Preserved feedforward but impaired top-down processes in the vegetative state

Frontoparietal cortex is involved in the explicit processing (awareness) of stimuli. Frontoparietal activation has also been found in studies of subliminal stimulus processing. We hypothesized that an impairment of top-down processes, involved in recurrent neuronal message-passing and the generation of long-latency electrophysiological responses, might provide a more reliable correlate of consciousness in severely brain-damaged patients, than frontoparietal responses. We measured effective connectivity during a mismatch negativity paradigm and found that the only significant difference between patients in a vegetative state and controls was an impairment of backward connectivity from frontal to temporal cortices. This result emphasizes the importance of top-down projections in recurrent processing that involve high-order associative cortices for conscious perception.     

Cross-linking cellular prion protein triggers neuronal apoptosis in vivo

Neuronal death is a prominent, but poorly understood, pathological hallmark of prion disease. Notably, in the absence of the cellular prion protein (PrPC), the disease-associated isoform, PrPSc, appears not to be intrinsically neurotoxic, suggesting that PrPC itself may participate directly in the prion neurodegenerative cascade. Here, cross-linking PrPC in vivo with specific monoclonal antibodies was found to trigger rapid and extensive apoptosis in hippocampal and cerebellar neurons. These findings suggest that PrPC functions in the control of neuronal survival and provides a model to explore whether cross-linking of PrPC by oligomeric PrPSc can promote neuronal loss during prion infection.     

PAMELA measurements of cosmic-ray proton and helium spectra

Protons and helium nuclei are the most abundant components of the cosmic radiation. Precise measurements of their fluxes are needed to understand the acceleration and subsequent propagation of cosmic rays in our Galaxy. We report precision measurements of the proton and helium spectra in the rigidity range 1 gigavolt to 1.2 teravolts performed by the satellite-borne experiment PAMELA (payload for antimatter matter exploration and light-nuclei astrophysics). We find that the spectral shapes of these two species are different and cannot be described well by a single power law. These data challenge the current paradigm of cosmic-ray acceleration in supernova remnants followed by diffusive propagation in the Galaxy. More complex processes of acceleration and propagation of cosmic rays are required to explain the spectral structures observed in our data.     

Two class III chitin synthases specifically localized in appressoria and haustoria of Puccinia graminis f. sp. tritici

Rust fungi like Puccinia graminis f. sp. tritici are known to change their cell wall properties upon entering the plant tissue. Immunohistochemistry revealed the cellular localization of two class III chitin synthase isoforms in rust mycelia developing on and in the host plant. Isoform IIIa is restricted to fungal infection structures growing on the surface of the plant, such as germ tubes and, predominantly, appressoria. Isoform IIIb is found exclusively in haustoria developed inside the plant. Thus, the rust fungus uses at least two chitin synthase isoforms with specialized functions in the differentiation of infection structures during the biotrophic plant-pathogen-interaction.     

Hydrological structure and erosion damage caused by concentrated flow in cultivated catchments

This study analyses the between-catchment variability of rill volumes produced by concentrated flow erosion during winter in the northern part of the Paris Basin. The working hypotheses were that (i) runoff concentrates along channels determined by topography or by agricultural practices; (ii) rill length is a major component of rill volume variability on a catchment scale; (iii) rill cross-sectional areas are controlled by the size of upslope runoff-contributing areas connected to the corresponding channels. Two samples, one of 20 zero order catchments and the other of 15 catchments, were surveyed. For each catchment, the runoff collector network was modelled from topographical and agricultural information, and split into homogeneous segments. Each segment was characterized by its slope gradient (SL), the soil susceptibility to rill erosion (SSE) and the size of the upslope runoff-contributing areas (RCA) connected to it. These areas were identified by the structural state of their soil surface. The frequency of rill occurrence was highly correlated with RCA and SL. The rill cross-sectional areas of eroded channels were correlated with RCA, SL and SSE. Catchment erosion rates were estimated by adding together the predicted rill volumes for each segment within the catchment. These estimations were closely correlated with observed rill erosion rates. The relative spatial position of runoff collectors must be taken into account when examining the damage caused by concentrated flow erosion.     

UN ECE ICP Materials: Dose-Response Functions on Dry and Wet Acid Deposition Effects After 8 Years of Exposure

The main results of the International Co-operative Programme on Effects on Materials, including Historic and Cultural Monuments (ICP Materials) within the United Nations Economic Commission for Europe (UN ECE) are summarised. The 8-year field exposure programme involves 39 test sites in 12 European countries and in the United States and Canada. Dose-response functions (DRF) expressing the effect of dry and wet deposition as individual terms have been obtained for a wide range of materials including bronze, copper, weathering steel, zinc, aluminium, nickel, tin, stone materials, paint coatings and glass materials. The DRF's includes parameters that are easily available on different geographical scales and can be used for mapping areas of increased corrosion rates and for calculation of costs.     

Discrimination of recombinant and pituitary-derived bovine and porcine growth hormones by peptide mass mapping

Somatotropins, which are used in cattle for growth and lactating performances, are difficult to reliably detect because no direct method exists. Reversed-phase high-performance liquid chromatography (RP-HLC) coupled to electrospray ionization quadrupole mass spectrometry (ESI/MS) has been developed to separate and characterize the N-terminal peptides resulting from tryptic cleavage of natural and recombinant growth hormones from different species (bovine, porcine, and human) and suppliers. Conditions for tryptic digestion were optimized. This technique was found to be optimal to cleave efficiently the N-terminal peptide of the proteins without releasing too much noise from the matrix. Characterization of the peptides through ESI(+)-MS allowed natural and recombinant growth hormones from bovine and porcine species with N-terminal amino acid sequences differing from one amino acid residue to be discriminated. However, the studied human growth hormones had similar primary sequences that did not permit any discrimination between recombinant and natural forms, thus confirming the known identity of these hormones. Protein digestions with pepsin and chymotrypsin were also compared but were not conclusive due to the too small N-terminal peptides released after proteolysis.