Inverse dynamic modelling of jumping in the red-legged running frog, Kassina maculata

Although the red-legged running frog, Kassina maculata, is secondarily a walker/runner, it retains the capacity for multiple locomotor modes, including jumping at a wide range of angles (nearly 70 deg). Using simultaneous hind limb kinematics and single-foot ground reaction forces, we performed inverse dynamics analyses to calculate moment arms and torques about the hind limb joints during jumping at different angles in K. maculata. We show that forward thrust is generated primarily at the hip and ankle, while body elevation is primarily driven by the ankle. Steeper jumps are achieved by increased thrust at the hip and ankle and greater downward rotation of the distal limb segments. Because of its proximity to the GRF vector, knee posture appears to be important in controlling torque directions about this joint and, potentially, torque magnitudes at more distal joints. Other factors correlated with higher jump angles include increased body angle in the preparatory phase, faster joint openings and increased joint excursion, higher ventrally directed force, and greater acceleration and velocity. Finally, we demonstrate that jumping performance in K. maculata does not appear to be compromised by presumed adaptation to walking/running. Our results provide new insights into how frogs engage in a wide range of locomotor behaviours and the multi-functionality of anuran limbs

As catadoras de mangaba no Programa de Aquisição de Alimentos - PAA: um estudo de caso em Sergipe.

O artigo trata da experiência de um grupo de mulheres extrativistas na comercialização de frutas silvestres, no âmbito do Programa de Aquisição de Alimentos (PAA), no estado de Sergipe. O quadro de análise insere-se no debate sobre pobreza e políticas públicas para grupos específicos no espaço rural. O foco aqui são as autodenominadas "catadoras de mangaba", que assumiram uma identidade coletiva baseada no uso comum de recursos com baixo impacto ambiental e pertencem ao Movimento das Catadoras de Mangaba (MCM). Embora tenham sido recentemente reconhecidas como sujeitos de direitos específicos, vivenciam a diminuição dos recursos, sobre os quais praticam o extrativismo, e as dificuldades de comercialização resultantes da insegurança relativa ao acesso aos frutos e à sazonalidade. A pesquisa foi realizada entre 2008 e 2011 por meio de observação direta e entrevistas abertas e semiestruturadas. Os principais resultados mostram que o PAA tem influenciado no aumento da renda, do consumo e da autoestima. Houve reordenamento da rotina diária das catadoras de mangaba que, para participar do programa, relegaram atividades tradicionais a segundo plano. As regras do programa foram ressignificadas e adaptadas localmente. Constata-se o aumento da solidariedade entre as catadoras participantes, paralelamente à intensificação da concorrência pelos frutos

Extensive degeneracy, Coulomb phase and magnetic monopoles in an artificial realization of the square ice model

Artificial spin ice systems have been introduced as a possible mean to investigate frustration effects in a well-controlled manner by fabricating lithographically-patterned two-dimensional arrangements of interacting magnetic nanostructures. This approach offers the opportunity to visualize unconventional states of matter, directly in real space, and triggered a wealth of studies at the frontier between nanomagnetism, statistical thermodynamics and condensed matter physics. Despite the strong efforts made these last ten years to provide an artificial realization of the celebrated square ice model, no simple geometry based on arrays of nanomagnets succeeded to capture the macroscopically degenerate ground state manifold of the corresponding model. Instead, in all works reported so far, square lattices of nanomagnets are characterized by a magnetically ordered ground state consisting of local flux-closure configurations with alternating chirality. Here, we show experimentally and theoretically, that all the characteristics of the square ice model can be observed if the artificial square lattice is properly designed. The spin configurations we image after demagnetizing our arrays reveal unambiguous signatures of an algebraic spin liquid state characterized by the presence of pinch points in the associated magnetic structure factor. Local excitations, i.e. classical analogues of magnetic monopoles, are found to be free to evolve in a massively degenerated, divergence-free vacuum. We thus provide the first lab-on-chip platform allowing the investigation of collective phenomena, including Coulomb phases and ice-like physics.Comment: 26 pages, 10 figure

FAN1 controls mismatch repair complex assembly via MLH1 retention to stabilize CAG repeat expansion in Huntington's disease

CAG repeat expansion in the HTT gene drives Huntington’s disease (HD) pathogenesis and is modulated by DNA damage repair pathways. In this context, the interaction between FAN1, a DNA-structure-specific nuclease, and MLH1, member of the DNA mismatch repair pathway (MMR), is not defined. Here, we identify a highly conserved SPYF motif at the N terminus of FAN1 that binds to MLH1. Our data support a model where FAN1 has two distinct functions to stabilize CAG repeats. On one hand, it binds MLH1 to restrict its recruitment by MSH3, thus inhibiting the assembly of a functional MMR complex that would otherwise promote CAG repeat expansion. On the other hand, it promotes accurate repair via its nuclease activity. These data highlight a potential avenue for HD therapeutics in attenuating somatic expansion

