Phosphorylethanolamine--the major constituent of the phosphomonoester peak observed by 31P-NMR on developing dog brain

Cerebral phosphoester signals measured by 31P magnetic resonance spectroscopy at 3 and 7 Tesla

Abnormal cell membrane metabolism is associated with many neuropsychiatric disorders. Free phosphomonoesters and phosphodiesters, which can be detected by in vivo 31P magnetic resonance spectroscopy (MRS), are important cell membrane building blocks. However, the quantification of phosphoesters has been highly controversial even in healthy individuals due to overlapping signals from macromolecule membrane phospholipids (MP). In this study, high signal-to-noise ratio (SNR) cerebral 31P MRS spectra were acquired from healthy volunteers at both 3 and 7 Tesla. Our results indicated that, with minimal spectral interference from MP, the [phosphocreatine (PCr)]/[phosphocholine (PC) + glycerophosphocholine (GPC)] ratio measured at 7 Tesla agreed with its value expected from biochemical constraints. In contrast, the 3 Tesla [PCr]/[PC+GPC] ratio obtained using standard spectral fitting procedures was markedly smaller than the 7 Tesla ratio and than the expected value. The analysis suggests that the commonly used spectral model for MP may fail to capture its complex spectral features at 3 Tesla, and that additional prior knowledge is necessary to reliably quantify the phosphoester signals at low magnetic field strengths when spectral overlapping is significant.

Mild Neonatal Brain Hypoxia-Ischemia in Very Immature Rats Causes Long-Term Behavioral and Cerebellar Abnormalities at Adulthood

Systemic hypoxia-ischemia (HI) often occurs during preterm birth in human. HI induces injuries to hinder brain cells mainly in the ipsilateral forebrain structures. Such HI injuries may cause lifelong disturbances in the distant regions, such as the contralateral side of the cerebellum. We aimed to evaluate behavior associated with the cerebellum, to acquire cerebellar abundant metabolic alterations using in vivo 1H magnetic resonance spectroscopy (1H MRS), and to determine GFAP, NeuN, and MBP protein expression in the left cerebellum, in adult rats after mild early postnatal HI on the right forebrain at day 3 (PND3). From PND45, HI animals exhibited increased locomotion in the open field while there is neither asymmetrical forelimb use nor coordination deficits in the motor tasks. Despite the fact that metabolic differences between two cerebellar hemispheres were noticeable, a global increase in glutamine of HI rats was observed and became significant in the left cerebellum compared to the sham-operated group. Furthermore, increases in glutamate, glycine, the sum of glutamate and glutamine and total choline, only occurred in the left cerebellum of HI rats. Remarkably, there were decreased expression of MBP and NeuN but no detectable reactive astrogliosis in the contralateral side of the cerebellum of HI rats. Taken together, the detected alterations observed in the left cerebellum of HI rats may reflect disequilibrium in the glutamate-glutamine cycle and a delay in the return of glutamine from astrocytes to neurons from hypoxic-ischemic origin. Our data provides in vivo evidence of long-term changes in the corresponding cerebellum following mild neonatal HI in very immature rats, supporting the notion that systemic HI could cause cell death in the cerebellum, a distant region from the expected injury site.

HIGHLIGHTS

-Neonatal hypoxia-ischemia (HI) in very immature rats induces hyperactivity toward adulthood.-1H magnetic resonance spectroscopy detects long-term cerebellar metabolic changes in adult rats after neonatal HI at postnatal day 3.-Substantial decreases of expression of neuronal and myelin markers in adult rats cerebellum after neonatal cortical mild HI.

Review: magnetic resonance spectroscopy studies of pediatric major depressive disorder

Introduction. This paper focuses on the application of Magnetic Resonance Spectroscopy (MRS) to the study of Major Depressive Disorder (MDD) in children and adolescents. Method. A literature search using the National Institutes of Health's PubMed database was conducted to identify indexed peer-reviewed MRS studies in pediatric patients with MDD. Results. The literature search yielded 18 articles reporting original MRS data in pediatric MDD. Neurochemical alterations in Choline, Glutamate, and N-Acetyl Aspartate are associated with pediatric MDD, suggesting pathophysiologic continuity with adult MDD. Conclusions. The MRS literature in pediatric MDD is modest but growing. In studies that are methodologically comparable, the results have been consistent. Because it offers a noninvasive and repeatable measurement of relevant in vivo brain chemistry, MRS has the potential to provide insights into the pathophysiology of MDD as well as the mediators and moderators of treatment response.

Magnetic Resonance Spectroscopy Emerges as a Quantitative Diagnostic Tool and an Aid to Therapeutic Procedures

These new developments show the value of MR in studying a phase of metabolism hitherto unavailable, namely that of “preventive” study prior to significant lactate formation and surely prior to the cell damage edema and cell death so characteristic of stroke and heart disease. We believe that these approaches can be developed appropriately for clinical application and will thereby open a new type of diagnosis and therapy.

Mitochondrial dysfunction in bipolar disorder: evidence from magnetic resonance spectroscopy research

Magnetic resonance spectroscopy (MRS) affords a noninvasive window on in vivo brain chemistry and, as such, provides a unique opportunity to gain insight into the biochemical pathology of bipolar disorder. Studies utilizing proton ((1)H) MRS have identified changes in cerebral concentrations of N-acetyl aspartate, glutamate/glutamine, choline-containing compounds, myo-inositol, and lactate in bipolar subjects compared to normal controls, while studies using phosphorus ((31)P) MRS have examined additional alterations in levels of phosphocreatine, phosphomonoesters, and intracellular pH. We hypothesize that the majority of MRS findings in bipolar subjects can be fit into a more cohesive bioenergetic and neurochemical model of bipolar illness that is both novel and yet in concordance with findings from complementary methodological approaches. In this review, we propose a hypothesis of mitochondrial dysfunction in bipolar disorder that involves impaired oxidative phosphorylation, a resultant shift toward glycolytic energy production, a decrease in total energy production and/or substrate availability, and altered phospholipid metabolism.

