Mammalian liver fatty acid binding protein (L-FABP) is a small cytosolic protein in various tissues including liver, small intestine and kidney and is thought to play a crucial role in intracellular fatty acid tra⁄cking and metabolism. To better understand its tissue-speci¢c regulation during zebra¢sh hepatogenesis, we isolated 5P P-£anking sequences of the zebra¢sh L-FABP gene and used a green £uorescent protein (GFP) transgenic strategy to generate liver-speci¢c transgenic zebra¢sh. The 2.8-kb 5P P-£anking sequence of zebra¢sh L-FABP gene was su⁄cient to direct GFP expression in liver primordia, ¢rst observed in 2 dpf embryos and then continuously to the adult stage. This pattern of transgenic expression is consistent with the expression pattern of the endogenous gene. F2 inheritance rates of 42^51% in all the seven transgenic lines were consistent with the ratio of Mendelian segregation. Further, hhex and zXbp-1 morphants displayed a visible liver defect, which suggests that it is possible to establish an in vivo system for screening genes required for liver development. ß

Some freshwater (FW) teleosts are capable of acclimating to seawater (SW) when challenged; however, the related energetic and physiological consequences are still unclear. This study was conducted to examine the changes in expression of gill Na(+)-K(+)-ATPase and creatine kinase (CK) in tilapia (Oreochromis mossambicus) as the acute responses to transfer from FW to SW. After 24 h in 25 ppt SW, gill Na(+)-K(+)-ATPase activities were higher than those of fish in FW. Fish in 35 ppt SW did not increase gill Na(+)-K(+)-ATPase activities until 1.5 h after transfer, and then the activities were not significantly different from those of fish in 25 ppt SW. Compared to FW, the gill CK activities in 35 ppt SW declined within 1.5 h and afterward dramatically elevated at 2 h, as in 25 ppt SW, but the levels in 35 ppt SW were lower than those in 25 ppt SW. The Western blot of muscle-type CK (MM form) was in high association with the salinity change, showing a pattern of changes similar to that in CK activity; however, levels in 35 ppt SW were higher than those in 25 ppt SW. The activity of Na(+)-K(+)-ATPase highly correlated with that of CK in fish gill after transfer from FW to SW, suggesting that phosphocreatine acts as an energy source to meet the osmoregulatory demand during acute transfer.

Freshwater (FW)teleosts are capable of acclimating to seawater (SW) following such a transfer from FW. However, their osmoregulating mechanisms are still unclear, particularly those In the brain. The present study was conducted to examine acute changes that occur In brain Na+•K+•ATPase activity, creatine kinase (CK) activity, creatine, creatinine contents, and ATP Ievels of tllapla (Oreochromls mossamblcus) in response to this transition. After transfer to SW (25 ppt), the Na+•K+•ATPase activity was maintained for 8 hr at higher levels than that In FW. In contrast, In 35 ppt SW, Na+•K+•ATPase was maintained at a even higher level than in FW for the first 2 hr. Brain Na+•K+• ATPase contents in both the 25 and 35 ppt SW groups were significantly elevated within 1 and 0.5 hr after transfer from FW, respectively. Interestingly, brain CK activities and content (hemodlmer of the B subunit [BB] form) in both the 25 and 35 ppt SW groups were significantly elevated within 1 hr after transfer from FW. The ATP contents In 35 ppt SW Increased abruptly within 0.5 hr, and then gradually decreased during the next 2 hr. Unlike the 35 ppt group that declined In ATP contents, the 25 ppt group leveled off within 24 hr. The elevations In CK activity and creatine levels after transfer from FW to SW Imply that abrupt salinity changes alter phosphocreatlneJCK ratio. Such changes are needed to satisfy the Increases In the energetic requirement of the cotransport mechanisms mediating osmcregulation.