Effect of Schizochytrium limacinum supplementation to a low fish-meal diet on growth performance, lipid metabolism, apoptosis, autophagy and intestinal histology of Litopenaeus vannamei

In this experiment, we aimed to evaluate the relationship between the addition of Schizochytrium limacinum to low fish meal diets on growth performance, apoptosis, autophagy, lipid metabolism, and intestinal health of Lipenaeus vanamei. The diet containing 25% fish meal was used as a positive control (FM) and the other three diets contained 15% fish meal and were supplemented with 0, 0.3, and 0.6% S. Limacinum (LF, LFLD, LFHD). The shrimp (0.22 ± 0.00 g) were divided into four replicates of 40 shrimp per tank and fed four times daily to apparent satiation for 8 weeks. Results showed that the final weight (FBW) and weight gain rate (WGR) of shrimp fed FM and LFHD diets were significantly increased compared to those fed the LFLD diet (P<0.05), and there was no significant difference in survival rate (SR) and feed conversion rate (FCR) among the groups (P>0.05). Supplementation of S. Limacinum in low fish meal diets had no effects on shrimp body composition (P<0.05). There were significant differences (P<0.05) in low-density lipoprotein (LDL-C) glucose (GLU), triglycerides (TG), and total cholesterol (TC) in the hemolymph of shrimp fed the LF diet compared to those fed the LFLD and LFHD diets. HE staining and transmission electron microscopy (TEM) results showed that the microvilli height, mucosal folds height, mucosal folds width and muscle layer thickness in the intestine of shrimp fed the LF diet were significantly reduced compared to those fed the other three diets (P<0.05). Swelling of the endoplasmic reticulum and irregular mitochondria in the gut of shrimp fed the LF diet was also observed by TEM, and the endoplasmic reticulum and mitochondria of shrimp fed the LFHD diet returned to a healthy state. Hepatopancreas genes expression results were showed that the gene expression of 5′ -AMP-activated protein kinase (ampk), stearoyl-CoA desaturase (scd1), acetyl-CoA carboxylase 1 (acc1), and malonyl-CoA decarboxylase (mcd) of shrimp fed the LF diet was significantly increased compared to those fed the FM diet (P<0.05). The gene expression of sterol regulatory element-binding protein (srbep) and carnitine palmitoyl transferase 1 (cpt-1) of shrimp fed the LFLD diet was significantly increased compared to those fed the LF diet (P<0.05). The gene expression of acc1, mcd and scd1 of shrimp fed the LFHD diet was significantly reduced compared to those fed the LF diet (P<0.05). Results of genes expression associated with apoptosis in the hepatopancreas showed that the gene expression of B lymphocytoma-2 (bcl-2), BCL2 associated X apoptosis regulator (bax) and cysteinyl aspartate specific proteinase 8 (caspase 8) of shrimp fed the LF diet was significantly reduced compared to those fed the FM diet (P<0.05). The gene expression of bcl-2 of shrimp fed the LFHD diet was significantly reduced compared to those fed the LF diet (P<0.05). Genes related to autophagy in the hepatopancreas showed that the expression of autophagy-related protein 12 (atg 12), autophagy-related protein 13 (atg 13) and beclin1 of shrimp fed LF the diet was significantly reduced compared to those fed the FM diet (P<0.05). The gene expression of atg 12 and atg 13 of shrimp fed the LFHD diet was significantly increased compared to those fed the LF diet (P<0.05). In summary, reducing fish meal is detrimental to the growth performance and intestinal health of shrimp, and 0.6% S. Limacinum supplementation can improve the growth performance, promotes hepatopancreas lipid metabolism, reduces apoptosis, promotes autophagy and improve intestinal health of Litopenaeus vannamei

Influence of emotional labor on organizational commitment in government logistics personnel: The mediating effect of job burnout and the moderating effect of perceived organizational support.

The study aimed to explore the influence of emotional labor on organizational commitment, we also investigated the mediating effect of job burnout and the moderating effect of perceived organizational support, 234 employees of government logistics participated our research. The results showed that: The surface behaviors of emotional labor had no effect on job burnout. Deep behaviors had a negative effect on job burnout. The surface behaviors of emotional labor had no effect on organizational commitment. Deep behaviors had a positive effect on organizational commitment. Job burnout had a negative effect on organizational commitment. Job burnout mediated the interaction of emotional labor and organizational commitment partially. Perceived organizational support does not significantly moderate the interaction of job burnout on organizational commitment.</p

Exploration of Copula Models Use in Risk Assessment for Freezing and Snow Events: A Case Study in Southern China

Due to cold waves, low and extremely low temperatures occur every winter. Sudden cooling can cause freezing and snow disasters, which seriously affect transportation, power, safety, and other activities, resulting in serious economic losses. Based on precipitation and average temperature data from 258 national meteorological stations over the past 70 years, this study established a historical freezing and snow event data set, extracting the accumulated precipitation intensity (API) and accumulated temperature intensity (ATI). We selected the optimal distribution function and joint distribution function for each station and calculated the univariate and bivariate joint return periods. The return period accuracy plays an important role in risk assessment results. By comparing the calculations with the real return period for historical extreme events, we found that the bivariate joint return period based on a copula model was more accurate than the univariate return period. This is important for the prediction and risk assessment of freezing and snow disasters. Additionally, a risk map based on the joint return period showed that Jiangsu and Anhui, as well as some individual stations in the central provinces, were high-risk areas; however, the risk level was lower in Chongqing and the southern provinces

Lipopolysaccharide Induces Autophagic Cell Death through the PERK-Dependent Branch of the Unfolded Protein Response in Human Alveolar Epithelial A549 Cells

Background: Alveolar epithelial cell death plays a critical role in the pathogenesis of lipopolysaccharide (LPS)-induced acute lung injury. Increased autophagy has a dual effect on cell survival. However, it is not known whether autophagy promotes death or survival in human alveolar epithelial cells exposed to LPS. Methods: Genetic and pharmacological approaches were used to evaluate the effect of autophagy on A549 cell viability upon LPS exposure. The endoplasmic reticulum (ER) stress and unfolded protein response (UPR) pathways were examined with immunoblotting studies to further explore underlying mechanisms. Results: Treatment with LPS (50 µg/ml) led to autophagy activation and decreased cell viability in A549 cells. Blocking autophagy via short interfering RNA or inhibitor significantly decreased, whereas rapamycin increased, the LPS-induced effect on viability. ER stress was activated in LPS-stimulated A549 cells, and ER stress inhibitor reduced LPS-induced autophagy. LPS activated only the PERK pathway and had rarely effect on the ATF6 and IRE1 branches of the UPR in A549 cells. Moreover, the knockdown of PERK and ATF4 attenuated LPS-induced autophagy and promoted cell survival. Conclusion: In human alveolar epithelial A549 cells, LPS induces autophagic cell death that depends on the activation of the PERK branch of the UPR upon ER stress