1,721,475 research outputs found
Hard fairness versus proportional fairness in wireless communications: the single-cell case
No full textTechniques to assess bone ultrastructure organization: orientation and arrangement of mineralized collagen fibrils
No full textPost-processing technique for improved assessment of hard tissues in the submicrometer domain using local synchrotron radiation-based computed tomography
Full text linkDuring the last two decades micro-computed tomography has become the method of choice for the non-destructive assessment and quantitative morphometry of hard tissues in three dimensions. With the advent of third-generation synchrotron radiation sources, micro-computed tomography in the micrometer range has become feasible and has been employed to analyze local bone tissue properties. However, owing to limitations regarding the tradeoff between object size and spatial resolution, non-destructive conventional global computed tomography of hard tissues, such as bone, remains unachievable in the submicrometer domain so far. Here, we report on a post-processing technique for the assessment of hard tissues using local synchrotron radiation-based computed tomography, which overcomes this experimental limitation
Investigation of microcracks in trabecular bone using synchrotron radiation based micro-computed tomography (SR?CT)
No full textQuantitative phenotyping of bone fracture repair: a review
No full textFracture repair is a complex process that involves the interaction of numerous molecular factors, cell lineages and tissue types. These biological processes allow for an impressive feat of engineering: an elastic soft callus is progressively replaced by a more rigid and mineralized callus. During this reparative phase, the healing bone is exposed to a risk of re-fracture. Bone volume and bone quality are the two major factors determining the strength of the callus. Although both factors are important, often only bone volume is analyzed and reported in preclinical studies. Recent developments in techniques for examining bone quality in the callus will enable the rapid and detailed analysis of its material properties and its microstructure. This review aims to give an overview of the methods available for quantitatively phenotyping the bone callus in preclinical studies such as Raman spectroscopy, nanoindentation, scanning acoustic microscopy, in vivo micro-computed tomography (micro-CT) and high-resolution micro-CT. Consolidated and emerging experimental methods are described with a focus on their applicability, and with examples of their utilization
Studying osteocytes within their environment
No full textIt is widely hypothesized that osteocytes are the mechano-sensors residing in the bone's mineralized matrix which control load induced bone adaptation. Diving to their inaccessibility it has proved challenging to generate quantitative in vivo experimental data which supports this hypothesis. Recent advances in in situ imaging, both in non-living and living specimens, have provided new insights into the role of osteocytes in the skeleton. Combined with the retrieval of biochemical information from mechanically stimulated osteocytes using in vivo models, quantitative experimental data is now becoming available which is leading to a more accurate understanding of osteocyte function. With this in mind, here we review i) state of the art ex vivo imaging modalities which are able to precisely capture osteocyte structure in 3D, ii) live cell imaging techniques which are able to track structural morphology and cellular differentiation in both space and time, and iii) in vivo models which when combined with the latest biochemical assays and microfluidic imaging techniques can provide further insight on the biological function of osteocytes.This article is part of a Special Issue entitled "The Osteocyte"
Soft-tissue and phase-contrast imaging at the Swiss Light Source
No full textRecent results show that bone vasculature is a major contributor to local tissue porosity, and therefore can be directly linked to the mechanical properties of bone tissue. With the advent of third generation synchrotron radiation (SR) sources, micro-computed tomography (?CT) with resolutions in the order of 1 ?m and better has become feasible. This technique has been employed frequently to analyze trabecular architecture and local bone tissue properties, i.e. the hard or mineralized bone tissue. Nevertheless, less is known about the soft tissues in bone, mainly due to inadequate imaging capabilities. Here, we discuss three different methods and applications to visualize soft tissues. The first approach is referred to as negative imaging. In this case the material around the soft tissue provides the absorption contrast necessary for X-ray based tomography. Bone vasculature from two different mouse strains was investigated and compared qualitatively. Differences were observed in terms of local vessel number and vessel orientation. The second technique represents corrosion casting, which is principally adapted for imaging of vascular systems. The technique of corrosion casting has already been applied successfully at the Swiss Light Source. Using the technology we were able to show that pathological features reminiscent of Alzheimer"s disease could be distinguished in the brain vasculature of APP transgenic mice. The third technique discussed here is phase contrast imaging exploiting the high degree of coherence of third generation synchrotron light sources, which provide the necessary physical conditions for phase contrast. The in-line approach followed here for phase contrast retrieval is a modification of the Gerchberg-Saxton-Fienup type. Several measurements and theoretical thoughts concerning phase contrast imaging are presented, including mathematical phase retrieval. Although up-to-now only phase images have been computed, the approach is now ready to retrieve the phase for a large number of angular positions of the specimen allowing application of holotomography, which is the three-dimensional reconstruction of phase images
A quantitative framework for the 3D characterization of the osteocyte lacunar system
No full textAssessing the role of osteocyte lacunae and the ways in which they communicate with one another is important for determining the function and viability of bone tissue. Osteocytes are able to play a significant role in bone development and remodeling because they can receive nourishment from, interact with, and communicate with other cells. In this sense the immediate environment of an osteocyte is crucial for understanding its function. Modern imaging techniques, ranging from synchrotron radiation-based computed tomography (SR CT) to confocal laser scanning microscopy, produce large volumes of high-quality imaging data of bone tissue on the micrometer scale in rapidly shortening times. These images often contain tens of thousands of osteocytes and their lacunae, void spaces which enclose the osteocytes. While theoretically possible, quantitative analysis of the osteocyte lacunar system is too time consuming to be practical without highly automated tools. Moreover, quantitative morphometry of the osteocyte lacunar system necessitates clearly defined, robust, and three-dimensional (3D) measures. Here, we introduce a framework for the quantitative characterization of millions of osteocyte lacunae and their spatial relationships in 3D. The metrics complement and expand previous works looking at shape and number density while providing novel measures for quantifying spatial distribution and alignment. We developed model, in silico systems to visualize and validate the metrics and provide a concrete example of the attribute being classified with each metric. We then illustrate the applicability to biological samples in a first study comparing two strains of mice and the effect of growth hormone. We found significant differences in shape and distribution between strains for alignment. The proposed quantitative framework can be used in future studies examining differences and treatment effects in bone microstructure at the cell scale. Furthermore, the proposed strategy for quantitative bone cell morphometry will allow investigating structure–function relationships in bone tissue, for example by linking cellular morphometry to bone remodelin
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