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161.
Dexamethasone induces gelsolin synthesis and altered morphology in L929 cells 总被引:1,自引:1,他引:0
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When L929 cells are exposed to 5 μg/ml dexamethasone, synthesis of a 90,000 M(r) polypeptide is induced within 12 h. Flattening of the cells begins at about this time and progresses to become quite prominent after 48 h of exposure. Two-dimensional PAGE and partial proteolytic fingerprints identify the 90,000 M(r) polypeptide as gelsolin, a Ca(++)-dependent inhibitor of actin polymerization. Thus, this system provides evidence that gelsolin may have a role in regulating cell shape in response to physiological agents such as glucocorticoids. 相似文献
162.
Costing eradications of alien mammals from islands 总被引:2,自引:0,他引:2
T. L. F. Martins M. de L. Brooke G. M. Hilton S. Farnsworth J. Gould & D. J. Pain 《Animal Conservation》2006,9(4):439-444
The ability to estimate costs of alien species eradications is essential for a rigorous assessment of priorities for island restoration. Using a global data file from 41 islands, mostly gleaned from the 'grey' literature, we show that the cost of vertebrate eradications can be satisfactorily predicted if island area and species to be eradicated are known. About 72% of the variation in cost can be explained by island area, whereas, for a given area, rodent eradications are 1.7–3.0 times more expensive than ungulate eradications. Costs per hectare decrease with island size. Restricting the analysis to roughly half the data set, the relatively homogeneous half concerned with New Zealand islands, we identify two further influences on cost: date of eradication and distance to the main airport (an indicator of remoteness). For a given area, costs have declined over time but increase with island remoteness. This information therefore provides conservation planners with a robust, if preliminary, estimate of the cost of any proposed eradication programme. 相似文献
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165.
Effects of point‐count duration on estimated detection probabilities and occupancy of breeding birds
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Matthias Leu Matthew L. Farnsworth Erica Fleishman David S. Dobkin Rick D. Scherer Barry R. Noon Brett G. Dickson 《Journal of Field Ornithology》2017,88(1):80-93
Increasingly, point‐count data are used to estimate occupancy, the probability that a species is present at a given location; occupancy accounts for imperfect detection, the probability that a species is detected given that it is present. To our knowledge, effects of sampling duration on inferences from models of bird occupancy have not been evaluated. Our objective was to determine whether changing count duration from 5 to 8 min affected inferences about the occupancy of birds sampled in the Chesapeake Bay Lowlands (eastern United States) and the central and western Great Basin (western United States) in 2012 and 2013. We examined the proportion of species (two doves, one cuckoo, two swifts, five hummingbirds, 11 woodpeckers, and 122 passerines) for which estimates of detection probability were ≥ 0.3. For species with single‐season detection probabilities ≥ 0.3, we compared occupancy estimates derived from 5‐ and 8‐min counts. We also compared estimates for three species sampled annually for 5 yr in the central Great Basin. Detection probabilities based on both the 5‐ and 8‐min counts were ≥ 0.3 for 40% ± 3% of the species in an ecosystem. Extending the count duration from 5 to 8 min increased the detection probability to ≥ 0.3 for 5% ± 0.5% of the species. We found no difference in occupancy estimates that were based on 5‐ versus 8‐min counts for species sampled over two or five consecutive years. However, for 97% of species sampled over 2 yr, precision of occupancy estimates that were based on 8‐min counts averaged 12% ± 2% higher than those based on 5‐min counts. We suggest that it may be worthwhile to conduct a pilot season to determine the number of locations and surveys needed to achieve detection probabilities that are sufficiently high to estimate occupancy for species of interest. 相似文献
166.
Guanghui Lin John Adams Blake Farnsworth Yongdan Wei Bruno D. V. Marino Joseph A. Berry 《Oecologia》1999,119(1):97-108
The ecosystem-level carbon uptake and respiration were measured under different CO2 concentrations in the tropical rainforest and the coastal desert of Biosphere 2, a large enclosed facility. When the mesocosms
were sealed and subjected to step-wise changes in atmospheric CO2 between daily means of 450 and 900 μmol mol−1, net ecosystem exchange (NEE) of CO2 was derived using the diurnal changes in atmospheric CO2 concentrations. The step-wise CO2 treatment was effectively replicated as indicated by the high repeatability of NEE measurements under similar CO2 concentrations over a 12-week period. In the rainforest mesocosm, daily NEE was increased significantly by the high CO2 treatments because of much higher enhancement of canopy CO2 assimilation relative to the increase in the nighttime ecosystem respiration under high CO2. Furthermore, the response of daytime NEE to increasing atmospheric CO2 in this mesocosm was not linear, with a saturation concentration of 750 μmol mol−1. In the desert mesocosm, a combination of a reduction in ecosystem respiration and a small increase in canopy CO2 assimilation in the high CO2 treatments also enhanced daily NEE. Although soil respiration was not affected by the short-term change in atmospheric CO2 in either mesocosm, plant dark respiration was increased significantly by the high CO2 treatments in the rainforest mesocosm while the opposite was found in the desert mesocosm. The high CO2 treatments increased the ecosystem light compensation points in both mesocosms. High CO2 significantly increased ecosystem radiation use efficiency in the rainforest mesocosm, but had a much smaller effect in the
desert mesocosm. The desert mesocosm showed much lower absolute response in NEE to atmospheric CO2 than the rainforest mesocosm, probably because of the presence of C4 plants. This study illustrates the importance of large-scale experimental research in the study of complex global change
issues.
