Cardiac magnetic resonance spectroscopy

The article reviews cardiac magnetic resonance spectroscopy (MRS) in Canada. 31P MRS has been used to study cardiac energetics and intracellular pH in hearts subjected to ischemia-reperfusion and to evaluate the effects of pharmacological interventions. 23Na, 87Rb, and 7Li MRS have provided unique probes to study ion balance and fluxes in intact tissue under normal and stressful physiological conditions. 1H MRS has been used to monitor the accumulation of lactate and lipids in hearts subjected to ischemia-reperfusion and follow the effects of diet on cardiac lipid levels and function. The isolated rat heart has been used most commonly to study the effects of pharmacological agents on energy balance, pH, ion fluxes, and contractile function of the heart subjected to ischemia-reperfusion. The pig heart has been developed as an alternative to the rodent heart because its metabolism is more similar to that of the human heart. Human atrial appendages have been useful in evaluating the effects of preservation strategies (temperature, composition of preservation solutions) on energy levels. The pig heart model has been useful in evaluating the effects of preservation solutions on cardiac function of hearts destined for transplantation. An isolated blood-perfused pig heart model has been developed to assess the effects of cardioplegic strategies on the preservation of contractile function of hearts following surgery on the heart. An in vivo canine model has been used to study myocardial infarction and the effects of therapies to reduce the infarct zones and areas of the heart at risk of infarction. Studies of human hearts in vivo have provided insight into the metabolic adaptations that occur in individuals living at high altitudes.     

Proton magnetic resonance spectroscopy in primary blepharospasm

Single-volume proton magnetic resonance spectroscopy, localized to basal ganglia, was carried out in 10 patients with primary blepharospasm (PB) to assess the levels of N-acetyl aspartate (NAA), creatine-phosphocreatine, and choline-containing compounds. NAA was reduced significantly in patients compared with control subjects. This result suggests a striatal neuronal loss in PB.     

Clinical applications of magnetic resonance spectroscopy

Neurospectroscopy measures a neuronal marker, energy and redox state, specific fuels of tissue respiration, maturation, and possibly myelination. It provides diagnostic patterns of altered neurochemistry. Current clinical uses range from intensive care in neonates to dementia in the elderly and include tumor and stroke management, prognosis in hemorrhage and trauma, white matter, inflammatory diseases, and AIDS. Inborn errors, metabolic and systemic diseases, subclinical hepatic encephalopathy, hyponatremia, and "coma" have been elucidated. Automation, single-voxel MRS, chemical shift imaging, quality control, and outcome analyses are discussed. With no remaining impediments to clinical use, neurospectroscopy has changed the way we look at diseases of the brain.     

Spin-lattice relaxation in ammonium compounds with a complex molecular dynamics

Expressions are derived for the initial relaxation rate 1/T1 of protons and deuterons of nontunnelling NH4 and ND4 groups reorienting about various symmetry axes in solids. The reorientation rates are modified by a trigonal, tetragonal or monoclinic distortion of the predominantly cubic hindering potential. When the rates differ sufficiently from each other, two T1 minima are observed with a characteristic ratio. Experiments were performed in NH4VO3, (NH4)2S2O8, (NH4)2PtCl4, and their deuterated modifications, which all exhibit two T1 minima. In NH4VO3 and ND4VO3 the relaxation and spectral data agree rather well with the model of trigonal distortion. Also (NH4)2S2O8 has a preferred threefold axis but there, the large tunnel splitting of protons has to be taken into account before an agreement is reached. All the purely reorientational models fail with (NH4)2PtCl4, where, instead, the ammonium groups are proposed to be ordered into domains at low temperatures. The groups inside the domains and boundary regions give rise to the high- and low-temperature T1 minima, respectively. The boundaries are also believed to give rise to the narrow component in the deuteron spectrum at low temperatures. Evidence for a proton tunnelling frequency of 32 MHz is found in (NH4)2PtCl4.     

