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In the current study, we examined the socio-demographic characteristics and attitudes of Indian mothers, their knowledge about behaviors related to Attention Deficit Hyperactivity Disorder (ADHD) and the relationship with ADHD diagnosis among their children. Previous research showed 11.3% of primary school children in India have been diagnosed with ADHD, yet little research has been conducted on how mothers perceive these behaviors. A survey was completed by 100 mothers with children aged between 4–12 years. The Centers for Disease Control (CDC) ADHD Checklist for Children was used to assess the presence of ADHD symptoms in Indian children. The surveys were analyzed to identify maternal ADHD knowledge, socio-demographic characteristics and attitudes associated with ADHD within the context of Indian culture using SPSS. It was determined that the gender of the child, the geographical location the mother was raised, willingness of mother to seek professional help, mother's knowledge on handling child's behavior and mother's knowledge on ADHD were significantly associated with ADHD. Further analyses revealed that a lack of knowledge of ADHD and handling child's behavior were most associated with anADHD diagnosis based on the CDCADHD checklist.

A recently developed quantum mechanical approach devoted to the study of unstable species in solution was applied to isomeric radicals resulting from the addition of hydrogen atoms to thymine. The ...

La decomposition radio-induite de l'ADN fait intervenir des processus radicalaires. Une serie de lesions choisies parmi les produits majeurs de degradation des bases a ete mesuree dans de l'ADN isole expose au rayonnement γ en solution aqueuse aeree. Les modifications sont alors dues aux radicaux hydroxyles produits par la radiolyse de l'eau (effet indirect) et les quatre bases sont efficacement degradees. L'arrachement d'electrons aux bases par photosensibilisation pour produire leur radical cation, a ete utilise comme modele de l'effet direct. La quantification des bases modifiees montre que la guanine est preferentiellement degradee. Cette observation peut s'expliquer par le plus faible potentiel d'oxydation de cette base ainsi que par les phenomenes de transfert de charge vers les guanines.

La 8-oxo-7,8-dihydro-2'-desoxyguanosine (8-oxodGuo) est une lesion oxydative majeure de l'ADN. Divers protocoles d'extraction d'ADN vegetal ont ete optimises dans le but de quantifier la 8-oxodGuo dans l'ADN total d'une suspension cellulaire d'Arabidopsis thaliana en utilisant la chromatographie liquide haute performance couplee a un detecteur electrochimique (CLHP-EC). Nos resultats montrent que l'ADN peut etre oxyde artefactuellement au cours de son extraction. L'utilisation de chelateurs de metaux permet de reduire le niveau de base de 8-oxodGuo a 3,3 ± 0,1 8-oxodGuo/10 5 Gua et d'augmenter la reproductibilite des experiences. L'etude des effets des rayons γ sur les cellules de plantes a mis en evidence que l'oxydation de la guanine de l'ADN est tres faible in vivo (formation de 15 8-oxodGuo/10 9 Gua par Gy).

The presence of a N-(2-deoxy-D-erythro pentofuranosyl)urea (henceforth referred to as deoxyribosylurea) residue, ring fragmentation product of a thymine, in a frameshift situation in the sequence 5'd(AGGACCACG).d(CGTGGurTCCT) has been studied by 1H and 31P nuclear magnetic resonance and molecular dynamics. At equilibrium, two species are found in slow exchange. We observe that the deoxyribosylurea residue can be either intra- or extrahelical within structures which otherwise do not deviate strongly from that of a B-DNA as observed by NMR. Our study suggests that this is determined by the nature and number of hydrogen bonds which this residue can form as a function of two possible isomers. There are two possible structures for the urea side chain, either cis or trans for the urido bond which significantly changes the hydrogen bonding geometry of the residue. In the intrahelical species, the cis isomer can form two good hydrogen bonds with the bases on the opposite strand in the intrahelical species, A4 and C5, which is not the case for the trans isomer. This results in a kink in the helical axis. For the major extrahelical species, the situation is reversed. The trans isomer is able to form two good hydrogen bonds, with G13 on the same strand and A7 on the opposite strand. For the extrahelical species, the cis isomer can form only one hydrogen bond. In this major structure the NMR data show that the bases which are on either side of the deoxyribosylurea residue in the sequence, G14 and T16, are stacked over each other in a way similar to a normal B-DNA structure. This requires the formation of a loop for the backbone between these two residues. This loop can belong to one of two families, right- or left-handed. In a previous study of an abasic frameshift [Cuniasse et al. (1989) Biochemistry 28, 2018-2026], a left-handed loop was observed, whereas in this study a right-handed loop is found for the first time in solution. The deoxyribosylurea residue lies in the minor groove and can form both an intra- and an interstrand hydrogen bond.

