Power matters in closing the phenotyping gap

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.     

Long-term trends of continental-scale PCB patterns studied using a global atmosphere–ocean general circulation model

Continental-scale distribution and inter-continental transport of four polychlorinated biphenyl (PCB) congeners (28, 101, 153, 180) from 1950 to 2010 were studied using the global multicompartment chemistry transport model MPI-MCTM. Following identical primary emissions for all PCB congeners into air, most of the burden is stored in terrestrial (soil and vegetation) compartments. Thereby, PCB-28, PCB-101 and PCB-153 show a shift of the soil burden maxima from source to remote regions. This shift is downwind with regard to the westerlies for Eurasia and upwind for North America and more prominent for the lighter PCBs than for PCB-153 or PCB-180. In meridional direction, all congeners' distributions underwent a northward migration in Eurasia and North America since the 1950s. Inter-continental transport from Eurasian sources accounts largely for contamination of Alaska and British Columbia and determines the migration of the PCB distribution in soil in North America. Trans-Pacific transport occurs mainly in the gas phase in boreal winter (December-January-February) at 3-4 km altitude and is on a multi-year time scale strongly linked to the atmospheric pressure systems over the Pacific. Inter-continental transport of the lighter, more volatile PCBs is more efficient than for the heavier PCBs.     

Bioavailability of copper,cadmium, zinc,and lead in tropical savanna soils assessed by diffusive gradient in thin films (DGT) and ion exchange resin membranes

The technique of diffusion gradient in thin films (DGT) for assessing bioavailable metals has not been tested under field conditions. We assessed the relationships of DGT- and cation exchange resin-membrane-measured concentrations of Cd, Cu, Pb, and Zn with plant uptake of the metals under greenhouse and field conditions. In the greenhouse, the effective concentrations of Cu, Pb, and Zn by DGT correlated significantly with uptake by sorghum (Sorghum bicolor), but cation exchange resin-membrane-measured concentrations of Cd, Pb, and Zn did not correlate with sorghum uptake. In the field, the DGT-measured concentrations of Cd, Pb, and Zn were not linearly related to uptake Cd, Pb, and Zn by lettuce (Lactuca sativa) except for Cu uptake (r = 0.87, p < 0.05). Similarly, it was only the resin-membrane-extractable Pb that correlated with Pb uptake by lettuce (r = 0.77; p < 0.05). However, fitting non-linear regression models improved the plant metal uptake predictions by DGT-measured bioavailable Cd, Cu, Pb, and Zn under field conditions. In conclusion, the DGT technique was fairly predictive of bioavailability in the greenhouse, but not in the field.     

Effect of Plantings on Radiation of Highway Noise

The body of information presented in this paper is directed to those individuals concerned with the location of highways relative to either existing or planned residential communities. The paper treats in depth the expected attenuation of automobile and particularly diesel tractor-trailer generated hoise by the interposition of extensive and dense planting of trees and shrubs between the highway and the community. The results of research, by the author and others cited in the paper, gives clear indication that a belt of dense man-made growth of tall trees and underbrush can give as much as 5 to 8 dB truck/car noise reduction per 100 ft of planting depth. Natural growth of deep forests were measured to give from 3 to 5 dB attenuation per 100 ft of planting depth. Planting depth of at least 100 ft is required to give reliable results, with tree heights of 40-50 ft desirable and densities of 50-70 ft visibility needed for good effect.

The paper provides considerable experimental verification by an analysis of the current literature. The types of noise sources in cars and trucks are briefly treated as are community reactions to noise from such sources. The dBA is used as the accepted measure for characterizing truck and automobile noise. Both spherical and cylindrical radiation of sound are discussed for low density and high density traffic, respectively.

The paper concludes with an example of attenuation of a typical truck noise by spherical and cylindrical radiation for low- and high-density traffic and a 200-ft deep planting of dense, mature forest. It is concluded that a mature belt of either coniferous or deciduous forest with underbrush can produce barely acceptable noise levels in the community which is separated by such a noise barrier from a heavily traveled highway.     