Effect of lithium on phosphoinositide metabolism in human brain: a proton decoupled (31)P magnetic resonance spectroscopy study

BACKGROUND

The objective of our study was to evaluate whether lithium increases brain phosphomonoester (PME) levels in human subjects.

METHODS

Proton decoupled (31)P magnetic resonance spectra were obtained from eight healthy volunteers before and after the administration of lithium carbonate, 450 mg b.i.d., for 7 and 14 days.

RESULTS

Pairwise comparisons of the mole percent PME revealed a significant increase from baseline at day 7 and day 14 of lithium administration.

CONCLUSIONS

An increase in PME concentration with 7 and 14 days of lithium administration in the human brain in vivo was observed. Because the inositol-1-monophosphate contributes to the PME peak, this result suggests that some of the initial actions of lithium may occur through a reduction of myo-inositol, which in turn may initiate a cascade of secondary changes at different levels of signal transduction process and gene expression in brain, effects that are ultimately responsible for the therapeutic benefits of lithium.

31P Nuclear magnetic resonance spectroscopy findings in bipolar illness: a meta-analysis

Published literature comparing 31P MR brain spectra of bipolar patients to healthy controls was evaluated, focusing on phosphomonoester (PME)/phosphodiester (PDE) resonance areas because these metabolites are related to membrane phospholipids and membrane defects in bipolar disorder have been suggested. Studies comparing PME and/or PDE values of bipolar subjects to values observed in healthy controls were reviewed. Data from the studies meeting our inclusion criteria (8 reports involving 139 bipolar and 189 comparison subjects) were grouped according to the mood state of the subjects. Meta-analyses of data were performed to compare PME and PDE levels of euthymic bipolar patients to healthy controls, as well as comparing PME levels during euthymia in bipolar subjects to values observed during manic and depressed states. The PME values of euthymic bipolar patients were found to be significantly lower than PME values of healthy controls. Depressed bipolar patients had significantly higher PME values in comparison to euthymic bipolar patients. No significant difference could be detected between the PDE values of bipolars and controls. This meta-analysis found support for trait- and possibly state-dependent abnormalities of membrane phospholipid metabolism, which may reflect a dysregulation in brain-signal transduction systems of relevance in bipolar illness.

Chronic lithium and sodium valproate both decrease the concentration of myo-inositol and increase the concentration of inositol monophosphates in rat brain

One of the mechanisms underlying lithium's efficacy as a mood stabilizer in bipolar disorder has been proposed to be via its effects on the phosphoinositol cycle (PI-cycle), where it is an inhibitor of the enzyme converting inositol monophosphates to myo-inositol. In contrast, sodium valproate, another commonly used mood stabilizer, appears to have no direct effects on this enzyme and was thus believed to have a different mechanism of action. In the present study, high resolution nuclear magnetic resonance (NMR) spectroscopy was used to study the chronic effects of both lithium and sodium valproate on the concentrations of myo-inositol and inositol monophosphates in rat brain. As predicted, lithium-treated rats exhibited a significant increase in the concentration of inositol monophosphates and a significant decrease in myo-inositol concentration compared to saline-treated controls. However, unexpectedly, sodium valproate administration produced exactly the same results as lithium administration. These novel findings suggest that both lithium and sodium valproate may share a common mechanism of action in the treatment of bipolar disorder via actions on the PI-cycle.

Muscle abnormalities in juvenile dermatomyositis patients: P-31 magnetic resonance spectroscopy studies

OBJECTIVE

To characterize metabolic abnormalities in the muscles of children with the juvenile variant of dermatomyositis (JDM) by the use of noninvasive P-31 magnetic resonance spectroscopy (MRS).

METHODS

Thirteen patients with JDM (ages 4-16 years) were studied. Biochemical status was evaluated with P-31 MRS by determining the concentrations of the high-energy phosphate compounds, ATP and phosphocreatine (PCr), ratios of inorganic phosphate (Pi) to PCr (Pi:PCr ratio), levels of free cytosolic ADP, and phosphorylation potentials (PPs) during rest, exercise, and recovery.

RESULTS

Significant metabolic abnormalities were observed in the thigh muscles of 10 severely affected patients during rest, 2 graded levels of exercise, and recovery. Mean ATP and PCr levels in the muscles of JDM patients were 35-40% below the normal control values (P < 0.003). These data, along with elevated Pi:PCr ratios, higher ADP levels, and abnormal values for PPs, indicated defective oxidative phosphorylation in the mitochondria of diseased JDM muscles. MRS findings were normal in 2 additional patients who had improved with prednisone treatment and in 1 patient who had no muscle weakness (amyopathic variant of JDM).

CONCLUSION

JDM patients can be monitored with noninvasive P-31 MRS without sedation. Biochemical defects in energy metabolism are concordant with the weakness and fatigue reported by JDM patients. Quantitative MRS data are useful for evaluating patients and optimizing drug treatment regimens.

Brain biochemistry using magnetic resonance spectroscopy: relevance to psychiatric illness in the elderly

Magnetic resonance spectroscopy (MRS) allows for the noninvasive study of cerebral biochemistry. It has been used to investigate cerebral metabolic changes associated with mental illness in vivo and in vitro. In this review, we will discuss the application of MRS to psychiatric illness in the elderly. Following a brief description of the basic principles of MRS, the use of phosphorus (31P) and proton (1H) MRS to enable a better understanding of normal brain aging, dementia (Alzheimer's disease, multiple subcortical infarct dementia, Down syndrome, frontotemporal dementia, vascular dementia, age-associated memory impairment, and other dementias), major depression, and electroconvulsive therapy is detailed.

