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Biomedical subjects

B Mazoyer

Publications and source records attributed to B Mazoyer.

At least 73 records · Page 4Linked to original sources
PubMed1993

Assessment of coronary reserve in man: comparison between positron emission tomography with oxygen-15-labeled water and intracoronary Doppler technique.

This study compared positron emission tomography (PET) using oxygen-15-labeled water for measurement of coronary reserve with intracoronary Doppler in patients with left anterior descending artery stenosis and patients with no coronary lesion and a coronary reserve 3 as assessed by the invasive technique. To determine whether PET measurement of coronary reserve is altered by partial volume effect, patients with left ventricular dysfunction due to idiopathic cardiomyopathy were studied with both techniques. Direct ultrasonic measurement of coronary reserve was performed the day prior to the PET study: a Doppler catheter was placed in the proximal left anterior descending artery; mean velocity was recorded at baseline and after dipyridamole administration. Using a time-of-flight PET system, patients underwent: (1) an intravenous bolus of oxygen-15-labeled water at baseline and 4 to 6 min after intravenous infusion of dipyridamole using the same protocol as for Doppler study and (2) a 18F-fluorodeoxyglucose (FDG) myocardial imaging. Oxygen-15 time-activity curves were recorded in myocardial regions of interest (ROIs) drawn on a static FDG image. Using the left ventricular time-activity curve as an input function, a standard model with a single-tissue compartment was fitted to the PET data; myocardial blood flow was estimated as the blood-to-tissue transfer rate constant. Coronary reserve measured by PET was well correlated with the measured by intracoronary Doppler (r = 0.98, p < 0.001 for global population). This PET method is an accurate and reliable tool to noninvasively measure coronary reserve in patients, even in those with left ventricular dysfunction.

Blood Flow Velocity↗
PubMed1992

Evidence for a common network of brain structures involved in parkinsonian tremor and voluntary repetitive movement.

Repeated measurements of regional cerebral blood flow (rCBF) were obtained in 7 patients who underwent a stereotactic thalamic electrode implantation in the nucleus ventralis intermedius (nVIM) of the thalamus for severe hemi-parkinsonian tremor. Using positron emission tomography and oxygen-15 labelled water, rCBF was studied in each patient in two conditions: in absence of tremor, e.g. under nVIM electrical stimulation, and in presence of tremor. X-ray tomograms permitted individual definition of anatomical regions of interest. In presence of tremor, normalized rCBF increases were observed in the following regions: postcentral (13.6 +/- 8.4%, P = 0.0003), precentral (7.7 +/- 8.8%, P = 0.016), paracentral (7.7 +/- 8.4%), supplementary motor (8.2 +/- 10.4%, P = 0.025), caudate nucleus (5.7 +/- 7.6%, P = 0.03), vermis (9.7 +/- 7.3%, P = 0.007), cerebellar grey nuclei (9 +/- 6%, P = 0.016) on the electrode side and on the contralateral vermis (17.8 +/- 7.5%, P = 0.0003) and cerebellar grey nuclei (22 +/- 6.3%, P = 0.0004). These results clearly indicate an activation of the sensory-motor cortex, as well as an involvement of the supplementary motor area and the cortico-cerebellar pathways in Parkinsonian resting tremor (PRT). They demonstrate that PRT shares common network of brain structures with repetitive voluntary movement.

Aged↗
PubMed1992

Different mental imagery abilities result in different regional cerebral blood flow activation patterns during cognitive tasks.

Using regional cerebral blood flow (rCBF) imaging, two populations having high and low imagery abilities were compared at rest and while performing two cognitive tasks: silent verb conjugation and mental imagery. The imagery task produced an rCBF increase in the left visual association and left frontal cortices in both groups. Differences between high and low imagers were observed on global and regional flow responses to cognitive tasks: low imagers showed a whole cortex CBF increase during both tasks; high imagers showed a right dominance in the visual association cortex in all conditions, and in the parietal association cortex at rest.

Adult↗
PubMed1992

Thalamocortical diaschisis: positron emission tomography in humans.

