Evolutionary processes,dispersal limitation and climatic history shape current diversity patterns of European dragonflies

We investigated the effects of contemporary and historical factors on the spatial variation of European dragonfly diversity. Specifically, we tested to what extent patterns of endemism and phylogenetic diversity of European dragonfly assemblages are structured by 1) phylogenetic conservatism of thermal adaptations and 2) differences in the ability of post‐glacial recolonization by species adapted to running waters (lotic) and still waters (lentic). We investigated patterns of dragonfly diversity using digital distribution maps and a phylogeny of 122 European dragonfly species, which we constructed by combining taxonomic and molecular data. We calculated total taxonomic distinctiveness and mean pairwise distances across 4192 50 × 50 km equal‐area grid cells as measures of phylogenetic diversity. We compared species richness with corrected weighted endemism and standardized effect sizes of mean pairwise distances or residuals of total taxonomic distinctiveness to identify areas with higher or lower phylogenetic diversity than expected by chance. Broken‐line regression was used to detect breakpoints in diversity–latitude relationships. Dragonfly species richness peaked in central Europe, whereas endemism and phylogenetic diversity decreased from warm areas in the south‐west to cold areas in the north‐east and with an increasing proportion of lentic species. Except for species richness, all measures of diversity were consistently higher in formerly unglaciated areas south of the 0°C isotherm during the Last Glacial Maximum than in formerly glaciated areas. These results indicate that the distributions of dragonfly species in Europe were shaped by both phylogenetic conservatism of thermal adaptations and differences between lentic and lotic species in the ability of post‐glacial recolonization/dispersal in concert with the climatic history of the continent. The complex diversity patterns of European dragonflies provide an example of how integrating climatic and evolutionary history with contemporary ecological data can improve our understanding of the processes driving the geographical variation of biological diversity.     

Faster cytotoxicity with age: Increased perforin and granzyme levels in cytotoxic CD8 + T cells boost cancer cell elimination

A variety of intrinsic and extrinsic factors contribute to the altered efficiency of CTLs in elderly organisms. In particular, the efficacy of antiviral CD8⁺ T cells responses in the elderly has come back into focus since the COVID‐19 pandemic outbreak. However, the exact molecular mechanisms leading to alterations in T cell function and the origin of the observed impairments have not been fully explored. Therefore, we investigated whether intrinsic changes affect the cytotoxic ability of CD8⁺ T cells in aging. We focused on the different subpopulations and time‐resolved quantification of cytotoxicity during tumor cell elimination. We report a surprising result: Killing kinetics of CD8⁺ T cells from elderly mice are much faster than those of CD8⁺ T cells from adult mice. This is true not only in the total CD8⁺ T cell population but also for their effector (T_EM) and central memory (T_CM) T cell subpopulations. TIRF experiments reveal that CD8⁺ T cells from elderly mice possess comparable numbers of fusion events per cell, but significantly increased numbers of cells with granule fusion. Analysis of the cytotoxic granule (CG) content shows significantly increased perforin and granzyme levels and turns CD8⁺ T cells of elderly mice into very efficient killers. This highlights the importance of distinguishing between cell‐intrinsic alterations and microenvironmental changes in elderly individuals. Our results also stress the importance of analyzing the dynamics of CTL cytotoxicity against cancer cells because, with a simple endpoint lysis analysis, cytotoxic differences could have easily been overlooked.     

