Biomechanical properties of articular cartilage after high hydrostatic pressure treatment]

AIM: Reconstruction of bone defects due to malignant tumors can be realized by several methods. Up to now, two methods, irradiation and autoclaving, are available for extracorporeally devitalizing resected tumor-bearing osteochondral segments. Previous investigations have shown that human normal and tumor cells in culture were irreversibly impaired when subjected to extracorporeal high hydrostatic pressure (HHP) of 350 MPa. The aim of this study was to examine the biomechanical and immunohistochemical properties of cartilage after exposure to HHP MATERIALS AND METHODS: Osteochondral segments of bovine femoral condyles were exposed to pressure of 300 and 600 MPa (n=20 each). Biomechanical and biological properties of untreated and treated segments were evaluated by repetitive ball indention testing and immunohistochemical labelling aggrecan, link protein and collagen II. The contralateral segments served as untreated control. RESULTS: No significant alterations concerning stiffness and relaxation of osteochondral segments even after 600 MPa were observed. Immunohistochemically, staining was positive in all cases and no differences in the labeling pattern of proteoglycanes were observed between untreated and HHP-treated specimens. CONCLUSION: These findings give hope that HHP eventually will be used as a new gentle way of treating resected cartilage and bone without alteration of biomechanical properties to inactivate tumor cells in order to allow autologous reimplantation.     

Activation of glucosidase via stress-induced polymerization rapidly increases active pools of abscisic acid

Abscisic acid (ABA) is a phytohormone critical for plant growth, development, and adaptation to various stress conditions. Plants have to adjust ABA levels constantly to respond to changing physiological and environmental conditions. To date, the mechanisms for fine-tuning ABA levels remain elusive. Here we report that AtBG1, a beta-glucosidase, hydrolyzes glucose-conjugated, biologically inactive ABA to produce active ABA. Loss of AtBG1 causes defective stomatal movement, early germination, abiotic stress-sensitive phenotypes, and lower ABA levels, whereas plants with ectopic AtBG1 accumulate higher ABA levels and display enhanced tolerance to abiotic stress. Dehydration rapidly induces polymerization of AtBG1, resulting in a 4-fold increase in enzymatic activity. Furthermore, diurnal increases in ABA levels are attributable to polymerization-mediated AtBG1 activation. We propose that the activation of inactive ABA pools by polymerized AtBG1 is a mechanism by which plants rapidly adjust ABA levels and respond to changing environmental cues.     

Resolving subcellular plant metabolism

Plant cells are characterized by a high degree of compartmentalization and a diverse proteome and metabolome. Only a very limited number of studies has addressed combined subcellular proteomics and metabolomics which strongly limits biochemical and physiological interpretation of large‐scale ’omics data. Our study presents a methodological combination of nonaqueous fractionation, shotgun proteomics, enzyme activities and metabolomics to reveal subcellular diurnal dynamics of plant metabolism. Subcellular marker protein sets were identified and enzymatically validated to resolve metabolism in a four‐compartment model comprising chloroplasts, cytosol, vacuole and mitochondria. These marker sets are now available for future studies that aim to monitor subcellular metabolome and proteome dynamics. Comparing subcellular dynamics in wild type plants and HXK1‐deficient gin2‐1 mutants revealed a strong impact of HXK1 activity on metabolome dynamics in multiple compartments. Glucose accumulation in the cytosol of gin2‐1 was accompanied by diminished vacuolar glucose levels. Subcellular dynamics of pyruvate, succinate and fumarate amounts were significantly affected in gin2‐1 and coincided with differential mitochondrial proteome dynamics. Lowered mitochondrial glycine and serine amounts in gin2‐1 together with reduced abundance of photorespiratory proteins indicated an effect of the gin2‐1 mutation on photorespiratory capacity. Our findings highlight the necessity to resolve plant metabolism to a subcellular level to provide a causal relationship between metabolites, proteins and metabolic pathway regulation.     

A novel approach to describe a U1 snRNA binding site

RNA duplex formation between U1 snRNA and a splice donor (SD) site can protect pre-mRNA from degradation prior to splicing and initiates formation of the spliceosome. This process was monitored, using sub-genomic HIV-1 expression vectors, by expression analysis of the glycoprotein env, whose formation critically depends on functional SD4. We systematically derived a hydrogen bond model for the complementarity between the free 5' end of U1 snRNA and 5' splice sites and numerous mutations following transient transfection of HeLa-T4+ cells with 5' splice site mutated vectors. The resulting model takes into account number, interdependence and neighborhood relationships of predicted hydrogen bond formation in a region spanning the three most 3' base pairs of the exon (-3 to -1) and the eight most 5' base pairs of the intron (+1 to +8). The model is represented by an algorithm classifying U1 snRNA binding sites which can or cannot functionally substitute SD4 with respect to Rev-mediated env expression. In a data set of 5' splice site mutations of the human ATM gene we found a significant correlation between the algorithmic classification and exon skipping (P = 0.018, chi2-test), showing that the applicability of the proposed model reaches far beyond HIV-1 splicing. However, the algorithmic classification must not be taken as an absolute measure of SD usage as it may be modified by upstream sequence elements. Upstream to SD4 we identified a fragment supporting ASF/SF2 binding. Mutating GAR nucleotide repeats within this site decreased the SD4-dependent Rev-mediated env expression, which could be balanced simply by artificially increasing the complementarity of SD4.     