Effects of lithium and amphetamine on inositol metabolism in the human brain as measured by 1H and 31P MRS

BACKGROUND

The clinical effectiveness of lithium may be due to its decreasing the intracellular concentration of myo-inositol and increasing that of its inositol monophosphate precursors, which is known as the inositol depletion hypothesis.

METHODS

Magnetic resonance spectroscopy (MRS) was used to measure the concentration of both myo-inositol (1H MRS) and phosphomonoesters (PME) [31P MRS], in healthy volunteers in a double-blind placebo-controlled study. MRS measurements were made at baseline, again on the 7th day of lithium (1200 mg, n = 10) or placebo (n = 6) administration, and again on day 8, 2 hours following oral administration of 20 mg dextroamphetamine to stimulate the phosphoinositol (PI) cycle.

RESULTS

Subjects who received lithium showed a greater increase in PME ratios in response to amphetamine administration than did placebo-treated subjects.

CONCLUSIONS

The present results support the hypothesis that lithium administration blocks the conversion of inositol monophosphates to myo-inositol, and that this effect is especially apparent following PI cycle stimulation. The effects of lithium treatment on myo-inositol in healthy volunteers in vivo are uncertain, and may have to await improvements in the ability to measure myo-inositol in the brain.

Altered brain metabolism in the C57BL/Wld mouse strain detected by magnetic resonance spectroscopy: association with delayed Wallerian degeneration?

In the C57BL/Wld(s) (Wld) mouse strain, both PNS and CNS axonal disintegration during Wallerian degeneration is dramatically slowed, with isolated axons being able to conduct compound action potentials (CAPs) for several weeks post-transection. The ability to conduct a CAP signifies the presence of an intact plasma membrane, normal ion gradients, and functioning ion channels. In neurons, ion homeostasis is primarily regulated by the Na(+)-K(+)-ATPase, which utilizes approximately 50% of neuronal energy output. To investigate the possibility that the Wld mutation prolongs axonal degeneration by conferring a more favorable energetic status to neurons or alters metabolism, we used 31P and 1H magnetic resonance spectroscopy (MRS) to compare the cerebral and muscle energy metabolism, membrane phospholipid contents, and water-soluble metabolites of Wld and wild-type (C57BL/6J [6J], and BALB/c) mouse strains. We first demonstrate that, with advancing age, transected Wld CNS nerves degenerate faster, paralleling previous findings in the PNS. We found significantly decreased phosphocreatine and phosphomonoester concentrations in the brains of Wld mice at 1- and 2-months of age compared to both 6J and BALB/c mice, but we failed to find differences in the adenylate (ATP, ADP, or AMP) or phospholipid concentrations. In another excitable tissue, skeletal muscle, no differences in energy-containing metabolites were detected. High resolution 1H MRS indicated that at 1 month of age, Wld brains have cytosolic levels of glutamate and phosphocholine that are significantly decreased, relative to total N-acetyl aspartate content. Our results demonstrate that delayed Wallerian degeneration in the C57BL/Wld mouse strain is associated with altered cerebral metabolism, although these changes may be secondary to the mutation.

Cerebral phosphorus metabolite abnormalities in opiate-dependent polydrug abusers in methadone maintenance

This study evaluated cerebral phosphorus metabolites in opiate-dependent polydrug abusers in methadone maintenance therapy (MMT) and determined whether metabolite profiles differed based on treatment duration. Phosphorus magnetic resonance spectroscopy (31P-MRS) data were acquired with the ISIS volume localization method from a 50-mm thick axial brain slice through the orbitofrontal and occipital cortices. Study subjects included 15 MMT subjects, seven having undergone treatment for an average of 39 +/- 23 weeks (mean +/- S.D.) and eight having undergone treatment for 137 +/- 53 weeks, as well as an age matched comparison group (n = 16). The methadone dose administered on the study day averaged 70.5 +/- 17.1 mg and was statistically equivalent in short- and long-term subgroups. MMT subjects (n = 15) differed from control subjects in percent phosphocreatine (%PCr) levels (-13%), and in both phosphomonoester (%PME, +13%) and phosphodiester (%PDE, +10%) levels, which likely reflect abnormalities in energy and phospholipid metabolism, respectively. There were no sex effects or group by sex interaction effects on these measures. In short-term MMT treatment subjects, abnormal %PCr (-18%), %PME (+20%) and %PDE (+17%) levels were found compared with control subjects. The only metabolite abnormality detected in long-term MMT subjects was decreased %PCr (-9%), in spite of continued illicit drug abuse. From these data, we conclude that polydrug abusers in MMT have 31P-MRS results consistent with abnormal brain metabolism and phospholipid balance. The nearly normal metabolite profile in long-term MMT subjects suggests that prolonged MMT may be associated with improved neurochemistry.

Inositol levels are decreased in postmortem brain of schizophrenic patients

BACKGROUND

A previous study reported decreased levels of inositol in frontal cortex of postmortem brain from bipolar patients and suicide victims. The aim of the present study was to test the specificity of this finding.

METHODS

Inositol and the enzyme that synthesizes it, inositol monophosphatase, were measured in postmortem brain tissue from frontal and occipital cortex and cerebellum from 10 schizophrenic patients and the previously reported controls. Inositol levels were assayed gas-chromatographically as trimethylsilyl derivatives with mannitol as an internal standard. Inositol monophosphatase activity in brain homogenates was measured as the difference between phosphate release from inositol-l-phosphate in the absence and in the presence of Li+.

RESULTS

Inositol was significantly reduced in all three areas in the schizophrenic patient' brains: inositol monophosphatase was unchanged. Postmortem interval did not correlate with inositol levels and did not differ between control group and schizophrenic patients.

