Biomedical subjects

C Evrard

Publications and source records attributed to C Evrard.

At least 19 recordsLinked to original sources

PubMed2005

Subcellular localization of neural-specific NPDC-1 protein.

NPDC-1 is a gene specifically expressed in neural cells when they stop to divide and begin to differentiate. Immunocytochemical study analysis of differentiated PC12 cells transfected with NPDC-tag vectors showed that NPDC-1 is transported in vesicles from the Golgi apparatus to the cell membrane and is then likely internalized into endosomes. The protein colocalized, at least partially, with synaptic vesicle proteins: synaptophysin, synaptobrevin 2, and Rab3 GEP (Rab3 GTP/GDP exchange protein). Moreover, subcellular fractionation of rat brain showed that crude synaptic membrane and crude synaptic vesicle fractions were enriched in NPDC-1. Although NPDC-1 bound Rab3 GEP in vitro, it seems unlikely to be involved in Ca2+-dependent exocytosis and, thus, in synaptic vesicle trafficking.

Animals↗

PubMed2004

Functional analysis of the NPDC-1 gene.

Mouse NPDC-1 (Neural Proliferation Differentiation and Control-1) is specifically expressed in neural cells when they stop dividing and start to differentiate. The NPDC-1 protein has been shown to interact with the E2F1 transcription factor, D-type cyclins and Cdk2. Immunocytochemical studies and subcellular fractionation of rat brains disclosed a partial colocalization of NPDC-1 with synaptic vesicle proteins, suggesting additional functional interactions. Here, we report the characterization of the mouse and human genes that were found to display very similar structures. We mapped the human gene to chromosome 9q34.3. No obvious pathological defect has been previously linked to this region. In order to gain further insights into its function(s), we generated null mice for the NPDC-1 gene. We did not detect any macroscopic phenotypical defect. Analysis of the upstream sequence of the mouse NPDC-1 gene delineated two regions involved in its negative and positive transcriptional regulation. Evidence for the regulation of NPDC-1 by Krox family transcription factors is presented.

Animals↗

PubMed2001

A twinned monoclinic crystal form of human peroxiredoxin 5 with eight molecules in the asymmetric unit.

The monoclinic crystal form of human peroxiredoxin 5 with eight molecules in the asymmetric unit was obtained under exactly the same conditions as the tetragonal form with one molecule in the asymmetric unit, except that the latter was briefly cryosoaked with halide for derivatization. A merohedral twinning was observed, which is rather unusual in the monoclinic system and only possible with particular unit-cell dimensions. After detwinning the native and a mercury derivative, the structure was solved by the SIR method with the help of the non-crystallographic symmetry. The packing of the monoclinic and tetragonal forms are compared, with special attention to the role of bromide ions in the change of space group after crystallization. The availability of nine (eight monoclinic plus one tetragonal) independent molecules allows an analysis of the mobility. The two Cys residues implicated in the peroxide-reduction mechanism are located in rigid regions but are covered by mobile loops.

Crystallization↗

PubMed2001

Crystal structure of human peroxiredoxin 5, a novel type of mammalian peroxiredoxin at 1.5 A resolution.

The peroxiredoxins define an emerging family of peroxidases able to reduce hydrogen peroxide and alkyl hydroperoxides with the use of reducing equivalents derived from thiol-containing donor molecules such as thioredoxin, glutathione, trypanothione and AhpF. Peroxiredoxins have been identified in prokaryotes as well as in eukaryotes. Peroxiredoxin 5 (PRDX5) is a novel type of mammalian thioredoxin peroxidase widely expressed in tissues and located cellularly to mitochondria, peroxisomes and cytosol. Functionally, PRDX5 has been implicated in antioxidant protective mechanisms as well as in signal transduction in cells. We report here the 1.5 A resolution crystal structure of human PRDX5 in its reduced form. The crystal structure reveals that PRDX5 presents a thioredoxin-like domain. Interestingly, the crystal structure shows also that PRDX5 does not form a dimer like other mammalian members of the peroxiredoxin family. In the reduced form of PRDX5, Cys47 and Cys151 are distant of 13.8 A although these two cysteine residues are thought to be involved in peroxide reductase activity by forming an intramolecular disulfide intermediate in the oxidized enzyme. These data suggest that the enzyme would necessitate a conformational change to form a disulfide bond between catalytic Cys47 and Cys151 upon oxidation according to proposed peroxide reduction mechanisms. Moreover, the presence of a benzoate ion, a hydroxyl radical scavenger, was noted close to the active-site pocket. The possible role of benzoate in the antioxidant activity of PRDX5 is discussed.

