Search

Extracellular pH is an important biomarker in many diseases yet a routine method for imaging tissue pH has not been established in the clinic. Paramagnetic chemical exchange saturation transfer (paraCEST) agents are well-suited for imaging tissue pH because the basis of CEST, chemical exchange, is inherently sensitive to pH. Several previous pH-sensitive paraCEST agents were based upon with an exchanging Ln 3+ bound water molecule as the CEST antenna but this design often added additional line-broadening of the bulk water signal due to T 2 exchange. We report here a pH-sensitive paraCEST agent that lacks an inner-sphere water molecule but contains one Ln-bound -OH group for CEST activation. The Yb 3+ - complex, Yb( 1 ), displayed a single, highly-shifted CEST peak originating from the exchangeable Yb-OH proton, the frequency of which changed over the biologically relevant pH range. CEST images of phantoms ranging in pH from 6-8 demonstrate the potential of this agent for imaging pH. Initial rodent imaging studies showed that Gd( 1 ) remains in the vascular system much longer than anticipated but is cleared slowing via renal filtration.

International audience; Monoclinic and cubic europium-doped Gd2O3 structures were selectively synthesized by the glycine–nitrate process by fine control of the synthesis temperature through the crucial fuel/oxidant ratio. The cubic phase is obtained under fuel-rich conditions, whereas stoichiometric conditions induce the simultaneous formation of cubic and monoclinic polymorphs. The samples were subjected to appropriate sintering to obtain highly crystalline and carbon-free materials. The average nanoparticle (NP) size determined by TEM for these nanopowders (23 nm) agrees with the average crystallite sizes obtained from XRD Rietveld analysis; therefore, the particles are monocrystalline. Both electron energy loss spectroscopy (EELS) and photoluminescence studies showed that the europium-doped NPs are highly luminescent, and the Eu3+ ions are homogeneously distributed over the whole material as well as over the two gadolinium crystallographic sites of the cubic phase. These fluorescent NPs exhibit relaxivities that define them as potential T1 contrast agents for further biomedical applications.

Stomach cancer belongs to the most common malignant tumors in Portugal. Main causal factors are age, dietary habits, smoking, and Helicobacter pylori infections. As these factors do not only operate on different time dimensions, such as age, period, or birth cohort, but may also vary along space, it is of utmost interest to model temporal and spatial trends jointly. In this paper, we analyze incidence of stomach cancer in Southern Portugal between 1998 and 2006 for females and males jointly using a spatial multivariate age-period-cohort model. Thus, we avoid age aggregation and allow the exploration of heterogeneous time trends between males and females across age, period, birth cohort, and space. Model estimation is performed within a Bayesian setting assuming (gender specific) smoothing priors. Our results show that the posterior expected rate of stomach cancer is decreasing for all counties in Southern Portugal and that males around 70 have a two times higher risk of getting stomach cancer compared with their female counterparts. We further found that, except for some few counties, the spatial influence is almost constant over time and negligible in the southern counties of Southern Portugal.

International audience; The lanthanide (Ln3+) complexes of three cyclen-based ligands containing three methylphosphonate pendant arms were studied, the ligands being 1,4,7,10-tetraazacyclododecane-1,4,7-triyltris(methylphosphonic acid) (H6do3p), 3-[4,7,10-tris(phosphonomethyl)-1,4,7,10-tetraazacyclododec-1-yl]propanoic acid (H7do3p1pr), and 10-(3-hydroxypropyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyltris(methylphosphonic acid) (H6do3p1ol). The three macrocyclic ligands form complexes of very high thermodynamic stability with all studied Ln3+ ions. Kinetic studies showed that the acid-assisted dissociation of Ce3+ complexes of these ligands is much faster than for the complex of the related ligand H8dotp [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayltetrakis(methylphosphonic acid)]. The number of water molecules coordinated to the Eu3+ and Gd3+ complexes was estimated to be < 1 for the do3p1ol ligand but ca. 1 for the other two ligands, as obtained by time-resolved luminescence spectroscopy and by 1H and 17O relaxometric measurements. The NMR spectroscopic data indicate the existence of a considerable contribution from second-sphere water molecules to the relaxivity of all the Gd3+ complexes studied. The 1H and 31P NMR spectra of the Eu3+, Yb3+ and Lu3+ complexes showed that the propionate arm in the [Ln(do3p1pr)]4- complexes and the propanol arm in the [Ln(do3p1ol)]3- complexes are not bound to the Ln3+ ion. The [Ln(do3p)]3- and [Ln(do3p1pr)]4- complexes have a clear preference for the TSAP (twisted square antiprismatic) isomer, while both SAP (square antiprismatic) and TSAP isomers are present in solutions of the [Ln(do3p1ol)]3- complexes.

