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Biomedical subjects

F Lavenne

Publications and source records attributed to F Lavenne.

At least 19 recordsLinked to original sources
PubMed1998

Paradoxical metabolic response of the human brain to a single electroconvulsive shock.

Regional brain protein synthesis was evaluated with positron emission tomography (PET) and L-(S-[11C]methyl)methionine ([11C]MET) in depressive patients, before and 3 h after an electroconvulsive shock (ECS), when energy supply is restored, and in healthy volunteers. Depressive patients presented apparent lower protein synthesis than normals, in agreement with known reduction of cerebral activity. In contrast, ECS resulted in a significant increase (56%, P < 0.05) in global cortical protein synthesis. This paradoxical hyperactivation of cellular protein metabolism in response to seizures and the fact that synaptic activity is further reduced after electroconvulsive therapy (ECT), may provide new insights for understanding the mechanism of action of ECT.

Adult↗
PubMed1998

Allodynia after lateral-medullary (Wallenberg) infarct. A PET study.

We used PET to study regional cerebral blood flow (rCBF) changes in nine patients with unilateral central pain after a lateral medullary infarct (Wallenberg's syndrome). All patients presented, on the abnormal side, a combination of hypaesthesia to noxious and thermal stimuli and allodynia to rubbing of the skin with a cold object (i.e. abnormal pain to innocuous stimulation). The rCBF responses during allodynia were compared with those obtained during stimulation of the normal side using (i) a cold non-noxious stimulus identical to that applied to the painful side, and (ii) an electrical high-frequency stimulus at painful ranges. Statistical analysis disclosed two abnormal patterns of rCBF change during allodynia. First, there is a quantitative change whereby the blood flow response was out of proportion with the actual intensity of the stimulus, i.e. the pattern of activation by innocuous rubbing of the skin was in our patients identical to that previously reported in response to painful stimuli in normal subjects. This pattern concerned primarily the contralateral thalamus in its lateral half and the primary and somatosensory areas, as well as inferior parietal [Brodmann area (BA) 39/40], anterior insular (BA 6) and medial prefrontal (BA 10) cortices. Thalamic over-activity may reflect abnormal transduction and amplification of sensory inputs after spinothalamic deafferentation. This might be responsible for both increased rCBF in multiple cortical targets and the perceived shift of stimulus intensity from innocuous to painful ranges. The second abnormality associated with allodynic sensation was qualitative. It concerned exclusively the contralateral cingulate gyrus, which did not exhibit the usual pain-related rCBF increase reported in normal subjects. This abnormal cingulate response may account for the peculiar response of lateral medullary infarct patients to allodynic pain, which is not simply perceived as an exaggerated pain sensation, but as a new, strange and extremely unpleasant feeling, not previously experienced by the patients.

Adult↗
PubMed1997

Positron emission tomography during motor cortex stimulation for pain control.

We studied regional changes in cerebral flood flow (rCBF) in 9 patients undergoing motor cortex stimulation (MCS) for pain control. Significant increase in rCBF was observed in the lateral thalamus ipsilateral to MCS probably reflecting corticothalamic connections from motor/premotor areas. Subsignificant increases were observed in the anterior cingulate, left insula and upper brainstem. Mean rCBF in the anterior cingulate increased during MCS in patients with good analgesic efficacy, while it decreased in those with poor clinical outcome; conversely, thalamic rCBF increased in the two groups, albeit to a greater extent in patients with good clinical results. Our results support a model of MCS action whereby activation of thalamic nuclei directly connected with motor and premotor cortices would entail a cascade of synaptic events in other pain-related structures, including the anterior cingulate and the periaqueductal gray. MCS could influence the affective-emotional component of chronic pain by way of cingulate activation, and lead to descending inhibition of pain impulses by activation of the brainstem. Such effects may be obtained only if thalamic activation reaches a 'threshold' level, below which the analgesic cascade would not be successfully triggered.

Adult↗
PubMed1996

A controlled positron emission tomography study of obsessive and neutral auditory stimulation in obsessive-compulsive disorder with checking rituals.