Amino Acid Sequence↗

PubMed2001

[HBME-1 immunostaining in thyroid pathology].

The aim of this study was to evaluate wether HBME-1 immunohistochemical analysis can reliably differentiate benign thyroid lesions from thyroid carcinomas. Fifty benign and 87 malignant lesions were analyzed. All papillary carcinomas (67/67) were HBME-1 positive, as well as 14 of 20 follicular well-differentiated carcinomas and 13 of 29 atypical follicular adenomas and 4 out of 21 goiters were weakly and focally positive. HBME-1 highlighted micronests of papillary carcinomas. The reactivity of HBME-1 in the tall-cell variant of papillary carcinomas was apical and stronger than in classical papillary carcinomas. Positive HBME-1 immunostaining is in support of the diagnosis of the follicular variant of papillary carcinoma and highlights micropapillary carcinomas. HBME-1 may be of additional value in the diagnosis of thyroid malignancy.

Adenocarcinoma, Follicular↗

PubMed2000

NPDC-1, a regulator of neural cell proliferation and differentiation, interacts with E2F-1, reduces its binding to DNA and modulates its transcriptional activity.

We have previously identified NPDC-1, a neural factor involved in the control of proliferation and differentiation, and we have shown that the stable introduction of NPDC-1 into transformed cells down-regulates cell proliferation both by increasing the generation time and by suppressing transformed properties. The data presented here indicate that, in vitro, NPDC-1 is able to interact with the transcription factor E2F-1 and some cell cycle proteins, such as D-cyclins and cdk2. In addition, two-hybrid experiments in mammalian cells show that the interaction between NPDC-1 and E2F-1 can also occur in vivo. This interaction reduces the binding of E2F-1 to DNA and its transcriptional activity. Taken together, the data suggest that NPDC-1 could influence cell cycle progression and neural differentiation through its association with E2F-1.

Animals↗

PubMed2000

Volume changes of isolated human K562 leukemia cells induced by electric field pulses.

Electropermeabilization of immobilized human leukemia K562 cells was studied by measuring changes in cell volume. Such changes reflect mass transfer between the cell and external medium. Electropermeabilization was carried out in an isosmotic water-sorbitol medium with a range of electric field strengths from 500 to 800 V. cm(-1), corresponding to low-energy levels. Electroporation of the K562 cell membrane was found to provoke an inflow of sorbitol and a corresponding osmotic inflow of water and/or an outflow of intracellular solutes due to Fick diffusion. Such flows were found to involve the shrinkage, swelling, or rupture of K562 cells, depending on the characteristics of the electric field and of the physiological state of cells. The behavior of immobilized cells was observed during their exposure to the electric field. The response in immobilized cell volume corresponded with the theoretical pore size and pore opening time, permitting an explanation of the behavior of cell suspensions subject to electrical fields.

Cell Size↗

PubMed2000

Bronchial stump aspergillosis.

Two cases of bronchial stump aspergillosis were diagnosed 5 and 6 years after pneumonectomy for lung cancer. In each case, the fungal mass was endoscopically removed using standard forceps. A recurrence of the fungal mass persisted until all visible protruding nylon threads in the airway lumen were destroyed with a Nd:YAG laser. Removal of the visible suture is necessary for eliminating the infection. No additional local or systemic antifungal therapy is needed.

Aspergillosis↗

PubMed1999

Histidine modification and mutagenesis point to the involvement of a large conformational change in the mechanism of action of phage lambda lysozyme.

