Adult tiger beetles Cicindela gemmata modify their foraging strategy in different hunting contexts

Predator-prey interaction has long been an interesting item in the research of animal behaviors. Given that live prey can damage their predators, predators must trade foraging efficiency for safety while hunting, but the extent of this trade-off is not yet clear. Tiger beetles display diversity in their diets and hunting strategies, and hence, they become an ideal system to address how self-security affects foraging efficiency. We addressed this question in captive adult tiger beetles Cicindela gemmata. By offering several types of arthropod and plant foods, we confirmed that C. gemmata is carnivorous. We found that C. gemmata hunt by either ambushing or chasing their prey, and that they switch between strategies based on differences in the number of prey, the prey status and encounter rate, and the number of predators. Ambushing success increased with the number of prey but decreased with prey encounter rate. Chasing success decreased as prey body size and encounter rate increased. Foraging Cicindela gemmata often gave up an attack when it was nonfatal. This active giving up of hunting may be a consequence of a trade-off between foraging efficiency and self-security. Therefore, it is an adaptive response to the risk of injury when hunting for larger live prey.

Human Navigational Strategy for Intercepting an Erratically Moving Target in Chase and Escape Interactions

Pursuit and interception of moving targets are fundamental skills of many animal species. Although previous studies in human interception behaviors have proposed several navigational strategies for intercepting a moving target, it is still unknown which navigational strategy humans use in chase-and-escape interactions. In the present experimental study, by using two one-on-one tasks as seen in ball sports, we showed that human interception behaviors were statistically consistent with a time-optimal model. Our results provide the insight about the navigational strategy for intercepting a moving target in chase-and-escape interactions, which may be common across species.

Associations between Fitness Measures and Change of Direction Speeds with and without Occupational Loads in Female Police Officers

Female police officers may be required to pursue offenders on foot while wearing occupational loads. The aim of this study was to determine relationships between fitness measures and change of direction speed (CODS) in female police officers and the influence of their occupational loads. Retrospective data were provided for 27 female police officers (age = 32.19 ± 5.09 y, height = 162.78 ± 5.01 cm, and mass = 71.31 ± 13.42 kg) and included fitness measures of: lower-body power (standing long jump (SLJ)), upper-body and trunk muscle endurance (push-up (PU) and sit-up (SU)), aerobic power (estimated VO2max), and CODS (Illinois agility test). The CODS test was performed without and with occupational load (10 kg). Paired sample t-tests (between-load conditions) and Pearson's correlations (relationships between measures) were performed with linear regression analysis used to account for the contribution of measures to unloaded and loaded CODS performance. CODS was significantly slower when loaded (unloaded = ~23.17 s, loaded = ~24.14 s, p < 0.001) with a strong, significant relationship between load conditions (r = 0.956, p < 0.001). Moderate to strong, significant relationships were found between all fitness measures ranging from estimated VO2max (r = -0.448) to SU (r = -0.673) in the unloaded condition, with the strength of these relationships increasing in the loaded condition accounting for 61% to 67% of the variance, respectively. While unloaded agility test performance was strongly associated with loaded performance, female police officer CODS was significantly reduced when carrying occupational loads. A variety of fitness measures that influence officer CODS performances become increasingly important when occupational loads are carried.

A reference-based protein degradation assay without global translation inhibitors

Although it is widely appreciated that the use of global translation inhibitors, such as cycloheximide, in protein degradation assays may result in artefacts, these inhibitors continue to be employed, owing to the absence of robust alternatives. We describe here the promoter reference technique (PRT), an assay for protein degradation with two advantageous features: a reference protein and a gene-specific inhibition of translation. In PRT assays, one measures, during a chase, the ratio of a test protein to a long-lived reference protein, a dihydrofolate reductase (DHFR). The test protein and DHFR are coexpressed, in the yeast Saccharomyces cerevisiae, on a low-copy plasmid from two identical P _TDH3 promoters containing additional, previously developed DNA elements. Once transcribed, these elements form 5'-RNA aptamers that bind to the added tetracycline, which represses translation of aptamer-containing mRNAs. The selectivity of repression avoids a global inhibition of translation. This selectivity is particularly important if a component of a relevant proteolytic pathway (e.g. a specific ubiquitin ligase) is itself short-lived. We applied PRT to the Pro/N-end rule pathway, whose substrates include the short-lived Mdh2 malate dehydrogenase. Mdh2 is targeted for degradation by the Gid4 subunit of the GID ubiquitin ligase. Gid4 is also a metabolically unstable protein. Through analyses of short-lived Mdh2 as a target of short-lived Gid4, we illustrate the advantages of PRT over degradation assays that lack a reference and/or involve cycloheximide. In sum, PRT avoids the use of global translation inhibitors during a chase and also provides a "built-in" reference protein.

Comparison of the chase effects of avidin, streptavidin, neutravidin, and avidin-ferritin on a radiolabeled biotinylated anti-tumor monoclonal antibody

Injection of avidin can decrease the background radioactivity due to a radiolabeled biotinylated monoclonal antibody. We compared the chase effects of avidin, streptavidin, neutravidin, and avidin-conjugated ferritin on a radiolabeled antitumor monoclonal antibody in tumor-bearing nude mice. A radioiodine-labeled biotinylated monoclonal antibody (OST7) was administered to athymic mice bearing osteogenic sarcomas. After 24 h, an avidin, streptavidin, neutravidin or avidin-conjugated ferritin chaser was intravenously injected into the mice. At 2 h after the chase, the biodistribution of the radiolabeled monoclonal antibody was determined. Clearance from the blood was dose-dependently accelerated by avidin and its effect was 10-fold stronger than that of neutravidin or avidin-ferritin. Streptavidin did not promote clearance of the biotinylated antibody. Avidin was the most effective chasing agent for improving the biodistribution of the radiolabeled biotinylated monoclonal antibody among the four avidin derivatives tested.