CONCLUSIONS

These results suggest an abnormality of second messenger precursor availability in common with schizophrenia and affective psychopathology.

Study of the maturation of the child's brain using 31P-MRS

The maturation of human cerebrum and cerebellum in 37 normal children aged 4 months to 13 years 8 months was evaluated by 31P-magnetic resonance spectroscopy using two different conditions of repetition time (TR) (TR = 3 seconds and 15 seconds) in each region. The results were as follows. First, the PME/PDE, PCr/gamma-ATP and Pi/PCr ratios differed between the cerebrum and the cerebellum. The PME/PDE and PCr/gamma-ATP ratios were greater in the cerebellum than in the cerebrum. However, the Pi/PCr ratio was smaller in the cerebellum than in the cerebrum. At TR = 3 seconds, the ratio of (PME/PDE ratio in the cerebellum)/(PME/PDE ratio in the cerebrum) and the ratio of (PCr/gamma-ATP ratio in the cerebellum)/(PCr/gamma-ATP ratio in the cerebrum) manifested a nearly constant value independent of age. Second, the phosphomonoester peak in the cerebrum contained a substance with a longer relaxation time than 3 seconds; this substance was present in large amounts in the early period, then gradually decreased during maturation.

Proton-decoupled phosphorus-31 magnetic resonance spectroscopy in the evaluation of native and well-functioning transplanted kidneys

RATIONALE AND OBJECTIVES

To evaluate whether decoupling improves signal-to-noise ratio and frequency resolution of in vivo kidney spectra, and to compare native and well-functioning transplant kidneys.

METHODS

Proton decoupling in conjunction with three-dimensional chemical shift imaging (3D-CSI) in phosphorus-31 magnetic resonance (MR) spectroscopy was used with a spatial resolution of 64 cm3 and 17-minute acquisition time to compare native (n = 10) and well-functioning transplant (n = 9) kidneys.

RESULTS

Proton decoupling improved peak amplitudes by almost 30%, as well as chemical shift resolution of in vivo kidney spectra. No statistically significant differences in phosphometabolite ratios and renal spectra were observed between healthy volunteers and patients with nonrejecting transplants. The phosphodiester-phosphomonoester ratio was 3.02 +/- 0.88, phosphomonoester-inorganic phosphate ratio was 1.07 +/- 0.44, and inorganic phosphate-adenosine triphosphate ratio was 0.58 +/- 0.22 after correction for saturation effects.

CONCLUSION

Improved spectra of native and transplant kidneys can be obtained in vivo with MR spectroscopy by using a short acquisition time.

Quantitation of phosphorus metabolites in newborn human brain using internal water as reference standard

A new method for noninvasive, in vivo quantitation of cerebral phosphorus (31P) metabolites is described. The technique employs point-resolved spectroscopy (PRESS) to obtain both 31P-metabolite and proton (1H) water spectra: brain water is used as an internal concentration reference. Spin-spin relaxation times (T2s) of cerebral 31P metabolites are much longer than the minimum echo time (TE) usable on a spectrometer equipped with actively shielded gradient coils. With short-TE (approximately 10 ms) 31P PRESS, T2 relaxation is minimal and phase modulation of the nucleotide triphosphate (NTP) multiplets can be accounted for 1H water spectra were acquired using several TEs so that extra- and intracellular water signals could be separated from that due to cerebrospinal fluid. Prior calibration of the 31P and 1H spectrometer channels and an assumed brain-water concentration enabled estimations of metabolite concentrations. Using this method, mean 31P metabolite concentrations in the brains of eight normal infants of gestational plus postnatal age 34 to 39 wk were: phosphomonoester (PME) 5.6 (SD 0.9); inorganic phosphate 1.4 (0.4); mobile phosphodiester 2.3 (0.6); phosphocreatine 2.9 (0.3); nucleotide triphosphate 2.8 (0.6); and total mobile phosphate 21.4 (2.8) mmol/kg wet.

Phosphorus magnetic resonance spectroscopy of human masseter muscle

Masseter muscle metabolism is poorly understood. 31P Magnetic Resonance Spectroscopy (MRS) provides an opportunity for non-invasive study of muscle metabolism during rest, exercise, and recovery. The aim of this study was to investigate the changes in high-energy phosphates and pH in human masseter muscle associated with exertional pain. Phosphates and pH were measured with 31P Magnetic Resonance at 2.0 Tesla. The bite force was simultaneously measured with a force transducer. Continuous biting at maximum voluntary bite force (MVBF) and two intermittent biting exercises with different duty cycles were performed to pain intolerance. The light intermittent exercise did not produce pain. Brief MVBF requested at the beginning, during, and end of each exercise showed no decay. Qualitatively, changes in phosphates were similar to those reported from comparable limb muscle exercises: increased inorganic phosphate (Pi), decreased phosphocreatine (PCr), and no changes in ATP level. Quantitatively, however, the Pi/PCr ratio did not reach the levels reported in limb muscles during similar exercises. Also, the pH changed very little. Thus, the lack of fatigue was no surprise, since the level of changes in Pi/PCr and pH, reported to be associated with fatigue in limb muscles, was far less in the masseter. Pain development toward the end of the heavy exercises prevented further depletion of metabolites. Thus, the lack of fatigue generally postulated for the masseter muscle may not be due to resistance to fatigue of these fibers, but rather to the presence of pain preventing the fatigue. However, no specific metabolic changes associated with exertional pain were found.

