Contrasting effects of nitric oxide and corticotropin- releasing factor within the dorsal periaqueductal gray on defensive behavior and nociception in mice

The anxiogenic and antinociceptive effects produced by glutamate N-methyl-D-aspartate receptor activation within the dorsal periaqueductal gray (dPAG) matter have been related to nitric oxide (NO) production, since injection of NO synthase (NOS) inhibitors reverses these effects. dPAG corticotropin-releasing factor receptor (CRFr) activation also induces anxiety-like behavior and antinociception, which, in turn, are selectively blocked by local infusion of the CRF type 1 receptor (CRFr1) antagonist, NBI 27914 [5-chloro-4-(N-(cyclopropyl)methyl-N-propylamino)-2-methyl-6-(2,4,6-trichlorophenyl)aminopyridine]. Here, we determined whether i) the blockade of the dPAG by CRFr1 attenuates the anxiogenic/antinociceptive effects induced by local infusion of the NO donor, NOC-9 [6-(2-hydroxy-1-methyl-2-nitrosohydrazino)-N-methyl-1-hexanamine], and ii) the anxiogenic/antinociceptive effects induced by intra-dPAG CRF are prevented by local infusion of N(ω)-propyl-L-arginine (NPLA), a neuronal NOS inhibitor, in mice. Male Swiss mice (12 weeks old, 25-35 g, N = 8-14/group) were stereotaxically implanted with a 7-mm cannula aimed at the dPAG. Intra-dPAG NOC-9 (75 nmol) produced defensive-like behavior (jumping and running) and antinociception (assessed by the formalin test). Both effects were reversed by prior local infusion of NBI 27914 (2 nmol). Conversely, intra-dPAG NPLA (0.4 nmol) did not modify the anxiogenic/antinociceptive effects of CRF (150 pmol). These results suggest that CRFr1 plays an important role in the defensive behavior and antinociception produced by NO within the dPAG. In contrast, the anxiogenic and antinociceptive effects produced by intra-dPAG CRF are not related to NO synthesis in this limbic midbrain structure

The Role of Snow on Microwave Emission and Scattering over First-Year Sea Ice

The primary objective of this paper is to investigate the geophysical and therniodynarnic effects of snow on sea ice in defining the electromagnetic (EM) interaction within the microwave portion of the spectrum. We combine observational evidence of both the physical and thermodynamic characteristics of snow with direct measurements of scattering and emission at a variety of frequencies. We explain our observational results using various "state-of-the-art" forward scattering and emission models. Results show that geophysical characteristics of snow effect emission above about 37 GHz and above 5 GHz for active microwave scattering. We understand these effects to be driven by grain size and its contribution to volume scattering in both passive and active interactions within the volume. With snow cover, the Brewster angle effect is not significant and there is a gradual rise in emission from 10 to 37 GHz. We find emissivity to be dominated by direct emission from saline ice through the snow layer. Hence, the influence of grain size is small but the trend is clearly a drop in total emission as the grain size increases. We find that the role of the volume fraction of snow on emission and scattering is a complex relationship between the number density of scatterers relative to the coherence of this scattering ensemble. At low volume fractions, we find that independent scattering dominates, resulting in an increase in albedo and the extinction coefficient of the snow with frequency. The thermodynamic effects of snow on microwave scattering and emission are driven by the role that thermal diffusivity and conductivity play in the definition of brine volumes at the ice surface and within the snow volume. Prior to the presence of water in liquid phase within the snow volume, we find that the indirect effects are dominated by an impedance matching process across the snow-ice interface. We find that the complex permittivity at the snow-ice interface is considerably higher than over the bare ice surface. Our results showed that only a small change occurs between the cold and warm cases at lower frequencies, but as expected, the change in emissivity is larger at higher frequencies. Once water in liquid phase appears within the snow cover, we find that both emission and scattering are directly affected by the high complex permittivity of this volume fraction within the snow layer. © 1998 IEEE

Tackling the minority: sulfate-reducing bacteria in an archaea-dominated subsurface biofilm

Archaea are usually minor components of a microbial community and dominated by a large and diverse bacterial population. In contrast, the SM1 Euryarchaeon dominates a sulfidic aquifer by forming subsurface biofilms that contain a very minor bacterial fraction (5%). These unique biofilms are delivered in high biomass to the spring outflow that provides an outstanding window to the subsurface. Despite previous attempts to understand its natural role, the metabolic capacities of the SM1 Euryarchaeon remain mysterious to date. In this study, we focused on the minor bacterial fraction in order to obtain insights into the ecological function of the biofilm. We link phylogenetic diversity information with the spatial distribution of chemical and metabolic compounds by combining three different state-of-the-art methods: PhyloChip G3 DNA microarray technology, fluorescence in situ hybridization (FISH) and synchrotron radiation-based Fourier transform infrared (SR-FTIR) spectromicroscopy. The results of PhyloChip and FISH technologies provide evidence for selective enrichment of sulfate-reducing bacteria, which was confirmed by the detection of bacterial dissimilatory sulfite reductase subunit B (dsrB) genes via quantitative PCR and sequence-based analyses. We further established a differentiation of archaeal and bacterial cells by SR-FTIR based on typical lipid and carbohydrate signatures, which demonstrated a co-localization of organic sulfate, carbonated mineral and bacterial signatures in the biofilm. All these results strongly indicate an involvement of the SM1 euryarchaeal biofilm in the global cycles of sulfur and carbon and support the hypothesis that sulfidic springs are important habitats for Earth's energy cycles. Moreover, these investigations of a bacterial minority in an Archaea-dominated environment are a remarkable example of the great power of combining highly sensitive microarrays with label-free infrared imaging