Effects of dietary arginine and lysine levels on growth performance and biochemical parameters of juvenile Japanese flounder Paralichthys olivaceus

ABSTRACT: To investigate the effects of disproportionate levels of dietary arginine and lysine on juvenile Japanese flounder Paralichthys olivaceus , growth performance and biochemical parameters were evaluated by feeding five test diets, comprising different levels of arginine and lysine, to triplicate groups of juveniles (initial bodyweight 1.85 g) for 40 days. Crystalline amino acids were supplemented to test diets to correspond to the amino acid pattern found in the whole body protein of the Japanese flounder, except for arginine and lysine. After the feeding trials, plasma arginine, lysine and urea levels, excreted ammonia-N, and liver arginase activity were analysed. Survival, specific growth rate, feed conversion efficiency, and apparent protein retention were adversely affected ( P  <   0.05) by the deficiency in dietary arginine or lysine concentrations. An excess of either lysine or arginine in the diet did not depress growth when the diets contained adequate levels of either arginine or lysine, proving that there is no evidence for an arginine–lysine antagonism. Results for plasma arginine, lysine and urea levels, excreted ammonia, and liver arginase activity also demonstrated that Japanese flounder juveniles are not sensitive to excess dietary levels of lysine and arginine.     

Role of sodium bicarbonate on the initiation of sperm motility in the Japanese eel

ABSTRACT:   In order to find out the role of sodium bicarbonate (NaHCO₃) on the initiation of sperm motility in the Japanese eel Anguilla japonica , interactions were investigated between NaHCO₃ and various reagents (K⁺ channel blocker 4-aminopyridine [4-AP], ammonium chloride [NH₄Cl], sodium acetate and calcium chloride [CaCl₂]) that could regulate internal factors (intracellular K⁺, intracellular pH [[pH]_i] and intracellular Ca²⁺) in sperm motility. Contradictory effects of NaHCO₃ were observed (i.e. an inhibitory effect when 4-AP was absent and a promoting effect when 4-AP was present). Sodium bicarbonate inhibited the initiation of sperm motility in the Japanese eel. However, NaHCO₃ restored the motility of immotile sperm that 4-AP inhibited. The inhibitory effect of NaHCO₃ disappeared with the addition of NH₄Cl, which raised [pH]_i, but the promoting effect was not affected by [pH]_i. Although NaHCO₃ recovered motility in the presence of 4-AP, this recovery was also observed with the addition of CaCl₂ instead of NaHCO₃. In the initiation of sperm motility in the Japanese eel, two roles for NaHCO₃ are suggested: an inhibitory role relating to the regulation of [pH]_i and a promoting role relating to the uptake of another initiation factor, which could be Ca²⁺.     

Lipid distribution in branching coral Montipora digitata

>ABSTRACT: The lipid profile was studied along the branch length, from the top, middle to base portion, of coral Montipora digitata to gain more insight into the physiological significance of lipids in the coral energy budget. The lipids of M. digitata consisted of seven major lipid classes: polar lipid, sterol, free fatty acid, unknown lipids 1 and 2, triacylglycerol (TG), and wax ester. The concentration of storage lipids, TG, and wax ester showed a top–base gradient along the length, whereas the levels of free fatty acid and unknown lipids showed a base–top gradient. The proportions of polar lipid and sterol in the top portion of the branch were slightly higher than those in the base portion. This observation appeared to be compatible with the view that the increased energy expenditure for proliferation enhanced the mobilization of the storage fuel lipids of wax ester and TG rather than the structure lipids of polar lipids and sterols at the top portion of the branch. Compositions of fatty acid also showed a length-wise diversity. The top portion had a lower proportion of palmitic acid (16   :   0) in all lipid classes of fatty acid ester, suggesting that this fatty acid was preferentially mobilized at the top portion, probably for the growth of coral cells.     

Cytotoxicity of surfactants to the FHM-sp cell line

Cytotoxicity of eight surfactants was determined by the neutral red assay with the fathead minnow (FHM)-sp cell line, a cell line in suspension culture from fish. The toxicity ranking of the surfactants was benzalkonium chloride > benzethonium chloride > sodium linear - dodecylbenzene–sulfonate (LAS) > potassium laurate > sodium dodecylsulfate > polyoxyethylene(20)sorbitan monolaurate > polyoxyethylene(20)sorbitan monooleate > betaine. The toxicity ranking of the surfactants classified into four groups based on the ion of the hydrophilic group was cationic surfactants > anionic surfactants > non-ionic surfactants > amphipathic surfactants. The FHM-sp cells, as well as the chinook salmon embryo (CHSE)-sp cells, could be inoculated directly to the microplate wells without dispersion by trypsin treatment of cell sheets at room temperature. Therefore, the cytotoxicity assay of the surfactants could be carried out quickly by using the FHM-sp cell line. The FHM-sp cell line had similar or higher sensitivity to sodium dodecylsulfate compared with several cell lines from mammals. The cytotoxicity assay could be shortened by the procedure exposing the surfactants to the FHM-sp cells before the cell monolayer formation in the microplate wells. To use the FHM-sp cell line as a screening tool prior to in vivo testing, studies on the correlation between in vivo data and in vitro data on the toxicity of surfactants are necessary.     

Chemical, physical and sensory changes of small abalone meat during cooking

ABSTRACT:   Small abalone meats were heated at 80°C and 98°C for 0–120 min and the differences in chemical, physical and sensory changes of the cooked meats were investigated. The decrease in moisture and weight and the increase in browning and Hunter's b -value were relatively higher for cooking at 98°C than at 80°C. After cooking for 20–120 min, the total amount of adenosine triphosphate and its related compounds on a dry weight basis decreased by 17–27% at 80°C and by 30–39% at 98°C; the total amount of free amino acids on a dry weight basis changed insignificantly at 80°C but decreased by 22–35% after cooking at 98°C. The meats cooked at 80°C were higher in cutting force whereas the levels in the samples cooked at 98°C did not decrease until samples had been cooked for 60 min. The hydroxyproline content showed little change during cooking except for in samples cooked at 98°C for 120 min, in which the content was found to be low. The extended cooking at 80°C improved the acceptability of small abalone meat, whereas only the acceptability score of aroma increased significantly for cooking at 98°C.     

Microcystin production during algal bloom occurrence in Laguna de Bay, the Philippines

ABSTRACT:   The amount of microcystin in Microcystis aeruginosa bloom was investigated during the rainy season of 1999 in Laguna de Bay, the Philippines. Bloom samples taken from the West Bay and East Cove stations of the lake were studied in relation to the characteristics of environmental conditions. Four types of microcystins, microcystin-LR (MC-LR), microcystin-RR (MC-RR), 6(Z)-Adda-microcystin-RR, and 3-desmethylmicrocystin-LR were identified from the natural bloom samples among which MC-LR was the most dominant type of microcystin. Production of microcystin (88.6 µg/100 mg dried cells) was highest during the first sampling week that coincided with high water transparency and high conductivity. The occurrence of a strong typhoon during the second sampling week had changed the environment drastically, which was characterized by low water transparency, high turbidity, low water temperature, and with trace amounts of MC-LR detected at the East Cove station. Thus, toxin production over time as well as the relationship between Microcystis production and toxin concentration could not be fully evaluated.