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International audience; Cost-effective and portable MRI systems operating at Earth-field would be helpful in poorly accessible areas or in developing nations. Furthermore Earth-field MRI can provide new contrasts opening the way to the observation of pathologies at the biochemical level. However low-field MRI suffers from a dramatic lack in detection sensitivity even worsened for molecular imaging purposes where biochemical specificity requires detection of dilute compounds. In a preliminary spectroscopic approach, it is proposed here to detect protease-driven hydrolysis of a nitroxide probe thanks to electron-nucleus Overhauser enhancement in a home-made double resonance system in Earth-field. The combination of the Overhauser effect and the specific enzymatic modification of the probe provides a smart contrast reporting the enzymatic activity. The nitroxide probe is a six-line nitroxide which lines are shifted according to its substrate/product state, which requires quantum mechanical calculations to predict EPR line frequencies and Overhauser enhancements at Earth field. The NMR system is equipped with a 13-mT prepolarization coil, a 153-MHz EPR coil and a 2-kHz NMR coil. Either prepolarized NMR or DNP-NMR without prepolarization provide NMR spectra within 3 min. The frequency dependence of Overhauser enhancement was in agreement with theoretical calculations. Protease-mediated catalysis of the nitroxide probe could only be measured through the Overhauser effect with 5 min time resolution. Future developments shall open the way for the design of new low-field DNP-MRI systems.

T1 and T2 relaxation times combined with 31 P spectroscopy have been proven efficient for muscular disease characterization as well as for pre- and post-muscle stimulation measurements. Even though 31 P spectroscopy can already be performed during muscle exercise, no method for T1 and T2 measurement enables this possibility. In this project, a complete setup and protocol for multi-parametrical MRI of the rat gastrocnemius before, during and after muscle stimulation at 4.7 and 7 T is presented. The setup is fully MRI compatible and is composed of a cradle, an electro-stimulator and an electronic card in order to synchronize MRI sequences with muscle stimulation. A 2D triggered radial-encoded Look-Locker sequence was developed, and enabled T1 measurements in less than 2 min on stimulated muscle. Also, a multi-slice multi-echo sequence was adapted and synchronized for T2 measurements as well as 31 P spectroscopy acquisitions in less than 4 min in both cases on stimulated muscle. Methods were validated on young rats using different stimulation paradigms. Then they were applied on older rats to compare quantification results, using the different stimulation paradigms, and allowed observation of metabolic changes related to aging with good reproducibility. The robustness of the whole setup shows wide application opportunities.

International audience; Lactate is an efficient neuronal energy source, even in presence of glucose. However, the importance of lactate shuttling between astrocytes and neurons for brain activation and function remains to be established. For this purpose, metabolic and hemodynamic responses to sensory stimulation have been measured by functional magnetic resonance spectroscopy and blood oxygen level-dependent (BOLD) fMRI after down-regulation of either neuronal MCT2 or astroglial MCT4 in the rat barrel cortex. Results show that the lactate rise in the barrel cortex upon whisker stimulation is abolished when either transporter is down-regulated. Under the same paradigm, the BOLD response is prevented in all MCT2 down-regulated rats, while about half of the MCT4 down-regulated rats exhibited a loss of the BOLD response. Interestingly, MCT4 down-regulated animals showing no BOLD response were rescued by peripheral lactate infusion, while this treatment had no effect on MCT2 down-regulated rats. When animals were tested in a novel object recognition task, MCT2 down-regulated animals were impaired in the textured but not in the visual version of the task. For MCT4 down-regulated animals, while all animal succeeded in the visual task, half of them exhibited a deficit in the textured task, a similar segregation into two groups as observed for BOLD experiments. Our data demonstrate that lactate shuttling between astrocytes and neurons is essential to give rise to both neurometabolic and neurovascular couplings, which form the basis for the detection of brain activation by functional brain imaging techniques. Moreover, our results establish that this metabolic cooperation is required to sustain behavioral performance based on cortical activation.

This chapter presents the local context of Smith’s stay in Toulouse. The capital of the Languedoc was inhabited by many British people, mainly elements of the Jacobite diaspora. Smith and his pupil found there a remarkable guide, Abbe Colbert of Castlehill, a Scot, born in Inverness in a Presbyterian family, thanks to whom the Grand Colbert had been able to claim an aristocratic ascendance, who entered a career in the Gallican Church and was vicar general of Lomenie de Brienne, Archbishop of Toulouse, and future minister of Louis XVI. Contrarily to Smith, Abbe Colbert was very fond of correspondence and social networks, hence the numerous anecdotes he supplied on Smith in Toulouse. Townshend’s letter to the Duke presents the traveller’s duties in detail.