Ten nondepressed patients with obsessive-compulsive disorder (OCD) who were characterized by predominant checking rituals were compared with 10 age- and sex-matched control subjects. Hemispheric and regional cerebral blood flow levels (rCBF) were measured with positron emission tomography (H2 15O) across four conditions: rest, auditory stimulation with idiosyncratic normal or abnormal obsession, auditory stimulation with neutral verbal stimuli, and rest. Order of neutral and obsessive stimulation was randomized. Higher subjective responses to obsessive than to neutral stimulation were found in both groups; subjective response was higher in OCD patients when obsessive stimulation was presented first. A four-way analysis of variance (group x stimulation order x hemisphere x condition [neutral or obsessive stimulation]) was performed on stimulation minus rest normalized rCBF values. Control subjects had significantly higher rCBF in the thalamus and putamen. A trend toward higher rCBF in OCD patients was found in the superior temporal regions. When neutral stimulation was presented first, rCBF was significantly higher in the caudate region of control subjects. Obsessive stimulation was associated with higher rCBF than neutral stimulation in orbitofrontal regions in both groups of subjects. Under obsessive stimulation, superior temporal and orbitofrontal activities were correlated in OCD patients but not in control subjects. Our study suggests specific abnormalities of information processing in the basal ganglia and temporal structures of compulsive checkers.

Adult↗
PubMed1996

Source propagation of interictal spikes in temporal lobe epilepsy. Correlations between spike dipole modelling and [18F]fluorodeoxyglucose PET data.

Source localization methods were applied to interictal spikes from scalp EEGs and correlated with metabolic (PET scan) data in eight patients suffering from drug-resistant temporal lobe epilepsy (TLE). Dipolar sources, [18F]fluorodeoxyglucose (18FDG)-PET data and anatomical images (MRI) were projected into the same three-dimensional coordinates system. Averaged spikes were adequately modelled by two or three dipolar sources with different onset time of activation but overlapping activity (mean residual variance 3.4 +/- 2.1%). Although, in all patients, spike modelling demonstrated dipolar sources in both mesial and lateral temporal cortex, dipole propagation was consistent with the early involvement of only one of these two areas (mesio-temporal, five patients; lateral and polar neocortex, three patients). Six patients showed a unilateral interictal decrease in glucose uptake, as measured with 18FDG-PET, in the temporal lobe ipsilateral to the EEG spike focus. Temporal hypometabolism was bilateral in one patient and absent in the remaining case. When projected onto PET-scan slices, the dipolar sources of these patients were always included within the hypometabolic area. However, within the hypometabolic zone, the decrease in glucose uptake was not found to be more pronounced in regions containing dipoles. Therefore the spatio-temporal spread of neuronal hyperactivity underlying interictal spiking suggests the presence of preferential epileptogenic networks inside the hypometabolic temporal lobe. Fusion of bioelectric, metabolic and anatomical data proves to be a convenient way of summarizing multimodal information from non-invasive investigations in TLE patients entering an epilepsy surgery programme, and suggests that both interictal spike dipole modelling and 18FDG-PET data might be useful, as a complement to ictal electro-clinical data, in the presurgical evaluation of such patients.

Adult↗
PubMed1996

Perfusion-MVO2 mismatch during inotropic stress in CAD patients with normal contractile function.

With the use of[11C]acetate, positron emission tomography (PET) permits exploration of myocardial blood flow (MBF) and oxidative metabolism (MVo2) coupling. PET imaging was performed at rest and under dobutamine infusion in 8 normal subjects and 10 coronary artery disease (CAD) patients with significant single-vessel left anterior descending (LAD) stenosis (> 70%) and normal regional left contractile function at rest. Resting MBF and MVo2 were similar in remote and LAD regions of normal subjects and patients. During dobutamine infusion, MBF and myocardial flow reserve were lower in LAD regions of patients compared with remote regions (MBF: 1.49 +/- 0.42 and 2.06 +/- 0.57 ml.g-1.min-1, P < 0.01; reserve: 1.73 +/- 0.59 and 2.14 +/- 0.47, P < 0.01, respectively), whereas MVo2 expressed as kmono (an index of MVo2) and metabolic reserve were similar (kmono: 0.106 +/- 0.021 vs. 0.107 +/- 0.017 min-1; reserve: 1.88 +/- 0.32 vs. 1.98 +/- 0.37, respectively). This is the first human study showing that, in normal contractile regions at rest but perfused by stenosed artery, a disparate rise in MVo2 relative to the rise in myocardial perfusion occurs during increased cardiac work induced by dobutamine. This flow-metabolism uncoupling probably reflects an increase in O2 extraction.

