Simultaneous non-parametric confidence intervals for survival probabilities from censored data

In medical studies with censored data Kaplan and Meier's product limit estimator has frequent use as the estimate of the survival function. Simultaneous confidence intervals for the survival function at various time points constitute a useful addition to the analysis. This study compares several such methods. We consider in a simulation investigation two whole curve confidence bands and four methods based on the Bonferroni inequality. The results show that three Bonferroni-type methods are essentially equivalent, all being better than the other methods when the number of time points is small (3 or 5).     

Prion protein is ubiquitinated after developing protease resistance in the brains of scrapie-infected mice

Although the key event in the pathology of prion diseases is thought to be the conversion of cellular prion protein (PrP(C)) to the protease-resistant scrapie species termed PrP(Sc), the factors that contribute to neurodegeneration in scrapie-infected animals are poorly understood. One probable determinant could be when the accumulation of PrP(Sc) in infected brain overwhelms the ubiquitin-proteasome system and triggers the degenerative cascade. In the present study, it was found that in mouse brains infected with the ME7 scrapie strain, the level of ubiquitin protein conjugates increased significantly at approximately 144 days post-infection (pi) when clinical signs first become apparent. This elevation correlated with the detection of protease-resistant PrP(Sc) and a decline in two endopeptidase activities associated with proteasome function. However, ubiquitination of PrP was only detected at the terminal stage, 3 weeks after the development of clinical symptoms (approximately 165 days pi). These results suggest that ubiquitination of PrP is a late event phenomenon and this conjugation occurs after the formation of protease-resistant PrP(Sc). Whether this post-translational modification and the impairment of proteasome function are pivotal events in the pathogenesis of prion diseases remains to be determined.     

微量酶标夹心杂交法定量检测人iNOS-mRNA

目的：建立一种高灵敏度、高特异性、精确、简便的微孔板酶联夹心杂交技术，对人iNOS-mRNA进行定量检测。方法：设计两条特异探针，其中一条为捕获探针，5'端连接氨基，能与微孔板表面的NOS基团共价结合，“竖直”地包被在微孔中，另一个为检测探针，3'端带有生物素标记。用脂多糖（LPS）刺激人外周血单个核细胞24 h后，提取巨噬细胞总RNA，进行RT-PCR扩增，PCR产物热变性后加入到已包被捕获探针的微孔板内，并加入检测探针进行夹心杂交，最后加入亲和素-辣根过氧化物酶（AV-HRP）及底物，在450 nm波长检测杂交信号。结果：该方法检测iNOS-mRNA的灵敏度明显高于RT-PCR-琼脂糖凝胶电泳；特异性高，RT-PCR和酶联夹心杂交均无非特异阳性信号出现；精密度良好。结论：本方法操作简单、灵敏度高、特异性强、结果数据化，适合于iNOS-mRNA的定量检测。     

微量酶联夹心杂交法定量检测hIL-8 mRNA PCR扩增产物

目的:建立一种灵敏度高、特异性强、定量、精确、操作简便的微孔板酶联夹心杂交技术,定量检测人IL-8 mR-NA。方法:针对人IL-8 mRNA逆转录聚合酶链反应产物一条链的不同区域序列设计一对特异探针,其中一条为捕获探针,5′端用活性氨基修饰,与微量DNA结合板表面的NOS基团共价结合,“竖直”地包被在微孔板内;另一条检测探针的3′端标记生物素,和辣根过氧化物酶结合。提取人外周血单个核细胞总RNA,进行RT-PCR扩增IL-8 mRNA,双链DNA产物经热变性后加入已包被捕获探针的微孔板内进行杂交,加入检测探针与已杂交的产物结合,经亲和素-辣根过氧化物酶系统检测杂交信号。结果:该法灵敏度为检出16个循环的PCR产物、5×103个PBMCs中的IL-8 mRNA、检测PCR终产物的最高稀释倍数为1∶256阳性;特异性试验非目的扩增片段酶联杂交检测未检出阳性杂交信号;精密度试验CV为5.2%。结论:该方法具有操作简便、灵敏度高、特异性强等优点,适合IL-8 mRNA PCR扩增产物的定量检测。     

Use of the enzyme-linked immunosorbent assay for measurement of allergen-specific antibodies

A sensitive and specific enzyme-linked immunosorbent assay (ELISA) for allergen-specific IgG antibodies is described. Various solid-phase supports (microtiter plates), coating procedures, binding kinetics, and presentation of allergen in the assay were investigated. Using optimal conditions the indirect ELISA, in which the allergen is coated onto the well, was capable of detecting 2.4 ng/ml specific IgG antibodies to bee venom phospholipase A2(PLA2). The sandwich ELISA, in which the allergen was immobilized via specific antibody precoated onto the well, detected 0.24 ng/ml IgG antibodies to PLA2.     

Sampling‐based estimation for massive survival data with additive hazards model

For massive survival data, we propose a subsampling algorithm to efficiently approximate the estimates of regression parameters in the additive hazards model. We establish consistency and asymptotic normality of the subsample‐based estimator given the full data. The optimal subsampling probabilities are obtained via minimizing asymptotic variance of the resulting estimator. The subsample‐based procedure can largely reduce the computational cost compared with the full data method. In numerical simulations, our method has low bias and satisfactory coverage probabilities. We provide an illustrative example on the survival analysis of patients with lymphoma cancer from the Surveillance, Epidemiology, and End Results Program.     

抗体夹心酶联免疫吸附法测定重组E.coli L-天冬酰胺酶及药代动力学研究

目的建立大鼠血浆中重组E.coli L-天冬酰胺酶的抗体夹心酶联免疫吸附测定法,并进行药代动力学研究。方法应用重组E.coli L-天冬酰胺酶免疫家兔,分离IgG,用DEAE-纤维素柱色谱纯化,辣根过氧化物酶标记抗体,建立抗体夹心酶联免疫吸附法,测定大鼠血浆中重组E.coli L-天冬酰胺酶浓度。结果方法的线性范围为1～64 U·L^-1,血药浓度与时间的关系符合二房室模型,初期和末端的T_1/2分别为0.50～0.57 h和2.45～3.02 h,AUC与剂量成正比。结论建立的抗体夹心酶联免疫吸附法在灵敏度、特异性、线性范围、精密度和回收率等方面,满足药代动力学研究要求。实验方法和重组E.coli L-天冬酰胺酶在大鼠中的药代动力学参数为临床研究提供了手段和依据。     

A note on the empirical Bayes heterogeneity variance estimator in meta-analysis

This paper focuses on the empirical Bayes (EB) or Mandel-Paule estimator of the heterogeneity variance in meta-analysis, which was discussed by Morris and proposed in earlier publications by Mandel and Paule in an inter-laboratory context. The relationship of the EB estimator to other heterogeneity variance estimators typically used in meta-analysis is explored, and approximate variance estimators for the EB estimate of the heterogeneity variance are proposed based on the M-estimation method. Statistical inference for the overall treatment effect using the EB estimator and the proposed standard errors is discussed using two example data sets from meta-analysis applications.