Neural Effects on Cardiac Rate and Rhythm

The importance of autonomic discharge emanating from high neural regions rostral to the medulla oblongata on heart rhythm was first recognized in the classical studies by Schiff and Danilewsky during the late nineteenth century. Only in the last two decades, however, has a precise description of these neural effects on heart rhythm become possible. Crucial to these more recent advances have been improvements in technology which have permitted application of discrete electrical stimuli to various regions of the brain as well as continuous monitoring of heart rate and arterial pressure. These studies, reported here, represent a portion of a broader research project carried out in the neurophysiological laboratory of the Medical College of Virginia for a number of years and aimed at clarification of the role of autonomic discharge from higher neural centers on organ function

Mineral Type and Solution Chemistry Affect the Structure and Composition of Actively Growing Bacterial Communities as Revealed by Bromodeoxyuridine Immunocapture and 16S rRNA Pyrosequencing

© 2016, Springer Science+Business Media New York. Understanding how minerals affect bacterial communities and their in situ activities in relation to environmental conditions are central issues in soil microbial ecology, as minerals represent essential reservoirs of inorganic nutrients for the biosphere. To determine the impact of mineral type and solution chemistry on soil bacterial communities, we compared the diversity, composition, and functional abilities of a soil bacterial community incubated in presence/absence of different mineral types (apatite, biotite, obsidian). Microcosms were prepared containing different liquid culture media devoid of particular essential nutrients, the nutrients provided only in the introduced minerals and therefore only available to the microbial community through mineral dissolution by biotic and/or abiotic processes. By combining functional screening of bacterial isolates and community analysis by bromodeoxyuridine DNA immunocapture and 16S rRNA gene pyrosequencing, we demonstrated that bacterial communities were mainly impacted by the solution chemistry at the taxonomic level and by the mineral type at the functional level. Metabolically active bacterial communities varied with solution chemistry and mineral type. Burkholderia were significantly enriched in the obsidian treatment compared to the biotite treatment and were the most effective isolates at solubilizing phosphorous or mobilizing iron, in all the treatments. A detailed analysis revealed that the 16S rRNA gene sequences of the OTUs or isolated strains assigned as Burkholderia in our study showed high homology with effective mineral-weathering bacteria previously recovered from the same experimental site