Identification of the configuration of neosartorin by long-range nuclear Overhauser effect measurements

The relative configuration of the two xanthene units of neosartorin, a new ergochrome biosynthesised by the soil mould Neosartorya fischeri, was determined using a 1D double-pulsed field gradient spin-echo NOESY experiment. It was found that both units have the same relative stereochemistry. Long-range nonbonding interactions between the substituents of different xanthene units stabilise the nonplanar configuration of the two aromatic rings A and A' connecting both monomer units of neosartorin.     

Biosorption of uranium and thorium

Selected samples of waste microbial biomass originating from various industrial fermentation processes and biological treatment plants have been screened for biosorbent properties in conjunction with uranium and thorium in aqueous solutions. Biosorption isotherms have been used for the evaluation of biosorptive uptake capacity of the biomass which was also compared to an activated carbon and the ion exchange resin currently used in uranium production processes. Determined uranium and thorium biosorption isotherms were independent of the initial U or Th solution concentration. Solution pH affected the exhibited uptake. In general, lower biosorptive uptake was exhibited at pH 2 than at pH 4. No discernible difference in uptake was observed between pH 4 and pH 5 where the optimum pH for biosorption lies. The biomass of Rhizopus arrhizus at pH 4 exhibited the highest uranium and thorium biosorptive uptake capacity (g) in excess of 180 mg/g. At an equilibrium uranium concentration of 30 mg/liter, R. arrhizus removed approximately 2.5 and 3.3 times more uranium than the ion exchange resin and activated carbon, respectively. Under the same conditions, R. arrhizus removed 20 times more thorium than the ion exchange resin and 2.3 times more than the activated carbon. R. arrhizus also exhibited higher uptake and a generally more favorable isotherm for both uranium and thorium than all other biomass types examined.     

Correlative In Vivo 2 Photon and Focused Ion Beam Scanning Electron Microscopy of Cortical Neurons

Correlating in vivo imaging of neurons and their synaptic connections with electron microscopy combines dynamic and ultrastructural information. Here we describe a semi-automated technique whereby volumes of brain tissue containing axons and dendrites, previously studied in vivo, are subsequently imaged in three dimensions with focused ion beam scanning electron microcopy. These neurites are then identified and reconstructed automatically from the image series using the latest segmentation algorithms. The fast and reliable imaging and reconstruction technique avoids any specific labeling to identify the features of interest in the electron microscope, and optimises their preservation and staining for 3D analysis.     

Fatty acid modification of Wnt1 and Wnt3a at serine is prerequisite for lipidation at cysteine and is essential for Wnt signalling

The Wnt family of proteins is a group of extracellular signalling molecules that regulate cell-fate decisions in developing and adult tissues. It is presumed that all 19 mammalian Wnt family members contain two types of post-translational modification: the covalent attachment of fatty acids at two distinct positions, and the N-glycosylation of multiple asparagines. We examined how these modifications contribute to the secretion, extracellular movement and signalling activity of mouse Wnt1 and Wnt3a ligands. We revealed that O-linked acylation of serine is required for the subsequent S-palmitoylation of cysteine. As such, mutant proteins that lack the crucial serine residue are not lipidated. Interestingly, although double-acylation of Wnt1 was indispensable for signalling in mammalian cells, in Xenopus embryos the S-palmitoyl-deficient form retained the signalling activity. In the case of Wnt3a, the functional duality of the attached acyls was less prominent, since the ligand lacking S-linked palmitate was still capable of signalling in various cellular contexts. Finally, we show that the signalling competency of both Wnt1 and Wnt3a is related to their ability to associate with the extracellular matrix.     

How does population genetic diversity change over time? An experimental seed bank study of Atriplex tatarica (Chenopodiaceae)

Atriplex tatarica is an annual, early successional, facultative halophilic species of frequently disturbed human-made habitats in Central and Eastern Europe. We investigated to what extent the plants grown from seeds extracted from soil seed bank differed genetically to mature aboveground plants in experimental populations of A. tatarica over two successive years. At each of five plots 50 aboveground plants and 50 plants extracted from seeds stored in soil were assayed for allozyme analysis in 2003 and 2004. At the start of experiment, we introduced 1000 seeds of the study species into each of five experimental plots. While the species dominated in all of the experimental plots in the first year, the second year A. tatarica coverage decreased dramatically. Overall allele frequencies of soil seeds and mature plants showed significant differences between life history stages in both years, but not within years in soil seeds as well as mature plants stages. While mature plants showed a significantly greater amount of single and multilocus heterozygosity in both consecutive years, comparison between years did not yield any significant differences. In the same way, despite a relatively large seed bank the species population genetic parameters, i.e. allelic richness (A), observed heterozygosity (H_o), gene diversity (H_s), inbreeding coefficient (F_IS) and fixation index (F_ST), did not change over years between as well as within life history stages. The soil seeds and mature plants significantly differed in H_o, H_s and F_IS, while the A and F_ST were not significantly different between life history stages.     

