Muscle metabolism in patients with polymyositis simultaneously evaluated by using 31P-magnetic resonance spectroscopy and near-infrared spectroscopy.

Simultaneous measurements of muscle energy metabolism using (31)P-magnetic resonance spectroscopy ((31)P-MRS) and the kinetics of muscular oxygen metabolism using near-infrared spectroscopy (NIRS) were conducted in polymyositis (PM) patients. The subjects were 12 PM patients (age 45 +/- 12 years) and 12 normal controls (age 41 +/- 12 years). The muscle phosphocreatine (PCr) index and intracellular pH (pHi) were determined with (31)P-MRS and the changes in intramuscular oxygenated (oxy-Hb), deoxygenated (deoxy-Hb), and total haemoglobin (total Hb) were evaluated with NIRS . The pHi and PCr index before steroid therapy in PM patients were significantly lower during exercise than in normal controls, and their recovery was statistically significantly delayed compared with the controls. The pattern of changes in NIRS over time before steroid therapy in PM patients differed from that in normal controls. There were smaller changes in deoxy-Hb and oxy-Hb during exercise, and total Hb decreased during exercise. In contrast, the kinetics of muscular metabolism after steroid therapy showed changes similar to those seen in normal controls. Simultaneous (31)P-MRS and NIRS measurements to determine the kinetics of muscular metabolism are expected to be useful as a noninvasive approach for the evaluation of treatment effects in PM patients.

Energy metabolism and cerebral blood flow during cytotoxic brain edema induced by 6-aminonicotinamide.

We investigated the progression of cytotoxic brain edema induced by 6-aminonicotinamide (6-ANA), a potent antimetabolite of nicotinamide, by measuring the time courses of changes in brain tissue water state (with MRI), histology (with H&E staining), energy metabolism (with 31P-NMR), brain hemoglobin concentration (with near-infrared spectroscopy; NIRS), cerebral blood flow and volume (CBF. CBV), mean arterial blood pressure (MABP), and brain activity (with EEG) up to 10 hours (h). Change in cerebrovascular autoregulation was also investigated. 6-ANA (120 mg/kg) was administered intraperitoneally to 30 male Wistar rats (250-350 g). After 10 h, the T2-weighted signal intensity was increased (p < 0.05), and H&E staining showed severe vacuolation of glial cells. ATP production/consumption and intracellular pH were well maintained up to 10 h, while the intensity of the phosphomonoesters (PME) signal was significantly increased (p < 0.05). Oxygen consumption gradually decreased from 4 to 10 h. CBF and MABP were all significantly increased (by 2.5-fold for CBF) (p < 0.05). Theta and delta wave amplitudes were reduced at 10 h. In summary, 6-ANA (120 mg/kg) induced cytotoxic brain edema from 4 to 10 h. Energy balance and brain activity were well maintained up to 10 h, though cerebrovascular autoregulation was impaired.

Distribution of brain oedema in the contralateral hemisphere after cerebral infarction: repeated MRI measurement in the rat.

The appearance of local cerebral dysfunction at remote regions from the focus in the acute stage of stroke (diaschisis) is well known, but its mechanism has not been established. We have analysed serial MR images of the infarcted brain of rats to evaluate the distribution of oedema. Forty-seven Sprague-Dawley rats were anaesthetized with halothane, and the right middle cerebral artery (MCA) was permanently occluded via the intraluminal approach using a nylon 2-0 suture. At 3, 6, 9 and 24 hours after the occlusion, coronal T(2)-weighted MR images were taken and the signal intensity (SI) was computed at each region of the brain. After occlusion of the right MCA, SI increased diachronically up to 24 hours on the occluded side of the cortex (52.9+/-3.2 to 104.8+/-22.4) and striatum, which are within the perfusion territory of the MCA. SI increment was also observed at the hippocampus, alveus hippocampi and pyriform lobe, which are not within the territory of the MCA, and at some regions of the contralateral side (52.5+/-4.8 to 69.4+/-14.8 at the cortex). These changes were prominent in ischaemia-vulnerable portions, mild in the cortex, and minimal in the striatum. This contralateral side SI increment indicates remote oedema, which corresponds to diaschisis. We suggest that the mechanism of this remote contralateral oedema is the movement of extravasated protein from the lesion.

Sequential changes in MR water proton relaxation time detect the process of rat brain myelination during maturation.

