皮下注射血管内皮生长因子基因提高大鼠背部随意皮瓣活力的实验研究

目的 探索基因治疗在组织移植方面的方法。应用 构建并体外扩增表达质粒pcDNA3.1/Zeo( )-VEGF165，以之直接皮下注射转染SD大鼠背部随意皮瓣模型。通过与对照组相比较，观察其对皮瓣活力的影响，并采集组织行免疫组化检查。结果 基因转染组在毛细血管周围及肌间隙可见VEGF的沉积，与对照组相比皮瓣的平均成活面积显著增加。结论 皮下注射的基因在组织中能够表达VEGF，增加皮瓣活力，是一种简单有效的基因治疗方法。     

Computer aided diagnosis system for the Alzheimer's disease based on partial least squares and random forest SPECT image classification

This letter shows a computer aided diagnosis (CAD) technique for the early detection of the Alzheimer's disease (AD) by means of single photon emission computed tomography (SPECT) image classification. The proposed method is based on partial least squares (PLS) regression model and a random forest (RF) predictor. The challenge of the curse of dimensionality is addressed by reducing the large dimensionality of the input data by downscaling the SPECT images and extracting score features using PLS. A RF predictor then forms an ensemble of classification and regression tree (CART)-like classifiers being its output determined by a majority vote of the trees in the forest. A baseline principal component analysis (PCA) system is also developed for reference. The experimental results show that the combined PLS-RF system yields a generalization error that converges to a limit when increasing the number of trees in the forest. Thus, the generalization error is reduced when using PLS and depends on the strength of the individual trees in the forest and the correlation between them. Moreover, PLS feature extraction is found to be more effective for extracting discriminative information from the data than PCA yielding peak sensitivity, specificity and accuracy values of 100%, 92.7%, and 96.9%, respectively. Moreover, the proposed CAD system outperformed several other recently developed AD CAD systems.     

Bell miner associated dieback: nutrient cycling and herbivore crown damage in Eucalyptus propinqua

Various interactions appear to be involved in bell miner associated dieback (BMAD) of eucalypts. Native bell miner birds (Manorina melanophrys) defend the psyllids from predation by other birds while a dense understorey (notably Lantana camara) appears to favour the bell miners. The understory is likely to influence soil nutrient availability to the trees by changing the carbon to nitrogen ratio. We investigated the link between soil and leaf nutrient status and crown health as measured by crown index (CI) for Eucalyptus propinqua. Study sites included Bald Knob State Forest (SF), Donaldson SF, Mt Lindesay SF around Woodenbong and two locations on a Toonumbar private property in north-eastern New South Wales. Comparison of E. propinqua leaf macro- and micronutrient status using the ‘paired data sign test’ detected leaf nutrient differences between lightly and severely BMAD-affected tree crowns. Single and multivariate analysis investigated nutrient association with CI. Sign test results across all sites indicated that leaf iron content in trees with low CI (less healthy trees) was significantly higher (P = 0.01) than in healthy trees. In the three SFs the affected crowns also had significantly higher nitrogen to potassium ratios (P = 0.02). Other elements correlated with low CI were low boron (P = 0.06) across all sites and high zinc (P = 0.09) and low sodium values (P = 0.09) for Toonumbar sites. The correlation between soil and leaf nutrients was not significant and we found no significant correlations between soil nutrients and CIs. We did not detect any clear association between understorey (L. camara) and soil nutrients. During leaf sampling we found few psyllids but many concealer moth caterpillars. The scarcity of psyllids during sampling, inconclusive nutrient cycling results and nutrient correlations with CI were likely to be due to drought. Resampling under normal weather conditions with more typical organic matter decomposition rates is recommended.     

Retrospective Analyses for Hypothesis Generation A Commentary on the Pack Trial (Prevention of Atherosclerotic Complications with Ketanserin)

Publication of the results of a large-scale randomized control trial (RCT) of the anti-serotonin drug ketanserin in patients with intermittent claudication offers an opportunity to examine the validity of retrospective subgroup analyses to generate hypotheses for further validation. This was prompted by an unanticipated adverse interaction which occurred in a subgroup of patients receiving both ketanserin and potassium-losing diuretics. The quality of the study ranked it in the 99th percentile of over 400 RCTs evaluated by a quality scoring system. The subgroup analysis resulted from the emergence during the study of a highly significant excess mortality in the patients on diuretics (relative risks 0.88 for those on ketanserin alone, 0.95 on potassium-sparing and 2.44 for those on potassium-losing diuretics (P = 0.007). External validity was evident from data in the literature indicating that a rare tendency of the many drugs that prolong the QT interval to cause torsade de pointes and fatal arrhythmias is exacerbated by hypokalemia of the degree caused by potassium losing diuretics. When the keganserin and-placebo treated Ratients also on potassium-losing diuretics are removed from the analyses there is a 23% reduction iri endpoints which the power is no longer sufficient to detect as significant. There is also an apparent lag phase. Further study of the drug is clearly indicated.     

