本研究旨在探讨不同蛋白质水平日粮对绵羊胰岛素样生长因子-1(IGF-1)和生长激素(GH)分泌及基因mRNA表达量的影响,为科学配置肉羊饲料及研究肉羊生长发育提供基础。选择6月龄体重相近的多胎萨福克公羔18只,随机分为3组,分别饲喂不同蛋白...本研究旨在探讨不同蛋白质水平日粮对绵羊胰岛素样生长因子-1(IGF-1)和生长激素(GH)分泌及基因mRNA表达量的影响,为科学配置肉羊饲料及研究肉羊生长发育提供基础。选择6月龄体重相近的多胎萨福克公羔18只,随机分为3组,分别饲喂不同蛋白质水平的日粮(低蛋白日粮、中蛋白日粮和高蛋白日粮)。采用ELISA方法和SYBR Green Real-time PCR方法检测日粮不同蛋白质水平对不同生长发育阶段(30、60、90和120d)羔羊外周血中IGF-1、GH浓度和皮肤组织中基因表达的影响。结果显示,日粮蛋白质水平显著影响绵羊平均日增重、外周血中IGF-1和GH的浓度以及皮肤组织IGF-1基因的表达丰度,而未显著影响GH基因的表达丰度。结果提示,随着日粮蛋白质水平的升高,绵羊生长发育快,外周血中IGF-1浓度增加,GH浓度降低,IGF-1基因表达量增加。展开更多
Objective To construct four recombinant Lactococcus lactis strains exhibiting high β-galactosidase activity in fusion or non-fusion ways, and to study the influence factors for their protein expression and secretion....Objective To construct four recombinant Lactococcus lactis strains exhibiting high β-galactosidase activity in fusion or non-fusion ways, and to study the influence factors for their protein expression and secretion. Methods The gene fragments encoding β-galactosidase from two strains of Loctobacillus bulgaricus, wch9901 isolated from yogurt and 1.1480 purchased from the Chinese Academy of Sciences, were amplified and inserted into lactococcal expression vector pMG36e. For fusion expression, the open reading frame of the β-galactosidase gene was amplified, while for non-fusion expression, the open reading frame of the β-galactosidase gene was amplified with its native Shine-Dalgarno sequence upstream. The start codon of the β-galactosidase gene partially overlapped with the stop codon of vector origin open reading frame. Then, the recombinant plasmids were transformed into Escherichia coli DH5α and Lactococcus lactis subsp, lactis MG1363 and confirmed by determining β-galactosidase activities. Results The non-fusion expression plasmids showed a significantly higher β-galactosidase activity in transformed strains than the fusion expression plasmids. The highest enzyme activity was observed in Lactococcus lactis transformed with the non-fusion expression plasmids which were inserted into the β-galactosidase gene from Lactobacillus bulgaricus wch9901. The β-galactosidase activity was 2.75 times as high as that of the native counterpart. In addition, β-galactosidase expressed by recombinant plasmids in Lactococcus lactis could be secreted into the culture medium. The highest secretion rate （27.1%） was observed when the culture medium contained 20 g/L of lactose. Conclusion Different properties of the native bacteria may have some effects on the protein expression of recombinant plasmids. Non-fusion expression shows a higher enzyme activity in host bacteria. There may be a host-related weak secretion signal peptide gene within the structure gene of Lb. bulgaricus β-galactosidase, and its translation pr展开更多
文摘本研究旨在探讨不同蛋白质水平日粮对绵羊胰岛素样生长因子-1(IGF-1)和生长激素(GH)分泌及基因mRNA表达量的影响,为科学配置肉羊饲料及研究肉羊生长发育提供基础。选择6月龄体重相近的多胎萨福克公羔18只,随机分为3组,分别饲喂不同蛋白质水平的日粮(低蛋白日粮、中蛋白日粮和高蛋白日粮)。采用ELISA方法和SYBR Green Real-time PCR方法检测日粮不同蛋白质水平对不同生长发育阶段(30、60、90和120d)羔羊外周血中IGF-1、GH浓度和皮肤组织中基因表达的影响。结果显示,日粮蛋白质水平显著影响绵羊平均日增重、外周血中IGF-1和GH的浓度以及皮肤组织IGF-1基因的表达丰度,而未显著影响GH基因的表达丰度。结果提示,随着日粮蛋白质水平的升高,绵羊生长发育快,外周血中IGF-1浓度增加,GH浓度降低,IGF-1基因表达量增加。
基金a scientific research grant from Health Bureau of Sichuan Province (No. F0201)
文摘Objective To construct four recombinant Lactococcus lactis strains exhibiting high β-galactosidase activity in fusion or non-fusion ways, and to study the influence factors for their protein expression and secretion. Methods The gene fragments encoding β-galactosidase from two strains of Loctobacillus bulgaricus, wch9901 isolated from yogurt and 1.1480 purchased from the Chinese Academy of Sciences, were amplified and inserted into lactococcal expression vector pMG36e. For fusion expression, the open reading frame of the β-galactosidase gene was amplified, while for non-fusion expression, the open reading frame of the β-galactosidase gene was amplified with its native Shine-Dalgarno sequence upstream. The start codon of the β-galactosidase gene partially overlapped with the stop codon of vector origin open reading frame. Then, the recombinant plasmids were transformed into Escherichia coli DH5α and Lactococcus lactis subsp, lactis MG1363 and confirmed by determining β-galactosidase activities. Results The non-fusion expression plasmids showed a significantly higher β-galactosidase activity in transformed strains than the fusion expression plasmids. The highest enzyme activity was observed in Lactococcus lactis transformed with the non-fusion expression plasmids which were inserted into the β-galactosidase gene from Lactobacillus bulgaricus wch9901. The β-galactosidase activity was 2.75 times as high as that of the native counterpart. In addition, β-galactosidase expressed by recombinant plasmids in Lactococcus lactis could be secreted into the culture medium. The highest secretion rate （27.1%） was observed when the culture medium contained 20 g/L of lactose. Conclusion Different properties of the native bacteria may have some effects on the protein expression of recombinant plasmids. Non-fusion expression shows a higher enzyme activity in host bacteria. There may be a host-related weak secretion signal peptide gene within the structure gene of Lb. bulgaricus β-galactosidase, and its translation pr
