[Infantilization: the elderly dependent person is an adult].
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Activities of Daily Living↗
Biomedical subjects
A Lebrun
Publications and source records attributed to A Lebrun.
Non-pathogenic Actinobacillus isolates antigenically and biochemically similar to Actinobacillus pleuropneumoniae: a novel species?
Two unusual Actinobacillus isolates were recovered from pigs with no clinical signs, no lesions and no history of swine pleuropneumonia. Two representative strains (9953L55 and 0347) analyzed in this study were initially biochemically and antigenically identified as A. pleuropneumoniae serotypes 1 and 9, respectively, by traditional identification methods. Both strains presented, however, negative results with three A. pleuropneumoniae-specific PCR tests and revealed in particular the absence of the apxIV toxin genes. However, both strains produced and secreted ApxII toxin although they only harbored the toxin genes apxIICA, which is an uncommon feature for any of the known A. pleuropneumoniae serotypes. Upon experimental inoculation of pigs, these strains proved to be totally non-pathogenic. Animals infected with one of the strains produced antibodies that cross-react with A. pleuropneumoniae serotypes 1-9-11-specific LC-LPS ELISA. Phylogenetic analysis based on 16S rRNA gene sequence analysis revealed that these strains form a separate phylogenetic group that is distinct from other Actinobacillus species and is particularly different from A. pleuropneumoniae.
Actinobacillus↗
Antibody response to an autogenous vaccine and serologic profile for Streptococcus suis capsular type 1/2.
An autogenous vaccine was developed, using sonicated bacteria, with a strain of Streptococcus suis capsular type 1/2. The objectives of this study were to evaluate the antibody response following vaccination and to assess the changes in antibody levels in pigs from a herd showing clinical signs of S. suis capsular type 1/2 infection in 6- to 8-week-old pigs. An enzyme-linked immunosorbent assay using the vaccine antigen was standardized. Results from a preliminary study involving 2 control and 4 vaccinated 4-week-old pigs indicated that all vaccinated pigs produced antibodies against 2 proteins of 34 and 43 kDa, respectively, and, in 3 out of 4 vaccinated pigs, against the 117-kDa muramidase-released protein. For the serologic profile, groups of 30 pigs from the infected herd were blood sampled at 2, 4, 6, 8, and 10 weeks of age. The lowest antibody level was observed between weeks 6 and 8, presumably corresponding to a decrease in maternal immunity. A marked increase was seen at 10 weeks of age, shortly after the onset of clinical signs in the herd. For the vaccination field trial, newly weaned, one-week-old piglets were divided into 2 groups of 200 piglets each (control and vaccinated); blood samples were collected from 36 piglets in each group at 2-week intervals for 12 weeks. A significant increase (P < 0.05) in antibody response was observed 4 weeks following vaccination and the level of antibodies stayed high until the end of the experiment. In the control group, the increase was only observed at 13 weeks of age, probably in response to a natural infection. The response to the vaccine varied considerably among pigs and was attributed, in part, to the levels of maternal antibodies at the time of vaccination. No outbreak of S. suis was observed in the control or vaccinated groups, so the protection conferred by the vaccine could not be evaluated.
Animals↗
Modeling multi-component protein-DNA complexes: the role of bending and dimerization in the complex of p53 dimers with DNA.
We used molecular modeling to study the optimal conformation of the complex between two p53 DNA-binding domain monomers and a 12 base-pair target DNA sequence. The complex was constructed using experimental data on the monomer binding conformation and a new approach to deform the target DNA sequence. Combined with an internal/helicoidal coordinate model of DNA, this approach enables us to bend the target sequence in a controlled way while respecting the contacts formed with each p53 monomer. The results show that the dimeric complex favors DNA bending towards the major groove at the dimer junction by a value close to experimental findings. In contrast to inferences from earlier models, the calculation of key contributions to the free energy of the complexes indicates a determinant role for DNA in the formation of the complex with the dimer of the p53 DNA-binding domains.
Binding Sites↗
Specific expression of matrix metalloproteinases 1, 3, 9 and 13 associated with invasiveness of breast cancer cells in vitro.
