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Biomedical subjects

C Dumas

Publications and source records attributed to C Dumas.

At least 19 recordsLinked to original sources
PubMed2006

[Medical treatment in peripheral arterial disease: a professional practice study in 262 patients].

PURPOSE: Antiplatelet agents (APA), statins and angiotensin converting enzyme inhibitors (ACEI) are effective to reduce the risk of cardio-vascular events in patients with peripheral arterial disease (PAD). Few data are available on the actual prescription of these drugs in outpatients and on the effect of hospital care on the level of prescription. METHODS: Retrospective study of patients hospitalized with a confirmed diagnosis of PAD over a one-year period. Comparison of medical treatments on admission and on discharge. RESULTS: 262 patients were included. Mean age was 73 +/- 11 years, and 29% of the patients were women. APA were present in 64% on admission and in 83% when discharged (P < 0.0001). A statin was present in 29% on admission and in 38% when discharged (P = 0.001). ACEI were present in 27% on admission and in 32% when discharged (P= 0.02). A vasodilator was present in 47% on admission and 52% when discharged (P = 0.1). 35% of the patients had isolated PAD. Compared to the patients with associated clinical coronary or cerebro-vascular disease, they were less frequently discharged on statins (respectively 26 and 45%, p = 0.003) and on ACEI (respectively 23 et 38%, P = 0.016) whereas APA were equally prescribed (respectively 82 and 84%, P= 0.7). CONCLUSION: APA were prescribed to a majority of outpatients and the level of prescription was further improved when patients were discharged from the hospital. Statins and ACEI were insufficiently prescribed. On the other hand, vasodilator therapy remained still largely prescribed, despite the lack of any strong effect on morbidity and survival.

Aged↗
PubMed2006

An optical supernova associated with the X-ray flash XRF 060218.

Long-duration gamma-ray bursts (GRBs) are associated with type Ic supernovae that are more luminous than average and that eject material at very high velocities. Less-luminous supernovae were not hitherto known to be associated with GRBs, and therefore GRB-supernovae were thought to be rare events. Whether X-ray flashes--analogues of GRBs, but with lower luminosities and fewer gamma-rays--can also be associated with supernovae, and whether they are intrinsically 'weak' events or typical GRBs viewed off the axis of the burst, is unclear. Here we report the optical discovery and follow-up observations of the type Ic supernova SN 2006aj associated with X-ray flash XRF 060218. Supernova 2006aj is intrinsically less luminous than the GRB-supernovae, but more luminous than many supernovae not accompanied by a GRB. The ejecta velocities derived from our spectra are intermediate between these two groups, which is consistent with the weakness of both the GRB output and the supernova radio flux. Our data, combined with radio and X-ray observations, suggest that XRF 060218 is an intrinsically weak and soft event, rather than a classical GRB observed off-axis. This extends the GRB-supernova connection to X-ray flashes and fainter supernovae, implying a common origin. Events such as XRF 060218 are probably more numerous than GRB-supernovae.

Journal Article↗
PubMed2006

[Conjunctival biopsy: a useful procedure for the diagnosis of sarcoidosis].

PURPOSE: To highlight the advantages of conjunctival biopsy in order to confirm the diagnosis of sarcoidosis. CASE REPORT: A 78-year-old woman presented with unilateral vitreitis. The examination of the conjunctive of right and left eyes revealed multiple, translucent, pale yellow nodules the size of millet grains located in the lower fornix. The diagnosis of sarcoidosis was suspected by an increased level of angiotensin-converting enzyme and bilateral hilar lymphadenopathies. A biopsy from conjunctival nodules showed noncaseating epithelioid and gigantocellular granulomas, confirming the diagnosis of sarcoidosis. CONCLUSION: Although underused, conjunctival biopsy seems to be both a safe and effective tool in the diagnosis of sarcoidosis.

Aged↗
PubMed2006

Chromosomal aneuploidy in African Wildcat somatic cells and cloned embryos.

