David Thomas Armstrong

Research Interests

My research is in the area of endocrine regulation of the reproductive system, with emphasis on interactions between the endocrine and immune systems and their roles in initiation and successful outcome of pregnancy. Investigations of the actions of gonadotrophic and steroid hormones and cytokines in ovarian regulation, focus on cellular communication within the ovary, and how somatic cells of the follicle influence maturation and developmental competence of the oocyte. The research utilizes in vitro techniques including culture of isolated animal and human ovarian cells, oocyte maturation and fertilization and embryo culture. In vivo approaches utilize several animal models including rodents, non-human primates, pigs and cattle. This research involves collaboration with several members of the Discipline of Obstetrics and Gynaecology, including Drs Robert Gilchrist, Robert Norman, Mark Nottle, Lou Warnes and Jeremy Thompson, and PhD students Priya Duggal and Rebecca Thomas.

Besides contributing to a fuller understanding of basic mechanisms of follicle cell regulation, this research has practical objectives such as development of improved ovarian stimulation and insemination protocols for domestic animals to enhance fertility and accelerate genetic improvement through application of current and emerging reproductive technologies. For example, recent research in collaboration with Dr Colin Earl, South Australia Research and Development Institute (SARDI) has led to development of new approaches to ovarian stimulation and in vitro maturation that enable developmentally competent oocytes to be obtained from calves as young as 2-3 months of age, a procedure that is currently being applied in Australia to accelerate the rate of genetic gain in beef cattle.

Another project with important potential for commercial application, conducted in collaboration with Dr Sarah Robertson and students Sean O’Leary and Melanie Sutton, is investigating effects of immunomodulating factor(s) in seminal plasma that influence endometrial and ovarian functions necessary for pregnancy maintenance. Studies of the effects of components of semen on ovarian cytokine production in pigs have led to field tests currently underway of a new approach to increasing litter size through enhanced ovulation and corpus luteum function.

Hypotheses developed through research with the various animal species, where appropriate, are examined for possible relevance to human reproduction through close collaboration with clinical and scientific members of the Human Reproductive Medicine Unit.

Funding

Specific research projects currently funded by external granting agencies are as follows:

• Role of reactive oxygen species in embryo development and survival. Research grant from the Medical Research Council of Canada, in collaboration with Drs Tom Kennedy and Andrew Watson, University of Western Ontario, Canada, and Stanley Leibo, University of New Orleans, USA.
• Seminal plasma cytokines as determinants of ovulation, embryo survival and pregnancy success.  Collaborative project with Dr Sarah Robertson funded by the Australian Pig Research and Development Corporation.
• The marmoset monkey as a model for in vitro maturation of human oocytes. Collaborative project with Dr Rob Gilchrist and Prof R.J. Norman, funded by the Australian National Health and Medical Research Council.
• Development of cloning technology for the production of transgenic pigs. Collaborative research grant with Dr Mark Nottle, funded jointly by the Australian Research Council "SPIRT" scheme and BresaGen.
• Effects of seminal plasma on ovarian functions. ARC Small Grant in collaboration with Prof RJ Norman.

Recent Publications

Bagg MA, Vassena R, Papasso-Brambilla E, Grupen CG, Armstrong DT, Gandolfi F. Changes in ovarian, follicular, and oocyte morphology immediately after the onset of puberty are not accompanied by an increase in oocyte developmental competence in the pig. Theriogenology 2004;62(6):1003-11.

Gangnuss S, Sutton-McDowall ML, Robertson SA, Armstrong DT. Seminal plasma regulates corpora lutea macrophage populations during early pregnancy in mice. Biol Reprod 2004;71(4):1135-41.

Gilchrist RB, Ritter LJ, Armstrong DT. Oocyte-somatic cell interactions during follicle development in mammals. Anim Reprod Sci 2004;82-83:431-46.

Harvey AJ, Kind KL, Pantaleon M, Armstrong DT, Thompson JG. Oxygen-regulated gene expression in bovine blastocysts. Biol Reprod 2004;71(4):1108-19.

Hickey TE, Marrocco DL, Gilchrist RB, Norman RJ, Armstrong DT. Interactions between androgen and growth factors in granulosa cell subtypes of porcine antral follicles. Biol Reprod 2004;71(1):45-52.

O'Leary S, Jasper MJ, Warnes GM, Armstrong DT, Robertson SA. Seminal plasma regulates endometrial cytokine expression, leukocyte recruitment and embryo development in the pig. Reproduction 2004;128(2):237-47.

Thomas RE, Armstrong DT, Gilchrist RB. Bovine cumulus cell-oocyte gap junctional communication during in vitro maturation in response to manipulation of cell-specific cyclic adenosine 3',5'-monophosophate levels. Biol Reprod 2004;70(3):548-56.

