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B Michel

Publications and source records attributed to B Michel.

At least 19 recordsLinked to original sources
PubMed2006

[Diagnosis and management of cervicofacial congenital teratomas: about 4 cases, literature review and restatement].

Cervicofacial teratomas are rare developmental lesions, more often benign in their histology. They can lead to respiratory distress and death caused by airway obstruction at birth. Prenatal diagnosis raises on ultrasound examination precising locoregional consequences of the tumor and surgical possibilities. In the propitious cases, prenatal MRI examination is useful to precise tumor's limits and cerebral status of the foetus. At birth, coordinate management involving anaesthetists, paediatricians and specialized surgeons decrease morbidity and mortality. Complete early surgical excision must be managed as soon as possible and planned thanks to TDM end MRI examination.

Abortion, Induced↗
PubMed2006

[Tumoral and pilotropic mycosis fongoides without mucin: evolution towards a pustulous erythroderma].

INTRODUCTION: Pilotropic mycosis fongoides is a particular form of the disease, because of its clinical and histological aspects, its poor prognosis and its resistance to treatment. We report a case of pilotropic mycosis fongoides without mucinosis, immediately tumoral, the fatal progression of which was marked by the occurrence of pustular erythroderma. OBSERVATION: In 1998 a 69 year-old man presented with infiltrated erythro-squamatous plaques and nodules on the limbs associated with follicular lesions predominating on the cervical-cephalic area. Histological explorations revealed a pilotropic infiltrate with atypical CD4+ CD8 CD30 T-cells, without epidermotrophism or mucinosis. Study of genetic rearrangements found a clone lymphocyte T-cell in the skin. Diagnosis of pilotropic mycosis fongoides at the tumoral stage was made and, despite various treatments, the disease developed towards fatal pustular erythroderma. DISCUSSION: At the onset of its progression, pilotropic mycosis fongoides is sometimes difficult to distinguish from classical mycosis fongoides, during which follicular involvement is often seen. However it is important to differentiate these entities because of the poor prognosis of pilotropic mycosis fongoides. Development of tissue micro dissection techniques and lymphocyte T-cell clones from human skin would help to separate these cutaneous T-cell lymphoma sub-groups. Our case report is original because of the absence of dermal mucinosis combined with an immediately tumoral form and the progression towards generalized pustulosis. It also underlines the poor prognosis and resistance to treatment of pilotropic mycosis fongoides.

Aged↗
PubMed2006

Are desmoglein autoantibodies essential for the immunopathogenesis of pemphigus vulgaris, or just "witnesses of disease"?

Pemphigus vulgaris (PV) is fascinating to dermatologists, epithelial biologists and immunologists alike, as its pathogenesis has been clarified to a much greater extent than that of most other organ-specific autoimmune diseases, and as it has provided abundant novel insights into desmoglein biology and pathology along the way. Historically, the most influential PV pathogenesis concept is that of Stanley and Amagai. This concept holds that autoantibodies against desmogleins are both essential and sufficient for epidermal blister formation (acantholysis) by impeding the normal functioning of these major adhesion proteins. However, as with most good theories, this landmark concept has left a number of intriguing and important questions open (or at least has not managed to answer these to everyone's satisfaction). Moreover, selected dissenting voices in the literature have increasingly called attention to what may or may not be construed as inconsistencies in this dominant PV pathogenesis paradigm of the recent past. The present debate feature therefore bravely rises to the challenge of re-examining the entire currently available evidence, as rationally and as undogmatically as possible, by provocatively asking a carefully selected congregation of experts (who have never before jointly published on this controversial topic!) to discuss how essential anti-desmoglein autoantibodies really are in the immunopathogenesis of PV. Not surprisingly, some of our expert "witnesses" in this animated debate propose diametrically opposed answers to this question. While doing so, incisive additional questions are raised that relate to the central one posed, and our attention is called to facts that may deserve more careful consideration than they have received so far. Together with the intriguing (often still very speculative) complementary or alternative pathogenesis scenarios proposed in the following pages, this offers welcome "food for thought" as well as very specific suggestions for important future research directions--within and beyond the camp of PV aficionados. The editors trust that this attempt at a rational public debate of the full evidence that is currently at hand will constructively contribute to further dissecting the exciting--and clinically very relevant!--immunopathogenesis of PV in all its complexity.

