The effect of a constant efflux on solute movement to a root

This paper presents two analytical solutions to solute uptake and release by a root (the root exhibits efflux) when both mass and diffusive flows are considered and the water content of the soil is maintained constant. The first solution is for a constant solute concentration at some finite distance from the root, while the second is when there is no solute recharge from the soil outside a cylinder coaxle with the root.Several examples are presented to show the effect of the effluxive term. It is shown that the point where the ratio of efflux to initial ion concentration in solution is equal to the difference between root absorbing power and water flux at the root, is critical to nutrient depletion or buildup at the root surface. It is also shown for the case of no recharge that the concentration profiles when efflux is considered are markedly different than where efflux is not considered.Contribution from the Purdue Agric. Exp. Stn., West Lafayette, IN, 47907. Journal Paper Number7458.     

Demonstration of differential quantitative requirements for NSF among multiple vesicle fusion pathways of GLUT4 using a dominant-negative ATPase-deficient NSF

In this study, we investigated the relative participation of N-ethylmaleimide-sensitive factor (NSF) in vivo in a complex multistep vesicle trafficking system, the translocation response of GLUT4 to insulin in rat adipose cells. Transfections of rat adipose cells demonstrate that over-expression of wild-type NSF has no effect on total, or basal and insulin-stimulated cell-surface expression of HA-tagged GLUT4. In contrast, a dominant-negative NSF (NSF-D1EQ) can be expressed at a low enough level that it has little effect on total HA-GLUT4, but does reduce both basal and insulin-stimulated cell-surface HA-GLUT4 by approximately 50% without affecting the GLUT4 fold-translocation response to insulin. However, high expression levels of NSF-D1EQ decrease total HA-GLUT4. The inhibitory effect of NSF-D1EQ on cell-surface HA-GLUT4 is reversed when endocytosis is inhibited by co-expression of a dominant-negative dynamin (dynamin-K44A). Moreover, NSF-D1EQ does not affect cell-surface levels of constitutively recycling GLUT1 and TfR, suggesting a predominant effect of low-level NSF-D1EQ on the trafficking of GLUT4 from the endocytic recycling compared to the intracellular GLUT4-specific compartment. Thus, our data demonstrate that the multiple fusion steps in GLUT4 trafficking have differential quantitative requirements for NSF activity. This indicates that the rates of plasma and intracellular membrane fusion reactions vary, leading to differential needs for the turnover of the SNARE proteins.     

A high-throughput screen utilizing the fluorescence of riboflavin for identification of lumazine synthase inhibitors

A high-throughput screening method based on the competitive binding of a lumazine synthase inhibitor and riboflavin to the active site of Schizosaccharomyces pombe lumazine synthase was developed. This assay is sensitive, simple, and robust. During assay development, all of the known active inhibitors tested were positively identified. Preliminary high-throughput screening in 384-well format resulted in a Z factor of 0.7. The approach utilizes a thermodynamic assay to bypass the problems associated with the instabilities of both lumazine synthase substrates that complicate the use of a kinetic assay in a high-throughput format, and it removes the time element from the assay, thus simplifying the procedure.     

Johnson-McMillin syndrome: report of a new case with novel features

BACKGROUND: Johnson-McMillin syndrome (JMS) is a rare neuroectodermal disorder characterized by alopecia, ear malformations, conductive hearing loss, anosmia/hyposmia, and hypogonadotropic hypogonadism. It is inherited in an autosomal dominant manner; however, the causative gene has not yet been identified. CASE: Herein we report a patient with this condition who exhibits many of the features previously described, including alopecia, malformed auricles, conductive hearing loss, facial asymmetry, and developmental delays. Interestingly, she also has features that have not yet been reported, such as preauricular pits and tags, broad depressions at the lateral aspects of the eyes, and an abnormal left lower eyelid. CONCLUSIONS: In addition to demonstrating a pattern of anomalies consistent with JMS, this patient has several unique features. This phenotype supports the involvement of the branchial arches in the embryologic basis of this condition.     

Multispecies assessment of core areas and connectivity of desert carnivores in central Iran

Aim

Central Iran is a priority area for biodiversity conservation, which is threatened by encroachment on core habitats and fragmentation by roads. The goal of this study was to identify core areas and connectivity corridors for a set of desert carnivores by predicting habitat suitability and calculating resistant kernel, factorial least‐cost path modelling and graph network indices.

