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Biomedical subjects

M Benoit

Publications and source records attributed to M Benoit.

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

Differences in zero-force and force-driven kinetics of ligand dissociation from beta-galactoside-specific proteins (plant and animal lectins, immunoglobulin G) monitored by plasmon resonance and dynamic single molecule force microscopy.

Protein-carbohydrate interactions are involved in diverse regulatory processes. To help understand the mechanics and kinetics of dissociation of receptor-ligand complexes, we have analyzed the separation of lactose and the N-glycan chains of asialofetuin (ASF) from three lectins and an immunoglobulin G fraction by surface plasmon resonance at zero force and by atomic force microscopy with variations of the external force. While the (AB)2 agglutinins from Ricinus communis (RCA) and Viscum album (VAA) show structural homology, the homodimeric galectin-1 from bovine heart (BHL) has no similarity to the two plant lectins except for sharing this monosaccharide specificity. The beta-galactoside-binding immunoglobulin G (IgG) fraction from human serum provides a further model system with distinct binding-site architecture. The k(off) constants for the two plant agglutinins were independent of the nature of the ligand at 1.1-1.3 x 10(-3) s(-1), whereas the geometry of ligand and binding site presentation affected this parameter for BHL (0.5 x 10(-3) s(-1) for lactose and 1 x 10(-3) s(-1) for ASF) and IgG (1.3 x 10(-3) s(-1) for lactose and 0.55 x 10(-3) s(-1) for ASF). When assessing comparatively the rupture forces at a loading rate of 3 nN/s with lactose as ligand, 34 +/- 6 pN (BHL), 36 +/- 4 pN (IgG), 47 +/- 7 pN (VAA), and 58 +/- 9 pN (RCA) were measured. For the same loading rate the rupture forces for the receptor-ASF interactions were found to be 37 +/- 3 pN (BHL), 43 +/- 5 pN (VAA), 45 +/- 6 pN (IgG), and 65 +/- 9 pN (RCA). The variation of the pulling velocity revealed in all cases a linear dependence between the rupture force and the natural logarithm of the loading rate. Performing probability density and Monte Carlo calculations, the potential barrier widths, which determine the inverse dynamic dependence with the rate of force elevation, increased from 4 A (RCA) and 7 A (VAA and IgG) to 10 A (BHL) for the receptor-lactose interactions. Presenting ASF as ligand potential widths of 4 A for RCA and IgG and 6 A for VAA and BHL were obtained. Since the dissociation kinetics at zero force apparently cannot predict the behavior in force-driven experiments, these results reveal new insights into biological functions. The dissociation kinetics under force helps to explain the difference in the toxic potency of VAA and RCA and points to a function of the galectin in cis-crosslinking and in transient trans-bridging.

Animals↗
PubMed2000

Vaccine properties of antigens entrapped in microparticles produced by spray-drying technique and using various polyester polymers.

The present study investigated the suitability of various microparticles produced by spray-drying technique to entrap and preserve the physiochemical and biological properties of an antigen. These microparticles were constituted either by poly(lactide) polymers characterized by various molecular weight or poly(lactide-co-glycolide) polymers. The recombinant 28 kDa glutathione S-transferase of Schistosoma mansoni (rSm28GST) characterized by major epitopes involved in the active site of this enzyme was selected as model antigen. The microparticles were characterized by a mean size </=5 microm and an antigen loading of approximately 2% (w/w). The analysis by SDS-PAGE electrophoresis of the rSm28GST released from microparticles confirmed the conservation of its physicochemical characteristics. The conservation of the native structure of the entrapped antigen was confirmed by detecting its enzymatic activity after release from microparticles. A single intraperitoneal immunization of mice with rSm28GST entrapped in microparticles resulted in a specific antibody response, which remained high for at least 7 months. The analysis of the isotype profile indicated that immunized mice primarily produced anti-rSm28GST immunoglobulin (Ig) G1 with the coexistence of lower IgG2a and IgG2b levels. Finally, the recognition of the major epitopic regions and the neutralization of the enzymatic activity of the rSm28GST by the antisera confirmed the specificity of the response against the native structure of the antigen. These results confirmed the integrity of the entrapped antigen. Moreover, our results supported the hypothesis that the duration of antigen release is the limiting factor for the duration of antibody production. Indeed, the use of polymers characterized by different molecular weights allowed us to modify the duration of the immune response. Together, these results demonstrated that microencapsulation of an antigen by spray-drying preserved its crucial characteristics required to generate an effective humoral immune response after a single-dose administration.

Animals↗
PubMed2000

Discrete interactions in cell adhesion measured by single-molecule force spectroscopy.

