participation of free radicals in formation of ruptures in macromolecules, low-molecular products of polysaccharides decomposition, carbonyl, carboxyl, and peroxide groups in the macromolecules. The reaction schemes for principal transformation pathways of polysaccharides free radicals account for ultimate molecular products of the radiolysis. Effects of the adsorbed structured water on formation and conversions of free radicals, of postradiation polymer decomposition, and radiation protection of polysaccharides are discussed.

Free Radicals↗
PubMed2003

Development of Dose-Based Release Limits for Unrestricted Release of a Radiochemistry Laboratory.

Current regulations for unrestricted release are based on annual dose equivalent. Unless one desires to use very conservative "screening levels," dose modeling must be accomplished to derive an areal or volumetric limit or concentration value for release purposes. Such derived limits are referred to as "Derived Concentration Guideline Levels" (DCGL). This paper describes the process employed to derive DCGLs for building surfaces contaminated with uranium and its decay progeny based on annual dose equivalent and the innovative means employed during the derivation.

Journal Article↗
PubMed2005

[Preparation of 125I-oligonucleotide-long-circulation liposomes].

OBJECTIVE: To investigate the preparation and the encapsulation efficiency of 125I-oligonucleotide(ON)-long-circulation liposomes (LCL). METHODS: (1) Oligonucleotide was labeled with 125I using thallium chloride tetrahydrate (TICl3) as an oxidizing agent. 125I-oligonucleotide was separated from free 125I by Sephadex G25 column chromatography. The following radiolabeling efficiency, radiochemistry purity and specific radioactivity were obtained respectively. Subsequently, the stability of 125I-ON was observed. (2) 125I-ON-LCL were prepared by means of reverse-phase evaporation. The quality of 125I-ON-LCL was evaluated after the crude LCL were repeatedly extruded through 400 nm, 200 nm, 100 nm polycarbonate membranes consecutively. Results (1) The radiolabeling efficiency, radiochemistry purity and specific radioactivity of 125I-antisense oigonucleotide (ASON) were (72.80 +/- 0.68)%, (98. 33 +/- 0.39)% and (0.63 +/- 0.11) MBq/microg; of 125I-sense oigonucleotide (SON) were (72.21 +/- 0.60)%, (98.28 +/- 0.36)%, (0.63 +/- 0.14) MBq/microg; and of 125I-nonsense oligonucleotide (NON) were (72.77 +/- 0.81)%, (98.42 +/- 0.40)%, (0.62 +/- 0.11) MBq/microg, respectively. (2) The radiochemistry purity of 125I-ON, in 0.01 mol/L HEPES buffer and human serum at 1 h, 2 h and 4 h were all above 93%, 80%, respectively. (3) LCL formulations were 115 nm in mean diameter with a PDI (polydispersibility index) of 0.103 and Zeta potential of -29.23. The encapsulation efficiencies of 125I-ASON, 125I-SON and 125I-NON were (66.21 +/- 0.21)%, (70.93 +/- 0.03)% and (67.67 +/- 0.10)% respectively. CONCLUSION: LCL were prepared in high loading efficiency for 125I-ON with small particle sizes and symmetric distributions.

Antineoplastic Agents↗
PubMedDate not supplied

The radiochemist's role in the quality evaluation and assessment of radiological data in environmental decision making.

The quality evaluation and assessment of radiological data is the final step in the overall environmental data decisionprocess. This quality evaluation and assessment process is performed outside of the laboratory, and generally the radiochemist is not involved. However, with the laboratory quality management systems in place today, the data packages of radiochemical analyses are frequently much more complex than the project/program manager can effectively handle and additionally, with little involvement from radiochemists in this process, the potential for misinterpretation of radiological data is increasing. The quality evaluation and assessment of radiochemistry data consists of making three decisions for each sample and result, remembering that the laboratory reports all the data for each analyses as well as the uncertainty in each of these analyses. Therefore, at the data evaluation and assessment stage, the decisions are: (1) is the radionuclide of concern detected (each data point always has a number associated with it?); (2) is the uncertainty associated with the result greater than would normally be expected; and (3) if the laboratory rejected the analyses is there serious consequences to other samples in the same group? The need for the radiochemist's expertise for this process is clear. Quality evaluation and assessment requires the input of the radiochemist particularly in radiochemistry because of the lack of redundancy in the analytical data. This paper describes the role of the radiochemist in the quality assessment of radiochemical data for environmental decision making.

Data Collection↗
PubMed2007

Carbon-11 labeling chemistry based upon [11C]methyl iodide.

