Polygraphic recording in the rat by a miniaturized radiotelemetric technic]

The authors describe the results obtained on rats by a method of four channel telemetric recording system. The transmitter with a range of a few meters, has a pass band from 0,3 to 400 Hz, weighs 4 grams and can operate autonomously for a minimum of 10 days.     

Time course localization of immunoglobulin M monoclonal antibody and its fragments in leukemic tumor-bearing mice

Summary In vivo localization of a mouse monoclonal antibody (F₂-10.23 IgM) binding leukemic L 1210 cells was studied in DBA/2 mice bearing an L 1210 tumor. F(ab)₂ fragments were prepared and their specific binding to L 1210 cells was analyzed by flow cytofluorometry. Radiolocalization studies were performed by using ¹²⁵I- or ¹³¹I-labeled IgM monoclonal antibody or its F(ab')₂ fragments to ascertain their capacity to visualize the L 1210 tumor. F(ab)₂ fragments were cleared more rapidly than the whole IgM; the clearance was as fast in healthy as in tumor-bearing mice. The tumor-to-muscle ratio observed 24 h after injection of ¹²⁵I-radiolabeled F(ab)₂ fragments and ¹²⁵I-radiolabeled IgM was 10; the radioactivity level in the blood with F(ab)₂ fragments was lower than with IgM, and so -camera imaging was workable with F(ab)₂ fragments without background substraction. The tumor localization was studied over a period of 5 days by recording the distribution of the iodinated fragments in the tumor-bearing leg compared with that in the normal leg, and by computer analysis of the region of interest. F(ab)₂ fragments gave better results than intact IgM in tumor visualization. Nevertheless, the rapid clearance of this antibody or its F(ab)₂ fragments make them hardly suitable as carriers of toxic drugs. Abbreviations used are: MEM Minimum essential medium; SDS sodium dodecylsulfate; PAGE polyacrylamide gel electrophoresis     

New potential model for molecular dynamic simulation of liquid HF. I—Parameter optimization for charge equilibration method

In order to build a complete potential model to perform classical molecular dynamic simulations of liquid HF, a new optimization method is proposed to obtain transferable parameters for charge equilibration method on the basis of ab initio reference data. The optimized parameters (the electronegativity χ and the Slater orbital exponent ζ for H and F atoms) appear to be able to reproduce the variations of the electrostatic potential calculated from an ab initio method in a liquid phase of HF molecules for different thermodynamic conditions. It is concluded that the proposed method is general, precise and efficient to obtain transferable and realistic parameters.     

The lipid charge density at the bilayer surface modulates the effects of melittin on membranes

The influence of melittin on two DMPA membrane systems at pH 4.2 and 8.2 has been investigated by solid-state 31P and 2H NMR, as a function of temperature and peptide concentration. Melittin promotes greater morphological changes for both systems in the fluid phase, the effect being larger at pH 4.2. Close inspection of fatty acyl chain dynamics suggests that some parallels can be drawn between the DMPA/melittin at pH 8.2 and PC/melittin systems. In addition, at pH 8.2 a direct neutralization at the interface of one of the lipid negative charges by a positive charge of the peptide occurs, as can be monitored by 31P NMR at the molecular level. For the system at pH 4.2 and at high temperature, a lipid-to-peptide molar ratio of 30 is sufficient to transform the whole system into an isotropic phase, proposed to be inverted micelles. When the system is cooled down towards the gel phase one observes an intermediate hexagonal phase in a narrow range of temperature.     

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.     

The NFP locus of Medicago truncatula controls an early step of Nod factor signal transduction upstream of a rapid calcium flux and root hair deformation

Establishment of the Rhizobium-legume symbiosis depends on a molecular dialogue, in which rhizobial nodulation (Nod) factors act as symbiotic signals, playing a key role in the control of specificity of infection and nodule formation. Using nodulation-defective (Nod-) mutants of Medicago truncatula to study the mechanisms controlling Nod factor perception and signalling, we have previously identified five genes that control components of a Nod factor-activated signal transduction pathway. Characterisation of a new M. truncatula Nod- mutant led to the identification of the Nod Factor Perception (NFP) locus. The nfp mutant has a novel phenotype among Nod- mutants of M. truncatula, as it does not respond to Nod factors by any of the responses tested. The nfp mutant thus shows no rapid calcium flux, the earliest detectable Nod factor response of wild-type plants, and no root hair deformation. The nfp mutant is also deficient in Nod factor-induced calcium spiking and early nodulin gene expression. While certain genes controlling Nod factor signal transduction also control the establishment of an arbuscular mycorrhizal symbiosis, the nfp mutant shows a wild-type mycorrhizal phenotype. These data indicate that the NFP locus controls an early step of Nod factor signal transduction, upstream of previously identified genes and specific to nodulation.