Les régulateurs de croissance d'insectes (RCI), mimiques de l'hormone juvénile,en tant que moyen de lutte morphogénétique et ovicide contre les tordeuses des vergers

Résumé La métamorphose des insectes est régie par un équilibre hormonal complexe dans lequel l'hormone juvénile (HJ) joue un rôle important. Au dernier stade larvaire, la teneur en HJ est particulièrement faible dans le corps de l'insecte. Si un régulateur de croissance d'insectes (RCI)-un mimétique de l'HJ-est appliqué à ce moment-là, la mue nymphale est pertubée provoquant des déformations morphogénétiques caractéristiques. La teneur en HJ est également très faible dans les ufs fraîchement pondus. Les traitements aux RCI peuvent par conséquent perturber le développement embryonnaire de certaines espèces et produire ainsi un effet ovicide. Depuis quelques années deux RCI-le fenoxycarb et le CGA 45 128-ont été testés pour leur activité morphogénétique sur le dernier stade larvaire de quelques ravageurs tels qu'Adoxophyes orana F.v.R., ainsi que pour leur activité ovicide sur les ufs frais de Cydia pomonella L. et Grapholita funebrana Tr. Après quelques années d'expérimentation et de commercialisation des RCI dans les vergers européens, il s'avère que l'utilisation de ces produits peu toxiques, sélectifs et peu nocifs pour la faune utile, constitue une amélioration considérable pour l'aménagement de la lutte intégrée.

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Insect growth regulators (IGR), mimics of juvenile hormone, as morphological and ovicidal means of control against orchard tortricids

Summary Metamorphosis is regulated by a complex hormonal balance in which juvenile hormone (JH) plays an important part. At the last larval instar the content of JH is particularly low in the insect body. If an insect growth regulator (IGR) — a mimic of JH-is applied at this time, the pupal moult may be disturbed with the characteristic morphogenetical deformations. The JH content is also very low in freshly laid eggs. Therefore IGR treatments may disturb the embryonic development of some species and produce an ovicidal activity. During a few years two IGR-fenoxycarb and CGA 45128-were evaluated for their morphogenetical effect on the last larval instar of Adoxophyes orana F.v.R. and their ovicidal effect on freshly laid eggs of Cydia pomonella L. and Grapholita funebrana Tr. After a few years of experimentation with both compounds and of commercialisation of fenoxycarb in European orchards, IGR confirmed to present a considerable improvement in integrated pest management due to selectivity, and low mammal toxicity.

     

Beta-adrenergic receptor characteristics of postnatal rat myocardial cell preparations

Summary Primary mycolardial cell cultures and freshly isolated cardiac cells in suspension resprensent two isolated, whole cell models for investigating cellular transsarcolemmal⁴⁵Ca⁺⁺ exchange in response to a receptor-coupled stimulus. Studies were performed to characterize beta-adrenergic receptor binding, beta-adrenergic receptor mediated cellular calcium (⁴⁵Ca⁺⁺) exchange, and viability in purified primary myocardial cell cultures and freshly isolated cardiac cells in suspension obtained from 3-to 3-d-old Sprague-Dawley rats. In addition, beta-adrenergic receptor binding was characterized in whole-heart crude membrane preparations. All three preparations had saturable beta-adrenergic binding sites with the antagonist [¹²⁵I]iodopindolol ([¹²⁵I]IPIN). The suspensions had a significantly lower B _max (42±6 fmol/mg protein) than the membranes and cultures (77±8 and 95±10 fmol/mg protein, respectively). The K _D of the cultures (218±2.0 pM) was significantly higher than that for the suspensions (107 ±1.3 pM) and membranes (93±1.3 pM). Viability was significantly lower in the suspensions (57%) when compared to 94% viability in myocardial cell cultures after 3 h of incubation in Kreb's Henseleit buffer. Incubation of the cultures with 5.0×10⁻⁷ M isoproterenol resulted in a significant increase in⁴⁵Ca⁺⁺ exchange as early as 15 s. In contrast,⁴⁵Ca⁺⁺ exchange into the suspensions was not increased. Although both primary cell cultures and cardiac cells in suspension possess saturable beta-adrenergic receptors, only the monolayer cultures exhibited functional beta-adrenergic receptor-mediated⁴⁵Ca⁺⁺ exchange. Of the two intact cell models investigated, these data suggest that primary myocardial cell cultures are more suitable than cell suspensions for investigating beta-adrenergic receptor binding and functions in the postnatal rat heart. This research was supported by The University of Texas Research Institute, a grant from the Texas Advanced Research Technology Program awarded to S. W. Leslie and R. E. Wilcox, and contract 223-86-2109 from the Food and Drug Administration.     

