Ralph Müller


Last Name

Müller

First Name

Ralph

ORCID

0000-0002-5811-7725

Organisational unit

03565 - Müller, Ralph / Müller, Ralph

Search Results

Publications 1 - 10 of 659
  • Automated compartmental analysis for high-throughput skeletal phenotyping in femora of genetic mouse models
    Item type: Journal Article
    Kohler, Thomas; Stauber, Martin; Donahue, Leah R.; et al. (2007)
    Bone
  • Structural reorganization and preorganization in enzyme active sites
    Item type: Journal Article
    Smith, A.J.; Müller, Ralph; Toscano, M.D.; et al. (2008)
    Journal of the American Chemical Society
  • Analysis of mechanical properties of cancellous bone under conditions of simulated bone atrophy
    Item type: Journal Article
    Müller, Ralph; Rüegsegger, Peter (1996)
    Journal of Biomechanics
  • Effects of Early Life Stress on Bone Homeostasis in Mice and Humans
    Item type: Journal Article
    Würtz-Kozak, Karin; Roszkowski, Martin; Cambria, Elena; et al. (2020)
    International Journal of Molecular Sciences
    Bone pathology is frequent in stressed individuals. A comprehensive examination of mechanisms linking life stress, depression and disturbed bone homeostasis is missing. In this translational study, mice exposed to early life stress (MSUS) were examined for bone microarchitecture (μCT), metabolism (qPCR/ELISA), and neuronal stress mediator expression (qPCR) and compared with a sample of depressive patients with or without early life stress by analyzing bone mineral density (BMD) (DXA) and metabolic changes in serum (osteocalcin, PINP, CTX-I). MSUS mice showed a significant decrease in NGF, NPYR1, VIPR1 and TACR1 expression, higher innervation density in bone, and increased serum levels of CTX-I, suggesting a milieu in favor of catabolic bone turnover. MSUS mice had a significantly lower body weight compared to control mice, and this caused minor effects on bone microarchitecture. Depressive patients with experiences of childhood neglect also showed a catabolic pattern. A significant reduction in BMD was observed in depressive patients with childhood abuse and stressful life events during childhood. Therefore, future studies on prevention and treatment strategies for both mental and bone disease should consider early life stress as a risk factor for bone pathologies.
  • The Effect of Level and Downhill Running on Cortical and Trabecular Bone in Growing Rats
    Item type: Journal Article
    Hamann, Nina; Kohler, Thomas; Müller, Ralph; et al. (2012)
    Calcified Tissue International
  • Nano-3D-printed Photochromic Objects
    Item type: Working Paper
    Ulrich, Sebastian; Wang, Xiaopu; Rottmar, Markus; et al. (2020)
    ChemRxiv
    A new class of photoresist is described for direct laser writing of photoswitchable 3D microstructures. The material comprising off-stoichiometric thiol-ene photo-clickable resins enables rapid two-photon laser processing of highly complex structures and facile post-modification with photoswitches. The microstructures were functionalized with a series of donor-acceptor Stenhouse adducts (DASAs) photoswitches with different excitation wavelength. The versatility of thiol–ene photo-click reaction enabled fine-tuning of the network structure and physical properties as well as the type and concentration of DASA photoswitches. When exposed to visible light, these microstructures exhibit excellent photo-responsiveness and undergo reversible color-changing via photoisomerization of DASA moieties. We describe that the weak fluorescence of DASAs can be used as a reporter of photoswitching, color changes, and thermal recovery, allowing the reading of DASA-containing sub-micrometric structures in 3D. This work delivers a new approach for custom microfabrication of 3D photochromic objects with molecularly engineered color and responsiveness.
  • Effects of μCT radiation on tissue engineered bone-like constructs
    Item type: Journal Article
    Kraehenbuehl, Thomas P.; Stauber, Martin; Ehrbar, Martin; et al. (2010)
    Biomedical Engineering / Biomedizinische Technik
  • A multi-stack registration technique to improve measurement accuracy and precision across longitudinal HR-pQCT scans
    Item type: Journal Article
    Whittier, Danielle E.; Walle, Matthias; Schenk, Denis; et al. (2023)
    Bone
