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Biomedical subjects

M Hommel

Publications and source records attributed to M Hommel.

At least 145 records · Page 8Linked to original sources
PubMed1986

[Magnetic resonance imaging in multiple sclerosis. Sensitivity and correlation with the clinical picture].

The aim of imaging the brain in Multiple Sclerosis (MS) is to prove the dissemination of lesions, so critical for the diagnosis and so difficult to ascertain clinically. Our study included 21 patients with clinically definite (12) and probable (9) MS. A 21 patients underwent a neurological standard examination, a double-dose delayed CT scan and a Magnetic Resonance Imaging with a superconducting 0.5 Tesla magnet. Jointed slices were performed with a T2-weighted Spin-Echo sequence (TE 60, 120; TR 2000 msec). MRI detected 640 lesions in 20 patients while CT scan detected only 24 lesions in 9 patients. Technical limiting factors are discussed. Abnormalities in MRI were high-intense spots, blotches and streaks, located predominantly in the periventricular area. Capping lesions were common around the ventricular horns. "Plaques" were visualized in the posterior fossa. For each patient, the total surface of the lesions was calculated and was found to be related with the presence of lesions and with the cortical atrophy on CT scan. A correlation between the surface of lesions calculated by MRI and the disability scale was found especially in the group of patients with clinically proven cerebral lesions, while patients with predominantly spinal forms had a significantly lower surface of lesions. This finding could yield a new quantitative evaluation of the MS pathologic process which could be used to assess therapeutic efficacy.

Adult↗
PubMed1985

Effects of tiapride in tardive dyskinesia.

Tiapride, a selective D2 dopaminergic receptor blocking agent from the substituted benzamide class, was evaluated in a blind video-controlled trial in 10 psychiatric patients with tardive dyskinesia. There was a significant decrease in dyskinesia with a parallel increase in parkinsonism. This relationship between two opposite effects on movement suggests a common pathophysiological basis lying on a reciprocal hyper- and hypoactivity of the dopaminergic striatal system. Nevertheless, other mechanisms may be involved, for the evolution of individual parkinsonian and dyskinesia scores is not necessarily opposite: the tiapride-induced parkinsonism was generally acceptable and in two cases, the dyskinesia scores were reduced without an increase in parkinsonism. Therefore, more dyskinetic patients have to be evaluated in long-term studies with tiapride, before this drug could be recommended in tardive dyskinesia, when dyskinetic movements become intolerable.

Adult↗
PubMed1985

[Isolated ipsilateral lateropulsion caused by bulbar hematoma].

A case of hematoma involving probably the reticular formation of the medulla oblongata is reported. Examination showed a soft palate paresis and an ipsilateral axial lateropulsion without vertigo or oculomotor disorders. The mechanism of the lateropulsion is discussed. During the spontaneous recovery a transient hydrocephalus was observed.

Aged↗
PubMed1985

[Left anterior choroidal artery syndrome with language disorders and constructional apraxia].

The infarction in the territory of the anterior choroidal artery may induce a sensory motor impairment and neuropsychological symptoms close to those observed in some thalamic lesions. In a right handed man with a left sided infarction, language disturbances and constructional apraxia were observed. Cerebral blood flow measurements were performed 4 days after the stroke with the 133Xenon inhalation method. A decrease of mean hemispheric values was observed on both sides but more so on the left hemisphere, in the left frontoparietal regions. 98 days after the stroke language and constructional apraxia have partially improved. We have drawn a parallel between blood flow variations and neuropsychological signs. The cortical deafferentation caused by the interruption of the thalamo-cortical projections may explain the focalized decrease in cerebral blood flow values in the left hemisphere.

Adult↗
PubMed1984

[Paralysis of the hypoglossal nerve caused by 2 aneurysms and a dissecting aneurysm of the internal carotid artery].

Palsies of the lower cranial nerves caused by a compressive pathological carotid artery are not common. Three cases of paralysis of the hypoglossal nerve, hypoglossal and vagus, hypoglossal, glossopharyngeal and vagus nerves, are reported. In 2 patients the symptoms were related to an extracranial carotid artery aneurysm below the base of the skull and in 1 patient to a spontaneous carotid dissecting aneurysm. It is possible that some localized arterial dissecting aneurysms evolve to a localized aneurysmal sac, especially if they are located between Cl and the base of the skull. The tongue paralysis disappeared in 2 patients.