Emphasis was placed in this work on the measurement of purine oxidation products generated upon nano- and picosecond UV laser biphotonic photolysis of 2‘-deoxyadenosine, 2‘-deoxyguanosine, calf thy...

L'adenine-N1-oxyde est une lesion de l'ADN resultant de l'effet indirect du rayonnement solaire par action du peroxyde d'hydrogene sur l'adenine. Son dosage dans l'ADN, jusqu'ici obtenu par la methode du post-marquage radioactif etait long et fastidieux. Nous proposons ici l'utilisation de l'electrophorese capillaire, dont la sensibilite et la facilite de mise en oeuvre permettent une evaluation rapide du taux de modification d'un ADN.

La 5,6-dihydroxy-5,6-dihydro-5-methyl-2'-desoxycylidine est un produit d'oxydation radicalaire de la 5-methyl-2'-desoxycytidine (m 5 dCyd) forme par l'action des radicaux hydroxyles et par photosensibilisation en presence de menadione. Des experiences de marquage isotopique avec I' 18 O nous ont permis de proposer un mecanisme de formation de la 5,6-dihydroxy-5,6-dihydro-5-methyl-2'-desoxycytidine via le cation radical de la m 5 dCyd.

Bulky DNA adducts and 8-oxo-7,8-dihydro-2´-deoxyguanosine (8-oxodGuo) were measured in gill DNA of benzo[a]pyrene (B[a]P)-exposed mussels (50 mg kg(-1) dw day(-1)), respectively by the (32)P-post-labelling technique and high performance liquid chromatography coupled to electrochemical detection assay. A time-course study was performed for both biomarkers and their potential use for marine biomonitoring discussed for the sentinel species studied. In gills, B[a]P-related DNA adducts were positively correlated with B[a.

The 13C NMR spectra of several diastereomers of radiation-induced decomposition products of thymidine and thymine (its homologue without a sugar moiety at N-1) were interpreted in terms of the conformational features of the pyrimidine ring. The study was based on the analysis of the changes in 13C chemical shifts of the pyrimidine ring due to through-space interactions between the different substituents. First, γ effects between the substituents at C-6 (hydroxyl, hydroperoxyl or 2,2,4,4-tetramethylpiperidone-N-oxyl) and the methyl group at C-5 were considered. Then these steric effects were combined with hydrogen bonding interactions between the hydroxyl group at C-5 and the carbonyl at C-4. This made it possible to account for the observed changes in the 13C chemical shifts of the pyrimidine ring. The 5,6-saturated pyrimidine moiety is proposed to adopt a half-chair conformation with the substituent at carbon C-6 in a pseudo-axial position.

Nous avons montre dans des travaux anterieurs que les hydrates de cytosine constituaient les principales lesions photo-induites de l'ADN susceptibles d'etre excisees par l'endonuclease III. Il en est de meme pour l'hydrate d'uracile, le produit de desamination de la 6-hydroxy-5,6-dihydrocytosine, qui est aussi elimine de l'ADN par l'activite glycosylasique de l'endonuclease III (1,2). Plus recemment il a ete aussi montre que cette meme endonuclease III etait capable d'exciser les photohydrates de thymine formes par irradiation UV dans le poly(dA-( 3 H)dT) (3). Dans la presente etude qui constitue un prolongement de ces differents travaux, nous nous sommes efforces de rechercher si le photohydrate de 5-methycytosine pouvait etre forme par irradiation UV. Pour cela nous avons synthetise le substrat ( 3 H-methyl)poly(dG-mdC).poly(dG-mdC) par incubation du poly(dG-dC).poly(dG-dC) avec la (3H)-S-adenosylmethionine et l'ADN methylase. Il est important de noter que l'action de l'endonuclease III sur ce polynucleotide irradie ne conduit pas a la liberation des photohydrates de 5-methylcytosine et de leurs produits de desamination, a savoir les isomeres cis et trans de la 6-hydroxy-5.6-dihydrothymine. Toutefois, on observe la presence de la base 5-methylcytosine dans la solution irradiee de ( 3 H-methyl)poly(dG-mdC).poly(dG-mdC). Il faut aussi ajouter que cette reaction n'est significativement importante qu'en presence d'oxygene. Ces travaux devraient permettre de mieux connaitre le role biologique des dommages photoinduits de la 5-methylcytosine.