    Background: Recent applications of high-resolution peripheral quantitative computed tomography (HR-pQCT) have demonstrated that changes in local bone remodelling can be quantified in vivo using longitudinal three-dimensional image registration. However, certain emerging applications, such as fracture healing and joint analysis, require larger multi-stack scan regions that can result in stack shift image artifacts. These artifacts can be detrimental to the accurate alignment of the bone structure across multiple timepoints. The purpose of this study was to establish a multi-stack registration protocol for evaluating longitudinal HR-pQCT images and to assess the accuracy and precision error in comparison with measures obtained using previously established three-dimensional longitudinal registration. Methods: Three same day multi-stack HR-pQCT scans of the radius (2 stacks in length) and tibia (3 stacks in length) were obtained from 39 healthy individuals who participated in a previous reproducibility study. A fully automated multi-stack registration algorithm was developed to re-align stacks within a scan by leveraging slight offsets between longitudinal scans. Stack shift severity before and after registration was quantified using a newly proposed stack-shift severity score. The false discovery rate for bone remodelling events and precision error of bone morphology and micro-finite element analysis parameters were compared between longitudinally registered scans with and without the addition of multi-stack registration. Results: Most scans (82 %) improved in stack alignment or maintained the lowest stack shift severity score when multi-stack registration was implemented. The false discovery rate of bone remodelling events significantly decreased after multi-stack registration, resulting in median false detection of bone formation and resorption fractions between 3.2 to 7.5 % at the radius and 3.4 to 5.3 % at the tibia. Further, precision error was significantly reduced or remained unchanged in all standard bone morphology and micro-finite element analysis parameters, except for total and trabecular cross-sectional areas. Conclusion: Multi-stack registration is an effective strategy for accurately aligning multi-stack HR-pQCT scans without modification of the image acquisition protocol. The algorithm presented here is a viable approach for performing accurate morphological analysis on multi-stack HR-pQCT scans, particularly for advanced application investigating local bone remodelling in vivo.
  • Local Mechanical Stimuli Regulate Bone Formation and Resorption in Mice at the Tissue Level
    Item type: Journal Article
    Schulte, Friederike A.; Ruffoni, Davide; Lambers, Floor M.; et al. (2013)
    PLoS ONE
    Bone is able to react to changing mechanical demands by adapting its internal microstructure through bone forming and resorbing cells. This process is called bone modeling and remodeling. It is evident that changes in mechanical demands at the organ level must be interpreted at the tissue level where bone (re)modeling takes place. Although assumed for a long time, the relationship between the locations of bone formation and resorption and the local mechanical environment is still under debate. The lack of suitable imaging modalities for measuring bone formation and resorption in vivo has made it difficult to assess the mechanoregulation of bone three-dimensionally by experiment. Using in vivo micro-computed tomography and high resolution finite element analysis in living mice, we show that bone formation most likely occurs at sites of high local mechanical strain (p<0.0001) and resorption at sites of low local mechanical strain (p<0.0001). Furthermore, the probability of bone resorption decreases exponentially with increasing mechanical stimulus (R2 = 0.99) whereas the probability of bone formation follows an exponential growth function to a maximum value (R2 = 0.99). Moreover, resorption is more strictly controlled than formation in loaded animals, and ovariectomy increases the amount of non-targeted resorption. Our experimental assessment of mechanoregulation at the tissue level does not show any evidence of a lazy zone and suggests that around 80% of all (re)modeling can be linked to the mechanical micro-environment. These findings disclose how mechanical stimuli at the tissue level contribute to the regulation of bone adaptation at the organ level.
Publications 1 - 10 of 659