For the Glory of Athens: Xenophon’s Hipparchikos <Logos>, a technical treatise and instruction manual on ideal leadership

Xenophon’s Peri hippikes <technees>, “On Horsemanship,” and the Hipparchikos <logos>, “the Cavalry Commander”, writings which can be regarded as technical works with a didactic purpose, are almost unknown. Xenophon was interested in problems of leadership and the exercise of power (For the titles of the both writings and the analogous supplementary terms “technees” and “logos” compare Breitenbach, 1966, 1761. Angled brackets are used by modern editors of ancient texts as text-critical signs and are inserted here because “peri hippikes” and “hipparchikos” are adjectives and cannot stand alone; “technees” and “logos” are supplied as absent, but implied, substantives. The conventional signs “<>” clarify this supplementary act for the modern reader.). The “Cavalry Commander” (ca. 365 B.C.) intended for the instruction of potential hipparchs (calvary commanders) is simultaneously political and didactic and technical; in this text, categories of leadership that had been developed in earlier works are combined in a powerful manner. Xenophon constructed “leaders” as exempla (“examples”) of correct behaviour; military and political theory are synthesised. The Hipparchikos logos, as a didactic work, aims to produce specialists who master their techné (“art” or “skill”), to develop their ideal qualities. Both texts are directed at an Athenian society, in which the cavalry had lost their significance and pride as a result of recent political turbulence. Xenophon hoped to reform the cavalry for the benefit of Athens. The basic question of the didactic work is: how can I become the best hipparch, how can I go beyond simply filling the office, and instead develop it for the well-being of the polis and thus serve the city? The art of leadership consists in dealing with subordinates in such a manner that they obey and follow voluntarily—still an innovative and modern approach today.     

Embracing the Complexity: Surfacing Problem Situations with Multiple Actors of the Pineapple Value Chain in Uganda

The complexity of local situations in which agricultural value chains are enacted requires a systemic understanding when seeking to improve interlinked livelihoods. Studying the fresh pineapple value chain in Uganda offers an illustrative example. Individually negotiated and context-specific actor relationships, along with their connected activities can be revealed by conceptualizing the chain as a purposeful human activity system. We followed a systems learning approach to elicit value chain actors’ perspectives on factors influencing their activities while surfacing relevant problem situations, resolutions and constraints. Participatory methods, including cognitive mapping, were used to spark dialogue during meetings with only farmers, traders and brokers and also with mixed groups. The results present the multiple natural, technical and social factors identified by value chain actors leading to losses and benefits to their income. System driving and shaping influences included infrastructure, seasonality, perishability and weather conditions. Process-oriented analysis of multi-stakeholder discussions revealed feedback cycles related to fragmentation of the chain. This resulted from and contributed to problematic communication, price fluctuations and challenges in actor relations. For example, actors proposed uniform pricing and debated the implications. Although the systemic perspective brought forward actors’ awareness of potential benefits of improved collaboration and recognition of interdependent activities, it also exposed barriers. Participatory systems learning helped to capture actors’ room of maneuver, and can support processes towards actor-driven change.     

Colon cancer cell-derived 12(S)-HETE induces the retraction of cancer-associated fibroblast via MLC2, RHO/ROCK and Ca<Superscript>2+</Superscript> signalling

Retraction of mesenchymal stromal cells supports the invasion of colorectal cancer cells (CRC) into the adjacent compartment. CRC-secreted 12(S)-HETE enhances the retraction of cancer-associated fibroblasts (CAFs) and therefore, 12(S)-HETE may enforce invasivity of CRC. Understanding the mechanisms of metastatic CRC is crucial for successful intervention. Therefore, we studied pro-invasive contributions of stromal cells in physiologically relevant three-dimensional in vitro assays consisting of CRC spheroids, CAFs, extracellular matrix and endothelial cells, as well as in reductionist models. In order to elucidate how CAFs support CRC invasion, tumour spheroid-induced CAF retraction and free intracellular Ca²⁺ levels were measured and pharmacological- or siRNA-based inhibition of selected signalling cascades was performed. CRC spheroids caused the retraction of CAFs, generating entry gates in the adjacent surrogate stroma. The responsible trigger factor 12(S)-HETE provoked a signal, which was transduced by PLC, IP3, free intracellular Ca²⁺, Ca²⁺-calmodulin-kinase-II, RHO/ROCK and MYLK which led to the activation of myosin light chain 2, and subsequent CAF mobility. RHO activity was observed downstream as well as upstream of Ca²⁺ release. Thus, Ca²⁺ signalling served as central signal amplifier. Treatment with the FDA-approved drugs carbamazepine, cinnarizine, nifedipine and bepridil HCl, which reportedly interfere with cellular calcium availability, inhibited CAF-retraction. The elucidation of signalling pathways and identification of approved inhibitory drugs warrant development of intervention strategies targeting tumour–stroma interaction.     

