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Geoffrey Donald Thorburn 1930–1996

Written by G. Jenkin, J.R.G. Challis, J.S. Robinson and I.R. Young.

Introduction

Professor Geoffrey Donald Thorburn AO passed away on 28 October 1996. He graduated in Medicine from the University of Sydney in 1956 and began his scientific career as a cardiovascular-renal physiologist. His career, in which he undertook pioneering research and teaching in many fields of physiology, spanned 35 years and three continents. He is recognised internationally as one of the founders of contemporary fetal physiology research. He was Head of the Department of Physiology at Monash University from 1981 until his retirement in 1995, but continued active research right up until his death. He was made an Officer of the Order of Australia in 1995 β€˜for service to medicine and research in the field of fetal physiology’. Geoff was a wonderful mentor and friend to all who were touched by him. He was an outstanding scientist and academic.

Fetal physiology has emerged as an independent discipline within physiology during Geoffrey Thorburn’s lifetime. This young discipline had its origins in the northern hemisphere, largely due to the studies of Barcroft, Huggett, Barron and Dawes and their protΓ©gΓ©s. The theoretical framework for fetal physiology was founded on experimental work conducted, under general anaesthesia, in acute experiments on fetal sheep and goats. By the 1960s, it was recognized that, although influenced by the mother and the placenta, the fetus has considerable autonomy. The investigation of the endocrine components of this autonomy and its modulation by the placenta and parturition were to become major foci of Geoffrey Thorburn’s research career. In the latter part of the twentieth century, two Australasians, Sir Graham (Mont) Liggins and Geoffrey Thorburn, working collaboratively and competitively but never in the same laboratory, led the intellectual growth and development of fetal, placental, maternal and neonatal physiology, sometimes collectively known as perinatal physiology.

Biographical Outline

Geoffrey was born in the Sydney suburb of Marrickville on 2 February 1930, the son of Donald Cyril Thorburn, a commercial traveller, and Vera Sabina Thorburn (nΓ©e Collings), a company secretary. He had one sibling, an elder sister, Shirley.

Geoffrey attended Canterbury Boys High School and went on to obtain his MB BS (1954) and BMedSci (1956) degrees from the University of Sydney where he was contemporaneous with Gustav Nossal and Jacques Miller. In 1958, he married Alison Isabel Quodling, the daughter of a farmer from Leeton, New South Wales. Their children, Nicholas, Holly and Angela were always at the forefront of his thoughts and he spoke of them often. Geoff and Alison were a most hospitable couple and their home was always welcoming to visitors and the venue for many parties and informal social occasions.

In the late 1950s and early 1960s, Geoff obtained a sequence of research fellowships including a two-year appointment in the laboratory of Clifford Barger at Harvard between 1961 and 1963 that led to his first academic appointment, a Senior Lectureship that he took up in the School of Physiology at the University of New South Wales in 1963. In 1966, he moved to the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Division of Animal Production at Prospect in western Sydney. In 1973, he left CSIRO, where he had reached the position of Chief Research Scientist, to join the Nuffield Institute for Medical Research and the Nuffield Department of Obstetrics and Gynaecology in Oxford as an Honorary Consultant Obstetrician and Gynaecologist and a member of the external staff of the Medical Research Council. Here he established an active research group, some of whom subsequently followed him to Australia and remained with him for the remainder of his research career. During this period, he became seriously ill with a chronic autoimmune condition, granulomatous vasculitis or Wegener’s granulomatosis, that remained with him for the rest of his life.

Geoffrey Thorburn and Dr Jeremy Sigger examine a polygraph recording relating fetal conscious state to breathing movements, 1981.

Finally, his ambition to head a department of physiology in Australia was realized when he was appointed to a chair at the University of Queensland in 1977. In 1981, he became Head of the Department of Physiology at Monash University in Melbourne, where he remained until his retirement. Soon after his return to Australia, he obtained a National Health and Medical Research Council of Australia (NH&MRC) program grant for a ten-year period. This was followed by a continuous sequence of NH&MRC grants β€” the final one being awarded after his death β€” and Australian Research Council (ARC) project grants, as well as a plethora of other grants.

Geoff passed away on 28 October 1996 at the age of 66 years, finally succumbing to complications arising from the medical condition and its treatment that had dogged him for more than twenty years.

Among his many honours and awards, those he considered most significant were the Marshall Medal of the United Kingdom’s Society for the Study of Fertility (1989), his Fellowship of the Ύ«Ά«ΚΣΖ΅ (1991), and his appointment in 1995 as an Officer of the Order of Australia in recognition of his services to medicine and research in the field of fetal physiology. In 1997, he was posthumously awarded the first Honorary Fellowship ad eundem of the Royal Australian College of Obstetricians and Gynaecologists, and in 2008 he was one of only fifteen recipients of the Monash University 50th Anniversary Research Awards, acknowledging the exceptional contribution by the recipients to their field of research and to the community during the fifty years of Monash University’s existence. His major honours and awards were:

  • 2008 Monash University 50th Anniversary Research Award (posthumous award)
  • 1997 Honorary Fellow ad eundem, Royal Australian College of Obstetricians and Gynaecologists (posthumous award) 1995 Officer of the Order of Australia (AO)
  • 1993 Inaugural John Patrick Research Professor, University of Western Ontario, London, Ontario, Canada
  • 1991 Fellow of the Ύ«Ά«ΚΣΖ΅
  • 1991 Samuel Rudin Visiting Professor, Columbia University, New York, USA
  • 1989 Christensen Fellow, St. Catherine’s College, University of Oxford, UK 1989 Marshall Medallist, Society for the Study of Fertility, UK
  • 1989 Goding Lecturer, Australian Society for Reproductive Biology, Monash University
  • 1986 The Lilley Lecturer, American Perinatal Research Society, Arizona, USA
  • 1985 Commonwealth Senior Medical Research Fellow, Physiological Laboratory, University of Cambridge, UK
  • 1984 The Malpas Lecturer, University of Oxford, UK 1983 Inaugural President, Australian Perinatal Society
  • 1979 Inaugural President, Federation of Perinatal Societies of Asia and Oceania
  • 1975 Member, WHO Study Section on Fetal Growth Retardation, Geneva, Switzerland
  • 1966 Recipient of Young Investigator’s Award of the IIIrd International Congress of Nephrology, Washington DC, USA
  • 1961 Travelling Fellow, Life Insurance Medical Research Fund of Australia and New Zealand

Technological Advances Set His Research Agenda

Any analysis of Geoffrey Thorburn’s scientific career must begin outside perinatal and reproductive physiology. His research career began during his undergraduate years when he obtained the degree of BSc (Medicine) with Honours. The research conducted for his Honours thesis resulted in his first publication, on new synthetic antispasmodics related to papaverine. This appeared as a letter in Nature in 1954 (1). The NH&MRC supported this study and the majority of his subsequent projects.

This early period also gives us insight into his desire to adopt and develop new techniques (2), a trait that was to remain with him throughout his life. Indeed, in his later years, after many years as Professor and Head of Physiology at Monash University, he enrolled in a β€˜hands on’ molecular biology training course to ensure that this rapidly developing science could also be used to address central questions in perinatal physiology.

