Red clothing increases perceived dominance,aggression and anger

The presence and intensity of red coloration correlate with male dominance and testosterone in a variety of animal species, and even artificial red stimuli can influence dominance interactions. In humans, red stimuli are perceived as more threatening and dominant than other colours, and wearing red increases the probability of winning sporting contests. We investigated whether red clothing biases the perception of aggression and dominance outside of competitive settings, and whether red influences decoding of emotional expressions. Participants rated digitally manipulated images of men for aggression and dominance and categorized the emotional state of these stimuli. Men were rated as more aggressive and more dominant when presented in red than when presented in either blue or grey. The effect on perceived aggression was found for male and female raters, but only male raters were sensitive to red as a signal of dominance. In a categorization test, images were significantly more often categorized as ‘angry’ when presented in the red condition, demonstrating that colour stimuli affect perceptions of emotions. This suggests that the colour red may be a cue used to predict propensity for dominance and aggression in human males.     

Key mutations stabilize antigen‐binding conformation during affinity maturation of a broadly neutralizing influenza antibody lineage

Affinity maturation, the process in which somatic hypermutation and positive selection generate antibodies with increasing affinity for an antigen, is pivotal in acquired humoral immunity. We have studied the mechanism of affinity gain in a human B‐cell lineage in which two main maturation pathways, diverging from a common ancestor, lead to three mature antibodies that neutralize a broad range of H1 influenza viruses. Previous work showed that increased affinity in the mature antibodies derives primarily from stabilization of the CDR H3 loop in the antigen‐binding conformation. We have now used molecular dynamics simulations and existing crystal structures to identify potentially key maturation mutations, and we have characterized their effects on the CDR H3 loop and on antigen binding using further simulations and experimental affinity measurements, respectively. In the two maturation pathways, different contacts between light and heavy chains stabilize the CDR H3 loop. As few as two single‐site mutations in each pathway can confer substantial loop stability, but none of them confers experimentally detectable stability on its own. Our results support models of the germinal center reaction in which two or more mutations can occur without concomitant selection and show how divergent pathways have yielded functionally equivalent antibodies. Proteins 2014; 83:771–780. © 2014 The Authors. Proteins: Structure, Function, and Bioinformatics Published by Wiley Periodicals, Inc.     

Viral expression of insulin-like growth factor-I enhances muscle hypertrophy in resistance-trained rats.

Muscle hypertrophy is the product of increased drive through protein synthetic pathways and the incorporation of newly divided satellite cells. Gains in muscle mass and strength can be achieved through exercise regimens that include resistance training. Increased insulin-like growth factor-I (IGF-I) can also promote hypertrophy through increased protein synthesis and satellite cell proliferation. However, it is not known whether the combined effect of IGF-I and resistance training results in an additive hypertrophic response. Therefore, rats in which viral administration of IGF-I was directed to one limb were subjected to ladder climbing to test the interaction of each intervention on muscle mass and strength. After 8 wk of resistance training, a 23.3% increase in muscle mass and a 14.4% increase in peak tetanic tension (P(o)) were observed in the flexor hallucis longus (FHL). Viral expression of IGF-I without resistance training produced a 14.8% increase in mass and a 16.6% increase in P(o) in the FHL. The combined interventions produced a 31.8% increase in muscle mass and a 28.3% increase in P(o) in the FHL. Therefore, the combination of resistance training and overexpression of IGF-I induced greater hypertrophy than either treatment alone. The effect of increased IGF-I expression on the loss of muscle mass associated with detraining was also addressed. FHL muscles treated with IGF-I lost only 4.8% after detraining, whereas the untreated FHL lost 8.3% muscle mass. These results suggest that a combination of resistance training and overexpression of IGF-I could be an effective measure for attenuating the loss of training-induced adaptations.     