La 5-methylcytosine est un constituant mineur de l'ADN de mammiferes et d'autres organismes eucaryotes superieurs. Il apparait que cette base joue un role important dans le controle de l'expression des genes et d'autres processus physiologiques. Des mutations somatiques et germinales semblent se produire preferentiellement aux sites des residus 5-methylcytosine. Nous avons entrepris la determination des produits de modification des residus de 5-methylcytosine apres action de rayonnements ou d'agents oxydants

The radical oxidation capability of several classes of iron minerals, including biotite, hematite, magnetite, minette, nemalite, pyrite, vivianite and two chrysotiles (asbestos), was investigated by using a double experimental approach. One involved the electron spin resonance spin-trapping measurement of organic radicals obtained by the reaction of activated oxygen species, released upon incubation of the minerals in phosphate buffered solutions with formate used as the target molecule. In addition, the formation of mineral-mediated oxidation purine decomposition products, including 7,8-dihydro-8-oxo-2'-deoxyguanosine and 7,8-dihydro-8-oxo-2'-deoxyadenosine, was searched within nucleosides and DNA by using specific and sensitive HPLC electrochemical assays. Emphasis was placed on the mechanistic aspects of the radical oxidation reactions involved in the formation of the two C(8) hydroxylated purine decomposition products.

Ultraviolet A radiation (UVA, 320-400 nm) is mutagenic and induces genomic damage to skin cells. N-acetyl-cysteine (NAC), selenium and zinc have been shown to have antioxidant properties and to exhibit protective effects against UVA cytotoxicity. The present work attempts to delineate the effect of these compounds on genomic integrity of human skin fibroblasts exposed to UVA radiation using the single cell gel electrophoresis (SCGE) or Comet assay. The cells were incubated with NAC (5 mM), sodium selenite (0.6 microM) or zinc chloride (100 microM). Then cells were embedded in low melting point agarose, and immediately submitted to UVA fluences ranging from 1 to 6J/cm2. In the Comet assay, the tail moment increased by 45% (1 J/cm2) to 89% (6J/cm2) in non-supplemented cells (p)

Une etude comparative des reactions des radicaux hydroxyles et des especes oxydantes du reactif de Fenton avec l’ADN et ses nucleosides a ete effectuee. Cette etude repose sur l’identification des produits diamagnetiques provenant de la transformation de radicaux transitoires instables. Ce travail a plus particulierement porte sur les reactions d’oxydation radicalaire des nucleosides puriniques. Il est interessant de noter que les radicaux oxydants puriniques peuvent etre reduits par des agents reducteurs tels que la vitamine C ou le N, N, N’, N’-tetramethyl p-phenylenediamine. Les differences observees dans la nature des produits formes lors de la reaction de Fenton ne resultent pas des especes mises en jeu, radicaux OH ou ions ferryles, mais de la presence de sulfate de fer(Il) qui peut modifier la nature des reactions chimiques des radicaux formes transitoirement.