Radiochemistry with the short-lived positron emitter 11C (half-life 20.38 min) represents special challenges in terms of synthesis time and labeling techniques. The recent developments in 11C radiochemistry have steadily expanded the number of 11C labeled compounds. This chapter addresses selected chemical and technical aspects of 11C chemistry based on the readily available labeling precursors [11 C]methyl iodide and, to a lesser extent, [11C]methyl triflate. Special emphasis is placed on heteroatom methylation reactions and 11C-C bond formations.

Alkylation↗
PubMed1995

Technetium-99, iodine-129 and tritium in the waters of the Savannah River Site.

Surface water samples were collected from streams on and around the Savannah River Site (SRS) to assess current 3H, 99Tc, and 129I concentrations in the water. The SRS is a nuclear facility operated by Westinghouse Savannah River Company for the US Department of Energy. Water quality parameters were measured at the time of collection using field portable instrumentation. The tritium activity was determined by liquid scintillation spectrometry. The isotopes, 99Tc and 129I, were determined by isotope dilution/inductively coupled plasma-mass spectrometry (D.M. Beals, Determination of technetium-99 in aqueous samples by isotope dilution inductively coupled plasma-mass spectrometry. Presented at the 3rd International Conference on Nuclear and Radiochemistry, Vienna, September 1992, unpublished data; D.M. Beals, P. Chastagner and P.K. Turner, Analysis of iodine-129 in aqueous samples by inductively coupled plasma-mass spectrometry. Presented at the 38th Annual Conference on Bioassay, Analytical and Environmental Radiochemistry, Santa Fe, NM, November 1992). Elevated activities of 3H, 99Tc, and 129I were found in some surface streams of the SRS, principally due to migration of ground water from beneath old seepage basins, however the levels in the waters leaving the SRS are well below any regulatory guidelines.

Fresh Water↗
PubMed2005

Microfluidic reactor for the radiosynthesis of PET radiotracers.

Here we show the first application of a microfabricated reaction system to PET radiochemistry, we term "microfluidic PET". The short half-life of the positron emitting isotopes and the trace chemical quantities used in radiolabelling make PET radiochemistry amenable to miniaturisation. Microfluidic technologies are capable of controlling and transferring tiny quantities of liquids which allow chemical and biochemical assays to be integrated and carried out on a small scale. Such technologies provide distinct advantages over current methods of PET radiochemical synthesis. To demonstrate "proof of principle" we have investigated the radiohalogenation of small and large molecular weight molecules using the microfluidic device. These reactions involved the direct radioiodination of the apoptosis marker Annexin V using iodine-124, the indirect radioiodination of the anti-cancer drug doxorubicin from a tin-butyl precursor and the radiosynthesis of 2-[(18)F]FDG from a mannose triflate precursor and fluorine-18 and hence provide a test bed for microfluidic reactions. We demonstrate the rapid radioiodination of the protein Annexin V (40% radiochemical yield within 1 min) and the rapid radiofluorination of 2-[(18)F]FDG (60% radiochemical yield within 4s) using a polymer microreactor chip. Chromatographic analysis showed that the labelling efficiency of the unoptimised microfluidic chip is comparable to conventional PET radiolabelling reactions.

Bioreactors↗
PubMed2000

Development of a beta-spectrometer using PIPS technology

Various anthropogenic sources contribute to the inventory of long live beta-emitters in the environment. Studies have been carried out to obtain the 90Sr distribution in environment in order to estimate its impact in terms of radiation exposure to humans. The Laboratory routinely measures 90Sr by proportional counter after radiochemistry. An incomplete radiochemical separation leads to a deposit submitted to count polluted by natural beta-emitters. In order to confirm the result, 90Y (daughter of 90Sr), is extracted from the final radiochemical fraction and counted. The 90Y decreasing (T(1/2) = 2.67 days) is checked by successive counts over 64 h. The delay between the end of radiochemistry and the counting is imposed by 15 days to allow radioactive equilibrium between 90Sr and 90Y to be established. In order to remove this delay the purity of the 90Sr fraction source can be verified by beta-spectrometry. Thus, a beta-spectrometer is under development in collaboration with Canberra Semi-Conductor and Canberra Electronic. It consists in a PIPS detector where several silicon layers are combined. Initial results will be presented in this paper.

Journal Article↗
PubMed2002

Radiopharmaceutical chemistry for positron emission tomography.

Radiopharmaceutical chemistry includes the selection, preparation, and preclinical evaluation of radiolabeled compounds. This paper describes selection criteria for candidates for positron emission tomography (PET) investigations. Practical aspects of nucleophilic and electrophilic (18)F-fluorinations and (11)C-methylations are described. These aspects include production of fluorine-18 and carbon-11, workup of fluorine-18, (18)F radiochemistry, production of [(11)C]methyl iodide and triflate, and (11)C-methylation radiochemistry.

Carbon Radioisotopes↗