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- IfB - Institut für Bioengineering (686) (remove)
Bilaterale stromale Hornhauttrübungen sind für den Augenarzt eine differenzialdiagnostische Herausforderung. Im folgenden Beitrag werden 2 Patieninnen (30 und 36 Jahre) mit unterschiedlich stark ausgeprägter stromaler diffuser Hornhauttrübung vorgestellt. Patientin 1 war kleinwüchsig (114 cm) und Patientin 2 normal groß (172 cm). Beide Patientinnen wiesen veränderte Gelenkstrukturen an Hand und Fußgelenken sowie diffuse stromale Hornhauttrübungen auf. Des Weiteren lagen eine Mitral- und Aorteninsuffizienz (Patientin 1) bzw. eine Aorteninsuffizienz (Patientin 2) vor. Die stromalen diffusen Hornhauttrübungen ließen im Zusammenhang mit den Gelenkveränderungen ein Scheie-Syndrom vermuten. Therapeutisch ist bei Patienten mit Visusminderung eine (lamelläre) Keratoplastik sinnvoll.
An optimization method is developed to describe the mechanical behaviour of the human cancellous bone. The method is based on a mixture theory. A careful observation of the behaviour of the bone material leads to the hypothesis that the bone density is controlled by the principal stress trajectories (Wolff’s law). The basic idea of the developed method is the coupling of a scalar value via an eigenvalue problem to the principal stress trajectories. On the one hand this theory will permit a prediction of the reaction of the biological bone structure after the implantation of a prosthesis, on the other hand it may be useful in engineering optimization problems. An analytical example shows its efficiency.
The CellDrum technology (The term 'CellDrum technology' includes a couple of slightly different technological setups for measuring lateral mechanical tension in various types of cell monolayers or 3D-tissue constructs) was designed to quantify the contraction rate and mechanical tension of self-exciting cardiac myocytes. Cells were grown either within flexible, circular collagen gels or as monolayer on top of respective 1-mum thin silicone membranes. Membrane and cells were bulged outwards by air pressure. This biaxial strain distribution is rather similar the beating, blood-filled heart. The setup allowed presetting the mechanical residual stress level externally by adjusting the centre deflection, thus, mimicking hypertension in vitro. Tension was measured as oscillating differential pressure change between chamber and environment. A 0.5-mm thick collagen-cardiac myocyte tissue construct induced after 2 days of culturing (initial cell density 2 x 10(4) cells/ml), a mechanical tension of 1.62 +/- 0.17 microN/mm(2). Mechanical load is an important growth regulator in the developing heart, and the orientation and alignment of cardiomyocytes is stress sensitive. Therefore, it was necessary to develop the CellDrum technology with its biaxial stress-strain distribution and defined mechanical boundary conditions. Cells were exposed to strain in two directions, radially and circumferentially, which is similar to biaxial loading in real heart tissues. Thus, from a biomechanical point of view, the system is preferable to previous setups based on uniaxial stretching.
All cells generate contractile tension. This strain is crucial for mechanically controlling the cell shape, function and survival. In this study, the CellDrum technology quantifying cell's (the cellular) mechanical tension on a pico-scale was used to investigate the effect of lipopolysaccharide (LPS) on human aortic endothelial cell (HAoEC) tension. The LPS effect during gram-negative sepsis on endothelial cells is cell contraction causing endothelium permeability increase. The aim was to finding out whether recombinant activated protein C (rhAPC) would reverse the endothelial cell response in an in-vitro sepsis model. In this study, the established in-vitro sepsis model was confirmed by interleukin 6 (IL-6) levels at the proteomic and genomic levels by ELISA, real time-PCR and reactive oxygen species (ROS) activation by florescence staining. The thrombin cellular contraction effect on endothelial cells was used as a positive control when the CellDrum technology was applied. Additionally, the Ras homolog gene family, member A (RhoA) mRNA expression level was checked by real time-PCR to support contractile tension results. According to contractile tension results, the mechanical predominance of actin stress fibers was a reason of the increased endothelial contractile tension leading to enhanced endothelium contractility and thus permeability enhancement. The originality of this data supports firstly the basic measurement principles of the CellDrum technology and secondly that rhAPC has a beneficial effect on sepsis influenced cellular tension. The technology presented here is promising for future high-throughput cellular tension analysis that will help identify pathological contractile tension responses of cells and prove further cell in-vitro models.