Compartment-dependent activities of Wnt3a/β-catenin signaling during vertebrate axial extension

Extension of the vertebrate body results from the concerted activity of many signals in the posterior embryonic end. Among them, Wnt3a has been shown to play relevant roles in the regulation of axial progenitor activity, mesoderm formation and somitogenesis. However, its impact on axial growth remains to be fully understood. Using a transgenic approach in the mouse, we found that the effect of Wnt3a signaling varies depending on the target tissue. High levels of Wnt3a in the epiblast prevented formation of neural tissues, but did not impair axial progenitors from producing different mesodermal lineages. These mesodermal tissues maintained a remarkable degree of organization, even within a severely malformed embryo. However, from the cells that failed to take a neural fate, only those that left the epithelial layer of the epiblast activated a mesodermal program. The remaining tissue accumulated as a folded epithelium that kept some epiblast-like characteristics. Together with previously published observations, our results suggest a dose-dependent role for Wnt3a in regulating the balance between renewal and selection of differentiation fates of axial progenitors in the epiblast. In the paraxial mesoderm, appropriate regulation of Wnt/β-catenin signaling was required not only for somitogenesis, but also for providing proper anterior–posterior polarity to the somites. Both processes seem to rely on mechanisms with different requirements for feedback modulation of Wnt/β-catenin signaling, once segmentation occurred in the presence of high levels of Wnt3a in the presomitic mesoderm, but not after permanent expression of a constitutively active form of β-catenin. Together, our findings suggest that Wnt3a/β-catenin signaling plays sequential roles during posterior extension, which are strongly dependent on the target tissue. This provides an additional example of how much the functional output of signaling systems depends on the competence of the responding cells.     

Extended High Circular Polarization in the Orion Massive Star Forming Region: Implications for the Origin of Homochirality in the Solar System

We present a wide-field (∼6′ × 6′) and deep near-infrared (K _s band: 2.14 μm) circular polarization image in the Orion nebula, where massive stars and many low-mass stars are forming. Our results reveal that a high circular polarization region is spatially extended (∼0.4 pc) around the massive star-forming region, the BN/KL nebula. However, other regions, including the linearly polarized Orion bar, show no significant circular polarization. Most of the low-mass young stars do not show detectable extended structure in either linear or circular polarization, in contrast to the BN/KL nebula. If our solar system formed in a massive star-forming region and was irradiated by net circularly polarized radiation, then enantiomeric excesses could have been induced, through asymmetric photochemistry, in the parent bodies of the meteorites and subsequently delivered to Earth. These could then have played a role in the development of biological homochirality on Earth.     

Amphibian chytrid fungus and ranaviruses in the Northwest Territories, Canada

Pathogens can cause serious declines in host species, and knowing where pathogens associated with host declines occur facilitates understanding host-pathogen ecology. Suspected drivers of global amphibian declines include infectious diseases, with 2 pathogens in particular, Batrachochytrium dendrobatidis (Bd) and ranaviruses, causing concern. We explored the host range and geographic distribution of Bd and ranaviruses in the Taiga Plains ecoregion of the Northwest Territories, Canada, in 2007 and 2008. Both pathogens were detected, greatly extending their known geographic distributions. Ranaviruses were widespread geographically, but found only in wood frogs. In contrast, Bd was found at a single site, but was detected in all 3 species of amphibians in the survey area (wood frogs, boreal chorus frogs, western toads). The presence of Bd in the Northwest Territories is not congruent with predicted distributions based on niche models, even though findings from other studies at northern latitudes are consistent with those same models. Unexpectedly, we also found evidence that swabs routinely used to collect samples for Bd screening detected fewer infections than toe clips. Our use and handling of the swabs was consistent with other studies, and the cause of the apparent lack of integrity of swabs is unknown. The ranaviruses detected in our study were confirmed to be Frog Virus 3 by sequence analysis of a diagnostic 500 bp region of the major capsid protein gene. It is unknown whether Bd or ranaviruses are recent arrivals to the Canadian north. However, the genetic analyses required to answer that question can inform larger debates about the origin of Bd in North America as well as the potential effects of climate change and industrial development on the distributions of these important amphibian pathogens.     

Dynamic effects of oviposition site on offspring sexually-selected traits and scaling relationships

The expression of sexually-selected traits such as bright plumage, exaggerated antlers, and elongated eyestalks can be highly influenced by environmental factors, including the behaviors of mothers. Many recent studies have described the ways that maternal behavior can influence the expression of sexually-selected traits in offspring, however, few studies have investigated if and how such maternal effects might change, over time, in natural populations. Here, we examine the influence of maternal oviposition site on the expression of offspring sexually-selected traits in four successive cohorts of the heliconia bug, Leptoscelis tricolor (Hemiptera: Coreidae). Female heliconia bugs lay eggs on multiple host plant species, and offspring remain on these plants for the entirety of growth and development. We found that natal plant species had significant effects on the expression of male sexually-selected traits and the degree of sexual dimorphism. Moreover, these effects changed over time for later cohorts, concurrent with changes in host plant resources. Our results suggest that maternal effects can be a significant and dynamic influence on the sexually-selected traits of offspring. Such environmental effects on sexually-selected traits could have broad implications for the processes and outcomes of sexual selection.     

Can Economic Incentives Resolve Conservation Conflict: The Case of Wild Deer Management and Habitat Conservation in the Scottish Highlands

Market-based economic incentives are increasingly perceived as a cost-effective approach to biodiversity conservation but empirical evidence to substantiate this claim is lacking. Using both qualitative and quantitative data analysis this paper investigates the potential role of market incentives to increase venison production as a mechanism to resolve conflicts over wild red deer management in the Scottish Highlands. Our analysis suggests the approach is unlikely to be effective because investments in venison production would bring conflict with more important non-pecuniary objectives of landownership such as ‘sporting quality’ and ‘exclusivity’. At a broader level we urge caution when considering the deployment of economic instruments to resolve contemporary conservation conflicts where profit maximisation is not the dominant objective and/or where the target group is extremely wealthy.     

