Macrogeographic population structure in a parasitic nematode with avian hosts

Much remains to be discovered about the population genetic structure of parasites, despite the importance of such knowledge to understanding the processes involved in the spread of drug resistance through populations. Here we present a study of population genetic diversity in Trichostrongylus tenuis, an avian parasitic nematode infecting both poultry and game birds, where anthelmintic use is common. We examined diversity of nicotinamide dehydrogenase subunit 4 (nad4) mtDNA sequences within and between seven locations: five in the UK (red grouse hosts), one in Iceland (domestic goose) and one in Norway (willow grouse). Within-UK comparisons showed high nucleotide diversity (pi=0.015, n=23) but no structure between locations (Phi(ST)=0.022, P=0.27), with over 97% of variation distributed within-hosts. The highest diversity was found in Iceland (pi=0.043, n=4), and the lowest in Norway (pi=0.003, n=4). Differentiation between countries was considerable (Phi(CT)=0.44, P<0.05), in spite of the potential mixing effects of gene flow via migrating wild hosts and the poultry trade. However, significant pairwise F(ST) values were found only between Norway and the other locations. Phylogenetic analysis provided statistical support for a separate clade for Norwegian samples only, with unresolved diversity leading to a star-shaped relationship between Icelandic and UK haplotypes. These results suggest that Norwegian T. tenuis are isolated, but that there is some connectivity between UK and Icelandic populations. Although anthelmintic resistance has not yet been reported for T. tenuis, the population structure is such that emerging resistance has the potential to spread by gene flow over a large geographic scale.     

Identification of management risk factors for VTEC O157 in young-stock in England and Wales

We conducted a cross-sectional study on 255 cattle farms in England and Wales to identify risk factors for verocytotoxin-producing E. coli O157 (VTEC). Exposure variables were collected at the levels of the farm and of the group of young-stock within the farms. On each farm a group of young-stock (6-18 months of age) was sampled to establish VTEC status. In our multiple logistic regression, farm VTEC status was associated with access to springs (OR: 0.31, CI95%: 0.12, 0.78) and assessing the wetness of the bedding material less frequently than daily (OR: 3.89 CI95%: 1.5, 10.2). At group-level we found no associated risk factors for animals housed outdoors in fields. Significant for groups housed in pens were wet bedding (wet OR: 3.43, CI95%: 1.3, 9.4; very wet OR: 4.24, CI95%: 1.2, 14.6), number of animals in the group (10-15 OR: 2.72, CI95%: 0.75, 9.9, 16-24, OR: 3.78, CI95%: 1.2, 12.3; >25 OR: 3.78, CI95%: 1.1, 12.7) and feeding straw (OR: 2.29, CI95%: 1.2, 5.5).     

Formulation of vegetable fat pellets with pheromone and Beauveria bassiana to control the larger grain borer,Prostephanus truncatus (Horn)

The use of hydrogenated rapeseed oil as a carrier for conidia of the entomopathogenic fungus Beauveria bassiana (Bals) Vuill was investigated as part of a research programme on the control of the larger grain borer, Prostephanus truncatus (Horn). Melting the oil, which is solid at temperatures below 32 °C, allows the incorporation of materials such as aggregation pheromones and conidia; sudden cooling produces solid fat pellets. In attraction tests conducted with pellets containing P truncatus aggregation pheromone, significantly higher numbers of beetles were attracted to pellets containing pheromone at a concentration of 4 ml litre⁻¹ compared to control pellets for at least four weeks when held in Petri dishes in the laboratory and for at least six weeks when pellets held in insect traps were exposed to outside conditions. The attraction was retained over a period of storage in glass bottles; pellets stored in the freezer or incubator (at −10 °C or 27 °C) attracted beetles according to the pheromone level for the duration of the work (14 and 13 months respectively). When pheromones and conidia were incorporated into the same pellets they could be stored in a freezer or refrigerator retaining over 80% viability after 51 weeks; those stored in an incubator at 27 °C showed significantly lower germination at 20.7–27.2% after the same time. There was an indication that the pheromone caused a slight reduction in the viability of conidia, although this may have been just a slight delay in the speed of germination. Rapid dose transfer from pellets with conidia with and without the addition of pheromone was demonstrated. Insects were exposed to pellets for 24 hours and 96–100% mortality was observed in treatments containing conidia within six days of exposure. © 1999 Society of Chemical Industry     

Effects of plant growth-promoting rhizobacteria on the molecular responses of maize under drought and heat stresses: A review

Drought and heat are major environmental stresses that continually influence plant growth and development. Under field conditions, these stresses occur more frequently in combination than alone, which magnifies corresponding detrimental effects on the growth and productivity of agriculturally important crops. Plant responses to such abiotic stresses are quite complex and manifested in a range of developmental, molecular, and physiological modifications that lead either to stress sensitivity or tolerance/resistance. Maize (Zea mays L.) is known for its sensitivity to abiotic stresses, which often results in substantial loss in crop productivity. Bioaugmentation with plant growth-promoting rhizobacteria (PGPR) has the potential to mitigate the adverse effects of drought and heat stresses on plants. Hence, this is considered a promising and eco-friendly strategy to ensure sustainable and long-term maize production under adverse climatic conditions. These microorganisms possess various plant growth-promoting (PGP) characteristics that can induce drought and heat tolerance in maize plants by directly or indirectly influencing molecular, metabolic, and physiological stress responses of plants. This review aims to assess the current knowledge regarding the ability of PGPR to induce drought and heat stress tolerance in maize plants. Furthermore, the drought and heat stress-induced expression of drought and heat stress response genes for this crop is discussed with the mechanisms through which PGPR alter maize stress response gene expression.     