Revealing structure and assembly cues for Arabidopsis root-inhabiting bacterial microbiota

The plant root defines the interface between a multicellular eukaryote and soil, one of the richest microbial ecosystems on Earth. Notably, soil bacteria are able to multiply inside roots as benign endophytes and modulate plant growth and development, with implications ranging from enhanced crop productivity to phytoremediation. Endophytic colonization represents an apparent paradox of plant innate immunity because plant cells can detect an array of microbe-associated molecular patterns (also known as MAMPs) to initiate immune responses to terminate microbial multiplication. Several studies attempted to describe the structure of bacterial root endophytes; however, different sampling protocols and low-resolution profiling methods make it difficult to infer general principles. Here we describe methodology to characterize and compare soil- and root-inhabiting bacterial communities, which reveals not only a function for metabolically active plant cells but also for inert cell-wall features in the selection of soil bacteria for host colonization. We show that the roots of Arabidopsis thaliana, grown in different natural soils under controlled environmental conditions, are preferentially colonized by Proteobacteria, Bacteroidetes and Actinobacteria, and each bacterial phylum is represented by a dominating class or family. Soil type defines the composition of root-inhabiting bacterial communities and host genotype determines their ribotype profiles to a limited extent. The identification of soil-type-specific members within the root-inhabiting assemblies supports our conclusion that these represent soil-derived root endophytes. Surprisingly, plant cell-wall features of other tested plant species seem to provide a sufficient cue for the assembly of approximately 40% of the Arabidopsis bacterial root-inhabiting microbiota, with a bias for Betaproteobacteria. Thus, this root sub-community may not be Arabidopsis-specific but saprophytic bacteria that would naturally be found on any plant root or plant debris in the tested soils. By contrast, colonization of Arabidopsis roots by members of the Actinobacteria depends on other cues from metabolically active host cells.     

TNF receptor 1 genetic risk mirrors outcome of anti-TNF therapy in multiple sclerosis

Although there has been much success in identifying genetic variants associated with common diseases using genome-wide association studies (GWAS), it has been difficult to demonstrate which variants are causal and what role they have in disease. Moreover, the modest contribution that these variants make to disease risk has raised questions regarding their medical relevance. Here we have investigated a single nucleotide polymorphism (SNP) in the TNFRSF1A gene, that encodes tumour necrosis factor receptor 1 (TNFR1), which was discovered through GWAS to be associated with multiple sclerosis (MS), but not with other autoimmune conditions such as rheumatoid arthritis, psoriasis and Crohn’s disease. By analysing MS GWAS data in conjunction with the 1000 Genomes Project data we provide genetic evidence that strongly implicates this SNP, rs1800693, as the causal variant in the TNFRSF1A region. We further substantiate this through functional studies showing that the MS risk allele directs expression of a novel, soluble form of TNFR1 that can block TNF. Importantly, TNF-blocking drugs can promote onset or exacerbation of MS, but they have proven highly efficacious in the treatment of autoimmune diseases for which there is no association with rs1800693. This indicates that the clinical experience with these drugs parallels the disease association of rs1800693, and that the MS-associated TNFR1 variant mimics the effect of TNF-blocking drugs. Hence, our study demonstrates that clinical practice can be informed by comparing GWAS across common autoimmune diseases and by investigating the functional consequences of the disease-associated genetic variation.     

Continental-scale patterns of canopy tree composition and function across Amazonia

The world's greatest terrestrial stores of biodiversity and carbon are found in the forests of northern South America, where large-scale biogeographic patterns and processes have recently begun to be described. Seven of the nine countries with territory in the Amazon basin and the Guiana shield have carried out large-scale forest inventories, but such massive data sets have been little exploited by tropical plant ecologists. Although forest inventories often lack the species-level identifications favoured by tropical plant ecologists, their consistency of measurement and vast spatial coverage make them ideally suited for numerical analyses at large scales, and a valuable resource to describe the still poorly understood spatial variation of biomass, diversity, community composition and forest functioning across the South American tropics. Here we show, by using the seven forest inventories complemented with trait and inventory data collected elsewhere, two dominant gradients in tree composition and function across the Amazon, one paralleling a major gradient in soil fertility and the other paralleling a gradient in dry season length. The data set also indicates that the dominance of Fabaceae in the Guiana shield is not necessarily the result of root adaptations to poor soils (nodulation or ectomycorrhizal associations) but perhaps also the result of their remarkably high seed mass there as a potential adaptation to low rates of disturbance.