At the end of 1764, Smith and the Duke attended the annual session of the Estates of Languedoc in Montpellier. The composition of the Estates was complicated as it combined a representation by orders and a representation of the territories. During the following months spent in Toulouse, the travellers from Scotland were much more integrated in the local elites. Smith was especially close to the Riquets who were the heirs of Pierre Riquet, the builder of the Canal of Languedoc. The Riquets were in charge of the management of the Canal which was celebrated by Smith in the Wealth of Nations. At the end of their stay, Smith took down the testimony of Abbe Colbert in the Douglas Case.

This chapter deals with the circumstances of Adam Smith’s visit in (visit to or stay in) Toulouse. When he left Britain for his only voyage on the continent, Adam Smith was 42 years old. After his studies at the University of Glasgow, he had enrolled in the University of Oxford. His book the Theory of Moral Sentiments, whose first edition was published in 1759, had brought him some fame. The book had been quickly translated into French. It had drawn the attention of Charles Townshend, a British politician, later Chancellor of the Exchequer, who charged Smith to accompany his stepson with accompanying the future Duke of Buccleuch during this Grand Tour. The proposal was very attractive as it allowed Smith to meet the French Philosophers and obtain a comfortable retribution.

This chapter considers the Calas affair that made Toulouse famous (or infamous) at the beginning of the 1760s. The city was the seat of a very old university since 1229, whose foundation was imposed on the Count of Toulouse after the crusade against the Albigeois, whose crushing was followed by the imposition of a strict Catholicism. The city also had a riding Academy, several freemason lodges, and several societes savantes. But the city life was dominated by an important Parlement, which considered itself as a part of the sovereignty in the Kingdom of France. This Parlement did not hesitate to contest the King’s decisions and played a decisive part in the condemnation of Jean Calas. Smith published some reflections on the martyrdom of Calas in the Theory of Moral Sentiments (TMS) last edition.

Alkoxyamine 1 is selectively hydrolyzed by chymotrypsin and substilisin A into alkoxyamine 2H+ for which C–ON bond homolysis occurred with a 4-fold increase in rate constants compared to 1 while non-specific proteases had no effect. This highlights the triggering effect of enzymes. This is a proof of concept for a theranostic approach for treating solid tumors using enzyme-activated alkoxyamines releasing a cytotoxic alkyl radical and a stable nitroxide as a contrast agent for Overhauser-enhanced MRI.

Nuclear magnetic resonance (NMR) spectroscopy offers the opportunity to measure cerebral metabolite contents in vivo and noninvasively. Thanks to technological developments over the last decade and the increase in magnetic field strength, it is now possible to obtain good resolution spectra in vivo in the rat brain. Neuroenergetics (i.e., the study of brain metabolism) and, especially, metabolic interactions between the different cell types have attracted more and more interest in recent years. Among these metabolic interactions, the existence of a lactate shuttle between neurons and astrocytes is still debated. It is, thus, of great interest to perform functional proton magnetic resonance spectroscopy (1H-MRS) in a rat model of brain activation and monitor lactate. However, the methyl lactate peak overlaps lipid resonance peaks and is difficult to quantify. The protocol described below allows metabolic and lactate fluctuations to be monitored in an activated brain area. Cerebral activation is obtained by whisker stimulation and 1H-MRS is performed in the corresponding activated barrel cortex, whose area is detected using blood-oxygen-level-dependent functional magnetic resonance imaging (BOLD fMRI). All steps are fully described: the choice of anesthetics, coils, and sequences, achieving efficient whisker stimulation directly in the magnet, and data processing.

WOS:000434089500009; International audience; A nitroxide carrying a peptide specific to the binding pocket of the serine proteases chymotrypsin and cathepsin G is prepared. This peptide is attached as an enol ester to the nitroxide. Upon enzymatic hydrolysis of the peptide, the enol ester moiety is transformed into a ketone moiety. This transformation affords a difference of 5G in phosphorus hyperfine coupling constant between the electronic paramagnetic resonance (EPR) signals of each nitroxide. This property is used to monitor the enzymatic activity of chymotrypsin and cathepsin G by EPR. Michaelis constants were determined and match those reported for conventional optical probes.

