Conformation of heparin studied with macromolecular hydrodynamic methods and X-ray scattering

The hydrodynamic characteristics of heparin fractions in a 0.2 M NaCl solution have been determined. Experimental values varied over the following ranges: the sedimentation coefficient (at 20.0 °C), 1.3<s₀×10¹³<3.2 s; the Gralen coefficient (sedimentation concentration-dependence parameter), 10<k_s<70 cm³ g^–1; the translational diffusion coefficient, 3.9<D₀×10⁷<15.4 cm² s^–1; the intrinsic viscosity, 7.9<[]<40 cm³ g^–1. Combination of s₀ with D₀ using the Svedberg equation yielded molecular weights in the range 3.9<M×10^–3<37 g mol^–1. The value of the mass per unit length of the heparin molecule, M_L, was determined using the theory of hydrodynamic properties of a weakly bending rod, giving M_L=570±50 g nm^–1 mol^–1. The equilibrium rigidity, Kuhn segment length (A=9±2 nm) and hydrodynamic diameter (d=0.9±0.1 nm) of heparin were evaluated on the basis of the worm-like coil theory without the excluded volume effect, using the combination of hydrodynamic data obtained from fractions of different sizes. Small-angle X-ray scattering for three heparin fractions allowed an estimate for the cross-sectional radius of gyration as 0.43 nm; from the evolution with the macromolecule contour length of the radius of gyration, a value for the Kuhn segment length of 9±1 nm was obtained. A good correlation is thus observed for the conformational parameters of heparin from hydrodynamic and X-ray scattering data. These values describe heparin as a semi-rigid polymer, with an equilibrium rigidity that is essentially determined by a structural component, the electrostatic contribution being negligible in 0.2 M NaCl.Presented at the conference for Advances in Analytical Ultracentrifugation and Hydrodynamics, 8–11 June 2002, Grenoble, France     

Glycine,Serine, and Leucine Metabolism in Different Regions of Rat Central Nervous System

We have investigated the glycine, serine and leucine metabolism in slices of various rat brain regions of 14-day-old or adult rats, using [1-¹⁴C]glycine, [2-¹⁴C]glycine, L-[3-¹⁴C]serine and L-[U-¹⁴C]leucine. We showed that the [1-¹⁴C]glycine oxidation to CO₂ in all regions studied occurs almost exclusively through its cleavage system (GCS) in brains of both 14-day-old and adults rats. In 14-day-old rats, the highest oxidation of [1-¹⁴C]glycine was in cerebellum and the lowest in medulla oblongata. In these animals, the L-[U-¹⁴C]leucine oxidation was lower than the [1-¹⁴C]glycine oxidation, except in medulla oblongata where both oxidations were the same. Serine was the amino acid that showed lowest oxidation to CO₂ in all structure studied. In adult rats brains, the highest oxidation of [1-¹⁴C]glycine was in cerebral cortex and the lowest in medulla oblongata. We have not seen difference in the lipid synthesis from both glycine labeled, neither in 14-day-old rats nor in adult ones, indicating that the lipids formed from glycine were not neutral. Lipid synthesis from serine was significantly high than lipid synthesis and from all other amino acids studied in all studied structures. Protein synthesis from L-[U-¹⁴C]leucine was significantly higher than that from glycine in all regions and ages studied.     

Do Solitary Bees Osmia cornuta Latr. and Osmia lignaria Cresson Use Proximal Visual Cues to Localize Their Nest?

Female Osmia repeatedly return to their nest to provision it with food and building material. The present study investigates the bees' nest localization performance by modifying visual cues in the near-vicinity of the nest. Each of several arrays of nesting holes was surrounded by four geometrical shapes. Removing some or all of the shapes reduced the proportion of direct returns but never prevented a bee from finding the appropriate array and, within that array, its own nest. The more the pattern was modified, the higher was the error score and the longer the delay, but no bee failed finally to find its nest. Shifting the pattern as well as the whole array of holes shifted homing orientation accordingly. There was no effect of the positions of the removed shapes, of contrast inversion, or of modifying the holes array. Our data are discussed in the light of the snapshot theory.     

