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Biomedical subjects

G Marchal

Publications and source records attributed to G Marchal.

At least 37 records · Page 2Linked to original sources
PubMed2000

45/47 kilodalton (APA) antigen capture and antibody detection assays for the diagnosis of tuberculosis.

SETTING: APA complex (45/47 kDa) is an antigen specifically excreted by Mycobacterium tuberculosis and could therefore be a good candidate for diagnosis. OBJECTIVES: To develop three APA immunocapture ELISA assays using monoclonal antibodies (Mabs) and one IgG anti-APA ELISA test, and to determine their usefulness for the diagnosis of tuberculosis in Madagascar. DESIGN: For the Ag assays, 23 negative sputum and serum samples and 64 pairs of sputum and serum from active smear-positive patients (PTM+) were tested. For antibody assay, 116 negative controls, 143 PTM+ and 54 extra-pulmonary tuberculosis patients were tested. RESULTS: The sensitivities of the APA antigen detection assays were low (less than 40%) for a specificity of 95.6%, using either monoclonal antibodies or clinical specimens. The anti-APA serology was more sensitive (76.9% for PTM+ patients) but less specific (73.2%). Due to their poor predictive values, these tests cannot be recommended for the routine diagnosis of tuberculosis in Madagascar.

Antibodies, Bacterial↗
PubMed2000

Review of MR mammography techniques.

Many of the new techniques of MRI have promising characteristics for the further improvement of sensitivity and specificity but there remains a large place for clinical trials to evaluate the practical value of the different new approaches. The authors review the general MRI rules that determine image quality and comment on the use-fullness of innovations in MR mammography.

Breast Diseases↗
PubMed1999

Decreased capacity of recombinant 45/47-kDa molecules (Apa) of Mycobacterium tuberculosis to stimulate T lymphocyte responses related to changes in their mannosylation pattern.

The Apa molecules secreted by Mycobacterium tuberculosis, Mycobacterium bovis, or BCG have been identified as major immunodominant antigens. Mass spectrometry analysis indicated similar mannosylation, a complete pattern from 1 up to 9 hexose residues/mole of protein, of the native species from the 3 reference strains. The recombinant antigen expressed in M. smegmatis revealed a different mannosylation pattern: species containing 7 to 9 sugar residues/mole of protein were in the highest proportion, whereas species bearing a low number of sugar residues were almost absent. The 45/47-kDa recombinant antigen expressed in E. coli was devoid of sugar residues. The proteins purified from M. tuberculosis, M. bovis, or BCG have a high capacity to elicit in vivo potent delayed-type hypersensitivity (DTH) reactions and to stimulate in vitro sensitized T lymphocytes of guinea pigs immunized with living BCG. The recombinant Apa expressed in Mycobacterium smegmatis was 4-fold less potent in vivo in the DTH assay and 10-fold less active in vitro to stimulate sensitized T lymphocytes than the native proteins. The recombinant protein expressed in Escherichia coli was nearly unable to elicit DTH reactions in vivo or to stimulate T lymphocytes in vitro. Thus the observed biological effects were related to the extent of glycosylation of the antigen.

Amino Acid Sequence↗
PubMed1999

Murine natural killer T(NKT) cells [correction of natural killer cells] contribute to the granulomatous reaction caused by mycobacterial cell walls.

Mice injected with deproteinized cell walls prepared from the strain H37rv of Mycobacterium tuberculosis develop a granuloma-like lesion in which NKT cells are predominant. NKT cells play a primary role in the granulomatous response, because the latter does not occur in Jalpha281(-/-) mice, which miss NKT cells. The glycolipidic fraction of the cell walls is responsible for the recruitment of NKT cells; the recruiting activity is associated with fractions containing phosphatidylinositolmannosides. These results define a powerful experimental set up for studying the in vivo induction of NKT cell responses to microbial components.

Animals↗
PubMed1999

Noninvasive measurements of infarct size after thrombolysis with a necrosis-avid MRI contrast agent.

