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F Dumas

Publications and source records attributed to F Dumas.

At least 19 recordsLinked to original sources
PubMed2006

Multidirectional chromosome painting reveals a remarkable syntenic homology between the greater galagos and the slow loris.

We report on the first reciprocal chromosome painting of lorisoids and humans. The chromosome painting showed a remarkable syntenic homology between Otolemur and Nycticebus. Eight derived syntenic associations of human segments are common to both Otolemur and Nycticebus, indicative of a considerable period of common evolution between the greater galago and the slow loris. Five additional Robertsonian translocations form the slow loris karyotype, while the remaining chromosomes are syntenically equivalent, although some differ in terms of centromere position and heterochromatin additions. Strikingly, the breakpoints of the human chromosomes found fragmented in these two species are apparently identical. Only fissions of homologs to human chromosomes 1 and 15 provide significant evidence of a cytogenetic link between Lemuriformes and Lorisiformes. The association of human chromosomes 7/16 in both lorisoids strongly suggests that this chromosome was present in the ancestral primate genome.

Animals↗
PubMed2005

Mapping genomic rearrangements in titi monkeys by chromosome flow sorting and multidirectional in-situ hybridization.

We developed chromosome painting probes for Callicebus pallescens from flow-sorted chromosomes and used multidirectional chromosome painting to investigate the genomic rearrangements in C. cupreus and C. pallescens. Multidirectional painting provides information about chromosomal homologies at the subchromosomal level and rearrangement break points, allowing chromosomes to be used as cladistic markers. Chromosome paints of C. pallescens were hybridized to human metaphases and 43 signals were detected. Then, both human and C. pallescens probes were hybridized to the chromosomes of another titi monkey, C. cupreus. The human chromosome paints detected 45 segments in the haploid karyotype of C. cupreus. We found that all the syntenic associations proposed for the ancestral platyrrhine karyotype are present in C. cupreus and in C. pallescens. The rearrangements differentiating C. pallescens from C. cupreus re one inversion, one fission and three fusions (two tandem and one Robertsonian)that occurred on the C. cupreus lineage. Our results support the hypothesis that karyological evolution in titi monkeys has resulted in reduction in diploid number and that species with higher diploid numbers (with less derived, more ancestral karyotypes)are localized in the centre of the geographic range of the genera, while more derived species appear to occupy the periphery.

Animals↗
PubMed2004

Sewage impact on shellfish microbial contamination.

Coastal areas are frequently contaminated by microorganisms of human origin, due to high population density and low seawater renewal. To evaluate the impact of wastewater input on shellfish quality, a study was conducted in Brittany (France) over a period of 20 months. A hydrodynamic model was used to simulate wastewater impact on microbial water quality. To validate the model, wastewater from the three main sewage treatment plants and shellfish from three sites were sampled monthly. Bacterial indicators (E. coli), F-RNA phages were searched for by culture and noroviruses by RT-PCR and hybridisation. These microorganisms were detected in the three effluents and clams, with no marked seasonal variation. The microbial concentrations in the two oyster beds, distant from the effluent outfall, were low, and only three of the samples were positive for norovirus. For simulation, the winter wastewater inputs of E. coli and phages were calculated and an estimation for norovirus flux was made from the epidemic situation in the population. The microbial behaviour was included in the model by a decay-rate factor. Results from the model calculations were found to be very similar to E. coli and phage concentrations observed in shellfish. For noroviruses, the model indicated that shellfish distant from the wastewater input were under the detection limit of the RT-PCR method. This study demonstrated the use of modelisation to interpret norovirus contamination in various areas.

Animals↗
PubMed2002

Mechanisms of disturbed motor control in ankle weakness during gait after stroke.