Several matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) were studied in highly invasive (MDA-MB-231) and slightly invasive (MCF-7, T47D, BT-20) breast cancer cell lines. Investigations were carried out at the protein level and/or at the mRNA level, either in cells cultured as monolayers on plastic, or in cells seeded on a thin layer of Matrigel basement membrane matrix. Analysis of MMP expression by RT-PCR showed expression of MMP-1. MMP-3, and MMP-13 in highly invasive MDA-MB-231 cells, but not in slightly invasive cell lines. The extracellular secretion of MMP-1 and MMP-3 by MDA-MB 231 cells could be also shown by ELISA. TIMP-1 and TIMP-2 mRNAs were found in all cell lines, however, the extracellular secretion of both TIMPs was much higher in MDA-MB-231 cells than in the other cell lines. When the cells were cultured on Matrigel matrix, MMP-9 expression was induced in MDA-MB-231 cells only, as assessed by RT-PCR and zymography experiments. The invasive potential of MDA-MB-231 cells evaluated in vitro through Matrigel was significantly inhibited by the MMP inhibitor BB-2516, by 25% and 50% at the concentrations of 2 x 10(-6) M and 10(-5) M, respectively. In conclusion, our data show that highly invasive MDA-MB-231 cells but not slightly invasive T47D, MCF-7 and BT-20 cells express MMP-1, MMP-3, MMP-9 and MMP-13. MMP-9 which is specifically up-regulated by cell contact to Matrigel, may play a key role in the invasiveness of MDA-MB-231 cells through basement membranes.
Base Sequence↗
Atypical Actinobacillus pleuropneumoniae isolates that share antigenic determinants with both serotypes 1 and 7.
In the present study, the characterization of 3 atypical isolates of Actinobacillus pleuropneumoniae is presented. Two isolates (1B and 27E) showed positive reactions in coagglutination, immunodiffusion, and indirect hemagglutination tests for serotypes 1 and 7, whereas the third isolate (26B) reacted with antisera to serotypes 1, 4, and 7. These atypical isolates of A. pleuropneumoniae possessed a capsular polysaccharide (CPS) antigenically related to serotype 1 as well as an O-chain lipopolysaccharide antigenically related to serotype 7 or to serotypes 4 and 7, as shown by the use of monoclonal antibodies. Results of toxin profile and virulence assays for mice and pigs showed them to be more related to A. pleuropneumoniae serotype 7 field isolates. All 3 isolates induced antibodies mainly against serotype 7/4 O-long-chain lipopolysaccharide (LC-LPS) and, to a lesser extent, to the CPS of serotype 1, in experimentally infected pigs. Diagnostic laboratories that use a LC-LPS-based enzyme-linked immunosorbent assay (ELISA) for serodiagnosis of A. pleuropneumoniae infection in swine would probably diagnose herds infected with these atypical isolates as being infected by A. pleuropneumoniae serotypes 7 or 4, whereas those that use a CPS-based ELISA would probably consider them as infected by A. pleuropneumoniae serotype 1.
Actinobacillus Infections↗
Modeling DNA deformations induced by minor groove binding proteins.
Molecular modeling is used to demonstrate that the major structural deformations of DNA caused by four different minor groove binding proteins, TBP, SRY, LEF-1, and PurR, can all be mimicked by stretching the double helix between two 3'-phosphate groups flanking the binding region. This deformation reproduces the widening of the minor groove and the overall bending and unwinding of DNA caused by protein binding. It also reproduces the principal kinks associated with partially intercalated amino acid side chains, observed with such interactions. In addition, when protein binding involves a local transition to an A-like conformation, phosphate neutralization, via the formation of protein-DNA salt bridges, appears to favor the resulting deformation.
Base Sequence↗
Identification of Actinobacillus pleuropneumoniae strains of serotypes 7 and 4 using monoclonal antibodies: demonstration of common LPS O-chain epitopes with Actinobacillus lignieresii.
