Reliability analysis of semi-automatic train door systems in service on today's rolling stock of the SNCB

This article analyses the reliability of semi-automatic train door systems that are in use on today’s rolling stock of the SNCB. For the analysis several databases of the SNCB concerning both operation and maintenance were thoroughly screened. These databases are briefly explained and scaling factors are applied to compare the performance of different series of rolling stock relative to each other. Conclusions are made out of the available data

Local genetic adaptation to grazing pressure of the green alga Desmodesmus armatus in a strongly connected pond system

Dispersal potentially homogenizes genetic variation among populations and thus may prevent local genetic adaptation. If selection gradients are strong and the selection response efficient, however, local genetic adaptation may persist in the face of high dispersal rates. We compared grazing-resistance traits among populations of the green microalga Desmodesmus armatus, which inhabit ponds that are ecologically different but part of a strongly interconnected pond system. Desmodesmus clones were isolated from a clear-water and a turbid pond. For 16 clones from an internal transcribed spacer 2 clade with low sequence variation (1.3%) corresponding morphologically to D. armatus, coenobial dimensions and the average number of cells per coenobium, in both the absence and the presence of water conditioned by their main grazer, the waterflea Daphnia, were determined. Clones from the clear-water pond had four-celled coenobia with a higher greatest axial linear dimension and an increased average number of cells per coenobium in response to Daphnia kairomone, contrary to clones from the turbid pond. Unexpectedly, they were also characterized by a lower average number of cells per coenobium. No differences among populations were detected for cell length. Genetic variation was present in both populations for all traits, except for the response to kairomone. Continuous dispersal through overflows and rivulets in this pond system is thus incapable of preventing strong among-population genetic differentiation for ecological relevant traits, testifying both to the capacity of phytoplankton populations to adapt to local conditions and to the importance of grazing as a structuring factor in natural phytoplankton populations

Evaluating predictive markers for viral rebound and safety assessment in blood and lumbar fluid during HIV-1 treatment interruption

Background: Validated biomarkers to evaluate HIV-1 cure strategies are currently lacking, therefore requiring analytical treatment interruption (ATI) in study participants. Little is known about the safety of ATI and its long-term impact on patient health. Objectives: ATI safety was assessed and potential biomarkers predicting viral rebound were evaluated. Methods: PBMCs, plasma and CSF were collected from 11 HIV-1-positive individuals at four different timepoints during ATI (NCT02641756). Total and integrated HIV-1 DNA, cell-associated (CA) HIV-1 RNA transcripts and restriction factor (RF) expression were measured by PCR-based assays. Markers of neuroinflammation and neuronal injury [neurofilament light chain (NFL) and YKL-40 protein] were measured in CSF. Additionally, neopterin, tryptophan and kynurenine were measured, both in plasma and CSF, as markers of immune activation. Results: Total HIV-1 DNA, integrated HIV-1 DNA and CA viral RNA transcripts did not differ pre- and post-ATI. Similarly, no significant NFL or YKL-40 increases in CSF were observed between baseline and viral rebound. Furthermore, markers of immune activation did not increase during ATI. Interestingly, the RFs SLFN11 and APOBEC3G increased after ATI before viral rebound. Similarly, Tat-Rev transcripts were increased preceding viral rebound after interruption. Conclusions: ATI did not increase viral reservoir size and it did not reveal signs of increased neuronal injury or inflammation, suggesting that these well-monitored ATIs are safe. Elevation of Tat-Rev transcription and induced expression of the RFs SLFN11 and APOBEC3G after ATI, prior to viral rebound, indicates that these factors could be used as potential biomarkers predicting viral rebound

Removal of the N-glycosylation sequon at position N116 located in p27 of the respiratory syncytial virus fusion protein elicits enhanced antibody responses after DNA immunization

Prevention of severe lower respiratory tract infections in infants caused by the human respiratory syncytial virus (hRSV) remains a major public health priority. Currently, the major focus of vaccine development relies on the RSV fusion (F) protein since it is the main target protein for neutralizing antibodies induced by natural infection. The protein conserves 5 N-glycosylation sites, two of which are located in the F2 subunit (N27 and N70), one in the F1 subunit (N500) and two in the p27 peptide (N116 and N126). To study the influence of the loss of one or more N-glycosylation sites on RSV F immunogenicity, BALB/c mice were immunized with plasmids encoding RSV F glycomutants. In comparison with F WT DNA immunized mice, higher neutralizing titres were observed following immunization with F N116Q. Moreover, RSV A2-K-line19F challenge of mice that had been immunized with mutant F N116Q DNA was associated with lower RSV RNA levels compared with those in challenged WT F DNA immunized animals. Since p27 is assumed to be post-translationally released after cleavage and thus not present on the mature RSV F protein, it remains to be elucidated how deletion of this glycan can contribute to enhanced antibody responses and protection upon challenge. These findings provide new insights to improve the immunogenicity of RSV F in potential vaccine candidates

