Synergy between medical informatics and bioinformatics: facilitating genomic medicine for future health care

In this paper, we review the results of BIOINFOMED, a study funded by the European Commission (EC) with the purpose to analyse the different issues and challenges in the area where Medical Informatics and Bioinformatics meet. Traditionally, Medical Informatics has been focused on the intersection between computer science and clinical medicine, whereas Bioinformatics have been predominantly centered on the intersection between computer science and biological research. Although researchers from both areas have occasionally collaborated, their training, objectives and interests have been quite different. The results of the Human Genome and related projects have attracted the interest of many professionals, and introduced new challenges that will transform biomedical research and health care. A characteristic of the 'post genomic' era will be to correlate essential genotypic information with expressed phenotypic information. In this context, Biomedical Informatics (BMI) has emerged to describe the technology that brings both disciplines (BI and MI) together to support genomic medicine. In recognition of the dynamic nature of BMI, institutions such as the EC have launched several initiatives in support of a research agenda, including the BIOINFOMED study.

1H NMR spectroscopy study of the dynamic properties of glycogen in solution by steady-state magnetisation measurement with off-resonance irradiation

The dynamics of size-selected fractions of glycogen in solution have been investigated by proton NMR spectroscopy, using a recently described relaxation study method which relies on strong offresonance irradiation. The dependence of the steady-state magnetisation on angle and intensity of the effective radio-frequency field was measured and compared to theoretical curves derived from different models of motion. Absence or presence of contributions to relaxation from molecular motions on the microsecond time scale can be tested with this method, without having to resort to models. We found that glycogen dipolar relaxation did not result from isotropic Brownian rotation, and despite some contribution from slow motion (> 1 microsecond) to relaxation in glycogen alpha-particles extracted from rat liver, bulk movement of the molecules did not appear to participate in averaging the dipolar term to zero. Whereas hepatic glycogen rat beta-particles and commercial oyster glycogen displayed very similar relaxation properties, alpha-particles showed significantly different behaviour. However, all results were compatible with a diversity of movements within the molecule, ranging from freely rotating pyranoside rings through collective chain motion and possibly to bulk movement of the beta sub-units within the alpha-particle.

[Exercise intolerance caused by muscular phosphorylase kinase deficiency. Contribution of in vivo metabolic studies]

A 33 year old man has been presenting since childhood an exertional muscle pain syndrome without myoglobinuria. Muscle biopsy revealed a vacuolar myopathy with glycogen excess in subsarcolemmal and intermyofibrillar spaces which was confirmed by electron microscopy. Plasma production of ammonia was abnormally high during exercise on a bicycle ergometer while the raise of lactate was normal. NMR spectroscopy showed an increased muscle glycogen content, with a slight and delayed drop of the pH during exercise. Phosphorylase b kinase activity was undetectable in muscle specimen whereas activities of others enzymes of carbohydrate metabolism were normal. Clinical presentation of our patient is compared to that of the reported cases of phosphorylase b kinase deficiency.

C13 NMR spectroscopy of lipids: a simple method for absolute quantitation

There is both epidemiological and experimental evidence of the effect of fatty acid molecular structure, particularly the degree of saturation in fatty acyl chains, on the growth and regulation of certain tumours. In vivo carbon nuclear magnetic resonance spectroscopy has previously been shown to offer a non invasive technique for the evaluation of proportions of monounsaturated, polyunsaturated and saturated fatty acids in human adipose tissue. We present a simple method, which uses both endogenous water and fat as reference, to quantify in molar terms these lipid sub-categories for tissues other than pure fat. This could provide additional information in the debate on the protective effect in cancer of high polyunsaturated fatty acid (PUFA) diet. The method was validated by characterization of a lipid emulsion of known composition in various experimental set-ups and was applied to measure the lipid composition of the calves of two volunteers. Limitations and perspectives of the method are discussed.