Proton magnetic resonance spectroscopy of brain tumors: an in vitro study

The ability of proton magnetic resonance spectroscopy (1H MRS) to diagnose brain tumors was investigated using in vitro high-resolution spectra. Fifty-eight surgically excised samples of brain tumors (12 glioblastomas, 4 anaplastic astrocytomas, 6 astrocytomas, 12 meningiomas, 6 neurinomas, 4 chordomas, 3 craniopharyngiomas, 2 pituitary adenomas, 2 malignant lymphomas, 1 ependymoma, 1 medulloblastoma, and metastatic brain tumors including 3 pulmonary adenocarcinomas, a hepatocellular carcinoma, and a renal cell carcinoma) and 4 nontumorous lobectomized brains were examined by in vitro 1H MRS. N-Acetyl-aspartate was demonstrated in normal tissues but could not be detected in nonneuroectodermal tumors. Total creatine was decreased in all brain tumors in comparison with normal brain tissues, but was relatively higher in neuroectodermal tumors than in other brain tumors. Choline-containing compounds were present in all tumors except craniopharyngioma, and their concentrations were particularly high in a metastatic brain tumor from hepatocellular carcinoma. The concentration of glycine was high in neuroectodermal tumors, whereas that of taurine was high in medulloblastoma, pituitary adenoma, and renal cell carcinoma. Alanine was increased in meningioma, glioma, and pituitary adenoma. Neurinoma had the largest inositol content among the tumors examined. Thus each type of brain tumor exhibited a characteristic MR spectrum. These data suggested that in vivo 1H MRS might provide clinically useful information about tumor metabolism and aid in the differential diagnosis of tumors. Although excellent anatomical localization of tumors can be readily obtained by MR imaging, MRS may provide additional information in cases in which the differential diagnosis of tumors by MR imaging is difficult.

Effects of ACTH treatment on cerebral phosphorus metabolites in infants with the West syndrome

Concentrations of phosphorus metabolites in brains of 4 infants with the West syndrome were measured by 31P MRS before and during ACTH treatment. Although intracellular pH, phosphocreatine/ATP ratio and phosphocreatine/inorganic phosphate ratio in the patients were similar to those in the controls and did not change after the ACTH treatment, phosphomonoesters/phosphodiesters ratio in the patients always decreased with ACTH treatment. These results indicate that ACTH may accelerate the maturation of phospholipids metabolism in infant brains, and the observed change may relate to the efficacy of ACTH treatment against the West syndrome.

Viability of the neonatal rat isolated brainstem preparation by 31P MRS

The isolated brainstem-spinal axis from the neonatal rat is an established model for studying neuronal responses of the ventilatory control system, however, its viability has not been clearly established. We studied the brainstem-spinal axis from newborn rats at 8.5 T with 31P NMR spectroscopy. The relative pattern of high energy phosphates (HEPs) was similar to that reported for the in vivo neonatal brain. The average pHi was 0.2 to 0.4 units less than the pHi for the in vivo neonatal brain. The HEPs and pHi were stable for 6 h, suggesting extended in vitro viability.

Phosphorus-31 magnetic resonance spectroscopy and ventricular enlargement in bipolar disorder

Phosphorus-31 magnetic resonance spectroscopy (31P-MRS) was used to examine whether reduced levels of phosphomonoesters (PME) were correlated with ventricular enlargement in 40 patients with bipolar disorder and 60 age-matched normal control subjects. Ventricular enlargement was assessed by magnetic resonance imaging (1H-MRI) using the following three methods: Evans ratio (ER), Huckman number (HN), and minimum distance of caudate nuclei (MDCN). Although MDCN and ER were significantly larger in the patient group, no significant correlations were found between 31P-MRS and 1H-MRI. PME was negatively correlated with age in bipolar disorder. Decreased levels of PME were found only in bipolar I disorder. Intracellular pH was positively correlated with duration of lithium treatment. These results suggest that the observed PME reduction was not related to ventricular enlargement, but the issue should be further studied with volumetric MRI analysis.

A 31P and 1H-NMR investigation in vitro of normal and abnormal human liver

Spectral changes in human hepatic tumours and possible systemic effects of tumour on host liver were assessed by 31P and 1H in vitro NMR spectroscopy. The 1H and 31P spectra from liver tumour biopsies showed significant elevation in phosphoethanolamine, phosphocholine, taurine, citrate, alanine, lactate and glycine, and significant reduction in GPE (glycerophosphoethanolamine), GPC (glycerophosphocholine), creatine and threonine compared to histologically normal tissue. 31P-NMR spectra obtained from histologically normal tissue within tumour-bearing livers showed significant elevation in phosphoethanolamine and phosphocholine compared to data from liver biopsies from nontumour-bearing patients (pancreatitis). These results suggest that alterations in membrane metabolism in host liver can be detected by 31P-NMR.

Inhibition of cytosolic human forebrain choline acetyltransferase activity by phospho-L-serine: a phosphomonoester that accumulates during early stages of Alzheimer's disease

There is no satisfactory explanation for the cholinergic deficit characteristic of Alzheimer's disease. We have performed a series of experiments which demonstrate that (a) an inhibitor of cytosolic human brain choline acetyltransferase is present in the cytosol of Alzheimer brain tissue, (b) human brain cytosolic choline acetyltransferase activity is inhibited by phospho-L-serine in a competitive manner. Cytosol was prepared from human forebrain or amygdala and the Km for choline and acetyl CoA of the choline acetyltransferase were 750 microM and 12.5 microM, respectively. Phospho-L-serine was found to be a competitive inhibitor of this enzyme with respect to choline but not with respect to acetyl CoA with a Ki of 750 microM for the human forebrain and 3 mM for human amygdala. These concentrations of phospho-L-serine are present in brain tissue at early stages of Alzheimer's disease. Several other phosphomonoesters and phosphodiesters that are increased in Alzheimer's disease were either less inhibitory or without effect. The addition of heat denatured and non-heat denatured cytosol from Alzheimers forebrain inhibited the choline acetyltransferase activity present in control human brain cytosol. The inhibitory activity of the Alzheimers cytosol was retained in TCA deproteinized samples and removed by dialysis or by alkaline phosphatase treatment. Dialysis of the cytosol increased the choline acetyltransferase activity of 5 of 8 Alzheimer's disease samples from 21 to 118% with p values of < 0.025 or < 0.001, respectively. These observations provide evidence that an endogenous non-proteinaceous, dialyzable, phosphomonoester, present in Alzheimers brain inhibits the choline acetyltransferase of both control and Alzheimers brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations in brain phosphorous metabolism in bipolar disorder detected by in vivo 31P and 7Li magnetic resonance spectroscopy

