LC50

To determine the effective concentration range, 5 concentrations at one log apart are tested initially. Twenty embryos are treated at each concentration for each compound. Mortality is recorded each day. If the LC50 cannot be established from the results of the initial trial, additional concentrations are tested.

Teratogenicity/Developmental Toxicity

Due to its ex-uterous development, the zebrafish embryo is unique suitable for thorough assessment of teratogenicity and developmental toxicity. The development of the internal organs and tissues can be quickly examined under a dissecting microscope. The teratogenic index of a compound is determined by scoring more than 20 endpoints over a range of concentrations.

Gene Expression Analysis

Toxicity-targeted microarray: Drug effects on the expression of toxicity related genes are examined by a targeted microarray that contains approximately 200 genes involved in xenobiotic metabolism, inflammatory response, apoptosis, stress response, cell proliferation, cell cycle, and signal transduction.

Toxicogenomic analysis using microarrays. The changes in the expression levels of toxicity related genes in response to drug treatment are examined with targeted microarrays.

In situ hybridization: Drug effects on the expression of specific genes are analyzed by whole mount in situ hybridization.

Assessment of caspase-3 expression by in situ hybridization. Embryos at 24 hpf were treated 20 µg/ml neomycin (B) for 24 hours. Compared to control (A), increased expression of caspase-3 was observed in the midbrain (mb), hindbrain (hb), epiphysis (ep), pharyngeal arch (pa) and ear (e) after drug treatment (B), indicating occurrence of apoptosis in theses tissues.