The essential requirement for Runx1 in the development of the sternum

Runx1 is highly expressed in chondroprogenitor and osteoprogenitor cells and in vitro experiments suggest that Runx1 is important in the early stages of osteoblast and chondrocyte differentiation. However, because Runx1 knockout mice are early embryonic lethal due to failure of hematopoiesis, the role of Runx1 in skeletogenesis remains unclear. We studied the role of Runx1 in skeletal development using a Runx1 reversible knockout mouse model. By crossing with Tie2-Cre deletor mice, Runx1 expression was selectively rescued in the endothelial and hematopoietic systems but not in the skeleton. Although Runx1^Re/Re embryos survived until birth and had a generally normal skeleton, the development of mineralization in the sternum and some skull elements was significantly disrupted. In contrast to wild-type embryos, the sternum of E17.5 Runx1^Re/Re embryos showed high levels of Sox-9 and collagen type II expression and lack of development of hypertrophic chondrocytes. In situ hybridization analysis demonstrated that, in contrast to the vertebrae and long bones, the sternum of wild-type embryos expresses high levels of Runx1, but not Runx2, the master regulator of skeletogenesis. Thus, although Runx1 is not essential for major skeletal development, it does play an essential role in the development of the sternum and some skull elements.     

Whole Blood Gene Expression Profiles of Patients with a Past Aneurysmal Subarachnoid Hemorrhage

BackgroundThe pathogenesis of development and rupture of intracranial aneurysms (IA) is largely unknown. Also, screening for IA to prevent aneurysmal subarachnoid hemorrhage (aSAH) is inefficient, as disease markers are lacking. We investigated gene expression profiles in blood of previous aSAH patients, who are still at risk for future IA, aiming to gain insight into the pathogenesis of IA and aSAH, and to make a first step towards improvement of aSAH risk prediction.ConclusionsNo gene expression differences were present in blood of previous aSAH patients compared to controls, besides one differentially co-expressed gene network without a clear relevant biological function. Our findings suggest that gene expression profiles, as detected in blood of previous aSAH patients, do not reveal the pathogenesis of IA and aSAH, and cannot be used for aSAH risk prediction.     

Initial effects of experimental warming on carbon exchange rates, plant growth and microbial dynamics of a lichen-rich dwarf shrub tundra in Siberia

Biological soil crusts can affect seed germination and seedling establishment. We have investigated the effect of biological soil crusts on seed water status as a potential mechanism affecting seed germination. The seed water potential of two annual grasses, one exotic Bromus tectorum L. and another native Vulpia microstachys Nutt., were analyzed after placing the seeds on bare soil, on a crust that contains various lichens and mosses (mixed crust), or on a crust dominated by the crustose lichen Diploschistes muscorum (Scop.) R. Sant. (Diploschistes crust). Seed water potential and germination were similar on the bare soil and the mixed crust, except for the initial germination of V. microstachys, which was higher on the mixed crust than on the bare soil. For the two grasses studied, seed water potential was significantly higher on the bare soil and mixed crust than on the Diploschistes crust. These differences in water potential correlated with differences in germination, which was much lower on the lichen crust. Experiments were conducted under two watering regimens. Increasing the frequency of watering amplified the differences in seed water potential and germination between the Diploschistes crust and the other two surfaces. For a particular watering regimen, the bare soil, mixed crust, and Diploschistes crust received the same amount of water, but they reached significantly different water potentials. Throughout the experiments, the water potential of the soil and mixed crust remained above −0.6 MPa, while there was a marked decline in the water potential of the Diploschistes surface to about −4 MPa. To ascertain that water was the major factor limiting germination on the Diploschistes crust, we conducted germination tests in an environment with 100% relative humidity. Under these conditions, germination on the Diploschistes crust was similar to that on the bare soil. However, the seeds that germinated on the Diploschistes crust did not penetrate this surface and approximately 60% of their root tips became necrotic. Our results indicate that the presence of D. muscorum can inhibit seedling establishment by two mechanisms: a reduction in seed water absorption and an increase in root tip mortality.     

The dual effect of internal tetramethylammonium ions on the open states of the sodium channel in the squid giant axon.

