Lipoic (thioctic) acid increases brain energy availability and skeletal muscle performance as shown by in vivo31P-MRS in a patient with mitochondrial cytopathy

A woman affected by chronic progressive external ophthalmoplegia and muscle mitochondrial DNA deletion was studied by phosphorus magnetic resonance spectroscopy (³¹P-MRS) prior to and after 1 and 7 months of treatment with oral lipoic acid. Before treatment a decreased phosphocreatine (PCr) content was found in the occipital lobes, accompanied by normal inorganic phosphate (Pi) level and cytosolic pH. Based on these findings, we found a high cytosolic adenosine diphosphate concentration [ADP] and high relative rate of energy metabolism together with a low phosphorylation potential. Muscle MRS showed an abnormal work-energy cost transfer function and a low rate of PCr recovery during the post-exercise period. All of these findings indicated a deficit of mitochondrial function in both brain and muscle. Treatment with 600 mg lipoic acid daily for 1 month resulted in a 55% increase of brain [PCr], 72% increase of phosphorylation potential, and a decrease of calculated [ADP] and rate of energy metabolism. After 7 months of treatment MRS data and mitochondrial function had improved further. Treatment with lipoate also led to a 64% increase in the initial slope of the work-energy cost transfer function in the working calf muscle and worsened the rate of PCr resynthesis during recovery. The patient reported subjective improvement of general conditions and muscle performance after therapy. Our results indicate that treatment with lipoate caused a relevant increase in levels of energy available in brain and skeletal muscle during exercise.     

31P magnetic resonance spectroscopy study of cerebral metabolism in developing dog brain and its relationship to neuronal function.

Cerebral metabolism and neuronal function of prefrontal brain cortex were studied in 6 dog litters from birth to 3 months of age. Noninvasive phosphorus magnetic resonance spectroscopy (31P-MRS) was used to observe longitudinal biochemical changes in the phosphorus compounds associated with cerebral metabolism. Neurological tests, examining reflex, motor and sensory nerve function, were performed in conjunction with the 31P-MRS study. During the neonatal period, exponential increases in PCr, Pi, and phophodiesters preceded neurological changes. Phosphomonoesters showed an exponential, nearly linear, decrease and PCr/Pi was maintained during the 3-month period. Developmental increases in high energy phosphates and the maintenance of PCr/Pi indicate that the increased energy demands of the developing animal are met by increased mitochondrial function (ATP turnover).     

Leber's hereditary optic neuropathy: genetic, biochemical, and phosphorus magnetic resonance spectroscopy study in an Italian family

Three siblings of a family affected with Leber's hereditary optic neuropathy (LHON) showed a mitochondrial DNA mutation at position 11778. The lactate response to a standardized effort was increased in only one case. Muscle biopsies and biochemistry of muscle and platelet mitochondrial enzymes were normal. All patients showed an altered energy metabolism during exercise and during recovery after exercise on phosphorus 31-magnetic resonance spectroscopy (31P-MRS) of muscle. Brain 31P-MRS showed a decreased energy reserve (decreased PCr/Pi ratio) in all patients. 31P-MRS noninvasively demonstrated an altered mitochondrial energy metabolism in muscle and, for the first time, in the brains of LHON patients.     

A 31P-magnetic resonance spectroscopy and biochemical study of the movbr mouse: Potential model for the mitochondrial encephalomyopathies

³¹P-magnetic resonance spectroscopy (³¹P-MRS) provides new biochemical information on mitochondrial disorders affecting brain and muscle. To elucidate the mechanisms of mitochondrial abnormalities, however, animal models are needed. We assessed the mo^vbr (mottled viable brindled) mouse for its value in studying (1) energetics of a mitochondrial disorder and (2) ³¹P-MRS changes associated with mitochondrial abnormalities in vivo. The maximal activity of succinate-cytochrome c reductase was significantly reduced in mo^vbr muscle compared to controls, whereas cytochrome oxidase activity was only reduced in mo^vbr brain. ³¹P-MRS of mo^vbr brain showed an increased pH, but no changes in any metabolite ratios. The phosphocreatine (PCr) recovery rate after exercise was reduced in muscles from mo^vbr mice, indicating impairment of oxidative metabolism. We conclude that mo^vbr brain and muscle tissue have biochemical abnormalities consistent with mitochondrial impairment. The PCr recovery rate, measured by ³¹P-MRS, was sensitive to the muscle abnormality. This strain is best described as having chronic mitochondrial dysfunction. © 1997 John Wiley & Sons, Inc. Muscle Nerve 20: 1352–1359, 1997     

