Detoxification of ochratoxin A,a food contaminant: Prevention of growth of Aspergillus ochraceus and its production of ochratoxin A

The toxicity of ochratoxin A (OTA), a mycotoxin produced by fungi ofAspergillus orPenicillium genera is now well documented. Its nephrotoxicity, immunosuppression, teratogenicity, and carcinogenicity have been widely studied. Physical and biochemical methods have been studied to prevent these toxinogenicAspergillus andPenicillium from producing OTA, and/or to destroy the mycotoxin when already produced in a liquid or a solid medium. Repeated freezing at ? 20?C and thawing at + 26?C aleatory reduce OTA production in a liquid medium. Exposure to UV B for different periods of time is efficient in preventing OTA production in a liquid medium. Gamma-irradiation from 2 to 5 kGy gives good results in preventing the production of OTA or destroying it when already produced. Carboxypeptidase is very efficient at 5 units/50 ml in a liquid medium for cleaving the OTA already produced.     

The incidence, numbers and types of Listeria monocytogenes isolated from farm bulk tank milks

Bulk tank milk from 160 producers was tested for Listeria monocytogenes at three monthly intervals over 1 year. Twenty-five producers were positive, most on a single occasion, only seven were positive on three or more of the four samplings. Listeria monocytogenes numbers were low, usually <1 ml^-1, the highest was 35 ml^-1. All isolates were serotype 1, the use of multilocus enzyme electrophoresis on representative isolates gave nine different electrophoretic types, two have been associated with listeriosis in humans or animals, a further two had only been isolated from one other source (silage or faeces), while the majority (5) were unique to milk.     

The role of fish-poultry integration on fish growth performance,yields and economic benefits among smallholder farmers in sub-Saharan Africa,Tanzania

Aquaculture practices from sub-Saharan Africa are characterised by low production, owing to improper technology. Production can be increased through integrating fish farming with other existing on-farm activities, particularly livestock husbandry. We assessed the role of fish-poultry integration on all male Nile tilapia, Oreochromis niloticus growth performance, yields and economic benefits among smallholder farmers in sub-Saharan Africa, Tanzania. The study also compared phytoplankton species composition, abundance and biomass between the fish-poultry integration and non-integrated system. After 180 days of the experiment, all male O. niloticus cultured under fish-poultry integration exhibited significantly higher growth rates than those in the non-integrated system (p < 0.05). Gross fish yield (GFY), net fish yield (NFY) and net annual yields (NAY) obtained from fish-poultry integration were significantly higher than those from non-integrated system (p < 0.05). Partial enterprise budget analysis revealed that fish-poultry integration was more profitable than the non-integrated system. Moreover, fish-poultry integrated system produced significantly higher phytoplankton abundance and biomass than those from the non-integrated system. Results demonstrate that rural smallholder farmers can achieve higher growth rate, farm net yields and income by integrating all male O. niloticus with other on-farm activities than practising a stand-alone fish culture system.     

Supplemental food affects thrips predation and movement of Orius laevigatus (Hemiptera: Anthocoridae) and Neoseiulus cucumeris (Acari: Phytoseiidae)

Two experiments were done to examine the predation of thrips, and the movement of Orius laevigatus Fieber and Neoseiulus cucumeris (Oudemans) in the presence and absence of two supplemental food sources, pollen and the fungus Trichoderma viride. The presence of pollen led to a 55% reduction in predation of the thrips by N. cucumeris and a 40% reduction in thrips predation by O. laevigatus, in experiments using single predators. The presence of fungus had no significant effect on thrips predation by either of the natural enemy species. Movement of the natural enemies was examined in a multiple predator experiment, and this showed that O. laevigatus was more likely to remain on the plant in the presence of thrips and when supplemental food, either pollen or fungus, was present. For N. cucumeris, there was no association between the presence of thrips and the mite, with the majority of the mites being found on the leaves where pollen was present. Although the single and multiple predator experiments were done at different times, the indications are that the predation rates of the N. cucumeris do not differ greatly between the two experiments, suggesting that there may be a potential interference effect between the mites, which is not present for O. laevigatus. The significance of these results for the use of supplemental food sources in biological control is discussed.     

