2014- : Scaling of the cardiovascular system in mammals
Collaborators: R Seymour (Adelaide), A Fuller (Witwatersrand, S Africa), E Snelling (Pretoria)
In vertebrate animals, the heart provides the work that propels blood to the lungs and the body, providing the exchange of oxygen and carbon dioxide that cells need to function. Given the role that the heart plays, the metabolic cost of the heart should vary with body size in the same fashion that metabolic rate of the whole animal does. But it doesn’t. It has become evident that the energetic cost of the circulation is not directly related to metabolic rate, neither in the same group nor between groups. By measuring heart work and aspects of the morphology of the heart and circulatory system, we aim to understand the factors that influence heart work in vertebrates of different sizes and different heart structure.
2017- : Heat balance in humans – the effect of climate change on human activity
Collaborators: D Mitchell (Witwatersrand, S Africa), M Kearney (Melbourne)
While several health impacts of climate change have been widely reported, there has been limited discussion of how human physical activity will be impacted. We use empirical data on the upper limit of the prescriptive zone for humans to show that an index that is often used to assess human heat stress (the wet-bulb temperature) is a poor predictor of the prescriptive zone. We developed a different approach that was published in 2011, using rational heat balance modelling to incorporate every route of heat exchange. That approach yields a much better prediction of the prescriptive zone. We use that model with global historical data, and climate projections, to assess the way that climate change will limit economic and leisure activity when conditions exceed the ability of humans to thermoregulate.
2014- : Circadian rhythms, health, and longevity
Collaborators: D Blache, G Goh, P Mark (UWA), Y Ootsuka (Flinders),
While the core body temperature of mammals and birds exhibits a circadian rhythm that is controlled by a master clock in the brain, it has become clear that the rhythm of body temperature can reset molecular clocks in peripheral tissues. Evidence is emerging that strong, robust circadian rhythms are associated with health, while disrupted or attenuated rhythms are indicative of disease. Using rodent and insect models, we manipulate the circadian pattern of core body temperature and measure variables including longevity and health related outcomes. The pharmacological manipulation of body temperature offers a promising route to alter, and is some cases remedy, cases where circadian rhythms are disrupted.
2013- : Heat stress in sheep
Collaborators: A Barnes (Murdoch), K Vesterdorf (UWA)
Taking production animals from temperate Australia across the equator during live export presents the animals with a degree of thermal stress. We have studied ways to ameliorate strain and improve welfare during live export. We began by characterising the physiology of chronic exposure to thermal stress, where acute stress had only been studied previously, and provided evidence that an electrolyte supplement could reduce the impact of thermal stress.
1999- : Thermal physiology and ecology of large African bovids
Collaborators: D Mitchell, A Fuller (Witwatersrand, S Africa)
What began in the late 1990’s as interesting research into the thermal physiology of African bovids has become topical as South Africa faces the possibility of its tourism industry being decimated as its iconic species become extinct due to climate change. Our research investigates the physiological and behavioural mechanisms that animals use to maintain homeothermy, the plasticity in these mechanisms, and the potential for heterothermy.
1999- : Thermoregulation and energy balance in marsupials
Collaborators: TJ Dawson (UNSW), A Munn (U Syd), P Withers (UWA)
Homeothermy probably preceded the split that gave rise to the marsupial and eutherian mammals, but there are some differences in the mechanisms used to achieve it. We have been studying those mechanisms in the laboratory and the patterns of body temperature in the wild. Studies of how kangaroos respond to heat load is important because they are nocturnal and so exposed to heat load during the resting phase of their nychthemeral rhythm, in contrast to most bovids that are diurnally active. We also study of the effect of coat physical properties on radiant heat load, leading to the conclusion that selection for different phenotypes of coat colour is a potential means of adaptation to climate change.
1998- : The physiology of avian fever
Collaborators: D Gray, M Marais (Witwatersrand, S Africa)
While the processes of immune activation and the acute phase response, including fever, are well characterised in mammals, very little is known about birds, despite the security threat posed by avian influenza. Our research has been aimed at characterising the acute phase response, and the mediators of that response, using the Pekin duck as our model. We have shown that the response to Gram-negative infection is unimodal and proportional to the challenge imposed, and that steroids mediate the response. The latter may help explain the very different responses of restrained and free-ranging birds to identical immune stimuli, a finding that has implications for the way research is conducted.
2004-2006: Giraffe hemodynamics
Collaborators: Mitchell G (Wyoming), Mitchell D (Wits)
An old and ongoing problem in comparative physiology is how giraffe have adapted to the physical stresses posed by their morphology, especially gravitational stress. Specifically, we were interested in how hydrostatic pressure is overcome to perfuse a brain two metres above the heart. Our specific hypothesis was whether a siphon system could operate between the jugular veins and the carotid arteries. We showed clearly that it could not.
SCIE5515 - Global Challenges in Biomedical Science
APHB5505 - Advanced Studies in Physiology
PHYL2002 - Cell Physiology
APHB5504 - Advanced Techniques in Physiology
PHYL3003 - Physiology of Nutrition and Metabolism
PHYL3004 - Physiology of Integrated Organ Function
ANHB3310/20 - Human Biology: Applications and Investigations
Roles and responsibilities
Because my curiosity is easily aroused in an interesting problem, our lab has collaborations in diverse areas. Recent examples are work in fields as diverse as giraffe hemodynamics, alpaca nutrition, and animal ethics and welfare. But the underlying theme is constant – a desire to understand how animals work (to borrow a term from Knut Schmidt-Nielsen).
Being diverse is hopefully an advantage as ‘integrative physiology’ (the word integrative is surely redundant) comes more into vogue. The generalists will have the big picture overview required to put results into whole-organism or whole-ecosystem paradigms. This lab aims to provide that capacity.
South Africa- University of the Witwatersrand: Prof. Duncan Mitchell, Prof. Andrea Fuller, Prof. David Gray. Ongoing collaboration since the 1990’s
USA- University of Wyoming: Prof. Graham Mitchell
Germany- University of Giessen: Prof. Claus Jessen (now retired)
Germany- Johann Wolfgang Goethe University: Prof. Elke Schleucher Research collaboration and co-supervision of students
Germany- Max Planck Institute for Ornithology: Germany Prof. Niels Rattenborg
Saudi Arabia- National Wildlife Research Centre: Prof. Mohammed Shobrak
Department of Primary Industries, NSW
Agriculture Department, Western Australia
LiveCorp, Meat and Livestock Australia
New South Wales Department of Environment and Climate Change (formerly National Parks and Wildlife Service)
Rio Tinto Ltd
University of Sydney
Honorary Professorial Research Fellow1 Jan 2012 → …
Research expertise keywords
- Thermoregulatory and cardiovascular physiology