Social feeding decisions in horses (Equus caballus)

Like many other herbivores, in a natural environment equids feed on rather evenly distributed resources. However, the vegetation in their vast habitats constantly changes. If food is plentiful only little competition occurs over food, and in non-competitive situations domestic horses tend to return to the same feeding site until it is overgrazed. In contrast, they compete over limited food for which the social status of the individuals appears to be important. Especially in ruminants several studies have proved an influence of social organisations, rank, sex and the depletion of feeding sites on the feeding behaviour of individuals. However, it is not yet understood whether and how social aspects affect horses' feeding decisions. Curiosity about the influence of social rank on the horses' feeding decisions between two, equally with high-quality surplus food-filled buckets placed in different social feeding conditions, led us to create the test below. The observer horses were alternately tested with a dominant and a subordinate demonstrator placed in one of the three different positions. We conclude that domestic horses use social cognition and strategic decision making in order to decide where to feed in a social feeding situation. When possible they tend to return to the same, continuously supplied feeding site and switch to an "avoidance tendency" in the presence of dominant horses or when another horse is already feeding there. Thus, the social rank and the position of conspecifics affect the feeding strategy of horses.     

Comparative pappus micromorphology of edelweiss (Leontopodium,Gnaphalieae, Asteraceae) with implications for taxonomy,ecology and evolution

We analysed pappus characters in 31 of the c. 34 accepted Leontopodium spp. (edelweiss). Micromorphological pappus character states were useful for discriminating between individual species and intrageneric groups. The pappus differs in number, length, breadth, surface structure, colour and the tips of the bristles. Several features characterize single species, for example a unique fan‐like tip that is only found in L. franchetii. Leontopodium section Nobilia is supported by unusual pappus characters. Experimental evidence shows that the pappus of Leontopodium, previously thought to be caducous, is well suited for wind dispersal of the fruit. One clear trend is that species growing in sparsely vegetated, high‐altitude regions often have more numerous and longer pappus bristles, particularly on the female flowers.     

Heterologous envelope immunogens contribute to AIDS vaccine protection in rhesus monkeys

Because a strategy to elicit broadly neutralizing anti-human immunodeficiency virus type 1 (HIV-1) antibodies has not yet been found, the role of an Env immunogen in HIV-1 vaccine candidates remains undefined. We sought to determine whether an HIV-1 Env immunogen genetically disparate from the Env of the challenge virus can contribute to protective immunity. We vaccinated Indian-origin rhesus monkeys with Gag-Pol-Nef immunogens, alone or in combination with Env immunogens that were either matched or mismatched with the challenge virus. These animals were then challenged with a pathogenic simian-human immunodeficiency virus. The vaccine regimen included a plasmid DNA prime and replication-defective adenoviral vector boost. Vaccine regimens that included the matched or mismatched Env immunogens conferred better protection against CD4(+) T-lymphocyte loss than that seen with comparable regimens that did not include Env immunogens. This increment in protective immunity was associated with anamnestic Env-specific cellular immunity that developed in the early days following viral challenge. These data suggest that T-lymphocyte immunity to Env can broaden the protective cellular immune response to HIV despite significant sequence diversity of the strains of the Env immunogens and can contribute to immune protection in this AIDS vaccine model.     

Effects of Kv1.2 intracellular regions on activation of Kv2.1 channels

Depolarizing voltage steps activate voltage-dependent K(+) (Kv) channels by moving the voltage sensor, which triggers a coupling reaction leading to the opening of the pore. We constructed chimeric channels in which intracellular regions of slowly activating Kv2.1 channels were replaced by respective regions of rapidly activating Kv1.2 channels. Substitution of either the N-terminus, S4-S5 linker, or C-terminus generated chimeric Kv2.1/1.2 channels with a paradoxically slow and approximately exponential activation time course consisting of a fast and a slow component. Using combined chimeras, each of these Kv1.2 regions further slowed activation at the voltage of 0 mV, irrespective of the nature of the other two regions, whereas at the voltage of 40 mV both slowing and accelerating effects were observed. These results suggest voltage-dependent interactions of the three intracellular regions. This observation was quantified by double-mutant cycle analysis. It is concluded that interactions between N-terminus, S4-S5 linker, and/or C-terminus modulate the activation time course of Kv2.1 channels and that part of these interactions is voltage dependent.     

The chicken leukocyte receptor complex: a highly diverse multigene family encoding at least six structurally distinct receptor types

The chicken Ig-like receptors (CHIR) have been described as two Ig domain molecules with long cytoplasmic tails containing inhibitory motifs. In this study, we demonstrate that CHIR form a large family, with multiple members showing great sequence variability among members as well as a great diversity in domain organization and properties of the transmembrane and cytoplasmic segments. We characterize various novel receptor types with motifs indicative of inhibitory, activating, or both functions. In addition to the inhibitory receptors with two ITIM, receptors with a single immunoreceptor tyrosine-based switch motif or receptors lacking a cytoplasmic domain were isolated. Activating receptors with a short cytoplasmic domain and a transmembrane arginine assembled with the newly identified chicken FcepsilonRIgamma chain. Three bifunctional receptor types were characterized composed of one or two C2-type Ig-like domains, a transmembrane region with a positively charged residue and combinations of cytoplasmic motifs such as ITIM, immunoreceptor tyrosine-based switch motif, and YXXM. RT-PCR revealed distinct expression patterns of individual CHIR. All receptor types shared a conserved genomic architecture, and in single Ig domain receptors a pseudoexon replaced the second Ig exon. Southern blot analyses with probes specific for the Ig1 domain were indicative of a large multigene family. Of 103 sequences from the Ig1 domain of a single animal, 41 unique sequences were obtained that displayed extensive variability within restricted Ig regions. Fluorescence in situ hybridization localized the CHIR gene cluster to microchromosome 31 and identified this region as orthologous to the human leukocyte receptor complex.     

Novel α-pinene-derived mono- and bisphosphinite ligands: Synthesis and application in catalytic hydrogenation

Novel mono- and bisphosphinite (−)-pinane-based ligands have been synthesized from (−)-α-pinene. Mixed with [(COD)₂Rh]⁺[BF₄]⁻, these ligands displayed moderate up to high catalytic activity in hydrogenation of dimethyl itaconate with dihydrogen. It has been observed that the structure of the ligand, the reaction temperature and solvent are important to define productivity of the phosphinite-based Rh-catalysts. Bisphosphinite ligands in hydrogenation reactions suffered from an Arbuzov rearrangement, leading to fast deactivation of the hydrogenation catalyst. In contrast, monophosphinite-derived Rh-catalysts showed increased productivity as well as thermal stability. An almost quantitative conversion of dimethyl itaconate has been achieved at elevated temperatures in toluene. Alternatively, hydrogenation of dimethyl itaconate with monophosphinite ligands has been carried out in MeOH at room temperature or 40 °C and has led to a nearly quantitative conversion.