Influence of cell volume changes on protein synthesis in isolated hepatocytes of air-breathing walking catfish (<Emphasis Type="Italic">Clarias batrachus</Emphasis>)

The present study aimed at determining the effect of cell volume changes on protein synthesis, measured as the incorporation of [³H]leucine into acid-precipitable protein, in isolated hepatocytes of air-breathing walking catfish (Clarias batrachus). The rate of protein synthesis, which was recorded to be 10.02 ± 0.10 (n = 25) nmoles mg⁻¹ cell protein h⁻¹ in isotonic incubation conditions, increased/decreased significantly by 18 and 48%, respectively, following hypo- (−80 mOsmol l⁻¹)/hypertonic (+80 mOsmol l⁻¹) incubation conditions (adjusted with NaCl), with an accompanying increase/decrease of hepatic cell volume by 12 and 20%, respectively. Similar cell volume-sensitive changes of protein synthesis were also observed when the anisotonicity of incubation medium was adjusted with mannitol. Increase of hepatic cell volume by 9%, due to addition of glutamine plus glycine (5 mM each) to the isotonic control incubation medium, led to a significant increase of protein synthesis by 14%. Decrease of hepatic cell volume by 15 and 18%, due to addition of dibutyl-cAMP and adenosine in isotonic control incubation medium, led to a significant decrease of protein synthesis by 30 and 34%, respectively. Thus, it appears that the increase/decrease of hepatic cell volume, caused either by changing the extracellular osmolarity or by the presence of amino acids or certain other metabolites, leads to increase/decrease of protein synthesis, respectively, and shows a direct correction (r = 0.99) between the hepatic cell volume and protein synthesis in walking catfish. These cell volume-sensitive changes of protein synthesis probably help this walking catfish in fine tuning the different metabolic pathways for better adaptation during cell volume changes and also to avoid the adverse affects of osmotic stress. This is the first report of cell volume-sensitive changes of protein synthesis in hepatic cells of any teleosts.     

Effects of solid-state enzymatic treatments on the antioxidant properties of wheat bran

This study evaluated the potential of solid-state enzyme treatments to release insoluble bound antioxidants such as phenolic acids from wheat bran, thereby improving its extractable and potentially bioaccessible antioxidant properties including scavenging capacities against peroxyl (ORAC), ABTS cation, DPPH and hydroxyl radicals, total phenolic contents, and phenolic acid compositions. Investigated enzyme preparations included Viscozyme L, Pectinex 3XL, Ultraflo L, Flavourzyme 500L, Celluclast 1.5L, and porcine liver esterase. Results showed significant dose-dependent increases in extractable antioxidant properties for some enzyme preparations, and Ultraflo L was found to be the most efficient enzyme, able to convert as much as 50% of the insoluble bound ferulic acid in wheat bran to the soluble free form. The effect of moisture content on these solid-state enzyme reactions was also evaluated and found to be dependent on enzyme concentration. These data suggest that solid-state enzyme treatments of wheat bran may be a commercially viable post-harvest procedure for improving the bioaccessibility of wheat antioxidants.     

Novel chitosan-derived nanomaterials and their micelle-forming properties

Six novel N-alkyl-N-dimethyl and N-alkyl-N-trimethyl chitosan derivatives were chemically synthesized and characterized using FT-IR, 1H NMR, 13C NMR, differential scanning calorimetry (DSC), and X-ray diffraction spectrometry (XRD). The alkyl groups included octyl (C8H17-), decanyl (C10H21-), and lauryl (C12H25-). These chitosan derivatives were also evaluated for their micelle-forming properties using dynamic light scattering (DLS) and transmission electron microscopy (TEM) techniques. All six chitosan derivatives were capable of forming polymeric micelles in water with an average particle diameter ranging from 36 to 218 nm. Both N-octyl-N-dimethyl and N-octyl-N-trimethyl chitosan derivatives formed nanomicelles under the experimental conditions, with an average particle diameter of 36.0 and 52.5, respectively. Both the length of alkyl group and the N-trimethylation degree of the chitosan derivatives altered the size of their polymeric micelles. To further understand the effect of N-alkyl substitution degree of chitosan derivatives on size of their micelles, additional five N-octyl-N-trimethyl chitosan derivatives with N-alkyl substitution degree ranging from 8 to 58% were prepared and their micelle sizes were determined. The results showed that the diameter of the nanomicelles was proportional to the degree of N-octyl substitution. These data suggest that novel N-alkyl-N-dimethyl and N-alkyl-N-trimethyl chitosan derivatives may form nanomicelles. Additional research is required to further investigate the potential value-added utilization of these chitosan derivatives in controlled release and targeted delivery of hydrophobic bioactive food factors.