In the present study, we compared the incidence of aneuploidy in in vitro fertilized domestic cat embryos (DSH-IVF) with that of African Wildcat (AWC) cloned embryos reconstructed with AWC fibroblast donor cells from different passages (AWC-NT). Fibroblast cells were cultured to passages 1 (P1), 3 (P3), 4 (P4), and 9 (P9), after which cells at each passage were karyotyped and serum-starved before being frozen for nuclear transfer. AWC-NT embryos were produced by fusion of a single AWC somatic cell at P1, P3, P4, or P9 to enucleated domestic cat cytoplast derived from in vitro matured (IVU) oocytes. DSH-IVF embryos were produced after IVU oocytes were fertilized in vitro with domestic cat spermatozoa. To determine chromosome numbers, embryos (2-4-cell) or fibroblast cells were cultured in medium containing 0.28 microg/mL of Colcemid for 22-24 h or 15-24 h, respectively. Subsequently, embryos and cells were placed in hypotonic solution, fixed, and stained for analysis of chromosome spreads by bright field microscopy. Chromosomal abnormalities in AWC fibroblast cells increased progressively during culture in vitro: P1 (43%), P3 (46%), P4 (62%), and P9 (59%). In fibroblast cells, hypoploidy (94/202, 46%) was the major chromosomal abnormality, and it occurred more frequently than hyperploidy (14/202, 7%; p < 0.05). While the percentage of hyperploid cells remained stable during all passages, the proportion of hypoploidy in fibroblast cells increased significantly after P4. The overall incidence of chromosomal abnormalities in AWC-NT embryos at P1 (45%), P3 (60%), and P4 (50%) was similar to that of the fibroblast cells from which they were derived; however, the incidence was higher for embryos reconstructed with donor fibroblasts at P9 (89%). Hypoploidy was the most common chromosomal abnormality observed in either AWC-NT or DSH-IVF embryos. AWCNT embryos reconstructed with donor cells at early passages (P1, P3, and P4) had similar frequencies of chromosomal diploidy, as did DSH-IVF embryos. Accordingly, based on the present results, for NT we are currently using cat donor cells at early passages, when the percentage of cells with chromosomal abnormalities is low. It is recommended that the chromosomal stability of each cell line be analyzed before use as NT donor cells to reduce the incidence of chromosomal anomalies in reconstructed embryos and to possibly produce a subsequent increase in cloning efficiency.

Aneuploidy↗
PubMed2005

Divalent ion-dependent swelling of tomato bushy stunt virus: a multi-approach study.

Time-resolved small-angle X-ray and neutron scattering (SAXS and SANS) in solution were used to study the swelling reaction of TBSV upon chelation of its constituent calcium at mildly basic pH. SAXS intensities comprise contribution from the protein capsid and the RNA moiety, while neutron scattering, recorded in 72% D2O, is essentially due to the protein capsid. Cryo-electron micrographs of compact and swollen virus were used to produce 3D reconstructions of the initial and final conformations of the virus at a resolution of 13 A and 19 A, respectively. While compact particles appear to be very homogeneous in size, solutions of swollen particles exhibit some size heterogeneity. A procedure has been developed to compute the SAXS pattern from the 3D reconstruction for comparison with experimental data. Cryo-electron microscopy thereby provides an invaluable starting (and ending) point for the analysis of the time-resolved swelling process using the scattering data.

Cations, Divalent↗
PubMed2004

Spontaneous chromosome doubling results from nuclear fusion during in vitro maize induced microspore embryogenesis.

A multidisciplinary study was carried out to analyse the chromosome doubling process during the early stages of in vitro maize microspore embryogenesis. The main stages (microspore derivatives) that were formed in the course of the culture were analysed. Chromosome number was determined from squashed cells, and DNA content was measured by cytometry. In parallel, an ultrastructural analysis of the microspore derivatives demonstrated the occurrence of a nuclear fusion process. It seems likely that nuclear fusion ensures chromosome doubling at early stages of induced microspore embryogenesis. It occurs precisely at the 5/7 day stage in the embryonic domain and probably leads to polyploidy in the endosperm domain of the microspore derivatives. As a conclusion a scheme summarises the results and proposes an interpretation of the sequence of chromosome doubling events during early maize microspore embryogenesis. Understanding of this process will be important for future efforts to increase the percentage of homozygous plants for crop improvement.