Animals↗
PubMed2004

Possible apoptotic mechanism in epidermal cell acantholysis induced by pemphigus vulgaris autoimmunoglobulins.

Through a still unclear mechanism, pemphigus vulgaris autoantibodies (PV-IgG) induce intra-epidermal acantholytic lesions responsible for severe to fatal skin wounding. We present evidence that PV lesions contain apoptotic keratinocytes, and that cell death is induced in the lesional tissue apparently before cell separation. These data suggest that apoptosis could be the cause of the acantholytic phenomenon. We show that PV-IgG and an antibody against Fas receptor (anti-FasR) induce lesions in vitro in a similar way, causing: (1) secretion of soluble FasL; (2) elevated cellular amounts of FasR, FasL (soluble and membranal), Bax and p53 proteins; (3) reduction in levels of cellular Bcl-2; (4) enrichment in caspase 8, and activation of caspases 1 and 3; (5) co-aggregation of FasL and FasR with caspase 8 in membranal death-inducing signaling complex (DISC). Hence, the Fas-mediated death signaling pathway seems to be involved in lesion formation. Moreover, we have shown that in skin organ cultures and in keratinocyte cultures, PV-IgG can induce caspase activation and DNA fragmentation, and caspase inhibitors can prevent the formation of PV-IgG-induced epidermal lesions. Altogether, these results suggest that PV-IgG-induced acantholysis may proceed through the death-signaling pathway. They highlight new perspectives on mechanisms of tissue damage in autoimmune diseases.

Acantholysis↗
PubMed2002

["The 5 words": a simple and sensitive test for the diagnosis of Alzheimer's disease].

OBJECTIVE: Alzheimer's disease (AD) is under-diagnosed in France. Today only an estimated 50% of patients are identified. Diagnosis of AD is particularly difficult because the amnesic syndrome, characteristic of the disease, is often confused with memory dysfunction that is frequent during the process of aging. The improvement in the diagnostic conditions of AD relies on the availability of a simple and reliable tool for screening memory disorders of organic origin. METHOD: The 5-word test studies the recall of a short list, which the physician ensures the patient has registered. Its construction permits the identification of patients exhibiting objective memory disorders. A validation study has been conducted in 86 patients suffering from AD and 126 persons complaining of functional memory disorders. RESULTS: The study has shown the sensitivity (91%) and specificity (87%) of the 5-word test in identifying patients with AD. CONCLUSION: This is a rapid (2 minutes) and simple test that is easy to use in medical practice for the screening of AD.

Age Factors↗
PubMed2001

Rescue of arrested replication forks by homologous recombination.

DNA synthesis is an accurate and very processive phenomenon; nevertheless, replication fork progression on chromosomes can be impeded by DNA lesions, DNA secondary structures, or DNA-bound proteins. Elements interfering with the progression of replication forks have been reported to induce rearrangements and/or render homologous recombination essential for viability, in all organisms from bacteria to human. Arrested replication forks may be the target of nucleases, thereby providing a substrate for double-strand break repair enzyme. For example in bacteria, direct fork breakage was proposed to occur at replication forks blocked by a bona fide replication terminator sequence, a specific site that arrests bacterial chromosome replication. Alternatively, an arrested replication fork may be transformed into a recombination substrate by reversal of the forked structures. In reversed forks, the last duplicated portions of the template strands reanneal, allowing the newly synthesized strands to pair. In bacteria, this reaction was proposed to occur in replication mutants, in which fork arrest is caused by a defect in a replication protein, and in UV irradiated cells. Recent studies suggest that it may also occur in eukaryote organisms. We will review here observations that link replication hindrance with DNA rearrangements and the possible underlying molecular processes.