WOS:000445759000010; International audience; Pulmonary inflammatory diseases are a major burden worldwide. They have in common an influx of neutrophils. Neutrophils secrete unchecked proteases at inflammation sites consequently leading to a protease/inhibitor imbalance. Among these proteases, neutrophil elastase is responsible for the degradation of the lung structure via elastin fragmentation. Therefore, monitoring the protease/inhibitor status in lungs non-invasively would be an important diagnostic tool. Herein we present the synthesis of a MeO-Suc-(Ala)(2)-Pro-Val-nitroxide, a line-shifting elastase activity probe suitable for Electron Paramagnetic Resonance spectroscopy (EPR) and Overhauser-enhanced Magnetic Resonance Imaging (OMRI). It is a fast and sensitive neutrophil elastase substrate with K-m = 15 +/- 2.9 mu M, k(cat)/K-m = 930,000 s(-1) M-1 and K-m = 25 +/- 5.4 mu M, k(cat)/K-m = 640,000 s(-1) M-1 for the R and S isomers, respectively. These properties are suitable to detect accurately concen trations of neutrophil elastase as low as 1 nM. The substrate was assessed with broncho-alveolar lavages samples derived from a mouse model of Pseudomonas pneumonia. Using EPR spectroscopy we observed a clear-cut difference between wild type animals and animals deficient in neutrophil elastase or deprived of neutrophil Elastase, Cathepsin G and Proteinase 3 or non-infected animals. These results provide new preclinical ex vivo and in vivo diagnostic methods. They can lead to clinical methods to promote in time lung protection.

There is an increasing interest in developing novel imaging strategies for sensing proteolytic activities in intact organisms in vivo. Overhauser-enhanced MRI (OMRI) offers the possibility to reveal the proteolysis of nitroxide-labeled macromolecules thanks to a sharp decrease of the rotational correlation time of the nitroxide moiety upon cleavage. In this paper, this concept is illustrated in vivo at 0.2 T using nitroxide-labeled elastin orally administered in mice. In vitro, this elastin derivative was OMRI-visible and gave rise to high Overhauser enhancements (19-fold at 18 mm nitroxide) upon proteolysis by pancreatic porcine elastase. In vivo three-dimensional OMRI detection of proteolysis was carried out. A keyhole fully balanced steady-state free precession sequence was used, which allowed 3D OMRI acquisition within 20 s at 0.125 mm(3) resolution. About 30 min after mouse gavage, proteolysis was detected in the duodenum, where Overhauser enhancements were 7.2 ± 2.4 (n = 7) and was not observed in the stomach. Conversely, orally administered free nitroxides or pre-digested nitroxide-labeled elastin were detected in the mouse's stomach by OMRI. Combined with specific molecular probes, this Overhauser-enhanced MRI technique can be used to evaluate unregulated proteolytic activities in various models of experimental diseases and for drug testing.

Overhauser-enhanced MRI (OMRI) offers the potentiality of detecting low-concentrated species generated by specific biological processes. However molecular imaging applications of OMRI need significant improvement in spatial localization. Here it is shown that 3D-OMRI of a free radical injected in tumor-bearing mice can be performed at high anatomical resolution at a constant field. A 30 mm cavity operating at 5.43 GHz was inserted in a C-shaped magnet for proton MRI at 0.194 T. Nude mice with or without brain-implanted C6 rat glioma were positioned in the cavity and injected with TOPCA (1-oxyl-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrole-3-carboxylic acid). OMRI was performed in 3D within several minutes in the brain region without high overheating of the animals. Voxel size was 0.5 × 0.5 × 1 mm3, providing good delineation of brain regions. Signal amplifications ranged from 2 in tumors to 10 in vessels several minutes after TOPCA injection. Time-course of signal enhancement could be measured by 2D OMRI at 15 s time intervals in a localized thin slice. The method opens the way for molecular imaging of biological activities able to generate OMRI-visible free radicals. Copyright © 2012 John Wiley & Sons, Ltd.

Superconducting quantum interference filters, or SQIFs, are a promising class of highly sensitive magnetometers benefiting from a highly peaked and symmetric magnetic response at zero-input flux. They can be used in magnetometry, e.g., in wideband applications. A simple solution to increase further their sensitivity is to add a superconducting flux concentrator (SFC) to their design. Using the ion irradiation process, we designed a meander-shaped SQIF enhanced with an SFC. The SFC improved the SQIF transfer factor by a factor of 8.4. However, high temperature superconducting (HTSc) devices are vulnerable to flux pinning, which can severely hinder their response. On the one hand, HTSc technologies alleviate the burden of cryogenics. On the other hand, applications that use SFCs in noisy and unshielded environments will become possible only if a better understanding of how this flux impacts the device’s properties is achieved. We studied the relationship between the field present during the cooling process of the SQIF antenna (thereafter called “cooling field”) and the evolution of its DC response. We developed a simple and phenomenological model and were able to reproduce the degradation of the SQIF response. This work demonstrates the usability of SFC-enhanced SQIFs based on ion irradiated junctions in rather harsh conditions, in particular, an unshielded environment, and also gives an insight into the implications that such conditions cause on the application of SFCs in general.