Location

Iran.

Methods

We used an ensemble model (EM) of habitat suitability methods to predict the potential habitats of leopard, cheetah, caracal, wild cat, sand cat and grey wolf and used resistant kernel and factorial least‐cost path modelling to identify important core habitats and corridors between patches. We also used a graph network analysis to quantify the importance of each core patch to landscape connectivity.

Results

Potential habitats of the studied carnivores appeared to be strongly influenced by prey density, annual precipitation, topographical roughness, shrubland density and anthropogenic factors. Most of the core patches were covered by protected areas and no‐hunting areas. This may be attributed to the relatively high resistance outside protected areas leading to isolated occupied patches. Patch importance to connectivity was significantly correlated with patch extent, density of dispersing individuals and probability of occurrence in the core patch.

Main conclusions

Our findings revealed that prey abundance in core habitat is critically important, and has higher influence than habitat area per se. In addition, our analysis provided the first map of landscape connectivity for multiple species in Iran and revealed that conserving these species requires integrated landscape‐level management to reduce mortality risk and protect core areas and linkages among them. These results will assist the development of multispecies conservation strategies to protect core areas for carnivores.

     

A comparison of regression methods for model selection in individual‐based landscape genetic analysis

Anthropogenic migration barriers fragment many populations and limit the ability of species to respond to climate‐induced biome shifts. Conservation actions designed to conserve habitat connectivity and mitigate barriers are needed to unite fragmented populations into larger, more viable metapopulations, and to allow species to track their climate envelope over time. Landscape genetic analysis provides an empirical means to infer landscape factors influencing gene flow and thereby inform such conservation actions. However, there are currently many methods available for model selection in landscape genetics, and considerable uncertainty as to which provide the greatest accuracy in identifying the true landscape model influencing gene flow among competing alternative hypotheses. In this study, we used population genetic simulations to evaluate the performance of seven regression‐based model selection methods on a broad array of landscapes that varied by the number and type of variables contributing to resistance, the magnitude and cohesion of resistance, as well as the functional relationship between variables and resistance. We also assessed the effect of transformations designed to linearize the relationship between genetic and landscape distances. We found that linear mixed effects models had the highest accuracy in every way we evaluated model performance; however, other methods also performed well in many circumstances, particularly when landscape resistance was high and the correlation among competing hypotheses was limited. Our results provide guidance for which regression‐based model selection methods provide the most accurate inferences in landscape genetic analysis and thereby best inform connectivity conservation actions.     

Forest cover and level of protection influence the island-wide distribution of an apex carnivore and umbrella species,the Sri Lankan leopard (<Emphasis Type="Italic">Panthera pardus kotiya</Emphasis>)

Apex predators fulfil potentially vital ecological roles. Typically wide-ranging and charismatic, they can also be useful surrogates for biodiversity preservation, making their targeted conservation imperative. The Sri Lankan leopard (Panthera pardus kotiya), an endangered, endemic sub-species, is the island’s apex predator. Of potential keystone importance, this carnivore also fulfills “umbrella” and “flagship” criterion and is of high ecological and existence value. Apex predator conservation requires identifying factors underlying distribution, so we used multi-scale maximum entropy modelling with sampling bias correction to investigate a broad suite of relevant ecological, climatic and anthropogenic factors in order to identify potentially suitable leopard habitat. Presence locations were determined from 15 years of surveys, observations and verified reports. The best bias correction procedure and scale were uncertain, so we employed a novel method of using information from all models across analyses to determine top models and identify influential variables. Leopard presence was most strongly linked to the landscape proportion encompassed by Protected Areas strictly limiting human presence, with more porous Protected Areas less influential. All three forest composition and configuration metrics investigated (area weighted mean patch size, patch density and forest connectivity) were influential, with increased patch size and higher connectivity predicting better habitat suitability for leopards. Habitat suitability was also better where cropland extent and urban patch size were small. In summary, ground-level protection and natural forest extent and connectivity are of profound importance to Sri Lankan leopard distribution and are key factors in ensuring the ecological integrity of the island’s faunal assemblages.