Juxtacortical susceptibility changes in progressive multifocal leukoencephalopathy at the gray-white matter junction correlates with iron-enriched macrophages.

Objective: Describe magnetic resonance imaging (MRI) susceptibility changes in progressive multifocal leukoencephalopathy (PML) and identify neuropathological correlates.

Methods: PML cases and matched controls with primary central nervous system lymphoma (PCNSL) were retrospectively identified. MRI brain at 3 T and 7 T were reviewed.

A comparison of alendronate to varying magnitude PEMF in mitigating bone loss and altering bone remodeling in skeletally mature osteoporotic rats.

Pulsed electromagnetic field (PEMF) treatments stimulate bone formation activities though further work is needed to optimize its therapeutic benefit. PEMF can generate local potential gradients and electric currents that have been suggested to mimic bone electrochemical responses to load. In line with this reasoning, a recent publication reported that PEMF application on isolated bone tissue induced detectable micro-vibrations (doi:https://doi.

Substrate concentration influences effective radial diffusion coefficient in canine cortical bone.

Transport of nutrients and waste across osseous tissue is dependent on the dynamic micro and macrostructure of the tissue; however little quantitative data exists examining how this transport occurs across the entire tissue. Here we investigate in vitro radial diffusion across a section of canine tissue, at dimensions of several hundred microns to millimeters, specifically between several osteons connected through a porous microstructure of Volkmann's canals and canaliculi. The effective diffusion coefficient is measured by a "sample immersion" technique presented here, in which the tissue sample was immersed in solution for 18-30 h, image analysis software was used to quantify the solute concentration profile in the tissue, and the data were fit to a mathematical model of diffusion in the tissue.

Pulsed electromagnetic field treatment enhances healing callus biomechanical properties in an animal model of osteoporotic fracture.

Delayed bone healing has been noted in osteoporosis patients and in the ovariectomized (OVX) rat model of estrogen-depletion osteopenia. Pulsed electromagnetic field (PEMF) devices are clinically approved as an adjunct to cervical fusion surgery in patients at high risk for non-fusion and for the treatment of fracture non-unions. These bone growth stimulating devices also accelerate the healing of fresh fracture repair in skeletally mature normal rats but have not been tested for efficacy to accelerate and/or enhance the delayed bone repair process in OVX rats.

Lipids and collagen matrix restrict the hydraulic permeability within the porous compartment of adult cortical bone.

In vivo the hydraulic permeability of cortical bone influences the transport of nutrients, waste products and signaling molecules, thus influencing the metabolic functions of osteocytes and osteoblasts. In the current study two hypotheses were tested: the presence of (1) lipids and (2) collagen matrix in the porous compartment of cortical bone restricts its permeability. Our approach was to measure the radial permeability of adult canine cortical bone before and after extracting lipids with acetone-methanol, and before and after digesting collagen with bacterial collagenase.

Oxygen diffusion through natural extracellular matrices: implications for estimating "critical thickness" values in tendon tissue engineering.

Oxygen is necessary for maintaining cell proliferation and viability and extracellular matrix (ECM) production in 3-dimensional tissue engineering. Typically, diffusion is the primary mode for oxygen transport in vitro; thus, ensuring an adequate oxygen supply is essential. In this study, we determined the oxygen diffusion coefficients of 3 natural ECMs that are being investigated as construct scaffolds for tendon tissue engineering: small-intestine submucosa (SIS), human dermis (Alloderm), and canine fascia lata.

Mechanical conditioning of cell-seeded small intestine submucosa: a potential tissue-engineering strategy for tendon repair.

Our long-term objective is to enhance tendon repair by delivering cells on natural biologic scaffolds to the repair site. Clinical outcomes may be improved by first preconditioning these cell-seeded constructs in bioreactors to enhance their properties at implantation and to deliver cells expressing a desired phenotype. In this work, we have investigated the effect of in vitro mechanical conditioning on small-intestine submucosa (SIS) scaffolds seeded with primary tendon cells (tenocytes).