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1.
In clinical and epidemiological studies, there is a growing interest in studying the heterogeneity among patients based on longitudinal characteristics to identify subtypes of the study population. Compared to clustering a single longitudinal marker, simultaneously clustering multiple longitudinal markers allow additional information to be incorporated into the clustering process, which reveals co-existing longitudinal patterns and generates deeper biological insight. In the current study, we propose a Bayesian consensus clustering (BCC) model for multivariate longitudinal data. Instead of arriving at a single overall clustering, the proposed model allows each marker to follow marker-specific local clustering and these local clusterings are aggregated to find a global (consensus) clustering. To estimate the posterior distribution of model parameters, a Gibbs sampling algorithm is proposed. We apply our proposed model to the primary biliary cirrhosis study to identify patient subtypes that may be associated with their prognosis. We also perform simulation studies to compare the clustering performance between the proposed model and existing models under several scenarios. The results demonstrate that the proposed BCC model serves as a useful tool for clustering multivariate longitudinal data. 相似文献
2.
Ariel Paracampo Marina Solis Carlos Bonetto 《International journal of environmental health research》2015,25(1):96-103
Chlorpyrifos is the most used insecticide in Argentina. Cnesterodon decemmaculatus is a widely distributed, endemic fish from Neotropical America. It attains high densities in the shallow water assemblages of Argentina and Brazil. The aim of this study was to assess the acute toxicity of chlorpyrifos to C. decemmaculatus. The mean 96-h LC50 of three independent determinations was 105.3 (±?3.1) μg/L. Sublethal effects were observed. Swimming behavioral changes at each chlorpyrifos exposure concentration were reported. C. decemmaculatus represents a good model for ecotoxicological risk assessment. 相似文献
3.
Questionnaire data may contain missing values because certain questions do not apply to all respondents. For instance, questions addressing particular attributes of a symptom, such as frequency, triggers or seasonality, are only applicable to those who have experienced the symptom, while for those who have not, responses to these items will be missing. This missing information does not fall into the category ‘missing by design’, rather the features of interest do not exist and cannot be measured regardless of survey design. Analysis of responses to such conditional items is therefore typically restricted to the subpopulation in which they apply. This article is concerned with joint multivariate modelling of responses to both unconditional and conditional items without restricting the analysis to this subpopulation. Such an approach is of interest when the distributions of both types of responses are thought to be determined by common parameters affecting the whole population. By integrating the conditional item structure into the model, inference can be based both on unconditional data from the entire population and on conditional data from subjects for whom they exist. This approach opens new possibilities for multivariate analysis of such data. We apply this approach to latent class modelling and provide an example using data on respiratory symptoms (wheeze and cough) in children. Conditional data structures such as that considered here are common in medical research settings and, although our focus is on latent class models, the approach can be applied to other multivariate models. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
4.
Akira Ishih Toshio Miyase Tohru Suzuki Francis W. Muregi Mamoru Terada 《Journal of natural medicines》2007,61(2):213-216
Febrifugine and isofebrifugine alkaloid mixtures extracted from the leaves and buds of Hydrangea macrophylla var. Otaksa, collected during different months, in Japan, were quantified using high-performance liquid chromatography. Leaves collected
during the flowering season, namely from June to August, contained 0.16–0.31 mg/g of the alkaloid mixture, whereas those collected
from September to December had less than 0.03 mg/g of the mixture. However, extracts of buds harvested from October to February
contained a consistently larger amount (more than 0.49 mg/g) of the alkaloids. Hot-water extracts from the leaves and buds
collected during different seasons were evaluated for antimalarial activity against Plasmodium yoelii 17XL in mice. The extract of leaves collected in August demonstrated high antimalarial activity, and all mice that received
the extract survived the infection. In contrast, the extract of leaves collected in December showed little activity. The extract
of buds collected in December cleared parasites, but with subsequent mortality to mouse. The present results show that the
amount of antimalarial agent—febrifugine and isofebrifugine mixture—in H. macrophylla var. Otaksa is both part- and season-dependent, suggesting that the choice of plant parts and their harvesting season are important factors
worth considering in the pharmacological use of medicinal plants. 相似文献
5.
12种中草药的乙醇提取液对印鼠客蚤的毒效研究 总被引:4,自引:1,他引:3
目的:探讨中草药灭蚤的可行性。方法:用乙醇提出12种中草药的可溶成分,以瓶膜法测定其对印鼠客蚤的毒力。结果:在0.5g/ml(生药)的浓度下,10种中草药对印鼠客蚤有速效击倒作用,其中鸡血藤、巴豆仁、除虫菊花的10min击倒率大于50%;5种中草药的KD_(50)小于15min,比2%DDVP为优;巴豆仁接触30min恢复24h死亡率为70%。结论:除虫菊花、黎芦、鸡血藤、巴豆仁、贯众用于杀蚤有一定价值。 相似文献
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8.
致倦库蚊有机磷抗性相关扩增酯酶B基因的多样性 总被引:5,自引:0,他引:5
本实验从佛山和成都两地的致倦库蚊群体中筛选出3个酯酶类型不同的有机磷(OP)抗性品系,FS-1、FS-2和CD-1品系。各品系的酯酶基因B扩增水平、酯酶活性和OP抗性水平三者一致。各品系酯酶B基因限制性酶切片段比较分析表明,我国的OP抗生库蚊群体中不仅有世界性分布的酯酶B1和B2,而且在佛山和成都地区各有一个新的独立扩增的酯酶B,分别命名为B6和B7。 相似文献
9.
温经化瘀合剂临床疗效观察与研究 总被引:1,自引:0,他引:1
张华山 《浙江中医药大学学报》2004,28(1):27-30
目的:验证"温经化瘀舍剂"对妇女寒凝血瘀型痛经的治疗效果;方法:将符合中医诊断标准寒凝血瘀型痛经患者,随机分为2组,分别给予"温经化瘀合剂"和"痛经宁冲剂"进行治疗;结果:治疗组总有效率达95%,对照组总有效率80.5%,治疗组优于对照组,治疗组痊愈率48.3%,对照组痊愈率14.6%,治疗组明显优于对照组.实验动物无明显急性毒性反应,能减轻二甲苯引起的小鼠耳肿胀度,减少缩宫素所致大鼠扭体反应次数,和前列腺素E1所致小鼠扭体反应次数,对大鼠离体子宫有双向调节作用,证明"温经化瘀舍剂"具有镇痛、抗炎作用. 相似文献
10.