Performance of nymphal and adult Nezara viridula on selected alternate host plants

Laboratory studies with the southern green stink bug, Nezara viridula (L.) (Hemiptera: Pentatomidae), feeding on seeds or fruits of some alternate host plants, demonstrated differences in nymphal survival and development time, and body weight at adult emergence. Lowest mortalities (25%) were observed for nymphs on fruits of dakota mustard [Brassica kaber (DC.)] and siberian motherwort (Leonurus sibiricus L.). On fruits of castor bean (Ricinus communis L.) nymph mortality was ca. 60%, and on mature seeds of L. sibiricus ca. 75%. Total development time from second instar to adult ranged from ca. 26 days on B. kaber to ca. 42 days on R. communis. Fresh body weight at adult emergence was greatest for nymphs on L. sibiricus and lowest on R. communis. Adult survival after 30 days and mean longevity was greater on L. sibiricus than on the remaining foods, being drastically reduced on R. communis. In general, reproductive performance on all foods was similar, except R. communis, on which no female reproduced. Female weight gain of N. viridula was generally greater on L. sibiricus On R. communis, adults lost weight during their first week and showed the lowest weight gain at the end of day 29. Field observations coupled with these laboratory studies suggest that in the Warta area (northern Paraná state, Brazil, 23° 11 S), L. sibiricus and B. kaber are important alternate food plants in the seasonal phenology of N. viridula. R. communis, however, is of poor nutritional quality, serving primarily as a refuge.

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Résumé L'alimentation au laboratoire de N. viridula avec les graines et les fruits de diverses plantes a entraîné différentes mortalités larvaires, différentes vitesses de développement et des différences dans les poids des adultes à l'émergence. Les mortalités les plus faibles (25%) on été observées avec les fruits de Brassica kaber DC. et de Leonurus sibiricus L.Avec les fruits de Ricinus communis L., la mortalité larvaire était de 60%; sur graines mûres de L. sibiricus, elle était de 75%. La durée du développement du second stade à l'adulte a varié de 26 jours sur B. kaber à 42 jours sur R. communis. Le poids frais des adultes à l'émergence était le plus élevé avec L. sibiricus et le plus faible avec de R. communis. La longévité des adultes au-delà de 30 jours était la plus élevée avec L. sibiricus, et était fortement réduite avec R. communis. Dans l'ensemble, la reproduction était de même importance avec les différents aliments, à l'exception de R. communis avec lequel les femelles ne se reproduisaient pas. Le gain de poids des femelles était généralement supérieur avec L. sibiricus; avec R. communis les adultes ont perdu du poids pendant la première semaine et ont présenté le plus faible gain à la fin du 29ème jour.Des observations dans la nature, associées à ces expériences de laboratoire, laissent supposer que dans la zone de Warta (au Nord de l'état de Paraná, 23° 11 S, au Bresil), L. sibiricus et B. kaber sont des plantes hôtes alternatives importantes dans la phénologie saisonnière de N. viridula. Cependant, R. communis, de faible valeur alimentaire, sert avant tout de refuge.

     

Isolation and characterization of phage F9-11 from a lysogenicDeleya halophila strain

Thirty-eight strains ofDeleya halophila species were examined for production of phage after mitomycin C induction. Thirty-two of them were able to inhibit growth of some other strains. Phage F9-11, isolated fromD. halophila strain F9-11, showed an isometric head and a noncontractile tail. The effects of salt concentrations variation on the stability and replication of this phage were established. Its replication was possible at a wide range of marine salt concentrations, from 2.5% to 15% (wt/vol). Stability seems to be influenced by osmolarity of medium rather than by NaCl level. The euryhaline character showed by F9-11 phage is evoked as an important factor for the survival of this phage in its environment.     

Industrial yeast strain improvement: construction of strains having the killer character and capable of utilizing starch

Summary A hybrid of Saccharomyces cerevisiae with the ability to utilize starch and to produce the killer toxin was constructed by the protoplast fusion technique. The hybrid was obtained in two steps. In the first, a wild killer strain was fused with a laboratory strain (S. cerevisiae STA2). A fusion product which carried the killer factor and the ability to grow on starch was selected. In the second step, this hybrid was fused with a baker's yeast.     

Occurrence of a Large Ca2+-Independent Release of Glutamate During Anoxia in Isolated Nerve Terminals (Synaptosomes)

Isolated rat cerebral cortical synaptosomes made anoxic by addition of cyanide developed an inhibition of the Ca2+-dependent release of glutamate 2 min after the addition of the metabolic inhibitor when the intrasynaptosomal ATP/ADP ratio decreased below 1.7. In contrast, cyanide induced a continuous efflux of glutamate through a Ca2+-independent pathway that accounted for the release of 25% of total intrasynaptosomal glutamate in 5 min. The results suggest that a Ca2+-independent release of glutamate could be implicated in the neurotoxic action of this amino acid during anoxia.     

Active glycolysis and glycogenolysis in early stages of primary cultured hepatocytes. Role of AMP and fructose 2.6-bisphosphate

Summary This study examines the factors involved in the rapid glycolysis and glycogenolysis that occur during the first stages of hepatocyte culture: a) Shortly after seeding glycolysis, estimated as lactate released to culture medium, increased 10 times in comparison to that reported in vivo. By 8 to 9 h of culture, hepatocytes were nearly glycogen-depleted even in the presence of insulin. b) 6-Phosphofructo-2-kinase remained 100% active during this period. The proportion of the initial active phosphorylase (87%) decreased to 57% by 7 h of culture. c) Fructose 2,6-bisphosphate content was initially similar to that found in liver of fed animals, decreased after seeding and increased thereafter up to four times the initial concentration. In spite of changes in the concentration of this activator, the glycolytic rate remained high and constant. d) ADP and AMP increased sharply after cell plating, reaching values 1.7 and 3.5 times higher. The rise in AMP levels may be involved in the activation of glycolysis and glycogenolysis, because this metabolite is known to act as an allosteric activator of phosphofrucktokinase and glycogen phosphorylase. This metabolic situation resembles that of cells under hypoxia. Part of this work was presented at the 38th Annual Meeting of the Tissue Culture Association, Washington, DC, May 1987.     

