The interactive effects of ethinylestradiol and progesterone on transcriptional expression of genes along the hypothalamus-pituitary-thyroid axis in embryonic zebrafish (Danio rerio).

Progestins and estrogens are widespread in various aquatic environments and their potential endocrine disruption effects to aquatic organisms have drawn growing concern. However, their combined effects in aquatic organisms remain elusive. The aim of the present study was to assess the effects of the binary mixtures of gestodene (GES) and 17α-ethinylestradiol (EE2) on the hypothalamic-pituitary-thyroid (HPT) axis of zebrafish (Danio rerio) using the eleuthero-embryos. Embryos were exposed to GES and EE2 alone or in combination at concentrations ranging from 41 to 5329 ng L-1 (nominal ones from 50 to 5000 ng L-1) for 48 h, 96 h and 144 h post fertilization (hpf). The results showed that the transcripts of the genes along the HPT axis displayed pronounced alterations. There was no clear pattern in the change of the transcripts of these genes over time and with concentrations. However, in general, the transcripts of the genes were inversely affected by EE2 (increase 0.5 to 4.2-folds) and GES (inhibition 0.4 to 4.9-folds), and their mixtures showed interactive effects in embryonic zebrafish. In addition, physiological data (mortality, malformation, body length and heart rate etc.) denoted higher toxicity of the two chemicals in combination than alone based on the developmental toxicity and neurotoxicity (locomotor behavior). These results indicated that the interactive effects of these two chemicals might be different between at the transcriptional level and at the whole organismal level. In summary, GES and EE2 affect the HPT axis (related genes expression and thyroid hormones (THs) levels) and exhibit developmental toxicity and neurotoxicity.

Effect of urea feeding on transforming and migrating soil fluorine in a tea garden of hilly region.

The hilly region of western Sichuan is famous for producing Mengding-mountain tea in China. However, it is very easy to enrich fluorine (F) in tea, which recently raised people's concern on fluorosis. In this study, we simulated the local special climate conditions, especially the natural precipitation through column leaching experiment to investigate the effect of fertilization on F desorption from soil. The results suggested different fertilizers could greatly affect desorption of F from soil, but only urea (CO(NH2)2) could significantly and continuously promote the dissolution of F from soil. Furthermore, to reveal the effect of CO(NH2)2 on migration of F from soil to tea, field plots experiment in a tea garden was carried out. The results showed that CO(NH2)2 promoted soil acidification continuously, resulting in the increase of dissolved F and Al content in soil, which were migrated to tea in the form of F-Al complex. Therefore, the key to reducing the F content in tea is to alleviate soil acidification and reduce F-Al complex content in soil. Most importantly, with CO(NH2)2 addition, the contents of F in tea increased significantly from first bud to fifth bud in comparison with those of without CO(NH2)2, especially in 2016, indicating the accelerating and prolonging enrichment of F in tea by adding CO(NH2)2. This study would have important guidance for controlling F mitigation from soil to tea by managing fertilizers application and anthropogenic activities.