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121.
Acorn dispersal estimated by radio-tracking 总被引:2,自引:0,他引:2
Bird-dispersed seeds are difficult to track, especially in the case of long-distance dispersal events. To estimate the oak
dispersal distance and the seed shadow generated by the European jay (Garrulus glandarius), we inserted radio-transmitters in 239 acorns, placed them in bird-feeders and then located them by radio-tracking. Using
this methodology we located the exact caching site of 94 Quercus ilex and 54 Q. suber acorns and determined the caching habitat characteristics (vegetation type, distance, spatial distribution). The results
show that: (1) there is no differences in the dispersal distance distribution between the different acorn species or sizes,
(2) dispersal distances range from approximately 3 m up to approximately 550 m (mean = 68.6 m; median = 49.2 m), (3) recently
abandoned fields and forest tracks were the sites preferred by jays to cache acorns, whereas fields and shrublands were avoided
and (4) seed shadows showed acorn aggregation zones (i.e. clusters of caches) close to the feeder as well as isolated caches
at longer distances. The results also suggest that radio-transmitters are a cheap and reliable way to determine seed shadows
and quantify both seed dispersal and post-dispersal seed predation for medium to large seeds. 相似文献
122.
Ethylene insensitivity results in down-regulation of rubisco expression and photosynthetic capacity in tobacco 总被引:2,自引:0,他引:2
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Little is known about the effect of hormones on the photosynthetic process. Therefore, we studied Rubisco content and expression along with gas exchange parameters in transgenic tobacco (Nicotiana tabacum) plants that are not able to sense ethylene. We also tested for a possible interaction between ethylene insensitivity, abscisic acid (ABA), and sugar feedback on photosynthesis. We measured Rubisco content in seedlings grown in agar with or without added sugar and fluridone, and Rubisco expression in hydroponically grown vegetative plants grown at low and high CO(2). Furthermore, we analyzed gas exchange and the photosynthetic machinery of transformants and wild-type plants grown under standard conditions. In the presence of exogenous glucose (Glc), agar-grown seedlings of the ethylene-insensitive genotype had lower amounts of Rubisco per unit leaf area than the wild type. No differences in Rubisco content were found between ethylene-insensitive and wild-type seedlings treated with fluridone, suggesting that inhibition of ABA production nullified the effect of Glc application. When larger, vegetative plants were grown at different atmospheric CO(2) concentrations, a negative correlation was found between Glc concentration in the leaves and Rubisco gene expression, with stronger repression by high Glc concentrations in ethylene-insensitive plants. Ethylene insensitivity resulted in plants with comparable fractions of nitrogen invested in light harvesting, but lower amounts in electron transport and Rubisco. Consequently, photosynthetic capacity of the insensitive genotype was clearly lower compared with the wild type. We conclude that the inability to perceive ethylene results in increased sensitivity to Glc, which may be mediated by a higher ABA concentration. This increased sensitivity to endogenous Glc has negative consequences for Rubisco content and photosynthetic capacity of these plants. 相似文献
123.
SIRT1 deacetylase protects against neurodegeneration in models for Alzheimer's disease and amyotrophic lateral sclerosis 总被引:11,自引:0,他引:11
Kim D Nguyen MD Dobbin MM Fischer A Sananbenesi F Rodgers JT Delalle I Baur JA Sui G Armour SM Puigserver P Sinclair DA Tsai LH 《The EMBO journal》2007,26(13):3169-3179
A progressive loss of neurons with age underlies a variety of debilitating neurological disorders, including Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS), yet few effective treatments are currently available. The SIR2 gene promotes longevity in a variety of organisms and may underlie the health benefits of caloric restriction, a diet that delays aging and neurodegeneration in mammals. Here, we report that a human homologue of SIR2, SIRT1, is upregulated in mouse models for AD, ALS and in primary neurons challenged with neurotoxic insults. In cell-based models for AD/tauopathies and ALS, SIRT1 and resveratrol, a SIRT1-activating molecule, both promote neuronal survival. In the inducible p25 transgenic mouse, a model of AD and tauopathies, resveratrol reduced neurodegeneration in the hippocampus, prevented learning impairment, and decreased the acetylation of the known SIRT1 substrates PGC-1alpha and p53. Furthermore, injection of SIRT1 lentivirus in the hippocampus of p25 transgenic mice conferred significant protection against neurodegeneration. Thus, SIRT1 constitutes a unique molecular link between aging and human neurodegenerative disorders and provides a promising avenue for therapeutic intervention. 相似文献
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126.
