Biomedical subjects

B Vincent

Publications and source records attributed to B Vincent.

At least 19 recordsLinked to original sources

PubMed2003

Adsorption isotherm and atomic force microscopy studies of the interactions between polymers and surfactants on steel surfaces in hydrocarbon media.

The adsorption isotherms for certain polymer and surfactant molecules (and in some cases their mixtures) on stainless steel beads from isooctane have been obtained, together with corresponding adsorbed layer thicknesses, using an atomic force microscope. The polymer is a terminally functionalised (ethylene diamine), low molecular weight polyisobutylene (PIB) derivative and the surfactants are basically alkyl or alkyl phenol alkoxylate molecules, which in one case has been derivatised with an amino functionality. The results indicate the presence of multilayers at the stainless steel-isooctane interface. Theoretical analysis of the surfactant adsorption isotherms suggests molecular aggregation at the interface with an aggregation number between 2 and 6, at the highest coverages. The adsorption of the polymer is reduced in the presence of the surfactant molecules. The polymer leaches metal ions from the steel surface at higher concentrations.

Journal Article↗

PubMed2002

Controlled release of 4-nitroanisole from poly(lactic acid) nanoparticles.

The controlled release of 4-nitroanisole from polylactide nanoparticles with different morphologies is reported. Two theoretical equations have been used in an attempt to fit the experimental results. Good agreement between theory and experiment was found for short release time. The estimated values of the diffusion coefficient of 4-nitroanisole in these nanoparticles, at short times (up to 50% release), were all approximately 10(-19) m(2)s(-1). At long time some differences in release behaviour were observed for different morphologies.

Anisoles↗

PubMed2001

Structure formation from mesoscopic soft particles.

In this work, the aggregation of mesoscopic gel particles (soft colloids) has been experimentally investigated. The interaction between particles was controlled through the addition of salt, above the critical coagulation concentration, resulting in aggregation with finite bond energies. Attention has been paid to the structure of the clusters formed in the process as well as to the aggregation kinetics. The results indicate that the clusters are fractal and the kinetics of aggregation can be described through the dynamic scaling solution of the Smoluchowski equation. As the energy minimum increases in depth the resultant clusters pass from a very compact structure to typical diffusion-limited cluster aggregation (DLCA) fractal dimension values. In addition, the kinetics of growth change from those observed in reaction controlled aggregation to DLCA. These results can be explained within the framework of a reversible growth model, arising from the fact that aggregation takes place in an energy minimum of restricted depth. Moreover, they show that structure and kinetics decouple for such a soft sphere system, in contrast to what is encountered for DLCA and reaction-limited processes. Finally, an unexpected return to a reaction controlled aggregation kinetics was observed for sufficiently deep energy minima, which could be due to the polymerlike particularities of the soft particles considered in this work.

Journal Article↗

PubMed2001

Large-scale analysis of the Alu Ya5 and Yb8 subfamilies and their contribution to human genomic diversity.

We have utilized computational biology to screen GenBank for the presence of recently integrated Ya5 and Yb8 Alu family members. Our analysis identified 2640 Ya5 Alu family members and 1852 Yb8 Alu family members from the draft sequence of the human genome. We selected a set of 475 of these elements for detailed analyses. Analysis of the DNA sequences from the individual Alu elements revealed a low level of random mutations within both subfamilies consistent with the recent origin of these elements within the human genome. Polymerase chain reaction assays were used to determine the phylogenetic distribution and human genomic variation associated with each Alu repeat. Over 99 % of the Ya5 and Yb8 Alu family members were restricted to the human genome and absent from orthologous positions within the genomes of several non-human primates, confirming the recent origin of these Alu subfamilies in the human genome. Approximately 1 % of the analyzed Ya5 and Yb8 Alu family members had integrated into previously undefined repeated regions of the human genome. Analysis of mosaic Yb8 elements suggests gene conversion played an important role in generating sequence diversity among these elements. Of the 475 evaluated elements, a total of 106 of the Ya5 and Yb8 Alu family members were polymorphic for insertion presence/absence within the genomes of a diverse array of human populations. The newly identified Alu insertion polymorphisms will be useful tools for the study of human genomic diversity.

Alu Elements↗

PubMed2001

The disintegrins ADAM10 and TACE contribute to the constitutive and phorbol ester-regulated normal cleavage of the cellular prion protein.

