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F Maillet

Publications and source records attributed to F Maillet.

At least 19 recordsLinked to original sources
PubMed2006

Late ureteral stenosis following renal transplantation: risk factors and impact on patient and graft survival.

The aim of this retrospective study of a cohort of 1787 consecutive kidney transplantations was to analyze the risk factors associated with the occurrence of ureteral stenosis and the impact of ureteral stenosis on graft and patient survival. Between January 1990 and December 2002, 1787 renal transplantations were performed at our center. Only stenosis observed after the first month, were considered. Among the parameters studied were: donor age and serum creatinine before procurement; recipient age, cold ischemia time, delayed graft function (DGF), number of arteries and the presence of a double J stent. The follow-up parameters were the number and timing of acute rejection episodes, cytomegalovirus (CMV) infection, acute pyelonephritis, renal function and death. Ureteral stenosis occurred in 4.1% of patients and was correlated with donor age > 65 years (p = 0.001), kidneys with more than 2 arteries (p = 0.009) and DGF (p = 0.016). Ureteral stenosis did not affect 10-year patient and graft survival rates, which were respectively 90% and 64% for the stenosis group, 86% and 63% for the no-stenosis group (p = NS). These data suggest an important role for donor age, number of renal arteries and DGF for the occurrence of ureteral stenosis following renal transplantation.

Adult↗
PubMed2001

The HCL gene of Medicago truncatula controls Rhizobium-induced root hair curling.

The symbiotic infection of the model legume Medicago truncatula by Sinorhizobium meliloti involves marked root hair curling, a stage where entrapment of the microsymbiont occurs in a chamber from which infection thread formation is initiated within the root hair. We have genetically dissected these early symbiotic interactions using both plant and rhizobial mutants and have identified a M. truncatula gene, HCL, which controls root hair curling. S. meliloti Nod factors, which are required for the infection process, induced wild-type epidermal nodulin gene expression and root hair deformation in hcl mutants, while Nod factor induction of cortical cell division foci was reduced compared to wild-type plants. Studies of the position of nuclei and of the microtubule cytoskeleton network of hcl mutants revealed that root hair, as well as cortical cells, were activated in response to S. meliloti. However, the asymmetric microtubule network that is typical of curled root hairs, did not form in the mutants, and activated cortical cells did not become polarised and did not exhibit the microtubular cytoplasmic bridges characteristic of the pre-infection threads induced by rhizobia in M. truncatula. These data suggest that hcl mutations alter the formation of signalling centres that normally provide positional information for the reorganisation of the microtubular cytoskeleton in epidermal and cortical cells.

Acetyltransferases↗
PubMed2000

Four genes of Medicago truncatula controlling components of a nod factor transduction pathway.

Rhizobium nodulation (Nod) factors are lipo-chitooligosaccharides that act as symbiotic signals, eliciting several key developmental responses in the roots of legume hosts. Using nodulation-defective mutants of Medicago truncatula, we have started to dissect the genetic control of Nod factor transduction. Mutants in four genes (DMI1, DMI2, DMI3, and NSP) were pleiotropically affected in Nod factor responses, indicating that these genes are required for a Nod factor-activated signal transduction pathway that leads to symbiotic responses such as root hair deformations, expressions of nodulin genes, and cortical cell divisions. Mutant analysis also provides evidence that Nod factors have a dual effect on the growth of root hair: inhibition of endogenous (plant) tip growth, and elicitation of a novel tip growth dependent on (bacterial) Nod factors. dmi1, dmi2, and dmi3 mutants are also unable to establish a symbiotic association with endomycorrhizal fungi, indicating that there are at least three common steps to nodulation and endomycorrhization in M. truncatula and providing further evidence for a common signaling pathway between nodulation and mycorrhization.

Gene Expression Regulation, Plant↗
PubMed2000

[Phase II trial evaluating the effect of megestrol acetate-prednisolone combination in the treatment of anorexia during the palliative-care phase of lung cancer].