The aim of the present study was to measure the formation of eight base modifications in the DNA of cells exposed to either low-LET ((60)Co gamma rays) or high-LET ((12)C(6+) particles) radiation. For this purpose, a recently optimized HPLC-MS/MS method was used subsequent to DNA extraction and hydrolysis. The background level of the measured modified bases and nucleosides was shown to vary between 0.2 and 2 lesions/10(6) bases. Interestingly, thymidine glycols constitute the main radiation-induced base modifications, with an overall yield of 0.097 and 0.062 lesion/10(6) bases per gray for gamma rays and carbon heavy ions, respectively. Both types of radiations generate four other major degradation products, in the following order of decreasing importance: FapyGua5-HmdUrd5-FordUrd8-oxodGuo. The yields of formation of FapyAde and 8-oxoAde are one order of magnitude lower than those of the related guanine modifications, whereas the radiation-induced generation of 5-OHdUrd was below the limit of detection of the assay. The efficiency for both types of radiation to generate base damage in cellular DNA is low because the highest yield per gray was 0.097 thymine glycols per 10(6) DNA bases. As a striking observation, the yield of formation of the measured DNA lesions was found to be, on average, twofold lower after exposure to high-LET radiation ((12)C(6+)) than after exposure to low-LET gamma radiation. These studies show that the HPLC-MS/MS assay provides an accurate, reliable and sensitive method for measuring cellular DNA base damage.

Cyclopurine deoxynucleosides are common DNA lesions generated by exposure to reactive oxygen species under hypoxic conditions. The S and R diastereoisomers of cyclodeoxyadenosine on DNA were investigated separately for their ability to block 3' to 5' exonucleases. The mammalian DNA-editing enzyme DNase III (TREX1) was blocked by both diastereoisomers, whereas only the S diastereoisomer was highly efficient in preventing digestion by the exonuclease function of T4 DNA polymerase. Digestion in both cases was frequently blocked one residue before the modified base. Oligodeoxyribonucleotides containing a cyclodeoxyadenosine residue were further employed as templates for synthesis by human DNA polymerase eta (pol eta). pol eta could catalyze translesion synthesis on the R diastereoisomer of cyclodeoxyadenosine. On the S diastereoisomer, pol eta could catalyze the incorporation of one nucleotide opposite the lesion but could not continue elongation. Although pol eta preferentially incorporated dAMP opposite the R diastereoisomer, elongation continued only when dTMP was incorporated, suggesting bypass of this lesion by pol eta with reasonable fidelity. With the S diastereoisomer, pol eta mainly incorporated dAMP or dTMP opposite the lesion but could not elongate even after incorporating a correct nucleotide. These data suggest that the S diastereoisomer may be a more cytotoxic DNA lesion than the R diastereoisomer.

Activated human neutrophils secrete myeloperoxidase, which generates HOCl from H2O2 and Cl(-). We have found that various (2'-deoxy)nucleosides react with HOCl to form chlorinated (2'-deoxy)nucleosides, including novel 8-chloro(2'-deoxy)guanosine, 5-chloro(2'-deoxy)cytidine, and 8-chloro(2'-deoxy)adenosine formed in yields of 1.6, 1.6, and 0.2%, respectively, when 0.5 mM nucleoside reacted with 0.5 mM HOCl at pH 7.4. The relative chlorination, oxidation, and nitration activities of HOCl, myeloperoxidase, and activated human neutrophils in the presence and absence of nitrite were studied by analyzing 8-chloro-, 8-oxo-7,8-dihydro-, and 8-nitro-guanosine, respectively, using guanosine as a probe. 8-Chloroguanosine was always more easily formed than 8-oxo-7,8-dihydro- or 8-nitro-guanosine. Using electrospray ionization tandem mass spectrometry, we show that several chlorinated nucleosides including 8-chloro(2'-deoxy)guanosine are formed following exposure of isolated DNA or RNA to HOCl. Micromolar concentrations of tertiary amines such as nicotine and trimethylamine dramatically enhanced chlorination of free (2'-deoxy)nucleosides and nucleosides in RNA by HOCl. As the G-463A polymorphism of the MPO gene, which strongly reduces myeloperoxidase mRNA expression, is associated with a reduced risk of lung cancer, chlorination damage of DNA /RNA and nucleosides by myeloperoxidase and its enhancement by nicotine may be important in the pathophysiology of human diseases associated with tobacco habits.

