Enhancement of dietary protein digestion by conjugated bile acids

BACKGROUND & AIMS: Conjugated bile acids promote absorption of dietary lipids by solubilizing them in mixed micelles. Bile acids are not considered to facilitate the digestion of other nutrients. METHODS: The effect of conjugated bile acids on the rate of protein hydrolysis by trypsin and chymotrypsin was examined in vitro. Common dietary proteins and 2 bacterial glutenases (proposed oral therapies for celiac sprue) were proteolyzed in the absence or presence of a 10 mmol/L conjugated bile acid mixture, simulating human bile composition. Lipolysis products (monoolein) and fatty acid were also evaluated to simulate postprandial intestinal contents. RESULTS: Conjugated bile acids dramatically enhanced the proteolysis of several dietary proteins, including beta-lactoglobulin, bovine serum albumin, myoglobin, and a commercially available dietary protein supplement. For beta-lactoglobulin, a cow's milk allergen that is resistant to pepsin cleavage, bile acids enhanced its proteolysis by pancreatic proteases even after incubation under gastric conditions. Exposure of prolyl endopeptidases to bile acids made them more susceptible to pancreatic proteases under simulated intestinal conditions. The conjugated bile acid effect was most pronounced in the presence of dihydroxy bile acids and was observable at bile concentrations below the critical micellar concentration but to a much greater extent at concentrations above the critical micellar concentration. CONCLUSIONS: We propose that, in addition to promoting lipid absorption, conjugated bile acids affect the digestion and assimilation of dietary proteins by accelerating hydrolysis by pancreatic proteases. These findings have implications for intraluminal protein breakdown and assimilation in the upper small intestine.     

麻疹病毒多肽抗原免疫原性分析

目的分析麻疹病毒(measles virus,MV)主要多肽抗原成分,筛选可用于麻疹病毒特异性抗体诊断的抗原成分。方法应用SDS-聚丙烯酰胺凝胶电泳(SDS-PAGE)和免疫印迹技术(immunoblots,IB)对比分析细胞抗原与麻疹病毒抗原,确定病毒多肽抗原的存在,利用不同时期免疫动物的多克隆抗体分析病毒多肽抗原免疫原性的强弱。结果SDS-PAGE和多克隆抗体免疫印迹结果表明,麻疹病毒分子量为60 kD和55 kD抗原的免疫原性最强,72 kD抗原性较弱,200 kD抗原性最弱。结论针对麻疹病毒60 kD和55 kD抗原成分的抗体检测可以作为麻疹病毒感染的早期诊断指标。     

Protective activity of andrographolide and arabinogalactan proteins from Andrographis paniculata Nees. against ethanol-induced toxicity in mice

To find out the active principles against ethanol-induced toxicity in mice, Andrographis paniculata Nees. (Ap) was chosen and isolated andrographolide (ANDRO) and arabinogalactan proteins (AGPs). ANDRO was detected by HPTLC, FTIR and quantified by HPLC (10mg/g of Ap powder). AGPs was detected by beta-glucosyl Yariv staining of SDS-PAGE gel, FTIR and quantified by single radial gel diffusion assay with beta-glucosyl Yariv reagent (0.5mg/g Ap powder). The mice are pretreated intra-peritoneally (i.p.) with different doses (62.5, 125, 250, and 500mg/kg) of body weight of mice] of ANDRO and AGPs for 7 days and then ethanol (7.5g/kg of body weight) was injected, i.p. Besides, silymarin was used as standard hepatoprotective agent for comparative study with ANDRO and AGPs. The ameliorative activity of ANDRO and AGP against hepatic renal alcohol toxicity was measured by assessing GOT, GPT, ACP, ALP and LP levels in liver and kidney. It has been observed that pretreatment of mice with ANDRO and AGPs at 500mg/kg of body weight and 125mg/kg of body weight respectively could able to minimize the toxicity in compare to ethanol treated group as revealed by the different enzymatic assay in liver and kidney tissues and the results were comparable with silymarin. Hence, out of several ill-defined compounds present in Ap, ANDRO and AGPs are the potential bioactive compounds responsible for protection against ethanol-induced toxicity.     

