Galanin immunoreactivity increased in chicken supraoptic neurons after activation of the vasotocin system at oviposition

The avian arginine vasotocin (AVT) synthesized in the hypothalamic magnocellular neurons and released from the posterior pituitary is known to be involved in the regulation of uterine contractions for oviposition in chickens. However, regulation of AVT synthesis and release within the magnocellular hypothalamus has not been elucidated. Galanin, the oviposition inducing factor in the oviduct of the hen, has been demonstrated to have sexually dimorphic stimulatory action in oxytocin- and vasopressin neurons in the mammalian hypothalamus. In this study, galanin and AVT immunoreactivity was investigated around the time of oviposition in the supraoptic nucleus (SON) to determine if galanin modulates AVT synthesis and/or release. Within SON neurons increased AVT immunoreactivity before oviposition and the decreased AVT immunoreactivity after oviposition implied function-related peptide release. The significantly increased number of galanin neurons co-localizing with AVT immediately after oviposition suggests that galanin is involved in the negative feedback to limit AVT release in the SON. Thus, these data support the idea that AVT in the SON is involved in central regulation of oviposition and that AVT release could be modulated by the neuropeptide galanin.     

Homologous recombination in real time: DNA strand exchange by RecA

Homologous recombination, the exchange of strands between different DNA molecules, is essential for proper maintenance and accurate duplication of the genome. Using magnetic tweezers, we monitor RecA-driven homologous recombination of individual DNA molecules in real time. We resolve several key aspects of DNA structure during and after strand exchange. Changes in DNA length and twist yield helical parameters for the protein-bound three-stranded structure in conditions in which ATP was not hydrolyzed. When strand exchange was completed under ATP hydrolysis conditions that allow protein dissociation, a "D wrap" structure formed. During homologous recombination, strand invasion at one end and RecA dissociation at the other end occurred at the same rate, and our single-molecule analysis indicated that a region of only about 80 bp is actively involved in the synapsis at any time during the entire reaction involving a long ( approximately 1 kb) region of homology.     

Species richness of herbivores on exotic host plants increases with time since introduction of the host

Aim Species richness of insect herbivores feeding on exotic plants increases with abundance as well as range size of the host in the area of introduction. The formation of these herbivore assemblages requires a certain amount of time, and the richness of insect faunas should also increase with the length of time an exotic plant has been present in the introduced range. Location Central Europe. Methods We analysed the variation in species richness of leaf‐chewing Lepidoptera larvae and sap‐sucking Auchenorrhyncha (Hemiptera) associated with 103 exotic woody plant species in Germany in relation to time since introduction, range size, growth form (trees versus shrubs), biogeographical origin (distance from Central Europe) and taxonomic isolation of the host plant (presence or absence of a native congener in the introduced area). Results Using simple correlation analyses we found for Lepidoptera and Auchenorrhyncha that species richness increased with time since introduction of the host plant. For the Lepidoptera the increase of species richness with time since introduction remained significant even after removing the effects of all other independent variables. Main conclusions Our results provide some evidence that assemblages of insects on exotic plants do not reach saturation within a time scale of few hundred years. This contrasts with previous findings for crop plants.     

Production of epoxide hydrolases in batch fermentations of <Emphasis Type="Italic">Botryosphaeria rhodina</Emphasis>

The filamentous fungus Botryosphaeria rhodina (ATCC 9055) was investigated related to its ability for epoxide hydrolase (EH) production. Epoxide hydrolase activity is located at two different sites of the cells. The larger part is present in the cytosol (70%), while the smaller part is associated to membranes (30%). In media optimization experiments, an activity of 3.5 U/gDW for aromatic epoxide hydrolysis of para-nitro-styrene oxide (pNSO) could be obtained. Activity increased by 30% when pNSO was added to the culture during exponential growth. An increase of enzyme activity up to 6 U/gDW was achieved during batch-fermentations in a bioreactor with 2.7 l working volume. Evaluation of fermentations with 30 l working volume revealed a relation of oxygen uptake rate to EH expression. Oxygen limitation resulted in a decreased EH activity. Parameter estimation by the linearization method of Hanes yielded Km values of 2.54 and 1.00 mM for the substrates S-pNSO and R-pNSO, respectively. vmax was 3.4 times higher when using R-pNSO. A protein purification strategy leading to a 47-fold increase in specific activity (940 U/mgProtein) was developed as a first step to investigate molecular and structural characteristics of the EH.     

Expressed sequence tag-derived microsatellite markers of perennial ryegrass (Lolium perenne L.)