The interaction of the negatively charged Ln3+ chelate Ln–DOTP with β- and γ-cyclodextrins bearing ammonium groups at the upper rim (CD+s) was investigated using mass spectrometry and NMR spectroscopic techniques. Mass spectroscopy shows the presence of 1:1 adducts of Ln–DOTP and both β- or γ-CD+. The peak intensities increased upon increasing the pH of the samples from 7 to 9.0, suggesting an increase in the strength of the interaction. Lanthanide induced 1H NMR chemical shifts and relaxation ratesmeasured in aqueous solutions confirmed the presence of these adducts. The strength of the interactions appeared to be dependent on the pH, reflecting the strong electrostatic interactions between the oppositely charged host CD+ and guest Ln–DOTP chelate. Evaluation of the lanthanide induced relaxation rates showed that the Ln–DOTP does not enter the cavity of the CDs, but remains above it with a distance of 10–11 A between the Ln3+ ion and the centre of the CD. Molecular modelling indicated that hydrogen bonds between the functionalized groups participating in the interaction sites contribute to the adduct stabilization. The apparent binding constants at pH 7 and 9 were obtained by using relaxometric measurements at 9 MHz. Fitting the NMRD profiles showed an increase in the number of second-sphere water molecules surrounding the phosphonate pendant arms of the Ln–DOTP chelate upon its interaction with the CDs. A brief description of the PARACEST properties of the supramolecular systems formed by Tm–DOTP and the positively charged CDs is presented. Both CDs display a shift of the saturation transfer peaks of the ammonium functions by the Tm complex, with an accentuated effect observed for the γ-CD derivative.

Sources of hepatic glycogen synthesis during an oral glucose tolerance test were evaluated in six healthy subjects by enrichment of a 75-g glucose load with 6.67% [U-13C]glucose and 3.33% [U-2H7]glucose and analysis of plasma glucose and hepatic uridine diphosphate–glucose enrichments (sampled as urinary menthol glucuronide) by 2H and 13C nuclear magnetic resonance. The direct pathway contribution, as estimated from the dilution of [U-13C]glucose between plasma glucose and glucuronide, was unexpectedly low (36 ± 5%). With [U-2H7]glucose, direct pathway estimates based on the dilution of position 3 2H-enrichment between plasma glucose and glucuronide were significantly higher (51 ± 6%, P = 0.05). These differences reflect the exchange of the carbon 4, 5, and 6 moiety of fructose-6-phosphate and glyceraldehyde-3-phosphate catalyzed by transaldolase. As further evidence of this exchange, 2H-enrichments in glucuronide positions 4 and 5 were inferior to those of position 3. From the difference in glucuronide positions 5 and 3 enrichments, the fraction of direct pathway carbons that experienced transaldolase exchange was estimated at 21 ± 4%. In conclusion, the direct pathway contributes only half of hepatic glycogen synthesis during an oral glucose tolerance test. Glucose tracers labeled in positions 4, 5, or 6 will give significant underestimates of direct pathway activity because of transaldolase exchange. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc.

Hepatic triglyceride (HTG) accumulation from peripheral dietary sources and from endogenous de novo lipogenesis (DNL) was quantified in adult Sprague–Dawley rats by combining in vivo localized 1H MRS measurement of total hepatic lipid with a novel ex vivo2H NMR analysis of HTG 2H enrichment from 2H-enriched body water. The methodology for DNL determination needs further validation against standard methodologies. To examine the effect of a high-fat diet on HTG concentrations and sources, animals (n = 5) were given high-fat chow for 35 days. HTG accumulation, measured by in vivo1H MRS, increased significantly after 1 week (3.85 ± 0.60% vs 2.13 ± 0.34% for animals fed on a standard chow diet, P, Funded by: Portuguese Foundation for Science and Technology. Grant Numbers: SFRH/BD/17010/2005, POCTI/QUI/55603/2004 and Portuguese Foundation for Science and Technology/Luso-Espanhola Collaborative Actions. Grant Number: GRICES/CSIC 00620.

We investigated by 13C nuclear magnetic resonance (NMR) the mechanisms underlying Li+ effects on glutamatergic and GABAergic neurotransmission systems in the adult rat brain and in primary cultures of cortical neurons and astrocytes during the metabolism of (1-13C) glucose or (2-13C) acetate. Adult male rats receiving a single dose of Li+ intraperitoneally (7 mmol/kg) were infused 2 hr later, for 60 min, with (1-13C) glucose (80 μmol/min/kg) or (2-13C) acetate (240 μmol/min/ kg). High-resolution 13C NMR spectra of brain extracts prepared after the infusion revealed that Li+ significantly decreased the incorporation of 13C in glutamate and GABA (γ-aminobutyric acid) carbons from (1-13C) glucose, but not from (2-13C) acetate. To complement the in vivo approach, primary cultures of cortical neurons or astrocytes were incubated with 1 mM uniformly 13C-labeled glucose or 5 mM (2-13C) acetate, in the absence and presence of increasing Li+ concentrations up to 15 mM. Under these conditions, Li1 significantly decreased neuronal glucose uptake in a concentration-dependent manner without apparent effects on astrocytic acetate uptake. Extracts prepared at the end of the incubations showed that Li+ significantly decreased the incorporation of 13C labeling into GABA carbons from its precursor glutamate in neurons, but such a decrease into glutamine carbons in astrocytes was not statistically significant. Our results indicate that the effects of Li+ are mediated through a reduction of neuronal glucose uptake, resulting in a decrease of glutamatergic and GABAergic neurotransmission without apparent effects on astrocytic metabolism. © 2008 Wiley-Liss, Inc., Funded by: Fundação para a Ciência e a Tecnologia (F.C.T.), Portugal and FEDER. Grant Numbers: POCTI/1999/BCI/36160, PRAXIS XXI/BD/21462/99; Spanish Ministry of Education and Science. Grant Numbers: SAF 2001-2245, SAF 2004-03197; Institute of Health Carlos III. Grant Numbers: FISss C03/08, C03/155, C03/10, PI051530, PI051845 and Community of Madrid, Spain.

