Biomedical subjects

Klaus Mueller

Publications and source records attributed to Klaus Mueller.

5 recordsLinked to original sources

PubMed2006

Effect of the reduction of superoxide dismutase 1 and 2 or treatment with alpha-tocopherol on tumorigenesis in Atm-deficient mice.

Atm-deficient mice, a cancer-prone model of the human disease ataxia-telangiectasia, display increased levels of oxidative stress and damage. Chronic treatment of these mice with the nitroxide antioxidant and superoxide dismutase (SOD) mimetic Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) resulted in an increased latency to tumorigenesis. We initially hypothesized that the chemopreventative effect of Tempol was due to its SOD mimetic activity reducing cellular oxidative stress and damage. However, it is also possible that the chemopreventative effect of Tempol results from mechanisms other than directly reducing superoxide radical-induced oxidative stress and damage. To help distinguish between these possibilities, we attempted to genetically increase oxidative stress in Atm-deficient mice by either removing cytosolic Sod1 or reducing mitochondrial Sod2, or we attempted to decrease oxidative stress by treatment of Atm-deficient mice with alpha-tocopherol. Surprisingly, we found that reducing both Atm and Sod1 or Atm and Sod2 did not shorten latency to tumorigenesis or significantly affect life span. Furthermore, continuous administration of alpha-tocopherol did not affect latency to thymic lymphomas. Thus, genetically reducing Sod in Atm-deficient mice or treatment with alpha-tocopherol had no effect on survival or tumorigenesis, suggesting that the chemopreventative effect of Tempol may be at least partially independent of its effects on reducing oxidative damage and stress.

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PubMed2005

Primary intrasellar schwannoma: clinical, aetiopathological and surgical considerations.

Schwannomas originating within the sella turcica are extremely rare. We describe the clinical, radiological and intraoperative findings of a patient with an intrasellar and suprasellar schwannoma. Gross total tumour removal was performed by a trans-sphenoidal approach. Perivascular or ectopic Schwann cells, lateral nerve plexus within the cavernous sinus, as well as Schwann cells from small nerve twigs of the dura are some of the current histopathological hypotheses for the origin of these lesions.

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PubMed2002

Changes in brain functional homogeneity in subjects with Alzheimer's disease.

Imaging studies have reported marked reductions in brain glucose metabolism in Alzheimer's Disease (AD). However, less is known about disruptions in the patterns of brain metabolic activity. Here we questioned whether AD affects the patterns of homogeneity/heterogeneity in brain metabolism. PET images of 35 AD subjects were compared with those of 35 controls. A template was applied to extract a cortical rim, which was partitioned into 990 contiguous regions. Estimates of metabolic homogeneity were obtained using the coefficient of variation (CV). The CV of the entire cortex was found to be significantly larger in AD, suggesting increased heterogeneity at the whole brain level. In contrast, regional CV was significantly lower in AD in temporal and parietal cortices, which were the regions that along with the precuneus had the largest metabolic decrements, though the precuneus had increased CV. The enhanced heterogeneity for the global cortical pattern most likely reflects variability in the degree of pathology among brain regions as well as neuroanatomical disconnection. The enhanced homogeneity in parietal and temporal cortices is likely to reflect loss of regional differentiation (i.e. macrocolumnar disorganization). The enhanced CV in precuneus, despite its marked reductions in metabolism, suggests that increases in regional homogeneity in parietal and temporal cortices are not a mere reflection of the decrement in metabolism.

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PubMedDate not supplied

The Lattice-boltzmann method for simulating gaseous phenomena.

We present a physically-based, yet fast and simple method to simulate gaseous phenomena. In our approach, the incompressible Navier-Stokes (NS) equations governing fluid motion have been modeled in a novel way to achieve a realistic animation. We introduce the Lattice Boltzmann Model (LBM), which simulates the microscopic movement of fluid particles by linear and local rules on a grid of cells so that the macroscopic averaged properties obey the desired NS equations. The LBM is defined on a 2D or 3D discrete lattice, which is used to solve fluid animation based on different boundary conditions. The LBM simulation generates, in real-time, an accurate velocity field and can incorporate an optional temperature field to account for the buoyancy force of hot gas. Because of the linear and regular operations in each local cell of the LBM grid, we implement the computation in commodity texture hardware, further improving the simulation speed. Finally, textured splats are used to add small scale turbulent details, achieving high-quality real-time rendering. Our method can also simulate the physically correct action of stationary or mobile obstacles on gaseous phenomena in real-time, while still maintaining highly plausible visual details.

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PubMedDate not supplied

Visual simulation of heat shimmering and mirage.

We provide a physically-based framework for simulating the natural phenomena related to heat interaction between objects and the surrounding air. We introduce a heat transfer model between the heat source objects and the ambient flow environment, which includes conduction, convection, and radiation. The heat distribution of the objects is represented by a novel temperature texture. We simulate the thermal flow dynamics that models the air flow interacting with the heat by a hybrid thermal lattice Boltzmann model (HTLBM). The computational approach couples a multiple-relaxation-time LBM (MRTLBM) with a finite difference discretization of a standard advection-diffusion equation for temperature. In heat shimmering and mirage, the changes in the index of refraction of the surrounding air are attributed to temperature variation. A nonlinear ray tracing method is used for rendering. Interactive performance is achieved by accelerating the computation of both the MRTLBM and the heat transfer, as well as the rendering on contemporary graphics hardware (GPU).

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