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排序方式: 共有220条查询结果,搜索用时 31 毫秒
111.
DENIS FOURNIER JULIEN FOUCAUD ANNE LOISEAU SANDRINE CROS‐ARTEIL HERV JOURDAN JR
ME ORIVEL JULIEN LE BRETON JEAN CHAZEAU ALAIN DEJEAN LAURENT KELLER ARNAUD ESTOUP 《Molecular ecology resources》2005,5(2):239-242
Highly polymorphic genetic markers provide a useful tool for estimating genetic parameters in studies of the evolution of sociality in insects. We isolated and characterized 12 polymorphic microsatellite loci in the invasive ant, Wasmannia auropunctata, and described experimental conditions for PCR (polymerase chain reaction) multiplexing and simultaneously genotyping these loci in two sets of five and seven markers. The number of alleles per locus ranged from two to 14 and the observed heterozygosity ranged from 0.233 to 0.967. Moreover, results of cross‐species amplification tests are reported in three other species of Wasmannia and in two species of the genus Allomerus. 相似文献
112.
Large herbivores affect the stoichiometry of nutrients in a regenerating woodland ecosystem 总被引:1,自引:0,他引:1
Previous studies on the effects of herbivores on nutrient cycling have given little consideration to the relationship between soil nitrogen (N) and phosphorus (P) availability. Here we examined how browsing by red deer influences the relative availability of N and P in a regenerating woodland ecosystem. We found that removal of browsing by fencing for 14 years led to a shift from N toward P limitation of the dominant tree species Betula pubescens . This was evidenced by a significant increase in foliar N:P ratio of B. pubescens as a result of removal of browsing; mean N:P ratio of foliage from browsed areas was 13.2 suggesting that trees growing in browsed areas were N limited, whereas foliage from unbrowsed areas had a mean N:P ratio of 15.8, suggesting that these areas were more P limited. Further evidence of a shift toward P limitation in unbrowsed areas came from the finding that root uptake of labelled 32 P was significantly greater in roots collected from unbrowsed than browsed trees. Soil phosphatase activity did not significantly differ between browsed and unbrowsed areas. Our data indicate therefore that herbivores have the potential to significantly affect the stoichiometry of N and P in forest ecosystems. 相似文献
113.
Monocrotaline (MCT) is a hepatotoxic pyrrolizidine alkaloid that is derived from plants; exposure may occur by consumption of contaminated grains, herbal teas and medicines. MCT can cause liver damage. We investigated the antioxidant effects of selenium (Se) and vitamin E against the toxic effects of MCT. Female Wistar albino rats were divided into four groups: a control group, an MCT group, an MCT + Se group, and an MCT + vitamin E group. Liver tissues were harvested, fixed, processed to paraffin and sections were cut. Anti-von Willebrand factor (vWF) immunohistochemistry, terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL), and hematoxylin and eosin staining were performed. Serum and liver tissue glutathione (GSH), catalase (CAT), and glutathione peroxidase (GPx) levels were measured. Histopathological and TUNEL data showed significantly increased liver damage in the MCT group compared to controls. Histopathological and TUNEL staining indicated significant improvements in the MCT + vitamin E and MCT + Se groups compared to the MCT group. MCT significantly reduced the serum GSH level and GPx activity, and liver GPx activity. Biochemical data indicated a significant improvement in serum GSH level in the MCT + vitamin E group compared to the MCT group. We suggest that vitamin E and Se afford limited protection against MCT hepatotoxicity. 相似文献
114.
LISA WINGATE ULLI SEIBT† KADMIEL MASEYK‡ JÉRÔME OGÉE§ PEDRO ALMEIDA¶ DAN YAKIR‡ JOAO S. PEREIRA¶ MAURIZIO MENCUCCINI 《Global Change Biology》2008,14(9):2178-2193
The oxygen stable isotope composition (δ18O) of CO2 is a valuable tool for studying the gas exchange between terrestrial ecosystems and the atmosphere. In the soil, it records the isotopic signal of water pools subjected to precipitation and evaporation events. The δ18O of the surface soil net CO2 flux is dominated by the physical processes of diffusion of CO2 into and out of the soil and the chemical reactions during CO2–H2O equilibration. Catalytic reactions by the enzyme carbonic anhydrase, reducing CO2 hydration times, have been proposed recently to explain field observations of the δ18O signatures of net soil CO2 fluxes. How important these catalytic reactions are for accurately predicting large‐scale biosphere fluxes and partitioning net ecosystem fluxes is currently uncertain because of the lack of field data. In this study, we determined the δ18O signatures of net soil CO2 fluxes from soil chamber measurements in a Mediterranean forest. Over the 3 days of measurements, the observed δ18O signatures of net soil CO2 fluxes became progressively enriched with a well‐characterized diurnal cycle. Model simulations indicated that the δ18O signatures recorded the interplay of two effects: (1) progressive enrichment of water in the upper soil by evaporation, and (2) catalytic acceleration of the isotopic exchange between CO2 and soil water, amplifying the contributions of ‘atmospheric invasion’ to net signatures. We conclude that there is a need for better understanding of the role of enzymatic reactions, and hence soil biology, in determining the contributions of soil fluxes to oxygen isotope signals in atmospheric CO2. 相似文献
115.
