BackgroundExposure to arsenic is a critical risk factor in the complex interplay among genetics, the environment, and human disease. Despite the potential for in utero exposure, the mechanism of arsenic action on vertebrate development and disease is unknown.ObjectivesThe objective of this study was to identify genes and gene networks perturbed by arsenic during development in order to enhance understanding of the molecular mechanisms of arsenic action.MethodsWe exposed zebrafish embryos at 0.25–1.25 hr postfertilization to 10 or 100 ppb arsenic for 24 or 48 hr. We then used total RNA to interrogate genome microarrays and to test levels of gene expression changes by quantitative real-time polymerase chain reaction (QPCR). Computational analysis was used to identify gene expression networks perturbed by arsenic during vertebrate development.ResultsWe identified a set of 99 genes that responded to low levels of arsenic. Nineteen of these genes were predicted to function in a common regulatory network that was significantly associated with immune response and cancer (p < 10−41). Arsenic-mediated expression changes were validated by QPCR.ConclusionsIn this study we demonstrated that arsenic significantly down-regulates expression levels of multiple genes potentially critical for regulating the establishment of an immune response. The data also provide molecular evidence consistent with phenotypic observations reported in other model systems. Additional mechanistic studies will help explain molecular events regulating early stages of the immune system and long-term consequences of arsenic-mediated perturbation of this system during development.

Plants of Halophila johnsonii Eiseman were exposed, in mesocosms, to either pulsed hyposalinity treatments of 30, 15, 10, and 8 or gradual salinity reductions of two every 2 days. When salinity was pulsed, survivorship ([80 %) and maximum quantum yields ([0.7) were high in the 30 and 15 salinity treatments, but both declined in the 10 and 8 salinity treatments. Leaf osmolality declined with respect to salinity treatment, but the difference between leaf and media osmolality remained relatively constant (675 ± 177 mmol kg -1 ). In contrast, when salinity was gradually reduced, survivorship remained high from salinities of 30 to 4, and maximum quantum yields remained high from salinities of 30 to 6. Leaf osmolality declined linearly with respect to media osmolality and, similar to the pulsed treatments, the difference between leaf and media osmolality remained relatively constant from salinities of 30 to 2 (638 ± 161 mmol kg -1 ). Trolox equivalent antioxidant capacity declined over time in both pulsed and gradual salinity reduction. The results indicate that H. johnsonii is more tolerant of hyposalinity than has previously been reported and that gradually reducing salinity extended its lowsalinity tolerance threshold by approximately a salinity of 10.