脂质沉积性肌病骨骼肌磁共振31磷波谱的临床价值研究

目的探讨脂质沉积性肌病(LSM)患者骨骼肌磁共振31磷波谱(31P-MRS)改变特征,以及在LSM辅助诊断和疗效评价方面的临床价值。方法对12例LSM患者在治疗前后和11例对照者分别进行31P-MRS扫描,获取波谱图像,计算谱线中无机磷酸盐(Pi)、磷酸肌酸(PCr)及三磷酸腺苷(ATP)的峰下面积,记录Pi/ATP、PCr/ATP和Pi/PCr的比值,计算Pi、PCr、细胞内pH(pHint)、二磷酸腺苷(ADP)和磷酸化潜能(PP)的值,并比较LSM患者治疗前和对照组、LSM患者治疗前后上述31P-MRS指标的差异。结果 LSM患者治疗前的PCr、PCr/ATP和PP较对照组明显降低(P<0.05),Pi/PCr和ADP较对照组明显升高(P<0.05),Pi、Pi/ATP和pHint与对照组比较无明显差异(P>0.05);LSM患者治疗后的PCr、PCr/ATP和PP较治疗前明显升高(P<0.05),ADP较治疗前明显降低(P<0.05),Pi、Pi/ATP、Pi/PCr和pHint与治疗前比较无明显差异(P>0.05)。结论31P-MRS可无创性检测LSM患者肌肉组织的能量代谢变化,有利于LSM的辅助诊断,并可运用于LSM患者的疗效评价。     

Energy metabolism measured by 31P magnetic resonance spectroscopy in the healthy human brain

Background and purposePhosphorous magnetic resonance spectroscopy (31P-MRS) allows a non-invasive analysis of phosphorus-containing compounds in vivo. The present study investigated the influence of brain region, hemisphere, age, sex and brain volume on 31P-MRS metabolites in healthy adults.Materials and methodsSupratentorial brain 31P-MRS spectra of 125 prospectively recruited healthy volunteers (64 female, 61 male) aged 20 to 85 years (mean: 49.4 ± 16.9 years) were examined with a 3D-31P-MRS sequence at 3T, and the compounds phosphocreatine (PCr), inorganic phosphate (Pi) and adenosine triphosphate (ATP) were measured. From this data, the metabolite ratios PCr/ATP, Pi/ATP and PCr/Pi were calculated for different brain regions. In addition, volumes of gray matter, white matter and cerebrospinal fluid were determined.ResultsFor all metabolite ratios significant regional differences and in several regions sex differences were found. In some brain regions and for some metabolites hemispheric differences were detected. In addition, changes with aging were found, which differed between women and men.ConclusionsThe present results indicate that 31P-MRS metabolism varies throughout the brain, with age and between sexes, and therefore have important practical implications for the design and the interpretation of future 31P-MRS studies under physiological conditions and in patients with various cerebral diseases.     

Evidence for a relationship between body mass and energy metabolism in the human brain

Cerebral energy metabolism has been suggested to have an important function in body weight regulation. We therefore examined whether there is a relationship between body mass and adenosine triphosphate (ATP) metabolism in the human brain. On the basis of our earlier findings indicating a neuroprotective preferential energy supply of the brain, as compared with peripheral muscle on experimentally induced hypoglycemia, we examined whether this physiological response is preserved also in low-weight and obese participants. We included 45 healthy male subjects with a body mass index (BMI) ranging from 17 to 44 kg/m². Each participant underwent a hypoglycemic glucose-clamp intervention, and the ATP metabolism, that is, the content of high-energy phosphates phosphocreatine (PCr) and ATP, was measured repeatedly by ³¹phosphor magnetic resonance spectroscopy (³¹P-MRS) in the cerebral cortex and skeletal muscle. Results show an inverse correlation between BMI and high-energy phosphate content in the brain (P<0.01), whereas there was no such relationship found between skeletal muscle and BMI. The hypoglycemic clamp intervention did not affect the ATP metabolism in both tissues. Our data show an inverse correlation between BMI and cerebral high-energy phosphate content in healthy humans, suggesting a close relationship between energetic supply of the brain and body weight regulation.     

