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The integral role of apoptosis in the pathogenesis of cardiovascular diseases has been extensively studied and characterized in recent years. The study of cell death in the vasculature has significantly contributed to our knowledge of vascular disease pathology and has played a role in identifying potential therapeutic strategies for these diseases. This chapter describes a number of standard, widely used protocols for detecting and quantifying apoptosis in vessel wall cells and tissue. These techniques include terminal deoxynucleotidyl transferase dUTP nick-end labeling staining for DNA fragmentation, Hoechst staining for chromatin condensation, Annexin V staining, labeling for phosphatidylserine externalization, Western blot assessment of caspase cleavage, immunofluorescence detection of caspase activation, assessment of mitochondrial membrane depolarization and cytochrome c release, and a splenocyte assay for quantifying susceptibility to immune cell-mediated apoptosis. [ABSTRACT FROM AUTHOR]

Conservation biological control (CBC) involves the manipulation of the environment to favour the natural enemies of pests. Alternative agricultural practices, such as organic farming, are more biodiversity-friendly than conventional agricultural practices and generally lead to greater predator species richness and abundance. This is desirable from a conservation perspective, but it is unclear how greater predator diversity affects biological control. Unfortunately, the predator ecology literature provides little guidance: increasing the number of predator species has been shown to enhance, diminish, and not affect prey suppression. In this chapter we explore how the experimental approach used in biodiversity and ecosystem functioning (BEF) studies, which focus on the ecological consequences of species loss, may be used to study how increasing predator diversity affects biological control. The notable features of this approach are: 1) realistic levels of species richness (i.e., < 2 predator species), 2) the use of substitutive, rather than additive, experimental designs, and 3) experimentally distinguishing the effect of species richness from the effects of species abundance, composition, and identity. This experimental approach can be used to identify which components of predator biodiversity—species richness, abundance, composition, and identity—should be targeted by CBC practitioners to maximize pest suppression. Further, it can be used to assess whether predator biodiversity conservation and biological control are truly compatible goals. Ultimately, we hope that this chapter will serve to motivate future research into this important problem. [ABSTRACT FROM AUTHOR]

One of the most challenging questions in biological control has been whether the single best natural enemy will provide greater suppression of the abundance of an arthropod pest than a combination of natural enemies due to the effects of competition for a shared resource (the pest). From a theoretical perspective, simple predator-prey models clearly indicate that for multiple natural enemies sharing a single pest, only a single natural enemy will persist in the system, the species that can reduce the pest to the lowest equilibrium density. In addition, the biological control record of natural enemy introductions against invasive insect pests suggests that establishment rates are higher for projects with single versus multiple introductions, and that competitive exclusion can result from a sequence of parasitoid introductions against a pest. From natural field populations, however, it is clear that insect herbivores frequently support a diverse assemblage of both parasitoid and predator species suggesting that resource partitioning can mediate the effects of competition. So how important are competitive interactions in the context of biological control? Here, I consider the asymmetries of competition among natural enemies of arthropod pests, the incidence of competitive exclusion, the mechanisms of coexistence and their consequences for the success of biological control, and the need for a more experimental approach to the study of competition among natural enemies. [ABSTRACT FROM AUTHOR]

Predicting the direct and indirect effects of natural enemies on herbivorous insects in species-rich, highly connected arthropod food webs can be extremely difficult. Community ecologists developed the keystone species concept to help simplify this task. Keystone species are species that have disproportionately large effects on the abundance of many interacting species in a community. Keystone species, however, can be difficult to identify in some communities and the effect of species that seem to play key roles in community dynamics often vary dramatically in both space and time. In some communities, pairwise interactions among species may alter the community-wide effect of a species such that it functions as a keystone species. In this chapter, we term this a ‘keystone interaction' and explore the possibility that mutualisms involving ants and honeydew-producing Hemipterans may alter the abundance and distribution of many species in a predictable manner via increased ant predation in the presence of Hemipterans. Mutualisms involving ants and honeydew-producing insects are incredibly widespread in terrestrial ecosystems and may alter the structure of entire arthropod communities. We review cases where these mutualisms result in interference of biological control via intraguild predation of important biological control agents as well as cases where ant mutualisms result in enhanced biological control via intensified ant predation of important plant-damaging herbivores. In addition, we report the results of our own work involving the ecological consequences of fire ant-aphid mutualisms. We conclude that ant-Hemiptera mutualisms rarely disrupt biological, but instead these mutualisms often increase the effectiveness of ants as biological control agents via the removal of insect herbivores that are more important pests than the Hemipterans that benefit from ant mutualisms. [ABSTRACT FROM AUTHOR]