Phage lambda lysozyme (lambdaL) is structurally related to other known lysozymes but its mechanism of action is different from the classical lysozyme mechanism, acting as a transglycosidase rather than a hydrolase. As two conformations have been revealed by the crystal structure, we investigated the effect of mutating and modifying a histidine located near to or far from the active site in the respective closed and open conformations. Whereas its asparagine mutation has little or no effect on activity, its N-carbethoxylation inactivates the enzyme. This provide further evidence for the involvement of the closed conformation and for the need of conformational mobility in lambdaL function.

Bacteriophage lambda↗

PubMed1999

Andrews thoracoplasty as a treatment of post-pneumonectomy empyema: experience in 23 cases.

BACKGROUND: Andrew's thoracopleuroplasty has been described for treating tuberculous empyemas with bronchopleural fistulas. We report on its utilization for treating postpneumonectomy empyemas. METHODS: During a 25 year period, 23 patients underwent thoracopleuroplasty for treating postpneumonectomy empyemas, after a period of drainage-irrigation of the cavity. Seven patients presented with persistent bronchial fistula at operation. After resection of the costal arches surrounding the infected cavity, the cavity was cleaned, and the external parietal plane was sutured to the mediastinal plane. Only drainage of the subscapular space was left in place. RESULTS: Postoperative mortality was 4.3%. Postoperative recovery was simple in 17 cases, whereas a superficial abscess was evacuated in 3 cases. The procedure failed in 3 cases, which were treated by open thoracostomy (2), and by reenlargment of the thoracopleuroplasty (1). The sequelae were mainly a diminution of the shoulder mobility, especially when the first rib was resected. CONCLUSIONS: Thoracopleuroplasty may safely treat postpneumonectomy empyemas, even those with bronchial fistulas. Most patients are definitively and rapidly cured with limited sequelae.

Adult↗

PubMed1999

Scimitar syndrome with pulmonary arteriovenous fistulas.

Right abnormal pulmonary venous return into the inferior vena cava associated with abnormal fissure, dextrocardia, and systemic arterial supply of a variable degree, are the characteristics of the scimitar syndrome. We report on a patient in whom this rare syndrome was associated with pulmonary arteriovenous fistulas within the involved lung.

Adult↗

PubMed1999

Desmoid fibromatosis of the shoulder and of the upper chest wall following a clavicular fracture.

A desmoid tumor of the shoulder girdle infiltrating the upper chest wall and weighing 1500 g was almost completely removed in an 18-year-old man, 27 months after a bifocal fracture of the clavicule. Thirteen years later, the patient was free of recurrence. The interval time between trauma and diagnosis, as the particular characteristics of aggressive fibromatosis, strongly support a major causal role of the clavicular fracture in the occurrence of this tumor.

Accidents, Traffic↗

PubMed1999

The incorporation of a non-natural amino acid (aza-tryptophan) may help to crystallize a protein and to solve its crystal structure. Application to bacteriophage lambda lysozyme.

Until now, wild-type bacteriophage lambda lysozyme had been impossible to crystallize. This difficulty could be overcome by the replacement of the four tryptophan residues by aza-tryptophans. Analysis of the intermolecular and intramolecular contacts in this modification allows understanding of the differences in behaviour between the native and modified molecules. Furthermore, this mutation was very useful for the creation of new heavy-atom binding sites and for the solution of the non-crystallographic symmetry, which is extremely important for phase improvement. This procedure seems to be generally applicable, at least in the search for new possibilities for heavy-atom binding sites.

Aza Compounds↗

PubMed1999

Crystal structure of the EF-hand parvalbumin at atomic resolution (0.91 A) and at low temperature (100 K). Evidence for conformational multistates within the hydrophobic core.

Several crystal structures of parvalbumin (Parv), a typical EF-hand protein, have been reported so far for different species with the best resolution achieving 1.5 A. Using a crystal grown under microgravity conditions, cryotechniques (100 K), and synchrotron radiation, it has now been possible to determine the crystal structure of the fully Ca2+-loaded form of pike (component pI 4.10) Parv.Ca2 at atomic resolution (0.91 A). The availability of such a high quality structure offers the opportunity to contribute to the definition of the validation tools useful for the refinement of protein crystal structures determined to lower resolution. Besides a better definition of most of the elements in the protein three-dimensional structure than in previous studies, the high accuracy thus achieved allows the detection of well-defined alternate conformations, which are observed for 16 residues out of 107 in total. Among them, six occupy an internal position within the hydrophobic core and converge toward two small buried cavities with a total volume of about 60 A3. There is no indication of any water molecule present in these cavities. It is probable that at temperatures of physiological conditions there is a dynamic interconversion between these alternate conformations in an energy-barrier dependent manner. Such motions for which the amplitudes are provided by the present study will be associated with a time-dependent remodeling of the void internal space as part of a slow dynamics regime (millisecond timescales) of the parvalbumin molecule. The relevance of such internal dynamics to function is discussed.