We showed previously that PrPc undergoes constitutive and phorbol ester-regulated cleavage inside the 106-126 toxic domain of the protein, leading to the production of a fragment referred to as N1. Here we show by a pharmacological approach that o-phenanthroline, a general zinc-metalloprotease inhibitors, as well as BB3103 and TAPI, the inhibitors of metalloenzymes ADAM10 (A disintegrin and metalloprotease); and TACE, tumor necrosis factor alpha-converting enzyme; ADAM17), respectively, drastically reduce N1 formation. We set up stable human embryonic kidney 293 transfectants overexpressing human ADAM10 and TACE, and we demonstrate that ADAM10 contributes to constitutive N1 production whereas TACE mainly participates in regulated N1 formation. Furthermore, constitutive N1 secretion is drastically reduced in fibroblasts deficient for ADAM10 whereas phorbol 12,13-dibutyrate-regulated N1 production is fully abolished in TACE-deficient cells. Altogether, our data demonstrate for the first time that disintegrins could participate in the catabolism of glycosyl phosphoinositide-anchored proteins such as PrPc. Second, our study identifies ADAM10 and ADAM17 as the protease candidates responsible for normal cleavage of PrPc. Therefore, these disintegrins could be seen as putative cellular targets of a therapeutic strategy aimed at increasing normal PrPc breakdown and thereby depleting cells of the putative 106-126 "toxic" domain of PrPc.

ADAM Proteins↗

PubMed2001

Stability in Colloidal Mixtures Containing Particles with a Large Disparity in Size.

An experimental approach, based on turbidity measurements, is proposed for studies of the stability in colloidal mixtures containing particles with large disparity in size. The main advantage of this approach is that it permits investigations even under conditions of comparable particle number concentrations of the two colloidal populations. Binary mixtures containing a poly(vinyl acetate) (PVAc) latex and a Ludox AS-40 silica sol were investigated. The silica particles were much smaller than the latex ones. The experimental stability factors were compared with the theoretical values computed on the basis of the Kihira-Ryde-Matijevic model (J. Chem. Soc., Faraday Trans. 88(16), 2379 (1992)) for interaction between spherical particles with unevenly distributed surface charges. All the experimental results support the idea that, even when both sols are negatively charged, the small silica particles are adsorbed onto the latex surface. Under these conditions, the heteroaggregates, which are composed of PVAc cores surrounded with silica particles, can be modeled as PVAc particles having "modified" surface characteristics (i.e., average Stern potential and varying extents of the surface charge segregation). Copyright 2001 Academic Press.

Journal Article↗

PubMed2001

Endogenous beta-amyloid production in presenilin-deficient embryonic mouse fibroblasts.

Genetic and biochemical evidence have led to the suggestion that presenilins could be the long-searched-for gamma-secretase, the proteolytic activity that generates the carboxy terminus of amyloid beta-peptides. This activity is also thought to be responsible for the release of the Notch intracellular domain (NICD) from Notch. Here, we report the production of endogenous secreted and intracellular 40- and 42-amino-acid Abeta peptides in mouse fibroblasts deficient in presenilin 1, presenilin 2 or both. We show that the endogenous production of Abeta40 and Abeta42 was not altered by presenilin deficiency. By contrast, inactivating presenilin genes fully abolished NICD production. These data indicate that Abeta and NICD production are distinct catabolic events. Also, even though NICD formation is indeed presenilin dependent, endogenous secreted and intracellular beta-amyloid peptides are still generated in absence of presenilins, indicating that there is a gamma-secretase activity distinct from presenilins, at least in murine fibroblasts.

Amyloid beta-Peptides↗

PubMed2001

Astrocytes down-regulate neuronal beta-amyloid precursor protein expression and modify its processing in an apolipoprotein E isoform-specific manner.

Alzheimer's disease is the most frequent neurodegenerative disorder in the aged population and is characterized by the deposition of the 40/42-residue amyloid beta protein (A beta), a proteolytic fragment of the beta-amyloid precursor protein (APP). A common apolipoprotein E (apoE) polymorphism is associated with an increased risk of developing the disease. In order to assess the putative relationship between apoE and amyloidogenesis in the CNS, we prepared primary cortical neurons overexpressing humanized APP695 bearing the Swedish mutation (hAPP(695sw)) and we analysed APP expression and processing after: (i) coculture with primary astrocytes from wild-type, apoE-deficient (E0) mice, or mice overexpressing human apoE2, E3, or E4; (ii) treatment with conditioned media from apoE0, E2, E3 or E4 astrocytes; and (iii) treatment with human recombinant ApoE or human apoE purified from conditioned media of stably transfected RAW264 cells (E2, E3 and E4). Interestingly, a strong decrease in APP expression was observed only when neurons were cocultured with astrocytes (and independently of the apoE genotype considered), suggesting that cell-cell contact is required. Moreover, apoE4-secreting astrocytes, but not recombinant or purified apoE4, significantly increased A beta production and decrease sAPP alpha secretion only when cultured in direct contact with neurons, whereas apoE2 astrocytes had a protective effect. We conclude that astrocytes: (i) strongly regulate neuronal APP expression in primary neurons, and (ii) promote the amyloidogenic pathway in an apoE4-dependent manner. Thus, apoE and astrocytic factor(s) may modulate the pathogenesis of Alzheimer's disease.

