Studies on the oviposition and longevity ofIlione albiseta [Dipt.: Sciomyzidae] — Potential biological control agent of liver fluke

The effect of 5 constant temperatures (10, 14, 17, 20 and 23°C) on the oviposition and longevity ofIlione albiseta was investigated. Most eggs were laid at 14–17°C and mean oviposition period declined progressively above and below 14°C. There was no significant difference between oviposition rates or preoviposition periods at each constant temperature, but the mean number of days between egg laying for each female was significantly greater at 10 °C than at 17, 20 and 23 °C than at 20 °C. The percentage of infertile eggs laid ranged from 9.2% at 23 °C to 17.9 % at 20 °C and these eggs tended to be laid at the beginning and end of each oviposition period. A possible association between sex ratio of the emergent adult and temperature is also discussed.      

A replication study of human exposure to 60-Hz fields: effects on neurobehavioral measures.

The purpose of this study was to reproduce and extend an earlier investigation of the effects of human exposure to combined, 60-Hz electric and magnetic fields. This paper presents the neurobehavioral results. Thirty men participated in one training session and four testing sessions. Subjects were randomly assigned to two groups. The 18 subjects in Group I were exposed (9 kV/m, 20 microT) and sham exposed in two counterbalanced orders. In Group II, half of 12 subjects were exposed (9 kV/m, 20 microT) every session, and the remaining half were sham exposed every session. The study was doubly blinded. Measures of cardiac interbeat interval, event-related brain potentials, and performance were obtained before, during, and after exposures. As in the earlier study, exposure to the combined field resulted in a statistically significant slowing of heart rate, in changes in late components of event-related brain potentials, and in decreased errors on a choice reaction-time task. In addition, field effects on several other measures approached statistical significance. The physiological measures obtained during exposure indicated that effects were greatest soon after the field was switched on, and again when it was switched off. The data indicate that changes in exposure level may be more important than duration of exposure for producing effects in human beings.     

Purification and properties of a F420-nonreactive,membrane-bound hydrogenase from Methanosarcina strain Gö1

The distribution of the F₄₂₀-reactive and F₄₂₀-nonreactive hydrogenases from the methylotrophic Methanosarcina strain Gö1 indicated a membrane association of the F₄₂₀-nonreactive enzyme. The membrane-bound F₄₂₀-nonreactive hydrogenase was purified 42-fold to electrophoretic homogeneity with a yield of 26.7%. The enzyme had a specific activity of 359 mol H₂ oxidized · min^-1 · mg protein^-1. The purification procedure involved dispersion of the membrane fraction with the detergent Chaps followed by anion exchange, hydrophobic and hydroxylapatite chromatography. The aerobically prepared enzyme had to be reactivated anaerobically. Maximal activity was observed at 80°C. The molecular mass as determined by native gel electrophoresis and gel filtration was 77000 and 79000, respectively. SDS gel electrophoresis revealed two polypeptides with molecular masses of 60000 and 40000 indicating a 1:1 stoichiometry. The purified enzyme contained 13.3 mol S^2-, 15.1 mol Fe and 0.8 mol Ni/mol enzyme. Flavins were not detected. The amino acid sequence of the N-termini of the subunits showed a higher degree of homology to cubacterial uptake-hydrogenases than to F₄₂₀-dependent hydrogenases from other methanogenic bacteria. The physiological function of the F₄₂₀-nonreactive hydrogenase from Methanosarcina strain Gö1 is discussed.Abbreviations transmembrane electrochemical gradient of H^- - CoM-SH 2-mercaptoethanesulfonate - F₄₂₀ (N-l-lactyl--l-glutamyl)-l-glutamic acid phospodiester of 7,8-didemethyl-8-hydroxy-5-deazariboflavin-5-phosphate - F₄₂₀H₂ reduced F₄₂₀ - HTP-SH 7-mercaptoheptanoylthreonine phosphate - Mb. Methanobacterium - PMSF phenylmethyl-sulfonylfluoride - Cl₃AcOH trichloroacetic acid     

Amino acid substitution analysis of E. coli thymidylate synthase: The study of a highly conserved region at the N-terminus

Amino acid substitution analysis within a highly conserved region of Escherichia coli thymidylate synthase (TS), using suppression of amber mutations by tRNA suppressors, has yielded a bank of 124 new mutationally altered TS proteins. These mutant proteins have been used to study the structure-function relationship of the Escherichia coli TS protein at the N-terminus corresponding to residues 20 through 35. This region contains a block of amino acids whose sequence has been well conserved among other known TS proteins from various organisms. Positions 20 through 25 contain a surface loop structure and positions 26 through 35 encompass a β-strand. We find that residues surrounding a β-bulge structure within the β-strand are particularly sensitive to amino acid substitution, suggesting that this structure is maintained by a highly ordered packing arrangement. Three residues in the surface loop that are present at the base of the substrate binding pocket are also sensitive to amino acid substitution. The remainder of the conserved sites, including those at the dimer interface, are tolerant to most, if not all, of the substitutions tested. © 1992 Wiley-Liss, Inc.     