To investigate further the relations between cortical energy metabolism and neuropsychological impairment after unilateral thalamic lesion, 55 patients underwent positron emission tomography studies of either cortical oxygen consumption or glucose utilisation, including eight repeat studies, at times ranging from 4 days to 98 months after the onset of the lesion [stroke (n = 44) or stereotaxic VL-Vim thalamotomy performed for movement disorders (n = 11)]. Patients with thalamotomy were also studied preoperatively and the surgery induced a significant fall in cortical metabolism on both sides (more so ipsilaterally); post-operatively the magnitude of the ipsilateral cortex hypometabolism was positively correlated to the severity of global neuropsychological impairment; similar but less significant findings were obtained for the ipsilateral/contralateral cortical metabolic asymmetry. With respect to the whole patient sample, the cortical metabolic asymmetry was initially pronounced, with subsequent monoexponential recovery, in the cognitively impaired study group, but it was only mild and showed no meaningful trend for recovery in the cognitively unaffected study group; yet even soon (< 3 months) after thalamic lesion there was a noticeable overlap of individual asymmetry values among the two study groups. These results lend further support to the view that the neuropsychological impairment that frequently follows unilateral thalamic lesions is reflected in a depression of synaptic activity in both the overlying and the contralateral cerebral cortices. For individual patients, this study also illustrates the potentially misleading nature of the measured cortical metabolic asymmetry with respect to neuropsychological status, especially at late times after lesion, in part because side to side metabolic ratios do not reflect bilateral changes.

Adult↗
PubMed1992

Regional cerebral blood flow in childhood autism: a SPECT study.

OBJECTIVE: The authors investigated a possible cortical brain dysfunction associated with infantile autism. METHOD: They measured regional cerebral blood flow with single photon emission computed tomography (SPECT) and xenon-133 in 21 children with primary autism (according to DSM-III-R criteria). Five cortical brain areas including frontal, temporal, and sensory association cortices were examined in order to test the recent hypothesis of cerebral dysfunction in primary autism. Anatomical references for each subject were obtained with computerized tomography or magnetic resonance imaging and were used to delimit the regions of interest for SPECT analysis. RESULTS: When the results from the group with primary autism were compared with an age-matched group of nonautistic children with slight to moderate language disorders (N = 14), no cortical regional abnormalities were found. CONCLUSIONS: It appears that there is no regional cortical dysfunction in primary autism; however, in light of methodological limitations, one cannot exclude the possibility of more localized or subcortical brain dysfunctions in autism.

Autistic Disorder↗
PubMed1991

The estimated density of D2 striatal receptors in schizophrenia. A study with positron emission tomography and 76Br-bromolisuride.

The striatal D2 receptors of 19 untreated schizophrenics and 14 normal control subjects were investigated with PET and 76Br-bromolisuride. The ratio of radioactivity in the striatum to that in the cerebellum was taken as an index of the striatal D2 receptor density. There was no significant difference between the control and the schizophrenic groups, nor any difference between subgroups of patients defined by clinical type or course of illness, and no relationship between the striatum:cerebellum activity ratio and SANS or SAPS ratings of symptoms. Unlike in the controls, this ratio was not correlated with age in schizophrenics. This study suggests that there is no quantitative abnormality of striatal D2 dopamine receptors in schizophrenia.

Adolescent↗
PubMed1990

Effects of anterior corpus callosum section on cortical glucose utilization in baboons. A sequential positron emission tomography study.

