Ceramide triggers budding of exosome vesicles into multivesicular endosomes

Intraluminal vesicles of multivesicular endosomes are either sorted for cargo degradation into lysosomes or secreted as exosomes into the extracellular milieu. The mechanisms underlying the sorting of membrane into the different populations of intraluminal vesicles are unknown. Here, we find that cargo is segregated into distinct subdomains on the endosomal membrane and that the transfer of exosome-associated domains into the lumen of the endosome did not depend on the function of the ESCRT (endosomal sorting complex required for transport) machinery, but required the sphingolipid ceramide. Purified exosomes were enriched in ceramide, and the release of exosomes was reduced after the inhibition of neutral sphingomyelinases. These results establish a pathway in intraendosomal membrane transport and exosome formation.     

Lyso-phosphatidylcholine is a signal in the arbuscular mycorrhizal symbiosis

The arbuscular mycorrhizal (AM) symbiosis represents the most widely distributed mutualistic root symbiosis. We report that root extracts of mycorrhizal plants contain a lipophilic signal capable of inducing the phosphate transporter genes StPT3 and StPT4 of potato (Solanum tuberosum L.), genes that are specifically induced in roots colonized by AM fungi. The same signal caused rapid extracellular alkalinization in suspension-cultured tomato (Solanum lycopersicum L.) cells and induction of the mycorrhiza-specific phosphate transporter gene LePT4 in these cells. The active principle was characterized as the lysolipid lyso-phosphatidylcholine (LPC) via a combination of gene expression studies, alkalinization assays in cell cultures, and chromatographic and mass spectrometric analyses. Our results highlight the importance of lysophospholipids as signals in plants and in particular in the AM symbiosis.     

Eumelanins and pheomelanins: characterization by electron spin resonance spectroscopy

Synthetic dopa melanin and cysteinyldopa melanin have different electron spin resonance spectra. Data are reported for mixtures of these melanins and for dopa-cysteinyldopa copolymers, which are spectroscopically similar. A simple parameterization of the spectra allows estimation of the relative amounts of (i) dopa melanin and cysteinyldopa melanin in mixtures and of (ii) dopa and cysteinyldopa incorporated into copolymers. Several natural eumelanins and pheomelanins have been characterized and shown to be copolymers.     

Freedom and rules: the acquisition and reprogramming of a bird's learned song

Canary song is hierarchically structured: Short stereotyped syllables are repeated to form phrases, which in turn are arranged to form songs. This structure occurs even in the songs of young isolates, which suggests that innate rules govern canary song development. However, juveniles that had never heard normal song imitated abnormal synthetic songs with great accuracy, even when the tutor songs lacked phrasing. As the birds matured, imitated songs were reprogrammed to form typical canary phrasing. Thus, imitation and innate song constraints are separate processes that can be segregated in time: freedom in youth, rules in adulthood.     

Elephant-induced structural changes in the vegetation and habitat selection by large herbivores in an African savanna

African elephants can affect the quality of the habitat of other species by breaking or uprooting trees and shrubs in savannas. Their effect on vegetation has been widely studied but less is known about the effects of such vegetation changes on other animals. We studied how changes in the vegetation caused by elephants influence the selection of microhabitats by five African herbivore species (giraffe, kudu, steenbok, impala, and zebra) in Hwange National Park, Zimbabwe. There was no clear significant effect of overall elephant-induced vegetation changes on microhabitat selection except for the small species (steenbok and impala) that used vegetation modified by elephants preferentially. This is consistent with a medium-term browsing facilitation hypothesis. More subtle possible effects were detected for larger browsers (giraffe and kudu). They selected areas with broken and uprooted plants and avoided coppiced areas. All of the browsers selected sites characterized by plants uprooted and broken by elephants, which were associated with a higher visibility, and ultimately a better probability of detecting an approaching predator, suggesting that perceived predation risk plays an important role in microhabitat selection. These results illustrate how elephants can initiate indirect effects that influence microhabitat selection by other herbivores. Understanding the indirect effects of elephants through changes in food availability and predation risk thus needs further investigation. The results of this study do not provide support for the hypothesis that elephant-induced changes in the structure of habitats have caused the declines in the populations of the other herbivores in the study area.     

The impact of high speed, high volume traffic axes on brown bears in Slovenia

The Ljubljana-Razdrto highway and the parallel Ljubljana-Trieste railway cut through critical brown bear (Ursus arctos) habitat in south-central Slovenia. These high speed, high volume traffic axes are located close to the main dispersal corridor for bears from the Dinaric Mountain range into the Alps. We analyzed radiotracking data of 15 individual bears that lived within 10 km of the highway, compared transportation related and overall known bear mortality, and analyzed the spatial distribution of bear-vehicle accidents. The highway posed a home range boundary to resident bears, but was not an absolute barrier. Transportation-related mortality was high in the vicinity of the highway and railway, and averaged 31% of the total known local mortality from 1992 to 1999. At present the detrimental impact of transportation routes on the bear population in Slovenia is modest due to the high density of bears and the low density of highways—but new highways are planned or already under construction. Managers have to be aware that, due to bears large home ranges and long dispersal distances, a single highway affects bears from a huge area—emphasizing the importance of international cooperation and a landscape approach in highway planning.     

