The use of microgel iron oxide nanoparticles in studies of magnetic resonance relaxation and endothelial progenitor cell labelling.

In vivo tracking of stem cells after transplantation is crucial for understanding cell-fate and therapeutic efficacy. By labelling stem cells with magnetic particles, they can be tracked by Magnetic Resonance Imaging (MRI). We previously demonstrated that microgel iron oxide nanoparticle (MGIO) provide superior tracking sensitivity over commercially available particles.

Microgel iron oxide nanoparticles for tracking human fetal mesenchymal stem cells through magnetic resonance imaging.

Stem cell transplantation for regenerative medicine has made significant progress in various injury models, with the development of modalities to track stem cell fate and migration post-transplantation being currently pursued rigorously. Magnetic resonance imaging (MRI) allows serial high-resolution in vivo detection of transplanted stem cells labeled with iron oxide particles, but has been hampered by low labeling efficiencies. Here, we describe the use of microgel iron oxide (MGIO) particles of diameters spanning 100-750 nm for labeling human fetal mesenchymal stem cells (hfMSCs) for MRI tracking.

In vivo assessment of mouse hindleg intramyocellular lipids by 1H-MR spectroscopy.

Rationale And Objectives: (1)H-magnetic resonance spectroscopy ((1)H-MRS) has proved to be the sole in vivo technique able to measure intramyocellular lipids (IMCL) in both humans and animals. Mouse models are now widely used for physiologic studies and drug discovery. However, IMCL assessment using (1)H-MRS is hindered in this animal model by the small muscle size and strong contamination from the extramyocellular lipid (EMCL) signal.

Biomimetic MRI contrast agent for imaging of inflammation in atherosclerotic plaque of ApoE-/- mice: a pilot study.

Objective: Atherosclerosis involves an inflammatory process characterized by cellular and molecular responses. A slow-clearance blood-pool paramagnetic agent (CMD-A2-Gd-DOTA: P717) chemically modified to create a functionalized product (F-P717) for targeting inflammation in vessel walls was evaluated in vivo in mice.

Methods And Results: Carboxylate and sulfate groups were grafted onto the macromolecular paramagnetic Gd-DOTA-dextran backbone.

Effects of chloramphenicol on brain energy metabolism using 31P spectroscopy: influences on sleep-wake states in rat.

Effects of chloramphenicol (antibiotic inhibiting complex-1 of respiratory chain) and thioamphenicol (TAP, a structural analog of CAP inactive on complex-1) were examined on cerebral energy metabolites and sleep-wake cycle architecture in rat. In the first group, animals were chronically equipped with a cranial surface resonator and (31)P spectroscopic measurements were performed using a 2 T magnetic resonance spectrometer (operating frequency 34.46 MHz).

High-resolution contrast-enhanced MRI of atherosclerosis with digital cardiac and respiratory gating in mice.

Atherosclerosis initially develops predominantly at the aortic root and carotid origin, where effective visualization in mice requires efficient cardiac and respiratory gating. The present study sought to first compare the high-resolution MRI gating performance of two digital gating strategies using: 1) separate cardiac and respiratory signals (double-sensor); and 2) a single-sensor cardiorespiratory signal (ECG demodulation), and second, to apply an optimized processing technique to dynamic contrast-enhanced (CE) carotid origin vessel-wall imaging in mice. High-resolution MR mouse heart and aortic arch images were acquired by ECG signal detection, digital signal processing, and gating signal generation modeled using Simulink (MathWorks, USA).

Real-time gating system for mouse cardiovascular MR imaging.

Mouse cardiac MR gating using ECG is affected by the hostile MR environment. It requires appropriate signal processing and correct QRS detection, but gating software methods are currently limited. In this study we sought to demonstrate the feasibility of digital real-time automatically updated gating methods, based on optimizing a signal-processing technique for different mouse strains.

Reference signal extraction from corrupted ECG using wavelet decomposition for MRI sequence triggering: application to small animals.