Muscle phosphoglycerate mutase (PGAM) deficiency in the first Caucasian patient: biochemistry,muscle culture and31P-MR spectroscopy

Muscle phosphoglycerate mutase (PGAM) deficiency has been so far identified in only six patients, five of these being African Americans. We report the results of clinical, morphological, biochemical, muscle culture and³¹P-MR spectroscopy studies in the first Caucasian patient with muscle PGAM deficiency. A 23-year-old man had a 10-year history of cramps after physical exertion with one episode of pigmenturia. Neurological examination and EMG study were normal. ECG and echocardiography revealed hypertrophy of the interventricular septum and slight dilatation of the left chambers of the heart. Muscle biopsy revealed increased glycogen content and some accumulation of mitochondria. Muscle PGAM activity was markedly decreased (6.5% and 9.7% of control value in two different biopsies). Citrate synthase and other mitochondrial respiratory chain enzyme activities were much higher than normal. In contrast to the marked decrease of PGAM activity observed in muscle biopsy, total enzyme activity in the patient's aneural muscle culture was normal, being represented exclusively by BB isoenzyme. The deficiency of PGAM-MM isoenzyme was reproduced in the patient's innervated muscle culture. Muscle³¹P-MR spectroscopy showed accumulation of phosphomonoesters only on fast glycolytic exercise. On aerobic exercise, V_max, calculated from the work-energy cost transfer function, showed an increase consistent with the morphological and biochemical evidence of mitochondrial proliferation. This might represent a sort of compensatory aerobic effort in an attempt to restore muscle power.     

Muscle energy metabolism in female DMD/BMD carriers: a 31P-MR spectroscopy study.

31P nuclear magnetic resonance spectroscopy (31P-MRS) was used to investigate the energy metabolism of the gastrocnemius muscle in 16 DMD/BMD female carriers. No significant difference was found with the controls in the resting muscle, while all carriers showed a decreased ability to perform work, and a higher Pi/PCr ratio for comparable relative levels of steady-state work. The rate of postexercise recovery of PCr/Pi ratio was lower in all carriers. The decreased rate of PCr/Pi recovery appears to be mainly due to a decreased rate of Pi recovery. Our findings show abnormal muscle energy metabolism in DMD/BMD female carriers.     

Amphetamine effects on dopamine release and synthesis rate studied in the Rhesus monkey brain by positron emission tomography

Summary Positron emission tomography (PET) was used in a multitracer protocol to evaluate D-amphetamine induced effects on dopamine biosynthesis rate and release in propofol anesthetized Rhesus monkeys.l-[-¹¹C]DOPA was used as biochemical probe to study the brain dopamine biosynthesis rate whilst dopamine release was followed by the binding displacement of the [¹¹C]-radiolabelled dopamine receptor antagonists, raclopride and N-methylspiperone. Studies were performed with either a constant rate intravenous infusion of D-amphetamine aiming at plasma concentrations of 0.2 to 25 ng/ml or with intravenous bolus doses of 0.1 and 0.4 mg/ kg. Decreased binding of the dopamine receptor antagonists was measured in both modes of D-amphetamine administration but notably [¹¹C]N-methylspiperone was less able to sense D-amphetamine induced release of dopamine. At plasma concentrations aimed above 1 ng/ml a levelling off of the binding of [¹¹C]raclopride at 68 ± 8.1% of the baseline value indicated that displacement was only possible from a fraction of the binding sites. Amphetamine was observed to increase the rate constant forl-[-¹¹C]DOPA utilization in the brain. This was most likely due to an acutely induced subsensitivity of presynaptic dopamine receptors.l-[-¹¹C]DOPA and [¹¹C]raclopride were found suitable to indicate changes in dopamine synthesis rate and release respectively using PET and can be used to mirror drug-induced changes of brain dopaminergic function.     

