Muscle glycogen recovery after exercise measured by13C-magnetic resonance spectroscopy in humans: effect of nutritional solutions

The rate of glycogen resynthesis in human skeletal muscle after glycogen-depleting exercise is known to depend on carbohydrate intake and is reported to reach a platean after an adequate amount of carbohydrate (CHO) consumption. Efforts to maximize the rate of glycogen storage by changing the type and form of CHO, as well as by adding proteins or lipids have yielded inconsistent results. The objective of this study was to assess whether isocaloric addition of proteins and arginine to a CHO diet in the first 4 h after an endurance exercise would increase the rate of glycogen synthesis. The CHO solution, given twice at a 2 h interval according to earlier optimized protocols, contained 1.7 g CHO kg^{body weight}. The effects of this solution were compared to those of an isocaloric solution containing 1.2 g CHO/kg^{body weight} plus 0.5 g protein/kg^{body weight} (including 5 g arginine). Glycogen was measured in quadriceps muscle in vivo with natural abundance¹³C-magnetic resonance spectroscopy before exercise and twice after exercise, before and at the end of a 4-h period following the intake of one of the solutions. Eight subjects took part in a randomized cross-over trial separated by at least 1 week. Glycogen synthesis was found to be significantly increased with both regimes compared to a zero-caloric placebo diet, but no significant difference in glycogen resynthesis was found between the CHO-only diet and the one supplemented by proteins and arginine. It is estimated that significance would have been reached for an increase of 34%, while the effectively measured synthesis rates only differed by 5%.     

Influence of cytosolic pH onin vivo assessment of human muscle mitochondrial respiration by phosphorus magnetic resonance spectroscopy

The authors present anin vivo phosphorus magnetic resonance spectroscopy systematic study on the effects of cytosolic pH on skeletal muscle mitochondrial respiration in human calf muscle. In 49 normal subjects, the effect of cytosolic pH on kinetics of phosphocreatine and adenosine diphosphate recovery and on maximum rate of mitochondrial adenosine triphosphate production (Q_max) was evaluation. The results show a strong relationship between the rate of postexercise phosphocreatine recovery and the lowest value of cytosolic pH reached during recovery from exercise (termed minimum pH;r=0.89); in constrast, both adenosine diphosphate recovery halftime andQ _max were independent of cytosolic pH at the end of exercise.     

Knee extension dynamometer: a new device for dynamic isokinetic magnetic resonance spectroscopy experiments

In the present study we introduce a new device for exercise magnetic resonance spectroscopy (MRS). It operates in a standard whole-body scanner. Mechanical exertion unit allows maximal 10° to 15° short-arc knee extensions. The device operates hydraulically and is based on isokinetic movement. The force and work conducted are automatically controlled by the electronic control and computer unit. A small surface coil placed on the vastus medialis muscle allows the collection of spectra without interfering spectra from nearby resting muscles. The force used for the extensions can be followed simultaneously as a curve on the screen in the operator's room and the data is transferred to a personal computer for later analysis. Total work and fatigue percentage are also calculated by the device. It also allows the use of different isokinetic exercise protocols. The measurements of force proved reliable in repeat measurements using an isokinetic test device as a control.This device has been used clinically for over a year, is easy to operate, and offers reliable measurements. It is well suited to trials where muscle energy states versus time are followed since it allows noninvasive simultaneous quantification of muscle performance and collecting MRS spectra at rest, during exercise, and in the recovery phase.     

31P magnetic resonance spectroscopy of the liver in an infant with galactosaemia

Sequential studies of the liver of an infant with galactosaemia were made by phosphorus magnetic resonance spectroscopy (31P MRS). A peak attributable to galactose 1-phosphate (gal 1-P) was seen in early liver spectra. This peak diminished during dietary therapy in the early months of life, corresponding to a falling level of gal 1-P in red blood cells.     

