Anatomy, Physiology and Human Biology

Comparative Physiology of Adaptation

Further Information


Contact a supervisor for detailed information on student research projects

 Professor Shane Maloney
Professor Shane Maloney

 Professor Stuart Bunt
Professor Stuart Bunt

 

 

The School of Anatomy, Physiology and Human Biology offers a diverse range of student research topics.

Our group is interested in the physiological mechanisms whereby animal species (including humans) adapt to environmental stressors. We focus mainly on thermal and osmotic stress, but exercise, inanition (starvation), and infection are also studied. Most experimental work is on systems level adaptations, but organ level adaptations are also studied. Our long-term aim is to identify specific adaptations that allow animals to survive and reproduce in challenging environments, and to identify how “homeostasis” handles the trade-offs when simultaneous challenges are presented to an organism, (such as combined thermal and osmotic stress, or combined inanition [starvation] and infection stress). Prospective Honours students with a background in General Systems Physiology, Exercise Physiology, Applied Animal Physiology, or Comparative Physiology are encouraged to apply. Depending on the project chosen a background in Cell Physiology could be an advantage.

Students will be exposed to a range of approaches and techniques including (in non-human animals) recovery anesthesia and surgery, implantation of physiological recording equipment, blood sampling for hormone measurement, and husbandry techniques for various species. In human research we use state of the art equipment to record physiological parameters in ambulatory subjects, including core and skin temperature transmitters, ambulatory blood pressure recording equipment, laser Doppler skin blood flow techniques, and infra-red thermography for surface temperature measurement.


Ion channel expression in the hearts of thermoneutral and cold exposed mice        

(With Prof. Phil Withers, Animal Biology)

Project Outline

The normal housing temperature for mice in most animal houses is below their thermoneutral zone, meaning that they are chronically cold exposed. Such exposure results in morphological and physiological changes, including larger body size, larger heart size, and elevated food intake and metabolism. During the light phase of the daily cycle, the resting heart rate (HR) of a mouse exposed to 30°C is about 375 beats/min. The resting HR increases by about 25 beats/min for every 1°C decrease in Ta below 30°C. When both arms of the autonomic nervous system are blocked, the heart beats at its intrinsic rate (i.e., the rate in a heart isolated from its nervous supply). Such autonomic blockade in a resting human results in an increase in HR because, at rest, parasympathetic tone dominates the control of the heart rhythm. At 22°C, the autonomic blockade of mice results in a decrease in HR, implying that the “resting” HR is sustained by elevated sympathetic tone. When mice are tested at 30°C, autonomic blockade results in an increase in HR because resting HR is dominated by parasympathetic input, just as it is in resting thermoneutral humans. The physiological demands on the heart are clearly impacted by exposure to cold. This project will investigate if changes in cardiac demand are associated with changes in the density or distribution of the ion channels that underlie heart function. Sub-projects may look at chronic versus acute cold exposure, or post-weaning versus pre-weaning exposure, or post-natal versus pre-natal exposure.

Project is suitable for

Honours, Masters and PhD

Supervisor

Professor Shane Maloney

Other Supervisor

Professor Livia Hool, Cardiac Electrophysiology Lab, APHB

Essential qualifications

For Honours: An appropriate undergraduate degree with a minimum weighted average of 65% in the level 3 subjects that comprise the relevant major, from an approved institution. Applicants will be assessed on a case-by-case basis.

For Masters or PhD : An appropriate Honours degree or equivalent research experience from an approved institution. Applicants will be assessed on a case-by-case basis.

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Undernutrition and the defense of body temperature in the cold

Project Outline

The normal response of mammals to cold exposure involves peripheral vasoconstriction and an increase in metabolism. The former reduces heat loss from the skin while the latter increases heat production, helping to defend core body temperature. It is becoming clear that short term changes in energy (food) intake are detected by the body and that these signals have consequences for energy demanding activities like inflammation and reproduction. We would like to test whether these short-term signals also influence the energy demands for heat production during cold exposure. Human subjects will be exposed to cold while core and skin temperatures, as well as metabolic rate and skin blood flow are measured. Each subject will be exposed to the same cold stimulus twice, once while well fed and once after a period of reduced energy intake. The physiological responses will be compared.