Phosphorus-31 magnetic resonance spectroscopy (MRS), able to detect membrane metabolism and intracellular pH as well as energy metabolism in vivo, was applied to 17 bipolar patients in the manic state and the euthymic state. In nine of these patients, brain lithium concentration was simultaneously determined by means of lithium-7 MRS in order to clarify the effect of treatment with lithium on brain phosphorous metabolism. Both phosphomonoester (PME) peak area and intracellular pH were found to be higher in the manic state than in the euthymic state. These values in the euthymic state were lower than those in normal controls whose ages and sexes were matched with the patients. However, PME and intracellular pH did not correlate to brain lithium concentration. These findings coincide with a hypothesis that patients with bipolar disorder may have membrane abnormality in their euthymic state and state-dependent alteration of catecholaminergic activity may be a secondary phenomenon.

NMR spectroscopy: current status and future possibilities

Nuclear magnetic resonance (NMR) spectroscopy is now established as a non-invasive method of studying metabolism in living systems, ranging from cellular suspensions to man. With respect to clinical applications, recent developments include the successful implementation of new techniques for spatial localisation, and in particular the acquisition of excellent 1H spectra from selected regions of the human brain. Localised 1H spectroscopy opens the way to monitoring a wide range of compounds that are inaccessible to 31P NMR, and should add considerably to the information that is available from 31P studies. NMR spectroscopy does, however, have its limitations, which arise primarily from the fact that it is an insensitive technique. This lack of sensitivity limits the spatial resolution for metabolic studies, and means that metabolites must be present at fairly high concentrations in order to produce detectable signals. In this article, we illustrate the scope and limitations of NMR spectroscopy by describing a few examples of studies undertaken on animals and humans.

Determination of saturation factors in 31P NMR spectra of the developing human brain

In order to assess the influence of longitudinal relaxation on previously reported variations in 31P NMR signals during brain development, we used an accelerated two-point technique to determine T1 at 2.35 Tesla in 8 min. Comparison between 10 normal neonates (age range 37-46 weeks postconception) and 10 healthy infants (age range 80-157 weeks postconception) indicated that T1 does not vary substantially during the first year of life, except in the phosphomonoester (PME) region of the spectra. T1 of total PME decreases with age which we could explain by its variable multicomponent nature: The signal from (unresolved) components at the downfield shoulder of PME (attributed mostly to phosphorylethanolamine at 6.72 ppm) with a T1 of at least 6.4 s decreases with age relative to contributions from other phosphomonoester compounds resonating predominantly at the upfield side of the peak (approximately 6.3 ppm), with T1 below 2.9 s. Because the T1 heterogeneity of PME may depend on its relative composition, quantitative 31P NMR spectroscopy may require an assessment of the influence of longitudinal relaxation on the signal amplitudes in each measurement.

Brain phosphorous metabolism in depressive disorders detected by phosphorus-31 magnetic resonance spectroscopy

Brain phosphorus metabolism was measured in 22 patients with depressive disorders. Ten of them had DSM-III-R bipolar disorder, and 12 had major depression. In bipolar patients, phosphomonoester (PME) and intracellular pH were significantly increased in the depressive state than in the euthymic state, while those values in the euthymic state were significantly low as compared to age-matched normal controls. Phosphocreatine (PCr) was significantly decreased in severely depressed patients compared to mild depressives. These findings suggest that high energy phosphate metabolism, intracellular pH and membrane phospholipid metabolism are altered in depressive disorders.

31P nuclear magnetic resonance study of phospholipid metabolites in ischemic liver

To assess the metabolic alterations induced by normothermic hepatic ischemia, 31P nuclear magnetic resonance analysis was performed on liver samples using perchloric acid extraction. In particular, phosphomonoesters and phosphodiesters, the intermediary metabolites of membrane phospholipid turnover, were characterized precisely and quantitated. Phosphocholine and phosphoethanolamine, the precursors of phospholipid anabolism, did not change, while the phosphodiesters decreased. In contrast, alpha-glycerophosphate, which is both a precursor of phospholipid synthesis and the intermediary product of phospholipid degradation, markedly increased following 30 min of normothermic ischemia. These findings suggest that cellular phospholipids are actively degraded during normothermic hepatic ischemia.

31P MRS as an early prognostic indicator of patient response to chemotherapy

In this study 31P spectral changes were closely monitored following the initial administration of cytotoxic drugs and related to five parameters of patient response. Pre- and postchemotherapy 31P MRS examinations were performed on 16 patients with large, malignant tumors. These included four tumor types: (i) lymphoma (n = 7), (ii) breast carcinoma (n = 4), (iii) musculoskeletal tumors (n = 4), and (iv) adenocarcinoma (n = 1). A mean of 5 spectra/patient (range 2-10) was performed following the initial chemotherapy. The spectral trends exhibited by 14 of 16 patients reached "points of maximum change," after which they began to revert toward prechemotherapy values. In 2 of 16 patients that did not respond to the initial chemotherapy regimen, no spectral trends were observed. The degree of change of certain spectral parameters, namely, decreases in PME, PME/PDE, PME/PCr, PME/NTP, PDE/PCr, and tumor pH, as well as increases in the ratios Pi/PME and Pi/PDE, were associated with good patient response and separated responders from nonresponders. Pi/PME appears the most promising for discriminating partial from complete responders.