A comprehensive classification of contrast agents currently used or under development for magnetic resonance imaging (MRI) is presented. Agents based on small chelates, macromolecular systems, iron oxides and other nanosystems, as well as responsive, chemical exchange saturation transfer (CEST) and hyperpolarization agents are covered in order to discuss the various possibilities of using MRI as a molecular imaging technique. The classification includes composition, magnetic properties, biodistribution and imaging applications. Chemical compositions of various classes of MRI contrast agents are tabulated, and their magnetic status including diamagnetic, paramagnetic and superparamagnetic are outlined. Classification according to biodistribution covers all types of MRI contrast agents including, among others, extracellular, blood pool, polymeric, particulate, responsive, oral, and organ specific (hepatobiliary, RES, lymph nodes, bone marrow and brain). Various targeting strategies of molecular, macromolecular and particulate carriers are also illustrated.

Five DOTA-like ligands lacking a water molecule in the first coordination sphere of their Gd III complexes, namely the phosphinates H 4 DOTP H , H 4 DOTP hm and H 4 DOTP Et , and the phosphonate monoesters H 4 DOTP OEt and H 4 DOTP OBu , were synthesized with the aim of exploring the influence of the second hydration sphere on the relaxivity of Gd III complexes. The H 4 DOTP H , H 4 DOTP hm and H 4 DOTP OEt ligands and their Ln III complexes were characterized by potentiometry and time-resolved luminescence; the Gd III complexes are thermodynamically much less stable than that of H 4 DOTA, and no water is coordinated in the inner sphere. The crystal structures of the free ligand H 4 DOTP OEt and of the Gd III complexes of H 4 DOTP H and H 4 DOTP OEt were determined by X-ray diffraction. The complexes have the expected octadentate coordination mode with an N 4 O 4 arrangement; no water molecule is bound to the Gd III ion. Information on the structures of the Ln III complexes of all five ligands in aqueous solution were obtained from 1 H and 31 P NMR spectra. The NMR spectra of the [Ln(DOTP hm )]- and [Ln(DOTP Et )]- complexes show that these compounds have a clear preference for a specific arrangement of phosphorus atoms which gives rise to the symmetrical RRRR (or SSSS) isomer. However, many diastereoisomers were observed for all other complexes. Ln III -induced 17 O NMR shift data reveal that the spatial location of the second-sphere water molecules for the two groups of complexes differs. The parameters governing the effect of the second hydration sphere on the relaxivity of the Gd III complexes of all ligands were evaluated by EPR, variable-temperature 17 O NMR spectroscopy and 1 H NMRD re-laxometry. The presence of second-sphere water molecules is clearly confirmed, depending on the character of the pendant arms. As the relaxivity does not depend significantly on the nature of the phosphorus substituents and/or on the isomerism present in solution, the second-sphere water molecules should be located close to the phosphorus-oxygen atoms.

The behaviour of the cyclic trimeric V v complex [V 3 O 3 (μ-0) 3 (dmpp) 3 (H 2 O)](H 2 O) 2 , V 3 L 3 , (L = Hdmpp = 3-hydroxy-1,2-dimethyl-4-pyridinone) was studied in methanol and methanol/water solutions by using 51 V and 1D- and 2D 1 H NMR spectroscopy. Red crystals, isolated from a highly concentrated methanol solution of the trimeric complex, were analysed by X-ray crystallography. The solid-state structure of the compound showed the presence of a new dinuclear V v cluster and allowed for its formulation as a [V 2 O 2 (μ-O)-(dmpp) 2 (OCH 3 ) 2 ] complex, V 2 Y 2 L 2 (Y = OCH 3 ). This complex crystallises in the monoclinic system: P2 1 /c, a = 8.4573(11) A, b = 15.034(2) A and c = 15.849(2) A, β = 105.300(2)°, V = 1943,7(4)A 3 , Z = 2, and R 1 (wR 2 ) = 0.0492(0.1706). The trimer V 3 L 3 complex dissolved in a dry methanol solution fully decomposes, as shown by the 51 V NMR signals at -388, -450 and -551 ppm, which are assigned to a monomer complex [VO(OMe)(dmpp) 2 ] (VYL 2 ), the dimer V 2 Y 2 L 2 and the monomethyl ester of monovanadate, V 1 Y (V 1 = monovanadate; Y = OCH 3 ), respectively. In methanol/water solutions, a new 51 V NMR signal appears at δ = -492 ppm, which is assigned to the [VO 2 (dmpp)(H 2 O) 2 ] (VL) complex. When the percentage of water in the mixture increases, the relative intensities of the V 2 Y 2 L 2 and V 1 Y signals decrease sharply, and a broad signal at -488 ppm appears, corresponding to the original V v trimer complex, which is the only species present in 94 % water. A temperature-dependent 1 H NMR study of a CD 3 OD solution of V 3 L 3 confirmed the presence, at room temperature, of the dinuclear V 2 L 2 complex and the VL 2 species. At temperatures below 0 °C down to -50 °C, the appearance of new signals reflects the presence of isomers for the V 2 Y 2 L 2 and VYL 2 species with different stabilities and symmetries. 2D 1 H homonuclear NMR exchange experiments (EXSY) allowed us to establish the isomeric equilibria that take place in solution, and indicates intramolecular exchange between the two ligands of the major isomer of VYL 2 and intermolecular exchange between the major and minor isomers of species of different nuclearity, V 2 Y 2 L 2 and VYL 2 . However, no evidence was found for intermolecular exchange between the major isomers and between the minor isomers of species of different nuclearity or between isomers of species of the same nuclearity.