Energy or information? The role of seed availability for reproductive decisions in edible dormice

The edible dormouse is a specialized seed predator which is highly adapted to the fluctuations of food availability caused by mast seeding of beech and oak trees. Dormice produce young just in time with maximum food availability, and can completely skip reproduction in years with a lack of seeding. Because their decision to reproduce or not in any particular year is made long before the ripe seeds are available, it seems that dormice can anticipate the upcoming mast situation. We tested the hypothesis that the presence of high caloric food in spring affects their reproductive decision. Therefore, we supplementary fed dormice in a field experiment from spring to early summer with sunflower seeds, which also contain a high amount of energy. Supplemental feeding caused significant increases in the proportion of reproducing females and reproductively active males. These results suggest that edible dormice may use the occurrence of an energy rich food resource to predict the autumnal mast situation. Further, our data indicate that the decision to reproduce was not the result of an increased body mass due to the consumption of surplus food, but that sufficient seed abundance acts as an environmental signal to which dormice adjust their reproduction.     

Molecular systematics,evolution and zoogeography of the stonefly genus Siphonoperla (Insecta: Plecoptera,Chloroperlidae)

The stonefly genus Siphonoperla Zwick, 1967 (Chloroperlidae) ranges from the Atlas Mountains of North Africa, throughout Europe and east to the Lesser Caucasus Mountains in Armenia. Systematic relationships within the genus are unknown. We provide the first molecular phylogenetic reconstruction of the genus, based on sequence variation of 1348 bp of the mitochondrial cytochrome c oxidase subunit I gene and relate this phylogeny to a few key morphological features as well as zoogeographical perspectives. A total of 15 taxa (32 individuals), including four outgroup species (Chloroperla Newman, 1836 and Xanthoperla Zwick, 1967 ) were screened. Monophyly of Siphonoperla, as well as each purported taxon was supported, with net pairwise distances ranging from 0.7% to 13.7%. Within‐taxon variability ranged from 0% to 6.2%, whereby the upper value relates to Siphonoperla torrentium Pictet, 1841 represented in our sample by three allopatric subspecific taxa. These taxa, displayed as a polytomy with an estimated time to the most recent common ancestor of about 5.4 Myr, are also shown to have distinct genitalia. These data could be used to support a species‐level distinction for the three subspecific taxa. Siphonoperla ranged from 13% (Xanthoperla) to 16.2% (Chloroperla) divergent from the outgroup genera. The recently described Siphonoperla ottomoogi, Graf, 2008 from Austria is not closely related to the sympatric Siphonoperla montana Pictet, 1841 and is a minimum of 7.8% divergent from congenerics, supporting its status as a micro‐endemic relict surviving on the edge of Alpine glaciation throughout the Pleistocene. Overall, the genus shows the highest levels of diversification in the Mediterranean and Southeast regions whereby at least some of the species found in Central Europe today may have persisted there in peri‐glacial refugia throughout the Pleistocene.     

Experimental Studies on Work Functions of Li+ Ions and Electrons in the Battery Electrode Material LiCoO2: A Thermodynamic Cycle Combining Ionic and Electronic Structure

The release of Li⁺ from stoichiometric LiCoO₂ (LCO) – a typical battery electrode material – is investigated by means of thermionic emission. Analysis of the data leads to an ionic work function of w_Li+(LCO) = 4.1 eV. Combination of this value with the electronic work function w_e? (LCO) = 5.1 eV, also measured in this work by photoelectron spectroscopy, and with information available from the literature allows the set up, for the first time, of a complete thermodynamic cycle for a Li//LiCoO₂ battery. An open circuit cell voltage of 2.4 eV is derived in line with available literature information. The proof‐of‐principle study presented here provides experimental data on the binding energy values, i.e., chemical potentials, of Li⁺‐ions and electrons and thus of Li‐atoms in LiCoO₂ as a battery cathode and is expected to open access to a better understanding and thus to a better design of battery materials.     

Limnisch‐subterrane copepoden der gattung parastenocaris kessler aus mittelamerika∗

Als Ergebnis von erstmaligen Grundwasseruntersuchungen in Mittelamerika werden aus El Salvador und Honduras 6 neue Arten und 2 neue Formen des Genus Parastenocaris beschrieben, abgebildet und diskutiert.

Parastenocaris erweist sich auch in Mittelamerika als eine verbreitete und häufige Leitform des limnischen Mesopsammals. Sie ist im Ufergrundwasser von Flüssen und Seen fast regelmäßig anzutreffen. Eine der neuen Arten, P. pan‐americana n. sp., wird gleichzeitig auch aus Peru gemeldet, ist also außergewöhnlich weit verbreitet. Die Art lebt außer im limnischen Grundwasser auch im brackigen Küstengrundwasser des sandigen Strandes der pazifischen und kari‐bischen Küste; sie muß also sehr euryhalin sein.

Keine der gefundenen Arten läßt deutliche Verwandtschaft zu altweltlichen Arten erkennen. Drei von ihnen sind untereinander eng verwandt und gehören zu der neubeschriebenen, wahrscheinlich neotropisch‐endemischen panamericana‐Gruppe. Zwei der anderen Arten stehen sich untereinander gleichfalls nahe und gehören möglicherweise zu einer zweiten neotropischen Artengruppe.

Die übrige subterrane Fauna des Untersuchungsgebietes scheint sehr arm zu sein.

Die Untersuchungen werden fortgesetzt.