The surface coat of bloodstream forms of Trypanosoma musculi from mice

Iodination and immunoprecipitation techniques together with indirect fluorescent antibody tests identified two polypeptides (SP) of molecular weights 88,000–92,000 and 66,000–70,000 in the surface coat of bloodstream forms of the mouse trypanosome, Trypanosoma musculi. As parasites multiply and enter the early plateau phase of infection the 88,000–92,000 SP is present while the 66,000–70,000 SP is only detectable after the mid-plateau phase. Western blotting of parasite extracts showed that the 88,000–92,000 SP was present throughout the course of infection, but it appears to become masked by the 66,000–70,000 SP or possibly immunoglobulin from about 16 days after infection. Based on results when Western blots of parasite extracts were probed with antibodies affinity purified against the 88,000–92,000 SP, the two SP appear to be immunologically related and the smaller may be a cleavage product of the larger. This would explain why affinity purified antibodies to each SP bound to trypanosomes collected 8 days after infection, when only the 88,000–92,000 is detectable in parasite extracts. However, the failure of antibodies affinity purified against the 66,000–70,000 SP to bind to the 88,000–92,000 SP in Western blots suggests that the smaller SP has some epitopes that are immunologically distinct from those of the larger SP.     

934株自血培养分离致病菌的病原学分析

目的了解中山大学附属第一医院2002年到2005年自血培养标本中分离的致病细菌的耐药状况和菌群分布特征。方法采用全自动血培养仪进行培养,血培养报阳后转种血平板,用VITEK-60鉴定所分离致病菌,药敏试验用K-B法。结果4年间血培养共分离出934株病原细菌,其中大肠埃希菌、金黄色葡萄球菌、肺炎克雷伯菌,是该院引起血液感染的主要致病细菌。药物敏感试验显示革兰阴性杆菌对亚胺培南、哌拉西林/他唑巴坦、头孢哌酮/舒巴坦的敏感性最高,而革兰阳性球菌对万古霉素及替考拉宁的敏感性最高。结论血液感染患者的死亡率较高,应重视导致血液感染致病菌的病原学研究,以利于疾病的治疗。     

Improved Logrank-Type Tests for Survival Data Using Adaptive Weights

Summary .  For testing for treatment effects with time-to-event data, the logrank test is the most popular choice and has some optimality properties under proportional hazards alternatives. It may also be combined with other tests when a range of nonproportional alternatives are entertained. We introduce some versatile tests that use adaptively weighted logrank statistics. The adaptive weights utilize the hazard ratio obtained by fitting the model of Yang and Prentice (2005,  Biometrika   92 , 1–17). Extensive numerical studies have been performed under proportional and nonproportional alternatives, with a wide range of hazard ratios patterns. These studies show that these new tests typically improve the tests they are designed to modify. In particular, the adaptively weighted logrank test maintains optimality at the proportional alternatives, while improving the power over a wide range of nonproportional alternatives. The new tests are illustrated in several real data examples.     

Recent population decline and selection shape diversity of taxol-related genes

Taxanes are defensive metabolites produced by Taxus species (yews) and used in anticancer therapies. Despite their medical interest, patterns of natural diversity in taxane-related genes are unknown. We examined variation at five main genes of Taxus baccata in the Iberian Peninsula, a region where unique yew genetic resources are endangered. We looked at several gene features and applied complementary neutrality tests, including diversity/divergence tests, tests solely based on site frequency spectrum (SFS) and Zeng's compound tests. To account for specific demography, microsatellite data were used to infer historical changes in population size based on an Approximate Bayesian Computation (ABC) approach. Polymorphism-divergence tests pointed to positive selection for genes TBT and TAT and balancing selection for DBAT. In addition, neutrality tests based on SFS found that while a recent reduction in population size may explain most statistics' values, selection may still be in action in genes TBT and DBAT, at least in some populations. Molecular signatures on taxol genes suggest the action of frequent selective waves with different direction or intensity, possibly related to varying adaptive pressures produced by the host-enemy co-evolution on defence-related genes. Such natural selection processes may have produced taxane variants still undiscovered.     

外科深部真菌感染的病原学分析

目的分析外科住院患者合并真菌感染状况。方法分离的真菌用API 20C AUX真菌鉴定条,用ATB FUNGUS-2进行药敏试验。结果真菌的种类分布中第1位是白色念珠菌占53%,第2位是热带念珠菌占20%,第3位是光滑念珠菌占14%,第4位是近平滑念珠菌占4%,第5位是其余念珠菌占2%;真菌在外科各区分布中,外科ICU占42%,移植外科占25%;真菌在各类标本分布中,痰占43%,尿液占13%,粪便占10%,引流液占9%,血液占7%;真菌对药物5-氟胞嘧啶、两性霉素B、氟康唑、伊曲康唑的药物敏感性分别是93%、98.9%、90.8%、59.8%。结论外科真菌感染集中在重症病区(ICU),分离的致病真菌主要是白色念珠菌、热带念珠菌、光滑念珠菌,真菌对两性霉素B敏感性最高。     