Specificity of temporal amygdala atrophy in Alzheimer's disease: quantitative assessment with magnetic resonance imaging

The aim of the study was to assess the specificity of temporal amygdala (TA) atrophy with magnetic resonance imaging (MRI) by comparing a group of early impaired patients with Alzheimer's disease (AD) with 'other types of dementia' and controls. In this prospective case-control study, 41 patients were selected: 12 with probable AD according to NINCDS-ADRDA and CERAD inclusion and exclusion criteria, 14 with other types of dementia and 15 age-matched control subjects. Two radiologists blindly measured the TA volumes on coronal oblique contiguous slices with a 1.5-tesla MRI scanner. TA volume measurements obtained by the 2 observers and right-left TA values were not significantly different. A significant TA atrophy was found in the AD group as compared to the other groups, with 39.7% (p < 0.001) difference in TA volumes between AD and other types of dementia groups and 41.4% (p < 0.0005) difference between AD and control groups. There was no significant difference between other types of dementia and control groups. There was an overlap between the three groups for 4 patients. TA atrophy assessed with MRI could be of diagnostic value in AD, especially in the early stage of the disease.

Impairment of the exercise-induced increase in muscle perfusion in McArdle's disease

In McArdle's disease (myophosphorylase deficiency) exercise intolerance is generally attributed to a lack of glycogenolysis, which decreases energy production during exercise. Magnetic resonance imaging data have recently suggested an impairment of the increase in muscle perfusion during exercise in these patients. We have tested this hypothesis by direct measurement of local muscle perfusion increase. Increase in muscle perfusion was assessed by positron emission tomography with oxygen-15 labelled water in five patients with McArdle's disease and five age- and sex-matched healthy volunteers. Radioactivity was measured in both forearms before and after exercise of the right forearm. The exercise intensity was biochemically assessed by in vivo phosphorus-31 magnetic resonance spectroscopy. The estimated increase in muscle perfusion with exercise was 5.7+/-5.5-fold in the patients (range 1.5-12.8) and 22.3+/-12.0-fold in the healthy subjects (range 10.1-37) (P=0.022). The results show a significant impairment of increase in muscle perfusion with exercise in McArdle's disease. Thus patients may suffer not only from a direct lack of glycogenolysis but also from indirectly impaired vasodilation.

Phospholipid abnormalities in early Alzheimer's disease. In vivo phosphorus 31 magnetic resonance spectroscopy

OBJECTIVE

To determine whether changes in phosphomonoester and phosphodiester levels could be detected in vivo with phosphorus magnetic resonance spectroscopy in the early stage of Alzheimer's disease (AD).

DESIGN

Survey-type of case-control study using neuropsychological testing as criterion standard with blinded data analysis.

SETTING

Patients were from a neurology clinic in Paris, France. The controls were from the community. Magnetic resonance measurements were performed in the prefrontal region of the brain with a clinical 1.5-T scanner. Blinded data analysis.

PARTICIPANTS

Twenty-four patients with mild AD and 15 age-matched healthy volunteers. Subjects were separated into two groups, both composed of patients with AD and healthy volunteers. Two successive acquisition protocols were used in the two groups.

RESULTS

A significant increase in the phosphomonoester-total phosphorus ratio was found in patients with AD compared with controls. In this series, use of a ratio above 11% as a threshold to test our sample yielded an 83.3% sensitivity and a 73.3% specificity test for AD. Other metabolite ratios (inorganic phosphate, phosphodiesters, phosphocreatine, and nucleotide phosphates to total phosphorus) were not significantly different between patients and controls. No metabolite ratio correlated with the neuropsychological status as assessed by the Mini-Mental State Examination.

CONCLUSION

Changes in phospholipid metabolism can be detected in vivo in the early stage of AD. Discrepancies in the literature may be due to differences in technical setting or in subject population types.

Defect in the lipoyl-bearing protein X subunit of the pyruvate dehydrogenase complex in two patients with encephalomyelopathy

Among the many metabolic encephalomyelopathies caused by deficiencies in the pyruvate dehydrogenase complex (PDHC), nearly all involve its E1 subunit. We describe two new familial cases of PDHC deficiency with encephalomyelopathy, chronic lactic acidemia, and a normal E1 subunit of PDHC but deficiency in another component. Activity of PDHC was measured in cultured skin fibroblasts and skeletal muscle, and immunoblot studies were performed on mitochondrial extracts from skin fibroblasts. Spectra of muscle tissue, obtained in vivo with phosphorus 31 nuclear magnetic resonance, were recorded both at rest and with exercise. The PDHC activity was markedly reduced to 10% to 20% of normal values in both cultured skin fibroblasts and skeletal muscle. Immunoblotting of skin fibroblast mitochondrial extracts showed a specific deficiency in the protein X component of PDHC but normal E1, E2, and E3 components. Spectra obtained with 31P nuclear magnetic resonance showed alterations compatible with those found in mitochondrial myopathies. This is the second description of an encephalomyelopathy associated with a specific absence of the lipoyl-containing protein X component, which has a structural role in the formation of a functional PDHC.