An expressed sequence tag (EST) library of the key grassland species perennial ryegrass (Lolium perenne L.) has been exploited as a resource for microsatellite marker development. Out of 955 simple sequence repeat (SSR) containing ESTs, 744 were used for primer design. Primer amplification was tested in eight genotypes of L. perenne and L. multiflorum representing (grand-) parents of four mapping populations and resulted in 464 successfully amplified EST-SSRs. Three hundred and six primer pairs successfully amplified products in the mapping population VrnA derived from two of the eight genotypes included in the original screening and revealed SSR polymorphisms for 143 ESTs. Here, we report on 464 EST-derived SSR primer sequences of perennial ryegrass established in laboratory assays, providing a dedicated tool for marker assisted breeding and comparative mapping within and among forage and turf grasses. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Morphometrics and SEM analysis of the species pair Lithobius mutabilis L. Koch, 1862 and L. glacialis Verhoeff, 1937 (Chilopoda: Lithobiomorpha)

The sets of morphological characters of two nominal species in the genus Lithobius Leach, 1814, Lithobius mutabilis L. Koch, 1862 and Lithobius glacialis Verhoeff, 1937, were studied in order to test specific dissimilarity. Morphometrics were examined and analysed statistically. In addition, a comparative SEM analysis of external characters was made. Morphometrically significant differences between the species were found concerning body length, the width ratio of the head to the 5th tergite, the number of antennal articles, and the length/width proportions of certain articles (e.g. the femur) of the 15th legs of males. Because of these and several additional differences, such as in tergite surface structure, modifications to the 15th legs of males, the structure of the female gonopod claws, and between the ecological profiles, L. glacialis, which is found in the high Alps at altitudes above timberline (1300 m), can be distinguished clearly from L. mutabilis. This study demonstrates another example for a cryptic species pair, a common phenomenon between lowland and alpine populations of small invertebrates. The combination of morphometrics and SEM offers a powerful methodology for resolving previously uncertain questions in the species-level taxonomy of centipedes.     

Do nutrients and invertebrate herbivory interact in an artificial plant community?

The addition of nutrients has been shown to decrease the species richness of plant communities. Herbivores feed on dominant plant species and should release subdominant species from competitive exclusion at high levels of nutrient availability with a severe competitive regime. Therefore, the effects of nutrients and invertebrate herbivory on the structure and diversity of plant communities should interact. To test this hypothesis, we used artificial plant communities in microcosms with different levels of productivity (applying fertilizer) and herbivory (adding different numbers of the snail, Cepaea hortensis, and the grasshopper, Chorthippus parallelus). For analyses, we assigned species to three functional groups: grasses, legumes and (non-leguminous) herbs. With the addition of nutrients aboveground biomass increased and species richness of plants decreased. Along the nutrient gradient, species composition shifted from a legume-dominated community to a community dominated by fast-growing annuals. But only legumes showed a consistent negative response to nutrients, while species of grasses and herbs showed idiosyncratic patterns. Herbivory had only minor effects, and bottom–up control was more important than top–down control. With increasing herbivory the biomass of the dominant plant species decreased and evenness increased. We found no interaction between nutrient availability and invertebrate herbivory. Again, species within functional groups showed no consistent responses to herbivory. Overall, the use of the functional groups grasses, legumes and non-leguminous herbs was of limited value to interpret the effects of nutrients and herbivory during our experiments.     

Spatio-temporal niche separation of planktonic Betaproteobacteria in an oligo-mesotrophic lake

We investigated the diversity of planktonic Betaproteobacteria and the seasonal population changes of betaproteobacterial taxa in an oligo-mesotrophic lake (Piburger See, Austria). Focus was put on the vertical distribution of the investigated populations and on differences between their respective cell fractions with apparent amino acid incorporation. On average, 66% of betaproteobacterial cells and 73% of their diversity could be attributed to four clades within three lineages that were further analysed by fluorescence in situ hybridization. The numbers of bacteria from the R-BT subclade of the beta I lineage and from the PnecB subgroup of the beta II lineage were rather constant throughout the water column. In contrast, members of another subgroup of beta II (PnecC) and bacteria related to Methylophilus (beta IV) were particularly numerous in the oxygen-depleted zone. In general, only moderate seasonal changes in abundance were observed in the upper water layers, whereas there was a clear relationship between decreasing oxygen levels and the rise of bacteria from the PnecC and beta IV clades in deeper strata. On average, almost 80% of beta I bacteria, but < 15% of cells from the beta IV clade, showed amino acid incorporation. Our results suggest that the studied populations occupy distinct vertical and ecophysiological niches in Piburger See.     

Loss of nucleoplasmic LAP2alpha-lamin A complexes causes erythroid and epidermal progenitor hyperproliferation

Lamina-associated polypeptide (LAP) 2alpha is a chromatin-associated protein that binds A-type lamins. Mutations in both LAP2alpha and A-type lamins are linked to human diseases called laminopathies, but the molecular mechanisms are poorly understood. The A-type lamin-LAP2alpha complex interacts with and regulates retinoblastoma protein (pRb), but the significance of this interaction in vivo is unknown. Here we address the function of the A-type lamin-LAP2alpha complex with the use of LAP2alpha-deficient mice. We show that LAP2alpha loss causes relocalization of nucleoplasmic A-type lamins to the nuclear envelope and impairs pRb function. This causes inefficient cell-cycle arrest in dense fibroblast cultures and hyperproliferation of epidermal and erythroid progenitor cells in vivo, leading to tissue hyperplasia. Our results support a disease-relevant model in which LAP2alpha defines A-type lamin localization in the nucleoplasm, which in turn affects pRb-mediated regulation of progenitor cell proliferation and differentiation in highly regenerative tissues.