Alzheimer Disease↗

PubMed2001

AIDS-related alveolar hemorrhage: a prospective study of 273 BAL procedures.

STUDY OBJECTIVES: To evaluate the frequency and diagnostic significance of alveolar hemorrhage (AH) in HIV-infected patients. DESIGN: A 3-year prospective cohort study. SETTING: A university hospital in Paris, France. PATIENTS: Two hundred forty-three HIV-infected patients undergoing 273 BAL procedures during the study period. METHODS: AH was assessed by using the Golde score. Data on the patients treated and observed in our institution were collected, as well as on their survival rate 12 months after undergoing BAL. Risk factors for AH were sought by comparing patients with AH (cases) and those without AH (control subjects). RESULTS: AH frequently occurred but usually was subclinical and cytologically mild. AH did not alter the 12-month survival rate. AH always was associated with at least one specific AIDS-related pulmonary disorder, and the following four independent risk factors were identified in a stepwise forward logistic regression model: pulmonary Kaposi's sarcoma (KS; odds ratio [OR], 5.3; 95% confidence interval [CI], 1.8 to 16.7; p = 0.003), cytomegalovirus (CMV) pneumonia (OR, 9.8; 95% CI, 1 to 100; p = 0.05), hydrostatic pulmonary edema (OR, 16.4; 95% CI, 1.8 to 142; p = 0.01), and platelet count < 60,000 cells/microL (OR, 5.6; 95% CI, 1.5 to 20; p = 0.009). CONCLUSIONS: AH is frequently diagnosed during BAL in HIV-infected patients. Its presence may point to an underlying cause, such as pulmonary KS, CMV pneumonia, or hydrostatic pulmonary edema, or to triggering factors such as thrombocytopenia.

AIDS-Related Opportunistic Infections↗

PubMed2001

[Lemierre's syndrome: a case report].

We report a case of Lemierre's syndrome with a pleuropulmonary complication. Lemierre's syndrome is a rare etiology of lung abscess. The diagnosis is clinical and microbiological (anaerobic organisms). This syndrome associates an acute oropharyngeal infection with septic thrombophlebitis of the internal jugular vein (sometimes many days before the lung lesion) and pulmonary abscess formation. Clinicians should be aware of this syndrome that is fatal in 10% of patients, usually after delayed or missed diagnosis. The frequency of Lemierre's syndrome would be higher if antibiotics were given only to pharyngitis patients positive for streptococcus.

Adult↗

PubMed2000

Charge heteroaggregation between hard and soft particles.

In this paper, the heteroaggregation of opposite sign hard and soft colloidal particles has been studied by static and dynamic light scattering. The structure of the aggregates, as well as the aggregation kinetics, have been investigated. At low electrolyte concentration, where both long-range electrostatic repulsive and attractive forces are present, the aggregates were found to be more open than expected for diffusion-limited cluster aggregation (DLCA). However, the aggregate size time evolution is characteristic of diffusion-controlled processes. At high electrolyte concentration, where DLCA would be expected, very compacted clusters were found, as well as very rapid aggregation, leading to high polydispersity. These latter findings are interpreted in terms of the differences in the homoaggregation speeds for the hard and soft particles.

Journal Article↗

PubMed2000

Phorbol ester-regulated cleavage of normal prion protein in HEK293 human cells and murine neurons.

