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  • Author or Editor: D. 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.

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According to the number of people lost in earthquakes during 20th century as well as in a single (March 4, 1977) earthquake during this century (1574 people, including 1424 in Bucharest), Romania can be ranked the 3rd country in Europe, after Italy and Turkey. Romania is followed by the former Yugoslavia and by the Greece (Bolt 1995, Coburn and Spence 1992). The World Bank loss estimation after the 1977 earthquake (Report No. P-2240-RO, 1978) indicates that from the total loss (2.05 Billion US) more than 2/3 was in Bucharest, where 32 tall buildings collapsed. Half of the total loss was accumulated from buildings damage. The 1977 direct loss and indirect consequences of loss mark probably the starting point of economical decay of Romania during the next decade. They also explain the present concern of civil engineers and Romanian Government for assessment and reduction of seismic risk in Romania. The World Map of Natural Hazards prepared by the Münich Re (1998) indicates for Bucharest: "Large city with Mexico-city effect". The map focuses the dangerous phenomenon of long (1.6 s) predominant period of soil vibration in Bucharest during strong Carpathians Vrancea earthquakes. The Bucharest and Lisbon are the only two European cities falling into Mexico-city category. International experts and organizations agreed that Bucharest is the capital city in Europe characterised by the highest seismic risk. The paper presents:  1. Codes and standards for design of earthquake resistance of structures (1940-2000) and the draft of the new seismic Romanian code P100; 2. The structure of existing building stock in Bucharest;  3. The most vulnerable to earthquake categories of buildings, located on the soft soil condition of Bucharest: -tall reinforced concrete buildings in central Bucharest built prior to 1940 and severely damaged by the past 1977 event;tall reinforced concrete buildings with soft ground-floor built in Bucharest prior to 1977. Hospitals buildings, university buildings and other buildings, classified as having a high risk of severe damage/collapse in case of a strong earthquake; Enlargement of the existing seismic networks of Romania  by two recent projects of INCERC and State Inspectorate for Construction and of NCERR and Japan International Cooperation Agency. In the last 6 months in Romania, the two projects provided about 50 (18 in Bucharest) digital Kinemetrics instruments (K2 and ETNA): in free field condition, in deep boreholes as well as in tall buildings.

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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.

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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.

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