BACKGROUND: Gadophrin-2 is a new MRI contrast agent with high affinity for necrotic myocardium. The aim of the study was to evaluate whether noninvasive measurements of infarct size after thrombolysis are possible with gadophrin-2-enhanced MRI. METHODS AND RESULTS: Coronary artery thrombosis was induced in 3 groups of dogs by the copper-coil technique. Thrombolytic therapy together with aspirin and heparin was initiated after 90 minutes of occlusion. One day (group A), 2 days (group B), or 6 days (group C) after infarction, gadophrin-2 was injected intravenously (50 micromol. kg-1). In vivo T1-weighted segmented turbo-FLASH, in vivo T2-weighted segmented half-Fourier turbo spin echo (HASTE), and T1- and T2-weighted spin-echo MRI of the excised heart were performed 24 hours after gadophrin-2 injection. Regions of strong enhancement were observed on T1-weighted images. Planimetry of short-axis MR images and of corresponding triphenyltetrazolium chloride (TTC)-stained left ventricular (LV) slices showed a close correlation between the enhanced areas and TTC-negative areas for both in vivo (r2=0.98, P<0.0001; mean difference, 0.9+/-2.0% [SD] of the LV volume [LVV]) and postmortem (r2=0.99, P<0.0001; mean difference, 0.9+/-1.4% of LVV) measurements. T2-weighted images overestimated the infarct size by 8.1+/-5.4% of LVV. The mean infarct size was 10.8+/-11.6% of LVV (group A), 22.4+/-11.7% (group B), and 5.1+/-9.3% (group C). CONCLUSIONS: In this animal model, in vivo gadophrin-2-enhanced MRI could precisely determine infarct size after thrombolytic therapy. This technique may be very useful for the noninvasive evaluation of infarct size after reperfusion for AMI.

Animals↗
PubMed1999

A role for lymphotoxin beta receptor in host defense against Mycobacterium bovis BCG infection.

To investigate the role of membrane lymphotoxin (LT)alpha1 / beta2 and its LTbeta receptor (LTbetaR) in the protective immune response to Mycobacterium bovis bacillus Calmette-Guérin (BCG) infection, we have used a soluble fusion molecule (LTbetaR-IgG1). LTbetaR-Ig treatment interferes with granuloma formation mainly in the spleen by inhibiting macrophage activation and nitric oxide synthase activity. In addition, a large accumulation of eosinophils was observed in the spleen of LTbetaR-Ig-treated infected mice. Decreased blood levels of IFN-gamma and increased IL-4 were also observed, suggesting that the LTbetaR pathway is important in BCG infection to favor a Th1 type of immune response. The treatment of transgenic mice expressing high blood levels of a soluble TNFR1-IgG3 fusion protein with LTbetaR-Ig resulted in a still higher sensitivity to BCG infection, and extensive necrosis in the spleen. In conclusion, these results suggest that the LTbetaR and the TNFR pathways are not redundant in the course of BCG infection and protective granuloma formation: the LTbetaR pathway appears to be important in spleen granuloma formation, whereas the TNFR pathway has a predominant role in other tissues.

Animals↗
PubMed1999

Comparison of iron oxide particles (AMI 227) with a gadolinium complex (Gd-DOTA) in dynamic susceptibility contrast MR imagings (FLASH and EPI) for both phantom and rat brain at 1.5 Tesla.

The goal of the study was to compare, in phantom and normally perfused rat brain tissue, a superparamagnetic iron oxide particle-based contrast agent (AMI 227) with a low-molecular-weight gadolinium chelate, gadolinium tetraazacyclododecanetetraacetic acid (Gd-DOTA), in two susceptibility contrast magnetic resonance imaging (MRI) modes [fast low-angle shot sequence (FLASH) and echoplanar imaging (EPI)]. A phantom consisting of dilution series of both contrast agents was manufactured. Dilutions were obtained with isotonic serum from the available agent solutions (0.5 mmol Gd/mL Gd-DOTA; 350 mumol Fe/mL AMI 227). Eighteen rats were studied. Contrast agent (0.1 mL) was bolus injected in each rat, and dynamic MRI was performed (first pass of the contrast agent) in rat brain. The doses of AMI 227 injected were extrapolated from the phantom experiment: 0.2 mmol/kg body weight of Gd-DOTA and 7, 14, and 28 mumol Fe/kg body weight of AMI 227 were injected. For both sequences, signal-to-noise ratios (S/N) were measured on each tube of the phantom and on rat brain from each image of the dynamic imaging. S/N was plotted versus contrast dilution (phantom) and versus time (rats). In the FLASH sequence, a well-shaped curve (S/N decrease, S/N peak decrease, S/N increase) of the first pass of the contrast agent was demonstrated for Gd-DOTA and for AMI 227 (7 mumol Fe/kg body weight). In the EPI sequence, a well-shaped curve was demonstrated for Gd-DOTA, and a plateau effect was noted for both concentrations of AMI 227. With the FLASH technique, dynamic susceptibility contrast imaging of rat brain can be performed with very low concentrations of AMI 227 compared with the Gd-DOTA concentration (0.2 mmol Gd/kg body weight) used in clinical practice. This could be of interest in perfusion imaging, because it may allow for first-pass susceptibility imaging after administration of a small volume in a narrow bolus.

