Analysis of cerebral structural changes in systemic lupus erythematosus by proton MR spectroscopy.

Purpose: To determine whether cerebral atrophy in systemic lupus erythematosus is associated with decreased levels of the neuronal marker N-acetyl-aspartic acid.

Methods: Two groups of patients with systemic lupus erythematosus were studied, those with significant atrophy (n = 11) and those without significant atrophy (n = 10), using proton MR spectroscopy on a 1.5-T imaging unit.

Enhanced tumor imaging with pokeweed mitogen.

Traditional tumor imaging with biotracer techniques relies solely on the target specificity of the biomolecule. We hypothesize that specific imaging is possible by altering the rate of tissue clearance (both normal and aberrant) of any given radiotracer. Pokeweed mitogen (PWM) as a biomodulator, represents a class of molecules which regulate cellular differentiation and cell-cell interactions and, as part of these mechanisms alter tissue clearance rates (both normal and aberrant).

The magnetic properties and water dynamics of the red blood cell: a study by proton-NMR lineshape analysis.

The magnetic properties and water dynamics of human red blood cells were examined by analysis of the water proton spectra of suspensions of oxygenated, deoxygenated, carbon monoxide-treated, and methemoglobin-containing cells at a magnetic field strength of 7.05 T. Total lineshape analysis of spectra from deoxygenated red blood cell suspensions was performed to determine the transmembrane water exchange rate, the contribution of diffusion in local magnetic field gradients to the transverse relaxation rate, and the difference between the intra- and extracellular chemical shifts of water protons.

Multivoxel 1H-MRS of stroke.

Proton nuclear magnetic resonance spectroscopy is a noninvasive technique allowing the localized, in vivo detection of proton-containing brain metabolites. We used this technique to study eight patients with cerebral infarction or ischemia. A stimulated echo-pulse sequence with chemical shift imaging was used to acquire spectra from multiple contiguous 4-cc volumes extending from the site of ischemia to the opposite hemisphere.

On the origin of paramagnetic inhomogeneity effects in whole blood.

Asymmetric 7 T proton NMR signals of water in RBC suspensions containing intracellular deoxyhemoglobin are composites of chemically shifted extracellular and intracellular resonances broadened by gradient diffusion and modulated by transmembrane water exchange. This allows assessment of field dependences of acute hematoma intensities in proton MRIs at lower field strengths (less than or equal to 1.5 T).

Triple-quantum-coherence-filtered imaging of sodium ions in vivo at 4.7 tesla.

The tissue distribution of sodium ions which generate triple-quantum coherence (TQC) in vivo is determined from images. A technique for filtering conventional sodium images, so that signal is obtained only from sodium ions which have a correlation time appropriate for producing TQC, is described. The utility of TQC-filtered sodium images is demonstrated in a study of tumors implanted in a nude rat model, where the intensity of the TQC signal from sodium ions in the growing margin of the tumor is observed to be 200-250% greater than that from surrounding tissue.

The line shapes of the water proton resonances of red blood cells containing carbonyl hemoglobin, deoxyhemoglobin, and methemoglobin: implications for the interpretation of proton MRI at fields of 1.5 T and below.

The 300 MHz (7 T) water proton resonances of suspensions of red blood cells containing paramagnetic deoxyhemoglobin or methemoglobin can be resolved into two broad lines assignable to intra- and extracellular water which undergoes rapid T2 relaxation by diffusion in magnetic field gradients induced by the intracellular paramagnets. The width of the resolved lines allowed an estimate of the maximum contribution that diffusion makes to T2 relaxation at 7 T. The dependence of the diffusion contribution on the square of the strength of the static magnetic field suggest that diffusion makes a small contribution to water proton T2 relaxation at 1.

Physiologic intracranial calcification with hyperintensity on MR imaging: case report and experimental model.

CT and MR imaging showed basal ganglia calcification that appeared as high signal intensity on T1-weighted images of a patient with pseudohypoparathyroidism. MR imaging of an experimental model of calcium phosphate suspensions showed a signal similar to that seen in the patient. Additionally, T1 and T2 relaxation times of the solutions were measured and showed decreases in both parameters with increasing calcium phosphate concentrations.

Lactate observation in vivo by spectral editing in real time.

We have developed a novel in vivo proton MR spectroscopy magnetization transfer method for detection of lactate in ischemic tissue in the presence of interfering fat proton resonances. Pyruvate is magnetically labeled with a saturation pulse and, when converted to lactate, the lactate retains the label. Difference of spectra obtained with and without a saturation pulse contain no fat resonances.

Fluorine-19 NMR imaging of glucose metabolism.

Metabolic imaging reflecting glucose metabolism in the glycolytic and aldose reductase sorbitol (ARS) pathways was performed noninvasively in rat using fluorinated glucose analogs, 2-fluoro-2-deoxy-D-glucose (2-FDG) or 3-fluoro-3-deoxy-D-glucose (3-FDG), and fluorine-19 (19F) nuclear magnetic resonance (NMR) imaging. 19F images of 2-FDG-6-phosphate, a main metabolite of 2-FDG in the glycolytic pathway, showed high glucose utilization in the brain, spinal cord, and heart. Images of 3-fluoro-3-deoxy-D-sorbitol (3-FDSL), a main metabolite of 3-FDG in the ARS pathway, demonstrated the heterogeneous nature of the spatial distribution of aldose reductase activities, being highest in the brain and lens.

