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Plant-herbivore chemical signals and behavioral plasticity may enhance parasitoid host-foraging efficacy in the field; however, no studies have quantified the potential benefits from these factors under field-type conditions. The effect of plant-herbivore signals and learning on the foraging efficacy of Microplitis croceipes was quantified by directly observing and recording total and sequential duration of various foraging behaviors relative to 5 randomly placed herbivore-damaged and host-infested cotton plants and 20 undamaged and non-host-infested plants. Microplitis croceipes spent significantly more time searching (flying and antennation) on host infested versus uninfested plants. Antennation time was significantly and negatively correlated with successive host stings. Contrary to expectations of increased duration, flight time remained constant throughout the foraging bout, which may indicate that there was some learning associated with flight. These results suggest that plant-herbivore chemical signals and learning enhances the foraging efficacy of M. croceipes. 相似文献
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First appearing in 2000, and with 20,000 copies sold as it entered its sixth printing in 2004, Richard Trudgen's Why Warriors Lie down and Die is a minor publishing phenomenon. Although scholarly forums have generally ignored the book, Christian media outlets, the popular press and neo‐conservative political activists have enthusiastically received and promoted it. An examination of the merits of Why Warriors Lie down and Die suggests that its popularity is only partly explained by original observations or insights on the part of the author. The most important explanation, and implication, of the book's remarkable take‐up lies in the opportune way in which it corresponds with now ascendant neo‐conservative political perspectives on indigenous policy. 相似文献
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Kate Jolly 《BMJ (Clinical research ed.)》1991,303(6804):716-717
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Controlled generation of reactive oxygen species orchestrates numerous physiological signaling events (Finkel, T. (2011) Signal transduction by reactive oxygen species. J. Cell Biol. 194, 7–15). A major cellular target of reactive oxygen species is the thiol side chain (RSH) of Cys, which may assume a wide range of oxidation states (i.e. −2 to +4). Within this context, Cys sulfenic (Cys-SOH) and sulfinic (Cys-SO2H) acids have emerged as important mechanisms for regulation of protein function. Although this area has been under investigation for over a decade, the scope and biological role of sulfenic/sulfinic acid modifications have been recently expanded with the introduction of new tools for monitoring cysteine oxidation in vitro and directly in cells. This minireview discusses selected recent examples of protein sulfenylation and sulfinylation from the literature, highlighting the role of these post-translational modifications in cell signaling. 相似文献
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Jason L. Schamber James S. Sedinger David H. Ward Kate R. Hagmeier 《Journal of Field Ornithology》2007,78(1):74-82
ABSTRACT. Latitudinal variation in population structure during the winter has been reported in many migratory birds, but has been documented in few species of waterfowl. Variation in environmental and social conditions at wintering sites can potentially influence the population dynamics of differential migrants. We examined latitudinal variation in sex and age classes of wintering Pacific Black Brant ( Branta bernicla nigricans ). Brant are distributed along a wide latitudinal gradient from Alaska to Mexico during the winter. Accordingly, migration distances for brant using different wintering locations are highly variable and winter settlement patterns are likely associated with a spatially variable food resource. We used resightings of brant banded in southwestern Alaska to examine sex and age ratios of birds wintering at Boundary Bay in British Columbia, and at San Quintin Bay, Ojo de Liebre Lagoon, and San Ignacio Lagoon in Baja California from 1998 to 2000. Sex ratios were similar among wintering locations for adults and were consistent with the mating strategy of geese. The distribution of juveniles varied among wintering areas, with greater proportions of juveniles observed at northern (San Quintin Bay and Ojo de Liebre Lagoon) than at southern (San Ignacio Lagoon) locations in Baja California. We suggest that age-related variation in the winter distribution of Pacific Black Brant is mediated by variation in productivity among individuals at different wintering locations and by social interactions among wintering family groups. 相似文献
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Summary In the Chihuahuan Desert of southern New Mexico, both water and nitrogen limit the primary productivity of Larrea tridentata, a xerophytic evergreen shrub. Net photosynthesis was positively correlated to leaf N, but only in plants that received supplemental water. Nutrient-use efficiency, defined as photosynthetic carbon gain per unit N invested in leaf tissue, declined with increasing leaf N. However, water-use efficiency, defined as the ratio of photosynthesis to transpiration, increased with increasing leaf N, and thus these two measures of resource-use efficiency were inversely correlated. Resorption efficiency was not significantly altered over the nutrient gradient, nor was it affected by irrigation treatments. Leaf longevity decreased significantly with fertilization although the absolute magnitude of this decrease was fairly small, in part due to a large background of insect-induced mortality. Age-specific gas exchange measurements support the hypothesis that leaf aging represents a redistribution of resources, rather than actual deterioration or declining resource-use efficiency. 相似文献
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J H de Lange N W Schipper G J Schuurhuis T K ten Kate T H van Heijningen H M Pinedo J Lankelma J P Baak 《Cytometry》1992,13(6):571-576
Changes in intracellular drug localization accompany doxorubicin resistance in multidrug resistant tumor cells. The purpose of this study was to develop a method to quantify these changes and so detect different levels of resistance. Tumor cells were incubated with the fluorescent anthracycline doxorubicin (excitation at 480 nm; emission maximum at 560-590 nm) and were quantified using laser scanning microscopy. The fluorescent mode was used to record the intracellular drug distribution, whereas the absorption mode was used to define the nuclear and cytoplasmic boundaries. The cell compartments were delineated interactively on an image processing system and the ratio nuclear fluorescence/cytoplasmic fluorescence (N/C ratio) was determined. N/C ratios were: 1.8 in the Chinese hamster ovarian cell line AUXB1 and 0.1 in its MDR subline CHRC5; 3.8 in the human squamous lung cancer cell line SW-1573 and 1.8 and 0.4 in its MDR sublines SW-1573/2R120 and SW-1573/2R160, respectively; and 3.6 in the human myeloma cell line 8226/S and 2.1 and 1.0 in its MDR sublines 8226/Dox4 and 8226/Dox40, respectively. The doxorubicin distribution was independent of the doxorubicin concentration within a range from 1-32 microM. Furthermore, the progressive mean of the nuclear/cytoplasmic doxorubicin fluorescence ratio showed that a minimal sample size of 30 cells is necessary for reliable results. The results of two independent assessments showed a high reproducibility (r = 0.97). Thus, with the method described in this paper, it is possible to detect relatively low levels of doxorubicin resistance (factor 8). 相似文献
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