Field Trials for in Situ Decontamination of Heavy Metal Polluted Soils using Crops of Metal-Accumulating Plants

Certain wild plants as well as crop plants, so-called hyperaccumulators, are able to accumulate large amounts of heavy metals in aerial parts. This property may be exploited for the clean-up of soil contaminated by metals (phytoremediation), if the yield and metal accumulation are big enough to finish remediation within a reasonable period (e.g. five years). Therefore, the ability of various plants to accumulate zinc and cadmium were compared in field trials. The wild species Thlaspi caerulescens and Alyssum murale as well as the tree Salix viminalis showed a strong ability to accumulate zinc and cadmium. However, phytoremediation of investigated soils contaminated with cadmium (6.6 ppm) or zinc (810 ppm) lasts too long based on present technology. Literature data and preliminary experiments indicate that major obstacles could be overcome: Yield and metal-uptake rates have to be increased dramatically in order to allow remediation within reasonable periods.     

Large‐scale identification of hot spots for soil carbon demand under climate change and bioenergy production

Global change scenarios predict an increased risk for declining amounts of soil organic matter (SOM) for Central Germany. Within this region the production of bioenergy is one important strategy to counteract the rising anthropogenic CO₂‐emissions. Both issues have a close connection: SOM is an important basis for soil productivity and requires a steady reproduction flux. Bioenergy production requires productive soils and partly consumes plant biomass C. Therefore, the available amount for SOM reproduction is reduced. This study provides a methodology for the large‐scale identification of areas with possible conflicts between bioenergy production and SOM reproduction based on (1) the prediction of climate change impact on SOM reproduction and (2) an analysis of the regional distribution of biogas plants. With the C demand index (CDI) and the capacity index (CAP), two indicators were developed which enable the identification of hot spots of high carbon demand for SOM reproduction due to climate change and the usage of bioenergy. As a result of low data requirements, the indicators are widely applicable and transferable to other large‐scale studies. The proposed methodology was applied to Central Germany as a pilot region. Results indicate a growing demand (10–40%) of fresh organic C from biomass for SOM production in comparison to the current level. The analysis reveals that the bioenergy C demand is not evenly distributed within the study region. It also shows some regional clustering. Furthermore, the analysis identifies certain hot spots of a high C demand, where a high capacity of biogas production may conflict with rising demands for biomass to mitigate climate change effects on SOM storage. The hot spot areas—identified and selected on a large scale—can subsequently be analyzed in more detail on a local to farm scale by using high‐resolution data and models which enable the quantification of soil C dynamics.     

An animal model for interface tissue formation in cemented hip replacements

OBJECTIVE: To create a model in sheep for investigation of early changes related to the formation of an interface membrane in hip prosthesis. STUDY DESIGN: Experimental study. ANIMALS: Twenty-four female adult Swiss Alpine sheep. METHODS: Sheep were divided into 2 groups of 12 for unilateral cemented total hip arthroplasty. In Group I, the prosthesis was fixed with retrograde cement gun injection to achieve a complete cement mantle, whereas in Group II a primary cement mantle defect was produced. Groups I and II were further divided into 2 sub-groups with study end points of 2 and 8.5 months after surgery. Radiographs were evaluated postoperatively and at euthanasia for migration of the femoral component and bone resorption. Histologic sections were evaluated semiquantitatively for changes in cell types and numbers, and bone reactions; and quantitatively for size of interface membrane and new bone formation. RESULTS: Radiographically, there tended to be an increase in bone resorption and periosteal bone formation throughout the femoral shaft in Group II compared with Group I, but this was only statistically significant at the region of the femoral neck (R5) at both time periods (P<.05). Semiquantitative histologic evaluation revealed significant increases (P<.05) in cellularity, numbers of fibroblasts, giant cells, macrophages, and mononuclear cells, in Group II primarily at 2 months after surgery. This was also true for interface membrane formation and bone remodeling. Quantitative data showed an increased in the size of the interface membrane and area of bone formation at 8.5 months in Group II. CONCLUSIONS: The cement defect model offered controlled and repeatable production of an interface membrane. The results suggest that a primary cement mantle defect could be a possible trigger for implant instability, eliciting a cascade of biomechanical and molecular events in bone tissue leading to aseptic loosening. CLINICAL RELEVANCE: The results show the effect of defects in the cement mantle in promoting interface membrane formation. Long-term and biochemical studies are required to evaluate the relevance of this interface membrane formation.