Proton magnetic resonance spectroscopy of the central,transition and peripheral zones of the prostate: assignments and correlation with histopathology

Proton magnetic resonance spectroscopy (MRS) is used to compare the chemistry of the transition, central and peripheral zones of the prostate. The assignments are made using two-dimensional correlated spectroscopy and the results compared with histopathology. The chemistry associated with benign prostatic hyperplasia (BPH), prostate intraepithelial neoplasia (PIN) and malignant biopsy tissues are described. There are distinct MR spectral patterns for glandular and stromal BPH, PIN and adenocarcinoma. Importantly, there are also different spectral patterns from BPH in the transitional and central zones when compared to BPH in the peripheral zone. A pattern recognition method is used to analyze the MR spectra from the biopsy specimens. The resultant mathematical classifiers generated a high level of accuracy (sensitivity and specificity of 100 and 97%). It was found that for this accuracy to be achieved, the classifiers need to be developed by comparing the spectra with specialist serial sectioned histopathology. With serial sectioned pathology the pattern recognition method was capable of identifying less than 5% of adenocarcinoma in a given piece of tissue. Many of the chemicals identified in the biopsy specimens are available for inspection from the prostate, in vivo, at 3 T.     

In vivo quantification of response to treatment in patients with multiple myeloma by <Superscript>1</Superscript>H magnetic resonance spectroscopy of bone marrow

Object Magnetic resonance imaging (MRI) is the gold standard non-invasive technique to detect malignant disease in the bone marrow. Proton magnetic resonance spectroscopy (MRS) can be performed as a quick adjunct to routine spinal MRI. We performed proton MRS to patients with multiple myeloma (MM) at diagnosis and after treatment to investigate the possible correlation of MRS data with response to therapy. Patients and methods Twenty-one patients with newly diagnosed MM underwent combined MRI/MRS explorations of a transverse center section in the fifth lumbar vertebral body. MRS was acquired with STEAM and 40 ms TE. Areas of unsuppressed water and lipid resonances were used to calculate the lipid-to-water ratio (LWR). Results No association was detected between initial LWRs and the clinical characteristics of patients. Post treatment MRS was available in 16 patients of whom 11 (69%) presented an LWR increase, this included all complete responders (8/8, 100%, P = 0.012). A post-treatment LWR value equal to or larger than one is proposed as a non-invasive marker of complete response to treatment. Conclusion Only patients responding to treatment presented a significant increase in bone marrow LWR after therapy. MRS may provide an adequate quantification of response to chemotherapy in patients with MM.     

1H magnetic resonance spectroscopy studies of cerebral metabolism in children

This article summarizes some applications of¹H magnetic resonance spectroscopy in the investigation of children with brain disease. Studies are described of children with inborn errors of metabolism, including lactic acidoses and mitochondrial disorders, ornithine carbamoyl transferase deficiency (a disorder of the urea cycle), and Canavan's disease (a disorder of N-acetylaspartate metabolism). Applications in epilepsy are also discussed.     

Role of magnetic resonance methods in the evaluation of prostate cancer: an Indian perspective

The challenges in detection, localization, and staging of prostate cancer have prompted the investigation of the role of various magnetic resonance (MR) methodologies in a large cohort of men prior to biopsy. The identification of suspicious areas of malignancy was carried out using magnetic resonance imaging (MRI), magnetic resonance spectroscopic imaging (MRSI) and diffusion-weighted imaging (DWI). Our data shows that apparent diffusion coefficient (ADC) may be a reliable marker to differentiate normal, benign, and malignant prostate tissues similar to the metabolite ratio. Also, the combined use of MRSI and DWI improves the diagnosis of prostate cancer. In this review, we present our experience on the use of MRI, MRSI and DWI methods in the assessment of prostate cancer in Indian men. Further, analysis of the comparison of the ADC and the metabolite ratio values reported in the literature across various patient populations are presented. An erratum to this article can be found at     

Muscle glycogen recovery after exercise measured by 13C-magnetic resonance spectroscopy in humans: effect of nutritional solutions

