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991.
Background: Long non-coding RNAs(lncRNAs) may regulate gene expression in numerous biological processes including cellular response to xenobiotics.The exposure of living organisms to 2,3,7,8-tetrachlorodibenzo-p-dioxin(TCDD),a persistent environmental contaminant,results in reproductive defects in many species including pigs.The aims of the study were to identify and characterize lncRNAs in porcine granulosa cells as well as to examine the effects of TCDD on the lncRNA expression profile in the cells.Results: One thousand six hundred sixty-six lncRNAs were identified and characterized in porcine granulosa cells.The identified lncRNAs were found to be shorter than mRNAs.In addition,the number of exons was lower in lncRNAs than in m RNAs and their exons were longer.TCDD affected the expression of 22 lncRNAs(differentially expressed lncRNAs [DELs]; log2 fold change ≥ 1,P-adjusted 0.05) in the examined cells.Potential functions of DELs were indirectly predicted via searching their target cis-and trans-regulated protein-coding genes.The coexpression analysis revealed that DELs may influence the expression of numerous genes,including those involved in cellular response to xenobiotics,dioxin metabolism,endoplasmic reticulum stress and cell proliferation.Aryl hydrocarbon receptor(AhR) and cytochrome P450 1 A1(CYP1 A1) were found among the trans-regulated genes.Conclusions: These findings indicate that the identified lncRNAs may constitute a part of the regulatory mechanism of TCDD action in granulosa cells.To our knowledge,this is the first study describing lncRNAs in porcine granulosa cells as well as TCDD effects on the lncRNA expression profile.These results may trigger new research directions leading to better understanding of molecular processes induced by xenobiotics in the ovary.  相似文献   
992.
ObjectiveTo investigate the effect of plasma concentrations obtained by a low dose constant rate infusion (CRI) of racemic ketamine or S-ketamine on the nociceptive withdrawal reflex (NWR) in standing ponies.Study designProspective, blinded, cross-over study.AnimalsSix healthy 5-year-old Shetland ponies.MethodsPonies received either 0.6 mg kg−1 racemic ketamine (group RS) or 0.3 mg kg−1 S-ketamine (group S) intravenously (IV), followed by a CRI of 20 μg kg−1minute−1 racemic ketamine (group RS) or 10 μg kg−1minute−1 S-ketamine (group S) for 59 minutes. The NWR was evoked by transcutaneous electrical stimulation of a peripheral nerve before drug administration, 15 and 45 minutes after the start of the bolus injection and 15 minutes after the end of the CRI. Electromyographic responses were recorded and analysed. Arterial blood was collected before stimulation and plasma concentrations of ketamine and norketamine were measured enantioselectively using capillary electrophoresis. Ponies were video recorded and monitored to assess drug effects on behaviour, heart rate (HR), mean arterial blood pressure (MAP) and respiratory rate.ResultsThe NWR was significantly depressed in group RS at plasma concentrations between 20 and 25 ng mL−1 of each enantiomer. In group S, no significant NWR depression could be observed; plasma concentrations of S-ketamine (9–15 ng mL−1) were lower, compared to S-ketamine concentrations in group RS, although this difference was not statistically significant. Minor changes in behaviour, HR and MAP only occurred within the first 5–10 minutes after bolus drug administration in both groups.ConclusionAntinociceptive activity in standing ponies, demonstrated as a depression of the NWR, could only be detected after treatment with racemic ketamine. S-ketamine may have lacked this effect as a result of lower plasma concentrations, a more rapid metabolism or a lower potency of S-ketamine in Equidae so further investigation is necessary.  相似文献   
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995.
Conservationists, managers, and land planners are faced with the difficult task of balancing many issues regarding humans impacts on natural systems. Many of these potential impacts arise from local-scale and landscape-scale changes, but such changes often covary, which makes it difficult to isolate and compare independent effects arising from humans. We partition multi-scale impacts on riparian forest bird distribution in 105 patches along approximately 500 km of the Madison and Missouri Rivers, Montana, USA. To do so, we coupled environmental information from local (within-patch), patch, and landscape scales reflecting potential human impacts from grazing, invasive plant species, habitat loss and fragmentation, and human development with the distribution of 28 terrestrial breeding bird species in 2004 and 2005. Variation partitioning of the influence of different spatial scales suggested that local-scale vegetation gradients explained more unique variation in bird distribution than did information from patch and landscape scales. Partitioning potential human impacts revealed, however, that riparian habitat loss and fragmentation at the patch and landscape scales explained more unique variation than did local disturbances or landscape-scale development (i.e., building density in the surrounding landscape). When distribution was correlated with human disturbance, local-scale disturbance had more consistent impacts than other scales, with species showing consistent negative correlations with grazing but positive correlations with invasives. We conclude that while local vegetation structure best explains bird distribution, managers concerned with ongoing human influences in this system need to focus more on mitigating the effects of large-scale disturbances than on more local land use issues. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
996.
Mediterranean landscapes are dynamic systems that undergo temporal changes in composition and structure in response to disturbances, such as fire. Neither landscape patterns nor driving factors that affect them are evenly distributed in space. Accordingly, disturbances and biophysical factors interact in space through time. The aim of this paper is to assess the relative influence of topography and fire on the landscape patterns of a large forested area located in Sierra de Gredos (Central Spain) through time. A series of Landsat MSS images from 1975 to 1990, and a digital elevation model (DEM) were used to map fires, assess topographical complexity and evaluate changes in landscape composition and structure. Functional regions across the entire landscape were identified using different classification criteria (i.e., percentage burned area and topographic properties) to model topographic and fire impacts at regional scales. A canonical variance partition method, with a time series split-plot design, quantified the relative influence and co-variation of topography and fire on land cover patterns through time. Main results indicated that analyzing portions of the landscape under similar environmental conditions and fire histories, the effects of different fire regimes on the spatio-temporal dynamics of main land covers can be highlighted. However, the impact of fire on landscape patterns was high variable among regions due to the different regeneration abilities of main land covers, the topographic constraints and the fire histories of each region. Hence, broad patterns of fire related variance and co-variation with topography emerged across the entire area due to the different conditions of each landscape portion in which this large Mediterranean landscape was divided. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
997.