This study investigated the role of paresis, excessive antagonist coactivation, increased muscle-tendon passive stiffness and spasticity in the reduced stance phase plantarflexor moment (Mmax) and swing phase dorsiflexion during gait (DFmax) in subjects with a recent (<6 months post-stroke) hemiparesis (patients). The gait pattern of the paretic and non-paretic sides was evaluated in 30 patients (aged 57.8+/-10.8 years), whereas only one side was evaluated in 15 healthy controls (aged 59.1+/-9.8 years) while walking at natural and very slow speeds. Peak plantarflexor moment (Mmax) and peak medial gastrocnemius (MG) activation during the stance phase, as well as peak dorsiflexion angle (Dfmax) and peak tibialis anterior (TA) activation during the swing phase, were retained for analysis. In addition, a coactivation index and a plantarflexor spasticity index were calculated for both the stance and the swing phase, and plantarflexor passive stiffness was evaluated on an isokinetic dynamometer. The results showed that Mmax on the paretic and non-paretic sides were both reduced compared with control values at natural speed. This reduction was combined to a low MG activation (paresis) on the paretic side. On the non-paretic side, the reduced plantarflexor moment was related to excessive coactivation levels. The swing phase Dfmax tended to be reduced (not significantly) on the paretic side of the patients compared with control values. This reduction was neither associated with excessive antagonist coactivation nor to plantarflexor hyperactive stretch reflexes, but rather to an increased plantarflexor passive stiffness. In some of the patients, however, an increased TA activation that overcame the plantarflexor passive stiffness allowed for normal DFmax values. The functional consequences of the disturbed mechanisms of motor control observed in both the paretic and non-paretic sides are discussed.

Adult↗
PubMed2001

An Agrobacterium VirE2 channel for transferred-DNA transport into plant cells.

Transferred DNA (T-DNA) transfer from Agrobacterium tumefaciens into eukaryotic cells is the only known example of interkingdom DNA transfer. T-DNA is a single-stranded segment of Agrobacterium's tumor-inducing plasmid that enters the plant cell as a complex with the bacterial virulence proteins VirD2 and VirE2. The VirE2 protein is highly induced on contact of A. tumefaciens with a plant host and has been reported to act in late steps of transfer. One of its previously demonstrated functions is binding to the single-stranded (ss) T-DNA and protecting it from degradation. Recent experiments suggest other functions of the protein. A combination of planar lipid bilayer experiments, vesicle swelling assays, and DNA transport experiments demonstrated that VirE2 can insert itself into artificial membranes and form channels. These channels are voltage gated, anion selective, and single-stranded DNA-specific and can facilitate the efficient transport of single-stranded DNA through membranes. These experiments demonstrate a VirE2 function as a transmembrane DNA transporter, which could have applications in gene delivery systems.

Agrobacterium tumefaciens↗
PubMed2001

Anticipatory locomotor control for obstacle avoidance in mid-childhood aged children.

The present work explored the anticipatory locomotor adjustments during obstacle avoidance by eight children aged 7--9 years. Analyses involved kinematic, kinetic and muscle mechanical power patterns at each lower limb joint, as well as electromyographic data from five muscles. The children demonstrated adult-like limb displacements and general dynamic strategies for obstacle clearance. However, when normalized to body mass, amplitudes of certain muscle power bursts related to anticipatory locomotor adjustments were decreased from those reported in the literature for adults, and an absence of the usual antagonistic knee extensor power burst at the end of the stance phase was frequently observed. The data suggest that the expression of anticipatory locomotor adjustments is still maturing during mid-childhood.

Adult↗
PubMed2001

Carcinoembryonic gene member 2 mRNA expression as a marker to detect circulating enterocytes in the blood of colorectal cancer patients.

BACKGROUND: The aim of this study was to report our experience with a new molecular tool to detect circulating enterocytes in the blood of patients with colorectal cancer. METHODS: The study included 193 individuals: 78 patients with colorectal cancer and 115 controls composed of patients with benign colorectal diseases (n = 16), patients with noncolorectal cancer (n = 31), healthy individuals (n = 62), and healthy bone marrow transplantation donors (n = 6). A nested reverse transcriptase-polymerase chain reaction with specific primers for the carcinoembryonic gene member 2 (CGM2) was used to detect circulating enterocytes in the peripheral blood of 78 patients with colorectal cancer. The blood (n = 109) or the bone marrow (n = 6) of the 115 controls was studied to test the absence of CGM2 illegitimate transcription in nucleated blood cells and nucleated blood cell progenitors. The assay sensitivity was effective in detecting 1 CGM2-positive cell per 10(6) nucleated blood cells. RESULTS: Fifty-nine percent (46/78) of patients with colorectal cancer were found positive whereas all negative controls remained negative. Positivity rates were 38% (3/8) in Dukes' A classification, 43% (9/21) in Dukes' B, 77% (23/30) in Dukes' C, and 58% (11/19) in Dukes' D. CONCLUSIONS: The clinical significance of enterocyte detection in the blood of colorectal cancer patients by means of this CGM2 messenger RNA assay needs further evaluation.

Adult↗
PubMed2001

Sucrose transport through maltoporin mutants of Escherichia coli.

