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51.
J H Scharf 《Gegenbaurs morphologisches Jahrbuch》1974,120(3):297-298
52.
Previous experimental studies of competition among foragers rarely distinguished between exploitation and interference competition.
In many systems this separation is experimentally impossible without interfering with the natural behavior of the animals.
Consequently, these studies can only demonstrate the combined effect of interference and exploitation on the forager’s feeding
rate, namely, it usually decreases in a decelerating rate as a function of density. We suggest here a simple experimental
and statistical procedure that facilitates the separation of the effects of interference from those of exploitation. This
procedure includes manipulation of both predator density and the foraging experiment duration. The statistical analysis is
based on multiple linear regression. The working assumption is that exploitation can be neglected at the beginning of the
foraging experiment because, initially, predators do not experience diminishing returns in prey capture rates. Using both
the results of an individual-based simulation and a field experiment dataset of gerbils foraging for seeds in an artificial
food patch located in the field, we demonstrate that our procedure can successfully detect and separate the effect of interference
from the combined overall effect of competition (i.e., interference plus exploitation).
Inon Scharf and Ido Filin contributed equally to this paper. 相似文献
53.
The behaviors of both cheZ-deleted and wild-type cells of Escherichia coli were found to be very sensitive to the level of expression of CheZ, a protein known to accelerate the dephosphorylation of the response regulator CheY-phosphate (CheY-P). However, cells induced to run and tumble by the unphosphorylated mutant protein CheY13DK106YW (CheY**) failed to respond to CheZ, even when CheZ was expressed at high levels. Therefore, CheZ neither affects the flagellar motors directly nor sequesters CheY**. In in vitro cross-linking studies, CheY** promoted trimerization of CheZ to the same extent as wild-type CheY but failed to induce the formation of complexes of higher molecular weight observed with CheY-P. Also, CheY** could be cross-linked to FliM, the motor receptor protein, nearly as well as CheY-P. Thus, to CheZ, CheY** looks like CheY, but to FliM, it looks like CheY-P. 相似文献
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There are few studies investigating the influence of vagally mediated reflexes on the cardiovascular response to apneas. In 12 sedated preinstrumented pigs, we studied the effects of vagotomy during apneas, controlling for apnea periodicity and thoracic mechanical effects. Nonobstructive apneas were produced by paralyzing and mechanically ventilating the animals, then turning the ventilator off and on every 30 s. Before vagotomy, relative to baseline, apnea caused increased mean arterial pressure (MAP; +19 +/- 25%, P < 0.05), systemic vascular resistance (SVR; +33 +/- 16%, P < 0.0005), and heart rate (HR; +5 +/- 6%, P < 0.05) and decreased cardiac output (CO) and stroke volume (SV; -16 +/- 10% P < 0.001). After vagotomy, no significant change occurred in MAP, SVR, and SV during apneas, but CO and HR increased relative to baseline. HR was always greater ( approximately 14%, P < 0.01) during the interapneic interval compared with during apnea. We conclude that vagally mediated reflexes are important mediators of the apneic pressor response. HR increases after apnea termination are related, at least in part, to nonvagally mediated reflexes. 相似文献
60.
Human and mouse RAD17 genes: identification, localization, genomic structure and histological expression pattern in normal testis and seminoma 总被引:4,自引:0,他引:4