Specific GABAA circuits for visual cortical plasticity

Weak inhibition within visual cortex early in life prevents experience-dependent plasticity. Loss of responsiveness to an eye deprived of vision can be initiated prematurely by enhancing gamma-aminobutyric acid (GABA)-mediated transmission with benzodiazepines. Here, we use a mouse "knockin" mutation to alpha subunits that renders individual GABA type A (GABA(A)) receptors insensitive to diazepam to show that a particular inhibitory network controls expression of the critical period. Only alpha1-containing circuits were found to drive cortical plasticity, whereas alpha2-enriched connections separately regulated neuronal firing. This dissociation carries implications for models of brain development and the safe design of benzodiazepines for use in infants.     

Maplike representation of celestial E-vector orientations in the brain of an insect

For many insects, the polarization pattern of the blue sky serves as a compass cue for spatial navigation. E-vector orientations are detected by photoreceptors in a dorsal rim area of the eye. Polarized-light signals from both eyes are finally integrated in the central complex, a brain area consisting of two subunits, the protocerebral bridge and the central body. Here we show that a topographic representation of zenithal E-vector orientations underlies the columnar organization of the protocerebral bridge in a locust. The maplike arrangement is highly suited to signal head orientation under the open sky.     

Simulation of chromium transport in the unsaturated zone for predicting contaminant entries into the groundwater

Heavy metal contaminations in the top‐soil layers can impose serious threats to groundwater quality. A seepage water prognosis of probable future contaminant entries at the groundwater surface has to take into account the emission characteristics of the source zone and the reactive transport of the contaminated leachate through the unsaturated zone. Here, a possible approach is presented, exemplarily for a site contaminated with chromium, encompassing batch elution experiments, unsaturated soil column leaching experiments with flow interruption, soil monolith lysimeter experiments, and numerical modeling of non‐equilibrium solute transport. The prognosis provides a long‐term prediction of Cr concentrations at the groundwater surface. It must be emphasized, that the modeling results are uncertain, because several of the parameters in the simulations can be determined only with significant errors. Additionally, the approach is not applicable routinely for every hazardous waste site. Our study reveals, however, that reactive contaminants can possibly reach the groundwater at hazardous concentrations within very short time.     

Microbial diversity in three floodplain soils at the Elbe River (Germany)

Microbial communities in floodplain soils are exposed to periodical flooding. A long-term submerged Eutric Gleysol (GLe), an intermediate flooded Eutric Fluvisol (FLe), and a short-time flooded Mollic Fluvisol (FLm) at the Elbe River (Germany) with similar organic carbon contents (C_org) between 8.1% and 8.9% were selected to test the quality of phospholipid fatty acids (PLFA), soil microbial carbon (C_mic), basal respiration (BR), metabolic quotient (qCO₂), and C_mic/C_org ratio to characterize and discriminate these soils with microbial parameters.The three floodplain soils can be differentiated by C_mic and by total PLFA-biomass. Due to the different flooding durations and the time since the soils were last flooded C_mic and PLFA-biomass increase in the order GLe<FLe<FLm. Both parameters correlate significantly (r=0.999;p<0.05). The C_mic/C_org ratios are low in comparison to terrestrial soils and revealed the same ranking over the three soils like C_mic. Contrary, qCO₂ and BR are highest in GLe and lowest in FLm according to inundation regime. The diminished C_mic, high BR, and high qCO₂ values in GLe seem to be an unspecific response of aerobic soil microorganisms on the long flooding period and the resulting short time for developing after last flooding as well as the low pH value. Different plant communities and their residues may influence the microbial diversity additionally.The PLFA profiles were dominated by the group of saturated fatty acids that together constituted almost 62-72% of the total fatty acids identified in the soils. In GLe all groups of PLFA, inclusive monounsaturated fatty acids, are lowest and in FLm highest, while in FLe the PLFA fractions show an intermediary amount of the three soils. The FLm had most of the time aerobic conditions and revealed therefore the highest C_mic, PLFA-biomass, especially monounsaturated fatty acids, C_mic/C_org ratio as well as relatively low BR and qCO₂ value. These indicate that microorganisms in FLm are more efficiently in using carbon sources than those in GLe and FLe.All 26 identified PLFA were found in FLe and FLm, while the polyunsaturated fungi biomarker 18:2ω6,9c could not be detected in GLe. In this long-time submerged soil the environmental conditions which microorganisms are exposed might be disadvantageous for fungi.     

