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Ammonia oxidation, performed by specialized microorganisms belonging to the Bacteria and Archaea, is the first and most limiting step of soil nitrification. Nitrification has not yet been examined in young volcanic soils. The aim of the present work was to evaluate the abundance and diversity of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in acidic volcanic soils (andisols) of different defined ages to determine their relative contribution to nitrification and soil colonization. Soil was collected from three vegetated sites on Llaima Volcano (Chile) recolonized after lava eruptions in 1640, 1751 and 1957. Quantitative polymerase chain reaction, terminal restriction fragment length polymorphism and clone sequence analyses of the amoA gene were performed for the AOA and AOB communities. All soils showed high nitrification potentials, but they were highest in the younger soils. Archaeal amoA genes outnumbered bacterial amoA genes at all sites, and AOA abundances were found to be proportional to the nitrification potentials. Sequencing indicated the presence of AOA related to Nitrososphaera and Nitrosotalea, and AOB related primarily to Nitrosospira and sporadically to Nitrosomonas. The study showed that both AOA and AOB are early colonizers of andisols, but that AOA outnumber AOB and play an important role in nitrification., (© 2013 Society for Applied Microbiology and John Wiley & Sons Ltd.)

6.7-Dimethoxy-3-cyano-3.4-dihydrocarbostyril (7A61, 1), a 2-quinolinone derivative, showed interesting cardiotonic properties in vitro. It exerted potent positive inotropic effects, without any change in heart rate, in guinea pig atrial preparations, and its effects were not dependent upon inhibition of phosphodiesterases, opening of Na+ channels, or inhibition of adenosine receptors. Notwithstanding its structural relationships with milrinone, vesnarinone, and other quinolinones endowed with cardiotonic activity, it appeared that 7A61 does not share any of the main mechanisms of action involved in the pharmacological activity of these compounds. Other experiments also excluded the involvement of other well known mechanisms of cardiac stimulation, such as adrenergic receptor activation or opening of Ca++ channels, the mode of action of 7A61 remaining unexplained. However, contrary to milrinone, 7A61 did not exert cardiotonic effects in human ventricular muscle preparations, thus discouraging further investigation. Although the lack of effect on human heart could not be predicted from the results obtained in several cardiac preparations commonly used in laboratory investigations, the scarce efficacy of 7A61 in comparison with milrinone in dog and cat papillary muscle and in guinea pig ventricular muscle suggests the utility of the latter preparations in laboratory experiments aimed at selecting new potential cardiotonic agents.