The second phase of Geoffrey Thorburn’s career in science began in 1958 when, after completing his medical residency year, he joined Paul Korner in the Department of Physiology at the University of Sydney. It extends through the years he spent in Cliff Barger’s laboratory at Harvard Medical School and those following his return to Sydney when he was appointed a lecturer in Paul Korner’s new Department of Physiology at the University of New South Wales in 1963. This was a crucial period in his development as a scientist, as he himself later acknowledged:

I was very fortunate in having the opportunity of training with Professor Paul Korner at the Department of Physiology at the University of Sydney. An outstanding scientist, he gave me a wonderful basic training in physiology and introduced me to the work ethic. An extremely hard worker himself, he would not tolerate either laziness or fools. I was also fortunate in obtaining a travelling fellowship to spend two years working with Professor A. Clifford Barger in the Department of Physiology at Harvard Medical School. During this time, I was made aware of the high scientific standard required to maintain an international scientific reputation and this has influenced my subsequent work and endeavour.

During this period, he defined the conditions for the estimation of cardiac output using the forward part of dye dilution curves. He defined the effects of anaesthesia, environmental temperature, type of flow and valvular incompetence in experimental animals and, where possible, in man (3, 4, 6, 7). These studies were extended when he introduced the use of the inert radioactive isotope Krypton 85 to measure the flow of blood to localized areas of organs. This innovative method was used to measure the effects of haemorrhagic hypotension on the intra-renal distribution of renal blood flow. It resulted in the publication of a citation classic (9) and formed the basis of his MD thesis in 1972. These studies required the application of sophisticated mathematical methods that Geoff himself devised, having obtained the requisite training at MIT during his period in Boston. He also used this technique to determine the effects of heat, catecholamines and acetylcholine on blood flow to the testis in conscious rams (12). This latter study was his introduction to reproductive physiology and to the research opportunities offered by CSIRO at Prospect, then a rural suburb outside Sydney.

Rapid technical advances introduced Geoffrey Thorburn to fetal and reproductive physiology soon after he took up a position as a research scientist at the CSIRO Division of Animal Production at Prospect in 1966. However, the reason for his move into fetal physiology was not technical but intellectual, since he set out to determine the effects of the kidney on the metabolism and elimination of growth hormone. In order to investigate this in a healthy anephric animal, the fetus was chosen as it was correctly reasoned that the placenta and the mother would maintain fetal homeostasis in the absence of the fetal kidneys. The means to achieving this aim was a technical one whereby several groups in Australasia and in North America, including Geoffrey Thorburn with the group at Prospect, implanted the then newly developed polyvinyl intravascular catheters into sheep or goat fetuses. This seemingly simple step revolutionized the study of fetal physiology. For the first time, it was possible to implant, and maintain for many weeks, vascular catheters in the fetus. A major advantage of this technique was that investigations could be undertaken in healthy, conscious animals that had recovered from the effects of surgery, with the new-found ability to access all manner of data from an organism that had hitherto been impossible to study directly in an undisturbed state. Even though this occurred only about forty years ago, the rapidity with which the technique was accepted and adopted resulted in several groups and scientists, including Geoffrey Thorburn, arguing that they achieved this landmark breakthrough first.

In studying the effects of the kidney on growth hormone, initially the Prospect group simply ligated the fetal renal pedicles. Later it was recognized that fetal nephrectomy was a very simple extension of the ligation of the pedicles and that the fetus continued to grow in utero after this insult. These studies led to Geoffrey Thorburn’s contribution to a major CIBA symposium, β€˜Size at Birth’, in 1974 (51).

Removal of the fetal kidneys reduced fetal size at birth and many of the features of these lambs resembled those found in anephric human fetuses. Parturition occurred earlier in animals carrying nephrectomized fetuses, which was considered to be due to premature activation of the fetal pituitary adrenal axis (see later), since removal of either the adrenal glands or the pituitary from the fetus caused prolonged pregnancy. Lambs born after nephrectomy were found dead and, in addition to being small, had delayed skeletal development. Significantly, the concentrations of growth hormone in the fetus were unchanged after fetal nephrectomy, and this hormone is now believed not to be a major regulator of somatic growth before birth.

The second technical step that established the Prospect group as leaders in reproductive endocrine and fetal physiology was the development of β€˜sensitive, yet simple, protein binding methods for the determination of steroids’ (Bassett and Hinks 1969) that required only 0.5 mL of blood. These were used to determine the peripheral concentrations of progesterone throughout the oestrous cycle and pregnancy, initially in the sheep and subsequently in a range of species (16, 20). Only a few years earlier, Roger Short and his colleagues had chosen to study steroid concentrations during the oestrous cycle in the cow, but their assay required one litre of blood for each determination of progesterone. The latter assays precluded study of fetal endocrinology since the total blood volume of the fetus of almost all species would have been insufficient for a single determination. The use of protein binding methods to determine blood steroid concentrations immediately made redundant the novel technique of utero-ovarian vein to mammary vein anastomosis devised by Mattner and Thorburn (24) to investigate the control of utero-ovarian function by obtaining venous blood directly draining these organs. The third achievement at Prospect, that completed this revolution, was Ron Cox’s production of antisera to a wide range of established and more recently defined hormones, ushering in a new era dominated by the technique of radioimmunoassay with its advantages of improved sensitivity and specificity compared with the earlier protein binding assays. The whole field of fetal endocrinology was suddenly opened up for investigation by an adventurous and skilful experimental surgeon, working in close collaboration with accomplished assayists and biochemists.

The basic design of the experimental studies undertaken by Geoffrey Thorburn during the rest of his life was defined by the Prospect group and others in the late 1960s. This involved studies of the endocrine control of parturition, or of fetal growth and development, by the classical technique of ablation of an organ or endocrine gland, and/or replacement infusions of physiological or pharmacological amounts of a hormone or metabolite under investigation.

Ovarian Function

The new assays developed at Prospect in collaboration with Ron Cox were used to determine the concentrations of progesterone, oestradiol-17Ξ² and, soon afterwards, prostaglandin F2Ξ± (PGF2Ξ±) in domestic animals throughout the oestrous cycle. Transient decreases in progesterone concentrations were found to coincide with peaks of PGF2Ξ± (47, 56) and it was found that exogenous PGF2Ξ± infused into the ovarian artery or vein, induced luteolysis (34). This study confirmed the view of McCracken et al. (1973) that PGF2Ξ± is the signal inducing luteal regression in the sheep. Later studies suggested that, in sheep, the corpus luteum might be subject to tonic inhibition by prostaglandins (71). In his later years, Geoffrey fondly recalled this push to identify the physiological luteolysin, largely because of the intellectual stimulation that arose from the friendly rivalry between his group and those of Jim Goding of the Victorian Animal Research Institute at Werribee and John McCracken in the USA. Again, several of the key studies conducted at Prospect relied on Geoffrey’s surgical virtuosity. For example, he successfully separated the network of small ovarian arteries from the utero-ovarian vein, resulting in prolongation of the life of the corpus luteum and, conversely, he also showed that implantation of small pieces of gelatin sponge soaked in prostaglandin F2Ξ± (PGF2) under the adventitia of the vein caused premature demise of the corpus luteum. Together, these two observations were critical to establish the countercurrent mechanism of luteolysis, whereby PGF2Ξ± secreted by the uterus into the utero-ovarian vein diffuses through the walls of the vein and into the ovarian arteries to reach the corpus luteum and terminate its secretion of progesterone.