Animals↗
PubMed1999

Motion-responsive regions of the human brain.

Functional magnetic resonance imaging was used to map motion responsive regions of the human brain by contrasting passive viewing of moving and stationary randomly textured patterns. Regions were retained as motion responsive if they reached significance either in the group analysis or in the majority of hemispheres in single-subject analysis. They include well-known regions, such as V1, hMT/V5+, and hV3A, but also several occipito-temporal, occipito-parietal, parietal, and frontal regions. The time course of the activation was similar in most of these regions. Motion responses were nearly identical for binocular and monocular presentations. Flicker-induced-activation introduced a dichotomy amongst these motion responsive regions. Early occipital and occipito-temporal regions responded well to flicker, while flicker responses gradually vanished as one moved to occipito-parietal and then parietal regions. Finally, over a more than four-fold range, stimulus diameter had little effect on the motion activations, except in V1.

Adult↗
PubMed1999

Rostral vermian cortical dysplasia: MRI.

The MRI findings in rostral vermian dysplasia are described for the first time. Defective foliation and abnormal fissuration of the rostral vermis can clearly be depicted on coronal images. The abnormalities are limited to the anterior lobe of the vermis and its hemisphere extension. A hypothesis is put forward to explain the abnormalities. It is suggested that the vermian changes result from an intrauterine insult at the end of the first trimester. There appears to be a variable degree of expression and associated cerebellar and cerebral cortical abnormalities can be seen. The clinical significance of these findings remains incompletely understood but may be related to the severity of the abnormalities. It is also suggested that a mild degree of vermian rostral dysplasia may represent an incidental imaging finding.

Adolescent↗
PubMed1999

Time-resolved MR angiography of the upper abdomen: initial clinical experience.

In this study, thirty-eight patients with a variety of upper abdominal diseases were examined with three-dimensional time-resolved MR angiography (7 sec/data set). Visualisation of arterial and venous anatomy was excellent in the majority of patients. Moreover, subtraction images could be calculated and organ perfusion could be assessed. It is concluded that this technique opens new perspectives for a comprehensive evaluation of vascular and parenchymal disease.

Abdomen↗
PubMed1999

Screening applications for MRI in the detection of upper abdominal disease: comparative study of non-contrast-enhanced single-shot MRI and contrast-enhanced helical CT.

PURPOSE: To compare the value of 'push-button' single-shot non-contrast-enhanced MRI and contrast-enhanced helical CT for detection of upper abdominal disease. METHODS: In 120 patients, images obtained with non contrast-enhanced single-shot MRI (T2: double echo HASTE, and T1: turbo FLASH) and contrast-enhanced helical CT were compared. Lesions or abnormalities were divided in 8 anatomical categories (1: liver; 2: pancreatobiliary; 3: kidney/adrenal gland; 4: retroperitoneum; 5: vascular; 6: spleen; 7: gastrointestinal tract and peritoneum; 8: base of thorax) and classified as follows: 2: seen at MRI only; 1: better seen at MRI; 0: no difference; -1: better seen at CT; -2: seen at CT only. Also recorded were the 'door-to-door' examination times. RESULTS: Of a total of 629 abnormalities, 594 were detected at MRI (94 %) and 536 at CT (85 %). CT offered better results in two categories only: retroperitoneum (mean score: -0.68) and vascular (mean score -0.87). Mean examination times were 19 min for CT and 14.8 min for MRI. CONCLUSION: Unenhanced single-shot MRI is a valuable first step of a comprehensive upper abdominal MR exam and may even be the final step in many patients.

Abdomen↗
PubMed1999

MRI of non-ischemic vascular disease: aneurysms and vascular malformations.

Due to flow-void phenomena, MRI is of great value in the demonstration of cerebral aneurysms and vascular malformations as well as of related parenchymal changes and hemorrhagic complications. Magnetic resonance angiography can produce vascular images which are of importance in the diagnosis and follow-up of the lesions.

Brain↗
PubMed1999

Transcatheter embolization of hepatic arteriovenous fistulas in Rendu-Osler-Weber disease: a case report and review of the literature.

A patient with hereditary hemorrhagic telangiectasia and diffuse intrahepatic arteriovenous fistulas developed secondary high-output ventricular failure and pulmonary hypertension. A serial staged hepatic arterial coil embolization was performed with long-term resultant haemodynamic and clinical improvement. The methods of this procedure and related complications are discussed.