Monoclonal antibodies (Mabs) against Actinobacillus pleuropneumoniae serotype 7 were produced and characterized. Three Mabs directed against surface polysaccharides were selected. One of the Mabs was directed against a capsular polysaccharide epitope (CPS) of A. pleuropneumoniae serotype 7 whereas two other Mabs reacted with different epitopes of the LPS O-chain. One of the latter reacted with the reference strain of serotype 7 and the other one with serotypes 7 and 4. These three Mabs were used to test, by Dot-ELISA, 508 field strains of A. pleuropneumoniae. None of the strains belonging to other serotypes different from serotypes 4 and 7 were positive with the Mabs. Used in combination, the CPS and one of the LPS O-chain directed Mabs were shown to be suitable for serotyping since they detected 100% of serotype 7 strains. In this study, we confirm for the first time that A. pleuropneumoniae serotype 4 is present in North America. Finally, both O-chain specific Mabs also reacted with the O-chain of Actinobacillus lignieresii. The cross-reactivity between the two species was confirmed using sera from pigs experimentally infected with A. pleuropneumoniae serotype 7 and A. lignieresii, using immunoblotting and ELISA. This is the first report of a specific cross-reactivity between the LPS of these bacterial species.
Actinobacillus↗
Modelling DNA stretching for physics and biology.
We have used internal coordinate molecular mechanics calculations to study how the DNA double helix deforms upon stretching. Results obtained for polymeric DNA under helical symmetry constraints suggest that two distinct forms, an unwound ribbon and a narrow fibre, can be formed as a function of which ends of the duplex are pulled. Similar results are also obtained with DNA oligomers. These experiments lead to force curves which exhibit a plateau as the conformational transition occurs. This behaviour is confirmed by applying an increasing force to DNA and observing a sudden length increase at a critical force value. It is finally shown some DNA binding proteins can also stretch DNA locally, to conformations related to those created by nanomanipulation.
Bacterial Proteins↗
Modeling the mechanics of a DNA oligomer.
DNA stretching and strand separation have been studied by molecular mechanics using an oligomer which has been the subject of nanomanipulation experiments (Noy et al., Chem. Biol. 4, 519, 1997). Adiabatic mapping of conformational energy carried out as a function of stretching leads to force/extension curves in good correlation with the experimental results. Other types of deformation are also modeled and compared with the experimental results obtained on polymeric DNA. The results highlight overall similarities, but point to thermodynamic differences and also to local base sequence effects which can be expected to play an important role at the level of biologically induced structural deformations.
Computer Simulation↗
Production of virulence-related proteins by Canadian strains of Streptococcus suis capsular type 2.
The production of muramidase-released protein (MRP), extracellular protein factor (EF) and hemolysin (suilysin) by 101 Canadian field strains of Streptococcus suis capsular type 2 is described. Most strains (72%) isolated from diseased pigs were MRP-EF- and only 1 strain was MRP+EF+. This strain was also the only 1 to produce the hemolysin. Thirteen strains (15%) were MRP+ EF- and only 3 strains were MRP* EF-. All the strains isolated from clinically healthy pigs as well as a bovine and 2 human isolates had a MRP-EF- phenotype. In addition, 7 strains (8%) had a MRPS phenotype, which had so far been described for S. suis capsular type 1. In conclusion, most Canadian field isolates of S. suis capsular type 2 tested in this study do not produce the virulence-related proteins described so far for this bacterial pathogen.
Animals↗
Local DNA stretching mimics the distortion caused by the TATA box-binding protein.
X-ray structures of the TATA box-binding protein complexed with its DNA target show that the nucleic acid is severely bent away from the protein and also strongly unwound. We have used molecular mechanics and energy mapping to understand how such an unusual conformation can be induced. The results show that simple deformation pathways involving local stretching or unwinding of DNA reproduce many features of the experimental structure. Notably, kinked junctions with the flanking B-DNA regions occur without the need for any specific local
DNA↗
Unusual DNA conformations.
DNA is on the move across conformational space. Duplexes diversity and, joined by triplexes, quadruplexes, loops, bulges and multiarmed junctions, open the route to a bewildering array of increasingly complex conformations. In addition to this structural growth, DNA has come under increasing scrutiny thanks to the development of chemical and physical techniques for deforming its conformation and probing its properties. These investigations help us to learn more about the mechanics and the activity of this remarkably versatile macromolecule.
DNA↗
Modelling extreme stretching of DNA.
