Single-cell detection by gradient echo 9.4 T MRI: a parametric study.

Recent studies have shown that cell migration can be monitored in vivo by magnetic resonance imaging after intracellular contrast agent incorporation. This is due to the dephasing effect on proton magnetization of the local magnetic field created by a labelled cell. Anionic iron oxide nanoparticles (AMNP) are among the most efficient and non-toxic contrast agents to be spontaneously taken up by a wide variety of cells. Here we measured the iron load and magnetization of HeLa tumour cells labelled with AMNP, as a function of the external magnetic field. High-resolution gradient echo 9.4 T MRI detected individual labelled cells, whereas spin echo sequences were poorly sensitive. We then conducted a systematic study in order to determine the gradient echo sequence parameters (echo time, cell magnetization and resolution) most suitable for in vivo identification of single cells.

In vivo 2D magnetic resonance spectroscopy of small animals.

Localized in vivo NMR spectroscopy, chemical shift imaging or multi-voxel spectroscopy are potentially useful tools in small animals that are complementary to MRI, adding biochemical information to the mainly anatomical data provided by imaging of water protons. However the contribution of such methods remains hampered by the low spectral resolution of the in vivo 1D spectra. Two-dimensional methods widely developed for in vitro studies have been proposed as suitable approaches to overcome these limitations in resolution. The different homonuclear and heteronuclear sequences adapted to in vivo studies are reviewed. Their specific contributions to the spectral resolution of spectroscopic data and their limitations for in vivo investigations are discussed. The applications to experimental models of pathological processes or pharmacological treatment in mainly brain and muscle are presented. According to their combined sensitivity, acquisition duration and spatial resolution, the heteronuclear 2D experiments, which are mainly used for 1H detected-13C spectroscopy after administration of 13C-labeled compounds, appear to be less efficient than 1H detected-13C 1D methods at high field. However, the applications of 2D proton homonuclear methods show that they remain the best tools for in vivo studies when an improved resolution is required.

In-vivo high resolution three-dimensional MRI studies of rat joints at 7 T.

It is important to obtain high resolution images of joints for the study of disease, especially in rodent experimental models. We optimized (1)H magnetic resonance imaging three-dimensional sequences at 7 T, with lipid signal suppression, and T(1) and T(2) measurements for in-vivo experiments on rat joints, in order to assess the effectiveness of high-field MRI. The method was validated by applying it to the early diagnosis of arthritis. We studied the progress of rheumatoid arthritis in an arthritic rat model. We observed the rats' knees for 21 days after inducing arthritis. The images acquired over one hour had a high resolution of 1.75 x 10(-3) mm(3), (105 x 105 x 145 microm(3)) which allowed us to spot the early stages of joint degeneration, such as bone erosion, and to observe an apparent 'MRI' loss of cartilage thickness, attributed to dehydration of the cartilage tissue. The MR images obtained during the early stages of rheumatoid arthritis enabled us to study joint changes accurately before any histological signs of attack were visible.

Two-year stability of borderline personality measures.

Two-year stability coefficients were computed for several measures of borderline personality disorder within a nonclinical sample (n = 65) that included individuals with significant borderline features. Overall, the stability coefficients were modest (r ranging from .28 to .62; intraclass correlations ranging from .26 to .62). Stability values for each of the self-report measures under study were higher than those for the interview-based measure of BPD features, and, in some cases, these values varied as a function of the prototypicality of the subsamples examined. Analyses conducted to identify moderator effects provided no evidence that the stability of BPD scores was moderated by change in personal distress level; however, changes in BPD self-report scores were related to changes in level of negative affectivity.

Chemical modifications of the vasoconstrictor peptide angiotensin II by nitrogen oxides (NO, HNO2, HOONO)--evaluation by mass spectrometry.

