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Biomedical subjects

C Thomsen

Publications and source records attributed to C Thomsen.

At least 109 records · Page 6Linked to original sources
PubMed1995

Muscle strength, voluntary activation and cross-sectional muscle area in patients with fibromyalgia.

The objectives were to determine whether the low muscle strength in fibromyalgia is due to lack of exertion and to determine the relation between strength and muscle area. Secondarily we examined the voluntary muscle strength of the different muscles of the leg. The twitch interpolation technique was used to estimate the degree of central activation and the 'true' quadriceps muscle strength. Muscle cross-sectional area was determined with magnetic resonance imaging (MRI). The estimated 'true' muscle strength was 91 Nm (S.D. = 34 Nm) in 15 fibromyalgia patients compared with 125 Nm (28 Nm) in 14 healthy controls (P < 0.02). The 'true' strength divided by the sum of the maximal areas of the four bellies of the quadriceps muscle was lower, being 1.56 Nm/cm2 (0.32 Nm/cm2) in fibromyalgia patients compared with 2.11 Nm/cm2 (0.39 Nm/cm2) in the controls (P < 0.001). The voluntary muscle strength of the flexor muscles of the knee and of the plantar flexors of the ankle was markedly reduced in patients, but no significant differences could be observed in the strength of the dorsal flexors of the ankle. In conclusion, a reduction of the estimated 'true' quadriceps muscle strength per unit area of about 35% was found in fibromyalgia patients.

Activities of Daily Living↗
PubMed1995

Comparison of the effects on the diurnal blood pressure, glucose, and lipid levels of a diet rich in monounsaturated fatty acids with a diet rich in polyunsaturated fatty acids in type 2 diabetic subjects.

The influence on blood pressure, glucose metabolism, and lipid levels of an exchange of polyunsaturated fatty acids with monounsaturated fatty acids in the diet was compared in 16 Type 2 diabetic outpatients. In a cross-over study design the patients were randomly assigned to 3 weeks treatments with a diet containing 30% energy as monounsaturated fatty acids, or an isoenergetic diet with 30% energy as polyunsaturated fatty acids. The contents of total fat, saturated fatty acids, cholesterol, and fibre were similar in the two diets. On the last days of the two diet periods, 24-h ambulatory blood pressure was measured and the responses of glucose, hormones, and lipids to a carbohydrate rich test meal were measured. As compared with the polyunsaturated fatty acids diet, the monounsaturated fatty acids diet reduced 24-h systolic (129 +/- 11 vs 124 +/- 8 mmHg (mean +/- SD), p = 0.02) and diastolic blood pressure (76 +/- 11 vs 73 +/- 8 mmHg, p = 0.02). The two diets had similar, beneficial effects on glycaemic control, and cholesterol and lipoprotein concentrations. A diet rich in monounsaturated fatty acids has beneficial effects on the blood pressure, while similar effects on glucose and lipid levels are observed in normotensive Type 2 diabetic subjects.

Blood Glucose↗
PubMed1995

[3H]-L-2-amino-4-phosphonobutyrate labels a metabotropic glutamate receptor, mGluR4a.

1. The ligand binding site of subtype mGluR4a of the metabotropic glutamate receptor family was characterized by using [3H]-L-2-amino-4-phosphonobutyrate ([3H]-L-AP4) binding. 2. Specific [3H]-L-AP4 binding to membranes prepared from baby hamster kidney (BHK) cells transfected with a vector encoding mGluR4a accounted for 60-70% of the total binding whereas no specific binding of [3H]-L-AP4 was observed to membranes prepared from BHK cells expressing the vector only. 3. Specific binding of [3H]-L-AP4 to mGluR4a was detectable at 0 degree C, was saturated with 10 min and enhanced by Cl(-)-ions but not by divalent cations (Mg2+, Ca2+, Mn2+). 4. [3H]-L-AP4 binding showed a maximal binding density (Bmax) of 3.0 +/- 0.5 pmol mg-1 protein and an affinity (KD) of 441 nM. A modest decrease in affinity was observed in the presence of 0.1 mM guanosine-5'-O-(3-thio)trisphosphate-gamma-S, the KD being 761 nM and the Bmax 3.4 +/- 0.6 pmol mg-1 protein. 5. The following rank order of affinity for mGluR4a was observed: L-AP4 = L-serine-O-phosphate > glutamate = (2S,1S,2S)-2-(carboxycyclopropyl)-glycine > 1-amino-3-(phosphonomethylene)cyclobitanecar-boxylate > > (1S,3R)-1-aminocyclopentane-1,3-dicarboxylate = quisqualate > ibotenate. 6. A highly significant correlation was observed between the potencies of the compounds to inhibit forskolin-stimulated cyclic AMP-formation in BHK cells expressing mGluR4a and the affinity for displacement of [3H]-L-AP4 binding from mGluR4a suggesting that this binding site is functionally relevant. 7. In conclusion, [3H]-L-AP4 is a suitable radioligand for characterizing mGluR4a when expressed in BHK cells. Interestingly, a significant correlation was found between the ability of various compounds to displace [3H]-L-AP4 binding from mGluR4a and the previously observed potencies for inhibition of synaptic transmission via L-AP4 sensitive glutamatergic pathways. These data support the hypothesis that the L-AP4 receptor is contained within the mGluR family.

