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Biomedical subjects

J Cadet

Publications and source records attributed to J Cadet.

At least 181 records · Page 10Linked to original sources
PubMed1978

Final products obtained from the gamma radiolysis of frozen aqueous solutions of thymidine.

The final radiation products obtained by gamma-irradiation of frozen aqueous solutions of thymidine have been identified as 5,6-dihydro-5,6-dihydroxythy-midine, 5,6-dihydrothymidine, thymidine dimers, 1-(2-deoxy-beta-D-threo-pento-furanosyl)-thymine, 1-(2-deoxy-alpha-L-threo-pentofuranosyl)-thymine, thymine and 5,6-dihydrothymine. The nature of the radiation products could be explained on the basis of the radical structures reported earlier.

Cobalt Radioisotopes↗
PubMed1976

Isomerisation and conformation studies of (+)- and (-)6-hydroxy-5, 6-dihydrouridine.

(1) "Uridine hydrates" i.e. (+)- and (-)6-hydroxy-5, 6-dihydrouridine were formed under gamma irradiation in a deaerated aqueous solution of uridine. (2) The structures of two diastereoisomers were determined by spectroscopic measurements (infrared, ultraviolet and NMR) and verified by stereospecific synthesis; uridine hydrates were prepared by mild reduction of trans(+)- and (-)iodohydrins with acetic acid and zinc power. (3) The carbon 6 epimerisation of uridine hydrates 6R or 6S was performed in triated water (pH 5.5, 30 degrees C) and at the same time tritium incorporation on carbon 5 was noted. The mechanism of these reactions could be explained by the opening of the N1-C6 bond of the pyrimidine ring, followed by ketoenolisation reaction of carbons 4 and 5. (4) The 250 MHz NMR analysis has allowed us to determine the nucleoside conformations. Nucleosides had mainly the S(C2' endo) conformation. A slight preference of gauche-gauche (gg) rotamer of the exocyclic hydroxymethyl group was noted and the aglycone was in the anti conformation.

Isotope Labeling↗
PubMed1976

Gamma radiolysis of thymine in oxygen-free aqueous solution in the presence of electron affinic radiosensitizers: identification of stable products.

Radiosensitizers react with nucleic radicals by addition and by electron transfer reactions. We report the steady-state gamma radiolysis of 1 mM thymine in oxygen-free aqueous solutions containing different classes of radiosensitizing drugs: N-oxyl-free radicals (TAN and TMPN), quinones (menadione and naphtoquinone), nitroheterocyclic compounds (metronidazole and 5-nitro-2-furoic acid) and N-ethylmaleimide. Two classes of thymine degradation products were isolated by thin-layer chromatography and characterized by spectroscopic measurements. The main products, irrespective of radiosensitizers, resulting from oxidation reaction were identified as the cis and trans isomers of 5,6-dihydroxy-5,6-dihydrothymine, N-pyruvyl-N'-formylurea, 6-hydroxy-5,6-dihydrothymine and 5-hydroxy-5,6-dihydrothymine. In the experimental conditions used only N-oxyls and to a lesser extent NEM reacted with 5-hydroxy-5,6-dihydrothymin-6-yl radical, giving stable covalently-bonded addition products with a high yield. TAN showed a higher binding ability with respect to TMPN, which is in good agreement with the rate-constants previously reported for these bimolecular reactions.

Cyclic N-Oxides↗
PubMed1975

[Separation of the four diastereoisomers of 6-hydroxy-5, 6-dihydrothymidine formed by gama-radiolysis of thymidine in deaerateed aqueous solution (author's transl)].

The compounds produced by gamma irradiation of deaerated aqueous solutions of thymidine have been isolated by thin-layer chromatography. The separation of (+) and (-) trans and cis diastereoisomers of thymidine "hydrates" has been carried out. Correlations between conformations given by nuclear magnetic resonance spectra and RF values are discussed.

Chromatography, Thin Layer↗
PubMed1975

Comparison of radiolysis products of thymine and thymidine with e.s.r. results.

Radicals determined by e.s.r. spectrometry of irradiated thymine or thymidine and radiolytic products generated under tha ction of gamma rays in aerated aqueous solutions have been compared. This comparison lies mainly in the fact that a radical R gives rapidly the corresponding peroxide ROOH. The authors have isolated and characterized twenty peroxides, i.e., the four isomers cis (-), cis (+), trans (-), trans(+) of 6-hydroperoxy-5-hydroxy-5,6-dihydrothymidine; the four isomers cis (-), cis (+), trans (-), trans (+) of 5-hydroperoxy-6-hydroxy-5,6-dihydrothymidine; 5-hydroperoxy-2-deoxyuridin;cis and trans 6-hydroperoxy-5-hydroxy-5,6-dihydrothymine; cis and trans 5-hydroperoxy-6-hydroxy-5,6-dihydrothymine; 5-hydroperoxymethyl-uracil; 5-hydroperoxy-5,6-dihydrothymine;cis and trans 6-hydroperoxy-5,6-dihydrothymine; 5-hydroperoxy-5-methyl barbituric acid; 5-hydroperoxy-5-methyl hydantoin; trans 5,6-dihydroperoxy-5,6-dihydrothymine. Most of thethymine and thymidine radicals hypothesized or described in the literature were correlated to these peroxides. However, the presence of certain peroxides could not be explained by recognized radicals. Taking advantage of this fact, the existence of new thymine or thymidine radicals so far unknown can be predicted.

Chromatography, Thin Layer↗
PubMed1975

Synthesis and spectroscopic properties of two classes of 5,6-dihydrothymidine derivatives. Action on the Ehrlich's ascites cells thymidine kinase.

Trans (+) and (-) 6-alkoxy-5-bromo-5,6 dihydrothymidine and trans (+) and (-) 6-alkoyloxy-5-bromo-5,6-dihydrothymidine compounds have been prepared. The synthesis of these substances (alkoxy : methoxy, ethoxy, butyloxy and isoamyloxy and alkoyloxy : acetoxy and bensovloxy) is described. Diastereoisomers of all products have been isolated by thin layer chromatography and their spectroscopic properties (IR, UV, NMR, mass spectrometry) studied. These compounds have been shown to be competitive inhibitors of Ehrlich's ascites cells thymidine kinase with respect ot thymidine.

Animals↗