Background: Present developments in Nuclear Magnetic Resonance (NMR) imaging techniques strive for improved spatial and temporal resolution performances. However, trying to achieve the shortest gradient rising time with high intensity gradients has its drawbacks: It generates high amplitude noises that get superimposed on the simultaneously recorded electrophysiological signals, needed to synchronize moving organ images. Consequently, new strategies have to be developed for processing these collected signals during Magnetic Resonance Imaging (MRI) examinations.

Sucrose solution freezing studied by magnetic resonance imaging.

Ice formation of a 20% w/v sucrose solution was monitored during the freezing process by magnetic resonance imaging (MRI). An original experimental setup was designed with oil as a cooling fluid that allows accurate control of the temperature. The NMR signal intensity of particular sampled volumes was observed during the entire cooling period, from 0 to -50 degrees C, showing a peak characteristic to a transition before the loss of the signal.

In vivo magnetic resonance imaging of large spontaneous aortic aneurysms in old apolipoprotein E-deficient mice.

Unlabelled: Old ApoE-deficient mice were studied in vivo by magnetic resonance imaging (MRI) to prospectively evaluate vascular remodeling associated with atherosclerotic lesions.

Material And Methods: Old female ApoE-/- mice on a normal diet were followed by MRI at 2 Tesla for a 3-month period and killed for histopathology. Aortic dimensions were measured and compared.

Kinetics of anaerobic metabolism in human skeletal muscle: influence of repetitive high-intensity exercise on sedentary dominant and non-dominant forearm. A 31P NMR study.

Potential differences were assessed between the dominant (D) and non-dominant (ND) forearms of sedentary subjects during anaerobic exercise. Subjects performed voluntary concentric contractions of D and ND forearm muscle during a series of three high-intensity (60% of the maximal voluntary contraction force (MVC)) exercise bouts. The time-dependent changes in intracellular pH (pH(i)), Pi, and PCr concentrations, and their relation to muscular work were examined using 31P magnetic resonance spectroscopy (MRS) techniques, and revealed that D forearm metabolic kinetics in sedentary individuals are improved during repetitive high-intensity exercise compared to their respective ND forearm muscle.

Retrospective intra-scan motion correction.

This paper analyzes the effects of intra-scan motion and demonstrates the possibility of correcting them directly in k-space with a new automatic retrospective method. The method is presented for series of 2D acquisitions with Cartesian sampling. Using a reference k-space acquisition (corrected for translations) within the series, intra-scan motion parameters are accurately estimated for each trajectory in k-space of each data set in the series resulting in pseudo-random sample positions.

High-resolution magnetic resonance imaging at 2 Tesla: potential for atherosclerotic lesions exploration in the apolipoprotein E knockout mouse.

Introduction: The aim of the present study was to evaluate the potential of high-resolution MRI at 2 Tesla (T) for direct noninvasive imaging of the aortic wall in a mouse model of atherosclerosis.

Material And Methods: A specific mouse antenna was developed and sequence parameters were adjusted. T(1)- and T2-weighted images of abdominal aorta were obtained at 2 T with a spatial resolution of 86 x 86 x 800 microm3 in vivo.

Trabecular alveolar bone in the human mandible: a dual-energy x-ray absorptiometry study.

Objective: The purpose of this study was to evaluate the potential use of dual energy x-ray absorptiometry for the assessment of bone mineral content and bone mineral density before implant placement.

Materials And Methods: The material examined consisted of 63 mandibular bone specimens cut from 21 fresh cadavers (11 men; 10 women). Three specimens were cut per cadaver in the incisal, premolar, and molar regions.

[NMR radiofrequency microcoil design: usefulness of electromagnetic simulation].

The extraction of the Nuclear Magnetic Resonance (NMR) spectra of samples having smaller and smaller volumes is a real challenge. Either these reductions of volume are dictated by the difficulties of production of sufficiently large samples or by necessities of miniaturisation of the analysing system, in both cases a careful design of the radiofrequency coil, ensuring an optimum reception of the NMR signal, is required. We have also evaluated the usefulness of electromagnetic simulation software for the design and optimisation of these radio-frequency coils, which are more and more used in biology and health research projects.