The noninvasive imaging of atherosclerotic plaques at an early stage of atherogenesis remains a major challenge for the evaluation of the pathologic state of patients at high risk of acute coronary syndromes. Recent studies have emphasized the importance of platelet–endothelial cell interactions in atherosclerosis-prone arteries at early stages, and the prominent role of P-selectin in the initial loose contact between platelets and diseased vessel walls. A specific MR contrast agent was developed here for the targeting, with high affinity, of P-selectin expressed in large amounts on activated platelets and endothelial cells. For this purpose, PEGylated dextran/iron oxide nanoparticles [PEG, poly(ethylene glycol)], named versatile ultrasmall superparamagnetic iron oxide (VUSPIO) particles, labeled with rhodamine were coupled to an anti-human P-selectin antibody (VH10). Flow cytometry and microscopy experiments on human activated platelets were highly correlated with MRI (performed at 4.7 and 0.2 T), with a 50% signal decrease in T2 and T1 values corresponding to the strong labeling of activated vs resting platelets. The number of 1000 VH10–VUSPIO nanoparticles attained per activated platelet appeared to be optimal for the detection of hypo- and hyper-signals in the platelet pellet on T2- and T1-weighted MRI. Furthermore, in vivo imaging of atherosclerotic plaques in ApoE mice at 4.7 T showed a spatial resolution adapted to the imaging of intimal thickening and a hypo-signal at 4.7 T, as a result of the accumulation of VH10–VUSPIO nanoparticles in the plaque. Our work provides support for the further assessment of the use of VH10–VUSPIO nanoparticles as a promising imaging modality able to identify the early stages of atherosclerosis with regard to the pertinence of both the target and the antibody-conjugated contrast agent used. Copyright © 2010 John Wiley & Sons, Ltd.

The purpose of this study was to demonstrate the feasibility of steady-state True fast imaging with steady precession (TrueFISP) four-dimensional imaging of mouse heart at high resolution and its efficiency for cardiac volumetry. Three-dimensional cine-imaging of control and hypoxic mice was carried out at 4.7 T without magnetization preparation or ECG-triggering. The k-space lines were acquired with the TrueFISP sequence (pulse repetition time/echo time = 4/2 ms) in a repeated sequential manner. Retrospective reordering of raw data allowed the reconstruction of 10 three-dimensional images per cardiac cycle. The acquisition scheme used an alternating radiofrequency phase and sum-of-square reconstruction method. Black-blood three-dimensional images at around 200 mum resolution were produced without banding artifact throughout the cardiac cycle. High contrast to noise made it possible to estimate cavity volumes during diastole and systole. Right and left ventricular stroke volume was significantly higher in hypoxic mice vs controls (20.2 +/- 2 vs 15.1 +/- 2; P < 0.05, 24.9 +/- 2 vs 20.4 +/- 2; P < 0.05, respectively). In conclusion, four-dimensional black-blood TrueFISP imaging in living mice is a method of choice to investigate cardiac abnormalities in mouse models.

Purpose To examine the ability of TrueFISP imaging for evaluating tumor size in mouse brain at high field. Materials and Methods Brains of healthy and glioma-implanted nude mice were imaged at 4.7T and 9.4T. 3D imaging was performed with TrueFISP and T2w-RARE. Radiofrequency pulses with alternating phase and the sum-of-squares reconstruction method were used in TrueFISP imaging. The contrast-to-noise ratio (CNR) was evaluated in healthy and in tumoral brain regions. Results Banding artifact was correctly suppressed in TrueFISP images thanks to the method used. The signal-to-noise ratio (SNR) and CNR were comparable in TrueFISP and T2w-RARE images at 4.7T, but acquisition was around 4 times shorter with TrueFISP. Tumor was well detected at 4.7T with TrueFISP, but CNR between tumor and healthy tissue was low at 9.4T. Conclusion TrueFISP is efficient and fast to perform brain imaging at 4.7T. Multiple TrueFISP acquisitions with phase-cycled radiofrequency (RF) pulses and sum-of-squares reconstruction allow suppression of banding artifact. Tumoral regions were well detected and the method allows longitudinal studies of tumor growth. J. Magn. Reson. Imaging 2008;28:497–503. © 2008 Wiley-Liss, Inc.

