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1.
AB Zarafi AM Emechebe AD Akpa O Alabi 《Archives Of Phytopathology And Plant Protection》2013,46(4):261-268
Pearl millet downy mildew (DM) incidence, severity and yield losses of two pearl millet varieties (local and improved) due to the disease were determined in the field. Significant differences in the disease incidence and severity were recorded in the plots sown with metalaxyl-treated seeds and those sown with non-treated seeds, indicating the efficacy of the fungicide on the fungus. Yield losses due to non-treatment of seeds with metalaxyl was 40.88 and 45.39% in a local variety and 43.00 and 18.60% in an improved variety in the 2000 and 2001 cropping seasons respectively. Significant differences between plots sown with metalaxyl-treated and those sown with non-treated seeds were obtained for other yield components such as 1000-grains weight, panicle length and weight. 相似文献
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Guðmundur J. Óskarsson Asta Gudmundsdottir Sveinn Sveinbjörnsson Þorsteinn Sigurðsson 《Marine Biology Research》2016,12(1):16-29
The Northeast Atlantic mackerel (Scomber scombrus) has been extending its summer feeding distribution north and west, including around Iceland, since around 2006. The objective of this study is to quantify the weight gain and total food consumption of mackerel and to evaluate the food competition between mackerel and herring (Clupea harengus) feeding in the marine ecosystem around Iceland during the summers 2009–2011. Mackerel feeding in Icelandic waters gained around 43% on average in weight during these summers. Based on swept-area abundance estimates of mackerel from an international survey in 2011 and available estimates of food conversion efficiency in mackerel, the weight gain in Icelandic waters in 2011 corresponded to a total consumption of around 3.4 (2.4?4.5) million tonnes. Overall, 98% of 2314 mackerel, 91% of 398 Icelandic summer-spawning herring and 96% of 424 Norwegian spring-spawning herring stomachs, collected over the summers 2009?2011, contained food. The mean weight of the stomach content of mackerel was higher than for herring in all the years. While the stomach content weight of mackerel was generally highest in southeastern and southwestern areas, it was highest for herring in western, eastern and northern areas. Analysis of stomach contents showed that Copepoda were the most important food of mackerel in most areas, while Copepoda and Euphausiacea were the most important food items for herring. Fish prey contributed a higher proportion in stomachs of mackerel than herring, although relatively low for both species. 相似文献
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A series of substituted 1-glucosyl-2-benzoylhydrazines were synthesized and their pseudo-first-order rate constants for hydrolysis were determined at pH 4, 5, 6 at 50 degrees C. All the compounds hydrolyzed quickly (t(1/2)<3h) at pH 4.0, but were increasingly stable as the pH approached neutrality. 相似文献
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Background
Organisms are capable of developing different phenotypes by altering the genes they express. This phenotypic plasticity provides a means for species to respond effectively to environmental conditions. One of the most dramatic examples of phenotypic plasticity occurs in the highly social hymenopteran insects (ants, social bees, and social wasps), where distinct castes and sexes all arise from the same genes. To elucidate how variation in patterns of gene expression affects phenotypic variation, we conducted a study to simultaneously address the influence of developmental stage, sex, and caste on patterns of gene expression in Vespula wasps. Furthermore, we compared the patterns found in this species to those found in other taxa in order to investigate how variation in gene expression leads to phenotypic evolution. 相似文献5.
