Comparison of static immersion and intravenous injection systems for exposure of zebrafish embryos to the natural pathogen Edwardsiella tarda

<p>Abstract</p> <p>Background</p> <p>The zebrafish embryo is an important <it>in vivo </it>model to study the host innate immune response towards microbial infection. In most zebrafish infectious disease models, infection is achieved by micro-injection of bacteria into the embryo. Alternatively, <it>Edwardsiella tarda</it>, a natural fish pathogen, has been used to treat embryos by static immersion. In this study we used transcriptome profiling and quantitative RT-PCR to analyze the immune response induced by <it>E. tarda </it>immersion and injection.</p> <p>Results</p> <p>Mortality rates after static immersion of embryos in <it>E. tarda </it>suspension varied between 25-75%, while intravenous injection of bacteria resulted in 100% mortality. Quantitative RT-PCR analysis on the level of single embryos showed that expression of the proinflammatory marker genes <it>il1b </it>and <it>mmp9 </it>was induced only in some embryos that were exposed to <it>E. tarda </it>in the immersion system, whereas intravenous injection of <it>E. tarda </it>led to <it>il1b </it>and <it>mmp9 </it>induction in all embryos. In addition, microarray expression profiles of embryos subjected to immersion or injection showed little overlap. <it>E. tarda</it>-injected embryos displayed strong induction of inflammatory and defense genes and of regulatory genes of the immune response. <it>E. tarda</it>-immersed embryos showed transient induction of the cytochrome P450 gene <it>cyp1a</it>. This gene was also induced after immersion in <it>Escherichia coli </it>and <it>Pseudomonas aeruginosa </it>suspensions, but, in contrast, was not induced upon intravenous <it>E. tarda </it>injection. One of the rare common responses in the immersion and injection systems was induction of <it>irg1l</it>, a homolog of a murine immunoresponsive gene of unknown function.</p> <p>Conclusions</p> <p>Based on the differences in mortality rates between experiments and gene expression profiles of individual embryos we conclude that zebrafish embryos cannot be reproducibly infected by exposure to <it>E. tarda </it>in the immersion system. Induction of <it>il1b </it>and <it>mmp9 </it>was consistently observed in embryos that had been systemically infected by intravenous injection, while the early transcriptional induction of <it>cyp1a </it>and <it>irg1l </it>in the immersion system may reflect an epithelial or other tissue response towards cell membrane or other molecules that are shed or released by bacteria. Our microarray expression data provide a useful reference for future analysis of signal transduction pathways underlying the systemic innate immune response versus those underlying responses to external bacteria and secreted virulence factors and toxins.</p

Random Resonators and Prelocalized Modes in Disordered Dielectric Films

Areal density of disorder-induced resonators with a high quality factor, $Q\gg 1$, in a film with fluctuating refraction index is calculated theoretically. We demonstrate that for a given $kl>1$, where $k$ is the light wave vector, and $l$ is the transport mean free path, when {\em on average} the light propagation is diffusive, the likelihood for finding a random resonator increases dramatically with increasing the correlation radius of the disorder. Parameters of {\em most probable} resonators as functions of $Q$ and $kl$ are found.Comment: 6 pages including 2 figure

Statistics of transmission in one-dimensional disordered systems: universal characteristics of states in the fluctuation tails

We numerically study the distribution function of the conductance (transmission) in the one-dimensional tight-binding Anderson and periodic-on-average superlattice models in the region of fluctuation states where single parameter scaling is not valid. We show that the scaling properties of the distribution function depend upon the relation between the system's length $L$ and the length $l_s$ determined by the integral density of states. For long enough systems, $L \gg l_s$, the distribution can still be described within a new scaling approach based upon the ratio of the localization length $l_{loc}$ and $l_s$. In an intermediate interval of the system's length $L$, $l_{loc}\ll L\ll l_s$, the variance of the Lyapunov exponent does not follow the predictions of the central limit theorem and this scaling becomes invalid.Comment: 22 pages, 12 eps figure

Compared to conventional, ecological intensive management promotes beneficial proteolytic soil microbial communities for agro-ecosystem functioning under climate change-induced rain regimes

Projected climate change and rainfall variability will affect soil microbial communities, biogeochemical cycling and agriculture. Nitrogen (N) is the most limiting nutrient in agroecosystems and its cycling and availability is highly dependent on microbial driven processes. In agroecosystems, hydrolysis of organic nitrogen (N) is an important step in controlling soil N availability. We analyzed the effect of management (ecological intensive vs. conventional intensive) on N-cycling processes and involved microbial communities under climate change-induced rain regimes. Terrestrial model ecosystems originating from agroecosystems across Europe were subjected to four different rain regimes for 263 days. Using structural equation modelling we identified direct impacts of rain regimes on N-cycling processes, whereas N-related microbial communities were more resistant. In addition to rain regimes, management indirectly affected N-cycling processes via modifications of N-related microbial community composition. Ecological intensive management promoted a beneficial N-related microbial community composition involved in N-cycling processes under climate change-induced rain regimes. Exploratory analyses identified phosphorus-associated litter properties as possible drivers for the observed management effects on N-related microbial community composition. This work provides novel insights into mechanisms controlling agro-ecosystem functioning under climate change

(U-Th)/He zircon dating of Chesapeake Bay distal impact ejecta from ODP site 1073

Single crystal (U‐Th)/He dating has been undertaken on 21 detrital zircon grains extracted from a core sample from Ocean Drilling Project (ODP) site 1073, which is located ~390 km northeast of the center of the Chesapeake Bay impact structure. Optical and electron imaging in combination with energy dispersive X‐ray microanalysis (EDS) of zircon grains from this late Eocene sediment shows clear evidence of shock metamorphism in some zircon grains, which suggests that these shocked zircon crystals are distal ejecta from the formation of the ~40 km diameter Chesapeake Bay impact structure. (U‐Th/He) dates for zircon crystals from this sediment range from 33.49 ± 0.94 to 305.1 ± 8.6 Ma (2σ), implying crystal‐to‐crystal variability in the degree of impact‐related resetting of (U‐Th)/He systematics and a range of different possible sources. The two youngest zircon grains yield an inverse‐variance weighted mean (U‐Th)/He age of 33.99 ± 0.71 Ma (2σ uncertainties n = 2; mean square weighted deviation = 2.6; probability [P] = 11%), which is interpreted to be the (U‐Th)/He age of formation of the Chesapeake Bay impact structure. This age is in agreement with K/Ar, 40Ar/39Ar, and fission track dates for tektites from the North American strewn field, which have been interpreted as associated with the Chesapeake Bay impact event

Effect of stroke rate on the distribution of net mechanical power in rowing

The aim of this study was to assess the effect of manipulating stroke rate on the distribution of mechanical power in rowing. Two causes of inefficient mechanical energy expenditure were identified in rowing. The ratio between power not lost at the blades and generated mechanical power (P