Mechanical disruption of seagrass in the digestive tract of the dugong

The cheek teeth in dugongs are considered to be largely non-functional whereas the oral horny pads are important both in mechanical disruption of the diet and in conveying seagrass through the mouth. Particle size distributions of digesta from 41 dead stranded dugongs were examined to investigate the relationship between degree of food breakdown, gut region and functional surface area of the mouthparts. The in vitro ease of fracture of major dietary seagrass species were compared. The rate of food breakdown through the gut appears to be more closely linked to fibre level of the diet than to size or age of the dugong and its mouthparts. Low fibre seagrass, for example Halophila ovalis, breaks down at a faster rate than high fibre seagrass, for example Zostera capricorni both in dugong guts and in vitro. Several structural characteristics of seagrass, including level and arrangement of fibre, and water content, make it particularly amenable to mechanical breakdown. The soft mouthparts of the dugong are highly modified so that the entire oral cavity functions to crush low fibre seagrasses. Thus, the dugong has developed an efficient method of food ingestion and mastication that is suited to processing large quantities of soft seagrass during short dive times. The potential cost to the dugong in having lost its hard dental surfaces is that it has become restricted to a low fibre diet.

Zinc and vitamin A supplementation in Indigenous Australian children hospitalised with lower respiratory tract infection: a randomised controlled trial

Objective: To evaluate the efficacy of supplementation with zinc and vitamin A in Indigenous children hospitalised with acute lower respiratory infection (ALRI). Design: Randomised controlled, 2-by-2 factorial trial of supplementation with zinc and vitamin A. Setting and participants: 187 Indigenous children aged < 11 years hospitalised with 215 ALRI episodes at Alice Springs Hospital (April 2001 to July 2002). Interventions: Vitamin A was administered on Days 1 and 5 of admission at a dose of 50 000 IU (infants under 12 months), or 100 000 IU; and zinc sulfate was administered daily for 5 days at a daily dose of 20 mg (infants under 12 months) or 40 mg. Main outcome measure: Time to clinical recovery from fever and tachypnoea, duration of hospitalisation, and readmission for ALRI within 120 days. Results: There was no clinical benefit of supplementation with vitamin A, zinc or the two combined, with no significant difference between zinc and no-zinc, vitamin A and no-vitamin A or zinc + vitamin A and placebo groups in time to resolution of fever or tachypnoea, or duration of hospitalisation. Instead, we found increased morbidity; children given zinc had increased risk of readmission for ALRI within 120 days (relative risk, 2.4; 95% CI, 1.003–6.1). Conclusion: This study does not support the use of vitamin A or zinc supplementation in the management of ALRI requiring hospitalisation in Indigenous children living in remote areas. Even in populations with high rates of ALRI and poor living conditions, vitamin A and zinc therapy may not be useful. The effect of supplementation may depend on the prevalence of deficiency of these micronutrients in the population.

Predictors of an antibiotic prescription by GPs for respiratory tract infections: a pilot

Background. Antibiotics are over-prescribed for respiratory tract infections in Australia. Objectives. The aim of this study was to describe the clinical predictors of GPs' prescribing of antibiotics. Methods. We used Clinical Judgment Analysis to study the responses of GPs to hypothetical paper-based vignettes of a 20-year-old with a respiratory tract infection. The nature of four symptoms and signs (colour of nasal mucous discharge; soreness of the throat; presence of fever; and whether any cough was productive of sputum) was varied and their effect on prescribing measured using logistic regression. Results. Twenty GPs participated. The nature of each symptom and sign significantly predicted prescribing of an antibiotic. Cough productive of yellow sputum; presence of sore throat; fever; and coloured nasal mucus increased the probability of an antibiotic being prescribed. Conclusions. GPs are influenced by clinical signs and symptoms to use antibiotics for respiratory infections for which there is poor evidence of efficacy from the literature.