Received: 30 October 1998 / Accepted: 2 December 1998 相似文献
167.
Rossberg AG Farnsworth KD Satoh K Pinnegar JK 《Proceedings. Biological sciences / The Royal Society》2011,278(1712):1617-1625
A central question in community ecology is how the number of trophic links relates to community species richness. For simple dynamical food-web models, link density (the ratio of links to species) is bounded from above as the number of species increases; but empirical data suggest that it increases without bounds. We found a new empirical upper bound on link density in large marine communities with emphasis on fish and squid, using novel methods that avoid known sources of bias in traditional approaches. Bounds are expressed in terms of the diet-partitioning function (DPF): the average number of resources contributing more than a fraction f to a consumer's diet, as a function of f. All observed DPF follow a functional form closely related to a power law, with power-law exponents independent of species richness at the measurement accuracy. Results imply universal upper bounds on link density across the oceans. However, the inherently scale-free nature of power-law diet partitioning suggests that the DPF itself is a better defined characterization of network structure than link density. 相似文献
168.
Veera Kainulainen Yurui Tang Thomas Spillmann Susanne Kilpinen Justus Reunanen Per EJ Saris Reetta Satokari 《BMC microbiology》2015,15(1)
Background
For a good probiotic candidate, the abilities to adhere to intestinal epithelium and to fortify barrier function are considered to be crucial for colonization and functionality of the strain. The strain Lactobacillus acidophilus LAB20 was isolated from the jejunum of a healthy dog, where it was found to be the most pre-dominant lactobacilli. In this study, the adhesion ability of LAB20 to intestinal epithelial cell (IECs) lines, IECs isolated from canine intestinal biopsies, and to canine, porcine and human intestinal mucus was investigated. Further, we studied the ability of LAB20 to fortify the epithelial cell monolayer and to reduce LPS-induced interleukin (IL-8) release from enterocytes.Results
We found that LAB20 presented higher adhesion to canine colonic mucus as compared to mucus isolated from porcine colon. LAB20 showed adhesion to HT-29 and Caco-2 cell lines, and importantly also to canine IECs isolated from canine intestinal biopsies. In addition, LAB20 increased the transepithelial electrical resistance (TER) of enterocyte monolayers and thus strengthened the intestinal barrier function. The strain showed also anti-inflammatory capacity in being able to attenuate the LPS-induced IL-8 production of HT-29 cells.Conclusion
In conclusion, canine indigenous strain LAB20 is a potential probiotic candidate for dogs adhering to the host epithelium and showing intestinal barrier fortifying and anti-inflammatory effects.Electronic supplementary material
The online version of this article (doi:10.1186/s12866-014-0337-9) contains supplementary material, which is available to authorized users. 相似文献169.
The positive role and application of highly accurate mass measurements in proteomics is well documented. The new generation of hybrid FTMS and Q-TOF instruments, including the LTQ-Orbitrap (OT), is remarkable in their ability to routinely produce single-digit to subppm statistical mass accuracy while maintaining high analytical sensitivity. The use of mass calibrants (lock masses) to reduce the systematic error of mass-to-charge measurements has also been reported and, in some cases, incorporated in the instrument control software by the instrument manufacturers. We evaluated the use of one such calibrant in the OT (e.g., polydimethylcyclosiloxane, PCM) to study its impact on the rate of phosphopeptide annotation and found it to lack robustness under normal laboratory conditions. Therefore, we devised a strategy to improve its performance by increasing the external abundance of calibrant molecules in laboratory air. This resulted in a more robust performance of the preprogrammed lock mass recalibration feature as evidenced by improvements in both statistical mass accuracy and peptide annotation rates. 相似文献
170.