Biomedical subjects

H Dauchel

Publications and source records attributed to H Dauchel.

8 recordsLinked to original sources

PubMed2003

FORRepeats: detects repeats on entire chromosomes and between genomes.

MOTIVATION: As more and more whole genomes are available, there is a need for new methods to compare large sequences and transfer biological knowledge from annotated genomes to related new ones. BLAST is not suitable to compare multimegabase DNA sequences. MegaBLAST is designed to compare closely related large sequences. Some tools to detect repeats in large sequences have already been developed such as MUMmer or REPuter. They also have time or space restrictions. Moreover, in terms of applications, REPuter only computes repeats and MUMmer works better with related genomes. RESULTS: We present a heuristic method, named FORRepeats, which is based on a novel data structure called factor oracle. In the first step it detects exact repeats in large sequences. Then, in the second step, it computes approximate repeats and performs pairwise comparison. We compared its computational characteristics with BLAST and REPuter. Results demonstrate that it is fast and space economical. We show FORRepeats ability to perform intra-genomic comparison and to detect repeated DNA sequences in the complete genome of the model plant Arabidopsis thaliana.

Algorithms↗

PubMed2001

Isolation of a flax pectin methylesterase promoter and its expression in transgenic tobacco.

Pectin methylesterases (PME) catalyze the de-esterification of methoxylated pectins in plant cell walls. We have isolated a 1.9 kb regulatory region upstream from the Lupme3 coding sequence of Linum usitatissimum L. (flax) using a 'Polymerase Chain Reaction (PCR) walking' strategy. Two 5' truncated deletion fragments (1.5 and 0.44 kb) of this potential promoter sequence were inserted upstream of the gus reporter gene in order to study their expression in transgenic plants. These constructs were transferred into Nicotiana tabacum, a heterologous system using Agrobacterium tumefaciens. Expression of the reporter gene was analyzed in regenerated transgenic plants and calli to study the promoter activities of these sequences. This expression was observed in calli with both constructs. In contrast, expression in organs was only detected in tobacco plants transformed with the largest (1.5 kb) construct. This long fragment triggered expression in roots and immature or vitrified leaves. Expression in both organs was localized in the vasculature, but also detected in the root meristem. These results are the first evidence, to our knowledge, of the spatial and temporal regulation of a specific pme promoter of flax. Localization of Lupme3 promoter activity in vascular tissues of immature organs provides an insight into the role of this PME isoform in cell elongation and differentiation.

Journal Article↗

PubMed1995

Activation of the endothelium by IL-1 alpha and glucocorticoids results in major increase of complement C3 and factor B production and generation of C3a.

Constitutive secretion of complement C3 and factor B by the endothelial cell (EC) is lowered by therapeutic concentrations of glucocorticoids such as hydrocortisone or dexamethasone, whereas regulatory protein factor H production is increased by these hormones. In contrast, the proinflammatory cytokine IL-1 alpha has a stimulatory effect on C3 and factor B secretion by the endothelium and an inhibitory effect on factor H secretion. In this study, we examined the combined effect of IL-1 alpha and glucocorticoids on C3 and factor B expression by the endothelial cell. When dexamethasone or hydrocortisone were added to IL-1 alpha, significant potentialization of IL-1 alpha-induced stimulation of C3 and factor B production was observed, occurring at various concentrations of either stimuli. Dose-response experiments indicate that, in vitro, optimal concentrations are in the range of 10(-7) to 10(-5) M for dexamethasone and 50-200 U for IL-1 alpha. In contrast, dexamethasone counteracts, in an additive way, the inhibitory effect of IL-1 alpha on regulatory complement protein factor H production by EC. Such a potentialization between glucocorticoids and IL-1 alpha was not observed for another marker of endothelial activation, IL-1 alpha-induced stimulation of coagulation tissue factor expression. The association of glucocorticoids and IL-1 alpha therefore appears to be a specific and major stimulus for the secretion of complement C3 and factor B, two acute-phase proteins, by the endothelium. As a result of the in vitro endothelium stimulation by glucocorticoids and IL-1 alpha, C3a is generated in the vicinity of the endothelial cell. This study further suggests that complement activation, with its deleterious consequences, may result from the stimulation of endothelium in situations where high levels of IL-1 alpha and endogenous glucocorticoids coexist, such as in septic shock.

Cells, Cultured↗

PubMed1993

Local and systemic activation of the whole complement cascade in human leukocytoclastic cutaneous vasculitis; C3d,g and terminal complement complex as sensitive markers.