Cell Fusion↗
PubMed2003

Resting energy expenditure and substrate utilisation rate in children with constitutional leanness or obesity.

BACKGROUND & AIM: The influence of energy expenditure on body weight regulation, in the absence of organic disease, has never been studied in a paediatric population covering a broad range of body weights. The aim of this study was to investigate resting energy metabolism in children with constitutional leanness, normal body weight, or common obesity. METHODS: Fourteen children with constitutional leanness, 16 children with obesity, and controls were studied. Resting energy expenditure and postabsorptive substrate utilisation rate were measured by indirect calorimetry and body composition was assessed from skinfold thicknesses. RESULTS: As compared to the predicted value calculated from the regression equation of resting energy expenditure on fat-free mass in the controls, resting energy expenditure was decreased in lean children (P=0.002), whereas no difference was found in obese children. In obese children and the overall population, fat mass was positively correlated with fat oxidation rate. In each group and in the overall population, fat oxidation rate was positively correlated to resting energy expenditure. CONCLUSIONS: Constitutionally lean children have a low resting metabolic rate, probably adaptive in nature. In obese children, resting energy expenditure is increased in proportion to the fat-free mass, and fat balance is the main determinant of energy balance. These data suggest a constitutional regulation of body weight.

Adipose Tissue↗
PubMed2001

Structure of rat parvalbumin with deleted AB domain: implications for the evolution of EF hand calcium-binding proteins and possible physiological relevance.

Among the EF-hand Ca(2+)-binding proteins, parvalbumin (PV) and calbindin D9k (CaB) have the function of Ca(2+) buffers. They evolved from an ancestor protein through two phylogenetic pathways, keeping one pair of EF-hands. They differ by the extra helix-loop-helix (AB domain) found in PV and by the linker between the binding sites. To investigate whether the deletion of AB in PV restores a CaB-like structure, we prepared and solved the structure of the truncated rat PV (PVratDelta37) by X-ray and NMR. PVratDelta37 keeps the PV fold, but is more compact, having a well-structured linker, which differs remarkably from CaB. PvratDelta37 has no stable apo-form, has lower affinity for Ca(2+) than full-length PV, and does not bind Mg(2+), in contrast to CaB. Structural differences of the hydrophobic core are partially responsible for lowering the calcium-binding affinity of the truncated protein. It can be concluded that the AB domain, like the linker of CaB, plays a role in structural stabilization. The AB domain of PV protects the hydrophobic core, and is required to maintain high affinity for divalent cation binding. Therefore, the AB domain possibly modulates PV buffer function.

Amino Acid Sequence↗
PubMed2001

Expression, purification, crystallization and preliminary X-ray analysis of the cathelicidin motif of the protegrin-3 precursor.

Numerous precursors of antibacterial peptides with unrelated sequences share a similar prosequence which belongs to the cathelicidin family of proteins. The three-dimensional structure of this cathelicidin motif, which contains two disulfide bonds, has not yet been reported. The cathelicidin motif (ProS) of the protegrin-3 precursor was overexpressed in Escherichia coli as a His-tagged protein. The His(6) tag was removed by thrombin cleavage. ProS was purified to homogeneity and single crystals were obtained by the hanging-drop vapour-diffusion method at pH 3-4. Preliminary X-ray diffraction analysis indicated that these crystals belong to the hexagonal space group P6(1)22 or P6(5)22, with unit-cell parameters a = b = 51.42, c = 134.25 A. These crystals diffracted beyond 2.75 A (1.9 A at ESRF) and contain one molecule per asymmetric unit.

Amino Acid Motifs↗
PubMed2001

Derivatization of glucose and 2-deoxyglucose for transition metal complexation: substitution reactions with organometallic 99mTc and Re precursors and fundamental NMR investigations.

