Heterogeneous nucleotide occupancy stimulates functionality of phage shock protein F, an AAA+ transcriptional activator

The catalytic AAA+ domain (PspF1-275) of an enhancer-binding protein is necessary and sufficient to contact sigma54-RNA polymerase holoenzyme (Esigma54), remodel it, and in so doing catalyze open promoter complex formation. Whether ATP binding and hydrolysis is coordinated between subunits of PspF and the precise nature of the nucleotide(s) bound to the oligomeric forms responsible for substrate remodeling are unknown. We demonstrate that ADP stimulates the intrinsic ATPase activity of PspF1-275 and propose that this heterogeneous nucleotide occupancy in a PspF1-275 hexamer is functionally important for specific activity. Binding of ADP and ATP triggers the formation of functional PspF1-275 hexamers as shown by a gain of specific activity. Furthermore, ATP concentrations congruent with stoichiometric ATP binding to PspF1-275 inhibit ATP hydrolysis and Esigma54-promoter open complex formation. Demonstration of a heterogeneous nucleotide-bound state of a functional PspF1-275.Esigma54 complex provides clear biochemical evidence for heterogeneous nucleotide occupancy in this AAA+ protein. Based on our data, we propose a stochastic nucleotide binding and a coordinated hydrolysis mechanism in PspF1-275 hexamers.     

The role of nocturnal vision in mate choice: females prefer conspicuous males in the European tree frog (Hyla arborea)

Nocturnal frog species rely extensively on vocalization for reproduction. But recent studies provide evidence for an important, though long overlooked, role of visual communication. In many species, calling males exhibit a conspicuous pulsing vocal sac, a signal bearing visually important dynamic components. Here, we investigate female preference for male vocal sac coloration—a question hitherto unexplored—and male colour pattern in the European tree frog (Hyla arborea). Under nocturnal conditions, we conducted two-choice experiments involving video playbacks of calling males with identical calls and showing various naturally encountered colour signals, differing in their chromatic and brightness components. We adjusted video colours to match the frogs'' visual perception, a crucial aspect not considered in previous experiments. Females prefer males with a colourful sac and a pronounced flank stripe. Both signals probably enhance male conspicuousness and facilitate detection and localization by females. This study provides the first experimental evidence of a preference for specific vocal sac spectral properties in a nocturnal anuran species. Vocal sac coloration is based on carotenoids and may convey information about male quality worthwhile for females to assess. The informative content of the flank stripe remains to be demonstrated.     

Evolution cyclique des glandes cérébrales au cours de l'intermue chez Lithobius forficatus L. (Myriapode Chilopode)

Résumé Chez le Chilopode Lithobius forficatus L., les cellules parenchymateuses des glandes cérébrales présentent, durant l'intermue, un cycle sécrétoire caractérisé essentiellement par l'évolution de l'activité golgienne. Pendant les périodes de sécrétion, les ribosomes, groupés en polysomes, et les éléments ergastoplasmiques sont très abondants; pendant les périodes de repos, les ribosomes sont isolés et l'ergastoplasme est vésiculeux. Les autres organites cellulaires montrent peu de variations.Le cycle sécrétoire ne se superpose pas exactement au cycle d'intermue; il commence lors de la prémue. Peu de temps après l'exuviation, il est possible d'observer des figures qui semblent liées au rejet du produit de sécrétion. L'étude ultrastructurale des glandes cérébrales en fonction de l'intermue confirme l'existence de l'activité cyclique mise en évidence par les résultats expérimentaux.

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Ultrastructural signs of cyclic secretory activity in the cerebral glands of Lithobius forficatus during intermolt

Summary During the molting cycle of Lithobius forficatus L. (Chilopoda), the parenchymal cells of the cerebral glands exhibit signs of cyclic secretory activity consisting essentially of changes in the appearance of the Golgi complex. During active periods of secretion, polysomes and ergastoplasmic elements are very numerous; free ribosomes and vesiculated ergastoplasmic cisternae characterize the periods of inactivity. Other cytoplasmic organelles undergo few variations. The secretory cycle as determined by cytological criteria does not exactly match the molting cycle. The first ultrastructural signs of activity appear during premolt. Shortly after ecdysis, images suggesting the release of secretory material can be observed. The electron microscopic data on cyclic changes during intermolt substantiate the existence of activity cycles in the cerebral glands as determined by physiological experiments.

     

Comparaison des divers types d'adultoides chezLocusta migratoria L.

Conclusion on aurait pu s'attendre à ce que les adultoïdes (stades Vbis) se groupent sur la même droite que les stades V normaux et les adultes prématurés (V) sur celle des imagos (fig. 6). On voit qu'il n'en est rien et que cela tient à ce que la croissance des organes du vol à la fin du développement larvaire deLocusta migratoria n'est pas représentée par une droite d'allométrie unique, mais présente une discontinuité à chacune des dernières mues, de sorte que les adultoïdes ne sont pas des stades V géants mais un stade supplémentaire ajouté au développement normal, et les imagos prématurés ne sont pas des adultes nains mais des adultes privés d'une partie de leur évolution larvaire.     

Genome-wide analysis of gene expression during Xenopus tropicalis tadpole tail regeneration

Background

During liver development, intrahepatic bile ducts are thought to arise by a unique asymmetric mode of cholangiocyte tubulogenesis characterized by a series of remodeling stages. Moreover, in liver diseases, cells lining the Canals of Hering can proliferate and generate new hepatic tissue. The aim of this study was to develop protocols for three-dimensional visualization of protein expression, hepatic portal structures and human hepatic cholangiocyte tubulogenesis.