Using VLAD scores to have a look insight ICU performance: towards a modelling of the errors

Rationale, aims and objectives Mortality prediction models using logistic regression analysis play a pivotal role in intensive care quality evaluation, allowing a hospital's performance to be compared with a standard. However, when a difference between predicted and observed mortality exists, that is, the numerator of the Variable Life Adjusted Display (VLAD) score, the investigation for a possible explanation could be arduous. In this article we tested the ability of Bayesian Network (BN) to identify factors determining the negative discrepancy between expected and actual outcomes recorded in four Italian intensive care units (ICUs). Methods A BN was implemented to predict the extent of the expected‐observed distance quantified by the VLAD score. BN performance was compared with those of a set of tools including Linear Model, Random Forest Regression Tree analysis, Artificial Neural Networks and Support Vector Machine. Results BN allows the identification of critical areas responsible for bad performance. Compared with other techniques, BN always explains a higher variance percentage and it shows similar or superior discrimination ability. Conclusions BN, being able to guide interpretation of covariates role by means of a graphic representation of relationships, confirms its utility particularly where many interactions between predictors exist and when a coherent set of theories regarding which variables are related and how is not available.     

EPID对鼻咽癌IMRT随机摆位误差的监测

目的研究电子射野影像装置在鼻咽癌调强放射治疗(IMRT)过程中进行随机摆位误差监测的可行性。方法2006年3月～2007年12月随机抽取鼻咽癌IMRT患者96例,应用EPID在放疗过程中每周拍摄正侧位一次,共拍摄1016张。放疗前先采集CT定位后治疗计划系统中的数字重建射野图像片为参考图像,与治疗过程中实时采集的验证图像配准,测量随机摆位误差。结果在左右、头脚、腹背方向的摆位误差分别是(1.34±1.30)mm,(1.35±1.38)mm,(1.44±1.20)mm。结论EPID的应用可以及时发现放疗随机摆位误差,针对性提高技术员摆位的准确性,是质量控制和质量保证的有力工具。     

Racial and Geographic Differences in Mammography Screening in St. Louis City: A Multilevel Study

To examine racial differences in mammography use and its determinants in the City of St. Louis, MO, USA, we recruited women age 40 or older using random-digit dialing to (1) examine the difference in mammography use between white women and African American women and (2) identify individual- and census-tract-level risk factors of nonadherence to mammography. During telephone interviews, we inquired about mammography use and several demographic, psychosocial, and health behavior variables. We determined the residential census tracts of study subjects using a geographic information system. The rate of mammography use was 68.0% among white women and 74.7% among African American women (P = 0.022). African American women were more likely to have mammograms than white woman (adjusted odds ratio [OR] = 1.71; 95% confidence interval [CI] = 1.09-2.69). System-level barriers to mammography and heavy smoking were associated with lower mammography use among both white and African American women. Personal-experience barriers to mammography and no physician recommendation also were independently associated with mammography use among white women. White women residing within a historic geographic cluster area of late-stage breast cancer were less likely to have mammograms (adjusted OR = 0.42, 95% CI = 0.22-0.80), while African American women residing within a historic geographic cluster area of late-stage breast cancer were equally likely to have mammograms (adjusted OR = 0.79, 95% CI = 0.28-2.24). Neither individual- nor census-tract-level socioeconomic status was associated with mammography screening. These findings suggest that there may be a greater need for increasing mammography use among white women, especially in the historic cluster area of late-stage breast cancer in St. Louis.     

广义线性混合效应模型及其应用

[目的]探讨广义线性混合效应模型在医学研究领域中的作用。[方法]通过实例分析说明模型的实际应用。[结果]将实例中的多中心临床实验数据中不能直观观测到的中心的效应以随机应项纳入型来解决由于来自同一中心可能造成的观测间不独立的问题，模型很好地处理了此类数据。[结论]广义线性混合效应模型可以分析观测间相关、因变量为非正态分布的非独立数据。