Thyroid Disruption by Di-n-Butyl Phthalate (DBP) and Mono-n-Butyl Phthalate (MBP) in Xenopus laevis

BACKGROUND: Di-n-butyl phthalate (DBP), a chemical widely used in many consumer products, is estrogenic and capable of producing seriously reproductive and developmental effects in laboratory animals. However, recent in vitro studies have shown that DBP and mono-n-butyl phthalate (MBP), the major metabolite of DBP, possessed thyroid hormone receptor (TR) antagonist activity. It is therefore important to consider DBP and MBP that may interfere with thyroid hormone system. METHODOLOGY/PRINCIPAL FINDINGS: Nieuwkoop and Faber stage 51 Xenopus laevis were exposed to DBP and MBP (2, 10 or 15 mg/L) separately for 21 days. The two test chemicals decelerated spontaneous metamorphosis in X. laevis at concentrations of 10 and 15 mg/L. Moreover, MBP seemed to possess stronger activity. The effects of DBP and MBP on inducing changes of expression of selected thyroid hormone response genes: thyroid hormone receptor-beta (TRβ), retinoid X receptor gamma (RXRγ), alpha and beta subunits of thyroid-stimulating hormone (TSHα and TSHβ) were detected by qPCR at all concentrations of the compounds. Using mammalian two-hybrid assay in vitro, we found that DBP and MBP enhanced the interactions between co-repressor SMRT (silencing mediator for retinoid and thyroid hormone receptors) and TR in a dose-dependent manner, and MBP displayed more markedly. In addition, MBP at low concentrations (2 and 10 mg/L) caused aberrant methylation of TRβ in head tissue. CONCLUSIONS: The current findings highlight potential disruption of thyroid signalling by DBP and MBP and provide data for human risk assessment

Navigating the Social Terrain with Google Latitude

Although researchers have been building location-based social services for some time now, sharing one???s location has only recently been introduced to the more general population. This paper examines real-world adoption of and resistance to Google Latitude, a social mobile-device application for people to share their locations. We report findings from an analysis of semistructured interviews with 21 participants using grounded theory. Our research reveals how interviewees perceive the social affordances of location-sharing applications to be conceptually intertwined with the conventions of other social networking and communication technologies; Our findings emphasize that many participants felt pressured to not only adopt social applications such as location-sharing, but also to be responsive and accessible at all times. Participants perceived technology-mediated social interactions (such as ???friending??? someone) as highly symbolic, and as problematic if they did not strictly adhere to the established social etiquette. We also found that participants??? perception of the social norms around using Latitude varied widely, affecting how and whether participants used the system