Frequency of the ΔF508 deletion and G551D,R553X and G542X mutations in Yugoslav CF patients

Summary A study was undertaken to find the frequency of the F508 deletion and those of the G551D, R553X and G524X mutations among the mainly Slavic population of Serbia, Bosnia, Herzegovina, and Montenegro and compare the frequencies determined with those in other European populations. The F508 mutation was found to account for about 70% of CF genes in central Jugoslavia, where its frequency is significantly higher than elsewhere in Southern European populations.     

Contrasting breeding systems in twoEriotheca (Bombacaceae) species of the Brazilian cerrados

The pollination biology and breeding systems ofEriotheca pubescens andE. gracilipes have been studied. These two species occur as trees in cerrado vegetation, the neotropical savannas of Central Brazil, with partially sympatric distributions. They have similar phenology and floral structure, although the flowers ofE. pubescens are larger. Both species have nectar flowers pollinated by largeAnthophoridae bees but the main pollinators of each species differ in size. The species have markedly different breeding systems: late-acting self-incompatibility inE. gracilipes and apomixis stimulated by pollination inE. pubescens.     

Mechanism of action of levonorgestrel: in vitro metabolism and specific interactions with steroid receptors in target organs.

Levonorgestrel (LNG) is a synthetic steroid that displays potent progestional and androgenic effects but it lacks estrogen-like activity. To examine the mode of action of this progestin, we studied its metabolism in vitro in target organs and the specific interactions of LNG and its metabolites with putative steroid receptors. The results demonstrated that [³H]LNG was efficiently converted to A-ring reduced derivatives when incubated with rat hypothalamus and pituitary. Under optimal incubation conditions, [³H]5-dihydro LNG (5-LNG) and [³H]3-5-tetrahydro LNG (3,5-LNG) were identified as the major metabolic conversion products, while [³H]3ß, 5-LNG formation occured to a lesser extent. A-ring reduction of LNG was NADPH-dependent. Assessment of the relative binding affinities of LNG and its derivatives to progesterone (PR), androgen (AR) and estrogen (ER) receptors by displacement analysis revealed that unchanged LNG binds with high affinity to PR and AR but not to ER. 5-LNG exhibited a diminished though significant interactions with PR and an enhanced binding affinity for AR as compared with LNG, indicating that 5-reduction of LNG increases its affinity for AR. The most striking finding was that further reduction of the 5-LNG molecule at C-3 abolished its binding activity to PR, AR, and even to ER. The overall data provides a plausible explanation for the lack of estrogen agonistic action of LNG and for its potent progestational and androgenic effects.     

Glutamic acid decarboxylase of embryonic avian retina cells in culture: Regulation byγ-aminobutyric acid (GABA)

1. Retina-cell aggregate cultures expressed glutamate decarboxylase activity (L-glutamate 1-carboxylase; EC 4.1.1.15) as a function of culture differentiation. 2. Glutamic acid decarboxylase (GAD) activity was low in the initial phases of culture and increased eight-fold until culture day 7, remaining high up to day 13 (last stage studied). 3. The addition of GABA to the culture medium 24 h after cell seeding almost totally prevented the expression of GAD activity. 4. In association with decreased enzyme activity, aggregates exposed to GABA did not display immunoreactivity for GAD, suggesting that GAD molecules were either lost from GABAergic neurons or significantly altered with GABA treatment. 5. Control, untreated aggregates showed intense GAD immunoreactivity in neurons. Positive cell bodies were characterized by a thin rim of labeled cytoplasm with thickest labeling at the emergence of the main neurite. 6. Heavily labeled patches were also observed throughout the aggregates, possibly reflecting regions enriched in neurites. 7. The GABA-mediated reduction of GAD immunoreactivity was a reversible phenomenon and could be prevented by picrotoxin.     

Purification and properties ofl-serine dehydratase fromLactobacillus fermentum ATCC 14931

l-Serine dehydratase fromLactobacillus fermentum was purified 100-fold. It was stabilized by the presence of 1 mM l-cysteine in 50 mM phosphate buffer. M_r=150,000 was determined by gel filtration. The enzyme consists of four apparently identical subunits (M_r=40,000) that were observed after treatment with sodium dodecyl sulfate. The apparent K_m forl-serine was 65 mM. Fe⁺⁺ was required for the enzymatic activity, and the apparent K_m value for this reaction was 0.55 mM. Maximum enzymatic activity was observed at 45°C and pH 8.0 in 50 mM phosphate buffer. At pH values different from the optimum, a positive cooperativity between substrate molecules was observed. The activation energy of the reaction was 11,400 and 22,800 cal × mol^–1 for temperature values more than and less than 35°C respectively. The purified enzyme showed a maximum absorption between 400 and 420 nm, indicating the presence of pyridoxal-5-phosphate (PLP) as a prosthetic group. The PLP concentration was 0.027 µmoles per milligram of protein. The data suggest that there is 1 mol of PLP for each protein subunit.