Calcium (45Ca) accumulation and transport in chicory (Cichorium intybus L.) root during bud development (forcing)

The lower part (4 cm) of the witloof chicory tap-root (15 cm) was immersed in a complete nutrient solution for 21 days, in the darkness at 18°C and at high RH. This process of forcing which leads to the emergence of an etiolated bud (chicon) was associated with a decrease in root dry weight. Although the amount of calcium in the root and the root cationic exchange capacity remained constant during forcing, the net uptake of calcium, negligible at the onset of forcing, progressively increased to a rate after ten days of 45 mol day^–1. Absorption of ⁴⁵Ca remained at a constant high rate, while the initially low upward migration of ⁴⁵Ca within the root and the chicon accelerated markedly. This upward migration was associated with a progressive decline in the release of newly absorbed ⁴⁵Ca. The data support the hypothesis that calcium acquisition by witloof chicory root is predominantly determined by calcium efflux. As the forcing progressed, the influx remained almost constant while a large decrease in the efflux led to a net uptake of calcium. Upward translocation was probably linked to the formation of new negative exchange sites within the growing chicon. The hypothesis that calcium movement occurred along a preferential pathway (xylem vessels) or involved a mass movement through the root is discussed.     

The alpha-glucosyltransferases of bacteriophages T2, T4 and T6. A comparison of their primary structures

Summary With the aim of comparing the primary structures of gene products coded for by T-even bacteriophages we constructed clone libraries of the DNAs of bacteriophages T2 and T6. Using hybrid M13 phages carrying the gene for the T4-coded -glucosyl transferase (gt) we isolated corresponding T2 and T6 clones. The nucleotide sequences of the three gt genes and the amino acid sequences derived were compared. The differences between the genes and their products are discussed in terms of structure, function and evolutionary aspects.Abbreviations bp base pair - gt glucosyl transferase - HMC 5-hydroxymethyl cytosine - orf open reading frame - Xgal 5-bromo-4-chloro-3-indolyl--d-galactoside     

Lymphocyte subpopulations of regional lymph nodes in human colon and gastric adenocarcinomas

 In order to study the host immune response to tumours, previous knowledge of the cellular composition of regional draining lymph nodes is necessary. Enlarged regional lymph nodes are a common finding in colon and gastric adenocarcinomas. We have studied the cellular composition of normal non-reactive and of regional draining lymph nodes of colon and gastric adenocarcinomas. In normal non-reactive lymph nodes, T lymphocytes (CD2⁺, CD7⁺) constituted the largest fraction of the lymphoreticular cells. These lymphocytes were mainly CD4⁺, and there were more cells expressing the CD45RA isoform of the CD45 antigen than CD45RO. Reactive lymph nodes presented a decreased proportion of CD4⁺ CD45RA⁺ cells and an increased number of B cells. Although most of the T cells in the reactive nodes were CD4⁺ CD45RO⁺, their proportion was similar to that found in normal non-reactive nodes. We studied the presence of the molecules CD28 and CD80 involved in the processes of interaction and activation of T and B lymphocytes. The CD28 molecule was found in all the T lymphocytes, while the CD80 molecule was weakly expressed on the B lymphocyte membrane. Received: 4 January 1996 / Accepted: 28 May 1996     

Carbohydrate specificity of IgM autoantibodies to CD45 in Systemic Lupus Erythematosus

Patients with SLE develop IgM autoantibodies to different isoforms of CD45, the major surface membrane protein tyrosine phosphatase on lymphocytes and other nucleated hemopoietic cells. Because such autoantibodies could have a potential role in the development of immune dysfunction in this disorder, we performed a series of experiments to characterize their antigenic specificity further. Blots of recombinantE. coli fusion proteins encoded by exons 3–7 of the p220 and p180 isoforms were uniformly non-reactive with SLE IgM, suggesting that anti-CD45 autoantibodies in SLE are directed against conformational and/or carbohydrate epitopes, rather than linear polypeptide epitopes. This issue was examined further using chemically and enzymatically modified CD45 purified from T cells by lectin affinity chromatography as substrates. Treatment of CD45 with 25 mM sodium-m-periodate, sufficient to abrogate binding to various lectins, abolished the reactivity with SLE anti-CD45 autoantibodies. On the other hand, digestion of CD45 with neuraminidase enhanced the binding of anti-CD45 autoantibodies from some of the SLE sera. This result probably reflects decreased steric hindrance or charge repulsion because the binding of mouse monoclonal antibodies directed against linear polypeptide epitopes of CD45 was similarly enhanced. Digestion of CD45 with N-glycosidase F had no effect on autoantibody staining. Taken together, these data suggest that IgM anti-CD45 autoantibodies in SLE recognize non-sialylated carbohydrate determinants in the highly O-glycosylated polymorphic domains of CD45.Abbreviations SLE systemic lupus erythematosus - SBA soybean agglutinin - RCAI Ricinus communis agglutinin - SNL Sambucus nigra lectin - MBP maltose binding protein - mAb monoclonal antibody - WGA wheat germ agglutinin     

