Mitochondrial creatine kinase functional development in post-natal rat skeletal muscle. A combined polarographic/31P NMR study

Mitochondrial creatine kinase (Mi-CK) function in viable mitochondria from developing rat skeletal muscle was assessed both by polarographic measurements of creatine-induced respiration and 31P NMR spectroscopy measurements of phosphocreatine (PCr) synthesis. Creatine-induced respiration was observed in very young rats and increased by 50% to 35 days of age. PCr synthesis was present in 7 day old animals and increased by 300% reaching levels measured in 35 day and adult muscle. Unlike reports showing Mi-CK enzymatic activities but no mitochondrial function in several situations, a concomitant progression of enzymatic activity and mitochondrial function was evidenced during the developmental stages of skeletal muscle Mi-CK in altricious animals. These results correlated with the progressive pattern of muscle differentiation during development of motricity in such animals. The observation that Mi-CK is functional in skeletal muscle mitochondria very early after birth, strongly favors the notion that adaptations in skeletal muscle of Mi-CK knock-out mice occur early.

Quality assessment in in vivo NMR spectroscopy: I. Introduction, objectives, and activities

By enabling noninvasive measurements of tissue biochemistry, nuclear magnetic resonance spectroscopy (MRS) provides a unique means of characterizing tissues. Differences in equipment, techniques, and methodology between different laboratories cause major difficulties when comparing results, whether from measurements of tissue metabolism, or from the effects of different therapies. This is of concern in critically evaluating work from different laboratories and centres, causing potential difficulties in reproducing results, limiting the establishment of MRS as a standard method of diagnosis and of characterising disease and response to therapy in the laboratory and clinic. It also poses particular problems in establishing the multicentre clinical trials of MRS that are now required to provide adequate statistical power in confirming the encouraging preliminary clinical observations. These difficulties arise principally from imperfect localization of signal from selected regions of interest in the body, and from the subsequent analyses of the MRS spectra. Improvement is possible by establishing agreed procedures for test measurements and for data analysis, and by using appropriate test objects and test substances to establish the quality of measurements. A concerted research project on characterisation of biological tissues by NMR, principally concerned with MR imaging (MRI), was activated in 1984 by the European Economic Community as part of its third Medical and Health Research Programme, under the auspices of the Biomedical Engineering Concerted Actions' Committee (COMAC-BME). In 1988, this project was prolonged for 5 years, when the programme was expanded to encompass MRS.(ABSTRACT TRUNCATED AT 250 WORDS)

Potential biological targets for anti-Alzheimer drugs

The stunning accumulation of data on the physiopathology of Alzheimer's disease is a real hinderance to pharmacologists who have to make decisions as to what molecules should be assessed first in man. Considering the cumbersomeness and cost of clinical trials in that field, a review of potential targets for drugs that are supposed to be active against the disease has become necessary, for a true definition of the rational justifications of trials to be envisaged.

Lipoproteins in heart transplantation: proton magnetic resonance spectroscopy of plasma

Despite the major improvement in immunosuppressive therapy, noninvasive detection of heart graft rejection remains a challenge. As lipoproteins are involved in several immunomodulation mechanisms, we studied their proton NMR spectra in plasma from patients after heart transplantation. NMR data were compared to clinical and functional evaluation of rejection process. The total linewidth (TLW) of methyl and methylene peaks, mainly arising from lipoproteins, were significantly lower for patients without a rejection process than for patients before surgery and patients with evidences of a rejection process. When TLW values are referred to TLW on the 8th day for each patient, the sensitivity and the specificity of the test are increased, with resulting positive and negative predictive values of 90 and 91%, respectively. The results obtained on more than 400 samples from 46 patients justify the use of proton NMR spectroscopy as a clinical tool.

Phosphocreatine and pH recovery without restoration of mechanical function during prolonged activity of rat gastrocnemius muscle: an in vivo 31P NMR study

Metabolic impairment in skeletal muscle was suggested to be involved in the development of local mechanical fatigue but until now results have dealt with short activity periods whereas little data on exhaustive and prolonged exercises are available. Stimulations of rat leg muscle lasting 45 min were induced by tetanic trains delivered via sciatic nerve at five different rhythms. Energy metabolism of the stimulated gastrocnemius muscle was followed by 31P NMR spectroscopy using surface coil while mechanical function was recorded. Our data showed a decrease in the force level to very low values a few minutes after exercise onset. This mechanical impairment only induced a transient metabolic failure followed by rapid restoration of high phosphocreatine (PCr) values and intracellular pH, without mechanical recovery. In addition, at the end of exercise, the PCr content was proportional to the fatigue level. As these experiments could not have impaired neuromuscular junction, the data would indicate that fatigue was maintained by a mechanism which does not appear to depend directly on muscle cell energy stores.