International audience; Invivo investigations of enzymatic processes using non-invasive approaches are a long-lasting challenge. Recently, we showed that Overhauser-enhanced MRI is suitable to such a purpose. A -phosphorylated nitroxide substrate prototype exhibiting keto-enol equilibrium upon enzymatic activity has been prepared. Upon enzymatic hydrolysis, a large variation of the phosphorus hyperfine coupling constant (a(P)=4G) was observed. The enzymatic activities of several enzymes were conveniently monitored by electronic paramagnetic resonance (EPR). Using a 0.2T MRI machine, invitro and invivo OMRI experiments were successfully performed, affording a 1200% enhanced MRI signal invitro, and a 600% enhanced signal invivo. These results highlight the enhanced imaging potential of these nitroxides upon specific enzymatic substrate-to-product conversion.

International audience; Two commercial statistical copolymers of ethylene oxide and propylene oxide, Jeffamine (R) M-2005 (PEO5-st-PPO37) and M-2070 (PEO46-st-PPO13), exhibiting lower critical solution temperature (LCST) in water, were grafted onto the surface of ultra-small superparamagnetic iron oxide nanoparticles (USPIOs) using silanization and amide-bond coupling reactions. The LCSTs of the polymers in solution were measured by dynamic light scattering (DLS) and nuclear magnetic resonance (NMR). In accordance with the compositions of EO vs. PO, the transition temperature was measured to be 22 +/- 2 degrees C for M-2005 by both DLS and NMR, while the LCST was much higher, 52 +/- 2 degrees C, for M-2070 (a second transition was also detected above 80 degrees C by NMR in that case, ascribed to the full dehydration of chains at the molecular level). The resulting polymer-grafted USPIOs exhibit a temperature-responsive colloidal behaviour, their surface reversibly changing from hydrophilic below LCST to hydrophobic above it. This phenomenon was utilised to design thermo-sensitive contrast agents for MRI. Transverse relaxivities (r(2)) of the USPIO@PEO5-st-PPO37 core-shell nanoparticles were measured at 8.25, 20, 60, and 300 MHz. Nuclear magnetic resonance dispersion (NMRD) profiles, giving longitudinal relaxivities (r(1)) between 0.01 and 60 MHz, were acquired at temperatures ranging from 15 to 50 degrees C. For all tested frequencies except 300 MHz, both r(1) and r(2) decrease with temperature and show an inflection point at 25 degrees C, near the LCST. To illustrate the interest of such polymer-coated USPIOs for MRI thermometry, sample tubes were imaged on both low-field (8.25 MHz/0.194 Tesla) and high-field (300 MHz/7.05 Tesla) MRI scanners with either T-1-or T-2*-weighted spin echo sequences. The positive contrast on low-field MR images and the perfect linearity of the signal with a T-2*-weighted sequence over the entire temperature range 15-50 degrees C render these LCST polymer coated USPIOs interesting positive contrast agents, also working as "nano-thermometers".

The model of the cooperatives is a model that have already studied. Nevertheless the situations of the marginalized populations remain difficult in our country. This article aims to find some possible solutions that can be developped using this a network of cooperatives to help varius population to cooperate., Le modèle de la coopérative est un modèle déjà bien étudié dans nos économies. Les situations des personnes marginalisées demeurent délicates dans nos pays. Cet article se propose aux regards de situations décrites d’explorer des axes de solutions.

International audience; Theranostics combines therapeutic and diagnostic or drug deposition monitoring abilities of suitable molecules. Here we describe the first steps of building an alkoxyamine-based theranostic agent against cancer. The labile alkoxyamine ALK-1 (t(1/2) = min at 37 degrees C) cleaves spontaneously to generate (1) a highly reactive free alkyl radical used as therapeutic agents to induce cell damages leading to cell death and (2) a stable nitroxide used as contrast agent for Overhauser-enhanced magnetic resonance imaging (OMR). The ALK-1 toxicity was studied extensively in vitro on the glioblastoma cell line U87-MG. Cell viability appeared to be dependent on ALK-1 concentration and on the time of the observation following alkoxyamine treatment. For instance, the LC50 at 72 h was 250 mu M. Data showed that cell toxicity was specifically due to the in situ released alkyl radical. This radical induced oxidative stress, mitochondrial changes, and ultimately the U87 cell apoptosis. The nitroxide production, during the alkoxyamine homolysis, was monitored by OMRI, showing a progressive MRI signal enhancement to 6-fold concomitant to the ALK-1 homolysis. In conclusion, we have demonstrated for the first time that the alkoxyamines are promising molecules to build theranostic tools against solid tumors.

