Bibenzyls and dihydroisocoumarins from white salsify (Tragopogon porrifolius subsp. porrifolius)

A phytochemical investigation of three accessions of Tragopogon porrifolius L. subsp. porrifolius (Asteraceae, Lactuceae) yielded three new bibenzyl derivatives, 5,4'-dihydroxy-3-alpha-l-rhamnopyranosyl-(1-->3)-beta-d-xylopyranosyloxybibenzyl, 2-carboxyl-3,4'-dihydroxy-5-beta-d-xylopyranosyloxybibenzyl, tragopogonic acid (2'carboxyl-3',5',4'-trihydroxyphenylethanone) and three dihydroisocoumarin derivatives, including the new natural product 6-O-methylscorzocreticoside I. One of the isolated bibenzyl derivatives is considered to be a precursor to the biosynthesis of dihydroisocoumarins. Structures of new compounds were established by HR mass spectrometry, extensive 1D and 2D NMR spectroscopy, and CD spectroscopy. Moreover, radical scavenging activities of the polyphenolic compounds were measured using the 2,2-diphenyl-1-picrylhydrazyl assay; two of the bibenzyls showed moderate and two of the dihydroisocoumarins showed weak radical scavenging activities. The chemosystematic impact of bibenzyls and dihydroisocoumarins is discussed briefly.     

Nucleo-cytoplasmic shuttling of Axin, a negative regulator of the Wnt-beta-catenin Pathway

Axin is a negative regulator of the Wnt pathway essential for down-regulation of beta-catenin. Axin has been considered so far as a cytoplasmic protein. Here we show that, although cytoplasmic at steady state, Axin shuttles in fact in and out of the nucleus; Axin accumulates in the nucleus of cells treated with leptomycin B, a specific inhibitor of the CRM1-mediated nuclear export pathway and is efficiently exported from Xenopus oocyte nuclei in a RanGTP- and CRM1-dependent manner. We have characterized the sequence requirement for export and identified two export domains, which do not contain classical nuclear export consensus sequences, and we show that Axin binds directly to the export factor CRM1 in the presence of RanGTP.     

Stilbenoids from Tragopogon orientalis

A phytochemical investigation of Tragopogon orientalis L. (Asteraceae, Cichorieae) yielded the natural products 6'-O-(7,8-dihydrocaffeoyl)-alpha,beta-dihydrorhaponticin, 3'-O-methyl-alpha,beta-dihydrorhaponticin, and (S)-3-(4-beta-glucopyranosyloxybenzyl)-7-hydroxy-5-methoxyphtalide as well as known compounds alpha,beta-dihydrorhaponticin, 3-(4-methoxybenzyl)-5,7-dimethoxyphthalide, p-dihydrocoumaric acid methyl ester, and 1-hydroxypinoresinol-1-O-beta-glucopyranoside. The structures were established by HR mass spectrometry, extensive 1D and 2D NMR spectroscopy, and CD spectroscopy. Moreover, the radical scavenging activities of the major compounds were measured using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The chemosystematic impact of the occurrence of stilbene derivatives in T. orientalis is discussed.     

Precision MRI-based joint surface and cartilage density analysis of the knee joint using rapid water-excitation sequence and semi-automatic segmentation algorithm]

The aim of this study was to analyse the precision of three-dimensional joint surface and cartilage thickness measurements in the knee, using a fast, high-resolution water-excitation sequence and a semiautomated segmentation algorithm. The knee joint of 8 healthy volunteers, aged 22 to 29 years, were examined at a resolution of 1.5 mm x 0.31 mm x 0.31 mm, with four sagittal data sets being acquired after repositioning the joint. After semiautomated segmentation with a B-spline Snake algorithm and 3D reconstruction of the patellar, femoral and tibial cartilages, the joint surface areas (triangulation), cartilage volume, and mean and maximum thickness (Euclidean distance transformation) were analysed, independently of the orientation of the sections. The precision (CV%) for the surface areas was 2.1 to 6.6%. The mean cartilage thickness and cartilage volume showed coefficients of 1.9 to 3.5% (except for the femoral condyles), the value for the medial femoral condyle being 9.1%, and for the lateral condyle 6.5%. For maximum thickness, coefficients of between 2.6 and 5.9% were found. In the present study we investigate for the first time the precision of MRI-based joint surface area measurements in the knee, and of cartilage thickness analyses in the femur. Using a selective water-excitation sequence, the acquisition time can be reduced by more than 50%. The poorer precision in the femoral condyles can be attributed to partial volume effects that occur at the edges of the joint surfaces with a sagittal image protocol. Since MRI is non-invasive, it is highly suitable for examination of healthy subjects (generation of individual finite element models, analysis of functional adaptation to mechanical stimulation, measurement of cartilage deformation in vivo) and as a diagnostic tool for follow-up, indication for therapy, and objective evaluation of new therapeutic agents in osteoarthritis.     

RanBP3 influences interactions between CRM1 and its nuclear protein export substrates

We investigated the role of RanBP3, a nuclear member of the Ran-binding protein 1 family, in CRM1-mediated protein export in higher eukaryotes. RanBP3 interacts directly with CRM1 and also forms a trimeric complex with CRM1 and RanGTP. However, RanBP3 does not bind to CRM1 like an export substrate. Instead, it can stabilize CRM1–export substrate interaction. Nuclear RanBP3 stimulates CRM1-dependent protein export in permeabilized cells. These data indicate that RanBP3 functions by a novel mechanism as a cofactor in recognition and export of certain CRM1 substrates. In vitro, RanBP3 binding to CRM1 affects the relative affinity of CRM1 for different substrates.     

