Thesis (M.Sc.)--Chulalongkorn University, 1997

Acute toxicity and sub-acute effects of Derris trifoliata leaves extract on histological and ultratructural alteration of Nile tilapia Oreochromis niloticus liver were studied. The experiments were performed under laboratory conditions with static renewal test-type. The fish were investigated for growth (indicated by length and weight), relative liver weight index, histological and ultrastructural alteration of liver during 5 months. The median lethal concentration (96-h LC₅₀) for acute toxicity was 1.99 mg/L. Base on this value, a sub-acute concentration for this study was calculated to 0.02 mg/L. From light microscopic study, the histological changes of hepatic tissue comprised of swelling, vacuolation and fat droplets accumulation in hepatocytes, hemorrhagic inflammation, macrophage invasion, fibrosis, foci and diffused necrosis. Histochemical studies indicated that the treated liver were less in glycogen storagen storage but much more lipid accumulation than control groups. The ultrastructural alterations of hepatocyte consisted of mitochondrial contraction and/or swelling, proliferation and fragmentation of RER, shifting of RER to SER, increasing of secondary lysosome. Hepatic cell injuries and liver tissue lesions were increased along the continuous exposure of 5 months experimental period. Hence, these cellular changes were time dependent effect. Additionally, a significant (p≤0.5) reduction in growth was observed in 3rd month tilled 5th month of treated groups. The relative liver weight index was also significant (p≤0.5) increased in the 4th month of experiment.