Season-long variation in expression of Cry1Ac gene and efficacy of Bacillus thuringiensis toxin in transgenic cotton against Helicoverpa armigera (Lepidoptera: Noctuidae).

The insertion of genes encoding insecticidal Cry1A delta-endotoxins from the bacterium Bacillus thuringiensis Berliner variety kurstaki (Bt) into varieties of cotton (Gossypium spp.) was undertaken to assist in the control of a range of lepidopteran pests. In Australia, where Helicoverpa armigera (Hübner) and Helicoverpa punctigera (Wallengren) are major pests, the level of control is useful, but not complete, because efficacy declines as the crop matures. Fluctuations in the efficacy of Bt cotton, to the extent that some insects survive, provide opportunities for H. armigera to develop resistance to the Bt toxin. Therefore, variations in the efficacy of Bt cotton need to be understood if we are to plan rational resistance management strategies to retard the rate of the development of resistance. We measured the changes in efficacy associated with plant development over the growing season, in the field and glasshouse. In addition, the levels of Cry1Ac protein toxin and cry1Ac RNA were determined. In this first demonstration of the relationship between these three factors, we found that the developmental decline in bioefficacy in field-grown plants was associated with reduced cry1Ac transcript levels and Bt toxin levels in postsquaring cotton. In addition, changes in plant chemistry associated with the maturation of the cotton plant were observed to contribute to changes in the efficacy of Bt toxin. Results from the field and glasshouse suggested that variations in efficacy within the growing season and between seasons also may be influenced by environmental factors.

Changes in Cry1Ac Bt transgenic cotton in response to two environmental factors: temperature and insect damage.

The efficacy of Cry1Ac Bacillus thuringiensis (Bt) cotton plants against field populations of Helicoverpa armigera (Hübner) has been inconsistent over the growing season. Any reduction in efficacy (where efficacy is the capacity of the plant to affect the survival of the insect) increases the opportunities for H. armigera to evolve resistance to Bt toxin. Changes in efficacy could be due to changes at the level of gene expression and/or in the physiological makeup of the plant and may be induced by environmental conditions. Two environmental factors, temperature and insect damage, were investigated. Temperature was found to affect efficacy, whether plants were grown at different temperatures continuously or were exposed to a change in temperature for a short period. Damage caused by chewing insects (H. armigera larvae) produced a dramatic increase in the efficacy of presquare Bt cotton. In contrast, damage by sucking insects (aphids) did not induce changes in efficacy. Changes in efficacy seemed to be mediated through modification of the physiological background of the plant rather than changes in the level of Cry1Ac expression or in the concentration of the Bt toxin. The impact of the non-Bt responses of plants on strains of H. armigera should be evaluated. It is possible that by enhancing existing defensive mechanisms of plants, the rate of evolution of resistance to Bt toxins could be retarded by increasing the plants overall toxicity through the additive effects of the toxins and plant defenses.

Encephaloceles: a review 1971-1990.

Fifty-two patients with an occipital encephalocele were managed at our institution between 1971-1990 inclusive. The case notes of fifty-one patients were available for review. Thirty-four of the patients presented in the first decade of the study. Fifty-seven per cent (29) developed hydrocephalus and 18 of these required shunting. The overall one year mortality was 23% (12) but only one patient died within the last decade. Of 23 patients followed up by postal questionnaire to general practitioners; 14 had no obvious deficit and 9 had a combination of deficits. Only one death occurred after one year of life in a child with a very severe handicap.

Plant-toxin interactions in transgenic Bt cotton and their effect on mortality of Helicoverpa armigera (Lepidoptera: Noctuidae).

