排序方式: 共有86条查询结果,搜索用时 15 毫秒
11.
This study gives an overview of status and distribution of signal crayfish (Pacifastacus leniusculus), the first NICS in Estonia and its influence on native noble crayfish (Astacus astacus) populations. The first specimen of signal crayfish was caught during the monitoring of noble crayfish in North Estonia in 2008. The signal crayfish has since been found in three additional sites. Test fishing has indicated that the abundance of signal crayfish has been fluctuating between years and among localities. It has had strong negative impact on abundance of one noble crayfish population. The disconnected distribution of signal crayfish strongly suggests that these populations are the result of human-assisted introductions. Real-time PCR analyses proved that signal crayfish carry the causative agent of the crayfish plague, an oomycete Aphanomyces astaci, thus contributing to its spread. Mortalities in noble crayfish populations had been caused by A. astaci strains from A, B and E genotype group. 相似文献
12.
Miia H. Leskinen Elina J. Hautaniemi Anna M. Tahvanainen Jenni K. Koskela Marika P??llysaho Antti J. Tikkakoski Mika K?h?nen Tiit K??bi Onni Niemel? Jukka Mustonen Ilkka H. P?rsti 《PloS one》2014,9(8)
Background
Liquorice ingestion often elevates blood pressure, but the detailed haemodynamic alterations are unknown. We studied haemodynamic changes induced by liquorice consumption in 20 subjects versus 30 controls with average blood pressures of 120/68 and 116/64 mmHg, respectively.Methods
Haemodynamic variables were measured in supine position before and after two weeks of liquorice consumption (daily glycyrrhizin dose 290–370 mg) with tonometric recording of radial blood pressure, pulse wave analysis, and whole-body impedance cardiography. Thirty age-matched healthy subjects maintaining their normal diet were studied as controls.Results
Two weeks of liquorice ingestion elevated peripheral and central systolic and diastolic blood pressure (by 7/4 and 8/4 mmHg, 95% confidence intervals [CI] 2-11/1-8 and 3-13/1-8, respectively, P<0.05), and increased extracellular volume by 0.5 litres (P<0.05 versus controls). Also augmentation index adjusted to heart rate 75/min (from 7% to 11%, 95% CI for change 0.3-7.5, P<0.05) and aortic pulse pressure (by 4 mmHg, 95% CI 1-7, P<0.05) were elevated indicating increased wave reflection from the periphery. In contrast, peripheral (−3/−0.3 mmHg) and central blood pressure (−2/−0.5 mmHg), aortic pulse pressure (−1 mmHg), and augmentation index adjusted to heart rate 75/min (from 9% to 7%) decreased numerically but not statistically significantly without changes in extracellular volume in the control group. Heart rate, systemic vascular resistance, cardiac output, and pulse wave velocity did not differ between the groups.Conclusions
Two weeks of daily liquorice consumption increased extracellular volume, amplified pressure wave reflection from the periphery, and elevated central systolic and diastolic blood pressure.Trial Registration
EU Clinical Trials Register EudraCT 2006-002065-39</url>ClinicalTrials.gov NCT01742702相似文献13.
Temporal and spatial variation of larval parasitism in non-outbreaking populations of a folivorous moth 总被引:2,自引:0,他引:2
In order to assess the role of parasitoids in the regulation of non-outbreaking populations of Epirrita autumnata, a geometrid lepidopteran with outbreaking populations in northern Europe, we examined the temporal and spatial variation
of larval parasitism in southwestern Finland during 6 successive years. The study was carried out on two spatial scales, among
trees within sites of about 1 ha and among sites separated by distances of 2–10 km, using experimental and observational approaches
respectively. The overall percent parasitism was independent of host density on both spatial scales, while temporally it fluctuated
only little. Of the two main parasitoids, the commoner one, Protapanteles immunis, showed a variable response to host density on the larger spatial scale and negative density dependence on the smaller scale.
Temporally, parasitism caused by this species was independent of host density. Another parasitoid, Phobocampe bicingulata, showed positive density dependence on the smaller spatial scale and had a variable response on the larger scale, but exhibited
negative density dependence over time. The results of this study caution against drawing conclusions concerning population
regulation on the grounds of spatial density dependence alone. Larval parasitoids apparently do not maintain low densities
in the E. autumnata populations studied. However, they may suppress E. autumnata densities to a level low enough for density-dependent mortality factor(s) to become regulating. Among other mortality factors
of E. autumnata, pupal predation has been found to be temporally positively density-dependent.
