Biomedical subjects

M Seghier

Publications and source records attributed to M Seghier.

4 recordsLinked to original sources

PubMed2001

Language representation in a patient with a dominant right hemisphere: fMRI evidence for an intrahemispheric reorganisation.

Studies have suggested that congenital left hemispheric (LH) frontal arteriovenous malformations (AVMs) are associated with an early transfer of language to right hemisphere (RH) frontal regions. The question remains whether such anatomofunctional reorganisation is due to RH compensatory abilities or to a general principle of lateral shift. In this study, we used fMRI language paradigms to investigate the case of a patient presenting aphasic symptoms following an haemorrhage due to a right frontal AVM. Prior to surgery, fMRI showed that language processing was confined to the RH, suggesting that language had not shifted during childhood from this congenitally dominant RH to the LH. After surgery, the patient presented severe aphasia that recovered to presurgical level within 70 days. At this time, fMRI showed that language tasks were still not associated with activations in the LH. These results suggest that the principles of early cerebral reorganisation after congenital lesions may differ in the RH and the LH. In addition, they support the idea that efficient restoration of language is achieved if a sufficiently large neuronal network is preserved around the lesion.

Adult↗

PubMed2001

Genomic features of intertypic recombinant sabin poliovirus strains excreted by primary vaccinees.

The trivalent oral poliomyelitis vaccine (OPV) contains three different poliovirus serotypes. It use therefore creates particularly favorable conditions for mixed infection of gut cells, and indeed intertypic vaccine-derived recombinants (VdRec) have been frequently found in patients with vaccine-associated paralytic poliomyelitis. Nevertheless, there have not been extensive searches for VdRec in healthy vaccinees following immunization with OPV. To determine the incidence of VdRec and their excretion kinetics in primary vaccinees, and to establish the general genomic features of the corresponding recombinant genomes, we characterized poliovirus isolates excreted by vaccinees following primary immunization with OPV. Isolates were collected from 67 children 2 to 60 days following vaccination. Recombinant strains were identified by multiple restriction fragment length polymorphism assays. The localization of junction sites in recombinant genomes was also determined. VdRec excreted by vaccinees were first detected 2 to 4 days after vaccination. The highest rate of recombinants was on day 14. The frequency of VdRec depends strongly on the serotype of the analyzed isolates (2, 53, and 79% of recombinant strains in the last-excreted type 1, 2, and 3 isolates, respectively). Particular associations of genomic segments were preferred in the recombinant genomes, and recombination junctions were found in the genomic region encoding the nonstructural proteins. Recombination junctions generally clustered in particular subgenomic regions that were dependent on the serotype of the isolate and/or on the associations of genomic segments in recombinants. Thus, VdRec are frequently excreted by vaccinees, and the poliovirus replication machinery requirements or selection factors appear to act in vivo to shape the features of the recombinant genomes.

Animals↗

PubMed2000

Moving illusory contours activate primary visual cortex: an fMRI study.

Identifying the cortical areas activated by illusory contours provides valuable information on the mechanisms of object perception. We applied functional magnetic resonance imaging to identify the visual areas of the human brain involved in the perception of a moving Kanizsa-type illusory contour. Our results indicate that, in addition to other cortical regions, areas V5 and V1 are activated. Activity in area V1 was particularly prominent.

Adult↗

PubMed1998

[Introduction to a study of specific antibodies (IgG and IgM) detection with ELISA in the diagnosis of poliomyelitis].

Samples of single sera collected from 38 patients with different clinical diagnosis were studied in order to perform ELISA techniques with the purpose of detecting poliomyelitis IgG and IgM antibodies. The résults were compared through antibody titration by neutralization test. 21 pairs of sera from infants suffering from acute flaccid paralysis were studied by ELISA-IgM, ELISA-IgG and neutralization test. Stool samples were collected from 20 of the latter patient. Wild poliovirus type 1 was isolated in 8 cases. ELISA-IgM technique was positive in 14 cases. The true positive poliomyelitis diagnosis was based on the persistence of flaccid paralysis 60 days after the onset and on wild poliovirus isolation with significant increase in antibody level. 16 cases were classified as poliomyelitis, 2 cases as non poliomyelitic paralysis and 3 cases as undetermined. 16 out of the 18 well established diagnosis were in agreement (88.8%) with the detection or not of IgM antibodies by ELISA. The specificity of these IgM ELISA antibodies was examined by studying 11 cases of lymphocytic meningitis. Cross reaction in serological responses between polioviruses and coxsackieviruses was observed. These cross reactions should be evaluated by studying a greater number of cases. The poliovirus ELISA-IgM is a sensitive, economical and rapid method to be used in poliomyelitis diagnosis to complete the neutralizing test and virus isolation.

Antibody Specificity↗