Aminobutyrates↗
PubMed1995

MR flow quantification with cardiovascular applications: a short overview.

We present a short overview of the potential of magnetic resonance imaging (MRI) for quantification of flow in the cardiovascular system. The most widespread method for creation of MRI flow information utilized flow-sensitizing magnetic field gradients. Objects that move in the varying magnetic field introduced by such gradients change their precession frequency and therefore obtain a velocity-dependent offset phase angle. The exact phase behaviour for different types of gradients and motion patterns can be calculated and a very simple linear relationship is predicted by theory as well as confirmed in experiments between constant velocity and phase angle. Phase-sensitive flow MRI (velocity mapping) is frequently performed as a two-dimensional gradient-echo technique with flow sensitivity (flow encoding) in the through-plane direction, but other encoding directions are possible. Parameters that can be determined from a velocity map are linear velocity in each voxel, vessel area and flow rate. In the case of a stenotic vessel, the trans-stenotic pressure gradient can also be estimated. The velocity mapping method has been extensively used for cardiac flow studies in adult patient groups, e.g. for indirect measurements of coronary artery flow and for the study of aortic valve diseases. In children, the method has recently been used to determine shunt volumes in congenital heart disease. We conclude that flow investigation with MRI may in the future present a good alternative for the clinical evaluation of cardiovascular disorders.

Adult↗
PubMed1995

Simultaneous 31P-NMR spectroscopy and EMG in exercising and recovering human skeletal muscle: a correlation study.

A large number of studies have shown amplitude and spectral changes of the electromyogram during exercise, leading to several theories of how these changes might be related to the underlying metabolic changes. The amplitude and spectral changes are generally interpreted as changes in motor unit recruitment and a reduction of the muscle fiber conduction velocity due to proton or lactate accumulation. This study focuses on the causality of spectral changes of the surface electromyogram and proton or lactate accumulation and how the changes in motor unit recruitment are related to the metabolic status of the muscle. Simultaneous 31P-nuclear magnetic resonance spectroscopy and surface electromyography were performed during sustained static exercise and recovery in healthy volunteers and a patient with McArdle's disease. A clear dissociation between the median power frequency of the surface electromyogram and pH was seen in the healthy volunteers during recovery and during exercise in the patient with McArdle's disease. The results indicate that proton or lactate accumulation is not primarily responsible for the spectral changes of the surface electromyogram as previously suggested. The motor unit recruitment (as judged by the root mean square of the surface electromyogram) increased hyperbolically during the submaximal static exercise, with decreasing phosphocreatine-to-P(i) ratio reaching maximum at 0.6 (exhaustion), and seems to constitute a consistent metabolic limit to the exercise. The increased myoelectrical activity seen after exercise is not caused by an incomplete recovery of phosphorous metabolism, pH, or lactate but could probably be an impairment of the excitation-contraction coupling.

Adult↗
PubMed1995

31P NMR spectroscopy and electromyography during exercise and recovery in patients with fibromyalgia.

OBJECTIVE: To investigate whether patients with fibromyalgia (FM) have normal motor unit recruitment in relation to muscle metabolism during exhausting exercise and recovery, and whether the reduced voluntary muscle force normally seen is related to a smaller muscle size. METHODS: Female patients with FM and sedentary controls were examined using simultaneous 31P nuclear magnetic resonance spectroscopy (NMR) and surface electromyography (SEMG) during exhaustive static exercise of the anterior tibial muscle and during recovery. The maximum voluntary contraction force was estimated, and the maximum cross sectional muscle area was evaluated using 1H NMR imaging. The sedentary controls were matched to patients for sex, age and, as far as possible, daily physical activity levels. RESULTS: Patients with FM had reduced maximum voluntary contraction force in relation to the sedentary controls, despite having similar muscle size. In general the myoelectrical-metabolic relation during exercise and recovery was normal in patients with FM. CONCLUSION: The less extreme changes in motor unit recruitment and metabolism during exhaustive exercise indicated a lower exercise tolerance that could be connected with the lower physical activity levels.

