Effect of stocking density on growth performance, digestive enzyme activities, and nonspecific immune parameters of Palaemonetes sinensis.

Palaemonetes sinensis is a new breed of shrimp with great potential for aquaculture, which has been confirmed in our previous production tests. However, there are limited reports about this species and its biological information is scarce. This study describes the effect of stocking density on the growth, digestive enzyme activities, and nonspecific immunity of P. sinensis with an initial average body weight was 0.25 ± 0.02 g. Groups of shrimps were reared at four different initial densities (2.5, 5, 10, and 20 individuals·L-1). After 30 days of culture, the results indicated that the final body weight, weight gain, and specific growth rate were higher in shrimps grown in groups of 10 individuals·L-1 than other groups, but the survival rates of these shrimp were significantly lower than those reared in group of 2.5 or 5 individuals·L-1. The trypsin, amylase, and lipase activities of shrimp significantly decreased with increase in stocking density. Nonspecific immune indicators decreased significantly with increase in density, but there were no significant differences between the 2.5 and 5 individuals·L-1 groups in terms of the total haemocyte count (THC), phenoloxidase activity (PO), lysozyme (LZM), catalase (CAT), and superoxide dismutase (SOD). These results suggest that increasing the stocking density from 2.5 to 5 individuals·L-1 did not affect any of the detected indicators of P. sinensis, but there are shelter in farming mode is better for culture of P. sinensis up to 10 individuals L-1.

Protective effects of quercetin on UVB irradiation­induced cytotoxicity through ROS clearance in keratinocyte cells.

Human skin is the body's largest organ that protects against diverse environmental injuries. However, ultraviolet (UV) radiation, which induces a transient increase in the intracellular level of reactive oxygen species (ROS) and leads to a variety of injuries and various skin diseases, has deleterious effects on living organisms. Quercetin is a naturally occurring compound with strong antioxidant action and can successfully scavenge free radicals. In the present study, we investigated the effects and the mechanism of quercetin on UVB­induced cytotoxicity in keratinocyte (HaCaT) cells. The results of this study showed that quercetin (20 µM) significantly blocked UVB irradiation (15 mJ/cm2)­induced intracellular ROS generation. In addition, the ROS clearing ability of quercetin prevented cell membrane and mitochondria from ROS attack and inhibited cell membrane fluidity decrease and mitochondrial membrane depolarization. Moreover, the outflow of cytochrome c and apoptosis were markedly inhibited. These results suggest that the protective effect of quercetin against UVB irradiation­induced toxicity is mainly mediated by the ROS scavenging ability. Thus, quercetin is a potential agent against UVB irradiation­induced skin damage.