Measurements of in vivo energy metabolism in experimental cerebral ischaemia using 31P-NMR for the evaluation of protective effects of perfluorochemicals and glycerol

Effects of perfluorochemical (PFC) and glycerol on energy metabolism in cerebral ischaemia were examined by the sequential measurements of in vivo ³¹P-NMR spectrum using topical magnetic resonance (TMR). Experimental cerebral ischaemia was induced in forty-five Wistar rats by a four-vessel occlusion method. The ³¹P-NMR spectrum and the EEG were monitored during preischaemic and ischaemic periods and after circulation was restored for various periods up to 240 min. There were several peaks in the ³¹P-NMR spectrum of the preischaemic rat brain; β-ATP, α-ATP, γ-ATP, phosphocreatine (PCr), phosphodiesters, inorganic phosphate (Pi) and sugar phosphate. As soon as the ischaemia was induced, PCr and ATP decreaseq and Pi increased. The chemical shift of the increased Pi peak decreased, showing acidosis of the brain tissue. After circulation was restored following the 30 min ischaemia, recovery of the ³¹ P-NMR spectrum occurred within 30 min in all sixteen untreated rats. Recovery of the ³¹P-NMR spectrum was induced by recirculation only in half of the six rats in the untreated 60 min ischaemia group. None of the six rats in the untreated group showed recovery of the spectrum after 120 min ischaemia. When 20% Fluosol-DA was administered at a dose of 20 ml/kg before the induction of ischaemia, all eight rats showed recovery of the spectrum after 120 min ischaemia. Moreover, four of six rats treated with both PFC and glycerol showed temporary recovery even after 240 min ischaemia. The results showed that measurements of in vivo ³¹P-NMR spectrum using TMR are very valuable for examining the energy metabolism of cerebral ischaemia, as well as to evaluate the effect of therapeutic drugs on cerebral ischaemia.     

Cerebral intracellular pH regulation during hypercapnia in unanesthetized rats: aP nuclear magnetic resonance spectroscopy study

The energy metabolism and the brain intracellular pH regulation under arterial CO₂ tensions of 25–90 mm Hg were investigated in unanesthetized spontaneously breathing rats by in vivo phosphorus nuclear magnetic resonance spectroscopy (³¹P NMR). The³¹P brain spectra, recorded with a high resolution spectrometer (AM 400 Brucker), allowed repeated non-invasive measurements of cerebral pH (pHi), phosphocreatine (PCr), inorganic phosphate (Pi) and adenosine triphosphate (ATP) levels in 15 rats breathing a gas mixture containing 21% O₂, N₂, and a varied percentage of CO₂. The pHi decreased significantly when thep_a CO₂ was increased by hypercapnia. The percentage of pH regulation, estimated from the linear regression analysis of pHi versus the logarithm of thep_a CO₂ was 78%. This result indicates that spontaneously breathing unanesthetized animals have better pHi regulation under hypercapnia than do paralyzed mechanically-ventilated animals under anesthesia. It also indicates a higher pH regulation ability in the range of hypercapnia investigated than that estimated for higher levels of hypercapnia in previous studies on unanesthetized animals, suggesting that there is a threshold for this highly efficient regulation. Furthermore, there were no significant correlations between the PCr, ATP and Pi levels and thep_a CO₂ levels during hypercapnia. This indicates that physiological variations of the CO₂ tension in the blood, and consequently in the brain parenchyma, have little effect on cerebral energy metabolism in unanesthetized spontaneously breathing animals.     

Slower recovery of muscle phosphocreatine in malignant hyperthermia-susceptible individuals assessed by 31P-MR spectroscopy

Our aim was to develop an exercise protocol using ³¹P-magnetic resonance spectroscopy (³¹P-MRS), which can discriminate between malignant hyperthermia-susceptible (MHS) individuals and controls. MRS spectra of the forearm muscles were recorded at rest, during and after a standardized exercise protocol in 10 MHS patients and compared with spectra obtained in 10 controls. There was no difference in resting intracellular pH (pHi) or PCr/ (Pi+PCr) ratio between the groups (PCr = phosphocreatine, Pi = inorganic phosphorus). At the end of the exercise and during the initial recovery phase, the pHi and PCr/(Pi+PCr) ratio were significantly lower in the MHS group ([pHi: 6.37 (0.07) for MHS vs 6.70 (0.05) for controls, P < 0.005; PCr/(Pi+PCr): 0.784 (0.017) for MHS vs 0.954 (0.020) for controls, P < 0.0005]). For PCr/ (Pi+PCr), complete separation between the two groups was observed during the initial recovery phase. The mean recovery time of PCr/ (Pi+PCr) was 0.57 min for the control group and 1.28 min for the MHS group. The slower recovery of PCr/ (Pi+PCr) is likely to be caused by a combination of several factors, including the lower pHi in MHS subjects at the start of recovery (inhibiting ATP production) and excessive sarcoplasmic calcium overload (causing continued enzyme activation and ATP consumption). Our exercise protocol can be a valuable adjunct to discriminate between MHS and non susceptible subjects. Received: 10 July 1996 Received in revised form: 7 August 1997 Accepted: 11 August 1997     

