Obstacle avoidance in social groups: : new insights from asynchronous models

For moving animals, the successful avoidance of hazardous obstacles is an important capability. Despite this, few models of collective motion have addressed the relationship between behavioural and social features and obstacle avoidance. We develop an asynchronous individual-based model for social movement which allows social structure within groups to be included. We assess the dynamics of group navigation and resulting collision risk in the context of information transfer through the system. In agreement with previous work, we find that group size has a nonlinear effect on collision risk. We implement examples of possible network structures to explore the impact social preferences have on collision risk. We show that any social heterogeneity induces greater obstacle avoidance with further improvements corresponding to groups containing fewer influential individuals. The model provides a platform for both further theoretical investigation and practical application. In particular, we argue that the role of social structures within bird flocks may have an important role to play in assessing the risk of collisions with wind turbines, but that new methods of data analysis are needed to identify these social structures

Fishing for nutrients in heterogeneous landscapes : modelling plant growth trade-offs in monocultures and mixed communities

The problem of how best to find and exploit essential resources, the quality and locations of which are unknown, is common throughout biology. For plants, the need to grow an efficient root system so as to acquire patchily distributed soil nutrients is typically complicated by competition between plants, and by the costs of maintaining the root system. Simple mechanistic models for root growth can help elucidate these complications, and here we argue that these models can be usefully informed by models initially developed for foraging fish larvae. Both plant and fish need to efficiently search a spatio-temporally variable environment using simple algorithms involving only local information, and both must perform this task against a backdrop of intra- and inter-specific competition and background mortality. Here we develop these parallels by using simple stochastic models describing the growth and efficiency of four contrasting idealized root growth strategies. We show that plants which grow identically in isolation in homogeneous substrates will typically perform very differently when grown in monocultures, in heterogeneous nutrient landscapes and in mixed-species competition. In particular, our simulations show a consistent result that plants which trade-off rapid growth in favour of a more efficient and durable root system perform better, both on average and in terms of the best performing individuals, than more rapidly growing ephemeral root systems. Moreover, when such slower growing but more efficient plants are grown in competition, the overall community productivity can exceed that of the constituent monocultures. These findings help to disentangle many of the context-dependent behaviours seen in the experimental literature, and may form a basis for future studies at the level of complex population dynamics and life history evolution

Base-modified UDP-sugars reduce cell surface levels of P-selectin glycoprotein 1 (PSGL-1) on IL-1β-stimulated human monocytes

P-selectin glycoprotein ligand-1 (PSGL-1, CD162) is a cell-surface glycoprotein that is expressed, either constitutively or inducibly, on all myeloid and lymphoid cell lineages. PSGL-1 is implicated in cell–cell interactions between platelets, leukocytes and endothelial cells, and a key mediator of inflammatory cell recruitment and transmigration into tissues. Here, we have investigated the effects of the β-1,4-galactosyltransferase inhibitor 5-(5-formylthien-2-yl) UDP-Gal (5-FT UDP-Gal, compound 1) and two close derivatives on the cell surface levels of PSGL-1 on human peripheral blood mononuclear cells (hPBMCs). PSGL-1 levels were studied both under basal conditions, and upon stimulation of hPBMCs with interleukin-1β (IL-1β). Between 1 and 24 hours after IL-1β stimulation, we observed initial PSGL-1 shedding, followed by an increase in PSGL-1 levels on the cell surface, with a maximal window between IL-1β-induced and basal levels after 72 h. All three inhibitors reduce PSGL-1 levels on IL-1β-stimulated cells in a concentration-dependent manner, but show no such effect in resting cells. Compound 1 also affects the cell surface levels of adhesion molecule CD11b in IL-1β-stimulated hPBMCs, but not of glycoproteins CD14 and CCR2. This activity profile may be linked to the inhibition of global Sialyl Lewis presentation on hPBMCs by compound 1, which we have also observed. Although this mechanistic explanation remains hypothetical at present, our results show, for the first time, that small molecules can discriminate between IL-1β-induced and basal levels of cell surface PSGL-1. These findings open new avenues for intervention with PSGL-1 presentation on the cell surface of primed hPBMCs and may have implications for anti-inflammatory drug development

Cellular and molecular mechanisms of IMMunE dysfunction and Recovery from SEpsis-related critical illness in adults: An observational cohort study (IMMERSE) protocol paper

Sepsis is a common illness. Immune responses are considered major drivers of sepsis illness and outcomes. However, there are no proven immunomodulator therapies in sepsis. We hypothesised that in-depth characterisation of sepsis-specific immune trajectory may inform immunomodulation in sepsis-related critical illness. We describe the protocol of the IMMERSE study to address this hypothesis. We include critically ill sepsis patients without documented immune comorbidity and age-sex matched cardiac surgical patients as controls. We plan to perform an in-depth biological characterisation of innate and adaptive immune systems, platelet function, humoral components and transcriptional determinants of the immune system responses in sepsis. This will be done at pre-specified time points during their critical illness to generate an illness trajectory. The sample size for each biological assessment is different and is described in detail. In summary, the overall aim of the IMMERSE study is to increase the granularity of longitudinal immunology model of sepsis to inform future immunomodulation trials

Platelets as autonomous drones for hemostatic and immune surveillance

Platelets participate in many important physiological processes, including hemostasis and immunity. However, despite their broad participation in these evolutionarily critical roles, the anucleate platelet is uniquely mammalian. In contrast with the large nucleated equivalents in lower vertebrates, we find that the design template for the evolutionary specialization of platelets shares remarkable similarities with human-engineered unmanned aerial vehicles in terms of overall autonomy, maneuverability, and expendability. Here, we review evidence illustrating how platelets are uniquely suited for surveillance and the manner in which they consequently provide various types of support to other cell types.J.L. Li is supported by Agency for Science, Technology and Research funding. A. Zarbock is supported by Deutsche Forschungsgemeinschaft (ZA428/13-1 and INST211/604-2 A05). A. Hidalgo is supported by Plan Estatal de Investigación Científica y Técnica y de Innovación 2013–2016 (SAF2015-65607-R and PCIN-2014-103), Programa Estatal de I+D+i Orientada a los Retos de la Sociedad Retos Investigación I+D+i from MECI, and cofunding from Fondo Europeo de Desarrollo Regional. Centro Nacional de Investigaciones Cardiovasculares Carlos III is supported by the MECI and the Pro CNIC Foundation and is a Severo Ochoa Center of Excellence (MECI award SEV-2015-0505).S