Die Aufgaben des Kerns während der Oogenese der Teleosteer

Zusammenfassung Das Verhalten des Kerns während der Oogenese der Süßwasserteleosteer wurde in allen Stadien cytologisch und histochemisch untersucht.Die Vorstadien der Meiose laufen wie bei anderen Tierarten in der ganz jungen Oocyte ab. Das Pachytän-Stadium konnte noch mit Sicherheit beobachtet werden.In der Dotterbildungsphase der Oocyten wird der Kern extrem blasenförmig. DNS-haltige Strukturen können nicht mehr nachgewiesen werden. Im Oocytenstadium II wurden im Kern Gebilde gefunden, die das Aussehen von Lampenbürstenchromosomen haben. Diese Lampenbürstenchromosomen konnten nur an fixiertem Material beobachtet werden.Nach Auflösung des blasenförmigen Kerns vollzieht sich die erste Reifeteilung noch im Ovarium des Fisches ganz kurz vor der Ablaiche.Die Bildung der zahlreichen Randnucleolen im Oocytenstadium I erfolgt in der Nähe der Kernmembran bei Anwesenheit von feulgenpositivem Heterochromatin. Die Randnucleolen ergeben positive Ninhydrin-Reaktion, enthalten zunächst aber keine nachweisbaren Mengen an RNS. Erst zu Beginn des Oocytenstadiums II sind bestimmte Bezirke der Randnucleolen stark RNS-haltig.Im Innern des Kerns bilden sich im Oocytenstadium II wesentlich kleinere Nucleolen aus, die RNS-haltig sind.     

Influence of sexual maturity on feeding, growth and energy stores of wild Atlantic salmon parr

Maturing Salmo salar parr had significantly lower short-term energy stores (indicated by hepato-somatic index) in August, and significantly lower energy stores and growth rate (indicated by RNA : DNA) in September than immature parr captured from the same stream sites on the same date. There were no significant differences in gut fullness or protein concentrations, suggesting that up to early September the main energetic consequences of maturation were a reduction in allocations to growth and short-term energy storage, but not a mobilization of long-term stored energy in the form of proteins. These are the first observations of relative food intake and energy storage for maturing parr under natural conditions, and also the first to assess growth effects on wild fish before completion of the maturation process.     

A continuum mechanical porous media model for vertebroplasty: Numerical simulations and experimental validation

The outcome of vertebroplasty is hard to predict due to its dependence on complex factors like bone cement and marrow rheologies. Cement leakage could occur if the procedure is done incorrectly, potentially causing adverse complications. A reliable simulation could predict the patient-specific outcome preoperatively and avoid the risk of cement leakage. Therefore, the aim of this work was to introduce a computationally feasible and experimentally validated model for simulating vertebroplasty. The developed model is a multiphase continuum-mechanical macro-scale model based on the Theory of Porous Media. The related governing equations were discretized using a combined finite element–finite volume approach by the so-called Box discretization. Three different rheological upscaling methods were used to compare and determine the most suitable approach for this application. For validation, a benchmark experiment was set up and simulated using the model. The influence of bone marrow and parameters like permeability, porosity, etc., was investigated to study the effect of varying conditions on vertebroplasty. The presented model could realistically simulate the injection of bone cement in porous materials when used with the correct rheological upscaling models, of which the semi-analytical averaging of the viscosity gave the best results. The marrow viscosity is identified as the crucial reference to categorize bone cements as ‘high- ’or ‘low-’ viscosity in the context of vertebroplasty. It is confirmed that a cement with higher viscosity than the marrow ensures stable development of the injection and a proper cement interdigitation inside the vertebra.

     

Probability landscapes for integrative genomics

Background  

The comprehension of the gene regulatory code in eukaryotes is one of the major challenges of systems biology, and is a requirement for the development of novel therapeutic strategies for multifactorial diseases. Its bi-fold degeneration precludes brute force and statistical approaches based on the genomic sequence alone. Rather, recursive integration of systematic, whole-genome experimental data with advanced statistical regulatory sequence predictions needs to be developed. Such experimental approaches as well as the prediction tools are only starting to become available and increasing numbers of genome sequences and empirical sequence annotations are under continual discovery-driven change. Furthermore, given the complexity of the question, a decade(s) long multi-laboratory effort needs to be envisioned. These constraints need to be considered in the creation of a framework that can pave a road to successful comprehension of the gene regulatory code.     

Ecological impact of alien marine fishes: insights from freshwater systems based on a comparative review

Hydrobiologia - We review the literature of marine non-indigenous fishes (NIF) in order to summarize information on their ecological impacts and to compare successful invading freshwater fishes...