Adult↗
PubMed1983

Surface alterations of erythrocytes in Plasmodium falciparum malaria. Antigenic variation, antigenic diversity, and the role of the spleen.

The surface of erythrocytes infected with late developmental stages of Plasmodium falciparum is profoundly altered and new antigenic determinants can be detected by surface immunofluorescence using immune squirrel monkey serum. The expression of these parasite-specific antigenic determinants on the surface of the host erythrocyte can be modulated by the presence or absence of the spleen and by immune pressure. An antigenic switch occurred when a cloned population of the Ugandan Palo Alto strain of P. falciparum was transferred from a splenectomized into an intact monkey and this switch was reversible. In another strain (Indochina-1), we showed that the parasites isolated during secondary and recrudescent peaks expressed erythrocyte-associated surface antigens different from the parasites isolated during the primary infection; six variant antigenic types distinct from the original population were isolated in this way. The passive transfer of immune serum can induce antigenic variation and this can occur in a cloned parasite. The various mechanisms of antigenic variation in P. falciparum are discussed in the context of strain-specific diversity and the role of antigenic diversity in acquired immunity.

Animals↗
PubMed1983

Parasite sequestration in Plasmodium falciparum malaria: spleen and antibody modulation of cytoadherence of infected erythrocytes.

Sequestration, the adherence of infected erythrocytes containing late developmental stages of the parasite (trophozoites and schizonts) to the endothelium of capillaries and venules, is characteristic of Plasmodium falciparum infections. We have studied two host factors, the spleen and antibody, that influence sequestration of P. falciparum in the squirrel monkey. Sequestration of trophozoite/schizont-infected erythrocytes that occurs in intact animals is reduced in splenectomized animals; in vitro, when infected blood is incubated with monolayers of human melanoma cells, trophozoite/schizont-infected erythrocytes from intact animals but not from splenectomized animals bind to the melanoma cells. The switch in cytoadherence characteristics of the infected erythrocytes from nonbinding to binding occurs with a cloned parasite. Immune serum can inhibit and reverse in vitro binding to melanoma cells of infected erythrocytes from intact animals. Similarly, antibody can reverse in vivo sequestration as shown by the appearance of trophozoite/schizont-infected erythrocytes in the peripheral blood of an intact animal after inoculation with immune serum. These results indicate that the spleen modulates the expression of parasite alterations of the infected erythrocyte membrane responsible for sequestration and suggest that the prevention and reversal of sequestration could be one of the effector mechanisms involved in antibody-mediated protection against P. falciparum malaria.

Animals↗
PubMed1983

Immunity to malarial antigens on the surface of Plasmodium falciparum-infected erythrocytes.

An indirect immunofluorescence test with fresh non-fixed infected blood as antigen was used to show that antibody in human sera from the Gambia recognized antigens on the surface of Plasmodium falciparum-infected human erythrocytes. Surface immunofluorescence was detected on 90% of erythrocytes infected with trophozoites and schizonts produced in continuous culture of isolates from the Gambia (FCR 3/K+), Brazil and Thailand. Fluorescence was equally strong with a Gambian parasite clone (FCR 3/K-) that lacked knobs, an ultrastructural modification of the erythrocyte membrane associated with parasite sequestration. Immunofluorescence could not be detected with an isolate from Uganda. The surface antigenicity of parasitized erythrocytes was eliminated by chymotrypsin and trypsin treatment. Fluorescence was specific for the surface of trophozoite- and schizont-infected cells on the condition that fresh erythrocytes were added to cultures every 4-5 days (subculture); if fresh erythrocytes were not added for over 2 weeks, a large percentage of non-infected erythrocytes also bound antibody. Normal erythrocytes incubated with media from these cultures also gave positive surface immunofluorescence. Thus, there are two types of antigenicity on erythrocytes: one expressed on infected erythrocytes and another passively absorbed from media to normal erythrocytes when parasites are not subcultured for long periods.

Absorption↗
PubMed1982

[Blood biorheology and ischemic cerebrovascular accidents].

