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The design of DNA directed nitrogen mustards has led to the development of compounds with increased specificity for DNA and enhanced cytotoxicity compared to similar untargeted mustards. By linking an intercalating anthraquinone chromophore to a nitrogen mustard function it was anticipated that such compounds would also have the potential to irreversibly inhibit the topoisomerase II (topo II) enzyme.

Phosphoproteins interact with calcium minerals in numerous biological systems but despite the importance of this phenomenon it is little understood. The interaction of phosphoproteins with calcium minerals is observed in milk where caseins interact with calcium phosphate to form micelles. Further understanding of this interaction was sought through two approaches. First, the adsorption isotherms for binding of the casein β-CN A and its N-terminal phosphopeptide (β-CN (f1-25)) to crystalline dicalcium phosphate dihydrate (DCPD) were measured. Secondly, attempts were made to grow co-crystals of calcium ions with phosphopeptides or with phosphoserine. A method of measuring phosphoprotein and phosphopeptide adsorption to DCPD was developed. From the adsorption isotherms the affinity and capacity of adsorption could be determined using a model of the adsorption process. Adsorption isotherms for β-CN A were all described using a simple Langmuir model of adsorption, adsorption occurring to identical and independent sites on the DCPD crystals. β-CN (f1-25) appears to adsorb to the same adsorption sites as β-CN A and also to a second family of adsorption sites which have a lower intrinsic affinity but which are more abundant. Adsorption isotherms for β-CN (f1-25) were described using a modified version of the Langmuir model in which there are two sets of adsorption sites. A term was included to allow for cooperative adsorption to the second set of adsorption sites. The effects of methylation of lysyl residues, buffer pH, incubation temperature, the presence of 6.0 M urea in the buffer and of crystal size were all examined. The adsorption of β-CN (f1-25) to DCPD crystals appears to be athermal since the measured isotherm does not change significantly with temperature (over the measured range), requiring that adsorption is due to an entropy gain. Comparison of the results of the β-CN A and β-CN (f1-25) adsorption experiments suggests that adsorption probably occurs <i>via</i> the N-terminal region of β-CN A, consistent with the hypothesis that the binding of phosphoproteins to calcium minerals occurs primarily through their phosphoseryl residues.

The thesis describes investigations into the responsiveness of the neuroendocrine oxytocin system to hypernatraemic stimulation during pregnancy in the rat. The effects of acute intraperitoneal and intravenous hyperosmotic saline were investigated in virgin rats and in pregnant rats after 16 and 21 days of gestation. Plasma oxytocin concentration was measured by radioimmunoassay, and the inhibitory effects of endogenous opioids and exogenous opiates on the osmotic stimulation of oxytocin secretion were also investigated. The response of the oxytocin system to intraperitoneal hyperosmotic saline was strikingly attenuated at day 21 of pregnancy. These results reveal a reduced influence of the osmoregulatory input to oxytocin neurones in pregnancy. Experiments to test whether endogenous opioids, angiotensin II or acute ovarian hormone effects were involved in this reduced oxytocin activity during pregnancy indicated that it was independent of these factors. However, the oxytocin response of 21 day pregnant rats to the intravenous administration of hyperosmotic saline after the opioid antagonist naloxone was significantly elevated. This may be due to an increased sensitivity of oxytocin neurones to changes in plasma volume produced by the intravenous infusion of hyperosmotic saline that is absent when administered by the intraperitoneal route. The sites of the osmoreceptors regulating the response of oxytocin neurones to changes in plasma osmolality were investigated in virgin rats. This involved the discrete application of hyperosmotic saline into the brain using infusion and microdialysis techniques. The results of these experiments indicate that the osmoreceptors are partly in the lamina terminalis but through their direct osmosensitivity the magnocellular oxytocin neurones themselves function as osmoreceptors.

The aim of this thesis was to investigate the effects of antiprogestins on the endometrium and menstrual cycle. When the antiprogestin mifepristone was given to women in a daily dose of 2 mg/day for 30 days, ovulation was either inhibited or delayed. In those women in whom ovulation was suppressed, it would appear that mifepristone prevented the positive feedback effect of oestradiol as no LH surge occurred in spite of preovulatory levels of oestradiol. The main site of action of the antiprogestin in this respect would appear to be the pituitary as there was no significant change in the frequency or amplitude of LH pulses during treatment. Even when ovulation did occur during treatment, the development of a secretory endometrium was delayed. Endometrial biopsies taken from two such subjects, one and four days after a plasma LH surge, were devoid of early secretory changes which would usually be expected at this stage of a normal cycle indicating that during treatment with mifepristone implantation would be unlikely to be successful. In women in whom ovulation was inhibited, follicle growth continued and the persistent follicle developed into a functional or non-functional cyst. Although the endometrium in these cases was exposed to the effects of high levels of unopposed oestrogen, there were no mitoses and no evidence of hyperplasia. Some immunostaining for the cell proliferation markers Ki67 and PCNA could however be detected. Since these markers detect the presence of cells throughout all phases of the cell cycle it is possible that mifepristone affects the entry of cells into the mitotic phase of the cell cycle and may therefore prevent endometrial hyperlasia. Administration of a single dose of the antiprogestin onapristone (400 mg) or mifepristone (200 mg) in the early luteal phase (LH+2) delayed the development of a secretory endometrium.