Received: 19 October 1999 / Accepted: 10 January 2000 相似文献
14.
In order to understand biotic patterns and their changes in nature there is an obvious need for high-quality seamless measurements of such patterns. If remote sensing methods have been applied with reasonable success in terrestrial environment, their use in aquatic ecosystems still remained challenging. In the present study we combined hyperspectral remote sensing and boosted regression tree modelling (BTR), an ensemble method for statistical techniques and machine learning, in order to test their applicability in predicting macrophyte and invertebrate species cover in the optically complex seawater of the Baltic Sea. The BRT technique combined with remote sensing and traditional spatial modelling succeeded in identifying, constructing and testing functionality of abiotic environmental predictors on the coverage of benthic macrophyte and invertebrate species. Our models easily predicted a large quantity of macrophyte and invertebrate species cover and recaptured multitude of interactions between environment and biota indicating a strong potential of the method in the modelling of aquatic species in the large variety of ecosystems. 相似文献
15.
Noble crayfish (Astacus astacus) is listed as vulnerable by the IUCN Red List of Threatened Species in Europe. However, very little is known about genetic
diversity and structuring of noble crayfish populations, mainly because of the lack of informative genetic markers. We describe
the isolation and characterization of the first microsatellite markers for this species, which were obtained by screening
4,000 recombinant clones. Eight loci revealed polymorphisms in a panel of 172 individuals from seven populations in Northern
Europe. Number of alleles per locus ranged from two to 10 (average 4.4) and heterozygosity levels among populations varied
from 0 to 0.80 for H
o and from 0 to 0.72 for H
e. 相似文献
16.
Leho Tedersoo Lauri Laanisto Saleh Rahimlou Aurèle Toussaint Tiit Hallikma Meelis Pärtel 《植被学杂志》2018,29(3):560-568
Plants associated with symbiotic N‐fixing bacteria play important roles in early successional, riparian and semi‐dry ecosystems. These so‐called N‐fixing plants are widely used for reclamation of disturbed vegetation and improvement of soil fertility in agroforestry. Yet, available information about plants that are capable of establishing nodulation is fragmented and somewhat outdated. This article introduces the NodDB database of N‐fixing plants based on morphological and phylogenetic evidence (available at https://doi.org/10.15156/bio/587469 ) and discusses plant groups with conflicting reports and interpretation, such as certain legume clades and the Zygophyllaceae family. During angiosperm evolution, N‐fixing plants became common in the fabid rather than in the ‘nitrogen‐fixing’ clade. The global GBIF plant species distribution data indicated that N‐fixing plants tend to be relatively more diverse in savanna and semi‐desert biomes. The compiled and re‐interpreted information about N‐fixing plants enables accurate analyses of biogeography and community ecology of biological N fixation. 相似文献
17.
18.
19.
Bożena Szal Agata Jastrzębska Marek Kulka Karolina Leśniak Anna Podgórska Tiit Pärnik Hiie Ivanova Olav Keerberg Per Gardeström Anna M. Rychter 《Planta》2010,232(6):1371-1382
The MSC16 cucumber (Cucumis sativus L.) mitochondrial mutant was used to study the effect of mitochondrial dysfunction and disturbed subcellular redox state
on leaf day/night carbon and nitrogen metabolism. We have shown that the mitochondrial dysfunction in MSC16 plants had no
effect on photosynthetic CO2 assimilation, but the concentration of soluble carbohydrates and starch was higher in leaves of MSC16 plants. Impaired mitochondrial
respiratory chain activity was associated with the perturbation of mitochondrial TCA cycle manifested, e.g., by lowered decarboxylation
rate. Mitochondrial dysfunction in MSC16 plants had different influence on leaf cell metabolism under dark or light conditions.
In the dark, when the main mitochondrial function is the energy production, the altered activity of TCA cycle in mutated plants
was connected with the accumulation of pyruvate and TCA cycle intermediates (citrate and 2-OG). In the light, when TCA activity
is needed for synthesis of carbon skeletons required as the acceptors for NH4
+ assimilation, the concentration of pyruvate and TCA intermediates was tightly coupled with nitrate metabolism. Enhanced incorporation
of ammonium group into amino acids structures in mutated plants has resulted in decreased concentration of organic acids and
accumulation of Glu. 相似文献
20.