A Novel Method for Viewing Heavy Metal Stained and Embedded Biological Tissue by Field Emission Scanning Electron Microscopy

Backscattered electron (BSE) imaging was used to display heavy metal stained biological structures of various embedded specimens. Samples were fixed, stained and embedded in resin blocks as with preparation for the transmission electron microscope (TEM). Blocks were trimmed to center the specimens in a trapezoidal face of up to 5 mm2 and their sides painted with conductive silver paint leaving the face uncovered. Blocks were sputter coated with 6-8 nm of silver, chromium or aluminum, with aluminum providing the best specimen contrast in BSE mode. Samples were examined in a field emission scanning electron microscope operated at a high emission current of 50 μA. Both the fixation protocol and microscope operating parameters were optimized to maximize the number of BSE available from the smallest probe. An accelerating voltage of 10 keV was found optimal for resolution and contrast. The technique allowed the direct visualization of embedded samples at resolutions beyond light microscopy with good contrast, without cutting sections, and avoiding grid bars obscuring areas of interest. The two dimensional images provided averaged information on the internal structures of the specimens in relation to the predicted emission depth of the BSE. The technique could be used for rapid diagnostics in pathological examinations, or for routine preselection of areas of interest within a sample face before final trimming for ultrathin sectioning for higher resolution TEM study

Evaluation of risk factors leading to soil destabilisation on the south coastal sandplain of Western Australia

The problems of wind erosion in part of the south coast of Western Australian sandplain area were described previously (Gorddard et al, 1981) with 7.3 per cent of cleared and 18.3 per cent of the cropped area showing evidence of sand blasting. Department of Agriculture trials have shown that the loss of the top four millimetres of top soil from pastured paddocks can reduce following crop yields by up to 20 per cent (Marsh and Carter, 1983). Animal production problems associated with wind erosion of soils have not been quantified, but a number of problems such as reduced carrying capacity and nutritional problems are seen as significant throughout the area. Farmer opinion suggests that high grazing pressures are a major contributing factor to wind erosion however Gorddard et al (1981) were unable to identify any empirical relationship between stocking rate, cropping practice and erosion risk

New developments in footrot control

The eradication policy for footrot in sheep adopted by the Western Australian Department of Agriculture has produced an overall decline in the number of properties with the disease. Our knowledge of the disease has improved substantially as a result of the research conducted at the Slabany Regional Veterinary Laboratory in recent years. Laboratory tests now sssist stock inspectors and veterinary officers to distinguish between different forms of footrot and to quarantine and eradicate accordingly. The recent discovery of more effective foot-bathing solutions by officers of the Victorian Department of Agriculture will greatly assist further eradication procedures. Western Australia\u27s sheep industry can now be optimistic that the level of footrot will remain low

Quantitative or Qualitative: Selecting the Right Methodological Approach for Credible Evidence

This article provides insight into how an adequate approach to selecting methods can establish credible and actionable evidence. The authors offer strategies to effectively support Extension professionals, including program developers and evaluators, in being more deliberate when selecting appropriate qualitative and quantitative methods. In addition, several examples of commonly used measures are described to help in determining their applicability for evaluating Extension programs. Benefits and challenges of select methods are discussed as well as pitfalls to avoid that can derail the evaluative process. Lastly, a few cases are shared to present how Extension is aiming to establish credible evidence through state efforts and at the national level. The authors discuss the use of practical designs (e.g., common measures) that offer a more uniform way of evaluating programs. Examples are also included to highlight the effective use of Extension reporting systems that aim to streamline data collection, evaluation, and reporting as a means to ensure more credibility

The AddAB helicase–nuclease catalyses rapid and processive DNA unwinding using a single Superfamily 1A motor domain

The oligomeric state of Superfamily I DNA helicases is the subject of considerable and ongoing debate. While models based on crystal structures imply that a single helicase core domain is sufficient for DNA unwinding activity, biochemical data from several related enzymes suggest that a higher order oligomeric species is required. In this work we characterize the helicase activity of the AddAB helicase–nuclease, which is involved in the repair of double-stranded DNA breaks in Bacillus subtilis. We show that the enzyme is functional as a heterodimer of the AddA and AddB subunits, that it is a rapid and processive DNA helicase, and that it catalyses DNA unwinding using one single-stranded DNA motor of 3′→5′ polarity located in the AddA subunit. The AddB subunit contains a second putative ATP-binding pocket, but this does not contribute to the observed helicase activity and may instead be involved in the recognition of recombination hotspot sequences

Survey of parasite control practices in sheep and cattle

Farms in the Albany, Esperance, Jerramungup and Katanning districts were surveyed to determine parasite control strategies currently used, to evaluate the adoption of recommended control practices and to detect areas of ineffective parasite control. For cattle, the number of drenches given in the low rainfall zone was higher than the number given in the high rainfall zone