Adult↗
PubMed1995

The effect of lorazepam tolerance and withdrawal on metabotropic glutamate receptor function.

Mice were exposed to lorazepam (4 mg/kg) or vehicle by continuous infusion by implanted (s.c.) osmotic minipumps that were removed after 7 days. Dose-response curves for stimulation of phosphoinositide (PI) hydrolysis by the selective metabotropic glutamate receptor (mGluR) agonist, (1S,3R)-1-aminocyclopentane dicarboxylic acid [(1S,3R)-ACPD] were performed with cortical slices from mice treated with lorazepam or vehicle for 7 days and subject to 0, 1, 2, 3, 4 and 7 days of withdrawal. The efficacy of (1S,3R)-ACPD to stimulate PI hydrolysis was increased significantly at 2 and 3 days of lorazepam withdrawal when compared with responses in control slices. The effect was blocked by the mGluR antagonist, L-2-amino-3-phosphonopropionate (L-AP3). Enhancement of PI hydrolysis in cortical slices from mice at 2 days of discontinuation from 7 days exposure to lorazepam was also observed with agonists of alpha 1 adrenergic and histamine receptors, but not with agonists of muscarinic or serotonin receptors when compared with responses in control slices. Intracerebroventricular infusion of L-AP3 significantly increased pentylenetetrazol-seizure threshold in mice withdrawn for 2 days from 7 days of exposure to lorazepam, but showed no effect in comparable vehicle-exposed mice. These data suggest that PI-coupled mGluRs may be implicated in regulation of GABAergic functionality as observed after withdrawal from prolonged exposure to lorazepam.

Animals↗
PubMed1995

Texture analysis in quantitative MR imaging. Tissue characterisation of normal brain and intracranial tumours at 1.5 T.

The diagnostic potential of texture analysis in quantitative tissue characterisation by MR imaging at 1.5 T was evaluated in the brain of 6 healthy volunteers and in 88 patients with intracranial tumours. Texture images were computed from calculated T1 and T2 parameter images by applying groups of common first-order and second-order grey level statistics. Tissue differentiation in the images was estimated by the presence or absence of significant differences between tissue types. A fine discrimination was obtained between white matter, cortical grey matter, and cerebrospinal fluid in the normal brain, and white matter was readily separated from the tumour lesions. Moreover, separation of solid tumour tissue and peritumoural oedema was suggested for some tumour types. Mutual comparison of all tumour types revealed extensive differences, and even specific tumour differentiation turned out to be successful in some cases of clinical importance. However, no discrimination between benign and malignant tumour growth was possible. Much texture information seems to be contained in MR images, which may prove useful for classification and image segmentation.

Algorithms↗
PubMed1995

Increased brain water self-diffusion in patients with idiopathic intracranial hypertension.

PURPOSE: To investigate changes in brain water diffusion in patients with idiopathic intracranial hypertension. METHODS: A motion-compensated MR pulse sequence was used to create diffusion maps of the apparent diffusion coefficient (ADC) in 12 patients fulfilling conventional diagnostic criteria for idiopathic intracranial hypertension and in 12 healthy volunteers. RESULTS: A significantly larger ADC was found within subcortical white matter in the patient group (mean, 1.16 x 10(-9) m2/s) than in the control group (mean, 0.75 x 10(-9) m2/s), whereas no significant differences were found within cortical gray matter, the basal nuclei, the internal capsule, or the corpus callosum. Four of 7 patients with increased ADC in subcortical white matter also had increased ADC within gray matter. CONCLUSION: Measurement of diffusion coefficients in vivo demonstrated increased local water mobility within subcortical white matter in 7 patients with idiopathic intracranial hypertension that otherwise appeared normal on conventional MR imaging. Further studies are necessary to assess the clinical significance of these observations.

Adolescent↗
PubMed1995

Deuterium MR spectroscopy at 4.7 T. Quantification of tumour and subcutaneous tissue blood flow in animal models.

Deuterium MR spectroscopy was used for the determination of tissue blood flow (TBF). The tracer D2O was injected into the tissue of interest, and tracer washout was followed using a 4.7 T spectroscopy/imaging unit. Normal subcutaneous tissue in rats was studied, as well as tissue influenced by vasoactive agents (papaverine and adrenaline). The vasoactive agents introduced changes of 40% in TBF, compared with normal tissue. Normal tissue measurements were repeated using various D2O injection volumes (5-400 microliters). The injection volume 5 microliters gave TBF 11.7 +/- 2.0 ml/100 g.min (mean +/- 1 SD). This value was 40% higher than corresponding values observed at larger injection volumes (200-400 microliters). This injection volume effect is probably partly due to a capillary dilution caused by tracer administration, and partly related to the non-physiological deuterium signal decrease observed in dead rats. Blood flow measurements in human colon tumours implanted in nude mice showed a rather poor reproducibility, not improved by the use of a multiple site injection technique.