Amygdala atrophy in Alzheimer's disease. An in vivo magnetic resonance imaging study

OBJECTIVES

To study the ability of magnetic resonance imaging to measure the volume of the amygdala and detect amygdala atrophy in patients with early Alzheimer's disease.

DESIGN

Prospective case-control study and "blind" measurements.

SETTING

Subjects were ambulatory outpatients selected from an institutional practice in Paris, France.

PATIENTS

We studied 11 patients with probable Alzheimer's disease according to National Institute of Neurologic and Communicative Disorders and Stroke/Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA) and Consortium to Establish a Registry for Alzheimer's Disease (CERAD) inclusion and exclusion criteria, as well as six age-matched control subjects.

INTERVENTION

None.

MAIN OUTCOME MEASURE

A 1.5-T magnetic resonance imager was used to acquire the images. Two neuroradiologists independently and blindly measured the volume of the right and left amygdalas on high-resolution contiguous slices. In addition, other cerebral structures, ie, the sylvian fissures, temporal lobes, lateral and third ventricles, corpus callosum, and hippocampal formation, were measured on a single slice.

RESULTS

The values obtained by the two observers correlated highly (r = .90), and interrater variability was 13%. The Alzheimer's disease group showed significant (33%, P < .0001) atrophy of the amygdala when compared with the control group. The other structures showed less variation.

CONCLUSION

Significant amygdala atrophy can be detected in vivo in patients with early Alzheimer's disease by means of standard magnetic resonance imaging. This technique may be useful in the early diagnosis of Alzheimer's disease.

MR imaging as a potential diagnostic test for metabolic myopathies: importance of variations in the T2 of muscle with exercise

OBJECTIVE

Most metabolic myopathies (like glycogenoses and mitochondrial myopathies) are related to inborn errors of muscle energy metabolism and often present clinically as exercise intolerance (inability to sustain normal exercise). We investigated whether the previously observed absence of normal exercise-induced variation in the T2 of muscle in McArdle's disease (a metabolic myopathy caused by muscle phosphorylase deficiency) was specific for this disease and whether the variations in T2 could be used for screening patients suspected of having metabolic myopathy.

SUBJECTS AND METHODS

Exercise-induced variations in proton MR signal and in intracellular pH were studied in the forearm flexor muscles of nine healthy subjects and 49 patients with exercise intolerance due to muscle pain, suggesting a metabolic myopathy. The relative increase in T2, delta T2/T2, was measured from MR spin-echo images before and after exercise. Phosphocreatine (used as a control of the degree of exercise) and intracellular pH were measured from phosphorus-31 spectra before and during exercise. The progressive 4.5-min handgrip exercise reached maximal exertion capability at the end of exercise and decreased phosphocreatine to less than 50% of its rest value.

RESULTS

Variations in T2 and end-exercise pH were correlated. The nine healthy subjects showed a delta T2/T2 ranging from +19% to +44% (but little T1 variation). Ten patients with McArdle's disease showed only slight delta T2/T2 (0-10%). There was no overlap with values for healthy subjects, but there was some with values for other patients. Of the 21 subjects with a delta T2/T2 less than 19%, 19 had a metabolic myopathy. The other two had a congenital neuromuscular disorder (one central core disease, one nemaline myopathy) with type I fiber predominance (type I muscle fibers are characterized by a high oxidative metabolism and a low lactic acid production).

CONCLUSION

The altered increase in T2 was sensitive but not specific for McArdle's disease. However, as variations in T2 reflect variations in pH, they seem to be specific for myopathies in which there is little exercise-induced decrease in pH (some metabolic myopathies and congenital neuromuscular disorders with type I fiber predominance) among patients in whom exercise intolerance is the main symptom. Our results suggest that MR imaging might be useful as a screening test for these diseases.

