Towards quantification of myelin by solid-state MRI of the lipid matrix protons.

Purpose: Direct assessment of myelin has the potential to reveal central nervous system abnormalities and serve as a means to follow patients with demyelinating disorders during treatment. Here, we investigated the feasibility of direct imaging and quantification of the myelin proton pool, without the many possible confounds inherent to indirect methods, via long-T suppressed 3D ultra-short echo-time (UTE) and zero echo-time (ZTE) MRI in ovine spinal cord.

Methods: ZTE and UTE experiments, with and without inversion-recovery (IR) preparation, were conducted in ovine spinal cords before and after DO exchange of tissue water, on a 9.

Tracking inflammation in the epileptic rat brain by bi-functional fluorescent and magnetic nanoparticles.

Correct localization of epileptic foci can improve surgical outcome in patients with drug-resistant seizures. Our aim was to demonstrate that systemically injected nanoparticles identify activated immune cells, which have been reported to accumulate in epileptogenic brain tissue. Fluorescent and magnetite-labeled nanoparticles were injected intravenously to rats with lithium-pilocarpine-induced chronic epilepsy.

A Surrogate Measure of Cortical Bone Matrix Density by Long T2 -Suppressed MRI.

Magnetic resonance has the potential to image and quantify two pools of water within bone: free water within the Haversian pore system (transverse relaxation time, T2 > 1 ms), and water hydrogen-bonded to matrix collagen (T2 ∼ 300 to 400 μs). Although total bone water concentration quantified by MRI has been shown to scale with porosity, greater insight into bone matrix density and porosity may be gained by relaxation-based separation of bound and pore water fractions. The objective of this study was to evaluate a recently developed surrogate measurement for matrix density, single adiabatic inversion recovery (SIR) zero echo-time (ZTE) MRI, in human bone.

Bi-component T2 * analysis of bound and pore bone water fractions fails at high field strengths.

Osteoporosis involves the degradation of the bone's trabecular architecture, cortical thinning and enlargement of cortical pores. Increased cortical porosity is a major cause of the decreased strength of osteoporotic bone. The majority of cortical pores, however, are below the resolution limit of MRI.

AMP promotes oxygen consumption and ATP synthesis in heart mitochondria through the adenylate kinase reaction: an NMR spectroscopy and polarography study.

Adenylate kinase plays an important role in cellular energy homeostasis by catalysing the interconversion of adenine nucleotides. The goal of present study was to evaluate the contribution of the adenylate kinase reaction to oxidative ATP synthesis by direct measurements of ATP using (31) P NMR spectroscopy. Results show that AMP can stimulate ATP synthesis in the presence or absence of ADP.

Expression level and subcellular localization of heme oxygenase-1 modulates its cytoprotective properties in response to lung injury: a mouse model.

Premature infants exposed to hyperoxia suffer acute and long-term pulmonary consequences. Nevertheless, neonates survive hyperoxia better than adults. The factors contributing to neonatal hyperoxic tolerance are not fully elucidated.

The molecular and metabolic influence of long term agmatine consumption.

Agmatine (AGM), a product of arginine decarboxylation, influences multiple physiologic and metabolic functions. However, the mechanism(s) of action, the impact on whole body gene expression and metabolic pathways, and the potential benefits and risks of long term AGM consumption are still a mystery. Here, we scrutinized the impact of AGM on whole body metabolic profiling and gene expression and assessed a plausible mechanism(s) of AGM action.

31P NMR relaxation of cortical bone mineral at multiple magnetic field strengths and levels of demineralization.

Recent work has shown that solid-state (1) H and (31) P MRI can provide detailed insight into bone matrix and mineral properties, thereby potentially enabling differentiation of osteoporosis from osteomalacia. However, (31) P MRI of bone mineral is hampered by unfavorable relaxation properties. Hence, accurate knowledge of these properties is critical to optimizing MRI of bone phosphorus.

Direct magnetic resonance detection of myelin and prospects for quantitative imaging of myelin density.

Magnetic resonance imaging has previously demonstrated its potential for indirectly mapping myelin density, either by relaxometric detection of myelin water or magnetization transfer. Here, we investigated whether myelin can be detected and possibly quantified directly. We identified the spectrum of myelin in the spinal cord in situ as well as in myelin lipids extracted via a sucrose gradient method, and investigated its spectral properties.