In vivo skeletal muscle mitochondrial function in Leber's hereditary optic neuropathy assessed by 31P magnetic resonance spectroscopy

We used ³¹P magnetic resonance spectroscopy (³¹P-MRS) to asses in vivo skeletal muscle mitochondrial function in 10 Leber's hereditary optic neuropathy patients/carriers with a mitochondrial DNA (mtDNA) mutation at one of three nucleotide positions, 11,778, 14,484, and 3,460. We studied one affected patient for each mutation and two unaffected carriers with the 11,778 or 3,460 mutation and three carriers with 14,484. All subjects were homoplasmic except the two 3,460 carriers, who showed 80% and 15% of mutated mtDNA. ³¹P-MRS at rest disclosed some abnormalities in all subjects. In particular, the phosphorylation potential was below the normal range in all cases. During recovery from exercise, the maximum rate of mitochondrial ATP production (V_max) was reduced to 27% of normal in the 11,778 mutation and to 53% in the 14,484 mutation patient/carrier groups. Mitochondrial V_max was within the normal range in all subjects with the 3,460 mutation but correlated inversely with the percentage of mutated mtDNA. This in vivo study shows that the 11,778 mutation causes a mitochondrial impairment more severe than the 14,484 and that the 3,460 mutation results in only a mild depression of muscle mitochondrial function.     

Low brain intracellular free magnesium in mitochondrial cytopathies.

The authors studied, by in vivo phosphorus magnetic resonance spectroscopy (31P-MRS), the occipital lobes of 19 patients with mitochondrial cytopathies to clarify the functional relation between energy metabolism and concentration of cytosolic free magnesium. All patients displayed defective mitochondrial respiration with low phosphocreatine concentration [PCr] and high inorganic phosphate concentration [Pi] and [ADP]. Cytosolic free [Mg2+] and the readily available free energy (defined as the actual free energy released by the exoergonic reaction of ATP hydrolysis, i.e., deltaG(ATPhyd)) were abnormally low in all patients. Nine patients were treated with coenzyme Q10 (CoQ), which improved the efficiency of the respiratory chain, as shown by an increased [PCr], decreased [Pi] and [ADP], and increased availability of free energy (more negative value of deltaG(ATPhyd)). Treatment with CoQ also increased cytosolic free [Mg2+] in all treated patients. The authors findings demonstrate low brain free [Mg2+] in our patients and indicate that it resulted from failure of the respiratory chain. Free Mg2+ contributes to the absolute value of deltaG(ATPhyd). The results also are consistent with the view that cytosolic [Mg2+] is regulated in the intact brain cell to equilibrate, at least in part, any changes in rapidly available free energy.     

31P magnetic resonance spectroscopy in the frontal lobe of major depressed patients

Most research with ³¹P-magnetic resonance spectroscopy (³¹P-MRS) in affective disorders has been done in the field of bipolar disturbances. Reduced frontal and temporal lobe phosphomonoester (PME) concentrations were measured in the euthymic state, whereas increased values were found in the depressed state. In bipolar-II patients reduced phosphocreatine (PCr) concentrations were reported in the euthymic, depressed, and manic state. The aim of the present study was to explore whether PME and PCr were also altered in the frontal lobe of major depressed, unipolar patients. Therefore, we used ³¹P-MRS to investigate the relative phospholipid and high-energy phosphate concentrations in the frontal lobe of 14 unipolar patients, mostly medicated, and 8 age-matched controls. We found increased PME and decreased ATP values. Other ³¹P-MRS parameters were not different in both groups. Phosphomonoester percentages correlated negatively with the degree of depression. Thus, the main alterations found in bipolar depressed patients could also be demonstrated in unipolar depressed patients. The results are discussed with regard to disturbed phospholipid and intracellular high-energy phosphate metabolism in depressed patients. Received: 2 December 1997 / Accepted: 14 July 1998     