The focus of this chapter is to review the main available data on the UV-mediated damage to nucleic acid components. Emphasis is placed on both the main UVB- and UVA-induced DNA photoproducts together with the mechanisms of their formation. The survey also includes information obtained within cellular DNA, taking into account the limitations of the different analytical methods that were applied to monitor the formation of the DNA damage. This concerns on the one hand, UVB radiation-induced DNA damage that is produced by direct absorption of UVB photons, and on the other, UVA damage generated through photosensitization reactions that involve the absorption of the UVA light by endogenous photosensitizers.

The aim of the work was to measure DNA damage induced within tumoral human monocytes by gamma rays, UVA radiation, and exogenous photosensitizers. The accurate HPLC-EC assay was used to determine the level of 8-oxodGuo. The formation of FapyGua and FapyAde was monitored by HPLC/GC-MS analyses after formic acid hydrolysis at room temperature. For this purpose, cells were exposed to relatively high doses of gamma rays and UVA radiation. The extent of formation of FapyGua in the DNA of cells exposed to gamma rays was estimated to be more than 2-fold higher than that of 8-oxodGuo, i.e., about 0. 027 lesion per 10(6) bases per Gy. The yield of FapyAde was estimated to be 1 order of magnitude lower. The latter results were used to calibrate the alkaline comet assay associated with DNA N-glycosylases. The latter approach allowed the determination of the background level (0.11-0.16 Fpg-sensitive site/10(6) bases) and the yields of strand breaks and DNA base damage upon low irradiation doses. Insights into the mechanism of radiation-induced DNA damage were gained from these measurements. A major involvement of (1)O(2) with respect to hydroxyl radicals and type I photosensitization was thus observed within cells exposed to UVA radiation.

The formation of cyclobutane pyrimidine dimers (CPD) and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) was investigated in Chinese hamster ovary cells upon exposure to either UVC, UVB, UVA or simulated sunlight (SSL). Two cell lines were used, namely AT3-2 and UVL9, the latter being deficient in nucleotide excision repair and consequently UV sensitive. For all types of radiation, including UVA, CPD were found to be the predominant lesions quantitatively. At the biologically relevant doses used, UVC, UVB and SSL irradiation yielded 8-oxodGuo at a rather low level, whereas UVA radiation produced relatively higher amounts. The formation of CPD was 10(2) and 10(5) more effective upon UVC than UVB and UVA exposure. These yields of formation followed DNA absorption, even in the UVA range. The calculated relative spectral effectiveness in the production of the two lesions showed that efficient induction of 8-oxodGuo upon UVA irradiation was shifted toward longer wavelengths, in comparison with those for CPD formation, in agreement with a photosensitization mechanism. In addition, after exposure to SSL, about 19% and 20% of 8-oxodGuo were produced between 290-320 nm and 320-340 nm, respectively, whereas CPD were essentially (90%) induced in the UVB region. However, the ratio of CPD to 8-oxodGuo greatly differed from one source of light to the other: it was over 100 for UVB but only a few units for UVA source. The extent of 8-oxodGuo and CPD was also compared to the lethality for the different types of radiation. The involvement of 8-oxodGuo in cell killing by solar UV radiation was clearly ruled out. In addition, our previously reported mutation spectra demonstrated that the contribution of 8-oxodGuo in the overall solar UV mutagenic process is very minor.

2'-Deoxycytidine glycols (5,6-dihydroxy-5, 6-dihydro-2'-deoxycytidine) are major products of the hydroxyl radical-induced oxidation of 2'-deoxycytidine resulting from either a Fenton reaction or exposure to ionizing radiation. Because of their instability, however, the glycols have not previously been characterized. Instead, the impetus has been placed on the primary decomposition products of 2'-deoxycytidine glycols, which includes 5-hydroxy-2'-deoxycytidine, 5-hydroxy-2'-deoxyuridine, and 2'-deoxyuridine glycols. Here, we have identified one of the four possible diastereomers of 2'-deoxycytidine glycols by product analyses of decomposition products, (1)H NMR, and mass spectrometry. This glycol was observed to decompose with a half-life of 50 min at 37 degrees C in buffered neutral solutions and preferentially undergo dehydration to 5-hydroxy-2'-deoxycytidine. The rate of decomposition was strongly dependent on pH (2-10) and the concentration of phosphate ion (10-300 mM). Next, we report on the deamination of cytosine glycols to uracil glycols in oxidized DNA using acid hydrolysis and high performance liquid chromatography analysis with electrochemical detection to monitor 5-hydroxycytosine and 5-hydroxyuracil. The results showed that the lifetime of cytosine glycols is greatly enhanced in DNA (34-fold; half-life, 28 h), and that deamination accounts for at least one-third of the total decomposition. The relatively long lifetime of cytosine glycols in DNA suggests that this important class of DNA oxidation products will be significantly involved in repair and mutagenesis processes.

