Activation of EphA receptor tyrosine kinase inhibits the Ras/MAPK pathway

Interactions between Eph receptor tyrosine kinases (RTKs) and membrane-anchored ephrin ligands critically regulate axon pathfinding and development of the cardiovascular system, as well as migration of neural cells. Similar to other RTKs, ligand-activated Eph kinases recruit multiple signalling and adaptor proteins, several of which are involved in growth regulation. However, in contrast to other RTKs, activation of Eph receptors fails to promote cell proliferation or to transform rodent fibroblasts, indicating that Eph kinases may initiate signalling pathways that are distinct from those transmitted by other RTKs. Here we show that stimulation of endogenous EphA kinases with ephrin-A1 potently inhibits the Ras/MAPK cascade in a range of cell types, and attenuates activation of mitogen-activated protein kinase (MAPK) by receptors for platelet-derived growth factor (PDGF), epidermal growth factor (EGF) and vascular endothelial growth factor (VEGF). In prostatic epithelial cells and endothelial cells, but not fibroblasts, treatment with ephrin-A1 inhibits cell proliferation. Our results identify EphA kinases as negative regulators of the Ras/MAPK pathway that exert anti-mitogenic functions in a cell-type-specific manner.     

Effect of peptidyltransferase inhibitors on ribonuclease P activity from Dictyostelium discoideum – Effect of antibiotics on RNase P

The effect of several peptidyltransferase inhibitors on ribonuclease P activity from Dictyostelium discoideum was investigated. Among the inhibitors tested puromycin, amicetin and blasticidin S revealed a dose-dependent inhibition of tRNA maturation. Blasticidin S and amicetin do not compete with puromycin for the same site on the enzyme, suggesting the existence of distinct antibiotic binding sites on D. discoideum RNase P. Inhibition experiments further indicate that binding sites for blasticidin S and amicetin overlap.     

Seasonal differences in energy expenditure,flight characteristics and spatial utilization of Dalmatian Pelicans Pelecanus crispus in Greece

Animals typically adjust their behaviour to their changing environment throughout the annual cycle, modulating key processes such as the timing of breeding and the onset of migration. Such behavioural changes are commonly manifested in the movements and the energetic balance of individuals in relation to their species‐specific physiological characteristics, habitat attributes and the environmental properties of their distribution ranges. We used GPS and acceleration data collected using transmitters on free‐ranging birds to quantify annual movement patterns and estimate energy expenditure of the Dalmatian Pelican Pelecanus crispus, a large, soaring avian species which performs short‐distance migration and spends its entire annual cycle in mid‐latitudes. To assess the representativeness of our results, the transmitter effect was also tested. We found that daily trends in the overall dynamic body acceleration (ODBA; a proxy for energy expenditure) differed among seasons, with the highest values occurring during spring and the lowest during winter. Long inter‐lake flights were very rare in winter, and the number of flights and ODBA during spring was higher than during summer, suggesting greater motivation to move in spring. Although transmitters may have affected the birds, as none of the tagged birds bred, we found seasonal differences in behaviour and activity level. The observed patterns in differences in activity levels, long‐distance flights and flight characteristics between seasons suggest an annual rhythm of energy expenditure. These findings allow a better understanding of bird phenology, specifically regarding adaptations to wintering in a cold climate by reducing movement‐driven energy expenditure. Finally, the identification of periods with high and low energy expenditure may guide future conservation efforts by adjusting conservation plans in accordance with changing needs during the annual cycle.     

Eicosapentaenoic acid but not docosahexaenoic acid restores skeletal muscle mitochondrial oxidative capacity in old mice