At the same time, detailed morphological analysis of the corpus luteum demonstrated electron-dense granules, which led Gemmell, Thorburn and colleagues to suggest that progesterone was contained in secretory granules (46, 55). This hypothesis was to remain with Thorburn in Oxford and Queensland as his group continued trying to accrue evidence for this subcellular localization of progesterone. The variation in the number of granules seemed consistent with secretion of hormones such as progesterone. However, the group in Queensland failed to find a progesterone-binding protein that could account for the electron microscopical appearance of the granules (120). Further examination of the hypothesis led to the conclusion that progesterone was intercalated in cell membranes and not in protein-bound forms in luteal secretory granules. Rice and Thorburn later showed that oxytocin was localized in the secretory granules of the corpus luteum (143). They also demonstrated the presence of neurophysin in this tissue. This study concluded one of Geoffrey Thorburn’s least successful ventures in science.

The Trigger to Parturition

The newly developed micro-method for the determination of glucocorticoids (Bassett and Hinks 1969) was used by Bassett and Thorburn (17) to define the pre-parturient changes in glucocorticoids. The finding of an exponential increase in the cortisol concentration in fetal plasma was consistent with the results of Liggins’ classic experiments of fetal hypophysectomy, adrenalectomy and infra-fetal infusion of adrenocorticotrophic hormone (ACTH) or glucocorticoids, and it definitively confirmed Liggins’ hypothesis that birth in the sheep is triggered by cortisol secretion from the fetal adrenal cortex. It is appropriate that an extensive review of these classic studies should have been jointly authored by Liggins and Thorburn in two chapters of Marshall’s Physiology of Reproduction (206, 207). These studies left Thorburn with a lasting ambition to identify the ultimate trigger to parturition.

In studies beginning at Prospect and continuing at Oxford, Queensland and Monash Universities, Thorburn, together with the present authors and their graduate students, collaborated with other scientists from different disciplines to define the changes in oestradiol-17Ξ², progesterone, progesterone metabolites, cortisol, prostaglandins F2Ξ± and E2, ACTH and higher molecular weight precursors of ACTH preceding parturition in the sheep and goat (61, 68, 88, 140, 200, 202, 203). These studies did not identify one single trigger for parturition, but there was an evolution of thought contained within these studies suggesting that the initiating site, and hence the trigger, might reside in the placenta rather than the fetal hypothalamo-pituitary adrenal axis. The notion of the placenta as the site of a trigger for parturition received impetus when Abigail Fowden from Cambridge, while on sabbatical leave in Thorburn’s laboratory, showed that undernutrition led to increased output of prostaglandin E2 from the placenta (158). In earlier experiments, PGE2 had been shown to cause an increase in the plasma concentration of cortisol in fetal sheep (68). Other studies had shown that the concentrations of ACTH fluctuated greatly during an infusion of ACTH1–24 in animals with an intact hypothalamo pituitary-adrenal axis, but not in hypophysectomised animals (68, 88). Together these studies indicated to Thorburn that an alteration in the secretion of pituitary ACTH may not be obligatory to the initiation of parturition.

The next crucial experiment was, in fact, delayed many years. In the interval, Ross Young and Gerry Silverberg, a neurosurgeon visiting Monash University from Stanford, were encouraged by Thorburn to improve the technique of hypophysectomy. The resulting microneurosurgical technique using a parapharyngeal approach continued through the basisphenoid bone, allowed direct visual inspection of the pituitary fossa and provided an intact specimen of the pituitary for examination, which was not available with the earlier subfrontal lobe approach and in situ ablation. The new hypophysectomy technique also avoided damage to hypothalamic and surrounding structures, ending debates about which structures had been damaged by the surgical procedure and whether the hypophysectomy was complete.

Thorburn used this technique to show that a constant, low dose of ACTH infused into the hypophysectomised fetus resulted in birth at the expected time irrespective of the duration of the ACTH infusion (203, 219). These exciting findings, and other related studies, showed that the ratio of high molecular weight ACTH precursors to ACTH1–39, regulates the responsiveness of the fetal adrenal cortex to ACTH, but that the cortisol surge that initiates birth does not depend on an increase in circulating ACTH. More importantly, they reinforced the hypothesis that the β€˜clock’ for birth may reside outside the hypothalamopituitary unit, the most likely place for this being the placenta. If this is correct, then it may be possible to combine our observations of the well-defined endocrine regulation of parturition in sheep and goats with the recent suggestion that the clock for human parturition also resides in the placenta (McLean et al. 1995). In the years since Thorburn’s death, Sam Mesiano, a former Monash graduate student from Thorburn’s laboratory, has received considerable acclaim for his novel hypothesis that human parturition depends on a change in the expression of progesterone receptor subtypes in the myometrium, a change that also depends on placental prostaglandin synthesis (Mesiano 2004; Mesiano et al. 2007). Geoff would have been deeply proud had he known that Mesiano would be chosen to deliver the President’s Oration at the 2006 meeting of the premier group for the presentation of research in this field, the Society for Gynecological Investigation. Geoff had certainly been prescient when he recognized Sam Mesiano’s ingenuity while he was conducting his PhD studies and did all he could to foster his scientific development.

Thorburn’s interest in the role of cortisol in the control of parturition also extended to many collaborative studies on the maturation of organ systems essential for postnatal survival. A study of the effect of cortisol on neonatal lung surfactant led to dramatic consequences when, while in Oxford, Thorburn encouraged Colin Morley, a paediatrician, and Graham Jenkin to examine the physical nature of the pulmonary surfactant. Thorburn’s uncanny ability to find the crucial collaborator led him to Alex Bangham, a physical chemist at the ARC Institute at Babraham. Together they isolated sheep surfactant and argued that it functions on the air-liquid interface as it is delivered there in β€˜dry’ form. This led to submission of their findings to Nature (96), these being published after a long delay due to the journal’s inability to find suitable referees for this novel concept. These were the initial studies leading to production of an artificial surfactant in Cambridge by Morley and his colleagues that led, in turn, to the therapeutic use of surfactant that today saves the lives of many premature infants.

Control of Fetal Growth and Development

The early experiments on the clearance and regulation of growth hormone in the fetus were followed by systematic examination of the endocrine regulation of growth in the fetus. Initially, Thorburn and his colleagues, particularly his first graduate student, Peter Hopkins, defined the effects of thyroidectomy on the growth of the fetal sheep (37). This species has a low placental permeability to thyroxine, making it a useful species to test the effects of replacement of thyroxine after thyroidectomy or hypophysectomy. Subsequent studies showed that the concentration of insulin-like growth factor-I (IGF-I) in fetal blood may be more dependent on thyroxine than on growth hormone in fetal life (165).