Cell-cell adhesion mediated by specific cell-surface molecules is essential for multicellular development. Here we quantify de-adhesion forces at the resolution of individual cell-adhesion molecules, by controlling the interactions between single cells and combining single-molecule force spectroscopy with genetic manipulation. Our measurements are focused on a glycoprotein, contact site A (csA), as a prototype of cell-adhesion proteins. csA is expressed in aggregating cells of Dictyostelium discoideum, which are engaged in development of a multicellular organism. Adhesion between two adjacent cell surfaces involves discrete interactions characterized by an unbinding force of 23 +/- 8 pN, measured at a rupture rate of 2.5 +/- 0.5 microm s-1.

Animals↗
PubMed2000

Performance of the ImmunoCard STAT! E. coli O157:H7 test for detection of Escherichia coli O157:H7 in stools.

ImmunoCard STAT! E. coli O157:H7 (Meridian Diagnostics, Inc., Cincinnati, Ohio) is a novel rapid (10-min) test for the presence of Escherichia coli O157:H7 in stools. The test may be performed either directly on stool specimens or on an overnight broth culture of stool. In a multicenter prospective study, 14 of 14 specimens positive by culture for E. coli O157:H7 were positive by the ImmunoCard STAT! O157:H7 test, and there were no false positives from 263 culture-negative specimens. In a retrospective study, the test was positive in 339 (81%) of 417 stored culture-positive specimens and the specificity was 95% (98 of 103 specimens). No false positives were associated with alternate stool pathogens. The ImmunoCard STAT! O157:H7 test has high sensitivity and specificity.

Enzyme-Linked Immunosorbent Assay↗
PubMed2000

Affinity imaging of red blood cells using an atomic force microscope.

We used an atomic force microscope (AFM) to produce an image of a mixed layer of group A and O red blood cells with a contrast based only on the measured strength of a specific receptor-ligand pair. The image was obtained by measuring and plotting for each image pixel the adhesion force between the mixed RBC layer and the AFM tip functionalized with Helix pomatia lectin. The high specificity of that lectin for the N -acetylgalactosamine-terminated glycolipids present in the membrane of group A RBCs enabled us to discriminate between the two cell populations and to produce an image based on affinity contrast. The rupture force of the adhesion events leading to the image formation were quantitatively analyzed and compared to rupture forces measured with the same AFM tip on N-acetylgalactosamine tethered to agarose beads. The mean rupture force was found to be 65 pN when measured on the group A RBCs and 35 pN on the agarose beads. These results show that the adhesion, mediated by only a few receptor-ligand pairs, produces sufficient contrast for the affinity image formation.

ABO Blood-Group System↗
PubMed2000

Assessing African American adolescents' risk for suicide attempts: attachment theory.

The threat of separation from a parent theoretically increases the risk of adolescent suicide attempts. The present study evaluated this and other hypothesized risk factors in a sample of adolescent suicide attempters and nonsuicidal controls, using the Psychiatric Consultation Checklist (Lyon, 1987). Stepwise logistic regression was used to predict group membership. It was found that threat of separation from a parental figure, insomnia, neglect, substance abuse, suicidal ideation, and failing grades were the strongest predictors of suicide attempt. Ten predictor variables correctly identified 97% of suicide attempters and 86% of nonattempters. Unexpected findings included high levels of truancy, threatening others, and separation from a parent before the age of 12 among nonattempters.

Adolescent↗
PubMed1998

Interactions between trophoblast and uterine epithelium: monitoring of adhesive forces.

At embryo implantation, it is postulated that the initial contact between blastocyst and maternal tissues is by adhesion of the trophoblast to the uterine epithelium. This cell-to-cell interaction is thought to be critical for implantation, although the actual adhesive forces have never been determined. In the present study, the atomic force microscope (AFM) was used to study the adhesion between human uterine epithelial cell lines (HEC-1-A; RL95-2) and human trophoblast-type cells (JAR). Specific interaction forces of these epithelia via their apical cell poles were determined on the basis of approach-and-separation cycles. For this purpose, the AFM tip was functionalized with JAR cells, then brought to the surface of uterine epithelial monolayers and was kept in contact for different periods of time (ms, 1, 10, 20, 40 min). The approach force curves displayed repulsive interactions for both HEC-1-A and RL95-2 cells. However, RL95-2 cells (with a smooth surface structure and a thin glycocalyx) showed lower values of the repulsive regime than HEC-1-A cells (with a rough surface structure and a thick glycocalyx). After having overcome repulsive interactions, the initial contact was followed by adhesive interactions. For contact times of 20 and 40 min, RL95-2 cells, but not HEC-1-A cells, showed specific JAR binding, i.e. the separation force curves displayed repeated rupture events in the range of 1-3 nN with a distance between 7-15 microm and, thereafter, a final rupture event at a distance of up to 45 microm. These features point to the formation of strong cell-to-cell bonds. Collectively, these studies provide the first definition of interaction forces between the trophoblast and the uterine epithelium, and are consistent with the hypothesis that an RL95-2-like architecture of uterine epithelial cells, i.e. an non-polarized phenotype, is essential for apical adhesiveness for the human trophoblast.

Cell Adhesion↗
PubMed1996

Posterolateral fusion for radicular pain in isthmic spondylolisthesis.

