A New Model and Method for Understanding Wolbachia-Induced Cytoplasmic Incompatibility

Wolbachia are intracellular bacteria transmitted almost exclusively vertically through eggs. In response to this mode of transmission, Wolbachia strategically manipulate their insect hosts' reproduction. In the most common manipulation type, cytoplasmic incompatibility, infected males can only mate with infected females, but infected females can mate with all males. The mechanism of cytoplasmic incompatibility is unknown; theoretical and empirical findings need to converge to broaden our understanding of this phenomenon. For this purpose, two prominent models have been proposed: the mistiming-model and the lock-key-model. The former states that Wolbachia manipulate sperm of infected males to induce a fatal delay of the male pronucleus during the first embryonic division, but that the bacteria can compensate the delay by slowing down mitosis in fertilized eggs. The latter states that Wolbachia deposit damaging “locks” on sperm DNA of infected males, but can also provide matching “keys” in infected eggs to undo the damage. The lock-key-model, however, needs to assume a large number of locks and keys to explain all existing incompatibility patterns. The mistiming-model requires fewer assumptions but has been contradicted by empirical results. We therefore expand the mistiming-model by one quantitative dimension to create the new, so-called goalkeeper-model. Using a method based on formal logic, we show that both lock-key- and goalkeeper-model are consistent with existing data. Compared to the lock-key-model, however, the goalkeeper-model assumes only two factors and provides an idea of the evolutionary emergence of cytoplasmic incompatibility. Available cytological evidence suggests that the hypothesized second factor of the goalkeeper-model may indeed exist. Finally, we suggest empirical tests that would allow to distinguish between the models. Generalizing our results might prove interesting for the study of the mechanism and evolution of other host-parasite interactions

Revisiting the relevance of economic theory to hotel revenue management education and practice in the era of Big Data

Abstract This paper explores the role of economics in hospitality education and industry practice, with a particular focus on revenue management, and puts forward an argument for a return to the inclusion of economic theory in UK hospitality education, not seen since the 1990s. Given the increasing amounts of pricing data available to both managers and customers and the consequent market complexities now seen, developing economic literacy is demonstrated to be a crucial skill required for future hospitality graduates, allowing them to make successful revenue decisions and sense-check with confidence the decisions made by automated revenue systems. Economic literacy is defined as a balanced understanding of economic theory that can be applied in real-life business scenarios, extending beyond simple consideration of supply and demand to a mixture of neoclassical and behavioural approaches to economics

Differentially expressed profiles in the larval testes of Wolbachia infected and uninfected Drosophila

BACKGROUND: Wolbachia are endosymbiotic bacteria that are frequently found in arthropods and nematodes. These maternally inherited bacteria manipulate host reproduction by several mechanisms including cytoplasmic incompatibility (CI). CI is the most common phenotype induced by Wolbachia and results in the developmental arrest of embryos derived from crosses between Wolbachia-infected males and uninfected females. Although the molecular mechanisms of CI are currently unknown, several studies suggest that host sperm is modified by Wolbachia during spermatogenesis. RESULTS: We compared the gene expression of Drosophila melanogaster larval testes with and without the wMel strain of Wolbachia to identify candidate genes that could be involved in the interaction between Wolbachia and the insect host. Microarray, quantitative RT-PCR and in situ hybridization analyses were carried out on D. melanogaster larval testes to determine the effect of Wolbachia infection on host gene expression. A total of 296 genes were identified by microarray analysis to have at least a 1.5 fold change [q-value < 5%] in expression. When comparing Wolbachia-infected flies to uninfected flies, 167 genes were up-regulated and 129 genes down-regulated. Differential expression of genes related to metabolism, immunity, reproduction and other functions were observed. Quantitative RT-PCR (qRT-PCR) confirmed 12 genes are differentially expressed in the testes of the 3rd instar larvae of Wolbachia-infected and uninfected flies. In situ hybridization demonstrated that Wolbachia infection changes the expression of several genes putatively associated with spermatogenesis including JH induced protein-26 and Mst84Db, or involved in immune (kenny) or metabolism (CG4988-RA). CONCLUSIONS: Wolbachia change the gene expression of 296 genes in the larval testes of D. melanogaster including genes related to metabolism, immunity and reproduction. Interestingly, most of the genes putatively involved in immunity were up-regulated in the presence of Wolbachia. In contrast, most of the genes putatively associated with reproduction (especially spermatogenesis) were down-regulated in the presence of Wolbachia. These results suggest Wolbachia may activate the immune pathway but inhibit spermatogenesis. Our data provide a significant panel of candidate genes that may be involved in the interaction between Wolbachia and their insect hosts. This forms a basis to help elucidate the underlying mechanisms of Wolbachia-induced CI in Drosophila and the influence of Wolbachia on spermatogenesis