Cortical glucose utilization was measured under light anaesthesia using positron emission tomography and 18F-fluorodeoxyglucose before and serially after stereotaxic anterior corpus callosum section in 3 adult baboons (Papio papio); in 1 animal needles were introduced but callosotomy was not performed ('sham' operation). Lesion efficacy was verified by x-ray computerized tomography and by postmortem examination which indicated effective anterior two-thirds callosal section in all 3 baboons, as well as a small contusional area in the medial frontal cortex. A two-way layout analysis of variance performed on the regional cerebral metabolic rate of glucose (CMRGlc) data obtained in the frontotemporal, temporal and occipital areas revealed significant effects for both the time and the region factors (P less than 0.00001 for each); the time effects indicated a significant initial metabolic depression (P less than 0.01) at day 11 and 18, and a subsequent recovery (P less than 0.01 to 0.05) at day 98. Average CMRGlc changes from preoperative values at successive studies were -23%, -27%, -17%, -8% and +2%, and -17%, -21%, -10%, -5% and +6% in the 'surgically approached' and the contralateral frontotemporal area, respectively. The frontotemporal/occipital CMRGlc ratio was significantly depressed at days 11, 18 and 32 (P less than 0.01, 0.01 and 0.05, respectively), indicating a transient postoperative alteration in the cortical metabolic pattern. In the 'sham' animal, surgery induced negligible metabolic effects. Our results indicate that effective anterior corpus callosum section induces a transient bilateral depression of cortical metabolism, which predominates in the anterior parts of the brain, while metabolic recovery suggests efficient neuronal adaptation. These functional effects in the cortex may underlie the transient behavioural changes that follow anterior callosotomy in man.

Animals↗
PubMed1990

Effects of capsular or thalamic stroke on metabolism in the cortex and cerebellum: a positron tomography study.

We used positron emission tomography to study the cortical and cerebellar metabolic rates in 21 strictly selected patients with pure internal capsular infarct (n = 8), thalamocapsular hemorrhage (n = 6), or pure thalamic stroke (n = 7). Significant diffuse ipsilateral cortical hypometabolism relative to 62 controls free of cerebrovascular risk factors was frequently, although not consistently, found in the 13 patients with thalamocapsular or thalamic lesions and neuropsychological impairment but was absent from the eight patients with pure internal capsule infarct and free of neuropsychological deficit. These data suggest that damage to the thalamus or the thalamocortical projections is important in the development of ipsilateral cortical hypometabolism and that the latter may underlie the associated neuropsychological impairment. Significant contralateral cerebellar hypometabolism relative to 49 controls was found in three of six patients with pure internal capsule infarct, suggesting a pathogenetic role for the corticopontocerebellar system. However, the occurrence of hypometabolism in two of six patients with thalamic lesions indicates that this phenomenon may also result either from damage to the ascending cerebellothalamocortical system or indirectly from hypofunction of the cerebral cortex. No systematic association was observed between crossed cerebellar hypometabolism and ipsilateral ataxia.

Analysis of Variance↗
PubMed1990

Striatal D2 dopaminergic receptors assessed with positron emission tomography and [76Br]bromospiperone in untreated schizophrenic patients.

Striatal D2 dopaminergic receptors of 12 drug-free schizophrenic patients and 12 normal subjects were investigated with positron emission tomography and [76Br]bromospiperone. Patients were classified according to DSM-III criteria, and their clinical symptoms were rated according to Andreasen's negative and positive symptom scales. The ratio of striatal to cerebellar radioactivity was taken as an index of striatal D2 dopamine receptor density. There was no significant difference between the control subjects and the overall schizophrenic group and no significant relationship between this index and the symptom ratings. However, state-dependent variables could partly account for the striatal D2 receptor density variability.

Adult↗
PubMed1990

Left prefrontal glucose hypometabolism in the depressed state: a confirmation.

The resting-state cerebral metabolic rates for glucose of 10 severely depressed patients (seven bipolar and three unipolar) were compared, before and after treatment with tricyclic antidepressants, to those of 10 control subjects of similar age by means of positron emission tomography and the fluorodeoxyglucose method. Significant left-right prefrontal asymmetry was present in the patients before but not after successful treatment, suggesting that medication can reduce this asymmetry. Also, significant hypofrontality and whole-cortex hypometabolism were found in the patients in the depressed state and persisted in the treated state, despite clinical improvement, suggesting that these abnormalities are not state dependent.

Adult↗
PubMed1989

Time course of effects of unilateral lesions of the nucleus basalis of Meynert on glucose utilization by the cerebral cortex. Positron tomography in baboons.

