Modeling the effect of information quality on risk behavior change and the transmission of infectious diseases

How the quality of information about the prevalence of an infectious disease affects individuals’ incentives to adopt self-protective actions to reduce the risk of infection is studied using an economic/game-theoretic model of epidemics. In the model, agents make inferences regarding the current prevalence of a disease by observing the health status of a subset of the population. Therefore, the higher the number of agents whose infection status can be observed, the better one’s information about the current prevalence is. In particular, it is assumed that an agent’s estimate of the current prevalence depends on observations of the current health status of other agents and on the agent’s estimate of past prevalence, and that the agent places more weight on the current observations in forming an estimate of the prevailing prevalence when the number of observations increases. It is shown that the likelihood of eradicating an infectious disease through behavioral changes depends critically on the amount of information that individuals have access to, which also determines whether prevalence will be relatively stable or will exhibit cyclical patterns over time. Increasing the amount of information that individuals possess may lower the likelihood of eradication.     

Rapid adaptation: a new dimension for evolutionary perspectives in ecology

Although the study of adaptation is central to biology, two types of adaptation are recognized in the biological field: physiological adaptation (accommodation or acclimation; an individual organism’s phenotype is adjusted to its environment) and evolutionary–biological adaptation (adaptation is shaped by natural selection acting on genetic variation). The history of the former concept dates to the late nineteenth and early twentieth centuries, and has more recently been systemized in the twenty-first century. Approaches to the understanding of phenotypic plasticity and learning behavior have only recently been developed, based on cellular–histological and behavioral–neurobiological techniques as well as traditional molecular biology. New developments of the former concepts in phenotypic plasticity are discussed in bacterial persistence, wing di-/polymorphism with transgenerational effects, polyphenism in social insects, and defense traits for predator avoidance, including molecular biology analyses. We also discuss new studies on the concept of genetic accommodation resulting in evolution of phenotypic plasticity through a transgenerational change in the reaction norm based on a threshold model. Learning behavior can also be understood as physiological phenotypic plasticity, associating with the brain–nervous system, and it drives the accelerated evolutionary change in behavioral response (the Baldwin effect) with memory stock. Furthermore, choice behaviors are widely seen in decision-making of animal foragers. Incorporating flexible phenotypic plasticity and learning behavior into modeling can drastically change dynamical behavior of the system. Unification of biological sciences will be facilitated and integrated, such as behavioral ecology and behavioral neurobiology in the area of learning, and evolutionary ecology and molecular developmental biology in the theme of phenotypic plasticity.     

非人灵长类雌性等级的研究方法

在非人灵长类动物等级研究中, 有关判定与描述优势等级方法的选择至关重要。早期对旧大陆灵长类的等级研究主要关注雄性, 对雌性涉猎较少。目前主要应用攻击-屈服、取食、携婴、相互理毛等行为标准来研究灵长类的雌性等级, 也发现不同的物种往往有不同的雌性等级模式。依据社群结构的完整性将其分为线性等级与非线性等级, 并采用不同的方式进行描述。本文通过查阅文献资料, 对雌性等级的研究内容、判定标准以及描述方式进行论述, 以便抛砖引玉提高非人灵长类雌性等级的研究水平。     

Information‐theory‐based model selection for determining the main vector and period of transmission of Potato virus Y

Potato virus Y (PVY, genus Potyvirus, family Potyviridae) is transmitted non‐persistently by aphids. It causes major losses in potato production (Solanum tuberosum), especially following seed tuber‐borne infection of plants. To limit the risk of PVY infection, seed potato production is located preferably in regions where vector pressure is low. The northern‐most high‐grade seed potato production area (HG zone) of Europe is in Finland. The aim of this study was to determine the incidence of aphid species with documented ability to transmit PVY and to use a modelling approach to determine their relative importance as vectors of PVY in the HG zone of Finland. Winged aphids were caught from six to seven potato fields in each of three growing seasons (2007–09) using yellow pan traps that were examined twice a week. Identification of more than 30 000 individuals indicated that 37% of the aphids belonged to nine species reported to transmit PVY. Incidence of PVY in seed lots was low (0–5.6%) and the seasonal increase of PVY incidence was also low in the potato crops. No potato‐colonising aphids were found on the plants in any of the years. The seasonal increase in PVY incidence was modelled using aphid counts in traps, the relative vector efficiencies of the aphids, virus resistance of cultivars, and the initial infection rate of the seed tubers as explanatory variables in generalised linear mixed modelling. Akaike's information criterion was employed to find the best set of explanatory variables for PVY in harvested tubers. Results of this modelling approach showed that the incidence of seed‐borne PVY infection and the early‐season vector flights are the most important factors contributing to the incidence of PVY in the yield. Compared to models with data from all potential vector species, models containing data from Aphis fabae only showed a better model fit with regard to the incidence of PVY in the harvested tubers. The explanatory power of the models was lost when A. fabae was omitted from the vector data, suggesting that other species play a negligible role as vectors of PVY in the HG zone of Finland. Results can be used to devise appropriate strategies for enhanced control of PVY.     

