Proportional hazards model with random effects

We propose a general proportional hazards model with random effects for handling clustered survival data. This generalizes the usual frailty model by allowing a multivariate random effect with arbitrary design matrix in the log relative risk, in a way similar to the modelling of random effects in linear, generalized linear and non-linear mixed models. The distribution of the random effects is generally assumed to be multivariate normal, but other (preferably symmetrical) distributions are also possible. Maximum likelihood estimates of the regression parameters, the variance components and the baseline hazard function are obtained via the EM algorithm. The E-step of the algorithm involves computation of the conditional expectations of functions of the random effects, for which we use Markov chain Monte Carlo (MCMC) methods. Approximate variances of the estimates are computed by Louis' formula, and posterior expectations and variances of the individual random effects can be obtained as a by-product of the estimation. The inference procedure is exemplified on two data sets.     

巴曲酶对沙土鼠脑缺血再灌注损伤的影响(英文)

目的:研究巴曲酶对沙土鼠脑缺血再灌注(Ir)期间海马存活锥体细胞数目,神经行为学,海马ATP和羟自由基含量的影响。方法:阻断沙土鼠双侧颈总动脉造成前脑缺血10min。高效液相测定海马ATP和2,3-DHBA的含量。结果:Ir组沙土鼠脑缺血后d7存活锥体细胞数(7±4)％少于Bat组的(45±16)％。在脑缺血后d3和d6时,Ir组沙土鼠的探究活动次数多于Bat组的120％和140％。在再灌注60min时,Ir组沙土鼠ATP水平低于Bat Ⅰ和Ⅱ组(82％和89％),但2,3-DHBA的含量高于Bat Ⅰ和Ⅱ组(2.6和2.4倍)。结论:巴曲酶具有减少脑缺血再灌注后延迟性神经元死亡和羟自由基产生的作用。     

丹酚酸A对培养的大鼠肝星状细胞增殖与胶原生成的作用(英文)

目的:研究丹酚酸A对培养的大鼠肝星状细胞增殖与胶原生成的影响。方法:用链酶蛋白酶与胶原酶对肝脏进行原位灌流消化,Nycodenz密度梯度离心分离大鼠肝星状细胞,传一代培养。MTT法与[~3H]TdR掺入法测定细胞增殖。丽春红染色、图象分析法半定量细胞胶原沉积量,ELISA法测定细胞培养上清中Ⅰ型胶原分泌量,检测细胞层总蛋白量校正细胞数。RT-PCR法分析前胶原α_2(Ⅰ)基因的表达。结果:丹酚酸A 100μmol/L引起部分细胞脱壁与死亡,有一定毒性反应。丹酚酸A 0.1-10μmol/L对细胞形态无明显影响。丹酚酸A1-100μmol/L浓度依赖性抑制细胞增殖,降低胶原沉积量与Ⅰ型胶原分泌量。丹酚酸A1-10μmol/L对前胶原α_2(Ⅰ)mRNA表达均有明显抑制作用。结论:丹酚酸A抑制肝星状细胞增殖与胶原表达,是丹参抗肝纤维化的主要有效成分之一,抑制肝星状细胞活化是其抗肝纤维化的主要作用机制。     

Isolation of a novel protein tyrosine phosphatase inhibitor, 2-methyl-fervenulone, and its precursors from Streptomyces

High-throughput screening identified an extract from Streptomyces sp. IM 2096 with inhibitory activity toward several protein tyrosine phosphatases (PTPs). Four 1,2,4-triazine compounds 2096A-D (1-4) were isolated from this extract and their structures elucidated by interpretation of spectroscopic data and confirmed by degradation and synthesis. The novel glycocyamidine derivatives 1 and 2 are diastereomers and may interconvert. Both are inactive in the PTP inhibition assay. Compounds 1 and 2 are unstable and partially decompose to 3 and glycocyamidine (5) at room temperature. Compound 3, known as MSD-92 or 2-methyl-fervenulone, is a broad-specificity PTP inhibitor with comparable potency to vanadate. The imidazo[4, 5-e]-1,2,4-triazine (4), inactive in the PTP-inhibition assay, may be a degradation product of 3.     

Four new clerodane diterpenoids from Callicarpa pentandra

Leaf extracts of Callicarpa pentandra provided four new clerodane-type diterpenoids (1-4), of which 1, 2, and 4 have ring-A-contracted structures. Their structures and stereochemistry were established by spectral data interpretation, and for 3 also by single-crystal X-ray diffraction.     

