Quantitative descriptions of resource choice in ecological models

This article reviews the subject of resource choice by consumers. It is concerned with how such choice has been and should be represented in quantitative ecological models. This requires consideration of the dynamics of behavioral change and the fitness consequences of different resource intake rates. The topic is important because of the impact of choice on the functional response of the consumer to each of the resources it consumes. A variety of open questions related to choice are addressed. These include: the relationship between optimal diet choice and switching; the relationship between adaptive choice of two or resources and type-3 functional responses to a single resource; whether switching behavior requires choice and whether choice always results in switching behavior; why partial preferences are observed; whether choice between habitats is fundamentally different from choice within habitats; how between-individual variation in parameters related to resource use alters functional responses measured at the population level. The impacts of choice on stability are discussed briefly. The costs of increased resource use and the type of nutritional interactions between resources are particularly important determinants of adaptive resource choice, and are considered in some detail.     

RP463: a stabilized technetium-99m complex of a hydrazino nicotinamide derivatized chemotactic peptide for infection imaging.

A HYNIC-conjugated chemotactic peptide (fMLFK-HYNIC) was labeled with (99m)Tc using tricine and TPPTS as coligands. The combination of fMLFK-HYNIC, tricine, and TPPTS with (99m)Tc produced a ternary ligand complex [(99m)Tc(fMLFK-HYNIC)(tricine)(TPPTS)] (RP463). RP463 was synthesized either in two steps, in which the binary ligand complex [(99m)Tc(fMLFK-HYNIC)(tricine)(2)] (RP469) was formed first and then reacted with TPPTS, or in one step by direct reduction of [(99m)Tc]pertechnetate with stannous chloride in the presence of fMLFK-HYNIC, tricine, and TPPTS. The radiolabeling yield for RP463 was usually >/=90% using 10 microg of fMLFK-HYNIC and 100 mCi of [(99m)Tc]pertechnetate. Unlike RP469, which decomposed rapidly in the absence of excess tricine coligand, RP463 was stable in solution for at least 6 h. [(99)Tc]RP463 was prepared and characterized by HPLC and electrospray mass spectrometry. In an in vitro assay, [(99)Tc]RP463 showed an IC(50) of 2 nM against binding of [(3)H]fMLF to receptors on PMNs. [(99)Tc]RP463 also induces effectively the superoxide release of polymorphonuclear leukocytes (PMNs) with an EC(50) value of 0.2 +/- 0.2 nM. The localization of RP463 in the infection foci was assessed in a rabbit infection model. RP463 was cleared from the blood faster than RP469 and was excreted mainly through the renal system. As a result of rapid blood clearance and increased uptake, the target-to-background ratios continuously increased from 1.5 +/- 0.2 at 15 min postinjection to 7.5 +/- 0.4 at 4 h postinjection. Visualization of the infected area could be as early as 2 h. A transient decrease in white blood cell count of 35% was observed during the first 30 min after injection of the HPLC-purified RP463 in the infected rabbit. This suggests that future research in this area should focus on developing highly potent antagonists for chemotactic peptide receptor or other receptors on PMNs and monocytes.     

The effects of interacting species on predator-prey coevolution

Simple optimization models are used to explore the effects that an additional species has on predator-prey coevolution. The additional species is either an alternative prey or a higher-level predator that consumes the first predator species. Results indicate that a variety of effects on predator-prey coevolution are possible. In general, the additional species does not decouple evolutionary changes in the predator and the prey, and often leads to stronger coupling. The manner in which predator and prey adaptations combine to determine the predator's capture rate has a major effect on how an additional species influences the coevolutionary responses of the original pair of species.