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In Drosophila melanogaster, the male seminal fluid contains proteins that are important for reproductive success. Many of these proteins are synthesised by the male accessory glands and are secreted into the accessory gland lumen, where they are stored until required. Previous studies on the identification of Drosophila accessory gland' proteins have largely focused on characterisation of male-specific accessory gland cDNAs from D. melanogaster and, moni···.recently, Drosophila simulans. The work presented in this' thesis identified thirty proteins in the accessory gland of D. melanogaster. Fourteen proteins have predicted secretory signals and thus are secreted accessory gland proteins. They included protein-folding and stressresponse proteins, a hormone, a lipase, a serpin, a cysteine-rich protein and three peptidases, a pro-enzyme form of a cathepsin K-like cysteine peptidase, Angiotensin converting enzyme and a y-glutamyl transpeptidase. Biochemical assays of the peptidase levels show the y-glutamyl transpeptidase and Angiotensin converting enzyme are reduced in mated males accessory gland suggesting their prescence in the seminal fluid. The ultrastructure of the accessory gland and secretions were investigated by electron microscopy. The filamentous contents of the secondary cells and lumen were studied by negative staining electron microscopy and cryo-electron microscopy as well as by proteomic methodologies. The major protein component of the filaments was identified as Acp36DE, which is known to be involved in sperm storage thus suggesting that is the role for the filaments.

Throughout the course of this Thesis, a range of different, yet parallel, experimental techniques were employed to investigate ion channels and control of motility in the liver fluke. In the first experimental study, voltage-gated potassium channels and control of motility were investigated using isometric tension recording studies. All of the classical potassium channel blockers employed had some form of excitatory effect on spontaneous contractions of the liver fluke. Of the more selective blockers tested, only the Kv I subfamily blocker, correolide, and the Kv 1.4 subtype blockers, zero potassium solution and riluzole, had any affect on spontaneous contractions. The results suggest a functional role for voltage-gated potassium channels in the contractility of fluke body wall, and imply that the Kv1.4 subtype may be involved. In the second experimental study, calmodulin and control of motility in the liver fluke was investigated. Immunohistochemical studies showed calmodulin immunostaining in all three ofthe welldistinguished muscle systems ofthe fluke, in addition to the vitelline cells and neural tissue. However, none of the calmodulin or myosin light chain kinase inhibitors had any effect on the spontaneous contractions of the fluke body muscle strips in isometric tension recordings. The results suggest that calmodulin plays a role in muscle systems as well as vitelline cells and neural tissue however its involvement in contractility is still not clear. The final experimental study investigated voltage-gated calcium channels and calcium store release channels and control of motility in the fluke. Findings from isometric tension recordings revealed that all of the mammalian L-type calcium channel blockers effected spontaneous contractions of the fluke body muscle, suggesting that L-type calcium channels play functional roles in fluke contractility and have similarity to mammalian L-type calcium channels. Such findings were supported by sequencing of part of a fluke (1.1 subunit, which was found to share 75% identity to the corresponding region of a channel subunit in Schistosoma mansoni, and this protein most closely resembles an L-type calcium channel in vertebrates.

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The DAZ (Deleted in Azoospermia) gene is located on the human Y chromosome and is associated with male infertility in humans. An autosomal form of this gene (DAZ-like (Dazl)) is present in all mammals and is expressed in germ cells, the Dazl itself being an RNA binding protein. Transgenic homozygous Dazl knockout (KO) male and female mice are infertile due to loss of almost all germ cells in early neonatal life. However, in heterozygous (het) females there is a significant increase in ovulation rate and litter size in comparison to their homozygous wild type (wt) littermates, in spite of lower levels of plasma Follicle Stimulating Hormone (FSH), suggesting an alteration in follicle senstiviity to FSH. The aims of this study were to assess follicle numbers in ovaries and follicle FSH-sensitivity in het mice compared to wt mice. The present studies suggest that, although Dazl is an oocyte-specific gene, the putative protein(s) that Dazl affects through RNA binding in the oocyte targets granulosa cells. The influence of Dazl on follicle development occurs through the single copy of Dazl enhancing FSH sensitivity, but the exact mechanism of Dazl on the granulosa cells is unknown. The studies presented in this thesis suggest that follicles from the Dazl het mice have accelerated growth because of a reduced threshold for FSH that allows them to remain for a longer duration within the critical FSH threshold for follicle growth. In addition, this study suggests that the percentage of healthy and atretic follicles in the Dazl wt and het mice is similar in untreated and oFF-treated mice, but that after FSH treatment there are more healthy follicles in het mice. It could be concluded that, in the adult after follicle activation and recruitment into the pool of growing follicles, a single copy of Dazl results in maintained follicle growth, because of increased FSH-sensitivity. Thus, more larger follicles achieve dominance and these subsequently ovulate, leading to an increased litter size.