Results

Protocols were developed to digitally visualize portal vessel branching and protein expression of hepatic cell lineage and extracellular matrix deposition markers in three dimensions. Samples from human prenatal livers ranging from 7 weeks + 2 days to 15½ weeks post conception as well as adult normal and acetaminophen intoxicated liver were used. The markers included cytokeratins (CK) 7 and 19, the epithelial cell adhesion molecule (EpCAM), hepatocyte paraffin 1 (HepPar1), sex determining region Y (SRY)-box 9 (SOX9), laminin, nestin, and aquaporin 1 (AQP1). Digital three-dimensional reconstructions using CK19 as a single marker protein disclosed a fine network of CK19 positive cells in the biliary tree in normal liver and in the extensive ductular reactions originating from intrahepatic bile ducts and branching into the parenchyma of the acetaminophen intoxicated liver. In the developing human liver, three-dimensional reconstructions using multiple marker proteins confirmed that the human intrahepatic biliary tree forms through several developmental stages involving an initial transition of primitive hepatocytes into cholangiocytes shaping the ductal plate followed by a process of maturation and remodeling where the intrahepatic biliary tree develops through an asymmetrical form of cholangiocyte tubulogenesis.

Conclusions

The developed protocols provide a novel and sophisticated three-dimensional visualization of vessels and protein expression in human liver during development and disease.     

Effects of Mercuric Chloride on the Hydraulic Conductivity of Tomato Root Systems (Evidence for a Channel-Mediated Water Pathway)

A pressure-flux approach was used to evaluate the effects of HgCl2 on water transport in tomato (Lycopersicon esculentum) roots. Addition of HgCl2 to a root-bathing solution caused a large and rapid reduction in pressure-induced root water flux; the inhibition was largely reversible upon addition of [beta]-mercaptoethanol. Root system hydraulic conductivity was reduced by 57%. There was no difference between treatments in the K+ concentration in xylem exudate. The results are consistent with the presence of a protein-mediated path for transmembrane water flow in tomato roots.     

Antibodies to influenza A virus in wild birds across Mongolia, 2006-2009

Wild waterbirds sampled July 2006-September 2009 in Mongolia were tested for antibodies to avian influenza (AI) virus with the use of a commercially available blocking enzyme-linked immunosorbent assay. Antibodies were detected in 25% (572/2,282) of tested birds representing 26 species, and all antibody-positive samples were from 12 species in the orders Anseriformes and Charadriiformes. The highest antibody prevalence was in Ruddy Shelducks (Tadorna ferruginea; 61.7%; n=261; 95% confidence interval [CI] 55.8-67.6%), Whooper Swans (Cygnus cygnus; 38.4%; n=242; 95% CI 32.3-44.5%), Swan Geese (Anser cygnoides; 15%; n=127; 95% CI 8.6-21.4%), Bar-headed Geese (Anser indicus; 13%; n=738; 95% CI 10.3-15.1%), and Mongolian Gulls (Larus mongolicus; 3.9%; n=255; 95% CI 1.3-6.5%). There was no significant temporal or spatial variation in the presence of antibodies in the sampled species. However, Bar-headed Geese and Mongolian Gulls showed spatial variation in antibody prevalence in 2007 and 2008, respectively. Our study provides insights into the hatch year waterbirds' exposure to AI virus at their natal and molting sites in Mongolia.     

A Chemically Defined Medium for Rabbit Embryo Cryopreservation

This study evaluates a new synthetic substitute (CRYO3, Ref. 5617, Stem Alpha, France) for animal-based products in rabbit embryo cryopreservation solutions. This evaluation was performed using two approaches: a thermodynamic approach using differential scanning calorimetry and a biological approach using rabbit embryo slow-freezing. During the experiment, foetal calf serum (FCS) was used as a reference. Because FCS varies widely by supplier, three different FCS were selected for the thermodynamic approach. The rabbit embryo slow-freezing solutions were made from Dulbecco''s phosphate buffer saline containing 1.5 M Dimethyl Sulfoxide and 18% (v.v⁻¹) of CRYO3 or 18% (v.v⁻¹) of FCS. These solutions were evaluated using four characteristics: the end of melting temperature, the enthalpy of crystallisation (thermodynamic approach) and the embryo survival rates after culture and embryo transfer (biological approach). In the thermodynamic approach, the solutions containing one of the three different FCS had similar mean thermodynamic characteristics but had different variabilities in the overall data with aberrant values. The solution containing CRYO3 had similar thermodynamic properties when compared to those containing FCS. Moreover, no aberrant value was measured in the solution containing CRYO3. This solution appears to be more stable than the solutions containing a FCS. In the biological approach, the in vitro embryo survival rates obtained with the solution containing CRYO3 (73.7% and 81.3%) and with the solution containing a FCS (77.6% and 71.9%) were similar (p = 0.7). Nevertheless, during the in vivo evaluation, the implantation rate (21.8%) and the live-foetuses rate (18.8%) of the CRYO3 group were significantly higher than the implantation rate (7.1%, p = 0.0002) and the live-foetuses rate (5.3%, p = 0.0002) of the FCS group. The pregnancy rate was also higher in the CRYO3 group compared to the FCS group (81.3% and 43.8%, respectively, p = 0.066). We conclude that CRYO3 can be used as a chemically defined substitute for animal-based products in rabbit embryo cryopreservation solutions.