Human temporal bones versus mechanical model to evaluate three middle ear transducers

A life-size mechanical middle ear model and human temporal bones were used to evaluate three different middle ear transducers for implantable hearing aids: the driving rod transducer (DRT), the floating mass transducer (FMT) or vibrant sound bridge, and the contactless transducer (CLT). Results of the experiments with the mechanical model were within the range of the results for human temporal bones. However, results with the mechanical model showed better reproducibility. The handling of the mechanical model was considerably simpler and less time-consuming. Systematic variations of mounting parameters showed that the angle of the rod has virtually no effect on the output of the DRT, the mass loading on the cable of the FMT has a larger impact on the output than does the tightness of crimping, and the output level of the CLT can be increased by 10 dB by optimizing the mounting parameters.

Augmentation of mechanical properties in osteoporotic vertebral bones--a biomechanical investigation of vertebroplasty efficacy with different bone cements

Recent clinical trials have reported favorable early results for transpedicular vertebral cement reinforcement of osteoporotic vertebral insufficiencies. There is, however, a lack of basic data on the application, safety and biomechanical efficacy of materials such as polymethyl-methacrylate (PMMA) and calciumphospate (CaP) cements. The present study analyzed 33 vertebral pairs from five human cadaver spines. Thirty-nine vertebrae were osteoporotic (bone mineral density < 0.75 g/cm2), 27 showed nearly normal values. The cranial vertebra of each pair was augmented with either PMMA (Palacos E-Flow) or experimental brushite cement (EBC), with the caudal vertebra as a control. PMMA and EBC were easy to inject, and vertebral fillings of 20-50% were achieved. The maximal possible filling was inversely correlated to the bone mineral density (BMD) values. Cement extrusion into the spinal canal was observed in 12% of cases. All specimens were subjected to axial compression tests in a displacement-controlled mode. From load-displacement curves, the stiffness, S, and the maximal force before failure, Fmax, were determined. Compared with the native control vertebrae, a statistically significant increase in vertebral stiffness and Fmax was observed by the augmentation. With PMMA the stiffness increased by 174% (P = 0.018) and Fmax by 195% (P = 0.001); the corresponding augmentation with EBC was 120% (P = 0.03) and 113% (P = 0.002). The lower the initial BMD, the more pronounced was the augmentation effect. Both PMMA and EBC augmentation reliably and significantly raised the stiffness and maximal tolerable force until failure in osteoporotic vertebral bodies. In non-porotic specimens, no significant increase was achieved.

IDH/MGMT-driven molecular classification of low-grade glioma is a strong predictor for long-term survival

BACKGROUND Low-grade gliomas (LGGs) are rare brain neoplasms, with survival spanning up to a few decades. Thus, accurate evaluations on how biomarkers impact survival among patients with LGG require long-term studies on samples prospectively collected over a long period. METHODS The 210 adult LGGs collected in our databank were screened for IDH1 and IDH2 mutations (IDHmut), MGMT gene promoter methylation (MGMTmet), 1p/19q loss of heterozygosity (1p19qloh), and nuclear TP53 immunopositivity (TP53pos). Multivariate survival analyses with multiple imputation of missing data were performed using either histopathology or molecular markers. Both models were compared using Akaike's information criterion (AIC). The molecular model was reduced by stepwise model selection to filter out the most critical predictors. A third model was generated to assess for various marker combinations. RESULTS Molecular parameters were better survival predictors than histology (ΔAIC = 12.5, P< .001). Forty-five percent of studied patients died. MGMTmet was positively associated with IDHmut (P< .001). In the molecular model with marker combinations, IDHmut/MGMTmet combined status had a favorable impact on overall survival, compared with IDHwt (hazard ratio [HR] = 0.33, P< .01), and even more so the triple combination, IDHmut/MGMTmet/1p19qloh (HR = 0.18, P< .001). Furthermore, IDHmut/MGMTmet/TP53pos triple combination was a significant risk factor for malignant transformation (HR = 2.75, P< .05). CONCLUSION By integrating networks of activated molecular glioma pathways, the model based on genotype better predicts prognosis than histology and, therefore, provides a more reliable tool for standardizing future treatment strategies.

Distinct carbon sources indicate strong differentiation between tropical forest and farmland bird communities

The conversion of forest into farmland has resulted in mosaic landscapes in many parts of the tropics. From a conservation perspective, it is important to know whether tropical farmlands can buffer species loss caused by deforestation and how different functional groups of birds respond to land-use intensification. To test the degree of differentiation between farmland and forest bird communities across feeding guilds, we analyzed stable C and N isotopes in blood and claws of 101 bird species comprising four feeding guilds along a tropical forest-farmland gradient in Kenya. We additionally assessed the importance of farmland insectivores for pest control in C4 crops by using allometric relationships, C stable isotope ratios and estimates of bird species abundance. Species composition differed strongly between forest and farmland bird communities. Across seasons, forest birds primarily relied on C3 carbon sources, whereas many farmland birds also assimilated C4 carbon. While C sources of frugivores and omnivores did not differ between forest and farmland communities, insectivores used more C4 carbon in the farmland than in the forest. Granivores assimilated more C4 carbon than all other guilds in the farmland. We estimated that insectivorous farmland birds consumed at least 1,000 kg pest invertebrates km−2 year−1. We conclude that tropical forest and farmland understory bird communities are strongly separated and that tropical farmlands cannot compensate forest loss for insectivorous forest understory birds. In tropical farmlands, insectivorous bird species provide a quantitatively important contribution to pest control.