Three-dimensional visualization of rat brain microvasculature following permanent focal ischaemia by synchrotron radiation.

OBJECTIVE: Identifying morphological changes that occur in microvessels under both normal and ischaemic conditions is crucial for understanding and treating stroke. However, conventional imaging techniques are not able to detect microvessels on a micron or sub-micron scale without angiography. In the present study, synchrotron radiation (SR)-based X-ray in-line phase contrast imaging (ILPCI) was used to acquire high-resolution and high-contrast images of rat brain tissues in both normal and ischaemic states. METHODS: ILPCI was performed at the Shanghai Synchrotron Radiation Facility, Shanghai, China, without the use of contrast agents. CT slices were reformatted and then converted into three-dimensional (3D) reconstruction images to analyse subtle details of the cerebral microvascular network. RESULTS: By using ILPCI, brain vessels up to 11.8 µm in diameter were resolved. The number of cortical and penetrating arteries detected were found to undergo a remarkable decrease within the infarct area. 3 days after permanent ischaemia, vascular masses were also observed in the peripheral region of the infarcts. CONCLUSION: SR-based ILPCI-CT can serve as a powerful tool to accurately visualize brain microvasculature. The morphological parameters of blood vessels in both CT slices and 3D reconstructions were determined, and this approach has great potential for providing an effective diagnosis and evaluation for rehabilitation therapy for stroke. ADVANCES IN KNOWLEDGE: In the absence of contrast agent, the 3D morphologies of the brain microvasculature in normal and stroke rats were obtained using SR-based ILPCI. SR imaging is a sensitive and promising method which can be used to explore primary brain function.

Analysis of the dynamic permeation experiment with implication to cartilaginous tissue engineering.

In the present study, a I-D dynamic permeation of a monovalent electrolyte solution through a negatively charged-hydrated cartilaginous tissue is analyzed using the mechano-electrochemical theory developed by Lai et al. (1991) as the constitutive model for the tissue. The spatial distributions of stress, strain, fluid pressure, ion concentrations, electrical potential, ion and fluid fluxes within and across the tissue have been calculated. The dependencies of these mechanical, electrical and physicochemical responses on the tissue fixed charge density, with specified modulus, permeability, diffusion coefficients, and frequency and magnitude of pressure differential are determined. The results demonstrate that these mechanical, electrical and physicochemical fields within the tissue are intrinsically and nonlinearly coupled, and they all vary with time and depth within the tissue.

Streaming potential of human lumbar anulus fibrosus is anisotropic and affected by disc degeneration.

The streaming potential responses of non-degenerate and degenerate human anulus fibrosus were measured in a one-dimensional permeation configuration under static and dynamic loading conditions. The goal of this study was to investigate the influence of the changes in tissue structure and composition on the electrokinetic behavior of intervertebral disc tissues. It was found that the static streaming potential of the anulus fibrosus depended on the degenerative grade of the discs (p = 0.0001) and on the specimen orientation in which the fluid flows (p = 0.0001). For a statically applied pressure of 0.07 MPa, the ratio of streaming potential to applied pressure ranged from 5.3 to 6.9 mV/MPa and was largest for Grade I tissue with axial orientation and lowest for Grade III tissue with circumferential orientation. The dynamic streaming potential responses of anulus fibrosus were sensitive to the degeneration of the disc: the total harmonic distortion factor increased by 108%, from 3.92 +/- 0.66% (mean +/- SD) for Grade I specimens to 8.15 +/- 3.05% for Grades II and III specimens. The alteration of streaming potential reflects the changes in tissue composition and structure with degeneration. To our knowledge, this is the first reported data for the streaming potential of human intervertebral disc tissues. Knowledge of the streaming potential response of the intervertebral disc provides an understanding of potentially important signal transduction mechanisms in the disc and of the etiology of intervertebral disc degeneration.