新型饲料添加剂“促转素”饲喂肥育猪效果初探

本试验选用32头体重15kg左右的杜×长×大仔猪,随机分成4组,即3个试验组和1个对照组。试验Ⅰ、Ⅱ、Ⅲ组在全价饲料中分别添加0.3%、0.6%、0.9%促转素。Ⅳ组为对照组,饲料中不添加促转素。试验结果表明:Ⅰ、Ⅱ、Ⅲ、Ⅳ组60d平均个体净增重分别为39.06、38.01、34.27、34.63kg/头;料重比分别为2.18、2.36、2.45、2.43:1,其中Ⅰ组料重比最低,比对照组低10.3%。

新型饲料添加剂“促转素”大鼠30天喂养试验研究

新型饲料添加剂"促转素"是由甜菊糖提取废弃物研制而成的,对动物具有促生长、提高饲料利用率、防病抗应激等作用。我们与江西省疾病防治控制中心用小鼠对该产品进行了大鼠30天喂养试验,该产品分别按12、6、3ml/kg·BW的剂量。给予各组大鼠,连续30d,结果表明:试验期间动物生长活动正常,被毛浓密有光泽。各剂量组动物体重、食物利用率、主要脏体比对照组比较差异无显著性(P>0.05)。对照组和各剂量组的白细胞计数及其分类、红细胞计数、血红蛋白及各项生化指标(谷丙转氨酶、谷草转氨酶、尿素氮、肌酐、胆固醇、甘油三脂、血糖、总蛋白、白蛋白)均在本实验室正常参考值范围内。各组动物大体解剖与主要脏器病理组织检查均未见意义的病理变化。

Differentiation of embryonic stem cells into insulin-producing cells promoted by Nkx2.2 gene transfer

AIM： To investigate the ability of a genetically altered embryonic stem （ES） cell line to generate insulin-producing cells in vitro following transfer of the Nkx2.2 gene.METHODS： Hamster Nkx2.2 genes were transferred into mouse ES cells. Parental and Nkx2.2-transfected ES cells were initiated toward differentiation in embryoid body （EB） culture for 5 d and the resulting EBs were transferred to an attached culture system. Dithizone （DTZ）, a zincchelating agent known to selectively stain pancreatic beta cells, was used to detect insulin-producing cells.The outgrowths were incubated in DTZ solution （final concentration, 100μg/mL） for 15 rain before being examined microscopically. Gene expression of the endocrine pancreatic markers was also analyzed by RT-PCR. In addition, insulin production was determined immunohistochemically and its secretion was examined using an ELISA.RESULTS： DTZ-stained cellular clusters appeared after approximately 14 d in the culture of Nkx2.2-transfected ES cells （Nkx-ES cells）, which was as much as 2 wk earlier, than those in the culture of parental ES cells （wt-ES）. The frequency of DTZ-positive cells among total cultured cells on day 28 accounted for approximately 1.0% and 0.1% of the Nkx-ES- and wt-ES-derived EB outgrowths, respectively. The DTZ-positive cellular clusters were found to be immunoreactive to insulin, while the gene expressions of pancreatic-duodenal homeobox 1 （PDX1）, proinsulin 1 and proinsulin 2 were observed in the cultures that contained DTZ-positive cellular clusters.Insulin secretion was also confirmed by ELISA, whereas glucose-dependent secretion was not demonstrated.CONCLUSION： Nkx2.2-transfected ES cells showed an ability to differentiate into insulin-producing cells.

The Enhancement of CO2 Chemical Absorption by K2CO3 Aqueous Solution in the Presence of Activated Carbon Particles

The enhancement of chemical absorption of CO2 by K2CO3/H2O absorbents in the presence of activated carbon （AC） particles was investigated. The results show that the gas absorption rates can be enhanced significantly in the presence of AC particles, and the maximum enhancement factor 3.7 was observed at low stirring intensities. The enhancement factor increased rapidly with the solid loading during the initial period of absorption and then be- came mild gradually to a maximum value. Both the liquid-solid contact area and the probability of solid particles residing at the gas-liquid interface decreased with the increase of the particle size, leading to a negative effect on the enhancement of mass transfer. The influence of the particles on gas absorption decreased with the reaction rate. The stirring speed changed the interfacial coverage and mass transfer rate on the liquid side and consequently affected the mass transfer between the gas and liquid phases; the enhancement factor decreased with the stirring intensity. A heterogeneous two-zone model was proposed for predicting the enhancement factor and the calculated results agreed well with the experimental data.

水牛胎儿成纤维细胞电转染条件的优化

高活力的转基因细胞的制备是转基因克隆动物研究的关键环节。为了高效制备转基因细胞,外源基因转入水牛胎儿成纤维细胞的条件需要优化。采用组织块贴壁法分离获得水牛胎儿成纤维细胞,经染色体核型分析表明获得的细胞具有正常的生物学功能,可用于细胞转染。采用电穿孔法将载体EGFP-N1导入水牛胎儿成纤维细胞,分别比较不同电压(200V,250V,300V,350V)、不同电击时间(5ms,10ms,15ms)和不同细胞代数(第3代、第5代、第10代)的转染效率,并利用优化的电转染条件将乳腺特异性表达的水牛促乳素(PRL)基因导入水牛胎儿成纤维细胞,G418筛选获单克隆并进行鉴定。结果发现电压为300 V,脉冲时间为10 ms时,细胞GFP阳性率为35.5%,转染效率较高。随传代次数的增加,细胞的转染效率下降;传至第10代的细胞转染效率显著低于第3代的水牛胎儿成纤维细胞(30%VS 35.5%,P<0.05)。运用优化条件转染、筛选可获得转PRL单克隆细胞,转染效率为2.1×10-5(84/4×106)。挑取单克隆细胞扩大培养,经PCR鉴定和核型分析,证实单克隆稳定整合促乳素基因,并且核型分析正常,可作为核供体,用于生产水牛转基因克隆胚胎。为采用体细胞克隆技术生产水牛转基因胚胎奠定了基础。