Interactions in a tritrophic acarine predator– prey metapopulation system: prey location and distance moved by Phytoseiulus persimilis (Acari: Phytoseiidae)

The between-plant movement of the predatory mite Phytoseiulus persimilis was studied in a greenhouse. The aims were to determine the distance moved by P. persimilis and the response of the predator to the location of a plant infested with two-spotted spider mite, Tetranychus urticae. In addition, we tested whether the predator exhibits random movement between plants or whether its dispersal is oriented. We found that a high proportion of the predators released on a central plant were able to reach plants at the periphery provided the plants were connected to the central plant with 'bridges'. The results further showed that P. persimilis does not disperse randomly to the surrounding plants. The distribution of immigrants was influenced by the position of an infested plant in the neighbourhood, but light/shadow effects in the greenhouse may also influence the choice of direction. The likely implications of the findings for biological control are discussed. © Rapid Science Ltd. 1998     

Exact log-rank tests for unequal follow-up

The asymptotic log-rank and generalized Wilcoxon tests are the standard procedures for comparing samples of possibly censored survival times. For comparison of samples of very different sizes, an exact test is available that is based on a complete permutation of log-rank or Wilcoxon scores. While the asymptotic tests do not keep their nominal sizes if sample sizes differ substantially, the exact complete permutation test requires equal follow-up of the samples. Therefore, we have developed and present two new exact tests also suitable for unequal follow-up. The first of these is an exact analogue of the asymptotic log-rank test and conditions on observed risk sets, whereas the second approach permutes survival times while conditioning on the realized follow-up in each group. In an empirical study, we compare the new procedures with the asymptotic log-rank test, the exact complete permutation test, and an earlier proposed approach that equalizes the follow-up distributions using artificial censoring. Results confirm highly satisfactory performance of the exact procedure conditioning on realized follow-up, particularly in case of unequal follow-up. The advantage of this test over other options of analysis is finally exemplified in the analysis of a breast cancer study.     

Distribution-free ROC analysis using binary regression techniques

Receiver operating characteristic (ROC) regression methodology is used to identify factors that affect the accuracy of medical diagnostic tests. In this paper, we consider a ROC model for which the ROC curve is a parametric function of covariates but distributions of the diagnostic test results are not specified. Covariates can be either common to all subjects or specific to those with disease. We propose a new estimation procedure based on binary indicators defined by the test result for a diseased subject exceeding various specified quantiles of the distribution of test results from non-diseased subjects with the same covariate values. This procedure is conceptually and computationally simplified relative to existing procedures. Simulation study results indicate that the approach has fairly high statistical efficiency. The new ROC regression methodology is used to evaluate childhood measurements of body mass index as a predictive marker of adult obesity.     

The Use of Multiple Outcomes Analysis in Neurotoxicity: An Example from the New Zealand Study of Offspring of Mothers Exposed to Methyl Mercury

Neurotoxicity has become an important area in the study of the risk to children of noncarcinogens. Many of the tests used to evaluate neurotoxic effects in neurotoxic studies are psychometric tests to assess cognitive, motor, and perceptual performance in individuals in order to determine the presence of psychological problems, impaired educational achievement, or neurological abnormalities. The underlying assumption of these procedures are that a test performance deficit is indicative of a neurological disability, and that such disability derives from the prenatal exposure to an offending substance. The usual analytic paradigm for discerning environmental impacts is to analyze the scores of a particular subtest in a battery taken separately as the dependent variable with regression analysis, which adjusts for cultural background, educational level, and socioeconomic status. The impact of this analysis is to determine the correlation of each of the psychometric test results to exposure. We show a statistical method to simultaneously analyze the multiple outcomes of many tests using General Estimating Equations (GEE) to determine if a correlation exists between the global measure of all these tests and exposure adjusted for covariates of interest and the correlation among the dependent psychometric variables. We show the application of this method to the results of children whose mothers were exposed to mercury during pregnancy.     

Automated image analysis to improve bead ingestion toxicity test counts in the protozoan Tetrahymena pyriformis

AIMS: To improve bead ingestion counts in Tetrahymena pyriformis by automated image analysis as an alternative to direct-counts. METHODS AND RESULTS: Fluorescent latex beads were added to T. pyriformis cultures for ingestion tests. The number of beads ingested by 25 cells was counted directly by epifluorescence microscopy and compared with similar data from image analysis. anova indicated that counts were not significantly different (P < 0.05). The image analysis particularly provided advantages in terms of speed. CONCLUSIONS: The image analysis is superior to direct beads counting in T. pyriformis particularly in terms of speed of analysis. SIGNIFICANCE AND IMPACT OF THE STUDY: The image analysis method is very rapid and will allow many more toxicological analyses to be undertaken with less operator error.