Gudmundsdottir KB Aalbaek B Sigurdarson S Gunnarsson E 《Journal of applied microbiology》2004,96(5):913-921
AIMS: The purpose of this study was to examine the diversity of Listeria monocytogenes strains from healthy sheep, winter feed and environment of sheep farms in Iceland. METHODS AND RESULTS: A total of 104 L. monocytogenes isolates from animals, winter feed and environment on 10 Icelandic sheep farms were compared by serotyping, ribotyping, and pulsed-field gel electrophoresis with ApaI and AscI. The isolates were divided into 24 genotypes, all identified as serovars 1/2a, 1/2b, or 4b. Nine genotypes were detected on more than one farm. On three of the farms there seemed to be a dominant strain of L. monocytogenes. Isolates from incidents of listeriosis in animals occurring on two of the farms belonged to the genotype most commonly found on the particular farm. Nine of the 24 genotypes found on the sheep farms have been associated with disease in animals and/or humans elsewhere in Iceland. CONCLUSIONS: Certain strains of L. monocytogenes seem to be widely distributed on Icelandic sheep farms. On some farms there appears to be a dominant strain of L. monocytogenes. Incidents of listeriosis in animals may tend to be associated with strains commonly found on the farm. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrates the diversity of L. monocytogenes present in healthy sheep and their environment. 相似文献
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Bjarki Stefansson Linda Helgadóttir Sigridur Olafsdottir Ágústa Gudmundsdottir Jón B. Bjarnason 《Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology》2010,155(2):186-194
Atlantic cod trypsin I is a highly active cold-adapted protease. This study aimed at further characterization of this enzyme with respect to kinetic parameters, sites of autolysis and stability. For that purpose, trypsin I was purified by anion exchange chromatography. Its purity and identity was verified by SDS-PAGE analysis and mass spectrometry. Concomitantly, another cod trypsin isozyme, trypsin X, previously only described from its cDNA sequence was detected in a separate peak from the ion exchange chromatogram. There was a stepwise increase in the catalytic efficiency (kcat/Km) of cod trypsin I obtained with substrates containing one to three amino acid residues. As expected, the activity of trypsin I was maintained for longer periods of time at 15 °C than at higher temperatures. The residues of the trypsin I molecule most sensitive to autolysis were identified using Edman degradation. Eleven autolytic cleavage sites were detected within the trypsin I molecule. Unfolding experiments demonstrated that autolysis is a contributing factor in the stability of trypsin I. In addition, the data shows that cod trypsin I is less stable towards thermal unfolding than its mesophilic bovine analogue. 相似文献
7.
Li Q Sankaranarayanan J Hawk M Tran VT Brown JL Gudmundsdottir AD 《Photochemical & photobiological sciences》2012,11(4):744-751
The irradiation of ester 1 in methanol and chloroform does not yield any photoproducts, whereas the photolysis of 1 in dry argon-saturated benzene produces cyclobutanol 4, which is converted to lactone 5 by the addition of HCl. Laser-flash photolysis of ester 1 demonstrates that 1 undergoes intramolecular H-atom abstraction to form the biradical 2 (λ(max)~ 310 nm, τ = 200 ns, benzene), which intersystem crosses to photoenols, Z-3 (λ(max)~ 380 nm, τ = 30-60 μs, benzene) and E-3 (λ(max)~ 380 nm, τ = 11 ms, benzene). Density functional theory calculations were performed to support the proposed mechanism for forming cyclobutanol 4 and to explain how steric demand facilitates photoenol E-3 to form cyclobutanol 4 rather than lactone 5. 相似文献
8.
Altered binding and transport of vitamin B12 resulting from insertion mutations in the Escherichia coli btuB gene 总被引:11,自引:0,他引:11
A Gudmundsdottir C Bradbeer R J Kadner 《The Journal of biological chemistry》1988,263(28):14224-14230
The BtuB protein of Escherichia coli is a multifunctional outer membrane receptor required for the binding and uptake of vitamin B12, bacteriophage BF23, and the E colicins. The btuB gene was mutagenized by the insertion of 6-base pair linkers into each of ten HpaII sites distributed throughout the coding region. Receptor function was measured with the mutated genes present in single or multiple copies. All of the mutant proteins were found in the outer membrane in similar amounts, although two of them were susceptible to cleavage by endogenous proteolytic activity. The vitamin B12 transport activity mediated by five of the mutants was essentially identical to that of the wild type. Four mutations (insertions after amino acids 50, 252, and 412, and a duplication of residues 434-472) reduced uptake activity to less than 2% of parental, whereas insertions at residues 343 and 434 had less severe effect. The insertions at residues 50 and 252 appeared to slow the rate of cobalamin binding to the receptor; the defect in the former mutant was partially corrected by elevated calcium levels. The insertion at residue 412 did not affect the rate of substrate binding but slowed its release from the receptor. Most of the receptors conferred susceptibility to phage BF23 and the E colicins, although several mutants were altered in the degree of their sensitivity to the lethal agents. None of the mutations affected the entry of only one type of ligand. Thus, several receptor domains have been implicated in substrate binding and energy coupling. 相似文献
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Ballard C Lana MM Theodoulou M Douglas S McShane R Jacoby R Kossakowski K Yu LM Juszczak E;Investigators DART AD 《PLoS medicine》2008,5(4):e76