| Research Topic:
The survival of newborn infants is
critically dependent upon the lungs immediately taking over from the
placenta as the organ of gas exchange; however ten percent of babies are
born prematurely and experience medical problems which impact their
survival (Post & Copland, 2002). It is evident that development and
maturation of the lung at, and around, the time of birth entails a
complex interaction of physical, physiological, and biochemical
processes. My project aims to address aspects of all three of these
components in the developing lung of two marsupials, the tammar wallaby
(Macropus eugenii) and the fat-tailed dunnart (Sminthopsis
crassicaudata). Marsupials represent the group of mammals in which
reproduction is characterised by a short intrauterine gestation followed
by a lengthy lactation in the pouch; meaning that much differentiation
of physiological and biochemical functions, and the development of their
organ systems, occurs in the pouch This makes them an ideal model for
studying the development of organs such as the lung.
The physical aspects of lung development
The physical, or structural, changes taking
place over the perinatal period in the wallaby and dunnart are being
investigated by phase contrast synchrotron imaging with collaborators at
Monash University and SPring-8 radiation facility, Japan, as well as
more traditional techniques like electron and light microscopy.
The physiological aspects of marsupials
breathing at birth
Previous investigations by members and
collaborators of our laboratory have led to the conclusion that newborn
marsupials are capable of gas exchange through the skin. In fact, up to
95% of gas exchange is subcutaneous in the Julia Creek dunnart during
the first day of post-natal life, making the skin almost completely
responsible for exchange of oxygen and carbon dioxide. The tammar
wallaby however is born much larger and on average subcutaneous exchange
only accounts for approximately 30% of total gas exchange. I will be
investigating this phenomenon of breathing through the skin in the
fat-tailed dunnart and determining whether CO2
drive occurs across the lung or skin in proportion to the lung/skin
ratio and if ventilation can be stimulated earlier if the animal is
challenged.
The biochemical aspects of lung development
One aim of this study is to use high
throughput gene expression technology to investigate developmental,
structural and functional changes in the lungs of the developing
wallaby. Microarray technology, and the accompanying computational
analysis, will allow an investigation of the genes which are
differentially expressed during different stages of development in the
lung of the neonatal tammar wallaby.
Links to the dairy industry??
The notion that components within milk (the
sole food source of newborn mammals) can influence and direct the
physiological development of the offspring is now widely accepted. Milk
is known to contain molecules that aid in development of the
immunodefense system of the newborn as well as elicit behavioural
(analgesic), neurological, physiological and vasoregulatory responses,
and modulators of digestive and gastrointestinal functions, and
anticariogenecity.
Microarray data from the tammar wallaby
mammary gland has been generated by scientists at DPI Attwood throughout
lactation, and gene expression profiles will be analysed and correlated
to the produced lung data in this study, enabling determination of
possible candidate genes coding for bioactives present in milk that may
play a role in lung development.
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