Steady-state nuclear localization of exportin-t involves RanGTP binding and two distinct nuclear pore complex interaction domains

Vertebrate tRNA export receptor exportin-t (Xpo-t) binds to RanGTP and mature tRNAs cooperatively to form a nuclear export complex. Xpo-t shuttles bidirectionally through nuclear pore complexes (NPCs) but is mainly nuclear at steady state. The steady-state distribution of Xpo-t is shown to depend on its interaction with RanGTP. Two distinct Xpo-t NPC interaction domains that bind differentially to peripherally localized nucleoporins in vitro are identified. The N terminus binds to both Nup153 and RanBP2/Nup358 in a RanGTP-dependent manner, while the C terminus binds to CAN/Nup214 independently of Ran. We propose that these interactions increase the concentration of tRNA export complexes and of empty Xpo-t in the vicinity of NPCs and thus increase the efficiency of the Xpo-t transport cycle.     

Patellar cartilage deformation in vivo after static versus dynamic loading

The objective of this study was to test the hypothesis that static loading (squatting at a 90 degrees angle) and dynamic loading (30 deep knee bends) cause different extents and patterns of patellar cartilage deformation in vivo. The two activities were selected because they imply different types of joint loading and reflect a realistic and appropriate range of strenuous activity. Twelve healthy volunteers were examined and the volume and thickness of the patellar cartilage determined before and from 90 to 320s after loading, using a water excitation gradient echo MR sequence and a three-dimensional (3D) distance transformation algorithm. Following knee bends, we observed a residual reduction of the patellar cartilage volume (-5.9+/-2.1%; p<0.01) and of the maximal cartilage thickness (-2.8+/-2.6%), the maximal deformation occurring in the superior lateral and the medial patellar facet. Following squatting, the change of patellar cartilage volume was -4.7+/-1.6% (p<0.01) and that of the maximal cartilage thickness -4.9+/-1.4% (p<0.01), the maximal deformation being recorded in the central aspect of the lateral patellar facet. The volume changes were significantly lower after squatting than after knee bends (p<0.05), but the maximal thickness changes higher (p<0.05). The results obtained in this study can serve to validate computer models of joint load transfer, to guide experiments on the mechanical regulation of chondrocyte biosynthesis, and to estimate the magnitude of deformation to be encountered by tissue-engineered cartilage within its target environment.     

Chemical mutagenesis--a promising technique to increase metal concentration and extraction in sunflowers

Since most of the metal-hyperaccumulating wild plants only produce very low biomass and many high-yielding crops accumulate only moderate amounts of metals, the current research is mainly focused on overcoming these limitations and the optimization of metal phytoextraction. The main goal of the present study was the improvement of metal concentration and extraction properties of Helianthus annuus L by chemical mutagenesis (the non-GMO approach). Sunflowers--hybrid cultivar Salut and inbred lines-were treated with the chemical mutagen ethyl methanesulfonate (EMS). The effect of chemical mutagenesis on metal concentration in and extraction by new sunflower M1 and M2 mutants was directly assessed on a metal-contaminated field in Raft, Switzerland. Mutants of the M2 generation showed a 2-3 times higher metal shoot concentration than the control plants. The best M2 sunflower "giant mutant" 14/185/04 showed a significantly enhanced metal extraction ability: 7.5 times for Cd, 9.2 times for Zn, and 8.2 times for Pb in aboveground parts, as compared to the control plants. Theoretical calculations for the phytoextraction potential of new sunflower variants note that the best sunflower mutant can produce up to 26 t dry matter per hectare and remove 13.3 kg Zn per hectare and year at the sewage sludge contaminated site of Raft; that is a gain factor of 9 compared to Zn extraction by sunflower controls. Furthermore, the use of sunflower oil and biomass for technical purposes (lubricants, biodiesel, biogas) should produce an additional value and improve the economical balance of phytoextraction.     

Electrochemical synthesis and X-ray crystal structures of beta-D-2-phenylselenyl-1,3,4,6-tetra-O-acetylglucopyranose and alpha-D-2-phenylselenyl-1,3,4,6-tetra-O-acetylmannopyranose

Electrochemical acetoxyphenylselenation of 3,4-dihydro-2H-pyran and D-3,4,6-tri-O-acetylglucal was studied. The constant current electrolysis (50mA) of dihydropyran and diphenyl diselenide in an acetic acid solution of tetramethylammonium chloride was performed at room temperature in an undivided cell using a graphite anode and an aluminum cathode and yielded trans-DL-2-acetoxy-3-phenylselenyltetrahydropyran (27%), in agreement with Markovnikov's rule. The analysis of the 1H NMR spectral data showed that the acetoxy and phenylselenyl groups adopt axial positions in the most stable conformation of this compound due to the anomeric effect. Under the same conditions D-3,4,6-tri-O-acetylglucal afforded D-2-phenylselenyl-1,3,4,6-tetra-O-acetylglucopyranose and D-2-phenylselenyl-1,3,4,6-tetra-O-acetylmannopyranose, which were separated by column chromatography and isolated in 87% overall yield (isomer ratio 60:40). The structures of these compounds were established by spectral data. Single crystal X-ray structure determinations of the diastereomers are reported.