The archaeal transamidosome for RNA-dependent glutamine biosynthesis

Archaea make glutaminyl-tRNA (Gln-tRNA^Gln) in a two-step process; a non-discriminating glutamyl-tRNA synthetase (ND-GluRS) forms Glu-tRNA^Gln, while the heterodimeric amidotransferase GatDE converts this mischarged tRNA to Gln-tRNA^Gln. Many prokaryotes synthesize asparaginyl-tRNA (Asn-tRNA^Asn) in a similar manner using a non-discriminating aspartyl-tRNA synthetase (ND-AspRS) and the heterotrimeric amidotransferase GatCAB. The transamidosome, a complex of tRNA synthetase, amidotransferase and tRNA, was first described for the latter system in Thermus thermophilus [Bailly, M., Blaise, M., Lorber, B., Becker, H.D. and Kern, D. (2007) The transamidosome: a dynamic ribonucleoprotein particle dedicated to prokaryotic tRNA-dependent asparagine biosynthesis. Mol. Cell, 28, 228–239.]. Here, we show a similar complex for Gln-tRNA^Gln formation in Methanothermobacter thermautotrophicus that allows the mischarged Glu-tRNA^Gln made by the tRNA synthetase to be channeled to the amidotransferase. The association of archaeal ND-GluRS with GatDE (K_D = 100 ± 22 nM) sequesters the tRNA synthetase for Gln-tRNA^Gln formation, with GatDE reducing the affinity of ND-GluRS for tRNA^Glu by at least 13-fold. Unlike the T. thermophilus transamidosome, the archaeal complex does not require tRNA for its formation, is not stable through product (Gln-tRNA^Gln) formation, and has no major effect on the kinetics of tRNA^Gln glutamylation nor transamidation. The differences between the two transamidosomes may be a consequence of the fact that ND-GluRS is a class I aminoacyl-tRNA synthetase, while ND-AspRS belongs to the class II family.     

Beyond Global Warming Potential: A Comparative Application of Climate Impact Metrics for the Life Cycle Assessment of Coal and Natural Gas Based Electricity

In the ongoing debate about the climate benefits of fuel switching from coal to natural gas for power generation, the metrics used to model climate impacts may be important. In this article, we evaluate the life cycle greenhouse gas emissions of coal and natural gas used in new, advanced power plants using a broad set of available climate metrics in order to test for the robustness of results. Climate metrics included in the article are global warming potential, global temperature change potential, technology warming potential, and cumulative radiative forcing. We also used the Model for the Assessment of Greenhouse‐gas Induced Climate Change (MAGICC) climate‐change model to validate the results. We find that all climate metrics suggest a natural gas combined cycle plant offers life cycle climate benefits over 100 years compared to a pulverized coal plant, even if the life cycle methane leakage rate for natural gas reaches 5%. Over shorter time frames (i.e., 20 years), plants using natural gas with a 4% leakage rate have similar climate impacts as those using coal, but are no worse than coal. If carbon capture and sequestration becomes available for both types of power plants, natural gas still offers climate benefits over coal as long as the life cycle methane leakage rate remains below 2%. These results are consistent across climate metrics and the MAGICC model over a 100‐year time frame. Although it is not clear whether any of these metrics are better than the others, the choice of metric can inform decisions based on different societal values. For example, whereas annual temperature change reported may be a more relevant metric to evaluate the human health effects of increased heat, the cumulative temperature change may be more relevant to evaluate climate impacts, such as sea‐level rise, that will result from the cumulative warming.     

Representing Representation: Integration between the Temporal Lobe and the Posterior Cingulate Influences the Content and Form of Spontaneous Thought

When not engaged in the moment, we often spontaneously represent people, places and events that are not present in the environment. Although this capacity has been linked to the default mode network (DMN), it remains unclear how interactions between the nodes of this network give rise to particular mental experiences during spontaneous thought. One hypothesis is that the core of the DMN integrates information from medial and lateral temporal lobe memory systems, which represent different aspects of knowledge. Individual differences in the connectivity between temporal lobe regions and the default mode network core would then predict differences in the content and form of people’s spontaneous thoughts. This study tested this hypothesis by examining the relationship between seed-based functional connectivity and the contents of spontaneous thought recorded in a laboratory study several days later. Variations in connectivity from both medial and lateral temporal lobe regions was associated with different patterns of spontaneous thought and these effects converged on an overlapping region in the posterior cingulate cortex. We propose that the posterior core of the DMN acts as a representational hub that integrates information represented in medial and lateral temporal lobe and this process is important in determining the content and form of spontaneous thought.     

