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J Cadet

Publications and source records attributed to J Cadet.

204 records · Page 12Linked to original sources
PubMedDate not supplied

Measurement of oxidative damage at pyrimidine bases in gamma-irradiated DNA.

Oxidized nucleobases represent one of the main classes of damage induced in DNA by ionizing radiation. Emphasis was placed in this work on the measurement of four oxidized pyrimidine bases, including 5-(hydroxymethyl)uracil (5-HMUra), 5-formyluracil (5-ForUra), 5-hydroxycytosine (5-OHCyt), and 5-hydroxyuracil (5-OHUra), in isolated DNA upon exposure to gamma radiation in aerated aqueous solution. For this purpose, both high performance liquid chromatography associated with electrochemical detection (HPLC-EC) and gas chromatography coupled to mass spectrometry (GC-MS) were used. Conditions of hydrolysis of the N-glycosidic bond were carefully checked in order to achieve a quantitative release of the lesions. We showed that 60% formic acid treatment leads to the decomposition of the four lesions studied. On the other hand, hydrolysis based on the use of either 88% formic acid or 70% hydrogen fluoride in pyridine (HF/Pyr) allowed the quantitative release of the modified bases, with the exception of 5-HMUra when the latter reagent was utilized. A dose course study of the radiation-induced formation of 5-HMUra and 5-ForUra in DNA by using the GC-MS assay showed that the latter lesion was produced in a 2.1-fold higher yield than the former one. HF/Pyr and 88% formic acid hydrolysis provided similar results for 5-ForUra, indicating the reliability of both techniques for the measurement of this lesion. For 5-OHUra and 5-OHCyt, the level of modification determined by GC-MS analysis was higher after 88% formic acid treatment than upon HF/Pyr hydrolysis. When DNA was enzymatically digested and analyzed by HPLC-EC for 5-OHdCyd and 5-OHdUrd, the results were very close to those obtained by GC-MS following HF/Pyr treatment. It was concluded that additional amounts of both 5-OHUra and 5-OHCyt are produced during the 88% formic acid treatment from radiation-induced 5,6-saturated pyrimidine precursors. It is likely that cytosine and uracil diols are involved in this reaction. The radiochemical yields of formation (in mumol.J-1) for the products studied are in the following decreasing order: 5-ForUra (0.0083) > 5-OHCyt (0.0046) > 5-HMUra (0.0039) > 5-OHUra (0.0035).

Animals↗
PubMedDate not supplied

5-(phenylthiomethyl)-2'-deoxyuridine as an efficient photoreactive precursor to generate single and multiple lesions within DNA fragments.

5-(Phenylthiomethyl)-2'-deoxyuridine was successfully incorporated into DNA oligomers by automated DNA synthesis using phosphoramidite chemistry. UV exposure of the latter thionucleoside containing oligonucleotides under anaerobic and aerobic conditions gives rise to specific base lesions. The photoproducts have been isolated and further characterized on the basis of NMR and mass spectrometric analyses.

DNA↗
PubMedDate not supplied

New synthesis of 5-carboxy-2'-deoxyuridine and its incorporation into synthetic oligonucleotides.

5-Carboxy-2'-deoxyuridine is a methyl oxidation product of thymidine. It can be formed by the menadione-mediated photosensitization of thymidine in aerated aqueous solution. Here in we present a new four-step synthesis of the 5-carboxy-2'-deoxyuridine phosphoramidite building block based on the alkaline hydrolysis of 5-trifluoromethyl-2'-deoxyuridine. The phosphoramidite derivative has been incorporated at defined sites into oligonucleotides using the solid phase synthesis approach.

Amides↗
PubMedDate not supplied

MALDI-TOF mass spectrometry as a powerful tool to study enzymatic processing of DNA lesions inserted into oligonucleotides.

MALDI-TOF mass spectrometry measurements, coupled with either exonuclease or DNA N-glycosylases digestions of lesion-containing oligonucleotides, were used to assess biochemical features of several oxidative DNA damage. The latter analytical approach was shown to be an informative and efficient alternative technique to conventional electrophoresis and chromatographic analyses.

Animals↗
PubMedDate not supplied

Intrastriatal infusion of amiloride increases rotations in 6-OHDA lesioned rats and "down-regulates" D2 receptors in the striatum and 5-HT2A receptors in the cortex.

Intrastriatal infusion of amiloride and 12-0-tetradeconoyl phorbol-13-acetate (TPA) in 6-OHDA lesioned rats increased the apomorphine (APO)-induced rotation. This behavioral effect occurred in the presence of a decrease in the density and an increase in the affinity of D2 dopamine receptors in the striatum. There was an associated decrease in the number of 5-HT2A receptors labelled with ketanserin in the cortex on the side of infusion. These results suggest that the inositol second-messenger system may be involved in the regulation of D2-dopamine receptors in the striatum and dopamine mediated behavior in the 6-OHDA lesioned rats. They also indicate a possible role for the inositol second messenger system in the regulation of 5-HT2A receptors.

Amiloride↗