Adipose Tissue↗
PubMed1995

Use of an enhanced gradient system for diffusion MR imaging with motion-artifact reduction.

PURPOSE: A spin-echo diffusion-sensitized pulse sequence using high gradients (23 mT/m) is introduced. MATERIAL AND METHODS: In order to minimize motion artefacts, velocity-compensating gradients, ECG-triggering and post-processing with phase correction and raw data averaging using navigator echoes was performed. The in vitro ratio of diffusion coefficients for water and acetone was determined and the water self-diffusion coefficient at different temperatures was evaluated. The pulse sequence was tested in 7 healthy volunteers and in 2 tumour patients with astrocytomas of grades I-II and III-IV. Both single-slice and multi-slice techniques were used. RESULTS: The incorporation of phase correction clearly improved the quality of both diffusion-encoded images and the calculated diffusion maps. Mean values of the diffusion coefficients in vivo were for CSF 2.66 x 10(-9) m2/s and for white and grey matter 0.69 x 10(-9) m2/s and 0.87 x 10(-9) m2/s, respectively. CONCLUSION: Velocity-compensating gradients in combination with a high gradient strength were shown to be useful for in vivo diffusion MR imaging.

Adult↗
PubMed1994

Effects of bromohomoibotenate on metabotropic glutamate receptors.

(S)-Bromohomoibotenic acid [(S)-BrHIbo] stereoselectively antagonized glutamate-stimulated phosphoinositide (PI) hydrolysis in baby hamster kidney (BHK) cells expressing mGluR1a in a competitive manner with an IC50 of 250 microM. However, (S)-BrHIbo did not inhibit (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid [(1S,3R)-ACPD]-induced PI hydrolysis in rat hippocampal slices (S)- or (R)-BrHIbo did not show any effects on forskolin-stimulated cAMP-formation in BHK cells expressing mGluR2 or mGluR4 but did displace [3H]2-amino-4-phosphonobutyrate ([3H]AP4) binding from rat corticalmembranes with high affinities (IC50 = 1.0 microM and 1.1 microM, respectively). These data suggest that (S)-BrHIbo may interest with multiple PI-coupled glutamate receptors, however, at concentrations that are several fold higher than for displacement of [3H]AP4 binding from rat cortical membranes.

Aminobutyrates↗
PubMed1994

[Magnetic resonance spectroscopy in fibromyalgia. A study of phosphate-31 spectra from skeletal muscles during rest and after exercise].

31phosphorus nuclear magnetic resonance (31P NMR) spectroscopy of painful calf muscle was performed in 12 patients with fibromyalgia and 7 healthy subjects during rest, aerobic and anaerobic exercising conditions, and postexercise recovery. Ratios of inorganic phosphate and creatine phosphate (Pi/PCr) and pH were calculated from the collected 31P NMR spectra. Resting values of Pi/PCr were normal in the patients. Patients only tolerated 49% of the workload tolerated by the controls (P = 0.005). Patients and controls had similar rates of Pi/PCr and pH changes during work and recovery. The controls were able to change their Pi/PCr and pH more than the patients, due to the greater workload reached. However, statistical significance was only reached for the anaerobic static exercise (P = 0.003). It was concluded that fibromyalgia patients have a reduced voluntary capacity for work, but with a biochemical response to work and recovery similar to healthy subjects.

Adult↗
PubMed1994

24-hour lithium concentration in human brain studied by Li-7 magnetic resonance spectroscopy.

Brain and serum lithium concentrations were measured every second hour during a 24-hr period following lithium intake, and again 48-hr later in two normal subjects in steady state lithium treatment receiving lithium carbonate (Priadel Synthelabo) once every evening. The brain-lithium concentration was measured by 7Li magnetic resonance spectroscopy (MRS). The brain lithium level was found to undulate in a peak-trough pattern that followed the serum lithium profile, although in an attenuated form. The brain/serum lithium concentration ratio varied considerably during the 48-hr period, ranging from 0.5 to 1.3, but the ratio was independent of the serum-lithium concentration. The median half-life for lithium was 28 hr in the brain, and 16 hr in serum. The brain lithium concentration in the morning was about 75% of the clinically relevant standard 12-hr serum lithium concentration. The finding that brain lithium undulates during the day means that MRS measurements of brain lithium can only be compared if carried out under standard conditions that include a fixed interval following lithium intake and an identical treatment regimen.

Adult↗