Individual variation in prey choice in a predator-prey community

One predator-two prey community models are studied with an emphasis on individual variation in predator behavior. The predator behaves according to a well-known prey choice model. The behavioral model predicts that predators should always attack the primary prey (more profitable prey of the two), but only attack the alternative prey (less profitable prey of the two) when the density of the primary prey is below a threshold density. The predator that accepts the alternative prey does not discriminate between the primary and alternative prey (all-or-nothing preference for the alternative prey). However, empirical studies do not result in clear all-or-nothing responses. Previous models examined the relaxation of the all-or-nothing response by assuming partial preference (e.g., predators preferentially forage on the primary prey even when they also attack the alternative prey). In this study, I consider individual variation in two predator traits (prey density perception and handling time) as the sources of the variation in the threshold density, which can make empirical data appear deviated from the expectation. I examine how community models with partial preference and individual variation differ in their dynamics and show that the differences can be substantial. For example, the dynamics of a model based on individual variation can be more stable (e.g., stable in a wider parameter region) than that of a model based on partial preference. As the general statistical property (Jensen’s inequality) is a main factor that causes the differences, the results of the study have general implications to the interpretation of models based on average per-capita rates.     

Mobile phones, radiofrequency fields, and health effects in children--epidemiological studies

In 2004, when WHO organized a workshop on children's sensitivity to electromagnetic fields, very few studies on radiofrequency fields were available. With the recent increase in mobile phone use among children and adolescents, WHO has identified studies on health effects in this age-group as a high priority research area. There are no empirical data supporting the notion that children and adolescents are more susceptible to RF exposure, but the number of studies is still relatively small. There are a few cross-sectional studies on well-being, cognitive effects and behavioral problems, and some cohort studies, mainly of maternal use of mobile phones during pregnancy. Cancer outcomes have been studied in relation to environmental RF exposure, e.g. from transmitters, and only one study on mobile phone use in children and adolescents and brain tumor risk has been published. Several methodological limitations need to be taken into consideration when interpreting the findings of the epidemiological studies. The cross-sectional design does not allow determination of the temporal sequence of exposure and outcome, and for several outcomes there is a large potential for reversed causality, i.e. that the outcome causes an increased RF exposure rather than the opposite. Biases such as recall errors in self-reported mobile phone use, lack of confounding control, e.g. of other aspects of mobile phone use than RF fields, trained behaviors, and pubertal development, makes causal interpretations impossible. Future studies need to include prospectively collected exposure information, incident outcomes, and proper confounding control. Monitoring of brain tumor incidence trends is strongly recommended.     

A behavioral-economic analysis of the essential value of brands

Recently, Hursh and Silberberg (2008) have advanced a behavior-economic approach to measure the value of reinforcers, in which demand elasticity is measured relative to the point at which price is zero, a technique that allows for comparisons across reinforcers that show different consumption patterns or across different dosages or magnitudes of the same reinforcer. The authors have proposed an exponential model in which the elasticity coefficient measures the essential value of reinforcers. The application of the exponential model in various experiments has shown that it provided a good fit to the data and supplied different theoretically consistent results. Considering that this previous research has either been experimentally based or has involved nonhuman participants, the present work examined the application of the model to the analysis of changes in consumption of brands with changes in prices, employing data from actual consumers buying brands of food products in grocery shopping, differing in the level of informational (i.e., socially mediated) and utilitarian (i.e., product mediated) reinforcement they offered. Purchase information concerning two products was obtained from a consumer panel, which included data related to purchases of more than 1600 consumers during 52 weeks. The model, calculated for different brands, fitted the data only moderately, but its parameters showed good reliability across stores. The essential value of brands showed significant increases with increases in brand informational reinforcement. The results indicate the reliability of the measure of essential value as its application is extended from the closed setting of the laboratory to the open settings of the marketplace and to symbolic secondary reinforcers.     