Biological control of Pythium damping‐off by seed‐treatment with pseudomonas putida: Relationship with ethanol production by pea and soybean seeds

The relationship between biocontrol activity of Pseudomonas putida strain N1R against Pythium ultimum on pea and soybean seeds and the reduction in ethanol evolution by imbibed seeds was investigated under different treatment conditions, including temperature and numbers of seed‐applied cells of the bacterium. Treatment with strain N1R increased emergence at all temperatures, except for soybean at 12 °C and reduced ethanol concentration in the spermosphere of imbibed seeds at several temperatures. The concentration of bacterial cells in the seed treatment suspension also significantly affected biocontrol efficiency and reduced ethanol production, especially in pea seeds. In contrast, the duration (0–7 h) of submergence of seeds in bacterial suspension had little effect on biocontrol activity of N1R, although submergence of soybean seeds reduced their emergence even in the absence of the pathogen or biocontrol agent. Competition for seed‐derived compounds, including ethanol, is suggested to be one possible mechanism of biocontrol of Pythium by strain N1R, which is not known to produce antifungal antibiotics.     

Feeding range of Sitona regensteinensis Hbst. (Coleoptera: Curculionidae), a potential agent for biological control of Cytisus scoparius (L.) link (Broom) in New Zealand

The weevil Sitona regensteinensis is being considered for biological control of Cytisus scoparius in New Zealand. Adult feeding tests demonstrated that while foliage of C scoparius was preferred, weevils fed also on Chamaecytisus palmensis and Lupinus arboreus. Tests with the root‐feeding larval stage have yet to be completed.     

A Comparison of the Efficacy of Nuclear Polyhedrosis and Granulosis Viruses in Spray and Bait Formulations for the Control of Agrotis segetum (Lepidoptera: Noctuidae) in Maize

Agrotis segetum nuclear polyhedrosis virus (AsNPV) and granulosis virus (AsGV), propagated in laboratory cultures of A. segetum in England and A. ipsilon in Spain, respectively, were applied to plots of maize plants at the one‐ to four‐leaf stage of growth. Plots were arranged in a 6 x 6 Latin square design and infested with second‐instar A. segetum larvae (the common cutworm). Each virus was applied in separate treatments by two application methods; as an aqueous spray containing 0.1% Agral as a wetting agent, and as a bran bait. The NPV was applied at a rate of 4 X 10¹² polyhedra/ha, and the GV at 4 X 10¹³ granules/ha. Soil and plants were sampled for larvae on three occasions following virus treatment: 24 h, 4 days and 11 days. The larvae were reared on diet in the laboratory, until death or pupation, to examine the rate and level of viral infection. Infection data showed 87.5% and 91% NPV infection and 12.5% and 55% GV infection in spray and bait treatments, respectively, in larvae sampled 24 h after treatment. In larvae sampled 4 days after treatment, the results were 78% and 100% NPV infection, and 13% and 6% GV infection. A total of only six larvae were retrieved on day 11. In both treatments larvae infected with AsNPV died significantly more rapidly and at an earlier instar than those infected with AsGV, indicating that AsNPV appears to have better potential as a control agent for A. segetum.     

Environment-specific amino acid substitution tables: tertiary templates and prediction of protein folds.

The local environment of an amino acid in a folded protein determines the acceptability of mutations at that position. In order to characterize and quantify these structural constraints, we have made a comparative analysis of families of homologous proteins. Residues in each structure are classified according to amino acid type, secondary structure, accessibility of the side chain, and existence of hydrogen bonds from the side chains. Analysis of the pattern of observed substitutions as a function of local environment shows that there are distinct patterns, especially for buried polar residues. The substitution data tables are available on diskette with Protein Science. Given the fold of a protein, one is able to predict sequences compatible with the fold (profiles or templates) and potentially to discriminate between a correctly folded and misfolded protein. Conversely, analysis of residue variation across a family of aligned sequences in terms of substitution profiles can allow prediction of secondary structure or tertiary environment.     

The sinking ark: pollution and the worldwide loss of biodiversity

Humans are making increasing demands on natural ecosystems. One recent study has concluded that our species is consuming or diverting some 40% of the net photosynthetic productivity of our planet. Many habitats are being converted to simpler systems which provide more harvestable goods to people. As a result, genetic diversity, species and whole ecosystems are disappearing; some scientists suggest that as many as 25% of the world's species could be lost in the next several decades.The sinking ark is usually characterized in terms of pollution, habitat loss, poaching, introduced species and illegal trade in wildlife products, but these are symptoms rather than causes. At a more fundamental level, many of the same factors which have enabled pollution to become such a problem have also been responsible for the loss in biodiversity; the most important factor is that the effects of pollutants on biodiversity have been considered an externality, an unintended side effect of industrial activity which brought measurable benefits to people. Development activities which have depleted biodiversity have proven profitable only because the real costs have been hidden.Keeping the ark afloat will require the Five-I Approach: investigation (learning how natural systems function); information (ensuring that the facts are available to inform decisions); incentives (using economic tools to help conserve biodiversity); integration (promoting a cross-sectoral approach to conserving biodiversity); and international support (building productive collaboration for conserving biodiversity).