Two-dimensional transferred-echo double resonance study of molecular motion in a fluorinated polycarbonate

A case-control study was undertaken to provide information about the role of some husbandry practices and farm characteristics in the epidemiology of bovine tuberculosis in the Veneto Region. Twenty-seven breeding herds where a positive result to the single intradermal cervical tuberculin test was confirmed by post-mortem examination were compared with seventy-four herds which had been free of the disease for at least three years. Epidemiological information was collected on farms. The factors taken into account in the study were chosen on the basis of their epidemiological plausibility and of the local livestock characteristics. Multiple logistic regression was applied to analyse the data. Factors identified as possibly involved in increasing the risk of bovine tuberculosis in the Veneto Region were the presence of mixed (dairy and beef) enterprises (OR = 4.9, P = 0.001) and of cattle purchase (OR = 5.8; P = 0.003). Other factors (such as herd size, housing system, summer mountain pasture, possible contact with wild animals, and indirect contacts with other herds) did not appear to significantly contribute to tuberculosis presence in this area. The results of this case-control study support the hypothesis that in the Veneto Region bovine tuberculosis infection is still associated with classical risk factors both (directly or indirectly) related to cattle movements.     

Proton magnetic resonance spectroscopy in patients with glial tumors: a multicenter study

Budding yeast (Saccharomyces cerevisiae) Rap1p has been expressed in fission yeast (Schizosaccharomyces pombe) under the control of the regulatable fructose bisphosphatase (fbp) promoter. When the fbp promoter was derepressed, cells containing the complete RAP1 gene failed to show any significant growth, suggesting that Rap1p is toxic. A derivative of Rap1p that has a temperature-sensitive mutation in the DNA-binding domain was not toxic in cells grown at 37 degrees C, a temperature at which DNA binding by rap1p(ts) is severely inhibited. Removal of a short region downstream of the DNA-binding domain, including a region previously shown to be essential for Rap1p toxicity in budding yeast, also abolished the toxic effect. The toxic effect of Rap1p has therefore been conserved between two distantly related yeasts. In budding yeast, overexpression of Rap1p also caused changes to the lengths of the telomeric repeats. No effects on telomeres were detected in fission yeast.     

Proton magnetic resonance spectroscopy in children with Sturge-Weber syndrome

Quantitative proton magnetic resonance spectroscopy was performed on six children with Sturge-Weber syndrome following gadolinium enhanced magnetic resonance imaging (MRI). MRI revealed only unilateral involvement in all cases. The mean concentration (mmol/kg wet weight) of the neuronal marker N-acetyl-aspartate was significantly reduced by 37% in the ipsilateral gadolinium enhanced volume of interest compared to a similarly placed contralateral volume of interest (5.39 +/- 1.70 [SD] vs 8.50 +/- 1.14, P < .005, two-tailed paired Student's t-test). Decreased N-acetyl-aspartate in the ipsilateral volume of interest was observed in all patients studied. No significant differences were found in the concentrations of creatine/phosphocreatine or choline compounds between the ipsilateral and contralateral volumes of interest. These findings give possible new insight into the pathophysiology of this disease and suggest that quantitative proton magnetic resonance spectroscopy may be useful for the early characterization and monitoring of neuronal dysfunction or loss in infants and children with Sturge-Weber syndrome.     