In Australia, transgenic cotton plants expressing the cry1Ac gene from Bacillus thuringiensis Berliner variety kurstaki are less toxic to first-instar Helicoverpa armigera (Hübner) after the plant is producing fruit. We developed two bioassay methods (leaf mush, leaf disk) to test if the physiological state of the plants explained changes in toxicity and a third method (diet incorporation) was developed to quantify the toxicity of Bt leaves when mixed in chickpea diet. Cry1Ac protein was less toxic to H. armigera larvae when the protein was mixed with leaves from fruiting versus presquare conventional cotton. Differences in LC50 varied from 2.4- to 726-fold, depending on the source of toxin and conventional plant material. These results suggest that plant-toxin interactions in fruiting cotton are reducing the toxicity of the Cry1Ac protein. The possible role of tannins in these changes is discussed.

Rapid antibody-based field test to distinguish between Helicoverpa armigera (Lepidoptera: Noctuidae) and Helicoverpa punctigera (Lepidoptera: Noctuidae).

Helicoverpa armigera (Hübner) and Helicoverpa punctigera (Wallengren) are the two most important insect pests of cotton production in Australia and require application of insecticides to control them. H. armigera has developed resistance to several insecticides but H. punctigera has not. Cost-effective management of insecticide resistance requires that growers be able to determine the proportion of H. armigera eggs or young larvae present on their crop before applying insecticides. This is impossible visually. We generated two monoclonal antibodies that reacted with the insect protein "lipophorin" and were capable of discriminating individuals of the two species at all life-stages. The antibodies were incorporated into a rapid test kit that was tested under field conditions over two growing seasons. Results obtained with the kit agreed closely with those obtained by rearing larvae through to second instar.

"Through-glass" injuries.

This prospective trial collected all cases where injuries had resulted from the hand passing through or striking glass and had been referred to a hand injury service during 1 year. Eighty-seven cases were referred and the factors relating to these injuries were examined. A record was made of the structures damaged, the surgery performed and prevailing socioeconomic factors. These injuries were very costly in terms of morbidity, surgical effort and time, with significant resource implications. The study appears to confirm other reports that current legislation on glazing safety was too long delayed and is inadequate now that it is in place.

Transcutaneous electrical nerve stimulation following appendicectomy: the placebo effect.

A controlled trial was undertaken to compare the efficacy of transcutaneous electrical nerve stimulation (TENS) with standard intramuscular opiate analgesia in the management of postoperative pain following appendicectomy. Consecutive patients undergoing emergency appendicectomy were randomised into control, sham TENS and active TENS groups. There was a significant decrease in pain severity and analgesic intake in both active and sham TENS groups when compared with the control group (P less than 0.01). No difference was demonstrated in pain severity between active and sham TENS groups but the active TENS group required slightly less analgesia. These results suggest that the major benefit of TENS in the postappendicectomy patient is due to its 'placebo effect' and its use in this situation cannot be recommended.

Solar concentrator flux distributions using backward ray tracing.

Flux distributions produced by parabolic and circular cylinder solar concentrators subject to surface slope errors and defocusing are determined. The technique developed traces a set of rays from a point on the absorber back through the concentrator optics to the sun. The solar flux at the absorber point is the sum of the flux associated with each ray. Various models of the solar disk are introduced by weighting the flux associated with each ray as a function of where it strikes the solar disk.

Omental transposition flap for gross locally recurrent breast cancer.

BACKGROUND: The omentum has been employed to cover the defect produced after resection of gross breast cancer recurrence for nearly three decades. METHODS: A series of 11 patients undergoing omental transposition flap for very wide resection of gross local recurrence (LR) of breast cancer is reported. The median age was 39 years, with a short interval (median = 21 months) from the treatment of the primary tumour to LR. Local recurrence was gross and predominantly inflammatory. RESULTS: All except one patient had lymphovascular invasion in the recurrent tumour. The omental graft was 100% viable but one patient required re-application of further split-thickness skin graft. The mean hospital stay was 16 days. Two cases of seroma formation were encountered. New recurrence developed around the periphery of the flap in eight patients after a median duration of local control of only 2.5 months. Eight patients died with metastatic disease after a median period of 6 months, six patients with uncontrolled local disease. Five patients were free from LR in over half of their remaining period of life. CONCLUSION: Omentoplasty is a safe and reliable procedure but the length of palliation achieved is often far from satisfactory.