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81.
Marklund M Landberg R Åman P Kamal-Eldin A 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2011,879(9-10):647-651
Alkylresorcinols (AR) are amphiphilic compounds present at high concentrations in the outer parts of wheat and rye kernels. Due to their specificity to whole grain and bran products of these cereals, AR and their metabolites have been proposed as biomarkers for intake of such foods. Two alkylresorcinol metabolites, 3,5-dihydroxybenzoic acid (DHBA) and 3-(3,5-dihydroxyphenyl)-1-propanoic acid (DHPPA), have previously been quantified in human urine using two different methodologies: high-performance liquid chromatography coupled to a coulometric electrode array detector (HPLC-CEAD) and gas chromatography in combination with mass spectrometry (GC-MS). In this study, these two methodologies were compared by analysing 114 urine samples from free-living Swedish subjects consuming their habitual diet. Data were evaluated by graphical investigation of difference-plots and statistical inference of agreement was assessed by weighted Deming regression analysis. The median DHBA concentrations were 11 μM (GC-MS) and 13 μM (HPLC-CEAD), respectively. Both difference-plot and regression analysis showed a small but statistically significant additive bias, with HPLC-CEAD resulting in a slightly higher DHBA concentration than GC-MS. The median concentration of DHPPA was 18 μM for both methods. Examination of the difference-plot of DHPPA did not indicate any systematic difference between the methods, but regression analysis showed small but statistically significant constant and proportional biases. The conclusion was that the two methodologies are equally suitable for analysis of alkylresorcinol metabolites in human urine and that any small systematic differences observed are most likely of limited practical importance. 相似文献
82.
Koivula MJ 《ZooKeys》2011,(100):287-317
Classic studies have successfully linked single-species abundances, life-history traits, assemblage structures and biomass of carabid beetles to past and present, human-caused environmental impacts and variation in ‘natural’ conditions. This evidence has led many to suggest carabids to function as ‘indicators’ − a term that bears multiple meanings. Here, a conservation-oriented definition for an indicator is used, carabid indicator potential from seven views is evaluated, and ways to proceed in indicator research are discussed. (1) Carabid species richness poorly indicates the richness and abundance of other taxa, which underlines the importance of using multiple taxa in environmental assessments. The ability of assemblage indices and specialist or functional-group abundances to reflect rare species and habitats should be examined in detail. (2) Experimental evidence suggests that carabids may potentially serve as keystone indicators. (3) Carabids are sensitive to human-altered abiotic conditions, such as pesticide use in agro-ecosystems and heavy metal contamination of soils. Carabids might thus reflect ecological sustainability and ‘ecosystem health’. (4) Carabid assemblages host abundant species characteristic of particular habitat types or successional stages, which makes them promising dominance indicators. (5) Carabids reflect variation in ‘natural’ conditions, but vegetation and structural features are more commonly adopted as condition indicators. Carabids nevertheless provide yet another, equally accurate, view on the structure of the environment. (6) Carabids may function as early-warning signalers, as suggested by recent studies linking climate and carabid distributions. (7) Carabids reflect natural and human-caused disturbances and management, but the usefulness of these responses for conservation purposes requires further research. In summary, European carabids appear useful model organisms and possibly indicators because they are diverse, taxonomically and ecologically well-known, efficiently reflect biotic and abiotic conditions, are relevant at multiple spatial scales, and are easy to collect in sufficiently large numbers to allow statistical analyses. The assumption that carabid responses would reflect rare environmental conditions or the responses of rare and threatened species ‒ crucial information for conservationists and managers ‒ has not yet been critically evaluated. Even if it holds, the usefulness will be context dependent: species and their populations vary, conditions vary, questions put forward vary, and assessment goals vary. 相似文献
83.
84.
High temperature and bacteriophages can indirectly select for bacterial pathogenicity in environmental reservoirs 总被引:1,自引:0,他引:1
Friman VP Hiltunen T Jalasvuori M Lindstedt C Laanto E Örmälä AM Laakso J Mappes J Bamford JK 《PloS one》2011,6(3):e17651
The coincidental evolution hypothesis predicts that traits connected to bacterial pathogenicity could be indirectly selected outside the host as a correlated response to abiotic environmental conditions or different biotic species interactions. To investigate this, an opportunistic bacterial pathogen, Serratia marcescens, was cultured in the absence and presence of the lytic bacteriophage PPV (Podoviridae) at 25°C and 37°C for four weeks (N = 5). At the end, we measured changes in bacterial phage-resistance and potential virulence traits, and determined the pathogenicity of all bacterial selection lines in the Parasemia plantaginis insect model in vivo. Selection at 37°C increased bacterial motility and pathogenicity but only in the absence of phages. Exposure to phages increased the phage-resistance of bacteria, and this was costly in terms of decreased maximum population size in the absence of phages. However, this small-magnitude growth cost was not greater with bacteria that had evolved in high temperature regime, and no trade-off was found between phage-resistance and growth rate. As a result, phages constrained the evolution of a temperature-mediated increase in bacterial pathogenicity presumably by preferably infecting the highly motile and virulent bacteria. In more general perspective, our results suggest that the traits connected to bacterial pathogenicity could be indirectly selected as a correlated response by abiotic and biotic factors in environmental reservoirs. 相似文献
85.
