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101.
102.
Power matters in closing the phenotyping gap 总被引:1,自引:0,他引:1
Meyer CW Elvert R Scherag A Ehrhardt N Gailus-Durner V Fuchs H Schäfer H Hrabé de Angelis M Heldmaier G Klingenspor M 《Die Naturwissenschaften》2007,94(5):401-406
Much of our understanding of physiology and metabolism is derived from investigating mouse mutants and transgenic mice, and
open-access platforms for standardized mouse phenotyping such as the German Mouse Clinic (GMC) are currently viewed as one
powerful tool for identifying novel gene-function relationships. Phenotyping or phenotypic screening involves the comparison of wild-type control mice with their mutant or transgenic littermates. In our study, we explored
the extent to which standardized phenotyping will succeed in detecting biologically relevant phenotypic differences in mice
generated and provided by different collaborators. We analyzed quantitative metabolic data (body mass, energy intake, and
energy metabolized) collected at the GMC under the current workflow, and used them for statistical power considerations. Our
results demonstrate that there is substantial variability in these parameters among lines of wild-type C57BL/6 (B6) mice from
different sources. Given this variable background noise in mice that serve as controls, subtle phenotypes in mutant or transgenic
littermates may be overlooked. Furthermore, a phenotype observed in one cohort of a mutant line may not be reproducible (to
the same extent) in mice coming from a different environment or supplier. In the light of these constraints, we encourage
researchers to incorporate information on intrastrain variability into future study planning, or to perform advanced hierarchical
analyses. Both will ultimately improve the detectability of novel phenotypes by phenotypic screening.
Carola W. Meyer and Ralf Elvert contributed equally to this work. 相似文献
103.
The neonatal incidence rate of Down syndrome (DS) is well-known to accelerate strongly with maternal age. This non-linearity
renders mere accumulation of defects at recombination during prolonged first meiotic prophase implausible as an explanation
for DS rate increase with maternal age, but might be anticipated from chromosomal drive (CD) for trisomy 21. Alternatively,
as there is selection against genetically disadvantaged embryos, the screening system that eliminates embryos with trisomy
21 might decay with maternal age. In this paper, we provide the first evidence for relaxed filtering stringency (RFS) to represent
an adaptive maternal response that could explain accelerating DS rates with maternal age. Using historical data, we show that
the proportion of aberrant live births decrease with increased family size in older mothers, that inter-birth intervals are
longer before affected neonates than before normal ones, and that primiparae exhibit elevated levels of DS incidence at higher
age. These findings are predicted by adaptive RFS but cannot be explained by the currently available alternative non-adaptive
hypotheses, including CD. The identification of the relaxation control mechanism and therapeutic restoration of a stringent
screen may have considerable medical implications. 相似文献
104.
Osvaldo Salazar Manuel Casanova Thomas Kätterer 《Agriculture, ecosystems & environment》2011,140(1-2):123-136
Soil organic carbon (SOC) and total nitrogen (N) stocks in an agroforestry system with water harvesting were analysed in a field experiment and the results compared with those of other crop management systems in the Mediterranean zone of central Chile. Agroforestry with water harvesting showed higher positive effects on N stocks, mainly in the upper soil layer, than the other crop management systems. However, soil analysis revealed a lack of differences between treatments, a fact that might be related mainly to the short study time (12 years) and the high spatial variability in these soil properties at the experimental site. In addition, the Introductory Carbon Balance Model that simulates N processes (ICBM/N) was evaluated for simulating trends in SOC and N stocks in the field experiment. Soil data collected between 1996 and 2008 in the field experiment and primarily literature data sets were used to test ICBM/N and its performance was evaluated by considering uncertainty in model inputs using Generalised Likelihood Uncertainty Estimation (GLUE) methodology. The GLUE estimates (5% and 95%) and measured SOC and N stocks were in satisfactory agreement. The observed SOC and N stocks were bracketed by the uncertainty bands in 70% and 80% of the simulations, respectively. Sensitivity analysis showed the model to be most sensitive to C parameters, such as the humification coefficient (h). The results of this study show that ICBM/N can be an effective tool for estimating SOC and N stocks from agroforestry combined with water harvesting systems in the Mediterranean zone of central Chile over the medium term. However, they also indicate that additional data sets are needed to redefine the parameter distributions in the model and thus to predict trends in SOC and N stocks in the future. 相似文献
105.
For more than 30 million years, in early Mesozoic Pangea, ??rauisuchian?? archosaurs were the apex predators in most terrestrial ecosystems, but their biology and evolutionary history remain poorly understood. We describe a new ??rauisuchian?? based on ten individuals found in a single locality from the Middle Triassic (Ladinian) Santa Maria Formation of southern Brazil. Nine articulated and associated skeletons were discovered, three of which have nearly complete skulls. Along with sedimentological and taphonomic data, this suggests that those highly successful predators exhibited some kind of intraspecific interaction. Other monotaxic assemblages of Triassic archosaurs are Late Triassic (Norian-Rhaetian) in age, approximately 10 million years younger than the material described here. Indeed, the studied assemblage may represent the earliest evidence of gregariousness among archosaurs, adding to our knowledge on the origin of a behavior pattern typical of extant taxa. 相似文献
106.