Angiography↗
PubMed1999

Assessment of iron oxide particles (AMI 227) and a gadolinium complex (Gd-DOTA) in dynamic susceptibility contrast MR imagings (FLASH and EPI) in a tumor model implanted in rats.

The objective of our study was to assess the feasibility of dynamic susceptibility contrast MR technique after bolus injection of SPIO and Gd-DOTA in a tumor model implanted in rats. Tumors were subcutaneously implanted in 24 rats. A FLASH sequence and EPI were evaluated. Different doses of AMI 227 and Gd-DOTA were assessed. Mean signal intensity vs. time curves were plotted. Well-shaped curves of the first pass of the contrast agent were only obtained with Gd-DOTA. According to these results it appears difficult to assess tumor blood volume with USPIO dynamic susceptibility contrast imaging.

Animals↗
PubMed1999

Squamous cell carcinoma of the sinonasal cavities.

Squamous cell carcinoma of the sinonasal cavity is an uncommon neoplasm. The symptoms of this tumor are aspecific, and the diagnosis is often made in an advanced stage of disease. Imaging is necessary for evaluating paranasal extension and possible intracranial spread, orbital involvement, infratemporal extension, spread to the nasopharynx, oropharynx, or oral cavity, and spread along neurovascular bundles or perineural spread. Sinonasal cancers are studied with CT or MRI, and in many cases both modalities are used, as they often offer complementary information. The CT and MRI appearance of this kind of tumor is reviewed in this article.

Carcinoma, Squamous Cell↗
PubMed1999

Human cortical regions involved in extracting depth from motion.

We used functional magnetic resonance imaging (fMRI) to investigate brain regions involved in extracting three-dimensional structure from motion. A factorial design included two-dimensional and three-dimensional structures undergoing rigid and nonrigid motions. As predicted from monkey data, the human homolog of MT/V5 was significantly more active when subjects viewed three-dimensional (as opposed to two-dimensional) displays, irrespective of their rigidity. Human MT/V5+ (hMT/V5+) is part of a network with right hemisphere dominance involved in extracting depth from motion, including a lateral occipital region, five sites along the intraparietal sulcus (IPS), and two ventral occipital regions. Control experiments confirmed that this pattern of activation is most strongly correlated with perceived three-dimensional structure, in as much as it arises from motion and cannot be attributed to numerous two-dimensional image properties or to saliency.

Adolescent↗
PubMed1999

Voxel-based mapping of irreversible ischaemic damage with PET in acute stroke.

Objective mapping of irreversible tissue damage in the acute stage of ischaemic stroke would be useful for prognosis and in assessing the efficacy of therapeutic manoeuvres in impeding extension of infarction. From our database of 30 patients studied with 15O-PET within 5-18 h after onset of first-ever middle cerebral artery territory stroke, we extracted a subgroup of 19 survivors (age 74.6 +/- 8.5 years) in whom late CT coregistered with PET was available to determine final infarct topography. By means of a voxel-based analysis of the PET data, we determined putative thresholds for irreversible tissue damage as the lower limit of the 95% confidence interval calculated from all voxels within the ultimately non-infarcted brain parenchyma ipsilateral to the insult. The following values were found: 8.43 ml/100 ml/min, 0.87 ml/100 ml/min, 1.64 ml/100 ml, 0.27 and 2.21/min, for cerebral blood flow (CBF), oxygen consumption (CMRO2), blood volume (CBV), oxygen extraction fraction and the ratio CBF : CBV, respectively. Voxels below these thresholds occurred significantly more frequently in the final infarct region than in the non-infarcted parenchyma for CBF and CMRO2 (P = 0.016 and P = 0.0045, respectively, Wilcoxon test), but not for the other PET variables. Furthermore, with both CBF and CMRO2, the percentage of irreversible tissue damage voxels in the affected hemisphere relative to the opposite hemisphere was significantly positively correlated to both the volume of final infarct and the neurological outcome at 2 months (all P < 0.005, Spearman ranked test). These findings validate our voxel-based CBF and CMRO2 thresholds for probabilistic mapping of irreversible tissue damage within the 5-18 h interval after stroke onset; however, whether they would be applicable to earlier intervals remains to be determined. Transfer of our procedure for determination of irreversible tissue damage thresholds to other imaging modalities such as single proton emission computed tomography and diffusion-weighted MRI should be straightforward.

Aged↗