Intravenous Iodinated Contrast Agents Amplify DNA Radiation Damage at CT

PURPOSE To determine the effect of the use of iodinated contrast agents on the formation of DNA double-strand breaks during chest computed tomography (CT). MATERIALS AND METHODS This study was approved by the institutional review board, and written informed consent was obtained from all patients. This single-center study was performed at a university hospital. A total of 179 patients underwent contrast material-enhanced CT, and 66 patients underwent unenhanced CT. Blood samples were taken from these patients prior to and immediately after CT. In these blood samples, the average number of phosphorylated histone H2AX (γH2AX) foci per lymphocyte was determined with fluorescence microscopy. Significant differences between the number of foci that developed in both the presence and the absence of the contrast agent were tested by using an independent sample t test. RESULTS γH2AX foci levels were increased in both groups after CT. Patients who underwent contrast-enhanced CT had an increased amount of DNA radiation damage (mean increase ± standard error of the mean, 0.056 foci per cell ± 0.009). This increase was 107% ± 19 higher than that in patients who underwent unenhanced CT (mean increase, 0.027 foci per cell ± 0.014). CONCLUSION The application of iodinated contrast agents during diagnostic x-ray procedures, such as chest CT, leads to a clear increase in the level of radiation-induced DNA damage as assessed with γH2AX foci formation.

English and French causal connectives in contrast

Discourse connectives are often said to be language specific, and therefore not easily paired with a translation equivalent in a target language. However, few studies have assessed the magnitude and the causes of these divergences. In this paper, we provide an overview of the similarities and discrepancies between causal connectives in two typologically related languages: English and French. We first discuss two criteria used in the literature to account for these differences: the notion of domains of use and the information status of the cause segment. We then test the validity of these criteria through an empirical contrastive study of causal connectives in English and French, performed on a bidirectional corpus. Our results indicate that French and English connectives have only partially overlapping profiles and that translation equivalents are adequately predicted by these two criteria.