Electron microscope and optical diffraction studies on glycerol-extracted insect flight muscle fibres relaxed by pyrophosphate

Zusammenfassung Elektronenmikroskopische Aufnahmen von einfacher Filament-Lagen Mg-Pyrophosphaterschlaffter Fasern der dorsolongitudinalen Flugmuskulatur vonLethocerus spec. gleichen weitgehend dem Bild ATP-erschlaffter Muskeln. Optische Transformationen scheinen dagegen die Charakteristika von ATP-erschlafften Fasern und solchen, die sich im Rigor mortis befinden, zu kombinieren. Die Überführung der Fasern aus einer Mg-Pyrophosphat- in eine Rigor-Lösung stellte das Rigor-Muster wieder her.

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Supported by a short term fellowship of the EMBO to one of us (G.B.).

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Acknowledgment. We are greatly indebted to Dr.Louise N. Johnson, P. Eagle andL. J. Stumpp, Oxford, Dept. of Zoology, for their help with the optical diffraction measurements, to Mrs.Hiltrud Gülker for her expert technical assistance and to Prof.Pringle and Dr.R. T. Tregear for their hospitality and many helpful discussions and criticism.     

Histone H2AX-dependent GABA(A) receptor regulation of stem cell proliferation

Stem cell self-renewal implies proliferation under continued maintenance of multipotency. Small changes in numbers of stem cells may lead to large differences in differentiated cell numbers, resulting in significant physiological consequences. Proliferation is typically regulated in the G1 phase, which is associated with differentiation and cell cycle arrest. However, embryonic stem (ES) cells may lack a G1 checkpoint. Regulation of proliferation in the 'DNA damage' S/G2 cell cycle checkpoint pathway is known for its role in the maintenance of chromatin structural integrity. Here we show that autocrine/paracrine gamma-aminobutyric acid (GABA) signalling by means of GABA(A) receptors negatively controls ES cell and peripheral neural crest stem (NCS) cell proliferation, preimplantation embryonic growth and proliferation in the boundary-cap stem cell niche, resulting in an attenuation of neuronal progenies from this stem cell niche. Activation of GABA(A) receptors leads to hyperpolarization, increased cell volume and accumulation of stem cells in S phase, thereby causing a rapid decrease in cell proliferation. GABA(A) receptors signal through S-phase checkpoint kinases of the phosphatidylinositol-3-OH kinase-related kinase family and the histone variant H2AX. This signalling pathway critically regulates proliferation independently of differentiation, apoptosis and overt damage to DNA. These results indicate the presence of a fundamentally different mechanism of proliferation control in these stem cells, in comparison with most somatic cells, involving proteins in the DNA damage checkpoint pathway.     

Proton Exchange Membranes for Fuel Cells Challenges and Recent Developments

The current technology of proton exchange membrane fuel cells （PEMFC） is based on perfluorosulfonic acid （PFSA） membranes （e. g. Nation ） as electrolyte. It operates on pure hydrogen and oxygen/air at typically 80℃ with high power density and long-term durability. For the membranes to be conductive, a minimum threshold of absorbed water molecules is about 6 to 7 mole per sulfonic site. The highest conductivity is only obtained under fully hydrated conductions, i.e. 21 - 22 mole water per sulfonic acid site. In other words, the proton conductivity is achieved by the locally liquid-like hydrophilic domain of the nanostructure. This strong dependence of conductivity on the water content in membranes limits the operational temperature of PEMFC below 100 ℃.     

Recent decline in the global land evapotranspiration trend due to limited moisture supply

More than half of the solar energy absorbed by land surfaces is currently used to evaporate water. Climate change is expected to intensify the hydrological cycle and to alter evapotranspiration, with implications for ecosystem services and feedback to regional and global climate. Evapotranspiration changes may already be under way, but direct observational constraints are lacking at the global scale. Until such evidence is available, changes in the water cycle on land?a key diagnostic criterion of the effects of climate change and variability?remain uncertain. Here we provide a data-driven estimate of global land evapotranspiration from 1982 to 2008, compiled using a global monitoring network, meteorological and remote-sensing observations, and a machine-learning algorithm. In addition, we have assessed evapotranspiration variations over the same time period using an ensemble of process-based land-surface models. Our results suggest that global annual evapotranspiration increased on average by 7.1?±?1.0?millimetres per year per decade from 1982 to 1997. After that, coincident with the last major El Ni?o event in 1998, the global evapotranspiration increase seems to have ceased until 2008. This change was driven primarily by moisture limitation in the Southern Hemisphere, particularly Africa and Australia. In these regions, microwave satellite observations indicate that soil moisture decreased from 1998 to 2008. Hence, increasing soil-moisture limitations on evapotranspiration largely explain the recent decline of the global land-evapotranspiration trend. Whether the changing behaviour of evapotranspiration is representative of natural climate variability or reflects a more permanent reorganization of the land water cycle is a key question for earth system science.     

Monetary Aggregates to Improve Early Output Gap Estimates in the Euro Area: An Empirical Assessment

Output gap estimates at the current edge are subject to severe revisions. This study analyzes whether monetary aggregates can be used to improve the reliability of early output gap estimates as proposed by several theoretical models. A real‐time experiment shows that real M1 can improve output gap estimates for euro area data. For many periods the cyclical component of real M1 shows good results, while a forecasting strategy based on projecting GDP series seems to be more robust and provides superior results during the Great Recession. Broader monetary aggregates provide no superior information for output gap estimates. Copyright © 2015 John Wiley & Sons, Ltd.     

Investigations and prospects of Fabry-Perot antennas: a review

Fabry-Perot (FP) antennas have characteristics of planar structures combined with high gain, and they have been widely used in wireless communications. With the...     

Kontraktiles redox-system bestehend aus reinem polyvinylalkohol in gegenwart von 2-methylnaphtochinon-1,4

Summary Crosslinked foils of pure (commercial) polyvinylalcohol, swollen in an acetate-puffer (pH=5), in presence of 2-methylnaphtochinon 1,4 and platinum are found to act as redox-muscles contracting and dilating when treated with hydrogen and oxygen.Mechanical stretching of the filaments is associated with a shift of the redox-potential.     

Prokaryotic cells of the deep sub-seafloor biosphere identified as living bacteria

Chemical analyses of the pore waters from hundreds of deep ocean sediment cores have over decades provided evidence for ongoing processes that require biological catalysis by prokaryotes. This sub-seafloor activity of microorganisms may influence the surface Earth by changing the chemistry of the ocean and by triggering the emission of methane, with consequences for the marine carbon cycle and even the global climate. Despite the fact that only about 1% of the total marine primary production of organic carbon is available for deep-sea microorganisms, sub-seafloor sediments harbour over half of all prokaryotic cells on Earth. This estimation has been calculated from numerous microscopic cell counts in sediment cores of the Ocean Drilling Program. Because these counts cannot differentiate between dead and alive cells, the population size of living microorganisms is unknown. Here, using ribosomal RNA as a target for the technique known as catalysed reporter deposition-fluorescence in situ hybridization (CARD-FISH), we provide direct quantification of live cells as defined by the presence of ribosomes. We show that a large fraction of the sub-seafloor prokaryotes is alive, even in very old (16 million yr) and deep (> 400 m) sediments. All detectable living cells belong to the Bacteria and have turnover times of 0.25-22 yr, comparable to surface sediments.