Nitric oxide (NO) and angiotensin II are natural regulators of blood pressure. Under aerobic conditions, NO is transformed into its higher oxides (N2O4, NO2, NO/NO2 or N2O3) and oxoperoxonitrate (currently named peroxynitrite) by coupling with superoxide. Previous studies have shown that these reactive nitrogen species should be involved in vivo in the transformation of cysteine and tyrosine into the corresponding nitrosothiol and 3-nitrotyrosine. In the present study, attention has been focused on the relative reactivities of HNO2, peroxynitrite, and NO in the presence of dioxygen, towards the arginine and tyrosine residues of the peptide angiotensin II. Nitration of the tyrosine residue is clearly the main reaction with peroxynitrite. By contrast, besides 20% of nitration of the tyrosine residue, NO in the presence of dioxygen leads to nitrosation reactions with the arginine residue similar to those observed with HNO2 at pH 5, possibly through the intermediate N2O3 reactive species. Angiotensin II is converted for the most part to peptides having lost either a terminal amine function or the whole guanido group, leading respectively to citrulline-containing angiotensin II or to a diene derivative. Identification established mainly by tandem mass spectrometry of peptidic by-products allows us to propose a cascade of nitrosations of all the amine functions of the arginine residue. Further in vivo studies show that transformations of the arginine residue in angiotensin II do not alter its vasoconstrictive properties, whereas nitration of the tyrosine residue totally inhibits them.

Mapping the active site of factor Xa by selective inhibitors: an NMR and MD study.

The structure of two selective inhibitors, Ac-Tyr-Ile-Arg-Ile-Pro-NH2 and Ac-(4-Amino-Phe)-(Cyclohexyl-Gly)-Arg-NH2, in the active site of the blood clotting enzyme factor Xa was determined by using transferred nuclear Overhauser effect nuclear magnetic resonance (NMR) spectroscopy. They represent a family of peptidic inhibitors obtained by the screening of a vast combinatorial library. Each structure was first calculated by using standard computational procedures (distance geometry, simulated annealing, energy minimization) and then further refined by systematic search of the conformation of the inhibitor docked in the active site and repeating the simulated annealing and energy minimization. The final structure was optimized by molecular dynamics simulations of the inhibitor-complex in water. The NMR restraints were kept throughout the refinement. The inhibitors assume a compact, very well defined conformation, embedded into the substrate binding site not in the same way as a substrate, blocking thus the catalysis. The model allows to explain the mode of action, affinity, and specificity of the peptides and to map the active site.

Borderline personality disorder features in nonclinical young adults: 2. Two-year outcome.

Borderline personality disorder (BPD) is thought to develop by early adulthood, and it is characterized by lack of control of anger, intense and frequent mood changes, impulsive acts, disturbed interpersonal relationships, and life-threatening behaviors. We describe data from a 2-year follow-up study of nonclinical young adults who, at study entry, exhibited a significant number of BPD features. Individuals with borderline features were more likely to have academic difficulties over the succeeding 2 years, and these participants were more likely to meet lifetime criteria for a mood disorder and to experience interpersonal dysfunction than their peers at the 2-year follow-up assessment. These findings indicate that BPD features are associated with poorer outcome even within a nonclinical population.

Phase-sensitive two-dimensional experiment on living animals.

This report describes the first 1H-1H phased spectrum obtained in vivo from the hind-leg muscles of an intact mouse. TOCSY correlations can follow the complete spin system and give a more detailed graph of each molecule than can COSY. TOCSY is also better suited than COSY for studying long fatty-acid chains. All the peaks are in phase in a TOCSY experiment and the intensities of the cross-correlation peaks are less sensitive to low digitalization in the t1 domain than are those of COSY. The improvement in sensitivity was estimated by measuring the volumes of the cross-correlation peaks in COSY and TOCSY spectra.

In vivo 2D 1H NMR of mdx mouse muscle and myoblast cells during fusion: evidence for a characteristic signal of long chain fatty acids.

We have previously demonstrated that 2D 1H NMR is suitable for studying cerebral metabolism. The same technique was used to study the hind leg muscle of normal (C57BL10) and dystrophic (mdx) mice. The results were compared to preliminary results for cultured muscle cells to determine the origin of fatty acid signals.