Reported is the outcome for 25 patients in whom spondylolisthesis with radicular pain was treated by posterolateral fusion alone (Group A). These outcomes are compared with those obtained in 23 other patients with the same symptomatology and spondylolisthesis treated by root release and posterolateral fusion (Group B). Most patients had Grade I or II isthmic spondylolisthesis. Results were assessed functionally and radiographically with an average followup of 32 months. Posterolateral fusion in situ provided excellent or good results in 88% of patients according to the modified classification of Stauffer and Coventry. In Group A, radicular pain at exertion disappeared in 92% of patients, and radicular pain at rest disappeared in 88%. In Group B, radicular pain at exertion disappeared in 65% of patients, and radicular pain at rest disappeared in 70%. There was no significant statistical difference between the 2 groups. Resection of the loose lamina and root decompression do not seem to be mandatory. The overall fusion rate was 81%. Instrumentation in case of instability and the use of allografts are advised.

Adolescent↗
PubMed1995

A single photon emission computed tomography study of cerebral regional perfusion changes induced by a learning task in subjects with mild memory impairment.

Fifteen nondemented subjects with memory complaints underwent serial single photon emission computed tomography (SPECT) studies with technetium-99m-d, l-hexamethyl-propylene amine oxime (HMPAO) as tracer. Scans were carried out under a baseline conditions and during the learning phase of the Memory Efficiency Profile (MEP), a combined visual perception and memory task developed by Rey. Results indicate a positive correlation between activation, as indexed by HMPAO uptake, and neuropsychological assessment. Right temporal activation was correlated with MEP immediate recall. The right cerebellum was correlated with both MEP immediate and delayed recall. This study suggests that SPECT can show cortical activation during cognitive performance in subjects with mild memory impairment.

Aged↗
PubMed1993

Impact of violence on children and adolescents: report from a community-based child psychiatry clinic.

The Children's National Medical Center is located in the inner-city area of Washington, DC. As is nationally now well publicized, the drug-related violence in Washington has earned the area the dubious title of "murder capital of the world." Our outpatient child and adolescent psychiatry clinic at Children's Hospital provides walk-in services during daytime hours, Monday through Friday. Access to services is available at other times through the emergency room.

Adolescent↗
PubMed1991

The effect of food and antacids on lansoprazole absorption and disposition.

Bioavailability of lansoprazole, a new gastric proton pump inhibitor, was investigated in 12 healthy subjects. Each subject received in random order, lansoprazole (30 mg) alone or associated with standard meal or with antacids (aluminium and magnesium hydroxides) or one hour later than antacids. Lansoprazole and metabolite (sulfone (AG 1813), sulfide (AG 1777) and hydroxylated (AG 1908) metabolites) plasma concentrations were determined using a specific high pressure liquid chromatographic assay procedure, with a limit of detection of 2 ng/ml. The time to peak was significantly later with food (p less than 0.001) and its magnitude was significantly decreased (600 +/- 330 ng/ml vs 1151 +/- 344 ng/ml, p less than 0.001). The bioavailability of lansoprazole was significantly decreased by food, about 27%, (p less than 0.05) and slightly decreased by concomitant administration of antacids (NS), the effect was more pronounced in male subjects (p less than 0.05). Lansoprazole is presented as an enteric-coated granules, the concomitant administration of antacids, increasing the gastric pH, increased the absorption rate of lansoprazole. When antacids were administered one hour before lansoprazole, no effect was observed on lansoprazole bioavailability. This study showed that lansoprazole must be administered in fasting state and not simultaneously with antacids.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed1988

[Isolated tracheoesophageal fistulas. Apropos of 3 cases revealed in the newborn].

We report here on 3 cases of isolated tracheoesophageal fistula. This corresponds to approx. 2.7% of esophageal congenital abnormalities treated in our service. In all 3 cases, diagnosis could be evoked in the neonate in front of respiratory symptoms appearing with feeding. Esophageal contrast radiological studies confirmed in all cases the fistula and its level C7-T1. No other invasive investigation was necessary to the diagnosis. We did not observe associated malformations. Surgical approach was made by a right cervical incision to obtain in good conditions divisions of the fistula and suture of the esophageal and tracheal ends; in one case, a muscular flap was interposed. Followup and longterm results (up to 17 years) were excellent, with one case of regressive recurrent laryngeal nerve paresthesia.

Age Factors↗
PubMed1986

[In vitro bactericidal activity of polyvinylpyrrolidone iodine on Neisseria gonorrhoeae].

A standardized methodology was used to study the in vitro behavior of different strains of Neisseria gonorrhoeae when treated with povidone-iodine. The bactericidal activity of the antiseptic was appraised using the dilution-neutralization technique on four gonococcal strains, two of which produced a beta-lactamase. Bactericidal activity in aqueous medium was observed down to a dilution of 1/128. This result specifies the conditions under which this antiseptic is active against Neisseria gonorrhoeae.

Microbial Sensitivity Tests↗