The β-phosphorus hyperfine coupling constant in nitroxide: part 3: titration of water by electron paramagnetic resonance.

Recently, we showed that the phosphorus hyperfine coupling constant aPβ of persistent cyclic nitroxides decreased with the normalized polarity Reichardt's constant E. Thus, we investigated the changes in aPβ in binary mixtures of solvents. The sensitivity of aPβ to the solvent was high enough to allow us to perform water titration in THF, 1,4-dioxane, and acetonitrile by EPR.

Alkoxyamines: toward a new family of theranostic agents against cancer.

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) = 50 min at 37 °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 (OMRI).

Accurate determination of the oxidative phosphorylation affinity for ADP in isolated mitochondria.

Background: Mitochondrial dysfunctions appear strongly implicated in a wide range of pathologies. Therefore, there is a growing need in the determination of the normal and pathological integrated response of oxidative phosphorylation to cellular ATP demand. The present study intends to address this issue by providing a method to investigate mitochondrial oxidative phosphorylation affinity for ADP in isolated mitochondria.

Real-time 3D MRI of contrast agents in whole living mice.

A specific mouse whole body coil and a dedicated gradient system at 4.7 T were coupled with an ultra-fast 3D gradient echo MRI and keyhole reconstruction technique to obtain 3D whole-body dynamic T(1)-weighted or T(2)*-weighted imaging. The technique was used to visualize the real-time distribution of non-targeting T(1) and T(2)* contrast agent (CA) in a glioma-bearing mouse model.

Acetate and succinate production in amoebae, helminths, diplomonads, trichomonads and trypanosomatids: common and diverse metabolic strategies used by parasitic lower eukaryotes.

Parasites that often grow anaerobically in their hosts have adopted a fermentative strategy relying on the production of partially oxidized end products, including lactate, glycerol, ethanol, succinate and acetate. This review focuses on recent progress in understanding acetate production in protist parasites, such as amoebae, diplomonads, trichomonads, trypanosomatids and in the metazoan parasites helminths, as well as the succinate production pathway(s) present in some of them. We also describe the unconventional organisation of the tricarboxylic acid cycle associated with the fermentative strategy adopted by the procyclic trypanosomes, which may resemble the probable structure of the primordial TCA cycle in prokaryotes.

4D retrospective black blood trueFISP imaging of mouse heart.

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.

Alteration of mitochondrial oxidative phosphorylation in aged skeletal muscle involves modification of adenine nucleotide translocator.

The process of skeletal muscle aging is characterized by a progressive loss of muscle mass and functionality. The underlying mechanisms are highly complex and remain unclear. This study was designed to further investigate the consequences of aging on mitochondrial oxidative phosphorylation in rat gastrocnemius muscle, by comparing young (6 months) and aged (21 months) rats.

Trypanosomatid genomes contain several subfamilies of ingi-related retroposons.

Retroposons are ubiquitous transposable elements found in the genomes of most eukaryotes, including trypanosomatids. The African and American trypanosomes (Trypanosoma brucei and Trypanosoma cruzi) contain long autonomous retroposons of the ingi clade (Tbingi and L1Tc, respectively) and short nonautonomous truncated versions (TbRIME and NARTc, respectively), as well as degenerate ingi-related retroposons devoid of coding capacity (DIREs). In contrast, Leishmania major contains only remnants of extinct retroposons (LmDIREs) and of short nonautonomous heterogeneous elements (LmSIDERs).

In vivo quantification of blood velocity in mouse carotid and pulmonary arteries by ECG-triggered 3D time-resolved magnetic resonance angiography.

Blood flow velocity is a functional parameter of fundamental importance in diagnosis and follow-up of various vascular diseases. Vascular pathologies can be efficiently studied in animal models, especially in small rodents. ECG-gated magnetic resonance imaging (MRI) assessment of blood velocity in small animals is a challenge because of limited spatial resolution and high-frequency physiological parameters.

Role of transposable elements in trypanosomatids.