Hydrolytic Enzyme Production is Associated with Candida Albicans Biofilm Formation from Patients with Type 1 Diabetes

Oral candidosis is common in patients with diabetes mellitus, as yeasts, particularly Candida albicans, have the propensity to colonise, form biofilms and release hydrolytic enzymes which cause inflammation. This study aimed to investigate these characteristics in isolates from three groups of patients with type 1 diabetes: individuals with better controlled diabetes (BCD; ≥6 <8%), individuals with poorly controlled diabetes (PCD; ≥8%) and non-diabetics (ND; HbA_1c <5.9%). The biomass (Bm), phospholipase (P_z), haemolysin (H_z) and proteinase (Pr_z) were assessed using a microtitre biofilm assay and agar-based hydrolytic enzyme assays. Biofilm formation was significantly increased in the PCD group compared to ND and BCD groups (P < 0.05). No significant differences in P_z levels were observed between groups, whereas both H_z and Pr_z were significantly greater in the diabetes groups than in the healthy control group (P < 0.05). Statistically significant correlations were found to exist between the HbA_1c levels of the patients and the Bm (R = 0.384; P = 0.033), haemolysin activity (R = ?0.455; P = 0.010) and proteinase activity (R =  ?0.531; P = 0.002). There was no apparent correlation between the Bm and P_z activity (R = ?0.305; P = 0.053) or H_z activity (R = ?0.100; P = 0.296). However, a negative correlation was found between Bm and Pr_z values (R = ?0.343; P = 0.030). These data suggest that biofilm formation is likely to play a role in the pathogenicity of oral candidosis, and in patients with diabetes, this may be due to the ability of C. albicans to adapt to the altered physiological environment. The production of hydrolytic enzymes is independently associated with this growth modality.     

Building-Associated Neurological Damage Modeled in Human Cells: A Mechanism of Neurotoxic Effects by Exposure to Mycotoxins in the Indoor Environment

Damage to human neurological system cells resulting from exposure to mycotoxins confirms a previously controversial public health threat for occupants of water-damaged buildings. Leading scientific organizations disagree about the ability of inhaled mycotoxins in the indoor environment to cause adverse human health effects. Damage to the neurological system can result from exposure to trichothecene mycotoxins in the indoor environment. This study demonstrates that neurological system cell damage can occur from satratoxin H exposure to neurological cells at exposure levels that can be found in water-damaged buildings contaminated with fungal growth. The constant activation of inflammatory and apoptotic pathways at low levels of exposure in human brain capillary endothelial cells, astrocytes, and neural progenitor cells may amplify devastation to neurological tissues and lead to neurological system cell damage from indirect events triggered by the presence of trichothecenes.     

Establishment of a resource population of SLA haplotype-defined Korean native pigs

The highly polymorphic porcine major histocompatibility complex (MHC), or the swine leukocyte antigens (SLA), has been repeatedly associated with variations in swine immune response to pathogens and vaccines as well as with production traits. The SLA antigens are also important targets for immunological recognition of foreign tissue grafts. We recently established a resource population of Korean native pigs as models for human transplantation and xenotransplantation research. In this study, 115 animals derived from three generations of the Korean native pigs were genotyped for three SLA class I (SLA-2, SLA-3 and SLA-1) and three SLA class II loci (DRB1, DQB1, DQA) using PCR with sequence-specific primers (PCR-SSP) at the allele group resolution. A total of seven SLA haplotypes (Lr-5.34, Lr-7.23, Lr-31.13, Lr-56.23, Lr-56.30, Lr-59.1, Lr-65.34), comprising six unique class I and five unique class II haplotypes, were characterized in the founding animals. Class I haplotype Lr-65.0 and class II haplotype Lr-0.34 were novel; and together with Lr-56.0 these haplotypes appeared to be breed-specific. In the progeny population, Lr-7.23 and Lr-56.30 appeared to be the most prevalent haplotypes with frequencies of 34.7% and 31.6%, respectively; the overall homozygosity was 27.4%. This resource population of SLA-defined Korean native pigs will be useful as large animal models for various transplantation and xenotransplantation experiments, as well as for dissecting the roles of SLA proteins in swine disease resistance and production traits.     

Recommendation of short tandem repeat profiling for authenticating human cell lines, stem cells, and tissues

Cell misidentification and cross-contamination have plagued biomedical research for as long as cells have been employed as research tools. Examples of misidentified cell lines continue to surface to this day. Efforts to eradicate the problem by raising awareness of the issue and by asking scientists voluntarily to take appropriate actions have not been successful. Unambiguous cell authentication is an essential step in the scientific process and should be an inherent consideration during peer review of papers submitted for publication or during review of grants submitted for funding. In order to facilitate proper identity testing, accurate, reliable, inexpensive, and standardized methods for authentication of cells and cell lines must be made available. To this end, an international team of scientists is, at this time, preparing a consensus standard on the authentication of human cells using short tandem repeat (STR) profiling. This standard, which will be submitted for review and approval as an American National Standard by the American National Standards Institute, will provide investigators guidance on the use of STR profiling for authenticating human cell lines. Such guidance will include methodological detail on the preparation of the DNA sample, the appropriate numbers and types of loci to be evaluated, and the interpretation and quality control of the results. Associated with the standard itself will be the establishment and maintenance of a public STR profile database under the auspices of the National Center for Biotechnology Information. The consensus standard is anticipated to be adopted by granting agencies and scientific journals as appropriate methodology for authenticating human cell lines, stem cells, and tissues.