Révision des Xylocopinae (Hymenoptera : Apidae) de France et de Belgique

Cette publication présente les résultats d’une étude de 6.263 spécimens de Xylocopinae récoltés en France métropolitaine (France continentale et Corse) et en Belgique et qui proviennent de récoltes personnelles et de 63 institutions et collections privées. Les Xylocopinae de France sont représentées par 11 espèces du genre Ceratina et 4 espèces du genre Xylocopa. Seules deux de ces espèces sont présentes en Belgique : Xylocopa violacea (L.) et Ceratina cyanea (Kirby). Un nouveau sous-genre pour le genre Ceratina est décrit : Dalyatina n. subg. Il comporte l’espèce méditerranéenne Ceratina parvula Smith présente en France, ainsi que six autres espèces d’Afrique subsaharienne. Pour chaque genre, sous-genre et espèce, les auteurs fournissent une diagnose, une diagnose différentielle, la liste des fleurs visitées, la liste des sites de nidification, la carte de distribution en France métropolitaine, un diagramme phénologique et une clé d’identifi cation des genres, sous-genres et espèces. La systématique, la biogéographie, l’écologie et le sexe ratio des espèces sont présentés et discutés. Les Xylocopinae apparaissent comme très largement polylectiques mais montrent une très nette affinité envers les Lamiaceae, les Asteraceae Cardueae et, pour le genre Xylocopa, envers les Fabaceae. Toutes les espèces présentent une phénologie estivale qui s’étend d’avril à septembre. Le sexe-ratio de la plupart des espèces est biaisé vers les femelles. Aucun mâle de C. parvula, pour 120 femelles, n’a été observé ce qui suggère que, en France du moins, l’espèce pourrait se reproduire par parthénogenèse thélytoque comme c’est le cas de C. dallatorreana Friese. La publication comprend 62 dessins au trait, 18 photos au microscope électronique à balayage, 17 cartes, 14 graphiques de phénologie, une liste de 232 espèces de fleurs visitées par les Xylocopinae, dont 176 observations originales, et 171 références.     

Vacuolar ethylene formation does not depend on membrane potential

Enzymatic synthesis of ethylene in the vacuole is assumed to require membrane integrity. The possibility that this reflects dependence on the vacuolar membrane potential was investigated. Vacuoles were released from protoplasts isolated from leaves of Vicia faba L. cv. Cyprus. The dependence of the ethylene-forming activity on tonoplast integrity was re-examined by immobilization of the vacuoles in a cross-linked polymeric matrix and subsequent permeabilization of the tonoplast with toluene, a pore-forming reagent. The relationship between the vacuolar ethylene formation and the membrane potential of free vacuoles was investigated by following the uptake of thiocyanate using permeabilized, depolarized and hyperpolarized vacuoles. Toluene and the proton conductor carbonyl cyanide m -chlorophenylhydrazone (CCCP) caused loss of ethylene-forming activity and depolarized the vacuolar membrane potential. However, depolarization of the membrane potential with choline chloride and hyperpolarization by ATP did not affect ethylene biosynthesis. These conflicting results lead to the conclusion that vacuolar ethylene biosynthesis is not dependent on the vacuolar membrane potential. The possibility that the inhibition of ethylene biosynthesis by toluene and CCCP may result from direct hydrophobic interactions between these compounds and hydrophobic components of the ethylene-forming enzyme is discussed.     

Impact of vCJD on blood supply.

Variant Creutzfeldt-Jakob disease (vCJD) is an at present inevitably lethal neurodegenerative disease which can only be diagnosed definitely post mortem. The majority of the approximately 200 victims to date have resided in the UK where most contaminated beef materials entered the food chain. Three cases in the UK demonstrated that vCJD can be transmitted by blood transfusion. Since BSE and vCJD have spread to several countries outside the UK, it appears advisable that specific risk assessments be carried out in different countries and geographic areas. This review explains the approach adopted by Germany in assessing the risk and considering precautionary measures. A fundamental premise is that the feeding chain of cattle and the food chain have been successfully and permanently cleared from contaminated material. This raises the question of whether transmissions via blood transfusions could have the potential to perpetuate vCJD in mankind. A model calculation based on actual population data showed, however, that this would not be the case. Moreover, an exclusion of transfusion recipients from blood donation would add very little to the safety of blood transfusions, but would have a considerable impact on blood supply. Therefore, an exclusion of transfusion recipients was not recommended in Germany.     

Melatonin and thyroxine response to pollution in white stork nestlings (Ciconia ciconia): aspects of rhythmicity and age

There is growing evidence that ubiquitous environmental contaminants may interfere with vertebrate endocrine systems. The selected endocrine biomarkers are used to indicate the condition of free-ranging populations of wildlife, including avian species. The aim of this study was to determine the impact of environment quality on serum thyroxine (T4) and melatonin (Mel) in white stork nestlings (Ciconia ciconia) living in different locations: small villages in natural areas surrounded by forests and crop fields, near the city and near the copper smelter. We extended our analyses to examine the hormones' day-night changes in conjunction with chicks' age. Total serum T4 and Mel was measured by RIA. T4 level, as a decisive measure of thyroid hormone productivity, was significantly lower in the nestlings exposed to pollutants from the copper smelter. Mel, as a well-known scavenger of free radicals, was elevated in the nestlings in the area near the copper smelter. This study indicates that alteration in T4 and Mel levels could be a useful marker of exposure of nestling wild storks to different toxic substances in field studies. Mel is postulated to be a susceptible defensive molecule as a protective mechanism for organisms.     

