Elevation of the Extracellular Concentrations of Glutamate and Aspartate in Rat Hippocampus During Transient Cerebral Ischemia Monitored by Intracerebral Microdialysis

Rats were implanted with 0.3-mm-diameter dialysis tubing through the hippocampus and subsequently perfused with Ringer's solution at a flow rate of 2 microliter/min. Samples of the perfusate representing the extracellular fluid were collected over 5-min periods and subsequently analyzed for contents of the amino acids glutamate, aspartate, glutamine, taurine, alanine, and serine. Samples were collected before, during, and after a 10-min period of transient complete cerebral ischemia. The extracellular contents of glutamate and aspartate were increased, respectively, eight- and threefold during the ischemic period; the taurine concentration also was increased 2.6-fold. During the same period the extracellular content of glutamine was significantly decreased (to 68% of the control value), whereas the concentrations of alanine and serine did not change significantly during the ischemic period. The concentrations of gamma-aminobutyric acid (GABA) were too low to be measured reliably. It is suggested that the large increase in the content of extracellular glutamate and aspartate in the hippocampus induced by the ischemia may be one of the causal factors in the damage to certain neurons observed after ischemia.     

Timing and abundance as key mechanisms affecting trophic interactions in variable environments

Climatic changes are disrupting otherwise tight trophic interactions between predator and prey. Most of the earlier studies have primarily focused on the temporal dimension of the relationship in the framework of the match–mismatch hypothesis. This hypothesis predicts that predator's recruitment will be high if the peak of the prey availability temporally matches the most energy‐demanding period of the predators breeding phenology. However, the match–mismatch hypothesis ignores the level of food abundance while this can compensate small mismatches. Using a novel time‐series model explicitly quantifying both the timing and the abundance component for trophic relationships, we here show that timing and abundance of food affect recruitment differently in a marine (cod/zooplankton), a marine–terrestrial (puffin/herring) and a terrestrial (sheep/vegetation) ecosystem. The quantification of the combined effect of abundance and timing of prey on predator dynamics enables us to come closer to the mechanisms by which environment variability may affect ecological systems.     

Moth species richness,abundance and diversity in fragmented urban woodlands: implications for conservation and management strategies

Urban expansion threatens global biodiversity through the destruction of natural and semi-natural habitats and increased levels of disturbance. Whilst woodlands in urban areas may reduce the impact of urbanisation on biodiversity, they are often subject to under or over-management and consist of small, fragmented patches which may be isolated. Effective management strategies for urban woodland require an understanding of the ecology and habitat requirements of all relevant taxa. Yet, little is known of how invertebrate, and in particular moth, assemblages utilise urban woodland despite being commonly found within the urban landscape. Here we show that the abundance, species richness, and species diversity of moth assemblages found within urban woodlands are determined by woodland vegetation character, patch configuration and the surrounding landscape. In general, mature broadleaved woodlands supported the highest abundance and diversity of moths. Large compact woodlands with proportionally less edge exposed to the surrounding matrix were associated with higher moth abundance than small complex woodlands. Woodland vegetation characteristics were more important than the surrounding landscape, suggesting that management at a local scale to ensure provision of good quality habitat may be relatively more important for moth populations than improving habitat connectivity across the urban matrix. Our results show that the planting of broadleaved woodlands, retaining mature trees and minimising woodland fragmentation will be beneficial for moth assemblages.     

Rarely successful polyploids and their legacy in plant genomes

Polyploidy, or whole genome duplication, is recognized as an important feature of eukaryotic genome evolution. Among eukaryotes, polyploidy has probably had the largest evolutionary impact on vascular plants where many contemporary species are of recent polyploid origin. Genomic analyses have uncovered evidence of at least one round of polyploidy in the ancestry of most plants, fueling speculation that genome duplications lead to increases in net diversity. In spite of the frequency of ancient polyploidy, recent analyses have found that recently formed polyploid species have higher extinction rates than their diploid relatives. These results suggest that despite leaving a substantial legacy in plant genomes, only rare polyploids survive over the long term and most are evolutionary dead-ends.     