For better understanding of the behavior of water molecules in the animal brain, changes in magnetic resonance water proton relaxation processes were studied in the rat during maturation. Midbrains of male Wistar rats were removed at various time points ranging from 2 to 70 days after birth. Changes in relaxation time (water proton longitudinal relaxation time by the inversion recovery, and water proton transverse relaxation time by the spin echo and the Carr-Purcell-Meiboom-Gill pulse sequence (CPMG)) and water content were then determined for various stages of brain development. During maturation both water proton longitudinal relaxation time and water proton transverse relaxation time values decreased and this finding paralleled the decline in water content. Using the CPMG pulse sequence, the transverse relaxation time values were observed to separate into two components after 21 days. Morphologically, the most prominent change at the matured stage of midbrain development in the rat is myelination. Water proton relaxation time, which can be estimated using the CPMG pulse sequence, showed a close correlation with myelination in the central nervous system.

Effects of age on muscle energy metabolism and oxygenation in the forearm muscles.

PURPOSE: The effects of aging on muscle metabolism and oxygenation have not yet been elucidated. We evaluated the effects of aging on energy metabolism and oxygenation in sedentary healthy subjects by simultaneously measuring 31P-magnetic resonance spectroscopy (MRS) and near-infrared spectroscopy (NIRS). METHODS: Nine young (28.1 +/- 5.0 yr) and nine older (61.4 +/- 4.6 yr) healthy subjects were studied. The 31P-MR spectrum was obtained every 15 s during and after hand gripping exercise. Intracellular pH (pHi) and PCr/(PCr+Pi) [PCr: phosphocreatine, Pi: inorganic phosphate] were calculated as an index of energy metabolism. The time constant of the PCr/(PCr+Pi) recovery (tau PCr) was calculated. With NIRS, we evaluated the recovery rates of oxygenated (RHbO2) and deoxygenated hemoglobin (RHb) during the initial 10 s of recovery. RESULTS: The PCr/(PCr+Pi) and pHi at rest and at completion of the exercise and tau PCr did not differ between young and older subjects. However, RHbO2 and RHb were significantly slower in older subjects than in young subjects. CONCLUSIONS: The results suggest that muscle energy metabolism in the forearm muscle was not affected by aging. The slower RHbO2 and RHb in older subjects suggested impaired O2 supply, which was probably due to impaired peripheral circulation caused by the process of aging.

Increased production of nitrotyrosine in lung tissue of rats with radiation-induced acute lung injury.

The purposes of this study were 1) to identify the nitric oxide (NO) synthase (NOS) isoform responsible for NO-mediated radiation-induced lung injury, 2) to examine the formation of nitrotyrosine, and 3) to see whether nitrotyrosine formation and lung injury are reduced by an inducible NOS (iNOS) inhibitor, aminoguanidine. The left hemithorax of rats was irradiated (20 Gy), and the degree of lung injury, the expression of NOS isoforms, and the formation of nitrotyrosine and superoxide were examined after 2 wk. iNOS mRNA was induced, and endothelial NOS mRNA was markedly increased in the irradiated lung. Nitrotyrosine was detected biochemically and immunohistochemically. Aminoguanidine prevented acute lung injury as indicated by decreased protein concentration and lactate dehydrogenase activity in bronchoalveolar lavage fluid and improved NMR parameters and histology. Furthermore, the formation of nitrotyrosine was significantly reduced in the aminoguanidine group. We conclude that iNOS induction is a major factor in radiation-induced lung injury and that nitrotyrosine formation may participate in the NO-induced pathogenesis.

Time domain reflectometry: measurement of free water in normal lung and pulmonary edema.

The free water content of lung tissue was investigated by dielectric spectroscopy in normal lungs and in pulmonary edema induced by oleic acid in rats. The dielectric relaxation in a frequency range of 10(7) to 10(10) Hz was measured with the time domain reflectometry method at 25 degreesC. Three dielectric relaxation processes were analyzed for the lung tissue. A high-frequency process around 10 GHz was attributed to the orientation of free water molecules based on the relaxation time [log tauh (in s) = -11.03]. The dielectric strength (Delta epsilon) of this high-frequency peak (Delta epsilonh) should reflect the amount of free water in the tissue. Because the measured Delta epsilonh depended on the air content of the lung samples, the value of Delta epsilonh was corrected for the air content of each sample as determined by the point-counting method in the area where the time domain reflectometry data were obtained. The lungs of rats that received an injection of oleic acid had a significantly increased free water content [(Delta epsilonh of lung/Delta epsilon of pure water) x density of pure water] compared with that in the normal lung (0.76 vs. 0.59 g/cm3). These results indicate that free water occupies approximately 60% of the total volume of normal lung tissue and that there is an increase in free water in pulmonary edema.

Mitochondrial dysfunction of human muscle in chronic alcoholism detected by using 31P-magnetic resonance spectroscopy and near-infrared light absorption.