Synthetic strategies for the bifunctionalization of glucose and 2-deoxyglucose at position C-1 for transition metal coordination are reported. In particular organometallic technetium and rhenium complexes for potential use in diagnostic nuclear medicine were synthesized and investigated. Specifically, a common iminodiacetic acid (IDA) moiety was O-glycosidically connected through an ethylene spacer group to produce the pure alpha- (in case of 2-deoxyglucose) and beta-anomer (in case of glucose). Reaction of the sugar derivatives with the organometallic precursor [M(H2O)3(CO)3]+ (M = 99mTc, Re) produced single products in high yield, which are water-soluble and water-stable. The displacement of the three water molecules of the metal precursor and thus the tridentate coordination of the metal-tricarbonyl core exclusively via the amine and the two carboxylic acid functionalities of the IDA chelate was verified by means of 1D and 2D 1H NMR spectroscopy, mass spectrometry, and IR spectroscopy. The radioactive-labeled products (99mTc) proved their excellent stability in vitro in physiological phosphate buffer (pH = 7.4) and human plasma over a period of 24 h at 37 degrees C.

Deoxyglucose↗
PubMed2001

The S-locus receptor kinase is inhibited by thioredoxins and activated by pollen coat proteins.

The self-incompatibility response in Brassica allows recognition and rejection of self-pollen by the stigmatic papillae. The transmembrane S-locus receptor kinase (SRK), a member of the receptor-like kinase superfamily in plants, mediates recognition of self-pollen on the female side, whereas the S-locus cysteine-rich protein (SCR) is the male component of the self-incompatibility response. SCR is presumably located in the pollen coat, and is thought to be the SRK ligand. Although many receptor-like kinases have been isolated in plants, the mechanisms of signal transduction mediated by these molecules remain largely unknown. Here we show that SRK is phosphorylated in vivo within one hour of self-pollination. We also show that, in vitro, autophosphorylation of SRK is prevented by the stigma thioredoxin THL1 in the absence of a ligand. This inhibition is released in a haplotype-specific manner by the addition of pollen coat proteins. Our data indicate that SRK is inhibited by thioredoxins and activated by pollen coat proteins.

Brassica↗
PubMed2001

MOMP, a divergent porin from Campylobacter: cloning and primary structural characterization.

We report a structural analysis at the molecular level of MOMP from Campylobacter, a gram-negative bacteria responsible for diarrhea. The corresponding gene was cloned and sequenced. Sequence comparison of seven MOMP sequences (three extracted from protein databases and four determined in this study) from distinct strains indicated alternation of preserved and divergent regions. No other significant sequence similarities could be detected. Comparison of MOMP with the crystal structures of other porins strongly suggested that it might adopt a similar fold and revealed the conservation of the monomer-monomer interface. The conservation clustered in the regions comprising or interacting with the loop L2. On the contrary, strands not involved in the interface are more divergent. Proteolysis assays and biochemical treatment supported the proposed model. Our study suggested that MOMP belong to the maltoporin super-family sharing common structural motifs. In view of this model we discuss its specificity and its global stability.

Amino Acid Sequence↗
PubMed2001

Molecular characterisation of two novel maize LRR receptor-like kinases, which belong to the SERK gene family.

Genes encoding two novel members of the leucine-rich repeat receptor-like kinase (LRR-RLK) superfamily have been isolated from maize (Zea mays L.). These genes have been named ZmSERK1 and ZmSERK2 since features such as a putative leucine zipper (ZIP) and five leucine rich repeats in the extracellular domain, a proline-rich region (SPP) just upstream of the transmembrane domain and a C-terminal extension (C) after the kinase domain identify them as members of the SERK (somatic embryogenesis receptor-like kinase) family. ZmSERK1 and ZmSERK2 are single-copy genes and show 79% identity among each other in their nucleotide sequences. They share a conserved intron/exon structure with other members of the SERK family. In the maize genome, ZmSERK1 maps to position 76.9 on chromosome arm 10L and ZmSERK2 to position 143.5 on chromosome arm 5L, in regions generally not involved in duplications. ZmSERK1 is preferentially expressed in male and female reproductive tissues with strongest expression in microspores. In contrast, ZmSERK2 expression is relatively uniform in all tissues investigated. Both genes are expressed in embryogenic and non-embryogenic callus cultures.

