Myometrial maxi-K channel beta1 subunit modulation during pregnancy and after 17beta-estradiol stimulation

In Saccharomyces cerevisiae the nicotinic acid moiety of NAD+ can be synthesized from tryptophan using the kynurenine pathway or incorporated directly using nicotinate phosphoribosyl transferase (NPT1). We have identified the genes that encode the enzymes of the kynurenine pathway and for BNA5 (YLR231c) and BNA6 (YFR047c) confirmed that they encode kynureninase and quinolinate phosphoribosyl transferase respectively. We show that deletion of genes encoding kynurenine pathway enzymes are co-lethal with the Deltanpt1, demonstrating that no other pathway for the synthesis of nicotinic acid exists in S. cerevisiae. Also, we show that under anaerobic conditions S. cerevisiae is a nicotinic acid auxotroph.     

Choice,performance and heritability of performance of specialist and generalist insect herbivores towards cacalol and seneciphylline,two allelochemicals of Adenostyles alpina (Asteraceae)

We compared the effects of a sesquiterpene (ST, cacalol) and a pyrrolizidine alkaloid (PA, seneciphylline), both occurring in Adenostyles alliariae, on food choice and performance of specialist and generalist insect herbivores which are all known to feed or live on A. alliariae. In choice experiments we investigated whether the compounds were preferred, deterrent or had no effect. All specialist species Aglaostigma discolor (Hymenoptera, Tenthredinidae), Oreina cacaliae (Coleoptera, Chrysomelidae) and O. speciosissima avoided feeding when confronted with the combination of compounds. Only larvae of A. discolor avoided the single ST treatment as well. Larvae of the generalist species Callimorpha dominula (Lepidoptera, Arctiidae), Cylindrotoma distinctissima (Diptera, Tipulidae) and Miramella alpina (Caelifera, Acrididae) generally avoided feeding from PA, ST and PAST treatments. The only exception were caterpillars of C. dominula which were indiscriminate towards PA when naive, and preferred to feed on the PA treatment when they had experienced the compound before. Performance, measured as the growth of larvae on the different treatments in a no choice situation over a period of 10–17 days, was not different between treatments in the specialist leaf beetles O. cacaliae and O. speciosissima. Their avoidance of the combination treatment in the choice experiments had no obvious effect on growth when forced to feed from the treatment. In the generalist C. dominula only the high concentration combination treatment (PAST) reduced growth of the larvae due to decreased consumption. In C. distinctissima we found reduced growth in all treatments except one (PA3%). Poor growth performance in C. distinctissima was due to postingestive physiological effects of all treatments and additionally to consumption reduction in high‐dose ST treatments. Genetic variability (broad sense heritability) of growth performance metabolism varied in accordance with the specialization degree of the species. O. cacaliae, the most specialized species, had no significant heritability; O. speciosissima, the less specialized specialist, had a heritability of 0.46; C. dominula, the PA adapted generalist species, had a heritability of 0.64; C. distinctissima, the generalist with no apparent adaptations, had a heritability of 0.84.     

Conserved amino acids in each subunit of the heteroligomeric tRNA m1A58 Mtase from Saccharomyces cerevisiae contribute to tRNA binding

In Saccharomyces cerevisiae, a two-subunit methyltransferase (Mtase) encoded by the essential genes TRM6 and TRM61 is responsible for the formation of 1-methyladenosine, a modified nucleoside found at position 58 in tRNA that is critical for the stability of tRNA(Met)i The crystal structure of the homotetrameric m1A58 tRNA Mtase from Mycobacterium tuberculosis, TrmI, has been solved and was used as a template to build a model of the yeast m1A58 tRNA Mtase heterotetramer. We altered amino acids in TRM6 and TRM61 that were predicted to be important for the stability of the heteroligomer based on this model. Yeast strains expressing trm6 and trm61 mutants exhibited growth phenotypes indicative of reduced m1A formation. In addition, recombinant mutant enzymes had reduced in vitro Mtase activity. We demonstrate that the mutations introduced do not prevent heteroligomer formation and do not disrupt binding of the cofactor S-adenosyl-L-methionine. Instead, amino acid substitutions in either Trm6p or Trm61p destroy the ability of the yeast m1A58 tRNA Mtase to bind tRNA(Met)i, indicating that each subunit contributes to tRNA binding and suggesting a structural alteration of the substrate-binding pocket occurs when these mutations are present.     