Voltage-clamp recordings of INa in squid axons dialysed with Cs or TMA, and bathed in low Na choline seawater, showed that, except close to threshold, the initial peak of fast-inactivating current was invariably decreased by TMA, whereas the non-inactivating current in the steady state was simultaneously increased. The results suggest that although TMA does not act directly on the movements of the voltage sensors that activate the sodium system, it blocks single-channel conductance in a voltage-dependent fashion in both the open states of the Na channel, while it has an entirely different type of action by increasing the probability of late openings in the steady state. Another difference between the two open states was that the sodium permeability coefficient had a Q10 of 1.8 in the initial open state, whereas in the steady state the effect of temperature was much smaller or even negative.     

The ecology of Black Guillemot Cepphus grylle grylle chicks in the Baltic Sea region: insights into their diet,survival, nest predation and moment of fledging

Capsule: The diet of Black Guillemot Cepphus grylle grylle chicks in the Baltic Sea region was dominated by Viviparous Eelpout Zoarces viviparus. Risk of nest predation by avian and mammalian predators was perceived to be low, and hatching and fledging success were high.

Aims: To gain insight into the ecology of nestling Black Guillemots in the Baltic Sea region to fill knowledge gaps and benefit its conservation.

Methods: Two island groups in the Baltic Sea were visited several times during the breeding season of 2014 and 2015 to monitor nestling survival and fledging. In addition, camera traps were used in 2014 to monitor prey brought to chicks by adults and record possible nest predation events.

Results: Hatching success was 0.89 and 0.73 in 2014 and 2015, respectively, and fledging success was very high (0.95 and 0.97). No incidences of avian or mammalian predation were observed. Chicks fledged at night between 32 and 38 days after hatching. Viviparous Eelpout made up 95% of the prey items brought to the chicks by adults.

Conclusions: The hatching rate and fledging rate of the Black Guillemot was high in our study region. Juveniles seemed highly dependent on the availability of eelpout. Changes in the abundance of this species may therefore have negative effects on chick survival.     

Characterization of AAV vector particle stability at the single-capsid level

Virus families have evolved different strategies for genome uncoating, which are also followed by recombinant vectors. Vectors derived from adeno-associated viruses (AAV) are considered as leading delivery tools for in vivo gene transfer, and in particular gene therapy. Using a combination of atomic force microscopy (AFM), biochemical experiments, and physical modeling, we investigated here the physical properties and stability of AAV vector particles. We first compared the morphological properties of AAV vectors derived from two different serotypes (AAV8 and AAV9). Furthermore, we triggered ssDNA uncoating by incubating vector particles to increasing controlled temperatures. Our analyses, performed at the single-particle level, indicate that genome release can occur in vitro via two alternative pathways: either the capsid remains intact and ejects linearly the ssDNA molecule, or the capsid is ruptured, leaving ssDNA in a compact entangled conformation. The analysis of the length distributions of ejected genomes further revealed a two-step ejection behavior. We propose a kinetic model aimed at quantitatively describing the evolution of capsids and genomes along the different pathways, as a function of time and temperature. This model allows quantifying the relative stability of AAV8 and AAV9 particles.     

Sample preservation for determination of organic compounds: microwave versus freeze-drying

In search of a reliable drying method, which might be used evenunder field conditions, microwave drying was compared to freeze-dryingof plant material. Leaves of Ananas comosus and Avicennia germinansas well as buds and phloem of Acer pseudoplatanus were usedand checked for one or more of the following substances: sugars,sugar alcohols, organic and amino acids, total nitrogen, andglycinebetaine. With most samples good agreement was achieved between the twodrying methods. Only in the case of the Ananas comosus leaves,which exhibited low pH and high water content, did appreciabledifferences occur in organic and amino acids. Besides that,sucrose was the compound most susceptible to alterations, whichwas especially evident when leaves of Sambucus nigra were driedin the two different compartments (condenser compartment, dryingbell jar) of the freeze-dryer in use. For Ananas comosus leaf samples it was shown that microwavingcan also be used prior to extraction of tissue sap. Key words: Microwave, freeze-drying, drying method, tissue sap, organic solutes