Data-adaptive longitudinal model selection in causal inference with collaborative targeted minimum loss-based estimation

Causal inference methods have been developed for longitudinal observational study designs where confounding is thought to occur over time. In particular, one may estimate and contrast the population mean counterfactual outcome under specific exposure patterns. In such contexts, confounders of the longitudinal treatment-outcome association are generally identified using domain-specific knowledge. However, this may leave an analyst with a large set of potential confounders that may hinder estimation. Previous approaches to data-adaptive model selection for this type of causal parameter were limited to the single time-point setting. We develop a longitudinal extension of a collaborative targeted minimum loss-based estimation (C-TMLE) algorithm that can be applied to perform variable selection in the models for the probability of treatment with the goal of improving the estimation of the population mean counterfactual outcome under a fixed exposure pattern. We investigate the properties of this method through a simulation study, comparing it to G-Computation and inverse probability of treatment weighting. We then apply the method in a real-data example to evaluate the safety of trimester-specific exposure to inhaled corticosteroids during pregnancy in women with mild asthma. The data for this study were obtained from the linkage of electronic health databases in the province of Quebec, Canada. The C-TMLE covariate selection approach allowed for a reduction of the set of potential confounders, which included baseline and longitudinal variables.     

High-throughput single nucleotide polymorphism genotyping in wheat (Triticum spp.)

Over the past few years, considerable progress has been made in high-throughput single nucleotide polymorphism (SNP) genotyping technologies, largely through the investment of the human genetics community. These technologies are well adapted to diploid species. For plant breeding purposes, it is important to determine whether these genotyping methods are adapted to polyploidy, as most major crops are former or recent polyploids. To address this problem, we tested the capacity of the multiplex technology SNPlex™ with a set of 47 wheat SNPs to genotype DNAs of 1314 lines that were organized in four 384-well plates. These lines represented different taxa of tetra- and hexaploid Triticum species and their wild diploid relatives. We observed 40 markers which gave less than 20% missing data. Different methods, based on either Sanger sequencing or the MassARRAY^® genotyping technology, were then used to validate the genotypes obtained by SNPlex™ for 11 markers. The concordance of the genotypes obtained by SNPlex™ with the results obtained by the different validation methods was 96%, except for one discarded marker. Furthermore, a mapping study on six markers showed the expected genetic positions previously described. To conclude, this study showed that high-throughput genotyping technologies developed for diploid species can be used successfully in polyploids, although there is a need for manual reading. For the first time in wheat species, a core of 39 SNPs is available that can serve as the basis for the development of a complete SNPlex™ set of 48 markers.     

Nucleotide sequence of a regulatory region of the uidA gene in Escherichia coli K12

Summary Multiple regulatory events are involved in the expression of the uidA gene. A regulatory region of this gene has been located on a 460 base pair Sau3A-EcoRI fragment and its nucleotide sequence was determined by the dideoxy method using pEMBL plasmids. A preliminary analysis of this sequence revealed the presence of numerous palindromic structures with some overlaps.     

Crab cryptofauna (Brachyura and Anomura) of Tikehau,Tuamotu Archipelago,French Polynesia

A detailed survey of the carcinological cryptofauna in Tikehau atoll in the Tuamotus, was made: (1) to determine whether Tikehau atoll has a diverse fauna; (2) to compare it with a high island Polynesian reef; (3) to identify the distribution pattern of crabs in relation to depth and to different structures of the atoll; and (4) to compare these results with those obtained in Madagascar, La Réunion and Mauritius. Sixty five species were collected at 13 sites. Cluster analysis based on Sanders' index of affinity revealed one main group of species occurring on outer slopes and another occurring on all reef-flat and lagoonal sites. The crustacean cryptofauna occurring in the atoll appears to be impoverished in comparison to that found on Polynesian high island reefs and on Malagasian reefs. However, all outer reef slope sites at the 3 localities studied share some species in common.