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Biomedical subjects

M Levasseur

Publications and source records attributed to M Levasseur.

At least 37 records · Page 2Linked to original sources
PubMed1994

Brain metabolism after recurrent insulin induced hypoglycaemic episodes: a PET study.

Neuropsychological testing was carried out and the rate of oxygen metabolism in the brain was measured by PET in 15 highly selected patients with type 1 diabetes. The aim was to investigate the impact on the brain of hypoglycaemic comas resulting from insulin treatment. No significant difference was found between nine patients with a history of more than 10 hypoglycaemic comas and six others who denied any history of such events. These data suggest that intensified insulin treatment, although increasing the frequency of hypoglycaemic coma, may not always be harmful for the brain. This may be explained by the limited duration of hypoglycaemic coma induced by conventional insulin treatment.

Adult↗
PubMed1993

Patterns of use of obstetrical interventions in 12 countries.

Recent obstetrical practice trends in 12 countries were surveyed. There was a 3-fold difference in caesarean section rates and a 10-fold difference in instrumental vaginal delivery rates among countries. There was a net increase in the caesarean section rate of all countries over the study period and a net decrease in the instrumental vaginal delivery rate of some countries. There was a decrease in the caesarean section rate during the last year of observation in Australia, Denmark and Finland. In general, countries with high caesarean rates also had high instrumental vaginal delivery rates. There was no consistent relationship between use of caesarean section and use of instrumental vaginal delivery, although in several countries increasing use of caesarean section was accompanied by decreasing use of instrumental vaginal delivery. Oxytocin use rates were associated positively with instrumental delivery but not with caesarean section rates. While it was not possible to determine the proportions of women who received appropriate obstetrical care, we can infer that a significant proportion of interventions were unnecessary or only marginally beneficial. Continued increases in rates of obstetrical intervention are unlikely to result in improvements in birth outcome overall and may pose a risk to mothers and their newborns.

Australia↗
PubMed1992

Brain energy metabolism in bilateral paramedian thalamic infarcts. A positron emission tomography study.

Positron emission tomography (PET) studies of the cerebral metabolic rate of oxygen (CMRO2) were performed in seven consecutive patients with bilateral paramedian thalamic infarcts (BPTI), selected on neuroradiological and clinical criteria. The latter consisted of sudden onset of coma or confusion followed by a persistent amnesia of varying severity, with or without language impairment and frontal lobe signs. There was a highly significant decrease of CMRO2 for the whole cortex as well as for all the regions analysed: medial-frontal, latero-frontal, temporal, sensorimotor and posterior associative cortex. The mean regional metabolic ratios (region/whole cortex CMRO2) were not significantly different from controls, indicating an essentially uniform effect in the cortex, except the sensorimotor ratio which was significantly increased. Diffuse cortical hypometabolism most likely reflects thalamo-cortical deafferentation secondary to damage to the 'non-specific' thalamic nuclei, while sparing of the latero-ventral thalamus presumably explains the relative preservation of the sensorimotor cortex metabolism. Although no clear-cut individual relationship was found between magnitude of cortical hypometabolism and the severity and pattern of neuropsychological impairment, the data suggest that the former underlies and/or reflects the latter. Further studies with higher resolution PET devices might shed more light on the relationships between distinct cognitive patterns and specific topography of cortical hypometabolism in BPTI patients.

Adult↗
PubMed1992

Cortical metabolism in posterolateral thalamic stroke: PET study.

In 8 patients with small unilateral posterolateral thalamic (or, in one case, thalamocapsular) stroke (infarction or hemorrhage) selected on strict clinical (pure hemisomatosensory deficit without hemiparesis, visual field defect or neuropsychological impairment) and MRI criteria, we studied cortical energy metabolism using positron emission tomography with the 18F-fluorodeoxyglucose or the 15O-oxygen method. We found no significant ipsi- or contra-lateral metabolic depression either in the whole cortical mantle or in the sensorimotor cortex. These results support the hypothesis that location of thalamic stroke is a major determinant of the ipsilateral cortical hypometabolism characteristic of cognitively impaired patients with thalamic lesions and further emphasize the influence of the "non-specific" thalamocortical system on resting cortical metabolism. The lack of sensorimotor cortex hypometabolism in our patients suffering from hemidysesthesia and/or -hyperpathia also suggests that cortical metabolism is unaltered in thalamic pain.

Aged↗
PubMed1992

Stroboscopic computerized determination of humeral rotation in overarm throwing.

Analysis of the final phase of the overarm handball throw was carried out by a microcomputerized treatment of photographic images taken simultaneously in two grid layouts. Reflective stickers on the joints of the throwing arm (shoulder, elbow, wrist) allowed the coordinates of these three points to be measured against a reference on the wall. Using a mathematical treatment and Euler matrices, the movement could be studied in space. The results confirmed that humeral rotation occurs during the overarm handball throw. Initial external rotation was immediately followed with internal rotation about 40 ms before ball release.

Adolescent↗
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

In-vivo SPECT imaging of D2 receptor with iodine-iodolisuride: results in supranuclear palsy.