Molecular Cloning and Characterization of a Superoxide Dismutase (sod) Gene in Pneumocystis carinii

This work reports the isolation and characterization of a gene encoding a superoxide dismutase (SOD. EC.1.15.1.1.) from Pneumocystis carinii derived from rat. Sense and antisense oligonucleotides, deduced from SOD amino acid sequences from a wide variety of organisms, allowed amplification of a 669 bp genomic DNA fragment specific to this P. carinii. RACE-PCR was used to obtain the major pan of the complementary DNA; the 5- and 3'-genomic regions were obtained respectively from a Mbo I subgenomic library and from an amplified fragment using oligonucleotides designed from the cDNA sequence. Comparison of genomic and cDNA sequences showed an open reading frame of 660 bp interrupted by seven small introns. The deduced amino acid sequence contained 220 residues. Protein sequence alignment demonstrated the highest homology (50.5% identity. 70.3% similarity) with Saccharomyces cerevisiae manganese-SOD (MnSOD) suggesting that P. carinii SOD belongs to the mitochondrial MnSOD group. A putative targeting peptide found at the 5'-end of the P. carinii SOD sequence also suggested its mitochondrial localization.     

Lysozyme crystal growth, as observed by small angle X-ray scattering, proceeds without crystallization intermediates

A combination of small angle X-ray scattering and gel techniques was used to follow the kinetics of protein crystal growth as a function of time. Hen egg white lysozyme, at different protein concentrations, was used as a model system. A new sample holder was designed, in which supersaturation is induced in the presence of salt by decreasing the temperature. It had been shown previously that a decrease in temperature and/or an increase in crystallizing agent induces an increase in the attractive interactions present in the lysozyme solutions, the lysozyme remaining monomeric. In the present paper we show that similar behaviour is observed in NaCl when agarose gels are used. During crystal growth, special attention was paid to determine whether oligomers were formed as the protein in solution was incorporated in the newly formed crystals. From these first series of experiments, we did not find any indication of oligomer formation between monomer in solution and crystal. The results obtained are in agreement with the hypothesis that lysozyme crystals in NaCl grow by addition of monomeric particles. Received: 28 July 1997 / Revised version: 4 December 1997 / Accepted: 5 December 1997     

In vitro interactions between bone marrow stromal cells and hippocampal slice cultures

Bone marrow stromal cells (BMSCs) are capable of differentiating into various cell types including brain cells. Several groups have also demonstrated trophic effects of MSC grafts in experimental ischemia models. However, the underlying molecular mechanisms of these effects are not fully understood. We developed an “in vitro graft model” which consisted in a coculture of GFP-expressing BMSCs and hippocampal organotypic slice cultures. Total marrow cells (MCs) or BMSCs after one (BMSC^1P) or five passages (BMSC^5P) were transplanted on hippocampal slices. During the 10 days of our experiments, MCs and BMSC^1P migrated toward the tissue, but their total number remained constant. Conversely, the number of BMSC^5P decreased over the 10 days of the experiment, and no migration could be detected. Using immunohistochemistry, we observed that the hippocampal slices induced the expression of neural antigens in very few grafted cells, but MCs and BMSC^1P improved the conservation of the hippocampal slice culture. Similar experiments using BMSC^5P did not produce any significant change. We conclude that the number of passages greatly influence BMSCs survival rate, migration and neuroprotective capacities.     

Behavioral syndrome in a native and an invasive hymenoptera species

Recent studies have focused on the role of behavior in biological invasions. Individuals may differ consistently in time for several behavioral traits (personality) which covary (behavioral syndrome) resulting in different behavioral types, some of them favoring invasion. Social hymenopterans have a strong potential to be invaders and their success depends primarily on the foundresses’ ability to found viable colonies. They are expected to be active, explorative and bold for optimally establishing their nest. In Europe, 2 hornet species coexist: the native Vespa crabro and the invasive Vespa velutina. These 2 species may compete for nesting sites and we suggest that the initial success of V. velutina has been favored by its behavior in outperforming V. crabro for the traits involved in nest initiation. Here, we (i) defined the personality of V. crabro and V. velutina, (ii) tested for the existence of behavioral syndrome in these species, and (iii) compared their performances using an open‐field test. Our results show that V. crabro foundresses behave consistently but not V. velutina; this lack of consistency being mainly due to reduced variance among individuals. This result questions the possibility of detecting consistent behavioral differences in species having recently undergone a strong bottleneck. Both species exhibit the same correlations between activity, boldness and exploration and V. velutina clearly outperforms V. crabro for all traits. Our results suggest that activity, boldness, and exploration are implicated in both hornet nest initiation and invasion process which contributed to explain why social hymenopterans are so successful at colonization.