New insights on ctenophore neural anatomy: immunofluorescence study in Pleurobrachia pileus (Müller, 1776)

Ctenophores are non-bilaterian animals sharing with cnidarians and bilaterians the presence of sensory receptors, nerve cells, and synapses, absent in placozoans and sponges. Although recent immunofluorescence studies have renewed our knowledge of cnidarian neuro-anatomy, ctenophores have been much less investigated despite their importance to understanding the origin and early evolution of the nervous system. In this study, the neuro-anatomy of the ctenophore Pleurobrachia pileus (Müller, 1776) was explored by whole-mount fluorescent antibody staining using antibodies against tyrosylated -tubulin, FMRFamide, and vasopressin. We describe the morphology of nerve nets and their local specializations, and the organization of the aboral neuro-sensory complex comprising the apical organ and polar fields. Two distinct nerve nets are distinguished: a mesogleal nerve net, loosely organized throughout body mesoglea, and a much more compact “nerve net” with polygonal meshes in the ectodermal epithelium. The latter is organized as a plexus of short nerve cords. This epithelial nervous system contains distinct sub-populations of dispersed FMRFamide and vasopressin immunoreactive nerve cells. In the aboral neuro-sensory complex, our most significant observations include specialized nerve nets underlying the apical organ and polar fields, a tangential bundle of actin-rich fibers (interpreted as a muscle) within the polar fields, and distinct groups of neurons labeled by anti-FMRFamide and anti-vasopressin antibodies, within the apical organ floor. These results are discussed in a comparative perspective.     

Methyl-beta-cyclodextrin induces mitochondrial cholesterol depletion and alters the mitochondrial structure and bioenergetics

There is growing evidence of mitochondrial membrane raft-like microdomains that are involved in the apoptotic pathway. The aim of this study was to investigate the effect of methyl-beta-cyclodextrin (MβCD), being a well-known lipid microdomain disrupting agent and cholesterol chelator, on the structure and bioenergetics of rat liver mitochondria (RLM). We observed that MβCD decreases the function of RLM, induces changes in the mitochondrial configuration state and decreases the calcium chloride-induced swelling. These data suggest that disruption of mitochondrial raft-like microdomains by cholesterol efflux on one hand impairs mitochondrial bioenergetics, but on the other hand it protects the mitochondria from swelling.     

Mobilization of bone marrow-derived progenitor cells in acute coronary syndromes

Two hypotheses explain the role of adult progenitor cells in myocardial regeneration. Stem cell plasticity which involves mobilization of stem cells from the bone marrow and other niches, homing to the area of tissue injury and transdifferentiation into functional cardiomyocytes. Alternative hypothesis is based on the observations that bone marrow harbors a heterogenous population of cells positive for CXCR4 - receptor for chemokine SDF-1. This population of non-hematopoietic cells expresses genes specific for early muscle, myocardial and endothelial progenitor cells (EPC). These tissue-committed stem cells circulate in the peripheral blood at low numbers and can be mobilized by hematopoietic cytokines in the setting of myocardial ischemia. Endothelial precursors capable of transforming into mature, functional endothelial cells are present in the pool of peripheral mononuclear cells in circulation. Their number significantly increases in acute myocardial infarction (AMI) with subsequent decrease after 1 month, as well as in patients with unstable angina in comparison to stable coronary heart disease (CHD). There are numerous physiological and pathological stimuli which influence the number of circulating EPC such as regular physical activity, medications (statins, PPAR-gamma agonists, estrogens), as well as numerous inflammatory and hematopoietic cytokines. Mobilization of stem cells in AMI involves not only the endothelial progenitors but also hematopoietic, non-hematopoietic stem cells and most probably the mesenchymal cells. In healthy subjects and patients with stable CHD, small number of circulating CD34+, CXCR4+, CD117+, c-met+ and CD34/CD117+ stem cells can be detected. In patients with AMI, a significant increase in CD34+/CXCR4+, CD117+, c-met+ and CD34/CD117+ stem cell number the in peripheral blood was demonstrated with parallel increase in mRNA expression for early cardiac, muscle and endothelial markers in peripheral blood mononuclear cells. The maximum number of stem cells was found early in ST-segment elevation myocardial infarction (<12 hours) with subsequent decrease through the 7-day follow-up and with concomitant changes in the levels of cytokines involved in the inflammatory response and stem cell recruitment. Moreover, peak expression of cardiac muscle and endothelial markers occurred at the same time as the most significant increase in CD34/CXCR4+ stem cell number. The SDF-1/CXCR-4 axis seems particularly important in stem/muscle progenitor cell homing, chemotaxis, engraftment and retention in ischaemic myocardium. The significance of autologous stem cells mobilization in terms of cardiac salvage and regeneration needs to be proved in humans but it seems to be a reparative mechanism triggered early in the course of acute coronary syndromes.