Thomas RE, Thompson JG, Armstrong DT, Gilchrist RB. Effect of Specific Phosphodiesterase Isoenzyme Inhibitors During In Vitro Maturation of Bovine Oocytes on Meiotic and Developmental Capacity. Biol Reprod 2004;71:1142-1149.

Gilchrist RB, Morrissey MP, Ritter LJ, Armstrong DT. Comparison of oocyte factors and transforming growth factor-beta in the regulation of DNA synthesis in bovine granulosa cells. Mol Cell Endocrinol 2003;201(1-2):87-95.

Grupen CG, McIlfatrick SM, Ashman RJ, Boquest AC, Armstrong DT, Nottle MB. Relationship between donor animal age, follicular fluid steroid content and oocyte developmental competence in the pig. Reprod Fertil Dev 2003;15(2):81-7.

Thomas RE, Armstrong D, Gilchrist RB. Bovine Cumulus Cell-Oocyte Gap Junctional Communication During In Vitro Maturation in Response to Manipulation of Cell-Specific Cyclic Adenosine 3', 5' - Monophosphate Levels. Gynaecological Endocrinology 2003;16:443-46.

Duggal PS, Ryan NK, Van der Hoek KH, Ritter LJ, Armstrong DT, Magoffin DA, et al. Effects of leptin administration and feed restriction on thecal leucocytes in the preovulatory rat ovary and the effects of leptin on meiotic maturation, granulosa cell proliferation, steroid hormone and PGE2 release in cultured rat ovarian follicles. Reproduction 2002;123(6):891-8.

O'Leary S, Robertson SA, Armstrong DT. The influence of seminal plasma on ovarian function in pigs--a novel inflammatory mechanism? J Reprod Immunol 2002;57(1-2):225-38.

Ryan NK, Woodhouse CM, Van der Hoek KH, Gilchrist RB, Armstrong DT, Norman RJ. Expression of leptin and its receptor in the murine ovary: possible role in the regulation of oocyte maturation. Biol Reprod 2002;66(5):1548-54.

Thomas RE, Armstrong DT, Gilchrist RB. Differential effects of specific phosphodiesterase isoenzyme inhibitors on bovine oocyte meiotic maturation. Dev Biol 2002;244(2):215-25.

Ingman WV, Owens PC and Armstrong DT(2000)Differential regulation by FSH and IGF-I of extracellular matrix IGFBP-5 in bovine granulosa cells: effect of association with the oocyte. Mol Cell Endocrinol164:53-58.

Li R, Norman RJ, Armstrong DT and Gilchrist RB(2000)Oocyte-secreted factor(s) determine functional differences between bovine mural granulosa cells and cumulus cells. Biol Reprod63:839-845.

Duggal PS, van der Hoek KH, Milner CR, Ryan NK, Armstrong DT, Magoffin DA and Norman RJ(2000)The in vivo and in vitro effects of exogenous leptin on ovulation in the rat.Endocrinology141:1971-1976.

Luciano AM, Modina S, Pocar P, Gandolfi F, Lauria A and Armstrong DT(2000)Effect of cell-to-cell contact on in vitro DNA synthesis and apoptosis responses of bovine granulosa cells and cumulus cells to insulin-like growth factor-I and epidermal growth factor.Biol Reprod63:1590-1596.

Gilchrist RB, Rowe DB, Ritter LJ, Robertson SA, Norman RJ and Armstrong DT(2000)The effect of granulocyte-macrophage colony-stimulating factor deficiency on ovarian follicular cell function.J Reprod Fertil120:283-292.

Armstrong DT(2001)Effects of maternal age on oocyte developmental competence.Theriogenology55:1303-1322.

Gilchrist RB, Ritter LJ and Armstrong DT(2001)Mouse oocyte mitogenic activity is developmentally coordinated throughout folliculogenesis and meiotic maturation.Dev Biol240:289-299.

O’Leary S, Robertson SA, Armstrong DT (2002)The influence of seminal plasma on ovarian function in pigs – a novel inflammatory mechanism Journal of Reproductive Immunology. (in press)

Thomas RE, Armstrong DT,Gilchrist RB(2002)Differential effects of specific phosphodiesterase isoenzyme inhibitors on bovine oocyte meiotic maturation.Developmental Biol. (accepted 24/10/01 – MS DBIO2001-0467)

Ryan NK, Woodhouse CM, Van Der Hoek K, Gilchrist RB, Armstrong DT, Norman RJ2002Expression of leptin and its receptor in the murine ovary:possible role in the regulation of oocyte maturation.Biology of Reproduction. (accepted 27/7/01 - #01319)

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