Stretched DNA Investigated Using Molecular-Dynamics and Quantum-Mechanical Calculations

We combined atomistic molecular-dynamics simulations with quantum-mechanical calculations to investigate the sequence dependence of the stretching behavior of duplex DNA. Our combined quantum-mechanical/molecular-mechanical approach demonstrates that molecular-mechanical force fields are able to describe both the backbone and base-base interactions within the highly distorted nucleic acid structures produced by stretching the DNA from the 5′ ends, which include conformations containing disassociated basepairs, just as well as these force fields describe relaxed DNA conformations. The molecular-dynamics simulations indicate that the force-induced melting pathway is sequence-dependent and is influenced by the availability of noncanonical hydrogen-bond interactions that can assist the disassociation of the DNA basepairs. The biological implications of these results are discussed.     

Role of commercial harbours and recreational marinas in the spread of non-indigenous fouling species

The role of commercial harbours as sink and source habitats for non-indigenous species (NIS) and the role of recreational boating for their secondary spread were investigated by analysing the fouling community of five Italian harbours and five marinas in the western Mediterranean Sea. It was first hypothesised that NIS assemblages in the recreational marinas were subsets of those occurring in commercial harbours. However, the data did not consistently support this hypothesis: the NIS pools of some marinas significantly diverged from harbours even belonging to the same coastal stretches, including NIS occurring only in marinas. This study confirms harbours as hotspots for marine NIS, but also reveals that numbers of NIS in some marinas is higher than expected, suggesting that recreational vessels effectively facilitate NIS spread. It is recommended that this vector of NIS introduction is taken into account in the future planning of sustainable development of maritime tourism in Europe.     

Structure-toxicity relationships for different types of dinuclear platinum complexes

Nine structurally distinct dinuclear platinum complexes have been evaluated in a novel model system for the investigation of renal epithelial toxicity of platinum drugs. The results showed that these compounds are toxic when applied at the basolateral side of renal epithelia, whereas their toxic effects on the apical side are negligible. Such a difference in toxicity of the complexes has been found to result from their poor uptake through the apical membrane, as compared to the basolateral membrane. Toxicity of the compounds on the basolateral side varies depending on their structure. Structure-toxicity relationships for the group of complexes with rigid ligands and for the group of complexes with flexible ligands are discussed. Among the dinuclear complexes with rigid ligands, sterically hindered complexes are less toxic, due to their poor uptake and low reactivity towards glutathione. Within the group of complexes with flexible ligands, cis-configured isomers are more toxic than their trans-counterparts.     

Comparison and confirmation of SNP-bud burst associations in European beech populations in Germany

European beech (Fagus sylvatica L.) is one of the most important forest tree species in Central Europe. Climate change scenarios predict an increase in annual mean temperatures that may cause earlier bud burst in spring, potentially leading to an increased late frost-risk. Despite the ecologic and economic importance of beech, knowledge about the molecular basis of bud burst is still scarce in this species. Here, an association analysis was used to detect SNPs that are significantly associated with beech bud burst. A translocation experiment was established with progenies of six different beech populations from three widely separated regions in Northeast, Central, and Southwest Germany. In total, 600 individuals of the translocation experiment were genotyped using a set of 46 SNPs located in bud burst candidate genes. The association analysis revealed seven SNPs significantly associated with bud burst, each SNP explaining only a few percent of the observed phenotypic variation. Since the same SNP set was used in a previous association analysis with European beech, we were able to compare and confirm significant associations between SNPs and bud burst in distinct beech populations growing in different environments.