Post-transcriptional gene silencing of ribosomal protein S6 kinase 1 restores insulin action in leucine-treated skeletal muscle

Excessive nutrients, especially amino acids, impair insulin action on glucose metabolism in skeletal muscle. We tested the hypothesis that the branched-chain amino acid leucine reduces acute insulin action in primary myotubes via a negative feedback mechanism involving ribosomal protein S6 kinase 1 (S6K1). The effect of S6K1 on glucose metabolism was determined by applying RNA interference (siRNA). Leucine (5 mM) reduced glucose uptake and incorporation to glycogen by 13% and 22%, respectively, compared to the scramble siRNA-transfected control at the basal level. Leucine also reduced insulin-stimulated Akt phosphorylation, glucose uptake and glucose incorporation to glycogen (39%, 39% and 37%, respectively), and this reduction was restored after S6K1 silencing. Depletion of S6K1 enhanced basal glucose utilization and protected against the development of impaired insulin action, in response to excessive leucine. In conclusion, S6K1 plays an important role in the regulation of insulin action on glucose metabolism in skeletal muscle. Received 22 December 2008; received after revision 19 February 2009; accepted 23 February 2009     

短链脂肪酸与肠道菌群

根据近年来国外有关研究进展,综述了肠道短链脂肪酸(SCFAs)的产生、代谢及其重要生理功能。介绍了肠道菌群在SCFA产生代谢中的重要作用。     

复合溶剂萃取法用于直馏柴油脱酸的研究

本文在[5]的基础上,进一步开发出复合溶剂萃取法用于直馏柴油脱酸和回收环烷酸的工艺流程。研究表明,该工艺的环烷酸脱除率达97%以上,精制后柴油质量满足GB252-77质量标准;复合溶剂经蒸馏回收可循环使用,同时得到了环烷酸副产品;该工艺不产生三废,有利于环境保护,克服了柴油碱电精制和硫酸中和法回收环烷酸的缺点。     

土壤和苔藓植物中游离脂肪酸的高效液相色谱荧光测定及质谱鉴定

合成了新型荧光试剂1,2-苯并．3,4-二氢咔唑-9-乙基对甲苯磺酸酯,以此作为柱前衍生化试剂对19种游离脂肪酸(FFA)进行了优化衍生．在Eclipse XDB—C8色谱柱上,采用梯度洗脱对19种游离脂肪酸(FFA)衍生物进行了完全基线分离及定量分析．荧光检测激发和发射波长分别为λex=333nm,λex=390nm．多数脂肪酸的线性回归系数大于0．9989,检测限在24．8～80．37fmol．采用APCI大气压化学电离源的正离子模式,实现了土壤和苔藓中FFA组分的定性．方法具有稳定良好的重现性,对实际样品测定结果满意．     

不同水平脂肪酸钙对瘤胃发酵的影响

本试验选用4只装有永久瘤胃瘘管的羯羊,采用4×4拉丁方设计;对照组羊饲喂基础日粮,3个试验组在基础日粮中分别添加脂肪酸钙2%、4%和6%。探讨日粮中添加保护油脂对绵羊瘤胃发酵的影响。结果表明,日粮中添加脂肪酸钙对瘤胃液pH值、乙酸、丙酸、丁酸浓度、乙酸与丙酸之比值没有明显影响。     

两种海洋微藻脂肪酸组成研究

为了筛选多不饱和脂肪酸含量高的微藻,对两种海洋微藻,三角褐指藻（Phaeodactylum triorrutum）和等鞭金藻（Isochrysis gal-bana）进行了室内培养,并对其脂肪酸组成进行了研究。结果表明：三角褐指藻含有较高的C16:O、C16:1和C20:5（EPA）,仅含有微量的C20:4不含有C22:6（DHA）,多不饱和脂肪酸占总脂肪酸的23.8％。而等鞭金藻主要脂肪酸为C14:0、C16:0、C18:2、C18:3、C22:6（DHA）,不含有C20:4,仅有少量的EPA,多不饱和脂肪酸占总脂肪酸的比例高达49.8％。两种微藻脂肪酸组成显示出明显的种间差异。     

有机酸及降解条件对壳聚糖降解速度的影响

试验研究了不同有机酸及反应时间、温度、酸的浓度对壳聚糖降解速度的影响。壳聚糖在不同的有机酸中降解速度有很大差别,在草酸、柠檬酸、琥珀酸、苹果酸、酒石酸中的降解速度以草酸中为最快,苹果酸中为最慢。随反应时间延长,壳聚糖分子量减小的趋势变缓;降解速度随温度的升高而加快,在50~70℃条件下降解速度最快;随有机酸浓度的增加,壳聚糖降解速度也增加。     

钼矾磷和钨矾磷杂多酸铵盐的制备与结构表征

制备Keggin结构的钼钒鳞和钨钒磷杂多酸铵盐并对其进行了元素分析和红外光谱、紫外光谱表征,并且将它作为催化剂用于苯直接羟基化合成苯酚的反应中进行了评价。     

缺锌对大鼠脑和血液中微量元素及游离脂肪酸含量的影响

为了探讨锌营养状况对大鼠血液、脑中某些微量些微量元素和游离脂肪酸含量的影响进行了两系列实验,结果表明,饲料缺锌使大姒血液锌、脑铁含量降低而肪铜含量升高;同时使血液软脂酸（Ｃ１６：０）、硬脂酸（Ｃ１８：０）、油酸（Ｃ１８：１）以及脑Ｃ１６：０、Ｃ１８：０、Ｃ１８：１、亚油酸（Ｃ１８：２）、花生四烯酸（Ｃ２０：４）含量升高,而血液Ｃ１８：２、Ｃ２０：４含量降低。此结果提示,锌可影响脑组织微量元素和脂肪     

Rayleigh light scattering and its applications to biochemical analysis

The recent applications of light scattering technique in biochemical analysis have been reviewed. The mechanic theories of resonance light scattering and Rayleigh light scattering (RLS), the relationships and differences between them, their applications and the interference factors in biochemistry analysis have been covered. By contrasting Rayleigh light scattering with double scattering and anti-scattering, the advantages of RLS have been pointed out. Finally, some prospects for the future application of this technique have been given.