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Biomedical subjects

J F Le Bas

Publications and source records attributed to J F Le Bas.

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

Muscular metabolism during oxygen supplementation in patients with chronic hypoxemia.

The effects of supplemental oxygen (O2) versus air on working calf muscle metabolism were studied in seven patients with stable chronic obstructive pulmonary disease (COPD) and chronic hypoxemia (PaO2 = 57 +/- 3 SE mm Hg) and seven age-matched control subjects. Oxygen and air were randomly administrated at 24-h intervals, and O2 flow rate was adjusted to correct hypoxemia (PaO2 = 87 +/- 4 mm Hg) in the COPD group. The relative concentrations of ATP, phosphocreatine (PCr), inorganic phosphate (Pi), phosphomonoesters (PME), and the intracellular pH (pHi) were determined with 31P magnetic resonance spectroscopy at rest, during a graded standardized and localized exercise protocol (360 active plantar flexions), and during recovery. In resting muscle no significant effect of added O2 was demonstrable in each group with regard to pHi, Pi/PCr, and ATP/(PCr+Pi+PME) ratios. Mechanical data were similar between the two groups and between the two tests during the whole exercise. The indices of muscular oxidative metabolism (Pi/PCr and pHi at the end of exercise and recovering PCr resynthesis rate) were impaired in the COPD group compared with that in the control group during air (all p < 0.05). All these parameters were significantly improved with added O2 in the COPD group (p < 0.05), whereas no similar effects were observed in the control group. However, these beneficial effects were incomplete since the exercising Pi/PCr ratio remained higher in the COPD group than in the control group during added O2. This energetic muscular impairment could correspond to tissular damage related to chronic hypoxemia.

Aged↗
PubMed1992

Magnetic resonance imaging of the liver by oblique sections.

The authors have applied magnetic resonance imaging (MRI) to the anatomic study of the liver by comparing cadaveric sections with those obtained with MRI. This study deals with sections oblique in relation to a sagittal or frontal plane, whose orientation is determined from landmarks visible on transverse sections. Oblique sections were made in 10 cadavers using an original method. First, adjacent transverse sections were made of the frozen trunk and two landmarks were located in these sections: the course of the middle hepatic v. and the direction of the division of the portal venous trunk. The transverse sections were then stacked and the block so reconstituted was refrozen and then cut in adjacent oblique sections oriented either along the plane of the middle hepatic v. (sagittal oblique sections) or along the plane of division of the portal venous trunk (frontal oblique sections). Oblique MRI sections were made in 15 healthy volunteers, mainly based on the same venous landmarks but sometimes on other landmarks visible on the transverse sections. Oblique MRI sections can be made in the plane of any anatomic structure located in the transverse sections in order to define its position. Sections based on identical landmarks differently oriented in different subjects allow for definition of the individual anatomy of the liver investigated. The frontal oblique sections clearly show the course of the trunk of the portal v. and the junctions of the hepatic vv. with the inferior vena cava. The sagittal oblique sections are particularly useful for investigating the thinnest part of the left side of the liver and also the caudate lobe.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatic Veins↗
PubMed1992

Relationship between levodopa-independent symptoms and central atrophy evaluated by magnetic resonance imaging in Parkinson's disease.

Thirty patients with Parkinson's disease were studied for the purpose of investigation relations between motor symptoms and cerebral atrophy evaluated by magnetic resonance imaging (MRI). Axial symptoms (gait disorder, postural instability and difficulty in arising from a chair), assessed at the time of maximum clinical improvement, were significantly correlated with frontal atrophy, while no correlation was found between the basal parkinsonian disability score and cerebral atrophy. It is suggested that frontal atrophy observed by MRI is linked with axial motor symptoms resulting from non-dopaminergic lesions. The origin of this atrophy is unknown.

Aged↗
PubMed1992

Metabolism and aerobic capacity of skeletal muscle in chronic respiratory failure related to chronic obstructive pulmonary disease.

The calf muscle energy metabolism of 8 stable chronic obstructive pulmonary disease (COPD) patients with chronic respiratory failure (arterial oxygen tension (Pao2) 7.7 +/- 0.4 kPa or 58 +/- 3 mmHg) was studied, using 31-phosphorus magnetic resonance spectroscopy (31P MRS). MRS spectra were acquired at rest and during the course of 360 pedal movements at 20, 35 and 50% of the maximal voluntary contraction (MVC) and during recovery. Eight healthy age-matched subjects served as the control group. No significant differences between groups were observed in resting muscle, as regards intracellular pH, Pi/PCr ratio (Pi: inorganic phosphate; PCr: phosphocreatine) and the relative ATP expressed as the ratio beta ATP/PCr + Pi + PME (PME: phosphomonoester). Although effective power outputs were similar for both groups at each work level, COPD patients exhibited a higher Pi/PCr ratio than health controls (3.34 +/- 0.89 vs 0.49 +/- 0.05 at 50% MVC; p less than 0.01) and a lower pHi (6.65 +/- 0.11 vs 7.06 +/- 0.02 at 50% MVC; p less than 0.01). PCr resynthesis during recovery was slower in patients than in control subjects (t1/2 PCr 1.27 +/- 0.26 min vs 0.47 +/- 0.05 min; p less than 0.05). These results suggest impairment of aerobic capacity in a non-ventilatory working muscle, which may be due to hypoxaemia in patients with chronic respiratory failure.