Simultaneous temperature and regional blood volume measurements in human muscle using an MRI fast diffusion technique

The thermal dependence of the translational diffusion coefficient and of the regional blood volume was investigated in vivo by using a special MR pulsed gradient technique with reduced sensitivity to bulk tissue motion. Measurements were done at 0.5 T, using a small gradient insert. The diffusion coefficient of muscle water was calibrated against thermocouple-measured temperature in vitro, both with the muscle fibers parallel and perpendicular to the diffusion gradient. The maximum muscle temperature variation obtained by percutaneous conduction was -8.8 +/- 1.6 degrees C under cooling and +3.7 +/- 1.6 degrees C under heating, from basal state. Simultaneously the fractional regional blood volume decreased by a factor of 3.5 under cooling and increased by a factor of 2.7 under heating. Due to the interdependence of microcirculation and tissue temperature, this technique may be used to follow heat production or deposition in living tissue (muscle exercise, electromagnetic irradiation, etc.).

Simultaneous temperature and regional blood volume measurements in human muscle using an MRI fast diffusion technique

The thermal dependence of the translational diffusion coefficient and of the regional blood volume was investigated in vivo by using a special MR pulsed gradient technique with reduced sensitivity to bulk tissue motion. Measurements were done at 0.5 T, using a small gradient insert. The diffusion coefficient of muscle water was calibrated against thermocouple-measured temperature in vitro, both with the muscle fibers parallel and perpendicular to the diffusion gradient. The maximum muscle temperature variation obtained by percutaneous conduction was -8.8 +/- 1.6 degrees C under cooling and +3.7 +/- 1.6 degrees C under heating, from basal state. Simultaneously the fractional regional blood volume decreased by a factor of 3.5 under cooling and increased by a factor of 2.7 under heating. Due to the interdependence of microcirculation and tissue temperature, this technique may be used to follow heat production or deposition in living tissue (muscle exercise, electromagnetic irradiation, etc.).

Temperature changes induced in human muscle by radio-frequency H-1 decoupling: measurement with an MR imaging diffusion technique. Work in progress

To investigate temperature increases in tissues during magnetic resonance (MR) imaging or spectroscopy, the authors measured temperature changes in vitro and in vivo (leg of a volunteer) in a condition simulating hydrogen-1 decoupling in MR spectroscopy. Noninvasive measurements were obtained by using the temperature dependence of the translational diffusion coefficient of water. Temperature was measured at 0.5 T (86 MHz) by using a stimulated-echo sequence that included intense gradient pulses and a procedure reducing sensitivity to bulk tissue motion. Calibration curves of the diffusion coefficient against thermocouple-measured temperature were obtained for a gelatin phantom and bovine muscle. Temperature changes were 5.3 degrees C +/- 0.5 at 2.5 cm from the coil in gelatin and 7.7 degrees C +/- 0.5 at 0.7 cm in bovine muscle. The temperature changed by 4.9 degrees C +/- 1.9 at 2.2 cm from the coil in the calf muscle of a volunteer. The H-1 decoupling protocol can be adapted (modifications in transmission power, duty cycle) to reduce heating effects to below safety recommendations.

Single-input double-tuned Foster-type probe circuit

Synthesizing two different values of inductance from a given sample coil for use in a single-input double-tuned circuit is possible by means of three extra LC elements. A detailed analysis with derived equations shows how to calculate the circuit component values and what to expect from this kind of probe. It also derives the upper limit of the trap coil/sample coil inductance ratio beyond which no solution exists to double-tune the 31P-1H probe. The general expression for the channel efficiency shows that the latter is a function not only of the inductance of the coils, but also of their quality factor and of the operating frequencies. A numerical example is given illustrating good agreement between experiment and theory provided high quality rf capacitors are used.

Long-term relationship between acute rhabdomyolysis and abnormal high-energy phosphate metabolism potentiated by ischemic exercise

Relative concentrations of inorganic phosphate [Pi]r, creatine phosphate [CP]r, adenosine triphosphate [ATP]r, and intracellular pH (pHi) were determined by 31P-NMR spectroscopy in the flexores digitorum muscles. The measurements were performed at rest, during bouts of rhythmic exercises at different powers, including one with restricted blood supply, and during recovery. Normal subjects (N) and subjects with previous histories of exercise hyperthermia (EH) were compared. No significant difference was found between N and EH subjects at rest. During exercise [ATP]r was not affected, except in EH subjects exercising under partial muscle ischemia (P less than 0.001); in both N and EH, [CP]r and pHi decreased, and the higher the load the more pronounced the reduction. These changes were significantly larger in EH patients than in N (P less than 0.05), and the differences were dramatically increased by reducing blood supply (P less than 0.001). During recovery, the return to the control values was much slower in EH patients than in N, in particular for pHi after the exercise under partial ischemia. In conclusion, the fact that metabolic disorders are still patent long after the EH occurrence supports the possibility of latent myopathy and of a persistent metabolic disorder. Thus, 31P-NMR spectroscopy could be a useful noninvasive test to detect EH susceptibility in at-risk subjects.