Project is suitable for

Honours, Masters and PhD

Supervisor

Professor Shane Maloney

Essential qualifications

For Honours: An appropriate undergraduate degree with a minimum weighted average of 65% in the level 3 subjects that comprise the relevant major, from an approved institution. Applicants will be assessed on a case-by-case basis.

For Masters or PhD : An appropriate Honours degree or equivalent research experience from an approved institution. Applicants will be assessed on a case-by-case basis.

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Does extracranial cooling really reduce brain temperature independently of arterial blood temperature?

Project Outline

It has become established in the last few years that cooling the brain reduces the long term effects of brain trauma such as stroke or ischemia. But the easiest way to cool the brain is to cool the body, and cooling the body creates problems of its own and can make the situation worse. The ideal treatment would be a means to cool the brain but leave the body at its usual temperature. That may sound easy but there is evidence that the main determinant of brain temperature is the temperature of the arterial blood reaching it. Despite this, many groups continue to test ‘extracranial selective brain cooling’ as a means to reduce brain temperature. We will use a rabbit model to look at brain – blood temperature coupling in several situations: during hypo- and hyper-capnia (which alter brain blood flow), and with ice packs applied to the cranium and a heater applied to the body. The data generated will provide good evidence for or against the possibility of brain – blood uncoupling. Techniques used will include an acute anesthetized rabbit preparation (like PHYL3002) with thermocouple measurement of temperatures. Students will be required to have done PHYL3002 and to have been an active participant in the techniques performed in the rabbit labs.

Project is suitable for

Honours, Masters and PhD

Supervisor

Professor Shane Maloney

Essential qualifications

For Honours: An appropriate undergraduate degree with a minimum weighted average of 65% in the level 3 subjects that comprise the relevant major, from an approved institution. Applicants will be assessed on a case-by-case basis.

For Masters or PhD : An appropriate Honours degree or equivalent research experience from an approved institution. Applicants will be assessed on a case-by-case basis.

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Basal metabolic rate in mammals - How much does metabolism fall during anaesthesia?

(With Prof. Phil Withers and Dr Sean Tomlinson, Animal Biology)

Project Outline

The measurement of basal metabolic rate requires that an animal be rested, post-absorptive, awake, and within its thermoneutral zone. Measurements are made with an animal in a respirometry chamber (which measures metabolic rate by indirect calorimetry, the measurement of oxygen consumption and carbon dioxide production) and are usually made during the quiet-phase of the animal’s circadian cycle. These measurements are often confounded by animal movement and restlessness. Recent analyses indicate that the average small mammal has to remain in a chamber for 8 hours before a reliable estimate of BMR can be made. Some researchers have taken to lightly anesthetising animals before they place them into the metabolism chamber, which removes the confounding effect of animal restlessness. But to date no one has compared the awake BMR of small mammals to the anesthetised MR. During this project we will make measure both the awake BMR and the anesthetised MR of the same individuals, using mice and some other small  mammals.

Project is suitable for

Honours, Masters and PhD

Supervisor

Professor Shane Maloney

Essential qualifications

For Honours: An appropriate undergraduate degree with a minimum weighted average of 65% in the level 3 subjects that comprise the relevant major, from an approved institution. Applicants will be assessed on a case-by-case basis.

For Masters or PhD : An appropriate Honours degree or equivalent research experience from an approved institution. Applicants will be assessed on a case-by-case basis.

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A Role for Prostaglandins in the Vasodilator Skin Blood Flow Response to Heat Exposure and Exercise?

