Deuterium double quantum-filtered NMR studies of peripheral and optic nerves.

Objective: Characterization of the nerve components by deuterium double quantum-filtered magnetization transfer (DQF-MT) NMR.

Methods: Nerves were equilibrated in deuterated saline and H single-pulse and H DQF-MT NMR spectra were measured, enabling the separation of the different water compartments, according to their quadrupolar splittings.

Results: Rat sciatic and brachial nerves and porcine optic nerve immersed in deuterated saline yielded H DQF spectra composed of three pairs of quadrupolar-split signals assigned to the water in the collagenous compartments and the myelin bilayer and one narrow signal assigned to the axonal water.

Identification of water compartments in spinal cords by H double quantum filtered NMR.

In H double quantum filtered (DQF) NMR, the various water compartments are characterized by their different residual quadrupolar interactions. The spectral separation between the different signals enables the measurement of the relaxation of each compartment and the magnetization transfer (MT) between them. In the current study, five water compartments were identified in the H DQF spectra of porcine spinal cord.

Sialo-CEST: chemical exchange saturation transfer NMR of oligo- and poly-sialic acids and the assignment of their hydroxyl groups using selective- and HSQC-TOCSY.

Chemical exchange saturation transfer (CEST) is an NMR method that takes advantage of proton exchange between solute and solvent molecules in dynamic equilibrium, enabling the detection of the solute NMR signals with enhanced sensitivity. Herein, we report that the hydroxyl groups in a naturally occurring polysaccharide, α-2,8 polysialic acid in aqueous solution, yield very significant CEST effects even at 37°C where the resonances of the hydroxyl groups are not directly observed. We also report the assignments of the hydroxyl groups for the polymer and its oligomeric building blocks, from monomer to hexamer.

Monitoring of the effect of intervertebral disc nucleus pulposus ablation by MRI.

In order to investigate intervertebral disc (IVD) degeneration and repair, a quantitative non-invasive tool is needed. Various MRI methods including qCPMG, which yields dipolar echo relaxation time (T(DE)), magnetization transfer contrast (MTC), and (1)H and (2)H double quantum filtered (DQF) MRI were used in the present work to monitor changes in rat IVD after ablation of the nucleus pulposus (NP), serving as a model of severe IVD degeneration. In the intact IVD, a clear distinction between the annulus fibrosus (AF) and the NP is obtained on T(2) and T(DE) weighted images as well as on MTC maps, reflecting the high concentration of ordered collagen fibers in the AF.

Multinuclear NMR and microscopic MRI studies of the articular cartilage nanostructure.

Studies of the structure of articular cartilage by a number of NMR spectroscopic and imaging techniques are reviewed. Advantage is taken of the fact that the NMR investigations can be done non-invasively on the intact tissue and do not require sectioning, slicing and decalcification as in the case of electron microscopy. The different contributions to 1H T2 relaxation are described and it is pointed out that ignoring the biexponential behavior of the transverse relaxation can lead to serious errors in the proton density measurements and the T2 characterization of the articular cartilage.

Comparison of the effects of mechanical and osmotic pressures on the collagen fiber architecture of intact and proteoglycan-depleted articular cartilage.

One of the functions of articular cartilage is to withstand recurrent pressure applied in everyday life. In previous studies, osmotic pressure has been used to mimic the effects of mechanical pressure. In the present study, the response of the collagen network of intact and proteoglycans (PG)-depleted cartilage to mechanical and osmotic pressures is compared.

Neotendon formation induced by manipulation of the Smad8 signalling pathway in mesenchymal stem cells.

Tissue regeneration requires the recruitment of adult stem cells and their differentiation into mature committed cells. In this study we describe what we believe to be a novel approach for tendon regeneration based on a specific signalling molecule, Smad8, which mediates the differentiation of mesenchymal stem cells (MSCs) into tendon-like cells. A biologically active Smad8 variant was transfected into an MSC line that coexpressed the osteogenic gene bone morphogenetic protein 2 (BMP2).

Multinuclear NMR and MRI studies of the maturation of pig articular cartilage.

The maturation of pig articular cartilage was followed by (2)H in-phase double quantum filtered (IP-DQF) spectroscopic MRI, (1)H T(2) MRI, and (23)Na DQF and triple quantum filtered MRS. The results all lead to the conclusion that the order and density of the collagen fibers in articular cartilage increase from birth to maturity. At birth, both (2)H IP-DQF signal and (1)H T(2) were homogeneous throughout the cartilage and their values independent of the orientation of the plug relative to the magnetic field.

The effect of decalcification on the microstructure of articular cartilage assessed by 2H double quantum filtered spectroscopic MRI.

2H quadrupolar splitting of deuterated water molecules is a sensitive measure of the order and density of the collagen fibers in articular cartilage. In the calcified zone, near the bone, two pairs of quadrupolar split satellites were previously observed. To examine whether the large splitting observed originates from the presence of calcium ions and hydroxyapatite, one-dimensional 2H single and double quantum filtered spectroscopic imaging were performed on articular cartilage-bone plugs before and after decalcification.

The effect of detachment of the articular cartilage from its calcified zone on the cartilage microstructure, assessed by 2H-spectroscopic double quantum filtered MRI.

Most studies on articular cartilage properties have been conducted after detachment of the cartilage from the bone. In the present work we investigated the effect of detachment on collagen fiber architecture. We used one-dimensional (2)H double quantum filtered MRI on cartilage bone plugs equilibrated in deuterated saline.

Mapping the fiber orientation in articular cartilage at rest and under pressure studied by 2H double quantum filtered MRI.

The one-dimensional (2)H double quantum filtered (DQF) spectroscopic imaging technique was used to study the orientation of collagen fibers in articular cartilage. The method detects only water molecules in anisotropic environments, which in cartilage is caused by their interaction with the collagen fibers. A large quadrupolar splitting was observed in the calcified zone and a smaller splitting in the radial zone.

Changes in axonal morphology in experimental autoimmune neuritis as studied by high b-value q-space (1)H and (2)H DQF diffusion magnetic resonance spectroscopy.

Experimental autoimmune neuritis (EAN) has been studied in rat sciatic nerves by a combination of high b-value (1)H and (2)H double quantum filtered (DQF) diffusion MRS. The signal decays of water in the (1)H and (2)H DQF diffusion MRS were found to be not monoexponential and were analyzed using the q-space approach. The q-space analysis of the (1)H diffusion data detected two diffusing components, one having broad and the other having narrow displacement profiles.

Copper-induced peroxidation of liposomal palmitoyllinoleoylphosphatidylcholine (PLPC), effect of antioxidants and its dependence on the oxidative stress.

In an attempt to deepen our understanding of the mechanisms responsible for lipoprotein peroxidation, we have studied the kinetics of copper-induced peroxidation of the polyunsaturated fatty acid residues in model membranes (small, unilamellar liposomes) composed of palmitoyllinoleoylphosphatidylcholine (PLPC). Liposomes were prepared by sonication and exposed to CuCl(2) in the absence or presence of naturally occurring reductants (ascorbic acid (AA) and/or alpha-tocopherol (Toc)) and/or a Cu(I) chelator (bathocuproinedisulfonic acid (BC) or neocuproine (NC)). The resultant oxidation process was monitored by recording the time-dependence of the absorbance at several wavelengths.