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The European Standards Committee on Oxidative DNA Damage (ESCODD) was set up to resolve the problems associated with the measurement of background levels of oxidative DNA damage (in particular 8-oxo-7,8-dihydroguanine, or 8-oxoGua) in human cells. A tendency for DNA oxidation to occur during sample preparation prior to chromatography has been recognized as the source of a very substantial artefact. To assess the success of attempts to eliminate the artefact, ESCODD has distributed to its members standard samples of pig liver and HeLa cells for analysis. Estimates of 8-oxoGua in pig liver, using chromatographic techniques, ranged from 2.23 to 441 per 10(6) guanines, with a median of 10.47 per 10(6) guanines. Chromatographic analysis of HeLa cell DNA gave a range of 1.84 to 214 per 10(6) guanines with a median of 5.23 per 10(6) guanines. HeLa cell DNA was also analysed by an enzymic approach, in which whole cell DNA was treated with formamidopyrimidine DNA glycosylase, which nicks DNA at sites of 8-oxoGua, and the breaks measured with the comet assay, alkaline unwinding or alkaline elution. Values with these methods ranged from 0.06 to 4.988-oxoGua per 10(6) guanines, with a median of 0.79 per 10(6) guanines. Although there are clearly still serious discrepancies between methods and laboratories, the lowest estimates by chromatography (arguably those in which the artefact was best controlled) are only 2.5 times higher than the median value obtained with the enzymic approach.

n engl j med 356;22 www.nejm.org may 31, 2007 2329 To the Editor: In the Case Record of a patient with respiratory insufficiency, presented by Boyer et al. (Jan. 25 issue),1 the discussants do not mention a condition known to be associated with idiopathic pulmonary hemosiderosis and to have implications for its management: celiac disease. The association is referred to as the Lane–Hamilton syndrome.2 It is important to recognize this condition, since treatment of celiac disease with a gluten-free diet could lead to the remission of idiopathic pulmonary hemosiderosis.3 Although both celiac disease and idiopathic pulmonary hemosiderosis are believed to be immunologically mediated, the pathogenetic link between them is not clear. A recent systematic review identified 20 patients with the Lane–Hamilton syndrome.4 Of these, 16 had been prescribed a gluten-free diet, with improvement documented in 12. Patients with idiopathic pulmonary hemosiderosis should be screened for celiac disease, even in the absence of gastrointestinal symptoms, by means of serologic testing for antiendomysial antibodies. If the test is positive, an intestinal biopsy should be carried out to confirm the disease, because a gluten-free diet is very effective for the regression of both celiac disease and idiopathic pulmonary hemosiderosis.

Le but de l'etude est de determiner si une derivatisation quantitative peut etre obtenue a une vitesse raisonnable et sous des conditions douces. Influence du pH