Microsatellite instability at selected tetranucleotide repeats is associated with p53 mutations in non-small cell lung cancer

Microsatellite alterations are useful clonal markers for the early detection of cancer. An increase in microsatellite instability has been observed at certain tetranucleotide repeat markers (AAAGn) in lung, head and neck, and bladder cancer. However, the genetic mechanism underlying these elevated microsatellite alterations at selected tetranucleotide repeat (EMAST) tumors is still unknown. The p53 gene plays an important role in maintaining genome integrity by repairing damaged DNA. Therefore, we tested 88 non-small cell lung cancers with a panel of 13 microsatellite markers previously shown to exhibit frequent instability and also performed p53 sequence analysis in these tumors. Thirty-one of these 88 cancers (35%) demonstrated a novel allele [EMAST(+)] in > or =1 of these 13 microsatellite markers. p53 mutations were detected in 50 of 88 (57%) cancers and were significantly (P = 0.001) more common in EMAST(+) tumors (25 of 31; 81%) than in EMAST(-) tumors (25 of 57; 44%). Among squamous cell cancers, p53 mutations were detected significantly (P = 0.04) more frequently in EMAST(+) tumors (17 of 19; 89%) than in EMAST(-) tumors (10 of 18; 55%). Similarly, among primary adenocarcinomas, p53 mutations were present in 67% of the EMAST(+) tumors and in 35% of EMAST(-) adenocarcinomas. None of the 31 EMAST(+) tumors demonstrated high frequency microsatellite instability when examined with a reference panel of five mono- and dinucleotide markers. Primary lung cancers with microsatellite alterations at selected tetranucleotide repeats have a high frequency of p53 mutations and do not display a phenotype consistent with defects in mismatch repair.     

ARHI is the center of allelic deletion on chromosome 1p31 in ovarian and breast cancers

In our previous work, we had characterized ARHI as an imprinted putative tumor-suppressor gene in ovarian and breast cancers. ARHI is expressed in primary breast and ovarian cell lines but largely absent from the corresponding malignant tumors. Moreover, the non-imprinted functional allele is typically deleted in malignant cells. Since ARHI had been mapped to 1p31, a common deletion site in breast and ovarian cancer and male germ-cell tumors, in this study, we set out to define precisely the physical location of ARHI at 1p31 and to determine if this location lies within the smallest common region of deletion in breast and ovarian cancers. To this end, we first carried out radiation hybrid mapping of ARHI and surrounding markers, followed by a high-resolution study of loss of heterozygosity at 1p31 in 49 ovarian and breast cancers. Combining a radiation hybrid map and a physical map of the region encompassing ARHI, 3 discrete regions of minimal deletion were found at 1p31 in breast and ovarian cancers. ARHI is the most common deletion region at 1p31. Two other less common regions of deletion were found centromeric to this gene. One of them centered on D1S207 and the other one included and was proximal to D1S488. We also confirmed the preferential loss of non-imprinted functional allele in 7 of 9 tumor specimens. These data support the possibility that ARHI is a tumor-suppressor gene and suggest that additional tumor-suppressor genes may lie proximal to ARHI at 1p31. The data obtained from our study should aid in the identification and characterization of genes in this novel imprinted region.     

Chiral analysis of selected dopamine receptor antagonists in serum using capillary electrophoresis with cyclodextrin additives

Dopamine D-2 receptor antagonists' eticlopride and sulpiride were determined in serum using capillary electrophoresis with cyclodextrin additives. Chiral resolution of S(-) and R(+) sulpiride and eticlopride were achieved using 2% sulfated-beta-cyclodextrin (S-beta-CD) in 20 mM citrate run buffer (pH 2.90). A 72-cm fused silica capillary operated in the reversed polarity mode voltage of 20 kV was used for the analysis. The analytes of interest were isolated from serum using a solid phase extraction procedure with recoveries in excess of 85% for all four enantiomers. The D-2 receptor antagonist (-) butaclamol was used as internal standard. The limits of detection were 0.3 and 0.1 microg/ml for S(-) and R(+) eticlopride and for S(-) and R(+) sulpiride, respectively, in 1 ml of serum. The limits of quantitation were 2 and 1 microg/ml for S(-) and R(+) eticlopride, and for S(-) and R(+) sulpiride, respectively. Calibration curves were linear over the 2-20 micro/ml range for eticlopride and 1-20 microg/ml range for sulpiride. The coefficients of determination were greater than 0.99 (n = 12 for eticlopride and n = 15 for sulpiride). Precision and accuracy of the method were 0.27-6.38 and 0.20-3.60% for S(-) eticlopride, 2.33-4.28 and 0.80-5.73%, for R(+) eticlopride, 3.46-6.84 and 0.80-4.26%, for S(-) sulpiride; and 4.71 -6.47 and 2.00-6.67%, for R(+)-sulpiride, respectively.     

Authentication of an animal crude drug, Zaocys, by diagnostic PCR

A pair of diagnostic primers for distinguishing the Chinese crude drug Zaocys (Zaocys dhumandes) from its substitutes was designed based on the sequence data of the original animal of the drug and substitutes. Total DNAs were extracted from genuine crude drug and 5 of its substitutes, as well as from 12 species of original animal of the snake crude drug. Diagnostic PCRs were performed using the primers with these total DNAs as a template, annealing at 60-65 degrees C. Positive amplifications were obtained from all DNA templates of Zaocys, whereas negative amplifications were obtained from that of others. The results indicate that Zaocys samples could be definitely distinguished from its substitutes by diagnostic PCR, and no incorrect discrimination was found under the same reaction conditions. The advantages of the method in the authentication of crude drugs are also discussed in the present paper.