Metal (Fe, Zn, Cu, Pb and Cd) concentration patterns in components of a macrophyte-based coastal lagoon ecosystem

Information on the metal biological fate in macrophyte-based coastal lagoons is provided; this information can contribute to the assessment of the environmental effects of metal pollution and to the development of predictive models for rational management of coastal lagoons. Iron, Zn, Cu, Pb and Cd concentrations in the dominant invertebrate and fish species of Monolimni Lagoon, Mediterranean Sea, as well as in potential major sources for metal accumulation in these animals (water, sediments, angiosperms, seaweeds), were measured. Principal Component Analysis (PCA) was conducted using metal concentrations in invertebrates and fishes. All five metal concentrations loaded significantly on the first PCA axis; however, Zn and Cu loadings were less significant than Cd and even less than Fe and Pb ones. The samples of deposit-feeding invertebrates were separated from those of the rest of the organisms (browsing, herbivorous and carnivorous invertebrates, carnivorous gobies and muscle tissues of detritivorous mullets) along the first PCA axis. Deposit-feeding invertebrates displayed the highest Fe and Pb contents, and in general, the highest or comparatively high Cd, Zn and Cu ones. Carnivorous gobies showed comparatively high Zn contents and carnivorous shrimps the highest Cu ones, while muscle tissues of detritivorous mullets had low metal loads. In addition, there was no essential increase in metal concentrations corresponding to the increasing trophic level (autotrophs, to herbivores, to carnivores). Our findings suggest that (a) the variability in Fe, Pb and Cd contents in invertebrates and gobies depends at least to some extent on interspecific differences in feeding habits—deposit feeders accumulated the highest metal amounts probably due to high rates of uptake from sediments, (b) the variability in Zn and Cu concentrations in these organisms depends also on other interspecific differences apart from those in feeding habits, (c) metal accumulation in mullet muscle tissues does not depend markedly on feeding habits and (d) the trophic transfer of macrophyte-bound metals to the coastal lagoon food web is of relatively minor importance.     

Proinflammatory Markers,Insulin Sensitivity,and Cardiometabolic Risk Factors in Treated HIV Infection

Treated HIV infection and HIV‐lipoatrophy increases risk of cardiovascular disease (CVD) and type 2 diabetes mellitus (T2DM). Circulating inflammatory molecules may, in part, explain this increased risk. This study examined circulating inflammatory molecules in treated HIV infection in relation to insulin sensitivity, lipids total body, and intramyocellular fat, compared to insulin‐resistant obesity (an index group at high risk of diabetes). Detailed metabolic phenotypes were measured in 20 treated HIV‐infected men (with and without subcutaneous lipoatrophy) vs. 26 insulin‐resistant obese men (IR‐O, n = 26), including inflammatory molecules, insulin sensitivity, total body fat (TBF), visceral fat (visceral adipose tissue (VAT)), and intramyocellular lipid (IMCL). C‐reactive protein (CRP) levels in treated HIV were similar to those in IR‐O, despite lower TBF and greater insulin sensitivity in treated HIV. In HIV‐lipoatrophy, CRP was higher than that found in IR‐O. Adiponectin was similar between treated HIV and IR‐O, but significantly lower in those with HIV‐lipoatrophy. In treated HIV, subjects with higher CRP had significantly higher total cholesterol, VAT, and IMCL. In treated HIV, subjects with lower adiponectin had significantly lower HDL and higher triglycerides, glucose, VAT, and IMCL. In conclusion, a proinflammatory milieu equivalent to that of insulin‐resistant obesity characterizes lean men with treated HIV infection, worse in those with subcutaneous lipoatrophy. These factors may contribute to the accelerated diabetogenesis and cardiac risk observed in treated HIV infection.     

Use of forest canopy by European red squirrelsSciurus vulgaris in Northern Greece: claws and the small branch niche

Moving and standing in trees impose multiple problems to arboreal mammals. Among them, the major ones are the negotiation of slender terminal branches and of large vertical supports. Both microhabitats are important as they have been linked alternatively to the evolutionary loss of claws in early primates. Therefore, rates of use of these different supports by claw-bearing arboreal mammals may offer insights to their actual significance in the adaptive evolution of early primates. In this context, canopy, tree crown, branch size, inclination, and texture use were recorded on four adult free ranging European red squirrelsSciurus vulgaris Linnaeus, 1758 in a mixed coniferous forest in northern Greece.S. vulgaris was mainly arboreal, exploiting the terminal branch zone, using frequently oblique and intermediately textured supports<5 cm and moderately large vertical branches. Furthermore, comparative data from other sciurid species and clawed primates showed positive correlations of small and horizontal support use, and negative ones of vertical support use to body mass. These findings show that keeled functional claws do not impede habitual use of slender branches and may not facilitate efficient climbing on large vertical trunks. These observations partly question the association between habitual use of the small branch niche and primate adaptations and lend support to alternative hypotheses, underscoring the importance of inquiring for more complex mechanisms that lead to the evolution of the unique set of primate morphological adaptations.