Effect of the sampling rate on magnetic resonance imaging.

Effects of the sampling rate on spatial resolution and the signal-to-noise ratio in spin-echo MR imaging were calculated. The theoretical results suggest that as T2* decreases, due to either static magnetic field inhomogeneities or shortened T2 relaxation times, the calculated optimum sampling rate increases accordingly. Since biological tissues exhibit wide variations in their magnetic susceptibilities and T2 relaxation times for various isotopes but modern magnets are characterized by good magnetic field homogeneity, the optimum sampling rate should exhibit an observable dependence on the tissue type.

31P and 23Na NMR studies of the structure and lability of the sodium shift reagent, bis(tripolyphosphate)dysprosium(III) ([Dy(P3O10)]7-) ion, and its decomposition in the presence of rat muscle.

The 31P NMR of aqueous [Dy(P3O10)2]7- demonstrates that it is in slow exchange with P3O5-10 on the NMR time scale. In the presence of tissue, [Dy(P3O10)2]7- decomposes to PO4 with an accompanying slow change of the tissue 23Na NMR of extracellular Na+ ion in several NMR distinguishable extracellular sites.

A combined spectroscopic study of the solution conformation of bradykinin.

CD, NMR and laser Raman spectroscopy have been used in a complementary fashion to study the conformation of bradykinin and related peptides. The results are interpreted to mean that the secondary structure of bradykinin in aqueous solution is a time average of two interconverting structures - one disordered and the other partially ordered. The peptide evidently spends a maximum of about 20% of its time in the partially ordered conformation which features a hydrogen-bonded structure at the C-terminus, most likely a gamma-turn with Pro7 as the second residue.

Carbon-13 nuclear magnetic resonance studies of cyanocobalamin and several of its analogues.

The carbon-13 nuclear magnetic resonance spectrum of cyanocobalamin in aqueous solution has been interpreted. The assignments are based on the earlier biosynthetic studies with carbon-13-enriched precursors and on the present systematic analysis of the spectra of cyanocobalamin, cyanocobalamin lactone, cyanocobalamin lactam, cyanoepicobalamin, and several cyanocobalaminmonocarboxylic acids. The interpretation of the spectrum of cyanocobalamin greatly simplifies the structure determination of new corrinoids and should prove very helpful in future studies of these compounds.

13C nuclear magnetic resonance studies of the biosynthesis by Microbacterium ammoniaphilum of L-glutamate selectively enriched with carbon-13.

13C NMR of isotopically enriched metabolites has been used to study the metabolism of Microbacterium ammoniaphilum, a bacterium which excretes large quantities of L-glutamic acid into the medium. Biosynthesis from 90% [1-13C]glucose results in relatively high specificity of the label, with [2,4-13C2]glutamate as the major product. The predominant biosynthetic pathway for synthesis of glutamate from glucose was determined to be the Embden Meyerhof glycolytic pathway followed by P-enolpyruvate carboxylase and the first third of the Krebs cycle.

Carbon-13 nuclear magnetic resonance study of protonation of methotrexate and aminopterin bound to dihydrofolate reductase.

Methotrexate, aminopterin, and folate have been synthesized with 90% enrichment of C-2 with 13C. 13C nuclear magnetic resonance has been used to examine the state of protonation of the pteridine ring of these compounds under various conditions and gives much more clear-cut results than most other methods. For the free compounds the following pK values were obtained: methotrexate, 5.

Effect of temperature upon the circular dichroism of bradykinin.

Analysis of the effect of temperature on the circular dichroism spectrum of bradykinin has led to a more precise understanding of the solution conformation of the peptide. Circular dichroism and 13C n.m.

13C nuclear magnetic resonance study of the cis-trans isomerism in X-Pro-Pro tripeptides.

13C nuclear magnetic resonance has been used to characterize quantitatively the cis-trans isomerism about both peptide bonds in the tripeptides Ser-Pro-Pro and Arg-Pro-Pro. Detailed pH titration data indicate that the configuration about both peptide bonds is closely linked to titration of the terminal carboxyl group and, to a lesser extent, to titration of the terminal amino group. The Pro2 C-3 resonance has been found particularly useful for interpretation due to its sensitivity to the isomerization about both peptide bonds.

Carbon-13 nuclear magnetic resonance of heme carbonyls. Cytochrome c and carboxymethyl derivatives of cytochrome c.

Carbonyl complexes of horse cytochrome c and various carboxymethylated derivatives have been examined using 13C NMR (carbon-13 nuclear magnetic resonance) spectroscopy. The multiplicity and chemical shift of the 13CO resonance were found to be functions of pH and the extent of alkylation. Correlations have been made among prominent features of the chemical shift titration curves and changes in the environment of the heme.