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- Author or Editor: V. Lungu x
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Abstract
The radiation stability of methionine-35S and selenomethionine75Se was investigated using the methods of thin-layer chromatography, gas chromatography and ESR. Radiation decomposition of methionine-35S mainly consists in an oxidation process and in the release of volatile products. The ESR-spectra of irradiated DL-methionine indicated a strong localization of the unpaired electrons on sulfur atoms. Radiation damage to selenomethionine-75Se as a function of radiation dose proved an increased stability of this compound, and its radiation decomposition consists in the formation of oxidized products and by direct rupture of the selenium bonds accompanied by the formation of volatile compounds like CH3SeH and SeH2. The self-radiolysis of the aqueous solution of selenomethionine-75Se during its storage in air leads, however, to a lower decomposition rate which consists in the release of inorganic selenium and in an oxidation process.
Abstract
This study is focused on the chelating process of two phosphonates with biological activity and therapeutic potential, HEDP (1-hydroxy-ethylidene-diphosphonic acid) and TTHMP (triethylene-tetramine-hexamethylene-phosphonic acid) with therapeutic radiometals 188Re (T 1/2 = 17 hrs, E βmax = 2.12 MeV, E γ= 155 keV) and 177Lu (T 1/2 = 6.7 days, E βmax = 490 keV, E γ = 208 keV). The ligand structure effect on the in vitro stability and on the biological affinity of the therapeutic agents was investigated. The radiochemical purity of the labeled compounds was higher than 95%, showing a good in vitro stability, up to 48 hours. The in vivo biodistribution studies, performed in rats, show a rapid and quantitative accumulation of both labeled compounds in bones and rapid elimination via the urinary tract. The maximum values of the bone uptake were ranged from 75.14% (injected dose/g organ) for 188Re-TTHMP to 94.10% for 177Lu-TTHMP. The structure of the chelates determines the kinetic of bone accumulation processes of labeled phosphonates. Its influence on the biodistribution of the radiolabeled phosphonates reveals that luthetium forms more stable chelate with polyphosphonate in respect to diphosphonate. On the other hand, the less reactive rhenium coupled with HEDP shows a better in vivo behavior than Re-TTHMP.
Abstract
In order to determine the radiochemical impurities in pertechnetate solution as well as that of unbound99mTc in its colloid and complex compounds, in indium chloride solution and related compounds, paper chromatography on Whatman No. 1, thin-layer chromatography on silica gel plates, and paper electrophoresis were applied. A simple method for the determination of radionuclidic purity was developed.
Abstract
The aim of this study was to evaluate the effect of methyl donor biovectors as cocktail formulation in cancer therapy. Based on our previous results regarding the pharmacokinetic of [Methyl-14C] Choline and [Methyl-3H] S-Adenosyl-Methionine (SAM) in presence of Folic Acid and their properties in the regulation of transmethylation metabolism, a cocktail solution of SAM, Choline and Folic Acid was prepared taking into account the previosly established molar ratios. The studies regarding the therapeutic effect of cocktail solution were effectuated on RS1 tumor bearing animal models. For evaluation of tumour cell proliferation we used the [Methyl-3H]-Thymidine with 25 Ci/mmol specific activity. The biodistribution studies were perfomed on untreated and treated tumuor bearing animals. The animal lots dedicated for treatment with methyl donors cocktail were treated with 200 μL cocktail for 4 days. After finishing the treatment, both untreated and treated animal lots were injected with 150 μCi [Methyl-3H]-Thymidine. Biodistribution studies were performed at 2, 4 and 8 hours post injection. The biodistribution results showed that at tumor level the uptake of [Methyl-3H]Thymidine is higher in the untreated animals (0.78%ID/g at 2 h, 1.07%ID/g at 4 h and 1.35%ID/g at 8 h) than in treated animals (0.06%ID/g at 2 h, 0.11%ID/g at 4 h and 0.13%ID/g at 8 h). The results regarding the Homocysteine levels in investigated animals show a decreasing of Homocysteine concentration up to normal values for treated animals.