Nous avons utilise la methode des cometes associee a des ADN-glycosylases, pour estimer les dommages de l'ADN dans des cellules apres l'exposition a un rayonnement gamma ou apres photosensibilisation par le bleu de methylene ou l'acridine orange. Une calibration de la methode des cometes a permis de mesurer le niveau basal et les taux de formation de 8-oxodGuo ainsi que le nombre de cassures de brins et de sites alcali labiles.

Most of the physical and chemical processes involved in DNA damage induction have been characterized in general terms, both for UV and for ionizing radiations. The relative contributions of direct energy absorption and of indirect damage via reactive intermediates are broadly understood. Thus we have a general, although incomplete, picture of the influence of radiation type (wavelength for UV; quality or linear energy transfer (LET) for ionizing radiations) on biological outcome. Some aspects of the dose-effect relationships for DNA damage induction and of the kinetics of its repair are understood. These relationships provide key information for the development of mechanistic models of human risk/exposure relationships.

To determine the distribution of base damage within isolated DNA upon oxidation by three type I photosensitizers in aerated aqueous solution.Aqueous solutions of DNA were exposed to UVA in the presence of riboflavin, benzophenone or menadione. Then, eight modified nucleobases were measured, using HPLC-EC, GC-MS or HPLC with fluorescence detection.The three photosensitizers led to a predominant degradation of guanine bases within DNA. The relative yield of the three main guanine degradation products measured in DNA was similar with the three sensitizers. 8-OxodAdo was also produced in an almost constant yield with respect to its guanine analogue. The yield of oxidized pyrimidines was lower and was found to depend on the photosensitizer used. The results were compared with the yield of photosensitization-induced degradation of the 2'-deoxyribonucleosides.The favoured photosensitized degradation of guanine within DNA may be explained by its lower oxidation potential with respect to that of the other bases, together with the occurrence of charge transfer through DNA. The base modification pattern determined in the present work is different from that obtained upon reaction of hydroxyl radicals. Under the latter conditions, pyrimidine oxidation products were generated more efficiently than by photosensitized one-electron oxidation.

The tetraruthenated porphyrin, mu-[meso-5,10,15,20-tetra(pyridyl)porphyrin]tetrakis[bis-(bipyridine) chloride ruthenium(II)] (TRP) is a supramolecular cationic species. The aim of the present investigation was to evaluate the photodynamic properties of TRP and Zn-TRP to damage DNA with emphasis on the mechanistic aspects. The ability for tetraruthenated porphyrin derivatives to induce photosensitization reactions has been determined using 2'-deoxyguanosine as a DNA model compound. The main photooxidation products of the targeted nucleoside were identified and classified according to their mechanisms of formation, involving either a radical pathway (type I) or a singlet oxygen-mediated mechanism (type II). Quantification of the different oxidation products provides a means to evaluate the relative contribution of type I and type II pathways associated with the oxidative photosensitization of 2'-deoxyguanosine by tetraruthenated porphyrin derivatives. Results indicate that 1O2 plays a major role in the mechanism of photooxidation mediated by these porphyrin derivatives. In addition an increase of the photosensitizing effect in the presence of zinc is observed. For each sensitizer, the ratio between type II and type I photoproducts has been calculated and compared to that of other known dyes such as methylene blue and riboflavin.