The rate of glycogen resynthesis in human skeletal muscle after glycogen-depleting exercise is known to depend on carbohydrate intake and is reported to reach a plateau after an adequate amount of carbohydrate (CHO) consumption. Efforts to maximize the rate of glycogen storage by changing the type and form of CHO, as well as by adding proteins or lipids have yielded inconsistent results. The objective of this study was to assess whether isocaloric addition of proteins and arginine to a CHO diet in the first 4 h after an endurance exercise would increase the rate of glycogen synthesis. The CHO solution, given twice at a 2 h interval according to earlier optimized protocols, contained 1.7 g CHO/kg(body weieght) The effects of this solution were compared to those of an isocaloric solution containing 1.2 g CHO/kg(body weight) plus 0.5 g protein/kg(body weight) (including 5 g arginine). Glycogen was measured in quadriceps muscle in vivo with natural abundance 13C-magnetic resonance spectroscopy before exercise and twice after exercise, before and at the end of a 4-h period following the intake of one of the solutions. Eight subjects took part in a randomized cross-over trial separated by at least 1 week. Glycogen synthesis was found to be significantly increased with both regimes compared to a zero-caloric placebo diet, but no significant difference in glycogen resynthesis was found between the CHO-only diet and the one supplemented by proteins and arginine. It is estimated that significance would have been reached for an increase of 34%, while the effectively measured synthesis rates only differed by 5%.     

Regional proton nuclear magnetic resonance spectroscopy differentiates cortex and medulla in the isolated perfused rat kidney

Volume-localized proton nuclear magnetic resonance spectroscopy was used as an assay of regional biochemistry in the isolated perfused rat kidney. This model eliminated artifacts caused by respiratory and cardiac motion experiencedin vivo. Immersion of the kidney under its venous effluent reduced the susceptibility artifacts evoked by tissue-air interfaces. The rapid acquisition with relaxation enhancement imaging sequence was used for scout imaging. This gave excellent spatial resolution of the cortex, outer medulla, and inner medulla. Spectra were then acquired in 10 minutes using the volume-selective multipulse spectroscopy sequence from voxels with a volume of approximately 24 μL located within the cortical or medullary regions. Spectral peaks were assigned by the addition of known compounds to the perfusion medium and by comparison with spectra of protein-free extracts of cortex and medulla. The medullary region spectra were characterized by signals from the osmolytes betaine, glycerophosphorylcholine, and inositol. The spectra from the cortex were more complex and contained lesser contributions from osmolytes.     

Enhancement characteristics of hepatic focal nodular hyperplasia and its scar by dynamic magnetic resonance imaging

Rationale and objectives: To determine the relationship between the lesion and the scar enhancement characteristics in a series of hepatic Focal Nodular Hyperplasia (FNH) lesions studied with dynamic MR imaging.Methods: Nine patients with FNH were studied. The slice showing the largest scar was selected for the dynamic single slice T1-weighted Gradient-echo sequence before and after contrast administration (15 images, one every 20 s). Analysis was performed with ROI measurements in the lesion and the scar. Signal-intensity and enhancement curves were obtained from both structures.Results: Dynamic MRI showed the typical homogeneous early enhancement of the lesion with delayed enhancement of the scar. The scar enhanced early and vigorously in all cases. Two patterns of enhancement curves were defined. In the parallel pattern, both curves started early, quickly reaching a plateau maintained over time (77.8%). In the divergent pattern the curve of the scar was above the curve of the FNH (22.2%). after the maximum slope was reached, with progressive separation of the curves.Conclusion: There is a hypervascular scar enhancement within FNH lesions with either a parallel or divergent course after the maximum early enhancement.     

