Binding of a tritiated enkephalinergic analog (FK 33-824) to a mitochondrial fraction of rat brain

FK-33-824 (Try-D-Ala-Gly-MePhe-Met(O)ol) is a potent enkephalin analog which has been tritium labelled with a high specific radioactivity (41 Ci/mmole). The labelled drug exhibits specific and saturable binding to rat brain crude mitochondrial fraction. Specific binding is inhibited by low concentrations of morphine, levallorphan and beta-endorphin, suggesting that FK 33-824 [3H] binds preferentially to mu opiate sites. Binding studies at equilibrium and kinetics of formation and dissociation of the labelled ligand-receptor complex indicate that FK 33-824 [3H] binds to two classes of specific sites. Their affinities are distinguishable at 0 degree (KD = 1.3 and 5.8 nM) and very close to each other at 37 degree (KD = 1.9 nM).     

Sunflower seed protein: size and charge heterogeneity in subunits of the globulin fraction

The subunit heterogeneity of the globulin fraction of sunflower seeds was investigated by two dimensional electrophoresis, using isoelectric focusing in the first dimension and sodium dodecyl sulphate polyacrylamide gel electrophoresis in the second dimension. Under non reducing conditions, intermediary subunits B, C and D (molecular weight 54 000, 48 000 and 40 000, respectively) were focused within a pI range 5.4-6.0 but intermediary subunits A (molecular weight 60 000) focused within a pI range 6.3-6.8. Under reducing conditions the electrophoretic patterns show that intermediary subunits consist in large "acidic" and small "basic" subunits linked by disulphide bonds. The large subunits of B species are more acidic and less heterogeneous than the corresponding subunits of the A species. These results confirm that helianthinin had a "legumin-type" structure.     

In vivo impedance of the aerial organs of some mono- and dicotyledonous plants

In vivo impedance of the aerial organs of some mono- and dicotyledonous plants. We measure in this paper the electrical capacitance and resistance of aerial organs of some plants, grown in the laboratory (sunflower, pumpkin, and maize, of different ages) or bought at the market (sorrel), in a range of 34 frequencies, from 40 Hz to 100 kHz. The electrospectrometric curves of the leaves aged 14 days of the dicotyledoneous studied are close to each other.     

A simple framework to describe the regulation of gene expression in prokaryotes

Based on the bimolecular mass action law and the derived mass conservation laws, we propose a mathematical framework in order to describe the regulation of gene expression in prokaryotes. It is shown that the derived models have all the qualitative properties of the activation and inhibition regulatory mechanisms observed in experiments. The basic construction considers genes as templates for protein production, where regulation processes result from activators or repressors connecting to DNA binding sites. All the parameters in the models have a straightforward biological meaning. After describing the general properties of the basic mechanisms of positive and negative gene regulation, we apply this framework to the self-regulation of the trp operon and to the genetic switch involved in the regulation of the lac operon. One of the consequences of this approach is the existence of conserved quantities depending on the initial conditions that tune bifurcations of fixed points. This leads naturally to a simple explanation of threshold effects as observed in some experiments.     

Innate immunity in early chordates and the appearance of adaptive immunity

In the urochordate Ciona intestinalis some membrane Immunoglobulin superfamily members with ancestral features of antigen receptors are homologs of vertebrate adhesion molecules acting as virus receptors. They include the following: the junction adhesion molecule (reovirus receptor) (JAM), the Cortical thymocyte marker of Xenopus (CTX family) (Coxsackie's virus receptor) and the poliovirus receptor (PVR). In humans these genes belong to the same linkage group, of which 4 paralogous groups exist. This situation is consistent with the notion that the Ciona set of genes would correspond to a preduplication state. In addition, the human region 3q13 and its paralogs, harbour genes remotely related to the nectin family that can be detected in Protostomes (human CRTAM and CD80-86 related to Drosophila Beat). In addition, this linkage group contains several CDs important for the immune system CD166, CD47 and many members of the tetraspanin family. The VC1-like core of the nectin is homologous to the VCI core of the MHC-linked tapasin and to the VC1 segments of, for example, specific antigen receptors of vertebrates, and could be related to a primitive antigen receptor gene. It is suggested that the virus binding property of the members of this family was exploited, and that they were recruited in the vertebrate immune system following the introduction of the somatic rearrangement machinery. In this way the adaptive immune system could have developed from a set of receptors involved in a primitive local innate immunity involving NF-kappaB-mediated apoptosis.     