Rye chromosome arm 3RS encodes a homodimeric inhibitor of insect α-amylase

A new inhibitor of insect -amylase, designated RDAI-1, has been purified from rye (Secale cereale L.) endosperm. RDAI-1 is homologous to wheat homodimeric inhibitors. This homology is supported by their similar N-terminal amino-acid sequences, inhibitory activities towards amylases from Tenebrio molitor (Coleoptera) and human saliva, and aggregative properties in gel-filtration chromatography. The gene encoding RDAI-1, IdhaR1, is located on the short arm of chromosome 3R, which is homoeologous with wheat chromosome arms 3BS and 3DS, where the genes for homodimeric inhibitors have been previously mapped.     

Sequence of the gene for a NAD(P)-dependent formaldehyde dehydrogenase (class III alcohol dehydrogenase) from a marine methanotroph Methylobacter marinus A45

Abstract A fragment of Methylobacter marinus A45 DNA has been cloned and sequenced, and an open reading frame has been identified that could code for a 46-kDa polypeptide. Comparison of the deduced amino acid sequence of the polypeptide against the protein data bank has revealed strong similarity with a number of alcohol dehydrogenases, with highest similarity towards class III alcohol dehydrogenases, which recently have been shown to be identical to glutathione-dependent formaldehyde dehydrogenases. We were unable to measure appreciable levels of NAD(P)-dependent formaldehyde dehydrogenases or alcohol dehydrogenase activities using aldehydes or primary or secondary alcohols in cell-free extracts from batch cultures of M. marinus A45. However, formaldehyde dehydrogenases activity was detected on zymograms. Our data suggest that, although NAD(P)-linked formaldehyde dehydrogenase or alcohol dehydrogenase activities are undetectable in cell-free extracts of most methylotrophs employing the ribulose monophosphate pathway for formaldehyde assimilation and dissimilation, the gene encoding formaldehyde dehydrogenase is present in M. marinus A45 and may be present in more of these organisms as well.     

Computer simulation and interpretation of45Ca efflux profile patterns

Summary Stimulations or inhibitions by various agents of⁴⁵Ca efflux from prelabeled cells or tissues display distinct and reproducible profile patterns when the results are plotted against time as fractional efflux ratios (FER). FER is the fractional efflux of⁴⁵Ca from stimulated cells divided by the fractional efflux from a control unstimulated group. These profile patterns fall into three categories: peak patterns, exponential patterns, and mixed patterns. Each category can be positive (stimulation) or negative (inhibition). The interpretation of these profiles is difficult because⁴⁵Ca efflux depends on three variables: the rate of calcium transport out of the cell, the specific activity of the cell compartment from which the calcium originates, and the concentration of free calcium in this compartment. A computer model based on data obtained by kinetic analyses of⁴⁵Ca desaturation curves and consisting of two distinct intracellular pools was designed to follow the concentration of the traced substance (⁴⁰Ca), the tracer (⁴⁵Ca), and the specific activity of each compartment before, during, and after the stimulation or the inhibition of calcium fluxes at various pool boundaries. The computer model can reproduce all the FER profiles obtained experimentally and bring information which may be helpful to the interpretation of this type of data. Some predictions of the model were tested experimentally, and the results support the views that a peak pattern may reflect a sustained change in calcium transport across the plasma membrane, that an exponential pattern arises from calcium mobilization from an internal subcellular pool, and that a mixed pattern may be caused by a simultaneous change in calcium fluxes at both compartment boundaries.     

Effects of Na readmission on cellular45Ca fluxes in Na-Depleted guinea pig taenia coli

Summary The removal of Na from the medium causes a cellular Ca uptake in the smooth muscle of the guinea pig taenia coli which is rapidly reversed if medium Na is readmitted. This net extrusion was characterized in tissues which were first Na-depleted in a zero-Na (sucrose) solution. Li was able to substitute for Na in mediating this effect. K was also able to mimic Na in this respect if the depolarization-mediated Ca influx caused by the isotonic K solution was blocked with 10^–5 m D-600. The net Ca extrusion upon Na readmission was due to a small decrease in Ca influx, as well as a marked increase in the transmembrane Ca efflux rate, as revealed by⁴⁵Ca washout experiments. The increased⁴⁵Ca efflux upon Na readmission could be mimicked by Li, K, choline and tris. We conclude that the Na/Ca-exchange hypothesis is insufficient to explain these data, in that both Ca extrusion and⁴⁵Ca efflux can be stimulated in the absence of a Na gradient, or in the absence of any monovalent cationic gradient. These observations are discussed in terms of a possible intracellular competition of Ca and monovalent cations for anionic binding sites, as well as with regard to a possible direct stimulation of a plasmalemmal CaATPase by monovalent cations.