On the significance of structural vegetation elements for caterpillar thermoregulation in two peat bog butterflies: Boloria eunomia and B. aquilonaris

Purpose

Temperature profoundly impacts on distribution and habitat-use of organisms. The development of ectothermous caterpillars does not depend on host plant quality only, but also on the availability of suitable thermal conditions. Selection for thermally favorable microclimates (i.e. behavioral thermoregulation) is a primary mechanism of temperature control, and caterpillars can be either (or alternately) temperature conformers (i.e. passively adopting ambient temperature conditions) or thermoregulators (i.e. able to some extent to elevate or decrease their body temperature relative to ambient temperature). Here, we addressed the functional significance of different structural vegetation elements for the behavioral thermoregulation by caterpillars of two butterfly species.

Results

Weather conditions influenced the caterpillar detection probability within host plant patches, indicating that caterpillars can hide and use suitable microclimates provided by vegetation structures to cope with weather variations. This is why we (1) evaluated the heterogeneity in temperature conditions provided by these structures, (2) quantified the influence of ambient temperature and light intensity on caterpillar body temperature, and (3) tested how position on structure, substrate color and exposition influenced caterpillar body temperature. As expected, vegetation structures provided heterogeneous temperature and sun exposition conditions, while caterpillar body temperature was dependent on ambient temperature and light intensity. But body temperature was additionally influenced by the position on vegetation structures, substrate color and exposition.

Conclusions

These results suggest that there is no unique and fixed structure in the vegetation subsuming the best thermal conditions for caterpillars. We argue that a better understanding of the thermal properties of vegetation structures is essential for correctly understanding caterpillar habitat-use and the behavioral mechanisms driving their body thermoregulation. Conceptually this means that thermal conditions should be included in the definition of a species' functional habitat. Practically this may influence the choice of appropriate habitat management for species of conservation concern.     

Multi-timescale dynamics study of FKBP12 along the rapamycin-mTOR binding coordinate

Drugs can affect function in proteins by modulating their flexibility. Despite this possibility, there are very few studies on how drug binding affects the dynamics of target macromolecules. FKBP12 (FK506 binding protein 12) is a prolyl cis-trans isomerase and a drug target. The immunosuppressant drug rapamycin exerts its therapeutic effect by serving as an adaptor molecule between FKBP12 and the cell proliferation regulator mTOR (mammalian target of rapamycin). To understand the role of dynamics in rapamycin-based immunosuppression and to gain insight into the role of dynamics in the assembly of supramolecular complexes, we used ¹⁵N, ¹³C, and ²H NMR spin relaxation to characterize FKBP12 along the binding coordinate that leads to cell cycle arrest. We show that sequential addition of rapamycin and mTOR leads to incremental rigidification of the FKBP12 backbone on the picosecond-nanosecond timescale. Both binding events lead to perturbation of main-chain and side-chain dynamics at sites distal to the binding interfaces, suggesting tight coupling interactions dispersed throughout the FKBP12-rapamycin interface. Binding of the first molecule, rapamycin, quenches microsecond-millisecond motions of the FKBP12 80's loop. This loop provides much of the surface buried at the protein-protein interface of the ternary complex, leading us to assert that preorganization upon rapamycin binding facilitates binding of the second molecule, mTOR. Widespread microsecond-millisecond motions of the backbone persist in the drug-bound enzyme, and we provide evidence that these slow motions represent coupled dynamics of the enzyme and isomerization of the bound drug. Finally, the pattern of microsecond-millisecond dynamics reported here in the rapamycin complex is dramatically different from the pattern in the complex with the structurally related drug FK506. This raises the important question of how two complexes that are highly isomorphic based on high-resolution static models have such different flexibilities in solution.