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Title: Ovarian follicle growth and yolk formation in the New World marsupial Monodelphis domestica
Author: Butcher, Liza
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1995
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Abstract:
The adult Monodelphis domestica ovary was found to be similar to that of the eutherian mammal possessing follicles in various stages of development, corpora lutea and interstitial tissue. Polyovular follicles, containing between two and eleven oocytes, were found in approximately 25% of the individuals observed. Folliculogenesis proceeded in an identical manner to that in the eutherian but oocyte growth continued throughout follicular development. It therefore did not conform to the strict biphasic pattern of follicle growth previously described in eutherian and marsupial species. Oestrous cycles were monitored and, contrary to previous studies, female M domestica isolated from males continued to exhibit oestrous cycles. All females appeared to exhibit repetitive cycles of ovarian follicle growth accompanied by changes in the reproductive tract. If exposed to the stimulus of a male, a group of large follicles completed their development and ovulation occurred. In the absence of such stimulus, these follicles became atretic and were replaced by a successive wave of follicles. At the ultrastructural level, the growth and development of the oocyte was accompanied by an increase in the number of its organelles and a change in their distribution which reflected the metabolic activity involved during such growth. Apart from the conventional organelles found within oocytes, lamellar complexes and two unusual forms of mitochondria were observed at different stages of development. Smooth endoplasmic reticulum and Golgi bodies appeared to be responsible for the formation of multivesicular bodies which were first observed in the oocytes of primary follicles. As the multivesicular bodies increased in size they became more flocculent in nature until they formed transparent vesicles which exhibited no polarity. These then coalesced to form a large vesicular mass, occupying most of the central region of the oocyte, which was identical to the "yolk" mass described in other marsupial species. Histochemical analyses revealed that in smaller oocytes the cytoplasm consisted mostly of carbohydrate and protein but during development this was replaced by the yolk vesicles. The nature of these vesicles remained undetected by histochemical staining and it was only by means of molecular probe labelling that lipid was detected. Autoradiographical analysis revealed that metabolites were transported from the circulation into the oocytes and that this uptake was fairly uniform in all developmental stages of oocyte. For the first time in a marsupial, individual preantral follicles were cultured in vitro. Although follicles grew for up to 8 days, and sometimes exceeded the size where antrum formation was observed in vivo, definite antrum formation was not achieved.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.788653  DOI: Not available
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