Adult↗
PubMed1994

Effects of GABAA receptors activation on brain glucose metabolism in normal subjects and temporal lobe epilepsy (TLE) patients. A positron emission tomography (PET) study. Part I: Brain glucose metabolism is increased after GABAA receptors activation.

Though gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the human central nervous system, the metabolic response to GABA system activation remains imperfectly known. We studied in vivo with positron emission tomography (PET) the variations of glucose metabolism in the human brain after stimulation of the GABAA receptors by systemic administration of the specific GABAA agonist, 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP). These investigations were performed in three normal volunteers and as part of presurgical evaluation for temporal lobe epilepsy in six patients. While clinical and electroencephalographic (EEG) monitoring showed a sedative effect and sleepiness after THIP administration, glucose metabolism was paradoxically increased in grey matter structures, which are known to have a high density of GABAA receptors. These findings suggest that the pharmacological activation of GABA pathways, although inhibitory and producing a decrease of vigilance, increases the energetic demand at least during a phase of GABA agonist action, probably at the synaptic or at the glial cell level.

Adult↗
PubMed1994

Effects of GABAA receptors activation on brain glucose metabolism in normal subjects and temporal lobe epilepsy (TLE) patients. A positron emission tomography (PET) study. Part II: The focal hypometabolism is reactive to GABAA agonist administration in TLE.

Positron emission tomography (PET) using [18F]fluorodeoxyglucose (FDG) was used to study the metabolic response of focal hypometabolism to the administration of a specific GABAA agonist (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol), THIP, in six temporal lobe epilepsy (TLE) patients. After THIP injection, the increase of glucose metabolism in the hypometabolic focus was larger than the mean increase reported in the whole brain (Part I; Epilepsy Res., 19 (1994) 45-54). Within the hypometabolic focus, this increase was significantly higher in regions with the lowest basal metabolic level. This metabolic response in the hypometabolic focus, observed in the absence of any epileptic discharge during FDG accumulation and PET data acquisition, suggests that GABAA receptors are up-regulated or, at least, preserved in TLE.

Adult↗
PubMed1993

Relief of akinesia by apomorphine and cerebral metabolic changes in Parkinson's disease.

The cerebral metabolic rate of glucose was measured in 14 Parkinson's disease patients with severe on-off fluctuations. Two positron emission tomography (PET) scans with [18F]fluorodeoxyglucose were performed, one after a challenge of subcutaneous apomorphine at a dose able to relieve akinesia within 15 min and the other with the vehicle. Apomorphine reduced glucose utilization by 4-6% in the lenticular nuclei and the occipital cortex and by 6-9% in the thalamic nuclei, but this effect was not statistically significant. Thus, central stimulation of dopamine receptors by apomorphine in advanced Parkinson's disease is not associated with cerebral metabolic changes as assessed by PET. Despite a dramatic improvement of the motor state, the global neuronal activity in the striatum and its downstream projections remains stable, suggesting an equilibrium between excitatory and inhibitory dopaminergic activities.

Aged↗
PubMed1991

Metabolic patterns associated with non-specific magnetic resonance imaging abnormalities in temporal lobe epilepsy.

We investigated the cerebral metabolic patterns associated with non-specific hyperintense T2-weighted image on Magnetic Resonance Imaging (MRI) in Temporal Lobe Epilepsy (TLE). Nineteen patients suffering from TLE with a normal CT scan underwent Positron Emission Tomography (PET) using 18F-fluorodeoxyglucose; 8 had hyperintense T2-weighted image on MRI in the epileptogenic temporal lobe and 11 had a normal MRI. Interictally, PET exhibited focal hypometabolism in all the patients with hyperintense T2-weighted image and in 8 of the 11 whose MRI was normal. The hypometabolic area was significantly more extensive in patients with hyperintense T2-weighted image in whom it always encompasses the site of the MRI abnormality. Moreover, these patients had higher metabolic asymmetry index in the temporal and parietal lobes than patients with a normal MRI. One patient with mesial temporal hyperintense T2-weighted image underwent an ictal PET, which showed that the focal hypermetabolism fitted remarkably with the site and size of the abnormal MR signal. Thus, non-specific hyperintense T2-weighted images are associated with particular interictal and ictal metabolic patterns which might suggest that these MRI abnormalities reflect an epileptogenic lesion.

