Cell responses to xenobiotics: comparison of MCF7 multi-drug- and mussel blood cell multi-xenobiotic-defense mechanisms

Multi-drug resistance (MDR) in MCF7 breast cancer cells and multi-xenobiotic resistance (MXR) in mussel (Mytilus edulis) blood cells (MBC) are well known mechanisms that contribute to the decrease in intracellular concentrations of many unrelated but cytotoxic compounds. In the present work, we have carried out comparative investigations of the MDR/MXR protective mechanisms using a rapid colorimetric assay for cell viability and calcein accumulation for MDR/MXR activities. These studies were performed using cultured MCF7 and MBC before and after in vitro exposure to xenobiotics. Our results indicate that a 5-day exposure to doxorubicin or vincristine decreased calcein accumulation in MBC which is consistent with an induction of multi-xenobiotic resistance. The increase in calcein accumulation provoked by 1-h treatment with 50 microM verapamil was much lower in MBC when compared to the P-glycoprotein overexpressing MCF7 cell line. We conclude that such microplate assays could be used in primary cultures of MBC to estimate the effects of various chemicals on MXR activity.     

Evidence of systematic errors in FK5

Analyses of FK5 stars observed in 1986 with the Carlsberg Automatic Meridian Circle on La Palma and the automatic meridian circle at Bordeaux Observatory produce evidence of systematic errors in the FK5 reaching 0 ^. 1 in size.     

On internal wave dynamics in the northern basin of the lake of Lugano

Abstract

Data collected from the Lake of Lugano during 3 July to 17 August 1979 are analysed for internal gravity wave motions. We demonstrate that a two-layer linear model is capable of explaining the internal wave response. A numerical finite difference procedure is used to determine the seiche periods and eigenfunctions of this model. The computed results (periods and phase differences between station pair interfacial displacements are then compared with the measured data. This comparison demonstrates that four conspicuous internal mode periods can be identified with fair to excellent statistical coherence between data-set pairs and that even higher order modes can be detected but with less statistical confidence. This identification proves that for the Lake of Lugano, no recourse has to be made to multi-layer models that would account for higher order baroclinicity.     

Hydrochemical and sedimentary responses of paired High Arctic watersheds to unusual climate and permafrost disturbance,Cape Bounty,Melville Island,Canada

High Arctic river responses to changing hydroclimatic and landscape processes are poorly understood. In non‐glacierized basins, snowmelt and rainfall generate river discharge, which provides first order control over fluxes. Further factors include the seasonality of precipitation, seasonal active layer development, and permafrost disturbance. These controls were evaluated in terms of sedimentary and biogeochemical fluxes from paired catchments at Cape Bounty, Melville Island, Nunavut during 2006–2009. Results indicate that the source of runoff can be more important than the amount of runoff for sediment, solutes, and organic yields. Although the snowmelt period is typically the most important time for these yields, heavy late summer precipitation events can create disproportionately large yields. Rainfall increases yields because it hydrologically connects areas otherwise isolated. Inorganic solute yields from late summer rainfall are higher because the thick active layer maximizes hydrologic interactions with mineral soils and generates high solute concentrations. Results also indicate that while the catchments are broadly similar, subtle topographic differences result in important inter‐catchment differences in runoff and suspended and dissolved loads. The East watershed, which had less extensive permafrost disturbance, consistently had higher concentrations of dissolved solids. These higher dissolved fluxes cannot therefore be explained by thermokarst features, but rather by deeper active layer development, due to a greater proportion of south‐facing slopes. Although warm temperatures in 2007 led to extensive active layer disturbance in the West watershed, because the disturbances were largely hydrologically disconnected, the total disturbed area was small, and inter‐annual variability in discharge was high, there was no detectable response in dissolved loads to disturbances. Sediment availability increased after 2007, but yields have largely returned to pre‐disturbance levels. Results indicate that seasonality and frequency‐magnitude characteristics of projected increases in precipitation must be considered along with active layer changes to predict the fluvial sedimentary and biogeochemical response to regional climate change. Copyright © 2011 John Wiley & Sons, Ltd.     