Amino Acid Sequence↗
PubMed2001

[Reproduction and development in flowering plants].

Why mark the centenary of the independent discovery of double fertilization by Sergius Nawashin (1898) and Léon Guignard (1899), when biology has progressed so much since the beginning of the XXth century? This discovery still constitutes one of the key references in plant biology: double fertilization is unique to flowering plants among all living organisms. This meeting is also the occasion to associate angiosperm fertilization with developmental biology because of the localization of this event in the flower. Very important and significant progress has been made in elucidating flower development during the last ten years. And today it is possible to understand the diversity of floral structure present in the angiosperms in the context of a underlying mechanism of flower development inherited from their common ancestor. This special issue also allows a survey of these two broad scientific fields, plant reproduction and plant development (flower and embryo). It might also attract new, talented young scientists.

Botany↗
PubMed2001

Two large Arabidopsis thaliana gene families are homologous to the Brassica gene superfamily that encodes pollen coat proteins and the male component of the self-incompatibility response.

The male component of the self-incompatibility response in Brassica has recently been shown to be encoded by the S locus cysteine-rich gene (SCR). SCR is related, at the sequence level, to the pollen coat protein (PCP) gene family whose members encode small, cysteine-rich proteins located in the proteo-lipidic surface layer (tryphine) of Brassica pollen grains. Here we show that the Arabidopsis genome includes two large gene families with homology to SCR and to the PCP gene family, respectively. These genes are poorly predicted by gene-identification algorithms and, with few exceptions, have been missed in previous annotations. Based on sequence comparison and an analysis of the expression patterns of several members of each family, we discuss the possible functions of these genes. In particular, we consider the possibility that SCR-related genes in Arabidopsis may encode ligands for the S gene family of receptor-like kinases in this species.

Alleles↗
PubMed2001

Differential contribution of cytoplasmic Ca2+ and Ca2+ influx to gamete fusion and egg activation in maize.

In multicellular organisms, gamete fusion triggers a set of events, collectively known as egg activation, that leads to the development of a new individual. Every species that has been studied shows at least one rise in cytoplasmic Ca2+ concentration ([Ca2+]Cyt) after gamete fusion which is believed to be involved in activation. Yet the source and regulation of this Ca2+ signal and the way it is transduced inside the zygote are controversial. In higher plants, in vitro fertilization (IVF) has enabled the description of a rise in [Ca2+]Cyt (ref. 4) that is sufficient for activation, and of a Ca2+ influx that spreads as a wavefront from the fusion site The relationship between these two responses is unknown. Using a new combination of methods that simultaneously monitor the extracellular flux with a Ca2+-vibrating probe, and [Ca2+]Cyt by widefield imaging, we directly determined that the Ca2+ influx precedes the [Ca2+]Cyt elevation by 40-120 s. In addition, results from experiments using the Ca2+-channel inhibitor gadolinium (Gd3+) suggest that the Ca2+ influx may be necessary for sperm incorporation. We also present evidence for a putative sperm-dependent Gd3+-insensitive localized Ca2+ influx confined to the fusion point.

Calcium Channel Blockers↗
PubMed2001

Intrahaplotype polymorphism at the Brassica S locus.

The S locus receptor kinase and the S locus glycoproteins are encoded by genes located at the S locus, which controls the self-incompatibility response in Brassica. In class II self-incompatibility haplotypes, S locus glycoproteins can be encoded by two different genes, SLGA and SLGB. In this study, we analyzed the sequences of these genes in several independently isolated plants, all of which carry the same S haplotype (S(2)). Two groups of S(2) haplotypes could be distinguished depending on whether SRK was associated with SLGA or SLGB. Surprisingly, SRK alleles from the two groups could be distinguished at the sequence level, suggesting that recombination rarely occurs between haplotypes of the two groups. An analysis of the distribution of polymorphisms along the S domain of SRK showed that hypervariable domains I and II tend to be conserved within haplotypes but to be highly variable between haplotypes. This is consistent with these domains playing a role in the determination of haplotype specificity.

Base Sequence↗