Binding Sites↗

PubMed1999

[Pleural mesotheliomas. Current knowledge].

Pleural mesotheliomas are rare primary tumors of the pleura. Three groups are classified under the term mesothelioma: 1) benign pleural mesothelioma for which complete surgical treatment is curative with a good prognosis; 2) localized malignant mesothelioma which is a fibrosarcoma, best treated by wide en-bloc resection; 3) diffuse malignant mesothelioma which is mainly of epithelial type. The prognosis is poor in spite of all therapeutic approaches using irradiation, chemotherapy and surgery, alone or in combination, and long-term survivals are uncommon. Two surgical approaches are currently available for patients with diffuse mesothelioma: radical extrapleural pneumonectomy and pleurectomy/decortication. Rigorous combinations of multimodality therapy are needed to improve local control and survival.

Combined Modality Therapy↗

PubMed1999

[Pleural fibromas: a review based on 12 cases].

The authors report 12 cases of pleural fibroma, which is a rare benign tumor, usually discovered incidentally. However, these tumors are sometimes associated with a paraneoplastic syndrome, or may lead to compressive symptoms related to their large size. Radical resection is mandatory because recurrence may occur, sometimes several years later with a malignant behavior. Long-term follow-up is therefore necessary to detect any recurrence, particularly when certain prognostic factors are initially present.

Adult↗

PubMed1998

Crystal structure of the lysozyme from bacteriophage lambda and its relationship with V and C-type lysozymes.

Like other lysozymes, the bacteriophage lambda lysozyme is involved in the digestion of bacterial walls. This enzyme is remarkable in that its mechanism of action is different from the classical lysozyme's mechanism. From the point of view of protein evolution, it shows features of lysozymes from different classes. The crystal structure of the enzyme in which all tryptophan residues have been replaced by aza-tryptophan has been solved by X-ray crystallography at 2.3 A using a combination of multiple isomorphous replacement, non-crystallographic symmetry averaging and density modification techniques. There are three molecules in the asymmetric unit. The characteristic structural elements of lysozymes are conserved: each molecule is organized in two domains connected by a helix and the essential catalytic residue (Glu19) is located in the depth of a cleft between the two domains. This cleft shows an open conformation in two of the independent molecules, while access to the cavity is much more restricted in the last one. A structural alignment with T4 lysozyme and hen egg white lysozyme allows us to superpose about 60 C alpha atoms with a rms distance close to 2 A. The best alignments concern the helix preceding the catalytic residue, some parts of the beta sheets and the helix joining the two domains. The results of sequence alignments with the V and C lysozymes, in which weak local similarities had been detected, are compared with the structural results.

Amino Acid Sequence↗

PubMed1998

Developmental pattern of expression of NPDC-1 and its interaction with E2F-1 suggest a role in the control of proliferation and differentiation of neural cells.

We have previously identified NPDC-1, a gene specifically expressed in neural cells and involved in the control of cell proliferation and differentiation. In the present study, we have investigated the expression of this gene during mouse development and the interactions of the NPDC-1 protein with cell cycle regulatory proteins. The data show that NPDC-1 mRNA begins to be expressed in a variety of neural structures when the precursors enter into their terminal differentiation. They also indicate that in adult brain, the expression patterns of NPDC-1 and E2F-1 mRNA largely overlap. In addition, the NPDC-1 protein is able to interact directly with the transcription factor E2F-1 that participates in the regulation of the cell cycle, cell survival, and apoptosis. The present results suggest that NPDC-1 might be involved in the terminal differentiation and survival of neural cells and might act through interactions with E2F-1.

Animals↗