Selected-states magnetic-resonance spectroscopy: A potential method for huge improvement in sensitivity

The theoretical development of a method called Selected-States Magnetic-Reson ance Spectroscopy (SSMRS) is presented. The approach uses the Stern-Gerlach interaction for periodic displacement of paramagnetic elements by a periodically variable magnetic-field gradient. Measurement is performed by the method of Elasto-Magnetic–Resonance Spectroscopy (EMRS). The implementation of the proposed method has promising potential in magnetic resonance (MR), including huge improvement in sensitivity, measurement of MR parameters for selected Zeeman states and investigation of microviscosity in a medium containing paramagnetic elements

Ex-vivo magnetic resonance image texture analysis can discriminate genotypic origin in bovine meat

International audienceTexture analysis (TA) combined with dedicated gradient echo magnetic resonance imaging (MRI) at high field provides specific parametric T-2* maps of connective tissue and allows statistical analysis of the resulting texture. The present study clearly demonstrates that MRI-TA of bovine meat can discriminate between muscle types Gluteo biceps and Pectoralis profundus, and between genotype origins corresponding to the mutation on the myostatin gene: normal +/+, heterozygous mhl+ or homozygous double-muscled mh/mh Belgian White Blue bulls. Values of interclass separations reflect the significantly different collagen and fat contents in these genotypes. To our knowledge, no previous study has demonstrated such a correlation between MRI texture and genetics-related modifications

1H NMR structural characterization of the cytochrome c modifications in a micellar environment.

International audienceThe interaction of cytochrome c with micelles of sodium dodecyl sulfate was studied by proton NMR spectroscopy. The protein/micelles ratio was found to be crucial in controlling the extent of the conformational changes in the heme crevice. Over a range of ratios between 1:30 and 1:60, the NMR spectra of the ferric form display no paramagnetic signals due to a moderately fast exchange between intermediate species on the NMR time scale. This is consistent with an interconversion of bis-histidine derivatives (His18-Fe-His26 and His18-Fe-His33). Further addition of micelles induces a high-spin species that is proposed to involve pentacoordinated iron. The resulting free binding site, also encountered in the ferrous form, is used to complex exogenous ligands such as cyanide or carbon monoxide. Attribution of the heme methyls was performed by means of exchange spectroscopy through ligand exchange or electron transfer. The heme methyl shift pattern of the micellar cyanocytochrome in the ferric low spin form is different from the pattern of both the native and the cyanide cytochrome c adduct, in the absence of micelles, reflecting a complete change of the heme electronic structure. Analysis of the electron self-exchange reaction between the two redox states of the micellar cyanocytochrome c yields a rate constant of 2.4 x 10(4) M(-1) s(-1) at 298 K, which is surprisingly close to the value observed in the native protein

Magnetic resonance spectroscopy and fluorescence microscopy to investigate mobile lipids in sensitive, resistant and reverting K562 cells and their membranes.

International audienceThe erythroleukaemic K562 cell line and its adriamycin resistant counterpart were used to study resistance, its reversion and their consequences on the levels and localisation of lipids detected in proton nuclear magnetic resonance (NMR) spectra. On whole cells, the mobile lipids giving rise to a NMR signal were significantly decreased in the resistant cells when compared to the sensitive ones; these lipids recovered partially in the reverting cells. According to the spinlattice relaxation times (T1), the lipids detected appeared to be in a similar environment in sensitive and reverting cells. In membrane-enriched fractions, mobile lipid levels were not significantly different in the sensitive and reverting cell lines but decreased in resistant ones. Moreover, lipid droplets stained with a fluorescent Nile red lipophilic probe showed the presence of highly fluorescent particles in the samples in which NMR detected high levels of mobile lipids. These results suggest the participation of cytosolic lipid droplets in NMR signals in drug sensitive and reverting cells and open the question of the relative roles of these droplets and of the membrane lipids in the lipid metabolic pathways associated with drug resistance in cancer cells

An in-vivo magnetic resonance imaging study of the olfactory bulbectomized rat model of depression.

International audienceThe olfactory bulbectomized (OB) rat is a well-accepted animal model of depression. The present magnetic resonance imaging (MRI) investigation demonstrates alterations in signal intensities in cortical, hippocampal, caudate and amygdaloid regions in OB animals, but not in sham operated controls. Ventricular enlargement was also evident in OB animals. These alterations have implications with regard to the face and construct validity of this model

Is magnetic resonance imaging texture analysis a useful tool for cell therapy in vivo monitoring?

International audienceAssessment of anti-tumor treatment efficiency is usually done by measuring tumor size. Treatment may however induce changes in the tumor other than tumor size. Magnetic Resonance Imaging Texture Analysis (MRI-TA) is presently used to follow activated lymphocyte cell therapy. We used a 7T microimager to acquire high-resolution MR images of an experimental liver metastasis from colon carcinoma in rats treated (n = 4) or not (n = 3) with a cell therapy product. MRI-TA was then performed with Linear Discriminant Analysis and showed: i) a significant variation of tumor texture with tumor growth and ii) a significant modification in the texture of tumors treated with activated lymphocytes compared with untreated tumors. T2-weighted images or volume calculation did not evidence any difference. MRI-TA appears as a promising method for early detection and follow-up of response to cell therapy