Ethylene and IAA interactions in the inhibition of photoperiodic flower induction of <Emphasis Type="Italic">Pharbitis nil</Emphasis>

It has been shown that both IAA and ethylene application inhibit flower induction in the short-day plant Pharbitis nil. However application of IAA has elevated ethylene production in this plant, as well. Strong enhancement of ethylene production is also correlated with the night-break effect, which completely inhibits flowering. In order to determine what the role of IAA and ethylene is in the photoperiodic flower induction in Pharbitis nil, we measured changes in their levels during inductive and non-inductive photoperiods, and the effects of ethylene biosynthesis and action inhibitors on inhibition of flowering by IAA. Our results have shown that the inhibitory effect of IAA on Pharbitis nil flowering is not physiological but is connected with its effect on ethylene biosynthesis.     

Susceptibility of insecticide-susceptible and wild house flies (Diptera: Muscidae) to abamectin on whitewashed and unpainted wood

Unpainted plywood panels treated with 0.1% abamectin (avermectin B1) provided greater than 90% control of house flies, Musca domestica L., susceptible to insecticides for 4 wk and greater than 70% control for 7 wk compared with 46-92% control observed with permethrin at the same time and rate of application. Efficacy of abamectin on whitewashed panels was similar to that observed on unpainted panels, whereas permethrin was ineffective on whitewashed panels at all rates tested (range, 0.001-0.1%) at all intervals after treatment. Bioassays of newly colonized house flies resistant to permethrin indicated that wild populations may be cross-resistant to abamectin.     

Mechanisms of TonB-catalyzed iron transport through the enteric bacterial cell envelope

The recent solution of enteric bacterial porin structure, and new insights into the mechanism by which outer membrane receptor proteins recognize and internalize specific ligands, advocates the re-evaluation of TonB-dependent transport physiology. In this minireview we discuss the potential structural features of siderophore receptors and TonB, and use this analysis to evaluate both existing and new models of energy and signal transduction from the inner membrane to the outer membrane of gram-negative bacteria.     

Structural and immunochemical studies on the lipopolysaccharide of the ‘T-antigen’-containing mutant Proteus mirabilis R14/1959

Abstract In DOC-PAGE, lipopolysaccharide (LPS) of Proteus mirabilis R14/1959 (Rb-type) mutant showed a ladder-like migration pattern indicating the presence of a high molecular weight polysaccharide chain. The isolated polysaccharide, called T-antigen because of similarity with the T1 chain of Salmonella friedenau LPS, contained d -glucose, d -galacturonic acid ( d -GalA), and d -GlcNAc in molar ratios 2:1:1 and was structurally different from the O-antigen of the parental S-strain P. mirabilis S1959 but identical to the O-antigen of another S-strain Proteus penneri 42. The importance of a d -GalA( l -Lys)-containing epitope, most likely present in the core region of LPS, and of GalA present in the T-antigen chain in manifesting the serological specificity of P. mirabilis R14/1959 were revealed using rabbit polyclonal homologous and heterologous R- and O-specific antisera and the appropriate antigens, including synthetic antigens which represent partial structures of various Proteus LPS.     

Amino-modified silicate gels prepared by sol-gel processing as metal-ion sorbents

Two series of amino-modified silicate gels prepared by sol-gel processing were used to absorb Cu(II), Ni(II), Co(II), Mn(II) and Cr(III) from aqueous solutions. These easily prepared sorbents with various content of primary amino groups in series (A) or primary and secondary amino groups in series (AA) have reasonable stability. The gel composition, time and concentration dependence of the uptake of the metal ions by these materials were studied systematically. These materials would be further used as supports to disperse catalytically active phases by conventional wet chemical procedures. Apart from this they demonstrate potential for the preconcentration aid for transition metal analysis.     

Evolution of the ferric enterobactin receptor in gram-negative bacteria.