Ecologie des Dermestidae,une famille de Coléoptères nécrophages associée aux cadavres squelettisés

Lorsqu’un animal meurt, son cadavre forme un écosystème local instable et éphémère où différentes communautés d’insectes nécrophages vont se nourrir. Cette étude a pour but de caractériser les relations entre deux familles fréquentes en contextes médico-légal : les Diptères Calliphoridae et les Coléoptères Dermestidae. Des expériences de choix binaire (olfactomètres en T) et de prédation des Dermestes sur les larves de Diptères ont constitué le 1er axe de notre étude. Il en ressort que l’espèce D. maculatus (adultes et larves) n’exerce qu’une très faible prédation sur les larves de L. sericata. En absence de nourriture, les Dermestes sont néanmoins capables de prédater les pupes de L. sericata, et donc de faire disparaitre ces traces particulièrement importantes en entomologie médico-légale et en archéo-entomologie. Le second axe s’est focalisé sur les relations de compétition et d’agrégation entre D. maculatus et D. haemorrhoidalis. Les résultats obtenus n’ont pas mis en évidence de mécanismes de compétition ou d’exclusion entre ces deux espèces pourtant amenées à fréquenter simultanément le même habitat et à exploiter les mêmes ressources. Placées en condition de choix binaire (2 spots identiques), les 2 espèces s’agrègent ensemble. Mais le développement conjoint de ces 2 espèces sur une seule source de nourriture non limitante entraine une baisse significative du taux de survie chez les deux espèces. Au vu de ces résultats, nous avons conclu à la possibilité d’une coexistence de ces différentes espèces (L. sericata, D. maculatus et D. haemorrhoidalis) sur un cadavre.     

Status of the so-called African pygmy elephant (Loxodonta pumilio (NOACK 1906)): phylogeny of cytochrome b and mitochondrial control region sequences

Among the African elephants, it has been unanimously acknowledged that the forest elephants (cyclotis form) are peculiar, so that they have been elevated to the specific rank. The development of molecular analyses of extant Loxodonta has only focused on two forms yet: the savannah form (africana) and the forest form (cyclotis), disregarding the so-called pygmy elephants (pumilio or fransseni) the systematic status of which has been debated since their discovery. Therefore, we have sampled nine dwarfed-labelled specimens in collection and eight specimens of typical forest elephants that we compared to three savannah elephants and two Asian elephants. Because of the degraded nature of the nuclear DNA content in bone samples of old specimens, we assayed mitochondrial markers; 1961 bp of the mitochondrial genome were sequenced (over a continuous range spanning the cytochrome b gene, tRNA Thr, tRNA Pro, hypervariable region 1 and central conserved region of the control region). Pumilio and cyclotis are not sister-taxa: the phylogenetic analyses rather account for the inclusion of the so-called pygmy elephants within a monophyletic group of forest elephants sensu lato. The internal structure of this clade reveals to depend on isolation and remoteness between populations, characteristics that may have been extensively influenced by climatic variations during the Quaternary period. We conclude that the specific taxon Loxodonta pumilio (or Loxodonta fransseni) should be abandoned.     

Impact of spatial heterogeneity on a predator-prey system dynamics

This paper deals with the study of a predator-prey model in a patchy environment. Prey individuals moves on two patches, one is a refuge and the second one contains predator individuals. The movements are assumed to be faster than growth and predator-prey interaction processes. Each patch is assumed to be homogeneous. The spatial heterogeneity is obtained by assuming that the demographic parameters (growth rates, predation rates and mortality rates) depend on the patches. On the predation patch, we use a Lotka-Volterra model. Since the movements are faster that the other processes, we may assume that the frequency of prey and predators become constant and we would get a global predator-prey model, which is shown to be a Lotka-Volterra one. However, this simplified model at the population level does not match the dynamics obtained with the complete initial model. We explain this phenomenom and we continue the analysis in order to give a two-dimensional predator-prey model that gives the same dynamics as that provided by the complete initial one. We use this simplified model to study the impact of spatial heterogeneity and movements on the system stability. This analysis shows that there is a globally asymptotically stable equilibrium in the positive quadrant, i.e. the spatial heterogeneity stabilizes the equilibrium.     