Aged↗
PubMed1992

Exertional heatstroke and muscle metabolism: an in vivo 31P-MRS study.

An impairment of muscle energy metabolism has been suggested as a predisposing factor for, as well as a consequence of exertional heatstroke (EHS). Thirteen young men were investigated 6 months after a well-documented EHS using 31Phosphorus Magnetic Resonance Spectroscopy (31P-MRS). The relative concentrations of ATP, phosphocreatine (PCr), inorganic phosphate (Pi), phosphomonoesters (PME), and the intracellular pH (pHi) were determined at rest, during a graded standardized exercise protocol (360 active plantar flexions) and during recovery. Also the leg tissue blood flow was determined by venous occlusion plethysmography during the MRS procedure. Sixteen age-matched healthy male volunteers served as control group. In resting muscle, there were no significant differences between the groups as regards pHi, Pi/PCr, and ATP/PCr+Pi+PME ratios. During steady state exercise conditions, effective power outputs were similar for both groups at each level of exercise: 20, 35, and 50% of maximal voluntary contraction (MVC) of the calf muscle. No significant differences were shown between the two groups in Pi/PCr, pHi, or changes of leg blood flow at each level of exercise. At 50% MVC, Pi/PCr was 0.48 +/- 0.08 vs 0.47 +/- 0.05 (P = 0.96), pHi was 6.94 +/- 0.03 vs 6.99 +/- 0.02, respectively (P = 0.13). Finally, the rate of PCr resynthesis during recovery was not significantly different between the two groups: t1/2 PCr = 0.58 +/- 0.07 vs 0.50 +/- 0.05 min, respectively (P = 0.35). Therefore, no evidence of an impairment of muscle energy metabolism was shown in the EHS group during a standardized submaximal exercise using 31P-MRS performed 6 months after an EHS.

Adenosine Triphosphate↗
PubMed1991

Impairment of muscular metabolism in chronic respiratory failure. A human 31P MRS study.

The calf muscle metabolism of 7 patients with stable chronic respiratory failure (PaO2 below 65 Torr) was studied using 31P NMR spectroscopy. NMR spectra were acquired at rest, during the course of 360 pedal movements at 20, 35 and 50% of the maximal voluntary contraction (MVC) and during recovery. Eight normal aged-matched subjects served as a control group. In resting muscle, no significant differences were observed between both groups as regards intracellular pH, inorganic phosphate/phosphocreatine (Pi/PCr) and beta-ATP/PCr + Pi + phosphomonoester (PME) ratios. Although effective power outputs were similar for both groups at each work level, patients exhibited a higher Pi/PCr ratio than healthy controls (3.19 +/- 1.01 vs 0.49 +/- 0.05 at 50% MVC; p less than 0.01) and a lower pHi (6.65 +/- 0.11 vs 7.06 +/- 0.02 at 50% MVC; p less than 0.01). Moreover, PCr resynthesis during recovery was slower in patients than in control subjects (t1/2 PCr = 1.26 +/- 0.30 vs 0.47 +/- 0.05 min; p = 0.01). These results suggest impairment of aerobic capacity in a non-ventilatory working muscle, probably due to hypoxemia in patients with chronic respiratory failure.

Adenosine Triphosphate↗
PubMed1990

Prospective study of lacunar infarction using magnetic resonance imaging.

Using computed tomography and magnetic resonance imaging, we prospectively studied 100 patients hospitalized with a lacunar infarct. Our aim was to evaluate the capabilities of magnetic resonance imaging in the detection and delineation of lacunes in a project of clinicotopographic correlations. Seventy-nine patients had a classic lacunar syndrome; 35 had pure motor stroke, 26 had ataxic hemiparesis, seven had sensorimotor stroke, and 11 had pure sensory stroke. A miscellaneous group of 21 patients had less typical lacunar syndromes, primarily with brainstem signs and symptoms. Among a total of 153 lacunes, magnetic resonance imaging detected at least one lacune appropriate to the symptoms in 89 patients. In 16 patients at least two lesions correlated with the clinical features, and precise clinicotopographic correlations were possible in 68 patients. Magnetic resonance imaging was more effective when it was performed a few days after the stroke. Lesions causing different types of lacunar syndromes had significantly different volumes, suggesting that the size of the lesion may influence clinical features. Magnetic resonance imaging may be the imaging technique of choice in the study of lacunar syndromes.

