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Title: Follicular growth and atresia in the mare
Author: Pedersen, H. G.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2001
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The growth and atresia in equine follicles has received little attention although the mare is a unique model because of the size of the animal and the ovarian follicles. The size of the animal allows ultrasound scanning to monitor follicle dynamics in vivo and the size of each follicle allows for several parameters being studied without having to pool follicles together and thereby potentially introducing errors. Several studies in the equine species have focused on follicle dynamics, others on atresia and follicular fluid hormone levels and yet others on the oocyte, but none have combined all of these areas. The aims of this thesis were to establish whether granulosa cells of regressing equine follicles degenerate via an apoptotic mechanism and whether the presence of apoptotic cell death in granulosa cells was correlated with other indices of follicle health such as steroid hormone levels and oocyte quality. At first each parameter was investigated in detail on a microscopic level: oocyte chromatin configuration, cumulus morphology, follicle wall atresia, granulosa cell apoptosis and steroid content in follicular fluid. Then followed a whole animal approach with monitoring of follicular growth via ultrasonography. In the end all knowledge was put together when studying ovaries recovered at different stages of the cycle in an attempt to reveal when selection took place and how this was reflected in the parameters of the individual follicle. Oocyte chromatin configuration was found to change from even distribution within the germinal vesicle, through different degrees of condensation to metaphase stages with increasing apoptosis or atresia of the follicle. The puzzle of the condensed chromatin configuration may be part of the normal development but also an end-stage chromatin configuration. The relationship between cumulus morphology and chromatin configuration was described and compact cumulus morphology was associated with young oocyte chromatin configurations and fully expanded cumuli were correlated with metaphase chromatin.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available