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Abstract: In this study, the cell size, viability, respiratory burst (RB) and mitochondrial membrane potential (MMP) of lipopolysaccharide (LPS)-treated haemocytes from Litopenaeus vannamei were measured by flow cytometry, and phenoloxidase (PO) activity of the cell supernatants was also determined. Three concentrations of LPS (1, 3 and 5µgml−1) were used to determine the effects of LPS on haemocytes. The results revealed that haemocytes treated by LPS in vitro showed conspicuous dose- and time-dependent decreases in cell size and viability. The addition of trypsin inhibitor (TI) which inhibits serine proteinases further delayed the cell size reduction and cell death caused by LPS, implying that serine proteinases were involved in the cell responses. PO activities of the supernatants from LPS-treated cells were significantly higher than that from the control. These results indicated that cell size reduction caused by LPS appeared to be related to degranulation of semigranular and granular cells to release components of proPO system. RB activities were induced by LPS, but not by PMA. Sustaining and tremendous increase of RB occurred during the course of experiment, suggesting that LPS is a more efficient activator to RB of L. vannamei haemocytes than PMA. Specially, MMP of the LPS-treated haemocytes rose at first and then dropped, and which was significantly lower than that of control after 120min incubation with LPS. The initial increase in MMP may have a relation to energy supply for cellular processes, and the later decrease of MMP represent cell apoptosis. Decreases on cell viability and MMP may be related to the overfull product of ROS which oxidized mitochondrial membrane and cell constituents. Though LPS stimulated PO activity of L. vannamei, LPS at the concentrations used in the present study is cytotoxic. These facts suggest that LPS should be carefully used as immunomodulator for shrimp. [Copyright &y& Elsevier]

Abstract: Ferritin is a storage protein that plays a key role in iron metabolism. In this study, the gene expression of ferritin in hepatopancreas, muscle and eye of white shrimp Litopenaeus vannamei were analysed by quantitative real-time PCR after exposure to pH stress. The results showed the expression level in the hepatopancreas and eye were about 5 times to those of beta-actin, whereas lower expression levels in muscle were about 1/2 to those of beta actin. The gene expressions of ferritin in hepatopancreas and muscle were up regulated at 1.5 h after exposure to pH stress, but down-regulated in eye slightly. The ferritin transcript in hepatopancreas of white shrimp L. vannamei at pH 9.3 and pH 5.6 treatments increased significantly in 1.5 h and 12 h post-challenge respectively, but both returned to the original values in 24h post-challenge. The present result showed that ferritin expression in tissue of L.vannamei was induced by acute pH stress and ferritin induction varied in response to duration of induction and acidic or alkaline pH treatment, and was more sensitive to high pH than low pH. [Copyright &y& Elsevier]

Abstract: This study examined the effects of dietary tocopheryl acetate (vitamin E) and salinity on muscle superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) activity and gill Na+/K+-ATPase activity in Litopenaeus vannamei. Three diets containing 0, 100 and 600 mg tocopheryl acetate kg−1 diet, respectively, were fed to shrimp (40–50 mg) for 35 days. Subsequently, shrimp were subjected to an acute salinity change (30‰ to 5, 15, 30, and 50‰) for 24 h. Significantly (P <0.05) increased SOD, CAT, GPX and Na+/K+-ATPase activities were observed in shrimp fed diets supplemented with vitamin E compared to shrimp fed the unsupplemented control diet. In addition, when exposed to 5 and 50‰, total SOD, CAT and GPX activities of shrimp in all dietary groups were decreased (P <0.05) compared to shrimp held in 30‰, with the exception of SOD in shrimp fed E-600 at 50‰ and GPX in shrimp fed E-100 at 5‰, which did not show a significant decrease (P>0.05). A similar trend was observed in Na+/K+-ATPase activity of shrimp fed the control diet. Na+/K+-ATPase activity of shrimp fed the vitamin E-supplemented diet showed no significant variation response to acute salinity changes. Supplementation of vitamin E in diet could enhance the resistance of shrimp to acute changes in salinity. However, the higher dose of vitamin E supplement was not significantly different from the moderate dose. The results demonstrated that vitamin E might have a potentially useful role as an effective antioxidant by regulating osmotic balance and resistance to salinity changes in shrimp. [Copyright &y& Elsevier]