Carbon 13 NMR study of glycogen metabolism in the baboon liver in vivo

In vivo glycogen metabolism was investigated at 2 Tesla by 13C NMR in the baboon liver. Two concentric surface coils were used for 13C observation and proton decoupling, respectively. Spectra were acquired in 2 to 10 minutes with a 60 ms repetition time. After 3 hours of glucose infusion in the 48 hr fasted animal, 3 g of 99%-enriched [1-13C]glucose were injected. The distribution of the label on C-1 and also C-2, C-5 and C-6 of glycogen indicated 65% and 35% contributions of the direct and indirect pathways to glycogen synthesis from glucose, respectively. The results show that hepatic metabolic pathways and rates can be followed in vivo in large animals by 13C NMR at 2 Tesla.

In vivo 13C-NMR evaluation of glycogen content in a patient with glycogen storage disease

Glycogen storage disease was suspected in a 10-month-old boy. Initial technical problems did not permit the determination of the precise enzyme, deficiency, and type VI glycogen storage disease was only diagnosed at the age of 2 years. In the mean time, natural abundance 13C nuclear magnetic resonance evaluation of muscular and hepatic glycogen content indicated normal muscular glycogen and increased hepatic glycogen in our patient, a finding which strongly argued for the diagnosis of type VI glycogen storage disease. Even though the use of nuclear magnetic resonance might seem, in this situation, a somewhat circuitous means of reaching the diagnosis, it appears that nuclear magnetic resonance could provide a useful tool for a non-invasive diagnosis of glycogen storage diseases.

Complementarity of magnetic resonance spectroscopy, positron emission tomography and single photon emission tomography for the in vivo investigation of human cardiac metabolism and neurotransmission

The three techniques allowing the noninvasive study of cardiac metabolism, namely magnetic resonance spectroscopy (MRS), positron emission tomography (PET) and single photon emission computed tomography (SPET), all use external detection with stable or radioactive isotopes. These techniques yield different information. PET is quantitative and very sensitive, and therefore only tracer amounts of molecules need to be injected. It allows neurotransmitters and receptors to be studied and a global view of metabolism (oxygen consumption, glucose and fatty acid utilization) to be obtained. SPET also has good sensitivity, but uses gamma-emitting isotopes of heteroatoms. Their longer half-lives allow follow-up for hours or days. MRS is based on stable elements with high (hydrogen 1, phosphorus 31, fluorine 19...) or low (carbon 13, Deuterium) natural abundance. It has very low sensitivity and only millimolar concentrations of substrates can be detected, but various parts of metabolism can be studied. The in vivo measurement of myocardial concentration of substances has many problems that are common to all three techniques (measurement of the volume, measurement of the quantity of each molecule, resolution, partial volume effect, improvement of the signal-to-noise ratio, movement of the organ). The complementarity of the techniques is illustrated by their applications to the study of cardiac metabolism. For instance, the energy metabolism can be studied by 31P-MRS, which detects the high-energy compounds ATP and phosphocreatine, and 13C-MRS yields information on the tricarboxylic acid cycle activity. PET and SPET allow the utilization of fatty acids, the normal fuels of the heart, to be studied. During ischaemia, PET with 18F-fluorodeoxyglucose (18FDG) can determine the glucose consumption and 1H-MRS shows the increase in lactic acid, reflecting anaerobic glycolysis. Comparison of the use of acetate labelled with 11C for PET or 13C for MRS shows the potentials and limitations of each technique. Myocardial perfusion can be evaluated directly with various PET tracers or indirectly with thallium 201 or various technetium-99m-labelled tracers by SPET. No MRS marker of perfusion is so far clinically available. Mainly SPET and PET are used clinically for the investigation of ischaemic heart disease as well as cardiomyopathies, but some initial results using 31P-MRS are being obtained.