Molecular modelling with Jumna is used to study extreme stretching of the DNA double helix. The results, which correlate well with recent nanomanipulation experiments, show how the double helix can be extended to twice its normal length before its base pairs break. Depending on the way the duplex is stretched two types of conformation can occur, either an unwound flat ribbon or a narrow fibre with negatively inclined base pairs. The energetics of both types of deformation are similar and existing structures show that at least the flat ribbon form can exist locally under biological conditions.
Base Sequence↗
DNA: an extensible molecule.
The force-displacement response of a single duplex DNA molecule was measured. The force saturates at a plateau around 70 piconewtons, which ends when the DNA has been stretched about 1.7 times its contour length. This behavior reveals a highly cooperative transition to a state here termed S-DNA. Addition of an intercalator suppresses this transition. Molecular modeling of the process also yields a force plateau and suggests a structure for the extended form. These results may shed light on biological processes involving DNA extension and open the route for mechanical studies on individual molecules in a previously unexplored range.
Chemical Phenomena↗
Modeling a strand exchange tetraplex conformation.
Molecular modeling had been used to study the conformation and the energetics of 4-stranded DNA complexes formed by strand exchange between two duplexes. Both isolated strand exchange tetraplexes (SET's) and duplex-tetraplex complexes are found to be stable. Hydrogen bonding between the major groove faces of the base pairs within each base tetrad is shown to be specific, allowing tetrad formation only between DNA duplexes having identical base sequences. Such structures can explain the recent experimental observations of Gaillard and Strauss concerning the complexation of two DNA containing poly(dCA) tracts and may be of relevance to genetic recombination mechanisms.
DNA↗
Description of six new capsular types (29-34) of Streptococcus suis.
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Animals↗
Thermodynamic and structural properties of r(ACC) as revealed by ultraviolet electronic absorption, circular dichroism, 1H-NMR spectroscopy and Monte Carlo simulations.
UV absorption, circular dichroism (CD) and 1H NMR, associated with Monte Carlo (MC) molecular structure simulations have been applied to the study of the trinucleoside diphosphate: r(ACC). The MC study which has been conducted as a function of temperature, is based on random variations of the nucleotide conformational angles, i.e. phosphodiester chain torsional angles and sugar pucker pseudorotational angles. All of the chemical bond lengths and valence angles remained fixed during the structural simulation, except those of the sugar pucker. Six different initial structures have been selected in order to explore the molecular conformational space as completely as possible. This simulation procedure led to distinct families of equilibrium conformations at 283, 298 and 318 K. The thermodynamical parameters such as variations in entropy, enthalpy and also melting temperature (delta SX0, delta HX0 and Tm) of the stacking (X) equilibrium were obtained from UV absorption and circular dichroism (CD) spectra recorded over a 80K temperature range. Chemical shifts (delta), vicinal coupling constants (3Jk,l), and cross-relaxation rate (sigma k,l) of trimers were measured at 400.13 MHz over a range of concentrations (2-13 mM) and temperatures (283-333K). Least-squares fitting of the experimental chemical shifts to simple models of association (A) and stacking equilibria allowed separation of the variations in the delta values (delta delta X and delta delta A) due to either phenomenon. The three NMR data sets (delta delta X, 3Jk,l, and sigma k,l) were then evaluated for the minima conformers obtained with the MC stimulations. Theoretical values of delta delta X were estimated using the results of an ab initio study while the coupling constant data were simulated with Karplus-type equations. Finally, the relaxation data were simulated from the distance matrices using treatment for cases of both slow conformational exchange accompanied by rapid small-amplitude fluctuations about the minima structures. A consistent picture of the large amplitude deformations (torsional angle variation) of these trimers has emerged from the present study. Optimized conformational blends at 283,296 and 318K were obtained by least-squares fitting of the experimental data to the theoretical ones, while considering the populations as adjustable parameters. As it would be expected, the right-handed helical conformation (A-RNA type) is found to be the major stacked species, in the temperature range of 283 to 318K. Limited evidence for bulged structures has been obtained, whereas novel reverse-stacked and half-stacked conformers also presented theoretical data compatible with the NMR observables of aqueous r(ACC).
Circular Dichroism↗