Application of isotope dilution mass spectrometry: determination of ochratoxin A in the Canadian Total Diet Study

Analytical methods are generally developed and optimized for specific commodities. Total Diet Studies, representing typical food products ‘as consumed’, pose an analytical challenge since every food product is different. In order to address this technical challenge, a selective and sensitive analytical method was developed suitable for the quantitation of ochratoxin A (OTA) in Canadian Total Diet Study composites. The method uses an acidified solvent extraction, an immunoaffinity column (IAC) for clean-up, liquid chromatography-tandem mass spectrometry (LC-MS/MS) for identification and quantification, and a uniformly stable isotope-labelled OTA (U-[13C20]-OTA) as an internal recovery standard. Results are corrected for this standard. The method is accurate (101% average recovery) and precise (5.5% relative standard deviation (RSD)) based on 17 duplicate analysis of various food products over 2 years. A total of 140 diet composites were analysed for OTA as part of the Canadian Total Diet Study. Samples were collected at retail level from two Canadian cities, Quebec City and Calgary, in 2008 and 2009, respectively. The results indicate that 73% (102/140) of the samples had detectable levels of OTA, with some of the highest levels of OTA contamination found in the Canadian bread supply

Vaccines against toxoplasma gondii : challenges and opportunities

Development of vaccines against Toxoplasma gondii infection in humans is of high priority, given the high burden of disease in some areas of the world like South America, and the lack of effective drugs with few adverse effects. Rodent models have been used in research on vaccines against T. gondii over the past decades. However, regardless of the vaccine construct, the vaccines have not been able to induce protective immunity when the organism is challenged with T. gondii, either directly or via a vector. Only a few live, attenuated T. gondii strains used for immunization have been able to confer protective immunity, which is measured by a lack of tissue cysts after challenge. Furthermore, challenge with low virulence strains, especially strains with genotype II, will probably be insufficient to provide protection against the more virulent T. gondii strains, such as those with genotypes I or II, or those genotypes from South America not belonging to genotype I, II or III. Future studies should use animal models besides rodents, and challenges should be performed with at least one genotype II T. gondii and one of the more virulent genotypes. Endpoints like maternal-foetal transmission and prevention of eye disease are important in addition to the traditional endpoint of survival or reduction in numbers of brain cysts after challenge

Seed germination and recolonisation of Zostera capricorni after grazing by dugongs

A seagrass meadow dominated by Zostera capricorni Aschers. was intensively grazed by dugongs (Dugong dugon Müller) between November 1992 and January 1993, leaving a bare sand surface. In less than a year densities had returned to pre-grazing levels with shoot densities of around 11,000 m−2 by August 1993. Recovery of the seagrass appears to have been augmented by a high incidence of sexual reproduction. The flowering season was between August and March, with a peak in December (1219 ± 338.8 flowering shoots m−2; 11.8% of all shoots). Seeds were found in the sediment throughout the year with least in late winter and early spring (August to November). Germinating seeds were found in the sediment throughout the year with the highest number and proportion in May (86 ± 30.5 m−2 and 22%). Seed production was considerably higher at this site than has been found in previous studies of Z. capricorni

Marine macroalgae from the Gulf of Carpentaria, tropical northern Australia

Over the last two decades, CSIRO surveys of the seagrass communities in the south-western Gulf of Carpentaria and at Groote Eylandt, the Northern Territory, have provided opportunities for the collection of marine macroalgae from this poorly explored, remote region. Although the cruises did not concentrate on macroalgal communities which typically grow on rocky substrates, 64 specific and subspecific taxa of marine Chlorophyta, Phaeophyceae and Rhodophyta were collected, including 30 species newly recorded for the Gulf. The majority of Gulf species also occur on the tropical eastern Australian coast. One hundred and thirteen macroalgal taxa are now known to occur in the Gulf of Carpentaria, the number from the present study supplemented by collections from the 1948 Arnhem Land Expedition and from an ethnobiological study on Groote Eylandt during the 1970s. Twelve species are recorded by all three Gulf studies and 23 species are reported by two studies. The relatively low number of species common to more than one study is thought to result from each study's narrow sampling window which fails to adequately document the considerable spatial and temporal variability of macroalgal species. Accordingly, the number of species presently recorded for the Gulf is considered to be an underestimate of macroalgal biodiversity for the region. It is clear that further detailed taxonomic and ecological investigations are urgently required before the full extent of macroalgal biodiversity in tropical Australia can be appreciated

The effect of ant biopores on water infiltration in soils in undisturbed bushland and in farmland in a semi-arid environment

Data were collected on the morphology of selected ant species' nests in farmland and naturally vegetated environments on two contrasting soils. The majority of ant nests have one central channel or biopore with chambers branching off the channel. The ant biopore ranges in diameter from 1-200 mm and can extend to depths of 60 cm below the soil surface. The nest entrance or biopore remains open virtually all through the year. Biopore densities range from 0.7 to 1.9 biopores m - 2 in the various habitats with lower biopore densities in grey sandy loam compared with yellow sand sites regardless of land use. The effect of ant biopores on water infiltration was measured in situ using the disc permeameter at negative ( - 5, -10, - 40 mm) tensions and at positive ( + 10 mm) pressure. The effect of ant biopores on steady-state water infiltration rates was not significant at -10 and - 40 mm negative tensions. However, when tensions were raised to - 5 mm there was a detectable difference between water infiltration rates over the control area and the rates recorded over ant nests. But it was only under positive pressure that water infiltration over ant nests was significantly greater than the control soil. Hence ant biopores will only transmit water down the soil profile when the soil is saturated and water is ponding on the soil surface