Untersuchung der spannungsinduzierten Aktivierung heteromerer HCN2/HCN4-Schrittmacherkanäle und deren Ligandenabhängigkeit

HCN (Hyperpolarisation-Activated and Cyclic Nucleotide-Modulated) -Kanäle sind vor allem für ihre Schrittmacherfunktion im Herzen und im Gehirn bekannt sind. In Säugetieren existieren vier Isoformen, HCN1 bis HCN4. In der vorliegenden Arbeit steht ein Vergleich des heteromeren HCN24-Kanals, bestehend aus HCN2- und HCN4-Untereinheiten, mit den entsprechenden homomeren Kanälen, die aus vier gleichen Untereinheiten zusammengesetzt sind, im Vordergrund. Dabei ist von besonderem Interesse, in welchem Ausmaß eine Variation der Kanalzusammensetzung zu Unterschieden im Schaltverhalten führen kann. Dazu wurden die Isoformen HCN2 und HCN4 der Maus nach RNA-Injektion in Xenopus laevis Oozyten exprimiert und mit Hilfe der Patch-Clamp-Technik untersucht. Dabei zeigte sich, dass die Koexpression von mHCN2- und mHCN4-Untereinheiten zum Einbau funktioneller heteromerer HCN24-Kanäle in die Oozytenmembran führt und dass heteromere HCN24-Kanäle von homomeren HCN2- und HCN4-Kanälen verschiedene elektrophysiologische Eigenschaften aufweisen. Die spannungsinduzierte Aktivierung heteromerer HCN24-Kanäle wurde allein durch die schneller aktivierende Untereinheit bestimmt. Heteromere HCN24-Kanäle zeigten eine weniger stark ausgeprägte Autoinhibition als die homomeren HCN2- und HCN4-Kanäle. Weiterhin ergab ein Vergleich verschiedener Patch-Clamp-Konfigurationen, dass heteromere HCN24-Kanäle wahrscheinlich stärker durch intrazelluläre Faktoren moduliert werden als die homomeren Kanäle. Die in der vorliegenden Arbeit erhobenen Daten zeigen, dass heteromere HCN24-Kanäle elektrophysiologische Eigenschaften aufweisen, die sich nicht durch die Kombination der Eigenschaften homomerer HCN2- und HCN4-Kanäle erklären lassen. Dies lässt vermuten, dass die Bildung heteromerer HCN-Kanäle eine Möglichkeit darstellt, das Schaltverhalten der HCN-Kanäle in vivo an gewebespezifische Anforderungen anzupassen

Assessing Relationships Among Autonomy, Supportive Leadership, and Burnout in Public Elementary Teachers

AbstractStress and burnout among teachers are serious problems because of the negative consequences associated with them that have contributed to the current crisis in the American education system. Until the problems of teacher stress and burnout are understood and addressed, efforts to restructure American education cannot succeed. This study assessed the relationships among perceived autonomy, perceived transformational leadership style and burnout in public elementary teachers, and the moderating/mediating influence of teacher orientation (Montessori and traditional) on burnout levels. An integration of Maslach’s multi-dimensional burnout theory, self-determination theory, and the theory of transformational leadership formed the theoretical foundation of the study. A nonexperimental correlational design was used with survey methodology. A convenience sample of 82 public elementary teachers were recruited via educator social media sites and professional associations. Participants completed an online survey via Survey Monkey. Multiple regression analyses determined strong negative relationships among the predictor variables and the three dimensions of burnout as well as the significant predictive power of the independent variables. Moderation analyses determined a significant influence of teacher orientation across these relationships. The mediation analysis determined that teaching autonomy was a significant mediator between teacher orientation and emotional exhaustion burnout. The results from this study may be used for positive social change by developing strategies to mitigate burnout in public elementary teachers, increase engagement, improve teacher retention, ultimately improving student achievement and engagement

NcDNAlign: Plausible multiple alignments of non-protein-coding genomic sequences

Genome-wide multiple sequence alignments (MSAs) are a necessary prerequisite for an increasingly diverse collection of comparative genomic approaches. Here we present a versatile method that generates high-quality MSAs for non-protein-coding sequences. The NcDNAlign pipeline combines pairwise BLAST alignments to create initial MSAs, which are then locally improved and trimmed. The program is optimized for speed and hence is particulary well-suited to pilot studies. We demonstrate the practical use of NcDNAlign in three case studies: the search for ncRNAs in gammaproteobacteria and the analysis of conserved noncoding DNA in nematodes and teleost fish, in the latter case focusing on the fate of duplicated ultra-conserved regions. Compared to the currently widely used genome-wide alignment program TBA, our program results in a 20- to 30-fold reduction of CPU time necessary to generate gammaproteobacterial alignments. A showcase application of bacterial ncRNA prediction based on alignments of both algorithms results in similar sensitivity, false discovery rates, and up to 100 putatively novel ncRNA structures. Similar findings hold for our application of NcDNAlign to the identification of ultra-conserved regions in nematodes and teleosts. Both approaches yield conserved sequences of unknown function, result in novel evolutionary insights into conservation patterns among these genomes, and manifest the benefits of an efficient and reliable genome-wide alignment package. The software is available under the GNU Public License at http://www.bioinf.uni-leipzig.de/Software/NcDNAlign/

Computational RNomics of Drosophilids

Recent experimental and computational studies have provided overwhelming evidence for a plethora of diverse transcripts that are unrelated to protein-coding genes. One subclass consists of those RNAs that require distinctive secondary structure motifs to exert their biological function and hence exhibit distinctive patterns of sequence conservation characteristic for positive selection on RNA secondary structure. The deep-sequencing of 12 drosophilid species coordinated by the NHGRI provides an ideal data set of comparative computational approaches to determine those genomic loci that code for evolutionarily conserved RNA motifs. This class of loci includes the majority of the known small ncRNAs as well as structured RNA motifs in mRNAs. We report here on a genome-wide survey using RNAz

Compositional Changes in Two Small Mammal Communities During Succession in Southeastern Virginia

Changes in the composition of two small mammal communities were studied during 8 and 9 years of ecological succession in southern Chesapeake. Virginia. Using monthly live-trapping on grids of similar size and history since their abandonment as agricultural fields, we learned that house mice were early colonists on one grid but not the other. Two species of herbivorous rodent and the granivorous eastern harvest mouse were numerically dominant on both grids across the study. Some species disappeared early on one grid but persisted to the end at the other. The two arboreal small mammals, golden and white-footed mice, were most predictable between sites, showing up at year 8, after significant woody elements were present on the grids. The greatest abundances of small mammals (and probably greatest total biomass too) were seen between years 4 and 6 of ecological succession