To survive a predator’s attack successfully, animals choose appropriate actions from multiple escape responses. The motor performance of escape response governs successful survival, which implies that the action selection in escape behaviour is based on the trade-off between competing behavioural benefits. Thus, quantitative assessment of motor performance will shed light on the biological basis of decision-making. To explore the trade-off underlying the action selection, we focused on two distinct wind-elicited escape responses of crickets, running and jumping. We first hypothesized a trade-off between speed and directional accuracy. This hypothesis was rejected because crickets could control the escape direction in jumping as precisely as in running; further, jumping had advantages with regard to escape speed. Next, we assumed behavioural flexibility, including responsiveness to additional predator’s attacks, as a benefit of running. The double stimulus experiment revealed that crickets running in the first response could respond more frequently to a second stimulus and control the movement direction more precisely compared to when they chose jumping for the first response. These data suggest that not only the motor performance but also the future adaptability of subsequent behaviours are considered as behavioural benefits, which may be used for choosing appropriate escape reactions.

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Escape behavior is essential for animals to avoid attacks by predators. In some species, multiple escape responses could be employed. However, it remains unknown what aspects of threat stimuli affect the choice of an escape response. We focused on two distinct escape responses (running and jumping) to short airflow in crickets and examined the effects of multiple stimulus aspects including the angle, velocity, and duration on the choice between these responses. The faster and longer the airflow, the more frequently the crickets jumped. This meant that the choice of an escape response depends on both the velocity and duration of the stimulus and suggests that the neural basis for choosing an escape response includes the integration process of multiple stimulus parameters. In addition, the moving speed and distance changed depending on the stimulus velocity and duration for running but not for jumping. Running away would be more adaptive escape behavior.

To elucidate the role of recombinant human colony-stimulating factors (CSFs) for expanding peripheral blood (PB) CD34+ cells, these cells were purified up to 94.5% +/- 1.3% and the effects of individual and combined CSFs on the proliferation and differentiation of these cells were studied in a 7-day suspension culture. The majority of CD34+ cells coexpressed CD38 (81.8% +/- 5.1%), but was negative for CD33 (88.5% +/- 3.4%). Among the individual CSFs examined, recombinant interleukin-3 (rIL-3) was identified as the most potent factor for expanding PB progenitor cells and increased nonerythroid progenitor cells 13- +/- 4- fold (P < .01). Recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF), recombinant granulocyte-CSF (rG-CSF), recombinant macrophage-CSF (rM-CSF), rIL-6, rIL-11, and recombinant stem cell factor (rSCF) did not alone expand nonerythroid progenitor cells. A combination of 5 CSFs, ie, rIL-3, rIL-6, rGM-CSF, rG-CSF, and rSCF, was identified as the most potent combination of those tested and increased nonerythroid progenitor cells 57- +/- 11-fold. After a 7-day suspension culture of CD34+ cells with these 5 CSFs, CD34+ cells expanded 14.5- fold, and CD34+/CD33- cells and CD34+/CD33+ cells were also expanded 2.9-fold and 307-fold, respectively. Most secondary colonies derived from expanded cells were small; however, the absolute number of large- sized colonies expanded 5.9- +/- 3.3-fold. Thus, the combination of CSFs can achieve a degree of amplification of PB CD34+ cells. The capability of in vitro expansion of PB CD34+ cells as an adjunct to PB stem cell transplantation is worthy of consideration.

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