Dynamic clinical prediction models for discrete time‐to‐event data with competing risks—A case study on the OUTCOMEREA database

The development of clinical prediction models requires the selection of suitable predictor variables. Techniques to perform objective Bayesian variable selection in the linear model are well developed and have been extended to the generalized linear model setting as well as to the Cox proportional hazards model. Here, we consider discrete time‐to‐event data with competing risks and propose methodology to develop a clinical prediction model for the daily risk of acquiring a ventilator‐associated pneumonia (VAP) attributed to P. aeruginosa (PA) in intensive care units. The competing events for a PA VAP are extubation, death, and VAP due to other bacteria. Baseline variables are potentially important to predict the outcome at the start of ventilation, but may lose some of their predictive power after a certain time. Therefore, we use a landmark approach for dynamic Bayesian variable selection where the set of relevant predictors depends on the time already spent at risk. We finally determine the direct impact of a variable on each competing event through cause‐specific variable selection.     

Evaluation of the phytoremediation potential of Arundo donax L. for nickel-contaminated soil

This study investigates the accumulation and distribution of nickel in Arundo donax L. parts to assess the potential use of this plant in phytoremediation of Ni-contaminated soils. The effect of ethylene diamine tetra-acetic acid (EDTA) and nutrient solution containing NPK on the plant was proped. A 35-day pot experiment was performed in the laboratory and the pots were irrigated with Ni-contaminated solution combined or not with EDTA and NPK. The growth of plants was evaluated at the end of the experiment. The accumulation of Ni was analyzed by atomic absorption spectroscopy (AAS). The obtained results indicate that the plant was able to survive with high Ni content. The growth and the concentrations of Ni in the plant tissues were less affected. In the absence of the amendments, Ni was accumulated in the stems and leaves. However, the addition of NPK significantly reduced Ni concentration in the stems and leaves. The application of EDTA enhanced Ni uptake in roots. The translocation factor (TF) was greater than 1, which categorizes A. donax L. as a great candidate for Ni phytoextraction. A. donax L. is suitable for phytoremediation of Ni. This investigation contributes to the studies on the potential of phytoremediation technologies in Algeria.     

MIC-A allele profiles and HLA class I associations in Behçet's disease

Recently a new family of non-classical MHC molecules, the MHC class I chain-related protein (MIC), encoded by genes located in the major histocompatability complex have been identified. On the basis of the location of MIC genes and the structure and expression of MIC molecules it has been postulated that MIC may be a susceptibility factor in Behçet's disease (BD). We investigated the association of the 16 described external domain alleles and the transmembrane triplet repeats of MIC-A with BD in a Middle Eastern population. DNA from ninety-five patients and 102 age- and sex-matched controls were analyzed by polymerase chain reaction using allele specific primers. Our results show an increase of MIC-A*009 in the BD patient group 44/95 (46%) compared with controls 24/102 (24%) (χ²=11.3, OR=2.8, P=0.00078). MIC-A*009 was also found to be strongly associated with HLA-B51 in the patients 39/44 (88%) when compared with controls 10/24 (42%) (χ²=4, P=0.04). MIC-A*009 was also found in linkage disequilibrium with HLA-B52, but only in controls. The A6 form of a MIC-A transmembrane triplet repeat was found to be significantly raised in the patients (80/95; 84%;) compared with controls (58/102, 57%) (χ²=17.5, OR=4, P=0.000028). Although the MIC-A associations described are highly significant, the association with HLA-B51 independently remains the most significant factor (χ²=56.8, P<10^–6). The data suggests that as both MIC-A*009 and A6 are in strong linkage disequilibrium with HLA-B51, they are unlikely to be the susceptibility gene for BD but may be markers for additional risk factors.     

Optimal conditions for blastogenic response of peripheral blood lymphocytes to T and B cell mitogens in cynomolgus monkeys

Optimal conditions for the mitogen-induced proliferation of T and B lymphocytes of cynomolgus monkeys were determined. The T cell mitogens concanavalin A and phytohemagglutinin, at concentrations of 1.25–10 μg/ml and 1.25–10 μg/ml, respectively, and the T and B cell mitogen pokeweed mitogen, at concentrations of 0.2–10 μg/ml, induced high lymphoproliferative responses, the average stimulation index (SI) being 34–93. Since suitable mitogens have not been reported for monkey B cells, we tested three types of lipopolysaccharide (LPS): two derived from Escherichia coli—one extracted with phenol and one extracted with trichloroacetic acid (TCA); and one derived from Salmonella typhimurium, extracted with phenol. All three LPS had a high mitogenic effect for monkey lymphocytes, with SI of 2.3–6.4. The highest response was observed for 25 μg/ml of Salmonella LPS, and the addition of trypsin to the culture augmented the proliferative response of low or non-responder lymphocytes. © 1994 Wiley-Liss, Inc.