Force generation in glycerinated insect-flight muscles without ATP

Zusammenfassung Durch Zugabe und durch Auswaschen von Mg-Pyrophosphat (0,5 mM) oder Mg-Tripoly-Phosphat (1 mM) konnten (in Abwesenheit von ATP) in glyzerinextrahierten Fasern von fibrillären Insektenmuskeln (Lethocerus maximus) reversible Kontraktionszyklen und Änderungen des Dehnungswiderstandes bewirkt werden.

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Supported by Grant No. Ru 154/b of the Deutsche Forschungsgemeinschaft. The excellent technical assistance of Mrs.Helgard Jung is gratefully acknowledged.     

Regulierung des Wasserhaushaltes bei der Hämodialyse (Kompensation und Überkompensation des kolloidosmotischen Druckes des Blutes durch Verwendung polyelektrolythaltiger Dialysierlösungen bei der künstlichen Niere

Summary Addition of polyelectrolytes, in particular of the sodium salt of carboxymethylcellulose, makes it possible to obtain for the use in artificial kidneys dialyzing liquids which are in thermodynamic equilibrium with blood, both with respect to salts and water, or which even permit removal of water from the blood, as well as urea and related substances (the dialyzing liquid being at will hypertonic with respect to blood), the salt content of blood remaining in all these cases unaffected. These dialyzing liquids might be particularly useful for cases combined with oedema.

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Vorgetragen am Kongress der «3^o riunioni medico chirurgiche internazionali», Turin 1957; erste Mitteilung hierüber im VortragvonW. Kuhn am Staffmeeting des Bürgerspitals Basel am 2. Februar 1955.     

Ethical principles and guidelines for scientific experiments on animals

Ethical principles and guidelines for scientific experiments on animals     

Das beim Gefrieren von Gelen entstehende Eis

Summary Highly swollen gels which contain, in addition to a large amount of solvent, a spatial network formed by chains of a high polymer, show an abnormal lowering of the freezing point. This is caused by the fact that the network prevents the formation of macroscopically undisturbed crystals.If, in the course of freezing at this lower temperature, a conglomerate of microcrystals were created corresponding in size to the width of the network, one should be able to observe a broadening of the X-ray interference lines. Experiments have shown that no measurable broadening takes place.This is explained by the assumption that a crystal which is prevented from growing in the normal way by the surrounding filaments of the gel, when cooled to a suitably low temperature grows crystallites with a small cross-section corresponding to the mesh size. The crystallites thus formed are orientated in a crystallographically exact manner toward their supporting crystal and parallel to each other. Therefore, when reaching the necessary height, they unite to larger, ordered crystalline regions which incorporate the polymeric filaments. This explains the observed sharpness of the X-ray interferences as well as the observation that, upon heating of a frozen gel, the melting does not occur at the same low temperature as the freezing, but closer to the melting point of macroscopic ice.     

Praemia

Ohne Zusammenfassung     

Augenrückbildung und Lichtstinn beiAnoptichthys jordani Hubbs und Innes

Summary After hatching, young individuals of the Mexican blind characinAnoptichthys jordani Hubbs and Innes possess small, movable eyes. In the course of growth, the eyes are overlapped by skinfolds and tend to sink into the depth of the orbital cavity. Lens and pupilar opening may disappear and degeneration is to be found in the retina.Even very young blind characins seem to have no vision of movements, while they are able to perceive light. The lower limit is about 0.12 Lux of light intensity. Experiments concerning the localisation of this perception of light are in progress.     

Two-dimensional spectroscopy of electronic couplings in photosynthesis

Time-resolved optical spectroscopy is widely used to study vibrational and electronic dynamics by monitoring transient changes in excited state populations on a femtosecond timescale. Yet the fundamental cause of electronic and vibrational dynamics--the coupling between the different energy levels involved--is usually inferred only indirectly. Two-dimensional femtosecond infrared spectroscopy based on the heterodyne detection of three-pulse photon echoes has recently allowed the direct mapping of vibrational couplings, yielding transient structural information. Here we extend the approach to the visible range and directly measure electronic couplings in a molecular complex, the Fenna-Matthews-Olson photosynthetic light-harvesting protein. As in all photosynthetic systems, the conversion of light into chemical energy is driven by electronic couplings that ensure the efficient transport of energy from light-capturing antenna pigments to the reaction centre. We monitor this process as a function of time and frequency and show that excitation energy does not simply cascade stepwise down the energy ladder. We find instead distinct energy transport pathways that depend sensitively on the detailed spatial properties of the delocalized excited-state wavefunctions of the whole pigment-protein complex.     

Design principles of a bacterial signalling network

Cellular biochemical networks have to function in a noisy environment using imperfect components. In particular, networks involved in gene regulation or signal transduction allow only for small output tolerances, and the underlying network structures can be expected to have undergone evolution for inherent robustness against perturbations. Here we combine theoretical and experimental analyses to investigate an optimal design for the signalling network of bacterial chemotaxis, one of the most thoroughly studied signalling networks in biology. We experimentally determine the extent of intercellular variations in the expression levels of chemotaxis proteins and use computer simulations to quantify the robustness of several hypothetical chemotaxis pathway topologies to such gene expression noise. We demonstrate that among these topologies the experimentally established chemotaxis network of Escherichia coli has the smallest sufficiently robust network structure, allowing accurate chemotactic response for almost all individuals within a population. Our results suggest that this pathway has evolved to show an optimal chemotactic performance while minimizing the cost of resources associated with high levels of protein expression. Moreover, the underlying topological design principles compensating for intercellular variations seem to be highly conserved among bacterial chemosensory systems.