The influence of landmarks on the systematic search behaviour of the desert isopod Hemilepistus reaumuri

Summary The desert isopod Hemilepistus reaumuri uses embankments of faeces, which each family builds around the entrance of its burrow, as an aid to homing after a foraging excursion. Though an isopod must touch its family's embankment (outer radius 8–15 cm) with its antennae before it can detect it, this landmark eases the return to the burrow appreciably. However, this advantage is imperiled by problems with similar landmarks. If during foraging the isopod goes astray and has to search for its landmark it also explores most of the alien families' embankments it detects, at least until it has located the burrow entrance within it. But it is not trapped by such similar landmarks. Whereas an isopod explores its own embankment until it comes to its burrow, digging for hours if the burrow entrance happens to be covered by sand, it leaves an alien embankment after most a few minutes and resumes its search. This shows that the isopod is able to distinguish this landmark from its own, probably by the same chemical badge it uses for the identification of family members. A desert isopod must explore alien embankments predominantly because it is not able to distinguish an alien embankment which is near its own burrow and may intersect its own embankment from others. Even when the animal explores and embankment in vain for a long time it could simply have overlooked its own burrow's entrance. In addition the isopod does not recognize an alien embankment which it has already explored. Therefore during a longer search, it has to explore an alien embankment again and again. H. reaumuri solves these identification problems, which correspond to the problems of other arthropods using landmarks for orientation, in a very successful manner. By repeatedly returning to a particular area it searches there more intensively, the greater the probability that its burrow is in this area according to the information, independent of landmarks, available to the animal. In most cases when it detects a particular alien embankment it explores it for a constant short time (on average 20.4 s). It follows that the isopod explores an alien embankment more intensively, the greater the probability that its burrow is within it. In this simple manner it approximately fulfills the rules of the best mathematical procedures that have recently been developed for solving search problems in which an object detected must be explored for some time before it can be distinguished from the real target. Theoretically these procedures are more successful than the search behaviour of H. reaumuri, but they require that either a particular landmark can be identified with certainty by exploration or that at least it can be recognized on a later contact. Although H. reaumuri does not meet these requirements, the success of its search behaviour is almost identical to that of the mathematical procedures.     

Current issues and uncertainties in the measurement and modelling of air-vegetation exchange and within-plant processing of POPs

Air-vegetation exchange of POPs is an important process controlling the entry of POPs into terrestrial food chains, and may also have a significant effect on the global movement of these compounds. Many factors affect the air-vegetation transfer including: the physicochemical properties of the compounds of interest; environmental factors such as temperature, wind speed, humidity and light conditions; and plant characteristics such as functional type, leaf surface area, cuticular structure, and leaf longevity. The purpose of this review is to quantify the effects these differences might have on air/plant exchange of POPs, and to point out the major gaps in the knowledge of this subject that require further research. Uptake mechanisms are complicated, with the role of each factor in controlling partitioning, fate and behaviour process still not fully understood. Consequently, current models of air-vegetation exchange do not incorporate variability in these factors, with the exception of temperature. These models instead rely on using average values for a number of environmental factors (e.g. plant lipid content, surface area), ignoring the large variations in these values. The available models suggest that boundary layer conductance is of key importance in the uptake of POPs, although large uncertainties in the cuticular pathway prevents confirmation of this with any degree of certainty, and experimental data seems to show plant-side resistance to be important. Models are usually based on the assumption that POP uptake occurs through the lipophilic cuticle which covers aerial surfaces of plants. However, some authors have recently attached greater importance to the stomatal route of entry into the leaf for gas phase compounds. There is a need for greater mechanistic understanding of air-plant exchange and the 'scaling' of factors affecting it. The review also suggests a number of key variables that researchers should measure in their experiments to allow comparisons to be made between studies in order to improve our understanding of what causes any differences in measured data between sites.     

The morphogenesis of ephyra in Coronatae (Cnidaria,Scyphozoa)

The morphogenesis of ephyrae of Atorella vanhoeffeni Bigelow, 1909 (Werner, 1967) and of Nausithoe maculata Jarms, 1990 during strobilation is described. We found differences in the developmental pattern of marginal structures and structural changes of longitudinal muscle tubes in particular. During strobilation the polyp’s tetraradiate symmetry is passed to the ephyra of both taxa as a tetraradiate central symmetry that we consider a major plesiomorphic character. The present results also indicate divergent patterns of ephyra development during strobilation that lead to variable marginal symmetries of ephyrae and thus of medusae. Therefore, the marginal symmetry of medusae of N. maculata is octoradiate and of A. vanhoeffeni is hexaradiate. We conclude the latter is stated as derived pattern. These results lead us to maintain both families Nausithoidae and Atorellidae.     

Exemplifying whole-plant ozone uptake in adult forest trees of contrasting species and site conditions

Whole-tree O3 uptake was exemplified for Picea abies, Fagus sylvatica and Larix decidua in stands at high and low altitude and contrasting water availability through sap flow measurement in tree trunks, intrinsically accounting for drought and boundary layer effects on O3 flux. O3 uptake of evergreen spruce per unit foliage area was enhanced by 100% at high relative to low elevation, whereas deciduous beech and larch showed similar uptake regardless of altitude. The responsiveness of the canopy conductance to water vapor and, as a consequence, O3 uptake to soil moisture and air humidity did not differ between species. Unifying findings at the whole-tree level will promote cause-effect based O3 risk assessment and modeling.