The potential distribution of German wasps (Vespula germanica) in Argentina

Abstract

In the early 1980s, the German wasp (Vespula germanica) arrived in Argentina and became established in northern Patagonia. We use an ecoclimatic computer‐based program (CLIMEX) to predict the potential spread of wasps to other areas of the country. The model suggests that much of Argentina does not appear to be very suitable for the species’ establishment. However, more suitable areas than those currently colonised by the wasp occur in the centre of the country. Based on CLIMEX results, we suggest that, if the wasps ever break through the barrier of unfavourable habitat that surrounds their current distribution, they will continue dispersing to those areas. Notwithstanding this, factors other than climate may explain why German wasps are firmly established in areas otherwise considered to be inhospitable for the species.     

Accounting for greenhouse gas emissions from the degradation of chemicals in the environment

The International Journal of Life Cycle Assessment - The degradation of chemicals in the environment is often excluded from life cycle assessment (LCA) studies. This paper describes a method to...     

Effect of mutation at the interface of Trp-repressor dimeric protein: a steered molecular dynamics simulation

The strength of key interfacial contacts that stabilize protein–protein interactions have been studied by computer simulation. Experimentally, changes in the interface are evaluated by generating specific mutations at one or more points of the protein structure. Here, such an evaluation is performed by means of steered molecular dynamics and use of a dimeric model of tryptophan repressor and in-silico mutants as a test case. Analysis of four particular cases shows that, in principle, it is possible to distinguish between wild-type and mutant forms by examination of the total energy and force–extension profiles. In particular, detailed atomic level structural analysis indicates that specific mutations at the interface of the dimeric model (positions 19 and 39) alter interactions that appear in the wild-type form of tryptophan repressor, reducing the energy and force required to separate both subunits.     

Centelloside accumulation in leaves of Centella asiatica is determined by resource partitioning between primary and secondary metabolism while influenced by supply levels of either nitrogen,phosphorus or potassium

In the present study we aimed to investigate the relevance of either N, P or K supply for herb and leaf yield and for centelloside concentrations in Centella asiatica L. Urban leaves. In this regard, we elucidated the causal relationship between assimilation rate, leaf N, P and K concentrations, herb and leaf production, and centelloside accumulation. The experiments were conducted consecutively in a greenhouse where C. asiatica was grown in hydroponic culture and fertigated with nutrient solutions at either 0, 30, 60, 100 or 150% of the N, P or K amount in a standard Hoagland solution. In general, the increase in N, P or K supply enhanced assimilation rate and herb and leaf yield. However, exceeding specific thresholds, the high availability of one single nutrient caused lower leaf N concentrations and a decline in assimilation rate and plant growth. Irrespective of N, P and K supply, the leaf centelloside concentrations were negatively associated with herb and leaf yield, which is in accordance with the assumptions of the carbon/nutrient balance and the growth differentiation balance hypotheses. Moreover, we found strong negative correlations between saponins and leaf N concentrations, while the respective sapogenins were negatively correlated with K concentrations. Using C. asiatica as model system, our experiments reveal for the first time that the accumulation of saponins and sapogenins is affected by resource allocation between primary and secondary metabolism and that besides carbon, also nutrient availability is relevant for the regulation of the centelloside synthesis. Finally, our results highlight the huge potential of optimized and carefully controlled mineral nutrition of medicinal plants for steering the bio-production of high-quality natural products.     

The essential nucleolar yeast protein Nop8p controls the exosome function during 60S ribosomal subunit maturation

The yeast nucleolar protein Nop8p has previously been shown to interact with Nip7p and to be required for 60S ribosomal subunit formation. Although depletion of Nop8p in yeast cells leads to premature degradation of rRNAs, the biochemical mechanism responsible for this phenotype is still not known. In this work, we show that the Nop8p amino-terminal region mediates interaction with the 5.8S rRNA, while its carboxyl-terminal portion interacts with Nip7p and can partially complement the growth defect of the conditional mutant strain Δnop8/GAL::NOP8. Interestingly, Nop8p mediates association of Nip7p to pre-ribosomal particles. Nop8p also interacts with the exosome subunit Rrp6p and inhibits the complex activity in vitro, suggesting that the decrease in 60S ribosomal subunit levels detected upon depletion of Nop8p may result from degradation of pre-rRNAs by the exosome. These results strongly indicate that Nop8p may control the exosome function during pre-rRNA processing.     

Feedback structures of northern small rodent populations

Regular oscillations of northern small rodents (lemmings, voles and mice) have fascinated ecologists for decades. In particular, cycles exhibited by Fennoscandian voles have inspired population ecologists to propose several hypotheses for their underlying causes. Although there is now some agreement that the interaction with specialist predators is involved, many aspects remain enigmatic, one being the precise ecological mechanism involved in the first-order feedback effect (i.e. direct density dependence). In this paper we evaluate the relative importance of first and second-order negative feedback on small rodent dynamics in 64 data sets, assess the evidence of non-linearity in the feedback structure, and look for similarities and/or differences between species and places. A clear feature of our analysis was the highly consistent pattern of first-order dynamics across species and locations, suggesting the importance of intra-specific interactions independent of local environmental conditions. Second-order feedback generally showed a large degree of variation and appears to be strongly dependent on environmental conditions and locality. There seems to be no consistent latitudinal pattern or non-linearity in the feedback responses. We conclude that northern small rodent populations are basically regulated by both highly consistent first-order feedback (e.g. intra-specific competition, functional responses of generalist predators) and less consistent, site-specific second-order effects (e.g. numerical responses of specialist predators or food plants).     

Ethanol facilitates consummatory extinction

Rats given access to an empty sipper tube after having obtained 32% sucrose in the same situation undergo extinction of consummatory behavior (cE). Ethanol (0.75 and 1 g/kg, i.p.) accelerated cE when administered before the second extinction session. The effect was not attributable to increased activity or state-dependent reduction in consummatory behavior. These data are discussed in the context of research on the effects of ethanol on behavioral assays involving incentive downshifts.