Process monitoring of virus-like particle reassembly by diafiltration with UV/Vis spectroscopy and light scattering

Virus-like particles (VLPs) have shown great potential as biopharmaceuticals in the market and in clinics. Nonenveloped, in vivo assembled VLPs are typically disassembled and reassembled in vitro to improve particle stability, homogeneity, and immunogenicity. At the industrial scale, cross-flow filtration (CFF) is the method of choice for performing reassembly by diafiltration. Here, we developed an experimental CFF setup with an on-line measurement loop for the implementation of process analytical technology (PAT). The measurement loop included an ultraviolet and visible (UV/Vis) spectrometer as well as a light scattering photometer. These sensors allowed for monitoring protein concentration, protein tertiary structure, and protein quaternary structure. The experimental setup was tested with three Hepatitis B core Antigen (HBcAg) variants. With each variant, three reassembly processes were performed at different transmembrane pressures (TMPs). While light scattering provided information on the assembly progress, UV/Vis allowed for monitoring the protein concentration and the rate of VLP assembly based on the microenvironment of Tyrosine-132. VLP formation was verified by off-line dynamic light scattering (DLS) and transmission electron microscopy (TEM). Furthermore, the experimental results provided evidence of aggregate-related assembly inhibition and showed that off-line size-exclusion chromatography does not provide a complete picture of the particle content. Finally, a Partial-Least Squares (PLS) model was calibrated to predict VLP concentrations in the process solution. values of 0.947–0.984 were reached for the three HBcAg variants. In summary, the proposed experimental setup provides a powerful platform for developing and monitoring VLP reassembly steps by CFF.     

Prescribing diatom morphology: toward genetic engineering of biological nanomaterials

The formation of inorganic materials with complex form is a widespread biological phenomenon (biomineralization). Among the most spectacular examples of biomineralization is the production by diatoms (a group of eukaryotic microalgae) of intricately nanopatterned to micropatterned cell walls made of silica (SiO2). Understanding the molecular mechanisms of diatom silica biomineralization is not only a fundamental biological problem, but also of great interest in materials engineering, as the biological self-assembly of three-dimensional (3D) inorganic nanomaterials has no man-made analog. Recently, insight into the molecular mechanism of diatom silica formation has been obtained by structural and functional analysis of biomolecules that are involved in this process. Furthermore, the rapid development of diatom molecular genetics has provided new tools for investigating the silica forming machinery of diatoms and for manipulating silica biogenesis. This has opened the door for the production, through genetic engineering, of unique 3D nanomaterials with designed structures and functionalities.     

Stopping vs. staging: the difference between a hop and a jump

Places where migrant birds stop to rest, drink, and eat at are often described as either stopover or staging sites. Attempts have been made to differentiate between these two terms but they are frequently used interchangeably. Some authors have equated staging sites with sites that attract large concentrations (many thousands) of birds, a definition that others have expanded to include long stopover durations and significant rates of refueling on predictable, abundant prey. It has also been suggested that birds using staging sites are those that employ a jumping strategy during migration. I argue that while all sites where birds rest and feed during migration are stopover sites, further classification of stopover sites is of ecological and conservation value. I propose that sites with abundant, predictable food resources where birds prepare for an energetic challenge (usually a long flight over a barrier such as an ocean or a desert) requiring substantial fuel stores and physiological changes without which significant fitness costs are incurred are most appropriately described as staging sites.     

Can the meiotic sex ratio explain the sex ratio bias in adult populations in the dioicous moss Drepanocladus lycopodioides?

Sex ratio variation is commonly observed in natural populations of many organisms with separate sexes and genetic sex determination, including bryophytes. Most bryophyte populations exhibit female-skewed expressed adult sex ratios, generally inferred from counts of sexually mature plants. For the rarely sexually reproducing perennial dioicous moss Drepanocladus lycopodioides, we showed that a female bias also exists in the genetic adult sex ratio, using a specifically designed molecular sex-associated marker. Here, we investigated whether the meiotic spore sex ratio contributes to the observed bias in genetic adult sex ratio in natural populations. Earlier attempts to study meiotic sex ratios have involved commonly cultivated ruderals that rapidly express sex in the laboratory. We established single-spore cultures from field-collected sporophytes from these populations and used the marker to assess the sex of individual sporelings. Spore germinability was (near) complete, and mortality among sporelings was virtually absent. The true meiotic sex ratio did not differ from equality, but strongly differed both from the observed genetic sex ratios in the natural adult populations, and from the European scale genetic sex ratio. We conclude that the biased population sex ratios in this species arise at life cycle stages after spore germination. Sexual dimorphism may selectively favour female proliferation during some phase of gametophyte development. Based on methodological progress, we successfully used a perennial study species with rare sexual reproduction, which significantly broadens the life history spectrum investigated in bryophyte sex ratio studies.