Non-invasive quantification of brain glycogen absolute concentration.

The only currently available method to measure brain glycogen in vivo is 13C NMR spectroscopy. Incorporation of 13C-labeled glucose (Glc) is necessary to allow glycogen measurement, but might be affected by turnover changes. Our aim was to measure glycogen absolute concentration in the rat brain by eliminating label turnover as variable.

Gadonanotubes as ultrasensitive pH-smart probes for magnetic resonance imaging.

With their nanoscalar, superparamagnetic Gd(3+)-ion clusters (1 x 5 nm) confined within ultrashort (20-80 nm) single-walled carbon nanotube capsules, gadonanotubes are high-performance T1-weighted contrast agents for magnetic resonance imaging (MRI). At 1.5 T, 37 degrees C, and pH 6.

Multiple-frequency EPR spectra of two aqueous Gd3+ polyamino polypyridine carboxylate complexes: a study of high field effects.

In the search for highly efficient magnetic resonance imaging contrast agents, polyamino polypyridine carboxylate complexes of Gd3+ have shown unusual properties with both very rapid and very slow electron spin relaxation in solution observed by electron paramagnetic resonance. Since the relationship between the molecular structure and the electron spin properties remains quite obscure at this point, detailed studies of such complexes may offer useful clues for the design of Gd3+ compounds with tailored electronic features. Furthermore, the availability of very high-frequency EPR spectrometers based on quasi-optical components provides us with an opportunity to test the existing relaxation theories at increasingly high magnetic fields and observation frequencies.

Relaxivity of Gd-based contrast agents on X nuclei with long intrinsic relaxation times in aqueous solutions.

The relaxivity of commercially available gadolinium (Gd)-based contrast agents was studied for X-nuclei resonances with long intrinsic relaxation times ranging from 6 s to several hundred seconds. Omniscan in pure 13C formic acid had a relaxivity of 2.9 mM(-1) s(-1), whereas its relaxivity on glutamate C1 and C5 in aqueous solution was approximately 0.

Destroying gadofullerene aggregates by salt addition in aqueous solution of Gd@C(60)(OH)(x) and Gd@C(60)[C(COOH(2))](10).

A combined proton relaxivity and dynamic light scattering study has shown that aggregates formed in aqueous solution of water-soluble gadofullerenes can be disrupted by addition of salts. The salt content of fullerene-based materials will strongly influence properties related to aggregation phenomena, therefore, their behavior in biological or medical applications. In particular, the relaxivity of gadofullerenes decreases dramatically with phosphate addition.

Rotational dynamics account for pH-dependent relaxivities of PAMAM dendrimeric, Gd-based potential MRI contrast agents.

The EPTPA5) chelate, which ensures fast water exchange in GdIII complexes, has been coupled to three different generations (5, 7, and 9) of polyamidoamine (PAMAM) dendrimers through benzylthiourea linkages (H5EPTPA = ethylenepropylenetriamine-N,N,N',N'',N''-pentaacetic acid). The proton relaxivities measured at pH 7.4 for the dendrimer complexes G5-(GdEPTPA)111, G7-(GdEPTPA)253 and G9-(GdEPTPA)1157 decrease with increasing temperature, indicating that, for the first time for dendrimers, slow water exchange does not limit relaxivity.

GdIII complexes with fast water exchange and high thermodynamic stability: potential building blocks for high-relaxivity MRI contrast agents.

On the basis of structural considerations in the inner sphere of nine-coordinate, monohydrated Gd(III) poly(aminocarboxylate) complexes, we succeeded in accelerating the water exchange by inducing steric compression around the water binding site. We modified the common DTPA(5-) ligand (DTPA=(diethylenetriamine-N,N,N',N",N"-pentaacetic acid) by replacing one (EPTPA(5-)) or two (DPTPA(5-)) ethylene bridges of the backbone by propylene bridges, or one coordinating acetate by a propionate arm (DTTA-prop(5-)). The ligand EPTPA(5-) was additionally functionalized with a nitrobenzyl linker group (EPTPA-bz-NO(2) (5-)) to allow for coupling of the chelate to macromolecules.