Using sodium dodecyl sulfate-polyacrylamide gel electrophoresis of iron-deficient and replete cell envelopes, 59Fe-siderophore uptake studies, and Western immunoblots and cytofluorimetric analyses with monoclonal antibodies (MAbs), we surveyed a panel of gram-negative bacteria to identify outer membrane proteins that are structurally related to the Escherichia coli K-12 ferric enterobactin receptor, FepA. Antibodies within the panel identified FepA epitopes that are conserved among the majority of the bacteria tested, as well as epitopes present in only a few of the strains. In general, epitopes of FepA that are buried in the outer membrane bilayer were more conserved among gram-negative bacteria than epitopes that are exposed on the bacterial cell surface. The surface topology and tertiary structure of FepA are quite similar in E. coli and Shigella flexneri but differ in Salmonella typhimurium. Of the 18 different genera tested, 94% of the bacteria transported ferric enterobactin, including members of the previously unrecognized genera Citrobacter, Edwardsiella, Enterobacter, Haemophilus, Hafnia, Morganella, Neisseria, Proteus, Providencia, Serratia, and Yersinia. The ferric enterobactin receptor contains at least one buried epitope, recognized by MAb 2 (C. K. Murphy, V. I. Kalve, and P. E. Klebba, J. Bacteriol. 172:2736-2746, 1990), that is conserved within the structure of an iron-regulated cell envelope protein in all the bacteria that we have surveyed. With MAb 2, we identified and determined the Mr of cell envelope antigens that are immunologically related to E. coli FepA in all the gram-negative bacteria tested. Collectively, the library of anti-FepA MAbs showed unique patterns of reactivity with the different bacteria, allowing identification and discrimination of species within the following gram-negative genera: Aeromonas, Citrobacter, Edwardsiella, Enterobacter, Escherichia, Haemophilus, Hafnia, Klebsiella, Morganella, Neisseria, Proteus, Providencia, Pseudomonas, Salmonella, Serratia, Shigella, Vibrio, and Yersinia.     

Susceptibility of house flies (Diptera: Muscidae) and five pupal parasitoids (Hymenoptera: Pteromalidae) to abamectin and seven commercial insecticides.

Assays of five commercial insecticides applied as residual sprays at label rates to plywood indicated the most toxic insecticide overall for pteromalid parasitoids of house flies, Musca domestica L., was Atroban (permethrin), followed by Ciodrin (crotoxyphos), Rabon (tetrachlorvinphos), Ectrin (fenvalerate), and Cygon (dimethoate). Insecticide-susceptible house flies were susceptible to all five insecticides (mortality, 62-100%). Flies that were recently colonized from populations on dairy farms in New York were susceptible only to Rabon. Urolepis rufipes (Ashmead) was the most susceptible parasitoid species overall to these insecticides, followed by Muscidifurax raptor Girault & Sanders, Nasonia vitripennis Walker, Pachycrepoideus vindemmiae (Rondani), and Spalangia cameroni Perkins. Compared with susceptible flies, newly colonized flies showed moderate resistance to avermectin B1a (abamectin). Abamectin was more toxic to all of the parasitoids except N. vitripennis and S. cameroni than to newly colonized house flies when exposed for 90 min to plywood boards treated with 0.001-0.1% abamectin. Space sprays with Vapona (dichlorvos) killed all of the parasitoids and susceptible flies and 64% of the newly colonized flies when insects were placed directly in the path of the spray; mortality was substantially lower among flies and parasitoids protected under 5 cm of wheat straw. Space sprays with Pyrenone (pyrethrins) killed greater than 86% of all insects exposed to the spray path except for the newly colonized flies (1% mortality); mortality of insects protected under straw was low (less than 12%) except for S. cameroni (76%). Because responses of the five parasitoids to the different insecticides varied considerably, general conclusions about parasitoid susceptibility to active ingredients, insecticide class, or method of application were not possible.     

Leptin impairs myogenesis in C2C12 cells through JAK/STAT and MEK signaling pathways

Reduced lean body mass in genetically obese (ob/ob) or anorectic/cachectic subjects prompted us to verify the hypothesis whether leptin, white adipose tissue cytokine, might be a negative organizer of myogenesis. Recombinant leptin (100 ng/mL) stimulated mitogenesis together with the raise in T^202/Y²⁰⁴P-ERK1/2 protein expression. Concomitantly, it impaired cell viability and muscle fiber formation from C2C12 mouse myoblasts. Detailed acute and chronic studies with the use of metabolic inhibitors revealed that both JAK/STAT3 and MEK/MAPK but not PI3-K/AKT/GSK-3β signaling pathways were activated by leptin, and that STAT3 (Y⁷⁰⁵P-STAT3) and MEK (T^202/Y²⁰⁴P-ERK1/2) mediate these effects. In contrary, insulin evoked PI3-K-dependent phosphorylation of AKT (S⁴⁷³) and GSK-3β (S⁹) and insulin surpassed leptin-dependent inhibition of myogenic differentiation in PI3-K-dependent manner. GSK-3β seems to play dual role in muscle development. Insulin-dependent effect on GSK-3β (S⁹P-GSK-3β) led to accelerated myotube construction. In contrary, leptin through MEK-dependent manner caused GSK-3β phosphorylation (Y²¹⁶P-GSK-3β) with resultant drop in myoblast fusion. Summing up, partially opposite effects of insulin and leptin on skeletal muscle growth emphasize the importance of interplay between these cytokines. They determine how muscle mass is gained or lost.