Non-Invasive Bioluminescence Imaging of β-Cell Function in Obese-Hyperglycemic [ob/ob] Mice

Background

Type 2 diabetes results from failure of the β-cells to compensate for increased insulin demand due to abnormal levels of metabolic factors. The ob/ob(lep-/-) mouse has been extensively studied as an animal model of type 2 diabetes. Previous studies have shown a correlation between β-cell function and bioluminescent imaging in lean genetically engineered mice. The ability to noninvasively monitor β-cell function in ob/ob mice could provide new information on β-cell regulation in type 2 diabetes.

Methods

To create the B6 Albino ob/ob MIP-luc mice (ob/ob-luc), the ob/ob mouse was crossed with the CD1 MIP-luc mouse. All mice were backcrossed over multiple generations to ensure the genetic background of the transgenic mice was over 96% similar to the background of the original ob/ob mouse. Animal weight, blood glucose levels, insulin in plasma, and in vivo bioluminescence (BLI) were monitored weekly or biweekly for up to 70 weeks of age. BL imaging was performed using IVIS Spectrum (Perkin Elmer) and calculated by integrating the bioluminescence signal between 5 and 10 min after i.v. injection of D-luciferin. Insulin immunohistochemistry determined islet beta cell count and insulin secretion assay determined islet insulin function.

Results

There were significant increases in BLI and insulin levels as the ob/ob-luc mice aged while glucose levels gradually decreased. Ob/ob-luc were sacrificed at different time points to determine ex vivo BLI, islet function and total β-cell numbers using a cell counting training algorithm developed for the Vectra image analysis system (Perkin Elmer). The number of β-cells increased as the mice aged and all three ex vivo measurements correlated with BLI.

Conclusions

The ob/ob-luc mice can serve as a model of metabolic stress, similar to human type 2 diabetes using BLI as a surrogate marker for β-cell function.     

How does Reynoutria invasion fit the various theories of invasibility?

Questions: 1. How does species richness of recipient communities affect Reynoutria invasion? 2. How does Reynoutria invasion change host community structure? 3. Are there any differences in habitat preferences among three closely related Reynoutria taxa? 4. How does the genetic structure of Reynoutria populations change along the course of a river? Location: River Jizera basin, north Bohemia, Czech Republic. Methods: Nine 0.25 km² plots were chosen along the river. Within each plot all main habitat types were determined and sampled using the Braun‐Blanquet scale to determine the invasibility of various communities. The patches invaded by Reynoutria taxa and surrounding Reynoutria‐free vegetation in the same habitat type were sampled as relevé pairs to compare the composition of invaded and non‐invaded vegetation. In addition, to characterize the genetic structure of Reynoutria populations along the river, 30 samples from different clones were collected. Results and conclusions: 1. The species richness of communities has no influence on the success of Reynoutria invasion in the area studied. The combination of environmental conditions and propagule spread is more important to the invasion success than the number of species in the host community. 2. Reynoutria invasion greatly reduces species diversity. 3. R. japonica invaded more habitat types than R. sachalinensis and R.×bohemica. The hybrid R.×bohemica outcompetes the parental taxa at sites where both taxa co‐occur. 4. Isozyme analysis revealed phenotype variability in the hybrid in contrast to the parental taxa. Different hybrid phenotypes are distributed randomly on the middle and lower reaches of the River Jizera; one of them dominates and the other three occur occasionally. This pattern supports the hypothesis that sexual reproduction occasionally occurs within Reynoutria taxa.     

The cause of the prevalent directions of the spiral grain patterns in conifers

 A new theory is presented on the cause of the prevalent directions of the spiral grain patterns found in conifers. The hypothesis is based upon the assumption that spiral grain has a function, i.e. that it represents a growth strategy to ensure survival of the trees. The mechanical function of the tree trunk is placed in focus, that is the ability of the trees to withstand external mechanical loads, mainly from wind. Spiral grain is an optimized growth feature when the trees are exposed to combined bending and torsion. Torsion occurs when the crown is asymmetric in the plane perpendicular to the wind direction. Systematic crown asymmetry, with heavier crowns on the south side, was confirmed by measuring the crown projections on 253 sparsely grown pines; 76.7% of the trees had longer branches on the south than on the north side, and the average length difference was 40.8 cm. By studying wind maps it was seen that most of the coniferous forests have prevailing westerly winds, which, when combined with the crown asymmetry, leads to a prevailing torque. Right-handed spiral grain in the outermost layers of mature trees is proposed to be a strategy to withstand this torque, i.e. to avoid stem breakage. Received: 30 June 1997 / Accepted: 17 November 1997