Dissection of NT3 functions in vivo by gene replacement strategy.

The development of the peripheral nervous system is governed in part by a family of neurotrophic factors that signal through Trk tyrosine kinase receptors. Neurotrophin 3 (NT3) ablation in mice causes a more severe neuronal phenotype than deletion of its receptor TrkC, suggesting that NT3 acts also through other non-preferred Trk receptors. To study the role of low-affinity ligand receptor interactions in vivo, we have replaced the Nt3 gene with the gene for brain-derived neurotrophic factor (BDNF), a TrkB ligand. As in NT3 and TrkC null mice, the proprioception system of these mutants failed to assemble. However, sensory fiber projections in the embryonic spinal cord suggest chemotropic effects of BDNF in vivo. In the dorsal root ganglia, the developmental dynamic of neuron numbers demonstrates that NT3 is required for activation of TrkB during neurogenesis and that TrkA is required during target tissue innervation. In the inner ear, the ectopic BDNF rescued the severe neuronal deficits caused by NT3 absence, indicating that TrkB and TrkC activate equivalent pathways to promote survival of cochlear neurons. However, specific increased innervation densities suggest unique functions for BDNF and NT3 beyond promoting neuronal survival. This mouse model has allowed the dissection of specific spatiotemporal Trk receptor activation by NT3. Our analysis provides examples of how development can be orchestrated by complex high- and low-affinity interactions between ligand and receptor families.     

Effects of citronella oil (Cymbopogon winterianus Jowitt ex Bor) on Spodoptera frugiperda (J. E. Smith) midgut and fat body

The armyworm, Spodoptera frugiperda, is the principal pest of corn in Brazil. Control is achieved primarily by synthetic insecticides, which cause problems for the agro-ecosystem. Alternative methods of control are under investigation and citronella (Cymbopogon winterianus) essential oil appears to be a promising agent. We investigated the effects of citronella oil using histological, histochemical and immunohistochemical methods. The midgut of larvae treated with citronella exhibited altered epithelium including cytoplasmic protrusions, columnar cell extrusion, pyknotic nuclei, and increased periodic acid-Schiff positive granules. Regenerative cells in the epithelium of the midgut increased in number, which facilitated subsequent regeneration of this tissue. After exposure to citronella, trophocytes, the principal cell type of the fat body, possessed enlarged vacuoles and mitotic bodies, and contained reduced amounts of glycogen, lipid, and protein. Citronella oil caused morphological changes of the midgut and reduction of stored resources in the fat body, which may adversely affect insect reproduction and survival.     

Variable thermal stress tolerance of the reef-associated symbiont-bearing foraminifera Amphistegina linked to differences in symbiont type

Coral Reefs - Adaptation, acclimatization and symbiont diversity are known to regulate thermal tolerance in corals, but the role of these mechanisms remains poorly constrained in other...     

Total sleep deprivation does not significantly degrade semantic encoding

ABSTRACT

Sleep deprivation impairs performance on cognitive tasks, but it is unclear which cognitive processes it degrades. We administered a semantic matching task with variable stimulus onset asynchrony (SOA) and both speeded and self-paced trial blocks. The task was administered at the baseline and 24 hours later after 30.8 hours of total sleep deprivation (TSD) or matching well-rested control. After sleep deprivation, the 20% slowest response times (RTs) were significantly increased. However, the semantic encoding time component of the RTs remained at baseline level. Thus, the performance impairment induced by sleep deprivation on this task occurred in cognitive processes downstream of semantic encoding.     

Light scattering on PHA granules protects bacterial cells against the harmful effects of UV radiation

Numerous prokaryotes accumulate polyhydroxyalkanoates (PHA) in the form of intracellular granules. The primary function of PHA is the storage of carbon and energy. Nevertheless, there are numerous reports that the presence of PHA granules in microbial cells enhances their stress resistance and fitness when exposed to various stress factors. In this work, we studied the protective mechanism of PHA granules against UV irradiation employing Cupriavidus necator as a model bacterial strain. The PHA-accumulating wild type strain showed substantially higher UV radiation resistance than the PHA non-accumulating mutant. Furthermore, the differences in UV-Vis radiation interactions with both cell types were studied using various spectroscopic approaches (turbidimetry, absorption spectroscopy, and nephelometry). Our results clearly demonstrate that intracellular PHA granules efficiently scatter UV radiation, which provides a substantial UV-protective effect for bacterial cells and, moreover, decreases the intracellular level of reactive oxygen species in UV-challenged cells. The protective properties of the PHA granules are enhanced by the fact that granules specifically bind to DNA, which in turn provides shield-like protection of DNA as the most UV-sensitive molecule. To conclude, the UV-protective action of PHA granules adds considerable value to their primary storage function, which can be beneficial in numerous environments.