Phosphatidylethanolamine metabolism in rat liver after partial hepatectomy. Control of biosynthesis of phosphatidylethanolamine by the availability of ethanolamine

The effect of partial (70%) hepatectomy on phosphatidylethanolamine (PE) synthesis was studied in rat liver during the first 4 post-operative days. Between 4 and 96 h after partial hepatectomy, the mass of PE increased from 30% to 80% of sham-operation values. In line with the increase in PE mass, the rate of PE synthesis in vivo from [14C]ethanolamine was stimulated 1.6- and 1.3-fold at 22 and 48 h after partial hepatectomy respectively. Surprisingly, the activity of CTP:phosphoethanolamine cytidylyltransferase (EC 2.7.7.14) was virtually unchanged after partial hepatectomy. In addition, neither ethanolamine kinase (EC 2.7.1.82) nor ethanolaminephosphotransferase (EC 2.7.8.1) showed any changes in activity over the time period studied. Hepatic levels of ethanolamine and phosphoethanolamine were drastically increased after partial hepatectomy, as compared with sham operation, whereas levels of CDP-ethanolamine and microsomal diacylglycerol were not affected. Interestingly, partial hepatectomy caused the concentration of free ethanolamine in serum to increase from 29 microM to approx. 50 microM during the first day after surgery. In hepatocytes isolated from non-operated animals, incorporation of [3H]ethanolamine into PE was stimulated by increasing the ethanolamine concentration from 10 up to 50 microM, whereas the radioactivity associated with phosphoethanolamine only increased at ethanolamine concentrations higher than 30 microM. Taken together, our results indicate that the observed increase in serum ethanolamine concentration after partial hepatectomy is probably responsible for both the increase in PE biosynthesis and the accumulation of ethanolamine and phosphoethanolamine in regenerating liver.

Glycolytic inhibition and calcium overload as consequences of exogenously generated free radicals in rabbit hearts

Free radicals have been implicated in the pathogenesis of reperfusion injury, but it is unclear how they exert their deleterious effects on cellular metabolism. Several lines of indirect evidence suggest that free radicals elevate intracellular Ca2+ concentration ([Ca2+]i) and inhibit glycolysis as part of their mechanism of injury. We tested these ideas directly in hearts subjected to hydroxyl radicals produced by the Fenton and Haber-Weiss reactions. Nuclear magnetic resonance spectra were obtained from Langendorff-perfused rabbit hearts before, during, and after 4 min of perfusion with H2O2 (0.75 mM) and Fe(3+)-chelate (0.1 mM). Isovolumic left ventricular pressure exhibited progressive functional deterioration and contracture after exposure to H2O2 + Fe3+. Phosphorus nuclear magnetic resonance (NMR) spectra revealed partial ATP depletion and sugar phosphate accumulation indicative of glycolytic inhibition. To measure [Ca2+]i, fluorine NMR spectra were acquired in a separate group of hearts loaded with the Ca2+ indicator 5F-BAPTA [5,5'-difluoro derivative of 1,2-bis-(o-aminophenoxy)ethane- N,N,N',N'-tetraacetic acid]. Mean time-averaged [Ca2+]i increased from 347 +/- 14 nM in control to 1,026 +/- 295 nM 4 min after free radical generation (means +/- SEM, n = 7), and remained elevated thereafter. We conclude that free radicals induce clear-cut, specific derangements of cellular metabolism in the form of glycolytic inhibition and calcium overload. The observed increase in [Ca2+]i suggests that the deleterious effects of free radicals are at least partially mediated by secondary changes in cellular calcium homeostasis.

Measurement of brain phosphoinositide metabolism in bipolar patients using in vivo 31P-MRS

In vivo phosphorus-31 magnetic resonance spectroscopy (31P-MRS) was used to measure phosphorus metabolism in the brains of manic patients treated with lithium carbonate. The phosphomonoester (PME) peak was elevated in the manic state in patients with DSM-IIIR bipolar disorder compared to the euthymic state and to drug-free normal controls. Elevation of the PME peak may be caused by lithium-induced accumulation of inositol 1-phosphate in the brain.

Metabolites in the developing rat liver--a proton nuclear magnetic resonance spectroscopic study

We have used 1H-NMR spectroscopy in vitro to investigate metabolite changes in the rat liver in the first 21 days of life. The principle findings are firstly that betaine, a metabolite of choline, was relatively low (1-2 mumol/g) on days 1-7, then rose sharply to 5-6 mumol/g by day 19, whereas approximately reciprocal changes occurred in taurine levels. Secondly the lactate levels were remarkably low (0.1-0.8 mumol/g) on days 1-7. Changes in two other choline derivatives, phosphocholine (PC) and glycerophosphorylcholine (GPC) are also reported. The results are discussed in the context of the origin of these metabolites in the neonatal period, their levels in the adult (180 day-old) rat and the significance of the measured changes in metabolite levels during liver development.

31P NMR spectroscopy of 9L cell line in culture: differential effects of high temperature on anchored cells and spheroids

The differential effects of high temperature on 9L rat gliosarcoma cells cultured in two distinctive forms, namely, anchored monolayer cells and multicellular spheroids, were investigated using 31P nuclear magnetic resonance spectroscopy. The critical temperatures resulting in irreversible changes in cellular energetics were found to be significantly different: 45 degrees C for anchored cells and 43 degrees C for multicellular spheroids, respectively. Phosphomonoester levels in multicellular spheroids were found to be consistently higher than those in anchored monolayer cells regardless of the temperature to which they were exposed. The study demonstrates that tissue derived from a single cell line may exhibit different metabolic properties depending on its growth pattern.