As noted earlier, the effects of fetal nephrectomy on the growth of the fetus had been defined during the Prospect period. At Monash University, Geoffrey reinvestigated the mechanism underlying growth retardation in this model. With biochemist Christopher Browne and graduate student Christine Beanland, it was shown that anephric fetuses have disturbances of insulin-like growth factor binding proteins (213). The role of the pancreas was also examined in chemical ablative studies using streptozotocin, a toxic analogue of glucose. However, these studies were rapidly superseded by the more direct but technically difficult approach of fetal pancreatectomy developed by Fowden and her colleagues (Fowden and Comline 1984; Fowden and Hay 1988).

Shortly before Thorburn went to CSIRO Prospect, George Alexander had devised a remarkably simple experiment of surgical excision of the majority of placental attachment sites to answer the question: does the placenta limit the growth of the fetus? This technique was combined with chronic catheterization of the fetus when Geoffrey Thorburn encouraged one of us (JSR), then a young obstetrician, to determine how restriction of placental growth retarded fetal growth. These experiments showed that the growth-restricted fetuses were chronically hypoxaemic and hypoglycaemic (104, 112). These change in oxygenation and substrate supplies induce endocrine changes that alter the distribution of these scarce resources, leading to the disproportionate growth pattern that characterizes the growth-restricted fetus.

Thorburn’s support for studies on the role of the insulin-like growth factors developed from these studies on growth restriction. Highlights amongst these studies of IGFs were characterization of an IGF receptor

(142) and identification of a high molecular weight IGF binding protein that is specific for IGF-II (159). In related studies, two of Thorburn’s graduate students investigated the regulation of the plasma concentrations of pituitary growth hormone, prolactin and thyroid stimulating hormone and placental lactogen. None of the neuro-endocrine regulators of the pituitary hormones altered the concentrations of ovine placental lactogen and the primary role of this placental hormone still remains to be discovered.

Most of the early experiments on the effects of fetal hypophysectomy described above were confined to late pregnancy, but the new transphenoidal technique for fetal hypophysectomy was exploited by Young and Thorburn to examine the effects of early hypophysectomy on growth of the fetus and on the output of hormones from the placenta. Early, unlike late, hypophysectomy caused severe growth restriction. However, some organs continued to grow at the same rate as controls, indicating that growth of the brain, liver and kidneys in the fetus is not under pituitary control. Placental steroidogenesis and prostaglandin E2 biosynthesis were reduced by the early fetal hypophysectomy, but the output of placental lactogen was again independent of pituitary control. The group concluded that placental lactogen may determine the growth rate of organs that are unaffected by fetal hypophysectomy (200).

Fetal Behavioural State

Soon after Thorburn returned to Australia to the University of Queensland, Richard Harding and Graham Jenkin joined him from Oxford, and David Walker subsequently joined the group in Melbourne. In a series of ongoing studies, Richard Harding has established the importance of lung liquid and breathing movements for normal growth of the fetal lung. The breathing movements of the fetus are linked to its conscious state, and governed in part by placenta-derived prostaglandin E2,now accepted as critical for the maintenance of the fetal circulation and other aspects of the fetal state.

Thorburn’s increasing conviction that the placenta regulated fetal activity and function by releasing short-lived substances into the fetal circulation led to an examination of the effects of agonists released by the placenta on fetal behavioural state. The initial impetus to these studies was the observation of Joe Kitterman and his colleagues that prostaglandin E2 infusions to the fetus inhibited fetal breathing movements (Kitterman et al. 1979; Wallen et al. 1986). Thorburn reasoned that substances released by the placenta that affect fetal behaviour should have a short half-life. This was considered essential to ensure rapid clearance at birth and adaptation to life ex utero. Early studies developing this hypothesis led to others investigating the effects of PGE2 on the hypothalamo-pituitary adrenal axis. Emphasis then moved to adenosine, which also inhibits fetal breathing movements, since concentrations in the fetal circulation are five-fold higher than in the adult. The concentrations of both PGE2 and adenosine fall rapidly when the umbilical cord is ligated. In his last NH&MRC grant application (which was renewed posthumously), Thorburn proposed the hypothesis that the fetus exists in a semi-anaesthetised state, maintained by steroid metabolites released by the placenta into the fetal circulation. His colleagues David Walker and Jonathan Hirst have subsequently substantiated this novel hypothesis.

Conclusion

This memoir relates to the scientific work of Geoffrey Thorburn. However, to restrict this account to an analysis of his contribution to perinatal physiology would underestimate his contribution to the broader discipline of physiology. Although Geoffrey Thorburn was a clear and concise writer and an enthusiastic public speaker, he was without doubt at his best when he was thinking through a problem in discussion with his colleagues. Few could match his ability for doing this from the floor of a conference, even when hundreds were listening to him. Other venues for these discussions were many and varied, ranging from discussion of presentations in workshops, or even when a small group had the opportunity to benefit from his ability for lateral thought, combined with an exceptional memory and knowledge of his subject. Many a colleague has been nonplussed by Geoffrey’s accurate quotes of their papers, often including their own long-forgotten interpretations of the experiments and concepts under debate. While these discussions were often assisted by a glass of beer or wine, it is all the more impressive that many of them occurred when Geoffrey was confined by his recurring ill-health.

Geoff was a voracious learner and a divergent thinker, forever incorporating newly discovered or newly learned knowledge obtained from diverse domains into his hypotheses. In his attempts to understand the physiology of human birth, he learned about the processes governing oviposition in monotremes, birds and reptiles, parturition in marsupials and evolution. He believed firmly in the value of the comparative approach in identifying fundamental mechanisms and, to that end, he had an encyclopaedic knowledge of reproductive processes in non-human species. Geoff had an extraordinary ability to formulate hypotheses drawing from his formidable knowledge of biology and medicine.

This approach led to the generation of innumerable flow charts and schemas representing his thoughts, which he would discuss energetically with his colleagues and other scientists and which he would publish β€” often as flow diagrams in refereed papers, reviews and book chapters. While some of these schemas were so complex that several of his colleagues regarded them as too speculative, they were characteristic of Geoff’s process for the discovery of new knowledge, allowing the identification of key ideas that could be refined into testable hypotheses. Although often speculative, his hypotheses were often proved to be correct through rigorous scientific investigation. When his ideas were disproven, he would cheerfully put them aside and embark on his next hypothesis. To work with such a creative, original yet discriminating thinker was an extremely exciting experience that had deep formative effects on the authors as well as on many other collaborators and students.

No account of the scientific contribution of Geoffrey Thorburn would be complete without comment on the effects of his recurring ill-health on his career. His first encounter with a health obstacle occurred in a practical class in physiology, when he was found to have a conduction defect in his heart. In 1973, while in Oxford, his health deteriorated significantly, and he maintained that this contributed to his not succeeding in his first attempt to be appointed to a chair of physiology in Australia. His research flourished during his period in Oxford, despite several life-threatening episodes attributable to granulomatous vasculitis that would have stopped the scientific careers of all but the most determined. For long periods his research staff, colleagues and visitors discussed their science with Geoffrey by his sick bed at home or in hospital. Many of his best papers and reviews were completed in these difficult circumstances. His success brought new invitations to head research units in Britain, but his health prevented more than a detailed discussion of the potential of each. New treatments of his health problems brought their own new life-threatening crises but, through all of these, Geoffrey Thorburn continued to explore concepts relating to parturition and fetal growth. In his later years, Geoff also experienced the health problems that commonly afflict aging people, but he always managed to control them and never allowed them to interfere with his intellectual life.