Development of anti-cancerous theranostic agents is a vivid field. This article describes a theranostic approach that relies on the triggering of cancer cell death by generation of alkyl radicals at the right place and at the right time using the presence of active proteases in the tumour environment. Alkoxyamines (R1R2NOR3) are labile molecules that homolyze into nitroxides (R1R2NO˙) and reactive alkyl radicals (R3˙). They are used as a source of active alkyl radicals for curing and nitroxides for monitoring by Overhauser-enhanced magnetic resonance imaging (OMRI). Herein, the requirements needed for applying alkoxyamines are described: (i) highly selective activation of the alkoxyamine by specific proteases; (ii) fast homolysis of the alkoxyamine C–ON bond at physiological temperature; (iii) activation of cell death processes through an increase of the local oxidative stress or potential re-activation of the immune system due to short-lived alkyl radicals; and (iv) imaging of the tumor and the drug release by sensing the nitroxide by OMRI.

International audience; Development of anti-cancerous theranostic agents is a vivid field. This article describes a theranostic approach that relies on the triggering of cancer cell death by generation of alkyl radicals at the right place and at the right time using the presence of active proteases in the tumour environment. Alkoxyamines ((RRNOR3)-R-1-N-2) are labile molecules that homolyze into nitroxides ((RRNO center dot)-R-1-N-2) and reactive alkyl radicals (R-3 center dot). They are used as a source of active alkyl radicals for curing and nitroxides for monitoring by Overhauser-enhanced magnetic resonance imaging (OMRI). Herein, the requirements needed for applying alkoxyamines are described: (i) highly selective activation of the alkoxyamine by specific proteases; (ii) fast homolysis of the alkoxyamine C-ON bond at physiological temperature; (iii) activation of cell death processes through an increase of the local oxidative stress or potential re-activation of the immune system due to short-lived alkyl radicals; and (iv) imaging of the tumor and the drug release by sensing the nitroxide by OMRI.

There is an increasing interest in developing novel imaging strategies for sensing proteolytic activities in intact organisms in vivo. Overhauser-enhanced MRI (OMRI) offers the possibility to reveal the proteolysis of nitroxide-labeled macromolecules thanks to a sharp decrease of the rotational correlation time of the nitroxide moiety upon cleavage. In this paper, this concept is illustrated in vivo at 0.2 T using nitroxide-labeled elastin orally administered in mice. In vitro, this elastin derivative was OMRI-visible and gave rise to high Overhauser enhancements (19-fold at 18 mm nitroxide) upon proteolysis by pancreatic porcine elastase. In vivo three-dimensional OMRI detection of proteolysis was carried out. A keyhole fully balanced steady-state free precession sequence was used, which allowed 3D OMRI acquisition within 20 s at 0.125 mm(3) resolution. About 30 min after mouse gavage, proteolysis was detected in the duodenum, where Overhauser enhancements were 7.2 ± 2.4 (n = 7) and was not observed in the stomach. Conversely, orally administered free nitroxides or pre-digested nitroxide-labeled elastin were detected in the mouse's stomach by OMRI. Combined with specific molecular probes, this Overhauser-enhanced MRI technique can be used to evaluate unregulated proteolytic activities in various models of experimental diseases and for drug testing.

A funding organization and grant for the fifth author were incorrectly omitted from the Funding Statement. The following sentence should be read as the second sentence of the Funding Statement: "Neha Koonjoo was supported by TRAILDNP from the public grant of the French 'Agence Nationale de la Recherche' within the context of the Investments for the Future Program, referenced ANR-10-LABX-57 and named TRAIL."

Overhauser-enhanced MRI (OMRI) offers the potentiality of detecting low-concentrated species generated by specific biological processes. However molecular imaging applications of OMRI need significant improvement in spatial localization. Here it is shown that 3D-OMRI of a free radical injected in tumor-bearing mice can be performed at high anatomical resolution at a constant field. A 30 mm cavity operating at 5.43 GHz was inserted in a C-shaped magnet for proton MRI at 0.194 T. Nude mice with or without brain-implanted C6 rat glioma were positioned in the cavity and injected with TOPCA (1-oxyl-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrole-3-carboxylic acid). OMRI was performed in 3D within several minutes in the brain region without high overheating of the animals. Voxel size was 0.5 × 0.5 × 1 mm³ , providing good delineation of brain regions. Signal amplifications ranged from 2 in tumors to 10 in vessels several minutes after TOPCA injection. Time-course of signal enhancement could be measured by 2D OMRI at 15 s time intervals in a localized thin slice. The method opens the way for molecular imaging of biological activities able to generate OMRI-visible free radicals.

