Toxicity of Aqueous L-Selenomethionine and Tert-Butyl Hydroperoxide Exposure to Zebrafish (Danio rerio) Embryos Following Tert-Butyl Hydroquinone Treatment

Selenomethionine alleviated fluoride-induced toxicity in zebrafish (Danio rerio) embryos by restoring oxidative balance and rebuilding inflammation homeostasis

Fish are target organisms that are extremely susceptible to fluoride pollution, and an increase in fluoride load will damage multiple systems of fish. Selenomethionine (Se-Met) at low levels has been reported to alleviate oxidative damage and inflammation caused by toxic substances, but whether it can alleviate fluoride-induced toxicity in zebrafish embryos has not been elucidated. In this study, the intervention effects of Se-Met on developmental toxicity, oxidative stress and inflammation in zebrafish embryos exposed to fluoride were determined. Our results showed that fluoride accumulated in larvae and induced developmental toxicity in zebrafish embryos, caused oxidative damage and apoptosis, increased significantly the MPO and LZM activities and the levels of the inflammation-related genes IL-1β, IL-6, TNF-α, IL-10 and TGF-β. Moreover, fluoride significantly increased the levels of ERK2, JNK, p38 and p65 in MAPKs and NF-κB pathways. Se-Met-treatment alleviated the adverse effects induced by fluoride, and all of the above indicators induced by fluoride returned to near control levels with increasing concentrations and time. However, treatment with Se-Met-alone also markedly increased the levels of IL-6, TNF-α, IL-10, TGF-β, ERK2 and JNK. In short, these data demonstrated that Se-Met-could alleviate fluoride-induced toxicity in zebrafish embryos by restoring oxidative balance and rebuilding inflammation homeostasis, although low levels of Se-Met-alone had certain toxic effects on zebrafish embryos. Taken together, Se-Met-plays an important role in preventing toxic damage induced by fluoride in zebrafish embryos, although it has certain toxic effects.

Microfluidic devices for behavioral screening of multiple Zebrafish Larvae: Design investigation process

Microfluidic devices have been introduced for phenotypic screening of zebrafish larvae in both fundamental and pre-clinical research. One of the remaining challenges for the broad use of microfluidic devices is their limited throughput, especially in behavioural assays. Previously, we introduced the tail locomotion of a semi-mobile zebrafish larva evoked on-demand with electric signal in a microfluidic device. Here, we report the lessons learned for increasing the number of specimens from one to four larvae in this device. Multiple parameters including loading and testing time per fish and loading and orientation efficiencies were refined to optimize the performance of modified designs. Simulations of the flow and electric field within the final device provided insight into the flow behavior and functionality of traps when compared to previous single-larva devices. Outcomes led to a new design which decreased the testing time per larva by approximately 60%. Further, loading and orientation efficiencies increased by more than 80%. Critical behavioural parameters such as response duration and tail beat frequency were similar in both single and quadruple-fish devices. The developed microfluidic device has significant advantages for greater throughput and efficiency when behavioral phenotyping is required in various applications, including chemical testing in toxicology and gene screening. This article is protected by copyright. All rights reserved.

Lifetime Chronicles of Selenium Exposure Linked to Deformities in an Imperiled Migratory Fish

Aquatic ecosystems worldwide face growing threats from elevated levels of contaminants from human activities. Toxic levels of selenium (Se) shown to cause deformities in birds, fish, and mammals can transfer from parents to progeny during embryonic development or accumulate through Se-enriched diets. For migratory species that move across landscapes, tracking exposure to elevated Se is vital to mitigating vulnerabilities. Yet, traditional toxicological investigations resolve only recent Se exposure. Here, we use a novel combination of X-ray fluorescence microscopy and depositional chronology in a biomineral to reveal for the first time provenance, life stage, and duration of toxic Se exposure over the lifetime of an organism. Spinal deformities observed in wild Sacramento Splittail (Pogonichthys macrolepidotus), an imperiled migratory minnow, were attributed to elevated Se acquired through maternal transfer and juvenile feeding on contaminated prey. This novel approach paves the way for diagnosing sources, pathways, and potential for a cumulative exposure of Se relevant for conservation.