Adolescent↗
PubMed1988

Cardiovascular risk factors in a sample of a rural Belgian population: the Bellux MONICA Study.

A sample of 1949 subjects of the population of the Belgian province of Luxembourg was screened for levels of cardiovascular risk factors. Cigarette smoking was more prevalent among males (51%) than among females (17%). The relationship between smoking and socio-economic status was inverse in males (M) and direct in females (F). Blood pressure (BP) measurements showed definite high BP in 10% of this sample, and 60% of those with definite high BP were not taking any hypertensive drugs. The average total cholesterol value was 6.49 mmol/L in M and 6.45 mmol/L in F. F had lower values than M at a younger age, but higher values than M at an older age. The high-density lipoprotein cholesterol was higher in F (1.57 mmol/L) than in M (1.27 mmol/L). Diabetes was present in 4.2% of this sample. In nearly half of these participants, the disease had been discovered during the screening. Obesity was especially frequently among F in all three age groups. In conclusion, the main cardiovascular risk factors were found to be at a fairly high level in this population sample.

Adult↗
PubMed1986

Alteration of left ventricular diastolic filling in hypertensive patients: effects of nitrendipine and atenolol.

This study was undertaken to determine the chronic effects of a long-acting calcium-channel blocker (nitrendipine) on resting left ventricular filling abnormalities in ten patients with essential hypertension. Radionuclide left ventricular curves of these hypertensive patients were compared with the curves of twelve normal volunteers and of eight asymptomatic older patients. The curves were analyzed for ejection fraction, peak filling rate (normalized for end-diastolic counts and for stroke counts), time to peak filling rate and filling fraction in the first-third of diastole normalized for cycle length. Heart rate and ejection fraction were similar in both control groups and hypertensive patients before and after nitrendipine. Before nitrendipine, diastolic filling parameters were significantly different in the hypertensive patients as compared with the volunteers and with the asymptomatic aged patients: peak filling rate was lower, time to peak filling rate was longer and the first-third filling fraction was smaller. After six weeks of nitrendipine therapy, systolic and diastolic blood pressure decreased significantly. After nitrendipine, the time to peak filling rate decreased and the first-third filling fraction and the peak filling rate (normalized for stroke counts) increased significantly. The acute oral administration of 100 mg atenolol induced a further decrease in systolic blood pressure and a significant decrease in heart rate. The effect of combining nitrendipine and atenolol on diastolic indexes was a preserved effect on time to peak filling rate and on the first-third filling fraction. These results suggest that short-term therapy with nitrendipine improves early diastolic dysfunction in hypertensives: the addition of a beta-blocking agent further improved the early diastolic indexes.

Adult↗
PubMed1985

[Role of adrenergic beta receptor partial agonists in left ventricular failure of ischemic origin. Value of xamoterol (ICI 118,587, Corwin)].