Divergence and evolution of assortative mating in a polygenic trait model of speciation with gene flow

Assortative mating is an important driver of speciation in populations with gene flow and is predicted to evolve under certain conditions in few‐locus models. However, the evolution of assortment is less understood for mating based on quantitative traits, which are often characterized by high genetic variability and extensive linkage disequilibrium between trait loci. We explore this scenario for a two‐deme model with migration, by considering a single polygenic trait subject to divergent viability selection across demes, as well as assortative mating and sexual selection within demes, and investigate how trait divergence is shaped by various evolutionary forces. Our analysis reveals the existence of sharp thresholds of assortment strength, at which divergence increases dramatically. We also study the evolution of assortment via invasion of modifiers of mate discrimination and show that the ES assortment strength has an intermediate value under a range of migration‐selection parameters, even in diverged populations, due to subtle effects which depend sensitively on the extent of phenotypic variation within these populations. The evolutionary dynamics of the polygenic trait is studied using the hypergeometric and infinitesimal models. We further investigate the sensitivity of our results to the assumptions of the hypergeometric model, using individual‐based simulations.     

Predator identity and time of day interact to shape the risk–reward trade-off for herbivorous coral reef fishes

Non-consumptive effects (NCEs) of predators occur as prey alters their habitat use and foraging decisions to avoid predation. Although NCEs are recognized as being important across disparate ecosystems, the factors influencing their strength and importance remain poorly understood. Ecological context, such as time of day, predator identity, and prey condition, may modify how prey species perceive and respond to risk, thereby altering NCEs. To investigate how predator identity affects foraging of herbivorous coral reef fishes, we simulated predation risk using fiberglass models of two predator species (grouper Mycteroperca bonaci and barracuda Sphyraena barracuda) with different hunting modes. We quantified how predation risk alters herbivory rates across space (distance from predator) and time (dawn, mid-day, and dusk) to examine how prey reconciles the conflicting demands of avoiding predation vs. foraging. When we averaged the effect of both predators across space and time, they suppressed herbivory similarly. Yet, they altered feeding differently depending on time of day and distance from the model. Although feeding increased strongly with increasing distance from the predators particularly during dawn, we found that the barracuda model suppressed herbivory more strongly than the grouper model during mid-day. We suggest that prey hunger level and differences in predator hunting modes could influence these patterns. Understanding how context mediates NCEs provides insight into the emergent effects of predator–prey interactions on food webs. These insights have broad implications for understanding how anthropogenic alterations to predator abundances can affect the spatial and temporal dynamics of important ecosystem processes.     

末次盛冰期环境恶化对中国北方旧石器文化的影响

末次冰期间冰段时,中国北方地区水热条件普遍较好,旧石器文化也比较发达。然而,进入末次盛冰期后,随着气温的普遍降低和降水量的明显减少,草原和沙漠带急速向南扩张,动物群也大举南迁。对于这种严酷的生存环境,中国北方的旧石器文化是如何响应的呢?本文以宁夏彭阳PY01-02,PY03和PY05等地点的地层剖面和石制品的研究为基础,首先提出彭阳地点群地层沉积相由河湖相沉积迅速转变为黄土堆积说明由末次冰期间冰段到末次盛冰期自然环境发生了剧烈变化。其次,通过对上述两种不同沉积相中出土石制品的大小、重量、原料以及技术上的比较说明随着环境的变化石制品本身也发生了相应的变化。下层河湖相堆积中出土的石制品粗大笨重,主要以各种石英岩为原料,与同期泾水上游旧石器文化的特征相近,应是当地文化特征的一种具体体现。上层马兰黄土中的石制品的普遍较小,主要以石英和燧石为原料,其中用燧石制成的细石器具有宁夏灵武水洞沟下文化层同类制品的特征,而用石英制成的小石器则同海原一带的史前文化有着较为密切的联系,据此作者推测这可能与史前人类在环境日益恶劣的情况下向南迁移有关。山西南部地区的下川和柿子滩遗址的地层和石制品证据亦表明,末次盛冰期前后该地区旧石器文化的明显差异可能也与末次盛冰期环境恶化时人类的迁徙有关。最后,中国北方地区考古遗址的空间分布变化为上述史前人类南迁的推测提供了有力证据。因此,作者认为末次冰期的环境恶化对中国北方旧石器文化的影响具有普遍性。