In biological control in its simplest form only direct interactions between the control agent and the pest and potential non-targets are considered. Ecologists are however amassing an ever increasing body of evidence for the importance of indirect effects in ecological communities. Indirect effects are the effects of one species on another mediated by at least one intermediate species. An example is so-called apparent competition which is the negative indirect effect that prey species have on each other when they share natural enemies. This effect is thought to play a particularly significant role in phytophagous insect communities where the scope for resource competition is limited. We show that there is experimental evidence for apparent competition amongst phytophagous insects. We describe a community of aphids and their parasitoids, predators and pathogens that we have been studying for over 10 years. We discuss how this species-rich community in a relatively natural environment may be structured by indirect effects. Returning to biological control we discuss how these ideas from community ecology can be applied to enhance pest control and to assess the ecological risks of the introduction of control agents. Introducing or encouraging species that share natural enemies with a target pest may lead to increased pest control through an apparent competition effect by boosting the natural enemy population. We conclude that although occasional attempts are made, such techniques are currently still much underutilised. Equally, we show how indirect effects may cause or increase the impact of introduced control agents on native flora and fauna but that these possible effects are rarely taken into account. [ABSTRACT FROM AUTHOR]

Insect parasitoids are a major mortality factor for their herbivore hosts. Parasitoids typically interact, within their guild and between trophic levels, with several organisms from their community. Both intra- and interspecific competitions occur and the intensity of this competition influences the population dynamics of parasitoids. A female parasitoid may face several types of competition from females of her own species or from different species or from either conspecific or heterospecific females. The strategies evolved by parasitoids to cope with competition have implications both for the population dynamics of these species and for their use as biological control agents. The response of parasitoids to the type and intensity of competition varies at the level of the species, population and individual. In addition, a female parasitoid may change her response to competition depending on the conditions under which she developed and the experience she gained. [ABSTRACT FROM AUTHOR]

Most studies of host-parasite systems consider the interaction between one host and one parasite species. The aim of this chapter is to illustrate how the presence of other interacting species can influence the outcome of particular host-pathogen/parasite interactions. We begin with a brief review of the disease literature considering three broad categories of interactions: (i) cases with one pathogen/parasite and multiple shared hosts; (ii) cases with one host and multiple shared pathogens and/or parasites; (iii) cases with generally one host and pathogen but considering the influence of other interacting species such as natural enemies or competitors. We then consider some specific examples drawn from investigations into the use of fungal entomopathogens for biological control of locusts and grasshoppers. These case histories serve to highlight how an understanding of more complex trophic or guild interactions could help in improving the safety and effectiveness of biological control using pathogens. [ABSTRACT FROM AUTHOR]

Omnivorous predators that also feed on plants (omnivores) are important natural enemies of pest herbivores in many biological control programs. Bottom-up influences of the plant on the biology of these omnivores have been shown to have considerable influence on their interactions with target prey species. Likewise, plants should affect how these omnivores interact with other members of the natural enemy guild in biological control settings. Using community models, we show that intra-guild predation (IGP) by omnivores, in contrast to "pure predators" that do not feed on plants, could be affected by plant quality, and plant toxins. These models suggest that plants should affect IGP by omnivores in two ways: in the short-term by affecting the tendency of omnivores to engage in IGP, and in the long-term, by affecting both herbivore and omnivore population dynamics. We review the available literature effects of plant traits (plant quality, plant toxins, plant hairs, and plant kairomones) on IGP in omnivorous and pure predator species. Although plant traits do affect the nature and intensity of IGP by omnivores, we conclude that the effects are idiosyncratic, and are specific to the species involved. [ABSTRACT FROM AUTHOR]

The use of single versus multiple natural enemies in biological control remains controversial, largely due to the possibility for antagonistic interactions among predators (e.g., intraguild predation and cannibalism) that can reduce the potential for the top-down control of pest herbivores. Using a natural system, Spartina cordgrass and its associated community of arthropods (herbivores, strict predators and intraguild predators), we created 29 different treatment combinations of predators that varied in richness (number of predator species) and trophic composition (proportion of strict to intraguild predators) and measured the ability of each to reduce the density of a key herbivore (the planthopper Prokelisia dolus) in the system. We then calculated food-web connectance (the fraction of all possible directed feeding links that are realized in a food web) for each of the experimental food webs. Notably, food-web connectance is enhanced by predator-predator interactions such as intraguild predation and cannibalism. We found a significant negative relationship between food-web connectance and the ability of the predator complex to reduce prey populations. Specifically, well-connected food webs comprised of mostly intraguild predator species were far less effective at suppressing herbivores than webs consisting largely of strict predators. Importantly, trophic composition of the food web was more influential than predator richness in affecting top-down control. We also discovered that a food web comprised of multiple predators was more effective in suppressing herbivores when the structural complexity of the habitat was increased, a result that was attributable to spatial refuges for intraguild prey and relaxed intraguild predation. Thus, in this system, habitat structure has the potential to transform a well-connected food web into a less-connected one by reducing feeding links resulting from intraguild predation and cannibalism. Because of the remarkable similarity of the Spartina system to tropical Asian rice, this finding provides encouragement that the effectiveness of the predator complex can be enhanced by management practices that increase the structural complexity of the habitat and thereby dampen intraguild predation. Last, we discuss how food-web analyses might be used to evaluate particular combinations of predators for more effective biological control. [ABSTRACT FROM AUTHOR]

