Research Focus
My research is focused on the hormonal regulation of the differentiation and function of ovarian follicles. The mammalian ovary contains a pool of non-growing, primordial follicles; we are studying the signals that stimulate follicles to leave this resting pool and initiate growth, as well as factors that inhibit the initiation of growth. The conditions that allow continued follicular growth in vitro, especially the transition from primary to secondary follicles are also an area of current interest.
The mechanisms by which a few follicles are selected to complete development and ovulate are also of particular interest and we are studying the role of changes in the IGF system in this critical stage in follicular differentiation. I am particularly interested in the differentiation and relative roles of the two endocrine cell types in the follicle, the theca and granulosa cells, and in the relative roles of the two pituitary gonadotropins, LH and FSH, in the regulation of follicular function. We are elucidating some of the interactions between these two cell types by isolating and culturing theca and granulosa cells from follicles at defined stages of follicular development. Currently, those studies are focused on the differentiation of the two cell types, and their roles in the changes in production of hormones such as progesterone, oxytocin, and prostaglandins, during the period just before ovulation.
Cattle are the primary animal model for these studies. A variety of techniques, ranging from ultrasonography to monitor the growth and regression of follicles over time in vivo, classical endocrine methods (i.e., immunoassay), and histological morphometry to analyses at the molecular level, are employed in experiments in vivo and in vitro.
Publications
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Relationship of fertility to patterns of ovarian follicular development and associated hormonal profiles in dairy cows and heifers. Journal of Animal Science. 74:1943-1952. 1996
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Regulation of steroidogenesis in bovine preovulatory follicles. Journal of Animal Science. 66:1-8.1988
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The growth and differentiation of ovarian follicles during the bovine estrous cycle. Theriogenology. 29:95-109. 1988
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Changes in plasma concentrations of gonadotrophins, preovulatory follicular development and luteal function associated with bovine follicular fluid-induced delay of oestrus in heifers. Reproduction. 76:609-621. 1986
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Growth and regression of ovarian follicles during the follicular phase in heifers undergoing spontaneous and PGF-2-alpha-induced luteolysis. Reproduction. 77:211-219. 1986