Nyyssönen M Piskonen R Itävaara M 《Environmental pollution (Barking, Essex : 1987)》2008,154(2):192-202
The development of biological treatment technologies for contaminated environments requires tools for obtaining direct information about the biodegradation of specific contaminants. The potential of functional gene array analysis to monitor changes in the amount of functional marker genes as indicators of contaminant biodegradation was investigated. A prototype functional gene array was developed for targeting key functions in the biodegradation of naphthalene, toluene and xylenes. Internal standard probe based normalization was introduced to facilitate comparison across multiple samples. Coupled with one-colour hybridization, the signal normalization improved the consistency among replicate hybridizations resulting in better discrimination for the differences in the amount of target DNA. During the naphthalene biodegradation in a PAH-contaminated soil slurry microcosm, the normalized hybridization signals in naphthalene catabolic gene probes were in good agreement with the amount of naphthalene-degradation genes and the production of 14CO2. Gene arrays provide efficient means for monitoring of contaminant biodegradation in the environment. 相似文献
107.
The effect of nitrogen on biomass production, shoot elongation and relative density of the mosses Pleurozium schreberi, Hylocomium splendens and Dicranum polysetum was studied in a chamber experiment. Monocultures were exposed to 10 N levels ranging from 0.02 to 7.35 g N m−2 during a 90-day period. All the growth responses were unimodal, but the species showed differences in the shape parameters of the curves. Hylocomium and Pleurozium achieved optimum biomass production at a lower N level than Dicranum. Pleurozium had the highest biomass production per tissue N concentration. Tolerance to N was the widest in Dicranum, whereas Hylocomium had the narrowest tolerance. Dicranum retained N less efficiently from precipitation than the other two species, which explained its deviating response. All species translocated some N from parent to new shoots. The results emphasize that the individual responses of bryophytes to N should be known when species are used as bioindicators. 相似文献
108.
Long-term survey of heavy-metal pollution, biofilm contamination and diatom community structure in the Riou Mort watershed, South-West France 总被引:4,自引:0,他引:4
Morin S Duong TT Dabrin A Coynel A Herlory O Baudrimont M Delmas F Durrieu G Schäfer J Winterton P Blanc G Coste M 《Environmental pollution (Barking, Essex : 1987)》2008,151(3):532-542
In a metal-polluted stream in the Riou Mort watershed in SW France, periphytic biofilm was analyzed for diatom cell densities and taxonomic composition, dry weight and metal bio-accumulation (cadmium and zinc). Periphytic diatom communities were affected by the metal but displayed induced tolerance, seen through structural impact (dominance of small, adnate species) as well as morphological abnormalities particularly in the genera Ulnaria and Fragilaria. Species assemblages were characterized by taxa known to occur in metal-polluted environments, and shifts in the community structure expressed seasonal patterns: high numbers of Eolimna minima, Nitzschia palea and Pinnularia parvulissima were recorded in Summer and Autumn, whereas the species Surirella brebissonii, Achnanthidium minutissimum, Navicula lanceolata and Surirella angusta were dominant in Winter and Spring. Commonly used indices such as the Shannon diversity index and Specific Pollution Sensitivity Index reflected the level of pollution and suggest seasonal periodicity, the lowest diversities being observed in Summer. 相似文献
109.
Wiessner A Kuschk P Jechorek M Seidel H Kästner M 《Environmental pollution (Barking, Essex : 1987)》2008,155(1):125-131
Sulphur cycling and its correlation to removal processes under dynamic redox conditions in the rhizosphere of helophytes in treatment wetlands are poorly understood. Therefore, long-term experiments were performed in laboratory-scale constructed wetlands treating artificial domestic wastewater in order to investigate the dynamics of sulphur compounds, the responses of plants and nitrifying microorganisms under carbon surplus conditions, and the generation of methane. For carbon surplus conditions (carbon:sulphate of 2.8:1) sulphate reduction happened but was repressed, in contrast to unplanted filters mentioned in literature. Doubling the carbon load caused stable and efficient sulphate reduction, rising of pH, increasing enrichment of S(2-) and S(0) in pore water, and finally plant death and inhibition of nitrification by sulphide toxicity. The data show a clear correlation of the occurrence of reduced S-species with decreasing C and N removal performance and plant viability in the experimental constructed wetlands. 相似文献
110.
Contribution of Spartina maritima to the reduction of eutrophication in estuarine systems 总被引:2,自引:0,他引:2
Sousa AI Lillebø AI Caçador I Pardal MA 《Environmental pollution (Barking, Essex : 1987)》2008,156(3):628-635
Salt marshes are among the most productive ecosystems in the world, performing important ecosystem functions, particularly nutrient recycling. In this study, a comparison is made between Mondego and Tagus estuaries in relation to the role of Spartina maritima in nitrogen retention capacity and cycling. Two mono-specific S. maritima stands per estuary were studied during 1 yr (biomass, nitrogen (N) pools, litter production, decomposition rates). Results showed that the oldest Tagus salt marsh population presented higher annual belowground biomass and N productions, and a slower decomposition rate for litter, contributing to the higher N accumulation in the sediment, whereas S. maritima younger marshes had higher aboveground biomass production. Detritus moved by tides represented a huge amount of aboveground production, probably significant when considering the N balance of these salt marshes. Results reinforce the functions of salt marshes as contributing to a reduction of eutrophication in transitional waters, namely through sedimentation processes. 相似文献