Distribution of Escherichia coli O157 in bovine fecal pats and its impact on estimates of the prevalence of fecal shedding

The distribution of Escherichia coli O157 in bovine feces was examined by testing multiple samples from fecal pats and determining the density of E. coli O157 in immunomagnetic separation (IMS)-positive fecal samples. The density of E. coli O157 in bovine feces was highly variable, differing by as much as 76,800 CFU g(-1) between samples from the same fecal pat. The density in most positive samples was <100 CFU g(-1), the limit of reliable detection by IMS. Testing only one 1-g sample of feces per pat with IMS may result in a sensitivity of detection as low as 20 to 50%. It is therefore probable that most surveys have greatly underestimated the prevalence of E. coli O157 shedding in cattle and the proportion of farms with shedding cattle. The sensitivity of the detection of E. coli O157 in bovine feces can be as much as doubled by testing two 1-g samples per pat rather than one 1-g sample.     

Stereoselective and improved syntheses and anticancer testing of 3'-O-silatranylthymidines

A stereoselective synthesis of 3′-O-((R,R,R)-trimethylsilatranyl)thymidine (R,R,R-1) and synthesis of 3′-O-silatranylthymidine (5) via an improved silatranylation procedure using tetrakis(dimethylamino)silane are reported. Diastereomeric mixture 1 showed more activity than R,R,R-1 or 5 in a primary anticancer screen against breast, CNS, and lung cell lines; demonstrating the import of the configuration and presence, respectively, of the silatrane methyl groups for growth inhibition.     

The effect of temperature on the functional response of Phytoseiulus persimilis (Acari: Phytoseiidae)

Environmental variables, such as temperature, are important in determining the efficiency of biological control in ornamental crops. This paper examines the effect of temperature on the functional response of adult female Phytoseiulus persimilis to eggs of the spider mite, Tetranychus urticae. The functional response was determined using a new functional response assay technique with plant stems as an arena, rather than leaf discs. The use of plant stems allows the influence that plant structure has on predation to be incorporated into the assay. Control assays were also used (without predators) to estimate natural losses of prey. The data were analysed using a binomial model, with the use of Abbot's formula to correct for the losses in the controls. A combined equation to describe the effect of temperature and prey density on the predation rate of Phytoseiulus persimilis was derived. The results showed that more prey are eaten as the temperature increases from 15 degrees C to 25 degrees C, but the number of prey eaten then declines at 30 degrees C, although not to the levels seen at 20 degrees C. The implication of these results for biological control in ornamental crops, where the temperature can often exceed 30 degrees C, is discussed.     

Nuclear gene trees and the phylogenetic relationships of the mangabeys (Primates: Papionini)

Phylogenetic relationships of mangabeys within the Old World monkey tribe Papionini are inferred from analyses of nuclear DNA sequences from five unlinked loci. The following conclusions are strongly supported, based on congruence among trees derived for the five separate gene regions: (1) mangabeys are polyphyletic within the Papionini; (2) Cercocebus is the sister taxon to the genus Mandrillus; and (3) Lophocebus belongs to a clade with Papio and Theropithecus, with Papio as its most likely sister taxon. Morphologically based phylogenies positing mangabey monophyly were evaluated by mapping the sequences for each locus on these trees. The data seem to fit these trees poorly in both maximum-parsimony and likelihood analyses. Incongruence among nuclear gene trees occurred in the interrelationships among Lophocebus, Papio, and Theropithecus. Several factors that may account for this incongruence are discussed, including sampling error, random lineage sorting, and introgression.      

Modelling the vector pathway and infection of humans in an environmental outbreak of Escherichia coli O157

Quantifying the transfer of Escherichia coli O157 from the environment to humans is essential for understanding outbreaks, establishing the infectious dose of the organism and proposing safeguards. We modelled the pathogen loading shed onto a field by sheep immediately prior to a scout camp where 18 scouts and two adults were infected with E. coli O157. We estimated the dose ingested (4-24 organisms) which is in agreement with the low infective dose reported previously for this organism in food outbreaks. These data closely fit a surrogate Shigella dose-response model which can be used as a basis for risk assessment.