[Is there a correlation between back pain and stability of the lumbar spine in pregnancy? A model-based hypothesis]. / Besteht ein Zusammenhang zwischen Rückenschmerz und der Stabilität der lumbalen Wirbelsäule in der Schwangerschaft? : Eine modellbasierte Hypothese.

During pregnancy approximately 50% of women suffer from low back pain (LBP), which significantly affects their everyday life. The pain could result in chronic insomnia, limit the pregnant women in their ability to work and produce a reduction of their physical activity. The etiology of the pain is still critically discussed and not entirely understood. In the literature different explanations for LBP are given and one of the most common reasons is the anatomical changes of the female body during pregnancy; for instance, there is an increase in the sagittal moments because of the enlarged uterus and fetus and the occurrence of hyperlordosis.The aim of this study was to describe how the anatomical changes in pregnant women affect the stability and the moments acting on the lumbar spine with the help of a simplified musculoskeletal model.A two-dimensional musculoskeletal model of the lumbar spine in the sagittal plane consisting of five lumbar vertebrae was developed. The model included five centres of rotation and three antagonistic pairs of paraspinal muscles. The concept of altered acting torques during pregnancy was explored by varying the geometrical arrangements. The situations non-pregnant, pregnant and pregnant with hyperlordosis were considered for the model-based approach. These simulations were done dependent on the stability of the erect posture and local countertorques of every lumbar segment.In spite of the simplicity of the model and the musculoskeletal arrangement it was possible to maintain equilibrium of the erect posture at every lumbar spinal segment with one minimum physiological cross-sectional area of all paraspinal muscles. The stability of the musculoskeletal system depends on the muscular activity of the paraspinal muscles and diminishing the muscular activity causes unstable lumbar segments.The relationship between the non-pregnant and the pregnant simulations demonstrated a considerable increase of acting segmental countertorques. Simulating an increased lordosis for the pregnant situation in the sagittal plane substantially reduced these acting countertorques and therefore the demand on the segmental muscles.It is assumed that hyperlordosis is a physiological adaptation to the anatomical changes during pregnancy to minimize the segmental countertorques and therefore the demand on the segmental muscles.Further, it can be expected that an enhanced muscle activity caused by selective activity of lumbar muscles increases the stability of the lumbar spine and may improve the situation with LBP during pregnancy.

Optimizing syngeneic orthotopic murine bladder cancer (MB49).

The syngeneic orthotopic murine bladder cancer model MB49 is hampered by unreliable tumor implantation. We optimized this model by a simple modification of the standard implantation technique in three groups of mice. Fifty thousand (group I), 20,000 (group II), or 10,000 (group III) tumor cells were implanted into cauterized bladders by transurethral instillation, and dwell time was prolonged to 3 h. Tumor take, survival, and bladder weights were determined as outcome variables. To verify whether this modification maintained its sensitivity to topical immunotherapy, an initial tumor load of 100,000 MB49 cells was given, and mice were treated intravesically with Bacillus Calmette-Guérin or phosphate-buffered saline. The prolonged dwell time of tumor cells resulted in take rates of 100% in all three groups. Survival and bladder weights were significantly correlated with the number of instilled cells. Even with the highest tumor load, Bacillus Calmette-Guérin therapy improved survival and reduced bladder weights significantly, as compared to PBS. Thus, the modified model is highly reliable and maintains its susceptibility to topical immunotherapy.

Exposing local symmetries in distorted driven lattices via time-averaged invariants.

Time-averaged two-point currents are derived and shown to be spatially invariant within domains of local translation or inversion symmetry for arbitrary time-periodic quantum systems in one dimension. These currents are shown to provide a valuable tool for detecting deformations of a spatial symmetry in static and driven lattices. In the static case the invariance of the two-point currents is related to the presence of time-reversal invariance and/or probability current conservation. The obtained insights into the wave functions are further exploited for a symmetry-based convergence check which is applicable for globally broken but locally retained potential symmetries.

Inhibition of bladder carcinoma cell adhesion by oligopeptide combinations in vitro and in vivo.

PURPOSE: A presumed reason for the high recurrence rate of superficial bladder cancer after transurethral tumor resection is the reimplantation of tumor cells. Because tumor cell adhesion to the extracellular matrix is mediated by integrin molecules, we tested specific integrin receptor blocking oligopeptides to prevent this mechanism. MATERIALS AND METHODS: An in vitro cell adherence assay with various bladder cancer cell lines and extracellular matrices, including fibronectin, collagen type I, laminin and combinations, was used to analyze the inhibition of tumor cell adhesion by the matrix specific oligopeptides GRGDS, DGEA and EILDV. In therapeutic in vivo experiments the orthotopic murine bladder tumor model MB49 was used. The ability of oligopeptides to interfere with tumor cell adhesion and consecutive tumor outgrowth was evaluated and compared with that of nonspecific peptides, commercially available irrigation fluid and single dose epirubicin chemotherapy. RESULTS: In vitro fibronectin specific oligopeptides showed a concentration dependent inhibition of tumor cell adherence to fibronectin, whereas adhesion to laminin, collagen and combined matrices was not inhibited. In contrast, combinations of integrin receptor blocking oligopeptides were highly active. In vivo local tumor take was not affected by irrigation fluid, nonspecific peptides or monospecific oligopeptides alone, whereas the combination of the 3 oligopeptides effectively inhibited tumor outgrowth. CONCLUSIONS: Combining oligopeptides with various specificities significantly inhibited tumor cell adhesion and tumor outgrowth. Application of this principle in a clinical setting may be an effective method for reducing the recurrence rate of superficial bladder cancer.