Meta-analysis of neural systems underlying placebo analgesia from individual participant fMRI data

The brain systems underlying placebo analgesia are insufficiently understood. Here we performed a systematic, participant-level meta-analysis of experimental functional neuroimaging studies of evoked pain under stimulus-intensity-matched placebo and control conditions, encompassing 603 healthy participants from 20 (out of 28 eligible) studies. We find that placebo vs. control treatments induce small, widespread reductions in pain-related activity, particularly in regions belonging to ventral attention (including mid-insula) and somatomotor networks (including posterior insula). Behavioral placebo analgesia correlates with reduced pain-related activity in these networks and the thalamus, habenula, mid-cingulate, and supplementary motor area. Placebo-associated activity increases occur mainly in frontoparietal regions, with high between-study heterogeneity. We conclude that placebo treatments affect pain-related activity in multiple brain areas, which may reflect changes in nociception and/or other affective and decision-making processes surrounding pain. Between-study heterogeneity suggests that placebo analgesia is a multi-faceted phenomenon involving multiple cerebral mechanisms that differ across studies

Programa de aquisição de alimentos: possibilidade para conservação dos recursos de uso comum em comunidade extrativista?

O nosso objetivo neste artigo é analisar os reflexos do PAA sobre o acesso aos recursos de uso comum, questionando seus efeitos sobre a conservação desses recursos numa comunidade extrativista. A hipótese que orienta a reflexão é que, num contexto de manutenção de desigualdades estruturais, especialmente agrárias, a possibilidade de remuneração percebida como satisfatória pelas extrativistas resulte numa intensificação do uso dos recursos nas áreas de acesso comum. Como estes já vêm sendo gradativamente diminuídos pela concentração fundiária, esse aumento pode acarretar em ameaças às práticas tradicionais de conservação. A pesquisa foi realizada por meio de um estudo de caso, com observação direta e registro das atividades de coleta e beneficiamento dos frutos e da ?entrega? aos representantes do PAA, e entrevistas estruturadas e semi-abertas com extrativistas, lideranças e mediadores. Os resultados indicam a confirmação da hipótese, pois, tanto nos discursos dos entrevistados, quanto nas observações é evidente a intensificação do uso dos recursos em áreas de acesso comum em decorrência da concentração fundiária nas terras onde se encontram tais recursos, demandando um debate sobre as possibilidades de sua conservação. Constatamos que estas evidências não constituem efeitos diretos do PAA, mas são parte de um processo que vem se delineando nos últimos anos na localidade, com a destinação das áreas, antes de acesso comum, para outras atividades como agricultura, carcinicultura e infraestrutura de turismo

Microparticles Carrying Sonic Hedgehog Favor Neovascularization through the Activation of Nitric Oxide Pathway in Mice

BACKGROUND: Microparticles (MPs) are vesicles released from plasma membrane upon cell activation and during apoptosis. Human T lymphocytes undergoing activation and apoptosis generate MPs bearing morphogen Shh (MPs(Shh+)) that are able to regulate in vitro angiogenesis.METHODOLOGY/PRINCIPAL FINDINGS: Here, we investigated the ability of MPs(Shh+) to modulate neovascularization in a model of mouse hind limb ischemia. Mice were treated in vivo for 21 days with vehicle, MPs(Shh+), MPs(Shh+) plus cyclopamine or cyclopamine alone, an inhibitor of Shh signalling. Laser doppler analysis revealed that the recovery of the blood flow was 1.4 fold higher in MPs(Shh+)-treated mice than in controls, and this was associated with an activation of Shh pathway in muscles and an increase in NO production in both aorta and muscles. MPs(Shh+)-mediated effects on flow recovery and NO production were completely prevented when Shh signalling was inhibited by cyclopamine. In aorta, MPs(Shh+) increased activation of eNOS/Akt pathway, and VEGF expression, being inhibited by cyclopamine. By contrast, in muscles, MPs(Shh+) enhanced eNOS expression and phosphorylation and decreased caveolin-1 expression, but cyclopamine prevented only the effects of MPs(Shh+) on eNOS pathway. Quantitative RT-PCR revealed that MPs(Shh+) treatment increased FGF5, FGF2, VEGF A and C mRNA levels and decreased those of α5-integrin, FLT-4, HGF, IGF-1, KDR, MCP-1, MT1-MMP, MMP-2, TGFβ1, TGFβ2, TSP-1 and VCAM-1, in ischemic muscles. CONCLUSIONS/SIGNIFICANCE: These findings suggest that MPs(Shh+) may contribute to reparative neovascularization after ischemic injury by regulating NO pathway and genes involved in angiogenesis