Emeline Julie Ribot1,2, Line Pourtau1,3, Philippe Massot1,3, Pierre Voisin1,3, Eric Thiaudiere1,3, JeanMichel Franconi1,3 and Sylvain Miraux1,3 1Centre de Resonance Magnetique des Systemes Biologiques, Universite Bordeaux Segalen, CNRS 2Imaging Research Laboratories, Robarts Research Institute, The University of Western Ontario 3Laboratory of Excellence TRAIL, Translational Research and Advanced Imaging Laboratory, University of Bordeaux 1,3France 2Canada

International audience; The noninvasive imaging of atherosclerotic plaques at an early stage of atherogenesis remains a major challenge for the evaluation of the pathologic state of patients at high risk of acute coronary syndromes. Recent studies have emphasized the importance of platelet-endothelial cell interactions in atherosclerosis-prone arteries at early stages, and the prominent role of P-selectin in the initial loose contact between platelets and diseased vessel walls. A specific MR contrast agent was developed here for the targeting, with high affinity, of P-selectin expressed in large amounts on activated platelets and endothelial cells. For this purpose, PEGylated dextran/iron oxide nanoparticles [PEG, poly(ethylene glycol)], named versatile ultrasmall superparamagnetic iron oxide (VUSPIO) particles, labeled with rhodamine were coupled to an anti-human P-selectin antibody (VH10). Flow cytometry and microscopy experiments on human activated platelets were highly correlated with MRI (performed at 4.7 and 0.2 T), with a 50% signal decrease in T(2) and T(1) values corresponding to the strong labeling of activated vs resting platelets. The number of 1000 VH10-VUSPIO nanoparticles attained per activated platelet appeared to be optimal for the detection of hypo- and hyper-signals in the platelet pellet on T(2) - and T(1) -weighted MRI. Furthermore, in vivo imaging of atherosclerotic plaques in ApoE mice at 4.7 T showed a spatial resolution adapted to the imaging of intimal thickening and a hypo-signal at 4.7 T, as a result of the accumulation of VH10-VUSPIO nanoparticles in the plaque. Our work provides support for the further assessment of the use of VH10-VUSPIO nanoparticles as a promising imaging modality able to identify the early stages of atherosclerosis with regard to the pertinence of both the target and the antibody-conjugated contrast agent used. Copyright © 2010 John Wiley & Sons, Ltd.

Levosimendan is a calcium sensitizer developed for the treatment of heart failure. It increases contractile force by enhancing the sensitivity of myofilaments to calcium. Besides this sensitizing effect, the drug has also been reported to show some inhibitory action on phosphodiesterase 3 (PDE3). The inotropic effects of levosimendan have been studied on guinea pig paced perfused hearts by using modular control analysis (MoCA) (Diolez P, Deschodt-Arsac V, Raffard G, Simon C, Santos PD, Thiaudiere E, Arsac L, Franconi JM. Am J Physiol Regul Integr Comp Physiol 293: R13–R19, 2007.), an integrative approach of heart energetics using noninvasive31P NMR. The aim was to evaluate quantitatively the respective effects of this drug on energy supply and demand modules. Under our experimental conditions, 0.7 μM levosimendan induced a 45% increase in paced heart output associated with a 7% decrease in phosphocreatine and a negligible increase in oxygen consumption. Because MoCA allows in situ study of the internal regulations in intact beating heart energetics, it was applied to describe quantitatively by which routes levosimendan exerts its inotropic action. MoCA demonstrated the absence of any significant effect of the drug on the supply module, which is responsible for the lower increase in oxygen consumption, compared with epinephrine, which increases the ratio between myocardial oxygen consumption and cardiac contraction. This result evidences that, under our conditions, a possible effect of levosimendan on PDE3 activity and/or intracellular calcium remains very low on mitochondrial activity and insignificant on integrated cardiac energetics. Thus, levosimendan inotropic effect on guinea pig heart depends almost entirely on the calcium-sensitizing properties leading to myofilament activation and the concomitant activation of energy supply by the decrease in PCr, therefore improving energetic efficiency of contraction.