Geoffrey was captivated by large ideas that integrate seemingly unrelated data obtained from disparate spheres of knowledge, and he was intellectually adventurous, putting personal considerations behind his overarching objective to understand complex biological systems. When preparing grant applications, he would often send drafts to his competitors for comment, knowing that they would provide the most telling criticisms of his ideas β€” a strategy that helped to improve his success rate although it required considerable mental and psychological fortitude. His success in obtaining research funds, together with his careful selection of staff and research students, ensured that his research group maintained the critical size required for internationally competitive experimental work using chronic fetal sheep preparations. His continuous support and nurture of his graduate students, scientists and clinicians ensured that they began their independent careers well schooled in writing papers, reviews and grant applications. Many of these now occupy chairs in clinical and physiological sciences throughout the world and perhaps this legacy is the most telling measure of his own professional success. The inspirational way in which Geoff ran his research groups and, subsequently, his whole Department at Monash University is recognized and remembered by all his colleagues, including many who were not directly associated with his broad field of research interests.

Geoffrey Thorburn was a distinguished academic leader with a distinctive personal style. He eschewed formal meetings in favour of an open-door approach. Any staff member or student could usually see Geoff within a day of seeking an appointment, even if it meant staying until late in the day. Often he would interrupt his own workflow and call them in while they were seeking a booking with his secretary. He was a passionate and formidable advocate for his department at Monash and this was instrumental in maintaining the success that had been established by his predecessors, Archie McIntyre and Bob Porter, both Fellows of the Ύ«Ά«ΚΣΖ΅. He was a strong believer in traditional academic values and insisted on high standards based on rigorous assessment of student learning. He was a gifted teacher and, for many years, he chose to teach the intricacies of renal physiology to MB BS students, a task that daunts many a lecturer. Another important talent was the ability to identify and recruit research and academic staff who would collaborate and synergize. He didn’t try to manage these collaborations at close quarters, but was content to encourage and monitor them while they evolved naturally, which they did to great effect. He was an outstanding scientist and academic.

About this memoir

This memoir was originally published in Historical Records of Australian Science, vol.20, no.1, 2009. It was written by:

  • G. Jenkin. Monash Immunology and Stem Cell Laboratories, Monash University, Clayton, Vic. 3800, Australia. Corresponding author. Email: graham.jenkin@med.monash.edu.au
  • J. R. G. Challis. Michael Smith Foundation for Health Research, Vancouver, Canada.
  • J. S. Robinson. Department of Obstetrics & Gynaecology, University of Adelaide, Adelaide, SA 5000, Australia.
  • I. R. Young. Department of Physiology, Monash University, Clayton, Vic. 3800, Australia.

Numbers in brackets refer to the bibliography.

Acknowledgements

The authors thank Monash University for permission to reproduce the photograph of Professor Thorburn and Dr Sigger. The photograph was taken by Richard Crompton.