Paired bedrock and boulder 10Be concentrations resulting from early Holocene ice retreat near Jakobshavn Isfjord,western Greenland

We measured in situ cosmogenic ¹⁰Be in 16 bedrock and 14 boulder samples collected along a 40-km transect outside of and normal to the modern ice margin near Sikuijuitsoq Fjord in central-west Greenland (69°N). We use these data to understand better the efficiency of glacial erosion and to infer the timing, pattern, and rate of ice loss after the last glaciation. In general, the ages of paired bedrock and boulder samples are in close agreement (r² = 0.72). Eleven of the fourteen paired bedrock and boulder samples are indistinguishable at 1σ; this concordance indicates that subglacial erosion rates are sufficient to remove most or all ¹⁰Be accumulated during previous periods of exposure, and that few, if any, nuclides are inherited from pre-Holocene interglaciations. The new data agree well with previously-published landscape chronologies from this area, and suggest that two chronologically-distinct land surfaces exist: one outside the Fjord Stade moraine complex (～10.3 ± 0.4 ka; n = 7) and another inside (～8.0 ± 0.7 ka; n = 21). Six ¹⁰Be ages from directly outside the historic (Little Ice Age) moraine show that the ice margin first reached its present-day position ～7.6 ± 0.4 ka. Early Holocene ice margin retreat rates after the deposition of the Fjord Stade moraine complex were ～100–110 m yr^?1. Sikuijuitsoq Fjord is a tributary to the much larger Jakobshavn Isfjord and the deglaciation chronologies of these two fjords are similar. This synchronicity suggests that the ice stream in Jakobshavn Isfjord set the timing and pace of early Holocene deglaciation of the surrounding ice margin.     

Plants versus streams: Their groundwater-mediated competition at “El Morro,” a developing catchment in the dry plains of Argentina

Our understanding of how groundwater mediates evapotranspiration/streamflow partitioning is still fragmented and catchment studies under changing vegetation conditions can provide a useful frame for integration. We explored this partition in a flat sedimentary dry catchment in central Argentina in which the replacement of native vegetation with rainfed crops was accompanied by the abrupt formation of groundwater-fed streams by subsurface erosion (i.e., sapping) episodes. Historical records indicated widespread water table rises (~0.3 m y⁻¹ on average). Groundwater level and stream baseflow fluctuated seasonally with minima in the warm rainy season, indicating that evaporative discharge rather than rainfall shapes saturated flows. Diurnal groundwater level fluctuations showed that plant uptake was widespread where water tables are shallow (<3 m) but restricted to deep-rooted Prosopis forests where they are deep (7–10 m). MODIS and LANDSAT NDVI revealed a long-term greening for native vegetation, new wetlands included, but not for croplands, suggesting more limited evapotranspiration-groundwater level regulation under agriculture. Close to the deepest (20 m) and most active incisions, groundwater level and greenness declined and stream baseflow showed no seasonal fluctuations, hinting decoupling from evapotranspiration. Intense ecological and geomorphological transformations in this catchment exposed the interplay of five mechanisms governing evapotranspiration/streamflow partition including (a) unsaturated uptake and both (b) riparian and (c) distributed uptake from the saturated zone by plants, as well as (d) deepening incisions and (e) sediment deposits over riparian zones by streams. Acknowledging the complex interplay of these mechanisms with groundwater is crucial to predict and manage future hydrological changes in the dry plains of South America.     

The changing social relations of a community-based mangrove forest project in Zanzibar

Coastal areas in East Africa are experiencing rapid economic, resource management, demographic and technological shifts. In response diverse Community-based Natural Resource Management (CBNRM) applications have been embraced to provide mutual conservation and use benefits. These initiatives have met with mixed success in practice. Reflecting on the limitations of past research using common pool resources theory theory to study CBNRM we use insights from actor oriented theory combined with satellite image analysis to describe and discuss the forces dynamically influencing institutional and mangrove forest cover change at Kisakasaka, Zanzibar focussing on the formal CBNRM project period between 1996 and 2001, but also considering the period before and after this. We examine the shifting social relations that affected the performance and viability of the formal CBNRM arrangements. An integrated approach was taken to the presentation and discussion of results where it was possible to enrich and expand explanations of socio-environmental change, which was driven by a lack of government support, the undermining effects of party political divisions, and the lack of institutional adaptive capacity. We conclude that this was a useful approach to explain CBNRM intervention events at Kisakasaka.