免疫印迹法检测EGF刺激下小鼠神经细胞MEK2的改变

目的:探讨免疫印迹法检测EGF刺激下小鼠神经细胞中参与信号转导的磷蛋白分子MEK2的改变.方法:培养新生乳小鼠神经细胞,给予不同时间点EGF刺激后提取蛋白质,bradford定量并进行SDS-PAGE凝胶电泳,当电泳结束后利用半干式不连续转移缓冲系统将凝胶上的蛋白质转移到PVDF支持膜上,结合免疫印迹和曝光自显影,即得到了EGF刺激下小鼠神经细胞中磷蛋白分子(MEK2)的免疫印迹图谱.结果:成功地获得了EGF刺激下小鼠神经细胞中磷蛋白分子(MEK2)的免疫印迹图谱.结论:利用此组合方法可以检测EGF刺激下小鼠神经细胞中参与信号转导的磷蛋白分子.实验证明本课题所采用的磷蛋白分析鉴定方法行之有效.     

点带石斑鱼过敏原分离、鉴定与纯化

目的 对点带石斑鱼的主要过敏原进行分离、鉴定与纯化.方法 通过十二烷基硫酸钠-聚丙炳酰胺凝胶电泳 (SDS-PAGE)分离点带石斑鱼的蛋白质组份,采用免疫印迹 (Western-blotting)方法鉴定过敏原,通过离子交换层析对主要过敏原进行初步纯化.结果 SDS-PAGE结果显示,点带石斑鱼粗提液含有13条蛋白带,含量高的有8条,分子量分别为43,34,28,25,22,17,15,9kD;Western-blotting显示,对点带石斑鱼过敏患者的阳性混合血清能与其中4个蛋白条带起反应,分子量分别为34,28,24,22kD.离子交换层析可初步纯化出22kD的过敏原蛋白.结论 初步分离得到分子量为22kD的点带石斑鱼主要过敏原,为临床诊断和治疗鱼类过敏性疾病提供理论依据.     

腰果主要过敏原分离鉴定与纯化

目的 对腰果的主要过敏原进行分析、鉴定与纯化。方法 通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)电泳分离腰果的蛋白质组份,采用免疫印迹(Western-blotting)方法鉴定过敏原,通过离子交换层析对腰果主要过敏原进行初步纯化。结果 腰果粗提液SDS-PAGE显示有10条蛋白条带,Western-blotting显示对腰果过敏患者的阳性混合血清能与其中2个蛋白条带起反应,分子量分别为21kD和11kD。离子交换层析可初步纯化出21和11kD的过敏原蛋白。结论 对腰果过敏原成功进行分离和鉴定,并初步纯化出腰果的主要过敏原。     

HPV16E7基因的原核克隆及表达

目的:探讨从喉癌组织中HPV16 E7蛋白的原核克隆及表达.方法:采用PCR方法扩增HPV16 E7基因,经BamH Ⅰ和Hind Ⅲ双酶切后插入相同酶切pET28a(+)载体,转化JM109感受态细胞,并进行阳性克隆筛选.经IPTG对重组质粒进行蛋白诱导表达,SDS-PAGE和Western blot检测目标蛋白表达情况.结果:成功构建了原核表达质粒pET28/E7、HPV16 E7融合蛋白在BL21(DE3)菌株中高效表达.结论:HPV16 E7融合蛋白的表达为进一步深入研究HPV16E7蛋白的生物学特性及其致细胞转化的作用机制奠定了基础.     

钩端螺旋体轴丝的分离纯化和SDS-PAGE分析

作者应用差速离心和蔗糖密度梯度离心法,分离纯化了钩端螺旋体(钩体)轴丝,并在电镜下观察其超微结构。用SDS-PAGE分析了轴丝蛋白组成和分子量。比较了三株不同毒力、不同种属钩体的轴丝蛋白。结果显示轴丝由6～7种蛋白质构成,分子量为26～80kd,三株钩体都有分子量为31.5kd的蛋白质。讨论了轴丝在钩体分类及钧体病诊断中应用的可能性。