References

  1. Bassett, J. M. and N. T. Hinks (1969). Micro-determination of corticosteroids in ovine peripheral plasma: effects of venipuncture, corticotrophin, insulin and glucose. J. Endocrinol. 44(3), 387–403.
  2. Fowden, A. L. and R. S. Comline (1984). The effects of pancreatectomy on the sheep fetus in utero. Q. J. Exp. Physiol. 69(2), 319–330.
  3. Fowden, A. L. and W. W. Hay, Jr. (1988). The effects of pancreatectomy on the rates of glucose utilization, oxidation and production in the sheep fetus. Q. J. Exp. Physiol. 73(6), 973–984.
  4. Kitterman, J. A., et al. (1979). Stimulation of breathing movements in fetal sheep by inhibitors of prostaglandin synthesis. J. Dev. Physiol. 1(6), 453–466.
  5. McCracken, J. A., et al. (1973). The physiological role of prostaglandin F2alpha in corpus luteum regression. Adv. Biosci. 9, 599–624.
  6. McLean, M., et al. (1995). A placental clock controlling the length of human pregnancy. Nat. Med. 1(5), 460–463.
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  125. Gemmell R. T., Quirk S. J., Jenkin G. and Thorburn G. D. (1983) Ultrastructural evidence of variation in the number of secretory granules within the granulosa cells of the sheep corpus luteum. Cell Tiss. Res. 230, 631–638.
  126. Jenkin G., Cookson C. I. and Thorburn G. D. (1983) The interaction of human endometrial and myometrial steroid receptors with isoxazol derivative of 17Ξ±-ethinyl testosterone (danazol) used in the treatment of endometriosis. Clin. Endocrin. 19, 377–388.
  127. McDonald B. J., Waters M. J., Richards M. D., Thorburn G. D. and Hopkins P. S. (1983) Effect of epidermal growth factor on wool fibre morphology and skin histology. Res.Vet. Sci. 35, 91–99.
  128. McMillen I. C., Jenkin G., Robinson J. S. and Thorburn G. D. (1983) Concentrations of prolactin in the plasma of fetal sheep and in amniotic fluid in late gestation and during dexamethasone-induced parturition. J. Endocrin. 99, 107–114.
  129. Taylor M. J., Jenkin G., Robinson J. S. and Thorburn G. D. (1983) Effect of intrauterine death and fetectomy on ovine placental lactogen production. Res. Vet. Sci. 35, 22–24.
  130. Taylor M. J., McMillen I. C., Jenkin G., Robinson J. S. and Thorburn G. D. (1983) The regulation of ovine placental lactogen: the role of the fetal hypothalamic-pituitary axis. J. Develop. Physiol. 5, 251–258.
  131. Taylor M. J., Robinson J. S., Jenkin G. and Thorburn G. D. (1983) Ovine placental lactogen concentrations during premature delivery induced by infusion of dexamethasone or adrenocorticotrophin to the fetus. J. Endocrin. 98, 197–200.
  132. Elson S.D.,Browne C.A.and Thorburn G.D. (1984) Identification of epidermal growth factor-like activity in human male reproductive tissues and fluids. J. Clin. Endocrin. Metab. 58, 589–594.
  133. Elson S.D.,Browne C.A.and Thorburn G.D. (1984) Extraction and purification of murine epidermal growth factor. Biochem. Intl 8, 427–435.
  134. Fosang A. J., Handley C. J., Santer V., Lowther D. A. and Thorburn G. D. (1984) Pregnancy related changes in the connective tissue of the ovine cervix. Biol. Reprod. 30, 1223–1235.
  135. Harding R., Rawson J. A., Griffiths P. A. and Thorburn G. D. (1984) The influences of acute hypoxia and sleep states on the electrical activity of the cerebellum in the sheep fetus. Electroencephalography and Clin. Neurophys. 57, 166–173.
  136. Jenkin G., Gemmell R. T. and Thorburn G. D. (1984) Induction of transient functional luteolysis in cyclic sheep by a 3Ξ²-hydroxysteroid dehydrogenase inhibitor. J. Endocrin. 100, 61–66.
  137. Harper C. M., Ford V. L. and Thorburn G. D. (1984) Isolation of choriomammotropin from the ovine placentome. Aust. J. Biol. Sci. 37, 63–70.
  138. Harper C. M. and Thorburn G. D. (1984) Inhibition of prostaglandin synthesis by ovine allantoic fluid: acute reduction in inhibitory activity during late gestation. Can. J. Phys. Pharm. 62, 1152–1157.
  139. Thorburn G. D., Harding R., Jenkin G., Parkington H. and Sigger J. N. (1984) Control of uterine activity in the sheep. J. Develop. Physiol. 6, 31–43.
  140. Jenkin G., Jorgensen G., Thorburn G. D., Buster J. and Nathanielsz P. W. (1985) Induction of premature delivery in sheep following infusion of cortisol to the fetus: 1. The effect of maternal administration of prostagens. Can. J. Phys. Pharm. 63, 500–508.
  141. Jenkin G. and Thorburn G. D. (1985) Inhibition of progesterone secretion by a 3Ξ²hydroxysteroid dehydrogenase inhibitor in late pregnant sheep. Can. J. Phys. Pharm. 63, 136–142.
  142. Mesiano S., Browne C. A. and Thorburn G. D. (1985) Detection of endogenous epidermal growth factor-like activity in the developing chick embryo. Develop. Biol. 110, 23–28.
  143. Owens P.C.,Waters M.J.,Thorburn G.D.and Brinsmead M. W. (1985) Insulin-like growth factor receptor in fetal lamb liver: characterization and developmental changes. Endocrin. 117, 982–990.
  144. Rice G. E. and Thorburn G. D. (1985) Sub-cellular localization of oxytocin in the ovine corpus luteum. Can. J. Phys. Pharm. 63, 309–319.
  145. Risbridger G. P., Leach Harper C. M., Wong M. H. and Thorburn G. D. (1985) Gestational changes in prostaglandin production by ovine fetal trophoblast cells. Placenta 6, 117–126.
  146. Schuijers J. A., Walker D. W., Browne C. A. and Thorburn G. D. (1986) Effect of hypoxemia on plasma catecholamine concentrations in intact and immunosympathectomized fetal lambs. Am. J. Physiol. 251(P2), R893–R900.
  147. Bocking A. D., McMillen I. C., Harding R. and Thorburn G. D. (1986) Effect of reduced uterine blood flow on fetal and maternal cortisol. J. Develop. Physiol. 8, 237–245.
  148. Carter J., Reynoldson J. A., Harper C. M., Heywood L. H. and Thorburn G. D. (1986) Lack of production of thromboxane A2 by the sheep heart following coronary occlusion. Comp. Biochem. Physiol. 83C, 387–392.
  149. Carter J., Reynoldson J. A. and Thorburn G. D. (1986) Myocardial ischaemia following electrical stimulation of the left circumflex coronary artery in sheep: a role for thromboxane A2? Comp. Biochem. Physiol. 83C, 393–399.
  150. Carter J., Reynoldson J. A. and Thorburn G. D. (1986) The effects of certain vasodilating Prostaglandins on the coronary and hindlimb vascular beds of the conscious sheep. Com. Biochem. Physiol. 83C, 401–406.
  151. Carter J., Reynoldson J. A. and Thorburn G. D. (1986) The effects of vasoconstricting prostanoids on the coronary and hindlimb vascular beds of the conscious sheep. Comp. Biochem. Physiol. 83C, 407–412.
  152. Hirst J., Rice G. E., Jenkin G. and Thorburn G. D. (1986) Secretion of oxytocin and progesterone by ovine corpora lutea in vitro. Biol. Reprod. 35, 1106–1114.
  153. Hooper S. B., Walker D. W. and Thorburn G. D. (1986) Cannulation of the utero-ovarian vein in intact ewes: hormone concentrations and blood gas levels during the oestrous cycle and early pregnancy. Acta Endocrin. 112, 253–262.
  154. Hooper S., Watkins W. B. and Thorburn G. D. (1986) Oxytocin-associated neurophysin and prostaglandin F2Ξ± concentrations in the uteroovarian vein of pregnant and non-pregnant sheep. Endocrin. 119, 2590–2597.
  155. Jephcott E. H., McMillen I. C., Rushen J., Hargreaves A. and Thorburn G. D. (1986) Effect of electroimmobilisation on ovine plasma concentrations of Ξ²-endorphin, Ξ²-lipotrophin, cortisol and prolactin. Res.Vet. Sci. 41, 371–377.