Reprogramming of bone marrow mesenchymal stem cells into cardiomyocytes

We have isolated a cardiomyogenic cell line (CMG cell) from murine bone marrow mesenchymal stem cells. The cells showed a fibroblast-like morphology, but the morphology changed after 5-azacytidine exposure. They began spontaneous beating after 2 weeks, and expressed ANP and BNP. Electron microscopy revealed a cardiomyocyte-like ultrastructure. These cells had several types of action potentials: sinus-node-like and ventricular-cell-like action potentials. The isoform of contractile protein genes indicated that their muscle phenotype was similar to fetal ventricular cardiomyocytes. They expressed alpha 1A, alpha 1B, alpha 1D, beta 1, and beta 2 adrenergic and M1 and M2 muscarinic receptors. Stimulation with phenylephrine, isoproterenol and carbachol increased ERK phosphorylation and second messengers. Isoproterenol increased the beating rate, which was blocked with CGP20712A (beta 1-selective blocker). These findings indicated that cell transplantation therapy for the patients with heart failure might possibly be achieved using the regenerated cardiomyocytes from autologous bone marrow cells in the near future.     

Theory of degenerate coding and informational parameters of protein coding genes

The theory of degenerate coding is presented in a way enabling further application to molecular biology. There are two kinds of redundancy of a degenerate code. The first is due to the excess in codon length and the second to the code degeneracy. If the code is asymmetrically degenerate, the second kind of redundancy can be profitable for control of error rate. This control can be performed just by selective synonymous codon usage. Utilisation of the genetic code is partially influenced by this theoretical possibility. In particular the degree of error protectivity is well correlated with deviation from equiprobability in synonymous codon usage. The biological significance of this fact is discussed.     

Evolution and selection of reproduction

The examination of the official records from Artas, Isère (North Dauphiné, France), provides nearly continuous information from 1540 to 1900. These allowed us to study the twinning during this period, to specify its importance, its evolution, and its links with diverse other characteristics of reproduction. The number of twins per 1000 births is on a general average very close to 11. It seems to decrease during the last four centuries. However, the variability is very high from one year to another or one decade to another, including the composition of twins (identical or different sex), with the result that no statistical argument allows us to reject the null hypothesis. Numerous data have been collected that support a partially genetic determinism in twinning. The number of children in families with twins is clearly higher that in other families. Age of death of the mother of twins is higher than that of the mother of single births. With the result that 'gemellity', fecundity and longevity are related. On the other hand, the perinatal and infant death rate is much higher for twins than for single births, so that the percentage of 'useful' children is very low for twins. There is therefore, at the same time, selection and counter-selection. The momentary importance of either could explain the extent of variation of the 'gemellity' rate. The compensations, at short or long time, between the two processes could explain the roughly constant rate of 'gemellity' during the last four centuries.     

Finite element analysis of the cranium: Validity,sensitivity and future directions

Finite element analysis (FEA) is increasingly applied in skeletal biomechanical research in general, and in fossil studies in particular. Underlying such studies is the principle that FEA provides results that approximate reality. This paper provides further understanding of the reliability of FEA by presenting a validation study in which the deformations experienced by a real cadaveric human cranium are compared to those of an FE model of that cranium under equivalent simulated loading. Furthermore, model sensitivity to simplifications in segmentation and material properties is also assessed. Our results show that absolute deformations are not accurately predicted, but the distribution of the regions of relatively high and low strains, and so the modes of global deformation, are reasonably approximated.     

Ants impact the composition of the aquatic macroinvertebrate communities of a myrmecophytic tank bromeliad

In an inundated Mexican forest, 89 out of 92 myrmecophytic tank bromeliads (Aechmea bracteata) housed an associated ant colony: 13 sheltered Azteca serica, 43 Dolichoderus bispinosus, and 33 Neoponera villosa. Ant presence has a positive impact on the diversity of the aquatic macroinvertebrate communities (n = 30 bromeliads studied). A Principal Component Analysis (PCA) showed that the presence and the species of ant are not correlated to bromeliad size, quantity of water, number of wells, filtered organic matter or incident radiation. The PCA and a generalized linear model showed that the presence of Azteca serica differed from the presence of the other two ant species or no ants in its effects on the aquatic invertebrate community (more predators). Therefore, both ant presence and species of ant affect the composition of the aquatic macroinvertebrate communities in the tanks of A. bracteata, likely due to ant deposition of feces and other waste in these tanks.