The unseen majority: soil microbes as drivers of plant diversity and productivity in terrestrial ecosystems 总被引:31,自引:1,他引:30
Microbes are the unseen majority in soil and comprise a large portion of life's genetic diversity. Despite their abundance, the impact of soil microbes on ecosystem processes is still poorly understood. Here we explore the various roles that soil microbes play in terrestrial ecosystems with special emphasis on their contribution to plant productivity and diversity. Soil microbes are important regulators of plant productivity, especially in nutrient poor ecosystems where plant symbionts are responsible for the acquisition of limiting nutrients. Mycorrhizal fungi and nitrogen-fixing bacteria are responsible for c. 5–20% (grassland and savannah) to 80% (temperate and boreal forests) of all nitrogen, and up to 75% of phosphorus, that is acquired by plants annually. Free-living microbes also strongly regulate plant productivity, through the mineralization of, and competition for, nutrients that sustain plant productivity. Soil microbes, including microbial pathogens, are also important regulators of plant community dynamics and plant diversity, determining plant abundance and, in some cases, facilitating invasion by exotic plants. Conservative estimates suggest that c. 20 000 plant species are completely dependent on microbial symbionts for growth and survival pointing to the importance of soil microbes as regulators of plant species richness on Earth. Overall, this review shows that soil microbes must be considered as important drivers of plant diversity and productivity in terrestrial ecosystems. 相似文献
116.
Margot ME Gosman Dirkje S Postma Judith M Vonk Bea Rutgers Monique Lodewijk Mieke Smith Marjan A Luinge Nick HT ten Hacken Wim Timens 《Respiratory research》2008,9(1):1-9
Background
Surfactant protein D (SP-D), an innate immune molecule, plays an important protective role during airway inflammation. Deficiency of this molecule induces emphysematous changes in murine lungs, but its significance in human COPD remains unclear.Methods
We collected bronchoalveolar lavage fluid from 20 subjects with varying degrees of COPD (8 former smokers and 12 current smokers) and 15 asymptomatic healthy control subjects (5 never smokers, 3 remote former smokers, and 7 current smokers). All subjects underwent a complete medical history and pulmonary function testing. SP-D was measured by Enzyme-Linked ImmunoSorbent Assay. Statistical analysis was performed using nonparametric methods and multivariable linear regression for control of confounding. The effect of corticosteroid treatment on SP-D synthesis was studied in vitro using an established model of isolated type II alveolar epithelial cell culture.Results
Among former smokers, those with COPD had significantly lower SP-D levels than healthy subjects (median 502 and 1067 ng/mL, respectively, p = 0.01). In a multivariable linear regression model controlling for age, sex, race, and pack-years of tobacco, COPD was independently associated with lower SP-D levels (model coefficient -539, p = 0.04) and inhaled corticosteroid use was independently associated with higher SP-D levels (398, p = 0.046). To support the hypothesis that corticosteroids increase SP-D production we used type II alveolar epithelial cells isolated from adult rat lungs. These cells responded to dexamethasone treatment by a significant increase of SP-D mRNA (p = 0.041) and protein (p = 0.037) production after 4 days of culture.Conclusion
Among former smokers, COPD is associated with lower levels of SP-D and inhaled corticosteroid use is associated with higher levels of SP-D in the lung. Dexamethasone induced SP-D mRNA and protein expression in isolated epithelial cells in vitro. Given the importance of this molecule as a modulator of innate immunity and inflammation in the lung, low levels may play a role in the pathogenesis and/or progression of COPD. Further, we speculate that inhaled steroids may induce SP-D expression and that this mechanism may contribute to their beneficial effects in COPD. Larger, prospective studies are warranted to further elucidate the role of surfactant protein D in modulating pulmonary inflammation and COPD pathogenesis. 相似文献117.