Short and long-term changes in cerebral [14C]-2-deoxyglucose uptake in the MPTP-treated marmoset: relationship to locomotor activity

Summary The short-term (0.7 ± 0.1 months post-MPTP) and long-term effects (36.7 ± 4.4 months) of MPTP treatment on motor behaviour and [¹⁴C]-2DG uptake were investigated in the common marmoset. The subcutaneous administration of MPTP greatly reduced locomotor activity (–94% with respect to controls) and induced motor disability in the short-term MPTP-treated marmoset group. In the long-term MPTP group, MPTP treatment did not significantly affect locomotor activity (–27% with respect to controls) and there was partial recovery of motor disability.In the short-term MPTP group, there were increases in [¹⁴C]-2DG uptake in the GP1 (+31 to +37%), SNc (+34 to +42%), VTA (+35%), LC (+23%), PPN (+19%) and in the VA (+19%), VL (+20%) and AM (+17%) thalamic nuclei. [¹⁴C]-2DG uptake was decreased in the STN (–15%). In the long-term MPTP group, [¹⁴C]-2DG uptake was increased in the GP1 (+18%), SNc (+27%), VTA (+25%), PPN (+19%), ventral caudate nucleus (+18 to +23%), NAc (+22%), F.Ctx (+18%) and in the VA (+34%), VL (+28%), AV (+33%) and AM (+24%) thalamic nuclei. [¹⁴C]-2DG uptake was unchanged in the STN.The increase in metabolic activity of the surviving DA neurones and/or the reactive gliosis may account for the initial increase in [¹⁴C]-2DG uptake in the SNc and VTA. On the other hand, in the long-term MPTP-treated animals the increase in [¹⁴C]-2DG uptake in the SNc (though less than in the short-term MPTP group), ventral caudate and NAc may reflect the regenerative changes in the dopaminergic system in these areas. Despite the behavioural recovery, [¹⁴C]-2DG uptake remained elevated in the target areas for medial paludal output (the thalamic nuclei and PPN). However, the attenuation of the changes in [¹⁴C]-2DG uptake in the GP1 and STN of longterm MPTP-treated marmosets suggest that the striato-GPl and GP1-STN outputs closely reflect motor function in this primate model of Parkinson's disease.Anatomical abbreviations AM anteromedial thalamus - AV anteroventral thalamus - CeM centromedian thalamus - d dorsal - F.Ctx frontal cortex - GP1 lateral segment of globus pallidus - GPm medial segment of globus pallidus - HBl lateral habenular - HBm medial habenular - IC inferior colliculus - l lateral - LC locus coeruleus - m medial - MD mediodorsal thalamus - NAc nucleus accumbens - OT olfactory tubercle - PPN pedunculopontine nucleus - Rt reticular thalamus - SNc substantia nigra pars compacta - SNr substantia nigra pars reticulata - STN subthalamic nucleus - v ventral - VA ventral anterior thalamus - VL ventral lateral thalamus - VTA ventral tegmental area Chemical abbreviations DA dopamine - GABA gamma aminobutyric acid - MPP⁺ 1-methyl-4-phenylpyridinium ion - MPTP 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine - [¹⁴C]-2DG [¹⁴C]-2-deoxyglucose     

Effect of dantrolene on KCl- or NMDA-induced intracellular Ca2+ changes and spontaneous Ca2+ oscillation in cultured rat frontal cortical neurons