The ideal sympathomimetic derivative should possess the positive inotropic and relaxing effects of catecholamines whilst remaining free of their side-effects. Theoretically, such properties could be present in beta 1-adrenoceptor partial agonists. Xamoterol (ICI 118,587, Corwin; ISA 43 p. 100) seems to be the most promising beta 1 partial agonist. The aim of the study was to determine if the beneficial effects of Xamoterol were maintained during long term administration. Xamoterol (200 mg twice dialy) was administered to 14 patients with anterior myocardial infarction and moderate heart failure (class II-III NYHA). After 3 months' therapy, left ventricular function improved as indicated by reduction in left ventricular (LV) end-diastolic pressure (23 +/- 5 to 16 +/- 5 mm Hg; P less than 0.0005), LV end-diastolic volume (153 to 140 ml/m2; P less than 0.05) and in LV end-systolic volume especially in 11 patients with a control end-systolic volume less than 100 ml/m2 (- 15 p. 100; P less than 0.05). LV inotropic state was also enhanced as indicated by 21 p. 100 increases in EMax, the maximal LV pressure/volume ratio (P less than 0.02) and 20 p. 100 increases in the ratio end-systolic stress/ end-systolic volume (P less than 0.02). Myocardial oxygen consumption was unchanged, global lactate extraction fraction increased from 20 +/- 18 to 33 +/- 14 p. 100 (P less than 0.05) and LV alanine release was reduced (-1.7 to -0.2 muMol/min; P less than 0.05). The rate of LV pressure fall accelerated from 57 to 52 ms (P less than 0.05) and the mean diastolic wall stress was reduced by 35 p. 100 (P less than 0.05), reflecting the improvement in LV relaxation and diastolic function. Thus, the beneficial effects of Xamoterol were maintained after prolonged therapy particularly in patients with class II-III heart failure; patients in class IV benefited less from this therapy. No tachyphylaxis or side-effects were observed.

Administration, Oral↗
PubMed1984

Acute and long-term effects of nitrendipine on resting and exercise hemodynamics in essential hypertension.

The hemodynamic effects of nitrendipine have been studied at rest and during exercise in eight patients with mild to moderate essential hypertension. Acutely, nitrendipine (20 mg) induced at rest a decrease in arterial blood pressure (from 194/100 to 151/78 mm Hg) and an increase in heart rate (from 81 to 101 beats/min); the cardiac output was unchanged and the systemic vascular resistances fell by 30%. Similar changes were observed during exercise, i.e., a decrease in arterial blood pressure (from 245/106 to 204/87 mm Hg) and in systemic vascular resistances (-25%) with an increase in heart rate (from 133 to 142 beats/min). After chronic treatment during 55 days (average daily dose was 46 mg), the hypotensive effects of nitrendipine were similar, although less marked, both at rest and during exercise; the tachycardia noted after acute intake disappeared after chronic therapy. The addition of atenolol (100 mg) at the end of the chronic study in six patients further reduced arterial blood pressure at rest (138/80 mm Hg) and during exercise (180/91 mm Hg); the heart rate decreased to 60 beats/min at rest and 94 beats/min during exercise. These data show that nitrendipine is a potent antihypertensive agent that induces an important fall in the systemic vascular resistances both at rest and during exercise; during chronic therapy, these antihypertensive effects were maintained while the reflex tachycardia disappeared. The addition of atenolol during chronic therapy contributed to the normalization of the resting and exercise arterial blood pressures in nearly all patients.

Adult↗
PubMed1976

Superiority of developed over total pressure for heart contractility indices in dogs.

The independence of indices of contractility to Starling effects was tested in 6 closed-chest dogs. After vagal and beta-receptors blockade, indices calculated with total left ventricular isometric pressure (TP), were shown to be strongly dependent of rises in end-diastolic pressure (LVEDP) induced by dextran infusion. At LVEDP of 14.6 +/- 1.5, 22.2 +/- 1.1 and 32.8 +/- 1.5 mm Hg (+/- SEM), the peak value of velocity of the contractile elements calculated with total pressure (peak VCE, TP) diminished by 21, 40 and 50%, and the extrapolated value of VCE, TP at zero total pressure (Vmax, TP) diminished by 15, 30 and 44%. In contrast, indices calculated with developed pressure (DP = TP-LVEDP) at the same LVEDP were much less influenced, particularly the extrapolated value of VCE, DP at zero DP (V max, DP5) and (peak dP/dt)/DP did not significantly change. During angiotensin infusion, expected decreases in TP indices secondary to LVEDP rises were partially masked by simultaneous increases in contractility, and DP indices tended to rise. On the other hand, with minimal changes in LVEDP, as during calcium injection and paired stimulation, increases in TP and DP indices demonstrate inotropic effects equally well. Our study also shows that, besides Vmax calculated with DP, the instantaneous ratio of peak dP/dt and DP can also be proposed as a simpler and thus more convenient index of contractility independent of volume changes.

Angiotensin II↗