OBJECTIVES: Anorexia is one of the most frequent complaints in patients who have reached the palliative-care phase of lung cancer. Megestrol acetate (or medroxyprogesterone acetate) and corticosteroids have been used with success, but the effect of their combination remains unknown. We conducted a phase II trial to assess the impact of combination therapy. PATIENTS AND METHODS: Patients with lung cancer given palliative care and who developed anorexia with or without weight loss were given 320 mg/d megestrol acetate in 2 doses and 40 mg/d prednisolone in one dose in the morning for 1 month. The principal outcome criterion was anorexia assessed on a visual analog scale prior to treatment and then at day 15 and day 30. Variation in daily calorie intake and weight were also recorded. We used an Armitage sequential plan to determine the number of inclusions necessary and the preference method (closed schema) to evaluate the principal outcome criterion. RESULTS: Inclusions were stopped after the eighth patient (giving p<0.05) as we observed a significant improvement in patient appetite. Daily calorie intake improved significantly (p<0.0001), by 39.18% the first 15 days and 16.57% more the next 15 days. Body weight improved significantly by 5.4% in one month (p=0.5). No treatment-related complication occurred during the study period or during the six consecutive months. CONCLUSIONS: The megestrol acetate-prednisolone combination was found to improve anorexia in patients with lung cancer in the palliative-care phase and allowed a significant improvement in calorie intake and body weight.

Adult↗
PubMed1999

Structure of the Mesorhizobium huakuii and Rhizobium galegae Nod factors: a cluster of phylogenetically related legumes are nodulated by rhizobia producing Nod factors with alpha,beta-unsaturated N-acyl substitutions.

Rhizobia are symbiotic bacteria that synthesize lipochitooligosaccharide Nod factors (NFs), which act as signal molecules in the nodulation of specific legume hosts. Based on the structure of their N-acyl chain, NFs can be classified into two categories: (i) those that are acylated with fatty acids from the general lipid metabolism; and (ii) those (= alphaU-NFs) that are acylated by specific alpha,beta-unsaturated fatty acids (containing carbonyl-conjugated unsaturation(s)). Previous work has described how rhizobia that nodulate legumes of the Trifolieae and Vicieae tribes produce alphaU-NFs. Here, we have studied the structure of NFs from two rhizobial species that nodulate important genera of the Galegeae tribe, related to Trifolieae and Vicieae. Three strains of Mesorhizobium huakuii, symbionts of Astragalus sinicus, produced as major NFs, pentameric lipochitooligosaccharides O-sulphated and partially N-glycolylated at the reducing end and N-acylated, at the non-reducing end, by a C18:4 fatty acid. Two strains of Rhizobium galegae, symbionts of Galega sp., produced as major NFs, tetrameric O-carbamoylated NFs that could be O-acetylated on the glucosamine residue next to the non-reducing terminal glucosamine and were N-acylated by C18 and C20 alpha,beta-unsaturated fatty acids. These results suggest that legumes nodulated by rhizobia synthesizing alphaU-NFs constitute a phylogenetic cluster in the Galegoid phylum.

Acylation↗
PubMed1999

Expression of CD21 is developmentally regulated during thymic maturation of human T lymphocytes.

CD21, the C3d/CD23/Epstein-Barr virus (EBV), receptor is expressed at low density on cells of the T lineage. Immature thymocytes express CD21 with high density. In the present study, we have analyzed the expression of CD21 during intrathymic maturation of T cells. An intense staining for CD21 was observed at the double-negative stage and at the stage of early acquisition of CD4. CD21 expression was decreased at the double-positive and single-positive stages, to then reach levels similar to those of peripheral blood T cells. Staining of thymus sections showed a bright fluorescent signal on thymocytes entering the thymus in the cortical region. Taking advantage of the immature phenotype of cells expressing high amounts of CD21 (CD21(++)), we depleted thymocyte suspensions in CD3(+) and CD8(+) cells to study the properties of CD21 on this cell subset. Triggering of CD21 with its ligands iC3b, CD23 and anti-CD21 mAb did not alter the proliferative response of thymocytes to IL-7, and did not induce the differentiation of early cells into CD4(+)CD8(+) thymocytes. Immunoprecipitation did not reveal any molecule associated with CD21 that could play a signaling role in thymocytes. Finally, EBV induced a down-regulation of CD21 and an up-regulation of CD1 in CD21(++) thymocytes. Taken together, our observations demonstrate a regulated expression of CD21 on human thymocytes and suggest that the CD21(++) subset may be a target for EBV. We further suggest that CD21 on early thymocytes acts as a ligand for CD23-expressing cells in the thymus.