Glycolytic atp production estimated from31p magnetic resonance spectroscopy measurements during ischemic exercisein vivo

In an oxygen-depleted muscle, glycolytically produced ATP is inversely related to the ([ATP] + creatine phosphate [PCr]) decrease because ATP, PCr, and glycolysis are virtually the only energy sources under these conditions. In particular, the onset of glycolysis or any appreciable increase in the rate of glycolytic ATP production will lead to a slower rate of ([ATP] + [PCr]) breakdown at a given energy consumption. To quantify this relationship, endurance athletes performed isometric foot plantar flexion (20% of a test force [TF],n=10; 50% TF,n=5) during local arterial occlusion. Parameters of energy metabolism were measured with³¹P magnetic resonance spectroscopy (³¹P-MRS). During exercise, [PCr] decreased to 80±10 (20% TF) and 11±4% (50% TF) of its resting concentration, and pH dropped from 7.04 0.01 to 6.98±0.10 (20% TF) and from 7.03±0.02 to 6.70 0.10 (50% TF). In both experiments, two phases of ([ATP] + [PCr]) decrease were observed: an initial faster decrease was followed by a slower decline. The latter phase started at about the time when the pH began to drop. The difference between a line extrapolated from the slope of the initial phase and the measured ([ATP] + [PCr]) decrease was used as an estimate for glycolytically produced ATP. This estimate and pH were significantly correlated withr=–0.97 (20% TF) andr=–0.99 (50% TF). These results indicate that glycolytically produced ATP can be estimated from the ([ATP] + [PCr]) decrease during exercise.     

Valproic acid intoxication identified by1H and1H-13C correlated NMR spectroscopy of urine samples

Analysis of biological fluids by proton and carbon nuclear magnetic resonance spectroscopy (¹H and¹³C NMR) is a promising tool in clinical biology. We used this method for rapid toxicological screening in the case of two suicide attempts. For each case, a urine sample was analysed at 300 MHz by 1D and 2D sequences (TOCSY and HMBC) in a short experimental time. Quantification was performed by peak integration on the 1D¹H NMR spectrum. For the two patients, results showed the same resonances of the major metabolite, valproyl-O-glucuronide at concentrations of 121 and 44 mmol/l.     

Validation of glutathione quantitation from STEAM spectra against edited 1H NMR spectroscopy at 4T: application to schizophrenia

Objective: Quantitation of glutathione (GSH) in the human brain in vivo using short echo time ¹ H NMR spectroscopy is challenging because GSH resonances are not easily resolved. The main objective of this study was to validate such quantitation in a clinically relevant population using the resolved GSH resonances provided by edited spectroscopy. A secondary objective was to compare several of the neurochemical concentrations quantified along with GSH using LCModel analysis of short echo time spectra in schizophrenia versus control. Materials and Methods: GSH was quantified at 4T from short echo STEAM spectra and MEGA-PRESS edited spectra from identical volumes of interest (anterior cingulate) in ten volunteers. Neurochemical profiles were quantified in nine controls and 13 medicated schizophrenic patients. Results: GSH concentrations as quantified using STEAM, 1.6 ± 0.4 μmol/g (mean ± SD, n=10), were within error of those quantified using edited spectra, 1.4 ± 0.4 μmol/g, and were not different (p=0.4). None of the neurochemical measurements reached sufficient statistical power to detect differences smaller than 10% in schizophrenia versus control. As such, no differences were observed. Conclusions: Human brain GSH concentrations can be quantified in a clinical setting using short-echo time STEAM spectra at 4T.     

Visualization of cardiac involvement in patients with systemic sarcoidosis applying contrast-enhanced magnetic resonance imaging

5. Summary Contrast-enhanced MRI may serve as a sensitive noninvasive tool for the detection and follow-up of myocardial involvement in patients with systemic sarcoidosis.     

