Protein synthesis in different tissues of mature rainbow trout (Salmo gairdneri r.). influence of triploidy

Polyvinylpyrolidone-functionalized silver nanoparticles do not affect aerobic performance or fractional rates of protein synthesis in rainbow trout (Oncorhynchus mykiss)

Aerobic performance in fish is linked to individual and population fitness and can be impacted by anthropogenic contaminants. Exposure to some engineered nanomaterials, including silver nanoparticles (nAg), reduces rates of oxygen consumption in some fish species, but the underlying mechanisms remain unclear. In addition, their effects on swim performance have not been studied. Our aim was to quantify the impact of exposure to functionalized nAg on aerobic scope and swim performance in rainbow trout (Oncorhychus mykiss) and to characterize the contribution of changing rates of protein synthesis to these physiological endpoints. Fish were exposed for 48 h to 5 nm polyvinylpyrolidone-functionalized nAg (nAgPVP; 100 μg L^-1) or 0.22 μg L^-1 Ag⁺ (as AgNO₃), which was the measured quantity of Ag released from the nAgPVP over that time period. Aerobic scope, critical swimming speed (U_crit), and fractional rates of protein synthesis (K_s), were then assessed, along with indicators of osmoregulation and cardiotoxicity. Neither nAgPVP, nor Ag⁺ exposure significantly altered aerobic scope, its component parts, or swim performance. K_s was similarly unaffected in 8 tissue types, though it tended to be lower in liver of nAgPVP treated fish. The treatments tended to decrease gill Na⁺/K⁺-ATPase activity, but effects were not significant. The latter results suggest that a longer or more concentrated nAgPVP exposure may induce significant effects. Although this same formulation of nAgPVP is bioactive in other fish, it had no effects on rainbow trout under the conditions tested. Such findings on common model animals like trout may thus misrepresent the safety of nAg to more sensitive species.

The effect of temperature on post-prandial protein synthesis in juvenile barramundi, Lates calcarifer

The experiment aimed to measure post-prandial protein synthesis at three different temperatures. Juvenile barramundi (10.81+/-3.46 g) were held at 21, 27 and 33 degrees C and fed to satiation daily. Samples were taken over a 24h period at 0 (24h after the previous meal) and then at 4, 8, 12 and 24h after feeding to measure protein synthesis in the white muscle, liver and remaining carcass. Protein synthesis at 27 and 33 degrees C peaked 4h after feeding in all tissues and returned to pre-feeding rates by 12h. At 21 degrees C protein synthesis remained constant over 24h in all tissues. While the concentration of RNA remained stable over the 24h cycle and across temperatures, the ribosomal activity increased after feeding. This meant k(RNA), not the absolute amount of RNA, was the driving force underlying the post-prandial increase in protein synthesis. However, relative differences in protein synthesis between tissues were attributed to differences in RNA concentration. There was a significant positive relationship between white muscle and whole body protein synthesis. This was the first study to show an interaction between temperature and the time after feeding on protein synthesis for an ectotherm, and that a post-prandial peak in protein synthesis only occurred under optimum temperature conditions.