Methanotrophic symbionts provide carbon for photosynthesis in peat bogs

Wetlands are the largest natural source of atmospheric methane, the second most important greenhouse gas. Methane flux to the atmosphere depends strongly on the climate; however, by far the largest part of the methane formed in wetland ecosystems is recycled and does not reach the atmosphere. The biogeochemical controls on the efficient oxidation of methane are still poorly understood. Here we show that submerged Sphagnum mosses, the dominant plants in some of these habitats, consume methane through symbiosis with partly endophytic methanotrophic bacteria, leading to highly effective in situ methane recycling. Molecular probes revealed the presence of the bacteria in the hyaline cells of the plant and on stem leaves. Incubation with (13)C-methane showed rapid in situ oxidation by these bacteria to carbon dioxide, which was subsequently fixed by Sphagnum, as shown by incorporation of (13)C-methane into plant sterols. In this way, methane acts as a significant (10-15%) carbon source for Sphagnum. The symbiosis explains both the efficient recycling of methane and the high organic carbon burial in these wetland ecosystems.     

Direct observation of electron dynamics in the attosecond domain

Dynamical processes are commonly investigated using laser pump-probe experiments, with a pump pulse exciting the system of interest and a second probe pulse tracking its temporal evolution as a function of the delay between the pulses. Because the time resolution attainable in such experiments depends on the temporal definition of the laser pulses, pulse compression to 200 attoseconds (1 as = 10(-18) s) is a promising recent development. These ultrafast pulses have been fully characterized, and used to directly measure light waves and electronic relaxation in free atoms. But attosecond pulses can only be realized in the extreme ultraviolet and X-ray regime; in contrast, the optical laser pulses typically used for experiments on complex systems last several femtoseconds (1 fs = 10(-15) s). Here we monitor the dynamics of ultrafast electron transfer--a process important in photo- and electrochemistry and used in solid-state solar cells, molecular electronics and single-electron devices--on attosecond timescales using core-hole spectroscopy. We push the method, which uses the lifetime of a core electron hole as an internal reference clock for following dynamic processes, into the attosecond regime by focusing on short-lived holes with initial and final states in the same electronic shell. This allows us to show that electron transfer from an adsorbed sulphur atom to a ruthenium surface proceeds in about 320 as.     

Structure of the apoptotic protease-activating factor 1 bound to ADP

Apoptosis is executed by caspases, which undergo proteolytic activation in response to cell death stimuli. The apoptotic protease-activating factor 1 (Apaf-1) controls caspase activation downstream of mitochondria. During apoptosis, Apaf-1 binds to cytochrome c and in the presence of ATP/dATP forms an apoptosome, leading to the recruitment and activation of the initiator caspase, caspase-9 (ref. 2). The mechanisms underlying Apaf-1 function are largely unknown. Here we report the 2.2-A crystal structure of an ADP-bound, WD40-deleted Apaf-1, which reveals the molecular mechanism by which Apaf-1 exists in an inactive state before ATP binding. The amino-terminal caspase recruitment domain packs against a three-layered alpha/beta fold, a short helical motif and a winged-helix domain, resulting in the burial of the caspase-9-binding interface. The deeply buried ADP molecule serves as an organizing centre to strengthen interactions between these four adjoining domains, thus locking Apaf-1 in an inactive conformation. Apaf-1 binds to and hydrolyses ATP/dATP and their analogues. The binding and hydrolysis of nucleotides seem to drive conformational changes that are essential for the formation of the apoptosome and the activation of caspase-9.     

14-3-2 protein in rat brain synapses

Summary The distribution of the 14-3-2 protein in rat brain synapses was studied by immuno electron microscopy. The protein was localized to the postsynaptic web and to the postsynaptic membrane, but was also prominent both in the presynaptic membrane and in the presynaptic densities. No significant activity was observed in the synaptic vesicles.Acknowledgments. Our sincere thanks to Mrs Ulla Svedin, Eng., for skilled technical assistance. This work was supported by grants from the Swedish Medical Research Council, the Medical Faculty of Göteborg, Tore Nilson's Foundation for Medical Research and by the Swedish-Italian Group of Neurobiology. A. G. received financial support from Consiglio Nazionale delle Ricerche (CNR, ROME).     

Chromosomenaberrationen in Tumorasziteszellen des Ehrlich-Karzinoms der Maus nach Röntgenbestrahlungin vivo bei verschiedenen Sauerstoffpartialdrucken

Summary The frequency of radio-induced fragments of chromosomes increases in ascites-cells of the Ehrlich-carcinoma at higher oxygen partial pressure, to which test animals are exposed during irradiation.     

Quantitative measurements of microscopic changes in the vascular bed

Résumé Une méthode d'analyse quantitative du fer dans l'hémoglobine a été développée, utilisant la fluorescence aux rayons X. Elle est appliquée à des tissus vivants pour l'enregistrement de changements très faibles dans la circulation sanguine dans des fragments microscopiques.     

Immunohistochemical studies on phenylethanolamine-N-methyltransferase,dopa-decarboxylase and dopamine-β-hydroxylase

Zusammenfassung PNMT konnte mit Hilfe einer immunohistochemischen Fluoreszenzmethode ausschliesslich in bestimmten Markzellen der Nebenniere nachgewiesen werden. DDK wurde in Markzellen der Nebenniere, in peripheren und zentralen Katecholamin- und Serotoninneuronen gefunden. DBH kam in Markzellen der Nebenniere und nur in peripheren und zentralen Noradrenalinneuronen vor.     

Sex chromatin as a marker in some rabbit cells

Zusammenfassung In frisch isolierten Kaninchenfibroblasten-und Leukocyten kann kein Geschlechtsdimorphismus festgestellt werden. Nach einigen Tagen Zellkultivierung findet man in 84–93% (durchschnittlich 91,5%) der weiblichen Fibroblasten den Geschlechtschromatinkörper. Nur 0–2% (durchschnittlich 0,5%) der männlichen Fibroblasten weisen ein dem Geschlechtschromatinkörper ähnliches Gebilde auf. In Leukocytenkulturen sind die entsprechenden Zahlen 82–90% (durchschnittlich 89%) für weibliche, 0–1% (durchschnittlich 0,3%) für männliche Zellen. Diese Daten lassen den Geschlechtschromatinkörper als brauchbaren Zellmarkierer beim Kaninchen erscheinen.