Effects of a glucokinase activator on hepatic intermediary metabolism: study with 13C-isotopomer-based metabolomics.

GKAs (glucokinase activators) are promising agents for the therapy of Type 2 diabetes, but little is known about their effects on hepatic intermediary metabolism. We monitored the fate of (13)C-labelled glucose in both a liver perfusion system and isolated hepatocytes. MS and NMR spectroscopy were deployed to measure isotopic enrichment.

Implications of noise and resolution on mechanical properties of trabecular bone estimated by image-based finite-element analysis.

Recent advances in micro-magnetic resonance imaging (microMRI) now allow noninvasive assessment of mechanical properties of trabecular bone (TB) in vivo by micro finite-element analysis. The first aim of this work was to address the implications of limited resolution and signal-to-noise ratio on elastic properties of TB derived under conditions of in vivo imaging via simulation at various resolutions and noise levels on the basis of models derived from microCT images at 21 microm isotropic voxel size from cores of cadaveric human TB (n = 13) from three anatomic sites. The second aim was to compare how elastic constants derived from actual MR images at 9.

3-isobutylmethylxanthine inhibits hepatic urea synthesis: protection by agmatine.

We previously showed that agmatine stimulated hepatic ureagenesis. In this study, we sought to determine whether the action of agmatine is mediated via cAMP signaling. A pilot experiment demonstrated that the phosphodiesterase inhibitor, 3-isobutylmethylxanthine (IBMX), inhibited urea synthesis albeit increased [cAMP].

Indirect measurement of regional axon diameter in excised mouse spinal cord with q-space imaging: simulation and experimental studies.

Q-space imaging (QSI), a diffusion MRI technique, can provide quantitative tissue architecture information at cellular dimensions not amenable by conventional diffusion MRI. By exploiting regularities in molecular diffusion barriers, QSI can estimate the average barrier spacing such as the mean axon diameter in white matter (WM). In this work, we performed ex vivo QSI on cervical spinal cord sections from healthy C57BL/6 mice at 400 MHz using a custom-designed uniaxial 50T/m gradient probe delivering a 0.

Changes in T1 and T2 observed in brain magnetic resonance imaging with delivery of high concentrations of oxygen.

Objective: The aim of this study was to clarify the relative contributions of the amount of oxygen in the blood, and vasoconstriction/dilation responsible for changes in T1 and T2 observed in brain during hyperoxia.

Methods: T1 and T2 values of the cerebral cortex and pituitary gland in mice were determined in room air. After room air was changed to either 100% oxygen (n = 8) or carbogen (n = 8), T1 and T2 values were again determined.

Metabolic and ionic coupling factors in amino acid-stimulated insulin release in pancreatic beta-HC9 cells.

Fuel stimulation of insulin secretion from pancreatic beta-cells is thought to be mediated by metabolic coupling factors that are generated by energized mitochondria, including protons, adenine nucleotides, and perhaps certain amino acids (AA), as for instance aspartate, glutamate, or glutamine (Q). The goal of the present study was to evaluate the role of such factors when insulin release (IR) is stimulated by glucose or AA, alone or combined, using (31)P, (23)Na and (1)H NMR technology, respirometry, and biochemical analysis to study the metabolic events that occur in continuously superfused mouse beta-HC9 cells contained in agarose beads and enhanced by the phosphodiesterase inhibitor IBMX. Exposing beta-HC9 cells to high glucose or 3.

Agmatine stimulates hepatic fatty acid oxidation: a possible mechanism for up-regulation of ureagenesis.

We demonstrated previously in a liver perfusion system that agmatine increases oxygen consumption as well as the synthesis of N-acetylglutamate and urea by an undefined mechanism. In this study our aim was to identify the mechanism(s) by which agmatine up-regulates ureagenesis. We hypothesized that increased oxygen consumption and N-acetylglutamate and urea synthesis are coupled to agmatine-induced stimulation of mitochondrial fatty acid oxidation.

Mineral volume and morphology in carotid plaque specimens using high-resolution MRI and CT.

Objective: High-resolution MRI methods have been used to evaluate carotid artery atherosclerotic plaque content. The purpose of this study was to assess the performance of high-resolution MRI in evaluation of the quantity and pattern of mineral deposition in carotid endarterectomy (CEA) specimens, with quantitative micro-CT as the gold standard.

