Effects of sub-minimal inhibitory concentrations of EDTA on growth of Escherichia coli and the release of lipopolysaccharide

Abstract Release of lipopolysaccharide from E. coli was studied in the presence of sub-minimal inhibitory concentrations of ethylenediaminetetraacetic acid (EDTA). In untreated cells no release was detected with 50 mM Mg²⁺ in the medium, but a steady release of over 50% of the synthesized lipopolysaccharide was observed with 0.1 mM Mg²⁺. EDTA at MIC/8 led to a 2- to 3-fold higher release, presumably by an adjustment of the concentration of unchelated Mg²⁺ to a value still sustaining normal growth but giving rise to a highly unstable outer membrane. No structural difference was observed between cell-bound and released lipopolysaccharide.     

Contrasting effects of PACAP and carbachol on [Ca]i and inositol phosphates in human neuroblastoma NB-OK-1 cells

The effects of PACAPs on [Ca²⁺]_i were compared to those of carbachol in human neuroblastoma NB-OK-1 cells. PACAP(1–27) and PACAP(1–38) increased [Ca²⁺]_i in a biphasic manner: a transient rise and a secondary plateau. The transient phase reflected the mobilization of [Ca²⁺]_i pool(s) via the inositol phosphate pathway. The modest sustained plateau required extracellular Ca²⁺. Carbachol also increased [Ca²⁺]_i in a biphasic manner, but it mobilized intracellular Ca²⁺ pool(s) with a higher efficacy than PACAPs, then greatly increased Ca²⁺ entry, this being accompanied by a more marked and prolonged elevation of IP₃ and IP₄ than with PACAPs. It is likely that cAMP-mediated phosphorylations due to PACAPs facilitated desensitization at the PACAP receptor-phospholipase C level, so that there was less Ca²⁺ handling through PACAP receptors than with muscarinic M₁ receptors.     

Conformational properties of Eu(III) complexes of 3,3′; 5,3″-polymethylene bridged derivatives of 2,2′; 6,2″-terpyridine

The complex [Eu(tpy)₃](ClO₄)₃ where TPY=2,2′; 6,2″-terpyridine, has been prepared and reexamined. The complex appears to be stable in acetonitrile solution with respect to decomplexation of the ligands but the addition of water does cause partial replacement of tpy. Analogous complexes have been prepared with 3,3′; 5,3″-polymethylene bridged derivatives of tpy having two or three carbons in the bridge. The bridging enforces a cisoid geometry of the ligand and prohibits its replacement by added water. An X-ray determination was carried out for [Eu(3b)₃](ClO₄)₃, where 3b=3,3′; 5,3″-dimethylene tpy, which crystallizes in the monoclinic space group P2₁/c with a=11.908(4), b=15.768(5), c=29.513(9) Å, β=93.60(2)°, μ=13.5 cm⁻¹ and Z=4. The complex forms a tricapped trigonal prism with each of the ligands adopting the same dl conformation. Variable temperature NMR analysis of the bridged ligand complexes indicates that conformational inversion of the bound ligand is not a concerted process and barriers for inversion of individual methylene units can be estimated from coalescence of the signals from the geminal methylene protons. The luminescence properties of the bridged tpy complexes are similar to the parent unbridged system.     

Pattern recognition in DNA sequences and its application to consensus foot-printing

We consider the problem of comparing several nucleic acid sequencesto identify words occurring imperfectly (patterns with no gap)with unusual frequency. Methods for computing, representing,and inspecting interactively the structure of such repeatingmotifs in nucleic acids and more generally any text are described.Multiple sequences are treated as one large concatenate. Ina preprocessing step, a lexical index is created to providerapid string matching for the enumeration of the words matchinga pattern. For given word features (word length, minimal frequency),a sequence profile is displayed. The profile can be inspectedinteractively with on-line algorithms. Applications to the identificationof regulatory elements in DNA regions involved in the controlof gene expression are presented. Our program (‘DNA-Lexemics’)runs on the Macintosh.     

