Teleost polarization vision: how it might work and what it might be good for

In this review, we will discuss the recent literature on fish polarization vision and we will present a model on how the retina processes polarization signals. The model is based on a general retinal-processing scheme and will be compared with the available electrophysiological data on polarization processing in the retina. The results of this model will help illustrate the functional significance of polarization vision for both feeding behaviour and navigation. First, we examine the linkage between structure and function in polarization vision in general.     

Long‐term allelopathic control of phytoplankton by the submerged macrophyte Elodea nuttallii

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The effect of leg preference on postural stability in healthy athletes

In research regarding postural stability, leg preference is often tested and controlled for. However, leg preference may vary between tasks. As athletes are a group of interest for postural stability testing, we evaluated the effect of five leg preference tasks categorization (step up, hop, ball kick, balance, pick up) on single-leg postural stability of 16 field hockey athletes. The ‘center of pressure speed’ was calculated as the primary outcome variable of single-leg postural stability. Secondary variables were ‘mean length of the GRF vector in the horizontal plane’, ‘mean length of the ankle angular velocity vector’, and ‘mean length of the hip angular velocity vector’, as well as the separate outcomes per degree of freedom. Results showed that leg preference was inconsistent between leg preference tasks. Moreover, the primary and secondary variables yielded no significant difference between the preferred and non-preferred legs, regardless of the applied leg preference task categorization (p>0.05). The present findings do not support the usability of leg preference tasks in controlling for bias of postural stability. In conclusion, none of the applied leg preference tasks revealed a significant effect on postural stability in healthy field hockey athletes.     

Snapshots of pre-rRNA structural flexibility reveal eukaryotic 40S assembly dynamics at nucleotide resolution

Ribosome assembly in eukaryotes involves the activity of hundreds of assembly factors that direct the hierarchical assembly of ribosomal proteins and numerous ribosomal RNA folding steps. However, detailed insights into the function of assembly factors and ribosomal RNA folding events are lacking. To address this, we have developed ChemModSeq, a method that combines structure probing, high-throughput sequencing and statistical modeling, to quantitatively measure RNA structural rearrangements during the assembly of macromolecular complexes. By applying ChemModSeq to purified 40S assembly intermediates we obtained nucleotide-resolution maps of ribosomal RNA flexibility revealing structurally distinct assembly intermediates and mechanistic insights into assembly dynamics not readily observed in cryo-electron microscopy reconstructions. We show that RNA restructuring events coincide with the release of assembly factors and predict that completion of the head domain is required before the Rio1 kinase enters the assembly pathway. Collectively, our results suggest that 40S assembly factors regulate the timely incorporation of ribosomal proteins by delaying specific folding steps in the 3′ major domain of the 20S pre-ribosomal RNA.     

Towards mapping the late Quaternary vegetation change of Europe

The number of well-dated pollen diagrams in Europe has increased considerably over the last 30 years and many of them have been submitted to the European Pollen Database (EPD). This allows for the construction of increasingly precise maps of Holocene vegetation change across the continent. Chronological information in the EPD has been expressed in uncalibrated radiocarbon years, and most chronologies to date are based on this time scale. Here we present new chronologies for most of the datasets stored in the EPD based on calibrated radiocarbon years. Age information associated with pollen diagrams is often derived from the pollen stratigraphy itself or from other sedimentological information. We reviewed these chronological tie points and assigned uncertainties to them. The steps taken to generate the new chronologies are described and the rationale for a new classification system for age uncertainties is introduced. The resulting chronologies are fit for most continental-scale questions. They may not provide the best age model for particular sites, but may be viewed as general purpose chronologies. Taxonomic particularities of the data stored in the EPD are explained. An example is given of how the database can be queried to select samples with appropriate age control as well as the suitable taxonomic level to answer a specific research question.     

Acclimation effects of heat waves and elevated [CO2] on gas exchange and chlorophyll fluorescence of northern red oak (Quercus rubra L.) seedlings

Heat wave frequency and intensity are predicted to increase. We investigated whether repeated exposure to heat waves would induce acclimation in Quercus rubra seedlings and considered [CO₂] as an interacting factor. We measured gas exchange and chlorophyll fluorescence of seedlings grown in 380 (C _A) or 700 (C _E) μmol CO₂ mol^?1, and three temperature treatments (ambient, ambient +3 °C, and an ambient +12 °C heat wave every fourth week). Measurements were performed during the third and fourth +12 °C heat waves (July and August 2010) at Whitehall Forest, GA, USA. Additionally, previously unexposed seedlings were subjected to the August heat wave to serve as a control to determine acclimation of seedlings which were previously exposed. Seedlings with a history of heat wave exposure showed lower net photosynthesis (A _net) and stomatal conductance (on average ?47 and ?38 %, respectively) than seedlings with no such history, when both were subjected to the same +12 °C heat wave. During both heat waves, A _net significantly declined in the +12 °C treatment compared with the other treatments. Additionally, the A _net decline during the August compared with the July heat wave was stronger in C _E than in C _A, suggesting that elevated [CO₂] might have had a negative effect on acclimation capacity. We conclude that seedlings subjected to consecutive heat waves will moderate stomatal conductance outside the heat wave, to reduce water usage at lower temperatures, increasing survival at the expense of carbon assimilation.