Several studies have suggested the involvement of biogenic monoaminergic neurotransmission in bipolar disorder and in the therapy for this disease. In this study, the effects of the mood-stabilizing drugs lithium, carbamazepine or valproate on the dopaminergic and adrenergic systems, particularly on D2-like and beta-adrenergic receptors, were studied both in cultured rat cortical neurones and in rat prefrontal cortex. In vitro and in vivo data showed that stimulation of beta-adrenergic receptors with isoproterenol increased cyclic adenosine monophosphate (cAMP) levels and this effect was significantly inhibited by lithium, carbamazepine or valproate. The activation of dopamine D2-like receptors with quinpirole decreased the isoproterenol-induced rise in cAMP in control conditions. This inhibition was observed in vivo after chronic treatment of the rats with carbamazepine or valproate, but not after treatment with lithium or in cultured rat cortical neurones after 48 h exposure to the three mood stabilizers. Dopamine D2 and beta1-adrenergic receptors were found to be co-localized in prefrontal cortical cells, as determined by immunohistochemistry, but western blot experiments revealed that receptor levels were differentially affected by treatment with the three mood stabilizers. These data show that mood stabilizers affect D2 receptor-mediated regulation of beta-adrenergic signalling and that each drug acts by a unique mechanism.

The synthesis and characterization of a new class of DTPA bisamide-linked glycoconjugates of different sugars (lactose, Lac, and galactose, Gal) and valencies (di and tetra) and their Ln(III) complexes is reported. The 1H NMR spectra of the Sm(III) and Eu(III) complexes of DTPAGal2, DTPAGal4, and DTPALac2 obtained between 7 and 80 ºC, indicate that most (if not all) of the four possible diastereoisomeric pairs of structures, resulting from the chirality of the three bound DTPA nitrogen atoms, are present in solution, with different relative populations. The dynamic effects of racemization of the central nitrogen on the NMR spectra show that this process is in fast exchange at 60 ºC for the Sm(III) complexes and in slow exchange at 7 ºC for the Eu(III) complexes. The in vitro r1 nuclear magnetic relaxation dispersion (NMRD) of the water protons of the Gd(III)-DTPA bis-amide glycoconjugate containing two lactosyl moieties, Gd(III)-DTPALac2, was studied, yielding the molecular parameters that govern its relaxivity. Its r1 value, at 25 oC and 20 MHz, is 13% higher than that reported for Gd(III) chelates of lower molecular weight DTPA-bisamides, such as DTPA-BMA, consistent with a five times longer tau-R value. The water exchange rate, kex, and the electron spin relaxation parameters of the Gd(III)-DTPALac2 complex are within the usual range for similar Gd(III)-DTPA bisamide chelates., EU COST Action D18 “Lanthanide chemistry for diagnosis and therapy”. Fundação para a Ciência e Tecnologia - POCTI/QUI/47005/2002. FEDER. Swiss National Science Foundation. Swiss Federal Office for Education and Science.

The ligand H5dotasa (=(alphaRS)-alpha-(carboxymethyl)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) is a H4dota-like macrocyclic ligand with a carboxymethyl CH2COOH substituent at the C(alpha) atom of one of the four acetate pendant arms of H4dota (=1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid), present as a racemic mixture of (alphaR) and (alphaS) enantiomers. The protonation constants of the ligand were determined by potentiometry, giving values close to those of H4dota except for the extra pK3 value of 5.35 assigned to protonation of the extra carboxylate group in the alpha-substituted (=succinic acid) pendant arm. The 1H-NMR spectra of H5dotasa at different pH values are too complex to allow the determination of its microscopic protonation scheme, due to the presence of multiple isomeric structures in solution. The thermodynamic stability constant of its Gd3+ chelate was determined by a potentiometric method, and the value obtained, log KML=27.2 (0.2), is higher than for the [Gd(dota)(OH2)]- complex. The solution structure of the asymmetric Ln3+ chelates of dotasa was studied by 1H-NMR spectroscopy, indicating the presence of four isomers, corresponding to the combination of the antiprismatic (M) and twisted antiprismatic (m) helicities of the pendant arms and to the (alphaR) and (alphaS) configurations at the substituted pendant arm. The m/M isomer ratio decreases along the lanthanide series, with the m isomer decreasing from 90% at La to ca. 50% from Eu-Lu. This shows that the expected m isomer population of the [Gd(dotasa)(OH2)]2- complex is higher than for the unsubstituted [Gd(dota)(OH2)]- (ca. 15%) but lower than for a Gd3+ chelate of an alpha,alphaprime,alphaPrime,alphaprimeprimeprime-tetrasubstituted (RRRR)-configurated dota (ca. 70%). Thus the stabilization of the m isomer by C' monosubstitution at the dota acetate pendant arm in [Gd(dotasa)(OH2)]2- is responsible for its increased H2O-exchange rate and higher relaxivity.