Cell Differentiation↗
PubMed1999

Nodule-inducing activity of synthetic Sinorhizobium meliloti nodulation factors and related lipo-chitooligosaccharides on alfalfa. Importance of the acyl chain structure.

Sinorhizobium meliloti nodulation factors (NFs) elicit a number of symbiotic responses in alfalfa (Medicago sativa) roots. Using a semiquantitative nodulation assay, we have shown that chemically synthesized NFs trigger nodule formation in the same range of concentrations (down to 10(-10) M) as natural NFs. The absence of O-sulfate or O-acetate substitutions resulted in a decrease in morphogenic activity of more than 100-fold and approximately 10-fold, respectively. To address the question of the influence of the structure of the N-acyl chain, we synthesized a series of sulfated tetrameric lipo-chitooligosaccharides (LCOs) having fatty acids of different lengths and with unsaturations either conjugated to the carbonyl group (2E) or located in the middle of the chain (9Z). A nonacylated, sulfated chitin tetramer was unable to elicit nodule formation. Acylation with short (C8) chains rendered the LCO active at 10(-7) M. The optimal chain length was C16, with the C16-LCO being more than 10-fold more active than the C12- and C18-LCOs. Unsaturations were important, and the diunsaturated 2E,9Z LCO was more active than the monounsaturated LCOs. We discuss different hypotheses for the role of the acyl chain in NF perception.

Carbohydrate Sequence↗
PubMed1998

Genetic complementation of rhizobial nod mutants with Frankia DNA: artifact or reality?

Two divergent reports have been published on the genetic complementation of rhizobial nod mutants using Frankia DNA. In 1991 putative Frankia cosmid library clones were reported to restore normal nodulation properties to Rhizobium leguminosarum biovar viciae nodD::Tn5, but no supporting sequence data were published. In 1992 a second group reported a failure to find any evidence of functional complementation of various rhizobial nod mutants by Frankia DNA (nodA, nodB and nodC). Complementation tests of nine NodR. leguminosarum bv. viciae or Sinorhizobium meliloti Tn5 mutants (nodA-, nodB-, nodC-, nodD-, nodF-, nodL-, nodH-) were thus performed using a Frankia gene library in pLAFR3 to clarify this situation. Rhizobial transconjugants obtained by tri-parental matings were screened for restoration of the nodulation phenotype on their host plants, Vicia sativa subsp. nigra or Medicago sativa. Nodulation was observed on plants inoculated with transconjugants of the R. leguminosarum bv. viciae nodC::Tn5 mutant. The Nod+ rhizobial transconjugants were isolated and analysed. The Nod+ phenotype of these transconjugants was found to be due to Tn5 excision/transposition. No functional complementation was found with any of the mutants used, suggesting that rhizobial complementation of nod mutants with Frankia DNA is unlikely to occur.

Actinomycetales↗
PubMed1997

New anionic polyelectrolyte hydrogel for corneal surgery.

A new high-water-content (78%) anionic polyelectrolyte hydrogel was obtained by phase inversion (demixion) of a polymer solution containing 9.0% poly(acrylonitrile sodium methallylsulphonate), 85.0% dimethylformamide, and 6.0% saline solution (0.9% NaCl). The hydrogel is permeable to water, saline, urea, creatinine, glucose, human albumin, and saline-dissolved oxygen. Investigation of the interactions between human serum and surfaces prepared with the new yielded hydrogel, compared to serum interaction with silica-free silicone (RTV), regenerated cellulose (Cuprophan), MMA/PVP copolymer (Lidofilcon), PMMA (Perspex), FIFE (Gore-Tex), and poly(acrylonitrile sodium methallylsulphonate) hemodialysis membrane (AN-69), showed the hydrogel and hemodialysis membrane (both prepared with AN-69 copolymer) to be the only materials devoid of complement (C')-activating ability.