Die Bestimmung der Wasserspannungs- /Wasserleitfähigkeits-Beziehung von Bodenaggregaten

Determination of the unsaturated hydraulic conductivity of soil aggregates by use of microtensiometers The hydraulic properties of single aggregates were measured with the use of microtensiometers. They are small enough (tip diameter 1 mm, length 1–2 mm) that two of them can be installed inside an aggregate within a distance of 1–3 mm. The changes of water suction are measured with pressure transducers and recorded by a micro-computer. Results obtained for different aggregates show, that at the same water suction, the hydraulic conductivity of single aggregates is up to 2 orders of magnitude smaller than that of the bulk soil. The cross-over-suction value for aggregates can also be derived.     

Genotypical differentiation of Prototheca isolates of milk samples from mastitis affected cattle in Germany

To elucidate the spectra of Prototheca species and P. zopfii genotypes in milk samples from mastitis affected cattle, 200 Prototheca-isolates of 57 German dairy cattle barns were analyzed by species- and genotype- specific PCR and RFLP analysis. The investigations showed that 177 (88.5%) of all isolates represented P. zopfii genotype 2, 21 (10.5%) isolates represented P. blaschkeae and two (1.0%) P. zopfii genotype 1. Therefore mainly P. zopfii genotype 2 but also P. blaschkeae act in the epidemiology of mastitis in cattle, whereas the role of P. blaschkeae in development of bovine protothecal mastitis should be further explored in epidemiological studies. In this study P. blaschkeae was demonstrated for the first time in association with bovine mastitis in Germany.     

Differentiation of viable, apoptotic and necrotic cells in bronchoalveolar lavage fluid of normal horses and horses with recurrent airway obstruction

Proinflammatoric cytokines are released extracellularly during necrosis. These lead to inflammation and destruction of surrounding tissues. The aim of this study was to compare the number of viable, apoptotic and necrotic cells in the bronchoalveolar lavage fluid (BALF) of normal horses and horses with recurrent airway obstruction (RAO) and to determine if fluorescence microscopy is a reliable method for this examination. A group of six normal horses and a group of ten horses with RAO were examined. Samples were assessed using annexin-V and propidium iodide immunofluorescence assay and examined by fluorescence microscopy (16 horses) and flow cytometry (nine of 16 horses). We found no significant differences in percentages of apoptotic and viable cells between both groups. The number of necrotic cells was significantly increased in horses with RAO counted by fluorescence microscopy. Cells with high granularity and macrophages had a significantly higher percentage of necrotic cells than lymphocytes. There was a good agreement between both methods. No significant differences were detected. The correlation between both methods is significant. Higher amounts of necrotic cells in the bronchial lumina of horses with RAO could be a reason for tissue damage and continuous lung tissue inflammation. Fluorescence microscopy was applicable for examination of BALF. Therapy should be aimed at the reduction of necrotic cells in the bronchial lumina. Further studies are required to find ways to reduce inflammatory cell infiltration and necrosis in bronchial lumina.     

Multi-site validation of a soil organic matter model for arable fields based on generally available input data

The paper describes a simplified carbon balance model, derived from the CANDY model, which works in annual time steps requiring only clay content, soil type of the German classification system “Reichsbodenschätzung”, average air temperature and rainfall as site characteristics, a value for organic carbon content as the initial value as well as crop yield and organic matter amendments as management data.The Candy Carbon Balance (CCB) model has been validated using a dataset from 40 long-term experiments situated in Central Europe including 391 treatments with a total number of 4794 C_org observations. Statistical measures to prove model validity were mean error (ME = − 0.001) and root mean square error (RMSE = 0.119). In addition a number of tests were performed to make sure that the model has no systematic error for different types of site conditions and management activities. After this successful validation the CCB model is considered applicable for advisory service for arable fields on a wide range of site conditions. Due to the poor representation of clay soils in this study some more model tests on these soils would be recommendable.     

The configuration of the Cu(2+) binding region in full-length human prion protein compared with the isolated octapeptide

The cellular prion protein (PrP(C)) is a copper binding protein. The molecular features of the Cu(2+) binding sites have been investigated and characterized by spectroscopic experiments on PrP(C)-derived peptides and the correctly folded human full-length PrP(C) (hPrP-[23-231]). These experiments allowed us to distinguish two different configurations of copper binding. The different copper complexes depend on sequence context, buffer conditions and stoichiometry of copper. The combined information of spectroscopic data from our EXAFS, EPR and ENDOR experiments was used to create models for these two copper complexes. A large number of conformations of these models were calculated using molecular mechanics computations, and the simulated spectra of these structures were compared with our experimental data. Common features and differences of the copper binding motifs are discussed in this paper and it remains for future investigations to study whether different configurations are associated with different functional states of PrP(C).