Mitochondrial dysfunction is often observed in aging skeletal muscle and is implicated in age‐related declines in physical function. Early evidence suggests that dietary omega‐3 polyunsaturated fatty acids (n‐3 PUFAs) improve mitochondrial function. Here, we show that 10 weeks of dietary eicosapentaenoic acid (EPA) supplementation partially attenuated the age‐related decline in mitochondrial function in mice, but this effect was not observed with docosahexaenoic acid (DHA). The improvement in mitochondrial function with EPA occurred in the absence of any changes in mitochondrial abundance or biogenesis, which was evaluated from RNA sequencing, large‐scale proteomics, and direct measurements of muscle mitochondrial protein synthesis rates. We find that EPA improves muscle protein quality, specifically by decreasing mitochondrial protein carbamylation, a post‐translational modification that is driven by inflammation. These results demonstrate that EPA attenuated the age‐related loss of mitochondrial function and improved mitochondrial protein quality through a mechanism that is likely linked with anti‐inflammatory properties of n‐3 PUFAs. Furthermore, we demonstrate that EPA and DHA exert some common biological effects (anticoagulation, anti‐inflammatory, reduced FXR/RXR activation), but also exhibit many distinct biological effects, a finding that underscores the importance of evaluating the therapeutic potential of individual n‐3 PUFAs.     

Postnatal Dynamics of Developmental Stability and Canalization of Lizard Head Shape Under Different Environmental Conditions

Developmental stability (DS) and canalization are key determinants of phenotypic variation. To provide a better understanding of how postnatal growth is involved in determining the effects of DS and canalization on phenotypic variation, we studied within- and among-individual variation in head shape in ontogenetic series of lizards inhabiting urban and rural environments. Urban lizards exhibited increased fluctuating asymmetry during the early postnatal stages, but asymmetry levels decreased during growth. By contrast, asymmetry remained constant across the investigated size range in the rural population. In addition, urban juveniles were more variable for symmetric shape and deviated more from the group shape-size allometric trajectory, but both indices declined across ontogeny. Congruent patterns of within- and among-individual variation suggest that both DS and canalization may rely on similar underlying mechanisms. Further, the ontogenetic reduction of variation in the urban population suggests that compensatory growth may aid in buffering phenotypic variation and correcting deviances from the established developmental path. Alternatively, passive mechanisms and population dynamics may also explain the decrease of phenodeviants in urban populations. Significant correlations between symmetric and asymmetric shape, as well as similar integration patterns between the two populations, suggest that similar developmental mechanisms regulate head shape in both environments. Overall, these results highlight the relevance of both pre- and post-natal dynamics in determining levels of phenotypic variation, enhancing our understanding of how organisms respond to perturbations to DS and canalization under stressful conditions.     

Common Ancestry Is a Poor Predictor of Competitive Traits in Freshwater Green Algae

Phytoplankton species traits have been used to successfully predict the outcome of competition, but these traits are notoriously laborious to measure. If these traits display a phylogenetic signal, phylogenetic distance (PD) can be used as a proxy for trait variation. We provide the first investigation of the degree of phylogenetic signal in traits related to competition in freshwater green phytoplankton. We measured 17 traits related to competition and tested whether they displayed a phylogenetic signal across a molecular phylogeny of 59 species of green algae. We also assessed the fit of five models of trait evolution to trait variation across the phylogeny. There was no significant phylogenetic signal for 13 out of 17 ecological traits. For 7 traits, a non-phylogenetic model provided the best fit. For another 7 traits, a phylogenetic model was selected, but parameter values indicated that trait variation evolved recently, diminishing the importance of common ancestry. This study suggests that traits related to competition in freshwater green algae are not generally well-predicted by patterns of common ancestry. We discuss the mechanisms by which the link between phylogenetic distance and phenotypic differentiation may be broken.     

Probing Membrane Protein Interactions with Their Lipid Raft Environment Using Single-Molecule Tracking and Bayesian Inference Analysis

The statistical properties of membrane protein random walks reveal information on the interactions between the proteins and their environments. These interactions can be included in an overdamped Langevin equation framework where they are injected in either or both the friction field and the potential field. Using a Bayesian inference scheme, both the friction and potential fields acting on the ε-toxin receptor in its lipid raft have been measured. Two types of events were used to probe these interactions. First, active events, the removal of cholesterol and sphingolipid molecules, were used to measure the time evolution of confining potentials and diffusion fields. Second, passive rare events, de-confinement of the receptors from one raft and transition to an adjacent one, were used to measure hopping energies. Lipid interactions with the ε-toxin receptor are found to be an essential source of confinement. ε-toxin receptor confinement is due to both the friction and potential field induced by cholesterol and sphingolipids. Finally, the statistics of hopping energies reveal sub-structures of potentials in the rafts, characterized by small hopping energies, and the difference of solubilization energy between the inner and outer raft area, characterized by higher hopping energies.     