Biocompatible Materials↗
PubMed1996

The common nodABC genes of Rhizobium meliloti are host-range determinants.

Symbiotic bacteria of the genus Rhizobium synthesize lipo-chitooligosaccharides, called Nod factors (NFs), which act as morphogenic signal molecules on legume hosts. The common nodABC genes, present in all Rhizobium species, are required for the synthesis of the core structure of NFs. NodC is an N-acetylglucosaminyltransferase, and NodB is a chitooligosaccharide deacetylase; NodA is involved in N-acylation of the aminosugar backbone. Specific nod genes are involved in diverse NF substitutions that confer plant specificity. We transferred to R. tropici, a broad host-range tropical symbiont, the ability to nodulate alfalfa, by introducing nod genes of R. meliloti. In addition to the specific nodL and nodFE genes, the common nodABC genes of R. meliloti were required for infection and nodulation of alfalfa. Purified NFs of the R. tropici hybrid strain, which contained chitin tetramers and were partly N-acylated with unsaturated C16 fatty acids, were able to elicit nodule formation on alfalfa. Inactivation of the R. meliloti nodABC genes suppressed the ability of the NFs to nodulate alfalfa. Studies of NFs from nodA, nodB, nodC, and nodI mutants indicate that (i) NodA of R. meliloti, in contrast to NodA of R. tropici, is able to transfer unsaturated C16 fatty acids onto the chitin backbone and (ii) NodC of R. meliloti specifies the synthesis of chitin tetramers. These results show that allelic variation of the common nodABC genes is a genetic mechanism that plays an important role in signaling variation and in the control of host range.

Acylation↗
PubMed1996

Human lymphocytes shed a soluble form of CD21 (the C3dg/Epstein-Barr virus receptor, CR2) that binds iC3b and CD23.

We report on a soluble (s) form of CD21 (the C3dg/Epstein-Barr virus receptor, CR2) that is spontaneously released by B and T lymphocytes. Immunoprecipitation with anti-CD21 mAb of culture supernatants of surface and biosynthetically labeled B and T cell lines revealed a single band with an apparent molecular mass of 135 kDa. The molecule exhibited a molecular mass 10 kDa lower than that of membrane CD21. The release of soluble CD21 (sCD21) was time dependent and correlated with a parallel decrease in the expression of the membrane-associated molecule. The protein was also found in culture supernatants of tonsillar B cells and normal human thymocytes. Epitopic analysis using combinations of anti-CD21 monoclonal antibodies (mAb) indicated that sCD21 and membrane CD21 were similarly recognized by mAb directed against short consensus repeats (SCR) 1-2, SCR 4-5 and SCR 9-11. Affinity-purified sCD21 was capable of binding to purified human iC3b and to human recombinant CD23, as assessed by enzyme-linked immunosorbent assay and by using the BIAcore technology. In addition, normal human serum was found to contain a soluble form of CD21 that exhibited a similar molecular mass to that of the molecule shed by B and T cells in culture. The serum form of CD21 was recognized by all anti-CD21 mAb that we tested and showed a high reactivity with mAb directed against SCR 1-2. Our observations suggest that B and T cells shed the extracellular portion of CD21 and release a soluble molecule that retains the ligand-binding properties of CD21, thus having a potential role in immunoregulation.

B-Lymphocytes↗
PubMed1995

Rhizobium tropici nodulation factor sulfation is limited by the quantity of activated form of sulfate.

Rhizobium tropici is a broad host-range symbiont of Phaseolus vulgaris. This bacterium produces a mixture of sulfated and non-sulfated N-methylated pentameric nodulation (Nod) factors. To understand the genetic bases of the partial sulfation of R. tropici Nod factors, which might be involved in the broad host-range of this species, we introduced in R. tropici CFN299 the recombinant plasmid pGMI515 carrying a set of nodulation (nod) genes of R. meliloti, including those involved in the sulfation of R. meliloti Nod factors. The CFN299 (pGMI515) transconjugant produced only sulfated Nod factors, but approximately half of them were no more N-methylated. Mutations in R. meliloti nodH gene did not decrease the Nod factor sulfation whereas inactivation of the nodPQ genes restored the production of a mixture of sulfated and non-sulfated molecules. These results suggest that the limiting step in R. tropici Nod factor sulfation is the production of activated sulfate donors. Mutations in the R. meliloti nodFEG and nodH genes did not change the N-methylation pattern, whereas mutations in nodPQ increased the degree of N-methylation, suggesting a metabolic link between sulfation and methylation of R. tropici Nod factors.