Maltoporin (LamB) and sucrose porin (ScrY) reside in the bacterial outer membrane and facilitate the passive diffusion of maltodextrins and sucrose, respectively. To gain further insight into the determinants of solute specificity, LamB mutants were designed to allow translocation of sucrose, which hardly translocates through wild-type LamB. Three LamB mutants were studied. (a) Based on sequence and structure alignment of LamB with ScrY, two LamB triple mutants were generated (R109D, Y118D,D121F; R109N,Y118D,D121F) to mimic the ScrY constriction. The crystal structure of the first of these mutants was determined to be 3.2 A and showed an increased ScrY-like cross-section except for D109 that protrudes into the channel. (b) Based on this crystal structure a double mutant was generated by truncation of the two residues that obstruct the channel most in LamB (R109A,Y118A). Analysis of liposome swelling and in vivo sugar uptake demonstrated substantial sucrose permeation through all mutants with the double alanine mutant performing best. The triple mutants did not show a well-defined binding site as indicated by sugar-induced ion current noise analysis, which can be explained by remaining steric interference as deduced from the crystal structure. Binding, however, was observed for the double mutant that had the obstructing residues truncated to alanines.

Alanine↗
PubMed2001

Actin and annexins I and II are among the main endothelial plasmalemma-associated proteins forming early glucose adducts in experimental diabetes.

An immunochemical and biochemical study was performed to reveal which of the endothelial plasma membrane proteins become glycated during the early phases of diabetes. The blood front of the lung microvascular endothelial plasmalemma was purified by the cationic colloidal silica method from normal and diabetic (streptozotocin-induced) rats and comparatively analyzed by two-dimensional electrophoresis. No major qualitative differences in the general spectrum of endothelial plasmalemmal proteins were recorded between normoglycemic and hyperglycemic animals. By probing with anti-glucitollysine antibodies, we found that at 1 month after the onset of diabetes, several endothelial membrane polypeptides contained glucose covalently linked to their lysyl residues. Ten days of insulin treatment restored euglycemia in the diabetic animals and completely abolished the membrane nonenzymatic glycosylation. All the glycated polypeptides of the endothelial plasma membrane belong to the peripheral type and are associated with its cytoplasmic face (cell cortex). They were solubilized by buffers of high pH and were not detected in the lung cytosolic fraction (100,000 g). By microsequencing, the major proteins labeled by the anti-glucitollysine have been identified as being actin, annexin I, annexin II, the p34 subunit of the Arp2/3 complex, and the Ras suppressor protein-1. Conversely, the intrinsic endothelial membrane proteins do not seem to be affected by hyperglycemia. This defines the internal face of the endothelial plasma membrane, particularly the cortical cytoskeleton, as a preferential target for nonenzymatic glycosylation in diabetes, with possible consequences on the fluidity of the endothelial plasmalemma and impairment of the endothelial mechanotransducing ability.

Actins↗
PubMed2000

Extended sugar slide function for the periplasmic coiled coil domain of ScrY.

Several bacterial outer membrane proteins have a periplasmic extension whose structure and function remain elusive. Here, the structure/function relationship of the N-terminal periplasmic domain of the sucrose-specific outer membrane channel ScrY was investigated. Circular dichroism and analytical centrifugation demonstrated that the N-terminal domain formed a parallel, three-stranded coiled coil. When this domain was fused to the maltose-specific channel LamB, permeation of maltooligosaccharides in liposomes increased with increasing sugar chain length whereas wild-type LamB showed the opposite effect. Current fluctuation analysis demonstrated increased off-rates for sugar transport through the fusion protein. Moreover, equilibrium dialysis showed an affinity of sucrose for the isolated N-terminal peptide. Together these results demonstrate a novel function for coiled coil domains, operating as an extended sugar slide.

Alkylation↗
PubMed2000

Sugar transport through maltoporin of Escherichia coli. Role of polar tracks.

The three-dimensional structure of the maltooligosaccharide specific outer membrane channel LamB of Escherichia coli complexed with sugar molecules revealed a hypothetical transport pathway. Sugars are supposed to slide over a stretch of aromatic residues facilitated by continuous making/breaking of hydrogen bonds between the hydroxyl groups of the sugars and charged amino acids, the "polar tracks." The effect of nine single and three multiple mutations in the polar track residues was investigated by current fluctuations, liposome swelling assays, and in vivo uptake of radiolabeled substrates. Additionally, sugar transport through wild-type LamB was investigated by current fluctuation analysis in water and deuterium. This way the effects on k(on) and k(off) could be investigated separately. Analyses of the various mutants revealed a strong effect on the k(on) values. Because steering to the binding site requires only a few interactions, consequently the loss of even one bond will have a strong effect. Deuterium experiments, which changed the characteristic of all hydrogen bonds, showed a strong effect on k(off) rates, because at this stage the sugar has numerous interactions with the channel. Furthermore, all the mutations induces a strong decrease of in vivo uptake of sugars. These results clearly demonstrate the importance of the polar track residues on both on and off rates in sugar transport and reveal a strong cooperative effect of hydrogen bond formation.