(With Prof Brian Dawson, Human Movement and Exercise Science)

Project Outline

When humans are placed in situations where enhanced heat loss is required to maintain thermal balance, skin blood flow increases. An elevation in skin blood flow is achieved by reduction of vascular resistance in the skin. It is clear that central thermal input is important and leads to a reduction in vasoconstrictor tone and activation of a vasodilator system. For many years it was thought that the vasodilator system was mediated by Nitric Oxide, but subsequent study in humans has offered little support for NO mediation. The system seems to involve sympathetic cholinergic nerves, but the mediator is not Acetyl Choline. Attention has thus turned to Non-Adrenergic-Non-Cholinergic (NANC) mediators released from these nerves. In skeletal muscle prostagladins and histamine have been implicated in ACh induced vasodilation, and so an involvement of these mediators in skin blood flow is possible. The project will involve exposing subjects to high ambient temperature (37°C) and light exercise, while core body temperature, skin blood flow, and skin temperatures are measured. Blood pressure and heart rate will also be recorded. Three experiments will be performed in random order 1) Control, 2) prostaglandin blockade, 3) histamine blockade. The results will have implications for sport and general medicine, because drugs that inhibit prostaglandins and histamine are freely available and they may be important in the etiology of heat illness.

Project is suitable for

Honours, Masters and PhD

Supervisor

Professor Shane Maloney

Essential qualifications

For Honours: An appropriate undergraduate degree with a minimum weighted average of 65% in the level 3 subjects that comprise the relevant major, from an approved institution. Applicants will be assessed on a case-by-case basis.

For Masters or PhD : An appropriate Honours degree or equivalent research experience from an approved institution. Applicants will be assessed on a case-by-case basis.

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Vibration enhanced cooling of hyperthermic subjects

Project Outline

This project concerns the physiology of heat transfer. Exercise and heat exposure can lead to heat storage in the body and the state of hyperthermia. That state is associated with decrements in physical and mental performance, and can precipitate heat stroke, a medical emergency that can result in death. Strategies for cooling hyperthermic people involve methods to enhance heat transfer from the body to the environment, but can be hindered by the body’s physiological responses to cold stimuli. For example, placing the body, or parts of it, into cold water causes a reduction in blood flow in the skin of the cooled area, while blood flow is critical for transferring heat from the body’s core to the skin where it is lost to the environment. We recently showed that vibration as low frequency causes a vasodilation in the hands despite exposure to ice-water. The result was enhanced heat transfer and a faster decrease in core temperature. We would like now to test whether the response is specific to the hands, or whether whole body vibration can enhance skin blood flow in hyperthemric subjects exposed to cold air.

Project is suitable for

Honours, Masters and PhD

Supervisor

Professor Shane Maloney

Essential qualifications

For Honours: An appropriate undergraduate degree with a minimum weighted average of 65% in the level 3 subjects that comprise the relevant major, from an approved institution. Applicants will be assessed on a case-by-case basis.

For Masters or PhD : An appropriate Honours degree or equivalent research experience from an approved institution. Applicants will be assessed on a case-by-case basis.

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Physical MicroCT studies of vascularisation

Project outline

a) Taking advantage of the new high resolution scanner in CMCA in QEII we have been investigating the structure of the sheep rete, a complex network of capillaries below the brain used to cool the sheep’s brain under water stress. We wish to see how the efficiency of this structure varies between sheep and between sheep strains to identify the best heat adapted sheep, suitable for the Australian climate.

b) Blood supply of the nasal cavities, this is one of the last areas of human anatomy yet to be understood. Nose bleeds are a common, and usually innocuous, occurrence. However, as nasal vessels are embedded in the nasal conchae they may be unable to contract after damage and exanguination has occurred following epistaxis. This area is notopriously difficult to dissect. This project would involve injection of iodine into the facial and maxillary arteries followed by use of the microCT to produce hish resolution angiograms of the nasal vasculature.

Project is suitable for

Honours, Masters, PhD

Supervisor

Prof Stuart Bunt

Other Supervisors

Prof. Shane Maloney

Essential qualifications

For Honours: Some second and/or third year units in human anatomy and physiology

For Masters or PhD: Anatomy and physiology background

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