We report a novel ((13)C, (2)H) nuclear magnetic resonance (NMR) procedure to investigate lactate recycling through the monocarboxylate transporter of the plasma membrane of cells in culture. C6 glioma cells were incubated with [3-(13)C]lactate in Krebs-Henseleit Buffer containing 50% (2)H(2)O (vol/vol) for up to 30 hr. (13)C NMR analysis of aliquots progressively taken from the medium, showed: (1) a linearly decreasing singlet at approximately 20.85 parts per million (ppm; -0.119 micromol/mg protein/hr) derived from the methyl carbon of [3-(13)C]lactate; and (2) an exponentially increasing shifted singlet at approximately 20.74 ppm (0.227 micromol/ mg protein/hr) from the methyl carbon of [3-(13)C, 2-(2)H]lactate. The shifted singlet appears because during its transit through the cytosol, [3-(13)C]lactate generates [3-(13)C, 2-(2)H]lactate in the lactate dehydrogenase (LDH) equilibrium, which may return to the incubation medium through the reversible monocarboxylate carrier. The methyl group of [3-(13)C, 2-(2)H]lactate is shifted -0.11 ppm with respect to that of [3-(13)C]lactate, making it possible to distinguish between both molecules by (13)C NMR. During incubations with 2.5 mM [1-(13)C]glucose and 3.98 mM [U-(13)C(3)]lactate or with 2.5 mM [1-(13)C]glucose and 3.93 mM [2-(13)C]pyruvate, C2-deuterated lactate was produced only from [1-(13)C]glucose or [U-(13)C(3)]lactate, revealing that this deuteration process is redox sensitive. When [1-(13)C]glucose and [U-(13)C(3)]lactate were used as substrates, no significant [3-(13)C]lactate production from [1-(13)C]glucose was detected, suggesting that glycolytic lactate production may be stopped under the high lactate concentrations prevailing under mild hypoxic or ischemic episodes or during cerebral activation.

In this work, we studied the effect of intracellular 3',5'-cyclic adenosine monophosphate (cAMP) on Li+ transport in SH-SY5Y cells. The cells were stimulated with forskolin, an adenylate cyclase activator, or with the cAMP analogue, dibutyryl-cAMP. It was observed that under forskolin stimulation both the Li+ influx rate constant and the Li+ accumulation in these cells were increased. Dibutyryl-cAMP also increased Li+ uptake and identical results were obtained with cortical and hippocampal neurons. The inhibitor of the Na+/Ca2+ exchanger, KB-R7943, reduced the influx of Li+ under resting conditions, and completely inhibited the effect of forskolin on the accumulation of the cation. Intracellular Ca2+ chelation, or inhibition of N-type voltage-sensitive Ca2+ channels, or inhibition of cAMP-dependent protein kinase (PKA) also abolished the effect of forskolin on Li+ uptake. The involvement of Ca2+ on forskolin-induced Li+ uptake was confirmed by intracellular free Ca2+ measurements using fluorescence spectroscopy. Exposure of SH-SY5Y cells to 1 mm Li+ for 24 h increased basal cAMP levels, but preincubation with Li+, at the same concentration, decreased cAMP production in response to forskolin. To summarize, these results demonstrate that intracellular cAMP levels regulate the uptake of Li+ in a Ca(2+)-dependent manner, and indicate that Li+ plays an important role in the homeostasis of this second messenger in neuronal cells.

A simple and sensitive NMR method for quantifying excess 13C-enrichment in positions 2 and 3 of lactate by 1H NMR spectroscopy of the lactate methyl signal is described. The measurement requires neither signal calibrations nor the addition of a standard and accounts for natural abundance 13C-contributions. As a demonstration, the measurement was applied to sim3 mumol of lactate generated by erythrocyte preparations incubated with [2-13C]glucose to determine the fraction of glucose metabolized by the pentose phosphate pathway (PP). PP fluxes were estimated from the ratio of excess 13C-enrichment in lactate carbon 3 relative to carbon 2 in accordance with established metabolic models. Under baseline conditions, PP flux accounted for 7 ± 2% of glucose consumption while in the presence of methylene blue, a classical activator of PP activity, its contribution increased to 27 ± 10% of total glucose consumption (P < 0.01). Magn Reson Med 51:1283-1286, 2004. © 2004 Wiley-Liss, Inc.

In this paper we explore Gd(3+)-doped zeolite NaY nanoparticles for their potential application as a contrast agent in magnetic resonance imaging (MRI). The nanoparticles have an average size of 80-100 nm, as determined by TEM and XRD. A powdered sample loaded with La3+ was characterised by means of multinuclear solid-state NMR spectroscopy. The NMR dispersion (NMRD) profiles obtained from aqueous suspensions of samples with Gd3+ doping ratios of 1.3-5.4 wt% were obtaining at different temperatures. The relaxivity increases drastically as the Gd3+ loading decreases, with values ranging between 11.4 and 37.7 s-1 mM-1 at 60 MHz and 37 degrees C. EPR spectra of aqueous suspensions of the samples suggest that an interaction between neighbouring Gd3+ ions within the same particle produces a significant increase in the transversal electronic relaxation rates in samples with a high Gd3+ content. The experimental NMRD and EPR data are explained with the use of a model that considers the system as a concentrated aqueous solution of Gd3+ in the interior of the zeolite that is in exchange with the bulk water outside the zeolite. The results obtained indicate that the Gd3+ ion is immobilised in the interior of the zeolite and that the relaxivity is mainly limited by the relatively slow diffusion of water protons from the pores of the zeolite channels into the bulk water.