Magnetic resonance spectroscopy: use in monitoring MELAS treatment

BACKGROUND: Sodium dichloroacetate has been used to treat patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes (MELAS). Magnetic resonance spectroscopy (MRS) has been used to assess cerebral metabolism in MELAS, but to our knowledge, the findings of serial MRS studies performed after therapeutic intervention of strokelike episodes have not been reported. METHODS: Proton MRS was serially used to measure brain metabolites in strokelike regions and in clinically uninvolved brain regions in a patient with MELAS. PATIENT: A patient with MELAS and a strokelike episode clinically improved after treatment with sodium dichloroacetate. An elevated lactate-creatine ratio in the "stroke" region decreased on MRS studies after treatment. After a second episode, the lactate-creatine ratio increased from baseline in a region of the brain that was normal on magnetic resonance imaging scans. CONCLUSIONS: To our knowledge, this is the first study to assess the response to treatment of a MELAS strokelike episode and the first to show an increase in the lactate-creatine ratio in a brain region that was associated with a clinical abnormality, even though it appeared normal on magnetic resonance imaging. We conclude that MRS may help to monitor therapeutic efficacy in mitochondrial encephalomyopathies.     

Magnetic resonance spectroscopy detects cancer in draining lymph nodes

The spread of cancer cells to draining lymph nodes is an important prognostic factor for many cancers and influences postoperative therapy in patients. Histopathology is used routinely to assess if lymph nodes contain metastases. There are, however, time and resource constraints on the volume of lymph node tissue that can be examined by the pathologist in a routine laboratory (less than 2% of each node), thus major sampling errors are possible. Conventional histopathology also relies on identifying aggregates of malignant cells for a positive diagnosis. Proton (1H) magnetic resonance (MR) spectroscopy can detect chemical changes, specifically increased levels of lactate, choline, fucose and amino acids, in lymph nodes infiltrated by cancer. Increase in lactate indicates the presence of anaerobically respiring cells, whereas choline reports that the cells are replicating. Since MR spectroscopy can identify early infiltration by malignant cells, before cell clusters are visible under the light microscope, it detects micrometastases in lymph nodes missed histopathologically. Furthermore, MR spectroscopy eliminates sampling errors since the entire lymph node is examined.     

Quantitative proton magnetic resonance spectroscopy of childhood adrenoleukodystrophy

Cerebral metabolic disturbances in patients with childhood adrenoleukodystrophy (ALD) were assessed by quantitative localized proton MRS. Patient monitoring by follow-up MRS studies served to identify putative markers for disease onset and progression. Whereas normal-appearing white matter of neurologically asymptomatic patients is characterized by slightly elevated concentrations of choline-containing compounds (Cho), an increase of both Cho and myo-inositol (Ins) seems to indicate the onset of demyelination. Markedly elevated concentrations of Cho, Ins, and glutamine in affected white matter reflect active demyelination and glial proliferation. A simultaneous reduction of the concentrations of N-acetylaspartate and glutamate is consistent with neuronal damage or loss. The observation of elevated lactate is in line with inflammation and/or macrophage infiltration. The more severe metabolic disturbances in cerebral ALD correspond to progressive demyelination, neuroaxonal loss and gliosis leading to clinical deterioration and eventually death. The detection of MRS abnormalities before the onset of neurological symptoms may help in the selection of patients for bone marrow transplantation (BMT). Stabilization and partial reversal of metabolic abnormalities is demonstrated in a patient after BMT.     

Proton magnetic resonance spectroscopy of excised pig liver

After evaluating ex vivo pig liver by 1H magnetic resonance spectroscopy (1H-MRS) using a 1.5 Tesla super-conducting unit, the assignment of peaks was reevaluated in vitro using a 9.4 Tesla superconducting unit. The portal vein was cannulated and perfused by cooled Euro-Collins solution, and pig liver was removed and preserved in the solution. Five to 8 g of the liver was excised before and after preservation, then extracted by perchloric acid (PCA). In 1H-MRS of PCA extracted pig liver, large peaks of fatty acid disappeared, while peaks of the choline group from 3.2-3.3 ppm were clearly observed. Using high performance liquid chromatography (HPLC) and 31P (phosphorus)-MRS, the 3.23 ppm peak was determined as glycerophosphorylcholine (GPC), which diminished after preservation. The chronological change of GPC in PCA extracted pig liver was able to be observed by 1H-MRS. GPC peak may play a role as an indicator in evaluating preserved liver by 1H-MRS.