Sureda A Ferrer MD Tauler P Maestre I Aguiló A Córdova A Tur JA Roche E Pons A 《Free radical research》2007,41(8):874-883
We studied the effects of intense exercise on the neutrophil antioxidant enzyme activities and gene expression. Blood samples were taken from seven cyclists in basal conditions and 3 h after two competition stages of 165 km. Serum creatine kinase (CK) activity, plasma carbonyl derivatives and uric acid levels increased after exercise. The cycling stage induced neutrophilia and increased myeloperoxidase (MPO) activity and reactive oxygen species (ROS) production. Antioxidant enzyme activities (catalase, glutathione peroxidase and superoxide dismutase) decreased after exercise, although gene expression increased. Immunocytochemistry showed catalase (CAT) enzyme equally distributed between the cytoplasm and organelles before exercise, and after exercise the cytoplasmic CAT levels were reduced and were absent in the compartments. After in vitro stimulation with opsonized zymosan (OZ) the extracellular CAT levels increased. This suggests a CAT secretion in order to avoid neutrophil-induced oxidative damage at a local level or to regulate the function of ROS as extracellular signalling molecules. 相似文献
127.
Cell dynamic adhesion and elastic properties probed with cylindrical atomic force microscopy cantilever tips 总被引:1,自引:0,他引:1
Rico F Roca-Cusachs P Sunyer R Farré R Navajas D 《Journal of molecular recognition : JMR》2007,20(6):459-466
Cell adhesion is required for essential biological functions such as migration, tissue formation and wound healing, and it is mediated by individual molecules that bind specifically to ligands on other cells or on the extracellular matrix. Atomic force microscopy (AFM) has been successfully used to measure cell adhesion at both single molecule and whole cell levels. However, the measurement of inherent cell adhesion properties requires a constant cell-probe contact area during indentation, a requirement which is not fulfilled in common pyramidal or spherical AFM tips. We developed a procedure using focused ion beam (FIB) technology by which we modified silicon pyramidal AFM cantilever tips to obtain flat-ended cylindrical tips with a constant and known area of contact. The tips were validated on elastic gels and living cells. Cylindrical tips showed a fairly linear force-indentation behaviour on both gels and cells for indentations >200 nm. Cylindrical tips coated with ligands were used to quantify inherent dynamic cell adhesion and elastic properties. Force, work of adhesion and elasticity showed a marked dynamic response. In contrast, the deformation applied to the cells before rupture was fairly constant within the probed dynamic range. Taken together, these results suggest that the dynamic adhesion strength is counterbalanced by the dynamic elastic response to keep a constant cell deformation regardless of the applied pulling rate. 相似文献
128.
129.
Optimising the capacity of field trials to detect the effect of genetically modified maize on non‐target organisms through longitudinal sampling
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J. Comas B. Lumbierres C. Comas X. Pons R. Albajes 《The Annals of applied biology》2015,166(2):183-195
To assess risks of cultivation of genetically modified crops (GMCs) on non‐target arthropods (NTAs), field tests are necessary to verify laboratory results and in situations where exposure pathways are very complex and cannot be reproduced in the laboratory. A central concern in the design of field trials for this purpose is whether the tests are capable of detecting differences in the abundance or activity of NTAs in a treated crop in comparison with a non‐treated comparator plot. The detection capacity of a trial depends on the abundance and variability of the taxon, the values assumed for type I (α) and II (β) errors, and the characteristics of the trial and statistical design. To determine the optimal trial layout and statistical analysis, 20 field trials carried out in Spain from 2000 to 2009 to assess risks of GMCs on NTAs were examined with α and β set at 0.05 and 0.20, respectively. In this article we aim to determine the optimal number of sampling dates during a season, or longitudinal samples, in the design of field trials for assessing effects of GM maize on NTAs, and the ones that contribute most to achieving detectable treatment effects (dc) less than 50% of the mean of the control. Detection capacities are a function of the number of individual samples taken during the season but a high number of samples is rarely justified because gains of repeated sampling can be relatively low. These gains depend primarily on field tests relative experimental variability in individual samplings (i.e. experimental variability relative to the mean of the control in each sampling date) which in turn depends on the sampling method (visual counts, pitfall traps or yellow sticky traps) and the density (or abundance) of the taxon in question. Taxa showing more density (or abundance) have less relative experimental variability. The smaller the experimental variability, the lower the profit of increasing the number of sampling dates. Sticky traps have a good effect detection capacity and need very few sampling dates, whereas visual counts and pitfall traps have a poorer effect detection capacity and need more individual samples to achieve dc values lower than 50%. In maize field trials, it is recommended to concentrate sampling efforts in certain growth stages; the optimal ones for achieving an acceptable detection capacity are variable but, in general, samples in the first half of the season render better detection capacity than samples in the second half. 相似文献
130.
Sara González-García Carles Martinez Gasol Maria Teresa Moreira Xavier Gabarrell Joan Rieradevall i Pons Gumersindo Feijoo 《The International Journal of Life Cycle Assessment》2011,16(5):465-477