A new trinuclear oxovanadium(V) complex with the anionic dmpp ligand (Hdmpp = 3-hydroxy-1,2-dimethyl-4-pyridinone), [V3O6(dmpp)3(H2O)](H2O)2, was isolated from the reaction of Hdmpp, KOH and sodium metavanadate at pH 4.5. The solid state structure of the [V3O6(H2O)(dmpp)3](H2O)2 complex, investigated by X-ray diffraction methods, was found to contain a cyclic trinuclear metal cluster. This complex crystallises in the monoclinic system: P21/n, a =

Copper(II) mononuclear complexes with the polyazamacrocyclic ligands NOTA (1,4,7-triazacyclononane-N,N′,N″triacetate), DOTA (1,4,7,10-tetraazacyclo-dodecane-N,N′,N″,N″′-tetraacetate), NOTP [1,4,7-triazacyclononane-N,N′,N″-tris(methylenephosphonate)] and DOTP [1,4,7,10tetraazacyclododecane-N,N′,N″,N‴-tetrakis(methylenephosphonate)] were characterised in aqueous solution by electronic absorption spectrophotometry and electron paramagnetic resonance (EPR) spectroscopy. While two isomeric species were detected by EPR spectroscopy in frozen samples of the polycarboxylate complexes, only one complex form was found for the poly(methylenephosphonate) systems. The results obtained are in accordance with a six-coordinate pattern for the metal centre, yielding tetragonally distorted complexes in solution, in agreement with previously reported studies on CuII complexes, both in solution and in the solid state.

The interactions between α-, β-, and γ-CD and the TmIII chelates of the macrocyclic polyaminopolycarboxylates DOTA and NOTA were studied with the use of 1H- and 13C-NMR shift and relaxation rate measurements. Interactions were only observed between Tm(DOTA)- and γ-CD. The structure and the stability of the concerning supramolecular structures was elucidated by fitting of the NMR titration curves to a theoretical model. It appears that an inclusion compound is formed, where the hydrophobic macrocyclic part of the chelate sits in the γ-CD cavity. This inclusion compound binds a second Tm(DOTA)- molecule at the outside lower rim of the CD cone. The binding occurs probably via hydrogen bonds between non-chelated carboxylate oxygen atoms of the concerning Tm(DOTA)- and CH2OH groups of the γ-CD molecule, which are in a favorable position due to opening of the γ-CD cone angle as a result of the inclusion of the first γ-CD. http://dx.doi.org/10.1002/(SICI)1099-0682(19990202)1999:23.0.CO;2-W

A set of parameters consistent with the CHARMM force field has been determined for molecular dynamics simulations of several DOTA– and DOTP–Ln(III) chelates. Bonding and van der Waals parameters were derived from the available experimental data and analogy to similar ones in the existing force field. Net atomic charges were derived from ab initio calculations at the Hartree–Fock level to reproduce molecular electrostatic potentials (ESPs), with an effective core potential (ECP) basis set for the metal ion and the 6-31G* basis set for the ligand atoms. The charges are consistent with the TIP3P water model. Preliminary molecular dynamics simulations of the lanthanide chelates in aqueous solution were performed using the Nose–Hoover thermostat at 300 K. The new parameters correctly predicted the molecular structures and stability of the chelates major and minor isomers. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 73: 237–248, 1999

The front cover picture shows gives an impression on the breadth of coverage of this Cluster Issue on Metal-Based Magnetic Resonance Imaging Probes. Superimposed on an angiographic MRI image are the zeolite cages for Gd3+ and the mode of action of this probe from the review by J. A. Peters and K. Djanashvili (top) and a depiction of the principle of magnetoluminescent contrast agents for dual MRI and luminescence imaging (V. C. Pierre et al., bottom right). Representative of papers on different approaches to optimize the efficacy of contrast agents are the PARACEST properties of the large Tm-DOTP–cyclodextrin complex of C. F. G. C. Geraldes et al. (bottom left) and the high relaxivity associated with two bis(aqua) complexes of M. Mazzanti et al. (center left). We thank the authors for making their graphics available for use on the cover and Dr. Giorgio Gatti for the time-consuming creation of this attractive picture.

The host–guest complex formed in aqueous solution between γ-cyclodextrin (γ-CD) and the macrocyclic paramagnetic shift reagent TmDOTP5− was examined by NMR spectroscopy. Paramagnetic lanthanide-induced shifts (LIS) and spin-lattice relaxation rate enhancements in the proton resonances of γ-CD on binding of TmDOTP5− were used to define the position of the guest anion within the host cavity. A proportionality constant which relates pseudo-contact shifts induced by TmDOTP5− to the geometrical position of each ligand nucleus (previously determined from a LIS study of the TmDOTP5− complex) was used to determine a fully bound LIS value for each γ-CD proton. These values, in combination with experimental LIS data from TmDOTP5− titrations at constant γ-CD concentration, were then used to obtain the association constant for the host-guest complex (3.9–4.5 mol l−1). These constants were indicative of a weak host-guest interaction and consistent with the location of the TmDOTP5− binding site reported by the LIS values well above the center of the γ-CD cavity.

The Gd3+ complexes of three new phosphorus containing tetraaza macrocycles (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakis (methylene ethylphosphonic acid), H4DOTEP; 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakis (methylene phosphonic acid monoethylester), H4DOTPME; and the corresponding n-butyl ester, H4DOTPMB) were prepared and examined for possible use as MRI contrast agents. Although thermodynamically and kinetically less stable than Gd(DOTA)- in saline and HSA solution, the stability of these new macrocyclic complexes appears to be sufficiently high for in vivo applications. NMRD relaxivity profiles of the three complexes indicate that the number of inner sphere water molecules for these chelates is < or = 1 and that the more hydrophobic chelate, Gd(DOTPMB), binds to human serum albumin (HSA). Biodistribution studies of the radioactive 153Sm or 159Gd chelates in rats, gamma imaging of the 153Sm chelates in rats, and proton MRI studies of the nonradioactive Gd3+ chelates in rabbits all indicate that the DOTPMB complexes accumulate preferentially in the liver, spleen, and small intestines while the more hydrophilic DOTEP and DOTPME complexes appear to display renal clearances similar to other low molecular weight contrast agents.