  156. Rice G. E., Jenkin G. and Thorburn G. D. (1986) A comparison of particle-associated progesterone and oxytocin in the ovine corpus luteum. J. Endocrin. 108, 109–116.
  157. Rice G. E. and Thorburn G. D. (1986) Stimulation of ovine choriomammotrophin release, in vitro, by phospholipase C. Placenta 7, 533–542.
  158. Rice G. E. and Thorburn G. D. (1986) Characterization of particle-associated choriomammotropin and progesterone in the ovine placenta. J. Endocrin. 111, 217–223.
  159. Fowden A. L., Harding R., Ralph M. M. and Thorburn G. D. (1987) The nutritional regulation of plasma prostaglandin E concentrations in the fetus and pregnant ewe during late gestation. J. Physiol. 394, 1–12.
  160. Hey A. W., Browne C. A. and Thorburn G. D. (1987) Fetal sheep serum contains a high molecular weight insulin-like growth factor (IGF) binding protein that is acid stable and specific for IGF-II. Endocrin. 121, 1975–1984.
  161. Hooper S. B. and Thorburn G. D. (1987) Prostaglandin F2Ξ± and oxytocin release during persistence of the corpus luteum in sheep. Acta Endocrin. 115, 469–477.
  162. Jephcott E. H., McMillen I. C., Rushen J. and Thorburn G. D. (1987) A comparison of the effect of electroimmobilisation and/or shearing procedure on ovine plasma concentrations of Ξ²-endorphin/Ξ²-lipotrophin and cortisol. Res. Vet. Sci. 43, 97–100.
  163. McKay S. A., Jenkin G. and Thorburn G. D. (1987) Peripheral plasma concentrations of pregnenolone sulphate, pregnenolone, progesterone and 20Ξ±-hydroxy-4-pregnen-3-one in ewes throughout the oestrous cycle. J. Endocrin. 113, 231–237.
  164. McMillen I. C., Thorburn G. D. and Walker D. W. (1987) Diurnal variations in plasma concentrations of cortisol, prolactin, growth hormone and glucose in the fetal sheep and pregnant ewe during late gestation. J. Endocrin. 114, 65–72.
  165. Malecki J., Jenkin G. and Thorburn G. D. (1987) Passive immunization of pregnant goats against ovine LH. J. Endocrin. 114, 431–436.
  166. Mesiano S., Young I. R., Baxter R. C., Hintz R. L., Browne C. A. and Thorburn G. D. (1987) Effect of hypophysectomy with and without thyroxine replacement on growth and circulating concentrations of insulin-like growth factors I and II in the fetal lamb. Endocrin. 120, 1821–1830.
  167. Rice G. E., Wong M. H., Ralph M. M. and Thorburn G. D. (1987) Ovine allantoic fluid inhibition of prostaglandin synthesis in cotyledonary microsomes. J. Endocrin. 114, 295–300.
  168. Rice G. E., Wong M. H. and Thorburn G. D. (1987) Identification of a phospholipase inhibitor present in myometrium of pregnant ewes. Prostaglandins 34, 593–597.
  169. Schuijers J. A., Walker D. W., Browne C. A. and Thorburn G. D. (1987) Peripheral and brain tissue catecholamine content in intact and anti-NGF treated fetal sheep. Am. J. Physiol. 252, R7–R12.
  170. Hey A. W., Browne C. A. and Thorburn G. D. (1988) Purification and characterization of a fetal somatomedin from the sheep: similarity to IGF-II. Endocrin. 122, 12–21.
  171. Hirst J. J., Rice G. E., Jenkin G. and Thorburn G. D. (1988) Control of oxytocin secretion by ovine corpora lutea: effects of arachidonic acid, phospholipases and Prostaglandins. Endocrin. 122, 774–781.
  172. Jephcott E. H., McMillen I. C., Congdon P. and Thorburn G. D. (1988) Electroimmobilization and ovine plasma cortisol concentrations: effect of current intensity, current duration and diazepam. Res. Vet. Sci. 44, 21–24.
  173. McMillen I. C., Mercer J. D. and Thorburn G. D. (1988) Pro-opiomelanocortin messenger RNA levels in the fetal sheep pituitary fall before birth. J. Mol. Endocrin. 1, 141–145.
  174. Mesiano S., Wickham P. J. D., Young I. R., Browne C. A. and Thorburn G. D. (1988) Continuous measurement of biparietal distance in the intact and hypophysectomized fetal sheep using ultrasound. J. Develop. Physiol. 10, 347–356.
  175. Mesiano S., Young I. R., Browne C. A. and Thorburn G. D. (1988) Failure of acid-ethanol treatment to prevent interference by binding proteins in radioligand assays for the insulin-like growth factors. J. Endocrin. 119, 453–460.
  176. Nathanielsz P. W., Buster J. E., Jenkin G., Jorgensen G. and Thorburn G. D. (1988) Induction of premature delivery in sheep following infusion of cortisol to the fetus: the effect of maternal progestagen treatment on the C21-steroid-17Ξ±-hydroxylase, C-17,20lyase and aromatase pathways. J. Devel. Physiology 10, 257–270.
  177. Rice G. E., Wong M. H. and Thorburn G. D. (1988) Gestational changes in prostaglandin synthase activity of ovine cotyledonary microsomes. J. Endocrin. 118, 265–270.
  178. Zemdegs I. Z., McMillen I. C., Walker D. W., Thorburn G. D. and Nowak R. (1988) Diurnal rhythms in plasma melatonin concentrations in the fetal sheep and pregnant ewe during late gestation. Endocrin. 123, 284–289.
  179. Andrianakis P., Walker D. W., Ralph M. M. and Thorburn G. D. (1989) Effect of inhibiting prostaglandin synthesis in pregnant sheep with 4-amino antipyrine under normothermic and hyperthermic conditions. Am. J. Obstet. Gynecol. 161, 241–247.
  180. Andrianakis P., Walker D. W., Ralph M. M. and Thorburn G. D. (1989) Effects of hyperthermia on fetal and maternal plasma prostaglandin concentrations and on uterine activity in pregnant sheep. Prostaglandins 38, 541–555.
  181. Burke J. L., Rice G. E., Ralph M. M. and Thorburn G. D. (1989) Effects of calcium availability on the release of ovine choriomammatropin from cotyledonary cells incubated in vitro. Comp. Biochem. Physiol. 93, 489–492.
  182. Fowden A. L., Harding R., Ralph M. M. and Thorburn G. D. (1989) Nutritional control of respiratory and other muscular activities in relation to plasma prostaglandin E in the fetal sheep. J. Develop. Physiol. 11, 253–262.
  183. Hey A. W., Browne C. A., Simpson R. J. and Thorburn G. D. (1989) Simultaneous isolation of insulin-like growth factors I and II from adult sheep serum. Biochem et Biophys Acta 997, 27–35.
  184. McMillen I. C., Jenkin G., Haji-Baba A., Browne C. A. and Thorburn G. D. (1989) Effect of Ξ³3or Ξ³2 melanocyte stimulating hormone on steroidogenesis in the fetal sheep during late gestation. Life Sci. 44, 563–569.
  185. Mesiano S., Young I. R., Browne C. A. and Thorburn G. D. (1989) Hypophysectomy of the fetal lamb leads to a fall in the plasma concentration of insulin-like growth factor I (IGF-I), but not IGF-II. Endocrin. 124, 1485–1491.
  186. Ralph M. M., Lee C. S. and Thorburn G. D. (1989) Identification and characterization of monolayer cultures of sheep trophoblast cells maintained in bicameral culture chambers. Biol. Reprod. 41, 481–489.
  187. Tyson L., Browne C. A., Jenkin G. and Thorburn G. D. (1989) The clearance and distribution of murine epidermal growth factor in the sheep. J. Endocrin. 132, 121–130.
  188. Wlodek M. E., Thorburn G. D. and Harding R. (1989) Bladder contractions and micturition in fetal sheep: their relationship to behavioural states. Am. J. Physiol. 257, R1526–R1532.
  189. Young I. R., Mesiano S., Hintz R., Caddy D. J., Ralph M. M., Browne C. A. and Thorburn G. D. (1989) Growth hormone and testosterone can independently stimulate the growth of hypophysectomised prepubertal lambs, without any alteration in circulating concentrations of insulin-like growth factors. J. Endocrin. 121, 563–570.