Transposable elements constitute 2-5% of the genome content in trypanosomatid parasites. Some of them are involved in critical cellular functions, such as the regulation of gene expression in Leishmania spp. In this review, we highlight the remarkable role extinct transposable elements can play as the source of potential new functions.

Fumarate is an essential intermediary metabolite produced by the procyclic Trypanosoma brucei.

The procyclic stage of Trypanosoma brucei, a parasitic protist responsible for sleeping sickness in humans, converts most of the consumed glucose into excreted succinate, by succinic fermentation. Succinate is produced by the glycosomal and mitochondrial NADH-dependent fumarate reductases, which are not essential for parasite viability. To further explore the role of the succinic fermentation pathways, we studied the trypanosome fumarases, the enzymes providing fumarate to fumarate reductases.

Improvement in production and purification bioprocesses of bacterially expressed anti-alphaIIbbeta3 human single-chain FV antibodies.

Production of anti-alphaIIbbeta3 (anti-alphaIIbbeta3)-binding single-chain FV (scFv) fragments obtained from combinatorial libraries of IgG human antibodies is of broad interest for imaging and treatment of acute coronary syndromes. The objective of our work was to design an optimized production of one selected anti-alphaIIbbeta3-binding scFv fragment for subsequent in vivo animal studies. Fed-batch fermentation was initiated with 2TY media supplemented with 0.

Spatial and temporal control of transgene expression in vivo using a heat-sensitive promoter and MRI-guided focused ultrasound.

Background: Among the techniques used to induce and control gene expression, a non-invasive, physical approach based on local heat in combination with a heat-sensitive promoter represents a promising alternative but requires accurate temperature control in vivo. MRI-guided focused ultrasound (MRI-FUS) with real-time feedback control allows automatic execution of a predefined temperature-time trajectory. The purpose of this study was to demonstrate temporal and spatial control of transgene expression based on a well-defined local hyperthermia generated by MRI-FUS.

Functional MRI of the kidney.

Functional MR imaging of the kidney has a great potential of development because the functional parameters, which can be approached noninvasively, are multiple: glomerular filtration, tubular concentration and transit, blood volume and perfusion, diffusion, and oxygenation. Until now, its limitations in clinical applications are due to the difficulties in obtaining reproducible and reliable information in this mobile organ and, sometimes, in understanding the physiologic substrate of the signal changes observed. These approaches require either endogeneous contrast agents, such as water protons (for perfusion and diffusion) or deoxyhemogobin (for oxgenation), or exogeneous contrast agents such as gadolinium chelates (for filtration and perfusion) or iron oxide particles (for perfusion).

Top down analysis ceramide-induced mitochondrial dysfunctions: role of mitochondrial swelling.

Mitochondrial role in ceramide-induced apoptosis pathway remains unclear. Direct effects of ceramide on mitochondria (cytochrome c release, respiratory chain inhibition, oxygen radicals production..

Single-coil surface imaging using a radiofrequency field gradient.

A method for in-plane imaging of large objects as compared to the RF coil is proposed based on the use of a single specially designed surface coil, without using B(0) gradients. A constant B(1) gradient was generated along the main axis of a ladder-shaped coil, and RF-encoding along the direction of the gradient made it possible to obtain spin-density profiles. Successive acquisitions of profiles obtained by translation of the NMR coil resulted in distorted images-due to the presence of non-zero gradients perpendicular to the constant gradient-that were successfully processed using a mathematical treatment based on linear combinations of calculated altered images from single-pixel objects.

Aminomethylphosphonate and 2-aminoethylphosphonate as (31)P-NMR pH markers for extracellular and cytosolic spaces in the isolated perfused rat liver.

Aminomethylphosphonate (NMePo) and 2-aminoethylphosphonate (NEthPo) were evaluated as alternative pH indicators in the isolated perfused rat liver using (31)P-nuclear magnetic resonance (NMR). NMePo did not distribute within cells and remained in the extracellular space. It exhibited pH titration with a low pK(a) value (5.

An echo-shifted gradient-echo MRI method for efficient diffusion weighting.