We previously examined the effect of alcohol on muscle energy metabolism in chronic alcoholics by using 31P-magnetic resonance spectroscopy. Measurements of intracellular pH and PCr index [PCr/(PCr + Pi)] during resting, hand grasping, and recovery in the left flexor digitorum superficialis muscle of alcoholics with neurological signs showed a marked decrease and delayed recovery of pH, but rapid recovery of PCr index indicating that the muscle produces lactate during and after exercise to maintain the ATP level. To clarify the reason for this preference for anaerobic metabolism, we conducted simultaneous measurements of the muscle blood supply during and after exercise by using the near-infrared light method and energy metabolism by using 31P-magnetic resonance spectroscopy. In alcoholics with neurological signs, we observed a significant increase of oxyhemoglobin after exercise with a slight increase of total hemoglobin. In healthy volunteers and chronic alcoholics without neurological signs, such an overshoot of oxyhemoglobin was not observed. We conclude that chronic alcoholics with neurological signs have an abnormality of aerobic metabolism owing to muscle mitochondrial dysfunction.

Early damage to lung tissue after irradiation detected by the magnetic resonance T2 relaxation time.

We sought to determine whether nuclear magnetic resonance relaxation times of water in tissue would be useful to detect molecular damage in lung tissue within 2 weeks after irradiation. Tissue samples were obtained from the lungs of rats at various times between 1 and 14 days after exposure of a hemithorax to 20 Gy 60Co gamma irradiation. The spin-lattice relaxation time, T1, was measured by the inversion recovery method, and the spin-spin relaxation time, T2, was measured by both the Hahn spin-echo (Hahn T2) and the Carr-Purcell-Meiboom-Gill (CPMG T2) methods. The T2 of lung tissue could be divided into two components, T2 fast (T2f) and T2 slow (T2s), which reflected changes in the intracellular and extracellular water, respectively. The CPMG T2f increased significantly 3 days after irradiation (66.3 +/- 2.3 ms compared to 60.8 +/- 2.6 ms), and the CPMG T2s increased significantly 1 day after irradiation (155 +/- 11 ms compared to 138 +/- 7 ms), prior to the observation of abnormalities upon examination of the lung by light microscopy. The CPMG T2 values increased further up to 14 days after irradiation when significant increases were observed in values for T1, Hahn T2 and water content. Our results indicate that the molecular derangement in irradiated lung tissue was detected by the CPMG T2 measurement in the very early stage, and that MRI may be superior to conventional radiographs for detecting the early damage to lung tissue after irradiation.

Dependence of transverse relaxation time T2 of biologic tissues on the interpulse delay time in Carr-Purcell-Meiboom-Gill (CPMG) measurements.

To determine the transverse relaxation time (T2) of biological tissues in nuclear magnetic resonance measurements, the Carr-Purcell-Meiboom-Gill (CPMG) method has been recommended to avoid the effect of external magnetic field inhomogeneity on T2 values. However, a dependence of T2 on the interpulse delay time (IPDT) in the CPMG measurements has been shown for biological tissues. The present study examined the dependence of the T2 on IPDT for muscle, lung (passively collapsed or degassed), and brain tissues. It was found that the CPMG T2 of the lung was strongly dependent upon the IPDT, in contrast to muscle and brain tissues. The IPDT dependence of the CPMG T2 for lung tissue, which was lessened by degassing, was affected by the magnetic field inhomogeneity due to air-tissue interfaces, but not by the spin-locking effect, since the T2 measured by the Carr-Purcell-Freeman-Hill (CPFH) method did not show this dependence. These results should aid in the evaluation of T2 values for biological tissues measured under various conditions and by different techniques.

Nuclear magnetic resonance study of lung water compartments in the rat.

Nuclear magnetic resonance transverse relaxation time (T2) was previously measured in studies of lung water. The T2 decay curves for peripheral lung tissue were found to be multiexponential with two T2 components: T2 fast (T2f) and T2 slow (T2s). This behavior was explained by the compartmentalization of water, in which the protons of water are restricted and do not undergo rapid exchange between the compartments. We investigated the origin of the water for these T2 components using excised rat lungs. The effect of magnetic field inhomogeneity due to air-tissue interfaces was examined by degassing some lungs. The contribution of intravascular water was examined by perfusing the lungs with oil or NaCl solutions. Degassing produced a greater increase in the T2f than the T2s component, indicating that the water in the alveolar walls exposed to air spaces contributed to the T2f. Perfusion with oil decreased the T2s, indicating that intravascular water contributed to the T2s component. The effects of intravascular osmotic pressure on the T2f and T2s components suggest that intracellular water is related to the T2f component.