  190. Burgess K. M., Ralph M. M., Jenkin G. and Thorburn G. D. (1990) Effect of oxytocin and estradiol on uterine prostaglandin release in non-pregnant and early pregnant ewes. Biol. Reprod. 42, 822–833.
  191. Hirst J. J., Rice G. E., Jenkin G. and Thorburn G. D. (1990) Regulation of oxytocin secretion by the ovine corpus luteum: effect of activators of protein kinase C. J. Endocrin. 124, 225–232.
  192. Hooper S. B., Coulter C. L., Deayton J. M., Harding R. and Thorburn G. D. (1990) Fetal Endocrine response to prolonged hypoxemia in sheep. Am. J. Physiol. 259, R703–R708.
  193. Jephcott E. H., Lynn R. D., Thorburn G. D. and McMillen I. C. (1990)The effects of electroimmobilisation on blood gas and pH status in sheep. Res. Vet. Sci. 48, 314–320.
  194. Rice G. E., Wong M. H., Hollingworth S. and Thorburn G. D. (1991) Prostaglandin G/H synthase activity in ovine cotyledons: a gestational profile. Eicosanoids 3, 231–236.
  195. Wei G., Rice G. E. and Thorburn G. D. (1991) Prostaglandin E2 and F2Ξ± in mid-pregnant rat uterus and at parturition. Prost. Leukotr. Ess. Fatty Acids 40, 27–30.
  196. Hooper S. B., Harding R., Deayton J. and Thorburn G. D. (1992) Role of Prostaglandins in the metabolic responses of the fetus to hypoxia. Am. J. Obstet. Gynecol. 166, 1568–1575.
  197. Rice G. E., Payne M. J., Wong M. H. and Thorburn G. D. (1992) Immunoreactive prostaglandin G/H synthase content increases in ovine cotyledons during late gestation. Placenta 13, 429–437.
  198. Wlodek M.E.,Harding R. and Thorburn G.D. (1992) Fetal-maternal fluid and electrolyte relationships during chronic fetal urine loss in sheep. Am. J. Physiol. 263, F671–F679.
  199. Wlodek M., Harding R. and Thorburn G. D. (1992) The influence of gestational age and onset of labour on determinants of fetal-maternal fluid and electrolyte balance in sheep. J. Devel. Physiol. 18, 111–119.
  200. Burgess K. M., Jenkin G., Ralph M. M. and Thorburn G. D. (1992) Effect of the antiprogestin RU486 on uterine sensitivity to oxytocin in ewes in late pregnant sheep. J. Endocrin. 134, 353–360.
  201. Deayton J. M., Young I. R. and Thorburn G. D. (1993) Early hypophysectomy of sheep fetuses: effects on growth, placental steroidogenesis and prostaglandin production. J. Reprod. Fertil. 97, 513–520.
  202. Thorburn G. D. (1993) A speculative review of parturition in the mare. Equine Vet. J. Suppl. 14, 41–49.
  203. Deayton J. M., Young I. R., Hollingworth S. A., White A., Crosby S. R. and Thorburn G. D. (1994) Effect of late hypothalamo-pituitary disconnection on the development of the HPA axis in the ovine fetus and the initiation of parturition. J. Neuroendocrin. 6, 25–31.
  204. Jacobs R. A., Young I. R., Hollingworth S. A. and Thorburn G. D. (1994) Chronic administration of low doses of adrenocorticotropin to hypophysectomized fetal sheep leads to normal term labor. Endocrin. 134, 1389–1394.
  205. Wlodek M.E.,Harding R.and Thorburn G.D. (1994) Effects of inhibition of prostaglandin synthesis on flow and composition of fetal urine, lung liquid and swallowed fluid in sheep. Am. J. Obstet. Gynecol. 170, 186–195.
  206. Young I. R. and Thorburn G. D. (1994) Prostaglandin E2, fetal maturation and ovine parturition. Aust. NZ J. Obstet. Gynaecol. 34, 342–346.
  207. Liggins G. C. and Thorburn G. D. (1994) Initiation of parturition. In Marshall’s Physiology of Reproduction, 4th ed, Vol. 3: Pregnancy and Lactation, Part Two, ed. G. E. Lamming, Chapman and Hall, London. pp. 863–1002.
  208. Thorburn G. D. and Liggins G. C. (1994) Role of fetal pituitary-adrenal axis and placenta in the initiation of parturition. In Marshall’s Physiology of Reproduction, 4th ed, Vol. 3: Pregnancy and Lactation, Part Two, ed. G. E. Lamming, Chapman and Hall, London. pp. 1003–1036.
  209. Ford M. M., Young I. R. and Thorburn G. D. (1995) Prostaglandins and the maintenance of pregnancy in goats. J. Reprod. Fertil. Suppl. 49, 555–559.
  210. Thorburn G. D. (1995) The placenta and the control of fetal breathing movements. Reprod. Fertil. Dev. 7, 557–594.
  211. Carr G. A., Jacobs R. A., Young I. R., Schwartz J., White A., Crosby S. and Thorburn G. D. (1995) Development of adrenocorticotropin-(1–39) and precursor peptide secretory responses in the fetal sheep during the last third of gestation. Endocrin. 136, 5020–5027.
  212. Schwartz J., Kleftogiannis F., Jacobs R., Thorburn G. D., Crosby S. R. and White A. (1995) Biological activity of adrenocorticotropic hormone precursors on ovine adrenal cells. Am. J. Physiol. 268, E623–E629.
  213. HollingworthS.A.,DeaytonJ.M.,YoungI.R. and Thorburn G. D. (1995) Prostaglandin E2 administered to fetal sheep increases the plasma concentration of adrenocorticotropin (ACTH) and the proportion of ACTH in low molecular weight forms. Endocrin. 136, 1233–1240.
  214. Beanland C., Browne C., Young R., Owens J., Walton P. and Thorburn G. (1995) Fetal plasma insulin-like growth factor-binding protein-3 concentrations are elevated following bilateral nephrectomy in fetal sheep. Reprod. Fertil. Dev. 7, 345–349.
  215. Young I. R., Deayton J. M., Hollingworth S. A. and Thorburn G. D. (1996) Continuous intrafetal infusion of prostaglandin E2 prematurely activates the hypothalamo-pituitary-adrenal axis and induces parturition in sheep. Endocrin. 137, 2424–2431.
  216. Xiao Q., Challis J. R., Fraser M., Wlodek M. E., Thorburn G. D., Cuttita F., Hill D. J., St-Pierre S., Spindel E. R. and McDonald T. J. (1996) Locations and molecular forms of gastrin-releasing peptide-like immunoreactive entities in ovine pregnancy. Peptides 17, 489–495.
  217. Nicol M. B., Hirst J. J., Walker D. and Thorburn G. D. (1997) Effect of alteration of maternal plasma progesterone concentrations on fetal behavioural state during late gestation. J. Endocrin. 152, 379–386.
  218. Crossley K. J., Nicol M. B., Hirst J. J., Walker D. W. and Thorburn G. D. (1997) Suppression of arousal by progesterone in fetal sheep. Reprod. Fertil. Dev. 9, 767–773.
  219. Wlodek M. E., Hooper S. B., Thorburn G. D., Tester M. L. and Harding R. (1998) Effects of prostaglandin E2 on renal function and lung liquid dynamics in foetal sheep. Clin. Exp. Pharmacol. Physiol. 25, 805–812.
  220. Poore K. R., Young I. R., Canny B. J. and Thorburn G. D. (1998) Studies on the role of ACTH in the regulation of adrenal responsiveness and the timing of parturition in the ovine fetus. J. Endocrin. 158, 161–171.
  221. Poore K. R., Young I. R., Canny G. J. and Thorburn G. D. (1998) Angiotensin II infusion in vivo does not modulate cortisol secretion in the late-gestation ovine fetus. Am. J. Physiol. 275, R357–R362.
  222. Ford M. M., Young I. R., Caddy D. J. and Thorburn G. D. (1998) Fetal and maternal Endocrine changes approaching parturition in the goat: lack of evidence for Prostaglandins E2 and F2Ξ± as signals for luteolysis. Biol. Reprod. 58, 1065–1070.
  223. Ford M. M., Thorburn G. D., Caddy D. J. and Young I. R. (1999) Pulsatile output of prostaglandin F2Ξ± does not increase around the time of luteolysis in the pregnant goat. Biol. Reprod. 61, 411–415.

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