Adenine N1-oxide is a DNA lesion whose formation involves the specific oxidation of the adenine base by hydrogen peroxide under nonradical conditions. The damage may be measured using a HPLC/32P-postlabeling method, which however cannot be used for routine analysis. We propose herein as an alternative an immunological assay which allows a rapid evaluation of the level of adenine N1-oxide in DNA exposed to oxidative stress. Two polyclonal antibodies were raised using two different strategies for the coupling of the hapten to the protein. The first approach is based on the universal method of Erlanger and Beiser, whereas the preparation of the second antigen involves the conjugation of a morpholino derivative of adenosine N1-oxide to the carrier protein. The affinity and the specificity of those antibodies were determined by competitive enzyme-linked immunosorbent assay. The antibody obtained by the traditional method shows some cross-reactivity with normal nucleotides, whereas for the other antiserum, the selectivity was found to be higher. Therefore, this polyclonal antibody was used to quantify the level of adenine N1-oxide in calf thymus DNA oxidized either by m-chloroperbenzoic acid or by hydrogen peroxide. The detection limit of the assay is four residues of adenine N1-oxide per 10(6) normal bases. The level of adenine N1-oxide in nonmodified DNA was lower than the detection limit of the assay, whereas in mCPB- and H2O2-modified DNA, it could be up to 14 and 0.7 adenine N1-oxide residues per 10(4) normal bases, respectively.

The urinary excretion of 5-(hydroxymethyl)uracil (5-HMUra), one of the major oxidative modifications of thymine, was investigated in 134 healthy volunteers living in North Italy. Overnight urine was collected, and a questionnaire was completed on smoking habits and exposure to environmental tobacco smoke (ETS). 5-HMUra was analyzed by GC/MS, following urine purification by HPLC. 5-HMUra excretion showed an approximately normal distribution, ranging from 0.08 to 0.84 (mean 0.44) nmoles/kg/8 hr and from 3.2 to 18.7 (mean 8.5) nmoles/mmoles creatinine. 5-HMUra excretion was significantly higher in women than in men and in smokers than in non-smokers when results were expressed as the ratio to creatinine. Slightly higher levels of 5-HMUra excretion, expressed as nmoles/mmoles creatinine, were also found in subjects highly exposed to ETS, monitored either as the number of hours of exposure or as the number of smokers in the workplace and at home. Our results show that the urinary excretion of 5-HMUra is higher than that of other oxidized nucleobases, including 8-oxo-7,8-dihydroguanine, and can be slightly modified by environmental factors such as tobacco smoke. These findings suggest that measurement of urinary excretion of 5-HMUra could be useful as a biomarker of oxidative DNA damage and repair, though further research is needed to support these data.

La detection des bases oxydees dans l'ADN cellulaire constitue un defi analytique puisque la sensibilite requise doit etre de l'ordre d'une modification pour un million de bases normales. Dans ce but, la chromatographie gazeuse couplee a la spectrometrie de masse (CG-SM) a ete tres utilisee au cours de ces dernieres annees. Neanmoins, la comparaison des resultats obtenus par cette technique, avec ceux resultant de la mise en oeuvre d'autres methodes comme la chromatographie liquide haute performance couplee a une detection amperometrique (CLHP-EC), faisait apparaitre une surestimation de la quantite de bases oxydees dans les analyses par CG-SM. L'etude comparative des deux methodes nous a permis de demontrer que cette surestimation etait due a une oxydation artefactuelle des bases de l'ADN durant l'etape de derivation necessaire avant l'analyse par CG-SM. Cette oxydation peut-etre evitee par une purification prealable des bases modifiees avant l'etape de derivation. Dans ces conditions, les resultats obtenus sont comparables a ceux donnes par la methode CLHP-EC.

In a search for more active radioprotective compounds, we have prepared and examined a series of model molecules in which the radioprotective beta-aminothiol unit (free or derivatized as acetate or phosphorothioate) is tethered to the DNA-binding chromophores quinoline and acridine through links of variable length. The modifying activity of these 'hybrid' molecules was estimated by measuring the formation of 8-oxo-2'-deoxyguanosine (8-oxodGuo) in double-strand DNA upon exposure to gamma-rays in oxygen-free solution in the presence of the drugs. We show that all hybrid molecules protect the guanine moiety from oxidation more efficiently than the parent beta-aminothiol units. The degree of protection is the highest for the molecules in which the thiol is linked to the strong binding intercalator acridine through a long polyaminochain.