Deficient and excess dietary selenium levels affect growth performance, blood cells apoptosis and liver HSP70 expression in juvenile yellow catfish Pelteobagrus fulvidraco.

We investigated the effects of deficient and excess dietary selenium (Se) on growth, blood cells apoptosis and liver heat shock protein 70 (HSP70) expression in juvenile yellow catfish (Pelteobagrus fulvidraco). After 8 weeks, yellow catfish (initial weight: 2.12 ± 0.01 g) fed isonitrogenous and isolipid diets containing <0.05 (deficient dietary Se) or 6.5 (excess dietary Se) mg Se/kg displayed a significantly lower weight gain ratio (WGR) than those fed a diet containing 0.23 (normal dietary Se) mg Se/kg. As dietary Se levels increased, liver Se concentration, glutathione peroxidase activity and the hepatosomatic index increased significantly. Plasma glucose concentration was highest in the normal treatment compared with the excess dietary Se treatment. Both deficient and excess dietary Se lead to increased reactive oxygen species (ROS) production and apoptosis ratio in blood cells, whereas only excess dietary Se increased their cytoplasmic free-Ca(2+) (CF-Ca(2+)) concentration. Excess dietary Se also resulted in the highest level of HSP70 expression, thereby possibly providing a protective mechanism against oxidative stress. These results indicate that both deficient and excess dietary Se restrained the growth of juvenile yellow catfish and caused oxidative stress. The overproduction of ROS may act as a signal molecule mediate apoptosis when dietary Se deficiency. Both ROS and CF-Ca(2+) were recorded when dietary Se excess, suggesting that Ca(2+) may be activated by Se and play a major role during Se-induced oxidative stress and cell apoptosis.

[Determination of 39 fatty acids in liver of rats by gas chromatography-mass spectrometry].

Fatty acids not only form phospholipids that contribute to the formation of cell membranes but also participate in many metabolic activities, such as energy storage and cell signal transduction. The liver plays a key role in the synthesis and metabolism of fatty acids. The composition and contents of fatty acids in the liver are closely related to body health. Most fatty acid-detection methods require a large sample size and can detect only a small number of fatty acids. Therefore, a sensitive and efficient method to determine fatty acids in the liver is urgently required. Herein, a method based on gas chromatography-mass spectrometry (GC-MS) was established for the simultaneous determination of 39 fatty acids in 1.1 mg of liver tissue. Different extraction methods and derivatization conditions were compared to develop an optimal sample-treatment method. The performance of two different columns in separating the target fatty acids were also compared. A total of 10 mg of liver was added to 450 µL of normal saline and ground at -35 ℃ to obtain a homogenate. Next, 50 µL of the homogenate (equivalent to 1.1 mg of liver) was added with 750 µL of chloroform-methanol (1∶2, v/v) to extract total fatty acids. The fatty acid extracts were dried under nitrogen, and then derivatized at 100 ℃ for 90 min after being added with methanol containing 5% sulfuric acid. The fatty acid methyl esters were extracted with hexane and then separated on an SP-2560 capillary column (100 m×0.25 mm×0.2 µm; Supelco, USA) via GC-MS. The results revealed that all 39 fatty acid methyl esters detected had good linearities in the certain mass concentration ranges with correlation coefficients (R2) greater than 0.9940. The limits of detection (LOD) and quantification (LOQ) of these methyl esters in the liver were 2-272 ng/mg and 7-906 ng/mg, respectively. The accuracy and precision of the method were evaluated by spiking the liver homogenate with tridecylic acid and eicosanoic acid at low (0.09 µg/mg), moderate (0.90 µg/mg), and high (5.40 µg/mg) concentration levels. The recoveries ranged from 82.4% to 101.0% with an intraday relative standard deviations (RSDs) (n=5) of 3.2%-12.0% and interday RSDs (n=3) of 5.4%-13.4%. The method was successfully applied to detect fatty acids in the livers of four healthy male Sprague-Dawley (SD) rats and four male SD rats with abnormal liver function induced by perfluorooctane sulfonate (PFOS). PFOS is a persistent organic pollutant. Twenty-six fatty acids were detected in the livers of both groups. Among the fatty acids investigated, pentadecanoic acid (C15∶0), γ-linolenic acid (C18∶3n6), and elaidic acid (C18∶1n9t) cannot be detected by the methods reported in the literature. By contrast, the method developed in this study could separate the isomers of oleic acid (elaidic acid, C18∶1n9t; oleic acid, C18∶1n9c) and linolenic acid (linolelaidic acid, C18∶2n6t; linoleic acid, C18∶2n6c). In conclusion, the developed method is simple and can detect a large number of fatty acids using small sample amounts and few reagents. More importantly, it could successfully separate fatty acid isomers. These findings indicate that the developed method is suitable for the detection of fatty acid composition and contents in the liver in clinical and experimental research.

[Distribution characteristics of surface soil organic carbon and total nitrogen in forest plantation of hilly area of Taihang Mountains, Chin]. / å¤ªè¡Œå±±ä½Žå±±ä¸˜é™µåŒºäººå·¥æž—è¡¨å±‚åœŸå£¤æœ‰æœºç¢³å’Œå ¨æ°®åˆ†å¸ƒç‰¹å¾.

To explore the effects of forest types and slope positions on the content of soil organic carbon (SOC) and total nitrogen (TN) in the lower hilly area of Taihang Mountains, we examined the distribution pattern of SOC and TN contents in Quercus variabilis plantation (Qo), and Platycladus orientalis plantation (Po), and abandoned land (Al). The results showed that in the same forest type or slope position, the contents of SOC and TN gradually decreased with increasing soil depth. Under different slope conditions, the contents of SOC and TN showed the tendency of upper-slope (U) > middle-slope (M) > lower-slope (L) in the planted forests (Qo and Po), but showed the tendency of L>U>M in Al. Under different forest types, the contents of SOC and TN in the U and M showed the trend of Qo>Po>Al. At the LS, the contents of SOC and TN of Al were the highest. The C/N ratio followed an order of Qo>Po> Al at U and M, while Qo>Al> Po at L. Within the same forest type, C/N of different slopes was different, but not significant. Our results suggested that the adaptability of the Qo plantation is the best in the lower hilly area of Taihang Mountains.