Exercise-induced muscle modifications: study of healthy subjects and patients with metabolic myopathies with MR imaging and P-31 spectroscopy

Exercise-induced variations in proton signal intensity at magnetic resonance (MR) imaging and in intracellular pH were studied in the forearm muscles of healthy subjects and patients with muscular glycogenoses. The relative increase in T2 was measured from MR images obtained at 0.5 T, and end-exercise pH was measured with surface coil phosphorus-31 spectroscopy at 2 T. Eight healthy subjects showed a relative increase in T2 ranging from 20% to 44% in the flexor digitorum superficialis muscle and a drop in pH ranging from 0.35 to 1.1. Seven patients with muscular glycogenosis (six with McArdle disease and one with phosphofructokinase deficiency) showed only a slight variation in T2 (0%-17%) and no decrease in pH. Variations in T2 and in end-exercise pH were found to be correlated, perhaps reflecting the stimulation of muscular perfusion caused by acidosis.

[Abnormalities of the skeletal muscle in hypertrophic cardiomyopathy. Spectroscopy using phosphorus-31 nuclear magnetic resonance]

There have been several reports of electromyographic and histological changes of striated skeletal muscle, especially of the type I oxidative fibres, in hypertrophic cardiomyopathy. In order to determine whether these anomalies also cause metabolic changes, a P-31 magnetic resonance spectroscopic study was undertaken at rest and on exercise in 5 pauci-symptomatic patients and 10 control subjects. The 5 patients had primary hypertrophic cardiomyopathy without alteration of systolic function or signs of congestive cardiac failure (Stages I or II). There were no clinical signs of myopathy. None of the patients were receiving betablocker therapy at the time of investigation. No significant difference was observed at rest. Intracellular acidosis was particularly pronounced in 2 of the 5 patients at the peak of exercise. In addition, the phosphocreatine recovery time (T1/2) was longer in the patient group (3.4 +/- 1.7 vs 1.6 +/- 0.9 mn; p less than 0.01) suggesting a mitochondrial metabolic oxidation abnormality. These results suggest that some patients with primary hypertrophic cardiomyopathy have abnormalities of mitochondrial oxidation in their striated skeletal muscle which can be demonstrated by P-31 magnetic resonance spectroscopy. This would suggest a global abnormality of striated muscle which, at a more advanced stage of the disease, could account for decreased effort tolerance in these patients.

Diagnosis of muscular glycogenosis by in vivo natural abundance 13C NMR spectroscopy

Natural abundance 13C NMR (nuclear magnetic resonance) spectroscopy was used to distinguish patients suffering from muscle glycogenosis type V (McArdle's disease) from normal subjects by measuring their muscle glycogen content at rest. Proton-decoupled 13C spectra were obtained in 10-15 min from calf muscles at rest. The ratio of the glycogen/creatine signal areas was 12.9 +/- 1.7 in four McArdle's disease patients and 2.0 +/- 0.7 in seven normal subjects. This technique thus allows the non-invasive diagnosis of muscle glycogenosis.

[Spectroscopy of the liver in vivo using nuclear magnetic resonance. A new approach in hepatic physiopathology]

Nuclear magnetic resonance (NMR) spectroscopy is a non-invasive means of detecting numerous compounds, thus enabling real-time studies to be carried out on such topics as energy metabolism, intracellular pH and main intermediate metabolism pathways. This method has been used for several years to study perfused livers and rat livers in vivo, but its application to man has just begun. We describe some of its principal uses, with emphasis on the possibilities it offers to investigate the metabolic pathways. With the rapid advances made in this field, and particularly spectroscopic imaging, NMR spectroscopy should prove valuable in four main branches of research: understanding of physiological and pathological metabolic mechanisms, diagnosis with the possibility of functional tests, follow-up and assessment of new medical treatments, and pharmacology.

Discriminant factor analysis of 31P NMR spectroscopic data in myopathies

Discriminant factor analysis (DFA) enables one to distinguish among diagnostic groups using diagnostic variables. It provides discriminant functions that are linear combinations of the diagnostic variables and that optimally separate diagnostic groups. It was used to enhance the accuracy of 31P NMR data in the diagnosis of myopathies. DFA allowed a good separation of normal subjects, congenital neuromuscular disorders with type I fiber predominance, and McArdle's diseases. It elicited an unexpected homogeneity of idiopathic rhabdomyolyses, the metabolic origin of which is unknown, and suggested that the abnormality could involve the mitochondrial oxidative metabolism in some of them. In mitochondrial myopathies, an expected heterogeneity is shown by DFA. It may allow an automatic diagnosis of some myopathies from 31P NMR data or guide biochemists by comparing biochemical features of a new patient to those of previously established groups.

