From atopy to zinc-responsive dermatosis

Anthony Chadwick, winner of the 1997 Frank Beattie Travel Scholarship, reports on his study trip to the USA, where he attended a veterinary dermatology conference in Nashville, Tennessee, and spent two weeks at the dermatology unit of Cornell University     

Intramedullary spinal cord metastasis of a primary lung tumour in a dog

A dog was presented with signs of subacute, progressive myelopathy. A tentative diagnosis of a diffuse intramedullary spinal cord mass was made using contrast radiography (myelography). At autopsy a solitary, large bronchoalveolar carcinoma was detected in a lung lobe. Histological examination of the cranial thoracic spinal cord revealed a tumour which was similar, but not identical, to the lung tumour. Immunohistochemistry helped to confirm that the spinal lesion was a metastasis of the lung tumour.     

Permethrin as a residual insecticide against cockroaches

The pyrethroid permethrin was shown to be active against Blattella germanica, Periplaneta americana and Blatta orientalis. In laboratory tests on plywood panels the best formulation was a 25% wettable powder which showed an initial LC₅₀ of 10 mg m^?2 against B. germanica and lost activity at the weekly rate of 1.9 mg m^?2. An initial deposit of 108 mg m^?2 gave 50% kill after one year. The synergist piperonyl butoxide diminished residual performance. In one field trial, good control was maintained for more than four months with an initial deposit of 50 mg m^?2, the smallest dose used. From this and other trials, the recommended rate of application for general use in long-term control is 100 mg m^?2. A distinctive slow expellent action against B. germanica was seen in field trials.     

Factors which influence the knockdown effect of insecticide products

Knockdown in insects following application of an insecticide may be defined as the state of intoxication and partial paralysis which usually precedes death. Pyrethroid insecticides cause knockdown within a few minutes in contrast to the slower action of other groups of compounds. Users throughout the world have varying interpretations of knockdown and may apply different emphasis depending upon the species involved and local application techniques. To obtain valid assessments it is necessary to carry out tests under the most realistic conditions possible and to see that the effects of variations in procedure are taken into full account. Some factors which influence knockdown are: single rapid dosing or continuous pick-up during the observation period; size and distribution of spray-droplets; size of test chamber; interaction in mixtures of synergist and insecticides; use of organic solvents or water-based formulations. Examples of these are given.     

Developing optimal abatement strategies for the effects of sulphur and nitrogen deposition at European scale

Integrated Assessment Models were successfully used to provide input to the negotiations for the Oslo Protocol on Further Reductions of Sulphur Emissions, finalized within the United Nations Economic Commission for Europe Convention on Long-range Transboundary Air Pollution in Oslo in June 1994. The techniques developed within this framework will be extended now to the simultaneous analysis of sulphur and nitrogen deposition. In addition to acidification, atmospheric deposition of nitrogen contributes to eutrophication of certain ecosystems, through a nutrient effect, and originates from the long-range transport of emissions of both oxidised and reduced nitrogen (NO_x and NH₃). Modelling reductions in nitrogen deposition thus introduces a need to establish multi-pollutant multi-effect modelling techniques. This paper investigates the development of a model set up to examine reductions of these pollutants in an economically and environmentally efficient manner. The control of nitrogen deposition encompasses action across several economic sectors, particularly the power, transport and agricultural sectors. Combining sulphur and nitrogen deposition limits on a European scale will require a flexible modelling approach and the issues governing possible approaches are presented.     

Inadequacy of diversity indices in discerning metal mine drainage effects on a stream invertebrate community

The benthic invertebrates of the Dolores River in southwest Colorado were sampled during three seasons in an area of historic mine drainage. Benthic density exhibited significantly lower values below the mine drainage. However, the number of species did not decrease significantly, indicating that the effect of the mine drainage was primarily non-selective (i.e. favoring no one taxon). This pattern was seasonal with the least effects evident in summer and the greatest effects found in spring. Diversity indices used to assess the effects of this stress on the invertebrate community were MargalePs, Simpson's, Shannon-Weaver's, Brillouin's, and the Biotic Condition Index. None of the indices tested adequately responded to a decreasing trend in the benthic density when number of species remained constant. The indices did respond to a combination of low density and number of species or to the predominant representation by one species. The Biotic Condition Index actually increased at the stations with the lowest density and number of species. Diversity indices appear to be inadequate in assessing a non-selective stress.