1998年5月-2000年10月间调查了梅州柚果贮藏期的真菌病害,它们是:①柚果绿霉病(Penicilliumdigitatum),②柚果炭疽病(Collettrichumgloeosporioides),③柚果黑腐病(Alternariacitri),④柚果焦腐病(Diplodianatalensis)和⑤柚果酸腐病(Oosporacitri-aurantii)等5种.从几种安全性高的保鲜剂中筛选出1个混用配方,该配方对柚果贮藏防腐保鲜效果明显,贮藏5个月无病斑果达100%,6个月也只有20%的柚果出现少量病斑,且柚果几项质量指标较好. 相似文献
118.
The Influence of Soil Biodiversity on Hydrological Pathways and the Transfer of Materials between Terrestrial and Aquatic Ecosystems 总被引:8,自引:0,他引:8
R. D. Bardgett J. M. Anderson V. Behan-Pelletier L. Brussaard D. C. Coleman C. Ettema A. Moldenke J. P. Schimel D. H. Wall 《Ecosystems》2001,4(5):421-429
The boundaries between terrestrial and aquatic ecosystems, known as critical transition zones (CTZ), are dynamic interfaces
for fluxes of water, sediment, solutes, and gases. Moreover, they often support unique or diverse biotas. Soils, especially
those of riparian zones, have not been recognized as CTZ even though they play a critical role in regulating the hydrologic
pathways of infiltration and leaching, or runoff and erosion, which can cumulatively affect biogeochemical processes and human
livelihoods at landscape scales. In this review, we show how the processes that regulate hydrologic fluxes across and through
soil CTZ are influenced by the activities of soil biota. Our message is fourfold. First, there are a variety of ways in which
soil biodiversity, in terms of richness and dominance, can influence hydrological pathways in soil and thus the transfer of
materials from terrestrial to aquatic ecosystems. Second, the influence of soil organisms on these hydrological pathways is
very much interlinked with other environmental, soil biophysical, and vegetation factors that operate at different spatial
and temporal scales. Third, we propose that the influence of soil biodiversity on hydrological pathways is most apparent (or
identifiable), relative to other factors, in situations that lead to the dominance of certain organisms, such as larger fauna.
Fourth, soils are buffered against environmental change by biophysical properties that have developed over long periods of
time. Therefore, the effects of changes in soil biodiversity on hydrological processes at the ecosystem scale might be delayed
and become most apparent in the long term.
Received 25 February 2000; accepted 11 December 2000. 相似文献
119.
Bardgett RD Richter A Bol R Garnett MH Bäumler R Xu X Lopez-Capel E Manning DA Hobbs PJ Hartley IR Wanek W 《Biology letters》2007,3(5):487-490
When glaciers retreat they expose barren substrates that become colonized by organisms, beginning the process of primary succession. Recent studies reveal that heterotrophic microbial communities occur in newly exposed glacial substrates before autotrophic succession begins. This raises questions about how heterotrophic microbial communities function in the absence of carbon inputs from autotrophs. We measured patterns of soil organic matter development and changes in microbial community composition and carbon use along a 150-year chronosequence of a retreating glacier in the Austrian Alps. We found that soil microbial communities of recently deglaciated terrain differed markedly from those of later successional stages, being of lower biomass and higher abundance of bacteria relative to fungi. Moreover, we found that these initial microbial communities used ancient and recalcitrant carbon as an energy source, along with modern carbon. Only after more than 50 years of organic matter accumulation did the soil microbial community change to one supported primarily by modern carbon, most likely from recent plant production. Our findings suggest the existence of an initial stage of heterotrophic microbial community development that precedes autotrophic community assembly and is sustained, in part, by ancient carbon. 相似文献
120.
RAFAEL G. SEVILLA AMALIA DIEZ MICHAEL NORN OLIVIER MOUCHEL MARC JR
ME VRONIQUE VERREZ‐BAGNIS HILDE VAN PELT LAURENCE FAVRE‐KREY GRIGORIOS KREY THE FISHTRACE CONSORTIUM JOS M. BAUTISTA 《Molecular ecology resources》2007,7(5):730-734
This report describes a set of 21 polymerase chain reaction primers and amplification conditions developed to barcode practically any teleost fish species according to their mitochondrial cytochrome b and nuclear rhodopsin gene sequences. The method was successfully tested in more than 200 marine fish species comprising the main Actinopterygii family groups. When used in phylogenetic analyses, its combination of two genes with different evolutionary rates serves to identify fish at the species level. We provide a flow diagram indicating our validated polymerase chain reaction amplification conditions for barcoding and species identification applications as well as population structure or haplotyping analyses, adaptable to high‐throughput analyses. 相似文献