A segmented magnetic resonance imaging (MRI) method is introduced with time-efficient diffusion weighting resulting in total imaging times similar to those of single-shot methods. The approach is based on the principles of echo shifting with a train of observations (PRESTO) MRI sequence. The time efficiency of the sequence is based on the use of diffusion gradient pulses that also serve to shift the echo train to the next TR period, resulting in TE > TR.

Role of intracellular buffering power on the mitochondria-cytosol pH gradient in the rat liver perfused at 4 degrees C.

The factors regulating the amplitude and the pH gradient between cytosol and mitochondria (DeltapHmito-cyt) were investigated in the isolated rat liver perfused at 4 degrees C. Liver ATP content, pH, and buffering power of cytosolic and mitochondrial compartments were evaluated in situ using phosphorus-31 nuclear magnetic resonance spectroscopy. No DeltapHmito-cyt was detected in the liver perfused without bicarbonate.

Flow cytometric analysis of mitochondrial activity in situ: application to acetylceramide-induced mitochondrial swelling and apoptosis.

Changes in mitochondrial matrix volume were studied both on isolated mitochondria and in situ on CHME 5 human microglia and monoblastoid U 937 cells using multiparametric flow cytometric analysis. The use of specific effectors of mitochondrial activity (oligomycin and KCN) allowed the demonstration, on whole cells, of a strict correlation between light scattering and mitochondrial volume changes: mitochondrial swelling induced a concomitant increase in forward scattering, and decrease in side scattering of the cell population. The technique was applied to the study of the early phases of acetyl-ceramide-induced apoptosis, which has been associated with mitochondrial dysfunction in several cellular systems.

Mitochondrial permeability transition during hypothermic to normothermic reperfusion in rat liver demonstrated by the protective effect of cyclosporin A.

The purpose of this study was to test the hypothesis that mitochondrial permeability transition might be implicated in mitochondrial and intact organ dysfunctions associated with damage induced by reperfusion after cold ischaemia. Energetic metabolism was assessed continuously by 31P-NMR on a model system of isolated perfused rat liver; mitochondria were extracted from the livers and studied by using top-down control analysis. During the temperature transition from hypothermic to normothermic perfusion (from 4 to 37 degrees C) the ATP content of the perfused organ fell rapidly, and top-down metabolic control analysis of damaged mitochondria revealed a specific control pattern characterized by a dysfunction of the phosphorylation subsystem leading to a decreased response to cellular ATP demand.

Cytosolic pH regulation in perfused rat liver: role of intracellular bicarbonate production.

The contribution of metabolic bicarbonate to cytosolic pH (pHcyto) regulation was studied on isolated perfused rat liver using phosphorus-31 NMR spectroscopy. Removal of external HCO3- decreased proton efflux from 18.6+/-5.

Magnetization transfer imaging of rat brain under non-steady-state conditions. Contrast prediction using a binary spin-bath model and a super-lorentzian lineshape.

Magnetization transfer contrast imaging using turbo spin echo and continuous wave off-resonance irradiation was carried out on rat brain in vivo at 4.7 T. By systematically varying the off-resonance irradiation power and the offset-frequency, the signal intensities obtained under steady-state for both transverse and longitudinal magnetization were successfully analyzed with a simple binary spin-bath model taking into account a free water compartment and a pool of protons with restricted motions bearing a super-Lorentzian lineshape.

Magnetization transfer fast imaging of implanted glioma in the rat brain at 4.7 T: interpretation using a binary spin-bath model.

C6 glioma cells were implanted in the left caudate nucleus of the rat brain. Histologic studies confirmed the presence of neoplastic tissue surrounded by a thin edematous region. Proton magnetization transfer contrast (MTC) fast imaging, using continuous wave off-resonance irradiation, was performed in vivo at 4.

Analysis of carbon metabolism in cultured cerebellar and cortical astrocytes.

Carbon metabolism was investigated in cerebellar and cortical astrocytes cultured for 15 or 35 days. The consumption rates of exogenous carbon sources--amino acids and glucose--and the production rates of exported metabolites--citrate, lactate, alanine and glutamine--were determined. The specific 13C-enrichment of lactate and glutamine carbons were determined after cell incubation with [1-13C]glucose.