Bacterial Outer Membrane Proteins↗
PubMed2000

Consequences of hydrophobic mismatch between lipids and melibiose permease on melibiose transport.

The structural and functional consequences of a mismatch between the hydrophobic thickness d(P) of a transmembrane protein and that d(L) of the supporting lipid bilayer were investigated using melibiose permease (MelB) from Escherichia coli reconstituted in a set of bis saturated and monounsaturated phosphatidylcholine species differing in acyl-chain length. Influence of MelB on the midpoint gel-to-liquid-phase transition temperature, T(m), of the saturated lipids was investigated through fluorescence polarization experiments, with 1,6-diphenyl-1,3,5-hexatriene as the probe, for varying protein/lipid molar ratio. Diagrams in temperature versus MelB concentration showed positive or negative shifts in T(m) with the short-chain lipids DiC12:0-PC and DiC14:0-PC or the long-chain lipids DiC16:0-PC and DiC18:0-PC, respectively. Theoretical analysis of the data yielded a d(L) value of 3.0 +/- 0.1 nm for the protein, similar to the 3.02 nm estimated from hydropathy profiles. Influence of the acyl chain length on the carrier activity of MelB was investigated in the liquid phase, using the monounsaturated PCs. Binding of the sugar to the transporter showed no dependence on the acyl chain length. In contrast, counterflow and Deltapsi-driven experiments revealed strong dependence of melibiose transport on the lipid acyl chain length. Similar bell-shaped transport versus acyl chain length profiles were obtained, optimal activity being supported by diC16:1-PC. On account of a d(P) value of 2.65 nm for the lipid and of various local constraints which would all tend to elongate the acyl chains in contact with the protein, one can conclude that maximal activity was obtained when the hydrophobic thickness of the bilayer matched that of the protein.

Acylation↗
PubMed2000

Oriented channels reveal asymmetric energy barriers for sugar translocation through maltoporin of Escherichia coli.

Sugar transport through maltoporin of Escherichia coli was investigated. This protein facilitates maltooligosaccharide translocation via a binding site in the channel. Because incorporation of the protein into the bilayer results in randomly orientated channels, we re-examined the postulated symmetric translocation model by reconstitution of maltoporin under an externally applied field. Upon binding of bacteriophage lambda, which exploit surface-exposed loops of maltoporin as the receptor, sugar permeation, but not the ion current, was blocked. Thus using the phage-to-probe orientation we were able to show that the channels were approximately 80% directionally inserted into the bilayer. Moreover, asymmetry of the channel was revealed because sugar entrance through the 'open' periplasmic side of maltoporin was similarly reduced. Here a new asymmetrical two-barrier model is presented. Based on liposome-swelling assays and current-fluctuation analysis we conclude that the periplasmic side of the porin shows a two- to threefold higher energy barrier than the extracellular loop-side of the channels.

Bacterial Outer Membrane Proteins↗
PubMed2000

[Concurrent concentrated radio-chemotherapy of epidermoid cancer of the esophagus. Long-term results of a phase II national multicenter trial in 122 non-operable patients (FFCD 8803)].