Experimental evidence that evolutionary relatedness does not affect the ecological mechanisms of coexistence in freshwater green algae

The coexistence of competing species depends on the balance between their fitness differences, which determine their competitive inequalities, and their niche differences, which stabilise their competitive interactions. Darwin proposed that evolution causes species' niches to diverge, but the influence of evolution on relative fitness differences, and the importance of both niche and fitness differences in determining coexistence have not yet been studied together. We tested whether the phylogenetic distances between species of green freshwater algae determined their abilities to coexist in a microcosm experiment. We found that niche differences were more important in explaining coexistence than relative fitness differences, and that phylogenetic distance had no effect on either coexistence or on the sizes of niche and fitness differences. These results were corroborated by an analysis of the frequency of the co‐occurrence of 325 pairwise combinations of algal taxa in > 1100 lakes across North America. Phylogenetic distance may not explain the coexistence of freshwater green algae.     

Comparing Multiple Criteria for Species Identification in Two Recently Diverged Seabirds

Correct species identification is a crucial issue in systematics with key implications for prioritising conservation effort. However, it can be particularly challenging in recently diverged species due to their strong similarity and relatedness. In such cases, species identification requires multiple and integrative approaches. In this study we used multiple criteria, namely plumage colouration, biometric measurements, geometric morphometrics, stable isotopes analysis (SIA) and genetics (mtDNA), to identify the species of 107 bycatch birds from two closely related seabird species, the Balearic (Puffinus mauretanicus) and Yelkouan (P. yelkouan) shearwaters. Biometric measurements, stable isotopes and genetic data produced two stable clusters of bycatch birds matching the two study species, as indicated by reference birds of known origin. Geometric morphometrics was excluded as a species identification criterion since the two clusters were not stable. The combination of plumage colouration, linear biometrics, stable isotope and genetic criteria was crucial to infer the species of 103 of the bycatch specimens. In the present study, particularly SIA emerged as a powerful criterion for species identification, but temporal stability of the isotopic values is critical for this purpose. Indeed, we found some variability in stable isotope values over the years within each species, but species differences explained most of the variance in the isotopic data. Yet this result pinpoints the importance of examining sources of variability in the isotopic data in a case-by-case basis prior to the cross-application of the SIA approach to other species. Our findings illustrate how the integration of several methodological approaches can help to correctly identify individuals from recently diverged species, as each criterion measures different biological phenomena and species divergence is not expressed simultaneously in all biological traits.     

Autologous Tumor Lysate-Pulsed Dendritic Cell Immunotherapy with Cytokine-Induced Killer Cells Improves Survival in Gastric and Colorectal Cancer Patients

Gastric and colorectal cancers (GC and CRC) have poor prognosis and are resistant to chemo- and/or radiotherapy. In the present study, the prophylactic effects of dendritic cell (DC) vaccination are evaluated on disease progression and clinical benefits in a group of 54 GC and CRC patients treated with DC immunotherapy combined with cytokine-induced killer (CIK) cells after surgery with or without chemo-radiotherapy. DCs were prepared from the mononuclear cells isolated from patients using IL-2/GM-CSF and loaded with tumor antigens; CIK cells were prepared by incubating peripheral blood lymphocytes with IL-2, IFN-γ, and CD3 antibodies. The DC/CIK therapy started 3 days after low-dose chemotherapy and was repeated 3–5 times in 2 weeks as one cycle with a total of 188.3±79.8×10⁶ DCs and 58.8±22.3×10⁸ CIK cells. Cytokine levels in patients'' sera before and after treatments were measured and the follow-up was conducted for 98 months to determine disease-free survival (DFS) and overall survival (OS). The results demonstrate that all cytokines tested were elevated with significantly higher levels of IFN-γ and IL-12 in both GC and CRC cohorts of DC/CIK treated patients. By Cox regression analysis, DC/CIK therapy reduced the risk of post-operative disease progression (p<0.01) with an increased OS (<0.01). These results demonstrate that in addition to chemo- and/or radiotherapy, DC/CIK immunotherapy is a potential effective approach in the control of tumor growth for post-operative GC and CRC patients.