DNA Replication↗
PubMed2001

Circles: the replication-recombination-chromosome segregation connection.

Crossing over by homologous recombination between monomeric circular chromosomes generates dimeric circular chromosomes that cannot be segregated to daughter cells during cell division. In Escherichia coli, homologous recombination is biased so that most homologous recombination events generate noncrossover monomeric circular chromosomes. This bias is lost in ruv mutants. A novel protein, RarA, which is highly conserved in eubacteria and eukaryotes and is related to the RuvB and the DnaX proteins, gamma and tau, may influence the formation of crossover recombinants. Those dimeric chromosomes that do form are converted to monomers by Xer site-specific recombination at the recombination site dif, located in the replication terminus region of the E. coli chromosome. The septum-located FtsK protein, which coordinates cell division with chromosome segregation, is required for a complete Xer recombination reaction at dif. Only correctly positioned dif sites present in a chromosomal dimer are able to access septum-located FtsK. FtsK acts by facilitating a conformational change in the Xer recombination Holliday junction intermediate formed by XerC recombinase. This change provides a substrate for XerD, which then completes the recombination reaction.

Amino Acid Sequence↗
PubMed2001

Three-dimensional structure of the lithostathine protofibril, a protein involved in Alzheimer's disease.

Neurodegenerative diseases are characterized by the presence of filamentous aggregates of proteins. We previously established that lithostathine is a protein overexpressed in the pre-clinical stages of Alzheimer's disease. Furthermore, it is present in the pathognomonic lesions associated with Alzheimer's disease. After self-proteolysis, the N-terminally truncated form of lithostathine leads to the formation of fibrillar aggregates. Here we observed using atomic force microscopy that these aggregates consisted of a network of protofibrils, each of which had a twisted appearance. Electron microscopy and image analysis showed that this twisted protofibril has a quadruple helical structure. Three-dimensional X-ray structural data and the results of biochemical experiments showed that when forming a protofibril, lithostathine was first assembled via lateral hydrophobic interactions into a tetramer. Each tetramer then linked up with another tetramer as the result of longitudinal electrostatic interactions. All these results were used to build a structural model for the lithostathine protofibril called the quadruple-helical filament (QHF-litho). In conclusion, lithostathine strongly resembles the prion protein in its dramatic proteolysis and amyloid proteins in its ability to form fibrils.

Alzheimer Disease↗
PubMed2001

Impairment of lagging strand synthesis triggers the formation of a RuvABC substrate at replication forks.

The holD gene codes for the psi subunit of the Escherichia coli DNA polymerase III holoenzyme, a component of the gamma complex clamp loader. A holD mutant was isolated for the first time in a screen for mutations that increase the frequency of tandem repeat deletions. In contrast to tandem repeat deletions in wild-type strains, deletion events stimulated by the holD mutation require RecA. They do not require RecF, and hence do not result from the recombinational repair of gaps, arguing against uncoupling of the leading and lagging strand polymerases in the holD mutant. The holD recBC combination of mutations is lethal and holD recBts recCts strains suffer DNA double-strand breaks (DSBs) at restrictive temperature. DSBs require the presence of the Holliday junction-specific enzymes RuvABC and are prevented in the presence of RecBCD. We propose that impairment of replication due to the holD mutation causes the arrest of the entire replisome; consequently, Holliday junctions are formed by replication fork reversal, and unequal crossing over during RecA- and RecBCD-mediated re-incorporation of reversed forks causes the hyper-recombination phenotype.

Bacterial Proteins↗
PubMed2001

Micromosaic immunoassays.