Effect of chronic alcohol intake on energy metabolism in human muscle.

We investigated the effect of alcohol on muscle energy metabolism by using 31P magnetic resonance spectroscopy in 12 chronic alcoholics [6 with neurological signs and symptoms (such as cerebellar ataxia or diplopia) and 6 without neurological signs or symptoms], compared with five healthy subjects who also received acute alcohol loading. Intracellular pH and phosphocreatine (PCr) index [PCr/ (PCr + Pi)] were measured during rest, exercise, and recovery in the left flexor digitorum superficialis muscle. In healthy subjects, acute alcohol loading did not influence the changes of muscle pH and PCr index. Alcoholics with neurological signs showed marked decreases in muscle intracellular pH and PCr index during exercise and a marked delay of pH recovery after exercise. There was no delay of PCr index recovery. Alcoholics without neurological signs showed slight decreases in intracellular pH and PCr index, but rapid recovery of both intracellular pH and PCr index was observed. Marked decrease and delayed recovery in pH, but rapid recovery of PCr index, indicate that the muscle of patients with neurological signs produced lactate during and after exercise to maintain the ATP level, which implies that anaerobic metabolism is favored over aerobic metabolism in these patients.

Magnetic resonance relaxation times in acute hydrostatic pulmonary edema induced by noradrenaline in rats.

Models of pulmonary edema have been used to study the nuclear magnetic resonance (NMR) characteristics of lung water. Several investigators have measured changes in the relaxation times in the permeability type of pulmonary edema, but relatively few have measured relaxation times in the hydrostatic type of pulmonary edema. In this study we determined the characteristics of NMR relaxation times T1, T2 (Hahn spin-echo decay) and water content in acute hydrostatic pulmonary edema induced by noradrenaline administration in rats. Changes in T1 and T2 showed a significant prolongation in hydrostatic pulmonary edema. T2 decay curves for peripheral lung tissues were multiexponential and fit two components [T2 fast (T2f) and T2 slow (T2s)]. With two-component T2 analysis, T2s showed greater prolongation than did T2f. The increase in T2s was significantly correlated with an increase in water content, but the increase in the T2f value was not correlated with water content or with a change in T2s. The T2s component, which likely reflected changes in interstitial water, was more closely related than the T2f component to an increase in water content in hydrostatic pulmonary edema. Results suggested that regional changes in hydrostatic pulmonary edema may be evaluated by multicomponent T2 analysis.

Muscle energy metabolism and nutritional status in patients with chronic obstructive pulmonary disease. A 31P magnetic resonance study.

We investigated the relationship between nutritional status and muscle energy metabolism during exercise in 18 male patients with chronic obstructive pulmonary disease (COPD) and 15 male control subjects using 31P nuclear magnetic resonance spectroscopy (31P-MRS). The patients and control subjects were further categorized as in either a well-nourished (% ideal body weight, % IBW > or = 90) or malnourished (% IBW < 90) state. Muscle energy metabolism was evaluated by determining the ratios PCr/(PCr + Pi) (PCr, phosphocreatine; Pi, inorganic phosphate), and ATP/(PCr + Pi + ATP). The exercise consisted of repetitive hand grips performed against a load. The work rate was normalized for the individual's lean muscle mass by dividing work performed by the forearm fat-free cross-sectional area, which was calculated using 1H-MRS. The PCr/(PCr + Pi) values during exercise did not correlate with the % IBW in any of the groups of control subjects or COPD patients. Furthermore, the PCr/(PCr + Pi) did not correlate with the normalized work rate in either the well-nourished or malnourished subject groups. However, there were correlations within the groups of control subjects and COPD patients. The PCr/(PCr + Pi) values for the normalized work rate were consistently lower in the COPD patients than in the control subjects. These findings suggest that the altered muscle metabolism in COPD patients is not affected by their nutritional status.

[Nuclear magnetic resonance relaxation times for human lung cancer and lung tissues].

We investigated the nuclear magnetic resonance (NMR) relaxation times, T1 and T2, for lung cancer tissue, and other samples of lung tissue obtained from surgical specimens. The samples were nine squamous cell carcinoma, five necrotic squamous cell carcinoma, 15 adenocarcinoma, two benign mesothelioma, and 13 fibrotic lungs. The relaxation times were measured with a 90 MHz NMR spectrometer and the results were correlated with histological changes. The values of T1 and T2 for squamous cell carcinoma and mesothelioma were significantly longer than those of adenocarcinoma and fibrotic lung tissue. There were no significant differences in values of T1 and T2 between adenocarcinoma and lung tissue. The values of T1 and T2 for benign mesothelioma were similar to those of squamous cell carcinoma, which suggested that increases in T1 and T2 are not specific to malignant tissues.