Traditionally, people have inhabited places with ready access to fresh water.
Today, over 50% of the global population lives in urban areas, and water
can be directed via tens of kilometres of pipelines. Still, however, a large
part of the world''s population is directly dependent on access to natural
freshwater sources. So how are inhabited places related to the location of
freshwater bodies today? We present a high-resolution global analysis of how
close present-day populations live to surface freshwater. We aim to increase the
understanding of the relationship between inhabited places, distance to surface
freshwater bodies, and climatic characteristics in different climate zones and
administrative regions. Our results show that over 50% of the
world''s population lives closer than 3 km to a surface freshwater body, and
only 10% of the population lives further than 10 km away. There are,
however, remarkable differences between administrative regions and climatic
zones. Populations in Australia, Asia, and Europe live closest to water.
Although populations in arid zones live furthest away from freshwater bodies in
absolute terms, relatively speaking they live closest to water considering the
limited number of freshwater bodies in those areas. Population distributions in
arid zones show statistically significant relationships with a combination of
climatic factors and distance to water, whilst in other zones there is no
statistically significant relationship with distance to water. Global studies on
development and climate adaptation can benefit from an improved understanding of
these relationships between human populations and the distance to fresh
water. 相似文献
86.
Background
Thermostable enzymes have several benefits in lignocellulose processing. In particular, they potentially allow the use of increased substrate concentrations (because the substrate viscosity decreases as the temperature increases), resulting in improved product yields and reduced capital and processing costs. A short pre-hydrolysis step at an elevated temperature using thermostable enzymes aimed at rapid liquefaction of the feedstock is seen as an attractive way to overcome the technical problems (such as poor mixing and mass transfer properties) connected with high initial solid loadings in the lignocellulose to ethanol process. 相似文献87.
Background
Behavioral paradigms applied during human recordings in electro- and magneto- encephalography (EEG and MEG) typically require 1–2 hours of data collection. Over this time scale, the natural fluctuations in brain state or rapid learning effects could impact measured signals, but are seldom analyzed.Methods and Findings
We investigated within-session dynamics of neocortical alpha (7–14 Hz) rhythms and their allocation with cued-attention using MEG recorded from primary somatosensory neocortex (SI) in humans. We found that there were significant and systematic changes across a single ∼1 hour recording session in several dimensions, including increased alpha power, increased differentiation in attention-induced alpha allocation, increased distinction in immediate time-locked post-cue evoked responses in SI to different visual cues, and enhanced power in the immediate cue-locked alpha band frequency response. Further, comparison of two commonly used baseline methods showed that conclusions on the evolution of alpha dynamics across a session were dependent on the normalization method used.Conclusions
These findings are important not only as they relate to studies of oscillations in SI, they also provide a robust example of the type of dynamic changes in brain measures within a single session that are overlooked in most human brain imaging/recording studies. 相似文献88.
89.
90.
Mustonen AM Puukka M Pyykönen T Nieminen P 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2005,175(5):357-363
The aim of this study was to investigate the adaptations of protein metabolism to seasonal fasting in an actively wintering boreal carnivore. Fifty farm-bred male American minks Mustela vison were divided into a fed control group and four experimental groups fasted for 2, 3, 5 or 7 days. The responses of nitrogen metabolism to wintertime food deprivation were determined by measuring the rate of weight loss, the tissue total protein concentrations and the plasma amino acid, urea, ammonia, uric acid and total protein levels. The mink has relatively poor adaptations to food deprivation, as it is not able to prolong phase II of fasting with fat as the major metabolic fuel. Instead, the species has to derive a part of its energy requirements from the breakdown of body proteins. The end product of protein catabolism—urea— accumulates in its circulation, and the mink may not be able to recycle urea-N. Although the mink can still have a high body fat percent at the end of the 7-day fast, it appears to enter phase III of fasting with stimulated proteolysis during this period. 相似文献