Immunoassays are widely used for medical diagnostics and constitute the principal method of detecting pathogenic agents and thus of diagnosing many diseases. These assays, which are most often performed in well plates, would be greatly improved by a practical method to pattern a series of antigens on a flat surface and to localize their binding to many analytes. But no obvious method exists to expose a planar surface successively to a series of antigens and analytes. Here, we present miniaturized mosaic immunoassays based on patterning lines of antigens onto a surface by means of a microfluidic network (muFN). Solutions to be analyzed are delivered by the channels of a second muFN across the pattern of antigens. Specific binding of the target antibodies with their immobilized antigens on the surface results in a mosaic of binding events that can readily be visualized in one screening using fluorescence. It is thus possible to screen solutions for antibodies in a combinatorial fashion with great economy of reagents and at a high degree of miniaturization. Such mosaic-format immunoassays are compatible with the sensitivity and reliability required for immunodiagnostic methods.

Enzyme-Linked Immunosorbent Assay↗
PubMed2001

The replication-recombination connection: insights from genomics.

One amazing characteristic of DNA processing enzymes is their breakneck speed. However, considering the metabolic traffic on DNA, it is not surprising that accidents that interrupt the replication process and require immediate repair occur. Recombination is an example of a repair mechanism, and as a result of accidents, the arrested or broken fork becomes the recombination substrate. Repair proteins are on hand to assist at accident sites, but responses may be sensitive to conditions and depend on the organism. Genomics has been used to identify genetic clues that indicate the occurrence of accidents and to detect sites of recombination. DNA and protein features that may affect replication and recombination are examined and discussed.

Bacteria↗
PubMed2001

Clinical comparison of the effectiveness of novel sonic instruments and curettes for periodontal debridement after 2 months.

AIM: The aim of this study was to evaluate in vivo the effectiveness of scaling and root planing of new oscillating instruments (Periosonic) using a sonic handpiece compared to hand curettes with a split mouth design after 2 months. METHODS: 11 patients with adult periodontitis participated in this study. Plaque index (PII) (O'Leary), bleeding on probing (BOP), probing pocket depth (PPD), recession (REC) and clinical attachment level (CAL) were recorded at baseline and 2 months after treatment. After oral hygiene instruction, 2 randomly assigned quadrants per patient were scaled and root planed with curettes (control side) and the remaining 2 quadrants with the Periosonic instruments 1 and 2 (test side). The student t-test for paired data was used to test the significance of difference between test and control sides. RESULTS: There was no statistical difference (p>0.05) between the 2 sides for the improvement of the clinical parameters excepted for the group with initial PPD of 4-6 mm (test: 1.3+/-0.4 mm PPD reduction, control: 1.6+/-0.4 mm). For PPD > or =7 mm, the test side had better clinical improvement in attachment levels (2.2+/-0.9 mm), less recession (-0.4+/-0.5 mm) with lower PPD reduction (2.4+/-0.6 mm) than the control side (AL: 1.6+/-1.8 mm; REC: -1.3+/-0.7 mm, PPD reduction: 3.0+/-1.4 mm). CONCLUSION: This clinical study demonstrated that Periosonic(R) instruments are clinically at least as effective as curettes in PPD reduction when initial PPD is < or =6 mm and show better clinical attachment level improvement with less recession for initial PPD of > or =7 mm.

Adult↗
PubMed2001

Affinity capture of proteins from solution and their dissociation by contact printing.

Biological experiments at the solid/liquid interface, in general, require surfaces with a thin layer of purified molecules, which often represent precious material. Here, we have devised a method to extract proteins with high selectivity from crude biological sample solutions and place them on a surface in a functional, arbitrary pattern. This method, called affinity-contact printing (alphaCP), uses a structured elastomer derivatized with ligands against the target molecules. After the target molecules have been captured, they are printed from the elastomer onto a variety of surfaces. The ligand remains on the stamp for reuse. In contrast with conventional affinity chromatography, here dissociation and release of captured molecules to the substrate are achieved mechanically. We demonstrate this technique by extracting the cell adhesion molecule neuron-glia cell adhesion molecule (NgCAM) from tissue homogenates and cell culture lysates and patterning affinity-purified NgCAM on polystyrene to stimulate the attachment of neuronal cells and guide axon outgrowth.

Animals↗
PubMed2001

Inhibitory effect of reactive oxygen species on angiotensin I-converting enzyme (kininase II).

