Physiology of the germinal disc region in preovulatory follicles of the chicken ovary
Tischkau, Shelley Ann
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https://hdl.handle.net/2142/19298
Description
Title
Physiology of the germinal disc region in preovulatory follicles of the chicken ovary
Author(s)
Tischkau, Shelley Ann
Issue Date
1995
Doctoral Committee Chair(s)
Bahr, Janice M.
Department of Study
Molecular and Integrative Physiology
Discipline
Physiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Animal Physiology
Language
eng
Abstract
The germinal disc region (GDR) has been hypothesized to be growth center of the avian preovulatory follicle. This investigation was undertaken to examine critical aspects of the physiology of the GDR with respect to its role in the proliferation and differentiation of the granulosa layer. Specifically, the objectives were: (1) to determine if proliferation and differentiation of granulosa cells overlying the germinal disc was different throughout the final stages of follicular development than granulosa cells located as far from the germinal disc as possible (distal granulosa cells); (2) to examine the effects of LH on proliferation and differentiation of granulosa cells overlying the germinal disc and distal granulosa cells; (3) to determine if plasminogen activator production by the GDR is associated with proliferation; (4) to determine if gradients of proliferation and differentiation are present within an individual preovulatory follicle; and (5) to investigate the production of proliferation-stimulating and steroidogenesis-inhibiting factors by the GDR. The major findings were: (1) granulosa cells overlying the germinal disc proliferate faster and are less differentiated than distal granulosa cells; (2) LH inhibits proliferation of the GDR but has no effect on differentiation of the GDR; (3) GDRs produce high amounts of plasminogen activator through follicular development; (4) plasminogen activator production by the GDR in response to LH depends on the stage of maturation of the follicle; (5) diametrically opposed gradients of proliferation and differentiation present within an individual follicle are established and maintained by the secretion of one or more proliferation-stimulating and steroidogenesis-inhibiting factors by the GDR; and (6) epidermal growth factor, transforming growth factor $\alpha$, transforming growth factor $\beta$ and tumor necrosis factor $\alpha$ are secreted by the GDR. These data clearly illustrate that the GDR regulates follicular growth by secreting specific, paracrine-acting growth factors. The research presented in this thesis emphasize the unique role of the female gamete in follicle selection, development and maturation, culminating in ovulation.
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