In order to investigate the effects of a partial cholinergic deafferentation on the functional activity of the cortex, the cerebral metabolic rate of glucose (CMRGlu) was measured with positron emission tomography and 18F-2-fluoro-2-deoxy-D-glucose in 5 baboons (Papio anubis) both before and serially following stereotaxic electrocoagulation of the left nucleus basalis of Meynert (NbM). Four days postlesion, significant metabolic depression was present in the entire ipsilateral cerebral cortex, most marked in the frontotemporal region, and which slowly recovered close to normal within 6-13 weeks. Postmortem studies showed that the lesions were located largely in the NbM, and that a significant decrease in choline-acetyltransferase (ChAT) activity was present in the ipsilateral frontal, temporal and parietal cortices. The animal with the most limited histological lesion showed the least decrease in both ChAT activity and CMRGlu. There was a highly significant linear correlation between the regional cortical decreases in CMRGlu (early postlesion data) and in ChAT activity. These results indicate that cholinergic deafferentation induces a proportional metabolic depression in the cortex. However, compensatory mechanisms operate to restore the cortical metabolic activity gradually despite sustained cholinergic denervation, pointing to pre- and/or postsynaptic adaptation (plasticity). Moreover, unilateral NbM lesions also induced a significant reduction in contralateral CMRGlu, which also demonstrated recovery. Several mechanisms are discussed to explain this contralateral effect, but the most likely implicates a transcallosal depression of function as a result of ipsilateral effects of the NbM lesion. These metabolic effects of cholinergic deafferentation in the primate provide new insight into the mechanisms of cortical dysfunction, and the recovery thereof, following subcortical lesions. In addition, our findings have some relevance to the cortical consequences of cholinergic deafferentation observed in dementia of Alzheimer type.

Animals↗
PubMed1989

Obsessive-compulsive and other behavioural changes with bilateral basal ganglia lesions. A neuropsychological, magnetic resonance imaging and positron tomography study.

Eight patients are reported who shared the combination of bilateral basal ganglia lesions and a frontal lobe-like syndrome. The main features were inertia and loss of drive, with preservation of intellectual function. Some patients showed stereotyped activities with compulsive and obsessive behaviour which were sometimes highly elaborate in pattern. Extrapyramidal clinical signs were absent or mild. Brain damage, related to anoxic or toxic encephalopathy, was demonstrated by CT scans and MRI. The lesions appeared to be confined to the lentiform nuclei, particularly affecting the pallidum, although there was generalized brain atrophy in 2 cases. Positron emission tomography (PET) in 7 patients revealed hypometabolism of the prefrontal cortex relative to other parts of the brain. The PET studies suggest dysfunction of the prefrontal cortex as a result of damage to the lentiform nuclei. These clinical, anatomical and functional observations emphasize the role of the circuits linking the prefrontal associative cortex and some specific areas of the neostriatum, including the pallidum. The existence of distinct nonoverlapping circuits in the motor field or in the associative field can explain the fact that basal ganglia lesions may give rise to a clinical picture that is either purely motor, purely behavioural (as in some of our patients), or both. Similarities existed between some symptoms found in our patients and certain features of major psychiatric illnesses such as severe depression, catatonic schizophrenia, and obsessive-compulsive disorder. This raises the hypothesis that some aspects of these psychiatric disorders could be related to structural and physiological disturbances in the systems linking the frontal associative cortex and the basal ganglia.

Adult↗
PubMed1989

Local brain haemodynamics and oxygen metabolism in cerebrovascular disease. Positron emission tomography.

Using position emission tomography (PET) and equilibrium imaging with oxygen-15 labelled gases, the cerebral blood flow (CBF), blood volume (CBV), oxygen extraction fraction (OEF) and oxygen consumption rate (CMRO2) were measured in multiple regions of interest over the cerebral cortex of 5 control subjects, 4 patients with strictly unilateral longstanding carotid artery occlusion, 1 patient with middle cerebral artery embolic stroke in the acute stage, and 4 patients with subcortical stroke and no cervical arterial disease. In each control subject, the regional CBV was linearly and positively correlated with both CBF and CMRO2, while the local mean transit time (t = CBV/CBF) was uniformly distributed, reflecting the local adaptation of both the vascular tone and the capillary density to the metabolic demand at constant cerebral perfusion pressure that characterizes the normal brain. In patients with subcortical stroke, cortical blood volume was reduced in proportion to the matched reduction in CBF and CMRO2, suggesting that the metabolic depression resulting from cortical deafferentation increases the resting tone of pial vessels. Unilateral carotid occlusion induced larger CBV and t, and steeper slopes of the CBV-CBF relationship, particularly on the occluded but also on the patent side. The assessment of the local cerebral perfusion pressure (CPP) as judged by the ratio CBF/CBV in 3 patients with focally raised OEF and preserved or reduced CMRO2, allowed the demonstration in multiple cerebral regions of single patients of two well-known physiological phenomena: the autoregulation of CBF, followed by the rise of the OEF as local CPP falls further. In addition, the depression of CMRO2 in the ischaemic cortex was associated with a trend for CBV to return towards normal values, compared with the maximally elevated CBV found in oligaemic but metabolically normal areas. This suggests that a process of metabolic vasoconstriction may participate, among other factors, in the vascular collapse that occurs, and would serve to regenerate some haemodynamic reserve, at very low CPP levels.