Intraguild predation is claimed to be ubiquitous in nature. It also occurs among natural enemies in biological control systems, where one natural enemy (the intraguild predator) attacks another species of natural enemy (the intraguild prey), whereas they also compete for the same pest. We review the theory of intraguild predation and its consequences for biological control for two different scenarios. 1. The intraguild predator is the superior natural enemy ($i.e.$ reduces the pest population the most). In this case, the intraguild predator will exclude the intraguild prey, thus there will be no intraguild predation in the long term. 2. The intraguild prey is the superior natural enemy. In this case, the intraguild predator and intraguild prey may coexist or the intraguild predator can exclude the intraguild prey. Theory predicts for this scenario that pest numbers will always be lowest when only the intraguild prey is present. Hence, the occurrence of intraguild predation in cropping systems would never result in increased control, but can result in decreased control. We subsequently review experimental tests of the effect of intraguild predation among natural enemies on the population dynamics of pests. Contrary to expectations, we find that intraguild predation often did not result in an increase of pest populations, even when the intraguild predator was the inferior natural enemy. Often, the presence of the intraguild predator had no effect or even resulted in a decrease of pest populations. Although the number of studies was limited, we scanned the literature to identify possible causes for the discrepancy of experimental results with theoretical predictions. We specifically evaluated trends in the effects with respect to the length of the study period, the spatial scale at which experiments were carried out, the number of species involved in the studies and the spatial complexity of the experimental arenas. There was a slight trend towards experiments of longer duration showing less positive effects on pest densities, but no clear effect of spatial scale. All studies that showed positive effects on pest densities were studies with 3 species, but the number of studies with more than 3 species was small. Spatial complexity had mixed effects on experimental results. In conclusion, it is clear that intraguild predation most often does not increase pest densities as was predicted from theory, but more research is needed to reveal why theory does not meet practice. [ABSTRACT FROM AUTHOR]

The experimental literature on the effects of intraguild predation on population growth rates of herbivorous arthropod prey has expanded substantially in the last decade, creating a body of results that can be used to test hypotheses relevant to biological control. Here we present a formal meta-analysis of the published experimental literature to assess two hypotheses: (1) intraguild predation causes an increase in the density of the shared herbivore prey, and (2) ‘coincidental intraguild predation', in which a predatory arthropod (the ‘intraguild predator') consumes a herbivore that harbors a developing parasitoid (the ‘intermediate predator'), is less likely to disrupt biological control than is ‘omnivorous intraguild predation', in which the intermediate predator is consumed directly. The meta-analysis reveals that intraguild predation does not universally cause an increase in the density of the shared prey; instead, the mean effect size viewed across all studies is not significantly different from zero, and there is strong variability in effects across studies. The meta-analysis also reveals a marginally significant difference between the effects of coincidental and omnivorous intraguild predation: inclusion of a coincidental intraguild predator significantly enhances biological control, at least in the short-term trials included in our database, whereas inclusion of an omnivorous intraguild predator has little overall effect. Thus, our analysis highlights the diversity of effects generated by intraguild predators within arthropod communities. The discrepancy between theory and empirics appears likely to stem from their different time-frames, with theory often emphasizing equilibria and experimentation examining instead short-term transients, and also with the artificial simplification of arthropod communities depicted in theoretical treatments. More work, both theoretical and empirical, is needed to bridge the gap between theory and observation and to develop a deeper understanding of factors generating the observed diversity of intraguild predator effects. [ABSTRACT FROM AUTHOR]

A major objective of pharmacoepidemiology is to estimate the effects of drugs when they are prescribed after marketing. This is difficult because drug exposure is not a stable phenomenon and may be associated with factors that may also be related to the outcome of interest, such as indication for prescribing. The great challenge of pharmacoepidemiology is to obtain an accurate estimate, i.e., "without error," of the relationship between drug exposure and health status. One great challenge facing the future in pharmacoepidemiology is the ability to control adequately for "indication for prescribing" at the analysis stage. The development of population pharmacokinetics and pharmacodynamics, as well as pharmacogenetics, should also provide useful information for interpreting pharmacoepidemiology results with regard to drug exposure.