The effect of BAY K-8644 on cytotoxic edema induced by total ischemia of rat brain.

The calcium channel activator BAY K-8644, a dihydropyridine (DHP) derivative, has been shown to possess neurochemical and behavioral activities, but its effect on ischemic brain damage has remained unknown. This report describes the effect of the drug on the progression of cytotoxic edema induced by total ischemia of the brain, evaluated by measuring the time constant, k, of elongation of the 1H-NMR relaxation time (T2) after brain biopsy. Twenty-six male Wistar rats were divided into four groups, (a) control (saline) group (n = 10), (b) BAY K-8644 vehicle group (n = 4), (c) BAY K-8644 0.03 mg/kg group (n = 6) and (d) BAY K-8644 0.3 mg/kg group (n = 6). The k value of group (d), 18.2 +/- 5.8 min (mean +/- SD), was significantly higher compared with those of groups (a) 10.3 +/- 1.6, (b) 11.8 +/- 1.5 and (c) 9.8 +/- 3.3 min (p < 0.01 by ANOVA). These results indicate that BAY K-8644 delayed the progression of cytotoxic edema induced by total ischemia of the rat brain.

31P-NMR study of skeletal muscle metabolism in patients with chronic respiratory impairment.

To evaluate the energy metabolism of peripheral skeletal muscle during exercise in patients with chronic respiratory impairment, the 31P-nuclear magnetic resonance (NMR) spectra of forearm muscle were investigated in nine patients and nine age-matched control subjects. We calculated the phosphocreatine (PCr) to PCr + inorganic phosphate (PI) ratio, the time constant of PCr recovery and the intracellular pH. The exercise consisted of repetitive hand grips against a 2-kg load every 3 s for 6 min (0.33 W). The patients showed a marked decrease in the PCr/(PCr + PI) ratio and pH in the muscle during exercise in contrast to the control subjects whose PCr/(PCr + PI) showed a minor decrease without any change in pH. The relationship between PCr utilization and pH demonstrated that anaerobic glycolysis switched on earlier in patients with chronic respiratory impairment. A split PI peak was observed in five of nine patients during exercise. The PCr/(PCr + PI) ratio during the last minute of exercise correlated significantly with the vital capacity (% predicted), with the FEV1/FVC, with the body weight, with the maximum strength of hand grip, and with the muscle mass. The results indicate impaired oxidative phosphorylation and the early activation of anaerobic glycolysis in the muscles of patients with chronic respiratory impairment. Several factors related to chronic respiratory impairment, such as disuse, malnutrition and dysoxia, would contribute to the metabolic changes observed in the muscles examined.

Suppression of water shift into intracellular space by TA-3090 (calcium entry blocker) measured with NMR.

In order to clarify the effects of TA-3090 (calcium entry blocker) on the suppression of water after ischaemic events, 16 measurements of T2f were continuously performed on brain biopsy (for 2-60 min) obtained from treated and control Wistar rats. The time constant (k) and NMR parameters (T2f,(O) delta T2f, T2fmax(T2f(O) + delta T2f) were obtained from 16 values of T2f. The values of k in Wistar rats treated with intravenously administrated TA-3090 (0.5 mg/kg) were significantly prolonged as compared to that of control. There were no significant differences of maximum prolongation of T2f(T2fmax(T2f(O) + delta T2f) among three groups. Since the prolongation of T2f after biopsy reflects the water shift from extra to intracellular space, the increments of time constant indicates that TA-3090 suppresses the water shift into intracellular space. Our present results suggest that TA-3090 prevents some processes involved in irreversible cell damage and suppresses the cytotoxic brain oedema in the incomplete ischaemic area where non-competitive calcium channel is inactive.

Effect of glutamate and its antagonist on shift of water from extra- to intracellular space after cerebral ischaemia.

The effects of glutamate and the excitatory amino acid antagonist, MK-801, were investigated on the time course of the shift of water from extracellular to intracellular space (progression or cytotoxic oedema) after total brain ischaemia in rats. Administration of sodium glutamate intravenously before ischaemia accelerated the shift of water dose-dependently. On the contrary, preischaemic administration of MK-801, an NMDA antagonist, delayed the progression of cytotoxic oedema due to brain ischaemia. We consider that glutamate and NMDA antagonists may have important roles in the development and prevention of cytotoxic oedema in the ischaemic state.