Summary Dantrolene has been known to affect intracellular Ca²⁺ concentration ([Ca²⁺]_i) by inhibiting Ca²⁺ release from intracellular stores in cultured neurons. We were interested in examining this property of dantrolene in influencing the [Ca²⁺]_i affected by the NMDA receptor ligands, KCl, L-type Ca²⁺ channel blocker nifedipine, and two other intracellular Ca²⁺-mobilizing agents caffeine and bradykinin. Effect of dantrolene on the spontaneous oscillation of [Ca²⁺]_i was also examined. Dantrolene in M concentrations dose-dependently inhibited the increase in [Ca²⁺]_i elicited by NMDA and KCl. AP-5, MK-801 (NMDA antagonists), and nifedipine respectively reduced the NMDA and KCl-induced increase in [Ca²⁺]_i. Dantrolene, added to the buffer solution together with the antagonists or nifedipine, caused a further reduction in [Ca²⁺]_i to a degree similar to that seen with dantrolene alone inhibiting the increase in [Ca₂₊]_i caused by NMDA or KCl. At 30 M, dantrolene partially inhibited caffeine-induced increase in [Ca²⁺]_i whereas it has no effect on the bradykinin-induced change in [Ca²⁺]_i. The spontaneous oscillation of [Ca²⁺]_i in frontal cortical neurons was reduced both in amplitude and in base line concentration in the presence of 10 M dantrolene. Our results indicate that dantrolene's mobilizing effects on intracellular Ca²⁺ stores operate independently from the influxed Ca²⁺ and that a component of the apparent increase in [Ca²⁺]_i elicited by NMDA or KCl represents a dantrolene-sensitive Ca₂₊ release from intracellular stores. Results also suggest that dantrolene does not affect the IP₃-gated release of intracellular Ca²⁺ and that the spontaneous Ca²⁺ oscillation is, at least partially, under the control of Ca²⁺ mobilization from internal stores.Abbreviations AP-5 (±)-2-amino-5-phosphonopentanoic acid - AMPA amino-3-hydroxy-5-methyl-isoxazole-4-propionate - BSS balanced salt solution - CNS central nervous system - CICR Ca²⁺-induced Ca²⁺ release - DCKA 5,7-dichlorokynurenate - DNasel deoxyribonuclease I - DMEM Dulbecco's Modified Eagle's Medium - EGTA ethylene glycol-bis(-aminoethyl ether)N,N,N,N,-tetraacetic acid - FCS fetal calf serum - fura-2-AM 1-(2-(5-carboxyoxazol-2-yl)-6-aminobenzofuran-5-oxy-2-ethane-N,N,N,N-te-traacetic acid, pentaacetoxymethyl ester - HEPES N-[2-hydroxyethyl] piperazine-N-[2-ethanesulfonic acid] - [Ca ²⁺] _i intracellular free Ca²⁺ concentration - LTP long-term potantiation - MK-801 (5R, 10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,b]-cyclohepten-5,10-imine hydrogen maleate - NMDA N-methyl-D-aspartate     

Succinoxidase activity in reticular neurons of hyperactive rats

Summary The succinoxidase activity of single neurons from the reticular formation was measured with the Cartesian diver technique. The average activity of nerve cell bodies from the nucleus gigantocellularis or pontis caudalis from control rats was 4.5 l O₂×10^–4 per hour at 37°C. After rats had received --iminodipropionitrile, the succinoxidase activity of the same type neuron increased to an average of 8.0 l O₂×10^–4. It was suggested that this increase was of etiological significance for the symptoms of hyperactivity which developed later. Also when --iminodipropionitrile had been added to the reticular neurons from normal rats in vitro, the succinoxidase activity increased to 8.4 l O₂×10^–4 per hour.Supported by USPH Grant NB 1305.     

Reduced oxidative muscle metabolism in chronic fatigue syndrome

The purpose of this study was to determine if chronic fatigue syndrome (CSF) is characterized by abnormalities in oxidative muscle metabolism. Patients with CFS according to Centers for Disease Control (CDC) criteria (n = 22) were compared to normal sedentary subjects (n = 15). CFS patients were also tested before and 2 days after a maximal treadmill test. Muscle oxidative capacity was measured as the maximal rate of postexercise phosphocreatine (PCr) resynthesis using the ADP model (V_max) in the calf muscles using ³¹P magnetic resonance spectroscopy. V_max was significantly reduced in CFS patients (39.6 ± 2.8 mmol/L/min, mean ± SE) compared to controls (53.8 ± 2.8 mmol/L/min). Two days postexercise there was no change in resting inorganic phosphate (Pi)/PCr or V_max in the CFS patients (n = 14). In conclusion, oxidative metabolism is reduced in CFS patients compared to sedentary controls. In addition, a single bout of strenuous exercise did not cause a further reduction in oxidative metabolism, or alter resting Pi/PCr ratios. © 1996 John Wiley & Sons, Inc.