Sylvatic plague is a major factor influencing the dynamics of black-tailed prairie dog (Cynomys ludovicianus) colonies in the western Great Plains. We studied the nesting response of the mountain plover (Charadrius montanus), a grassland bird that nests on prairie dog colonies, to plague-driven dynamics of prairie dog colonies at three sites in the western Great Plains. First, we examined plover nest distribution on colonies that were previously affected by plague, but that had been recovering (expanding) for at least 6 years. Plovers consistently nested in both young (colonized in the past 1–2 years) and old (colonized for 6 or more years) portions of prairie dog colonies in proportion to their availability. Second, we examined changes in plover nest frequency at two sites following plague epizootics, and found that mountain plover nest numbers declined relatively rapidly (≤2 years) on plague-affected colonies. Taken together, our findings indicate that available plover nesting habitat associated with prairie dog colonies closely tracks the area actively occupied by prairie dogs each year. Given the presence of plague throughout most of the mountain plover’s breeding range in the western Great Plains, important factors affecting plover populations likely include landscape features that determine the scale of plague outbreaks, the distance that plovers move in response to changing breeding habitat conditions, and the availability and quality of alternate breeding habitat within the landscape.  相似文献   
998.
The land cover pattern in the Lake Balaton catchment (Hungary) has been changing since decollectivization in the 1990s. These land cover changes significantly impact the landscape connectivity, controlling the influx of sediments into the lake. A comparison of high resolution land cover maps from 1981, 2000 and 2005 showed a significant extensification of the agriculture with land cover conversions from arable land and vineyards to grassland and forest. For each land unit transition probabilities were assessed using logistic regression techniques to evaluate to which extent land cover changes are controlled by physical or socio-economic parameters. A stochastic land cover allocation algorithm was applied to generate future land cover patterns. The landscape connectivity for each of the simulated land cover patterns was assessed by means of a distributed routing algorithm. The simulations suggest that further land abandonment in the upslope parts of the catchment will cause a non-linear reduction of average soil erosion rates. The changes, however, have a relatively low impact on the sediment volume entering the lake because of the land unit’s poor connectivity with permanent river channels. The major contributors to the lakes sediment load are the vineyards near the lakeshore. They are likely to be maintained because of their touristic value. A significant reduction of the total sediment input in the lake can be expected only if soil conservation measures in the vineyards near the shorelines are undertaken.  相似文献   
999.
Customary land-use practices create distinctive cultural landscapes, including landscapes where abandoned settlements host vegetation that attracts wild animals. Understanding how landscape patterns relate to land-use history can help clarify the ecological effects of particular land uses. This study examines relationships between chimpanzee habitat selection and Maninka settlement practice, to determine how settlement history has affected chimpanzee habitat in Mali’s Bafing Biosphere Reserve, where conservation practitioners assume that the characteristic settlement pattern reflects a process of settlement expansion into undisturbed habitat. Three types of data are reported: (1) ethnographic interviews on settlement history and practice; (2) systematic sampling of chimpanzee habitat use; and (3) ground-based mapping of settlement sites, surface water, and fruit-tree patches. These data show that the Maninka have a shifting settlement system, meaning that most sites are occupied for only relatively brief periods; and that some abandoned settlement sites host fruit-tree patches that are seasonally important chimpanzee habitat. Two main conclusions are: (1) settlement expansion has not occurred; instead, historic settlement has created habitat that is both attractive and available to chimpanzees. Anthropogenic habitat does not appear to be vital for chimpanzee survival, but it spatially and temporally supplements natural habitats. (2) Conservation policies meant to reduce the presumed threat of settlement expansion may have initiated an unintended, long-term threat of habitat loss for chimpanzees. While settlement practices may be a component of short-term threats to chimpanzees, such as hunting, when addressing these threats conservation practitioners should consider long-term settlement processes to avoid creating new threats.  相似文献   
1000.
Wind farms are positioned in open landscapes and may cause loss of wildlife habitat due to disturbance, fragmentation, and infrastructure development. Especially flocking geese, swans, ducks and waders are regarded as vulnerable to wind farm development. We compared past and current displacement effects of two onshore wind farms and a line of land-based turbines on spring-staging pink-footed geese (Anser brachyrhynchus) to see if there was evidence of habituation. In one wind farm area, geese previously (1998) (Larsen and Madsen 2000) kept a distance of c. 200 m (the distance at which 50% of peak densities is reached) and they did not go between the turbines; today (2008) they keep a distance of c. 100 m, but do still not enter the wind farm area. In another wind farm, where foraging geese previously (2000) kept a distance of more than 100 m and did not enter the wind farm, they now (2008) forage between the wind turbines and keep a distance of c. 40 m to turbines. In 1998, geese kept a distance of 125 m to a line of turbines, compared to 50 m now. We conclude that geese have behaviorally adapted to changing landscapes created by wind farms. The difference in avoidance between the sites may be due to the sizes of the turbines which in this study were small in both rotor-swept area and in height compared to more recent “industry standard” of 2.5 and 3.0 MW turbines. The study points to the need for longer term studies to properly assess the impact of wind farms on wildlife, including consequent increased risks from inclement weather events of feeding, rafting, and migrating waterfowl.  相似文献   
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