Methods And Results: High-resolution MRI and CT were compared in 20 CEA specimens.

A new approach for simultaneous measurement of ADC and T2 from echoes generated via multiple coherence transfer pathways.

The study of rotational and translational diffusion requires the measurement of both T2 and apparent diffusion coefficient (ADC), quantities that are typically measured in separate experiments. The exploitation of echoes generated via multiple coherence transfer pathways offers an opportunity for measuring T2 and ADC values simultaneously in a single experiment. A series of RF pulses can generate multiple echoes via different coherence pathways with each one being uniquely encoded.

Magnetization transfer micro-MR imaging of live excised lamprey spinal cord: characterization and immunohistochemical correlation.

Background And Purpose: Membrane constituents may play a key role in the magnetization transfer (MT) effect. In lamprey spinal cord, axonal diameters range from <1 microm in the dorsal region to 20-40 microm in the ventral region. There is a corresponding range of axonal, and hence cell membrane, density.

Water content measured by proton-deuteron exchange NMR predicts bone mineral density and mechanical properties.

Unlabelled: NMR was used to measure matrix water content in normal and hypomineralized cortical bone. Water content showed an inverse relationship with mineral content, suggesting it could serve as a surrogate measure for the bone's degree of mineralization.

Introduction: So far, true bone mineral density (DMB; degree of mineralization of bone) can not be measured nondestructively.

Differential effects of glucose and glyburide on energetics and Na+ levels of betaHC9 cells: nuclear magnetic resonance spectroscopy and respirometry studies.

In the present study, noninvasive (31)P and (23)Na(+)-nuclear magnetic resonance (NMR) technology and respirometry were used to compare the effect of high glucose (30 mmol/l) with the effect of the antidiabetic sulfonylurea (SU) compound glyburide (GLY) on energy metabolism, Na(+) flux, insulin, and cAMP release of continuously superfused beta-HC9 cells encapsulated in microscopic agarose beads. Both high glucose and GLY increased oxygen consumption in beta-HC9 cells (15-30%) with a maximal effect at 8 mmol/l for glucose and at 250 nmol/l for GLY. At the same time, insulin release from beta-cells increased by 15- and 25-fold with high glucose or GLY, respectively.

Metabolism of 13C galactose by lymphoblasts from patients with galactosemia determined by NMR spectroscopy.

In order to assess the pathways by which galactose is metabolized by galactose-1-phosphate uridyltransferase (GALT) deficient cells, lymphoblasts from 10 galactosemic patients with defined genotypes (six Q188R homozygotes, two S153L homozygotes, and two with homozygous deletions) were incubated with 1mM 1- or 2-13C galactose for 2.5 and 5 h. The 13C-labeled metabolites were identified and quantified using nuclear magnetic resonance and the results were compared to that obtained with cells from eight normal individuals.

Magnetic resonance microimaging of intraaxonal water diffusion in live excised lamprey spinal cord.

Anisotropy of water diffusion in axon tracts, as determined by diffusion-weighted MRI, has been assumed to reflect the restriction of water diffusion across axon membranes. Reduction in this anisotropy has been interpreted as degeneration of axons. These interpretations are based primarily on a priori reasoning that has had little empirical validation.

Visualization of individual axons in excised lamprey spinal cord by magnetic resonance microscopy.

The direct visualization of axons within their native tissue environment by magnetic resonance (MR) microscopy is presented for the first time in the excised larval sea lamprey spinal cord. A home-built transverse radio frequency coil of 1.5 mm diameter was used in conjunction with a commercial 400 MHz MR microscopy system, implementing both 2-D and 3-D imaging pulse sequences.

Diffusion of exchangeable water in cortical bone studied by nuclear magnetic resonance.

The rate-limiting step in the delivery of nutrients to osteocytes and the removal of cellular waste products is likely diffusion. The transport of osteoid water across the mineralized matrix of bone was studied by proton nuclear magnetic resonance spectroscopy and imaging by measuring the diffusion fluxes of tissue water in cortical bone specimens from the midshaft of rabbit tibiae immersed in deuterium oxide. From the diffusion coefficient (D(a) = (7.