1. Somatic angiotensin I-converting enzyme (ACE) is a protein that contains two similar domains (N- and C-terminal), each possessing an active site. We have examined the effects of a generator of hydroxyl radicals (g*OH: 2,2'-azo-bis(2-amidinopropane)) and hydrogen peroxide (H2O2) on ACE using an in vitro approach. 2. The generator of hydroxyl radicals inactivated ACE in a time (2-6 h)- and concentration (0.3-3 mmol/L)-dependent manner at 37 degrees C. When ACE was coincubated for 4 h with g*OH (3 mmol/L), its activity decreased by 70%. Addition of dimethylthiourea or mannitol + methionine, two *OH scavengers, resulted in a significant protection of ACE activity. Mercaptoethanol and dithiotreitol, two thiol-reducing agents, also efficiently protected ACE activity. 3. The hydrolysis of two natural and domain-specific substrates was explored. The hydrolysis of angiotensin I, preferentially cleaved by the C-domain, was significantly inhibited (57-58%) after 4 h exposure to g*OH (0.3-1 mmol/L). Under the same conditions of exposure, the hydrolysis of N-acetyl-Ser-Asp-Lys-Pro, a specific substrate for the N-domain, was only slightly inhibited by 1 mmol/L g*OH. 4. Hydrogen peroxide, another source of *OH, was used. After exposure to H2O2 (3 mmol/L; 4 h), an 89% decrease in ACE activity was observed. Pretreatment with the iron chelator deferoxamine (1 mmol/L) attenuated H2O2-mediated ACE inactivation, demonstrating that the effect of H2O2 was partly due to its conversion into *OH (Fenton reaction). 5. In summary, our findings demonstrate that g*OH and H2O2 inhibit ACE activity and suggest a preferential action of g*OH on the C-domain of the enzyme.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2001

Viability of rep recA mutants depends on their capacity to cope with spontaneous oxidative damage and on the DnaK chaperone protein.

Replication arrests due to the lack or the inhibition of replicative helicases are processed by recombination proteins. Consequently, cells deficient in the Rep helicase, in which replication pauses are frequent, require the RecBCD recombination complex for growth. rep recA mutants are viable and display no growth defect at 37 or 42 degrees C. The putative role of chaperone proteins in rep and rep recA mutants was investigated by testing the effects of dnaK mutations. dnaK756 and dnaK306 mutations, which allow growth of otherwise wild-type Escherichia coli cells at 40 degrees C, are lethal in rep recA mutants at this temperature. Furthermore, they affect the growth of rep mutants, and to a lesser extent, that of recA mutants. We conclude that both rep and recA mutants require DnaK for optimal growth, leading to low viability of the triple (rep recA dnaK) mutant. rep recA mutant cells form colonies at low efficiency when grown to exponential phase at 30 degrees C. Although the plating defect is not observed at a high temperature, it is not suppressed by overexpression of heat shock proteins at 30 degrees C. The plating defect of rep recA mutant cells is suppressed by the presence of catalase in the plates. The cryosensitivity of rep recA mutants therefore results from an increased sensitivity to oxidative damage upon propagation at low temperatures.

DNA Helicases↗
PubMed2000

Association of APOE promoter but not A2M polymorphisms with risk of developing Alzheimer's disease.

The APOE4 allele is widely accepted as a major risk factor for late-onset Alzheimer's disease (AD). Recently, it has been reported that polymorphisms in the APOE promoter and in the alpha2-macroglobulin gene (A2M) are associated with AD. We have analyzed the distribution of APOE alleles, -219T/G APOE promoter polymorphism, and A2M/A2Mdel polymorphism in a large case-control study. Our results showed that APOE genotype was the only informative marker of AD risk contrary to -219T/G and A2M/A2Mdel polymorphism. In AD patients however, a strong linkage disequilibrium was observed between the T allele of -219T/G polymorphism and APOE4 allele. This result indicates that -219T/G APOE promoter polymorphism is a risk factor for AD by increasing the APOE4-associated risk.

Aged↗