Correction of distortions due to the pulsed magnetic field gradient-induced shift in B0 field by postprocessing

Gradient pulses used in most localization techniques induce time-dependent shifts in B0 that strongly distort NMR signals. A postprocessing correction method requiring no additional hardware is proposed. The phase shift produced by the B0 shift is calculated from a reference free induction decay (FID) and used to correct any FID acquired with the same sequence.

Change in human cardiac rhythm induced by a 2-T static magnetic field

The influence of a 2-T static magnetic field on the cardiac rhythm was studied with 24-hour electrocardiographic monitoring in 12 healthy volunteers for 1 hour before exposure, 1 hour during exposure, and 22 hours after exposure. Four other subjects were exposed to 1 T, and nine control subjects were exposed to 0 T. In the 2-T group, the mean cardiac cycle length (CCL) was 912 msec +/- 83 before exposure. A significant 17% increase in CCL was observed after 10 minutes of exposure. No further significant variation was observed during exposure, and the CCL was back to preexposure values 10 minutes after exposure. No other arrhythmogenic effect was noted during the 24-hour monitoring. No statistically significant change was observed at either 0 or 1 T. The magnetically induced blood-flow potentials superimposed on the T wave were observed. The CCL increase during exposure could reflect a direct or indirect effect of magnetic fields on the sinus node, which is probably harmless in healthy subjects. However, its safety in dysrhythmic patients remains to be determined.

[The value of NMR spectroscopy in the study of myocardial ischemia and in cardiovascular pharmacology]

Nuclear magnetic resonance spectroscopy is a non-destructive method used to investigate the intracellular repercussions of experimental myocardial ischaemia. The effectiveness of drugs or cardioplegic agents in preserving myocardial metabolism during and immediately after ischaemia can be tested on various models. The results obtained in different experiments and the metabolic studies conducted in patients treated with cardiotropic drugs illustrate the value of this method in cardiovascular pharmacology.

Phosphorus NMR spectroscopy study of muscular enzyme deficiencies involving glycogenolysis and glycolysis

We used phosphorus NMR spectroscopy to study 16 patients with muscular enzyme deficiencies affecting glycogenolysis and glycolysis. Study of phosphomonoester (Pm) kinetics and intracellular pH during exercise and recovery provided criteria for the distinction of these metabolic myopathies by NMR spectroscopy. The Pm peak was undetectable in patients lacking debrancher enzyme or phosphorylase. By contrast, in phosphofructokinase (PFK) or phosphoglycerate kinase (PGK) deficiency, the Pm peak was larger than that of inorganic phosphate in exercise, whereas it was always smaller in normal subjects. During recovery, the disappearance of Pm was slower in PGK than in PFK deficiency.

Alpha and beta subunits of glycoprotein hormones in argyrophil pituitary tumors with small granule cells

A group of 33 functionless pituitary tumors with small argyrophil groups (SAG) were collected from a series of 200 pituitary adenomas (16.5% of all adenomas). Histologically, the tumors showed an unusually high frequency of trabecular patterns, perivascular pseudo-rosettes, and oncocytoid transformation. Immunoreactivity for glycoprotein hormone alpha-chain was found in more or less numerous cells of 20 cases (64.5% of SAG tumors). Thirteen of these cases also showed specific beta-chain immunoreactivity, especially for follicle-stimulating hormone (FSH) beta-chain, which was present in 11 tumors. Various admixtures of immature, oncocytic, sparsely granulated, and densely granulated cells were observed ultrastructurally, with prevalence of the latter cell variants in tumors showing immunoreactive cells and prevalence of the former cell variants in tumors lacking immunoreactive cells. It is suggested that some relationship may exist between SAG cell (glycoprotein hormone precursor cells?) tumors--or at least part of them--and glycoprotein hormone cell lines. Anyway, whatever their origin and interpretation, SAG cell tumors seem to represent a distinct clinicopathologic entity.