Effect of aging on phosphate metabolites of rat brain as revealed by the in vivo and in vitro 31P NMR measurements

Changes of phosphate metabolism in brains of neonate, weaning and adult rats were compared using both in vivo and in vitro nuclear magnetic resonance spectra. Ratios of phosphocreatine/nucleoside triphosphate (PCr/NTP) were the same in neonatal brain in both in vivo and in vitro studies, but not in weaning and adult brains. This discrepancy may have resulted from extended cerebral hypoxia due to slowed freezing of the brain by the increased skull thickness and brain mass in the weaning and adult rats. Variations in in vitro extraction condition for this age-related study may lead to systematic errors in the adult rats. Nevertheless, the phosphomonoester/nucleoside triphosphate (PME/NTP) ratios in extracts of brain from neonatal rats were higher than those obtained in vivo. In addition, the glycerophosphorylethanolamine plus glycerophosphorylcholine/nucleoside triphosphate (GPE+GPC/NTP) ratios, which were not measurable in vivo, showed age-dependent increase in extracts of rat brain. Some of the phosphomonoester and phosphodiester molecules in rat brain may be undetectable in in vivo NMR analysis because of their interaction with cellular components. The total in vitro GPE and GPC concentration in brain from neonatal rat was estimated to be 0.34 mmole/g wet tissue.

Developmental adaptations in cytosolic phosphate content and pH regulation in the sheep heart in vivo

This study examines adaptations in myocardial cytosolic phosphate content and buffering capacity that occur in vivo as a function of development. Phosphate metabolites were monitored in an open chest sheep preparation using a 31P magnetic resonance surface coil over the left ventricle. Newborn lambs (aged 4-9 d, n = 5) underwent exchange transfusion with adult blood to reduce blood-borne 2,3-diphosphoglycerate contamination of the heart monophosphate and phosphomonoester resonances, thus allowing determination of these phosphate concentrations. The blood-exchanged newborns and mature controls (aged 30-60 d, n = 5) were infused with 0.4 N hydrochloric acid to decrease pH from greater than 7.35 to less than 7.00. Simultaneously, intracellular and extracellular pH were determined from the chemical shifts of the respective phosphate peaks and compared to arterial blood pH. Findings were as follows: (a) diphosphoglycerate contribution to the cardiac spectrum was found to be negligible, (b) significant decreases in cytosolic phosphate (P less than 0.03) and phosphomonoester (P less than 0.01) content occurred with maturation, and (c) large decreases in extracellular pH (greater than 0.5 U) in both groups were similarly associated with only small changes in intracellular pH (less than 0.1 U). Change in cytosolic phosphate content implies that alterations occur in the phosphorylation potential with resulting effects on regulation of myocardial respiration, and cardiac energetics.

In vitro 31P NMR spectroscopy of the reproductive organs of the male rat: an improved preparation method

In vitro 31P spectroscopy can be applied to disentangle the broad resonances in in vivo 31P NMR spectra of the reproductive organs of the male rat. However, adenosinetriphosphate (ATP) and glycerophosphocholine (GPC), present in large amounts in vivo, are nearly completely absent in vitro. With a modified PCA extraction method, in which the organs were lyophilized before extraction, a large amount of ATP and GPC could be found in vitro. This new extraction method is probably not only restricted to in vitro analysis of the testis but is likely to be useful for analysis of other organs such as kidney and liver.

High-resolution NMR spectroscopy of cerebral white matter in multiple sclerosis

Multiple sclerosis (MS) lesions have been shown by conventional methods to have major alterations in water and myelin lipid contents. To characterize these abnormalities more efficiently, NMR spectroscopy was used to evaluate water content by measuring relaxation times at 0.5 and 2.0 T. Subsequently, cholesterol content was obtained by using 1H NMR spectroscopy, while 31P NMR spectroscopy allowed measurement of the four main phospholipids and the inorganic phosphate concentrations in normal and pathological cerebral white matter samples. The relaxation times were significantly prolonged in MS lesions relative to normal white matter. Measured in different sample types, T1 and T2 times increased with water content. Moreover, the T2 of normal-appearing white matter was considerably lengthened. Analysis of white matter lipid composition using this method gave accurate values, which showed a significant decrease in phospholipids and cholesterol content in MS samples.

Image-guided 31P magnetic resonance spectroscopy of normal and transplanted human kidneys

Image-guided 31-phosphorus magnetic resonance spectroscopy (MRS) was used to obtain spatially localized 31P spectra of good quality from healthy normal human kidneys and from well-functioning renal allografts. A surface coil of 14 cm diameter was used for acquiring phosphorus signals solely from a volume-of-interest located within the kidney. To determine the effects of kidney transplantation on renal metabolism, patients with well functioning allografts were studied. Little or no phosphocreatine in all spectra verifies the absence of muscle contamination, and is consistent with proper volume localization. The intensity ratio of phosphomonoesters (PME) to adenosine triphosphate (ATP) resonances in transplanted kidneys (PME/ATP = 1.1 +/- 0.4) was slightly elevated (P = 0.2) compared to that of healthy normal kidneys (PME/ATP = 0.8 +/- 0.3). The inorganic phosphate (Pi) to ATP ratio was similar in the two groups (Pi/ATP = 1.1 +/- 0.1 in transplanted kidneys vs. 1.2 +/- 0.6 in normal kidneys). Acid/base status, as evidenced from the chemical shift of Pi, was the same in both normal controls and transplanted kidneys. Despite the practical problems produced by organ depth, respiratory movement, and tissue heterogeneity, these results demonstrate that image-guided 31P MR spectra can reliably be obtained from human kidneys.