Low-field magnetic resonance imaging of the pelvis in patients with anal dynamic graciloplasty: initial experience

The aim of this study was to determine whether low-field magnetic resonance (MR) imaging can safely and accurately depict inflammatory changes in patients with anal dynamic graciloplasty, in whom high-field MR imaging is contraindicated and ultrasonography and computed tomography are inadequate. A 0.2-T field-strength MR examination was performed in six patients with anal dynamic graciloplasty malfunction in whom reoperation was contemplated. The following sequences were applied:T ₂-weighted turbo spinecho with fat saturation,T ₁-weighted conventional spin-echo, and contrastenhancedT ₁-weighted conventional spin-echo with fat saturation. Results indicated that none of the patients experienced relevant discomfort, pacemaker malfunction, or electrode dislocation with low-field MR imaging. Inflammatory pelvic changes were visualized in four patients and atrophy of the transposed gracilis muscle in another. Surgery was thus avoided in the four, who underwent conservative treatment for their pelvic inflammation. It was concluded that these prelininary results demonstrate the feasibility of MR imaging with a low field strength in patients with anal dynamic graciloplasty. In such patients, in whom diagnostic imaging had been problematic, the potential for safe and accurate visualization will be a boon to treatment planning.     

Metabolic changes in the rat brain after a photochemical lesion treated by stem cell transplantation assessed by 1H MRS

Object  Metabolite changes in an experimental lesion in the rat cortex and in the contralateral hemisphere after the intravenous administration of mesenchymal stem cells (MSCs) were assessed by proton MR spectroscopy to verify the impact of the cell treatment on the brain tissue. Materials and methods  Wistar rats with a photochemical cortical lesion and transplanted MSCs or sham transplanted rats were examined. Proton spectra were obtained from the lesion and from the contralateral cortex. Results  Magnetic resonance spectroscopy revealed a gradual recovery of the damaged tissue; however, we found no significant differences in metabolite concentrations in the lesioned hemisphere between treated and untreated animals. Higher concentrations of glutamate and N-acetyl aspartate were found in the contralateral hemisphere in cell-treated animals compared to untreated ones. Lesioned animals showed neurogenesis in the contralateral hemisphere; the number of newly generated cells in stem cell-treated animals was 50% higher than those observed in untreated animals. Conclusion  No direct impact of cell transplantation was observed in the lesion. However, changes in the contralateral hemisphere suggest that the transplanted MSCs might stimulate repair processes and plasticity resulting in the generation of newborn cells, which might enable the faster adoption of the damaged tissue’s function by healthy tissue.     

Transient global brain ischemia in young and aged rats: differences in severity and progression, but not localisation, of lesions evaluated by magnetic resonance imaging

A model of transient global brain ischemia consisting of bilateral occlusion of common carotid arteries for 10 min and mild hypoxia (15% O₂−85% N₂) for 20 min was studied by means of MRI in young and aged Fischer 344 rats (3–4 and 24–26 months, respectively). Ischemia was assessed by full suppression of spontaneous EEG activity, which reappeared and normalized similarly in the two age-groups. The survival of young with respect to aged rats was considerably higher both at 24 h (20/20, i.e. 100% vs 12/16, i.e. 75%) and at 48 h (16/20, i.e. 80% vs 6/16, i.e. 38%). The localisation of brain lesions, their severity and progression were evaluated by a diffusion-weighted MRI (DWI) sequence at 24 and 48 h post-ischemia. There were no DWI-detectable lesions in eight out of 20 young and two out of 12 aged rats. The localisation of DWI-detected lesions was rather similar in rats of the two age-groups. In fact, the cerebral cortex, mainly parietal, occipital and temporal lobes were damaged in 83% of young and 90% of aged rats. The respective percentages for the thalamus were 83 and 60%, for the striatum 58 and 50%, and for the hippocampus 25 and 30%. The lesions present in the cerebral cortex and the thalamus were considerably more severe in aged than in young rats. In conclusion, in spite of similar localisation of ischemic lesions in the two age-groups, their incidence was higher, appearance more rapid and severity more pronounced in aged with respect to young rats. This resulted in a considerably higher mortality of the former. The overall data indicate that the age issue is very important in experimental ischemia research.