Growth-related gene expression in Nicotiana tabacum mesophyll protoplasts

Eight cDNAs whose genes are more strongly expressed in suspension cells in growth phase than in stationary phase and at a low level in mature leaves have been isolated. The corresponding mRNAs are abundantly accumulated in young plant organs and in germinating seeds but are almost undetectable in mature plant tissues and dry seeds. Six of these cDNAs were characterized by comparison of nucleotide and protein sequences to the EMBL and SWISSPROT databanks. These eight growth-related genes are expressed in protoplasts isolated from Nicotiana tabacum mesophyll cells shortly after preparation (4 h). Two of them are expressed in freshly isolated protoplasts (early genes), while the other six are detected after 4 h of culture (late genes). Seven are more abundantly expressed in protoplasts than in growing plant organs while one growth-related gene is weakly expressed in protoplasts, as is the histone H₄ gene. They seem to be induced in protoplasts by a synergistic effect of wounding and maceration. Sustained expression of the early genes is dependent on the presence of sucrose in the culture medium.     

Mouse chromosome 19

Chair of Committee for Mouse Chromosome 19     

Bayesian estimation of two-part joint models for a longitudinal semicontinuous biomarker and a terminal event with INLA: Interests for cancer clinical trial evaluation

Two-part joint models for a longitudinal semicontinuous biomarker and a terminal event have been recently introduced based on frequentist estimation. The biomarker distribution is decomposed into a probability of positive value and the expected value among positive values. Shared random effects can represent the association structure between the biomarker and the terminal event. The computational burden increases compared to standard joint models with a single regression model for the biomarker. In this context, the frequentist estimation implemented in the R package frailtypack can be challenging for complex models (i.e., a large number of parameters and dimension of the random effects). As an alternative, we propose a Bayesian estimation of two-part joint models based on the Integrated Nested Laplace Approximation (INLA) algorithm to alleviate the computational burden and fit more complex models. Our simulation studies confirm that INLA provides accurate approximation of posterior estimates and to reduced computation time and variability of estimates compared to frailtypack in the situations considered. We contrast the Bayesian and frequentist approaches in the analysis of two randomized cancer clinical trials (GERCOR and PRIME studies), where INLA has a reduced variability for the association between the biomarker and the risk of event. Moreover, the Bayesian approach was able to characterize subgroups of patients associated with different responses to treatment in the PRIME study. Our study suggests that the Bayesian approach using the INLA algorithm enables to fit complex joint models that might be of interest in a wide range of clinical applications.     

In Vitro and Molecular Docking Evaluation of Larvicidal Effects of Essential Oils of Five Aromatic Plants on the Fall Armyworm Spodoptera frugiperda JE. Smith (Lepidoptera: Noctuidae) from Ivory Coast

Faced with the serious consequences resulting from the abusive and repeated use of synthetic chemicals, today rethinking crop protection is more than necessary. It is in this context that the essential oils of the Lamiaceae Ocimum gratissimum and Ocimum canum, the Poaceae Cymbopogon citratus and nardus and a Rutaceae Citrus sp. of known chemical compositions were experimented. The evaluation of the larvicidal potential of the essential oils was done by the method of topical application of the test solutions, on the L1−L2 stage larvae from the first generation of S. frugiperda obtained after rearing in an air-conditioned room. Lethal concentrations (LC₁₀, LC₅₀ and LC₉₀) were determined after 48 h. After assessing the larvicidal potential of essential oils, molecular docking was carried out to study protein-ligand interactions and their propensity to bind to insect enzyme sites (AChE). The essential oil of O. gratissimum was the most effective with the lowest lethal concentrations (LC₁₀=0.91 %, LC₅₀=1.91 % and LC₉₀=3.92 %). The least toxic oil to larvae was Citrus sp. (LC₁₀=5.44 %, LC₅₀=20.50 % and LC₉₀=77.41 %). Molecular docking revealed that p-cymene and thymol from O. gratissimum essential oil are structurally similar and bind to the AChE active site via predominantly hydrophobic interactions and a H-bond with Tyr374 in the case of thymol. The essential oil of O. gratissimum constitutes a potential candidate for the development of biological insecticides for the fight against insect pests and for the protection of the environment.