Toward a universal measure of robustness across model organs and systems

The development of an individual must be capable of resisting the harmful effects of internal and external perturbations. This capacity, called robustness, can make the difference between normal variation and disease. Some systems and organs are more resilient in their capacity to correct the effects of internal disturbances such as mutations. Similarly, organs and organisms differ in their capacity to be resilient against external disturbances, such as changes in temperature. Furthermore, all developmental systems must be somewhat flexible to permit evolutionary change, and understanding robustness requires a comparative framework. Over the last decades, most research on developmental robustness has been focusing on specific model systems and organs. Hence, we lack tools that would allow cross-species and cross-organ comparisons. Here, we emphasize the need for a uniform framework to experimentally test and quantify robustness across study systems and suggest that the analysis of fluctuating asymmetry might be a powerful proxy to do so. Such a comparative framework will ultimately help to resolve why and how organs of the same and different species differ in their sensitivity to internal (e.g., mutations) and external (e.g., temperature) perturbations and at what level of biological organization buffering capacities exist and therefore create robustness of the developmental system.     

The correlation of vectorcardiographic changes to blood lactate concentration during an exercise test

In this study, the correlations between blood lactate concentration (BLC), different vector electrocardiogram (VECG) parameters, ventilatory parameters and heart rate during exercise and recovery periods were investigated. The aim was to clarify the relationships between VECG parameters and different exercise intensity markers. Six (25–37 years old) nonathlete, healthy, male participants took part in the study. All participants performed two different bicycle ergospirometric protocols (P1 and P2) in order to attain different lactate levels with different heart rate profiles. A principal component regression (PCR) approach is introduced for preprocessing the VECG components. PCR was compared to Sawitzcy Golay and wavelet filtering methods using simulated data. The performance of the PCR approach was clearly better in low signal-to-noise ratio (SNR) situations, and thus, it enables reliable VECG estimates even during intensive exercise. As a result, strong positive mean individual correlations between BLC and T-wave kurtosis (P1: r = 0.86 and P2: r = 0.8, p < 0.05 in 12/12 measurements) and negative correlation between BLC and cos RT (P1: r = ?0.7, P2: r = ?0.62, p < 0.05 in 8/12 measurements) were observed. The results of this study indicate that VECG parameters (in addition to heart rate) can make a significant contribution to monitoring of exercise intensity and recovery.     

Use of flow cytometry for the adhesion analysis of Streptococcus pyogenes mutant strains to epithelial cells: investigation of the possible role of surface pullulanase and cysteine protease, and the transcriptional regulator Rgg

Background  

Flow cytometry based adherence assay is a potentially powerful but little used method in the study of bacterial binding to host structures. We have previously characterized a glycoprotein-binding activity in Streptococcus pyogenes called 'strepadhesin' binding to thyroglobulin, submaxillar mucin, fetuin and asialofetuin. We have identified surface-associated pullulanase (PulA) and cysteine protease (SpeB) as carriers of strepadhesin activity. In the present paper, we investigated the use of flow cytometry as a method to study the binding of Rgg, SpeB and PulA knock-out strains to cultured human epithelial cells.     

Biomolecules at phase boundaries

Experimental and theoretical studies of biomolecules at water surfaces and metal surfaces are presented. We studied lecithin molecules (monolayers) and phospholipase A₂ at a water surface with molecular dynamics (MD) simulations. Results were compared with those obtained for a pure water surface. We also studied amino acids at a TiO₂ surface with thermal desorption spectroscopy in the presence and absence of water.     

GENERA ARE OFTEN BETTER THAN SPECIES FOR DETECTING EVOLUTIONARY CHANGE IN THE FOSSIL RECORD: A REPLY TO SALESA ET AL.

In their technical comment Salesa et al. (2011) raise several issues, including an important topic affecting most, or perhaps all, paleoecological studies—the difficulty of determining a reasonable way to deal with taxonomy. Specifically, Salesa et al. draw our attention to a taxonomic revision of Iberian Anchitherium ( Sánchez et al. 1998 ), that we failed to follow in our study ( Eronen et al. 2010 ), and express concerns that a different handling of Anchitherium taxonomy would have affected our results and conclusions.     

EVALUATION OF ELEVATED PLOIDY AND ASEXUAL REPRODUCTION AS ALTERNATIVE EXPLANATIONS FOR GEOGRAPHIC PARTHENOGENESIS IN EUCYPRIS VIRENS OSTRACODS

Transitions from sexual to asexual reproduction are often coupled with elevations in ploidy. As a consequence, the importance of ploidy per se for the maintenance and spread of asexual populations is unclear. To examine the effects of ploidy and asexual reproduction as independent determinants of the success of asexual lineages, we sampled diploid sexual, diploid asexual, and triploid asexual Eucypris virens ostracods across a European wide range. Applying nuclear and mitochondrial markers, we found that E. virens consists of genetically highly differentiated diploid sexual populations, to the extent that these sexual clades could be considered as cryptic species. All sexual populations were found in southern Europe and North Africa and we found that both diploid asexual and triploid asexual lineages have originated multiple times from several sexual lineages. Therefore, the asexual lineages show a wide variety of genetic backgrounds and very strong population genetic structure across the wide geographic range. Finally, we found that triploid, but not diploid, asexual clones dominate habitats in northern Europe. The limited distribution of diploid asexual lineages, despite their shared ancestry with triploid asexual lineages, strongly suggests that the wider geographic distribution of triploids is due to elevated ploidy rather than to asexuality.     

Experimental evidence for the use of density based interspecific social information in forest birds

Reproductive success and habitat preference are generally assumed to be negatively associated with densities of con- and heterospecific competitors. However, recent theoretical studies have suggested that in some cases habitat preference may have a nonlinear unimodal function in relation to con- or heterospecific competitor densities – intermediate densities being preferred. Such a pattern is expected if con- or heterospecific densities are used as a proximate cue in habitat selection, which may produce benefits by reducing searching costs and providing information about current habitat quality and costs of competition. At low density the use of such cues, and hence habitat selection, are hampered, whereas at high density costs of competition exceed the benefits of using cues, leading to avoidance. Here, we tested this hypothesis by examining whether arboreal migratory birds use the density of resident titmice ( Parus spp.) in habitat selection decisions. Many migrants and titmice species share similar resource needs making titmice density a reliable source of information for migrants. At the scale of habitat patches, we experimentally created a range of titmice densities from low to very high and subsequently measured the density response of migrants. In contrast to the unimodal habitat preference hypothesis, the average species number and total density of migratory birds were positively and linearly correlated with manipulated titmice density. Thus, migrants probably use titmice density as a relative indicator of habitat quality (abundance or quality of food) because foliage gleaners that share similar food resource with titmice, but not ground foragers, showed a positive association with manipulated titmice density. These results emphasize the positive effect of interspecific social information on habitat choice decisions and diversity of migratory bird community.     

Troglochaetus beranecki Delachaux (Polychaeta, Archiannelida) in esker groundwaters of Finland: a new class of limnic animals for northern Europe

The presence of Troglochaetus beranecki is reported in the phreatic groundwater of eskers in southern Finland within the area covered by glaciers during the last glacial epoch. The hitherto known distribution of this species includes central and southern Europe and parts of northern America, but it has not previously been found in northern Europe, where groundwater invertebrates have generally been assumed to be lacking. The limit of distribution of this species is now moved 1500 km to the north-east. This revised version was published online in July 2006 with corrections to the Cover Date.