Body size and dispersal mode as key traits determining metacommunity structure of aquatic organisms

Relationships between traits of organisms and the structure of their metacommunities have so far mainly been explored with meta-analyses. We compared metacommunities of a wide variety of aquatic organism groups (12 groups, ranging from bacteria to fish) in the same set of 99 ponds to minimise biases inherent to meta-analyses. In the category of passive dispersers, large-bodied groups showed stronger spatial patterning than small-bodied groups suggesting an increasing impact of dispersal limitation with increasing body size. Metacommunities of organisms with the ability to fly (i.e. insect groups) showed a weaker imprint of dispersal limitation than passive dispersers with similar body size. In contrast, dispersal movements of vertebrate groups (fish and amphibians) seemed to be mainly confined to local connectivity patterns. Our results reveal that body size and dispersal mode are important drivers of metacommunity structure and these traits should therefore be considered when developing a predictive framework for metacommunity dynamics

Lack of Phylogeographic Structure in the Freshwater Cyanobacterium Microcystis aeruginosa Suggests Global Dispersal

Background : Free-living microorganisms have long been assumed to have ubiquitous distributions with little biogeographic signature because they typically exhibit high dispersal potential and large population sizes. However, molecular data provide contrasting results and it is far from clear to what extent dispersal limitation determines geographic structuring of microbial populations. We aimed to determine biogeographical patterns of the bloom-forming freshwater cyanobacterium Microcystis aeruginosa. Being widely distributed on a global scale but patchily on a regional scale, this prokaryote is an ideal model organism to study microbial dispersal and biogeography. Methodology/Principal Findings : The phylogeography of M. aeruginosa was studied based on a dataset of 311 rDNA internal transcribed spacer (ITS) sequences sampled from six continents. Richness of ITS sequences was high (239 ITS types were detected). Genetic divergence among ITS types averaged 4% (maximum pairwise divergence was 13%). Preliminary analyses revealed nearly completely unresolved phylogenetic relationships and a lack of genetic structure among all sequences due to extensive homoplasy at multiple hypervariable sites. After correcting for this, still no clear phylogeographic structure was detected, and no pattern of isolation by distance was found on a global scale. Concomitantly, genetic differentiation among continents was marginal, whereas variation within continents was high and was mostly shared with all other continents. Similarly, no genetic structure across climate zones was detected. Conclusions/Significance : The high overall diversity and wide global distribution of common ITS types in combination with the lack of phylogeographic structure suggest that intercontinental dispersal of M. aeruginosa ITS types is not rare, and that this species might have a truly cosmopolitan distribution

Priority effects in experimental populations of the cyanobacterium Microcystis

The arrival order of colonists in developing populations can have a lasting influence on community and population structure, a phenomenon referred to as priority effects. To explore whether such priority effects are important in determining strain composition of populations of the cyanobacterium Microcystis, four Microcystis strains, isolated from a single lake and differing in functional traits, were grown during 4 weeks in the laboratory in all possible pairwise combinations, with the two strains either inoculated at the same time or with a time lag of 1 week, in the presence or absence of grazing Daphnia magna. The relative abundance of strains in the mixtures was assessed using denaturing gradient gel electrophoresis, and the growth rate of each strain in the mixtures was determined for the last 2 weeks of the experiment. We observed strong effects of inoculation order on the final population structure, and these effects were influenced by grazing Daphnia. The priority effects were strain-specific and occurred in two directions: some of the strains grew slower while others grew faster when inoculated second compared with when inoculated first. Our results indicate that priority effects may have a profound impact on strain composition of Microcystis populations

Trophic coupling in the microbial food web of a eutrophic shallow lake (Lake Visvijver, Belgium)

Two fractionation experiments were carried out to study trophic interactions in the microbial food web in the shallow eutrophic lake Visvijver. Despite an order of magnitude difference in biomass of bacteria, heterotrophic nanoflagellates (HNF) and ciliates between the two experiments, the trophic interactions observed were similar. Bacteria were consumed by HNF and oligotrich ciliates, oligotrich ciliates fed on HNF as well as bacteria and cyclopoid copepod nauplii preyed on the oligotrich ciliates. While cyclopoid copepods had no effect on any component of the microbial food web, Daphnia fed on bacteria and HNF. No or a weak and slow trophic cascade occurred from oligotrich ciliates to HNF and bacteria. The lack of a pronounced trophic cascade was ascribed to the importance of the omnivorous oligotrich ciliates in the microbial food web. In both experiments, removal of trophic levels by size fractionation resulted in changes in the identity of the dominant bacterivores, but this had little effect on total bacterial grazing losses. Bacterial community composition (monitored in the second experiment using DGGE analysis), on the contrary, was more strongly influenced by changes in the identity of the dominant bacterivores, suggesting the presence of a 'cryptic trophic cascade'