We assessed the potential use of [123I]iodolisuride (ILIS), a new iodine ergolene derivative, to study human striatal D2 dopamine receptors with SPECT. In normal subjects, we found that the tracer accumulated preferentially in striatum. This was prevented by high doses of haloperidol. The striatal accumulation was maximal between 60 and 180 min after injection. The striatum-to-cerebellum radioactivity concentration ratio as an index of specific binding, measured 60 min after injection, was 1.52 +/- 0.19 (mean +/- s.d.) in controls and 1.36 +/- 0.11 in patients with supranuclear palsy (p less than 0.03). Our results show that ILIS may be used to study D2 receptors with SPECT. In-vivo changes of D2 receptors in human brain may be detected with this method.

Adult↗
PubMed1992

[Early weight-bearing after osteosynthesis by THS hip screw in cervico-trochanteric fractures].

A second generation hip screw was designed in the laboratory to allow unlimited immediate weight-bearing in elderly patients with cervico-trochanteric fractures. The use of this device in 300 operated patients demonstrated that it provided the same capacity for weight-bearing as total hip prostheses, but with a lower morbidity and better and longer lasting functional results. Thus, in patients with a mean age of 77 years, one half of whom suffered from an unstable fracture: the operation was minimally traumatic (reduction on an orthopaedic table, no surgical access to the fracture site, operating time less than one hour); complications were consequently rare (no deep sepsis, no dislocation) in contrast with 5 to 10% of deep sepsis or dislocation with prostheses; early unlimited weight-bearing was permitted by the 5th day in every case and was achieved by the 10th day in more than 80% of cases (30% of whom were able to walk unassisted with crutches); an essential point, the design of the material prevented dismantling on weight-bearing and preserved the morphology of the hip (telescoping of the fracture site never exceeded 20 mm, mean:11 mm). Consolidation was obtained in every case by 6 to 8 weeks. The mortality at 3 months was identical to that observed with prostheses (18%, related to physiological age). The length of hospital stay and the duration of rehabilitation were considerably shortened, as 37% of patients returned to their previous residence by the 45th postoperative day. This resulted in a marked saving in medical costs for each patient (as patients previously returned home after an average of 145 days).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

[Slowly progressive apraxia: a MRI and positron tomography in 4 cases].

Four right-handed patients (69, 58 and 68 year-old men; 85 year-old woman) complained of motor difficulties with their left hand (3 cases), or both hands predominant on the left side (1 case). Continuous (1 case) or intermittent (2 cases) myoclonus was noted in the left arm. These disorders gradually progressed for 3 to 10 years. Clinical examination disclosed absence of motor, sensory (except in 1 case), or visual deficit. There were no cerebellar signs, no parkinsonian features (except for mild rigidity in 1 case), and no oculomotor abnormality. On the other hand, neuropsychological examination showed evidence of visuo-constructive apraxia in all cases, dressing apraxia in 3/4 cases and writing impairment in 3/4 cases. There was no amnesia, no aphasia and no intellectual impairment. MRI showed atrophy of the parietal areas, predominant on the right side. A positron emission tomography study was performed in all cases, and twice in 1 case. Cortical energy metabolism was measured using either 18 F-fluorodeoxyglucose or 15 O-Oxygen, to calculate the cerebral metabolic rate of glucose (CMRglu) or oxygen (CMRO2) respectively. Cortical metabolism was significantly decreased in the whole cortex of the right hemisphere in 3 cases, and was also reduced in the cortex of the left hemisphere, significantly in 1/3 studied planes. Moreover, regional metabolic indices (CMRO2 or CMRglu/cortex) showed a significant decrease in both the right and left posterior associative areas (temporo-parieto-occipital cortex), predominantly marked on the right side in 3 cases, indicating bilateral cortical dysfunction. At follow-up, one patient became progressively demented, another had visuo-spatial disorders indicating a lesion of both parietal areas. The relationships of our cases with the slowly progressive apraxia syndrome and with corticobasal degeneration are discussed.

Aged↗
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

[Opthalomoplegic migraine].

We report the case of a 24 year old man with a 22 year history of attacks of migraine without aura and attacks of ophthalmoplegic migraine. A persistent right 3rd nerve palsy appeared after the 17th attack. Although its existence has been debated, ophthalmoplegic migraine is recognized as such in the International Headache Society (IHS) classification. A review of published cases satisfying the IHS diagnostic criteria for ophthalmoplegic migraine is presented.

Adult↗
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

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.

Adenosine Triphosphate↗
PubMed1988

Two genes encoding 'minor' legumin polypeptides in pea (Pisum sativum L.). Characterization and complete sequence of the LegJ gene.

A genomic clone from pea (Pisum sativum L.) contains all of one gene encoding a 'minor' (B-type) legumin polypeptide, and most of a second very similar gene. The two genes, designated LegJ and LegK, are arranged in tandem, separated by approx. 6 kb. A complete sequence of gene LegJ and its flanking sequences is given, with as much of the sequence of gene LegK as is present on the genomic clone. Hybridization of 3' flanking sequence probes to seed mRNA, and sequence comparisons with cDNA species, suggested that gene LegJ, and probably gene LegK, was expressed. The partial amino acid sequences of 'minor' legumin alpha- and beta-polypeptides were used to confirm the identity of these genes. The transciption start in gene LegJ was mapped. The 5' flanking sequence of gene LegJ contains a sequence conserved in legumin genes from pea and other species, which is likely to have functional significance in control of gene expression. Sequence comparisons with legumin genes and cDNA species from Vicia faba and soya bean show that separation of legumin genes into A- and B-type subfamilies occurred before separation of the Viciae and Glycinae tribes.

Base Sequence↗