Nuclear magnetic relaxation dispersion (NMRD) profiles and ESR linewidths have been measured for a series of neutral Gd(3+)-triazamacrocyclic complexes and compared with previous data for the simplest member of the macrocyclic triaza series, Gd(NOTA), and for the widely studied linear triaza complex, Gd(DTPA)2-. Water proton relaxivities and their temperature dependence were found to vary widely with the size of the triaza macrocycle and the identity of the side-chain chelating groups. The number of rapidly exchanging water molecules directly coordinated to the Gd3+ ion (q) was found to vary from 2 to 4 for eight of the ten complexes examined and a linear relationship between the 50-MHz relaxivity value and integral values of q is presented for this series of complexes. tau s values derived from ESR linewidths for some of the complexes are in reasonable agreement with those derived from their NMRD profiles; however, those complexes which either tended to form aggregates in solution or gave evidence for multiple averaged solution structures showed broad, near Lorentzian linewidths which were clearly not dominated by the electron spin relaxation time (tau s).

Intracellular [Na+], [H+], and [ATP] and mechanical performance were measured in the isovolumic perfused rat heart during ischemia. The concentration of intracellular sodium, [Na+]i, was determined by atomic absorption spectroscopy under control conditions, and [Na+] was monitored by 23Na NMR spectroscopy at 1-min intervals under control conditions and during global ischemia. [ATP], [H+], and [Pi] were measured by 31PNMR in a separate group under identical conditions. The control [Na+]i measured by atomic absorption was 30.7 ± 3.3 mM(mean ± SD, n = 6), and [Na+]i measured by NMR was 6.2 ± 0.5 mM(n = 3). Brief ischemia (10 min) was associated with a 54% increase in [Na+]i which reversed completely with reperfusion. Developed pressure also returned to control values upon reperfusion. Prolonged ischemia (30 min) produced continuous further accumulation of sodium (0.53 mM/min, r2 = 0.99). [H+] also increased approximately linearly early in ischemia (0.084 μM/min, r2 = 0.97). The rate of increase in [Na+]i was more than 4000 times greater than the increase in [H+] on a molar basis. Nevertheless, [H+]/[Na+] increased early in ischemia because the proportional change in [H+] was greater than that in [Na+] i. These results indicate that (1) intracellular sodium measured by NMR in the functioning heart is about 20% of total intracellular sodium; (2) intracellular acidosis and accumulation of sodium develop simultaneously during global ischemia; (3) increased intracellular sodium content is not in itself an indicator of irreversible injury; and (4) recovery of mechanical performance is associated with return of [Na+] (measured by NMR) to baseline after brief ischemia. The mechanism of the increase in sodium content detected by NMR is unknown. © 1990 Academic Press, Inc.

Tm(DOTP)5−, the thulium(III) complex of 1,4,7,10-tetraazacyclododecane N,N′,N″,N‴tetra(methylenephosphonate), is introduced as a 23Na1 shift agent for use in discrimination of the NMR resonances of intra- and extracellular 23Na+ ions in perfused rat hearts. The novel shift agent is directly compared to the widely used Dy(TTHA)3- (dysprosium(III) triethylenetetraminehexaacetate). © 1990 Academic Press, Inc.

Lithium salts have been in use for the treatment of bipolar disorder for more than 50 years, but their pharmacological mode of action remains a matter of conjecture. Li+ and Mg2+ share many physicochemical properties. Not surprisingly, many reported cellular targets for Li+ action involve Mg2+-activated enzymes, which are inhibited by Li+. In this Account, we describe results from our and other laboratories that suggest that a competition mechanism between Li+ and Mg2+ ions for Mg2+-binding sites in cellular components is the underlying theme in putative mechanisms of Li+ action.

In this paper we report the synthesis and the characterization of the novel ligand H5EPTPA-C16 ((hydroxymethylhexadecanoyl ester)ethylenepropylenetriaminepentaacetic acid). This ligand was designed to chelate the GdIII ion in a kinetically and thermodynamically stable way while ensuring an increased water exchange rate (kex) on the GdIII complex due to steric compression around the water binding site. The attachment of a palmitic ester unit to the pendant hydroxymethyl group on the ethylenediamine bridge yields an amphiphilic conjugate that forms micelles in aqueous solution with a long tumbling time (R). The critical micelle concentration (CMC = 0.34 mM) of the amphiphilic [Gd(EPTPA-C16)(H2O)]2- chelate was determined by variable concentration proton relaxivity measurements. A global analysis of the data obtained in variable temperature and multiple field 17O NMR, and 1H NMRD measurements allowed the determination of parameters governing relaxivity for [Gd(EPTPA-C16)(H2O)]2-; this is the first time that paramagnetic micelles with optimized water exchange are investigated. The water exchange rate was found to be kex298 = 1.7×108 s-1, very similar to that previously reported for the nitrobenzyl derivative [Gd(EPTPA-bz-NO2)(H2O)]2- (kex298 = 1.5×108 s-1). The rotational dynamics of the micelles was analysed using the Lipari-Szabo approach. The micelles formed in aqueous solution show a considerable flexibility, with a local rotational correlation time of the GdIII segments, lO298 = 330 ps, being much shorter than the global rotational correlation time of the supramolecular aggregates, gO298 = 2100 ps. This internal flexibility of the micelles is responsible for the only limited increase of the proton relaxivity observed on micelle formation (r1 = 22.59 mM-1s-1 for the micelles vs. 9.11 mM-1s-1 for the monomer chelate (20 MHz; 25°C))., Fundação para a Ciência e a Tecnologia (FCT) - POCTI/QUI/47005/2002). EU Cost Action D18 "Lanthanide chemistry for diagnosis and therapy". Swiss National Science Foundation. Swiss Federal Office for Education and Science.