Blood hyperviscosity is usually observed in ischemic stroke. Our purpose was to study relations between viscosity and the different parameters of blood that influence viscosity, and to search abnormalities of circadian rhythms. 18 stroke patients (8 females and 10 males mean 65.4 years) and 12 normal subjects (4 females and 8 males, mean 68 years) were studied. The measures were realised within the 48 hours after stroke at 6 p.m. and 12 p.m. and the fourth day at 6 p.m. and 12 p.m., by means of a Taylor-Couette type rheometer. Stroke patients have a significant increase of their blood viscosity, but without elevation of blood hematocrit or fibrinogen within 48 hours. Stroke patients have no nocturnal decrease of viscosity, and they don't present the normal circadian periodicity. Perhaps would this phenomenon explain the diurnal variations in occurrence of strokes?

Adult↗
PubMed1982

[Bromazepam in anxiety. Clinical evaluation (author's transl)].

In an open study, 30 patients with anxiety were treated with bromazepam 6 to 9 mg/day and followed-up for 15 days either as out-patients or in hospital. The results, assessed by anxiety scores, showed a 71,4% improvement, which was often perceptible as early as the third day of treatment. The best responses were obtained in patients who had not previously received anxiolytic drugs and in those who had less anxiety at the beginning of treatment. In two cases the drug was discontinued on account of daytime drowsiness.

Adolescent↗
PubMed1982

Expression of strain-specific surface antigens on Plasmodium falciparum-infected erythrocytes.

Antigenic determinants present on the surface of squirrel monkey erythrocytes infected with late developmental stages of P. falciparum were recognized through their ability to bind antibodies present in the serum of immune monkeys. Two different assays were used to demonstrate the presence of these antigenic determinants on the cell surface: the fluorescent labelling of intact cells in suspensions and the binding to protein A-Sepharose. Such determinants appear to be strain-specific and have, for a given strain, a variable expression according to whether the parasites are taken from intact or splenectomized animals or whether they have been grown in vitro.

Animals↗
PubMed1982

[Modification of extrapyramidal signs by apomorphine associated with various dopaminergic antagonists].

An acute administration of various doses of apomorphine, a dopaminergic agonist, and of dopaminergic receptor blockers (domperidone, sulpiride, haloperidol), was double-blindly achieved in a parkinsonian patient also suffering from dyskinesia. Apomorphine improved tremor and dyskinesia proportionnally to the dose. Domperidone did not prevent from this beneficial effect whereas sulpiride or haloperidol revealed a competitive antagonism versus apomorphine.

Aged↗
PubMed1981

Interactions of Plasmodium falciparum infected erythrocytes with ligand-coated agarose beads.

The binding of normal and Plasmodium falciparum-infected squirrel monkey erythrocytes to columns of ligand-coated agarose beads was compared. Concanavalin A, ricin, soybean and peanut agglutinin-coated beads retain erythrocytes containing large developmental stages of the parasite preferentially to ring-containing erythrocytes or to normal erythrocytes. Binding is inhibited by the sugar corresponding to the lectin's specificity. Preferential binding does not occur with wheat germ or Ulex europaeus agglutinin-coated beads. When infected blood is preincubated in immune serum, infected erythrocytes are specifically retained by Protein A-coated beads. These peculiar binding properties reflect modifications of the infected erythrocyte membrane.

Agglutinins↗
PubMed1981

Plasmodium knowlesi variant antigens are found on schizont-infected erythrocytes but not on merozoites.

In this report, we demonstrate that the variable antigens present on the surface of Plasmodium knowlesi-infected erythrocytes could not be found on the surface of merozoites. A number of technical problems had to be solved to make such a comparative study possible, including the purification of merozoites by affinity columns and gradient centrifugation, the use of hyperimmune rabbit sera instead of monkey sera, and the use of immunocytological methods (indirect immunofluorescence antibody test and electron microscopy with ferritin-labeled antibodies) instead of the schizont-infected cell agglutination test. To ensure that these new techniques were valid for variant-specific serotyping, we compared two well-characterized variant populations with both the standard and the new methods. The removal of variant antigens from the surface of infected erythrocytes by proteolytic enzymes provides further information on the biochemical nature of these antigens.

Animals↗