High-resolution X-ray Micro-computed Tomography Research Articles

Effects of vegetation restoration on soil aggregate microstructure quantified with synchrotron-based micro-computed tomography

Vegetation restoration is expected to improve soil microstructure and therefore enhance soil stability and reduce soil erosion. The objective of this study was to evaluate the effect of long-term vegetation restoration on the modification of aggregate microstructure with synchrotron-based high resolution X-ray micro-computed tomography (SR-μCT). Triplicate aggregates (5-mm diameter) from (a) severely eroded bare land (BL) and (b) two decades of vegetation restoration land (RL) from Ultisol, Southern China, were collected and scanned with 9μm voxel-resolution at SSRF (Shanghai Synchrotron Radiation Facility). ImageJ software and multifractal theory were used to analyze and quantify aggregate pore structure. Aggregate water stability, mechanical stability, and basic soil properties were also evaluated. Results showed that aggregate water stability and SOM content significantly increased in the RL treatment, while aggregate mechanical stability showed an inverse trend. The microstructure of aggregates had evolved from a very dense massive microstructure to a more porous hierarchical microstructure after two decades of vegetation restoration. Porosity, macro-porosity, fraction of elongated pores, and specific surface area were significantly higher in the RL aggregates as compared to the BL aggregates. Multifractal scaling was observed for the pore structure of the studied aggregates. Generalized dimensions (Dq) were significantly higher in the RL treatment as compared to BL treatment, indicating improved pore system after vegetation restoration. This improved microstructure of RL aggregates was attributed to the increased SOM that prompted soil aggregation. This study showed the positive effects of vegetation restoration on soil microstructure and water stability, which was beneficial to the reduction of soil erosion and to the improvement of soil quality in this region.

Sustained swimming increases the mineral content and osteocyte density of salmon vertebral bone

This study addresses the effects of increased mechanical load on the vertebral bone of post-smolt Atlantic salmon by forcing them to swim at controlled speeds. The fish swam continuously in four circular tanks for 9 weeks, two groups at 0.47 body lengths (bl) × s(-1) (non-exercised group) and two groups at 2 bl × s(-1) (exercised group), which is just below the limit for maximum sustained swimming speed in this species. Qualitative data concerning the vertebral structure were obtained from histology and electron microscopy, and quantitative data were based on histomorphometry, high-resolution X-ray micro-computed tomography images and analysis of bone mineral content, while the mechanical properties were tested by compression. Our key findings are that the bone matrix secreted during sustained swimming had significantly higher mineral content and mechanical strength, while no effect was detected on bone in vivo architecture. mRNA levels for two mineralization-related genes bgp and alp were significantly upregulated in the exercised fish, indicating promotion of mineralization. The osteocyte density of the lamellar bone of the amphicoel was also significantly higher in the exercised than non-exercised fish, while the osteocyte density in the cancellous bone was similar in the two groups. The vertebral osteocytes did not form a functional syncytium, which shows that salmon vertebral bone responds to mechanical loading in the absence of an extensive connecting syncytial network of osteocytic cell processes as found in mammals, indicating the existence of a different mechanosensing mechanism. The adaptive response to increased load is thus probably mediated by osteoblasts or bone lining cells, a system in which signal detection and response may be co-located. This study offers new insight into the teleost bone biology, and may have implications for maintaining acceptable welfare for farmed salmon.

Three-Dimensional Analysis of the Vestibular End Organs in Relation to the Stapes Footplate and Piston Placement

Measurements of the proximity of the membranous labyrinth to the stapes footplate show considerable variation. Largely, such measurements have been from histologic sections of fixed temporal bones, which may be affected by shrinkage artifact and perspective distortion in the 2-dimensional plane. To overcome these problems, the present study undertook an analysis of the 3-dimensional (3D) architecture of the relationship of the stapes to the membranous labyrinth using high-resolution X-ray micro-computed tomography. Eleven temporal bones were fixed with Karnovsky's fixative (known to minimize shrinkage), soaked in 2% osmium tetroxide, and scanned in a micro-computed tomography scanner. The otic capsule was intact to exclude sectioning artifact, and no alcohol was used to avoid tissue shrinkage. Measurements were taken in a vertical plane to provide distances from the utricle and saccule to the footplate, and 3D reconstruction of the spatial relationship of these structures was carried out. The relationship of these structures to a stapes piston also was studied. The safest area of piston placement was the central and inferior part of the footplate. This was safe up to 0.5 mm depth at all areas except posterosuperiorly where the utricular macula is, on average, only 0.61 mm away from the footplate. The angle of insertion of the piston also influences the end result. Two-dimensional information about vestibular end organ location should serve as a guideline only because the operative field is 3D, and the relationship of the piston to the vestibular labyrinth changes with the angle of placement.

Glucocorticoid-Induced Osteoporosis in Growing Mice Is Not Prevented by Simultaneous Intermittent PTH Treatment

Glucocorticoids (GCs) are widely used in medicine for treatment of chronic diseases. Especially in children, prolonged treatment causes growth retardation and early onset of osteoporosis. Human parathyroid hormone (PTH) has an anabolic effect on bone when administrated intermittently. The aim of the present study was to examine whether a combined therapy of dexamethasone (DEX) and PTH could prevent the detrimental effects of GC on cortical and trabecular bone in the femur and vertebrae of growing mice. Three-week-old female FVB mice were treated with control, DEX, PTH, or a combination of DEX and PTH by daily subcutaneous injections. After 4 weeks, animals were killed and the femur and L5 vertebra were isolated. Cortical and trabecular bone parameters and relative calcium density were measured by high-resolution X-ray micro-computed tomography (micro-CT). In the femur, PTH can reverse the effects of DEX on bone volume to control. However, it cannot reverse the undermineralization, which most likely is a strong contributor to bone fragility. In the vertebra, PTH improves bone volume to some extent but does not restore the values to normal. It augments the negative effect of DEX on mineralization. We conclude that the detrimental effects of DEX in the growing skeleton cannot be prevented by simultaneous PTH treatment.

Correlation of High-Resolution X-Ray Micro-Computed Tomography with Bioluminescence Imaging of Multiple Myeloma Growth in a Xenograft Mouse Model

Multiple myeloma (MM) is an incurable B-cell neoplasia in which progressive skeletal lesions are a characteristic feature. Earlier we established an animal model for human MM in the immune-deficient RAG2-/-γc-/- mouse, in which the growth of luciferase-transduced MM cells was visualized using noninvasive bioluminescence imaging (BLI). This model appeared well suited to study disease progression and response to therapy by identifying the location of various foci of MM tumor growth scattered throughout the skeleton and at subsequent time points the quantitative assessment of the tumor load by using BLI. We report here on the corresponding high-resolution X-ray micro-computed tomographic (micro-CT) analysis to study skeletal defects in the mice with full-blown MM. Several anatomical derangements were observed, including abnormalities in geometry and morphology, asymmetrical bone structures, decreased overall density in the remaining bone, loss of trabecular bone mass, destruction of the inner microarchitecture, as well as cortical perforations. Using the combination of BLI, micro-CT imaging, and immune-histopathological techniques, we found a high correlation between the micro-CT-identified lesions, exact tumor location, and infiltration leading to structural lesions and local bone deformation. This confirms that this animal model strongly resembles human MM and has the potential for studying the biology of MM growth and for preclinical testing of novel therapies for MM and for repair of MM-induced bone lesions.

Fumonisins in Maize: Can We Reduce Their Occurrence?

Fumonisins in Maize: Can We Reduce Their Occurrence?