In this article the single family of conformations of adenosine 5′-monophosphate (5′AMP) in aqueous solution previously obtained using the lanthanide ions as nuclear magnetic resonance (NMR) probes is shown to disagree with the conformational data available from independent NMR methods, such as coupling constants and nuclear Overhauser enhancement analysis. The original lanthanide experimental data is reinterpreted assuming the contribution of different conformers to the observed magnetic perturbations. The average conformation obtained for 5′ AMP agrees quite satisfactorily with the other independent conformational information.

The E/Z configurational equilibrium of the nitroethylenic moiety of the antiulcer agent ranitidine was studied in aqueous solution and in DMSO-d6 and CDCl3 using 1H and 13C NMR spectroscopy. In aqueous solution the room temperature E/Z isomerization of the unprotonated nitroketenediamine moiety is fast on the NMR time scale, but becomes slow for the species protonated at this moiety owing to intramolecular hydrogen bonding between the nitro group and a neighbouring NH2R+ group. In DMSO-d6 a free energy of activation of the order of 70 kJ mol−1 was estimated for the E/Z isomerization of the unprotonated moiety of ranitidine, in good agreement with values previously found for 2,2-disubstituted nitroethylene model compounds.

The conformation of the dinucleotide adenylyl(3'-5')adenosine 2'-phosphate (ApA2'p) in aqueous solution at different pH values and temperatures has been studied using the lanthanide(III) ethylenodiaminetetraacetate(EDTA) 1:1 complexes as shift and relaxation probes. The conformational analysis, based on mixing different conformations in fast exchange within the nuclear magnetic resonance time scale, agrees well with the results from vicinal coupling constants and dimerization shifts obtained for the metal-free system. The dinucleotide exists in a temperature-dependent and pH-dependent conformational equilibrium between unstacked and base-stacked forms. At neutral pH and low temperature, the stacked form predominates, and it is a predominantly right helical structure, characterized as an anti, 3E, g-, g- g-, g'g', gg, 3E, anti conformation. This situation contrasts with adenylyl(3'-5')adenosine (ApA), where both right and left helices contribute to the stacked form. The nucleotidyl units of the unstacked form of ApA2'p have average conformations which are very similar to those of the corresponding mononucleotides in similar conditions.

The NH, CH and CC stretching regions at 3100-3400 cm−1, 2800-3000 cm−1 and 1000-1150 cm−1, respectively, and the low-frequency accordion-like vibration region, have been investigated by Raman spectroscopy for the octyl-, nonyl-, dodecyl-, tetradecyl- and hexadecyl-normal primary amines series, at different temperatures and for different physical states. The spectra were interpreted in terms of structural changes, particularly of the conformations of the paraffin chains, the chain length and the physical state. The changes in the NH region were associated mainly with molecular association, whereas the changes in the other spectral regions studied were associated mainly with the molecular packing of the chains.

The magnetic field dependence of the solvent water proton longitudinal relaxation rate 1/T1 (the NMRD profile) has been measured for solutions of chelates of Gd3+ and Mn2+ ions with two different polyaza macrocyclic ligands: 1, 4, 7-triazacyclononane-N, N′, N″,-triacetic acid (NOTA) and 1, 4, 7, 10-tetraazacyclododecane-N, N′, N″, N‴,-tetraacetic acid (DOTA). Studies were carried out mainly near physiological pH, but the pH dependence was also examined in some cases. The results are compared with published data for complexes of Gd3+ and Mn2+ ions with ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetie acid (DTPA). Competition experiments for the NOTA and DOTA chelates with EDTA and DTPA were also performed. It is found that, over the field range in which NMR imaging is currently being done, different symmetries of otherwise similar chemical ligands can alter 1/T1 of solvent protons by factors of up to three. The ligand environment can influence the relaxation times of the electronic spin moments of the ions, as well as their coordination number, thereby changing both the inner and outer sphere contributions to the relaxivities of the complexes. The relevance of these results to questions of efficiency and toxicity of these chelates as agents for enhancement of contrast in NMR images is discussed. © 1986 Academic Press, Inc.

An efficient method has been found for the preparation of cyclic monodithioacetats of 1,3-dicarbonyl compounds using boron trifluoride etherate as the acid catalyst. Asymmetric 1,3-diketones react regioselectively in most of the cases tried. A study of the 13C and 1H nmr characteristics of these compounds has been carried out.

Macroscopic and microscopic protonation of the title compounds (I)-(III), prepared by published methods, is studied using potentiometry and multinuclear magnetic resonance spectroscopy.