Self-incompatibility triggers programmed cell death in Papaver pollen

Sexual reproduction in many angiosperm plants involves self-incompatibility (SI), which is one of the most important mechanisms to prevent inbreeding. SI is genetically controlled by the S-locus, and involves highly specific interactions during pollination between pollen and the pistil on which it lands. This results in the rejection of incompatible ('self') pollen, whereas compatible ('non-self') pollen is allowed to fertilize the plant. In Papaver rhoeas, S-proteins encoded by the stigma component of the S-locus interact with incompatible pollen, triggering a Ca2+-dependent signalling network, resulting in the inhibition of pollen-tube growth. Programmed cell death (PCD) is a mechanism used by many organisms to destroy unwanted cells in a precisely regulated manner. Here we show that PCD is triggered by SI in an S-specific manner in incompatible pollen. This provides a demonstration of a SI system using PCD, revealing a novel mechanism to prevent self-fertilization. Furthermore, our data reveal that the response is biphasic; rapid inhibition of pollen-tube growth is followed by PCD, which is involved in a later 'decision-making' phase, making inhibition irreversible.     

The role of increasing temperature variability in European summer heatwaves

Instrumental observations and reconstructions of global and hemispheric temperature evolution reveal a pronounced warming during the past approximately 150 years. One expression of this warming is the observed increase in the occurrence of heatwaves. Conceptually this increase is understood as a shift of the statistical distribution towards warmer temperatures, while changes in the width of the distribution are often considered small. Here we show that this framework fails to explain the record-breaking central European summer temperatures in 2003, although it is consistent with observations from previous years. We find that an event like that of summer 2003 is statistically extremely unlikely, even when the observed warming is taken into account. We propose that a regime with an increased variability of temperatures (in addition to increases in mean temperature) may be able to account for summer 2003. To test this proposal, we simulate possible future European climate with a regional climate model in a scenario with increased atmospheric greenhouse-gas concentrations, and find that temperature variability increases by up to 100%, with maximum changes in central and eastern Europe.     

Increased seasonality in Middle East temperatures during the last interglacial period

The last interglacial period (about 125,000 years ago) is thought to have been at least as warm as the present climate. Owing to changes in the Earth's orbit around the Sun, it is thought that insolation in the Northern Hemisphere varied more strongly than today on seasonal timescales, which would have led to corresponding changes in the seasonal temperature cycle. Here we present seasonally resolved proxy records using corals from the northernmost Red Sea, which record climate during the last interglacial period, the late Holocene epoch and the present. We find an increased seasonality in the temperature recorded in the last interglacial coral. Today, climate in the northern Red Sea is sensitive to the North Atlantic Oscillation, a climate oscillation that strongly influences winter temperatures and precipitation in the North Atlantic region. From our coral records and simulations with a coupled atmosphere-ocean circulation model, we conclude that a tendency towards the high-index state of the North Atlantic Oscillation during the last interglacial period, which is consistent with European proxy records, contributed to the larger amplitude of the seasonal cycle in the Middle East.     

Störung der Atemmotorik durch Parasympathicomimetica,verglichen mit der Wirkung von Reizstoffen Reizstoffen

Summary In experiments on mice, it was found, that the peculiar disturbance of respiratory movements which was demonstrated formerly as the effect of injected reflexogenic irritants (Veratrin, Veratrum-alcaloids, Andromedotoxin etc.), as well as of airborne irritant gases, can also be produced by suitable doses of parasympathicomimetic bronchoconstrictors (Prostigmin, Mestinon, Paraoxon, Parathion, Physostigmin). This confirms the explanation of the phenomenon formerly given by the authors as a reflex reaction initiated by a brief bronchoconstriction.     

Does nitrogen mustard mimic the X-ray effects in any case?

Résumé Les effets de l'ypérite nitrée sur le cerveau et yeux de l'embryon du rat blanc ont été analysés. Seulement les embryons présentant un aspect normal ont été coupés et colorés. De larges centres de nécrose ont été trouvés sur les coupes tandis que les «rosettes» n'ont pas pu être décelées.Bien que connue comme radiomimétique, l'yperite nitrée ne mime pas les rayons X en ce qui concerne la formation des «rosettes» dans le cerveau.     

The control of contraction activation by the membrane potential

Summary Force measurements under voltage-clamp control were performed in short toe muscles of the frog. The results show a) that the activation of force development and its repriming process can at least qualitatively be correlated to charge movement kinetics; b) that caffeine improves EC coupling by potentiating the potential dependent activation process.This work was supported by DFG (SFB 114 Bionach) and DAAD.