Cellular prion protein (PrP(c)) undergoes a proteolytic attack at the 110/111 downward arrow112 peptide bond, whereas the PrP isoform (PrP(res)) that accumulates in the brain tissue in Creutzfeldt-Jakob disease reveals an alternate cleavage site at about residue 90. Interestingly, the normal processing of PrP occurs inside the 106-126 amino acid region thought to be responsible for the neurotoxicity of the pathogenic prions, whereas PrP(res) cleavage preserves this potentially toxic domain. Therefore, any molecular mechanisms leading to enhanced cleavage at the 110/111 downward arrow112 peptide bond could be of potential interest. We set up TSM1 neurons and HEK293 stable transfectants overexpressing the wild-type or 3F4-tagged murine PrP(c), respectively. Both mock-transfected and PrP(c)-expressing cell lines produced an 11-12-kDa PrP fragment (referred to as N1), the immunological characterization of which strongly suggests that it corresponds to the N-terminal PrP(c) fragment derived from normal processing. We have established that the recovery of secreted N1 is increased by the protein kinase C agonists PDBu and PMA in a time- and dose-dependent manner in both cell lines. In contrast, secretion of N1 remains unaffected by the inactive PDBu analog alphaPDD and by the protein kinase A effectors dibutyryl cAMP and forskolin. Overall, our data indicate that the normal processing of PrP(c) is up-regulated by protein kinase C but not protein kinase A in human cells and murine neurons.

Amino Acid Sequence↗

PubMed2000

Effect of estradiol on neuronal Swedish-mutated beta-amyloid precursor protein metabolism: reversal by astrocytic cells.

Alzheimer's disease is the most frequent neurodegenerative disorder in the aged population and is characterized by the deposition of the 40/42-residue amyloid beta protein (Abeta), a proteolytic fragment of the beta-amyloid precursor protein (APP). Recently, it has been shown that physiological doses of estradiol reduce the generation of endogenous Abeta in primary cortical neurons. Here we investigate the influence of estrogen in amyloidogenesis and sAPPalpha secretion in the CNS. By means of primary cortical neurons overexpressing humanized APP(695) bearing the Swedish mutation (hAPP(695sw)), we analyzed APP maturation in the absence or in the presence of estrogen. We show that estrogen at a 2 microM concentration increases the release of the neuroprotective sAPPalpha fragment but does not reduce the release of Abeta in primary neurons overexpressing the Swedish-mutated form of APP. Furthermore, neurons cocultured with astrocytic cells or grown with astrocytes conditioned media do not exhibit the estrogen-induced increase in sAPPalpha secretion. Altogether, our data indicate that astrocytes interfere with estrogen in the regulation of sAPPalpha secretion, probably via secreted factor(s).

Alzheimer Disease↗

PubMed2000

Preparation and Swelling Properties of Poly(NIPAM) "Minigel" Particles Prepared by Inverse Suspension Polymerization.

The characterization of temperature- and pH-sensitive poly-N-isopropylacrylamide (poly-NIPAM) microgel particles, produced by surfactant-free emulsion polymerization, has been extensively reported. In the work described here poly(NIPAM) gel particles, cross-linked with N-N'-methylenebisacrylamide (BA), have been produced using inverse suspension polymerization. These particles have been termed "minigels" here since they are somewhat larger than conventional microgels. Results suggest that minigel particles are formed as a dilute suspension, within the aqueous dispersed (droplet) phase. The hydrodynamic diameter of the minigel particles produced in this work is </=2.5 µm, at 25 degrees C. The effects of temperature and pH changes, variation in cross-linker concentration, and incorporation of a charged comonomer (methacrylic acid, MAA) have been investigated. Both poly(NIPAM-BA) and poly(NIPAM-BA-MAA) minigel particles are temperature sensitive with swelling behavior consistent with comparable microgels. Variations in pH were found to effect the size of minigels containing ionizable groups (such as a carboxylate) by a mechanism of increased electrostatic repulsion of charged groups with increasing pH. Overall, the production of temperature- and/or pH-sensitive polymers by inverse suspension polymerization results in particles with swelling characteristics similar to those produced by emulsion polymerization, albeit with differing particle sizes. Copyright 2000 Academic Press.

Journal Article↗

PubMed2000

Intraneuronal Abeta42 accumulation in human brain.