OBJECTIVES: Concomitant radiochemotherapy improves survival from inoperable esophageal cancer compared to radiotherapy alone. Several regimens of radiotherapy (standard or concentrated split course radiotherapy) are used, however the optimum protocol remains to be determined. The aim of this study was to analyze the efficacy and tolerance of concentrated concomitant split course radiochemotherapy. Prognostic factors as well as those positively influencing complete response were also studied. METHODS: This multicentric phase II trial looked at patients with histologically proven, inoperable, squamous cell esophageal carcinoma without metastases or invasion of the tracheobronchial mucosa. Treatment included 3 cycles of chemotherapy by 5-FU continuous infusion (800 mg/m2.d D1-D5, D22-D26, D43-D47), cisplatin (70 mg/m2 D2, D23, D44) and radiotherapy 15 Gy/5d (D1-D5, D22-26, D43-D47). Efficacy was analyzed by endoscopy, biopsy and computerized axial tomography during the 12th week of treatment. RESULTS: The trial included 122 patients from 21 centers (110 M and 12F, mean age 63.1 +/- 8.6 years, range 40-78). In accordance with the TNM-UICC classification (1978), 8 patients were classified stage I (T1 N0), 13 stage II (T2 N0), 100 stage III (T3 and/or N1) and stage was unknown in 1 patient. Median follow-up was 63 months. Treatment was complete in half of the patients. 5 premature deaths (4.1%) were recorded over the treatment period, one of which was directly linked to the toxicity of the treatment. 16% of patients showed at least one severe side-effect. 117 patients received all 3 cycles of the treatment, 88 of them without delay, and all were evaluated. 58 (47.5% of the patients included) showed a complete response with a negative biopsy, 36 (29.5%) showed a partial response, 13 (10.7%) were stable and 10 (8.2%) showed progressive disease. The median duration of complete responses was 11.5 months. Symptomatically, dysphagia improved in 80% of the cases, performance status in 40%, and weight gain was observed in 30% of the patients with weight loss. At evaluation, oral feeding was impossible in 4 patients only and possible in 113 patients; however, endoscopic treatment of the dysphagia remained necessary in 28 patients. Median survival in the 122 patients included was 13.0 +/- 1.6 months and survival rates were 52.9, 29.8 and 12.1% at 1, 2 and 5 years, respectively. Three pretherapeutic prognostic factors influenced survival in a multivariate analysis: initial severe dysphagia (risk of premature death increased 3-fold in the first year), circumferential extension and the differentiated nature of the tumor (risk of death doubled regardless of the time delay). Factors influencing a complete clinical response were an early tumor stage, a poorly differenciated tumor in patients older than 65, and no circumferential extension. The risk of recurrence was 54.8% at 1 year in the 58 patients with complete remission. Complete circumferential extension and a well or moderately differentiated tumour influenced recurrence. CONCLUSION: This trial confirms the efficacy and good tolerance of concentrated split course radiochemotherapy in patients with inoperable esophageal cancer with a 5-year survival rate of 12%. This reinforces the need for a comparative trial (split course irradiation vs standard irradiation) such as the one currently being conducted in France.

Adult↗
PubMed1999

The transmembrane protein bacterioopsin affects the polarity of the hydrophobic core of the host lipid bilayer.

Influence of the transmembrane protein bacterioopsin (the retinal-free form of bacteriorhodopsin) on the polarity of egg-phosphatidylcholine bilayers was studied by means of a steady-state and time-resolved fluorescence approach exploiting the solvatochromic properties of the 2-anthroyl fluorophore. Introduced in phosphatidylcholine molecules in the form of 8-(2-anthroyl)octanoic acid, this fluorophore probed the hydrocarbon core of the lipid bilayer. As previously shown (E. Pérochon et al., Biochemistry 31 (1992) 7672-7682), water molecules were detected in this region of the terminal part of the lipid acyl chains. Their number was considerably reduced upon addition of bacterioopsin to the lipids. This was assessed by a blue shift in the fluorescence emission spectra of the probe and a marked decrease in the fractional population of fluorophores interacting with water, to the benefit of those experiencing a hydrophobic environment. In agreement with current theories, this decrease in the hydration of the bilayer may be linked to an increase in the acyl chain order and a decrease in the lateral diffusion coefficient of lipids near the protein. The data obtained at high protein concentration accounts for a protein/lipid interface which is much less hydrated than the hydrophobic core of a protein-free lipid bilayer.

Bacteriorhodopsins↗
PubMed1999

Is the protein/lipid hydrophobic matching principle relevant to membrane organization and functions?

Biological membranes are complex and well-organized multimolecular assemblies composed of a wide variety of protein and lipid molecular species. If such a diversity in protein and lipid polar headgroup structures may easily be related to a large panel of functions, the wide dispersion in acyl chain length and structure which the lipids display is more difficult to understand. It is not required for maintaining bilayer assembly and fluidity. Direct information on the lateral distribution of these various molecular species, on their potential specificity for interaction between themselves and with proteins and on the functional implications of these interactions is also still lacking. Because hydrophobic interactions play a major role in stabilizing membrane structures, we suggest considering the problem from the point of view of the matching of the hydrophobic surface of proteins by the acyl chains of the lipids. After a brief introduction to the hydrophobic matching principle, we will present experimental results which demonstrate the predictive power of the current theories and then, we will introduce the new and important concept of protein/lipid sorting in membranes. Finally, we will show how the hydrophobic matching condition may play a key role in the membrane organization and function.

Biological Transport↗