Carbohydrate Sequence↗
PubMed1995

Effect of substituted dextran derivative on complement activation in vivo.

A soluble dextran derivatized with carboxylic groups (73%) and benzylamide sulphonate groups (15%), termed CMDBS 25, exhibited significant anticomplementary activity in the absence of anticoagulant activity. The polysaccharide inhibited both classical and alternative pathway-dependent complement activation in human and rat serum in vitro. Simultaneous administration of CMDBS 25 (100 mg) and crushed Sephadex G25 (20 mg) into normal Lewis rats suppressed systematic complement consumption that was induced by Sephadex in the animals by 98% for 1 h. Two consecutive injections of 100 mg of CMDBS at 1 h interval resulted in total suppression of systemic complement activation for 2 h and in 50% suppression for an additional 2 h. Infusion of CMDBS alone was well tolerated and had no effect on CH50 in serum in vivo. Our results demonstrate that CMDBS 25 exhibits anticomplementary properties in vivo and suggest that the polymer represents a potential therapeutic agent for pathological conditions associated with complement activation.

Animals↗
PubMed1995

In Rhizobium meliloti, the operon associated with the nod box n5 comprises nodL, noeA and noeB, three host-range genes specifically required for the nodulation of particular Medicago species.

In Rhizobium meliloti, the genes required for nodulation of legume hosts are under the control of DNA regulatory sequences called nod boxes. In this paper, we have characterized three host-specific nodulation genes, which form a flavonoid-inducible operon down-stream of the nod box n5. The first gene of this operon is identical to the nodL gene identified by Baev and Kondorosi (1992) in R. meliloti strain AK631. The product of the second gene, NoeA, presents some homology with a methyltransferase. nodL mutants synthesize Nod factors lacking the O-acetate substituent. In contrast, in strains carrying a mutation in either noeA or noeB, no modification in Nod-factor structure or production could be detected. On particular hosts, such as Medicago littoralis, mutants of the n5 operon showed a very weak nodule-forming ability, associated with a drastic decrease in the number of infection threads, while nodulation of Medicago truncatula or Melilotus alba was not affected. Thus, nodL noeA and noeB are host-specific nodulation genes. By using a gain-of-function approach, we showed that the presence of nodL, and hence of O-acetylated Nod factors, is a major prerequisite for confering the ability to nodulate alfalfa upon the heterologous bacterium Rhizobium tropici.

Acetylation↗
PubMed1994

The Rhizobium meliloti regulatory nodD3 and syrM genes control the synthesis of a particular class of nodulation factors N-acylated by (omega-1)-hydroxylated fatty acids.

Rhizobia elicit the formation of nitrogen-fixing nodules on specific legume hosts. Rhizobium meliloti nodulation (nod) genes control a signal exchange between the two symbiotic partners during infection and the early steps of nodulation. The regulatory nodD1, nodD2 and nodD3 genes are involved in the specific perception of different plant and environmental signals and activate the transcription of the nod operons. Once activated, the structural nod genes specify the synthesis of diffusible lipo-oligosaccharides, the Nod factors, which signal back to the plant. R. meliloti Nod factors are sulfated chito-oligosaccharides which are mono-N-acylated by unsaturated C16 fatty acids or by a series of C18 to C26 (omega-1)-hydroxylated fatty acids. In this paper we show that the regulatory nodD3 gene and another symbiotic regulatory gene, syrM, which mediate bacterial responses to plant signals that differ from those involving nodD1 and nodD2, determine the synthesis of Nod factors with different acyl moieties. nodD3 and syrM are required for the synthesis of Nod factors N-acylated by the (omega-1)-hydroxylated fatty acids. This regulatory mechanism makes possible the qualitative adaptation of bacterial Nod signal production to plant signals in the course of the symbiotic process.

Acylation↗