Alzheimer's disease (AD) is characterized by the deposition of senile plaques (SPs) and neurofibrillary tangles (NFTs) in vulnerable brain regions. SPs are composed of aggregated beta-amyloid (Abeta) 40/42(43) peptides. Evidence implicates a central role for Abeta in the pathophysiology of AD. Mutations in betaAPP and presenilin 1 (PS1) lead to elevated secretion of Abeta, especially the more amyloidogenic Abeta42. Immunohistochemical studies have also emphasized the importance of Abeta42 in initiating plaque pathology. Cell biological studies have demonstrated that Abeta is generated intracellularly. Recently, endogenous Abeta42 staining was demonstrated within cultured neurons by confocal immunofluorescence microscopy and within neurons of PS1 mutant transgenic mice. A central question about the role of Abeta in disease concerns whether extracellular Abeta deposition or intracellular Abeta accumulation initiates the disease process. Here we report that human neurons in AD-vulnerable brain regions specifically accumulate gamma-cleaved Abeta42 and suggest that this intraneuronal Abeta42 immunoreactivity appears to precede both NFT and Abeta plaque deposition. This study suggests that intracellular Abeta42 accumulation is an early event in neuronal dysfunction and that preventing intraneuronal Abeta42 aggregation may be an important therapeutic direction for the treatment of AD.

Adult↗

PubMed2000

[Yellow nail syndrome. Three cases].

Yellow nail syndrome is an uncommon diagnosis established on the basis of clinical presentation with slow-growing yellow discolored nails, lymphedema, and pulmonary manifestations. We report 3 new cases with their pulmonary component.

Adult↗

PubMed2000

[Value of MR imaging in the diagnosis of benign uterine conditions].

Benign diseases of the uterus can be evaluated by ultrasound, magnetic resonance imaging (MRI), hysterography, hysterosonography and hysteroscopy. The purpose of this review of the literature is to discuss the role of MRI among the different imaging modalities for the diagnosis of mullerian abnormalities of the uterus, endometrial disease, fibroids and adenomyosis. Particular attention is brought to comparative multi-modality studies. The MRI technique, indication and diagnostic criteria for various pathological conditions of the uterus are described. The use of MRI appears to be cost-effective in the diagnosis of complex mullerian abnormalities, endometrial thickening following treatment by tamoxifen, selection of candidates for selective myomectomy and the follow-up of medically treated adenomyosis.

Female↗

PubMed2000

[Comparison of endoscopic ultrasound and magnetic resonance imaging in severe pelvic endometriosis].

UNLABELLED: Deep pelvic endometriosis may lead to severe pain, the treatment of which may require complete surgical resection of lesions. Digestive infiltration is a difficult therapeutic problem. Preoperative diagnosis is difficult and digestive infiltration may remain unknown with incomplete resection and sometimes repeated surgery. Both magnetic resonance imaging (MRI) and endoscopic ultrasonography are able to detect rectosigmoid infiltration but their usefulness in the preoperative staging is still to be evaluated. The aim of this work was to evaluate and compare both techniques in the preoperative detection of deep pelvic endometriosis, particularly digestive infiltration. PATIENTS AND METHODS: From 1996 to 1998, 48 women with painful deep pelvic endometriosis had preoperative imaging exploration with endoscopic ultrasonography and MRI, and were operated on in order to attempt complete endometriosis resection. Patients were proposed for laparoscopic resection if endoscopic ultrasonography and/or MRI did not reveal digestive infiltration or for open resection if endoscopic ultrasonography and/or MRI were positive for digestive infiltration. RESULTS: Endoscopic ultrasonography and/or MRI led to suspicion of digestive endometriosis in 16 patients. Surgical resection was performed in 12 and digestive wall invasion was histologically demonstrated. At final follow-up, all patients had a dramatic decrease of their symptoms. The remaining 4 patients refused digestive resection and had only laparoscopic gynecologic resection. Infiltration although not histologically proven was very likely both on operative findings and clinical evolution. Digestive infiltration was preoperatively excluded in the 32 other patients. All had a laparoscopic treatment without digestive resection and pain diminished in all patients. In the 12 patients group who had digestive resection, digestive infiltration was correctly diagnosed by endoscopic ultrasonography in all cases (no false negative) whereas MRI, even with the use of endocoil antenna, led to correct diagnosis in 8 out of 12 cases. When endoscopic ultrasonography was negative for digestive infiltration, laparoscopic resection of lesions at surgery appeared complete in all cases. For the 16 patients with presumed digestive infiltration, sensitivity of endoscopic ultrasonography and MRI was 100 and 75% respectively, with a 100% specificity in both cases. MRI appeared very accurate for the detection of ovarian endometriotic locations. MRI was more sensitive but less specific than endoscopic ultrasonography for the diagnosis of isolated endometriotic recto-vaginal septum and utero-sacral ligaments lesions. CONCLUSION: Endoscopic ultrasonography was the best technique for the diagnosis of digestive endometriotic infiltration, which complicates the therapeutic strategy. MRI, however, allows more complete staging of other pelvic endometriotic lesions.

Adnexal Diseases↗