Agent-Based Modeling of a Non-tâtonnement Process for the Scarf Economy: The Role of Learning

In this paper, we propose a meta-learning model to hierarchically integrate individual learning and social learning schemes. This meta-learning model is incorporated into an agent-based model to show that Herbert Scarf’s famous counterexample on Walrasian stability can become stable in some cases under a non-tâtonnement process when both learning schemes are involved, a result previously obtained by Herbert Gintis. However, we find that the stability of the competitive equilibrium depends on how individuals learn—whether they are innovators (individual learners) or imitators (social learners), and their switching frequency (mobility) between the two. We show that this endogenous behavior, apart from the initial population of innovators, is mainly determined by the agents’ intensity of choice. This study grounds the Walrasian competitive equilibrium based on the view of a balanced resource allocation between exploitation and exploration. This balance, achieved through a meta-learning model, is shown to be underpinned by a behavioral/psychological characteristic

Heterogeneity, Price Discovery and Inequality in an Agent-Based Scarf Economy

In this chapter, we develop an agent-based Scarf economy with het- erogeneous agents, who have private prices and adaptively learn from their own experiences and those of others through a meta-learning model. We study the factors affecting the efficacy of price discovery and coordination to the Walrasian Equilibrium. We also find that payoff inequality emerges endoge- nously over time among the agents and this is traced back to intensity of choice (a behavioural parameter) and the associated strategy choices. Agents with high intensities of choice suffer lower payoffs if they do not explore and learn from other agents

Influence of different body mass index cut-off values in assessing the nutritional status of adolescents in a household survey Influência de distintos valores críticos do índice de massa corporal na avaliação do estado nutricional de adolescentes em inquérito domiciliar

The purpose of this study was to evaluate the anthropometric nutritional status of the adolescent population of Niterói, Rio de Janeiro State, Brazil, and the influence of changes in the adopted body mass index (BMI) cut-offs in the nutritional status assessment of the adolescent population. A population-based survey conducted in 2003 obtained data from a probabilistic sample of 1,734 households and 523 adolescents. The multiple proportions test and prevalence ratios were used to analyze differences between estimates obtained from different BMI cut-offs. Changes in cut-off values from the old to the new recommendation of the World Health Organization (WHO) resulted in a significant increase in overweight prevalence among total, male and female adolescent population (25%, 27% and 23%, respectively) (p < 0.05). There were significant increases in the prevalence of low-BMI-for-age among the total (29% increase) and male (39%) adolescent populations when the proposal of the International Obesity Task Force was compared to current WHO BMI-for-age cut-offs (p < 0.05). It is shown that a simple change in cut-off values used to define the anthropometric nutritional status can significantly modify the nutritional profile of an adolescent population.<br>Este artigo tem por objetivo avaliar o estado nutricional antropométrico da população adolescente residente em Niterói, Rio de Janeiro, Brasil, bem como a influência das mudanças nos valores críticos de índice de massa corporal (IMC) na avaliação do estado nutricional dessa população. Uma pesquisa amostral probabilística de base populacional conduzida em 2003 obteve dados de 1.734 domicílios e 523 adolescentes. Testes para múltiplas proporções e razões de prevalência foram utilizados para analisar as diferenças entre estimativas obtidas segundo distintos valores críticos de IMC. Mudanças nos pontos de corte da antiga para a atual recomendação da Organização Mundial da Saúde (OMS) resultaram em aumentos significativos nas prevalências de sobrepeso entre o total de adolescentes, meninos e meninas (25%, 27% e 23%, respectivamente) (p < 0,05). A proposta da International Obesity Task Force resultou em uma redução significativa de 29% e 39% na prevalência de baixo-IMC-para-idade entre o total de adolescentes e meninos, respectivamente, quando comparada à recomendação atual da OMS (p < 0,05). Foi evidenciado que uma simples mudança nos valores de corte empregados na definição do estado nutricional pode alterar significativamente o perfil nutricional de uma população adolescente