     

Spatiotemporal Resolution of Rab9 and CI‐MPR Dynamics in the Endocytic Pathway

Rab9 is a small GTPase that localizes to the trans‐Golgi Network (TGN) and late endosomes. Its main function has long been connected to the recycling of mannose‐6‐phosphate receptors (MPRs). However, recent studies link Rab9 also to autophagy and lysosome biogenesis. In this paper, using confocal imaging, we characterize for the first time the live dynamics of the Rab9 constitutively active mutant, Rab9Q66L. We find that it localizes predominantly to late endosomes and that its expression in HeLa cells disperses TGN46 and cation‐independent (CI‐MPR) away from the Golgi yet, has no effect on the retrograde transport of CI‐MPR. We also show that CI‐MPR and Rab9 enter the endosomal pathway together at the transition stage between early, Rab5‐positive, and late, Rab7a‐positive, endosomes. CI‐MPR localizes transiently to separate domains on these endosomes, where vesicles carrying CI‐MPR attach and detach within seconds. Taken together, our results demonstrate that Rab9 mediates the delivery of CI‐MPR to the endosomal pathway, entering the maturing endosome at the early‐to‐late transition.      

Environmental change and rain forests on the Sunda shelf of Southeast Asia: drought, fire and the biological cooling of biodiversity hotspots

Environmental change during the Quaternary period has caused changes in the composition and structure of vegetation on the Sunda shelf of Southeast Asia. Climatic conditions drier than the present, particularly during the peak of the last ice age, led to a reduction in the extent of rain forests. Most recently, there has been a close association between drought and the occurrence of major, rain forest fires. Although many rain forest trees show adaptations to periodic drought, this is not the case for frequent or intense fires. Over evolutionary time-scales, major fires may thus have been largely confined to driver vegetation types, such as monsoon and deciduous forests, and only infrequently penetrated rain forest areas. Continental-scale distribution patterns for rain forest species reveal a number of biodiversity hotspots that are consistent for a broad range of taxonomically unrelated taxa. These biodiversity hotspots account for a relatively small part of the total extent of rain forest; they may also represent ecologically relatively stable areas. This paper discusses the location and extent of biodiversity hotspots on the Sunda shelf within the context of past and present environmental change. It finds that whatever the history of biodiversity hotspots, they are increasingly threatened by contemporary environmental change, notably a trend towards increasingly frequent and intense fires. The paper concludes that the trend is likely to continue, without major changes in those activities that degrade and precondition to fire remaining areas of rain forest.     

DNA barcoding of South Africa’s ornamental freshwater fish – are the names reliable?

Trade in freshwater ornamental fish in South Africa is currently regulated by a ‘blacklist’ to prevent potentially invasive taxa from establishing in the country. Because its effective implementation requires accurate identification, the aim of the present study was to test whether DNA barcoding is a useful tool to identify freshwater fishes in the South African pet trade. A total of 351 aquarium fish specimens, representing 185 traded taxa, were sequenced for the mitochondrial COI barcoding marker in 2011 and 2012. Lake Malawi cichlids were treated as a single group due to a lack of resolution in their COI marker, resulting in a data set of 137 successfully sequenced taxa. The Barcode Of Life Database (BOLD) and GenBank were used for taxonomic assignment comparisons. The genetic identification matched the scientific name inferred from the trade name for 60 taxa (43.8%) using BOLD, and for 67 taxa (48.9%) using GenBank. A genetic ID could not be assigned in 47 (34.3%) cases using BOLD and in 37 cases (27%) using GenBank. Whereas DNA barcoding can be a useful tool to help identify imported freshwater fishes, it requires further development of publicly available databases to become a reliable means of identification.     

Influence of an Acrylic Polymer Blend on the Physical Stability of Film-Coated Theophylline Pellets

The purpose of this study was to investigate the physical stability of a coating system consisting of a blend of two sustained release acrylic polymers and its influence on the drug release rate of theophylline from coated pellets. The properties of both free films and theophylline pellets coated with the polymer blend were investigated, and the miscibility was determined via differential scanning calorimetry. Eudragit^® RS 30 D was plasticized by the addition of Eudragit^® NE 30 D, and the predicted glass transition temperature (T _g) of the blend was similar to the experimental values. Sprayed films composed of a blend of Eudragit^® NE 30 D/Eudragit^® RS 30 D (1:1) showed a water vapor permeability six times greater than films containing only Eudragit^® NE 30 D. The presence of quaternary ammonium functional groups from the RS 30 D polymer increased the swellability of the films. The films prepared from the blend exhibited stable permeability values when stored for 1 month at both 25°C and 40°C, while the films which were composed of only Eudragit^® NE 30 D showed a statistically significant decrease in this parameter when stored under the same conditions. Eudragit^® NE 30 D/Eudragit^® RS 30 D (1:1)-sprayed films decreased in elongation from 180% to 40% after storage at 40°C for 1 month, while those stored at 25°C showed no change in elongation. In coated pellets, the addition of Eudragit^® RS 30 D to the Eudragit^® NE 30 D increased the theophylline release rate, and the pellets were stable when stored at 25°C for a period of up to 3 months due to maintenance of the physico-mechanical properties of the film. Pellets stored at 40°C exhibited a decrease in drug release rate over time as a result of changes in film physico-mechanical properties which were attributed to further coalescence and densification of the polymer. When the storage temperature was above the T _g of the composite, instabilities in both drug release rate and physical properties were evident. Stabilization in drug release rate from coated pellets could be correlated with the physico-mechanical stability of the film formulation when stored at temperatures below the T _g of the polymer.