Aged↗
PubMed1990

Hemiplegia in posterior cerebral artery occlusion.

We report 4 patients with hemiplegia due to a posterior cerebral artery occlusion. Associated clinical signs were aphasia, alexia or a neglect syndrome, hemianopia, and hemisensory loss. Hemiplegia was due to infarction in the lateral midbrain. The level of the occlusion in the posterior cerebral artery may be located distal to the junction with the posterior communicating artery.

Aged↗
PubMed1990

[Cortical pain. Clinical, electrophysiologic and topographic study of 12 cases].

Vascular lesions of the cerebral cortex sparing the thalamus (MRI or CT with reconstructions) may be accompanied by burning or constrictive pain which suggests thalamic pain as it affects one half of the body and is associated with induced pain. Summation hyperpathia is rare; allodynia is more common and sometimes isolated (2 cases). Cortical pain may be paroxysmal, and in 3 of our patients it progressed like a jacksonian seizure. The territory of pain is also the site of global or spinothalamic hypoaesthesia (5 cases). Early SEPs are abolished or of low amplitude (8 cases). The lesion is located in area SI or extends to the thalamo-parietal radiations; in 11 out of 12 patients it was located in the minor hemisphere. Two physiopathological theories are discussed: hyperactivity of the intralaminar thalamus relieved from cortical inhibition, or denervation hyperactivity related to the cortical or subcortical lesion.

Adult↗
PubMed1990

Apparently primary malignant melanoma of the cerebellopontine angle. One case.

We report a case of primary malignant melanoma of the cerebellopontine angle. This tumour showed RMI features that were totally different from those reported for secondary melanomas, and therefore its nature could not be suspected before surgery. Intracranial primary melanomas are so rare that no other published case is available for comparison, and our tentative explanations for the atypical RMI signals cannot be supported by evidence from the literature.

Cerebellar Neoplasms↗
PubMed1989

Pure sensory stroke due to a pontine lacune.

A 53-year-old hypertensive man presented with the sudden onset of an isolated lemniscal sensory syndrome of the entire left side of his body. Magnetic resonance images showed a small lacune in the right paramedian pons corresponding to the location of the medial lemniscus.

Cerebral Infarction↗
PubMed1989

[Bone manifestations disclosing Hodgkin's disease and non-Hodgkin's malignant lymphoma. Analysis of 11 cases].

Bone localizations revealing Hodgkin's disease or non-Hodgkin's malignant lymphoma, are unusual. We are reporting 11 recent cases collected in rheumatology and haematology departments, including 4 where a comprehensive study of X-rays, scintigrams, axial tomograms and nuclear magnetic resonance imaging was performed. Review of the literature as well as our experience concerning the type of onset of the bone involvement, the clinical correlation, the imaging techniques, have led us to consider nuclear magnetic resonance as a decisive factor which should be offered at an early stage in the diagnostic approach.

Adult↗
PubMed1989

Spinal metastases of carotid paraganglioma. One case and review of the literature.

Paragangliomas of the carotid body are uncommon tumours usually regarded as benign or locally malignant. Metastasis occurs in 5 to 25% of the cases, involving mainly the liver, lung and bones. A case of carotid body tumour without histological evidence of malignancy but with local invasion and, subsequently, multiple spinal metastases is reported. Since the histological prognosis of the initial tumour is impossible to make in most cases, the authors underline the importance of signs of local invasion which is predictive of metastasis and requires regular monitoring with radionuclide bone scanning and MRI.

Adult↗
PubMed1989

Magnetic resonance imaging in ischaemic accidents of the brain stem.

Seven cases of ischaemic accident affecting the brain stem are reported. There were two lacunar infarctions and five infarctions due to occlusion of major arteries (two lateral medullary infarctions, one pontine infarction and two thalamo-mesencephalic infarctions). In every case the abnormalities detected at MRI were concordant with the clinical findings. The authors underline the value of MRI in establishing clinico-topographic correlations in vivo and in differentiating lacunar infarctions from infarctions due to stenosis of major arteries in the vertebro-basilar system.

Aged↗
PubMed1989

Apparently isolated, spontaneous haematomas of the brain stem. Seven cases explored by CT and MRI.

The authors present seven cases of apparently isolated spontaneous haematomas of the brain stem detected by computerized tomography (CT). Magnetic resonance imaging (MRI) was performed in all patients, and in three of these on two occasions at different stages of the lesion. Changes in MRI signal according to the moment this examination was carried out (acute, subacute or chronic stage) are described. In two of three patients operated upon the haematoma was found to be due to an occult vascular malformation.

Adolescent↗