We have studied complement activation both in plasma samples and in lesional skin from patients with leukocytoclastic cutaneous vasculitis (LCV). Enzyme immunoassay (EIA) quantification of the complement activation markers, C3d,g and the terminal complement complex (TCC) in plasma, showed that their levels were significantly increased in 66% and 55% of the patients, respectively (n = 29) compared with healthy controls, whereas the standard measurements of C3, factor B, C1q, C4 and C2 were generally within normal range. Elevations of C3d,g and TCC levels in plasma were significantly correlated. Importantly, a significant correlation was found between the severity of the vasculitis and both C3d,g and TCC plasma levels. Immunofluorescence studies of skin biopsy specimens demonstrated simultaneous presence of perivascular dermal deposits of C3d,g and TCC in lesional skin from 96% and 80% respectively of the patients (n = 25). There was a significant correlation between the intensity of the deposits of both markers. Clusterin, a TCC inhibitory protein, was always found at the same sites of perivascular TCC deposits. Immunofluorescence studies at the epidermal basement membrane zone (BMZ) revealed in each case deposits of C3d,g which were accompanied by TCC deposits in 52% of the biopsy specimens. These data demonstrate that there is a local and systemic activation of the whole complement cascade in human LCV. The presence of both C3d,g and clusterin-associated TCC perivascular deposits suggests an intervention of a regulatory mechanism of local complement activation in LCV. Finally, measurement of plasma C3d,g and TCC appears to be a sensitive indicator of systemic complement activation and disease severity in LCV.

Aged↗

PubMed1992

In vitro biosynthesis of complement factor I by human endothelial cells.

We have studied the secretion of the complement regulatory protein factor I by human umbilical vein endothelial cells (HUVEC). Northern and Western blot analysis and biosynthetic labeling experiments indicate that HUVEC secrete factor I at very low levels in basal conditions and that this secretion is significantly enhanced by interferon-gamma. Analysis of the proteolytic inactivation of C3b by HUVEC supernatants show that factor I is secreted in a functional form and can promote the specific proteolytic inactivation of C3b to iC3b. Together with previous studies establishing the secretion of complement factor H by HUVEC, this work demonstrates that the endothelial cell is able to secrete in its environment two complement regulatory proteins, factor I and factor H, which can mediate the degradation of C3b to iC3b. The secretion of factor I by HUVEC provides a useful in vitro model to analyze the modulation of this secretion and may be relevant to the local deposition of iC3b at the surface of the endothelium during the inflammatory reaction.

Cells, Cultured↗

PubMed1992

Differential modulation by glucocorticoids of alternative complement protein secretion in cells of the monocyte/macrophage lineage.

The effect of the synthetic glucocorticoid dexamethasone (DXM) on the secretion by human monocytes of alternative complement proteins C3, factor B and factor H was investigated. Results indicated that DXM modulates this secretion in a direction which would be consistent with its anti-inflammatory properties. DXM, at therapeutic concentrations, had a suppressive effect on C3 and factor B secretion and a stimulatory effect on factor H secretion by monocytes. This differential modulation on C3, factor B and factor H secretion was similar in mature macrophages. Together with previous studies showing that DXM had a suppressive effect on C3 and factor B secretion and a stimulatory effect on factor H secretion by human endothelial cells, our results indicate that DXM appears to have the general property of regulating local production of complement components so as to control complement activation.

Cell Differentiation↗

PubMed1990

Expression of complement alternative pathway proteins by endothelial cells. Differential regulation by interleukin 1 and glucocorticoids.

We have studied the secretion of proteins of the alternative pathway of complement C3, factor B and factor H by human umbilical vein endothelial cells (HUVEC). Results showed that factor H and factor B are quantitatively secreted in abundance whereas C3 could only be detected when the cells are maintained in culture during long periods of time. Interferon-gamma stimulated factor H, factor B and, to a lesser extent, C3 secretions. Interleukin (IL) 1 had a differential effect on spontaneous C3, factor B and factor H secretions. In the presence of IL 1, there was a significant secretion of C3 occurring within a short period of culture. IL 1 also stimulated factor B secretion. There was a synergistic stimulating effect between IL 1 and interferon-gamma to bring C3 and factor B productions by HUVEC to very high levels. In contrast, factor H secretion was consistently inhibited by IL 1. Local increase in C3 and factor B secretions by endothelial cells in the presence of IL 1 may have important implications in the inflammatory reaction. In striking contrast, the glucocorticoid dexamethasone (DXM) had modulatory effects which are consistent with its anti-inflammatory properties. DXM, at therapeutic concentrations, decreased C3 and factor B secretions and increased factor H secretion. Local modulation of complement protein secretion by DXM appears to be a new mechanism by which this glucocorticoid may control inflammation.

Complement C3b Inactivator Proteins↗

PubMed1990

[Study of the complement system. General principles and perspectives].

Measurement of complement in clinical medicine is traditionally based on the determination of CH50 and immunochemical and/or functional measurement of complement proteins C1q, factor B, C3 and C4. The interpretation of these measurements, as far as complement activation is concerned, can however be difficult as these tests do not allow to discriminate between consumption due to activation, hereditary deficiency, increased rate of synthesis or even hyposynthesis. This explains why their use as markers of evolutivity in diseases where complement activation is occurring has given variable results. New tests for complement activation have been more recently introduced. These are mainly the measurements of the anaphytotoxins, the degradation products of C3 and the membrane attack complex. As these tests reflect more directly complement activation, they may be more reliable markers. The immunochemical and functional measurements of C1-inhibitor are of special interest as they are the tests which allow definitive diagnosis of the hereditary angio-oedema. General principles for the interpretation of the different tests used to evaluate the complement system are presented and discussed.

Anaphylatoxins↗