ALBERT

Description: In the marine gastropod Littorina saxatilis differences in relative shell apertural form between two ecotypes from NW Spain have been associated with an environmental cline related to the degree of wave exposure. Such differences have been claimed to have a strong genetic basis, with little influence of phenotypic plasticity. However, dietary changes are expected to affect the growth rate and, potentially, the shell shape, and could thus challenge the adaptive interpretation of the polymorphism. To address this issue we performed a laboratory experiment to grow one of these ecotypes under different food treatments with the aim of testing differences in shell growth. We then investigated the correlation of shell size and shape to quantify the impact of growth on shell aperture. Our results reveal significant dietary effects, an increase in growth rate leading to larger relative apertural size. However, this change occurs in the opposite direction to that expected from the differences between the two ecotypes in nature. This is in line with the low contribution of phenotypic plasticity to the polymorphism observed in previous studies.

Description: The most commonly used biomass estimate for microalgae is obtained from cell biovolume, usually calculated from microscopically measured linear dimensions. Although reliable, this is a highly time-consuming and specialized technique. Automated sampling devices that acquire images of cells and use pattern recognition techniques to identify the images have been developed as an alternative to microscopy-based methods. There are some aspects of automatic sampling and classification methods, however, which can be improved for the analysis of field samples including living and non-living particles. In this work, we demonstrate how the accuracy of a state-of the-art technique for plankton classification (Support Vector Machine) can be improved up to 86% if a previous automated step designed to remove non-living images is included. There is a tendency with the currently applied automatic methods to misestimate cell biovolume due to the two-dimensionality of the images. Here, we present a data set of more than 500 samples to show that the greatest effect is caused by the incorrect estimation of biovolume of the chain-forming diatoms. This results in an overestimate of biomass of between 20 and 100% where chain-forming diatoms represent more than the 20% of the biomass of the sample. We show how the classification method can be adapted to provide not only taxonomic but also the morphological classification of cells in order to obtain a more reliable estimate of biovolume according to the predicted cell shape, in a way comparable with microscopy-based estimates.

Description: Aims Environmental gradients are drivers of species diversity; however, we know relatively little about the evolutionary processes underlying these relationships. A potentially powerful approach to studying diversity gradients is to quantify the phylogenetic structure within and between assemblages arrayed along broad spatial and environmental gradients. Here, we evaluate the phylogenetic structure of plant assemblages along an environmental gradient with the expectation that the habitat specialization of entire lineages is an important evolutionary pattern influencing the structure of tree communities along environmental gradients. Methods We evaluated the effect of several environmental variables on the phylogenetic structure of plant assemblages in 145 plots distributed in northwestern South America that cover a broad environmental gradient. The phylogenetic alpha diversity was quantified for each plot and the phylogenetic beta diversity between each pair of plots was also quantified. Both the alpha and beta diversity measures were then related to spatial and environmental gradients in the study system. Important Findings We found that gradients in temperature and potential evapotranspiration have a strong relationship with the phylogenetic alpha diversity in our study system, with phylogenetic overdispersion in low temperatures and phylogenetic clustering at higher temperatures. Further, the phylogenetic beta diversity between two plots increases with an increasing difference in temperature, whereas annual precipitation was not a significant predictor of community phylogenetic turnover. We also found that the phylogenetic structure of the plots in our study system was related to the degree of seasonal flooding and seasonality in precipitation. In particular, more stressful environments such as dry forests and flooded forests showed phylogenetic clustering. Finally, in contrast with previous studies, we find that phylogenetic beta diversity was not strongly related to the spatial distance separating two forest plots, which may be the result of the importance of the three independent mountain ranges in our study system, which generate a high degree of environmental variation over very short distances. In conclusion, we found that environmental gradients are important drivers of both phylogenetic alpha and phylogenetic beta diversities in these forests over spatial distance.

Description: Hyaluronan (HA) is one of the major components of the extracellular matrix. Several solid tumors produce high levels of HA, which promotes survival and multidrug resistance (MDR). HA oligomers (oHAs) can block HA effects. However, little is known about the role of HA in hematological malignancies. The aim of this work was to determine whether HA or its oligomers can modulate the proliferation of leukemia cells as well as their effect on MDR. Receptors and signaling pathways involved were also analyzed. For this purpose, the human leukemic cell lines K562 and Kv562, which are sensitive and resistant to Vincristine (VCR), respectively, were used. We demonstrated that HA induced cell proliferation in both cell lines. On K562 cells, this effect was mediated by cluster differentiation 44 (CD44) and activation of both phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) and mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) pathways, whereas on Kv562 cells, the effect was mediated by receptor for hyaluronan-mediated motility (RHAMM) and PI3K/Akt activation. The inhibition of HA synthesis by 4-methylumbelliferone (4MU) decreased cell line proliferation and sensitized Kv562 to the effect of VCR through P-glycoprotein (Pgp) inhibition, in both cases with senescence induction. Moreover, oHAs inhibited K562 proliferation mediated by CD44 as well as Akt and ERK down-regulation. Furthermore, oHAs sensitized Kv562 cells to VCR by Pgp inhibition inducing senescence. We postulate that the synthesis of HA would promote leukemia progression mediated by the triggering of the above-mentioned proliferative signals. These findings highlight the potential use of oHAs and 4MU as coadjuvant for drug-resistant leukemia.

Description: Samples from a monthly monitoring programme in the Cantabrian Sea were analysed with a FlowCAM-based automated technique. The estimates of abundance, biomass size spectra and taxonomic diversity of nano- and microplankton communities were compared with those obtained by traditional microscopical analysis of the same samples. The structure and abundance of a preserved plankton sample determined using FlowCAM showed minimal differences compared with traditional microscopical estimates. The effects of sample preservation and inaccuracies in the automatic classification are the main causes of discrepancies in the size structure determination between the two approaches. However, the synoptic understanding of the seasonal variation in the abundance, biomass and diversity obtained from the two methods is similar. Our results suggest that the natural variations in the community attributes explored are of greater magnitude than the error introduced by the methods and that the fully automatic method is adequate to explore these variations.