The purpose of this study was to demonstrate the feasibility of steady-state True fast imaging with steady precession (TrueFISP) four-dimensional imaging of mouse heart at high resolution and its efficiency for cardiac volumetry. Three-dimensional cine-imaging of control and hypoxic mice was carried out at 4.7 T without magnetization preparation or ECG-triggering. The k-space lines were acquired with the TrueFISP sequence (pulse repetition time/echo time = 4/2 ms) in a repeated sequential manner. Retrospective reordering of raw data allowed the reconstruction of 10 three-dimensional images per cardiac cycle. The acquisition scheme used an alternating radiofrequency phase and sum-of-square reconstruction method. Black-blood three-dimensional images at around 200 mum resolution were produced without banding artifact throughout the cardiac cycle. High contrast to noise made it possible to estimate cavity volumes during diastole and systole. Right and left ventricular stroke volume was significantly higher in hypoxic mice vs controls (20.2 +/- 2 vs 15.1 +/- 2; P0.05, 24.9 +/- 2 vs 20.4 +/- 2; P0.05, respectively). In conclusion, four-dimensional black-blood TrueFISP imaging in living mice is a method of choice to investigate cardiac abnormalities in mouse models.

9 pages; International audience; Background: Proteolysis, involved in many processes in living organisms, is tightly regulated in space and time under physiological conditions. However deregulation can occur with local persistent proteolytic activities, e.g. in inflammation, cystic fibrosis, tumors, or pancreatitis. Furthermore, little is known about the role of many proteases, hence there is a need of new imaging methods to visualize specifically normal or disease-related proteolysis in intact bodies. Methodology/Principal Findings: In this paper, a new concept for non invasive proteolysis imaging is proposed. Overhauser-enhanced Magnetic Resonance Imaging (OMRI) at 0.2 Tesla was used to monitor the enzymatic hydrolysis of a nitroxide-labeled protein. In vitro, image intensity switched from 1 to 25 upon proteolysis due to the associated decrease in the motional correlation time of the substrate. The OMRI experimental device used in this study is consistent with protease imaging in mice at 0.2 T without significant heating. Simulations show that this enzymatic-driven OMRI signal switch can be obtained at lower frequencies suitable for larger animals or humans. Conclusions/Significance: The method is highly sensitive and makes possible proteolysis imaging in three dimensions with a good spatial resolution. Any protease could be targeted specifically through the use of taylor-made cleavable macromolecules. At short term OMRI of proteolysis may be applied to basic research as well as to evaluate therapeutic treatments in small animal models of experimental diseases.

An inversion recovery (IR) artifact was used to delineate the blood/wall boundary in left ventricles. The artifact consisted of a hypointensity signal in pixels located at the boundary of two contiguous tissues with different T1 relaxation times. The feasibility of measuring the ejection fraction using the artifact was tested in ten healthy volunteers, with two IR snapshot-FLASH sequences possessing different times of repetition (TR = 11msec and TR = 3.5msec) and appropriate times of inversion. The comparison with a cine-MRI sequence showed that ejection fraction measurements are feasible when performed with a snapshot-FLASH sequence that has a sufficiently short TR (3.5msec). J. Magn. Reson. Imaging 2001;13:461–466. © 2001 Wiley-Liss, Inc.

Objectifs Le premier objectif est de presenter l’instrumentation utile pour la realisation d’explorations morphologiques, fonctionnelles et metaboliques sur le petit animal par IRM (aimant, systeme de gradients, antennes …). Les specifications requises pour ces materiels seront aussi abordees. Le second objectif est de presenter des sequences d’aquisition qui vont mobiliser l’instrumentation decrite precedemment dans la realisation d’investigations en haute resolution sur le petit animal. Resume L’IRM est la methode d’imagerie non invasive qui possede la resolution spatiale la plus elevee au cœur d’organes vivants opaques. La possibilite de realiser des explorations volumiques, associee a la richesse et au caractere modulable des contrastes entre les tissus, en font un outil de choix pour l’imagerie du petit animal. Il est cependant necessaire d’utiliser une instrumentation differente de celle utilisee classiquement en imagerie radiologique. L’indispensable augmentation de la resolution spatiale requiere l’acquisition de systemes de gradients tres intenses. La diminution du rapport signal sur bruit induite par la reduction de la taille du voxel necessite la mise en place d’une veritable strategie d’optimisation de la sensibilite. Celle-ci conditionne le choix de l’intensite de l’aimant, la selection des antennes et le type de sequences a mettre en œuvre. Conclusion Afin de lever le verrou de la faible sensibilite de la mesure, de nombreuses voies sont actuellement explorees. Elles solicitent des modifications instrumentales, l’utilisation d’agents de contraste ou de sequences d’acquisition specifiques.