Arterial Occlusive Diseases↗
PubMed1989

SPECT analysis of recent cerebral infarction.

We measured regional cerebral blood flow and [123I]iodoamphetamine (IMP) uptake in 16 patients with unilateral brain infarcts during the subacute period (Day 3 to Day 50) and again after 3 months. Our results show that the central and peripheral areas described earlier in the chronic period were already differentiated in the subacute period. The central area presented a short phase of luxury perfusion and a longer phase of IMP hyperfixation. The peripheral area showed both a slight regional cerebral blood flow decrease and an early IMP uptake decrease similar to those previously found in the chronic period. Contralateral regional cerebral blood flow during the subacute period, considered normal, was significantly lower than that during the chronic period.

Acetazolamide↗
PubMed1988

Morphological and kinetic abnormalities of platelets in hypercholesterolemic rabbits.

Hypercholesterolemia (HC = hypercholesterolemia or hypercholesterolemic) was produced in rabbits by feeding them diets supplemented with cholesterol and peanut oil. Platelet counts and volumes, white cell counts, reticulocyte counts, and hematocrits were determined at intervals for 8-12 weeks in blood from HC animals and controls on a normal rabbit diet. Microthrombocytosis was a consistent occurrence in the presence of HC, developing as early as 2 weeks into the diet. Microthrombocytosis was generally associated with normal platelet counts, but mild thrombocytosis occurred late in the diet at the time of the highest levels of serum cholesterol (greater than 1300 mg/dl). Platelets from HC rabbits were morphologically normal by transmission electron microscopy. Survivals of 51Cr-labeled platelets from HC and non-HC rabbits were measured in HC and non-HC recipients. The results identified an intrinsic defect in the ability of HC platelets to survive in the circulation. They also confirmed previous findings of an environmental defect in HC that causes shortened platelet survival.

Animals↗
PubMed1988

Survival of rabbit platelets labeled with gallium 67.

The viability of rabbit platelets labeled with radioactive gallium was determined to analyze the feasibility of using platelets labeled with gallium 68 as an imaging reagent for positron emission tomography. Platelets were labeled with a complex of the longer lived gallium 67 and mercaptopyridine-N-oxide (MPO) or with sodium chromate Cr 51. Their survival after transfusion was measured. Labelling efficiency of 67Ga-MPO was 6.5% to 45.8% (26.8% +/- 2.8%) when platelets were suspended in saline solution, but was much lower (1.6% +/- 0.8%) in plasma. Platelets labeled with either radioisotope in a saline medium survived as well as platelets labeled with 51Cr in plasma. Recovery values 1 hour after transfusion and mean platelet survivals were 68.6% +/- 4.9% and 3.4 +/- 0.2 days for 67Ga in saline solution, 76.5% +/- 6.8% and 3.8 +/- 0.5 days for 51Cr in saline solution, and 73.7% +/- 7.4% and 3.6 +/- 0.5 days for 51Cr in plasma. Labeled platelet concentrates always contained extra radioactivity not firmly bound to viable platelets. A postlabeling wash in saline solution did not reduce this contamination and resulted in reduction of the number of viable platelets. The results showed that rabbit platelets labeled with 67Ga-MPO survived in the circulation as well as those labeled by a standard protocol with sodium chromate Cr 51.

Animals↗