1H- and 2H-NMR study of bovine serum albumin solutions

Frozen, native and denatured bovine serum albumin solutions have been studied with a wide-band NMR pulse spectrometer. Both macromolecular and water protons spin-spin and spin-lattice relaxation times--t2m, t1m, t2w, t1w--have been measured between 170 and 360 K. In the native sample, the t2m process is the tumbling rate of the bovine serum albumin molecules. It gives to the spin-lattice relaxation an omega 0(-2) frequency dependence at room temperature in the studied frequency range, 6-90 MHz. An additional process contributes to t1m-1; it arises from internal backbone or segmental motions and provides a lower frequency behaviour. On denaturation, bovine serum albumin molecules lose their tumbling motion and form a rigid network, while internal backbone motions seem unaffected. Calorimetric Cp measurement confirms the occurrence of a phase transition upon denaturation. 1H and 2H spin-lattice relaxation times of water protons depend mainly on bound water mobility. 1H and 2H t2w depend also on the tertiary structure of bovine serum albumin and on its mobility, because of a fast exchange process between water and some protein protons (or deutons), while a cross-relaxation process between protein and water protons contributes to 1H t1w. Denaturation has no influence on bound water motional properties and bound water population.

Aminergic neurotransmitter and water content changes in rats after transient forebrain ischemia

We have studied changes of cerebral monoamine metabolism and water content, during recirculation following global transient ischemia (20 min) using the four-vessel occlusion model in rats. Levels of monoamines and their metabolites were determined in cortex, striatum, hippocampus, and hypothalamus. Water content was evaluated by weight and by the analysis of T1 and T2 relaxation times in 1H-nuclear magnetic resonance. Norepinephine levels decreased; 3,4-dihydroxyphenylethylamine, 3,4-dihydroxyphenylacetic acid, and 5-hydroxytryptamine levels oscillated and levels of the end products homovanillic acid and 5-hydroxyindole-3-acetic acid increased. The regional changes were qualitatively similar but quantitatively different, and were greatest in the hippocampus, illustrating the concept of neuronal selective vulnerability. The changes suggest an initial monoamine depletion and catabolism due to massive release from stores followed by autoregulatory processes. The water content increased moderately, with a maximum at 1 h. The variations of T1 were similar, positively correlated with water content and more pronounced in the cortex than in the white matter. T2 was markedly altered over the entire 24-h period. Those latter parameters are positively correlated with 5-hydroxytryptamine concentration in the hypothalamus consistent with a relationship between 5-hydroxytryptamine and cerebral edema.

T1 and T2 proton nuclear magnetic resonance (N.M.R.) relaxation times in vitro and human intracranial tumours. Results from 98 patients

137 samples of intracranial tumours have been studied in proton NMR spectroscopy. T1 and T2 relaxation times are above those of normal grey and white matter. Differential diagnosis between benign and malignant brain tumours does not seem feasible upon proton T1 and T2 alone. Histological correlations allowed us to specify secondary changes accounting for T1 and T2 variations (oedema, microcyst, stroma reaction, necrosis).

[Proton nuclear magnetic resonance in the pharmacologic study of cerebral edema]

Wistar male rats have been orally administered 2 mg X kg-1j-1 of triethyltin (TET) chloride for 5 consecutive days. The result was a cerebral edema which constituted a reproducible and useful experimental model for pharmacological screening of drugs used in ageing. Water content modifications and clinical behaviour for 11 days from the beginning of experiment have been linked to T1 and T2 proton relaxation times measured by nuclear magnetic resonance (1H-NMR). The observation of 3 central nervous system structures, which differ in white matter content, has lead to the conclusion that NMR is a more sensitive technique to follow up the edema evolution than the water content measurement alone; it has also allowed to discriminate intra from extra-cellular edema (osmotic and TET edema), and has proved the action of two drugs which are used in aging process treatment on the TET edema (dihydroergotoxine 2 X 10 mg X kg-1j-1 and (--) eburnamonine 2 X 50 mg X kg-1j-1). In the future the mastery of this technology will be used to study other nuclei (Na, K, P) which will bring more physiopathological informations and to pharmacological investigations of the brain by NMR tomography or focalised NMR.

Evaluation of human thyroid tumors by proton nuclear magnetic resonance

Proton nuclear magnetic resonance (NMR) was used in a study of 40 patients with thyroid tumors following partial or total thyroidectomy. Three patient groups were considered: those with nodules showing increased uptake, those with solitary nodules with decreased uptake, and those with multinodular goiters. Spin-lattice and spin-spin relaxation times (T1 and T2) were measured on samples of nodular and extranodular tissue from each patient. Increased T1 and T2 were observed for benign cold nodules, an increase in T1 alone for nodules with increased uptake, and a wide fluctuation in T1 and T2 for multinodular goiters. The four cancers in the series did not show a distinctive proton NMR pattern in comparison with the other nodular structures studied. The results point to the feasibility of applying NMR techniques to the detection of thyroid disease.

The effect of a constant and uniform magnetic field on mouse brain: a study by magnetic nuclear resonance

Modifications in brain functions after exposure to a constant magnetic field have been noted in animals. For some authors, the main factor is the action of magnetic fields on tissular water. The relaxation times obtained by proton nuclear magnetic resonance should therefore be modified. Mice were placed in a 0.6 T constant magnetic field for 2 h. Their brain relaxation times (spin-lattice T1 and spin-spin T2), were measured 1-5 d after exposure and do not seem compatible with an initial and important modification of the water structure.